Institute of Materials Science - Technische Universität Darmstadt

Transcription

Annual Report
2011
Faculty of
Materials and Geo Sciences
Contents
Dean’s Office .................................................................................................................. 4
Institute of Materials Science ......................................................................................... 6
PREFACE ........................................................................................................................ 6
PHYSICAL METALLURGY ....................................................................................................... 10
CERAMICS GROUP .............................................................................................................. 16
ELECTRONIC MATERIALS...................................................................................................... 26
SURFACE SCIENCE .............................................................................................................. 36
ADCANCED THIN FILM TECHNOLOGY ..................................................................................... 48
DISPERSIVE SOLIDS ............................................................................................................. 50
STRUCTURE RESEARCH........................................................................................................ 64
MATERIALS ANALYSIS ......................................................................................................... 69
MATERIALS MODELLING DIVISION ......................................................................................... 76
MATERIALS FOR RENEWABLE ENERGIES ................................................................................. 87
PHYSICS OF SURFACES......................................................................................................... 94
JOINT RESEARCH LABORATORY NANOMATERIALS .................................................................... 99
MECHANICS OF FUNCTIONAL MATERIALS ............................................................................. 106
COLLABORATIVE RESEARCH CENTER (SFB) .......................................................................... 111
DIPLOMA THESES IN MATERIALS SCIENCE ....................................................................... 115
BACHELOR THESES IN MATERIALS SCIENCE ..................................................................... 118
PHD THESES IN MATERIALS SCIENCE ............................................................................. 119
MECHANICAL WORKSHOP ............................................................................................. 121
ELECTRICAL WORKSHOP ............................................................................................... 121
Institute of Applied Geosciences ................................................................................ 122
PREFACE .................................................................................................................... 122
PHYSICAL GEOLOGY AND GLOBAL CYCLES ............................................................................ 124
HYDROGEOLOGY .............................................................................................................. 134
ENGINEERING GEOLOGY .................................................................................................... 139
GEOTHERMAL SCIENCE AND TECHNOLOGY ........................................................................... 140
APPLIED SEDIMENTOLOGY .................................................................................................. 151
GEO-RESOURCES AND GEO-HAZARDS .................................................................................. 158
GEOMATERIAL SCIENCE ..................................................................................................... 167
TECHNICAL PETROLOGY WITH EMPHASIS IN LOW TEMPERATURE PETROLOGY............................. 176
ENVIRONMENTAL MINERALOGY .......................................................................................... 183
DIPLOMA THESES IN APPLIED GEOSCIENCES .................................................................... 189
MASTER THESES TROPHEE IN APPLIED GEOSCIENCES ...................................................... 190
PHD THESES IN APPLIED GEOSCIENCES .......................................................................... 190
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. Andreas Hoppe
(until 31st March 2011)
Prof. Dr. Matthias Hinderer
(since 1st April 2011)
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 large scale projects:
Dr. Sonja Laubach
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
M.V. Hohmann, P. Ágoston, A. Wachau, T.J.M. Bayer, J. Brötz, K. Albe, A. Klein,
Orientation Dependent Ionization Potential of In2O3: A Natural Source for Inhomogeneous
Barrier Formation at Electrode Interfaces in Organic Electronics, J. Phys.: Cond. Mat. 23,
334203 (2011); doi: 10.1088/0953-8984/23/33/334203
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Dean’s Office
J. Deuermeier, J. Gassmann, J. Brötz, A. Klein, Reactive magnetron sputtering of Cu2O:
Dependence on oxygen pressure and interface formation with ITO, J. Appl. Phys., Vol. 111,
113704 (2011); doi:10.1063/1.3592981
Renard, L.; Elhamzaoui, H.; Jousseaume, B.; Toupance, T.; Laurent, G.; Ribot, F.; Saadaoui,
H.; Brötz, J.; Fuess, H.; Riedel, R.; Gurlo, A.; Low-temperature H2 sensing in self-assembled
organotin thin films; Chem. Commun., 47(5) (2011) 1464-1466.
F. Muench, S. Kaserer, U. Kunz, I. Svoboda, J. Brötz, S. Lauterbach, H.-J. Kleebe, C. Roth,
W. Ensinger; Electroless synthesis of platinum and platinum–ruthenium nanotubes and their
application in methanol oxidation; JOURNAL OF MATERIALS CHEMISTRY, 21 (2011)
6286-6291.
Jacke, S. Song, J. Dimesso, L. Broetz, J. Becker, D. Jaegermann, W., Temperature dependent
phosphorous oxynitride growth for all-solid-state batteries JOURNAL OF POWER SOURCES,
Vol. 196, 6911-6914, DI 10.1016/j.jpowsour.2010.12.022, AUG 15 2011
Structural characterisation of textured gold nanowires Maurer, F; Brötz, J ; Miehe, G;
Karim, S; Fuess, H, INTERNATIONAL JOURNAL OF NANOTECHNOLOGY Volume: 8
Issue: 10-12 Special Issue: SI Pages: 855-867 Published: 2011
Dean’s Office
5
Institute of Materials Science
Preface
Dear colleagues and friends,
The year 2011 was an eventful and successful year for the Department of Materials and
Geo Sciences of TU Darmstadt. Details of the activities and achievements related to the
Institute of Applied Geosciences are highlighted by the director of the institute, Prof. H.-J.
Kleebe, on page 122.
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. The contribution of every single one of them added to
the results presented here. 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 increased once again; expenses rose from €
10.2 million in 2010 to € 12.6 million in 2011 and also in terms of teaching a milestone
was reached by finishing the elaboration of the Master course, which has already been
accredited by ASIIN. The Master course, being an international study course where all
courses are held in English, saw its first students in the winter semester 2011/12.
2011 was also the first year having students graduate from the Bachelor course. Most of
them want to graduate as a Master of Science in Materials Science and are therefore
continuing their studies as students of the consecutive Master course offered by our
department. The Bachelor course of our department is still gaining in popularity as is
reflected by a new record number of 140 freshmen starting in the winter semester
2011/12, which means a 40% increase as against the previous year, as can be seen in
Figure 1.
For the first time, a new kind of scholarship, the so-called "Deutschlandstipendium", was
awarded to 91 students of TU Darmstadt, 3 of whom being students of the Institute of
Materials Science. Regardless of the university in Germany this scholarship always means a
donation of € 300 per month, independent of the financial situation of the candidate. One
half of the grant is financed by the German Government, the other half is donated by
enterprises. The fundraising process and the selection of scholars is organised by the
respective university.
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Preface
Coordinated Research Proposals
The institute was involved in two large-scale proposals in 2011: SubMateK, applying for a
LOEWE Center of Excellence funded by the Hessian State Government, which was
coordinated by Prof. Alff together with Prof. Oechsner from the Department of Mechanical
Engineering, and TAIFUN, applying for a Center of Excellence funded by the German
Federal and State Governments, the coordinators of which are Prof. Riedel and Prof. Rödel.
For TAIFUN, the pre-proposal had already been handed in in 2010. For SubMateK, a preproposal was composed due in April 2011. Both pre-proposals received a positive
evaluation and therefore successfully reached the next evaluation stepm meaning that both
initiatives were invited to elaborate a full proposal. The full proposals were submitted
according to schedule in September (TAIFUN) and December (SubMateK), respectively.
Another initiative, namely the Graduate School of Energy Sciences and Engineering, in
which the Department of Materials and Geosciences is involved together with other
Departments of TU Darmstadt, was established within the framework of the Excellence
initiative. The decisions on all three proposals, i.e. SubMateK, TAIFUN, and the Graduate
School, are not due before June 2012. All three initiatives mark the interdisciplinary
approach the university is promoting and for which the Department of Materials and
Geoscience is ideal since its subjects combine various sciences like chemistry, physics,
electrical and mechanical engineering.
Fig. 1: Number of students (without Ph. D. students) in Materials Science at Technische Universität Darmstadt
over the past 10 years. Until SS08, the freshmen refer to the Diploma course, thereafter to the Bachelor
course.
Preface
7
Faculty Members
Two new professorships were inaugurated, namely Jun.-Prof. Dr. Bai-Xiang Xu and Prof.
Dr. Ralph Krupke, who are heading the groups "Mechanics of Functional Materials" and
"Molecular Nanostructures" respectively. We welcome both as new professors to our
institute. In 2012, another two new faculty members will be appointed, Prof. Dr. Christina
Trautmann (head of the group Ion Beam-Modified Materials) and Prof. Dr. Oliver
Gutfleisch (head of the group Functional Materials).
Prof. Heilmaier left the Department of Materials and Geosciences to take up a position as
Director at the Karlsruhe Institute of Technology (KIT) in December 2011. In March 2012,
Prof. Roth (group of Renewable Energies) will as well leave for the Karlsruhe Institute of
Technology (KIT). She will, however, remain with the Department of Materials and
Geosciences as an APL-Professor for three more years. We wish both of them all the best for
their future careers.
Buildings and Lab/Office Space
The steadily increasing number of both staff and students (see Fig. 1) at the Institute of
Materials Science causes a continuous need for more office and lab space. Therefore, we
appreciate that two more stories were added to the CSI-building L1|08, which now
comprises four floors. The Dispersive Solids division having moved there in August 2011,
the 2nd and 4th floor are now occupied by the groups Dispersive Solids (Prof. Riedel), Joint
Research Laboratory Nanomaterials (Prof. Hahn), Molecular Modelling (Prof. Albe), Physics
of Surfaces (Prof. Stark), and Surface Science (Prof. Jaegermann). However, to meet the
needs of our growing research activities, it is planned to erect a new building with lab and
office space in Böllenfalltorweg. The building will be shared with the Chemistry
Department and its completion is scheduled for late spring 2013.
Mechanical Workshop
After the retirement of the head of the mechanical workshop, Jochen Korzer, in 2010, we
are glad to have found a new head in Jochen Rank in 2011. Jochen Rank previously gained
a lot of experience in the Departments of Chemistry and Mechanical Engineering and now
manages the mechanical workshop at our institute with great commitment, enthusiasm,
and success. We welcome him to our Department. It is also good news that we will soon
purchase a CNC lathe for the mechanical workshop thanks to a grant from the president.
Outstanding New Equipment
The electron microscopy facility of our department was significantly upgraded by the
acquisition of a highly sophisticated new Cs-corrected TEM providing a resolution of 0.8 Å
and a focused ion beam (FIB) instrument for nanostructuring of materials and sophisticated
lamellae preparation of samples for microscopy. This, together with the recent acquisition
of other instruments, means that the Competence Centre Materials Characterisation is now
provided with the appropriate equipment to rank among the world's top addresses in
materials characterization.
Honours, Awards and Special Achievements
In 2011, we were proud to celebrate a number of awarded prizes and special achievements:
Dr. Olivier Guillon received the Masing Memorial Award. This prize is awarded by the
German Society for Materials Science (DGM) for independent research work in the broader
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Preface
field of physical metallurgy achieved by young scientists. Dr. Guillon also received the
Materials Science and Technology Prize given to young European materials scientists or
engineers in recognition of a significant contribution to a field in Materials Science and
Engineering. In addition, Dr. Guillon was awarded with the R. L. Coble Award for Young
Scholars, the annual prize of the American Ceramic Society for the world's best young
scientist in the field of ceramics. Dr. Guillon is the first young scientist working in Germany
to receive this award. In the meantime, he has accepted an offer for a professorship at the
Friedrich-Schiller-Universität in Jena.
Prof. Hartmut Fuess received the "MaWi-Ehrennadel" for his long-term efforts and
commitment for the Institute of Materials Science. Dr. Martin Schidleja was awarded the
prize of the "Vereinigung von Freunden der Technischen Universität zu Darmstadt e.V." for
his outstanding academic achievements in his doctoral thesis.
As usual, the annual awarding of the "MaWi Prize" formed part of the MaWi summer party.
The prize winners in 2011 were Ruben Bischler from the division Joint Research Laboratory
Nanomaterials for his Diploma thesis on "Tailored Nanostructured Metal Borides," and Ralf
Witte, also from the Joint Research Laboratory Nanomaterials, whose Diploma thesis is
about "Magnetic Phenomena in Fe-Sc Nanoglasses." The 3rd prize was awarded to Matthias
Ehmke for his contribution regarding “Electric fatigue and aging processes in lead-free BNTBT-KN ferroelectrics.” Last but not least, Dr. Yuri Genenko successfully finished his
habilitation colloquium.
Social Events
As every year, our annual summer party was scheduled shortly before the summer break, it
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 in the period between the past winter semester and the
present summer semester. The prize winners have already been named above.
It was for the first time in December 2011 that we celebrated a year-end ceremony for all
research groups, staff members and students, something that is formally considered to be
the continuation of our traditional MaWi christmas party. Due to the increased number of
attendants, this event had to be held in the building of the cafeteria at the Lichtwiese. The
celebration including the social programme was organized by PD Dr. Boris Kastening, Heinz
Mohren, and students (Fachschaft). During the graduation party the graduates of the year
received their certificates (Bachelor, Diploma, and PhD). This being the most important
part of the programme, we will now start a new tradition by celebrating Bachelor and
Master graduates at the MaWi summer party and PhD graduates at the year-end ceremony.
This annual report shall provide you with some information on the most prominent
research activities of the individual groups conducted in 2011 which you will find in detail
on the following pages.
Prof. Ralf Riedel
Dean of the Department
Preface
9
Physical Metallurgy
Research and teaching of the Physical Metallurgy group in general focus on a deeper
understanding of the relationships between processing, microstructure and properties of
metallic materials. The major goal of this research is on the one hand to quantitatively
describe existing materials with respect to their processing and performance in order to
fully exploit their application potential. On the other hand, we search for and subsequently
develop novel alloy systems with improved properties by utilizing the basic principles of
physical metallurgy. If potential alloy systems may be identified, it is of not only prime
importance to extensively characterize these materials with respect to the foreseen
application but also to give appropriate feedback to the material developers for further
optimization.
Our current research deals with Al, Mg and Ti based light alloys, steels, nickel-base
superalloys and refractory alloys. Mechanical properties such as creep, fatigue and wear are
mainly studied including their interaction with corrosion and oxidation phenomena. Recent
progress includes functionally graded materials as well as improvements in the wear
resistance of metallic alloys by mechanical surface treatments. The major research topics on
which our group presently concentrates are first, ultra-fine grained (UFG) materials which
created special interest in recent years, as they favorably combine very high strength with
good ductility. In several research projects the evolution and the mechanical properties of
these microstructures are investigated and new forming processes for the continuous
production of UFG-bulk materials are developed in collaboration with the department of
mechanical engineering. Second, development of structural metallic materials which could
withstand applications in air at temperatures beyond 1200°C would be attractive not only
from scientific but also industrial standpoints. A successful alloy development would
eventually allow for a substitution of single-crystalline nickel-base superalloys in gas
turbine applications.
Teaching covers basic courses on phase transformation in metals and alloys (including
phase diagrams), mechanical properties of (structural) engineering materials and
fundamentals of deformation and fracture. Special courses are given on solidification and
heat treatment mechanisms, quantitative image analysis for the characterization of
microstructures and high temperature alloys. Extensive laboratory exercises on all levels are
offered to facilitate and intensify the technical understanding in these topics and to improve
the practical skills for investigating metallic materials.
The Physical Metallurgy group has numerous collaborations with other groups within the
department and with others of Darmstadt Technical University, in particular with
Mechanical Engineering through the DFG CRC 666. On the national level, cooperation in
academia is characterized by the close relation to the other members of the WAW
(Wissenschaftlicher Arbeitskreis der Universitätsprofessoren der Werkstofftechnik e.V.).
Internationally, we have a continuing cooperation with groups from Australia, Czech
Republic, France, UK, Ukraine, Canada and USA which also includes exchange of students
and scientists. Strong relations with industry (Daimler-Benz, Ecoroll, Heraeus, Opel, PfalzFlugzeugwerke, Plansee, VW) give multiple opportunities for scientific interaction and
personal exchange. Department members participate in and organize national and
international conferences, seminars and workshops thereby gathering information which
supports to keep teaching and research on an actual level.
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Physical Metallurgy
Staff Members
Head
Prof. Dr. Martin Heilmaier
Research Associates
Prof. Dr. Clemens Müller
Dr.-Ing. Enrico Bruder
Dipl.-Ing. Katharina von Klinski-Wetzel
Technical Personnel
Ulrike Kunz
Claudia Wasmund
Secretaries
Christine Hempel
PhD Students
Dipl.-Ing. Florian Gang
Dipl.-Ing. Daniel Janda
Dipl.-Ing. Vanessa Kaune
Dipl.-Phys. Peter Pörsch
Dipl.-Ing. Jan Scheil
Dipl.-Ing. Daniel Schliephake
Dipl.-Ing. Lukas Schlicker
Dipl.-Ing. Jennifer Schuster
Dipl.-Ing. Christoph Seemüller
Dipl.-Ing. Jörn Niehuesbernd
Diploma Students
Christoph Baumann
Karsten Fischer
Michael Bachmann
Ioannis Sprenger
Rudolf Seiler
George Bedenian
Ruben Heid
Franziska Resch
Kathrin Barth
Research Fellow
Dr. Shanmugasundaram Tharangaju
Guest Scientists
Dr. Yongzhong Zhan
Xiaojiao Yu
Petra Neuhäusel
Michael Rohloff
Research Projects
“Beyond Nickelbase Superalloys” (DFG research unit FOR 727, 2007-2013).
“Bulk UFG-Materials Produced by Rotary Swaging”, joint project with PTU-Darmstadt, DFG,
since 10/2008.
“Directional Solidification of Multiphase Metallic High Temperature Materials Beyond
Nickelbase Superalloys”, DFG, since 08/2010.
“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.
“FeAl-based Alloys - Materials, Casting Process and Exhaust Gas Turbocharger”, joint
project with one academic and 4 industrial partners, BMWi, since 08/2010.
“Grain and Phase Boundary Segregation in Multiphase Mo-borosilicides”, SHaRE User
Facility at Oak Ridge National Laboratory, Office of Basic Energy Sciences, U.S. Department
of Energy, 07/2010 - 06/2012.
“Hybrid Silicide-Based Lightweight Components for Turbine and Energy Applications
(HYSOP)”, collaborative project with 7 European partners,EU, since 10/2010.
“Improved Wear Resistance of Forming Tools by Mechanical Surface Treatments” joint
project with PTU-Darmstadt, AIF, since 09/2006.
“Microstructure and Mechanical Properties of Bifurcated Sheet Profiles”, in SFB 666 of the
Physical Metallurgy
11
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 2009.
Publications
J. H. Schneibel, M. Heilmaier, G. Hasemann, T. Shanmugasundaram: Temperature
dependence of the strength of fine- and ultrafine-grained materials, Acta Materialia 59 (2011),
1300-1308.
O. Hassomeris, G. Schumacher, M. Krüger, M. Heilmaier, J. Banhart: Phase Continuity in
High Temperature Mo-Si-B Alloys: A FIB-Tomography Study, Intermetallics 19 (2011), 470475.
M. Mousa, N. Wanderka, M. Timpel, S. Singh, M. Krüger, M. Heilmaier, J. Banhart:
Modification of Mo-Si alloy microstructure by small additions of Zr, Ultramicroscopy 111
(2011), 706-710.
P. Susila, D. Sturm, M. Heilmaier, B.S. Murty, V.S. Sarma: Effect of yttria particle size on the
microstructure and compression creep properties of nanostructured oxide dispersion
strengthened ferritic (Fe-12Cr-2W-0.5Y2O3) alloy, Mater. Sci. Eng. A528 (2011), 4579-4584.
S. Burk, B. Gorr, M. Krüger, M. Heilmaier, H.-J. Christ: Oxidation behaviour of Mo-Si-B-(X)
alloys: Macro- and Microalloying (X= Cr, Zr, La2O3), JOM 63, No. 12, (2011), 32-36.
E. Bruder, M.O. Görtan, P. Groche, C. Müller: Severe Plastic Deformation by Equal Channel
Angular Swaging, Mater. Sci. Forum 667-669 (2011), 103-107.
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Physical Metallurgy
UFG-surface layer on DD11 mild steel profiles produced by Linear Bend Splitting
V. Kaune, C. Müller
Department of Materials Science, TU Darmstadt, D-64287 Darmstadt, Germany
ABSTRACT: An approach to improve global properties of a component is the generation of
an ultrafine-grained (UFG)-surface layer induced by surface severe plastic deformation
(S2PD). Linear Bend Splitting (LBS) is a new continuous process, which generates
bifurcated profiles in integral style from plain metal sheet. Due to the high deformation in
the splitting zone, an UFG-microstructure develops on the surface of the produced flanges
up to a depth of several hundred microns. On the low alloyed mild steel DD11, the
microstructure, the mechanical properties and the deformation behavior of the linear bend
split profiles are investigated.
INTRODUCTION: Severe plastic deformation (SPD)-processes have been established to be
one of the effective methods to generate microstructures in the sub micrometer or even
nanometer regime in various kinds of metals. Typically used SPD-techniques are Equal
Channel Angular Pressing (ECAP), High Pressure Torsion (HPT) or Accumulative RollBonding (ARB), which are based on grain refinement due to the introduction of high strains
into the bulk material [1, 2]. The ultrafine-grained (UFG) microstructures exhibit
outstanding mechanical and physical properties, e.g. high strength [3, 4], enhanced fatigue
strength [5] and high corrosion resistance [6]. The combination of a coarse-grained interior
with an UFG-surface layer is a promising approach to improve the properties of materials or
components, since material failures are mostly initiated from the surface (wear, corrosion,
crack initiation) [7, 8]. To obtain UFG-surface layers, various Surface SPD (S2PD)-processes
have been developed, such as surface mechanical attrition treatment (SMAT) [9], large
strain machining [10] or gradation rolling [11]. However, these processes exhibit high
process duration or a restriction to batch application, which implicates a disadvantage with
regard to a continuous production. One approach which enables the continuous production
of UFG-surface layers is the S2PD-process Linear Bend Splitting (LBS). This massive cold
forming process enables the generation of flanges in integral style out of any position of a
metal sheet. Based on a die bent semi finished product, the LBS process generates a profile
with a newly created flange, a thinned area and two webs with initial thickness (Fig. 1).
Fig. 1: Linear bend split profile (with flange, thinned area and webs), location of tensile specimens and
direction of hardness measurements
Physical Metallurgy
13
EXPERIMENTAL: The material used in this investigation was hot rolled DD11 mild steel
with a ferritic–perlitic microstructure and an average grain size of 16 µm. The linear bend
split profiles were investigated using EBSD (Electron Backscatter Diffraction)
measurements, hardness indentations and tensile tests, notably in the most deformed areas,
i.e. flange, thinned area and the splitting center (see Fig. 1). In addition, the deformation
behavior of the flanges containing an ultrafine-grained microstructure is investigated.
RESULTS AND DISCUSSION: The S2PD-process Linear Bend Splitting (LBS) generates an
ultrafine-grained (UFG) microstructure in the flange, the splitting center and the thinned
area (Fig. 2, left). Perpendicular to the split surface a microstructural gradient exists with a
thickness of the UFG layer of 400 µm-500 µm (Fig. 2, right). Parallel to the surface the
microstructure exhibit in the flange respectively thinned area homogenous grain sizes and
constant mechanical properties. Thereby, the thinned area shows a slightly finer
microstructure and higher hardness/strength compared to the flange.
Fig. 2: EBSD-measurements at the thinned area (left), splitting center (middle) and flange (right) in a depth of
25 µm and 500 µm and Effective grain sizes of the different surface regions within the profile
The local properties depend on the distance to the split surface. On the basis of a developed
correlation between hardness and strength, the local strength at the UFG surface can be
calculated to 1200 MPa [12]. These mechanical properties of the UFG-surface layer
increase the potential for various industrial applications, especially where improved wear
resistance is required or good fatigue properties are desired as long as the maximum stress
arises in the UFG region (e.g. bending load stress).
14
Physical Metallurgy
Fig. 3: Tensile tests of the as received material, the thinned area and the flange of the linear bend split profile
The global properties of the profiles are dominated by the characteristic properties of UFGmicrostructures in terms of high strength, but low uniform elongation and work hardening
(Fig. 3) [13, 14]. The flanges show a ductile deformation and fracture behavior in terms of
necking and dimples, but secondary cracks occur in the UFG part of the fracture surface.
These cracks are orientated parallel to the split surface and indicate weakened grain
boundaries and grain boundary sliding due to the LBS process. Hence, the profiles show a
ductile but low formability under a subsequent tensile load.
References:
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
T.G. Langdon, J. Mater. Sci. 42 (2007) 3388-3397.
R.Z. Valiev, Y. Estrin, Z. Horita, T.G. Langdon, M.J. Zehetbauer, Y.T. Zhu, JOM 58 (2006) 33-39.
R.Z. Valiev, I.V. Alexandrov, Y.T. Zhu, T.C. Lowe, JMR 17 (2002) 5-8.
N. Tsuji, J. Phys.: Conf. Ser. 165 (2009).
H. Mughrabi, H.W. Höppel, M. Kautz, Scripta Mater. 51 (2004) 807-812.
P. Frint, M. Hockauf, D. Dietrich, T. Halle, M.F.-X.Wagner, T. Lampke, J. Mater. Sci. 43 (2008) 74097417.
X. Wu, N. Tao, Y. Hong, B. Xu, J. Lu, K. Lu, Acta Mater. 50 (2002) 2075-2084.
K. Lu, J. Lu, Mater. Sci. Eng. A 375-377 (2004) 38-45.
N.R. Tao, J. Lu, K. Lu, Mater. Sci. Forum 579 (2008) 91-108.
M.R. Shankar, S. Chandrasekar, A.H. King, W.D. Compton, Acta Mater. 53 (2005) 4781-4793.
R. Neugebauer, A. Sterzing, M. Bergmann, Mat.-wiss. u. Werkstofftech. 42 (2011) 593-598.
V. Kaune, C. Müller, Mater. Sci. Eng. A 535 (2012) 1-5.
N. Krasilnikov, W. Wojkowski, R. Valiev, Mater. Sci. Eng. A 397 (2005) 330-337.
N. Tsuji, Y. Ito, Y. Saito, Y. Minamino, Scripta Mater. 47 (2002) 893–899.
Physical Metallurgy
15
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, lead-free
high-temperature dielectrics and lead-containing high-temperature piezoceramics can be
obtained and extensively characterized electrically and mechanically.
The scientific effort can be grouped as follows:
I.
Processing and sintering of oxides
Dr. Olivier Guillon - Emmy Noether independent junior research group
Following topics are investigated:
 Continuum mechanical description of sintering in the case of ceramic films and laminates
(modelling of shrinkage, stress state, curvature during co-sintering…)
 Measurement of densification behaviour and viscous parameters by means of sinterforging
 Macroscopic and microscopic characterization of sintering anisotropy under mechanical
loading and geometrical constraint provided by a substrate
 Drying of thin films from suspensions and conditions for cracking
 Sintering mechanisms of electrical Field Assisted Sintering Technique and processing of
dense nanocrystalline materials
 Effect of particle size on the phase transformation behaviour of oxides using chip
calorimetry and TEM.
The considered Materials are mainly Al2O3, ZrO2, ZnO as well as materials for LTCC (Low
Tempera-ture Cofired Ceramics) and SOFC (Solid Oxide Fuel Cell) applications.
II. Mechanical properties of ceramics and composites
Dr. Ludwig Weiler
Work on mechanical properties is geared towards an improved understanding of fracture
strength, fracture toughness, R-curve behaviour and subcritical crack growth.
Together with several European research groups we prepare and characterize metalceramic composites and metal-ceramic functionally graded materials
Materials under consideration are Al2O3/Cu and Al2O3/Al.
III. Electrical properties of ferroelectrics
Dr. Torsten Granzow
Materials with a crystalline structure lacking a center of inversion display a multitude of
peculiar physical effects, they are therefore prime candidates both for fundamental
scientific research as well as practical technical applications. Therefore the focus of the
work in this group lies on the reaction of non-centrosymmetric materials to different
external stimuli like electric fields, mechanical loads or high temperatures. Ferroelectric
behavior and domain switching are of particular interest. Typical objects of the studies are
polycrystalline materials based on perovskite structures, which form the most extended and
16
Ceramics Group
diverse group of polar materials. These materials are always ferroelastic as well as
ferroelectric in the non-cubic phase. The general aim is to develop the understanding of the
basic physical principles that allows improvement of the properties of the material or to
optimize the use of existing properties in a given application.
One topic of investigation is the effect of combined electrical and mechanical loading on
domain structures. In this context, the method of stress-supported poling was developed: a
high degree of polarization can be reached with comparably small electric fields if a
mechanical load is applied perpendicular to the poling direction. The mechanical and
electrical behavior of donor- and acceptor-doped materials is investigated. The data will be
used to develop a mathematical model that allows a prediction of the development of
polarization and strain during an arbitrary electrical, mechanical and thermal procedure
from as few parameters as possible.
Apart from the research on ferroelectric properties, transitions between different polar
phases or polar and non-polar phases are also of interest. One observes a stabilization or
destabilization of long-range ferroelectric order by controlled introduction of charged
defects, e.g. by a reduction treatment. The work is closely connected to that of the group
developing new lead-free piezoelectric materials, as their superior properties are tied to the
existence of a high-temperature phase that is probably relaxor-like.
The work in this group is embedded in the Collaborative Research Center 595 on electrical
fatigue in ferroelectric materials. The aim is to identify the causes for degradation of a
material during use of a device and eliminate them as far as possible. Another topic within
this project is the connection between domain structure, reversible and irreversible domain
wall motion, large-signal parameters such as polarization and strain, and small-signal
parameters like the components of the dielectric and piezoelectric tensors.
IV. 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
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.
Ceramics Group
17
V. Mechanical properties of ferroelectrics
Dr. Kyle Webber
The focus of this research group is on the mechanical behavior of ferroelectric materials,
specifically the impact of ferroelasticity on fracture and high temperature constitutive
behavior. To this end, the fracture behavior of novel high toughness piezoceramics is being
investigated as part of an EU Project for the potential inclusion in actuator applications in
extreme environments, such as wind turbines and active damping of motor vibrations.
Work has focused on determining the change in R-curve behavior from an addition of
second phase of tetragonal stabilized zirconia as well as the transition from inter- to
transgranular fracture. Additional investigations on the high temperature constitutive
behavior of ferroelectric materials are also underway. A novel experimental arrangement
has been constructed capable of measuring the strain and polarization of samples in
response to uniaxial compressive stress at temperatures up to approximately 400 °C. This
has been used to investigate hard and soft PZT up to the Curie temperature as well as
current lead-free compositions with more complex phase structures. Phase field modeling is
used to better understand the switching and fatigue behavior of the materials considered.
Staff Members
Head
Prof. Dr. Jürgen Rödel
Research Associates
Dr. Torsten Granzow
Dr. Olivier Guillon
Dr. Wook Jo
Dipl. Phys. Irene Mieskes
Dr. Silke Schaab
Dr. Sebastian Schwarz
Dr. Kyle Webber
Dr. Ludwig Weiler
Dr. Jami Winzer
Technical Personnel
Dipl.-Ing. Emil Aulbach
Dipl.-Ing. Gundel Fliß
Michael Heyse
Secretaries
Roswita Geier
Gila Völzke
PhD Students
M. Sc. Matias Acosta
Dipl.-Ing. Eva Anton
Dipl.-Ing. Raschid Baraki
Dipl.-Ing. Robert Dittmer
Dipl.-Phys. Daniel Franzbach
Dipl.-Ing. Claudia Groh
Dipl.-Ing. Gerrit Günther
Dipl.-Ing. Christine Jamin
Dipl.-Ing. Markus König
Dipl.-Ing. Thorsten Leist
Dipl.-Phys. Mie Marsilius
Dipl.-Ing. Eva Sapper
Dipl.-Ing. Silke Schaab
Dipl.-Ing. Florian Schader
Dipl.-Phys. Deborah Schneider
Dipl.-Ing. Yohan Seo
Dipl.-Chem. Ina Uhlmann
M. Sc. Jami Winzer
M. Sc. Jiadong Zang
Diploma+Bachelor
Students
Raschid Baraki
Philipp Geiger
Lucas Hamm
Rebecca Hentschel
Timo Prenzer
Florian Schader
André Schmidt
Malte Voegeler
18
Ceramics Group
Research Fellow
Juri Koruza
Tomas Muchenik Cena
Michelle Nolan
Suyan Tu
Guest Scientists
Prof. Edwin Garcia (Purdue University)
Prof. Mark Hoffman (Univ. of New South Wales, Sydney)
Prof. Jacob Jones (University of Florida)
Prof. Sergei Kalinin (Oak Ridge Nat. Lab.)
Prof. Ho-Yong Lee (Sunmoon University, Korea)
Prof. Joe Trodahl (Victoria Univ. Wellington, NZ)
Prof. Xiaoli Tan (Iowa State University)
Dr. Haibo Zhang (University Beijing)
Dr. Ke Wang (AvH)
Zilin Yan
Dr. Hailong Zhang
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)
 Melting of ceramic nanoparticles: Application to transient liquid phase sintering
(DFG 2006–2011)
 Synthesis and characterization of nanostructured materials by FAST sintering
(DFG 2006-2011)
 Drying of Thin Films (DFG 2006–2011)
 Thin film sintering: liquid phase vs. solid state sintering (DFG 2008-2011)
 Printed Electronics: Thin film ZnO (Merck 2006-2011)
 Effect of load and temperature on domain switching (DFG 2008-2011)
 Development of new lead –free piezoceramics (ADRIA, state funding, 2008-2013)
 Development of new high-temperature piezoceramics (ADRIA, state funding, 2008-2013)
 Toughening of ferroelectrics (EU 2009-2012)
 Stress and strain fields in ferroelectrics
(Graduate school “computational engineering” 2009-2012)

Metal-ceramic composites (EU 2010-2012)

High-temperature dielectrics (DFG 2010-2013)

Mechanical compliance at phase transition points in lead-free ferroelectrics
(DFG 2011-2014)

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)
Ceramics Group
19
Publications
Seo, Yo-Han; Benčan, Andreja; Koruza, Jurij; Malič, Barbara; Kosec, Marija; Webber,
Kyle G.; Compositional Dependence of R-curve Behavior in Soft Pb(Zr1−xTix)O3 Ceramics,
JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 94 (12) pp. 4419-4425. ISSN
00027820
Tan, Xiaoli; Ma, Cheng; Frederick, Joshua; Beckman, Sarah; Webber, Kyle G.;
The Antiferroelectric ↔ Ferroelectric Phase Transition in Lead-Containing and Lead-Free
Perovskite Ceramics, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 94 (12) pp. 40914107. ISSN 00027820
Anton, Eva-Maria; Jo, Wook; Damjanovic, Dragan; Rödel, Jürgen; Determination of
depolarization temperature of (Bi1/2Na1/2)TiO3-based lead-free piezoceramics, JOURNAL
OF APPLIED PHYSICS, 110 (9) 094108(1-14). ISSN 00218979
Luo, Zhenhua; Granzow, Torsten; Glaum, Julia; Jo, Wook; Rödel, Jürgen; Hoffman,
Mark; Effect of Ferroelectric Long-Range Order on the Unipolar and Bipolar Electric Fatigue in
Bi1/2Na1/2TiO3-Based Lead-Free Piezoceramics, JOURNAL OF THE AMERICAN CERAMIC
SOCIETY, 94 (11) pp. 3927-3933. ISSN 00027820
Franzbach, Daniel J.; Xu, Bai-Xiang; Mueller, Ralf; Webber, Kyle G.; The effects of
polarization dynamics and domain switching energies on field induced phase transformations
of perovskite ferroelectrics, APPLIED PHYSICS LETTERS, 99 (16) 162903-(1-3). ISSN
00036951
Jo, Wook; Schaab, Silke; Sapper, Eva; Schmitt, Ljubomira A.; Kleebe, Hans-Joachim;
Bell, Andrew J.; Rödel, Jürgen; On the phase identity and its thermal evolution of lead free
(Bi1/2Na1/2)TiO3-6 mol% BaTiO3, JOURNAL OF APPLIED PHYSICS, 110 (7) 074106-1074106-9. ISSN 00218979
Glaum, Julia; Granzow, Torsten; Schmitt, Ljubomira Ana; Kleebe, Hans-Joachim;
Rödel, Jürgen, Temperature and driving field dependence of fatigue processes in PZT bulk
ceramics, ACTA MATERIALIA, 59 (15) pp. 6083-6092. ISSN 13596454
Bernard, D.; Guillon, Olivier; Combaret, N.; Plougonven, E.; Constrained sintering of
glass films: Microstructure evolution assessed through synchrotron computed
microtomography, ACTA MATERIALIA, 59 (16) pp. 6228-6238. ISSN 13596454
Tran, Vu Diem Ngoc; Han, Hyoung-Su; Yoon, Chang-Ho; Lee, Jae-Shin; Jo, Wook;
Rödel, Jürgen; Lead-free electrostrictive bismuth perovskite ceramics with thermally stable
field-induced strains, MATERIALS LETTERS, 65 (17-18) pp. 2607-2609. ISSN 0167577X
Webber, Kyle G.; Seo, Yo-Han; Lee, Ho-Yong; Aulbach, Emil; Jo, Wook; Rödel, Jürgen;
R-Curve Behavior of Pb(Mg1/3Nb2/3)O3-29 mol% PbTiO3 Single Crystals: The Effect of
Crystallographic Orientation and Grain Structure, JOURNAL OF THE AMERICAN CERAMIC
SOCIETY, 94 (9) pp. 2728-2730. ISSN 00027820
Winzer, Jami; Weiler, Ludwig; Pourquet, Jeanne; Rödel, Jürgen; Wear behaviour of
interpenetrating alumina–copper composites, WEAR, 271 (11-12) pp. 2845-2851. ISSN 00431648
Drahus, Michael D.; Jakes, Peter; Erdem, Emre; Schaab, Silke; Chen, Jun; Ozerov,
Mykhaylo; Zvyagin, Sergei; Eichel, Rüdiger-A.; Manganese-doped (1−x)BiScO_{3}–
xPbTiO_{3} high-temperature ferroelectrics: Defect structure and mechanism of enhanced
electric resistivity, PHYSICAL REVIEW B, 84 (6) 064113-1-064113-8. ISSN 1098-0121
20
Ceramics Group
Ehmke, Matthias; Glaum, Julia; Jo, Wook; Granzow, Torsten; Rödel, Jürgen;
Stabilization of the Fatigue-Resistant Phase by CuO Addition in (Bi1/2Na1/2)TiO3-BaTiO3,
JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 94 (8) p. 2473. ISSN 00027820
Langer, Jochen; Hoffmann, Michael J.; Guillon, Olivier; Electric Field-Assisted Sintering
and Hot Pressing of Semiconductive Zinc Oxide: A Comparative Study, JOURNAL OF THE
AMERICAN CERAMIC SOCIETY, 94 (8) pp. 2344-2353. ISSN 00027820
Seils, Sascha; Baraki, Raschid; Jamin, Christine; Guillon, Olivier; Free-Standing
Patterned Ceramic Structures Obtained by Soft Micromolding, ADVANCED ENGINEERING
MATERIALS, 13 (6) pp. 502-508. ISSN 14381656
Chung, Yung-Bin; Park, Hyung-Ki; Lee, Dong-Kwon; Jo, Wook; Song, Jean-Ho; Lee,
Sang-Hoon; Hwang, Nong-Moon; Low temperature deposition of crystalline silicon on glass
by hot wire chemical vapor deposition, JOURNAL OF CRYSTAL GROWTH, 327 (1) pp. 57-62.
ISSN 00220248
Jo, Wook; Rödel, Jürgen; Electric-field-induced volume change and room temperature phase
stability of (Bi1/2Na1/2)TiO3-x mol. % BaTiO3 piezoceramics, APPLIED PHYSICS LETTERS,
99 (4) 042901-1-042901-3. ISSN 00036951
Dittmer, Robert; Jo, Wook; Daniels, John; Schaab, Silke; Rödel, Jürgen; Relaxor
Characteristics of Morphotropic Phase Boundary (Bi1/2Na1/2)TiO3-(Bi1/2K1/2)TiO3
Modified with Bi(Zn1/2Ti1/2)O3, JOURNAL OF THE AMERICAN CERAMIC SOCIETY n/a.
ISSN 00027820
Daniels, John E.; Jo, Wook; Rödel, Jürgen; Rytz, Daniel; Donner, Wolfgang; Structural
origins of relaxor behavior in a 0.96(Bi[sub 1/2]Na[sub 1/2])TiO[sub 3]–0.04BaTiO[sub 3]
single crystal under electric field, APPLIED PHYSICS LETTERS, 98 (25) 252904-1-252904-3.
ISSN 00036951
Guillon, Olivier; Cao, Shaoyong; Chang, Jaemyung; Wondraczek, Lothar; Boccaccini,
Aldo R.; Effect of uniaxial load on the sintering behaviour of 45S5 Bioglass® powder
compacts, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 31 (6) pp. 999-1007. ISSN
09552219
Anton, Eva-Maria; Jo, Wook; Trodahl, Joe; Damjanovic, Dragan; Rödel, Jürgen; Effect
of K0.5Na0.5NbO3on Properties at and off the Morphotropic Phase Boundary in
Bi0.5Na0.5TiO3–Bi0.5K0.5TiO3Ceramics, JAPANESE JOURNAL OF APPLIED PHYSICS, 50
(5) 055802.1-055802.7. ISSN 0021-4922
Kwon, O-Jong; Jo, Wook; Ko, Kyeong-Eun; Kim, Jae-Yeol; Bae, Sung-Hwan; Koo,
Hyun; Jeong, Seong-Min; Kim, Jin-Sang; Park, Chan; Thermoelectric properties and
texture evaluation of Ca3Co4O9 prepared by a cost-effective multisheet cofiring technique,
JOURNAL OF MATERIALS SCIENCE, 46 (9) pp. 2887-2894. ISSN 0022-2461
Marsilius, Mie; Granzow, Torsten; Jones, Jacob L.; Quantitative comparison between the
degree of domain orientation and nonlinear properties of a PZT ceramic during electrical and
mechanical loading, JOURNAL OF MATERIALS RESEARCH, 26 (09) pp. 1126-1132. ISSN
0884-2914
Frederick, Joshua; Tan, Xiaoli; Jo, Wook; Strains and Polarization During
Antiferroelectric-Ferroelectric Phase Switching in
Pb0.99Nb0.02[(Zr0.57Sn0.43)1−yTiy]0.98O3 Ceramics, JOURNAL OF THE AMERICAN
CERAMIC SOCIETY, 94 (4) pp. 1149-1155. ISSN 00027820
Guillon, Olivier; Partial Constrained Sintering of Ceramic Layers on Metallic Substrates: A
Comparison Between Modeling and Experiments, JOURNAL OF THE AMERICAN CERAMIC
SOCIETY, 94 (4) pp. 1040-1045. ISSN 00027820
Ceramics Group
21
Leist, Thorsten; Webber, Kyle G.; Jo, Wook; Granzow, Torsten; Aulbach, Emil; Suffner,
Jens; Rödel, Jürgen; Domain switching energies: Mechanical versus electrical loading in Ladoped bismuth ferrite–lead titanate, JOURNAL OF APPLIED PHYSICS, 109 (5) 054109-1.
ISSN 00218979
Schmitt, Ljubomira A.; Kling, Jens; Hinterstein, Manuel; Hoelzel, Markus; Jo, Wook;
Kleebe, Hans-Joachim; Fuess, Hartmut; Structural investigations on lead-free
Bi1/2Na1/2TiO3-based piezoceramics, JOURNAL OF MATERIALS SCIENCE, 46 (12) pp.
4368-4376. ISSN 0022-2461
Dittmer, Robert; Jo, Wook; Damjanovic, Dragan; Rödel, Jürgen; Lead-free hightemperature dielectrics with wide operational range, JOURNAL OF APPLIED PHYSICS, 109
(3) 034107-1. ISSN 00218979
Luo, Zhenhua; Glaum, Julia; Granzow, Torsten; Jo, Wook; Dittmer, Robert; Hoffman,
Mark; Rödel, Jürgen; Bipolar and Unipolar Fatigue of Ferroelectric BNT-Based Lead-Free
Piezoceramics, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 94 (2) pp. 529-535.
ISSN 00027820
Marsilius, Mie; Granzow, Torsten; Jones, Jacob L.; Effect of electrical and mechanical
poling history on domain orientation and piezoelectric properties of soft and hard PZT
ceramics, SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS, 12 (1) 015002. ISSN
1468-6996
Simons, Hugh; Daniels, John; Jo, Wook; Dittmer, Robert; Studer, Andrew; Avdeev,
Maxim; Rödel, Jürgen; Hoffman, Mark; Electric-field-induced strain mechanisms in leadfree 94%(Bi[sub 1/2]Na[sub 1/2])TiO[sub 3]–6%BaTiO[sub 3], APPLIED PHYSICS
LETTERS, 98 (8) 082901-1. ISSN 00036951
Jo, Wook; Daniels, John E.; Jones, Jacob L.; Tan, Xiaoli; Thomas, Pamela A.;
Damjanovic, Dragan; Rödel, Jürgen; Evolving morphotropic phase boundary in lead-free
(Bi[sub 1/2]Na[sub 1/2])TiO[sub 3]–BaTiO[sub 3] piezoceramics, JOURNAL OF APPLIED
PHYSICS, 109 (1) 014110-1-014110-7. ISSN 00218979
Langer, Jochen; Hoffmann, Michael J. Guillon, Olivier; Electric Field-Assisted Sintering in
Comparison with the Hot Pressing of Yttria-Stabilized Zirconia, JOURNAL OF THE
AMERICAN CERAMIC SOCIETY, 94 (1) pp. 24-31. ISSN 00027820
McKie, Amanda; Winzer, Jami; Sigalas, Iakovos; Herrmann, Mathias; Weiler, Ludwig;
Rödel, Jürgen; Can, Nedret; Mechanical properties of cBN–Al composite materials,
CERAMICS INTERNATIONAL, 37 (1) pp. 1-8. ISSN 02728842
Jo, Wook; Ollagnier, Jean-Baptiste; Park, Jong-Lo; Anton, Eva-Maria; Kwon, O-Jong;
Park, Chan; Seo, Hyun-Ho; Lee, Jong-Sook; Erdem, Emre; Eichel, Rüdiger-A.; Rödel,
Jürgen; CuO as a sintering additive for (Bi1/2Na1/2)TiO3–BaTiO3–(K0.5Na0.5)NbO3 leadfree piezoceramics, JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 31 (12) pp. 2107217. ISSN 09552219
22
Ceramics Group
Stress-Dependent Phase Transitions in Perovskite Ferroelectrics
Dr. Kyle Webber
Perovskite ferroelectrics are commercially important materials, which are widely used as
actuators, sensors, and transducers. Discovered almost 70 years ago, barium titanate
(BaTiO3) is an important material for discrete and multilayer capacitors because of its high
relative dielectric permittivity. BaTiO3 has received renewed interest as an end member in
novel large unipolar strain lead-free ferroelectrics, such as (1-x-y)(Bi1/2Na1/2)TiO3–
xBaTiO3–y(K0.5Na0.5)NbO3. Recent governmental regulations in Europe and elsewhere
strictly limiting the use of toxic materials have driven the search for environmentally
friendly alternatives.
BaTiO3 undergoes three well-known first order structural phase transitions. Previous
experimental investigations on stress-dependent phase transitions have primarily focused
on the effect of hydrostatic and radial pressure on the dielectric properties and the Curie
point of single crystal and polycrystalline BaTiO3. An increasing hydrostatic pressure was
found to destabilize the lower symmetry phase, leading to a linear decrease in the Curie
point. Conversely, radial compression perpendicular to the polarization stabilized the polar
order, which was found to result in a nonlinear increase in the Curie point. There have,
however, been comparatively few studies on the influence of uniaxial pressure. [1, 2]
The present study focused on the effect of uniaxial compressive stress-dependent
tetragonal-cubic phase transformation behavior of unpoled, single crystal and
polycrystalline BaTiO3. During experimentation the real part
of the relative dielectric
permittivity was determined as a function of temperature and uniaxial stress. In the
unloaded state both single crystal and polycrystalline BaTiO3 displayed permittivitytemperature behavior consistent with previous investigations; an increasing temperature
resulted in an initial decrease in permittivity, followed by a subsequent peak in permittivity
occurring at the Curie point. The Curie point (TC) of both polycrystalline and single crystal
BaTiO3 was observed to rise with increasing mechanical compressive stress with a rate of
0.05 and 0.19 °C/MPa, respectively (Fig 1a). In addition, a comparable shift in the CurieWeiss temperature (was also observed to be -0.1 and -0.19 °C/MPa for polycrystalline and
single crystal samples, respectively (Fig 1b)).
Previous researchers have assumed that the Curie-Weiss temperature was stress
independent, which is typically done to determine the shift of the Curie point with stress.
 is of the
TC for single crystal BaTiO3, strongly indicating that the effect cannot be
neglected. This necessitates the rethinking of current theories on the effect of external fields
on the phase transformation behavior of perovskite ferroelectrics.
Ceramics Group
23
20
Single Crystal
Polycrystal
15
0
(a)
(b)
-5
10
 (°C)
Tc (°C)
-10
5
-15
-20
-25
-30
0
0
50
-35
100 150 200 250 300
0
Compressive Stress (MPa)
50
100 150 200 250 300
Compressive Stress (MPa)
Figure 1. Shift of Curie point Tc (a) and Curie-Weiss temperature  (b) of single crystal (red squares) and
polycrystalline (blue circles) BaTiO3 due to uniaxial mechanical compressive stress.
This is particularly significant for ferroelectric thin films, where in-plane strains are large
enough to generate new phases [3] and induce ferroelectricity [4], as well as sensors,
transducers, and actuators, where mechanical preloads can be significant. From an
expansion of the free elastic Gibbs energy density in terms of polarization (LandauGinsburg-Devonshire formalism) an expression for the shift of the Curie point and CurieWeiss temperature for a single tetragonal ferroelectric domain can be found
(
)
[
(
)
]
(1)
where
is the permittivity of free space, C is the Curie constant, Q12 and Q11 are
components of the electrostriction tensor, and X is the extensional stress. Interestingly, from
Cshear stresses.
An additional consequence of the stress-dependent phase transition behavior in
ferroelectrics is that the first Landau coefficient in the Gibbs free energy, i.e., the linear
dielectric stiffness, becomes stress dependent. Typically, this coefficient is defined as
(
)⁄
(2)
which assumes that is independent of both electric field and stress. An extension of this
classical definition is proposed to account for the effects of stress on the free energy density
of a ferroelectric domain, such that
(3)
24
Ceramics Group
where is the applied stress and
stress.
is a constant that accounts for the dependence of
on
Additional experimental and analytical work is required to determine the form and the
magnitudes of . A primary experimental difficultly is the measurement of temperature
dependent dielectric behavior with a stress applied parallel to the polarization direction. An
increasing temperature results in the decrease of the ferroelastic coercive stress, which
leads to eventual switching of the polarization perpendicular to the applied stress. Planned
future investigations include the inclusion of Equation (3) into a FEM-based phase field
model to study the effects on domain wall translation.
References:
[1] Takagi, Y, E Sawaguchi, and T Akioka, On the Effect of Mechanical Stress upon the Permittivity of
Barium Titanate. Journal of the Physical Society of Japan, 3(4): 270-271 (1948)
[2] Suchanicz, J, et al., Uniaxial Pressure Effect on the Dielectric Properties of the BaTiO3 Single
Crystals. Ferroelectrics, 366(1): 3-10 (2008)
[3] Zeches, RJ, et al., A Strain-Driven Morphotropic Phase Boundary in BiFeO3. Science, 326(5955):
977-980 (2009)
[4] Haeni, JH, et al., Room-temperature ferroelectricity in strained SrTiO3. Nature, 430(7001): 758761 (2004)
Ceramics Group
25
Electronic Materials
The department Electronic Materials 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 electronics. Three major research topics
are presently addressed:



Electronic and optoelectronic properties of organic semiconductors.
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. Beside 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.
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 (phos26
Electronic Material Properties
phors) 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:Eu2+ 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. Graham Appleby
Dr.-Ing. Andrea Gassmann
Dr. Joachim Hillenbrand
Dr. Christian Melzer
Dr. Chandra Suman
Dr. Sergey V. Yampolskii
Dr. Sergej Zhukov
Dr.-Ing. Jörg Zimmermann
Technical Personnel
Gabriele Andreß
Sabine Hesse
Helga Janning
Bernd Stoll
Secretary
Gabriele Kühnemundt
PhD Students
Dipl.-Ing. Eva Feldmeier
Dipl.-Ing. Lorenz Kehrer
Dipl.-Phys. Oliver Ottinger
M. Sc. Oili Pekkola
Dipl.-Phys. Jörg Schütrumpf
Dipl.-Ing. Katja Stegmaier
Dipl.-Ing. Tobias Könyves-Toth
M. Sc. Dan Walker
Diploma Students
Paul Mundt
Elmar Kersting
Lars Riekehr
Tobias Weiher
Stefan Winter
Guest Scientists
Prof. Ivan H. Bechtold
Dr. Gregorio Coutò Faria
Prof. Dr. Sergei Fedosov
Prof. Dr. Lucas F. Santos
Chung-Hwa Wang
27
Research Projects
Fatigue of organic semiconductor components (SFB (DFG), 2003-2014)
Phenomenological modelling of bipolar carrier transport in organic semiconducting devices
under special consideration of injection, transport and recombination phenomena (SFB
(DFG), 2003-2014)
Polarization and charge in electrically fatigued ferroelectrics (SFB (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)
Tetracene based materials for OFET and OLED applications (Förderkennzeichen: Patent
Portfolio “Organic semiconductors”, IPB, 2008-2011)
Charge carrier injection and transport in doped organic light-emitting diodes (TOPAS,
BMBF-OSRAM OS, 2009-2011)
Influence of oxygen and water on the optical properties of the x-ray storage phosphor
CsBr:Eu2+ (DFG, 2009-2011)
Development of fibre-based organic semiconductor devices for textile applications
(LUMOLED, BMBF/ VDI/ VDE/ IT, 2010-2012)
Publications
G. A. Appleby, J. Zimmermann, S. Hesse, and H. von Seggern, Photoluminescence and
photostimulated luminescence of oxygen impurities in CsBr, JOURNAL OF APPLIED PHYSICS
109 (2011), 013507.
S. Zhukov, S. Fedosov, H. von Seggern, Piezoelectrets from sandwiched porous
polytetrafluoroethylene (ePTFE) films: influence of porosity and geometry on charging
properties, J. Phys. D: Appl. Phys. 44 (2011), 105501.
S. Zhukov, S. Fedosov, H. von Seggern, Importance of geometry and breakdown field on the
piezoelectric d33 coefficient of corona charged ferroelectret sandwiches, JOURNAL OF PHYSICS
D: APPLIED PHYSICS 44 (2011), 105501.
C. Koughia, A. Edgar, C. R. Varoy, G. Okada, H. von Seggern, G. Belev, C. Y. Kim, R.
Sammynaiken, S. Kasap, Samarium-doped fluorochlorozirconate glass-ceramics as redemitting x-ray phosphors, JOURNAL OF THE AMERICAN CERAMIC SOCIETY 94 (2011),
543-550.
G. A. Appleby, P. Kroeber, J. Zimmermann, and H. von Seggern, Influence of oxygen doping
and hydration on photostimulated luminescence of CsBr and CsBr:Eu2+, J. Appl. Phys. 109
(2011), 073510.
28
S. V. Yampolskii, Y. A. Genenko, C. Melzer, H. von Seggern, Self-consistent model of unipolar
transport in organic semiconductor diodes: Accounting for a realistic density-of-states
distribution, JOURNAL OF APPLIED PHYSICS 109 (2011), 073722.
E. J. Feldmeier, C. Melzer, Multiple colour emission from an organic light-emitting transistor,
ORGANIC ELECTRONICS 12 (2011) 1166–1169.
C. Koughia, G. Okada, D. Tonchev, S. Kasap, A. Edgar, C. R. Varoy, H. von Seggern, Optical
and selected thermal properties of samarium-doped fluorochlorozirconate (FCZ) glass-ceramics:
Formation and growth of BaCl2 nanocrystals in FCZ glass-ceramics, JOURNAL OF NONCRYSTALLINE SOLIDS 357 (2011), 2272-2277.
K. Stegmaier, A. Fleissner, H. Janning, S. Yampolskii, C. Melzer, H. von Seggern, Influence
of electrical fatigue on hole transport in poly(p-phenylenevinylene)-based organic lightemitting diodes, JOURNAL OF APPLIED PHYSICS 110 (2011) 034507.
G. C. Faria, R. M. Faria, E. R. deAzevedo, H. von Seggern, Temperature dependence of the
drift mobility of poly(9,9'-dioctylfluorene-co-benzothiadiazole)-based thin-film devices,
JOURNAL OF PHYSICAL CHEMISTRY C 115 (2011), 25479-25483.
29
Oxygen-related threshold voltage shifts in thiophene-based field-effect transistors
Lorenz A. Kehrer, Christian Melzer and Heinz von Seggern
10
-4
10
-4
10
-5
10
-5
10
-6
10
-6
10
-7
10
-7
10
-8
10
-9
10
-8
10
-9
10
-10
(1) Dark
(2) Illuminated
(3) Illuminated
(4) Dark
(5) Illuminated
(6) Dark
-40 -30 -20 -10
a)
ID (A)
ID (A)
Printed organic electronic circuits have a great potential as low cost electronics for everyday
use, e.g., in radio frequency identification tags. One of the most investigated and promising
material for such application is poly(3-hexylthiophene) (P3HT) which exhibits electrical
instabilities caused by gases, humidity or light. Such instabilities may be useful for sensing
applications, but hamper the reliability of organic devices. E.g. illuminating top-gated
P3HT-based p-type organic field-effect transistors (OFETs) in electron accumulation mode
in the visible spectral range results in a substantial threshold voltage shift Vth and an
increase in the off-current by about three orders of magnitudes. Both phenomena require
the presence of oxygen and are persistent for days at room temperature. The origin of this
long-lasting instability is attributed to traps which are induced in the semiconductor by
oxygen incorporation creating a charge-transfer-complex (CTC) of oxygen and P3HT [1].
The illumination of the devices in electron accumulation with wavelengths in the range of
the fundamental absorption of P3HT (< 650 nm) is sufficient for an optical filling of
those traps by electrons. This electron trapping shifts the threshold voltage and increases
the doping level by accumulation of charge compensating holes. The optically induced
instabilities of P3HT-based organic FETs are illustrated in figure 1.
0
VG (V)
10
20
30
10
40
-10
(1) Dark
(2) Illuminated
(3) Illuminated
(4) Dark
(5) Illuminated
(6) Dark
-40 -30 -20 -10
b)
0
10
20
30
40
VG - Vth (V)
Figure 1: a) Forward and backward sweeps of transfer curves of the OFETs recorded at VD = -20 V with and
without white-light illumination. The OFETs exhibit a W/L ratio of 1000 and were exposed to oxygen by
storing them in ambient conditions before measuring the transfer curves in a nitrogen-filled glovebox.
Under illumination in electron accumulation an essential shift of the threshold voltage can be observed. b)
Forward sweeps of the same transfer curves where the applied gate voltages have been corrected by the
respective threshold voltages changes.
Figure 1a shows that the P3HT-based thin-film transistors are stable in the dark (curve 1)
and under illumination as long as the transistor is operated in hole accumulation, i.e, at
negative gate bias (curve 2). By applying positive gate biases (electron accumulation) and
by additionally illuminating the devices with visible light, the transfer characteristics start
to alter for successive measurement cycles (curve 3). In particular two effects are identified
which can be associated to the aforementioned instability mechanism: The off-current
increases by about three orders of magnitude and the drain current shifts to positive gate
voltages. These effects are stable during the following measurements performed in the dark
(curve 4). The slight decrease in the off-current is due to the missing photo current in the
30
dark (curve 4). A second sweep under illumination (curve 5) creates the same changes as
the first sweep under illumination, but the impact on the change of the device
characteristics is much weaker. While the first sweep under illumination shifted the
threshold voltage from -3.8 V to +15.6 V (Vth = 19.4 V), the second illumination step
shifts the threshold voltage only from +15.6 V to +17.9 V (Vth = 2.3 V). After four
illumination steps the changes are already saturated.
In figure 1b the same transfer characteristics are replotted as a function of the effective gate
voltage (VG-Vth) where VG has been corrected by the respective threshold voltage Vth
obtained for the individual cycles. The result demonstrates that the only effects observed
are a light-induced threshold voltage shift and an increase in the off-current while the
resulting field-effect mobility remains unchanged. The drain currents are identical in the
on-regime (VG-Vth<0), but differ by about three two orders of magnitude in the off-regime
(VG-Vth>0). The fact that mainly a positive threshold voltage shift is induced suggests that
trapped electrons are introduced by the optical treatment at positive gate biases. Since
negative charges in the bulk will be compensated by mobile holes a p-doping of the P3HT
results thereby increasing the off-current of the transistor. The long lasting decay of the
doping also suggests that a fast recombination of both carrier species does not occur.
By storing identical transistors under different environmental conditions, we investigated
the origin of the remanent charge carriers. Therefore two sets of transistors were processed
with two different 500 nm thick insulators each consisting of Polymethylmethacrylate
(PMMA) and PIC01, an insulator provided by PolyIC, respectively. One set was stored
under ambient conditions and the second set was stored under oxygen-free conditions
inside a nitrogen-filled glovebox. After one week all devices were characterized in the
glovebox to avoid any additional oxygen contamination. Figure 2 illustrates the evolution of
the threshold voltages on the storage conditions. At first, Vth is determined in the dark for
the two storage conditions in order to avoid additional trapping. In this initial state the
devices with PMMA show a positive threshold voltage and the devices with PIC01 show a
negative one. In both cases the absolute values of |Vth| are smaller than 5 V. Since this
behavior was observed for all studied transistors it can be concluded that the utilized
insulator is partially responsible for the threshold voltage of the individual P3HT-based
devices. After four measuring cycles of the transfer characteristic under illumination a
positive threshold voltage shift of more than 10 V has been observed for all transistors
stored under ambient conditions and a weaker threshold shift of < 5 V for all transistors
stored in the nitrogen atmosphere.
From those results it seems reasonable to assign the shift of Vth to the already mentioned
oxygen-induced charge-transfer states, whose amount is reduced after long term storage in
the glovebox due to diffusion of oxygen out of the device [2]. In field-effect transistors the
amount of trapped charges ntr can be estimated from the areal capacitance of the gate
dielectric Ĉ and the threshold voltage shift Vth according to the following equations:
Cˆ  Vth

and Cˆ  0
ntr 
d
e
where all the used quantities assume there common meaning. With a gate insulator
thickness d = 500 nm and a dielectric constant = 3.5 the areal capacitance is calculated
to 6.2∙10-9 F/cm². Taking the observed threshold voltage shift of about Vth = 10 V we can
determine a trapped or remanent charge density of 4  1011 cm-2 localized at the P3HToxygen charge-transfer complexes at the dielectric/ P3HT interface.
31
Insulator / Storage atmosphere
20
PIC01 / Ambient
PIC01 / Nitrogen
PMMA / Ambient
PMMA / Nitrogen
15
Vth (V)
10
5
0
te d
na
mi
I l lu
(3)
60
0s
@
mi
I l lu
(2)
(4)
na
75
te d
e
tat
ls
tia
Ini
(1 )
°C
Treatment steps
-5
Figure 2: Vth of the differently
stored transistors with PMMA and
PIC01 as insulating materials as a
function
of
the
following
treatments. (1): after exposure to
ambient conditions and nitrogen in
the nitrogen filled glovebox. (2):
after four illumination steps under
nitrogen
atmosphere
directly
following (1). (3): after a heating
step of 600 s at 75 °C directly
following (2). (4): after four
additional illumination steps in
nitrogen directly following (3). All
treatments were performed within
one hour in the nitrogen filled
glovebox.
By increasing the temperature the temporal decay of the optically-induced threshold
voltage shift can be accelerated. Keeping the devices with the two different gate insulators
for 600 s at 75 °C is sufficient to completely remove the light-induced threshold voltage
shifts. As presented in figure 2 a heating step at 75 °C for 600 s in an oxygen-free
atmosphere shifts Vth back to its initial value independent on the storage conditions or the
gate insulator. After having released the trapped electrons and thereby removing the
induced shift of the threshold voltage, it is possible to recharge the devices by an
illumination step in the glovebox. This is an indication of the long term stability of the
P3HT-oxygen complexes in the system and it demonstrates that these complexes can be
charged and discharges reversibly. We want to clearly point out that the relaxation of the
optically induced threshold voltage shift itself takes a few days and is much faster than the
diffusion of oxygen out of the device, which takes a couple of weeks [2]. At elevated
temperatures, e.g. 75 °C, it requires hours to reduce the saturation value of the possible
threshold voltage back to its initial value. Therefore the discharging of the relevant traps is
significantly shorter than the loss of trap sites by oxygen diffusion out of the active layer.
For practical applications, like P3HT-based logic elements it has to be stated that the
discussed oxygen-induced instability is relevant cases where the FETs are held in the offstate in ambient conditions and under light exposure. Under these operational conditions a
substantial electric field exists inside the P3HT layer and illumination leads to the
investigated changes in the FET characteristics affecting the functionality of the employed
logic circuits.
References:
[1] M. S. A. Abdou, F. P. Orfino, Y. Son, and S. Holdcroft, Journal of the American Chemical Society, 1997,
119, 4518-4524.
[2] L. A. Kehrer, S. Winter, R. Fischer, C. Melzer, and H. von Seggern, Synthetic Metals, 2012, 161, 2558 – 2561.
32
Influence of oxygen and water on photostimulated luminescence of CsBr
and CsBr:Eu2+
J. Zimmermann, G. A. Appleby, P. Kroeber, and H. von Seggern
CsBr:Eu2+ storage-phosphor is of interest for radiography applications as it can be grown in
the form of needle structured imaging with higher spatial resolution compared to
commercial X-ray imaging plates. In a storage phosphor irradiation generates electron-hole
pairs, where the electrons are stored as metastable F-centers and the holes are trapped
adjacent to the Eu2+-ions. The spatial distribution of the filled traps represents a latent
image of the imaging object. The x-ray image is read out by photostimulation with visible
light which frees the electrons from the F-centers leading to recombination with the
trapped holes. The recombination energy is transferred to Eu2+-ions which emit the so
called photostimulated luminescence (PSL) whose intensity as a function of the spatial
location of the exciting laser beam forms the radiograph.
Oxygen is a natural impurity in CsBr and it contributes to the PSL-process. Water influences
the PSL yield drastically if Eu2+ is involved. Enhancement of the PSL yield of CsBr:Eu2+
have been observed following simple hydration of CsBr:Eu2+ at room temperature, which
can increase the PSL efficiency of a dry sample by up to a factor of 25 [1]. It is proposed
that the Eu2+ ions are not attracting holes without water, which could be explained by a
missing compensation for the divalent Europium ion e. g. by O2- or a Cs-vacancy adjacent to
Eu2+, and thus the coulombic repulsion of electrons.
We investigated the effect of oxygen concentration on the PL and PSL properties of CsBr:O2and CsBr:Eu2+,O2-, as well as the effect of hydration on these materials.
CsBr purified from oxygen were doped with CsOH.xH2O and in a second step hydrogen was
removed by calcinating the resultant CsBr:OH- together with NH4Br. CsBr:Eu2+,O2- samples
were prepared by doping CsBr:O2- with 0.5 mol% EuBr2 or EuBr3.xH2O and dried, sintered
and annealed.
To study the effects of hydration on CsBr:Eu2+,O2-, samples were exposed to an atmosphere
of 99% relative humidity for hydration times of 10 to 60 minutes. To investigate the
stability of the PSL enhanced CsBr:Eu2+,O2- (hereafter referred to as CsBr.xH2O:Eu2+,O2-)
powdered samples were exposed to different annealing temperatures.
Reduced CsBr and CsBr:O2- show a single Gaussian PSL-emission peak at 460 nm (Fig. 1) as
reported in [2] for low oxygen concentrations. CsBr:O2- with oxygen concentrations of 0.04
to 0.05 mol% show a second peak at 379 nm which increases in intensity with increasing
oxygen concentration. At oxygen concentrations larger than 0.1 mol%, this peak completely
dominates the PSL emission. It arises from the CsBr matrix as it is also seen in the PL
spectra of reduced CsBr in [2]. With low oxygen concentrations, the PSL process leads to
emission from the luminescent oxygen ions. In the case of high oxygen concentrations the
formation of oxygen agglomerates are considered to take place which are no longer
stimulable by the electron hole decay. Therefore this energy is transferred to the CsBr
lattice, stimulating luminescence from the lattice rather than from the oxygen ions
themselves.
33
Fig. 1 PSL emission spectra for powdered
CsBr:O2- samples following irradiation at
300 K and stimulated at 690 nm.
Fig. 2 F-center absorption spectra for powdered CsBr:O2samples following irradiation at 300 K. Inset: FWHM of
these absorption spectra.
Absorption measurements of x-irradiated CsBr:O2- (Fig. 2) consist of the well-known Fcenter of CsBr at 690 nm. It can be seen that the F-center concentration increases up to a
concentration of 1.00 mol% oxygen, and then decreases with higher concentrations. The
incorporated divalent oxygen impurities are charge compensated in the monovalent CsBr
matrix by bromide-vacancies, which form F-centers during irradiation. The absorption of
these oxygen generated F-centers is perturbed by the nearby oxygen ions which leads to the
broadening of the spectra indicated by the increasing FWHM of the spectra with increasing
oxygen concentration (inset to Fig. 2). With the relatively high oxygen concentration of
5.00 mol%, both the F-center concentration and the FWHM decreases, which we attribute
to agglomeration.
As prepared dry powdered samples of CsBr:Eu2+,O2- are yellow in color and exhibit only
weak PSL. There is no significant influence of oxygen concentration on the PSL emission
intensity for dry samples. After exposure to air for 5 min to 60 min, the samples become
white while the PSL intensity remains unchanged. Following hydration for 10 min to 60
min the PSL intensity increases by up to a factor of 25 [1]. PSL emission intensity of
CsBr:Eu2+ and CsBr:Eu2+,O2- increase strong following hydration for 40 min, while the
effect of oxygen concentration on the PSL intensity of CsBr:Eu2+,O2- is that the PSL
intensity is slightly higher with concentrations up to 0.05 mol%, and decreases with
increasing oxygen concentrations (Fig. 3).
Fig. 3 PSL emission intensity of powder and pellet
samples of CsBr.H2O:Eu2+,O2- following hydration
and then annealing for 30 min at various
temperatures. The dashed line indicates the PSL
intensity of the samples prior to hydration. All
data was recorded at 300 K.
34
Fig. 4 PL emission intensity of Eu2+ excited at 254
nm and the CsBr matrix emission excited at 200
nm for CsBr.H2O:Eu2+,O2- following hydration and
then annealing at various temperatures. The
dotted line indicates the PL intensity of Eu2+ prior
to hydration while the dashed line indicates the
PL intensity of the CsBr matrix prior to hydration.
All data was recorded at 300 K.
The increase in PSL emission intensity in samples with up to 0.05 mol% oxygen doping
most likely is due to formation of oxygen correlated anion vacancies which ease the
formation of F-centers during x-irradiation. Despite the increase in F-center generation up
to 1.00 mol% of oxygen as shown in Fig. 2 the anion vacancies density created by the 0.05
mol% seem to be sufficient for the normally applied x-ray doses. With higher oxygen
concentrations the subsequent decrease in PSL emission is probably caused by competition
between O2- and Eu2+ luminescence centers following photostimulation.
In both cases, oxygen free and oxygen containing CsBr:Eu the water molecules enhance the
PSL sensitivity, but they can be removed at higher temperatures. Fig. 4 shows the evolution
of the 379 nm intrinsic emission of the CsBr matrix during annealing (stimulated at 200
nm). The loss of PL and PSL emission from Eu2+ following high temperature annealing is
considered to be initially due to the driving out of the tightly bound water molecules which
form (Eu2+-H2O)-complexes whereat H2O sits in an Cs vacancy adjacent to Eu2+ [3], and
finally due to the migration and agglomeration of the now highly mobile Eu2+-ions in
which concentration quenching of luminescence occurs. This removal of a homogeneous
distribution of Eu2+-ions from the matrix is also likely to be the cause of the reappearance
of the luminescence emission from the CsBr matrix. Further hydration of these annealed
CsBr.xH2O:Eu2+,O2- samples is unable to restore the PSL activity, indicating that the
thermal annealing and associated quenching of PSL emission in CsBr.H2O:Eu2+,O2- is an
irreversible process.
It can be concluded that strong PSL from CsBr:Eu2+,O2- samples is only observable
following exposure to moisture, probably due to the creation of dipoles of Eu2+ and a Cs
vacancy with a trapped H2O molecule. It was demonstrated that oxygen doping in
CsBr:Eu2+ and subsequent hydration initially improves the PSL efficiency by a small factor
due to an increase in F-center concentration, however, oxygen of higher concentratian
compete with the Eu2+ and ultimately decrease the PSL considerably.
References:
[1] G. A. Appleby, J. Zimmermann, S. Hesse, O. Karg, and H. von Seggern, J. Appl. Phys. 105, 2009,
073511.
[2] G. A. Appleby, J. Zimmermann, S. Hesse, and H. von Seggern, J. Appl. Phys., 109, 2011,
013507.
[3] H. Vrielinck, F. Loncke, J.-P. Tahon, P. Leblans, P. Matthys, F. Callens, Phys. Rev. B 83, 2011,
054102.
35
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, electron
diffraction, ion scattering, 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.
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.
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.
36
Surface Science
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. Wolfram Calvet
Dr. Feng Chen
Dr. Gennady Cherkashinin
Dr. Lucangelo Dimesso
Dr. Xianjin Feng
Dr. René Hausbrand
Dr. Alexander Issanin
Dr. Susanne Jacke
PD Dr. Bernhard Kaiser
Apl. Prof. Dr. Andreas Klein
Dr. Quanbao Ma
Dr. Thomas Mayer
Dr. Robert Schafranek
Dr. Hermann-Josef Schimper
Dr. Krishnakumar Velappan
Technical Personnel
Vitaliy Bezkorovaynyy
Dipl. Ing. Erich Golusda
Kerstin Lakus-Wollny
Dr. Lorenz Nedelmann
Andreas Swirschuk
Christina Spanheimer
Secretaries
Marga Lang
PhD Students
Tobias Adler
Alireza Barati
Thorsten Bayer
Dirk Becker
Andreas Decker
Murugasen Eswaran
Eduard Feldmeier
Dominic Fertig
Anne Fuchs
Jürgen Gassmann
Cosmina Ghinea
Corinna Hein
René Hock
Johannes Türck
Jürgen Ziegler
Mareike Hohmann
Shunyi Li
Julia Maibach
Eric Mankel
Andreas Naumann
Thi Thanh Dung Nguyen
Karsten Rachut
Judith Schaffner
Stefan Schmid
Anja Schneikart
Andrè Schwöbel
Sebastian Siol
André Wachau
Karsten Rachut
Diploma Students
Aiko Bünting
Jan Morasch
Markus Motzko
Silvia Vestweber
Mirko Weidner
Guests
Jenna Curry
Jonas Deuermeier
Gaku Imamura
Dr. Mikhail V. Lebedev
Lauren Stützman
Surface Science
37
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)
Transparent organic phosphorescent devices for application in lighting systems (Osram
2009-2011)
Gradients in Cu(In,Ga)Se2 thin film solar cells (BMBF 2009-2012)
P-I-N solar cells with alternative highly-absorbing semiconductors (BMBF 2010-2013)
LOEWE Schwerpunkt AdRIA (LOEWE-Hessen: 2008-2011)
Nanostruktursysteme zur Licht-induzierten Wasserstoffentwicklung („H2-NanoSolar“, BMBF
2009-2012)
Synthese, Charakterisierung und Testung von Katalysatoren für die regenerative Erzeugung
von Wasserstoff („H2ECO2“, Evonik 2010-2012)
Electrochemistry of Surfaces (CSI-DFG, 2008-2012)
Inorganic-organic hybride materials for photovoltaic application (BMBF 2008-2011)
Organic Photovoltaics for Integrated Energy Supply (BMBF 2008-2011)
Morphology and Electronic Structure of Organic/Organic and Organic/Metal-Oxid Hybrid
Systems, Innovation Lab GmbH Heidelberg of the BMBF leading edge cluster Forum
Organic Electronics (BMBF 2009-2012)
n-i-p CdTe Hochleistungs-Dünnschichtsolarzellen: Wissensbasierte
Materialien, Bauelemente und Präparation (BMU 2008-2011)
Optimierung
der
Elektrochemie für Elektromobilität – Verbund Süd (BMBF 2009-2011)
Funktionsmaterialien und Materialanalytik zu Lithium-Hochleistungsbatterien (2009-2011)
Hybridstrukturen aus Phosphoolivinen des Typs LiMPO4 mit C-Nanofilamenten für LiIonen-Batterien, SPP Nanomat (DFG 2008-2012)
Insertionsverbindungen und Elektrolyte für Lithium-Ionenbatterien
Anwendungen, Verbundvorhaben LISA (BMBF 2008-2011)
für
solare
Grenzflächen und dünne Schichten von Ionenleitern: elektronische Struktur,
elektrochemische Potentiale, Defektbildung und Degradationsmechanismen, SFB 595-A3
(DFG 2003-2014)
Herstellung und Charakterisierung von Li-Ionen Dünnschichtbatterien SFB-D5 (DFG 20072011)
9D-Sense Autonomous Nine Degrees of Freedom Sensor Module (BMBF/VDI 2011 – 2014)
Solid State Lithium Batterien mit organischen Kathoden (Novaled 2011 – 2014)
38
Surface Science
Publications
Decker, Andreas Suraru, Sabin-Lucian Rubio-Pons, Oscar Mankel, Eric Bockstedte,
Michel Thoss, Michael Wuerthner, Frank Mayer, Thomas Jaegermann, Wolfram;
Toward Functional Inorganic/Organic Hybrids: Phenoxy-allyl-PTCDI Synthesis, Experimentally
and Theoretically Determined Properties of the Isolated Molecule, Layer Characteristics, and
the Interface Formation of Phenoxy-allyl-PTCDI on Si(111):H Determined by SXPS and DFT
JOURNAL OF PHYSICAL CHEMISTRY C, Vol.115, 21139-21150 DI 10.1021/jp205294h,
NOV 3 2011
Schneider, Joerg J. Khanderi, Jayaprakash Popp, Alexander Engstler, Joerg Tempel,
Hermann Sarapulova, Angelina Bramnik, Natalia N. Mikhailova, Daria Ehrenberg,
Helmut Schmitt, Ljubomira A. Dimesso, Lucangelo Foerster, Christoph Jaegermann,
Wolfram; Hybrid Architectures from 3D Aligned Arrays of Multiwall Carbon Nanotubes and
Nanoparticulate LiCoPO(4): Synthesis, Properties and Evaluation of Their Electrochemical
Performance as Cathode Materials in Lithium Ion Batteries; EUROPEAN JOURNAL OF
INORGANIC CHEMISTRY Vol. 28, 4349-4359 DI 10.1002/ejic.201100217, OCT 2011
Schaffner, Judith Motzko, Markus Tueschen, Alexander Swirschuk, Andreas Schimper,
Hermann-Josef Klein, Andreas Modes, Thomas Zywitzki, Olaf Jaegermann, Wolfram;
12% efficient CdTe/CdS thin film solar cells deposited by low-temperature close space
sublimation JOURNAL OF APPLIED PHYSICS, Vol. 110, 064508, DI 10.1063/1.3639291,
SEP 15 2011
Krishnakumar, V. Han, J. Klein, A. Jaegermann, W., CdTe thin film solar cells with
reduced CdS film thickness THIN SOLID FILMS, Vol.519, 7138-7141, DI 10.1016/j.tsf.
2010.12.118, AUG 31 2011
Zakutayev, Andriy Tate, Janet Xie, Sujing Gibbons, Brady J. Platt, Heather A. S.
Keszler, Douglas A. Barati, Alireza Klein, Andreas Jaegermann, Wolfram, Interdiffusion
at the BaCuSeF/ZnTe interface, THIN SOLID FILMS, Vol. 519, 7369-7373, DI
10.1016/j.tsf.2010.12.125, AUG 31 2011
Schaffner, J. Feldmeier, E. Swirschuk, A. Schimper, H. -J. Klein, A. Jaegermann, W.,
Influence of substrate temperature, growth rate and TCO substrate on the properties of CSS
deposited CdS thin films, THIN SOLID FILMS, Vol. 519, 7556-7559, DI 10.1016/j.tsf.2010.
12.181, AUG 31 2011
Feldmeier, E. M. Fuchs, A. Schaffner, J. Schimper, H. -J. Klein, A. Jaegermann, W.,
Comparison between the structural, morphological and optical properties of CdS layers
prepared by Close Space Sublimation and RF magnetron sputtering for CdTe solar cells
THIN SOLID FILMS, Vol. 519, 7596-7599, DI 10.1016/j.tsf.2011.01.088, AUG 31 2011
Dimesso, Lucangelo Spanheimer, Christina Jacke, Susanne Jaegermann, Wolfram,
Synthesis and characterization of three-dimensional carbon foams-LiFePO(4) composites
JOURNAL OF POWER SOURCES, Vol.196, 6729-6734, DI 10.1016/j.jpowsour.2010.
11.015, AUG 15 2011
Jacke, S. Song, J. Dimesso, L. Broetz, J. Becker, D. Jaegermann, W., Temperature
dependent phosphorous oxynitride growth for all-solid-state batteries JOURNAL OF POWER
SOURCES, Vol. 196, 6911-6914, DI 10.1016/j.jpowsour.2010.12.022, AUG 15 2011
Surface Science
39
Dimesso, Lucangelo Spanheimer, Christina Jacke, Susanne Jaegermann, Wolfram,
Synthesis and characterization of LiFePO(4)/3-dimensional carbon nanostructure composites
as possible cathode materials for Li-ion batteries
IONICS, Vol. 17, 429-435, DI 10.1007/s11581-011-0521-y, JUN 2011
Han, Junfeng Liao, Cheng Jiang, Tao Spanheimer, C. Haindl, G. Fu, Ganhua
Krishnakumar, V. Zhao, Kui Klein, A. Jaegermann, W., An optimized multilayer structure
of CdS layer for CdTe solar cells application JOURNAL OF ALLOYS AND COMPOUNDS, Vol.
509, 5285-5289, DI 10.1016/j.jallcom.2010.12.085, APR 28 2011
Dimesso, Lucangelo Jacke, Susanne Spanheimer, Christina Jaegermann, Wolfram,
Investigation on 3-dimensional carbon foams/LiFePO(4) composites as function of the
annealing time under inert atmosphere, JOURNAL OF ALLOYS AND COMPOUNDS Vol. 509,
3777-3782, DI 10.1016/j.jallcom.2010.12.187, MAR 3 2011
Junfeng Han Spanheimer, C. Haindl, G. Ganhua Fu Krishnakumar, V. Schaffner, J.
Chunjie Fan Kui Zhao Klein, A. Jaegermann, W., Optimized chemical bath deposited CdS
layers for the improvement of CdTe solar cellsSolar Energy Materials and Solar Cells, Vol 95,
816-820, DI 10.1016/j.solmat.2010.10.027, March 2011
Jie Song Jacke, S. Becker, D. Hausbrand, R. Jaegermann, W.; Stabilization of Thin Film
LiCoO 2 Electrode by LiPON Coating Electrochemical and Solid-State Letters, Vol. 14, DI
10.1149/1.3511772, Feb. 2011
Klein, Andreas Siepchen, Bastian Spaeth, Bettina Mankel, Eric Mayer, Thomas
Jaegermann, Wolfram; Resonant photoemission shake-up satellites from semiconductors with
shallow 3d and 4d core levels; PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS,
Vol. 248, 309-313, DI 10.1002/pssb.201046272, FEB 2011
Han, Junfeng Liao, Cheng Jiang, Tao Fu, Ganhua Krishnakumar, V. Spanheimer, C.
Haindl, G. Zhao, Kui Klein, A. Jaegermann, W., Annealing effects on the chemical deposited
CdS films and the electrical properties of CdS/CdTe solar cells, MATERIALS RESEARCH
BULLETIN, Vol. 46, 194-198, DI 10.1016/j.materresbull.2010.11.014, FEB 2011
Song, Jie Jacke, Susanne Cherkashinin, Gennady Schmid, Stefan Dong, Quanfeng
Hausbrand, Rene Jaegermann, Wolfram, Valence Band Offsets of LiPON/LiCoO(2) HeteroInterfaces Determined by X-ray Photoelectron Spectroscopy, ELECTROCHEMICAL AND SOLID
STATE LETTERS, Vol. 14, A189-A191, DI 10.1149/2.006112esl
Schafranek, Robert Li, Shunyi Chen, Feng Wu, Wenbin Klein, Andreas,
PbTiO$_3$/SrTiO$_3$ interface: Energy band alignment and its relation to the limits of Fermi
level variation, Phys. Rev. D, Vol. 84, 045317, doi/10.1103/PhysRevB.84.045317 , 2011 Jul
Pashchanka, Mikhail; Hoffmann, Rudolf C.; Gurlo, Aleksander; Swarbrick, Janine C.;
Khanderi, Jayaprakash; Engstler, Joerg; Issanin, Alexander; Schneider, Joerg J.,
A molecular approach to Cu doped ZnO nanorods with tunable dopant content
DALTON TRANSACTIONS, Vol. 40, 4307-4314, DOI: 10.1039/c0dt01567a, 2011
Schneider, Joerg J.; Hoffmann, Rudolf C.; Issanin, Alexander; Dilfer, Stefan,
Zirconia and hafnia films from single source molecular precursor compounds: Synthesis,
characterization and insulating properties of potential high k-dielectrics
MATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE
MATERIALS, Vol. 176, 965-971, DOI: 10.1016/j.mseb.2011.05.024, AUG 15 2011
40
Surface Science
Hoffmann, Rudolf C.; Differ, Stefan; Issanin, Alexander; Schneider, Joerg J.,
Field-effect transistor performance of zinc oxide thin films derived from molecular based
alkoxyalkyl zinc compounds, PHYSICA STATUS SOLIDI A-APPLICATIONS AND
MATERIALS SCIENCE, Vol. 208, 1708-1713, DOI: 10.1002/pssa.201026694, JUL 2011
C. Pusch, H. Hoche, C. Berger, R. Riedel, E. Ionescu, A. Klein, Influence of the PVD
sputtering method on structural characteristics of SiCN-coatings — Comparison of RF, DC
and HiPIMS sputtering and target configurations, Surface & Coatings Technology 205,
S119 (2011); doi: 10.1016/j.surfcoat.2011.04.095
J Pohl, A Klein, K Albe, Role of copper interstitials in CuInSe2: First-principles calculations
Phys. Rev. B 84, 121201(R) (2011); doi: 10.1103/PhysRevB.84.121201
M.V. Hohmann, P. Ágoston, A. Wachau, T.J.M. Bayer, J. Brötz, K. Albe, A. Klein,
Orientation Dependent Ionization Potential of In2O3: A Natural Source for Inhomogeneous
Barrier Formation at Electrode Interfaces in Organic Electronics, J. Phys.: Cond. Mat. 23,
334203 (2011); doi: 10.1088/0953-8984/23/33/334203
S. Li, C. Ghinea, T. Bayer, M. Motzko, R. Schafranek, A. Klein, Electrical properties of
(Ba,Sr)TiO3 thin films with Pt and ITO electrodes: Dielectric and rectifying behaviour
J. Phys.: Cond. Mat. 23, 334202 (2011); doi: 10.1088/0953-8984/23/33/334202
F. Chen, R. Schafranek, W. Wu, A. Klein, Reduction induced Fermi level pinning at the
interfaces between Pb(Zr,Ti)O3 and Pt, Cu and Ag metal electrodes, J. Phys. D: Appl. Phys.
44, 255301 (2011); doi:10.1088/0022-3727/44/25/255301.
J. Deuermeier, J. Gassmann, J. Brötz, A. Klein, Reactive magnetron sputtering of Cu2O:
Dependence on oxygen pressure and interface formation with ITO, J. Appl. Phys., Vol. 111,
113704 (2011); doi:10.1063/1.3592981
M.I. Ahmad, C. Fasel, T. Mayer, S.S. Bhattacharya, H. Hahn, High temperature stability
of nanocrystalline anatase powders prepared by chemical vapour synthesis under varying
process
parameters,Applied
Surface
Science,
Vol.
257,
6761-6767,
DOI:
10.1016/j.apsusc.2011.02.121, MAY 15 2011
S. Schaefer, A. Petersen, T.A. Wagner, R. Kniprath, D. Lingenfelser, A. Zen, T.
Kirchartz, B. Zimmermann, U. Wuerfel, X. Feng, T. Mayer, Influence of the indium tin
oxide/organic interface on open-circuit voltage, recombination, and cell degradation in
organic small-molecule solar cells,PHYSICAL REVIEW B,
Vol.: 83, 165311, DOI:
10.1103/PhysRevB.83.165311, APR 16 2011
A. Fuchs, H.-J. Schimper, A. Klein, W. Jaegermann, Photoemission Studies on Undoped
SnO2 Buffer Layers for CdTe Thin Film Solar Cells,Energy Procedia, Vol. 10, 149-155,
doi:10.1016/S1876-6102(11)02800-1, 2011
Surface Science
41
Investigations on LiMPO4 (M = Fe, Co, Mn) / carbon foams composites as cathode
materials for Li-ions battery
L. Dimesso, C. Spanheimer, S. Jacke, T.T.D. Nguyen, W. Jaegermann
Since the discovery by Padhi [1], lithium iron phosphate (LiFePO4) is a promising cathode
material due to its good thermal stability, the relatively low costs for synthesis and low
environmental impact [2]. However one of the main drawbacks of olivine LiFePO4 for the
commercial application is its low electronic conductivity and low lithium-ion diffusivity
across the LiFePO4/FePO4 interface [3] during the charge/discharge processes. The purpose
of the investigation is the preparation, characterization and development of new 3Dcomposites as high power cathode materials for Li-ion batteries. Among the new cathode
materials, the transition metals containing phosphates (LiMPO4, with M = Fe, Co, Ni, Mn)
have gained considerable interest. Improvements in energy per unit area and high-rate
discharge capabilities are two of the benefits that may be realized by using 3-D cells. The
use of carbon foams has several advantages: (i) they have low specific resistance (400 –
2500 µΩm); (ii) they allow easier assembly of the positive and negative collectors that
operate together in the battery; (iii) the porosity of the carbon foam allows a greater
infiltration of the electrolyte into the battery leading to a better electrical contact; (iv)
many configurations are possible depending on the particular applications.
The composites have been prepared by using a Pechini-assisted sol-gel process. Detailed
descriptions of the preparation conditions of the composites can be found in [4, 5].
Aqueous solutions containing lithium, metal transitions ions and phosphates have been
prepared, heated up to 80°C and kept at that temperature for 2-4 h. The composites were
prepared by soaking the commercial foams in the starting aqueous solution. After soaking,
the foams were rinsed slightly with water and dried out by heating at 130°C for 24 h in
vacuum.
The micrographs in Figure 1a-b show the morphological surface of the used foams. In the
untreated foam, the porous architecture of the foams with hierarchical pore size
distribution in micro-, meso-, and macropore ranges can be clearly recognized (Figure 1a).
In the previous work the authors observed the presence of numerous apertures, suggesting
that the interior pore system is interlaced and the nanoporous architecture is uniform.
While the carbon serves as an electron conductor, the pores, when filled with liquid
electrolyte, serve as a source of Li+ ions.
Fig. 1: HREM pictures of a) carbon foam
as delivered; b) carbon foam - LiFePO4
composites after annealing at 600°C for
0.4 h prepared by soaking
1A
42
1B
Surface Science
The micrographs of the LiFePO4 / carbon foams composites prepared by soaking and after
annealing at 600°C for 15 minutes under nitrogen are shown in Figure 1b (as example).
The micrograph shows a very homogeneous coating of the foam surface and consequently a
more homogeneous morphology. By soaking, the foam surface is covered by a continuous
layer of liquid in which the Li+, Fe2+ and (PO4)3- ions are uniformly distributed. The slow
evaporation of the solvent leads to a “uniform” layer on the foam surface. After annealing
under nitrogen for 0.4 h, the formation of a uniform layer of crystalline LiFePO 4 can be
observed (Figure 1b).
Voltage (V)
0.2
I (mA)
Fig. 2: a) CV curve recorded
for the composites after
annealing at T 600°C for 10
h; b) discharge profile at
C/25 discharge rate for
composite samples that
were annealed at T = 600°C
for different times
4.0
0.3
3.6
0.1
0.0
st
1ndCycle
2 Cycle
rd
3 Cycle
th
4 Cycle
th
5 Cycle
th
6 Cycle
-0.1
-0.2
-0.3
2.4
2.8
3.2
3.6
4.0
t = 0.4 h
3.2
t = 10 h
2.8
20
0
40
60
80
100
-1
Specific capacity (mAhg )
Voltage (V)
2A
t=5h
2B
The voltammetric curves (CV) for the composites annealed at 600°C for 10 h are shown in
Figure 2a. At high annealing times (t ≥ 5 h), a slight higher peak voltage separation was
observed (0.13V) during the charging and discharging cycles, whereas the first cycle
showed a different shape only. This indicates clearly that the electrochemical kinetics was
improved by the annealing. One of the possible explanations is the low polarization
overpotential leading to higher Li-diffusion rates. This overpotential usually emerges from a
combination of Li-diffusion rates and the intrinsic activation barrier of transferring
electrons which could be high due to the small size of the particles that is to say to the high
interparticle surface. By increasing the annealing time, the growth of the particles is
expected that means a lower interparticle surface, consequently a lower energy barrier for
the Li-diffusion in the composite. Moreover, the presence of a carbon layer on the LiFePO4
as detected by the XPS analysis could improve the electronic conduction leading possibly to
an improvement of the electrochemical processes.
The composites have been prepared into electrodes and cycled at different C-rates ranging
from C/25 to C/2.5. The discharge profiles in Figure 2b have noticeably curved profiles
even at such a low discharge rate of C/25 for t = 0.4 h and t = 10 h respectively. The 3.4 V
voltage drops as the cell discharges due to polarization. On the other site, a less curved
profile can be observed in the sample annealed for t = 5 h confirming the good quality of
the sample.
The experimental data of the LiFePO4 / carbon foams composites (Fe chosen as example)
showed an enhancement of the electrochemical performance of the LiMPO4 systems (M =
Fe, Co, Mn) used as cathode materials.
Surface Science
43
References
[1] A.K. Padhi, K.S. Nanjundaswamy, J.B. Goodenough, Phospho-olivines as positive-electrode
materials for rechargeable lithium batteries, J. Electrochem. Soc. 144 (1997) 1188
[2] D.H. Kim, J. Kim, Synthesis of LiFePO4 nanoparticles and their electrochemical properties, J.
Phys. Chem. Solids 68 (2007) 734
[3] A.S. Andersson, B. Kalska, L. Haggstrom, J.O. Thomas, Lithium extraction/insertion in LiFePO4:
an X-ray diffraction and Mössbauer spectroscopy study, Solid State Ionics 130 (2000) 41
[4] L. Dimesso, C. Spanheimer, S. Jacke, W. Jaegermann, Synthesis and characterization of 3dimensional carbon foams - LiFePO4 composites, (15th IMLB Special Issue), J. Power Sources,
(2011), 196(16), 6729-6734 (doi: 10.1016/j.jpowsour.2010.11.015)
[5] L. Dimesso, S. Jacke, C. Spanheimer, W. Jaegermann, Investigation on 3-dimensional
carbon/LiFePO4 composites as function of the annealing time under inert atmosphere, J. Alloys
Compd. 509 (2011) 3777 - 3782
44
Surface Science
Cathode/electrolyte interfaces in Li-ion batteries: a surface science approach
R. Hausbrand, D. Becker, J. Song, S. Jacke, G. Cherkashinin, and W. Jaegermann
Li-ion batteries are a hot topic of research due to possible applications in the areas of electromobility and micro-electronics. The advantages of Li-ion batteries over conventional batteries are a
comparable high energy density, low self-discharge and long life time. Nevertheless, the envisioned
applications demand more stable batteries with even better performance, i.e. higher energy density
and longer life-time.
Lithium-ion batteries consist of two electrodes (negative and positive, also termed anode and
cathode) separated by an electrolyte, a phase which conducts (Li-) ions but no electrons. During
operation of a Li-ion battery, Li-ions are shuttled from one electrode to the other, passing the
electrode/electrolyte interfaces. In many cases, next to the Li-ion transport, side reactions take place
at these interfaces and interlayers form, leading to degradation of the battery performance, i.e. less
capacity and power capability. Such a side reaction is the oxidation of the electrolyte at the cathode,
contributing to the formation of the solid-electrolyte interface (SEI).
Principally, the interface between an electrode material and an electrolyte is an interface
between a mixed (electron and ion) conductor (electrode) and a pure ion conductor (electrolyte).
Interfaces between two conductors (ionic or electronic) are characterized by the presence of an
electric contact potential caused by the equilibration of the electrochemical potential of mobile
charge carrier species at the interface (see e.g. [1-3]). The contact potential is distributed between
any interfacial dipole layer and a space charge region. The alignment of energy levels (for electrons
or ions, respectively) at the interface depends on the original positions of the energy levels within
the two solids, the position of the chemical potential of the mobile species as well as on the
formation of an interfacial dipole layer. Discontinuities and bending of energy levels at interfaces
constitute energy barriers for charge carriers. Therefore the energy level alignment and shape of
inner electric potential gradient have significant influence on the rate of charge transfer at the
interface.
The electronic energy level alignment between electrolyte and cathode material is of interest
with respect to electron transfer reactions at the interface. In fact, the electronic alignment
determines at which charging level of the cathode a hole transfer to the highest occupied molecular
orbital (HOMO) becomes possible (see [4]). Thus the stability of the interface is determined by the
relative positions of the electronic energy levels at the interface between cathode material and
electrolyte. We believe that the determination of the electronic energy level alignment at the
interface may also allow insights into the transfer resistance of ions at the interface, as it reflects the
contact potential between the two phases (or inner electric potential gradients, respectively).
The contact potential and the electronic energy level alignment, as well as the chemical
structure of the interface, is principally accessible by a surface science approach, i.e.
surface/interface analysis using photoelectron spectroscopy. In such an experiment, the interface is
built-up step by step (e.g. by thin film deposition or low temperature adsorption) and analyzed after
each step. While this methodology is quite elaborate, requiring integrated ultra-high vacuum (UHV)
systems, it offers a wealth of information. Here we report such type of analysis for the interface of
the well-known cathode material LiCoO2, once with an amorphous solid electrolyte (LiPON) [5-6]
and once with a common solvent species (diethyl carbonate, DEC) [7].
For the experiments, RF-sputtered thin film LiCoO2 cathodes were used as substrate, onto
which either LiPON was deposited by RF-sputter deposition or DEC was adsorbed at very low
temperature (nitrogen cooled manipulator). In case of LiPON, the investigation was carried out in
an integrated UHV-system belonging to the surface science group (DaiSy-Mat), XPS-spectra were
recorded using a PHI 5700 spectrometer and monochromatized Al Kα radiation. In case of DEC,
Surface Science
45
the experiment was performed using the SoLiAS station at the BESSY II synchrotron facility. All
spectra were recorded with a kinetic energy of around 100 eV.
When LiPON is deposited onto LiCoO2, its chemical structure differs significantly from the one
in the bulk (fig 1, left), while changes at the surface of LiCoO2 remain minor (not shown). At the
interface, the amorphous electrolyte is rich in triply bound nitrogen, which is taken as sign for a
comparably high Li-ion conductivity in the interfacial layer. Using the binding energy differences
between a core level valence band maxima in the bulk for each material and the binding energy
difference of the two core levels at the interface, the valence band offset was determined to be 1.15
eV and 0.65 eV for LiPON deposited at room temperature and at 200°C, respectively (fig. 1, right).
The dependence of the valence band offset on the deposition temperature can be related to differing
valence band edges of the LiPON, edges in the LiPON, which exhibits a different chemical
structure when deposited at higher temperature. The data indicate that the interfacial dipole
potential is similar for the two deposition temperatures, which may be used in the future to
understand the Li-ion transfer resistance at these interfaces in more detail.
LiPON
LiCoO2
LiCoO2
Anode
1.15 eV at RT
EVB
Decreasing conductivity
Fig. 1: Composition of LiPON (left) and schematic drawing of energy alignment (right) at the LiCoO 2/LiPON interface.
Exposure to DEC-vapor leads physisorbed and chemisorbed/reacted species on the surface of
LiCoO2. Figure 2 shows the carbon signal after an exposition of 0.5L (left) and after the experiment
and subsequent desorption at room temperature. The latter is viewed as signature of the
chemisorbed/reacted species. The data thus clearly indicate chemical interaction between DEC and
LiCoO2.
3
0.5 L
-CH3
3
DesRT
25x10
Intensity [arb. units]
-CH215
O
=
Intensity [arb. units]
20x10
10
-O-C-O5
20
15
10
5
0
0
280
282
284
286
288
290
binding energy [eV]
292
294
296
280
282
284
286
288
290
binding energy [eV]
292
294
296
Fig. 2: SXPS spectra of carbon signal (C1s) after adsorption of DEC (nominally 0,5L, left) and after adsorption of 8L
with subsequent desorption at room temperature (right). The latter can be viewed as the signature of chemisorbed and/or
reacted species
Subsequent exposure leads to an increase in the amount of adsorbed species and to band
bending, illustrated in figure 3 (left) by the decrease of the Co substrate signal and its shift in
46
Surface Science
binding energy, respectively. First evaluation of the valence band data (not shown) yields a position
of the HOMO of the adsorbed species 4 eV lower than the valence band maximum of LiCoO 2. The
situation at the interface is schematically drawn on the right hand side of figure 3. The band bending
indicates that charge separation has taken place at the interface, i.e. that a space charge layer has
formed in the LiCoO2. In the present case, charge separation can principally be caused by the
movement of electrons/holes, ions or both. The position of the HOMO far below the valence band
does not favor hole transfer from the LiCoO2 to the adsorbed species, indicating movement of Liions out of the LiCoO2.
Li is fully intercalated in the LiCoO2 used in the present investigations and the material is
therefore in its discharged state. Charging will lead to more positive potentials and a higher driving
force for oxidation of the electrolyte, i.e. a shift of the Fermi level of LiCoO2 and band structure in
the volume downwards, but electron transfer may be inhibited by activation energies (band-bending
upwards at the interface). Notably, in the case of DEC, the presence of Li-salt is expected to change
the band alignment at the interface.
Ads.-/
react.
layer
EVac
EC
+
η
+
EV
+
EB
Band bending
HOMO
LiCoO2
Fig. 3: Evolution of intensity and binding energy of cobalt signal (Co3p) with exposition (left) and schematic drawing
of electronic energy levels and band bending at the interface (right)
In summary, the interface formation between a cathode material (LiCoO2) and a solid electrolyte
(LiPON) as well as a liquid electrolyte species (DEC) has been studied by surface analytical
methods. In both cases, interlayers are formed. Moreover, the energetic situation does not favor hole
transfer from the LiCoO2 to the electrolyte or electrolyte species (i.e. oxidation of the electrolyte).
In the case of DEC, we think that Li-ions may be involved in the formation of the contact potential.
References
1.
2.
3.
4.
5.
6.
7.
Maier, J., Physical Chemistry of Ionic Materials. 2004, Chichester: John Wiley and Sons, Ltd.
Sze, S.M., Physics of Semiconductor Devices. 1981, Singapore: John Wiley and Sons, Inc.
Weppner, W., Fundamental Aspects of Electrochemical, Chemical and Electrostatic Potentials in
Lithium Batteries, in Materials for Lithium-Ion Batteries, C.a.S. Julien, Z., Editor. 1999, Kluwer
Academic Publishers: Dordrecht. p. 401-412.
Goodenough, J.B. and Y. Kim, Challenges for Rechargeable Li Batteries. Chemistry of Materials,
2010. 22(3): p. 587-603.
Jacke, S., et al., Investigation of the solid-state electrolyte/cathode LiPON/LiCoO2 interface by
photoelectron spectroscopy. Ionics, 2010. 16(9): p. 769-775.
Song, J., et al., Valence Band Offsets of LiPON/LiCoO(2) Hetero-Interfaces Determined by X-ray
Photoelectron Spectroscopy. Electrochemical and Solid State Letters, 2011. 14(12): p. A189A191.
Becker, D., et al., in preparation
Surface Science
47
Adcanced 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
(EIES).
The class of oxide ceramics, in particular with perovskite (derived) structures, comprises a
stunning variety of new functional materials. 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, Chalmers University of Technology, and Hyderabad University.
Throughout 2011 Lambert Alff was working also as a Dean of Studies in the faculty of
Materials Science. In this time, the new Master of Science program in Materials Science has
started. Lambert Alff has been elected a member of the Senat of TU Darmstadt.
Staff Members
Head
Prof. Dr. Lambert Alff
Research Associates
Dr. Anastasiya Kolchynska
Dr. Jose Kurian
Dr. Philipp Komissinskiy
Technical Personnel
Dipl.-Ing. Gabi Haindl
Jürgen Schreeck
Secretary
Marion Bracke
48
Advanced Thin Film Technology
PhD Students
Dipl.-Ing. Mehrdad Baghaie
Dipl.-Ing. Erwin Hildebrandt
Dipl.-Ing. Stefan Hirsch
Dipl. Phys. Reiner Retzlaff
Dipl. Chem. Mehran Vafaee
Dipl.-Ing. Alexander Buckow
Dipl.-Ing. Sandra Hildebrandt
Dipl.-Ing. Aldin Radetinac
BTech. Vikas Shabadi MSc.
Diploma Students
Maximilian Fries
Katharina Kupka
Research Projects
Superconductivity in water intercalated NaxCoO2 thin films (TU Darmstadt, TU Braunschweig,
and Max-Planck-Institute for Solid State Research, Stuttgart) (DFG 2006-2011)
Superconductivity and magnetism in the phase diagram of bulk La2-xCexCuO4±δ
investigated by muon-spin spectroscopy and neutron scattering (TU Darmstadt, PSI,
Helmholtzzentrum Berlin) (DFG 2009-2011)
Novel arsenic free pnictide superconductors (SPP 1458) (DFG 2010 - 2012)
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 2008-2012)
LOEWE-Centre AdRIA: Adaptronik – Research, Innovation, Application (HMWK 2008 - 2010)
Oxide-MBE (MPI-FKF/TUD 2007-2012)
Publications
Lambert Alff, Andreas Klein, Philipp Komissinskiy, and Jose Kurian; Vapor phase deposition
of oxides. Ceramics Science and Technology, Volume 3: Synthesis and Processing, I.-W.
Chen and R. Riedel eds., pp. 269-290, Wiley-VCH Verlag GmbH, Weinheim, Germany
(2011).
E. Hildebrandt, J. Kurian, M. M. Müller, T. Schroeder, H.-J. Kleebe, and L. Alff. Controlled
oxygen vacancy induced p-type conductivity in HfO2-x thin films. Appl. Phys. Lett. 99, 112902
(2011).
A. Radetinac, K. S. Takahashi, L. Alff, M. Kawasaki, and Y. Tokura. Single-crystalline
Sr2MoO4 films grown by pulsed laser deposition. J. Cryst. Growth 322, 38-40 (2011).
R. Hord, G. Cordier, K. Hofmann, A. Buckow, G. Pascua, H. Luetkens, L. Alff, and B. Albert.
Transitions between lanthanum cuprates: crystal structures of T', orthorhombic and K2NiF4type La2CuO4. Z. Anorg. Allg. Chem. 637, 1114 (2011).
R. M. Öksüzoglu, M. Yildirim, H. Cinar, E. Hildebrandt, and L. Alff. Effect of Ta buffer and
NiFe seed layers on pulsed-DC magnetron sputtered Ir20Mn80Co90Fe10 exchange bias. J.
Magn. Magn. Mater. 323, 1827 - 1834 (2011).
M. Baghaie Yazdi, M.-L. Goyallon, T. Bitsch, A. Kastner, M. Schlott, and L. Alff. Transparent
magnetic oxide thin flms of Fe3O4 on glass. Thin Solid Films 519, 2531 - 2533 (2011).
M. Vafaee, M. S. Ghamsari, and S. Radiman. Highly concentrated zinc oxide nanocrystals sol
with strong blue emission. Journal of Luminescence 131, 155-158 (2011).
Advanced Thin Film Technology
49
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 polymerpyrolysis, 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.
50
Dispersive Solids
Staff Members
Head
Prof. Dr. rer. nat. habil. Prof. h. c. Dr. h. c. Ralf Riedel
Research
Associates
Dr. Dmytro Dzivenko
Dr. Magdalena Graczyk-Zajac
Dr. Aleksander Gurlo
Dr. Emanuel Ionescu
Technical
Personnel
Dipl.-Ing. Claudia Fasel
Secretaries
Su-Chen Chang
Natallia Hurlo
Karen Böhling
Nadine Arnold
PhD Students
Dipl.-Ing. Miria Andrade
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
Dipl.-Ing. Benjamin Papendorf
M.Tech. Ravi Mohan Prasad
Dipl.-Ing. Lukas Mirko Reinold
M.Sc. Cristina Schitco
M.Tech. Mahdi Seifollahi Bazarjani
Dipl.-Ing. Vassilios Siozios
Dipl.-Ing. Alexander Uhl
M.Sc. Jia Yuan
Dipl.-Ing. Carmen Elena Zvoriste
Diploma and
Master Students
Laurent Couturier
Edouard Dassonville
Amon Klausmann
Michael Krämer
Catherine Lottmann
Van Lam Nguyen
Lukas Mirko Reinhold
Alexander Uhl
Bachelor
Students
Daniel Bick
Richard Günzler
Lukas Riemer
Dispersive Solids
Dr. Gabriela Mera
Prof. Dr. Norbert Nicoloso
Dr. Liviu Toma
M.Sc. Monika Wilamowska
51
Guest Scientists
Dr. Eng. Koji Morita, National Institute for Materials Science, Ibaraki,
Japan
Dr. Mirabbos Hojamberdiev, Institute of General and Inorganic
Chemistry, Uzbekistan Academy of Sciences, Uzbekistan
Dr. Ken Niwa, Department of Materials Science and Engineering,
University of Nagoya, Japan
Prof. Yuichi Ikuhara, Institute of Engineering Innovation, University of
Tokyo, Japan
Vallachira Pradeep, Universita degli Studi di Trento, Italy
Sarabjeet Kaur, Research Institute, C.S.I.R., Bhopal, India
Dr. Rahul Harshe,
(Engineers), India
Research
and
Development
Establishment
Stephanie Kaiser, Fraunhofer Insitute of Ceramic Technology and
Systems, IKTS, Hermsdorf, Germany
Janka Ihring, Fraunhofer Insitute of Ceramic Technology and Systems,
IKTS, Hermsdorf, Germany
Anne Serin, National Graduate School of Chemistry, Montpellier,
France
Scarlett J. Widgeon, Department of Chemical Engineering and
Materials Science, University of California, Davis, USA
Prof. I-Wei Chen, Skirkanich Professor of Materials Innovation,
Department of Materials Science and Engineering, Philadelphia, USA
Prof. Dr. Corneliu Balan, Politehnica, University of Bucharest, Faculty
of Enegetics, Hydraulics Department, Bucharest, Romania
Dr. Tomáš Plachký, Institute of Inorganic Chemistry, Slovak Academy
of Sciences, Bratislava, Slovakia
Guanwei Liu, State Key Lab of New Ceramics and Fine Processing
Department of Materials Science and Engineering Tsinghua University,
Beijing, China
Dr. Olim N. Ruzimuradov, Department of General Chemistry,Faculty of
Chemistry, National University of Uzbekistan, Tashkent, Uzbekistan
Dr. Ishikawa, Institute of Engineering Innovation, University of Tokyo,
Japan
52
Dispersive Solids
Research Projects
Molecular Routes to SiMBCN Ceramic Nanocomposites (M = Zr, HF) (China Council
Scholarship (CSC), Donghua University, Shanghai, China, Sep. 2011 – Aug. 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)
Keramische
SiCN-basierte
Hartstoffschichten
Substratwerkstoffe (DFG, June 2011 – June 2014)
für
thermisch
hochbeanspruchte
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 – June
2013)
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)
FUNEA-Functional Nitrides for Energy Applications (Coordination, EU - Marie Curie Initial
Training Network, Feb. 2011 – Jan. 2015)
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 2013)
Schwerpunkt Mikrosystemtechnik im Förderprogramm "IKT 2020 - Forschung für
Innovationen" (BMBF VDI/VDE/IT, Jan. 2011 – June 2013)
Nanostructure and Calorimetry of Amorphous SiCN and SiBCN (DFG, April 2010 – March
2013)
Thermoresistant Ceramic Membrane with Integrated Gas Sensor for High Temperature
Separation and Detection of Hydrogen and Carbon Monoxide (DFG, Aug. 2010 – July
Synthesis, nanostructure and applications of metal carbodiimides (founded by NIMS,
Japan, Nov. 2010 – Oct. 2012)
Dispersive Solids
53
Non Aqueous Sol-Gel Synthesis of Boron Carbide Based Materials (US Army International
Technolog, Aug. 2009 – June 2012)
Indium oxide (In2O3) under high pressure: rational design of new polymorphs and
characterisation of their physico-chemical properties (DFG, June 2009 – May 2012)
Herstellung
und
Charakterisierung
polymerabgeleiteter
Nanokomposite (Diploma Thesis, Dec. 2011 – June 2012)
Siliciumoxycarbid/CNT-
Herstellung und Charakterisierung Sol-Gel-basierter SiOx/GO-Komposite (Bachelor Thesis,
Dec. 2011 – March 2012)
Herstellung Siliciumoxycarbid-basierter Mikrokomponenten mittels Soft-LithographieVerfahren (Bachelor Thesis, Dec. 2011 – March 2012)
Unterstützung Exzellenzprojekte (Dezernat Forschung, Jan 2010 – Jan 2012)
SPP 1181: Nanoskalige anorganische Materialien durch molekulares Design: Neue
Werkstoffe für zukunftsweisende Technologien (Coordination of DFG SPP 1181 – Nanomat,
Nov. 2005 – Dec. 2011)
Untersuchung zum Druckkriechverhalten polymerabgeleiteter Siliciumoxycarbid-Keramiken
bei hohen Temperaturen (Bachelor Thesis, Aug. 2011 – Nov. 2012)
Polymerabgeleitete
SiCO/HfO2
und
SiCN/HfO2
Keramik-Nanokomposite
Höchsttemperaturanwendung (DFG SPP 1181 – Nanomat, Jan. 2007 – Sep. 2011)
für
Synthesis and High-Temperature Annealing of Novel SiHfBCN Ceramic Composites (Master
Thesis, March 2011 – Sep. 2011)
Polysilazan-abgeleitete SiCN-Schichten für thermisch hochbeanspruchte Substratwerkstoffe
(Diploma Thesis, March 2011 – Aug. 2011)
Entwurf und Charakterisierung gedruckter piezoresistiver Dehnungssensoren aus
Polysiloxan-CNT-basierten Kompositen (Diploma Thesis in cooperation with FB
Elektrotechnik, Dec. 2010 – May 2011)
High-Pressure High Temperature Synthesis of Novel Binary and Ternary Superhard Phases
in the Si-C-N System (DFG SPP 1236, May 2008 – April 2011)
Research Program „Mikrosysteme“ – Integration neuartiger Funktions- und
Konstruktionswerkstoffe und deren Anwendung in einem miniaturisierten Ventilsystem –
INFUNK (BMBF, Oct. 2008 – April 2011)
Development and Structure Formation Mechanism of Self-Supported Ceramic Networks for
Multifunctional Applications (Humboldt Fundation, Aug. 2010 – July 2011)
54
Dispersive Solids
Modelling of composite pressure cylinder rupture in aerospace application (Diploma Thesis
in cooperation with Airbus Operation GmbH, Hamburg und Grenoble INP Phelma, France,
Nov. 2010 – April 2011)
Detailed characterisation of different grades of cast irons and cast steels – composition
of subject cards (Diploma Thesis in cooperation with Ferry Capitain, Joinville, France, Sep.
2010 – March 2011)
Neue Anodenmaterialien für Li-Ionen-Batterien (Diploma Thesis, Sep. 2010 – Feb. 2011)
Entwicklung neuer Prozesse für die Atmosphärendruckplasmadeposition zur Erzeugung
industriell einsetzbarer Oberflächen (Diploma Thesis in cooperation with Siemens AG,
Erlangen, Sep. 2010 – Feb. 2011)
Improvement of the weld seam corrosion resistance of longitudinally welded condenser
tubes through enhancement of the manufacture and heat treatment process (Diploma
Thesis in cooperation with Mannheim Power Alstom, TTTMC, Power Plant Chemistry, Sep.
2010 – Feb. 2011)
Publications
Suffner, J,; Scherer, T.; Wang, D.; Fasel, C.; Jaworska, L.; Hahn, H.; Microstructure and
high-temperature deformation behavior of Al2O3-TiO2 obtained from ultra-high-pressure
densification of metastable powders; Acta Mater., 59(20) (2011) 7592-7601.
Matizamhuka, W.R.; Sigalas, I.; Herrmann, M.; 4 Dubronvinsky, L.; Dubrovinskaia ,
N.; Miyajima, N.; Mera, G.; Riedel , R.; Characterization of the Materials Synthesized by
High Pressure-High Temperature Treatment of a Polymer Derived t-BC2N Ceramic; Materials,
4(12) (2011) 2061-2072.
Gurlo, A.; Clarke, D.; High-sensitivity hydrogen detection: hydrogen-Induced swelling of
multiple cracked palladium films on compliant substrates; Angew. Chem. Int. Edit., 50(43)
(2011) 10130-10132.
Seifollahi Bazarjani, M.; Kleebe, H.-J.; Müller, M.M.; Fasel, C.; Baghaie Yazdi, M.;
Gurlo, A.; Riedel, R.; Nanoporous Silicon Oxycarbonitride Ceramics Derived from
Polysilazanes In situ Modified with Nickel Nanoparticles; Chem. Mater., 23(18) (2011) 41124123.
Soehn, M.; Zils, S.; Nicoloso, N.; Roth, C.; Effective debundling of carbon nanotubes and
simultaneous synthesis of Pt nanoparticles by Nafion (R) induced emulsions; J. Power Sources,
196(15) (2011) 6079-6084.
Boyko, T.D.; Zvoriste, C.E.; Kinski, I.; Riedel, R.; Hering, S.; Huppertz, H.; Moewes, A.;
Anion ordering in spinel-type gallium oxonitride; Phys. Rev. B 84(8) (2011) 085203.
Dispersive Solids
55
Pashchanka, M.; Hoffmann, R.C.; Gurlo, A.; Swarbrick, J.C.; Khanderi, J.; Engstler, J.;
Issanin, A.; Schneider, J.J.; A molecular approach to Cu doped ZnO nanorods with tunable
dopant content; Dalton T., 40(16) (2011) 4307-4314.
Martínez-Crespiera, S.; Ionescu, E.; Schlosser, M.; Flittner, K.; Mistura, G.; Riedel, R.;
Schlaak, H.F.; Fabrication of Silicon Oxycarbide-Based Microcomponents via
Photolithographic and Soft Lithography Approaches; Sensor Actuat. A-Phys., 169(1) (2011)
242-249.
Sedlacek, J.; Galusek, D.; Riedel, R .; Hoffmann, M.J.; Sinter-HIP of polymer-derived
Al2O3-SiC composites with high SiC contents; Mater. Lett., 65(15-16) (2011) 2462-2465.
Graczyk-Zajac, M.; Fasel, C.; Riedel, R.; Polymer-derived-SiCN ceramic/graphite composite
as anode material with enhanced rate capability for lithium ion batteries; J. Power Sources,
196(15) (2011) 6412-6418.
Toma, L.; Fasel, C.; Lauterbach, S.; Kleebe, H.-J.; Riedel, R.; Influence of nano-aluminum
filler on the microstructure of SiOC ceramics; J. Eur. Ceram. Soc., 31(9) (2011) 1779-1789.
Tamayo, A.; Rubio, J.; Rubio, F.; Oteo, J.L.; Riedel, R.; Texture and micro-nanostructure
of porous silicon oxycarbide glasses prepared from hybrid materials aged in different solvents;
J. Eur. Ceram. Soc., 31(9) (2011) 1791-1801.
Pusch, C.; Hoche, H.; Berger, C.; Riedel, R.; Ionescu, E.; Klein, A.; Influence of the PVD
sputtering method on structural characteristics of SiCN-coatings – comparison of RF-, DC- and
HiPIMS-sputtering and target configurations; Surf. Coat. Tech., 205(2) (2011) S119-S123.
Andrade, M.; Dzivenko, D.; Miehe, G.; Boehler, R.; Hintzen, H. T.; Riedel, R.; Highpressure high-temperature synthesis and structure of beta-MgSiN2; Phys. Status Solidi-R, 5(56) (2011) 196-198.
Martinez-Crespiera, S.; Ionescu, E.; Kleebe, H.-J.; Riedel, R.; Pressureless synthesis of
fully dense and crack-free SiOC bulk ceramics via photo-crosslinking and pyrolysis of a
polysiloxane; J. Eur. Ceram. Soc., 31(5) (2011) 913-919.
Ahmad, M.I.; Fasel, C.; Mayer, T.; Bhattacharya, S.S.; Hahn, H.; High temperature
stability of nanocrystalline anatase powders prepared by chemical vapour synthesis under
varying process parameters; Appl. Surf. Sci., 257(15) (2011) 6761-6767.
Papendorf, B.; Nonnenmacher, K.; Ionescu, E.; Kleebe, H.-J.; Riedel, R.; Strong
Influence of Polymer Architecture on the Microstructural Evolution of Hafnium-AlkoxideModified Silazanes upon Ceramization; Small, 7(7) (2011) 970–978.
Böhme, M.; Ionescu, E.; Fu, G.; Ensinger, W.; Cerium (IV) oxide nanotubes prepared by
low temperature deposition at normal pressure; Nanotechnology, 22(6) (2011) 065602.
56
Dispersive Solids
Chavez, R.; Ionescu, E.; Balan, C.; Fasel, C.; Riedel, R.; Effect of Ambient Atmosphere on
the Cross-Linking Behavior of Polysilazanes; J. Appl. Polym. Sci., 119(2) (2011) 794-802.
Galusek, D.; Klement, R.; Sedláček, J.; Balog, M.; Fasel, C.; Zhang, J.; Crimp, M.A.;
Riedel, R.; Al2O3–SiC composites prepared by infiltration of pre-sintered alumina with a
poly(allyl)carbosilane; J. Eur. Ceram. Soc., 31(1-2) (2011) 111-119.
Nuffer, J.; Riedel, R.; Reply to the "Comment on 'Piezoresistive Effect in SiOC Ceramics for
Integrated Pressure Sensors"; J. Am. Ceram. Soc., 94(1) (2011) 290.
Böhme, M.; Ionescu, E.; Fu, G.; Ensinger, W.; Room temperature synthesis of indium tin
oxide nanotubes with high precision wall thickness by electroless deposition; Beilstein J.
Nanotechnol., 2 (2011) 119-126.
Gurlo, A.; Nanosensors: towards morphological control of gas sensing activity. SnO 2, In2O3,
ZnO and WO3 case studies; Nanoscale, 3(1) (2011) 154-165.
Renard, L.; Elhamzaoui, H.; Jousseaume, B.; Toupance, T.; Laurent, G.; Ribot, F.;
Saadaoui, H.; Brötz, J.; Fuess, H.; Riedel, R.; Gurlo, A.; Low-temperature H2 sensing in
self-assembled organotin thin films; Chem. Commun., 47(5) (2011) 1464-1466.
Kamrani, S.; Hesabi, Z.R., Riedel, R.; Reihani, S.M.S.; Synthesis and Characterization of
Al-SiC Nanocomposites Produced by Mechanical Milling and Sintering; Adv. Comp. Mater.,
20(1) (2011) 13-27.
Patents
Chavez Medellin, R.; Zimmermann, A.; Aichele, W.; Ionescu, E.; Riedel, R.; New
tetraamino-disiloxane useful for producing thermoplastic polyimide-based polymers; Patent
Number(s): DE102010001071-A1; WO2011089111-A1.
Dispersive Solids
57
Nanoporous Silicon Oxycarbonitride Ceramics Derived from
Polysilazanes In situ Modified with Nickel Nanoparticles
Mahdi Seifollahi Bazarjani,† Hans-Joachim Kleebe,† Mathis M. Müller,† Claudia Fasel,†
Mehrdad Baghaie Yazdi,† Aleksander Gurlo,†,‡ and Ralf Riedel†
†Technische Universität Darmstadt, Fachbereich Material-und Geowissenschaften, Petersenstrasse 23, D64287 Darmstadt, Germany
‡School of Engineering and Applied Sciences, Harvard University, 29 Oxford Street, Cambridge,
Massachusetts 02138, United States
Chem. Mater. 2011, 23, 4112–4123, DOI: 10.1021/cm200589n
Ni-polysilazane precursors were synthesized from polysilazane and trans[bis(2aminoetanol-N,O)diacetato-nickel(II)]. The Ni-polysilazane precursors are superparamagnetic indicating formation of nanosized nickel particles (∼2-3 nm) confirmed by
HRTEM as well. The as-obtained Ni-polysilazane precursors were thermolized at 700 °C
and transformed to ceramic nanocomposites, manifesting a nanoporous structure, revealing
a BET surface area of 215 m²/g, a micropore surface area of 205 m²/g, and a micropore
volume of 0.113 cm3/g. Although Si-C-N-(O) ceramics derived from the native polysilazane
are nonporous, the pronounced development of porosity in the Ni/Si-C-N-(O) system was
attributed to (i) the stabilizing effect of carbosilane bonds, which prohibit the formation of
macropores during thermolysis; (ii) the reduced barrier for heterogeneous pore nucleation
as a result of in situ created nickel nanoparticles; and (iii) the reduced viscous flow of the
pores due to the presence of nickel nanoparticles and turbostratic carbon. The formation of
turbostratic carbon is due to the reactions catalyzed by nickel nanoparticles that result in
graphene stacking as inferred from the STA-MS studies.
As the formation mechanism, structure, composition and the porosity characteristics of the
Ni/Si-C-N-(O) nanocomposites differ significantly from those of the Si-C-N-(O) ceramics,
this implies a common mechanism involved in the formation of nickel nanoparticles,
precipitation of turbostratic carbon and the development of porosity. These common
features are as follows:
(i) The nickel nanoparticles in the Ni-polysilazane precursors reduce the critical barrier
for the formation of gaseous species during the polymer-to-ceramic transformation
and facilitate the heterogeneous nucleation of pores due to the release of
gasmolecules such as H2 andCH4.72 As the rigid carbosilane bonds formed in the Nipolysilazane precursors are not affected at the temperatures of transamination and
exchange reactions (200-500 °C),3,34 the distillation of large polymer fragments does
not occur. In this way the formation of macropores and the abnormal pore growth is
significantly constrained. Furthermore, higher cross-linking due to the formation of
carbosilane units enhances the evolved pore stability during the polymer (Nipolysilazane precursors) to ceramic nanocomposite (Ni/Si-C-N-(O)) transformation.73
(ii) The dehydrogenation-active nickel nanoparticles decrease the starting temperature of
the formation of turbostratic carbon by some hundred degrees. The previous studies
showed that the turbostratic carbon reinforces the mechanical stability of the surrounding matrices.74 This effect could be easily understood if we consider the
structure of turbostratic carbon as being constructed of hexagonal basal planes of
perfect graphene sheets which are randomly rotated along the c axis (instead of
58
Dispersive Solids
regular ... ABAB... stacking),75 graphene itself possesses the highest intrinsic
strength.76 Accordingly, the turbostratic carbon with higher mechanical stability than
that of the neighboring nanoporous matrix behaves as in situ formed nanofiller, and
subsequently reinforces the nanoporous structure and reduces the nanopores collapse
as a result of viscous flow,68,69,71 stabilizing the micro/mesoporosity developed in the
entire matrix of the Ni/Si-C-N-(O) nanocomposites.
Figure 1. HRTEM images of the thermolysis product of the (a) polysilazane HTT (reference sample) and that of
the (b_d) Ni_polysilazane precursor S3 with the Ni(II) complex content of 40 wt % upon thermolysis at 700 °C.
The thermolysis product of the polysilazane HTT is fully amorphous, as indicated by the inset (diffraction
patterns obtained by Fourier filtered transform (FFT)). In contrast to a, the Ni/Si-C-N-(O) nanocomposite
revealed a dark, spherical contrast resulting from the precipitation of crystalline nickel nanoparticles, 2-3 nm in
diameter. Note that in the Ni/Si-C-N-(O) nanocomposite the turbostratic carbon was observed throughout the
entire sample, suggesting a strong catalytic reaction of the nickel nanoparticles. No lattice fringes or lattice
points are seen in the nickel nanoparticles in b and c; however, when using a rather high defocus setting of
the objective lens (first pass band), the crystallinity of even very small nanoparticles could be verified in d.
Conclusions
In summary, a novel strategy to synthesize nanoporous ceramics is proposed. The addition
of a Ni(II) complex to a polysilazane effectively turn a nonporous polymer derived ceramic
to a nanoporous material. Nickel nanoparticles formed in situ during the synthesis of Nipolysilazane precursors play a major role in modifying the mechanism of polymer-toceramic transformation. They facilitate the precipitation of turbostratic carbon and the
heterogeneous nucleation of pores. Furthermore, replacement of unstable silazane linkages
Dispersive Solids
59
by stable carbosilane bonds which are not affected by the main polymer chain
depolymerization during thermolysis, prohibits the distillation of small polymer fragments
limiting pore growth and formation of macrovoids.
References
(3)
(34)
(68)
(69)
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(76)
60
Colombo, P.; Riedel, R.; Soraru, G. D.;Kleebe, H. J., Polymer Derived Ceramics: From NanoStructure to Applications; EStech Publications: Lancaster, PA, 2010; p 476.
Yive, N. S. C. K.; Corriu, R. J. P.; Leclercq, D.; Mutin, P. H.; Vioux, A. Chem. Mater. 1992, 4,
141.
Sanchez-Jimenez, P. E.; Downs, J. A.; Raj, R. J. Am. Ceram. Soc. 2010, 93, 2567.
Lipowitz, J.; Rabe, J. A.; Frevel, L. K.; Miller, R. L. J. Mater. Sci. 1990, 25, 2118.
Galusek, D.; Reschke, S.; Riedel, R.; Dressler, W.; Sajgalik, P.; Lencees, Z.; Majling, J. J. Eur.
Ceram. Soc. 1999, 19, 1911.
Borek, T. T.; Ackerman, W.; Hua, D. W.; Paine, R. T.; Smith, D. M. Langmuir 1991, 7, 2844.
Izaak, T. I.; Babkina, O. V.; Lyamina, G. V.; Svetlichnyi, V. A. Russian J. Phys. Chem. A 2008,
82, 2111.
Williams, H. M.; Dawson, E. A.; Barnes, P. A.; Rand, B.; Brydson, R. M. D.; Brough, A. R. J.
Mater. Chem. 2002, 12, 3754.
Chasiotis, I.; Ozkan, T.; Naraghi, M. Carbon 2010, 48, 239.
Sjostrom, H.; Ivanov, I.; Johansson, M.; Hultman, L.; Sundgren, J. E.; Hainsworth, S. V.; Page,
T. F.; Wallenberg, L. R. Thin Solid Films 1994, 246, 103.
Hone, J.; Lee, C.; Wei, X. D.; Kysar, J. W. Science 2008, 321, 385.
Dispersive Solids
Strong Influence of Polymer Architecture on the
Microstructural Evolution of Hafnium-Alkoxide-Modified
Silazanes upon Ceramization
Benjamin Papendorf,* Katharina Nonnenmacher,+ Emanuel Ionescu,*
Hans-Joachim Kleebe,+ and Ralf Riedel*
*
Technische Universität Darmstadt, Institut für Materialwissenschaft, Petersenstrasse 23,
D-64287 Darmstadt, Germany
+
Technische Universität Darmstadt, Institut für Angewandte Geowissenschaften, Schnittspahnstrasse 8,
D-64287 Darmstadt, Germany
Small, 7(7) (2011) 970–978, DOI: 10.1002/smll.201001938
The present study focuses on the synthesis and ceramization of novel hafniumalkoxidemodified silazanes as well as on their microstructure evolution at high
temperatures. The synthesis of hafnia-modified polymer-derived SiCN ceramic
nanocomposites is performed via chemical modifi cation of a polysilazane and of a
cyclotrisilazane, followed by cross-linking and pyrolysis in argon atmosphere. Spectroscopic
investigation (i.e., NMR, FTIR, and Raman) shows that the hafnium alkoxide reacts with
the N–H groups of the cyclotrisilazane; in the case of polysilazane, reactions of N–H as well
as Si–H groups with the alkoxide are observed. Consequently, scanning and transmission
electron microscopy studies reveal that the ceramic nanocomposites obtained from
cyclotrisilazane and polysilazane exhibited markedly different microstructures, which is a
result of the different reaction pathways of the hafnium alkoxide with cyclotrisilazane and
with polysilazane. Furthermore, the two prepared ceramic nanocomposites are
unexpectedly found to exhibit extremely different hightemperature behavior with respect to
decomposition and crystallization; this essential difference is found to be related to the
different distribution of hafnium throughout the ceramic network in the two samples. Thus,
the homogeneous distribution of hafnium observed in the polysilazane-derived ceramic
leads to an enhanced thermal stability with respect to decomposition, whereas the local
enrichment of hafnium within the matrix of the cyclotrisilazane-based sample induces a
pronounced decomposition upon annealing at high temperatures. The results indicate that
the chemistry and architecture of the precursor has a crucial effect on the microstructure of
the resulting ceramic material and consequently on its high-temperature behavior.
Polysilazane HTT1800 and cyclotrisilazane (CTS) were reacted with hafnium(IV) nbutoxide at ambient temperature. The reactions were investigated by means of NMR,
Fourier-Transform IR (FTIR) and Raman spectroscopy. Whereas CTS can only react at its
N–H bonds with hafnium(IV) n-butoxid, HTT1800 additionally has Si–H groups, which
might also be involved in the reaction with the hafnium(IV) n-butoxide.
Dispersive Solids
61
Figure 1. TEM bright-field images of the samples pyrolyzed at 1100 °C: a,c) the HTT1800-based ceramic and
b,d) the CTS-based material. The TEM bright-field images (a,b) are complementary to the SEM images given in
Figure 5 since no Hf-segregation is visible in (a) while dark contrast lines are depicted in (b), indicative of a
local enrichment of Hf. Insets of (a) and (b) show the corresponding SAED images. Note that the origin of
such elongation in Hf-dispersion is still not known. The corresponding HRTEM images given in (c) and (d)
clearly show that no local enrichment of Hf is present in (c) while in (d) a dark band (Hf-phase) runs diagonal
through the image.
Figure 2. XRD patterns of CTS- and HTT1800-based ceramics annealed at 1300 and 1600 °C in argon atmosphere.
62
Dispersive Solids
Conclusion
The present study clearly emphasizes the influence of the chemistry and molecular
architecture of preceramic polymers on the microstructural evolution and high-temperature
behavior of the ceramic materials derived from the polymers. Ceramic nanocomposites
based on the SiHfCNO-system with extremely different microstructures have been obtained
from two different preceramic compounds, namely from a polymeric organosilazane and
from an organocyclosilazane monomer. The organosilazanes were modifi ed with hafnium
alkoxide and subsequently pyrolyzed in argon atmosphere up to different temperatures
above 1000 °C. Electron microscopic investigation (SEM and TEM) of the microstructure of
both samples showed a homogeneous dispersion of hafnium in the bulk SiCN matrix on the
atomic scale in case of HTT1800 as the precursor. In contrast, the ceramic derived from
CST is characterized by a pronounced local enrichment of hafnium, leading to threadlike
precipitation of amorphous hafnia. The difference in the microstructural features between
both samples is thought to be a consequence of the different reactivity of the preceramic
silazanes with respect to hafnium n -butoxide. Thus, the Hf dispersion throughout the SiCN
bulk material is mainly determined by the architecture of the preceramic silazane obtained
upon chemical modification with hafnium n-butoxide. Subsequent annealing experiments
showed that the microstructural features are essentially preserved up to temperatures as
high as 1600 °C.
In addition to the relationship between the preceramic polymer architecture and the
microstructure of the resulting ceramics, a strong effect of the hafnium distribution
throughout the ceramic network on the high-temperature stability of the samples was
found. Whereas the local enrichment of hafnium within the ceramic SiCN network derived
from CST was found to be disadvantageous with respect to the thermal stability at 1600 °C,
the HTT1800-sample revealed a homogeneous distribution of hafnium within the ceramic
matrix and was found to exhibit a significantly improved stability in terms of decomposition
of the SiCN matrix.
Dispersive Solids
63
Structure Research
In the year 2011, we installed a new six-circle surface diffractometer for heavy sample
environments. An UHV-system for the evaporation of metals has been designed and built,
together with a transportable baby chamber for Synchrotron campaigns. The Guiniercamera has been tested together with the Tübingen-cryostat (15K-300K), and the CAD4
kappa-diffractometer has been renovated and equipped with a Ag tube for highly absorbing
single crystals.
Staff Members
Head
Prof. Dr. rer. nat. Wolfgang Donner
Prof. Dr.-Ing. Dr. h.c. Hartmut Fueß
Research Associates
Dr. Joachim Brötz
Dipl. Phys. Martin Mühlbauer
Dr. Marton Major
Dr. Ljubomira Schmitt
Dr. Oleksandr Dolotko
Dr. Azza Amin
Technical Personnel
Dipl. Ing. Heinz Mohren
Jean-Christophe Jaud
Ingrid Svoboda
Sabine Foro
Secretary
Maria Bense
PhD Students
Dipl.-Ing. Toni André Groß
Dipl.-Ing. Hanna Hahn
Dipl.-Ing. Jens Kling
Dipl.-Ing. Dominic Stürmer
M.Sc. Qiran Li
Guest Scientists
Dr. Sevi Öz, Ankara
University, Turkey
Prof. Dr. Ismael Saadoune,
Université Cadi Ayyad, Maroc
Research Projects
DAAD exchange program with Slovakia (2006-2011).
Structural investigations into the electric fatigue in piezo-ceramics (DFG-SFB, 2011-2014)
Development of electrode materials for high capacitance devices (IDS-FunMat, 2011-2013)
The electronic structure of TiO2, VO2 and related transition-metal oxides: A joined electrondensity study of materials in position, momentum and phase space (DFG, 2009-2011)
Correlated momentrum, charge and magnetization density in the kagome staircase system
Co3V2O8, (DFG, 2009-2011)
64
Structure Research
Publications
Daniels, J. E.; Jo, W.; Roedel, J.; Rytz, D.; Donner, W., Structural origins of relaxor behavior
in a 0.96(Bi1/2Na1/2)TiO3-0.04BaTiO3 single crystal under electric field, Appl. Phys. Lett., 98:
252904 (2011)
Deuermeier, J.; Gassmann, Brötz, J.; Klein, A., Reactive magnetron sputtering of Cu2O:
Dependence on oxygen pressure and interface formation with indium tin oxide
J. Appl. Phys., 109: 113704 (2011)
Donner, W.; Chen, C.; Liu, M.; Jacobson, A. J.; Lee, Y.-L.; Gadre, M.; Morgan, D., Epitaxial
strain-induced chemical ordering in La0.5Sr0.5CoO3-delta films on SrTiO3
Chem. Mater. 23. 984 (2011)
Heiba, Z. K.; Mohamed, M. B.; Abdalslam, M. A.; Fuess, H., Structure, microstructure and
magnetic properties of mixed rare earth oxide Dy1-xErxO3, Cryst Res. Techn. (2011)
Hinterstein, M.; Rouquette, J.; Haines, H.; Paquet, Ph.; Knapp, M.; Glaum, J.; Fuess, H.,
Structural description of the macroscopic piezo and -ferroelectric properties of lead zirconatetitanate, Phys. Rev. Lett., 107: 077602 (2011)
Hinterstein, M.; Hoelzel, M.; Kungl, H.; Hoffmann, M. J.; Ehrenberg, H.; Fuess, H., In situ
neutron diffraction study of electric field induced structural transitions in lanthanum doped
lead zirconate titanate, Z. Kristallogr.,226: 155-162 (2011)
Hohmann, M. V.; Ágoston, P.; Wachau, A.; Bayer, T.J.M.; Brötz, J.; Albe, K.; Klein, A.,
Orientation dependent ionization potential of In2O3: A natural source for inhomogeneous
barrier formation at electrode interfaces in organic electronics
J. Phys. Cond. Mat., 23: 334203 (2011)
Ishihara, H.; Natano, N.; Horiuchi, K.;. Terao, H.; Svoboda, I.; Fuess, H., NQR, DSC, and xray structure studies of pyridinium tetrabromozincate and pyridinium tetrabromocadmate
(C5H5NH)2MBr4 . nH2O (M = Zn and Cd; n = 0.1: Phase transitions and weak hydrogen bond
interactions, Z. Naturf., 66b: 1261-1269 (2011)
Jacke, S.; Song, J.; Dimesso, L.; Brötz, J.; Becker, D.; Jaegermann, W.; Temperature
dependent phosphorous oxynitride growth for all-solid-state batteries
J. Power Sources, 196: 6911-6914 (2011)
Jakes, J.; Blickhan, N.; Jekewitz, T.; Drochner, A.; Vogel, H.; Fuess, H.; Eichel, R.A.
Interplay between defect structure and catalytic activity in the Mo10-xVx Oy mixed-oxide system:
ChemPhysChem, 12: 3578-3583 (2011)
Muench, F.; Kaserer, S.; Kunz, U.; Svoboda,I.; Brötz, J.;Lauterbach, S.; Kleebe, H.-J.;Roth,
C.; Ensinger; W., Electroless synthesis of platinum and platinum–ruthenium nanotubes and
their application in methanol oxidation, J. Mat. Chem., 21: 6286-6291 (2011)
Structure Research
65
Nemec, I.; Herchel, R.; Boča, R.; Svoboda, I.; Trávniček, Z.; Dlháň, L.; Matelkovc, K.; Fuess, H.
Heterobimetallic assemblies of Ni(II) complexes with a tetradentate amine ligand and
diamagnetic cyanidometallates, Inorg. Chem. Act., 366: 366-372 (2011)
Renard, L.; Elhamzaoui, H.; Jousseaume, B.; Toupance, Th.; Robot, F.; Saadaoui, H.; Brötz,
J.; Fuess, H.; Gurlo, A., Low temperature hydrogen sensing in self-assembled organotin thin
film, Chem. Commun., 47(1): 464-1466 (2011)
Schierholz, R.; Fuess, H., Symmetry of domains in morphotropic PbZr1-xTixO3 ceramics
Phys. Rev.B, 84: 064122 (2011)
Schmitt, L. A.; Kling, J.; Hinterstein, M.; Hoelzel, M.; Jo, W.; Klebe, H.J.; Fuess, H.
Structural investigations on lead-free Bi1/2Na1/2TiO3 based piezoceramics
J. Mater. Sci., 4368-4376 (2011)
Singh, A.; Senyshyn, A.; Fuess H.; Pandey, D., Ferroelectric and antiferrodistortive phase
transition in the multiferroic (Bi0.8Ba0.2)(Fe0.8Ti0.2)O3: A high temperature neutron powder
diffraction study, J. Appl. Phys., 110: 024111 (2011)
Singh, A.; Senyshyn, A.; Fuess, H.; Chatterji, T.; Pandey, P., Neutron powder diffraction
study of nuclear and magnetic structures of multiferroic (Bi0.8Ba0.2)(Fe0.8Ti0.2)O3: Evidence for
isostructural phase transition and magnetoelastic and magnetoelectric couplings
Phys. Rev. B, 83(5): 054406 (2011)
Takali, F.; Njeh, A.; Fuess, H.; Ben Ghozlen, M. H., X-ray diffraction measurement of residual
stress in epitaxial ZnO/α-Al2O3 thin film, Mech. Res. Comm.(2011)
Structural characterisation of textured gold nanowires Maurer, F; Brötz, J ; Miehe, G;
Karim, S; Fuess, H, INTERNATIONAL JOURNAL OF NANOTECHNOLOGY Volume: 8
Issue: 10-12 Special Issue: SI Pages: 855-867 Published: 2011
92 papers in Acta Cryst. E
66
Structure Research
Diffuse Scattering and the Relaxor Behavior of Single Crystal,
Lead-Free Piezo-Materials
J. Daniels, W. Jo, J. Rödel, D. Rytz, W. Donner
Piezoelectric materials find applications as sensors and actuators, e.g. in fuel injectors and
inkjet printers. Most industrially used piezo-stacks contain lead, an element that is toxic
even in small quantities. It is therefore desirable – and demanded by the EU – to develop
lead-free materials with electro-mechanical properties comparable to the existing
technology. One of the more promising candidates is bismuth sodium titanate (BNT) and
some of its alloys. BNT is a so-called relaxor ferroelectric, i.e. it displays a frequencydependence of the ferrolectric properties that is most likely caused by small structural
fluctuations called „polar nano-regions“ (PNR).
Fig. 1: (h k 0.5) planes of diffuse scattering for, (a) initial crystal, and (b) an applied electric field of 4.6kV/mm.
(c) shows line scans along the (h -1.5 0.5) direction taken from the areas outlined by dashed boxes in (a) and
(b). The estimated background intensity level is indicated in (c). Radial intensity artefacts are caused by
detector saturation errors during data collection.
Structure Research
67
We used Ba-doped BNT (BNT-BT) as a model system to study the nature of the PNR and its
relation to the relaxor-behavior. Structural fluctuations show up in diffraction studies as
diffuse scattering, and the dependence of the diffuse scattering on an applied electric field
should yield information about the atomic structutre of the PNR. The subject of the study
was a single crystal of BNT containing 4 at-% BT; the crystal was illuminated by high
energy x-rays at the European Synchrotron Radiation Facility in Grenoble (BL ID15B). The
resulting intensity distribution in a two-dimensional cut of reciprocal space is shown in
Fig.1: sharp half-order reflections that are due to a superstructure of tilted oxygen
octahedra are connected by diffuse streaks. The diffuse streaks and the half-order
reflections both react upon the application of an electric field: the streak intensity decreases
and the reflections become more narrow.
Fig. 2: Temperature-dependent permittivity of the unpoled and the poled BNT-4BT single crystal sample. Note
the frequency dispersion. The insets are the derivative of the permittivity with respect to temperature, where
the difference between the dielectric behaviour of the unpoled and the poled samples is more clearly visible.
We designed a structural model for the diffuse scattering in which the streaking of the halforder reflections is caused by stacking faults in the octahedral tilt sequence. The application
of an electric field dissolves some of the stacking faults (that serve as PNR’s) and the
frequency dependence of the electrical permittivity is changed by this structural
modification (see Fig. 2). We are now working on a quantitative description of the stacking
fault structure.
Reference:
J.E. Daniels, W. Jo, J. Rödel, D. Rytz, W. Donner, Appl. Phys. Lett., 98, 252904 (2011).
68
Structure Research
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:
Nanochannels, nanowires and nanotubes: Utilizing polymer foils which were irradiated
by high energy ions, a set of nanostructures can be produced with a variety of applications.
Nanochannels, produced by chemical etching of the irradiated foils, can be transformed
into bio-specific sensors or into devices with selective transport properties, depending on
the functional groups that are attached to their surfaces. The research is concerned with
facile and versatile ways to achieve this attachment as well as with applications, e.g. as
sensors for protein analytes or as logic gates.
By filling the channels nanowires can be obtained which can be freed from the template by
dissolution of the latter. Nanowires can be used for fundamental research, e.g. the
investigation of the Kondo effect, but also as nanowire arrays in sensor applications, e.g. as
gas sensors.
By altering the filling process the resulting structure is not a wire but a tube. The
correlation of synthesis conditions, morphological parameters and properties is investigated
and optimized towards the utilization in catalysis, particle separation and sensor
technology.
This work is conducted in collaboration with the GSI Helmholtzzentrum für Schwerionenforschung.
Materials in Radiation Fields: The degradation under intense ionizing radiation is
investigated for different materials, such as semiconductors, amorphous magnetic alloys,
polymers, graphite and scintillators. Many of those materials will be used in components
(beam guiding magnets, beam dump, detectors) of the next generation accelerator facility
at the GSI Helmholtzzentrum für Schwerionenforschung. In situ characterization is
performed at the M-branch of the UNILAC experimental hall in the GSI by various
analytical tools, e.g. FT-IR and UV/VIS measurements as well as mass spectrometry.
Thin film preparation: Surface coatings and surface modifications are prepared on a scale
from single molecular layers to films of about 200 nm thickness. The preparation technique
depends on the purpose of the treatment, which can be, to name a few: 1) the synthesis of
a functional material, e.g. a gas sensor prepared by electrochemical deposition, or a leadfree piezoelectric thin film prepared by spin- or dip-coating of a sol-gel solution. 2) the
synthesis of an additional top-layer to improve certain parameters, e.g. the corrosion
protection of light metals and their alloys by atomic layer deposition, or the friction
coefficient by addition of a diamond-like carbon layer via plasma based ion deposition. 3)
alteration of the surface layer, e.g. increase of hardness or adhesion by implantation of
ions.
Materials Analysis
69
Thin film analysis: Apart from the analysis of the self-synthesized samples mentioned
above a variety of in-house techniques as well as externally available measurement facilities
are used for characterization and fault analysis in collaboration with other research groups
and institutes. This includes for example oxygen and hydrogen diffusion measurements in
bulk samples of ferroelectrics by SIMS or the investigation of the binding states of thin
carbonitride films with the substrate by NEXAFS at Bessy II, jointly with the PTB. Other
techniques involved are mainly ion beam based – like RBS, NRA and ERDA – but not
exclusively so, e.g. positron annihilation spectroscopy is also applied.
Staff Members
Head
Prof. Dr. Wolfgang Ensinger
Research Associates
Dr. Mubarak Ali
Dr. Adam G. Balogh
Dr. Stefan Flege
Dr. Peter Hoffmann
Dr. Olaf Baake
Dr. Christiane Brockmann
Dr. Ruriko Hatada
Technical Personnel
Renate Benz
Brunhilde Thybusch
Secretaries
Antje Pappenhagen
PhD Students
Anton Belousov
Eiko Gütlich
Umme Habiba Hossain
Stefan Hummelt
Markus Krause
Vincent Lima
Saima Nasir
Quoc Hung Nguyen
Tim Seidl
Sebastian Wiegand
Mario Böhme
Engy El-Haddad
Martin Hottes
Sebastian Kamps
Renuka Krishnakumar
Falk Münch
Cornelia Neetzel
Markus Rauber
Christian Stegmann
Diploma Students
Marc Adamiak
Martin Hottes
Jonathan Griebel
Anke Schachtsiek
Bachelor Students
Thomas Paul Kaleja
Stefan Vogel
Guest Scientists
Prof. Nhu-Tarnawska Hoa Kim-Ngan, Pedagogical University of
Cracow, Poland
Prof. Zbiegnew Tarnawski, AGH University, Krakow, Poland
Dr. S. Duvanov, National Academy of Sciences of Ukraine
A. Kramchenkov, National Academy of Sciences of Ukraine
Barbara Lyson, AGH University, Krakow, Poland
Karolina
70
Drogowska,
AGH
University,
Krakow,
Poland
Materials Analysis
Research Projects
Preparation of lead free piezo electric thin films (LOEWE Adria, 2008 – 2014)
Preparation of thick actuator films on the basis of lead free piezo materials (LOEWE Adria,
2010 – 2011)
Investigation of scintillators for high current applications at UNILAC (GSI, 2008 – 2011)
FAIR accelerator: Investigations of alterations of material properties by beam losses
(BMBF/GSI, 2009 – 2012)
FAIR accelerator: Scintillator materials for diagnostics of high currents (BMBF/GSI, 2009 –
2012)
Simulations on the influence of swift ion irradiation on materials of FAIR-components (GSI,
2010-2013)
Investigation of the influence of swift ion irradiation on polymers and composite materials
of FAIR-components (GSI, 2010-2013)
Investigation of the chemical bindings in interfaces of boron- and siliconcarbonitrides with
the substrate (DFG, 2010 – 2012, jointly with PTB Berlin)
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)
Investigation of technologically important nanostructured materials via high resolution ion
beam analysis (DLR, 2011-2013)
Publications
Muench, F.; Kunz, U.; Neetzel, C.; Lauterbach, S.; Kleebe, H.-J.; Ensinger, W., 4(Dimethylamino)pyridine as a powerful auxiliary reagent in the electroless synthesis of gold
nanotubes, LANGMUIR, 27: 430–435 (2011)
Boehme, M.; Fu, G.; Ionescu, E.; Ensinger, W., Cerium (IV) oxide nanotubes prepared by low
temperature deposition at normal pressure, Nanotechnology, 22: 065602 (2011)
Boehme, M.; Ensinger, W., Fabrication of zinc oxide nanotubes by chemical bath deposition
using ion track-etched templates, IEEE Trans. Nanotech., 10: 63-69 (2011)
Boehme, M.; Ionescu, E.; Fu, G.; Ensinger, W., Room temperature synthesis of indium tin
oxide nanotubes with high precision wall thickness by electroless deposition
Beilstein Journal of Nanotechnology, 2: 119-126 (2011)
Materials Analysis
71
Ali, M.; Tahir, M. N.; Siwy, Z.; Neumann, R.; Tremel, W.; Ensinger, W., Hydrogen peroxide
sensing with horseradish peroxidase-modified polymer single conical nanochannels, Anal.
Chem, 83: 1673–1680 (2011)
Ali, M.; Ramirez, P.; Nawaz Tahir, M.; Mafe, S.; Siwy, Z.; Neumann, R.; Tremel, W.;
Ensinger, W. Biomolecular conjugation inside synthetic polymer nanopores via glycoprotein–
lectin interaction, Nanoscale, 3: 1894-1903 (2011)
Baake, O.; Seidl, T.; Hossain, U. H.; Delgado, A. O.; Bender, M.; Severin, D.; Ensinger, W.
An apparatus for in situ spectroscopy of radiation damage of polymers by bombardment with
high-energy heavy ions, Rev. Sci. Instrum., 82: 045103 (2011)
Muench, F.; Kaserer, S.; Kunz, U.; Svoboda, I.; Brötz, J.; Lauterbach, S.; Kleebe, H.-J., Roth,
C.; Ensinger, W., Electroless synthesis of platinum and platinum–ruthenium nanotubes and
their application in methanol oxidation, J. Mater. Chem., 21: 6286-6291 (2011)
Boehme, M., Ensinger, W., From nanowheat to nanograss: A preparation method to achieve
free standing nanostructures having a high length/diameter aspect ratio
Adv. Eng. Mater., 13: 373-375 (2011)
Suchanicz, J.; Kim-Ngan, N.-T.; Konieczny, K.; Jankowska-Sumara, I.; Balogh, A. G., Soft
and hybrid-doped Pb(Zr,Ti)O3 ceramics under stress, electric field, and temperature
loading, J. Appl. Phys., 109: 104105 (2011)
Radecka, M.; Pamula, E.; Trenczek-Zajac, A.; Zakrzewska, K.; Brudnik, A.; Kusior, E.; KimNgan, N.-T.; Balogh, A. G., Chemical composition, crystallographic structure and
impedance spectroscopy of titanium oxynitride TiNxOy thin films, Solid State Ionics, 192:
693-698 (2011)
Kurbatov, D.; Opanasyuk, A.; Duvanov, S. M.; Balogh, A. G.; Khlyap, H., Growth kinetics
and stoichiometry of ZnS films obtained by close-spaced vacuum sublimation technique, Solid
State Sci., 13: 1068-1071 (2011)
Rauber, M.; Alber, I.; Müller, S.; Neumann, R.; Picht, O.; Roth, D., Schökel, A.; ToimilMolares, M. E.; Ensinger, W., Highly-ordered supportless three-dimensional nanowire
networks with tunable complexity and interwire connectivity for device integration,
Nanolett., 11 2304–2310 (2011)
Boehme, M.; Voelklein, F.; Ensinger, W., Low cost chemical sensor device for supersensitive
pentaerythritol tetranitrate (PETN) explosive detection based on titanium dioxide nanotubes
Sensors Actuat B-Chemical, 158: 286-291 (2011)
Muench, F.; Rauber, M.; Stegmann, C.; Lauterbach, S.; Kunz, U.; Kleebe, H.-J.; Ensinger,
W., Ligand-optimized electroless synthesis of silver nanotubes and their activity in the
reduction of 4-nitrophenol, Nanotechnology, 22: 415602 (2011)
72
Materials Analysis
Hoffmann, P.; Fainer, N.; Kosinova, M.; Baake, O.; Ensinger, W., Compilation on synthesis,
characterization, and properties of carbonitrides of silicon and boron in: Silicon CarbideMaterials, Processing and Applications in Electronic Devices, Ed. Mukherjee, M.; InTech
(2011), ISBN 978-953-307-968-4.
Flege, S.; Hatada, R.; Baba, K.; Ensinger, W., Fluorine and carbon ion implantation and
deposition on metals by plasma source ion implantation
Surf. Coat. Tech., 206: 963-966 (2011)
Flege, S.; Hatada, R.; Baba, K.; Ensinger, W., Methane plasma-based ion implantation of
metallic and galvanically oxidized tantalum, Surf. Coat. Tech., 206: 951-954 (2011)
Ali, M.; Nasir, S., Nguyen, H. Q.; Sahoo, J. K.; Tahir, M. N.; Tremel, W.; Ensinger, W.
Metal ion affinity-based biomolecular recognition and conjugation inside synthetic polymer
nanopores modified with iron–terpyridine complexes
J. Am. Ceram. Soc., 133: 17307-17314 (2011)
Hatada, R.; Flege, S.; Ensinger, W.; Baba, K., Comparison of the surface modification of
tungsten and gold by methane plasma source ion implantation, IEEE T. Plasma Sci., 39: 30803084 (2011)
Baba, K.; Hatada, R.; Ensinger, W.; Flege, S, Deposition of diamond-like carbon films on
inner wall surfaces of millimeter size diameter steel tubes by plasma source ion implantation
IEEE T. Plasma Sci, 39: 3140-3143 (2011)
Muench, F.; Oezaslan, M.; Seidl, T.; Lauterbach, S.; Strasser, P.; Kleebe, H.-J.; Ensinger, W.
Multiple activation of ion track etched polycarbonate for the electroless synthesis of metal
nanotubes Appl. Phys. A-Mater., 105: 847-854 (2011)
Kim-Ngan, N.-T. H.; Havela, L.; Adamska, A. M.; Daniš, S.; Pešička, J.; Macl, J.; Eloirdi, R.;
Huber, F.; Gouder, T.; Balogh, A. G., Characterization of U-based thin films: the UFe2+x case
J. Phys.: Conference Series, 303: 012012 (2011)
Westmeier, W.; Odoj, R.; Tyutyunnikov, S. I.; Hashemi-Nezhad, S. R.; Ensinger, W.;
Zamani-Valasiadou, M.; Brandt, R.; Thomauske, B. ,Experiments on transmutation of
longlived radioactive wast, ATW – Int. J. Nuclear Power, 56: 620-628 (2011)
Alber, I.; Sigle, W.; Müller, S.; Neumann, R.; Picht, O.; Rauber, M.; van Aken, P. A., ToimilMolares, M. E., Visualization of multipolar longitudinal and transversal surface plasmon
modes in nanowire dimers ACS Nano, 5; 9845–9853, (2011) DOI: 10.1021/nn2035044
Materials Analysis
73
Light-triggered Ionic Transport Through Photosensitive Synthetic Nanopores
S. Nasir, Q.H. Nguyen, M. Ali, and W. Ensinger
The generation of nanofluidic systems that respond to external stimuli are crucial to mimic
and exploit the functionality of ion channels in living organisms. To achieve active control
over ionic transport, the pore surface is decorated with a variety of functionalities that
respond to external stimuli such as solution pH-value, temperature, light and biomolecules.
The design of nanopores sensitive to ultraviolet (UV) light still constitutes a challenge for
current technologies. Unlike a chemical stimulus, UV light is noninvasive and the whole
process can be tuned by manipulating the light wavelength. Here, we describe a novel
technique in which photolabile protecting groups (PPGs) were immobilised onto the pore
surface to miniaturise photosensitive nanofluidic devices. For this purpose, polyethylene
terephthalate (PET) foils of 12µm thickness were irradiated with swift heavy ions (Au at
11.4 MeV/u) with either a single ion or 5×108 ions cm-2 at the UNILAC linear accelerator
(GSI, Darmstadt). The fabrication of a single conical nanopore and an array of cylindrical
nanopores is achieved through well known asymmetric and symmetric track-etching
techniques [1], respectively. Track-etched nanopores contain carboxylic acid (-COOH)
groups on the surface and pore walls. The -COOH groups were exploited for the
immobilisation of 4-oxo-4-(pyren-4-ylmethoxy) butanoic acid (PYBA) as a photolabile
molecule in a two-step reaction process. Firstly, -COOH groups were converted into amine
groups by reacting with ethylenediamine via carbodiimide coupling chemistry. Secondly,
surface amine groups were allowed to react with PYBA molecules in the presence of N-(3dimethylaminopropyl)-N′-ethylcarbodiimide.
Fig. 1: Schematic presentation of
wettability changes occuring in PYBAmodified nanopores after UV-light
irradiation-induced photodegradation of
PYBA and subsequent creation of a
charged surface state [2].
For the case of a single conical nanopore, the success of chemical modification reactions
was corroborated by measuring the current–voltage (I–V) characteristics, which are
dictated by the electrostatic interaction of the charged pore surface with the mobile ions in
an electrolyte solution. Figure 2a shows that after amination the permselectivity of the
nanopore is switched from cation- to anion-selective, leading to the inversion of current
rectification due to the change of pore surface charge from negative (COO-) to positive
(NH3+). As expected, the immobilisation of PYBA molecules resulted in the loss of surface
charge due to the presence of uncharged terminal pyrene moieties (Fig.1). Eventually, the
PYBA-modified pore behaved like an ohmic resistor (Fig. 2a). Upon UV365nm light
74
Materials Analysis
irradiation, the ester bonds adjoining the pyrene chromophore were cleaved, resulting in
the generation of -COOH functionalities on the surface and inner pore walls (Fig.1), which
restores the cation-selective behaviour of the pore. Figure 2b shows permeation data of
methylviologen (MV2+) and naphthalene disulfonate (NDS2-) transported per cm2 of the
PYBA-modified membrane containing an array of cylindrical nanopore (~ 20 ± 3nm)
before and after UV treatment [2].
(a)
1.0
-
Current (nA)
–COO
Light off
+
–NH3
0.5
Light on
0.0
-0.5
-1.0
-2
(b)
-1
0
1
2
-2
-1
0
1
2
Voltage (V)
Voltage (V)
Before UV irradiation
After UV irradiation
Nanomoles per cm
2
12
2+
2+
MV
2NDS
MV
2NDS
9
Fig. 2:
a)I/V-characteristics
of the single conical nanopore
with carboxyle and amine
groups (left), and PYBA-modified
pore before and after UVirradiation
(right)
b)Permeation data (nanomoles
transported as a function of
time) of charged analytes
(methylviologen
cation,
naphthalene disulfonate anion)
through
a
PYBA-modified
multipore membrane, before
and after UV-induced PYBA
bond cleavage
6
3
0
40
80
120
Time (min)
160
40
80
120
160
Time (min)
In conclusion, we demonstrated the design of a light-gated nanofluidic device based on
synthetic nanopores modified with photolabile PYBA molecules. UV light treatment leads to
the generation of hydrophilic groups and concomitant permselective transport of ionic
species through the nanopores. It is anticipated that such nanofluidic devices will readily
find applications in light-induced sensing and controlled drug release processes.
References:
[1]
M. Ali, S. Nasir, H.Q. Nguyen, J.K. Sahoo, M.N. Tahir, W. Tremel, W. Ensinger, J. Am. Chem. Soc. 133
(2011) 17307.
[2] M. Ali, S. Nasir, P. Ramirez, I. Ahmed, H.Q. Nguyen, L. Fruk, S. Mafe, W. Ensinger, Adv. Funct. Mater.
22 (2012) 390.
This work has financially been supported by Beilstein-Institut in Frankfurt/Main in the frame of the project
NanoBiC.
Materials Analysis
75
Materials Modelling Division
The research of the Materials Modelling Division is focused on multi-physics modelling of
defect structures in functional oxides, 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. In 2011 a new high-performance CPU-GPU hybrid machine with 840 processor
cores, which was funded by a BMBF-grant, became operational.
The current research topics are:
 Functional oxides
o Defects and diffusion in TCOs
o New lead-free ferroelectrics: Ordering effects and defects
o Finite-size effects in oxide nanoparticles
 Nanoalloys
o Plasticity of nanocrystalline metals and alloys
o Metallic nanoglasses
o Nanophase diagrams
o Metallic nanoparticles under nanoextrusion
 Energy materials
o Interfaces in Li-intercalation batteries
o CIS/CIGS absorber materials
o High-pressure phases of nitrogen
o 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. A new master course on “Theoretical materials science”
is currently under preparation.
76
Materials Modeling Division
Staff Members
Head
Prof. Dr. Karsten Albe
Emeritus Professor
Prof. Dr. Hermann Rauh, M.A., C.Phys., F.Inst.P., F.I.M.
(since April 2011)
Research Associates
Dr. Antti Tolvanen
Dr. Jochen Rohrer
PD Dr. Yuri Genenko (since April 2011)
Dr. Galina Yampolskaya (since April 2011)
Dr. Sergey Yampolskii (since April 2011)
Secretary
Renate Hernichel
PhD Students
Dipl.-Ing. Peter Agoston
M.Sc. Daniel Sopu
Dipl.-Phys. Johann Pohl
Dipl.-Ing. Manuel Diehm
Dipl.-Ing. Yvonne Ritter
Dipl.-Ing. Melanie Gröting
Dipl.-Ing. Silke Hayn
Dipl.-Ing. Jonathan Schäfer
Dipl.-Ing. Arno Fey
M.Sc. Olena Lenchuk
Diploma Students
Arno Fey
Ofer Hirsch
Bachelor Students
Konstanze Kalcher
Stephen Weitzner
Research Fellow
Dr. Guang-Tong Ma (AvH)
Guest Scientist
Konstantin Avchachov
Research Projects
Forschergruppe 714, Plasticity of nanocrystalline metals and alloys,
(DFG AL 578/7-2, 2006-2012)
Quantenmechanische Computersimulationen zur Elektronen- und Defektstruktur oxidischer
Materialien (SFB 595, Teilprojekt C1, 2007-2014)
77
Atomistische Computersimulationen von Defekten und deren Bewegung in Metalloxiden
(SFB 585, Teilprojekt C2, 2003-2014)
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, 2010–2012))
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 Gläser mit nanoskaligen
Sekundärphasen (DFG AL578/13-1, 2011–2013)
Atomic scale modeling of metallic nanoparticles embedded in nanoscale carbon structures
(DFG KO 3861/2-1, 2010–2012)
Bleifreie Piezokeramiken, LOEWE-Schwerpunkt ADRIA (HMWK, 2011-2013)
BMBF-GRACIS, Chemische Gradienten in CU(In,Ga)Se2 Solarzellen: Grenzflächenuntersuchungen und theoretische Modellierung
(03SF0359E, 2009-2012)
PPP Finnland, Atomic level simulations of structure and growth of nanoalloys
(DAAD 2011–2013)
PhD-Theses
Agoston, Peter, Point defect and surface properties of In2O3 and SnO2: A comparative study
by first-principles methods , [Online-Edition: urn:nbn:de:tuda-tuprints-27811] ,
TU Darmstadt (2011).
D. Sopu, Molecular Dynamics Simulations of Metallic Nanoglasses.
[Online-Edition: urn:nbn:de:tuda-tuprints-28453] TU Darmstadt (2011).
Y. Ritter, Molecular Dynamics Simulations of Structure-Property Relationships in Cu-Zr
Metallic Glasses. [Online-Edition: urn:nbn:de:tuda-tuprints-28685] TU Darmstadt (2012).
78
Publications
J. Pohl, K. Albe, Thermodynamics and kinetics of the copper vacancy in CuInSe2, CuGaS2 ,
CuInSe2, and CuGaS2 from screened-exchange hybrid density functional theory,
J. Appl. Phys., 110 (2011) 109905.
J. Pohl, K. Albe, Void formation in melt-grown silicon studied by molecular dynamics
simulations: From grown-in faulted dislocation loops to vacancy clusters , App. Phys. Lett., 99
(2011) 081910.
J. Pohl, A. Klein, K. Albe, Role of copper interstitials in CuInSe2: First-principles calculations.
Phys. Rev. B (Rapid Comm.), 84 (2011) 121201.
Y. Ritter, K. Albe, Thermal annealing of shear bands in deformed metallic glasses: Recovery
mechanisms in Cu64Zr36 studied by molecular dynamics simulations ,
Acta Mat. (2011), 59, 7082-7094.
Y. Ritter, D. Sopu, H. Gleiter, K. Albe, Structure, stability and mechanical properties of
internal interfaces in Cu64Zr36 nanoglasses studied by MD simulations , Acta Mat., 59 (2011)
6588-6593.
N. Q. Vo, J. Schäfer, R. S. Averback, K. Albe, Y. Askenazy, P. Bellon, Reaching theoretical
strengths in nanocrystalline Cu by grain boundary doping , Scripta Mat., 65 (2011) 660-663.
M. V. Hohmann, P. Agoston, A. Wachau, T. J. M. Bayer, J. Brötz, K. Albe, A. Klein,
Orientation dependent ionization potential of In2O3: A natural source for inhomogeneous
barrier formation at electrode interfaces in organic electronics, J. Phys. Cond. Mater. , 23
(2011) 334203.
P. Agoston, K. Albe, Thermodynamic stability, stoichiometry, and electronic structure of bccIn2O3 surfaces. Phys. Rev. B, 84 (2011) 045311.
D. Sopu, J. Kotakoski, K. Albe, Finite-size effects in the phonon density of states of
nanostructured germanium: A comparative study of nanoparticles, nanocrystals, nanoglasses,
and bulk phases. Phys. Rev. B, 83 (2011) 245416.
M. Gröting, S. Hayn, K. Albe, Chemical order and local structure of the lead-free relaxor
ferroelectric Na1/2Bi1/2TiO3, J. Solid State Chem., 184 (2011) 2041.
W. N. Li, H. L. Duan, K. Albe, J. Weissmüller, Line stress of step edges at crystal surfaces.
Surf. Sci., 605 (2011) 947.
J. Schäfer, A. Stukowski, K. Albe, Plastic deformation of nanocrystalline Pd-Au alloys: On the
interplay of grain boundary solute segregation, fault energies and grain size , Acta Mater., 59
(2011) 2957.
79
P. Agoston, K. Albe, Disordered reconstructions of the reduced SnO2-(110) surface, Surf. Sci.,
605 (2011) 714.
D. Sopu, Y. Ritter, H. Gleiter, K. Albe, Deformation behavior of bulk and nanostructured
metallic glasses studied via molecular dynamics simulations , Phys. Rev. B, 83 (2011)
100202
P. Agoston, K. Albe, R. M. Nieminen, M. J. Puska, Reply: “Comment on Intrinsic n-type
Behavior in Transparent Conducting Oxides: A Comparative Hybrid-Functional Study of In2O3,
SnO2, and ZnO”, Phys. Rev. Lett., 106 (2011) 069602
D. Gross, R. Müller, M. Müller, B. Xu, K. Albe, On the origin of inhomogenous stress and
strain distributions in single-crystalline metallic nanoparticles, Int. J. Mat. Res. 102 (2011)
743
C. Koerber, A. Wachau, P. Agoston, K. Albe, A. Klein, Self-limited oxygen exchange kinetics
at SnO2 surfaces, Phys. Chem. Chem. Phys., 13 (2011) 3223-3226.
S.V. Yampolskii, Y.A. Genenko, C. Melzer, and H. von Seggern, Self-consistent model of
unipolar transport in organic semiconductor diodes: accounting for a realistic density-ofstates distribution, J. Appl. Phys., 109 (2011) 073722 .
K. Stegmaier, A. Fleissner, H. Janning, S.V. Yampolskii, C. Melzer, and H. von Seggern,
Influence of electrical fatigue on hole transport in poly(p-phenylenevinylene)-based organic
light-emitting diodes J. Appl. Phys., 110 (2011) 034507 .
Y. A. Genenko, H. Rauh, and P. Krüger, Finite-element simulations of hysteretic ac losses in a
bilayer superconductor/ferromagnet heterostructure subject to an oscillating transverse
magnetic field, Appl. Phys. Lett., 98 (2011) 152508.
K. Albe, P. Agoston, J. Pohl, Ab-initio modeling of defects in semiconductors, in, Advanced
Characterization Techniques for Thin Film Solar Cells“ edited by Daniel Abou-Ras, Thomas
Kirchartz and Uwe Rau, Wiley-VCH (2011), p. 479-497
80
Chemical order and local structure of the lead-free relaxor ferroelectric Na1/2Bi1/2TiO3
Melanie Gröting, Silke Hayn, Karsten Albe
Na1/2Bi1/2TiO3 (NBT) is a model relaxor ferroelectric with two different cations (Na+ and
Bi3+) on the A-site of the perovskite structure. NBT-based materials show extraordinarily
high strains and are amongst the most promising candidates to substitute the toxic
PbZr1/2Ti1/2O3 (PZT) in piezeoelectric applications. Especially, recent results on N
Na1/2Bi1/2TiO3-BaTiO3-K1/2Na1/2NbO3 (NBT-BT-KNN) solid solutions revealed promising
piezoelectric properties.[1,2]
The origin of this material’s relaxor behavior is still controversial, but in B-site mixed
perovskites it is generally associated with heterovalent disorder.[3] NBT has aliovalent
cations on the A-site (Na+ and Bi3+) in the exact ratio 1:1. For B-site mixed perovskites
chemical ordering is generally understood.[4] Order, commonly rock-salt (111)-order,
occurs when the charge difference between the cation species occupying the same
crystallographic site is q≥2.
In contrast, A-site ordering is much less common. There exist only a few examples where Asite order is experimentally found. Examples can be found in a review recently published by
King and Woodward.[5] They show that A-site order commonly occurs in {001}-layers, but
that charge differences between the cations of q≥2 are not sufficient to cause ordering.
Systematic oxygen vacancies, vacancies in the A-sublattice or B-site ordering are necessary
to stabilize chemical A-site order in mixed perovskites.
In order to gain insights into the chemical ordering tendency, its driving force and the
consequences for the local structure we investigated six different cation configurations in
2x2x2 (pseudo)cubic perovskite supercells using total energy calculations based on
electronic density functional theory. We calculated total energies of the different Bi/Naorders in ideal cubic perovskite
structures
and
in
relaxed
structures, the results are shown in
Fig. 1 (contributions from ionic and
cell shape relaxation are given
separately). In the ideal perovskites
the different configurations reveal
only small variations in total
energy of less than 120 meV, with
110-order being the most favored
and 001-order being the most
unfavored order type. Taking
structural relaxations into account
the maximal difference is almost
doubled (220 meV). The most
Fig. 1: Total energies from DFT calculations in ideal perovskite stable structure now is the layered
(green) and relaxed structures (blue and red). The total energy 001-configuration, while the rockof the ideal perovskite 001 is set to zero. Energy changes from salt ordered system 111 becomes
cell shape relaxation (red) are very small.
the most unfavored one.
81
In the perovskite structure oxygen is quasioctahedrally coordinated by Bi/Na- and Ti-atoms,
with two Ti-atoms in the apical positions of the
octahedron at a distance of a/2 and four Bi/Naatoms in the equatorial positions at a distance of
a 2 , resulting in six possible oxygen
environments characterized by the Bi/Na4xNa,
4xBi,
1xBi/3xNa,
Fig. 2: Oxygen environments in the 2xBi/2xNa coordination:
(cis)- and 2xBi/2xNa (trans)-coordination. The 3xBi/1xNa, and 2xBi/2xNa in cis- or transcis-coordination allows relaxation of the oxygen coordination, the latter two are shown in Fig. 2.
anion while the trans-coordination does not.
Oxygen ions are expected to displace, if there are
significant differences in size, charge or bond strength of the coordinating cations and if the
oxygen ion is not an inversion center. Hence, among the six possible coordinations, there
are three where no displacement of the oxygen ion is possible (inversion symmetry),
namely 4xNa, 4xBi and 2xBi/2xNa (trans), one coordination where displacing is severely
facilitated 2xBi/2xNa (cis), while in 3xBi/1xNa and 1xBi/3xNa smaller displacements
towards the Bi ions can occur. These displacements can help to release local stresses and to
compensate local charge imbalances, thus stabilizing certain configurations. Local ionic
displacements are observed mainly on the oxygen sublattice in the exact way postulated by
Knapp,[6] while almost no displacements on the two cation sublattices are observed.
Moreover structural relaxation can reverse the stability of the considered configurations
with respect to the ideal perovskite structure. In the rock-salt ordered structure all oxygen
anions are in the 2xBi/2xNa (trans) coordination, which explains why this configuration
does not relax at all.
We report for the first time on displacive disorder on the oxygen sublattice, which up to
now has been neglected in experimental studies and should be investigated in more detail
in future research.
In order to identify the driving force for these oxygen displacements we present partial
densities of state in Fig. 3, before and after relaxation of the chemical configuration 001 in
comparison with 111. It can be seen that upon relaxation additional Bi 6s-states arise at the
top of the valence band. Although the maximum of 6s-states stays below the valence band
around -10.0 eV, there is a significant increase of the state density in the anti-bonding
region above -2 eV, these states mix with both the Bi 6p-states and the O 2p-states, which is
characteristic for the formation of a stereochemically active Bi3+ lone pair.[7] This
hybridization of Bi 6sp─O 2p states leads to a considerable energy gain, which increases the
stability especially of structures with layers of high Bi-concentrations in {001}-planes. This
kind of planes was considered by Kreisel et al. to explain the diffuse scattering patterns
indicative for Guinier-Preston-Zones.[8]
Generally, chemical ordering will occur if there is a decisive energy difference between a
most favored ordered configuration and other structures and if this energy difference is
higher than the entropy contribution of mixing. We find an energy difference of 34 meV
between the two most stable structures with 001- and 10-01-order.
The entropy contribution of mixing to the free energy in the disordered state can be
approximated by the configurational entropy of an ideal solution with xBi=xNa=0.5 by
-TS=-kBT [- xBiln xBi - xNaln xNa]
82
Fig. 3: Densities of states of chemical configurations 111 (left) and 001 (right) before (black dotted line) and
after relaxation (filled). Energies are given relative to the valence band maximum. On structural relaxation possible in all structures except the 111 configuration - band gaps are enlarged and changes especially of the
Bi 6s- and O 2p-state densities occur.
This approximation gives a lower limit for the ordering temperature, since the ideal
solution model is overestimating the mixing entropy. At sintering conditions the energy
equivalent TS is more than twice the obtained energy difference between the most stable
ordered states, thus the disordered state is favored over all ordered states. The critical
temperature is about 570 K. Chemical long-range ordering can therefore be ruled out, but
short-range ordering with alternating layers of Bi and Na along 001 -directions is still
possible to occur. Thus, depending on synthesis conditions, different degrees of short-range
order can be expected.
References:
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
W. Jo, T. Granzow, E. Aulbach, J. Rödel, D. Damjanovic, J. Appl. Phys., 105 (2009) 094102.
J. Rödel, W. Jo, K. T. P. Seifert, E. M. Anton, T. Granzow, D. Damjanovic, J. Amer.
Cer.
Soc. 92 (2009) 1153-1177.
A. A. Bokov, Z. G. Ye, J. Mat. Sci. 41 (2006) 31-52.
P. K. Davies, H. Wu, A. Y. Borisevich, I. E. Molodetsky, L. Farber, Ann. Rev. Mat. Res.
38
(2008) 369-401.
G. King, P. M. Woodward, J. Mat. Chem. 20 (2010) 5785-5796.
M. C. Knapp, P. M. Woodward, J. of Sol. State Chem. 179 (2006) 1076- 1085.
L. A. Olsen, J. Lopez-Solano, A. Garcia, T.Balic-Zunic, E. Makovicky, J. Sol. Stat. Chem. 183
(2010) 2133-2143.
J. Kreisel, P. Bouvier, B. Dkhil, P. A. Thomas, A. M. Glazer, T. R. Welberry, B.
Chaabane,
M. Mezouar, Phys. Rev. B 68 (2003) 014113.
83
Optical transmittance of photonic structures
with logarithmically similar dielectric constituents
H. Rauh, G.I. Yampolskaya, S.V. Yampolskii
Photonic crystals in the traditional sense are regularly structured, synthetic composites
made up of materials with different refractive indices. The spatial variation of the refractive
index significantly modifies the spectral characteristics of electromagnetic waves, bringing
about features such as transparency bands and stop bands or bandgaps. It would be
extremely desirable to find optical-mirror and filter properties—high reflectance over some
range of frequency and high transmittance, or selectivity, otherwise—united in one single
photonic device. Exploring photonic structures which reveal transparency at low
frequencies, but opacity, or possibly selectivity, at higher frequencies, thus suggests itself.
By means of a vector potential approach, we have explored, both analytically and
numerically, the optical transmittance of one-dimensional photonic structures in the form
of logarithmically similar, layered stacks made up of pairs of lossless dielectric plates,
assuming linearly polarized electromagnetic radiation at normal incidence. Resorting to an
analysis of the respective photonic modes, the dependence on frequency (or, equivalently,
the variation with the characteristic structural length) of the optical property addressed has
been established for a singly logarithmic stack (Fig. 1) as well as for two of its symmetric
derivatives, an outbound doubly logarithmic stack (Fig. 2 (left)) and an inbound doubly
logarithmic stack (Fig. 2 (right)).
Fig. 1: Schematic view of a singly logarithmic stack with dielectric constituents a (red) and b (yellow)
embracing four unit cells, characterized by a layering of the type abab... (left) or baba... (right) and excited by
normally incident electromagnetic radiation with the electric (magnetic) field oriented parallel to the x-axis
and the magnetic (electric) field oriented parallel to the y-axis of a Cartesian coordinate system x, y, z.
Fig. 2: Schematic view of an outbound doubly logarithmic stack (left) and of an inbound doubly logarithmic
stack (right) with dielectric constituents a (red) and b (yellow) embracing eight unit cells, characterized by a
layering of the type abab...abba...baba and excited by normally incident electromagnetic radiation with the
electric (magnetic) field oriented parallel to the x-axis and the magnetic (electric) field oriented parallel to the
y-axis of a Cartesian coordinate system x, y, z.
84
Let us consider a series of one-dimensional, layered stacks of pairs of dielectric plates based
on one or two sets of m  2 unit cells numbered by the index μ, spreading infinitely along
the x- and y-directions, with respective extent dμ in the z-direction of a Cartesian coordinate
system x, y, z. Each unit cell includes alternating constituents a and b characterized by
respective thicknesses da,μ=αdμ and db,μ=βdμ with definite structural parameters
0<α,β<1, where α+β =1, so that dμ=da,μ+db,μ, for μ=1, 2, ... , m. The stacks
themselves reveal logarithmic similarity by dint of reduced thicknesses da,μ and db,μ, and
therefore reduced lateral extent dμ, when following the sequence μ =1, 2, ... , m, such that
the ratio of the thicknesses of any corresponding successive plates, and hence the ratio of
the widths of any two adjacent unit cells, is the same constant,
da,μ+1/da,μ=db,μ+1/db,μ=dμ+1/dμ≡  introducing the fixed structural parameter 0<τ<1,
which admits the representations da,μ=ατμ−1d1 and db,μ=βτμ−1d1, and consequently
dμ= τμ−1d1. The total lateral extent of the first μ unit cells thus is lμ =

 d ≡
 1




1
1
d1 and
the respective distances at which the constituents a and b accommodated in the next unit
cell terminate are la,μ+1=lμ+da,μ+1 and lb,μ+1=lμ+db,μ+1 for μ=1, 2, ... , m−1. The
optical properties of the constituents a and b are supposed to be entirely determined by
fixed values of the principal components of their respective tensors of electric permittivity
εν=εa>1 and εν=εb>1 for ν = x, y, neglecting electromagnetic dispersion as well as
dissipation and assuming in-plane crystalline isotropy.
Our investigations yielded the following key results: (i) the transmittance of the singly
logarithmic stack shows single oscillatory maxima of almost full height at low frequencies
and total quench, i.e. full reflectance, at larger frequencies, combining properties of a
practically ideal transmission filter and of a perfect mirror alike (Fig. 3); (ii) the
transmittance of the outbound doubly logarithmic stack shows twinned oscillatory maxima
of full height at low frequencies, supplemented with a sharp, full resonance at a higher
frequency against a background of suppressed transparency, revealing traits of a practically
Fig. 3: Transmittance Tsl of the singly logarithmic stack of total lateral extent lm as a function of the normalized
frequency ωd1/2πc in the case of linearly polarized electromagnetic radiation due to on-axis propagation, for
the structural parameters m = 25, α = 0.1, β = 0.9, τ = 0.95 and the dielectric parameters εa = 20, εb = 1.5,
referring to a layering of the type abab... (left) and, respectively, baba… (right).
ideal transmission filter and of a perfect band-pass filter at the same time (Fig. 4 (left));
(iii) the transmittance of the inbound doubly logarithmic stack shows twinned oscillatory
maxima of full height at low frequencies, supplemented with a series of pairs of sharp
85
spikes of full transparency for higher frequencies against a background of suppressed
transparency, equally revealing traits of an ideal transmission filter and of a perfect bandpass filter at the same time (Fig. 4 (right)).
Fig. 4: Transmittance Tdl(o) of the outbound doubly logarithmic stack (left) and Tdl(i) of the inbound doubly
logarithmic stack (right) of total lateral extent 2lm as a function of the normalized frequency ωd1/2πc in the
case of linearly polarized electromagnetic radiation due to on-axis propagation, for the structural parameters
m = 25, α = 0.1, β = 0.9, τ = 0.95 and the dielectric parameters εa = 20, εb = 1.5, referring to a layering of the
type abab...abba...baba.
The sharp, full resonance of the transmittance found in the case of the outbound stack and
the pairs of sharp spikes of full transparency found in the case of the inbound stack derive
from different origins: the former is due to a localized photonic mode associated with the
internal defect of the outbound stack; the latter, in contrast, arise from extended photonic
modes that spread across the entire domain of the inbound stack. Our study proves that
one-dimensional photonic structures generated by logarithmically similar dielectric
constituents are indeed capable of unfolding desirable and useful optical properties in one
single photonic device: transparency at low frequencies, but opacity, or selectivity, at higher
frequencies.
86
Materials for Renewable Energies
Research in the Renewable Energies group focuses on nanoscaled catalysts applied
predominantly in low and intermediate temperature fuel cells, but also in heterogeneous
catalysis applications, using advanced ex situ, in situ, and, in particular, operando
techniques. The systematic structural and electrochemical characterization 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 cyclic
voltammetry (CV) and single cell fuel cell experiments. 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, e.g. electron conducting
oxides and polymers, which do not suffer from corrosion in the severe conditions of the
cathode side 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. Furthermore, shape-selected nanoparticles are 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 membrane-electrode assemblies (MEA) allowing for a welldefined 3D architecture. Electron microscopy is applied for the electrodes’ detailed
characterization. For this specific purpose, new techniques have been developed and
established in the group starting from sample preparation by ultramicrotomy and Wood’s
alloy infiltration to very sophisticated mapping methods. For the first time, the focused ion
beam (FIB) technique was applied to obtain 3D reconstructions of the porous electrodes.
•
In situ studies
In situ and operando X-ray absorption studies play an important role in our recent activities
with respect to the systematic investigation of reaction and degradation mechanisms. A
special 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 membrane-electrode assembly (MEA). By this approach, electrode areas with
more severe degradation can be identified. In addition to the 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 with further catalyst
optimization. In 2011, the novel technique has been applied to direct methanol fuel cells
and HT-PEM fuel cells, and a “cross-talk” between both electrodes via protons was
unravelled.
Since March 2011, Prof. Roth holds a group leader position at the Institute for Applied
Materials (IAM) – Energy Storage Systems (ESS) (Head: Prof. Helmut Ehrenberg) at
Karlsruher Institute of Technology (KIT) in Karlsruhe. Research at IAM-ESS focuses on
electrochemical storage technology in general, while the Roth group is in particular
interested in redox-flow batteries.
Financial support is provided by DFG, BMWi, BMBF, and EU as well as by the respective
synchrotron facilities and industrial partners. The group`s research interests are covered by
a lecture on “Applied electrochemistry: fuel cells and batteries” and a practical course “Xray absorption spectroscopy – fundamentals and data analysis”. Furthermore, a workshop
on “Scientific work and presentation skills” is mandatory for the bachelor students.
87
Staff Members
Head
Prof. Dr.-Ing. Christina Roth
Secretaries
Maria Bense
(joint with Profs. Donner and Xu)
PhD Students
Dipl.-Ing. Susanne Zils
MSc. Ditty Dixon
Dipl.-Ing. Sebastian Kaserer
Dipl.-Ing. (FH) Hanno Butsch
(extern)
Dipl.-Ing. Alexander Schökel
Dipl.-Ing. Benedikt Peter
Dipl.-Ing. André Wolz
Diploma Students
Manfred Kerner
Christoph Rakousky (extern)
Joachim Langner
Christoph Schwöbel
Guest Scientists
Manoj Krishnan (DAAD)
Research Projects
German-Canadian fuel cell cooperation (BMWi project 2010-2012)
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
F. Ettingshausen, J. Suffner, S. Kaserer, H. Hahn, C. Roth, ’Sb-doped SnO2 hollow spheres
offering micro and nano porosity for the fuel cell electrode structure’, Advanced Energy
Materials 1 (4) (2011) 648-654, DOI: 10.1002/aenm.201100077.
M. Soehn, S. Zils, N. Nicoloso, C. Roth, ’Effective debundling of CNTs and simultaneous
synthesis of Pt nanoparticles by Nafion® induced emulsions’, J. Power Sources 196 (2011),
6079-6084.
D. Dixon, K. Wippermann, J. Mergel, A. Schoekel, S. Zils, C. Roth, ’Degradation effects at
the methanol inlet, outlet and center region of a stack MEA operated in DMFC’, J. Power
Sources 196 (2011) 5538-5545.
F. Muench, S. Kaserer, U. Kunz, I. Svoboda, S. Lauterbach, H.-J. Kleebe, C. Roth, W.
Ensinger, ’Electroless synthesis of platinum and platinum-ruthenium nanotubes and their
application in methanol oxidation’, J. Mater. Chem. 21 (2011) 6286-6291.
M. Rauber, I. Alber, S. Müller, R. Neumann, O. Picht, C. Roth, A. Schoekel, M. E.
Toimil-Molares, W. Ensinger, “Highly-ordered supportless 3-D nanowire networks with
tuneable complexity and interwire connectivity for device integration”, Nano Letters 11 (6)
(2011) 2304-2310.
C. Roth, D. E. Ramaker, 'EXAFS investigations of PEM fuel cells'. Modern Aspects of
Electrochemistry, ed. C. Vayenas, 51, chapter 3 (2011) 159-201.
88
Effective debundling of CNTs and simultaneous synthesis of Pt
nanoparticles by Nafion® induced emulsions
Matthias Soehn, Susanne Zils, Norbert Nicoloso, Christina Roth
Carbon nanotubes, discovered by Iijima in 1991 [1], show unique properties regarding
chemical stability, electronic conductivity and tensile strength. They also provide a high
surface area of up to 2200 m2g-1, which is essential for good catalytic activity. Without
oxidative treatment hydrophobic surface properties can be observed. Depending on their
morphology, carbon nanotubes (CNT) are separated into single wall (SWNT) and multi
wall nanotubes (MWNT). Both types have a high aspect ratio with diameters of 1-20 nm
and lengths of a few micrometers. Many groups focus on carbon nanotubes as a
replacement for the commercial carbon black as catalyst support. Carbon nanotubes have
the disadvantage that they apparently offer less anchor sites for the deposition of metallic
nanoparticles. Therefore, they require specific pre-treatments, as for example the addition
of hydrophilic groups by acid treatment or organic groups like diazonium salts. However,
probably due to their higher crystallinity they undergo less support corrosion in the extreme
environment of PEM fuel cells.
A common way to deposit nanometer-sized catalyst particles with a narrow size distribution
homogeneously on a high-surface area carbon support, for instance Vulcan XC-72 or Ketjen
black, is reduction via ethylene glycol as described by Bock et al. [2]. This method is rather
facile, reproducible and also cheap, as compared to chemical vapour deposition and the
like. It is also suitable to deposit Pt on CNTs, but unfortunately the 1-dimensional nature of
the CNTs is prone to form aggregates and “nests” in ethylene glycol or other polar liquids.
These cannot easily be penetrated by the reactants. And thus, it proves difficult to obtain
homogeneous nanoparticle dispersions on CNTs, especially at the high metal loadings
required for direct methanol fuel cells (DMFC). Usually, surfactants like sodium dodecyl
sulfate or block copolymers are used to mediate between polar liquids and CNTs. For fuel
cell operation and also other catalytic reactions, these have to be removed prior to their
application, as they might affect further reactions negatively. Moreover, surfactants seem to
increase the contact resistances within a CNT buckypaper.
This paper presents a method to debundle and finely disperse CNTs in aqueous solution by
using Nafion® ionomer and butyl acetate to form a stable emulsion [3]. This helps to make
a larger fraction of the CNTs accessible to the reducing agent, so that 3 nm Pt particles with
a very narrow size distribution are homogeneously deposited on the support. In the same
step, the CNTs are coated with Nafion® to improve their ionic conductivity. This appears to
be also advantageous for the final electrode manufacturing step, since it allows applying
the conventional airbrush technique also in those cases, in which CNTs are used as support
material.
Catalyst synthesis
60 mg multi wall carbon nanotubes (Elicarb© from Thomas Swan, U.K.) are mixed and
stirred with 60 ml nitric acid (68%) and treated with ultrasound (Hielscher UPV 100) for
10 min to remove metallic impurities. After diluting with water, the suspension is vacuumMaterials for Renewable Energies
89
filtrated over a 47 mm polycarbonate membrane with 0.4 µm pore size. Remaining acid is
removed by rinsing with water several times. The wet CNT residue is removed from the
polycarbonate membrane and mixed with 60 ml butyl acetate while stirring and ultrasonic
treatment for 10 min, leading to a homogeneous dispersion. For the platinum precursor
solution, 145 mg potassium hexachloroplatinate (Sigma-Aldrich) is dissolved in 10 ml
ultrapure water at 50°C. 60 ml ethylene glycol and the platinum precursor solution are
mixed with the MWNT-butylacetate dispersion in a 250 ml round bottom flask. After
adding 0.5 ml of 5% Nafion® solution (Dupont D521) and another 15 min of ultrasonic
treatment and stirring, the two phase boundary between the liquids disappears and a
homogeneous milky-grey emulsion is created.
The emulsion is heated in an oil bath from room temperature to 170°C and the mixture is
held for 120 min under reflux conditions while stirring. Samples are taken during the
synthesis for a detailed investigation by XRD. After cooling down, the catalyst-solvent
mixture is filtered over a polycarbonate filter. Rinsing with 1:1 isopropanol-water removes
the remaining ethylene glycol and butyl acetate. After removal of the filter, the wet residue
is mixed with 30 ml isopropanol and 30 ml water by ultrasonic treatment to create a
sprayable ink. Nafion® and/or PTFE solution can be added here.
MEA preparation and electrochemical investigation by IV curves
For membrane preconditioning, pieces of Nafion® 117 are heated up to 80°C in 500 ml of 1
M sulphuric acid with 20 ml of 30% hydrogen peroxide solution for 2 h. After rinsing with
DE-water, the membrane is fixed to a heated table (110°C) by means of a mild vacuum.
Airbrush is used to apply the aqueous catalyst ink onto the membrane. 2 ml ink is sprayed
on each side, which corresponds to a maximum Pt loading of 0.2 mg cm-2. Each layer is
allowed to dry before it is covered by the next one.
The MEA is covered with two pieces of carbon cloth and fixed between gold-plated stainless
steel plates with a meander flow field. The cell is fed with pure H2 and O2 at atmospheric
pressure. Both gases are humidified by bubblers at 90°C. The cell temperature is set to 75
°C. After a couple of hours in cell conditioning, IV curves are recorded in potentiostatic
mode with an electronic load, compensating contact resistances.
Results and discussion
Nafion® induced emulsions
A mixture of CNTs and butyl acetate leads to a homogeneous black dispersion after
ultrasonic treatment. Adding ethylene glycol and yellow-coloured aqueous K2PtCl6 solution,
a sharp phase boundary is observed (Fig. 1, left). Even with strong ultrasonic treatment it is
not possible to mix the phases. If some Nafion® solution is added, a stable grey emulsion is
created, however. Obviously, Nafion® acts like a surfactant. Microscopic analysis shows
spheres (diameter of ~50 µm) with a black shell in clear liquid (Fig. 1, middle). To
distinguish ethylene glycol and butyl acetate, fluorescin (CAS: 2321-07-5) is used as
colouring agent. Without the black MWNTs, it can be clearly seen in Figure 1 right that the
colourless butyl acetate is located inside the spheres, whereas the ethylene glycol phase
remains outside. This effect can be explained by the amphiphilic nature of Nafion ® with its
hydrophobic tetrafluoroethylene chains and hydrophilic SO3- groups. A Critical Micelle
Concentration (CMC) could not be detected by diluting experiments with the Nafion ®
solution. Therefore, the influence of other surfactants could be excluded.
90
Figure 1: left: CNT-butylacetate phase (black) and ethylene glycol with platinum precursor (yellow) before
ultrasonic treatment; middle: micro spheres of butyl acetate with walls of CNT- Nafion® composite in ethylene
glycol; right: ethylene glycol (coloured yellow with fluorescin) and butyl acetate (inside the spheres) without
CNTs.
For the observed effects we assume a model as depicted in Figure 2: Nafion ® acts as an
emulsifying agent and forms the boundary between ethylene glycol and butyl acetate. The
carbon nanotubes tend to move towards the hydrophobic side chains of the Nafion ®
molecules. This leads to a high interface area of approx. 12 m² for this 120 ml batch,
providing an excellent debundling of the CNTs, which increases the homogeneity of the
following deposition of nanoscaled platinum particles. Concurrently, Nafion® and CNTs are
perfectly mixed, which is essential for a good three-phase contact of the catalyst particles.
Butyl acetate has been chosen because it was reported by Uchida [4] that a Nafion®
solution tends to form colloids with solvents having a dielectric constant between 3 and 10.
Figure 2: Modell of CNT – Nafion® emulsion and formation of the micro spheres.
91
Structural and electrochemical characterization
Figure 3 proves the uniform distribution of platinum on the multi walled carbon nanotubes.
The derived particle statistics show a narrow size distribution of 3 nm ± 0.5 nm, providing
a high active area for catalytic reactions. This has been verified by XRD measurements
during the catalyst synthesis. The yield of the platinum deposition is nearly 100 %, as no
traces of Pt could be found in the filtrate using XRF analysis (not shown here).
Pt particle size distribution
40
rel. Frequency
35
rel. Frequency (%)
30
25
20
15
10
5
0
1
2
3
4
5
6
7
Particle size (nm)
Figure 3: TEM image of Pt/MWNTs after synthesis and corresponding particle size distribution.
Dispersions of carbon nanotubes and water form paper-like structures while drying. If this
dispersion is dried directly on a sheet of Nafion® 117, the residue is very inhomogeneous
because the resulting CNT paper tends to shrink during drying, while the highly
hygroscopic Nafion® substrate swells. Both effects can be prevented using a heated vacuum
table for the substrate and a conventionally-applied airbrush technique [5] for applying the
aqueous Pt/MWNT/Nafion® dispersion. Here, the good blending between Nafion® and
MWNTs leads to a good dispersion of solid matter in water/isopropanol. Consequently,
agglomerations are prevented, which could otherwise block the nozzle of the airbrush
device. The liquid is separated into small droplets during spraying, which dry immediately
on the heated Nafion® surface. Thus, shrinking is limited to a very small region and a
homogeneous dull black surface can be obtained. Each layer is allowed to dry by moving
the airbrush pistol in serpentine movements. The mechanical stability of the electrode was
suitable for different layer thicknesses. The electrode material sticks tightly to the
membrane even without any additional temperature or pressure treatment. A porous feltlike nanotubes-structure can be observed, which provides a good electrical contact to the
GDL as well as an excellent permeability for gases.
The suitability of such a membrane-electrode assembly (MEA) for fuel cell applications was
demonstrated in single cell fuel cell tests. The MEA with a platinum loading of 0.2 mg cm-2
on each side was equipped with a conventional carbon gas diffusion layer and tested in a
fuel cell test bench with pure H2 and O2. After a few hours of operation, an IV curve was
recorded. Power densities up to 450 mW cm-2 were observed and the suitability of the novel
synthesis technique thus demonstrated.
92
Conclusion
The presented work describes a new emulsion-based method to finely disperse CNTs in a
polar liquid. It significantly reduces aggregation of the support material by providing an
excellent debundling of the CNTs during synthesis. Consequently, the support is easily
accessible to the hydrophilic Pt precursors so that even at high metal loadings necessary for
DMFC operation a high dispersion of the catalytically active nanoparticles was obtained. By
using Nafion® as a surfactant, a homogeneous distribution of the proton conductive
ionomer in the electrode was achieved. The resulting Pt/MWNT/Nafion® composite
material is more hydrophilic than the untreated MWNTs, which is needed to create a
homogeneous ink suitable for airbrush spraying onto a hot substrate. Nafion® contents
were optimized for both synthesis and fuel cell operation. Consequently, highly efficient
CNT electrodes could be manufactured as proven by characteristic IV curves with peak
power densities of 770 mW cm-2.
Acknowledgments
Financial support by the EC integrated project CANAPE (Contract No. 500096) is gratefully
acknowledged. We also want to thank C. Fasel, J.C. Jaud and D. Stuermer for TGA and
XRD measurements.
References
S. IIJIMA, HELICAL MICROTUBULES OF GRAPHITIC CARBON , NATURE. 354 (1991) 56-58.
C. BOCK, C. PAQUET, M. COUILLARD , G.A. BOTTON, B.R. MACDOUGALL , SIZE-SELECTED SYNTHESIS OF
PTRU NANO -CATALYSTS: REACTION AND SIZE CONTROL MECHANISM , JOURNAL OF THE AMERICAN
CHEMICAL SOCIETY. 126 (2004) 8028-8037.
M. SOEHN, S. ZILS, N. NICOLOSO , C. ROTH, EFFECTIVE DEBUNDLING OF CNTS AND SIMULTANEOUS
SYNTHESIS OF P T NANOPARTICLES BY N AFION® INDUCED EMULSIONS, JOURNAL OF POWER SOURCES. 196
(2011) 6079-6084.
M. UCHIDA, Y. AOYAMA, N. EDA, A. OHTA, INVESTIGATION OF THE MICROSTRUCTURE IN THE CATALYST
LAYER AND EFFECTS OF BOTH PERFLUOROSULFONATE IONOMER AND PTFE-LOADED CARBON ON THE
CATALYST L AYER OF POLYMER ELECTROLYTE FUEL C ELLS, JOURNAL OF THE ELECTROCHEMICAL SOCIETY.
142 (1995) 4143-4149.
M.S. WILSON, S. GOTTESFELD , HIGH PERFORMANCE CATALYZED MEMBRANES OF ULTRA -LOW PT
LOADINGS FOR POLYMER E LECTROLYTE FUEL CELLS, JOURNAL OF THE ELECTROCHEMICAL SOCIETY. 139
(1992) L28-L30.
93
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 important tools.
Staff Members
Head
Prof. Dr. Robert Stark
Research Associates
Dr. Suman Agarwal
Dr. Marek Janko
Technical Personnel
N.N
Secretary
Imke Murschel
PhD Students
Dipl.-Biol. Elke Kämmerer
Dipl.-Min. Maximilian Köhn
Dipl.-Phys. Agnieska Voß
Bachelor, Master, and Silke Pufahl
Diploma Students
Sandra Schäfer
Sandro Setzer
Dr. Christian Dietz
M. Sc. Kim Lieu Phuong (LMU)
M.Sc. Assma Siddique
M.Sc. Limor Zemel
Lukas Romanowski
Marcus Schulze
Research Projects
Titanomagnetite STA 1026/2-1 (LMU, DFG 2007 – 2011)
Nanostruktur und Benetzungseigenschaften von Porenraumoberflachen (LMU, BMBF 2008
– 2011)
Funktionale Polymer-Peptidoberflächen (CSI, 2010 – 2012)
Influence of elasticity, density and chemical composition of extracellular matrices on the
spatiotemporal dynamics of plasma membranes (CSI, 2010 – 2012)
Wafer cleaning (Industrie 2011 - 2012)
Low friction coatings (Industrie 2011 – 2012)
94
Physics of Surfaces
Publications
Bauer M., Davydovskaya P., Janko M., Kaliwoda M., Petersen N., Gilder S. and Stark R. W.
Raman spectroscopy of laser-induced oxidation of titanomagnetites; J. RAMAN SPECTROSC.
2011; 42:1413 – 1418
Wei T., Gong J., Rössle S. C., Jamitzky F., Heckl W. M., Stark R. W. A leucine-rich repeat
assembly approach for homology modeling of the human TLR5-10 and mouse TLR11-13
ectodomains; J. MOL. MODEL. 17 (2011) 27-36.
Peter D., Dalmer M., Lechner A., Gigler A. M., Stark R. W., Bensch W. Measurement of the
mechanical stability of semiconductor line structures in drying liquids with application to
pattern collapse. J. MICROMECH. MICROENG; 21 (2011) 025001.
Gorbushina A. A., Kempe A., Rodenacker K., Jütting U., Altermann W., Stark, R. W., Heckl,
W. M., Krumbein, W. E.; Quantitative 3-dimensional Image Analysis of Mineral Surface
Modifications – Chemical, Mechanical and Biological; GEOMICROBIOLOGY J. 28 (2011)
172 – 184
Physics of Surfaces
95
Mechanical stability of semiconductor line structures in drying liquids
D. Peter1, M. Dalmer1, A. Lechner2, A. M Gigler3, R. W Stark4 and W. Bensch5
1 Lam Research AG, SEZ Str. 1, 9500 Villach, Austria
2 Department of Microsystems Engineering, FH Regensburg, 93049 Regensburg
3 Department of Earth and Environmental Sci., LMU München, 80333 München
4 Center of Smart Interfaces & Institute of Materials Science, TU Darmstadt, 64287 Darmstadt
5 Department of Inorganic Chemistry, Christian-Albrechts-Universität zu Kiel, 24098 Kiel
Each wafer of a state-of-the-art dynamic random access memory (DRAM) product is subject
to more than 100 cleaning steps during the manufacturing process. Current cleaning
techniques can be categorized into two technologies: ‘dry’ cleaning based on plasmas or
vapors or ‚wet’ cleaning based on liquids, such as the RCA (‘Radio Corporation of America’)
cleaning sequence [1]. A typical wet cleaning technique includes etching of the surface
layer and rinsing the contamination, such as, polymers, particles, or metal ions, from the
surface. As the requirements for material loss are becoming increasingly strict, this limits
the etching of the surface layer and therefore the choice of possible cleaning approaches
[2]. High aspect ratio structures such as stacked capacitors, shallow trench insulators, and
gate structures are very sensitive to lateral forces. These not only occur in advanced
cleaning processes, but also during basic wet processing due to drag forces in the fluid,
centrifugal forces during spin cleaning, or capillary forces [3].
Forces need to be controlled for a non-damaging wet cleaning process. To ensure optimum
process performance with future and therefore smaller technology generations, a better
understanding of the stability of high aspect ratio structures is required. To this end, the
stability of nanostructures with respect to lateral forces has been characterized mostly in air
[4–8]. However, the liquid media used in wet processing may also affect the stability of the
nanostructures, for example by stress corrosion processes or viscous effects. We thus
investigate the lateral stability of polysilicon line structures against an AFM tip in various
solvents. The damage size was influenced by the physical properties of the liquid.
AFM-induced collapse
To induce collapse of the line structures, low feedback parameters were used such that the
AFM tip did not follow the local topography. Thus, the tip exerted lateral forces on the test
structure (Figure 1). Typically, the following events occurred: (i) The AFM tip touched the
wall-like structure only on the top because of the high aspect ratio of the structure
compared to the geometry of the AFM tip. (ii) Without the topographic feedback, the tip
exerted lateral forces on the structure. The force increased proportionally with the torsional
stiffness of the cantilever, up to the point where the stress induced by the AFM tip exceeded
the fracture limit of the line structure (figure 2).
(a)
(b)
Figure 1. Principle of lateral force microscopy (a) and tip induced collapse (b).
96
Physics of Surfaces
Test structures and media
The structures for fracture testing were purchased from IMEC (Leuven, Belgium). The
patterns consisted of lines with a length of a few millimeters. Each line consisted of a stack
of 100 nm polysilicon on top of a thin silicon oxy-nitride (2.4 nm) layer, with a SiO2 cap of
50 nm as shown in figures 2(a) and (b). The nominal line width was 40 nm with a spacing
of 1 μm and for the visualization of the damage also 50 nm structures with a spacing of
approximately 200 nm were used.
The liquids used for the experiments included isopropanol (IPA, VLSI grade), propylene
carbonate (PC, IUPAC: 4- methyl-1,3-dioxolan-2-one (Selectipur)), and de-ionized water
(DI water, 18.2 M� (Milli-Q)). DI water mixtures with sucrose were used to obtain higher
viscosities. Two solutions of 30 wt% and 40 wt% sucrose were prepared and are referred to
as S30 and S40. The samples and the AFM tip were completely immersed in the liquid. The
amount of liquid was sufficiently large such that the thickness of the liquid (several
millimeters) did not influence the AFM measurements.
Figure 2. The design of the patterns (a) and two SEM micrographs showing a set of line structures (b).
The shape of the damage generated with the AFM tip was similar for all tested media. The
yield line of the structure was always symmetrically curved which indicates a conchoidal
fracture. Differences were observed in the lengths of the broken parts of the line. The
corresponding debris usually consisted of only a single piece (figure 3).
Fracture mechanism
A stress corrosion crack (SCC) process is a possible candidate to explain the fracture. SCC
lowers the absolute fracture strength of the Si−O−Si bonds. Such a process has been
observed for polysilicon [9] and single-crystal silicon [10] in DI water. However, the
opposite was also reported for the latter [11]. Michalske et al [12] suggested a model for a
SCC process for silicon oxide. It explains the reduced stability of the Si−O−Si bond due to
the bond angle variation which increases its chemical reactivity. Thus, no influence of the
surface tension, density, or viscosity would be expected on the fracture force.
Figure 3. SEM micrograph of characteristic round damage as observed for tests in air. Sample covered in Pt
for better contrast.
Physics of Surfaces
97
Figure 4. Experimental collapse forces in various media. The box encloses 50%. The asterisks denote the
extreme values measured. For every medium there are data points from at least 20 different measurements
except for S30 and PC+IPA .
The SCC process is a very slow process, and crack tip velocities between 10 −6 and 10−7 m
s−1 are expected [11], much smaller than the Rayleigh wave speed in silicon (2–3 km s−1)
at which cracks usually propagate. Taking into account that the fracture process occurs
within less than 2 ms would allow SCC-assisted rupture lengths of only a few nanometers.
Thus, SCC can only be responsible for a small part of the rupture line, which is 40 nm
perpendicular to the line and larger than 300 nm along with the line.
Characteristic differences occurred in the lengths of the generated damage mainly
depending on the bulk properties of the liquid media. The fracture force (Fig. 4) and the
damage size (not sgown) did not correlate with each other. A two-step breaking model
seems favorable where the fracture force is determined by the crack initiation and the
damage size determined in a second step by the bulk of the surrounding liquid. A stress
corrosion crack process has to be excluded due to the time scale of the rupture. For the
crack initiation, a stress corrosion crack process on the surface can explain the influence of
the surrounding media. With further reduction of the line width in future structures, a
higher influence of the media on the mechanical stability is expected.
References:
[1] Kern W and Puotinen D A 1970 RCA Rev. 31 187
[2] International Technology Roadmap for Semiconductors, Front End Processes 2007 www.itrs.net
[3] TanakaT,MorigamiMandAtodaN1993Japan.J.Appl. Phys. 32 6059
[4] Kim T G, Wostyn K, Mertens P W, Busnainan A A and Park J G 2010 Nanotechnology 21 015708
[5] Peter D, Dalmer M, Kruwinus H, Lechner A, Gaulhofer E and Bensch W 2008 ECS Trans. 13 323
[6] Kim T G, Wostyn K, Mertens P W, Busnainan A A and Park J G 2007 ECS Trans. 11 123
[7] Kawai A and Kaneko Y 2000 Japan. J. Appl. Phys. 39 1426
[8] KimS-K,JungM-H,KimH-W,WooS-GandLeeH2005 Nanotechnology 16 2227
[9] Kahn H, Ballarini R, Bellante J J and Heuer A H 2002 Science 298 1215
[10] KomaiK,MinoshimaKandInoueS1998Microsyst.Technol. 5 30
[11] WongBandHolbrookRJ1987J.Electrochem.Soc.1342254
[12] Michalske T A and Freiman S W 1983 J. Am. Ceram. Soc. 66 284
98
Physics of Surfaces
Joint Research Laboratory Nanomaterials
The Joint Research Laboratory Nanomaterials was established in 2004 to enhance the
cooperation between the Institute for Nanotechnology at the Karlsruhe Institute of
Technology and the Institute of Materials Science at the Technische Universität Darmstadt.
Start-up funds to establish the laboratory were provided by both institutions and the State
of Hessen. Scientific personnel is financed by the Institute for Nanotechnology at Karlsruhe
Institute of Technology and by external grants of funding agencies in Germany and of the
EU as well as by industrial cooperations. The laboratory interacts in several areas with
research groups in Materials Science and Chemistry. The research activities are
concentrated in the area of nanoparticulate systems, their synthesis and processing,
microstructural characterization and their properties. The focus is currently on developing
nonporous structures as bulk materials and as thin films for the development of tailored
and tuneable nanomaterials with applications ranging from printable electronics to energy
materials. An additional engineering focus of the research is on the stability of
nanostructured materials under operation conditions, such as high temperatures and gas
environments, as well as the study of mechanical performance of nonporous structures. The
nanomaterials are prepared using Chemical Vapor Synthesis and Nebulized Spray Pyrolysis
starting from metal-organic precursors and metal salts. Using these methods a wide range
of nanostructures can be synthesized. In addition to several synthesis systems,
characterization equipment is available including X-ray diffraction, nitrogen adsorption,
light scattering and Zeta potential, gas chromatography and, in cooperation with the
Surface Science Group, special equipment for in-situ characterization of battery materials
using surface analytical techniques.
Staff Members
Head
Prof. Dr.-Ing. Horst Hahn (Director Institute for Nanotechnology)
Research Associates
Dr. Matti Oron-Carl
Dr. Ruzica Djenadic
Secretary
Renate Hernichel
PhD Students
Dipl.-Ing. Peter Marek
Dipl.-Ing. Mohsen Pouryazdan
Dipl.-Ing. Philipp Leufke
Dipl.-Ing. Babak Nasr
Dipl.-Ing. Nina Schweikert
M.Sc. Dechao Wang
Dipl.-Ing. Clemens Wall
Dipl.-Phys. Sebastian Becker
Dipl.-Ing. Azad Jaberi Darbandi
Dipl. Phys. Arne Fischer
Dipl. Ing. Holger Hain
Dipl. Ing. Klaus Maximilian
Dipl. Ing. Aaron Weis
Dipl. Ing. Ralf Witte
M.Sc. Cahit Benel
M.Sc. Cheng Huang
Diploma Students
Ruben Bischler
Ralf Witte
Dr. Martin Hollertz
Dr. Mohammad Ghafari
99
Research Projects
EU-Projekt, 7th Framework, MAHEATT FP7-ENERGY-NMP-2008-2011
Plastizität in Nanokristallinen Metallen und Legierungen (DFG HA 1344/22-2,2009 -2012)
Tuneable 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 262/1-1, 2009 – 2011)
Investigation of non-equilibrium phonon populations in biased metallic single-walled
carbon nanotubes (DFG OR 262/1-2, 2011-2013)
MIME – Molecule Interferometry and Metrology (DFG HH 1344/24-1, 2008 – 2011)
Reversibles Durchstimmen der elektronischen Transporteigenschaften in oxidischen
leitfähigen Nanostrukturen zur Anwendung im Bereich der druckbaren Elektronik (DFG HA
1344/25-1, 2010 – 2013)
HMWK III.3.2 – 408/07.001, Investitionsfonds und Forschungsförderung (2009 – 2011)
Förderung durch Mittel des Helmholtz Institut Ulm (2010-2014)
Publications
J. Suffner, D. Wang, C. Kübel, H. Hahn; Metastable phase formation during flame spray
pyrolysis of ZrO2(Y2O3)-Al2O3 nanoparticles. Scripta Materialia, 2011. 64 781-784
A. Castrup, C. Kübel, T. Scherer, H. Hahn; Microstructure and residual stress of magnetron
sputtered nanocrystalline palladium and palladium gold films on polymer substrates. J. Vac.
Sci. Technol. A 29 (2), 021013-1 – 021013-6
G. Günther, E. Aulbach, H. Hahn, O. Guillon; High-temperature chip calorimeter with
atmosphere control. Thermochimica Acta 522,1-2 (2011), 77-85
J. Suffner, T. Scherer, D. Wang, C. Fasel, L. Jaworska, H. Hahn; Microstructure and High
Temperature Deformation Behavior of Al2O3 –TiO2 Obtained from Ultra High Pressure
Densification of Metastable Powders. Acta Materialia 59 (2011), 7592-7601
S. Dasgupta, R. Kruk, N. Mechau, H. Hahn; Inkjet printed, high mobility inorganic-oxide
field effect transistors processed at room temperature. ACS Nano 5 (12),(2011) 9628-9638
J. Suffner, S. Kaserer, H. Hahn, C. Roth, F. Ettingshausen; Sb-doped SnO2 hollow spheres
offering micro and nano porosity for the fuel cell electrode structure. Advanced Energy
Materials 1, 4 (2011), 648-654
100
P.L. Marek, H. Hahn, T.S. Balaban; On the way to biomimetic dye aggregate solar cells.
Energy & Environmental Science 4, 7 (2011), 2366-2378
Imteyaz Ahmad, C. Fasel, Th. Mayer; et al., High temperature stability of nanocrystalline
anatase powders prepared by chemical vapour synthesis under varying process parameter
Applied Surface Science 257, 15 (2011) 6761-6767
S. Indris, M. Scheuermann, S. Becker, V. Sepelak, R. Kruk, J. Suffner, F. Gyger, C.
Feldmann, A. Ulrich, H. Hahn; Local structural disorder and relaxation of Sn02
Nanostructures studies by 119Sn MAS NMR and 119Sn Mössbauer Spectroscopy. Journal of
Physical Chemistry 115, 14 (2011), 6433-6437
Y.
Zhang,
H.
Hahn;
Characterization
of
the
free
volume
in
a
Zr(45.0)Cu(39.3)Al(7.0)Ag(8.7) bulk metallic glass by reverse Monte Carlo simulation and
density measurements. Journal of Non-crystalline Solids 357, 5 (2011), 1420-1425
D.J. Babu, A.J. Darbandi, J. Suffner, SS Bhattacharya, H. Hahn; Flame spray synthesis of
nano lanthanum strontium manganite for solid fuel cell applications. Transactions of the
Indian Institute of Metals 64, 1-2 (2011), 181-184
101
Nanoglasses - a way to new amorphous structures
R. Witte, T. Feng, J. Fang, R. Kruk, M. Ghafari, R. A. Brand, H. Gleiter, H. Hahn
The relation of structure and properties has been ever since of fundamental importance in
materials science and, consequently, tailoring material properties is a major interest in
materials research. Two developments had a major impact on materials science and opened
new research fields: (1) the discovery of amorphous metals by the Duwez Group in the
1960s [1], which meanwhile led to bulk metallic glasses with many technological
applications and (2) the introduction of nanocrystalline materials by H. Gleiter in the 1980s
with research activities worldwide and many industrial applications [2]. The combination
of the structural features of these two materials classes, i.e. an amorphous, disordered
structure and a high density of internal interfaces, will give rise to a new class of
nanostructured, amorphous materials, denoted nanoglasses [3].
Nanoglasses are produced from glassy nanoparticles (NPs) which are synthesized in an
inert-gas condensation process (IGC) in a controlled environment (either He-gas or UHV).
In a subsequent in-situ compaction step, the NPs form the solid nanoglass.
Microstructurally, nanoglasses may be described by amorphous regions connected by
interfaces [3]. The atomic density in the interfaces is reduced compared to the core of the
particles. This is shown schematically in Fig. 1. Indeed, it was found by small-angle X-ray
scattering and positron annihilation lifetime spectroscopy, that the interfacial regions in a
Fe25Sc75 nanoglass exhibit a reduced atomic density or an enhanced free volume of up to
6% per atom [4]. Furthermore, it can be anticipated that the interfacial regions have a
different electronic structure due to large changes of the number of nearest neighbors and
changed interatomic distances. As a consequence, the properties of amorphous material can
be tailored by varying the concentration of interfaces, i.e. by a variation of the initial
particle size.
Fig. 1. Schematics of the atomic density distribution in a nanoglass (Figure taken from [4]).
A first example of a material property which is drastically modified by the introduction of
interfaces in a metallic glass have been found for a Fe90Sc10 nanoglass prepared by the IGC
process and consolidation [5]. Characterization has been performed by XRD, scanning
tunnelling microscopy (STM), Mössbauer spectroscopy and SQUID magnetometry. The
amorphous Fe90Sc10 is a perfect model system for the investigation, as the magnetic
properties are known to depend strongly on atomic density and local atomic arrangements.
The results obtained from the Fe90Sc10 nanoglass (NG) have been compared with the
102
corresponding conventional metallic glass (MG) with identical composition as a reference,
prepared by melt spinning.
Fig. 2 displays STM images of a Fe90Sc10 nanoglass sample after mechanical polishing. The
granular nanostructure can be clearly seen. From the line scan a particle size of about 10
nm (in agreement with TEM investigations on the loose nanopowder, not shown here) with
grooves of about 1 nm depth indicating the interfacial regions. It should be noticed that the
STM image contains information on the topography of the sample surface as well as on the
electronic structure. Further investigations are carried out in order to distinguish between
these two contributions.
Fig. 2. STM images of polished surfaces of a Fe90Sc10 nanoglass. The granular nanostructure is clearly
pronounced. The inset shows a linescan on the indicated positions.
Fig. 3 a) and b) show room temperature Mössbauer spectra of reference metallic glass and
nanoglass. The spectrum of the reference sample exhibits a broad distribution of (nonmagnetic) quadrupole splitting (QS), typical of paramagnetic amorphous alloys in
agreement with an earlier investigation [6]. Surprisingly, the Mössbauer spectrum of the
nanoglass of the identical composition is completely different. It exhibits a broad magnetic
sextet resulting from magnetic order in the material. As ferromagnetism has not been
observed at room temperature for any of the compositions studied in amorphous FexSc100-x
[7], chemical inhomogeneities, e.g. Sc segregation to the surface of the NPs, cannot
account for the observed ferromagnetism in the nanoglass at ambient temperature.
103
Fig. 3. a) and b) Mössbauer spectra measured at RT of the reference metallic glass and the nanoglass.
Based on the structural model of amorphous regions connected by interfaces, the
Mössbauer spectrum of the nanoglass is fitted using two components. The first represents a
paramagnetic component fitted with a QS distribution, and the second component is a
distribution of magnetic hyperfine fields. The magnetic component is associated with the
interfacial regions and the paramagnetic areas with the cores of the primary nanoparticles.
These observations may be understood in the context of the Bethe-Slater formalism which
describes the sign and magnitude of the magnetic exchange interaction in Fe and Fe-based
alloys depending strongly on the interatomic spacing. An increase of the average volume
per atom, as in the case of the interfacial regions in the nanoglasses, will result in a larger
ground state magnetic moment and, thus, an increase of TC.
The average magnetic moment per Fe atom <MFe> was determined by magnetometry. Fig.
4 shows hysteresis measurements at 300 K and at 10 K. As expected from the Mössbauer
experiments the nanoglass is ferromagnetic at 300 K and the sample saturates in an
external field of 4.5 T. At 10 K <MFe> reaches a value of about 1.74 µB in an applied field
of 4.5 T.
104
Fig. 4. Magnetization measurements of a Fe90Sc10 nanoglass at 10 K and 300 K.
From the combination of the average magnetization and the local spectroscopic information
obtained from Mössbauer spectroscopy at 10 K (not shown, fraction of the the interfacial
component: 35%), the magnetic moment of the Fe atoms located in the interfaces MFeIF is
determined, yielding an average magnetic moment per Fe atom in the interfacial regions of
2.4 to 2.6 µB. This compares to a saturation magnetization of about 1.5 µB in the metallic
reference glass.
In conclusion, the introduction of interfaces in a metallic Fe90Sc10 glass, results in drastic
changes of the magnetic properties, namely an increase of the transition temperature and
enhanced local magnetic moments in the interfaces.
References
[1] Klement, W., Willens, R., and Duwez, P., Nature 187, 869-870 (1960).
[2] Gleiter, H. Proceedings of the Second Risø International Symposium on Metallurgy and Materials
Science, 15-22 (1981).
[3] Gleiter, H. Acta Mater. 56, 5875-5893 (2008).
[4] Fang, J. X., Vainio, U., Würschum, R., Wang, X.L., Wang, D., Ghafari, M., Jiang, F., Sun, J.,
Hahn, H., Gleiter, H., NanoLetters, 12, 458-463 (2012).
[5] Witte, R., Fang, J.X., Feng, T., Ghafari, M., Kruk, R., Brand, R.A., Wang, D., Hahn, H., Gleiter,
H., submitted to NanoLetters (2012).
[6] Day, R., Dunlop, J., Foley, C., Ghafari, M., and Pask, H., Solid State Com. 56, 843-845 (1985)
[7] Müller, M., Ghafari, M., Banihashemi, S., Stahl, B., and Hahn, H., Phys. Stat. Sol. A 189, 10431049 (2002)
105
Mechanics of Functional Materials
The research group was established in August 2011. We are interested in continuum
modeling and numerical simulation of functional materials and systems. Functional
materials and systems usually involve different phenomena at a variety of length scales,
and 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. The current research topics include:
Phase field simulation of ferroelectric domain structures. As one of the typical
functional materials, ferroelectric ceramics have the electromechanical coupling effect,
which is intrinstically based on the micro-domain structures in the material. We are
engaged in continuum modeling of the ferroelectric domain structures via the phase field
theory. The developed model characterizes itself by a clear cut physical definition of the
material parameters and was verified with experimental results as for several typical
micromechanical and homogenized mesoscopic material responses. The model was also
used to study the nonlinear fracture properties in ferroelectric single crystals.
Nonlinear electromechanical modeling and simulation of dielectric elastomer.
Unlike the piezoelectric ceramics, the deformable dielectric elastomer provides large
actuation displacement (up to 200%) but small actuation forces. Instead of the perovskite
lattice structure in piezoelectric, the coupling effects of dielectric elastomer rely on
the electrostatic force on the material polarization, which can be represented as
eigenstress, i.e. the Maxwell stress. Nonlinear analytical and numerical models have been
developed to investigate the deformation and the electromechanical stability issue of
dielectric elastomer actuators.
Analytical solutions on micromechanics and elasticity theory: Micromechanics are of
great importance to study the effective properties of heterogeneous materials such as
composites and polycrystalline materials. The foundation of micromechanics and the
analytical homogenization approaches is the Eshelby inclusion problem. Studies have been
conduncted regarding the inclusion geometry, interface properties, and the average values
of the non-uniform stress and strain fields inside an inclusion.
106
Staff Members
Head
J. Prof. Ph.D Baixiang Xu
Research Associates
Dipl. -Ing. Peter Stein
Secretaries
Frau Maria Bense
PhD Students
M. Sc. Shabeer Khan
Publications
B.-X. Xu, R. Mueller, M.-Z. Wang; The Eshelby property of sliding inclusions, Ach. Appl.
Mech., 81 (2011) 19-35.
D. J. Franzbach, B.-X. Xu, R. Mueller, K.G. Webber; The effects of polarization dynamics
and domain switching energies on field induced phase transformations of perovskite
ferroelectrics; Appl. Phys. Letter, 99 (2011), 162903.
D. Gross, R. Mueller, M. Mueller, B.-X. Xu, K. Albe; On the origin of inhomogeneous stress
and strain distributions in single-crystalline metallic nanoparticles; Int. J. Mat. Res. (formerly
Z. Metallkd.) 102 (2011), 743-747.
107
Continuum mechanical modelling and simulation of functional materials
Bai-Xiang Xu, Ralf Müller, Dietmar Gross, Markus Klassen
Phase field simulation of ferroelectric domain structures
What makes the ferroelectrics favorable in application is primarily their large electromechanical coupling effect. This coupling is intrinsically based on its microstructure. In
particular, perovskite ferroelectrics, one of the most important families in ferroelectrics,
undergoes a cubic-to-tetragonal phase transformation when the material is cooled down
below its Curie temperature. This phase transformation introduces spontaneous
polarization and strain, with six variants determined by the crystallographic orientation of
the polarization. Groups of unit cells with polarization of the same direction are called
domains, which are separated by domain walls. The interaction of this micro domain
structure with external electrical and/or mechanical loadings enables eventually the
electro-mechanical coupling effect. Due to the heterogeneity and the micro scale, the
switchable domain structure is not directly accessible to mesoscopic experimental
measurements. Limited by the computation cost, atomistic simulation may also be
insufficient for a fully understanding of the microstructure and its influences. The phase
field theory has become an increasingly important simulation approach in the study of
morphological evolution of heterogeneous materials and has lately been introduced to
simulate the polarization and domain structure evolution of ferroelectrics. The method
replaces the usual interface conditions by a partial differential equation for the evolution of
the order parameter, i.e. the spontaneous polarization. The domain wall is therefore
smoothed out with a finite thickness. The formulation is based on a free energy functional
which includes the electrical enthalpy, the domain separation energy (polynomial of the
order parameter) and the interfacial energy (the gradient term of the order parameter).
The domain structure evolution is then treated as the consequence of the minimization
process of the total free energy of the system, requiring no switching criteria and no prior
assumption on domain geometries.
A 3D implementation of the model was completed using the finite element method with the
program FEAP. An implicit time integration is used for the evolution, and the Newton
iteration is adopted for the nonlinear system of equations. As an example, the domain
structure evolution of a BaTiO3 single crystal has been simulated, in which the volume force
and charge are neglected. The material is under traction free and charge free boundary
conditions, and for the polarization the zero flux condition is adopted. Starting from an
initial random distribution, the domain structure evolves eventually to a vortex structure,
with all the polarizations parallel to the surface, see Fig. 1.
108
Fig. 1: Domain structure evolution (from left to right) of a free standing ferroelectric single crystal under
charge free boundary condition.
Dynamic analysis of dielectric elastomer actuators (DEA)
Dielectric elastomers are widely used for artificial muscles and haptic displays, thanks to its
practical features e.g. large deformation, low cost and high fracture toughness. Due to the
electromechanical coupling effect, dielectric elastomers can be actuated under an electric
loading. To achieve various applications, the material works usually under dynamic electric
loadings, and hence the dynamic response of the material should be taken into account.
The material behaviour of dielectric elastomers is strongly nonlinear in both geometry and
constitutive relations. In this work the dynamic response of dielectric elastomers with
stretching deformation under merely electric loading is studied. An electrode-elastomerelectrode sandwich structure shown in Fig. 2, which is the prototype of a dielectric
elastomer actuator (DEA), is considered in the modelling. Due to the incompressibility of
the material and the homogeneity of the actuator, the equation of motion can be given as
an ordinary differential equation of the stretch of the actuactor in the thickness direction.
By using the Euler-Lagrange equation, the equation of motion for the DEA has been
derived. The nonlinear equation was solved numerically with software Matlab. For a DEA of
5mm x 5mm x 1mm under constant electric field and starting from a rest undeformed
configuration, the vibration diagram is presented in Fig. 3(a). It can be seen that the
frequency of the vibration varies with the applied electric potential: the higher the
potential is, the smaller the vibration frequency becomes. Nonlinear dependence of the
vibration amplitude on the applied electric potential is also shown in Fig. 3(b), in
comparison with the compression of the DEA for the quasi-static case. Results show that at
the critical state before instability, the DEA with dynamic effects can reach the maximal
deformation of around 51% under the nominal electric field of 21.28 kV/mm.
Fig. 2: DEA.
Fig. 3: Vibration under constant electric field.
109
Dependence of the DEA performance on the frequency of the applied electric loading is
studied, while the amplitude of the nominal electric field remains constant. Results show
that the DEA experiences oscillations with varying amplitudes under the harmonic electric
loading. Dynamic blow-up is detected at frequencies between 340 Hz and 405 Hz. It
implies that the applied frequency coincides with one of the natural frequencies, and thus
resonance effects occur. For the frequency slightly below or above the resonance frequency
range, the vibration remains stable. In Fig. 4 are the motions and the phase diagrams of the
DEA under the harmonic excitation with the frequencies 335 Hz and 410 Hz, respectively.
The system experiences strong oscillations under these two frequencies. After introducing a
damping effect, the oscillation is damped out to be constant vibration, as shown in Fig.
5(a). The amplitude of the constant vibration after damping is documented. It is shown
that a large peak appears around 346 Hz.
Fig. 4. Phase diagram.
Fig. 5: The resonance effect.
110
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 17 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. Jürgen Rödel.
Contact:
SFB 595 Electrical Fatigue in Functional Materials
Institute of Materials Science
Petersenstr. 23
64287 Darmstadt
Tel.: +49 6151 16 - 6362, 6315
Fax: +49 6151 16 - 6363, 6314
Building/Room: L201 / 55
E-mail:
roedel@ceramics.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.
111
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
B7
P.I.: Prof. H. v. Seggern / Prof. A. Klein
Topic: Dynamics of electrical properties in fatigued PZT
112
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
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
113
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
114
Diploma Theses in Materials Science
Lukas Schlicker, Wärmebehandlung von Aluminium AA6060 und Entwicklung eines
Polierverfahrens zur Probenpräparation für VHCF- Ermüdungsexperimente, 30.03.2011
Christoph Baumann, Creep and Fatigue Behaviour of a Hafnium-free Version of Alloy
RR1000, 08.03.2011
Martin Hottes, Untersuchung der Mikrostruktur, Zusammensetzung und Oberfläche von
galvanisch hergestellten Nickelfolien in Bezug auf ihre korrosiven Eigenschaften, 30.03.2011
Katrin Barth, Mikrostruktur, Oxidation und mechanische Eigenschaften von EisenAluminiden, 28.03.2011
Jürgen Ziegler, Präparation und Charakterisierung von GaP-Halbleiterelektroden für die
photoelektrochemische Wasserspaltung, 28.02.2011
Laurent Couturier, Detailed characterization of different grades of spheroidal cast ironsComposition of subject cards
, 15.03.2011
Caterine Lottmann, Influence of the weld seam corrosion resistance of longitudinally welded
condenser tubes through enhancement of the manufacture and heast treatment process,
28.02.2011
Lukas Mirko Reinold, Neue Anodenmaterialien für Lithiumionenbatterien, 25.02.2011
Rudolf Seiler, Entwicklung einer Kurzzeit-Prüfmethode für Beschichtungen auf Metallen,
26.04.2011
Ruben Heid, Einfluss von gießtechnischen Prozessschwankungen auf das Eigenschaftsspektrum
crashrelevanter Aluminium-Druckgusslegierungen, 31.04.2011
Silvia Vestweber, Optische Charakterisierung von Bariumstrontiumtitanat, 31.05.2011
Adnan Adilovic, Einfluss des Herstellungsverfahrens auf die mechanischen Eigenschaften von
Stahlfeinblechen, 04.05.2011
Ahmed Kariouh, Organische Solarzellen auf Basis von Merocyaninfarbstoffen- Herstellung
unter verschiedenen Atmosphären, 28.02.2011
Florian Schader, Die Temperaturabhängigkeit der dielektrischen Eigenschaften bleifreier
Ferroelektrika unter mechanischer Belastung, 28.02.2011
Lars Riekehr, Funktionalisierung polymerer Dielektrika für organische Feldeffekttransistoren,
31.05.2011
Paul Mundt, Organische Leuchtdioden auf zylindrischen Substraten, 31.05.2011
115
Aiko Bünting, Ladungsträgerinjektion in Bariumstrontiumtitanat mit Hilfe dünner Zinnoxid,
14.07.2011
Edouard Dassonville, Modelling of composite pressure cylinder rupture in aerospace
application, 02.05.2011
Sylvain Moissonnier, Comparison of different concepts of TRIP, DP and FB steels, 26.04.2011
Tobias Weiher, Ladungsstabilität in Polyvinylidendifluorid, 07.07.2011
Jörn Niehuesbernd, Mechanisches Legieren von Kupfer-Chrom, 20.07.2011
Mirko Weidner, Elektrische, optische und strukturelle Charakterisierung gesputterter
Zinnoxid-Schichten, 31.05.2011
Manfred Kerner, Mikrowellenunterstütze Polyolsynthese von Platinnanopartikeln auf
verschiedenen Kohlenstoffträgern, 27.05.2011
Aldin Radetinac, Dünnschichtwachstum von SrMoO3 mittels gespulster Laserablation (PLD)
zur Anwendung als Elektrodenmaterial für Ba0,6Sr0,4TiO3 Varaktoren, 11.07.2011
Marc Henryk Adamiak, Tests an Schwefelsensoren für das Floatbad
Floatkammeratmosphäre im Labor und unter Indistriebedingungen, 29.07.2011
und
die
Raschid Baraki, Einfluss eines E-Feldes auf das Sinterverhalten, 06.05.2011
Amon
Elias
Klausmann,
Entwicklung
neuer
Prozesse
für
die
Atmosphärendruckplasmadeposition zur Erzeugung industriell einsetzbarer Oberflächen,
30.05.2011
Franziska Resch, Elektrische Leitfähigkeit und Wärmekapazität von CuCr-Kontaktwerkstoffen
verschiedener Zusammensetzungen, 29.07.2011
Philip Jan Reckers, Photoelektronenspektroskopie an einer Merocyanin/C60 Grenzflächen,
30.06.2011
Klaus Wedlich, Bewertung eines leitfähigen, stromtragfähigen und co-sinterfähigen
Materialsystems für Interkonnektoren, 04.10.2011
Markus
Motzko,
Aluminiumdotiertes
Zinkoxid
Cadmiumtellurid-Dünnschichtsolarzellen, 11.08.2011
als
Frontkontaktmaterial
für
Arno Fey, Thermodynamic stability of Cadmium and Zinc Stannate and their point defects: A
comparative study using first-principles methods, 01.07.2011
André Schwöbel, Dünnschichttransistoren auf Basis von (Ba, Sr)TiO3, 29.09.2011
116
Ioannis Sprenger, Bestimmung der Austrittsarbeit von Kupfer und Chrom und des
Legierungssystems Cu-Cr, 10.10.2011
Krystyna Bachtin, Untersuchung der Alterungsstabilität stabilisierter Katalysatoren für die
PEM-Brennstoffzellen, 19.09.2011
Ruben Precht, Herstellung und Charakterisierung von anorganisch-organischen Schichten zur
Anwendung in LEDs, 06.10.2011
Alexander Uhl, Herstellung und Charakterisierung Polymer-abgeleiteter SiCN-Schichten auf
MoSiB-Substraten, 29.09.2011
Joachim Klett, Optimierung von GaP-Rückkontakten zur photochemischen Wasserspaltung,
07.10.2011
Charlotte Cochard, Modelisation of photovoltaic process for artificial synthesis applications,
12.09.2011
Lydia Colom, Pickling inhibitor behaviour on steel surfaces in different acidic media,
07.09.2011
Boris Gusarov, Solution processed amorphous GalnZn oxide Thin-film transistors,
02.09.2011
Valliere Lande De, Tailored platinum zircomia interface for improved exhaust gas sensors,
15.09.2011
Nguyen Van Lam, Molecular Approaches to Novel SiHfBCN Ceramic Nanocomposites:
Synthesis and High Temperature Behavior, 13.09.2011
Soleimani Doecheh, Study of Krypton/Xenon Storage and Separation in Micropous
Frameworks, 02.09.2011
Omar Pecho, Thin Ni-CGO Films for micro-Solid Oxide Fuel Cell Anode Application,
15.09.2011
117
Bachelor Theses in Materials Science
Michael Brilz,
30.09.2011
Statische
Debye-Waller-Faktoren
von
(1-x)Bi0.5Na0.5TiO3-BaTiO3,
Marcus Schulze, Mikrostrukturierte Polyelektrolyt-Filme, 08.08.2011
Hans Florian Wardenga, Deintercalation of sodium and intercalation of water in NaxCoO2
thin films made by pulsed laser deposition technique, 16.09.2011
Sandra Schäfer, Strukturierung biofunktionaler Beschichtungen, 30.09.2011
Constanze Kalcher, Molekulardynamische Simulation mechanischer Eigenschaften von
metallischen Gläsern , 28.09.2011
Silke Christina Pufahl, Veränderung der Steifigkeit und der Elastizität von Kollagen unter
UV-A Bestrahlung, 04.10.2011
Ralph Dachauer, Oxidationseigenschaften von mechanisch legierten Eisenaluminiden mit bis
zu 5 at% Titan, 09.11.2011
Jari Uhde, Oxidationsverhalten von mechanisch legiertem Fe3Al mit Mikrolegierungszusätzen
von Nb und Zr, 21.10.2011
Tanju Sirman, Mechanisches Legieren von Wolfram und Kupfer, 10.10.2011
Malte Vögler, Einfluss der Temperatur und korngröße auf die Bruchzähigkeit von
Bleizirkonat-Titanat Keramik, 01.09.2011
Christian Lohaus, Synthese verschiedener rußgeträgerter Pt-Ru-Au Katalysatoren und
Untersuchung des Degradationsverhaltens, 14.10.2011
Lukas Hamm, Systematische Untersuchung der gezielten Beeinflussbarkeit
Kristallstrukturen und Morphologie von Aluminiumphosphaten, 13.10.2011
von
Andreas Eva, Synthese von Li(Ni1/3Mn1/3Co1/3)O2 und Li(Ni1/2Co1/2)O2 mittels Sol-Gel
Technik als Targetmaterial für die gepulste Leserdeposition (PLD), 31.10.2011
Thomas Paul Kaleja, Templatgestützte Synthese asymmetrischer Cu-Mikrodrähte sowie die
Untersuchung der Auswirkun organischer Additive auf den elektrochemischen
Herstellungsprozess, 15.12.2011
Anke Silvia Ulrich, Organische Heterogrenzflächen für die solare Energiewandlung:
synchrotroninduzierte Photoelektronenspektroskopie am Modellsystem DH6T/C60, 18.11.2011
Richard
Günzler,
Untersuchung
zum
Druckkriechverhalten
Siliciumoxcarbid-Keramiken bei hohen Temperaturen, 24.11.2011
118
polymerabgeleiteter
Bachelor Theses in Materials Science
PHD Theses in Materials Science
Enrico Bruder; Thermische Stabilität von Stählen mit ultrafeinkörnigen Gradientengefügen
und deren mechanische Eigenschaften, 18.1.2011
Jens Suffner; Synthese und mechanische Eigenschaften ultrafeinkörniger ZrO2(Y2O3) - Al2O3
Komposite aus metastabilen Pulvern, 21.1.2011
Frank Ettingshausen; Elektrodendegradation in Polymerelektrolyt-Membran Brennstoffzellen,
7.3.2011
Markus König; Herstellung und Charakterisierung des Sinterverhaltens von dünnen Schichten
und Massivkörpern aus nanoskaligem Zinkoxid, 31.3.2011
Thorsten Leist; Herstellung und Schaltverhalten neuer bismuthaltiger Hochtemperaturpiezokeramiken, 8.3.2011
Carmen Elena Zvoriste; High-Pressure Synthesis, Crystal Structure and Physical Properties of
Gallium Oxonitride, 9.3.2011
Peter Agoston; Point Defect and Surface Properties of In2O3 and SnO2: A Comparative Study
by First-Principles Methods, 6.7.2011
Eva-Maria Anton; Elektrische Eigenschaften, Struktur und Depolarisationsverhalten von
Bi1/2Na1/2TiO3-Bi1/2K1/2TiO3-basierten bleifreien Piezokeramiken, 26.8.2011
Aiswarya Bhaskar; Investigations on LiM0.5Mn1.5O4 (M = Fe, Co, Ni) Spinels as High-Volt
Cathode Materials for Rechargeable Lithium-Ion Batteries, 6.4.201
Ricardo Chavez; Synthese thermoplastischer Si-basierter Polymere mit hoher thermischer
Beständigkeit für die Herstellung von Bauteilen, 23.08.2011
Gregorio Couto Faria; Structure and dynamics of poly(9,9-dioctylfluoren-2,7-diyl-cobenzothiadiazole) (F8BT) and correlations with its electrical properties, 16.9.2011
Eiko Gütlich; Abbildungseigenschaften von Szintillatoren für Schwerionenstrahlen und
diesbezügliche Modellrechnungen, 19.7.2011
Shunyi Li; Grenzflächenmodifizierung kathodenzerstäubter (Ba, Sr)TiO3-Dünnschichten,
22.6.2011
Margarete Mie Marsilius; Schaltverhalten ferroelektrisch-ferroelastischer Materialien,
01.06.2011,
Mohamed Bakr Mohmoud Mohamed; Physical properties of doped multiferroic GaFeO3,
5.4.2011
119
Silke Schaab; Influence of charged defects on the polarization dynamics and phase transitions
in the relaxor ferroelectric PLZT, 25.05.2011
Bastian Siepchen, Modelluntersuchungen an Heterogrenzflächen von II-Vi-Halbleitern,
1.4.2011
Daniel Sopu; Molecular Dynamics Simulations of Metallic Nanoglasses, 1.9.2011
Jami Susan Winzer; Production and Characterisation of Alumina-Copper Interpenetrating
Composites, 29.09.2011,
Toni André Groß; Synthese und Charakterisierung von Spinell-Sialon, 18.10.2011,
Jens Kling, Strukturuntersuchungen an bleifreien Ferroelektrika mittels TEM, 5.12.2011
Yvonne Ritter; Molecular Dynamics Simulations of Structure-Property Relationships in Cu-Zr
Metallic Glasses, 16.12.2011
Katja Stegmaier; Elektrische Ermüdung polymerbasierter organischer Leuchtdioden, 4.11.201
Alan Logéat; Experimental Study on Lithium-conducting Garnet Ceramics as Solid Electrolyte,
9.12.2011
120
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 2011 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
Mechanical and Electrical Workshop
121
Institute of Applied Geosciences
Preface
Many of todays major societal challenges are to a large extent geoscientific challenges. The
efficient management of water- and 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 has continued its efforts to focus its research activities
as well as the study programs on our key topics in Water – Energy – Environment.
Our international master’s program TropHEE (Tropical Hydrogeology, Engineering Geology
and Environmental Management) started the reaccreditation process with a reshaped
curriculum that focuses now even more on water and water/environmental management.
14 students from around the world, mostly supported by grants from DAAD and BMBF,
enrolled this year. However, we are very pleased to see that TropHEE attracts an
increasingly number of students from Germany and Europe, indicating the ample
importance of the covered topics.
Our consecutive Bachelor and Masters program Angewandte Geowissenschaften is fully
implemented now and proves to be very attractive for prospective students. In October
2011, about 160 freshmen enrolled in our Bachelor program, which is an about 4-fold
increase compared to the number of freshmen we had last year. We are very pleased by this
upgrowth and attribute it, next to some demographic reasons, to our focused and now
visible research profile.
However, this development comes to a
time where our 50 year old building in
the Schnittspahnstraße undergoes
major stepwise refurbishment. This
was absolutely necessary due to the
outdated and frequently failing
infrastructure. Five groups of the
institute are therefore now located in
the Mornewegstraße close to the main
train station, while three groups, some
laboratories, the lecture hall and
seminar rooms remained in the
Schnittsphanstraße.
The
hydrochemistry labs have been moved to a
facility in Biebesheim. This situation requires increased efforts from everybody to keep the
institute ‘alive’ and to handle the sheer number of students. However, we are very excited
about the prospects of a modern and inspiring working environment that already takes
shape.
122
Institute for Applied Geosciences - Preface
End of 2011, Prof. Andreas Henk from Freiburg accepted the call from the TU Darmstadt to
join the faculty at the Institute of Applied Geosciences and, in March 2012, he will be chair
of the Fachgebiet Engineering Geology. We all are very excited about this positive
development and look forward to welcome Prof. Henk early next year.
As it is the tradition in Geosciences to conclude the 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 was rather croweded but, finally, everyone was ‘baptised’
and officially a new member of the geology students.
Institute of Applied Geosciences - Preface
123
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.
124
Staff Members
Head
Prof. Dr. Stephan Kempe
Research Associates
Dr. Günter Landmann
Technical Personnel
Ingrid Hirsmüller
Secretaries
Kirsten Herrmann
PhD Students
Shahrazad Abu-Ghazleh
Hans-Peter Hubrich
Diploma Students
Ingo Bauer
Jürgen Krumm
Research Projects
Geomorphology and Paleoclimatology of Lake Lisan Terraces, Dead Sea, Jordan (DFG,
DAAD).
Global quantification of the CO2-sink chemical weathering and the resulting riverine
transports of dissolved solids into coastal waters (DFG).
Tectonic structure of the southern boundary of the Harz Mountain and its development
since the Permian.
Within the frame of a PhD-Study Hans-Peter Hubrich will carry out a new geological
mapping of the southern Harz mountain range. Objective is a regional map in the scale
1:10 000 that will cover an area of 5 x 100 km. The approach includes:
 Compilation of about 40 unpublished maps carried out as diploma thesis.
 Compilation of results obtained during students mapping courses.
 Assimilation of existing geological maps (small sub-areas and ‘GK 25’) after careful
consideration of own mapping results.
First results are already available covering the area Badenhausen (near Osterode) to Bad
Sachsa. These include the petrographic characterisation of the carbonates, maps of Karst
features and Quaternary deposits as well as a fault map. It turns out that about 50 % of the
faults are striking around 120°. The project is expected to be completed in 2012.
Publications
Abu Ghazleh, S., Abed, A.-A., Kempe, S., 2011: The dramatic drop of the Dead Sea:
background, rates, impacts and solutions. – In: Badescu, V. & Cathcart, R.B. (eds.), Macroengineering Seawater in/and Unique Environments. Arid Lowlands and Water Bodies
Rehabilitation, Springer, Heidelberg: 77-105.
Hartmann, J., Levy, J., Kempe, S., 2011: Increasing dissolved silica trends in the Rhine
River: an effect of recovery from high P loads? – Limnology, 12: 63-73. DOI
10.1007/s10201-010-0322-4.
125
Landmann, G., Steinhauser, G., Sterba, J.H., Kempe, S., Bichler, M., 2011: Geochemical
fingerprints by activation analysis of tephra layers in Lake Van sediments, Turkey. - Applied
Radiation and Isotopes 69: 929-935.
Kazmierczak, J., Kempe, S., Kremer, B., López-Garcia, P., Moreira, D., & Tavera, R., 2011:
Hydrochemistry and microbialites of the alkaline caldera Lake Alchichica, Mexico. – Facies:
57: 543-570. DOI 10.1007/s10347-010-0255-8.
Kempe, S., Hubrich, H.P., 2011: Inscriptions of historically known persons in Postojnska
jama. –Acta Carsologica 40(2): 397-415.
Kempe, S., Kazmierczak, J., 2011: Soda lakes. – In: Reitner, J., and Thiel, V. (eds.)
Encyclopedia of Geobiology, Springer, 824-829.
Kempe, S., Kazmierczak, J., 2011: Soda ocean hypothesis. – In: Reitner, J., and Thiel, V.
(eds.) Encyclopedia of Geobiology, Springer, 829-833.
126
Lake Van, Turkey: Evidence for a lake level drop of 500 m in the period 20-15 ka BP
Günter Landmann and Stephan Kempe
Lake Van, the largest soda lake on Earth and the 3rd largest closed lake by volume, is
located on the Eastern Anatolian High Plateau, Turkey (Fig. 1). As a terminal lake, its level
reacts very sensitively to climate changes and its great depth of 451 m allows it to survive
even pronounced dry periods. It is thus the major climate recorder in the Near East. Results
of 19 sediment cores taken from different water depths were used to reconstruct the lake
level history (Fig. 2; Tab. 1; Landmann, 1996; Landmann et al., 1996). All cores taken from
the main basin and most of the cores from shallower depth can be correlated by means of
twelve tephra layers deposited by volcanic eruptions but also by other conspicuous marker
layers and lamination patterns. Because slumping and turbidites occur frequently in this
tectonically active region, careful correlation between cores is important to assure the
completeness of the sediment column of each core.
Fig. 1: Map of Lake Van with the location of cores taken in 1974 (triangles), in 1990 (circles) and of core VAN
04-2 (Litt et al., 2009; grey circle).
A high stand up to 70-80 m above the present lake level is documented by terrace
sediments (Schweizer, 1975; Valeton 1978), yielding a floating varve chronology of 606
years fixed by 14C-dating to the period 20.1-20.7 cal. ka BP (Kempe et al., 2002). This
varved section is underlain by sandy gravel marking the transgression of the glacial lake
and overlain by a slumped, 6 m thick section representing the start of a pronounced
regression of the lake.
127
Fig. 2: Lake level fluctuations of Lake Van in the past 21 ka (redrawn after Landmann et al., 1996). Shaded
areas mark major periods with a negative water balance. Maximum depth of Lake Van today is 451 m; the
dotted line gives the present lake level at about 1650 m a.s.l. The white arrow marks the time period when
Lake Van level was below 1222 m a.s.l. discussed in the present paper.
Tab. 1 Features used for lake level reconstruction (Landmann et al., 1996; Reimer et al., 2009).
Feature
Interpretation
Remarks
several dated levels from cores of
different depth
dated ca. level
on/offset of varves
water depth at core locality >/< 40 m
Artemesia pellets
salinity 80-100 per mill
archaeological sites
Urartu high stand
terraces above present level
level still stands
sublacustrine terraces
level still stands
ca. dated level
14
highest terrace is dated by C
(Kempe et al., 2002)
not dated
pollen data
e.g., Van Zeist & Woldering (1978)
climate proxy
increasing Mg-carbonates
increasing terrigenous
material
18
increasing δ O of carbonate
Regression
Regression
increasing salinity
shorten of distance from river
mouth
data from Lemcke (1996)
increasing porosity
Transgression
decreasing salinity
Regression
In the paper we present new evidence that the lake fell dry at around 15 ka BP, i.e. within 5
ka after the lake reached its glacial high stand 70-80 m above its present level. This
evidence is derived from sediment cores covering the last 15 ka. Sediment of the deep main
basin is continuously varved back to 14.7 ka BP. Two cores (K10 and K6; Fig. 1), penetrate
the laminated layers and reach hard, not laminated sediment that contains:
 Clasts of 1-3 cm large pumice lapilli and up to 5 mm large pyroxene phenocrysts.
Concentration of particles >1 mm increase significantly within the not laminated layers
demonstrating the increase of transport energy.
128
 Ooids with a nucleus consisting of clay minerals and an aragonitic cortex. The micritic
aragonite of some ooids reveals concentric structures showing enhanced Si, Mg and Fe
concentrations. Aragonitic ooids were also described from the Great Salt Lake, Utah,
where the Mg/Ca ratio of the water is > 20 (e.g., Fabricius and Klingele, 1970). For
comparison the Mg/Ca ratio of Lake Van is > 40 today (Reimer, 1995). According to
Füchtbauer (1988) recent ooid formation takes place almost exclusively in warm, very
shallow (1-2 m) water.
 Coated grains with a nucleus formed mainly from clay minerals and a zonal cortex
consisting mainly of Fe and S. The diameter of the nucleus is about 100 µm, the
thickness of the cortex ranges from 38 to 70 µm. Shrinkage cracks appear between
nucleus and cortex. The multi-phase structure of the grain allowed only semiquantitative analysis. Microprobe mapping revealed a zonal structure of the cortex with
maximum concentration of Fe and S inwards, decreasing and replaced by Si, Al, Mg and
traces of P towards the outer rim. Smaller grains (< 10 µm) showing high concentration
of Ti and Ca are distributed on the surface, whereby the first are especially found on the
nucleus and the latter especially on the cortex. Due to its spherical shape and the
element composition we assume that the cortex has been primarily build as pyrite which
is now weathered. Pyrite is known to form by early diagenesis under reduced conditions
and weathers fast in contact with oxygen.
 Formation of secondary minerals. Semi quantitative EDX analysis of a fragmented grain,
1.2 mm long and about 0.8 mm wide, detected mainly the element Fe (56-59 weight
percent) and traces of S, Si, Na, F and Mg. The main element composition resembles
those of goethite, a weathering mineral common in tropical soil.
 Iron oxide schlieren indicating that the sediment was oxygenated. Today, the zone of
sulphate reduction starts immediately below the water-sediment interface (Reimer et al.,
2009). Such situation may have prevailed for the last 13.4 ka as revealed by an abrupt
increase of the organic sediment fraction at that time. Only sediments older than this
were oxygenated.
 Ostracode shells from four different unknown species of the family Limnocytheridae.
Adult (size 0.3-0.6 mm) and juvenile shells of ostracodes are well preserved, suggesting
that these sediments were not transported. Recent ostracodes of the family
Limnocytheridae are found in habitats having a salinity of 0 to 10 ppt. Since the species
have not yet been determined, the salinity of their habitats can only be estimated but
may be 18 ppt at most (Ian Boomer, University Birmingham, personal communication).
These textures are interpreted as being the result of a lake level regression to below 428 m
and a consecutive transgression. This interpretation is supported by the pollen record
showing a very low total concentration of pollen and spores within the unvarved sediment
section but high concentration of Artemesia and Chenopodiaceae (Van Zeist and Woldering,
1978; Wick et al., 2003; Litt et al., 2009). Pollen grains from steppe plants such as
Artemisia and chenopods are common during cooler and/or drier phases (Litt, personal
communication).
A low lake level during the Late Glacial period is also deduced from high concentration of
terrigenous material within the sediment of the unvarved section. Sedimentation velocity of
clastics depends mainly on grain size and density. Coarse and dense particles are deposited
close to the river mouths while fine particles are distributed lake-wide. At Lake Van, this
scheme leads to an increase of terrigenous material (and annual sediment deposition) with
129
decreasing distance from shore. High concentration of terrigenous material therefore
indicates a low lake level, equivalent to a short distance between river mouth and core
locality.
Core K6 (Fig. 1; total core length 992 cm) can be correlated with core K10 down to the
core depth of 920 cm, corresponding to an age of about 13 650 a BP (Landmann, 1996).
Below, it contains a slumped section (920-935 cm) followed by regularly laminated
sediment supposed to represent the shallow lake phase. Accumulation rate within this
section is 10.8 mm a-1, that is more than 20-fold higher than the average accumulation rate
for the past 14.7 ka.
Evidence for this regression in the period 20-15 ka BP is also derived from pore water
chemistry. Salinity in all cores reveals a linear increase downcore reflecting upward
diffusion of salt (Reimer et al, 2009). During the regression increasingly concentrated
brines formed that penetrated into the pore space of the sediment by replacing older pore
water of lower salinity. Water balance calculation suggest that a lake level drop of 500 m
within less than 5000 years can not be explained by a low precipitation alone but must also
have been caused by a higher evaporation than today. A simultaneous lake level drop is
also reported for Lake Lisan, the precursor of the Dead Sea (e.g., Landmann et al., 2002).
References:
[1]
Fabricius, F.H., Klingele, H., 1970. Ultrastrukturen von Ooiden und Oolithen: Zur Genese und
Diagenese quartärer Flachwasserkarbonate des Mittelmeeres. Verh. Geol. Bundesanst., 594-617.
[2]
Füchtbauer, H., Richter, D.K., 1988. Karbonatgesteine. In: Füchtbauer, H. (Ed.) Sedimente und
Sedimentgesteine. E. Schweizerbart’sche Verlagsbuchhandl., Stuttgart, 233-434.
[3]
Kempe, S., Landmann, G., Müller, G., 2002. A floating varve chronology from the Last Glacial
Maximum terrace of Lake Van/Turkey. Zeitschr. f. Geomorph. 126, 97-114.
[4]
Landmann, G., 1996. Van See/Türkei: Sedimentologie, Warvenchronologie und Paläoklima der letzten
15 000 Jahre. Ph.D. Thesis, Facult. Geosci. Univ. Hamburg.
[5]
Landmann, G., Abu Qudaira, G.M., Shawabkeh, K., Wrede, V., Kempe, S., 2002. Geochemistry of Lisan
and Damya Formation in Jordan and implications on palaeoclimate. Quatern. Int. 89/1, 45-57.
[6]
Landmann, G., Reimer, A., Kempe, S., 1996. Climatic induced lake level changes of Lake Van/Turkey
during the transition Pleistocene/ Holocene. Global Biogeochem. Cy. 10(4), 797-808.
[7]
Lemcke, G., 1996. Paläoklimarekonstruktion am Van See (Ostanatolien, Türkei). Ph.D. Thesis 11786,
Eid. Techn. Hochsch.
[8]
Litt, T., Krastel, S., Sturm, M., Kipfer, R., Örcen, S., Heumann, G., Franz, S.O., Ülgen, U.B., Niessen, F.,
2009. ’PALEOVAN’ International Scientific Drilling Programm (ICDP): site survey results and
perspectives. Quat. Sci. Rev. 28, 1555-1567.
[9]
Reimer, A., 1995. Hydrochemie und Geochemie der Sedimente und Porenwässer des hochalkalinen
Van Sees in der Osttürkei. Ph.D. Thesis, Facult. Geosci. Univ. Hamburg.
Reimer, A., Landmann, G., Kempe, S., 2009. Lake Van, Eastern Anatolia, hydrochemistry and history.
Aquat. Geochem. 15, 195-222.
[10]
[11]
Schweizer, G., 1975. Untersuchungen zur Physiogeography von Ostanatolien und Nordwestiran.
Tübinger Geogr. Studien 60, 139.
[12]
Valeton, I., 1978. A morphological and petrological study of the terraces around Lake Van. In: Degens,
E.T., Kurtman, F. (Eds.) The Geology of Lake Van. Miner. Res. Explor. Inst. Turkey 169, Ankara, 64-80
[13]
Van Zeist, W., Woldering, H., 1978. A postglacial pollen diagram from Lake Van in eastern Anatolia.
Rev. Paleobot. Palynol. 26, 249-276.
[14]
Wick, L., Lemcke, G., Sturm, M., 2003. Evidence of Late-Glacial and Holocene climatic change and
human impact in eastern Anatolia: high resolution pollen, charcoal, isotopic and geochemical records
from the laminated sediments of Lake Van, Turkey. The Holocene 13, 665-675.
130
Atmospheric CO2 consumption by chemical weathering in North America
Nils Moosdorf, Jens Hartmann, Ronny Lauerwald, Benjamin Hagedorn and
Stephan Kempe
CO2 consumption by chemical weathering is an integral part of the boundless carbon cycle,
whose spatial patterns and controlling factors on continental scale are still not fully
understood. A dataset of 338 river catchments throughout North America was used to
empirically identify predictors of bicarbonate fluxes by chemical weathering and interpret
the underlying controlling factors. Detailed analysis of major ion ratios enables distinction
of the contributions of silicate and carbonate weathering and thus quantifying CO2
consumption. Extrapolation of the identified empirical model equations to North America
allows the analysis of the spatial patterns of the CO2 consumption by chemical weathering.
Runoff, lithology and land cover were identified as the major predictors of the riverine
bicarbonate fluxes and the associated CO2 consumption. Other influence factors, e.g.
temperature, could not be established in the models. Of the distinguished land cover
classes, artificial surfaces, dominated by urban areas, increase bicarbonate fluxes most,
followed by shrubs, grasslands, managed lands, and forests. The extrapolation results in an
average specific bicarbonate flux of 0.3 Mmol km-2 a-1 by chemical weathering in North
America, of which 64% originates from atmospheric CO2, and 36% from carbonate mineral
dissolution. Chemical weathering in North America thus consumes 50 Mt atmospheric CO2C per year. About half of that originates from 10% of the area of North America.
Fig. 1: Observed specific
bicarbonate fluxes of the
considered
monitorring
stations (from Mossdorfer
et al., 2011, Geochim.
Cosmochim.
Acta
75,
7829–7854).
The
estimated
strength of individual predictors differs from previous studies. This highlights the need for a
globally representative set of regionally calibrated models of CO2 consumption by chemical
weathering, which applies very detailed spatial data to resolve the heterogeneity of earth
surface processes.
131
Distribution, sizes, function and heritage importance of the Harrat Al Shaam desert
kites: the largest prehistoric stoneworks of mankind?
Stephan Kempe and Ahmad Al-Malabeh
The Harrat Al Shaam, the lava deserts of Jordan, features the largest concentration of
desert kites so far analyzed (e.g., Kempe & Al-Malabeh, 2010a). Our GoogleEarth count
runs to at least 530 such kites, while aerial photography counts yielded 1155 kites (see
Kennedy, 2011, Table 1). In Saudi Arabia we have counted 254 more and Kennedy (2011)
counted 407 kites in Syria. Few kites occur also in Turkey, on the Sinai and in Usbekistan.
This shows that the largest numbers of kites is concentrated in Jordan, forming a significant
part of its prehistoric heritage.
Desert kites are km-long stone wall constructions, consisting of two or more widely gaping
guiding walls that converge to an opening (gate) behind a small sill. Behind is a walled
enclosure. In the early stages, these enclosures were bag-like, later clover-like and in the
latest development they attain a ha-sized, star-shaped shape. At the apexes of the inward
curved enclosure walls, so called “blinds” were erected, 3 to 5 m wide stone circles. Some
kites have well over a dozen of such circles (Fig. 1). These circles were interpreted as
“hides” for hunters to shoot gazelle. However, we argue that these were the actual traps.
Once the gazelle had jumped into them, they could not jump out again lacking forward
speed. More than 95% of the Jordanian kites open SE ward, arranged in eight chains
extending N-S throughout the Harrat, thus effectively intercepting animal migration
towards Syria and the Mediterranean Coast. In all probability they were built in early
Neolithic times to intercept gazelle (G. subgutturosa). We present statistical evaluation of
two such chains: The Eastern Border Chain and the Usaykim-Safawi Chain. Both chains
follow sections of the eastern Harrat border and are thus comparable in situation. Analysis
shows that the kites of the Eastern Border Chain are significantly larger than those of the
Usaykim-Safawi Chain, both concerning their guiding wall length as well as the sizes of
their enclosures. However, the Usaykim-Safawi Chain has more of the older kite types (bagand clover-shaped) and may therefore have been occupied first. The overall length of walls
existing in this chain (including guiding walls, enclosure perimeters and the additional
meander walls and meander section walls) amount to 264 km. This allows estimating that
the entire wall length exiting in the Harrat may be as much as 3780 km representing a
stone volume half of that of the Cheops pyramid. Thus the Harrat Al-Sham desert kites are
a most valuable and yet not well-known part of the heritage of Jordan. Many kites,
however, have already been destroyed due to field clearing and bulldozing.
132
Fig. 1: Kite No 18 (32° 5.719'N - 37° 6.525'E) of the Usaykhim Castle - Safawi Chain. The kite has clearly
elongated ventral wings with elongated blinds along their apexes. It is well preserved and was built according
to a clear design. Later alterations include a wall cutting off the northern wing to create an animal pen. The
kite is the second structure at this place, to the north the walls of an earlier, unfinished kite is visible. Building
started with the curved enclosure walls and some guiding wall sections. This kite had a straight ventral wall,
perpendicular to the gate way. This apparently represents an earlier design that was abandoned and replaced
by the design with ventral wings. In the older kite there is also a “circular path” of unknown purpose. Note
that NE is up.
References:
[1]
[2]
Kempe, S., Al-Malabeh, A., 2010: Hunting kites (‘desert kites’) and associated structures along
the eastern rim of the Jordanian Harrat: A geo-archaeological Google Earth Images Survey. –
Zeitschrift für Orient-Archäologie 10(3): 46-86.
Kennedy, D., 2011: The “works of the old men” in Arabia: remote sensing in interior Arabia. –
J. Archaeol. Sci. in press.
133
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.
We are especially excited about the funding for a second phase of our water resources
management project in Saudi Arabia, which is a part of the BMBF funded joined project
IWAS. The cooperation with our partners from the Helmholtz Center for Environmental
Research (UFZ) in Leipzig, GIZ/Dornier consult in Riyadh, and with the Ministry of Water
and Electricity in Saudi Arabia (MOWE) proved to be very successful. Two field sites in
Saudi Arabia are in operation now and data on climatic parameters are collected and also
automatically on unsaturated zone moisture contents in high spatial and temporal
resolution. The field activities are complemented by two PhD students focusing on process
oriented studies in the laboratory and one PhD student focusing on the hydrogeochmical
evolution of the large aquifers on the Arabian Peninsula.
A strategic collaboration was established with the IWW Water Center in Mülheim. IWW is a
private non-profit research institute with a focus on drinking water. Six departments carry
out basic and applied research covering the entire drinking water supply chain: Water
resources management, Water technology, Water networks, Water quality, Applied
Microbiology, and Management consulting. Projects are directed to the impact of climate
change and risk management, to environmental behavior of pollutants, to economic
evaluation of technologies, to integrated water resources management, to the development
of sustainability indicators and to financing needs of adaptation processes. Prof. Dr.
Christoph Schüth was elected as one of five Scientific Director at IWW for the department
of water resources management. First joined projects were initiated, e.g. on the fate of
nitrate in the Hessian Ried, funded by the Hessian Agency for the Environment and
Geology (HLUG). As the building of the Institute of Applied Geosciences in the
Schnittspahnstraße is currently undergoing major refurbishment, part of the laboratories of
the hydrogeology group moved to the Biebesheim office of IWW. We are hosted there at the
facility of the Wasserverband Hessisches Ried (WHR) in a modern laboratory building,
which is gratefully acknowledged.
Dr. Andreas Kallioras left the group as he was offered a tenure track position at the
Technical University of Athens in the School of Mining and Metallurgical Engineering.
However, he will continue to cooperate with us on the project in Saudi Arabia. Three new
PhD students joined the group, Abidur Khan, working on a project concerning heavy metal
contamination of surface water and groundwater in Dhaka city Bangladesh, Anja Wolf,
working on water quality issues at the Three Gorges Dam in China (together with IWW),
and Laith Latai, working on the detection of oil spills and water contamination in the
Kirkuk area in Irak using remote sensing techniques. We are very excited to expand our
international focus into other regions of the world with severe environmental problems.
134
Hydrogeology
Staff Members
Head
Prof. Dr. Christoph Schüth
Research Associates
Dr. Irina Engelhardt
Dr. Thomas Schiedek
Technical Personnel
CTA Rainer Brannolte
Chem. Ing. Claudia Cosma
Chem. Ing. Zara Neumann
PhD Students
Dipl. Geol. Sybille Ambs
MSc Abidur Khan
MSc Heike Pfletschinger
Dipl.I ng. Nils Michelsen
MSc Engy El Hadad
MSc Ahmed Abdulhamza
MSc Michaela Laxander
Dipl. Ing. Anja Wolf
MSc Mustafa Yasin
MSc Laith Latai
Diploma Students
Christoph Kludt
Manuel Lindstedt
Isimemem Osemwegi
Berhane Asfaw
Research Fellow
Dr. Andreas Kallioras
Guest Scientists
Prof. Dr. Adnan Afaj
Research Projects
Management of regional groundwater resources – Saudi Arabia (BMBF: 2011-2013).
SAFIRA 2: The treatment train approach (BMBF: 2009-2011)
Improved management of contaminated aquifers by Integration of source tracking,
monitoring tools and decision strategies – INCOME (EU-Life program: 2008-2012)
Ermittlung der Relevanz von ‘Cold Condensation’ Prozessen in Mittel- und Hochgebirgen
(DFG: 2008-2011)
Prozessorientierte Untersuchung zum Nitratabbauvermögen der Grundwasserkörper im
Hessischen Ried (HLUG: 2011-2013)
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
Ravbar, N., Engelhardt, I., Goldscheider, N. (2011); Anomalous behaviour of specific
electrical conductivity at a karst spring induced by variable catchment boundaries: the case
of the Podstenjsek spring, Slovenia .- Hydrological Processes, 25: 2130-2140.
Engelhardt, I., Piepenbrink, M., Trauth, N., Stadler, S., Kludt, C., Schulz, M. Schüth, C. &
Ternes, T.A. (2011): Comparison of tracer methods to quantify hydrodynamic exchange
within the hyporheic zone. - Journal of Hydrology, 400: 255-266.
Hydrogeology
135
Soil column experiments to quantify groundwater recharge
in arid areas
Heike Pfletschinger, Irina Engelhardt, Christoph Schüth
The quantification of vadose zone water fluxes in arid regions poses many difficulties due
to low water input, coupled thermal and isothermal processes, spatial and temporal highly
variable meteorological conditions as well as measurement errors. Nevertheless, water flux
processes in the vadose zone have to be understood and quantified as they govern rates of
direct groundwater recharge.
To quantify vadose zone water fluxes under
controlled conditions, laboratory soil column
experiments were developed that mimic
atmospheric and soil water conditions as they
can be expected in arid regions (Fig. 1). The
experimental setup allowed to measure water
content and temperature distribution within a
90 cm deep soil profile in high temporal and
spatial resolution using a TDR Taupe cable
[1] and TDR rod sensors. At the top of the
column, a head space with con-trollable air
stream, water input and applied temperature
accounted for the simulation of changing
atmospheric conditions. At the column
bottom, temperature and outflow pressure
were applied to obtain a tempera-ture
gradient within the column and water
discharge
under
controlled
pressure
conditions.
Fig. 1: Experimental setup
The setup with the two TDR sensor systems was tested in a two-stage experiment. The
column was filled with the silica sand having a volumetric water content of 0.07 cm3/cm3.
The temperature was fixed at 50°C at the top and at 15°C atthe bottom. The inflowing air
stream was applied with a constant flow of 5 l/min and a relative humidity between 5 and
10%. The suction at the bottom was held constant at 60 mbar. First, a uniform overhead
irrigation of 0.55 mm/min was applied until steady-state conditions were reached for
column water content, temperature distribution, water outflow and evaporation. After
stopping overhead irrigation, measurements continued until again steady state was reached
for the aforementioned parameters. Figure 2 (left) shows the results of the overhead
irrigation phase. Initially, the volumetric water content in the upper part of the column
increased to a maximum of 0.13 cm3/cm3, indicating unsaturated downward flow of
water. Discharge at the bottom of the column started about 5 h after irrigation started.
After overhead irrigation stopped, the sand drained within about 10 h to a homogenous
water content of 0.09 cm3/cm3 (Fig. 2 right). Within the first hour of drainage, water
content in the upper profile part rapidly decreased inducing a significant lowering of the
unsaturated hydraulic conductivity. Due to higher water contents at the bottom of the
136
Hydrogeology
column, water moved faster to the lower end until equilibrium was reached throughout the
whole column. Thus, drainage appeared to be almost homogeneous in the entire column.
Fig. 2: left: Infiltration front and discharge during wetting with continuous irrigation of 0.55 mm/min
measured with the TDR cable (continuous line) and TDR point measurements (circles). Right: Water content
and evaporation during drainage and drying measured with the TDR cable (continuous line) and TDR point
measurements (circles).
The experimental setup in general proved to be applicable to study water fluxes in the
vadose zone in high resolution. In the controlled column experiments, textbooklike
infiltration curves could be obtained using the TDR ‘Taupe’ cable. The TDR cable sensor is
therefore an ideal tool to obtain continuous soil saturation profiles and thus to trace
wetting and evaporation fronts. However, its installation, as well as the interpretation of
data, needs some care and is limited at the sensor transition and thus, in the experimental
setup, at the column top.
According to the experiments, a numerical model was set up in Hydrus-1D, simulating
coupled water, vapor and temperature fluxes in variably-saturated media (Šimunek et al.,
2009). Hydraulic and thermal soil parameters, which are implemented into the model,
were calibrated with experimental data of water content and temperature profiles at
different times as well as transient water discharge and evaporation. Amongst the
calibrated parameters, those controlling high saturated flow were less sensitive than those
controlling evaporation and drainage, whereas highest sensitivities were obtained for the
air entry pressure of the retention function of Brooks and Corey [3]. With the calibrated
model, predictive scenario modeling was performed representing annual changing soil
Hydrogeology
137
moisture conditions to identify parameters of primary importance for possible groundwater
recharge in arid regions. The predictive modeling emphasized the high importance of single
precipitation amounts on deep infiltration and percolation which can induce groundwater
recharge. For annually low precipitation amounts, the residual water content of the
ambient soil mainly determines percolation processes. Vapor fluxes, induced by
temperature gradients, plays a major role in total water fluxes under low saturated
conditions.
In conclusion, the laboratory experiments were a good tool for first estimates of vadose
zone water fluxes under arid conditions and were essential for the model setup and
calibration. Based on the calibrated model further predictions upon vertical water fluxes
and deep percolation for critical meteorological conditions could be made. By this, the
model offers a valuable tool for groundwater management issues, especially regarding
smart field observation and measurement schemes and initial predictions on soil water
states for expected future hydrological and microclimatological changes.
References:
[1]
[2]
[3]
138
Brandelik A, Huebner C, Schuhmann R (1998) Moisture sensor for large area layers. German
patent no. 4432687, European patent no. 0804724, US patent no. 5942904, 16 June 1998.
Šimonek J., Šejna M., Saito H., Sakai M., van Genuchten M.T. (2009) The Hydrus-1D software
package for simulating the movement of water, heat, and multiple solutes in variably
saturated media. Version 4.08. HYDRUS Software Series 3. Department of Environmental
Sciences. University of California. Riverside. USA. pp. 330.
Brooks RH, Corey AT (1964) Hydraulic properties of porous media. Hydrology Papers No. 3.
Colorado State Univ, Fort Collins.
Hydrogeology
Engineering Geology
Engineering Geology is an applied earth science and a branch of the applied geology which
requires multidisciplinary knowledge within both, natural sciences (geology, chemistry,
physics, mathematics) and engineering sciences. The common aims of all special subjects
contributing to engineering geology are the investigation, the use, the protection and the
remediation of the upper parts of the earth's crust.
Engineering Geology seizes the behaviour of rocks and rock masses according to the genetic
material properties and their development in earth’s history. It quantifies the mechanical,
physical and hydromechanical characteristics and the behaviour of soils and rocks in detail
and in the assembly.
Important corresponding special subjects are soil and rock mechanics, civil services,
foundation engineering, tunnel and cavity construction, drilling technology, measurement
engineering and applied subjects of hydrology and hydrogeology, petrology and
geochemistry. Engineering geology has thus strong relations with geotechnical engineering.
It translates the results and knowledge of the geosciences into the engineering
requirements.
Engineering Geology contributes to the fact that buildings of all kinds can be built and
heated surely and economically. For this purpose the building ground and other
underground conditions for engineering structures, such as geothermal power plants, traffic
routes (e.g. roads, bridges, tunnels) as well as other infrastructure such as caverns, dams,
pipelines as well as buildings such as high rise buildings, halls, wind power stations as well
as water-structural plants such as water gates, dams, and dykes, are investigated.
At present, the Chair of Engineering Geology is represented by the Chair of Geothermal
Science and Technology. However, in March 2012, Prof. Andreas Henk from Freiburg will
join our faculty and continue to represent this important topic in applied geosciences. We
all wish Prof. Henk a successful start in 2012 and look forward to welcome him at the TU
Darmstadt.
Institute of Applied Geosciences – Engineering Geology
139
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. Since
September 2009 Prof. Sass holds this chair and in October 2009 the position of associate
professor was filled. This position is hold by PD Dr. Götz, focussing on the facies-related
characterization of geothermal reservoirs.
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 (TUD HydroThermikum) started already in 2007 and was continued in
2011. Field courses and excursions in 2011 focused on geothermal energy in China, New
Zealand, Jordan, Germany and the Netherlands.
Staff Members
Head
Prof. Dr. Ingo Sass
Associate Professor
PD Dr. Annette E. Götz (in June 2011 call to the Rhodes
University, Südafrika)
Research Associates
M.Sc. Achim Aretz
M.Sc. Selcuk Erol
Dipl.-Geol. Philipp Mikisek
Dipl.-Ing. Robert Priebs
Dr. Wolfram Rühaak
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Dipl.-Ing. Kristian Bär
Dipl.-Ing. M.Sc. Sebastian Homuth
Dipl.-Ing. M.Sc. Johanna Rüther
Dipl.-Ing. Johannes Stegner
Technical Personnel
Gabriela Schubert
Rainer Seehaus
Secretaries
Simone Roß-Krichbaum
Dunja Sehn
PhD Students
Dipl.-Ing. Hauke Anbergen
M.Sc. Yixi Gu
Dipl.-Ing. Heiko Huber
M.Sc. Liang Pei
M.Sc. Sana’a Al-Zyoud
Dipl.-Geol. Ulf Gwildis
Dipl.-Geol. Clemens Lehr
Diploma Students
Barbara Breuer (Diplom)
Jan Hesse (Diplom)
Matthias Nehler (Diplom)
Johanna Rüther (Diplom)
Andreas Schumann (Diplom)
Bastian Welsch (Diplom)
Oliver Geist (Diplom)
Ulrike Klaeske (Diplom)
Robert Priebs (Diplom)
Raffael Schäffer (Diplom)
Michael Thomson (M.Sc., RES)
Marcin Wronowski (M.Sc., RES)
Guest Scientists
ERASMUS
Viktor Hlavička, BSc,
TU Budapest, Ungarn
Máté Tóth, BSc, TU Budapest,
Ungarn
DAAD
Prof. Dr. B.N. Upreti, Tribhuvan
University Kathmandu, Nepal
EU-Programm Pioneer into
Practice (PiP)
Dr inż. Łukasz Szałata,
Universität Breslau, Polen
Guest Lecturers
Dr.-Ing. Ulrich Burbaum (CDM Consult Alsbach)
Prof. Dr. Rolf Bracke (Geothermiezentrum Bochum)
Dr. Thomas Nix (LBEG Hannover)
Prof. Dr. Martin Sauter (Universität Göttingen)
Dr. Tomas Fernandez-Steeger (RWTH Aachen)
Prof. Dr. Ákos Török (TU Budapest)
Research Projects started in 2011
Mitteltiefer Hochtemperatur-Erdsonden-Wärmespeicher (MHEW) zum Betrieb konventioneller
Wärmeversorgungsnetze ohne Wärmepumpen
Research proposal, Bundesministerium für Wirtschaft und Technologie,
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: 2010-2012, FRAPORT AG
Charakterisierung des Geothermischen Reservoirpotenzials des Permokarbons in Hessen und
Rheinland-Pfalz
Funding: 2 Years, Bundesministeriums für Umwelt, Naturschutz und Reaktorsicherheit
141
Entwicklung von wartungsarmen PEHD-Filterelementen für oberflächennahe geothermische
Brunnenanlagen
Funding: 3 Jahre, Deutsche Bundesstiftung Umwelt
Quantitativer Einfluss des Wasserhaushalts, der Umwelttemperatur und der geothermischen
Kennwerte auf die Wärmeableitung erdverlegter Starkstromkabel
Research proposal, NATURpur Institut für Klima- und Umweltschutz
Rock and Hydrothermal Fluid Interactions and Their Impacts on Permeability, Reservoir
Enhancement and Rock Stability
Research proposal, DAAD
Research Projects continued and finalized in 2011
Rock mechanical and geothermal evaluation of basaltic rocks in Harrat Al-Shaam, Jordan –
DAAD-funded project in collaboration with Hashemite University of Jordan, Zarqa.
3D-Model of the deep geothermal potential of the Federal State of Hesse/Germany – Funding:
HMUELV (Hessian Ministry for Environment, Energy, Agriculture and Consumer
Protection); in collaboration with HLUG (Hessian Agency for the Environment and
Geology).
Scientific consulting and supervision of an enhanced hydrothermal power plant system, Upper
Rhine Valley – private client, confidential.
Soil abrasion effects on tunnel boring machines – Industry-funded project (CDM Inc. Seattle)
in collaboration with Pennstate University, Institute of Soil and Rockmechanics.
Long-term effect of a seasonal thermal storage on the subsurface: a case study from the Upper
Muschelkalk, SW Germany – Industry-funded project (CDM Consult GmbH, Crailsheim) in
collaboration with ITW, University of Stuttgart.
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.
Cooperation with the School of Renewable Energy Science (RES), Akureyri, Iceland
The cooperation between the Chair of Geothermal Science and Technology and RES was
established in 2008. In 2009, the TU Darmstadt Energy Center signed to collaborate with
RES in energy research and education. Prof. Sass continued his lectures as part of the RES
Master Programme in Geothermal Energy. Two students from RES joined the group of Prof.
Sass at TUD in 2011 to prepare and finish their Master theses.
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Publications
Arndt, D., Bär, K., Fritsche, J.-G., Kracht, M., Sass, I. & Hoppe, A. (2011): 3D structural
model of the Federal State of Hesse (Germany) for geo-potential evaluation. ZDGG, 162 (4):
353-369.
Bär, K., Arndt, D., Fritsche, J.-G., Götz, A.E., Kracht, M., Hoppe, A. & Sass, I. (2011): 3DModellierung der tiefengeothermischen Potenziale von Hessen: Eingangsdaten und
Potenzialausweisung. ZDGG, 162 (4): 371-388.
Bär, K., Felder, M., Götz, A.E., Molenaar, N. & Sass, I. (2011): The Rotliegend Reservoir
System of the nor-thern Upper Rhine Graben (Germany): From Pores to Production. Geophysical Research Abstracts, Vol. 13: EGU2011-A-1190, Abstracts of the Contributions
of the EGU General Assembly; Wien.
Bär, K., Felder, M., Götz, A.E., Molenaar, N. & Sass, I. (2011): The Rotliegend Reservoir
System of the northern Upper Rhine Graben (Germany): From Outcrop Analogue Studies to
Geothermal Reservoir Assessment. - International Conference and Exhibition (ICE) 2011,
American Association of Petroleum Geologists (AAPG), Mailand.
Burbaum, U., Böhme, T. & Sass, I. (2011): Hydroschildvortrieb im Lauenburger Ton:
Untersuchungen zur Adhäsivität des Baugrunds. Geotechnik, 34(2): 108-114.
Diersch, H.-J.G., Bauer, D., Heidemann, W., Rühaak, W. & Schätzl, P. (2011): Finite element
modeling of borehole heat exchanger systems - Part 1. Fundamentals. Computers &
Geosciences. [in press]
Diersch, H.-J.G., Bauer, D., Heidemann, W., Rühaak, W. & Schätzl, P. (2011): Finite element
modeling of borehole heat exchanger systems - Part 2. Numerical simulation. Computers &
Geosciences. [in press]
Götz, A.E. (2011): The Anisian Carbonates of the Peri-Tethys Basin: from Reservoir
Characterization to Subsurface Utilization. - International Conference and Exhibition (ICE)
2011, American Association of Petroleum Geologists (AAPG), Mailand. (Poster)
Götz, A.E. & Lenhardt, N. (2011): The Anisian carbonate ramp system of Central Europe
(Peri-Tethys Basin): sequences and reservoir characteristics. Acta Geologica Polonica, 61(1):
59-70.
Homuth, S., Götz, A.E., Sass, I. (2011): Outcrop analogue studies for reservoir
characterization of deep geothermal systems in Upper Jurassic limestone formations (South
Germany). - International Conference and Exhibition (ICE) 2011, American Association of
Petroleum Geologists (AAPG), Mailand.
Homuth, S., Götz, A.E. & Sass, I. (2011): Outcrop analogue studies for reservoir
characterization and prediction of deep geothermal systems in the Molasse Basin, Germany. Geophysical Research Abstracts, Vol. 13, EGU 2011-999, Wien. (
Homuth, S., Hamm, K. & Sass, I. (2011): Borehole Heat Exchanger Logging and Cement
Hydration Heat Analyses for the Determination of Thermo-Physical Parameters. Bulletin of
Engineering Geology and the Environment. [in review]
Huber, H., Arslan, U., Stegner, J. & Sass, I. (2011): Experimental and numerical modelling of
geothermal energy transport, Proceedings 13th International Conference of the International
Association for Computer Methods and Advances in Geomechanics (IACMAG 2011),
Melbourne, Australia, 09.-11.05.2011, Vol. 1, 455-459.
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Huber, H., Arslan, U., Stegner, J. & Sass, I. (2011): Inaccuracies in geothermal field tests. International Conference on Advances in Geotechnical Engineering (ICAGE 2011), 07.09.11.2011, Perth, Australia.
Mikisek, P., Bauer, D., Homuth, S., Götz, A.E., Heidemann, W., Sass, I. & MüllerSteinhagen, H. (2011): Thermal Effect of a Borehole Thermal Energy Store on the Subsurface.
Geothermics. [in review]
Philipp, S., Parchwitz, S. & Götz, A.E. (2011): Geothermal Potential of the Upper
Muschelkalk in Northeastern Germany. - Geophysical Research Abstracts, Vol. 13: EGU2011A-2487, Abstracts of the Contributions of the EGU General Assembly; Wien.
Rüther, J., Björnsson, A., Hamm, K., Homuth; S. & Sass, I. (2011): Validation of a newlydeveloped thermal conductivity sensing system using Icelandic basalts. Geothermics. [in
review]
Sass, I. (2011): Empfehlungen des Arbeitskreises Geothermie. Oberflächennahe Geothermie
„Planung, Bau, Betrieb und Qualitätssicherung“. FH-DGG und FI-DGGT/DGG. [accepted]
Sass, I. & Bär, K. (2011): Identification of a hydrothermal reservoir system in the northern
Upper Rhine Graben (Germany). HADES Workshop, GNS Science, Taupo, Neuseeland (25.
Mai 2011)
Sass, I. & Burbaum, U. (2011): Geotechnische Analyse zum Schadensfall Staufen. Geotechnik.
[in review]
Sass, I. & Götz, A.E. (2011): The Thermofacies Concept. - Proceedings of the 36th Stanford
Geothermal Workshop; Stanford.
Sass, I. & Lehr, C. (2011): Improvements on the thermal response test evaluation applying the
cylinder source theory. - Proceedings of the 36th Stanford Geothermal Workshop; Stanford.
Sass, I. & Götz, A.E. (2011): Geothermal Reservoir Characterization: A Thermofacies Concept.
Terra Nova. [accepted]
Siratovich, P., Homuth, S., Björnsson, A. & Sass, I. (2011): Thermal Stimulation of
Geothermal Reservoirs and Laboratory Investigation of Thermally Induced Fractures. - 2011
GRC Annual Meeting, San Diego, California.
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Outcrop analogue studies for reservoir characterization of deep geothermal systems
in Upper Jurassic limestone formations (South Germany)
Sebastian Homuth
The utilization of deep geothermal systems is based on a detailed knowledge of their
distinct reservoir characteristics. In the early stages of hydrothermal reservoir exploration,
the thermo-physical characterization of the reservoir is mainly accomplished by evaluation
of already existing drilling data in the vicinity of the target area and in some cases seismic
surveys. For reservoir predictions, the main geothermal parameters such as permeability,
porosity, thermal conductivity, thermal diffusivity, specific heat capacity and reservoir heat
flow have to be quantified. In addition to these thermo-physical parameters in-situ stress
field analysis and structural tectonic data is important to assess.
Outcrop analogue studies enable the determination and correlation of thermo-physical
parameters and structural geology data with regional facies patterns. An outcrop analogue
investigation examines the same rock formations (stratigraphy, lithology, facies) as the
potential reservoir formations from which fluids at according depth are discharged.
An outcrop analogue study of the target formation Malm of the Upper Jurassic, which is the
most promising formation for deep geothermal projects in the German Molasse Basin, has
to include facies studies following a thermofacies concept [1]. For the economic utilization
of deep geothermal reservoirs, a sufficient high flow rate of thermal waters throughout the
reservoir to the production well is necessary. This flow rate is mainly controlled by the
reservoir permeability. In the Molasse Basin in southeast Germany the limestone formations
of the Upper Jurassic contain the main flow paths through tectonic elements such as faults,
joints and fractures, and to some extend also, typically for limestone formations, through
karst phenomena.
To characterize those fracture controlled reservoirs the orientation of fractures, fracture
width, surface roughness of fractures as well as the connectivity of fractures and possible
secondary mineralization in the fracture system is important. These analyses enable to
assess the natural or due to stimulation measures artificially generated possible reservoir
permeability in advance of drilling operations. To forecast geometries and further
properties of existing fracture systems in three dimensions for geothermal appropriate
depth, the definition of seismic analyses is not sensitive enough [2]. Also drill cores from
exploration drillings are often not available or giving only a limited set of information.
Therefore, it is necessary to obtain thermo-physical and structural geological data from
outcrops, like it is done in the petroleum exploration [3]. Finally, the correlation of distinct
sedimentary facies and their thermo-physical parameters may contribute to establish
integrated structural 3D reservoir models.
The inferred predictions from the laboratory testing can be validated with actual drilling
data and pump test data from recent drill sites. Due to the fact that a precise classification
of facies zones in the target depth of the geothermal reservoir is not possible, the outcrop
analogue study is focusing on the two different facies areas exposed in the Southern
German Swabian and Franconian Alb.
According to the Dunham classification of carbonate rocks the following facies types are
detected in the study area: mudstones, wackestones, grain-/packstones and rud/floatstones.
The investigations are carried out on three different scales: (1) The macro scale including
an outcrop mapping to detect the litho types, structural elements and facies patterns in the
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outcrop; (2) the meso scale, to determine thermo-physical properties of different litho types
in the laboratory; and (3) the micro scale, to analyze microstructures, cements, porosities,
etc. in thin sections.
To determine the thermo-physical properties of the sampled formations a thermal
conductivity scanner (optical scanning method after [4] and an air driven permeameter [5]
and porosimeter are used.
The matrix permeability of all measured carbonates is quite low except for some
grainstones with higher permeabilities and porosities. Thick-bedded and platy limestones
show thermal conductivities around 2 Wm-1K-1, characteristic for limestones. Permeabilities
range from 0.05 mD to 100 mD. Mudstones (marly limestones) have lower thermal
conductivities than thick bedded and platy limestones, by having the same range of
permeabilities as the thick-bedded limestones. The thermal conductivities of different reefal
limestones show values of 1.8 to 2.5 Wm-1K-1. Due to the higher content of secondary
mineralized silicates in the reefal structures, these carbonates show the highest values of
thermal conductivity of all studied carbonates. The comparatively high thermal conductivity
corresponds to low permeability.
In general it can be inferred that the Swabian mud-dominated facies have lower
permeabilities than the Franconian reef-dominated facies. The only exception is for the
grainstones of the Swabian facies which have 1-2 magnitude higher permeabilities as the
mud-dominated Swabian carbonates.
The data shows in general very low permeability for all types of investigated carbonates, so
no hydraulically effective support from the matrix of the Malm aquifer can be inferred.
However, in places the Malm aquifer is very productive, being able to produce discharge
rates of over 100 l/s. So the main hydraulic flow must be related to fracture systems and
karst phenomena. By looking at karst structures two general facies related karstification
structures can be observed: (1) In terms of thick-bedded or platy limestone facies
karstification occurs only along major fractures and faults; (2) in case of reefal limestones
and bioclastic limestones the karstification occurs on a larger scale due to the primary and
secondary porosity of these facies.
The thermo-physical parameters are determined on oven dried samples. To obtain realistic
parameters under reservoir conditions, it is possible to calculate these values for water
saturated rocks under reservoir pressure and temperature conditions for relevant depths
[6,7,8]. These parameters can be validated in a Thermo-Triax-Cell simulating the existing
temperature and pressure conditions in the target horizon of a geothermal reservoir and
furthermore induces a pore pressure on the rock sample. This device offers the opportunity
to determine permeabilities from outrop samples under realistic reservoir conditions.
First results show that 3D prognosis of reservoir properties by applying facies models to the
deeper subsurface can be implemented as an additional exploration tool. The determination
of geothermal reservoir properties serves to distinguish between petrothermal and
hydrothermal systems and can also be used for optimized drilling design purposes. Outcrop
analogue studies offer effective opportunities to gain data to be transferred to greater
depths and higher temperatures which lead to a better understanding of production
capacities of geothermal reservoirs. Furthermore, these studies provide a sufficient data
base to determine thermo-physical reservoir characteristics of the rock matrix of geothermal
reservoir formations. Facies concepts are applied as an exploration tool producing
conservative results. Adding information of secondary porosities, karstification and stress
field into a reservoir model will lead to higher reservoir capacities. Based on the
investigation of the matrix parameters the sustainable heat transport into the utilized
146
geothermal reservoir can be assessed. Thus, the long term capacities for different utilization
scenarios can be calculated more precisely. Investigations on the lateral extension and
facies heterogenity will give insight on the transmissibility of different target horizons. The
thermofacies related characterization and prediction of geothermal reservoir parameters is
therefore a powerful tool for the design, extension, operation and quality management of
planned and existing geothermal reservoir, respectively. The key to reliable reservoir
prognosis, reservoir stimulation, and sustainable reservoir utilization is to integrate
thermofacies and structural geology data into 3D reservoir models.
References:
[1]
[2]
[3]
[4]
[5]
[6]
[7]
[8]
Sass, I. & Götz, A.E. (2011): The Thermofacies Concept. - Proceedings of the 36th Workshop
on Geothermal Reservoir Engineering Stanford University, SGP-TR-191; Stanford, California.
Philipp, S., Hoffmann, S., Müller, C., Gudmundsson, A. 2005. Verringerung des
Fündigkeitsrisikos für tiefengeothermische Projekte durch strukturgeologische Geländestudien
und Numerische Modell. Geothermische Jahrestagung 2005, Unterschleißheim, 113–124.
Jahn, F., Graham, M., Cook, M. 2008. Hydrocarbon Exploration & Production, Volume 55,
Second Edition (Developments in Petroleum Science), Elsevier Science, 470.
Popov, Y.A., Berezin, V.V., Semionov, V.G. & Korosteliov, V.M. (1985): Complex detailed
Investigations of the thermal properties of Rocks on the basis of a moving point Source.
Earth Physics Vol. 21, No. 1, Izvestiya.
Jaritz, R. (1999): Quantifizierung der Heterogenität einer Sandsteinmatrix am Beispiel des
Stubensandsteins (Mittlerer Keuper, Württemberg). – Tübinger Geol. Arbeiten, C 48: 104 S.,
Tübingen.
Pape, H.G., Clauser, C. & Iffland, J. (2000): Variation of Permeability with Porosity in
Sandstone Diagenesis Interpreted with a Fractal Pore space Model. Pure appl. geophys., 157:
603-619. Basel.
Vosteen, H.D. & Schellschmidt, R. (2003): Influence of temperature on thermal conductivity,
thermal capacity and thermal diffusivity for different types of rock. Physics and Chemistry of
the Earth, 28: 499 509.
Popov, Y., Tertychnyi, V., Romushkevich, R., Korobkov, D. & Pohl, J. (2003): Interrelations
Between Thermal Conductivity and Other Physical Properties of Rocks: Experimental Data.
Pure Appl. Geophys., 160: 1137 1161. Basel.
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3D-Model of the deep geothermal potential of the federal state of Hesse/Germany
Kristian Bär, Dirk Arndt, Johann-Gerhard Fritsche, Matthias Kracht,
Ingo Sass & Andreas Hoppe
Within the scope of the research project “3D-Model of the deep geothermal potentials of
Hesse” the deep geothermal potential of the Federal State of Hesse was quantified and
assessed in a qualitative analysis. The quantification of the heat stored under ground and
the qualitative analysis was done for different geothermal systems. These are hydrothermal
and petrothermal systems, as well as fault zones and deep borehole heat exchangers.
Fig. 1: View onto the southern part of the northern
Upper Rhine Graben, the Odenwald and the HorloffGraben region northeast of Frankfurt. The model is five
times vertically exaggerated. [1]
Fig. 2: View of the hydrothermal potential of the
Rotliegend in die northern Upper Rhine Graben
(five times vertically exaggerated)
For the assessment of the deep geothermal potential, knowledge of the geological structure
and the geothermal properties of the potential reservoir rocks are indispensable. Therefore,
a 3D model of the deep geothermal potential of the Federal State of Hesse (Germany) has
been developed [1].
The modelling was conducted using the software GOCAD. More than 4150 well data from
the Hessian well database, hosted by the Geological Survey of Hesse (HLUG), as well as
from the Hydrocarbon Well Database of the German Geological Surveys, hosted by the
Geological Survey of Lower Saxony (LBEG), were used. Furthermore, all geological crosssections from geological maps and from other literature were taken into account.
Additional data such as contour maps, palaeogeographic maps and existing structural
models were used. In order to provide uncertainty information to third party users, it was
148
integrated into the model itself. Stratigraphic Grids were created from the structural model,
attributed with rock physical data [2].
Systematic measurements of thermophysical and hydraulic rock properties such as thermal
conductivity, heat capacity and permeability of relevant geologic formations have been
combined with in-situ temperature measurements, hydrothermal upwelling zones,
characteristics of geological faults and were added to the 3D geological structural model.
Using a multiple criteria approach, the various rock and reservoir properties were assessed
incorporating their relevance for the different geothermal systems to allow the qualitative
analysis.
Therefore, threshold values for each parameter were defined specifying whether the
potential is very high, high, medium, low or very low. This method was tested for the onedimensional case (virtual drilling) and the two-dimensional case (geological- geothermical
cross-sections) before being applied to the 3D model.
Depending on these parameters, the model is highly capable to evaluate geopotentials. The
presented method for geopotential evaluation is based on the Analytic Hierarchy Process
(AHP), which is a very common Multiple Criteria Decision Support System. The method can
be used to identify and visualise different geopotentials cell based using many different
parameters determining each potential. In addition to the evaluation of the deep
geothermal potential the model and the presented method can be used to evaluate further
geopotentials. The intersection of different potentials may then help to identify and
visualise their conflicts of use and their synergetic use, respectively.
The resulting geothermal model, which incorporates the quantification and the qualitative
analysis, is an important tool, which can be used at an early stage of the planning phase for
the design of geothermal power plants. Furthermore, it allows quantification of the deep
geothermal potential and is intended to be an instrument for public information.
References:
[1]
[2]
Arndt, D., Bär, K., Fritsche, J.-G., Kracht, M., Sass, I. & Hoppe, A. (2011): 3D structural model
of the Federal State of Hesse (Germany) for geo-potential evaluation. – Z. dt. Ges. Geowiss.
162 (4): 353–370, Stuttgart (Schweizerbart).
Bär, K., Arndt, D., Fritsche, J.-G., Götz, A.E., Kracht, M., Hoppe, A. & Sass, I. (2011): 3DModellierung der tiefengeothermischen Potenziale von Hessen – Eingangsdaten und
Potenzialausweisung. – Z. dt. Ges. Geowiss., 162 (4): 371–377, Stuttgart (Schweizerbart).
149
Effect of hydrothermal alteration on rock properties in active geothermal setting
Philipp Mikisek, Greg Bignall, Sepulveda, Ingo Sass
Hydrothermal alteration records the physical-chemical changes of rock and mineral phases
caused by the interaction of hot fluids and wall rock, which can impact effective
permeability, porosity, thermal parameters, rock strength and other rock properties. In this
project, an experimental approach has been used to investigate the effects of hydrothermal
alteration on rock properties. A rock property database of contrastingly altered rock types
and intensities has been established. The database details horizontal and vertical
permeability, porosity, density, thermal conductivity and thermal heat capacity for ~300
drill core samples from wells THM12, THM13, THM14, THM17, THM18, THM22 and TH18
in the Wairakei-Tauhara geothermal system (New Zealand), which has been compared with
observed hydrothermal alteration type, rank and intensity obtained from XRD analysis and
optical microscopy. Samples were selected from clay-altered tuff and intercalated siltstones
of the Huka Falls Formation, which acts as a cap rock at Wairakei-Tauhara, and tuffaceous
sandstones of the Waiora Formation, which is a primary reservoir-hosting unit for lateral
and vertical fluid flows in the geothermal system. The Huka Falls Formation exhibits
argillic-type alteration of varying intensity, while underlying Waiora Formations exhibits
argillic- and propylithic-type alteration.
Fig. 1: Measurement equipment to analyse thermal and hydraulic rock properties and selected core samples of
the Wairakei-Tauhere geothermal system.
We plan to use a tempered triaxial test cell at hydrothermal temperatures (up to 200°C)
and pressures typical of geothermal conditions, to simulate hot (thermal) fluid percolation
through the rock matrix of an inferred “reservoir”. Compressibility data will be obtained
under a range of operating (simulation reservoir) conditions, in a series of multiple week or
month-long experiments that will monitor change in permeability and rock strength
accompanying advancing hydrothermal alteration intensity caused by the hot brine
interacting with the rock matrix. We suggest, our work will provide new baseline
information concerning fluid-rock interaction processes in geothermal reservoirs, and their
effects on rock properties, that will aid future decision-making, resource management and
sustainable use of geothermal resources.
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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 group of
Prof. Schüth (Hydrogeology) and Prof. Sass (Geothermics) 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.
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), Gießen (soil sciences), 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 in 2011, which will extent our
abilities for subsurface surveys down to several hundred meters and through materials,
weakly penetrable by electromagnetic waves. 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 2011, the group participated in the DFG Research Unit RiftLink
(http://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 processes, palaeoenvironmental reconstructions and georisk
assessments. Field work was undertaken in East Africa, the Alps, and Saudi Arabia. The
project in Saud Arabia runs in the context of exploring deep water resources together with
151
Prof. Schüth (Hydrogeology) and in cooperation with the GIZ (Gesellschaft für
I(nternational Zusammenarbeit; früher GTZ), the UFZ (Umweltforschungszentrum HalleLeipzig), 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.
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). In September, Jianguang Zhang commenced with
his PhD work in the sedimentology group supported by a Chinese grant. A new PhD was
started to investigate the cuases of natural radioactivity in deep groundwaters of Saudi
Arabia.
Prof. Hinderer has been elected as member and speaker of the "Wissenschaftlicher Beirat
Beschleunigungsmassenspektrometer, DFG University of Cologne” by the DFG senat
commission of common geoscientific research (DFG-Senatkommission für Geowissenschaftliche Gemeinschaftsaufgaben). He is also the representative of the German-speaking
sedimentologists (Section of Sedimentology in Geologische Vereinigung and SEPM-CES)
and he is coorganizer of the SEDIMENT conference in Hamburg 2012.
Staff Members
Head
Prof. Dr. Matthias Hinderer
Research Associates
Dr. Jens Hornung
Postdoctoral Students
Martin Kastowski
PhD Students
Hussain Al-Ajmi
Alexander Bassis
Weihua Bian
Dennis Brüsch
Daniel Franke
Technical Personnel
Erich Wettengl
(until 30.5.2011)
Secretary
Kirsten Herrmann
152
Dr. Olaf Lenz
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 643/71).
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 (2 PhD theses).
Sedimentology, dynamic stratigraphy and hydrofacies model of the Wajid group
(Southwestern Saudi Arabia). (PhD thesis financed by Umweltforschungszentrum LeipzigHalle, GIZ Eschborn, and the Ministry of Water and Energy in Riyadh, Saudi Arabia),
Analysis of radioactive anomalies in Paleozoic.mesozoic aquifers of the Arabian Platform
(PhD thesis).
Publications
Frechen, M., Ellwanger, D., Hinderer, M., Lämmermann-Barthel, J., Neeb, I. & Techmer,
A.,(2010): Reply to Preusser et al. On Frechen et al..”Late Pleistocene fluvial dynamics in
the Hochrhein Valley and the Upper Rhine Graben: chronological frame. Int. Journal of
Earth Sciences, Springer-Verlag. DOI 10.1007/s00531-011-0638-2
Hornung, J. & Hinderer, M. (2011): Depositional dynamics and preservation potential in a
progradational lacustrine to fluvial setting: Implications for high resolution sequence
stratigraphy (Upper Triassic, NW-China). SEPM Spec. Publ. 97.
Keller, M, Hinderer, M., Al Ajmi, H. & Rausch, R. (2011): Paleozoic glacial depositional
environments of SW Saudi Arabia: Process and Product. Spec. Publication Geological
Society of London, 354: 129-152.
Kastowksi, M., Hinderer, M. & Vecsei, A. (2011): Long term carbon burial in European
lakes: analysis and estimate. Global Biogeochemical Cycles, 25.
Lenz, O.K., Wilde, V., Riegel, W. (2011): Short-term fluctuations in vegetation and
phytoplankton during the Middle Eocene greenhouse climate: a 640-kyr record from the
Messel oil shale (Germany). International Journal of Earth Sciences 100 (8): 1851-1874;
DOI 10.1007/s00531-010-0609-z
153
Lenz, O.K., Wilde, V., Riegel, W. (2011): Lake Messel, an extraordinary archive for the
middle Eocene greenhouse climate. In: Lehmann, T., Schaal, S.F.K. (eds.): The World at the
Time of Messel: Puzzles in Palaeobiology, Palaeoenvironment, and the History of Early
Primates. Frankfurt am Main, 102 -103.
Riegel, W., Wilde, V., Lenz, O.K. (2011): The edge of the sea at the time of Messel:
Mangroves and related coastal wetlands in the Eocene of the Helmstedt mining district. In:
Lehmann, T., Schaal, S.F.K. (eds.): The World at the Time of Messel: Puzzles in
Palaeobiology, Palaeoenvironment, and the History of Early Primates. Frankfurt am Main,
141-142.
154
Towards better accuracy of the TDR-method:
Substrate sensitive moisture detection based on dielectric permittivity variations
Frank Owenier, Jens Hornung und Matthias Hinderer
Dielectric permittivity is an important parameter for all investigations based on
electromagnetic waves (e.g. GPR = Ground Penetration Radar and TDR = Time-domain
Reflectance measurements). In combination with the electric conductivity, it is crucial for
the determination of the propagation velocity, the reflection coefficient and the decay of
the electromagnetic wave. GPR and TDR measurements became widely used techniques to
investigate the structure of the shallow subsurface and their change in humidity in the field.
This includes monitoring of water infiltration, soil water content, shallow groundwater, as
well as structural and geotechnical properties of soils and shallow rock formations.
Frequency-dependent measurements of permittivity were carried-out with an impedance
analyzer, which works in a frequency range from 10MHz up to 1GHz [1, 2]. This is inside
the range of TDR applications (20KHz up to 20GHz) and ground penetrating radar (40MHz
up to 900MHz).
Fig. 1: Comparison of the pure reference materials (“endmembers”) with the Topp equation; measurements
at 200MHz.
The relationship between dielectric permittivity and volumetric moisture content of the
sample material is described in polynomial equations of third degree in the form
y=ax3+bx2+cx+d. The much-used Topp equation can be applied only in exceptional
cases, or determined in the cases for which the curve was originally designed [3]. As part of
this work, for the most important sediments (sand, clay, and carbonate) a relation between
the volumetric moisture content and dielectric permittivity was established (Fig.1). The
results show that there are clear correlations between the composition of the sediment on
the one side and the permittivity associated with the water content on the other side. As
part of the work, different bulk densities were considered. It was worked out that the
influence of water on the permittivity is larger than that of the porosity. Consequently, the
method is applicable both to undisturbed, as to disordered samples and designed to be
155
applied directly in the field for these different substrate compositions in mobile devices or
for permanent installations after compositional laboratory analyses. Hence, four factoral
diagrams were established to individually calibrate each of the four factors of the polynom
of third degree to moisture contents in relationship of a three principal component
substrate (Fig. 2a-d).
Fig. 2: Figure 20c-d: Ternary diagrams sand-carbonate-illite of the polynominal equation between permittivity
(Real part) and volumetric moisture of the type y = ax3+bx2+cx+d.
To use these diagrams the sedimentological composition of soil or other materials has to be
derived from standard laboratory or simple field tests and its composition plotted into the
triangular diagrams. Then at the point of composition the value for the four factors a, b, c,
and d can be read off the corresponding diagram.
The provided diagrams are valid for a frequency range of 50MHz to 1GHz. The clay mineral
in these ternary diagrams is illite, as it was used for mixed substrates. Because of the large
differences in the electrical behavior of various clay minerals the model is valid for illitebearing soils (or on soils with clay minerals that have a similar cation exchange capacity as
illite). In any case, investigations of the clay mineralogy (XRD investigations) should be
156
obtained. In these ternary diagrams, the results for the real part of permittivity habe been
registered. The imaginary parts of permittivity of the measured samples (apart from very
clay-rich substrates) are by a factor of 4 to 16 lower than the real parts, so that electrical
loss for most substrates has only a minor influence.
In two case studies natural materials were measured and compared to the predicted results.
Deviations were less than 10% whearas traditional calibration shows deviations up to 160250%. For natural minerals it has been shown that different clay mineral compositions lead
to differences in the imaginary part of permittivity. The precise knowledge of the
composition of the substrate of vital importance for TDR measurements.
References:
[1]
Owenier, F., Hornung, J. & Hinderer, M. (2011): Dielectric permittivity of geologi materials at
different water contents – measurements with an impedance analyzer. 2011 6th International
Workshop on Advanced Ground Penetrating Radar, Aaachen, 22-24 June 2011.
[2]
Salat,
C.
&
Junge,
A.
(2010):
Dielectric
fractions of soil samples from eastern Spain
(1), 1-9.
[3]
Topp, G.C., Davis, J.L., Annan, A.P. (1980): Electromagnetic determination of soil water
content: measurements in coaxial transmission lines. Water Resources Research, H. 16 (3),
574-582. Formation of maar-diatreme-volcanoes. International Maar Conference. Terra Nostra
2000/6:284-291.
permittivity
at 200MHz.
of
fine-grained
Geophysics. 75
157
Geo-Resources and Geo-Hazards
In times of rapid population growth and the resulting extension 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 as well as the prevention of the consequences of big natural phenomena
turning into catastrophes more and more often is often not understood by decision makers
who were not able to spend long years of studies on understanding the four-dimensional
space-time-development of our earth. On the other hand, the metabolism of cities with its
growing needs for clean water and raw material for constructions simultaneously egesting
waste into its neighbourhood require a thorough understanding of its undergrounds and
peripheries as well as safe construction sites.
Geo Information Systems (GIS) and 3D-techniques like gOcad are powerful tools to qualify
and to quantify resources and hazards in the peripheries of urban areas as they enable the
aggregation of complex geological and spatial data to thematic maps for a better
understanding and interpretation.
Staff Members
Head
Prof. Dr Andreas Hoppe
Research Associates
Dipl.-Geoökol. Monika Hofmann
Dipl.-Geol. Ina Lewin
Dr. Rouwen Lehné
PhD students
Dipl.-Ing. Dirk Arndt
Dipl.-Geogr. Constanze Bückner
Dipl.-Geogr. Sigrid Hade
Dipl.-Geol. Marie Luise Mayer
Students
Anna Ender
Hanna Reinheimer
Marie Mohr
Nicole Mertz
Kristel Franklin
Kevin England
Technical Personnel
Dipl.-Kartogr. (FH) Ulrike Simons
Holger Scheibner
Secretary
Pia Cazzonelli
Guest Scientist
Prof. Dr. Prem B. Thapa (Georg Forster Research Fellow,
Alexander von Humboldt Foundation)
Research Projects
The interdisciplinary project about the “Intrinsic Logic of Cities” funded by a Hessian
initiative for excellence (LOEWE program) where Andreas Hoppe served as speaker of an
interdisciplinary group concentrating an “Urban Development and Sustainability” resulted
in a book on “Space and Time of Cities” and the concept for a “A Comparison of Cities in
Maps illuminating the Interdependencies between Natural Framework Conditions and
Socialisation” elaborated by Andreas Hoppe and Constanze Bückner.
158
Prem Thapa from Tribhuvan University of Nepal is performing a research on modelling of
landslide hazard and 3D geology in the Lesser Himalaya, central Nepal. Modelling
processes have revealed that critical factors effect for spatial localisation of landslides in
diverse geo-environmental conditions are due to slope gradient and orientation of rock
discontinuities with respect to hill-slopes. The validation of model is manifested by success
and prediction rates which ranged from 90% to 94%. Integration of computed landslide
hazard in 3D geological perspective has demonstrated that optimised approach of implicit
structural modelling from sparse data is quite useful to interpret geologic-boundary
surfaces for evaluating the geo-hazard and risk.
Rouwen Lehne with Marie-Luise Mayer continued with a 4D reconstruction of the uppermost layers (Quaternary) in the northern Upper Rhine Graben in a project supported by
the Hessian Geological Survey (HLUG) in order to evaluate the geopotentials of nearsurface resources and hazards. A geodetic measurement program to detect recent
movements in the Northern Upper Rhine Valley in cooperation with the Czech Academy of
Sciences (Prague) and supported by DFG was continued.
Ina Lewin elaborates a 3D model for a small area in the Neogene Hanau-Seligenstadt Basin
between the Odenwald and Spessart Mts based on drillings and radar mapping. Those
investigations serve for a groundwater model combining local sedimentological architecture
with hydraulic data as well as high-resolution temperature data gained from several
multiparameter stations in monitoring wells. The project is supported by the local water
distributor (Zweckverband Gruppenwasserwerk Dieburg) in order to find fast flow paths
between their pumping wells and nearby sand and gravel pit.
Dirk Arndt completed a goCad based 3D model of the Federal State of Hesse showing the
top of Quarternary and Tertiary, Muschelkalk, Buntsandstein, Zechstein, Rotliegend and
Pre-Permian. A new AHP (Analytic Hierarchy Process) based method was developed and
implemented allowing to evaluate geo-potentials from the gridded and attributed volumes
in 3D. The work is part of an R&D project evaluating the deep seated geothermal potential
for Hesse (financed by the Hessian Ministry of Economy).
Monika Hofmann evaluates geo-resources and geo-hazards for a sustainable growth of the
fast growing megacity of Belo Horizonte (Minas Gerais, Brazil) with a spatial decision
support system after having compiled, interpreted, and stored all relevant geoscientific
information in an electronic data base.
The investigation in Olympia (Greece) to decipher the Holocene evolution of landscape (in
cooperation with the German Archeological Institute, DAI) continued. Recent efforts
resulted in a high precision Digital Elevation Model (1:5.000). Additionally, a drilling
campaign and radon measurements on prominent faults have been carried out.
Andreas Hoppe serves as chief-editor of the “Zeitschrift der Deutschen Gesellschaft für
Geowissenschaften” (ZDGG; listed in ISI) and has been appointed as consulting editor of
Geological Quaterly. As speaker of the Evenarí Forum for German-Jewish Studies at
Technische Universität Darmstadt he organized for the winter term 2011/2012 a series of
lectures on “Jewish Life in Germany after Auschwitz”.
159
Publications
Arndt, D., Bär, K., Fritsche, J.-G., Kracht, M., Sass, I. & Hoppe, A. (2011): 3D structural
model of the Federal State of Hesse (Germany) for geo-potential evaluation. – Z. dt. Ges.
Geowiss., 162 (4): 353-369, Stuttgart.
Bär, K., Arndt, D., Fritsche, J.G., Götz, A.E., Hoppe, A., Kracht, M. & Sass, I. (2011): 3DModellierung der tiefengeothermischen Potenziale von Hessen – Eingangsdaten und
Potenzialausweisung. – Z. dt. Ges. Geowiss., 162 (4): 371-388, Stuttgart.
Bückner, C. (2011): Der Eigenlogik mit dem Netzwerk auf der Spur - GIS als Werkzeug in
der interdisziplinären Stadtforschung. – ArcAktuell 2/2011: 17.
Hoppe, A., ed. (2011): Raum und Zeit der Städte – Städtische Eigenlogik und Jüdische
Kultur seit der Antike. – 229 p., Frankfurt am Main (Campus Verlag) [ISBN 978-3-59339536-4].
Hoppe, A. (2011): Vorwort. – In A. Hoppe, ed.: Raum und Zeit der Städte, 7-9, Frankfurt
am Main (Campus Verlag).
Hoppe, A. (2011): Geowissenschaften und die Eigenlogik der Städte. – In A. Hoppe, ed.:
Raum und Zeit der Städte, 25-46, Frankfurt am Main (Campus Verlag).
Hoppe, A., Hofmann, M., Lehné, R. & Simons, U. (2011): Spatial decision support systems
for geopotentials in the periphery of urban areas. - Freiberger Forschungshefte C 358 (C.
Breitkreuz & H.-J. Gursky, eds.: Geo-risk management – a German Latin American
approach): 131-134, Freiberg.
Hoppe, A. & Schüth, C. (2011): Waterworks Biebesheim and groundwater enrichment in
the northern Upper Rhine Graben. - Freiberger Forschungshefte C 358 (C. Breitkreuz & H.J. Gursky, eds.: Geo-risk management – a German Latin American approach): 173-175,
Freiberg.
Lang, S., Hornung, J., Krbetschek, M., Ruckwied, K. & Hoppe, A. (2011): Tektonik und
Sedimentation am Rand des Oberrheingrabens in Darmstadt im Mittel- und Oberpleistozän.
– Geol. Jb. Hessen 137: 19-53, Wiesbaden.
Lehné, R.J., ed. (2011): GIS and 3D-modelling in geosciences.- Z. dt. Ges. Geowiss. 162
(4): 351-451, Stuttgart .
Schumann, A, Arndt D., Wiatr, T, Götz, A.E. & Hoppe, A. (2011): High-Resolution 3D Terrestrial LaserScanning of a Mineral Deposit for Extraction Management Optimization. – Z.
dt. Ges. Geowiss. 162 (4): 435-442, Stuttgart.
Thapa, P. B. (2011): Landslide susceptibility modelling in the central Nepal Lesser Himalaya. – Z. dt. Ges. Geowiss., 162 (4): 405-420, Stuttgart.
160
3D geological modelling of the Lesser Himalaya, central Nepal
P. B. Thapa1,2, D. Arndt2, A. Hoppe2, R. Lehné2
1
Department of Geology, Tri-Chandra Campus, Tribhuvan University, Kathmandu, Nepal
Institut für Angewandte Geowissenschaften, Technische Universität Darmstadt, Germany
2
Background
An enhanced technique of three dimensional (3D) geological modelling is carried out in the
Lesser Himalaya, central Nepal using geological object computer aided design (GOCAD).
The modelling site is bounded by the latitudes 2737’38” and 2745’37” N, and the longitudes 8457’38” and 8508’2” E. It covers an area of 254.7 km2 and is characterized by
complex mountainous terrain with elevation ranging from 540 m to 2503 m. Litho-stratigraphy comprises six different units consisting of sedimentary, metamorphic and igneous
rocks, Precambrian to Palaeozoic in age (Stöcklin & Bhattarai 1977). Low- to mediumgrade metamorphic rocks such as meta-sandstones, slates, phyllites, marbles, quartzites and
schists are the main lithology. Limestone crops out in the eastern region whereas granite intrusion occurs in the western and southern parts. The area is geo-dynamically represented
by the closure of the Mahabharat Synclinorium. The attitude of strata is variable; in general, strata in the southern belt are dipping 32–85 northeast to north and 45–81 to
southwest in the northern belt.
3D Geological Modelling
3D geological modelling is often performed to represent, and eventually
better understand the geometric,
topological and physical properties of
geological objects. A 3D geomodel
provides new information either visually or by performing quantitative
analyses in the modelled geological
objects (Lee 2004, Zlatanova et al.
2004). In recent years, geomodelling
has upgraded classical maps by providing a definite 3D description. Structural information and an appropriate Fig. 1: Projected lithological boundaries (outcrop curves),
extension of the major geological units representative cross section and orientation vectors.
of the area can be extracted from the
models.
Mathematically
and
geometrically derived 3D geological models are important for volume and shape of the
geological features. Even for non-specialists, a model is self-explanatory. Skilled geologist
may know how to translate 3D into 2D but no matter how experienced one can be, this
mental translation is bound to be qualitative, hence inaccurate and sometimes incorrect.
Therefore, interactive and quantitative aspects of 3D geomodelling open up entirely new
perspectives.
Tools for 3D modelling are mainly designed for data-rich environment. However many geological investigations are limited to sparse or poorly distributed data. This research has applied the innovative way to compute model using optimum available data which include
161
lithological boundaries, representative cross section and orientation vectors (Fig. 1).
Considering nature of data, the model setup is made by means of implicit approach (Caumon et al. 2007) to interpolate the data; a GOCAD workflow integrates model properties
for determining the spatial locations/geometry.
ArcGIS functions were used to create a spatial database. GIS Shapefiles were imported in
GOCAD as point or curve objects and converted into analytical format. The topographic surface was created from point set data of digital elevation model (DEM). Other imported geoobjects (outcrop boundary curves, orientation vector points) were projected vertically on it.
Geological cross section was imported as 2D voxet and digitised in curves. The coordinates
of an orientation vector (v) were implemented from the dip direction θ (azimuth) and dip 
angles through the following trigonometric formula (Eq. 1):
 sin( )  cos( ) 
v  cos( )  cos( )


cos( )
(1)
To support interpolation, the 3D vector has to be oriented normal (perpendicular) to the
stratigraphic layers. By controlling the representation in space of the orientation vector, it
takes advantage of a variety of interpolation scheme.
The model configuration was performed by setting appropriate constraints by means of
various GOCAD plugins and then discrete smooth interpolation (DSI) algorithm was run to
compute rock strata geometry. The DSI optimizes all three spatial coordinates of mesh vertices. It allows to interpolate the functions of  the discrete model, like geometry or properties, while honouring a set of constraints Ci. The algorithm converges towards a solution
(Eq. 2);
R*   
     R            c
c
 
(2)
cC 
where, R(|) is the local roughness at node , (|c) is a constraint defined for node , 
is a stiffness coefficient, and c, . are weight coefficients (Mallet 2002). This generic
method permits the usage of heterogeneous data as constraints for the interpolation. It is
always reproducible, on what primary data an interpolated object is based on. Iteration of
DSI interpolation generates a smooth surface, the boundary of which coincides with lines
representing the original boundary surface and four stratigraphic bottom surfaces were obtained. In some cases, surface adjustment was also made locally by region interpolation.
After building all the surfaces of geological units, surfaces have to be selected to delimit top
and base while outer borders of both surfaces are given by the area of interest (AOI). In order to model the main stratigraphic units, the DEM is used as top surface while the base is a
surface with a constant depth about 2500 m below mean sea level. A systematic sequence
of steps has built the rock strata units from base to top. The operations are automatic or interactive and allow options to improve the modelling. Finally, a 3D volume model was constructed as Model3D (Fig. 2) that revealing a syncline structure and intrusive bodies. Dynamic visualisation is possible from slicing tool by moving in all directions.
162
Fig. 2: 3D geological model of the Lesser Himalaya, central Nepal.
It can be concluded that optimised approach of implicit structural modelling from sparse
data is quite illustrative and can interpret geologic-boundary surfaces where boreholes data
are not available. Moreover, the modelling of subsurface geometry and properties is a key
element to understand geo-hazard and risk which will be incorporated in the further development of this research. In geo-hazard (e.g. mass movement) workflow, natural property of
surfaces will become more critical rather than volume.
Acknowledgment: The first author is grateful to the Alexander von Humboldt Foundation
for a research fellowship.
References:
[1]
[2]
[3]
[4]
[5]
Caumon, G., Antoine, C. & Tertois, A.-L. (2007): Building 3D geological surfaces from field
data using implicit surfaces. - in 27th GOCAD meeting. Nancy (France), pp. 6.
Lee, J. (2004): A Spatial Access-Oriented Implementation of a 3-D GIS Topological Data
Model for Urban Entities, GeoInformatica, 8(3): 237–264.
Mallet, J.-L. (2002): Geomodeling. - Applied geostatistics series, Oxford University Press, New
York, 599 p.
Stöcklin, J. & Bhattarai, K. D. (1977): Geology of Kathmandu Area and Central Mahabharat
Range, Nepal Himalaya, Kathamdnu: HMG/UNDP Mineral Exploration Project. Technical
Report, New York (Unpublished).
Zlatanova, S., Rahman, A. A. & Shi, W. (2004): Topological models and frameworks for 3D
spatial objects, Computers & Geosciences, 30(4): 419–428.
163
Improvement of groundwater models by additionally use of detailed sedimentological
and hydraulical data – Example: Babenhausen (Hesse, Germany)
I. Lewin, A. Hoppe, C. Schüth
Institut für Angewandte Geowissenschaften, Technische Universität Darmstadt, Germany
Babenhausen is located south of Frankfurt am Main in the Hanau-Seligenstadt Basin. Lang
(2007) proved there a shifting of the river Main from a western position in the Pliocene to
an eastern position in the Upper Pleistocene which caused in the vicinity of Babenhausen
an interfingering of fluvial sediments of the river Main with fluvial sediments of the local
high areas. For that reason there is a heterogeneous series of clay, silt, as well as sand and
gravel which is actually mined in dredging lakes. As the fluvial sediments also bear a productive aquifer which is intensely used, a possible contamination of the groundwater by
sand and gravel mining has to be excluded.
The objective of this study is to identify preferential flowpaths in this system by developing
a transient groundwater model between a dredging lake and a pumping well. The collection of detailed sedimentological and hydraulical data is of particular importance. They will
be integrated in a geological 3D object model including its specific values of hydraulical
conductivity.
Test site
The least distance between
dredging lake east of Babenhausen
and a pumping well is 430 m. A
test site with a size of 50 m to 40
m has been installed in between. It
is located in the riparian zone of
the dredging lake and has seven
multi-level monitoring wells in
two transects parallel to the lakefront. Most of the monitoring
wells were built by direct-push
methods. Especially, a dual tube
method has been used in order to
extract
undisturbed
sediment
samples. There are two monitoring
wells with a diameter of two inch
and a depth of about 15 m, four
monitoring wells with a diameter Fig. 1:Ground penetrating radar and monitoring wells with logs of
of one inch and a depth of about hydraulical conductivities and grain sizes (z-scaling: 5)
15 to 25 m and one with a
diameter of two inch inside the
lake. All monitoring wells consist
of HDPE filter-screens with filter slots of 0.3 mm along its whole lengths.
164
Sedimentological data
In order to visualise the heterogeneities of fluvial sediments and to analyse the size of
sediment-structures at the test site, ground penetrating radar was used (Fig.1).In the upper
part we detected lateral accretion elements (9.5 m wide and 0.6 m high) which are typical
for meandering river systems. The lower part shows channel structures with cross-bedding
(10.0 m wide and 0.8 m high) which are typical for braided river systems.
Furthermore, we analysed the undisturbed sediment samples layer-oriented by sieve and
sedimentation analysis (Fig. 2).
We calculated hydraulic conductivities between 1,02•10-3 and 7,46•10-9 m/s. Multi-layer
pumping tests in the monitoring wells showed hydraulic conductivities between 2,43•10-4
and 3,34•10-6 m/s (Drefke 2010), about one order of magnitude lower compared to the
sieve and sedimentation analysis.
This difference might be a result of the multi-layer pumping test itself: pumping tests were
done every meter and cover 80 cm. So the multi-layer pumping tests do not fit with the
depth and thickness of sediment layers. The calculated hydraulic conductivities for multilayer pumping test are cumulative values of several
sediment layers.
Hydraulical data
In order to monitor the
groundwater table digital data
loggers were installed in the
monitoring wells. Additionally,
five monitoring wells were
equipped with automatic data
loggers for monitoring water
temperatures in high resolution
continuously in depths between
2.1 and 8.7 m. These depths are
configured by the results of
layer-oriented sieve analysis in
order to observe layers with
high hydraulic conductivities,
separated through layers with
low hydraulic conductivities. In
three monitoring wells 8
temperature
probes
were
installed and two monitoring
wells got 4 temperature probes.
During a pumping test in a
drinking water well 430 m
away from the test site we
detected variable groundwater
temperatures, for example in
well GWM_K1 in a depth of 4,7
m at the beginning of the
pumping test temperature in-
Fig. 2: Hydraulic conductivities of sieve and sedimentation analysis
compared with hydraulic conductivities of multi-layer pumping
tests for GWM_T1A / GWM_T1B
165
creased and with the end of the pumping test temperature decreased (Fig. 3). In the depth
of 7,6 and 8,7 m daily variations of temperature have been measured. Minimum
temperature is in each case at about noon, likely due to daily variations of temperature in
the dredging lake, time-delayed by silting layer.
Fig. 3: Groundwater temperature in well GWM_K1 during pumping test in drinking water well
Outlook
Further investigations will extrapolate and integrate the data from the test site as well in
the depth as in the vicinity of test site and drinking water well. A geological 3D object
model, including those characteristic values of hydraulic conductivity will be the basis of a
transient groundwater model. It will be calibrated with the help of a tracer test between the
test site and the drinking water well which is actually running.
Acknowledgement
The financial support of this study by the local drinking water supply “Zweckverband Gruppenwasserwerk Dieburg” is gratefully acknowledged.
References:
[1]
Drefke, C. (2010): Identifikation von differentieller Advektion in einem porösen Lockergesteinsaquifer zwischen Baggersee & Rohwassergewinnungsbrunnen mittels tiefenorientierter
Korngrößenanalyse,
Multilevel-Pumpversuchen
&
Multilevel-Temperaturmessungen.
Studienarbeit, TU Darmstadt, unveröffentlicht.
[2] Lang, S. (2007): Die geologische Entwicklung der Hanau-Seligenstädter Senke (Hessen,
Bayern). Dissertation, TU Darmstadt, http://elib.tu-darmstadt.de/diss/000782/.
166
Geomaterial Science
Geomaterial Science (formerly Applied Mineralogy) explores the formation/processing
conditions, composition, microstructure and properties of minerals, rocks in addition to
material science related compounds. The study of the latter material group focuses on both
basic science and potential industrial applications. Research activities include a
comprehensive characterization of relevant natural and synthetic phases, their performance
under pressure, temperature, deformation and local chemical environment 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, deformation behaviour
and 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
material properties.
An important aspect of the Fachgebiet Geomaterial Science is the application of
transmission electron microscopy (TEM) techniques for the detailed micro/nano-structural
characterization of solids. TEM in conjunction with spectroscopic analytical tools such as
energy-dispersive X-ray spectroscopy (EDS), electron energy-loss spectroscopy (EELS) and
energy filtered imaging (GIF) are employed for detailed microstructure and defect
characterization on the atomic scale. High-resolution imaging of local defects in addition to
chemical analysis with high lateral resolution (down to a few nanometers) is similarly
applied to high-performance materials as well as natural minerals.
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 (spinel), interface
structures in polycrystals, high-temperature microstructures, and the study of
biomineralisation and biomaterials.
In 2011, four new electron microscopes were installed at the Fachbereich 11, Material- and
Geosciences, which allow for state-of-the-art material characterization on the atomic scale.
Staff Members
Head
Prof. Dr. Hans-Joachim Kleebe
Research Associates
Dr. Stefan Lauterbach
Dr. Ingo Sethmann
Postdoctoral Students
Dr. Ana Ljubomira Schmitt
Dr. Andrew Stewart
Geomaterial Science
167
PhD Students
Jens Kling
Horst Purwin
Margarete Schloßer
Mathis M. Müller
Stefania Hapis
Stefanie Schultheiß
Scientific Assistant
Dr. Gerhard Miehe
Senior Scientist
Prof. Dr. Wolfgang F. Müller
Diploma Students
Anja Christmann
Holger Wüst
Technical Personnel
Bernd Dreieicher
Secretary
Angelika Willführ
Katharina Nonnenmacher
Xiaoke Mu
Eric Detemple
Dmitry Tyutyunnikov
Cigdem Özsoy
Miriam Höner
David Wiesemann
Research Projects
TEM Investigations on Cubic Crystal Shapes of Corundum-Type Indium Oxide; Novel HighPressure Phases
Mechanisms of Electrochemical Corrosion of Polycrystalline SiC Ceramics (DFG 20072011).
Polymer-derived SiCO/HfO2 and SiCN/HfO2 Ceramic Nanocomposites for Ultrahightemperature Applications, SPP-1181 (DFG 2007-2012)
Investigation of Strengthened Hydroxyapatit/ß-Tricalcium Phosphate Composites with
Tailored Porosity (DFG 2008-2011)
Nanostructure and Calorimetry of Amorphous SiCN and SiBCN Ceramics (DFG 2009-2012)
Indium oxide (In203) under high pressure: rational design of new polymorphs and
characterisation of their physico-chemical properties (DFG 2009-2012)
Structural Investigations of Fatigue in Ferroelectrics, SFB-595,
Characterization of Lead-Free Ferroelectrics (DFG 2007-2014).
detailed
TEM
Temperature and Pressure Dependence of the Fe2+/Fe3+-Ratio in Omphacite for ReCalibration of the Fe-Mg Geothermometer (DFG 2007-2011)
TEM Characterization of Various Materials/Composites in the LOEWE Excellence Initiative
AdRIA (Adaptronik – Research, Innovation, Application)
Investigation of the Atomic and Electronic Structure of Perovskite-MultilayerHeterojunctions (in collaboration with the MPI Stuttgart, Prof. P. van Aken)
168
Geomaterial Science
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)
Publications
Müller, M.M., Kleebe, H.-J., Lauterbach, S., Zito, G. (2011): Crystallographic orientation
relationship between bastnaesite, fluocerite and cerianite observed in a crystal from the
pikes peak pegmatites, Zeitschrift für Kristallographie, 226, 467-475.
Muench, F., Kaserer, S., Kunz, U., Svoboda, I., Brötz, J., Lauterbach, S., Kleebe, H.-J. Roth,
C., Ensinger, W. (2011): Electroless synthesis of platinum and platinum-ruthenium
nanotubes and their application in methanol oxidation, Journal of Materials Chemistry 21,
6286-6291.
Muench, F., Kunz, U., Neetzel, C., Lauterbach, S., Kleebe, H.-J., Ensinger, W. (2011): 4(Dimethylamino)pyridine as a Powerful Auxiliary Reagent in the Electroless Synthesis of
Gold Nanotubes, Langmuir, 27, 430-435.
Papendorf, B., Nonnenmacher, K., Ionescu, E., Kleebe, H.-J., Riedel, R. (2011): Strong
Influence of Polymer Architecture on the Microstructural Evolution of Hafnium-AlkoxideModified Silazanes upon Ceramization, Small, 7, 970-978.
Glaum, J., Granzow, T., Schmitt, L.A., Kleebe, H.-J., Rödel, J., (2011): Temperature and
driving field dependence of fatigue processes in PZT bulk ceramics, ACTA Materialia,
59, 6083-6092.
Martinez-Crespiera, S., Ionescu, E., Kleebe, H.-J., Riedel, R. (2011): Pressureless synthesis
of fully dense and crack-free SiOC bulk ceramics via photo-crosslinking and pyrolysis of a
polysiloxane, Journal or the European ceramic society, 31, 913-919.
Schmitt, L.A., Kling, J., Hinterstein, M., Hoelzel, M., Jo, W., Kleebe, H.-J., Fuess, H.
(2011): Structural investigations on lead-free Bi(1/2)Na(1/2)TiO(3)-based piezoceramics,
Journal of Materials Science, 46, 4368-4376.
Toma, L., Fasel, C., Lauterbach, S., Kleebe, H.-J., Riedel, R. (2011): Influence of nanoaluminum filler on the microstructure of SiOC ceramics, Journal of the European Ceramic
Society, 31, 1779-1789.
Hildebrandt, E., Kurian, J., Müller, M.M., Schroeder, T., Kleebe, H.-J., Alff, L. (2011):
Controlled oxygen vacancy induced p-type conductivity in HfO(2-x) thin films, Applied
Physics Letters, 99, Article number 112902.
Bazarjani, M.S., Kleebe, H.-J., Müller, M.M., Fasel, C., Yazdi, M.B., Gurlo, A., Riedel, R.
(2011): Nanoporous Silicon Oxycarbonitride Ceramics Derived from Polysilazanes In situ
Modified with Nickel Nanoparticles, Chemistry of Materials, 23, 4112-4123.
Geomaterial Science
169
Jo, W., Schaab, S., Sapper, E., Schmitt, L.A., Kleebe, H.-J., Bell, A.J., Rödel, J. (2011): On
the phase identity and its thermal evolution of lead free (Bi(1/2)Na(1/2))TiO(3)-6 mol%
BaTiO(3), Journal of Applied Physics, 110, Article Number 074106.
Muench, F., Rauber, M., Stegmann, C., Lauterbach, S., Kunz, U., Kleebe, H.-J., Ensinger, W.
(2011): Ligand-optimized electroless synthesis of silver nanotubes and their activity in the
reduction of 4-nitrophenol, Nanotechnology, 22, Article Number: 415602.
Muench, F., Oezaslan, M., Seidl, T., Lauterbach, S., Strasser, P., Kleebe, H.-J., Ensinger, W.
(2011): Multiple activation of ion track etched polycarbonate for the electroless synthesis of
metal nanotubes, Applied Physics A-Materials Science & Processing, 105, 847-854.
170
Geomaterial Science
Fe3+/ΣFe ratios in clinopyroxene and garnet
as a function of temperature
Horst Purwin, Stefan Lauterbach, Hans-Joachim Kleebe
Institute for Applied Geosciences, Geomaterial Science, Technische Universität Darmstadt,
Germany
The garnet-clinopyroxene geothermometer is one of the most widely applied methods for
obtaining equilibrium temperatures of eclogites and other (ultra)basic metamorphic rocks
containing garnet and clinopyroxene (e.g., garnet-peridotites). It is based on a Fe2+-Mg
exchange reaction between these two minerals. However, in former studies, only the total
iron content of the samples, determined by electron probe micro-analysis (EPMA), was
considered for the calibration of this geothermometer (e.g.,[1], [2], [3], [4]), since it was
assumed that the ferric iron content in the experiments was negligible. Due to previous
studies, the calibration experiments must have produced garnets and clinopyroxenes with
substantial Fe3+ contents, and the reason for the unreliability of Fe-Mg exchange
geothermometry is deduced to uncertainties of the Fe3+ content in natural phases and
phases generated in the experiments from which the thermometer formulations were
calibrated [5]. As a step forward to improve the garnet-clinopyroxene geothermometer we
investigate the Fe3+ content in synthetic clinopyroxene and garnet as a function of
temperature in order to explore the effect of considering or neglecting Fe3+ on
geothermometry.
Synthetic eclogite of the system CaO-FeO-Fe2O3-MgO-Al2O3-SiO2 was produced in
graphite/Pt capsules at a pressure of 30 kbar and temperatures ranging from 1000°C1300°C using a Belt apparatus. One long-term experiment with a run period of two months
was performed at 800°C and 25 kbar in a piston-cylinder apparatus The oxidation state
(expressed as Fe3+/ΣFe ratio) of clinopyroxene and garnet was investigated by electron
energy-loss spectroscopy (EELS). This method is performed on a transmission electron
microscope (TEM) providing a high spatial resolution which is required for measuring the
phases near grain boundaries. The combination of EELS and energy-dispersive X-ray
spectroscopy (EDS) allow a quantification of Fe2+ and Fe3+. In addition to EDS, main
element composition was also determined by EPMA in samples produced at 1000°C1300°C. At 800°C the small grain sizes of < 2 μm prohibit “clean” microprobe analyses of
one phase.
Run products consist of clinopyroxene, garnet and quartz assemblages (Figure 1). A typical
EEL spectrum of synthetic clinopyroxene is shown in Figure 2. Based on a modified L3/L2
intensity ratio the Fe3+/ΣFe ratio of the sample can be calculated [6]. The results show
significant amounts of ferric iron in both, clinopyroxene and garnet. Temperature
calculations using phase compositions obtained by EDS were found to yield a rough
estimate of the equilibrium temperature but not a precise one which is required to assess
the influence of Fe3+ on geothermometric calculations. For the latter purpose, EPMA data is
needed, also from the samples produced at 800°C. Since in these fine-grained samples, the
low spatial resolution of EPMA (approximately 3 µm) only allows mixed analyses of two or
three phases (garnet-clinopyroxene, garnet/clinopyroxene-quartz and garnet-clinopyroxene-quartz), it is planned to obtain the compositional data of garnet and
clinopyroxene indirectly by constructing a triangle of the “hypothetical mixtures”, in which
the end-points correspond to the “clean” compositions of the three phases.
Geomaterial Science
171
Fig. 1: Back-scattered electron image of synthetic eclogite, produced at 1100°C and 30 kbar, consisting of
garnet (Gt), clinopyroxene (Cpx) and quartz (Qz).
Fig. 2: Typical EEL spectrum of synthetic clinopyroxene (synthesis conditions: 1100°C, 30 kbar) showing the
iron L2,3-edge. The spectrum was treated as described by [6] in order to determine the Fe3+/ΣFe ratio from a
modified integral L2,3 white-line intensity ratio. The quantification according to [6] includes an absolute error
of 5% Fe3+/ΣFe.
References:
[1]
[2]
[3]
[4]
[5]
[6]
172
Ellis, D.J. & Green, D.H. (1979), An experimental study of the effect of Ca upon garnet-clinopyroxene
Fe-Mg exchange equilibria, Contrib. Mineral. Petrol., 71, 13-22
Krogh, E.J. (1988), The garnet-clinopyroxene Fe-Mg geothermometer – a reinterpretation of existing
experimental data, Contrib. Mineral. Petrol., 99, 44-48
2+
Ai, Y. (1994), A revision of the garnet-clinopyroxene Fe -Mg exchange geothermometer, Contrib.
Mineral. Petrol., 115, 467-473
Nakamura, D. (2009), A new formulation of the garnet-clinopyroxene geothermometer based on
accumulation and statistical analysis of a large experimental data set, J metamorph. Geol., 27, 495-508
Canil, D. & O’Neill, H.St.C. (1996), Distribution of ferric iron in some upper-mantle assemblages, J.
Petrology, 37, 609-635
van Aken, P.A., Liebscher, B., Styrsa, V.J.(1998), Quantitative determination of iron oxidation states in
minerals using Fe L2,3-edge electron energy-loss near-edge structure spectroscopy. Phys. Chem.
Minerals, 25, 323-327.
Geomaterial Science
Electrochemical corrosion of silicon carbide ceramics
U. Sydow1, M. Herrmann2, M.M. Müller3, H.-J. Kleebe3, A. Michaelis1,2
1
Technical University Dresden, Institute of Materials Science, Dresden, Germany
2
Fraunhofer Institute for Ceramic Technologies and Systems,
Winterbergstraße 28, Dresden, Germany
3
Technische Universität Darmstadt, Institute of Applied Geosciences, Darmstadt, Germany
Silicon carbide materials are nowadays widely used in wear applications, i.e., as sealings
for pumps which convey a wide range of media in industrial applications. The corrosion
resistance of SiC ceramics strongly depends on the preparation technology and the
composition. The solid phase sintered SiC materials (SSiC), which normally contain only
some B4C and a small volume fraction of carbon secondary phase, exhibit in a wide range
of media and conditions an excellent corrosion resistance. Even in HF solutions SSiC shows
a high stability in contrast to other Si based ceramics [1-2]. The high corrosion resistance of
the SSiC materials is – besides the good tribological properties – the reason for the use of
these materials in sealings and in other chemical equipments [3].
SiC itself is an intrinsic semiconductor and has specific electrical resistivities as low as some
m [3]. Commonly used sintering additives such as boron or aluminium enhance the
conductivity of the material, especially if the materials are tempered at elevated
temperatures. Therefore, electrochemical corrosion can be a cause of severe material
degradation. Damage patterns for SiC sealings have been reported which strongely suggest
electrochemical corrosion as the primary cause for material degradation [4]. The corrosion
rates of ceramics are generally very small as compared to metal corrosion. Though some
features of the electrochemical corrosion of SiC like SiO2 passive layer formation in acids
are established, no detailed information about the mechanisms and the correlation between
microstructure and corrosion resistivity are available as yet [5-7].
The standard reduction potentials are given relative to the normal hydrogen electrode
(NHE):
In acidic environments:
SiO2 + 4H+ + 4e- ⇄ Si + 2H2O
E° = -0.857 V
(1)
SiO2 + C + 4H+ + 4e- ⇄ SiC + 2H2O
E° = -0.673 V
(2)
SiO2 + 6H + CO + 6e ⇄ SiC + 3H2O
E° = -0.276 V
(3)
E° = -0.222 V
(4)
E° = -1.698 V
(6)
E° = -1.515 V
(7)
E° = - 1.113 V
(8)
E° = - 0.149 V
(9)
+
-
+
-
SiO2 + 8H + CO2 + 8e
⇄ SiC + 4H2O
In alkaline environments:
SiO32- + 3H2O + 4e- ⇄ Si + 6OHSiO32SiO32SiO32-
+ C + 3H2O + 4e ⇄ SiC + 6OH
-
-
+ 4H2O + CO + 6e- ⇄ SiC + 8OH+ 5H2O +
CO32-
Geomaterial Science
+ 8e ⇄ SiC + 12OH
-
-
173
TEM studies were performed on a SSiC material upon electrochemical attack in acidic
medium. A CM20STEM microscope (FEI, Eindhoven, The Netherlands), equipped with an
energy-dispersive X-ray spectrometer (EDS) was employed, operating at 200 keV. TEM foil
preparation was performed using standard ceramographic techniques of grinding, polishing
and Ar-ion thinning. However, in order to preserve the thin surface layer formed upon
electrocorrosion, the sample was ground from the backside down to 80 mm and
subsequently ion thinned also from the backside (using only one Ar-gun). Finally, the
sample was lightly carbon coated in order to minimize charging under the incident electron
beam.
Fig. 1: TEM micrograph of the sample SSiC-D after electrochemical corrosion in 0.5 M H2SO4 at 2V. The central
grain shown in (a) reveals a nearly unaffected SiC grain; while the neighbouring particles are transformed to
amorphous SiO2 (compare EDS spectra to the right). Note the electrochemical attack is strongly pronounced
at grain boundaries (see inset (b)), reflecting the initial microstructure.
A detailed analysis of the corroded surface in H2SO4 by transmission electron microscopy
(TEM) revealed a strong attack at the grain boundaries and the formation of an oxide layer.
This SiO2 layer represents the initial microstructure, i.e., the individual SiC grains are
transformed into amorphous SiO2, as can be seen in Figure 1. Here, the central grain is still
crystalline SiC, while the surrounding particles are predominantly composed of silica (see
EDS spectra to the right). It is not clear yet, why the corrosive attack at grain boundaries is
more pronounced, but it is assumed that those interfaces are less ordered (different
orientation of the neighbouring grains) and, therefore, promote the electrochemical attack
along SiC grain boundaries.
174
Geomaterial Science
In alkaline media, an anisotropic electrochemically etched pattern with deep pits is formed.
Above pH values of 12, silicon dioxide is unstable and no amorphous silicon dioxide layer
can be found after anodic oxidation in NaOH. This explains the differences of damage
patterns in acidic and alkaline media: predominant formation of SiO2 in acidic media
(Equations (2-4)) and by the preferential formation of soluble silicate species in alkaline
media (Eqs. (7-9)). Also in alkaline solutions the electrochemical attack depends on the
crystallographic orientation.
The results reveal that the corrosion rate of the SiC is strongly correlated with the local
conductivity. This is also in agreement with the fact that for the SiC materials with low
conductivity a much lower corrosion rate was typically observed.
References:
[1]
[2]
[3]
[4]
[5]
[6]
[7]
K.A. Schwetz, J. Hassler, cfi/Ber. DKG, 2002, 79(11), D14-D19.
M. Herrmann, J. Schilm, G. Michael, cfi/Ber. DKG, 2003, 80(4), E27.
K.A. Schwetz, in: R. Riedel, (Ed.), Handbook of Ceramic Hard Materials, Wiley-VCH,
Weinheim, 2000, 683-748.
F. Meschke, A. Kailer, cfi/Ber. DKG, 2003, 81(8), E19.
R. Divakar, S.G. Seshadri, M. Srinivasan, J. Am. Ceram. Soc., 1989, 72(5), 780.
G.S. Cook, J.A. Little, J.E. King, Br. Corros. J., 1994, 29(3), 183.
Andrews, M. Herrmann, M. Sephton, C. Machio, A. Michaelis, J. Eur. Ceram. Soc., 2007, 27,
2127.
Geomaterial Science
175
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:

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:

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
176
Technical Petrology with Emphasis in Low Temperature
basin analyses, hydrocarbon exploration, geothermic prospections and energy
researches.
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
palaeogeothermics, and in the external orogens investigation.
research,
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:

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 (Silesia, SW Poland and southern Norway).

Determination of water-rock interaction and water chemistry in the basement
crystalline ground waters and their usage as potable water (Odenwald, Bergstraße,
Hesse, Germany).
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 NW Turkey
A broad analytical spectrum must be applied in low-temperature petrology due to very
small grain-size. In the Technical Petrology group, general microscopy (MPV coal reflection
microscopy, fluorescence microscopy, transmitted light microscopy) and basically XRD
177
powder and texture studies (Clay and XRD Laboratory and a research XRD Laboratory
recently installed with thankful help by Merck KGaA) can be combined with ICP-AES, TOC,
AOX and gas chromatography (GC-ECD, GC-MS) in the Organic Geochemical Laboratory
(installed with thankful help by the Hessische Industriemüll GmbH). A XRF laboratory
(Wave-dispersive BRUKER S8-Tiger) was installed in 2008 and is maintained together with
the research groups of Chemical Analytics and Environmental Mineralogy.
Staff Members
Head
Prof. Dr. Rafael Ferreiro Mählmann
Research Associates
Dr. Ronan Le Bayon
PD Dr. Eckardt Stein
Dr. Branimir Šegvić
Diploma- and
BSc-MSc Students
Alexej Philipp
Alexander Müller
Christian Adam
Erika Dörner
Rebecca Kämmerling
Robert Priebs
Technical Personnel
Dr. Norbert Laskowski
Secretary
Natali Vakalopoulou Buffet
Guest Scientist
Prof. Dr. Ömer Bozkaya (ERASMUS)
Research Projects
Petrology of the Phyllite-Diabas-zone at the Kaschana pass in the Stara Planina of central
Bulgaria – (DAAD, ERASMUS. Cooperation with St. Kl. Ohridski University of Sofia, BG).
Structural, stratigraphic and diagenetic analysis of the Jurassic-Early Cretaceous foreland
Trojan-basin in central North Bulgaria – (DAAD, ERASMUS. Cooperation with St. Kl.
Ohridski University of Sofia, BG).
Origin of the ophiolite-related Al-(Mg) metamorphites – case study of sapphirine and
corundum amphibolites from the Central Dinaridic Ophiolite Zone (CDOB, NE Bosnia and
Herzegovina). – (DFG and DAAD. Cooperation with University of Heidelberg).
Geochronology and tectono-thermal history of the Penninic-Austroalpine boundary (Arosa
Zone) in Eastern Switzerland; a multi-methodical comparison of methods. - (SNF and
Willkomm Fond. Cooperation with University of Bern, CH and Department für Zivilschutz,
Bern, CH).
Composition, manufacture technology, and circulation of Hellenistic pottery from Eastern
Adriatic: a case study of three archaeological sites in Dalmatia (Croatia). – (MZOS.
Cooperation with University of Zadar and University of Zagreb, HR).
178
Very low to low-temperature coal and clay-mineral indicators, comparative application
from diagenesis to green- and blueschist facies. – (No founding. Cooperation with
University of Basel, CH).
Organic matter studies on graptolite-schist, their hydrocarbon potential and maturation
level to determine the palaeo-geothermal history and to elucidate geodynamic processes
(Bulgaria and Turkey). – (Different national science founds and DAAD. Cooperation with
St. Kl. Ohridski University of Sofia, BG and University of Sivas, TR).
Experimental kinetic study of organic matter maturation: an appraisal of pressure,
temperature and time effects on reflectance properties of vitrinite. - (DFG. Cooperation
with University of Frankfurt a. M.; University of Mainz; University of Göttingen and
Stanford University, USA).
Bituminite parameters to determine thermal metamorphism - field data and experimental
studies. - (Different science founds and DAAD, ERASMUS. Cooperation with University of
Chile, Santiago de Chile, CL; Institutul Geologic al Romaniei, Bucharest, RO; University
Complutense, Madrid, E; Stanford University, USA; Peking University, China and ETH
Zürich, CH, St. Kl. Ohridski University of Sofia, BG and University of Sivas, TR).
Clay-mineral formation in soils developed in the weathering zones of pyrite-bearing schists:
A case-study from the abandoned pyrite mine in Wieściszowice, Lower Silesia, SW Poland
(Cooperation with the Warsaw University of Technology, PL and Jagiellonian University of
Krakow, PL)
Publications
Le Bayon, R., Brey, G.P.; Ernst, W.G. and Ferreiro Mählmann, R. (2011): Experimental
kinetic study of organic matter maturation: Time and pressure effects on vitrinite
reflectance at 400 °C, Organic Geochemistry, v. 42, p. 340-355.
Uzarowicz, Ł., Skiba, S., Skiba, M. and Šegvić, B. (2011) Clay-mineral formation in soils
developed in the weathering zone of pyrite-bearing schists: A case study from the
abandoned pyrite mine in Wieściszowice, Lower Silesia, Sw Poland, Clays and Clay
Minerals, v. 59, p. 581-594. doi: 10.1346/CCMN.2011.0590604.
Kandler, K., Schütz, L., Jäckel, J., Lieke, K., Emmel, C., Müller-Ebert, D., Ebert, M.,
Scheuvens, D., Schladitz, A., Šegvić, B., Wiedensohler, A. and Weinbruch, S. (2011)
Ground-based off-line aerosol measurements at Praia, Cape Verde, during the Saharan
Mineral Dust Experiment: microphysical properties and mineralogy, Tellus B, doi:
10.1111/j.1600-0889.2011.00546.x.
179
Experimental investigations on vitrinite reflectance: toward a tool to model
maturation and metamorphic conditions in low temperature metasedimentary
terranes
Le Bayon Ronan, Ferreiro Mählmann Rafael
There are many reasons to study the metamorphism in low to very low temperature
metamorphic terranes, but all are ultimately related to a fuller understanding of the Earth’s
geodynamic evolution. It is very difficult to carry out metamorphic studies in terranes
consisting mostly of low temperature metamorphic rocks because such conditions lead to
sluggish reactions. Furthermore, the methods (e.g., b0 value) constraining the metamorphic
conditions are often/only qualitative and have limitations.
An alternative method is to use organic matter to estimate the metamorphic conditions in
the very low to low temperature metasedimentary terranes. The presence of vitrinite
phytoclasts provide an opportunity to understand metamorphic and geodynamic evolution
by determining rock pressure– temperature conditions and the degree of maturity with
respect to hydrocarbon generation. Nevertheless, clarification of the physical parameters
that control vitrinite reflectance is necessary.
We carried out laboratory rate studies to elucidate and quantify the effects of time (t),
temperature (T) and pressure (P) on vitrinite reflectance (VR). A series of confined system
maturation experiments was conducted at various pressures (from 2 to 25 kbar) and
temperatures (from 200 to 450 °C). Experiments were performed on xylite of swamp
cypress and involved run lengths from 0 s to dozens of days.
Our experimental results demonstrate temperature and heating time to be important
variables that promote VR increase and therefore the maturation of Type III organic
material. VR increases with time at each investigated pressure. Despite rapid initial kinetics,
the increase in VR decelerates with time at each pressure. When VR < ~1.3-1.5%,
increasing pressure reduces the rate of VR increase and hence retards the initial VR
enhancement with time. The retarding effect of pressure on VR increase diminishes with
enhancing VR. The retardation of VR increase is insignificant for geological maturation at T
≥ 300 °C because a VR of ~1.3-1.5% is attained in only a few hours or days. When VR >
~1.3-1.5%, increasing pressure counteracts the deceleration of VR increase with time and
thus greatly enhances the increase in VR with time. The strong effect of the experimental
heat-up on VR is obvious even for very short experiments and must be corrected in kinetic
analysis. The evolution of VR with heating time, temperature and pressure from an initial
VR of 0% is well described at the investigated experimental P–T conditions by our new
power law rate equation
VR(P, T, t) = (k(P, T) t)^n(P, T)
where the exponent n(P, T) and the rate constant k(P, T) depend on P and T. We regard
this preliminary kinetic formulation as a step toward a general equation describing VR
evolution as a function of time, pressure and temperature for Type III organic matter. This
VR rate equation will be a useful tool to model VR in sedimentary basins and to estimate
the P–T–t conditions in metamorphic terranes occurring in various tectonic settings (e.g.,
exhumed subducted terranes, collided terranes in orogenic wedges). This will aid to gain
insight into geodynamic evolution of sedimentary and metamorphic terranes and to
improve hydrocarbon generation modeling in sedimentary basins.
180
Composition and manufacture technology of hellenistic fineware recovered from
dalmatian coast (croatia)
Branimir Šegvić1, Lucijana Šešelj 2, Rafael Ferreiro Mählmann1
1
Technische Universität Darmstadt, Institute of Applied Geosciences, Technical Petrology,
Darmstadt, Germany
2
University of Zadar, Department of History, HR-23000 Zadar, Croatia
Commencing with the 4th century BC, Greek colonisation became widely present along the
Croatian Adriatic coast. Simultaneously, a number of native settlements have been
established.
For our study on the Hellenistic ceramic manufacture technology, we have chosen pottery
from three archaeological sites: (i) the Hellenistic sanctuary at Cape Ploca, (ii) the native
settlement Resnik, and (iii) the Greek colony Issa (Vis) (Fig. 1a). The analysed pottery were
locally produced and therefore the comparison of the pottery manufacture-levels of Greek
communities (Vis) with the native ones (Resnik and Cape Ploca) is of interest [1].
Fig. 1: Geographic map of middle Dalmatia, showing archaeological sites of analysed potsherd recovery (a)
and XRD patterns showing different compositions of analysed ceramics (b).
Our analysis included artefacts spanning from the 3rd to the late 1st century BC. All
analysed shards depict similar petrographical features, like low porosity and partly vitrified
dark (Vis) or reddish matrix (Cape Ploca and Resnik). Temper material consists mainly of
Qtz, Cal and few grog fragments. Generally, fine silt-sized and amount of temper Qtz, Fsp
and Ms, signify that they were natural ingredients of raw material. Hence, the pottery-paste
preparation was primarily simple and seldom involved artificially added materials or
granulometric separation.
XRD analysis revealed that in part of samples from Caple Ploca and Resnik, traces of 10 Å
phyllosilicates were preserved (Fig. 1b), which limits the firing to 450-600 °C. Presence of
Cal corroborates that finding, along with observed effect of clay mineral rehidroxylation,
posterior to firing. The EMPA analyses revealed presence of “metamorphosed vermiculite”,
known to emerge in schistoic metapelites at around 550 °C and low pressures.
Furthermore, presence of Alm is also reported, setting the upper limit of firing to ~900 °C.
On the other hand, samples from Vis, apart from having the highest content of amorphous
181
matter (Fig. 1b), are featured by the presence of newly formed phases like Mel, And, Pig
and An. Structurally, these phases are reported to appear as fibro-nematoblastic laths of
clear habitus, merged within the glass pockets of andesitic composition. Moreover, the
strong vitrification of these potsherds is witnessed by SEM analysis through the creation of
uniformly distributed, partly coalesced, spherical voids. Such a microstructure is taken as
an indicator for elevated sintering temperatures, ranging between 850 and 1050 °C, which
is in line with the formation of clusters of Ca-silicates and silica rich glasses.
Prior to contacts with Greeks all native pottery in Croatia was hand-made and open-fired,
implying the coarse fabric of clay vessels. For the first time in Hellenistic period the new
technology of pottery making (e.g. wheel, kiln-firing) was introduced in the region. Greek
pottery is fired at higher temperatures for a longer period, under controlled conditions,
thus depicting better quality. The indigenous pottery is fired at lower temperatures and its
quality oscillates. This was probably due to the demanding market and massive production
and not the lack of technological knowledge.
References:
[1]
Šegvić, B., Šešelj, L., Slovenec, Da., Lugović, B., Ferreiro Mählmann R. On the provenance,
manufacture technology and circulation of Hellenistic pottery from Eastern Adriatic: a case
study of three archaeological sites in Dalmatia (Croatia). Submitted to Geoarchaeology 2010.
182
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 the particulate matter 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.
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 (UMB) in Ås (Norway).
Staff Members
Head
Prof. Dr. Stephan Weinbruch
Research Associates
PD Dr. Martin Ebert
Dr. Nathalie Benker
Postdocs
Dr. Dirk Scheuvens
Dr. Annette Worringen
Dr. Konrad Kandler
Technical Personnel Thomas Dirsch
Secretaries
Astrid Zilz
PhD Students
Dipl.-Met. Dörthe Müller-Ebert
Dipl.-Ing. Kirsten Lieke
Dipl.-Ing. Thomas Herrmann
Diploma Students
Simon Jäckel
Miriam Küpper
Franziska Fischer
Katharina Schütze
Bachelor Students
Markus Hartmann
Carolin Tissen
Research Fellow
Dipl.-Ing. Hauke Gorzawski
183
Research Projects
Environmental scanning electron microscopical studies of ice-forming nuclei (DFG
Forschergruppe INUIT).
Electron microscopy of Saharan mineral dust (DFG Forschergruppe SAMUM).
Source apportionment of rural and urban aerosols.
Characterization of volcanic aerosols from the Eyjafjallajökull eruption.
Characterization of working place aerosols (National Institute of Occupational Health, Oslo,
Norway).
Environmental scanning electron microscopical studies of the hygroscopic behaviour of
individual aerosol particles.
Influence of traffic on the surface of monuments.
Influence of traffic control on PM and NOX imissions.
Publications
Gjønnes K., Skogstad A., Hetland S., Ellingsen D.G., Thomassen Y., and Weinbruch S.
(2011): Characterization of workplace aerosols in the manganese alloy production industry
by electron microscopy, Anal. Bioanal. Chem., 399, 1011-1020.
Berlinger B., Benker N., Weinbruch S., L’Vov B., Ebert M., Koch W., Ellingsen D.G., and
Thomassen Y. (2011): Physicochemical characterization of different welding aerosols.,
Anal. Bioanal. Chem., 399, 1773-1780.
Schumann U., Weinzierl B., Reitebuch O., Schlager H., Minikin A., Forster C., Baumann R.,
Sailer T., Graf K., Mannstein H., Voigt C., Rahm S., Simmet R., Scheibe M., Lichtenstern M.,
Stock P., Rüba H., Schäuble D., Tafferner A., Rautenhaus M., Gerz T., Ziereis H.,
Krautstrunk M., Mallaun C., Gayet J.-F., Lieke K., Kandler K., Ebert M., Weinbruch S., Stohl
A., Gasteiger J., Groß S., Freudenthaler V., Wiegner M., Ansmann A., Tesche M., Olafsson
H., and Sturm K. (2011): Airborne observations of the Eyjafjalla volcano ash cloud over
Europe during air space closure in April and May 2010., Atmospheric Chemistry and Physics,
11, 2245-2279.
Ebert M., Worringen A., Benker N., Mertes S., Weingartner E., and Weinbruch S. (2011):
Chemical composition and mixing-state of ice residuals sampled within mixed phase
clouds., Atmospheric Chemistry and Physics, 11, 2805-2816.
Formenti P., Schütz L., Balkanski Y., Desboeufs K., Ebert M., Kandler K., Petzold .,
Scheuvens D., Weinbruch S., and Zhang D. (2011): Recent progress in understanding
physical and chemical properties of African and Asian mineral dust., Atmospheric Chemistry
and Physics, 11, 8231-8256.
Kandler K., Schütz L., Jäckel S., Lieke K., Emmel C., Müller-Ebert D., Ebert M., Scheuvens
D., Schladitz A., Segvic B., Wiedensohler A., and Weinbruch S. (2011a): Ground-based off-
184
line aerosol measurements at Praia, Cape Verde, during the Saharan Mineral Dust
Experiment: microphysical properties and mineralogy., Tellus B, 63, 459-474.
Kandler K., Lieke K., Benker N., Emmel C., Küpper M., Müller-Ebert D., Ebert M., Scheuvens
D., Schladitz A., Schütz L., and Weinbruch S. (2011b): Electron microscopy of particles
collected at Praia, Cape Verde, during the Saharan Mineral Dust Experiment: particle
chemistry, shape, mixing state and complex refractive index., Tellus B, 63, 475-496.
Lieke K., Kandler K., Scheuvens D., Emmel C., von Glahn C., Petzold A., Weinzierl B., Veira
A., Ebert M., Weinbruch S., and Schütz L. (2011): Particle chemical properties in the
vertical column based on aircraft observations in the vicinity of Cape Verde Islands., Tellus
B, 63, 497-511.
Scheuvens D., Kandler K., Küpper M., Lieke K., Zorn S.R., Ebert M., Schütz L., and
Weinbruch S. (2011): Individual-particle analysis of airborne dust samples collected over
Morocco in 2006 during SAMUM 1., Tellus B, 63, 512-530.
Ansmann A, Petzold A, Kandler K, Tegen I, Wendisch M, Müller D, Weinzierl B, Müller T,
Heintzenberg J (2011): Saharan Mineral Dust Experiments SAMUM-1 and SAMUM-2: What
have we learned? Tellus 63B, 403 – 429. doi: 10.1111/j.1600-0889.2011.00555.x.
Knippertz P, Tesche M, Heinold B, Kandler K, Toledano C, Esselborn M (2011): Dust
Mobilization and Aerosol Transport from West Africa to Cape Verde—a Meteorological
Overview of SAMUM-2. Tellus 63B, 430 – 447. doi: 10.1111/j.1600-0889.2011.00544.x.
Schladitz A, Müller T, Nowak A, Kandler K, Lieke K, Massling A, Wiedensohler A (2011):
In-situ aerosol characterization at Cape Verde. Part 1: Particle number size
distributions, hygroscopic growth, and state of mixing of the marine and Saharan dust
aerosol. Tellus 63B, 531 – 548. doi: 10.1111/j.1600-0889.2011.00569.x.
Müller T, Schladitz A, Kandler K, Wiedensohler A (2011): Spectral particle absorption
coefficients, single scattering albedos, and imaginary parts of refractive indices from ground
based in-situ measurements at Cape Verde Island during SAMUM-2. Tellus 63B, 573 – 588.
doi: 10.1111/j.1600-0889.2011.00572.x.
Petzold A, Veira A, Mund S, Esselborn M, Kiemle C, Weinzierl B, Hamburger T, Ehret G,
Lieke K, Kandler K (2011): Mixing of mineral dust with urban pollution aerosol over Dakar
(Senegal): Impact on dust physico-chemical and radiative properties. Tellus 63B, 619 – 634.
doi: 10.1111/j.1600-0889.2011.00547.x.
Groß S, Gasteiger J, Freudenthaler V, Wiegner M, Geiß A, Schladitz A, Toledano C, Kandler
K, Tesche M, Ansmann A, Wiedensohler A (2011): Characterization of the planetary
boundary layer during SAMUM-2 by means of lidar measurements. Tellus 63B, 695 – 705.
doi: 10.1111/j.1600-0889.2011.00557.x.
Gasteiger J, Wiegner M, Groß S, Freudenthaler V, Toledano C, Tesche M, Kandler K
(2011): Modeling lidar-relevant optical properties of complex mineral dust aerosols. Tellus
63B, 725 – 741. doi: 10.1111/j.1600-0889.2011.00559.x.
185
Köhler C H, Trautmann T, Lindermeir E, Vreeling W, Lieke K, Kandler K, Weinzierl B, Groß
S, Tesche M, Wendisch M (2011): Thermal IR Radiative Properties of Mixed Mineral Dust
and Biomass Aerosol during SAMUM-2. Tellus 63B, 751 – 769. doi: 10.1111/j.16000889.2011.00563.x.
Heinold B, Tegen I, Schepanski K, Tesche M, Esselborn M, Freudenthaler V, Groß S,
Kandler K, Knippertz P, Müller D, Schladitz A, Toledano C, Weinzierl B, Ansmann A,
Althausen D, Müller T, Petzold A, Wiedensohler A (2011): Regional modelling of Saharan
dust and biomass burning smoke – Part 1: Model description and evaluation. Tellus 63B,
781 – 800. doi: 10.1111/j.1600-0889.2011.00570.x.
Wagner, R., Ajtai, T., Kandler, K., Lieke, K., Linke, C., Müller, T., Schnaiter, M. and Vragel,
M. (2011): Complex refractive indices of Saharan dust samples at visible and near UV
wavelengths: a laboratory study, Atmospheric Chemistry and Physics Discussions 11,
21363–21427.
Engelmann, R., Ansmann, A., Horn, S., Seifert, P., Althausen, D., Tesche, M., Esselborn, M.,
Fruntke, J., Lieke, K., Freudenthaler, V. and Groß, S. (2011): Doppler lidar studies of heat
island effects on vertical mixing of aerosols during SAMUM-2, Tellus B 63, 448–458.
2. Tagungsbeiträge (Proceedings)
Scheuvens D., Dirsch T., Küpper M., Ebert M., and Weinbruch S. (2011): Schadstoffe an
der Christuskirche in Mainz und am Bayerischen Nationalmuseum in München:
Einzelpartikelanalyse, PM-Messungen und Auswertungen von ZIMEN-Daten., In:
Wirkung verkehrsbedingter Immissionen auf Baudenkmäler, IFS Bericht 37/2011, 55-77.
186
Aerosol deposition in the main African dust transport region: establishing a long-term
time series at Sao Vicente, Cape Verde
K. Kandler1, L. Mendes Neves2, N. Niedermeier3, and T. Müller3
1
Institute of Applied Geosciences, Technische Universität Darmstadt, Germany
2
Instituto de Nacional de Meteorologie e Geofisica, Mindelo, Cape Verde
3
Institut für Troposphärenforschung, Leipzig, Germany
Mineral dust is one of the dominating aerosol species in the atmosphere. Particularly, the
tropical North Atlantic Ocean is heavily affected by dust, changing cloudiness, precipitation,
nutrient fluxes into the ocean, radiation balance etc. A number of field experiments with
different foci recently investigated dust properties (e. g., SAMUM, AMMA, SHADE, PRIDE,
GERBILS). However, these experiments usually lasted a short time, usually a few weeks,
some a season. As a result, they captured a low number of dust episodes only. Given the
highly episodic nature of dust outbreaks and a potential inter-annual variation, the question
arises, how these experiments should be rated with respect to an annual average, or how
they can be compared to each other. This actual problem arises from the nonexistence of
longer time series in the tropical North Atlantic Ocean (except at Barbados; Trapp et al,
2010).
While the shortcomings in the past can’t be changed, a quasi-continuous measurement of
aerosol deposition was installed in the middle of December 2012 at the Cape Verde
Atmospheric Observatory (http://ncasweb.leeds.ac.uk/capeverde/), at the Island of Sao
Vicente Island, Cape Verde. Aerosol deposition is measured by a passive aerosol sampler,
modified from Ott and Peters (2008) “type A – flat plates” by introduction of a liquid trap
and lowering the recipient position slightly below the level of the lower plate. 25 mm
diameter aluminum stubs coated with standard electron microscopy carbon adhesives were
used as sampling surface. The analysis was made with an acceleration voltage of 20 kV and
a beam diameter of 2.6 nm. The particles were classified according to their chemical
composition into eight classes (Fig. 1). For details on the materials and methods as well as
the data processing refer to Kandler et al (2011).
Three samples in December 2011 could be analyzed as a start of the time series (total of
1841) particles. Trajectory calculations (HYSPLIT/GDAS) showed that during all period
dust was transported straight from Mauritania and South Morocco to Cape Verde (about 24
to 30 h transport time from the coast), so the differences in dust abundance – also seen in
the aerosol volume concentrations measured by Scanning Mobility Particle Sizer and
Aerodynamic Particle Sizer (74, 33 and 48 cm3/m3 for SVS_101/2/3) – are most probably
linked to dust emission variation.
The relative abundance of dust increases with the particle size between 1.5 and 10 µm (Fig.
1). The ratio of quartz to the silicate dust varies between 0.1 and 0.3. Sulfate plays a minor
role during the more maritime periods and is absent during the dustier phase. Interestingly,
the amount of mixed particles (internal mixtures of dust and sea-salt) is largely higher for
particles of 5 – 10 µm diameter than for those with 2.5 – 5 µm. This points to an increased
deposition flux of dust particles internally mixed with sea-salt, as proposed by Zhang
187
(2008). It indicates that during the observed dust intrusions, larger pure particles have
already been removed by sedimentation.
Oxides
Quartz
Silicates
Mixtures
Chlorides
Sulfates
Carbonates
Other
SVS_101
2011-12-13 16:30 to
2011-12-14 17:30
SVS_102
2011-12-14 17:30 to
2011-12-16 12:30
SVS_103
2011-12-16 12:30 to
2011-12-19 14:30
0.0
0.2
0.4
0.6
0.8
relative abundance
1.0
0.0
0.2
0.4
0.6
0.8
relative abundance
1.0
0.0
0.2
0.4
0.6
0.8
1.0
relative abundance
Fig. 1: Relative abundance of different particle species in the aerosol sediment at Sao Vicente, Cape Verde.
Left: 1.5 - 2.5 µm; center: 2.5 - 5 µm; right: 5 µm
References:
[1]
[4]
Kandler, K., Lieke, K., Benker, N. et al. (2011) Electron microscopy of particles collected at
Praia, Cape Verde, during the Saharan Mineral dust experiment: particle chemistry, shape,
mixing state and complex refractive index. Tellus 63B, 475-496.
Ott, D.K., Peters, T. (2008) A Shelter to Protect a Passive Sampler for Coarse Particulate
Matter, PM10-2.5. Aerosol Sci. Technol. 42, 299-309.
Trapp, J.M., Millero, F.J., Prospero, J.M. (2010) Temporal variability of the elemental
composition of African dust measured in trade wind aerosols at Barbados and Miami. Mar.
Chem. 120, 71-82.
Zhang, D. (2008) Effect of sea salt on dust settling to the ocean. Tellus 60B, 641-646.
188
[2]
[3]
Diploma Theses in Applied Geosciences
Bauer, Ingo; Geologie, Petrographie und Pyroductgenese des Kahuku-Ranch-Gebietes, Big
Island, Hawaii, 04.11.2011
Breuer, Barbara; Ingenieur- und hydrogeologische Untersuchungen zum Schadensfall
Staufen im Breisgau, 11.04.2011
Ceglarek, Jan; Detailuntersuchung sedimentologischer Prozesse an einem quartären alpinen
Schwemmfächer, mittels eines mit Georadar aufgenommenen dreidimensionalen
Untergrundmodels (Illgrabenfächer, Schweiz), 31.03.2011
Fiedler, Holger; Untersuchung der Vergleichbarkeit von Adhäsionsversuchen mit flachen
und kegelförmigen Teststempeln an bindigen Böden, 12.07.2011
Fischer, Franziska; Chemische Charakterisierung der Aerosolpartikel des Hinter- und
Vordertaunus, 23.08.2011
Hoppe, Nadja; Die Chemie einer Hochwasserwelle des Rheins, 06.01.2011
Jäckel, Simon; Charakterisierung und Optimierung eines Staubdosiersystems für PM10Äquivalenzuntersuchungen, 27.10.2011
Kludt, Christoph; Arzneimittelabbau in Abhängigkeit von der Redoxzonierung im
Interaktionsbereich zwischen Oberflächen- und Grundwasser - am Beispiel des
Schwarzbachs, 06.07.2011
Müller, M. Mathis; Sintermechanismen im LiF dotierten Mg-Al-Spinell, 05.05.2011
Priebs, Robert; Properties of Geothermal Reservoir Rocks: Comparison between Ohaaki
Field (NZ) and Saar-Nahe-Basin (GER), 12.09.2011
Rohm, Melanie; Golddekoration von CdSe/CdS Hetero-Nanostrukturen - Synthese und
elektronenmikroskopische Untersuchungen, 06.01.2011
Rüther, Johanna; Thermofazielle Interpretation des Permokarbons im Sprendlinger Horst,
21.09.2011
Schumann, Andreas; Die Kalklagerstätte Großenlüder-Müs - Fazies, Tektonik und 3DModellierung, 15.02.2011
Diploma Theses in Applie Geosciences
189
Master Theses TropHEE in Applied Geosciences
Asfaw, Berhane; Chlorine and carbon isotope effects during reductive dechlorination of TCE
and cis-DCE using ZVI in bench scale column experiments, 07.03.2011
Khan, Abidur; Analysis and determination of soil moisture content profile by the application
of pilot Time Domain Reflectometry (TDR) prototype sensors, 14.02.2011
Osemwegie, Isimemen; Geochemical and isotopic composition of groundwater from hand
dug wells within the precarious settlements of Southern Abidjan, Cote d'Ivoire, 02.05.2011
Xiao, Lu; Water Quality in Western Uganda - Evaluation of human impact, 10.11.2011
PhD Theses in Applied Geosciences
Shahrazad Abu Ghazleh; Lake Lisan and the Dead Sea: Their Level Changes and the
Geomorphology of their Terraces, 9.2.2011
Martin Kastowski; Abschätzung der Kohlenstoffspeicherung und freisetzung in Seen
Europas - Ein Beitrag zur Eingrenzung der fehlenden Senke im globalen
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Kirsten Inga Lieke; Distribution and Mixing State of Saharan Dust in the Vertical Column
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190
Master- and PhD Theses in Applie Geosciences
Materials Science:
Petersenstraße 23 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
191
Master- and PhD Theses in Applie Geosciences

Institute of Materials Science - Technische Universität Darmstadt

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