Institute of Materials Science - Technische Universität Darmstadt

Transcription

Annual Report
2013
Faculty of
Materials and Geo Sciences
Contents
Dean’s Office .................................................................................................................. 4
Institute of Materials Science ......................................................................................... 6
PHYSICAL METALLURGY ....................................................................................................... 12
CERAMICS GROUP .............................................................................................................. 21
ELECTRONIC MATERIAL PROPERTIES...................................................................................... 30
SURFACE SCIENCE .............................................................................................................. 38
ADVANCED THIN FILM TECHNOLOGY ..................................................................................... 50
DISPERSIVE SOLIDS ............................................................................................................. 53
STRUCTURE RESEARCH........................................................................................................ 70
MATERIALS ANALYSIS ......................................................................................................... 75
MATERIALS MODELLING DIVISION ......................................................................................... 87
MATERIALS FOR RENEWABLE ENERGIES ................................................................................. 98
PHYSICS OF SURFACES....................................................................................................... 111
JOINT RESEARCH LABORATORY NANOMATERIALS .................................................................. 116
MECHANICS OF FUNCTIONAL MATERIALS ............................................................................. 120
FUNCTIONAL MATERIALS ................................................................................................... 126
ION-BEAM MODIFIED MATERIALS........................................................................................ 135
MOLECULAR NANOSTRUCTURES.......................................................................................... 142
COLLABORATIVE RESEARCH CENTER (SFB) .......................................................................... 146
DIPLOMA THESES IN MATERIALS SCIENCE ....................................................................... 150
BACHELOR THESES IN MATERIALS SCIENCE ..................................................................... 152
MASTER THESES IN MATERIALS SCIENCE......................................................................... 154
PHD THESES IN MATERIALS SCIENCE ............................................................................. 155
MECHANICAL WORKSHOP ............................................................................................. 157
ELECTRICAL WORKSHOP ............................................................................................... 157
Institute for Applied Geosciences .............................................................................. 158
PREFACE .................................................................................................................... 158
PHYSICAL GEOLOGY AND GLOBAL CYCLES ............................................................................ 160
HYDROGEOLOGY .............................................................................................................. 172
ENGINEERING GEOLOGY .................................................................................................... 177
GEOTHERMAL SCIENCE AND TECHNOLOGY ........................................................................... 187
APPLIED SEDIMENTOLOGY .................................................................................................. 197
GEO-RESOURCES AND GEO-HAZARDS .................................................................................. 203
GEOMATERIAL SCIENCE ..................................................................................................... 212
ELECTRON CRYSTALLOGRAPHY ........................................................................................... 221
TECHNICAL PETROLOGY WITH EMPHASIS IN LOW TEMPERATURE PETROLOGY............................. 223
ENVIRONMENTAL MINERALOGY .......................................................................................... 226
DIPLOMA THESES IN APPLIED GEOSCIENCES .................................................................... 230
MASTER THESES IN APPLIED GEOSCIENCES...................................................................... 230
MASTER THESES TROPHEE IN APPLIED GEOSCIENCES ...................................................... 231
BACHELOR THESES IN APPLIED GEOSCIENCES .................................................................. 232
PHD THESES IN APPLIED GEOSCIENCES .......................................................................... 233
Faculty of Materials and Geo Sciences
3
Dean’s Office
Staff Members
Dean:
Prof. Dr. Ralf Riedel
Vice dean:
Prof. Dr. Christoph Schüth
Dean of studies Materials Science:
Prof. Dr. Lambert Alff
Dean of studies Applied Geosciences:
Prof. Dr. Matthias Hinderer
Scientific coordinator, department
and Materials Science:
PD Dr. Boris Kastening
Scientific coordinator, Applied Geosciences:
Dr. Karl Ernst Roehl
Secretary of department:
Renate Ziegler-Krutz
Secretary of personnel and finances:
Christine Hempel
Competence center for materials characterization:
Dr. Joachim Brötz
IT group:
Dipl. –Ing. (BA) Andreas Hönl
Building services:
Dipl. –Ing. Heinz Mohren
Coordination of the KIVA project:
Dr. Silvia Faßbender
Public relations:
Marion Bracke
Media Design:
Thomas Keller
Publications of Permanent Members of the Dean's Office
Boris Kastening
Anisotropy and universality in finite-size scaling: Critical Binder cumulant of a twodimensional Ising model
Phys. Rev. E 87, 044101/1-4 (2013), arXiv:1209.0105, DOI:10.1103/PhysRevE.87.044101
Siol, Sebastian; Straeter, Hendrik; Brueggemann, Rudolf; Broetz, Joachim; Bauer, Gottfried
H.; Klein, Andreas; Jaegermann, Wolfram;
PVD of copper sulfide (Cu2S) for PIN-structured solar cells;
JOURNAL OF PHYSICS D-APPLIED PHYSICS Volume: 46 Issue: 49 Article Number:
495112 (2013)
4
Dean’s Office
Pfeifer, Verena; Erhart, Paul; Li, Shunyi; Rachut, Karsten; Morasch, Jan; Broetz, Joachim;
Reckers, Philip; Mayer, Thomas; Ruehle, Sven; Zaban, Arie; Mora Sero, Ivan; Bisquert,
Juan; Jaegermann, Wolfram; Klein, Andreas;
Energy Band Alignment between Anatase and Rutile TiO2;
JOURNAL OF PHYSICAL CHEMISTRY LETTERS Volume: 4 Issue: 23 Pages: 41824187 (2013)
Labrini, Mohamed; Saadoune, Ismael; Scheiba, Frieder; Almaggoussi, Abdelmajid;
Elhaskouri, Jamal; Amoros, Pedro; Ehrenberg, Helmut; Broetz, Joachim;
Magnetic and structural approach for understanding the electrochemical behavior of
LiNi0.33Co0.33Mn0.33O2 positive electrode material;
ELECTROCHIMICA ACTA Volume: 111 Pages: 567-574 (2013)
Muench, Falk; Oezaslan, Mehtap; Rauber, Markus; Kaserer, Sebastian; Fuchs, Anne;
Mankel, Eric; Broetz, Joachim; Strasser, Peter; Roth, Christina; Ensinger, Wolfgang;
Electroless synthesis of nanostructured nickel and nickel-boron tubes and their performance as
unsupported ethanol electrooxidation catalysts
JOURNAL OF POWER SOURCES Volume: 222 Pages: 243-252 (2013)
Dean’s Office
5
Institute of Materials Science
Preface
Dear colleagues and friends,
The year 2013 was another successful period for the Department of Materials and Geo
Sciences of TU Darmstadt. Details of the activities and achievements related to the
individual departmental institutes, namely Materials Science and Applied Geosciences, are
highlighted below.
We would like to express our gratitude to all members of the Department – the mechanical
workshop staff, technical and administrative staff, students working on their diploma and
bachelor theses, Ph.D. students, and postdocs – for the outstanding effort and remarkable
enthusiasm they put into their work. Without their contributions the performance and the
results presented here would not have been possible. We aim to sustain and promote the
motivating and fruitful atmosphere at our institute in order to continue our commitment
and success in the time to come.
Materials Science
The amount of acquired third party funding has reached a nearly constant value in the
order of 10 million Euro. Presently, the total number of students (bachelor & master) in
materials science amounts round about 500. The number of freshmen of the bachelor study
course Materials Science in the winter semester 2013/14 reached 94 (see Figure 1). The
new master course Energy Science and Engineering which is an interdisciplinary field of
study and which is administratively organized by our Department successfully developed in
its second year. The master course presently counts 61 students of which 36 were freshmen
in the WS 2013/14. Last not least, the master course Energy Science and Engineering was
accredited in spring 2013.
The Materials Science and Geo Sciences Department’s Materialium Graduate School has
been further strengthened and now accommodates 30 PhD students, while the total
number of PhD students of Materials Science exceeds by now 150. The research-oriented
doctorate program culminating in award of the degree of “Dr.-Ing.” or “Dr. rer. nat.” fosters
an interdisciplinary integration of the various Ph.D. studies between research groups inside
and outside of the Materials Science Department. During specific events, Ph.D. students
present their current scientific problems and methods, providing a forum for close
interdisciplinary problem solving that stimulates synergy between research groups.
Research is always a collaborative enterprise! Professors of Materialium are particularly
committed to supporting their Ph.D. students. For instance, they strongly encourage
participation at international conferences and publication in refereed research journals,
which is bolstered by the high number of coordinated research programs in Materials
Science at TU Darmstadt. Moreover, Materialium is a member of Ingenium, the umbrella
organisation of graduate schools at TU Darmstadt.
6
Institute of Materials Science - Preface
Fig. 1: All students (except Ph.D. students) and freshmen (Diplom until WS 07/08, B.Sc. from WS 08/09) of
Materials Science at TU Darmstadt.
Coordinated Research Proposals
The institute was actively involved in a variety of coordinated research project applications.
Among them one new proposal was successfully evaluated in 2013 in the frame of the
LOEWE Priority Program supported by the Hessian State Government. The scientific topic
of this research program is related to “The Reduction and Substitution of Rare Earth
Elements in High Performance Permanent Magnets” (Response) and is coordinated by Prof.
Gutfleisch. The official start of this coordinated research is January 01, 2014.
This initiative marks the interdisciplinary approach the university is promoting and for
which the Department of Materials and Geo Science is ideal since its subjects combine
various sciences like chemistry, physics, electrical and mechanical engineering.
Preface
7
Faculty Members
In 2013 we had two important events related to the faculty staff members. First, in spring
2013, Prof. Dr. Karsten Durst started as the new head of the group Physical Metallurgy. He
is the successor of Prof. Dr. Martin Heilmaier, who left the Department of Materials and
Geosciences to take up a position as Director at the Karlsruhe Institute of Technology (KIT)
in December 2011. Second, in late autumn 2013 Prof. Dr. Jürgen Rödel, the head of the
group Nonmetallic Inorganic Materials, was elected as Vice President for research of TU
Darmstadt. We wish both colleagues a successful start for their new and responsible
positions.
Prof. Dr. Karsten Durst
Prof. Dr. Jürgen Rödel
Buildings and Lab/Office Space
In the course of the completion of the new “Hörsaal- und Medienzentrum” the street names
of campus Lichtwiese have been renamed since autumn 2013. Accordingly, the address of
the Dean’s office as well as that of the Materials science building has been changed to
Alarich-Weiss-Str. 2. The office building L1|08, where the groups of Prof. Albe, Prof. Hahn,
Prof. Jaegermann, Prof. Krupke, Prof. Riedel, and Prof. Xu are hosted, have now the postal
address Jovanka-Bontschits-Str. 2.
In September 2013 we moved into our new lab and office building denoted as M3 which
stands for “Molecules, Magnets and Materials”. In an official ceremonial act, the building
was inaugurated in the presence of the TU President and Chancellor on October 29. The
Functional Materials group of Prof. Gutfleisch as well as the Physics of Surfaces group of
Prof. Stark have found their new homes in this state of the art and functional building.
8
New M3 lab and office building.
Honours, Awards and Special Achievements
In 2013, the following precious awards were granted to faculty members of the materials
science department:
Prof. Fueß received an honorary doctorate of the University of Vilnius in Lithuania for his
outstanding research and for his continuing and fruitful scientific collaboration with the
university. Prof. Hahn was awarded with the Franklin Mehl Award of The Minerals, Metals
and Materials Society (TMS), USA, for his exceptional research in Materials Science. Dr.
Robert Dittmer received a young investigator award, namely the “Nachwuchspreis” of the
“Deutsche Gesellschaft für Materialkunde” (DGM).
Prof. Dr. Hartmut Fueß
Preface
Prof. Dr. Horst Hahn
Dr. Robert Dittmer
9
At the suggestion of the Department of Materials and Geosciences, the TU Darmstadt has
solemnly conferred Prof. Dr. Jean Etourneau, Professor Emeritus at the University of
Bordeaux 1, the honorary doctorate. Thereby the TU Darmstadt recognizes his pioneering
contributions to the field of materials chemistry and materials science as well as his great
commitment to advance scientific communication and cooperation in Europe.
TU-President Hans Jürgen Prömel (right) with TU-Honorary Doctor Prof. Jean Etourneau. Photo: Felipe Fernandes
As usual, the annual awarding of the "MaWi Prize" formed part of the MaWi summer party.
The 1st prize was awarded to Ruben Heid from the division PhM for his Diploma thesis on
“Einfluss von gießtechnischen Prozessschwankungen auf das Eigenschaftsspektrum
crashrelevanter Aluminium-Druckgusslegierungen;” 2nd prizes were awarded to Tim
Niewelt from the division OF for his Diploma thesis about “Analyse von Defekten in
kristallinem Silizium” and to Joachim Langner from the division EE for his Diploma thesis
about “Ionische Flüssigkeiten als Elektrolyt, Co-Katalysator und Stabilisator in
Brennstoffzellen“. The 3rd prize was awarded to Christian Lohaus for his Bachelor thesis
about “Synthese verschiedener rußgeträgerter Pt-Ru-Au Katalysatoren und Untersuchung
des Degradationsverhaltens.”
Social Events and Awards
As every year, our annual summer party was scheduled shortly before the summer break,
being one of the most important social events of the Materials Science Institute. It has
become a tradition to use this festivity to award the MaWi prize to the three best students
having accomplished their Diploma or Master in the past winter semester.
10
The 1st prize was awarded to Christoph Rakousky from the division EE for his diploma
thesis “Neue Kohlenstoffkomponenten für Gasdiffusionsschichten. The award comes with
prize money of € 500. 2nd prizes for Diploma with honours were awarded to Andreas Liess
from the division EM and Maybritt Kühn from the division OF. Laura Ahmels from the
division PhM and Hans Justus Köbler from the division ST were awarded for best Bachelor
degree.
In December 2013 we celebrated the year-end ceremony for all research groups, staff
members and students, including the formal graduate celebration, where Bachelor, Master
and PhD students received their certificates. The celebration including the social
programme was organized by the Deanery´s team, in particular by PD Dr. Boris Kastening,
Heinz Mohren, Dr. Silvia Faßbender and our workshop team. For the first time this
ceremonial act took place in the new lecture hall and media centre, the “Hörsaal- und
Medienzentrum” on the Lichtwiese campus. Students passing their Bachelor, Master and
Diploma with honours in the past summer semester were awarded with the MaWi prize
which will be given away twice a year from now on. Namely, Andreas Taubel from the
division PoS was awarded for his Bachelor, Cornelia Hintze from the division DF for her
FAME-Master, Heide Humburg from the division NAW and Michel Kettner from the division
OF for their Master, and Jens Wehner from the division MM and Verena Pfeifer from the
division OF for their Diploma.
In the past summer semester four graduate students passed their PhD with honours. Robert
Dittmer from the division NAW, Erwin Hildebrandt from the division DS, Falk Münch from
the division MA, and Mahdi Seifollahi Bazarjani from the division DF received their PhD
certificate with honours during the ceremonial act.
Dean with Prize winners in the December awarding ceremony: Dr. E. Hildebrandt, J. Wehner, V. Pfeifer, A.
Taubel, Prof. R. Riedel, C. Hintze, H. Humburg, M. Kettner, Dr. R. Dittmer, Dr. M. Seifollahi Bazarjani.
On the following pages, this annual report shall provide you with some information on the
most prominent research activities of the individual groups conducted in 2013.
Prof. Ralf Riedel
Dean of the Department
Preface
11
Physical Metallurgy
The research group Physical Metallurgy at the TU Darmstadt in the department of materials
science works on the structure-property relationship of structural metallic materials and
thin hard coatings, focusing on the mechanical properties on both macroscopic as well as
microscopic length scales. The group is headed by Prof. Dr. Karsten Durst, who joined in
Mai 2013 TU Darmstadt from an affiliation at FAU Erlangen-Nürnberg. The group utilizes
and develops new testing methods for enhancing our understanding of the deformation
mechanism of structural materials on all length scales. Of main interest are the mechanical
properties of materials under various loading conditions (uniaxial, fatigue, wear or creep),
specifically relating the macroscopic material response to the micromechanical properties at
small length scales. New insights in the materials response are achieved by in-situ
mechanical testing approaches, where the material is being mechanical loaded and the
deformation is monitored by microscopic or spectroscopic means. Coupling the information
of the materials microstructure with the processing condition and the mechanical
properties, the group supports the development or enhancement of new structural
materials and coatings.
Currently the research deals with steels, Al-alloys, Cu and Ni-based alloys as well as a-C:H
coatings and nickel-base superalloys. One important class of materials are so called
ultrafine-grained or nanocrystalline materials, which are being processed by severe plastic
deformation processes. The materials microstructure is strongly refined by these processes,
leading to both strong and ductile materials. During processing, residual stresses can arise
in the microstructure. The research currently focuses on post treatment conditions for
adjusting the mechanical properties together with the residual stress for different
applications. Residual stresses are also important for the application of hard coatings on
ductile substrate. Together with partners, new processing conditions are being developed,
which allow for a design of the coating with respect to residual stress and mechanical
properties also under contact loading conditions. The determination of residual stress for
both ultrafine-grained metals and amorphous carbon coatings using local methods is also
shown as this years research highlight.
Staff Members
Head
Prof. Dr. K. Durst
Research Associates
Dr. E. Bruder
Prof. Dr. C. Müller
Technical Personnel
Ulrike Kunz
Claudia Wasmund
Petra Neuhäusel
Sven Frank
Secretaries
Christine Hempel
PhD Students
Dipl.-Ing. Vanessa Kaune
Dipl.-Ing. Thorsten Gröb
Dipl.-Ing. Jan Scheil
MSc. Farhan Javaid
Dipl.-Ing. Jennifer Bödeker
Dipl.-Ing. Jörn Niehuesbernd
Dipl.-Ing. Christoph Schmid
Diploma Students
Frederik Brohmann
Thorsten Gröb
Anke Scherf
Aletta Böcker
Moritz Elsaß
Master Students
Aniruddh Das
Jitendra Singh Rathore
Adb Alaziz
12
Institute of Materials Science - Physical Metallurgy
Bachelor Students
Paul Braun
Tobias Schmiedl
Kim Bergner
Oskar Kowalik
Theresa Schütz
Silke Innertsberger
Romana Schwing
Research Projects
“Effect of Load Frequency on the Fatigue Life of Aluminum Wrought Alloys in the VHCFRegime”, joint project with SzM-Darmstadt within the DFG Priority Programm 1466, DFG,
since 04/2010
“Microstructure and Mechanical Properties of Bifurcated Sheet Profiles”, in SFB 666 of the
DFG “Integral Sheet Metal Design with Higher Order Bifurcations”, since 06/2005.
“Technologies of Surface Modification of Bifurcated Profiles”, in SFB 666 of the DFG
“Integral Sheet Metal Design with Higher Order Bifurcations”, since 06/2009.
“Subsequent Formability of Bifurcated Profiles” in SFB 666 of the DFG “Integral Sheet
Metal Design with Higher Order Bifurcations”, since 06/2013.
“New Synthesis Methods top-down” in Priority Program LOEWE “Response
Ressourcenschonende Permanentmagnete durch optimierte Nutzung seltener Erden“, since
01/2014
“Damage Mechanims in Carbon Layer Systems”, DFG since 12/2011
“Influence of Glass Topology and Medium Range Order on the Deformation Mechanism in
Borosilcate Glasses – a Multiple Length Scale Approach”, DFG since 07/2012
DAAD scholarship Farhan Javaid since 07/2012
Publications
[1] Depner-Miller, U., Ellermeier, J., Scheerer, H., Oechsner, M., Bobzin, K., Bagcivan, N.,
Brögelmann, T., Weiss, R., Durst, K., Schmid, C.: Influence of application technology on the
erosion resistance of DLC coatings, Surface and Coatings Technology 237 (2013) pp. 284
[2] Ahmed, F., Krottenthaler, M., Schmid, C., Durst, K.: Assessment of stress relaxation
experiments on diamond coatings analyzed by digital image correlation and micro-Raman
spectroscopy, Surface and Coatings Technology 237 (2013) pp. 255
[3] Wheeler, J.M., Maier, V., Durst, K., Göken, M., Michler, J.: Activation parameters for
deformation of ultrafine-grained aluminium as determined by indentation strain rate jumps
at elevated temperature, Materials Science and Engineering A 585 (2013) pp. 108
[4] Ast, J., Durst, K: Nanoforming behaviour and microstructural evolution during
nanoimprinting of ultrafine-grained and nanocrystalline metals, Materials Science and
Engineering A 568 (2013) pp. 68
[5] Maier, V., Merle, B., Göken, M., Durst, K.: An improved long-term nanoindentation
creep testing approach for studying the local deformation processes in nanocrystalline
metals at room and elevated temperatures, Journal of Materials Research 28 (9) (2013) pp.
1177
13
[6] Krottenthaler, M., Schmid, C., Schaufler, J., Durst, K., Göken, M.: A simple method for
residual stress measurements in thin films by means of focused ion beam milling and digital
image correlation, Surface and Coatings Technology 215 (2013) pp. 247
[7] Schmid, C., Maier, V., Schaufler, J., Butz, B., Spiecker, E., Meier, S., Göken, M., Durst,
K.: Highly resolved analysis of the chemistry and mechanical properties of an a-C:H coating
system by nanoindentation and auger electron spectroscopy, Thin Solid Films 528 (2013)
pp. 263
[8] Hay, J., Maier, V., Durst, K., Göken, M Strain-rate sensitivity (SRS) of nickel by
instrumented indentation, Conference Proceedings of the Society for Experimental
Mechanics Series 6 (2013) pp. 47
[9] Kriegsmann, A., Müller, C.: Richtungsabhängigkeit der Rissausbreitung bei einem
gefügebedingten Übergang von rauigkeits- zu plastizitätsinduzierter Rissschließung an der
Legierung Ti-6Al-4V, Mat.-wiss. u.Werkstofftech. 2013, 44, No. 9, 749-752
[10] Schäfer, S.; Abedini, S.; Groche, P.; Bäcker, F.; Ludwig, C.; Abele, E.; Jalizi, B.; Müller,
C.; Kaune, V.; Verbindungstechniken durch die Technologie des SFB 666, In: Bauingenieur,
Springer VDI-Verlag, Düsseldorf, Vol. 1 (2013), 8-13
[11] Ludwig, C.; Hammen, V.; Groche, P.; Kaune, V.; Müller, C.; Fertigung
qualitätsoptimierter Spaltprofile durch Variation schnell änderbarer Prozessgrößen und
deren Einfluss auf die Materialeigenschaften, Materialwissenschaft und Werkstofftechnik,
Vol. 44 (2013), 601-611
[12] Karin, I.; Niehuesbernd, J.; Bruder, E.; Lipp, K.; Hanselka, H.; Müller, C.: FiniteElement analysis of a rolling contact model with anisotropic elastic material properties,
Materialwissenschaft und Werkstofftechnik, Vol. 44, 2013, 298-303
[13] Niehuesbernd, J.; Müller, C.; Pantleon, W.; Bruder, E.: Quantification of local and
global elastic anisotropy in ultrafine grained gradient microstructures, produced by linear
flow splitting, Materials Science and Engineering A, Vol. 560, 2013, 273-277
[14] Steitz, M.; Scheil, J.; Müller, C.; Groche, P.: Effect of Process Parameters on Surface
Roughness in Hammer Peening an Deep Rolling, Key Engineering Materials, 554-557
(2013), 1887-1901
[15] Scheil, J.; Müller, C.; Steitz, M.; Groche, P.: Influence of Process Parameters on
Surface Hardening in Hammer Peening and Deep Rolling. Key Engineering Materials, 554557 (2013), 1819-1827
[16] Groche, P.; Steitz, M.; Engels, M.; Scheil, J.; Müller, C.; Bräuer, G.; Weigel, K.:
Effizienzsteigerung
im
Werkzeugund
Formenbau
durch
maschinelle
Oberflächeneinglättung, EFB: Europäische Forschungsgesellschaft für Blechverarbeitung
e.V., (2013) 1-119. ISBN-13: 978-3867763981
[17] Steitz, M.; Weigel, K.; Weber, M.; Scheil, J.; Müller, C.: Coating of deep rolled and
hammer peened deep drawing tools, Advanced Materials Research, 769 (2013), 245-252
14
Advanced Methods for the Determination of Residual Stresses in complex Material
Systems
J. Niehuesbernd, C. Schmid, E. Bruder, C. Müller and K. Durst
Introduction
Residual stresses are present in many engineering components such as complex shaped
metallic profiles but also in thin protective coatings. These intrinsic stresses can originate
from diverse processing steps during manufacturing of the component like e.g. high plastic
deformation during forming processes of bulk materials or thermal mismatch between
substrate and coating during deposition at elevated temperatures. Since residual stresses
can strongly influence the lifetime and the overall performance of the final component in
operation, the knowledge of their magnitude as well as proper measurement methods are
crucial for reliable product design.
Nowadays, residual stress measurement techniques such as the hole drilling method for
bulk materials and thicker coatings or curvature measurement methods for thin amorphous
films are frequently used and well established. However, these measurement techniques
still suffer from certain disadvantages and limitations. The present article, which
summarizes the main results of the publications by Niehuesbernd et al. and Schmid et al.
[1,2], describes the measurement of residual stresses of two different material systems, a
bulk material as well as a thin amorphous coating, using different advanced
characterization methods. On the one hand, the hole drilling method in combination with
Electron Back Scatter Diffraction (EBSD) measurements and Finite Element Modeling
(FEM) is employed to assess the stress gradient within a graded and elastic anisotropic steel
profile. The results are compared to the isotropic case to analyse the influence of texture
and elastic anisotropy on the determination of the residual stress value. On the other hand,
a method based on combined Focused Ion Beam milling (FIB) and Digital Image
Correlation (DIC) is applied to determine the residual stress state of tungsten modified
amorphous carbon coatings of tailored mechanical properties deposited on steel substrates.
Moreover, the obtained properties of the coatings are correlated to the applied process
parameters during deposition.
Influence of gradients in the elastic anisotropy on the reliability of residual stresses
determined by the hole drilling method
Modern
forming
processes
often
introduce large strains and in most cases
significant strain gradients in the
material, which generally cause residual
stresses. Since plastic deformation also
leads
to
the
development
of
crystallographic textures, the influence of
these textures and texture gradients on
Fig. 1: a) Function principle of linear flow splitting,
determined residual stress distributions
b) profile and defined coordinate system
needs to be considered. Linear flow
splitting (LFS) is a process which involves complex forming conditions with steep strain
gradients and spacially varying deformation modes. By subjecting the edges of a sheet to
15
Fig. 2: Orientation distribution functions of measurements in 50 µm, 200 µm and 1000 µm beneath
the split surface. Only sections of the Euler space with a constant angle ϕ2 = 45° are shown.
severe plasticdeformation flanges are produced, leading to profiles with a double-Y shape
(Fig. 1). The heterogeneous material flow in combination with the severe strains leads to
steep microstructure [3] and yield strength gradients (Fig. 3), as well as strong
crystallographic textures and texture gradients in flange thickness direction [4,5]. In the
present investigation the ferritic stainless steel X6Cr16 (AISI 430/ 1.4016) was examined.
The initial sheet thickness was 2 mm and the flange length and thickness after LFS was 10
mm and 1 mm respectively. Orientation distribution funcions (ODF) obtained by EBSD on
cross sections of the flanges revealed typical
rolling textures with partial α-fibers
(red/vertical) and γ-fibers (blue/horizontal)
in near-surface layers (Fig. 2). With
increasing distance to the split surface the
texture intensity decreases significantly and
the rolling texture vanishes while shear
components like the Goss orientation
({110}<001>) appear.
The orientation data obtained by EBSD was
also used to calculate direction dependent
elastic properties. By rotating the single
Fig. 3: Approximated yield strength and Young’s
crystal stiffness tensor of iron (C11 = 230.1
modulus in feed direction (TD) in dependence of
the distance to the split surface.
GPa, C12 = 134.6 GPa, C44 = 116.6 GPa, [6])
according to the measured grain orientations
and averaging over all measurement points,
the direction dependent Young’s Modulus
can be determined. In the present
investigation the geometric mean was
utilized for averaging, which has proven to
be a suitable approximation [5,7,8]. The
Young´s modulus in feed direction (TD)
steeply drops from 244 GPa in near-surface
layers to approximately 212 GPa at the
bottom surface (Fig. 3).
Residual
stress
measurements
were
performed by the hole drilling method at the
Fig. 4: Residual stress levels in feed direction (TD)
flange top surface in combination with FEMfor the isotropic and the orthotropic case
obtained by FE-modelling
Simulations of the drilling process.
16
The geometry of the flange and the hole was modeled using the commercial FE solver
Abaqus. The flange was partitioned into 50 µm thick layers, which were assigned specific
yield strengths and stiffness tensors, corresponding to the experimental data. The residual
stress distribution was introduced by assigning each layer initial stress values in RD and TD.
In order to obtain depth dependent strain data, 50 µm thick slices were removed in a series
of steps and the resulting surface strains were acquired. These were compared to the
measured ones and the initially assigned stresses were varied iteratively until the
differences amounted to less than 0.5%. The same procedure was carried out for the elastic
isotropic case to assess the impact of anisotropy on the determined residual stress values.
The results of the FE-simulations of the drilling process reveal very high residual stress
levels in the feed direction (TD) of the split profiles (Fig. 4). Nearly 800 MPa of tensile
stress in a depth of 0.2 mm can be observed for the isotropic as well as for the anisotropic
(orthotropic) case. Up to this depth the relaxations are dominated by plastic deformation in
the vicinity of the hole, owing to the high residual stress levels. Therefore, the determined
residual stresses in both case show the same behavior. In a depth between 0.3 mm and
0.4 mm the stress levels for the orthotropic model are about 20 % higher than the ones for
the isotropic model. In this depth, the difference between the Young’s moduli of the two
models is only 3 %. It is reasonable to assume, that the stiffer upper layers in the
orthotropic model diminish the surface relaxation caused by the removal of a layer with a
lower stiffness in the examined direction. This means that for the isotropic model the
residual stresses in lower layers are highly underestimated. It is therefore concluded that
for the hole drilling method anisotropic elastic properties do not only influence the
determination of residual stresses in layers where anisotropy is present, but also in
subjacent layers which might have isotropic properties.
Residual stress measurement of thin amorphous coatings by means of FIB and DIC
Residual stresses of thin amorphous coatings are commonly assessed by means of curvature
measurement methods. These methods are based on the measurable change in curvature of
the substrate due to deposition of a coating with intrinsic stresses. The residual stress state
of the coating is then evaluated from the difference in curvature by use of Stoney’s equation
[9]. However, in this approach the used substrate has to meet certain requirements i.e. it
has to be a thin, elastically isotropic plate that is free to bend [10]. These substrates like
e.g. thin flat silicon wafers are mostly not relevant for technical applications of hard
coatings.
A method capable to measure residual stresses of thin
coatings, regardless of whether they are amorphous or
crystalline, on substrates of technical relevance was
proposed by Kang et al. [11]. This method is based on
the relaxation of residual stresses by focused ion beam
(FIB) milling and tracking of the resultant
displacements by means of digital image correlation
(DIC). The residual stress state in the coating is
quantified by evaluation of the observed displacement
fields by either analytical solutions or FE analysis using
the elastic properties of the coating e.g. determined by Fig. 5: FIB cross-sections of the coating
nanoindentation. In the literature different relaxation system CS2 revealing the basic structure
geometries, like a single slot [11], annular trenches or [2].
17
pillars [12,13] are proposed and successfully applied to determine residual stresses of
different kind of coating/substrate systems.
Here, a similar method was applied to assess residual stresses of three different tungsten
modified hydrogenated amorphous carbon (a-C:H:W) coatings CS1-CS3 with predefined
hardness values, ranging from 10 up to 16 GPa. The a-C:H:W coatings with a thickness of
1.6 µm were deposited on polished disks of cold work tool steel 1.2379 by reactive
unbalanced magnetron sputtering of a binder-free WC target in argon-ethine atmosphere
using an industrial coating equipment. Sufficient adhesion of the coating was achieved by
depositing an adhesive layer, consisting of different Cr- and WC-based layers.
Fig. 5 exemplarily shows a FIB cross-sections of the coating revealing the basic structure
consisting of adhesive layer and a-C:H:W functional layer which exhibits a weak columnar
microstructure. In order to obtain three coatings of predefined hardness, negative bias
voltage Ubias was adapted during deposition of the a-C:H:W layer according to a previously
created regression model. This model was obtained in previous work by variation of four
main process parameters of the used deposition process according to a central composite
design and measuring their influence on the mechanical properties of the a-C:H:W coating
by nanoindentation similar to the approach used in [14].
Fig. 6 shows the relation
between the hardness of the
coating
and
the process
parameters ethane flow rate
((C2H2)) and Ubias and the
good accordance between the
measured hardness of the three
different coatings with the
predicted values by the regression model.
Fig. 6: a) Regression model describing the relation between the
For the assessment of the hardness of the coating and the process parameters (C2H2) and
residual stress state of the Ubias with given positions of the selected coating systems CS1-CS3. b)
of the coatings measured by nanoindentation in
coatings, a double slit geometry Hardness
comparison with predicted hardness values given by the regression
as described in [15] was
model [2].
employed for relaxation of
internal stresses. The used
relaxation geometry leads to a
linear
and
symmetric
displacement gradient across
the remaining bar, facilitating
the evaluation of the displacements and the quantification of the corresponding
residual stress state. Therefore,
two high resolution SEM
images of the area of interest,
one before and one after the
Fig. 7: Experimental approach used for the determination of residual
stresses exemplarily demonstrated on a hydrogenated amorphous
carbon coating with residual compressive stresses of ca. -3 GPa.
Clearly a symmetric and linear displacement gradient across the
remaining bar can be observed.
18
FIB milling procedure
are taken. The milling
of
the
double-slit
geometry was conducted by an automated
procedure,
which
has
been
optimized to reduce FIB
damage and to attain
high milling accuracy.
Fig. 7 summarizes the
experimental approach,
exemplarily
demon- Fig. 8: Representative displacement gradients of coating CS1-CS3 obtained by
strated on a hydro- DIC and corresponding displacement vs. position plots of all five
measurements per coating system for the evaluation of relief strain (slope of
genated
amorphous linear regression) [2].
carbon coating with
residual
compressive
stresses
of
ca Table 1: Comparison of mechanical properties, relief strain and residual
ca. -3 GPa. To enable stresses of the coatings [2].
simple calculation of
coating
H in GPa
E in GPa
εrel. in %
σres. in GPa
residual stresses by use
CS1
9.4 ± 1.4 117 ± 12 0.34 ± 0.06 0.40 ± 0.07
of Hooke’s law, the
CS2
12.2 ± 1.0 145 ± 13 0.54 ± 0.07 0.79 ± 0.11
applied milling geometry, depth d and
CS3
14.8 ± 2.2 172 ± 20 0.92 ± 0.10 1.57 ± 0.18
distance w between the
two
slits,
was
previously optimized with regard to the coating thickness t. Further information about
proper relaxation geometry can be found elsewhere [16]. A total of 5 measurements per
coating were conducted for residual stress evaluation. Fig. 8 exemplarily shows one FIB
milled double-slit geometry of each coating superimposed with the resulting displacement
gradient obtained by DIC. A symmetric gradient across the remaining bar with maximum
displacements at the edges is found. Since the bars expand, coatings are subjected to
compressive residual stresses. Comparing all three gradients, it becomes evident that the
resultant displacements increase from CS1 to CS3, i.e. with increasing Ubias. Additional to
the gradients, the corresponding displacement vs. position plots of all five measurements
per coating system are shown. The slopes of linear regression of the displacement vs.
position plots (du/dx) give the respective relief strain εrel.. As already indicated by the
displacements, the relief strain also increases considerably with increasing Ubias. For the
coatings CS1-CS3, relief strain increases from 0.34 % to 0.92 % with corresponding
residual stress values between -0.40 GPa to -1.57 GPa. Table 1 summarizes the determined
properties of the coatings.
19
Conclusions
In the present article, two different approaches for the determination of residual stresses of
complex material systems both based on material removal are presented. The methods
were applied to a graded and elastically anisotropic steel profile and a thin amorphous
coating. For the assessment of the stress gradient within the steel profile, the hole drilling
method in combination with EBSD and FEM was employed and the influence of elastic
anisotropy on the determined residual stress values was shown. Further, the residual stress
state of three a-C:H:W coatings with tailored mechanical properties deposited on steel
substrates were assessed by means of focused ion beam milling of a double-slit geometry,
which causes the internal stresses to relax, and tracking of the resultant relief strain by
digital image correlation. Here a direct correlation between the coating properties and the
applied process parameters was obtained. The described methods are suitable for
determination of residual stresses of both amorphous and elastically anisotropic metallic
materials, giving important insight for further optimization of the materials.
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
J. Niehuesbernd, E. Bruder, C. Müller, submitted to Adv. Mater. Res. (2013)
C. Schmid, H. Hetzner, S. Tremmel, F. Hilpert, K. Durst, submitted to Adv. Mater. Res. (2013)
T. Bohn, E. Bruder, C. Müller, J. Mater. Sci. 43 (2008), 7307-7312
E. Bruder, J. Mater. Sci. 47 (2012), 7751-7758
J. Niehuesbernd, C. Müller, W. Pantleon, E. Bruder, Mat. Sci. Eng. A 560 (2013), 273-277
J. J. Adams, D. S. Agosta, R. G. Leisure, H. Ledbetter, J. of Appl. Phys. 100 (2006), 113530 1-7
S. Matthies, M. Humbert, Phys. Status Solidi B 177 (1993), K47-K50
S. Matthies, M. Humbert, J. Appl. Crystallogr. 28 (1995), 254-266
G.G. Stoney, Proc. R. Soc. Lond. A 82 (1909), 172-175
R.P. Vinci, J.J. Vlassak, Annu. Rev. Mater. Sci. 26 (1996), 431-62
K. J. Kang, N. Yao, M. Y. He, A.G. Evans, Thin Solid Films 443 (2003), 71-77
A.M. Korsunsky, M. Sebastiani, E. Bemporad, Surf. Coat. Technol. 205 (2010), 2393-2403.
M. Sebastiani, C. Eberl, E. Bemporad, G. M. Pharr, Mat. Sci. Eng. A 528 (2011), 7901– 7908
H. Hetzner, R. Zhao, S. Tremmel, S. Wartzack, in: K. D. Bouzakis, K. Bobzin, B. Denkena, M. Merklein
(Eds.), Proceedings of the 10th International Conference THE ''A'' Coatings 2013, Shaker, Aachen,
2013, 39-49
[15] M. Krottenthaler, C. Schmid, J. Schaufler, K. Durst, M. Göken, Surf. Coat. Technol. 215 (2013), 247252
[14] F. Ahmed, M. Krottenthaler, C. Schmid, K. Durst, Surf. Coat. Technol. 237 (2013), 255–260
20
Ceramics Group
The emphasis in the ceramics group is on the correlation between microstructure and
mechanical as well as functional properties. A number of processing methods are available
in order to accomplish different microstructure classes, to determine their specific
properties in an experiment and to rationalize these with straightforward modelling efforts.
Thus, a materials optimization is afforded which allows effective interplay between
processing, testing and modelling. In particular, new lead free piezoceramics and lead-free
high-temperature dielectrics can be obtained and extensively characterized electrically and
mechanically.
The scientific effort can be grouped as follows:
I.
Conductivity of Oxides
Dr. Till Frömling
Modulation of conductivity of oxide ceramics is usually achieved by doping and
temperature treatment in a large oxygen partial pressure range. However, electric and ionic
conductivity can also be changed by mechanical modifications. In this research group
conductivity is of oxide ceramics is modified by the following approaches
a) Induction of dislocations:
Dislocations are mechanically introduced into strontium titanate which can be plastically
deformed even at room temperature. Changes of the electric and ionic conductivity are,
amongst other methods, investigated by complex impedance spectroscopy and dcmeasurements. The aim of this project is to identify the defect chemical properties of
dislocation cores in strontium titanate and related materials.
b) Altering potential barriers in piezoelectric semiconductor materials:
In this project Schottky-barriers and varistor material based on ZnO are investigated as a
function of applied pressure.
II. Development of new piezoceramics
Dr. Wook Jo
In response to the recent demands for environmental friendly piezoelectric materials for
electrical and electronic applications, the principal focus of this group is the development of
non-toxic piezoceramics with electromechanical performance comparable to their leadcontaining counterparts. Among all the potentially promising candidates special attention
has been given to bismuth-based materials whose properties can be effectively tailored
using the so-called morphotropic phase boundary (MPB) concept. Extensive compositional
research has been performed on various bismuth-based solid solution systems that contain
a MPB between separating different crystal symmetries of the members. To better
understand the mechanisms governing the enhancement of electromechanical properties of
materials and to make our search for alternative materials more effective fundamental
scientific research on model systems have been performed in parallel to the compositional
investigations. We employ various characterization techniques such as macroscopic
dielectric, ferroelectric and ferroelastic property measurements as well as crystallographic
structural analyses based on synchrotron and neutron diffractions, Raman, nuclear
magnetic resonance, electron paramagnetic resonance spectroscopic techniques, and
Institute of Materials Science - Ceramics Group
21
transmission electron microscopy. We are also simultaneously establishing thermodynamic
and phenomenological models which are verified by the first principles calculations.
Currently, we have extensive and active international collaborations with eminent
ferroelectric groups throughout the world. In the last year, we also added work on KNNbased piezoceramics (collaborations with Prof. Ke Wang (Tsinghua University, China) and
Dr. Ruiping Wang (AIST, Japan) and work on BT-based piezoceramics to our research
scheme.
III. Mechanical properties of ferroelectrics
Dr. Kyle Webber
The focus of this research group is understanding the mechanical properties of ferroelectric
materials, particularly the influence of stress on the phase transformation behavior and
ferroelasticity at high temperature. Research over the last year has centered around
development of a high temperature fracture testing setup for characterizing crack growth
resistance behavior of ferroelastic materials as well as utilizing the newly developed
experimental arrangement for characterizing small signal dielectric, piezoelectric, and
elastic properties under large mechanical, electrical and thermal fields as a function of
frequency. Preliminary results have already given insight into the impact of stress on the
depolarization temperature of ferroelectric Pb(Zr,Ti)O3, which is commonly used in
actuation and sensing applications. In addition, the Emmy Noether research group, lead by
Kyle Webber, began in June and has been working on relaxor/ferroelectric composites and
mixed conducting cathode materials for solid oxide fuel cells. Both of these projects are
focused on understanding the influence of stress on the functional properties. Currently,
equipment is being developed to allow for the mechanical characterization of samples in a
atmosphere with an adjustable oxygen particle pressure.
Staff Members
Head
Prof. Dr. Jürgen Rödel
Research Associates
Dr. Till Frömling
Dr. Wook Jo
Dr. Jurij Koruza
Dipl. Phys. Irene Mieskes
Dr. Nikola Novak
Dr. Eric Patterson
Dr. Kyle Webber
Dr. Ludwig Weiler
Technical Personnel
Dipl.-Ing. Gundel Fliß
Dipl.-Ing. Daniel Isaia
Michael Heyse
Secretaries
Roswita Geier
Gila Völzke
PhD Students
M. Sc. Matias Acosta
M. Sc. Azatuhi Ayrikyan
Dipl.-Ing. Raschid Baraki
Dipl.-Ing. Martin Blömker
Dipl.-Ing. Laetitia Carrara
Dipl.-Ing. Robert Dittmer
Dipl.-Phys. Daniel Franzbach
M. Sc. Philipp Geiger
Dipl.-Ing. Claudia Groh
Dipl.-Ing. Christine Jamin
Dipl.-Ing. Markus Jung
Dipl.-Ing. Eva Sapper
Dipl.-Ing. Florian Schader
Dipl.-Phys. Deborah Schneider
Dipl.-Ing. Yohan Seo
M. Sc. Jiadong Zang
22
Diploma/
Bachelor/Master
Students
David Brandt
Johannes Dingeldein
Shenshen He
Heide Humburg
Manuel Kloos
Malte Vögler
Research Fellow
Dr. Ke Wang (AvH)
Dr. Haibo Zhang (AvH)
Guest Scientists
Prof. Dr. Satoshi Wada
Prof. Dr. Derek Sinclair
Prof. Dr. Mario Maglione
Dr. Philipp Veber
Dr. Ruiping Wang
Dr. Akira Ando
Dr. Soon-Jong Jeong
Prof. Dr. Chae Ill Cheon
Research Projects

Processing of textured ceramic actuators with high strain (SFB 595, 2003–2014)

Mesoscopic and macroscopic fatigue in doped ferroelectric ceramics (SFB 595, 2003–2014)

Development of new lead –free piezoceramics (ADRIA, state funding, 2008-2014)

Development of new high-temperature piezoceramics (ADRIA, state funding, 2008-2013)

Stress and strain fields in ferroelectrics (Graduate school “computational engineering” 20092017)

High-temperature dielectrics (DFG 2010-2013)

Mechanical compliance at phase transition points in lead-free ferroelectrics (DFG 20112014)

Lead-free piezoelectric single crystals with high strain: orientation dependence, polarization
rotation and morphotropic phase boundaries (DFG 2011-2014)

Energy absorption of ZnO varistors (DFG 2011-2014)

Ag-based electrical switches (state of Hesse / Umicore)

Emmy Noether Program: The Influence of Mechanical Loads on the Functional Properties
of Perovskite Oxides (DFG 2013-2018)
23
Publications
[1] Jamin, Christine ; Rasp, Tobias ; Kraft, Torsten ; Guillon, Olivier :
Constrained sintering of alumina stripe patterns on rigid substrates: Effect of stripe geometry.
[Online-Edition: http://dx.doi.org/10.1016/j.jeurceramsoc.2013.06.016]
In: Journal of the European Ceramic Society, 33 (15-16) pp. 3221-3230. ISSN 09552219
[Artikel], (2013)
[2] Yao, Fang-Zhou ; Glaum, Julia ; Wang, Ke ; Jo, Wook ; Rödel, Jürgen ; Li, Jing-Feng :
Fatigue-free unipolar strain behavior in CaZrO3 and MnO2 co-modified (K,Na)NbO3-based
lead-free piezoceramics.
[Online-Edition: http://dx.doi.org/10.1063/1.4829150]
In: Applied Physics Letters, 103 (19) 192907(1-4). ISSN 00036951, [Artikel], (2013)
[3] Zhukov, Sergey ; Genenko, Yuri A. ; Acosta, Matias ; Humburg, Heide ; Jo, Wook ;
Rödel, Jürgen ; von Seggern, Heinz :
Polarization dynamics across the morphotropic phase boundary in Ba(Zr0.2Ti0.8)O3x(Ba0.7Ca0.3)TiO3 ferroelectrics.
[4] Kling, Jens ; Jo, Wook ; Dittmer, Robert ; Schaab, Silke ; Kleebe, Hans-Joachim ;
Zhang, S. :
Temperature-Dependent Phase Transitions in the Lead-Free Piezoceramics (1 - x y)(Bi1/2Na1/2)TiO3-xBaTiO3-y(K0.5Na0.5)NbO3Observed byin situTransmission Electron
Microscopy and Dielectric Measurements.
[Online-Edition: http://dx.doi.org/10.1111/jace.12493]
In: Journal of the American Ceramic Society, 96 (10) pp. 3312-3324. ISSN 00027820
[Artikel], (2013)
[5] Seo, Yo-Han ; Vögler, Malte ; Isaia, Daniel ; Aulbach, Emil ; Rödel, Jürgen ; Webber,
Kyle G. :
Temperature-dependent R-curve behavior of Pb(Zr1−xTix)O3.
[Online-Edition: http://dx.doi.org/10.1016/j.actamat.2013.07.020]
In: Acta Materialia, 61 (17) pp. 6418-6427. ISSN 13596454, [Artikel], (2013)
[6] Amaral, Luís ; Jamin, Christine ; Senos, Ana M. R. ; Vilarinho, Paula M. ; Guillon,
Olivier :
Constrained sintering of BaLa4Ti4O15 thick films: Pore and grain anisotropy.
In: Journal of the European Ceramic Society, 33 (10) pp. 1801-1808. ISSN 09552219
[Artikel], (2013)
[7] Cumming, D. J. ; Sebastian, Tutu ; Sterianou, Iasmi ; Rödel, Jürgen ; Reaney, Ian M.:
Bi(Me)O3-PbTiO3 high TC piezoelectric multilayers.
[Online-Edition: http://dx.doi.org/10.1179/1753555713Y.0000000067]
In: Materials Technology: Advanced Performance Materials, 28 (5) pp. 247-253. ISSN
10667857, [Artikel], (2013)
24
[8] Glaum, Julia ; Simons, Hugh ; Acosta, Matias ; Hoffman, Mark ; Feteira, A. :
Tailoring the Piezoelectric and Relaxor Properties of (Bi1/2Na1/2)TiO3-BaTiO3via Zirconium
Doping.
[Online-Edition: http://dx.doi.org/10.1111/jace.12405]
In: Journal of the American Ceramic Society n/a-n/a. ISSN 00027820, [Artikel], (2013)
[9] Schader, Florian H. ; Aulbach, Emil ; Webber, Kyle G. ; Rossetti, George A. :
Influence of uniaxial stress on the ferroelectric-to-paraelectric phase change in barium titanate.
In: Journal of Applied Physics, 113 (17) 174103(1-9). ISSN 00218979, [Artikel], (2013)
[10] Tran, Vu Diem Ngoc ; Dinh, Thi Hinh ; Han, Hyoung-Su ; Jo, Wook ; Lee, Jae-Shin :
Lead-free Bi1/2(Na0.82K0.18)1/2TiO3 relaxor ferroelectrics with temperature insensitive
electrostrictive coefficient.
[Online-Edition: http://dx.doi.org/10.1016/j.ceramint.2012.10.046], In: Ceramics
International, 39 (Supplement 1) S119-S124. ISSN 02728842, [Artikel], (2013)
[11] Jo, Wook ; Daniels, John E. ; Damjanovic, Dragan ; Kleemann, Wolfgang ; Rödel,
Jürgen :
Two-stage processes of electrically induced-ferroelectric to relaxor transition in
0.94(Bi1/2Na1/2)TiO3-0.06BaTiO3.
[12] Han, Hyoung-Su ; Jo, Wook ; Kang, Jin-Kyu ; Ahn, Chang-Won ; Won Kim, Ill ; Ahn,
Kyoung-Kwan ; Lee, Jae-Shin :
Incipient piezoelectrics and electrostriction behavior in Sn-doped
Bi1/2(Na0.82K0.18)1/2TiO3 lead-free ceramics.
In: Journal of Applied Physics, 113 (15) 154102(1-6). ISSN 00218979, [Artikel], (2013)
[13] Schwarz, Sebastian ; Guillon, Olivier :
Two step sintering of cubic yttria stabilized zirconia using Field Assisted Sintering
Technique/Spark Plasma Sintering.
In: Journal of the European Ceramic Society, 33 (4) pp. 637-641. ISSN 09552219
[Artikel], (2013)
[14] Seo, Yo-Han ; Franzbach, Daniel J. ; Koruza, Jurij ; Benčan, Andreja ; Malič, Barbara ;
Kosec, Marija ; Jones, Jacob L. ; Webber, Kyle G. :
Nonlinear stress-strain behavior and stress-induced phase transitions in soft
Pb(Zr_{1−x}Ti_{x})O_{3} at the morphotropic phase boundary.
[Online-Edition: http://dx.doi.org/10.1103/PhysRevB.87.094116]
In: Physical Review B, 87 (9) 094116(1-11). ISSN 1098-0121, [Artikel], (2013)
25
[15] Rödel, Jürgen ; Seo, Yo-Han ; Benčan, Andreja ; Malič, Barbara ; Kosec, Marija ;
Webber, Kyle G. :
R-curves in transformation toughened lead zirconate titanate.
[Online-Edition: http://dx.doi.org/10.1016/j.engfracmech.2012.06.023]
In: Engineering Fracture Mechanics, 100 pp. 86-91. ISSN 00137944, [Artikel], (2013)
[16] Dittmer, Robert ; Webber, Kyle G. ; Aulbach, Emil ; Jo, Wook ; Tan, Xiaoli ; Rödel,
Jürgen :
Electric-field-induced polarization and strain in 0.94(Bi1/2Na1/2)TiO3–0.06BaTiO3 under
uniaxial stress.
[Online-Edition: http://dx.doi.org/10.1016/j.actamat.2012.11.012]
In: Acta Materialia, 61 (4) pp. 1350-1358. ISSN 13596454, [Artikel], (2013)
[17] Levin, I. ; Reaney, I. M. ; Anton, Eva-Maria ; Jo, Wook ; Rödel, Jürgen ; Pokorny, J. ;
Schmitt, L. A. ; Kleebe, H-J. ; Hinterstein, Manuel ; Jones, J. L. :
Local structure, pseudosymmetry, and phase transitions in Na_{1/2}Bi_{1/2}TiO_{3}–
K_{1/2}Bi_{1/2}TiO_{3} ceramics.
[18] Zang, Jiadong ; Jo, Wook ; Rödel, Jürgen :
Quenching-induced circumvention of integrated aging effect of relaxor lead lanthanum
zirconate titanate and (Bi1/2Na1/2)TiO3-BaTiO3.
In: Applied Physics Letters, 102 (3) 032901. ISSN 00036951, [Artikel], (2013)
[19] Dittmer, Robert ; Webber, Kyle G. ; Aulbach, Emil ; Jo, Wook ; Tan, Xiaoli ; Rödel,
Jürgen :
Optimal working regime of lead–zirconate–titanate for actuation applications.
[Online-Edition: http://dx.doi.org/10.1016/j.sna.2012.09.015]
In: Sensors and Actuators A: Physical, 189 pp. 187-194. ISSN 09244247, [Artikel], (2013)
[20] Salje, Ekhard K. H. ; Carpenter, Michael A. ; Nataf, Guillaume F. ; Picht, Gunnar ;
Webber, Kyle G. ; Weerasinghe, Jeevaka ; Lisenkov, S. ; Bellaiche, L. :
Elastic excitations in BaTiO_{3} single crystals and ceramics: Mobile domain boundaries and
polar nanoregions observed by resonant ultrasonic spectroscopy.
[21] Uhlmann, Ina ; Hawelka, Dominik ; Hildebrandt, Erwin ; Pradella, Jens ; Rödel,
Jürgen:
Structure and mechanical properties of silica doped zirconia thin films.
[Online-Edition: http://dx.doi.org/10.1016/j.tsf.2012.08.007]
In: Thin Solid Films, 527 pp. 200-204. ISSN 00406090, [Artikel], (2013)
26
Rocking Curve X-Ray Diffraction for Quantifying Dislocations
in SrTiO3 Single Crystals
Eric Patterson, Till Frömling, Kyle Webber, and Jürgen Rödel
Introduction:
Strontium titanate (SrTiO3 or STO) is frequently described as a model perovskite system
and its electrical properties have been studied over a wide range of conditions, including
oxygen partial pressure, temperature and electric field [1]. Single crystal STO shows a rare
ability among oxide materials to plastically deform when compressively stressed. It also
undergoes a ductile to brittle to ductile transition as a function of changing temperature
that has previously been shown [2-5]. Because it remains cubic over a wide range of
temperatures, the change in mechanical properties cannot be tied to phase transitions.
Current investigations on this system are directed towards understanding the relationship
between this plastic strain behavior, the dislocation network developed, and changes that
arise in the electrical conductivity of these perovskite single crystals. In previous work high
conductivity paths along dislocations were shown in STO single crystals via conductive
atomic force microscopy [6]. In order to analyze these properties, it is therefore essential to
have an accurate method to reliably quantify the plastic strain during deformation and
correlate this to a change in the dislocation density in a crystal after a given amount of
deformation. By investigating the relationship between dislocations and conductivity in
STO, we may be able to ascertain the mechanism of changes in electromechanical
properties in these materials.
Experimental Procedure:
In this work, strontium titanate single crystals oriented along the (001) growth direction
with dimensions of 4x4x8 mm3 (Alineason Materials Technology, GmbH) and optical
quality polished sides were examined. Compressive loading was done with a load frame
(Zwick/Roell Z030) with a loading rate of 25 N/s in a displacement controlled manner
using 32 µm limited steps, which were repeated 3 times in order to achieve approximately
1% plastic strain. The stress-induced uniaxial displacement of the specimen was measured
by a linear variable differential transformer (LVDT). The deformations were peformed in a
range of temperature from 25°C - 450°C. The samples were examined optically by polarized
light microscopy to observed the birefringence around the dislocation slip planes. X-ray
diffraction (XRD) rocking curve measurments were made before and after deformation of
the samples to observe changes in dislocation density following the methodolgy of Ayers, et
al [7].
The XRD rocking curve technique for dislocation density determination utilizes a positionlocked source with a Bartel’s monochromator attachment to focus the emerging x-ray beam
to a width of a few arcseconds. The theta is adjusted by tilting the sample and the detector
is moved as normal, albeit with an upper 2 limit of approximately 152°. Samples were
mounted to a goniometer head and aligned flat with respect to the diffraction plane using a
polarized light setup, such that the X-ray beam crosses lengthwise across the center of one
of the sample faces. The sample () and detector (2) were next rotated to the selected
diffraction planes, i.e. (001), (002), (003), and (004). Since the faces of the STO single
crystals are <001> oriented and not polycrystalline, a non-symmetric arrangement of -2
angles must be selected for all other peaks, i.e. (014), (024), (233), and (224).
Additionally, in order to reach the higher equivalent angles of  necessary for subsequent
27
density calculations, a motorized stage to control  was introduced and rotated to scan the
(233) and (224) planes at 33.69° and 45°, respectively.
The sample itself is finally rotated over a small range of angles around the peak location for
the given plane selected ( = -0.2° to 0.2°). The resulting peak is fitted via Gaussian or
Pseudo-Voigt fit, depending on symmetry and number of peaks and the full width at half
maximum (FWHM or ) is determined. Ideally only one peak should be present for a single
crystal, however, after deformation multiple peaks can sometimes be observed due to
increase and arrangement of the dislocation network. In Figure 1, a clear broadening of the
(001) after deformation of approximately 0.25% plastic strain is shown.
These
measurements were made for eight diffraction planes on each sample with a step size of
0.001° and a dwell time of 10 seconds per step. In the cases where  angle rotation was
needed, two equivalent scans were taken at 90± ° in order to account for differences in
edges and potential cracks intercepted by the beam at these rotated angles.
a)
b)
Figure 1: a) Schematic of Bartel’s monochromator and b) an example rocking curve result for a single
reflection before and after compression testing
A linear regression is fitted to a plot of FWHM2 as a function tan2, from the slope and
intercept of these lines two independent dislocation density values can be calculated. The
slope is associated with the strain around the dislocation and the intercept is related to the
angular rotation around the dislocation core.
Results and Discussion:
The polarized light microscopy revealed an increase in the density and uniformity of the
slip lines, as seen in Figure 2 for the (100) and (010) polished faces of the crystals
deformed at 25° and 300°C. The dark lines in the image are cracks that developed during
loading and unloading.
a)
b)
c)
25°
C
(100
)
(010
)
300°
C
(100
)
(010
)
Figure 2: a) Deformation of single crystal STO at various temperatures with resulting PLM at b) 25°C and c)
300°C
28
From the stress-strain plots, it is clear that with increasing temperature, the yield point of
the samples is decreased dramatically. It was lowered nearly by half from ~140MPa at
25°C to ~75MPa at 300°C. Next XRD rocking curve measurements were performed on the
samples and dislocation density was calculated based on the results of linear regression, as
shown for the examples in Figure 3 below.
a)
b)
Figure 3: Measured FWHM2 as a function of tan2
same 450°C crystal and c) PLM images for the 450°C crystal.
c)
450°
C
(100
(010
) b) two faces
) of the
-deformed, 25°C, and 300°C
A clear difference was found between non-deformed samples and those deformed to 1%
plastic strain. There was both an increase in the intercept value and in the slope compared
to the average of non-deformed samples. From further calculations, dislocation content was
shown to increase by 4x from 2.1x108 cm-2 in the initial state to 8.2x108 cm-2 after 1%
strain at 25°C. At 300°C, the dislocation content was increased even further to
approximately 9.7x108 cm-2. At 450°C, however, a different behavior was found depending
on the side of the crystal examined. In this case the (010) side was subsequently discovered
to bulge in the center, whereas the (100) face remained flat. The (100) side gives a
dislocation density value approximately the same as the 300°C case. This makes sense given
the higher degree of cracking that is apparent in the 450°C sample (Figure 3 c)).
The XRD technique will next be confirmed with further samples and with an etch pit
density evaluation, both at the surface and in the interior of the crystal. Now that this
method of increasing dislocations has been shown, it must be connected to changes in the
conductivity through impedance spectroscopy and oxygen diffusion using 18O annealing
and ToF SIMS analysis. This will be performed on these undoped samples and on Fe-doped
single crystals.
References
1
2
3
4
5
6
7
De Souza et al., Z. Metallkd. 94 [3], 218-225 (2003)
Brunner et al., J. Am. Ceram. Soc., 84 [5], 1161–63 (2001)
Brunner, Acta Materialia 54, 4999-5011 (2006)
Brunner, Mat. Sci. Eng. A, 483-484 521-524 (2008)
Yang, et al., J. Am. Ceram. Soc., 94 [9] 3104–3111 (2011)
Szot, et al., Nature Materials 5, 312 - 320 (2006)
Ayers, et al., J. Crystal Growth, 135, 71-77 (1994)
29
Electronic Material Properties
The Electronic Materials division introduces the aspect of electronic functional materials and
their properties into the Institute of Materials Science. The associated research concentrates
on the characterization of various classes of materials suited for implementation in
information storage and organic and inorganic electronics. Four major research topics are
presently addressed:




Electronic and optoelectronic properties of organic semiconductors.
Charge transport in inorganic semiconductor devices.
Charge transport and polarization in organic and inorganic dielectrics.
Photo- and photostimulated luminescence in inorganic phosphors.
For novel areas of application a worldwide interest exists in the use of organic
semiconductors in electronic and optoelectronic components, such as transistors and lightemitting diodes. So far, multicolour and full colour organic displays have been
implemented in commercially available cameras, car-radios, PDAs, mp3-players and even
television sets. Organic devices reaching further into the future will be simple logic circuits,
constituting the core of communication electronics such as chip cards for radio-frequency
identification (RFID) tags and maybe one day flexible electronic newspapers where the
information is continuously renewed via mobile networks. In view of the inevitable
technological development, the activities of the group are concerned with the
characterization of organic material properties regarding the performance of organic
electronic and optoelectronic devices. The major aspect deals with the charge carrier
injection and transport taking place in organic field-effect transistors (OFETs) and organic
light-emitting diodes (OLEDs). In particular, the performance of unipolar and ambipolar
light-emitting OFETs and the stability of OFETs and OLEDs are subjects of recent
investigations. To conduct these demanding tasks, various experimental techniques for
device fabrication and characterization are installed. Besides basic electric measurement
setups, a laser spectroscopy setup used for time-of-flight as well as for life-time
measurements and a Kelvin-probe atomic force microscope to visualize the potential
distribution of organic devices with nanometer resolution are available.
Even though organic electronics is an emerging field especially for consumer electronics
applications today's electronic devices still mainly rely on conventional silicon technology.
While organic semiconductors have excellent optoelectronic properties they in general
suffer from low charge carrier mobilities limiting the switching rates in organic transistors.
Yet, metal oxides like ZnO, InZnO (IZO) or InGaZnO (IGZO) can bridge the gap between
the high mobility semiconductors like silicon and the low mobility organic semiconductors.
Using metal-organic precursors or nanoparticulate dispersions easy processing procedures
like spin-coating or printing can be applied and yield rather high field-effect mobilities in
the order of 1-10 cm²V-1s-1 for the produced thin film transistors (TFTs). Current research
activities in the group concentrate on the optimization of the processing procedures
especially the decrease of annealing temperatures is desired to make the processes
compatible with organic substrates. Furthermore, the influence of the layer morphology
and the role of the gas atmosphere for the device performance as well as stability issues are
investigated.
30
Institute of Materials Science – Electronic Material Properties
In the field of polymer electrets current research comprises the characterization of surface
charge distribution, charge stability, and charge transport properties of fluoropolymers, as
well as their applications in acoustical transducers. Present investigations of charge
transport and polarization in organic dielectrics are directed towards the basic
understanding of polarization buildup and stabilization in PVDF and in novel microporous
dielectrics. Latter are scientifically interesting as model ferroelectric polymers. Moreover,
the fatigue behaviour of electrically stressed inorganic PZT ceramics is investigated. The
focus lies on preventing the operational fatigue of ferroelectric devices due to cyclic and
static electrical stress. The available equipment includes poling devices, such as corona and
high voltage setups, and a thermally stimulated current setup to investigate the energetic
trap structure in dielectrics as well as the thermal charging and discharging under high
electric fields. In addition, the laser induced pressure pulse (LIPP) method allows to
investigate the spatial distribution of stored charges in organic as well as in inorganic
ferroelectrics.
The field of photoluminescent and photostimulated luminescent (PSL) materials
(phosphors) is concerned with the synthesis and characterization of suited inorganic
compounds used as wavelength converters in fluorescent lamps and in scintillating and
information storing crystals. Present work is focused on x-ray detection materials, providing
improved resolution and high PSL-efficiency needed in medical imaging. In particular the
storage phosphors CsBr:Eu2+ and BaFBr:Eu2+ are under investigation. Research is
concentrated on the influence of humidity on the sensitivity of CsBr:Eu2+. Before and after
the treatment the materials are studied by means of spectroscopic methods as well as
scanning electron microscopy. The exchange of water during the thermal treatment is
measured in situ by thermal analysis methods. New synthesis methods for BaFBr:Eu 2+ used
in commercial image plates are of interest and new synthesis routes will be tested for other
storage phosphors and scintillators. On the one hand the mechanism of PSL-sensitization,
which is found to be mainly due to the incorporation of oxygen and water, is investigated.
On the other hand the implementation of BaFBr:Eu2+ powders into organic binders in order
to form image plates is in the focus of the work.
In the field of scintillators undoped and doped CsI is investigated concerning the afterglow.
This afterglow is unfavourable in medical applications like CT where a series of images is
made in a very short time. The task is to find the physical reason for this afterglow and a
way to suppress it.
Staff Members
Head
Prof. Dr.-Ing. Heinz von Seggern
Research Associates
Dr. Andrea Gassmann
Dr. Joachim Hillenbrand
Dr. Sergej Zhukov
Dr. Corinna Hein
Dr. Emanuelle Reis Simas
Dr. Jörg Zimmermann
Technical Personnel
Gabriele Andreß
Sabine Hesse
Helga Janning
Bernd Stoll
Secretary
Gabriele Kühnemundt
Institute of Materials Science – Surface Science
31
PhD Students
Tobias Könyves-Toth
Fabian Knoch
Oili Pekkola
Riitta Savikoski
Elmar Kersting
Paul Mundt
Florian Pfeil
Henning Seim
Bachelor Students
Frank Löffler
Florian Weyland
Stefan Schlißke
Master Students
Ralph Dachauer
Guest Scientists
Juliana Eccher
Dr. Anatoli Popov
Prof. Dr. Sergei Fedosov
Prof. Dr. Lucas F. Santos
Research Projects
Fatigue of organic semiconductor components (SFB 595 (DFG), 2003-2014)
Phenomenological modelling of bipolar carrier transport in organic semiconducting devices
under special consideration of injection, transport and recombination phenomena (SFB 595
(DFG), 2003-2014)
Polarization and charge in electrically fatigued ferroelectrics (SFB 595 (DFG), 2006-2014)
Development and optimization of tuneable optical filters and VCSEL based on piezoelectric
and electret actuators (TICMO Graduiertenkolleg 1037, 2007-2013)
Development of organic piezo sensors (LOEWE AdRIA 26200026, 2008-2014)
Thin film dielectrics for high performance transistors (DFG, 2012-2015)
Development of gate insulators for organic field effect transistors exploiting self-assembly of
block-copolymers (IDS-FunMat (EU), 2012-2015)
Piezoelectric properties of ferroelectrics (DFG, 2012-2015)
Preparation and characterization of metal-oxide field-effect transistors (MerckLab, 20092015)
High resolution, transparent image plates based on the storage phosphor CsBr:Eu2+ (DFG,
2013-2015)
Metal oxide based field-effect transistors with top gate geometry (Helmholtz Virtual
Institute, 2012-2017)
32
Publications
[1] Order Induced Charge Carrier Mobility Enhancement in Columnar Liquid Crystal Diodes
Eccher, Juliana; Faria, Gregorio C.; Bock, Harald; Seggern, Heinz; Bechtold, Ivan H.
ACS APPLIED MATERIALS & INTERFACES Volume: 5 Issue: 22 Pages: 11935-11943
Published: NOV 27 2013
[2] Molecular Origin of Charge Traps in Polyfluorene-Based Semiconductors
Faria, Gregorio C.; deAzevedo, Eduardo R.; von Seggern, Heinz
MACROMOLECULES Volume: 46 Issue: 19 Pages: 7865-7873 Published: OCT 8 2013
[3] Polarization dynamics across the morphotropic phase boundary in Ba(Zr0.2Ti0.8)O-3x(Ba0.7Ca0.3)TiO3 ferroelectrics
Zhukov, Sergey; Genenko, Yuri A.; Acosta, Matias; Humburg, Heide; Jo, Wook; Roedel, Juergen;
von Seggern, Heinz
APPLIED PHYSICS LETTERS Volume: 103 Issue: 15 Article Number: 152904 Published: OCT 7
2013
[4] Continuum modeling of charging process and piezoelectricity of ferroelectrets
Xu, Bai-Xiang; von Seggern, Heinz; Zhukov, Sergey; Gross, Dietmar
JOURNAL OF APPLIED PHYSICS Volume: 114 Issue: 9 Article Number: 094103 Published:
SEP 7 2013
[5] Self-consistent model of polarization switching kinetics in disordered ferroelectrics
Genenko, Yuri A.; Wehner, Jens; von Seggern, Heinz
JOURNAL OF APPLIED PHYSICS Volume: 114 Issue: 8 Article Number: 084101 Published:
AUG 28 2013
[6] Transit phenomena in organic field-effect transistors through Kelvin-probe force microscopy.
Melzer, Christian; Siol, Christopher; von Seggern, Heinz
Advanced materials (Deerfield Beach, Fla.) Volume: 25 Issue: 31 Pages: 4315-9 Published: 2013Aug-21 (Epub 2013 Apr 29)
[7] A new method to invert top-gate organic field-effect transistors for Kelvin probe investigations
Kehrer, Lorenz. A.; Feldmeier, Eva. J.; Siol, Christopher.; Walker, Daniel; Melzer, Christian; von
Seggern, Heinz
APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING Volume: 112 Issue: 2 Pages:
431-436 Published: AUG 2013
[8] High-performance n-channel thin-film transistors with acene-based semiconductors
Fapei Zhang; Melzer, Christian; Gassmann, Andrea.; von Seggern, Heinz; Schwalm, Thorsten;
Gawrisch, Christian; Rehahn, Matthias
Organic Electronics. Materials, Physics, Chemistry and Applications Volume: 14 Issue: 3 Pages:
888-96 Published: March 2013
33
[9] Comparative study of the luminescence properties of macro- and nanocrystalline MgO
using synchrotron radiation
Popov, Anatoli. I.; Shirmane, Liana; Pankratov, Vladimir.; Lushchik , A; Kotlov, Aleksei, Serga, V.
E.; Kulikova L. D.; Chikvaidze; Zimmermann, Jörg; NUCLEAR INSTRUMENTS & METHODS
IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND
ATOMS Volume: 310 Pages: 23-26 Published: SEP 1 2013
[10] Eu2+-doped csbr photostimulable x-ray storage Phosphors — analysis of defect structure by
High-frequency epr Peter Jakes, Jörg Zimmermann, Heinz von Seggern,
Andrew Ozarowski, Johan van Tol and Rüdiger-A. Eichel, FUNCTIONAL MATERIALS
LETTERS, Vol. 7, No. 1 (2013) 1350073 Published: Dec 2013
34
The influence of triplet excitons on the lifetime of polymer-based organic light
emitting diodes
Oili Pekkola, Andrea Gassmann, and Heinz von Seggern
In an organic light emitting diode (OLED) the ratio of singlet to triplet excitons formed is
1:3. In fluorescent devices the radiative decay of triplet excitons is forbidden by the spin
selection rules, and consequently only the singlet excitons decay radiatively. The high
concentration of non-radiatively decaying triplet excitons, combined with their long
lifetimes on the order of several µs to ms [1,2], arises the question about the influence of
the triplet excitons on the lifetime of fluorescent OLEDs.
In the present work, the concentration of triplet excitons in a Poly(p-phenylene vinylene)
(PPV)-based polymer is deliberately increased in order to investigate the influence of a
higher concentration of triplets on the degradation of the diodes. The increase in
concentration is achieved by converting part of the polymer singlet excitons to triplets. This
is done by blending the polymer with a triplet sensitizer additive, an organometallic
compound containing a platinum atom. The first excited singlet state of the sensitizer
molecule lies energetically lower than that of the polymer, which allows for a singlet
exciton transfer from the polymer to the sensitizer. On the sensitizer, a fast intersystem
crossing takes place, facilitated by the weakened spin selection rules due to the presence of
the heavy metal atom. The first excited triplet state of the sensitizer lies higher than that of
the polymer, and the triplet exciton can be subsequently transferred back to the polymer.
The energetic scheme of the complete singlet-to-triplet conversion is illustrated in Fig. 1.
Figure 1 Energy scheme showing the singlet-to-triplet
conversion processes. First, a singlet exciton energy
transfer (ET) from OC3C8-PPV to PtOEPK takes place,
followed by an intersystem crossing (ISC) to the
PtOEPK first excited triplet state. The triplet exciton is
subsequently transferred back to OC3C8-PPV, which
has an energetically lower first excited triplet state.
All presented devices are polymer-based OLEDs with a Poly(2-propoxy-5-(2'ethylhexyloxy)-phenylene (OC3C8-PPV) as the active material. In the sensitized diodes, the
polymer was blended with Platinum (II) octaethylporphyrine ketone (PtOEPK). All devices
consisted of an ITO anode, a PEDOT:PSS hole injection layer (40 nm), the active polymer
layer (130 nm) and a Ca cathode (20 nm) protected by an Al layer (100 nm). The devices
were fabricated in an inert nitrogen atmosphere. OC3C8-PPV was spin-coated from a
toluene solution with a concentration of 7.5 mg ml-1. The PtOEPK concentrations in
sensitized films were 0.1 and 1 wt%, respectively. After preparation, the polymer films were
annealed in the glovebox at 130 °C for 5 min. Finally, the top electrodes were vacuum
deposited through shadow masks at a base pressure of 10-6 mbar.
The singlet-to-triplet conversion can be verified with photoinduced absorption
measurements, where the intensity of the excited triplet state absorption of the polymer
35
increases in the presence of the triplet sensitizer. The conversion is also observed to take
place in electrically driven devices, which is manifested through a decrease in the
electroluminescence, pointing to a decreased population of the first excited singlet state of
the polymer. Additionally, no emission from the sensitizer is detected, indicating a
complete transfer of triplet excitons from the sensitizer back to the polymer.
Fig. 2 plots the lifetimes of the diodes with pristine and sensitized OC3C8-PPV layers. The
devices were operated at a constant current density of 50 mA/cm2. The graph shows the
normalized luminance values for a better comparison of the curves; the measured
luminance intensities are shown in the inset. The t5o lifetime of the diodes with pristine
OC3C8-PPV layers is 160 hours, whereas the devices with 0.1 wt% PtOEPK reach a t5o of
only 15 hours. This corresponds to a decrease of 91 %. Increasing the PtOEPK
concentration to 1 wt% leads to a t5o lifetime of only 2 hours, or a decrease of 99 % from
the value of the devices with the pristine polymer layers [3].
Figure 2 Luminance versus time plots of PLEDs with
pristine
OC3C8-PPV
(black
squares),
OC3C8PPV:PtOEPK (0.1 %) (orange circles) and OC3C8PPV:PtOEPK (1 %) (red triangles) illustrating the
deterioration of the t50 lifetime with increasing
sensitizer content. The inset shows the measured
absolute luminance values.
It can be concluded that the triplet excitons do shorten the lifetime of the PPV-based OLEDs
stongly. It is postulated that the heat generated by the non-radiative decay of the triplet
excitons could be partly responsible for the observed accelerated decay. In thermography
measurements it was observed that the temperature of a diode with pristine OC3C8-PPV
rises 5 K above room temperature after turning on the diode. After turning on, the
temperature stays constant for several hours of operation at a constant current density of
50 mA/cm2. The observed temperature rise of a diode with 1 wt% PtOEPK is 10 K and
therefore higher than that of the device with a pristine polymer layer. It is, however, likely
that the temperature increase of 5 K alone is not sufficient to explain the complete
acceleration in the degradation of the devices.
Another factor that could influence the fatigue of the devices with an increased
concentration of triplet excitons is the interaction of the triplet excitons with oxygen. The
triplet excitons of conjugated polymers are known to undergo energy transfer to oxygen in
triplet state [4–7], leading to the formation of singlet oxygen. It has been observed to attac
the vinylene bonds of PPV derivates, leading to chain scission [8]. The process has been
shown to take place even in inert atmosphere with oxygen concentration in the low ppm
range [6,7]. The higher concentration of triplet excitons in the diodes with the sensitized
layers is expected to lead to increased interaction with oxygen. This process could partly
contribute to the observed accelerated degradation. It is, however, presently not possible to
assign the phenomena responsible for the fatigue to a single process. Nevertheless, due to
the generally high concentration of triplet excitons in fluorescent OLEDs, the observed
36
accelerated degradation bears a significant importance for improving the stability of the
devices by engineering the triplet state population.
References:
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
L. Lin, H. Meng, J. Shy, S. Horng, L. Yu, C. Chen, H. Liaw, C. Huang, K. Peng, and S. Chen, Phys. Rev.
Lett. 90, 3 (2003).
H. Liao, H. Meng, S. Horng, J. Shy, K. Chen, and C. Hsu, Phys. Rev. B 72, 113203 (2005).
O. Pekkola, A. Gassmann, F. Etzold, F. Laquai, and H. von Seggern, Phys. Status Solidi
DOI:10.1002/pssa.201330411 (2014).
R. D. Scurlock, B. Wang, P. R. Ogilby, J. R. Sheats, and R. L. Clough, J. Am. Chem. Soc. 117, 10194
(1995).
A. Sperlich, H. Kraus, C. Deibel, H. Blok, J. Schmidt, and V. Dyakonov, J. Phys. Chem. B 115, 13513
(2011).
H. Y. Low, Thin Solid Films 413, 160 (2002).
B. H. Cumpston, I. D. Parker, and K. F. Jensen, J. Appl. Phys. 81, 3716 (1997).
T. Zyung and J.-J. Kim, Appl. Phys. Lett. 67, 3420 (1995).
37
Surface Science
The surface science division of the institute of materials science uses advanced surface
science techniques to investigate surfaces and interfaces of materials and materials
combinations of technological use. For this purpose integrated UHV-systems have been
built up which combine different surface analytical tools (photoemission, inverse
photoemission, electron diffraction, ion scattering, electron loss spectroscopy, scanning
probe techniques) with the preparation of thin films (thermal evaporation, close-spaced
sublimation, magnetron sputtering, MOCVD) and interfaces. The main research interest is
directed to devices using polycrystalline compound semiconductors and interfaces between
dissimilar materials. The perspectives of energy conversion (e.g. solar cells) or storage
(intercalation batteries) devices are of special interest. In addition, the fundamental
processes involved in chemical and electrochemical device engineering and oxide thin films
for electronic applications are investigated.
The main research areas are:
Electrochemical Interfaces
The aim of this research activity is the better understanding of electrochemical interfaces
and their application for energy conversion. In addition, empirically derived (electro-)
chemical processing steps for the controlled modification and structuring of materials is
investigated and further optimized. In the center of our interest are
semiconductor/electrolyte contacts.
Solar fuels
The direct solar light induced water splitting is investigated using photoelectrochemical
(electrode/electrolyte) or photocatalytic (particle) arrangements. New materials, design
structures, as well as interface engineering approached with advanced catalysts are
investigated. The catalysts are also tested for their application in water electrolysis.
Intercalation Batteries
The aim of this research activity is the better understanding of electronic properties of Liintercalation batteries and of their degradation phenomena. Typically all solid state
batteries are prepared and investigated using sputtering and CVD techniques for cathodes
and solid electrolytes. In addition, the solid-electrolyte interface and synthetic surface
layers are investigated as well as composite systems for increasing the capacity.
Thin film solar cells
The aim of this research activity is the testing and development of novel materials and
materials combinations for photovoltaic applications. In addition, the interfaces in
microcrystalline thin film solar cells are to be characterized on a microscopic level to
understand and to further improve the empirically based optimisation of solar cells.
Organic-inorganic interfaces and composites
In this research area we are aiming at the development of composites marterials for (opto-)
electronic applications. The decisive factors, which govern the electronic properties of
interfaces between organic and inorganic materials are studied.
38
Semiconducting Oxides
The aim of this research area is to understand electronic surface and interfaces properties
of oxides. We are mainly interested in transparent conducting oxide electrodes for solar
cells and organic LEDs but also in dielectric and ferroelectric perovskites.
Surface analysis
The UHV-surface science equipment and techniques using different and versatile integrated
preparation chambers is used for cooperative service investigations.
For the experiments we use integrated UHV-preparation and analysis-systems (UPS,
(M)XPS, LEISS, LEED), spectromicroscopy (PEEM) coupled with UHV-STM/AFM. We
further apply synchrotron radiation (SXPS, spectromicroscopy), scanning probe methods
(STM, AFM), and electrochemical measuring techniques. UHV-preparation chambers
dedicated for MBE, CVD, PVD and (electro)chemical treatment are available.
The members of the group are involved in basic courses of the department’s curriculum and
offer special courses on the physics, chemistry and engineering of semiconductor devices
and solar cells, on surface and interface science, and on thin film and surface technology
and electrochemistry.
Staff Members
Head
Prof. Dr. Wolfram Jaegermann
Research Associates
Dr.Gennady Cherkashinin
Dr. Lucangelo Dimesso
Dr. René Hausbrand
Dr. Alexander Issanin
PD Dr. Bernd Kaiser
Apl. Prof. Dr. Andreas Klein
Dr. Shunyi Li
Dr. Eric Mankel
Dr. Thomas Mayer
Dr. Hermann Schimper
Dr.Florent Yang
Technical Personnel
Dipl.-Ing. Erich Golusda
Kerstin Lakus-Wollny
Christina Spanheimer
Secretaries
Leslie Frotscher
Marga Lang
PhD Students
Dipl.-Ing. Thorsten Bayer
Dipl.-Ing. Dirk Becker
M.Sc. Mercedes Carillo Solano
M.Sc. Mariel Grace Dimamay
Dipl.-Ing. Dominic Fertig
Dipl.-Ing. Anne Fuchs
M. Sc. Stephan Hillmann
Dipl.-Ing. Mareike Hohmann
Dipl.-Ing. Jan Morasch
Dipl.-Ing. Markus Motzko
Dipl.-Ing. ThiThanh Dung Nguyen
Dipl.-Ing. Ruben Precht
Dipl.-Ing. Karsten Rachut
Dipl.-Ing. Philip Reckers
Dipl.-Ing. Anja Schneikart
Dipl.-Ing. André Schwöbel
M.Sc. Sebastian Siol
Dipl.-Ing. Johannes Türck
Dipl.-Ing. Mirko Weidner
Dipl.-Ing. Jürgen Ziegler
Master Students
Richard Günzler
Lukas Hamm
Michael Kettner
Christian Lohaus
Tobias Rödlmeier
Hans Wardenga
Guest Scientists
Dr. Lili Wu
39
Research Projects
Function and fatigue of conducting electrodes in organic LEDs, SFB 595-D3 (DFG 20032014)
Polarization and charge in electrically fatigued ferroelectrics, SFB 595-B7 (DFG 2007-2014)
Integriertes Graduiertenkolleg SFB 595 (DFG 2008-2014)
Tunable Integrated Components for Microwaves and Optics, Graduiertenkolleg 1037 (DFG
2004-2013)
P-I-N solar cells with alternative highly-absorbing semiconductors (BMBF 2010-2013)
LOEWE Schwerpunkt AdRIA (LOEWE-Hessen: 2008-2013)
Kosteneffiziente Produktionsverfahren für CdTe Solarzellen und kupferfreie Rückkontakte
(CTF Solar 2012 – 2013)
Boundary layers and thin films of ionic conductors: Electronic structure, electrochemical
potentials, defect formation and degradation mechanism SFB595-A3 (DFG 2003-2014)
Morphology and Electronic Structure of Organic/Organic and Organic/Metal-Oxid Hybrid
Systems, Innovation Lab GmbH Heidelberg oft he BMBF leading edge cluster Forum
Organic Electronics (BMBF 2009 – 2014)
9D-Sense Autonomous Nine Degrees of Freedom Sensor Module (BMBF/VDI 2011 – 2014)
Solid State Lithium Batterien mit organischen Kathoden (Novaled 2011 – 2014)
All Oxide PV (EU 2012 – 2014)
Inverted organic solar cells: Charge carrier extraction and interface characterization (DFG
2012- 2014)
Photoelectrochemical water splitting using adapted silicon based semiconductor tandem
structures (DFG 2012 – 2015)
Coordination SPP 1613 Solar H2 (DFG 2012 – 2015)
40
Publications
[1] Trost, S.; Zilberberg, K.; Behrendt, A.; Polywka, A.; Gorrn, P.; Reckers, P.; Maibach, J.;
Mayer, T.; Riedl, T.; Overcoming the "Light-Soaking" Issue in Inverted Organic Solar Cells by
the Use of Al:ZnO Electron Extraction Layers, ADVANCED ENERGY MATERIALS, 3 (2013)
1437-1444.
[2] Dimesso, L.; Spanheimer, C.; Jaegermann, W.; Influence of isovalent ions (Ca and Mg)
on the properties of LiCo0.9M0.1PO4 powders; JOURNAL OF POWER SOURCES, 243 (2013)
668-675
[3] Junfeng Han; Ganhua Fu; Krishnakumar, V.; Cheng Liao; Jaegermann, W.; Besland,
M.P.; Preparation and characterization of ZnS/CdS bi-layer for CdTe solar cell application;
JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 74 (2013), 1879-83
[4] Nguyen, T. T. D.; Dimesso, L.; Cherkashinin, G.; Jaud, J.C.; Lauterbach, S.; Hausbrand,
R.; Jaegermann, W.; Synthesis and characterization of LiMn1-x Fe (x) PO4/carbon nanotubes
composites as cathodes for Li-ion batteries; IONICS, 19 (2013), 1229-1240,
[5] Lebedev, M.V.; Kunitsyna, E.V. ; Calvet, W.; Mayer, T. ; Jaegermann, W.; Sulfur
Passivation of GaSb(100) Surfaces: Comparison of Aqueous and Alcoholic Sulfide Solutions
Using Synchrotron Radiation Photoemission Spectroscopy; JOURNAL OF PHYSICAL
CHEMISTRY C, 117 (2013), 15996-16004
[6] Bohne, L.; Pirk, T.; Jaegermann, W.; Investigations on the influence of the substrate on
the crystal structure of sputtered LiCoO2; JOURNAL OF SOLID STATE ELECTROCHEMISTRY
17 (2013), 2095-2099
[7] Han J.; Fu G.; Krishnakumar, V.; Liao, C.; Jaegermann, W.; CdS annealing treatments in
various atmospheres and effects on performances of CdTe/CdS solar cells; JOURNAL OF
MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 24 (2013), 2695-2700
[8] Hofle, S.; Do, H.; Mankel, E.; Pfaff, M.; Zhang, Z.H.; Bahro, D.; Mayer, T.; Jaegermann,
W.; Gerthsen, D.; Feldmann, C.; Lemmer, U.; Colsmann, A.; Molybdenum oxide anode buffer
layers for solution processed, blue phosphorescent small molecule organic light emitting diodes;
ORGANIC ELECTRONICS, 14 (2013), 1820-1824
[9] Maibach, J.; Mankel, E.; Mayer, T.; Jaegermann, W.; Synchrotron induced photoelectron
spectroscopy on drop casted donor/acceptor bulk heterojunction: Orbital energy line up in
DH6T/PCBM blends, SURFACE SCIENCE, 612 (2013), L9-L11
[10] Dimesso, L.; Spanheimer, C.; Jaegermann, W.; Zhang, Y.; Yarin, A. L.; LiCoPO4-3D
carbon nanofiber composites as possible cathode materials for high voltage applications;
ELECTROCHIMICA ACTA, 95 (2013), 38-42
[11] Cherkashinin, G.; Ensling, D.; Komissinskiy, P.; Hausbrand, R.; Jaegermann, W.;
Temperature induced reduction of the trivalent Ni ions in LiMO2 (M = Ni, Co) thin films;
SURFACE SCIENCE, 608 (2013), L1-L4
41
[12] Dimesso, L.; Spanheimer, C.; Jaegermann, W.; Effect of the Mg-substitution on the
graphitic carbon foams-LiNi1-yMgyPO4 composites as possible cathodes materials for 5 V
applications, MATERIALS RESEARCH BULLETIN, 48 (2013), 559-565
[13] Becker, D.; Cherkashinin, G.; Hausbrand, R.; Jaegermann, W.; XPS study of diethyl
carbonate adsorption on LiCoO2 thin films; SOLID STATE IONICS, 230 (2013), 83-85
[14] Maibach, J.; Mankel, E.; Mayer, T.; Jaegermann, W.; The band energy diagram of
PCBM-DH6T bulk heterojunction solar cells: synchrotron-induced photoelectron spectroscopy
on solution processed DH6T:PCBM blends and in situ prepared PCBM/DH6T interfaces;
JOURNAL OF MATERIALS CHEMISTRY C, 1 (2013), 7635-7642
[15] Seifollahi B., M.; Hojamberdiev, M.; Morita, K.; Zhu, G.; Cherkashinin, G.; Fasel, C.;
Herrmann, T.; Breitzke, H.; Gurlo, A.; Riedel, R.; Visible Light Photocatalysis with c-WO3–
x/WO3×H2O Nanoheterostructures In Situ Formed in Mesoporous Polycarbosilane-Siloxane
Polymer, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 135 (2013), 4467-4475
[16] S. Hoefle, H. Do, E. Mankel, M. Pfaff, Z. Zhang, D. Bahro, T. Mayer, W. Jaegermann,
D. Gerthsen, C. Feldmann, U. Lemmer, A. Colsmann; Molybdenum oxide anode buffer layers
for solution processed, blue phosphorescent small molecule organic light emitting diodes;
ORGANIC ELECTRONICS, 14 (2013) 1820-1824
[17] Vafaee, M. ; Baghaie Y. M. ; Radetinac, A. ; Cherkashinin, G. ; Komissinskiy, P. ; Alff,
L.; Strain engineering in epitaxial La[sub 1−x]Sr[sub 1+x]MnO[sub 4] thin films; JOURNAL
OF APPLIED PHYSICS, 113 (2013), 053906
[18] Babu, D. J.; Lange, M.; Cherkashinin, G.; Issanin, A.; Staudt, R.; Schneider, J.; Gas
adsorption studies of CO2 and N2 in spatially aligned double-walled carbon nanotube arrays;
J. CARBON, 61 (2013), 616-623
[19] H. Sträter, R. Brüggemann, S. Siol, A. Klein, W. Jaegermann and G. H. Bauer; Detailed
photoluminescence studies of thin film Cu2S for determination of quasi-Fermi level splitting
and defect level; J. APPL. PHYS., 114 (2013), 233506
[20] B. Siepchen, H. Schimper, A. Klein, W, Jaegermann; SXPS studies of single crystalline
CdTe/CdS interfaces; J. ELECTRON SPECTR. REL. PHENOM,. 190 (2013), 54-63
[21] H. Sträter, R. Brüggemann, S. Siol, A. Klein, W. Jaegermann and G. H. Bauer; Spectral
Calibrated and Confocal Photoluminescence of Cu2S Thin-Film Absorber; MAT. RES. SOC.
SYMP. PROC., 1538 (2013)
[22] V. Pfeifer, P. Erhart, S. Li, K. Rachut, J. Morasch, J. Brötz, P. Reckers, T. Mayer, S.
Rühle, A. Zaban, I. Mora Seró, J. Bisquert, W. Jaegermann, A. Klein; Energy Band Alignment
Between Anatase and Rutile TiO2 ; J. PHYS. CHEM. LETT., 4 (2013), 4182-4187
[23] S. Siol, H. Sträter, R. Brüggemann, J. Brötz, G. H. Bauer, A. Klein, W. Jaegermann;
PVD of Copper Sulfide Cu2S for PIN-structured solar cells; J. PHYS. D: APPL. PHYS. 46
(2013), 495112
42
[24] M.T. Uddin, Y. Nicolas, C. Olivier, T. Toupance, M. Müller, H.-J. Kleebe, K. Rachut, J.
Ziegler, A. Klein, W. Jaegermann ; Preparation of RuO2/TiO2 Mesoporous Heterostructures
and Rationalization of Their Enhanced Photocatalytic Properties by Band Alignment
Investigations; J. PHYS. CHEM. C, 117 (2013), 22098–22110
[25] V. Krishnakumar, A. Klein, W. Jaegermann; Studies on CdTe solar cell front contact
properties using X-ray Photoelectron Spectroscopy; THIN SOLID FILMS, 545 (2013), 548-557
[26] S. Li, J. Morasch, A. Klein, C. Chirila, L. Pintilie, L. Jia, K. Ellmer, M. Naderer, K.
Reichmann, M. Gröting, K. Albe; Influence of orbital contributions to valence band alignment
of Bi2O3, Fe2O3, BiFeO3, and Bi0.5Na0.5TiO3 ; PHYS. REV. B, 88 (2013), 045428
[27] K. Morita, G. Mera, K. Yoshida, Y. Ikuhara, A. Klein, H.-J. Kleebe, R. Riedel; Thermal
Stability, Morphology and Electronic Band Gap of Zn(NCN); SOLID STATE SCIENCES,
23(2013), 50-57
[28] A. Schneikart, H.-J. Schimper, A. Klein, W. Jaegermann; Efficiency limitations of
thermally evaporated thin film SnS solar cells; J. PHYS. D, 46 (2013), 305109
[29] V. Krishnakumar, A. Barati, H.-J. Schimper, A. Klein, W. Jaegermann; A possible way to
reduce absorber layer thickness in thin film CdTe solar cells; THIN SOLID FILMS 535 (2013),
233-236
[30] A. Klein; Transparent Conducting Oxides: Electronic Structure – Property Relationship
from Photoelectron Spectroscopy with in-situ Sample Preparation; J. AM. CERAM. SOC., 96
(2013), 331-345
[31] M.H. Rein, M. Hohmann, A. Thøgersen, J. Mayandi, A. Klein, and E.V. Monakhov; An
in situ XPS study of the initial stages of rf magnetron sputter deposition of indium tin oxide on
p-type Si substrate; APPL. PHYS. LETT., 102 (2013), 021606
[32] E. M. Hopper, Q. Zhu, J. Gassmann, A. Klein, T.O. Mason; Surface electronic properties
of polycrystalline bulk and thin film In2O3(ZnO)k compounds; APPL. SURF. SCI., 264 (2013),
811-815
Patents
[1] Photo-electrochemical cell for production of hydrogen and oxygen in water or electrolyte
based aqueous solution, has ion exchange film that is arranged between front and back
electrodes of electrochemical-layer structure
Patent Number: DE102012205258-A1; WO2013143885-A1
Patent Assignee: EVONIK IND AG
Inventor(s): HOCH S., MATTHIAS B., BUSSE J., CALVET W., KAISER B., JAEGERMANN
W., HAHN H., ZANTHOFF H., BLUG M.
43
Investigations of interface reactions between lithium and solid electrolyte
André Schwöbel, René Hausbrand and Wolfram Jaegermann
All-solid state Li-ion batteries are a hot topic of research due to possible applications in
various areas of energy storage such as micro-electronics and electro-mobility. All-solid
state devices feature high safety, low self discharge, high cycling stability and high energy
density. These favorable characteristics reflect the properties of inorganic solid electrolytes,
such as high thermal stability, low reactivity and low electronic conductivity. The use of
solid electrolytes allows the save use of metallic lithium in all-solid state devices or, if
applied as protective layer, also in conventional Li-ion batteries with liquid electrolyte.
Nevertheless, reactivity between lithium and solid electrolyte resulting in detrimental
interlayer formation (solid electrode solid electrolyte interface layer, SESEI-layer) still poses
a problem.
A solid state electrolyte which is commonly used in thin film batteries is LiPON, a nitrogensubstituted lithium phosphate glass which was first reported by Bates and coworkers [1].
LiPON is easy to synthezise by sputtering, owing to a broad composition range with a
reasonable ionic conductivity (10-6 S/cm). We apply a surface science approach to
investigate the reactivity between LiPON and lithium. In the experiments, lithium is
deposited stepwise onto a LiPON thin film substrate, and x-ray photo-electron spectroscopy
(XPS) is performed after each step (Fig. 1). Principally, such an approach allows also
insights into the formation of the electrochemical interface, i.e. the formation of the
electrochemical double layer and energy level alignment [2]. The experiments have been
performed on LiPON with different composition. In this contribution we report results for a
LiPON film with metaphosphate (LiPO3) character (Li1.4 PO2.2N0.7) [3], which has proven
functional in our model thin film cells.
Li
XPS
XPS
Li
XPS
Li
EL
EL
EL
Increasing Li deposition time
Figure 1: Schematic illustration of the interface experiment (EL: electrolyte). The approach allows the
investigation of reaction layers and energy level alignment.
The evolution of the core level and valence band spectra is shown in figure 2. At the
bottom, the spectra of the LiPON film before lithium deposition (denoted as is) are shown,
further up the spectra after different deposition times and at the top the spectra of the
sample after lithium deposition and additional oxygen exposure (denoted oxidized). The
O1s and N1s emissions of the pristine LiPON surface show shoulders to high binding
energies, demonstrating the presence of doubly coordinated oxygen and triply coordinated
nitrogen within the network. Upon lithium deposition, these features disappear and new
emissions appear to lower binding energies in all core level spectra (see figure 3 for a
44
detail of the N1s emission). Using literature, the new emissions are attributed to the
presence of Li2O, Li3N and Li3P, next to metallic lithium from the top layer.
Figure 2: Evolution of core level and valence band XP-spectra with lithium deposition time.
Figure 3: N1s XP-specta with triply (NT) and doubly (ND) coordinated nitrogen (left) and illustration of
nitrogen coordination in LiPON (right).
We conclude that contact of lithium with metaphosphate-type LiPON results in formation of
reduced nitrogen and phosphorous coupounds such as Li3N and Li3P, accompanied by the
the disruption of the network and the formation of Li2O and orthophosphate Li3PO4.
45
Experiments conducted on LiPON films with a more pronounced orthophosphate character
indicate that these compounds are more stable. We presume that the reaction is restricted
to the interface region due to low electronic conductivity of the reaction products, forming
an efficient passivation layer. Nevertheless, such layers can have a pronounced effect on the
Li-ion transfer resistance, and further evaluation is ongoing.
References:
[1]
Bates, J.B., et al., Electrical-Properties of Amorphous Lithium Electrolyte Thin-Films. Solid State Ionics,
1992. 53-6: p. 647-654.
[2]
Hausbrand, R., D. Becker, and W. Jaegermann, A Surface Science Approach to Cathode/Electrolyte
Interfaces in Li-ion Batteries: Contact Properties, Charge Transfer and Reactions accepted to Progress in
Solid State Chemistry.
[3]
Schwöbel, A., R. Hausbrand, and W. Jaegermann, In preparation.
46
Energy Band Alignment between Anatase and Rutile TiO2
Verena Pfeifer, Shunyi Li, Karsten Rachut, Jan Morasch, Philip Reckers, Thomas Mayer,
Wolfram Jaegermann, Andreas Klein
Titanium dioxide (TiO2) has been intensivley studied in the last two decades because of its
promising photocatalytic properties for energy-related applications. The two most common
modifications of TiO2 are anatase and rutile. It was observed that the mixed anatase/rutile
systems show more favorable photocatalytic properties than pristine ones of either
modification.[1-2] This synergistic effect has been attributed to a built-in driving force for
separation of photogenerated charge carriers. One of the explainations for this effect is
related to the energy band alignment that forms an energy barrier at the interface blocking
charge transfer between anatase and rutile. However, the exact band alignment of these
two modifications is still unclear. Early models which either align the valence band maxium
of anatase and rutile at the same level or locate the band edges of rutile inbetween those of
anatase cannot convincingly explain the observed synergistic phenomena. A more feasible
model would be a staggered energy band alignment, in which both the valence band
maximum and conduction band minimum of rutile are higher than those of anatase, as
suggested by Deák [3] and Scanlon.[4] In this case the photogenerated electrons move
preferentially to anatase and holes to rutile due to the energy band offsets. In order to
determine the band alignment between anatase and rutile TiO2 and to obtain further
understanding to the synergistic effect, the interface properties and electronic structures of
these two materials are studied by X-ray photoelectron spectroscopy (XPS) measurements
and density functional theory (DFT) calculations.
For the XPS experiments rutile single crystals and polycrystalline TiO2 thin films with pure
anatase phase deposited with reactive magnetron sputtering are used as substrates.
Degnerately Sn-doped In2O3 (ITO) and metallic RuO2 are deposited stepwise onto the
substrates as contact materials. After each incremental deposition step, photoelectron
spectra are recorded in situ to trace fhifts in the binding energies of core-levels emission
lines. The energy band alignment is finally derived independently for both contact
materials by applying transitivity rule, ΔEVB(A/R) = ΔEVB(A/X) – ΔEVB(R/X), where A, R, and
X represent anatase, rutile, and ITO or RuO2.
Fig. 1: Energy band diagrams for anatase/RuO2
and rutile/RuO2 interfaces derived from the
interface experiments. The band alignment at the
rutile/anatase interface is obtained using
transitivity from the figure by omitting the central
RuO2 layer and the band bendings. The resulting
valence and conduction band discontinuities at the
rutile/anatase interface derived from the
photoemission experiment are indicated by
superscript E, and those from DFT calculations are
indicated by superscript T.
47
For both contact materials, an offset between the valence band edges (ΔEVB) of anatase and
rutile of 0.7±0.1 eV has been determined, as illustrated in Fig. 1.By using the literature
values for the band gaps of anatase and rutile, a conduction band offset (ΔECB) of 0.5 eV
can be derived. This corresponds to a staggered energy band alignment similar to those
reported by Deák [3] and Scanlon.[4]
In order to obtain further insight regarding the origin of the band offsets at the
rutile/anatase interface, the electronics structure of both materials are analysed on a DFT
level. Comparison of the desity of states (DOS) (Fig. 2a) yields an offset of 0.63 eV for
valence band and 0.39 eV for conduction band, both in good agreement with the
experimental values (see Fig. 1). Further inspection of the valence band structure shows
that the DOSs of rutile and anatase are mostly very similar except the appearance of “tails”
at both top and bottom in case of rutile. The band structure of rutile in Fig. 2b shows that
the tails originate from a pronounced splitting of the topmost and bottommost levels in the
vicinity of the Γ point, which is entirely absend in anatase. The electronic origin of this
feature can be understood with the help of a Wannier function analysis,[5] which yields on
sp2- and pz-like orbital for each oxygen atom, as shown in Fig. 2c,d. The projection of the
band structure on this set of states yields the relative admixture illustrated by the color
coding in Fig. 2b. This analysis reveals that the topmost valence band of rutile near Γ point
is virtually exclusively of pz character and can thus be interpreted as a lone-pair orbital.
This explains the downward dispersion of the band away from the center of Γ.
Fig. 2: (a) Comparison of the
DOSs of rutile and anatase. The
energy scales have been aligned
based on the electrostatic
potential at the Ti cores. (b)
Band structure of rutile where
the color scale indicates the
respective admixture of oxygencentered (c) sp2-and (d) pz-like
orbitals. In (c), only one of the
three
individual
Wannier
functions that contribute to the
sp2-like orbital is shown. The
remaining lobs are oriented
along the other two O-Ti bonds.
48
In comparison, the pz-like orbital in anatase does not play a prominent role near the
valence band edge and the band structure generated in the same fashion does not exhibit a
splitting of states around the Γ point. These results suggest, that in rutile the pz-like orbital
are much closer to each other and exhibit stronger interaction and overlap, which results in
a larger splitting of the energy bands and consequently in a higher valence band maximum
energy and the appearance of the tail at the top of the valence band.
References:
[1]
[2]
[3]
[4]
[5]
Hurum, D. C.; Agrios, A. G.; Gray, K. A.; Rajh, T.; Thurnauer, M. C., J. Phys. Chem. B 2003, 107, 45454549.
Ohno, T.; Tokieda, K.; Higashida, S.; Matsumura, M., Appl. Catal., A 2003, 244, 383−391.
Deá k, P.; Aradi, B.; Frauenheim, T., J. Phys. Chem. C 2011, 115, 3443−3446.
Scanlon, D. O.; Dunnill, C. W.; Buckeridge, J.; Shevlin, S. A.; Logsdail, A. J.; Woodley, S. M.; Catlow, C.
R. A.; Powell, M. J.; Palgrave, R. G.; Parkin, I. P.; Watson, G. W.; Keal, T. W.; Sherwood, P.; Walsh, A.;
Sokol, A. A., Nat. Mater. 2013, 12, 798−801.
Marzari, N.; Mostofi, A. A.; Yates, J. R.; Souza, I.; Vanderbilt, D., Rev. Mod. Phys. 2012, 84,
1419−1475.
Institute of Materials Science - Surface Science
49
Advanced Thin Film Technology
The Advanced Thin Film Technology (ATFT) group works on advanced thin film deposition
techniques of novel materials. The group is specialized on physical vapor deposition
techniques such as pulsed laser deposition (PLD), advanced oxide molecular beam epitaxy
(ADOMBE) and dc/rf-magnetron sputtering. The ADOMBE system is an in-house
development and has been jointly financed by Max-Planck-Institute for Solid State Research
in Stuttgart and TU Darmstadt. PLD and ADOMBE are part of a cluster system allowing for
in-situ sample exchange between the different deposition methods and characterization
tools. The ADOMBE apparatus is a worldwide unique thin film deposition system which is
dedicated to the growth of complex oxides beyond thermodynamic equilibrium. It allows
for the simultaneous deposition of six elements from electron beam sources and further
elements evaporated from effusion cells. The molecular beams of each element can be
individually controlled by a feed back loop using electron impact emission spectroscopy.
The group is working mainly on oxide ceramics which show a stunning variety of new
functional properties. Examples are high-temperature superconductors, magnetic oxides for
spintronics, high-k dielectrics, ferroelectrics, and novel thermoelectric materials. As a vision
for future, new solid state matter can be created by building hetero- and composite
structures combining different oxide materials. While present day electronic devices heavily
rely on conventional semiconducting materials, a future way to create novel functional
devices could be based (completely) on oxide electronics.
The group uses a Rigaku SmartLab X-ray thin film diffractometer with rotating anode
("synchrotron in house"). Other characterization tools located in the Advanced Thin Film
Technology group include powder X-ray diffraction (XRD), X-ray photoemission
spectroscopy (XPS), high-resolution scanning electron microscopy (HREM) with light
element sensitive EDX, and SQUID magnetometry. A 16 Tesla magnet cryostat allowing
measurements down to liquid helium temperature has been installed. Another magnet
cryostat (10 T) lowers the available temperature range to below 300 mK. This cryostat also
contains high-frequency feed-throughs for electrical characterization (40 GHz). The group
is also using external large scale facilities as synchrotron radiation (ESRF, Grenoble) and
neutron reactors (ILL, Grenoble / HMI and DESY, Berlin) for advanced sample
characterization.
Close cooperation exists in particular with the Max-Planck-Institute for Solid State Research
in Stuttgart, with the Japanese company NTT in Atsugi near Tokio, with the University of
Tokio, and Chalmers University of Technology.
Throughout 2013 Lambert Alff was working also as a Dean of Studies in the faculty of
Materials Science and head of the Graduate School Materialium. Lambert Alff has also
worked as an elected a member of the Senat of TU Darmstadt.
Staff Members
Head
Prof. Dr. Lambert Alff
Research Associates
Dr. Ewrwin Hildebrandt
Dr. Jose Kurian
Dr. Philipp Komissinskiy
Technical Personnel
Dipl.-Ing. Gabi Haindl
Jürgen Schreeck
Secretary
Marion Bracke
50
Institute of Materials Science – Advanced Thin Film Technology
PhD Students
Dipl.-Ing. Mani Arzhang
Dipl.-Ing. Alexander Buckow
M. Sc. Dominik Gölden
Dipl.-Ing. Aldin Radetinac
M.Sc. Sareh Sabet
MTech. Sharath Ulhas
Dipl.-Ing. Mehrdad Baghaie
M. Sc. Niklas van Elten
Dipl.-Ing. Stefan Hirsch
Dipl. Phys. Reiner Retzlaff
BTech. Vikas Shabadi
Research Projects
Novel arsenic free pnictide superconductors (SPP 1458) (DFG 2013 - 2015)
Doped SrTiO3 for Microwave Applications and Multiferroics as novel materials for tunable
components, within DFG Research Training Group 1037 “Tunable Integrated Components
in Microwave Technology and Optics” (DFG 2008-2013)
Resistives Schalten in HfO2-basierten Metall-Isolator-Metall Strukturen für Anwendungen
im Bereich nicht-flüchtiger Speicher (DFG 2012-2013)
Novel oxid electrodes for all oxide varactors (DFG 2012-2014)
LOEWE-Centre AdRIA: Adaptronik – Research, Innovation, Application (HMWK 2011 2014)
Publications
[1] P. Lemmens, V. Gnezdilov, G. J. Shu, L. Alff, C. T. Lin, B. Keimer, and F. C. Chou.
Enhanced low-energy fluctuations and increasing out-of-plane coherence in vacancyordered NaxCoO2. Phys. Rev. B 88, 195151 (2013).
[2] Inventor(s): L. Alff, S. Hildebrandt, T. Kober, R. Teipen, A. T.Tham, R. Werthschützky
Plate-like glass structure for manufacturing pressure sensor, has recessed contour portion
that is surrounded by planar edge area, and specific glass surface whose surface roughness
value and diameter are set to predetermined ranges Patent Number(s): DE102011084457A1 ; EP2581722-A2.
[3] M. Baghaie Yazdi, K.-Y. Choi, D. Wulferding, P. Lemmens, and L. Alff. Raman study of
the Verwey transition in magnetite thin films. New Journal of Physics 15, 103032 (2013).
[4] R. Hord, G. Pascua, K. Hofmann, G. Cordier, J. Kurian, H. Luetkens, V. Pomjakushin,
M. Reehuis, B. Albert and L. Alff. Oxygen stoichiometry of low-temperature synthesized
metastable T'-La2CuO4. Supercond. Sci. Technol. 26, 105026 (2013).
[5] Mingwei Zhu, Philipp Komissinskiy, Aldin Radetinac, Mehran Vafaee, Zhanjie Wang,
and Lambert Alff. Effect of composition and strain on the electrical properties of LaNiO 3
thin films. Appl. Phys. Lett. 103, 141902 (2013).
[6] Sandra Hildebrandt, Philipp Komissinskiy, Marton Major, Wolfgang Donner, Lambert
Alff. Epitaxial growth and control of the sodium content in NaxCoO2 thin films. Thin Solid
Films 545, 291 (2013).
Institute of Materials Science - Advanced Thin Film Technology
51
[7] Alff, L. Magnetic Ceramics. in Ceramics Science and Technology Volume 4: Applications
(eds R. Riedel and I.-W. Chen), Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany,
2013.
[8] K.I. Lilova, R. Hord, L. Alff, B. Albert, A. Navrotsky.Thermodynamic Study of
Orthorhombic Tx and Tetragonal T′ Lanthanum Cuprate, La2CuO4. J. Solid State Chem. 204,
91 (2013).
[9] K. Y. Constantinian, Yu. V. Kislinskii, G. A. Ovsyannikov, A. V. Shadrin, A. E.
Sheyerman, A. L. Vasil’ev, M. Yu. Presnyakov, P. V. Komissinskiy. Interfaces in
superconducting hybrid heterostructures with an antiferromagnetic interlayer. Physics of
the Solid State 55, 461 (2013).
[10] Mehran Vafaee, Mehrdad Baghaie Yazdi, Aldin Radetinac, Gennady Cherkashinin,
Philipp Komissinskiy, and Lambert Alff. Strain engineering in epitaxial La1−xSr1+xMnO4 thin
films. J. Appl. Phys. 113, 053906 (2013).
[11] A Buckow, R Retzlaff, J Kurian and L Alff. Growth of superconducting epitaxial
LaNixBi2 pnictide thin films with a Bi square net layer by reactive molecular beam epitaxy
Supercond. Sci. Technol. 26, 015014 (2013).
[12] Gennady Cherkashinin, David Ensling, Philipp Komissinskiy, René Hausbrand,
Wolfram Jaegermann. Temperature induced reduction of the trivalent Ni ions in LiMO2 (M
= Ni, Co) thin films. Surface Science 608, L1–L4 (2013).
[13] Ina Uhlmann, Dominik Hawelka, Erwin Hildebrandt, Jens Pradella, Jürgen Rödel.
Structure and mechanical properties of silica doped zirconia thin ﬁlms. Thin Solid Films
527, 200 (2013).
[14] J. Kurian, A. Buckow, R. Retzlaff, L. Alff. Search for superconductivity in LaNiP2 (P =
Bi, Sb) thin films grown by reactive molecular beam epitaxy. Physica C 484, 171 (2013).
52
Institute of Materials Science - Advanced Thin Film Technology
Dispersive Solids
The main research interests of the group Dispersive Solids are directed towards the
development of novel strategies suitable for the synthesis of inorganic, oxidic and nonoxidic materials with properties beyond the state of the art. The materials of interest are
advanced oxidic and non-oxidic ceramics with extraordinary properties in terms of
thermal stability, hardness and electronic structure. Therefore, synthesis methods such as
polymer-pyrolysis, non-oxidic and oxidic sol-gel methods, chemical vapour deposition and
novel high pressure methods have been further developed.
The following topical issues are presently under investigation:
Polymer-Derived Ceramics
The thermolytic decomposition of suitable organosilicon polymers provides materials
which are denoted as polymer-derived ceramics (PDCs). The main emphasis is on the
synthesis and characterization of new ceramic materials in the B-C-N, Si-C-N, Si-O-C, Si(B,C)-N and Ti-(B-C)-N systems. The structural peculiarities, thermochemical stability,
mechanical and electrophysical properties of the PDCs have been investigated in a series
of PhD theses and research projects. Due to their outstanding thermochemical stability as
well as excellent oxidation and creep resistance at very high temperatures, the PDCs
constitute promising materials for high temperature applications. Another advantage of
the PDC route is that the materials can be easily shaped in form of fibres, layers or bulk
composite materials.
Finally the correlation of the materials properties with the molecular structure of the used
preceramic polymer is elaborated
Molecular Routes to Nanoscaled Materials
The aim is to develop concepts for the production of novel multifunctional inorganic
materials with a tailor-made nanoscaled structure. In accordance with the so-called
“bottom-up” approach, specific inorganic molecules are to be assigned to higher molecular
networks and solid-state structures in the form of molecular nanotools by means of
condensation and polymerisation processes.
High Pressure Chemistry
Ultra-high pressure techniques like laser heated diamond anvil cell (LH-DAC) or multi
anvil devices have been applied to synthesise novel solid state structures which cannot be
produced by other methods, for example, inorganic nitrides. Moreover, the materials
behaviour under pressure such as phase transformations and decomposition can be
analysed.
Functional Materials
Further research topics are related to the development of materials suitable for
applications in the fields of microelectromechanical systems (MEMS), optoelectronics
(LEDs), pressure, temperature and gas sensors as well as thermoresistant ceramic
membranes for high temperature gas separation.
The integration of state-of-the-art in situ and in operando spectroscopic methods is
applied to understand the mechanisms responsible for sensing and catalytic properties.
Institute of Materials Science - Dispersive Solids
53
Staff Members
Head
Prof. Dr. rer. nat. habil. Prof. h. c. Dr. h. c. Ralf Riedel
Research Associates
Dr. Dmytro Dzivenko
Dr. Magdalena GraczykZajac
PD Dr. Aleksander Gurlo
Dr. Emanuel Ionescu
Technical Personnel
Dipl.-Ing. Claudia Fasel
Secretaries
Su-Chen Chang
Tania Fiedler-Valderrama
(EU project)
Natallia Hurlo (substitute)
Shobha Herur (substitute)
PhD Students
Dipl.-Ing. Miria Andrade
M. Tech. Mahdi Seifollahi
Bazarjani
M. Sc. Shrikant Bhat
M. Tech. Maged Bekheet
M. Tech. Yan Gao
M. Sc. Sarabjeet Kaur
Dipl.-Ing. Jan Kaspar
Dipl.-Ing. Amon Klausmann
M. Sc. Wenjie Li
Dipl.-Ing. Christoph Linck
M. Tech. Ravi Mohan Prasad
Dipl.-Ing. Lukas Mirko Reinold
Dipl.-Ing. Felix Roth
M. Sc. Cristina Schitco
Dipl.-Ing. Lukas Schlicker
Dipl.-Ing. Alexander Uhl
M. Sc. Qingbo Wen
M. Sc. Jia Yuan
M. Sc. Cong Zhou
Dr. Gabriela Mera
Apl. Prof. Dr. Norbert Nicoloso
Dr. Ravi Mohan Prasad
M. Sc. Ahmad Choudhary
Diploma and Master Omar Ariobi
Students
Oliver Genschka
Xueying Hai
Cornelia Hintze
Chinomso Nwosu
Bachelor Students
Laszlo Horak
Moritz Liesegang
Mathias Storch
Maximilian Wimmer
Kerstin Wissel
Alexander Zimpel
Guest Scientists
Prof. Dilshat Tulyaganov, Turin Polytechnic University in
Tashkent, Tashkent, Uzbekistan
Prof. Zhaoju Yu, Department of Materials Science and
Engineering, College of Materials, Xiamen University, Xiamen
China
Michal Vetrecin, Institute of Inorganic Chemistry,Slovak Academy
of Sciences, Bratislava, Slovakia
Ondrej Hanzel, Institute of Inorganic Chemistry,Slovak Academy
of Sciences, Bratislava, Slovakia
54
Dr. Monika Wilamowska, Department of Chemical Technology,
Chemical Faculty, Gdansk University of Technology, Poland
Prof. Dr. Corneliu Balan, Politehnica, University of Bucharest,
Faculty of Enegetics, Hydraulics Departement, Bucharest,
Romania
Dr. Xingang Luan, Associate Professor, Northwestern University
Polytechnical, Schule für Materialien, Xian, Shaanxi, PR China
Prof. Linan An, Associate Professor and Director, Materials
Processing Laboratory, University of Central Florida, USA
Prof. Kathy Lu, Virginia Tech, College of Engineering, Department
of Materials Science and Engineering, Blacksburg, USA
Yohei Shimokawa, Department of Frontier Materials Graduate
School of Engineering, Nagoya Institute of Technology, Nagoya,
Japan
Research Projects
SiHfC(N) and SiHfN(C)-based Ultrahigh-Temperature Ceramic Nanocomposites (UHTCNCs) for EBC/TBC Applications (China Council Scholarship (CSC), Oct. 2012 - Oct. 2016)
Nanocomposites as anode materials for lithium ion batteries: Synthesis, thermodynamic
characterization and modeling of nanoparticular silicon dispersed in SiCN(O) and SiCObased matrices (DFG, Aug. 2010 - July 2016)
High-Temperature Piezoresistivity in SiOC - Untersuchungen zur HochtemperaturPiezoresistivität in kohlenstoffhaltigen Siliciumoxycarbid-Nanokompositen(DFG, May
2013 - April 2016)
Sensors Towards Terahertz (STT): Neuartige Technologien für Life Sciences, Prozess- und
Umweltmonitoring (HMWK-LOEWE, Jan. 2013 - Dec. 2015)
Mestabiles Indiumoxidhydroxid (InOOH) und Korund-Typ Indiumoxid (In2O3): Gezielte
Synthese, Einkristallzüchtung und in-situ Charakterisierung der Umwandlungspfade und
transienten Intermediaten (DFG, SPP 1415 "Kristalline Nichtgleichgewichtsstoffe", Jan.
2013 - Dec. 2015)
Ternary M-Si-N Ceramics: Single-Source-Precoursor Synthesis and Microstructure
Characterization (M = transition metal) (China Council Scholarship (CSC), Nov. 2012 Nov. 2015)
Molecular Routes to SiMBCN Ceramic Nanocomposites (M = Zr, HF) (China Council
Scholarship (CSC), Donghua University, Shanghai, China, Sep. 2011 - Aug. 2015)
55
FUNEA - Functional Nitrides for Energy Applications (Coordination, EU - Marie Curie
Initial Training Network, Feb. 2011 - Jan. 2015)
Novel functional ceramics with substitution of anions in oxidic systems (DFG, SFB 595,
project A4, Jan. 2003 - Dec. 2014)
Adaptronik - Research, Innovation, Anwendung (HMWK-Loewe-AdRIA, Oct. 2008 - Sep.
2014)
Polymer-Processing of Dense and Crack-Free SiC Monoliths (Doctor Thesis, Oct. 2011 Sep. 2014)
FUNEA - Gas seperation membranes (EU - Marie Curie Initial Training Network, Oct. 2011
- Sep. 2014)
FUNEA - Multifunctional perovskite nitrides (EU - Marie Curie Initial Training Network,
Oct. 2011 - Sep. 2014)
Keramische SiCN-basierte Hartstoffschichten
Substratwerkstoffe (DFG, June 2011 - June 2014)
für
thermisch
hochbeanspruchte
Untersuchung der Einflussparameter für die Biege- und Zugfestigkeitsverhalten oxidischer
Verbundkörper mit gefüllter Polysiloxanmatrix (Diploma Thesis, Dec. 2013 - June 2014)
High-Pressure High Temperature Synthesis of Novel Binary and Ternary Superhard Phases
in the B-C-N System (DFG, Feb. 2011 - Jan. 2014)
PrintSens: Nanoskalige gedruckte Hybridmaterialien als aktive Funktionselemente in
mikrostrukturierteen Sensorbauteilen (Schwerpunkt Mikrosystemtechnik im Förderprogramm "IKT 2020 - Forschung für Innovationen" (BMBF VDI/VDE/IT, Jan. 2011 December 2013)
Ceramic Nanocomposites for Applications in Extreme Environments (DAAD, Projekt-ID
54440408, Jan. 2012 - Dec. 2013)
Investigation of polymer-derived, carbon-rich SiOC ceramics as potential Na-ion storage
material (Bachelor Thesis, Sep. 2013 - Dec. 2013)
Synthesis of Dense SiOC Ceramics with tailored Carbon Content (March 2013 - Oct. 2013)
Thermoelektrika auf Basis von MSix/SiOC-Kompositen (Bachelor Thesis, June 2013 - Sep.
2013)
Synthesis of Vanadium-Carbide-Based Nanocomposites from Single-Source Precursors
(Diploma Thesis, April 2013 - Oct. 2013)
Sol-gel derived SiOC materials as anodes for Li-ion batteries (DFG, SFB 595, Aug. 2013 Sept. 2013)
56
Carbon-coated new Si-based composite anode materials for Li-ion batteries (FAME
intership, INP Grenoble-Phelma, May 2013 - Aug. 2013)
Material Anticipatio Studies for Heat disspation in Electric Switches (Master Thesis FAME
in Cooperation with Élève Ingénieure des Matériaux, Grenoble INP - PHELMA, France,
April 2013 - Sep. 2013)
Optmization of Mechanical and Conductivity Properties of Ply, Modified Polyethylene
Glycol and a Blend of Poe: NPEG Reinforced by Nanocrystalline Cellulose and Crosslinking
(Master Thesis FAME in Cooperation with Université Grenoble, LEPMI, Grenoble, France
March 2013 - Aug. 2013)
Multifunctional Graphene Nanocomposites (Master Thesis, Feb. 2013 - Aug. 2013)
Herstellung und Eigenschften von polymerabgeleiteten
(Bachelor Thesis, April 2013 - Aug. 2013)
SiOC-Precursorkeramiken
Thermoresistant Ceramic Membrane with Integrated Gas Sensor for High Temperature
Separation and Detection of Hydrogen and Carbon Monoxide (DFG, Aug. 2010 - July
2013)
Schwerpunkt Mikrosystemtechnik im Förderprogramm "IKT 2020 - Forschung für
Innovationen" (BMBF VDI/VDE/IT, Jan. 2011 - June 2013)
Au/Graphene Metamaterialstrukturen (EUMINAfab (EU) in Cooperation with university of
Frankfurt and TCD, Dublin, Jan. 2013 – June 2013)
Ionic liquids as electrolyte for Li-ion batteries (Bachelor Thesis, March 2013 – June 2013)
Non Aqueous Sol-Gel Synthesis of Boron Carbide Based Materials (US Army International
Technolog, Aug. 2009 - May 2013)
Synthesis and characterization of rare-earth cation-doped silicon carbonitride phosphors
(International Training Program of JSPS, May 2012 - April 2013)
Nanostructure and Calorimetry of Amorphous SiCN and SiBCN (DFG, April 2010 - March
2013)
Porous Carbon Impregnated with Polymer-Derived Ceramics as Anode Material for
Lithium-Ion Batteries (Bachelor Thesis, Jan. 2013 - April 2013)
Elektrische und mechanische Kontaktierung eines Hochtemperatur-Ultraschallwandlers
(Bachelor Thesis, Dec. 2012 – Feb. 2013)
Indium oxide (In2O3) under high pressure: rational design of new polymorphs and
characterisation of their physico-chemical properties (DFG, since June 2009)
57
Publications
[1] Wilamowska, M.; Graczyk-Zajac, M.; Riedel, R.; Composite materials based on polymerderived SiCN ceramic and disordered hard carbons as anodes for lithium-ion batteries;
JOURNAL OF POWER SOURCES, 244 (2013) 80-86.
[2] Kaspar, J.; Graczyk-Zajac, M.; Riedel, R.; Lithium insertion into carbon-rich SiOC
ceramics: Influence of pyrolysis temperature on electrochemical properties; JOURNAL OF
POWER SOURCES, 244 (2013) 450-455.
[3] Mera, G.; Menapace, I.; Widgeon, S.; Sen, S.; Riedel, R.; Photoluminescence of assynthesized and heat-treated phenyl-containing polysilylcarbodiimides: role of crosslinking
and free carbon formation in polymer-derived ceramics; APPLIED ORGANOMETALLIC
CHEMISTRY, 27(11) (2013) 630-638.
[4] Hojamberdiev, M.; Prasad, R.M.; Fasel, C.; Riedel, R.; Ionescu, E.; Single-sourceprec2ursor synthesis of soft magnetic Fe3Si- and Fe5Si3-containing SiOC ceramic
nanocomposites; JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 33(13-14) (2013)
2465–2472.
[5] Sen, S.; Widgeon, S.J.; Navrotsky, A.; Mera, G.; Tavakoli, A.; Ionescu, E.; Riedel, R.;
Carbon substitution for oxygen in silicates in planetary interiors; PROCEEDINGS OF THE
NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 110(40)
(2013) 15904-15907.
[6] Balazsi, C.; Dusza, J.; Lojkowski, W.; Riedel, R.; E-MRS 2012 Fall Meeting, September
17-21, Warsaw University of Technology Preface; JOURNAL OF THE EUROPEAN CERAMIC
SOCIETY, 33(12) (2013) SI 2215-2215.
[7] Morita, K.; Mera, G.; Yoshida, K.; Ikuhara, Y.; Klein, A.; Kleebe, H.-J.; Riedel, R.;
Thermal Stability, Morphology and Electronic Band Gap of Zn(NCN); SOLID STATE
SCIENCES, 23 (2013) 50-57.
[8] Li, W.; Ionescu, E.; Riedel, R.; Gurlo, A.; Can we predict the formability of perovskite
oxynitrides from tolerance and octahedral factors?; JOURNAL OF MATERIALS CHEMISTRY
A, 1 (2013) 12239-12245.
[9] Liu, G.; Kaspar, J.; Reinold, L.M.; Graczyk-Zajac, M.; Riedel, R.; Electrochemical
performance of DVB-modified SiOC and SiCN polymer-derived negative electrodes for lithiumion batteries; ELECTROCHIMICA ACTA, 106 (2013) 101-108.
[10] Gao, Y; Widgeon, S.J.; Tran, T.B.; Tavakoli, A.H.; Mera, G.; Sen, S.; Riedel, R.;
Navrotsky, A.; Effect of Demixing and Coarsening on the Energetics of Poly(boro)silazaneDerived Amorphous Si-(B-)C-N Ceramics; SCRIPTA MATERIALIA, 69(5) (2013) 347–350.
[11] Bekheet, M.F.; Schwarz, M.; Lauterbach, S.; Kleebe, H.-J.; Kroll, P.; Stewart, A.; Kolb,
U.; Riedel, R.; Gurlo, A.; In-situ high-pressure high-temperature experiments in multi-anvil
assembly’s with bixbyite-type In2O3 and synthesis of corundum-type and orthorhombic In2O3
polymorphs ; HIGH PRESSURE RESEARCH, 33(3) (2013) 697-711.
58
[12] Reinold, L.M.; Graczyk-Zajac, M.; Gao, Y.; Mera, G.; Riedel, R.; Carbon-Rich SiCN
Ceramics as High Capacity/High Stability Anode Material for Lithium-Ion Batteries;
[13] Nonnenmacher, K.; Kleebe, H.-J.; Rohrer, J.; Ionescu, E.; Riedel, R.; Carbon Mobility
in SiOC/HfO2 Ceramic Nanocomposites; JOURNAL OF THE AMERICAN CERAMIC
SOCIETY, 96(7) (2013) 2058–2060.
[14] Ionescu, E.; Terzioglu, C.; Linck, C.; Kaspar, J.; Navrotsky, A.; Riedel, R.;
Thermodynamic Control of Phase Composition and Crystallization of Metal-Modified Silicon
Oxycarbides; JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 96(6) (2013) 1899-1903.
[15] Bekheet, M.F.; Schwarz, M.R.; Lauterbach, S.; Kleebe, H.-J.; Kroll, P.; Riedel, R.;
Gurlo, A.; Orthorhombic In2O3 : a metastable polymorph of indium sesquioxide;
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION IN ENGLISH, 52(25) (2013) 6531-6535.
[16] Ionescu, E.; Mera, G.; Riedel, R.; Polymer-Derived Ceramics: Materials Design towards
Applications at Ultrahigh-Temperatures and in Extreme Environments; in „MAX Phases and
Ultra-High Temperature Ceramics for Extreme Environments“, Eds. Low, J.; Sakka, Y.; Hu,
C., IGI GLOBAL, Publishing (2013).
[17] Gurlo, A.; Ceramic Gas Sensors; in Advanced Ceramics Science and Technology
Volume 4: Applications (Eds. R. Riedel and I.-W. Chen), WILEY-VCH Verlag GmbH & Co.
KGaA, Weinheim, Germany (2013).
[18] Colombo, P.; Mera, G.; Riedel, R.; Sorarù, G.D.; Polymer-Derived Ceramics: 40 Years
of Research and Innovation; in Advanced Ceramics, in Ceramics Science and Technology
Volume 4: Applications (Eds. R. Riedel and I.-W. Chen), WILEY-VCH Verlag GmbH & Co.
KGaA, Weinheim, Germany (July 2013)
[19] Mera, G.; Ionescu, E.; Silicon-Containing Preceramic Polymers; ENCYCLOPEDIA OF
POLYMER SCIENCE AND TECHNOLOGY, available online since 24th of May 2013.
[20] Widgeon, S.; Mera, G.; Gao, Y.; Sen, S.; Navrotsky, A.; Riedel, R.; Effect of Precursor
on Speciation and Nanostructure of SiBCN Polymer-Derived Ceramics; JOURNAL OF THE
AMERICAN CERAMIC SOCIETY, 96(5) (2013) 1651–1659.
[21] Sellappan, P.; Guin, J.-P.; Rocherulle, J.; Celarie, F.; Rouxel, T.; Riedel, R.; Influence
of diamond particles content on the critical load for crack initiation and fracture toughness of
SiOC glass-diamond composites; JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 33(4)
(2013) 847-858.
[22] Hojamberdiev, M.; Bozgeyik, M.S.; Abdullah, A.M.; Bekheet, M.F.; Zhu, G.; Yan, Y.;
Xu, Y.; Okada, K.; Hydrothermal-induced growth of Ca10V6O25 crystals with various
morphologies in a strong basic medium at different temperatures; MATERIALS RESEARCH
BULLETIN, 48(4) (2013) 1388-1396.
[23] Sänze, S.; Gurlo, A.; Hess, C.; Monitoring Gas Sensors at Work: Operando RamanFTIR
Study of Ethanol Detection by Indium Oxide; ANGEWANDTE CHEMIE-INTERNATIONAL
EDITION IN ENGLISH, 52(13) (2013) 3607-3610.
59
[24] Drogowska, K.; Flege, S.; Rogalla, D.; Becker, H.-W.; Ionescu, E.; Kim-Ngan, N.-T.H.;
Balogh, A.G.; Hydrogen content analysis in hydrogen-charged PZT ferroelectric ceramics;
SOLID STATE IONICS, 235 (2013) 32-35.
[25] Bazarjani, M.S.; Hojamberdiev, M.; Morita, K.; Zhu, G.; Cherkashinin, G.; Fasel, C.;
Herrmann, T.; Breitzke, H.; Gurlo, A.; Riedel, R.; Visible Light Photocatalysis with c-WO3x/WO3×H2O Nanoheterostructures In situ Formed in Mesoporous Polycarbosilane-Siloxane
Polymer; JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 135(11) (2013) 4467- 4475.
[26] Pashchanka, M.; Prasad, R.M.; Hoffmann, R.C.; Gurlo, A.; Schneider, J.J.; InkjetPrinted Nanoscaled CuO for Miniaturized Gas-Sensing Devices; EUROPEAN JOURNAL OF
INORGANIC CHEMISTRY, 9 (2013) 1481-1487.
[27] Miehe, G.; Lauterbach, S.; Kleebe, H.-J.; Gurlo, A.; Indium hydroxide to oxide
decomposition observed in one nanocrystal during in situ transmission electron microscopy
studies; JOURNAL OF SOLID STATE CHEMISTRY, 198 (2013) 364-370.
[28] Knappschneider, A.; Litterscheid, C.; Dzivenko, D.; Kurzman, J.A.; Seshadri, R.;
Wagner, N.; Beck, J.; Riedel, R.; Albert, B.; Possible Superhardness of CrB4; INORGANIC
CHEMISTRY, 52 (2) (2013) 540-542.
[29] Bekheet, M.F.; Schwarz, M.R.; Müller, M.M.; Lauterbach, S.; Kleebe, H.-J.; Riedel,
R.; Gurlo, A.; Phase segregation in Mn-doped In2O3: in situ high-pressure high-temperature
synchrotron studies in multi-anvil assemblies; RSC ADVANCES, 3(16) (2013) 5357-5360.
[30] Mera, G.; Navrotsky, A.; Sen, S.; Kleebe, H.-J.; Riedel, R.; Polymer-Derived SiCN and
SiOC Ceramics – Structure and Energetics at the Nanoscale; JOURNAL OF MATERIALS
CHEMISTRY A, 1 (2013) 3826-3836.
[31] Papendorf, B.; Ionescu, E.; Kleebe, H.-J.; Linck, C.; Guillon, O.; Nonnenmacher, K.;
Riedel, R.; High-Temperature Creep Behavior of Dense SiOC-Based Ceramic Nanocomposites:
Microstructural and Phase Composition Effects; JOURNAL OF THE AMERICAN CERAMIC
SOCIETY, 96(1) (2013) 272–280.
[32] Jüttke, Y.; Richter, H.; Voigt, I.; Prasad, R. M.; Bazarjani, M. S.; Gurlo, A.; Riedel, R.
Polymer derived ceramic membranes for gas separation; Chemical Engineering Transactions
2013, 32, 1891-1896. DOI:10.3303/CET1332316
Books
Riedel, R. / Chen, I.-W.; Ceramics Science and Technology, Volume 4: Applications,
WILEY-VCH, July 2013, ISBN: 978-3-527-31158-3.
60
Orthorhombic In2O3: A Metastable Polymorph of Indium Sesquioxide
Maged F. Bekheeta, Marcus R. Schwarzb, Stefan Lauterbacha, Hans-Joachim Kleebea,
Peter Krollc, Ralf Riedela, and Aleksander Gurloa
a
Fachbereich Material- und Geowissenschaften, Technische Universität Darmstadt, 64287 Darmstadt
(Germany)
b
Technische Universität-Bergakademie Freiberg, Freiberg High Pressure Research Centre, Institut für
Anorganische Chemie, 09599 Freiberg (Germany)
c
Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, TX 7600190065 (USA)
Angew. Chem. (International Ed. in English), 52(25) (2013) 6531-6535.
As our results led to some discussion in the community,[1] we set out to explore alternative
high-pressure routes towards a large amount of the o’-In2O3 polymorph. The main goals of
this work are as follows: 1) to synthesize macroscopic quantities of o’-In2O3; 2) to recover
it to ambient pressure; and 3) to determine the crystal structure of o’-In2O3 under ambient
conditions. It is important to note that other corundum-type sesquioxides, including
Cr2O3,[2] Fe2O3,[3] and Al2O3,[4] transform to Rh2O3(II)-type structure under high pressure,
but none of them have been recovered to ambient conditions to date. Therefore, the
availability of Rh2O3(II)-type o’-In2O3 under ambient conditions will also contribute to
better understanding of the structural chemistry and properties of other binary oxides.
Our work differs from the previous studies[5,6,7] in three major aspects. First, we are
guided by theoretical calculations that suggest using the metastable corundum-type rhIn2O3 (for the specimen details we refer to references [8, 9]) as starting material for the
high-pressure synthesis of the orthorhombic o’-In2O3 polymorph. Computations indicate
that o’-In2O3 is lower in enthalpy than the rh-In2O3 for pressures above 6.4 GPa (arrow 1
in Figure 1 a) and thus below the c- to o’-In2O3 transition (arrow 2 in Figure 1 a).[8]
Both structures, rh-In2O3 and o’-In2O3, are connected by a diffusionless pathway via a
common monoclininc P2/c subgroup (in analogy to Al2O3).[1a] We computed the
activation barrier for the collective transition rh-In2O3  o’-In2O3 to 0.08 eV per atom,
which corresponds to a temperature of about 650 8C at the transition pressure (Figure 1
b). Consequently, we expect a fast transformation rh-In2O3  o’-In2O3 under high-pressure
high-temperature conditions.
Second, as we aim at high-yield synthesis, we choose multi-anvil and toroid cell apparatus
that allowed us to obtain macroscopic quantities (ca. 10–100 mm3) of o’-In2O3
polymorphs and also to grow macroscopic single crystals.[10] The synthesis in multi-anvil
cells is considered as a step towards an industrial scale synthesis, for example, in a belt
apparatus that allows circa 7 cm3 of material to be obtained under given conditions; a
similar pressure is applied in industrial synthesis of diamond and cubic boron nitride.[11]
Finally, we perform time-resolved synchrotron studies in multi-anvil assemblies to follow
hase transformations in situ under high-pressure high-temperature conditions. The phase
development in rh-In2O3 was monitored in situ by energy-dispersive X-ray diffractometry
at the two-stage 6–8 MAX200X multi-anvil high-pressure diffractometer of the GFZ
Potsdam (beamline W2, HASYLAB/DESY, Hamburg, Germany). New high-pressure/hightemperature multi-anvil assemblies for synchrotron studies developed at the Freiberg High
Pressure Research Centre are employed.[12] These assemblies have low X-ray absorption
and do not show any additional reflections from the sample environment (see the
Supporting Information).[13]
61
The complete transformation from rh-In2O3 to o’-In2O3 takes less than 20 seconds at 600
°C and 9 GPa (arrow 1 in Figure 2), indicating fast kinetics as expected for a diffusionless
transition. The XRD pattern of material rapidly quenched at 9 GPa from 600 °C to room
temperature possesses only o’-In2O3 reflections. During decompression at
room temperature, o’-In2O3 partially transforms to corundum-type rh-In2O3 at pressures
below 1.0 GPa (arrow 2 in Figure 2).
The structure refinement of the specimen recovered to ambient pressure confirms the
coexistence of o’-In2O3 (fraction: 80.0 wt%), rh-In2O3 (15.9 wt%), and o-InOOH (4.1
wt%) as a side phase (Figure 3b, Table 1).
In the next step, we explored whether the synthesis of o’-In2O3 could be reproduced ex
situ in a toroid-type highpressure device that allows even larger macroscopic quantities to
be obtained, as well as a fast compression/decompression rate and less experimental
preparation times compared to multi-anvil devices.[14] In a typical experiment, rh-In2O3
was compressed to 8 GPa and heated at about 1000–1100 °C for 10 minutes. Figure 3c
shows the X-ray powder diffraction pattern and Rietveld difference plot of the recovered
specimen. The structure refinement (Figure 3c, Table 1) confirmed our finding from the in
situ multi-anvil experiments and shows the coexistence of o’-In2O3 (fraction: 63.8 wt%),
rh-In2O3 (31.5 wt%), and o-InOOH (4.7 wt%). The o-InOOH probably arises from the
reaction between In2O3 and water under high-pressure and high-temperature
(hydrothermal) conditions.[15] Possible water sources include the pressure standard or the
sample itself. Interestingly, o-InOOH was also obtained as a side phase in recent synthesis
of InMnO3 and In-Mn-Fe-O perovskites and corundum-type In2-2xZnxSnxO3 oxides
performed at 6 GPa/1100–1500 °C and 7 GPa/1000 °C, respectively.[16]
In three In2O3 polymorphs, which are available at ambient conditions, indium is
octahedrally coordinated and oxygen tetrahedrally coordinated (Figure 4); the structural
differences between them lie in the stacking of {InO6} octahedra. In c-In2O3, the {InO6}
octahedra share corners and edges; in the other two it is the edges and faces. The o’-In2O3
is an orthorhombic distortion of the rh-In2O3 structure, in which each {InO6} octahedron
shares only two edges with other octahedra rather than three in rh-In2O3. The interatomic
distances are similar in all three structures; that is, the mean In_O distance is in the range
2.182–2.189 Å. o’-In2O3 is the densest polymorph, and the volume reduction from c-In2O3
and rh-In2O3 to o’-In2O3 is about 6 and 3%, respectively.
In summary, we succeeded in synthesizing the orthorhombic o’-In2O3 polymorph from
rhombohedral corundumtype rh-In2O3 under moderate high-pressure high-temperature
conditions (8–9 GPa, 600–1100 °C) in multi-anvil and toroid apparatus. We were able to
recover the polymorph to ambient pressure and temperature and to confirm its crystal
structure by X-ray and electron diffraction at these conditions to be the Rh2O3(II)-type.
Our experimental setup makes the orthorhombic o’-In2O3 polymorph available in large
quantities for further physico-chemical characterization and provides an opportunity to
grow o’-In2O3 as single crystals.
62
Figure 2. In situ energy-dispersive XRD patterns in
multi-anvil assemblies of a rh-In2O3 specimen
compressed at 9.0 GPa and heated up to 600 °C.
The tick marks refer to the calculated Bragg
positions of o’-In2O3 (bottom) and rh-In2O3 (top).
Arrows indicate the complete phase transition rhIn2O3  o’-In2O3 (1) and the partial o’-In2O3
transformation to rh-In2O3 (2).
Figure 1. a) A section of the enthalpy–pressure
(H–p) diagram for indium oxide polymorphs; cIn2O3 is a reference structure. Arrows indicate
transitions (1) rh-In2O3  o’-In2O3 and (2) c-In2O3
 o’-In2O3. b) The relative enthalpy (per formula
unit of In2O3) between o’-In2O3 and rh-In2O3
polymorphs at 0, 2, 4, and 6.4 GPa.
Table 1: Phase composition of initial and recovered materials.[a]
Specimen
rh-In2O3
o’-In2O3
o-InOOH
(R c, Z=6)
(Pbcn, Z=4)
(P21nm, Z=2)
starting material
(Figure 3a)
100%,
a=5.4814 (5)
c=14.4998(3)
-
-
recovered from 9 GPa/
600 °C (Figure 3b)
15.9%
a=5.4795(4)
c=14.4224
80%
a=7.9295(1)
b=5.4821(2)
c=5.5898(6)
4.1%
a=5.2587(9)
b=4.5660(5)
c=3.2669(6)
recovered from 8 GPa/
ca. 1100 °C (Figure 3c)
31.5%
a=5.4803(5)
c=14.4484(1)
63.8%
a=7.9208(1)
b=5.4881(6)
c=5.5977(1)
4.7%
a=5.2611(8)
b=4.5673(3)
c=3.2709(4)
[a] Fraction (wt%) and lattice parameters a, b, c [Å].
63
Figure 3. Structure refinement of the starting
material rh-In2O3 (a) and specimens recovered
from the in situ multi-anvil cell (b) and toroid (c)
experiments, showing observed and calculated
intensities. Tick marks refer to Bragg reflections of
o’-In2O3, rh-In2O3, and o-InOOH (bottom). Table 1
summarizes the results of the structure
refinement.
Figure 4. Coordination, density, and interatomic
distances (in Å) in In2O3 polymorphs at ambient
pressure. In and O atoms are shown as small and
large balls, respectively.
Notes and references
[1]
[2]
[3]
[4]
[5]
[6]
64
a) B. Xu, H. Stokes, J. J. Dong, J. Phys. Condens. Matter 2010, 22, 315403; b) A. Möller, P. Schmidt,
M. Wilkening, Nachr. Chem. 2009, 57, 239-251; c) F. J. Manjón, D. Errandonea, Phys. Status Solidi B
2009, 246, 9-31.
C. Wessel, R. Dronskowski, J. Solid State Chem. 2013, 199, 149-153.
G. K. Rozenberg, L. S. Dubrovinsky, M. P. Pasternak, O. Naaman, T. Le Bihan, R. Ahuja, Phys. Rev. B
2002, 65, 064112.
J. F. Lin, O. Degtyareva, C. T. Prewitt, P. Dera, N. Sata, E. Gregoryanz, H. K. Mao, R. J. Hemley, Nat.
Mater. 2004, 3, 389-393.
H. Yusa, T. Tsuchiya, J. Tsuchiya, N. Sata, Y. Ohishi, Phys. Rev. B2008, 78, 092107.
A. Gurlo, D. Dzivenko, P. Kroll, R. Riedel, Phys. Status Solidi RRL 2008, 2, 269-271.
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
a) D. Liu,W. W. Lei, B. Zou, S. D. Yu, J. Hao, K.Wang, B. B. Liu, Q. L. Cui, G. T. Zou, J. Appl. Phys.
2008, 104, 083506; b) J. Qi, J. F. Liu, Y. He, W. Chen, C. Wang, J. Appl. Phys. 2011, 109, 063520.
A. Gurlo, P. Kroll, R. Riedel, Chem. Eur. J. 2008, 14, 3306-3310.
a) M. Epifani, P. Siciliano, A. Gurlo, N. Barsan, U. Weimar, J. Am. Chem. Soc. 2004, 126, 4078-4079;
b) A. Gurlo, S. Lauterbach, G. Miehe, H.-J. Kleebe, R. Riedel, J. Phys. Chem. C 2008, 112, 9209-9213.
T. Irifune, Mineral. Mag. 2002, 66, 769-790.
E. Horvath-Bordon, R. Riedel, A. Zerr, P. F. McMillan, G. Auffermann, Y. Prots, W. Bronger, R. Kniep,
P. Kroll, Chem. Soc. Rev. 2006, 35, 987-1014.
M. Schwarz, T. Barsukova, C. Schimpf, D. Šimek, C. Lathe, D. Rafaja, E. Kroke in HASYLAB
Users´Meeting, Hamburg, Germany, 2010.
M. F. Bekheet, M. Schwarz, M. Mueller, S. Lauterbach, H. J. Kleebe, R. Riedel, A. Gurlo, RSC Adv.,
2013, 3, 5357-5360.
L. G. Khvostantsev, V. N. Slesarev, V. V. Brazhkin, High Pressure Res. 2004, 24, 371-383.
A. N. Christensen, N. C. Broch, Acta Chem. Scand. 1967, 21, 1046-1056.
a) D. A. Rusakov, A. A. Belik, S. Kamba, M. Savinov, D. Nuzhnyy, T. Kolodiazhnyi, K. Yamaura, E.
Takayama-Muromachi, F. Borodavka, J. Kroupa, Inorg. Chem. 2011, 50, 3559-3566; b) A. A. Belik, T.
Furubayashi, H. Yusa, E. Takayama-Muromachi, J. Am. Chem. Soc. 2011, 133, 9405-9412; c) C. A.
Hoel, J. M. G. Amores, E. Moran, M. A. Alario-Franco, J. F. Gaillard, K. R. Poeppelmeier, J. Am. Chem.
Soc. 2010, 132, 16479-16487.
65
Thermodynamic Control of Phase Composition and Crystallization of
Metal-Modified Silicon Oxycarbides
E. Ionescu,a C. Terzioglu,a C. Linck,a J. Kaspar,a A. Navrotsky,b and R. Riedela
a
Technische Universität Darmstadt, Institut für Materialwissenschaft, D-64287 Darmstadt, Germany
Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California Davis, Davis, California
95616
b
J. Am. Ceram. Soc., 96(6) (2013) 1899–1903.
Silicon oxycarbides modified with main group or transitionmetals (SiMOC) are usually
synthesized via pyrolysis of sol-gel precursors from suitable metal-modified orthosilicates
or polysiloxanes. In this study, the phase composition of different SiMOC systems (M =
Sn, Fe, Mn, V, and Lu) was investigated. Depending on the metal, different ceramic
phases formed. For M = Mn and Lu, MOx/SiOC ceramic nanocomposites were formed,
whereas other compositions revealed the formation of M/SiOC (M = Sn), MSix/SiOC (M
= Fe) or MCx/SiOC (M = V) upon pyrolysis. The different phase compositions of the
SiMOC materials are rationalized by a simple thermodynamic approach which generally
correctly predicts which type of ceramic nanocomposite is expected upon ceramization of
the metal-modified precursors. Calculations show that the thermodynamic stability of the
MOx phase with respect to that of the C–O system is the most important factor to predict
phase formation in polymer-derived SiMOC ceramic systems. A secondary factor is the
relative stability of metal oxides, silicates, carbides, and silicides.
Experimental Procedures
The synthesis of the precursors was performed as described elsewhere for SiZrOC and
SiHfOC7,8 via chemical modification of a polysilsesquioxane (MK Belsil PMS; Wacker,
Burghausen, Germany) with Fe(acac)3, Mn(acac)3, V(acac)3, VO(acac)2, Sn(ac)2, and
Lu(ac)3 (ac = acetate; acac = acetylacetonate). Thus, each 5 g of polysilsesquioxane PMS
was reacted with the corresponding amount of metal precursor at room temperature. For
the reactions with the Fe, Mn, V, and Sn containing precursors, xylene was used as a
solvent, whereas the reaction with Lu(ac)3 was performed in acetone. The amount of the
metal precursor was chosen to obtain after pyrolysis a weight ratio between SiOC and a
possible MOx phase (lowest oxide, which was assumed to precipitate) close to 70:30. To
calculate the needed amounts of metal precursors, a ceramic yield of 81 wt% upon
conversion of PMS into SiOC has been taken into account.7,8 In Table I, the amounts of the
metal precursors used for the chemical modification of PMS is presented. Thus, the
SiMOC-based ceramics were expected to exhibit similar MOx contents, between 30.9 and
36.7 wt% (see Table I).
After mixing PMS with the metal precursor, the reaction solution was stirred for 2 h at
room temperature. Subsequently, the solvent was removed under vacuum (10-2 mbar).
The metal-modified precursors were cross-linked at 250°C and pyrolyzed in argon at
1100°C. The ceramic yield of the precursor-to-ceramic transformation processes showed
values between 51.6 and 71.6 wt% (Table I).
66
Table I. Amounts of PMS and Metal Precursors Used as well as Ceramic Yields of the Syntheses of SiMOC Samples
Sample
Metal
PMS (g)
Metal precursor (g)
SiOC
SiFeOC
SiSnOC
SiMnOC
SiLuOC
SiVOC
SiVOC
Fe(III)
Sn(II)
Mn(III)
Lu(III)
V(III)
V(IV)
5
5
5
5
5
5
5
7.8
3.1
8.6
3.2
9.0
6.9
Expected content
of
MOx in SiMOC
(wt%)
34.1
36.7
36.2
30.9
33.1
36.3
Ceramic yield
(wt%)
Phase composition
upon
Pyrolysis at 1100°C
81.00
67.02
71.60
61.62
71.50
51.61
64.58
a-SiOC
Fe3Si/a-SiOC
Sn/a-SiOC
MnSiO3/a-SiOC
Lu2O3/a-SiOC
V8C7/a-SiOC
V8C7/a-SiOC
Results and Discussion
Pyrolysis of the metal-containing polyorganosiloxanes in Ar atmosphere at 1100°C results
in the formation of SiMOC ceramics, which were shown by XRD to exhibit different
crystalline phase compositions [Fig. 1(a)]. In SiFeOC, Fe3Si was observed, while the tincontaining precursor gave a Sn/SiOC ceramic composite. In both cases, Fe(III) and Sn(II)
were reduced to Fe(0) (as in Fe3Si alloy) and Sn(0). It is thought that the reducing
conditions during the pyrolysis of the precursors are responsible for the formation of the
metallic phases and are mainly due to the release of hydrogen and CO upon
ceramization.7 The Sn/SiOC ceramic did not change phase composition when annealed at
1300°C; whereas in Fe3Si/SiOC the crystallization of Fe5Si3 and b-SiC was found under
the same conditions [Fig. 1(b)]. Similar behavior was reported previously for
Fe3Si/SiCNO.18 Pyrolysis of the Mn-containing precursor led to a poorly crystalline
SiMnOC ceramic. The XRD pattern revealed the presence of MnSiO3 [Fig. 1(a)], which
was also observed upon annealing at 1300°C [Fig. 1(b)]. It is assumed that the phase
separation of MnO (at temperatures between 800°C and 1100°C) and its subsequent
reaction with the phase-separated silica at higher temperature leads to the formation of
the MnSiO3 phase. Such formation of binary and ternary oxides is analogous to the
behavior observed in SiZrOC and SiHfOC.7,9 However, the formation of MnSiO3 occurs at
lower temperatures than those for ZrSiO4 and HfSiO4, which crystallize at temperatures
exceeding 1400°C.7,9
Similar results were obtained in the case of the lutetiummodified precursor. Thus, at
1100°C poorly crystallized Lu2O3 was identified by XRD, whereas at 1300°C crystalline
Lu2Si2O7 was found (Fig. 1).
Different behavior was found for the vanadium-modified precursor. At both temperatures
a poorly crystalline V8C7 was detected, which can result from the reaction of vanadium
oxide with excess carbon (Fig. 1, as for SiVOC prepared upon pyrolysis of the V(ac)3modified precursor). Interestingly, both precursors, i.e., the V(III)- and the V(IV)-modified
polysilsesquioxanes led upon pyrolysis to the crystallization of V8C7 (i.e., formation of
SiOC/V8C7 nanocomposites).
The strong effect of the precursor composition on the phase evolution upon ceramization
reflects the reducing conditions during pyrolysis and annealing. Thus, it is obvious that
the thermodynamic stability of the metal oxides generated during pyrolysis plays a crucial
role. To assess this effect in more detail, thermodynamic data for the oxides (MOx) were
used, as depicted in the Ellingham diagrams in Fig. 2. Since all samples were synthesized
under the same pyrolysis conditions, the partial pressures of the volatiles (i.e., CO, CO2,
67
H2, and CH4) were not considered explicitly here. However, since carbon is present in all
cases, it is appropriate to make a direct comparison between the CO–C and MOx – M
equilibria. Since carbon is present in large amount in the investigated samples, the oxygen
fugacity is determined by the equilibrium 2 C + O2  2CO.
Fig. 1. X-ray diffraction (XRD) patterns for SiMOC
(M = Fe, Sn, Mn, Lu, V) pyrolyzed at 1100°C (a)
and 1300°C (b).
Fig. 2. Ellingham diagrams showing the Gibbs free
energy change of different oxides with respect to
the system C–O (the gray areas correspond to the
temperature range in which our samples were
prepared, i.e., between 1100°C and 1300°C).
Oxides with Gibbs free energies located in the
area above the CO line will get reduced by carbon
to their corresponding metals upon CO gas
release; whereas those located in the area below
the CO line will be stable against conversion into
metals (data taken from Ref. [24]).
68
Conclusion
In this study, we show that the thermodynamic stability of MOx with respect to the system
C–O plays a crucial role within the context of the ceramization process of metalmodified
polymers. Based on thermodynamic data of the respective oxides, the phase composition of
SiMOC/SiMCNO ceramics upon annealing at high temperatures can be predicted for
different metals. The prediction agrees with the experimental results from this study and
those reported in the literature for both SiMOC and SiMCNO ceramic composites.
However, in addition to the stability of the oxides with respect to reduction, some other
aspects must be taken into account for predicting the phase composition of
SiMOC/SiMCNO composites, such as thermodynamic stabilization through conversion into
silicates (for MOx being stable with respect to carbothermal conversion into M) or into
silicides or carbides (for MOx not being stable against carbothermal reduction). These
factors are summarized in Fig. 3.
A more rigorous computation of the thermodynamics of crystallization could employ free
energy minimization techniques. However, this would require some knowledge or
assumptions about the free energies of the metals dissolved in the initially homogeneous
ceramics. Such information is not currently available. The main point of this study is that
even a very simple thermodynamic approach predicts the observed phases formed with
remarkable accuracy.
Fig. 3. Predicted phase compositions of SiMOC and SiMCNO upon pyrolysis at 1100°C–1300°C. The oxides of
the red marked metals are stable with respect to their reduction and thus SiOC/MO x nanocomposites are
expected. Depending on the stability of the corresponding silicates (MSiO x), solid-state processes between MO
and the phase-separated silica may occur, as observed for the case of Mn (crystallization of MnSiO3) and Lu
(Lu2Si2O7) in this study. The oxides of the blue colored metals are not stable with respect to reduction by
carbon. Consequently, SiOC/M nanocomposites are predicted to form here. Also in this case, the relative
thermodynamic stability of the corresponding silicides or carbides will determine whether SiOC/MSi x or
SiOC/MCx nanocomposites will be generated.
References
[1] E. Ionescu, C. Linck, C. Fasel, M. Müller, H. J. Kleebe, and R. Riedel, “Polymer-Derived SiOC/ZrO2
Ceramic Nanocomposites With Excellent High-Temperature Stability,” J. Am. Ceram. Soc., 93 [1] 241–50 (2010).
[2] E. Ionescu, B. Papendorf, H. J. Kleebe, F. Poli, K. Muller, and R. Riedel, “Polymer-Derived Silicon
Oxycarbide/Hafnia Ceramic Nanocomposites. Part I: Phase and Microstructure Evolution During the
Ceramization Process,” J. Am. Ceram. Soc., 93 [6] 1774–82 (2010).
[3] A. Francis, E. Ionescu, C. Fasel, and R. Riedel, “Crystallization Behavior and Controlling Mechanism of
Iron-Containing Si-C-N Ceramics,” Inorg. Chem., 48 [21] 10078–83 (2009).
[4] E. Ionescu, B. Papendorf, H. J. Kleebe, and R. Riedel, “Polymer-Derived Silicon Oxycarbide/Hafnia
Ceramic Nanocomposites. Part II: Stability Toward Decomposition and Microstructure Evolution at
T»1000 Degrees C,” J. Am. Ceram. Soc., 93 [6] 1783–9 (2010).
[5] T. B. Reed, Free Energy of Formation for Binary Compounds. MIT Press, Cambridge, MA, 1971.
69
Structure Research
In the year 2013, we completed the home-made MBE-setup for metallic films. Now we can
grow thin metallic samples in Ultra High vacuum and transfer them, without braking the
vacuum, into a small x-ray baby chamber (see separate report). The baby chamber is
equipped with a hemisperical aluminum window and is not only compatible with our sixcircle diffractometer, but also with comparable instruments at various synchrotron sources.
Several neutron scattering campaigns were carried out in an effort to quantify the structure
and dynamics of defects in Ba-doped bismuth sodium titanate. In addition to measurements
of the diffuse scattering, we used the extended x-ray absorption fine structure to
characterize the local environment of the different species. Data evaluation is under way.
Staff Members
Head
Prof. Dr. Wolfgang Donner
Prof. Dr. Dr. h.c. Hartmut Fueß
Research Associates
Dr. Joachim Brötz
Dr. Marton Major
Dr. Ljubomira Schmitt
Dr. Azza Amin
Technical Personnel
Dipl. Ing. Heinz Mohren
Jean-Christophe Jaud
Maria Bense
Ingrid Svoboda
Sabine Foro
PhD Students
M. Sc. Qiran Li
M. Sc. Marco Léal
Dipl.-Ing. Florian Pforr
Dipl.-Ing. Dominik Stürmer
Master
Michael Brilz
Guest Scientists
Prof. Dr. Ismael Saadoune,
Université Cadi Ayyad, Maroc
Secretary
Prof. Dr. Anouar Njeh,
University of Sfax, Tunesia
Research Projects
Structural investigations into the electric fatigue in piezo-ceramics (DFG-SFB, 2011-2014)
Development of electrode materials for high capacitance devices (IDS-FunMat, 2013-2015)
Phase transitions in thin potassium sodium niobate films (IDS-FunMat, 2012-2015)
Influence of biaxial strain and texture on the elastic properties of Barium Strontium
Titanate thin films (AvH Lab Partnership, 2013-2015)
Publications
[1] Siol, Sebastian; Straeter, Hendrik; Brueggemann, Rudolf; Broetz, Joachim; Bauer,
Gottfried H.; Klein, Andreas; Jaegermann, Wolfram;
PVD of copper sulfide (Cu2S) for PIN-structured solar cells;
JOURNAL OF PHYSICS D-APPLIED PHYSICS Volume: 46 Issue: 49 Article Number:
495112 (2013)
70
Institute of Materials Science - Structure Research
[2] Pfeifer, Verena; Erhart, Paul; Li, Shunyi; Rachut, Karsten; Morasch, Jan;
Broetz, Joachim; Reckers, Philip; Mayer, Thomas; Ruehle, Sven; Zaban, Arie; Mora Sero,
Ivan; Bisquert, Juan; Jaegermann, Wolfram; Klein, Andreas;
Energy Band Alignment between Anatase and Rutile TiO2;
JOURNAL OF PHYSICAL CHEMISTRY LETTERS Volume: 4 Issue: 23 Pages: 41824187 (2013)
[3] Labrini, Mohamed; Saadoune, Ismael; Scheiba, Frieder; Almaggoussi,
Abdelmajid; Elhaskouri, Jamal; Amoros, Pedro; Ehrenberg, Helmut; Broetz, Joachim;
Magnetic and structural approach for understanding the electrochemical behavior of
LiNi0.33Co0.33Mn0.33O2 positive electrode material;
ELECTROCHIMICA ACTA Volume: 111 Pages: 567-574 (2013)
[4] Muench, Falk; Oezaslan, Mehtap; Rauber, Markus; Kaserer, Sebastian; Fuchs, Anne;
Mankel, Eric; Broetz, Joachim; Strasser, Peter; Roth, Christina; Ensinger, Wolfgang;
Electroless synthesis of nanostructured nickel and nickel-boron tubes and their performance as
unsupported ethanol electrooxidation catalysts
JOURNAL OF POWER SOURCES Volume: 222 Pages: 243-252 (2013)
[5] Z.K. Heiba, M.B. Mohamed, H. Fuess,
Structural and magnetic properties of Sm2-xMnxO3 nanoparticles, Materials Research Bull.
48, 3750-3755, 2013
[6] J. P. Patel, A. Senyshyn, H. Fuess, D. Pandey
Evidence for weak ferromagnetism, isostructural phase transition, and linear magnetoelectric
coupling in the multiferroic Bi0.8Pb0.2Fe0.9Nb0.1O3 solid solution
Phys. Rev. B 88 (10) 104108, 2013
[7] A. Senyshyn, O. Dolotko, M.J. Mühlbauer, K. Nikolowski, H. Fuess, H. Ehrenberg
Lithium Intercalation into Graphite Carbons Revisited: Experimental Evidence for Twisted
Bilayer Behavior
J. Electrochem. Soc. 160 (5) A 3198-A 3205, 2013
[8] S. Bhattacharjee, A. Senyshyn, H. Fuess, D. Pandey
Morin-Type spin-reorientation transition below the Neel transition in the monoclinic
compositions of (1-x) BiFeO3-xPbTiO(3) (x= 0.25 and 0.27): A combined dc magnetization
and x-ray and neutron powder diffraction study
Phys. Rev. B 87 (5) 05417, 2013
[9] H. Ehrenberg, A. Senyshyn, M. Hinterstein, H. Fuess
16. In Situ Diffraction Measurements: Challenges, Instrumentation, and Examples.
In E.J. Mittermeijer & U. Welzel (Eds)., Modern Diffraction Methods (528). Weinheim:
Wiley-VCH
[10] Epitaxial growth and control of the sodium content in NaxCoO2 thin films
Hildebrandt, S; Komissinskiy, P; Major, M; Donner, W; Alff, L
THIN SOLID FILMS Volume: 545 Pages: 291-295 DOI: 10.1016/j.tsf.2013.08.072
Published: OCT 31 2013
71
[11] Synthesis, structure and magnetic properties of Ni(II)-Co(II) heterodinuclear complexes
with ONNO type Schiff bases as ligands
Oz, S; Titis, J; Nazir, H; Atakol, O; Boca, R; Svoboda, I; Fuess, H
POLYHEDRON Volume: 59 Pages: 1-7 DOI: 10.1016/j.poly.2013.04.047 Published: AUG 1
2013
[12] Local structure, pseudosymmetry, and phase transitions in Na1/2Bi1/2TiO3K1/2Bi1/2TiO3 ceramics
Levin, I; Reaney, IM; Anton, EM; Jo, W; Rodel, J; Pokorny, J; Schmitt, LA; Kleebe, HJ;
Hinterstein, M; Jones, JL
PHYSICAL REVIEW B Volume: 87 Issue: 2 Article Number: 024113 DOI:
10.1103/PhysRevB.87.024113 Published: JAN 31 2013
72
A portable X-ray analysis chamber with in vacuo vertical transfer
Azza Amin, Herry Wedel, Michael Weber, Jochen Rank, and Wolfgang Donner
The x-ray diffraction analysis of reactive surfaces requires an Ultra High Vacuum (UHV)
environment and, at the same time, an x-ray transparent window. Furthermore, because of
space constraints on x-ray diffractometers, a UHV analysis chamber has to be lightweight,
compact and transferable. We designed and built a portable x-ray analysis chamber with a
hemispherical aluminum window. The sample holder can be moved vertically from the
transfer position to the measurement position using a dedicated in vacuo mechanism.
Fig. 1: Left: cross section of the UHV baby chamber in transfer position. The sample holder (dark green) is
transferred through the left CF-flange (yellow). Right: sample holder (dark green) in measurement position
inside the hemisperical window.
Figure 1 shows a cross section through the chamber: the black boxes represent the ion
getter pumps, which are battery-driven to facilitate transferabilty. The stainless steel body
ends with a CF100 flange that carries the x-ray window, mashined out of a solid piece of
high-strength Al alloy. Since the transfer of the sample holder from the growth chamber
takes place through the (yellow) CF38 flange on the left, the sample holder has to be lifted
into the x-ray window for measurements. In order to be in an eucentric position of the
diffractometer, the total height of the sample surface must not exceed 170 mm. This
prohibits the use of outside bellows or magnetic transfer rods for the vertical movement.
Instead, the vertical transfer has to be in vacuo. This design makes the chamber unique. A
stepper motor-driven worm drive takes the entire sample stage, including heater and
thermocouple contacts, on a 50 mm travel. All parts of the transfer mechanism are made of
UHV compatible materials and are therefore fully bakable.
Figure 2 shows an example of x-ray diffraction measurements made possible by the
chamber: a radial scan along the surface normal ([H0H]-direction) of a thin indium film on
tungsten. The film has been grown at a temperature of 130 K, annealed at 350 K, and then
transferred. Oscillations due to the finite thickness of the sample (Laue oscillations) are
visible on either side of the Bragg peak. A preliminary fitting reveals the thickness (24
monolayers) and the reason for the pronounced asymmetry of the Laue oscillations: the
coherent epitaxial growth leads to a strain gradient close to the film-substrate interface.
73
Fig. 2: Radial scan along the
[H 0 H] direction of a 24
monolayer
(6.7nm)
epitaxial
indium
W(001).
The
film
thin
on
asymmetric
Laue oscillations in the data
(circles) can be reproduced
assuming a model with a
vertical
gradient
in
the
lattice parameter (straight
line).
74
Materials Analysis
The Materials Analysis group participates in two of the five Research Clusters of the
Technische Universität Darmstadt: New Materials and Nuclear and Radiation Science. On the
one hand the group is concerned with the characterization of self-synthesized modern
materials, on the other hand with effects on materials caused by exposition to detrimental
influences like ion irradiation. The research aims for clarification of the correlation of
materials properties and synthesis or exposition parameters, respectively, by investigation
of the elemental composition and the chemical binding.
Current research topics are:
Advanced 3-D Nanoobjects: Nanochannels, -wires, -tubes, and –networks: In
collaboration with the GSI Helmholtz Centre for Heavy Ion Research, nanoporous
membranes are formed by ion irradiation of polymer foils producing latent ion damage
tracks which are chemically etched to nanochannels. These ion track (nano) filters can be
used for filtering particles from liquids, collecting aerosols, for gas separation, and for
analyzing small (bio)molecules. In the latter case, the nanochannel walls are chemically
modified so that the nanochannel sensor becomes sensitive and selective to certain
molecular species. Apart from polymer-based nanochannels, anodically oxidized aluminium
(AAO) is used. Filling the polymer or AAO nanochannels galvanically with metals, such as
copper, gold or platinum, and dissolving the templates, nanowires are formed. Here,
different metal deposition conditions are used in order to obtain monometal but also
multimetal (e.g. CuCo- and CuFe) nanowires.
By redox-chemical reactions, the nanochannel walls can be coated with metal or metal
oxide films, such as Ni, Cu, Ag, Au, Pt, Pd, and ZnO, SnO2, TiO2, In2O3, FexOy. Thus,
nanotubes can be formed. Here, different morphologies are available, ranging from smooth
compact nanotube walls to nanoporous walls to rough or peaked structures.
When the nanochannels are crossed, the resulting nanowires are interconnected, forming
nanowire networks. Dimensions, surface topography, microstructure, and crystallinity of
these nanostructures are investigated. Macroscopic properties such as thermal stability,
electrical conductivity and catalytic activity are analysed.
Additionally, the obtained properties are evaluated with respect to applications as sensors,
for gas flow or acceleration measurements, catalysts, for chemical reactions in
microreactors, or electrodes in fuel cells.
Thin film and coating deposition and analysis: In thin film and coating technology, the
identification of chemical compounds, phases and binding conditions is of basic
importance. Different methods are used for the formation of thin films (nanofilms), thick
films and coatings.
Surface modifications and layer deposition are performed via a plasma process. With
plasma immersion ion implantation (PIII) it is possible to alter several surface properties by
ion implantation. Different gaseous species are used such as oxygen, nitrogen and
hydrocarbons, depending on the property to be modified, e.g. hardness, wear resistance,
lifetime and biocompatibility. Using hydrocarbon gases films of diamond-like carbon (DLC)
are deposited. Research topics are the adhesion of the DLC films to different substrates and
the influence of the addition of different elements, especially metals, to the DLC films. The
films are investigated for their chemical and phase composition, microstructure, adhesion,
and in relation to biological applications, tribological properties, corrosion and wear
Institute of Materials Science - Materials Analysis
75
protection of metal substrates, wettability, and temperature stability. Since the PIII
technique is also suitable for complex shaped substrates, the treated substrates also include
samples such as tubes, where the focus in on the treatment of their inner surfaces.
Oxide films, such as lead-free piezoelectrics like sodium potassium niobate (NKN), are
prepared by the sol-gel technique combined with spin coating. The addition of NKN powder
to the films is investigated as a means to increase the film thickness.
Materials in radiation fields: Irradiation of materials with energetic particles (protons,
heavy ions) and electromagnetic radiation (X-rays, gamma-rays) may lead to degradation
of the materials’ properties. This happens to components in space vehicles, in nuclear
facilities and in particle accelerators. Polymers with their covalent bonds are particularly
sensitive towards ionizing radiation. Polyimide, vinyl polymers and fiber-reinforced
polyepoxides, which are components of superconducting beam guiding magnets at the
future FAIR synchrotron and storage rings, oxides such as alumina which are used as beamdiagnostic scintillator screens, and semiconductor components such as CCDs are irradiated
and characterized for their properties, such as polymeric network degradation, mechanical
strength, electrical resistance, dielectric strength, and optical properties. Apart from basic
questions on material’s degradation mechanisms by energetic radiation, the investigations
are used to estimate service life-times of the materials/components.
Staff Members
Head
Prof. Dr. Wolfgang Ensinger
Research Associates
Dr. Mubarak Ali
Dr. Adam G. Balogh
Dr. Stefan Flege
Dr. Ruriko Hatada
Dr. Peter Hoffmann
Dr. Falk Münch
Dr. Quoc Hung Nguyen
Technical Personnel
Renate Benz
Brunhilde Thybusch
PhD Students
Anton Belousov
Eva-Maria Felix
Umme Habiba Hossain
Martin Hottes
Renuka Krishnakumar
Stephan Lederer
Alice Lieberwirth
Vincent Lima
Saima Nasir
Cornelia Neetzel
Tim Seidl
Christian Stegmann
Sebastian Wiegand
Diploma and Master Alexandra Bobrich
Students
Nico Dams
Rene Fischer
Anja Habereder
Ulla Hauf
Nicolas Jansohn
Mario Klaric
Pejman Khamegir
Sandra Schäfer
Bachelor Students
Adjana Eils
Carolin Fritsch
Tim Hellmann
Christoph Kober
Jona Schuch
David Wieder
Guest Scientists
Prof. Dr. Takaomi Matsutani
Takehiko Matsuya
Evgenija Ermakova
76
Institute of Materials Science- Materials Analysis
Research Projects
Preparation of lead free piezo electric thin films (LOEWE centre AdRIA 2008–2014)
Simulations on the influence of swift ion irradiation on materials of FAIR-components (GSI,
2010–2013)
NanoC – Preparation, modification and characterization of nanochannels in polymer
membranes (Beilstein-Institut, 2009–2013)
NanoMag – Spin-dependent scattering in magnetic and Kondo nanowires (Beilstein-Institut,
jointly with Goethe Universität Frankfurt am Main, 2009–2013)
3-Dimensional micro-nano-integration for gas flow sensor technology (BMBF, 2011–2013,
jointly with Institut für Elektromechanische Konstruktionen, TU Darmstadt)
Electromechanical sensors with one-dimensional nano objects (BMBF, 2011–2013, jointly
with Institut für Elektromechanische Konstruktionen, TU Darmstadt)
Beam diagnosis and radiation damage diagnosis – Scintillator materials for high current
diagnosis (BMBF/GSI 2012–2015)
Beam diagnosis and radiation damage diagnosis – radiation damage of accelerator
components made out of plastics and countermeasures (BMBF/GSI 2012-2015)
New technologies for efficient solar energy systems (DFG, 2012–2013)
Investigation of technologically important nanostructured materials by high resolution ion
beam analysis (DLR, 2012-2013)
Publications
[1] F. Muench, M. Oezaslan, M. Rauber, S. Kaserer, A. Fuchs, E. Mankel, J. Brötz, C. Roth,
W. Ensinger;
Electroless Synthesis of Nanostructured Nickel and Nickel-Boron Tubes and their Performance
as Unsupported Ethanol Electrooxidation Catalysts,
[2] S. Wiegand, S. Flege, O. Baake, W. Ensinger;
Effect of different calcination temperatures and post annealing on the properties of 1,3
propanediol based Sol-Gel (Na0.5K0.5)NbO3 (NKN) thin films;
JOURNAL OF ALLOYS AND COMPOUNDS, 548 (2013) 38-45.
[3] F. Muench, A. Fuchs, E. Mankel, M. Rauber, S. Lauterbach, H.-J. Kleebe, W. Ensinger;
Synthesis of nanoparticle / ligand composite thin films by sequential ligand self assembly and
surface complex reduction;
JOURNAL OF COLLOID AND INTERFACE SCIENCE, 389 (2013) 23-30.
[4] K. Baba, R. Hatada, S. Flege, W. Ensinger, Y. Shibata, J. Nakashima, T. Sawase, T.
Morimura;
Preparation and antibacterial properties of Ag-containing diamond-like carbon films prepared
by a combination of magnetron sputtering and plasma source ion implantation;
VACUUM, 89 (2013) 179-184.
77
[5] W. Ensinger, E. Marin, L.Guzman;
Ion beam based composition and texture control of titanium nitride;
VACUUM 89 (2013) 229-232.
[6] B. Pollakowski, P. Hoffmann, M. Kosinova, O. Baake, V. Trunova, R. Unterumsberger,
W. Ensinger, B. Beckhoff;
Non-destructive and non-preparative chemical nanometrology of internal material interfaces at
tunable high information depths;
ANALYTICAL CHEMISTRY, 85 (2013) 193-200.
[7] S. Nasir, P. Ramirez, M. Ali, I. Ahmed, L. Fruk, S. Mafe, W. Ensinger;
Nernst-Planck model of photo-triggered, pH–tunable ionic transport through nanopores
functionalized with “caged” lysine chains;
JOURNAL OF CHEMICAL PHYSICS, 138 (2013) 034709.
[8] S. Wiegand, S. Flege, O. Baake, W. Ensinger;
Effect of Different Calcination Temperatures and Post Annealing on the Properties of Acetic
Acid Based Sol-Gel (Na0.5K0.5)NbO3 (NKN) Thin Films;
JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY, 29 (2013) 142-148.
[9] K. Drogowska, S. Flege, D. Rogalla, H.-W. Becker, E. Ionescu, N.-T.H. Kim-Ngan, A.G. Balogh;
Hydrogen content analysis in hydrogen-charged PZT ferroelectric ceramics;
SOLID STATE IONICS, 235 (2013) 32-35.
[10] M. N. Tahir, M. Ali, R. Andre, W. E. G. Müller, H. C. Schröder, W. Tremel, W. Ensinger;
Silicatein conjugation inside nanoconfined geometries through immobilized NTA–Ni(II)
chelates;
CHEMICAL COMMUNICATIONS 49, (2013) 2210-2212. DOI: 10.1039/C3CC38605H
[11] P. Ramirez, V. Gomez, M. Ali, W. Ensinger, S. Mafe;
Net currents obtained from zero-average potentials in single amphoteric nanopores;
ELECTROCHEMISTRY COMMUNICATIONS, 31 (2013) 137-140.
[12] A. A. Younis, W. Ensinger, M. M. B. El-Sabbah, R. Holze;
Corrosion protection of pure aluminium and aluminium alloy (AA7075) in salt solution with
silane-based sol–gel coatings;
MATERIALS AND CORROSION, 64 (2013) 276-283.
[12] W. Ensinger, S. Flege, R. Hatada, S. Ayata, T. Matsutani, K. Baba;
Hermetic Protection of Rings by Ion Beam Sputter Coating with a Broad Beam Ion Source and
a W-Shaped Hollow Sputter Target;
TRANSACTIONS OF THE MATERIALS RESEARCH SOCIETY OF JAPAN, 38 (2013) 97-100.
[13] M. Pavlovič, M. Miglierini, E. Mustafin, W. Ensinger, A. Šagátová, T. Seidl, M. Šoka;
Influence of xenon ion irradiation on magnetic susceptibility of soft-magnetic alloys;
Proceedings of the 19th International conference on APPLIED PHYSICS OF CONDENSED
MATTER (eds. J. Vajda, I. Jamnický), 2013, p. 78-81
[14] B. Lyson-Sypien, A. Czapla, M. Lubecka, E. Kusior, K. Zakrzewska, M. Radecka, A.
Kusior, A.G. Balogh, S. Lauterbach, H.-J. Kleebe;
Gas sensing properties of TiO2–SnO2 nanomaterials;
SENSORS AND ACTUATORS B: CHEMICAL, 187 (2013) 445–454.
78
[15] E. ElHaddad, W. Ensinger, C. Schüth;
Untersuchungen zur Sorptionsreversibilität von organischen Schadstoffen in Aktivkohle,
Holzkohle und Zeolith Y-200;
GRUNDWASSER, 18 (2013) 197-202.
[16] M. Ali, S. Nasir, I. Ahmed, L. Fruk, W. Ensinger;
Tuning nanopore surface polarity and rectification properties through enzymatic hydrolysis
inside nanoconfined geometries;
CHEMICAL COMMUNICATIONS, 49 (2013) 8770-8772.
[17] M. Ali, S. Nasir, P. Ramirez, J. Cervera, S. Mafe, W. Ensinger;
Carbohydrate-Mediated Biomolecular Recognition and Gating of Synthetic Ion Channels;
THE JOURNAL OF PHYSICAL CHEMISTRY C, 117 (2013) 18234-18242.
[18] S. Wiegand, S. Flege, W. Ensinger;
Comparison of the influence of titanium and chromium adhesion layers on the properties of
sol-gel derived NKN thin films;
JOURNAL OF SOL GEL SCIENCE AND TECHNOLOGY, 67 (2013) 654-659.
[19] Z. Tarnawski, Nhu-T. H. Kim-Ngan, K. Zakrzewska, K. Drogowska, A. Brudnik, A. G.
Balogh, R. Kužel, L. Havela, V. Sechovsky;
Hydrogen storage in Ti–TiO2 multilayers;
ADVANCES IN NATURAL SCIENCES: NANOSCIENCE AND NANOTECHNOLOGY, 4 (2013)
025004.
[20] A.A. Younis, W. Ensinger, R. Holze;
Impedance measurements at sol-gel based polysiloxane coatings on aluminium and its alloys;
in: LECTURE NOTES ON IMPEDANCE SPECTROSCOPY: Volume 4, 99-106, Ed. O. Kanoun,
CRC Press, 2013, ISBN 9781138001404.
[21] S. Quednau, F. Dassinger, M. Hottes, C. Stegmann, W. Ensinger, H.F. Schlaak;
Integration und Charakterisierung von Nanostrukturen in Mikrosysteme für sensorische
Anwendungen;
in: Proceedings: MIKROSYSTEMTECHNIK 2013, Eds. GMM, VDI/VDE-IT, ISBN 978-38007-3555-6.
[22] K. Drogowska, S. Flege, H.-W. Becker, Z. Tarnawski, K. Zakrzewska, A.G. Balogh
Physical properties of multilayer thin films of Ti-V and their hydrides studied by ion beam
analysis methods
in: Nanotechnology 2013: Advanced Materials, CNTs, Particles, Films and Composites
(Volume 1), p. 124-127, Ed. Nano Science and Technology, Institute, Crc PressI Llc, ISBN:
978-1-4822-0581-7.
79
Ag-containing Diamond-like carbon films deposited on the interior surface of a tube
R. Hatada, S. Flege, A. Bobrich, T. Matsutani, W. Ensinger
Adhesive Diamond-like carbon (DLC) films can be prepared by plasma immersion ion
implantation (PIII) which is also suitable for the treatment of 3D objects because it is a nonline of sight technique. The incorporation of a metal into the DLC film provides a possibility
to change the characteristics of the DLC film. For an improved biocompatibility Ag, Cu or
TiO2 nanoparticles can be added. One commonly used combination for this purpose is
simultaneous sputtering and hydrocarbon PIII. The properties of Ag-DLC films prepared by
silver magnetron sputtering and acetylene PIII were reported in refs. [1, 2].
If the coating is to be done on the inner surface of a tube, however, there is usually the
problem of an inhomogeneous distribution of the metal inside of the tube. There would be
a strong gradient of the metal concentration with increasing distance from the metal
source. Here, a different approach was developed. An auxiliary metal electrode along the
central axis of the tube is normally implemented to achieve a more homogeneous thickness
of the coating and to increase the energy of the plasma ions. This auxiliary electrode can be
used to provide metal ions, as well. Selecting a silver (or silver covered) electrode and
applying a negative DC voltage to it, sputtering of the electrode will occur which will then
distribute Ag particles inside of the tube.
So, a two step process was developed: in a first step a DLC film was deposited on the inside
of the tube. A negative high voltage pulser was connected to the tube, whereas the auxiliary
electrode was non-grounded. The latter was done to increase the plasma density within the
tube by directing the electrons towards the outside of the tube. In the second step the tube
was grounded and a negative DC voltage was applied to the auxiliary electrode. When the
plasma ions hit the electrode, they remove Ag atoms from the electrode which are then
incorporated into the DLC film. The composition of the plasma gas was also changed for the
second step, from a hydrocarbon gas to a mixture of argon and hydrocarbons.
Fig. 1: The two steps of the coating process, left: DLC deposition, right: Ag sputtering. AE: auxiliary electrode.
The resulting coating consists of a DLC film with Ag nanoparticles in its outer surface.
Earlier investigations [2] have shown that a few percent of Ag are already enough to
achieve an antibacterial effect.
The samples were characterized by secondary ion mass spectrometry depth profiling, X-ray
photoelectron and Raman spectroscopy and atomic force microscopy. The antibacterial
properties were checked by growth and survival tests of Staphylococcus aureus bacteria.
80
The silver concentration of the DLC films ranged from 0.6 to 6.6 at.% depending on the
chosen experimental conditions. Higher concentrations could be achieved using a higher
pressure during the deposition process. The sputtering time was between 1 and 2 hours for
the samples with the higher Ag concentrations.
The silver is mainly located in the top surface area of the samples. In depth profiles the Ag
intensity decreases slowly over the first 10 nm by about one order of magnitude. The slow
decrease is due to the agglomeration of the Ag into nanoscale silver crystals as can be seen
in TEM images [2] and due to the surface roughness of the samples.
According to AFM images the average surface roughness of a pure DLC sample is 0.4 nm.
The average surface roughness increases with Ag content up to 4.9 nm for the 6.6 at.% Ag
sample. This is due to the mentioned silver agglomeration but also because of roughening
caused by some sputtering of the DLC film during the second step of the process.
The ID/IG value of the samples from the Raman measurement changed only slightly and was
about 2.0.
The survival test of the S. aureus bacteria shows an obvious difference between a pure DLC
sample and one with 6.6 at.% Ag. While the sample on the left in Fig. 2 shows large areas
with surviving bacteria, the sample on the right does not show any sign of survived
bacteria. Here, the color is the indicator; the growing bacteria change the pH value of the
medium and thus cause a phenol red indicator to change its color.
Fig. 2: Results of the bacterial survival test. Left: pure DLC coating, right: DLC coating with 6.6 at.% Ag. The
brighter color on the left indicates bacterial growth.
It could be shown that it is possible to prepare DLC films containing silver on the inside of a
tube by the combination of plasma immersion ion implantation and DC sputtering of an
auxiliary electrode. Although the achievable Ag concentrations are only in the range of a
few atomic percent, this is sufficient to cause an antibacterial effect as demonstrated with S.
aureus bacteria.
References:
[1]
[2]
K. Baba, R. Hatada, S. Flege, W. Ensinger, Advances in Materials Science and Engineering, 2012
(2012), p. 536853.
K. Baba, R. Hatada, S. Flege, W. Ensinger, Y. Shibata, J. Nakashima, T. Sawase, T. Morimura, Vacuum,
89 (2013), pp. 179-184.
81
New activation processes for the electroless synthesis of metal nanotubes
Falk Münch, Wolfgang Ensinger
One focus of the materials analysis group is the fabrication of one-dimensional metal
nanomaterials such as nanotubes and nanowires by applying electroless plating to ion-track
etched templates. This class of metallization reactions can be categorized as autocatalytical,
surface-selective deposition from metastable solutions containing at least a metal complex
and a reducing agent [1]. In order to initiate the plating reaction on the substrate, its
surface usually has to be covered with metal nanoparticles which act as seeds for the metal
film nucleation. These substrate pre-treatments are called activation processes. The
synthesis of well-defined, complex metal nanomaterials is demanding concerning both the
quality of the plating and activation reactions [1].
In recent studies [2,3], we introduced a highly flexible and easily scalable process for the
activation of polymer substrates for consecutive electroless plating which is suitable for the
synthesis of metal nanomaterials. It is based on the absorption of a reducing agent by a
slightly swollen polymer substrate, followed by the precipitation of metal nanoparticles
(Fig. 1).
Fig. 1: Synthetic scheme of the new activation technique [2]. 1) In the presence of a suitable solvent or solvent
combination, the polymer substrate swells and absorbs a dissolved reducing agent (sensitization). 2) When the
sensitized substrate is brought into contact with metal salt solutions, nanoparticles precipitate on its surface
(activation). 3) Surface-conformal metal deposition is achieved by electroless plating. Copyright (2014)
Springer Publishing.
The outlined technique can be applied to polymers with significantly differing chemical
properties (e.g. ABS, PC, PET and PVA [3]) and allows to adjust the density, size and metal
type of the seeds [2,3]. Therefore, the substrate activity can be tailored for obtaining
optimum results in consecutive electroless depositions. Aside from a sufficient density of
82
small seeds, a high catalytic activity in the corresponding plating reaction proved to be
essential for the conformal metallization of challenging substrate morphologies with
nanoscale homogeneity [2,3]. The presented method is not restricted to the fabrication of
metal nanotubes (Fig. 2a,b), but can also be utilized for the preparation of two-dimensional
films (Fig. 2c) and the metallization of macroscopic work pieces (Fig. 2d).
Future studies aim to adopt the novel activation approach in the synthesis of well-defined,
mono- and multimetallic nanotubes for application in heterogeneous catalysis and sensing.
Fig. 2: a) SEM image of a field of free-standing copper nanotubes (the template was removed with
dichloromethane). b) Top-view of the nanotubes shown in a). c) SEM image of a silver film on ABS foil. d)
LEGO®-block electrolessly covered with silver. Copyright (2014) Elsevier B.V.
References:
[1]
[2]
[3]
F. Muench, S. Lauterbach, H.-J. Kleebe, W. Ensinger, Deposition of Nanofilms inside a Polymer Template:
Formation of Metal Nanotubes, E-J. SURF. SCI. NANOTECH. 10 (2012), 578-584.
F. Muench, S. Bohn, M. Rauber, T. Seidl, A. Radetinac, U. Kunz, S. Lauterbach, H.-J. Kleebe, C.
Trautmann, W. Ensinger, Polycarbonate activation for electroless plating by dimethylaminoborane
absorption and subsequent nanoparticle deposition, APPL. PHYS. A: MAT. SCI. PROCESS. 2014 (in
press), DOI: 10.1007/s00339-013-8119-z
F. Muench, A. Eils, M. E. Toimil-Molares, U. H. Hossain, A. Radetinac, C. Stegmann, U. Kunz, S.
Lauterbach, H.-J. Kleebe, W. Ensinger, Polymer activation by reducing agent absorption as a flexible tool
for the creation of metal films and nanostructures by electroless plating, SURF. COAT. TECHNOL. 2014
(in press), DOI: 10.1016/j.surfcoat.2014.01.024
83
Synthesis of oxidic copper and cobalt nanostructures of different morphologies
T. Matsutani, C. Neetzel, F. Muench, W. Ensinger
The investigation of bundled one-dimensional nanostructures by self-assembly methods can
be easily carried out by anisotropic crystal growth which is directly related to the crystal
structure. However, this process is limited to a few materials. In order to break the
symmetry of the crystal growth, nanowire synthesis can be driven by screw dislocation
where low precursor supersaturation and the presence of appropriate dislocation sources is
essential. [1]
In order to prepare morphology-controlled copper oxide/cobalt oxide heterostructures in
micro- and nanometer scale, we investigated two different synthesis routes that are related
to each other according to their mechanism but can be distinguished by their chemical
reaction route. However, in both cases a ligand is required to build strong complexes
resulting in low concentrations of free metal ions in the precursor solution. In the case of
copper and cobalt ions, we compared ammonia as well as tartrate.
The synthesis process via the ammonia route is accomplished with a three step route where
firstly a copper ammonia complex is generated, followed by a ligand exchange process
leading to the precipitation of copper hydroxide. By annealing, CuO is produced via
dehydratation.
Concentration ratios of the precursor solution as well as the resulting yields measured by
EDX are listed in Table 1. According to the yield composition, the turnover for copper oxide
is higher which can be explained by stronger copper ammonia complexes according to the
related complex stability constants.
Table 1: Composition and yield of CuO/Co3O4 heterostructures
Sample #
precursor
composition
Cu2+z1Co2+z2
yield
composition
CuO(x)Co3O4(y)
(1)
(2)
(3)
(4)
(5)
z1:z2 = 1:0
z1:z2 = 7:1
z1:z2 = 5:1
z1:z2 = 3:1
z1:z2 = 1:10
x:y = 1:0
x:y = 8.6:1
x:y = 6.9:1
x:y = 4.1:1
x:y = 1.2:10
Figure 1 depicts the resulting morphologies of samples (1) to (5). Pure copper oxide
deposition results in a network composed of needle-like structures with diameters of about
10 nm and lengths of 2 µm. With increasing Co3O4 and decreasing CuO content the
structure morphology changes from needle-like architectures to plate-formed shapes.
Obviously, the bundled network-like formation degenerates with decreasing copper content
in the precursor-solution which indicates that its concentration is crucial for the onedimensional growth process in aqueous solution under these conditions. Sample (5) shows
clearly identifiable thin plate structures of round shapes with diameters of approximately 5
µm. The reason for this observation can be explained by the crystal growth of the
intermediate cobalt hydroxide complex. Co(OH)2 consists of a layered structure where
neighboring layers are bound to each other by weak van der Waals forces. Thus, the (100)
plane is stable. [1]
84
For the fabrication of Cu2O nanostructures with low CoO contents in aqueous solution, we
applied the well-known Fehling’s reagent with -D-glucose as reducing and tartrate as
complexing agent. Tartrate generates a coordination complex with copper and cobalt metal
ions which on one hand decreases the concentration of the related free metal ions in the
solution and on the other hand prevents the undesirable precipitation of Co(OH) 2 and
Cu(OH)2. Additionally to the earlier procedure, the concentration of the reducing agent as
well as the concentration of copper and cobalt salts in the precursor solution is
indispensable. As listed in Table 2, the specific concentration of the Fehling and reducing
solution were varied in our experiments.
First, we synthesized pure Cu2O structures and varied the concentration of copper metal
ions in the precursor solution (samples (6) and (7)). As it is clearly recognizable (see
Figure 3(a) and 3(b)) needle-like structures can be obtained by adding a low concentration
(Table 2) of metal ions. An increasing amount of copper(II)ions already causes the
formation of particles with diameters of about 250 nm. Therefore, we kept the
concentration of the Cu2+ precursor constant and varied the concentration of cobalt ions in
order test the morphology influence of this species in a heterostructural precipitation. By
adding 1:1 = Cu2+:Co2+ (sample (8)) we observed cubic like structures with uniform
lateral edges of 100 nm as shown in Fig. 3. EDX as well as XRD measurements (not shown
here) confirm the precipitation of both cobalt and copper oxidic structures.
Table 2: Composition of initial Cu2+ and Co2+ for Fehling's reaction
Sample #
CuSO4.5H2O
[mol/L]
CoSO4.7H2O
[mol/L]
Na2C4H4O6
[mol/L]
(6)
(7)
(8)
(9)
0.004
0.006
0.004
0.004
-
-
0.004
0.0004
0.005
0.007
0.009
0.005
We expected to obtain structural analogies to sample (7) by keeping the concentration of
copper precursor ions constant and adding a 1:0.1 quantity of cobalt ions (sample (9)).
However, SEM investigations show that the morphology seems to be different (Fig. 3(d)).
Particles with diameters of approximately 50 nm agglomerate together at certain positions
resulting in a crossed one-dimensional growth in each direction. Thus, branched networks
could be obtained. The reason for these occurrences could be that -D-glucose acts as
surfactant and promotes the growth in a certain direction as it also described in the
literature. [2] On the other hand, such morphologies were not obtained for sample (7);
therefore, the addition of cobalt ions leads to a drastic change of the structural material
architecture.
However, this synthesis route seems to be more sensitive towards small changes of
concentration in the precursor solution. Moreover, the influence of the reducing material
should be considered accurately for further investigations.
The results indicate that, dependent on the precursor concentration of copper and cobalt
ions, it is possible to prepare morphology controlled heterostructures in a reproducible way.
Further investigations will be carried out for the fabrication of needle-like structures with
high Co3O4 contents.
85
Fig. 1: CuO/Co3O4 heterostructures
of different ratios: (a) sample (1),
(b) sample (2), (c) sample (3), (d)
sample (4)
Fig. 2: CuO/Co3O4
sample (5)
nanoplates:
Fig. 3: CuO nanoneedles obtained
by precipitation of Cu(OH)2 and
annealing
References:
[1]
[2]
86
Y. Li, Y. Wu, Chem. Mater. 2010, 22, 5537-5542.
G. Filipic, U Cvelbar, Nanotechnol., 2012, 23, 1-16
Materials Modelling Division
The research of the Materials Modelling Division is focused on multi-physics modelling of
defect structures in functional oxides, metallic nanoalloys and energy materials. We are
combining electronic structure calculations with atomistic modelling methods and
continuum descriptions depending on time and length scales involved.
Quantum mechanical calculations based on density functional theory are used for electronic
structure calculations. Large-scale molecular dynamics with analytical interatomic
potentials are the method of choice for studying kinetic processes and plastic deformation.
Kinetic lattice Monte-Carlo simulations are extensively used for simulations of diffusional
and transport processes on extended time scales. The group is operating several HPCcomputers and has access to the Hessian High Performance Computers in Frankfurt and
Darmstadt.
The current research topics are:
 Functional oxides
o New lead-free ferroelectrics: Ordering effects and defects
o Defects and diffusion in TCOs
o Finite-size effects in oxide nanoparticles
 Nanoalloys
o Plasticity of nanocrystalline metals and bulk metallic glasses
o Metallic nanoglasses
o Nanophase diagrams
o Metallic nanoparticles under nanoextrusion
 Energy materials
o Interfaces in Li-intercalation batteries
o Defects in CIS/CIGS absorber materials
o High-pressure phases of nitrogen
o Interfaces in Superalloys (Mo-Si-B)
Within the bachelor program the Materials Modelling Division is offering classes on
thermodynamics and kinetics as well as defects in materials. Lectures and lab classes on
simulation methods and programming techniques are offered as elective courses in both,
the bachelor and master program.
Institute of Materials Science - Materials Modelling Division
87
Staff Members
Head
Prof. Dr. Karsten Albe
Emeritus Professor
Prof. Dr. Hermann Rauh, M.A., C.Phys., F.Inst.P., F.I.M.
Secretary
Renate Hernichel
Research Associates
PD Dr. Yuri Genenko
Dr. Galina Yampolskya
Dr. Sergey Yampolskii
Dr. Alexander Stukowski
Dr. Jochen Rohrer
Dr. Omar Adjaoud
Dr. Uma Maheswari Sankara Subbiah
Dr. Marc Radu
Dr. Sabrina Sicolo
Scientific
Employees
PhD Students
M.Sc. Heide Humburg
Master Students
Konstanze Kalcher, Markus Mock
Bachelor Student
Leonie Koch
Research Fellow
Dr. Guang-Tong Ma (AvH)
Dipl.-Phys. Johan Pohl
Dipl.-Ing. Jonathan Schäfer
Dipl.-Ing. Manuel Diehm
Dipl.-Ing Melanie Gröting
Dipl.-Ing. Jonathan Schäfer
Dipl.-Ing. Arno Fey
Dipl.-Ing. Kai Meyer
Dipl.-Ing. Tobias Brink
M.Sc. Olena Lenchuk
M.Sc. Nam Ngo
Research Projects
Mikrostruktur und Stabilität von Nanogläsern (DFG AL 578/6-2)
Quantenmechanische Computersimulationen zur Elektronen- und Defektstruktur oxidischer
Materialien (SFB 595, Teilprojekt C1, 2007-2014)
Atomistische Computersimulationen von Defekten und deren Bewegung in Metalloxiden
(SFB 585, Teilprojekt C2, 2003-2014)
88
Phänomenologische Modellierung von Injektion, Transport und Rekombination in
Bauelementen aus organischen Halbleitern sowie aus nichtorganischen Ferroelektrika (SFB
C5, 2003-2014)
Erforschung der Phasenstabilität und Niederdrucksynthese von festem Stickstoff mittels
atomistischer Computersimulationen und Experimenten (DFG AL 578/3-2, 2010–2014))
Beyond Ni-Base Superalloys: Atomistische Modellierung des Einflusses von
Legierungszusätzen auf die Korngrenzeigenschaften in Mo-Si-B und Co-Re Superlegierungen (DFG Forschergruppe 727, AL 578/9-1, 2010–2013)
Nanosilicon dispersed in SiCN(O) and SiCO-based ceramic matrices derived from
preceramic polymers: new composite anode materials for lithium ion batteries.
(DFG SPP 1473 „Wendelib“, DFG AL 578/10-1, 2011–2013)
Mechanische und kinetische Eigenschaften metallischer
Sekundärphasen (DFG AL578/13-1, 2011–2013)
Gläser
mit
nanoskaligen
Bleifreie Piezokeramiken, LOEWE-Schwerpunkt ADRIA (HMWK, 2011-2014)
PPP Finnland, Atomic level simulations of structure and growth of nanoalloys
(DAAD 2011–2013)
Topological Engineering of Ultra-Strong Glasses (DFG AL 578/15-1, 2012-2014)
Modeling the electrocaloric effect in lead-free relaxor ferroelectrics: A combined atomisticcontinuum approach (DFG AL 578/16-1, 2012-2014)
HZB-Helmholtz Zentrum Berlin, Virtuelles Institut (HZB VH-VI-520 2012-2017)
Publications
K. Albe, Y. Ritter and D. Şopu, 'Enhancing the plasticity of metallic glasses: Shear band
formation, nanocomposites and nanoglasses investigated by molecular dynamics
simulations', Mechanics of Materials 67, 94 (2013)
H. Rauh and G. T. Ma, 'Hysteretic ac loss of a superconductor strip subject to an oscillating
transverse magnetic field: Geometrical and electromagnetic effects', J. Appl. Phys. 114,
193902 (2013)
S. Zhukov, Y. A. Genenko, M. Acosta, H. Humburg, W. Jo, J. Rödel, H. von Seggern, Heinz,
Polarization dynamics across the morphotropic phase boundary in Ba(Zr0.2 Ti0.8)O3x(Ba0.7Ca0.3)TiO3 ferroelectrics', Appl. Phys. Lett. 103, 152904 (2013)
A. Kobler, J. Lohmiller, J. Schäfer, M. Kerber, A. Castrup, A. Kashiwar, P. A. Gruber, K.
Albe, H. Hahn, C. Kübel, 'Deformation-induced grain growth and twinning in
nanocrystalline palladium thin films', Beilstein J. Nanotechnol. 4, 554 (2013)
89
J. Schäfer and K. Albe, 'Plasticity of nanocrystalline alloys with chemical order: on the
strength and ductility of nanocrystalline Ni–Fe', Beilstein J. Nanotechnol. 4, 542 (2013)
Y. A. Genenko, J. Wehner and H. von Seggern, 'Self-consistent model of polarization
switching kinetics in disordered ferroelectrics', J. Appl. Phys. 114, 084101 (2013)
G. T. Ma and H. Rauh, 'Thermo-electromagnetic properties of a magnetically shielded
superconductor strip: theoretical foundations and numerical simulations', Supercond. Sci.
Technol. 26,105001 (2013)
J. Rohrer and K. Albe, 'Insights into Degradation of Si Anodes from First-Principle
Calculations', J. Phys. Chem. C 117, 18796 (2013)
S. Goel, A. Stukowski, X. Luo, A. Agrawal and R. L. Reuben, 'Anisotropy of single-crystal
3C–SiC during nanometric cutting', Modelling Simul. Mater. Sci. Eng. 21, 065004 (2013)
P. Erhart, P. Träskelin and K. Albe, 'Formation and switching of defect dipoles in acceptordoped lead titanate: A kinetic model based on first-principles calculations', Phys. Rev. B 88,
024107 (2013)
K. Nonnenmacher, H.-J. Kleebe, J. Rohrer, E. Ionescu, R. Riedel and G. Soraru, 'Carbon
Mobility in SiOC/HfO2Ceramic Nanocomposites', J. Amer. Ceram. Soc. 96, 2058 (2013)
J. Pohl and K. Albe, 'Intrinsic point defects in CuInSe2 and CuGaSe2 as seen via screenedexchange hybrid density functional theory', Phys. Rev. B 87, 245203 (2013)
K. A. Avchaciov, Y. Ritter, F. Djurabekova, K. Nordlund and K. Albe, 'Controlled softening of
Cu64Zr36 metallic glass by ion irradiation', Appl. Phys. Lett. 102, 181910 (2013)
A. Tolvanen and K. Albe, 'Plasticity of Cu nanoparticles: Dislocation-dendrite-induced strain
hardening and a limit for displacive plasticity', Beilstein J. Nanotechnol. 4, 173 (2013)
H. S. Ruiz, A. Badia-Majos, Y. A. Genenko and S. V. Yampolskii, 'Strong Localization of the
Density of Power Losses in Type-II Superconducting Wires', IEEE Trans. Appl. Superconduct.
23, 8000404 (2013)
S. Li, J. Morasch, A. Klein, C. Chirila, L. Pintilie, L. Jia, K. Ellmer, M. Naderer, K.
Reichmann, M. Gröting, and K. Albe, 'Influence of orbital contributions to the valence band
alignment of Bi2O3, Fe2O3, BiFeO3, and Bi0.5Na0.5TiO3', Phys. Rev. B 88, 045428 (2013)
Proceedings
W. Witte, M. Powalla, D. Hariskos, A. Eicke, M. Botros, H.-W. Schock, A. Abou-Ras, R.
Mainz, H. Rodríguez-Alvarez, T. Unold, G. H. Bauer, R. Brüggemann, S. J. Heise, O.
Neumann, M. Meessen, J. Christen, F. Bertram, A. Klein, T. Adler, K. Albe, J. Pohl, M.
Martin, R. A. De Souza, L. Nagarajan, T. Beckers, C. Boit, J. Dietrich, M. Hetterich, Z.
Zhang, R. Scheer, H. Kempa and T. Orgis, 'Chemical Gradients in Cu(In,Ga)(S,Se)2 ThinFilm Solar Cells: Results of the GRACIS Project', In: 27th European Photovoltaic Solar
Energy Conference and Exhibition, Frankfurt am Main. EU PVSEC Proceedings (2013).
90
Degradation of Si anodes studied with first-priniciple methods
Jochen Rohrer and Karsten Albe
Silicon is considered as promising anode material for Li-ion batteries [1]. However, despite
its high mass-specific capacity, which is approximately ten times larger than that of
commercially used graphitic anodes, Si undergoes rapid degradation. The details of this
degradation are complex. However, roughly we can distinguish two failure modes. The first
is related to the consumption of electrolyte and a build up of a thick solid-electrolyte
interphase. The second is related to internal degradation of Si itself by means of cracking
and pulverization. Here [2] we focus on internal degradation.
We use density-function-theory calculations to study the structure and thermodynamics of
amorphous LixSi (x representing the ratio of Li to Si) that forms during Li intercalation and
deintercalation. Our calculations predict the existence of critical two-phase regions during
initial lithiation and initial delithiation. Within two-phase regions, large local and
inhomogeneous volume changes may lead to crack initiation. We also point out, how these
two-phase regions can be avoided and degradation due to internal cracking is minimized.
Fig. 1: Iterative replica scheme to generate
amorphous Li-Si model structures.
Figure 1 illustrates our protocol used to
generate model structures of amorphous LixSi
with varying Li content. Starting from a pure
crystalline Si model consisting 64 atom, LixSi
models with increasing Li content x are
generated using an iterative replica scheme. In
each step, five replica of the current LixSi model
are created and in each of the replica, eight Li
atoms are inserted to construct candidate
structures of Lix’Si. Each candidate structure is
then subjected to an equilibration run using ab
initio molecular-dynamics simulations at 700 K.
The equilibrated systems are finally fully
optimized and the lowest-energy system is
chosen as Lix’Si model for the current Li
concentration. The procedure is iterated up to a
concentration of x=4.75. Deintercalcation is
modeled accordingly by removing Li.
In Figure 2 we show calculated formation energies of Li-Si alloys as a function of the Li
content x. The left panel focuses on intercalation in crystalline Si. In agreement with hightemperature experiments [3], Li4.4Si is identified as global minimum. Initially, at low Li
content, a phase separation into crystalline Si and amorphous Li2.0Si is thermodynamically
favorable. Within this two-phase region, local inhomogeneous volume changes of +130%
take place and crack initiation can be expected. For x>2, a homogeneous one-phase region
is predicted and cracking is suppressed. At to x=3.625, we find a saddle point and further
intercalation again leads to a two-phase region where amorphous Li3.625Si and Li4.4Si
coexist. At the saddle point, the thermodynamic driving force for further intercalation
vanishes. This might be interpreted as a potential reason for crystallization of Li15Si4, which
is typically observed at room temperature [4].
91
Fig. 2: Structure and formation energies of amorphous LixSi model systems.
The right panel of Figure 2 focuses on delithiation. For a maximum Li content of x>3.75,
initial delithiation leads to two-phase regions (either Li4.4Si/Li3.625Si or Li15Si4/Li2.0Si).
Within these two-phase regions, there are again large inhomogeneous volume changes for
which crack formation can be expected; -15% in the former or -40% in the latter two-phase
region. At lower Li contents, a homogeneous one-phase region is predicted and full
delithiation leads to amorphous Si. Reinsertion into amorphous Si then proceeds
homogeneously and essentially without crack formation. From x=3.625 on, amorphous Si
behaves similar to crystalline Si.
In summary, our calculations identify various two-phase regions occurring during Li
intercalation or deintercalation in Si anodes. During corresponding phase conversion, large
local and inhomogeneous volume changes may initiate cracks which subsequently lead to
degradation due to particle fracturing. In amorphous Si, two-phase regions occur only
during delithiation and only if the Li content is larger than x=3.75. Thus, limiting the Li
content well below this critical value leads to homogeneous volume expansion and
contraction and minimizes internal particle fracture. As a consequence, capacity limited
cycling of amorphous Si anodes [5] leads to significantly enhanced cycling stability.
References:
[1]
[2]
[3]
[4]
[5]
92
U. Kasavajjula, C. Wang and J. A. Appleby, J. Power Sources 163, 1003(2007).
J. Rohrer and K. Albe, J. Phys. Chem. C 117, 18796 (2013).
R. A Sharma and R. N. Seefurth, J. Electrochem Soc. 123, 1763 (1976).
M. N. Obrovac and L. Christensen, Solid-State Lett. 7, A93 (2004).
A. Magasinski et al., Nat. Mater. 9, 353 (2010).
Low Temperature Heat Capacity of a Severely Deformed Metallic Glass
Jonas Bünz, Tobias Brink, Koichi Tsuchiya, Fanqiang Meng, Gerhard Wilde, Karsten Albe
Metallic glasses show distinct mechanical, electrical, and magnetical properties from their
crystalline counterparts. Like all glassy materials, they show a low-frequency peak in the
vibrational spectrum in excess of the Debye law and the spectrum of crystals. This so-called
boson peak is due to quasi-localized transverse vibrational modes associated with
“defective” soft local structures in the glass.[1-4] The boson peak, situated in the terahertz
region of the vibrational spectrum, also leads to an excess contribution to the lowtemperature heat capacity. This becomes visible by plotting the heat capacity c devided by
T3, so that the Debye T3-law reduces to a constant. Several different models for the
structural origin of the boson peak have been proposed but they all agree that its origins
are related to decreased elastic constants in spatially distributed regions. Plastic
deformation in metallic glasses is localized in structurally disturbed regions called shear
bands. The shear bands are therefore expected to influence the boson peak.
To analyze this contribution of the shear bands, we performed heat capacity measurements
on Zr50Cu40Al10 metallic glass. The glass was deformed under hydrostatic pressure torsion,
which produces a large volume
of regions with
structural
changes that can be considered a
“macroscopic shear band”.[5]
Heat capacity measurements
were
performed
using
differential scanning calorimetry
at low temperatures before and
after deformation. In addition,
the undeformed and deformed
samples were annealed and heat
capacity was measured again.
The results are shown in Figure
1a. The boson peak of the as-cast
glass does not significantly
change upon annealing. The
deformation-induced boson-peak
is increased over the as-cast state
and
reduces
again
with
annealing. If the annealing
temperature is high enough, the
boson peak will even reduce
below the as-cast state. X-ray
diffraction measurements show
no detectable crystallization.
To elucidate the exact origins of
the change in heat capacity, we
Fig. 1 Difference in heat capacity between glass and crystal. a)
conducted molecular dynamics Experimental data, annealing below 393 K was done for 7 days,
simulations on a deformed annealing at 743 K for 10 s. b) Simulation data, dashed lines are
sample of Cu64Zr36 metallic glass. data from shear bands, solid lines from the matrix.
93
We identified atoms belonging to
the shear band using the von
Mises local shear invariant η as
implemented in OVITO.[6] We
marked atoms with η > 0.2 as
belonging to the shear band and
all others as the matrix. The
phonon density of states (PDOS)
was calculated[7] separately for
shear band and matrix and is
shown in Figure 2. Using the
harmonic approximation of the
free energy, we calculated the
heat capacity from the PDOS as Fig. 2 Phonon density of states from computer simulation.
shown in Figure 1b. Solid lines in Dashed lines are data from shear bands, solid lines from the
these graphs represent data from matrix.
the matrix. Our results show that
the boson peak of the matrix stays unchanged during deformation and annealing. All
changes result from the shear band, represented by dashed lines. Upon deformation the
boson peak increases as in the experiment. Subsequent annealing relaxes the shear bands
again to a state with reduced boson peak. The simulations do not show a reduction of the
boson peak below the as-cast state. The reason is that the shear bands do not fully relax in
the computationally accessible time (40 ns in our simulations). To confirm a possible
transition to a state similar to the experiment, a much longer time scale would be needed.
All in all our findings clearly show the shear bands to be the origin of the deformationinduced boson peak, while the matrix stays intact during all processing. The experiment
supports this perspective as the change of the boson peak height for the undeformed
sample is minimal during annealing. Several studies find healing of shear bands under
annealing even at temperatures well below Tg.[8-10] In contrast, our measurements indicate
that the structure of the annealed shear band differs from the initial as-cast state. Diffusion
studies show accelerated diffusion constants in shear bands, which could promote
structural relaxation in these regions. The boson peak is an excess over the ordered state,
therefore the results of decreasing boson peak suggest short or medium range ordering.
Even beginning crystallization on the nanoscale is conceivable, as this would not be
detectable using X-ray diffraction.
References:
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
94
S. N. Taraskin et al., Phys. Rev. Lett. 86, 1255 (2001)
H. Shintani and H. Tanaka, Nat. Mater. 7, 870 (2008)
H. R. Schober, J. Non-Cryst. Solids 357, 501 (2011)
A. I. Chumakov et al., Phys. Rev. Lett. 106, 225501 (2011)
F. Meng et al., Appl. Phys. Lett. 101, 121914 (2012)
A. Stukowski, Modelling Simul. Mater. Sci. Eng. 18, 015012 (2010)
J. M. Dickey and A. Paskin, Phys. Rev. 188, 1407 (1969)
W. H. Jiang et al., Acta Mater. 53, 3469 (2005)
S. Xie and E. P. George, Acta Mater. 56, 5202 (2008)
Y. Ritter and K. Albe, Acta Mater. 59, 7082 (2011)
Hysteretic ac loss of a superconductor strip
subject to an oscillating transverse magnetic field
H. Rauh1 and G.T. Ma1,2
1
Institute of Materials Science, Darmstadt University of Technology, 64287 Darmstadt
2
Applied Superconductivity Laboratory, Southwest Jiaotong University, 610031 Chengdu
Thin type-II superconductor strips, plates and tapes have lately become the focus of much
attention in scientific and engineering research, since they are deemed promising elements
for both large-scale power and microelectronic device applications. It is not surprising
therefore that their response to imposed ac transport currents and applied ac magnetic
fields, or both, has been studied intensively. One of the most important characteristics
regarding their use is the hysteretic ac loss caused by excitations of the named sort. Applied
ac magnetic fields – our concern here – have been addressed in analytical calculations as
well as numerical analysis. Selected aspects for superconductor strips thereby include, e.g.,
the effects of demagnetization fields or those of external magnetic shields. However
fundamental these investigations may be, a systematic examination of geometrical and
electromagnetic effects owing to the superconductor strips themselves does not seem to
have come forth yet.
An obvious approximation at hand is the limit of infinitesimally thin superconductor strips,
ignoring variations of the induced current and the electromagnetic field across the
thickness of the strips. This ansatz has frequently been taken as a basis for theoretical
explorations and, particularly, invoked for estimating the hysteretic ac loss; it has the
distinct advantage of getting along with the concept of sheet current which allows
representations in mathematically comprehensible forms. Such an approach needs
justifying though by establishing its range of validity in tests against models that contain
surplus traits. Assessments of the influence on the hysteretic ac loss of the width/thickness
aspect ratio of a superconductor strip, with an ac transport current imposed, already exist.
We aim at similar investigations for a superconductor strip, with an ac magnetic field
applied, which crucially rely on an adequate characterization of the strip. Like on a
different occasion before, we go back to a ‘smoothed’ Bean model of the critical state made
up of a current-field relation derived from experiment. We confine ourselves to a purely
electromagnetic account, without coupling to a thermal field; that is, the environment of
the superconductor strip – in practice pervaded by a cooling liquid – is simply treated as a
vacuum. Such a course has proven to yield very accurate results even at high amplitudes of
the applied magnetic field.
To appraise geometrical and electromagnetic effects on the distributions of the magnetic
induction, the electric field, the current density, the power loss density inside the
superconductor strip, and whence on the hysteretic ac loss suffered by the superconductor
strip due to the presence of an oscillating transverse magnetic field, numerical simulations
were carried out, understanding that the strip is made of an yttrium-barium cuprate and
operated at the liquid nitrogen temperature of 77 K. We choose geometrical and materials
data that second-generation superconductors typically display. Proceeding from a
superconductor rod with quadratic cross section, i.e. a degenerate shape of the
superconductor strip for which the width/thickness aspect ratio e  2w d equals unity, we
studied the evolution of the above properties when the thickness of the strip d was

95


reduced, while the width 2w was kept fixed, such that the aspect ratio followed the
geometric progression e  1, 10, 100, 1000. In this procedure, the critical current density at
operating temperature/zero field was adjusted according to jc0  eI c0 4w2 with the total
critical current I c0 ,emulating its dependence on the thickness of the superconductor strip
as compared 
to a superconductor bulk. Some of our numerical evaluations are shown
graphically below.


Fig. 1 portrays the distribution of the magnetic induction B inside the superconductor strip
for different values of the amplitude of the applied magnetic field H a in the
electromagnetic steady state. Generally, this distribution reveals symmetry about the two
mirror planes of the superconductor strip. For thelowest amplitude of the applied magnetic
field, H a  1 A mm , the magnetic induction B is essentially confined 
to the marginal parts
of the strip, leaving most of its interior free of magnetic flux; the spatial localization and the
strength of the magnetic induction B near the edges of the strip build up when the aspect
ratio e augments. For the slightlyincreased amplitude of the applied magnetic field,

H a  5 A mm , the penetration of the magnetic field into the interior of the strip already
becomes tangible, giving rise
 to a pronounced inhomogeneous distribution of the magnetic
induction B throughout the strip; the spatial localization and the strength of the magnetic
 induction B near the edges of the strip again build up when the aspect ratio e augments.
For the highest amplitude of the applied magnetic field, H a  500 A mm , penetration of the
magnetic
field into the interior of the strip is developed to the full, bringing about a

virtually
homogeneous
profile of the magnetic induction B across the thickness of the strip

 the amplitude of the
as the aspect ratio e augments. Concisely and overall, an increase of

applied magnetic field H a eventually gives rise to complete filling of the strip with
magnetic flux, while the variations of the magnetic
induction B in the direction of the

applied magnetic field die away as the thickness of the strip abates.



Fig. 1: Distribution of the magnetic induction B (unit T ) inside a superconductor strip in the electromagnetic
steady state, calculated at maximum strength of an applied transverse magnetic field with amplitude
H a  1 A mm (top), H a  5 A mm (centre) and H a  500 A mm (bottom), assuming the values of the aspect
ratio e  1 , 10, 100, 1000. The scale of
of the strip is enlarged by the respective factor e in each
the thickness

case.

 96


Institute of Materials Science - MaterialsModelling Division

Fig. 2 illustrates the dependence of the normalized hysteretic ac loss U ac H a2 on H a H c ,
the normalized amplitude of the magnetic field applied to the superconductor strip in the
electromagnetic steady state, addressing a series of values of the aspect ratio e , together
with the prediction for the limiting case of an infinitesimally thin strip in the Bean model of
 field H 
the critical state. This introduces the characteristic magnetic
c , which may be
expressed as H c  I c0 2w , remembering the definition of the critical sheet current of such
 and materials data
a strip, and thus takes on the value H c  8 A mm from the geometrical
implied. A general trait revealed for whichever choice of the aspect
ratio e is that, starting

fromthe smallest value of the normalized amplitude of the applied magnetic field H a H c ,
a monotonic rise of the normalized
hysteretic ac loss U ac H a2 towards a maximum occurs,

followed by an asymptotically converging descent, as H a H c augments. Whereas the

geometrical effect controlled by the aspect ratio e is minute at large values
 of H a H c , it
becomes prominent at low values of H a H c where the normalized hysteretic ac loss

U ac H a2 abates rapidly, with a waning gradient, 
as the aspect ratio e augments. The Bean
model of the critical state adapted to an infinitesimally thin strip, often used
 for convenient

mathematical analysis neglecting
variations
of
electromagnetic
observables
(like the

magnetic induction or the current density) across the thickness of the strip, obviously
underestimates the normalized hysteretic ac loss U ac H a2at low and moderate values of
2
H a H c , but overestimates, or at least conserves, the normalized hysteretic ac loss U ac H a
at large values of H a H c .




Fig. 2: Normalized hysteretic ac loss U ac H a2 suffered by a superconductor strip as a function of the
normalized amplitude H a H c of the applied transverse magnetic field in the electromagnetic steady state,
assuming the values of the aspect ratio e  1 , 10, 100, 1000. The analytical result of an infinitesimally thin strip
in the Bean model of the criticalstate (dashed lines) is shown for comparison.

In conclusion, a theoretical
 approach with simultaneous regard of finite-geometrical aspects
and electromagnetic traits is called for if the hysteretic ac loss suffered by the
superconductor strip is to be reliably addressed. This is especially true in the range of low
and moderate amplitudes of the applied magnetic field, where ascertainments based on
Bean’s model of the critical state adapted to an infinitesimally thin strip yield clear
underestimates of the said observable. On the other hand, this limit seems sufficient for
determining the hysteretic ac loss at high amplitudes of the applied magnetic field –
irrespective of the real value of the aspect ratio of the strip – if only the field dependence of
the induced current is taken into account.
97
Materials for Renewable Energies
Research in the Renewable Energies group focuses on electrochemical energy technologies,
such as fuel cells and batteries. Novel catalysts, electrodes and electrode processing
techniques are being developed, but also sophisticated methods for their in-situ
characterization. Systematic structural and electrochemical characterization of the new
materials is carried out in order to unravel the structure-properties correlation. Techniques
used for structure analysis include X-ray absorption spectroscopy (XAS), transmission
electron microscopy (TEM), and X-ray diffraction (XRD), whereas the electrocatalytic
performance is tested in both model experiments and under realistic operation conditions.
The group’s recent scientific activities can be divided into the following three areas:

New catalyst concepts
Our main focus is on the design of alternative support materials for fuel cells, which do not
suffer from corrosion in the severe operation conditions and may be promising candidates
to replace the standard carbon support. Different morphologies, e.g. fibres or hollow
spheres, contribute to an improved control in 3D electrode design and thus allow for an
efficient mass transport. Furthermore, shape-selected nanoparticles exposing highly active
crystal facets are being investigated and indicate improved electrocatalytic activities.

Functional electrode design
Beyond the conventional preparation techniques, advanced layer-by-layer (LbL) techniques
are used in the fabrication of fuel cell electrodes allowing for a well-defined 3D
architecture. A likewise promising approach, which also offers high flexibility and a facile
up-scaling, is the electrospinning technique. Thin fibres with solid, porous, but also coreshell structure can be spun and deposited as an arbitrary mesh or in an aligned fashion.
These structures have been used as electrodes in both fuel cells and batteries. Electron
microscopy is applied for the electrodes’ detailed characterization. For this specific purpose,
new techniques have been developed and established in the group, as for instance the
focused ion beam (FIB) technique in cooperation with the HZB, Berlin. FIB/SEM was
applied to obtain 3D reconstructions of the porous fuel cell electrodes before and after
operation as well as for comparison of the different electrode processing techniques.

In situ studies
In situ and operando X-ray absorption studies play an important role in our activities with
respect to the systematic investigation of reaction and degradation mechanisms. A versatile
in situ sample environment has been designed and successfully implemented at various
synchrotron facilities. It enables the spatial and time resolved study of different areas of the
fuel cell electrodes in various operation conditions (direct methanol, direct ethanol
operation, but also for intermediate temperature PBI fuel cell studies). In addition to the
98
Institute of Materials Science - Materials for Renewable Energies
conventional EXAFS analysis the novel delta µ XANES technique is applied in cooperation
with Prof. David Ramaker, George Washington University. This technique enables us to
study adsorbates attached to the active catalyst surface, so that reaction mechanisms can be
followed directly during operation. The results provide important insights, which will help
to further catalyst optimization. In 2012, the delta µ XANES technique has been applied to
intermediate temperature PBI fuel cells. At the cathode side, the adsorption of phosphoric
acid species could be followed temperature and potential dependent. The effect of anode
humidification on CO poisoning at different temperatures was also studied, and the
importance of water being present at the anode side underlined.
In July 2012, Prof. Christina Roth was appointed full professor at the FU Berlin and now
heads the group Applied Physical Chemistry.
Financial support is provided by DFG, BMWi, BMBF, and EU as well as by the respective
synchrotron facilities and industrial partners.
Staff Members
Head
Prof. Christina Roth
Secretary
Maria Bense (joint with Prof. Donner and Prof. Xu)
PHD students
Dipl.-Ing. (FH) Hanno Butsch
Dipl.-Ing. Benedikt Peter
Dipl.-Ing. André Wolz
Diploma students
Anja Habereder
Dipl.-Ing. Sebastian Kaserer
Dipl.-Ing. Alexander Schökel
Research Projects
German-Canadian fuel cell cooperation (BMWi project 2010-2013)
New developments in intermediate temperature fuel cells (EU project 2010-2012)
New concepts for a controlled 3D design of porous electrodes (DFG project 2010-2013)
Publications
[1] F. Muench, M. Oezaslan, M. Rauber, S. Kaserer, A. Fuchs, E. Mankel, J. Brötz, P.
Strasser, C. Roth, W. Ensinger,
Electroless Synthesis of Nanostructured Nickel and Nickel-Boron Tubes and their Performance
as Unsupported Ethanol Electrooxidation Catalysts,
Journal of Power Sources 222 (2013), 243 – 252.
99
[2] S. Kaserer, K. M. Caldwell, D. E. Ramaker, C. Roth,
Analyzing the Influence of H3PO4 as Catalyst Poison in High Temperature PEM Fuel Cells Using
in-operando X-ray Absorption Spectroscopy,
J. Phys. Chem. C 117 (2013), 6210−6217.
[3] S. Kaserer, C. Rakousky, J. Melke, C. Roth,
Design of a reference electrode for high-temperature PEM fuel cells,
J. Appl. Electrochem. (2013) DOI: 10.1007/s10800-013-0567
100
Incorporation of Indium Tin Oxide Nanoparticles
in PEMFC Electrodes
André Wolz, Susanne Zils, David Ruch, Nicholas Kotov, Marc Michel, Christina Roth
Introduction
Carbon materials suffer from corrosion at the cathode of polymer electrolyte membrane
fuel cells (PEMFCs). In the presence of water, carbon support materials are oxidized to
carbon dioxide even at low potentials. Hence, nowadays it is very fashionable to look for
alternative support materials, like oxides or conductive polymers. The choice of a support
material other than carbon black makes it mandatory to think about the preparation
method of the electrode layer and its resulting electrode structure. The nano-sized oxide
particles have to be assembled differently from the sub-micrometer sized carbon black
particles to yield an equally promising structure. A schematic of such an electrode design is
depicted in Fig. 1.
Fig. 1. Schematic of a 3D electrode design incorporating nano-sized oxide support particles (Pt/ITO) and
Nafion-coated multi-walled carbon nanotubes (MWCNT/Nafion) into a fast sprayed multi-layer electrode.
The electrode structure is known to have a significant impact on the cell performance [1]. A
homogeneous and porous structure favors mass transport of the reactants, and a good
accessibility of the Pt nanoparticles results in a high Pt utilization. Recently, a novel
electrode preparation technique has been introduced by which it was possible to assemble
1D support materials into 3D networks [2, 3]. The networks had a multilayered
architecture of polyaniline and carbon nanotubes, both decorated with Pt, and the
electrodes reached 3 times higher Pt utilizations at the cathode side than conventional
electrodes. This technique is referred to as the ‘fast multilayer’ technique.
The same technique was used by Zils et al. [4] to manufacture electrodes with carbon black
material and Nafion layers, which were then compared to an airbrushed MEA with the
same catalyst composition. Focused ion beam tomography (FIB) measurements revealed a
101
much more homogenous structure with a small average pore size for the multilayer
electrode than for the airbrushed one. Single-cell tests furthermore demonstrated a two
times higher Pt utilization showing the suitability of this technique as a fast and easy
method for fuel cell electrode preparation.
This study shows the results for the incorporation of nano-sized alternative support
materials into advanced electrode architectures. It will give a first impression of how oxide
nanoparticles can be assembled in a fuel cell electrode. The obtained results will bridge the
gap between the previous results of electrochemical studies and the performance as catalyst
material in a real fuel cell environment.
Experimental
Pt decoration of ITO nanoparticles
ITO nanoparticles (NP) were decorated with Pt NP after a reduction of PtCl4 precursor by
sodium borohydride (NaBH4). 120 mg ITO NP and 51.8 mg PtCl4 (99.99+%) were
dispersed in 20 ml ultrapure water (MilliQ - MQ), the amount of PtCl4 corresponding to a
Pt loading of 20 wt%. After a homogenous dispersion was obtained, a solution of 51.8 mg
NaBH4 in 10 ml MQ was added. The dispersion turned black immediately. Afterwards, the
solution was diluted with deionized water, filtered through a 0.02 µm Anopore™ Inorganic
Membrane (Whatman®) and dried at 30°C under vacuum.
Functionalization of the multiwall carbon nanotubes (MWCNT)
The MWCNT were treated in concentrated acids in order to functionalize their surface and
to remove remaining amorphous carbon species. 20 mg MWCNT were dispersed in 6 ml
HNO3 (p.a., 65%) and 6 ml H2SO4 (ACS reagent, 95-98%) and sonicated for 30 min.
Afterwards, the nanotubes were diluted with copious amounts of MQ, filtered with a
0.45 µm polycarbonate track-etch membrane, rinsed with MQ water and dispersed in a
solution of 5 ml ethanol and MQ (80:20 by volume). A mixture of 0.34 ml Nafion ® solution
in 5 ml ethanol/MQ (80:20) solution was prepared and the MWCNT dispersion added
dropwise to the ionomer dispersion. As the second ink,40 mg of Pt/ITO (20 wt% Pt
loading) was dispersed in 10 ml ethanol/MQ solution (80:20).
Electrode preparation
Polymer electrolyte membranes of Nafion® 117 were purchased from Ion Power Inc., USA.
The membrane was mounted in a home built spraying plate with vacuum feature. The plate
was heated up to 80°C and a solution of 80 mg Pt on Vulcan-XC72 (HiSPEC™ 3000,
Johnson Matthey), 0.4 ml Nafion® 117 solution (5%), 3.6 ml MQ, and 12 ml ethanol was
coated onto the membrane by EcoSpray containers (Labo Chimie France). The cathode was
assembled by alternating layers of Pt/ITO and MWCNT/Nafion® (referred to as multilayer
electrode: ML-MEA). For comparison, a second electrode was sprayed, consisting of a
standard Pt/CB anode with the same loading used before and a Pt/CB cathode, with a Pt
loading and Nafion® content equal to the Pt/ITO cathode.
102
Structural characterization
The ITO supported Pt NP were characterized by X-ray diffraction (XRD). The XRD was
carried out with a X’Pert-Pro diffractometer in reflection geometry operating with Cu Kα1
and Kα2 radiation (λ=1.54060 Å). Rietveld refinement was used to estimate the particle
sizes of ITO and Pt. Scanning electron microscopy (SEM) was applied for the
characterization of the Pt/ITO electrode using a FEI Quanta 200 FEG, equipped with a field
emission gun operating at 15 kV.
Electrochemical characterization
Cyclic voltammograms (CVs) were measured with a Gamry Reference 600 potentiostat
(USA) in a standard glass three-compartment electrochemical cell (Bio-Logic SAS), with a
glassy carbon working electrode (Ø 3 mm, BASi Instruments, USA), a Pt wire serving as
counter electrode, and an Ag/AgCl reference electrode (ASL, Japan). The potential between
the working electrode (WE) and reference electrode was cycled 10 times between -0.21.2 V with a sweep rate of 50 mV s-1. The electrolyte was prepared with MQ water and
HClO4 (Sigma-Aldrich, 70%) at a concentration of 0.1 (M). The electrolyte was purged for
5 min with Ar.
Polarization curves of the electrodes were collected with a FuelCon Evaluator C50 test
bench (FuelCon AG, Germany), in which the Pt/ITO-MWCNT/Nafion® electrode was used
as cathode and the standard Pt/CB electrode as anode. Humidified hydrogen was fed to the
anode with a flow rate of 200 ml min-1 and high-purity oxygen was provided to the cathode
at a flow rate of 100 ml min-1. The anode/cathode gas humidifiers were set to 80°C and the
cell temperature to 75°C. The polarization curves were recorded automatically with the
software package FuelWork by increasing the current in 0.1 A steps after a steady state
potential has been reached.
Results and discussion
Pt nanoparticles on indium tin oxide nanoparticles have been considered as possible fuel
cell catalyst materials. However, tests in a real fuel cell environment are still lacking. After
the successful deposition of Pt on ITO the effect of electrode structure on the fuel cell
performance is studied. The assembly of Pt/ITO with 20 wt% Nafion® ionomer in the
electrode did not show any performance at all. This could be attributed to the very dense
electrode structure formed by the nano-sized support and the ionomer preventing the
desired gas transport. To enhance the porosity of the electrode network, the incorporation
of Pt/ITO catalyst into a multi-walled carbon nanotubes (MWCNTs) network (coated with
Nafion®) is proposed. The nanotube network has the advantage to be highly electron
conductive and the ionomer coating ensures the proton conductive character of the
electrode. The catalytic active species Pt on ITO is embedded into the structure during the
preparation process.
Single cell tests of the proposed electrode design have been performed, and the polarization
and power density curves can be found in Fig. 2. The novel electrode design reached a
maximum power density of 73 mW cm-2 at a current density of 0.12 A cm-2. The power
density is comparable to the conventionally prepared Pt/CB electrode. The Pt utilization for
the multilayer electrode is 1468 W g(Pt)-1 compared to 1723 W g(Pt)-1 for the standard
cathode.
103
Fig. 2. Comparison of the polarization and power density curves of the multilayer electrode design (Pt/ITOMWCNT/Nafion) and a conventionally prepared electrode (Pt/CB-Nafion).
It is remarkable that both MEAs show almost the same performance while possessing two
completely different morphologies. The spherical carbon black particles are in the
micrometer range with micro- and macropores, whereas the ITO particles are in the
nanometer range. The surface area of carbon black peaked at around 200 m2 g-1 and is
therefore much higher compared to ITO (27 m2 g-1 according to the supplier).
SEM micrographs have been recorded after the single cell measurements (Fig. 3). In the
crosssectional view, the electrode thickness was measured to be 5.4 µm. The low and high
magnification micrographs of the electrode surface indicate the mentioned network
structure provided by the multi-walled carbon nanotubes, in which the Pt/ITO component
is embedded. In Fig. 3, right single nanotube fibers are visible, and the structure seems to
be highly porous as intended.
Fig. 3. SEM micrographs of the advanced multi-layered electrode structure incorporating oxide-supported Pt
nanoparticles; in high magnification the carbon nanotubes can be seen.
104
Conclusion
This study showed a simple preparation technique for advanced electrode structures, which
succeeded in incorporating a nano-sized oxide supported Pt component (Pt/ITO) into a 3D
porous electrode network. Commercially available indium tin oxide (ITO) nanoparticles
(<50 nm) were used as support for Pt nanoparticles in combination with Nafion® coated
multi-walled carbon nanotubes (MWCNT) on the cathode side of a PEMFC. The MWCNT
promote a high electronic conductivity and help to form a porous network structure, which
was used to accomodate the Pt/ITO nanoparticles. The architecture favored the reactant
permeability, and a better accessibility of the active Pt sites was obtained. The conductivity
within the electrode was provided by only a negligible amount of highly conductive
MWCNTs. Single cell measurements show a maximum power density of 73 mW cm-2 and a
Pt utilization of 1468 mW mgPt-1 for the cathode. The performance data and the Pt
utilization are comparable to a standard Pt/carbon black electrode (Pt/CB) indicating that
it actually may be possible to replace carbon black by more stable oxides without a loss in
performance. Besides this, it is shown for the first time that ITO can serve as support
material under real fuel cell conditions. This might open the way to the manufacturing of
cost-efficient and easily prepared fuel cell electrodes with an enhanced long-term stability.
Acknowledgments
Financial support by the National Research Fund, Luxembourg is gratefully acknowledged.
We also want to thank C. Fasel, U. Kunz and J.-C. Jaud for their help with sample
preparation, TGA and XRD measurements.
References
[1]
[2]
[3]
[4]
R. O'Hayre, D. M. Barnett, F. B. Prinz, J. Electrochem. Soc. 2005, 152, A439.
A. Wolz, S. Zils, M. Michel, C. Roth, J. Power Sources 2010, 195, 8162.
S. Zils, A. Wolz, M. Michel, C. Roth, ECS Trans. 2010, 28, 33.
S. Zils, M. Timpel, T. Arlt, A. Wolz, I. Manke, C. Roth, Fuel Cells 2010, 10, 966.
105
In Situ and Time-Resolved XANES Study of the Electrooxidation of Ethanol on Pt
Julia Melke, Sebastian Kaserer, Alexander Schoekel, Dietmar Gerteisen, Ditty Dixon, Carsten
Cremers, David E. Ramaker, Christina Roth
Introduction
Ethanol is an attractive alternative fuel in polymer electrolyte fuel cells - thus its
electrochemical oxidation on Pt has been studied for several years [1-3]. The ethanol
oxidation reaction (EOR) is a complex multistep reaction that involves several adsorbed
species like acetyl, adsorbed acetate, carbon monoxide (CO) and CHx-species, and generally
yields some acetic acid, but mainly acetaldehyde along with the desired carbon dioxide as
final product. Except for the formation of acetaldehyde, oxidation to other products such as
acetic acid and carbon monoxide requires an oxygen atom source normally provided by the
activation or dissociation of water. The activation of water on Pt generally occurs around
0.55 V (RHE), and below this potential the Pt surface is covered mainly by CO(ads) and
CHx, as shown by various studies in the literature. Adsorbed acetate was observed to be
reversible and seems to reduce the number of available sites for the EOR. The EOR also
depends on anion adsorption from the electrolyte and the crystal structure of the catalysts.
X-ray absorption spectroscopy is especially suited to study reaction and degradation
mechanisms, such as the EOR, in-situ and under realistic operation conditions, since both
changes in the catalyst structure (EXAFS) and the kind and amount of adsorbates on the Pt
surface (delta µ XANES) can be followed at once. In our previous X-ray absorption
spectroscopy study, potential-dependent changes in the delta  XANES were observed
during the EOR at steady state conditions [4]. In contrast, for the first time in this work, we
report, time-resolved adsorbate coverages on a real working fuel cell anode during ethanol
oxidation. The ethanol oxidation reaction is studied using X-ray absorption spectroscopy
during chronoamperometric cell operation. The analysis of the XANES region of the Pt L3
edge by the delta μ XANES technique allows the coverage of the Pt surface with OH, n-fold
O and C-species to be followed in-situ. The current-voltage characteristics and the coverage
are modelled by means of a multi-step reaction mechanism based on a modified ButlerVolmer approach that additionally includes adsorbate-adsorbate lateral interactions. The
model is validated against experimental current and surface coverage data over time. With
the model, the importance of acetaldehyde formation via initial C-H vs O-H bond cleavage
is examined, the latter dominating at higher potentials on vacant sites remaining in the
oxygen coverage coming from water activation.
Experimental
Commercially-available carbon-supported Pt (40 wt% Pt on Vulcan XC-72) purchased from
Johnson Matthey was used as catalyst. The catalysts coated membranes (CCMs) were
prepared by spraying an ink on the polymer electrolyte Nafion®115. The ink was fabricated
by dispersion of the catalyst powder in high purity water and 5% Nafion® solution. The ink
106
was sprayed in several layers on the membrane, which was then dried for 1h at 130°C in a
drying chamber and pressed at 130°C with 1 KN cm-2.
X-ray absorption spectroscopy measurements were carried out at beamline X1 at Hasylab,
Hamburg in transmission mode for the Pt L3-edge at 11564 eV during electrochemical
operation. Therefore the CCM was sandwiched between Au-coated stainless steel endplates
with integrated, interdigitated flow fields and X-ray transparent Kapton foil windows.
Below the X-ray transparent window, a part of the cathode catalyst layer was removed.
Between flow field and electrode a Toray TGP H 90 gas diffusion layer was placed.
Hydrogen (N 5.0) was supplied at 50 ml min-1 by a flow controller (Bronkhorst,
Netherlands). The liquids were supplied at 1.2 ml min-1. Potentiostatic U/i curves were
recorded using a commercial potentiometer.
The electrochemical characterization was carried out in a fuel cell during half cell tests,
which means that the cathode side was fed with hydrogen instead of oxygen, serving as a
dynamic hydrogen electrode (DHE). First, the anode was measured in its dry state,
subsequently reduced with hydrogen at 50°C and then cooled down to ambient
temperature and flooded with high purity water. Potentials of 0.45 V and 0.75 V vs. DHE
were applied in order to use these measurements as reference data. This procedure was
followed by replacing the water with 1 M aqueous methanol solution and a potential of
0.45°V vs. DHE applied. Then again water was fed to the anode side and a potential of
0.75 V vs. DHE was held for at least 1.5 h to oxidize all carbon containing adsorbates
remaining on the surface. Finally, the water was replaced by 1 M aqueous ethanol solution
and several potentials were applied. At each potential step, several quick-EXAFS spectra
were recorded from E = 11300 eV to 12800 eV using a Si(111) double-crystal
monochromator. A thin Pt metal foil was used as reference for energy calibration. The
intensities of the focused beam and the transmitted beam were detected by three gas-filled
ion chambers in series.
EXAFS The EXAFS analysis was done for the water measurement at 0.45 V, only, to
estimate the particle size and the dispersion. Extraction of the EXAFS data from the
measured absorption spectra was performed with the programs Athena and Artemis. For
comparison, the catalyst particle size was also determined by XRD measurements of the
pristine catalyst powder. The particle size obtained was 2.7 nm by Rietveld refinement
using the Software FullProf.
XANES The XANES region was analyzed by the Δμ-technique. The absorption coefficient
was obtained equivalent to the EXAFS region, with the exception that the normalization
was carried out between 20 eV and 150 eV relative to the Pt L3 edge. The normalized data
were further aligned using the reference foil data. The ∆µ was obtained by subtracting the
measurement for water at 0.45 V vs. DHE from the appropriate spectra (Fig. 1).
MODELING The kinetics of the EOR was modeled by assuming that the dominant
contributions to the current originate from acetaldehyde and CO2 formation. Further, the
ethanol reaction rates are considered to be uniform and the same regardless of whether the
Pt site is located at a corner, edge, or terrace of the Pt cluster. The estimated Pt particles
size is around 1.6 nm, so that the fraction of face and edge-corners sites is about 0.8 and
0.2, respectively.
107
Figure 1. Δμ-results during ethanol oxidation at several potentials measured vs. DHE. For comparison
calculated Δμ by the FEFF8, labeled OH, O, and COatop, are shown. The simulations are reported previously.
The intrinsic rate of each reaction is given by a rate constant kf and kb determined by the
forward and backward activation energy ( kf/b = exp(-ΔGf/b/RT) ). The potential
dependence of the rate of each considered reaction step is described by a Butler Volmer
expression. In addition, a Frumkin isotherm is introduced in order to account for adsorbateadsorbate interactions on the surface. Each reaction is modeled as source or drain term for
the involved chemical species or charge carriers. These source and drain terms are coupled
by continuity equations, which are solved numerically using the Software Mathematica® 7.
Chemical reactions
The EOR is modeled via the reaction pathways summarized in Fig. 2: the formation of
acetaldehyde and CO2 is considered as products, with the former as the main reaction
product and the intermediate CO adsorbate enroute to the latter the main poison on this
catalyst blocking the EOR at lower potentials. The formation of adsorbed CHx and CO from
acetaldehyde is neglected in our kinetics model here. As summarized in Fig. 2, the model
includes parameters for 7 forward rates and 3 reverse rates (assuming 4 rates are
irreversible), with 6 symmetry coefficients (the two acetaldehyde rates are assumed to be
equal), and 6 Frumkin interaction coefficients (C1-C1,C1-C2,C1-O, C2-O, O-OH and O-O).
Reactants
Figure 2. Schematic of 7 reactions (3 assumed
to be in equilibrium) as indicated by heavy
arrows, 4 adsorbates (ethoxy* adsorbate
assumed to be a short-lived intermediate and
therefore not accumulating on surface), and 6
Frumkin interaction parameters indicated by 4
light dotted arrows and 2 squares.
108
Results and discussion
θ(ML/MASA)
Fig. 3 shows the time evolution of the measured (points) and simulated (lines) surface coverages
for different potential steps.
U = 0.55 V
θ(ML/MASA)
U = 0.85 V
U = 0.65 V
U = 0.9 V
U = 0.7 V
U = 0.92 V
θ(ML/MASA)
U = 0.6 V
θ(ML/MASA)
U = 0.80 V
θ(ML/MASA)
time /s
U = 0.75 V
 C-species
 O (n-fold)
 OH (atop)
measured
C-species
O (n-fold)
OH (atop)
simulated
time /s
Figure 3. Time-resolved OH(atop), O(n-fold) and C-species coverage for ethanol oxidation at several potentials
measured vs. DHE. Points refer to experimental data, solid lines show simulation results.
The starting potential of all steps was 0.45 V and hence at time t = 0 the surface is covered
mainly with C1-species as previously discussed. For all potential steps, except 0.55 V, a
decrease in C-species compared to the starting potential can be observed. In the potential
range between 0.6 V and 0.65 V the absolute decrease is small, but for long times the trend
becomes visible. At potentials U ≥ 0.7 V the decrease in C-species coverage is very obvious.
Furthermore, for potentials U < 0.75 V, only OH is observed apart from C-species. At
potentials U ≥ 0.75 V, coverage with OH(ads) decreases over time and in parallel O(ads)
formation is observed.
109
The comparison of the experimental and simulated coverages (Fig. 3) and the experimental
and simulated currents (not shown here) shows reasonable agreement. The behaviour of
the coverage, especially at potentials U ≥ 0.75 V is reproduced. For potentials U < 0.75 V
the very strong dynamic behavior seen in the simulated coverages at very short time scales
(10 s) was so far not measurable, since the time resolution in the XANES measurements is
too low and the signal-to-noise ratio too high. The current simulation reproduces the large
experimentally observed overshoot at the higher potentials U ≥ 0.75 V, but the small
experimentally observed overshoot in the current at lower potentials U < 0.75 V is not
reproduced.
Conclusion
This study shows for the first time, time-dependent adsorbate coverages of C-, OH- and Ospecies on carbon-supported Pt catalysts of a real CCM operated with ethanol as fuel. These
results were used to validate a detailed time-dependent kinetic model describing the
ethanol oxidation by a dual path mechanism, similar to what is found for methanol
oxidation. The two paths involve either acetaldehyde or CO2 formation by initial C-H bond
scission or acetaldehyde by initial O-H bond scission. It is remarkable that with this
relatively simple model involving C1 (CO and CHx), CH3CHOH, OH, and O adsorbates, all
measured quantities such as the time-dependent coverages and currents, can be reproduced
with a reasonable number of free parameters and in excellent agreement with the
experimental data.
Certainly other reactions may also play a role in the ethanol oxidation reaction, altering the
overall rate and distribution of products. We have emphasized in this work the reduction of
the number of parameters in the model (and hence the number of reactions), and therefore
the simplification of the kinetic model to the essential dominant reactions. Despite this
simplification, the kinetic model is able to simulate both the time dependent adsorbate
coverages and current; the adsorbate coverages available for the first time in this work. It is
hoped that knowledge of the adsorbate coverages on real catalysts under operating
conditions sufficiently validates this kinetic model, so that it can be used in a predictive
fashion to learn how to design new and better catalysts.
Acknowledgments
The kind support by S. Mangold and D. Batchelor from the ANKA synchrotron facility and A.
Webb and M. Hermann from the HASYLAB synchrotron facility is gratefully acknowledged.
References
[1]
[2]
[3]
[4]
110
Lamy, C.; Lima, A.; LeRhun, V.; Delime, F.; Coutanceau, C.; Léger, J.-M. J. Power Sources, 2002, 105,
283-296.
Parsons, R.; Vandernoot, T. J. Electroanal. Chem., 1988, 257, 9.
Wang, J.; Wasmus, S.; Savinell, R.F. J. Electrochem. Soc., 1995, 142, 4218-4224.
Melke, J; Schoekel, A.; Dixon, D.; Cremers, C.; Ramaker, D. E.; Roth, C. J. Phys. Chem. C, 2010, 114,
5914 –2925.
Physics of Surfaces
Physical properties of surfaces and interfaces are relevant in nearly all areas of science and
engineering. The fundamental interactions between surfaces, the surrounding fluid and
small objects in the fluid play an important role, for example in biology, biotechnology,
mechanical engineering, or petroleum geology. The common research question can be
expressed as “How does the interplay between physical surface properties, surface and
interface chemistry, and fluid flow affect the entire system?”
We follow an interdisciplinary approach focusing on physical, chemical and biological
properties of surfaces. The connection between surfaces and fluids is of particular interest
because it is essential in various technological systems. Our research targets at a better
understanding of the interplay between surface pattering (morphological and chemical)
and modification with the fluid flow. Experimental methods such as microscopy,
microfluidics, or spectroscopy are essential tools.
Staff Members
Head
Prof. Dr. Robert Stark
Research Associates
Dr. Suman Narayan
Dr. Marek Janko
Technical Personnel
Marie-Christine Apfel
Secretary
Imke Murschel
PhD Students
Dipl.-Biol. Elke Kämmerer
Dipl.-Min. Maximilian Köhn
M.Sc. Na Liu
Dipl.-Phys. Agnieska Voß
M. Sc. Kim Lieu Phuong (LMU)
M.Sc. Andreas Plog
Dipl.-Phys. Simon Schiwek
M.Sc. Assma Siddique
M.Sc. Limor Zemel
Bachelor students
Golo Zimmermann
Michael Marcus Schmitt
Erhan Aras
Martin Jäcklein
Andreas Taubl
Master Students
Silke Dittombée
Marcus Schulze
Dr. Christian Dietz
Research Projects
Funktionale Polymer-Peptidoberflächen (CSI, 2010 – 2014)
Wafer cleaning (Industrie 2011 - 2015)
Low friction coatings (Industrie 2011 – 2015)
Generation of composites from borides with tuneable electrical conductivities using
peptides optimized by genetic engineering; characterization of the bio-solid interactions by
modelling and AFM STA 1206/5-1 (DFG SPP 1569 2012 – 2014)
Institute of Materials Science - Physics of Surfaces
111
Publications
1. Hörner S., Fabritz S., Herce H. D., Avrutina O., Dietz C., Stark R. W., Cardoso M. C. and
Kolmar H. Cube-octameric silsesquioxane-mediated cargo peptide delivery into living cancer
cells. ORGANIC & BIOMOLECULAR CHEMISTRY. 2013; 11, 2258-2265.
2. Schenderlein H., Voss A., Stark R. W. and Biesalski M. Preparation and Characterization
of Light-Switchable Polymer Networks Attached to Solid Substrates. LANGMUIR. 2013; 29,
14, 4525-4534.
3. Maixner F., Overath T., Linke D., Janko M., Guerriero G., van den Berg B.H.J., Stade B.,
Leidinger P., Backes C., Jaremek M., Kneissl B., Meder B., Franke A., Egarter-Vigl E., Meese
E., Schwarz A., Tholey A., Zink A. and Keller A. Paleoproteomic study of the Iceman’s brain
tissue. CELLULAR AND MOLECULAR LIFE SCIENCES. 2013; 70, 3709-3722.
112
Quantitative measurement of the mechanical properties of human antibodies with
sub-10-nm resolution in a liquid environment
Agnieszka Voss, Christian Dietz, Robert W. Stark
The nanomechanical properties of single human immunoglobulin G and M antibodies were
measured in a liquid environment using a fast force-volume technique with sub-10-nm
spatial resolution. Ultrastructural details of these molecules were resolved in topographical
images. Simultaneously, important physical properties, such as elasticity, adhesion and
deformation, were measured. Considering their dimensions and adsorption onto the
substrate, the immunoglobulin M antibodies were highly flexible, with a low elastic
stiffness (34 ± 10) MPa and high deformability (1.5 ± 0.5) nm.
As shown in Fig. 1, PeakForce QNM allows one to resolve the morphology of tiny biological
samples with a high resolution in a liquid environment. Fig. 1(a) depicts a homogeneous
distribution of human IgM molecules adsorbed on mica. Figure 1(b) illustrates the overall
surface charge as a function of the pH value for mica and IgM antibodies. Mica is negatively
charged at all pH values, whereas IgM has an isoelectric point at 5.5 ± 1.0.1 The
measurements were performed at pH = 5.4, where the molecules are nearly uncharged.
Although the molecules are trapped at the surface by van der Waals forces or counterions
shared with the mica substrate, the molecules retain their flexibility.2,3 Most of the
antibodies reveal a typical pentameric structure, which is shown in Fig. 1(c). The five
subunits (Y-shaped branches - IgG) are held together by disulfide bonds in the center
region of the biomolecule (yellow), where the j-chain connects two IgG subunits via heavy
chains (blue). The IgG subunit consists of two identical heavy chains and two identical light
chains. Disulfide bonds bridge the heavy and the light chains (as shown in the lower part of
Fig. 1(c)). Fab and Fc fragments are designated by braces.4 Interestingly, the IgM molecules
apparent in Fig. 1(a) differ slightly in shape and size, most likely due to the different
positions of the Fab domains with respect to the central body of the molecule. This suggests
a high mechanical flexibility of the antibodies during the adsorption process.5 Additionally,
we imaged single IgG molecules adsorbed on mica. The Y-shaped morphology of the
molecule is apparent in the high-resolution topographical PeakForce QNM image of Fig. 1
(d). The observed molecular structures and their total sizes are in good agreement with
other studies.6,7 For a more detailed analysis of the morphology, we focused on two single
IgM pentamers and recorded highly resolved images (Fig. 2). From these images (Fig. 2(a)
and (b) top) and the respective cross-sectional profiles (bottom) drawn through the
horizontal positions (red arrows), we estimated the lateral and vertical dimensions of the
IgM. The average height of the IgM molecules was approximately 2.2 nm. Considering the
finite size of the tip (R = 7 nm) and the geometric ‘convolution’ between the tip shape and
the sample morphology,8 the apparent width of the molecules in the cross-sectional profile
of approximately 42 nm can be reduced to a lateral size of approximately 28 nm. Strikingly,
in Fig. 2(b), the Fab domains (reduced to a length of 7 nm) clearly stick out of the center
region, and in some cases, two single neighboring Fab domains within the IgG substructure
can be unambiguously distinguished (e.g., two fragments pointing to the left). The main
body consists of five Fc domains, including the J-chain, with an apparent diameter of 18
nm. These values are consistent with the dimensions of IgG and IgM found in earlier
studies.9,10,11 Comparing Fig. 2(a) with 2(b), the antibody in the left panel exhibits a clear
113
protrusion inside the main body, whereas the antibody in the right panel possesses a hollow
(see the blue arrows in the cross-sectional profile). We assume that the protrusion of the
molecule in Fig. 2(a) corresponds to the J-chain of IgM. In contrast, the molecule in Fig.
2(b) either lies upside-down, i.e., the protrusion points downward, or the J-chain does not
exist in this case, as postulated by Wiersma et al. 12
Figure 1. (a) Topographical image of IgM antibodies
adsorbed on mica in a liquid environment obtained in
peak-force tapping mode. (b) Illustration of the
overall surface charges of Si3Ni4, IgM and mica at
different pH values.1,13 (c) Schematic structure of IgM
(top) and IgG (bottom). (d) High-resolution
topographical image of a single IgG human antibody
adsorbed on mica in distilled water.
Figure 2. Highly magnified topography peak-force
tapping mode images of single IgM human
antibodies, revealing two possible orientations. (a)
The center region (j-chain) shows a protrusion from
the main body (top). (b) Upside down
configuration exhibiting a hollow in the center
region (top).
In addition to the topographical images, PeakForce QNM provides maps of several
mechanical surface properties, such as adhesion, elastic modulus (DMT-modulus), and
deformation. The results show that mechanical properties, such as the elasticity, can be
imaged with high resolution. Strikingly, the exact contour of single molecules becomes
apparent. The elastic modulus measured on IgM antibodies is very close to the value
recently reported by Martinez et al.10 The measured values of mica, however, deviated
slightly from the nominal elastic modulus (10 GPa). One reason for this difference could be
the insufficient indentation depth of the tip into the mica surface while sensing the
necessary mechanical response. A force limit of 300 - 800 pN was set to ensure the integrity
of the biomolecules which led to an average indentation depth of only 0.7 nm on mica.
These results show that the method allows one to quantify the mechanical properties of
heterogeneous samples even if the elasticity varies over orders of magnitude. However,
sensing the mechanical properties of soft biological systems adsorbed on hard substrates by
nanoindentation has to be carried out with care. The sharp tip can induce local strains
within the soft material which can exceed the linear material regime and hence, lead to a
damage of the sample surface.14 To address this problem, we limited the maximum load
300 - 800 pN during force curve acquisition to avoid damage to the biomolecules and to
minimize mechanical stress. Repeated probing of the same individual molecule did not lead
to a measurable degradation of topography or local stiffness. The morphology and
mechanical response of IgM molecules remained unchanged even after several scans over
114
the same area with a peak force of approximately 800 pN; however, some of the molecules
were slightly distorted in such a way that the Fab domains were marginally twisted.
Summary
We present a straightforward approach to simultaneously image and generate maps of the
mechanical properties of the human IgG and IgM antibodies adsorbed on mica.
Quantitative nanomechanical mapping is a method that provides high spatial resolution
with complementary information on adhesion, elasticity, or deformation. All of this
information is extracted from force-distance curves taken at a kHz acquisition rate. This
approach is non-destructive to soft samples under the operating parameters that were
applied in this study. The IgM sub-structure could be clearly resolved in water, suggesting
that the molecules lie in different positions on mica, where the Fab domains can be oriented
in various angles to each other. The analyses of the topographical data of IgM molecules
revealed the relatively large size of the Fab domains in comparison with its central portion,
where the j-chain is located. Strikingly, we were able to simultaneously measure the elastic
modulus of a stiff material, such as muscovite mica (1.3 ± 0.4) GPa, and a soft
biomolecule, such as IgM (34 ±10) MPa. The low stiffness found on IgM together with the
high deformability (1.5 ± 0.5 nm) in comparison with the dimensions of the molecule
(nominal height: 7 nm) corroborates the high flexibility of the antibodies. This flexibility
may be the key property that these antibodies are able to adopt confirmations to bind to a
large number of antigens with varying sizes and shapes and leads to a high mobility in the
organism.
References
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
Chiodi, F.; Sidén, Å.; Ösby, E., Electrophoresis 1985, 6, 124-128.
Hansma, H. G.; Laney, D. E., Biophys. J. 1996, 70, 1933-1939.
Pastre, D.; Pietrement, O.; Fusil, P.; Landousy, F.; Jeusset, J.; David, M. O.; Hamon, C.; Le Cam, E.;
Zozime, A., Biophys. J. 2003, 85, 2507-2518.
Alberts, B.; Johnson, A.; Lewis, J.; Raff, M.; Roberts, K.; Walter, P., Molecular Biology of the Cell.
Garland Science: New York, 2007.
Perkins, S. J.; Nealis, A. S.; Sutton, B. J.; Feinstein, A., J. Mol. Biol. 1991, 221, 1345-1366.
Makky, A.; Berthelot, T.; Feraudet-Tarisse, C.; Volland, H.; Viel, P.; Polesel-Maris, J., Sens. Act. B
2012, 162, 269-277.
Martinez, N. F.; Lozano, J. R.; Herruzo, E. T.; Garcia, F.; Richter, C.; Sulzbach, T.; Garcia, R.,
Nanotechnology 2008, 19, 384011.
Villarrubia, J. S., J. Res. Natl. Inst. Stan. 1997, 102, 425-454.
Czajkowsky, D. M.; Shao, Z., P. Natl. Acad. Sci. USA 2009, 106, 14960-14965.
Martinez-Martin, D.; Herruzo, E. T.; Dietz, C.; Gomez-Herrero, J.; Garcia, R., Phys. Rev. Lett. 2011,
106, 198101.
Kienberger, F.; Mueller, H.; Pastushenko, V.; Hinterdorfer, P., EMBO Rep 2004, 5, 579-583.
Wiersma, E. J.; Collins, C.; Fazel, S.; Shulman, M. J., J. Immunol. 1998, 160, 5979-5989.
Lin, X. Y.; Creuzet, F.; Arribart, H., J. Phys. Chem.-US 1993, 97, 7272-7276.
Dimitriadis, E. K.; Horkay, F.; Maresca, J.; Kachar, B.; Chadwick, R. S., Biophys. J. 2002, 82, 27982810.
115
Joint Research Laboratory Nanomaterials
The Joint Research Laboratory Nanomaterials was established in the year 2004 as a joint
project between the Institute for Materials Science (Technical University of Darmstadt) and
the Institute for Nanomaterials (INT) at the Karlsruhe Institute for Nanotechnology (KIT).
Its research focusses on the synthesis and characterisation of nanoparticles, nanoparticulate
layers, nanoporous as well as dense nanoscale materials. Special interest lies in the
determination of correlations between synthesis, interface and bulk properties and the
macroscopic functional and structural properties. An important building block is the
understanding of the surface, grain boundary and size effects on the physical material
properties, which can be significantly different from classical crystalline bulk materials.
Since a couple of years, the research has focused on energy materials (batteries, fuel cells).
In addition, (reversible) topochemical reactions (chemical and electrochemical) are also
under investigation, allowing for the adjustability of material properties.
One of the aims is to consistently develop an understanding of correlation between process
parameters and the resulting material properties. The materials of interest (nano- and
microcrystalline powders and films) are produced by a range of gas phase processes as well
as via solid-state reactions.
A huge variety of methods is available and in constant use for the characterisation of the assynthesized powders as well as bulk materials and thin-films, among them X-ray powder
diffraction, low-temperature N2 adsorption, dynamic light scattering, low and high
temperature impedance spectroscopy and cyclic voltammetry.
Staff Members
Head
Prof. Dr.-Ing. Horst Hahn (Director Institute for Nanotechnology)
Research Associates
Dr. Oliver Clemens
Dr. Ruzica Djenadic
Secretaries
Renate Hernichel
PhD Students
Dipl.-Ing. Mohsen Pouryazdan
Dipl.-Ing. Philipp Leufke
Dipl.-Ing. Nina Schweikert
Dipl.-Ing. Clemens Wall
Dipl.-Phys. Sebastian Becker
Dipl.-Ing. Christopher Loho
Dipl.-Ing. Ira Balaj
Dipl.-Ing. Miriam Botros
Dipl.-Ing. Alexander Benes
Dipl.-Ing. Ralf Witte
Dipl.-Phys. Tom Braun
Master Students
Dipl.-Ing. Ahmad Chodhary
Guest Scientists
Dipl.-Ing. Bojana Mojic, University Novi Sad Serbia
116
Dr. Mohammad Ghafari
Dr. Matti Oron-Carl
Dipl. Phys. Arne Fischer
Dipl. Ing. Holger Hain
Dipl. Ing. Klaus Maximilian
Dipl. Ing. Aaron Kobler
M.Sc. Cahit Benel
M.Sc. Cheng Huang
M.Sc. Garlapati Suresh Kumar
M.Sc. Massoud NazarianSamani
M.Sc. Mohammad Fawey
Institute of Materials Science - Joint Research Laboratory Nanomaterials
Research Projects
Tunable Magnetic Nanostructures. Property Characterization and Modeling (DFG HA
1344/28-1, 2010 – 2013)
Investigation of non-equilibrium phonon populations in biased metallic single-walled
carbon nanotubes (DFG OR 262/1-2, 2011-2013)
Reversibles Durchstimmen der elektronischen Transporteigenschaften in oxidischen
leitfähigen Nanostrukturen zur Anwendung im Bereich der druckbaren Elektronik (DFG HA
1344/25-1, 2010 – 2013)
Helmholtz Portfolio, Elektrospeicher im System – Zuverlässigkeit und Integration
(325/20514659/NANOMIKRO, 2012-2014)
Förderung durch Mittel des Helmholtz Institut Ulm (2010-2014)
Publications
SK Garlapati, N. Mishra, S. Dehm, R. Hahn, R. Kruk, H. Hahn, S. Dasgupta,
Electrolyte-gated, high mobility inorganic oxide transistors from printed metal halides, ACS
Applied Materials & Interfaces 5 (2013), 11498-11502, DOI: 10.1021/am403131j
X. Zhao, CM Wang, D. Wang, H. Hahn, M. Fichtner,
Ge-Cu nanoparticles produced by inert gas condensation and their application as anode
material for lithium ion batteries, Electrochemistry Communications 35 (2013), 116-119,
DOI: 10.1016/j.elecom.2013.08.016
A. Kobler, J. Lohmiller, J. Schaefer, M. Kerber, A. Castrup, A. Kashiwar, PA Gruber, K. Albe,
H. Hahn, C. Kuebel,
Deformation-induced grain growth and twinning in nanocrystalline palladium thin films,
Beilstein Journal of Nanotechnology 4 (2013), 554-566, DOI: 10.3762/bjnano.4.64
R. Witte, T. Feng, JX Fang, A. Fischer, M. Ghafari, R. Kruk, RA Brand, D. Wang, H. Hahn,
H. Gleiter,
Evidence for enhanced ferromagnetism in an iron-based nanoglass, Applied Physics Letters
103 (2013), 073106, DOI: 10.1063/1.4818493
A. Evans, C. Benel, AJ Darbandi, H. Hahn, J. Martynczuk, LJ Gauckler, M. Prestat,
Integration of spin-coated nanoparticulate-based La0.6Sr0.4CoO3-delta cathodes into microsolid oxide fuel cell membranes, Fuel Cells 13 (2013), 441-444, DOI:
10.1002/fuce.201300020
A. Kobler, A. Kashiwar, H. Hahn, C. Kuebel,
Combination of in situ straining and ACOM TEM: A novel method for analysis of plastic
deformation of nanocrystalline metals, Ultramicroscopy 128 (2013), 68-81, DOI:
10.1016/j.ultramic.2012.12.019
117
C. Benel, AJ Darbandi, R. Djenadic, A. Evans, R. Tolke, M. Prestat, H. Hahn,
Synthesis and characterization of nanoparticulate La0.6Sr0.4CoO3-delta cathodes for thin-film
solid oxide fuel cells, Journal of Power Sources 229 (2013), 258-264, DOI:
10.1016/j.jpowsour.2012.11.149
N. Schweikert, A. Hofmann, M. Schulz, M. Scheuermann, ST Boles, T. Hanemann, H. Hahn,
S. Indris,
Suppressed lithium dendrite growth in lithium batteries using ionic liquid electrolytes:
Investigation by electrochemical impedance spectroscopy, scanning electron microscopy, and in
situ Li-7 nuclear magnetic resonance spectroscopy, Journal of Power Sources 228 (2013),
237-243, DOI: 10.1016/j.jpowsour.2012.11.124
B. Nasr, Di Wang, R. Kruk, H. Rosner, H. Hahn, S. Dasgupta,
High-speed, low-voltage, and environmentally stable operation of electrochemically gated zinc
oxide nanowire field-effect transistors, Advanced Functional Materials 23 (2013), 1750-1758,
DOI: 10.1002/adfm.201202500
PM Leufke, R. Kruk, RA Brand, H. Hahn, In situ magnetometry studies of magnetoelectric
LSMO/PZT heterostructures,
Physical Review B 87 (2013), 094416, DOI: 10.1103/PhysRevB.87.094416
NS Arshad, GT Lach, M. Pouryazdan, H. Hahn, P. Bellon, SJ Dillon, RS Averback,
Dependence of shear-induced mixing on length scale, Scripta Materialia 68 (2013), 215-218,
DOI: 10.1016/j.scriptamat.2012.10.027
H. Shao, YL Xu, B. Shi, CS Yu, H. Hahn, H. Gleiter, JG Li,
High density of shear bands and enhanced free volume induced in Zr70Cu20Ni10 metallic glass
by high-energy ball milling, Journal of Alloys and Compounds 548 (2013), 77-81, DOI:
10.1016/j.jallcom.2012.08.132
AK Mishra, AJ Darbandi, PM Leufke, R. Kruk, H. Hahn,
Room temperature reversible tuning of magnetism of electrolyte-gated La0.75Sr0.25MnO3
nanoparticles, Journal of Applied Physics 113 (2013), 033913, DOI: 10.1063/1.4778918
C. Kuebel, A. Kobler, H. Hahn,
In-situ Deformation Analysis of Nanocrystalline Metals by Quantitative ACOM-STEM,
Advances in Imaging and Electron Physics 179 (2013), 172-174, WOS: 000323356800016
N. Chen, XT Shi, R. Witte, KS Nakayama, K. Ohmura, HK Wu, A. Takeuchi, H. Hahn, M.
Esashi, H. Gleiter, A. Inoue, DV Louzguine,
A novel Ti-based nanoglass composite with submicron-nanometer-sized hierarchical structures
to modulate osteoblast behaviors, Journal of Materials Chemistry B 1 (2013), 2568-2574,
DOI: 10.1039/c3tb20153h
B. Nasr, Z. Zhao-Karger, D Wang, R. Kruk, H. Hahn, S. Dasgupta,
Temperature tolerance study of high performance electrochemically gated SnO2 nanowire fieldeffect transistors, Journal of Materials Chemistry C 1 (2013), 2534-2539, DOI:
10.1039/c3tc00061c
118
O. Clemens, R. Haberkorn, M. Springborg, H. P. Beck
On aliovalent substitution on the Li site in LiMPO4: a X-ray diffraction study of the systems
LiMPO4-M1.5PO4 (= LixM1.5-x/2PO4; M = Ni, Co, Fe, Mn), Zeitschrift fuer Anorganische und
Allgemeine Chemie (2014), 640, (1), 173-183, DOI: 10.1002/zaac.201300376
119
Mechanics of Functional Materials
The research at the Division of Mechanics of Functional Materials is focused on the
constitutive modeling and the simulation of functional materials and systems, for instance
ferroelectric materials and lithium-ion battery electrodes. These materials are characterized
by a coupling of multiple physical fields at a variety of length-scales. Their macroscopic
responses depend on the microstructure and its thermodynamic kinetics. The main features
of our research therefore include coupled fields (e.g. mechanical, electrical, chemical),
microstructure evolution, mesoscopic material properties, and homogenization. Primary
tools of our research are continuum models and Finite Element numerical simulations.
Novel concepts such as phase-field models or Isogeometric Analysis are regarded to an
increasing extent in our work.
Phase field simulation of the domain structure of ferroelectric ceramics
Ferroelectrics are widely used as actuators, sensors, and memory devices. A characteristic
feature of ferroelectrics is that they possess different spontaneous polarization states.
Switching between these states can be achieved by application of an electric field, and the
cycling loading of a specimen gives rise to nonlinear hysteretic behavior.
Semiconductor properties have a significant impact on domain configurations in
ferroelectrics, in particular for doped materials. In order to assess these effects, a phasefield model is formulated that regards space charges due to donors and electronic charge
carriers. It allows quantitative studies on the role of space charges and electronic charge
carrriers in the stabilization of domain structures. By accounting for the semiconductor
properties of barium titanate, the appearance of depletion layers near electrodes can be
predicted. Furthermore, the stabilization of (otherwise instable) head-to-head and tail-totail domain structures through space charges can be demonstrated.
Simulations of initial tail-to-tail configurations with a tilted domain wall show that, upon
disregard of semiconductor features, the domain wall rotates into a vertical equilibrium
alignment as a result of driving moments. In contrast, when semiconduction is included in
the model, the equilibrium orientation of the domain wall depends on the donor
concentration.
Since electronic charges accumulate along the head-to-head and tail-to-tail domain walls,
they have electric conductivity, which can be studied by the phase-field model. To that end,
two defect systems are investigated: firstly, am ideal defect system where oxygen vacancies
are the only point defects, and secondly a realistic defect system where doping of
manganese gives rise to several kinds of point defects. This shows that the domain wall
conductivity enhanced by electrons or holes depends, among other factors, on the domain
configuration, the type of involved defects, and the concentration of point defects. Based on
these results, controversial experimental results on domain wall conductivity can be
explained.
Simulation of the electrocaloric effect of relaxor ferroelectrics
In recent years, the electrocaloric effect (ECE) has drawn much attention because of its
environment-friendliness and its higher efficiency compared with other traditional cooling
processes. In order to gain a better understanding of the ECE phenomenon, the polarization
switching behavior and the ECE are studied in both ferroelectrics (FEs) and relaxor
ferroelectrics (RFEs). Since fundamentally microscopic quantities are of interest here, a
lattice-based model is employed for these studies. This model takes into account four
120
Institute of Materials Science – Functional Materials
different energy contributions to the potential energy that significantly affect the material
behaviour. In addition to a Landau double well potential, dipole-dipole interactions,
gradient terms and the electrostatic energy of the system are regarded. The equilibrium
material behaviour at a specific temperature is evaluated by the Metropolis algorithm;
thereby, the polarization switching behaviour under an alternating external electrical field
and the influence of the domain size can be taken into account. Once an equilibrium state
has been achieved, the ECE is investigated using Creutz' algorithm. In order to account for
the different behaviour of FEs and RFEs, a random initial field is imposed on the RFE
samples whereas the FE models are treated without this random field. In the latter case,
without an external electric field, the equilibrium state exhibits large domain together with
very sharp phase transitions about the transition point. With increasing gradient energy,
this transition point is shifted towards higher temperatures. Throughout the polarization
switching process, the domain wall movement is easily recognizable. At the same time, the
remanent polarization is relatively strong, and the ECE peaks at the phase transition point.
The simulations with an imposed random field, on the other hand, do not show these large
domain sizes. Here, the phase transitions are much broader around the transition point and
the domain wall movement is not visible. When the polarization switches under the applied
electric field, the remanent polarization decreases. With increasing magnitude of the
random field, this phenomenon becomes more prominent. Other than in FE materials, the
ECE peak drifts towards lower temperatures in RFEs which, in turn, show a broader ECE
range.
Simulation of diffusion introduced stresses in the Lithium-ion batteries via
Isogeometric Analysis
Mechanical degradation of the active material has been identified as one of the root causes
of the degradation of Lithium-ion batteries, which can be observed macroscopically as a
gradual fade of the batteries' capacity. The understanding of the damage processes in the
electrodes’ particles and their influence on the mechanical-electrochemical properties is
hence of utmost importance.
The coupled electrochemical-mechanical processes in individual electrode particles are
described by continuum mechanics and higher-order Finite Element procedures based on
the concept of Isogeometric Analysis. Their application is motivated by higher-order
gradient/coupling terms arising from the thermodynamics of the problem; it allows for
stable implementation of the governing equations as well as for a unified treatment of
diverse particle shapes and electrode geometries.
Using these models the impact of material properties, charge rates, and particle shape on
the emerging stress levels can be assessed. The current model, restricted to the small-strain
regime, predicts stress-enhanced diffusion rates that, in turn, cause a stress relaxation effect
in the material. Furthermore, the model allows to show the stress distribution within
particles of varying aspect ratio which can be used to explain the higher resilience of thin,
needle-like particles against diffusion-induced degradation, compared with more bulkier,
compact particles (see attached short report).
In addition to large deformations of certain electrode materials, in situ TEM observations
have revealed the coexistence of lithium-poor and lithium-rich phases in the electrode
particles during charge and discharge, which suggests that the concentration of Li-ion does
not change gradually but experiences a gap at a certain interface. In order to capture this
behaviour, a Cahn-Hilliard phase-field model is currently developed that regards not only
the chemical aspects of the phase separation and diffusion, but also viscoplastic effects.
Institute of Materials Science – Mechanics of Functional Materials
121
Staff Members
Head
J. Prof. Dr. (Boshi) Bai-Xiang Xu
Research Associates
Dr.-Ing. Peter Stein
Secretaries
Maria Bense
PhD Students
Dipl.-Ing. Yinan Zuo
Ying Zhao, M.Sc.
Diploma Students
Timo Noll, B.Sc.
Habib Pouriayevali, PhD
Yangbin Ma, M.Sc.
Min Yi, M.Sc.
Research Projects
Phase-field simulation of ferroelectrics with defects (Project in DFG-SFB 595, 2012-2014)
Simulation of the electrocaloric effect of relaxor ferroelectrics (Project in DFG-SPP 1599,
2013-2015)
Isogeometric simulation of diffusion-induced stress in Lithium-ion battery electrodes
(Project in GSC CE, 2013-2015)
Publications
[1] B.-X. Xu, Y. Gao, M.Z. Wang,
Particle packing and the mean theory,
Physics Letters A, 377, 145-147, 2013
[2] B.-X. Xu, H. von Seggern, S. Zhukov, and D. Gross,
Continuum modeling of charging process and piezoelectricity of ferroelectrets,
J. Appl. Phys. 114, 094103 (2013)
[3] P. Stein, Y. Zhao, B.-X. Xu,
An analytical solution for the mechanically coupled diffusion problem in thin-film electrodes
Proc. Appl. Math. Mech. 13(1), 237-238, 2013
122
Isogeometric analyis of intercalation-induced stresses in Lithium-ion battery
electrode particles
Peter Stein & Bai-Xiang Xu
Lithium-ion batteries are an important energy storage system. They are the predominant
power source for portable electronic devices such as cellphones and tablet PCs. Their high
potential for application in hybrid electric vehicles or for the storage of renewable energy
can unfortunately not be exploited: in order to prevent (both spontaneous and gradual)
battery failure and to maintain a certain lifetime, the admissible charge rates and battery
capacities must be bounded from above.
In addition to electrochemical side-reactions, mechanical degradation of the battery
electrodes has been identified as one of the root causes of the gradual macroscopic fade of
a battery's capacity. Experimental observations indicate the emergence of high stresses
during cyclic charge processes, leading to particle fracture. Moreover, certain electrode
materials, for instance silicon with its tremendous theoretical storage capacity, also show
huge volumetric strains (values in the range of 270-400% have been reported in the
literature). That is, in addition to the fracture of individual electrode particles,
delamination of the whole electrode structure is a probable failure mechanism for these
batteries. Once a fragment of active material loses contact to the electrode it is no longer
available to intercalation, causing the observed capacity loss. The understanding of the
damage processes in the electrodes’ particles and their influence on the mechanicalelectrochemical properties is hence of utmost importance.
Lithium-ion battery cells comprise three main components: a cathode, which commonly
consists of a lithium compound such as LiCoO or LiFePO4 , an anode, which is often made
of Si or C, and an electrolyte. The electrodes exist in various designs, for instance as thin
film substrates, porous electrodes, or as nanowire assemblies. During charge processes, Li
ions migrate from the cathode through the electrolyte to the anode where they are
intercalated into the active anode material. This process is reversed during discharge.
In the present work, the intercalation process within a single electrode particle is described
by a diffusion model that is coupled to a linear elastostatic model (based on the assumption
that mechanical equilibrium is established much faster than ionic diffusion within the
particle). Thereby, the Fick diffusion is enhanced by a drifting term based on the gradient
of the hydrostatic mechanical stress field [1]. Accordingly, ions diffuse not only along the
negative concentration gradient but also from regions of high compressive stresses towards
regions of lower compressive stresses. The concentration field, in turn, affects the
mechanical stresses analogous to thermal expansion. That is, the intercalation of ions leads
to an isotropic swelling that relaxes, in an unconstrained body, the total stress levels.
Above model has been implemented in the Finite Element software FEAP using the concept
of Isogeometric Analysis that provides smooth, higher-order ansatz functions for the
discretization of the governing equations. This is justified by the higher-order gradients that
come into play due to the stress-gradient coupling terms. As these require C1-continuous
basis functions, common C0-continuous Finite Element methods cannot be employed.
Instead, mixed-variational formulations have to be used, as in [2]. As an alternative, this
123
coupling term is often neglected, leading to a partially coupled model, e.g. [3]. Simulations
performed for a spherical LiMn2O4 particle show the significance of the full coupling,
illustrated in Figure 1, which shows the tangential stresses along the radius of said particle.
It can be easily recognized that the full model (“Coupled”) predicts not only stresses of
lower magnitude, but also a stress relaxation effect. In the first stages of charging, a
compressive shell emerges in the particle that enhances the ion diffusion towards the
particle's core. Over time, this causes higher ion concentrations in the core region that
cause a reduction in the overall stress levels. The partially coupled model (“Decoupled”)
cannot describe such an effect and hence maintains the high stress levels that arise during
the process.
Fig. 1: Tangential stresses in a spherical particle of 5 µm radius under galvanostatic charge boundary
conditions. The plot shows the stresses along the particle's radius for different time steps, both for our model
(„Coupled“) and a partially coupled model („Decoupled“), illustrating the significance of the drift term.
Based on this model, parameter studies have been performed with respect to the influence
of material stiffness, charge boundary conditions, and particle shape [4]. The reveal that
the overall stress levels in the particles increase with both increasing material stiffness and
increasing charge rate, where the latter is typical for applications in hybrid electric vehicles.
The effect of shape variation is shown in Figure 2 that shows the distribution of the
maximum von Mises stresses for spheroidal particles of different aspect ratio. Thereby, the
particles' volume is kept fixed. As can be seen, the highest stresses develop in the needlelike particles as a „belt“ around their respective equator, where the material is constrained
by conditions similar to a cylinder. At the same time, towards the particles' tip, the material
can swell comparatively free, which allows for an equilibration of diffusion-induced
stresses. Moreover, the diffusion paths are relatively short in these particles, leading to
stress levels that are below those occurring in spherical particles. This explains
experimental observations of the higher robustness of slender particles against diffusioninduced degradation.
124
The stresses in the flat, lens-shaped particles, in contrast, greatly exceed those in the
spherical and prolate ellipsoidal particles – despite the short diffusion paths along their
semi-minor axis. In particular for low aspect ratios the material is subject to strong,
rotationally symmetric constraints. Thus, the particle can expand only slightly in order to
reduce the stresses arising from intercalation. It must therefore be concluded that such flat
electrode particles are prone to crack initiation and hence to an early onset of capacity fade.
Fig. 2: Von Mises stress distributions in oblate and prolate ellipsoidal particles for different parameters a. All
particles have the volume of a spherical particle with radius 5 µm. The models are shown at the respective time
steps corresponding to the peak stress levels. All particles exhibit the semi-axes a : (1/sqrt(a)) : (1(sqrt(a)), with
a indicated in each sub-figure.
References:
[1]
[2]
[3]
[4]
X. Zhang, W. Shyy, A.M. Sastry, J. Electrochem. Soc. 154 (2007) A910–A916.
Y.F. Gao, M. Zhou, J. Appl. Phys. 109 (2011) 014310.
Y.-T. Cheng, M.W. Verbrugge, J. Power Sources 190 (2009) 453–460.
P. Stein, B. Xu, Comput. Methods Appl. Mech. Engrg. 268 (2014), 225–244.
125
Functional Materials
The Functional Materials Research Group joined the Department of Material Science in
2012. Our main research interests are permanent magnets and magnetocaloric materials.
During 2013 the laboratory facilities have been extended and we have moved to our new
home in the M³ building. The healthy state of project funding has allowed us to grow to a
team of 29 researchers and students. 2013 was a productive year: We have published more
than 20 peer reviewed scientific journal papers and given more than 15 invited and many
contributed talks at international conference presentations. A highlight of 2013 was a joint
seminar with the project group for materials recycling and resource strategies, Fraunhofer
IWKS of which Oliver Gutfleisch is a director. This allowed the Darmstadt group to present
their research and learn about the activities at the Fraunhofer Institute. Another highlight
of the year was a 3 day group seminar at Kloster Bronnbach. In addition to our research
activities this year we have also increased our contribution to teaching at the department of
material science. Oliver Gutfleisch is now giving 3 lecture courses: “Functional Materials”,
“Materials Engineering”, and “Material Science for renewable energy systems”, the latter as
part of the new interdisciplinary Master of Energy Science course. Also this year the group
has introduced a new practical course for bachelor students dealing with “permanent
magnets in application” and is actively participating in the seminars of the bachelor and
master programmes.
The Outlook for 2014 for the group is good. The increased size of the group and additional
funding streams, including a 4.4 million€ state grant from the LOEWE initiative, will allow
the group to expand further and continue the high level of research.
Research Interests:
Permanent magnets:
Permanent magnets are used in a wide variety of industrial and household appliances, the
major applications being electrical motors and power generation. Currently these
applications require NdFeB magnets, which rely on rare earth elements such as Nd as well
as Dy, which is used to enhance the thermal stability. Rare Earth metals are expensive and
availability is predicted to become increasingly limited in the years to come. Our efforts
include a) reduction of heavy rare earth elements in Nd-Fe-B magnets without a loss in
performance and b) the study of novel rare earth free materials with energy densities
greater than those of hard ferrites (another class of widely used permanent magnets).
Our research on permanent magnets is now being supported by the Hessian Ministry
HMWK after a successful bid to the “LOEWE” program resulting in an additional 4.4 Mio. €
for work on resource efficient usage of rare earth elements; Project “RESPONSE”. This
project is supported for a minimum of 3 years starting in January 2014 and combines the
applied research at Fraunhofer with fundamental studies in chemistry, mechanical
engineering, and material science carried out at TU Darmstadt.
126
Magnetocaloric Materials:
Magnetic Refrigeration is an energy efficient cooling technology based on the reversible
magnetisation and demagnetisation of a magnetocaloric material by external magnetic
fields. The group’s activities include investigations into the improvement of the
magnetocaloric La(FeSi)13 compound, a promising material for room temperature
applications. This material is of particular interest for practical refrigerators due to its
sharp magnetic transition and the low toxicity of its constituent elements. Our research
focuses on both fundamental material aspects on how to improve this compound, e.g. by
substitution of other elements to tailor the transition properties, as well as practical aspects
of room temperature magnetic cooling. We have shown that using polymer bonded
magnetocaloric powder as heat exchangers is an inexpensive method, allowing flexibility in
terms of shape to obtain optimum conditions for heat transfer between the solid refrigerant
and the pumped heat exchange fluid. In addition to improving the La(FeSi) 13 compound,
the group studies the synthesis, structural and magnetic characterisation of new magneto
caloric materials, in particular reducing or eliminating the use of rare earth resources. Such
systems include for example Heusler alloys, Fe2P or MnB compounds. The magnetocaloric
research in our group is funded by two national and one European research grants.
Staff Members
Head
Prof. Dr. Oliver Gutfleisch
Research Associates
Dr. Semih Ener
Dr. Bianca Frincu
Dr. Barbara Kaeswurm
PD Dr. Michael Kuzmin
Dipl.-Ing. Marc Pabst
Dr. Iliya Radulov
Dr. Konstantin Skokov
Technical Personnel
Ms. Gabi Andress
Ms. Helga Janning
Dipl.-Ing. Bernd Stoll
Secretary
Ms Brigitte Azzara
PhD Students
M. Sc. Imants Dirba
Dipl.-Ing. Maximilian Fries
Dipl.-Phys. Tino Gottschall
Dipl.-Ing. Konrad Löwe
Dipl.-Wi.-Ing. Simon Sawatzki
Dipl.-Ing. Christoph Schwöbel
External:
M. Eng. Alexandru Lixandru
Dipl.-Phys. Fabian Rhein
M. Sc. Xi Lu
Master Students
Ms. Bahar Fayyazi
Mr. Anok Babu Nagaram
Mr. Farzin Ziaiee Tabary
Mr. Prasad Mishra Tarini
Bachelor Students
Mr. Valentin Brabänder
Ms Almut Dirks
Mr. Florian Esdar
Ms. Adjana Eilts
Guest Scientists
Prof. Toshiyuki Shima
B. Eng Hong Jian.
Mr. Dimitri Karpenkov
Institute of Materials Science –Functional Materials
127
Research Projects
EU, DFG, BMBF, AIF Projects and others
Publications
[1] O. Gutfleisch, K. Güth, T.G. Woodcock, L. Schultz, Recycling Used Nd-Fe-B Sintered
Magnets via a Hydrogen-Based Route to Produce Anisotropic, Resin Bonded Magnets,
Advanced Energy Materials 3 (2013) 151-155.
[2] K. Skokov, K.-H. Müller, J.D. Moore, J. Liu,. A.Y. Karpenkov, M. Krautz, O. Gutfleisch
Influence of thermal hysteresis and field cycling on the magnetocaloric effect in
LaFe11.6Si1.4, J. Alloys and Comp. 552 (2013) 310-317.
[3] S.V. Taskaev, M.D. Kuz’min, K.P. Skokov, D.Yu. Karpenkov, A.P. Pellenen, V.D.
Buchelnikov, O. Gutfleisch, Giant induced anisotropy ruins the magnetocaloric effect in
gadolinium, J. Magn. Magn. Mat. 331 (2013) 33-36.
[4] Y. Skourski,· J. Bartolomé, M.D. Kuz’min, K.P. Skokov, M. Bonilla, O. Gutfleisch, J.
Wosnitza, High-Field Transitions in ErFe11Ti and HoFe11Ti Single Crystals, J. Low Temp.
Phys. 170 (2013) 307-312.
[5] I. Lindemann, A. Borgschulte, E. Callini, A. Züttel, L. Schultz, O. Gutfleisch, Insight
into the decomposition pathway of the complex hydride Al 3Li4(BH4)13, Int. J. of
Hydrogen Energy 38 (2013) 2790-2795.
[6] S.K. Pal, L. Schultz, O. Gutfleisch, Effect of milling parameters on SmCo5 nanoflakes
prepared by surfactant-assisted high energy ball milling, J. Appl. Phys. 113 (2013)
013913_1-6.
[7] S. Garroni, C. Bonatto Minella, D. Pottmaier, C. Pistidda, C. Milanese, A. Marini, S.
Enzo, G. Mulas, , M. Dornheim, M. Baricco, O. Gutfleisch, S. Suriñach and M. Dolors
Baró, Mechanochemical synthesis of NaBH4 starting from NaH-MgB2 reactive hydride
composite system, Int. J. of Hydrogen Energy 38 (2013) 2363-2369.
[8] M. Moore, R. Sueptitz, A. Gebert, L. Schultz, O. Gutfleisch, Impact of magnetization
state on the corrosion of sintered Nd-Fe-B magnets for e-motor applications, Materials
and Corrosion 64 (2013) no 9999, p. 1-6.
[9] N.M. Dempsey, T.G. Woodcock, H. Sepehri-Amin, Y. Zhang, H. Kennedy, D. Givord, K.
Hono and O. Gutfleisch, High coercivity Nd-Fe-B thick films without heavy rare earth
additions, Acta. Mat. 61 (2013) 4920–4927.
[10] K.P. Skokov, A. Yu. Karpenkov, D. Yu. Karpenkov, O. Gutfleisch, The maximal cooling
power of magnetic and thermoelectric refrigerators with La(FeCoSi)13 alloys, J. Appl.
Phys. 113 (2013) 17A945.
[11] V. Khovaylo, M. Lyange, K.P. Skokov, O. Gutfleisch, R. Chatterjee, X. Xu, R. Kainuma,
Adiabatic Temperature Change in Metamagnetic Ni(Co)-Mn-Al Heusler Alloys, Materials
Science Forum 738-739 (2013) 446-450.
128
[12] C. Bonatto Minella, C. Pistidda, S. Garroni, P. Nolis, M. Dolors Baró, O. Gutfleisch, T.
Klassen, R. Bormann, M. Dornheim, Ca(BH4)2 + MgH2: desorption reaction and role of
Mg on its reversibility, J. Phys. Chem. C 117 (2013) 3846-3852.
[13] C. Bonatto Minella, E. Pellicer, E. Rossinyol, F. Karimi, C. Pistidda, S. Garroni, C.
Milanese, P. Nolis, M. Baró, O. Gutfleisch, K. Pranzas, A. Schreyer, T. Klassen, R.
Bormann, M. Dornheim, Chemical state, distribution and role of Ti- and Nb-based
additive on the Ca(BH4)2 system, J. Phys. Chem. C 117 (2013) 4394–4403.
[14] V. Pavlyuk, G. Dmytriv, I. Chumak, O. Gutfleisch, I. Lindemann, H. Ehrenberg, High
hydrogen content super-lightweight intermetallics from the Li-Mg-Si system, Int. J. of
Hydrogen Energy 38 (2013) 5724-5737.
[15] C. Bonatto Minella, I. Lindemann, P. Nolis, A. Kießling, M. Baró, M. Klose, L. Giebeler,
B. Rellinghaus, J. Eckert, L. Schultz, O. Gutfleisch, NaAlH4 confined in Ordered
Mesoporous Carbon, Int. J. of Hydrogen Energy 38 (2013) 8829–8837.
[16] S.V. Taskaev, V.D. Buchelnikov, A.P. Pellenen, M.D. Kuz'min, K.P. Skokov, D. Yu.
Karpenkov, D.S. Bataev, O. Gutfleisch, Influence of thermal treatment on
magnetocaloric properties of Gd cold rolled ribbons, J. Appl. Phys. 113 (2013)17A933.
[17] S.K. Pal, K. Güth, T. G. Woodcock, L Schultz, O. Gutfleisch, Properties of isolated single
crystalline and textured polycrystalline nano/sub-micrometre Nd2Fe14B particles obtained
from milling of HDDR powder, J. Phys. D: Appl. Phys. 46 (2013) 375004_1-8.
[18] R. Sueptitz, S. Sawatzki, M. Moore, M. Uhlemann, O. Gutfleisch and A. Gebert, Effect
of DyF3 on the corrosion behavior of hot‐pressed Nd–Fe–B permanent magnets, Materials
and Corrosion 2013, DOI: 10.1002/maco.201307303.
[19] S. Sawatzki, I. Dirba, L. Schultz, and O. Gutfleisch, Electrical and magnetic properties of
hot-deformed Nd-Fe-B magnets with different DyF3 additions, J. Appl. Phys. 114 (2013)
133902_1-5.
[20] V. Sokolovskiy, V. Buchelnikov, K. Skokov, O. Gutfleisch, D. Karpenkov et al.,
Magnetocaloric and magnetic properties of Ni2Mn12-xCuxGa Heusler alloys: An insight
from the direct measurements and ab initio and Monte Carlo calculations, J. Appl. Phys.
114 (2013) 183913_1-9
[21] J. Thielsch, D. Süss, L. Schultz,, O. Gutfleisch, Dependence of Coercivity on Length
Ratios in Sub-micron Nd2Fe14B Particles with Rectangular Prism Shape, J. Appl. Phys.
114 (2013) 223909_1-5.
[22] M.D. Kuzmin, A. Savoyant, R.Hayn, Ligand Field Parameters and the ground state of
Fe(II)phthalocyanine, J. Chem. Phys. 138 244308 (2013)
129
Grain boundary diffusion processes in Nd-Fe-B magnets
Simon Sawatzki, Imants Dirba, Almut Dirks, Konrad Löwe, and Oliver Gutfleisch
The heavy rare earth (HRE) element Dy is known to increase the temperature stability of
Nd-Fe-B permanent magnets for the use in high performance electric motors and generators
[1]. Its forecasted long term criticality and the lack of alternatives for Nd-Fe-B has led to
the development of the grain boundary diffusion process (GBDP) that reduces Dy without
losing much in remanent magnetisation [2]. In the GBDP the magnet is coated with Dy and
subsequently annealed at temperatures of about 900°C. At this temperature the Nd-rich
phase has melted and Dy diffuses along the grain boundaries. During cooling a thin
(Dy,Nd)2Fe14B shell forms around each individual grain, impeding the nucleation of
reversed magnetic domains in the reversed direction and thus increases coercivity. Several
investigations show improved magnetic properties of sintered magnets using DyF3 for the
GBDP [3,4].
In comparison to sintering, the hot-deformation is an alternative preparation method for
Nd-Fe-B magnets that benefits from a good temperature coefficient of coercivity due to its
nanocrystallinity but still suffers from being an expensive batch process. In hot-deformed
magnets the pressing time is much shorter and the process temperatures are much lower
(700-750°C, 2-10 min) compared to sintered magnets (1000-1100°C, several hours).
Therefore elements selectively diffuse along the grain boundaries during hot-deformation
instead of redistributing within the grains.
Fig. 1: Grain boundary diffusion in hot-deformed Nd-Fe-B magnets using DyF3
We first doped hot-compacted and die-upset Nd–Fe–B magnets with DyF3 (see figure 1).
Because of the nanocrystallinity of hot-compacted magnets, annealing is limited to 600°C
[5]. It was found, that during hot-compaction and die-upsetting DyF3 decomposes and
130
diffuses into the flake via the grain boundaries. Thereby, Dy replaces Nd and forms the
(Dy,Nd)2Fe14B phase that enhances coercivity. The excess Nd interacts with F and forms
RE-F or RE-O-F phases. These phases can either additionally increase or decrease coercivity.
Annealing of hot-compacted magnets at 600°C leads to an F diffusion along the flake
boundary and the formation of RE-F or RE-O-F phases. As a consequence the coercivity
increases for low (<1.2 wt.%Dy) and decreases for high Dy-F fractions (> 1.2wt.%Dy). In
die-upset magnets the oxide layer in the flake boundary is not present and F can directly
interact with the grain boundary phase adjacent the magnetic phase. As a result coercivity
decreases independent of the Dy-F fraction. Best results are obtained for 1.2 wt.% Dy
increasing the coercivity of die-upset magnets by 19 % while remanence is almost retained.
Furthermore the use of DyF3 in hot-compacted magnets was shown to increase the
electrical resistivity, which reduces eddy current losses in motor application and thus
reduces the Dy amount required [6].
Fig. 2: Effect of different low-melting eutectics on the magnetic properties of hot-compacted Nd-Fe-B magnets
In a further study we substituted DyF3 by several rare earth containing low-melting
eutectics and investigated the effect of annealing at 600°C on hot-compacted magnets [7].
The use of DyCu and subsequent annealing for 24 h leads to higher coercivities than DyNiAl
131
with similar remanences, which can be attributed to the lower melting point and thus
higher diffusion coefficient for DyCu. As Al and Cu are both known to reduce the melting
point of the Nd-rich grain boundary phase, the higher Cu-fraction in DyCu than the Alfraction in DyNiAl promotes the diffusion. The use of NdCu and NdAl slightly enhances
coercivity. Annealing of these samples did not lead further improvement of the magnetic
properties. To compare the effectiveness of the alloys commercially available Dy-containing
MQU-G powder with a homogeneous Dy-distribution of 3.85wt.%Dy was hot-compacted. It
shows a higher coercive force than for the annealed DyCu sample. The normalized increase
in coercivity of the MQU-G compared to a Dy-free MQU-F magnet is about 0.20 T/wt.%Dy.
For the annealed DyCu sample the normalized increase is 0.25 T/wt.%Dy (up to a range of
about 2wt.%Dy). This leads to a more effective use of Dy and therefore improved magnetic
properties by the use of low-melting eutectics, although the MQU-F powder was already
optimised for hot-deformation.
References:
[1]
[2]
[3]
[4]
[5]
[6]
[7]
132
O. Gutfleisch, M. A. Willard, E. Bruck, C. H. Chen, S. G. Sankar, and J. P. Liu, Adv. Mater. 23, 821
(2011).
th
K. Park, K. Hiraga, and M. Sagawa, in REPM Proceedings of 16 International Workshop on RE
Magnets and Their Applications, edited by H. Kaneko, M. Homma, and M. Okada (The Japan Institute
of Metals, Sendai, Japan, 2000), pp. 257–264.
H. Nakamura, K. Hirota, M. Shimao, T. Minowa, M. Honshima, Magnetic properties of extremely small
Nd–Fe–B sintered magnets, IEEETrans.Magn. 41(2005)3844–3846.
F. Xu, J. Wang, X.P. Dong, L.T. Zhang, J.S. Wu, Grain boundary microstructure in DyF 3-diffusion
processed Nd–Fe–B sintered magnets, J.Alloys Compd. 509 (2011) 7909–7914.
S. Sawatzki, I. Dirba, H. Wendrock, L. Schultz, and O. Gutfleisch, Diffusion processes in hot-deformed
Nd-Fe-B magnets with DyF3 additions, J. Magn. Magn. Mater. 358-359 (2014), 163-169
S. Sawatzki, I. Dirba, L. Schultz, and O. Gutfleisch, Electrical and magnetic properties of hot-deformed
Nd-Fe-B magnets with different DyF3 additions, J. Appl. Phys. 114, (2013) 133902.
S. Sawatzki, A. Dirks, B. Frincu, K. Löwe, and O. Gutfleisch, Coercivity enhancement in hot-pressed NdFe-B permanent magnets with low melting eutectics, J. Appl. Phys. 115 (2014) 17A705
La(FeSi)13 compounds for application in room temperature magnetic refrigeration
B. Kaeswurm, K.P. Skokov, I.A. Radulov, T. Gottschall, M. Fries, M.D. Kuzmin
and Oliver Gutfleisch
The Magnetocaloric effect is a change in thermodynamic state of a material when subjected
to an applied magnetic field. This phenomenon is long used in low temperature physics in
order to achieve temperatures in the milli Kelvin range. At TU Darmstadt we are
investigating materials which show this effect near room temperature and may potentially
be useful for a new energy efficient refrigeration technology. For optimal performance the
magnetic refridgerant should have a large Magnetocaloric effect, ie large change in entropy
under isothermal conditions, large adiabatic temperature change, low thermal hysteresis,
appropriate thermal and mechanical properties and a tuneable phase transition
temperature, which deterimines the operating temperature. A promising candidate material
is the La(FeSi)13 compound with the crystallographic NaZn13 structure. This material shows
a sharp magnetic transition which is accompanied by a large and reproducible
magnetocaloric effect. The transition temperature can be tuned by addition of other
elements on and off the crystallographic lattice sites. We focus our research on two strands:
i)
Improvement of the compound for example by the addition of other elements
which allows the transition properties to be tuned.
ii)
Study of the material properties under application conditions as a heat exchanger
giving information impacting on product design.
Partial replacement of La by other Rare Earth elements such as Ce, Pr or Nd has been
shown to optimise the magnetocaloric properties of LaFeSi compounds. Adding interstitial
H atoms increases the transition to above room-temperature, while maintaining the
thermodynamical first order character. A room-temperature transition can be obtained by
partial hydrogenation. However, when stored at the transition-temperature, internal
migration of hydrogen causes partially hydrogenated LaFeSi to undergo a magnetic phase
separation [1]. To overcome this, Mn is added which allows obtaining a room-temperature
transition after full hydrogenation. The fully hydrogenated material remains stable at roomtemperature but the Mn substitution reduces the entropy change ΔS as well as the adiabatic
temperature change ΔTAD. Substitution of Pr however, while also lowering the transition
temperature, has been shown to increase ΔS and ΔTAD [2]. We have carried out direct
measurements of adiabatic temperature change ΔTAD on La(FeSi)13 samples with partial Pr
substitution. Bulk samples of composition La1-xPrxFe11.6Si1.4 with x=0 to 0.4 were fabricated
by arc-melting. In an applied field of 2 T the transition temperature shifts from Tt= 208 for
the non-substituted sample to 190 K for x= 0.4. With increasing Pr content the transition
becomes increasingly more sharp indicating thermodynamically first order behaviour.The
adiabatic temperature change, ΔTAD as measured in our dedicated device, increased from
4.8 K for a Pr content of x=0.1 to ΔTAD = 5.4 K for a Pr content of x=0.4. As a next step
we will be investigating the magnetocaloric properties of hydrogenated LaPr(FeSi)13.
As part of the second strand of research into La-Fe-Si we are investigating how
magnetocaloric powder can be used in heat exchangers for use in a magnetocaloric test
bench. As mentioned above, La(Fe,Mn,Si)13Hx has a transition temperature around room
133
temperature and shows good magnetocaloric properties. Despite this, the material is not yet
being used in prototype demonstrators due to its poor mechanical properties.
Hydrogenation causes the material to be brittle and difficult to machine. Hence the material
needs to be compacted into a non-porous bulk in order to be used as a heat exchanger. In
the final device the heat exchanger is anticipated to consist of an assembly of thin, parallel
plates of 0.1-0.3 mm thickness with gaps of 0.1 mm between them [3]. We have shown
that adjusting the preparation route does not only affect the mechanical and thermal
properties of polymer-bonded magneto caloric powder, but that the magnetocaloric
properties can be vastly improved by choosing the right preparation conditions [4].
Fig. 1: Direct Measurement of the adiabatic
temperature change for bulk, powder and powder
compacted under 0.1 GPa with 5 wt % of silver
epoxy.
It was found that the adiabatic temperature change ΔTAD of polymer-bonded material is 10
% higher than for the initial bulk material. Direct Measurements of ΔTAD comparing bulk,
the same material crushed into powder, as well as after compaction under 0.1 GPa with 5
wt. % of silver epoxy is shown in Fig.1. After the optimum compaction conditions had been
established, we were able to assemble a heat exchanger, which can be seen in Fig 2. This
simple porous heat exchanger consists of plates of 0.6 mm thickness with channels of equal
length. This provides us with an easy, yet effective method of producing heat exchangers
form magnetocaloric powder.
Fig. 2: Heat exchanger made of polymer-bonded
LaFe11.6Si1.4 plates.
References:
[1] M. Krautz et al. J.Appl.Phys. 112 (2012) 083918
[2] S. Fujieda et al. J.Appl.Phys. 102 (2007) 023907
[3] M.D. Kuz’min, M. D. Appl. Phys. Lett. 90, 25 (2007) 251916
[4] K.P. Skokov et al. J.Appl.Phys. In press 2014
134
Ion-Beam Modified Materials
The research activities of this group are directly related to interaction processes of matter
with ion beams available at the accelerator facilities of the GSI Helmholtz Centre for Heavy
Ion Research. The interest in high-energy ions (MeV - GeV) is two fold (1) Developing a
better understanding of damage creation under dense and nanometric electronic excitations
and (2) using energetic ions as nanostructuring tool.
Present investigations concentrate on radiation hardness and performance limits of
functional materials to be applied in the future Facility for Antiproton and Ion Research
(FAIR). They are motivated by the risk of limited lifetime of specific materials and devices
under extreme radiation conditions of the future high-intensity beam facility. Beam
absorbers, collimators, targets, and stripper foils have to perform reliably in high-dose
environments, where they experience dimensional and structural changes, stresses and
degradation of properties that control thermal-shock and fatigue resistance. The studies
concentrate on carbon and carbon-based compound materials and characterization of
beam-induced effects by microscopic and spectroscopic techniques as well as by functional
tests (e.g., nanoindentation, bending test, infrared radiometry, thermo-mechanical and
electrical performance).
Nanostructuring with ion beams is based on the fact that at high kinetic energies, each ion
projectile creates a cylindrical track with a few nanometers in diameter which can be
converted into a nanometric channel by chemical etching. The small track size (few nm) in
combination with the large ion range (several tens of µm) allows the fabrication of highaspect ratio structures such as nanochannels, nanotubes, and nanowires. The ion-track
technology provides great flexibility in adjusting the diameter, length, and geometry of
nanostructures under well controllable conditions. Ion-track based nanostructures are
considered as excellent model systems to investigate the influence of size and geometry
effects on technologically relevant optical, electrical, and thermal properties.
The fabrication of nanostructures by means of ion-track technology requires several steps.
First, a thin polymer foil is irradiated with a defined number of energetic heavy ions.
Subsequent chemical etching dissolves the produced damage trails and converts the track of
each individual ion into an open channel. The size and the shape of this channel are
adjusted by controlling the etching conditions (e.g., temperature, time, concentration,
admixtures to etchant, etc.).
Most recent activities concentrate on the fabrication of high-aspect ratio oxide-based
nanotubes by applying atomic layer deposition in order to conformally coat the walls of
track-etched nanopores (more details are provided in the following report).
To produce nanowires, the material of interest is electrodeposited into the channels of the
track-etched polymer template. Specific experience is developed to grow semiconducting
ZnO nanowires for solar-energy applications as well as Bi1-xSbx and Bi2Te3 nanowires for
the study of quantum- and finite-size effects on their magnetotransport and
thermoelectrical properties. Another project investigates the crystallinity and composition
of AuAg alloy or Ag-Au-segmented nanowires. By selectively dissolving the silver
component, highly porous nanostructures or tailored nanowire dimers separated by a gap
of few nm are obtained. Electron energy loss spectroscopy (EELS) in a transmission
electron microscope allows the excitation of localized surface plasmon resonances. This
effect is of interest for application e.g. in surface enhanced Raman spectroscopy.
Institute of Materials Science – Ion Beam Modified Materials
135
Staff Members
Head
Prof. Dr. Christina Trautmann
PhD Students
Dipl. Ing. Loic Burr
Dipl. Phys. Marco Cassinelli
Dipl. Ing. Christian Hubert
M. Sc. Janina Krieg
Bachelor Students
Anthony Dunlap
Dipl. Ing. Katharina Kupka
Dipl. Phys. Liana Movsesyan
M. Sc. Anne Spende
Dipl. Ing. Michael F. Wagner
Research Projects
Fabrication of Bi-based nanowires and their characterisation with respect to thermoelectric
properties (FIAS 2011-2014)
Fabrication of semiconducting nanowires using the ion track technology (Beilstein Institute,
2012 – 2015)
Fabrication and controlled surface functionalisation of mesoporous SiO2 materials and iontrack nanochannels (DFG, Forschergruppe (FOR 1583), 2011-2014)
Radiation hardness of carbon stripper foils under high current UNILAC operation (BMBF,
Verbundforschung, 2012 – 2015)
Radiation hardness of carbon-based components for the future FAIR facility (GSI, 20122015)
Investigation of response of graphite and new composite materials for Super-FRS target and
beam catchers to intense ion beam-induced thermal stress waves (BMBF,
Verbundforschung, 2012 – 2015)
Publications
[1]
Muench, F., Bohn, S., Rauber, M., Seidl, T., Radetinac, A., Kunz, U., Lauterbach, S.,
Kleebe, H.J., Trautmann, C., Ensinger; W.; Polycarbonate activation for electroless plating by
dimethylaminoborane absorption and subsequent nanoparticle deposition, Applied Physics A:
Materials Science and Processing [2013] DOI: 10.1007/s00339-013-8119-z
[2]
Kuttich, B., Engel, M., Trautmann, C., Stühn, B.; Tailored nanochannels of nearly
cylindrical geometry analysed by small angle X-ray scattering, Applied Physics A: Materials
Science and Processing [2013] DOI: 10.1007/s00339-013-8167-4
[3]
Pietschmann, J.F., Wolfram, M.T., Burger, M., Trautmann, C., Nguyen, G., Pevarnik,
M., Bayer, V., Siwy, Z.; Rectification properties of conically shaped nanopores: consequences of
miniaturization, PHYSICAL CHEMISTRY CHEMICAL PHYSICS 15 [2013] 16917-16926,
DOI: 10.1039/C3CP53105H
136
Institute of Materials Science - Ion Beam Modified Materials
[4]
Afra, B., Rodriguez, M. D., Trautmann, C., Pakarinen, O.H., Djurabekova, F.,
Nordlund, K., Bierschenk, T. Giulian, R. Ridgway, M.C., Rizza, G., Kirby, N., Toulemonde,
M., Kluth, P.; SAXS investigations of the morphology of swift heavy ion tracks in alpha-quartz,
JOURNAL OF PHYSICS-CONDENSED MATTER 25 [2013] 045006, DOI: 10.1088/09538984/25/4/045006
[5]
Rodriguez, M. D., Afra, B., Trautmann, C., Kirby, N., Kluth, P., The influence of swift
heavy ion irradiation on the recrystallization of amorphous Fe80B20, MICROELECTRONIC
ENGINEERING 102 [2013] 64-66
[6]
Toulemonde, M., Benyagoub, A., Trautmann, C., Khalfaoui, N., Boccanfuso, M.,
Dufour, C., Gourbilleau, F., Grob, J.J., Stoquert, J.P., Costantini, J.M., Haas, F., Jacquet, E.,
Voss, K.-O., Meftah, A.,, Reply to "Comment on 'Dense and nanometric electronic excitations
induced by swift heavy ions in an ionic CaF2 crystal: Evidence for two thresholds of damage
creation”, PHYSICAL REVIEW B 87, [2013] 056102, DOI: 10.1103/PhysRevB.87.056102,
[7]
Merk, B.,; Voss, K.O., Mueller, I., Fischer, B.E., Jakob, B., Taucher-Scholz, G.
Trautmann, C., Durante, M.; Photobleaching setup for the biological end-station of the
Darmstadt heavy-ion microprobe Nuclear Instruments and Methods in Physics Research
Section B: Beam Interactions with Materials and Atoms 306 [2013] 81-84, DOI:
10.1016/j.nimb.2012.11.043
[8]
Khan, S.A., Tripathi, A., Toulemonde, M., Trautmann, C., Assmann, W.; Sputtering
yield of amorphous C-13 thin films under swift heavy-ion irradiation, Nuclear Instruments
and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
315 [2013] 34-38, DOI: 10.1016/j.nimb.2013.05.044
[9]
El-Said, A.S., Wilhelm, R.A., Facsko, S., Trautmann, C.; Surface nanostructuring of
LiNbO3 by high-density electronic excitations, Nuclear Instruments and Methods in Physics
Research Section B: Beam Interactions with Materials and Atoms 315 [2013] 265-268, DOI:
10.1016/j.nimb.2013.03.008
[10] Schauries, D.; Lang, M.; Pakarinen, O.H, Botis, Afra, B, Rodriguez, M.D.,
Djurabekova, F. , Nordlund, K., Severin, D., Bender, M., Li, W.X., Trautmann, C., Ewing,
R.C., Kirby, N., Kluth, P.; Temperature dependence of ion track formation in quartz and
apatite;Journal
of
Appl.
Crystallography
46
[2013]
1558-1563
DOI:
10.1107/S0021889813022802
[11] Medvedev, N. A., Volkov, A. E., Schwartz, K., Trautmann, C., Effect of spatial
redistribution of valence holes on the formation of a defect halo of swift heavy-ion tracks in LiF,
PHYSICAL REVIEW B 87, [2013] 104103
[12] Medvedev, N. A., Schwartz, K., Trautmann, C., Volkov, A. E., Formation of the defect
halo of swift heavy ion tracks in LiF due to spatial redistribution of valence holes, Phys. Status
Solidi B 250, 4, [2013] 850–857
137
[13] Li, W., Rodriguez, M. D., Kluth, P., Lang, M., Medvedev, N., Sorokin, M., Zhang, J.,
Afra, B., Bender, M., Severin, D., Trautmann, C, Ewing, R. C., Effect of doping on the
radiation response of conductive Nb–SrTiO3, Nuclear Instruments and Methods in Physics
Research Section B: Beam Interactions with Materials and Atoms 302 [2013] 40-477
[14] Dolde, F., Jakobi, I., Naydenov, B., Zhao, N., Pezzagna, S., Trautmann, C., Meijer, J.,
Neumann, P. Jelezko, F., Wrachtrup, J., Room-temperature entanglement between single
defect spins in diamond, Nature Physics 9, [2013] 139-143, DOI: 10.1038/nphys2545
[15] Krauser, J., Gehrke, H.-G., Hofsäss, H., Trautmann, C., Weidinger, A., Conductive
tracks of 30-MeV C60 clusters in doped and undoped tetrahedral amorphous carbon, Nuclear
Instruments and Methods in Physics Research B 307 [2013] 265–268, DOI:
10.1016/j.nimb.2012.12.081
[16] Stolterfoht, N.; Hellhammer, R.; Sulik, B.; Juhász, Z.; Bayer, V.; Trautmann, C.;
Bodewits, E.; Reitsma, G.; Hoekstra, R.; Areal density effects on the blocking of 3-keV Ne7+
ions guided through nanocapillaries in polymers, Physical Review A 88, [2013] 032902 [110]
[17] Fernandes, S., Pellemoine, F., Tomut, M., Avilov, M., Bender, M., Boulesteix, M.,
Krause, M., Mittig, W., Schein, M., Severin, D., Trautmann, C, In-situ electric resistance
measurements and annealing effects of graphite exposed to swift heavy ions, Nuclear
Instruments and Methods in Physics Research B: Beam Interactions with Materials and
Atoms 314 [2013] 125–129, DOI: 10.1016/j.nimb.2013.04.060
[18] Yamaki, T., Nuryanthi, N., Koshikawa, H., Asano, M., Sawada, S., Hakoda, T.,
Maekawa, Y., Voss, K. O., Severin, D., Seidl, T., Trautmann, C., Neumann, R., Ion-track
membranes of fluoropolymers: Toward controlling the pore size and shape, Nuclear
Instruments and Methods in Physics Research B: Beam Interactions with Materials and
Atoms 314 [2013] 77–81
138
High-Aspect-Ratio Nanotubes fabricated by Ion-Track Technology and
Atomic-Layer Deposition
A. Spende1,2, N. Sobel3, I. Alber1, C. Hess3, M. Lukas4, B. Stühn4, M.E. Toimil Molares1,
C. Trautmann1,2
1
GSI, Darmstadt, Germany; 2Materials Research, TU Darmstadt, Germany;
Eduard-Zintl-Institut fur Anorganische Chemie und Physikalische Chemie,
TU Darmstadt, Germany;
4
Experimental condensed matter physics, TU Darmstadt, Germany;
3
Nanotubes and nanochannels embedded in solid state membranes are of high relevance in
many different fields such as nanofluidics, catalysis, health care, or solar energy harvesting.
Suitable fabrication techniques for precise tailoring the dimensions and surface properties
of nanotubes are currently being developed and include, e.g., electroless deposition, sol-gel
processes, and atomic layer deposition (ALD). The latter offers the great opportunity to coat
embedded nanochannels conformaly, even if the nanochannels exhibit high aspect ratios.
Suitable templates with nanochannels are anodic alumina (AAO) [1] and track-etched
polymer membranes [2].
^
In this project, silicon dioxide (SiO2) nanotubes were fabricated by combining the ion-track
technology and ALD. The template was produced by irradiating 30-m thick polycarbonate
(PC) foils at the GSI linear accelerator UNILAC with 2 GeV heavy ions and a fluence of 109
ions/cm2. Subsequent chemical etching transforms each ion track into a cylindrical
nanochannel [3]. Depending on the etching time, cylindrical nanochannels of diameter 30,
55, and 400 nm were produced having an aspect ratio of 1000, 545, and 75, respectively.
The ALD coating was performed using a custom-built ALD system available in the group of
Prof. Christian Hess. SiO2-modified templates with nanochannels of various aspect ratios
were studied by scanning electron (SEM) and scanning transmission electron microscopy
(STEM) in SEM as well as by small angle X-ray scattering (SAXS). Figure 1 displays a
bundle nanotubes obtained by dissolving the polymer template by wet-chemical methods.
Many of the nanotubes are 30 µm long which corresponds to the thickness of the template
used. The outer diameter is constant evidencing that the ALD process provides
homogeneous coating along the full length of the track-etched nanochannels. The inset
shows a representative single SiO2 nanotube (outer diameter 55 nm, wall thickness 10 nm)
clearly demonstrating the tube-like shape of the ALD grown structure. The thickness of the
tube wall is in excellent agreement with the nominal layer thickness expected from the ALD
coating process. According to energy dispersive X-ray spectroscopy (EDX) and X-ray
photoelectron spectroscopy, the composition and stoichiometry of the material confirms the
formation of SiO2 tubes.
139
Fig. 1: SEM image of SiO2 nanotube bundle obtained by ALD coating of track-etched nanochannels and
subsequent dissolving the polymer template. The inset shows a STEM-in-SEM image of a single SiO2
nanotube with regular outer diameter of 55 nm and wall thickness 10 nm evidencing the homogeneous and
conform character of the ALD process.
To obtain further information on the homogeneity of the coating process for nanochannels
of various diameters, small angle x-ray scattering investigations are performed in the group
of Prof. Bernd Stühn yielding average channel radii and radius distributions of a large
number of track-etched nanochannels before and after the coating process. Figure 2 (left)
shows the SAXS intensity as a function of the scattering vector q for a 30-m thick template
before (orange) and after (red) deposition of a 10 nm thick SiO2 layer. The pronounced
ondulations are a clear indication for a small size distribution. The fact that these
ondulations also appear for SiO2-coated membranes is further proof of the high conformity
of the ALD process across the complete length of the high aspect ratio nanochannels as well
as over a large sample area. Compared to the untreated sample, the intensity ondulations of
the ALD coated sample shift to larger q values as expected for smaller channels. To deduce
the pore radius, radius dispersion, and wall thickness from the SAXS data, the
nanochannels are modelled as parallel tubes. Figure 2 (right) displays the calculated
nanochannel radii for various samples etched between 140 and 200 seconds and SiO2coated under identical conditions. As expected, the channel radii increase linearly with
increasing etching time. For all pore sizes, the radii of the coated channels are shifted by 10
nm to smaller values, in complete agreement with the nominal coating thickness of the ALD
process.
140
Fig. 2: Left: SAXS intensity as a function of scattering vector for a 30-µm thick PC membrane (track etched for
140 s) before (orange) and after (red) ALD coating of a 10 nm thick SiO 2 layer. Solid lines are fits assuming
cylindrical channel geometry. Right: Nanochannel radius deduced from SAXS as a function of the etching time
for coated (red) and uncoated (orange) samples. The vertical radius shift by 10 nm is in excellent agreement
with the nominal layer thickness acording to the ALD process.
In conclusion, SiO2 inorganic nanotubes have been fabricated by ALD in ion-track etched
polycarbonate membranes. Electron microscopy as well as SAXS provide clear evidence that
the coating process is homogeneous and shape conform for nanochannels of high aspect
ratios up to 1000. ALD-tailored surface modification of ion-track etched nanochannels
opens up new opportunities in the precise reduction of pore sizes below 15 nm for filtration
or purification applications.
Acknowledgment
Financial support by the DFG project FOR1583 gratefully acknowledged
References:
[1] C. Bae et.al, J. Mater. Chem. 18 (2008) 1362
[2] Elam et. al, Chem. Mater 11 (2003) 3507
[3] M. E. Toimil-Molares, Beilstein J. Nanotechnol. 3 (2012) 860
141
Molecular Nanostructures
The Joint Laboratory for Molecular Nanostructures has been established in 2011 to enhance
the cooperation between the Institute for Nanotechnology at the Karlsruhe Institute of
Technology (KIT) and the Institute of Materials Science at the Technische Universität
Darmstadt. The research focus of the labratory is on nanocarbon materials, in particular on
carbon nanotubes and graphene. Carbon nanotubes and graphene are made of a single
layer of covalently bonded carbon atoms. The electrical, optical, chemical and mechanical
properties of these molecular nanostructures are outstanding, which is why CNTs and
graphene are considered as important new materials for high speed electronics,
optoelectronics, sensing, coatings, material reinforcements and other potential applications.
The motivtation of the Joint Laboratory is to gain new and important insights into carbon
nanomaterials for enabling future applications. In 2013 funding for a Fourier-Transform
Photocurrent-Spectromicroscope using a Supercontinuum-Lightsource has been provided by
the German Science Foundation, the Insitute of Materials Science and the President of the
Technische Universität Darmstadt. The system will be used to study the optoelectronic
properties of materials and functional devices.
Staff Members
Head
Prof. Dr. Ralph Krupke
Research Associates
M.Sc. Asiful Alam
Secretaries
Renate Hernichel
PhD Students
Dipl.-Phys. Feliks Pyatkov (KIT) M.Sc.Wieland Reis (BASF)
M.Sc. Moritz Pfohl (KIT)
M.Sc.Wenshan Li (KIT)
Research Projects
Investigation of non-equilibrium phonon populations in biased metallic single-walled
carbon nanotubes (DFG OR 262/1-2, 2011-2013)
Publications
The Role of Nanotubes in Carbon Nanotube–Silicon Solar Cells; D. D. Tune, F. Hennrich, S.
Dehm, M. F. G. Klein, K. Glaser, A. Colsmann, J. G. Shapter, U. Lemmer, M. M. Kappes, R.
Krupke, B. S. Flavel; ADVANCED ENERGY MATERIALS 3 (2013) 1091, DOI
10.1002/aenm.201200949
Enhancing Raman signals with an interferometrically controlled AFM tip; M. Oron-Carl, R.
Krupke;
NANOTECHNOLOGY 24 (2013) 415701, DOI: 10.1088/0957-4484/24/41/415701
Electron-beam-induced direct etching of graphene; C. Thiele, A. Felten, T. J. Echtermeyer, A.
C. Ferrari, C. Casiraghi, H. v. Löhneysen, R. Krupke; CARBON 64 (2013) 84-91, DOI:
10.1016/j.carbon.2013.07.038
142
Institute of Materials Science - Molecular Nanostructures
Controlled modification of mono- and bilayer graphene in O2, H2 and CF4 plasmas; A. Felten,
A. Eckmann, J.-J. Pireaux, R. Krupke, C. Casiraghi; NANOTECHNOLOGY 24 (2013)
355705, DOI: 10.1088/0957-4484/24/35/355705
Separation of Single-Walled Carbon Nanotubes by 1-Dodecanol-Mediated Size-Exclusion
Chromatography; B. S. Flavel, M. M. Kappes, R. Krupke, F. Hennrich, ACS NANO 7 (2013)
3557-3564, DOI: 10.1021/nn4004956
Electroluminescence in Single Layer MoS2; R. S. Sundaram, M. Engel, A. Lombardo, R.
Krupke, A. C. Ferrari, Ph. Avouris, M. Steiner; NANO LETTERS 13 (2013) 1416-1421, DOI:
10.1021/nl400516a
Catalytic subsurface etching of nanoscale channels in graphite; M. Lukas, V. Meded, A.
Vijayaraghavan, L. Song, P. M. Ajayan, K. Fink, W. Wenzel, R. Krupke; NATURE
COMMUNICATIONS 4 (2013) 1379, DOI: 10.1038/ncomms2399
Single- and Double-Sided Chemical Functionalization of Bilayer Graphene; A. Felten, B. S.
Flavel, L. Britnell, A. Eckmann, P. Louette, J.-J. Pireaux, M. Hirtz, R. Krupke, C. Casiraghi;
SMALL 9 (2013) 631-639, DOI: 10.1002/smll.201202214
143
Catalytic subsurface etching of nanoscale channels in graphite
Maya Lukas1,2, Velimir Meded1,3, Aravind Vijayaraghavan1,4, Li Song5,6, Pulickel M. Ajayan6,
Karin Fink1, Wolfgang Wenzel1 & Ralph Krupke1,2,7
1
Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology, D-76021
Karlsruhe,Germany. 2DFG Center for Functional Nanostructures (CFN), D-76031 Karlsruhe,
Germany. 3Karlsruhe Institute of Technology (KIT), Steinbuch Centre for Computing, D76021 Karlsruhe, Germany. 4School of Computer Science, University of Manchester,
Manchester M13 9PL, UK. 5Research Center for Exotic Nanocarbons, Shinshu University,
Nagano 380-8553, Japan. 6Department of Mechanical Engineering and Materials Science,
Rice University, Houston, Texas 77005, USA. 7Department of Materials and Earth Sciences,
Technische Universität Darmstadt, D-64287 Darmstadt, Germany.
Summary from Nature Communications 4, Article number: 1379 | doi:10.1038/ncomms2399
Catalytic hydrogenation of graphite has recently attracted renewed attention as a route for
nanopatterning of graphene and to produce graphene nanoribbons. These reports show
that metallic nanoparticles etch the surface layers of graphite or graphene anisotropically
along the crystallographic zig-zag <11–20> or armchair <10–10> directions. The etching
direction can be influenced by external magnetic fields or the supporting substrate.
Recently we have reported the subsurface etching of highly oriented pyrolytic graphite by
Ni nanoparticles, to form a network of tunnels, as seen by scanning electron microscopy
and scanning tunnelling microscopy. In this new nanoporous form of graphite, the top
layers bend inward on top of the tunnels, whereas their local density of states remains
fundamentally unchanged. Engineered nanoporous tunnel networks in graphite allow for
further chemical modification and may find applications in various fields and in
fundamental science research.
Local hydrogenation of graphite catalysed by metallic nanoparticles has been known since
the 1970s [1–3]. This process results in straight nanoscale channels that have intersecting
angles of integer multiples of 30° [2]. In recent years it has attracted renewed attention as a
possible route for nanopatterning of graphene, especially for the production of graphene
nanoribbons. Metallic nanoparticles etch the surface layers of graphite [1–8], as well as
single-layer graphene sheets [9–10]. The process is anisotropic along the crystallographic
highsymmetry directions, that is, the zigzag <11–20> or armchair <10–10> directions.
Nanoparticles consisting of various metals, such as Ni [2,8,9,10], Fe [2,7], Pt [3], Co
[2,4,5] and Ag [6], are known to etch channels on graphite surfaces. It was shown that the
etching direction could be influenced by an external magnetic field when Co particles were
used [11]. Similarly, the etching direction on mono and few-layer graphene could be
controlled by the structure of the substrate [12–13]. To date, clear evidence has been
reported only for open channels on the surface of graphite, whereas subsurface etching
remains unclear [4,5,8]. In this study, we have demonstrated now the subsurface etching of
highly oriented pyrolytic graphite (HOPG) by Ni nanoparticles. Besides the well-known
open channels, a network of tunnels is produced, which can be probed by scanning electron
microscopy (SEM) and scanning tunnelling microscopy (STM) as shown in Figure 1. By
semiempirical quantum chemical and density functional theory calculations, we were able
to show that the top layers bend inward on top of the tunnels, whereas their local density
144
of states remains fundamentally unchanged. The etched material presents a new
nanoporous form of graphite with high potential for applications.
Fig. 1: (a) SEM image shows open channels (blue arrows), closed channels (red arrows) and subsurface catalyst
particles (green arrow). (b) An averaged SE intensity profile along the white line in (a) highlights the different
contrast of trenches and tunnels. (c) High-resolution STM images and (d) height profiles of a tunnel. Scale
bars: 500nm (a), 2nm (c).
References:
[1] Tomita, A. & Tamai, J.; Catal. 27, 293–300 (1972).
[2] Tomita, A. & Tamai, Y. J.; Phys. Chem. 78, 2254–2258 (1974).
[3] Santiesteban, J., Fuentes, S. & Yacaman, M. J.; J. Vac. Sci. Technol. A 1, 1198–1200 (1983).
[4] Schäffel, F. et al. Nano Res. 2, 695–705 (2009).
[5] Konishi, S., Sugimoto, W., Murakami, Y. & Takasu, Y.; Carbon 44, 2338–2356 (2006).
[6] Severin, N., Kirstein, S., Sokolov, I. M. & Rabe, J. P.; Nano Lett. 9, 457–461(2009).
[7] Datta, S. S., Strachan, D. R., Khamis, S. M. & Johnson, A. T. C.; Nano Lett. 8, 1912–1915 (2008).
[8] Ci, L. et al. Nano Res. 1, 116–122 (2008).
[9] Ci, L. et al.; Adv. Mater. 21, 4487–4491 (2009).
[10] Campos, L. C., Manfrinato, V. R., Sanchez-Yamagishi, J. D., Kong, J. & Jarillo-Herrero, P.;
Nano Lett. 9, 2600–2604 (2009).
[11] Bulut, L. & Hurt, R. H.; Adv. Mater. 22, 337–341(2010).
[12] Tsukamoto, T. & Ogino, T.; J. Phys. Chem. C 115, 8580–8585 (2011).
[13] Tsukamoto, T. & Ogino, T.; Carbon 50, 674–679 (2012).
145
Collaborative Research Center (SFB)
Collaborative Research Center (SFB)
“Electrical Fatigue in Functional Materials”
2003 – 2014
www.sfb595.tu-darmstadt.de
The center for collaborative studies (Sonderforschungsbereich) has been awarded by the
Deutsche Forschungsgemeinschaft in 2002 to TU Darmstadt and is centered in the
Department of Materials and Earth Sciences with important contributions from the
Department of Chemistry as well as the Mechanical Engineering Department of the
University of Karlsruhe. The center was renewed in 2006 and again in 2010 and is now in
the third and final four-year funding period.
It is comprised of a total of 19 projects and financial resources for the current four yearperiod of about 8 Mio. €. The center has an active guest program with guests visiting from
2 days to 3 months. In 2008, an integrated graduate school was also implemented with
graduate students visiting from other Universities for time frames between 1 to 12 months.
For specific information, please contact either the secretary of the center, Mrs. Gila Völzke,
or the director of the center, Prof. Karsten Albe.
Contact:
SFB 595 Electrical Fatigue in Functional Materials
Department of Materials Science
Alarich-Weiss-Str. 2
64287 Darmstadt
Tel.: +49 6151 16 - 6362
Fax: +49 6151 16 - 6363
Building/Room: L201 / 121
E-mail: albe@mm.tu-darmstadt.de
voelzke@ceramics.tu-darmstadt.de
Electrical fatigue in functional materials encompasses a set of phenomena, which lead to
the degradation of materials with an increasing number of electrical cycles. Electrical
cycling leads to both reversible and irreversible currents and polarisations. Ionic and
electronic charge carriers interact with each other and with microstructural elements in the
bulk as well as at interfaces (grain boundaries and domain walls) and interphases
(electrode/electrolyte). This in turn causes local changes in the distribution of electric
currents and electric potentials. As a consequence local overloads and material degradation
ensues and leads to irreversible loss of material properties. This material degradation can
lead finally to mechanical damage as well as to dissociation reactions. The basic
phenomena of electrical fatigue are not yet understood on a microscopic level.
A key feature of the center is therefore the steady comparison between theory and
experiment. This is utilized to find the physico-chemical origins of electrical fatigue as well
as to develop strategies for new materials and improved material combinations. The
materials of interest are ferroelectrics, electrical conductors (cathode materials for lithium
batteries and transparent conducting oxides) and semiconducting polymers.
The goal of this center of excellence is the understanding of the mechanisms leading to
electrical fatigue. An understanding of the experimental results is supported by concurrent
materials modelling which is geared to encompass different time and length scales from the
material to the component. In the third phase next to a quantitative modelling the
development of fatigue-resistant materials and in the case of ferroelectrics, lead-free
piezoceramics, is of particular focus.
146
Institute of Materials Science – Collaborative Research Center (SFB595)
Projects:
Division A: Synthesis
A1
P.I.: Prof. J. Rödel
Topic: Manufacturing of textured ceramics actuators with high strain
A2 [ended 2010]
P.I.: Prof. M. J. Hoffmann
Topic: Manufacturing and characterization of PZT-ceramics under dc loading
A3
P.I.: Prof. W. Jaegermann
Topic: Boundary layers and thin films of ionic conductors: Electronic structure,
electrochemical potentials, defect formation and degradation mechanisms
A4
P.I.: Prof. R. Riedel
Topic: Novel functional ceramics using anionic substitution in oxidic systems
A5
P.I.: Prof. M. Rehahn
Topic: Synthesis of semiconducting model polymers and their characterization before and
after cyclic electric fatigue
Division B: Characterization
B1 [ended 2010]
P.I.: Dr. R.-A. Eichel
Topic: EPR-Investigations of defects in ferroelectric ceramic material
B2 [ended 2010]
P.I.: Dr. A. G. Balogh
Topic: Investigations of the defect structure and diffusion in ferroelectric materials
B3
P.I.: Prof. H.-J. Kleebe / Prof. W. Donner
Topic: Structural investigations into the electrical fatigue in PZT
B4
P.I.: Prof. H. Ehrenberg
Topic: In-situ investigations of the degradation of intercalation batteries und their
modelling
147
B7
P.I.: Prof. H. v. Seggern / Prof. A. Klein
Topic: Dynamics of electrical properties in fatigued PZT
B8
P.I.: Prof. Christian Hess
Topic: In situ characterization of intercalation batteries using Raman spectroscopy
B9
P.I.: Prof. Gerd Buntkowsky / Dr. Hergen Breitzke
Topic: Characterization of structure-property relationships of functional materials using
solid state NMR
Division C: Modelling
C1
P.I.: Prof. K. Albe
Topic: Quantum mechanical computer simulations for electron and defect structure of
oxides
C2
P.I.: Prof. K. Albe
Topic: Atomistic computer simulations of defects and their mobility in metal oxides
C3 [ended 2010]
P.I.: Prof. R. Müller / Prof. W. Becker
Topic: Microscopic investigations into defect agglomeration and its effect on the mobility of
domain walls
C5
P.I.: Dr. Y. Genenko / Prof. H. v. Seggern
Topic: Phenomenological modelling of bipolar carrier transport in organic semiconducting
devices under special consideration of injection, transport and recombination phenomena
C6
P.I.: Jun. Prof. B. Xu
Topic: Micromechanical Simulation on Interaction of Point Defects with Domain Structure
in Ferroelectrics
148
Division D: Component properties
D1
P.I.: Prof. J. Rödel
Topic: Mesoscopic and macroscopic fatigue in doped ferroelectric ceramics
D3
P.I.: Prof. A. Klein
Topic: Function and fatigue of conducting electrodes in organic LEDs and piezoceramic
actuators
D4
P.I.: Dr. A. Gassmann / Prof. H. v. Seggern
Topic: Fatigue of organic semiconductor components
D5 [ended 2011]
P.I.: Prof. W. Jaegermann
Topic: Processing and characterization of Li-ion thin film batteries
D6
P.I.: Dr. Kyle G. Webber
Topic: The effect of electric field-induced phase transitions on the blocking force in leadfree ferroelectrics
Division T: Industry transfer
T1
P.I.: Prof. H. Ehrenberg
Topic: In operando investigations of fatigue of commercial battery types using neutron
tomography and diffraction
T2
P.I.: Prof. M. Hoffmann
Topic: Influence of PbO stoichiometry on microstructure and properties of PZT ceramics
and multilayer actuators
Integrated Graduate school
MGK
P.I.: Prof. A. Klein
149
Diploma Theses in Materials Science
Alexandra Bobrich; Beschichtung im Rohrinnern mit metallhaltigen DLC-Schichten und deren
Korrosionseigenschaften, 21.06.2013
Frederik Jan Brohmann; Bewertung der Vorgehensweise zur Ermittlung
bruchmechanischen Kenngrößen von Wärmedämmschichtsystemen, 29.07.2013
von
Nico Dams; Erprobung eines Hochtemperatur-Thermoelementes mit Rhenium-Mantel,
31.07.2013
Almut Dorothea
21.05.2013
Dirks;
Korngrenzdiffusionsprozesse
in
NdFeB-Permanentmagneten,
Moritz Elsaß; Charakterisierung von Wärmedämmschichtsystemen bei Variation der
Vorbeanspruchung und der Mikrostruktur, 29.07.2013
René Fischer; Herstellung und Untersuchung von hybriden SWCNT-PEDOT Elektroden für den
Einsatz in organischen Fotodioden, 22.07.2013
Philipp Torben Geiger; Selbstheilung von Siliciumkeramiken, 02.05.2013
Oliver Genschka; Synthese von Vanadiumcarbid-basierten Nanokompositen aus SingleSource-Präkursoren, 10.12.2013
Thorsten Gröb; Verformungsinduzierte Martensitbildung in ADI, 16.05.2013
Anja Habereder; Stickstoffdotierte
Brennstoffzellen, 16.05.2013
Kohlenstofffasern
als
Trägermaterial
in
PEM-
Ulla Hauf; Untersuchung zur Herstellung von Platin-Cerment-Verbund-Komponenten,
27.06.2013
Shenshen He; Herstellung und Charakterisierung von texturierten KNN-basierten bleifreien
piezoelektrischen Keramiken, 06.11.2013
Jan Christian Hellmann; Herstellung und Charakterisierung kathodenzerstäubter
Schichten für den Einsatz in Solarzellen, 04.06.2013
-
Belma Hota; Synthese metallischer Nanodrähte und deren Anwendung in transparenten
leitfähigen Schichten, 14.05.2013
Nicolas Jansohn; Entwicklung einer FeCo Legierung für die Anwendung im MIM Prozess,
04.11.2013
Wolfgang Paul Koch; Demage development in bidirectionally reinforced carbon fiber
composites, 04.06.2013
Ludmila Konrad; Impact of Catalyst Type on PEMFC Performance, 30.04.2013
150
Diploma Theses in Materials Science
Sonja Madloch; Characterization of surface plasmons of individual gold nanowires by
infrared spectroscopy, 29.04.2013
Michael Niederle; Sinterverhalten und –einfluss auf optische Eigenschaften von Cer-dotiertem
Yttrium-Aluminium-Granat, 02.12.2013
Verena Pfeifer; Grenzflächeneigenschaften von Anatas und Rutil, 21.05.2013
Anke Scherf; Mikrostruktur und Oxidationsverhalten fein lamellarer Fe-Al in situ
Kompositwerkstoffe, 21.05.2013
Simon Wallenborn; Technologie- und Prozessentwicklung von Festkörperelektrolytschichten:
Abscheidung sowie elektrische Leitfähigkeit von titanhaltigen Lithium-Phosphatgläsern,
28.11.2013
Jens Wehner; Statistical switching kinetics in ferroelectrics, 21.05.2013
Karen Wilken; Tandem Cells providing High Open Circuit Voltages for photoelectrochemical
Water Splitting, 17.05.2013
Bachelor Theses in Materials Science
151
David Brandt; Electromechanical Characterization of the
x(Ba0.7Ca0.3)TiO3 Lead-Free Piezoceramic System, 16.09.2013
(1-x)Ba(Zr0.2Ti0.8)O3-
Anthony Dunlap; Ion-beam Induced Structural Modifications of Carbon Foils, 02.09.2013
Adjana Eils; Optimierung der Quellaktivierung von Polymertemplaten zur stromlosen
Metallabscheidung, 18.09.2013
Fabian Johannes Grimm; Sintern strukturierter Aluminiumoxidschichten auf steifen
Substraten mit einer Glasphase, 24.09.2013
Carola Hahn; Construction of a high temperature resistivity measurement setup and
investigation of oxidation stability of SrMoO3 thin films, 07.11.2013
Tim Hellmann; Kobaltnanoröhrchen durch stromlose und elektrochemische Abscheidung in
ionenspurgeätzte Polykarbonat-Template, 13.09.2013
Laszlo Horak; Elektrische und
Ultraschallwandlern, 03.07.2013
mechanische
Kontaktierung
von
Hochtemperatur-
Silke Innetsberger; Untersuchung der Randeigenschaften geklopfter Werkstücke, 06.08.2013
Martin Jäcklein; Temperaturabhängige Topographie von Kollagen Typ I, 18.09.2013
Marcel Jost; Anwendung eines neuen Polierverfahrens zur Oberflächeneinglättung von
Ermüdungsproben und Herstellung von TEM-Proben, 13.03.2013
Peter Keil; Einfluss des Substratmaterials und der Substratrauheit auf das Sinterverhalten
strukturierter Aluminiumoxidschichten, 12.03.2013
Christoph Kipper; Herstellung und Charakterisierung von Kupfer-Platin-Nanoröhren,
13.12.2013
Christoph Kurt Josef Kober; Herstellung und Charakterisierung von Kalium-NatriumNiobat-Dickschichten über einen Sol-Gel-Prozess, 13.03.2013
Hans Justus Köbler; Synthese und Charakterisierung von Polyanilin-geträgerten Pt-Ru
Katalysatoren für die Direktmethanol-Brennstoffzelle, 31.01.2013
Leonie Koch; Atomistic simulation of shear localization in metallic glasses, 29.04.2013
Moritz Liesegang; Herstellung und Eigenschaften von kohlenstoffreichen polymerabgeleiteten
SiOC-Precursorkeramiken, 30.09.2013
Julian Mars; Struktur ionischer Flüssigkeiten auf molekularer Ebene, 18.02.2013
Sven Milla; Stromfreie Synthese metallischer Nanodraht- und Nanoröhrennetzwerke,
27.03.2013
152
Thomas Pohl; Herstellung und Charakterisierung von Eisen-dotierten BST-Dünnschichten,
21.10.2013
Stefan Schlißke; Elektronenleitung in OC3C8-PPV: Einfluss der elektrischen Ermüdung und
Rolle der Kontaktmaterialien, 02.04.2013
Michael Marcus Schmitt; Nanotribologische Untersuchungen von Polystyrol-Partikeln auf
Silizium-Oberflächen mit Hilfe des Rasterkraftmikroskops, 20.08.2013
Schrock, Adrian; Strukturelle Charakterisierung von NaNbO3 Einkristallen, 16.12.2013
Konrad Schubert; Rheoelektrische und Rheomikroskopische
Reaktionsharzen mit Kohlenstoffnanoröhren, 23.09.2013
Untersuchungen
an
Jona Schuch; Morphologieeinfluss bei der Synthese von oxydischen Kupfer/Cobalt
Heteronanomaterialien, 01.03.2013
Theresa Schütz; Korrosionsverhalten von hochgradig verformtem ferritischem Stahl,
14.05.2013
Romana Schwing; Prozessfensterbestimmung
Gusseisenwerkstoff EN-JS2070, 29.04.2013
der
ADI-Wärmebehandlung
für
den
Sebastian Steiner; Untersuchungen zur Ein- und Auslagerung von Lithium in LiAl- und
Silizium-Legierungsanoden, 15.02.2013
Mathias Storch; Untersuchung von polymer-abgeleiteten Si(O)C(N) Keramiken und
Si(O)C(N)/Hard-Carbon Kompositen als potentielle Na-Ionen Speichermaterialien,
16.12.2013
Andreas Taubel; Messung Elektrischer Feldverteilungen auf Metallmatrix-Verbundwerkstoffen
mittels Scanning Kelvin Probe Microscopy, 18.09.2013
Florian Weyland; Charakterisierung von selbstorganisierten Monolagen auf Al2O3 für
Transistoranwendungen, 05.08.2013
David Norbert Wieder; Messung des Kontaktwinkels auf durch Plasmaimmersion
modifizierten Oberflächen, 19.03.2013
Leoni Wilhelm; Der Gasphasensinterprozess in LiF dotiertem Mg-Al-Spinell, 08.05.2013
Maximilian Wimmer; Porous Carbon / Polymer-derived Ceramic Composites as Anode
Material for Li-Ion-Batteries, 15.04.2013
Golo Joachim Zimmermann; Untersuchung der Adhäsionsneigung von eloxiertem
Aluminium mittels Rasterkraftmikroskopie an Luft, 27.03.2013
Alexander Zimpel; Synthesis and High-Temperature Behavior of SiMgOC-Based Ceramic
Composites, 15.10.2013
153
Master Theses in Materials Science
Aniruddh Das; Investigation of microstructure and mechanical properties of brazed joints
with low silver containing brazing alloys, 05.11.2013
Thomas Geoffroy; Can a change in materials properties of N-MOSFET's lead to an increase of
the snapback voltage?, 03.09.2013
Xueying Hai; Material Anticipation Study for Heat Dissipation in Electric Switchgears,
30.08.2013
Lukas Hamm; Morphologie und elektrische Eigenschaften von nasschemisch hergestelltem
Kupfer-II-Oxid, 01.11.2013
Cornelia Hintze (Klepickij); Multifunctional Properties of Graphene-Silica Nanocomposites,
15.08.2013
Heide Ines Humburg; Effect of Doping on the Piezoelectric Properties of (Ba1-xCax)(ZryTi1y)O3, 04.09.2013
Michel Valentin Kettner; Ionic liquid gels as gate materials in organic field-effect transistors,
31.07.2013
Chinomso Nwosu; Optimization of mechanical and conductivity properties of poly
(oxyethylene) (poe), modified polyethylene glycol (npeg)and a blend of poe:npeg reinforced by
nanocrystalline cellulose and crosslinking, 02.09.2013
Tobias Rödlmeier; Dye-Sensitized Bulk Heterojunction Solar Cells with Small Molecules,
16.09.2013
Tanju Alexander Sirman; Pulsed Laser Deposition of Sr2CrWO6 double Perovskite thin films,
02.09.2013
Lukas Wardenga; Characterization of Zr and H doped In2O3 films deposited by radio
frequency magnetron sputtering, 04.12.2013
154
Master Theses in Materials Science
PHD Theses in Materials Science
Tobias Adler; Zn(O,S) Puffer Eigenschaften in Cu(In, Ga)Se2 Solarzellen, 26.11.2013
Sebastian Milan Becker; Zinn-haltige Oxide als Elektrodenmaterialien für Lithium-IonenBatterien, 31.01.2013
Jennifer Bödecker; Randschichtmodifikation von integral verzweigten Blechprofilen mit UFG
Gradientengefügen, 23.10.2013
Anna Castrup; Deformation Processes in Magnetron Sputtered Nanocrystalline Palladium and
Palladium Gold Films, 05.11.2013
Robert Dittmer; Lead-Free Piezoceramics - Ergodic and Nonergodic Relaxor Ferroelectrics
Based on Bismuth Sodium Titanate, 19.06.2013
Daniel Jason Franzbach; Field Induced Phase Transitions in Ferroelectric Materials,
02.09.2013
Yan Gao; Nanodomain Structure and Energetics of Carbon Rich SiCN and SiBCN PolymerDerived Ceramics, 27.11.2013
Melanie Gröting; Ab-initio Calculations of the Relaxor Ferroelectric Na1/2Bi1/2TiO3 and its
Solid Solutions, 03.05.2013
Hanna Christine Hahn; Chemische und strukturelle Untersuchung des Alterungsverhaltens
von kommerziellen Dreiwegekatalysatoren, 29.05.2013
Holger Stefan Hain; Spinelle als Anodenmaterialien für Lithium-Ionen-Akkumulatoren,
06.05.2013
Silke Hayn; First-principles calculations on structural and thermodynamic stability of
(Na1/2Bi1/2,Ba)TiO3 and Pb(Zr,Ti)O3, 11.02.2013
Sandra Hildebrandt; Synthesis and thin film growth of alkaline cobaltates NaxCoO2 and
LixCoO2, 18.02.2013
Erwin Matti Hildebrandt; Oxygen Engineered Hafnium Oxide Thin Films grown by Reactive
Molecular Beam Epitaxy, 28.02.2013
Vanessa Kaune; Entstehung und Eigenschaften von UFG Gradientengefüge durch
Spaltprofilieren und Spaltbiegen höherfester Stähle, 23.10.2013
Lorenz Kehrer; Sauerstoffinduzierte Defektzustände in Thiophen-basierten organischen
Feldeffekttransistoren, 24.01.2013
PhD Theses in Materials Science
155
Arne Kriegsmann; Richtungsabhängiges Rissausbreitungsverhalten in Gradientenwerkstoffen,
04.12.2013
Qiran Li; Development of electrode materials based on complex oxides for high capacitance
devices, 27.09.2013
Falk Adrian Münch; Stromlose Synthese metallischer Nanoröhren in ionenspurgeätzten
Polymertemplaten, 28.03.2013
Babak Nasr; Electrochemical Gating of Oxide Nanowire Transistors at Low Operating Voltage,
16.04.2013
Quoc Hung Nguyen; (Bio)Molecular Transport and Recognition in Heavy Ion Track-Etched
Polymeric Nanopores, 19.04.2013
Johan Pohl; Structure and properties of defects in photovoltaic, 23.01.2013
Jonathan Schäfer; Atomistic Simulations of Plasticity in Nanocrystalline Alloys, 31.01.2013
Nina Maria Schweikert; Impedanzspektroskopische Untersuchungen an Lithium-IonenBatterien, 30.01.2013
Tim Seidl; Radiation hardness of superconducting magnet insulation materials for FAIR,
30.01.2013
Mahdi Seifollahi Bazarjani; Micro- and Mesoporous Polymer Derived Ceramic
Nanocomposites with Tailored Functionalities for Energy and Environmental Applications,
27.11.2013
Yohan Seo; Toughening Mechanisms of Ferroelectrics, 23.08.2013
Md. Tamez Uddin; Metal oxide heterostructures for efficient photocatalysts, 16.09.2013
Mehran Vafaee Khanjani; Orbital Engineering of Pulsed Laser Deposited Single-layered
Manganite Thin Films, 29.11.2013
Daniel Walker; Improving Performance in Metal Oxide Field-effect Transistors, 21.06.2013
Zilin Yan; Microstructure evolution during sintering of ceramic multilayer capabilities:
nanotomography and discrete simulations, 17.10.2013
156
PHD Theses in Materials Science
Mechanical Workshop
The mechanical workshop of the Institute of Materials Science is designing, manufacturing
and modifying academic equipment for a broad range of projects. In the year 2013 the
workshop was involved in the following major projects:

Components for Evaporation System for Rotated Fibre Substrates

UHV-preparation chambers
(electro)chemical treatment

Components for six-circle diffractometer

Design and manufacturing of a protection chamber for x-rays with up to 150keV photons

UHV baby chamber for x-ray diffraction experiments
dedicated
for
MBE,
CVD,
PVD,
PLD
and
Staff Members
Head
Jochen Rank
Technical Personnel
Frank Bockhard
Volker Klügl
Ulrich Füllhardt
Herry Wedel
Electrical Workshop
The electrical workshop of the Institute of Materials Science was involved in the following
projects:

Maintenance and repair of various academic equipment like the Electron Probe
Micro-Analyzer (EPMA), Secondary Ion Mass Spectrometry (SIMS), sintering
furnace, Transmission Electron Microscopy (TEM), X-Ray powder Diffractometer
(XRD) and Molecular Beam Epitaxy (MBE)

Design and development of electronic components for specific research projects like
temperature control unit, data logging, power controller, high voltage amplifier,
high voltage power supply, measuring amplifier, high temperature furnace for
impedance measurements

Development of testing software (V-Basic / LabView / i-Tools)
Staff Members
Electronic Personnel
Michael Weber
Institute of Materials Science – Mechanical and Electrical Workshop
157
Institute for Applied Geosciences
Preface
Many of today’s major societal challenges are, to a large extent, geoscientific origin. The
efficient management of water as well as other geo-resources, the securing of our future
energy demands, or the understanding of the effects of the anthropogenic alteration of
global cycles are vital for the future development of our society.
The Institute of Applied Geosciences at the TU Darmstadt has continued its efforts to focus
research activities as well as the educational program on our key activities in Water –
Energy – Environment.
The first renovation phase of our 50 year old building is now completed and was celebrated
on October 25 by a nice gathering with our Chancellor Dr. Manfred Efinger. In the
meantime, all groups of the Institute, after having been separated for nearly one year,
moved back into the fully renovated building and are now located in their familiar
environment. We are very excited about the modern and inspiring working environment.
Our consecutive Bachelor and Masters program ‘Angewandte Geowissenschaften’ is fully
implemented and proves to be very attractive for prospective students. In October 2013,
The total number presently enrolled at the Institute of Applied Geosciences is 370 students.
In the focus of the 8th deep geothermal energy forum, held by the research group of Prof.
Ingo Sass on October 1st 2013 at the Institute of Applied Geosciences, were presentations of
the recent Hessian deep geothermal energy power plant projects and their public
participation campaigns.
158
Institute of Applied Geosciences – Preface
The strongly discussed topic of induced seismicity and the area of conflict between energy
exploitation and technological impact assessment were addressed in a public presentation
series focused on different aspects of man-made seismicity. The presentations took place
from June 2013 till February 2014 and were funded by the BUND Hesse and house of clean
energy.
The hydrogeology group of Prof. Christoph Schüth coordinates the EU FP 7 project
‘MARSOL – Managed Aquifer Recharge as a Solution to Water Scarcity and Drought’ with
21 partners from 7 countries. With a total budget of 8 Mio €, the main objective of
MARSOL is to demonstrate that MAR is a sound, safe and sustainable strategy which can be
applied with great confidence. Therefor, 8 field sites are operated in southern Europe using
different waters (treated waste water, desalinated water, and river water) while applying
different techniques to replenish depleted groundwater resources.
As it is a long standing tradition in Geosciences to conclude the academic year with the
‘Barbara Fest’, all faculty, staff and students got together to discuss the events of the year as
well as the future in a very friendly and positive atmosphere. Due to the high number of
freshmen, the welcome ceremony of the new students, who were babtized during this
event, was rather crowded but, finally, everyone was finally officially accepted as a new
member of the Institute of Applied Geosciences.
Institute of Applied Geosciences – Preface
159
Physical Geology and Global Cycles
In the solar system, Earth is a unique rocky planet with an ocean and an atmosphere. It is
inhabited by bacteria since about 4 billion years and by higher life – plants and animals –
since ca. 600 million years. Organisms, air, water, and rocks are interconnected in a never
ending cycle of matter and energy: The Earth System.
The crustal plates of Earth are driven by radioactive heat. This causes creation of new crust
at mid-oceanic ridges at rates of several centimeters per year. On the other side, plate
margins become subducted into the mantle again or fold up vast mountain ranges, like the
Alps and the Himalayas, combining rocks of very different origin. During subduction the
basaltic crust is partially melted, generating more felsic magmas which rise to form plutons
and to cause lines of andesitic volcanoes such as occurring around the entire Pacific Rim.
This is called the endogenic cycle of rocks.
At the same time Earth receives solar radiation which moves air and water in gigantic
cycles around the planet. Specifically the water cycle causes the denudation of mountains
by mechanical erosion and the leveling of plains by chemical weathering, the latter aided
tremendously by vegetation and its CO2-input to soils. This is called the exogenic cycle of
rocks.
This exogenic cycle is increasingly impacted by mankind. The radiation balance of the
atmosphere has been upset by the emission of carbon dioxide, methane, and other trace
gases. Earth is warming. Industrially produced chlorinated hydrocarbons have risen to the
stratosphere, weakening the protective ozone layer. Dust from traffic, industry and
agriculture produces reagents which alter air chemistry, causing unprecedented interactions
with the marine realm, vegetation and even rocks through acidification, excessive
deposition of nutrients and salts. Dry and wet deposition of anthropogenic (i.e. produced
by humans) particles can be measured world-wide. The population explosion caused the
intensification of agriculture and an alarming loss of topsoil while reducing the extent of
natural ecosystems at the same time. Artificial fertilization of soils causes wide-spread
nitrate pollution of shallow ground waters. Urbanization alters the water cycle above and
below ground. Local leakage of chemicals impacts soil, rivers and ground water. Civil
engineering causes alterations in almost all rivers world-wide, and even coastal oceans
show increasing eutrophication, siltation and ecosystem changes in the water column and
in their shallow sediments. Scars left by mining of minerals and fossil energy are visible
everywhere and cause increasing problems. Throughout the globe man has changed the
rate of natural processes. He spreads ever further into the landscape, utilizing regions and
building in areas which are not suitable for construction, considering their natural risks.
Thus, damage of natural catastrophes rise each year, endangering the world insurance
system. These processes and their consequences are topics in Environmental Geology.
Understanding Global Change and accepting the responsibility of mankind to conserve the
planet and its resources for future generations are prerequisites for ensuring a sustainable
development. The division of Physical Geology and Geological Cycles at the Institute for
Applied Geosciences addresses questions important to environmental geology both in the
present and in the geological past.
160
Institute of Applied Geosciences – Physical Geology and Global Cycles
Staff Members
Head
Prof. Dr. Stephan Kempe
Research Associates
Dr. Günter Landmann
Technical Personnel
Ingrid Hirsmüller
Secretaries
Kirsten Herrmann / Pia Cazzonelli
PhD Students
Ingo Bauer, Christina Bonanati
Diploma Students
Sven Philipp
Student research
projects
Jan Will
Hans-Peter Hubrich
Research Projects
3D Scanning of caves and speleogenetic process studies
Pyroducts (Lava Tunnels) in the Kahuku Ranch area, Hawaii Volcanoes National Park
Desert Kites in the Harrat of Jordan
Dekapolis Tunnel, a presumably >100 km long Roman aqueduct system in Northern
Jordan
Tectonic structure of the southern boundary of the Harz Mountain and its development
since the Permian
Paleoclimate of the Lake Van region (Eastern Anatolia) in the period 20-15 ka BP
Past climate reconstruction on sediment of the Layla Lake, Saudi Arabia
Publications
Articles and book chapters:
[1] Lauerwald, R., Hartmann, J., Moosdorf, N., Kempe, S., & Raymond, P.A. 2013: What
controls the spatial patterns of the riverine carbonate system? A case study for North
America. - Chemical Geology, 337-338: 114–127. DOI:10.1016/j.chemgeo.
2012.11.011
[2] Kempe, S., 2013: Morphology of speleothems in primary (lava-) and secondary caves.
- In: Shroder, J. (Editor in Chief), Frumkin, A. (Ed.), Treatise on Geomorphology.
Academic Press, San Diego, CA, vol. 6, Karst Geomorphology, pp. 267–285.
[3] Kempe, S., & Al-Malabeh, A., 2013: Desert kites in Jordan and Saudi Arabia:
Structure, statistics and function, a Google Earth study. – Quaternary International,
297: 126-146. http://dx.doi.org/10.1016/j.quaint.2013.02.013,
161
[4] Lauerwald, R., Hartmann, J., Moosdorf, N., Dürr, H.H., & Kempe, S., 2013: Retention
of dissolved silica within the fluvial systems oft he cconterminous USA. –
Biogeochemistry 112(1-3): 637-659. DOI: 10.1007/s1
0533-012-9754-8
[5] Kempe, S., & Al-Malabeh, A., 2013: New geoglyphs of the Jordanian Harrat. - Past
Horizons. May 10, http://www.pasthorizonspr.com/index.php/archives/05/2013/
new-geoglyphs-of-the-jordanian-harrat
[6] Kempe, S., Naumann, G., & Dunsch, B., 2013: Athanasius Kircher’s chapter XX „About
caves, fractures and the innumerable passages of the earth“ and the Grotto of
Antiparos from „Mundus subterraneus“, 1678, translated from Latin. – In: Filippi, M.
& Bosák, P. (eds.), Proceedings 16th Intern. Congr. Speleology, Brno, July 21 -28,
2013, Vol. 1: 59-64.
[7] Knolle, F., Kempe, S., & Travassos L.E.P., 2013: Nazi military use of German caves,
Dr. Benno Wolf and the world cave registry project. – In: Filippi, M. & Bosák, P.
(eds.), Proceedings 16th Intern. Congr. Speleology, Brno, July 21 -28, 2013, Vol. 1:
65-70.
[8] Bonanati, C., Bauer, I., & Kempe, S., 2013: Radon measurements in Austrian and
Slovenian caves with an Alphaguard instrument. – In: Filippi, M. & Bosák, P. (eds.),
Proceedings 16th Intern. Congr. Speleology, Brno, July 21 -28, 2013, Vol. 2: 479-484.
[9] Bauer, I., Kempe, S., & Bosted, P., 2013: Kahuenaha Nui (Hawaii): A cave developed
in four different lava flows. – In: Filippi, M. & Bosák, P. (eds.), Proceedings 16th
Intern. Congr. Speleology, Brno, July 21 -28, 2013, Vol. 3: 231-236.
[10] Bosted, P., Gracanin, T., Hackell, V., Bosted, A., Bauer, I., & Kempe, S., 2013: The
Keokeo lava tube system in Hawaii. – In: Filippi, M. & Bosák, P. (eds.), Proceedings
16th Intern. Congr. Speleology, Brno, July 21 -28, 2013, Vol. 3: 243-246.
162
Radon measurements in Austrian and Slovenian Caves with an
AlphaGuard Instrument
Christina Bonanati, Ingo Bauer, Stephan Kempe
In September 2012, radon and CO2 measurements were carried out in Lipiška jama and
Mačkovica in Slovenia and Austria’s Dachstein-Mammuthöhle. The AlphaGUARD proved to
be a suitable device for long- and short-term radon measurements in caves. Values ranged
from undetectable in some locations of Dachstein-Mammuthöhle to 4920 ± 549 Bq m-3 in
Mačkovica, presumably correlating with ventilation, material and size of the caves. A longterm measurement in Mačkovica revealed no diurnal variation pattern. In the old parts of
Dachstein-Mammuthöhle there is no threat for workers or tourists from radiation.
Overview
Radon is a tracer for cave climate and air circulation and can be a potential threat for
workers, speleologists or tourists. 222Rn is an inert noble gas, a naturally occurring
radioactive daughter product of 226Ra from the 238U decay chain with a half-life of only 3.82
days. It has a diffusion coefficient of around 1*10-6 m2s-1 2,3; the diffusivity of .Rn is limited
and dependent on the porosity and moisture of the material Various parameters affect the
radon concentration in cave air and its release from rocks, cave sediments and water:

Its emanation coefficient depends on mineralogy, density and porosity, grain-size and shape – moisture1 and the spatial occurrence of radon in the mineral grains2.

Diffusive and advective transport processes in the cave and mixing with ambient
atmospheric air. Ventilation is governed by the specific shape of the cave and can be
caused by pressure and temperature differences, the drag force from changes of water
levels, or harmonic movements which can occur due to compression of air.
Method
The measurement setup consists of an AlphaPUMP and the AlphaGUARD PQ 2000 PRO
(Genitron Instruments GmbH). Cave air was pumped into the ionisation chamber of the
AlphaGUARD. In order to determine the radon concentration in the air the ionisation
chamber was kept closed for a minimum of 11 minutes after it was filled, by connecting the
hoses with each other to produce a closed cycle. For the long-term measurement, the hoses
were taken off and the AlphaGUARD was put into diffusive mode in which every hour one
average value is documented. The AlphaGUARD measures and records simultaneously
atmospheric pressure, temperature and humidity with integrated sensors. CO2
concentration in the cave air was measured with a handheld DRÄGER Multi Gas Detector.
Measurements were carried out in September 2012 in Dachstein-Mammuthöhle (Austria)
and Mackovica and Lipiška jama (Slovenia).
• The Dachstein Mammut Höhle revealed the lowest Radon activity concentration in the
cave air. It ranged from undetectable (error bigger than value) to 233 ± 44 Bq m-3. The
generally low radon concentration reflects the strong ventilation and connection to outside
air. Furthermore it might be possible that the wet cave loam has an influence on a general
low exhalation rate of the cave material as water in the pore-space can decrease the
exhalation of radon 3,5.
163
• In Lipiška jama the measurements reveal a general increase of the radon and CO2
concentration with depth (Fig. 1). The strong ventilation occurring between the two
entrances gives rise to low radon concentrations at 340 ± 145 Bq m -3 in the “Drca” (L1). A
very high radon level at 3644 ± 500 Bq m-3 in the artificial passage at the end of the cave
(L8) reflects the impeded ventilation resulting in radon accumulation. High values were
also measured in the narrow passages of the “Labirint” (L8) which does not contain much
fine sediment and is not well
ventilated. Low values which
were measured in the “Kozinski
Rov” and the “Suhi Izvir”
suggests a connection with
outside air through fissures.
CO2 concentrations ranged
from 3000 ppm near the
entrance (L1) to 15 000 ppm in
front of the entrance to the
loamy passage (L9). Local,
however non-locatable CO2
sources
and
impeded
ventilation can give rise to the
high CO2 concentrations in the
lower parts of the cave.
Figure 1. Longitudinal cross-section6 of Lipiška jama with measurement locations.
• In Mackovica, measurements were done at two sites, M1 at the end of “Mala Dvorana”
and M2 below the entrance to “Velika Dvorana”. The average radon activity concentration
was 4585 Bq m-3. At site M2 the CO2 concentration was 0.15 Vol %. At this site, a long-term
diffusive measurement was run for 32 hours. During the measurement the air pressure
ranged from 969 to 965 mbar. In the first hours the radon values were around 4000 Bq m-3.
Then they constantly dropped down to 3104 ± 189 Bq m-3 until 5 p.m.. The drop is
coherent with a slight drop in pressure. However, even though air pressure rose again, the
radon level stayed constant until the next morning. The long-term radon measurement
shows no correlation with
ambient
atmospheric
air
temperature (Fig. 2). At the
time of the measurement
campaign water levels were
low everywhere. Thus it is
unlikely that there was a
change in water level in the
siphon at the back of the cave,
influencing the measurement
results. The student group
visiting the cave at the
beginning of the long-term
measurement might
have
affected the air movement.
Figure 2. Mackovica long-term radon monitoring.
164
Conclusion
•
•
•
•
•
The AlphaGUARD proves to be a suitable device for long- and short-term radon
measurements in caves.
The measured radon activity concentrations in the cave air are at least one order of
magnitude lower than the specific activities of the potential source material. Radioactive
equilibrium has not been reached. Reasons are the ventilation or impeded radon
exhalation due to moisture or low effective porosity of the material.
The highest radon levels were measured in Mackovica, the smallest of all three caves
with the least ventilation. The long-term measurements suggest that air temperature
outside the cave is not a driving force in ventilating the cave with outside air in summer.
In Lipišca jama, radon levels were also high, but lower values in deeper parts of the cave
suggest the existence of unknown pathways, enhancing the air circulation. Variation in
moisture or textural and chemical properties of the sediments may influence the
differences in radon levels in the less ventilated parts of the caves.
The measurement results from Dachstein-Mammuthöhle suggest a strong air circulation
and thus frequent mixing of cave air with ambient atmospheric air. The radon levels are
too low in order to be used for any study on air circulation within the cave. There is no
threat for workers or tourists from radiation.
References
1.
Adler, PM, Perrier F, 2008. Radon emanation in partially saturated porous media. Transport in porous
media, 78(2), 149-159.
2.
Washington JW, Rose W, 1990. Regional and temporal relations of radon in soil gas to soil temperature
and moisture. Geophysical Research Letters, 17(6), 829-832.
3.
Tanner AB, 1964. Radon migration in the ground: a review. In: Adams JAS, Lowder WM (Eds.), Natural
Radiation Environment, University of Chicago Press, Chicago, 161-190.
4.
Vaupoti J, 2010. Radon levels in carst caves in Slovenia. Acta Carsologica, 39(3), 503-512.
5.
Fleischer RL, 1987. Moisture and 222Rn-emanation. Health Phys. 52: 797–799.
6.
Jakofcic J, 2006. Longitudinal cross-section of Lipiška jama, cited in Cerkvenik R, 2012: Impacts of
visitors on cave’s physical environment and its protection, Dissertation, 405.
165
Proposed paleoclimate study on sediments of the Layla Lakes, Saudi Arabia:
First Results
Günter Landmann, Stephan Kempe, Cristoph Schüth
The Layla Lakes in the Centre of Saudi Arabia fell dry in the beginning of the 1990’s due to
groundwater mining. The lakes, fed by ascending groundwater, filled a series of sinkholes
that formed by hypogene karstification of the underlying Upper Jurassic anhydrite Hith
Formation. The lake sediment, here named ‘The Layla Formation’, is now accessible in
profiles at the sinkhole walls.
XRD-, XRF- and CNS-Analyses of 19 samples taken from such a profile show good
correlation between the different methods used and allow classification of the samples (Fig.
1). The samples from 2; 5; 6; 8.7; 8.95; 9.5 m depth contain mainly sparitic gypsum with
some calcite and trace elements. They form hard crust and are interpreted to represent
periods of drought.
Fig. 1. Comparison between concentrations determined by CNS- and XRF-analyses (filled circles) and intensity
of the main peaks of calcite (cc), gypsum (gy) and quartz (qz) measured by XRD-analyses (open circles) reveal
good correlation between the different methods. Samples with high SO3-content consist almost entirely of
gypsum, those with high CO2-content contain 60-85 % calcite. Vertical error bars give standard deviation of
double CNS-determinations.
166
Micritic calcite, with up to 3 % Mg in samples close to gypsum layers, precipitated due to
degassing of CO2 at times with a positive water balance when the lakes overflow (Fig. 1).
The changes in the composition of these cyclic series of chemical sediments therefore
carries paleoclimatic information.
The hydraulically powered direct push device Geoprobe was used close to the sinkhole
profile to obtain a continuous sediment profile. Due to compaction caused during coring,
the former 10.8 m long sediment column was reduced to 8.47 m (78 %), with highest
porosities occurring in the gypsum layers. An XRF-scan was done with a resolution of 1 cm
providing the relative concentration of the elements Al, Si, S, K, Ti, Sr, Zr, Br, Pb, Rb and
Ba. The core reveals a good stratigraphic correlation with the sinkhole profile (Fig. 2).
Fig. 2. The correlation between the XRF-Analyses of the sinkhole profile (black) and the XRF-scan of the core
(red) is based on element concentrations higher than mean values (given by dotted vertical lines). The
elements Si and Ti represent the clastic sediment corresponding to the blue areas, which mark the more humid
periods. Yellow areas indicate the gypsum layers, representing arid periods. Arrows at the depth axis give
theposition of dated materials (see text).
167
So far only one 14C-Analyses of a gastropod shell and one U/Th-date on carbonate is
available (Fig. 2). The old age of the shell collected from surface sediment is assumed to be
caused by the hard water effect of the ascending and old groundwater that fed the lake.
The proposal aims to date the sediments in more detail (14C and U/Th) and to validate the
preliminary hypotheses by correlating other profiles by sampling, and mineralogical and
geochemical analysis. Micropaleontological investigations (pollen, spores, diatoms and
other algae, thekamoeba, ostracods) are planed to reconstruct the climate and geochemical
environment in the center of Saudi Arabia, a region so far lacking upper Holocene climate
records.
168
3D-Scanning of Underground Cavities, Case Study: Entdeckungshalle,
Segeberger Höhle
Stephan Kempe1, Ingo Bauer1
1
Institute of Applied Geosciences, University of Technology Darmstadt, Schnittspahnstr. 9, D-64287 Darmstadt, Germany,
The Segeberger Höhle, Bad Segeberg, is the northern-most show cave in Germany, situated
in the “gypsum hat” of a salt dome in central Schleswig Holstein. The maze-like cave
developed in the shallow ground water body during the Holocene. It fell dry rather
recently, probably during the 19th century when salt mining was attempted at Segeberg.
The cave was discovered in 1913 during anhydrite and gypsum quarrying. The former
quarry serves today as an open air theater for the famous Karl May festival at Segeberg. The
festival today is a major economic factor for Bad Segeberg. The cave, in part, is very near to
the stage and the stability of its largest hall, the „Entdeckungshalle“ („Discovery Hall“), may
be of importance for the safety of the staff and visitors of the festival.
We therefore scanned the Entdeckungshalle with a Faro 3D 120 Scanner in order to
document all tectonic elements and assess the cave’s stability. Between the Entrance (St. 1)
and the weather doors at the southern end of the Hall (St.19) 19 scans were recorded.
Station 06 on the „Asselberg“ was recorded in high resolution to document the Hall for
later comparative scans in ordert o assess small alterations by breakdown. St. 07 was
deleted and replaced by St. 08. At nine places marks were mounted (iron plates of 40 mm
diameter) in order to place the magnetic reference spheres (14 cm) at exactly the same
locations for later scans. Scans 01-05 und 08-19 were combined into one 3D-Model with
the Faro Software SCENE (Fig. 1). The model contains 745 Mio. data points. Depending on
the distance of the scanner to the wall the resolution is between 1 and ca. 10 mm. All
stationen can be viewed individually and appear almost as black-and-white 360° panomara
photos because the Faro Scanner records not only X,Y, and Z data but also a reflection
value for each point. Due to this fact, differences in rock reflectivity and therefore
stratification are visible in the scans.
Fig. 1: View of the Entedeckungshalle, Segeberger Höhle, from above. Length of the section shown is ca. 100
m. The lines show the strike of the strata which are tilted here tot he vertical. X points East, Y North and Z
upward.
169
Results
The Entdeckungshalle is 98 m long (Fig. 2). Its highest point at the discovery hole is 12.5 m
above the cave’s floor. At this site the hall has a cross-section similar to a tipi with a floor
width of 9 m. 11.8 m south of the back wall (right on Fig. 2), the ceiling comes down to 5.8
m and then keeps more or less at a hight of 3.5 m.
Fig. 2: View of the entire length of the Entdeckungshalls in direction 189° from the outside. Pertinent features
are marked.
The Entdeckungshalle follows the NW-SE oriented strike of the strata that are tilted to the
vertical due to the upward movement of the saltdome (Fig. 1). Similarly, the passages near
the entrance and the columns that carry the SW wall of the Entdeckungshalle are composed
of vertically tilted strata. Along one of the stratification planes a vertical fault has evolved
that marks the crest of the hall in the NW and disappears into the cave’s wall about 10 m
SE of the passage leading to the cave’s entrance. In some places slick’n-sides are preserved,
showing vertical displacement. The anhydrite/gypsum strata show fine to coarse
lamination, affecting the form and width of the blocks that can detach from the ceiling.
A third, prominent tectonic element is joints that dip ca. 70° to the NW (Fig. 3, joints A to H
plus some smaller joints). Joints A and B form the back wall of the hall. In between them
they define a large, upward tapering, triangular block (green in Fig. 3) that is detached on
one side by the semi-vertical fault. Furthermore it is missing its foot support and could
potentially collapse. Nevertheless no recent collapse blocks are noticed. The explanation
may be that this block is still gypsyfying and expanding, therefore wedging itself into
position. Gypsification (hydration of anhydrite) causes a volume increase of 26 %
(according to density difference of the two minerals). Further investigation may
substantiate these conclusions. 3D-underground scanning proves to be a valueable tool to
investigate tectonic structure and hence stability of underground cavities.
170
Fig. 3: View from the outside at the NW-End of the Entdeckungshalle with major joints marked.
171
Hydrogeology
The Hydrogeology Group focuses on three main research areas, (I) the fate of organic
contaminants in the environment, (II) the development of novel methods to remediate soil
and groundwater contaminations, and (III), on water resources management from a local
to a regional scale. In all three research areas externally funded projects are currently
running, some as part of larger joint projects with national and international pertners.
Our water resources management project in Saudi Arabia, which was part of the BMBF
funded joined project IWAS, was phased out this year. However, we continue to focus on
water management in arid regions. We started a project on water quality in northern Africa
with partners from the Helmholtz Center for Envionmental Research in Leipzig (UFZ), from
the Federal Institute of Geosciences and Natural Resources (BGR) and others. Here we
focus on naturally occurring radioactivity in the fossil groundwaters in the large sandstone
aquifers in northern Africa that is of major concern.
We have been also successful in applying for a project in the 7th framework program of the
EU as coordinator. MARSOL (Managed Aquifer Recharge as a Solution to Water Scarcity
and Drought) has 20 partners in southern Europe and will operate 8 field sites in the
Mediterranean to demonstrate that Managed Aquifer recharge (MAR) is a sound, safe and
sustainable method to increase water resources in areas with dwindling water availability.
We are very excited to be in a key position to promote this technology.
Together with partners from our Institute and from the Civil- and Environmental
Engineering Department we submitted, as coordinators, a proposal in the LOEWE program
of the state of Hesse. The topic of the planned center is ‘Urban H2O’, dealing with all
aspects of water management in cities. We have been invited to submit a full proposal and
advanced to the final stage. A decision will be made in summer 2014 and we are very much
looking forward to have the chance to work on this relevant topic as a team of geoscientists
and engineers.
Staff Members
Head
Prof. Dr. Christoph Schüth
Research Associates
Dr. Laura Foglia
Dr. Thomas Schiedek
Dr. Annette Wefer-Roehl
PhD Students
Abidur Khan
Nils Michelsen
Layth Sahib
Christoph Kludt
Mustafa Yasin
Stefan Schulz
Anja Wolf
Layth Latai
Master Students
Christian Adam
Eunice Agyare Brago
Haftay Gebrehivot
Tanuja Gorele
Pamela LaForce
Asanka Thilakerathne
Indriani Preiß
Jannes Winnacker
Andreas Androulakakis
Suraya Fatema
Beatrice Kanyamuna
Terence Ngole
Anja Tögl
Sehab Uddin
Secretary
Pamela Milojevic
172
Institute of Applied Geosciences – Hydrogeology
Technical Personnel
Zara Neumann
Rauiner Branolte
Claudia Cosma
Research Projects
MARSOL - Managed Aquifer Recharge as a Solution to Water Scarcity and Droughts (EU2013-2015)
RADAQUA - Pilotstudie zur Einschätzung erhöhter Radionuklidkonzentrationen in Grundwässern der Arabischen Halbinsel und Nord-Afrikas (BMBF 2013-2014)
Prozessorientierte Untersuchung zum Nitratabbauvermögen der Grundwasserkörper im
Hessischen Ried (HLUG: 2012-2014)
Heavy metal contamination of surface water and groundwater resources in the industrial
area of Dhaka City, Bangladesh (BMBF-IPSWAT, 2011-2014)
Detection of oil spills and water contamination in the Kirkuk area, Irak, using remote
sensing data (DAAD 2011-2014)
Publications
[1] El Haddad, E., Ensinger, W., Schüth, C. (2013): Untersuchungen zur
Sorptionsreversibilität von organischen Schadstoffen in Aktivkohle, Holzkohle und Zeolith
Y-200. Grundwasser, 18, 197-203.
[2] Engelhardt, I., Rausch, R., Lang, U., Al-Saud, M., Schüth, C. (2013): Impact of
Preboreal to Subatlantic shifts in climate on groundwater resources on the Arabian
Peninsula. Environmental Earth Sciences, 69, 557-570.
[3] Engelhardt, I., Rausch, R., Keim, M., Al-Saud, M., Schüth, C. (2013): Surface and
subsurface conceptual model of an arid environment with respect to mid- and late
Holocene climate changes. Environmental Earth Sciences, 69, 537-555.
[4] Engelhardt, I., Prommer, H., Moore, C., Schulz, M., Schüth, C., Ternes, T. (2013):
Suitability of temperature, hydraulic heads, and acesulfame to quantify wastewater-related
fluxes in the hyporheic and riparian zone. Water Resources Research, 49, 426-440.
[5] Foglia, L., McNally, A., Harter, T. (2013): Coupling a spatiotemporally distributed soil
water budget with stream-depletion functions to inform stakeholder-driven management of
groundwater-dependent ecosystems. Water Resources Research, 49, 7292-7310.
[6] Foglia, L., Mehl, S.W., Hill, M.C., Burlando, P. (2013): Evaluating model structure
adequacy: The case of the Maggia Valley groundwater system, southern Switzerland. Water
Resources Research, 49, 260-282.
[7] Rasa, E., Foglia, L., Mackay, D.M., Skow, K. (2013): Effect of different transport
observations on inverse modeling results: case study of a long-term groundwater tracer test
monitored at high resolution. Hydrogeology Journal, 21, 1539-1554.
[8] Wolf, A., Bergmann, A., Wilken, R.D., Xu G., Bi, Y., Chen, H., Schüth, C. (2013):
Occurrence and distribution of dissolved organic trace substances in waters from the Three
Gorges Reservoir, China. Environmental Science and Pollution Research, 20, 7124-7139.
173
Occurrence and distribution of trace substances in the waters from the
Treee Gorges Reservoir, China
Anja Wolf, Axel Bergmann, Rolf-Dieter Wilken, Xu Gao, Yonghong Bi, Hao Chen,
Christoph Schüth
With a length of 6,300 km, the Yangtze River is the third largest river in the world Its
catchment covers 1,810,000 km2, about 20%of the area of China with a population of 450
million people. The Three Gorges Dam (TGD) impounds the Yangtze River for the world's
largest project for hydroelectric power generation in terms of installed capacity (18.2
million kW). The TGD also provides additional benefits, such as flood control, enhanced
navigability, or stimulation of tourism. However, there is an ongoing controversial debate
about the social and environmental impacts of the TGD. The impoundment of the 630-kmlong Three Gorges Reservoir (TGR) had a significant impact on the hydrological regime and
ecology up- and downstream of the TGD (Xu and Milliman 2009; Xu et al. 2011).
Upstream, huge industrial, residential, and agricultural areas were flooded. Hence,
considerable amounts of organic and inorganic pollutants were released into the reservoir.
Currently, there are additional anthropogenic pollutant sources, such as household sewage,
industrial discharge, wastewater treatment plant (WWTP) effluents, garbage dumping, and
agricultural runoff (Chang et al. 2010). Water quality in TGR is of major concern since
surface water is commonly used as raw water source for public water supply (Luo et al.
2011). Furthermore, the water from TGR is considered for the provision of freshwater to
the dryer northern part of China as part of the south to north water diversion project (Liang
2013).
Fig. 1: Sampling points in the TGR area. Map source: Yangtze-Hydro Project
In this study the water quality of the TGR) was evaluated in order to assess its suitability as
a raw water source for drinking water production Wolf et al. 2013). Therefore, water
samples from (1) surface water, (2) tap water, and (3) wastewater treatment plant
174
effluents were taken randomly in 2011–2012 in the area of the TGR (Fig. 1) and analyzed
for seven different organic contaminant groups (207 substances in total), applying nine
different analytical methods.
In the three sampled water sources, typical contaminant patterns were found (Fig. 2), i.e.,
pesticides and polycyclic aromatic hydrocarbons (PAH) in surface water with
concentrations of 0.020–3.5 μg/L and 0.004–0.12 μg/L, disinfection by-products in tap
water with concentrations of 0.050–79 μg/L, and pharmaceuticals in wastewater treatment
plant effluents with concentrations of 0.020–0.76 μg/L, respectively. The most frequently
detected organic compounds in surface water (45 positives out of 57 samples) were the
pyridine pesticides clopyralid and picloram. The concentrations might indicate that they are
used on a regular basis in the area of the TGR.
Three- and four-ring PAH were ubiquitously distributed, while the poorly soluble five- and
six-ring members, perfluorinated compounds, polychlorinated biphenyls, and
polybrominated diphenyl ethers, were below the detection limit. In general, the detected
concentrations in TGR are in the same range or lower compared to surface waters in
western industrialized countries, although contaminant loads can still be high due to a high
discharge. With the exception of the two pesticides, clopyralid and picloram, concentrations
of the investigated organic pollutants in TGR meet the limits of the Chinese Standards for
Drinking Water Quality GB 5749 (Ministry of Health of China and Standardization
Administration of China 2006) and the European Union (EU) Council Directive 98/83/EC
on the quality of water intended for human consumption (The Council of the European
Union 1998), or rather, the EU Directive on environmental quality standards in the field of
water policy (The European Parliament and The Council of the European Union 2008).
Therefore, the suggested use of surface water from TGR for drinking water purposes is a
valid option. Current treatment methods, however, do not seem to be efficient since organic
pollutants were detected in significant concentrations in purified tap water.
Fig. 2: Boxplot of the concentrations of the 24 detected organic compounds, sum of pesticides, sum of THM,
and sum of PAH in samples from a surface water, b tap water, and c WWTP effluents. The triangles in a and b
illustrate the limit values given by the Chinese Surface Water Standards and Drinking Water Quality Standards;
the squares are those given by the EU Environmental Quality Standards Directive and Drinking Water
Directive.
175
References
[1]
Chang X, MeyerMT, Liu X, Zhao Q, ChenH, Chen JA, Qiu Z, Yang L, Cao J, Shu W (2010):
Determination of antibiotics in sewage from hospitals, nursery and slaughter house, wastewater
treatment plant and source water in Chongqing region of Three Gorge Reservoir in China. Environ
Pollut 158(5):1444–1450.
[2]
Liang SM (2013): A joint water diversion plan for China. American Water Works Association
105(5):E264–E277
[3]
Luo H, Fu G, Peng M, Gong R, Xiang W, Wang H (2011): Centralized water supply in rural villages of
Three Gorges Reservoir. Chinese Rural Health Service Administration 31(9)
[4]
Wolf, A., Bergmann, A., Wilken, R.D., Xu G., Bi, Y., Chen, H., Schüth, C. (2013): Occurrence and
distribution of dissolved organic trace substances in waters from the Three Gorges Reservoir, China.
Environmental Science and Pollution Research, 20, 7124-7139.
[5]
Xu KH, Milliman JD (2009): Seasonal variations of sediment discharge from the Yangtze River before
and after impoundment of the Three Gorges Dam. Geomorphology 104(3–4):276–283
[6]
Xu XB, Tan Y, Yang GS, Li HP, SuWZ (2011): Impacts of China's Three Gorges Dam Project on net
primary productivity in the reservoir area. Sci Total Environ 409(22):4656–4662.
176
Engineering Geology
Engineering Geology is a branch of geology that deals with the characterization of soil, rock
and rock masses for the location, design, construction and operation of engineering works.
Typical tasks relate to foundation of roads and buildings, but also to underground
excavations like tunnels and caverns. The special focus of the Engineering Geology group at
Technische Universität Darmstadt is on reservoir geomechanics, i.e., the application of rock
mechanics as well as of techniques for stress and fracture characterization to depth of up to
5 km. In particular, numerical (finite element) models are used to predict the
corresponding subsurface conditions prior to drilling operations. Such predictive tools are
of great value not only for the optimal exploration and efficient use of hydrocarbon and
geothermal reservoirs, but also for CO2 sequestration sites as well as radioactive waste
repositories.
The present research activities of the group comprise several case studies applying
geomechanical modeling techniques to oil and gas reservoirs in the North German basin
and the Rhine Graben area as well as to a demonstration site in Australia. There the safe
subsurface storage of CO2 (CCS) is investigated. Other studies focus on the analysis of
surface outcrops which serve as analogs to subsurface reservoirs. Such outcrop analogs
provide a broader data base than the limited well data which usually is available for
reservoirs. Thus, they are ideal to test and validate the general modeling concepts used for
subsurface modeling later-on.
For research as well as teaching various software packages and powerful computing
facilities are available which allow to run 3D geomechanical reservoir models with several
millions of elements. In addition, new rock mechanical lab facilities like uniaxial, triaxial
and ultrasonic measurement devices have been established which allow to derive the
necessary reservoir-specific mechanical properties for input into the numerical simulations.
For field work and outcrop analog studies a terrestrial laser scanner allows for rapid
detection of fracture networks and determination of their geometrical and statistical
properties.
Staff Members
Head
Prof. Dr. Andreas Henk
Research Associates
M.Sc. Karsten Fischer
Dipl. Geol. Christian Heinz
M.Sc. Dennis Laux
Dipl. Geol. Christoph Wagner
Technical Personnel
Reimund Rosmann
Secretary
Dipl. Kffr. Stefanie Kollmann
Ph.D. students
M.Sc. Chiara Aruffo
Institute of Applied Geosciences – Engineering Geology
M.Sc. Bastian Weber
177
Research Projects
Prediction of tectonic stresses and fracture networks with geomechanical reservoir models
(DGMK Projekt 721, ExxonMobil, GDF SUEZ, RWE Dea)
PROTECT - PRediction Of deformation To Ensure Carbon Traps (BMBF)
Buidling and populating geomechanical reservoir models – a case study from the Upper
Rhine Graben (GDF SUEZ)
LIDAR-based analysis of fracture networks (PhD thesis)
Fracture prediction in fold-and-thrust belts – a worked example from the southern Pyrenees
(PhD thesis)
Publications
[1] Aruffo, C. M., Henk, A. and PROTECT Research Group, 2013: Seismo-mechanic
workflow to ensure CO2 storage in the Otway Basin, Australia. Extended Abstracts 75th
EAGE Conference and Exhibition, London.
[2] Aruffo, C.M. and PROTECT Research Group, 2013: Workflow for geomechanical
modeling to ensure CO2 storage in the Otway Basin, Australia – joint project PROTECT.
Proceedings 4th IGSC Conference, Berlin.
[3] Aruffo, C.M., Henk, A., 2013: Geomechanical workflow to ensure CO2 storage in Otway
Basin, Australia. Abstract volume CO2CRC Research Symposium, Hobart, Australia.
[4] Fischer, K., Henk, A., 2013: A workflow for building and calibrating 3-D geomechanical
models – a case study for a gas reservoir in the North German Basin. Solid Earth, 4: 1–9.
[5] Fischer, K., Henk, A., 2013: Field-scale geomechanical modeling of an intensely faulted
gas reservoir. Conference Proceedings ARMA 13-219, 47th US Rock Mechanics /
Geomechanics Symposium, San Francisco.
[6] Fischer, K., Henk, A., 2013: Generating and Calibrating 3D Geomechanical Reservoir
Models. Conference Proceedings, Extended Abstracts 75th EAGE Conference & Exhibition,
London.
[7] Fischer, K., Henk, A., 2013: Constructing Reservoir-Scale 3D Geomechanical FE-models
– A Refined Workflow for Model Generation and Calculation. DGMK-Tagungsbericht 20131, DGMK-ÖGEW Frühjahrstagung, Celle.
[8] Fischer, K., Henk, A., 2013: Geomechanical reservoir models for the prediction of
tectonic stress fields in deep geothermal reservoirs. Conference Proceedings, 19. Tagung für
Ingenieurgeologie, München.
178
[9] Laux, D., Henk, A., 2013: LIDAR in Geosciences – A quantitative analysis of fracture
networks in outcrops to improve input parameters for DFN modelling. Conference
Proceedings, Riegl LIDAR 2013 International User Conference, Wien.
[10] Laux, D., Henk, A., 2013: Charakterisierung von Trennflächengefügen in
Oberflächenaufschlüssen durch terrestrisches Laserscanning zur Erzeugung eines Discrete
Fracture Network Modells. DGMK-Tagungsbericht 2013-1, DGMK-ÖGEW Frühjahrstagung,
Celle.
[11] Laux, D., Henk, A., 2013: Erfassung von Trennflächengefügen mit dem terrestrischen
Laserscanner (TLS) als Eingabedaten für Discrete Fracture Network (DFN-) Modelle.
Conference Proceedings, 19. Tagung für Ingenieurgeologie, München.
[12] Wagner, C., Henk, A., 2013: Seismische Interpretation und Erstellung eines
geomechanischen Reservoirmodells – eine Fallstudie aus dem Oberrheingraben. DGMKTagungsbericht 2013-1, DGMK-ÖGEW Frühjahrstagung, Celle.
179
Geomechanical reservoir modeling –
workflow and case study from the North German Basin
Fischer, K.
There is an increasing importance for the optimal exploitation of conventional hydrocarbon
reservoirs to have detailed knowledge of the specific state of stress in a reservoir and to
gain clarity on the corresponding geomechanical implications. This knowledge is even
becoming mandatory for most unconventional plays. The local stress field directly affects,
for instance, wellbore stability, the orientation of hydraulically induced fractures, and –
especially in fractured reservoirs – permeability anisotropies. Robust information on the
locally prevailing stresses is thus ideally required prior to drilling. Numerical models based
on the finite element (FE) method are able to cope with the complexity of real reservoirs.
Acting as predictive tools, these models not only provide quantitative information on the
stress distribution, but also a process-based understanding of geomechanical reservoir
behavior.
This study evaluates the potential of geomechanical FE models for the prediction of local in
situ stress distribution and fracture networks in faulted reservoirs. The work of this study
was conducted in cooperation with three major operators in the E&P industry and
comprises two main parts. In the first methodological part, a generally applicable workflow
is developed for building geomechanical FE models and calibrating them to field data.
These models focus on spatial variations of in situ stress resulting from faults and contrasts
in mechanical rock properties. Special techniques are elaborated regarding the transfer of
the reservoir geometry from geological subsurface models to the numerical model and for
the most effective application of boundary conditions. Complex fault geometries and the
detailed topology of lithostratigraphic horizons can be considered on reservoir scale. In
combination with reservoir-specific material parameters the incorporated horizons establish
a mechanical stratigraphy inside the model. Faults are implemented as discrete planes by
2D interface elements. This allows fault-specific stresses and corresponding fault behavior
to be analyzed. The resulting geomechanical models comprise high spatial resolution and
several million elements. They are calculated in reasonable time spans by using highperformance computing. In addition, submodels resolving a detailed mechanical
stratigraphy can be integrated into the reservoir-wide modeling for local focus.
In the second part of the study, the workflow was successfully applied to an intensively
faulted gas reservoir in the North German Basin. Comprehensive datasets are provided by
the field operators and project partners for building and calibrating a detailed and truly
field-scale geomechanical model covering more than 400km². It incorporates a network of
86 faults and a mechanical stratigraphy of three layers comprising reservoir-specific
material parameters. For the static modeling approach, the present-day regional stress field
is applied as boundary condition. Static modeling results are compared to local stress
measurements, e.g. orientations from borehole breakouts and magnitudes from frac data.
After iterative calibration, the best-fit model reveals the recent in situ stress distribution and
individual fault behavior throughout the reservoir. The results show significant local
perturbations of stress magnitudes (max. ±10MPa over 1-2km distance) and only minor
deviations in stress orientation from the regional trend (max. ±25°). The strong
180
dependency on the specific fault trace, offset and interactions precludes the derivation of
generally valid rules for estimating stress variations and underlines the necessity of
numerical modeling. Analysis of fault-specific results indicates that critical stress states
occur most likely on NW-SE trending faults in the present-day stress field.
Fracture information is inferred from a (geo-)dynamic model focusing on the major stages
in the tectonic history of the reservoir and the respective past in situ stresses. Consequently,
paleo-stress fields are applied as boundary condition and material parameters are adjusted.
Correlation of fracture orientations and modeled paleo-stresses in the reservoir allows the
formation of fracture sets to be assigned to Triassic and Late Jurassic to Early Cretaceous
times. Increased perturbation intensity in the Late Jurassic to Early Cretaceous is related to
potential reactivation of NW-SE trending faults and explains the variability of the
corresponding fracture set. These results elucidate how stress perturbations can explain
fracture variability without the need for complex tectonic histories.
Furthermore, the dynamic model sheds light on fault zone permeability. Modeling indicates
that if cataclasis is responsible for a reduced fault permeability, then it will most likely
occur along E-W and NNE-SSW trending faults due to the high slip tendency values they
experienced in the tectonic past. Modeling results show no such increased geomechanical
exposure for NW-SE oriented faults. However, high dilation tendencies support the
possibility of activity of these faults in Late Jurassic times – as proposed by fracture
correlation. Low permeability of NW-SE trending faults is thus most likely the result of fluid
entry and illitization, which is also observed at a wellbore close to such a fault set.
The combination of static and dynamic modeling results suggests no significant impact of
critically stressed natural fractures on the recent hydraulic behavior of the entire reservoir.
Additionally tests of fault block refinements and submodels demonstrate their capability to
provide further increased spatial resolution in areas of particular interest. The submodel
generated for the northwestern part of the case study underlines the impact of the specific
connections of the fault network on the modeling results.
The outcome of this study confirms the high potential of geomechanical FE models to
reveal the specific in situ stress and fault behavior, and to infer fracture characteristics from
paleo-stresses. Beside the case study specific insights, the successfully applied and approved
workflow can be used for future modeling of stress-sensitive reservoirs. Furthermore, the
geomechanical models are not limited in application to the hydrocarbon industry. As
general tools for stress prediction in undrilled rock formations, they can also be applied to
deep geothermal reservoirs and underground engineering, for instance. The possibility of
characterizing fault behavior makes the models additionally valuable in the fields of carbon
capture and storage (CCS) and nuclear waste disposal.
Acknowledgements
This work has been funded by ExxonMobil Production Deutschland GmbH, Gaz de France
Suez E&P Deutschland GmbH and RWE Dea AG within the frame of the DGMK (Deutsche
Wissenschaftliche Gesellschaft für Erdöl, Erdgas und Kohle e.V.) project 721.
181
Fault stability assessment of the CO2CRC Otway Project, Australia –
a geomechanical approach
Aruffo, C.M., Henk, A. & PROTECT Research Group
Introduction
In the past years geosequestration reached the interest of public opinion as a technology
that can significantly reduce greenhouse emissions from the burning of fossil fuels. The
Australian government, through the CO2CRC (Cooperative Research Centre for Greenhouse
Gas Technologies), launched a pilot project for carbon dioxide storage in 2005 (Jenkins et
al. 2011). The CO2CRC Otway Project is located in Nirranda South, Victoria, Australia and
it is the first CO2 storage project of the southern hemisphere. CO2 sequestration utilizes an
existing depleted natural gas field, the Naylor Field. Gas used for storage contains about
80% CO2 and is produced from the adjacent Buttress Field. The CO2CRC Otway Project
aims to demonstrate that carbon capture and storage (CCS) is technically and
environmentally safe. Potential risks that could arise due to the subsurface injection of CO 2
are, among others, potential reactivation of faults and leakage of CO2 along them. This risk
can be addressed by an accurate analysis of stresses and fractures within the injection area.
Geomechanical modeling based on numerical methods provides a tool to understand the
state of stress in the reservoir and in the surrounding area and the changes that can occur
in response to CO2 sequestration. Fault stability and potential fault reactivation under
reservoir pressure and temperature changes can be also assessed through geomechanical
studies. Two different approaches have been followed in the present study both using
Finite Element (FE) techniques to provide a comprehensive geomechanical analysis of the
injection area. A structural analysis has been performed in order to describe the present-day
state of stress and the slip tendency of the faults under this stress condition. A one-way
coupled simulation allows to estimate the potential reactivation of the faults in response to
CO2 injection in the subsurface, using history matching techniques.
Geomechanical modelling approach
A geomechanical study of the injection site is required in order to ensure safe CO2 storage.
Two complementary modelling approaches have been followed to describe geomechanical
features that are relevant to geosequestration, with a particular interest on fault stability. A
3D geological model derived from a 3D seismic interpretation (Ziesch et al., in prep.) of a
public database of Otway basin (Urosevic et al. 2011) is the common basis for both models.
Area of interest surrounds the injection site and has a maximum width of 8x5 km. An
analysis of the tectonic stress field acting in the area of injection and its surrounding is
provided using the commercial software Ansys®. Based on the FE method, this software
allows to compute the in situ stresses for boundary conditions representing the regional
stresses in order to study the local stress perturbations related to changes in mechanical
properties as well as the presence of faults. Stability of faults is analysed from a structural
point of view, estimating the slip and dilation tendency of each fault under the present-day
stress conditions. The second geomechanical approach is a one-way coupled flow and
geomechanics simulation that takes into account also the influence of CO2 injection on the
182
local stresses. Flow model has been computed with the Finite Difference software Eclipse®,
while the geomechanical simulation has been performed using the Finite Element software
Visage®, both from Schlumberger. The aim in this case is to assess fault stability and
caprock integrity in relation to changes in pressure due to injection of CO2 in the
subsurface.
Structural geomechanical modelling
The build-up of a 3D geomechanical model using the Finite Element (FE) software Ansys®
requires the generation of a new volume model. The geometry is transferred from the
original 3D geological model through a series of horizon lines and auxiliary lines. Horizon
lines represent intersection between lithostratigraphic horizons and faults, while auxiliary
lines are necessary in order to better reproduce the topology of surface patches used for
reconstructing reservoir geometry (Henk and Fischer 2011). The model extends from the
earth’s surface to the underburden layer of the reservoir and comprises 5 lithostratigraphic
horizons and 10 faults (Fig. 1). Faults are modelled using contact elements, defined at both
sides of the fault surfaces. Contact elements are able to reproduce frictional sliding that
could occur between hanging wall and footwall. Mechanical properties from well logs and a
literature review (Bérard et al. 2008, Vidal-Gilbert et al. 2010) are incorporated in the
model through a layer-cake population process (Fig.1).
Top
2800 m
Dilwyn Fm
Timboon Fm/ Paaratte Fm
Skull Creek/Belfast Mudstone
Waarre Fm
Eumeralla Fm
Figure 1: Layer-cake model for 3D structural geomechanical simulation. Each colour corresponds to a different
lithostratigraphic unit.
Boundary conditions derived from regional tectonic stresses are applied to the model by
calibrated displacements. Results of this modelling approach include the description of the
tectonic stresses acting in the reservoir and its surrounding, and the local stress
perturbation related to the presence of faults and changes in mechanical parameters.
Furthermore this 3D geomechanical model contributes to provide answers to fault stability
issues through the estimation of slip and dilation tendency of faults under the in situ stress
conditions computed.
183
One-way coupled flow and geomechanics simulation
A one-way coupled flow and geomechanics simulation allows studying the response of
reservoir and surrounding rock to changes in pore pressure due to production/injection of
oil and gas. Although the same 3D geological model has been used, area of interest has
been modified after some preliminary geomechanical studies. For this second modelling
approach the 3D model has a width of 4x4 km, having its centre at the injection well
(Aruffo and Henk 2013). The reservoir model for the flow simulation is even smaller, as
injection of CO2 affects only the area immediately around the injection well. Flow model
has been computed using the Finite Difference software Eclipse® using a history matching
approach, constraining the model with injection data available. Simulation of CO2 injection
into the subsurface provides as results changes in pressure inside the reservoir. These
pressure data are used to couple the flow model with the geomechanical model, being used
as input inside the Finite Element (FE) software Visage®. The coupling scheme involves 5
time steps at which pressure data are passed to the geomechanical simulator as pressure
loads, so that effective stresses can be computed taking into account these pressure
variations. Population of the mechanical properties in this case follows a moving average
algorithm, taking into account vertical and lateral variation within the same
lithostratigraphic unit. Faults are modelled as discontinuities, represented by a list of grid
cells which intersect with the fault. Different material properties are assigned to each cell of
the faults, such as dip value, dip direction, normal stiffness, shear stiffness, cohesion,
friction angle, dilation angle and tensile strength. Regional tectonic stresses are again used
to provide boundary conditions for the simulation. Results from the one-way coupled
simulation comprise, among others, description of stress and strain in response to CO2. In
particular, effective stresses can be used to assess fault stability at each time step. MohrCoulomb failure criterion has been chosen for this analysis, and for each cell belonging to a
fault the distance to the failure envelope is calculated. The equation of the failure envelope
for the Mohr-Coulomb criterion is:
where σs is the shear stress, σn is the normal stress, C0 is the cohesion of the fault and μ is
the friction coefficient of the fault. Assumptions for the Otway Project site lead to assign a
value of 0.001MPa for cohesion, thus considering them almost cohesionless, and a friction
coefficient of 0.6 (van Ruth et al. 2007). Fault analysis conducted in this way revealed that
under these assumptions none of the fault cells reach the failure envelope for both linear
and non-linear analysis (Fig. 2). Results from numerical simulation have been compared
with previous analytical studies (Van Ruth et al., 2006 and 2007, Vidal-Gilbert et al., 2010)
and also with an analytical model which uses exactly the same mechanical parameters and
assumptions as the numerical study.
184
Figure 2: Mohr-Coulomb failure plot for faults (friction coefficient = 0.6) at the end of the injection stage. No
failure is computed for each time step.
Conclusions
Geomechanical aspects of CO2 storage in the Otway area have already been investigated by
van Ruth et al. (2006 and 2007) and Vidal-Gilbert (2010) during the assessment of the
area undertaken by CO2CRC. Their analytical analyses focused on the immediate area of
injection. The present work integrates these previous studies into a larger 3D
geomechanical model for the CO2CRC Otway Project. Among others, fault stability and
potential fault reactivation are considered to be critical factor of risk during
geosequestration. Furthermore the expansion of the model up to the earth’s surface, allows
to investigate also the stresses acting on the entire overburden, not only on the reservoir. A
3D structural geomechanical model describes the in situ stress and perturbations that may
occur locally near faults or due to changes in mechanical properties. This first model covers
an area of about 40 km2 and can assess fault stability under the present-day stress
conditions, computing slip and dilatation tendency of faults. Additionally, a one-way
coupled simulation model has been set up to study the impact of changes in pore pressure
on the effective stresses acting in the reservoir and its surrounding. The area of interested
has been restricted to 16 km2, following indications from preliminary geomechanical
simulations. A fault stability analysis in this second case has been performed for each time
step of the coupled simulation i.e. for different pressures acting on the reservoir. Modeling
results suggest that fault failure is not a factor of risk under the calculated present-day
stress conditions and the current assumptions regarding fault properties and the MohrCoulomb failure criterion.
Acknowledgments
This work was sponsored in part by the Australian Commonwealth Government through
the Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC). PROTECT
185
(PRediction Of deformation To Ensure Carbon Traps) is funded through the
Geotechnologien Programme (grant 03G0797) of the German Ministry for Education and
Research (BMBF). The PROTECT research group consists of Leibniz Institute for Applied
Geophysics in Hannover, Technical University Darmstadt, Helmholtz-Zentrum für
Umweltforschung in Leipzig, Trappe Erdöl Erdgas Consultant in Isernhagen (all Germany)
and Curtin University in Perth, Australia.
C.M.A. would like to thank the Applied Geomechanics Team of Schlumberger based in
Bracknell (UK) for their hospitality during a 3 month-internship. They provided invaluable
support for C.M.A’s work and gave her the opportunity to use their technology.
References
[1]
Aruffo, C. M. and Henk, A. [2013] Fault stability and potential fault reactivation analysis in Otway
Basin, Australia. Fourth EAGE CO2 Geological Storage Workshop.
[2]
Bérard, T., Sinha, B. K., van Ruth, T., John, Z. and Tan, C. [2008] Stress Estimation at the Otway CO2
Storage Site, Australia. SPE Asia Pacific Oil and Gas Conference and Exhibition, 26, Perth, Australia.
[3]
Henk, A. and Fischer, K. [2013] Building and calibrating 3D geomechanical reservir models - a worked
rd
example. 73 EAGE Conference & Exhibition.
[4]
Jenkins, C. R., Cook, P. J., Ennis-King, J., Undershultz, J., Boreham, C., Dance, T., de Caritat, P.,
Etheridge, D. M., Freifeld, B. M., Hortle, A., Kirste, D., Paterson, L., Pevzner, R., Schacht, U., Sharma,
S., Stalker, L. and Urosevic, M. [2011] Safe storage and effective monitoring of CO2 in depleted gas
fields. Proceedings of the National Academy of Sciences 109(2), E35-E41.
[5]
Urosevic, M., Pevzner, R., Shulakova, V., Kepic, A., Caspari, E. and Sharma, S. [2011] Seismic
monitoring of CO2 injection into a depleted gas reservoir–Otway Basin Pilot Project, Australia. Energy
Procedia 4(0), 3550-3557.
[6]
van Ruth, P. and Rogers, C. [2006] Geomechanical analysis of the Naylor structure, Otway Basin
Australia. CO2CRC (RPT06-0039), 26.
[7]
van Ruth, P., Tenthorey, E. and Vidal-Gilbert, S. [2007] Geomechanical Analysis of the Naylor
structure, Otway Basin, Australia - Pre-injection. CO2CRC (RPT07-0966), 27.
[8]
Vidal-Gilbert, S., Tenthorey, E., Dewhurst, D., Ennis-King, J., Van Ruth, P. and Hillis, R. [2010]
Geomechanical analysis of the Naylor Field, Otway Basin, Australia: Implications for CO2 injection and
storage. International Journal of Greenhouse Gas Control 4(5), 827-839.
[9]
Ziesch, J., Aruffo, C. M., Tanner, D. C., Beilecke, T., Weber, B., Dance, T., Tenthorey, E., Henk, A. and
Krawczyk, C. M. [in prep.] Structural evolution of the CO2CRC Otway Project pilot site, Australia: fault
dynamics based on quantitative 3D seismic intepretation. Basin Research.
186
Geothermal Science and Technology
Geothermal Energy is defined as the heat of the accessible part of the earth crust. It
contains the stored energy of the earth which can be extracted and used and is one part of
the renewable energy sources. Geothermal Energy can be utilized for heating and cooling
by applying heat pumps as well as it can be used to generate electricity or heat and
electricity in a combined heat and power system.
The field of Geothermal Science has natural scientific and engineering roots. Geothermal
Science connects the basic knowledge with the requirements of practical industry
applications. Geothermal Science is in interdisciplinary exchange with other applied
geological subjects such as hydrogeology and engineering geology and therefore is a logic
and proper addition to the research profile of the Technische Universität Darmstadt.
The broad implementation of geothermal energy applications and the utilization of the
underground as a thermal storage will help to reduce CO2 emissions and meet the
according national and international climate protection objectives. Furthermore, the
utilization of geothermal energy will strengthen the independency on global markets and
the utilization of domestic resources. Geothermal Energy will be an essential part of the
decentralized domestic energy supply and will contribute an important share of the desired
future renewable energy mix.
Regarding the worldwide rising importance of renewable energy resources, Geothermal
Science is one of the future's most important field in Applied Geosciences. In 2009, the
industry-funded Chair for Geothermal Science and Technology was established at the TU
Darmstadt – the first foundation professorship in energy science of the university.
The Chair of Geothermal Science and Technology deals with the characterization of
geothermal reservoirs, starting from basic analyses of thermo-physical rock properties,
which lead to sophisticated calculation of the reservoir potential of distinct rock units.
Reliable reservoir prognosis and future efficient reservoir utilisation is addressed in outcrop
analogue studies world-wide. Organisation of a highly qualified geothermal lab and
experimental hall (TUDA HydroThermikum) started already in 2007 and was continued in
2013. Field courses and excursions in 2013 focused on geothermal energy in New Zealand,
Jordan, Germany and Austria.
Staff Members
Head
Prof. Dr. Ingo Sass
Research Associates
M.Sc. Achim Aretz
M.Sc. Swaroop Chauhan
Dipl.-Ing. M.Sc. Sebastian
Homuth
Dipl.-Ing. Robert Priebs (until
31.03.2013)
Dr. Wolfram Rühaak
Dipl.-Ing. Johannes Stegner
Dr. Kristian Bär
M.Sc. Claus-Dieter Heldmann
Dipl.-Geol. Philipp Mielke
Dipl.-Ing. Mathias Nehler (until
31.05.2013)
Dipl.-Ing. M.Sc. Johanna Rüther
Dipl.-Ing. Rafael Schäffer
Dipl.-Ing. Bastian Welsch
Technical Personnel
Gabriela Schubert
Rainer Seehaus
Secretaries
Simone Roß-Krichbaum
Dunja Sehn (until 30.03.2013)
Institute of Applied Geosciences – Geothermal Science and Technology
187
PhD Students
Dipl.-Ing. Hauke Anbergen
Dipl.-Geol. Ulf Gwildis
Dipl.-Geol. Clemens Lehr
M.Sc. Daniel Schulte
Dipl.-Ing. Christoph Drefke
M.Sc. Yixi Gu
M.Sc. Liang Pei
Students
Bemmlott, Juliane
Brauner, Sebastian
Dönges, Florian
Hochstein, Tim
Hofheinz, Andreas
Jensen, Benjamin
Lewang, Alexander
Orendt, Robert
Ratz, Konstantin
Rybak, Thomas
Schmidt, Stefanie
Schmitz, Thomas
Schwalb,jörn
Sikora, Christiane
Trojanowski, Dominik
Weinert, Sebastian
Wiesner, Peter
Zimmermann, Philipp
Brand, Paul
Brettreich, Frank
Hesse, Jan
Hoffmann, Hellmuth
Hubert, Michel
Kappas, Jan-Dominik
Matzikanides, Damianos
Philipp, Alexej
Rautenberg, Stefan
Schedel, Markus
Schmitt, Tobias
Schreiter, Inga
Torres Melo Santos Craizer,
Rafaela
Weber, Jan Niklas
Weis, Julian
Yenna, Divya Sai Sri
Guest Scientists
Prof. Dr. Michael Alber (Ruhr-Universität Bochum, Ingenieurgeologie/Felsbau)
Dr. Jörg Baumgärtner (BESTEC GmbH)
Prof. Dr. Victor Bense (University of East Anglia, Norwich/
England)
JProf. Dr. Andreas Englert (Ruhr-Universität Bochum)
Prof. Dr. Jens Hartmann (Universität Hamburg)
Prof. Dr. Michael Himmelsbach (Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Hannover)
Prof. Dr. Michael Kersten (Johannes-Gutenberg Universität
Mainz)
Prof. Dr. Michael Kühn (Deutsches Geoforschungszentrum (GFZ)
Potsdam/Universität Potsdam)
Dr. Christian Lerch (Geschäftsführer der Pfalzwerke geofuture
Geofuture GmbH)
Dr. Naser Meqbel (Deutsches Geoforschungszentrum (GFZ)
Potsdam)
Prof. Dr. Horst Rüter (Geschäftsführer der HarbourDom GmbH,
Vizepräsident der Geothermischen Vereinigung)
Prof. Dr. Eva Schill (Université de Neuchâtel)
B.Sc. Chiranth Hedge, National Institute of Technology
Karnataka, Surathkal, Indien; 11 week Internship in Fracture
Flow Modelling
188
Guest Lecturers
Dr.-Ing. Ulrich Burbaum, CDM Consult Alsbach
Dr. Thomas Nix, LBEG Hannover
Prof. Dr. Christoph Spötl, Universität Insbruck
Dr. Thomas Kölbel, EnBW Karlsruhe
Dipl.-Geol. Stefan Knopf, Krebs und Kiefer Ingenieure, Karlruhe
Dipl.-Ing. Jörn Müller, CDMSmith Consult GmbH, Alsbach
Research Projects started in 2013
Simulation und Evaluierung von Kopplungs- und Speicherkonzepten regenerativer
Energieformen zur Heizwärmeversorgung
Funding: 1.5 years, Energietechnologieoffensive Hessen, HA Hessen Agentur GmbH
Entwicklung von numerischen Simulations- und Parameterschätzerverfahren zur ThermoHydro-Mechanisch gekoppelten Simulation des Untergrunds - Kurztitel: THM-Modul BMU/PTH
Research proposal, Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit
Integrated Methods for Advanced Geothermal Exploration - IMAGE
Geldgeber: EU - Seventh Framework Programme (FP7) - ENERGY.2013.2.4.1: Exploration
and assessment of geothermal reservoirs
Research Projects continued and finalized in 2013
Geothermische Untersuchungen an den Tiefbohrungen des Geothermieprojektes Geretsried
Funding: 2012-2013, ENEX Power Germany GmbH, ongoing
Market Report Study on Deep Geothermal Energy in Europe
Funding 2013, Ed. Züblin AG, finalized
Quantitativer Einfluss des Wasserhaushalts, der Umwelttemperatur und der geothermischen
Kennwerte auf die Wärmeableitung erdverlegter Starkstromkabel
Funding: 2 years, E.ON Bayern AG
Experimentelle Untersuchungen zur Verifizierung eines Mehrphasenmodells
Wärmetransportverhalten im Untergrund
Funding: 3 Years, Bundesministerium für Wirtschaft und Technologie
für
das
Machbarkeitsstudie „Machbarkeit und Nutzung von tiefer geothermischer Energie am
Flughafen Frankfurt
Funding: 2010-2013, FRAPORT AG
Charakterisierung des Geothermischen Reservoirpotenzials des Permokarbons in Hessen und
Rheinland-Pfalz
Funding: 3 Years, Bundesministeriums für Umwelt, Naturschutz und Reaktorsicherheit
189
Entwicklung von wartungsarmen PEHD-Filterelementen für oberflächennahe geothermische
Brunnenanlagen
Funding: 3 Years, Deutsche Bundesstiftung Umwelt
Scientific consulting and supervision of enhanced hydrothermal power plant systems, Upper
Rhine Valley
Private clients, confidential.
Evaluation of thermal response tests using a cylinder source approach (Type Curve Fitting
Method) – Industry-funded project (Geotechnisches Umweltbüro Lehr).
Development of a thermal conductivity measuring device for soil or cuttings
In collaboration with DIN-Innovation of normalisation and standardization.
Untersuchungen zur Radon-Emanation im Bereich der Heilquellen und Heilbrunnen Bad
Soden-Salmünsters
Funding: 6 months, Spessart-Therme Kur- und Freizeit GmbH
Wiss. Beratung Sanierung Spruedelfassungen Sprudelhof Bad Nauheim,
Funding: 18 months, Stiftung Sprudelhof Bad Nauheim
Quellbeweissicherung der Erdwärmebohrungen des Sporthotel Stock, Finkenberg, Tirol,
Österreich
Funding: 2 months, Sporthotel Stock GmbH
Publications
Anbergen, H. & Sass, I. (2013): Freeze-Thaw-Behaviour: Observations in Grouted Borehole
Heat Exchangers. - In: Thirty-Eighth Workshop on Geothermal Reservoir Engineering,
Stanford University, Stanford, California, February 11 - 13, SGP-TR-198.
Aretz, A., Bär, K., Sass, I. (2013): Charakterisierung des geothermischen Reservoirpotenzials
des Permokarbons in Hessen und Rheinland-Pfalz – thermophysikalische und hydraulische
Gesteinskennwerte. Swiss Bulletin für angewandte Geologie, Vol. 18/1, 2013, S. 33-41.
Arndt, D. & Bär, K. (2013): Geologische 3D-Modellierung und multikriterielle
Potenzialbestimmung. Geothermie.ch - Zeitschrift der Schweizerischen Vereinigung für
Geothermie SVG, 54: 22-24.
Chauhan, S., Rühaak, W., Enzmann, F., Khan, F., Mielke, P., Kersten, M., Sass, I. (2013):
Comparison of Micro X-ray Computer Tomography Image Segmentation Methods: Artificial
Neural Networks Verses Least Square Support Vector Machine'', Mathematics of Planet Earth,
Lecture Notes in Earth System Sciences, pp 141-143; DOI: 10.1007/978-3-642-32408-6_34.
Hegde, C., Rühaak, W, Sass, I. (2013) Evaluation of Modelling of Flow in Fractures. Proc. of
Int. Conf. on Advances in Civil Engineering, AETACE. DOI: 02.AETACE.2013.4.24
Homuth, S., Hamm, K., Sass, I. (2013): BHE logging and cement hydration heat analyses for
the determination of thermo-physical parameters. Bulletin of Engineering Geology and the
Environment, Volume 72, Issue 1, Page 93-100, Springer Verlag Berlin Heidelberg. DOI
10.1007/s10064-012-0455-2
190
Rühaak, W., & Sass, I., (2013): Applied Thermo-Hydro-Mechanical Coupled Modeling of
Geother-mal Prospection in the Northern Upper Rhine Graben. - In: Thirty-Eighth Workshop
on Geothermal Reservoir Engineering, Stanford University, Stanford, California, February
11 - 13, SGP-TR-198.
Rüther, J. & Sass, I. (2013): Entwicklung poröser Filterelemente aus hochdichtem Polyethylen
für geothermale Brunnenanlagen, bbr- Fachmagazin für Wasser und Leitungsbau, 04/2013,
64-69.
Sass, I. (2013, Gelbdruck): Empfehlungen des Arbeitskreises Geothermie. Oberflächennahe
Geother-mie „Planung, Bau, Betrieb und Qualitätssicherung“. FH-DGG und FI-DGGT/DGG.
Berlin, Germany, Ernst & Sohn.
Schäffer, R. & Sass, I. (2013): The Thermal Springs of Jordan. - Environmental Earth
Sciences. DOI 10.1007/s12665-013-2944-4.
191
Optimizing High Temperature Borehole Thermal Energy Storage Systems
Daniel O. Schulte, Bastian Welsch
Due to its seasonal changes, solar energy presents a suitable source to setup a storage
system with borehole heat exchangers (BHE). Excess heat is fed in during summer and
extracted in winter. A couple of requirements have to be met by such a system: the stored
heat must remain in place and the working fluid must maintain an extraction temperature
sufficiently high for the specific heating purpose at all times. Storing heat at temperature
levels of up to 90 °C has a key benefit, compared to low temperature energy storage,
because higher loading temperatures in the summer season result in higher unloading
temperatures during the heating period in winter. This makes the high temperature
storages suitable for applications in existing building stock with radiator heating systems.
Furthermore, a higher overall efficiency of the heating system can be achieved. However,
higher temperature levels in the storage system increase the heat losses, due to a higher
temperature gradient with respect to the surrounding subsurface. As ground temperature
increases with depth, the installation of deep borehole heat exchanger systems at depths of
400 m up to 1500 m is considered to minimize these thermal losses. In this study the
potential of High Temperature Borehole Thermal Energy Storages (HT-BTES) is presented.
The most important rock properties for HT-BTES are a high specific heat capacity, a
medium thermal conductivity and a low hydraulic conductivity. Igneous rocks from the
Paleozoic Odenwald Crystalline Basement seem to match all of these requirements. As part
of an outcrop analogue study 76 rock samples from the crystalline basement were collected
in the vicinity of Darmstadt. Further samples of the crystalline basement were taken from
two research boreholes close to the Messel Pit. Porosities and thermal conductivities were
determined from the collected samples to gain input parameters for numerical
underground models.
Figure 2: Numerical model of an exemplary borehole thermal energy storage. The storage consists of 4 BHEs
with a length of 1000 m and a distance of 10 m between the boreholes. The window on the right side shows
the positions of the BHEs on the model surface.
192
First calculations were made, using the finite element program FEFLOW [1] for modeling
the heat transport processes in the BHE and in the crystalline rocks. The initial results
indicate, that there is a strong dependence of the performance of such storage systems on
the alignment and the depth of the BHEs. Since drilling is the most critical cost factor, the
required number of BHE and the respective BHE length, need to be optimized. Thus,
various BTES configurations are compared. The previously optimized shape and parameters
of the BHEs, the overall length of the BHEs as well as the flow rate and the inlet
temperatures are kept constant, whereas the number of boreholes, the length of the
boreholes and the distance between the boreholes are varied, to identify the system designs
with the highest heat recovery rate possible. As a second step, possible variations of the
operational mode and other technical parameters are taken into account as well.
However, this “try-and-error-scheme” of parameter alteration in FEFLOW is very time
consuming. Thus, an efficient solution to this problem requires mathematical optimization
techniques, which minimize the number of
required iterations. A simplified MATLAB model is
developed to simulate the thermal behavior of a
HT-BTES. Our approach goes beyond the problems
discussed in Beck et al. [2013]: a more detailed
physical description of the underlying processes is
applied. The BHE storage system is simulated with
a set of MATLAB functions, which dynamically
calculate the conductive heat transport within the
subsurface, employing a finite element method
algorithm [3] and also the heat transfer within the
BHE [4]. To allow the computation of large
numbers of models to test different BHE set-ups, Fig. 3: Underground temperature distribution
the code uses a fully unstructured tetrahedron in 400 m depth with four BHE after 10 years
mesh, which is specifically refined around the BHE. of constant loading with 90°C in each BHE.
For the meshing TetGen [5] is used.
For solving the optimization problem, a Monte-Carlo technique [6] is applied as a
comparably simple approach. Additionally mathematical optimization algorithms will be
applied to evaluate their potential to solve these problems in a more efficient way: genetic
algorithms [7], which mimic natural selection in the process of developing an optimal
solution as well as simulated annealing [8], which iteratively improves a candidate solution
with respect to a quality threshold.
[1]
[3]
[4]
[5]
[6]
[7]
[8]
Diersch, H.-J., 2014. FEFLOW Finite Element Modeling of Flow, Mass and Heat Transport in Porous
and Fractured Media. Springer-Verlag Berlin Heidelberg, 384 p.
Alberty, J.,Carstensen, C. and Funken, S.A., 1999. Remarks around 50 lines of Matlab: short finite
element implementation, Numerical Algorithms, 20(2-3): 117-137.
Eskilson, P. and Claesson, J, 1988. Simulation model for thermally interacting heat extraction
boreholes, Numerical Heat Transfer, 13: 149-165.
Si, H., 2011. Constrained Delaunay tetrahedral mesh generation and refinement. Finite elements in
Analysis and Design, 46 (1-2): 33-46.
Sabelfeld, K.K.: Monte Carlo Methods in Boundary Value Problems, 1991. Springer Series in
Computational Physics: Springer-Verlag, Printed in the United States of America 281 p.
Goldberg, D.E., 1989. Genetic Algorithms in Search, Optimization and Machine Learning (1st ed.).
Addison-Wesley Longman Publishing Co., Inc., Boston, MA, USA, 372 p.
Kirkpatrick, S., Gelatt Jr., C.D., and Vecchi, M.P., 1983. Optimization by Simulated Annealing.
Science, 220 (4598), 671-680.
193
Investigation of hydrothermal springs and geothermal exploration of an Alpine
Marble Karst, Tuxertal, Tirol, Austria
Claus-Dieter Heldmann, Ingo Sass, Rafael Schäffer
The thermal springs in Hintertux are probably the highest of Europe in 1500 m above sea
level. More than 20 outlets originate with 20 °C in an alluvial fan at the foot of
Schmittenberg Mountain. For more than 150 years they are used for balneological and
medicinal purposes. Although they are well-known, no comprehensive genetic explanation
of the temperature anomaly’s origin is given yet. Since 2012 these and other sources of the
valley are under hydrochemical investigation. The hydrochemical characteristics are used to
identify the hydrogeochemical signatures of every geological unit and so associated with
the origin of every spring (fig. 1).
The Tuxertal is a sport region with energy-intensive tourism and a huge demand for
heating and water in spa attractions. The unique geology of an alpine karst aquifer,
reaching over the whole valley, bearing thermal springs and its geothermal potential is
under research now. The high solubility of the carbonates in the late Jurassic Hochstegen
Marble is the reason for the karstification. The first geothermal systems in these rocks was
installed in 2013 in the form of a 400 m deep borehole heat storage under a large hotel
complex for 1 GWh heating and 0.3 GWh cooling per year [1]. Before a sustainable,
feasible exploration can be started, investigations must deliver more data about geothermal
properties and explain dependencies between the aquifers and the thermal springs.
The hydrochemical field parameters temperature, electrical conductivity, pH value, redox
potential, oxygen saturation and the carbonate concentration were determined in-situ. The
concentrations of iron, manganese and the major ions were analyzed by atomic absorption
spectrometry and ion gas chromatography. Non-published hydrochemical data of
measurements from 1969 to 1974 and 1993 to 2008 were evaluated for showing annual
and seasonal trends and for correlation purposes. The study includes 6 thermal springs and
15 non-thermal springs. Borehole loggings of the Hochstegen Marble in Finkenberg and an
Enhanced Geothermal Response Test detected karst structures and high ground water
velocities below 200 m below surface.
The previous hypothesis of meteoric water seeping into the crevices of the gneisses
followed by local rising in fault zones during the Hochstegen Marble cannot explain the
composition of the thermal water. Although water can migrate in transregional faults like
the Olperer Shear Zone, their steep falling and distance does not fit to the hypothesis.
However the alpine geothermal gradient is so low that this scenario is difficult considering
hydraulic situations. The increased sodium and magnesium content shown in the analyses
remain unnoticed in hypothesis. The high Mg/Ca ratio results from magnesium enrichment
in dolomitized areas or maybe formations which are not considered in this area (e.g.
Aigerbach formation). In the new hypothesis a mixed origin is be assumed. If the origin of
the temperature anomaly is a crystalline reservoir, this can explain the contents of sulfate,
sodium and potassium. Due to concentrations approximately 50 % of the water volume
could originate from such a reservoir. Accordingly, higher reservoir temperatures must be
assumed, what is even underpinned by the magnesium corrected Na-K-Ca chemical
geothermometer giving 90 °C [2]. Because currently only little amount of the water is used
and only with the surface temperature of 20 °C, drilling wells into the heat plume will
provide more hot water.
194
Figure 1: Tectonic units and characteristic hydrochemical signatures attributed by Stiff diagrams, Tux Valley,
Tyrol, Austria. of the geothermal heat exchangers and surrounding springs at Finkenber [3].
Karst aquifers can affect advantageously the efficiency of geothermal systems due to its
elevated permeabilities. However, karst aquifer properties require special exploration and
exploitation. The marble karst aquifer of the Hochstegenformation was investigated to
construct a middle deep borehole heat exchange storage at Finkenberg, Austria.
Investigations of streams and springs all over the Tuxertal led to an attribution of
characteristic hydrochemical signatures to each tectonic unit in accordance to its lithology
195
(Fig. 1). Determining the surroundings of Finkenberg it became evident, that the geological
catchment of the Hochstegenformation reaches there from 840 to 2650 m above sea level.
Results of geological mapping and an exploration well showed that the tectonic situation is
much more complex than described in the official geologic map. The Hochstegenformation
can reach locally significant higher thicknesses than estimated before. In addition, the layer
sequence is more unconformable as supposed.
Karstified zones till 400 m depth could be detected within the boreholes (Fig. 2).
Groundwater flow velocities up to 14 m/d were measured. The drilling operations were
accompanied by a conservation of evidences at neighbouring springs. Thereby collected
data allow the calculation of gap flow velocities.
A total number of nine 400 m deep boreholes were drilled. The borehole heat exchange
storage system has an abstraction performance of 1 GWh/a and 400 MWh/a storage
performance. The successful conclusion of this project and gathered knowledge up to now
led to the idea to explore the Hochstegenformation for extensive geothermal use.
Exploration of a 1200 m deep well for hydrothermal use is in process now.
Figure 2: a): Geological map of the drilling site and location of the boreholes. b): Results of the logging in
borehole 6.
References
[1]
[2]
[3]
196
SASS, I. & LEHR, C. (2013): Design Parameter Acquisition of an Underground Heat Storage and
Extraction System. – Proc. Thirty-Eigth Workshop on Geothermal Reservoir Engineering Stanford
University, Stanford, California.
FOURNIER R. O. & POTTER R. W. (1979): Magnesium correction to the Na-K-Ca chemical
geothermometer, Geochimica and Cosmochimica, Vol. 43, pp 1543–1550.
SASS, I., HELDMANN, C.-D. & SCHÄFFER, R. (2014, submitted): Geothermische Erschließung und
hydrogeologische Beweissicherung des Hochstegenmarmors, Tuxertal. Grundwasser.
Applied Sedimentology
Sedimentary rocks cover about 75% of the earth’s surface and host the most important oil
and water resources in the world. Sedimentological research and teaching at the Darmstadt
University of Technology focus on applied aspects with specific emphasis on
hydrogeological, engineering and environmental issues. One key issue in this context is the
quantitative prediction of subsurface reservoir properties which is essential in modelling of
regional groundwater hydrology, oil and gas exploration, and geothermal exploitation.
However, also basic sedimentological research is carried out, e.g. the use of sediments as
archives in earth history to reconstruct geodynamic, climatic and environmental processes
and conditions in the past. To predict groundwater movement, pollutant transport or
foundations of buildings in sedimentary rocks a detailed knowledge about the hydraulic,
geochemical or geotechnical properties is needed which often vary about several
magnitudes. This kind of subsurface heterogeneity can be related to distinct
sedimentological patterns of various depositional systems. In addition, changes of
depositional systems with time can be explained by specific controlling parameters e.g.
changes in sea level, climate, sediment supply and are nowadays described by the concept
of sequence stratigraphy. The research in applied sedimentology also includes modelling of
erosion and sediment transport and its implication for the management of rivers and
reservoirs with the help of GIS.
For any subsurface management a quantitative 3D model is a prerequisite, either related to
water and geothermal energy or to gas, oil, and CO2 storage. Together with the groups of
Prof. Schüth (Hydrogeology), Prof. Sass (Geothermics), and Prof. Henk (Engineering
Geology) the sedimentology group focusses on detecting the large to meso-scale
sedimentary architecture and permeabilities of sedimentary reservoir rocks in order to
achieve an optimized subsurface management of water and renewable energy resources.
Dr. Hornung received a grant from Shell to analyse small-scale heterogeneities of porosities
and permeabilities of sedimentary rocks and their link to microfacies patterns.
To detect subsurface heterogeneities at a high resolution, the sedimentology group hosts a
georadar equipment for field measurements. This geophysical device is composed of
various antennas and a receiver unit. Sophisticated computer facilities are provided to
process the data and construct real 3D subsurface models. The group shares their
equipment and facilities with the Universities of Frankfurt (Applied geophysics), Tübingen
(Applied sedimentology), the RWTH Aachen and industrial partners. These institutions
founded the Georadar-Forum which runs under the leadership of Dr. Jens Hornung
(http://www.georadarforum.de/). Thanks to funding via a DFG research grant we could
invest into a shear wave measuring unit, which will extent our abilities for subsurface
surveys down to several hundred meters and through materials, weakly penetrable by
electromagnetic waves. Here we cooperate with the Leibniz Institute for Applied
Geophysics in Hannover. For quantification of reservoir properties a self-constructed facility
for permeability measurements of soil and rock materials exists which is further developed.
This lab is also fundamental to geothermal research.
In 2013, the group participated in the DFG Research Unit RiftLink (www.riftlink.de) and
two European Research Groups within the EUCORES Programme (TOPOEurope,
SedyMONT). The topic of these research projects are in the context of earth surface
Institute of Applied Geosciences – Applied Sedimentology
197
processes, palaeoenvironmental reconstructions and georisk assessments. For the DFG
Research Unit RiftLink we received an additional funding for one year from DFG.
Furthermore, a project in Saud Arabia runs in the context of exploring deep water resources
together with Prof. Schüth (Hydrogeology) and in cooperation with the GIZ (Gesellschaft
für I(nternational Zusammenarbeit), the UFZ (Umweltforschungszentrum Halle-Leipzig),
and the Ministry of Water and Energy of Saudi Arabia (MOEWE). The aim is to investiate
the storage properties of large sedimentary aquifers and their relation to the amount and
quality of substracted groundwater in a hyperarid area suffering from water scarcity. A
Saudi Arabian student from the MOEWE received his PhD from TU Darmstadt in 2013. This
forms the basis for further cooperation and future projects in the region. One outcome is
the submission of a DFG proposal in order to elucidate the provenance of the widespread
sandstones on the Arabian Peninsula which host most water resources of Saudi Arabia but
whose quality partly suffer from increased radioactivity. At the moment a second proposal
to MOEWE is prepared.
Based on previous work of the group several research initiatives are running at the
moment, e.g. past environmental pollution in Central Europe as reconstructed from lake
sediments, Mesozoic palaeoenvironmental evolution in NW China (initiative together with
University of Bonn and Jilin University, China), and high-resolution palaeoclimatic studies
in Messel and similar maar lakes (DFG). Jianguang Zhang continued his PhD with a
Chinese grant. Dr. Dorthe Pflanz joined the sedimentology group and prepared a DFG
proposal about palaeoclimatic implications of loess and sand dune deposits in southern
Hessen. Thanks to constructing a new gas pipeline from Gernheim to Hercherode she could
sample a complete transect from the Rhine plain to the central Odenwald. Several BSc and
MSc theses could be attached to this project. Based on this unique sample collection, Dr.
Pflanz could establish the first absolute chronology of these eolian deposits in southern
Hessen. The results have been presented on a conference and are now going to be
published.
Prof. Hinderer is still member and speaker of the "Wissenschaftlicher Beirat
Beschleunigungsmassenspektrometer, DFG University of Cologne” and was nominated by
the DFG senat commission of common geoscientific research (DFG-Senatkommission
Zukunftsaufgaben der Geowissenschaften). He is also the representative of the Germanspeaking sedimentologists (Section of Sedimentology in Geologische Vereinigung and
SEPM-CES) and co-organized the SEDIMENT conference in Tübingen 2013. He keeps on
being a member of the editorial board of the International Journal of Earth Sciences. In
2013, the vacant position for the technical personnel could be filled with Reimund
Rosmann who works part time also in the Engineering Geology group of Prof. Henk.
Staff Members
Head
Prof. Dr. Matthias Hinderer
Research Associates
Dr. Jens Hornung
Postdoctoral Students
Dorthe Pflanz
198
Dr. Olaf Lenz
PhD Students
Hussain Al-Ajmi
Alexander Bassis
Dennis Brüsch
Daniel Franke
Technical Personnel
Reimund Rosmann
Secretary
Kirsten Herrmann
Inge Neeb
Frank Owenier
Sandra Schneider
Jianguang Zhang
Research Projects
Linking source and sink in the Ruwenzori Mountains and adjacent rift basins, Uganda:
landscape evolution and the sedimentary record of extreme uplift: Subproject B3 of DFG
Research Group RIFT-LINK “Rift Dynamics, Uplift and Climate Change: Interdisciplinary
Research Linking Asthenosphere, Lithosphere, Biosphere and Atmosphere” (DFG HI 643/72).
Spatial distribution of modern rates of denudation from cosmogenic Nuclides and Sediment
Yields throughout the Alps (EUCORES programme TOPOEurope, Research Unit TOPO Alps,
IP 3, DFG HI 643/9-1).
High resolution 3D architectural analysis and chronology of alluvial fan deposits in
mountain landscapes: A case study of the Illgraben fan, Switzerland (EUCORES programme
TOPOEurope, Research Unit SedyMONT, IP 6, DFG HI 643/10-1).
Monitoring of soil water content with ground penetrating radar (PhD thesis).
Climatic and tectonic interplay in central Asian basins and its impact on paleoenvironment
and sedimentary systems during the Mesozoic (1 PhD thesis).
Sedimentology, dynamic stratigraphy and hydrofacies model of Paleozoic and Mesozoic
aquifers in Saudi Arabia. (PhD thesis financed by Umweltforschungszentrum Leipzig-Halle,
GIZ Eschborn, and the Ministry of Water and Energy in Riyadh, Saudi Arabia).
Provenance of Paleozoic clastic sediments and reasons for radioactive anomalies in
groundwaters on the Arabian Platform (PhD thesis)
Aggradation of alluvial fans in the Eastern Cordillera in response to humidity changes and a
climate gradient from the Altiplano to theAmazon Basin (two Master theses and
preparation of a DFG project)
Periglacial eolian sediments in southern Hessia, their chornology, and their genesis
(Diploma und BSc theses and preparation of a DFG project)
2-D heterogeneities of poroperm, ultrasonic and resistivity on sub-meter scale (funded by
Shell)
199
Publications
[1] Arp, G., Blumenberg, M., Hansen, B.T., Jung, D., Kolepka, C., Lenz, O.K., Nolte,
N., Poschlod, K., Reimer, A., Thiel, V. (2013): Chemical and ecological
evolution of the Miocene Ries impact crater lake, Germany: a reinterpretation
based on the Enkingen (SUBO 18) drill core. GSA Bulletin, doi:
10.1130/B3073.1.
[2] Hinderer, M., Kastowski, M., Kamelger, A., Bartolini, C., Schlunegger, F., (2013): River
loads and modern denudation of the Alps – a review, Earth Science Reviews.
[3] Hinderer, M., Pflanz, D., Schneider, S. (2013): Chemical denudation rates in the humid
tropics of East Africa and comparison with 10Be-derived erosion rates. WRI-14 Avignon
2013. Procedia Earth and Planetary Science.
[4] Lenhardt, N., Böhnel, H., Hinderer, M. & Hornung, J. (2013): Paleocurrent direction
measurements in volcanic settings by means of anisotropy of magnetic susceptibility: A case
study from the Lower Miocene Tepoztlán Formation (Transmexican Volcanic Belt, Central
Mexico). J. of Sedimentology
[5] Lenhardt, N., Herrmann, M. & Götz, A.E. (2013): Palynomorph preservation in
volcaniclastic rocks oft he Miocene Tepoztlan Formation (Central Mexico) and implications
for palaeoenvironmental reconstruction. Palaios 28(10): 710-723.
200
OSL- Dating of a glacial dune field in the upper Rhine valley: a transect study
Dorthe Pflanz1, Alexander Kunz2, Matthias Hinderer1
1
TU Darmstadt, Institute of Applied Geosciences, Schnittspahnstr. 9 D-64287 Darmstadt
National Taiwan University, Department of Geosciences,Luminescence Dating Laboratory,
No.1 Sec.4, Roosevelt Road, Taipei 106, Republic of China (Taiwan)
2
In this study aeolian sands are investigated which are largely extend in the Upper Rhine
Valley. Especially in the area of Darmstadt/Zwingenberg they form thick dune fields
covering the upper Lower Terrace of the Rhine River. The aeolian sands are subdivided into
different units by paleosoil horizons, gravel layers or unconformities indicating periods of
non-deposition. Transport and deposition of aeolian sands could only take place when the
flood plain of the Rhine river was dry (Löscher 1994). In this area, the sand forms parabolic
dune fields. This gives us a hint of dry climate with a steppe vegetation cover during
sedimentation. It is generally supposed that the main deposition of the sand happened
during the LGM and terminated during the Younger Dryas (Becker 1967). Several studies
show that the dunes were very likely reactivated during the Holocene (e.g. Baray & Zöller
1993; Semmel 1980). So far, however, no absolute ages for these dune deposits
(“Bergsträsser Flugsande”) were available. We took the opportunity to sample the dune belt
between Bickenbach and Seeheim-Jugenheim south of Darmstadt along a trench which was
shortly excavated for constructing a new gas pipeline. Besides Samples for OSL dating we
analysed grain sizes, carbonate content, and magnetic susceptibility.
Fig. 1: Position of the Gas- pipeline in the Northern Upper Rhine Graben.
201
OSL dating was done on quartz with a grain size of 100-150 µm using the SAR protocol
following Wintle and Murray (2006). Standard tests as preheat-dose recovery and dose
recovery test have been done to find the optimum parameters for the SAR protocol. Linear
modulated optical stimulated luminescence (LM-OSL) has been done for all samples. The
LM-OSL signal curves were analyzed using curve fitting procedures introduced by Choi et
al. (2006). Results show that the quartz OSL signal from all samples is dominated by the
fast component. Interestingly there are regional differences in the amount of medium and
slow components. This could indicate different source areas of the dune sands but needs
further investigation.
Fig. 2: Cross section of the investigated dune field and OSL dating results.
Preliminary OSL ages generally confirm that the major accumulation of the dune sands
happened during the LGM and lastest until the Younger Dryas, i.e. until 11600 years BP.
Moreover, Holocene reactiviation could be proved by two ages. Dating and further
sedimentological analysis is going on and a publication is under preparation. One diploma
thesis and one BSs thesis was attached to this study. The first author was appointed as a
temporal postdoc (Dr. Dorthe Pflanz) and prepared a DFG proposal for an own position.
This opportunity is highly acknowledged. The submission of the proposal is delayed
because of this unique chance to sample continuously a transect. It is now ready for
submission.
References
1.
2.
3.
4.
5.
6.
202
Choi, J. H., Duller, G. A. T., and Wintle, A. G. (2006): Analysis of quartz LM-OSL curves. Ancient TL 24, 9-20.
Baray, M. & Zöller, L. (1993): Aspekte der Thermolumineszenz-Datierung an spätglazialholozänen
Dünen im Oberrheingraben und in Brandenburg. – Berliner geogr. Arb., 78(1):1-33.
Becker, E. (1967): Zur stratigraphischen Gliederung der jungpleistozänen Sedimente im nördlichen
Oberrheintalgraben. – Eiszeitalter Gegenw., 18: 5-50.
Löscher, M. (1994): Zum Alter der Dünen auf der Niederterrasse im nördlichen Oberrheingraben.– Beih.
Veröff. Natursch. Landschaftspfl. Baden-Württemberg, 80: 17-22.
Semmel, A. (1980): Quartär. – In: Golwer, A. & Semmel, A.: Erläuterungen zur Geologischen Karte von
Hessen 1:25 000, Bl. 5917 Kelsterbach. – 3., neu bearb. Aufl.: 25-49.
Wintle, A. G., and Murray, A. S. (2006): A review of quartz optically stimulated luminescence
characteristics and their relevance in single-aliquot regeneration dating protocols. Radiation
Measurements 41, 369-391.
Geo-Resources and Geo-Hazards
Mes of rapid population growth and the resulting strain of the resilience of natural systems,
geosciences in particular have become an increasingly important research area. However,
geoscientific knowledge about material flows from and back into the environment and about
the prevention of catastrophic consequences of big natural phenomena is often not
understood by decision makers, who were not able to spend long years on understanding
the four-dimensional space-time-development of our earth. On the other hand, the
metabolism of cities, its growing needs for clean water and raw material for constructions
while simultaneously egesting waste into its neighbourhood, require a thorough
understanding of its undergrounds and peripheries as well as safe construction sites.
Computer based Geo Information Systems and 3 to 4D-techniques are powerful tools to
qualify and to quantify resources and hazards in the peripheries of urban areas. They enable
the aggregation of complex geological and spatial data to thematic maps for a better
understanding and interpretation by local decision makers.
Staff Members
Head
Prof. Dr. Andreas Hoppe
Research Associates
Dipl.-Geoökol. Monika Hofmann
Dr. Rouwen Lehné
Dipl.-Geol. Ina Lewin
Technical Personnel
Dipl.-Kartogr. (FH) Ulrike Simons
Secretaries
Pia Cazzonelli
PhD students
Hannah Budde (MSc Geowiss.)
Dipl.-Geogr. Constanze Bückner
Ingram Haase (Mag. Gesch./Geogr.)
Dipl.-Geol. Marie Luise Mayer
Students
Tobias Faißt (MSC), Shirin Gomez (MSc), Georg Kuhn (BSc),
Marie Mohr (BSc), Narmada Maheshani Rathnayake (MSc),
Shaojuan Xu (MSc), Stefan Wewior (BSc),
Student apprentices
Arola Moreras (Universidad de Catalunya in Barcelona,
during July-August 2013)
Guest Scientist
Prof. Dr. Prem B. Thapa (Tribhuvan University Kathmandu,
Nepal, during June 2013)
Prof. Dr. Joachim Karfunkel (Universidade Federal de Minas
Gerais in Belo Horizonte, Brazil, during November 2013)
Institute of Applied Geosciences – Geo-Resources and Geo-Hazards
203
Research Projects
Focus was still laid on the analysis and evaluation of geopotentials in the surroundings of
urban areas as well as on hazards based on mass movements. Tools do achieve these goals
were geoinformation systems (GIS) and 3D modelling (GOCAD).
First results have been compiled by Andreas Hoppe and Rouwen Lehné in a special volume
of the German Journal of Geosciences (ZDGG) on Urban Geology. Monika Hofmann
defended successfully her dissertation about the geopotentials in the north of the Brazilian
megalopolis Belo Horizonte. Hannah Budde continued to elaborate a 3D model for the RheinMain area in cooperation with the Hessian Geological Survey (HLUG). Constanze Bückner
investigates the relations between natural framework conditions and development of
German major cities. Ina Lewin elaborated a high resolution model of Quaternary sediments
in a test area east of the Odenwald and investigated the water exchange between a
dredging lake and a groundwater well in cooperation with the local water distributor (ZVG
Dieburg)
3D modelling of the Quaternary of the Northern Upper Rhine Graben was intensified by
Rouwen Lehné. Together with HLUG, he also started a GIS supported data base on geohazards in Hesse.
Mass movements in the Lesser Himalayas were analysed in two master theses co-orientated
by Prem Thapa (Katmandu). First steps to model future hazards in the Eastern Alps by
retreating ice and permafrost were done by Ingram Haase in cooperation with the University
of Natural Resources and Life Sciences in Vienna.
Distribution and quality of geopotentials in Estonia (i.e. oil shale and black shale) have been
investigated with GIS and GOCAD techniques by Rouwen Lehné and master students in cooperation with the Estonian Land Board.
Andreas Hoppe served as Chief Editor of the ZDGG and evaluated in April the education in
geology and mineral prospecting at the Siberian University in Yakutsk. Rouwen Lehné
served as speaker of the Section Geoinformatics within the German Geological Society
(DGG).
Publications
[1]
Bückner, C. (2013): Local Agenda 21: Natural resources in German urban sustainability
strategies. - Z. dt. Ges. Geowiss. 164/4: 535-539, Stuttgart.
[2]
Hofmann, M., Hoppe, A., Karfunkel, J. & Büchi, A. (2013): Regionalizing hydrological
soil properties in the Brazilian cerrado region using a semantic import model
approach. – In E.C. Lannon, ed., Drainage Basins and Catchment Management:
Classification, Modelling and Environmental Assessment, 50 pp., New York (Nova
Science Publ.) [ISBN: 978-1-62618-368-1]
[3]
Hoppe, A. (2013): Cities and geology. - Z. dt. Ges. Geowiss. 164/4: 517-524, Stuttgart.
204
[4]
Hoppe, A. & Lehné, R., eds. (2013): Urban Geology.– Z. dt. Ges. Geowiss. 164/4: 515-603,
Stuttgart (Schweizerbart).
[5]
Hoselmann, C. & Lehné, R. (2013): Neue Lithostratigraphie und ein geologisches 3DModell des nördlichen Oberrheingrabens. – Jahresbericht 2012 des Hessischen
Landesamtes für Umwelt und Geologie, 77-87, Wiesbaden.
[6]
Lamelas, M.T., Marinoni, O.T., de la Riva, J. & Hoppe, A. (2013): Spatial decision
support for sustainable land-use decision making: An application for industry site
planning and irrigation use in the surroundings of Zaragoza (Spain). – In J.M. PradoLorenzo & I.M. Garcia Sanchez, eds., Sustainable Development – New Research, 65-79,
7 figs., 1 table, New York (Nova Science Publ.) [ISBN 978-1-62081-903-6].
[7]
Lehné, R., Hoselmann, C., Heggemann, H., Budde, H. & Hoppe, A. (2013): Geological 3D
modelling in the densely populated metropolitan area Frankfurt/Rhine-Main. - Z. dt.
Ges. Geowiss. 164/4: 591-609, Stuttgart.
[8]
Panteleit, B., Jensen, S., Seiter, K., Budde, H. & McDiarmid, J. (2013): A regional and
geological groundwater flow model of Bremen (Germany): an example management
tool for resource administration.- Z. dt. Ges. Geowiss. 164/4: 569-580, Stuttgart.
205
Multi-criteria approach for 3D-modelling of geological horizons in the Lower
Main Plain, Germany
Hannah Budde(1), Christian Hoselmann(2), Rouwen Lehné(1), Heiner Heggemann(2),
Andreas Hoppe(1)
(1)
Technische Universität Darmstadt, Angewandte Geowissenschaften, Schnittspahnstr. 9, D-64287 Darmstadt
(2)
Hessisches Landesamt für Umwelt und Geologie (HLUG), Rheingaustr. 186, D-65203 Wiesbaden
Introduction:
The availability of near-surface geo-resources such as groundwater or sand and gravel
deposits plays a key role in urban development. Due to the increasing demand for land,
particularly in metropolitan areas, conflicts of utilization between different economic and
environmental interests often arise.
Therefore, in cooperation with the Hessian Agency for the Environment and Geology
(HLUG), a 3D geological model for a part of the metropolitan region of Frankfurt / RheinMain will be created to evaluate geo-potentials, model usage scenarios and to work out
criteria for the evaluation of land use conflicts. In the process, the model should always be
transparent concerning to its input data and thus easy comprehensible to third parties. The
aim of the model is to visualize important stratigraphic units like the Base Quaternary and
Tertiary. Depending on data availability, the space between will be further differentiated
stratigraphically. The 2,700 km² large project area focusses the subsidence sites of the
Lower Main Plain (Hanau Basin, Upper Rhine Graben, Mainz Basin, Wetterau Tertiary
depression) and is bounded by the Rhenish Slate Mountains (Rheinisches Schiefergebirge)
in the northwest and the Odenwald in the southeast (Fig. 1).
Frankfurt
am
Main
Wiesbade
n
Darmstad
t
Fig. 1: Elevation model of the project area from SRTM data. Scale in [m]. Colormap shows height above sea
level in [m]. Data source: Jarvis et al. (2008)
206
Methodology and data background:
Within the preparation of well data, a large number of inconsistent entries in the borehole
database were observed. Especially in the field of stratigraphy, differences in the
interpretation of layers depending on the processor and drilling year occur. Therefore, a
multi-criteria approach for the derivation of the horizons has been developed to avoid
model errors due to incorrect entries from the borehole database, to objectify the
stratigraphic classification, and to specify a size for the reliability of model areas. In this
process, each entry will be evaluated by its petrographic description and under specification
of the probability and with geological expert knowledge and regional experiences semiautomatically assigned to one stratigraphic unit (Fig. 2).
Fig. 2: Workflow. Evaluation of each borehole entry in terms of belonging to a specified stratigraphic
unit based on defined characteristic parameters.
Quaternary Main terrace
Pliocene
Fig. 3: Results of the classification of the layers entries in Quaternary terrace sediments and Pliocene
deposits using the evaluation matrix shown in relation to their spatial position
207
Characteristics and descriptive information about the lithology of each stratigraphic unit in
the project area have been derived based on publications that address the geology of the
Rhein-Main area (e.g. Gabriel et al. 2012, Hoselmann 2008), results from two projects,
i.e.3D_NORG (Hoselmann & Lehné 2012) and the Hanau Basin (Lang 2007), as well as
geological maps (scale 1:25,000) and river seismic (e.g. Haimberger et al. 2005). The
different parameters, such as color, carbonate content, grain size etc. will be weighted and
for each stratigraphic unit combined in a specific matrix. In addition to the development of
classification criteria from the literature, the definition of relevant keys and the query
criteria in a project-specific GIS is an essential part of the methodology.
Results:
First test runs are implemented for the layers Pliocene and Quaternary Rhine terrace
sediments and give consistent results (Fig. 3). About 3,000 out of the total 200,000 entries
comply with the defined criteria for Quaternary terrace sediments in the Lower Main Plain
to at least 70% and can therefore be used as markers for horizon modeling. Throughout the
area, they are spatially located above of the 500 entries that were classified as Pliocene.
The capacity of the information derived by this approach is verified semi-automatic as well
as visually by quality control and expert knowledge. Next steps will be the extension of the
matrix to more criteria like heavy minerals, as well as the deviation of point data sets for all
project relevant stratigraphic layers, e.g. the Untermain-Basalt-Formation or the
Arvernensis Gravels.
References:
[1]
[2]
[3]
[4]
[5]
[6]
[7]
208
Gabriel, G., Ellwanger, D., Hoselmann, C., Weidenfeller, M., Wielandt-Schuster, U. (2013): The
Heidelberg Basin, Upper Rhine Graben (Germany): a unique archive of Quaternary sediments in
Central Europe. Quaternary International, 292: 43-58.
Grimm, M.C., Wielandt-Schuster ,U., Hottenrott, M., Grimm, K.I. & Radtke,G. (2011):
Oberrheingraben. – In: Lange, J.-M. & Röhling, H.-G.[Hrsg.]: Stratigraphie von Deutschland IX Tertiär,
Teil 1: Oberrheingraben und benachbarte Tertiärgebiete. – Schriftenreihe dt. Ges. Geowiss., 75, 57 132; Hannover.
Haimberger, R., Hoppe, A., Schäfer, A. (2005):High-resolution seismic survey on the Rhine River in the
northern Upper Rhine Graben.Int. J. Earth Sci., 94: 657–668
Hoselmann, C. (2008): The Pliocene and Pleistocene fluvial evolution in the northern Upper Rhine
Graben based on results of the reasearch borehole at Viernheim (Hessen, Germany). Quaternary
Science Journal (Eiszeitalter und Gegenwart), 57/3-4: 286–315.
Hoselmann, C. & Lehné., R.J. (2012): Neue Lithostratigraphie und ein geologisches 3D-Modell des
nördlichen Oberrheingrabens – Hessisches Landesamt für Umwelt und Geologie – Jahresbericht 2012,
77-87.
Jarvis, A., Reuter, H.I., Nelson, A., Guevara E. (2008): Hole-filled seamless SRTM data V4.
International Centre for Tropical Agriculture (CIAT) http://srtm.csi.cgiar.org
Lang, S. (2007): Die geologische Entwicklung der Hanau-Seligenstädter Senke (Hessen, Bayern).
Dissertation an der Technischen Universität Darmstadt. (http://elib.tu-darmstadt.de/diss/000782).
Radon measurements in soil and ambient air in and around Darmstadt –
an investigation in a geological context
Georg Kuhn, Rouwen Lehné, Andreas Hoppe
Institute of Applied Geosciences, Technische Universität Darmstadt
Introduction
Radon is a radioactive noble gas which originates in decay series. Its natural occurrence in
soil as well as ambient air strongly is depending on the local mineralogical composition of
rocks and soil. High radon concentrations in and around Darmstadt are given due the
crystalline rocks of the Odenwald Mts. and migration paths (natural such as tectonic faults
and anthropogenic, e.g. openings in foundations) which enable radon to overcome larger
distances and accumulate into radon anomalies. They can be an indicator for recent
tectonic activities. High concentrations of radon, e.g. in poorly ventilated cellars, may also
pose a health hazards related alpha-emitting is supposed to be the second most reason for
lung cancer.
In Darmstadt, radon concentrations in soil air have been measured on the university´s
campus at Lichtwiese and Botanischer Garten as well as along the eastern master fault of
the Upper Rhine Graben in the city center accompanied by measurements of room air in
order to find possible connections to migration paths from the underground
In addition, radon measurements are currently under way along newly discovered faults in
the northern Upper Rhine Graben near Groß-Gerau in order to verify recent activities.
Measurements are embedded in works for setting up a geothermal power plant.
Actually, the measuring method described by Kemski et al. (1998) is widely used. However,
it measures the activity of radon only, without determining the quantity of soil air flowing
through the measurement chamber. Consequently, it is difficult to compare soils with
different permeabilities, so that it is intended to develop a standardised method which
combines the measurement of radon with the detection of CO2 in soil air. Furthermore, a
flow-meter will be installed in the measurement setup to log the actual air flow. This is
necessary to compare the different results of measurements in several soil types. Field
measurements of soil samples are complemented by analyses with gamma ray spectrometry
in order to determine the concentration of radium, the parent nuclide of radon. This is
necessary to differentiate between radon which is formed in situ and the radon which
migrates along the fault zones.
Darmstadt
Radon concentrations in the city are high due to its geological underground. While under
campus Lichtwiese and Botanischer Garten it is related to Permian volcanic rocks, the
center lies on gabbro in the east and is dissected by the eastern master fault of the Upper
Rhine Graben.
209
Campus Botanischer Garten
Several measurements of radon in the soil air show concentrations of > 50.000 Bq/m³, one
measurement exceeds 100.000 Bq/m³ (Fig. 1), very likely related to Permian basalts.
Therefore, radon concentration in room air has been measured in several campus buildings.
Results show uncritical concentrations. However, varying concentrations in different parts,
i.e. the Institute of Applied Geosciences, describe different modernity of one building (Fig. 1).
Fig. 1: Concentrations of radon in both soil and ambient air in the area of the campus Botanischer Garten of
Technische Universität Darmstadt (left) in the vicinity of the eastern master fault of the Upper Rhine Graben
(right)
While part B2/01 of the building erected in the 1960ies shows higher radon concentrations
in the room air, the concentrations in the recently modernized part B2/02 are very low,
indicating that either old migration paths have been closed or ventilation is effective in the
reduction of radon concentration. In building B2/01 both average radon concentrations of
136 Bq/m³ and maximum radon concentrations of more than 300 Bq/m³ exceed the
average concentration of radon in the air of closed rooms in Germany (49 Bq/m³, Menzler
et al. 2006) significantly. Therefore it is recommended (i) to ensure regular ventilation and
(ii) to repeat measurements because staff should not be exposed to concentrations of more
than 150 Bq/m³ over a longer period.
210
Darmstadtium
The darmstadtium is the city´s congress center and city palace. It is placed immediately on
the eastern master fault of the Upper Rhine Graben which separates fluvial Tertiary in the
west from gabbros in the east (Hoppe & Lang 2007). Here measurements of radon in soil
air have not been conducted. Ambient air in the building though shows very high
concentrations of radon in two of three rooms. The reason can be seen in favourable
migration conditions along the master fault (Fig. 1).
Groß-Gerau
Planning for a geothermal power plant near Trebur posed the question if tectonic faults in
the vicinity might be active recently and thus enable migration paths. In the frame of a
running co-operation with the local energy supplier (Überlandwerke Groß-Gerau) therefore
radon in soil air is currently measured. To increase the reliability of detected
concentrations, in addition CO2 and the flow rate are considered. Furthermore, soil samples
for every single measuring point will be analyzed for the presence of radium, the parent
nuclide of radon, in order to differentiate between radon that developed in situ and radon
that migrated to the measuring environment. The project thus progressively leads to both a
deeper understanding of the geological inventory and an improved methodology for
analyzing and interpreting soil gases. Results are expected for summer 2014.
References:
[1]
[2]
[3]
Hoppe, A. & Lang, S. (2007): The eastern master fault of the Upper Rhine Graben below the Science
and Conference Centre in Darmstadt (Germany). Z. dt. Ges. Geowiss. 158/1: 113-117, Stuttgart.
Kemski, J., Siehl, A, Stegemann, R., Valdivia-Manchego, M. (1998): Geogene Faktoren der
Strahlenexposition unter besonderer Berücksichtigung des Radonpotentials. Abschlussbericht zum
Forschungsvorhaben ST. Sch. 4106. Geologisches Institut der Universität Bonn.
Menzler S., Schaffrath-Rosario A., Wichman H.E., Kreienbrock, L. (2006): Abschätzung des
attributablen Lungenkrebsrisikos in Deutschland durch Radon in Wohnungen. Ecomed-Verlag,
Landsberg.
211
Geomaterial Science
The research group of Prof. Hans-Joachim Kleebe is active in the field of Geomaterial
Science (formerly Applied Mineralogy) and explores the formation/processing conditions,
composition, microstructure and properties of minerals and rocks in addition to material
science relevant compounds. The study of the latter material group focuses on both basic
science and potential industrial applications. Research activities include a comprehensive
characterization of natural and synthetic materials, their performance for example at
elevated temperature, local chemical variations as well as tailored synthesis experiments for
high-tech materials.
The experimental studies comprise the crystal chemistry of minerals and synthetic
materials, in particular, their crystal structure, phase assemblage and, in particular,
microstructure evolution. The microstructure variation (e.g., during exposure to high
temperature) has an essential effect on the resulting material properties, which is true for
synthetic materials as well as for natural minerals. Therefore, the main focus of most
research projects is to understand the correlation between microstructure evolution and
resulting material properties.
An important aspect of the Fachgebiet Geomaterial Science is the application of
transmission electron microscopy (TEM/STEM) techniques for the detailed micro/nanostructural characterization of solids. STEM in conjunction with spectroscopic analytical
tools such as energy-dispersive X-ray spectroscopy (EDS) and electron energy-loss
spectroscopy (EELS) are employed for detailed microstructure and defect characterization
down to the atomic scale. High-resolution imaging of local defects in addition to chemical
analysis with high lateral resolution is similarly applied to natural minerals as well as to
high-performance materials.
Recent research projects involve topics such as fatigue of ferroelectrics, re-calibration of the
clinopyroxene-garnet geothermometer with respect to small variations in the Fe2+/Fe3+ratio, defect structure in Bixbyite single crystals (and their corresponding exaggerated grain
growth), morphology of In2O3 nanocrystals, transparent ceramics (Mg-Al spinel), interface
structures in polycrystals, high-temperature microstructures, fatigue of ferroelectrics, and
the study of biomineralisation and biomaterials.
Staff Members
Head
Prof. Dr. Hans-Joachim Kleebe
Associated
Professors
Prof. Dr. Ute Kolb – Electron Crystallography
Prof. Dr. Peter van Aken, MPI Stuttgart, TEM/HRTEM/EELS
Research Associates
Dr. Stefan Lauterbach
Dr. Leopold Molina-Luna
Postdoctoral Students Dr. Ana Ljubomira Schmitt
212
Dr. Ingo Sethmann
Institute of Applied Geosciences – Geomaterial Science
PhD Students
Stefania Hapis
Cigdem Özsoy Keskinbora
Marc Rubat du Merac
Xiaoke Mu
Mathis M. Müller
Katharina Nonnenmacher
Scientific Assistant
Dr. Gerhard Miehe
Senior Scientist
Prof. Dr. Wolfgang F. Müller
Diploma Students
Angela P. Moissl
Sven Schild
Technical Personnel
Bernd Dreieicher
Secretary
Angelika Willführ
Michael Scherrer
Ekin Simsek
Stefanie Schultheiß
Dmitry Tyutyunnikov
Marina Zakhozheva
Leoni Wilhelm
Research Projects
Polymer-derived SiCO/HfO2 and SiCN/HfO2 Ceramic Nanocomposites for Ultrahightemperature Applications, SPP-1181 (DFG 2009-2014)
Investigation of Strengthened Hydroxylapatit/ß-Tricalcium Phosphate Composites with
Tailored Porosity (DFG 2008-2013)
Structural Investigations of Fatigue in Ferroelectrics,
Characterization of Lead-Free Ferroelectrics (DFG 2007-2014)
SFB-595,
detailed
TEM
TEM Characterization of Various Materials/Composites in the LOEWE Excellence Initiative
AdRIA (Adaptronik – Research, Innovation, Application 2011-2014)
Investigation of the Atomic and Electronic Structure of Perovskite-MultilayerHeterojunctions (in collaboration with the MPI Stuttgart, Prof. P. van Aken)
Phase Developments and Phase Transformations of Crystaline Non-Equilibrium Phases (in
collaboration with the MPI Stuttgart, Prof. P. van Aken)
Precipitation mechanisms of Ca-oxalate in the presence of Ca-phosphates and osteopontin
molecules related to kidney stone formation (DFG 2011-2013)
Microstructure Characterization and Correlation with Corresponding Properties, in
particular Hardness und Fracture Toughness, of Boron Suboxide Materials (DFG 20122015)
Microstructure Characterization of Polycrystalline Transparent Mg-Al-Spinel Samples; The
Effect of LiF Doping (Industry 2012-14)
Antibacterial Properties of Ag-modified Ca-Phosphate Scaffolds for Bone Replacement
Materials (DFG 2012-2013)
Microstructucure and Defect Control of Thin Film Solar Cells (Helmholtz Virtual Institute
2012-2018).
213
Publications
F. Muench, A. Fuchs, E. Mankel, M. Rauber, S. Lauterbach, H.-J. Kleebe, W. Ensinger,
“Synthesis of nanoparticle/ligand composite thin films by sequential ligand self assembly
and surface complex reduction”, Journal of Colloid and interface Science, 389 (2013) 2330.
B. Papendorf, E. Ionescu, H.-J. Kleebe, C. Linck, O. Guillon, K. Nonnenmacher, R. Riedel,
“High-Temperature Creep Behavior of Dense SiOC-Based Ceramic Nanocomposites:
Microstructural and Phase Composition Effects”, Journal of the American Ceramic Society,
96 [1] (2013) 272-280.
G. Mera, A. Navrotsky, S. Sen, H.-J. Kleebe, R. Riedel, “Polymer-deviced SiCN ceramics –
structure and energetic at the nanoscale”, Journal of Materials Chemistry A, 12 [1] (2013)
3826-3836.
M.F. Bekheet, M.R. Schwarz, M.M. Müller, S. Lauterbach, H.-J. Kleebe, R. Riedel, A. Gurlo,
“Phase segregation in Mn-doped In2O3: in situ high-pressure high-temperature synchrotron
studies in multi-anvil assemblies”, RSC Advances, 16 [3] (2013) 5357-5360.
S. Hayakawa, T. Kanaya, K. Tsuru, Shirosaky, A. Osaka, E. Fujii, K. Kawabata, G.
Gasqueres, C. Bonhomme, F. Babonneau, C. Jager, H.-J. Kleebe, “Heterogeneous structure
and in vitro degradation behavior of wet-chemically derived nanocrystalline siliconcontaining hydroxyapatite particles”, ACTA Biomaterialia, 1 [9] (2013) 4856-4867.
I. Levin, I.M. Reaney, E.M. Anton, W. Jo, J. Rodel, J. Pokorny, L.A. Schmitt, H.-J. Kleebe, M.
Hinterstein, J.L. Jons, “Local structure, pseudosymmetry, and phase transitions in
Na1/2Bi1/2TiO3-K1/2Bi1/2TiO3 ceramics”, Physical Review B, 2 [87] (2013) 024113.
M. Schlosser, S. Frols, U. Hauf, I. Setmann, S. Schultheiss, F. Pfeifer, H.-J. Kleebe,
“Combined Hydrothermal Conversion and Vapor Transport Sintering of Ag-Modified
Calcium Phosphate Scaffolds”, Journal of the American Ceramic Society, 2 [96] (2013)
4212-419.
G. Miehe, S. Lauterbach, H.-J. Kleebe, A. Gurlo, “Indium hydroxide to oxide decomposition
observed in one nanocrystal during in situ transmission electron microscopy studies”,
Journal of Solid State Chemistry, (2013) 364-370.
U. Sydow, K. Sempf, M. Herrmann, M. Schneider, H.-J. Kleebe, A. Michaelis,
“Electrochemical corrosion of liquid phase sintered silicon carbide ceramics”, Material and
Corosion-Werkstoffe und Korrosion, 3 [64] (2013) 218-224.
H. Purwin, S. Lauterbach, G.P. Brey, A.B. Woodland, H.-J. Kleebe, „An experimental study
of the Fe oxidation states in garnet and clinopyroxene as a function of temperature in the
system
CaO-FeO-Fe2O3-MgO-Al2O3-SiO2:
implications
for
garnet-clinopyroxene
geothermometry”, Contr. to Mineralogy and Petrology, 4 [165] (2013) 623-639.
214
M.F. Bekheet, MR. Schwarz, S. Lauterbach, H.-J. Kleebe, P. Kroll, R. Riedel, A. Gurlo,
“Orthorhombic In2O3: A Metastable Polymorph of Indium Sesquioxide”, Angewandte
Chemie-International Edition, 25, (2013) 6531-6535.
M. Herrmann , I. Sigalas, M. Thiele, MM. Muller, H.-J. Kleebe, A. Michaelis, „Boron
suboxide ultrahard materials“ Int. J. of Refractory Metals & Hard Materials, SI, [39] (2013)
53-60.
S. Schultheiss, I. Sethmann I., M. Schlosser, H.-J. Kleebe, “Pseudomorphic transformation
of Ca/Mg carbonates into phosphates with focus on dolomite conversion” Mineralogical
Magazine, 6, [77] [2013) 2725-2737.
M. Rubat du Merac, IE. Reimanis, C. Smith, H-J. Kleebe, MM. Müller, “Effect of Impurities
and LiF Additive in Hot-Pressed Transparent Magnesium Aluminate Spinel”, International
Journal of Applied Ceramic Technology, SI, [10] (2013) E33-E48.
K. Morita, G. Mera, K. Yoshida, Y. Ikuhara, A. Klein, H.-J. Kleebe, R. Riedel, “Thermal
stability, morphology and electronic band gap of Zn(NCN)”, Solid State Sciences, [23]
(2013) 50-57.
B. Lyson-Sypien, A. Czapla, M. Lubecka, A. Zakrzewska, M. Radecka, A. Kusior, A.G.
Balogh, S. Lauterbach, H.-J. Kleebe, “Gas sensing properties of TiO2-SnO2 nanomaterials”,
Sensors and Actuators B-Chemical, SI, [187] (2013) 445-454.
MT. Uddin, Y. Nicolas, C. Olivier, T. Toupance, M.M. Muller, H.-J. Kleebe, K. Rachut, J.
Ziegler, A. Klein, W. Jaegermann, “Preparation of RuO2/TiO2 Mesoporous Heterostructures
and Rationalization of Their Enhanced Photocatalytic Properties by Band Alignment
Investigations”, Journal of Physical Chemistry C, 42 [117] (2013) 22098-22100.
L. Molina-Luna, Leopoldo, R. Egoavil, S.Turner, T. Thersleff, J. Verbeeck, B. Holzapfel, O.
Eibl, G. Van Tendeloo, “Interlayer Structure in YBCO-coated Conductors Prepared by
Chemical Solution Deposition”, Supercond. Sci. & Tech., 26 [7] (2013) 075016-24.
T.T.D. Nguyen, L. Dimesso, G. Cherkashinin, J.C. Jaud, S. Lauterbach, R. Hausbrand, W.
Jaegermann, “Synthesis and characterization of LiMn1-xFe(x)PO4 carbon nanotubes
composites as cathodes for Li-ion batteries, ” Ionics 19 [9] 1229-1240.
M.F. Bekheet, M.R. Schwarz, S. Lauterbach, H.-J. Kleebe, P. Kroll, A. Stewart, U. Kolb, R.
Riedel, A. Gurlo, “In situ high pressure high temperature experiments in multi-anvil
assemblies with bixbyite-type In2O3 and synthesis of corundum-type and orthorhombic
In2O3 polymorphs,” High Pressure Research 33 [3] (2013) 697-711.
M.R. du Merac, H.-J. Kleebe, M.M. Muller, I.E. Reimanis, “Fifty Years of Research and
Development Coming to Fruition; Unraveling the Complex Interactions during Processing of
Transparent Magnesium Aluminate (MgAl2O4) Spinel”, Journal of the American Ceramic
Society, 11 [96] (2013) 3341-3365.
215
Sintering mechanisms of LiF-doped Mg-Al-Spinel
M.M. Müller, M. Rubat du Merac and H.-J. Kleebe
MgAl2O4 is considered a promising material for optical applications and hence object to
research for more than 40 years worldwide [1-4]. The densification mechanism of MgAl2O4
(hereafter termed spinel) doped with lithium fluoride (LiF) as transparent ceramic has been
intensively studied [5].
Optical transparency requires densification to a value near the theoretical density since
residual porosity, which acts as scattering source, has to be eliminated. In addition,
impurities and secondary phases have to be removed to avoid scattering or absorption of
the transmitted radiation (i.e. visible or IR light).
LiF greatly reduces the sintering temperature and facilitates densification at low
temperatures. However, the basic mechanisms behind the sintering process are still not
fully understood, as neither LiF nor an additional secondary phase is detectable in the final
product.
Based on individual studies Reimanis, Kleebe and Rozenburg [6-8] postulated three major
processes during sintering of spinel with LiF including
(i) Enhanced volume diffusion by incorporation of O-vacancies:
It is postulated that LiF can be incorporated into the spinel structure as described by
Kröger-Vinck notation as follows:

MgAl 2O4
3 LiF 
 LiMg  2 Li Al  3 FO  VO
/
//

Due to the necessary charge compensation, oxygen vacancies are predicted which enhance
volume diffusion in the spinel lattice, strongly promoting grain growth.
(ii) Dissolution – Reprecipitation:
At 840°C, molten LiF partially reacts with spinel by the formation of liquid MgF2 and solid
LiAlO2.
MgAl 2O4  3 LiF(l)  LiF : MgF2 (l)  2LiAlO 2 (s)
In the temperature range between 840°C and 1000°C, both the remaining LiF and the MgF 2
become gaseous,
LiF : MgF2 (l)  LiF(g)  MgF2 (g)
which is seen as the origin of the dewetting process.
This enables the back reaction above 1050°C to form a second generation of spinel and
gaseous LiF which can now the leave the system.
MgF2 (g)  2LiAlO 2 (s)  MgAl 2 O 4 (s)  2 LiF(g)
and (iii) Wetting – Dewetting:
At this early stage of sintering, the densification mechanism can be described by a classical
liquid phase sintering process facilitating particle rearrangement. At temperatures above
1000°C, no secondary phase is detectable along grain boundaries.
Since conventional sinter regimes for this material system are pressure supported the
geometry of sintered devises is limited. Therefore, the overall aims of the present study are
216
(i) to verify the postulated mechanisms and (ii) to transfer this knowledge to a pressure less
sinter process.
In a recent work it was shown that these mechanisms occur simultaneously interacting with
each other [9], however, the verification was made by indirect methods as for example the
double fringe technique introduced by D.R. Clark [10] for the wetting-dewetting
mechanism as shown in Figure 1.
Fig. 1: Defocus series of a spinel-spinel grain
boundary. The material was sintered at 900°C [a,b,c]
and 1100°C [d]. The double fringes occurring at 900°C
indicate a twice changing mean inner potential which
was interpreted as a wetting of the grain boundary.
At higher temperatures no wetting was observed.[9]
Recent experiments showed the reason for the twice changing mean inner potential
creating the double Fresnel fringes as an example of the high potential of probe-corrected
microscopes in the applied transmission electron microscopy and material science.
Using an ARM 200F operating at 200kV a series of high resolution STEM-EELS
investigations were performed at a polycrystalline spinel sample, sintered at 900°C,
consistently showing an incorporation of fluorine close to the grain boundaries as depicted
in Figure 2.
Fig. 2: HR-STEM image of a spinel-spinel grain boundary. When applying the defocus technique double Fresnel
fringes occurred but even in highest magnification no wetting could be shown. Instead, by using STEM EELS
techniques, an incorporation of fluorine in the first two atomic layers was observed at a sintering temperature
of 900°C.
217
This means that a) the double Fresnel fringes cannot only be created by an amorphous
layer of a secondary phase but also by additional incorporated elements and b) the wetting
mechanism occurs much earlier in the sintering process then postulated.
Furthermore, based on dedicated model experiments and a characterisation using e.g.
state-of-the-art electron microscopy it was shown for the first time that (a) a dissolutionreprecipation process occurs at significantly lower temperatures by the formation of a
variety of transient phases (Figure 3), (b) a vapour transport mechanism leads to a notable
mass transport involving the magnesium and (c) an exaggerated grain growth of a second
generation of spinel hinders the densification process.
Fig. 3: HR-SEM micrograph of MgO and LiAlO2 as
transient phases observed in a model experiment
at a sintering temperature of 900°C.
References
1. R.J. Bratton. Characterization and Sintering of Active MgAl2O4 Spinel, Am Ceram Soc Bull, 47 [9] (1968)
pp. 883-887.
2. M. Rubat du Merac, Marc, H.-J. Kleebe, M.M. Mueller and I.E. Reimanis, “Fifty Years of Research and
Development Coming to Fruition; Unraveling the Complex Interactions during Processing of Transparent
Magnesium Aluminate (MgAl2O4) Spinel” J. Am. Ceram. Soc., 96 [11] (2013) 3341-3365.
3. D.W. Roy, Hot-Pressed MgAl2O4 for Ultraviolet (UV), Visible and Infrared (IR) Optical Requirements, P.
Soc. Photo.-Opt. Inst., 297 (1981) pp. 13-18.
4. M. Shimada, T. Endo, T. Saito, and T. Sato, Fabrication of transparent spinel polycrystalline materials,
Mat. Let., 28 [4-6] (1996) pp. 413-15.
5. M. Rubat du Merac, I.E. Reimanis, C. Smith, H.-J. Kleebe and M.M. Mueller “Effect of Impurities and LiF
Additive in Hot-Pressed Transparent Magnesium Aluminate Spinel”, Int. J. App. Ceram. Tech. 10 [1]
(2013) pp. E33-E48.
6. I.E. Reimanis and H.-J. Kleebe, Reactions in the sintering of MgAl2O4 spinel doped with LiF. Int. J. Mat.
Res., 98 [12] (2007) pp. 1273-78.
7. K. Rozenburg, I.E. Reimanis, H.-J. Kleebe, and R.L. Cook, Chemical interaction between LiF and MgAl 2O4
spinel during sintering. J. Am. Ceram. Soc. 90 [7] (2007) pp. 2038-2042.
8. I.E. Reimanis and H.-J. Kleebe, A Review on the Sintering and Microstructure Development of Transparent
Spinel (MgAl2O4). J. Am. Ceram. Soc. 92 [7] (2009) pp.1472-1480.
9. M.M. Müller and H.-J. Kleebe, Sintering Mechanisms of LiF-Doped Mg-Al-Spinel, J. Am. Ceram. Soc., 95
[10] (2013) pp. 3022-3024.
10. D.R. Clarke, On the detection of thin intergranular films by electron microcopy, Ultramicroscopy 4 (1979)
pp. 33-44.
218
Electron Microscopy Studies of {100} Faults in Bixbyite Crystals
from the Thomas Range Rhyolite (Utah)
Stefan Lauterbach and Hans-Joachim Kleebe
Despite its simple composition, bixbyite is a rather uncommon manganese-iron oxide with a
general formula (Mn,Fe)2O3. It crystallises in the Ia3 cubic symmetry and is known as the
type mineral for the so-called bixbyite structure. It forms black cubic crystals with metallic
lustre that are occasionally truncated by small icositetrahedral faces at corners. The best
specimens of bixbyite are found at Thomas Range (Utah), where it occurs in the cavities of
the rhyolite host rock in association with topaz, pseudobrookite, braunite, hematite,
hausmannite, spessartine, beryl and quartz. Most of the bixbyite crystals from Thomas
Range with developed icositetrahedral forms show distinct reentrant facets at the halfway
of every edge of the cube, whereas such reentrants are absent on simple cubic crystals. On
the lustrous surfaces of the crystal, it is frequently observed that pairs of adjacent reentrant
pitches are linked by a band of parallel notches, crossing at the centres of each face of the
cube. According to the morphological features these crystals convincingly appear to be
{100} twins and are as such recognised in the mineralogical community. However, any
twinning operation on {100} planes of the centrosymmetric bixbyite structure would
produce an identical crystal, suggesting that {100} twins in bixbyite are crystallographically
not possible, and that these defects could be some yet unknown type of polytypic faults.
This fact attracted our attention to study the structure and chemistry of {100} planar faults
in bixbyite crystals from the Thomas Range locality.
Fig. 1: 20 mm large bixbyite crystal from Thomas Range
(Utah) with many reentrant facets, causing a jigsaw
appearance of the crystal edges. Each reentrant pitch
(arrows) is followed by slender notches that indicate the
presence of braunite-type {100} polytypic faults.
In order to disclose the nature of these defects
we used different methods of electron
microscopy. Scanning electron microscopy
combined with quantitative energy dispersive Xray spectroscopy was used to determine the
chemical composition of bulk bixbyite, while
high-resolution transmission electron microscopy
was employed to study the atomic structure of
the polytypic lamellae. Line analysis over a band of polytypic faults showed an increase in
Mn and decrease in Fe content in these areas. To prepare the TEM specimens the crystals
were cut parallel to [001] orientation from the fault-rich areas. HRTEM images of these
areas show clusters of polytypic faults running along {100} planes of the bixbyite structure.
The interfaces are atomically sharp and planar over large areas of the crystal. Occasionally
the faults make rectangular steps to the equivalent planes of the {100} family. Phase
contrast on the polytypic faults shows special features, which imply a periodic occupancy or
chemistry fluctuations in the fault planes. TEM/EDS analyses using for example the
multiple beam diameter method, which is particularly suited for determination of atomicscale composition of planar faults, clearly showed a presence of Si in the fault-rich areas
with a simultaneous increase of the Mn/Fe ratio (see inset in Figure 2). The composition of
219
the polytypic faults closely corresponds to a manganese silicate braunite, which is also
present in the paragenesis of the rhyolite vugs.
Fig. 2: HRTEM image of the host crystal bixbyite
with a polytypic planar fault of braunite Mn6SiO12.
The local enrichment in Si can be seen from the EDS
spectrum included as inset.
Our study showed that the bixbyite
crystals from the Thomas Range in Utah
are in fact not twinned, but contain
braunite-like polytypic lamellae coherently
intergrown along the {100} planes of the
host bixbyite single crystal [1]. Such defect
structures incorporated in the crystal act as
fast
diffusion
paths,
promoting
exaggerated grain growth, as observed in
[100]
the bixbyite samples from that very
bixbyite location, similarly observed in different
systems [2].
bixbyite
(Mn,Fe)2O3
Si-rich polytypic faults
braunite (Mn6SiO12)
Most recent studies focus on the observed phenomena that small bixbyite precipitations are
located precicely at the interface between braunite lamella and bixbyite (large) host crystal,
as shown in Figure 3. It is assumed that
such precipitates can only be incorporated
into the host crystal via the formation of a
new surface (of braunite), acting as
nucleation site.
Fig. 3: HR-STEM image of the host crystal bixbyite
with a polytypic planar fault of braunite and a small
bixbyite precipitate. The still open question is
whether the braunite lamella indeed runs
completely along the precipitate inter-face.
References
1. H.-J. Kleebe and S. Lauterbach, "Exaggerated Grain Growth in Bixbyite via Fast Diffusion Along Planar
Defects," Cryst. Res. Technol., 43 [11] (2008) 1143-49.
2. Recnik, M. Ceh and D. Kolar, "Polytype Induced Exaggerated Grain Growth in Ceramics“, J. Eur. Ceram.
Soc. 21 (2001) 2117-2121.
220
Electron Crystallography
Electron crystallography uses electron radiation to characterize the structure of matter by
imaging, diffraction and spectroscopy from fully crystalline over highly disordered to
amorphous materials. One of the most potential tools for solid state investigation in the
nano regime are transmission electron microscopes (TEM). Apart from imaging techniques
in parallel illumination, scanning methods, based on a sequential data collection, are
becoming more and more popular.
The scientific approach of this group lies mainly on the development of electron diffraction
techniques.
The Automated Diffraction Tomography (ADT) method, invented by this group, consists of
a new data collection concept and is applicable to nano particles down to a size of some
tens of nanometer. Using ADT, nearly kinematical 3D electron diffraction data can be
collected from a selected nano crsytal being suitable for „ab-initio“ structure solution, i.e.
based only on electron diffraction data. In contrast to high resolution imaging this approach
is applicable to material even highly sensitive tot he electron beam (e.g. drugs, MOFs,
zeolites, hybrid materials)
Fig. 1: Structural Sketch of the bismuth sulfate with the new „zeolite-like“ structure found at Alfenza mine and
solved from a 50nm crystal. Projection down a) [010] and b) [001]. Note the presence of channels with a
diameter of ~0.7 nm filled with disulfide anions. (Ref. 6)
Apart from the structure determination of highly crystalline nano particles even with
complicated structural features, a quantitative approach to describe disordered structures is
under development. It is planned to use approaches (e.g. pair distribution funktion) already
successfull are becoming applied to X-ray data.
Application as well as development of the above described ADT method has a high demand
for cooperation within the Materials- and Geosciences but also with other departments such
as chemistry, mathematics and informatics.
Prof. Kolb started to build up the group in the Institute of Applied Geosciences in November
2012. In addition she has been assigned as Equal Opportunities Officer.
Institute of Applied Geosciences – Electron Crystallography
221
Staff Members
Head
Prof. Dr. Ute Kolb
Diploma Students
Angela Patricia Moissl (MSc)
Secretary
Angelika Willführ
Publications
1) Applications of Automated Diffraction Tomography (ADT) on nanocrystalline porous
materials
Enrico Mugnaioli and Ute Kolb*, Microporous and Mesoporous Materials, 166 93-101
(2013)
2) Using FOCUS to solve zeolite structures from 3D electron diffraction data
Stef Smeets, L. B. McCusker, Ch. Baerlocher, E. Mugnaioli and U. Kolb, Applied
Crystallography, 46 1017-1023 (2013)
3) Application of delta recycling to electron ADT data from inorganic crystalline
nanovolumes
J. Rius, E. Mugnaioli, O. Vallcorba and U. Kolb, Acta Cryst A, 69 396-407 (2013)
highlighted article
4) In situ high pressure high temperature experiments in multi-anvil assemblies with
bixbyite-type In2O3 and synthesis of corundum-type and orthorhombic In2O3 polymorphs
M. F. Bekheet, M. Schwarz, S. Lauterbach, H.-J. Kleebe, P. Kroll, A. Stewart, U. Kolb, R.
Riedel and A. Gurlo, High Pressure Research, 33(3), 697-711 (2013)
5) Snapshots of the Formation of NaTi3O6(OH)x2H2O Nanowires: A Time-Resolved
XRD/HRTEM Study
Zeitschrift für Anorganische und Allgemeine Chemie, 639(14) 2521-2526 (2013)
222
Institute of Applied Geosciences – Electron Crystallography
Technical Petrology with Emphasis in Low Temperature Petrology
Petrology is devoted to study the genesis and the mineralogical evolution of a rock with a
specific bulk composition at various physical and chemical conditions. The scientific and
educational fields of this branch within the applied geosciences are based on crucial
knowledge in magmatic-, metamorphic-, hydrothermal petrology, mineralogy, structural
geology, tectonophysics, geothermal geology, sediment petrography, thermodynamics/
kinetics and geochemistry.
Technical Petrology aims to assess the physical and chemical properties of natural or
synthetic rocks for applied purposes at various physical and chemical conditions (e.g.
pressure, temperature, chemical composition). The Technical Petrology group is in
particular devoted to study the low temperature domain. These low temperature studies
serve as an aid to qualify and quantify processes occurring in hydrocarbon prospecting,
geothermal system, and geodynamic study.
The principal motivation of our Low-Temperature Petrology research group is to
understand and to quantify low temperature petrologic processes. For this purpose, an
effort is addressed to innovate new tools to calibrate and to model the metamorphic P-T-Xd-t conditions in low-grade rocks. A multidisciplinary approach is necessary because
crystallization and recrystallisation are not obvious at low temperature. Hence, our work
links field and experimental petrology, analytical methods, thermodynamic and kinetic
modelling. Similar approaches are easily applied in archaeometry in order to characterise a
range of firing temperatures and to describe recrystallisation processes of starting clay
material. Opposite to prograde diagenetic to metamorphic processes, presented working
philosophy is employed to describe the reverse cycles of destruction and weathering of
rocks and the formation of clays and techno soils.
The main research interests of the Technical Petrology Group are focussed on the following
topics:
Experimental Petrology (will be closed in 2014)

Synthesis and characterisation of the coalification processes by means of optical
parameters that are used to determine kinetics of maturation.

Synthesis and characterisation of mineral reactions as well as firing structures and
textures in ceramic materials. This aims to enhance knowledge on the ancient
pottery production technology and to assess its socially embedded impacts.
Coal Petrology (will be closed in 2014)

The application of vitrinite reflectance and other coal petrological parameters to
determine a grade of diagenesis and incipient metamorphism.

Development of geothermobarometers based on the maturation kinetics of vitrinite.
For the first time it will be possible to use barometric as well as thermometric models
to establish geothermal gradients. These can be used in orogenic researches,
sediment basin analyses, hydrocarbon exploration, geothermic prospections and
energy researches.
Institute of Applied Geosciences – Technical Petrology
223
o
Improvement of methods related to hydrocarbon exploration.
o
Improvement of methods related to the low-grade metamorphism characterisation.
o
Application of the bituminate reflectance in the kerogene research,
palaeogeothermics, and in the external orogens investigation.
Clay Mineralogy

The application of Kübler Index and other clay mineral parameters to determine a
grade of diagenesis and incipient metamorphism.

Development of Geothermobarometers based on the reaction kinetics in the reaction
progress and aggradation of clay minerals to micas. These can be used in orogenic
researches, sediment basin analyses, hydrocarbon exploration, and geothermic
prospections.
o
Improvement of methods related to hydrocarbon exploration.
o
Improvement of methods related to the low-grade metamorphism characterisation.
Archaeometry and Clay Mineralogy (will be closed in 2014)

Determination and investigation on the production technology of the Iron Age,
Hellenistic and Roman pottery fineware.
o
Determination of firing conditions and duration of peak ceramic firing.
o
Characterisation of applied raw material.
o
Provenance of exploited raw material.
o
Reconstruction of ancient trade routes by characterisation of nonlocal clayey raw and
temper material.
Environmental Geology

Reaction processes reconstruction that take place in the mining damps, recognition
of soil alteration via acid rock drainage, quantification of clay mineral degradation
and clay-rock-water interactions.

Determination of water-rock interaction and water chemistry in the basement
crystalline ground waters and their usage as potable water.
Low-Temperature Petrology s.l.

Orogen and palaeogeothermal researches in foreland basins of the Alps, Vosges,
Dinarides, Carpathians, Stara Planina (Bulgaria), Balkanides, Variscides of the
Bosporus and Turkey.
A broad analytical spectrum must be applied in low-temperature petrology due to very
small grain-size. Technical Petrology group maintains a Microscopy Laboratory (CCA coalreflection microscopy, MPV coal-reflection microscopy, fluorescence microscopy,
transmitted light microscopy). The former XRD laboratories (Clay and XRD Laboratory and
a research XRD Laboratory) had to be moved and merged with the awkward geochemical
laboratory. The ICP-AES, TOC, AOX and gas chromatography together with the Organic
Geochemical Laboratory was closed in 2012. A non-completed refurbishment of the
224
Geoscience Institute and missing financial support forced us to accept an adverse decision.
Due to the adjournment of the refurbishment of the building and the infrastructure the
situation did not change in 2013. On photographs of the laboratories the iniquitous
situation depended on development is documented on the wep page to testify the need to
get back ideal working conditions. A XRF laboratory (Wave-dispersive BRUKER S8-Tiger) is
maintained together with the groups of Chemical Analytics and Environmental Mineralogy.
Staff Members
Head
Prof. Dr. Rafael Ferreiro Mählmann
Research Associates
Dr. Lan Nguyen
Technical Personnel
Dr. Norbert Laskowski
Secretary
Natali Vakalopoulou Buffet
BSc-MSc Students
Tobias Necke
Research Projects
Please see information on the web page and the annual report 2012. No new projects were
funded and case of the head caused a dramatic scientific and third-party funds raid. Due to
internal evaluation rules the coal petrology research associate position was cut and
employment rules for research associates (12 years of temporary engagement) forced the
pullout of the second assistant, leaving in 2013 the health-threat head allone.
Recent projects in 2013 without funding:
The Zlatitsa para-series group, a new Palaeozoic lithostratigraphic member determined in
the Kashana section at the southern Stara Planina mountain range (Central Balkanides,
Bulgaria). Cooperation with the Universität Freiburg (D), Université de Genève (CH),
University of Sofia "St. Kl. Ohridski" (Bg).
Characterization of Fe-smectites from Nui Nua clay, Thanh Hoa province, Viet Nam and its
alteration potential considering for HLW repositories. Cooperation with the Ernst-MoritzArndt-Universität, Greifswald (D), Hanoi University of Science (Vietnam), Gesellschaft für
Anlagen- und Reaktorsicherheit mbH, Braunschweig (D), Vietnamese Academy of Science
and Technology.
Fossil Multiphase Normal Faults - Prime Targets for Geothermal Drilling in the Bavarian
Molasse Basin. Cooperation with the University of Alberta (Canada), GeoTec Consult,
Markt Schwaben (D), Loske Geosciences, Essen (D), GFZ - Helmholtz Centre Potsdam (D),
Exorca, Grünwald (D).
Determination of rock maturity using vitrinite like bituminite kinetics. A field and
laboratory study including liptinite and vitrinite reflectances. Implications for prospection
and engeneering geology in meta-sedimentary rocks. Cooperation with GFZ - Helmholtz
Centre Potsdam (D).
225
Environmental Mineralogy
Environmental mineralogy focuses its research on the characterization of individual aerosol
particles by electron beam techniques (high-resolution scanning electron microscopy,
transmission electron microscopy, environmental scanning electron microscopy).
We study individual aerosol particles in order to derive the physical and chemical
properties (e.g., complex refractive index, deliquescence behavior, ice nucleation) of the
atmospheric aerosol. These data are of great importance for modeling the global radiation
balance and its change due to human activities.
We are also interested in studying particle exposure in urban environments and at working
places. As aerosol particles may have adverse effects on human health, the knowledge of
the particle size distribution and the chemical and mineralogical composition of the
particles is of prime importance in order to derive the exact mechanisms of the adverse
health effects.
In addition, we also investigate particles as carriers of pollutants into Nordic and Arctic
ecosystems.
Our research is carried out in cooperation with the following national and international
partners: Max Planck Institute for Chemistry in Mainz, Institute for Atmosphere and
Environmental Sciences (University of Frankfurt) Institute for Atmospheric Physics
(University of Mainz), Institut für Steinkonservierung (IFS) in Mainz, Institute for
Meteorology and Climate Research (Karlsruhe Institute of Technology), Institute for
Tropospheric Research in Leipzig, Institute of Atmospheric Physics (German Aerospace
Center DLR) in Oberpfaffenhofen, Paul Scherrer Institute (Laboratory of Atmospheric
Chemistry) in Villigen (Switzerland), National Institute of Occupational Health (STAMI) in
Oslo (Norway), and the Norwegian University of Life Science (NMBU) in Ås (Norway).
Staff Members
Head
Prof. Dr. Stephan Weinbruch
Research Associates
APL Prof. Dr. Martin Ebert
Dr. Nathalie Benker
Postdocs
PD Dr. Konrad Kandler
Dr. Annette Worringen
Dr. Dirk Scheuvens
Technical Personnel Thomas Dirsch
Secretary
Astrid Zilz
PhD Students
Dipl.-Met. Dörthe Müller-Ebert
Dipl.-Ing. Katharina Schütze
Diploma Students
Katharina Schütze
Master Students
Markus Hartmann
Bachelor Students
Patrick Marschall
226
Dipl.-Ing. Thomas Herrmann
MSc Mark Scerri
Angela Moissl
Institute of Applied Geosciences – Environmental Mineralogy
Research Projects
Environmental scanning electron microscopical studies of ice-forming nuclei (DFG
Forschergruppe INUIT).
Electron microscopy of long-range transported mineral dust.
Source apportionment of rural and urban aerosols.
Sources of soot at work places (National Institute of Occupational Health, Oslo, Norway).
Influence of traffic on the surface of monuments.
Particle and organic pollutant emissions of coal burning in the Arctics.
Publications
Lieke, K.I., Kristensen, T.B., Korsholm, U.S., Sørensen, J.H., Kandler K. Weinbruch S.,
Ceburnis D., Ovadnevaite J., O’Dowd C.D., and Bilde M. (2013): Characterization of
volcanic ash from the 2011 Grímsvötn eruption by means of single-particle analysis.
Atmospheric Environment 79, 411-420.
Von Hobe M., Bekki S., Borrmann S., Cairo F., D’Amato F., Di Donfrancesco G., Dörnbrack
A., Ebersoldt A., Ebert M., Emde C., Engel I., Ern M., Frey W., Genco S., Griessbach S.,
Grooß J.-U., Gulde T., Günther G., Hösen E., Hoffmann L., Homonnai V., Hoyle C. R.,
Isaksen I.S.A., Jackson D.R., Jánosi I.M., Jones R.L., Kandler K., Kalicinsky C., Keil A.,
Khaykin S.M., Khosrawi F., Kivi R., Kuttippurath J., Laube J.C., Lefèvre F., Lehmann R.,
Ludmann S., Luo B.P., Marchand M., Meyer J., Mitev V., Molleker S., Müller R., Oelhaf H.,
Olschewski F., Orsolini Y., Peter T., Pfeilsticker K., Piesch C., Pitts M.C., Poole L.R., Pope
F.D., Ravegnani F., Rex M., Riese M., Röckmann T., Rognerud B., Roiger A., Rolf C., Santee
M.L., Scheibe M., Schiller C., Schlager H., Siciliani de Cumis M., Sitnikov N., Søvde O.A.,
Spang R., Spelten N., Stordal F., Sumińska-Ebersoldt O., Ulanovski A., Ungermann J.,
Viciani S., Volk C.M., vom Scheidt M., von der Gathen P., Walker K., Wegner T., Weigel R.,
Weinbruch S., Wetzel G., Wienhold F.G., Wohltmann I., Woiwode W., Young I.A.K.,
Yushkov V., Zobrist B., and Stroh F. (2013): Reconciliation of essential process parameters
for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions
(RECONCILE): activities and results. Atmospheric Chemistry and Physics 13 (18), 9233-9268.
Auras, M., Beer, S., Bundschuh, P., Eichhorn, J., Mach, M., Scheuvens D., Schorling M., von
Schumann J., Snethlage R., and Weinbruch S. (2013): Traffic-related immissions and their
impact on historic buildings: implications from a pilot study at two German cities.
Environmental Earth Sciences 69 (4), 1135-1147.
Scheuvens, D., Schütz, L., Kandler, K., Ebert, M., Weinbruch, S. (2013): Bulk composition
of northern African dust and its source sediments—A compilation. Earth-Science Reviews
116, 170-194.
Fries, E., Dekiff, J.H., Willmeyer, J. Willmeyer, J., Nuelle, M.-T., Ebert, M., Remy, D.
(2013): Identification of polymer types and additives in marine microplastic particles using
pyrolysis-GC/MS and scanning electron microscopy, Environmental Science-Processes &
Impacts 15, 1949-1956.
Weinbruch S., Nordby, K.C. (2013): Fatalities in High Altitude Mountaineering: A Review
of Quantitative Risk Estimates. High altitude medicine & biology 14 (4), 346-359.
227
Chemical composition, mixing state, size and morphology of ice nucleating particles
at the Jungfraujoch research station, Switzerland
Martin Ebert1, Annette Worringen1, Konrad Kandler1, Ludwig Schenk2, Stephan Mertes2, Susan
Schmidt3, Johannes Schneider3, Fabian Frank4, Björn Nillius4 and Stephan Weinbruch1
1
Institute of Applied Geosciences, Environmental Mineralogy, Darmstadt
2
Leibniz-Institute for Tropospheric Research, Leipzig
3
Max Planck Institute for Chemistry, Mainz
4
Frankfurt Institute for Atmospheric and Environmental Sciences Goethe-University
Frankfurt am Main
An intense field campaign from the Ice Nuclei Research Unit (INUIT) was performed in
January and February of 2013 at the High-Alpine Research Station Jungfraujoch (3580 m
a.s.l., Switzerland). Main goal was the assessment of microphysical and chemical properties
of free-tropospheric ice-nucelating particles. The ice-nucleating particles were discriminated
from the total aerosol with the ‘Fast Ice Nucleation CHamber’ (FINCH; University
Frankfurt) and the ‘Ice-Selective Inlet’ (ISI, Paul Scherer Institute) followed by a pumped
counter-stream virtual impactor. The separated ice-nucleating particles were then collected
with a nozzle-type impactor.
Finally, with the ICE Counter-stream Virtual Impactor (ICE-CVI) atmospheric ice crystals
are separated from the total aerosol and their water content is evaporated to retain the ice
residual particles, which are then also collected by impactor sampling.
All samples were analyzed in a high-resolution scanning electron microscope. By this
technique, the size, morphology, mixing-state and chemical composition are obtained for
each particle. In total 2838 ice nucleating particles were analyzed.
silicate
Ca - rich
soot
aged sea salt
carbonaceous
Pb
metal oxide
Figure 1: Secondary electron images of ice nuclei/residuals (IN/IR): a) alumosilcate; b) Ca-rich; c) soot;
d) metal oxide; e) aged sea salt; f) carbonaceous particle.
228
Originally more than 5000 potential IN/IR were analyzed in the samples from the three
IN/IR-selective pathways. SEM-EDX analysis revealed that in ICE-CVI samples about 60% of
the particles were aluminiumoxides, in the ISI samples ~75% of all detected particles were
silicon oxide spheres and in FINCH samples ~15% were alloy particles (Fe,Cr,Ni). These
particles were identified as instrumental artifacts and were not considered further.
Based on their chemical composition, the remaining particles were classified into seven
groups: silicates, metal oxides, Ca-rich particles, (aged) sea-salt, soot, sulphates and
carbonaceous material.
Figure 2: Average relative particle group number abundance of IN/IR at the Jungfraujoch station
measured by ISI, FINCH, and ICE-CVI.
The most frequent ice nucleating particles/ice residuals at the Jungfraujoch station are
silicates > carbonaceous particles > metal oxides. Calcium-rich particles and soot play a
minor role. Similar results are obtained by quasi-parallel measurements with an online
single particle laser ablation mass spectrometer (ALABAMA).
All the tested techniques for measuring ice nucleating particles perform similar from a
chemical point of view within the range of their uncertainties and low counting statistics
due to the low particle concentrations in free-tropospheric air. Thus, for the first time most
of the existing ice nucleation measurement techniques could be compared side by side
under real-world atmospheric conditions.
Acknowledgment
This project is founded by the DFG (INUIT, FOR 1525)
229
Diploma Theses in Applied Geosciences
Adam, Christian; Ermittlung von Chlorisotopen-Fraktionierungsfaktoren beim Abbau von
chlorierten Schadstoffen in wässriger Phase, 1.10.13
Brauner, Sebastian; Bemessung einer Rigole zur Reinfiltration
Grundwasser einer Altlastensanierung, 27.09.2013
von
gereinigtem
Helm, Johannes; Äolische Sedimente in Südhessen, 28.06.2013
Hesse, Jan; Untersuchung der thermophysikalischen Eigenschaften von Bettungsmaterialien
für Nieder- und Mittelspannungskabel, 05.11.2013
Schütze, Katharina; Organic pollutant and particle characterization from primary
atmospheric emission sources in the Arctic, 10.05.2013
Tunon Vettermann, Gabino; Outcrop analogue study of the Minjur Formation, Kingdom of
Saudi Arabia, 09.08.2013
Winicker, Jannes; Massenbilanzierung von persistenten organischen Schadstoffen in einem
urban belasteten Gewässer, 29.04.2013
Master Theses in Applied Geosciences
Dönges, Florian; Einsatz von Nanotechnologie zur Qualitätssicherung bei der Errichtung
von Erdwärmesonden, 20.12.2013
Faißt, Tobias; GIS-based landslide susceptibility modeling in the Lesser Himalaya of Central
Nepal, 15.08.2013
Heldmann, Claus; Die hydrothermalen Vorkommen im Zillertal, 11.01.2013
Preiß, Indriani; Anwendbarkeit einer Screeningmethode zur Bestimmung des
Nitratabbaupotentials mittels Redoxprofilmessungen in Grundwasserstellen im Hessischen
Ried, 28.02.2013
230
Diploma- and Master Theses in Applied Geosciences
Master Theses TropHEE in Applied Geosciences
Agyare, Eunice Brago; Influence of small scale mining operations on surface water quality
and possible treatment options in the Tarkwa area, 27.09.2013
Androulakakis, Andreas; Characterization of chromium species in surface and groundwater
samples for the Olatha area, Bangladesh, 10.12.2013
Fatema, Suraiya; Chlorine Isotope Effects During Sorption Of Organic Compounds On
Carbonaceous Materials, 11.01.2013
Gebrehiwot, Haftay Hailu; Assessing the Groundwater potential in Tigray region, Ethiopia,
using hydraulic and hydro-chemical methods, 07.10.2013
Gomez, Shirin; Analysis of quarternary landscape features in an Environmental and
economic aspect in NE Estonia using UDAR data + ArcGIS, 02.12.2013
Gorle, Tanuja; Laboratory experiments to study sorption reversibility of organic compounds
on carbonaceous materials, 29.07.2013
Kanyamuna, Beatrice; Hydrochemistry of Waters in the Laughing Waters Area of Lusaka,
Zambia, 30.9.13
Koju, Bishnu; A study of a medium deep BHE heat storage system for clean renewable
energy using numerical modeling, 02.01.2013
LaForce, Pamela; Comparison of Nitrate Values in Groundwater Samples to Nitrate Values
in Hessen Reed Dictated by Expected Nitrate Budget Calculation, 26.11.13
Nayebare, Gumoteyo Jacintha; Waste soil Interaction on deeply weathered bedrocks on the
mobility of nutrients, 30.09.2013
Ngole, Terence; Hydrochemical Investigation of Groundwater Quality in Viotic Kifissos
Basin (Greece) with Special Focus on Nitrate pollution, 07.01.2013
Odipo, Victor Onyango; Geo-information application in assessing on-farm soil loss at a
watershed context in Lower Nyando river basin, Western Kenya, 11.01.2013
Rathnayake, Armada; GIS-based landslide susceptibility and hazard modelling in the Lesser
Himalaya of Central Nepal, 22.03.2013
Thilakerathne, Asanka; Geochemical and isotopic characterization of groundwater from
shallow limestone aquifer system of Murunkan Basin, Sri Lanka, 02.09.2013
Tögl, Anja; Development of a method to determine groundwater recharge using stable
isotopes of soils with low water saturation, 09.10.2013
Uddin, Sehab; Sorption of Lead and Arsenic from Water to Hydroxyapatite & Ca-deficient
hydroxyapatite, 24.10.2013
Xu, Shaojuan; Using LIDAR data, GIS and remote sensing to evaluate landuse changes
associated with Estonian energy production, 05.12.2013
Master Theses TropHEE in Applied Geosciences
231
Bachelor Theses in Applied Geosciences
Anschütz, Sascha; Einfluss des Wassergehaltes auf Ultraschallmessungen bei Sandsteinen
des Pfälzer Waldes, 21.10.2013
Glock, Thimo; Ökologische Bewertung der Pollen- und Algenflora der miozänen
Seesedimente aus der Forschungsbohrung Nördlingen 1973, 02.09.2013
Haffke, Paul; Hydraulische und hydrochemische Untersuchungen der Vernässungsproblematik im Bereich der Weidsiedlung bei Weinheim, 19.07.2013
Krepp, Robin; Kompilation von boden- und felsmechanischen Kennwerten für das Quartär
und Tertiär des nördlichen bis mittleren Oberrheingrabens, 21.05.2013
Kuhn, Georg; Messung von Radonkonzentration in Boden- und Raumluft im Stadtgebiet
Darmstadt zur Beurteilung von Radonmigration im geodynamischem Kontext, 06.08.2013
Kurka, Sebastian; Standsicherheitsberechnungen von Böschungen auf der Grundlage von
Triaxialversuchen an Großproben, 31.03.2013
Kusch, Ramona; Entwicklung von Methoden zur Probenvorbereitung für geothermische
Laboruntersuchungen, 23.03.2013
Marshall, Patrick; Zusatzkonzentrationsanalyse bei industriell beeinflussten Messstellen,
08.07.2013
Mentges, Simon; Erste palynologische Bearbeitung der lakustrinen Sedimente aus dem
mitteleozänen Maar-See von Offenthal (Sprendlinger Horst, Süd-Hessen), 27.04.2013
Schildt, Sven; TEM Characterization of Electron Beam Irradiated Cu-Nanotubes, 01.11.13
Schröder, Daniel; Lithofazies und Architekturelementanalyse spätpleistozäner bis rezenter
Sedimente im NW Fuerteventuras (Kanarische Inseln), 10.02.2013
Schumacher, Christina; Sedimentological detailed modeling of an alluvial fan (Illgraben,
Switzerland) with GOCAD® based on ground penetrating radar data, 13.11.2013
Werner, Melanie; Ableitung homogener Sedimentkörper mit Hilfe von Bohrverzeichnissen
am Westrand des Oberrheingrabens, 05.07.2013
Wewior, Stefan; Messung von Radonkonzentrationen in der Bodenluft zur Beurteilung der
Aktivität von tektonischen Störungen im Raum Darmstadt, 14.05.2013
Zahn, Florian; Stratigraphie und ökologische Bewertung der Forschungsbohrung Messel
2004 A (Sprendlinger Horst, Nordhessen) mit Hilfe palynologischer Methoden, 30.09.2013
232
PhD Theses in Applied Geosciences
Hussain Al Ajmi: Sedimentology, stratigraphy and reservoir quality of the Paleozoic Wajid
Sandstone in SW Saudi Arabia, 15.03.2013 – Betreuer: Prof. Hinderer
Karsten Fischer: Geomechanical reservoir modeling – workflow and case study from the
North German Basin, 18.10.2013 – Betreuer: Prof. Henk
Monika Barbara Hofmann: GIS-based analysis of Geo-Potentials in the Northern Periphery
of Belo Horizonte, MG, Brazil, 15.11.2013 – Betreuer: Prof. Hoppe
Xiaoke Mu: TEM study of the structural evolution of ionic solids from amorphous to
polycrystalline phases in the case of alkaline earth difluoride systems – Experimental
exploration of energy landscape, 20.08.2013 – Betreuer: Prof. Kleebe
Stefanie Schultheiß; Pseudomorphe Mineralumwandlung von Calcit, Dolomit, Magnesit
und Witherit, 31.10.2013 – Betreuer: Prof. Kleebe
PhD Theses in Applied Geosciences
233
Materials Science:
Alarich-Weiss-Straße 2 L2/01
64287 Darmstadt
Applied Geosciences:
Schnittspahnstraße 9 B2 01/02
64287 Darmstadt
Phone: +49(0)6151/16-5377
Fax: +49(0)6151/16-5551
www.mawi.tu-darmstadt.de
Phone: +49(0)6151/16-2171
Fax: +49(0)6151/16-6539
www.iag.tu-darmstadt.de
For further information contact:
Dr. Joachim Brötz, Phone: +49(0)6151 / 16-4392; eMail: broetz@tu-darmstadt.de
Dipl.-Ing.(BA) Andreas Chr. Hönl, Phone: +49(0)6151 / 16-6325, eMail: ahoenl@matgeo.tu-darmstadt.de
234

Institute of Materials Science - Technische Universität Darmstadt

Transcription

Similar documents

PrimeFilm 1800 AFL Low-Cost 35mm Slide/Film Scanning Through

Institute of Materials Science - Technische Universität Darmstadt

08 - Rohrbasser - Electrophorese capillaire_projet PHARMELP

Institute of Materials Science - Technische Universität Darmstadt

R - imeko

this product is designed for use in closed course racing

Intelligence in Living Cells

Lapidus Bunionectomy

View paper - Romanian Neurosurgery

1512-1594 Gerardus Mercator, or Gerard Kremer as he was called

Value Of Land

EMERGING TRENDS IN MECHANICAL ENGINEERING

Smith AMS Diploma Alumni Newsletter 2015

Symposium Structural Durability Darmstadt