report - Technische Universität Darmstadt

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Annual
REPORT
DEPARTMENT OF MATERIALS AND EARTH SCIENCES
Annual Report Department of Materials and Earth Sciences | 5
6 | Annual Report Department of Materials and Earth Sciences
Dean‘s Office
Preface
Materials Science
About Us – Materials Science
Publications of Permanent Staff of the Dean‘s Office
Mechanical and Electrical Workshops
Research Groups
Advanced Thin Film Technology
Catalysts and Electrocatalysts
Dispersive Solids
Electronic Materials
Functional Materials
Ion-Beam Modified Materials
Joint Research Laboratory Nanomaterials
Material Analysis
Materials Modelling
Mechanics of Functional Materials
Molecular Nanostrutures
Nonmetallic-Inorganic Materials
Physical Metallurgy
Physics of Surfaces
Structure Research
Surface Sciences
Theses in Materials Science
Earth Sciences About Us – Earth Sciences Preface
Research Groups
Applied Sedimentology Geology
Engineering Geology
Environmental Mineralogy
Geomaterial Science
Geothermal Science and Technology
Technical Petrology
Theses in Applied Geosciences
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12
18
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28
34
54
62
72
84
93
104
116
124
133
149
164
172
180
193
204
206
208
209
216
232
240
252
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275
Dean‘s Office
Staff Members
Dean
Prof. Dr. Ralf Riedel
Vice Dean
Prof. Dr. Christoph Schüth
Departmental student jobs
administartion and TU-Bibliography Materials Science
Antje Pappenhagen
Coordination KIVA
Dean of studies
Materials Science
Prof. Dr. Wolfgang Donner
Geosciences
Prof. Dr. Matthias Hinderer
Scientific Coordinators
Materials Science and
Department
PD Dr. Boris Kastening
Geosciences
Dr. Karl Ernst Roehl
Secretariat
Departmental and Office of
Studies Materials Science
Renate Ziegler-Krutz
Office of Studies Geosciences
Kirsten Herrmann
Finances and Personnel
Christine Pommerenke
8 | Annual Report Department of Materials and Earth Sciences
Dr. Silvia Faßbender
Competence Center for
Materials Characterization
Dr. Joachim Brötz
IT Office Materials Science
Dipl.-Ing. (BA) Andreas
Hönl
Stefan Diefenbach
Building Services Manager
Materials Science
Dipl.-Ing. Heinz Mohren
Puplic Relations Materials
Science
Marion Bracke
Global Media Design
Thomas Keller
Preface
Dear colleagues and friends,
The present annual report summarizes the
highlights of the year 2015 of the Department of
Materials and Geo Sciences at TU Darmstadt.
Details of the activities and achievements related
to the individual departmental institutes, namely
Materials Science and Applied Geosciences, are
highlighted below.
On behalf of the faculty staff, I 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, master, and bachelor
theses, Ph.D. students, and postdocs – for the
outstanding effort and remarkable enthusiasm
they put into their work. Their engagement
significantly contributed to the performance of
the Department. We aim to sustain and promote
the motivating and fruitful atmosphere at our
Department in order to continue our commitment
and success in the time to come.
Annual
REPORT
INSTITUTE OF MATERIALS SCIENCE
10 | Institute of Materials Science
About Us
Research Groups
Theses
Materials Science | 11
About Us
Materials Science
The amount of acquired third party funding
has dropped from about 10 million Euro in
the last few years to 7.3 million Euro in 2015.
Presently, the total number of students (bachelor
& master) in materials science amounts round
about 500. The number of freshmen of the bachelor study course Materials Science in the winter
semester 2015/16 was 78 (see Figure 1).
The Materials Science and Geo Sciences
Department’s Graduate School “Materialium” has
been further developed and now accommodates
about 190 PhD students. The research-oriented
doctorate program culminating in the award of
the degree of “Dr.-Ing.” or “Dr. rer. nat.” fosters
an interdisciplinary integration of the various
Ph.D. studies between research groups inside and
12 | Materials Science
outside of the Materials Science Department. During specific events, Ph.D. students present their
current scientific problems and methods, providing a forum for close interdisciplinary problem
solving that stimulates synergy between research
groups. Professors of Materialium are particularly committed to supporting their Ph.D. students.
For instance, they strongly encourage participation at international conferences and
publication in refereed research journals, which
is bolstered by the high number of coordinated
research programs in Materials Science at TU
Darmstadt. Moreover, Materialium is a member of Ingenium, the umbrella organisation of
graduate schools at TU Darmstadt.
Materials Science
500
400
300
200
100
0
Freshman
Students (total)
Figure 1a: Development of the number of students in Materials Science over the past 15 years.
Coordinated Research Proposals
Presently, one main focus of the research
at the Materials Science Department is the
project RESPONSE funded by the Hessian State
Government. The scientific topic of this research
program is related to “The Reduction and Substitution of Rare Earth Elements in High Performance Permanent Magnets” (RESPONSE) and
is coordinated by Prof. Oliver Gutfleisch. This
initiative marks the interdisciplinary approach
the university is promoting and for which the
Department of Materials and Geo Science is
ideal since its subjects combine various sciences
like chemistry, physics, electrical and mechanical
engineering. End of January 2015, the Hessian
Minister of Environmental Affairs, Ms. Priska
Hinz, visited the research staff and facilities of
RESPONSE.
Another coordinated research project in
the LOEWE program, funded again by the
state of Hesse, was approved. The program
is denoted by iNAPO, which stands for ion
conducting nano pores, and is coordinated by
Prof. Wolfgang Ensinger. The focus of the
research is to study the structure and working
principles of biological sensors based on nano
pore channels.
Faculty Members and Affairs
End of March 2015, Junior-Prof. Dr. Kyle
Webber, the head of the the group “Electromechanics of Oxides” accepted a call to full professor at the University of Erlangen-Nuremberg.
There, he will establish a new research group
related to “Functional Ceramics”.
Since 2015 the Department hosts two
new Junior-Professors: a) On 1st of March,
Dr. Ulrike Kramm was appointed to head the
group “Catalysts and Electrocatalysts” in the
frame of the graduate school “Energy Science
and Engineering” funded by the Federal Excellence Initiative. b) One month later, Dr. Hongbin
Zhang was appointed to establish the group
“Theory of Magnetic Materials” in the frame
of the LOEWE program funded by the state of
Hesse.
The Department also recorded two habilitations, namely a) Dr. Emanuel Ionescu with the
research topic on “Ceramic Nanocomposites” and
b) Dr. Wojciech Pisula (presently at the
Max-Planck-Institute of Polymer Science in Mainz)
who studied “ Ceramic Nanocomposites with
Advanced Structural and Functional Properties.”
In April 2015, Prof. Christoph Schüth was reelected as Vice-Dean for another two years, until
March 31, 2017.
The Materials Science Department successfully completed the evaluation procedure and
is now in the process of working, out further
details related to the future directions in terms
of research and staff. In this context, in 2015 the
faculty negotiated an objective an agreement
on their future research and teaching targets
together with the executive committee of the TU
Darmstadt.
Honours, Awards and Special Achievements
In 2015, Junior-Prof. Baixiang Xu was awarded
with the prestigious Adolf-Messer-Prize for her
research in the field of “Mechanics of Functional
Materials”. This awards is granted with an
amount of 50.000 € to support and strengthen
the research studies of excellent young scientists.
The annual awarding of the “MaWi Prize”
was celebrated on the occasion of the year-end
ceremony on November 25. The Bachelor
prizes were awarded to Markus Frericks
(research group FM, thesis on “Charakterisierung der magnetokalorischen Eigenschaften von
(Mn,Fe)2(P,Si)-Legierungen”), to Arne Klomp
(research group DF, thesis on „Der Einfluss
von Keimbildnern und färbenden Komponenten
auf den Keramisierungsprozess und die Eigenschaften von Lithium-Alumosilicat-Glaskeramiken - Farbentwicklung durch Nukleation und
Keramisierung“) and to Mihail Slabki (research
group NAW, thesis on „Entwicklung eines Herstellungsverfahrens für papierabgeleitete poröse
Piezokeramiken auf Basis von 0,5Ba(Zr 0.2Ti0.8)
O3-0,5(Ba0.7Ca0.3)TiO3“),
Ms. Priska Hinz
Jun.- Prof. Dr. U. Kramm
Prof. Dr. C. Schüth
Prof. Dr. W. Ensinger
Jun.- Prof. Dr. H. Zhang
Dr. habil. E. Ionescu
Jun.-Prof. Dr. K. Webber
Dr. habil.W. Pisula
Jun.- Prof. Dr. (Boshi) B.-X. Xu
Imagery follow from left to right
The Master prizes were awarded to Andreas
Hubmann (research group OF, thesis on „Investigation of the Polarization Behavior of BaTiO3
Single Crystals“), to Laura Ahmels (research
group PhM, thesis on „Simulation and Validation
of Plastic Flow in ARMCO Iron during a Modified Compression Test“), and to Julian Mars
(research group ST, thesis on “Molecular scale
structures of ionic liquid interfaces in an electric
potential”).
The PhD prizes were awarded for “excellent”
promotions to Dr. Matias Acosta (research group
NAW, thesis on “Strain Mechanisms in Lead-Free
Ferroelectrics for Actuators”), to Arne Fischer
(research group GLNM, thesis on “Crystalline
and amorphous cluster-assembled nanomaterials, synthesized with a novel cluster deposition
system”), to Mareike Frischbier (research group
OF, thesis on “Die elektrischen Eigenschaften
von Indiumoxid-Dünnschichten: in-situ HallEffekt-Messungen zur Aufklärung des Einflusses
von Punktdefekten und Korngrenzen”), and to
Anne Fuchs (research group OF, thesis on “Der
Frontkontakt der CdTe-Dünnschichtsolarzelle:
Charakterisierung und Modifizierung von Pufferund Fensterschichten und deren Grenzflächen”).
Additionally, there was a competition for the
best Bachelor and Master research posters.
The first prize was awarded to Geoffrey Tan and
Tim Lienig, the second prize to Rana Yekani and
Paula Connor, and the third prize to Silvia Ulrich
and Nils Ulrich. All prize winners were Master
students.
Social Events
As every year, our annual summer party was
scheduled for middle of June, shortly before the
summer break, being one of the most important
social events of the Materials Science Institute.
In November 2015 we celebrated the yearend ceremony for all research groups, staff
members and students, including the formal
graduate celebration, where Bachelor, Master
and PhD students received their certificates.
The celebration including the social programme,
was organized by the Deanery´s team, in particular by PD Dr. Boris Kastening, Heinz Mohren,
Dr. Silvia Faßbender and our workshop team.
On the following pages, this annual report
shall provide you with some further information
on the most prominent research activities of the
individual groups conducted in 2015.
Prof. Ralf Riedel
Dean of the Department
Celebration for Bachelor, Master and PhD gradutates
Publications of Permanent Staff of the Dean‘s Office
[1]
Self-Supporting Metal Nanotube Networks Obtained by Highly Conformal Electroless Plating
Muench, F; De Carolis, DM; Felix, EM ; Broetz, J; Kunz, U;
Kleebe, HJ; Ayata, S; Trautmann, C; Ensinger, W CHEMPLUSCHEM, Volume: 80, Issue: 9, 1448-1456,
DOI: 10.1002/cplu.201500073, Published: SEP 2015
[2] Double-Walled Ag-Pt Nanotubes Fabricated by Galvanic Replacement and Dealloying: Effect of Composition on the Methanol Oxidation Activity
Schaefer, S; Muench, F ; Mankel, E ; Fuchs, A; Broetz, J;
Kunz, U; Ensinger, W
NANO, Volume: 10, Issue: 6, Article Number: 1550085
DOI: 10.1142/S179329201550085X, Published: AUG 2015
[3] Facile wet-chemical synthesis of differently shaped cuprous oxide particles and a thin film: Effect of catalyst morphology on the glucose sensing performance
Neetzel, C; Muench, F; Matsutani, T; Jaud, JC; Broetz, J;
Ohgai, T; Ensinger, W SENSORS AND ACTUATORS BCHEMICAL, Volume: 214, Pages: 189-196
DOI: 10.1016/j.snb.2015.03.011, Published: JUL 31 2015
[4] Lightweight aggregates produced from sand sludge and zeolitic rocks
Volland, S; Broetz, J; CONSTRUCTION AND BUILDING MATERIALS, Volume: 85, Pages: 22-29
DOI: 10.1016/j.conbuildmat.2015.03.018, Published: JUN 15 2015
[5] Deep and Shallow TiO2 Gap States on Cleaved Anatase Single Crystal (101) Surfaces, Nanocrystalline Anatase Films, and ALD Titania Ante and Post Annealing
Reckers, P; Dimamay, M ; Klett, J; Trost, S; Zilberberg, K; Riedl, T; Parkinson, BA; Broetz, J; Jaegermann, W; Mayer,
T JOURNAL OF PHYSICAL CHEMISTRY C, Volume: 119, Issue: 18, Pages: 9890-9898, DOI: 10.1021/acs.jpcc.5b01264, Published: MAY 7 2015
[6] Chemical and physical properties in layers and interfaces of nanolayered Si(100)/Ni/BCxNy stacks
Hoffmann, P; Kosinova, M; Flege, S; Broetz, J; Trunova, V;
Dietz, C; Ensinger, W X-RAY SPECTROMETRY, Volume: 44, Issue: 2, Pages: 48-53
DOI: 10.1002/xrs.2578, Published: MAR-APR 2015
18 | Publications of Permanent Staff of the Dean‘s Office
Mechanical Workshop
Staff Members
Head
Jochen Rank
Technical Personnel
Frank Bockhard
Ulrich Füllhardt
Volker Klügl
Herry Wedel
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 2014 the workshop was involved in the following major
projects:
•
•
•
•
•
Components for Evaporation System for Rotated Fibre Substrates
UHV-preparation chambers dedicated for MBE, CVD, PVD, PLD and (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
Electrical Workshop
Staff Members
Technical Personnel
Michael Weber
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)
Mechanical and Electrical Workshop | 19
20 | Research Groups – Materials Science
Research Groups
Materials Science – Research Groups | 21
Advanced Thin Film
Technology
Staff Members
Head
Prof. Dr. Lambert Alff
Research Associates
Dr. Erwin Hildebrand
Dr. Philipp Komissinskiy
Dr. Soumya Ray
Dr. Pradeep V.Sasikumar
Technical Personnel
Dipl-Ing. Gabi Haindl
Jürgen Schreeck
Secretaries
Marion Bracke
PhD Students
Dipl.-Ing. Mani Arzhang
Dipl.-Ing. Mehrdad Baghaie
Dipl.-Ing. Alexander Buckow
Supratik Dasgupta, MTech
Dominik Gölden, M. Sc.
Dipl.-Ing. Stefan Hirsch
Dipl.-Ing. Aldin Radetinac
Dipl.-Phys. reiner Retzlaff
Sareh Sabat, M. Sc.
Vikas Shabadi, BTech.
Sharath Ulhas, MTech.
Stefan Vogel, M. Sc.
22 | Advanced Thin film technology
Advanced Thin Film Technology
The Advanced Thin Film Technology (ATFT)
group works on advanced thin film deposition
techniques of novel materials. The group is specialized on physical vapor deposition techniques
such as pulsed laser deposition (PLD), advanced
oxide molecular beam epitaxy (ADOMBE) and
dc/rf-magnetron sputtering. The ADOMBE
system is an in-house development and has been
jointly financed by Max-Planck-Institute for Solid
State Research in Stuttgart and TU Darmstadt.
PLD and ADOMBE are part of a cluster system
allowing for in-situ sample exchange between the
different deposition methods and characterization tools. The ADOMBE apparatus is a worldwide unique thin film deposition system which
is dedicated to the growth of complex oxides
beyond thermodynamic equilibrium. It allows
for the simultaneous deposition of six elements
from electron beam sources and further elements
evaporated from effusion cells. The molecular
beams of each element can be individually controlled by a feed back loop using electron impact
emission spectroscopy.
The group is working mainly on oxide
ceramics which show a stunning variety of new
functional properties. Examples are high-temperature superconductors, magnetic oxides for
spintronics, high-k dielectrics, ferroelectrics, and
novel thermoelectric materials. As a vision for
future, new solid state matter can be created by
building hetero- and composite structures combi-
ning 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.
Throughout 2015 Lambert Alff was working
also as a head of the Graduate School Materialium. Lambert Alff has also worked as an elected
a member of the senate of TU Darmstadt.
Advanced Thin film technology | 23
Research Projects
•
Novel arsenic free pnictide superconductors (SPP 1458)
(DFG 2013 - 2015)
•
•
Resistives Schalten in HfO2-basierten Metall-Isolator-Metall
Strukturen für Anwendungen im Bereich nicht-flüchtiger Speicher (DFG 2012-2016)
•
LOEWE-Centre AdRIA: Adaptronik – Research, Innovation,
Application (HMWK 2011 - 2014)
•
EU/BMBF PANACHE (2014-2017)
•
LOEWE-Schwerpunkt RESPONSE
Novel oxid electrodes for all oxide varactors (DFG 2012-2014)
Publications
[1]Nicole L. LaHaye, Jose Kurian, Prasoon K. Diwakar, Lambert Alff, and Sivanandan S. Harilal
Femtosecond laser ablation-based mass spectrometry:
An ideal tool for stoichiometric analysis of thin films
Sci. Rep. 5, 13121 (2015)
doi: 10.1038/srep13121
[2] M. Zwiebler, J. E. Hamann-Borrero, M. Vafaee, P. Komissinskiy,
S. Macke, R. Sutarto, F. He, B. Büchner, G. A. Sawatzky, L. Alff,
J. Geck
Electronic depth profiles with atomic layer resolution from resonant soft x-ray reflectivity
New J. Phys. 17, 083046 (2015)
doi: 10.1088/1367-2630/17/8/083046
[3] F. Muench, B. Juretzka, S. Narayan, A. Radetinac, S. Flege,
S. Schaefer, R. Stark and W. Ensinger
Nano- and microstructured silver films synthesised by halide
assisted electroless plating
New J. Chem. 39, 6803 (2015)
doi: 10.1039/C5NJ00952A
[4] Scherf, D. Janda, M. Baghaie Yazdi, X. Li. F. Stein, M. Heilmaier
Oxidation Behavior of Binary Aluminium-Rich Fe–Al Alloys with a Fine-Scaled, Lamellar Microstructure
Oxid. Met. 83, 559–574 (2015)
doi: 10.1007/s11085-015-9535-6
[5] Imants Dirba, Philipp Komissinskiy, Oliver Gutfleisch and
Lambert Alff
Increased magnetic moment induced by lattice expansion from α-Fe to α'-Fe8N
J. Appl. Phys. 117, 173911 (2015)
doi: 10.1063/1.4919601
[6] D. S. Bick, S. U. Sharath, I. Hoffman, M. Major, J. Kurian, L. Alff
(001) and (111) Single-Oriented Highly Epitaxial CeO2 Thin Films on r-Cut Sapphire Substrates
J. Electron. Mater. 44, 2930-2938 (2015)
doi: 10.1007/s11664-015-3728-2
Publications
[7] Mingwei Zhu, Philipp Komissinskiy, Aldin Radetinac, Zhanjie Wang and Lambert Alff
Joint effect of composition and strain on the anomalous transport properties of LaNiO3 films
J. Appl. Phys. 117, 155306 (2015)
doi: 10.1063/1.4918661
[8] Reiner Retzlaff, Alexander Buckow, Philipp Komissinskiy, Soumya Ray, Stefan Schmidt, Holger Mühlig, Frank Schmidl, Paul Seidel,
Jose Kurian, and Lambert Alff
Superconductivity and role of pnictogen and Fe substitution in 112-LaPdxPn2 (Pn=Sb,Bi)
Phys. Rev. B 91, 104519 (2015)
doi: 10.1103/PhysRevB.91.104519
[9] Q.-R. Li, M. Major, M. Baghaie Yazdi, W. Donner, V. H. Dao,
B. Mercey, and U. Lüders
Dimensional crossover in ultrathin buried conducting SrVO3 layers
Phys. Rev. B 91, 035420 (2015)
doi: 10.1103/PhysRevB.91.035420
[10] Alexander Tkach, Mehrdad Baghaie Yazdi, Michael Foerster,
Felix Büttner, Mehran Vafaee, Maximilian Fries, and Mathias Kläui
Magnetoelectric properties of epitaxial Fe3O4 thin films on (011) PMN-PT piezosubstrates
Phys. Rev. B 91, 024405 (2015)
doi: 10.1103/PhysRevB.91.024405
[11] Dirba, M. Baghaie Yazdi, A. Radetinac, P. Komissinskiy, S. Flege,
O. Gutfleisch, L. Alff
Growth, structure, and magnetic properties of γ'-Fe4N thin films
J. Magn. Magn. Mater. 379, 151–155 (2015)
doi: 10.1016/j.jmmm.2014.12.033
Catalysts and
Electrocatalysts
Staff Members
Head
Prof. Dr. Ulrike. I. Kramm
Secretaries
Heide Rinnert
Postdoc
Dr. Ing. Nina Erinie
PhD candidates
Ionna Martinaiou
Ali Shahraei
Master Students
Fabian Grimm
Advanced research lab
Carolin Fritsch
28 | Catalysts and Electrocatalysts
Catalysts and Electrocatalysts
In 2015 the new chair on Catalysts and Electrocatalysts was created as joint calling of the
departments of Materials and Earth science
and Chemistry. The chair is implemented in the
Solar Fuels division of the Graduate School of
Excellence Energy Science and Engineering.
The current research focusses on the development of electrocatalysts (with main focus on fuel
cells) and their structure-property correlations.
In a standard combustion engine a fuel is
burned (oxidized by air) in order to generate
thermal energy that is converted by a turbine to
mechanical energy and eventually electric energy. Hence, the overall efficiency is limited by the
Carnot process and the efficiency of each energy
converter. Within the burning reaction the fuel is
oxidized and the oxidant is reduced in order to
form CO2 and H2O. In a fuel cell, these two half
reactions take place separated on two electrodes
the anode and cathode. On the anode a fuel (like
hydrogen, methanol or ethanol) is oxidized and on
the cathode the oxygen is reduced, both reactions
are catalysed by state-of the art Platinum-based
catalysts. The equilibrium potentials of both halfcell reactions defines the maximum energy that
can be taken out by this reaction. Hence, the main
advantage of a fuel cell is the direct conversion of
chemical energy into electric energy. In addition,
it is CO2 neutral if it is run with hydrogen or
alcohols generated from biomass.
A main problem directed to fuel cell research
are costs. Today, the platinum-based catalysts
contribute by about 25 % to the overall costs of a
fuel cell system, therefore limiting its economic
relevance. In this respect, Non-precious metal
catalysts of type Me-N-C are most promising, as
they would allow to replace most of the platinum
that is required today within a fuel cell system.
In addition to this, Me-N-C catalysts are significantly more tolerant towards impurities that are
typically found in fuels produced from bio mass.
These NPMC are high-temperature ceramics of different organometallic precursors
involving a metal (Me: different kinds of 3d
transition metals), nitrogen and carbon source.
Highest catalytic activities are achieved
with Fe-N-C catalysts. Based on 57Fe Mößbauer
spectroscopy several important insides in the
structural composition of these catalysts and the
nature of active sites were concluded.
In a collaboration with the Technical University of Berlin, Prof. Strasser, we were able to
elucidate for the first time a utilization factor
for these kind of non-precious metal catalysts,
see Figure 1 for illustration [1]. This utilization
factor is important for the exact determination
of turn-over frequencies and better evaluation of
the long-term stability in PEM-FC application.
Catalysts and Electrocatalysts | 29
A main problem for enabling the defined assignment of activity, selectivity and/ or stability
promotors in Me-N-C catalysts is given by the
structural composition which is usually highly
heterogeneous due to the high temperature
pyrolysis. In a recent work in collaboration
with researchers from the Helmholtz-Zentrum
Berlin für Materialien und Energie (HZB) and
the Freie Universität Berlin (FU) we present a
strategy of a purification treatment of Me-N-C
catalysts that comprises a heat treatment in
forming gas followed by an acid leaching step.
This purification treatment leads to a significant
reduction of inorganic by-products in some cases
even down to zero [2]. This is illustrated for an
(Fe,Co)-N-C catalyst in Figure 2. Therefore,
different structure units can be implemented in
a subsequent step in order to work out their contribution towards the electrocatalytic application.
In a collaboration with Prof. Feng’s group
(now TU Dresden) and Prof. Müllen (MPI Mainz)
a new template-free synthesis strategy for MeN-C (Me = Fe, Co or Fe+Co) was demonstrated
and the related catalysts characterized [3].
In future direction especially the limited
stability of these Fe-N-C catalysts has to be
understood in order to develop strategies for an
enhanced long term stability under PEM-FC
conditions. In this respect, we currently presented a comprehensive study of Fe-N-C catalysts
prepared by the oxalate-supported pyrolysis
of iron porphyrin with an intermediate acidleaching. Beside the structural characterization,
accelerate stress tests (AST) were performed in
collaboration with Prof. Arenz from the University of Copenhagen in order to compare the effect
of sulfur addition in the preparation step on the
stability of the catalysts under load conditions
and during start-up and shut-down conditions [4].
of physicochemical characterization of Me-N-C
catalysts for those spectroscopic techniques that
are best suited for the characterization of this
group of catalysts.
In addition to this, depending on the kind of
metal species these Me-N-C catalysts are also
applicable for other energy related reactions. This
includes the hydrogen evolution reaction (HER),
Oxygen evolution reaction (OER), CO2 reduction,
Hydrogen peroxide formation and reduction.
Just recently, we started activities in the
direction of alloy catalysts for the anodic oxidation reactions in different kinds of fuel cells.
As stated above, today, platinum-based
catalysts are utilized on both sites (anode and
cathode) of a fuel cell. However, an optimal
catalyst accelerates only the specifically desired
reaction whereas all other reactions are suppressed. Indeed, the capability of the platinum anode
catalyst to reduce oxygen is a main drawback that
leads to significant degradation of the overall FC
system. This is caused by the so called reverse
current mode that takes place during start-up and
shut-down conditions, when air is also penetrating the anodic side of a fuel cell system. Hence,
the idea is to develop alloy catalysts that are
nearly as active as platinum but where the ORR
is significantly suppressed.
So far, two laboratories were built up in 2015:
The preparation laboratory is equipped with a
slit-hinge furnance for pyrolysis of the NPMC
precursors at temperatures of up to 1100 °C in
defined gas atmospheres. Beside this, equipment
for wet-chemical precursor and nanoparticle
syntheses is available.
The electrochemistry laboratory has so far two
rotating disc electrode (RDE) test stations equipped with potentiostats (Nordic Electrochem.)
for the characterization of the different half-cell
reactions at room temperature conditions.
In a recently published book on Nanocarbons
for Advanced Energy Conversion a chapter on
the spectroscopic characterization of Me-N-C
catalysts for the oxygen reduction reaction
was implemented [5]. This book chapter gives
background information and selected examples
In 2016, the Mößbauer laboratory will be
equipped for characterization of iron and tin
species in different kinds of (catalyst) materials.
In addition to this, a fuel cell test station
will be installed for characterization of catalysts
under real operation conditions.
Figure 1: Illustration of the change in utilization factor (top images) for a catalyst
before and after the required subsequent treatments. Bottom images give a model of
the active site in Fe-N-C catalysts and the quantitative change in the utilization factor
induced by the subsequent treatments [1].
Figure 2: Effect of the purification treatment on the structural composition of (Fe,Co)-N-C catalysts as determined
by 57Fe Mößbauer spectroscopy (a, b). Within the spectra the two doublets D1 and D2 are assigned to different FeN4
sites, whereas the other sites are related to inorganic iron species. The overall iron and cobalt contents are also
iven. The Tafel plots in c) illustrate that the purification leads to a significant enhancement of ORR activity for these
catalysts [2].
References
[1] N.R. Sahraie, U.I. Kramm,
J. Steinberg, Y. Zhang, et al.,
Quantifying the density and
utilization of active sites in
non-precious metal oxygen
electroreduction catalysts,
Nature Commun. 6 (2015) 8618.
[2] U.I. Kramm, I. HerrmannGeppert, J. Behrends, K. Lips,
et al., On an easy way to prepare
Metal-Nitrogen doped Carbon with
exclusive presence of MeN4-type
sites active for the ORR:
J. Am. Chem. Soc., published
online (2015).
[3] S. Bruller, H.-W. Liang,
U.I. Kramm, J.W. Krumpfer,
et al., Bimetallic porous porphyrin
polymer-derived non-precious
metal electrocatalysts for
oxygen reduction reactions, J.
Mater. Chem. A 3 (47) (2015)
23799–23808.
[4] U.I. Kramm, A. Zana,
T. Vosch, S. Fiechter, et al., On the
structural composition and stability
of Fe-N-C catalysts prepared by an
intermediate acid leaching, Journal
of Solid State Electrochemistry,
published online (2015).
[6] U.I. Kramm, Spectroscopic
Analysis of nanocarbon-based
non-precious Metal Catalysts
for ORR: Volume 2, Wiley-VCH,
Weinheim, 2015.
Conference Participations and other Talks
[1] Ulrike I. Kramm, Invited talk “Controversies on Fe-N-C catalysts”, University of Freiburg i.Br., May.
[2] Ulrike I. Kramm, Invited talk “Me-N-C-Katalysatoren für die
Sauerstoffreduktion in Brennstoffzellen, Umicore, Hanau, June.
[3] Ulrike I. Kramm, Talk “Catalysts for PEM-FC”, Meeting of the Advanced Fuel Cell devision of the International Energy Agency (IEA) in Pfitztal, July.
[4] Ulrike I. Kramm, Poster “Influence of the structural composition of Me-N-C oxygen reduction electrocatalysts on the stability in
accelerated stress tests“, Wissenschaftsforum Chemie, Dresden, Aug.
[5]
Ioanna Martinaiou, F. Grimm, A. Huber, D. Schmeißer, U.I. Kramm, Talk, “Influence of the structural composition on the activity and stability of Me-N-C catalysts”, Electrolysis and Fuel cell Discussions (EFCD), La Grande Mott, France, Sept.
[6] F. Luo, S. Dresp, A. Bergmann, S. Kühl, U. I. Kramm, P. Strasser, Poster “Polyaniline derived non-noble metal catalysts for the oxygen reduction reaction”, EFCD, La Grande Mott, France, Sept.
[7]
Ulrike I. Kramm, Invited talk, “Structural characterization of
non-precious PEM-fuel cell catalysts by Mößbauer spectroscopy”,
International conference on the application of the Mößbauer effect (ICAME), Hamburg, Sept.
[8] N. Erini, S. Indris, H. Hahn, P.Strasser, U.I. Kramm, Poster
„Carbon-supported PtSn-alloys for the oxidation reaction in low temperature fuel cells”, ICAME Hamburg, Sept.
Dispersive Solids
Staff Members
Head
Prof. Dr. rer. nat.
habil. Prof. h. c. Ralf Riedel
Associated
Professors and Lectures
Apl. Prof. Dr. Norbert Nicoloso
PD Dr. Leonore Wiehl
Guest Professors
Prof. Dr. Zhaoju Yu
Research Associates
Dipl.-Ing. Anke Böttcher
Dr. Isabel Gonzalo de Juan
Dr. Magdalena Graczyk-Zajac
Dr. Emanuel Ionescu
Dr. Pradeep V.Sasikumar
Technical Personnel
Dipl-Ing. Claudia Fasel
Secretaries
Su-Chen Chang
Shoba Herur
(EU project FUNEA)
PhD Students
Dipl.-Ing. Miria Andrade
Shrikant Bhat, M.Sc.
Dario De Carolis, M. Sc.
Sarabjeet Kaur, M. Sc.
Dipl.-Ing. Amon Klausmann
Szu-Hsuan Lee, M. Sc.
Wenjie Li, M. Sc.
Dipl.-Ing. Christoph Linck
Xingmin Liu, M. Sc.
34 | Dispersive Solids
Dipl.-Ing. Lukas Mirko Reinold
Dipl.-Ing. Felix Roth
Cristina Schitco, M. Sc.
Dipl.-Ing. Lukas Schlicker
Christina Stabler, M. Sc.
Dipl.-Ing. Alexander Uhl
Dragoljub Vrankovic, M. Sc.
Hongguang Wang, M. Sc.
Qingbo Wen, M. Sc.
Jia Yuan, M. Sc.
Cong Zhou, M. Sc.
Diploma and Master Students
Blandine Barabé
Robert Brück
Dario De Carolis
Fangtong Xie
Hanna Verena Heyl
Benjamin Juretzka
Kai Kühne
Tarini Mishra
Sai Priya S.V.M.L Munagala
Sandeep Satyanarayana
Mathias Storch
Anke Silvia Ulrich
Dragoljub Vrankovic
Maximilian Wimmer
Kerstin Wissel
Bachelor Students
Jonas Heldt
Arne Jan Klomp
Michael Scherer
Guest Scientists
Yan Lu, Institute of Chemistry, Chinese Academy of
Sciences, Haidian, Beijing,
P.R. China
Qingqing Chen, Department
of Materials Science and
Engineering, Harbin Institute
of Technology, Harbin City,
Heilongjiang Province, P.R.
China
Sandeep Satyanarayana,
India
Dr. Sarika Verma, Powers,
Bhopal, India
Dr. Yun Wang, Aerospace Research Institute of Materials
& Processing Technology,
Beijing, P.R. China
Amr Mosallem, German
University of Cairo, Cairo,
Egypt
Prof. Dr. Corneliu
Balan, Politehnica, University of Bucharest, Faculty
of Enegetics, Hydraulics
Departement, Bucharest,
Romania
Prof. Zhaoju Yu, Department
of Materials Science and
Engineering, College of
Materials, Xiamen University, Xiamen, P.R. China
Lahrar El Hassane, Université de Limoges, Limoges,
France
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 non-oxidic materials
with properties beyond the state of the art.
The materials of interest are advanced oxidic
and non-oxidic ceramics with extraordinary
properties in terms of thermal stability, hardness
and electronic structure. Therefore, synthesis
methods such as polymer-pyrolysis, non-oxidic
and oxidic sol-gel methods, chemical vapour
deposition and novel high pressure methods have
been further developed.
The following topical issues are presently under
investigation:
Polymer-Derived Ceramics
The thermolytic decomposition of suitable
organosilicon polymers provides materials
which are denoted as polymer-derived ceramics
(PDCs). The main emphasis is on the synthesis
and characterization of new ceramic materials
in the B-C-N, Si-C-N, Si-O-C, Si-(B,C)-N and
Ti-(B-C)-N systems. The structural peculiarities, thermochemical stability, mechanical and
electrophysical properties of the PDCs have
been investigated in a series of PhD theses and
research projects. Due to their outstanding thermochemical stability as well as excellent oxidation and creep resistance at very high temperatures, the PDCs constitute promising materials
for high temperature applications. Another
advantage of the PDC route is that the materials
can be easily shaped in form of fibres, layers or
bulk composite materials. Finally the correlation
of the materials properties with the molecular
structure of the used preceramic polymer is
elaborated.
Molecular Routes to Nanoscaled Materials
The aim is to develop concepts for the production of novel multifunctional inorganic materials with a tailor-made nanoscaled structure.
In accordance with the so-called “bottom-up”
approach, specific inorganic molecules are to
be assigned to higher molecular networks and
solid-state structures in the form of molecular
nanotools by means of condensation and polymerisation processes.
High Pressure Chemistry
Ultra-high pressure techniques like laser
heated diamond anvil cell (LH-DAC) or multi anvil devices have been applied to synthesise novel
solid state structures which cannot be produced
by other methods, for example, inorganic nitrides.
Moreover, the materials behaviour under pressure
such as phase transformations and decomposition
can be analysed.
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.
Advanced polymer-derived ceramics are
developed for applications in the field of energy
conversion and storage.
Dispersive Solids | 35
High Pressure Synthesis of Novel Boron Oxynitride ‘B6N4O3’
with Sphalerite Type Structure
Shrikant Bhat,1 Leonore Wiehl,1 Leopoldo Molina-Luna,1 Enrico Mugnaioli, 2,3 Stefan Lauterbach,1
Sabrina Sicolo,1
Peter Kroll,4 Michael Duerrschnabel,1 Norimasa Nishiyama, 5 Ute Kolb, 3 Karsten Albe,1
Hans-Joachim Kleebe,1 and Ralf Riedel1*
Fachbereich Material- und Geowissenschaften, Technische Universität Darmstadt, Germany
Department of Physical Sciences, Earth and Environment, University of Siena, Italy
3
Institut für Physikalische Chemie, Johannes Gutenberg-Universität Mainz, Germany
4
Department of Chemistry and Biochemistry, UT Arlington, USA
5
DESY Hamburg , Germany
1
2
Chem. Mater. 27 (2015) 5907-5914, DOI: 10.1021/acs.chemmater.5b01706
Abstract
A novel crystalline boron oxynitride (BON)
phase has been synthesized under static
pressures exceeding 15 GPa and temperatures
above 1900 °C, from molar mixtures of B2O3
and h-BN. The structure and composition of the
synthesized product were studied using highresolution transmission electron microscopy, electron diffraction, automated diffraction tomography,
energy dispersive X-ray spectroscopy and electron
energy-loss spectroscopy (EELS). BON shows a
hexagonal cell (R3m, Z=3) with lattice parameters a = 2.55(5) Å and c = 6.37(13) Å, and a
crystal structure closely related to the cubic
sphalerite type. The EELS quantification yielded
42 at.% B, 35 at.% N and 23 at.% O (~ B:N:O = 6:4:3).
Electronic structure calculations in the
framework of Density Functional Theory have
been performed to assess the stabilities and
properties of selected models with the composition B6N4O3. These models contain ordered
structural vacancies and are superstructures of
the sphalerite structure. The calculated bulk
moduli of the structure models with the lowest formation enthalpies are around 300 GPa,
higher than for any other known oxynitride.
Introduction
In the present study, we report the first
synthesis of a novel boron oxynitride. Accordingly,
mechanical mixtures of h-BN and B2O3 powders
were used as starting materials for HP-HT experiments using a large volume press. The recovered
samples were studied using high-resolution transmission electron microscopy (HRTEM), electron
diffraction (ED), automated diffraction tomography (ADT), energy dispersive X-ray spectroscopy (EDX) and electron energy-loss spectroscopy (EELS). Calculations in the framework of
Density
Functional
Theory
(DFT)
have been performed to investigate the
structural,
electronic,
mechanical
and
thermodynamic
properties
of
proposed
models whose compositions have been suggested
by the EELS measurements.
Experiments
HP-HT Synthesis
The starting material for our synthesis was
prepared by ball-milling a mixture of hexagonal
BN (99.5% purity, Alfa Aesar) and B2O3 (99.98%
purity, Alfa Aesar) in the ratio of 3:1 (wt. %),
using zirconia anvils and balls. X-ray diffraction
patterns (see supporting information Figure S1)
of the starting materials show that the mixture
became completely amorphous after 4 h of ball
milling. HP-HT experiments (15.6 GPa and 1900°C
for 20 min) were performed in a Walker type
multi-anvil apparatus (6/8 type), installed (offline)
at DESY, Hamburg (more details in supporting information). After HP-HT treatment, the recovered
sample contained, besides c-BN, a new phase
(BON), which is described here.
Figure 1. Electron energy-loss spectrum (EELS) showing the B-K, N-K and O-K ionization edges after background subtraction.
The highlighted grey areas indicate the integration width used for quantification. The inset figure shows the electron energy-loss
near edge fine structure (ELNES) of the O-K edge (in order to reduce the noise, the data were smoothened by the Savitzky-Golay
method).
Computational Details
To identify structures with composition B6N4O3
and low enthalpy of formation at 20 GPa two
algorithms for the crystal structure search were
applied: the Ab-Initio Random Structure Search
(AIRSS)27 algorithm and the evolutionary
algorithm Universal Structure Predictor: Evolutionary Xtallography (USPEX)28-30. AIRSS works by
placing atoms randomly into a unit cell with random lattice parameters (under periodic boundary
conditions).
The atomic arrangement can be subjected to
specific symmetry elements or full space groups.
Subsequently, the full structure, positions and
cell parameters, is optimized. Screening for
B6N4O3 structures we used up to two symmetry
elements. Hence, we looked at structures with
Z=1 and Z=2. USPEX employs a self-improving evolutionary algorithm, the efficiency of
which stems from carefully designed variation
operators. We optimized all structures using
Density Functional Theory (DFT)31 methods as
implemented in the Vienna Ab-Initio Simulation
package (VASP)32-34 and determined the space
group of every model after full optimization of
atomic positions and cell parameters at 20 GPa.
The formation enthalpies of BON models have
been calculated with Local Density Approximation (LDA)35, and a selection of Generalized Gradient Approximation (GGA)36 functionals. The
mechanical, vibrational and electronic properties
of the materials of interest have been calculated
in the framework of the LDA. A cut-off of 500
eV has been used for the expansion of the wave
function into a plane wave basis set. The Brillouin
zone was sampled using Monkhorst–Pack grids37
with a resolution of at least 2π*0.04 Å-1. We optimized residual forces and stresses to better than
10-2 eV/Å and 0.1 GPa, respectively. The resulting
structures have been visualized with VESTA38.
Results and Discussion
Composition
Nano-sized crystals of BON with triangular
shape were identified in TEM images (see SI
Figure S2). EELS was performed to quantify
the composition of BON. The EELS spectrum
(Fig. 1) clearly shows the presence of boron, nitrogen and oxygen, but no carbon with the onset of Kionization edges at 187.5 eV (B), 399.7 eV (N) and
531.5 eV (O). The sp2 signature was not observed
in the fine structure of the B, N and O ionization
edges of the recorded electron energy-loss spectra, thus strongly indicating a sp3 type of bonding39-41.
After careful background subtraction, the ionization edges were treated using the Hartree-Slater
cross-section model.
The corresponding chemical quantification yielded 42 at.% B , 35 at.% N and23 at.%
O (=5.3 : 4.4 : 3). Because of the need for
balanced charges of the B3+, N3-, and O2- ions, the
composition should be a mixture of x BN and
y B2O3, which constrains the difference of the
number of boron and nitrogen ions to be two third
of the number of oxygen ions. Recalculation of the
EELS results accordingly gives 46.1 at.% B, 30.8
at.% N and 23.1 at.% O, or B:N:O = 6:4:3 which is
within the experimental error of ±10%12, 42.
Crystal Structure
Electron diffraction experiments were performed on triangular single crystals of BON less
than 50 nm in size. 3D diffraction intensity data
were collected coupling ADT and precession
electron diffraction (PED). The reflections could
be indexed using a hexagonal unit cell with a =
2.55 (5) Å, c = 6.37(13) Å and Z=3. Diffuse scattering along c* reveals a certain structural disorder along this direction. The symmetry is near to
cubic with acub = 3.63 Å, Z=4 (from Vcub = Vhex*4/3
= 47.83 Å3), with idealized hexagonal lattice parameters ahex(ideal) = 2.57 Å and chex(ideal) = 6.29
Å, which correspond to the experimental values
within the limits of error. The face-centered cubic cell corresponds to an R-centered hexagonal
cell where the rhombohedral cell is the common
primitive cell of both the hexagonal and the cubic
lattice (SI Figure S3).
Figure 2. (a) Unit cell of BON. (b) Left: Obverse main domain, Right: Reverse twin
domain due to spinel law.
Because of the presence of reflections, which
cannot be indexed by a single cubic or rhombohedral cell, respectively, the BON structure
was initially solved with respect to a hexagonal
lattice in space group P31 by direct methods using SIR 201143. The solution showed essentially
an arrangement of atoms similar to that of the
sphalerite structure of cubic boron nitride with
space group F-43m. Therefore, a high-symmetry
subgroup of F-43m, namely R3m (No. 160) was
chosen for further structure refinement (Fig. 2a).
The atomic positions from the direct-methods
solution are fully compatible with this space group
after a suitable origin shift. The whole set of measured reflections is compatible with the global extinction rules (-h+k+l=3n or h-k+l=3n) for two different rhombohedral settings (obverse or reverse)
of the hexagonal cell. The strongest reflections
(58 out of 164) were assigned to the obverse setting and another set of 60 less strong reflections
(with an overlap of 19) to the reverse setting. From
this fact we conclude that the crystal was twinned.
This view is also supported by the HRTEM image
(Fig. 3), which shows a (111) twin plane, according to the well-known spinel law as illustrated44
in Fig. 2b. It is equivalent to a mirror plane perpendicular to the hexagonal c-axis, which changes the orientation of the BN4 tetrahedra (down to
up), and in addition the setting of the hexagonal
unit cell from obverse to reverse. Accordingly
the diffraction pattern shows an overlay of the
obverse and reverse settings.
The crystal structure was refined in space
group R3m using the program SHELX-201345.
A spinel twin law was considered, whereby all
measured reflections apart from the very weakest could be indexed. The 99 indexed reflections
reduced to 53 unique reflections in R3m after merging of equivalents with Rint= 0.177 and
Rsigma= 0.074.
The atomic distribution of the elements on
the lattice sites was not evident from the primary structure solution. From the EELS results, the
chemical composition is B:N:O = 6:4:3. The unit
cell of the experimental structure (with three symmetrically equivalent pairs of atomic sites), however, is too small to allow for an ordered arrangement of 13 atoms. A more suitable description
may use a superstructure of sphalerite. However,
we did not detect any superstructure reflections,
which are expected to be very weak anyway, due
to the similarity of the B, N and O scattering factors. Hence, we observe an average structure with
cations and anions distributed statistically over
their respective lattice sites. It is reasonable to
assume that oxygen atoms together with nitrogen
atoms occupy anion positions. Since the number
of N+O atoms (anions) is larger than the number
of boron atoms (cations), cation sites are only partially occupied to achieve charge balance. These
requirements lead to occupancies of 4/7 (57%)
for nitrogen, 3/7 (43%) for oxygen and 6/7 (86%)
for boron, i.e. 14% of the cation sites are empty.
These are structural vacancies, such as known
e.g. in the spinel-type aluminium oxynitrides
(γ-ALON) 46, 47, not to be misinterpreted as point
defects.
The occupancies were fixed during structure
refinement, but isotropic displacement factors of
all atoms were allowed to refine freely and converged to reasonable values (cf. SI). This structure model was refined successfully and resulted
in a residual of R11= 0.189 (R1 = Σhkl | |Fobs| –
|Fcalc| | / Σhkl |Fobs|) and a refined twin fraction of
11%. A test refinement without oxygen atoms and
cation vacancies, i.e. with an ideal c-BN structure,
how ever worsened the fit. On the contrary, it was
even possible to refine (R1= 0.190) the chemical
composition under the constraint of balanced
charges which resulted in 46 at.% B, 32 at.% N
and 22 at.% O, in good agreement with the EELS
results.
The hexagonal BON structure (R3m, Z=3)
may be compared with the structure of cubic boron nitride (F-43m, Z=4) via their common primitive rhombohedral lattice (SI Figure S3). The unit
cell volume of BON (Vcub= 47.83 Å3) is slightly
larger than that reported for cubic boron nitride
with values48-50 of 47.28 Å3, 47.40 Å3 or 47.63 Å3.
Nitrogen and oxygen atoms are assumed to be
distributed statistically over the anion sites and
boron and structural vacancies are distributed
statistically over the cation sites (Fig. 2a). All atoms, N/O as well as B, are situated on three-fold
axes and mirror planes and show a slightly distorted tetrahedral coordination with three B-O/N
distances of 1.57(3) Å and one B-O/N distances
Figure 3. (a) High-resolution phase contrast image. The orange square denotes the area at which the
EDX spectrum shown in the inset was acquired. The blue triangles denote twin boundaries.
(b) Electron diffraction pattern of BON in [100]hex ([10-1]cubic) zone axis orientation. The spots can
be indexed with respect to a hexagonal (green) or cubic lattice (black), as shown in (d). The red line
indicates a {111} type twin plane, which can be seen in the HRTEM image. (c) Magnified view of
the area marked by the yellow box in (a). The red bordered inset is a simulated image of BON in
[100]hex ([10-1]cubic) zone axis orientation and contains 2x4 unit cells. (e) View of the crystal structure
(B: green, N/O: blue) projected along the hexagonal a-axis, overlaid on the simulated HRTEM
image.
of 1.58(10) Å, which are equal within the limits of
error. The reported B-N distances48-50 in c-BN of
1.566 Å, 1.567 Å or 1.570 Å are similar.
High Resolution Transmission Electron Microscopy
A HRTEM image in [100]hex zone axis orientation of the synthesized BON sample is given
in Fig. 3. The corresponding electron diffraction
pattern, is shown in Fig. 3b. The reflections could
be indexed with respect to a cubic lattice and correspond to d values (in Å) of 2.1 {111}, 1.8 (020),
1.3 {202}, 1.1 {131} and 0.9 {040}. A full indexation with respect to the cubic (black) and the
hexagonal (green) lattice is given in Fig. 3d. EDX
measurements (see the inset in Fig. 3a) confirmed
that the crystals with triangular morphology consistently contain considerable amounts of oxygen
along with boron and nitrogen. These findings are
also consistent with our earlier experimental results of the ternary BCN compounds where the
triangular shaped crystals showed the same composition22.
Fig. 3c shows an enlarged section of the HRTEM image that is compared with a simulated
image overlaid within the red frame. We used the
JEMS26 software to carry out multislice calculations (see SI Figure S4) by using the atomic model
from the crystal structure refinement of BON in
[100]hex zone axis orientation. In this thickness
and defocus range the bright dots correspond to
two atomic columns, i.e. B and N/O, being so
close that they cannot be separated using the employed imaging conditions, as can be seen in the
overlaid structure picture in Fig. 3e.
DFT calculations
DFT calculations were performed to identify
structures with the composition B6N4O3 suggested
by the EELS results and to analyze possible structural motifs. The structure searches performed at
20 GPa returned more than 2000 distinct structures. The candidates with lowest enthalpy at
20 GPa are two isoenergetic (within 0.01 eV per
formula unit) monoclinic structures (Cm). They
are best described as ordered sphalerite type
structures, with structural vacancies (1/7 of all
cation sites) tetrahedrally surrounded by oxygen
atoms. With only oxygen located adjacent to vacancies, these B6N4O3 structures exhibit all B and
N atoms four-fold coordinated, but O atoms threeand two-fold coordinated. The lattice parameters
(a, b, c, β, V) are 10.972 Å, 2.502 Å, 6.134 Å,
67.614°, 155.71 Å3 (“Cm-1”) and 8.229 Å, 2.477
Å, 7.454 Å, 96.008°, 151.11 Å3 (“Cm-2”). Due
to the size of the models and periodic boundary
conditions, the coordination tetrahedra of the
cation-vacancies share an oxygen atom and are
arranged in channels along the b-axis (Fig. 4a,
b). The structures differ only by the arrangement
of the channels on the (010) plane. All further
models close in enthalpy (0.1 eV/atom) to the Cm
structures are related to either the sphalerite or the
wurtzite type and share the common pattern of
cation vacancies surrounded by three (or four) O
atoms and one (or no) N atom.
We computed B6N4O3 formation enthalpies at
20 GPa according to the reaction:
4 c-BN + B2O3-II → B6N4O3,
where B2O3-II is the most stable form of B2O3 at
high pressure51. The different functionals yield a
formation enthalpy of about +0.9 eV at 20 GPa for
the two Cm models. (LDA: 0.92 eV, GGA: 0.88 to
0.94 eV depending on type, cf. details in Supporting Information). Settling on the LDA, we quantified the influence of the vacancy coordination
on stability by replacing, in the Cm-2 model, one
or all oxygen atoms in the coordination sphere of
the B vacancies with nitrogen atoms. When the
three-fold coordinated oxygen is replaced by a
N atom, the energy is raised by 2 eV per formula
unit; when nitrogen substitutes a two-fold coordinated oxygen, the resulting structure is 4 eV higher in energy than the ground state. The complete
replacement of the coordination sphere with nitrogen atoms raises the energy by 6.8 eV per formula
unit with respect to the ground state.
To estimate the influence of the vacancy
ordering on the stability of BON structures, we
created a larger structure model that introduces disorder by disrupting the vacancy channels
(“disordered” model, Fig. 4c). This model is based
on a 7×3×1 supercell of the hexagonal setting of
the cubic sphalerite structure. The optimized lattice parameters at 20 GPa are a = 17.35 Å, b = 7.43
Figure 4. Relaxed structures of the Cm-1 (a), Cm-2 (b), and disordered (c) BON models.
Boron atoms are depicted in green, nitrogen in light blue and oxygen in red. Green polyhedra
represent B-centered tetrahedra; vacancy-centered tetrahedra are depicted in pink.
Å and c = 6.07 Å. Omitting 1/7 of the cations, the
unit cell contains 54 boron, 36 nitrogen and 27 oxygen atoms. Nitrogen and oxygen atoms share the
anion positions. The model is set up in such a way
that the vacancies are not adjacent (do not share a
common atom surrounding them).
Therefore, their coordination sphere includes
three oxygen atoms and needs to be completed
by a nitrogen atom. The disordered model has a
formation enthalpy of +1.5 eV per formula unit at
20 GPa. From these results we infer that the presence of boron vacancies arranged in channels is a
crucial prerequisite for the stabilization of BON,
although the coordination environment of boron
vacancies has an even more dramatic effect on
stability than the disruption of the vacancy ordering. We computed yet another model corresponding to a cubic sphalerite structure with B occupying all cation sites, anion positions occupied by a
mixture of N (2/3) and O (1/3), and – for balancing
the charge – additional interstitial oxygen in 17%
of the octahedral interstices of the nitrogen sublattice. However, after geometry optimization the
model was severely distorted and was discarded
based on enthalpy arguments.
To compare the predicted properties of our
BON models with the calculated properties of
cubic BN, we calculated the electronic density of
states of c-BN and our BON models (see SI Figure
S5). With LDA, the calculated band-gap for c-BN
is 4.44 eV. As expected, this value severely underestimates the experimental band-gap of 6.36 eV52,
but still allows for a qualitative comparison with
the newly found oxynitride compound.
For Cm-1 and Cm-2 we calculate bandgaps
of 3.88 and 3.24 eV, respectively, which are
rather similar to the one calculated for the disordered structure (3.46 eV). The valence band
edge of the ordered structures is largely dominated by oxygen contributions with a low density of states, whereas the high density of nitrogen states at the Fermi level in the disordered
model reflects its lower stability. The vibrational
analysis of BON models, performed at both 0
and 20 GPa, returned only positive eigenvalues and, therefore, confirms the mechanical
stability of the structures at the pressures of interest.
The bulk moduli of the three materials have been
calculated by fitting their energy-volume dependence to the third-order Birch-Murnaghan equation of state53 (see SI Table S2). This procedure
yields for c-BN a bulk modulus of 398(4) GPa,
being in good agreement with the experimental
value of 396(2) GPa54. With the same procedure,
we find for the Cm models bulk moduli of 306(3)
and 298(4) GPa, respectively, and for the disordered model a value of 314(1) GPa.
Comparison of DFT models with experiment
We describe the experimentally determined
crystal structure of BON by a disordered model
using the smallest unit cell, because possible superstructure reflections due to O/N ordering are
expected to be very weak and we were not able to
detect them. The missing superstructure reflections
have the following effect on structure calculations.
If the true unit cell containing an ordered structure
is a multiple of the small cell we use to describe
the experimental structure, then the electron density distribution calculated from the diffraction
intensities is projected into this small cell. This
means, we see only an overlay of the (slightly different) structural motifs of the different parts of
the large cell. The unit cells of the DFT models
are larger than the experimental cell.
In order to test if a given structure model is
compatible with the measured intensities, we
have to handle the DFT models in an analogous
way, namely to project all atomic positions to the
experimental unit cell and average them. Details of the averaging strategies are given in the
Supporting Information including Table S3. The
averaged atomic positions from the DFT models
were tested against the measured reflection intensities by calculating a difference Fourier synthesis
using the SHELX program45. The same twin law
was used as in the experimental structure refinement. The results were rather promising with R1=
0.23 to 0.24 for the disordered DFT model and
R1= 0.19 to 0.20 for the ordered DFT models.
There is a clear preference for an ordered structure.
Conclusions
Our newly discovered BON reported here is the
first example of the existence of a crystalline
ternary oxynitride phase of boron and complements and extends the well-known group 13
element oxynitrides of aluminum and gallium.
The BON phase was synthesized in single-crystalline form by HP-HT technique. With EELS the
composition of individual nanocrystals was determined to be B6N4O3. Advanced methods in electron diffraction delivered high quality intensity
data, from which the crystal structure was solved
and a structural model of sphalerite type, similar
to c-BN, was refined. In the experimental model,
the primitive unit cell contains two atomic sites.
Nitrogen and oxygen share the anion position,
while boron and structural vacancies occupy the
cation position of the sphalerite-type to accommodate the B6N4O3 composition. Electron diffraction results do not show superstructure reflections.
Supporting first-principles calculations identify structures with composition B6N4O3 and low
enthalpy of formation at 20 GPa that agree with
experimental results, i.e. are compatible with the
intensities from electron diffraction. Among 2000
structure candidates we found that sphaleritetype
structures
are
generally
more
stable than wurtzite-type ones and that oxygen positions next to boron vacancies are
preferred over direct oxygen boron contacts.
Two (very similar) structure models in space
group Cm with one B6N4O3 unit per primitive unit
cell exhibit the lowest enthalpy of formation of
0.9 eV.
These monoclinic structure models contain
chains of cation vacancies. We analyzed a variety of models with disorder on cation and anion
positions and found the most favorable among
those with formation enthalpy of 1.5 eV (at 0 K).
Approximating the mixing entropy by an
ideal solution model, we estimate the entropy term
TΔSmix with 0.54eV per unit of B6N4O3 at T=1900°C.
The fact that this value is too small to compensate for the enthalpy difference between ordered and
disordered models, and the fact that electron diffraction intensities of ordered structure models
are in better agreement with experiment than
those of disordered models, may be taken as indication that the newly found BON crystal contains
substantial order.
Supporting Information
The Supporting Information is available free
of charge on the ACS Publications website at
DOI: 10.1021/acs.chemmater.5b01706.
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Research Projects
• Synthesis and Characterization of Advanced Functional Materials (China Scholarship Council (CSC), Oct. 2015 – Sept. 2019)
• Micropatterned Polymer-Derived Ceramic Catalysts and Sensors (DFG, Sept. 2015 – Aug. 2018)
• Tailored crystallization of inorganic pigments for decorative and functional applications (in cooperation with Merck KGaA
Darmstadt, Germany, Aug. 2015 – July 2018)
• Nanostructured organotin-based hybrid thin films for sensing and optics (IDS FunMat, Oct. 2014 – Sept. 2017)
• Electricalmagnetic properties of nano-scaled absorption filler reinforced porous ceramics derived from single-source-precursors (China Scholarship Council (CSC), Sept. 2014 – Aug. 2017)
• Hochtemperatur-Kriechverhalten SiOC-basierter Gläser und
Glaskeramiken (DFG, May 2014 – April 2017)
• Development of ultra abrasion resistant Hf- and Ta-based ceramic composites (KIMS, Jan. 2014 – Dec. 2016)
• RESPONSE (DFG, HMWK LOEWE, Jan. 2014 – Dec. 2016)
•
•
Nanocomposites as anode materials for lithium ion batteries: Synthesis, thermodynamic characterization and modeling of nanoparticular silicon dispersed in SiCN(O) and SiCO-based matrices (DFG, SPP1473, Aug. 2010 – Dec. 2016)
SiHfC(N) and SiHfN(C)-based Ultrahigh-Temperature Ceramic Nanocomposites (UHTC-NCs) for EBC/TBC Applications
(China Council Scholarship (CSC), Oct. 2012 - Oct. 2016)
• Mechanism of Li-storage in porous C-rich SiCN ceramics
(Master thesis, Dec. 2015 – May 2016)
• Nanostructured Silicon-based Anode Materials for Lithium-Ion Batteries (Master thesis, Oct. 2015 – April 2016)
• High-Temperature Piezoresistivity in SiOC - Untersuchungen zur Hochtemperatur-Piezoresistivität in kohlenstoffhaltigen
Siliciumoxycarbid-Nanokompositen
(DFG, May 2013 - April 2016)
Research Projects
• SnO2/SiOC composites as anode materials for Li-ion batteries (Master thesis, DAAD-IIT Master Sandwich Scholarships,
Sept. 2015 – March 2016)
• Synthesis and Bioactivity of SiCaMgOC Powders and Monoliths (Bachelor thesis, Nov. 2015 – Feb. 2016)
• Single-Source-Precursor Synthesis of Ta-Based Photocatalysts
(Bachelor thesis, Nov. 2015 – Feb. 2016)
• Formation and Characterization of Polymer Derived Ceramic Tribofilms (Master Thesis in cooperation with EVONIK, Darmstadt, Germany,
July 2015 – Dec. 2015)
• Single-Phase Si-M-N Ceramic Materials (M = early transition metal): Synthesis from Metal-Modified Polysilazanes and microstructural
characterization (DAAD PPP Japan, Jan. 2014 – Dec. 2015)
• Sensors Towards Terahertz (STT): Neuartige Technologien für Life Sciences, Prozess- und Umweltmonitoring (HMWK-LOEWE,
Jan. 2013 - Dec. 2015)
• Mestabiles Indiumoxidhydroxid (InOOH) und Korund-Typ Indiumoxid (In2O3): Gezielte Synthese, Einkristallzüchtung und in-situ Charakteri-
sierung der Umwandlungspfade und transienten Intermediaten (DFG, SPP 1415 „Kristalline Nichtgleichgewichtsstoffe“, Jan. 2013 - Dec. 2015)
• Particle design of core-shell particles for enamels (Master thesis,
June 2015 – Nov. 2015)
• Aerosol Deposition of Ceramic Layers (Master thesis in co operation with IEK-1, Forschungszentrum Jülich GmbH, Jülich, Germany,
June 2015 – Nov. 2015)
• Ternary M-Si-N Ceramics: Single-Source-Precoursor Synthesis and Microstructure Characterization (M = early transition metal) (China Council Scholarship (CSC), Nov. 2012 - Nov. 2015)
• Preparation of nanostructured coatings of organic biomolecules capped Ti oxynitrides (TiNO) for bioactive processes induced by photocatalysis (Internship with Cairo University, Cairo, Egypt, July 2015 – Oct. 2015)
• Synthesis of hierarchically porous materials (Master thesis in in
cooperation with Saint-Gobain C.R.E.E., Cavaillon Cedex, France,
March 2015 – Aug. 2015)
Research Projects
• Molecular Routes to SiHfBCN Ceramic Nanocomposites (China Council Scholarship (CSC), Sep. 2011 - Aug. 2015)
• Der Einfluss von Keimbildnern und färbenden Komponenten auf den Keramisiserungsprozess und die Eigenschaften von Lithium-Alumosili-
kat (Bachelor thesis, May 2015 – July 2015)
• Sn/SiOC and SnO2/SiOC composites as anode materials for Li-ion
batteries (Master thesis, Jan. 2015 – July 2015)
• Comparative study of the oxidation behavior of Al2O3 reinforced
siloxane at 700 °C (Master thesis in cooperation with Schunk Kohle-
stofftechnik GmbH, Heuchelheim, Germany, Dec. 2014 – May 2015)
• Synthese und Charakterisierung von temperaturstabilen Beschichtungen mit niedriger Oberflächenenergie auf anorganischer Basis am Beispiel HfO2 und ZrO2 (Master thesis in cooperation with Schott, Mainz,
Germany, Oct. 2014 – April 2015)
•
Untersuchungen des Einflusses verschiedener Aluminiumoxidschlicker auf deren Verstärkungsverhalten in Al2O3/Al2O -Verbunden (Diploma thesis in cooperation with Schunk, Heuchelheim, Germany, July 2014 – April 2015)
•
TiO2 flake morphology by tailored molten salt crystallization (Master thesis in cooperation with Merck KGaA, Performance MaterialsPigments Decoratives Research, Darmstadt, Germany, Oct. 2014 – March 2015)
• Untersuchung der thermooxidativen Alterung von Elastomeren (Master thesis in cooperation with Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF, Darmstadt, Germany, Oct. 2014 – March 2015)
• Investigation of Protective Diffusion coatings for refractory metals
(Master thesis in cooperation with DECHEMA Forschungsinstitut, Frankfurt a.M., Germany, October 2014 – March 2015)
• FUNEA - Functional Nitrides for Energy Applications (Coordination, EU - Marie Curie Initial Training Network, Feb. 2011 - Jan. 2015)
Publications
[1] Zouaghi, W.; Voss, D.; Gorath, M.; Nicoloso, N.; Roskos, H.G.; How good would the conductivity of graphene have to be to make
single-layer-graphene metamaterials for terahertz frequencies feasi-
ble?; CARBON, 94 (2015) 301-308.
[2] Klausmann, A.; Morita, K.; Johanns, K.E.; Fasel, C.; Durst, K.; Mera, G.; Riedel, R.; Ionescu, E.; Synthesis and high-temperature evolution of polysilylcarbodiimide-derived SiCN ceramic coatings; JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 35(14) (2015) 3771–3780.
[3] Schitco, C.; Bazarjani, M.S.; Riedel, R.; Gurlo, A.;
Ultramicroporous silicon nitride ceramics for CO2 capture;
JOURNAL OF MATERIALS RESEARCH, 30(19) (2015) 2958-2966.
[4] Bekheet, M.F.; Dubrovinsky, L.; Gurlo, A.; Compressibility and structural stability of spinel-type MnIn2O4; JOURNAL OF SOLID STATE CHEMISTRY, 230 (2015) 301-308.
[5] Riedel, R.; Special Issue: 8th International Symposium on Nitrides in Conjunction with the 7th International Workshop on Spinel Nitrides and Related Materials and the Annual Meeting of the Marie Curie ITN 7th Framework Programme FUNEA; JOURNAL OF THE EURO-
PEAN CERAMIC SOCIETY, 35(12) (2015) 3201-3201.
[6] Li, W.; Gurlo, A.; Riedel, R.; Ionescu, E.; Perovskite-type Solid
Solution SrMo1–xWx(O, N)3 Oxynitrides: Synthesis, Structure, and Magnetic Properties; ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE, 641(8-9) (2015) 1533-1539.
[7] Li, W.; Li, D.; Gurlo, A.; Shen, Z.; Riedel, R.; Ionescu, E.;
Synthesis and rapid sintering of dense SrA(O,N)3 (A = Mo, W)
oxynitride ceramics; JOURNAL OF THE EUROPEAN CERAMIC
SOCIETY, 35(12) SI (2015) 3273–3281.
[8] Yuan, J.; Luan, X.; Riedel, R.; Ionescu, E.; Preparation and hyd
rothermal corrosion behavior of Cf/SiCN and Cf/SiHfBCN ceramic matrix composites; JOURNAL OF THE EUROPEAN CERAMIC
SOCIETY, 35(12) (2015) 3329–3337.
[9] Mera, G.; Ishikawa, R.; Ionescu, E.; Ikuhara, Y.; Riedel, R.; Atomic-scale assessment of the crystallization onset in silicon
carbonitride; JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 35(12) (2015) 3355–3362.
Publications
[10] Bhat, S.; Wiehl, L.; Molina-Luna, L.; Mugnaioli, E.; Lauterbach, S.; Sicolo, S.; Kroll, K.; Duerrschnabel, M.; Nishiyama, N.; Kolb, U.; Albe, K.; Kleebe, H.-J.; Riedel, R.; High-Pressure Synthesis
of Novel Boron Oxynitride B6N4O3 with Sphalerite Type Structure; CHEMISTRY OF MATERIALS, 27(17) (2015) 5907–5914.
[11] Graczyk-Zajac, M.; Wimmer, M.; Neumann, C.; Riedel, R.;
Lithium intercalation into SiCN/disordered carbon composite. Part 1: Influence of initial carbon porosity on cycling performance/
capacity; JOURNAL OF SOLID STATE ELECTROCHEMISTRY, 19(9)SI (2015) 2763-2769.
[12] Bekheet, M.F.; Schwarz, M. R.; Kroll, P.; Gurlo, A.; Kinetic control in the synthesis of metastable polymorphs: Bixbyite-to-Rh2O3
(II)-to-corundum
transition in In2O3; JOURNAL OF SOLID STATE CHEMISTRY, 229 (2015) 278-286.
[13]
Tulyaganov, D.U.; Reddy, A.A.; Siegel, R.; Ionescu, E.; Riedel, R.; Ferreira, J.M.F.; Synthesis and in vitro bioactivity assessment of injectable bioglass−organic pastes for bone tissue repair;
CERAMICS INTERNATIONAL, 41(8) (2015) 9373–9382.
[14] Li, W., Li, D.; Gao, X.; Gurlo, A.; Zander, S.; Jones, P.;
Navrotsky, A.; Shen, J.Z.; Riedel, R.; Ionescu, E.; A study on the thermal conversion of scheelite-type ABO4 into perovskite-type AB(O,N)3; DALTON TRANSACTIONS, 44(17) (2015) 8238-8246.
[15] Zhou, C.; Gao, X.; Xu, Y.; Buntkowsky, G.; Ikuhara, Y.; Riedel, R.; Ionescu, E.; Synthesis and high-temperature evolution of
single-phase amorphous Si–Hf–N ceramics; JOURNAL OF
THE EUROPEAN CERAMIC SOCIETY, 35(7) (2015) 2007-2015.
[16] Ruzimuradov, O.; Sharipov, K.; Yarbekov, A.; Saidov, K.; Hojam-
berdiev, M.; Prasad, R.M.; Cherkashinin, G.; Riedel, R.;
A facile preparation of dual-phase nitrogen-doped TiO2–SrTiO3 macroporous monolithic photocatalyst for organic dye photodegrada-
tion under visible light; JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 35(6) (2015) 1815-1821.
[17]
Reinold, L.M.; Yamada, Y.; Graczyk-Zajac, M.; Munakata, H.; Kanamura, K.; Riedel, R.; The influence of the pyrolysis temperature on the electrochemical behavior of carbon-rich SiCN polymer-derived ceramics as anode materials in lithium-ion batteries;
JOURNAL OF POWER SOURCES, 282 (2015) 409-415.
[18] Mera, G.; Gallei, M.; Bernard, S.; Ionescu, E.; Ceramic Nanocom-
posites from Tailor-Made Preceramic Polymers; NANOMATERIALS, 5(2) (2015) 468-540.
Publications
[19]
Elbert, J.; Didzoleit, H.; Fasel, C.; Ionescu, E.; Riedel, R.; Stühn,B.;
Gallei, M.; Surface-Initiated Anionic Polymerization of
[1]Silaferrocenophanes for the Preparation of Colloidal Preceramic Materials; MACROMOLUCULAR RAPID COMMUNICATIONS, 36(7 SI)) (2015) 597–603.
[20]
Yu, Z.J.; Min, H.; Yang, L.; Feng, Y.; Zhang, P.; Riedel, R.; In-
fluence of the architecture of dendritic-like polycarbosilanes on the ceramic yield; JOURNAL OF THE EUROPEAN CERAMIC
SOCIETY, 35(4) (2015) 1161-1171.
[21] Roth, F.; Schmerbauch, C.; Ionescu, E.; Nicoloso, N.; Guillon, O.; Riedel, R.; High-temperature piezoresistive C/SiOC sensors; JOUR-
NAL OF SENSORS AND SENSOR SYSTEMS, 4(1) (2015) 133-136.
[22]
Shimokawa, Y.; Fujiwara, A.; Ionescu, E.; Mera, G.; Honda, S.; Iwamoto, Y.; Riedel, R.; Formation of aluminum nitride from metal–
organic precursors synthesized by reacting aluminum tri-chloride with bis(trimethylsilyl)carbodiimide; JOURNAL OF THE CERAMIC SOCIETY OF JAPAN, 123(1435) (2015) 106-113.
[23]
Graczyk-Zajac, M.; Reinold, L.M.; Kaspar, J.; Pradeep, V.S.;
Soraru, G.D.; Riedel, R.; New Insights into Understanding
Irreversible and Reversible Lithium Storage within SiOC and SiCN
Ceramics; NANOMATERIALS, 5(1) (2015) 233-245.
[24]
Pradeep, V.S.; Ayana, D.G.; Graczyk-Zajac, M.; Soraru, G.D.;
Riedel, R.; High Rate Capability of SiOC Ceramic Aerogels with Tailored Porosity as Anode Materials for Li-Ion Batteries;
ELECTROCHIMICA ACTA, 157 (2015) 41-45.
[25] Schitco, C.; Seifollahi Bazarjani, M.; Riedel, R.; Gurlo, A.;
NH3-assisted synthesis of microporous silicon oxycarbonitride
ceramics from preceramic polymers: a combined N2 and CO2 adsorption and small angle X-ray scattering study; JOURNAL OF MATERIALS CHEMISTRY A, 3 (2015) 805-818.
[26]
Yu, Z.J.; Yang, L.; Min, H.; Zhang, P.; Liu, A.H.; Riedel, R.;
High-ceramic-yield precursor to SiC-based ceramic: A hyperbranched polytitaniumcarbosilane bearing self-catalyzing units; JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 35(2) (2015) 851-858.
[27]
Umicevic, A.B.; Cekić, B.D.; Belosevic-Cavor, J.N.; Koteski, V.J.;
Papendorf, B.; Riedel, R.; Ionescu, E.; Evolution of the local structure at Hf sites in SiHfOC upon ceramization of a hafniumalkoxide-modified polysilsesquioxane: A perturbed angular correlation study; JOURNAL OF THE EUROPEAN CERAMIC
SOCIETY, 35(1) (2015) 29-35.
Electronic Materials
Staff Members
Head
Prof. Dr. Heinz von Seggern
Research Associates
Dr. Sergej Zhukov
Dr. Corinna Hein
Dr. Emanuelle Reis Simas
Dr. Evan S.H. Kang
Dr. Andrea Gassmann
PhD Students
Oili Pekkola
Elmar Kersting
Benedikt Sykora
Paul Mundt
Henning Seim
Master Students
Stefan Vogel
Christopher Wolf
Guest Scientists
Douglas J. Coutinho
54 | Electronic Materials
The Electronic Materials Properties
The Electronic Materials group introduces the
aspect of electronic functional materials and
their physics and properties into the Institute
of Materials Science. The associated research
concentrates on the characterization of various
classes of materials suited for implementation in
information storage and organic and inorganic
electronics. Four major research topics are presently addressed:
• Electronic and optoelectronic properties
of organic semiconductors.
• Charge transport in inorganic semiconductor devices.
• Charge transport and polarization in
organic and inorganic dielectrics.
• Photo- and photostimulated luminescence
in inorganic phosphors.
For novel areas of application a worldwide interest exists in the use of organic semiconductors in
electronic and optoelectronic components, such
as transistors and light-emitting 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 LAN. In view of the inevitable technological development, the activities
of the group are concerned with the characterization of organic material properties regarding
the performance of organic electronic and optoelectronic devices. The major aspect deals with
the charge carrier injection and transport taking
place in organic field-effect transistors (OFETs)
and organic light-emitting diodes (OLEDs).
In particular, the performance of unipolar and
ambipolar light-emitting OFETs and the stability of OFETs and OLEDs are subjects of recent
investigations. To conduct these demanding tasks,
various experimental techniques for device fabrication and characterization are installed. Besides
basic electric measurement setups, a laser spectroscopy setup used for time-of-flight as well as
for life-time measurements and a Kelvin-probe
atomic force microscope to visualize the potential distribution of organic devices with nanometer resolution are available.
Even though organic electronics is an emerging
field especially for consumer electronics applications, today’s electronic devices still mainly rely
on conventional silicon technology. While organic semiconductors have excellent optoelectronic
properties they, in general, suffer from low charge
carrier mobilities limiting the switching rates in
organic transistors. Yet, metal oxides like ZnO,
InZnO (IZO) or InGaZnO (IGZO) can bridge the
gap between the high mobility semiconductors
like silicon and the low mobility organic semiconductors. Using metal-organic precursors or
nanoparticle dispersions easy processing procedures like spin-coating or printing can be applied
and yield rather high field-effect mobilities in the
order of 1-10 cm2 V-1s-1 for the produced thin film
transistors (TFTs). Current research activities in
the group concentrate on the optimization of the
processing procedures of ZTO, especially the
decrease of annealing temperatures is desired to
make the processes compatible with organic substrates. Furthermore, the influence of the layer
morphology and the role of the gas atmosphere
for the device performance as well as stability issues are investigated.
Electronic Materials | 55
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 thermal charging and discharging under high
electric fields.
The field of photoluminescent and photostimulated luminescent (PSL) materials (phosphors)
is concerned with the synthesis and characterization of suited inorganic compounds used as
wavelength converters in fluorescent lamps and
in scintillating and information storing crystals.
Present work is focused on x-ray detection materials, providing improved resolution and high
PSL-efficiency needed in medical imaging. In
particular the storage phosphors CsBr:Eu2+ and
BaFBr:Eu2+ are under investigation. Research is
concentrated on the influence of humidity on the
sensitivity of CsBr:Eu2+.
Before and after the treatment the materials
are studied by means of spectroscopic methods
as well as scanning electron microscopy techniques. 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 to form image plates is in the
focus of the work.
The Effect of Multiple Ink-Jet Printed Zinc Tin Oxide Layers
on the TFT Performance
Benedikt Sykora and Heinz von Seggern
In 2004 Nomura et al. reported that In-GaZn-O shows good transistor properties even if
processed at room temperature [1]. This publication led to further interest in the scientific
community to work on transparent conducting oxides (TCO) for flexible electronics. The
main drawback of Indium-based TCOs is an
insufficient Indium supply in the world [2].
An alternative material in this class is zinc tin
oxide (ZTO), which has been widely studied as
a possible semiconductor for field-effect transistor applications because of its preferential band
transport [3]. ZTO films are mostly processed by
sputtering [4-7] or spin-coating processes [8-11].
The ink-jet printing process is more favorable because it is an additive process were no additional post processing like patterning with masks is
necessary, thereby leading to a reduction of the
production costs by 64 % [12]. Contributing to
this reduction in costs is that production waste
can be avoided and the scale of the process can be
increased [13]. Most of the TCOs are amorphous,
thus avoiding electron scattering at grain boundaries and creation of trap states, that normally
occurs in polycrystalline films [14].
Amorphous TCOs can also be adapted easier to a large scale production process [2, 12].
Recently, ZTO based transistors have been introduced by ink-jet printing, reporting mobilities
from 0.6 to 5.11 cm2 V -1s-1 [15-17]. But most of
them use the widely applied but toxic 2-methoxyethanol as a solvent, which is not suitable for potential industrial applications.
Here we report a novel precursor solution
route using non-toxic and cost efficient ethanol as
solvent. By applying the developed ink in a multilayer approach, printed ZTO transistors with a
mobility of up to 7.8 cm2 V -1s-1 and high on/off
ratios exceeding 108 were achieved.
To the best of our knowledge this is the highest
saturation mobility of an ink-jet printed ZTO
transistor. A precursor solution route to produce transparent, amorphous and smooth ZTO
layers was elaborated. The solution was produced by dissolving zinc nitrate hydrate and
tin(II) chloride in ethanol. This solution shows
precipitation, because the basidic tinchlorid is
not stable under hydrophilic conditions [18].
To avoid the formation of this tin hydroxychloride, 1 vol % hydrochlorid acid with a concentration of 34 wt% was added in order to oxidize the
tin2+ to tin4+ . This solution was then stirred for
at least 14 hours at room temperature. Before usage it was filtered through a 0.2 µm PTFE-filter.
To build functional transistors the precursor
solution with a concentration of 0.1 mole/l was
printed onto prestructured and commercially available substrates from Fraunhofer IPMS Dresden.
They are composed of a highly n-doped
Si substrate (n~1017 cm-3) of 675 µm. On this
substrate a 90 nm thick SiO2 layer is thermally
grown as the gate insulator, followed by interdigitated source/drain electrodes consisting of
30 nm of Au and 10 nm of ITO as an anchor layer. There are 16 prestructured transistors, from
these only the ones with L =20 µm ( W/L =500)
where analyzed to avoid short channel effects.
These substrates were cleaned by ultrasonication in acetone and propane-diol for 15 minutes.
They were then treated with an air plasma (70 W)
for 60 s in a home built vacuum chamber in combination with the RF-generator PFG 300 RF. For
the application of the ink a commercially available Dimatix DMP2831 desktop ink-jet printer
was used. After each printing step the printed
films were annealed at a temperature of 500 °C
on a preheated hot-plate in air for 10 min. The
electrical characterization took place within a nitrogen filled glovebox.
Figure 1 compares the transfer curves for the
4 transistors with various numbers of applied
ZTO layers. The inset of the Figure 1 shows the
used transistor layout. It has bee found, that the
transition between the off and the on state is improved if more layers are applied. Also a shift of
the threshold voltage towards the negative voltage region is clearly visible. In addition, the off
currents increase due to a general improvement
of the conductivity of the semiconductor with increased number of layers.
Also the hysteresis between the forward and
backward sweep indicated by arrows in Figure 1
is decreasing with the application of more layers.
All these effects point to an improved interface
between the SiO and the ZTO layer through the
reduction of electron trap states.
Table 1 summarizes the extracted values for
the saturation mobility (µsat), the threshold voltage (Vth ), the subthreshold swing (S.S.) and the
ratio between the on- and off-currents for one,
two, four and eight layers of semiconductor.
The transistor with one layer shows inferior properties to those with multiple layers. They exhibit
high mobility and current values.These transistors also show high on-to-off ratios exceeding
108.
The saturation mobility of 7.8 cm2 V -1s-1 is,
to the best of our knowledge, the highest reported
value for a printed ZTO transistor. In summary,
we have reported about an easy, cost efficient
and non-toxic precursor solution route for the
fabriacation of ZTO.
Field-effect transistors processed with multiple layers of ink-jet printed precursor solutions
revealed good device characteristics. The saturation mobility increased from 0.5 cm2 V -1s-1 for a
single layer device to 7.8 cm2 V -1s-1 for a device
composed of 8 layers. In addition the threshold
voltage and the subthreshold swing decreased
and the on-to-off current ratio increased with increasing number of layers. These transistor properties and the low costs/toxicity of the developed
precursor solution route could provide an alternative to the toxic solvent and indium containing
TCOs.
References
[1] K. Nomura, H. Ohta,
A. Takagi, T. Kamiya, M.
Hirano, and H. Hosono,
Nature 432, 488 (2004).
[2] J. F. Wager, B. Yeh,
R. L. Hoffman, and
D. a. Keszler, Current
Opinion in Solid State and
Materials Science 18, 53
(2014).
[3] C.-G. Lee, B. Cobb,
and A. Dodabalapur,
Applied Physics Letters
97, 203505 (2010).
[4] D. L. Young, H.
Moutinho, Y. Yan, and
T. J. Coutts, Journal of
Applied Physics 92, 310
(2002).
[5] H. Q. Chiang, J. F.
Wager, R. L. Hoffman, J.
Jeong, and D. a. Keszler,
86, 013503 (2005).
[6] J. S. Rajachidambaram, S. Sanghavi,
P. Nachimuthu, V.
Shutthanandan, T. Varga,
B. Flynn, S. Thevuthasan,
and G. S. Herman, Journal
of Materials Research 27,
2309 (2012).
[7] M. Fakhri, M.
Theisen, A. Behrendt,
P. Görrn, and T. Riedl,
104, 251603 (2014).
[8] S.-J. Seo, C. G. Choi,
Y. H. Hwang, and B.-S.
Bae, Journal of Physics
D: Applied Physics 42,
035106 (2009).
[9] T.-J. Ha and A.
Dodabalapur, Applied
Physics Letters 102,
123506 (2013).
[10] P. K. Nayak, M. N.
Hedhili, D. Cha, and H.
N. Alshareef, ACS applied
materials & interfaces 5,
3587 (2013).
[11] H. J. Jeon, K. B.
Chung, and J. S. Park,
Journal of Electroceramics 32, 319 (2014).
[12] E. Fortunato, P. Barquinha, and R. Martins,
Advanced Materials 24,
2945 (2012).
[13] M. Singh, H. M.
Haverinen, P. Dhagat, and
G. E. Jabbour, Advanced
Materials 22, 673 (2010).
[14] T. Kamiya and
H. Hosono, NPG Asia
Materials 2, 15 (2010).
[15] D. Kim, Y. Jeong, K.
Song, S.-K. Park, G. Cao,
and J. Moon, Langmuir
: the ACS journal of
surfaces and colloids 25,
11149 (2009).
[16] Y.-h. Kim, K.-h.
Kim, M. S. Oh, H. J. Kim,
J. I. Han, M.-k. Han, and
S. K. Park, IEEE Electron
Device Letters 31, 836
(2010).
[17] S.-H. Lee and W.-S.
Choi, Electronic Materials
Letters 10, 737 (2014).
[18] E. Riedel, Anorganische Chemie, 2nd ed.
(Walter de Gruyter, 1990)
p. 504.
Figure 1: Transfer curves containing drain currents ( ID ) for transistors based of increasing numbers of ZTO layers at a
source-drain voltage VDS of 30 V. The inset shows a representation of the transistor layout.
n0 of layers
μsat (cm2 v-1s-1)
Vth (V)
S.S. (V/dec.)
1
0.05
19.6
1.79
4
6.62
11.9
2
8
0.82
7.76
10.0
7.0
Ion/ Ioff
1.3 * 106
1.3 * 107
0.88
1.7 * 108
0.47
3.2 * 108
0.35
Table 1: The saturation mobility (μsat ), the threshold voltage ( Vth ) , the subthreshold slope (S.S.) and
the on to off current ratio for transistors composed of one, two, four or eight applied ZTO layers.
Research Projects
• Fatigue of organic semiconductor components (SFB 595 (DFG),
2003-2014)
• Phenomenological modelling of bipolar carrier transport in organic
semiconducting devices under special consideration of injection,
transport and recombination phenomena (SFB 595 (DFG), 2003-2014)
• Thin film dielectrics for high performance transistors (DFG, 2012-2015)
• Piezoelectric properties of ferroelectrics (DFG, 2012-2015)
• Preparation and characterization of metal-oxide field-effect transistors (MerckLab, 2009-2015)
• High resolution, transparent image plates based on the storage phosphor CsBr:Eu2+ (DFG, 2013-2015)
• Metal oxide based field-effect transistors with top gate geometry
(Helmholtz Virtual Institute, 2012-2017)
Publications
[1] Dynamics of energy level alignment at ITO/organic semiconductor
interfaces Coutinho,
Douglas J.; Faria, Gregorio C.; Faria, Roberto M.;
von Seggern, Heinz
ORGANIC ELECTRONICS Volume: 26 Pages: 408-414 Published: NOV 2015
[2] Polarization dynamics variation across the temperature- and com
position-driven phase transitions in the lead-free
Ba(Zr0.2Ti0.8)O-3-x(Ba0.7Ca0.3)TiO3 ferroelectrics
Zhukov, Sergey; Acosta, Matias; Genenko, Yuri A.; von Seggern, Heinz
JOURNAL OF APPLIED PHYSICS Volume: 118 Issue: 13 Article Number: 134104 Published: OCT 7 2015
[3]
Thermal Evaporation versus Spin-Coating: Electrical Performance
in Columnar Liquid Crystal OLEDs
Eccher, Juliana; Zajaczkowski, Wojciech; Faria, Gregorio C.; Bock, Harald; von Seggern, Heinz; Pisula, Wojciech; Bechtold, Ivan H.
ACS APPLIED MATERIALS & INTERFACES Volume: 7 Issue:
30 Pages: 16374-16381 Published: AUG 5 2015
[4]
Study of electrical fatigue by defect engineering in organic lightemitting diodes
Gassmann, Andrea; Yampolskii, Sergey V.; Klein, Andreas; Albe, Karsten; Vilbrandt, Nicole; Pekkola, Oili; Genenko, Yuri A.;
Rehahn, Matthias; von Seggern, Heinz
MATERIALS SCIENCE AND ENGINEERING B-ADVANCD
FUNCTIONAL SOLID-STATE MATERIALS
Volume: 192 Special Issue: SI Pages: 26-51 Published: FEB 2015
[5] Cross-linkable random copolymers as dielectrics for low-voltage
organic field-effect transistors
Simas, E. Reis; Kang, E. S. H.; Gassmann, A.; Katholing, E.;
Janietz, S.; von Seggern, Heinz
Staff Members
Head
Prof. Dr. Oliver Gutfleisch
Research Associates
Dr. Leopold Diop
Dr. Semih Ener
Dr. Barbara Kaeswurm
Dipl.-Ing. Marc Pabst
Santosh Pal, M. Sci.
Dr. Iliya Radulov
Dr. Konstantin Skokov
Administratvive Staff
Maija Laux, Ms
Sabine J. Crook, MA
Technical Personnel
Gabi Andress, Ms
Helga Janning, Ms
Dipl.-Ing Bernd Stoll
PhD Students
Dipl.-Phys. Dimitri Benke
Imants Dirba, M. Sc.
Dipl.-Ing. Maximilian Fries
Dipl.-Phys. Tino Gottschall
Tim Helbig, M. Sc.
Dipl.-Ing. Konrad Löwe
Dipl.-Wi.-Ing. Simon Sawatzki
Dipl.-Ing. Christoph Schwöbel
62 | Functional Materials
External
Alexandru Lixandru, M. Eng.
Iuliana Poenaru M. Sc
Dipl.-Phys. Fabian Rhein
Xi Lu, M. Sc.
Daniel Simon, M. Sc
Master Students
Bahar Fayyazi
Johannes Kroder
Moritz Liesegang
Shilpi Sharma
Daniel Simon
Bachelor Students
Tobias Braun
Marcus Frericks
Kirsten Friemert
Fabian Jäger
Tim Kolb
Benjamin Krah
Guest Scientists
Dr. Hossein Sepehri-Amin
Dr. Dmitry Karpenkov
The Functional Materials (FM) Group main
research interests span from new permanent
magnets for power applications to solid state
energy efficient magnetic cooling, ferromagnetic
shape memory alloys, magnetoelastomers for
adapted damping and actuation, magnetic nanoparticles for biomedical applications.
The criticality of strategic metals is addressed
by developing new recycling processes and
substitutional materials. Particular emphasis is
on tailoring structural and chemical properties
on the nanoscale. Permanent magnets are used
in a wide variety of industrial and household appliances, the major applications being electrical
motors and power generation. Currently these
applications require NdFeB magnets, which rely
on rare earth elements such as Nd as well as Dy,
which is used to enhance the thermal stability.
Rare Earth metals are expensive and availability
is predicted to become increasingly limited in the
years to come. Our efforts include
a) reduction of heavy rare earth
elements in Nd-Fe-B magnets without a loss in
performance and
b) the study of novel rare earth free
materials with energy densities greater than
those of hard ferrites (another class of widely
used permanent magnets).
Magnetocaloric materials heat up when placed
in a magnetic field and are potentially useful for a
new energy efficient technology for refrigeration.
Magnetic refrigeration is based on the reversible
magnetisation and demagnetisation of such a
magnetocaloric material by external magnetic
fields, resulting in a change in temperature.
The changes in temperature are transferred to the refrigerator volume by means
of heat exchangers. This technology simultaneously eliminates the need for harmful
refrigerant gases and reduces the energy
requirements and hence carbon dioxide emissions.
The group concentrates on both fundamental and
practical aspects of room temperature magnetic
cooling. This involves the study of fundamental
magnetocaloric material properties and the performance of the materials under test, as well as
potential impact on product design. This includes
work on resource efficient fabrication and the
design of demonstators.
The FM group works in close collaboration
with the Project Group for Materials Recycling
and Resource Strategy at the IWKS Frauhofer
Institute in Hanau, a group of which Prof. Gutfleisch is also chair. 2015 has been an exciting
year for the FM Group with the continuity of
the RESPONSE, DRREAM, ROMEO, SWIP
and REFREEPERMAG projects. This year has
also been a strong year for publications. We
have published almost 30 peer reviewed papers
in various international journals listed in this
document. The group has also been represented
at international conferences.
These included as highlights plenary
talks at DPG 2015 (Berlin) and ICM 2015
(Barcelona, Spain). In 2016 Prof. Gutfleisch will
bring the REPM (Rare Earth and Future Permanent Magnets and their Applications) workshop
to Darmstadt. The FM group has attended national meetings such as the annual DPG meeting in
Berlin. We have also strengthened our international reputation through international collaborations, receiving visitors from Spain, Japan and
Russia for both short and long term stays.
This year another highlight for the group was
a 3 day internal seminar in Trifels. This was an
opportunity to discuss our work in an informal
setting and take part in team building exercises.
Simon Sawatzki defended his doctoral thesis
on the “Grain boundary diffusion process in
nanocrystalline Nd-Fe-B permanent magnets”,
which was rewarded by the PhD commission
with highest honor (summa cum laude).
Functional Materials | 63
Increased Magnetic Moment Induced by Lattice
Expansion from α-Fe to α′-Fe8N
I. Dirba1, P. Komissinskiy1, O. Gutfleisch1,2 and L. Alff1
1
Material Science, TU Darmstadt, Alarich-Weiss-Str. 16, 64287 Darmstadt, Germany
2
Fraunhofer IWKS Project Group for Materials Cycles and Resource Strategy, 63450 Hanau, Germany
The rare earth crisis has stimulated researchers
worldwide to (re)address questions concerning
the magnetization and anisotropy of Fe based
material systems. One focus is on the ordered
compound αʹʹ-Fe16N2 for which besides an
increased magnetic moment per Fe atom even
a considerable anisotropy constant has been
reported. The technical use of αʹʹ-Fe16N2 is
severely hampered by its poor thermal stability.
In this paper, we address experimentally the
magnetization of α-Fe as a function of volume
expansion driven by nitrogen incorporation in the
iron-nitrogen system αʹ-Fe8Nx without ordering
of the interstitial nitrogen atoms.
We have extracted the c-axis lattice
parameter from θ–2θ scans and plotted them in
Figure 1, as a function of the nitrogen gas supply
during the thin film growth. The corresponding
number of dissolved nitrogen atoms per 100
iron atoms, X N, was calculated using the relation
c = 0.28664 + 0.00242 · X N reflects the nitrogen
content in αʹ-Fe8Nx. At the endpoint of the
series, the nitrogen concentration was such that
the unit cell expansion along the c-axis reached
a lattice spacing of 3.15 Å which corresponds
to the formation of αʹ-Fe8N1 with a c/a ratio of
approximately 1.1. The increase of the c-axis
is consistently observed in two independent
experimental series to be a linear function of the
nitrogen content in the plasma. This behavior is
consistent with Vegard’s law.
In-plane and out-of-plane magnetization
curves were obtained using a SQUID. We have
measured the bare substrates independently for
separating the thin film and substrate contributions to the magnetic signal. Pure iron films
(with a Ta capping layer in order to prevent
surface oxidation) were measured as a standard.
The in-plane hysteresis loops measured at 10 K
with the field aligned parallel to the Fe (110)
direction are shown in Figure 2. The volume
saturation magnetization reaches approx.
1900 ± 80 emu/cm3 for a film with a lattice
constant of c = 3.12 Å. This clearly indicates the
increased average magnetic moment per Fe atom.
Coercivity
increases
from
approximately 23 Oe for pure Fe to 350 Oe for
αʹ-Fe8N. The in-plane saturation field increases
with increasing nitrogen content of the thin films
(Fig. 2). Note that the pure α-Fe films display
already an increased anisotropy. This is due to
the large number of growth defects during the
low-temperature synthesis and the large lattice
mismatch to MgO. However, the increased
extrinsic anisotropy did not change the intrinsic
magnetization of the pure Fe films which was
close to 2.2 µ B per Fe atom.
The most important result of our experiments
is shown in Figure 3, where we show the magnetic moment per Fe atom in αʹ-Fe8Nx as a function
of the c-axis lattice parameter. In our data, there
is a clear increase in magnetic moment per Fe
following the lattice expansion. The maximal
value we have obtained is 2.61 ± 0.06 μ B per
Fe atom (corresponding to an increase as compared to α-Fe of about 17.5%). This maximal
value itself (independent to which origin it was
attributed) is in good agreement with experimental results in iron nitrides, and also in good
agreement with the theoretical predictions. The
key point here is that the increased magnetic
moment cannot be attributed to a specific stoichiometry, but it increases proportional to the lattice
expansion following the nitrogen incorporation
in αʹ-Fe8Nx. The increase in magnetic moment is
related to the increase of the Wigner-Seitz-radius
of α-Fe, which is a continuous function of the
amount of nitrogen interstitials.
Acknowledgements
I.D. thanks the BMBF for the financial
support within the Project No. 03X3582.
The authors thank the LOEWE project RESPONSE funded by the Ministry of Higher
Education, Research and the Arts (HMWK) of
the Hessen state. This work has been published:
I. Dirba, P. Komissinskiy, O. Gutfleisch and
L. Alff, Increased magnetic moment induced by
lattice expansion from αʹ-Fe to αʹ-Fe8N, Journal
of Applied Physics, 117 (2015) 173911.
Figure 1: Out-of-plane c-axis lattice
parameters of αʹ-Fe8Nx as a function of
the effective nitrogen flow during the film
growth. Two sample series have been
plotted. For series 2, we have offset the
N content by a constant value due to a
change in the nitrogen inlet.
Figure 2: In-plane hysteresis loops for Fe and
αʹ-Fe8Nx thin films measured by SQUID.
Figure 3: Magnetic moment per Fe atom in
αʹ-Fe8Nx in dependence of the lattice constant.
On the Preparation of La (Fe,Mn,Si)13Hx Polymer-Composites with
Optimized Magnetocaloric Properties
I. A. Radulov a, K. P. Skokov a, D. Yu. Karpenkov a,b, T. Gottschall a and O. Gutfleisch a,c
a
Materials Science, Technische Universität Darmstadt, 64287 Darmstadt, Germany
b
Faculty of Physics, Chelyabinsk State University, 454001 Chelyabinsk, Russia
c
Fraunhofer IWKS Project Group for Materials Cycles and Resource Strategy, 63450 Hanau, Germany
A successful use of the magnetocaloric material
in an active magnetic regenerator (AMR) requires
its machining into heat exchangers with good
mechanical and chemical stability. Most of the
magnetocaloric materials currently available for
room temperature application do not meet those
requirements, they are brittle and are susceptible
to corrosion. Adhesive-bonding techniques can
provide mechanical stability, corrosion protection and net shaped modules in a single step
manufacturing process.
However, the magnetocaloric properties of
the composite materials can be significantly
lowered during this process e.g. due to improper
adhesion, dilution, and compaction pressure. We
report on a comprehensive study of the influence
of powder particle size, adhesive type, adhesive
concentration and compaction pressure on the
magnetocaloric properties of polymer-bonded
La(Fe,Mn,Si)13H x material.
The magnetic entropy change D Sm was
calculated in two independent ways: from M(H)T
using the Maxwell relation and from specific heat
Cp, H(T) measured in zero field and in an external
field of μ 0 H=1.9 T. Both DSm (T) dependences
of the hydrogenated bulk sample are shown in
Figure 1 (left scale, open and filled circles). The
maximal DSm values in magnetic field change of
Dm0H=1.9T were found to be 14.8 J kg−1 K−1 from
magnetization data and DSm =14.7 J kg−1 K−1 from
specific heat data, which is a reasonable good
agreement between both methods. Figure 1 also
shows the DTad(T) (right scale, open squares)
of this large fragment of La(Fe,Mn,Si)13Hx.
At T=296 K the ΔTad(T) reaches the maximal
value of DTad =5.15±0.01K in magnetic
field
change
D m0H = 1.9T.
The DTad(T) of bulk La(Fe,Mn,Si)13H x is comparable or slightly higher than DTad (T) of Gd
metal. At the same time its DSm is three times
higher than the magnetic entropy change of Gd,
acting as a reference magnetocaloric material.
This makes La(Fe,Mn,Si)13H x very promising for
magnetic cooling at ambient temperature.
An important step in the adaptation of
La(Fe,Mn,Si)13H x powders for their usage in
active heat exchangers is the optimization of the
compaction pressure needed for the production
of polymer-bonded composites. The influence of
the compaction pressure on the magnetocaloric
properties was investigated by measuring the
DTad of rectangular shaped pellets prepared from
160 to 250 μm powder. The compaction pressure
was increased from 0.01 to 2 GPa. The experimental DTad(pcomp) dependence presented in
Figure 2 has a well pronounced maximum at
0.1 GPa and is decreasing monotonically in the
range 0.1–2 GPa. The reduction of the MCE
in samples compacted under pressures above
0.1 GPa can be explained by a comminution of the
160–250 μm fragments during the compaction.
The DTad and porosity of the polymer-bonded
samples, both as a function of the epoxy concentration, are depicted in Figure 3. The samples
with an epoxy concentration above 10 wt.%
demonstrate smaller DTad than the loose powder
due to the parasitic thermal loading of the binder,
while the sample with 5 wt.% of epoxy shows the
largest DTad =4.75K that even exceeds the value
of the loose powder (Figure 3, filled circles, right
scale). We associate this increase of the MCE
with the enhanced mechanical coupling between
the particles. By decreasing the amount of epoxy
below 5 wt.% samples become mechanically
unstable and cannot be used for heat exchangers.
12
• Tad
4
10
∆Sm [J kg-1K-1]
Figure 1: Magnetic entropy change
(left scale) and adiabatic temperature change (right scale) of bulk
La(Fe,Mn,Si)13Hx. ΔSm dependences
were calculated from magnetization
(open circle) and specific heat
filled circle) data. The ΔTad
dependence (open square) was
obtained by direct measurements.
5
• Sm from Cp
3
8
6
2
4
∆Tad [K]
14
∆Tmax
= 5.15 K
ad
• Sm from M(H)
1
2
µ0H = 1.9 T
0
290
300
T [K]
0
310
max
• Tad = 4.55 K
4.5
4.4
4.3
∆Tad [K]
loose powder
4.2
4.1
Figure 2: Adiabatic temperature change
of compacted La(Fe,Mn,Si)13Hx powder
samples, prepared from powders with a
particle size of 160–250 μm.
4.0
0.0
0.2
50
0.4
0.6
pcomp [GPa]
porosity
• Tad
0.8
1.0
(a)
4.6
∆Tad [K]
porosity [%]
40
Figure 3: Porosity (left scale, straight
lines) and adiabatic temperature
change (right scale dashed lines) in
samples compacted with different
wt.% of H27D epoxy, at 0.1 GPa
compaction pressure.
4.8
4.4
30
4.2
20
4.0
10
3.8
0
5
10
15
epoxy concentration [%]
20
Acknowledgements
The work of I. Radulov is supported by the German Federal Ministry of Education and Research
under the VIP Project no. 03V0540 (MagKal).
K. Skokov is grateful to the European Community’s 7th Framework Program under the Grant
agreement no. 310748 (DRREAM). D. Yu.
Karpenkov is supported by Russian Scientific
Foundation Grant no. 15-12-10008.
T. Gottschall and O. Gutfleisch thank the DFG
(SPP1599). The authors would like to thank M.
D. Kuz’min for fruitful discussions.
This work has been published:
I. A. Radulov, K. P. Skokov, D. Yu. Karpenkov,
T. Gottschall and O. Gutfleisch, Journal of
Magnetism and Magnetic Materials, 396 (2015)
228-236.
Publications
[1] B. Pulko, J. Tušek, J. D. Moore, B. Weise, K. Skokov, O. Mityashkin, A. Kitanovski, C. Favero, P. Fajfar, O. Gutfleisch, A. Waske,
A. Poredoš, Epoxy-bonded La-Fe-Co-Si magnetocaloric plates, JMMM 375 (2015) 65–73.
[2] K. Löwe, C. Brombacher, M. Katter, O. Gutfleisch, Temperature dependent Dy diffusion processes in Nd-Fe-B permanent magnets, Acta Mat. 83 (2015) 248–255.
[3] M. Moore, S. Roth, A. Gebert, L. Schultz, O. Gutfleisch, The effect of surface grain reversal on the AC losses of sintered Nd-Fe-B
permanent magnets, JMMM 375 (2015) 43-48.
[4] M. Krautz, A. Funk, K. P. Skokov, T. Gottschall, J. Eckert,
O. Gutfleisch, A. Waske, A new type of La(Fe,Si)13 based magnetocaloric composites with amorphous metallic matrix,
Scripta. Mat. 95 (2015) 50–53.
[5] M.X. Zhang, J. Liu, Y. Zhang, J.D. Dong, A.R. Yan, K.P. Skokov,
O. Gutfleisch, Large
entropy change, adiabatic temperature change, and small hysteresis in La(Fe,Mn)11.6Si1.4 strip-cast flakes, JMMM 377 (2015) 90–94.
[6] Hong Jian, K.P. Skokov, O. Gutfleisch, Microstructure and magnetic properties of Mn-Al C alloy powders prepared by ball milling,
J. Alloys and Comp. 622 (2015) 524–528
[7] H. Sepehri-Amin, T. Ohkubo, K. Hono, K. Güth, and O. Gutfleisch, Mechanism of the texture development in hydrogen-disproportionation-desorption-recombination (HDDR) processed Nd-Fe-B
powders, Acta Mat 85 (2015) 42–52.
[8] C. Bonatto Minella, S. Garroni, C. Pistidda, M.D. Baró, O. Gutfleisch, T. Klassen, M. Dornheim, Sorption properties and reversibility of Ti(IV) and Nb(V)-fluoride doped-Ca(BH4)2-MgH2 system, J. Alloys and Comp. 622 (2015) 989–994.
[9] I. Dirba, M. Baghaie Yazdi, A. Radetinac, P. Komissinskiy, S. Flege,
O. Gutfleisch, L. Alff, Growth, structure, and magnetic properties
of γ-Fe4N thin films, JMMM 379 (2015)151–155.
[10] T. Gottschall, K.P. Skokov, B. Frincu, O. Gutfleisch, Large reversi-
ble magnetocaloric effect in Ni-Mn-In-Co,
Appl. Phys. Lett. 106 (2015) 021901_1-4.
Publications
[11] J. Döntgen, J. Rudolph, T. Gottschall, O. Gutfleisch, S. Salomon,
A. Ludwig, and D. Hägele, Temperature dependent low-field
measurements of the magnetocaloric ΔT with sub-mK resolution in small volume and thin film samples,
Appl. Phys. Lett. 106 (2015) 032408_1-4.
[12]
M.E. Gruner, W. Keune, B. Roldan Cuenya, C. Weis, J. Landers,
S. Makarov, D. Klar, M. Y. Hu, E.E. Alp, J. Zhao, M. Krautz,
O. Gutfleisch, H. Wende, Element-resolved thermodynamics of magnetocaloric LaFe13-xSix, Phys. Rev. Lett. 114 (2015) 057202_1-6.
[13] A. Waske, L. Giebeler, B. Weise, A. Funk, M. Hinterstein, M. Herklotz, K.P. Skokov, S. Fähler, O. Gutfleisch and J. Eckert, Asymmetric First-Order Transition and Interlocked Particle State in Magnetocaloric La(Fe,Si)13, Physica Status Solidi (RRL) 1–5 (2015).
[14] S. Sawatzki, T.G. Woodcock, K. Güth, K.-H. Müller, O. Gutfleisch, Calculation of remanence and degree of texture from EBSD
orientation histograms and XRD rocking curves in (Nd,Dy)-Fe-B sintered magnets, JMMM 382 (2015) 219–224.
[15] S. Ener, K. Skokov, D.Yu Karpenkov, M.D. Kuzmin, O. Gutfleisch, Magnet properties of Mn70Ga30 prepared by cold rolling and
magnetic field annealing, JMMM 382 (2015) 265–270.
[16] O. Akdogan, H. Sepehri-Amin, N.M. Dempsey, T. Ohkubo, K. Hono, O. Gutfleisch, T. Schrefl, D. Givord, Preparation, characterization and modeling of ultra-high coercivity Sm-Co thin films, Adv. Electronics Mat. 1500009 1-8 (2015)
[17] S. Taskaev, K. Skokov, V. Khovaylo, V. Buchelnikov, A. Pellenen,
D. Karpenkov, M. Ulyanov, D. Bataev, A. Usenko, M. Lyange,
O. Gutfleisch, Effect of severe plastic deformation on the specific heat and magnetic properties of cold rolled Gd sheets,
J. Appl. Phys. 117 (2015) 123914_1-5.
[18]
P. McGuiness, O. Akdogan, A. Asali, S. Bance, F. Bittner,
J.M.D. Coey, N.M. Dempsey, J. Fidler, D. Givord, O. Gutfleisch,
M. Katter, D. Le Roy, S. Sanvito, T. Schrefl, L. Schultz, C. Schwöbl,
M. Soderžnik, S. Šturm, P. Tozman, K. Üstüner, M. Venkatesan,
T.G. Woodcock, K. Žagar, S. Kobe, Replacement and Original Magnet Engineering Options (ROMEO): A European 7th Framework project to develop advanced permanent magnets without, or with reduced use of, critical raw materials, JOM 67 no.6 (2015) 1306-1317
Publications
[19] I. Dirba, P. Komissinskiy, O. Gutfleisch, L. Alff, Increased
magnetic moment induced by lattice expansion from
a-Fe to αʹ-Fe8N, J. Appl. Phys. 117 (2015) 173911_1-7.
[20] F. Scheibel, T. Gottschall, K. Skokov, O. Gutfleisch,
M. Ghorbani-Zavareh, Y. Skourski, J. Wosnitza, O. Cakir,
M. Acet, M. Farle, Dependence of the inverse magnetocaloric effect on the field-application time in Mn3GaC and its
relationship to the kinetics of the phase transition,
J. Appl. Phys. 117 (2015) 233902_1-6.
[21] S.I. Makarov, M. Krautz, S. Salamon, K.P. Skokov, C.S. Teixeira, O. Gutfleisch, H. Wende, W. Keune, Local Electronic and Magnetic Properties of Pure and Mn-Containing Magnetocaloric LaFe13-xSix Compounds Inferred from Mössbauer Spectroscopy and Magneto-
metry, J. Phys. D: Appl. Phys. 48 (2015) 305006_1-12.
[22] A. Edström, M. Werwinski, J. Rusz, O. Eriksson, K.P. Skokov,
I.A. Radulov, S. Ener, M.D. Kuz’min, J. Hong, M. Fries,
D. Yu. Karpenkov, O. Gutfleisch, P. Toson , J. Fidler, Effect of
doping by 5d elements on magnetic properties of (Fe1−xCox)2B alloys, Phys. Rev. B 92 (2015) 174413_1-13.
[23] I.A. Radulov, K.P. Skokov, D. Yu. Karpenkov, T. Gottschall,
O. Gutfleisch, On the preparation of La(Fe,Mn,Si)13Hx
polymer-composites with optimized magnetocaloric properties, JMMM 396 (2015) 228–236.
[24] I.A. Radulov, K.P. Skokov, D. Yu. Karpenkov, T. Braun,
O. Gutfleisch, Polymer-bonded La(Fe,Mn,Si)13Hx Plates for Heat Exchangers, IEEE Trans. Mag. 51 (2015) 2501204_1-4.
[25] M.D. Kuzmin, K.P. Skokov, I. Radulov, C.A. Schwöbel,
W. Donner, S. Foro, M. Werwinski, J. Rusz, E. Delczeg-Czirjak,
O. Gutfleisch, Magnetic anisotropy of La2Co7,
J. Appl. Phys. 118 (2015) 053905_1-5.
[26] R. Gauß, O. Diehl, E. Brouwer, A. Buckow, K. Güth, O. Gutfleisch, Verfahren zum Recycling von seltenerdhaltigen Permanent
magneten, Chem. Ing. Tech. 87 no. 11 (2015) 1477-1485
[27] K. Ollefs, Ch. Schöppner, I. Titov, R. Meckenstock, F. Wilhelm,
A. Rogalev, J. Liu, O. Gutfleisch, M. Farle, H. Wende,
M. Acet, Magnetic ordering in magnetic shape memory alloy Ni-Mn-In-Co, Phys. Rev. B 92 (2015) 224429_1-7.
Ion-Beam Modified
Materials
Staff Members
Head
Prof. Dr. Christina Trautmann
PhD Students
Dipl.-Ing. Loic Burr
Dipl.-Ing. Marco Cassinelli
Dipl.-Ing. Christian Hubert
Janina Krieg, M. Sc.
Dipl.-Phys.. Liana Movsesyan
Romanenko Anton, M. Sc.
Anne Spende, M. Sc
Dipl.-Ing. Michael F. Wagner
Dipl.-Ing. Katharina Kupka
Master Students
Kröber, Philipp
Bachelor Students
Dietz Dominik
Gura Leonard
Porth, Carsten
Schnell Patrick
Ulrich Nils
Urban Marcel
Xu Yuan
72 | Ion-Beam Modified Materials
Ion-Beam Modified Materials
The scientific interest of this group is related to
interaction processes of energetic heavy ions with
matter and the application of ion beams as nanostructuring tool. The irradiation experiments are
performed at the linear accelerator UNILAC of
GSI using heavy projectiles with kinetic energies
between MeV and GeV (e.g., Au ions of about
10% velocity of light). Our research projects
focus on the interaction and damage processes of
heavy ions with matter as well as on the fabrication and characterization of ion-beam produced
nanostructures.
Current activities include the identification
of performance limits of materials to be used for
components in the future high-power accelerator
facility FAIR and in the LHC upgrade of CERN.
Carbon-based materials are considered to have
favorable properties including low-Z composition,
low cost, good thermo-mechanical properties and
excellent radiation hardness. The investigations
on graphite and various carbon-based materials
concentrated on the question how ion irradiation
affects the graphite structure and under which
conditions critical degradation of particularly
thermal, mechanical, and electrical properties
occurs. The characterization of beam-induced
modifications is performed by means of Raman
spectroscopy, x-ray diffraction, x-ray photo-electron spectroscopy, laser-flash analysis, micro/
nano-indentation and 4-point electrical resistivity
measurements.
Ion-track nanotechnology is based on the specific
property that each individual ion generates a
nanometer wide damage trail along its trajectory.
By selective chemical etching, the damage is
converted into an open high-aspect ratio channel.
Nanochannels are most commonly fabricated in
track-etched polymer films (typical thickness
10-30 µm) using polycarbonate or polyethylene
terephthalate. There is great interest in exploiting
nanopores with tailored properties for sensor
applications. For this, the pore walls of the nanochannels are modified by chemical methods or
more recently by atomic layer deposition (ALD)
which provides layer by layer, shape-conform
coatings.
Track-etched nanopores also serve as templates for the synthesis of nanowires of well-defined size, geometry and material composition.
Present activities concentrate on the fabrication
of AuAg alloy and porous gold nanowires and
the characterization of their electrical and optical
properties. Bi-compound nanowires are studied
with respect to their thermoelectric properties
(see extra report) and for testing properties of
nanostructured topological insulators. Furthermore, we synthesize and analyze cylindrical
ZnO and Cu2O nanowire arrays and networks as
model systems to study the photoelectrochemical performance of such hierarchical nanowire
structures for harvesting solar-energy via water
splitting.
Ion-Beam Modified Materials | 73
Low Temperature Annealing Effects on the Stability
of Bismuth Nanowires
M. Cassinelli1,2, A. Romanenko1,2, W. Sigle3, M.E. Toimil-Molares1, and C. Trautmann1,2
1
GSI Helmholtzzentrum Darmstadt, 2TU Darmstadt, 3MPI for Intelligent Systems, Stuttgart
The unique properties of bismuth (Bi) nanowires
and the theoretical predictions on their enhanced
thermoelectric efficiency two decades ago [1]
triggered the development of a wide variety of
growth and characterization methods, aiming
at measuring the thermoelectrical properties of
single Bi nanowires [2]. Since then unique size
dependent properties of Bi nanowires have been
highlighted [3-5]. However, the experimental
demonstration of an enhanced thermoelectric
efficiency remains a challenge possibly due to the
chemical and thermal instability of Bi nanowires
as well as the difficulties encountered to achieve
reliable and stable electrical contacts. Although
bulk Bi is known to be prone to oxidation, the
chemical stability of Bi nanowires at room and
moderate elevated temperatures had never been
reported. Here, we investigate the morphology
and the composition of single Bi nanowires
before and after annealing under controlled
conditions. By electrodeposition and ion-track
technology Bi nanowires with tailored geometry
and crystallinity are synthesized. Scanning electron microscopy (SEM), as well as transmission
electron microscopy (TEM) and energy dispersive x-ray analysis (EDX) are applied to analyze
the chemical and morphological changes of the
wires with very high spatial resolution [6].
Cylindrical Bi nanowires with average diameter 79, 30 and 18 nm were electrodeposited in the
channels of track-etched polymer membranes.
Pulsed electrochemical deposition was performed at room temperature applying U1 = -250
mV vs. SCE for t1 = 20ms and U2 = -150 mV vs.
SCE for t2 = 100 ms. The resulting nanowires are
highly textured consisting of long single-crystalline sections [7]. After dissolution of the polymer
membrane in dicholoromethane, the nanowires
are transferred onto Si wafers or Cu-lacey TEM
grids. For the annealing experiments a tube furnace (Carbolite HST 12/300) was employed using
a heating rate of 9 °C/min in all cases.
The analysis was performed in a JEOL JSM-7401F
SEM at GSI and a JEM ARM 200CF TEM at the
MPI for Intelligent Systems (Stuttgart, Germany).
Figures 1(a-d) show representative SEM
images of Bi nanowires with initial diameter
~30 nm before and after annealing. Before the
annealing, the nanowires exhibit a cylindrical
shape and a smooth surface, as expected (Fig.
1(a)). After annealing at 250°C for 2 h, the Bi
nanowires maintain the cylindrical shape but
few protuberances are visible on the surface
(Fig. 1(b)). After 20 h of annealing (Fig 1(c)), the
nanowires exhibit numerous protuberances along
their entire length. The density and size of the
protuberances increase significantly with longer
annealing times, as visible in Fig. 1(d).
Figure 1(e-g) displays images of Bi nanowires
with initial diameter (e) ~18, (f) ~30 and (g) ~79
nm, after being simultaneously annealed in air
at 250 °C for 20 h. The formation of protuberances with similar size relative to the initial wire
diameter is observed in all cases. However, the
number of protuberances seems to decrease with
increasing wire diameter.
The formation of protuberances observed for
these Bi nanowires in air at 250 °C, i.e. temperatures very close to the bulk melting temperature,
is very different from the morphological changes
previously observed for metal nanowires of
similar diameters, which were transformed via
Rayleigh instability into a chain of spheres after
being annealed in vacuum at temperatures well
below the bulk melting point [8,9]. However, Kolmakov et al. previously reported the formation of
similar protuberances for Sn nanowires annealed
in air [10]. The authors attributed the protuberances to the unevenness of an oxide layer formed
on the nanowire surface. They assumed that the
highest oxidation rate occurred along the grain
boundaries and other crystal defects, forming the
protuberances at those positions and maintaining
the integrity and shape of the wire.
Figure 1: SEM images of sections of Bi nanowires on Si substrates. (Left) Bi wire with initial
diameter 30 ± 4 nm (a) before and after annealing in air at 250 °C for (b) 2 h (c) 20 h, and (d) 100
h. (Right) Bi wires with initial diameter (e) 18 ± 3 nm, (f) 30 ± 4 nm, and (g) 79 ± 8 nm after
annealing in air at 250 °C for 20 h. Scale bar (100 nm) applies to all images.
To confirm and investigate the presence of an
oxide phase on our wires, the composition of Bi
nanowires with various diameters was analyzed
by TEM-EDX before and after annealing. Figure
2 shows the TEM images and the corresponding
EDX-line scans measured for Bi nanowires with
initial wire diameter ~18 nm before annealing
(a) and after annealing at 250 °C for (b,c) 2 h
and (d) 20 h. The line scans present the atomic
percentage of Bi (black) and oxygen (red) across
the wires.
The line scans in Fig. 2(a) display 30% oxygen in the as-prepared nanowires, indicating that
oxidation occurs already during the time between
wire drop-casting and TEM analysis (about 50 h).
In addition, the oxygen concentration increases
towards the edges of the wire, indicating a radial
inwards oxidation process. In Fig. 2(b) the atomic
percentages amount to ~60% O and ~40% Bi and
remain constant across the wire indicating the
complete transformation of the Bi nanowire into
Bi2O3 after annealing for 2h at 250 °C. In Fig. 2(c),
the line scan is performed on a protuberance and
the result indicates the same oxide composition
(Bi2O3). Fig. 2(d) presents the line scan made on a
segment of wire annealed for 20 hours at 250°C,
confirming that the nanowires are fully oxidized
to Bi2O3. Additional Raman spectroscopy measurements [6] also demonstrated the formation of
Bi2O3 nanowires by controlled annealing of Bi
wires. The formation of an oxide layer explains
the absence of Rayleigh instability effects in our
nanowires, because the melting point of Bi2O3
(817 °C) is significantly higher than that of pure
Bi (271.5 °C).
Based on our finding regarding oxidation, we
finally investigated the thermal stability of Bi2O3
nanowires. Bi nanowires with initial diameter
of ~30 nm were transferred onto Si substrates
and annealed for 20 hours at 250°C in air to
completely transform them into Bi2O3, as demonstrated by the TEM-EDX measurements in Fig.
2. Several samples of oxidized Bi nanowires were
then further annealed for 20 hours at different
temperatures near the Bi2O3 bulk melting point.
Figure 3 displays sections of (a) Bi2O3 nanowires
after the annealing of Bi nanowires for 20 hours
at 250°C. Subsequently, the Bi2O3 wires were
annealed for 20 hours at (b) 700, (c) 750 and (d)
800°C in air. For the wires in Fig.3(b) and (c),
a continuous structure was revealed, with rough
surface and protuberances. In general, the wires
roughness seems to be more pronounced with
annealing temperature. On the contrary, wires
annealed at 800°C (Fig. 3 (d)), do not any longer
show a continuous structure, but are fragmented
into chains of small spheres. This decay is known
as Rayleigh effect and was previously reported
for metallic nanowires, such as Au [8], Ag [9], Cu
[11] and Pt [12].
In conclusion, we studied the chemical and
morphological stability of Bi nanowires before
and after annealing in air as a function of time
and temperature. The surface of the wires became
rough after annealing at temperatures as low as
200 °C, while large protuberances developed at
about 250 °C. TEM-EDX and Raman spectroscopy measurements (not shown here) revealed
that the wires oxidize forming the α-phase of
Bi2O3. The nanowire oxidation process starts at
room temperature at the surface shortly after
dissolution of the polymer membrane. During
annealing oxidation continues towards the inner
part of the wire. This fast formation of an oxide
layer explains the difficulties encountered by
many groups to electrically characterize single Bi
nanowires. The results also provide a new route
for the synthesis of Bi2O3 nanowires by annealing
of Bi wires under controlled conditions. Bi2O3 is
an interesting semiconductor material suitable
for applications in many fields, such as sensors
and photovoltaic cells [13]. The thermal stability
of Bi2O3 nanowires annealed at 800°C follows
the Rayleigh instability behavior, resulting in
fragmentation of the oxidized wire into chains of
small spheres.
Acknowledgements
We thank the Deutsche Forschungsgemeinschaft (DFG) for financial support within the
priority program SPP 1386 and Prof. F. Völklein
for fruitful scientific discussions. M.C. thanks
FIAS and the Helmholtz Graduate School for
Hadron and Ion Research “HGS-HIRe” for the
financial support.
Figure 2: TEM images of Bi nanowires with initial diameter ~18 nm (a) as-prepared and after annealing in air at 250 °C for (b,c) 2 h and (d) 20 h.
The plots present TEM-EDX line scans corresponding to Bi (black) and O (red) atomic percentage content in the wires.
Figure 3: SEM images of sections of (a) Bi2O3 nanowires produced by annealing of Bi nanowires with initial diameter 30 ± 4 nm for 20 hours at
250°C. The Bi2O3 nanowires were subsequently annealed for 20 hours at (b) 700, (c) 750 and (d) 800°C.
The 100-nm scale bar applies for (a), (b) and (c).
References
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B 365, 668 (2015).
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Research Projects
•
Fabrication of Bi-based nanowires and their characterization with
respect to thermoelectric properties (FIAS 2011-2015)
•
Fabrication of semiconducting nanowires using the ion track technology
(Beilstein Institute, 2012 – 2015)
•
Fabrication and controlled surface functionalisation of mesoporous
SiO2 materials and ion-track nanochannels (DFG, Forschergruppe
(FOR 1583), 2011-2015)
•
Radiation hardness of carbon stripper foils under high current UNILAC
operation (BMBF, Verbundforschung, 2012 – 2015)
•
Radiation damage of carbon-based FAIR materials (2015-2018)
•
Investigation of response of graphite and new composite materials
for Super-FRS target and beam catchers to intense ion beam-induced
thermal stress waves (BMBF, Verbundforschung, 2012 – 2015)
Publications
[1]
Schlüter A.;· Kuhn C.;· Müller R.;· Tomut M.;· Trautmann C.;·
Weick, H.;· Plate C.; Phase field modelling of dynamic thermal fracture in the context of irradiation damage, CONTINUUM
MECHANICS AND THERMODYNAMICS, (2015) PP 1-12.
[2] Cassinelli, M.; Romanenko, A.; Reith, H.; Völklein, F.; Sigle, W.; Trautmann, C; Toimil-Molares, M.E.; Low temperature annealing effects on the stability of Bi nanowires. PHYS. STATUS SOLIDI A 213 (2016) 603-609.
[3] Movsesyan, L.; Schubert, I.; Yeranyan, L.; Trautmann, C.; ToimilMolares, M. E; Influence of electrodeposition parameters on the
structure and morphology of ZnO nanowire arrays and networks synthesized in etched ion-track membranes, SEMICONDUCTOR SCIENCE TECHNOLOGY 31 (2015) 014006.
[4] Perez-Mitta, G.; Albesa, A.G.; Knoll, W.; Trautmann, C.;
Toimil-Molares, M.E.; Azzaroni, O.; Host-guest supramolecular chemistry in solid-state nanopores: potassium-driven modulation of ionic transport in nanofluidic diodes, NANOSCALE 7, 38 (2015) 15594-15598
Publications
[5] Perez-Mitta, G.; Marmisolle, W.A.; Trautmann, C.; Toimil-Molares, M.E.; Azzaroni, O.; Nanofluidic Diodes with Dynamic Rectification Properties Stemming from Reversible Electrochemical Conversions in Conducting Polymers, JOURNAL OF THE AMERICAN
CHEMICAL SOCIETY 137, 49 (2015) 15382-15385
[6] Schauries, D.; Leino, A.A.; Afra, B.; Rodriguez, M.D.; Djurabekova, F.; Nordlund, K.; Kirby, N.; Trautmann, C.; Kluth, P.; Orientation dependent annealing kinetics of ion tracks in c-SiO2, JOURNAL OF APPLIED PHYSICS 118, 22 (2015) 224305
[7] Krauser, J.; Gehrke, H.G.; Hofsass, H.; Amani, J.; Trautmann, C.; Weidinger, A.; Electrical conduction of ion tracks in tetrahedral amorphous carbon: temperature, field and doping dependence and comparison with matrix data, NEW JOURNAL OF PHYSICS 17 (2015) 123009
[8] Tracy, C.L.; Lang, M.; Zhang, F.X.; Trautmann, C.; Ewing, R.C.; Phase transformations in Ln(2)O(3) materials irradiated with swift heavy ions, PHYSICAL REVIEW B 92, 17 (2015) 174101
[9] Muench, F.; De Carolis, D.M.; Felix, E.M.; Brotz, J.; Kunz, U.; Kleebe, H.J.; Ayata, S.; Trautmann, C.; Ensinger, W.; Self-Supporting Metal Nanotube Networks Obtained by Highly Conformal Electroless Plating, CHEMPLUSCHEM 80, 9 (2015) 1448-1456
[10] Burr, L.; Schubert, I.; Sigle, W.; Trautrnann, C.; Toimil-Molares, M.E.; Surface Enrichment in Au-Ag Alloy Nanowires and Investigation of the Dealloying Process, JOURNAL OF PHYSICAL CHEMISTRY C 119, 36 (2015) 20949-20956
[11] Th. Stöhlker, V. Bagnoud, K. Blaum, A. Blazevic, A. Bräuning
Demian, M. Durante, F. Herfurth, M. Lestinsky, Y. Litvinov, S. Neff, R. Pleskac, R. Schuch, S. Schippers, D. Severin, A. Tauschwitz, C. Trautmann, D. Varentsov, E. Widmann, on behalf of the APPA Collaborations; APPA at FAIR: From fundamental to applied research, NUCLEAR INSTRUMENTS AND METHODS IN
PHYSICS RESEARCH B 365 (2015) 680–685
[12] Christian Hubert, Kay Obbe Voss, Markus Bender, Katharina Kupka, Anton Romanenko, Daniel Severin, Christina Trautmann, Marilena Tomut; Swift heavy ion-induced radiation damage in isotropic graphite studied by micro-indentation and in-situ electrical resistivity, NUCLEAR INSTRUMENTS AND METHODS IN PHYSICS RESEARCH B 365 (2015) 509–514
Publications
[13] R. Thomaz, L.I. Gutierres, J. Morais, P. Louette, D. Severin, C.
Trautmann, J.J. Pireaux, R.M. Papaléo; Oxygen loss induced by swift heavy ions of low and high dE/dx in PMMA thin films, NUCLEAR INSTRUMENTS AND METHODS IN PHYSICS RESEARCH B 365 (2015) 578–582
[14] M. Cassinelli, S. Müller, Z. Aabdin, N. Peranio, O. Eibl, C. Trautmann, M.E. Toimil-Molares; Structural and compositional characterization of Bi1_xSbx nanowire, arrays grown by pulsed deposition to improve growth uniformity, NUCLEAR INSTRUMENTS AND METHODS IN PHYSICS RESEARCH B 365 (2015) 668–674
[15] F. Pellemoine, M. Avilov, M. Bender, R.C. Ewing, S. Fernandes, M. Lang, W.X. Li, W. Mittig, M. Schein, D. Severin, M. Tomut, C.
Trautmann, F.X. Zhang; Study on structural recovery of graphite irradiated with swift heavy ions at high temperature, NUCLEAR INSTRUMENTS AND METHODS IN PHYSICS RESEARCH B 365 (2015) 522–524
[16] D. Schauries, M.D. Rodriguez, B. Afra, T. Bierschenk, C. Trautmann, S. Mudie, P. Kluth; Size characterization of ion tracks in PET and PTFE using SAXS, NUCLEAR INSTRUMENTS AND METHODS IN PHYSICS RESEARCH B 365 (2015) 573–577
[17] Sebastian Dedera, Michael Burchard, Ulrich A. Glasmacher, Nicole Schöppner, Christina Trautmann, Daniel Severin, Anton Romanenko, Christian Hubert; On-line Raman spectroscopy of calcite and
malachite during irradiation with swift heavy ions, NUCLEAR INSTRUMENTS AND METHODS IN PHYSICS RESEARCH B 365 (2015) 564–568
[18] C. Mejía, M. Bender, D. Severin, C. Trautmann, Ph. Boduch, V. Bordalo, A. Domaracka, X.Y. Lv, R. Martinez, H. Rothard; Radiolysis and sputtering of carbon dioxide ice induced by swift Ti, Ni,and Xe ions, NUCLEAR INSTRUMENTS AND METHODS IN
PHYSICS RESEARCH B 365 (2015) 477–481
[19] Spende S.; Sobel N.; Lukas M.; Zierold R.; Riedl J.C.; Gura L.; Schubert I.; Montero Moreno J.J.; Nielsch K.; Stühn B.; Hess C.; Trautmann C.; Toimil-Molares M.E.; TiO2, SiO2, and Al2O3 coated nanopores and nanotubes produced by ALD in etched
ion-track membranes for transport measurements, NANO
TECHNOLOGY 26 (2015) 335301.
Publications
[20] Schauries, D. Afra, B. Rodriguez, M. D. Trautmann, C. Hawley, A. Kluth, P.; Ion track annealing in quartz investigated by small angle X-ray scattering, NUCLEAR INSTRUMENTS AND METHODS IN PHYSICS RESEARCH B 365 (2015) 380–383
[21] Yablinsky, CA; Devanathan, R; Pakarinen, J ; Gan, J; Severin, D; Trautmann, C; Allen, TR; Characterization of swift heavy ion ir
radiation damage in ceria, JOURNAL OF MATERIALS RE
SEARCH 30 (2015) 1473-1484
[22] Lang, M; Tracy, CL; Palomares, RI; Zhang, FX; Severin, D; Bender, M; Trautmann, C; Park, C; Prakapenka, VB; Skuratov, VA; Ewing, RC;
Characterization of ion-induced radiation effects in nuclear materials
using synchrotron x-ray technique, JOURNAL OF MATERIALS RESEARCH 30 (2015) 1366-1379
[23] Raul I. Palomares, Cameron L. Tracy, Fuxiang Zhang, Changyong Park, Dmitry Popov, Christina Trautmann, Rodney C. Ewing, Maik Lang; In situ defect annealing of swift heavy ion irradiated CeO2 and
ThO2 using synchrotron X-ray diffraction and a hydrothermal diamond anvil cell, JOURNAL OF APPLIED CRYSTALLO
GRAPHY 48 (2015) 711–717
[24] Nicolas Sobel, Christian Hess, Manuela Lukas, Anne Spende, Bernd Stühn, M. E. Toimil-Molares, Christina Trautmann; Conformal SiO2 coating of sub-100 nm diameter channels of polycarbonate etched ion-track channels by atomic layer deposition, BEILSTEIN J.
NANOTECHNOL 6 (2015), 472–479
[25] Perez-Mitta, G; Tuninetti, JS; Knoll, W; Trautmann, C; Toimil
Molares, ME; Azzaroni, O; Polydopamine Meets Solid-State Nan
opores: A Bioinspired Integrative Surface Chemistry Approach To Tailor the Functional Properties of Nanofluidic Diodes, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 137 (2015) 6011-6017
[26] Ina Schubert, Loic Burr, Christina Trautmann, Maria Eugenia Toimil-Molares; Growth and morphological analysis of segmented AuAg alloy nanowires created by pulsed electrodeposition in ion-track etched membranes, BEILSTEIN J. NANOTECHNOL. 6 (2015) 1272–1280
[27] Ina Schubert, Wilfried Sigle, Loic Burr, P. A. van Aken, Christina Trautmann, M. E. Toimil-Molares; Fabrication And Plasmonic Characterization Of Au Nanowires With Controlled Surface
Morphology, ADVANCED MATERIALS LETTERS 6 (2015) 377-382
Publications
[28]
S. Park, M. Lang, C. L. Tracy, J. Zhang, F. Zhang, C. Trautmann, M. D.
Rodriguez, P. Kluth, R. C. Ewing; Response of Gd2Ti2O7 and La2Ti2O7 to swift-heavy ion irradiation and annealing, ACTA MATERIALIA 93 (2015) 1–11
[29] K. Kupka, M. Tomut, P. Simon, C. Hubert, A. Romanenko, B. Lommel, C. Trautmann; Intense heavy ion beam-induced temperature effects in carbon-based stripper foils, JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY 305 ( 2015) 875-882
[30] Papaleo, R.M.; Thomaz, R.; Gutierres, L.I.; de Menezes, V.M.; Severin, D.; Trautmann, C.; Tramontina, D.; Bringa, E.M.; Grande, P.L.; Confinement Effects of Ion Tracks in Ultrathin Polymer Films, PHYSICAL REVIEW LETTERS 114 (2015) 18302
[31] Alencar, I.; Haussuhl, E.; Winkler, B.; Trautmann, C.; Schuster, B.; Severin, D.; In situ Resonant Ultrasound Spectroscopy during
irradiation of solids with relativistic heavy ions, ACTA
MATERIALIA 89 (2015) 60-72
[32] Lang, M.; Devanathan, R.; Toulemonde, M.; Trautmann, C.; Advances in understanding of swift heavy-ion tracks in complex ceramics, CURRENT OPINION IN SOLID STATE & MATERIALS SCIENCE 19 (2015) 39-48
[33] Schubert, I.; Sigle, W.; van Aken, P.A.; Trautmann, C.; Toimil
Molares, M.E.; STEM-EELS analysis of multipole surface plasmon modes in symmetry-broken AuAg nanowire dimers, NANOSCALE 7 (2015) 4935-4941
[34] Tracy, C.L., Lang, M., Pray, J.M.; Zhang, FX; Popov, D., Park, C.Y., Trautmann, Bender, M.; Severin, D.; Skuratov, V.A.; Ewing, R.C.; Redox response of actinide materials to highly ionizing radiation, NATURE COMMUNICATIONS 6 (2015) 6133
Joint Research
Laboratory
Nanomaterials
Staff Members
Head
Prof. Dr. Ing.-Horst Hahn
(Director Institute for
Nanotechnology)
Research Asscoiates
Dr. Oliver Clemens
Dr.-Ing. Ruzica Djenadic
Secretaries
Renate Hernichel
PhD Students
Dipl.-Ing. Christoph Loho
Dipl.-Ing. Miriam Botros
Dipl.-Ing Alexander Benes
Cahit Benel, M.Sc.
M. Nazarian-Samani, M.Sc.
Dipl.-Ing. Falk von Seggern
Dipl.-Ing. Mohsen Pouryazdan
Felix Joachim Neuper, M.Sc.
Wang Wu, M.Sc.
Serpil Tekoglu, M.Sc.
Sree Harsha Nandam, M.Sc.
Dipl.-Phys. Sebastian Becker
Dipl.-Ing. Ralf Witte
Alan Molinari, M.Sc.
Ankush Kashiwar, M.Sc.
Krishna Kanth, M.Sc.
Dipl.-Phys. Nicolas Gack
Geethu Balachandran, M.Sc.
Dipl.-Ing.Chem. T. T. D.
Nguyen
Murat Yavuz, M.Sc.
Dipl.-Ing Ira Balaj
Dipl.-Phys. Tom Braun
Mohammad Fawey, M.Sc.
Garlapati Suresh Kumar,
M.Sc.
Bachelor Students
Marcel Sadowski
Patrick Louis Knöchel
Master Students
Geoffrey Matthew Tan
84 | Joint Research laboratory nanomaterials
Joint Research Laboratory Nanomaterials
The Joint Research Laboratory Nanomaterials
was established in 2004 as a joint project between the Institute for Materials Science (Technical University Darmstadt) and the Institute of
Nanotechnology (INT) at the Karlsruhe Institute
of Technology (KIT). Its research focusses on the
synthesis and characterisation of nanoparticles,
nanoparticulate layers, nanoporous as well as
dense nanoscale materials. Special interest lies
in the determination of correlations between
synthesis, interface and bulk properties and the
macroscopic functional and structural properties.
An important building block is the understanding
of the surface, grain boundary and size effects
on the physical material properties, which can be
significantly different from classical crystalline
bulk materials. For the last few years, the research
has focused on energy materials for batteries and
fuel cells. In addition, (reversible) topochemical
reactions (chemical and electrochemical) are
under investigation, allowing for the tuning of
material properties.
The materials of interest (nano- and microcrystalline powders) are produced by a variety of
techniques, ranging from gas phase processes
(chemical vapour synthesis, CVS) and aerosol
based techniques (nebulized spray pyrolysis,
NSP) to solid-state reactions (SSR). Additionally, a variety of techniques are available for
the preparation of thin films: spin coating and
different modifications of the chemical vapour
deposition processes (CVD).
A multitude of methods is available and
in constant use for the characterisation of the
as-synthesized powders and thin-films as
well as their properties, among them X-ray
powder diffraction, low-temperature nitrogen
adsorption, dynamic light scattering, low and
high temperature impedance spectroscopy and
cyclic voltammetry.
Joint Research laboratory nanomaterials | 85
Advances in Solid Electrolytes for Lithium Ion Batteries and
on the Investigation of Proton Conductivity in a Cathode Material
for Solid Oxide Fuel Cells
Miriam Botros, Ruzica Djenadic, Patrick L. Knöchel, Christoph Loho, Oliver Clemens, Horst Hahn
Lithium-ion batteries are the fastest growing
and widely used type of batteries. Most of today
electronic devices use batteries containing liquid
electrolyte facing safety issues (e.g. dendrite
growth, leakage, and flammability). Therefore, development of a Li-ion conducting solid
electrolyte is a main focus of current battery
research, which potentially will lead to a safer
all-solid-state battery. Additionally to the safety
improvements, solid electrolytes offer stability
over a broad electrochemical potential as well as
a large temperature range, potentially allowing
for the use of high voltage cathode materials.
There are already several solid electrolyte materials with Li-ion conductivities equal or higher
than liquid electrolytes, however, these materials
are not stable over a wide potential range. The
main challenge is to produce a material, which
will combine all of the mentioned properties.
Among those materials, Li7-3xAlxLa3Zr2O12
has proved to be a promising candidate as solid
electrolyte for all solid state lithium ion batteries.
In a preliminary report1 we have already shown
that the material can be prepared by means of
nebulized spray pyrolysis (NSP) followed by
short sintering times. Latest research2 has now
shown that as prepared powder from the NSP
process can serve as a precursor for preparing
highly dense pellets by applying a field assisted
sintering technique (FAST) (see Figure 1a-d).
Comparing blocking Au-electrodes to non-blocking Li-electrodes allows for the determination
of area specific resistances, which are of crucial
importance for understanding the interface behavior between the electrolyte with the lithium
anode (see Figure 1e).
Solid Oxide Fuel Cells (SOFCs) can be used to
transform chemical energy stored in hydrogen
(and carbohydrates) into electrochemical energy.
In this respect, electrolytes used for separation
membranes can work on the principle of either
oxide ion or proton conduction. For the latter,
this will also imply that protons can be conducted within the electrode materials. Perovskite
compounds containing transition metal cations
(e. g. Fe, Co) are promising candidates for the
use as cathode materials within SOFCs. These
materials are known to exhibit mixed electron
and oxygen ion conductivity. In contrast,
proton conduction has not yet been reported for
those compounds, requiring the preparation of
composite cathodes with the addition of proton
conducting electrolyte (e. g. BaZr1-xYxO3-x/2) for
SOFC cells based on proton conduction.
Recent findings showed that perovskite
type barium ferrite BaFeO2.5 can be hydrated
to form compounds with compositions
BaFeO2.5x(OH)2x (2x ~ 1/3 (LW-BaFeO25 and
2x ~ 0.5 (HWBaFeO2.5) 3, with LWBaFeO2.5 showing vacancy order with high structural similarity to
BaFeO2.333F0.333 4 (see Figure 2a). Due to the high
stability of iron in a single valent +3 oxidation
state for those compounds, we succeeded to study
the proton conductivity in a broad range around
ambient temperature with reasonable values in
the range10 -6 to 10 -7 S cm-1 at RT. We also showed
that the materials possess increased conductivity compared to pure BaFeO2.5 by at least two
orders of magnitudes (see Figure 2b). Conductivities have been further compared to oxidized
BaFeO2.5+δ, where the oxidized form showed to
be a reasonable electron conductor(σ ~ 10 -2 –
10 -3 S cm-1) due to the presence of mixed valent
Fe3+ and Fe4+.
Figure 1. SEM micrographs
of as-synthesized powder (a),
annealed powder (b) and sintered
ceramic (c). (d) Temperature
dependent AC-impedance spectra
of Li7-3xLa3Zr2AlxO12 ceramics
with x = 0.17 with blocking (Au).
(a)
Figure 2. (a) Structure excerpt of LW-BaFeO2.5 at 4 K. The weak bond
between the strongly shifted oxygen ion to the Fe ion is shown as a
dashed red line, the shortened bond to a Ba ion is shown as a green
line. The position of the vacancies along the cubic [1 1 0]cub direction
is indicated by black crosses. Strong shifts of Fe and Ba ions are
shown as green and orange arrows.
(b)
(b) NYQUIST plots of impedance data recorded for BaFeO2.5 and LW-BaFeO2.5
at a temperature of 350 K. For LW-BaFeO2.5 a decrease of conductivity is found
on cooling the pellet after heating to 400 K.
References 1. Djenadic, R.; Botros, M.;
Benel, C.; Clemens, O.; Indris,
S.; Choudhary, A.; Bergfeldt,
T.; Hahn, H., Nebulized spray
pyrolysis of Al-doped
Li7La3Zr2O12 solid electrolyte for
battery applications. Solid State
Ionics 2014, 263, 49-56.
2. Botros, M.; Djenadic, R.;
Clemens, O.; Möller, M.; Hahn,
H., Field Assisted Sintering of
fine-grained Li7-3xLa3Zr2AlxO12
and the Influence of the Microstructure on the electrochemical
performance in contact with
Li-metal. J. Power Sources 2016,
309, 108-115.
3. Knöchel, P. L.; Keenan, P. J.;
Loho, C.; Reitz, C.; Witte, R.;
Knight, K. S.; Wright, A. J.;
Hahn, H.; Slater, P. R.;
Clemens, O., Synthesis,
structural characterisation and
proton conduction of two new
hydrated phases of barium
ferrite BaFeO2.5-x(OH)2x.
J. Mater. Chem. A 2016,
accepted.
4. Clemens, O., Structural
characterization of a new
vacancy ordered perovskite
modification found for
Ba3Fe3O7F (BaFeO2.333F 0.333):
Towards understanding of
vacancy ordering for different
perovskite-type ferrites. J.
Solid State Chem. 2015, 225,
261-270.
Research Projects
•
•
Emmy-Noether-Programm, Topochemische Fluorierung im Anwendungsfeld interkalationsbasierter Fluorid-Ionen-Batterien, maßgeschneiderter Eigenschaften sowie der Modifizierung dünner Filme (DFG CL551/2-1, 2015-2020)
Durchstimmbarer Magnetismus in massiven Ferromagneten durch reversiblen Einbau von Ionen (DFG HA 1344/34-1, 2015-2018)
• DAAD Forschungsstipendien, 91566936 und 91559414
• Helmholtz Portfolio, Elektrochemische Speicher im System –
Zuverlässigkeit und Integration (325/20514659/NANOMIKRO,
2012-2015)
• Förderung durch Mittel des Helmholtz Instituts Ulm (2010-2018)
Publications
[1]
Baby, T. T.; Garlapati, S. K.; Dehm, S.; Haeming, M.; Kruk, R.; Hahn, H.; Dasgupta, S., A General Route toward Complete Room Temperature Processing of Printed and High Performance Oxide Electronics. ACS Nano 2015, 9, (3), 3075-3083, http://dx.doi.org/10.1021/nn507326z
[2] Chen, N.; Wang, D.; Feng, T.; Kruk, R.; Yao, K.-F.; Louzguine
Luzgin, D. V.; Hahn, H.; Gleiter, H., A nanoglass alloying immiscible Fe and Cu at the nanoscale. Nanoscale 2015, 7, (15), 6607-6611,
http://dx.doi.org/10.1039/c5nr01406a
[3]
Chen, R.; Knapp, M.; Yavuz, M.; Ren, S.; Witte, R.; Heinzmann, R.; Hahn, H.; Ehrenberg, H.; Indris, S., Nanoscale spinel LiFeTiO4 for intercalation pseudocapacitive Li* storage. Phys. Chem. Chem. Phys. 2015, 17, (2), 1482-1488, http://dx.doi.org/10.1039/c4cp04655b
[4]
Chen, R.; Ren, S.; Knapp, M.; Wang, D.; Witter, R.; Fichtner, M.; Hahn, H., Disordered Lithium-Rich Oxyfluoride as a Stable Host for Enhanced Li* Intercalation Storage. Advanced Energy Materials 2015, 5, (9), http://dx.doi.org/10.1002/aenm.201401814
[5]
Chen, R.; Ren, S.; Yavuz, M.; Guda, A. A.; Shapovalov, V.; Witter, R.; Fichtner, M.; Hahn, H., Li* intercalation in isostructural Li2VO3 and Li2VO2F with O2- and mixed O2-/F- anions. Phys. Chem. Chem. Phys. 2015, 17, (26), 17288-17295, http://dx.doi.org/10.1039/c5cp02505b
[6] Clemens, O., Structural characterization of a new vacancy ordered perovskite modification found for Ba3Fe3O7F (BaFeO2.333F0.333): Towards understanding of vacancy ordering for different pero-
vskite-type ferrites. J. Solid State Chem. 2015, 225, 261-270,
http://dx.doi.org/10.1016/j.jssc.2014.12.027
[7] Clemens, O.; Berry, F. J.; Wright, A. J.; Knight, K. S.; Perez-Mato, J. M.; Igartua, J. M.; Slater, P. R., Reply to “Structural and magnetic behavior of the cubic oxyfluoride SrFeO2F studied by neutron
diffraction”. J. Solid State Chem. 2015, 226, 326-331,
http://dx.doi.org/10.1016/j.jssc.2015.02.022
[8] Fischer, A.; Kruk, R.; Hahn, H., A versatile apparatus for the
fine-tuned synthesis of cluster-based materials. Rev. Sci. Instrum. 2015, 86, (2), http://dx.doi.org/10.1063/1.4908166
[9] Fischer, A.; Kruk, R.; Wang, D.; Hahn, H., Magnetic properties of iron
cluster/chromium matrix nanocomposites. Beilstein Journal of Nano
technology 2015, 6, 1158-1163, http://dx.doi.org/10.3762/bjnano.6.117
Publications
[10]
Garlapati, S. K.; Baby, T. T.; Dehm, S.; Hammad, M.;
Chakravadhanula, V. S. K.; Kruk, R.; Hahn, H.; Dasgupta, S.,
Ink-Jet Printed CMOS Electronics from Oxide Semiconductors. Small 2015, 11, (29), 3591-3596, http://dx.doi.org/10.1002/smll.201403288
[11] Ghafari, M.; Sakurai, Y.; Peng, G.; Fang, Y. N.; Feng, T.; Hahn,
H.; Gleiter, H.; Itou, M.; Kamali, S., Unexpected magnetic behavior in amorphous Co90Sc10 alloy. Appl. Phys. Lett. 2015, 107, (13),
http://dx.doi.org/10.1063/1.4932113
[12] Howard, M. A.; Clemens, O.; Slater, P. R.; Anderson, P. A., Hydrogen absorption and lithium ion conductivity in Li6NBr3. J. Alloys Compd. 2015, 645, S174-S177, http://dx.doi.org/10.1016/j.jallcom.2015.01.082
[3]
Kamali, S.; Kilmametov, A.; Ghafari, M.; Itou, M.; Hahn, H.; Sakurai, Y., Controlling spin polarized band-structure by variation of vacancy intensity in nanostructures. Journal of Physics-Condensed Matter 2015, 27, (7), http://dx.doi.org/10.1088/0953-8984/27/7/075304
[14] Kobler, A.; Beuth, T.; Kloeffel, T.; Prang, R.; Moosmann, M.; Seherer,
T.; Walheim, S.; Hahn, H.; Kuebel, C.; Meyer, B.; Schimmel, T.;
Bitzek, E., Nanotwinned silver nanowires: Structure and mechanical properties. Acta Mater. 2015, 92, 299-308,
http://dx.doi.org/10.1016/j.actamat.2015.02.041
[15] Kobler, A.; Hodge, A. M.; Hahn, H.; Kuebel, C., Orientation dependent fracture behavior of nanotwinned copper. Appl. Phys. Lett. 2015, 106, (26), http://dx.doi.org/10.1063/1.4923398
[16] Mojic-Lante, B.; Djenadic, R.; Chakravadhanula, V. S. K.; Kuebel, C.; Srdic, V. V.; Hahn, H., Chemical Vapor Synthesis of FeOx-BaTiO3 Nanocomposites. J. Am. Ceram. Soc. 2015, 98, (6), 1724-1730,
http://dx.doi.org/10.1111/jace.13531
[17] Stijepovic, I.; Djenadic, R.; Srdic, V. V.; Winterer, M., Chemical vapour synthesis of lanthanum gallium oxide nanoparticles. J. Eur. Ceram. Soc. 2015, 35, (13), 3545-3552,
http://dx.doi.org/10.1016/j.jeurceramsoc.2015.05.020
[18] Chen, R.; Knapp, M.; Yavuz, M.; Heinzmann, R.; Wang, D.; Ren, S.; Trouillet, V.; Lebedkin, S.; Doyle, S.; Hahn, H.; Ehrenberg, H.; Indris, S., Reversible Li* Storage in a LiMnTiO4 Spinel and Its Structural Transition Mechanisms. J. Phys. Chem. C 2014, 118, (24), 12608-12616, http://dx.doi.org/10.1021/jp501618n
Publications
[19]
Dasgupta, S.; Wang, D.; Kuebel, C.; Hahn, H.; Baumann, T. F.;
Biener, J., Dynamic Control Over Electronic Transport in 3D Bulk Nanographene via Interfacial Charging. Adv. Funct. Mater. 2014, 24, (23), 3494-3500, http://dx.doi.org/10.1002/adfm.201303534
[20] Ekiz, E. H.; Lach, T. G.; Averback, R. S.; Mara, N. A.; Beyerlein, I. J.; Pouryazdan, M.; Hahn, H.; Bellon, P., Microstructural evolution of nanolayered Cu-Nb composites subjected to high pressure torsion (vol 72, pg 178, 2014). Acta Mater. 2014, 81, 528-528,
[21] Ekiz, E. H.; Lach, T. G.; Averback, R. S.; Mara, N. A.; Beyerlein,
I. J.; Pouryazdan, M.; Hahn, H.; Bellon, P., Microstructural evolution of nanolayered Cu-Nb composites subjected to high-pressure torsion. Acta Mater. 2014, 72, 178-191,
[22] Franke, O.; Leisen, D.; Gleiter, H.; Hahn, H., Thermal and plastic behavior of nanoglasses. J. Mater. Res. 2014, 29, (10), 1210-1216,
http://dx.doi.org/10.1557/jmr.2014.101
[23] Lohmiller, J.; Grewer, M.; Braun, C.; Kobler, A.; Kuebel, C.;
Schueler, K.; Honkimaeki, V.; Hahn, H.; Kraft, O.; Birringer, R.; Gruber, P. A., Untangling dislocation and grain boundary mediated plasticity in nanocrystalline nickel. Acta Mater. 2014, 65, 295-307, http://dx.doi.org/10.1016/j.actamat.2013.10.071
[24] Padmanabhan, K. A.; Sripathi, S.; Hahn, H.; Gleiter, H., Inverse Hall-Petch effect in quasi- and nanocrystalline materials. Mater. Lett. 2014, 133, 151-154, http://dx.doi.org/10.1016/j.matlet.2014.06.153
[25]
Ren, F.; Arshad, S. N.; Bellon, P.; Averback, R. S.; Pouryazdan, M.; Hahn, H., Sliding wear-induced chemical nanolayering in Cu-Ag,
and its implications for high wear resistance. Acta Mater. 2014, 72,
148-158, http://dx.doi.org/10.1016/j.actamat.2014.03.060
[26] Zhong, S.; Koch, T.; Walheim, S.; Roesner, H.; Nold, E.; Kobler, A.; Scherer, T.; Wang, D.; Kuebel, C.; Wang, M.; Hahn, H.; Schimmel, T.,
Self-organization of mesoscopic silver wires by electrochemical deposition. Beilstein Journal of Nanotechnology 2014, 5, 1285-1290, http://dx.doi.org/10.3762/bjnano.5.142
92 | Material Analysis
Material Analysis
Staff Members
Head
Prof. Dr. Wolfgang Ensinger
Research Associates
Dr. Mubarak Ali
Dr. Stefan Flege
Dr. Ruriko Hatada
Dr. Peter Hoffmann
Dr. Falk Münch
Technical Personnel
Renate Benz
Brunhilde Thybusch
PhD Students
Markus Antoni
Eva-Maria Felix
Martin Hottes
Renuka Krishnakumar
Stephan Lederer
Alice Lieberwirth
Vincent Lima
Sandra Schäfer
Torsten Walbert
Simon Wallenborn
Master Students
Svenja Heise
Sven Milla
Marcel Jost
Silke Wursthorn
Tobias Stohr
Guest Scientists
Xin Zhao
Material Analysis | 93
Materials Analysis Group
The Materials Analysis group participates in two
of the six Research Profile areas of the Technische Universität Darmstadt: From Material to
Product Innovation and Matter and Radiation
Science. On the one hand the group is concerned
with the characterization of self-synthesized
modern materials, on the other hand with effects
on materials caused by exposition to detrimental
influences like ion irradiation. The research
aims for clarification of the correlation of
materials properties and synthesis or exposition
parameters, respectively, by investigation of the
elemental composition and the chemical binding.
Current research topics are:
Advanced 3-D Nanoobjects: Nanochannels,
-wires, -tubes, and –networks: In collaboration
with the GSI Helmholtz Centre for Heavy Ion
Research, nanoporous membranes are formed by
ion irradiation of polymer foils producing latent
ion damage tracks which are chemically etched
to nanochannels. These ion track (nano) filters
can be used for filtering particles from liquids,
collecting aerosols, for gas separation, and for
analyzing small (bio)molecules. In the latter case,
the nanochannel walls are chemically modified
so that the nanochannel sensor becomes sensitive
and selective to certain molecular species. Apart
from polymer-based nanochannels, anodically
oxidized aluminium (AAO) is used. Filling the
polymer or AAO nanochannels galvanically with
metals, such as copper, gold or platinum, and
dissolving the templates, nanowires are formed.
Here, different metal deposition conditions are
used in order to obtain monometal but also multimetal (e.g. CuCo- and CuFe) nanowires.
By redox-chemical reactions, the nanochannel
walls can be coated with metal or metal oxide
films, such as Ni, Cu, Ag, Au, Pt, Pd, and ZnO,
SnO2, TiO2, In2O3, FexOy. Thus, nanotubes
can be formed. Here, different morphologies
are available, ranging from smooth compact
nanotube walls to nanoporous walls to rough or
peaked structures.
When the nanochannels are crossed, the
resulting nanowires are interconnected, forming
nanowire networks. Dimensions, surface topography, microstructure, and crystallinity of these
nanostructures are investigated. Macroscopic
properties such as thermal stability, electrical
conductivity and catalytic activity are analysed.
Additionally, the obtained properties are
evaluated with respect to applications as sensors,
for gas flow or acceleration measurements, catalysts, for chemical reactions in microreactors, or
electrodes in fuel cells.
Thin film and coating deposition and analysis: In thin film and coating technology, the
identification of chemical compounds, phases
and binding conditions is of basic importance.
Surface modifications and layer deposition
are performed via a plasma process. With plasma
immersion ion implantation (PIII) it is possible
to alter several surface properties by ion implantation. Different gaseous species are used such
as oxygen, nitrogen and hydrocarbons, depending on the property to be modified, e.g. hardness,
wear resistance, lifetime and biocompatibility.
Using hydrocarbon gases films of diamond-like
carbon (DLC) are deposited. Research topics
are the adhesion of the DLC films to different
substrates and the influence of the addition of
different elements, especially metals, to the DLC
films.
Materials Analysis Group
The films are investigated for their chemical and
phase composition, microstructure, adhesion, and
in relation to biological applications, tribological
properties, corrosion and wear protection of
metal substrates, wettability, and temperature
stability.
Since the PIII technique is also suitable for complex shaped substrates, the treated substrates also
include samples such as tubes, where the focus in
on the treatment of their inner surfaces.
Materials in radiation fields: Irradiation of
materials with energetic particles (protons, heavy
ions) and electromagnetic radiation (X-rays,
gamma-rays) may lead to degradation of the materials’ properties. This happens to components
in space vehicles, in nuclear facilities and in
particle accelerators. Polymers with their covalent bonds are particularly sensitive towards
ionizing radiation.
Polyimide, vinyl polymers and fiber-reinforced polyepoxides, which are components of
superconducting beam guiding magnets at the
future FAIR synchrotron and storage rings, oxides such as alumina which are used as beam-diagnostic scintillator screens, and semiconductor
components such as CCDs are irradiated and
characterized for their properties, such as polymeric network degradation, mechanical strength,
electrical resistance, dielectric strength, and
optical properties. Apart from basic questions on
material’s degradation mechanisms by energetic
radiation, the investigations are used to estimate
service life-times of the materials/components.
Green Electroless Plating of Palladium Nanotubes
Eva-Maria Felix and Wolfgang Ensinger
The traditional and well-established synthesis
method of electroless plating is a remarkably
simple and versatile technique for generating
high-aspect ratio metal nanotubes in combination
with polymer nanopore templates.1 In this technique toxic chemicals, such as cyanide as ligands
and hydrazine or sodium borohydride as reducing
agents, are often used.2
Since environmental and health issues gain
more and more attention, the combination of
nanotechnology and Green Chemistry offers new
opportunities to avoid harmful substances in the
synthesis of nanostructures. The 12 Principles
of Green Chemistry3 can be seen as guidelines
to remodel the old established synthesis routes
or to create new synthesis methods based on
environmentally harmless chemicals and procedures. Several studies proved that it is possible
to synthesize metal nanoparticles by using plant
extracts or biological compounds.4
Our studies demonstrated that the principles
cannot only be adopted to metal nanoparticle
synthesis. We modified the traditional method by
exchanging the toxic chemicals by non hazardous
substances.1,5 The replacements lead to sustainable plating solutions for the synthesis of welldefined palladium nanotubes (fig. 1).
Additionally, ICP-OES and XPS characterisations prove that those soft chemicals can lead a
nearly complete conversion of the metal source.
In order to illustrate that green synthesized
nanomaterials can be compared with conventionally prepared catalysts, the Pd nanotubes
were tested in a model reaction to determine
their catalytic activity. The reduction of
4-nitrophenol to 4-aminophenol by NaBH4 can
be followed by UV-Vis spectroscopy. The reaction has been used to test nanostructured catalysts and to determine their catalytic activities.
The catalysts realise a high conversion (fig. 2).
The reaction constant, which can be
obtained from the plot of ln(a/a0) versus time, is
6.0 ∙ 10 -2 s-1. 5
By choosing the facile synthesis method of
electroless plating in combination with the 12
Principles of Green Chemistry metal nanotubes
can be synthesised. It demonstrates that it is possible to exchange hazardous chemicals by safe
chemicals. The structures are an alternative to
other metallic nanostructures such as particles.
References
[1] E.-M. Felix, F. Muench,
W. Ensinger, RSC Advances, 4,
(2014) 24504-24510.
[2] C. R. K. Rao, D. C. Trivedi,
Coord. Chem. Rev. 249 (2005)
613-631.
[3] P. Anastas, N. Eghabli, Chem.
Soc. Rev., 39 (2010) 301-312.
[4] S. Iravani, Green Chem., 13
(2011) 2638-2650.
[5] E.-M. Felix, M. Antoni, I. Pause,
S. Schaefer, U. Kunz, N. Weidler,
F. Muench, W. Ensinger, Green
Chemistry, (2015) DOI:10.1039/
c5gc0135
Figure 1: SEM images of palladium nanotubes obtained by green electroless plating.
Figure 2: (A) UV-Vis spectrum of the decrease of 4-NP at 400 nm by using the Pd catalyst.
(B) Plot of ln(a/a0) versus tome for the reduction of 4-NP over the Pd NT catalyst.
Research Projects
•
Beam diagnosis and radiation damage diagnosis – Scintillator
materials for high current diagnosis (BMBF/GSI 2012–2015)
•
Beam diagnosis and radiation damage diagnosis – radiation damage
of accelerator components made out of plastics and countermeasures (BMBF/GSI 2012-2015)
• Preparation of rare earth free nano rods (LOEWE Response, 2014-2016)
• 1D based sensors for gases and magnetic fields 1D-SENSE (BMBF, 2014-2016)
•
MIT-Nano (DFG, 2015 – 2018)
•
Initiation and enhancement of bilateral cooperation on influence of nanostructured surfaces on cell growth (DFG, 2015 – 2016)
Publications
[1]
Sowa, K. Drogowska, L. Havela, A.G. Balogh
Hydrogen storage in Ti, V and their oxides-based thin films
Advances in Natural Sciences: Nanoscience and Nanotechnology 6, 013002, 2015
[2] I. Dirba, M.B. Yazdi, A. Radetinac, P. Komissinskiy, S. Flege,
O. Gutfleisch, L. Alff
Growth, structure, and magnetic properties of γ´-Fe4N thin films
Journal of Magnetism and Magnetic Materials 379, 151-155, 2015
[3] M. Hottes, F. Dassinger, F. Muench, M. Rauber, C. Stegmann, H. F. Schlaak, W. Ensinger
Patterned arrays of capped platinum nanowires with quasi-elastic mechanical response to lateral force
Applied Physics Letters 106, 053109, 2015
[4] M. Ali, S. Nasir, W. Ensinger
Bioconjugation-induced ionic current rectification in aptamermodified single cylindrical nanopores
Chemical Communications 51, 3454-3457, 2015
[5] M. Kompaniiets, O. V. Dobrovolskiy, C. Neetzel, W. Ensinger, M. Huth
Superconducting Proximity Effect in Crystalline Co and Cu
Nanowires Journal of Superconductivity and Novel Magnetism 28, 431-436, 2015
Publications
[6] V. Gomez, P. Ramirez, J. Cervera, S. Nasir, M. Ali, W. Ensinger,
S. Mafe
Converting external potential fluctuations into nonzero time-average electric currents using a single nanopore
Applied Physics Letters 106, 073701, 2015
[7] P. Hoffmann, M. Kosinova, S. Flege, J. Brötz, V. Trunova, C. Dietz,
W. Ensinger
Chemical and physical properties in layers and interfaces of nanolayered Si(100)/Ni/BCxNy stacks
X-Ray Spectrometry 44, 48-53, 2015
[8] M. Pavlovic, M. Miglierini, E. Mustafin, W. Ensinger, A. Šagátová,
M. Šoka
Radiation damage studies of soft magnetic metallic glasses irradiated with high-energy heavy ions
Radiation Effects and Defects in Solids 170, 1-6, 2015
[9] C. Neetzel, F. Muench, T. Matsutani, J.C. Jaud, J. Broetz, T. Ohgai,
W. Ensinger
Facile wet-chemical synthesis of differently shaped cuprous oxide particles and a thin film: Effect of catalyst morphology on the glucose sensing performance
Sensors and Actuators B: Chemical 214, 189-196, 2015
[10] V. Gomez, P. Ramirez, J. Cervera, S. Nasir, M. Ali, W. Ensinger,
S. Mafe
Charging a Capacitor from an External Fluctuating Potential using a Single Conical Nanopore
Scientific Reports 5, 9501, 2015
[11] U.H. Hossain, W. Ensinger
Decomposition and CO2 evolution of an aliphatic polymer under bombardment with high energy heavy ions
Polymer Degradation and Stability 119, 132-138, 2015
P. Hoffmann
Jens-Volker Kratz and Karl Heinrich Lieser: Nuclear and radio
chemistry. Fundamentals and applications, 3rd ed.
Analytical and Bioanalytical Chemistry 407, 5241-5242, 2015
[12] Surface Oxidation and Fast 18O Implant Diffusion in Nanostructured Layers of Ti-6Al-4V Alloy
S.M. Duvanov, A.G. Balogh
Journal of Nano- and Electronic Physics 7, 02028, 2015
Publications
[13] High-temperature scintillation of alumina under 32 MeV 63Cu5+ heavy-ion irradiation
S. Lederer, S. Akhmadaliev, J. von Borany, E. Gütlich, A. Lieberwirth, J. Zimmermann, W. Ensinger
Nuclear Instruments and Methods in Physics Research B 359, 161-166, 2015
[14] F. Muench, D. M. De Carolis, E.-M. Felix, J. Brötz, U. Kunz,
H.-J. Kleebe, S. Ayata, C. Trautmann, W. Ensinger
Self-Supporting Metal Nanotube Networks Obtained by Highly Conformal Electroless Plating
ChemPlusChem 80, 1448-1456, 2015
[15] S. Schaefer, F. Muench, E. Mankel, A. Fuchs, J. Brötz, U. Kunz,
W. Ensinger
Double-Walled Ag–Pt Nanotubes Fabricated by Galvanic
Replacement and Dealloying: Effect of Composition on the
Methanol Oxidation Activity
Nano 10, 1550085, 2015
[16] P. Ramirez, V. Gomez, J. Cervera, S. Nasir, M. Ali, W. Ensinger,
S. Mafe
Energy conversion from external fluctuating signals based on a
symmetric nanopores
Nano Energy 16, 375-382, 2015
[17] F. Muench, B. Juretzka, S. Narayan, A. Radetinac, S. Flege,
S. Schaefer, R. W. Stark, W. Ensinger
Nano- and microstructured silver films synthesised by halide
assisted electroless plating
New Journal of Chemistry 39, 6803-6812, 2015
[18] M. Ali, I. Ahmed, S. Nasir, P. Ramirez, C.M. Niemeyer, S. Mafe,
W. Ensinger
Ionic Transport through Chemically Functionalized Hydrogen
Peroxide-Sensitive Asymmetric Nanopores
ACS Applied Materials & Interfaces 7, 19541–19545, 2015
[19] F. Muench, M. Oezaslan, I. Svoboda, W. Ensinger
Electroless plating of ultrathin palladium films: self-initiated
deposition and application in microreactor fabrication
Materials Research Express 10, 105010, 2015
Publications
[20] M. Boehme, W. Ensinger
Developing Sensors based on TiO2 Nanotubes to Detect Explosives
in: Terri Camesano (ed.), NATO Science for Peace and Security Series A: Chemistry and Biology: Nanotechnology to Aid Chemical and Biological Defence, Springer 2015, ISBN 978-94-017-7217-4, p. 113-128
[21] S.M. Duvanov, A.V. Kabyshev, A.G. Balogh
in: Interaction of radiation with solids, Belarusian State University 2015, ISBN 978-985-553-304-8, pp. 217-219
[22] Q.H. Nguyen, M. Ali, S. Nasir, W. Ensinger
Transport properties of track-etched membranes having variable effective pore-lengths
Nanotechnology 26, 485502, 2015
[23] Z. Tarnawski, K. Zakrzewska, N.-T.H. Kim-Ngan, M. Krupska, S. Sowa, K. Drogowska, L. Havela, A.G. Balogh
Study of Ti, V and Their Oxides-Based Thin Films in the Search for Hydrogen Storage Materials
Acta Physica Polonica A 128, 431-440, 2015
[24] S. Flege, R. Hatada, M. Hoefling, A. Hanauer, A. Abel, K. Baba, W. Ensinger
Modification of diamond-like carbon films by nitrogen
incorporation via plasma immersion ion implantation
Nuclear Instruments and Methods in Physics Research B 365, Part A, 357-361, 2015
[25] U.H. Hossain, W. Ensinger
Experimental simulation of radiation damage of polymers in space applications by cosmic-ray-type high energy heavy ions and the resulting changes in optical properties
Nuclear Instruments and Methods in Physics Research B 365, Part A, 230-234, 2015
Publications
[26] A. Lieberwirth, W. Ensinger, P. Forck, S. Lederer
Response from inorganic scintillation screens induced by high
energetic ions
Nuclear Instruments and Methods in Physics Research B 365, Part B, 533-539, 2015
[27] S. Lederer, S. Akhmadaliev, P. Forck, E. Gütlich, A. Lieberwirth,
W. Ensinger
Thermal annealing behavior of α-Al2O3 scintillation screens
Nuclear Instruments and Methods in Physics Research B 365, Part B, 548-552, 2015
[28] F. Dassinger, H. F. Schlaak, M. Hottes, W. Ensinger
Mechanische Charakterisierung von metallischen
1D-Nanostrukturen
in: MikroSystemTechnik Kongress 2015, VDE/VDI-Gesellschaft Mikroelektronik, Mikrosystem- und Feinwerktechnik (GMM) (Ed.), 2015, ISBN 978-3-8007-4100-7
Materials Modelling
Staff Members
Head
Prof. Dr. Karsten Albe
Retired Professors
Prof. Dr. Hermann Rauh
M.A., C.Phys., F.Inst.P., F.I.M.
Secretaries
Renate Hernichel
Gabriele Rühl
Administrative Personnel
Robert Heitzmann
Research Associates
Dr. Yuri Genenko, PD
Dr. Alexander Stukowski
Dr. Jochen Rohrer
Dr. Omar Adjaoud
Dr. Sabrina Sicolo
PhD Students
Kai-Christian Meyer, M. Sc.
Dipl.-Ing. Tobias Brink
Olena Lenchuk, M. Sc.
Daniel Barragan-Yani, M. Sc.
Constanze Kalcher, M. Sc.
Markus Mock, M. Sc.
Master Students
Leonie Koch
Bachelor Students
Delwin Indigo Perera
Guest Scientists
Ashkan Moradabadi, M. Sc.
FU Berlin
104 | Materials Modelling
Materials Modelling
The research of the Materials Modelling Division
is focused on multi-scale modelling of defect
structures in functional oxides, energy materials, nanostructured metals and glasses. 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 HPC-computers and has access
to the Hessian High Performance Computers in
Frankfurt and Darmstadt.
The current research topics are:
•
Energy materials
• Interfaces in Li-intercalation
batteries
• Si-based anodes for intercalation batteries
• Dislocations in CIS/CIGS
absorber materials
• Creep resistant alloys
(Mo-Si-B)
•
Functional oxides
• Lead free relaxor materials
for electrocalorics
• Polarization dynamics in
ferroelectricy
• Theory of superconducting
materials
• Ionic conductivity of
(Na0.5Bi0.5)TiO3
•
Mechanical properties of nanostructured
metals and glasses
• Plasticity of metallic glasses
with secondary phases
• Structure and properties
of nanoglasses
• Creep resistant SiOC-based
glasses
• Mechanical of ODS steels
Within the Bachelor program the Materials
Modelling Division is offering classes on thermodynamics and kinetics as well as defects in
materials and programming techniques. In the
master program we are teaching lectures on theoretical materials science, lab classes on simulation
methods and several elective courses.
Materials Modelling | 105
Atomistic Computer Simulations of Amorphization in
Metal/Metallic-Glass Multilayer Systems
Tobias Brink, Daniel Şopu, Karsten Albe
Metals show a strong tendency to form crystalline, i.e., ordered phases. For unalloyed metals,
the thermodynamically stable phase is always
crystalline. Amorphous metal samples can be
synthesized by “freezing” them in the disordered
state. This can be achieved for example by employing high cooling rates or depositing atoms
with high energies or velocities. The resulting
amorphous state is metastable. This metastable
state can be made more favorable, although not
stable, by alloying. This material is then called a
metallic glass. Apart from these amorphization
processes driven by kinetic reasons, there are a
few circumstances in which metals amorphize for
energetic reasons. A well-known example is the
interface between two different crystal phases:
The order of the two phases is incompatible,
making a sharp interface of two adjacent crystals
energetically very unfavorable. The interface
becomes disordered in a process called solid
state amorphization (SSA). These examples are
illustrated in Figure 1.
Due to their rarity, amorphous metals are
interesting phases from a theoretical standpoint,
and may well be useful for novel or improved
practical applications. Amorphous glass/iron
multilayer systems, e.g., are promising candidates
for magnetic tunnel junctions [1]. One recently
discovered way of synthesizing such a system
was developed by Ghafari et al.: By sputtering
iron on a metallic glass substrate, they obtained a
thin amorphous film of iron, as long as the film
was not too thick [2]. Usually, iron will not be
stable in an amorphous state, even if sputtered on
an already disordered substrate. The question of
interest is if the observed process is simply due to
the conditions of the deposition process, or if the
reasons for the amorphization of iron are energetic. To that end we conducted molecular dynamics
computer simulations using the software LAMMPS. We chose a simple model system of a CuZr based metallic glass with an embedded copper
nanolayer. Just like iron, copper has a very strong
tendency to form ordered phases.
The simulation setup is shown in Figure 2 on the
left: We embedded crystalline copper nanolayers
(Cu) of different thickness in the metallic glass
(MG). By starting from a crystalline state, we
can exclude that any transformation is due to
deposition conditions that freeze the copper in
a disordered state. Instead, any SSA-like effect
must be due to energetic reasons. It can be seen
in the three simulation snapshots on the right of
Figure 2, that a thin film of copper will indeed
amorphize. We found a critical thickness of
about 1 nm, above which the copper will stay
crystalline. The order of magnitude of this
number agrees with the experiments by Ghafari
et al. [2]. The reason for the phase transition is
the interface energy: Despite the fact that there
is no interface between two mismatched crystals,
the glass–glass interface energy is lower than the
crystal–glass interface energy. This can compensate the unfavorable amorphous copper phase up
to a critical thickness [3].
Using computer simulations, we could prove
that the amorphization in the presented composite system is energetically driven. It stands
to reason that this phenomenon also appears in
different metallic multilayer systems. Due to the
energetic nature of the transition, the synthesis of
these systems should be easily achievable.
References
[1] Gao, L., X. Jiang,
S.-H. Yang, P. M. Rice,
T. Topuria, and S. S. P.
Parkin, Increased Tunneling
Magnetoresistance Using
Normally bcc CoFe Alloy
Electrodes Made Amorphous without Glass Forming Additives, Phys. Rev.
Lett., 102: 247205, 2009
[2] Ghafari, M., H. Hahn,
R. A. Brand, R. Mattheis,
Y. Yoda, S. Kohara,
R. Kruk, and S. Kamali,
Structure of iron nanolayers embedded in
amorphous alloys, Appl.
Phys. Lett., 100: 203108,
2012
[3] Brink, T., D. Şopu,
and K. Albe, Solid state
amorphization of Cu
nanolayers embedded in
a 6 Cu64Zr36glass, Phys.
Rev. B, 91: 184103, 2015
Figure 1: Routes for obtaining amorphous metals. Generally, the metal can either be kinetically trapped in the amorphous
state as shown in the routes on the left, or the transition can be energetically favorable. For the energetically favorable routes,
the amorphous phase is either stabilized by heterogeneities or by nanosize effects. All of these phenomena are related to
surfaces or interfaces. In our work, we investigated metallic nanolayers embedded in metallic glass, as shown on the far right.
Figure 2: Solid state amorphization of copper. The left picture shows the simulation setup: A copper nanolayer (blue) is inserted into
a metallic glass matrix (grey). The three simulation snapshots on the right show a cut through the nanolayer: A thin layer becomes
amorphous almost immediately. Disordered copper atoms are shown in orange.
Octahedral Tilt Transitions in the Relaxor Ferroelectric
Sodium Bismuth Titanate
Kai-Christian Meyer, Melanie Gröting and Karsten Albe
Sodium bismuth titanate Na1/2Bi1/2TiO3 (NBT)
and its solid solutions are lead-free ferroelectrics
which can potentially substitute lead containing
piezoelectric materials because of their promising dielectric and ferroelectric properties. [1]
NBT exhibits a broad maximum of the dielectric
permittivity over a wide temperature range and
is thus a relaxor material. Since relaxor materials
behave like spin-glasses with a high local entropy, they also show a pronounced electrocaloric
effect (ECE) where a considerable temperature
change of the material can be achieved by applying an electric field. Therfore, relaxors are also
considered as candidate materials for solid state
refrigeration.
NBT as the basis for different solid solutions
has several complicated phase transitions, involving cubic (C), tetragonal (T) orthorhombic
(O), rhombohedral (R) and monoclinic (M) symmetries. The phases are distinct due to different
oxygen octahedra tilt patterns and displacement
of the A- and B-cations which lead to polarization of the unit cell. Additionally, in-phase (T+)
and anti-phase (T-) tiltings of the octahedra exist
which both belong to the same tetragonal crystal
system. [2] Further, it is unclear if an order of the
A-cations exists or if they are disordered. [3]
While the relaxor behavior is usually explained by the presence of polar nanoregions
(PNRs) or random fields, the exact structural
origin of the relaxor properties of NBT is still not
clear. Polar nanoregions are thought to be a (polar) local deviation from the average (non-polar)
structure. [4]
In our study we investigate the influence of
two different A-cation orders, 111 (rock-salt)
and 001 (layered) on several properties such as
tilt transition barriers and tilt defect formation
energies. Figure 1 shows exemplarily one system
setup for an orthorhombic tilt defect (black)
in an rhombohedral matrix. The neighboring
octahdra show a slight deformation, but already
the second next neighbors are hardly influenced.
Figure 2 shows the tilt defect formation energies
for different defect / matrix combinations. The
tilt defect formation energies are the lowest
when a group <-> subgroup relation exist. This
relation means that the transition from one phase
to another is possible by a single phonon mode
(involving mainly the oxygen ions and sometimes
the A- and B-cations).
Further, the approximate size of the polar
nanoregions with a different tilt can be estimated
when the tilt defect has a lower or similar ground
state energy than the matrix. E.g orthorhombic
tilts inside a rhombohedral matrix become stable
for sizes around 40 Å, fig. 3. [5] This size can be
related to polar nanoregions since the polarization behaviour is different for the distinct phases.
We could also show that octahedral tilt transition energies behave are different between the
two studied A-cation orders. [5] In regions with
001-order it appears that tilt defects can be introduced more easily and therefore, the chemical
order can be seen as a possible explanation for the
local deviations from the average.
References
[1] J. Rödel, W. Jo, K.T.P. Seifert,
E.-M. Anton, T. Granzow, D.
Damjanovic, J. Am. Ceram. Soc. 92
(6), 1153–1177 (2009).
[2] K. Reichmann, A. Feteira and
M. Li, Materials 8, 8467–8495
(2015)
[3] M. Gröting, Silke Hayn,
Karsten Albe, Journal of Solid State
Chemistry 184, 2041–2046 (2011)
[4] A. A. Bokov Z.-G. Ye, Journal
of Material Science 41, 31–52
(2006).
[5] K.-C. Meyer, M. Gröting and
K. Albe. J. Solid State Chem. 227,
117 (2015).
Figure 1: 6x6x2 NBT supercell with a 111-order
of the sodium (yellow) and bismuth (purple)
ions. With one orthorhombic tilt defect (black)
in a rhombohedral tilted matrix. It can be seen
that the neighboring octahedra (dark gray) are
distorted.
Figure 2: Tilt defect energies for
various defect tilt and matrix tilt
combinations. Tilt defect formation
energies are the lowest when
a group ↔ subgroup relation between
the tilt phases exists.
Figure 3: Tilt defect energies for a tetragonal
anti-phase (T-) defect in an in-phase (T+)
matrix (red) and an orthorhombic tilt defect
in a rhombohedral matrix (blue). The lines
represent different models which extrapolate
the formation energies to larger tilt defect
clusters.
Description of Fatigue Effect on Polarization Switching
Dynamics in Bulk Ferroelectric Ceramics
Y.A. Genenko, S. Zhukov, J. Glaum, H. Kungl and H. von Seggern
Gradual degradation of ferroelectric materials
exposed to mechanical or electrical cycling load,
called fatigue, has a great impact on the dynamic
properties of ferroelectrics. The mechanisms
behind the irreversible alteration of the switching
dynamics require a consistent investigation of the
evolution of statistical distributions of switching
times as a main quantitative characteristic of dynamic properties. This analysis can be performed
by means of the Inhomogeneous Field Mechanism (IFM) model [1], which should, however,
be accordingly modified for the case of fatigued
materials.
The total polarization response of a disordered bulk ferroelectric is assumed to result from
superposition of local responses by independent
material regions:
(1)
where Em is an electric field applied to the ferroelectric, t the poling time, the mean cosine
of the polarization polar angle with respect to the
applied field direction, Q(τ) a weighted statistical
distribution function of the switching times and
p(t,τ) the local polarization switching law with
a switching time τ(E) depending on the local
electric field strength E. The statistical distribution of times Q(τ) can be related to the weighted
statistical distribution of the reduced field values
f(E/Em) as
(2)
Both functions Q(τ) and f(E/Em) are normalized
according to their statistical meaning:
(3)
In the course of electric fatigue, polarization
reversal gets blocked in unswitchable regions
corresponding effectively to τ = ∞ while the electric field E remains finite that violates the local
dependence τ(E). Relation (2) is thus violated as
well that affects the normalization conditions (3).
This state can be simpler described in terms
of characteristic switching frequencies ω=1/τ.
A corresponding statistical distribution function
can be then presented as
(4)
where h(ω) is a regular part of the distribution
while the singular δ-function represents the unswitchable share ν < 1 of the volume characterized
by ω=0 (i.e. τ = ∞). From Eq. (4), the switching
time and field distributions may be derived in the
form
(5)
where and describe the regular parts of
the distributions related to the regions switchable
in a finite time. Accordingly, the distribution
functions obey now the normalization conditions
while should now be substituted by
in Eq. (1).
(6)
As
an example of application of this concept a ceramic Pb (Zr52,5Ti47,5) O3+2%La was
investigated [2]. The switching time distributions, given in logarithmic representation
G (ln(τ/τ0)) = τ (τ) exemplarily in Fig. 2 for
the applied field Em = 1.5 kV/mm. appear to
be much broader than for the virgin material.
References
[1] Y.A. Genenko, S. Zhukov, S.V. Yampolskii, J.
Schütrumpf, R. Dittmer, W. Jo, H. Kungl, M. J. Hoffmann,
and H. von Seggern, Adv. Funct. Mater. 22, 2058 (2012).
[2] S. Zhukov, S. Fedosov, J. Glaum, T. Granzow, Y. A.
Genenko, H. von Seggern, J. Appl. Phys. 108, 014105
(2010).
Figure 1. Switching dynamics in PZT+2%La:
virgin (a) and after fatigue: (b) 105 and (c)
4.4*106 bipolar cycles. Symbols correspond to
the experimental results while solid lines to
the IFM-model calculations.
Figure 2. Switching time distributions at
Em=1.5 kV/mm for PZT+2%La ceramic with
different level of fatigue as indicated.
Research Projects
•
Hochtemperatur-Kriechverhalten
SiOC-basierter Gläser und Glaskeramiken
(DFG STU 611/1-1, 2014-2017)
(DFG RO 4542/2-1, 2014-2017)
•
Grenzflächenphänomene in ionenleitenden Systemen
(DFG AL 578/19-1, 2015-2018)
•
Tailoring nanoscaled features in novel steels for high-temperature
applications using ion beam modification (ODS-HiTs) (HGFJRG-411,
2014-2017)
•
Topological Engineering of Ultra-Strong Glasses (DFG AL 578/15-2,
2015-2018)
•
Design elektrokalorischer mehrlagiger Kühlelemente mit Hilfe von
Multiskalenmodellierung (DFG AL 578/16-2, 2015-2018)
•
Nanocomposites as anode materials for lithium ion batteries: Synthesis,
thermodynamic characterization and modeling of nanoparticular silicon
dispersed in SiCN(o) and SiCO-based matrices
(DFG SPP 1473 „WeNDeLIB“, DFG AL 578/10-2, 2014–2017)
•
Mikrostruktur und Stabilität von Nanogläsern (DFG AL 578/6-2,
2014-2017)
•
Microstructure control for thin film solar cells - Virtuelles Institut
(MICO-TFSC) (HZB VH-VI-520, 2012-2017)
•
Beyond Ni-Base Superalloys: Atomistische Modellierung des Einflusses
von Legierungszusätzen auf die Korngrenzeigenschaften in Mo-Si-B
und Co-Re Super-legierungen (DFG Forschergruppe 727, AL 578/9-1,
2010–2015)
•
Mechanische und kinetische Eigenschaften metallischer Gläser mit
nanoskaligen Sekundärphasen (DFG AL578/13-1, 2011–2015)
Publications
[1]
Lenchuk, Olena ; Rohrer, Jochen ; Albe, Karsten:
Atomistic modelling of zirconium and silicon segregation at twist and tilt grain boundaries in molybdenum.
Journal of Materials Science, 51, 1873-1881 (2015)
[2] Zhukov, Sergey ; Acosta, Matias ; Genenko, Yuri A. ;
von Seggern, Heinz :
Polarization dynamics variation across the temperature- and
composition-driven phase transitions in the lead-free
Ba(Zr0.2Ti0.8)O3−x (Ba 0.7Ca 0.3)TiO3 ferroelectrics.
Journal of Applied Physics, 118, 134104 (2015)
[3] Bhat, Shrikant ; Wiehl, Leonore ; Molina-Luna, Leopoldo ;
Mugnaioli, Enrico ; Lauterbach, Stefan ; Sicolo, Sabrina ;
Kroll, Peter ; Duerrschnabel, Michael ; Nishiyama, Norimasa ; Kolb, Ute; Albe, Karsten ; Kleebe, Hans-Joachim ; Riedel, Ralf :
High-Pressure Synthesis of Novel Boron Oxynitride
B6N4O3 with Sphalerite Type Structure.
Chemistry of Materials, 27, 5907-5914 (2015)
[4] Ma, Yang-Bin ; Albe, Karsten ; Xu, Bai-Xiang :
Monte Carlo simulations of the electrocaloric effect in relaxor
ferroelectrics.
IEEE Proceedings of the 2015 IEEE International Symposium on
Application of Ferroelectrics (ISAF) (2015)
[5]
Hörmann, Nicolas. G. ; Gross, Axel ; Rohrer, Jochen ;
Kaghazchi, Payam :
Stabilization of the γ-Sn phase in tin nanoparticles and nanowires.
Applied Physics Letters, 107, 123101 (2015)
[6] Meyer, Kai-Christian ; Gröting, Melanie ; Albe, Karsten :
Octahedral tilt transitions in the relaxor ferroelectric Na½ Bi½ TiO3.
Journal of Solid State Chemistry, 227, 117-122 (2015)
[7]
Genenko, Yuri A. ; Rauh, Hermann ; Kurdi, Samer :
Finite-element simulations of hysteretic alternating current losses in a
magnetically coated superconducting tubular wire subject to an
oscillating transverse magnetic field.
Journal of Applied Physics, 117, 243909 (2015)
Publications
[8]
Erhart, Paul ; Albe, Karsten :
Dopants and dopant–vacancy complexes in tetragonal lead titanate:
A systematic first principles study.
Computational Materials Science, 103, 224-230 (2015)
[9]
Ngô, Bao-Nam Dinh ; Stukowski, Alexander ; Mameka, Nadiia ; Markmann, Jürgen ; Albe, Karsten ; Weissmüller, Jörg :
Anomalous compliance and early yielding of nanoporous gold.
Acta Materialia, 93, 144-155 (2015)
[10]
Ma, Yang-Bin ; Albe, Karsten ; Xu, Bai-Xiang :
Lattice-based Monte Carlo simulations of the electrocaloric effect in ferroelectrics and relaxor ferroelectrics.
Physical Review B, 91, 184108 (2015)
[11] Rohrer, Jochen ; Moradabadi, Ashkan ; Albe, Karsten ;
Kaghazchi, Payam :
On the origin of anisotropic lithiation of silicon.
Journal of Power Sources, 293, 221-227 (2015)
[12] Brink, Tobias ; Şopu, Daniel ; Albe, Karsten :
Solid-state amorphization of Cu nanolayers embedded in a Cu 64 Zr36 glass.
Physical Review B, 91, 184103 (2015)
[13]
Şopu, Daniel ; Albe, Karsten :
Influence of grain size and composition, topology and excess free
volume on the deformation behavior of Cu–Zr nanoglasses.
Beilstein Journal of Nanotechnology, 6, 537-545 (2015)
[14]
Genenko, Yuri A. ; Glaum, Julia ; Hoffmann, Michael J. ;
Albe, Karsten :
Mechanisms of aging and fatigue in ferroelectrics.
Materials Science and Engineering: B, 192, 52-82 (2015)
SFB 595 Cooperation C1, C5, D1, T2
[15]
Gassmann, Andrea ; Yampolskii, Sergey V. ; Klein, Andreas ; Albe, Karsten ; Vilbrandt, Nicole ; Pekkola, Oili ;
Genenko, Yuri A. ; Rehahn, Matthias ; von Seggern, Heinz :
Study of electrical fatigue by defect engineering in organic lightemitting diodes.
SFB 595 Cooperation A5, C2, C5, D3, D4
Publications
[16]
Hausbrand, René ; Cherkashinin, Gennady ; Ehrenberg, Helmut; Gröting, Melanie ; Albe, Karsten ; Hess, Christian ;
Jaegermann, Wolfram :
Fundamental degradation mechanisms of layered oxide Li-ion battery cathode materials: Methodology, insights and novel approaches.
SFB 595 Cooperation A3, B4, B8, C1
[17]
Lenchuk, Olena ; Rohrer, Jochen ; Albe, Karsten :
Solubility of zirconium and silicon in molybdenum studied by
first-principles calculations.
Scripta Materialia, 97, 1-4 (2015)
[18] Witte, Wolfram ; Abou-Ras, Daniel ; Albe, Karsten ;
Bauer, Gottfried H. ; Bertram, Frank ; Boit, Christian ;
Brüggemann, Rudolf ; Christen, Jürgen ; Dietrich, Jens ;
Eicke, Axel ; Hariskos, Dimitrios ; Maiberg, Matthias ;
Mainz, Roland ; Meessen, Max; Müller, Mathias ;
Neumann, Oliver ; Orgis, Thomas ; Paetel, Stefan; Pohl, Johan ; Rodriguez-Alvarez, Humberto ; Scheer, Roland ;
Schock, Hans-Werner ; Unold, Thomas ; Weber, Alfons ; Powalla, Michael :
Gallium gradients in Cu(In,Ga)Se2 thin-film solar cells.
Progress in Photovoltaics: Research and Applications, 23, 717-733 (2015)
Mechanics of
Staff Members
Head
J. Prof. Dr. (Boshi)
Bai-Xiang Xu
Secretaries
Maria Bense
Research Associates
Habib Pouriayevali, PhD
Dr.-Ing. Peter Stein
Min Yi, PhD
PhD Students
Dipl.-Ing. Dagmar Eder-Goy
Yangbin Ma, M. Sc.
Shuai Wang, M. Sc.
Ying Zhao, M. Eng.
Bachelor/Master Students
Runqing Yang
Ziqi Zhou
Dominik Ohmer
116 | Mechanics of functional materials
Mechanics of Functional Materials
The research focus of the Division of Mechanics
of Functional Materials is on the constitutive
modeling and the simulation of functional materials and systems, for instance ferroic materials
and lithium-ion battery electrodes. These materials are characterized by a coupling of multiple
physical fields at a variety of length-scales. Their
macroscopic responses depend on the microstructure and its thermodynamic kinetics. The
main features of our research therefore include
coupled fields (e.g. mechanical, electrical, chemical), microstructural evolution, mesoscopic material properties, and homogenization. Primary
tools of our research are continuum models and
numerical simulations, predominantly using the
Finite Element method. Novel concepts such as
phase-field models or Isogeometric Analysis are
regarded to an increasing extent in our work.
Phase field simulation of the domain structure
of relaxor ferroelectrics
Relaxor ferroelectrics (Relaxors) are a group
of ferroelectrics with distinctive properties such
as large field-induced strains as well as a higher
dielectric permittivity than normal ferroelectric
materials. The outstanding electro-mechanical
coupling constants of relaxors make them useful
as core parts in sensors and actuators. One of the
main properties that distinguish relaxors from
conventional ferroelectrics is the existence of
polar nanoregions.
Numerical simulations have emerged as a
new tool to study the behavior of these materials,
owing to the rapid development of computer technology. A phase-field model is used to solve the
interface problems in phase transition. Diffuse
domain configurations can be intrinsically obtained by using an Allen-Cahn equation together
with a proper Landau energy. The consideration
of random fields (RFs) can represent the influence of the polar nanoregions on the domain
configuration and its corresponding evolution
equation.
In our recent results, we demonstrate the
effect of the RF strength on the macroscopic
behavior.
With higher RFs, both the remanent polarization
and the coercive field become smaller. In addition,
the domain size reduces and its configuration becomes more “twisted”. The piezoelectric behavior can be manipulated by mechanical loading,
and the core-shell structure of FE/RE composite
can be simulated by assuming different RFs.
The comparison of simulation and experimental
results demonstrate that our model reproduces
typical relaxor features, such as domain miniaturization, small remanent polarization, and large
piezoelectric response.
Simulation of the electrocaloric effect of relaxor ferroelectrics
Ferroic cooling has an attractive potential for
the reduction of energy or material consumption.
Solid state refrigeration using materials with
a significant electrocaloric effect (ECE) is a
viable alternative to concepts based on the magnetocaloric effect. We aim at investigating the
underlying physics of the ECE, utilizing the tools
of simulation. Through application/removal of
an electric field on ferroelectrics under adiabatic
conditions, the dipoles‘ alignment in the material
- and hence the entropy - changes. Consequently,
the temperature must change in order to accommodate this change in entropy and to keep the
total energy constant. This allows to obtain a
variation in temperature.
In order to investigate the ECE in both ferroelectrics and relaxor ferroelectrics, we proposed
a lattice-based model consisting of a phase-fieldtype potential energy and the thermal energy. By
combining the canonical and microcanonical ensemble, the ECE can be evaluated directly, rather
than indirectly through the Maxwell relation. The
random fields are incorporated into the electrostatic energy to mimic the relaxor behavior. This
shows that the temperature-induced polarization
change is moderate in the presence of random
fields, in contrast with the sharp change as observed in conventional ferroelectrics.
Our results also demonstrate that the freezing temperature is lowered by random fields,
while it is promoted by the domain wall energy.
Mechanics of functional materials | 117
Similarly, in presence of random fields, the ECE
peak shifts to lower temperature and its peak
value drops. The domain wall energy influences
the ECE in the opposite fashion: here, the peak
appears at higher temperatures with the peak
value increasing. Finally, our results show that
the ECE increases in three different stages with
the strength of the applied external field rather
than in a simple linear manner.
Simulation of diffusion-induced stresses
in Lithium-ion batteries via Isogeometric
Analysis
Mechanical degradation of the active material
has been identified as one of the root causes of the
degradation of Lithium-ion batteries, which can
be observed macroscopically as a gradual fade of
the batteries‘ capacity. The understanding of the
damage processes in the electrodes’ particles and
their influence on the mechanical-electrochemical properties is hence of utmost importance.
The coupled electrochemical-mechanical
processes in individual electrode particles
are described by continuum mechanics and
higher-order Finite Element procedures based
on the concept of Isogeometric Analysis. Their
application is motivated by higher-order gradient/
coupling terms arising from the thermodynamics
of the problem. This allows for stable implementation of the governing equations as well as for a
unified treatment of diverse particle shapes and
electrode geometries.
In addition to large deformations of certain
electrode materials, in situ TEM observations
have revealed the coexistence of lithium-poor
and lithium-rich phases in the electrode particles
during charge and discharge, which suggests that
the concentration of Li-ion does not change gradually but experiences a gap at a certain interface.
In order to capture this behavior, we developed a
Cahn-Hilliard phase-field model that regards not
only the chemical aspects of the phase separation
and diffusion, but also viscoplastic effects.
Phase field modelling of ferromagnetic
materials
Owing to their ferromagnetic property and
magneto-mechanical coupling, ferromagnetic
materials find wide industrial application, for
instance in magnetic data storage, sensors and
actuators, transducers, or micro-electro-mechanical systems. Viable applications and reasonable
design of devices based on ferromagnetic materials are highly dependent on the fundamental
understanding of these materials‘ microstructures. For materials with only ferromagnetic orderings, magnetic domains play a critical role in
determining both their micro- and macroscopic
properties. If the magneto-mechanical coupling
in the magnetostrictive materials is considered,
a mechanical scheme for tailing the properties
becomes possible. Ferromagnetic shape memory
alloys (FSMAs), which possess both ferroelastic
and ferromagnetic orderings, can produce large
strains under an external magnetic field due to
the martensitic phase transformation. By virtue
of the coupling between the ferroelastic and ferromagnetic orderings, the ferroelastic martensitic
variants can be manipulated by a magnetic field,
whereas the ferromagnetic domains are sensitive
to mechanical loading. Uncovering the evolution
of these microstructures in the above-mentioned
ferromagnetic materials is prerequisite for a deep
understanding and control of the microscopic
mechanism and macroscopic properties.
Continuum modeling and numerical simulation of polycrystalline materials
The investigation of the hardening behavior
and texture development in polycrystalline
materials is of high interest to both scientists
and the industry. Experimental results show
an intrinsic size-dependent response of such
materials along with inhomogeneous plastic
flow on the micro-scale. The existence of
boundary layers thereby plays an important role.
Their influence on dislocation movement can be
diverse, depending on, for instance, the misorientation of the adjacent grains. Study and prediction of these behaviors require incorporation of
atomistic slip systems, gradient description and
length scale parameters into the conventional
plasticity models.
In the current study, a well-defined gradient
crystal plasticity model is employed in order to
investigate the size-dependent strengthening behavior and orientation gradients in a large-grain
thin-sheet metal under mechanical loading. The
constitutive description is an extended crystal
plasticity model based on the microscopic force
balance and is consistent with thermodynamic
laws. Here, the free energy comprises two parts:
a hyperelastic description for large-deformation
compressible material and a function of dislocation densities via Peach–Koehler forces conjugate
to corresponding glide directions.
A non-local plastic flow rule in the form of
a partial differential equation is introduced,
incorporating energetic and dissipative gradient
strengthening as well as latent hardening in a
multi slip-system crystal. The proposed constitutive model is implemented in the FEM software
ABAQUS via a user-defined element subroutine,
where displacement components and dislocation
densities are treated as nodal degrees of freedom.
Nonlinear electromechanical modeling of
deformable dielectrics
Dielectric elastomer actuators (DEA) outperform most large displacement actuators in
terms of weight, cost, and efficiency. Besides
typical DEAs that exhibit an electrode-elastomer-electrode sandwich structure, we focus on
ferroelectrets. These are electrically charged
micro-porous foams that possess a very large
longitudinal piezoelectric effect and that have
received wide applications as sensors particularly
in acoustical devices. During a charging process,
electric breakdown (Paschen breakdown) may
take place in the air pores of the foam, thus introducing free charge pairs. These charges relocate
at the interfaces between the polymer and the
ionized medium. The development of this free
charge density along the interfaces is the key for
the piezoelectricity of ferroelectrets. In order to
simulate the hysteresis curve of the charge density development at the interfaces, nonlinear Finite
Element simulations based on internal variables
are employed, allowing a faithful reproduction of
experimental results.
Monte Carlo Simulation of the Electrocaloric Effect
Yangbin Ma, Karsten Albe, and Bai-Xiang Xu
We investigated the electrocaloric effect by utilizing a lattice-based Ginzburg-Landau-type Hamiltonian, which is comprised of a Landau-type
term at ground state, a dipole-dipole interaction
energy, a domain wall energy, and a contribution
of the electrostatic energy describing the coupling
to an external field. Through the combination of
a canonical and a microcanonical Monte Carlo
algorithm, we could evaluate the ECE directly.
All the phenomena can be interpreted explicitly
through the corresponding domain structures and
the entropy change.
Firstly, we applied the model to study the ECE
in BaTiO3-based relaxor ferroelectrics (RFEs)
[1]. Here, RFEs are represented by introducing
random fields that are coupled to the polarization. In RFEs with increasing random fields the
ECE peaks shifts to lower temperature due to the
pinning effect, thereby reducing the temperature
variation. A similar behavior can be observed
when we introduce random defects to represent
the random fields. In contrast, if the domain-wall
energy increases, the peak shifts to a higher
temperature, and the ECE becomes stronger.
RFEs can also be interpreted as ferroelectrics
with randomly distributed dipoles, allowing the
calculation of the corresponding ECE [2].
Secondly, we evaluated the ECE of
BaZrxTi1-xO3 by incorporating a single-well Landau-type for Zr-located unit cells, and by including a high-frequency permittivity depending on
the Zr-content. Since the long-range interaction
is present in the ferroelectrics, Zr-located unit
cells break the long-range order of Ti-located unit
cells. Therefore, with increasing Zr content the
ECE drops sharply within 0 ≤ x ≤ 0.3, while it decreases moderately for x ≥ 0.3. The experiments
were done for x = 0.0, 0.12, and 0.2, and show a
qualitative agreement with above prediction.
Thirdly, we studied the influence of defects
due to the oxygen-vacancy associates on the ECE
[3]. The results show that, depending on the density of anti-parallel defect dipoles, the ECE can
be positive or negative. Furthermore, for a high
density of defect dipoles, when a higher external
field is applied, a transition from a negative to
positive ECE can be observed. These effects are
caused by the interaction of the internal fields
induced by the defect dipoles with the external
fields. We illustrate the influences of the defect
concentrations and that of the external field in
Fig. 1. The corresponding phenomena can be
interpreted by the domain structures (see Fig. 2).
Lastly, we proposed a new ECE cycle that
offers the opportunity to enhance the ECE. One
additional procedure, i.e. application of an anti-parallel field, is performed after removal of the
parallel field. A sufficient magnitude of antiparallel field increases the configurational entropy.
This lead to a further drop of the corresponding
temperature in the low temperature range.
References
[1] Yang-Bin Ma, Karsten Albe,
and Bai-Xiang Xu; Lattice-based
Monte Carlo simulations of the
electrocaloric effect in ferroelectrics and relaxor ferroelectrics;
Physical Review B, 91 (2015)
184108(1-13).
and Bai-Xiang Xu; Monte Carlo
simulations of the electrocaloric
effect in relaxor ferroelectrics;
IEEE Proceedings of the 2015
IEEE International Symposium
on Application of Ferroelectrics
(ISAF) 203-206.
and Bai-Xiang Xu. Positive and
negative electrocaloric effect in
BaTiO3 in the presence of defect
dipoles. ArXiv e-prints, (2015).
Figure 1: Positive and negative
ECE. (a) ECE in the presence
of collinearly aligned parallel
defect dipoles for different
defect concentrations under
a given external field Eex. (b)
ECE as a function of Eex for a
defect concentration of 6%. (c)
Positive and negative ECE in
presence of anti-parallel dipoles.
When the defect density exceeds
a critical value, the resultant
internal anti-parallel field
overcomes Eex and a negative
temperature change (negative
ECE) can be observed. (d)
Influence of Eex in the presence
of anti-parallel defect dipoles
with a concentration of 3%.
When Eex surpasses the internal
field Ei induced by the anti-parallel defect dipoles, a negative
ECE appears only at the low
temperature region, whereas
the positive ECE dominates
at higher temperatures. Above
phenomena can be explained
by the domain structures at
the points I, II, III, A and B in
Fig. 2.
Figure 2: Domain structures for
the points I, II, III, A and B marked in Fig. 1. The external field
Eex is applied in the horizontal
direction, pointing to the right. (a)
and (b), (c) and (d), (e) and (f),
(g) and (h), and (i) and (j) show
the domain structures before
and after the adiabatic stage for
the points I, II, III, A, and B,
respectively. The black dots
with white arrows represent the
defect dipoles, either parallel or
anti-parallel to Eex. The red, blue,
yellow and green dots represent
the dipoles pointing respectively
to the left, to the right, to the top
and to the bottom.
Research Projects
• Simulation of the electrocaloric effect of relaxor ferroelectrics
(Project in DFG-SPP 1599, 2013-2015)
• Isogeometric simulation of diffusion-induced stress in Lithium-ion battery electrodes (Project in GSC CE, 2013-2015)
• Phase-field modeling of ferromagnetic materials
(Project in LOEWE Response)
Publications
[1]
Habib Pouriayevali and Bai-Xiang Xu; A Hardening
Description based on a Finite-Deformation Gradient Crystal Plasticity Model: Formulation and Numerical Implementation;
Proc. Appl. Math. Mech. 15 (2015), 343-344.
[2] Peter Stein and Bai-Xiang Xu; Isogeometric analysis of surface elasticity: a comparison with isoparametric FEM; Proc. Appl. Math. Mech. 15 (2015), 427-428.
[3] Bai-Xiang Xu, Shuai Wang and Min Yi; A finite element phase field model for relaxor ferroelectrics; Proc. Appl. Math. Mech. 15 (2015), 723-726.
[4] Min Yi and Bai-Xiang Xu; Phase field simulation on mechanically induced 180 degree switching in nanomagnets; Proc. Appl.Math.Mech. 15 (2015), 441-442.
[5] Ying Zhao, Peter Stein, and Bai-Xiang Xu; Phase field simulation
of the intercalation-induced stresses in the hyperelastic solids via isogeometric analysis; Proc. Appl. Math. Mech. 15 (2015), 443-444.
[6]
Ying Zhao, Peter Stein, and Bai-Xiang Xu; Isogeometric analysis of mechanically coupled Cahn-Hilliard phase segregation in hyperelastic electrodes of Li-ion batteries; Computer Methods in Applied Mechanics and Engineering, 297 (2015), 325-347.
[7]
Yang-Bin Ma, Karsten Albe, and Bai-Xiang Xu; Monte Carlo simula-
tions of the electrocaloric effect in relaxor ferroelectrics; IEEE Proceedings of the 2015 IEEE International Symposium on Applica-
tion of Ferroelectrics (ISAF) 203-206.
Publications
[8] Yang-Bin Ma, Karsten Albe, and Bai-Xiang Xu; Lattice-based Monte Carlo simulations of the electrocaloric effect in ferroelectrics and relaxor ferroelectrics; Physical Review B, 91 (2015) 184108(1-13).
[9] Min Yi, Bai-Xiang Xu, and Dietmar Gross; Mechanically induced deterministic 180° switching in nanomagnets; Mechanics of Materials 87 (2015), 40-49.
[10] Min Yi, Bai-Xiang Xu, and Zhigang Shen; 180° magnetization
switching in nanocylinders by a mechanical strain; Extreme
Mechanics Letters 3 (2015), 66-71.
[11] Min Yi, Bai-Xiang Xu, and Zhigang Shen; Effects of magneto
crystalline anisotropy and magnetization saturation on the mechani
cally induced switching in nanomagnets;
Journal of Applied Physics, 117 (2015), 103905-1.
[12] Dietmar Gross and Bai-Xiang Xu; Micromechanical modelling of cellular ferroelectrets by using internal variables; Procedia IUTAM, 12 (2015) 62-72.
Molecular
Nanostructures
Staff Members
Head
Prof. Dr. Ralph Krupke
Secretaries
Gabriele Rühl
PhD Students
Dipl.-Phys. Feliks Pyatkov KIT
Moritz Pfohl, M.Sc. (KIT)
Asiful Alam, M.Sc. (KIT)
Adnan Riaz, M.Sc. KIT
Wieland Reis, M.Sc. (BASF)
Wenshan Li, M.Sc. (KIT)
S. Neelakandhan, M.Sc. (KIT)
Master Students
Rana Yekani
124 | Molecular Nanostructures
Molecular Nanostructures
The
Joint
Laboratory
for
Molecular
Nanostructures has been established in 2011 to
enhance the cooperation between the Institute
for Nanotechnology at the Karlsruhe Institute of
Technology (KIT) and the Institute of Materials
Science at the Technische Universität Darmstadt.
The research focus of the labratory is on nanocarbon materials, in particular on carbon
nanotubes and graphene. Carbon nanotubes and
graphene are made of a single layer of covalently
bonded carbon atoms. The electrical, optical,
chemical and mechanical properties of these
molecular nanostructures are outstanding, which
is why CNTs and graphene are considered as im-
portant new materials for high speed electronics,
optoelectronics, sensing, coatings, material reinforcements and other potential applications. The
motivation of the Joint Laboratory is to gain new
and important insights into carbon nanomaterials
for enabling future applications. In 2013 funding
for a Fourier-Transform Photocurrent-Spectromicroscope using a Supercontinuum-Lightsource
has been provided by the German Science
Foundation, the Insitute of Materials Science
and the President of the Technische Universität
Darmstadt. The system has been commissioned
in 2014 and is used to study the optoelectronic
properties of materials and functional devices.
Molecular Nanostructures | 125
Light Emission, Light Detection and Strain Sensing with
Nanocrystalline Graphene
Adnan Riaz1,2, Felix Pyatkov1,3, Asiful Alam1,3, Simone Dehm1, Alexandre Felten4, Venkata S.K. Chakravadhanula1,6, Benjamin
S. Flavel1, Christian Kübel1,6,7, Uli Lemmer2,5 & Ralph Krupke1,2
Institute of Nanotechnology, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany. 2Light Technology Institute,
Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany. 3Department of Materials and Earth Sciences, Technische
Universität Darmstadt, 64287 Darmstadt, Germany. 4Research Center in Physics of Matter and Radiation, University of Namur,
Namur, Belgium. 5Institute of Microstructure Technology, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany.
6
Helmholtz Institute Ulm, 89081 Ulm, Germany. 7Karlsruhe Nano Micro Facility, Karlsruhe Institute of Technology, 76021
Karlsruhe, Germany.
1
Summary from Nanotechnology 26 (2015) 3849 | doi: 10.1021/nn506869hw
We demonstrate the waferscale synthesis of
nanocrystalline graphene on dielectric surfaces
by graphitization of a photoresist under high
vacuum annealing, where the thickness, the sheet
resistance and the transparency of the layer was
tailored by the process condition. The layer is entirely formed by sp2-hybridized carbon as proven
by XPS and Raman. The size of the graphitic
domains is on the order of 2 nm, consistent with
Raman and TEM measurements. Integrated into
devices, the material showed photocurrent generation under illumination. The response to light
could be traced to a bolometric origin, similar
to experiments on doped crystalline graphene.
Also light emission under electrical biasing was
observed.
The emission is due to heating of the layer,
and the extracted electron temperature and
power density is comparable to experiments
reported from crystalline graphene. Furthermore
a piezoresistive effect was observed that is significantly larger than in crystalline graphene and
indicates the importance of grain boundaries for
the appearance of piezoresistivity in graphene.
Hence nanocrystalline graphene appears be
an interesting material not only as an easy to
fabricate alternative to crystalline graphene for
nanoscale light detection and light generation but
also towards the fabrication of transparent and
flexible strain sensors.
In the following we present the results on the
synthesis and the characterization of nanocrystalline graphene (NCG). For the use of NCG for
light emission, light detection and strain sensing
we refer to the original publication [1].
Figure 1a shows an AFM image across an edge of
a structured 1 nm thin NCG layer on 800nmSiO2/
Si. The data shows that the surface roughness
of NCG is similar to the roughness of the SiO2
surface, indicating a conformal coating of the
substrate. The edge appears straight and shows
no sign of underetching. The NCG thickness was
adjusted by diluting the resist to yield a targeted
nominal thickness. The degree of control is
shown in Figure 1b. The sheet resistance of the
NCG is typically on the order of 20-80 kΩ/sq.,
depending on the NCG thickness and the type of
substrate, as can be seen in Figure 1c.
The mean value and the error bars were
obtained from measurements on 35 samples for
each data point. The sheet resistance values are
comparable to the 30 kΩ/sq. reported by Zhang
et al. [2] for 1 nm NCG, also formed at 1000 °C
albeit under reducing atmosphere. Compared to
CVD graphene [3] and carbon nanosheets [4] is
the sheet resistance of our NCG 2 orders of magnitude larger and six orders of magnitude smaller, respectively. Obviously the carrier transport
across grain boundaries has a large influence on
the overall resistance. The optical transparency
of a 6 nm thick NCG film on <0001> zcut Quartz
is shown in Figure 1d. The transmission increases
from 77% at 400 nm to 87 % at 1400 nm and
shows an enhanced absorption around 800 nm.
Normalized by the thickness, the optical
transmission of NCG is comparable to that of
graphene.
To determine the composition and the hybridisation of the NCG material we have analysed the
C 1s peak of the XPS signal and compared the
spectrum to data recorded on bilayer graphene
and graphite. Figure 2a shows that the C 1s signal
Figure 1: (a) Atomic force microscopy image of a patterned 1 nm thin nanocrystalline graphene layer on 800nm SiO2/Si substrate.
The inset shows an averaged cross section of the indicate area. Scale bar equals 1 μm. (b) Measured layer thickness versus nominal
thickness. (c) Sheet resistance versus nominal thickness of nanocrystalline graphene on various substrates as indicated. (d) Transmission
spectrum of 6 nm thick layer on <0001> z-cut Quartz. All nanocrystalline graphene samples have been synthesized at 1000°C@10h.
has a main peak at 284.4 eV similar to graphite,
and hence assigned it to the sp2 hybridised carbon
atoms. Also the width of ~1.2 eV fits very well to
bilayer graphene which has a similar thickness
as NCG. Some peak broadening towards higher
binding energy is observed for NCG, which could
have its origin in the nanocrystallinity of the
material. No additional elements besides Si and
O from the substrate were detected. Hence we
can safely conclude that our NCG is a graphitic
material with a high degree of sp2 hybridisation.
XPS also allows determining the thickness of the
carbon layer from the attenuation of the photoelectrons emanating from the SiO2. We have used
the Si 2p with an attenuation length of 3.5 nm and
obtained 0.95 nm for a 1 nm thick layer.
Hence the thickness determined by XPS
is consistent with the AFM measurement. All
samples were characterised by Raman spectroscopy to obtain an additional confirmation on the
hybridisation and to determine the crystallite size
La in the NCG layer. Figure 2b shows Raman
spectra of NCG on 800nm-SiO2/Si for different
nominal layer thickness.
Characteristic to all samples are broad D and
G modes, and the absence of a clear 2D peak,
similar to refs [2] and [4]. We used the pioneering
work of Ferrari and Robertson to determine the
hybridisation and crystallinity of our NCG [5]. In
Figure 2c we have compared the Gpeak position
and the intensity ratio I(D)/I(G) of the Dpeak to
the Gpeak of NCG with the data measured on
graphite, nanocrystalline graphite, diamond-like
carbon (DLC) with 20% sp3-content (aC) and
DLC with 85% sp3 (ta-C).
The NCG data fits well to the nanocrystalline graphite with 100% sp2 content, and hence
confirms nicely the XPS data. From the width
of the D and G modes we estimated the size of
La by referring to the work of Cançado et al. [8].
The D mode width corresponds accordingly to
La ≈ 45 nm, whereas the G mode width indicates
La ≈ 23 nm (Figure 2d). To discern the difference
we transferred a 2 nm thick NCG layer formed on
800nmSiO2/Si onto a TEM grid and performed
an SAED analysis. Preliminary data indicates
that the crystallite size determined via the width
of the D mode correlates better with the TEM
analysis than using the G mode width (not shown).
References
[1] Riaz et al, Nanotechnology 26
(2015) 3849
[2] Zhang et al.,
Chemical Communications. 49
(2013) 2789-91
[3] Bae et al., Nat Nanotechnol. 5
(2010) 1-5
[4] Nottbohm et al., Small 7 (2011)
874-83
[5] Ferrari et al., Phys Rev B. 64
(2001) 1-13
[6] Cancado et al., Phys Rev B. 76
(2007) 1-7
Figure 2: (a) XPS of 1 nm thick NCG layer on 800nm SiO2/Si, compared with bilayer graphene (BLG) and graphite. (b) Raman spectra
of NCG with various thicknesses, grown on 800nm SiO2/Si. The spectra are normalized to the D-peak and vertically shifted for clarity.
(c) Raman G-peak position and intensity ratio of D-peak and G-peak for NCG compared with data from Ferrari et al. [5] for graphite,
nanocrystalline graphite and two forms of DLC as explained in the text. The sp hybridisation is indicated. (d) Crystallite size La in NCG
determined from the full-width-at-half-maximum of the D- and G-peaks. The graph compiles data from all samples prepared in this work.
The dashed lines are extrapolated correlations based on the work of Cançado et al. [6].
Publications
[1] Light emission, light detection and strain sensing with nanocrystalline graphene; Adnan Riaz, Feliks Pyatkov, Asiful Alam, Simone Dehm, Alexandre Felten, Venkata Chakravadhanula, Benjamin Flavel, Christian Kübel, Uli Lemmer and Ralph Krupke;
Nanotechnology 26 (2015) 325202, 10.1088/0957-4484/26/32/325202
[2] Sorting of Double-Walled Carbon Nanotubes According to Their
Outer Wall Electronic Type via a Gel Permeation Method; Katherine E. Moore, Moritz Pfohl, Daniel D. Tune, Frank Hennrich, Simone Dehm, Venkata Sai K. Chakradhanula, Christian Kübel, Ralph Krupke, and Benjamin S. Flavel ACS NANO 9(4) (2015) 3849;
10.1021/nn506869h
132 | Nonmetallic-Inorganic Materials
NonmetallicInorganic Materials
Staff Members
Head
Prof. Dr. Jürgen Rödel
Research Associates
Dr. Till Frömling
Dr. Jurij Koruza
Dr. Nikola Novak
Dr. Eric Patterson
Dr. Eva Sapper
J. Prof. Dr. Kyle Webber
Technical Personnel
Patrick Breckner, M. Sc.
Dipl.-Ing. Gundel Fliß
Michael Heyse
Dipl.-Ing. Daniel Isaia
Secretaries
Roswita Geier
Gila Völzke
PhD Students
Matias Acosta, M. Sc.
Azatuhi Ayrikyan, M. Sc.
Dipl.-Ing. Raschid Baraki
Dipl.-Ing. Martin Blömker
Dipl.-Ing. Laetitia Carrara
Philipp Geiger, M. Sc.
Dipl.-Ing. Markus Jung
Peter Keil, M. Sc.
Hairui Liu, M. Sc.
Virginia Rojas, M. Sc.
Dipl.-Ing. Florian Schader
Dipl.-Phys. Deborah Schneider
Jan Schultheiß, M. Sc.
Malte Vögler, M. Sc.
David Brandt
An Phuc Hoang
Peter Keil
Lucas Porz
Lukas Riemer
Mikhail Slabki
Sebastian Steiner
Daniel Utt
Alexander Zimpel
Research Fellow
Dr. Yoshitaka Ehara (AvH)
Raziye Hayati
Noon Prasertpalichat
Dr. In-Tae Seo (AvH)
Liu Wenfeng
Huan Yu
Guest Scientists
Dr. Hyong-Su Han
Prof. Dr. George A. Rossetti, Jr.
Nonmetallic-Inorganic Materials | 133
The Nonmetallic-Inorganic Materials
The emphasis in the ceramics group is on the
correlation between microstructure and mechanical as well as functional properties. A number
of processing methods are available in order
to accomplish different microstructure classes, to determine their specific properties in an
experiment and to rationalize these with straightforward modelling efforts. Thus, a materials
optimization is afforded which allows effective
interplay between processing, testing and modelling. In particular, new lead free piezoceramics
and lead-free high-temperature dielectrics can be
obtained. Recently, we also embarked on studies
in the field of mechanically tuned electrical conductivity.
The scientific effort can be grouped as
follows:
I. Development of new piezoceramics
Dr. Jurij Koruza
In response to the recent demands for
environment-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 lead-containing
counterparts. Among the potentially promising
candidates are materials based on bismuth sodium titanate, barium titanate, and alkaline niobates. Extensive compositional research has been
performed on various solid solution systems that
contain either a morphotropic or a polymorphic
phase boundary between 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 has
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.
II. Conductivity of Oxides
Dr. Till Frömling
Modulation of conductivity of oxide ceramics
is usually achieved by doping and temperature
treatment in a large oxygen partial pressure range.
However, electric and ionic conductivity can also
be changed by mechanical modifications. In this
research group conductivity is of oxide ceramics
is modified by the following approaches
a) Induction of dislocations: Dislocations are
mechanically introduced into strontium titanate
which can be plastically deformed even at room
temperature. Changes of the electric and ionic
conductivity are, amongst other methods, investigated by complex impedance spectroscopy and
dc-measurements. The aim of this project is to
identify the defect chemical properties of dislocation cores in strontium titanate and related materials.
b) Acceptor doping of sodium bismuth titanate
(NBT) based material: Modification of oxygen
vacancy content to study its influence on ferroelectric properties and to investigate opportunities
for using NBT-material as oxygen conductor.
c) Altering potential barriers in piezoelectric
semiconductor materials: In this project Schottky-barriers and varistor material based on ZnO
are investigated as a function of applied pressure
The Nonmetallic-Inorganic Materials
III.Mechanical properties of ferroelectrics
IV.Electrocaloric properties of ferroelectrics
J. Prof. Dr. Kyle Webber
Dr. Nikola Novak
The focus of this research group is understanding
the mechanical properties of ferroelectric materials, particularly the influence of stress on the
phase transformation behavior and ferroelasticity
at high temperature. Research over the last year
has centered around development of a high temperature fracture testing setup for characterizing
crack growth resistance behavior of ferroelastic
materials as well as utilizing the newly developed
experimental arrangement for characterizing
small signal dielectric, piezoelectric, and elastic
properties under large mechanical, electrical and
thermal fields as a function of frequency. Preliminary results have already given insight into the
impact of stress on the depolarization temperature of ferroelectric Pb(Zr,Ti)O3, which is commonly used in actuation and sensing applications.
In addition, the Emmy Noether research
group, lead by Kyle Webber, began in June and
has been working on relaxor/ferroelectric composites and mixed conducting cathode materials
for solid oxide fuel cells. Both of these projects are
focused on understanding the influence of stress
on the functional properties. Currently, equipment is being developed to allow for the mechanical characterization of samples in a atmosphere
with an adjustable oxygen particle pressure.
In last decade the investigation of electrocaloric
(EC) properties of ferroelectric materials attend
considerable attention. The cooling effect which
can be achived in ferroelectrics if the applied
electric field is instantenuouslly withdrawen provide the possibility in developing a new cooling
technology based on solid-state cooling media.
Over the last year the work has focused on developing of high resolution calorimetric setup,
for characterizing the heat capacity properties
under electric field as well as direct electrocaloric measurement. The new characterization technique allow us to determine the EC properties
like adiabatic temperature change and cooling
power of the EC material. Within a DFG priority programme ´´Ferroic cooling´´ the project was
started with focus on investigation of EC properties of ferroelectrics with different nature of
phase transinon.
The mechanical modulated electrical conductivity represents a new multidisclipinary scientific area. Reacently, much attention has been
focused on piezoelectric semiconductor materials
such as: ZnO, GaN, InN, and CdS. Of the special
interest are the interaction effect of semiconducting and piezoelectric propertis present in this
materials.
This is of special interest due to potential application in new electronic components, like piezotronic transistor, sensors, and tuna bel diodes.
The research is focused on developing a Schottky
contact on ZnO single crystal and understanding
the influence of mechanical stress on electrical
conductivity and Schottky properties. However,
the challenging goal of the research represent the
elucidation of screening effect which compensate under stress developed piezoelectric charge,
hence the modulation of electrical conductivity is
minimized.
Core-Shell Microstructure in Lead-Free Bi1/2Na1/2TiO3-SrTiO3
Piezoceramics
Jurij Koruza, Virginia Rojas, Matias Acosta
Introduction:
Experimental Procedure:
Bi1/2Na1/2TiO3 (BNT)-based piezoelectrics are
considered one of the most promising lead-free
materials for the use in piezoelectric actuator
applications, due to their large electric-fieldinduced strain response. Strains of up to 0.45 %
at 8 kV/mm were reported, which is the largest
response among all polycrystalline lead-free
materials.1 The large electric fields needed to
induce the large strain can be reduced by the
addition of other perovskite systems, which destabilize the non-ergodic phase of BNT and induce the reversible field-induced phase transition
at room temperature. One such example is the
Bi1/2Na1/2TiO3-SrTiO3 (BNT-ST) system for which
large electric-field-induced strains were observed
at electric fields as low as 2 kV/mm.2
However, the influence of the microstructure on
the electromechanical properties of these materials
remains poorly understood. Many authors reported different values of piezoelectric properties for
materials with the same composition, indicating
a large influence of the processing parameters
and the material´s thermal history. The aim of
the present work was therefore to investigate the
formation mechanisms of the BNT-ST during the
calcination step and the formation of the microstructure during sintering.
The reagents Bi2O3, Na2CO3, TiO2 (anatase),
and SrCO3 were weighted according to the
stoichiometric
formula
0.75 Bi1/2Na1/2TiO30.25Sr TiO3, milled in a planetary mill, dried,
and finally calcined at different temperatures
for 2 h. The obtained powders were milled,
pressed into pellets with a diameter of 10 mm,
and sintered in covered alumina crucibles with
atmospheric powder at 1150 °C. The calcination
process was investigated by heating a mixture of
reagents with a rate of 5 K/min in the simultaneous thermo-gravimetric analyzer coupled to a
Fourier transform infrared spectrometer (STA-IR).
Furthermore, the phase development during the
calcination process was tracked by X-ray diffraction (XRD) measurements ex-situ.
Results and Discussion:
Figure 1a presents the results of the XRD analysis ex-situ, while Figure 1b shows the results
of the STA-IR measurement of a homogenized
mixture of reagents upon heating. The initial
mass loss of about 2.2 % up to 330 °C is related to the evaporation of the adsorbed atmospheric water and CO2, as well as the burn-out
of minor amounts of organic contaminants,
possibly introduced during the milling process.
This is supported by the XRD patterns that
remain almost unaltered up to 450 °C.The main
mass loss of 8.4 % was detected in the temperature range between 410 °C and 810 °C, resulting
from the decomposition of the carbonates as evidenced by the large CO2 peaks in the IR spectra.
This mass loss is in good agreement with the
theoretical mass loss of 8.6 %, calculated for the
investigated stoichiometric mixture due to CO2
evaporation.
Figure 1. Investigation of the calcination process
during the heating (5 K/min) of a homogenized mixture
of reagents using a) XRD analysis ex-situ and b)
STA-IR measurement.4
The mass loss between 410 °C and 610 °C and
the corresponding endothermic peak observed by differential thermal analysis (DTA)
at 587 °C are predominantly related to the
decompositions of the Na2CO3 and its reaction
with Bi2O3 and TiO2 to form the BNT phase. The
mass loss between 610 °C and 810 °C and the
endothermic peak at 795 °C can be ascribed to
the decomposition of the SrCO3 and its reaction
with the remaining TiO2 to form the ST phase (note that Bi2O3 was not detected at 700 °C).
During the calcination process and further
heating above 810 °C the diffusion between BNT
and ST phases results in the formation of an
inhomogeneous BNT-ST solid solution.
The different reaction temperatures of both
phases are therefore suggested to be the origin
of the formation of the core-shell microstructure
of BNT-ST, consisting of two solid solutions: a
BNT-rich core and ST-rich shell.3 The formation of a core-shell microstructure was confirmed by the inspection of the sintered samples
using scanning electron microscopy (Figure 2).
While no cores could be observed in the thermally-etched microstructures taken using secondary electrons (Figure 2a), several bright
regions can be seen in the images taken on
the polished surfaces using the backscattered
electrons (Figure 2b,c). All samples exhibited
a (14; 1∞)s type core-shell microstructure.3
The brighter color of the core regions indicates a higher concentration of heavier elements,
confirming the BNT-rich nature of the core.
A detailed compositional analysis of BNT-ST
calcined powders using transmission electron
microscopy revealed the existence of a Na- and
Bi-rich central region, confirming the presence
of a BNT-rich core, and a Sr-rich outer region of
the particle, indicating a ST-rich shell.4
The electromechanical analysis showed
a strong dependence of the sample´s large-signal
unipolar strain response on the microstructural parameters.4 The samples reaching a
relative density above 95 %, average grain
size above 2.5 μm, and core density below
0.075 cores/μm2 exhibited high strain values of
about 0.27 % (Figure 3).
These results once again underline the importance of understanding and controlling the
processing parameters during solid-state synthe-
References
[1] S. T. Zhang, A. B. Kounga, E. Aulbach, H.
Ehrenberg, and J. Rödel, Applied Physics Letters 91
(11), 112906 (2007).
[2] Y. Hiruma, Y. Imai, Y. Watanabe, H. Nagata, and
T. Takenaka, Applied Physics Letters 92 (26), 262904
(2008).
[3] M. Acosta, Ljubomira. A. Schmitt, Leopoldo
Molina-Luna, Michael C. Scherrer, Michael Brilz,
Kyle G. Webber, Marco Deluca, H. J. Kleebe,
Jürgen Rödel, and Wolfgang Donner, Journal of the
American Ceramic Society 98 (11), 3405 (2015).
[4] J. Koruza, V. Rojas, L. Molina-Luna, U. Kunz,
M. Duerrschnabel, H. J. Kleebe, and M. Acosta,
Journal of the European Ceramic Society 36 (4),
1009 (2016).
Figure 2. Microstructure of a BNT-ST sample sintered for 5 h at 1150 °C: a) polished and thermallyetched surface (secondary electrons)
and b) and c) polished surface (backscattered electrons).
Figure 3. Influence of the microstructural parameters (relative density, average grain size, and core density) on the unipolar electric-field
induced maximal strain.
Research Projects
• Stress and strain fields in ferroelectrics (Graduate school “computational
engineering” 2009-2017)
• Lead-free piezoelectric single crystals with high strain: orientation dependence, polarization rotation and morphotropic phase boundaries (DFG 2011-2015)
• Energy absorption of ZnO varistors (DFG 2011-2015)
• Ag-based electrical switches (state of Hesse / Umicore, 2012-2015)
• Emmy Noether Program: The Influence of Mechanical Loads on the Functional Properties of Perovskite Oxides (DFG 2013-2018)
• Cooling power in lead-free electrocaloric materials (DFG 2015-2018)
• Electrocaloric effect in lead-free relaxors and composites
(DFG 2015-2018)
• Fracture Toughness in bismuth-based lead-free piezoceramics
(DFG 2014-2017)
• Polarization switching in lead-free ferroelectrics: statistical theory
and experiments (DFG 2015-2018)
• KNN-based lead-free single crystals (EU IDS FunMat: 2013-2016)
Publications
[1]
Ehara, Yoshitaka ; Novak, Nikola ; Shintaro, Yasui ;
Itoh, Mitsuru ; Webber, Kyle G. :
Electric-field-temperature phase diagram of Mn-doped Bi0.5(Na0.9K0.1)0.5TiO3 ceramics.
[Online-Edition: http://dx.doi.org/10.1063/1.4938759]
In: Applied Physics Letters, 107 ISSN 00036951 [Artikel], (2015)
[2]
Porz, Lukas ; Sai, Wei ; Zhao, Jiamin ; Patterson, Eric A. ;
Liu, Bin :
Characterizing Brittle Fracture by Modeling Crack Deflection Angles from the Microstructure.
In: Journal of the American Ceramic Society (98) pp. 3690-3698. ISSN 00027820 [Artikel], (2015)
[3]
Glaum, Julia ; Simons, Hugh ; Hudspeth, Jessica M. ;
Acosta, Matias ; Daniels, John E.
Temperature dependent polarization reversal mechanism in 0.94(Bi1/2Na1/2)TiO3-0.06Ba(Zr0.02Ti0.98)O3 relaxor ceramics.
In: Applied Physics Letters (107) ISSN 00036951 [Artikel], (2015)
[4]
Malič, Barbara ; Koruza, Jurij ; Hreščak, Jitka ; Bernarding,
J. ; Wang, Ke ; Fisher G., John ; Benčan, Andreja :
Sintering of Lead-Free Piezoelectric Sodium Potassium
Niobate Ceramics. [Online-Edition: http://www.mdpi.com/1996-
1944/8/12/5449] In: Materials ISSN 1996-1944 [Artikel], (2015)
[5]
Huan, Yu ; Wang, Xiaohui ; Li, Longtu ; Koruza, Jurij :
Strong domain configuration dependence of the nonlinear
dielectric response in (K,Na)NbO3-based ceramics.
In: Applied Physics Letters (107) ISSN 00036951 [Artikel], (2015)
[6]
Acosta, Matias :
Strain Mechanisms in Lead-Free Ferroelectrics for Actuators.
[Online-Edition: http://tuprints.ulb.tu-darmstadt.de/id/eprint/5139]
Matias Acosta , Darmstadt [Dissertation], (2015)
[7]
Schneider, Deborah ; Rödel, Jürgen ; Rytz, Daniel ;
Granzow, Torsten :
Orientation-Dependence of Thermal Depolarization and Phase
Development in Bi1/2 Na1/2 TiO3-BaTiO3 Single Crystals.
In: Journal of the American Ceramic Society pp. 1-9. ISSN 00027820
[Artikel], (2015)
Publications
[8] Pirc, R. ; Rožič, B. ; Koruza, Jurij ; Malič, Barbara ;Kutnjak, Z.:
Anomalous dielectric and thermal properties of Ba-dopedPbZrO3 ceramics.
[Online-Edition: http://iopscience.iop.org/0953-8984/27/45/455902]
In: Journal of Physics: Condensed Matter, 27 ISSN 0953-8984
[Artikel], (2015)
[9] Hoeher, Robin ; Raidt, Thomas ; Novak, Nikola ;
Katzenberg, Frank ; Tiller, Joerg C. :
Shape-Memory PVDF Exhibiting Switchable Piezoelectricity.
[Online-Edition: http://onlinelibrary.wiley.com/doi/10.1002/
marc.201500410/ab...]
In: Macromolecular Rapid Communications ISSN 10221336
[Artikel], (2015)
[10]
Acosta, Matias ; Novak, Nikola ; Rossetti Jr., George A. ;
Rödel, Jürgen :
Mechanisms of electromechanical response in
(1 − x)Ba(Zr0.2Ti0.8)O3- x(Ba0.7Ca0.3)TiO3 ceramics.
In: Applied Physics Letters (107) [Artikel], (2015)
[11] Popovič, A. ; Bencze, L. ; Koruza, Jurij ; Malič, Barbara :
Vapour pressure and mixing thermodynamic properties of the KNbO3–NaNbO3system.
[Online-Edition: http://dx.doi.org/10.1039/c5ra11874c]
In: RSC Adv., 5 (93) pp. 76249-76256. ISSN 2046-2069
[Artikel], (2015)
[12]
Zhang, Haibo ; Xu, Peiwei ; Patterson, Eric A. ; Zang, Jiadong ; Jiang, Shenling ; Rödel, Jürgen :
Preparation and enhanced electrical properties of grain-oriented (Bi1/2Na1/2)TiO3-based lead-free incipient piezoceramics.
[Online-Edition: http://dx.doi.org/10.1016/j.jeurceramsoc.2015.03.012]
In: Journal of the European Ceramic Society, 35 (9) pp. 2501-2512. ISSN 09552219 [Artikel], (2015)
[13]
Baraki, Raschid ; Novak, Nikola ; Hofstätter, Michael ;
Supancic, Peter ; Rödel, Jürgen ; Frömling, Till :
Varistor piezotronics: Mechanically tuned conductivity in varistors.
In: Journal of Applied Physics, 118 (8) 085703(1-9). ISSN 0021-8979
[Artikel], (2015)
Publications
[14]
Vögler, Malte ; Acosta, Matias ; Brandt, David R. J. ;
Molina-Luna, Leopoldo ; Webber, Kyle G. :
Temperature-dependent R-curve behavior of the lead-free ferro-
electric 0.615Ba(Zr0.2Ti0.8)O3–0.385(Ba0.7Ca0.3)TiO3 ceramic.
[Online-Edition: http://dx.doi.org/10.1016/j.engfracmech.2015.06.069]
In: Engineering Fracture Mechanics, 144 pp. 68-77. ISSN 00137944
[Artikel], (2015)
[15]
Acosta, Matias ; Schmitt, Ljubomira A. ; Molina-Luna, Leopoldo ; Scherrer, Michael C. ; Brilz, Michael ; Webber, Kyle G. ;
Deluca, Marco ; Kleebe, Hans-Joachim ; Rödel, Jürgen ;
Donner, Wolfgang :
Core–Shell Lead–Free Piezoelectric Ceramics: Current Status and Advanced Characterization of the Bi1/2Na1/2TiO3–SrTiO3 System.
In: Journal of the American Ceramic Society (2015) pp. 1-8. ISSN 00027820 [Artikel], (2015)
[16]
Liu, Na ; Dittmer, Robert ; Stark, Robert W. ; Dietz, Christian :
Visualization of polar nanoregions in lead-free relaxors via piezo-
response force microscopy in torsional dual AC resonance tracking mode. [Online-Edition: http://dx.doi.org/10.1039/c5nr01326g]
In: Nanoscale (25) p. 10835. ISSN 2040-3364
[Artikel], (2015)
[17]
Jung, Markus ; Krausmann, J. ; Bender, M. ; Bachmann, J. ; Rödel, Jürgen :
Infiltration of silver into porous SnO2−x : influence of atmosphere, interfacial reactions, and surface properties.
[Online-Edition: http://dx.doi.org/10.1007/s10853-015-9043-8]
In: Journal of Materials Science, 50 (14) pp. 4962-4969. ISSN 0022-
2461 [Artikel], (2015)
[18]
Wang, Ruiping ; Wang, Ke ; Yao, Fangzhou ; Li, Jing-Feng ; Schader, Florian H. ; Webber, Kyle G. ; Jo, Wook ; Rödel, Jürgen :
Temperature Stability of Lead-Free Niobate Piezoceramics with
Engineered Morphotropic Phase Boundary.
[Online-Edition: http://dx.doi.org/10.1111/jace.13604]
In: Journal of the American Ceramic Society, 98 (7) pp. 2177-2182. ISSN 00027820 [Artikel], (2015)
Publications
[19]
Zakhozheva, M. ; Schmitt, Ljubomira A. ; Acosta, Matias ;
Guo, H. ; Jo, Wook ; Schierholz, Roland ; Kleebe, Hans-Joachim ; Tan, Xiaoli :
Wide Compositional RangeIn SituElectric Field Investigations on Lead-FreeBa(Zr0.2Ti0.8)O3−x(Ba0.7Ca0.3)TiO3Piezoceramic.
[Online-Edition: http://dx.doi.org/10.1103/PhysRevApplied.3.064018]
In: Physical Review Applied, 3 (6) ISSN 2331-7019
[Artikel], (2015)
[20] Koruza, Jurij ; Franzbach, Daniel J. ; Schader, Florian ;
Rojas, Virginia ; Webber, Kyle G. :
Enhancing the operational range of piezoelectric actuators by
uniaxial compressive preloading.
[Online-Edition: http://dx.doi.org/10.1088/0022-3727/48/21/215302]
In: Journal of Physics D: Applied Physics, 48 (21) 215302(1-8). ISSN 0022-3727
[Artikel], (2015)
[21]
Rödel, Jürgen ; Webber, Kyle G. ; Dittmer, Robert ; Jo, Wook ; Kimura, Masahiko ; Damjanovic, Dragan :
Transferring lead-free piezoelectric ceramics into application.
In: Journal of the European Ceramic Society, 35 (6) pp. 1659-1681. ISSN 09552219
[Artikel], (2015)
[22] Koruza, Jurij ; Rožič, B. ; Cordoyiannis, G. ; Malič, Barbara ; Kutnjak, Z. :
Large electrocaloric effect in lead-free K0.5Na0.5NbO3-SrTiO3
ceramics.
In: Applied Physics Letters, 106 (20) p. 202905. ISSN 0003-6951
[Artikel], (2015)
[23] Schader, Florian H. ; Morozov, Maxim ; Wefring, Espen T. ; Grande, Tor ; Webber, Kyle G. :
Mechanical stability of piezoelectric properties in ferroelectric
perovskites.
[Artikel], (2015)
Publications
[24]
Acosta, Matias ; Liu, Na ; Deluca, Marco ; Heidt, Sabrina ;
Ringl, Ines ; Dietz, Christian ; Stark, Robert W. ; Jo, Wook :
Tailoring ergodicity through selective A-site doping in
the Bi1/2Na1/2TiO3–Bi1/2K1/2TiO3 system.
[Artikel], (2015)
[25] Koruza, Jurij ; Rojac, Tadej ; Malič, Barbara Aliofkhazraei, Mahmood (ed.) :
Polar oxide nanopowders prepared by mechanical treatments
Handbook of Mechanical Nanostructuring, 2-Volume Set.
In: Handbook of Mechanical Nanostructuring. - Handbuch/Nach-
schlagewerk -, 2 - Volume Set. Wiley-VCH Verlag GmbH & Co KGaA, Weinheim , pp. 641-661. ISBN 978-3-527-33506-0
[Buchkapitel], (2015)
[26] Zhang, Ji ; Pan, Zhao ; Guo, Fei-Fei ; Liu, Wen-Chao ; Ning, Huanpo ; Chen, Y. B. ; Lu, Ming-Hui ; Yang, Bin ; Chen, Jun ; Zhang, Shan-Tao ; Xing, Xianran ; Rödel, Jürgen ; Cao, Wenwu ; Chen, Yan-Feng :
Semiconductor/relaxor 0–3 type composites without thermal
depolarization in Bi0.5Na0.5TiO3-based lead-free piezoceramics.
[Online-Edition: http://dx.doi.org/10.1038/ncomms7615]
In: Nature Communications, 6 6615(1-10). ISSN 2041-1723
[Artikel], (2015)
[27] Acosta, Matias ; Khakpash, Nasser ; Someya, Takumi ; Novak, Nikola ; Jo, Wook ; Nagata, Hajime ; Rossetti, George A. ;
Rödel, Jürgen :
Origin of the large piezoelectric activity in (1 − x)Ba(Zr0.2Ti0.8)
O3-x(Ba0.7Ca0.3)TiO3 ceramics.
[Online-Edition: http://dx.doi.org/10.1103/PhysRevB.91.104108]
In: Physical Review B, 91 (10) 104108(1-11). ISSN 1098-0121
[Artikel], (2015)
[28] Li, Ming ; Li, Linhao ; Zang, Jiadong ; Sinclair, Derek C. :
Donor-doping and reduced leakage current in Nb-doped Na0.5Bi0.
5TiO3.
In: Applied Physics Letters, 106 (10) 102904(1-5). ISSN 0003-6951
[Artikel], (2015)
Publications
[29] Sanlialp, Mehmet ; Shvartsman, Vladimir V. ; Acosta, Matias ; Dkhil, Brahim ; Lupascu, Doru C. :
Strong electrocaloric effect in lead-free 0.65Ba(Zr0.2Ti0.8)O3-0.35
(Ba0.7Ca0.3)TiO3 ceramics obtained by direct measurements.
In: Applied Physics Letters, 106 (6) 062901. ISSN 0003-6951
[Artikel], (2015)
[30] Ayrikyan, Azatuhi ; Rojas, Virginia ; Molina-Luna, Leopoldo ;
Acosta, Matias ; Koruza, Jurij ; Webber, Kyle G. :
Enhancing Electromechanical Properties of Lead-Free Ferroelectrics With Bilayer Ceramic/Ceramic Composites.
[Online-Edition: http://dx.doi.org/10.1109/TUFFC.2014.006673]
In: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 62 (6) pp. 997-1006. ISSN 0885-3010
[Artikel], (2015)
[31] Guo, Hanzheng ; Liu, Xiaoming ; Rödel, Jürgen ; Tan, Xiaoli :
Nanofragmentation of Ferroelectric Domains During Polarization Fatigue.
[Online-Edition: http://dx.doi.org/10.1002/adfm.201402740]
In: Advanced Functional Materials, 25 (2) pp. 270-277. ISSN 1616301X
[Artikel], (2015)
[32] Zhang, Haibo ; Groh, Claudia ; Zhang, Qi ; Jo, Wook ;
Webber, Kyle G. ; Rödel, Jürgen :
Large Strain in Relaxor/Ferroelectric Composite Lead-Free
Piezoceramics.
[Online-Edition: http://dx.doi.org/10.1002/aelm.201500018]
In: Advanced Electronic Materials n/a-n/a. ISSN 2199160X
[Artikel], (2015)
[33]
Daniel, L. ; Hall, D. A. ; Koruza, Jurij ; Webber, Kyle G. ;
King, A. ; Withers, P. J. :
Revisiting the blocking force test on ferroelectric ceramics using high energy x-ray diffraction.
[Artikel], (2015)
Publications
[34]
Hinterstein, Manuel ; Schmitt, Ljubomira A. ; Hoelzel, Markus ; Jo, Wook ; Rödel, Jürgen ; Kleebe, Hans-Joachim ; Hoffman, M. :
Cyclic electric field response of morphotropic
Bi1/2Na1/2TiO3-Ba-TiO3 piezoceramics.
In: Applied Physics Letters, 106 (22) 222904(1-5). ISSN 0003-6951
[Artikel], (2015)
[35] Jung, Markus :
Einfluss der Materialeigenschaften auf das elektrische Schaltverhalten von Ag/Sn02-Kontaktwerkstoffen.
TU Darmstadt
[Dissertation]
Note:
Darmstadt, Technische Universität, Diss. 2015
[36] Groh, Claudia :
Lead-Free Piezoceramics Relaxor/Ferroelectric Composites Based on Bismuth Sodium Titanate.
VVB Laufsweiler Verl. , Gießen
[Dissertation]
Note:
Zugl.: Darmstadt, Technische Universität, Diss.
[37] Humburg, Heide ; Acosta, Matias ; Jo, Wook ; Webber, Kyle G. ; Rödel, Jürgen :
Stress-dependent electromechanical properties of doped (Ba1−xCax)
(ZryTi1−y)O3.
In: Journal of the European Ceramic Society, 35 pp. 1209-1217. ISSN 09552219
[Artikel], (2014)
[38]
Zhukov, Sergey ; Acosta, Matias ; Genenko, Yuri A. ;
von Seggern, Heinz :
Polarization dynamics variation across the temperature- and
composition-driven phase transitions in the lead-free Ba(Zr0.2Ti0.8)
O3−x(Ba0.7Ca0.3)TiO3 ferroelectrics.
In: Journal of Applied Physics, 118 (13) 134104(1--10). ISSN 0021-8979
[Artikel], (2015)
Publications
[39]
Christmann, J. ; Müller, R. ; Webber, Kyle G. ; Isaia, Daniel ; Schader, Florian H. ; Kipfstuhl, S. ; Freitag, J. ; Humbert, A. :
Measurement of the fracture toughness of polycrystalline bubbly ice from an Antarctic ice core.
In: Earth System Science Data, 7 pp. 87-92.
[Artikel], (2015)
[40]
Deluca, Marco ; Picht, Gunnar ; Hoffmann, Michael J. ;
Rechtenbach, Annett ; Töpfer, Jörg ; Schader, Florian H. ;
Webber, Kyle G. :
Chemical and structural effects on the high-temperature mechanical behavior of (1−x)(Na1/2Bi1/2)TiO3-xBaTiO3 ceramics.
In: Journal of Applied Physics, 117 ISSN 00218979
[Artikel], (2015)
[41] Humburg, Heide ; Acosta, Matias ; Jo, Wook ; Webber, Kyle G. ; Rödel, Jürgen :
Stress-dependent electromechanical properties of doped
(Ba1−xCax)(ZryTi1−y)O3.
In: Journal of the European Ceramic Society, 35 pp. 1209-1217. ISSN 09552219
[Artikel], (2014)
[42] Ansell, Troy Y. ; Cann, David P. ; Sapper, Eva ; Rödel, Jürgen :
Thermal Depolarization in the High-Temperature Ternary
Piezoelectric SystemxPbTiO3-yBiScO3-zBi(Ni1/2Ti1/2)O3.
[Online-Edition: http://dx.doi.org/10.1111/jace.13268]
In: Journal of the American Ceramic Society, 98 (2) pp. 455-463. ISSN 00027820
[Artikel], (2014)
Physical Metallurgy
Staff Members
Head
Prof. Dr. Karsten Durst
Research Asscoiates
Dr. Enrico Bruder
Dr. K. Johanns
Prof. Dr. Clemens Müller
Hamad ur Rehman, M.Sc.
Technical Personnel
Ulrike Kunz
Sven Frank
Petra Neuhäusel
Claudia Wasmund
Secretaries
Christine Pommerenke
PhD Students
Laura Ahmels, M.Sc.
Richard Braak, M. Sc.
Sebastian Bruns, M. Sc.
Dipl.-Ing. Thorsten Gröb
Fahrhan Javaid, M. Sc.
Markus Kuhnt, M. Sc.
Dipl.-Ing. Jörn Niehuesbernd
Olena Prach, M. Sc.
Dipl.-Ing Jan Scheil
Dipl.-Ing. Christoph Schmid
Bachelor/ Master Students
Paul Braun
Sebastian Bruns
Asmamaw Molla Chekol
Thorsten Simon Eisele
Florian Falk
Chandanraj Gangaraju
Tom Christopher Keil
Alexnader Kremer
Christian Minnert
Anok Babu Nagram
Tobias Opitz
Lukas Schäfer
Theresa Schütz
Romana Schwing
Marius Specht
Golo Zimmerann
Physical Metallurgy | 149
Physical Metallurgy
The Physical Metallurgy research group (PhM)
in the department of materials science at TU
Darmstadt, headed by Prof. Dr.-Ing. Karsten
Durst, works on structure-property relationships
of structural metallic materials and thin hard
coatings with a focus on mechanical properties
from the microscopic to macroscopic length scale.
The group utilizes and develops state-of-the-art
testing methods for enhanced understanding of
the deformation mechanisms of structural materials. Of main interest are mechanical properties
of materials under various loading conditions
(uniaxial, fatigue, wear or creep), specifically
those relating the macroscopic material response
to the micromechanical properties at small length
scales. New insights in the materials response are
achieved through in-situ mechanical testing approaches, where material is mechanically loaded
and monitored by microscopic or spectroscopic
techniques simultaneously.
In 2015, the key investments in the research
equipment are finalized and the current research
highlight article features the possibilities of our
new Tescan Mira 3 XMH field emission gun
scanning electron microscope (FEG-SEM) for
in-situ thermomechanical testing.
In March 2015, PhM hosted a DGM symposium on “Mechanical characterization of materials
on a microstructural length scale”. The 1.5 day
meeting was quite successful, enabling discussion on current topics in micromechanical testing
approaches.
Several research projects have been newly
funded in 2015, among them two industrial PhD
projects. One project is in collaboration with the
Robert Bosch GmbH, working on ideal adhesion
systems for carbon coating systems. The project
in collaboration with the Vacuumschmelze
GmbH is related to amorphous metals for soft
magnetic application.
150 | Physical Metallurgy
Before Christmas in late December 2015, we
were quite happy to receive two funding letters
from the DFG. Therefor we are still part of
the second funding period of the DFG priority
program ultrastrong glasses. There we aim in
collaboration with the Otto Schott Institute in
Jena for ultrastrong borosilicate glasses. Specifically we want to understand the cracking,
shear flow and densification behavior of borosilicate glasses under indentation loading both
experimentally and by finite element modelling.
Secondly we have now a new project which
focuses on the nanoimprinting behavior of
metals. Within the project we want to study and
model the flow nanocrystalline metals micron
to nanoscale cavities, aiming at a hierarchical
structuring of metallic surfaces.
The new projects thereby strengthen our
activities in the field of thin films, magnetic
materials as well as deformation mechanism in
nanocrystalline materials.
In summer 2015 PhM attended an interdisciplinary lecture within the framework of the
“Quality Pact for Teaching”, a joint program
of the federal and the state governments to improve conditions for studying. The lecture was
organized by KIVA (Kompetenzentwicklung
durch interdisziplinäre Vernetzung von Anfang
an; Competence development through interdisciplinary cooperation from the very outset)
and brought together students of Architecture,
Mathematics, Physics and Material Science.
28 students from first and second year BSc. of
Material Science decided to follow this elective
course and gave a predominantly very positive
assessment on both quality of the tutors and
personal learning experience.
Group photo of the DGM meeting in March 2015
New High Resolution SEM for In-Situ Thermomechanical
Experiments
Introduction
The research group Physical Metallurgy recently
installed a new Tescan MIRA3-XM series high
resolution SEM, co-funded by the Major Research Instrumentation Program of the German
Research Foundation (DFG). The SEM and its
add-on devices and software packages provide
an excellent platform for a vast range of experiments from high resolution imaging to in-situ
thermomechanical treatments which are essential
for in-depth research on microstructures and
deformation mechanisms.
The system is equipped with a Schottky Field
Emitter providing a lateral resolution down to 1
nm and wide field optics which allow a very large
field of view. The SEM features two SE detectors
(EverhartThornley and in-lens) as well as three BSE detectors for high resolution, high temperature and low
voltage imaging.
The Deben Gen5 solid state detector allows the
imaging of single dislocations and stacking faults
whereas the cooled Tescan YAG detector is used to
visualize microstructures of samples with a surface
temperature of up to 800°C.
Another key aspect is the versatility of the
SEM for in-situ mechanical testing. It can be
equipped with a nanoindenter for site specific
testing of local properties or small samples and
with a tension-compression module with heating
unit for a variety of mechanical and thermomechanical experiments. In the following, some application examples of the SEM using the different
stages and detectors are presented.
Electron channeling contrast imaging (ECCI)
The Tescan MIRA3 SEM is equipped with a
four quadrant solid state BSE detector which
facilitates the swhanneling contrast imaging
(ECCI). The intensity of backscattered electron
is strongly influenced by the orientation of
crystal lattice planes with respect to the incident
beam. A slight local misorientation in deformed
regions can lead to different electron channeling
conditions compared to non-deformed neighboring regions which enables the imaging of defects
with enhanced contrast. Fig. 2(a) shows a ball
nanoindentation image obtained via ECCI on
coarse grained polycrystalline tungsten. Next to
the residual impression, there is a significant contrast showing a deformed region with higher dislocation density which is marked by a rectangle.
For better visualization, the highlighted region is
shown in Fig. 2(b) which illustrates the dislocation structure around the ball nanoindentation.
In future, the analysis of the local dislocation structure via ECCI will be used for a wide
range of investigations such as dislocations
at grain boundaries, crack tips or in highly
deformed regions of the materials after indentation testing. This information is important
for understanding the evolution of dislocation
microstructures, which are essential for the thermomechanical properties of metallic materials.
a)
Fig. 1: (a) Picture of newly installed high resolution SEM with members from the PhM group.
b)
View inside the chamber with (b) in-situ tensile table
installed and
c)
(c) Nanoindenter installed.
Fig. 2: ECCI images acquired around a ball indentation in Tungsten. The dark contrast in (b) stems from individual dislocations
induced by the indentation.
EBSD analysis with high spatial and angular
resolution
Electron Back Scatter Diffraction (EBSD)
is used to analyze the local orientation or
misorientation of individual grains based on
corresponding electron diffraction patterns.
The new SEM is equipped with an EDAX
Octane Plus SDD EDX and a DigiView high
resolution EBSD system which allows EBSD
mappings with up to 200 frames per second
on standard samples and 50-100 patterns per
second on severely deformed ultrafine grained
materials or when combining EDX and EBSD.
Grain size analysis
For nanocrystalline materials with a grain size
below 100 nm, conventional EBSD reaches its
resolution limits as the interaction volume of the
electron beam in which the diffraction pattern
is similar to or even larger than the grain size.
However, EBSD can still be utilized to analyze
nanocrystalline materials if a different measurement setup is being used. The size of the interaction volume can be reduced significantly when
using thin electron transparent samples, such as
those used for TEM investigations. The setup
for a transmission EBSD measurement is shown
in Fig. 3 together with the results on a severely
deformed CuZn5 alloy with ultrafine grained
microstructure.
While the micrograph appears to consist mostly
of grains in the 300 – 500nm range, the grain
size distribution clearly shows that the majority
of grains are well below 100 nm, which could not
be resolved in a standard EBSD setup. The analysis of the grain size distribution is of crucial for
understanding the processes in the alloys, which
enable the formation of an ultrafine grained
microstructure during severe plastic deformation.
Moreover, investigations on texture evolution or
thermal stability of such alloys also require high
resolution EBSD analysis.
Determination of dislocation density
EBSD can also be used for analyzing elastic and
plastic strains inside the material. For these applications, the angular resolution of EBSD can be
a limiting factor. The typical indexing approach
with an angular resolution of 0.5 to 1° can’t capture elastic strains and only allows a very rough
estimate of the so called geometrically necessary
dislocations (GNDs) if the dislocation density is
sufficiently high. The angular resolution can be
improved by about two orders of magnitude when
using a different approach for misorientation
measurements which is based on a digital image
cross correlation of high resolution diffraction
patterns. The same approach allows the determination of elastic strains with a resolution in the
order of 10 -4.
Fig. 3: Setup for transmission-EBSD (a) and grain map (b) with corresponding grain size distribution
(c) of a t-EBSD measurement on UFG CuZn5.
Fig. 4: High resolution Kernel Average Misorientation map of the plastic
zone under a ball nanoindentation in Tungsten.
Hence the visualization of small plastic strain
gradients and accurate quantification of GNDs
becomes feasible as well the measurement of
local residual stresses in a nondestructive way.
The potential of the cross correlation approach is
demonstrated in Fig. 4 showing the plastic zone
under a ball nanoindentation in Tungsten (same
indent as in Fig. 2). The high resolution Kernel
Average Misorientation (KAM) map illustrates
the strain gradients within the plastic zone and
evolving subgrain boundaries as dark lines with
sharp contrast. The resolved KAM range covers
more than two orders of magnitude from an orientation noise floor of approx. 0.01° (0.0002rad)
up to 5° (0.1rad) at subgrain boundaries.
In-situ mechanical testing
Within the SEM chamber, an MTII/Fullam
SEMtester universal testing machine (tension,
compression, bending) can be installed for in-situ
mechanical testing. Exchangeable load cells
facilitate experiments in a load range from a
few Newton up to 9 kN with crosshead velocities from < 1 µm/s to 80 µm/s. The device also
features a heating unit which allows in-situ heat
treatments and thermomechanical tests from RT
up to >1000°C. Fig. 5 shows an example for an
in-situ 3 point bending test in which the deformation behavior of ultrafine grained (UFG) steel is
studied. High resolution BSE images show that
the imposed bending displacements results in
the formation and growth of shear bands while
regions in between the shear bands remain strain
free.
The formation of shear bands or other instabilities like necking in tensile testing or the propagation of cracks are strongly influenced by the
material microstructure and loading condition.
Here, in-situ high resolution analysis offers the
unique possibility to correlate the instability with
the local microstructure and deformation state.
In-situ Nanoindentation
Finally, the MIRA3 can be equipped with a new
stage mounted cradle based in-situ nanoindenter
called NanoFlip (Nanomechanics Inc., USA).
The electromagnetic actuator of NanoFlip with a
maximum force of 50 mN is capable to perform
not only quasi-static but also dynamic testing in
vacuum with frequencies of up to 500 Hz. The
continuous measurement of contact stiffness or
continuous dynamics analysis during dynamical
testing allows for a detailed investigation of the
mechanical behavior of a wide range of materials.
Here the option of high speed data acquisition
with up to 100 kHz provided by NanoFlip is
beneficial for gaining a better understanding of
the underlying deformation mechanisms.
The high performance of the indenter enables test methods such as strain-rate jump tests
used to measure strain rate sensitivity on a very
local scale. Fehler! Verweisquelle konnte nicht
gefunden werden. illustrates the displacement
resolution and high speed data acquisition of the
NanoFlip exemplarily shown for strain-rate jump
test data measured on single crystal of CaF2.
Strain-rate variation leads to a significant change
in hardness in single crystalline CaF2 as shown
in Fig. (b). These type of measurements can also
be performed with the Nanomechanics and Keysight ex-situ nanoindenters which were recently
installed in the PhM group. Mounting a sample in
an SEM NanoFlip allows to automatically tilt the
indenter stage by 90° to align the sample either in
line with the SEM for high resolution imaging or
the indenter tip for in-situ testing.
Fig. 5: Growth of a shear band in UFG steel during 3 point bending test (x markers indicate same positions).
Fig. 6: a) Displacement resolution of actuator b) Hardness – Strain rate sensitivity on single crystalline CaF2
The high resolution imaging and analytic
capabilities of the SEM (EBSD and EDX) in
combination with high positioning accuracy of
the NanoFlip allow site specific testing of small
volumes such as individual phases in a complex
microstructure. This is exemplarily shown in
Fig. 7 for Austempered Ductile Iron (ADI), which
consists of several phases with different mechanical properties. Unlike martensite and ferrite
metastable austenite shows two characteristic
pop-ins which can be attributed to strain induced
transformation from austenite to martensite
(Fig. 7c). Especially the change in slope after the
pop-ins is characteristic for the martensitic transformation. Furthermore, the phase transformation
can be substantiated by an EBSD analysis in the
plastic zone underneath the indents, showing the
formation of martensite lamellae in metastable
austenite (Fig. 7b).
SEM video files captured during in-situ testing synchronized with the mechanical test data
enable time resolved correlation of specific test
events like inelastic deformation or fracture of the
sample under investigation with the correspondent mechanical data. Fig. X gives an example of
analyzing the cracking of a 1.5 µm thick a-C:H:W
coating deposited on steel substrate. A pillar with
a diameter of about 3.5 µm (Fig. 8a) was prepared
by FIB using a JEOL JIB 4600F.
Two pop-ins, a small and a large one, were
observed in the force displacement curve
(Fig. 8b). Both could be correlated to specific
failure mechanisms of the coating by means of
in-situ observation. The first small pop-in could
be attributed to cracking of the coating and
the second to catastrophic failure of the pillar
probably caused by delamination at the interface.
After the test the sample stage was rotated by 90°
and the sample was aligned in line with the SEM
for high resolution imaging and detailed failure
analysis.
The pillar was hit in its center, giving evidence
for the high positioning accuracy, and split in
three equal parts, which seem to be delaminated at the interface between the coating and the
steel substrate (Fig. 9a).
For the evaluation of the experimental data
Finite Element Analysis (FEA) is needed.
A qualitative good agreement between experiment and simulation was observed. Fig. 9b)
shows the crack propagation (rough textured
surface) before and after first pop-in together
with the correspondent force displacement
curves extracted from FEA. The force displacement curve of FEA also shows two popins. Here the opportunity to directly watch the
experiment synchronized with the mechanical
test data is of particular importance for the
analysis of the experiment and a fundamental
Summary
In situ micromechanical testing and high
resolution analysis of dislocations and lattice
misorientations inside the SEM opens an
important field for in-depth analysis of deformation mechanisms. The experimental insight
will facilitate the further understanding of
material microstructure / mechanical property
relationship which will support the development of new materials for different applications, ranging from thin films, nanostructured
metals to high temperature materials.
The continuous support by the DFG
(Deutsche Forschungsgemeinschaft, DAAD
(Deutscher Akademischer Austauschdienst)
and AIF (Arbeitsgemeinschaft industrielle
Forschungsvereinigungen)
is
greatfully
acknowledged.
Fig. 7: a) Typical microstructure of Austempered Ductile Iron, b) load displacement curves for different phases in ADI probed
with the NanoFlip and c) EBSD phase analysis in the plastic zone of an ident in metastable austenite showing the formation of
strain induced martensite (indicated by arrows).
Fig. 8: a) Side view of a FIB prepared pillar and b) load displacement curve of in-situ pillar splitting experiment with
correspondent SEM images before and just after the first pop-in.
Fig. 9: (a) Top view of the pillar
directly captured after testing and (b)
visualization of crack propagation before and after first pop-in together with
the correspondent force displacement
curves extracted from FEA. Here a
drop in force instead of displacement
is visible since the simulations were
performed under displacement control.
Research Projects
• Damaging mechanism in DLC coating systems. DFG, 2014 - 2016
• Influence of glass topology and medium range order on the deformation mechanism in borosilcate glasses – a multiple length scale approach. DFG (SPP), 2012 - 2015
• Influence of glass topology and medium range order on the deformation mechanism in borosilcate glasses – a multiple length scale approach. DFG (SPP), 2015 - 2018
• Amorphous soft magnetic materials. Industrial funded PhD project. 2015 - 2017
• Ableitung eines idealen Haftschichtsystems für diamantähnliche Kohlen-
stoffschichten (DLC) mittels mikrostrukturellen Analysemethoden. Robert Bosch GmbH, 2015- 2017
• Indentation Size Effects: Analysis of underlying mechanism using EBSD and TEM analysis. DAAD, 2012-2016
• Strengthening mechanism in rare earth Li-base Al-alloys. DAAD, 2014-2017
• EU project on residual stress - EU iStress- 604646, 2014-2016
• DFG grant for a Nanoindenter with high temperature and dynamic
indentation, 2014-2015
• DFG grant for a scanning electron microscope with EBSD detector and in-situ tensile tester, 2014-2015
• Werkzeugoberflächenoptimierung ADI. AiF/EFB-Projekt 16704, 2015-2016
• Gefüge und mechanische Eigenschaften verzweigter Blechstrukturen. DFG (SFB 666) 2013 – 2017
• Bewertung der nachträglichen Umformbarkeit von Spaltprofilen. DFG (SFB 666), 2013 – 2017
• Graduiertenkolleg. DFG (SFB 666), 2013 – 2017
• Ressourcenschonende Permanentmagnete durch optimierte Nutzung seltener Erden. LOEWE Schwerpunkt RESPONSE, 2014 – 2016
• Einfluss von Mikrostruktur- und Verformungsparametern auf die
Ermüdungseigenschaften von hochgradig verformtem Eisen. DFG,
2013 – 2016
Publications
[1]
M Sebastiani, K E Johanns, E G. Herbert, and G M Pharr. Measurement of Fracture Toughness by Nanoindentation Methods: Recent Advances and Future Challenges, Current Opinion in Solid State and Materials Science (2015).
[2] E G Herbert, P Sudharshan Phani, and K E Johanns. Nanoindentation of
Viscoelastic Solids: A Critical Assessment of Experimental Methods, Current Opinion in Solid State and Materials Science (2015).
[3] K Durst, V Maier. Dynamic nanoindentation testing for studying
thermally activated processes from single to nanocrystalline metals:
Current Opinion in Solid State and Materials Science 19 (6), 340-353 (2015)
[4]
A Klausmann, K Morita, KE Johanns, C Fasel, K Durst, G Mera,
R Riedel. Synthesis and high-temperature evolution of polysilylcarbodiimide-derived SiCN ceramic coatings: Journal of the European Ceramic Society 35 (14), 3771-3780 (2015)
[5] P Malchow, KE Johanns, D Möncke, S Korte-Kerzel, L Wondraczek. Composition and cooling-rate dependence of plastic deformation,
densification, and cracking in sodium borosilicate glasses during
pyramidal indentation: Journal of Non-Crystalline Solids 419, 97-109 (2015)
[6] V Maier, C Schunk, M Göken, K Durst. Microstructure-dependent
deformation behaviour of bcc-metals–indentation size effect and strain rate sensitivity: Philosophical Magazine 95 (16-18), 1766-1779 (2015)
[7] Z Sun, S Van Petegem, A Cervellino, K Durst, W Blum. Dynamic
recovery in nanocrystalline Ni: Acta Materialia 91, 91-100 (2015)
[8]
H ur Rehman, K Durst, S Neumeier, AB Parsa, A Kostka, G Eggeler. Nanoindentation studies of the mechanical properties of the μ phase in
a creep deformed Re containing nickel-based superalloy:
Materials Science and Engineering: A 634, 202-208 (2015)
[9]
W Blum, P Eisenlohr, M Prell, K Durst. Thermally activated flow in
soft and hard regions: Getting information on work hardening strain
and recovery strain from rate change tests
KOVOVE MATERIALY-METALLIC MATERIALS 53 (4),
199-205 (2015)
Publications
[10]
IC Choi, DH Lee, B Ahn, K Durst, M Kawasaki, TG Langdon,
J Jang. Enhancement of strain-rate sensitivity and shear yield strength
of a magnesium alloy processed by high-pressure torsion: Scripta
Materialia 94, 44-47 (2015)
[11] L. Wießner, T. Gröb, E. Bruder, P. Groche, C. Müller. Severe plastic deformation and incremental forming for magnetic hardening:
Applied Mechanics and Materials, Vol. 794, 152-159(2015)
Physics of Surfaces
Staff Members
Head
Prof. Dr. Robert Stark
Research Associates
Dr. Christian Dietz
Dr. Marek Janko
Dr. Suman Narayan
Administrative Personnel
Dipl.-Chem. Sabine Hesse
Secretaries
Imke Muschel
Melanie Schulze-Wenck
PhD Students
Dipl.-Phys. Agnieszka Voß
Dipl.-Min. Maximilian Köhn
Xije Jiang, M.Sc.
Dipl.-Phys. Svenja Bachmann
Dipl.-Phys. Simon Schiwek
Na Liu, M.Sc.
Assma Siddique, M.Phil.
Master Students
Pan Hu
Bachelor Students
Julia Auernhammer
Anna Lisa Hawlitschek
Kraun Bae
164 | Physics of Surfaces
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?”. A second focus is on
surface analysis of functional materials. With
advanced atomic microscope techniques we are
aim to get a better understanding between the
nanostructure and the macroscopic behavior of
functional materials.
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 many technological systems. Our research
portfolio targets at a better understanding of the
interplay between surface pattering (morphological and chemical) and modification with the fluid
flow. Experimental methods such as microscopy,
microfluidics, or spectroscopy are essential tools.
Physics of Surfaces | 165
Visualization of Polar Nanoregions in Lead-Free Relaxors
via Piezoresponse Force Microscopy in Torsional Dual AC
Resonance Tracking Mode
Na Liu, Robert Dittmer, Robert W. Stark, and Christian Dietz
Polar nanoregions (PNRs) play a key role in the
functionality of relaxor ferroelectrics; however,
visualizing them in lead-free relaxor ferroelectrics
with high lateral resolution is still challenging.
Thus, we studied herein the local ferroelectric domain distribution of the lead-free bismuth-based
( 1 - x ) ( B i 1/2N a 1/2T i O 3- B i 1/2K 1/2T i O 3) x(Bi1/2Mg1/2TiO3) piezoceramics which show a relaxor behavior using dual AC resonance tracking
(DART) piezoresponse force microscopy (PFM).
By utilizing excitation frequencies at either side
of the contact resonance peak of the torsional
cantilever vibration, an enhanced contrast in the
amplitude and phase images of the piezoresponse
can be achieved. Additionally, this tracking technique reduces the topographical crosstalk while
mapping the local electromechanical properties.
The true drive amplitude, drive phase, contact
resonant frequency and quality factor can be
estimated from DART-PFM data obtained using
vertically or torsionally vibrating cantilevers.
This procedure yields a three-dimensional quantitative map of the local piezoelectric properties
of the relaxor ferroelectric samples.
Using this approach, torsional (T) DART
allowed for the visualization of fine substructures within the monodomains, suggesting the
existence of PNRs in relaxor ferroelectrics. The
domain structures of the PNRs were visualized
with high precision, and the local electromechanical characteristics of the lead-free relaxor
ferroelectrics were quantitatively mapped.
Methodology
The basic principle of dual ac resonance
tracking (DART)2 piezoresponse force microscopy (PFM) is illustrated in Fig. 1a. A dual frequency electrical signal with two sinusoidal waves of
frequencies f1 and f 2 close to each other is applied
to a conductive cantilever that is brought into
contact with the ferroelectric sample surface.
The resulting cantilever deflection caused by the
electromechanical coupling between the tip and
the piezoelectric sample surface is recorded by
a photoelectric diode through a laser reflected
on the backside of the cantilever. The generated
signal is analyzed by two lock-in amplifiers,
providing the amplitudes A1 and A2 and the
phase shifts φ1 and φ2 at the two excitation frequencies, respectively. To track the instantaneous
contact resonant frequency during scanning, the
difference between the two amplitude responses,
ΔA = A1 − A2, is taken as an error signal for
the feedback loop. The principle of the contact
resonance tracking is illustrated in Fig. 1b. The
two excitation frequencies, f1 and f 2, are chosen
on either side of the tip-sample contact resonant
frequency, f 0, with the corresponding initial amplitudes, A1(f1) and A2(f 2), resulting in a constant
difference of ΔA = A1(f1) − A2(f 2).
When the contact resonance shifts during
imaging from f0 (solid line) to a smaller value f 0’
(dashed line) because of a change in the mechanical coupling between the tip and sample surface,
the amplitude A1 increases to A1’, whereas the
amplitude A2 decreases to A2’. In the case of a
positive shift of the contact resonant frequency,
the change of the amplitudes is reversed. Tracking of the contact resonance by a feedback loop
is realized by maintaining the amplitude difference ΔA at a constant value, through variation
of the driving frequencies, f1 and f 2. Thus far,
the DART-PFM mode has been reported in the
literature for flexural vibrations of the cantilever.2-3 We herein suggest applying this method
to torsional vibrations of the cantilever as well.
This torsional DART-PFM mode can be used
to characterize domains with an in-plane polarization complementary to conventional DART.
Detection of polar nanoregions
We found distinctive features in the TDART-PFM
amplitude signal with sharply defined boundary.
This observation becomes highly apparent when
focusing on the region displayed for both single
frequency (SF-) PFM (Fig. 2a) and TDART-PFM
(Fig. 2b). Only the TDART-PFM technique
reveals features that are considerably smaller
than hundreds of nanometers. Fig. 2c compares
the cross-sectional profiles obtained using both
Fig. 1 Principle of dual AC resonance tracking piezoresponse force microscopy. (a) Scheme and (b) contact
resonant frequency tracking principle.
techniques (SF-PFM - black line; TDART-PFM
- red line, for details refer to Ref. 1). The two
profiles depict similar tendencies except in the
region of the enlarged area highlighted by the
gray box. In this region, the profile measured by
TDART-PFM shows peaks invisible in the black
line obtained by SF-PFM, which corroborates the
visual impression of a higher contrast apparent in
Fig. 2b. In principle, noise and feedback lagging
or ringing might cause very tiny features in the
amplitude and phase images that can be misinterpreted as PNRs.
To corroborate the detectability of PNRs by
TDART, we focused on nanoscale features prevailing in the amplitude images. These features
were repeatedly scanned at scan angles parallel
and perpendicular to the cantilever axis (see ESI,
Fig. S7 of Ref. 1). The shape and structure of the
same nanoscale features irrespective of the scan
direction and their existence after repeated scans
demonstrate that noise or feedback induced artifacts as origin of such features can be excluded.
Furthermore, the similar trends of the
cross-sectional profiles in Fig. 2c outside the
region highlighted in gray indicate that the noise
level was similar for both imaging techniques.
Analyzing the width of the peaks within the
gray area in the profile through the full width at
half maximum, we measured a domain size of
approximately 50 nm (marked by a blue arrow).
We thus interpreted these tiny structures as the
signatures of PNRs, which are difficult to visualize with other microscopic techniques.
Conclusions
In summary, we applied a DART technique to
the torsional contact resonance of the cantilever.
Piezoresponse imaging in this mode resulted in
an enhanced contrast of the piezoresponse amplitude and phase signals as well as a reduced interference with topographical features. For DART,
we exerted a superimposed electrical driving field
to the piezoelectric domains with two distinctive
frequencies close to the contact resonance (one
below and one above), allowing for instantaneous
tracking of the true contact resonant frequency.
Fine domain features in the range of a few tens
of nanometers were observed by TDART, which
can be interpreted as the PNRs of the lead-free
relaxor ferroelectric.
These PNRs are correlated to the macroscopic peculiarities of relaxors, such as the large
electric field-induced strain. Hence, TDART
can contribute to a better understanding of the
complex interplay between the macroscopic
functionality and the nanoscopic piezoelectric
properties of lead-free relaxors. To acquire the
local electromechanical properties of the relaxor ferroelectric in three dimensions, we first
measured the piezoresponse of the sample in the
x-direction, rotated it by 90 ° to obtain the data
in the y-direction and subsequently imaged the
out-of-plane component at the same spot on the
surface. Simplifying the tip-sample surface contact mechanics with a decoupled, damped simple
harmonic oscillator model, we calculated four
important tip-sample characteristic parameters,
such as the true drive phase and amplitude, the
instantaneous contact resonant frequency and the
quality factor representative for the damping of
the tip-sample system.
We suggested a straightforward data representation of the obtained three-dimensional
dataset where we combine all values into one
single gray-scale image (z-direction) for each
parameter by including two arrows with the
distinctive color for the x- and y-directions
within each domain. The results showed that
the electromechanical sample properties differ
remarkably between the spatial directions. The
three-dimensional DART-PFM enabled the visualization of the spatial orientation of PNRs in the
relaxor ferroelectric.
References
(1) Liu, N.; Dittmer, R.; Stark, R.
W.; Dietz, C., Nanoscale 2015, 7,
11787-96.
(2) Gannepalli, A.; Yablon, D. G.;
Tsou, A. H.; Proksch, R.,
Nanotechnology 2011, 22, 355705.
(3) Rodriguez, B. J.; Callahan, C.;
Kalinin, S. V.; Proksch, R.,
Nanotechnology 2007, 18, 475504.
Fig. 2 Visualization of polar nanoregions. Ampliutde images for SF- (a) and TDART-PFM (b). (c)
Respective cross-sectional profiles for SF-(black line) and TDART-PFM (red line).
Research Projects
•
Wetting of DLC Coatings (Industry 2012 – 2015)
•
Wafer cleaning (Industry 2012 -2016)
•
UV-crosslinked collagen (DFG 2015-2017)
Publications
[1] S. Vowinkel, C. G. Schäfer, G. Cherkashinin, C. Fasel, F. Roth,N. Liu,
C. Dietz, E. Ionescu, and M. Gallei, 3D-Ordered Carbon Materials by Melt-Shear Organization for Tailor-Made Hybrid Core-Shell Polymer Particle Architectures. J. Mater. Chem. C 2015. DOI: 10.1039/
C5TC03483C
[2] Voss, A.; Dietz, C.; Stocker, A.; Stark, R., Quantitative measurement of the mechanical properties of human antibodies with sub-10-nm resolution in a liquid environment. Nano Research 2015, 8, 1987-1996.
[3] Schiwek, S.; Heim, L.-O.; Stark, R. W.; Dietz, C., Manipulation of polystyrene nanoparticles on a silicon wafer in the peak force tapping mode in water: pH-dependent friction and adhesion force. J. Appl. Phys. 2015, 117, 104303.
[4] Muench, F.; Juretzka, B.; Narayan, S.; Radetinac, A.; Flege, S.; Schaefer, S.; Stark, R. W.; Ensinger, W., Nano- and microstructured silver films synthesised by halide-assisted electroless plating. New J Chem 2015, 39, 6803-6812.
[5] Liu, N.; Dittmer, R.; Stark, R. W.; Dietz, C., Visualization of polar nanoregions in lead-free relaxors via piezoresponse force microscopy
in torsional dual AC resonance tracking mode. Nanoscale 2015, 7, 11787-11796.
[6] Janko, M.; Jocher, M.; Boehm, A.; Babel, L.; Bump, S.; Biesalski, M.; Meckel, T.; Stark, R. W., Cross-Linking Cellulosic Fibers with
Photoreactive Polymers: Visualization with Confocal Raman and Fluorescence Microscopy. Biomacromolecules 2015, 16, 2179-2187.
[7] Dietz, C.; Schulze, M.; Voss, A.; Riesch, C.; Stark, R. W., Bimodal frequency-modulated atomic force microscopy with small cantilevers. Nanoscale 2015, 7, 1849-1856.
[8] Acosta, M.; Liu, N.; Deluca, M.; Heidt, S.; Ringl, I.; Dietz, C.; Stark, R. W.; Jo, W., Tailoring ergodicity through selective A-site doping in the Bi1/2Na1/2TiO3–Bi1/2K1/2TiO3 system. J. Appl. Phys. 2015, 117, 134106.
[9] P. Hoffmann, M. Kosinova, S. Flege, J. Brötz, V. Trunova, C. Dietz, W. Ensinger, Chemical and physical properties in layers and interfaces of nanolayered Si(100)/Ni/BCxNy stacks. X-Ray Spectrometry 2015, 44, 48.
[10] C. G. Schäfer, T. Winter, S. Heidt, C. Dietz, T. Ding, J. J. Baumberg, and M. Gallei, Smart polymer inverse-opal photonic crystal films by melt-shear organization for hybrid core-shell architectures. J. Mater. Chem. C 2015, 3, 2204.
Structure Research
Staff Members
Head
Prof. Dr. Wolfgang Donner
Prof. Dr. Dr. h.c. Hartmut Fueß
Research Associates
Dr. Joachim Brötz
Dr. Ljubomira Schmitt
Dr. Marton Major
Dr. Azzain Amin
Technical Personnel
Dipl-Ing. Heinz Mohren
Ingrid Svoboda
Jean-Christophe Jaud
Sabine Foro
Secretaries
Maria Bense
PhD Students
Marwa Ben El Bahri, M. Sc.
Dipl.-Ing. Florian Pforr
Marco Léal, M. Sc.
Tom Faske, M. Sc.
Master/Diploma Students
Ahmad Ibrahim
Guest Scientists
Prof. Dr. Ismael Saadoune
Université Cadi Ayyad, Maroc
Prof. Dr. Anouar Njeh
University of Sax, Tunesia
172 | Structure Research
Structure Research
We setup a commercial Molecular Beam Epitaxy (MBE) system and tested it on the system
Bi / Si(001). The MBE system (Riber EVA 32
R&D) is capable of evaporating three metallic
sources at a time and uses a mass spectrometer
for deposition control. Thin metallic samples can
be grown in Ultra High vacuum and transfered,
without braking the vacuum, into a small x-ray
baby chamber.
We refurbished an image plate detector with
onsite readout (OBI) and set up a Debye-Scherrer
diffractometer. The diffractometer will be finally
used together with a 6 Tesla magnet to perform
x-ray diffraction experiments in a magnetic field.
Structure Research | 173
Use of a Laboratory Diffractometer to Perform Anomalous
Scattering Experiments on Epitaxial Films
Vikas Shabadi, Marton Major, and Wolfgang Donner
Alloy ordering in complex materials is always
hard to detect, since different ordering schemes
could lead to the same superlattice reflections.
One way to distinguish between different atom
types involved in the ordering is the use of anomalous scattering. Here the energy-dependence
of the atomic scattering factors is used to label
certain atoms in a scattering experiment. In most
cases synchrotron radiation is used to tune the
scattering factor, since the continuous spectrum
from a bending magnet can be filtered by a Si
double monochromator. In a laboratory source,
the continuous bremsstrahlung is too weak to
be used for monochromatization. However, the
characteristic radiation can also be used in some
cases to tune the scattering factors for maximum
contrast.
In a recent experiment, we looked at the
B-site ordering in a double-perovskite epitaxial
film. In Bi2FeCrO6, the Fe and Cr ions might
be able to arrange themselves in a long-range
B-site ordering scheme, thereby modifying the
magnetic behavior of this potential multiferroic.
The ordering of Fe and Cr ions would lead to
superstructure reflections whose intensities
would be proportional to the square of the difference of the respective form factors for iron and
chromium.
Figure 1 (left) shows the real and imaginary
parts of the form factors for iron and chromium
in a range of energies that is accessible with
laboratory sources.
The contrast between iron and chromium scatterers in a diffraction experiment can be calculated from this form factors and is shown in fig.1
(left, b). The largest obtainable contrast can be obtained using an x-ray energy just below and above
7000 eV. These happen to be the emission energies of cobalt K_α and cobalt K_β radiation.
Therefore we set up an experiment on a fourcircle diffractometer using a HOPG monochromator that was tuned to cobalt K_α and cobalt
K_β respectively.
Figure 1 (right) shows the results of two scans
along the [111]-direction of a 25 nm thin BFCO
film epitaxially grown on strontium titanate. In
the case of an ordering scheme involving iron
and chromium ions, we would expect a factor of
seven difference in the relative intensities of the
superlattice reflections (see fig.1 (left,b) ). In contrast, the relative intensities were approximately
the same for the two extreme energies. This is
the proof that the origin of the observed (111)
superlattice reflection can not be the ordering
of iron and chromium. Instead, we propose a
superstructure of oxygen octahedra tilts and/or
bismuth ion displacements.
The above experiment showed the capability
of laboratory x-ray sources, which can be used
(albeit in rare cases) to perform experiments that
were thought to be possible on at Synchrotron
radiation facilities.
Fig. 1: (a) The real and imaginary parts of the atomic form
factors of iron and chromium atoms plotted against energy
of radiation. (b) The calculated value of the
contrast plotted as a function of the radiation energy.
Figure 2: θ – 2θ measurements of the BFCO
film grown on STO (001) substrate measured
along the perovskite [111] direction at two
wavelengths – Co Kα and Co Kβ.
Research Projects
•
Magnetostriction measurements using x-ray diffraction
(LOEWE-RESPONSE, 2014-2016)
•
Development of electrode materials for high capacitance devices (IDS-FunMat, 2013-2015)
•
Phase transitions in thin potassium sodium niobate films
(IDS-FunMat, 2012-2015)
•
Influence of biaxial strain and texture on the elastic properties of Barium Strontium Titanate thin films (AvH Lab Partnership, 2013-2015)
Publications
[1]Acosta, M.; Schmitt, L. A.; Molina-Luna, L.; Scherrer, M. C.;
Brilz, M.; Webber, K. G.; Deluca, M.; Kleebe, H.J.; Roedel, J.;
Donner, W.;
Core-Shell Lead-Free Piezoelectric Ceramics: Current Status and Advanced Characterization of the Bi1/2Na1/2TiO3-SrTiO3 System
Journal of the American Ceramic Society, 98 (11) (2015) 3405-3422
DOI: 10.1111/jace.13853
[2] Cechova, D.; Svoboda, I.; Jomova, K.; Ruzickova, Z.; Valko, M.; Moncol, J.;
Synthesis, crystal structures and properties of coordination polymers from copper(II) adipate
Transition Metal Chemistry, 40 (8) (2015) 857-868
DOI: 10.1007/s11243-015-9982-6
[3] Zakhozheva, M.; Schmitt, L. A.; Acosta, M.; Guo, H.; Jo, W.;
Schierholz, R.; Kleebe, H. J.; Tan, X.;
Wide Compositional Range In Situ Electric Field Investigations on Lead-Free Ba(Zr0.2Ti0.8)O-3-x(Ba0.7Ca0.3)TiO3 Piezoceramic
Physical Review Applied, 3 (6) (2015)
DOI: 10.1103/PhysRevApplied.3.064018
[4] Yilmaz, N.; Oz, S.; Atakol, A.; Svoboda, I.;, Aydiner, B.;
Akay, M. A.; Atakol, O.;
An experimental and theoretical study toward the synthesis, structure and thermal decomposition of some nanolayered
Journal of Thermal Analysis and Calorimetry, 119 (3) (2015) 2321- 2328 DOI: 10.1007/s10973-014-4243-z
Publications
[5]Yavuz, M.; Knapp, M.; Indris, S.; Hinterstein, M.; Donner, W.;
Ehrenberg, H.;
X-ray total scattering investigation of Al0.57Sn0.43O1.71 nanoparticles
Journal of Applied Crystallography, 48 (2015) 1699-1705
DOI: 10.1107/s1600576715017203
[6] Uhrecky, R.; Svoboda, I.; Ruzickova, Z.; Koman, M.; Dlhan, L.;
Pavlik, J.; Moncol, J.; Boca, R.;
Synthesis, structure and magnetism of manganese and iron
dipicolinates with N,N '-donor ligands
Inorganica Chimica Acta, 425 (2015) 134-144
DOI: 10.1016/j.ica.2014.10.006
[7] Schmitt, L. A.; Kungl, H.;, Hinterstein, M.;, Riekehr, L.; Kleebe, H. J.; Hoffmann, M. J.; Eichel, R. A.; Fuess, H.;
The Impact of Heat Treatment on the Domain Configuration and Strain Behavior in Pb Zr,Ti O-3 Ferroelectrics
Journal of the American Ceramic Society, 98 (1) (2015) 269-277
DOI: 10.1111/jace.13253
[8] Salem, N. M. H.; Rashad, A. R.; El Sayed, L.; Foro, S.; Haase, W.; Iskander, M. F.;
Synthesis, characterization, molecular structure and supra
molecular architectures of some copper(II) complexes derived from salicylaldehyde semicarbazone
DOI: 10.1016/j.ica.2015.04.019
[9] Rammeh, N.; Fuess, H.;
Structural and Magnetic Investigation of the Double-Perovskite Ba2Co1-xFexReO6 (0 <= x <= 0.5)
Journal of Superconductivity and Novel Magnetism, 28 (7) (2015) 2209-2213
DOI: 10.1007/s10948-015-3020-y
[10] Nowotny, M.; Foro, S.; Heinschke, S.; Hoffmann, R. C.;
Schneider, J. J.;
1,2-Dithiooxalato-Bridged Heterobimetallic Complexes as
Single-Source Precursors for Ternary Metal Sulfide Semiconductors
European Journal of Inorganic Chemistry, 3 (2015) 512-519
DOI: 10.1002/ejic.201402990
[11] Nemec, I.; Herchel, R.;, Svoboda, I.; Boca, R.; Travnicek, Z.;
Large and negative magnetic anisotropy in Dithiooxalato
mononuclear Ni(II) Schiff base complexes
Dalton Transactions, 44 (20) (2015) 9551-9560
DOI: 10.1039/c5dt00600g
Publications
[12]Neetzel, C.; Muench, F.; Matsutani, T.; Jaud, J. C.; Broetz, J.; Ohgai, T.; Ensinger, W.;
Facile wet-chemical synthesis of differently shaped cuprous oxide particles and a thin film: Effect of catalyst morphology on the glucose sensing performance
Sensors and Actuators B-Chemical, 214 (2015) 189-196
DOI: 10.1016/j.snb.2015.03.011
[13] Mohamadi, M.; Ebrahimipour, S. Y.; Torkzadeh-Mahani, M.; Foro, S.; Akbari, A.;
A mononuclear diketone-based oxido-vanadium(IV) complex:
structure, DNA and BSA binding, molecular docking and anti
cancer activities against MCF-7, HPG-2, and HT-29 cell lines
Rsc Advances, 122 (5) (2015) 101063-101075
DOI: 10.1039/c5ra13715b
[14] Matelkova, K.; Boca, R.; Dlhan, L.; Herchel, R.; Moncol, J.;
Svoboda, I.; Maslejova, A.;
Dinuclear and polymeric (mu-formato)nickel(II) complexes: Synthesis, structure, spectral and magnetic properties
Polyhedron, 95 (2015) 45-53
[15] Li, Q. R.; Major, M., Yazdi, M. B.; Donner, W.; Dao, V. H.; Mercey, B.; Lueders, U.;
Dimensional crossover in ultrathin buried conducting SrVO3 layers
Physical Review B, 91 (3) (2015)
DOI: 10.1103/PhysRevB.91.035420
[16] Kuz’min, M. D.; Skokov, K. P.; Radulov, I.; Schwoebel, C. A.; Foro, S.; Donner, W.; Werwinski, M.; Rusz, J.; Delczeg-Czirjak, E.;
Gutfleisch, O.;
Magnetic anisotropy of La2Co7
Journal of Applied Physics, 118 (5) (2015)
DOI: 10.1063/1.4927849
[17]Kamel, M.; Mseddi, S.; Njeh, A.; Donner, W.; Ben Ghozlen, M. H.;
Acoustoelastic effect of textured (Ba,Sr)TiO3 thin films under an initial mechanical stress
Journal of Applied Physics, 118 (22) (2015)
DOI: 10.1063/1.49367841
[18] Hinterstein, M.; Schmitt, L. A.; Hoelzel, M.; Jo, W.; Roedel, J.;
Kleebe, H. J.; Hoffman, M.;
Cyclic electric field response of morphotropic Bi1/2Na1/2TiO3
BaTiO3 piezoceramics
Applied Physics Letters, 106 (22) (2015)
DOI: 10.1063/1.4922145
Publications
[19] Ebrahimipour, S. Y.; Sheikhshoaie, I.; Castro, J; Haase, W.;
Mohamadi, M.; Foro, S.; Sheikhshoaie, M.; Esmaeili-Mahani, S.;
A novel cationic copper(II) Schiff base complex: Synthesis,
characterization, crystal structure, electrochemical
evaluation, anti-cancer activity, and preparation of its metal oxide nanoparticles
DOI: 10.1016/j.ica.2015.03.0
[20] Self-Supporting Metal Nanotube Networks Obtained by Highly Conformal Electroless Plating
Muench, Falk, De Carolis, Dario M.,Felix, Eva-Maria, Broetz, Joachim
Kunz, Ulrike, Kleebe, Hans-Joachim, Ayata, Sevda, Trautmann, Christina, Ensinger, Wolfgang
ChemPlusChem 80, 1448-1456 (2015)
DOI: 10.1002/cplu.201500073
[21] Double-Walled Ag-Pt Nanotubes Fabricated by Galvanic
Replacement and Dealloying: Effect of Composition on
the Methanol Oxidation Activity
Schaefer, Sandra, Muench, Falk, Mankel, Eric, Fuchs, Anne, Broetz, Joachim, Kunz, Ulrike, Ensinger, Wolfgang
Nano 10, 1550085 (2015)
DOI: 10.1142/S179329201550085X
[22] Lightweight aggregates produced from sand sludge and zeolitic rocks
Volland, S., Broetz, J.
Construction and Building Materials 85, 22 (2015)
DOI: 10.1016/j.conbuildmat.2015.03.018
[23] Deep and Shallow TiO2 Gap States on Cleaved Anatase Single Crystal (101) Surfaces, Nanocrystalline Anatase Films, and ALD Titania Ante and Post Annealing
Reckers, Philip, Dimamay, Mariel, Klett, Joachim, Trost, Sara, Zilberberg, Kirill, Riedl, Thomas, Parkinson, Bruce A., Broetz, Joachim, Jaegermann, Wolfram, Mayer, Thomas
Journal of Physical Chemistry C 119, 9890 (2015)
DOI: 10.1021/acs.jpcc.5b01264
[24] Chemical and physical properties in layers and interfaces of nanolayered Si(100)/Ni/BCxNy stacks
Hoffmann, P., Kosinova, M., Flege, S., Broetz, J., Trunova, V., Dietz, C. Ensinger, W.
X-Ray Spectrometry 44, 48 (2015)
DOI: 10.1002/xrs.2578
Surface Science
Staff Members
Head
Prof.Dr. Wolfram Jaegermann
Research Associates
Dr. Gennady Cherkashinin
Dr. Lucangelo Dimesso
Dr. Mathias Fingerle
Dr. René Hausbrand
Dr. Bernhard Kaiser, PD
Apl. Prof. Dr. Andreas Klein
Dr. Eric Mankel
Dr. Thomas Mayer
Dr. Florent Yang
Secretaries
Leslie Frotscher
Marga Lang
Technical Personnel
Martin Berstorfer
Dipl.-Ing. Erich Golusda
Kerstin Lakus-Wollny
PhD Students
Mercedes Carillo-Solano,
M.SC
Mariel Grace
Dimamay, M. Sc.
Ralph Dachauer, M. Sc.
Getnet Deyu, M. Sc.
Jennifer Doerfer, M. Sc.
Conrad R. Guhl, M. Sc.
Andreas Hajduk, M. Sc.
Yannick Hermans, M. Sc.
Stephan Hillmann, M. Sc.
Andreas Hubmann, M. Sc.
180 | Surface Science
Shun Kashiwaya, M.Eng.
Dipl.-Ing. Maybritt Kühn
Christian Lohaus, M. Sc.
Dipl.-Ing. Jan Morasch
Dipl.-Ing. Markus Motzko
Dipl.-Ing. Ruben Precht
Dipl.-Ing. Philip Reckers
Jona Schuch, M. Sc.
Dipl.-Ing. Natalia Schulz
Thomas Späth, M. Sc.
Shasha Tao, M.Sc.
Dipl.-Phys. Sven Tengeler
Dipl.-Ing. Johannes Türck
Hans Wardenga, M. Sc.
Natascha Weidler, M. Sc.
Carolin Wittich, M. Sc.
Michael Wußler, M. Sc.
Dipl.-Ing. Jürgen Ziegler
Master Students
Robert Bianchi
Roman Buchheit
Thomas Cossuet
Ruth Giesecke
Christian Hoyer
Karoline Hoyer
Claudiu Mortan
Stephan Wagner
Halyna Volkova
Guest Scientists
Dr. Mikhail Lebedev
Prof. Bruce Parkinson
Prof. Tongqing Yang
Daniel Long
Surface Science
The surface science division of the institute of
materials science uses advanced surface science
techniques to investigate surfaces and interfaces
of materials and materials combinations of
technological use. For this purpose integrated
UHV-systems have been built up which combine
different surface analytical tools (photoemission,
inverse photoemission, electron diffraction, ion
scattering, electron loss spectroscopy, scanning
probe techniques) with the preparation of thin
films (thermal evaporation, close-spaced sublimation, magnetron sputtering, MOCVD) and
interfaces. The main research interest is directed
to devices using polycrystalline compound semiconductors and interfaces between dissimilar
materials. The perspectives of energy conversion
(e.g. solar cells) or storage (intercalation batteries) devices are of special interest. In addition,
the fundamental processes involved in chemical
and electrochemical device engineering and
oxide thin films for electronic applications are
investigated.
The main research areas are:
Electrochemical Interfaces
The aim of this research activity is the better
understanding of electrochemical interfaces
and their application for energy conversion. In
addition, empirically derived (electro-) chemical
processing steps for the controlled modification
and structuring of materials is investigated and
further optimized. In the center of our interest
are semiconductor/electrolyte contacts.
Solar fuels
The direct solar light induced water splitting
is investigated using photoelectrochemical
(electrode/electrolyte) or photocatalytic (particle)
arrangements. New materials, design structures,
as well as interface engineering approached with
advanced catalysts are investigated. The catalysts
are also tested for their application in water
electrolysis
Intercalation Batteries
The aim of this research activity is the
better understanding of electronic properties of
Li-intercalation batteries and of their degradation
phenomena. Typically all solid state batteries are
prepared and investigated using sputtering and
CVD techniques for cathodes and solid electro-
lytes. 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. 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.
Surface Science | 181
Interfaces in Thin Film Lio-Ion Batteries
René Hausbrand, André Schwöbel, Wolfram Jaegermann
All-solid Li-ion battery cells are currently under
investigation as batteries of the next generation,
promising high safety and high energy density.
All-solid cells feature a solid electrolyte, endowing them with their favorable properties, but
also resulting in the need for new processes
and advanced interface engineering. Thin film
batteries are all-solid Li-ion batteries with applications in microelectronics, and also well suited
for investigations of fundamental phenomena at
ionic solid-solid interfaces.
Thin film cells are commonly manufactured
by vacuum-based thin film deposition technology
using a glassy solid electrolyte such as LiPON.
In the surface science department, we prepare
electrolyte thin films, electrode/electrolyte layer
stacks and model thin film cells in order to investigate manufacture processes as well as interface properties. Thin film cells manufactured in
the group (Fig. 1) demonstrate typical properties
(see Fig. 2), with relevant interface resistances
(ca. 100 Ω.cm2, [1]) as evidenced in fig. 2 by the
voltage drop at the beginning of the discharge
cycle.
Current research topics regarding ionic
solid-solid interfaces, such as Li-ion electrode-electrolyte interfaces, are reaction layer formation, interfacial electrostatic potential drops,
and space charge layer (SCL) formation [2, 3].
Especially reaction layers and space charge layers
are potentially detrimental for the interface properties, i.e. are a possible cause of high interface
resistances. In the surface science group we use
photoelectron spectroscopy (XPS) and interface
experiments to investigate these issues [4, 5].
In order to study the interfaces in typical thin
film cells, and to explore the properties of LiPON
solid electrolyte, we performed interface experiments on LiCoO2-LiPON and LiPON-lithium
interfaces. A major outcome of such experiments
is the alignment of electronic energy levels and
the detection of possible band bending. Figure 3
shows the electronic band diagram of a thin film
cell established on basis of such experiments
[6-8], to our knowledge the first experimentally
determined diagram of this kind.
The band diagram demonstrates that band
bending (i.e. space charge layer formation) can
occur in LiCoO2 and likely also in LiPON. The
results indicate that at both interfaces, Li-ions are
injected into the solid electrolyte, or are adsorbed
at the interface, respectively. Next to the reaction
layer between LiPON and lithium [8], these space
charge layers are believed to contribute to the
interface resistance of the thin film cell.
The band diagram also demonstrates that
typical electrostatic potential drops at such interfaces are only several tenths of an electron volt,
and are likely rather independent on electrode
potential. Such information is highly relevant
for the design of low resistance solid-solid ionic
interfaces.
References
[1] Bates, J.B., et al.,
Thin-film lithium and
lithium-ion batteries. Solid
State Ionics, 2000. 135: p.
33-45.
[2] Maier, J., Physical
Chemistry of Ionic Materials. 2004, Chichester: John
Wiley and Sons, Ltd.
[3]Takada, K., Progress
and prospective of
solid-state lithium
batteries. Acta Materialia,
2013. 61(3): p. 759-770.
[4] Hausbrand, R.,
et al., Fundamental
degradation mechanisms
of layered oxide Li-ion
battery cathode materials:
Methodology, insights
and novel approaches.
Materials Science and
Engineering B-Advanced
Functional Solid-State
Materials,
2015. 192: p. 3-25.
[5] Hausbrand, R.,
D. Becker, and W.
Jaegermann, A surface science approach to cathode/
electrolyte interfaces in
Li-ion batteries: Contact
properties, charge transfer
and reactions. Progress
in Solid State Chemistry,
2014. 42(4): p. 175-183.
[6] Schwöbel, A., W.
Jaegermann, and R.
Hausbrand, Interfacial
energy level alignment
and energy level diagrams
for all-solid Li-ion cells:
Impact of Li-ion transfer
and double layer formation. Solid State Ionics,
http://dx.doi.org/10.1016/j.
ssi.2015.12.029.
[7] Hausbrand, R., et al.,
Surface and Interface
Analysis of LiCoO2 and
LiPON Thin Films by
Photoemission: Implications for Li-Ion Batteries.
Zeitschrift Fur Physikalische Chemie-International
Journal of Research in
Physical Chemistry &
Chemical Physics, 2015.
229(9): p. 1387-1414.
[8] Schwobel, A., R.
Hausbrand, and W.
Jaegermann, Interface
reactions between LiPON
and lithium studied by
in-situ X-ray photoemission. Solid State Ionics,
2015. 273: p. 51-54.
Figure 1: Thin film battery cells
Figure 2: Charge-discharge curve of thin film cell
Figure 3: Band diagram of thin film cell. Between LiPON and lithium,
a reaction layer is formed.
Perovskite Solar Cells
Ralph Dachauer, Michael Wussler, Claudiu Mortan, Thomas Mayer, Wolfram Jaegermann
Perovskite solar cells are a new type of solar cells
that are based on Methylammonium-Lead-Iodide
(MAPI, CH3NH3PbI3) thin film absorber layers.
These cells promise to be efficient, cheap in
production cost, and usage of abundant materials.
Thus far though, they exist only at the laboratory
scale. Following the activities of CdTe-solar
cells, the integrated vacuum system DAISY-SOL
was modified to build this new type of solar
cell in a vacuum based process. The redesign
of some deposition chambers and refinement of
the attached XPS system were the initial steps in
the implementation of this powerful tool to build
cell structures and analyze interface properties,
without contact of the samples to laboratory air.
Primary analysis of the new material included
the in house implementation and optimization of
the standard solution-based deposition process.
Reference cells with efficiencies exceeding
13 % are produced routinely. For the vacuum based cells, physical vapor deposition (PVD) of the
perovskite-absorber MAPI was studied. Because
this material consists of a volatile organic MAI
(CH3NH3I ) and a more thermally stable inorganic compound (PbI2), it is necessary to use two
separate evaporation sources. The result is a simultaneous deposition of the vapor and chemical
reaction on the substrate. This chemical reaction
requires energy provided by increased temperatures; however, at slightly to high temperatures,
degradation to PbI2 occurs by loss of MAI. In
order to increase this temperature window using
through increasing vapor pressure, closed space
sublimation (CSS) was applied successfully as
shown using x-ray diffraction XRD.
Additional annealing processes under inert
atmosphere have been shown to further improve
film quality and cell efficiency. The specific
parameters of the deposition and annealing processes have strong influence on the morphology
of the films, which were studied using SEM.
Using the new CSS processes, devices with efficiencies up to 5 % are produced currently. So
far, the most common and successful electron extraction contact for perovskite absorbers is TiO2.
The quality of this layer is most important as it
contributes to the charge separation and blocks
leakage current in the device. A new pyrolysis
apparatus was set up to provide high quality
layers with full coverage, high transparency and
optimal film thickness. The quality of this film
dominates most other effects, especially in the
thin film design of PVD-CSS fabricated cells.
The standard and most successful perovskite
solar cells are currently built with CH3NH3PbI3
(MAPI), but there remain major long-term stability issues that must be overcome before commercialization is possible. Therefore, a long-term test
bench with adjustable humidity, temperature and
atmosphere was constructed, where the cells are
maintained under simulated working conditions.
With this device, we will be able to study and
optimize the lifetime of these solar cells.
Also alternative perovskites materials are
synthesized in the group and their optoelectronic potential is studied. The primary aims of
this work include replacement of the toxic lead
by other elements, improving chemical and
temperature stability and identifying materials
with appropriate band gaps for tandem solar cell
application. Methylammonium was replaced by
the alkali atoms series and different organic complexes have been used. Some of these perovskites
exceeded 0.5% efficiency in these first rounds of
tests and the materials will be further optimized.
The most promising candidate for lead-free perovskite cells is CH3NH3SnI3 (MASI).
Following deposition of SnI2 via PVD, the
material is transformed with CH3NH3I into
MASI via a CSS process. Preliminary results
demonstrate efficiencies up to 1.7 % for the device performance and remarkably high quantum
efficiencies at low wavelength for these devices
prepared under vacuum.
Two advanced research labs, one Bachelor
thesis and two Master theses were successfully
completed in the group. Currently, one Bachelor student, three master students, three PhD
students, one postdoc and one technician are
engaged in the projects.
Research Projects
•
All Oxide PV (EU 2012 – 2015)
•
Photoelectrochemical water splitting using adapted silicon based
semiconductor tandem structures (DFG 2012 – 2015)
•
Coordination SPP 1613 Solar H2 (DFG 2012 – 2015)
•
Hess. Graduierte Programm für wissenschaflich-technologische
Grundlagen der Elektromobilität – HGP-E (HMWK 2013 – 2016)
•
Joint project „PeroSol“:vacuum based thin film solar cells with novel
organometal halide perovskite absorber (BMBF 2014 – 2017)
•
Interface engineering for the chemical and electronic passivation of
group III–phosphide semiconductors to be used in highly efficient
photoelectrochemical tandem cells for water splitting”
(DFG 2014 – 2017)
•
IDS-FunMat
(EU 2014 – 2017)
•
Surface modification by nanodipoles of transparent oxide electrodes for
organic semiconductor devices (FONDOLT) (BMBF/ VDI 2015 – 2018)
•
Correlation between surface potentials and surface oxygen exchange
coefficents of CeO2
(DFG 2015 – 2018)
•
Interface Phenomena in Ion Conducting Systems: Studies with
a Surface Science Approach
(DFG 2015 – 2018)
Research Projects
•
Conditioning of all solid state Lithium Ion Batteries with LiMP=4
(M=Co, Ni) thin film cathodes
(DFG 2015 – 2018)
•
EJD FunMat
(EU 2015 – 2019)
•
Design principles of organic electronics: Bulk and interface heterogeneities - Systematic chemical and electronic investigations of surfaces
and interfaces via photoemission spectroscopy (INTERPHASE)
(BMBF/ VDI 2015 – 2018)
•
Cathode materials for sodium ion batteries: electronic structure,
potential and degradation
(DFG – 2015 - 2018)
•
Mangan: Integration of novel manganese oxide catalysts with light
absorbing semiconductor structures
(BMBF 2015 – 2019)
•
Interface engineering for the chemical and electronical passivation of
group 3 phosphide semiconductors for the application in highly efficient
photoelectrochemical tandem cells for water splitting“
(DFG 2015 – 2018)
•
Photoelectrochemical water splitting using adapted silicon based
semiconductor multi-junction cell structures
(DFG 2015 – 2018)
•
SusHy – Edelmetallfreie Katalysatoren für die Wasserstoffproduktion
aus erneuerbaren Energiequellen – Sustainable Hydrogen
(Industrieprojekt EVONIK 2013-2016)
Publications
[1] Tselev, A. Klein, J. Gassmann, S. Jesse, Q. Li, S.V. Kalinin, and
N. Balke
Quantitative Nanometer-Scale Mapping of Dielectric Tunability
Advanced Materials Interfaces 2, 1500088 (2015); doi: 10.1002/
admi.201500088
[2] P.P. Aurino, A. Kalabukhov, N. Tuzla, E. Olsson, A. Klein, P. Erhart, Y.A. Boikov, I.T. Serenkov, V.I. Sakharov, T. Claeson, and D. Winkler
Reversible metal-insulator transition of Ar-irradiated LaAlO3/SrTiO3 interfaces
Phys. Rev. B 92, 155130 (2015); doi: 10.1103/PhysRevB.92.155130
[3] J. Türck, S. Siol, T. Mayer, A. Klein, and W. Jaegermann
Cu2S as ohmic back contact for CdTe solar cells
Thin Solid Films 582, 336-339 (2015); doi: 10.1016/j.tsf.2014.11.017
[4] A. Klein
Energy Band Alignment in Chalcogenide Thin Film Solar Cells from Photoelectron Spectroscopy
J. Phys.: Condens. Matter 27, 134201 (2015); doi: 10.1088/0953-8984/27/13/134201
[5]
H. Wardenga, M.V. Frischbier, M. Morales-Masis, and A. Klein
In-situ Hall-effect monitoring of vacuum annealing of
In2O3:H thin films
Materials 8, 561-574 (2015); doi: 10.3390/ma8020561
[6]
M.T. Uddin, Y. Nicolas, C. Olivier, L. Servant, T. Toupance, S. Li, A. Klein, and W. Jaegermann
Synthesis and Band Alignments Investigations of Novel RuO2/ZnO Nanoparticulate Heterostructures with Enhanced and Stable
Efficiencies in Photocatalytic Decomposition of Organic Pollutants
Phys. Chem. Chem. Phys. 17, 5090-5102 (2015);
doi: 10.1039/c4cp04780j
[7] S. Hillmann, K. Rachut, T. J. M. Bayer, S. Li, A. Klein
Application of atomic layer deposited Al2O3 as charge injection layer for high-permittivity dielectrics
Semicond. Sci. Technol. 30, 024012 (2015); doi: 10.1088/0268-1242/30/2/024012
Publications
[8]
A. Gassmann, S.V. Yampolskii, A. Klein, K. Albe, N. Vilbrandt,
O. Pekkola, Y.A. Genenko, M. Rehahn, and H. von Seggern
Study of electrical fatigue by defect engineering in organic
light-emitting diodes
Materials Science and Engineering: B 192, 26-51 (2015);
doi: 10.1016/j.mseb.2014.10.014
[9]
H. Borchert, D. Scheunemann, K. Frevert, F. Witt, A. Klein and
J. Parisi
Schottky Solar Cells with CuInS2 Nanocrystals as Absorber Material
Z. Phys. Chem. 229, 191-203 (2015); doi: 10.1515/zpch-2014-0595 [1]
[10]
Kaiser, W. Calvet, E. Murugasen, J. Ziegler, W. Jaegermann, S.E. Pust, F. Finger, S. Hoch, M. Blug, and J. Busse
Light induced hydrogen generation with silicon-based thin film
tandem solar cells used as photocathode
International Journal of Hydrogen Energy 40 (2015), 899;
doi: 10.1016/j.ijhydene.2014.11.012
[11] J. Pareja, C. Litterscheid, A. Molina, B. Albert, B. Kaiser, and
A. Dreizler
Effects of doping concentration and co-doping with cerium on the luminescence properties of Gd3Ga5O12:Cr3+ for thermometry applications
Optical Materials 47 (2015), 338; doi: 10.1016/j.optmat.2015.05.052
[12] F. Urbain, V. Smirnov, J.-P. Becker, U. Rau, J. Ziegler, B. Kaiser,
W. Jaegermann, and F. Finger,
Application and modeling of an integrated amorphous silicon tandem based device for solar water splitting
Solar Energy Materials and Solar Cells 140 (2015), 275; doi: 10.1016/j.
solmat.2015.04.013
[13] F. Urbain, V. Smirnov, J.P. Becker, U. Rau, J. Ziegler, F. Yang,
B. Kaiser, W. Jaegermann, S. Hoch, M. Blug, and F. Finger
Solar water splitting with earth-abundant materials using amorphous silicon photocathodes and Al/Ni contacts as hydrogen evolution catalyst
Chemical Physics Letters 638 (2015), 25; doi: 10.1016/
j.cplett.2015.08.018
Publications
[14] F. Yang, P. Allongue, F. Ozanam, J.N. Chazalviel
Thermal Stability of Organic Monolayers Covalently Grafted on Silicon Surfaces, In: Reactions and Mechanisms in Thermal Analysis of Advanced Materials (Ed. by A. Tiwari, B. Raj),
Wiley & Sons, Hoboken, New Jersey, pp. 3-38; doi: 10.1002/9781119117711.ch1
[15]
G. Cherkashinin, M. Motzko, N. Schulz, Thomas Späth, and
Wolfram Jaegermann
Electron spectroscopy study of Li[Ni,Co,Mn]O2/electrolyte interface: electronic structure, interface composition and device implications
Chemistry of Materials 27, 2875-2887 (2015); doi: 10.1021/cm5047534
[16]
O. Ruzimuradov, K. Sharipov, A. Yarbekov, K. Saidov,
M. Hojamberdiev, R. M. Prasad, G. Cherkashinin, and R. Riedel
A facile preparation of dual-phase nitrogen-doped TiO2–SrTiO3 macroporous monolithic photocatalyst for organic dye photodegradation under visible light
J. European Ceramic Society 35 (2015) 1815–1821 (2015).
doi:10.1016/ j.jeurceramsoc.2014.12.023
[17]
M. Motzko, M.A.C. Solano, W. Jaegermann, R. Hausbrand,
Photoemission Study on the Interaction Between LiCoO2 Thin Films and Adsorbed Water.
J. Phys. Chem. C 119, 23407-12 (2015); doi: 10.1021/acs.jpcc.5b05793
[18]
A. Schwöbel, R. Hausbrand, W. Jaegermann,
Interface reactions between LiPON and lithium studied by
in-situ X-ray photoemission.
Solid State Ionics. 273, 51-4 (2015); doi: 10.1016/j.ssi.2014.10.017
[19]
R. Hausbrand, G. Cherkashinin, H. Ehrenberg, M. Gröting, K. Albe,
C. Hess and W. Jaegermann
Fundamental degradation mechanisms of layered oxide Li-ion battery cathode materials: Methodology, insights and novel approaches.
Mater. Sci. Eng. B-Adv. 192, 3-25 (2015);
doi: 10.1016/ j.mseb.2014.11.014
[20]
R. Hausbrand, A. Schwöbel, W. Jaegermann, M. Motzko, D. Ensling,
Surface and Interface Analysis of LiCoO2 and LiPON Thin Films by Photoemission: Implications for Li-Ion Batteries.
Z. Phys. Chem. 229, 1387-414 (2015); doi: 10.1515/zpch-2014-0664
Publications
[21]
R. Precht, R. Hausbrand, W. Jaegermann,
Electronic structure and electrode properties of tetracyanoquinodimethane (TCNQ): a surface science investigation of lithium
intercalation into TCNQ.
Phys. Chem. Chem. Phys. 17, 6588-96 (2015); doi: 10.1039/c4cp05206d
[22]
M. Dimamay, T. Mayer, G. Hadziioannou, and W. Jaegermann,
Electronic and chemical structure of an organic light emitter
embedded in an inorganic wide-bandgap semiconductor:
Photoelectron spectroscopy of layered and composite structures
of Ir(BPA) and ZnSe
J. Appl. Phys. 117, 175501 (2015), doi: 10.1063/1.4919828
[23] M.F. Lichterman, S. Hu, M.H. Richter, E.J. Crumlin, S. Axnanda, M. Favaro, W. Drisdell, Z. Hussain, T. Mayer, B.S. Brunschwig, N.S. Lewis, Z. Liu, and H.-J. Lewerenz,
Direct observation of the energetics at a semiconductor/liquid junction by operando X-ray ph otoelectron spectroscopy,
Energy & Environmental Science 8, 2409 (2015); doi: 10.1039/
c5ee01014d
[24]
M.F. Lichterman, M.H. Richter, S. Hu, E.J. Crumlin, S. Axnanda, M. Favaro, W. Drisdell, Z. Hussain, T. Mayer, B. Brunschwig,
N.S. Lewis, H.J. Lewerenz, and Z. Liu,
Investigation of the Si/TiO2/Electrolyte Interface Using Operando Tender X-ray Photoelectron Spectroscopy,
ECS Trans. 66, 97 (2015); doi: 10.1149/06606.0097ecst
[25]
P. Reckers, M. Dimamay, J. Klett, S. Trost, K. Zilberberg,
T. Riedl, B.A. Parkinson, J. Broetz, W. Jaegermann, and T. Mayer,
Deep and Shallow TiO2 Gap States on Cleaved Anatase Single Crystal (101) Surfaces, Nanocrystalline Anatase Films, and ALD Titania Ante and Post Annealing,
J. Phys. Chem. C 119, 9890 (2015); doi: 10.1021/acs.jpcc.5b01264
[26]
M.H. Richter, M.F. Lichterman, S. Hu, E.J. Crumlin, T. Mayer, S. Axnanda, M. Favaro, W. Drisdell, Z. Hussain, B. Brunschwig, N.S. Lewis, Z. Liu, and H.J. Lewerenz,
Measurement of the Energy-Band Relations of Stabilized Si Photoanodes Using Operando
Ambient Pressure X-ray Photoelectron Spectroscopy,
ECS Trans. 66, 105 (2015); doi: 10.1149/06606.0105ecst
Publications
[27] M. Jesper, M. Alt, J. Schinke, S. Hillebrandt, I. Angelova,
V. Rohnacher, A. Pucci, U. Lemmer, W. Jaegermann,
W. Kowalsky, T. Glaser, E. Mankel, R. Lovrincic, F. Golling,
M. Hamburger, U. H. F. Bunz,
Dipolar SAMs Reduce Charge Carrier Injection Barriers in n-Channel Organic Field Effect Transistors,
Langmuir 31, 10303-10309 (2015); doi:
10.1021/acs.langmuir.5b02316
[28] L. Dimesso, C. Spanheimer, M. M. Mueller, H.-J. Kleebe,
W. Jaegermann,
Properties of Ca-containing LiCoPO4-graphitic carbon foam composites
Ionics 21, 2101-2107 (2015); doi: 10.1007/s11581-015-1408-0
[29] J.-F. Han, G.-H. Fu, V. Krishnakumar, H.-J. Schimper, C. Liao,
W. Jaegermann, M. P. Besland,
Studies of CdS/CdTe interface: Comparison of CdS films
deposited by close space sublimation and chemical bath deposition techniques,
Thin Solid Films 582, 290-294 (2015);
doi: 10.1016/j.tsf.2014.12.039
[30]
M. T. Uddin, O. Babot, L. Thomas, C. Olivier, M. Redaelli,
M. D’Arienzo, F. Morazzoni, W. Jaegermann, N. Rockstroh,
H. Junge, T. Toupance,
New Insights into the Photocatalytic Properties of
RuO2/TiO2Mesoporous Heterostructures for Hydrogen Production and Organic Pollutant Photodecomposition
J. Phys. Chem. C 119, 7006-7015 (2015); doi: 10.1021/jp512769u
[31]
M. T. Uddin, Y. Nicolas, C. Olivier, L. Servant, T. Toupance,
S. Y. Li, A. Klein, W. Jaegermann,
Improved photocatalytic activity in RuO2-ZnO nanoparticulate heterostructures due to inhomogeneous space charge effects
Phys. Chem. Chem. Phys. 17, 5090-5102 (2015);
doi: 10.1039/c4cp04780j
Theses in
Materials Science
Theses in Materials science | 193
Diploma Theses in Materials Science
•
Robert Brück; Untersuchung des Einflusses verschiedener Aluminiumoxidschlicker auf deren Verstärkaungsverhalten in Al2O3/Al2O3Verbunden, 28.04.2015
•
Andreas Hanauer; Aufbau, Einrichtung und Anwendung einer Anlage
zur Kombination von Plasmaimmersions-Ionenimplantation mit einem Magnetron-Sputtersystem, 24.01.2015
•
Christian Heidorn; evaluation der Optimierungspotentiale der Dicken
und Dotierungsmessungen an Siliciumcarbid-Epitaxie-Schichten, 14.01.2015
•
Yannic Hübner; Einfluss des Energieeintrags durch Oberflächenendverarbeitungsverfahren auf das Bauteil-Randzonen-Gefüge am Beispiel
St52-3, 17.09.2015
•
Kim, Young-Mi; (Betreuer: Prof. Kleebe) elektronenmikroskopische
Untersuchung zur Domänenkonfiguration in Lanthan und Eisen dotierten PZT-Keramiken im Bereich der morphotropen Phasengrenze, 08.11.2015
Bachelor Theses in Materials Science
•
Jamal Abu Shihada; Abscheidung und XPS/UPS-Analyse von
dünnen Lithiumoxidschichten, 06.11.2015
•
Min-Chul Kraun Bae; A novel approach to Fabrication of 3D
SU-8 microfluidic devices using water soluble and environmentally friendly sacrificial layers, 21.12.2015
•
Nicole Sabine Bein; Herstellung und Charakterisierung von
Titannitridschichten, 14.09.2015
•
Alena Katharina Bell; Grüne Synthese von Platin- und Platin-GoldNanostrukturen und deren Anwendung in der Methanol- und
Ethanoloxidation, 13.10.2015
•
Paula Marie Linde Connor; Untersuchung des Cu2O-Rückkontaktes für CdTe-Solarzellen, 11.02.2015
•
Artjom Derepa; Untersuchung des Einflusses der Probenhaltergeometrie auf die Eigenschaften von DLC-Schichten, 29.09.2015
•
Dominik Dietz; Electrodeposition of p-Cu2O nanowire networks for photoelectrochemical water splitting, 14.09.2015
•
Manuel Donzelli; Untersuchung zur Oberflächenbehandlung von gesputterten Lithiumcobaltoxid-Schichten, 06.03.2015
194 | Theses in Materials science
•
Thorsten Simon Eisele; Untersuchungen zum Substrateinfluss auf den
Rockwell-C- Haftfestigkeitstest am Beispiel von a-C:H Schichten Experiment und Simulation, 22.05.2015
•
Florian Falk; Experimentelle Untersuchung zur Änderung der
Materialeigenschaften durch spanende Bearbeitung, 23.09.2015
•
Markus Benjamin Frericks; Charakterisierung der magneto
kalorischen Eigenschaften von (Mn,Fe)2(P,Si)-Legierungen, 27.08.2015
•
Kirsten Friemert; Partial Sustitution of Iron in Cementite for
Magnetocaloric Applications, 17.09.2015
•
Axel Claus Grebhardt; Mechanische Eigenschaften & thermische Stabilität umgeformster PtW8-Drähte, 16.03.2015
•
Johannes Gabriel Große; Morphologie und Struktur von
Polyanilin-Schichten, 31.07.2015
•
Leonard Gordian Gura; Ionic Transport Studies of ALD-Coated Single Etched Ion-Track Nanopores, 14.09.2015
•
Anna Lisa Hawlitschek; Subsurface-Detektion und Charakterisierung
von superparamagnetischen Nanopartikeln mittels magnetischer
Rasterkraftmikroskopie, 16.11.2015
•
Thea Henrich; Gefügeeigenschaften von Werkstoffen hochfester Schrauben, 07.09.2015
•
Ramis Uwe Hertwig; Deposition and Characterisation of Reactive Sputtered RuO2 Thin Films, 22.07.2015
•
An-Phuc Hoang; Effects of sintering on the current-voltage-behaviour
and dielectric properties of ZrO2 doped Calcium Copper Titanate, 30.10.2015
•
Paul Hoffmann; Grüne templatbasierte Synthese von PalladiumNanoröhren, 31.07.2015
•
Jonas Hunka; Electrical Characterization of the Temperature Dependence of RRAM, 30.11.2015
•
Alexander Amand Janissek; SrMoO3-Dünnschichten auf
behandelten MgO-Substraten, 31.03.2015
•
Nico Kaiser; Reproduzierbarkeit des SrMoO3-Schichtwachstums mittels gepulster Laserablation, 13.05.2015
•
Tom Christopher Keil; Einfluss der Prozessparameter auf das mechanische Verhalten von Borosilikatglas, 30.10.2015
•
Arne Jan Klomp; Der Einfluss von Keimbildnern und färbenden Komponenten auf den Keramisierungsprozess und die Eigenschaften von Lithium-Alumosilicat- Glaskeramiken - Farbentwicklung durch Nekleation und Keramisierung, 28.07.2015
•
Benjamin Johannes Thomas Robert Krah; Korngrenzendiffusionsprozess an elektrophoretisch modifizierten NbFeB-Sinter-
magneten, 13.02.2015
•
Melanie Kranz; Elektrodeposition von Nickel-Eisen-Nanodrahtarrays und deren mechanische Charakterisierung, 16.03.2015
•
Chantal Kurpiers; Lokale Wärmebehandlung von Stegblechen, 10.12.2015
•
Tim Lienig; Investigation of Magnetic and Microstructural Properties of Proton Irradiated NdFeB, 16.03.2015
•
Christian Stefan Minnert; Einfluss des Kohlenstoffgehaltes auf die Austenitstabilität in ADI, 23.09.2015
•
Dominik Ohmer; Influence of surface stresses on diffusion processes in spherical and ellipsoidal particles, 22.07.2015
•
Isabelle Pause; Grüne Synthese von Palladium und Palladi-
um-Gold-Nanostrukturen und deren Anwendung in der Sensorik, 26.02.2015
•
Delwin Indigo Perera; Density Functional Theory Calculations on Tilt Grain Boundaries in Graphene, 05.08.2015
•
Carsten Porth; Ion-induced microstructural, mechanical and electrical properties changes in molybdenum-carbide-graphite composites, 09.10.2015
•
Simon Theophil Ranecky; Analytische und numerische Berechnung von Stromverteilungen und Wechselstromverlusten in abgeschirmten Supraleitern, 05.05.2015
•
Jesse Cornelius Riedl; Laserlegieren von kohlenstoffhaltigen Zusatz-
materialien zur Härtesteigerung von Einsatzstahl, 31.03.2015
•
Marcel Sadowski; Elektrochemische Charakterisierung von beschichteten LiCoO2-Dünnschichtkathoden für Lithium-Ionen Batterien, 24.11.2015
•
Lukas Schäfer; Einfluss der Grenzflächendichte auf die Koerzitivfeldstärke Hc bei ARMCO® und VACOFLUX17®, 17.09.2015
•
Nils Schäfer; Umformungsverhalten und Bake-Hardening-Potential austenitischer MnCr-Stähle, 02.11.2015
•
Patrick Schnell; Plasmonic Properties of annealed smooth and porous gold nanowires, 29.09.2015
•
Katharina Natalie Silvana Schuldt; Charakterisierung kathodenzerstäubter Gd-dotierter CeO2-Schichten, 15.09.2015
•
Marius Specht; Einfluss von Wärmebehandlungen auf das Verfor-
mungsverhalten von ultrafeinkörnigen Stählen, 01.10.2015
•
Tom Stein; Synthese und Charakterisierung von Gold- und SilberNanostrukturen basierend auf Grüner Chemie, 22.09.2015
•
Maximilian Stöhr; Variation des Frontkontakts in Perowskit-Solarzellen, 30.09.2015
•
Kyle Aaron Taylor; Refractory Metals and their Reaction with Silica Glass at High Temperatures, 16.03.2015
•
Nils Max Ulrich; Synthesis and Characterisation of ALD-Coated Conical Nanopores for Ion-Transport Studies, 09.10.2015
•
Marcel Urban; Laser flash analysis of swift heavy ion irradiated carbon-based materials, 27.02.2015
•
Daniel Thomas Utt; Processing and Characterization of Strontium Barium Niobate Ceramics for Electrocaloric Applications, 18.08.2015
•
Tobias Vogel; Verbesserung der Adhäsion von DLC-Schichten auf Kupfer, 22.09.2015
•
Yuan Xu; Effects of Swift Heavy Ion Irradiation on Molybdenum Carbide - Graphite (MoGR) Composites, 02.03.2015
•
Lukas Zeinar; Spark Plasma Sintering of PLD targets of Lithium and Sodium based Materials, 13.04.2015
•
Rabea Felicia Zeuch; Reaktive Magnetron-Kathodenzerstäubung von SnO2 und der Einfluss der Prozessparameter auf die elektrischen Eigenschaften, 22.09.2015
•
Alexander Zintler; Microstructure and chemistry of ZnO varistor grain boundaries, 30.04.2015
Master Theses in Materials Science
•
Markus Antoni; Inorganic Synthesis Methods for Nanostructured
Capacitors, 30.01.2015
•
Blandinge Barabe; Synthesis of hierarchically porous materials for water filtration, 28.08.2015
•
Kristina Braak; Orientation dependent Raman scattering in cellulose fibers, 22.01.2015
•
Sebastian Bruns; Fatigue behavior of LASER-welded sheet metal, 29.04.2015
•
ASMAMAW MOLLA CHEKOL; Influence of Processing
Parameters on Mechanical Properties of Nanocrystalline Nickel, 20.10.2015
•
Thomas COSSUET; Investigation of Sb2S3 thin films grown by
chemical bath deposition for ZnO-based solar cells, 26.10.2015
•
Dario Mariano De Carolis; TiO2 flake morphology by tailored molten salt crystallization, 30.04.2015
•
Chandanraj Gangaraju; Anisotropy of Fatigue Properties in
Ultra-Fine Grained ARMCO Iron Processed by Equal-Channel
Angular Pressing, 01.09.2015
•
Sabrina Heidt; Elektrisch leitfähige Filme mit kolloidaler Überstruktur, 27.04.2015
•
Svenja Karin Heise; Characterisation of Almandine Inlays in
Brooches of the 5th/6th Century Found in the Rhine-Main Area, 20.02.2015
•
Hanna Verena Heyl; Synthese und Charakterisierung von temperatur-
stabilen Beschichtungen mit niedriger Oberflächenenergie auf anorga-
nischer Basis am Beispiel HfO2 und ZrO2, 10.04.2015
•
Andreas Hilarius Hubmann; Investigation of the Polarization Behavior of BaTiO3 Single Crystals, 14.04.2015
•
Senan Jadeed; Microdensitometric Granularity Measurements of Industrial X-Ray Film Systems, 27.04.2015
•
Peter Keil; Influence of the Synthesis parameter on the Temperature and Pressure Behaviour of ZnO-based Varistors, 31.03.2015
•
Leonie Koch; Computer Simulations of Ordering Effects and
Dislocation Structures in High Entropy Alloys, 21.12.2015
•
Anna Krammer; Deped VO2 termochronic coatings for overheating protection in solar thermal collectors, 21.10.2015
•
Philipp Kröber; Optical characterisation of smooth and porous gold nanowires, 13.03.2015
•
Johannes Kroder; Reactive Crucible Method applied to the Heusler Systems Ni-Mn-Ga and Fe-Mn-Ga, 31.08.2015
•
Kai-Michael Kühne; Untersuchung der thermooxidativen Alterung von Elastomeren, 29.04.2015
•
Moritz Liesegang; Synthesis and Caracterization of High-Remanent Sm2(Co,Fe,Cu,Zr)17 Type Magnets, 03.11.2015
•
OLUWASAYO Inumidun Loto; Deposition and characterization of new chalcogenide materials for phase change memory applications, 16.09.2015
•
Léopold Macé; On the elctrical characterization of OxRAM nonvolatile memories, 09.09.2015
•
Julian Mars; Molecular scale structures of ionic liquid interfaces in an electric potential, 12.02.2015
•
Anne Martin; Generating ideal surface structure of PEEK implants and applying titanium to improve osteoconductivity, 09.09.2015
•
Sven Milla; Untersuchung von Iodausgasungen aus anorganisch stabilisiertem Polyamid 6.6, 24.03.2015
•
Anok Babu Nagaram; Effect of Zr-addition on carbide precipation in Ti-Nb processed by Metal Injection Moulding, 31.08.2015
•
Tobias Opitz; Investigation of induction heating and its influence on the properties of AlSi-coated boron alloyed steel for press
hardening, 29.01.2015
•
Amalia-Anastasia Papapanou; Fatigue and vibration endurance of thermoset composite materials, 30.09.2015
•
Sai Priya S. V. M. L. Munagala; Comparative study of the oxidation behaviour of Al2O3 reinforced siloxanes at 700 °C, 22.05.2015
•
Stefan Schlißke; Fabrication, characterization and optimization of inkjet printed polyimide structures, 13.03.2015
•
Jona Schuch; Plasma Enhanced Chemical Vapor Deposition of
Nickel-, Iron- and Nickel-Iron-Oxides for the Oxygen Evolution Reaction, 20.10.2015
•
Theresa Schütz; Untersuchungen zur Eigenspannungsmessung
mittels fokussiertem Ionenstrahl und digitaler Bildkorrelation
an Hartstoffschichten, 30.11.2015
•
Romana Schwing; Schädigungsverhalten von Diamant- und
DLC-beschichteten metallischen Werkstoffen, 30.11.2015
•
Shilpi Sharma; Mechanical Properties of the magnetocaloric
compound La(Fe,Si)13, 30.04.2015
•
Daniel Simon; Influence of microstructural parameters on the diffusion of heavy rare earth elements in sintered Nd-Fe-B permanent magnets, 31.03.2015
•
Varun Sridhar; Rolled up ITO based 3D tubular biosensors and
TiO2/Au fuel-free light driven nanomotors, 27.11.2015
•
Sebastian Steiner; Temperature and Frequency Dependent Oxygen Ion Conductivity in Doped and Non-Stoichiometric Sodium Bismuth Titanate Ceramics, 18.12.2015
•
Geoffrey Matthew Tan; Synthesis and characterization of transition metal oxide thin film cathode materials for Li-ion battery applications, 28.10.2015
•
Andreas Taubel; Study of magnetocaloric and microstructural properties of Heusler-type alloys, 22.12.2015
•
Zélie Tournoud; Electrodeposition of Stainless Steel, 02.09.2015
•
Anke Silvia Ulrich; Investigation of Protective Diffusion Coatings for Refractory Metals, 30.04.2015
•
Halyna Volkova; Schottky barrier formation in thin film heterostructures on ZnO substrates, 21.09.2015
•
Florian Weyland; Electrocaloric effect in bismuth sodium titanate based ceramics, 22.12.2015
•
Leoni Wilhelm; Elaboration and Evaluation of Methods to Join Metal on Cermet, 31.08.2015
•
Maximilian Wimmer; Sn/SiOC and SnO2/SiOC composite anode materials for Li-ion batteries, 21.07.2015
•
Christopher Wolf; Origin of time-dependent increase of charge carrier mobility of pentacene field-effect transistors with different gate dielectrics, 26.03.2015
•
Silke Wursthorn; Entwicklung eines galvanischen ZinkLegierungsverfahrens mit anschließender Passivierung, 30.03.2015
•
Fangtong Xie; Erhöhung der Temperaturstabilität von
CuCr2O4-Pigmenten in der Emaille durch SiO2/CeO2-Beschichtung, 30.11.2015
•
Farzin Ziaiee Tabary; Investigation of Pt-Nanoparticles as Catalysts for the Hydrogen Evolution Reaction, 16.02.2015
•
Golo Joachim Zimmermann; Evaluation of the Ductile to Brittle Transition Temperature and Strain Rate Sensitivity of Molybdenum by Indentation, Impact and Compression Testing, 30.07.2015
•
Alexander Zimpel; Piezoelectrically Induced Chemical Reactions, 21.10.2015
PhD Theses in Materials Science
•
Matias Acosta; Strain Mechanisms in Lead-Free Ferroelectrics for Actuators, 21.07.2015
•
Alexander Ulrich Buckow; Thin film deposition of arsenic free pnictide superconductors, 13.05.2015
•
Mercedes Alicia Carrillo Solano; Development of artificial Surface Layers for Thin Film Cathode Materials, 30.10.2015
•
Eduard Martin Feldmeier; Ambipolare Feldeffekttranistoren mit spannungsabhängiger Emissionsfarbe, 16.06.2015
•
Dominic Werner Fertig; Optimierung von p-GaP-Halbleitermaterialien zur photoelektrochemischen Wasserspaltung, 17.09.2015
•
Arne Stephen Fischer; Crystalline and amorphous cluster-assembled nanomaterials, synthesized with a novel cluster deposition system, 05.05.2015
•
Mareike Frischbier; Die elektrischen Eigenschaften von
Indiumoxid-Dünnschichten: in-situ Hall-Effekt-Messungen zur Aufklärung des Einflusses von Punktdefekten und Korngrenzen, 14.07.2015
•
Anne Maria Helga Fuchs; Der Frontkontakt der CdTe-Dünn-
schichtsolarzelle: Charakterisierung und Modifizierung von Puffer- und Fensterschichten und deren Grenzflächen, 13.01.2015
•
Mariel Grace Jama; Semiconductor Composites for Solid-State Lighting, 27.10.2015
•
Markus Stefan Jung; Einfluss der Materialeigenschaften auf das elektrische Schaltverhalten von Ag/SnO2-Kontaktwerkstoffen, 22.06.2015
•
Alexander Maximilian Kaus; Phosphoolivine als Kathodenmaterialien für Li-Ionen Batterien, 13.07.2015
•
Katharina von Klinski-Berger; Charakterisierung von
Kupfer-Chrom-Verbundwerkstoffen für die Schalttechnik, 22.04.2015
•
Tobias Könyves-Toth; Organische Halbleiterbauteile auf Fasersubstraten, 24.06.2015
•
Wenjie Li; Formability synthesis and properties of perovskite-type oxynitrides, 24.11.2015
•
Thi Thanh Dung Nguyen; Synthese und Charakterisierung von Lithium-Übergangsmetall-Phosphat/Kohlenstoff-Komposit-Kathoden-
materialien für Lithium-Ionen-Batterien, 22.12.2015
•
Mohsen Pouryazdan Panah; Shear-Induced Mixing in Metallic Systems, 02.06.2015
•
Lukas Mirko Reinold; SiCN based Anode Materials for Lithium-Ion Batteries, 23.12.2015
•
Simon Sawatzki; Der Korngrenzendiffusionsprozess in nanokristallinen Nd-Fe-B-Permanentmagneten, 04.12.2015
•
Cristina Schitco; NH3-Assisted Synthesis of Silicon Oxycarbonitride Ceramics for Gas Capture and Separation, 06.11.2015
•
Alexander Schökel; Ruthenium dissolution in direct methanol fuel cells, 06.03.2015
•
Andre Schwöbel; Präparation und Charakterisierung von LiPON Feststoffelektrolyt-Dünnschichten und deren Grenzflächen, 08.12.2015
•
Vassilios Siozios; Synthese und funktionelle Materialeigenschaften 2D-angeordneter SiC- und SiCN-Nanostrukturen, 11.09.2015
•
Agnieszka Voß; Hochaufgelöste mechanische Charakterisierung von Polymerschichten und Biomolekülen, 24.02.2015
•
Mirko Weidner; Fermi Level Determination in Tin Oxide by Photo-
electron Spectroscopy, 11.12.2015
•
Murat Yavuz; Investigation of Local and Average Structure in Li-ion Battery Electrode Materials by X-ray Diffraction, 11.12.2015
•
Jia Yuan; SiHf(B)CN-based ultra-high temperature ceramic nanocomposites: Single-source precursor synthesis and behavior in hostile environments, 12.10.2015
•
Jürgen Ziegler; Photoelektrosynthese von Wasserstoff mit
Silizium-Dünnschicht-Tandemsolarzellen, 27.07.2015
Habilitation in Materials Science
•
Emanuel Ionescu; Ceramic Nanocomposites with Advanced
Structural and Functional Properties, 04.05.2015
•
Wojciech Pisula; Impact of Molecular Design and Solution Processing
on Self-Assembly and Performance of Organic Semiconductors, 26.01.2015
Annual
REPORT
204 | Institut for applied geosciences
About Us
Research Groups
Theses
Institut for applied geosciences | 205
About US
Preface
Many of today’s major societal challenges are,
to a large extent, of geoscientific origin. The
efficient management of water as well as other
geo-resources, the securing of our future energy
demands, or the understanding of the effects of
the anthropogenic alteration of global cycles are
vital for the future development of our society.
The Institute for Applied Geosciences at the
Technische Universität Darmstadt has continued
its efforts to focus research activities as well as
its educational program on our key activities in
Water – Energy – Environment.
The EU-FP7 project MARSOL, coordinated
by the Hydrogeology group of Prof. Christoph
Schüth, went into its second year with project
workshops and meetings in Israel, Spain, Portugal and Italy. In these countries field sites for
Managed Aquifer Recharge (MAR) are operated
and the lessons learned were discussed and
presented to a broad audience of stakeholders
and policy makers. As a result of these activities,
additional projects have been generated with the
MARSOL partners, e.g. a bi-lateral project on the
hydrochemical aspects of MAR in Israel. We are
excited about the high international visibility of
MARSOL that opens the door to further cooperations all over Europe.
In the focus of the 10th deep geothermal
energy forum, held by the research group of Prof.
Ingo Sass on September 22th 2015 at the Institute
of Applied Geosciences, were presentations
of the recent Hessian deep geothermal energy
power plant projects and preliminary results of
recent research projects as well as discussions
on recent developments in the legislative basis of
deep geothermal energy in Germany.
In 2015, our successfully accredited consecutive Bachelor and Master program ’Angewandte
Geowissenschaften’ reached the third semester.
Altogether 335 Bachelor students and 132 Master
students are enrolled in winter term 2015/16.
The amount of our master students has increased
by ca. 50% since 2014/15. Again, the master
program turned out to be highly attractive for
external applicants who make up two third of all
master students. Students from the universities of
Mainz and Frankfurt even exceeded those having
passed their Bachelor´s degree in Darmstadt.
206 | Institut for applied geosciences
The main reason is the specific applied focus in
geosciences in Darmstadt, which is among only
few in Germany. For the first time, a separate
field course for the specialisation Environmental
Geochemistry was organised in the Taunus
area, whereas the traditional field course for the
specialisation Applied Geology was held in the
Zillertal area. Prof. Sass led a joint excursion
with the University of Bochum to Chile.
Also the international master course
TropHEE increasingly attracts students. Since
2013, the amount of students has doubled and in
winter term 2015/16 62 students are enrolled in
total. They are from 23 (!) different countries, in
particular from developing countries in Africa
and Asia. However, also students from South
America, the USA, New Zealand, and Eastern
Europe take part in this course. Every year
DAAD awards 5 to 8 scholarships to TropHEE
and support the course also financially.
Again, we could donate 6 Deutschlandstipendien to excellent students. Together with diploma
and PhD students, the total number of enrolled
students in winter term 2015/16 is 509 students.
Of those, the proportion of female students
slightly increased to 34%.
On July 17, 2015, we organized our second
celebration for our graduates, where their Diploma, BSc or MSc thesis was briefly introduced.
All students received a small item which should
serve as a nice memory of this very special event
in their scientific career.
The Institute is very grateful for the intensive help in organizing this event, in particular,
Gabriela Schubert (left in upper picture), Melanie
Werner and Angelika Willführ; without their
continuous support during the run-up of the
planed celebration, we would not have had such a
positive response from our alumni.
As it is a long standing tradition in Geosciences
to conclude the academic year with the ‘Barbara
Fest’, all faculty, staff and students got together to
discuss the events of the year as well as the future
in a very friendly and positive atmosphere. Due
to the high number of freshmen, the welcome
ceremony of the new students, who are baptized during this event, was rather crowded but,
finally everyone was officially accepted as a new
member of the Institute for Applied Geosciences.
Earth Sciences
500
400
300
200
100
0
Freshman
Students (total)
Development of the number of students in Materials Science over the past 15 years.
On July 17, 2015 the second celebration of our graduates took place, briefly introducing their Diploma, BSc or MSc thesis as
well as receiving a small gift to express our appreciation.
Institut for applied geosciences | 207
Research Groups
208 | Research Groups – Institut for applied geosciences
Applied Sedimentary
Geology
Staff Members
Head
Prof. Dr. Matthias Hinderer
Research Associates
Dr. Jens Hornung
Dr. Olaf Lenz
PhD Students
Alexander Bassis
Dennis Brüsch
Daniel Franke
Maryam Moshayedi
Anna Lewin
Inge Neeb
Frank Owenier
Sandra Schneider
Jianguang Zhang
Technical Personnal
Reimund Rosmann
Secretaries
Kirsten Herrmann
Applied Sedimentary Geology | 209
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. The sedimentology group follows a
210 | Applied Sedimentary Geology
multi-scale approach from cm (lab specimen) to
tens of kms (sedimentary basins) in order to gain
subsurface data which can be used in 3D models. This includes cooperations with the groups
of Prof. Schüth (Hydrogeology), Prof. Sass (Geothermics), and Prof. Henk (Engineering Geology) in order to achieve an optimized subsurface
management of water and renewable energy resources. Major focus is laid on large to meso-scale
architecture and permeabilities of sedimentary
reservoir rocks and petrophysical data generation
in the lab needed for upscaling.
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, Bonn, 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 and recently by the Hochschulpakt
we could invest into a shear wave seismic unit,
which will extent our abilities for subsurface surveys down to hundred meters and through materials, weakly penetrable by electromagnetic waves.
Here we cooperate with the Leibniz Institute for
Applied Geophysics in Hannover and the University of Hamburg. 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. Dr. Hornung
received a grant from Shell to analyse small-scale
heterogeneities of porosities and permeabilities of
sedimentary rocks and their link to microfacies
patterns. The industrial project with Shell enables
us to design and construct a scanning device for
automatized petrophysical screening of rocks.
This device started its operation in 2015 and provides a new dimension in petrophyiscal surveys of
rocks on the extended lab scale. Its development
was also embraced by industrial partners. On the
other hand, it well suits as a training facility for
students and offers new possibilities for bachelor
theses.
In 2015, the group still participated in the DFG Research Unit RiftLink
(http://www.riftlink.de/) which had been prolongated for one year. The topic of these research
projects are in the context of earth surface processes and palaeoenvironmental reconstructions.
Here still two funded PhD theses were running
in 2015. The research activities in Saudi Arabia
in cooperation with the GIZ (Gesellschaft für
International Zusammenarbeit), the UFZ (Umweltforschungszentrum Halle-Leipzig), and the
Ministry of Water and Energy of Saudi Arabia
(MOEWE) were completed. Anorther outcome of
our activities in Saudi Arabia is the acceptance of
a 3 years DFG proposal in order to elucidate the
provenance of the widespread sandstones on the
Arabian Peninsula and Ethiopia. Here a new PhD
candiate could be engaged. Field work in Ethiopia
took place in October 2015. Based on previous
work of the group several research initiatives are
running at the moment.
Prof. Hinderer is member of the coordination
board of the Schwerpunktprogramm “Hiatal Surfaces” together with the universities of Bochum
and Göttingen which had been submitted in
October 2015 to DFG. Jianguang Zhang continued his PhD with a Chinese grant. In December,
Prof. Hinderer was invited by the Emirate of
Sharka (VAE) to visit archeological excavations.
In this context, samples could be collected for the
PhD thesis of Susanne Lindauer. DFG supports
this thesis by financing analytical work.
In October 2015 a PhD thesis, financed by a
DAAD scholarship of an Iranian student, Maryam
Moshayesi, started. Main task of the project is the
detailed analysis of the organic material such as
pollen, spores and algae from the Eocene lake
Prinz von Hessen with the aim to reconstruct the
evolution of paleoenvironment and palaeoclimate
in Central Europe over a period of several hundred thousand years during the Paleogene greenhouse phase, the most recent greenhouse period
on Earth.
Until October 2015, Prof. Hinderer continued
to be the representative of the German-speaking
sedimentologists (Section of Sedimentology in
Geologische Vereinigung and SEPM-CES) and
co-organized the DGG-GV conference in Berlin
2015. He was asked to give key notes on international conferences (GeoBerlin), colloquia (Milano, Freiburg) and workshops (Summer School
on geomorphology in alpine regions, Feichten,
Österreich). He continued to be Dean of study
affairs.
Shells of South-East Arabia: First insights into their role for
the determination of the local reservoir effect
Susanne Lindauer1,4, Soraya Marali2, Bernd R. Schöne2 Matthias Hinderer1,
Hans-Peter Uerpmann 3, Bernd Kromer 4
Institute of Applied Geosciences, Technical University Darmstadt, Schnittspahnstr. 9, 64287 Darmstadt, Germany.
Institute of Geosciences, University of Mainz, Joh.-J.-Becherweg 21, 55128 Mainz, Germany.
3
Center for Scientific Archaeology, Eberhard-Karls-University Tübingen, Rümelinstraße 23, 72070 Tübingen, Germany
4
Curt-Engelhorn-Zentrum Archaeometry, Klaus-Tschira-Archaeometry-Centre, C4,8, 68159 Mannheim, Germany.
1
2
An important tool to establish absolute archeological chronologies of the southern Arabian
Peininsula are radiocarbon dating of widespread
available mollusc shells, because collagen and
charcoal are rarely conserved. The radiocarbon
ages of the frequently used mollusc species
Anadara (bivalve) and Terebralia (gastropod),
however, are affected by the reservoir effect
which leads to overestimated ages up to several
hundreds of years. Recently, we started a systematical approach to quantify the reservoir effect
of radiocarbon dating in South-East Arabia and
its dependence on species and environmental
influences such as climate and ocean water. We
sampled the molluscs shells at the Persian Gulf
and at the Gulf of Oman from modern beaches
and archeaological excavations to compare differences between both over time. Archeological
sites are from Neolithic time (5500 – 3000 BC)
and the Iron Age (1200 – 300 BC). Temporal
variability is considered in particular for the
Neolithic time interval with a rich record of
archeological sites. The modern samples should
help us to understand the mollusk system better
in comparison to their environment, like e.g.
Mangroves. For this purpose stable isotopes on
the shells provide a good, additional tool. Seasonal and lifelong shifts in stable isotope pattern
can be used to reconstruct life habits, growth
intervals and diet which are weakly known so far.
Deviations of past from modern pattern can be
interpreted in terms of paleoenvironmental and
paleoclimate change. Mangroves are important
ecosystems which made them important already
to our ancestors who settled close to Mangrove
forests using their wood as well as the food
resources that can be found within. During arid
times in the Emirates people would continuously
settled where Mountains are close to the shore
whereas we lack proof for settlements along
the coast of the Arabian Gulf which are far from
the mountains. This along with bad collagen
preservation is responsible for only few data
during certain time periods (“dark millennium”).
Main hypotheses are:
1) The reservoir effect along the coast of
the Arabian Sea is stronger than in the Persian Gulf area.
2) Temporal variability of the reservoir effect in the Persian Gulf area is stronger and shows tighter connections to palaeo
References climate change.
3) The known fluctuations of humidity
[1] Lindauer, S. and
during the Neolithic also affect the
B. Kromer (2013).
reservoir effect. Drier periods are “Carbonate sample
supposed to increase upwelling and thus preparation for 14c
dating using an elemen
increase the reservoir effect and vice tal analyzer.” Radiocarversa.
bon 55 (2-3): 364-372.
4) Severe changes such as the drop in humidity at around 4300 BC as known
[2] Lindauer, S., Marali
from speleothem records are also S., Schöne B.,R., Hinderer M., Uerpmann
reflected in the reservoir effect.
H-P., Kromer B. Shells
5) Seasonal and lifelong shifts in stable of South-East Arabia:
isotope pattern can be used to reconstruct First insights into their
life habits, growth intervals and diet
role for the determina
which are weakly known so far. tion of the local reservoir effect. Radiocarbon
Deviations of past from modern pattern 2015, 16.-20.11.2015 in
can be interpreted in terms of paleoDakar, Senegal.
environmental and paleoclimate change.
In December 2015, a second field campaign
to various archeological sites took place (see
picture). The stay was sponsered by the Emirate
of Sharja (United Arab Emirates).
[3] Uerpmann, H.-P.
(1990). “Radiocarbon
dating of shell middens
in the sultanate of
oman.” PACT 29 (IV.5):
335-347.
Sampling of mollusk shells in the archeological excavation of Khalba with partners from the Archaeological Service of
Sharja (UAE) in December 2015. In December 2015, a second field campaign to various archeological sites took place
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 643/7-2; 16-1).
• Climate-controlled aggradation of alluvial fans in southern Peru (various Master theses in cooperation with the universities of Münster and Hannover).
• 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
(PhD thesis, Chinese funding).
• Development of a database system for stratigraphic dating using
palnynomorphs (PhD thesis, Chinese funding).
• Provenance of Paleozoic clastic sediments and reasons for radioactive anomalies in groundwaters on the Arabian Platform (PhD thesis, partly GIZ funding)
• Paleozoic source to sink relationship around the northern Trans Gondwana Mountain Belt (East Africa, Arabia) (PhD thesis, DFG HI 643/13 together with Universität Göttingen)
• Periglacial eolian sediments in southern Hessia, their chronology, and their genesis (Diploma und BSc theses and preparation of a DFG project)
• 2-D heterogeneities of poroperm, ultrasonic and resistivity on sub-meter scale (Diploma und BSc theses, funded by Shell)
•
Climate and vegetation dynamics during the Eocene greenhouse of Central Europe: Palynological investigation of lacustrine sediments
from Lake „Prinz von Hessen“ (Hesse, Germany) (PhD thesis,
DAAD funding)
Publications
[1]Al-Ajmi, H.F., Keller, M., Hinderer, M., Filomena, C.M. (2015): Lithofacies, depositional environments, and stratigraphic architecture of the Wajid Group outcrops in southern Saudi Arabia.
GeoArabia 20/1: 49-94
[2]Inglis, G.N., Collinson, M., Riegel, W., Wilde, V., Robson, B.E., Lenz,
O.K, Pancost, R.D. (2015): Ecological and biogeochemical change in an early Paleogene peat-forming environment: linking biomarkers and palynology. Palaeogeography, Palaeoclimatology, Palaeoecology, 438: 245-255.
[3]Jadoon, I.A.K., Hinderer, M., Kausar, A.B., Qureshi, A.A., Baig, M.S.,
Basharat, M., Frisch, W. (2015): Structural Interpretation and Geo-Hazard Assessment of a Locking Line, 2005 Kashmir Earth
quake, Western Himalayas. Environmental Earth Sciences, Springer-Verlag.
[4]Kaufmann, G., Hinderer, M. & Romanov, D.: Shaping the Rwenzoris (2015): Balancing Uplift, Erosion, and Glaciation. Int. J. Earth Sci. DOI 10.1007/s00531-015-1174-2
[5]Jadoon, I., Hinderer, M., Wazir, B., Yousaf, R., Bahadar, S., Hassan, M., Jadoon, S. (2015): Structural styles, hydrocarbon prospects and potential in the Salt Range Potwar Plateau, North Pakistan. Arabian Journal of Geosciences 8: 5111 - 5125.
[6]Bassis, A., Hinderer, M., Meinhold, G. (2016): New insights into
the provenance of Saudi Arabian Palaeozoic sandstones from heavy mineral analysis and single-grain geochemistry. Sedimentary Geology 333: 100-114.
[7]Lenz, O.K., Wilde, V., Mertz, D.F, Riegel, W. (2015): New palynolo-
gy-based astronomical and revised 40Ar/39Ar ages for the Eocene maar lake of Messel (Germany). International Journal of Earth Sciences, 104: 873-889; doi: 10.1007/s00531-014-1126-2.
[8]Riegel, W., Lenz, O.K., Wilde, V. (2015): From open estuary to meandering river in a greenhouse world: an ecological case study from the Middle Eocene of Helmstedt, Northern Germany. PALAIOS 30: 304-326, doi: 10.2110/palo.2014.005.
[9]Rasmussen, C., Reichenbacher, B., Lenz, O.K., Altner, M., Penk, S.B.R., Prieto, J., Brüsch, D. (2015): Middle-late Miocene palaeo
environments, palynological data and a fossil fish Lagerstätte from
the Central Kenya Rift (E. Africa). Geological Magazine
(in press, published online 28.Dezember 2015;
http://dx.doi.org/10.1017/S0016756815000849).
Engineering
Geology
Staff Members
Head
Prof. Dr. Andreas Henk
Research Associates
Dr. Tobias Hergert
Dr. Karsten Reiter
Technical Personnal
Reimund Rosmann
Secretaries
Dipl.Kffr. Stefanie Kollmann
PhD Students
Chiara Aruffo, M. Sc.
Constantin Haug, M. Sc.
Dipl. Geol. Christian Heinz
Dennis Laux, M. Sc.
Dipl. Geol. Christoph
Wagner
Bastian Weber, M. Sc.
Master Students
Sascha Anschütz
Lothar Koch
Sebastian Kurka
Mushtaq Faisal
Saqib Pervez
Benjamin Schmitz
Georg Schulz
Stefan Wewior
Florian Zahn
216 | Engineering Geology
Engineering Geology
Engineering Geology is a branch of geology
that deals with the characterization of soil,
rock and rock masses for the location, design,
construction and operation of engineering works.
Typical tasks relate to foundation of roads and
buildings, but also to underground excavations
like tunnels and caverns. The special focus of
the Engineering Geology group at Technische
Universität Darmstadt is on reservoir geomechanics, i.e., the application of rock mechanics
as well as of techniques for stress and fracture
characterization to depth of up to 5 km.
In particular, numerical (finite element)
models are used to predict the corresponding
subsurface conditions prior to drilling operations.
Such predictive tools are of great value not only
for the optimal exploration and efficient use of
hydrocarbon and geothermal reservoirs, but also
for CO2 sequestration sites as well as radioactive
waste repositories.
In 2015 two new research associates joined
our team: Dr. Tobias Hergert (formerly Karlsruher Institut für Technologie) and Dr. Karsten
Reiter (formerly GFZ Deutsches GeoForschungsZentrum Potsdam). Both have comprehensive
expertise in geomechanical modeling and have
worked on various case studies in Turkey, Canada
and Switzerland, for example. They also brought
further knowledge with respect to in situ stress
measurements and geomechanical characterization of radioactive waste disposal sites to our
group. The two abstracts attached provide some
insights in their research work. In addition, a new
industry-funded PhD project has started which
deals with the potential for induced seismicity
in North German gas fields. Work in two other
projects, i.e., geomechanical modeling for part
of the central Rhine Graben as well as for a
demonstration site of subsurface CO2 storage in
Australia continued in 2015.
These research activities are reflected in
several papers and contributions to conferences
ranging from a stress map for Germany via
fracture characterization with terrestrial laser
scanning to geomechanical models for transform
margins in central Africa.
Research activities of our group won special
recognition as Dr. Chiara Aruffo received the
Gustavo Sclocchi theses award 2015 of the
Society of Petroleum Engineers, Italian section.
She left soon after her PhD to work for Royal
Dutch Shell in the Netherlands. We wish her all
the best for her future career.
With respect to teaching the updated
curriculum for engineering geology is now in
full effect for both the BSc and MSc programs
in applied geosciences. It comprises four
modules each consisting of a lecture and a
practical course (two field, one lab, one numerical
modeling). Topics range from general principles of
engineering geology (with special focus on
soil) in the BSc program to rock mechanics and
reservoir geomechanics in the MSc program.
A fifth module on underground construction is
given by an external lecturer, Dr. Ralf Plinninger of
Dr. Plinninger Geotechnik. Teaching also
included excursions which led to tunnel projects
in the Spessart Mountains and to in situ rock
mechanical labs in Switzerland.
Engineering Geology | 217
Stress Field Sensitivity Analysis at a Reservoir
Scale (Northern Switzerland) using Numerical
Geomechanical Modelling
T. Hergert1, O. Heidbach2, K. Reiter1 and S.B. Giger3
1
TU Darmstadt, 2 GFZ German Research Centre for Geosciences, 3 Nagra
A numerical geomechanical model is presented
to characterize the stress field at a candidate site
for a nuclear waste repository in Switzerland
(Zürich Nordost). Lithological formations of
approximately 20 to 200 m in thickness are
considered in the model through specific rock
properties as individual geomechanical units.
Special attention is given to the Opalinus Clay
(Lower Dogger), the designated host rock of high
level waste at the candidate site.The modeled
stress field is calibrated against stress data from
borehole breakouts and hydraulic fracturing
measurements conducted within the site. In
general the state of stress strongly correlates with
geomechanical properties. The stiff formations
show much higher stress anisotropy with higher SH magnitudes and lower Sh magnitudes
than the softer formations. In particular, it is
concluded that the stress field in the Opalinus
Clay is not very sensitive to changes in the
boundary conditions as the stiffer formations
(notably the limestones of the Upper Malm and
the Upper Muschelkalk) take up the far-field
tectonic stresses.
properties using different model assumptions and
by performing parameter studies (Hergert et al.
2015).
The parameter studies focus on the impact
of mechanical properties of sedimentary layers
and fault structures on the stress field in the
Opalinus Clay host rock. Effects of topography and
potential future ice cover are also investigated.
Introduction
The geological siting area Zürich Nordost
(ZNO) is one candidate site for a nuclear waste
repository in northern Switzerland (Fig. 1).
Knowledge of the in situ stress state is relevant
to evaluate engineering suitability and long-term
safety of underground structures. Direct (hydraulic fracturing) and indirect (borehole
breakouts) methods were used to constrain
the stress field from one deep well in the area
(Nagra, 2001). In this contribution we highlight
how numerical geomechanical modelling can
assist in characterizing the 3D stress field at a
siting or reservoir scale by honouring 1D point
measurements. Such forward models enable the
study of the relative sensitivity of the stress field
due to e.g. fault friction or elasto-plastic rock
Model set-up
The model covers an area of 20 km by 16 km
(Fig. 1). The bottom of the model is at 2500 m
below sea level. The geomechanical model is
based on a geological model that comprises
the structure of interfaces between different
formations derived by 3D seismic as well as
the geometry of the Neuhausen Fault. The fault
is implemented by frictional contact surfaces
allowing relative displacement. Among the
identified formations fourteen geomechanical
units were selected that are characterized by representative densities and elasto-plastic parameters. The rock mass is subjected to gravity.
The model volume is discretized into 589,000
hexahedron elements with linear approximation
Geological overview and tectonic setting
The geological siting area ZNO is located in
the northern part of the Central Swiss Molasse
Basin (Nagra, 2008). At the potential repository
level, the Opalinus Clay is part of the (partly
detached) Tabular Jura. Within the ZNO siting
area, the base of Opalinus Clay is buried at a
depth of approximately 400 to 900 m below
surface and its thickness ranges between approximately 100 and 120 m. The east of the siting
area is limited by the presence of the NW-SEstriking Neuhausen Fault, which is considered
as the westernmost border fault of the Lake
Constance-Hegau Graben.
Fig. 1. Stress map of Northern Switzerland based on the revised World Stress Map release 2008 (Heidbach et al. 2010,
Nagra 2013). Lines show the orientation of maximum horizontal stress SHmax. Orange rectangle marks the area covered by the
model; thick black line within the model area encircles the geological siting area ZNO (Nagra, 2008). Yellow circles show the
locations where stress magnitude data are available in the depth range of potential repositories (Basel, Benken, Schlattingen).
Colour-code of the model indicates the stratification.
functions. Each of the Mesozoic formations is
discretised by at least three layers of elements,
which corresponds to a vertical resolution of
about 20 m in the Mesozoic formations and
about 100 m lateral resolution. To constrain
the initial and boundary conditions for a base
model we use orientations of maximum horizontal stress (SHmax), stress regime information
(Fig. 1), magnitudes of the minimum horizontal
stress (Shmin) from hydraulic fracturing and a
semi-empirical relationship of the stress ratio
Sh/SV for overconsolidated, argillaceoussediments. Details of the technical workflow for
the initial stress implementation and calibration
procedure are given in Hergert et al. (2015) and
Heidbach et al. (2014).
Results
The model runs demonstrate that the stress
ratios SHmax/SV, Shmin/SV and SHmax/Shmin are
considerably reduced in the argillaceous
formations with respect to the stiffer formations
of e.g. the Malm and the upper and lower Muschelkalk (Fig. 2).
The stiffer formations are characterized by
higher stress ratios, higher differential stresses
and greater horizontal stress anisotropy than the
softer argillaceous formations. It can be concluded that the stiffer formations carry the main
load of the lateral tectonic push from the far-field.
In the base model the horizontal differential
stress SH-Sh is about 3-5 MPa in the Opalinus
Clay within the siting area.
The stress ratios Sh/SV, SH/SV and SH/Sh are
widely uniform and show variability of ≤ 10%
within the siting area with decreasing values with
increasing depth (Fig. 2).
Modelled stress magnitudes in the Opalinus
Clay at the site of the Benken well are Sh~14 MPa,
SV~15 MPa, SH~18 MPa and compare favourably
with the stress estimates from hydrofracturing
experiments (Fig. 3). Horizontal stresses east of
the Neuhausen Fault are ~3 MPa smaller in the
Opalinus Clay in agreement with the slightly
more extensive stress data from the Schlattingen
well a few kilometres further east.
There is an ambiguity regarding SH in the
sense that Sh data from Benken can be approximated with different boundary conditions at
differing SH magnitudes. The gravitational effect
of topography increases stresses below elevated
areas and reduced stress below topographic
depressions. In turn, tectonic far field stresses
increase horizontal stress in valleys. The effect
of topography is recognisable down to several
hundred metres depth. Particularly the NW of the
model area reveals topographical effects on the
host rock due to its proximity to the undulating
surface.
References
[1] Heidbach, O., Tingay,
M., Barth, A., Reinecker,
J., Kurfeß, D. and Müller,
B. [2010] Global crustal
stress pattern based on
the World Stress Map
database release 2008,
Tectonophysics, 482,
3-15, doi:10.1016/j.
tecto.2009.07.023.
[2] Heidbach, O. and
Reinecker, J. [2013]
Analyse des rezenten
Spannungsfeldes der
Nordschweiz, Nagra Arb.
Ber. NAB 12-05. Nagra,
Wettingen, Switzerland.
[3] Heidbach, O., Hergert,
T., Reiter, K. and Giger,
S.B. [2014] Local stress
field sensitivity analysis
- case study Nördlich
Lägern, Nagra Arb. Ber.
NAB 13-88. Nagra,
Wettingen, Switzerland.
[4] Hergert, T., Heidbach,
O., Reiter, K., Giger,
S. B., and Marschall,
P. [2015] Stress field
sensitivity analysis in a
sedimentary sequence
of the Alpine foreland,
northern Switzerland,
Solid Earth, 6, 2, 533-552,
doi: 10.5194/se-6-5332015.
[5] Klee, G. [2012]
Geothermal borehole
Schlattingen-1: Hydraulic fracturing stress
measurements. Unpubl.
Nagra Project Report.
Nagra, Wettingen.
[6] Klee, G. and Rummel,
F. [2000] Sondierbohrung
Benken: Hydrofrac
Spannungsmessungen
Teil I – Auswertung der
Feldmessungen. Unpubl.
Nagra Int. Ber. Nagra,
Wettingen.
[7] Nagra [2001]
Sondierbohrung Benken
– Untersuchungsbericht.
Textband und Beilagenband. Nagra Tech.
Bericht NTB 00-01.
Nagra, Wettingen.
Fig. 2. Stress ratios on north-south cross sections of the model ZNO through the Benken well. Thin
black lines in the model results show top and bottom of Opalinus Clay; vertical black line shows the
Benken well. Top figure shows considered geomechanical units in the model.
Fig. 3. Stress magnitudes from hydrofrac experiments (red diamonds and circles) in comparison with modelled Shmin
values (red curve). Blue line shows the modelled SHmax of one mode realization in comparison with estimates from
the various approaches to derive SHmax magnitudes from Shmin values. Data are from Klee and Rummel (2000) and Klee
(2012).
Statistical Stress Model Calibration
K. Reiter 1 and O. Heidbach 2
1
TU Darmstadt, 2 GFZ German Research Centre for Geosciences
The estimation of orientation and magnitude of
crustal stresses is crucial for the design phase of
technological and safe underground usage. As
usually only a few in-situ data are available, stress
prediction is challenging. Geomechanical-numerical modelling is the only tool, which allows
stress prediction that takes material properties
and inhomogeneities into account. The model
calibration is essential to find the best-fitting
stress results. The presented workflow allows the
statistically proved calibration to determine the
best-fit model. Furthermore, statistic tests speed
up the calibration process. The order in which
model-independent data are used for model
calibration pay attention to the interrelation between the stress components. Therefore, data of
vertical stress are tested first to optimize material
properties. Second, the orientation of the maximum horizontal stress is used to optimize
orientation of applied boundary conditions.
Finally, the magnitudes of minimum and maximum horizontal stress are varied to find the optimal strain, applied by the boundary conditions.
Introduction
The Earth’s crust is used by the mankind for
extraction of energy or minerals (hydrocarbon,
geothermal energy etc.), for interim storage sites
(gas and pressurized air), for way of transportation (tunnels) as well as for waste repositories
(nuclear and chemicals). A safe and efficient
underground usage is important, but also the
(long-term) stability is crucial for all, the operator, the society and environment. Potential users
of the underground need a good understanding of
the local stress state greatest before the first well.
This is important in terms of well stability or well
configuration of several corresponding wells, in
the case of reservoir stimulation by hydraulic
fracturing. (e.g. Bell and McLellan, 1995; Peska
and Zoback, 1995). An inadequate understanding
of the spatial stress variability during the planning phase of a reservoir is a crucial point for the
success (e.g. Brown, 2009; Duchane and Brown,
2002). However, stress prediction is also essential
for any cavity like tunnels or nuclear waste repositories (e.g. Fuchs and Müller, 2001; Gunzburger
and Magnenet, 2014; Heidbach et al., 2013).
The stress state is formally described with
a second rank tensor with six independent
components (e.g. Schmitt et al., 2012; Zang and
Stephansson, 2010). Assuming that the vertical
stress (SV) is a principal stress component,
the minimum and maximum horizontal stress
(SHmax and Shmin) respectively, are also principal
stresses. In this case the stress can be described
with only four components, i.e. the orientation of
SHmax as well as the three magnitudes of the principal stresses (SV, SHmax and Shmin). Data of SHmax
orientations are collected in the world stress map
database (WSM - Zoback, 1992; Heidbach et al.,
2010) since decades.
For the magnitude data only a first attempt of
database exists (Zang et al., 2012). The relation
between the stress magnitudes defines the stress
regime (faulting type) according Anderson’s
theory, which are thrust-, strike-slip- or normal
faulting regime (Anderson, 1951).
As stress data are sparsely distributed for
the most regions, geomechanical-numerical modeling is an important tool to predict the in-situ
stresses still in the design phase of an underground project. The method allows incorporation
of several petrological units and inhomogeneities
like faults or detachments. Such models provide
an estimate of the full stress tensor. Nevertheless,
such models need calibration versus available
in-situ stress data (e.g. Fischer and Henk, 2013;
Henk, 2009). But uncertainties of calibration are
usually unknown, as mostly just a few data are
available (e.g. Fischer and Henk, 2013; Buchmann and Connolly, 2007; Heidbach et al., 2013).
A major progress for reliability of models would
be availability of a sufficient amount of data,
so that a statistical calibration procedure could
be applied. Such statistically calibrated models
would improve the significance of numerical
stress models.
Fig. 1. Sketch of the calibration workflow. The geomechanical model is prepared
based on the model geometry, the material properties, the variable displacement
boundary conditions and the initial stress state. The numerically modelled total
stress tensor is calibrated on model independent in-situ stress data.
First the SV magnitude, by testing the density, second the SHmax orientation
testing the orientation of applied boundary conditions and third the Shmin and
SHmax magnitude is testing the offset of applied boundary conditions, until the
model fits all the model independent data.
In the case that data are available for several
or all stress components, the model have to be
calibrated in a reasonable order. This is important as some components of the stress tensor are
independent from boundary condition which will
be applied in a later stage to fit other in-situ data.
Calibration of geomechanical-numerical
stress models
Geomechanical-numerical models reproduce
simplified the geometry of the chosen investigation volume. The model geometry is based on
model-dependent data, which are seismic cross
sections, well data etc. This geometry is combined with the internal forces (material properties
like Young’s modulus, Poisson’s ratio) and external forces like body forces (gravity) as well as
surface forces (boundary conditions). Models are
calibrated versus model independent data which
are SV magnitudes from well logs, SHmax orientations from borehole breakouts, focal mechanisms
etc., Shmin magnitudes from hydraulic fracturing
(e.g. leak-off tests) as well as SHmax magnitudes
from overcoring (or calculated data).
The here presented workflow allows the
meaningful stepwise statistical calibration of
the model on the in-situ data. The statistic test
of one stress component compares each in-situ
stress magnitude or orientation with the model
outcome at the same position within the model.
The difference between both is ΔS:
∆S = SMeasured – Smodel (1)
As a best fit is intended, the median of all ΔS
(ΔS) from each stress component should be very
small. Therefore the calibration procedure seek
for a model where the median of ΔS is as small
as possible ( ΔS =0).
Order of data calibration
The stress component which have to be
tested first (Fig. 1) is the vertical stress (SV),
as SV is marginal influenced by later applied
variation of (horizontal) boundary conditions.
SV by majority is driven by the overburden
load of the sedimentary column as a function
of density and gravity. As gravity changes
only slightly on earth in general as well as
into accessible depth, rock density is the solely
variable for modellers to optimize the model
versus SV data. Each in-situ SV data is compared to the same point in the model (Eq. 2).
The best fit model is found when the (ΔSV= 0).
ΔSV = SVMeasured − SVModel (2)
After final definition of material properties,
the stress orientation has to be calibrated in the
second step (Fig. 1). A stress model will have
either a more or less isotropic horizontal stress
state (SHmax = Shmin) or an anisotropic stress
state (SHmax>Shmin). In an anisotropic case,
applied model boundary conditions are similar
(εx = εy). In such a case stress orientations will
be affected by inhomogeneitys within the model like topography, lateral changing density or
near to faults. This can lead to large variation
of orientations (e.g. Hergert et al., 2015). An
anisotropic stress state will be reached when a
different strain is applied to the model boundaries (εx = εy ).
As long as small differential stresses are
applied, model inhomogeneities have an influence. Above a certain strain ratio, the stress
pattern depends on the applied strain isotropy;
the stress pattern will change only slightly for
much larger applied strain ratios.
Fig. 2. Visualization of bivariate linear regression based on four models. (a and b): the median Shmin and the median SHmax are plotted depending on the northwest to south-east extension (pull) and the south-west to north-east shortening (push). The isolines of the median ΔShmin and ΔSHmax are colour coded.
(c) The isolines, where the median ΔShmin and ΔSHmax is zero are plotted alone. The intersection of both isolines indicated the push-pull values where the best-fit
model can be found (Reiter and Heidbach, 2014).
Therefore orientations of applied boundary
conditions have to be calibrated first, before
calibration of horizontal stress magnitudes. Each
orientation of applied boundary conditions are
tested using SHmax orientation data (e.g. borehole
breakouts or focal mechanisms from the WSM).
The Equation to calculate the differences
between the model and the in-situ date differs
to the general equation, as stress orientations
are circular data (0°=180°) and therefore
ΔSHmax Azi have to range between -90° and +90°
(Eq. 3) The best-fit can be found for boundary conditions which provide a tiny median
ΔSHmax Azi (HmaxAzi) = 0).
ΔSHmax Azi = SHmax Azi Meas−SHmax Azi Model
−90(sgn(SHmax Azi Meas−SHmax Azi Model−90) (3)
+sgn(SHmax Azi Meas−SHmax Azi Model+90))
The applied strain to a rock mass is mainly stored
elastically until failure. Up to the occurrence of
failure, the stress magnitude is a linear function
of rock properties and applied offset at the
model boundaries. Therefore, the SHmax and Shmin
magnitudes will be tested and calibrated together
in one calibration step (Fig. 1). Again differences
between the model and the in-situ data stress data
are calculated for each data point (Eqs. 4 and 5).
ΔShmin = Shmin Measured−Shmin Model (4)
ΔSHmax = SHmax Measured−SHmax Model (5)
The calculated ΔShmin and ΔSHmax of ≥ three models can be plotted separately in a push vs. pull
diagram (Fig. 2a and b). The push is parallel to the
SHmax orientation, where pull is perpendicular to
that. To highlight the linear dependency between
push and pull in an elastic model, colour coded
isolines are plotted. Each model along the light
blue line (Fig. 2a) would derive a model, which
fits well to the in-situ Shmin data. The same stands
for the light blue line in Fig. 2b and SHmax data.
As the determination of the best-fit model is
intended, the intersection of both light blue
lines from Fig. 2a and b would derive the
best-fit. This is done with a bivariate linear regression based on the spatial distribution of the
ΔShmin and ΔSHmax (Fig. 2c). This method provides two linear equations, where the intersection
can be calculated by equating both equations.
The result is an x and y value of applied push and
pull on the model boundaries, which derives the
boundary conditions of the best-fit model.
Alberta stress model
This work-flow is first applied for a crustal
scale model from the Alberta Basin. The model
extend is 1200 × 700 × 80 km. For the model
calibration 321 SHmax orientation data, 981 SV,
1720 Shmin as well as 2(+11) SHmax magnitude
data are available (Reiter and Heidbach, 2014).
The correlation coefficient between the model
and the data are in a range of r = 0.935 for SV
and r = 0.835 for Shmin for data sets with sufficient
amount of data.
Conclusion / Outlook
The calibration workflow allows calibration
of geomechanical-numerical stress model using
statistical methods, seeking for the best-fit
model. The general attempt is the minimization
of differences between in-situ stress data vs. the
model outcome, using the whole model median
as a measure for each data type. The calibration
procedure has the following order: Test of SV data
to optimize rock density, SHmax orientations to find
optimal orientation of boundary conditions and
Shmin and SHmax magnitudes in one step together
to optimize boundary displacements. However,
usually there are significant less data available.
Further investigation are needed, how much
data are necessary, to get a best-fit model with
assessable uncertainties.
Moreover, the question arises, under which
circumstances model results can be transferred
to other model regions with a similar tectonic
setting, i.g. the Alpine Molasse Basin?
References
[1] Anderson, E.M. [1951]
The Dynamics of Faulting and
Dyke Formation with Application
to Britain. 2nd ed. Oliver and
Boyd, London and Edinburgh.
[2] Bell, J.S. and McLellan, P.J.
[1995] Exploration and production
implications of subsurface rock
stresses in western Canada. In:
Proceedings of the Oil and Gas
Forum. 5.
[3] Brown, D.W. [2009] Hot dry
rock geothermal energy: important
lessons from Fenton Hill. In:
Thirty-Fourth Workshop on
Geothermal Reservoir Engineering.
Stanford, 3–6.
[4] Buchmann, T.J. and Connolly,
P.T. [2007] Contemporary
kinematics of the Upper Rhine
Graben: A 3D finite element
approach. Global and Planetary
Change, 58(1-4), 287–309.
[5] Duchane, D. and Brown,
D. [2002] Hot dry rock (HDR)
geothermal energy research and
development at Fenton Hill,
New Mexico. Geo-Heat Centre
Quarterly Bulletin, 23(3), 13–19.
[6] Fischer, K. and Henk, A.
[2013] A workflow for building
and calibrating 3-D geomechanical
models-A case study for a gas
reservoir in the North German
Basin. Solid Earth, 4(2), 347–355.
[7] Fuchs, K. and Müller, B.
[2001] World Stress Map of the
Earth : a key to tectonic processes
and technological applications.
Naturwissenschaften, 88(9),
357–371.
[8] Gunzburger, Y. and Magnenet,
V. [2014] Stress inversion and
basement-cover stress transmission
across weak layers in the Paris
basin, France. Tectonophysics, 617,
44–57.
[9] Heidbach, O., Hergert, T.,
Reinecker, J., Reiter, K., Giger, S.,
Vietor, T. and Marschall, P. [2013]
In Situ Stress in Switzerland-From
Pointwise Field Data to a 3D
Continuous Quantification.
In: International Workshop on
Geomechanics and Energy,
November 2013. EAGE, Lausanne,
1–4. Heidbach, O., Tingay, M.R.P.,
Barth, A., Reinecker, J., Kurfeß,
D. and Müller, B. [2010] Global
crustal stress pattern based on the
World Stress Map database release
2008. Tectonophysics,
482 (1-4), 3–15.
[10] Henk, A. [2009] Perspectives
of Geomechanical Reservoir
Models–Why Stress is Important.
Oil Gas: European Magazine,
35(1), 1–5.
[11] Hergert, T., Heidbach,
O., Reiter, K., Giger, S.B. and
Marschall, P. [2015] Stress field
sensitivity analysis in a sedimentary sequence of the Alpine foreland,
northern Switzerland. Solid Earth,
6(2), 533–552.
[12] Peska, P. and Zoback, M.D.
[1995] Compressive and tensile
failure of inclined well bores and
determination of in situ stress
and rock strength. Journal of
Geophysical Research, 100(B7),
12791–12811.
[13] Reiter, K. and Heidbach,
O. [2014] 3-D geomechanical-numerical model of the
contemporary crustal stress state
in the Alberta Basin (Canada).
Solid Earth, 5(2), 1123–1149.
Schmitt, D.R., Currie, C.A. and
Zhang, L. [2012] Crustal stress
determination from boreholes
and rock cores: Fundamental
principles. Tectonophysics, 580,
1–26.
[14] Zang, A. and Stephansson,
O. [2010] Stress Field of
the Earth’s Crust. Springer
Netherlands, Dordrecht.
Zang, A., Stephansson, O.,
Heidbach, O. and Janouschkowetz, S. [2012]World Stress
Map Database as a Resource
for Rock Mechanics and Rock
Engineering. Geotechnical and
Geological Engineering, 30(3),
625–646.
[15] Zoback, M.L. [1992]
First- and second-order patterns
of stress in the lithosphere:
The World Stress Map
Project. Journal of Geophysical
Research, 97(B8), 11703–11728.
Research Projects
• PROTECT - PRediction Of deformation To Ensure Carbon Traps (BMBF)
• Building and populating geomechanical reservoir models – a case study from the Upper Rhine Graben (GDF SUEZ)
• APIS – Assessment of production induced stress changes (DEA)
• LIDAR-based analysis of fracture networks (PhD thesis)
• Fracture prediction in fold-and-thrust belts – a worked example from the southern Pyrenees (PhD thesis)
• Numerical-geomechanical models of potential sites for radioactive waste disposal in Switzerland (Nagra)
Publications
[1]
Henk, A. & Nemcok, M. (2015): Lower-crust ductility patterns associated with transform margins. In: Nemcok, M., Rybar, S., Sinha, S.T., Hermeston, S. A. & Ledvényiová , L. (eds.): Transform Margins: Development, Controls and Petroleum Systems. Geological Society, London, Special Publications, 431, http://doi.org/10.1144/SP431.9
[2]
Hergert, T., Heidbach, O., Reiter, K., Giger, S. B., and Marschall, P.,
2015. Stress field sensitivity analysis in a sedimentary sequence of the Alpine foreland, northern Switzerland, Solid Earth, 6, 2, 533-552, doi: 10.5194/se-6-533-2015.
[3]
Krawczyk, C.M., Henk, A., Tanner, D.C., Trappe, H., Ziesch, J., Beilecke, T., Aruffo, C.M., Weber, B., Lippmann, A., Görke, U.-J., Bilke, L. & Kolditz, O. (2015): Seismic and sub-seismic deformation prediction in the context of geological carbon trapping and storage. Advanced Technologies in Earth Sciences, Springer,
ISBN 978-3-319-13929-6; pp. 97-113.
[4]
Laux, D., Henk, A., (2015).Terrestrial laser scanning and fracture network characterisation – perspectives for a (semi-) automatic analysis
of point cloud data from outcrops. Z. Dt. Ges. Geowiss.
(German J. Geosci.), 166 (1), p. 99-118.
[5] Nemcok, M., Henk, A. & Molcan, M. (2015): The role of pre-break-up heat flow on the thermal history of a transform margin. In: Nemcok, M., Rybar, S., Sinha, S.T., Hermeston, S. A. & Ledvényiová , L. (eds.): Transform Margins: Development, Controls and Petroleum Systems. Geological Society, London, Special Publications, 431,
http://doi.org/10.1144/SP431.4
[6] Reiter, K., Heidbach, O., Reinecker, J., Müller, B., und Röckel, T. 2015. Spannungskarte Deutschland 2015, Erdöl Erdgas Kohle 131, 11, 437–42.
[7] Haug, C., Hergert, T., Henk, A., & Nüchter, J.A., 2015. Numerical Simulation of Production-induced Fault Loading – Modeling Concept and Poroelastic Material Definition, 2nd EAGE Workshop on Geo
mechanics and Energy – The Ground as Energy Source and Storage, 13-15 October 2015, Celle, Germany (poster presentation).
Publications
[8] Henk, A., Fischer, K. & Aruffo, C.A. (2015): Geomechanical reservoir modeling for tectonic stress prediction – workflow and case studies. – 13th International Symposium on Rock Mechanics (ISRM Congress 2015), Montreal, 10. – 13.05.2015.
[9]
Heidbach, O., Hergert, T., Reiter, K., Giger, S.B., Marschall, P., 2015. 3D stress field sensitivity analysis on the scale of geological siting regions in Northern Switzerland with focus on Opalinus Clay, 6th International Clay Conference – Clays in natural and engineered barriers for radioactive waste confinement, March 23-26 2015, Brussels, Belgium.
[10] Hergert, T., Heidbach, O., Reiter, K. & Giger, S.B. , 2015. Stress Field
Sensitivity Analysis at a Reservoir Scale (Northern Switzerland) Using Numerical Geomechanical Modelling, 2nd EAGE Workshop
on Geomechanics and Energy – The Ground as Energy Source and Storage, 13-15 October 2015, Celle, Germany.
[11] Krawczyk, C.M., Tanner, D.C., Ziesch, J., Beilecke, T., Henk, A. & PROTECT Research Group (2015): Deformation prediction in the Otway Basin – a seismo-mechanical workflow for sub-/seismic fault detection. – 3rd EAGE Sustainable Earth Sciences Conference, 13-15 October, 2015, Celle, Germany.
[12] Laux, D., Henk, A., 2015. Application of Terrestrial Laser Scanning in geosciences for (semi-) automatic fracture network characterization and lithology determination. Conference Proceedings, Riegl LIDAR 2015 International User Conference, 5.5. – 7.5.2015, HongKong, China
.
[13] Reiter, K., & Heidbach, O., 2015. Statistical Stress Model Calibration, 2nd EAGE Workshop on Geomechanics and Energy – The Ground as Energy Source and Storage, 13-15 October 2015, Celle, Germany.
[14] Weber, B. & Henk, A. 2015. Incorporation of Spatial Variations in Elastic Rock Properties in the Geomechanical Model of the CO2CRC Otway Project, 2nd EAGE Workshop on Geomechanics and Energy –
The Ground as Energy Source and Storage, 13-15 October 2015, Celle, Germany.
Environmental
Mineralogy
Staff Members
Head
Prof. Dr. Stephan Weinbruch
Research Associates
APL Prof. Dr. Martin Ebert
Dr. Nathalie Benker
Postdocs
Dr. Konrad Knadler, PD
Dr. Dirk Scheuvens
Technical Personnel
Thomas Dirsch
Secretaries
Astrid Kern
PhD Students
Dipl..-Met. Dörthe Ebert
Mark Scerri, M. Sc
Dipl.-Ing. Katharina Schütze
Master Students
Markus Hartmann
Bachelor Students
Andreas Taufertshöfer
Alexander Gruhn
Pia Krüger
Advancend practical course
Sabine Hempel
232 | Environmental Mineralogy
Environmental Mineralogy
Environmental mineralogy focuses its research
on the characterization of individual aerosol particles by electron beam techniques (high-resolution scanning electron microscopy, transmission
electron microscopy, environmental scanning
electron microscopy).
We study individual aerosol particles in order
to derive the physical and chemical properties
(e.g., complex refractive index, deliquescence behavior, ice nucleation) of the atmospheric aerosol.
These data are of great importance for modeling
the global radiation balance and its change due to
human activities.
We are also interested in studying particle
exposure in urban environments and at working
places. As aerosol particles may have adverse
effects on human health, the knowledge of the
particle size distribution and the chemical and
mineralogical composition of the particles is of
prime importance in order to derive the exact
mechanisms of the adverse health effects.
In addition, we also investigate particles as
carriers of pollutants into Nordic and Arctic
ecosystems.
Our research is carried out in cooperation with
the following national and international partners:
Max Planck Institute for Chemistry in Mainz,
Institute for Atmosphere and Environmental
Sciences (University of Frankfurt) Institute for
Atmospheric Physics (University of Mainz),
Institut für Steinkonservierung (IFS) in Mainz,
Institute for Meteorology and Climate Research
(Karlsruhe Institute of Technology), Institute
for Tropospheric Research in Leipzig, Institute
of Atmospheric Physics (German Aerospace
Center DLR) in Oberpfaffenhofen, Paul Scherrer
Institute (Laboratory of Atmospheric Chemistry)
in Villigen (Switzerland), National Institute of
Occupational Health (STAMI) in Oslo (Norway),
and the Norwegian University of Life Science
(NMBU) in Ås (Norway).
Environmental Mineralogy | 233
Electron Microscope Stereogrammetry for
Modelling Mineral Dust
K. Kandler1, H. Lindqvist2, O. Jokinen3, T. Nousiainen4
1 Angewandte Geowissenschaften, Technische Universität Darmstadt, Darmstadt, Germany
2 Department of Atmospheric Science, Colorado State University, CO, USA
3 Department of Real Estate, Planning and Geoinformatics, Aalto University, Espoo, Finland
4 Finnish Meteorological Institute, Helsinki, Finland
The real, three-dimensional shape of dust particles is derived from pairs of scanning-electron
microscope (SEM) images by means of automated stereogrammetry. The resulting shape is homogeneously discretized. Internal structure with
respect to composition is approximated from the
localized chemical signals (energy-dispersive
X-ray fluorescence spectroscopy, EDS) in SEM.
Discrete-dipole-approximation computations for
the single dust particles reveal that scattering by
such realistic irregular shapes and heterogeneously composed particles differs notably from
scattering by a sphere, a spheroid or a Gaussian
random sphere, which all are frequently used
shape models for dust particles.
Introduction
Mineral dust particles continue to be an important and intriguing subject of light-scattering
research because of the abundance of atmospheric dust and, also, the lack of trivial solutions.
One of the complications is the vast variety of
shapes of mineral dust particles: they can be, for
instance, roundish, faceted, platy, or aggregated.
In addition, they are often unique mixtures of
different minerals and may possess structures
both internally and externally at different scales
[1]. Accurate light-scattering computations
require accounting for the particles’ realistic
shapes and structures. In the past, dust optical
properties have been computed using simplistic
or descriptive shape models that may mimic
some morphological details of real dust particles,
but are not directly derived from actual particle
shapes; some models are used because they appear to produce similar scattering features when
considering a shape-size distribution of particles
[2, 3].
In this study, we choose a different approach: we
derive the shape of single Saharan dust particles
directly from scanning-electron microscope
(SEM) observations by means of stereophotogrammetry [4], i.e. without applying any generalizing shape model.
Dust samples and sem imaging
The Saharan mineral dust sample, from
which the modeled particles were selected, was
collected during the SAMUM campaign over
Morocco on 6th June 2006 by an airborne cascade
impactor particle collection system (for details,
see [5]). The sample was sputter-coated with gold
(thickness approximately 10 nm). Single particles
were imaged with a FEI ESEM Quanta 200 FEG
at different angles by tilting the specimen stage
at a working distance of 10 mm. Secondary
and backscatter electron images were collected.
Backscatter electron images proved to yield
more reliable results with the following shape
reconstruction. An acceleration voltage of 20 kV
was used with a nominal lateral resolution better
than 3 nm. In addition to the imagery, localized
characteristic X-ray fluorescence was measured
with an energy-dispersive detector, yielding
atomic-composition maps of the particles.
Particle shape retrieval
The surface topography of the dust particle is
determined from a stereo pair of SEM images.
The process starts with finding a sparse set of
corresponding points between the images using
SIFT keypoints [6]. The sparse correspondences
are used to refine the image orientations and to
estimate a sparse set of 3-D object points in a
bundle adjustment assuming a parallel projection
geometry, which is well satisfied with images
taken with magnification factors above 1000
Fig. 1. Stereogrammetrically retrieved 3D model for an aggregated dust particle and its according simulated light scattering
(black line, labeled ‘dust’). Scattering by simplified model shapes is shown with gray, dashed lines. Scattering results are
integrated over a lognormal size distribution of identically-shaped scaled particles with a cross-section-weighted average particle
radius of 0.82 µm.
The correspondences are then densified using
affine least squares image matching techniques.
In this dense image matching phase, the correspondences are gradually expanded from the
sparse keypoint matches, which were compatible
in the bundle adjustment, to their neighborhoods
until the whole image has been filled up with observations at every pixel. Disparity and epipolar
constraints are applied to obtain smooth surfaces
and to avoid false matches. 3-D points are
reconstructed from the densely matched points
by forward intersection. The final point set is
triangulated into a dense surface model.
No manual editing of the model is needed.
Since the stereogrammetry-retrieved shape covers only half of the particle geometry, the other
half is constructed by assuming mirror symmetry
with respect to a horizontal plane determined
visually. Either mirroring or scaled mirroring
is applied [4]. The volume between the surfaces
is discretized into small volume elements called
dipoles.
Particle COMPOSITION retrieval
Internal structure and composition of the
particles cannot yet be retrieved automatically.
Instead, mineralogical interpretation of the visible features and the chemical composition maps
is necessary. Distinct structures are identified
any the according volume elements are manually
assigned with a complex refractive index fitting
the deduced mineralogical composition. Where
no distinct features are visible – neither in the
image, nor in the composition maps – a complex
refractive index fitting the composition of the
main particle matrix is used.
Results and discussion
Light scattering by the dust particles is
computed using the discrete-dipole approximation code ADDA [7]. Refractive indices are
chosen as functions of the approximated mineral
composition and literature data availability. The
computations are performed for monochromatic,
visible light at a wavelength λ = 0.55 µm.
In Fig. 1, we show example results for an
aggregated, inhomogeneous dust particle.
Stereogrammetric shape retrieval has mostly succeeded in capturing the irregular 3D
shape of the particle, including roughness
features of the surface but excluding the cavities or shadowed regions. Scattered intensity
(phase function, S11) and the degree of linear
polarization (-S12/S11) are also shown. Scattering
results for the simplified models (sphere, spheroid, Gaussian random sphere [8]) differ notably
from those of the stereogrammetrically modeled
dust particle.
Retrieving the dust particle shapes directly
from stereo images appears to be a useful method for single-scattering modeling. The obtained
shapes closely resemble the real particles. The
shapes can be used, e.g., as reference particles for
testing currently used optical models for dust. In
case large discrepancies are observed, improving
the optical models should be considered.
Obviously, the real test of the methodology
is when it is tested against measured single-scattering properties of real dust particles. For this,
more particle shapes should be derived and the
single-scattering computations should be extended for larger size ranges and/or wavelengths.
Moreover, a full 3D retrieval is necessary to
overcome the mirroring steps. Finally, an auto-
References
[1] G. Y. Jeong, and T. Nousiainen,
“TEM analysis of the internal
structures and mineralogy of Asian
dust particles and the implications
for optical modeling,”Atmos. Chem.
Phys. 14, 7233-7254 (2014).
[5] D. Scheuvens, K. Kandler,
M. Küpper, K. Lieke, S. Zorn,
M. Ebert, L. Schütz, and S. Weinbruch, “Indiviual-particle analysis of
airborne dust samples collected over
Morocco in 2006 during SAMUM
1,” Tellus 63B, 512-530 (2011).
[2] T. Nousiainen, “Optical modeling
of mineral dust particles: A review,”
J. Quant. Spectrosc. Ra. 110,
1261-1279 (2009).
[6] D. Lowe, “Distinctive Image
Features from Scale-Invariant
Keypoints,” Int. J. Comput.
Vision 60, 91-110 (2004).
[3] T. Nousiainen, and K. Kandler,
“Light scattering by atmospheric
mineral dust particles,” in Light
Scattering Reviews 9. Light
Scattering and Radiative Transfer,
A. A. Kokhanovsky, ed. (Springer
Praxis, Berlin, 2015), pp. 3-52.
[7] M. A. Yurkin, and A. G. Hoekstra,
“The discrete-dipole-approximation
code ADDA: Capabilities and known
limitations,” J. Quant. Spectrosc.
Radiat. Transfer 112, 2234-2247
(2011).
[4 ] H. Lindqvist, O. Jokinen,
K. Kandler, D. Scheuvens, and
T. Nousiainen, “Single scattering by
realistic, inhomogeneous mineral
dust particles with stereogrammetric
shapes,” Atmos. Chem. Phys. 14,
143-157 (2014).
[8] K. Muinonen, E. Zubko,
J. Tyynelä, Y. G. Shkuratov, and
G. Videen, “Light scattering by
Gaussian random particles with
discrete-dipole approximation,”
J. Quant. Spectrosc. Ra. 106,
360-377 (2007).
Research Projects
•
Environmental scanning electron microscopical studies of ice-forming
nuclei (DFG Forschergruppe INUIT).
•
Electron microscopy of long-range transported mineral dust.
•
Source apportionment of rural and urban aerosols.
•
Sources of soot at work places (National Institute of Occupational
Health, Oslo, Norway).
•
Influence of traffic on the surface of monuments.
•
Particle and organic pollutant emissions of coal burning in the Arctics.
Publications
[1]
Niedermeier N., Held A., Müller T., Heinhold B., Schepanski K.,
Tegen I., Kandler K., Ebert M., Weinbruch S., Read K., Lee J.,
Fomba K.W., Müller K., Herrmann H., and Wiedensohler A. (2014): Mass deposition fluxes of Saharan mineral dust to the tropical
northeast Atlantic Ocean: An intercomparison of methods,
Atmospheric Chemistry and Physics. 14, 2245-2266.
[2]
Hiranuma N., Augustin-Bauditz S., Bingemer H., Budke C., Curtius J., Danielczok A., Diehl K., Dreischmeier K., Ebert M., Frank F.,
Hoffmann N., Kandler K., Kiselev A., Koop T., Leisner T.,
Möhler O., Nillius B., Peckhaus A., Rose D., Weinbruch S., Wex H., Boose Y., DeMott P.J., Hader J.D., Hill T.C.J., Kanji Z.A.,
Kulkarni G., Levin E.J.T., McCluskey C.S., Murakami M.,Murray B.J., Niedermeier D., Petters M.D., O’Sullivan D., Saito A., Schill G.P.,
Tajiri T., Tolbert M.A., Welti A., Whale T.F., Wright T.P., and
Yamashita K. (2015): A comprehensive laboratory study on the
immersion freezing behavior of illite NX particles: a comparison of 17 ice nucleation measurement techniques., Atmospheric Chemistry and Physics, 15, 2489-2518.
[3] Arnoldussen Y.J., Skogstad A., Skaug V., Kasem M., Haugen A.,
Benker N., Weinbruch S., Apte R.N., and Zienolddiny S. (2015):
Involvement of IL-1 genes in the cellular responses to carbon nanotube exposure., Cytokine, 73, 128-137.
[4] Worringen A., Kandler K.,Benker N., Dirsch T., Mertes S., Schenk L., Kästner U., Frank F., Nillius B., Bundke U., Rose D., Curtius J.,
Kupiszewski P., Weingartner E., Vochezer P., Schneider J.,
Schmidt S., Weinbruch S, and Ebert M. (2015): Single-particle
characterization of ice-nucleating particles and ice particle residuals sampled by three different techniques., Atmospheric Chemistry and Physics, 15, 4161-4178.
[5] Küpper M., Weinbruch S., Skaug V., Skogstad A., Einarsdóttir Thornér E., Benker N., Ebert M., Chaschin V, and Thomassen Y. (2015): Electron microscopy of particles in the lungs of nickel refinery workers., Analytical and Bioanalytical Chemistry, 407, 6435-6445.
[6] Boltze, M., Jiang, W., Groer, St. & Scheuvens, D. (2015):
Stellungnahme: Wirksamkeit von Umweltzonen … und es gibt sie
doch (NO2).- Straßenverkehrstechnik, Heft 3: 186.
[7] Bundschuh, P., Auras, M., Kirchner, D., Scheuvens, D. & Seelos,
K. (2015): Expositionsprogramm zur Wirkung verkehrsbedingter Immissionen auf Natursteinoberflächen.- IFS-Bericht 49: 53–77.
Publications
[8] Scheuvens, D., Dirsch, T., Moissl, A., Küpper, M. & Weinbruch, S. (2015): Partikuläre Schadstoffe an Baudenkmälern.- IFS-Bericht 49: 55–77.
[9] Scheuvens, D., Kandler, K. & Weinbruch, S. (2015): Feinstaub
Filterung durch Vegetation – Untersuchungen an der Luftmessstation Mainz-Zitadelle.- IFS-Bericht 49: 145–155.
[10]
S. Schmidt, J. Schneider, T. Klimach, S. Mertes, L. P. Schenk,
J. Curtius, P. Kupiszewski, E. Hammer, P. Vochezer, G. Lloyd,
M. Ebert, K. Kandler, S. Weinbruch, S. Borrmann (2015): In-situ
single submicron particle composition analysis of ice residuals from mountain-top mixed-phase clouds in Central Europe. Atmos. Chem. Phys. Discuss. 15, 4677-4724. doi: 10.5194/acpd-15-4677-2015
[11] T. Nousiainen, K. Kandler (2015): Light scattering by atmospheric mineral dust particles. In: A. A. Kokhanovsky (ed.), Light Scattering Reviews 9, 3-52, Springer, Berlin. doi: 10.1007/978-3-642-37985-7_1
[12] B. Berlinger, M. D. Bugge, B. Ulvestad, H. Kjuus, K. Kandler,
D. G. Ellingsen (2015): Particle size distribution of workplace aerosols in manganese alloy smelters applying personal sampling strategy. Environ. Sci.: Processes Impacts 17, 2066-2073. doi: 10.1039/
c5em00396b
[13]
T. B. Kristensen, T. Müller, K. Kandler, N. Benker, M. Hartmann,
J. M. Prospero, A. Wiedensohler, F. Stratmann (2015): Properties of cloud condensation nuclei (CCN) in the trade wind marine boundary layer of the Eastern Caribbean Sea. Atmos. Chem. Phys. Discuss. 15, 30757-30791. doi: 10.5194/acpd-15-30757-2015
[14]
Schenk L. P., S Mertes, U Kästner, F Frank, B Nillius, U Bundke,
D Rose, S Schmidt, J Schneider, A Worringen, K Kandler,
N Bukowiecki, M Ebert, J Curtius, F Stratmann, Characterization and first results of an ice nucleating particle measurement system based on counterflow virtual impactor technique, Atmospheric Measurement Techniques Discussions, 10, 10585-10617, 2014.
[15] Schrod A., D. Danielczok, D. Weber, M. Ebert, E. S. Thomson, and H. G. Bingemer, Re-evaluating the Frankfurt isothermal static
diffusion chamber for ice nucleation, amt-2015-348, Special Issue: Results from the ice nucleation research unit (INUIT) (ACP/AMT Inter-Journal), 2015.
Geomaterial
Science
Staff Members
Head
Prof. Dr. Hans-Joachim
Kleebe
Associated Professors
Prof. Dr. Ute Kolb, Mainz,
Electron Crystallography
Prof. Dr. Peter van Aken,
MPI,
Stuttgart, TEM,HRTEM,EELS
Research Asscoiates
Dr. Stefan Lauterbach
Dr. Leopoldo Molina-Luna
Postdoc Students
Dr. Ana Ljubomira Schmitt
Dr. Ingo Sethmann
Dr. Michael Dürrschnabel
Dr. Laura Silvestroni
Secretaries
Angelika Willführ
PhD Students
Stefania Hapis
240 | Geomaterial Science
Cigdem Özsoy Keskinbora
Marc Rubat du Merac
Mathis M. Müller
Katharina Nonnenmacher
Pouya Moghimian
Ekin Simsek
Dmitry Tyutyunnikov
Carolin Wittich
Marina Zakhozheva
Dan Zhou
Lars Riekehr
Young-Mi Kim
Tobias Hill
Maximilian Trapp
Sabrina Seltenheim
Steffen Kausch
Cornelia Luft
Tobias Necke
Alexander Zintler
Kerstin Stricker
Technical Personnal
Bernd Dreieicher
Geomaterial Science
The research group of Prof. Hans-Joachim
Kleebe is active in the field of Geomaterial Science (formerly Applied Mineralogy) and explores
the formation/processing conditions, composition, microstructure and properties of minerals
in addition to materials that are important for
industrial applications. The study of the latter
material group focuses on both basic science and
potential applications. Research activities include
a comprehensive characterization of natural and
synthetic materials, their performance for example at elevated temperature, local chemical variations as well as tailored synthesis experiments for
high-tech materials.
The experimental studies comprise the crystal
chemistry of minerals and synthetic materials, in
particular, their crystal structure, phase assemblage as well as their microstructure evolution.
The microstructure variation (e.g., during exposure to high temperature) has an essential effect
on the resulting material properties, which is true
for synthetic materials as well as for natural minerals. Therefore, the main focus of most research
projects is to understand the correlation between
microstructure evolution and resulting material
properties.
An important aspect of the Fachgebiet Geomaterial Science is the application of scanning
and transmission electron microscopy (SEM/
TEM/STEM) techniques for the detailed micro/
nanostructural characterization of solids. STEM
for example in conjunction with spectroscopic
analytical tools such as energy-dispersive X-ray
spectroscopy (EDS) and electron energy-loss
spectroscopy (EELS) are employed for detailed
microstructure and defect characterization down
to the atomic scale. High-resolution imaging of
local defects in addition to chemical analysis
with high lateral resolution is similarly applied to
natural minerals as well as to high-performance
materials.
Recent research projects involve topics such
the domain structure in ferroelectrics, defect
structures in Bixbyite single crystals (and their
corresponding exaggerated grain growth),
morphology of In2O3 nanocrystals, transparent
ceramics such as Mg-Al spinel, interface structures in polycrystals, ultra-high temperature
materials and the study of biomineralisation and
biomaterials.
Geomaterial Science | 241
Design of a Novel Buffer Layer to Prevent SiC Fiber-MoSi2
Chemical Rreactions in Functionally Graded UHTCs
Laura Silvestroni and Hans-Joachim Kleebe
ZrB2 is an ultra-high temperature ceramic
(UHTC) possessing a melting point exceeding
3000°C and interesting physical properties. As
such, ZrB2 ceramics are considered potential
candidates for space and hypersonic components.
The main drawbacks that restrict the employment of ZrB2 ceramics for a wider spectrum of
applications are mainly related to its low damage
tolerance, poor oxidation resistance and relatively
high density. The introduction of discontinuous
SiC fibers can both increase the toughness of
ZrB2 above 6 MPa·m½ and notably decrease
the total weight (see also Figure 1). The class of
materials designated as functional graded material (FGM) was first introduced by Japan scientists
to decrease the thermal stresses in propulsion
and airframe structural systems of astronautical
flight vehicles.
This class of engineered materials are characterized by spatially varied microstructures
created by a non-uniform distribution of the
reinforcement phase with different properties,
sizes and shapes, as well as by interchanging the
role of reinforcement and matrix materials in a
continuous manner. FGMs exhibit a continuous
variation of material properties from one surface
to the other and thus eliminate local stress concentration generally encountered in laminated
multicomponent structures. Moreover, the addition of secondary phases such as MoSi2 can further
improve the high-temperature strength and, most
importantly, the oxidation performance of the
boride matrix.
The ultimate scope of the project is to obtain
a functionally graded (FG) composite made up
of a ZrB2-MoSi2 outer scale to provide oxidation
and ablation resistance and a progressively SiC
fiber-rich body to guarantee failure tolerance
and lighten the whole structure. The major
obstacle to overcome is the detrimental chemi-
cal reaction between Mo-compounds and SiC
fibers occurring during sintering, as depicted in
Figure 2, which leads to the microstructural
degradation of the fibers and, hence, to the loss
of their toughening function. In this respect,
the project is the project is focused on the
development of a novel ZrB2-based buffer scale
able to prevent chemical ractions between SiC
fibers and Mo-compounds and to the study of
the interdiffusion state across the interface, both
during sintering stage and upon oxidation. It is
envisioned to utilize mixtures of ZrB2 and Si3N4,
SiCN and HfSiN for the diffusion barrier. The
understanding of the chemical reactions across
the various layers will be fundamental for the
design of a novel UHTC.
The work plan foresees the development of
various baseline ceramic joints with different
composition of the buffer layer and a thorough
microstructural characterization of the as-sintered and oxidized specimens by transmission
electron microscopy. These analyses, coupled to
thermodynamic predictions, will be essential in
revealing local diffusion processes and will lead
to the definition of an optimized buffer layer
composition for the design of a functional UHTC.
Thermo-mechanical characterization and
arc-jet tests of the optimized composite will be
also carried out to assess the performance of
the novel material. The success of the project
rises from the synergistic effort of two institutes
possessing complementary experise: the Insitute
of Science and Technology for Ceramics, Faenza,
Italy (CNR-ISTEC), with extended know-how
on processing, microstructure and properties of
UHTCs and the Institute of Applied GeoSciences,
Darmstadt, Germany (TU-IAG), with advanced
microstructural characterization skills and long
lasting experience on interface characterization
via various TEM techniques.
Figure 1: SEM images of of a ZrB2-ZrS2-SiC fiber composite showing a) a panoramic overview and
b) a SiC fiber section illustrating the multi layered morphology after sintering. c)-f) TEM images
evidencing the fiber features with magnified views of d) the fiber core, e) the composition of the fiber
core (β-SiC, turbostratic carbon and amorphous SiCO) and f) the fiber shell.
Figure 2: Effect of the increasing sintering temperature on the morphology evolution of Hi-Nicalon SiC
fibers in a ZrB2 composite containing MoSi2 as sintering additive.
Entwicklung neuartiger, B6O-basierter Verschleißwerkstoffe
Hans-Joachim Kleebe und Matthias Herrmann
Die aus der Wechselwirkung der Al2O3-Y2O3Additive mit einer oberflächigen B2O3-Schicht
der B6O-Partikel resultierende Al2O3-Y2O3B2O3 Flüssigphase bedingt unabhängig von der
Sintertechnologie die Bildung einer weitestgehend homogen in den B6O-Kornzwickeln
verteilten Glasphase, welche mit abnehmender
Abkühlgeschwindigkeit bei der SPS > KVP
> HIP Verdichtung bzw. abnehmendem
B2O3/(Al2O3-Y2O3) Verhältnis zunehmend die
Tendenz zeigt in Form von Al- und Y-Boraten zu
kristallisieren. Abbildung 1 zeigt eine Übersicht,
der mittels Transmissionselektronenmikroskopie
(TEM) im Detail untersuchten Proben in der Gegenüberstellung. Auffällig ist die Verfeinerung
des Gefüges nach KVP Verdichtung, entsprechend der Gefügeübersicht in Abbildung 1. Bei
den hohen Additivgehalten ist die Sekundärphase
(und deren Verteilung) deutlich zu erkennen (mit
Pfeilen markiert).
Während die Proben, die mit geringen
Anteilen an Additiven verdichtet wurden,
noch einen gewissen Anteil an Restporosität
aufweisen, resultierte die Zugabe von 6 Vol.%
Sinterhilfsmittels in einer nahezu vollständigen
Verdichtung. Eine Besonderheit stellt die zusätzliche Bildung von bis zu mehreren 10 µm großen,
kompakten Al-Y-Boriden in den SPS-gesinterten
Werkstoffen dar, deren Verteilung und Größe
maßgeblich durch die Additivzusammensetzung
aber auch die Sintertemperatur und Atmosphäre
kontrolliert ist.
Ferner konnte eine lokale Phasenseparation
von Al(Mg)- und Y-Boraten in Kornzwickeln
nachgewiesen werden. Dagegen konnte nachgewiesen werden, dass die Bildung der Boride
nicht in hochdruckhergestellten Werkstoffen
stattfindet und in heißisostatisch gepressten
Werkstoffen auf Zusammensetzungen mit sehr
hoher Konzentrationen an Y2O3 beschränkt ist.
Im Rahmen des Projektes wurden sowohl die
Ursachen der Boridbildung bestimmt als auch
Strategien Ihrer Vermeidung entwickelt. Für
die additivfreie Sinterung wurden annähernd
vollständig verdichtete B6O-Werkstoffe nur unter
Hochdruckbedingungen bzw. in eingeschränkte
Maße auch über die SPS-Verdichtung erreicht
(allerdings mit schlechter Reproduzierbarkeit
infolge der Zersetzung des Materials bei hohen
Sintertemperaturen). Dagegen resultierte das heißisostatische Pressen unabhängig von den Sinterbedingungen (1800–1850 °C, 1–3 h) in Werkstoffe mit einer Restporosität von mindestens 7 %.
Neben der nicht-reaktiven Verdichtung wurde
ferner untersucht, inwiefern sich B6O-Werkstoffe
kostengünstig und ohne die Notwendigkeit der
vorherigen Synthese eines B6O-Pulvers auf Basis
reaktiver B/B2O3-Mischung herstellen lassen.
Dabei konnte gezeigt werden, dass die Verwendung von oxidischen Sinteradditiven auch
bei der reaktiven Werkstoffsynthese eine vollständige Verdichtung bei moderaten Sintertemperaturen von 1850 °C mittels SPS ermöglicht.
Bei geringerem Additivzusatz von 3 Vol.% zeigte
sich, dass bei der Verdichtung über HIP eine
geringe Restporosität auftritt, während die KVP
Verdichtung zu porenfreien Proben führte. Damit
eröffnen die Untersuchungen eine alternative
Herstellungsroutine zur bereits zuvor berichteten
(annähernd vollständigen) Verdichtung reaktiver
B/B2O3-Mischungen unter Einsatz von Hochdrucktechnologien bzw. dem Heißpressen bei
Temperaturen bis zu 2200 °C.
Zwar erfordert die reaktive Sinterung ähnliche Sinterparameter wie die nicht-reaktive
Verdichtung, jedoch zeigt sich neben dem Vorteil
einer höheren Kosteneffizienz, dass sich bei geeigneter Stöchiometrie der B/B2O3-Mischungen
Gefüge herstellen lassen, die gänzlich frei von
Boriden sind (Abbildung 2) und die Werkstoffe
so infolge einer gesteigerten Homogenität eine
höhere Festigkeit erwarten lassen [1].
Die Untersuchungen zum Kornwachstum in
Abhängigkeit von der Additivzusammensetzung/
Sintertemperatur mittels SPS bestätigen die Ergebnisse der Verdichtung mittels HIP, bei denen
Abbildung 1: TEM Hellfeld-Aufnahmen der untersuchten B6O Materialien in Abhängigkeit vom Herstellungsprozess und dem Additivgehalt. Deutlich ist eine Verfeinerung des Gefüges bei der KVP Verdichtung zu
erkennen.
Abbildung 2: TEM Aufnahmen von reaktiv bzw. nicht-reaktiv hergestellten SPS Proben mit 6 Vol.% Additivzusatz Al2O3/(Al2O3+Y2O3)=0.63. In beiden Fällen konnten bei entsprechender Additivzusammensetzung und
Volumenanteil die Boridbildung unterdrückt werden. Die mit Pfeilen markieren Bereiche zeigen Kornzwickel,
die mit der ausschließlich amorph (SAD=selected area diffraction; Inset) vorliegenden Sekundärphase gefüllt
sind.
für alle untersuchten Zusammensetzungen (auch
mit SiO2-Komponente) selbst bei 3 h Haltezeit
und Temperaturen bis 1850 °C keine signifikante
Vergröberung der Gefüge beobachtet wurde.
Allerdings wurde vereinzelt im unmittelbaren
Kontaktbereich der Probe mit der SiO2-haltigen
Glaskapsel eine Reaktionszone mit abnormalem
Wachstum von B6O beobachtet.
Der Einsatz höherer Sintertemperaturen
bei der heißisostatischen Verdichtung war auf
Grund der zu geringen Kapselstabilität nicht
möglich. Aus diesem Grund musste für die bei
Antragstellung ursprünglich für heißisostatisch
gepresste Werkstoffe angedachte Untersuchung
des Einflusses der Korngröße auf die mechanischen Eigenschaften auf SPS-Werkstoffe zurückgegriffen werden.
Eine der SPS Proben mit ausgeprägtem
Großkornwachstum wurde mittels TEM untersucht. Es zeigte sich, dass ähnlich wie bei
B4C die B6O Körner einen hohen Anteil an
Kristalldefekten (Stapelfehler) aufweisen. Im
Vergleich zu den großen Körnern, beobachtet
man in den Kornzwickeln ein relativ feinkörnige
Matrix, in der die Sekundärphase entsprechend
angereichert ist (DF Abbildungen). Interessanter
Weise konnte auch in dieser Probe eine teilweise
Entmischung innerhalb der glasbildenden Phase
nachgewiesen werden (Abbildungen 3 und 4). In
einigen Zwickeln befindet sich eine vornehmlich
Si,Al enthaltende Glasphase, während in anderen
Zwickeln ein hoher Y-Gehalt vorlag.
Die Analyse der Gitterkonstanten des B6O
macht deutlich, dass sich die B6O-Struktur im
Verlauf der Sinterung aufweitet, was wiederum
auf den zusätzlichen Einbau geringer Mengen
an Fremdatomen auf Leerstellen des B6O-Gitters hinweist: i) Sauerstoff aus der Interaktion
mit einer oxidischen Sekundärphase sowie ii)
Kohlenstoff aus der Sinteratmosphäre im Falle
der Verdichtung mittels SPS. Das Ausmaß der
Leerstellensubstitution im B6O ist vom Grad der
Umlösung von B6O bzw. dem Angebot an Kohlenstoff während der Sinterung abhängig.
Aufgrund einer vergleichsweise hohen Temperatur und der besonderen Sinteratmosphäre ist
daher die Gitteraufweitung bei der Verdichtung
mittels SPS wesentlich ausgeprägter als beim heißisostatischen Pressen bzw. der Hochdruckverdichtung. Es gibt auch signifikante Unterschiede
zwischen Werkstoffen mit und ohne oxidischen
Additiven, was ferner mit der unterschiedlichen
C-Konzentration korreliert.
Insbesondere die Ergebnisse zum Einbau
von Kohlenstoff in die B6O-Struktur erhärten
damit die Annahme einer möglichen, lückenlosen Mischkristallreihe zwischen B6O und B4C
Leider konnte der Einbau des Kohlenstoffs in das
B6O Gitter mittels TEM/STEM nicht eindeutig
nachgewiesen werden, da zum einen eine wenige
nm dicke C-Schicht aufgebracht wurde, um
Aufladungen an der Probenoberfläche durch den
Primärstrahl zu minimieren und ferner viele der
B6O Proben zur lokalen Kontamination neigen.
M. Herrmann, I. Sigalas, M. Thiele, M. M. Müller, H.-J. Kleebe, A. Michaelis; Boron suboxide
ultrahard materials, Int. J. Ref. Met. Hard Mater.,
39 53-60 (2013).
Abbildung 3: STEM BF/DF Abbildungen der Si-haltigen B6O Probe mit Riesenkornwachstum (SPS, 40 Mol.% Si,
1950°C). Deutlich sind in den großen Körnern ein hoher Anteil an Stapelfehlern erkennbar.
Abbildung 4: STEM BF Abbildung (links) der Si-haltigen B6O Probe mit Riesenkornwachstum (SPS, 40 Mol.%
Si, 1950°C) und rechts die entsprechenden EDX-Spektren zweier Kornzwickel, die auf eine Entmischung
innerhalb der Glasphase hinweist (Spektrum 82: Si,Al,Y / Spektrum 83: Al,Si).
Research Projects
• Polymer-derived SiCO/HfO2 and SiCN/HfO2 Ceramic Nanocomposites for Ultrahigh-temperature Applications, SPP-1181 (DFG 2009-2015).
• Structural Investigations of Fatigue in Ferroelectrics, detailed TEM
Characterization of Lead-Free Ferroelectrics (DFG 2007-2015).
• Investigation of the Atomic and Electronic Structure of Perovskite Multilayer-Heterojunctions (in collaboration with the MPI Stuttgart,
Prof. P. van Aken).
• Phase Developments and Phase Transformations of Crystaline Non Equilibrium Phases (in collaboration with the MPI Stuttgart,
Prof. P. van Aken).
• Microstructure Characterization and Correlation with Corresponding Properties, in particular Hardness und Fracture Toughness, of Boron Suboxide Materials (DFG 2012-2015).
• Microstructure Characterization of Polycrystalline Transparent
Mg-Al-Spinel Samples; The Effect of LiF Doping (Industry 2012-2015).
• Microstructucure and Defect Control of Thin Film Solar Cells
(Helmholtz Virtual Institute 2012-2018).
•
Hydrothermale Umwandlung von porösen Ca-Carbonat Biomineralen in
antibiotische und antiosteoporotische Ca-Phosphat-Knochenimplantat-Materialien mit eingelagerten Mg-, Sr-, Zn- und Ag-Ionen (DFG 2014–2016).
Publications
[1] L. Dimesso, C. Spanheimer, M.M. Müller, H.-J. Kleebe, and
W. Jaegermann, “Properties of Ca-containing LiCoPO4-graphitic carbon foam composites,” Ionics 21 [8] 2101-07 (2015).
[2] M.R. du Merac, I.E. Reimanis, and H.-J. Kleebe, “Electrochemical Impedance Spectroscopy of Transparent Polycrystalline Magnesium Aluminate (MgAl2O4) Spinel,” J. Am. Ceram. Soc., 98 [7] 2130-38 (2015).
[3] M. Zakhozheva, L.A. Schmitt, M. Acosta, H. Guo, W. Jo, R. Schier-
holz, H.-J. Kleebe, and X. Tan, “Wide Compositional Range In Situ Electric Field Investigations on Lead-Free
Ba(Zr 0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 Piezoceramic,” Phys. Rev. Appl., 3 [6] (2015).
[4] M. Hinterstein, L.A. Schmitt, M. Hoelzel, W. Jo, J. Rodel, H.-J. Kleebe, and M. Hoffman, “Cyclic electric field response of morphotropic Bi1/2Na1/2TiO3-BaTiO3 piezoceramics,” Appl. Phys. Lett., 106 [22] (2015).
[5] M. Jocher, M. Gattermayer, H.-J. Kleebe, S. Kleemann, and
M. Biesalski, “Enhancing the wet strength of lignocellulosic fibrous networks using photo-crosslinkable polymers,” Cellulose 22 [1] 581-91 (2015).
[6] L.A. Schmitt, H. Kungl, M. Hinterstein, L. Riekehr, H.-J. Kleebe, M.J. Hoffmann, R.A. Eichel, and H. Fuess, “The Impact of Heat Treatment on the Domain Configuration and Strain Behavior in Pb[Zr,Ti]O3 Ferroelectrics,” J. Am. Ceram. Soc., 98 [1] 269-77 (2015).
[7] M. Acosta, L.A. Schmitt, L. Molina-Luna, M.C. Scherrer, M. Brilz, K.G. Webber, M. Deluca, H.-J. Kleebe, J. Rödel, W. Donner. “Core-
shell lead-free piezoelectric ceramics: current status and advanced characterization of Bi1/2Na1/2TiO3-SrTiO3 system.” J. Am. Ceram. Soc., 98 [11], 3405-3422 (2015).
[8] S. Bhat, L. Wiehl, L. Molina-Luna, E. Mugnaioli, S. Lauterbach, S. Sicolo, P. Kroll, M. Duerrschnabel, N. Nishiyama, U. Kolb, K. Albe, H.-J. Kleebe, and R. Riedel, “High-Pressure Synthesis of Novel Boron Oxynitride B6N4O3 with Sphalerite Type Structure,” Chem. Mater.,
27 [17] 5907-14 (2015).
[9] F. Muench, D.M. De Carolis, E.M. Felix, J. Brotz, U. Kunz,
H.-J. Kleebe, S. Ayata, C. Trautmann, and W. Ensinger, “SelfSupporting Metal Nanotube Networks Obtained by Highly Conformal Electroless Plating,” Chem. Plus Chem., 80 [9] 1448-56 (2015).
Publications
[10] J. Koruza, V. Rojas, L. Molina-Luna, U. Kunz, M. Duerrschnabel,
H.-J. Kleebe, M. Acosta, “Formation of the core–shell microstructure in lead-free Bi1/2Na1/2TiO3-SrTiO3 piezoceramics and its influence on the electromechanical properties,” J. Eur. Ceram. Soc., 36 1009-1016 (2015).
[11] M. Erbe, J. Hänisch, R. Hühne, T. Freudenberg, A. Kirchner,
L. Molina-Luna, C. Damm, G. Van Tendeloo, S. Kaskel, L. Schultz,
B. Holzapfel, “BaHfO3 artificial pinning centres in TFA-MOD-derived YBCO and GdBCO thin films” Supercond. Sci. Technol., 28 114002 (2015).
[12] L. Molina-Luna, M. Duerrschnabel, S. Turner, M. Erbe, G. T
Martinez, S. Van Aert, B. Holzapfel, G. Van Tendeloo, “Atomic and electronic structures of BaHfO3-doped TFA-MOD-derived
YBa2Cu3O7-δ thin films,” Supercond. Sci. Technol. 28 115009 (2015).
[13] D. Thiry, L. Molina-Luna, E. Gautron, N. Stephant, A. Chauvin, K. Du, J. Ding, C.-H. Choi, P.-Y. Tessier, A.A. El Mel, “The Kirkendall Effect in Binary Alloys: Trapping Gold in Copper Oxide Nanoshells,”
Chem. Mater., 27 [18] 6374–6384 (2015).
[14] M. Vögler, M. Acosta, D.R.J. Brandt, L. Molina-Luna, K.G. Webber, “Temperature-dependent R-curve behavior of the lead-free ferro
electric 0.615Ba(Zr 0.2Ti0.8)O3-0.385(Ba0.7Ca0.3)TiO3 ceramic,
”Engineering Fracture Mechanics, 144 68-77 (2015).
[15] A. Hayrikyan, V. Rojas, L. Molina-Luna, M. Acosta, J. Koruza, K.G. Webber, “Enhancing Electromechanical Properties of Lead-Free Ferroelectrics with Bilayer Ceramic/Ceramic Composites,”
IEEE Transactions 62 [6] 997-1006 (2015).
[16] S. Saini, P. Mele, H. Honda, K. Matsumoto, K. Miyazaki,
L. Molina-Luna, P. E. Hopkins, “Influence of Postdeposition Cooling Atmosphere on Thermoelectric Properties of 2% Al-Doped ZnO
Thin Films Grown by Pulsed Laser Deposition,”
J. Electronic Materials 44 [6] 1547-1553 (2015).
[17] Bretos, T. Schneller, M. Falter, M. Bäcker, E. Hollmann,
R. Wördenweber, O. Eibl, G. Van Tendeloo, L. Molina-Luna,
“Solution-derived YBa2Cu3O7−δ (YBCO) superconducting films with BaZrO3 (BZO) nanodots based on reverse micelle stabilized
nano-particles,” J. Mater. Chem. C, 3 3971-3979 (2015).
Publications
[18]
A. El Mel, F. Boukli-Hacene, L. Molina-Luna, N. Bouts, A. Chauvin, D. Thiry, E. Gautron, N. Gautier, P.-Y. Tessier, “Unusual Dealloying Effect in Gold/Copper Alloy Thin Films: The Role of Defects and Column Boundaries in the Formation of Nanoporous Gold, “ ACS Applied Materials & Interfaces, 7 [4] 2310-21 (2015).
[19]
S. Saini, P. Mele, H. Honda, T. Suzuki, K. Matsumoto, K. Miyazaki, A. Ichinose, L. Molina Luna, R. Carlini, A. Tiwari, “Effect of self-
grown seed layer on thermoelectric properties of ZnO thin films,” Thin Solid Films (2015). doi:10.1016/j.tsf.2015.09.060
[20] P. Hołuj, C. Euler, B. Balke, U. Kolb, G. Fiedler, M.M. Müller,
T. Jaeger, P. Kratzer, and G. Jakob „Reduced thermal conductivity of TiNiSn/HfNiSn superlattices” Phys. Rev. B 92 [12] 125436 (2015)
[21] P. Hołuj, T. Jaeger, C. Euler, E.C. Angel, U. Kolb, M.M. Müller,
B. Balke, M.H. Aguirre, S. Populoh, A. Weidenkaff, and G. Jakob, “Half-Heusler superlattices as model systems for nanostructured thermoelectrics”, Phys. Status Solidi A, 1–7 201532445, (2015).
[22 P. Kumar, B. Willsch, M. Duerrschnabel, Z. Aabdin, R. Hoenig,
N. Peranio, F. Clement, D. Biro, O. Eibl, “Combined Microstructural and Electrical Characterization of Metallization Layers in Industrial Solar Cells,” Energy Procedia, 67 31-42 (2015).
[23] N. Peranio, Z. Aabdin, M. Duerrschnabel, O. Eibl, “Advanced
Structural Characterization of Bi2Te3 Nanomaterials,” in:
Thermoelectric Bi2Te3 Nanomateirals. Eds. O. Eibl, K. Nielsch,
N. Periano, F. Volklein, Wiley & Sons, 141-163 (2015).
Geothermal Science
and Technology
Staff Members
Head
Prof. Dr. Ingo Sass
Research Associates
Dr. Kristian Bär
Dr. Wolfram Rühaak
Technical Personnal
Gabriela Schubert
Rainer Seehaus
Secretaries
Simone Roß-Krichbaum
PhD Students
Achim Aretz , M.Sc.
Dipl.-Ing. Christoph Drefke
Claus-Dieter Heldmann, M.Sc.
Dipl.-Ing. Philipp Mielke
Dipl.-Ing. Johanna Rüther, M.Sc.
Daniel Schulte, M.Sc.
Markus Schedel, M.Sc.
Dipl.-Ing. Bastian Welsch
Swaroop Chauhan, M.Sc.
Yixi Gu, M.Sc.
Dipl.-Geol. Clemens Lehr
Liang Pei, M.Sc.
Dipl.-Ing. Rafael Schäffer
Dipl.-Ing. Johannes Stegner
Dipl.-Ing.Sebastian Weinert
Ines Betten
Christoph Blümmel
Walid El Dakak
Christophe Ledoux Dongmo
Maximilian Eckardt
Julian Formhals
Hellmuth Hoffmann
Katharina Knorz
Sascha Michaelis
Konstantin Ratz
Markus Schedel
Sabrina Schmiedt
Sofia Torrijos Crespo
Leandra Maren Weydt
Weiyi Yang
Hendrik Biewer
Frank Brettreich
Elisabeth Diehl
Martin Eberhardt
Alexandre Ferraz
Hanno Helming
Michel Hubert
David Konzack
Mario Milicevic
Luisa Sandkühler
Nicole Schindler
Christiane Sikora,
Jan Weber
Alica de Witt
252 | Geothermal Science and Technology
Reseacrch Follows
Marion Berger, (3 months)
Clement Crayssac, (3
months)
Mingliang Liu, (2 months)
Yaowu Cao, (2 months)
Valerie Galin, (3 months)
Xiaobo Zhang, (2 months)
Guest Scientists
Dr. rer.nat. Markus Neuroth,
RWE Power AG
Prof. Dr. Qinghai Guo,
University of Geosciences,
Wuhan, China
Prof. Florian Wellmann, PhD,
Graduate School AICES,
RWTH Aachen
Prof. Dr. Olaf Kolditz,
Helmholtz-Zentrum für
Umweltforschung GmbH –
UFZ, Leipzig
Guest Lecturers
Dr.-Ing. Ulrich Burbaum,
CDM Consult Alsbach
Geothermal Science and Technology
Geothermal Energy is defined as the heat of the
accessible part of the earth crust. It contains the
stored energy of the earth which can be extracted
and used and is one part of the renewable energy
sources. Geothermal Energy can be utilized for
heating and cooling by applying heat pumps as
well as it can be used to generate electricity or
heat and electricity in a combined heat and power
system.
The field of Geothermal Science has natural
scientific and engineering roots. Geothermal
Science connects the basic knowledge with the
requirements of practical industry applications.
Geothermal Science is in interdisciplinary
exchange with other applied geological subjects
such as hydrogeology and engineering geology
and therefore is a logic and proper addition to
the research profile of the Technische Universität
Darmstadt.
The broad implementation of geothermal energy applications and the utilization of the underground as a thermal storage will help to reduce
CO2 emissions and meet the according national
and international climate protection objectives.
Furthermore, the utilization of geothermal energy will strengthen the independency on global
markets and the utilization of domestic resources.
Geothermal Energy will be an essential part of
the decentralized domestic energy supply and
will contribute an important share of the desired
future renewable energy mix.
Regarding the worldwide rising importance of
renewable energy resources, Geothermal Science
is one of the future’s most important field in Applied Geosciences. In 2009, the industry-funded
Chair for Geothermal Science and Technology
was established at the TU Darmstadt – the first
foundation professorship in energy science of the
university.
The Chair of Geothermal Science and
Technology deals with the characterization of
geothermal reservoirs, starting from basic analyses of thermo-physical rock properties, which
lead to sophisticated calculation of the reservoir
potential of distinct rock units. Reliable reservoir
prognosis and future efficient reservoir utilisation is addressed in outcrop analogue studies
world-wide. Organisation of a highly qualified
geothermal lab and experimental hall (TUDA
HydroThermikum) started already in 2007 and
was continued in 2015. Field courses and excursions in 2015 focused on geothermal energy in
Chile, Germany and Austria.
Geothermal Science and Technology | 253
User Friendly 3D Processing og High Resolution X-Ray
Computer Tomography Rock Images based on Machine
Learning Techniques
Swarup Chauhan, Wolfram Rühaak, Ingo Sass
The identification of accurately segmented phases in images observed by X-ray microcomputer
tomography (XCT) is important for determining
the geometries of pore networks. Popular methods such as histogram thresholding, which are
commonly used for XCT image segmentation
exhibit a number of shortfalls.
In the project framework of SUGAR III – Submarine Gashydrat Ressourcen, we are developing
new software, which is built on machine learning
(ML) techniques, for the 2D/3D visualization of
XCT data. The segmentation and classification
of different phases are based on feature vector
selection and relative porosities and trends in
pore size distribution (PSD) can be computed.
The ML schemes have been implemented and the
preliminaty results are published in [1][2].
Figure 1, illustrates the segmentation and classi-
fication of a volcanic Andesite rock sample. The
relative porosity of 15.92 ± 1.77 % and pore size
distribution computed for Andesite using seven
ML techniques is in very good agreement to
experimental results of 17 ± 2 % obtained using
gas pycnometer.
Algorithms to calculate relative porosity, PSD
and total volume fraction of mineral, matrix and
pore phases are built in a user friendly graphical
interface. Currently, a MATLAB© based version
of the GUI has been released. For the year 2016,
the focus will be on optimizing computational
speed, accuracy of the ML techniques and validation studies for different types of XCT datasets.
References
[1] Chauhan, S, Rühaak, W., Khan,
F., Enzmann, F, Mielke, P.,
Kersten, M, Sass, I, (2015).
Processing of rock core
microtomography images: Using
seven different machine learning
algorithms.
4. GEO-CT/ -IMAGINGWORKSHOP.
Johannes Gutenberg-Universität
Mainz (JGU). 16.-17.11.2015.
[2] Chauhan, S. Rühaak, W.,
Khan, F., Enzmann, F., Mielke, P.,
Kersten, M., Sass, I.: Processing
of rock core microtomography
images: Using seven different
machine learning algorithms,
COMPUTERS & GEOSCIENCES, 86: 120-128,
ISSN 0098-3004, http://dx.doi.
org/10.1016/j.cageo.2015.10.013.
Figure 1: 2D/3D segmentation and classification of XCT Andesite images using unsupervised machine learning techniques.
Research Projects
• Geothermal Reservoir Analogs in Foreland Basins – „Malvonian“
(DAAD 2015 – 2016)
•
Schlüsseltechnologien und Modellierungsmethoden zur Errichtung von Enhanced Geothermal Systems – Key Technologies and Modeling
Methodologies for Establishing Enhanced Geothermal Systems – „KeyTEGS“ (DAAD 2014 2016)
• Entwicklung von wartungsarmen PEHD-Filterelementen für ober-
flächennahe geothermische Brunnenanlagen (Deutsche Bundesstiftung Umwelt (DBU) 2011 – 2015)
• Charakterisierung des Geothermischen Reservoirpotenzials des Permokarbons in Hessen und Rheinland-Pfalz (BMU & BMWI
2011 – 2015)
• Rock and Hydrothermal Fluid Interactions and Their Impacts on
Permeability, Reservoir Enhancement and Rock Stability
(DAAD 2011 – 2015)
•
Quantitativer Einfluss des Wasserhaushalts, der Umwelttemperatur und der geothermischen Kennwerte auf die Wärmeableitung erdverlegter Starkstromkabel (E.ON Innovation Center Distribution und Bayernwerk AG 2012 – 2015)
• Entwicklung von thermophysikalisch optimierten Bettungsmaterialen für Mittel- und Niederspannungskabeltrassen (HeidelbergCement, Baustoffe für Geotechnik GmbH & Co. KG 2012 – 2015)
Research Projects
• Reduzierung des Gebäudewärmebedarfs mittels geothermischer Speicher
- Entwicklung eines interagierenden Simulationsmodells (TU Darmstadt, Förderinitiative Interdisziplinäre Forschung 2014 – 2015)
•
•
•
•
•
Simulation und Evaluierung von Kopplungs- und Speicherkonzepten regenerativer Energieformen zur Heizwärmeversorgung (HA Hessen Agentur GmbH, Energietechnologieoffensive Hessen 2013 – 2015)
Integrated Methods for Advanced Geothermal Exploration - IMAGE (EU - Seventh Framework Programme (FP7) - ENERGY.2013.2.4.1: Exploration and assessment of geothermal reservoirs 2013 – 2017)
Interdisziplinäres Forschungsprojekt zur Messung, Bewertung und
Optimierung der Erwärmung und Strombelastbarkeit von erdverlegten Mittel- und Niederspannungskabelnetzen (TU Darmstadt, Förderinitiative Interdisziplinäre Forschung 2014 – 2015)
SUGAR III – Submarine Gashydrat Ressourcen. Entwicklung einer Auswertesoftware für 3D röntgentomographische Aufnahmen
(BMBF 2014 – 2016)
Ableitung von Berechnungs- und Verlegevorschriften und Entwicklung von Projektierungstools gemäß neu evaluierter Grenzwerte der Kabelbelastbarkeit im Bestand und für Neuverlegung unter Berücksichtigung stationärer und instationärer Strombelastung vor dem Hintergrund subsumiert bewerteter instationärer bodenphysikalischer Vorgänge(E.ON Innovation Center Distribution und Bayernwerk AG 2015 – 2018)
Publications
[1]
Al-Zyoud, S., Rühaak, W., Forootan, E., Sass, I.; Over Exploitation of Groundwater in the Centre of Amman Zarqa Basin - Jordan: Evaluation
of Well Data and GRACE Satellite Observations. RESOURCES, 4(4):819-830 (2015).
[2] Anbergen, H., Rühaak, W., Frank, J., Sass, I.: Numerical simulation of
a freeze-thaw-testing procedure for borehole heat exchanger grouts. CANADIAN GEOTECHNICAL JOURNAL, 52(8):1087-1100 (2015).
[3] Anbergen, H., Rühaak, W., Frank, J., Müller, J., Sass, I.: Numerical Simulation of Freezing-Thawing-Cycles in the Grout of Borehole Heat Exchangers. PROCEEDINGS WORLD GEOTHERMAL CONGRESS 2015, 19-24.4.2015, Melbourne, Australia. Melbourne (2015, peer reviewed)
[4]
Aretz, A., Bär, K., Götz, A. E., Sass, I., Outcrop analogue study of Permocarboniferous geothermal sandstone reservoir formations (northern Upper Rhine Graben): impact of mineral content, depositional environment and diagenesis on petrophysical properties. INTERNATIONAL JOURNAL OF EARTH SCIENCES (GEOLOGISCHE RUNDSCHAU) ISSN 1437-3254 (Print) 1437-3262 (Online) (2015)
[5] Aretz, A., Bär, K., Götz, A. E., Sass, I.: Facies and Diagenesis of
Permocarboniferous Geothermal Reservoir Formations (Upper Rhine Graben, SW Germany): Impact on Thermophysical and
Hydraulic Properties. PROCEEDINGS WORLD GEOTHERMAL CONGRESS 2015, 19.-25.04.2015, Melbourne. (2015, peer reviewed)
[6] Bär, K., Homuth, S., Rühaak, W., Schulte, D. O., Welsch, B., Sass, I.: Coupled Renewable Energy systems for seasonal High Temperature Heat storage via Medium Deep Borehole Heat Exchangers. PROCEEDINGS WORLD GEOTHERMAL CONGRESS 2015, 19.-
25.04.2015, Melbourne. (2015, peer reviewed)
[7] Bär, K., Sass, I. (2015): New Concept for the application of Outcrop Analogue Data for Geothermal Probability of Success (POS)
Studies – Examples of Projects in the Northern Upper Rhine Graben (Germany). PROCEEDINGS WORLD GEOTHERMAL CONGRESS 2015, 19.-25.04.2015, Melbourne. (2015, peer reviewed)
Publications
[8] Bär, K., Welsch, B., Schulte, D. O., Rühaak, W., Sass, I.: Coupling of Renewable Energies with Medium Deep Borehole Heat Exchangers to Cover the Annual Heat Demand of Larger Buildings by Seasonal High Temperature Heat Storage. ENERGY, SCIENCE AND
TECHNOLOGY 2015, 20.-22.05.2015, Karlsruhe. (2015, peer reviewed)
[9] Bär, K., Rühaak, W., Welsch, B., Schulte, D. O., Homuth, S., Sass, I.: Seasonal High Temperature Heat Storage with Medium Deep Borehole Heat Exchangers. ENERGY PROCEDIA, 76: 351-360. ISSN 18766102 (2015).
[10] Chauhan, S., Rühaak, W., Khan, F., Enzmann, F., Mielke, F., Kersten, M., Sass, I.: Rock core microtomography image processing - Segmen-
tation using seven different machine learning algorithms.
COMPUTERS & GEOSCIENCES, 86:120-128. ISSN 0098-3004, http://dx.doi.org/10.1016/j.cageo.2015.10.013. (2016).
[11] Drefke, C., Dietrich, J., Stegner, J., Balzer, C., Hinrichsen, V., Sass, I.:
Steigerung der thermischen Stromtragfähigkeit von Kabel-Hüll-
rohrsystemen. NETZPRAXIS 54 (11): 28-34. ISSN 1611-0412 (2015).
[12] Drefke, C., Stegner, J., Dietrich, J., Sass, I.: Influence of the Hydraulic Properties of Unconsolidated Rocks and Backfill Materials on the Change of the Thermophysical Characteristics by Heat Transfer.
PROCEEDINGS WORLD GEOTHERMAL CONGRESS 2015, 19.-24.04.2015, Melbourne. (2015, peer reviewed)
[13]
Freymark, J., Sippel, J., Scheck-Wenderoth, M., Bär, K., Stiller, M., Kracht, M., Fritsche, J.-G.: Heterogeneous crystalline crust controls the shallow thermal field – a case study of Hessen (Germany).
ENERGY PROCEDIA, 76:331-340. ISSN 18766102 (2015).
[14]
Homuth, S., Götz, A. E., Sass, I.: Physical Properties of the Geo-
thermal Carbonate Reservoirs of the Molasse Basin, Germany Outcrop Analogue vs. Reservoir Data. PROCEEDINGS WORLD GEOTHERMAL CONGRESS 2015, 19.-24.04.2015, Melbourne. (2015, peer reviewed)
Publications
[15]
Mielke, P., Prieto, A., Bignall, G., Sass, I.: Effect of Hydrothermal Alteration on Rock Properties in the Tauhara Geothermal Field,
New Zealand. PROCEEDINGS WORLD GEOTHERMAL
CONGRESS 2015, 19.-24.04.2015, Melbourne. (2015, peer reviewed)
[16] Mielke, P., Nehler, M., Bignall, G., Sass, I.: Thermo-physical rock properties and the impact of advancing hydrothermal alteration A case study from the Tauhara Geothermal Field, New Zealand. JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH, 301:14-28. ISSN 03770273 (2015).
[17]
Molenaar, N., Felder, M., Bär, K., Götz, A. E.: What classic greywacke (litharenite) can reveal about feldspar diagenesis: An example from Permian Rotliegend sandstone in Hessen, Germany. SEDIMENTARY GEOLOGY, 326: 79-93. ISSN 00370738 (2015)
[18] Nehler, M., Mielke, P., Bignall, G., Sass, I. Lollino, G., Giordan, D., Thuro, K., Carranza-Torres, C., Wu, F., Marinos, P., Delgado, C. (eds.) (2015): New Methods of Determining Rock Properties for Geothermal
Reservoir Characterization. ENGINEERING GEOLOGY FOR SOCIETY AND TERRITORY - VOLUME 6. Springer International Publishing, Cham., pp. 37-40. ISBN 978-3-319-09059-7
[19] Pei, L., Rühaak, W., Stegner, J., Bär, K., Homuth, S., Mielke, P.,
Sass, I.: Thermo-Triax: an Apparatus for Testing Petrophysical Properties of Rocks under Simulated Geothermal Reservoir
Conditions, GEOTECHNICAL TESTING JOURNAL 38(1) (2014) DOI: 10.1520/GTJ20140056.
[20] Rühaak, W.: 3-D interpolation of subsurface temperature data with known measurement error using Kriging, ENVIRONMENTAL EARTH SCIENCES, 73(4):1893-1900. (2015)
[21] Rühaak, W.; Anbergen, H.; Grenier, C.; McKenzie, J.; Kurylyk, B. L.; Molson, J.; Roux, N.; Sass, I.: Benchmarking numerical freeze/thaw models. ENERGY PROCEDIA, 76:301-310 (2015).
Publications
[22] Rühaak, W., Guadagnini, A., Geiger, S., Bär, K., Gu, Y., Aretz, A., Homuth, S., Sass, I.: Upscaling Thermal Conductivities of Sedimentary Formations for Geothermal Exploration. GEOTHERMICS, 58:49-61 (2015).
[23] Rühaak, W. Steiner, S., Welsch, B., Sass, I.: Prognosefähigkeit
numerischer Erdwärmesondenmodelle. GRUNDWASSER, 20(4): 243-
251 (2015). ISSN 1430-483X (Print) 1432-1165 (Online)
[24] Rühaak, W., Pei, L., Homuth, S., Bartels, J., Sass, I.: Thermo-Hydro
Mechanical-Chemical Coupled Modeling of Geothermal Doublet Systems in Limestones. PROCEEDINGS WORLD GEOTHERMAL CONGRESS 2015, 19.-24.04.2015, Melbourne. (2015, peer reviewed)
[25] Sass, I., Heldmann, C.-D., Lehr, C., Schäffer, R.: Hydrogeological Exploration of an Alpine Marble Karst for Geothermal Utilization.
PROCEEDINGS WORLD GEOTHERMAL CONGRESS 2015, 19.-
24.04.2015, Melbourne. (2015, peer reviewed)
[26] Sass, I., Rühaak, W., Bracke, R. (2015): Urban Heating. PR
OCEEDINGS WORLD GEOTHERMAL CONGRESS 2015, 19 – 24 April, Melbourne, Australia. (2015, peer reviewed)
[27] Sass, I., Brehm, D., Coldewey, W.G., Dietrich, J., Klein, R., Kellner, T., Kirschbaum, B., Lehr, C., Marek, A., Mielke, P., Müller, L., Panteleit, B., Pohl, S., Porada, J., Schiessl, S., Wedewardt, M., Wesche, D.: Empfehlung Oberflächennahe Geothermie - Planung, Bau, Betrieb und Überwachung - EA Geothermie. Ernst & Sohn, Berlin ISBN 978-3-433-02967-1 (2015).
[28] Schulte, D. O., Rühaak, W., Chauhan, S., Welsch, B., Sass, I.: A MATLAB Toolbox for Optimization of Deep Borehole Heat Ex
changer Arrays. PROCEEDINGS WORLD GEOTHERMAL
CONGRESS 2015, 19.-24.04.2015, Melbourne. (2015, peer reviewed)
[29] Schulte, D. O., Rühaak, W., Oladyshkin, S., Welsch, B., Sass, I.: Optimization of Medium-Deep Borehole Thermal Energy Storage
Systems, ENERGY TECHNOLOGY, 4:104-113. DOI: 10.1002/
ente.2015.00254. ISSN 2194-4296 (2015)
Publications
[30] Sippel, J., Bär, K., Kastner, O., Blöcher, G.; Scheck-Wenderoth,
M.; Huenges, E.: Runder Tisch GIS, e.V. (ed.) (2015): Untersuchung
des Tiefen-Geothermie-potenzials. LEITFADEN 3D-GIS UND
ENERGIE. Berlin, pp. 77-79.
[31] Stegner, J., Drefke, C., Sass, I.: New Methods for Determining the Thermophysical and Hydraulical Properties of Unconsolidated Rocks. PROCEEDINGS WORLD GEOTHERMAL CONGRESS 2015, 19.-24.04.2015, Melbourne. (2015, peer reviewed)
[32] Welsch, B., Rühaak, W., Schulte, D. O., Bär, K., Homuth, S., Sass, I.: A
Comparative Study of Medium Deep Borehole Thermal Energy Storage Systems Using Numerical Modelling. PROCEEDINGS WORLD GEOTHERMAL CONGRESS 2015, 19.-24.04.2015,
Melbourne. (2015, peer reviewed)
[33] Willershausen, I., Schulte, D. O., Azaripour, A., Weyer, V., Briseño,
B., Willershausen, B.: Penetration Potential of a Silver Diamine Fluoride Solution on Dentin Surfaces. An Ex Vivo Study.
CLINICAL LABORATORY, 61 (11) pp. 1695-1701. DOI: 10.7754/Clin.
Lab.2015.150401 (2015).
Technical Petrology
Staff Members
Head
Prof. Dr. Rafael
Ferreiro Mählman
Senior Scientist
Prof. Dr. Eckardt Stein
Secretaries
Astrid Kern
Technical Personnel
Dr. Norbert Laskowski
Research Associates
Dr. Lan Nguyen-Thanh
Sascha Kümmel
Marc Rothenbücher
Technical Petrology | 263
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:
264 | Technical Petrology
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.
Improvement of methods related to hydrocarbon exploration.
Improvement of methods related to the lowgrade metamorphism characterisation.
Stability of clay barriers
Natural bentonite is considered as a suitable
candidate for buffer material required for the
underground disposal of high level radioactive
waste (HLW). Repositories of HLW are commonly representing multibarrier systems. The host
rock is an important barrier and so is clay used as
backfill and buffer, that is the interface between
the canister with the radioactive waste and the
host rock. Backfill material is considered as a
safety barrier in the emplacement tunnel. There
are a number of concepts for the future disposal
of HLW in underground repositories. They are
based on the use of “multi-barrier” systems made
up of two basic factors: an engineered barrier and
host rock. The engineered barrier comprises metallic container (“canister”) containing vitrified
nuclear waste or spent nuclera fuel. The metallic
containers could be made of iron or copper. These
are placed in underground caverns within host
rock (e.g. shale, granite or salt), which constitutes
the natural geological barrier. Our research focuses on concepts of different countries of using
iron metallic castor and salt, crytallized rock
or claystone rocks formations as host rock and
bentonite acts as buffer and backfill materials .
The main question for this type of scenario is,
will bentonite be stable or not? In order to examine this question as well as to evaluate the long
term safety of the repository, it is necessary to
consider the stability of the buffer and backfill
components by laboratory testing and theoretical
modelling. Different smectitic rich clay and bentonite in the worlds are examined with the aims
are followed:
Stability of chemical structure and geotechnical paramters of smectite rich clays/bentonite
in contact with groundwater, cement and Fe
leachate from concrete and Fe-canister of multi
barrier systems. Kinetics dissolution of smectite
rich clays/bentonites under HLW-repository
conditions.
Natural Fe-rich clays as potential natural
analouges to buffer alteration processes, driven
by the presence of Fe and high alkaline groundwater in system.
Low-Temperature Petrology s.l
Orogen and palaeogeothermal researches
in foreland basins of the Alps, Vosges, Dinarides, Carpathians, Stara Planina (Bulgaria),
Balkanides, Variscides of the Bosporus and
Turkey. A broad analytical spectrum must be
applied in low-temperature petrology due to very
small grain-size. Technical Petrology group
maintains a Microscopy Laboratory (CCA
coalreflection microscopy, MPV coal-reflection microscopy, fluorescence microscopy,
transmitted light microscopy). The former XRD
laboratories (Clay and XRD Laboratory and
a research XRD Laboratory) had to be moved
and merged with the awkward geochemical
laboratory. The ICP-AES, TOC, AOX and gas
chromatography together with the Organic
Geochemical Laboratory was closed in 2012.
A non-completed refurbishment of the Geoscience Institute forced us to accept an adverse
decision. A XRF laboratory (Wave-dispersive
BRUKER S8-Tiger) is maintained together with
the groups of Chemical Analytics and Environmental Mineralogy.
Due to the adjournment of the refurbishment
of the building and the infrastructure the situation
did not change since 2012. On photographs of the
laboratories the iniquitous situation depended
on development is documented on the Web page
to testify the need to get back ideal working
conditions. In 2014 the negative development
in rejected funding continued. The economic
situation declined again and evaluation criteria
of the faculty forced the need to cut an assistant
position and thus some parts of the infrastructure
of the technical petrology group had to be closed
(Experimental Coal Petrology, Coal Petrology,
Archaeometry and part of the instrumental
analytics).
The rebuke against the head is a concealed
and perfidious way to erode scientific licence
and freedom of research causing damage on
the ambitious content in education of the specialism. It is to point out that the coal petrology
research associate (position being cut in 2013
due to employment rules for research associates 12 years of temporary engagement) Dr. Ronan
Le Bayon and the head were honoured by The
Society of Organic Petrology (TSOP) with five
reference papers on the society homepage, also
the appointment as convenors of a coal petrologic
session on the GeoFrankfurt 2014 and as guest
editors. A strong misfit between the evaluation
at the university and the reputation in the coal
community is evident. The reduction of the wide
research base in Germany will cause future damages in sciences.
Alteration of Expandable Clays in Reaction with Iron
and Percolated by High Brine Solutions
Horst-Jürgen Herberta, Jörn Kasbohmb, Lan Nguyen-Thanhc,1, Lothar Meyera, Thao Hoang-Minhd, Mingliang Xiea,
Rafael Ferreiro Mählmannc
a
Gesellschaft für Anlagen- und Reaktorsicherheit GmbH, Theodor-Heuss-Straße 4, 38122 Braunschweig, Germany
b
Institut für Geographie und Geologie, Universität Greifswald, Friedrich-Ludwig-Jahn-Straße 17A , 17487 Greifswald,
Germany
c
Institute of Applied Geosciences, Technische Universität Darmstadt, Schnittspahnstraße 9, 64287 Darmstadt, Germany
d
VNU University of Science, Vietnam National University, Hanoi, 334 Nguyen Trai road, Thanh Xuan district, Hanoi, Vietnam
Bentonites are suitable candidates as buffer and
backfill materials in HLW-repositories. The
main objective of this research was to enhance
the understanding of the interactions of bentonite
with iron in the near field of a HLW-repository. A
target was to recognize the mineralogical interaction of bentonite with iron powder simulating
the contact of bentonite with steel containers (by
different “clay/iron-interaction”-experiments).
Compacted MX80 bentonite and Friedland
clay were used as starting materials for clay/iron
interaction experiments in percolation systems.
Iron was added as native Fe-powder to the bentonite (ratio “bentonite : Fe0” = 10 :1) and after
that compacted to a raw density of 1.6 g/cm3.
Saturated NaCl- or IP21-solution were the two
agents for percolation in the different experiment
series. These experiments were conducted at
three different temperatures (25°C, 60°C, 90°C).
XRD and TEM – EDX measurements were
the major analytical techniques applied in this
research. FT-IR and XRF analyses were used as
additional tools for the characterization of the
structure and composition of the smectites.
In comparison to experiments at 90°C, the
compacted blocks have shown a non-homogenous behavior of former Fe-powder after finished
experiments at 25°C and 60°C. Brown and black
areas were clear to distinguish (figure 1) and
were investigated separately.
Smectite was the main phase and full
expandable in all reaction products. The peak
shapes of smectite indicated different processes
between run products from 25 °C experiments
and experiments with higher reaction temperatures. The run products of experiments at higher
temperature than 25 °C were characterized by
peak broadening. This peak broadening was
considered as result of strong dissolution and
precipitation processes during the experiment.
The chemical analyses also confirmed the loss of
Si and Al caused by percolation.
Smectite has shown different octahedral
Fe-amounts in the different reaction products
(proofed by XRD, TEM-EDX and FT-IR) and is
represented in figure 2. Also tetrahedral Si was
different in the different reaction products (proofed by TEM-EDX and FT-IR). The “Neoformation of Fe-bearing phases : Fe2+/Fetotal”-ratio
was applied to describe a pathway of alteration
through the different experimental setups. The
parameter “Neoformation of Fe-bearing phases”
contains the sum of neoformed structures identified by TEM-EDX and expressed in frequency-%
(figure 3). Especially, the mineral matter of
fraction < 2 μm has shown temporary Fe-bearing
neoformed sheet silicates like berthierine-saponite mixed layer phases (BS-ml), chlorite-saponite-trioctahedral vermiculite mixed layer
structures (CSV-ml) and cronstedtite-trioctahedral vermiculite mixed layer phases labeled as
CroV-ml. The occurrence of these phases was
partially limited to certain experimental conditions (figure 3a).
BS-ml phases were identified in experiments with IP21-solution at 25 °C and CroV-ml
structures were more common in experiments
with duration of 2 months. CSV-ml phases filled
the gap between BS-ml and CroV-ml.
“Illitization” was found to be the main
process of smectite alteration (figure 3b). This
process was supported by the percolation design
of these experiments. In several cases, smectitization was observed in case of highest degree of
Fe0-oxidation to Fe2+ and Fe2+-oxidation to Fe3+.
It was overriding the removing of dissolved Si by
percolation. Smectites were characterized by low
Figure 1. Visualization of different reaction degree of former Fe-powder at 25° and 60°C
and nearby homogenous behavior at 90°C
Figure 2. Proof of alteration of octahedral Fe-content in smectite Note: “XRD (EG): Ratio of Intensity “3.
Order : 2. Order” “ means the intensity ratio of 002- and 002-reflections for montmorillonite or 002/003- and
003/004-reflections of IS-ml in according to
Moore & Reynolds (1989).
octahedral Fe in cases of smectitization or low
degree of “illitization” (figure 3c). The alteration
of smectite was mainly pH-driven because of
high alkalic pH-value caused by the reducing environment during the highest intensity of the two
types of Fe-oxidation. The high alkalic pH-range
was responsible for a high degree of dissolution.
Smectite particles with low sheet stress (Al-rich
in octahedral sheet) resist the dissolution processes (figure 3c). Smectitization occurs, if the
amount dissolved Si is higher than the flow rate,
caused by percolation, can mitigate the dissolved
Si-amount.
These mineralogical alteration processes can
support the understanding of swelling pressure
and permeability measurements with FeCl2-solutions as additive to percolating agents (figure 4).
NaCl-solution: An increasing temperature of
experiments caused a rising swelling pressure (25
°C: < 5 bar; 60 °C: 5 – 10 bar; 90 °C > 10 bar).
Otherwise, the temperature has not affected the
data interval of permeability (3E-17 m² – 6E-14
m²). The variability of FeCl2-concentration in
the experiments caused a different development
in permeability. The permeability was reduced
mainly with increasing FeCl2-concentration.
IP21-solution: In these experiments, the
temperature has differentiated the permeability
(25 °C: < 1E-14 m²; 60 °C: > 1E-14 m²). Here,
the swelling pressure was not affected by temperature (nearby constant between 3 – 5 bar). The
impact of the variable FeCl2-concentration cannot be significantly identified. But it seems that
the behavior of permeability is also following the
development of NaCl-solutions.
Opalinus clay pore solution: The Opalinus solution represents low ion strength in comparison
to the experiments with NaCl- or IP21-solution.
Swelling pressure and permeability have covered in Opalinus-experiments a more extended
interval than in the two other mentioned experiments with high ion strength. In Opalinus
experiments, too, the temperature controlled the
swelling pressure like in NaCl-experiments, but
in the opposite direction (25 °C: ≥ 20 bar; 60
°C: 10 – 20 bar; 90 °C: < 10 bar). An increasing
experimental temperature reduced the resulting
swelling pressure. The temperature also affected
the permeability (25 °C: < 1E-18 m²; 60 °C:
1E-18 m²; 4E-17 m²; 90 °C: > 1E-16 m²). The
FeCl2-concentration has shown a similar impact
on swelling pressure or permeability as reported
in NaCl- and IP21-solution.
The experiments with NaCl-solution offer a
summarizing overview about assumed mechanisms to the possible impact of Fe on swelling
pressure and permeability (figure 5). The altered
smectite has shown with increasing Fe-concentration (FeCl2 between 0.1 and 10-4 mol FeCl2
in solution) three different types of modified
properties for swelling pressure and permeability: (i) swelling pressure increased and caused
a reduced permeability, (ii) swelling pressure
is reduced and the permeability is also reduced
and (iii) swelling pressure was constant and the
permeability was increased. In first case, process
was accompanied by reduced total charge of smectite in reaction products. That means the higher
pressure and reduced permeability is controlled
by the mineralogy of smectite (figure 5: see label
“SP ~ 1/Perm”). In the second case, XRD-data
indicate a precipitation of Fe-oxides in the low
temperatures experiments (figure 5: see label
“Fe-precipitation”). Si-precipitation is assumed
for high temperature experiments (90°C) indicated by TEM-investigations (figure 5: see label
“Si-precipitation”). Precipitation is cementing the
smectite aggregates and reduces the permeability
and also the swelling pressure. Expendability is
reduced by cementation of smectite aggregates.
Finally, in the last case a channel-formation due
to increased cementation was assumed as the
reason for the observed behavior (figure 5: see
label “channel formation”).
The observed chemical and mineralogical
changes of the smectites in contact with iron
were fast and very intensive. The intensity of the
interactions increased with increasing tempera-
Figure 3. Si- and Fe-behavior in neoformed clay minerals and smectite of run products from the MX80- and Friedland clay-series
(fraction < 2 μm; TEM-EDX-based a: Si/Al-ratio (footnote, right) and Fei/Fetotal-ratio (headnote, left) in mainly neoformed clay
minerals; b: ΔSitet in smectite (calculated by Sii – Sistart material); c: Fe-content of smectite in comparison to total Fe from all
clay minerals. (abbreviations for mixed layer-phases see table 1)
Figure 4. Development of swelling pressure and permeability of compacted MX80 bentonite with NaCl-solution (above),
IP21-solution (middle), and Opalinus clay pore water (below) with different concentrations of Fe (empty symbols – FeCl2 in the
pore space; filled symbols – bentonite mixed with 10 % Fe-powder; experiments performed at 25 °C (diamond); at 60 °C (square)
and 90 °C (triangle); size of empty symbols mirror the concentration of FeCl2 (between 0.1 and 10-4 mol FeCl2 in solution)
ture, with increasing ionic strength and with the
amount of native iron in the system. The observed
changes of swelling pressure and permeability
are also correlated with hydraulic properties
of the system. During the reaction smectite is
dissolved and SiO2(aq) liberated into the solution.
With increasing Fe2+ in the system the original
smectites were transformed in berthierinesaponite mixed-layers (ml) and further into chlorite-saponite ml. These mineralogical changes
are controlled by the velocity of dissolution of
the original smectite and the removal of SiO2(aq)
from the solution.
If removal of SiO2(aq) is faster than the
increase of SiO2(aq) in solution by smectite
dissolution an illitization process is favored.
Consequently, the swelling pressure is reduced
and permeability increases.
If more SiO2(aq) enters the solution than is
removed no more illite but new smectite can
be formed leading to an increase of swelling
pressure and a decrease of permeability. Swelling pressure and permeability however are not
dependent only on the total amount of swelling
smectite in the bentonite. These properties also
depend on the associated mineralogical changes
in the bentonite.
The described direct relations between
swelling pressure and permeability were additional affected by Fe- and Si-precipiation. Such
precipitations reduce the swelling pressure and
permeability with increasing Fe- or dissolved
Si-amount. Otherwise, a further increasing
Fe- or Si-cementation of particles can lead to a
formation of channels, which strongly increases
permeability. The swelling pressure is constant in
this phase of reaction.
References
[1] Herbert, H.-J., Kasbohm, J.,
Nguyen-Thanh, L., Meyer, L.,
Hoang-Minh, T., Xie, M.,
Ferreiro-Mählmann, R. (2016).
Alteration of expandable clays
by reaction with iron while being
percolated by high brine solutions.
Applied Clay Sciences 121-122,
174–187p.
[1] Moore, D. M.; Reynolds, R. C.,
1997. X-ray diffraction and the
identification and analysis of clay
minerals. Oxford University Press:
378 pp.
Figure 5. Assumed mechanism for the development of swelling pressure and permeability of com¬pacted MX80 bentonite with NaCl-solution with different concentrations of Fe (legend see figure 4)
Society Activities
•
Guest editor with Hans Albert Gilg, Stephen Hillier and Emilio Galán. Special issue about “Clay mineral indices in palaeo-geothermal studies, hydrocarbon and geothermal prospection”. Including the proceedings of
the third Frey-Kübler Symposium. Applied Clay Sciences (2016, submissions in progress).
•
Guest editor with Ralf Littke and Ronan Le Bayon. Special issue about “Organic petrology, organic geochemistry and mineralogy in sedimentary basin research”. International Journal of Coal Geology (2016, in press).
•
Convener and Chairperson with Hans Albert Gilg at the third Frey-Kübler Symposium at the 42th Clay Mineral Society (CMS) and EUROCLAY Conference. Session: “Clay mineral indices in palaeo-geo
thermal studies, hydrocarbon and geothermal prospection”. Edinburgh, Scotland GB (2015).
•
Member of the Scientific Program Committee at the 68th International Committee for Coal and Organic Petrology Meeting, Potsdam, Germany (2015).
Publications
[1] Moeck, I.S., Uhlig, S., Loske, B., Jentsch, A., Ferreiro Mählmann,
R., Hild, S. (2015) Fossil multiphase normal faults – prime targets for geothermal drilling in the Bavarian Molasse Basin? Proceeding World Geothermal Congress, 2015. Melboure, Australia, 19-25 April 2015.
[2]
Pusch, R., Kasbohm, J., Hoang-Minh, T., Knutson, S.,
Nguyen-Thanh, L. (2015) Holmehus clay a tertiary smectitic clay of potential use for isolation of hazardous waste. Engineering
Geology 188, 38-47.
[3]
Pusch, R., Kasbohm, J., Knutsson, S., Yang, T., Nguyen-Thanh, L. (2015) The role of smectite clay barriers for isolating high-level radioactive waste (HLW) in shallow and deep repositories.
Procedia Earth and Planetary Science 15, 680-687.
[4] Warr, L.N., Ferreiro Mählmann, R (2015) Recommendations for Kübler Index standardization. Clay Minerals 50, 282-285.
Research Projects
•
Temperature determination between 50 and 270 °C through fluid
inclusion microthermometry and vitrinite reflectance values in the
external parts of the Central Alps. Cooperation with Basel University
(CH) and RWTH Aachen (D).
•
Reliability of very low-grade metamorphic methods to decipher basin
evolution: case studies from basins of the Southern Vosges (NE France).
Cooperation with LaSalle Beauvais Geosciences Department, (F),
Geoscience Australia Resources Division (AU).
•
Low-grade study on the thermal evolution of wairarapa area,
North Island, New Zealand. Cooperation with LaSalle Beauvais
Geosciences Department, (F), UMR 8217 Géosystèmes, bâtiment SN5,
University of Lille (F), University of Picardie Jules-Verne (F), GNS
Science (NZ).
•
Mineralogical characterization of Di Linh bentonite, Vietnam:
A methodological approach using transmission electron microscopy and
X-ray diffraction. Cooperation with Vietnam National University, Hanoi
(Vietnam), Jörn-Kasbohm-Consulting, Greifswald (D), Greifswald
University (D), Vietnam Atomic Energy Institute (Vietnam), Advance
Technology Transfer and Consultancy Ltd. (Vietnam), Institute of
Geological Sciences and Vietnam Academy of Science and Technology
(Vietnam), Luleå University of Technology (S).
•
The Zlatitsa para-series group, a new Palaeozoic lithostratigraphic
member determined in the Kashana section at the southern Stara Planina mountain range (Central Balkanides, Bulgaria). Cooperation with the
Universität Freiburg (D), Université de Genève (CH), University of Sofia
“St. Kl. Ohridski“ (Bg).
•
Conversion mechanism of bentonite barriers. Cooperation with the
Ernst-Moritz-Arndt-Universität, Greifswald (D), Hanoi University of
Science (Vietnam), Gesellschaft für Anlagen- und Reaktorsicherheit
mbH, Braunschweig (D). The project will run from 01.01.2015 to
30.09.2017.
274 | Theses in Applied geosciences
Theses in Applied
Geosciences
Theses in Applied geosciences | 275
Diploma Theses in Applied Geosciences
•
Philipp, Alexej; Dreidimensionale Lagerstättenerkundung durch kombinierte Betrachtung von terrestrischem Laserscanning, Bohrloch-
daten und geoelektrischer Tomographie am Beispiel des Kalkstein-
bruchs Mauer/Kraichgau; 26.01.2015
•
Reiß, Diana; Einfluss der Geologie auf die Hydrogeologie von Flüssen in den Nördlichen Kalkalpen und den zentralen Ostalpen; 2.1.15
Bachelor Theses in Applied Geosciences
•
Achtstätter, Nadja; Polycyclische aromatische Kohlenwasserstoffe in Böden der Kanareninsel El Hierro - Untersuchungen zur räumlichen Verteilung und Beziehungen zur Passatzirkulation, Kohlenstoffgehalt sowie Salzgehalt; 3.6.15
•
Attardo, Simon; Erfassung des Trennflächengefüges im Rahmen einer Felshangsicherung bei Eppstein/Taunus; 30.9.15
•
Dohn, Johannes; GIS-gestützte Analyse von Senkungsstrukturen im Bereich des Blattes GK 5124 Bad Hersfeld; 17.9.15
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Gruhn; Alexander; Vergleichende Untersuchung der Aerosolzusammensetzung von unterschiedlichen Sammelmethoden am Beispiel von Zeitreihen vom Ragged Point auf Barbados; 2.6.15
•
Hasenstab, Eric; Palynologische Untersuchungen der Schwammfazies des eozänen Maar-Sees von Messel (Sprendlinger Horst, Südhessen); 31.8.15
•
Helming, Hanno; Experimenteller Vergleich von Durchlässigkeitsund Infiltrationsverhalten; 11.12.15
•
Hengsberger, Susanne; Investigating the influence of pH of desalinated water on the dissolution of Clacite in a test soil for managed aquifer; 27.8.15
•
Horneck, Louisa; GIS-gestützte Analyse von Senkungsstrukturen im Bereich des Blattes GK 5224 Eiterfeld; 17.7.15
•
Horch, Alica; Hydrochemisches Längsprofil der Gersprenz
(Odenwald); 28.5.15
•
Krüger, Pia; Partikeldeposition an der Residenz in Würzburg; 8.6.15
Bachelor Theses in Applied Geosciences
•
Kümmel, Sascha; Geochemie und Petrologie orogen- und kontaktmetamorpher Al-reicher Pelite (Vogesen/Frankreich); 22.6.15
•
•
Kunkel, Kevin; Dielektrizitätsmessungen von Tonmineralen und natürlichen Tonmineralgemischen aus Böden der Umgebung
Darmstadts; 26.10.15
Lange, Tristan; Ermittlung der Rohstoffverteilung einer Lagerstätte in Flörsheim-Weilbach; 22.1.15
•
•
Michael, Theresa; Hydrochemisches Längsprofil der Itter und des Gammelbachs (Odenwald); 29.7.15
•
Nowak, Torsten; Hydrochemisches Längsprofil der Weschnitz; 28.5.15
•
Raab, Moritz; Trennflächenaufnahme mit dem Terrestrischen Laser
scanning (TLS) im Bereich der Loreley/Mittelrheintal; 8.9.15
•
Schuster, Felix; Polychlorierte Biphenyle im Boden des Rheintals zwischen Koblenz und Bingen; 17.9.15
•
Stemke, Franziska; Hydrochemisches Längsprofil der Mümling (Odenwald); 30.7.15
Noll, Maike; Charakterization of the Soil Properties of an Ephemeral Stream Watershed in Israel; 23.3.15
•
Stricker, Kerstin; Model Experiments in the LiF-MgAl2O4 System; 16.2.15
•
Taufertshöfer, Andreas; Versuch einer Zusammenführung von Einzelpartikelanalysen von Massenspektrometrie und Rasterelektronenmikroskopie; 24.7.15
•
Wenzl, Lara; Bestimmung der Chlorisotope von chlorierten Ethenen zum Nachweis von Abbauprozessen im Grundwasser an einem ehemaligen Wäschereistandort; 18.2.15
Master Theses TropHEE in Applied Geosciences
•
Craizer, Rafaela; Development of a conceptual method for disposal of hazardous waste from military camps in conflict areas - Study case on the disposal of lithium metal batteries in Europe; 16.01.2015
•
El Dakak, Walid; Influence of temporal variation of rock Water saturation on shallow geothermal systems using Numerical modelling; 04.08.2015
•
Farhang, Sahand; Analysis of the Influences on Soil Moisture Trends in the Scott Valley (California, USA) and Spatiotemporal Analysis of Field Soil Moisture for Validating Satellite Estimates; 21.05.2015
•
Mahindawanscha, Amami; Intercomparison of Laboratory Techniques for Determination of Stable Isotopes in Soil Water; 12.1.15
•
Olukuewu, Abimbola; GIS-based Weights-of-Evidence Modelling of Landslide Susceptibility Mapping in Main-Kinzig and Wetterau Districs, Hessen; 9.11.15
•
Pratama, Edral; Application of Bayesian Approach – Based Weight of Evidence Method for good Landslide Susceptibility Analysis in the Main-Kinzig District; State of Hessen, Germany; 20.5.15
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Schumann, Philipp; Preliminary characterization of the hydro
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Vinci, Fabio; Analysis of the Influences of Soil Moisture Trends in the Scott Valley (California, USA) and Spatiotemporal Analysis of Field Soil Moisture for Validating Satellite Estimates; 9.3.15
Master Theses in Applied Geosciences
•
Anschütz, Sascha; Unaxial-, Spaltung und Dreipunktbiegeversuch im Vergleich von Laborexperiment und numerischer Simulation; 7.9.15
•
Betten, Ines; 3D-Laserscanning, DFN-Modellierung und Aufschluss-
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Hartmann, Markus; Automatisierte Bestimmung der hygroskopischen Eigenschaften von Aerosolpartikeln am Beispiel von gealtertem Wüstenstaub; 13.1.15
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Hatsukano, Kenji; First palynological investigation of lacustrines sediments of the eocene lake “Prinz of Hessen”; 29.1.15
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Hoffmann, Hellmuth; Petrophysikalische Eigenschaften der Mittel-
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Kurka, Sebastian; Bestimmung von Petrophysikalischen Kenngrößen mit dem terrestrischen Laserscanner (TLS); 14.8.15
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Marschall, Patrick; Column Experiments for Investigating Water Quality during Managed Aquifer Recharge; 22.4.15
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Michels, Ulrike; Untersuchung der Nitratabbauprozesse und deren Kinetik in quartären Sedimenten des Hessischen Rieds mittel Säulen-
experimenten; 17.3.15
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Neumann, Jacob; Development of a groundwater model for evaluating alternative water management solutions: the Scott Valley example, California; 13.3.15
Master Theses in Applied Geosciences
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Philipp, Sven; Hydrochemistry and Isotopic Analysis of Deep
(partly Thermal) Wells and Springs in NW-Slovenia; 12.2.15
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Ratz, Konstantin; Entwicklung eines Modellversuchs zur Verockerung von Kunstoffbrunnenfilterelementen; 23.2.15
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Schröder, Daniel; Charakterisierung der zweidimensionalen Heterogenität von Lithofaziestypen des Muschelkalks (Trias) in Bezug auf Ultraschall- Wellengeschwindigkeiten, Porosität, Permeabilität und elektrischem Widerstand; 9.11.15
•
Sikora, Christine; Strukturgeologische und geothermische
Analogstudie verkarsteter Karbonatgesteine im Bereich der Tunnelbaustelle Widderstall; 20.2.15
•
Torrijos Crespo, Sofia; Comparison of Enhanced Geothermal
Response Tests and comparison of performance for different types of Borehole Hest Exchangers; 28.1.15
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Wewior, Stefan; Lateral variety of fracture sets across folded turbidites of the Hecho Group (South-Central Pyrenees, Spain); 7.9.15
PhD Theses in Applied Geosciences
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Achim Gerhard Konrad Wolfgang Aretz; Aufschlussanalogstudie
zur geothermischen Reservoircharakterisierung des Permokarbons
im nördlichen Oberrheingraben, 17.12.2015
•
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the CO2CRC Otway site, Australia, 13.07.2015
•
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