Institute of Materials Science - Technische Universität Darmstadt
Transcription
Institute of Materials Science - Technische Universität Darmstadt
Annual Report 2013 Faculty of Materials and Geo Sciences Contents Dean’s Office .................................................................................................................. 4 Institute of Materials Science ......................................................................................... 6 PHYSICAL METALLURGY ....................................................................................................... 12 CERAMICS GROUP .............................................................................................................. 21 ELECTRONIC MATERIAL PROPERTIES...................................................................................... 30 SURFACE SCIENCE .............................................................................................................. 38 ADVANCED THIN FILM TECHNOLOGY ..................................................................................... 50 DISPERSIVE SOLIDS ............................................................................................................. 53 STRUCTURE RESEARCH........................................................................................................ 70 MATERIALS ANALYSIS ......................................................................................................... 75 MATERIALS MODELLING DIVISION ......................................................................................... 87 MATERIALS FOR RENEWABLE ENERGIES ................................................................................. 98 PHYSICS OF SURFACES....................................................................................................... 111 JOINT RESEARCH LABORATORY NANOMATERIALS .................................................................. 116 MECHANICS OF FUNCTIONAL MATERIALS ............................................................................. 120 FUNCTIONAL MATERIALS ................................................................................................... 126 ION-BEAM MODIFIED MATERIALS........................................................................................ 135 MOLECULAR NANOSTRUCTURES.......................................................................................... 142 COLLABORATIVE RESEARCH CENTER (SFB) .......................................................................... 146 DIPLOMA THESES IN MATERIALS SCIENCE ....................................................................... 150 BACHELOR THESES IN MATERIALS SCIENCE ..................................................................... 152 MASTER THESES IN MATERIALS SCIENCE......................................................................... 154 PHD THESES IN MATERIALS SCIENCE ............................................................................. 155 MECHANICAL WORKSHOP ............................................................................................. 157 ELECTRICAL WORKSHOP ............................................................................................... 157 Institute for Applied Geosciences .............................................................................. 158 PREFACE .................................................................................................................... 158 PHYSICAL GEOLOGY AND GLOBAL CYCLES ............................................................................ 160 HYDROGEOLOGY .............................................................................................................. 172 ENGINEERING GEOLOGY .................................................................................................... 177 GEOTHERMAL SCIENCE AND TECHNOLOGY ........................................................................... 187 APPLIED SEDIMENTOLOGY .................................................................................................. 197 GEO-RESOURCES AND GEO-HAZARDS .................................................................................. 203 GEOMATERIAL SCIENCE ..................................................................................................... 212 ELECTRON CRYSTALLOGRAPHY ........................................................................................... 221 TECHNICAL PETROLOGY WITH EMPHASIS IN LOW TEMPERATURE PETROLOGY............................. 223 ENVIRONMENTAL MINERALOGY .......................................................................................... 226 DIPLOMA THESES IN APPLIED GEOSCIENCES .................................................................... 230 MASTER THESES IN APPLIED GEOSCIENCES...................................................................... 230 MASTER THESES TROPHEE IN APPLIED GEOSCIENCES ...................................................... 231 BACHELOR THESES IN APPLIED GEOSCIENCES .................................................................. 232 PHD THESES IN APPLIED GEOSCIENCES .......................................................................... 233 Faculty of Materials and Geo Sciences 3 Dean’s Office Staff Members Dean: Prof. Dr. Ralf Riedel Vice dean: Prof. Dr. Christoph Schüth Dean of studies Materials Science: Prof. Dr. Lambert Alff Dean of studies Applied Geosciences: Prof. Dr. Matthias Hinderer Scientific coordinator, department and Materials Science: PD Dr. Boris Kastening Scientific coordinator, Applied Geosciences: Dr. Karl Ernst Roehl Secretary of department: Renate Ziegler-Krutz Secretary of personnel and finances: Christine Hempel Competence center for materials characterization: Dr. Joachim Brötz IT group: Dipl. –Ing. (BA) Andreas Hönl Building services: Dipl. –Ing. Heinz Mohren Coordination of the KIVA project: Dr. Silvia Faßbender Public relations: Marion Bracke Media Design: Thomas Keller Publications of Permanent Members of the Dean's Office Boris Kastening Anisotropy and universality in finite-size scaling: Critical Binder cumulant of a twodimensional Ising model Phys. Rev. E 87, 044101/1-4 (2013), arXiv:1209.0105, DOI:10.1103/PhysRevE.87.044101 Siol, Sebastian; Straeter, Hendrik; Brueggemann, Rudolf; Broetz, Joachim; Bauer, Gottfried H.; Klein, Andreas; Jaegermann, Wolfram; PVD of copper sulfide (Cu2S) for PIN-structured solar cells; JOURNAL OF PHYSICS D-APPLIED PHYSICS Volume: 46 Issue: 49 Article Number: 495112 (2013) 4 Dean’s Office Pfeifer, Verena; Erhart, Paul; Li, Shunyi; Rachut, Karsten; Morasch, Jan; Broetz, Joachim; Reckers, Philip; Mayer, Thomas; Ruehle, Sven; Zaban, Arie; Mora Sero, Ivan; Bisquert, Juan; Jaegermann, Wolfram; Klein, Andreas; Energy Band Alignment between Anatase and Rutile TiO2; JOURNAL OF PHYSICAL CHEMISTRY LETTERS Volume: 4 Issue: 23 Pages: 41824187 (2013) Labrini, Mohamed; Saadoune, Ismael; Scheiba, Frieder; Almaggoussi, Abdelmajid; Elhaskouri, Jamal; Amoros, Pedro; Ehrenberg, Helmut; Broetz, Joachim; Magnetic and structural approach for understanding the electrochemical behavior of LiNi0.33Co0.33Mn0.33O2 positive electrode material; ELECTROCHIMICA ACTA Volume: 111 Pages: 567-574 (2013) Muench, Falk; Oezaslan, Mehtap; Rauber, Markus; Kaserer, Sebastian; Fuchs, Anne; Mankel, Eric; Broetz, Joachim; Strasser, Peter; Roth, Christina; Ensinger, Wolfgang; Electroless synthesis of nanostructured nickel and nickel-boron tubes and their performance as unsupported ethanol electrooxidation catalysts JOURNAL OF POWER SOURCES Volume: 222 Pages: 243-252 (2013) Dean’s Office 5 Institute of Materials Science Preface Dear colleagues and friends, The year 2013 was another successful period for the Department of Materials and Geo Sciences of TU Darmstadt. Details of the activities and achievements related to the individual departmental institutes, namely Materials Science and Applied Geosciences, are highlighted below. We would like to express our gratitude to all members of the Department – the mechanical workshop staff, technical and administrative staff, students working on their diploma and bachelor theses, Ph.D. students, and postdocs – for the outstanding effort and remarkable enthusiasm they put into their work. Without their contributions the performance and the results presented here would not have been possible. We aim to sustain and promote the motivating and fruitful atmosphere at our institute in order to continue our commitment and success in the time to come. Materials Science The amount of acquired third party funding has reached a nearly constant value in the order of 10 million Euro. Presently, the total number of students (bachelor & master) in materials science amounts round about 500. The number of freshmen of the bachelor study course Materials Science in the winter semester 2013/14 reached 94 (see Figure 1). The new master course Energy Science and Engineering which is an interdisciplinary field of study and which is administratively organized by our Department successfully developed in its second year. The master course presently counts 61 students of which 36 were freshmen in the WS 2013/14. Last not least, the master course Energy Science and Engineering was accredited in spring 2013. The Materials Science and Geo Sciences Department’s Materialium Graduate School has been further strengthened and now accommodates 30 PhD students, while the total number of PhD students of Materials Science exceeds by now 150. The research-oriented doctorate program culminating in award of the degree of “Dr.-Ing.” or “Dr. rer. nat.” fosters an interdisciplinary integration of the various Ph.D. studies between research groups inside and outside of the Materials Science Department. During specific events, Ph.D. students present their current scientific problems and methods, providing a forum for close interdisciplinary problem solving that stimulates synergy between research groups. Research is always a collaborative enterprise! Professors of Materialium are particularly committed to supporting their Ph.D. students. For instance, they strongly encourage participation at international conferences and publication in refereed research journals, which is bolstered by the high number of coordinated research programs in Materials Science at TU Darmstadt. Moreover, Materialium is a member of Ingenium, the umbrella organisation of graduate schools at TU Darmstadt. 6 Institute of Materials Science - Preface Fig. 1: All students (except Ph.D. students) and freshmen (Diplom until WS 07/08, B.Sc. from WS 08/09) of Materials Science at TU Darmstadt. Coordinated Research Proposals The institute was actively involved in a variety of coordinated research project applications. Among them one new proposal was successfully evaluated in 2013 in the frame of the LOEWE Priority Program supported by the Hessian State Government. The scientific topic of this research program is related to “The Reduction and Substitution of Rare Earth Elements in High Performance Permanent Magnets” (Response) and is coordinated by Prof. Gutfleisch. The official start of this coordinated research is January 01, 2014. This initiative marks the interdisciplinary approach the university is promoting and for which the Department of Materials and Geo Science is ideal since its subjects combine various sciences like chemistry, physics, electrical and mechanical engineering. Preface 7 Faculty Members In 2013 we had two important events related to the faculty staff members. First, in spring 2013, Prof. Dr. Karsten Durst started as the new head of the group Physical Metallurgy. He is the successor of Prof. Dr. Martin Heilmaier, who left the Department of Materials and Geosciences to take up a position as Director at the Karlsruhe Institute of Technology (KIT) in December 2011. Second, in late autumn 2013 Prof. Dr. Jürgen Rödel, the head of the group Nonmetallic Inorganic Materials, was elected as Vice President for research of TU Darmstadt. We wish both colleagues a successful start for their new and responsible positions. Prof. Dr. Karsten Durst Prof. Dr. Jürgen Rödel Buildings and Lab/Office Space In the course of the completion of the new “Hörsaal- und Medienzentrum” the street names of campus Lichtwiese have been renamed since autumn 2013. Accordingly, the address of the Dean’s office as well as that of the Materials science building has been changed to Alarich-Weiss-Str. 2. The office building L1|08, where the groups of Prof. Albe, Prof. Hahn, Prof. Jaegermann, Prof. Krupke, Prof. Riedel, and Prof. Xu are hosted, have now the postal address Jovanka-Bontschits-Str. 2. In September 2013 we moved into our new lab and office building denoted as M3 which stands for “Molecules, Magnets and Materials”. In an official ceremonial act, the building was inaugurated in the presence of the TU President and Chancellor on October 29. The Functional Materials group of Prof. Gutfleisch as well as the Physics of Surfaces group of Prof. Stark have found their new homes in this state of the art and functional building. 8 Institute of Materials Science - Preface New M3 lab and office building. Honours, Awards and Special Achievements In 2013, the following precious awards were granted to faculty members of the materials science department: Prof. Fueß received an honorary doctorate of the University of Vilnius in Lithuania for his outstanding research and for his continuing and fruitful scientific collaboration with the university. Prof. Hahn was awarded with the Franklin Mehl Award of The Minerals, Metals and Materials Society (TMS), USA, for his exceptional research in Materials Science. Dr. Robert Dittmer received a young investigator award, namely the “Nachwuchspreis” of the “Deutsche Gesellschaft für Materialkunde” (DGM). Prof. Dr. Hartmut Fueß Preface Prof. Dr. Horst Hahn Dr. Robert Dittmer 9 At the suggestion of the Department of Materials and Geosciences, the TU Darmstadt has solemnly conferred Prof. Dr. Jean Etourneau, Professor Emeritus at the University of Bordeaux 1, the honorary doctorate. Thereby the TU Darmstadt recognizes his pioneering contributions to the field of materials chemistry and materials science as well as his great commitment to advance scientific communication and cooperation in Europe. TU-President Hans Jürgen Prömel (right) with TU-Honorary Doctor Prof. Jean Etourneau. Photo: Felipe Fernandes As usual, the annual awarding of the "MaWi Prize" formed part of the MaWi summer party. The 1st prize was awarded to Ruben Heid from the division PhM for his Diploma thesis on “Einfluss von gießtechnischen Prozessschwankungen auf das Eigenschaftsspektrum crashrelevanter Aluminium-Druckgusslegierungen;” 2nd prizes were awarded to Tim Niewelt from the division OF for his Diploma thesis about “Analyse von Defekten in kristallinem Silizium” and to Joachim Langner from the division EE for his Diploma thesis about “Ionische Flüssigkeiten als Elektrolyt, Co-Katalysator und Stabilisator in Brennstoffzellen“. The 3rd prize was awarded to Christian Lohaus for his Bachelor thesis about “Synthese verschiedener rußgeträgerter Pt-Ru-Au Katalysatoren und Untersuchung des Degradationsverhaltens.” Social Events and Awards As every year, our annual summer party was scheduled shortly before the summer break, being one of the most important social events of the Materials Science Institute. It has become a tradition to use this festivity to award the MaWi prize to the three best students having accomplished their Diploma or Master in the past winter semester. 10 Institute of Materials Science - Preface The 1st prize was awarded to Christoph Rakousky from the division EE for his diploma thesis “Neue Kohlenstoffkomponenten für Gasdiffusionsschichten. The award comes with prize money of € 500. 2nd prizes for Diploma with honours were awarded to Andreas Liess from the division EM and Maybritt Kühn from the division OF. Laura Ahmels from the division PhM and Hans Justus Köbler from the division ST were awarded for best Bachelor degree. In December 2013 we celebrated the year-end ceremony for all research groups, staff members and students, including the formal graduate celebration, where Bachelor, Master and PhD students received their certificates. The celebration including the social programme was organized by the Deanery´s team, in particular by PD Dr. Boris Kastening, Heinz Mohren, Dr. Silvia Faßbender and our workshop team. For the first time this ceremonial act took place in the new lecture hall and media centre, the “Hörsaal- und Medienzentrum” on the Lichtwiese campus. Students passing their Bachelor, Master and Diploma with honours in the past summer semester were awarded with the MaWi prize which will be given away twice a year from now on. Namely, Andreas Taubel from the division PoS was awarded for his Bachelor, Cornelia Hintze from the division DF for her FAME-Master, Heide Humburg from the division NAW and Michel Kettner from the division OF for their Master, and Jens Wehner from the division MM and Verena Pfeifer from the division OF for their Diploma. In the past summer semester four graduate students passed their PhD with honours. Robert Dittmer from the division NAW, Erwin Hildebrandt from the division DS, Falk Münch from the division MA, and Mahdi Seifollahi Bazarjani from the division DF received their PhD certificate with honours during the ceremonial act. Dean with Prize winners in the December awarding ceremony: Dr. E. Hildebrandt, J. Wehner, V. Pfeifer, A. Taubel, Prof. R. Riedel, C. Hintze, H. Humburg, M. Kettner, Dr. R. Dittmer, Dr. M. Seifollahi Bazarjani. On the following pages, this annual report shall provide you with some information on the most prominent research activities of the individual groups conducted in 2013. Prof. Ralf Riedel Dean of the Department Preface 11 Physical Metallurgy The research group Physical Metallurgy at the TU Darmstadt in the department of materials science works on the structure-property relationship of structural metallic materials and thin hard coatings, focusing on the mechanical properties on both macroscopic as well as microscopic length scales. The group is headed by Prof. Dr. Karsten Durst, who joined in Mai 2013 TU Darmstadt from an affiliation at FAU Erlangen-Nürnberg. The group utilizes and develops new testing methods for enhancing our understanding of the deformation mechanism of structural materials on all length scales. Of main interest are the mechanical properties of materials under various loading conditions (uniaxial, fatigue, wear or creep), specifically relating the macroscopic material response to the micromechanical properties at small length scales. New insights in the materials response are achieved by in-situ mechanical testing approaches, where the material is being mechanical loaded and the deformation is monitored by microscopic or spectroscopic means. Coupling the information of the materials microstructure with the processing condition and the mechanical properties, the group supports the development or enhancement of new structural materials and coatings. Currently the research deals with steels, Al-alloys, Cu and Ni-based alloys as well as a-C:H coatings and nickel-base superalloys. One important class of materials are so called ultrafine-grained or nanocrystalline materials, which are being processed by severe plastic deformation processes. The materials microstructure is strongly refined by these processes, leading to both strong and ductile materials. During processing, residual stresses can arise in the microstructure. The research currently focuses on post treatment conditions for adjusting the mechanical properties together with the residual stress for different applications. Residual stresses are also important for the application of hard coatings on ductile substrate. Together with partners, new processing conditions are being developed, which allow for a design of the coating with respect to residual stress and mechanical properties also under contact loading conditions. The determination of residual stress for both ultrafine-grained metals and amorphous carbon coatings using local methods is also shown as this years research highlight. Staff Members Head Prof. Dr. K. Durst Research Associates Dr. E. Bruder Prof. Dr. C. Müller Technical Personnel Ulrike Kunz Claudia Wasmund Petra Neuhäusel Sven Frank Secretaries Christine Hempel PhD Students Dipl.-Ing. Vanessa Kaune Dipl.-Ing. Thorsten Gröb Dipl.-Ing. Jan Scheil MSc. Farhan Javaid Dipl.-Ing. Jennifer Bödeker Dipl.-Ing. Jörn Niehuesbernd Dipl.-Ing. Christoph Schmid Diploma Students Frederik Brohmann Thorsten Gröb Anke Scherf Aletta Böcker Moritz Elsaß Master Students Aniruddh Das Jitendra Singh Rathore Adb Alaziz 12 Institute of Materials Science - Physical Metallurgy Bachelor Students Paul Braun Tobias Schmiedl Kim Bergner Oskar Kowalik Theresa Schütz Silke Innertsberger Romana Schwing Research Projects “Effect of Load Frequency on the Fatigue Life of Aluminum Wrought Alloys in the VHCFRegime”, joint project with SzM-Darmstadt within the DFG Priority Programm 1466, DFG, since 04/2010 “Microstructure and Mechanical Properties of Bifurcated Sheet Profiles”, in SFB 666 of the DFG “Integral Sheet Metal Design with Higher Order Bifurcations”, since 06/2005. “Technologies of Surface Modification of Bifurcated Profiles”, in SFB 666 of the DFG “Integral Sheet Metal Design with Higher Order Bifurcations”, since 06/2009. “Subsequent Formability of Bifurcated Profiles” in SFB 666 of the DFG “Integral Sheet Metal Design with Higher Order Bifurcations”, since 06/2013. “New Synthesis Methods top-down” in Priority Program LOEWE “Response Ressourcenschonende Permanentmagnete durch optimierte Nutzung seltener Erden“, since 01/2014 “Damage Mechanims in Carbon Layer Systems”, DFG since 12/2011 “Influence of Glass Topology and Medium Range Order on the Deformation Mechanism in Borosilcate Glasses – a Multiple Length Scale Approach”, DFG since 07/2012 DAAD scholarship Farhan Javaid since 07/2012 Publications [1] Depner-Miller, U., Ellermeier, J., Scheerer, H., Oechsner, M., Bobzin, K., Bagcivan, N., Brögelmann, T., Weiss, R., Durst, K., Schmid, C.: Influence of application technology on the erosion resistance of DLC coatings, Surface and Coatings Technology 237 (2013) pp. 284 [2] Ahmed, F., Krottenthaler, M., Schmid, C., Durst, K.: Assessment of stress relaxation experiments on diamond coatings analyzed by digital image correlation and micro-Raman spectroscopy, Surface and Coatings Technology 237 (2013) pp. 255 [3] Wheeler, J.M., Maier, V., Durst, K., Göken, M., Michler, J.: Activation parameters for deformation of ultrafine-grained aluminium as determined by indentation strain rate jumps at elevated temperature, Materials Science and Engineering A 585 (2013) pp. 108 [4] Ast, J., Durst, K: Nanoforming behaviour and microstructural evolution during nanoimprinting of ultrafine-grained and nanocrystalline metals, Materials Science and Engineering A 568 (2013) pp. 68 [5] Maier, V., Merle, B., Göken, M., Durst, K.: An improved long-term nanoindentation creep testing approach for studying the local deformation processes in nanocrystalline metals at room and elevated temperatures, Journal of Materials Research 28 (9) (2013) pp. 1177 Institute of Materials Science - Physical Metallurgy 13 [6] Krottenthaler, M., Schmid, C., Schaufler, J., Durst, K., Göken, M.: A simple method for residual stress measurements in thin films by means of focused ion beam milling and digital image correlation, Surface and Coatings Technology 215 (2013) pp. 247 [7] Schmid, C., Maier, V., Schaufler, J., Butz, B., Spiecker, E., Meier, S., Göken, M., Durst, K.: Highly resolved analysis of the chemistry and mechanical properties of an a-C:H coating system by nanoindentation and auger electron spectroscopy, Thin Solid Films 528 (2013) pp. 263 [8] Hay, J., Maier, V., Durst, K., Göken, M Strain-rate sensitivity (SRS) of nickel by instrumented indentation, Conference Proceedings of the Society for Experimental Mechanics Series 6 (2013) pp. 47 [9] Kriegsmann, A., Müller, C.: Richtungsabhängigkeit der Rissausbreitung bei einem gefügebedingten Übergang von rauigkeits- zu plastizitätsinduzierter Rissschließung an der Legierung Ti-6Al-4V, Mat.-wiss. u.Werkstofftech. 2013, 44, No. 9, 749-752 [10] Schäfer, S.; Abedini, S.; Groche, P.; Bäcker, F.; Ludwig, C.; Abele, E.; Jalizi, B.; Müller, C.; Kaune, V.; Verbindungstechniken durch die Technologie des SFB 666, In: Bauingenieur, Springer VDI-Verlag, Düsseldorf, Vol. 1 (2013), 8-13 [11] Ludwig, C.; Hammen, V.; Groche, P.; Kaune, V.; Müller, C.; Fertigung qualitätsoptimierter Spaltprofile durch Variation schnell änderbarer Prozessgrößen und deren Einfluss auf die Materialeigenschaften, Materialwissenschaft und Werkstofftechnik, Vol. 44 (2013), 601-611 [12] Karin, I.; Niehuesbernd, J.; Bruder, E.; Lipp, K.; Hanselka, H.; Müller, C.: FiniteElement analysis of a rolling contact model with anisotropic elastic material properties, Materialwissenschaft und Werkstofftechnik, Vol. 44, 2013, 298-303 [13] Niehuesbernd, J.; Müller, C.; Pantleon, W.; Bruder, E.: Quantification of local and global elastic anisotropy in ultrafine grained gradient microstructures, produced by linear flow splitting, Materials Science and Engineering A, Vol. 560, 2013, 273-277 [14] Steitz, M.; Scheil, J.; Müller, C.; Groche, P.: Effect of Process Parameters on Surface Roughness in Hammer Peening an Deep Rolling, Key Engineering Materials, 554-557 (2013), 1887-1901 [15] Scheil, J.; Müller, C.; Steitz, M.; Groche, P.: Influence of Process Parameters on Surface Hardening in Hammer Peening and Deep Rolling. Key Engineering Materials, 554557 (2013), 1819-1827 [16] Groche, P.; Steitz, M.; Engels, M.; Scheil, J.; Müller, C.; Bräuer, G.; Weigel, K.: Effizienzsteigerung im Werkzeugund Formenbau durch maschinelle Oberflächeneinglättung, EFB: Europäische Forschungsgesellschaft für Blechverarbeitung e.V., (2013) 1-119. ISBN-13: 978-3867763981 [17] Steitz, M.; Weigel, K.; Weber, M.; Scheil, J.; Müller, C.: Coating of deep rolled and hammer peened deep drawing tools, Advanced Materials Research, 769 (2013), 245-252 14 Institute of Materials Science - Physical Metallurgy Advanced Methods for the Determination of Residual Stresses in complex Material Systems J. Niehuesbernd, C. Schmid, E. Bruder, C. Müller and K. Durst Introduction Residual stresses are present in many engineering components such as complex shaped metallic profiles but also in thin protective coatings. These intrinsic stresses can originate from diverse processing steps during manufacturing of the component like e.g. high plastic deformation during forming processes of bulk materials or thermal mismatch between substrate and coating during deposition at elevated temperatures. Since residual stresses can strongly influence the lifetime and the overall performance of the final component in operation, the knowledge of their magnitude as well as proper measurement methods are crucial for reliable product design. Nowadays, residual stress measurement techniques such as the hole drilling method for bulk materials and thicker coatings or curvature measurement methods for thin amorphous films are frequently used and well established. However, these measurement techniques still suffer from certain disadvantages and limitations. The present article, which summarizes the main results of the publications by Niehuesbernd et al. and Schmid et al. [1,2], describes the measurement of residual stresses of two different material systems, a bulk material as well as a thin amorphous coating, using different advanced characterization methods. On the one hand, the hole drilling method in combination with Electron Back Scatter Diffraction (EBSD) measurements and Finite Element Modeling (FEM) is employed to assess the stress gradient within a graded and elastic anisotropic steel profile. The results are compared to the isotropic case to analyse the influence of texture and elastic anisotropy on the determination of the residual stress value. On the other hand, a method based on combined Focused Ion Beam milling (FIB) and Digital Image Correlation (DIC) is applied to determine the residual stress state of tungsten modified amorphous carbon coatings of tailored mechanical properties deposited on steel substrates. Moreover, the obtained properties of the coatings are correlated to the applied process parameters during deposition. Influence of gradients in the elastic anisotropy on the reliability of residual stresses determined by the hole drilling method Modern forming processes often introduce large strains and in most cases significant strain gradients in the material, which generally cause residual stresses. Since plastic deformation also leads to the development of crystallographic textures, the influence of these textures and texture gradients on Fig. 1: a) Function principle of linear flow splitting, determined residual stress distributions b) profile and defined coordinate system needs to be considered. Linear flow splitting (LFS) is a process which involves complex forming conditions with steep strain gradients and spacially varying deformation modes. By subjecting the edges of a sheet to Institute of Materials Science - Physical Metallurgy 15 Fig. 2: Orientation distribution functions of measurements in 50 µm, 200 µm and 1000 µm beneath the split surface. Only sections of the Euler space with a constant angle ϕ2 = 45° are shown. severe plasticdeformation flanges are produced, leading to profiles with a double-Y shape (Fig. 1). The heterogeneous material flow in combination with the severe strains leads to steep microstructure [3] and yield strength gradients (Fig. 3), as well as strong crystallographic textures and texture gradients in flange thickness direction [4,5]. In the present investigation the ferritic stainless steel X6Cr16 (AISI 430/ 1.4016) was examined. The initial sheet thickness was 2 mm and the flange length and thickness after LFS was 10 mm and 1 mm respectively. Orientation distribution funcions (ODF) obtained by EBSD on cross sections of the flanges revealed typical rolling textures with partial α-fibers (red/vertical) and γ-fibers (blue/horizontal) in near-surface layers (Fig. 2). With increasing distance to the split surface the texture intensity decreases significantly and the rolling texture vanishes while shear components like the Goss orientation ({110}<001>) appear. The orientation data obtained by EBSD was also used to calculate direction dependent elastic properties. By rotating the single Fig. 3: Approximated yield strength and Young’s crystal stiffness tensor of iron (C11 = 230.1 modulus in feed direction (TD) in dependence of the distance to the split surface. GPa, C12 = 134.6 GPa, C44 = 116.6 GPa, [6]) according to the measured grain orientations and averaging over all measurement points, the direction dependent Young’s Modulus can be determined. In the present investigation the geometric mean was utilized for averaging, which has proven to be a suitable approximation [5,7,8]. The Young´s modulus in feed direction (TD) steeply drops from 244 GPa in near-surface layers to approximately 212 GPa at the bottom surface (Fig. 3). Residual stress measurements were performed by the hole drilling method at the Fig. 4: Residual stress levels in feed direction (TD) flange top surface in combination with FEMfor the isotropic and the orthotropic case obtained by FE-modelling Simulations of the drilling process. 16 Institute of Materials Science - Physical Metallurgy The geometry of the flange and the hole was modeled using the commercial FE solver Abaqus. The flange was partitioned into 50 µm thick layers, which were assigned specific yield strengths and stiffness tensors, corresponding to the experimental data. The residual stress distribution was introduced by assigning each layer initial stress values in RD and TD. In order to obtain depth dependent strain data, 50 µm thick slices were removed in a series of steps and the resulting surface strains were acquired. These were compared to the measured ones and the initially assigned stresses were varied iteratively until the differences amounted to less than 0.5%. The same procedure was carried out for the elastic isotropic case to assess the impact of anisotropy on the determined residual stress values. The results of the FE-simulations of the drilling process reveal very high residual stress levels in the feed direction (TD) of the split profiles (Fig. 4). Nearly 800 MPa of tensile stress in a depth of 0.2 mm can be observed for the isotropic as well as for the anisotropic (orthotropic) case. Up to this depth the relaxations are dominated by plastic deformation in the vicinity of the hole, owing to the high residual stress levels. Therefore, the determined residual stresses in both case show the same behavior. In a depth between 0.3 mm and 0.4 mm the stress levels for the orthotropic model are about 20 % higher than the ones for the isotropic model. In this depth, the difference between the Young’s moduli of the two models is only 3 %. It is reasonable to assume, that the stiffer upper layers in the orthotropic model diminish the surface relaxation caused by the removal of a layer with a lower stiffness in the examined direction. This means that for the isotropic model the residual stresses in lower layers are highly underestimated. It is therefore concluded that for the hole drilling method anisotropic elastic properties do not only influence the determination of residual stresses in layers where anisotropy is present, but also in subjacent layers which might have isotropic properties. Residual stress measurement of thin amorphous coatings by means of FIB and DIC Residual stresses of thin amorphous coatings are commonly assessed by means of curvature measurement methods. These methods are based on the measurable change in curvature of the substrate due to deposition of a coating with intrinsic stresses. The residual stress state of the coating is then evaluated from the difference in curvature by use of Stoney’s equation [9]. However, in this approach the used substrate has to meet certain requirements i.e. it has to be a thin, elastically isotropic plate that is free to bend [10]. These substrates like e.g. thin flat silicon wafers are mostly not relevant for technical applications of hard coatings. A method capable to measure residual stresses of thin coatings, regardless of whether they are amorphous or crystalline, on substrates of technical relevance was proposed by Kang et al. [11]. This method is based on the relaxation of residual stresses by focused ion beam (FIB) milling and tracking of the resultant displacements by means of digital image correlation (DIC). The residual stress state in the coating is quantified by evaluation of the observed displacement fields by either analytical solutions or FE analysis using the elastic properties of the coating e.g. determined by Fig. 5: FIB cross-sections of the coating nanoindentation. In the literature different relaxation system CS2 revealing the basic structure geometries, like a single slot [11], annular trenches or [2]. Institute of Materials Science - Physical Metallurgy 17 pillars [12,13] are proposed and successfully applied to determine residual stresses of different kind of coating/substrate systems. Here, a similar method was applied to assess residual stresses of three different tungsten modified hydrogenated amorphous carbon (a-C:H:W) coatings CS1-CS3 with predefined hardness values, ranging from 10 up to 16 GPa. The a-C:H:W coatings with a thickness of 1.6 µm were deposited on polished disks of cold work tool steel 1.2379 by reactive unbalanced magnetron sputtering of a binder-free WC target in argon-ethine atmosphere using an industrial coating equipment. Sufficient adhesion of the coating was achieved by depositing an adhesive layer, consisting of different Cr- and WC-based layers. Fig. 5 exemplarily shows a FIB cross-sections of the coating revealing the basic structure consisting of adhesive layer and a-C:H:W functional layer which exhibits a weak columnar microstructure. In order to obtain three coatings of predefined hardness, negative bias voltage Ubias was adapted during deposition of the a-C:H:W layer according to a previously created regression model. This model was obtained in previous work by variation of four main process parameters of the used deposition process according to a central composite design and measuring their influence on the mechanical properties of the a-C:H:W coating by nanoindentation similar to the approach used in [14]. Fig. 6 shows the relation between the hardness of the coating and the process parameters ethane flow rate ((C2H2)) and Ubias and the good accordance between the measured hardness of the three different coatings with the predicted values by the regression model. Fig. 6: a) Regression model describing the relation between the For the assessment of the hardness of the coating and the process parameters (C2H2) and residual stress state of the Ubias with given positions of the selected coating systems CS1-CS3. b) of the coatings measured by nanoindentation in coatings, a double slit geometry Hardness comparison with predicted hardness values given by the regression as described in [15] was model [2]. employed for relaxation of internal stresses. The used relaxation geometry leads to a linear and symmetric displacement gradient across the remaining bar, facilitating the evaluation of the displacements and the quantification of the corresponding residual stress state. Therefore, two high resolution SEM images of the area of interest, one before and one after the Fig. 7: Experimental approach used for the determination of residual stresses exemplarily demonstrated on a hydrogenated amorphous carbon coating with residual compressive stresses of ca. -3 GPa. Clearly a symmetric and linear displacement gradient across the remaining bar can be observed. 18 Institute of Materials Science - Physical Metallurgy FIB milling procedure are taken. The milling of the double-slit geometry was conducted by an automated procedure, which has been optimized to reduce FIB damage and to attain high milling accuracy. Fig. 7 summarizes the experimental approach, exemplarily demon- Fig. 8: Representative displacement gradients of coating CS1-CS3 obtained by strated on a hydro- DIC and corresponding displacement vs. position plots of all five measurements per coating system for the evaluation of relief strain (slope of genated amorphous linear regression) [2]. carbon coating with residual compressive stresses of ca Table 1: Comparison of mechanical properties, relief strain and residual ca. -3 GPa. To enable stresses of the coatings [2]. simple calculation of coating H in GPa E in GPa εrel. in % σres. in GPa residual stresses by use CS1 9.4 ± 1.4 117 ± 12 0.34 ± 0.06 0.40 ± 0.07 of Hooke’s law, the CS2 12.2 ± 1.0 145 ± 13 0.54 ± 0.07 0.79 ± 0.11 applied milling geometry, depth d and CS3 14.8 ± 2.2 172 ± 20 0.92 ± 0.10 1.57 ± 0.18 distance w between the two slits, was previously optimized with regard to the coating thickness t. Further information about proper relaxation geometry can be found elsewhere [16]. A total of 5 measurements per coating were conducted for residual stress evaluation. Fig. 8 exemplarily shows one FIB milled double-slit geometry of each coating superimposed with the resulting displacement gradient obtained by DIC. A symmetric gradient across the remaining bar with maximum displacements at the edges is found. Since the bars expand, coatings are subjected to compressive residual stresses. Comparing all three gradients, it becomes evident that the resultant displacements increase from CS1 to CS3, i.e. with increasing Ubias. Additional to the gradients, the corresponding displacement vs. position plots of all five measurements per coating system are shown. The slopes of linear regression of the displacement vs. position plots (du/dx) give the respective relief strain εrel.. As already indicated by the displacements, the relief strain also increases considerably with increasing Ubias. For the coatings CS1-CS3, relief strain increases from 0.34 % to 0.92 % with corresponding residual stress values between -0.40 GPa to -1.57 GPa. Table 1 summarizes the determined properties of the coatings. Institute of Materials Science - Physical Metallurgy 19 Conclusions In the present article, two different approaches for the determination of residual stresses of complex material systems both based on material removal are presented. The methods were applied to a graded and elastically anisotropic steel profile and a thin amorphous coating. For the assessment of the stress gradient within the steel profile, the hole drilling method in combination with EBSD and FEM was employed and the influence of elastic anisotropy on the determined residual stress values was shown. Further, the residual stress state of three a-C:H:W coatings with tailored mechanical properties deposited on steel substrates were assessed by means of focused ion beam milling of a double-slit geometry, which causes the internal stresses to relax, and tracking of the resultant relief strain by digital image correlation. Here a direct correlation between the coating properties and the applied process parameters was obtained. The described methods are suitable for determination of residual stresses of both amorphous and elastically anisotropic metallic materials, giving important insight for further optimization of the materials. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] J. Niehuesbernd, E. Bruder, C. Müller, submitted to Adv. Mater. Res. (2013) C. Schmid, H. Hetzner, S. Tremmel, F. Hilpert, K. Durst, submitted to Adv. Mater. Res. (2013) T. Bohn, E. Bruder, C. Müller, J. Mater. Sci. 43 (2008), 7307-7312 E. Bruder, J. Mater. Sci. 47 (2012), 7751-7758 J. Niehuesbernd, C. Müller, W. Pantleon, E. Bruder, Mat. Sci. Eng. A 560 (2013), 273-277 J. J. Adams, D. S. Agosta, R. G. Leisure, H. Ledbetter, J. of Appl. Phys. 100 (2006), 113530 1-7 S. Matthies, M. Humbert, Phys. Status Solidi B 177 (1993), K47-K50 S. Matthies, M. Humbert, J. Appl. Crystallogr. 28 (1995), 254-266 G.G. Stoney, Proc. R. Soc. Lond. A 82 (1909), 172-175 R.P. Vinci, J.J. Vlassak, Annu. Rev. Mater. Sci. 26 (1996), 431-62 K. J. Kang, N. Yao, M. Y. He, A.G. Evans, Thin Solid Films 443 (2003), 71-77 A.M. Korsunsky, M. Sebastiani, E. Bemporad, Surf. Coat. Technol. 205 (2010), 2393-2403. M. Sebastiani, C. Eberl, E. Bemporad, G. M. Pharr, Mat. Sci. Eng. A 528 (2011), 7901– 7908 H. Hetzner, R. Zhao, S. Tremmel, S. Wartzack, in: K. D. Bouzakis, K. Bobzin, B. Denkena, M. Merklein (Eds.), Proceedings of the 10th International Conference THE ''A'' Coatings 2013, Shaker, Aachen, 2013, 39-49 [15] M. Krottenthaler, C. Schmid, J. Schaufler, K. Durst, M. Göken, Surf. Coat. Technol. 215 (2013), 247252 [14] F. Ahmed, M. Krottenthaler, C. Schmid, K. Durst, Surf. Coat. Technol. 237 (2013), 255–260 20 Institute of Materials Science - Physical Metallurgy Ceramics Group The emphasis in the ceramics group is on the correlation between microstructure and mechanical as well as functional properties. A number of processing methods are available in order to accomplish different microstructure classes, to determine their specific properties in an experiment and to rationalize these with straightforward modelling efforts. Thus, a materials optimization is afforded which allows effective interplay between processing, testing and modelling. In particular, new lead free piezoceramics and lead-free high-temperature dielectrics can be obtained and extensively characterized electrically and mechanically. The scientific effort can be grouped as follows: I. Conductivity of Oxides Dr. Till Frömling Modulation of conductivity of oxide ceramics is usually achieved by doping and temperature treatment in a large oxygen partial pressure range. However, electric and ionic conductivity can also be changed by mechanical modifications. In this research group conductivity is of oxide ceramics is modified by the following approaches a) Induction of dislocations: Dislocations are mechanically introduced into strontium titanate which can be plastically deformed even at room temperature. Changes of the electric and ionic conductivity are, amongst other methods, investigated by complex impedance spectroscopy and dcmeasurements. The aim of this project is to identify the defect chemical properties of dislocation cores in strontium titanate and related materials. b) Altering potential barriers in piezoelectric semiconductor materials: In this project Schottky-barriers and varistor material based on ZnO are investigated as a function of applied pressure. II. Development of new piezoceramics Dr. Wook Jo In response to the recent demands for environmental friendly piezoelectric materials for electrical and electronic applications, the principal focus of this group is the development of non-toxic piezoceramics with electromechanical performance comparable to their leadcontaining counterparts. Among all the potentially promising candidates special attention has been given to bismuth-based materials whose properties can be effectively tailored using the so-called morphotropic phase boundary (MPB) concept. Extensive compositional research has been performed on various bismuth-based solid solution systems that contain a MPB between separating different crystal symmetries of the members. To better understand the mechanisms governing the enhancement of electromechanical properties of materials and to make our search for alternative materials more effective fundamental scientific research on model systems have been performed in parallel to the compositional investigations. We employ various characterization techniques such as macroscopic dielectric, ferroelectric and ferroelastic property measurements as well as crystallographic structural analyses based on synchrotron and neutron diffractions, Raman, nuclear magnetic resonance, electron paramagnetic resonance spectroscopic techniques, and Institute of Materials Science - Ceramics Group 21 transmission electron microscopy. We are also simultaneously establishing thermodynamic and phenomenological models which are verified by the first principles calculations. Currently, we have extensive and active international collaborations with eminent ferroelectric groups throughout the world. In the last year, we also added work on KNNbased piezoceramics (collaborations with Prof. Ke Wang (Tsinghua University, China) and Dr. Ruiping Wang (AIST, Japan) and work on BT-based piezoceramics to our research scheme. III. Mechanical properties of ferroelectrics Dr. Kyle Webber The focus of this research group is understanding the mechanical properties of ferroelectric materials, particularly the influence of stress on the phase transformation behavior and ferroelasticity at high temperature. Research over the last year has centered around development of a high temperature fracture testing setup for characterizing crack growth resistance behavior of ferroelastic materials as well as utilizing the newly developed experimental arrangement for characterizing small signal dielectric, piezoelectric, and elastic properties under large mechanical, electrical and thermal fields as a function of frequency. Preliminary results have already given insight into the impact of stress on the depolarization temperature of ferroelectric Pb(Zr,Ti)O3, which is commonly used in actuation and sensing applications. In addition, the Emmy Noether research group, lead by Kyle Webber, began in June and has been working on relaxor/ferroelectric composites and mixed conducting cathode materials for solid oxide fuel cells. Both of these projects are focused on understanding the influence of stress on the functional properties. Currently, equipment is being developed to allow for the mechanical characterization of samples in a atmosphere with an adjustable oxygen particle pressure. Staff Members Head Prof. Dr. Jürgen Rödel Research Associates Dr. Till Frömling Dr. Wook Jo Dr. Jurij Koruza Dipl. Phys. Irene Mieskes Dr. Nikola Novak Dr. Eric Patterson Dr. Kyle Webber Dr. Ludwig Weiler Technical Personnel Dipl.-Ing. Gundel Fliß Dipl.-Ing. Daniel Isaia Michael Heyse Secretaries Roswita Geier Gila Völzke PhD Students M. Sc. Matias Acosta M. Sc. Azatuhi Ayrikyan Dipl.-Ing. Raschid Baraki Dipl.-Ing. Martin Blömker Dipl.-Ing. Laetitia Carrara Dipl.-Ing. Robert Dittmer Dipl.-Phys. Daniel Franzbach M. Sc. Philipp Geiger Dipl.-Ing. Claudia Groh Dipl.-Ing. Christine Jamin Dipl.-Ing. Markus Jung Dipl.-Ing. Eva Sapper Dipl.-Ing. Florian Schader Dipl.-Phys. Deborah Schneider Dipl.-Ing. Yohan Seo M. Sc. Jiadong Zang 22 Institute of Materials Science - Ceramics Group Diploma/ Bachelor/Master Students David Brandt Johannes Dingeldein Shenshen He Heide Humburg Manuel Kloos Malte Vögler Research Fellow Dr. Ke Wang (AvH) Dr. Haibo Zhang (AvH) Guest Scientists Prof. Dr. Satoshi Wada Prof. Dr. Derek Sinclair Prof. Dr. Mario Maglione Dr. Philipp Veber Dr. Ruiping Wang Dr. Akira Ando Dr. Soon-Jong Jeong Prof. Dr. Chae Ill Cheon Research Projects Processing of textured ceramic actuators with high strain (SFB 595, 2003–2014) Mesoscopic and macroscopic fatigue in doped ferroelectric ceramics (SFB 595, 2003–2014) Development of new lead –free piezoceramics (ADRIA, state funding, 2008-2014) Development of new high-temperature piezoceramics (ADRIA, state funding, 2008-2013) Stress and strain fields in ferroelectrics (Graduate school “computational engineering” 20092017) High-temperature dielectrics (DFG 2010-2013) Mechanical compliance at phase transition points in lead-free ferroelectrics (DFG 20112014) Lead-free piezoelectric single crystals with high strain: orientation dependence, polarization rotation and morphotropic phase boundaries (DFG 2011-2014) Energy absorption of ZnO varistors (DFG 2011-2014) Ag-based electrical switches (state of Hesse / Umicore) Emmy Noether Program: The Influence of Mechanical Loads on the Functional Properties of Perovskite Oxides (DFG 2013-2018) Institute of Materials Science - Ceramics Group 23 Publications [1] Jamin, Christine ; Rasp, Tobias ; Kraft, Torsten ; Guillon, Olivier : Constrained sintering of alumina stripe patterns on rigid substrates: Effect of stripe geometry. [Online-Edition: http://dx.doi.org/10.1016/j.jeurceramsoc.2013.06.016] In: Journal of the European Ceramic Society, 33 (15-16) pp. 3221-3230. ISSN 09552219 [Artikel], (2013) [2] Yao, Fang-Zhou ; Glaum, Julia ; Wang, Ke ; Jo, Wook ; Rödel, Jürgen ; Li, Jing-Feng : Fatigue-free unipolar strain behavior in CaZrO3 and MnO2 co-modified (K,Na)NbO3-based lead-free piezoceramics. [Online-Edition: http://dx.doi.org/10.1063/1.4829150] In: Applied Physics Letters, 103 (19) 192907(1-4). ISSN 00036951, [Artikel], (2013) [3] Zhukov, Sergey ; Genenko, Yuri A. ; Acosta, Matias ; Humburg, Heide ; Jo, Wook ; Rödel, Jürgen ; von Seggern, Heinz : Polarization dynamics across the morphotropic phase boundary in Ba(Zr0.2Ti0.8)O3x(Ba0.7Ca0.3)TiO3 ferroelectrics. [Online-Edition: http://dx.doi.org/10.1063/1.4824730] In: Applied Physics Letters, 103 (15) 152904(1-5). ISSN 00036951, [Artikel], (2013) [4] Kling, Jens ; Jo, Wook ; Dittmer, Robert ; Schaab, Silke ; Kleebe, Hans-Joachim ; Zhang, S. : Temperature-Dependent Phase Transitions in the Lead-Free Piezoceramics (1 - x y)(Bi1/2Na1/2)TiO3-xBaTiO3-y(K0.5Na0.5)NbO3Observed byin situTransmission Electron Microscopy and Dielectric Measurements. [Online-Edition: http://dx.doi.org/10.1111/jace.12493] In: Journal of the American Ceramic Society, 96 (10) pp. 3312-3324. ISSN 00027820 [Artikel], (2013) [5] Seo, Yo-Han ; Vögler, Malte ; Isaia, Daniel ; Aulbach, Emil ; Rödel, Jürgen ; Webber, Kyle G. : Temperature-dependent R-curve behavior of Pb(Zr1−xTix)O3. [Online-Edition: http://dx.doi.org/10.1016/j.actamat.2013.07.020] In: Acta Materialia, 61 (17) pp. 6418-6427. ISSN 13596454, [Artikel], (2013) [6] Amaral, Luís ; Jamin, Christine ; Senos, Ana M. R. ; Vilarinho, Paula M. ; Guillon, Olivier : Constrained sintering of BaLa4Ti4O15 thick films: Pore and grain anisotropy. [Online-Edition: http://dx.doi.org/10.1016/j.jeurceramsoc.2013.01.031] In: Journal of the European Ceramic Society, 33 (10) pp. 1801-1808. ISSN 09552219 [Artikel], (2013) [7] Cumming, D. J. ; Sebastian, Tutu ; Sterianou, Iasmi ; Rödel, Jürgen ; Reaney, Ian M.: Bi(Me)O3-PbTiO3 high TC piezoelectric multilayers. [Online-Edition: http://dx.doi.org/10.1179/1753555713Y.0000000067] In: Materials Technology: Advanced Performance Materials, 28 (5) pp. 247-253. ISSN 10667857, [Artikel], (2013) 24 Institute of Materials Science - Ceramics Group [8] Glaum, Julia ; Simons, Hugh ; Acosta, Matias ; Hoffman, Mark ; Feteira, A. : Tailoring the Piezoelectric and Relaxor Properties of (Bi1/2Na1/2)TiO3-BaTiO3via Zirconium Doping. [Online-Edition: http://dx.doi.org/10.1111/jace.12405] In: Journal of the American Ceramic Society n/a-n/a. ISSN 00027820, [Artikel], (2013) [9] Schader, Florian H. ; Aulbach, Emil ; Webber, Kyle G. ; Rossetti, George A. : Influence of uniaxial stress on the ferroelectric-to-paraelectric phase change in barium titanate. [Online-Edition: http://dx.doi.org/10.1063/1.4799581] In: Journal of Applied Physics, 113 (17) 174103(1-9). ISSN 00218979, [Artikel], (2013) [10] Tran, Vu Diem Ngoc ; Dinh, Thi Hinh ; Han, Hyoung-Su ; Jo, Wook ; Lee, Jae-Shin : Lead-free Bi1/2(Na0.82K0.18)1/2TiO3 relaxor ferroelectrics with temperature insensitive electrostrictive coefficient. [Online-Edition: http://dx.doi.org/10.1016/j.ceramint.2012.10.046], In: Ceramics International, 39 (Supplement 1) S119-S124. ISSN 02728842, [Artikel], (2013) [11] Jo, Wook ; Daniels, John E. ; Damjanovic, Dragan ; Kleemann, Wolfgang ; Rödel, Jürgen : Two-stage processes of electrically induced-ferroelectric to relaxor transition in 0.94(Bi1/2Na1/2)TiO3-0.06BaTiO3. [Online-Edition: http://dx.doi.org/10.1063/1.4805360] In: Applied Physics Letters, 102 (19) 192903(1-4). ISSN 00036951, [Artikel], (2013) [12] Han, Hyoung-Su ; Jo, Wook ; Kang, Jin-Kyu ; Ahn, Chang-Won ; Won Kim, Ill ; Ahn, Kyoung-Kwan ; Lee, Jae-Shin : Incipient piezoelectrics and electrostriction behavior in Sn-doped Bi1/2(Na0.82K0.18)1/2TiO3 lead-free ceramics. [Online-Edition: http://dx.doi.org/10.1063/1.4801893] In: Journal of Applied Physics, 113 (15) 154102(1-6). ISSN 00218979, [Artikel], (2013) [13] Schwarz, Sebastian ; Guillon, Olivier : Two step sintering of cubic yttria stabilized zirconia using Field Assisted Sintering Technique/Spark Plasma Sintering. [Online-Edition: http://dx.doi.org/10.1016/j.jeurceramsoc.2012.10.002] In: Journal of the European Ceramic Society, 33 (4) pp. 637-641. ISSN 09552219 [Artikel], (2013) [14] Seo, Yo-Han ; Franzbach, Daniel J. ; Koruza, Jurij ; Benčan, Andreja ; Malič, Barbara ; Kosec, Marija ; Jones, Jacob L. ; Webber, Kyle G. : Nonlinear stress-strain behavior and stress-induced phase transitions in soft Pb(Zr_{1−x}Ti_{x})O_{3} at the morphotropic phase boundary. [Online-Edition: http://dx.doi.org/10.1103/PhysRevB.87.094116] In: Physical Review B, 87 (9) 094116(1-11). ISSN 1098-0121, [Artikel], (2013) Institute of Materials Science - Ceramics Group 25 [15] Rödel, Jürgen ; Seo, Yo-Han ; Benčan, Andreja ; Malič, Barbara ; Kosec, Marija ; Webber, Kyle G. : R-curves in transformation toughened lead zirconate titanate. [Online-Edition: http://dx.doi.org/10.1016/j.engfracmech.2012.06.023] In: Engineering Fracture Mechanics, 100 pp. 86-91. ISSN 00137944, [Artikel], (2013) [16] Dittmer, Robert ; Webber, Kyle G. ; Aulbach, Emil ; Jo, Wook ; Tan, Xiaoli ; Rödel, Jürgen : Electric-field-induced polarization and strain in 0.94(Bi1/2Na1/2)TiO3–0.06BaTiO3 under uniaxial stress. [Online-Edition: http://dx.doi.org/10.1016/j.actamat.2012.11.012] In: Acta Materialia, 61 (4) pp. 1350-1358. ISSN 13596454, [Artikel], (2013) [17] Levin, I. ; Reaney, I. M. ; Anton, Eva-Maria ; Jo, Wook ; Rödel, Jürgen ; Pokorny, J. ; Schmitt, L. A. ; Kleebe, H-J. ; Hinterstein, Manuel ; Jones, J. L. : Local structure, pseudosymmetry, and phase transitions in Na_{1/2}Bi_{1/2}TiO_{3}– K_{1/2}Bi_{1/2}TiO_{3} ceramics. [Online-Edition: http://dx.doi.org/10.1103/PhysRevB.87.024113] In: Physical Review B, 87 (2) 024113(1-11). ISSN 1098-0121, [Artikel], (2013) [18] Zang, Jiadong ; Jo, Wook ; Rödel, Jürgen : Quenching-induced circumvention of integrated aging effect of relaxor lead lanthanum zirconate titanate and (Bi1/2Na1/2)TiO3-BaTiO3. [Online-Edition: http://dx.doi.org/10.1063/1.4788932] In: Applied Physics Letters, 102 (3) 032901. ISSN 00036951, [Artikel], (2013) [19] Dittmer, Robert ; Webber, Kyle G. ; Aulbach, Emil ; Jo, Wook ; Tan, Xiaoli ; Rödel, Jürgen : Optimal working regime of lead–zirconate–titanate for actuation applications. [Online-Edition: http://dx.doi.org/10.1016/j.sna.2012.09.015] In: Sensors and Actuators A: Physical, 189 pp. 187-194. ISSN 09244247, [Artikel], (2013) [20] Salje, Ekhard K. H. ; Carpenter, Michael A. ; Nataf, Guillaume F. ; Picht, Gunnar ; Webber, Kyle G. ; Weerasinghe, Jeevaka ; Lisenkov, S. ; Bellaiche, L. : Elastic excitations in BaTiO_{3} single crystals and ceramics: Mobile domain boundaries and polar nanoregions observed by resonant ultrasonic spectroscopy. [Online-Edition: http://dx.doi.org/10.1103/PhysRevB.87.014106] In: Physical Review B, 87 (1) 014106(1-10). ISSN 1098-0121, [Artikel], (2013) [21] Uhlmann, Ina ; Hawelka, Dominik ; Hildebrandt, Erwin ; Pradella, Jens ; Rödel, Jürgen: Structure and mechanical properties of silica doped zirconia thin films. [Online-Edition: http://dx.doi.org/10.1016/j.tsf.2012.08.007] In: Thin Solid Films, 527 pp. 200-204. ISSN 00406090, [Artikel], (2013) 26 Institute of Materials Science - Ceramics Group Rocking Curve X-Ray Diffraction for Quantifying Dislocations in SrTiO3 Single Crystals Eric Patterson, Till Frömling, Kyle Webber, and Jürgen Rödel Introduction: Strontium titanate (SrTiO3 or STO) is frequently described as a model perovskite system and its electrical properties have been studied over a wide range of conditions, including oxygen partial pressure, temperature and electric field [1]. Single crystal STO shows a rare ability among oxide materials to plastically deform when compressively stressed. It also undergoes a ductile to brittle to ductile transition as a function of changing temperature that has previously been shown [2-5]. Because it remains cubic over a wide range of temperatures, the change in mechanical properties cannot be tied to phase transitions. Current investigations on this system are directed towards understanding the relationship between this plastic strain behavior, the dislocation network developed, and changes that arise in the electrical conductivity of these perovskite single crystals. In previous work high conductivity paths along dislocations were shown in STO single crystals via conductive atomic force microscopy [6]. In order to analyze these properties, it is therefore essential to have an accurate method to reliably quantify the plastic strain during deformation and correlate this to a change in the dislocation density in a crystal after a given amount of deformation. By investigating the relationship between dislocations and conductivity in STO, we may be able to ascertain the mechanism of changes in electromechanical properties in these materials. Experimental Procedure: In this work, strontium titanate single crystals oriented along the (001) growth direction with dimensions of 4x4x8 mm3 (Alineason Materials Technology, GmbH) and optical quality polished sides were examined. Compressive loading was done with a load frame (Zwick/Roell Z030) with a loading rate of 25 N/s in a displacement controlled manner using 32 µm limited steps, which were repeated 3 times in order to achieve approximately 1% plastic strain. The stress-induced uniaxial displacement of the specimen was measured by a linear variable differential transformer (LVDT). The deformations were peformed in a range of temperature from 25°C - 450°C. The samples were examined optically by polarized light microscopy to observed the birefringence around the dislocation slip planes. X-ray diffraction (XRD) rocking curve measurments were made before and after deformation of the samples to observe changes in dislocation density following the methodolgy of Ayers, et al [7]. The XRD rocking curve technique for dislocation density determination utilizes a positionlocked source with a Bartel’s monochromator attachment to focus the emerging x-ray beam to a width of a few arcseconds. The theta is adjusted by tilting the sample and the detector is moved as normal, albeit with an upper 2 limit of approximately 152°. Samples were mounted to a goniometer head and aligned flat with respect to the diffraction plane using a polarized light setup, such that the X-ray beam crosses lengthwise across the center of one of the sample faces. The sample () and detector (2) were next rotated to the selected diffraction planes, i.e. (001), (002), (003), and (004). Since the faces of the STO single crystals are <001> oriented and not polycrystalline, a non-symmetric arrangement of -2 angles must be selected for all other peaks, i.e. (014), (024), (233), and (224). Additionally, in order to reach the higher equivalent angles of necessary for subsequent Institute of Materials Science - Ceramics Group 27 density calculations, a motorized stage to control was introduced and rotated to scan the (233) and (224) planes at 33.69° and 45°, respectively. The sample itself is finally rotated over a small range of angles around the peak location for the given plane selected ( = -0.2° to 0.2°). The resulting peak is fitted via Gaussian or Pseudo-Voigt fit, depending on symmetry and number of peaks and the full width at half maximum (FWHM or ) is determined. Ideally only one peak should be present for a single crystal, however, after deformation multiple peaks can sometimes be observed due to increase and arrangement of the dislocation network. In Figure 1, a clear broadening of the (001) after deformation of approximately 0.25% plastic strain is shown. These measurements were made for eight diffraction planes on each sample with a step size of 0.001° and a dwell time of 10 seconds per step. In the cases where angle rotation was needed, two equivalent scans were taken at 90± ° in order to account for differences in edges and potential cracks intercepted by the beam at these rotated angles. a) b) Figure 1: a) Schematic of Bartel’s monochromator and b) an example rocking curve result for a single reflection before and after compression testing A linear regression is fitted to a plot of FWHM2 as a function tan2, from the slope and intercept of these lines two independent dislocation density values can be calculated. The slope is associated with the strain around the dislocation and the intercept is related to the angular rotation around the dislocation core. Results and Discussion: The polarized light microscopy revealed an increase in the density and uniformity of the slip lines, as seen in Figure 2 for the (100) and (010) polished faces of the crystals deformed at 25° and 300°C. The dark lines in the image are cracks that developed during loading and unloading. a) b) c) 25° C (100 ) (010 ) 300° C (100 ) (010 ) Figure 2: a) Deformation of single crystal STO at various temperatures with resulting PLM at b) 25°C and c) 300°C 28 Institute of Materials Science - Ceramics Group From the stress-strain plots, it is clear that with increasing temperature, the yield point of the samples is decreased dramatically. It was lowered nearly by half from ~140MPa at 25°C to ~75MPa at 300°C. Next XRD rocking curve measurements were performed on the samples and dislocation density was calculated based on the results of linear regression, as shown for the examples in Figure 3 below. a) b) Figure 3: Measured FWHM2 as a function of tan2 same 450°C crystal and c) PLM images for the 450°C crystal. c) 450° C (100 (010 ) b) two faces ) of the -deformed, 25°C, and 300°C A clear difference was found between non-deformed samples and those deformed to 1% plastic strain. There was both an increase in the intercept value and in the slope compared to the average of non-deformed samples. From further calculations, dislocation content was shown to increase by 4x from 2.1x108 cm-2 in the initial state to 8.2x108 cm-2 after 1% strain at 25°C. At 300°C, the dislocation content was increased even further to approximately 9.7x108 cm-2. At 450°C, however, a different behavior was found depending on the side of the crystal examined. In this case the (010) side was subsequently discovered to bulge in the center, whereas the (100) face remained flat. The (100) side gives a dislocation density value approximately the same as the 300°C case. This makes sense given the higher degree of cracking that is apparent in the 450°C sample (Figure 3 c)). The XRD technique will next be confirmed with further samples and with an etch pit density evaluation, both at the surface and in the interior of the crystal. Now that this method of increasing dislocations has been shown, it must be connected to changes in the conductivity through impedance spectroscopy and oxygen diffusion using 18O annealing and ToF SIMS analysis. This will be performed on these undoped samples and on Fe-doped single crystals. References 1 2 3 4 5 6 7 De Souza et al., Z. Metallkd. 94 [3], 218-225 (2003) Brunner et al., J. Am. Ceram. Soc., 84 [5], 1161–63 (2001) Brunner, Acta Materialia 54, 4999-5011 (2006) Brunner, Mat. Sci. Eng. A, 483-484 521-524 (2008) Yang, et al., J. Am. Ceram. Soc., 94 [9] 3104–3111 (2011) Szot, et al., Nature Materials 5, 312 - 320 (2006) Ayers, et al., J. Crystal Growth, 135, 71-77 (1994) Institute of Materials Science - Ceramics Group 29 Electronic Material Properties The Electronic Materials division introduces the aspect of electronic functional materials and their properties into the Institute of Materials Science. The associated research concentrates on the characterization of various classes of materials suited for implementation in information storage and organic and inorganic electronics. Four major research topics are presently addressed: Electronic and optoelectronic properties of organic semiconductors. Charge transport in inorganic semiconductor devices. Charge transport and polarization in organic and inorganic dielectrics. Photo- and photostimulated luminescence in inorganic phosphors. For novel areas of application a worldwide interest exists in the use of organic semiconductors in electronic and optoelectronic components, such as transistors and lightemitting diodes. So far, multicolour and full colour organic displays have been implemented in commercially available cameras, car-radios, PDAs, mp3-players and even television sets. Organic devices reaching further into the future will be simple logic circuits, constituting the core of communication electronics such as chip cards for radio-frequency identification (RFID) tags and maybe one day flexible electronic newspapers where the information is continuously renewed via mobile networks. In view of the inevitable technological development, the activities of the group are concerned with the characterization of organic material properties regarding the performance of organic electronic and optoelectronic devices. The major aspect deals with the charge carrier injection and transport taking place in organic field-effect transistors (OFETs) and organic light-emitting diodes (OLEDs). In particular, the performance of unipolar and ambipolar light-emitting OFETs and the stability of OFETs and OLEDs are subjects of recent investigations. To conduct these demanding tasks, various experimental techniques for device fabrication and characterization are installed. Besides basic electric measurement setups, a laser spectroscopy setup used for time-of-flight as well as for life-time measurements and a Kelvin-probe atomic force microscope to visualize the potential distribution of organic devices with nanometer resolution are available. Even though organic electronics is an emerging field especially for consumer electronics applications today's electronic devices still mainly rely on conventional silicon technology. While organic semiconductors have excellent optoelectronic properties they in general suffer from low charge carrier mobilities limiting the switching rates in organic transistors. Yet, metal oxides like ZnO, InZnO (IZO) or InGaZnO (IGZO) can bridge the gap between the high mobility semiconductors like silicon and the low mobility organic semiconductors. Using metal-organic precursors or nanoparticulate dispersions easy processing procedures like spin-coating or printing can be applied and yield rather high field-effect mobilities in the order of 1-10 cm²V-1s-1 for the produced thin film transistors (TFTs). Current research activities in the group concentrate on the optimization of the processing procedures especially the decrease of annealing temperatures is desired to make the processes compatible with organic substrates. Furthermore, the influence of the layer morphology and the role of the gas atmosphere for the device performance as well as stability issues are investigated. 30 Institute of Materials Science – Electronic Material Properties In the field of polymer electrets current research comprises the characterization of surface charge distribution, charge stability, and charge transport properties of fluoropolymers, as well as their applications in acoustical transducers. Present investigations of charge transport and polarization in organic dielectrics are directed towards the basic understanding of polarization buildup and stabilization in PVDF and in novel microporous dielectrics. Latter are scientifically interesting as model ferroelectric polymers. Moreover, the fatigue behaviour of electrically stressed inorganic PZT ceramics is investigated. The focus lies on preventing the operational fatigue of ferroelectric devices due to cyclic and static electrical stress. The available equipment includes poling devices, such as corona and high voltage setups, and a thermally stimulated current setup to investigate the energetic trap structure in dielectrics as well as the thermal charging and discharging under high electric fields. In addition, the laser induced pressure pulse (LIPP) method allows to investigate the spatial distribution of stored charges in organic as well as in inorganic ferroelectrics. The field of photoluminescent and photostimulated luminescent (PSL) materials (phosphors) is concerned with the synthesis and characterization of suited inorganic compounds used as wavelength converters in fluorescent lamps and in scintillating and information storing crystals. Present work is focused on x-ray detection materials, providing improved resolution and high PSL-efficiency needed in medical imaging. In particular the storage phosphors CsBr:Eu2+ and BaFBr:Eu2+ are under investigation. Research is concentrated on the influence of humidity on the sensitivity of CsBr:Eu2+. Before and after the treatment the materials are studied by means of spectroscopic methods as well as scanning electron microscopy. The exchange of water during the thermal treatment is measured in situ by thermal analysis methods. New synthesis methods for BaFBr:Eu 2+ used in commercial image plates are of interest and new synthesis routes will be tested for other storage phosphors and scintillators. On the one hand the mechanism of PSL-sensitization, which is found to be mainly due to the incorporation of oxygen and water, is investigated. On the other hand the implementation of BaFBr:Eu2+ powders into organic binders in order to form image plates is in the focus of the work. In the field of scintillators undoped and doped CsI is investigated concerning the afterglow. This afterglow is unfavourable in medical applications like CT where a series of images is made in a very short time. The task is to find the physical reason for this afterglow and a way to suppress it. Staff Members Head Prof. Dr.-Ing. Heinz von Seggern Research Associates Dr. Andrea Gassmann Dr. Joachim Hillenbrand Dr. Sergej Zhukov Dr. Corinna Hein Dr. Emanuelle Reis Simas Dr. Jörg Zimmermann Technical Personnel Gabriele Andreß Sabine Hesse Helga Janning Bernd Stoll Secretary Gabriele Kühnemundt Institute of Materials Science – Surface Science 31 PhD Students Tobias Könyves-Toth Fabian Knoch Oili Pekkola Riitta Savikoski Elmar Kersting Paul Mundt Florian Pfeil Henning Seim Bachelor Students Frank Löffler Florian Weyland Stefan Schlißke Master Students Ralph Dachauer Guest Scientists Juliana Eccher Dr. Anatoli Popov Prof. Dr. Sergei Fedosov Prof. Dr. Lucas F. Santos Research Projects Fatigue of organic semiconductor components (SFB 595 (DFG), 2003-2014) Phenomenological modelling of bipolar carrier transport in organic semiconducting devices under special consideration of injection, transport and recombination phenomena (SFB 595 (DFG), 2003-2014) Polarization and charge in electrically fatigued ferroelectrics (SFB 595 (DFG), 2006-2014) Development and optimization of tuneable optical filters and VCSEL based on piezoelectric and electret actuators (TICMO Graduiertenkolleg 1037, 2007-2013) Development of organic piezo sensors (LOEWE AdRIA 26200026, 2008-2014) Thin film dielectrics for high performance transistors (DFG, 2012-2015) Development of gate insulators for organic field effect transistors exploiting self-assembly of block-copolymers (IDS-FunMat (EU), 2012-2015) Piezoelectric properties of ferroelectrics (DFG, 2012-2015) Preparation and characterization of metal-oxide field-effect transistors (MerckLab, 20092015) High resolution, transparent image plates based on the storage phosphor CsBr:Eu2+ (DFG, 2013-2015) Metal oxide based field-effect transistors with top gate geometry (Helmholtz Virtual Institute, 2012-2017) 32 Institute of Materials Science – Surface Science Publications [1] Order Induced Charge Carrier Mobility Enhancement in Columnar Liquid Crystal Diodes Eccher, Juliana; Faria, Gregorio C.; Bock, Harald; Seggern, Heinz; Bechtold, Ivan H. ACS APPLIED MATERIALS & INTERFACES Volume: 5 Issue: 22 Pages: 11935-11943 Published: NOV 27 2013 [2] Molecular Origin of Charge Traps in Polyfluorene-Based Semiconductors Faria, Gregorio C.; deAzevedo, Eduardo R.; von Seggern, Heinz MACROMOLECULES Volume: 46 Issue: 19 Pages: 7865-7873 Published: OCT 8 2013 [3] Polarization dynamics across the morphotropic phase boundary in Ba(Zr0.2Ti0.8)O-3x(Ba0.7Ca0.3)TiO3 ferroelectrics Zhukov, Sergey; Genenko, Yuri A.; Acosta, Matias; Humburg, Heide; Jo, Wook; Roedel, Juergen; von Seggern, Heinz APPLIED PHYSICS LETTERS Volume: 103 Issue: 15 Article Number: 152904 Published: OCT 7 2013 [4] Continuum modeling of charging process and piezoelectricity of ferroelectrets Xu, Bai-Xiang; von Seggern, Heinz; Zhukov, Sergey; Gross, Dietmar JOURNAL OF APPLIED PHYSICS Volume: 114 Issue: 9 Article Number: 094103 Published: SEP 7 2013 [5] Self-consistent model of polarization switching kinetics in disordered ferroelectrics Genenko, Yuri A.; Wehner, Jens; von Seggern, Heinz JOURNAL OF APPLIED PHYSICS Volume: 114 Issue: 8 Article Number: 084101 Published: AUG 28 2013 [6] Transit phenomena in organic field-effect transistors through Kelvin-probe force microscopy. Melzer, Christian; Siol, Christopher; von Seggern, Heinz Advanced materials (Deerfield Beach, Fla.) Volume: 25 Issue: 31 Pages: 4315-9 Published: 2013Aug-21 (Epub 2013 Apr 29) [7] A new method to invert top-gate organic field-effect transistors for Kelvin probe investigations Kehrer, Lorenz. A.; Feldmeier, Eva. J.; Siol, Christopher.; Walker, Daniel; Melzer, Christian; von Seggern, Heinz APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING Volume: 112 Issue: 2 Pages: 431-436 Published: AUG 2013 [8] High-performance n-channel thin-film transistors with acene-based semiconductors Fapei Zhang; Melzer, Christian; Gassmann, Andrea.; von Seggern, Heinz; Schwalm, Thorsten; Gawrisch, Christian; Rehahn, Matthias Organic Electronics. Materials, Physics, Chemistry and Applications Volume: 14 Issue: 3 Pages: 888-96 Published: March 2013 Institute of Materials Science – Surface Science 33 [9] Comparative study of the luminescence properties of macro- and nanocrystalline MgO using synchrotron radiation Popov, Anatoli. I.; Shirmane, Liana; Pankratov, Vladimir.; Lushchik , A; Kotlov, Aleksei, Serga, V. E.; Kulikova L. D.; Chikvaidze; Zimmermann, Jörg; NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS Volume: 310 Pages: 23-26 Published: SEP 1 2013 [10] Eu2+-doped csbr photostimulable x-ray storage Phosphors — analysis of defect structure by High-frequency epr Peter Jakes, Jörg Zimmermann, Heinz von Seggern, Andrew Ozarowski, Johan van Tol and Rüdiger-A. Eichel, FUNCTIONAL MATERIALS LETTERS, Vol. 7, No. 1 (2013) 1350073 Published: Dec 2013 34 Institute of Materials Science – Surface Science The influence of triplet excitons on the lifetime of polymer-based organic light emitting diodes Oili Pekkola, Andrea Gassmann, and Heinz von Seggern In an organic light emitting diode (OLED) the ratio of singlet to triplet excitons formed is 1:3. In fluorescent devices the radiative decay of triplet excitons is forbidden by the spin selection rules, and consequently only the singlet excitons decay radiatively. The high concentration of non-radiatively decaying triplet excitons, combined with their long lifetimes on the order of several µs to ms [1,2], arises the question about the influence of the triplet excitons on the lifetime of fluorescent OLEDs. In the present work, the concentration of triplet excitons in a Poly(p-phenylene vinylene) (PPV)-based polymer is deliberately increased in order to investigate the influence of a higher concentration of triplets on the degradation of the diodes. The increase in concentration is achieved by converting part of the polymer singlet excitons to triplets. This is done by blending the polymer with a triplet sensitizer additive, an organometallic compound containing a platinum atom. The first excited singlet state of the sensitizer molecule lies energetically lower than that of the polymer, which allows for a singlet exciton transfer from the polymer to the sensitizer. On the sensitizer, a fast intersystem crossing takes place, facilitated by the weakened spin selection rules due to the presence of the heavy metal atom. The first excited triplet state of the sensitizer lies higher than that of the polymer, and the triplet exciton can be subsequently transferred back to the polymer. The energetic scheme of the complete singlet-to-triplet conversion is illustrated in Fig. 1. Figure 1 Energy scheme showing the singlet-to-triplet conversion processes. First, a singlet exciton energy transfer (ET) from OC3C8-PPV to PtOEPK takes place, followed by an intersystem crossing (ISC) to the PtOEPK first excited triplet state. The triplet exciton is subsequently transferred back to OC3C8-PPV, which has an energetically lower first excited triplet state. All presented devices are polymer-based OLEDs with a Poly(2-propoxy-5-(2'ethylhexyloxy)-phenylene (OC3C8-PPV) as the active material. In the sensitized diodes, the polymer was blended with Platinum (II) octaethylporphyrine ketone (PtOEPK). All devices consisted of an ITO anode, a PEDOT:PSS hole injection layer (40 nm), the active polymer layer (130 nm) and a Ca cathode (20 nm) protected by an Al layer (100 nm). The devices were fabricated in an inert nitrogen atmosphere. OC3C8-PPV was spin-coated from a toluene solution with a concentration of 7.5 mg ml-1. The PtOEPK concentrations in sensitized films were 0.1 and 1 wt%, respectively. After preparation, the polymer films were annealed in the glovebox at 130 °C for 5 min. Finally, the top electrodes were vacuum deposited through shadow masks at a base pressure of 10-6 mbar. The singlet-to-triplet conversion can be verified with photoinduced absorption measurements, where the intensity of the excited triplet state absorption of the polymer Institute of Materials Science – Surface Science 35 increases in the presence of the triplet sensitizer. The conversion is also observed to take place in electrically driven devices, which is manifested through a decrease in the electroluminescence, pointing to a decreased population of the first excited singlet state of the polymer. Additionally, no emission from the sensitizer is detected, indicating a complete transfer of triplet excitons from the sensitizer back to the polymer. Fig. 2 plots the lifetimes of the diodes with pristine and sensitized OC3C8-PPV layers. The devices were operated at a constant current density of 50 mA/cm2. The graph shows the normalized luminance values for a better comparison of the curves; the measured luminance intensities are shown in the inset. The t5o lifetime of the diodes with pristine OC3C8-PPV layers is 160 hours, whereas the devices with 0.1 wt% PtOEPK reach a t5o of only 15 hours. This corresponds to a decrease of 91 %. Increasing the PtOEPK concentration to 1 wt% leads to a t5o lifetime of only 2 hours, or a decrease of 99 % from the value of the devices with the pristine polymer layers [3]. Figure 2 Luminance versus time plots of PLEDs with pristine OC3C8-PPV (black squares), OC3C8PPV:PtOEPK (0.1 %) (orange circles) and OC3C8PPV:PtOEPK (1 %) (red triangles) illustrating the deterioration of the t50 lifetime with increasing sensitizer content. The inset shows the measured absolute luminance values. It can be concluded that the triplet excitons do shorten the lifetime of the PPV-based OLEDs stongly. It is postulated that the heat generated by the non-radiative decay of the triplet excitons could be partly responsible for the observed accelerated decay. In thermography measurements it was observed that the temperature of a diode with pristine OC3C8-PPV rises 5 K above room temperature after turning on the diode. After turning on, the temperature stays constant for several hours of operation at a constant current density of 50 mA/cm2. The observed temperature rise of a diode with 1 wt% PtOEPK is 10 K and therefore higher than that of the device with a pristine polymer layer. It is, however, likely that the temperature increase of 5 K alone is not sufficient to explain the complete acceleration in the degradation of the devices. Another factor that could influence the fatigue of the devices with an increased concentration of triplet excitons is the interaction of the triplet excitons with oxygen. The triplet excitons of conjugated polymers are known to undergo energy transfer to oxygen in triplet state [4–7], leading to the formation of singlet oxygen. It has been observed to attac the vinylene bonds of PPV derivates, leading to chain scission [8]. The process has been shown to take place even in inert atmosphere with oxygen concentration in the low ppm range [6,7]. The higher concentration of triplet excitons in the diodes with the sensitized layers is expected to lead to increased interaction with oxygen. This process could partly contribute to the observed accelerated degradation. It is, however, presently not possible to assign the phenomena responsible for the fatigue to a single process. Nevertheless, due to the generally high concentration of triplet excitons in fluorescent OLEDs, the observed 36 Institute of Materials Science – Surface Science accelerated degradation bears a significant importance for improving the stability of the devices by engineering the triplet state population. References: [1] [2] [3] [4] [5] [6] [7] [8] L. Lin, H. Meng, J. Shy, S. Horng, L. Yu, C. Chen, H. Liaw, C. Huang, K. Peng, and S. Chen, Phys. Rev. Lett. 90, 3 (2003). H. Liao, H. Meng, S. Horng, J. Shy, K. Chen, and C. Hsu, Phys. Rev. B 72, 113203 (2005). O. Pekkola, A. Gassmann, F. Etzold, F. Laquai, and H. von Seggern, Phys. Status Solidi DOI:10.1002/pssa.201330411 (2014). R. D. Scurlock, B. Wang, P. R. Ogilby, J. R. Sheats, and R. L. Clough, J. Am. Chem. Soc. 117, 10194 (1995). A. Sperlich, H. Kraus, C. Deibel, H. Blok, J. Schmidt, and V. Dyakonov, J. Phys. Chem. B 115, 13513 (2011). H. Y. Low, Thin Solid Films 413, 160 (2002). B. H. Cumpston, I. D. Parker, and K. F. Jensen, J. Appl. Phys. 81, 3716 (1997). T. Zyung and J.-J. Kim, Appl. Phys. Lett. 67, 3420 (1995). Institute of Materials Science – Surface Science 37 Surface Science The surface science division of the institute of materials science uses advanced surface science techniques to investigate surfaces and interfaces of materials and materials combinations of technological use. For this purpose integrated UHV-systems have been built up which combine different surface analytical tools (photoemission, inverse photoemission, electron diffraction, ion scattering, electron loss spectroscopy, scanning probe techniques) with the preparation of thin films (thermal evaporation, close-spaced sublimation, magnetron sputtering, MOCVD) and interfaces. The main research interest is directed to devices using polycrystalline compound semiconductors and interfaces between dissimilar materials. The perspectives of energy conversion (e.g. solar cells) or storage (intercalation batteries) devices are of special interest. In addition, the fundamental processes involved in chemical and electrochemical device engineering and oxide thin films for electronic applications are investigated. The main research areas are: Electrochemical Interfaces The aim of this research activity is the better understanding of electrochemical interfaces and their application for energy conversion. In addition, empirically derived (electro-) chemical processing steps for the controlled modification and structuring of materials is investigated and further optimized. In the center of our interest are semiconductor/electrolyte contacts. Solar fuels The direct solar light induced water splitting is investigated using photoelectrochemical (electrode/electrolyte) or photocatalytic (particle) arrangements. New materials, design structures, as well as interface engineering approached with advanced catalysts are investigated. The catalysts are also tested for their application in water electrolysis. Intercalation Batteries The aim of this research activity is the better understanding of electronic properties of Liintercalation batteries and of their degradation phenomena. Typically all solid state batteries are prepared and investigated using sputtering and CVD techniques for cathodes and solid electrolytes. In addition, the solid-electrolyte interface and synthetic surface layers are investigated as well as composite systems for increasing the capacity. Thin film solar cells The aim of this research activity is the testing and development of novel materials and materials combinations for photovoltaic applications. In addition, the interfaces in microcrystalline thin film solar cells are to be characterized on a microscopic level to understand and to further improve the empirically based optimisation of solar cells. Organic-inorganic interfaces and composites In this research area we are aiming at the development of composites marterials for (opto-) electronic applications. The decisive factors, which govern the electronic properties of interfaces between organic and inorganic materials are studied. 38 Institute of Materials Science – Surface Science Semiconducting Oxides The aim of this research area is to understand electronic surface and interfaces properties of oxides. We are mainly interested in transparent conducting oxide electrodes for solar cells and organic LEDs but also in dielectric and ferroelectric perovskites. Surface analysis The UHV-surface science equipment and techniques using different and versatile integrated preparation chambers is used for cooperative service investigations. For the experiments we use integrated UHV-preparation and analysis-systems (UPS, (M)XPS, LEISS, LEED), spectromicroscopy (PEEM) coupled with UHV-STM/AFM. We further apply synchrotron radiation (SXPS, spectromicroscopy), scanning probe methods (STM, AFM), and electrochemical measuring techniques. UHV-preparation chambers dedicated for MBE, CVD, PVD and (electro)chemical treatment are available. The members of the group are involved in basic courses of the department’s curriculum and offer special courses on the physics, chemistry and engineering of semiconductor devices and solar cells, on surface and interface science, and on thin film and surface technology and electrochemistry. Staff Members Head Prof. Dr. Wolfram Jaegermann Research Associates Dr.Gennady Cherkashinin Dr. Lucangelo Dimesso Dr. René Hausbrand Dr. Alexander Issanin PD Dr. Bernd Kaiser Apl. Prof. Dr. Andreas Klein Dr. Shunyi Li Dr. Eric Mankel Dr. Thomas Mayer Dr. Hermann Schimper Dr.Florent Yang Technical Personnel Dipl.-Ing. Erich Golusda Kerstin Lakus-Wollny Christina Spanheimer Secretaries Leslie Frotscher Marga Lang PhD Students Dipl.-Ing. Thorsten Bayer Dipl.-Ing. Dirk Becker M.Sc. Mercedes Carillo Solano M.Sc. Mariel Grace Dimamay Dipl.-Ing. Dominic Fertig Dipl.-Ing. Anne Fuchs M. Sc. Stephan Hillmann Dipl.-Ing. Mareike Hohmann Dipl.-Ing. Jan Morasch Dipl.-Ing. Markus Motzko Dipl.-Ing. ThiThanh Dung Nguyen Dipl.-Ing. Ruben Precht Dipl.-Ing. Karsten Rachut Dipl.-Ing. Philip Reckers Dipl.-Ing. Anja Schneikart Dipl.-Ing. André Schwöbel M.Sc. Sebastian Siol Dipl.-Ing. Johannes Türck Dipl.-Ing. Mirko Weidner Dipl.-Ing. Jürgen Ziegler Master Students Richard Günzler Lukas Hamm Michael Kettner Christian Lohaus Tobias Rödlmeier Hans Wardenga Guest Scientists Dr. Lili Wu Institute of Materials Science – Surface Science 39 Research Projects Function and fatigue of conducting electrodes in organic LEDs, SFB 595-D3 (DFG 20032014) Polarization and charge in electrically fatigued ferroelectrics, SFB 595-B7 (DFG 2007-2014) Integriertes Graduiertenkolleg SFB 595 (DFG 2008-2014) Tunable Integrated Components for Microwaves and Optics, Graduiertenkolleg 1037 (DFG 2004-2013) P-I-N solar cells with alternative highly-absorbing semiconductors (BMBF 2010-2013) LOEWE Schwerpunkt AdRIA (LOEWE-Hessen: 2008-2013) Kosteneffiziente Produktionsverfahren für CdTe Solarzellen und kupferfreie Rückkontakte (CTF Solar 2012 – 2013) Boundary layers and thin films of ionic conductors: Electronic structure, electrochemical potentials, defect formation and degradation mechanism SFB595-A3 (DFG 2003-2014) Morphology and Electronic Structure of Organic/Organic and Organic/Metal-Oxid Hybrid Systems, Innovation Lab GmbH Heidelberg oft he BMBF leading edge cluster Forum Organic Electronics (BMBF 2009 – 2014) 9D-Sense Autonomous Nine Degrees of Freedom Sensor Module (BMBF/VDI 2011 – 2014) Solid State Lithium Batterien mit organischen Kathoden (Novaled 2011 – 2014) All Oxide PV (EU 2012 – 2014) Inverted organic solar cells: Charge carrier extraction and interface characterization (DFG 2012- 2014) Photoelectrochemical water splitting using adapted silicon based semiconductor tandem structures (DFG 2012 – 2015) Coordination SPP 1613 Solar H2 (DFG 2012 – 2015) 40 Institute of Materials Science – Surface Science Publications [1] Trost, S.; Zilberberg, K.; Behrendt, A.; Polywka, A.; Gorrn, P.; Reckers, P.; Maibach, J.; Mayer, T.; Riedl, T.; Overcoming the "Light-Soaking" Issue in Inverted Organic Solar Cells by the Use of Al:ZnO Electron Extraction Layers, ADVANCED ENERGY MATERIALS, 3 (2013) 1437-1444. [2] Dimesso, L.; Spanheimer, C.; Jaegermann, W.; Influence of isovalent ions (Ca and Mg) on the properties of LiCo0.9M0.1PO4 powders; JOURNAL OF POWER SOURCES, 243 (2013) 668-675 [3] Junfeng Han; Ganhua Fu; Krishnakumar, V.; Cheng Liao; Jaegermann, W.; Besland, M.P.; Preparation and characterization of ZnS/CdS bi-layer for CdTe solar cell application; JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS, 74 (2013), 1879-83 [4] Nguyen, T. T. D.; Dimesso, L.; Cherkashinin, G.; Jaud, J.C.; Lauterbach, S.; Hausbrand, R.; Jaegermann, W.; Synthesis and characterization of LiMn1-x Fe (x) PO4/carbon nanotubes composites as cathodes for Li-ion batteries; IONICS, 19 (2013), 1229-1240, [5] Lebedev, M.V.; Kunitsyna, E.V. ; Calvet, W.; Mayer, T. ; Jaegermann, W.; Sulfur Passivation of GaSb(100) Surfaces: Comparison of Aqueous and Alcoholic Sulfide Solutions Using Synchrotron Radiation Photoemission Spectroscopy; JOURNAL OF PHYSICAL CHEMISTRY C, 117 (2013), 15996-16004 [6] Bohne, L.; Pirk, T.; Jaegermann, W.; Investigations on the influence of the substrate on the crystal structure of sputtered LiCoO2; JOURNAL OF SOLID STATE ELECTROCHEMISTRY 17 (2013), 2095-2099 [7] Han J.; Fu G.; Krishnakumar, V.; Liao, C.; Jaegermann, W.; CdS annealing treatments in various atmospheres and effects on performances of CdTe/CdS solar cells; JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS, 24 (2013), 2695-2700 [8] Hofle, S.; Do, H.; Mankel, E.; Pfaff, M.; Zhang, Z.H.; Bahro, D.; Mayer, T.; Jaegermann, W.; Gerthsen, D.; Feldmann, C.; Lemmer, U.; Colsmann, A.; Molybdenum oxide anode buffer layers for solution processed, blue phosphorescent small molecule organic light emitting diodes; ORGANIC ELECTRONICS, 14 (2013), 1820-1824 [9] Maibach, J.; Mankel, E.; Mayer, T.; Jaegermann, W.; Synchrotron induced photoelectron spectroscopy on drop casted donor/acceptor bulk heterojunction: Orbital energy line up in DH6T/PCBM blends, SURFACE SCIENCE, 612 (2013), L9-L11 [10] Dimesso, L.; Spanheimer, C.; Jaegermann, W.; Zhang, Y.; Yarin, A. L.; LiCoPO4-3D carbon nanofiber composites as possible cathode materials for high voltage applications; ELECTROCHIMICA ACTA, 95 (2013), 38-42 [11] Cherkashinin, G.; Ensling, D.; Komissinskiy, P.; Hausbrand, R.; Jaegermann, W.; Temperature induced reduction of the trivalent Ni ions in LiMO2 (M = Ni, Co) thin films; SURFACE SCIENCE, 608 (2013), L1-L4 Institute of Materials Science – Surface Science 41 [12] Dimesso, L.; Spanheimer, C.; Jaegermann, W.; Effect of the Mg-substitution on the graphitic carbon foams-LiNi1-yMgyPO4 composites as possible cathodes materials for 5 V applications, MATERIALS RESEARCH BULLETIN, 48 (2013), 559-565 [13] Becker, D.; Cherkashinin, G.; Hausbrand, R.; Jaegermann, W.; XPS study of diethyl carbonate adsorption on LiCoO2 thin films; SOLID STATE IONICS, 230 (2013), 83-85 [14] Maibach, J.; Mankel, E.; Mayer, T.; Jaegermann, W.; The band energy diagram of PCBM-DH6T bulk heterojunction solar cells: synchrotron-induced photoelectron spectroscopy on solution processed DH6T:PCBM blends and in situ prepared PCBM/DH6T interfaces; JOURNAL OF MATERIALS CHEMISTRY C, 1 (2013), 7635-7642 [15] Seifollahi B., M.; Hojamberdiev, M.; Morita, K.; Zhu, G.; Cherkashinin, G.; Fasel, C.; Herrmann, T.; Breitzke, H.; Gurlo, A.; Riedel, R.; Visible Light Photocatalysis with c-WO3– x/WO3×H2O Nanoheterostructures In Situ Formed in Mesoporous Polycarbosilane-Siloxane Polymer, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 135 (2013), 4467-4475 [16] S. Hoefle, H. Do, E. Mankel, M. Pfaff, Z. Zhang, D. Bahro, T. Mayer, W. Jaegermann, D. Gerthsen, C. Feldmann, U. Lemmer, A. Colsmann; Molybdenum oxide anode buffer layers for solution processed, blue phosphorescent small molecule organic light emitting diodes; ORGANIC ELECTRONICS, 14 (2013) 1820-1824 [17] Vafaee, M. ; Baghaie Y. M. ; Radetinac, A. ; Cherkashinin, G. ; Komissinskiy, P. ; Alff, L.; Strain engineering in epitaxial La[sub 1−x]Sr[sub 1+x]MnO[sub 4] thin films; JOURNAL OF APPLIED PHYSICS, 113 (2013), 053906 [18] Babu, D. J.; Lange, M.; Cherkashinin, G.; Issanin, A.; Staudt, R.; Schneider, J.; Gas adsorption studies of CO2 and N2 in spatially aligned double-walled carbon nanotube arrays; J. CARBON, 61 (2013), 616-623 [19] H. Sträter, R. Brüggemann, S. Siol, A. Klein, W. Jaegermann and G. H. Bauer; Detailed photoluminescence studies of thin film Cu2S for determination of quasi-Fermi level splitting and defect level; J. APPL. PHYS., 114 (2013), 233506 [20] B. Siepchen, H. Schimper, A. Klein, W, Jaegermann; SXPS studies of single crystalline CdTe/CdS interfaces; J. ELECTRON SPECTR. REL. PHENOM,. 190 (2013), 54-63 [21] H. Sträter, R. Brüggemann, S. Siol, A. Klein, W. Jaegermann and G. H. Bauer; Spectral Calibrated and Confocal Photoluminescence of Cu2S Thin-Film Absorber; MAT. RES. SOC. SYMP. PROC., 1538 (2013) [22] V. Pfeifer, P. Erhart, S. Li, K. Rachut, J. Morasch, J. Brötz, P. Reckers, T. Mayer, S. Rühle, A. Zaban, I. Mora Seró, J. Bisquert, W. Jaegermann, A. Klein; Energy Band Alignment Between Anatase and Rutile TiO2 ; J. PHYS. CHEM. LETT., 4 (2013), 4182-4187 [23] S. Siol, H. Sträter, R. Brüggemann, J. Brötz, G. H. Bauer, A. Klein, W. Jaegermann; PVD of Copper Sulfide Cu2S for PIN-structured solar cells; J. PHYS. D: APPL. PHYS. 46 (2013), 495112 42 Institute of Materials Science – Surface Science [24] M.T. Uddin, Y. Nicolas, C. Olivier, T. Toupance, M. Müller, H.-J. Kleebe, K. Rachut, J. Ziegler, A. Klein, W. Jaegermann ; Preparation of RuO2/TiO2 Mesoporous Heterostructures and Rationalization of Their Enhanced Photocatalytic Properties by Band Alignment Investigations; J. PHYS. CHEM. C, 117 (2013), 22098–22110 [25] V. Krishnakumar, A. Klein, W. Jaegermann; Studies on CdTe solar cell front contact properties using X-ray Photoelectron Spectroscopy; THIN SOLID FILMS, 545 (2013), 548-557 [26] S. Li, J. Morasch, A. Klein, C. Chirila, L. Pintilie, L. Jia, K. Ellmer, M. Naderer, K. Reichmann, M. Gröting, K. Albe; Influence of orbital contributions to valence band alignment of Bi2O3, Fe2O3, BiFeO3, and Bi0.5Na0.5TiO3 ; PHYS. REV. B, 88 (2013), 045428 [27] K. Morita, G. Mera, K. Yoshida, Y. Ikuhara, A. Klein, H.-J. Kleebe, R. Riedel; Thermal Stability, Morphology and Electronic Band Gap of Zn(NCN); SOLID STATE SCIENCES, 23(2013), 50-57 [28] A. Schneikart, H.-J. Schimper, A. Klein, W. Jaegermann; Efficiency limitations of thermally evaporated thin film SnS solar cells; J. PHYS. D, 46 (2013), 305109 [29] V. Krishnakumar, A. Barati, H.-J. Schimper, A. Klein, W. Jaegermann; A possible way to reduce absorber layer thickness in thin film CdTe solar cells; THIN SOLID FILMS 535 (2013), 233-236 [30] A. Klein; Transparent Conducting Oxides: Electronic Structure – Property Relationship from Photoelectron Spectroscopy with in-situ Sample Preparation; J. AM. CERAM. SOC., 96 (2013), 331-345 [31] M.H. Rein, M. Hohmann, A. Thøgersen, J. Mayandi, A. Klein, and E.V. Monakhov; An in situ XPS study of the initial stages of rf magnetron sputter deposition of indium tin oxide on p-type Si substrate; APPL. PHYS. LETT., 102 (2013), 021606 [32] E. M. Hopper, Q. Zhu, J. Gassmann, A. Klein, T.O. Mason; Surface electronic properties of polycrystalline bulk and thin film In2O3(ZnO)k compounds; APPL. SURF. SCI., 264 (2013), 811-815 Patents [1] Photo-electrochemical cell for production of hydrogen and oxygen in water or electrolyte based aqueous solution, has ion exchange film that is arranged between front and back electrodes of electrochemical-layer structure Patent Number: DE102012205258-A1; WO2013143885-A1 Patent Assignee: EVONIK IND AG Inventor(s): HOCH S., MATTHIAS B., BUSSE J., CALVET W., KAISER B., JAEGERMANN W., HAHN H., ZANTHOFF H., BLUG M. Institute of Materials Science – Surface Science 43 Investigations of interface reactions between lithium and solid electrolyte André Schwöbel, René Hausbrand and Wolfram Jaegermann All-solid state Li-ion batteries are a hot topic of research due to possible applications in various areas of energy storage such as micro-electronics and electro-mobility. All-solid state devices feature high safety, low self discharge, high cycling stability and high energy density. These favorable characteristics reflect the properties of inorganic solid electrolytes, such as high thermal stability, low reactivity and low electronic conductivity. The use of solid electrolytes allows the save use of metallic lithium in all-solid state devices or, if applied as protective layer, also in conventional Li-ion batteries with liquid electrolyte. Nevertheless, reactivity between lithium and solid electrolyte resulting in detrimental interlayer formation (solid electrode solid electrolyte interface layer, SESEI-layer) still poses a problem. A solid state electrolyte which is commonly used in thin film batteries is LiPON, a nitrogensubstituted lithium phosphate glass which was first reported by Bates and coworkers [1]. LiPON is easy to synthezise by sputtering, owing to a broad composition range with a reasonable ionic conductivity (10-6 S/cm). We apply a surface science approach to investigate the reactivity between LiPON and lithium. In the experiments, lithium is deposited stepwise onto a LiPON thin film substrate, and x-ray photo-electron spectroscopy (XPS) is performed after each step (Fig. 1). Principally, such an approach allows also insights into the formation of the electrochemical interface, i.e. the formation of the electrochemical double layer and energy level alignment [2]. The experiments have been performed on LiPON with different composition. In this contribution we report results for a LiPON film with metaphosphate (LiPO3) character (Li1.4 PO2.2N0.7) [3], which has proven functional in our model thin film cells. Li XPS XPS Li XPS Li EL EL EL Increasing Li deposition time Figure 1: Schematic illustration of the interface experiment (EL: electrolyte). The approach allows the investigation of reaction layers and energy level alignment. The evolution of the core level and valence band spectra is shown in figure 2. At the bottom, the spectra of the LiPON film before lithium deposition (denoted as is) are shown, further up the spectra after different deposition times and at the top the spectra of the sample after lithium deposition and additional oxygen exposure (denoted oxidized). The O1s and N1s emissions of the pristine LiPON surface show shoulders to high binding energies, demonstrating the presence of doubly coordinated oxygen and triply coordinated nitrogen within the network. Upon lithium deposition, these features disappear and new emissions appear to lower binding energies in all core level spectra (see figure 3 for a 44 Institute of Materials Science – Surface Science detail of the N1s emission). Using literature, the new emissions are attributed to the presence of Li2O, Li3N and Li3P, next to metallic lithium from the top layer. Figure 2: Evolution of core level and valence band XP-spectra with lithium deposition time. Figure 3: N1s XP-specta with triply (NT) and doubly (ND) coordinated nitrogen (left) and illustration of nitrogen coordination in LiPON (right). We conclude that contact of lithium with metaphosphate-type LiPON results in formation of reduced nitrogen and phosphorous coupounds such as Li3N and Li3P, accompanied by the the disruption of the network and the formation of Li2O and orthophosphate Li3PO4. Institute of Materials Science – Surface Science 45 Experiments conducted on LiPON films with a more pronounced orthophosphate character indicate that these compounds are more stable. We presume that the reaction is restricted to the interface region due to low electronic conductivity of the reaction products, forming an efficient passivation layer. Nevertheless, such layers can have a pronounced effect on the Li-ion transfer resistance, and further evaluation is ongoing. References: [1] Bates, J.B., et al., Electrical-Properties of Amorphous Lithium Electrolyte Thin-Films. Solid State Ionics, 1992. 53-6: p. 647-654. [2] Hausbrand, R., D. Becker, and W. Jaegermann, A Surface Science Approach to Cathode/Electrolyte Interfaces in Li-ion Batteries: Contact Properties, Charge Transfer and Reactions accepted to Progress in Solid State Chemistry. [3] Schwöbel, A., R. Hausbrand, and W. Jaegermann, In preparation. 46 Institute of Materials Science – Surface Science Energy Band Alignment between Anatase and Rutile TiO2 Verena Pfeifer, Shunyi Li, Karsten Rachut, Jan Morasch, Philip Reckers, Thomas Mayer, Wolfram Jaegermann, Andreas Klein Titanium dioxide (TiO2) has been intensivley studied in the last two decades because of its promising photocatalytic properties for energy-related applications. The two most common modifications of TiO2 are anatase and rutile. It was observed that the mixed anatase/rutile systems show more favorable photocatalytic properties than pristine ones of either modification.[1-2] This synergistic effect has been attributed to a built-in driving force for separation of photogenerated charge carriers. One of the explainations for this effect is related to the energy band alignment that forms an energy barrier at the interface blocking charge transfer between anatase and rutile. However, the exact band alignment of these two modifications is still unclear. Early models which either align the valence band maxium of anatase and rutile at the same level or locate the band edges of rutile inbetween those of anatase cannot convincingly explain the observed synergistic phenomena. A more feasible model would be a staggered energy band alignment, in which both the valence band maximum and conduction band minimum of rutile are higher than those of anatase, as suggested by Deák [3] and Scanlon.[4] In this case the photogenerated electrons move preferentially to anatase and holes to rutile due to the energy band offsets. In order to determine the band alignment between anatase and rutile TiO2 and to obtain further understanding to the synergistic effect, the interface properties and electronic structures of these two materials are studied by X-ray photoelectron spectroscopy (XPS) measurements and density functional theory (DFT) calculations. For the XPS experiments rutile single crystals and polycrystalline TiO2 thin films with pure anatase phase deposited with reactive magnetron sputtering are used as substrates. Degnerately Sn-doped In2O3 (ITO) and metallic RuO2 are deposited stepwise onto the substrates as contact materials. After each incremental deposition step, photoelectron spectra are recorded in situ to trace fhifts in the binding energies of core-levels emission lines. The energy band alignment is finally derived independently for both contact materials by applying transitivity rule, ΔEVB(A/R) = ΔEVB(A/X) – ΔEVB(R/X), where A, R, and X represent anatase, rutile, and ITO or RuO2. Fig. 1: Energy band diagrams for anatase/RuO2 and rutile/RuO2 interfaces derived from the interface experiments. The band alignment at the rutile/anatase interface is obtained using transitivity from the figure by omitting the central RuO2 layer and the band bendings. The resulting valence and conduction band discontinuities at the rutile/anatase interface derived from the photoemission experiment are indicated by superscript E, and those from DFT calculations are indicated by superscript T. Institute of Materials Science – Surface Science 47 For both contact materials, an offset between the valence band edges (ΔEVB) of anatase and rutile of 0.7±0.1 eV has been determined, as illustrated in Fig. 1.By using the literature values for the band gaps of anatase and rutile, a conduction band offset (ΔECB) of 0.5 eV can be derived. This corresponds to a staggered energy band alignment similar to those reported by Deák [3] and Scanlon.[4] In order to obtain further insight regarding the origin of the band offsets at the rutile/anatase interface, the electronics structure of both materials are analysed on a DFT level. Comparison of the desity of states (DOS) (Fig. 2a) yields an offset of 0.63 eV for valence band and 0.39 eV for conduction band, both in good agreement with the experimental values (see Fig. 1). Further inspection of the valence band structure shows that the DOSs of rutile and anatase are mostly very similar except the appearance of “tails” at both top and bottom in case of rutile. The band structure of rutile in Fig. 2b shows that the tails originate from a pronounced splitting of the topmost and bottommost levels in the vicinity of the Γ point, which is entirely absend in anatase. The electronic origin of this feature can be understood with the help of a Wannier function analysis,[5] which yields on sp2- and pz-like orbital for each oxygen atom, as shown in Fig. 2c,d. The projection of the band structure on this set of states yields the relative admixture illustrated by the color coding in Fig. 2b. This analysis reveals that the topmost valence band of rutile near Γ point is virtually exclusively of pz character and can thus be interpreted as a lone-pair orbital. This explains the downward dispersion of the band away from the center of Γ. Fig. 2: (a) Comparison of the DOSs of rutile and anatase. The energy scales have been aligned based on the electrostatic potential at the Ti cores. (b) Band structure of rutile where the color scale indicates the respective admixture of oxygencentered (c) sp2-and (d) pz-like orbitals. In (c), only one of the three individual Wannier functions that contribute to the sp2-like orbital is shown. The remaining lobs are oriented along the other two O-Ti bonds. 48 Institute of Materials Science – Surface Science In comparison, the pz-like orbital in anatase does not play a prominent role near the valence band edge and the band structure generated in the same fashion does not exhibit a splitting of states around the Γ point. These results suggest, that in rutile the pz-like orbital are much closer to each other and exhibit stronger interaction and overlap, which results in a larger splitting of the energy bands and consequently in a higher valence band maximum energy and the appearance of the tail at the top of the valence band. References: [1] [2] [3] [4] [5] Hurum, D. C.; Agrios, A. G.; Gray, K. A.; Rajh, T.; Thurnauer, M. C., J. Phys. Chem. B 2003, 107, 45454549. Ohno, T.; Tokieda, K.; Higashida, S.; Matsumura, M., Appl. Catal., A 2003, 244, 383−391. Deá k, P.; Aradi, B.; Frauenheim, T., J. Phys. Chem. C 2011, 115, 3443−3446. Scanlon, D. O.; Dunnill, C. W.; Buckeridge, J.; Shevlin, S. A.; Logsdail, A. J.; Woodley, S. M.; Catlow, C. R. A.; Powell, M. J.; Palgrave, R. G.; Parkin, I. P.; Watson, G. W.; Keal, T. W.; Sherwood, P.; Walsh, A.; Sokol, A. A., Nat. Mater. 2013, 12, 798−801. Marzari, N.; Mostofi, A. A.; Yates, J. R.; Souza, I.; Vanderbilt, D., Rev. Mod. Phys. 2012, 84, 1419−1475. Institute of Materials Science - Surface Science 49 Advanced Thin Film Technology The Advanced Thin Film Technology (ATFT) group works on advanced thin film deposition techniques of novel materials. The group is specialized on physical vapor deposition techniques such as pulsed laser deposition (PLD), advanced oxide molecular beam epitaxy (ADOMBE) and dc/rf-magnetron sputtering. The ADOMBE system is an in-house development and has been jointly financed by Max-Planck-Institute for Solid State Research in Stuttgart and TU Darmstadt. PLD and ADOMBE are part of a cluster system allowing for in-situ sample exchange between the different deposition methods and characterization tools. The ADOMBE apparatus is a worldwide unique thin film deposition system which is dedicated to the growth of complex oxides beyond thermodynamic equilibrium. It allows for the simultaneous deposition of six elements from electron beam sources and further elements evaporated from effusion cells. The molecular beams of each element can be individually controlled by a feed back loop using electron impact emission spectroscopy. The group is working mainly on oxide ceramics which show a stunning variety of new functional properties. Examples are high-temperature superconductors, magnetic oxides for spintronics, high-k dielectrics, ferroelectrics, and novel thermoelectric materials. As a vision for future, new solid state matter can be created by building hetero- and composite structures combining different oxide materials. While present day electronic devices heavily rely on conventional semiconducting materials, a future way to create novel functional devices could be based (completely) on oxide electronics. The group uses a Rigaku SmartLab X-ray thin film diffractometer with rotating anode ("synchrotron in house"). Other characterization tools located in the Advanced Thin Film Technology group include powder X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), high-resolution scanning electron microscopy (HREM) with light element sensitive EDX, and SQUID magnetometry. A 16 Tesla magnet cryostat allowing measurements down to liquid helium temperature has been installed. Another magnet cryostat (10 T) lowers the available temperature range to below 300 mK. This cryostat also contains high-frequency feed-throughs for electrical characterization (40 GHz). The group is also using external large scale facilities as synchrotron radiation (ESRF, Grenoble) and neutron reactors (ILL, Grenoble / HMI and DESY, Berlin) for advanced sample characterization. Close cooperation exists in particular with the Max-Planck-Institute for Solid State Research in Stuttgart, with the Japanese company NTT in Atsugi near Tokio, with the University of Tokio, and Chalmers University of Technology. Throughout 2013 Lambert Alff was working also as a Dean of Studies in the faculty of Materials Science and head of the Graduate School Materialium. Lambert Alff has also worked as an elected a member of the Senat of TU Darmstadt. Staff Members Head Prof. Dr. Lambert Alff Research Associates Dr. Ewrwin Hildebrandt Dr. Jose Kurian Dr. Philipp Komissinskiy Technical Personnel Dipl.-Ing. Gabi Haindl Jürgen Schreeck Secretary Marion Bracke 50 Institute of Materials Science – Advanced Thin Film Technology PhD Students Dipl.-Ing. Mani Arzhang Dipl.-Ing. Alexander Buckow M. Sc. Dominik Gölden Dipl.-Ing. Aldin Radetinac M.Sc. Sareh Sabet MTech. Sharath Ulhas Dipl.-Ing. Mehrdad Baghaie M. Sc. Niklas van Elten Dipl.-Ing. Stefan Hirsch Dipl. Phys. Reiner Retzlaff BTech. Vikas Shabadi Research Projects Novel arsenic free pnictide superconductors (SPP 1458) (DFG 2013 - 2015) Doped SrTiO3 for Microwave Applications and Multiferroics as novel materials for tunable components, within DFG Research Training Group 1037 “Tunable Integrated Components in Microwave Technology and Optics” (DFG 2008-2013) Resistives Schalten in HfO2-basierten Metall-Isolator-Metall Strukturen für Anwendungen im Bereich nicht-flüchtiger Speicher (DFG 2012-2013) Novel oxid electrodes for all oxide varactors (DFG 2012-2014) LOEWE-Centre AdRIA: Adaptronik – Research, Innovation, Application (HMWK 2011 2014) Publications [1] P. Lemmens, V. Gnezdilov, G. J. Shu, L. Alff, C. T. Lin, B. Keimer, and F. C. Chou. Enhanced low-energy fluctuations and increasing out-of-plane coherence in vacancyordered NaxCoO2. Phys. Rev. B 88, 195151 (2013). [2] Inventor(s): L. Alff, S. Hildebrandt, T. Kober, R. Teipen, A. T.Tham, R. Werthschützky Plate-like glass structure for manufacturing pressure sensor, has recessed contour portion that is surrounded by planar edge area, and specific glass surface whose surface roughness value and diameter are set to predetermined ranges Patent Number(s): DE102011084457A1 ; EP2581722-A2. [3] M. Baghaie Yazdi, K.-Y. Choi, D. Wulferding, P. Lemmens, and L. Alff. Raman study of the Verwey transition in magnetite thin films. New Journal of Physics 15, 103032 (2013). [4] R. Hord, G. Pascua, K. Hofmann, G. Cordier, J. Kurian, H. Luetkens, V. Pomjakushin, M. Reehuis, B. Albert and L. Alff. Oxygen stoichiometry of low-temperature synthesized metastable T'-La2CuO4. Supercond. Sci. Technol. 26, 105026 (2013). [5] Mingwei Zhu, Philipp Komissinskiy, Aldin Radetinac, Mehran Vafaee, Zhanjie Wang, and Lambert Alff. Effect of composition and strain on the electrical properties of LaNiO 3 thin films. Appl. Phys. Lett. 103, 141902 (2013). [6] Sandra Hildebrandt, Philipp Komissinskiy, Marton Major, Wolfgang Donner, Lambert Alff. Epitaxial growth and control of the sodium content in NaxCoO2 thin films. Thin Solid Films 545, 291 (2013). Institute of Materials Science - Advanced Thin Film Technology 51 [7] Alff, L. Magnetic Ceramics. in Ceramics Science and Technology Volume 4: Applications (eds R. Riedel and I.-W. Chen), Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, 2013. [8] K.I. Lilova, R. Hord, L. Alff, B. Albert, A. Navrotsky.Thermodynamic Study of Orthorhombic Tx and Tetragonal T′ Lanthanum Cuprate, La2CuO4. J. Solid State Chem. 204, 91 (2013). [9] K. Y. Constantinian, Yu. V. Kislinskii, G. A. Ovsyannikov, A. V. Shadrin, A. E. Sheyerman, A. L. Vasil’ev, M. Yu. Presnyakov, P. V. Komissinskiy. Interfaces in superconducting hybrid heterostructures with an antiferromagnetic interlayer. Physics of the Solid State 55, 461 (2013). [10] Mehran Vafaee, Mehrdad Baghaie Yazdi, Aldin Radetinac, Gennady Cherkashinin, Philipp Komissinskiy, and Lambert Alff. Strain engineering in epitaxial La1−xSr1+xMnO4 thin films. J. Appl. Phys. 113, 053906 (2013). [11] A Buckow, R Retzlaff, J Kurian and L Alff. Growth of superconducting epitaxial LaNixBi2 pnictide thin films with a Bi square net layer by reactive molecular beam epitaxy Supercond. Sci. Technol. 26, 015014 (2013). [12] Gennady Cherkashinin, David Ensling, Philipp Komissinskiy, René Hausbrand, Wolfram Jaegermann. Temperature induced reduction of the trivalent Ni ions in LiMO2 (M = Ni, Co) thin films. Surface Science 608, L1–L4 (2013). [13] Ina Uhlmann, Dominik Hawelka, Erwin Hildebrandt, Jens Pradella, Jürgen Rödel. Structure and mechanical properties of silica doped zirconia thin films. Thin Solid Films 527, 200 (2013). [14] J. Kurian, A. Buckow, R. Retzlaff, L. Alff. Search for superconductivity in LaNiP2 (P = Bi, Sb) thin films grown by reactive molecular beam epitaxy. Physica C 484, 171 (2013). 52 Institute of Materials Science - Advanced Thin Film Technology Dispersive Solids The main research interests of the group Dispersive Solids are directed towards the development of novel strategies suitable for the synthesis of inorganic, oxidic and nonoxidic materials with properties beyond the state of the art. The materials of interest are advanced oxidic and non-oxidic ceramics with extraordinary properties in terms of thermal stability, hardness and electronic structure. Therefore, synthesis methods such as polymer-pyrolysis, non-oxidic and oxidic sol-gel methods, chemical vapour deposition and novel high pressure methods have been further developed. The following topical issues are presently under investigation: Polymer-Derived Ceramics The thermolytic decomposition of suitable organosilicon polymers provides materials which are denoted as polymer-derived ceramics (PDCs). The main emphasis is on the synthesis and characterization of new ceramic materials in the B-C-N, Si-C-N, Si-O-C, Si(B,C)-N and Ti-(B-C)-N systems. The structural peculiarities, thermochemical stability, mechanical and electrophysical properties of the PDCs have been investigated in a series of PhD theses and research projects. Due to their outstanding thermochemical stability as well as excellent oxidation and creep resistance at very high temperatures, the PDCs constitute promising materials for high temperature applications. Another advantage of the PDC route is that the materials can be easily shaped in form of fibres, layers or bulk composite materials. Finally the correlation of the materials properties with the molecular structure of the used preceramic polymer is elaborated Molecular Routes to Nanoscaled Materials The aim is to develop concepts for the production of novel multifunctional inorganic materials with a tailor-made nanoscaled structure. In accordance with the so-called “bottom-up” approach, specific inorganic molecules are to be assigned to higher molecular networks and solid-state structures in the form of molecular nanotools by means of condensation and polymerisation processes. High Pressure Chemistry Ultra-high pressure techniques like laser heated diamond anvil cell (LH-DAC) or multi anvil devices have been applied to synthesise novel solid state structures which cannot be produced by other methods, for example, inorganic nitrides. Moreover, the materials behaviour under pressure such as phase transformations and decomposition can be analysed. Functional Materials Further research topics are related to the development of materials suitable for applications in the fields of microelectromechanical systems (MEMS), optoelectronics (LEDs), pressure, temperature and gas sensors as well as thermoresistant ceramic membranes for high temperature gas separation. The integration of state-of-the-art in situ and in operando spectroscopic methods is applied to understand the mechanisms responsible for sensing and catalytic properties. Institute of Materials Science - Dispersive Solids 53 Staff Members Head Prof. Dr. rer. nat. habil. Prof. h. c. Dr. h. c. Ralf Riedel Research Associates Dr. Dmytro Dzivenko Dr. Magdalena GraczykZajac PD Dr. Aleksander Gurlo Dr. Emanuel Ionescu Technical Personnel Dipl.-Ing. Claudia Fasel Secretaries Su-Chen Chang Tania Fiedler-Valderrama (EU project) Natallia Hurlo (substitute) Shobha Herur (substitute) PhD Students Dipl.-Ing. Miria Andrade M. Tech. Mahdi Seifollahi Bazarjani M. Sc. Shrikant Bhat M. Tech. Maged Bekheet M. Tech. Yan Gao M. Sc. Sarabjeet Kaur Dipl.-Ing. Jan Kaspar Dipl.-Ing. Amon Klausmann M. Sc. Wenjie Li Dipl.-Ing. Christoph Linck M. Tech. Ravi Mohan Prasad Dipl.-Ing. Lukas Mirko Reinold Dipl.-Ing. Felix Roth M. Sc. Cristina Schitco Dipl.-Ing. Lukas Schlicker Dipl.-Ing. Alexander Uhl M. Sc. Qingbo Wen M. Sc. Jia Yuan M. Sc. Cong Zhou Dr. Gabriela Mera Apl. Prof. Dr. Norbert Nicoloso Dr. Ravi Mohan Prasad M. Sc. Ahmad Choudhary Diploma and Master Omar Ariobi Students Oliver Genschka Xueying Hai Cornelia Hintze Chinomso Nwosu Bachelor Students Laszlo Horak Moritz Liesegang Mathias Storch Maximilian Wimmer Kerstin Wissel Alexander Zimpel Guest Scientists Prof. Dilshat Tulyaganov, Turin Polytechnic University in Tashkent, Tashkent, Uzbekistan Prof. Zhaoju Yu, Department of Materials Science and Engineering, College of Materials, Xiamen University, Xiamen China Michal Vetrecin, Institute of Inorganic Chemistry,Slovak Academy of Sciences, Bratislava, Slovakia Ondrej Hanzel, Institute of Inorganic Chemistry,Slovak Academy of Sciences, Bratislava, Slovakia 54 Institute of Materials Science - Dispersive Solids Dr. Monika Wilamowska, Department of Chemical Technology, Chemical Faculty, Gdansk University of Technology, Poland Prof. Dr. Corneliu Balan, Politehnica, University of Bucharest, Faculty of Enegetics, Hydraulics Departement, Bucharest, Romania Dr. Xingang Luan, Associate Professor, Northwestern University Polytechnical, Schule für Materialien, Xian, Shaanxi, PR China Prof. Linan An, Associate Professor and Director, Materials Processing Laboratory, University of Central Florida, USA Prof. Kathy Lu, Virginia Tech, College of Engineering, Department of Materials Science and Engineering, Blacksburg, USA Yohei Shimokawa, Department of Frontier Materials Graduate School of Engineering, Nagoya Institute of Technology, Nagoya, Japan Research Projects SiHfC(N) and SiHfN(C)-based Ultrahigh-Temperature Ceramic Nanocomposites (UHTCNCs) for EBC/TBC Applications (China Council Scholarship (CSC), Oct. 2012 - Oct. 2016) Nanocomposites as anode materials for lithium ion batteries: Synthesis, thermodynamic characterization and modeling of nanoparticular silicon dispersed in SiCN(O) and SiCObased matrices (DFG, Aug. 2010 - July 2016) High-Temperature Piezoresistivity in SiOC - Untersuchungen zur HochtemperaturPiezoresistivität in kohlenstoffhaltigen Siliciumoxycarbid-Nanokompositen(DFG, May 2013 - April 2016) Sensors Towards Terahertz (STT): Neuartige Technologien für Life Sciences, Prozess- und Umweltmonitoring (HMWK-LOEWE, Jan. 2013 - Dec. 2015) Mestabiles Indiumoxidhydroxid (InOOH) und Korund-Typ Indiumoxid (In2O3): Gezielte Synthese, Einkristallzüchtung und in-situ Charakterisierung der Umwandlungspfade und transienten Intermediaten (DFG, SPP 1415 "Kristalline Nichtgleichgewichtsstoffe", Jan. 2013 - Dec. 2015) Ternary M-Si-N Ceramics: Single-Source-Precoursor Synthesis and Microstructure Characterization (M = transition metal) (China Council Scholarship (CSC), Nov. 2012 Nov. 2015) Molecular Routes to SiMBCN Ceramic Nanocomposites (M = Zr, HF) (China Council Scholarship (CSC), Donghua University, Shanghai, China, Sep. 2011 - Aug. 2015) Institute of Materials Science - Dispersive Solids 55 FUNEA - Functional Nitrides for Energy Applications (Coordination, EU - Marie Curie Initial Training Network, Feb. 2011 - Jan. 2015) Novel functional ceramics with substitution of anions in oxidic systems (DFG, SFB 595, project A4, Jan. 2003 - Dec. 2014) Adaptronik - Research, Innovation, Anwendung (HMWK-Loewe-AdRIA, Oct. 2008 - Sep. 2014) Polymer-Processing of Dense and Crack-Free SiC Monoliths (Doctor Thesis, Oct. 2011 Sep. 2014) FUNEA - Gas seperation membranes (EU - Marie Curie Initial Training Network, Oct. 2011 - Sep. 2014) FUNEA - Multifunctional perovskite nitrides (EU - Marie Curie Initial Training Network, Oct. 2011 - Sep. 2014) Keramische SiCN-basierte Hartstoffschichten Substratwerkstoffe (DFG, June 2011 - June 2014) für thermisch hochbeanspruchte Untersuchung der Einflussparameter für die Biege- und Zugfestigkeitsverhalten oxidischer Verbundkörper mit gefüllter Polysiloxanmatrix (Diploma Thesis, Dec. 2013 - June 2014) High-Pressure High Temperature Synthesis of Novel Binary and Ternary Superhard Phases in the B-C-N System (DFG, Feb. 2011 - Jan. 2014) PrintSens: Nanoskalige gedruckte Hybridmaterialien als aktive Funktionselemente in mikrostrukturierteen Sensorbauteilen (Schwerpunkt Mikrosystemtechnik im Förderprogramm "IKT 2020 - Forschung für Innovationen" (BMBF VDI/VDE/IT, Jan. 2011 December 2013) Ceramic Nanocomposites for Applications in Extreme Environments (DAAD, Projekt-ID 54440408, Jan. 2012 - Dec. 2013) Investigation of polymer-derived, carbon-rich SiOC ceramics as potential Na-ion storage material (Bachelor Thesis, Sep. 2013 - Dec. 2013) Synthesis of Dense SiOC Ceramics with tailored Carbon Content (March 2013 - Oct. 2013) Thermoelektrika auf Basis von MSix/SiOC-Kompositen (Bachelor Thesis, June 2013 - Sep. 2013) Synthesis of Vanadium-Carbide-Based Nanocomposites from Single-Source Precursors (Diploma Thesis, April 2013 - Oct. 2013) Sol-gel derived SiOC materials as anodes for Li-ion batteries (DFG, SFB 595, Aug. 2013 Sept. 2013) 56 Institute of Materials Science - Dispersive Solids Carbon-coated new Si-based composite anode materials for Li-ion batteries (FAME intership, INP Grenoble-Phelma, May 2013 - Aug. 2013) Material Anticipatio Studies for Heat disspation in Electric Switches (Master Thesis FAME in Cooperation with Élève Ingénieure des Matériaux, Grenoble INP - PHELMA, France, April 2013 - Sep. 2013) Optmization of Mechanical and Conductivity Properties of Ply, Modified Polyethylene Glycol and a Blend of Poe: NPEG Reinforced by Nanocrystalline Cellulose and Crosslinking (Master Thesis FAME in Cooperation with Université Grenoble, LEPMI, Grenoble, France March 2013 - Aug. 2013) Multifunctional Graphene Nanocomposites (Master Thesis, Feb. 2013 - Aug. 2013) Herstellung und Eigenschften von polymerabgeleiteten (Bachelor Thesis, April 2013 - Aug. 2013) SiOC-Precursorkeramiken Thermoresistant Ceramic Membrane with Integrated Gas Sensor for High Temperature Separation and Detection of Hydrogen and Carbon Monoxide (DFG, Aug. 2010 - July 2013) Schwerpunkt Mikrosystemtechnik im Förderprogramm "IKT 2020 - Forschung für Innovationen" (BMBF VDI/VDE/IT, Jan. 2011 - June 2013) Au/Graphene Metamaterialstrukturen (EUMINAfab (EU) in Cooperation with university of Frankfurt and TCD, Dublin, Jan. 2013 – June 2013) Ionic liquids as electrolyte for Li-ion batteries (Bachelor Thesis, March 2013 – June 2013) Non Aqueous Sol-Gel Synthesis of Boron Carbide Based Materials (US Army International Technolog, Aug. 2009 - May 2013) Synthesis and characterization of rare-earth cation-doped silicon carbonitride phosphors (International Training Program of JSPS, May 2012 - April 2013) Nanostructure and Calorimetry of Amorphous SiCN and SiBCN (DFG, April 2010 - March 2013) Porous Carbon Impregnated with Polymer-Derived Ceramics as Anode Material for Lithium-Ion Batteries (Bachelor Thesis, Jan. 2013 - April 2013) Elektrische und mechanische Kontaktierung eines Hochtemperatur-Ultraschallwandlers (Bachelor Thesis, Dec. 2012 – Feb. 2013) Indium oxide (In2O3) under high pressure: rational design of new polymorphs and characterisation of their physico-chemical properties (DFG, since June 2009) Institute of Materials Science - Dispersive Solids 57 Publications [1] Wilamowska, M.; Graczyk-Zajac, M.; Riedel, R.; Composite materials based on polymerderived SiCN ceramic and disordered hard carbons as anodes for lithium-ion batteries; JOURNAL OF POWER SOURCES, 244 (2013) 80-86. [2] Kaspar, J.; Graczyk-Zajac, M.; Riedel, R.; Lithium insertion into carbon-rich SiOC ceramics: Influence of pyrolysis temperature on electrochemical properties; JOURNAL OF POWER SOURCES, 244 (2013) 450-455. [3] Mera, G.; Menapace, I.; Widgeon, S.; Sen, S.; Riedel, R.; Photoluminescence of assynthesized and heat-treated phenyl-containing polysilylcarbodiimides: role of crosslinking and free carbon formation in polymer-derived ceramics; APPLIED ORGANOMETALLIC CHEMISTRY, 27(11) (2013) 630-638. [4] Hojamberdiev, M.; Prasad, R.M.; Fasel, C.; Riedel, R.; Ionescu, E.; Single-sourceprec2ursor synthesis of soft magnetic Fe3Si- and Fe5Si3-containing SiOC ceramic nanocomposites; JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 33(13-14) (2013) 2465–2472. [5] Sen, S.; Widgeon, S.J.; Navrotsky, A.; Mera, G.; Tavakoli, A.; Ionescu, E.; Riedel, R.; Carbon substitution for oxygen in silicates in planetary interiors; PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 110(40) (2013) 15904-15907. [6] Balazsi, C.; Dusza, J.; Lojkowski, W.; Riedel, R.; E-MRS 2012 Fall Meeting, September 17-21, Warsaw University of Technology Preface; JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 33(12) (2013) SI 2215-2215. [7] Morita, K.; Mera, G.; Yoshida, K.; Ikuhara, Y.; Klein, A.; Kleebe, H.-J.; Riedel, R.; Thermal Stability, Morphology and Electronic Band Gap of Zn(NCN); SOLID STATE SCIENCES, 23 (2013) 50-57. [8] Li, W.; Ionescu, E.; Riedel, R.; Gurlo, A.; Can we predict the formability of perovskite oxynitrides from tolerance and octahedral factors?; JOURNAL OF MATERIALS CHEMISTRY A, 1 (2013) 12239-12245. [9] Liu, G.; Kaspar, J.; Reinold, L.M.; Graczyk-Zajac, M.; Riedel, R.; Electrochemical performance of DVB-modified SiOC and SiCN polymer-derived negative electrodes for lithiumion batteries; ELECTROCHIMICA ACTA, 106 (2013) 101-108. [10] Gao, Y; Widgeon, S.J.; Tran, T.B.; Tavakoli, A.H.; Mera, G.; Sen, S.; Riedel, R.; Navrotsky, A.; Effect of Demixing and Coarsening on the Energetics of Poly(boro)silazaneDerived Amorphous Si-(B-)C-N Ceramics; SCRIPTA MATERIALIA, 69(5) (2013) 347–350. [11] Bekheet, M.F.; Schwarz, M.; Lauterbach, S.; Kleebe, H.-J.; Kroll, P.; Stewart, A.; Kolb, U.; Riedel, R.; Gurlo, A.; In-situ high-pressure high-temperature experiments in multi-anvil assembly’s with bixbyite-type In2O3 and synthesis of corundum-type and orthorhombic In2O3 polymorphs ; HIGH PRESSURE RESEARCH, 33(3) (2013) 697-711. 58 Institute of Materials Science - Dispersive Solids [12] Reinold, L.M.; Graczyk-Zajac, M.; Gao, Y.; Mera, G.; Riedel, R.; Carbon-Rich SiCN Ceramics as High Capacity/High Stability Anode Material for Lithium-Ion Batteries; JOURNAL OF POWER SOURCES, 236 (2013) 224-229. [13] Nonnenmacher, K.; Kleebe, H.-J.; Rohrer, J.; Ionescu, E.; Riedel, R.; Carbon Mobility in SiOC/HfO2 Ceramic Nanocomposites; JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 96(7) (2013) 2058–2060. [14] Ionescu, E.; Terzioglu, C.; Linck, C.; Kaspar, J.; Navrotsky, A.; Riedel, R.; Thermodynamic Control of Phase Composition and Crystallization of Metal-Modified Silicon Oxycarbides; JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 96(6) (2013) 1899-1903. [15] Bekheet, M.F.; Schwarz, M.R.; Lauterbach, S.; Kleebe, H.-J.; Kroll, P.; Riedel, R.; Gurlo, A.; Orthorhombic In2O3 : a metastable polymorph of indium sesquioxide; ANGEWANDTE CHEMIE-INTERNATIONAL EDITION IN ENGLISH, 52(25) (2013) 6531-6535. [16] Ionescu, E.; Mera, G.; Riedel, R.; Polymer-Derived Ceramics: Materials Design towards Applications at Ultrahigh-Temperatures and in Extreme Environments; in „MAX Phases and Ultra-High Temperature Ceramics for Extreme Environments“, Eds. Low, J.; Sakka, Y.; Hu, C., IGI GLOBAL, Publishing (2013). [17] Gurlo, A.; Ceramic Gas Sensors; in Advanced Ceramics Science and Technology Volume 4: Applications (Eds. R. Riedel and I.-W. Chen), WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany (2013). [18] Colombo, P.; Mera, G.; Riedel, R.; Sorarù, G.D.; Polymer-Derived Ceramics: 40 Years of Research and Innovation; in Advanced Ceramics, in Ceramics Science and Technology Volume 4: Applications (Eds. R. Riedel and I.-W. Chen), WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany (July 2013) [19] Mera, G.; Ionescu, E.; Silicon-Containing Preceramic Polymers; ENCYCLOPEDIA OF POLYMER SCIENCE AND TECHNOLOGY, available online since 24th of May 2013. [20] Widgeon, S.; Mera, G.; Gao, Y.; Sen, S.; Navrotsky, A.; Riedel, R.; Effect of Precursor on Speciation and Nanostructure of SiBCN Polymer-Derived Ceramics; JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 96(5) (2013) 1651–1659. [21] Sellappan, P.; Guin, J.-P.; Rocherulle, J.; Celarie, F.; Rouxel, T.; Riedel, R.; Influence of diamond particles content on the critical load for crack initiation and fracture toughness of SiOC glass-diamond composites; JOURNAL OF THE EUROPEAN CERAMIC SOCIETY, 33(4) (2013) 847-858. [22] Hojamberdiev, M.; Bozgeyik, M.S.; Abdullah, A.M.; Bekheet, M.F.; Zhu, G.; Yan, Y.; Xu, Y.; Okada, K.; Hydrothermal-induced growth of Ca10V6O25 crystals with various morphologies in a strong basic medium at different temperatures; MATERIALS RESEARCH BULLETIN, 48(4) (2013) 1388-1396. [23] Sänze, S.; Gurlo, A.; Hess, C.; Monitoring Gas Sensors at Work: Operando RamanFTIR Study of Ethanol Detection by Indium Oxide; ANGEWANDTE CHEMIE-INTERNATIONAL EDITION IN ENGLISH, 52(13) (2013) 3607-3610. Institute of Materials Science - Dispersive Solids 59 [24] Drogowska, K.; Flege, S.; Rogalla, D.; Becker, H.-W.; Ionescu, E.; Kim-Ngan, N.-T.H.; Balogh, A.G.; Hydrogen content analysis in hydrogen-charged PZT ferroelectric ceramics; SOLID STATE IONICS, 235 (2013) 32-35. [25] Bazarjani, M.S.; Hojamberdiev, M.; Morita, K.; Zhu, G.; Cherkashinin, G.; Fasel, C.; Herrmann, T.; Breitzke, H.; Gurlo, A.; Riedel, R.; Visible Light Photocatalysis with c-WO3x/WO3×H2O Nanoheterostructures In situ Formed in Mesoporous Polycarbosilane-Siloxane Polymer; JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 135(11) (2013) 4467- 4475. [26] Pashchanka, M.; Prasad, R.M.; Hoffmann, R.C.; Gurlo, A.; Schneider, J.J.; InkjetPrinted Nanoscaled CuO for Miniaturized Gas-Sensing Devices; EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, 9 (2013) 1481-1487. [27] Miehe, G.; Lauterbach, S.; Kleebe, H.-J.; Gurlo, A.; Indium hydroxide to oxide decomposition observed in one nanocrystal during in situ transmission electron microscopy studies; JOURNAL OF SOLID STATE CHEMISTRY, 198 (2013) 364-370. [28] Knappschneider, A.; Litterscheid, C.; Dzivenko, D.; Kurzman, J.A.; Seshadri, R.; Wagner, N.; Beck, J.; Riedel, R.; Albert, B.; Possible Superhardness of CrB4; INORGANIC CHEMISTRY, 52 (2) (2013) 540-542. [29] Bekheet, M.F.; Schwarz, M.R.; Müller, M.M.; Lauterbach, S.; Kleebe, H.-J.; Riedel, R.; Gurlo, A.; Phase segregation in Mn-doped In2O3: in situ high-pressure high-temperature synchrotron studies in multi-anvil assemblies; RSC ADVANCES, 3(16) (2013) 5357-5360. [30] Mera, G.; Navrotsky, A.; Sen, S.; Kleebe, H.-J.; Riedel, R.; Polymer-Derived SiCN and SiOC Ceramics – Structure and Energetics at the Nanoscale; JOURNAL OF MATERIALS CHEMISTRY A, 1 (2013) 3826-3836. [31] Papendorf, B.; Ionescu, E.; Kleebe, H.-J.; Linck, C.; Guillon, O.; Nonnenmacher, K.; Riedel, R.; High-Temperature Creep Behavior of Dense SiOC-Based Ceramic Nanocomposites: Microstructural and Phase Composition Effects; JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 96(1) (2013) 272–280. [32] Jüttke, Y.; Richter, H.; Voigt, I.; Prasad, R. M.; Bazarjani, M. S.; Gurlo, A.; Riedel, R. Polymer derived ceramic membranes for gas separation; Chemical Engineering Transactions 2013, 32, 1891-1896. DOI:10.3303/CET1332316 Books Riedel, R. / Chen, I.-W.; Ceramics Science and Technology, Volume 4: Applications, WILEY-VCH, July 2013, ISBN: 978-3-527-31158-3. 60 Institute of Materials Science - Dispersive Solids Orthorhombic In2O3: A Metastable Polymorph of Indium Sesquioxide Maged F. Bekheeta, Marcus R. Schwarzb, Stefan Lauterbacha, Hans-Joachim Kleebea, Peter Krollc, Ralf Riedela, and Aleksander Gurloa a Fachbereich Material- und Geowissenschaften, Technische Universität Darmstadt, 64287 Darmstadt (Germany) b Technische Universität-Bergakademie Freiberg, Freiberg High Pressure Research Centre, Institut für Anorganische Chemie, 09599 Freiberg (Germany) c Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, TX 7600190065 (USA) Angew. Chem. (International Ed. in English), 52(25) (2013) 6531-6535. As our results led to some discussion in the community,[1] we set out to explore alternative high-pressure routes towards a large amount of the o’-In2O3 polymorph. The main goals of this work are as follows: 1) to synthesize macroscopic quantities of o’-In2O3; 2) to recover it to ambient pressure; and 3) to determine the crystal structure of o’-In2O3 under ambient conditions. It is important to note that other corundum-type sesquioxides, including Cr2O3,[2] Fe2O3,[3] and Al2O3,[4] transform to Rh2O3(II)-type structure under high pressure, but none of them have been recovered to ambient conditions to date. Therefore, the availability of Rh2O3(II)-type o’-In2O3 under ambient conditions will also contribute to better understanding of the structural chemistry and properties of other binary oxides. Our work differs from the previous studies[5,6,7] in three major aspects. First, we are guided by theoretical calculations that suggest using the metastable corundum-type rhIn2O3 (for the specimen details we refer to references [8, 9]) as starting material for the high-pressure synthesis of the orthorhombic o’-In2O3 polymorph. Computations indicate that o’-In2O3 is lower in enthalpy than the rh-In2O3 for pressures above 6.4 GPa (arrow 1 in Figure 1 a) and thus below the c- to o’-In2O3 transition (arrow 2 in Figure 1 a).[8] Both structures, rh-In2O3 and o’-In2O3, are connected by a diffusionless pathway via a common monoclininc P2/c subgroup (in analogy to Al2O3).[1a] We computed the activation barrier for the collective transition rh-In2O3 o’-In2O3 to 0.08 eV per atom, which corresponds to a temperature of about 650 8C at the transition pressure (Figure 1 b). Consequently, we expect a fast transformation rh-In2O3 o’-In2O3 under high-pressure high-temperature conditions. Second, as we aim at high-yield synthesis, we choose multi-anvil and toroid cell apparatus that allowed us to obtain macroscopic quantities (ca. 10–100 mm3) of o’-In2O3 polymorphs and also to grow macroscopic single crystals.[10] The synthesis in multi-anvil cells is considered as a step towards an industrial scale synthesis, for example, in a belt apparatus that allows circa 7 cm3 of material to be obtained under given conditions; a similar pressure is applied in industrial synthesis of diamond and cubic boron nitride.[11] Finally, we perform time-resolved synchrotron studies in multi-anvil assemblies to follow hase transformations in situ under high-pressure high-temperature conditions. The phase development in rh-In2O3 was monitored in situ by energy-dispersive X-ray diffractometry at the two-stage 6–8 MAX200X multi-anvil high-pressure diffractometer of the GFZ Potsdam (beamline W2, HASYLAB/DESY, Hamburg, Germany). New high-pressure/hightemperature multi-anvil assemblies for synchrotron studies developed at the Freiberg High Pressure Research Centre are employed.[12] These assemblies have low X-ray absorption and do not show any additional reflections from the sample environment (see the Supporting Information).[13] Institute of Materials Science - Dispersive Solids 61 The complete transformation from rh-In2O3 to o’-In2O3 takes less than 20 seconds at 600 °C and 9 GPa (arrow 1 in Figure 2), indicating fast kinetics as expected for a diffusionless transition. The XRD pattern of material rapidly quenched at 9 GPa from 600 °C to room temperature possesses only o’-In2O3 reflections. During decompression at room temperature, o’-In2O3 partially transforms to corundum-type rh-In2O3 at pressures below 1.0 GPa (arrow 2 in Figure 2). The structure refinement of the specimen recovered to ambient pressure confirms the coexistence of o’-In2O3 (fraction: 80.0 wt%), rh-In2O3 (15.9 wt%), and o-InOOH (4.1 wt%) as a side phase (Figure 3b, Table 1). In the next step, we explored whether the synthesis of o’-In2O3 could be reproduced ex situ in a toroid-type highpressure device that allows even larger macroscopic quantities to be obtained, as well as a fast compression/decompression rate and less experimental preparation times compared to multi-anvil devices.[14] In a typical experiment, rh-In2O3 was compressed to 8 GPa and heated at about 1000–1100 °C for 10 minutes. Figure 3c shows the X-ray powder diffraction pattern and Rietveld difference plot of the recovered specimen. The structure refinement (Figure 3c, Table 1) confirmed our finding from the in situ multi-anvil experiments and shows the coexistence of o’-In2O3 (fraction: 63.8 wt%), rh-In2O3 (31.5 wt%), and o-InOOH (4.7 wt%). The o-InOOH probably arises from the reaction between In2O3 and water under high-pressure and high-temperature (hydrothermal) conditions.[15] Possible water sources include the pressure standard or the sample itself. Interestingly, o-InOOH was also obtained as a side phase in recent synthesis of InMnO3 and In-Mn-Fe-O perovskites and corundum-type In2-2xZnxSnxO3 oxides performed at 6 GPa/1100–1500 °C and 7 GPa/1000 °C, respectively.[16] In three In2O3 polymorphs, which are available at ambient conditions, indium is octahedrally coordinated and oxygen tetrahedrally coordinated (Figure 4); the structural differences between them lie in the stacking of {InO6} octahedra. In c-In2O3, the {InO6} octahedra share corners and edges; in the other two it is the edges and faces. The o’-In2O3 is an orthorhombic distortion of the rh-In2O3 structure, in which each {InO6} octahedron shares only two edges with other octahedra rather than three in rh-In2O3. The interatomic distances are similar in all three structures; that is, the mean In_O distance is in the range 2.182–2.189 Å. o’-In2O3 is the densest polymorph, and the volume reduction from c-In2O3 and rh-In2O3 to o’-In2O3 is about 6 and 3%, respectively. In summary, we succeeded in synthesizing the orthorhombic o’-In2O3 polymorph from rhombohedral corundumtype rh-In2O3 under moderate high-pressure high-temperature conditions (8–9 GPa, 600–1100 °C) in multi-anvil and toroid apparatus. We were able to recover the polymorph to ambient pressure and temperature and to confirm its crystal structure by X-ray and electron diffraction at these conditions to be the Rh2O3(II)-type. Our experimental setup makes the orthorhombic o’-In2O3 polymorph available in large quantities for further physico-chemical characterization and provides an opportunity to grow o’-In2O3 as single crystals. 62 Institute of Materials Science - Dispersive Solids Figure 2. In situ energy-dispersive XRD patterns in multi-anvil assemblies of a rh-In2O3 specimen compressed at 9.0 GPa and heated up to 600 °C. The tick marks refer to the calculated Bragg positions of o’-In2O3 (bottom) and rh-In2O3 (top). Arrows indicate the complete phase transition rhIn2O3 o’-In2O3 (1) and the partial o’-In2O3 transformation to rh-In2O3 (2). Figure 1. a) A section of the enthalpy–pressure (H–p) diagram for indium oxide polymorphs; cIn2O3 is a reference structure. Arrows indicate transitions (1) rh-In2O3 o’-In2O3 and (2) c-In2O3 o’-In2O3. b) The relative enthalpy (per formula unit of In2O3) between o’-In2O3 and rh-In2O3 polymorphs at 0, 2, 4, and 6.4 GPa. Table 1: Phase composition of initial and recovered materials.[a] Specimen rh-In2O3 o’-In2O3 o-InOOH (R c, Z=6) (Pbcn, Z=4) (P21nm, Z=2) starting material (Figure 3a) 100%, a=5.4814 (5) c=14.4998(3) - - recovered from 9 GPa/ 600 °C (Figure 3b) 15.9% a=5.4795(4) c=14.4224 80% a=7.9295(1) b=5.4821(2) c=5.5898(6) 4.1% a=5.2587(9) b=4.5660(5) c=3.2669(6) recovered from 8 GPa/ ca. 1100 °C (Figure 3c) 31.5% a=5.4803(5) c=14.4484(1) 63.8% a=7.9208(1) b=5.4881(6) c=5.5977(1) 4.7% a=5.2611(8) b=4.5673(3) c=3.2709(4) [a] Fraction (wt%) and lattice parameters a, b, c [Å]. Institute of Materials Science - Dispersive Solids 63 Figure 3. Structure refinement of the starting material rh-In2O3 (a) and specimens recovered from the in situ multi-anvil cell (b) and toroid (c) experiments, showing observed and calculated intensities. Tick marks refer to Bragg reflections of o’-In2O3, rh-In2O3, and o-InOOH (bottom). Table 1 summarizes the results of the structure refinement. Figure 4. Coordination, density, and interatomic distances (in Å) in In2O3 polymorphs at ambient pressure. In and O atoms are shown as small and large balls, respectively. Notes and references [1] [2] [3] [4] [5] [6] 64 a) B. Xu, H. Stokes, J. J. Dong, J. Phys. Condens. Matter 2010, 22, 315403; b) A. Möller, P. Schmidt, M. Wilkening, Nachr. Chem. 2009, 57, 239-251; c) F. J. Manjón, D. Errandonea, Phys. Status Solidi B 2009, 246, 9-31. C. Wessel, R. Dronskowski, J. Solid State Chem. 2013, 199, 149-153. G. K. Rozenberg, L. S. Dubrovinsky, M. P. Pasternak, O. Naaman, T. Le Bihan, R. Ahuja, Phys. Rev. B 2002, 65, 064112. J. F. Lin, O. Degtyareva, C. T. Prewitt, P. Dera, N. Sata, E. Gregoryanz, H. K. Mao, R. J. Hemley, Nat. Mater. 2004, 3, 389-393. H. Yusa, T. Tsuchiya, J. Tsuchiya, N. Sata, Y. Ohishi, Phys. Rev. B2008, 78, 092107. A. Gurlo, D. Dzivenko, P. Kroll, R. Riedel, Phys. Status Solidi RRL 2008, 2, 269-271. Institute of Materials Science - Dispersive Solids [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] a) D. Liu,W. W. Lei, B. Zou, S. D. Yu, J. Hao, K.Wang, B. B. Liu, Q. L. Cui, G. T. Zou, J. Appl. Phys. 2008, 104, 083506; b) J. Qi, J. F. Liu, Y. He, W. Chen, C. Wang, J. Appl. Phys. 2011, 109, 063520. A. Gurlo, P. Kroll, R. Riedel, Chem. Eur. J. 2008, 14, 3306-3310. a) M. Epifani, P. Siciliano, A. Gurlo, N. Barsan, U. Weimar, J. Am. Chem. Soc. 2004, 126, 4078-4079; b) A. Gurlo, S. Lauterbach, G. Miehe, H.-J. Kleebe, R. Riedel, J. Phys. Chem. C 2008, 112, 9209-9213. T. Irifune, Mineral. Mag. 2002, 66, 769-790. E. Horvath-Bordon, R. Riedel, A. Zerr, P. F. McMillan, G. Auffermann, Y. Prots, W. Bronger, R. Kniep, P. Kroll, Chem. Soc. Rev. 2006, 35, 987-1014. M. Schwarz, T. Barsukova, C. Schimpf, D. Šimek, C. Lathe, D. Rafaja, E. Kroke in HASYLAB Users´Meeting, Hamburg, Germany, 2010. M. F. Bekheet, M. Schwarz, M. Mueller, S. Lauterbach, H. J. Kleebe, R. Riedel, A. Gurlo, RSC Adv., 2013, 3, 5357-5360. L. G. Khvostantsev, V. N. Slesarev, V. V. Brazhkin, High Pressure Res. 2004, 24, 371-383. A. N. Christensen, N. C. Broch, Acta Chem. Scand. 1967, 21, 1046-1056. a) D. A. Rusakov, A. A. Belik, S. Kamba, M. Savinov, D. Nuzhnyy, T. Kolodiazhnyi, K. Yamaura, E. Takayama-Muromachi, F. Borodavka, J. Kroupa, Inorg. Chem. 2011, 50, 3559-3566; b) A. A. Belik, T. Furubayashi, H. Yusa, E. Takayama-Muromachi, J. Am. Chem. Soc. 2011, 133, 9405-9412; c) C. A. Hoel, J. M. G. Amores, E. Moran, M. A. Alario-Franco, J. F. Gaillard, K. R. Poeppelmeier, J. Am. Chem. Soc. 2010, 132, 16479-16487. Institute of Materials Science - Dispersive Solids 65 Thermodynamic Control of Phase Composition and Crystallization of Metal-Modified Silicon Oxycarbides E. Ionescu,a C. Terzioglu,a C. Linck,a J. Kaspar,a A. Navrotsky,b and R. Riedela a Technische Universität Darmstadt, Institut für Materialwissenschaft, D-64287 Darmstadt, Germany Peter A. Rock Thermochemistry Laboratory and NEAT ORU, University of California Davis, Davis, California 95616 b J. Am. Ceram. Soc., 96(6) (2013) 1899–1903. Silicon oxycarbides modified with main group or transitionmetals (SiMOC) are usually synthesized via pyrolysis of sol-gel precursors from suitable metal-modified orthosilicates or polysiloxanes. In this study, the phase composition of different SiMOC systems (M = Sn, Fe, Mn, V, and Lu) was investigated. Depending on the metal, different ceramic phases formed. For M = Mn and Lu, MOx/SiOC ceramic nanocomposites were formed, whereas other compositions revealed the formation of M/SiOC (M = Sn), MSix/SiOC (M = Fe) or MCx/SiOC (M = V) upon pyrolysis. The different phase compositions of the SiMOC materials are rationalized by a simple thermodynamic approach which generally correctly predicts which type of ceramic nanocomposite is expected upon ceramization of the metal-modified precursors. Calculations show that the thermodynamic stability of the MOx phase with respect to that of the C–O system is the most important factor to predict phase formation in polymer-derived SiMOC ceramic systems. A secondary factor is the relative stability of metal oxides, silicates, carbides, and silicides. Experimental Procedures The synthesis of the precursors was performed as described elsewhere for SiZrOC and SiHfOC7,8 via chemical modification of a polysilsesquioxane (MK Belsil PMS; Wacker, Burghausen, Germany) with Fe(acac)3, Mn(acac)3, V(acac)3, VO(acac)2, Sn(ac)2, and Lu(ac)3 (ac = acetate; acac = acetylacetonate). Thus, each 5 g of polysilsesquioxane PMS was reacted with the corresponding amount of metal precursor at room temperature. For the reactions with the Fe, Mn, V, and Sn containing precursors, xylene was used as a solvent, whereas the reaction with Lu(ac)3 was performed in acetone. The amount of the metal precursor was chosen to obtain after pyrolysis a weight ratio between SiOC and a possible MOx phase (lowest oxide, which was assumed to precipitate) close to 70:30. To calculate the needed amounts of metal precursors, a ceramic yield of 81 wt% upon conversion of PMS into SiOC has been taken into account.7,8 In Table I, the amounts of the metal precursors used for the chemical modification of PMS is presented. Thus, the SiMOC-based ceramics were expected to exhibit similar MOx contents, between 30.9 and 36.7 wt% (see Table I). After mixing PMS with the metal precursor, the reaction solution was stirred for 2 h at room temperature. Subsequently, the solvent was removed under vacuum (10-2 mbar). The metal-modified precursors were cross-linked at 250°C and pyrolyzed in argon at 1100°C. The ceramic yield of the precursor-to-ceramic transformation processes showed values between 51.6 and 71.6 wt% (Table I). 66 Institute of Materials Science - Dispersive Solids Table I. Amounts of PMS and Metal Precursors Used as well as Ceramic Yields of the Syntheses of SiMOC Samples Sample Metal PMS (g) Metal precursor (g) SiOC SiFeOC SiSnOC SiMnOC SiLuOC SiVOC SiVOC Fe(III) Sn(II) Mn(III) Lu(III) V(III) V(IV) 5 5 5 5 5 5 5 7.8 3.1 8.6 3.2 9.0 6.9 Expected content of MOx in SiMOC (wt%) 34.1 36.7 36.2 30.9 33.1 36.3 Ceramic yield (wt%) Phase composition upon Pyrolysis at 1100°C 81.00 67.02 71.60 61.62 71.50 51.61 64.58 a-SiOC Fe3Si/a-SiOC Sn/a-SiOC MnSiO3/a-SiOC Lu2O3/a-SiOC V8C7/a-SiOC V8C7/a-SiOC Results and Discussion Pyrolysis of the metal-containing polyorganosiloxanes in Ar atmosphere at 1100°C results in the formation of SiMOC ceramics, which were shown by XRD to exhibit different crystalline phase compositions [Fig. 1(a)]. In SiFeOC, Fe3Si was observed, while the tincontaining precursor gave a Sn/SiOC ceramic composite. In both cases, Fe(III) and Sn(II) were reduced to Fe(0) (as in Fe3Si alloy) and Sn(0). It is thought that the reducing conditions during the pyrolysis of the precursors are responsible for the formation of the metallic phases and are mainly due to the release of hydrogen and CO upon ceramization.7 The Sn/SiOC ceramic did not change phase composition when annealed at 1300°C; whereas in Fe3Si/SiOC the crystallization of Fe5Si3 and b-SiC was found under the same conditions [Fig. 1(b)]. Similar behavior was reported previously for Fe3Si/SiCNO.18 Pyrolysis of the Mn-containing precursor led to a poorly crystalline SiMnOC ceramic. The XRD pattern revealed the presence of MnSiO3 [Fig. 1(a)], which was also observed upon annealing at 1300°C [Fig. 1(b)]. It is assumed that the phase separation of MnO (at temperatures between 800°C and 1100°C) and its subsequent reaction with the phase-separated silica at higher temperature leads to the formation of the MnSiO3 phase. Such formation of binary and ternary oxides is analogous to the behavior observed in SiZrOC and SiHfOC.7,9 However, the formation of MnSiO3 occurs at lower temperatures than those for ZrSiO4 and HfSiO4, which crystallize at temperatures exceeding 1400°C.7,9 Similar results were obtained in the case of the lutetiummodified precursor. Thus, at 1100°C poorly crystallized Lu2O3 was identified by XRD, whereas at 1300°C crystalline Lu2Si2O7 was found (Fig. 1). Different behavior was found for the vanadium-modified precursor. At both temperatures a poorly crystalline V8C7 was detected, which can result from the reaction of vanadium oxide with excess carbon (Fig. 1, as for SiVOC prepared upon pyrolysis of the V(ac)3modified precursor). Interestingly, both precursors, i.e., the V(III)- and the V(IV)-modified polysilsesquioxanes led upon pyrolysis to the crystallization of V8C7 (i.e., formation of SiOC/V8C7 nanocomposites). The strong effect of the precursor composition on the phase evolution upon ceramization reflects the reducing conditions during pyrolysis and annealing. Thus, it is obvious that the thermodynamic stability of the metal oxides generated during pyrolysis plays a crucial role. To assess this effect in more detail, thermodynamic data for the oxides (MOx) were used, as depicted in the Ellingham diagrams in Fig. 2. Since all samples were synthesized under the same pyrolysis conditions, the partial pressures of the volatiles (i.e., CO, CO2, Institute of Materials Science - Dispersive Solids 67 H2, and CH4) were not considered explicitly here. However, since carbon is present in all cases, it is appropriate to make a direct comparison between the CO–C and MOx – M equilibria. Since carbon is present in large amount in the investigated samples, the oxygen fugacity is determined by the equilibrium 2 C + O2 2CO. Fig. 1. X-ray diffraction (XRD) patterns for SiMOC (M = Fe, Sn, Mn, Lu, V) pyrolyzed at 1100°C (a) and 1300°C (b). Fig. 2. Ellingham diagrams showing the Gibbs free energy change of different oxides with respect to the system C–O (the gray areas correspond to the temperature range in which our samples were prepared, i.e., between 1100°C and 1300°C). Oxides with Gibbs free energies located in the area above the CO line will get reduced by carbon to their corresponding metals upon CO gas release; whereas those located in the area below the CO line will be stable against conversion into metals (data taken from Ref. [24]). 68 Institute of Materials Science - Dispersive Solids Conclusion In this study, we show that the thermodynamic stability of MOx with respect to the system C–O plays a crucial role within the context of the ceramization process of metalmodified polymers. Based on thermodynamic data of the respective oxides, the phase composition of SiMOC/SiMCNO ceramics upon annealing at high temperatures can be predicted for different metals. The prediction agrees with the experimental results from this study and those reported in the literature for both SiMOC and SiMCNO ceramic composites. However, in addition to the stability of the oxides with respect to reduction, some other aspects must be taken into account for predicting the phase composition of SiMOC/SiMCNO composites, such as thermodynamic stabilization through conversion into silicates (for MOx being stable with respect to carbothermal conversion into M) or into silicides or carbides (for MOx not being stable against carbothermal reduction). These factors are summarized in Fig. 3. A more rigorous computation of the thermodynamics of crystallization could employ free energy minimization techniques. However, this would require some knowledge or assumptions about the free energies of the metals dissolved in the initially homogeneous ceramics. Such information is not currently available. The main point of this study is that even a very simple thermodynamic approach predicts the observed phases formed with remarkable accuracy. Fig. 3. Predicted phase compositions of SiMOC and SiMCNO upon pyrolysis at 1100°C–1300°C. The oxides of the red marked metals are stable with respect to their reduction and thus SiOC/MO x nanocomposites are expected. Depending on the stability of the corresponding silicates (MSiO x), solid-state processes between MO and the phase-separated silica may occur, as observed for the case of Mn (crystallization of MnSiO3) and Lu (Lu2Si2O7) in this study. The oxides of the blue colored metals are not stable with respect to reduction by carbon. Consequently, SiOC/M nanocomposites are predicted to form here. Also in this case, the relative thermodynamic stability of the corresponding silicides or carbides will determine whether SiOC/MSi x or SiOC/MCx nanocomposites will be generated. References [1] E. Ionescu, C. Linck, C. Fasel, M. Müller, H. J. Kleebe, and R. Riedel, “Polymer-Derived SiOC/ZrO2 Ceramic Nanocomposites With Excellent High-Temperature Stability,” J. Am. Ceram. Soc., 93 [1] 241–50 (2010). [2] E. Ionescu, B. Papendorf, H. J. Kleebe, F. Poli, K. Muller, and R. Riedel, “Polymer-Derived Silicon Oxycarbide/Hafnia Ceramic Nanocomposites. Part I: Phase and Microstructure Evolution During the Ceramization Process,” J. Am. Ceram. Soc., 93 [6] 1774–82 (2010). [3] A. Francis, E. Ionescu, C. Fasel, and R. Riedel, “Crystallization Behavior and Controlling Mechanism of Iron-Containing Si-C-N Ceramics,” Inorg. Chem., 48 [21] 10078–83 (2009). [4] E. Ionescu, B. Papendorf, H. J. Kleebe, and R. Riedel, “Polymer-Derived Silicon Oxycarbide/Hafnia Ceramic Nanocomposites. Part II: Stability Toward Decomposition and Microstructure Evolution at T»1000 Degrees C,” J. Am. Ceram. Soc., 93 [6] 1783–9 (2010). [5] T. B. Reed, Free Energy of Formation for Binary Compounds. MIT Press, Cambridge, MA, 1971. Institute of Materials Science - Dispersive Solids 69 Structure Research In the year 2013, we completed the home-made MBE-setup for metallic films. Now we can grow thin metallic samples in Ultra High vacuum and transfer them, without braking the vacuum, into a small x-ray baby chamber (see separate report). The baby chamber is equipped with a hemisperical aluminum window and is not only compatible with our sixcircle diffractometer, but also with comparable instruments at various synchrotron sources. Several neutron scattering campaigns were carried out in an effort to quantify the structure and dynamics of defects in Ba-doped bismuth sodium titanate. In addition to measurements of the diffuse scattering, we used the extended x-ray absorption fine structure to characterize the local environment of the different species. Data evaluation is under way. Staff Members Head Prof. Dr. Wolfgang Donner Prof. Dr. Dr. h.c. Hartmut Fueß Research Associates Dr. Joachim Brötz Dr. Marton Major Dr. Ljubomira Schmitt Dr. Azza Amin Technical Personnel Dipl. Ing. Heinz Mohren Jean-Christophe Jaud Maria Bense Ingrid Svoboda Sabine Foro PhD Students M. Sc. Qiran Li M. Sc. Marco Léal Dipl.-Ing. Florian Pforr Dipl.-Ing. Dominik Stürmer Master Michael Brilz Guest Scientists Prof. Dr. Ismael Saadoune, Université Cadi Ayyad, Maroc Secretary Prof. Dr. Anouar Njeh, University of Sfax, Tunesia Research Projects Structural investigations into the electric fatigue in piezo-ceramics (DFG-SFB, 2011-2014) Development of electrode materials for high capacitance devices (IDS-FunMat, 2013-2015) Phase transitions in thin potassium sodium niobate films (IDS-FunMat, 2012-2015) Influence of biaxial strain and texture on the elastic properties of Barium Strontium Titanate thin films (AvH Lab Partnership, 2013-2015) Publications [1] Siol, Sebastian; Straeter, Hendrik; Brueggemann, Rudolf; Broetz, Joachim; Bauer, Gottfried H.; Klein, Andreas; Jaegermann, Wolfram; PVD of copper sulfide (Cu2S) for PIN-structured solar cells; JOURNAL OF PHYSICS D-APPLIED PHYSICS Volume: 46 Issue: 49 Article Number: 495112 (2013) 70 Institute of Materials Science - Structure Research [2] Pfeifer, Verena; Erhart, Paul; Li, Shunyi; Rachut, Karsten; Morasch, Jan; Broetz, Joachim; Reckers, Philip; Mayer, Thomas; Ruehle, Sven; Zaban, Arie; Mora Sero, Ivan; Bisquert, Juan; Jaegermann, Wolfram; Klein, Andreas; Energy Band Alignment between Anatase and Rutile TiO2; JOURNAL OF PHYSICAL CHEMISTRY LETTERS Volume: 4 Issue: 23 Pages: 41824187 (2013) [3] Labrini, Mohamed; Saadoune, Ismael; Scheiba, Frieder; Almaggoussi, Abdelmajid; Elhaskouri, Jamal; Amoros, Pedro; Ehrenberg, Helmut; Broetz, Joachim; Magnetic and structural approach for understanding the electrochemical behavior of LiNi0.33Co0.33Mn0.33O2 positive electrode material; ELECTROCHIMICA ACTA Volume: 111 Pages: 567-574 (2013) [4] Muench, Falk; Oezaslan, Mehtap; Rauber, Markus; Kaserer, Sebastian; Fuchs, Anne; Mankel, Eric; Broetz, Joachim; Strasser, Peter; Roth, Christina; Ensinger, Wolfgang; Electroless synthesis of nanostructured nickel and nickel-boron tubes and their performance as unsupported ethanol electrooxidation catalysts JOURNAL OF POWER SOURCES Volume: 222 Pages: 243-252 (2013) [5] Z.K. Heiba, M.B. Mohamed, H. Fuess, Structural and magnetic properties of Sm2-xMnxO3 nanoparticles, Materials Research Bull. 48, 3750-3755, 2013 [6] J. P. Patel, A. Senyshyn, H. Fuess, D. Pandey Evidence for weak ferromagnetism, isostructural phase transition, and linear magnetoelectric coupling in the multiferroic Bi0.8Pb0.2Fe0.9Nb0.1O3 solid solution Phys. Rev. B 88 (10) 104108, 2013 [7] A. Senyshyn, O. Dolotko, M.J. Mühlbauer, K. Nikolowski, H. Fuess, H. Ehrenberg Lithium Intercalation into Graphite Carbons Revisited: Experimental Evidence for Twisted Bilayer Behavior J. Electrochem. Soc. 160 (5) A 3198-A 3205, 2013 [8] S. Bhattacharjee, A. Senyshyn, H. Fuess, D. Pandey Morin-Type spin-reorientation transition below the Neel transition in the monoclinic compositions of (1-x) BiFeO3-xPbTiO(3) (x= 0.25 and 0.27): A combined dc magnetization and x-ray and neutron powder diffraction study Phys. Rev. B 87 (5) 05417, 2013 [9] H. Ehrenberg, A. Senyshyn, M. Hinterstein, H. Fuess 16. In Situ Diffraction Measurements: Challenges, Instrumentation, and Examples. In E.J. Mittermeijer & U. Welzel (Eds)., Modern Diffraction Methods (528). Weinheim: Wiley-VCH [10] Epitaxial growth and control of the sodium content in NaxCoO2 thin films Hildebrandt, S; Komissinskiy, P; Major, M; Donner, W; Alff, L THIN SOLID FILMS Volume: 545 Pages: 291-295 DOI: 10.1016/j.tsf.2013.08.072 Published: OCT 31 2013 Institute of Materials Science - Structure Research 71 [11] Synthesis, structure and magnetic properties of Ni(II)-Co(II) heterodinuclear complexes with ONNO type Schiff bases as ligands Oz, S; Titis, J; Nazir, H; Atakol, O; Boca, R; Svoboda, I; Fuess, H POLYHEDRON Volume: 59 Pages: 1-7 DOI: 10.1016/j.poly.2013.04.047 Published: AUG 1 2013 [12] Local structure, pseudosymmetry, and phase transitions in Na1/2Bi1/2TiO3K1/2Bi1/2TiO3 ceramics Levin, I; Reaney, IM; Anton, EM; Jo, W; Rodel, J; Pokorny, J; Schmitt, LA; Kleebe, HJ; Hinterstein, M; Jones, JL PHYSICAL REVIEW B Volume: 87 Issue: 2 Article Number: 024113 DOI: 10.1103/PhysRevB.87.024113 Published: JAN 31 2013 72 Institute of Materials Science - Structure Research A portable X-ray analysis chamber with in vacuo vertical transfer Azza Amin, Herry Wedel, Michael Weber, Jochen Rank, and Wolfgang Donner The x-ray diffraction analysis of reactive surfaces requires an Ultra High Vacuum (UHV) environment and, at the same time, an x-ray transparent window. Furthermore, because of space constraints on x-ray diffractometers, a UHV analysis chamber has to be lightweight, compact and transferable. We designed and built a portable x-ray analysis chamber with a hemispherical aluminum window. The sample holder can be moved vertically from the transfer position to the measurement position using a dedicated in vacuo mechanism. Fig. 1: Left: cross section of the UHV baby chamber in transfer position. The sample holder (dark green) is transferred through the left CF-flange (yellow). Right: sample holder (dark green) in measurement position inside the hemisperical window. Figure 1 shows a cross section through the chamber: the black boxes represent the ion getter pumps, which are battery-driven to facilitate transferabilty. The stainless steel body ends with a CF100 flange that carries the x-ray window, mashined out of a solid piece of high-strength Al alloy. Since the transfer of the sample holder from the growth chamber takes place through the (yellow) CF38 flange on the left, the sample holder has to be lifted into the x-ray window for measurements. In order to be in an eucentric position of the diffractometer, the total height of the sample surface must not exceed 170 mm. This prohibits the use of outside bellows or magnetic transfer rods for the vertical movement. Instead, the vertical transfer has to be in vacuo. This design makes the chamber unique. A stepper motor-driven worm drive takes the entire sample stage, including heater and thermocouple contacts, on a 50 mm travel. All parts of the transfer mechanism are made of UHV compatible materials and are therefore fully bakable. Figure 2 shows an example of x-ray diffraction measurements made possible by the chamber: a radial scan along the surface normal ([H0H]-direction) of a thin indium film on tungsten. The film has been grown at a temperature of 130 K, annealed at 350 K, and then transferred. Oscillations due to the finite thickness of the sample (Laue oscillations) are visible on either side of the Bragg peak. A preliminary fitting reveals the thickness (24 monolayers) and the reason for the pronounced asymmetry of the Laue oscillations: the coherent epitaxial growth leads to a strain gradient close to the film-substrate interface. Institute of Materials Science - Structure Research 73 Fig. 2: Radial scan along the [H 0 H] direction of a 24 monolayer (6.7nm) epitaxial indium W(001). The film thin on asymmetric Laue oscillations in the data (circles) can be reproduced assuming a model with a vertical gradient in the lattice parameter (straight line). 74 Institute of Materials Science - Structure Research Materials Analysis The Materials Analysis group participates in two of the five Research Clusters of the Technische Universität Darmstadt: New Materials and Nuclear and Radiation Science. On the one hand the group is concerned with the characterization of self-synthesized modern materials, on the other hand with effects on materials caused by exposition to detrimental influences like ion irradiation. The research aims for clarification of the correlation of materials properties and synthesis or exposition parameters, respectively, by investigation of the elemental composition and the chemical binding. Current research topics are: Advanced 3-D Nanoobjects: Nanochannels, -wires, -tubes, and –networks: In collaboration with the GSI Helmholtz Centre for Heavy Ion Research, nanoporous membranes are formed by ion irradiation of polymer foils producing latent ion damage tracks which are chemically etched to nanochannels. These ion track (nano) filters can be used for filtering particles from liquids, collecting aerosols, for gas separation, and for analyzing small (bio)molecules. In the latter case, the nanochannel walls are chemically modified so that the nanochannel sensor becomes sensitive and selective to certain molecular species. Apart from polymer-based nanochannels, anodically oxidized aluminium (AAO) is used. Filling the polymer or AAO nanochannels galvanically with metals, such as copper, gold or platinum, and dissolving the templates, nanowires are formed. Here, different metal deposition conditions are used in order to obtain monometal but also multimetal (e.g. CuCo- and CuFe) nanowires. By redox-chemical reactions, the nanochannel walls can be coated with metal or metal oxide films, such as Ni, Cu, Ag, Au, Pt, Pd, and ZnO, SnO2, TiO2, In2O3, FexOy. Thus, nanotubes can be formed. Here, different morphologies are available, ranging from smooth compact nanotube walls to nanoporous walls to rough or peaked structures. When the nanochannels are crossed, the resulting nanowires are interconnected, forming nanowire networks. Dimensions, surface topography, microstructure, and crystallinity of these nanostructures are investigated. Macroscopic properties such as thermal stability, electrical conductivity and catalytic activity are analysed. Additionally, the obtained properties are evaluated with respect to applications as sensors, for gas flow or acceleration measurements, catalysts, for chemical reactions in microreactors, or electrodes in fuel cells. Thin film and coating deposition and analysis: In thin film and coating technology, the identification of chemical compounds, phases and binding conditions is of basic importance. Different methods are used for the formation of thin films (nanofilms), thick films and coatings. Surface modifications and layer deposition are performed via a plasma process. With plasma immersion ion implantation (PIII) it is possible to alter several surface properties by ion implantation. Different gaseous species are used such as oxygen, nitrogen and hydrocarbons, depending on the property to be modified, e.g. hardness, wear resistance, lifetime and biocompatibility. Using hydrocarbon gases films of diamond-like carbon (DLC) are deposited. Research topics are the adhesion of the DLC films to different substrates and the influence of the addition of different elements, especially metals, to the DLC films. The films are investigated for their chemical and phase composition, microstructure, adhesion, and in relation to biological applications, tribological properties, corrosion and wear Institute of Materials Science - Materials Analysis 75 protection of metal substrates, wettability, and temperature stability. Since the PIII technique is also suitable for complex shaped substrates, the treated substrates also include samples such as tubes, where the focus in on the treatment of their inner surfaces. Oxide films, such as lead-free piezoelectrics like sodium potassium niobate (NKN), are prepared by the sol-gel technique combined with spin coating. The addition of NKN powder to the films is investigated as a means to increase the film thickness. Materials in radiation fields: Irradiation of materials with energetic particles (protons, heavy ions) and electromagnetic radiation (X-rays, gamma-rays) may lead to degradation of the materials’ properties. This happens to components in space vehicles, in nuclear facilities and in particle accelerators. Polymers with their covalent bonds are particularly sensitive towards ionizing radiation. Polyimide, vinyl polymers and fiber-reinforced polyepoxides, which are components of superconducting beam guiding magnets at the future FAIR synchrotron and storage rings, oxides such as alumina which are used as beamdiagnostic scintillator screens, and semiconductor components such as CCDs are irradiated and characterized for their properties, such as polymeric network degradation, mechanical strength, electrical resistance, dielectric strength, and optical properties. Apart from basic questions on material’s degradation mechanisms by energetic radiation, the investigations are used to estimate service life-times of the materials/components. Staff Members Head Prof. Dr. Wolfgang Ensinger Research Associates Dr. Mubarak Ali Dr. Adam G. Balogh Dr. Stefan Flege Dr. Ruriko Hatada Dr. Peter Hoffmann Dr. Falk Münch Dr. Quoc Hung Nguyen Technical Personnel Renate Benz Brunhilde Thybusch PhD Students Anton Belousov Eva-Maria Felix Umme Habiba Hossain Martin Hottes Renuka Krishnakumar Stephan Lederer Alice Lieberwirth Vincent Lima Saima Nasir Cornelia Neetzel Tim Seidl Christian Stegmann Sebastian Wiegand Diploma and Master Alexandra Bobrich Students Nico Dams Rene Fischer Anja Habereder Ulla Hauf Nicolas Jansohn Mario Klaric Pejman Khamegir Sandra Schäfer Bachelor Students Adjana Eils Carolin Fritsch Tim Hellmann Christoph Kober Jona Schuch David Wieder Guest Scientists Prof. Dr. Takaomi Matsutani Takehiko Matsuya Evgenija Ermakova 76 Institute of Materials Science- Materials Analysis Research Projects Preparation of lead free piezo electric thin films (LOEWE centre AdRIA 2008–2014) Simulations on the influence of swift ion irradiation on materials of FAIR-components (GSI, 2010–2013) NanoC – Preparation, modification and characterization of nanochannels in polymer membranes (Beilstein-Institut, 2009–2013) NanoMag – Spin-dependent scattering in magnetic and Kondo nanowires (Beilstein-Institut, jointly with Goethe Universität Frankfurt am Main, 2009–2013) 3-Dimensional micro-nano-integration for gas flow sensor technology (BMBF, 2011–2013, jointly with Institut für Elektromechanische Konstruktionen, TU Darmstadt) Electromechanical sensors with one-dimensional nano objects (BMBF, 2011–2013, jointly with Institut für Elektromechanische Konstruktionen, TU Darmstadt) Beam diagnosis and radiation damage diagnosis – Scintillator materials for high current diagnosis (BMBF/GSI 2012–2015) Beam diagnosis and radiation damage diagnosis – radiation damage of accelerator components made out of plastics and countermeasures (BMBF/GSI 2012-2015) New technologies for efficient solar energy systems (DFG, 2012–2013) Investigation of technologically important nanostructured materials by high resolution ion beam analysis (DLR, 2012-2013) Publications [1] F. Muench, M. Oezaslan, M. Rauber, S. Kaserer, A. Fuchs, E. Mankel, J. Brötz, C. Roth, W. Ensinger; Electroless Synthesis of Nanostructured Nickel and Nickel-Boron Tubes and their Performance as Unsupported Ethanol Electrooxidation Catalysts, JOURNAL OF POWER SOURCES, 222 (2013) 243-252. [2] S. Wiegand, S. Flege, O. Baake, W. Ensinger; Effect of different calcination temperatures and post annealing on the properties of 1,3 propanediol based Sol-Gel (Na0.5K0.5)NbO3 (NKN) thin films; JOURNAL OF ALLOYS AND COMPOUNDS, 548 (2013) 38-45. [3] F. Muench, A. Fuchs, E. Mankel, M. Rauber, S. Lauterbach, H.-J. Kleebe, W. Ensinger; Synthesis of nanoparticle / ligand composite thin films by sequential ligand self assembly and surface complex reduction; JOURNAL OF COLLOID AND INTERFACE SCIENCE, 389 (2013) 23-30. [4] K. Baba, R. Hatada, S. Flege, W. Ensinger, Y. Shibata, J. Nakashima, T. Sawase, T. Morimura; Preparation and antibacterial properties of Ag-containing diamond-like carbon films prepared by a combination of magnetron sputtering and plasma source ion implantation; VACUUM, 89 (2013) 179-184. Institute of Materials Science - Materials Analysis 77 [5] W. Ensinger, E. Marin, L.Guzman; Ion beam based composition and texture control of titanium nitride; VACUUM 89 (2013) 229-232. [6] B. Pollakowski, P. Hoffmann, M. Kosinova, O. Baake, V. Trunova, R. Unterumsberger, W. Ensinger, B. Beckhoff; Non-destructive and non-preparative chemical nanometrology of internal material interfaces at tunable high information depths; ANALYTICAL CHEMISTRY, 85 (2013) 193-200. [7] S. Nasir, P. Ramirez, M. Ali, I. Ahmed, L. Fruk, S. Mafe, W. Ensinger; Nernst-Planck model of photo-triggered, pH–tunable ionic transport through nanopores functionalized with “caged” lysine chains; JOURNAL OF CHEMICAL PHYSICS, 138 (2013) 034709. [8] S. Wiegand, S. Flege, O. Baake, W. Ensinger; Effect of Different Calcination Temperatures and Post Annealing on the Properties of Acetic Acid Based Sol-Gel (Na0.5K0.5)NbO3 (NKN) Thin Films; JOURNAL OF MATERIALS SCIENCE & TECHNOLOGY, 29 (2013) 142-148. [9] K. Drogowska, S. Flege, D. Rogalla, H.-W. Becker, E. Ionescu, N.-T.H. Kim-Ngan, A.G. Balogh; Hydrogen content analysis in hydrogen-charged PZT ferroelectric ceramics; SOLID STATE IONICS, 235 (2013) 32-35. [10] M. N. Tahir, M. Ali, R. Andre, W. E. G. Müller, H. C. Schröder, W. Tremel, W. Ensinger; Silicatein conjugation inside nanoconfined geometries through immobilized NTA–Ni(II) chelates; CHEMICAL COMMUNICATIONS 49, (2013) 2210-2212. DOI: 10.1039/C3CC38605H [11] P. Ramirez, V. Gomez, M. Ali, W. Ensinger, S. Mafe; Net currents obtained from zero-average potentials in single amphoteric nanopores; ELECTROCHEMISTRY COMMUNICATIONS, 31 (2013) 137-140. [12] A. A. Younis, W. Ensinger, M. M. B. El-Sabbah, R. Holze; Corrosion protection of pure aluminium and aluminium alloy (AA7075) in salt solution with silane-based sol–gel coatings; MATERIALS AND CORROSION, 64 (2013) 276-283. [12] W. Ensinger, S. Flege, R. Hatada, S. Ayata, T. Matsutani, K. Baba; Hermetic Protection of Rings by Ion Beam Sputter Coating with a Broad Beam Ion Source and a W-Shaped Hollow Sputter Target; TRANSACTIONS OF THE MATERIALS RESEARCH SOCIETY OF JAPAN, 38 (2013) 97-100. [13] M. Pavlovič, M. Miglierini, E. Mustafin, W. Ensinger, A. Šagátová, T. Seidl, M. Šoka; Influence of xenon ion irradiation on magnetic susceptibility of soft-magnetic alloys; Proceedings of the 19th International conference on APPLIED PHYSICS OF CONDENSED MATTER (eds. J. Vajda, I. Jamnický), 2013, p. 78-81 [14] B. Lyson-Sypien, A. Czapla, M. Lubecka, E. Kusior, K. Zakrzewska, M. Radecka, A. Kusior, A.G. Balogh, S. Lauterbach, H.-J. Kleebe; Gas sensing properties of TiO2–SnO2 nanomaterials; SENSORS AND ACTUATORS B: CHEMICAL, 187 (2013) 445–454. 78 Institute of Materials Science- Materials Analysis [15] E. ElHaddad, W. Ensinger, C. Schüth; Untersuchungen zur Sorptionsreversibilität von organischen Schadstoffen in Aktivkohle, Holzkohle und Zeolith Y-200; GRUNDWASSER, 18 (2013) 197-202. [16] M. Ali, S. Nasir, I. Ahmed, L. Fruk, W. Ensinger; Tuning nanopore surface polarity and rectification properties through enzymatic hydrolysis inside nanoconfined geometries; CHEMICAL COMMUNICATIONS, 49 (2013) 8770-8772. [17] M. Ali, S. Nasir, P. Ramirez, J. Cervera, S. Mafe, W. Ensinger; Carbohydrate-Mediated Biomolecular Recognition and Gating of Synthetic Ion Channels; THE JOURNAL OF PHYSICAL CHEMISTRY C, 117 (2013) 18234-18242. [18] S. Wiegand, S. Flege, W. Ensinger; Comparison of the influence of titanium and chromium adhesion layers on the properties of sol-gel derived NKN thin films; JOURNAL OF SOL GEL SCIENCE AND TECHNOLOGY, 67 (2013) 654-659. [19] Z. Tarnawski, Nhu-T. H. Kim-Ngan, K. Zakrzewska, K. Drogowska, A. Brudnik, A. G. Balogh, R. Kužel, L. Havela, V. Sechovsky; Hydrogen storage in Ti–TiO2 multilayers; ADVANCES IN NATURAL SCIENCES: NANOSCIENCE AND NANOTECHNOLOGY, 4 (2013) 025004. [20] A.A. Younis, W. Ensinger, R. Holze; Impedance measurements at sol-gel based polysiloxane coatings on aluminium and its alloys; in: LECTURE NOTES ON IMPEDANCE SPECTROSCOPY: Volume 4, 99-106, Ed. O. Kanoun, CRC Press, 2013, ISBN 9781138001404. [21] S. Quednau, F. Dassinger, M. Hottes, C. Stegmann, W. Ensinger, H.F. Schlaak; Integration und Charakterisierung von Nanostrukturen in Mikrosysteme für sensorische Anwendungen; in: Proceedings: MIKROSYSTEMTECHNIK 2013, Eds. GMM, VDI/VDE-IT, ISBN 978-38007-3555-6. [22] K. Drogowska, S. Flege, H.-W. Becker, Z. Tarnawski, K. Zakrzewska, A.G. Balogh Physical properties of multilayer thin films of Ti-V and their hydrides studied by ion beam analysis methods in: Nanotechnology 2013: Advanced Materials, CNTs, Particles, Films and Composites (Volume 1), p. 124-127, Ed. Nano Science and Technology, Institute, Crc PressI Llc, ISBN: 978-1-4822-0581-7. Institute of Materials Science - Materials Analysis 79 Ag-containing Diamond-like carbon films deposited on the interior surface of a tube R. Hatada, S. Flege, A. Bobrich, T. Matsutani, W. Ensinger Adhesive Diamond-like carbon (DLC) films can be prepared by plasma immersion ion implantation (PIII) which is also suitable for the treatment of 3D objects because it is a nonline of sight technique. The incorporation of a metal into the DLC film provides a possibility to change the characteristics of the DLC film. For an improved biocompatibility Ag, Cu or TiO2 nanoparticles can be added. One commonly used combination for this purpose is simultaneous sputtering and hydrocarbon PIII. The properties of Ag-DLC films prepared by silver magnetron sputtering and acetylene PIII were reported in refs. [1, 2]. If the coating is to be done on the inner surface of a tube, however, there is usually the problem of an inhomogeneous distribution of the metal inside of the tube. There would be a strong gradient of the metal concentration with increasing distance from the metal source. Here, a different approach was developed. An auxiliary metal electrode along the central axis of the tube is normally implemented to achieve a more homogeneous thickness of the coating and to increase the energy of the plasma ions. This auxiliary electrode can be used to provide metal ions, as well. Selecting a silver (or silver covered) electrode and applying a negative DC voltage to it, sputtering of the electrode will occur which will then distribute Ag particles inside of the tube. So, a two step process was developed: in a first step a DLC film was deposited on the inside of the tube. A negative high voltage pulser was connected to the tube, whereas the auxiliary electrode was non-grounded. The latter was done to increase the plasma density within the tube by directing the electrons towards the outside of the tube. In the second step the tube was grounded and a negative DC voltage was applied to the auxiliary electrode. When the plasma ions hit the electrode, they remove Ag atoms from the electrode which are then incorporated into the DLC film. The composition of the plasma gas was also changed for the second step, from a hydrocarbon gas to a mixture of argon and hydrocarbons. Fig. 1: The two steps of the coating process, left: DLC deposition, right: Ag sputtering. AE: auxiliary electrode. The resulting coating consists of a DLC film with Ag nanoparticles in its outer surface. Earlier investigations [2] have shown that a few percent of Ag are already enough to achieve an antibacterial effect. The samples were characterized by secondary ion mass spectrometry depth profiling, X-ray photoelectron and Raman spectroscopy and atomic force microscopy. The antibacterial properties were checked by growth and survival tests of Staphylococcus aureus bacteria. 80 Institute of Materials Science- Materials Analysis The silver concentration of the DLC films ranged from 0.6 to 6.6 at.% depending on the chosen experimental conditions. Higher concentrations could be achieved using a higher pressure during the deposition process. The sputtering time was between 1 and 2 hours for the samples with the higher Ag concentrations. The silver is mainly located in the top surface area of the samples. In depth profiles the Ag intensity decreases slowly over the first 10 nm by about one order of magnitude. The slow decrease is due to the agglomeration of the Ag into nanoscale silver crystals as can be seen in TEM images [2] and due to the surface roughness of the samples. According to AFM images the average surface roughness of a pure DLC sample is 0.4 nm. The average surface roughness increases with Ag content up to 4.9 nm for the 6.6 at.% Ag sample. This is due to the mentioned silver agglomeration but also because of roughening caused by some sputtering of the DLC film during the second step of the process. The ID/IG value of the samples from the Raman measurement changed only slightly and was about 2.0. The survival test of the S. aureus bacteria shows an obvious difference between a pure DLC sample and one with 6.6 at.% Ag. While the sample on the left in Fig. 2 shows large areas with surviving bacteria, the sample on the right does not show any sign of survived bacteria. Here, the color is the indicator; the growing bacteria change the pH value of the medium and thus cause a phenol red indicator to change its color. Fig. 2: Results of the bacterial survival test. Left: pure DLC coating, right: DLC coating with 6.6 at.% Ag. The brighter color on the left indicates bacterial growth. It could be shown that it is possible to prepare DLC films containing silver on the inside of a tube by the combination of plasma immersion ion implantation and DC sputtering of an auxiliary electrode. Although the achievable Ag concentrations are only in the range of a few atomic percent, this is sufficient to cause an antibacterial effect as demonstrated with S. aureus bacteria. References: [1] [2] K. Baba, R. Hatada, S. Flege, W. Ensinger, Advances in Materials Science and Engineering, 2012 (2012), p. 536853. K. Baba, R. Hatada, S. Flege, W. Ensinger, Y. Shibata, J. Nakashima, T. Sawase, T. Morimura, Vacuum, 89 (2013), pp. 179-184. Institute of Materials Science - Materials Analysis 81 New activation processes for the electroless synthesis of metal nanotubes Falk Münch, Wolfgang Ensinger One focus of the materials analysis group is the fabrication of one-dimensional metal nanomaterials such as nanotubes and nanowires by applying electroless plating to ion-track etched templates. This class of metallization reactions can be categorized as autocatalytical, surface-selective deposition from metastable solutions containing at least a metal complex and a reducing agent [1]. In order to initiate the plating reaction on the substrate, its surface usually has to be covered with metal nanoparticles which act as seeds for the metal film nucleation. These substrate pre-treatments are called activation processes. The synthesis of well-defined, complex metal nanomaterials is demanding concerning both the quality of the plating and activation reactions [1]. In recent studies [2,3], we introduced a highly flexible and easily scalable process for the activation of polymer substrates for consecutive electroless plating which is suitable for the synthesis of metal nanomaterials. It is based on the absorption of a reducing agent by a slightly swollen polymer substrate, followed by the precipitation of metal nanoparticles (Fig. 1). Fig. 1: Synthetic scheme of the new activation technique [2]. 1) In the presence of a suitable solvent or solvent combination, the polymer substrate swells and absorbs a dissolved reducing agent (sensitization). 2) When the sensitized substrate is brought into contact with metal salt solutions, nanoparticles precipitate on its surface (activation). 3) Surface-conformal metal deposition is achieved by electroless plating. Copyright (2014) Springer Publishing. The outlined technique can be applied to polymers with significantly differing chemical properties (e.g. ABS, PC, PET and PVA [3]) and allows to adjust the density, size and metal type of the seeds [2,3]. Therefore, the substrate activity can be tailored for obtaining optimum results in consecutive electroless depositions. Aside from a sufficient density of 82 Institute of Materials Science- Materials Analysis small seeds, a high catalytic activity in the corresponding plating reaction proved to be essential for the conformal metallization of challenging substrate morphologies with nanoscale homogeneity [2,3]. The presented method is not restricted to the fabrication of metal nanotubes (Fig. 2a,b), but can also be utilized for the preparation of two-dimensional films (Fig. 2c) and the metallization of macroscopic work pieces (Fig. 2d). Future studies aim to adopt the novel activation approach in the synthesis of well-defined, mono- and multimetallic nanotubes for application in heterogeneous catalysis and sensing. Fig. 2: a) SEM image of a field of free-standing copper nanotubes (the template was removed with dichloromethane). b) Top-view of the nanotubes shown in a). c) SEM image of a silver film on ABS foil. d) LEGO®-block electrolessly covered with silver. Copyright (2014) Elsevier B.V. References: [1] [2] [3] F. Muench, S. Lauterbach, H.-J. Kleebe, W. Ensinger, Deposition of Nanofilms inside a Polymer Template: Formation of Metal Nanotubes, E-J. SURF. SCI. NANOTECH. 10 (2012), 578-584. F. Muench, S. Bohn, M. Rauber, T. Seidl, A. Radetinac, U. Kunz, S. Lauterbach, H.-J. Kleebe, C. Trautmann, W. Ensinger, Polycarbonate activation for electroless plating by dimethylaminoborane absorption and subsequent nanoparticle deposition, APPL. PHYS. A: MAT. SCI. PROCESS. 2014 (in press), DOI: 10.1007/s00339-013-8119-z F. Muench, A. Eils, M. E. Toimil-Molares, U. H. Hossain, A. Radetinac, C. Stegmann, U. Kunz, S. Lauterbach, H.-J. Kleebe, W. Ensinger, Polymer activation by reducing agent absorption as a flexible tool for the creation of metal films and nanostructures by electroless plating, SURF. COAT. TECHNOL. 2014 (in press), DOI: 10.1016/j.surfcoat.2014.01.024 Institute of Materials Science - Materials Analysis 83 Synthesis of oxidic copper and cobalt nanostructures of different morphologies T. Matsutani, C. Neetzel, F. Muench, W. Ensinger The investigation of bundled one-dimensional nanostructures by self-assembly methods can be easily carried out by anisotropic crystal growth which is directly related to the crystal structure. However, this process is limited to a few materials. In order to break the symmetry of the crystal growth, nanowire synthesis can be driven by screw dislocation where low precursor supersaturation and the presence of appropriate dislocation sources is essential. [1] In order to prepare morphology-controlled copper oxide/cobalt oxide heterostructures in micro- and nanometer scale, we investigated two different synthesis routes that are related to each other according to their mechanism but can be distinguished by their chemical reaction route. However, in both cases a ligand is required to build strong complexes resulting in low concentrations of free metal ions in the precursor solution. In the case of copper and cobalt ions, we compared ammonia as well as tartrate. The synthesis process via the ammonia route is accomplished with a three step route where firstly a copper ammonia complex is generated, followed by a ligand exchange process leading to the precipitation of copper hydroxide. By annealing, CuO is produced via dehydratation. Concentration ratios of the precursor solution as well as the resulting yields measured by EDX are listed in Table 1. According to the yield composition, the turnover for copper oxide is higher which can be explained by stronger copper ammonia complexes according to the related complex stability constants. Table 1: Composition and yield of CuO/Co3O4 heterostructures Sample # precursor composition Cu2+z1Co2+z2 yield composition CuO(x)Co3O4(y) (1) (2) (3) (4) (5) z1:z2 = 1:0 z1:z2 = 7:1 z1:z2 = 5:1 z1:z2 = 3:1 z1:z2 = 1:10 x:y = 1:0 x:y = 8.6:1 x:y = 6.9:1 x:y = 4.1:1 x:y = 1.2:10 Figure 1 depicts the resulting morphologies of samples (1) to (5). Pure copper oxide deposition results in a network composed of needle-like structures with diameters of about 10 nm and lengths of 2 µm. With increasing Co3O4 and decreasing CuO content the structure morphology changes from needle-like architectures to plate-formed shapes. Obviously, the bundled network-like formation degenerates with decreasing copper content in the precursor-solution which indicates that its concentration is crucial for the onedimensional growth process in aqueous solution under these conditions. Sample (5) shows clearly identifiable thin plate structures of round shapes with diameters of approximately 5 µm. The reason for this observation can be explained by the crystal growth of the intermediate cobalt hydroxide complex. Co(OH)2 consists of a layered structure where neighboring layers are bound to each other by weak van der Waals forces. Thus, the (100) plane is stable. [1] 84 Institute of Materials Science- Materials Analysis For the fabrication of Cu2O nanostructures with low CoO contents in aqueous solution, we applied the well-known Fehling’s reagent with -D-glucose as reducing and tartrate as complexing agent. Tartrate generates a coordination complex with copper and cobalt metal ions which on one hand decreases the concentration of the related free metal ions in the solution and on the other hand prevents the undesirable precipitation of Co(OH) 2 and Cu(OH)2. Additionally to the earlier procedure, the concentration of the reducing agent as well as the concentration of copper and cobalt salts in the precursor solution is indispensable. As listed in Table 2, the specific concentration of the Fehling and reducing solution were varied in our experiments. First, we synthesized pure Cu2O structures and varied the concentration of copper metal ions in the precursor solution (samples (6) and (7)). As it is clearly recognizable (see Figure 3(a) and 3(b)) needle-like structures can be obtained by adding a low concentration (Table 2) of metal ions. An increasing amount of copper(II)ions already causes the formation of particles with diameters of about 250 nm. Therefore, we kept the concentration of the Cu2+ precursor constant and varied the concentration of cobalt ions in order test the morphology influence of this species in a heterostructural precipitation. By adding 1:1 = Cu2+:Co2+ (sample (8)) we observed cubic like structures with uniform lateral edges of 100 nm as shown in Fig. 3. EDX as well as XRD measurements (not shown here) confirm the precipitation of both cobalt and copper oxidic structures. Table 2: Composition of initial Cu2+ and Co2+ for Fehling's reaction Sample # CuSO4.5H2O [mol/L] CoSO4.7H2O [mol/L] Na2C4H4O6 [mol/L] (6) (7) (8) (9) 0.004 0.006 0.004 0.004 - - 0.004 0.0004 0.005 0.007 0.009 0.005 We expected to obtain structural analogies to sample (7) by keeping the concentration of copper precursor ions constant and adding a 1:0.1 quantity of cobalt ions (sample (9)). However, SEM investigations show that the morphology seems to be different (Fig. 3(d)). Particles with diameters of approximately 50 nm agglomerate together at certain positions resulting in a crossed one-dimensional growth in each direction. Thus, branched networks could be obtained. The reason for these occurrences could be that -D-glucose acts as surfactant and promotes the growth in a certain direction as it also described in the literature. [2] On the other hand, such morphologies were not obtained for sample (7); therefore, the addition of cobalt ions leads to a drastic change of the structural material architecture. However, this synthesis route seems to be more sensitive towards small changes of concentration in the precursor solution. Moreover, the influence of the reducing material should be considered accurately for further investigations. The results indicate that, dependent on the precursor concentration of copper and cobalt ions, it is possible to prepare morphology controlled heterostructures in a reproducible way. Further investigations will be carried out for the fabrication of needle-like structures with high Co3O4 contents. Institute of Materials Science - Materials Analysis 85 Fig. 1: CuO/Co3O4 heterostructures of different ratios: (a) sample (1), (b) sample (2), (c) sample (3), (d) sample (4) Fig. 2: CuO/Co3O4 sample (5) nanoplates: Fig. 3: CuO nanoneedles obtained by precipitation of Cu(OH)2 and annealing References: [1] [2] 86 Y. Li, Y. Wu, Chem. Mater. 2010, 22, 5537-5542. G. Filipic, U Cvelbar, Nanotechnol., 2012, 23, 1-16 Institute of Materials Science- Materials Analysis Materials Modelling Division The research of the Materials Modelling Division is focused on multi-physics modelling of defect structures in functional oxides, metallic nanoalloys and energy materials. We are combining electronic structure calculations with atomistic modelling methods and continuum descriptions depending on time and length scales involved. Quantum mechanical calculations based on density functional theory are used for electronic structure calculations. Large-scale molecular dynamics with analytical interatomic potentials are the method of choice for studying kinetic processes and plastic deformation. Kinetic lattice Monte-Carlo simulations are extensively used for simulations of diffusional and transport processes on extended time scales. The group is operating several HPCcomputers and has access to the Hessian High Performance Computers in Frankfurt and Darmstadt. The current research topics are: Functional oxides o New lead-free ferroelectrics: Ordering effects and defects o Defects and diffusion in TCOs o Finite-size effects in oxide nanoparticles Nanoalloys o Plasticity of nanocrystalline metals and bulk metallic glasses o Metallic nanoglasses o Nanophase diagrams o Metallic nanoparticles under nanoextrusion Energy materials o Interfaces in Li-intercalation batteries o Defects in CIS/CIGS absorber materials o High-pressure phases of nitrogen o Interfaces in Superalloys (Mo-Si-B) Within the bachelor program the Materials Modelling Division is offering classes on thermodynamics and kinetics as well as defects in materials. Lectures and lab classes on simulation methods and programming techniques are offered as elective courses in both, the bachelor and master program. Institute of Materials Science - Materials Modelling Division 87 Staff Members Head Prof. Dr. Karsten Albe Emeritus Professor Prof. Dr. Hermann Rauh, M.A., C.Phys., F.Inst.P., F.I.M. Secretary Renate Hernichel Research Associates PD Dr. Yuri Genenko Dr. Galina Yampolskya Dr. Sergey Yampolskii Dr. Alexander Stukowski Dr. Jochen Rohrer Dr. Omar Adjaoud Dr. Uma Maheswari Sankara Subbiah Dr. Marc Radu Dr. Sabrina Sicolo Scientific Employees PhD Students M.Sc. Heide Humburg Master Students Konstanze Kalcher, Markus Mock Bachelor Student Leonie Koch Research Fellow Dr. Guang-Tong Ma (AvH) Dipl.-Phys. Johan Pohl Dipl.-Ing. Jonathan Schäfer Dipl.-Ing. Manuel Diehm Dipl.-Ing Melanie Gröting Dipl.-Ing. Jonathan Schäfer Dipl.-Ing. Arno Fey Dipl.-Ing. Kai Meyer Dipl.-Ing. Tobias Brink M.Sc. Olena Lenchuk M.Sc. Nam Ngo Research Projects Mikrostruktur und Stabilität von Nanogläsern (DFG AL 578/6-2) Quantenmechanische Computersimulationen zur Elektronen- und Defektstruktur oxidischer Materialien (SFB 595, Teilprojekt C1, 2007-2014) Atomistische Computersimulationen von Defekten und deren Bewegung in Metalloxiden (SFB 585, Teilprojekt C2, 2003-2014) 88 Institute of Materials Science - Materials Modelling Division Phänomenologische Modellierung von Injektion, Transport und Rekombination in Bauelementen aus organischen Halbleitern sowie aus nichtorganischen Ferroelektrika (SFB C5, 2003-2014) Erforschung der Phasenstabilität und Niederdrucksynthese von festem Stickstoff mittels atomistischer Computersimulationen und Experimenten (DFG AL 578/3-2, 2010–2014)) Beyond Ni-Base Superalloys: Atomistische Modellierung des Einflusses von Legierungszusätzen auf die Korngrenzeigenschaften in Mo-Si-B und Co-Re Superlegierungen (DFG Forschergruppe 727, AL 578/9-1, 2010–2013) Nanosilicon dispersed in SiCN(O) and SiCO-based ceramic matrices derived from preceramic polymers: new composite anode materials for lithium ion batteries. (DFG SPP 1473 „Wendelib“, DFG AL 578/10-1, 2011–2013) Mechanische und kinetische Eigenschaften metallischer Sekundärphasen (DFG AL578/13-1, 2011–2013) Gläser mit nanoskaligen Bleifreie Piezokeramiken, LOEWE-Schwerpunkt ADRIA (HMWK, 2011-2014) PPP Finnland, Atomic level simulations of structure and growth of nanoalloys (DAAD 2011–2013) Topological Engineering of Ultra-Strong Glasses (DFG AL 578/15-1, 2012-2014) Modeling the electrocaloric effect in lead-free relaxor ferroelectrics: A combined atomisticcontinuum approach (DFG AL 578/16-1, 2012-2014) HZB-Helmholtz Zentrum Berlin, Virtuelles Institut (HZB VH-VI-520 2012-2017) Publications K. Albe, Y. Ritter and D. Şopu, 'Enhancing the plasticity of metallic glasses: Shear band formation, nanocomposites and nanoglasses investigated by molecular dynamics simulations', Mechanics of Materials 67, 94 (2013) H. Rauh and G. T. Ma, 'Hysteretic ac loss of a superconductor strip subject to an oscillating transverse magnetic field: Geometrical and electromagnetic effects', J. Appl. Phys. 114, 193902 (2013) S. Zhukov, Y. A. Genenko, M. Acosta, H. Humburg, W. Jo, J. Rödel, H. von Seggern, Heinz, Polarization dynamics across the morphotropic phase boundary in Ba(Zr0.2 Ti0.8)O3x(Ba0.7Ca0.3)TiO3 ferroelectrics', Appl. Phys. Lett. 103, 152904 (2013) A. Kobler, J. Lohmiller, J. Schäfer, M. Kerber, A. Castrup, A. Kashiwar, P. A. Gruber, K. Albe, H. Hahn, C. Kübel, 'Deformation-induced grain growth and twinning in nanocrystalline palladium thin films', Beilstein J. Nanotechnol. 4, 554 (2013) Institute of Materials Science - Materials Modelling Division 89 J. Schäfer and K. Albe, 'Plasticity of nanocrystalline alloys with chemical order: on the strength and ductility of nanocrystalline Ni–Fe', Beilstein J. Nanotechnol. 4, 542 (2013) Y. A. Genenko, J. Wehner and H. von Seggern, 'Self-consistent model of polarization switching kinetics in disordered ferroelectrics', J. Appl. Phys. 114, 084101 (2013) G. T. Ma and H. Rauh, 'Thermo-electromagnetic properties of a magnetically shielded superconductor strip: theoretical foundations and numerical simulations', Supercond. Sci. Technol. 26,105001 (2013) J. Rohrer and K. Albe, 'Insights into Degradation of Si Anodes from First-Principle Calculations', J. Phys. Chem. C 117, 18796 (2013) S. Goel, A. Stukowski, X. Luo, A. Agrawal and R. L. Reuben, 'Anisotropy of single-crystal 3C–SiC during nanometric cutting', Modelling Simul. Mater. Sci. Eng. 21, 065004 (2013) P. Erhart, P. Träskelin and K. Albe, 'Formation and switching of defect dipoles in acceptordoped lead titanate: A kinetic model based on first-principles calculations', Phys. Rev. B 88, 024107 (2013) K. Nonnenmacher, H.-J. Kleebe, J. Rohrer, E. Ionescu, R. Riedel and G. Soraru, 'Carbon Mobility in SiOC/HfO2Ceramic Nanocomposites', J. Amer. Ceram. Soc. 96, 2058 (2013) J. Pohl and K. Albe, 'Intrinsic point defects in CuInSe2 and CuGaSe2 as seen via screenedexchange hybrid density functional theory', Phys. Rev. B 87, 245203 (2013) K. A. Avchaciov, Y. Ritter, F. Djurabekova, K. Nordlund and K. Albe, 'Controlled softening of Cu64Zr36 metallic glass by ion irradiation', Appl. Phys. Lett. 102, 181910 (2013) A. Tolvanen and K. Albe, 'Plasticity of Cu nanoparticles: Dislocation-dendrite-induced strain hardening and a limit for displacive plasticity', Beilstein J. Nanotechnol. 4, 173 (2013) H. S. Ruiz, A. Badia-Majos, Y. A. Genenko and S. V. Yampolskii, 'Strong Localization of the Density of Power Losses in Type-II Superconducting Wires', IEEE Trans. Appl. Superconduct. 23, 8000404 (2013) S. Li, J. Morasch, A. Klein, C. Chirila, L. Pintilie, L. Jia, K. Ellmer, M. Naderer, K. Reichmann, M. Gröting, and K. Albe, 'Influence of orbital contributions to the valence band alignment of Bi2O3, Fe2O3, BiFeO3, and Bi0.5Na0.5TiO3', Phys. Rev. B 88, 045428 (2013) Proceedings W. Witte, M. Powalla, D. Hariskos, A. Eicke, M. Botros, H.-W. Schock, A. Abou-Ras, R. Mainz, H. Rodríguez-Alvarez, T. Unold, G. H. Bauer, R. Brüggemann, S. J. Heise, O. Neumann, M. Meessen, J. Christen, F. Bertram, A. Klein, T. Adler, K. Albe, J. Pohl, M. Martin, R. A. De Souza, L. Nagarajan, T. Beckers, C. Boit, J. Dietrich, M. Hetterich, Z. Zhang, R. Scheer, H. Kempa and T. Orgis, 'Chemical Gradients in Cu(In,Ga)(S,Se)2 ThinFilm Solar Cells: Results of the GRACIS Project', In: 27th European Photovoltaic Solar Energy Conference and Exhibition, Frankfurt am Main. EU PVSEC Proceedings (2013). 90 Institute of Materials Science - Materials Modelling Division Degradation of Si anodes studied with first-priniciple methods Jochen Rohrer and Karsten Albe Silicon is considered as promising anode material for Li-ion batteries [1]. However, despite its high mass-specific capacity, which is approximately ten times larger than that of commercially used graphitic anodes, Si undergoes rapid degradation. The details of this degradation are complex. However, roughly we can distinguish two failure modes. The first is related to the consumption of electrolyte and a build up of a thick solid-electrolyte interphase. The second is related to internal degradation of Si itself by means of cracking and pulverization. Here [2] we focus on internal degradation. We use density-function-theory calculations to study the structure and thermodynamics of amorphous LixSi (x representing the ratio of Li to Si) that forms during Li intercalation and deintercalation. Our calculations predict the existence of critical two-phase regions during initial lithiation and initial delithiation. Within two-phase regions, large local and inhomogeneous volume changes may lead to crack initiation. We also point out, how these two-phase regions can be avoided and degradation due to internal cracking is minimized. Fig. 1: Iterative replica scheme to generate amorphous Li-Si model structures. Figure 1 illustrates our protocol used to generate model structures of amorphous LixSi with varying Li content. Starting from a pure crystalline Si model consisting 64 atom, LixSi models with increasing Li content x are generated using an iterative replica scheme. In each step, five replica of the current LixSi model are created and in each of the replica, eight Li atoms are inserted to construct candidate structures of Lix’Si. Each candidate structure is then subjected to an equilibration run using ab initio molecular-dynamics simulations at 700 K. The equilibrated systems are finally fully optimized and the lowest-energy system is chosen as Lix’Si model for the current Li concentration. The procedure is iterated up to a concentration of x=4.75. Deintercalcation is modeled accordingly by removing Li. In Figure 2 we show calculated formation energies of Li-Si alloys as a function of the Li content x. The left panel focuses on intercalation in crystalline Si. In agreement with hightemperature experiments [3], Li4.4Si is identified as global minimum. Initially, at low Li content, a phase separation into crystalline Si and amorphous Li2.0Si is thermodynamically favorable. Within this two-phase region, local inhomogeneous volume changes of +130% take place and crack initiation can be expected. For x>2, a homogeneous one-phase region is predicted and cracking is suppressed. At to x=3.625, we find a saddle point and further intercalation again leads to a two-phase region where amorphous Li3.625Si and Li4.4Si coexist. At the saddle point, the thermodynamic driving force for further intercalation vanishes. This might be interpreted as a potential reason for crystallization of Li15Si4, which is typically observed at room temperature [4]. Institute of Materials Science - Materials Modelling Division 91 Fig. 2: Structure and formation energies of amorphous LixSi model systems. The right panel of Figure 2 focuses on delithiation. For a maximum Li content of x>3.75, initial delithiation leads to two-phase regions (either Li4.4Si/Li3.625Si or Li15Si4/Li2.0Si). Within these two-phase regions, there are again large inhomogeneous volume changes for which crack formation can be expected; -15% in the former or -40% in the latter two-phase region. At lower Li contents, a homogeneous one-phase region is predicted and full delithiation leads to amorphous Si. Reinsertion into amorphous Si then proceeds homogeneously and essentially without crack formation. From x=3.625 on, amorphous Si behaves similar to crystalline Si. In summary, our calculations identify various two-phase regions occurring during Li intercalation or deintercalation in Si anodes. During corresponding phase conversion, large local and inhomogeneous volume changes may initiate cracks which subsequently lead to degradation due to particle fracturing. In amorphous Si, two-phase regions occur only during delithiation and only if the Li content is larger than x=3.75. Thus, limiting the Li content well below this critical value leads to homogeneous volume expansion and contraction and minimizes internal particle fracture. As a consequence, capacity limited cycling of amorphous Si anodes [5] leads to significantly enhanced cycling stability. References: [1] [2] [3] [4] [5] 92 U. Kasavajjula, C. Wang and J. A. Appleby, J. Power Sources 163, 1003(2007). J. Rohrer and K. Albe, J. Phys. Chem. C 117, 18796 (2013). R. A Sharma and R. N. Seefurth, J. Electrochem Soc. 123, 1763 (1976). M. N. Obrovac and L. Christensen, Solid-State Lett. 7, A93 (2004). A. Magasinski et al., Nat. Mater. 9, 353 (2010). Institute of Materials Science - Materials Modelling Division Low Temperature Heat Capacity of a Severely Deformed Metallic Glass Jonas Bünz, Tobias Brink, Koichi Tsuchiya, Fanqiang Meng, Gerhard Wilde, Karsten Albe Metallic glasses show distinct mechanical, electrical, and magnetical properties from their crystalline counterparts. Like all glassy materials, they show a low-frequency peak in the vibrational spectrum in excess of the Debye law and the spectrum of crystals. This so-called boson peak is due to quasi-localized transverse vibrational modes associated with “defective” soft local structures in the glass.[1-4] The boson peak, situated in the terahertz region of the vibrational spectrum, also leads to an excess contribution to the lowtemperature heat capacity. This becomes visible by plotting the heat capacity c devided by T3, so that the Debye T3-law reduces to a constant. Several different models for the structural origin of the boson peak have been proposed but they all agree that its origins are related to decreased elastic constants in spatially distributed regions. Plastic deformation in metallic glasses is localized in structurally disturbed regions called shear bands. The shear bands are therefore expected to influence the boson peak. To analyze this contribution of the shear bands, we performed heat capacity measurements on Zr50Cu40Al10 metallic glass. The glass was deformed under hydrostatic pressure torsion, which produces a large volume of regions with structural changes that can be considered a “macroscopic shear band”.[5] Heat capacity measurements were performed using differential scanning calorimetry at low temperatures before and after deformation. In addition, the undeformed and deformed samples were annealed and heat capacity was measured again. The results are shown in Figure 1a. The boson peak of the as-cast glass does not significantly change upon annealing. The deformation-induced boson-peak is increased over the as-cast state and reduces again with annealing. If the annealing temperature is high enough, the boson peak will even reduce below the as-cast state. X-ray diffraction measurements show no detectable crystallization. To elucidate the exact origins of the change in heat capacity, we Fig. 1 Difference in heat capacity between glass and crystal. a) conducted molecular dynamics Experimental data, annealing below 393 K was done for 7 days, simulations on a deformed annealing at 743 K for 10 s. b) Simulation data, dashed lines are sample of Cu64Zr36 metallic glass. data from shear bands, solid lines from the matrix. Institute of Materials Science - Materials Modelling Division 93 We identified atoms belonging to the shear band using the von Mises local shear invariant η as implemented in OVITO.[6] We marked atoms with η > 0.2 as belonging to the shear band and all others as the matrix. The phonon density of states (PDOS) was calculated[7] separately for shear band and matrix and is shown in Figure 2. Using the harmonic approximation of the free energy, we calculated the heat capacity from the PDOS as Fig. 2 Phonon density of states from computer simulation. shown in Figure 1b. Solid lines in Dashed lines are data from shear bands, solid lines from the these graphs represent data from matrix. the matrix. Our results show that the boson peak of the matrix stays unchanged during deformation and annealing. All changes result from the shear band, represented by dashed lines. Upon deformation the boson peak increases as in the experiment. Subsequent annealing relaxes the shear bands again to a state with reduced boson peak. The simulations do not show a reduction of the boson peak below the as-cast state. The reason is that the shear bands do not fully relax in the computationally accessible time (40 ns in our simulations). To confirm a possible transition to a state similar to the experiment, a much longer time scale would be needed. All in all our findings clearly show the shear bands to be the origin of the deformationinduced boson peak, while the matrix stays intact during all processing. The experiment supports this perspective as the change of the boson peak height for the undeformed sample is minimal during annealing. Several studies find healing of shear bands under annealing even at temperatures well below Tg.[8-10] In contrast, our measurements indicate that the structure of the annealed shear band differs from the initial as-cast state. Diffusion studies show accelerated diffusion constants in shear bands, which could promote structural relaxation in these regions. The boson peak is an excess over the ordered state, therefore the results of decreasing boson peak suggest short or medium range ordering. Even beginning crystallization on the nanoscale is conceivable, as this would not be detectable using X-ray diffraction. References: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] 94 S. N. Taraskin et al., Phys. Rev. Lett. 86, 1255 (2001) H. Shintani and H. Tanaka, Nat. Mater. 7, 870 (2008) H. R. Schober, J. Non-Cryst. Solids 357, 501 (2011) A. I. Chumakov et al., Phys. Rev. Lett. 106, 225501 (2011) F. Meng et al., Appl. Phys. Lett. 101, 121914 (2012) A. Stukowski, Modelling Simul. Mater. Sci. Eng. 18, 015012 (2010) J. M. Dickey and A. Paskin, Phys. Rev. 188, 1407 (1969) W. H. Jiang et al., Acta Mater. 53, 3469 (2005) S. Xie and E. P. George, Acta Mater. 56, 5202 (2008) Y. Ritter and K. Albe, Acta Mater. 59, 7082 (2011) Institute of Materials Science - Materials Modelling Division Hysteretic ac loss of a superconductor strip subject to an oscillating transverse magnetic field H. Rauh1 and G.T. Ma1,2 1 Institute of Materials Science, Darmstadt University of Technology, 64287 Darmstadt 2 Applied Superconductivity Laboratory, Southwest Jiaotong University, 610031 Chengdu Thin type-II superconductor strips, plates and tapes have lately become the focus of much attention in scientific and engineering research, since they are deemed promising elements for both large-scale power and microelectronic device applications. It is not surprising therefore that their response to imposed ac transport currents and applied ac magnetic fields, or both, has been studied intensively. One of the most important characteristics regarding their use is the hysteretic ac loss caused by excitations of the named sort. Applied ac magnetic fields – our concern here – have been addressed in analytical calculations as well as numerical analysis. Selected aspects for superconductor strips thereby include, e.g., the effects of demagnetization fields or those of external magnetic shields. However fundamental these investigations may be, a systematic examination of geometrical and electromagnetic effects owing to the superconductor strips themselves does not seem to have come forth yet. An obvious approximation at hand is the limit of infinitesimally thin superconductor strips, ignoring variations of the induced current and the electromagnetic field across the thickness of the strips. This ansatz has frequently been taken as a basis for theoretical explorations and, particularly, invoked for estimating the hysteretic ac loss; it has the distinct advantage of getting along with the concept of sheet current which allows representations in mathematically comprehensible forms. Such an approach needs justifying though by establishing its range of validity in tests against models that contain surplus traits. Assessments of the influence on the hysteretic ac loss of the width/thickness aspect ratio of a superconductor strip, with an ac transport current imposed, already exist. We aim at similar investigations for a superconductor strip, with an ac magnetic field applied, which crucially rely on an adequate characterization of the strip. Like on a different occasion before, we go back to a ‘smoothed’ Bean model of the critical state made up of a current-field relation derived from experiment. We confine ourselves to a purely electromagnetic account, without coupling to a thermal field; that is, the environment of the superconductor strip – in practice pervaded by a cooling liquid – is simply treated as a vacuum. Such a course has proven to yield very accurate results even at high amplitudes of the applied magnetic field. To appraise geometrical and electromagnetic effects on the distributions of the magnetic induction, the electric field, the current density, the power loss density inside the superconductor strip, and whence on the hysteretic ac loss suffered by the superconductor strip due to the presence of an oscillating transverse magnetic field, numerical simulations were carried out, understanding that the strip is made of an yttrium-barium cuprate and operated at the liquid nitrogen temperature of 77 K. We choose geometrical and materials data that second-generation superconductors typically display. Proceeding from a superconductor rod with quadratic cross section, i.e. a degenerate shape of the superconductor strip for which the width/thickness aspect ratio e 2w d equals unity, we studied the evolution of the above properties when the thickness of the strip d was Institute of Materials Science - Materials Modelling Division 95 reduced, while the width 2w was kept fixed, such that the aspect ratio followed the geometric progression e 1, 10, 100, 1000. In this procedure, the critical current density at operating temperature/zero field was adjusted according to jc0 eI c0 4w2 with the total critical current I c0 ,emulating its dependence on the thickness of the superconductor strip as compared to a superconductor bulk. Some of our numerical evaluations are shown graphically below. Fig. 1 portrays the distribution of the magnetic induction B inside the superconductor strip for different values of the amplitude of the applied magnetic field H a in the electromagnetic steady state. Generally, this distribution reveals symmetry about the two mirror planes of the superconductor strip. For thelowest amplitude of the applied magnetic field, H a 1 A mm , the magnetic induction B is essentially confined to the marginal parts of the strip, leaving most of its interior free of magnetic flux; the spatial localization and the strength of the magnetic induction B near the edges of the strip build up when the aspect ratio e augments. For the slightlyincreased amplitude of the applied magnetic field, H a 5 A mm , the penetration of the magnetic field into the interior of the strip already becomes tangible, giving rise to a pronounced inhomogeneous distribution of the magnetic induction B throughout the strip; the spatial localization and the strength of the magnetic induction B near the edges of the strip again build up when the aspect ratio e augments. For the highest amplitude of the applied magnetic field, H a 500 A mm , penetration of the magnetic field into the interior of the strip is developed to the full, bringing about a virtually homogeneous profile of the magnetic induction B across the thickness of the strip the amplitude of the as the aspect ratio e augments. Concisely and overall, an increase of applied magnetic field H a eventually gives rise to complete filling of the strip with magnetic flux, while the variations of the magnetic induction B in the direction of the applied magnetic field die away as the thickness of the strip abates. Fig. 1: Distribution of the magnetic induction B (unit T ) inside a superconductor strip in the electromagnetic steady state, calculated at maximum strength of an applied transverse magnetic field with amplitude H a 1 A mm (top), H a 5 A mm (centre) and H a 500 A mm (bottom), assuming the values of the aspect ratio e 1 , 10, 100, 1000. The scale of of the strip is enlarged by the respective factor e in each the thickness case. 96 Institute of Materials Science - MaterialsModelling Division Fig. 2 illustrates the dependence of the normalized hysteretic ac loss U ac H a2 on H a H c , the normalized amplitude of the magnetic field applied to the superconductor strip in the electromagnetic steady state, addressing a series of values of the aspect ratio e , together with the prediction for the limiting case of an infinitesimally thin strip in the Bean model of field H the critical state. This introduces the characteristic magnetic c , which may be expressed as H c I c0 2w , remembering the definition of the critical sheet current of such and materials data a strip, and thus takes on the value H c 8 A mm from the geometrical implied. A general trait revealed for whichever choice of the aspect ratio e is that, starting fromthe smallest value of the normalized amplitude of the applied magnetic field H a H c , a monotonic rise of the normalized hysteretic ac loss U ac H a2 towards a maximum occurs, followed by an asymptotically converging descent, as H a H c augments. Whereas the geometrical effect controlled by the aspect ratio e is minute at large values of H a H c , it becomes prominent at low values of H a H c where the normalized hysteretic ac loss U ac H a2 abates rapidly, with a waning gradient, as the aspect ratio e augments. The Bean model of the critical state adapted to an infinitesimally thin strip, often used for convenient mathematical analysis neglecting variations of electromagnetic observables (like the magnetic induction or the current density) across the thickness of the strip, obviously underestimates the normalized hysteretic ac loss U ac H a2at low and moderate values of 2 H a H c , but overestimates, or at least conserves, the normalized hysteretic ac loss U ac H a at large values of H a H c . Fig. 2: Normalized hysteretic ac loss U ac H a2 suffered by a superconductor strip as a function of the normalized amplitude H a H c of the applied transverse magnetic field in the electromagnetic steady state, assuming the values of the aspect ratio e 1 , 10, 100, 1000. The analytical result of an infinitesimally thin strip in the Bean model of the criticalstate (dashed lines) is shown for comparison. In conclusion, a theoretical approach with simultaneous regard of finite-geometrical aspects and electromagnetic traits is called for if the hysteretic ac loss suffered by the superconductor strip is to be reliably addressed. This is especially true in the range of low and moderate amplitudes of the applied magnetic field, where ascertainments based on Bean’s model of the critical state adapted to an infinitesimally thin strip yield clear underestimates of the said observable. On the other hand, this limit seems sufficient for determining the hysteretic ac loss at high amplitudes of the applied magnetic field – irrespective of the real value of the aspect ratio of the strip – if only the field dependence of the induced current is taken into account. Institute of Materials Science - Materials Modelling Division 97 Materials for Renewable Energies Research in the Renewable Energies group focuses on electrochemical energy technologies, such as fuel cells and batteries. Novel catalysts, electrodes and electrode processing techniques are being developed, but also sophisticated methods for their in-situ characterization. Systematic structural and electrochemical characterization of the new materials is carried out in order to unravel the structure-properties correlation. Techniques used for structure analysis include X-ray absorption spectroscopy (XAS), transmission electron microscopy (TEM), and X-ray diffraction (XRD), whereas the electrocatalytic performance is tested in both model experiments and under realistic operation conditions. The group’s recent scientific activities can be divided into the following three areas: New catalyst concepts Our main focus is on the design of alternative support materials for fuel cells, which do not suffer from corrosion in the severe operation conditions and may be promising candidates to replace the standard carbon support. Different morphologies, e.g. fibres or hollow spheres, contribute to an improved control in 3D electrode design and thus allow for an efficient mass transport. Furthermore, shape-selected nanoparticles exposing highly active crystal facets are being investigated and indicate improved electrocatalytic activities. Functional electrode design Beyond the conventional preparation techniques, advanced layer-by-layer (LbL) techniques are used in the fabrication of fuel cell electrodes allowing for a well-defined 3D architecture. A likewise promising approach, which also offers high flexibility and a facile up-scaling, is the electrospinning technique. Thin fibres with solid, porous, but also coreshell structure can be spun and deposited as an arbitrary mesh or in an aligned fashion. These structures have been used as electrodes in both fuel cells and batteries. Electron microscopy is applied for the electrodes’ detailed characterization. For this specific purpose, new techniques have been developed and established in the group, as for instance the focused ion beam (FIB) technique in cooperation with the HZB, Berlin. FIB/SEM was applied to obtain 3D reconstructions of the porous fuel cell electrodes before and after operation as well as for comparison of the different electrode processing techniques. In situ studies In situ and operando X-ray absorption studies play an important role in our activities with respect to the systematic investigation of reaction and degradation mechanisms. A versatile in situ sample environment has been designed and successfully implemented at various synchrotron facilities. It enables the spatial and time resolved study of different areas of the fuel cell electrodes in various operation conditions (direct methanol, direct ethanol operation, but also for intermediate temperature PBI fuel cell studies). In addition to the 98 Institute of Materials Science - Materials for Renewable Energies conventional EXAFS analysis the novel delta µ XANES technique is applied in cooperation with Prof. David Ramaker, George Washington University. This technique enables us to study adsorbates attached to the active catalyst surface, so that reaction mechanisms can be followed directly during operation. The results provide important insights, which will help to further catalyst optimization. In 2012, the delta µ XANES technique has been applied to intermediate temperature PBI fuel cells. At the cathode side, the adsorption of phosphoric acid species could be followed temperature and potential dependent. The effect of anode humidification on CO poisoning at different temperatures was also studied, and the importance of water being present at the anode side underlined. In July 2012, Prof. Christina Roth was appointed full professor at the FU Berlin and now heads the group Applied Physical Chemistry. Financial support is provided by DFG, BMWi, BMBF, and EU as well as by the respective synchrotron facilities and industrial partners. Staff Members Head Prof. Christina Roth Secretary Maria Bense (joint with Prof. Donner and Prof. Xu) PHD students Dipl.-Ing. (FH) Hanno Butsch Dipl.-Ing. Benedikt Peter Dipl.-Ing. André Wolz Diploma students Anja Habereder Dipl.-Ing. Sebastian Kaserer Dipl.-Ing. Alexander Schökel Research Projects German-Canadian fuel cell cooperation (BMWi project 2010-2013) New developments in intermediate temperature fuel cells (EU project 2010-2012) New concepts for a controlled 3D design of porous electrodes (DFG project 2010-2013) Publications [1] F. Muench, M. Oezaslan, M. Rauber, S. Kaserer, A. Fuchs, E. Mankel, J. Brötz, P. Strasser, C. Roth, W. Ensinger, Electroless Synthesis of Nanostructured Nickel and Nickel-Boron Tubes and their Performance as Unsupported Ethanol Electrooxidation Catalysts, Journal of Power Sources 222 (2013), 243 – 252. Institute of Materials Science - Materials for Renewable Energies 99 [2] S. Kaserer, K. M. Caldwell, D. E. Ramaker, C. Roth, Analyzing the Influence of H3PO4 as Catalyst Poison in High Temperature PEM Fuel Cells Using in-operando X-ray Absorption Spectroscopy, J. Phys. Chem. C 117 (2013), 6210−6217. [3] S. Kaserer, C. Rakousky, J. Melke, C. Roth, Design of a reference electrode for high-temperature PEM fuel cells, J. Appl. Electrochem. (2013) DOI: 10.1007/s10800-013-0567 100 Institute of Materials Science - Materials for Renewable Energies Incorporation of Indium Tin Oxide Nanoparticles in PEMFC Electrodes André Wolz, Susanne Zils, David Ruch, Nicholas Kotov, Marc Michel, Christina Roth Introduction Carbon materials suffer from corrosion at the cathode of polymer electrolyte membrane fuel cells (PEMFCs). In the presence of water, carbon support materials are oxidized to carbon dioxide even at low potentials. Hence, nowadays it is very fashionable to look for alternative support materials, like oxides or conductive polymers. The choice of a support material other than carbon black makes it mandatory to think about the preparation method of the electrode layer and its resulting electrode structure. The nano-sized oxide particles have to be assembled differently from the sub-micrometer sized carbon black particles to yield an equally promising structure. A schematic of such an electrode design is depicted in Fig. 1. Fig. 1. Schematic of a 3D electrode design incorporating nano-sized oxide support particles (Pt/ITO) and Nafion-coated multi-walled carbon nanotubes (MWCNT/Nafion) into a fast sprayed multi-layer electrode. The electrode structure is known to have a significant impact on the cell performance [1]. A homogeneous and porous structure favors mass transport of the reactants, and a good accessibility of the Pt nanoparticles results in a high Pt utilization. Recently, a novel electrode preparation technique has been introduced by which it was possible to assemble 1D support materials into 3D networks [2, 3]. The networks had a multilayered architecture of polyaniline and carbon nanotubes, both decorated with Pt, and the electrodes reached 3 times higher Pt utilizations at the cathode side than conventional electrodes. This technique is referred to as the ‘fast multilayer’ technique. The same technique was used by Zils et al. [4] to manufacture electrodes with carbon black material and Nafion layers, which were then compared to an airbrushed MEA with the same catalyst composition. Focused ion beam tomography (FIB) measurements revealed a Institute of Materials Science - Materials for Renewable Energies 101 much more homogenous structure with a small average pore size for the multilayer electrode than for the airbrushed one. Single-cell tests furthermore demonstrated a two times higher Pt utilization showing the suitability of this technique as a fast and easy method for fuel cell electrode preparation. This study shows the results for the incorporation of nano-sized alternative support materials into advanced electrode architectures. It will give a first impression of how oxide nanoparticles can be assembled in a fuel cell electrode. The obtained results will bridge the gap between the previous results of electrochemical studies and the performance as catalyst material in a real fuel cell environment. Experimental Pt decoration of ITO nanoparticles ITO nanoparticles (NP) were decorated with Pt NP after a reduction of PtCl4 precursor by sodium borohydride (NaBH4). 120 mg ITO NP and 51.8 mg PtCl4 (99.99+%) were dispersed in 20 ml ultrapure water (MilliQ - MQ), the amount of PtCl4 corresponding to a Pt loading of 20 wt%. After a homogenous dispersion was obtained, a solution of 51.8 mg NaBH4 in 10 ml MQ was added. The dispersion turned black immediately. Afterwards, the solution was diluted with deionized water, filtered through a 0.02 µm Anopore™ Inorganic Membrane (Whatman®) and dried at 30°C under vacuum. Functionalization of the multiwall carbon nanotubes (MWCNT) The MWCNT were treated in concentrated acids in order to functionalize their surface and to remove remaining amorphous carbon species. 20 mg MWCNT were dispersed in 6 ml HNO3 (p.a., 65%) and 6 ml H2SO4 (ACS reagent, 95-98%) and sonicated for 30 min. Afterwards, the nanotubes were diluted with copious amounts of MQ, filtered with a 0.45 µm polycarbonate track-etch membrane, rinsed with MQ water and dispersed in a solution of 5 ml ethanol and MQ (80:20 by volume). A mixture of 0.34 ml Nafion ® solution in 5 ml ethanol/MQ (80:20) solution was prepared and the MWCNT dispersion added dropwise to the ionomer dispersion. As the second ink,40 mg of Pt/ITO (20 wt% Pt loading) was dispersed in 10 ml ethanol/MQ solution (80:20). Electrode preparation Polymer electrolyte membranes of Nafion® 117 were purchased from Ion Power Inc., USA. The membrane was mounted in a home built spraying plate with vacuum feature. The plate was heated up to 80°C and a solution of 80 mg Pt on Vulcan-XC72 (HiSPEC™ 3000, Johnson Matthey), 0.4 ml Nafion® 117 solution (5%), 3.6 ml MQ, and 12 ml ethanol was coated onto the membrane by EcoSpray containers (Labo Chimie France). The cathode was assembled by alternating layers of Pt/ITO and MWCNT/Nafion® (referred to as multilayer electrode: ML-MEA). For comparison, a second electrode was sprayed, consisting of a standard Pt/CB anode with the same loading used before and a Pt/CB cathode, with a Pt loading and Nafion® content equal to the Pt/ITO cathode. 102 Institute of Materials Science - Materials for Renewable Energies Structural characterization The ITO supported Pt NP were characterized by X-ray diffraction (XRD). The XRD was carried out with a X’Pert-Pro diffractometer in reflection geometry operating with Cu Kα1 and Kα2 radiation (λ=1.54060 Å). Rietveld refinement was used to estimate the particle sizes of ITO and Pt. Scanning electron microscopy (SEM) was applied for the characterization of the Pt/ITO electrode using a FEI Quanta 200 FEG, equipped with a field emission gun operating at 15 kV. Electrochemical characterization Cyclic voltammograms (CVs) were measured with a Gamry Reference 600 potentiostat (USA) in a standard glass three-compartment electrochemical cell (Bio-Logic SAS), with a glassy carbon working electrode (Ø 3 mm, BASi Instruments, USA), a Pt wire serving as counter electrode, and an Ag/AgCl reference electrode (ASL, Japan). The potential between the working electrode (WE) and reference electrode was cycled 10 times between -0.21.2 V with a sweep rate of 50 mV s-1. The electrolyte was prepared with MQ water and HClO4 (Sigma-Aldrich, 70%) at a concentration of 0.1 (M). The electrolyte was purged for 5 min with Ar. Polarization curves of the electrodes were collected with a FuelCon Evaluator C50 test bench (FuelCon AG, Germany), in which the Pt/ITO-MWCNT/Nafion® electrode was used as cathode and the standard Pt/CB electrode as anode. Humidified hydrogen was fed to the anode with a flow rate of 200 ml min-1 and high-purity oxygen was provided to the cathode at a flow rate of 100 ml min-1. The anode/cathode gas humidifiers were set to 80°C and the cell temperature to 75°C. The polarization curves were recorded automatically with the software package FuelWork by increasing the current in 0.1 A steps after a steady state potential has been reached. Results and discussion Pt nanoparticles on indium tin oxide nanoparticles have been considered as possible fuel cell catalyst materials. However, tests in a real fuel cell environment are still lacking. After the successful deposition of Pt on ITO the effect of electrode structure on the fuel cell performance is studied. The assembly of Pt/ITO with 20 wt% Nafion® ionomer in the electrode did not show any performance at all. This could be attributed to the very dense electrode structure formed by the nano-sized support and the ionomer preventing the desired gas transport. To enhance the porosity of the electrode network, the incorporation of Pt/ITO catalyst into a multi-walled carbon nanotubes (MWCNTs) network (coated with Nafion®) is proposed. The nanotube network has the advantage to be highly electron conductive and the ionomer coating ensures the proton conductive character of the electrode. The catalytic active species Pt on ITO is embedded into the structure during the preparation process. Single cell tests of the proposed electrode design have been performed, and the polarization and power density curves can be found in Fig. 2. The novel electrode design reached a maximum power density of 73 mW cm-2 at a current density of 0.12 A cm-2. The power density is comparable to the conventionally prepared Pt/CB electrode. The Pt utilization for the multilayer electrode is 1468 W g(Pt)-1 compared to 1723 W g(Pt)-1 for the standard cathode. Institute of Materials Science - Materials for Renewable Energies 103 Fig. 2. Comparison of the polarization and power density curves of the multilayer electrode design (Pt/ITOMWCNT/Nafion) and a conventionally prepared electrode (Pt/CB-Nafion). It is remarkable that both MEAs show almost the same performance while possessing two completely different morphologies. The spherical carbon black particles are in the micrometer range with micro- and macropores, whereas the ITO particles are in the nanometer range. The surface area of carbon black peaked at around 200 m2 g-1 and is therefore much higher compared to ITO (27 m2 g-1 according to the supplier). SEM micrographs have been recorded after the single cell measurements (Fig. 3). In the crosssectional view, the electrode thickness was measured to be 5.4 µm. The low and high magnification micrographs of the electrode surface indicate the mentioned network structure provided by the multi-walled carbon nanotubes, in which the Pt/ITO component is embedded. In Fig. 3, right single nanotube fibers are visible, and the structure seems to be highly porous as intended. Fig. 3. SEM micrographs of the advanced multi-layered electrode structure incorporating oxide-supported Pt nanoparticles; in high magnification the carbon nanotubes can be seen. 104 Institute of Materials Science - Materials for Renewable Energies Conclusion This study showed a simple preparation technique for advanced electrode structures, which succeeded in incorporating a nano-sized oxide supported Pt component (Pt/ITO) into a 3D porous electrode network. Commercially available indium tin oxide (ITO) nanoparticles (<50 nm) were used as support for Pt nanoparticles in combination with Nafion® coated multi-walled carbon nanotubes (MWCNT) on the cathode side of a PEMFC. The MWCNT promote a high electronic conductivity and help to form a porous network structure, which was used to accomodate the Pt/ITO nanoparticles. The architecture favored the reactant permeability, and a better accessibility of the active Pt sites was obtained. The conductivity within the electrode was provided by only a negligible amount of highly conductive MWCNTs. Single cell measurements show a maximum power density of 73 mW cm-2 and a Pt utilization of 1468 mW mgPt-1 for the cathode. The performance data and the Pt utilization are comparable to a standard Pt/carbon black electrode (Pt/CB) indicating that it actually may be possible to replace carbon black by more stable oxides without a loss in performance. Besides this, it is shown for the first time that ITO can serve as support material under real fuel cell conditions. This might open the way to the manufacturing of cost-efficient and easily prepared fuel cell electrodes with an enhanced long-term stability. Acknowledgments Financial support by the National Research Fund, Luxembourg is gratefully acknowledged. We also want to thank C. Fasel, U. Kunz and J.-C. Jaud for their help with sample preparation, TGA and XRD measurements. References [1] [2] [3] [4] R. O'Hayre, D. M. Barnett, F. B. Prinz, J. Electrochem. Soc. 2005, 152, A439. A. Wolz, S. Zils, M. Michel, C. Roth, J. Power Sources 2010, 195, 8162. S. Zils, A. Wolz, M. Michel, C. Roth, ECS Trans. 2010, 28, 33. S. Zils, M. Timpel, T. Arlt, A. Wolz, I. Manke, C. Roth, Fuel Cells 2010, 10, 966. Institute of Materials Science - Materials for Renewable Energies 105 In Situ and Time-Resolved XANES Study of the Electrooxidation of Ethanol on Pt Julia Melke, Sebastian Kaserer, Alexander Schoekel, Dietmar Gerteisen, Ditty Dixon, Carsten Cremers, David E. Ramaker, Christina Roth Introduction Ethanol is an attractive alternative fuel in polymer electrolyte fuel cells - thus its electrochemical oxidation on Pt has been studied for several years [1-3]. The ethanol oxidation reaction (EOR) is a complex multistep reaction that involves several adsorbed species like acetyl, adsorbed acetate, carbon monoxide (CO) and CHx-species, and generally yields some acetic acid, but mainly acetaldehyde along with the desired carbon dioxide as final product. Except for the formation of acetaldehyde, oxidation to other products such as acetic acid and carbon monoxide requires an oxygen atom source normally provided by the activation or dissociation of water. The activation of water on Pt generally occurs around 0.55 V (RHE), and below this potential the Pt surface is covered mainly by CO(ads) and CHx, as shown by various studies in the literature. Adsorbed acetate was observed to be reversible and seems to reduce the number of available sites for the EOR. The EOR also depends on anion adsorption from the electrolyte and the crystal structure of the catalysts. X-ray absorption spectroscopy is especially suited to study reaction and degradation mechanisms, such as the EOR, in-situ and under realistic operation conditions, since both changes in the catalyst structure (EXAFS) and the kind and amount of adsorbates on the Pt surface (delta µ XANES) can be followed at once. In our previous X-ray absorption spectroscopy study, potential-dependent changes in the delta XANES were observed during the EOR at steady state conditions [4]. In contrast, for the first time in this work, we report, time-resolved adsorbate coverages on a real working fuel cell anode during ethanol oxidation. The ethanol oxidation reaction is studied using X-ray absorption spectroscopy during chronoamperometric cell operation. The analysis of the XANES region of the Pt L3 edge by the delta μ XANES technique allows the coverage of the Pt surface with OH, n-fold O and C-species to be followed in-situ. The current-voltage characteristics and the coverage are modelled by means of a multi-step reaction mechanism based on a modified ButlerVolmer approach that additionally includes adsorbate-adsorbate lateral interactions. The model is validated against experimental current and surface coverage data over time. With the model, the importance of acetaldehyde formation via initial C-H vs O-H bond cleavage is examined, the latter dominating at higher potentials on vacant sites remaining in the oxygen coverage coming from water activation. Experimental Commercially-available carbon-supported Pt (40 wt% Pt on Vulcan XC-72) purchased from Johnson Matthey was used as catalyst. The catalysts coated membranes (CCMs) were prepared by spraying an ink on the polymer electrolyte Nafion®115. The ink was fabricated by dispersion of the catalyst powder in high purity water and 5% Nafion® solution. The ink 106 Institute of Materials Science - Materials for Renewable Energies was sprayed in several layers on the membrane, which was then dried for 1h at 130°C in a drying chamber and pressed at 130°C with 1 KN cm-2. X-ray absorption spectroscopy measurements were carried out at beamline X1 at Hasylab, Hamburg in transmission mode for the Pt L3-edge at 11564 eV during electrochemical operation. Therefore the CCM was sandwiched between Au-coated stainless steel endplates with integrated, interdigitated flow fields and X-ray transparent Kapton foil windows. Below the X-ray transparent window, a part of the cathode catalyst layer was removed. Between flow field and electrode a Toray TGP H 90 gas diffusion layer was placed. Hydrogen (N 5.0) was supplied at 50 ml min-1 by a flow controller (Bronkhorst, Netherlands). The liquids were supplied at 1.2 ml min-1. Potentiostatic U/i curves were recorded using a commercial potentiometer. The electrochemical characterization was carried out in a fuel cell during half cell tests, which means that the cathode side was fed with hydrogen instead of oxygen, serving as a dynamic hydrogen electrode (DHE). First, the anode was measured in its dry state, subsequently reduced with hydrogen at 50°C and then cooled down to ambient temperature and flooded with high purity water. Potentials of 0.45 V and 0.75 V vs. DHE were applied in order to use these measurements as reference data. This procedure was followed by replacing the water with 1 M aqueous methanol solution and a potential of 0.45°V vs. DHE applied. Then again water was fed to the anode side and a potential of 0.75 V vs. DHE was held for at least 1.5 h to oxidize all carbon containing adsorbates remaining on the surface. Finally, the water was replaced by 1 M aqueous ethanol solution and several potentials were applied. At each potential step, several quick-EXAFS spectra were recorded from E = 11300 eV to 12800 eV using a Si(111) double-crystal monochromator. A thin Pt metal foil was used as reference for energy calibration. The intensities of the focused beam and the transmitted beam were detected by three gas-filled ion chambers in series. EXAFS The EXAFS analysis was done for the water measurement at 0.45 V, only, to estimate the particle size and the dispersion. Extraction of the EXAFS data from the measured absorption spectra was performed with the programs Athena and Artemis. For comparison, the catalyst particle size was also determined by XRD measurements of the pristine catalyst powder. The particle size obtained was 2.7 nm by Rietveld refinement using the Software FullProf. XANES The XANES region was analyzed by the Δμ-technique. The absorption coefficient was obtained equivalent to the EXAFS region, with the exception that the normalization was carried out between 20 eV and 150 eV relative to the Pt L3 edge. The normalized data were further aligned using the reference foil data. The ∆µ was obtained by subtracting the measurement for water at 0.45 V vs. DHE from the appropriate spectra (Fig. 1). MODELING The kinetics of the EOR was modeled by assuming that the dominant contributions to the current originate from acetaldehyde and CO2 formation. Further, the ethanol reaction rates are considered to be uniform and the same regardless of whether the Pt site is located at a corner, edge, or terrace of the Pt cluster. The estimated Pt particles size is around 1.6 nm, so that the fraction of face and edge-corners sites is about 0.8 and 0.2, respectively. Institute of Materials Science - Materials for Renewable Energies 107 Figure 1. Δμ-results during ethanol oxidation at several potentials measured vs. DHE. For comparison calculated Δμ by the FEFF8, labeled OH, O, and COatop, are shown. The simulations are reported previously. The intrinsic rate of each reaction is given by a rate constant kf and kb determined by the forward and backward activation energy ( kf/b = exp(-ΔGf/b/RT) ). The potential dependence of the rate of each considered reaction step is described by a Butler Volmer expression. In addition, a Frumkin isotherm is introduced in order to account for adsorbateadsorbate interactions on the surface. Each reaction is modeled as source or drain term for the involved chemical species or charge carriers. These source and drain terms are coupled by continuity equations, which are solved numerically using the Software Mathematica® 7. Chemical reactions The EOR is modeled via the reaction pathways summarized in Fig. 2: the formation of acetaldehyde and CO2 is considered as products, with the former as the main reaction product and the intermediate CO adsorbate enroute to the latter the main poison on this catalyst blocking the EOR at lower potentials. The formation of adsorbed CHx and CO from acetaldehyde is neglected in our kinetics model here. As summarized in Fig. 2, the model includes parameters for 7 forward rates and 3 reverse rates (assuming 4 rates are irreversible), with 6 symmetry coefficients (the two acetaldehyde rates are assumed to be equal), and 6 Frumkin interaction coefficients (C1-C1,C1-C2,C1-O, C2-O, O-OH and O-O). Reactants Figure 2. Schematic of 7 reactions (3 assumed to be in equilibrium) as indicated by heavy arrows, 4 adsorbates (ethoxy* adsorbate assumed to be a short-lived intermediate and therefore not accumulating on surface), and 6 Frumkin interaction parameters indicated by 4 light dotted arrows and 2 squares. 108 Institute of Materials Science - Materials for Renewable Energies Results and discussion θ(ML/MASA) Fig. 3 shows the time evolution of the measured (points) and simulated (lines) surface coverages for different potential steps. U = 0.55 V θ(ML/MASA) U = 0.85 V U = 0.65 V U = 0.9 V U = 0.7 V U = 0.92 V θ(ML/MASA) U = 0.6 V θ(ML/MASA) U = 0.80 V θ(ML/MASA) time /s U = 0.75 V C-species O (n-fold) OH (atop) measured C-species O (n-fold) OH (atop) simulated time /s Figure 3. Time-resolved OH(atop), O(n-fold) and C-species coverage for ethanol oxidation at several potentials measured vs. DHE. Points refer to experimental data, solid lines show simulation results. The starting potential of all steps was 0.45 V and hence at time t = 0 the surface is covered mainly with C1-species as previously discussed. For all potential steps, except 0.55 V, a decrease in C-species compared to the starting potential can be observed. In the potential range between 0.6 V and 0.65 V the absolute decrease is small, but for long times the trend becomes visible. At potentials U ≥ 0.7 V the decrease in C-species coverage is very obvious. Furthermore, for potentials U < 0.75 V, only OH is observed apart from C-species. At potentials U ≥ 0.75 V, coverage with OH(ads) decreases over time and in parallel O(ads) formation is observed. Institute of Materials Science - Materials for Renewable Energies 109 The comparison of the experimental and simulated coverages (Fig. 3) and the experimental and simulated currents (not shown here) shows reasonable agreement. The behaviour of the coverage, especially at potentials U ≥ 0.75 V is reproduced. For potentials U < 0.75 V the very strong dynamic behavior seen in the simulated coverages at very short time scales (10 s) was so far not measurable, since the time resolution in the XANES measurements is too low and the signal-to-noise ratio too high. The current simulation reproduces the large experimentally observed overshoot at the higher potentials U ≥ 0.75 V, but the small experimentally observed overshoot in the current at lower potentials U < 0.75 V is not reproduced. Conclusion This study shows for the first time, time-dependent adsorbate coverages of C-, OH- and Ospecies on carbon-supported Pt catalysts of a real CCM operated with ethanol as fuel. These results were used to validate a detailed time-dependent kinetic model describing the ethanol oxidation by a dual path mechanism, similar to what is found for methanol oxidation. The two paths involve either acetaldehyde or CO2 formation by initial C-H bond scission or acetaldehyde by initial O-H bond scission. It is remarkable that with this relatively simple model involving C1 (CO and CHx), CH3CHOH, OH, and O adsorbates, all measured quantities such as the time-dependent coverages and currents, can be reproduced with a reasonable number of free parameters and in excellent agreement with the experimental data. Certainly other reactions may also play a role in the ethanol oxidation reaction, altering the overall rate and distribution of products. We have emphasized in this work the reduction of the number of parameters in the model (and hence the number of reactions), and therefore the simplification of the kinetic model to the essential dominant reactions. Despite this simplification, the kinetic model is able to simulate both the time dependent adsorbate coverages and current; the adsorbate coverages available for the first time in this work. It is hoped that knowledge of the adsorbate coverages on real catalysts under operating conditions sufficiently validates this kinetic model, so that it can be used in a predictive fashion to learn how to design new and better catalysts. Acknowledgments The kind support by S. Mangold and D. Batchelor from the ANKA synchrotron facility and A. Webb and M. Hermann from the HASYLAB synchrotron facility is gratefully acknowledged. References [1] [2] [3] [4] 110 Lamy, C.; Lima, A.; LeRhun, V.; Delime, F.; Coutanceau, C.; Léger, J.-M. J. Power Sources, 2002, 105, 283-296. Parsons, R.; Vandernoot, T. J. Electroanal. Chem., 1988, 257, 9. Wang, J.; Wasmus, S.; Savinell, R.F. J. Electrochem. Soc., 1995, 142, 4218-4224. Melke, J; Schoekel, A.; Dixon, D.; Cremers, C.; Ramaker, D. E.; Roth, C. J. Phys. Chem. C, 2010, 114, 5914 –2925. Institute of Materials Science - Materials for Renewable Energies Physics of Surfaces Physical properties of surfaces and interfaces are relevant in nearly all areas of science and engineering. The fundamental interactions between surfaces, the surrounding fluid and small objects in the fluid play an important role, for example in biology, biotechnology, mechanical engineering, or petroleum geology. The common research question can be expressed as “How does the interplay between physical surface properties, surface and interface chemistry, and fluid flow affect the entire system?” We follow an interdisciplinary approach focusing on physical, chemical and biological properties of surfaces. The connection between surfaces and fluids is of particular interest because it is essential in various technological systems. Our research targets at a better understanding of the interplay between surface pattering (morphological and chemical) and modification with the fluid flow. Experimental methods such as microscopy, microfluidics, or spectroscopy are essential tools. Staff Members Head Prof. Dr. Robert Stark Research Associates Dr. Suman Narayan Dr. Marek Janko Technical Personnel Marie-Christine Apfel Secretary Imke Murschel PhD Students Dipl.-Biol. Elke Kämmerer Dipl.-Min. Maximilian Köhn M.Sc. Na Liu Dipl.-Phys. Agnieska Voß M. Sc. Kim Lieu Phuong (LMU) M.Sc. Andreas Plog Dipl.-Phys. Simon Schiwek M.Sc. Assma Siddique M.Sc. Limor Zemel Bachelor students Golo Zimmermann Michael Marcus Schmitt Erhan Aras Martin Jäcklein Andreas Taubl Master Students Silke Dittombée Marcus Schulze Dr. Christian Dietz Research Projects Funktionale Polymer-Peptidoberflächen (CSI, 2010 – 2014) Wafer cleaning (Industrie 2011 - 2015) Low friction coatings (Industrie 2011 – 2015) Generation of composites from borides with tuneable electrical conductivities using peptides optimized by genetic engineering; characterization of the bio-solid interactions by modelling and AFM STA 1206/5-1 (DFG SPP 1569 2012 – 2014) Institute of Materials Science - Physics of Surfaces 111 Publications 1. Hörner S., Fabritz S., Herce H. D., Avrutina O., Dietz C., Stark R. W., Cardoso M. C. and Kolmar H. Cube-octameric silsesquioxane-mediated cargo peptide delivery into living cancer cells. ORGANIC & BIOMOLECULAR CHEMISTRY. 2013; 11, 2258-2265. 2. Schenderlein H., Voss A., Stark R. W. and Biesalski M. Preparation and Characterization of Light-Switchable Polymer Networks Attached to Solid Substrates. LANGMUIR. 2013; 29, 14, 4525-4534. 3. Maixner F., Overath T., Linke D., Janko M., Guerriero G., van den Berg B.H.J., Stade B., Leidinger P., Backes C., Jaremek M., Kneissl B., Meder B., Franke A., Egarter-Vigl E., Meese E., Schwarz A., Tholey A., Zink A. and Keller A. Paleoproteomic study of the Iceman’s brain tissue. CELLULAR AND MOLECULAR LIFE SCIENCES. 2013; 70, 3709-3722. 112 Institute of Materials Science - Physics of Surfaces Quantitative measurement of the mechanical properties of human antibodies with sub-10-nm resolution in a liquid environment Agnieszka Voss, Christian Dietz, Robert W. Stark The nanomechanical properties of single human immunoglobulin G and M antibodies were measured in a liquid environment using a fast force-volume technique with sub-10-nm spatial resolution. Ultrastructural details of these molecules were resolved in topographical images. Simultaneously, important physical properties, such as elasticity, adhesion and deformation, were measured. Considering their dimensions and adsorption onto the substrate, the immunoglobulin M antibodies were highly flexible, with a low elastic stiffness (34 ± 10) MPa and high deformability (1.5 ± 0.5) nm. Results and Discussion As shown in Fig. 1, PeakForce QNM allows one to resolve the morphology of tiny biological samples with a high resolution in a liquid environment. Fig. 1(a) depicts a homogeneous distribution of human IgM molecules adsorbed on mica. Figure 1(b) illustrates the overall surface charge as a function of the pH value for mica and IgM antibodies. Mica is negatively charged at all pH values, whereas IgM has an isoelectric point at 5.5 ± 1.0.1 The measurements were performed at pH = 5.4, where the molecules are nearly uncharged. Although the molecules are trapped at the surface by van der Waals forces or counterions shared with the mica substrate, the molecules retain their flexibility.2,3 Most of the antibodies reveal a typical pentameric structure, which is shown in Fig. 1(c). The five subunits (Y-shaped branches - IgG) are held together by disulfide bonds in the center region of the biomolecule (yellow), where the j-chain connects two IgG subunits via heavy chains (blue). The IgG subunit consists of two identical heavy chains and two identical light chains. Disulfide bonds bridge the heavy and the light chains (as shown in the lower part of Fig. 1(c)). Fab and Fc fragments are designated by braces.4 Interestingly, the IgM molecules apparent in Fig. 1(a) differ slightly in shape and size, most likely due to the different positions of the Fab domains with respect to the central body of the molecule. This suggests a high mechanical flexibility of the antibodies during the adsorption process.5 Additionally, we imaged single IgG molecules adsorbed on mica. The Y-shaped morphology of the molecule is apparent in the high-resolution topographical PeakForce QNM image of Fig. 1 (d). The observed molecular structures and their total sizes are in good agreement with other studies.6,7 For a more detailed analysis of the morphology, we focused on two single IgM pentamers and recorded highly resolved images (Fig. 2). From these images (Fig. 2(a) and (b) top) and the respective cross-sectional profiles (bottom) drawn through the horizontal positions (red arrows), we estimated the lateral and vertical dimensions of the IgM. The average height of the IgM molecules was approximately 2.2 nm. Considering the finite size of the tip (R = 7 nm) and the geometric ‘convolution’ between the tip shape and the sample morphology,8 the apparent width of the molecules in the cross-sectional profile of approximately 42 nm can be reduced to a lateral size of approximately 28 nm. Strikingly, in Fig. 2(b), the Fab domains (reduced to a length of 7 nm) clearly stick out of the center region, and in some cases, two single neighboring Fab domains within the IgG substructure can be unambiguously distinguished (e.g., two fragments pointing to the left). The main body consists of five Fc domains, including the J-chain, with an apparent diameter of 18 nm. These values are consistent with the dimensions of IgG and IgM found in earlier studies.9,10,11 Comparing Fig. 2(a) with 2(b), the antibody in the left panel exhibits a clear Institute of Materials Science - Physics of Surfaces 113 protrusion inside the main body, whereas the antibody in the right panel possesses a hollow (see the blue arrows in the cross-sectional profile). We assume that the protrusion of the molecule in Fig. 2(a) corresponds to the J-chain of IgM. In contrast, the molecule in Fig. 2(b) either lies upside-down, i.e., the protrusion points downward, or the J-chain does not exist in this case, as postulated by Wiersma et al. 12 Figure 1. (a) Topographical image of IgM antibodies adsorbed on mica in a liquid environment obtained in peak-force tapping mode. (b) Illustration of the overall surface charges of Si3Ni4, IgM and mica at different pH values.1,13 (c) Schematic structure of IgM (top) and IgG (bottom). (d) High-resolution topographical image of a single IgG human antibody adsorbed on mica in distilled water. Figure 2. Highly magnified topography peak-force tapping mode images of single IgM human antibodies, revealing two possible orientations. (a) The center region (j-chain) shows a protrusion from the main body (top). (b) Upside down configuration exhibiting a hollow in the center region (top). In addition to the topographical images, PeakForce QNM provides maps of several mechanical surface properties, such as adhesion, elastic modulus (DMT-modulus), and deformation. The results show that mechanical properties, such as the elasticity, can be imaged with high resolution. Strikingly, the exact contour of single molecules becomes apparent. The elastic modulus measured on IgM antibodies is very close to the value recently reported by Martinez et al.10 The measured values of mica, however, deviated slightly from the nominal elastic modulus (10 GPa). One reason for this difference could be the insufficient indentation depth of the tip into the mica surface while sensing the necessary mechanical response. A force limit of 300 - 800 pN was set to ensure the integrity of the biomolecules which led to an average indentation depth of only 0.7 nm on mica. These results show that the method allows one to quantify the mechanical properties of heterogeneous samples even if the elasticity varies over orders of magnitude. However, sensing the mechanical properties of soft biological systems adsorbed on hard substrates by nanoindentation has to be carried out with care. The sharp tip can induce local strains within the soft material which can exceed the linear material regime and hence, lead to a damage of the sample surface.14 To address this problem, we limited the maximum load 300 - 800 pN during force curve acquisition to avoid damage to the biomolecules and to minimize mechanical stress. Repeated probing of the same individual molecule did not lead to a measurable degradation of topography or local stiffness. The morphology and mechanical response of IgM molecules remained unchanged even after several scans over 114 Institute of Materials Science - Physics of Surfaces the same area with a peak force of approximately 800 pN; however, some of the molecules were slightly distorted in such a way that the Fab domains were marginally twisted. Summary We present a straightforward approach to simultaneously image and generate maps of the mechanical properties of the human IgG and IgM antibodies adsorbed on mica. Quantitative nanomechanical mapping is a method that provides high spatial resolution with complementary information on adhesion, elasticity, or deformation. All of this information is extracted from force-distance curves taken at a kHz acquisition rate. This approach is non-destructive to soft samples under the operating parameters that were applied in this study. The IgM sub-structure could be clearly resolved in water, suggesting that the molecules lie in different positions on mica, where the Fab domains can be oriented in various angles to each other. The analyses of the topographical data of IgM molecules revealed the relatively large size of the Fab domains in comparison with its central portion, where the j-chain is located. Strikingly, we were able to simultaneously measure the elastic modulus of a stiff material, such as muscovite mica (1.3 ± 0.4) GPa, and a soft biomolecule, such as IgM (34 ±10) MPa. The low stiffness found on IgM together with the high deformability (1.5 ± 0.5 nm) in comparison with the dimensions of the molecule (nominal height: 7 nm) corroborates the high flexibility of the antibodies. This flexibility may be the key property that these antibodies are able to adopt confirmations to bind to a large number of antigens with varying sizes and shapes and leads to a high mobility in the organism. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] Chiodi, F.; Sidén, Å.; Ösby, E., Electrophoresis 1985, 6, 124-128. Hansma, H. G.; Laney, D. E., Biophys. J. 1996, 70, 1933-1939. Pastre, D.; Pietrement, O.; Fusil, P.; Landousy, F.; Jeusset, J.; David, M. O.; Hamon, C.; Le Cam, E.; Zozime, A., Biophys. J. 2003, 85, 2507-2518. Alberts, B.; Johnson, A.; Lewis, J.; Raff, M.; Roberts, K.; Walter, P., Molecular Biology of the Cell. Garland Science: New York, 2007. Perkins, S. J.; Nealis, A. S.; Sutton, B. J.; Feinstein, A., J. Mol. Biol. 1991, 221, 1345-1366. Makky, A.; Berthelot, T.; Feraudet-Tarisse, C.; Volland, H.; Viel, P.; Polesel-Maris, J., Sens. Act. B 2012, 162, 269-277. Martinez, N. F.; Lozano, J. R.; Herruzo, E. T.; Garcia, F.; Richter, C.; Sulzbach, T.; Garcia, R., Nanotechnology 2008, 19, 384011. Villarrubia, J. S., J. Res. Natl. Inst. Stan. 1997, 102, 425-454. Czajkowsky, D. M.; Shao, Z., P. Natl. Acad. Sci. USA 2009, 106, 14960-14965. Martinez-Martin, D.; Herruzo, E. T.; Dietz, C.; Gomez-Herrero, J.; Garcia, R., Phys. Rev. Lett. 2011, 106, 198101. Kienberger, F.; Mueller, H.; Pastushenko, V.; Hinterdorfer, P., EMBO Rep 2004, 5, 579-583. Wiersma, E. J.; Collins, C.; Fazel, S.; Shulman, M. J., J. Immunol. 1998, 160, 5979-5989. Lin, X. Y.; Creuzet, F.; Arribart, H., J. Phys. Chem.-US 1993, 97, 7272-7276. Dimitriadis, E. K.; Horkay, F.; Maresca, J.; Kachar, B.; Chadwick, R. S., Biophys. J. 2002, 82, 27982810. Institute of Materials Science - Physics of Surfaces 115 Joint Research Laboratory Nanomaterials The Joint Research Laboratory Nanomaterials was established in the year 2004 as a joint project between the Institute for Materials Science (Technical University of Darmstadt) and the Institute for Nanomaterials (INT) at the Karlsruhe Institute for Nanotechnology (KIT). Its research focusses on the synthesis and characterisation of nanoparticles, nanoparticulate layers, nanoporous as well as dense nanoscale materials. Special interest lies in the determination of correlations between synthesis, interface and bulk properties and the macroscopic functional and structural properties. An important building block is the understanding of the surface, grain boundary and size effects on the physical material properties, which can be significantly different from classical crystalline bulk materials. Since a couple of years, the research has focused on energy materials (batteries, fuel cells). In addition, (reversible) topochemical reactions (chemical and electrochemical) are also under investigation, allowing for the adjustability of material properties. One of the aims is to consistently develop an understanding of correlation between process parameters and the resulting material properties. The materials of interest (nano- and microcrystalline powders and films) are produced by a range of gas phase processes as well as via solid-state reactions. A huge variety of methods is available and in constant use for the characterisation of the assynthesized powders as well as bulk materials and thin-films, among them X-ray powder diffraction, low-temperature N2 adsorption, dynamic light scattering, low and high temperature impedance spectroscopy and cyclic voltammetry. Staff Members Head Prof. Dr.-Ing. Horst Hahn (Director Institute for Nanotechnology) Research Associates Dr. Oliver Clemens Dr. Ruzica Djenadic Secretaries Renate Hernichel PhD Students Dipl.-Ing. Mohsen Pouryazdan Dipl.-Ing. Philipp Leufke Dipl.-Ing. Nina Schweikert Dipl.-Ing. Clemens Wall Dipl.-Phys. Sebastian Becker Dipl.-Ing. Christopher Loho Dipl.-Ing. Ira Balaj Dipl.-Ing. Miriam Botros Dipl.-Ing. Alexander Benes Dipl.-Ing. Ralf Witte Dipl.-Phys. Tom Braun Master Students Dipl.-Ing. Ahmad Chodhary Guest Scientists Dipl.-Ing. Bojana Mojic, University Novi Sad Serbia 116 Dr. Mohammad Ghafari Dr. Matti Oron-Carl Dipl. Phys. Arne Fischer Dipl. Ing. Holger Hain Dipl. Ing. Klaus Maximilian Dipl. Ing. Aaron Kobler M.Sc. Cahit Benel M.Sc. Cheng Huang M.Sc. Garlapati Suresh Kumar M.Sc. Massoud NazarianSamani M.Sc. Mohammad Fawey Institute of Materials Science - Joint Research Laboratory Nanomaterials Research Projects Tunable Magnetic Nanostructures. Property Characterization and Modeling (DFG HA 1344/28-1, 2010 – 2013) Investigation of non-equilibrium phonon populations in biased metallic single-walled carbon nanotubes (DFG OR 262/1-2, 2011-2013) Reversibles Durchstimmen der elektronischen Transporteigenschaften in oxidischen leitfähigen Nanostrukturen zur Anwendung im Bereich der druckbaren Elektronik (DFG HA 1344/25-1, 2010 – 2013) Helmholtz Portfolio, Elektrospeicher im System – Zuverlässigkeit und Integration (325/20514659/NANOMIKRO, 2012-2014) Förderung durch Mittel des Helmholtz Institut Ulm (2010-2014) Publications SK Garlapati, N. Mishra, S. Dehm, R. Hahn, R. Kruk, H. Hahn, S. Dasgupta, Electrolyte-gated, high mobility inorganic oxide transistors from printed metal halides, ACS Applied Materials & Interfaces 5 (2013), 11498-11502, DOI: 10.1021/am403131j X. Zhao, CM Wang, D. Wang, H. Hahn, M. Fichtner, Ge-Cu nanoparticles produced by inert gas condensation and their application as anode material for lithium ion batteries, Electrochemistry Communications 35 (2013), 116-119, DOI: 10.1016/j.elecom.2013.08.016 A. Kobler, J. Lohmiller, J. Schaefer, M. Kerber, A. Castrup, A. Kashiwar, PA Gruber, K. Albe, H. Hahn, C. Kuebel, Deformation-induced grain growth and twinning in nanocrystalline palladium thin films, Beilstein Journal of Nanotechnology 4 (2013), 554-566, DOI: 10.3762/bjnano.4.64 R. Witte, T. Feng, JX Fang, A. Fischer, M. Ghafari, R. Kruk, RA Brand, D. Wang, H. Hahn, H. Gleiter, Evidence for enhanced ferromagnetism in an iron-based nanoglass, Applied Physics Letters 103 (2013), 073106, DOI: 10.1063/1.4818493 A. Evans, C. Benel, AJ Darbandi, H. Hahn, J. Martynczuk, LJ Gauckler, M. Prestat, Integration of spin-coated nanoparticulate-based La0.6Sr0.4CoO3-delta cathodes into microsolid oxide fuel cell membranes, Fuel Cells 13 (2013), 441-444, DOI: 10.1002/fuce.201300020 A. Kobler, A. Kashiwar, H. Hahn, C. Kuebel, Combination of in situ straining and ACOM TEM: A novel method for analysis of plastic deformation of nanocrystalline metals, Ultramicroscopy 128 (2013), 68-81, DOI: 10.1016/j.ultramic.2012.12.019 Institute of Materials Science - Joint Research Laboratory Nanomaterials 117 C. Benel, AJ Darbandi, R. Djenadic, A. Evans, R. Tolke, M. Prestat, H. Hahn, Synthesis and characterization of nanoparticulate La0.6Sr0.4CoO3-delta cathodes for thin-film solid oxide fuel cells, Journal of Power Sources 229 (2013), 258-264, DOI: 10.1016/j.jpowsour.2012.11.149 N. Schweikert, A. Hofmann, M. Schulz, M. Scheuermann, ST Boles, T. Hanemann, H. Hahn, S. Indris, Suppressed lithium dendrite growth in lithium batteries using ionic liquid electrolytes: Investigation by electrochemical impedance spectroscopy, scanning electron microscopy, and in situ Li-7 nuclear magnetic resonance spectroscopy, Journal of Power Sources 228 (2013), 237-243, DOI: 10.1016/j.jpowsour.2012.11.124 B. Nasr, Di Wang, R. Kruk, H. Rosner, H. Hahn, S. Dasgupta, High-speed, low-voltage, and environmentally stable operation of electrochemically gated zinc oxide nanowire field-effect transistors, Advanced Functional Materials 23 (2013), 1750-1758, DOI: 10.1002/adfm.201202500 PM Leufke, R. Kruk, RA Brand, H. Hahn, In situ magnetometry studies of magnetoelectric LSMO/PZT heterostructures, Physical Review B 87 (2013), 094416, DOI: 10.1103/PhysRevB.87.094416 NS Arshad, GT Lach, M. Pouryazdan, H. Hahn, P. Bellon, SJ Dillon, RS Averback, Dependence of shear-induced mixing on length scale, Scripta Materialia 68 (2013), 215-218, DOI: 10.1016/j.scriptamat.2012.10.027 H. Shao, YL Xu, B. Shi, CS Yu, H. Hahn, H. Gleiter, JG Li, High density of shear bands and enhanced free volume induced in Zr70Cu20Ni10 metallic glass by high-energy ball milling, Journal of Alloys and Compounds 548 (2013), 77-81, DOI: 10.1016/j.jallcom.2012.08.132 AK Mishra, AJ Darbandi, PM Leufke, R. Kruk, H. Hahn, Room temperature reversible tuning of magnetism of electrolyte-gated La0.75Sr0.25MnO3 nanoparticles, Journal of Applied Physics 113 (2013), 033913, DOI: 10.1063/1.4778918 C. Kuebel, A. Kobler, H. Hahn, In-situ Deformation Analysis of Nanocrystalline Metals by Quantitative ACOM-STEM, Advances in Imaging and Electron Physics 179 (2013), 172-174, WOS: 000323356800016 N. Chen, XT Shi, R. Witte, KS Nakayama, K. Ohmura, HK Wu, A. Takeuchi, H. Hahn, M. Esashi, H. Gleiter, A. Inoue, DV Louzguine, A novel Ti-based nanoglass composite with submicron-nanometer-sized hierarchical structures to modulate osteoblast behaviors, Journal of Materials Chemistry B 1 (2013), 2568-2574, DOI: 10.1039/c3tb20153h B. Nasr, Z. Zhao-Karger, D Wang, R. Kruk, H. Hahn, S. Dasgupta, Temperature tolerance study of high performance electrochemically gated SnO2 nanowire fieldeffect transistors, Journal of Materials Chemistry C 1 (2013), 2534-2539, DOI: 10.1039/c3tc00061c 118 Institute of Materials Science - Joint Research Laboratory Nanomaterials O. Clemens, R. Haberkorn, M. Springborg, H. P. Beck On aliovalent substitution on the Li site in LiMPO4: a X-ray diffraction study of the systems LiMPO4-M1.5PO4 (= LixM1.5-x/2PO4; M = Ni, Co, Fe, Mn), Zeitschrift fuer Anorganische und Allgemeine Chemie (2014), 640, (1), 173-183, DOI: 10.1002/zaac.201300376 Institute of Materials Science - Joint Research Laboratory Nanomaterials 119 Mechanics of Functional Materials The research at the Division of Mechanics of Functional Materials is focused on the constitutive modeling and the simulation of functional materials and systems, for instance ferroelectric materials and lithium-ion battery electrodes. These materials are characterized by a coupling of multiple physical fields at a variety of length-scales. Their macroscopic responses depend on the microstructure and its thermodynamic kinetics. The main features of our research therefore include coupled fields (e.g. mechanical, electrical, chemical), microstructure evolution, mesoscopic material properties, and homogenization. Primary tools of our research are continuum models and Finite Element numerical simulations. Novel concepts such as phase-field models or Isogeometric Analysis are regarded to an increasing extent in our work. Phase field simulation of the domain structure of ferroelectric ceramics Ferroelectrics are widely used as actuators, sensors, and memory devices. A characteristic feature of ferroelectrics is that they possess different spontaneous polarization states. Switching between these states can be achieved by application of an electric field, and the cycling loading of a specimen gives rise to nonlinear hysteretic behavior. Semiconductor properties have a significant impact on domain configurations in ferroelectrics, in particular for doped materials. In order to assess these effects, a phasefield model is formulated that regards space charges due to donors and electronic charge carriers. It allows quantitative studies on the role of space charges and electronic charge carrriers in the stabilization of domain structures. By accounting for the semiconductor properties of barium titanate, the appearance of depletion layers near electrodes can be predicted. Furthermore, the stabilization of (otherwise instable) head-to-head and tail-totail domain structures through space charges can be demonstrated. Simulations of initial tail-to-tail configurations with a tilted domain wall show that, upon disregard of semiconductor features, the domain wall rotates into a vertical equilibrium alignment as a result of driving moments. In contrast, when semiconduction is included in the model, the equilibrium orientation of the domain wall depends on the donor concentration. Since electronic charges accumulate along the head-to-head and tail-to-tail domain walls, they have electric conductivity, which can be studied by the phase-field model. To that end, two defect systems are investigated: firstly, am ideal defect system where oxygen vacancies are the only point defects, and secondly a realistic defect system where doping of manganese gives rise to several kinds of point defects. This shows that the domain wall conductivity enhanced by electrons or holes depends, among other factors, on the domain configuration, the type of involved defects, and the concentration of point defects. Based on these results, controversial experimental results on domain wall conductivity can be explained. Simulation of the electrocaloric effect of relaxor ferroelectrics In recent years, the electrocaloric effect (ECE) has drawn much attention because of its environment-friendliness and its higher efficiency compared with other traditional cooling processes. In order to gain a better understanding of the ECE phenomenon, the polarization switching behavior and the ECE are studied in both ferroelectrics (FEs) and relaxor ferroelectrics (RFEs). Since fundamentally microscopic quantities are of interest here, a lattice-based model is employed for these studies. This model takes into account four 120 Institute of Materials Science – Functional Materials different energy contributions to the potential energy that significantly affect the material behaviour. In addition to a Landau double well potential, dipole-dipole interactions, gradient terms and the electrostatic energy of the system are regarded. The equilibrium material behaviour at a specific temperature is evaluated by the Metropolis algorithm; thereby, the polarization switching behaviour under an alternating external electrical field and the influence of the domain size can be taken into account. Once an equilibrium state has been achieved, the ECE is investigated using Creutz' algorithm. In order to account for the different behaviour of FEs and RFEs, a random initial field is imposed on the RFE samples whereas the FE models are treated without this random field. In the latter case, without an external electric field, the equilibrium state exhibits large domain together with very sharp phase transitions about the transition point. With increasing gradient energy, this transition point is shifted towards higher temperatures. Throughout the polarization switching process, the domain wall movement is easily recognizable. At the same time, the remanent polarization is relatively strong, and the ECE peaks at the phase transition point. The simulations with an imposed random field, on the other hand, do not show these large domain sizes. Here, the phase transitions are much broader around the transition point and the domain wall movement is not visible. When the polarization switches under the applied electric field, the remanent polarization decreases. With increasing magnitude of the random field, this phenomenon becomes more prominent. Other than in FE materials, the ECE peak drifts towards lower temperatures in RFEs which, in turn, show a broader ECE range. Simulation of diffusion introduced stresses in the Lithium-ion batteries via Isogeometric Analysis Mechanical degradation of the active material has been identified as one of the root causes of the degradation of Lithium-ion batteries, which can be observed macroscopically as a gradual fade of the batteries' capacity. The understanding of the damage processes in the electrodes’ particles and their influence on the mechanical-electrochemical properties is hence of utmost importance. The coupled electrochemical-mechanical processes in individual electrode particles are described by continuum mechanics and higher-order Finite Element procedures based on the concept of Isogeometric Analysis. Their application is motivated by higher-order gradient/coupling terms arising from the thermodynamics of the problem; it allows for stable implementation of the governing equations as well as for a unified treatment of diverse particle shapes and electrode geometries. Using these models the impact of material properties, charge rates, and particle shape on the emerging stress levels can be assessed. The current model, restricted to the small-strain regime, predicts stress-enhanced diffusion rates that, in turn, cause a stress relaxation effect in the material. Furthermore, the model allows to show the stress distribution within particles of varying aspect ratio which can be used to explain the higher resilience of thin, needle-like particles against diffusion-induced degradation, compared with more bulkier, compact particles (see attached short report). In addition to large deformations of certain electrode materials, in situ TEM observations have revealed the coexistence of lithium-poor and lithium-rich phases in the electrode particles during charge and discharge, which suggests that the concentration of Li-ion does not change gradually but experiences a gap at a certain interface. In order to capture this behaviour, a Cahn-Hilliard phase-field model is currently developed that regards not only the chemical aspects of the phase separation and diffusion, but also viscoplastic effects. Institute of Materials Science – Mechanics of Functional Materials 121 Staff Members Head J. Prof. Dr. (Boshi) Bai-Xiang Xu Research Associates Dr.-Ing. Peter Stein Secretaries Maria Bense PhD Students Dipl.-Ing. Yinan Zuo Ying Zhao, M.Sc. Diploma Students Timo Noll, B.Sc. Habib Pouriayevali, PhD Yangbin Ma, M.Sc. Min Yi, M.Sc. Research Projects Phase-field simulation of ferroelectrics with defects (Project in DFG-SFB 595, 2012-2014) Simulation of the electrocaloric effect of relaxor ferroelectrics (Project in DFG-SPP 1599, 2013-2015) Isogeometric simulation of diffusion-induced stress in Lithium-ion battery electrodes (Project in GSC CE, 2013-2015) Publications [1] B.-X. Xu, Y. Gao, M.Z. Wang, Particle packing and the mean theory, Physics Letters A, 377, 145-147, 2013 [2] B.-X. Xu, H. von Seggern, S. Zhukov, and D. Gross, Continuum modeling of charging process and piezoelectricity of ferroelectrets, J. Appl. Phys. 114, 094103 (2013) [3] P. Stein, Y. Zhao, B.-X. Xu, An analytical solution for the mechanically coupled diffusion problem in thin-film electrodes Proc. Appl. Math. Mech. 13(1), 237-238, 2013 122 Institute of Materials Science – Mechanics of Functional Materials Isogeometric analyis of intercalation-induced stresses in Lithium-ion battery electrode particles Peter Stein & Bai-Xiang Xu Lithium-ion batteries are an important energy storage system. They are the predominant power source for portable electronic devices such as cellphones and tablet PCs. Their high potential for application in hybrid electric vehicles or for the storage of renewable energy can unfortunately not be exploited: in order to prevent (both spontaneous and gradual) battery failure and to maintain a certain lifetime, the admissible charge rates and battery capacities must be bounded from above. In addition to electrochemical side-reactions, mechanical degradation of the battery electrodes has been identified as one of the root causes of the gradual macroscopic fade of a battery's capacity. Experimental observations indicate the emergence of high stresses during cyclic charge processes, leading to particle fracture. Moreover, certain electrode materials, for instance silicon with its tremendous theoretical storage capacity, also show huge volumetric strains (values in the range of 270-400% have been reported in the literature). That is, in addition to the fracture of individual electrode particles, delamination of the whole electrode structure is a probable failure mechanism for these batteries. Once a fragment of active material loses contact to the electrode it is no longer available to intercalation, causing the observed capacity loss. The understanding of the damage processes in the electrodes’ particles and their influence on the mechanicalelectrochemical properties is hence of utmost importance. Lithium-ion battery cells comprise three main components: a cathode, which commonly consists of a lithium compound such as LiCoO or LiFePO4 , an anode, which is often made of Si or C, and an electrolyte. The electrodes exist in various designs, for instance as thin film substrates, porous electrodes, or as nanowire assemblies. During charge processes, Li ions migrate from the cathode through the electrolyte to the anode where they are intercalated into the active anode material. This process is reversed during discharge. In the present work, the intercalation process within a single electrode particle is described by a diffusion model that is coupled to a linear elastostatic model (based on the assumption that mechanical equilibrium is established much faster than ionic diffusion within the particle). Thereby, the Fick diffusion is enhanced by a drifting term based on the gradient of the hydrostatic mechanical stress field [1]. Accordingly, ions diffuse not only along the negative concentration gradient but also from regions of high compressive stresses towards regions of lower compressive stresses. The concentration field, in turn, affects the mechanical stresses analogous to thermal expansion. That is, the intercalation of ions leads to an isotropic swelling that relaxes, in an unconstrained body, the total stress levels. Above model has been implemented in the Finite Element software FEAP using the concept of Isogeometric Analysis that provides smooth, higher-order ansatz functions for the discretization of the governing equations. This is justified by the higher-order gradients that come into play due to the stress-gradient coupling terms. As these require C1-continuous basis functions, common C0-continuous Finite Element methods cannot be employed. Instead, mixed-variational formulations have to be used, as in [2]. As an alternative, this Institute of Materials Science – Mechanics of Functional Materials 123 coupling term is often neglected, leading to a partially coupled model, e.g. [3]. Simulations performed for a spherical LiMn2O4 particle show the significance of the full coupling, illustrated in Figure 1, which shows the tangential stresses along the radius of said particle. It can be easily recognized that the full model (“Coupled”) predicts not only stresses of lower magnitude, but also a stress relaxation effect. In the first stages of charging, a compressive shell emerges in the particle that enhances the ion diffusion towards the particle's core. Over time, this causes higher ion concentrations in the core region that cause a reduction in the overall stress levels. The partially coupled model (“Decoupled”) cannot describe such an effect and hence maintains the high stress levels that arise during the process. Fig. 1: Tangential stresses in a spherical particle of 5 µm radius under galvanostatic charge boundary conditions. The plot shows the stresses along the particle's radius for different time steps, both for our model („Coupled“) and a partially coupled model („Decoupled“), illustrating the significance of the drift term. Based on this model, parameter studies have been performed with respect to the influence of material stiffness, charge boundary conditions, and particle shape [4]. The reveal that the overall stress levels in the particles increase with both increasing material stiffness and increasing charge rate, where the latter is typical for applications in hybrid electric vehicles. The effect of shape variation is shown in Figure 2 that shows the distribution of the maximum von Mises stresses for spheroidal particles of different aspect ratio. Thereby, the particles' volume is kept fixed. As can be seen, the highest stresses develop in the needlelike particles as a „belt“ around their respective equator, where the material is constrained by conditions similar to a cylinder. At the same time, towards the particles' tip, the material can swell comparatively free, which allows for an equilibration of diffusion-induced stresses. Moreover, the diffusion paths are relatively short in these particles, leading to stress levels that are below those occurring in spherical particles. This explains experimental observations of the higher robustness of slender particles against diffusioninduced degradation. 124 Institute of Materials Science – Mechanics of Functional Materials The stresses in the flat, lens-shaped particles, in contrast, greatly exceed those in the spherical and prolate ellipsoidal particles – despite the short diffusion paths along their semi-minor axis. In particular for low aspect ratios the material is subject to strong, rotationally symmetric constraints. Thus, the particle can expand only slightly in order to reduce the stresses arising from intercalation. It must therefore be concluded that such flat electrode particles are prone to crack initiation and hence to an early onset of capacity fade. Fig. 2: Von Mises stress distributions in oblate and prolate ellipsoidal particles for different parameters a. All particles have the volume of a spherical particle with radius 5 µm. The models are shown at the respective time steps corresponding to the peak stress levels. All particles exhibit the semi-axes a : (1/sqrt(a)) : (1(sqrt(a)), with a indicated in each sub-figure. References: [1] [2] [3] [4] X. Zhang, W. Shyy, A.M. Sastry, J. Electrochem. Soc. 154 (2007) A910–A916. Y.F. Gao, M. Zhou, J. Appl. Phys. 109 (2011) 014310. Y.-T. Cheng, M.W. Verbrugge, J. Power Sources 190 (2009) 453–460. P. Stein, B. Xu, Comput. Methods Appl. Mech. Engrg. 268 (2014), 225–244. Institute of Materials Science – Mechanics of Functional Materials 125 Functional Materials The Functional Materials Research Group joined the Department of Material Science in 2012. Our main research interests are permanent magnets and magnetocaloric materials. During 2013 the laboratory facilities have been extended and we have moved to our new home in the M³ building. The healthy state of project funding has allowed us to grow to a team of 29 researchers and students. 2013 was a productive year: We have published more than 20 peer reviewed scientific journal papers and given more than 15 invited and many contributed talks at international conference presentations. A highlight of 2013 was a joint seminar with the project group for materials recycling and resource strategies, Fraunhofer IWKS of which Oliver Gutfleisch is a director. This allowed the Darmstadt group to present their research and learn about the activities at the Fraunhofer Institute. Another highlight of the year was a 3 day group seminar at Kloster Bronnbach. In addition to our research activities this year we have also increased our contribution to teaching at the department of material science. Oliver Gutfleisch is now giving 3 lecture courses: “Functional Materials”, “Materials Engineering”, and “Material Science for renewable energy systems”, the latter as part of the new interdisciplinary Master of Energy Science course. Also this year the group has introduced a new practical course for bachelor students dealing with “permanent magnets in application” and is actively participating in the seminars of the bachelor and master programmes. The Outlook for 2014 for the group is good. The increased size of the group and additional funding streams, including a 4.4 million€ state grant from the LOEWE initiative, will allow the group to expand further and continue the high level of research. Research Interests: Permanent magnets: Permanent magnets are used in a wide variety of industrial and household appliances, the major applications being electrical motors and power generation. Currently these applications require NdFeB magnets, which rely on rare earth elements such as Nd as well as Dy, which is used to enhance the thermal stability. Rare Earth metals are expensive and availability is predicted to become increasingly limited in the years to come. Our efforts include a) reduction of heavy rare earth elements in Nd-Fe-B magnets without a loss in performance and b) the study of novel rare earth free materials with energy densities greater than those of hard ferrites (another class of widely used permanent magnets). Our research on permanent magnets is now being supported by the Hessian Ministry HMWK after a successful bid to the “LOEWE” program resulting in an additional 4.4 Mio. € for work on resource efficient usage of rare earth elements; Project “RESPONSE”. This project is supported for a minimum of 3 years starting in January 2014 and combines the applied research at Fraunhofer with fundamental studies in chemistry, mechanical engineering, and material science carried out at TU Darmstadt. 126 Institute of Materials Science – Functional Materials Magnetocaloric Materials: Magnetic Refrigeration is an energy efficient cooling technology based on the reversible magnetisation and demagnetisation of a magnetocaloric material by external magnetic fields. The group’s activities include investigations into the improvement of the magnetocaloric La(FeSi)13 compound, a promising material for room temperature applications. This material is of particular interest for practical refrigerators due to its sharp magnetic transition and the low toxicity of its constituent elements. Our research focuses on both fundamental material aspects on how to improve this compound, e.g. by substitution of other elements to tailor the transition properties, as well as practical aspects of room temperature magnetic cooling. We have shown that using polymer bonded magnetocaloric powder as heat exchangers is an inexpensive method, allowing flexibility in terms of shape to obtain optimum conditions for heat transfer between the solid refrigerant and the pumped heat exchange fluid. In addition to improving the La(FeSi) 13 compound, the group studies the synthesis, structural and magnetic characterisation of new magneto caloric materials, in particular reducing or eliminating the use of rare earth resources. Such systems include for example Heusler alloys, Fe2P or MnB compounds. The magnetocaloric research in our group is funded by two national and one European research grants. Staff Members Head Prof. Dr. Oliver Gutfleisch Research Associates Dr. Semih Ener Dr. Bianca Frincu Dr. Barbara Kaeswurm PD Dr. Michael Kuzmin Dipl.-Ing. Marc Pabst Dr. Iliya Radulov Dr. Konstantin Skokov Technical Personnel Ms. Gabi Andress Ms. Helga Janning Dipl.-Ing. Bernd Stoll Secretary Ms Brigitte Azzara PhD Students M. Sc. Imants Dirba Dipl.-Ing. Maximilian Fries Dipl.-Phys. Tino Gottschall Dipl.-Ing. Konrad Löwe Dipl.-Wi.-Ing. Simon Sawatzki Dipl.-Ing. Christoph Schwöbel External: M. Eng. Alexandru Lixandru Dipl.-Phys. Fabian Rhein M. Sc. Xi Lu Master Students Ms. Bahar Fayyazi Mr. Anok Babu Nagaram Mr. Farzin Ziaiee Tabary Mr. Prasad Mishra Tarini Bachelor Students Mr. Valentin Brabänder Ms Almut Dirks Mr. Florian Esdar Ms. Adjana Eilts Guest Scientists Prof. Toshiyuki Shima B. Eng Hong Jian. Mr. Dimitri Karpenkov Institute of Materials Science –Functional Materials 127 Research Projects EU, DFG, BMBF, AIF Projects and others Publications [1] O. Gutfleisch, K. Güth, T.G. Woodcock, L. Schultz, Recycling Used Nd-Fe-B Sintered Magnets via a Hydrogen-Based Route to Produce Anisotropic, Resin Bonded Magnets, Advanced Energy Materials 3 (2013) 151-155. [2] K. Skokov, K.-H. Müller, J.D. Moore, J. Liu,. A.Y. Karpenkov, M. Krautz, O. Gutfleisch Influence of thermal hysteresis and field cycling on the magnetocaloric effect in LaFe11.6Si1.4, J. Alloys and Comp. 552 (2013) 310-317. [3] S.V. Taskaev, M.D. Kuz’min, K.P. Skokov, D.Yu. Karpenkov, A.P. Pellenen, V.D. Buchelnikov, O. Gutfleisch, Giant induced anisotropy ruins the magnetocaloric effect in gadolinium, J. Magn. Magn. Mat. 331 (2013) 33-36. [4] Y. Skourski,· J. Bartolomé, M.D. Kuz’min, K.P. Skokov, M. Bonilla, O. Gutfleisch, J. Wosnitza, High-Field Transitions in ErFe11Ti and HoFe11Ti Single Crystals, J. Low Temp. Phys. 170 (2013) 307-312. [5] I. Lindemann, A. Borgschulte, E. Callini, A. Züttel, L. Schultz, O. Gutfleisch, Insight into the decomposition pathway of the complex hydride Al 3Li4(BH4)13, Int. J. of Hydrogen Energy 38 (2013) 2790-2795. [6] S.K. Pal, L. Schultz, O. Gutfleisch, Effect of milling parameters on SmCo5 nanoflakes prepared by surfactant-assisted high energy ball milling, J. Appl. Phys. 113 (2013) 013913_1-6. [7] S. Garroni, C. Bonatto Minella, D. Pottmaier, C. Pistidda, C. Milanese, A. Marini, S. Enzo, G. Mulas, , M. Dornheim, M. Baricco, O. Gutfleisch, S. Suriñach and M. Dolors Baró, Mechanochemical synthesis of NaBH4 starting from NaH-MgB2 reactive hydride composite system, Int. J. of Hydrogen Energy 38 (2013) 2363-2369. [8] M. Moore, R. Sueptitz, A. Gebert, L. Schultz, O. Gutfleisch, Impact of magnetization state on the corrosion of sintered Nd-Fe-B magnets for e-motor applications, Materials and Corrosion 64 (2013) no 9999, p. 1-6. [9] N.M. Dempsey, T.G. Woodcock, H. Sepehri-Amin, Y. Zhang, H. Kennedy, D. Givord, K. Hono and O. Gutfleisch, High coercivity Nd-Fe-B thick films without heavy rare earth additions, Acta. Mat. 61 (2013) 4920–4927. [10] K.P. Skokov, A. Yu. Karpenkov, D. Yu. Karpenkov, O. Gutfleisch, The maximal cooling power of magnetic and thermoelectric refrigerators with La(FeCoSi)13 alloys, J. Appl. Phys. 113 (2013) 17A945. [11] V. Khovaylo, M. Lyange, K.P. Skokov, O. Gutfleisch, R. Chatterjee, X. Xu, R. Kainuma, Adiabatic Temperature Change in Metamagnetic Ni(Co)-Mn-Al Heusler Alloys, Materials Science Forum 738-739 (2013) 446-450. 128 Institute of Materials Science – Functional Materials [12] C. Bonatto Minella, C. Pistidda, S. Garroni, P. Nolis, M. Dolors Baró, O. Gutfleisch, T. Klassen, R. Bormann, M. Dornheim, Ca(BH4)2 + MgH2: desorption reaction and role of Mg on its reversibility, J. Phys. Chem. C 117 (2013) 3846-3852. [13] C. Bonatto Minella, E. Pellicer, E. Rossinyol, F. Karimi, C. Pistidda, S. Garroni, C. Milanese, P. Nolis, M. Baró, O. Gutfleisch, K. Pranzas, A. Schreyer, T. Klassen, R. Bormann, M. Dornheim, Chemical state, distribution and role of Ti- and Nb-based additive on the Ca(BH4)2 system, J. Phys. Chem. C 117 (2013) 4394–4403. [14] V. Pavlyuk, G. Dmytriv, I. Chumak, O. Gutfleisch, I. Lindemann, H. Ehrenberg, High hydrogen content super-lightweight intermetallics from the Li-Mg-Si system, Int. J. of Hydrogen Energy 38 (2013) 5724-5737. [15] C. Bonatto Minella, I. Lindemann, P. Nolis, A. Kießling, M. Baró, M. Klose, L. Giebeler, B. Rellinghaus, J. Eckert, L. Schultz, O. Gutfleisch, NaAlH4 confined in Ordered Mesoporous Carbon, Int. J. of Hydrogen Energy 38 (2013) 8829–8837. [16] S.V. Taskaev, V.D. Buchelnikov, A.P. Pellenen, M.D. Kuz'min, K.P. Skokov, D. Yu. Karpenkov, D.S. Bataev, O. Gutfleisch, Influence of thermal treatment on magnetocaloric properties of Gd cold rolled ribbons, J. Appl. Phys. 113 (2013)17A933. [17] S.K. Pal, K. Güth, T. G. Woodcock, L Schultz, O. Gutfleisch, Properties of isolated single crystalline and textured polycrystalline nano/sub-micrometre Nd2Fe14B particles obtained from milling of HDDR powder, J. Phys. D: Appl. Phys. 46 (2013) 375004_1-8. [18] R. Sueptitz, S. Sawatzki, M. Moore, M. Uhlemann, O. Gutfleisch and A. Gebert, Effect of DyF3 on the corrosion behavior of hot‐pressed Nd–Fe–B permanent magnets, Materials and Corrosion 2013, DOI: 10.1002/maco.201307303. [19] S. Sawatzki, I. Dirba, L. Schultz, and O. Gutfleisch, Electrical and magnetic properties of hot-deformed Nd-Fe-B magnets with different DyF3 additions, J. Appl. Phys. 114 (2013) 133902_1-5. [20] V. Sokolovskiy, V. Buchelnikov, K. Skokov, O. Gutfleisch, D. Karpenkov et al., Magnetocaloric and magnetic properties of Ni2Mn12-xCuxGa Heusler alloys: An insight from the direct measurements and ab initio and Monte Carlo calculations, J. Appl. Phys. 114 (2013) 183913_1-9 [21] J. Thielsch, D. Süss, L. Schultz,, O. Gutfleisch, Dependence of Coercivity on Length Ratios in Sub-micron Nd2Fe14B Particles with Rectangular Prism Shape, J. Appl. Phys. 114 (2013) 223909_1-5. [22] M.D. Kuzmin, A. Savoyant, R.Hayn, Ligand Field Parameters and the ground state of Fe(II)phthalocyanine, J. Chem. Phys. 138 244308 (2013) Institute of Materials Science –Functional Materials 129 Grain boundary diffusion processes in Nd-Fe-B magnets Simon Sawatzki, Imants Dirba, Almut Dirks, Konrad Löwe, and Oliver Gutfleisch The heavy rare earth (HRE) element Dy is known to increase the temperature stability of Nd-Fe-B permanent magnets for the use in high performance electric motors and generators [1]. Its forecasted long term criticality and the lack of alternatives for Nd-Fe-B has led to the development of the grain boundary diffusion process (GBDP) that reduces Dy without losing much in remanent magnetisation [2]. In the GBDP the magnet is coated with Dy and subsequently annealed at temperatures of about 900°C. At this temperature the Nd-rich phase has melted and Dy diffuses along the grain boundaries. During cooling a thin (Dy,Nd)2Fe14B shell forms around each individual grain, impeding the nucleation of reversed magnetic domains in the reversed direction and thus increases coercivity. Several investigations show improved magnetic properties of sintered magnets using DyF3 for the GBDP [3,4]. In comparison to sintering, the hot-deformation is an alternative preparation method for Nd-Fe-B magnets that benefits from a good temperature coefficient of coercivity due to its nanocrystallinity but still suffers from being an expensive batch process. In hot-deformed magnets the pressing time is much shorter and the process temperatures are much lower (700-750°C, 2-10 min) compared to sintered magnets (1000-1100°C, several hours). Therefore elements selectively diffuse along the grain boundaries during hot-deformation instead of redistributing within the grains. Fig. 1: Grain boundary diffusion in hot-deformed Nd-Fe-B magnets using DyF3 We first doped hot-compacted and die-upset Nd–Fe–B magnets with DyF3 (see figure 1). Because of the nanocrystallinity of hot-compacted magnets, annealing is limited to 600°C [5]. It was found, that during hot-compaction and die-upsetting DyF3 decomposes and 130 Institute of Materials Science – Functional Materials diffuses into the flake via the grain boundaries. Thereby, Dy replaces Nd and forms the (Dy,Nd)2Fe14B phase that enhances coercivity. The excess Nd interacts with F and forms RE-F or RE-O-F phases. These phases can either additionally increase or decrease coercivity. Annealing of hot-compacted magnets at 600°C leads to an F diffusion along the flake boundary and the formation of RE-F or RE-O-F phases. As a consequence the coercivity increases for low (<1.2 wt.%Dy) and decreases for high Dy-F fractions (> 1.2wt.%Dy). In die-upset magnets the oxide layer in the flake boundary is not present and F can directly interact with the grain boundary phase adjacent the magnetic phase. As a result coercivity decreases independent of the Dy-F fraction. Best results are obtained for 1.2 wt.% Dy increasing the coercivity of die-upset magnets by 19 % while remanence is almost retained. Furthermore the use of DyF3 in hot-compacted magnets was shown to increase the electrical resistivity, which reduces eddy current losses in motor application and thus reduces the Dy amount required [6]. Fig. 2: Effect of different low-melting eutectics on the magnetic properties of hot-compacted Nd-Fe-B magnets In a further study we substituted DyF3 by several rare earth containing low-melting eutectics and investigated the effect of annealing at 600°C on hot-compacted magnets [7]. The use of DyCu and subsequent annealing for 24 h leads to higher coercivities than DyNiAl Institute of Materials Science –Functional Materials 131 with similar remanences, which can be attributed to the lower melting point and thus higher diffusion coefficient for DyCu. As Al and Cu are both known to reduce the melting point of the Nd-rich grain boundary phase, the higher Cu-fraction in DyCu than the Alfraction in DyNiAl promotes the diffusion. The use of NdCu and NdAl slightly enhances coercivity. Annealing of these samples did not lead further improvement of the magnetic properties. To compare the effectiveness of the alloys commercially available Dy-containing MQU-G powder with a homogeneous Dy-distribution of 3.85wt.%Dy was hot-compacted. It shows a higher coercive force than for the annealed DyCu sample. The normalized increase in coercivity of the MQU-G compared to a Dy-free MQU-F magnet is about 0.20 T/wt.%Dy. For the annealed DyCu sample the normalized increase is 0.25 T/wt.%Dy (up to a range of about 2wt.%Dy). This leads to a more effective use of Dy and therefore improved magnetic properties by the use of low-melting eutectics, although the MQU-F powder was already optimised for hot-deformation. References: [1] [2] [3] [4] [5] [6] [7] 132 O. Gutfleisch, M. A. Willard, E. Bruck, C. H. Chen, S. G. Sankar, and J. P. Liu, Adv. Mater. 23, 821 (2011). th K. Park, K. Hiraga, and M. Sagawa, in REPM Proceedings of 16 International Workshop on RE Magnets and Their Applications, edited by H. Kaneko, M. Homma, and M. Okada (The Japan Institute of Metals, Sendai, Japan, 2000), pp. 257–264. H. Nakamura, K. Hirota, M. Shimao, T. Minowa, M. Honshima, Magnetic properties of extremely small Nd–Fe–B sintered magnets, IEEETrans.Magn. 41(2005)3844–3846. F. Xu, J. Wang, X.P. Dong, L.T. Zhang, J.S. Wu, Grain boundary microstructure in DyF 3-diffusion processed Nd–Fe–B sintered magnets, J.Alloys Compd. 509 (2011) 7909–7914. S. Sawatzki, I. Dirba, H. Wendrock, L. Schultz, and O. Gutfleisch, Diffusion processes in hot-deformed Nd-Fe-B magnets with DyF3 additions, J. Magn. Magn. Mater. 358-359 (2014), 163-169 S. Sawatzki, I. Dirba, L. Schultz, and O. Gutfleisch, Electrical and magnetic properties of hot-deformed Nd-Fe-B magnets with different DyF3 additions, J. Appl. Phys. 114, (2013) 133902. S. Sawatzki, A. Dirks, B. Frincu, K. Löwe, and O. Gutfleisch, Coercivity enhancement in hot-pressed NdFe-B permanent magnets with low melting eutectics, J. Appl. Phys. 115 (2014) 17A705 Institute of Materials Science – Functional Materials La(FeSi)13 compounds for application in room temperature magnetic refrigeration B. Kaeswurm, K.P. Skokov, I.A. Radulov, T. Gottschall, M. Fries, M.D. Kuzmin and Oliver Gutfleisch The Magnetocaloric effect is a change in thermodynamic state of a material when subjected to an applied magnetic field. This phenomenon is long used in low temperature physics in order to achieve temperatures in the milli Kelvin range. At TU Darmstadt we are investigating materials which show this effect near room temperature and may potentially be useful for a new energy efficient refrigeration technology. For optimal performance the magnetic refridgerant should have a large Magnetocaloric effect, ie large change in entropy under isothermal conditions, large adiabatic temperature change, low thermal hysteresis, appropriate thermal and mechanical properties and a tuneable phase transition temperature, which deterimines the operating temperature. A promising candidate material is the La(FeSi)13 compound with the crystallographic NaZn13 structure. This material shows a sharp magnetic transition which is accompanied by a large and reproducible magnetocaloric effect. The transition temperature can be tuned by addition of other elements on and off the crystallographic lattice sites. We focus our research on two strands: i) Improvement of the compound for example by the addition of other elements which allows the transition properties to be tuned. ii) Study of the material properties under application conditions as a heat exchanger giving information impacting on product design. Partial replacement of La by other Rare Earth elements such as Ce, Pr or Nd has been shown to optimise the magnetocaloric properties of LaFeSi compounds. Adding interstitial H atoms increases the transition to above room-temperature, while maintaining the thermodynamical first order character. A room-temperature transition can be obtained by partial hydrogenation. However, when stored at the transition-temperature, internal migration of hydrogen causes partially hydrogenated LaFeSi to undergo a magnetic phase separation [1]. To overcome this, Mn is added which allows obtaining a room-temperature transition after full hydrogenation. The fully hydrogenated material remains stable at roomtemperature but the Mn substitution reduces the entropy change ΔS as well as the adiabatic temperature change ΔTAD. Substitution of Pr however, while also lowering the transition temperature, has been shown to increase ΔS and ΔTAD [2]. We have carried out direct measurements of adiabatic temperature change ΔTAD on La(FeSi)13 samples with partial Pr substitution. Bulk samples of composition La1-xPrxFe11.6Si1.4 with x=0 to 0.4 were fabricated by arc-melting. In an applied field of 2 T the transition temperature shifts from Tt= 208 for the non-substituted sample to 190 K for x= 0.4. With increasing Pr content the transition becomes increasingly more sharp indicating thermodynamically first order behaviour.The adiabatic temperature change, ΔTAD as measured in our dedicated device, increased from 4.8 K for a Pr content of x=0.1 to ΔTAD = 5.4 K for a Pr content of x=0.4. As a next step we will be investigating the magnetocaloric properties of hydrogenated LaPr(FeSi)13. As part of the second strand of research into La-Fe-Si we are investigating how magnetocaloric powder can be used in heat exchangers for use in a magnetocaloric test bench. As mentioned above, La(Fe,Mn,Si)13Hx has a transition temperature around room Institute of Materials Science –Functional Materials 133 temperature and shows good magnetocaloric properties. Despite this, the material is not yet being used in prototype demonstrators due to its poor mechanical properties. Hydrogenation causes the material to be brittle and difficult to machine. Hence the material needs to be compacted into a non-porous bulk in order to be used as a heat exchanger. In the final device the heat exchanger is anticipated to consist of an assembly of thin, parallel plates of 0.1-0.3 mm thickness with gaps of 0.1 mm between them [3]. We have shown that adjusting the preparation route does not only affect the mechanical and thermal properties of polymer-bonded magneto caloric powder, but that the magnetocaloric properties can be vastly improved by choosing the right preparation conditions [4]. Fig. 1: Direct Measurement of the adiabatic temperature change for bulk, powder and powder compacted under 0.1 GPa with 5 wt % of silver epoxy. It was found that the adiabatic temperature change ΔTAD of polymer-bonded material is 10 % higher than for the initial bulk material. Direct Measurements of ΔTAD comparing bulk, the same material crushed into powder, as well as after compaction under 0.1 GPa with 5 wt. % of silver epoxy is shown in Fig.1. After the optimum compaction conditions had been established, we were able to assemble a heat exchanger, which can be seen in Fig 2. This simple porous heat exchanger consists of plates of 0.6 mm thickness with channels of equal length. This provides us with an easy, yet effective method of producing heat exchangers form magnetocaloric powder. Fig. 2: Heat exchanger made of polymer-bonded LaFe11.6Si1.4 plates. References: [1] M. Krautz et al. J.Appl.Phys. 112 (2012) 083918 [2] S. Fujieda et al. J.Appl.Phys. 102 (2007) 023907 [3] M.D. Kuz’min, M. D. Appl. Phys. Lett. 90, 25 (2007) 251916 [4] K.P. Skokov et al. J.Appl.Phys. In press 2014 134 Institute of Materials Science – Functional Materials Ion-Beam Modified Materials The research activities of this group are directly related to interaction processes of matter with ion beams available at the accelerator facilities of the GSI Helmholtz Centre for Heavy Ion Research. The interest in high-energy ions (MeV - GeV) is two fold (1) Developing a better understanding of damage creation under dense and nanometric electronic excitations and (2) using energetic ions as nanostructuring tool. Present investigations concentrate on radiation hardness and performance limits of functional materials to be applied in the future Facility for Antiproton and Ion Research (FAIR). They are motivated by the risk of limited lifetime of specific materials and devices under extreme radiation conditions of the future high-intensity beam facility. Beam absorbers, collimators, targets, and stripper foils have to perform reliably in high-dose environments, where they experience dimensional and structural changes, stresses and degradation of properties that control thermal-shock and fatigue resistance. The studies concentrate on carbon and carbon-based compound materials and characterization of beam-induced effects by microscopic and spectroscopic techniques as well as by functional tests (e.g., nanoindentation, bending test, infrared radiometry, thermo-mechanical and electrical performance). Nanostructuring with ion beams is based on the fact that at high kinetic energies, each ion projectile creates a cylindrical track with a few nanometers in diameter which can be converted into a nanometric channel by chemical etching. The small track size (few nm) in combination with the large ion range (several tens of µm) allows the fabrication of highaspect ratio structures such as nanochannels, nanotubes, and nanowires. The ion-track technology provides great flexibility in adjusting the diameter, length, and geometry of nanostructures under well controllable conditions. Ion-track based nanostructures are considered as excellent model systems to investigate the influence of size and geometry effects on technologically relevant optical, electrical, and thermal properties. The fabrication of nanostructures by means of ion-track technology requires several steps. First, a thin polymer foil is irradiated with a defined number of energetic heavy ions. Subsequent chemical etching dissolves the produced damage trails and converts the track of each individual ion into an open channel. The size and the shape of this channel are adjusted by controlling the etching conditions (e.g., temperature, time, concentration, admixtures to etchant, etc.). Most recent activities concentrate on the fabrication of high-aspect ratio oxide-based nanotubes by applying atomic layer deposition in order to conformally coat the walls of track-etched nanopores (more details are provided in the following report). To produce nanowires, the material of interest is electrodeposited into the channels of the track-etched polymer template. Specific experience is developed to grow semiconducting ZnO nanowires for solar-energy applications as well as Bi1-xSbx and Bi2Te3 nanowires for the study of quantum- and finite-size effects on their magnetotransport and thermoelectrical properties. Another project investigates the crystallinity and composition of AuAg alloy or Ag-Au-segmented nanowires. By selectively dissolving the silver component, highly porous nanostructures or tailored nanowire dimers separated by a gap of few nm are obtained. Electron energy loss spectroscopy (EELS) in a transmission electron microscope allows the excitation of localized surface plasmon resonances. This effect is of interest for application e.g. in surface enhanced Raman spectroscopy. Institute of Materials Science – Ion Beam Modified Materials 135 Staff Members Head Prof. Dr. Christina Trautmann PhD Students Dipl. Ing. Loic Burr Dipl. Phys. Marco Cassinelli Dipl. Ing. Christian Hubert M. Sc. Janina Krieg Bachelor Students Anthony Dunlap Dipl. Ing. Katharina Kupka Dipl. Phys. Liana Movsesyan M. Sc. Anne Spende Dipl. Ing. Michael F. Wagner Research Projects Fabrication of Bi-based nanowires and their characterisation with respect to thermoelectric properties (FIAS 2011-2014) Fabrication of semiconducting nanowires using the ion track technology (Beilstein Institute, 2012 – 2015) Fabrication and controlled surface functionalisation of mesoporous SiO2 materials and iontrack nanochannels (DFG, Forschergruppe (FOR 1583), 2011-2014) Radiation hardness of carbon stripper foils under high current UNILAC operation (BMBF, Verbundforschung, 2012 – 2015) Radiation hardness of carbon-based components for the future FAIR facility (GSI, 20122015) Investigation of response of graphite and new composite materials for Super-FRS target and beam catchers to intense ion beam-induced thermal stress waves (BMBF, Verbundforschung, 2012 – 2015) Publications [1] Muench, F., Bohn, S., Rauber, M., Seidl, T., Radetinac, A., Kunz, U., Lauterbach, S., Kleebe, H.J., Trautmann, C., Ensinger; W.; Polycarbonate activation for electroless plating by dimethylaminoborane absorption and subsequent nanoparticle deposition, Applied Physics A: Materials Science and Processing [2013] DOI: 10.1007/s00339-013-8119-z [2] Kuttich, B., Engel, M., Trautmann, C., Stühn, B.; Tailored nanochannels of nearly cylindrical geometry analysed by small angle X-ray scattering, Applied Physics A: Materials Science and Processing [2013] DOI: 10.1007/s00339-013-8167-4 [3] Pietschmann, J.F., Wolfram, M.T., Burger, M., Trautmann, C., Nguyen, G., Pevarnik, M., Bayer, V., Siwy, Z.; Rectification properties of conically shaped nanopores: consequences of miniaturization, PHYSICAL CHEMISTRY CHEMICAL PHYSICS 15 [2013] 16917-16926, DOI: 10.1039/C3CP53105H 136 Institute of Materials Science - Ion Beam Modified Materials [4] Afra, B., Rodriguez, M. D., Trautmann, C., Pakarinen, O.H., Djurabekova, F., Nordlund, K., Bierschenk, T. Giulian, R. Ridgway, M.C., Rizza, G., Kirby, N., Toulemonde, M., Kluth, P.; SAXS investigations of the morphology of swift heavy ion tracks in alpha-quartz, JOURNAL OF PHYSICS-CONDENSED MATTER 25 [2013] 045006, DOI: 10.1088/09538984/25/4/045006 [5] Rodriguez, M. D., Afra, B., Trautmann, C., Kirby, N., Kluth, P., The influence of swift heavy ion irradiation on the recrystallization of amorphous Fe80B20, MICROELECTRONIC ENGINEERING 102 [2013] 64-66 [6] Toulemonde, M., Benyagoub, A., Trautmann, C., Khalfaoui, N., Boccanfuso, M., Dufour, C., Gourbilleau, F., Grob, J.J., Stoquert, J.P., Costantini, J.M., Haas, F., Jacquet, E., Voss, K.-O., Meftah, A.,, Reply to "Comment on 'Dense and nanometric electronic excitations induced by swift heavy ions in an ionic CaF2 crystal: Evidence for two thresholds of damage creation”, PHYSICAL REVIEW B 87, [2013] 056102, DOI: 10.1103/PhysRevB.87.056102, [7] Merk, B.,; Voss, K.O., Mueller, I., Fischer, B.E., Jakob, B., Taucher-Scholz, G. Trautmann, C., Durante, M.; Photobleaching setup for the biological end-station of the Darmstadt heavy-ion microprobe Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 306 [2013] 81-84, DOI: 10.1016/j.nimb.2012.11.043 [8] Khan, S.A., Tripathi, A., Toulemonde, M., Trautmann, C., Assmann, W.; Sputtering yield of amorphous C-13 thin films under swift heavy-ion irradiation, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 315 [2013] 34-38, DOI: 10.1016/j.nimb.2013.05.044 [9] El-Said, A.S., Wilhelm, R.A., Facsko, S., Trautmann, C.; Surface nanostructuring of LiNbO3 by high-density electronic excitations, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 315 [2013] 265-268, DOI: 10.1016/j.nimb.2013.03.008 [10] Schauries, D.; Lang, M.; Pakarinen, O.H, Botis, Afra, B, Rodriguez, M.D., Djurabekova, F. , Nordlund, K., Severin, D., Bender, M., Li, W.X., Trautmann, C., Ewing, R.C., Kirby, N., Kluth, P.; Temperature dependence of ion track formation in quartz and apatite;Journal of Appl. Crystallography 46 [2013] 1558-1563 DOI: 10.1107/S0021889813022802 [11] Medvedev, N. A., Volkov, A. E., Schwartz, K., Trautmann, C., Effect of spatial redistribution of valence holes on the formation of a defect halo of swift heavy-ion tracks in LiF, PHYSICAL REVIEW B 87, [2013] 104103 [12] Medvedev, N. A., Schwartz, K., Trautmann, C., Volkov, A. E., Formation of the defect halo of swift heavy ion tracks in LiF due to spatial redistribution of valence holes, Phys. Status Solidi B 250, 4, [2013] 850–857 Institute of Materials Science - Ion Beam Modified Materials 137 [13] Li, W., Rodriguez, M. D., Kluth, P., Lang, M., Medvedev, N., Sorokin, M., Zhang, J., Afra, B., Bender, M., Severin, D., Trautmann, C, Ewing, R. C., Effect of doping on the radiation response of conductive Nb–SrTiO3, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 302 [2013] 40-477 [14] Dolde, F., Jakobi, I., Naydenov, B., Zhao, N., Pezzagna, S., Trautmann, C., Meijer, J., Neumann, P. Jelezko, F., Wrachtrup, J., Room-temperature entanglement between single defect spins in diamond, Nature Physics 9, [2013] 139-143, DOI: 10.1038/nphys2545 [15] Krauser, J., Gehrke, H.-G., Hofsäss, H., Trautmann, C., Weidinger, A., Conductive tracks of 30-MeV C60 clusters in doped and undoped tetrahedral amorphous carbon, Nuclear Instruments and Methods in Physics Research B 307 [2013] 265–268, DOI: 10.1016/j.nimb.2012.12.081 [16] Stolterfoht, N.; Hellhammer, R.; Sulik, B.; Juhász, Z.; Bayer, V.; Trautmann, C.; Bodewits, E.; Reitsma, G.; Hoekstra, R.; Areal density effects on the blocking of 3-keV Ne7+ ions guided through nanocapillaries in polymers, Physical Review A 88, [2013] 032902 [110] [17] Fernandes, S., Pellemoine, F., Tomut, M., Avilov, M., Bender, M., Boulesteix, M., Krause, M., Mittig, W., Schein, M., Severin, D., Trautmann, C, In-situ electric resistance measurements and annealing effects of graphite exposed to swift heavy ions, Nuclear Instruments and Methods in Physics Research B: Beam Interactions with Materials and Atoms 314 [2013] 125–129, DOI: 10.1016/j.nimb.2013.04.060 [18] Yamaki, T., Nuryanthi, N., Koshikawa, H., Asano, M., Sawada, S., Hakoda, T., Maekawa, Y., Voss, K. O., Severin, D., Seidl, T., Trautmann, C., Neumann, R., Ion-track membranes of fluoropolymers: Toward controlling the pore size and shape, Nuclear Instruments and Methods in Physics Research B: Beam Interactions with Materials and Atoms 314 [2013] 77–81 138 Institute of Materials Science - Ion Beam Modified Materials High-Aspect-Ratio Nanotubes fabricated by Ion-Track Technology and Atomic-Layer Deposition A. Spende1,2, N. Sobel3, I. Alber1, C. Hess3, M. Lukas4, B. Stühn4, M.E. Toimil Molares1, C. Trautmann1,2 1 GSI, Darmstadt, Germany; 2Materials Research, TU Darmstadt, Germany; Eduard-Zintl-Institut fur Anorganische Chemie und Physikalische Chemie, TU Darmstadt, Germany; 4 Experimental condensed matter physics, TU Darmstadt, Germany; 3 Nanotubes and nanochannels embedded in solid state membranes are of high relevance in many different fields such as nanofluidics, catalysis, health care, or solar energy harvesting. Suitable fabrication techniques for precise tailoring the dimensions and surface properties of nanotubes are currently being developed and include, e.g., electroless deposition, sol-gel processes, and atomic layer deposition (ALD). The latter offers the great opportunity to coat embedded nanochannels conformaly, even if the nanochannels exhibit high aspect ratios. Suitable templates with nanochannels are anodic alumina (AAO) [1] and track-etched polymer membranes [2]. ^ In this project, silicon dioxide (SiO2) nanotubes were fabricated by combining the ion-track technology and ALD. The template was produced by irradiating 30-m thick polycarbonate (PC) foils at the GSI linear accelerator UNILAC with 2 GeV heavy ions and a fluence of 109 ions/cm2. Subsequent chemical etching transforms each ion track into a cylindrical nanochannel [3]. Depending on the etching time, cylindrical nanochannels of diameter 30, 55, and 400 nm were produced having an aspect ratio of 1000, 545, and 75, respectively. The ALD coating was performed using a custom-built ALD system available in the group of Prof. Christian Hess. SiO2-modified templates with nanochannels of various aspect ratios were studied by scanning electron (SEM) and scanning transmission electron microscopy (STEM) in SEM as well as by small angle X-ray scattering (SAXS). Figure 1 displays a bundle nanotubes obtained by dissolving the polymer template by wet-chemical methods. Many of the nanotubes are 30 µm long which corresponds to the thickness of the template used. The outer diameter is constant evidencing that the ALD process provides homogeneous coating along the full length of the track-etched nanochannels. The inset shows a representative single SiO2 nanotube (outer diameter 55 nm, wall thickness 10 nm) clearly demonstrating the tube-like shape of the ALD grown structure. The thickness of the tube wall is in excellent agreement with the nominal layer thickness expected from the ALD coating process. According to energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy, the composition and stoichiometry of the material confirms the formation of SiO2 tubes. Institute of Materials Science - Ion Beam Modified Materials 139 Fig. 1: SEM image of SiO2 nanotube bundle obtained by ALD coating of track-etched nanochannels and subsequent dissolving the polymer template. The inset shows a STEM-in-SEM image of a single SiO2 nanotube with regular outer diameter of 55 nm and wall thickness 10 nm evidencing the homogeneous and conform character of the ALD process. To obtain further information on the homogeneity of the coating process for nanochannels of various diameters, small angle x-ray scattering investigations are performed in the group of Prof. Bernd Stühn yielding average channel radii and radius distributions of a large number of track-etched nanochannels before and after the coating process. Figure 2 (left) shows the SAXS intensity as a function of the scattering vector q for a 30-m thick template before (orange) and after (red) deposition of a 10 nm thick SiO2 layer. The pronounced ondulations are a clear indication for a small size distribution. The fact that these ondulations also appear for SiO2-coated membranes is further proof of the high conformity of the ALD process across the complete length of the high aspect ratio nanochannels as well as over a large sample area. Compared to the untreated sample, the intensity ondulations of the ALD coated sample shift to larger q values as expected for smaller channels. To deduce the pore radius, radius dispersion, and wall thickness from the SAXS data, the nanochannels are modelled as parallel tubes. Figure 2 (right) displays the calculated nanochannel radii for various samples etched between 140 and 200 seconds and SiO2coated under identical conditions. As expected, the channel radii increase linearly with increasing etching time. For all pore sizes, the radii of the coated channels are shifted by 10 nm to smaller values, in complete agreement with the nominal coating thickness of the ALD process. 140 Institute of Materials Science - Ion Beam Modified Materials Fig. 2: Left: SAXS intensity as a function of scattering vector for a 30-µm thick PC membrane (track etched for 140 s) before (orange) and after (red) ALD coating of a 10 nm thick SiO 2 layer. Solid lines are fits assuming cylindrical channel geometry. Right: Nanochannel radius deduced from SAXS as a function of the etching time for coated (red) and uncoated (orange) samples. The vertical radius shift by 10 nm is in excellent agreement with the nominal layer thickness acording to the ALD process. In conclusion, SiO2 inorganic nanotubes have been fabricated by ALD in ion-track etched polycarbonate membranes. Electron microscopy as well as SAXS provide clear evidence that the coating process is homogeneous and shape conform for nanochannels of high aspect ratios up to 1000. ALD-tailored surface modification of ion-track etched nanochannels opens up new opportunities in the precise reduction of pore sizes below 15 nm for filtration or purification applications. Acknowledgment Financial support by the DFG project FOR1583 gratefully acknowledged References: [1] C. Bae et.al, J. Mater. Chem. 18 (2008) 1362 [2] Elam et. al, Chem. Mater 11 (2003) 3507 [3] M. E. Toimil-Molares, Beilstein J. Nanotechnol. 3 (2012) 860 Institute of Materials Science - Ion Beam Modified Materials 141 Molecular Nanostructures The Joint Laboratory for Molecular Nanostructures has been established in 2011 to enhance the cooperation between the Institute for Nanotechnology at the Karlsruhe Institute of Technology (KIT) and the Institute of Materials Science at the Technische Universität Darmstadt. The research focus of the labratory is on nanocarbon materials, in particular on carbon nanotubes and graphene. Carbon nanotubes and graphene are made of a single layer of covalently bonded carbon atoms. The electrical, optical, chemical and mechanical properties of these molecular nanostructures are outstanding, which is why CNTs and graphene are considered as important new materials for high speed electronics, optoelectronics, sensing, coatings, material reinforcements and other potential applications. The motivtation of the Joint Laboratory is to gain new and important insights into carbon nanomaterials for enabling future applications. In 2013 funding for a Fourier-Transform Photocurrent-Spectromicroscope using a Supercontinuum-Lightsource has been provided by the German Science Foundation, the Insitute of Materials Science and the President of the Technische Universität Darmstadt. The system will be used to study the optoelectronic properties of materials and functional devices. Staff Members Head Prof. Dr. Ralph Krupke Research Associates M.Sc. Asiful Alam Secretaries Renate Hernichel PhD Students Dipl.-Phys. Feliks Pyatkov (KIT) M.Sc.Wieland Reis (BASF) M.Sc. Moritz Pfohl (KIT) M.Sc.Wenshan Li (KIT) Research Projects Investigation of non-equilibrium phonon populations in biased metallic single-walled carbon nanotubes (DFG OR 262/1-2, 2011-2013) Publications The Role of Nanotubes in Carbon Nanotube–Silicon Solar Cells; D. D. Tune, F. Hennrich, S. Dehm, M. F. G. Klein, K. Glaser, A. Colsmann, J. G. Shapter, U. Lemmer, M. M. Kappes, R. Krupke, B. S. Flavel; ADVANCED ENERGY MATERIALS 3 (2013) 1091, DOI 10.1002/aenm.201200949 Enhancing Raman signals with an interferometrically controlled AFM tip; M. Oron-Carl, R. Krupke; NANOTECHNOLOGY 24 (2013) 415701, DOI: 10.1088/0957-4484/24/41/415701 Electron-beam-induced direct etching of graphene; C. Thiele, A. Felten, T. J. Echtermeyer, A. C. Ferrari, C. Casiraghi, H. v. Löhneysen, R. Krupke; CARBON 64 (2013) 84-91, DOI: 10.1016/j.carbon.2013.07.038 142 Institute of Materials Science - Molecular Nanostructures Controlled modification of mono- and bilayer graphene in O2, H2 and CF4 plasmas; A. Felten, A. Eckmann, J.-J. Pireaux, R. Krupke, C. Casiraghi; NANOTECHNOLOGY 24 (2013) 355705, DOI: 10.1088/0957-4484/24/35/355705 Separation of Single-Walled Carbon Nanotubes by 1-Dodecanol-Mediated Size-Exclusion Chromatography; B. S. Flavel, M. M. Kappes, R. Krupke, F. Hennrich, ACS NANO 7 (2013) 3557-3564, DOI: 10.1021/nn4004956 Electroluminescence in Single Layer MoS2; R. S. Sundaram, M. Engel, A. Lombardo, R. Krupke, A. C. Ferrari, Ph. Avouris, M. Steiner; NANO LETTERS 13 (2013) 1416-1421, DOI: 10.1021/nl400516a Catalytic subsurface etching of nanoscale channels in graphite; M. Lukas, V. Meded, A. Vijayaraghavan, L. Song, P. M. Ajayan, K. Fink, W. Wenzel, R. Krupke; NATURE COMMUNICATIONS 4 (2013) 1379, DOI: 10.1038/ncomms2399 Single- and Double-Sided Chemical Functionalization of Bilayer Graphene; A. Felten, B. S. Flavel, L. Britnell, A. Eckmann, P. Louette, J.-J. Pireaux, M. Hirtz, R. Krupke, C. Casiraghi; SMALL 9 (2013) 631-639, DOI: 10.1002/smll.201202214 Institute of Materials Science - Molecular Nanostructures 143 Catalytic subsurface etching of nanoscale channels in graphite Maya Lukas1,2, Velimir Meded1,3, Aravind Vijayaraghavan1,4, Li Song5,6, Pulickel M. Ajayan6, Karin Fink1, Wolfgang Wenzel1 & Ralph Krupke1,2,7 1 Karlsruhe Institute of Technology (KIT), Institute of Nanotechnology, D-76021 Karlsruhe,Germany. 2DFG Center for Functional Nanostructures (CFN), D-76031 Karlsruhe, Germany. 3Karlsruhe Institute of Technology (KIT), Steinbuch Centre for Computing, D76021 Karlsruhe, Germany. 4School of Computer Science, University of Manchester, Manchester M13 9PL, UK. 5Research Center for Exotic Nanocarbons, Shinshu University, Nagano 380-8553, Japan. 6Department of Mechanical Engineering and Materials Science, Rice University, Houston, Texas 77005, USA. 7Department of Materials and Earth Sciences, Technische Universität Darmstadt, D-64287 Darmstadt, Germany. Summary from Nature Communications 4, Article number: 1379 | doi:10.1038/ncomms2399 Catalytic hydrogenation of graphite has recently attracted renewed attention as a route for nanopatterning of graphene and to produce graphene nanoribbons. These reports show that metallic nanoparticles etch the surface layers of graphite or graphene anisotropically along the crystallographic zig-zag <11–20> or armchair <10–10> directions. The etching direction can be influenced by external magnetic fields or the supporting substrate. Recently we have reported the subsurface etching of highly oriented pyrolytic graphite by Ni nanoparticles, to form a network of tunnels, as seen by scanning electron microscopy and scanning tunnelling microscopy. In this new nanoporous form of graphite, the top layers bend inward on top of the tunnels, whereas their local density of states remains fundamentally unchanged. Engineered nanoporous tunnel networks in graphite allow for further chemical modification and may find applications in various fields and in fundamental science research. Local hydrogenation of graphite catalysed by metallic nanoparticles has been known since the 1970s [1–3]. This process results in straight nanoscale channels that have intersecting angles of integer multiples of 30° [2]. In recent years it has attracted renewed attention as a possible route for nanopatterning of graphene, especially for the production of graphene nanoribbons. Metallic nanoparticles etch the surface layers of graphite [1–8], as well as single-layer graphene sheets [9–10]. The process is anisotropic along the crystallographic highsymmetry directions, that is, the zigzag <11–20> or armchair <10–10> directions. Nanoparticles consisting of various metals, such as Ni [2,8,9,10], Fe [2,7], Pt [3], Co [2,4,5] and Ag [6], are known to etch channels on graphite surfaces. It was shown that the etching direction could be influenced by an external magnetic field when Co particles were used [11]. Similarly, the etching direction on mono and few-layer graphene could be controlled by the structure of the substrate [12–13]. To date, clear evidence has been reported only for open channels on the surface of graphite, whereas subsurface etching remains unclear [4,5,8]. In this study, we have demonstrated now the subsurface etching of highly oriented pyrolytic graphite (HOPG) by Ni nanoparticles. Besides the well-known open channels, a network of tunnels is produced, which can be probed by scanning electron microscopy (SEM) and scanning tunnelling microscopy (STM) as shown in Figure 1. By semiempirical quantum chemical and density functional theory calculations, we were able to show that the top layers bend inward on top of the tunnels, whereas their local density 144 Institute of Materials Science - Molecular Nanostructures of states remains fundamentally unchanged. The etched material presents a new nanoporous form of graphite with high potential for applications. Fig. 1: (a) SEM image shows open channels (blue arrows), closed channels (red arrows) and subsurface catalyst particles (green arrow). (b) An averaged SE intensity profile along the white line in (a) highlights the different contrast of trenches and tunnels. (c) High-resolution STM images and (d) height profiles of a tunnel. Scale bars: 500nm (a), 2nm (c). References: [1] Tomita, A. & Tamai, J.; Catal. 27, 293–300 (1972). [2] Tomita, A. & Tamai, Y. J.; Phys. Chem. 78, 2254–2258 (1974). [3] Santiesteban, J., Fuentes, S. & Yacaman, M. J.; J. Vac. Sci. Technol. A 1, 1198–1200 (1983). [4] Schäffel, F. et al. Nano Res. 2, 695–705 (2009). [5] Konishi, S., Sugimoto, W., Murakami, Y. & Takasu, Y.; Carbon 44, 2338–2356 (2006). [6] Severin, N., Kirstein, S., Sokolov, I. M. & Rabe, J. P.; Nano Lett. 9, 457–461(2009). [7] Datta, S. S., Strachan, D. R., Khamis, S. M. & Johnson, A. T. C.; Nano Lett. 8, 1912–1915 (2008). [8] Ci, L. et al. Nano Res. 1, 116–122 (2008). [9] Ci, L. et al.; Adv. Mater. 21, 4487–4491 (2009). [10] Campos, L. C., Manfrinato, V. R., Sanchez-Yamagishi, J. D., Kong, J. & Jarillo-Herrero, P.; Nano Lett. 9, 2600–2604 (2009). [11] Bulut, L. & Hurt, R. H.; Adv. Mater. 22, 337–341(2010). [12] Tsukamoto, T. & Ogino, T.; J. Phys. Chem. C 115, 8580–8585 (2011). [13] Tsukamoto, T. & Ogino, T.; Carbon 50, 674–679 (2012). Institute of Materials Science - Molecular Nanostructures 145 Collaborative Research Center (SFB) Collaborative Research Center (SFB) “Electrical Fatigue in Functional Materials” 2003 – 2014 www.sfb595.tu-darmstadt.de The center for collaborative studies (Sonderforschungsbereich) has been awarded by the Deutsche Forschungsgemeinschaft in 2002 to TU Darmstadt and is centered in the Department of Materials and Earth Sciences with important contributions from the Department of Chemistry as well as the Mechanical Engineering Department of the University of Karlsruhe. The center was renewed in 2006 and again in 2010 and is now in the third and final four-year funding period. It is comprised of a total of 19 projects and financial resources for the current four yearperiod of about 8 Mio. €. The center has an active guest program with guests visiting from 2 days to 3 months. In 2008, an integrated graduate school was also implemented with graduate students visiting from other Universities for time frames between 1 to 12 months. For specific information, please contact either the secretary of the center, Mrs. Gila Völzke, or the director of the center, Prof. Karsten Albe. Contact: SFB 595 Electrical Fatigue in Functional Materials Department of Materials Science Alarich-Weiss-Str. 2 64287 Darmstadt Tel.: +49 6151 16 - 6362 Fax: +49 6151 16 - 6363 Building/Room: L201 / 121 E-mail: [email protected] [email protected] Electrical fatigue in functional materials encompasses a set of phenomena, which lead to the degradation of materials with an increasing number of electrical cycles. Electrical cycling leads to both reversible and irreversible currents and polarisations. Ionic and electronic charge carriers interact with each other and with microstructural elements in the bulk as well as at interfaces (grain boundaries and domain walls) and interphases (electrode/electrolyte). This in turn causes local changes in the distribution of electric currents and electric potentials. As a consequence local overloads and material degradation ensues and leads to irreversible loss of material properties. This material degradation can lead finally to mechanical damage as well as to dissociation reactions. The basic phenomena of electrical fatigue are not yet understood on a microscopic level. A key feature of the center is therefore the steady comparison between theory and experiment. This is utilized to find the physico-chemical origins of electrical fatigue as well as to develop strategies for new materials and improved material combinations. The materials of interest are ferroelectrics, electrical conductors (cathode materials for lithium batteries and transparent conducting oxides) and semiconducting polymers. The goal of this center of excellence is the understanding of the mechanisms leading to electrical fatigue. An understanding of the experimental results is supported by concurrent materials modelling which is geared to encompass different time and length scales from the material to the component. In the third phase next to a quantitative modelling the development of fatigue-resistant materials and in the case of ferroelectrics, lead-free piezoceramics, is of particular focus. 146 Institute of Materials Science – Collaborative Research Center (SFB595) Projects: Division A: Synthesis A1 P.I.: Prof. J. Rödel Topic: Manufacturing of textured ceramics actuators with high strain A2 [ended 2010] P.I.: Prof. M. J. Hoffmann Topic: Manufacturing and characterization of PZT-ceramics under dc loading A3 P.I.: Prof. W. Jaegermann Topic: Boundary layers and thin films of ionic conductors: Electronic structure, electrochemical potentials, defect formation and degradation mechanisms A4 P.I.: Prof. R. Riedel Topic: Novel functional ceramics using anionic substitution in oxidic systems A5 P.I.: Prof. M. Rehahn Topic: Synthesis of semiconducting model polymers and their characterization before and after cyclic electric fatigue Division B: Characterization B1 [ended 2010] P.I.: Dr. R.-A. Eichel Topic: EPR-Investigations of defects in ferroelectric ceramic material B2 [ended 2010] P.I.: Dr. A. G. Balogh Topic: Investigations of the defect structure and diffusion in ferroelectric materials B3 P.I.: Prof. H.-J. Kleebe / Prof. W. Donner Topic: Structural investigations into the electrical fatigue in PZT B4 P.I.: Prof. H. Ehrenberg Topic: In-situ investigations of the degradation of intercalation batteries und their modelling Institute of Materials Science – Collaborative Research Center (SFB595) 147 B7 P.I.: Prof. H. v. Seggern / Prof. A. Klein Topic: Dynamics of electrical properties in fatigued PZT B8 P.I.: Prof. Christian Hess Topic: In situ characterization of intercalation batteries using Raman spectroscopy B9 P.I.: Prof. Gerd Buntkowsky / Dr. Hergen Breitzke Topic: Characterization of structure-property relationships of functional materials using solid state NMR Division C: Modelling C1 P.I.: Prof. K. Albe Topic: Quantum mechanical computer simulations for electron and defect structure of oxides C2 P.I.: Prof. K. Albe Topic: Atomistic computer simulations of defects and their mobility in metal oxides C3 [ended 2010] P.I.: Prof. R. Müller / Prof. W. Becker Topic: Microscopic investigations into defect agglomeration and its effect on the mobility of domain walls C5 P.I.: Dr. Y. Genenko / Prof. H. v. Seggern Topic: Phenomenological modelling of bipolar carrier transport in organic semiconducting devices under special consideration of injection, transport and recombination phenomena C6 P.I.: Jun. Prof. B. Xu Topic: Micromechanical Simulation on Interaction of Point Defects with Domain Structure in Ferroelectrics 148 Institute of Materials Science – Collaborative Research Center (SFB595) Division D: Component properties D1 P.I.: Prof. J. Rödel Topic: Mesoscopic and macroscopic fatigue in doped ferroelectric ceramics D3 P.I.: Prof. A. Klein Topic: Function and fatigue of conducting electrodes in organic LEDs and piezoceramic actuators D4 P.I.: Dr. A. Gassmann / Prof. H. v. Seggern Topic: Fatigue of organic semiconductor components D5 [ended 2011] P.I.: Prof. W. Jaegermann Topic: Processing and characterization of Li-ion thin film batteries D6 P.I.: Dr. Kyle G. Webber Topic: The effect of electric field-induced phase transitions on the blocking force in leadfree ferroelectrics Division T: Industry transfer T1 P.I.: Prof. H. Ehrenberg Topic: In operando investigations of fatigue of commercial battery types using neutron tomography and diffraction T2 P.I.: Prof. M. Hoffmann Topic: Influence of PbO stoichiometry on microstructure and properties of PZT ceramics and multilayer actuators Integrated Graduate school MGK P.I.: Prof. A. Klein Institute of Materials Science – Collaborative Research Center (SFB595) 149 Diploma Theses in Materials Science Alexandra Bobrich; Beschichtung im Rohrinnern mit metallhaltigen DLC-Schichten und deren Korrosionseigenschaften, 21.06.2013 Frederik Jan Brohmann; Bewertung der Vorgehensweise zur Ermittlung bruchmechanischen Kenngrößen von Wärmedämmschichtsystemen, 29.07.2013 von Nico Dams; Erprobung eines Hochtemperatur-Thermoelementes mit Rhenium-Mantel, 31.07.2013 Almut Dorothea 21.05.2013 Dirks; Korngrenzdiffusionsprozesse in NdFeB-Permanentmagneten, Moritz Elsaß; Charakterisierung von Wärmedämmschichtsystemen bei Variation der Vorbeanspruchung und der Mikrostruktur, 29.07.2013 René Fischer; Herstellung und Untersuchung von hybriden SWCNT-PEDOT Elektroden für den Einsatz in organischen Fotodioden, 22.07.2013 Philipp Torben Geiger; Selbstheilung von Siliciumkeramiken, 02.05.2013 Oliver Genschka; Synthese von Vanadiumcarbid-basierten Nanokompositen aus SingleSource-Präkursoren, 10.12.2013 Thorsten Gröb; Verformungsinduzierte Martensitbildung in ADI, 16.05.2013 Anja Habereder; Stickstoffdotierte Brennstoffzellen, 16.05.2013 Kohlenstofffasern als Trägermaterial in PEM- Ulla Hauf; Untersuchung zur Herstellung von Platin-Cerment-Verbund-Komponenten, 27.06.2013 Shenshen He; Herstellung und Charakterisierung von texturierten KNN-basierten bleifreien piezoelektrischen Keramiken, 06.11.2013 Jan Christian Hellmann; Herstellung und Charakterisierung kathodenzerstäubter Schichten für den Einsatz in Solarzellen, 04.06.2013 - Belma Hota; Synthese metallischer Nanodrähte und deren Anwendung in transparenten leitfähigen Schichten, 14.05.2013 Nicolas Jansohn; Entwicklung einer FeCo Legierung für die Anwendung im MIM Prozess, 04.11.2013 Wolfgang Paul Koch; Demage development in bidirectionally reinforced carbon fiber composites, 04.06.2013 Ludmila Konrad; Impact of Catalyst Type on PEMFC Performance, 30.04.2013 150 Diploma Theses in Materials Science Sonja Madloch; Characterization of surface plasmons of individual gold nanowires by infrared spectroscopy, 29.04.2013 Michael Niederle; Sinterverhalten und –einfluss auf optische Eigenschaften von Cer-dotiertem Yttrium-Aluminium-Granat, 02.12.2013 Verena Pfeifer; Grenzflächeneigenschaften von Anatas und Rutil, 21.05.2013 Anke Scherf; Mikrostruktur und Oxidationsverhalten fein lamellarer Fe-Al in situ Kompositwerkstoffe, 21.05.2013 Simon Wallenborn; Technologie- und Prozessentwicklung von Festkörperelektrolytschichten: Abscheidung sowie elektrische Leitfähigkeit von titanhaltigen Lithium-Phosphatgläsern, 28.11.2013 Jens Wehner; Statistical switching kinetics in ferroelectrics, 21.05.2013 Karen Wilken; Tandem Cells providing High Open Circuit Voltages for photoelectrochemical Water Splitting, 17.05.2013 Bachelor Theses in Materials Science 151 Bachelor Theses in Materials Science David Brandt; Electromechanical Characterization of the x(Ba0.7Ca0.3)TiO3 Lead-Free Piezoceramic System, 16.09.2013 (1-x)Ba(Zr0.2Ti0.8)O3- Anthony Dunlap; Ion-beam Induced Structural Modifications of Carbon Foils, 02.09.2013 Adjana Eils; Optimierung der Quellaktivierung von Polymertemplaten zur stromlosen Metallabscheidung, 18.09.2013 Fabian Johannes Grimm; Sintern strukturierter Aluminiumoxidschichten auf steifen Substraten mit einer Glasphase, 24.09.2013 Carola Hahn; Construction of a high temperature resistivity measurement setup and investigation of oxidation stability of SrMoO3 thin films, 07.11.2013 Tim Hellmann; Kobaltnanoröhrchen durch stromlose und elektrochemische Abscheidung in ionenspurgeätzte Polykarbonat-Template, 13.09.2013 Laszlo Horak; Elektrische und Ultraschallwandlern, 03.07.2013 mechanische Kontaktierung von Hochtemperatur- Silke Innetsberger; Untersuchung der Randeigenschaften geklopfter Werkstücke, 06.08.2013 Martin Jäcklein; Temperaturabhängige Topographie von Kollagen Typ I, 18.09.2013 Marcel Jost; Anwendung eines neuen Polierverfahrens zur Oberflächeneinglättung von Ermüdungsproben und Herstellung von TEM-Proben, 13.03.2013 Peter Keil; Einfluss des Substratmaterials und der Substratrauheit auf das Sinterverhalten strukturierter Aluminiumoxidschichten, 12.03.2013 Christoph Kipper; Herstellung und Charakterisierung von Kupfer-Platin-Nanoröhren, 13.12.2013 Christoph Kurt Josef Kober; Herstellung und Charakterisierung von Kalium-NatriumNiobat-Dickschichten über einen Sol-Gel-Prozess, 13.03.2013 Hans Justus Köbler; Synthese und Charakterisierung von Polyanilin-geträgerten Pt-Ru Katalysatoren für die Direktmethanol-Brennstoffzelle, 31.01.2013 Leonie Koch; Atomistic simulation of shear localization in metallic glasses, 29.04.2013 Moritz Liesegang; Herstellung und Eigenschaften von kohlenstoffreichen polymerabgeleiteten SiOC-Precursorkeramiken, 30.09.2013 Julian Mars; Struktur ionischer Flüssigkeiten auf molekularer Ebene, 18.02.2013 Sven Milla; Stromfreie Synthese metallischer Nanodraht- und Nanoröhrennetzwerke, 27.03.2013 152 Bachelor Theses in Materials Science Thomas Pohl; Herstellung und Charakterisierung von Eisen-dotierten BST-Dünnschichten, 21.10.2013 Stefan Schlißke; Elektronenleitung in OC3C8-PPV: Einfluss der elektrischen Ermüdung und Rolle der Kontaktmaterialien, 02.04.2013 Michael Marcus Schmitt; Nanotribologische Untersuchungen von Polystyrol-Partikeln auf Silizium-Oberflächen mit Hilfe des Rasterkraftmikroskops, 20.08.2013 Schrock, Adrian; Strukturelle Charakterisierung von NaNbO3 Einkristallen, 16.12.2013 Konrad Schubert; Rheoelektrische und Rheomikroskopische Reaktionsharzen mit Kohlenstoffnanoröhren, 23.09.2013 Untersuchungen an Jona Schuch; Morphologieeinfluss bei der Synthese von oxydischen Kupfer/Cobalt Heteronanomaterialien, 01.03.2013 Theresa Schütz; Korrosionsverhalten von hochgradig verformtem ferritischem Stahl, 14.05.2013 Romana Schwing; Prozessfensterbestimmung Gusseisenwerkstoff EN-JS2070, 29.04.2013 der ADI-Wärmebehandlung für den Sebastian Steiner; Untersuchungen zur Ein- und Auslagerung von Lithium in LiAl- und Silizium-Legierungsanoden, 15.02.2013 Mathias Storch; Untersuchung von polymer-abgeleiteten Si(O)C(N) Keramiken und Si(O)C(N)/Hard-Carbon Kompositen als potentielle Na-Ionen Speichermaterialien, 16.12.2013 Andreas Taubel; Messung Elektrischer Feldverteilungen auf Metallmatrix-Verbundwerkstoffen mittels Scanning Kelvin Probe Microscopy, 18.09.2013 Florian Weyland; Charakterisierung von selbstorganisierten Monolagen auf Al2O3 für Transistoranwendungen, 05.08.2013 David Norbert Wieder; Messung des Kontaktwinkels auf durch Plasmaimmersion modifizierten Oberflächen, 19.03.2013 Leoni Wilhelm; Der Gasphasensinterprozess in LiF dotiertem Mg-Al-Spinell, 08.05.2013 Maximilian Wimmer; Porous Carbon / Polymer-derived Ceramic Composites as Anode Material for Li-Ion-Batteries, 15.04.2013 Golo Joachim Zimmermann; Untersuchung der Adhäsionsneigung von eloxiertem Aluminium mittels Rasterkraftmikroskopie an Luft, 27.03.2013 Alexander Zimpel; Synthesis and High-Temperature Behavior of SiMgOC-Based Ceramic Composites, 15.10.2013 Bachelor Theses in Materials Science 153 Master Theses in Materials Science Aniruddh Das; Investigation of microstructure and mechanical properties of brazed joints with low silver containing brazing alloys, 05.11.2013 Thomas Geoffroy; Can a change in materials properties of N-MOSFET's lead to an increase of the snapback voltage?, 03.09.2013 Xueying Hai; Material Anticipation Study for Heat Dissipation in Electric Switchgears, 30.08.2013 Lukas Hamm; Morphologie und elektrische Eigenschaften von nasschemisch hergestelltem Kupfer-II-Oxid, 01.11.2013 Cornelia Hintze (Klepickij); Multifunctional Properties of Graphene-Silica Nanocomposites, 15.08.2013 Heide Ines Humburg; Effect of Doping on the Piezoelectric Properties of (Ba1-xCax)(ZryTi1y)O3, 04.09.2013 Michel Valentin Kettner; Ionic liquid gels as gate materials in organic field-effect transistors, 31.07.2013 Chinomso Nwosu; Optimization of mechanical and conductivity properties of poly (oxyethylene) (poe), modified polyethylene glycol (npeg)and a blend of poe:npeg reinforced by nanocrystalline cellulose and crosslinking, 02.09.2013 Tobias Rödlmeier; Dye-Sensitized Bulk Heterojunction Solar Cells with Small Molecules, 16.09.2013 Tanju Alexander Sirman; Pulsed Laser Deposition of Sr2CrWO6 double Perovskite thin films, 02.09.2013 Lukas Wardenga; Characterization of Zr and H doped In2O3 films deposited by radio frequency magnetron sputtering, 04.12.2013 154 Master Theses in Materials Science PHD Theses in Materials Science Tobias Adler; Zn(O,S) Puffer Eigenschaften in Cu(In, Ga)Se2 Solarzellen, 26.11.2013 Sebastian Milan Becker; Zinn-haltige Oxide als Elektrodenmaterialien für Lithium-IonenBatterien, 31.01.2013 Jennifer Bödecker; Randschichtmodifikation von integral verzweigten Blechprofilen mit UFG Gradientengefügen, 23.10.2013 Anna Castrup; Deformation Processes in Magnetron Sputtered Nanocrystalline Palladium and Palladium Gold Films, 05.11.2013 Robert Dittmer; Lead-Free Piezoceramics - Ergodic and Nonergodic Relaxor Ferroelectrics Based on Bismuth Sodium Titanate, 19.06.2013 Daniel Jason Franzbach; Field Induced Phase Transitions in Ferroelectric Materials, 02.09.2013 Yan Gao; Nanodomain Structure and Energetics of Carbon Rich SiCN and SiBCN PolymerDerived Ceramics, 27.11.2013 Melanie Gröting; Ab-initio Calculations of the Relaxor Ferroelectric Na1/2Bi1/2TiO3 and its Solid Solutions, 03.05.2013 Hanna Christine Hahn; Chemische und strukturelle Untersuchung des Alterungsverhaltens von kommerziellen Dreiwegekatalysatoren, 29.05.2013 Holger Stefan Hain; Spinelle als Anodenmaterialien für Lithium-Ionen-Akkumulatoren, 06.05.2013 Silke Hayn; First-principles calculations on structural and thermodynamic stability of (Na1/2Bi1/2,Ba)TiO3 and Pb(Zr,Ti)O3, 11.02.2013 Sandra Hildebrandt; Synthesis and thin film growth of alkaline cobaltates NaxCoO2 and LixCoO2, 18.02.2013 Erwin Matti Hildebrandt; Oxygen Engineered Hafnium Oxide Thin Films grown by Reactive Molecular Beam Epitaxy, 28.02.2013 Vanessa Kaune; Entstehung und Eigenschaften von UFG Gradientengefüge durch Spaltprofilieren und Spaltbiegen höherfester Stähle, 23.10.2013 Lorenz Kehrer; Sauerstoffinduzierte Defektzustände in Thiophen-basierten organischen Feldeffekttransistoren, 24.01.2013 PhD Theses in Materials Science 155 Arne Kriegsmann; Richtungsabhängiges Rissausbreitungsverhalten in Gradientenwerkstoffen, 04.12.2013 Qiran Li; Development of electrode materials based on complex oxides for high capacitance devices, 27.09.2013 Falk Adrian Münch; Stromlose Synthese metallischer Nanoröhren in ionenspurgeätzten Polymertemplaten, 28.03.2013 Babak Nasr; Electrochemical Gating of Oxide Nanowire Transistors at Low Operating Voltage, 16.04.2013 Quoc Hung Nguyen; (Bio)Molecular Transport and Recognition in Heavy Ion Track-Etched Polymeric Nanopores, 19.04.2013 Johan Pohl; Structure and properties of defects in photovoltaic, 23.01.2013 Jonathan Schäfer; Atomistic Simulations of Plasticity in Nanocrystalline Alloys, 31.01.2013 Nina Maria Schweikert; Impedanzspektroskopische Untersuchungen an Lithium-IonenBatterien, 30.01.2013 Tim Seidl; Radiation hardness of superconducting magnet insulation materials for FAIR, 30.01.2013 Mahdi Seifollahi Bazarjani; Micro- and Mesoporous Polymer Derived Ceramic Nanocomposites with Tailored Functionalities for Energy and Environmental Applications, 27.11.2013 Yohan Seo; Toughening Mechanisms of Ferroelectrics, 23.08.2013 Md. Tamez Uddin; Metal oxide heterostructures for efficient photocatalysts, 16.09.2013 Mehran Vafaee Khanjani; Orbital Engineering of Pulsed Laser Deposited Single-layered Manganite Thin Films, 29.11.2013 Daniel Walker; Improving Performance in Metal Oxide Field-effect Transistors, 21.06.2013 Zilin Yan; Microstructure evolution during sintering of ceramic multilayer capabilities: nanotomography and discrete simulations, 17.10.2013 156 PHD Theses in Materials Science Mechanical Workshop The mechanical workshop of the Institute of Materials Science is designing, manufacturing and modifying academic equipment for a broad range of projects. In the year 2013 the workshop was involved in the following major projects: Components for Evaporation System for Rotated Fibre Substrates UHV-preparation chambers (electro)chemical treatment Components for six-circle diffractometer Design and manufacturing of a protection chamber for x-rays with up to 150keV photons UHV baby chamber for x-ray diffraction experiments dedicated for MBE, CVD, PVD, PLD and Staff Members Head Jochen Rank Technical Personnel Frank Bockhard Volker Klügl Ulrich Füllhardt Herry Wedel Electrical Workshop The electrical workshop of the Institute of Materials Science was involved in the following projects: Maintenance and repair of various academic equipment like the Electron Probe Micro-Analyzer (EPMA), Secondary Ion Mass Spectrometry (SIMS), sintering furnace, Transmission Electron Microscopy (TEM), X-Ray powder Diffractometer (XRD) and Molecular Beam Epitaxy (MBE) Design and development of electronic components for specific research projects like temperature control unit, data logging, power controller, high voltage amplifier, high voltage power supply, measuring amplifier, high temperature furnace for impedance measurements Development of testing software (V-Basic / LabView / i-Tools) Staff Members Electronic Personnel Michael Weber Institute of Materials Science – Mechanical and Electrical Workshop 157 Institute for Applied Geosciences Preface Many of today’s major societal challenges are, to a large extent, geoscientific origin. The efficient management of water as well as other geo-resources, the securing of our future energy demands, or the understanding of the effects of the anthropogenic alteration of global cycles are vital for the future development of our society. The Institute of Applied Geosciences at the TU Darmstadt has continued its efforts to focus research activities as well as the educational program on our key activities in Water – Energy – Environment. The first renovation phase of our 50 year old building is now completed and was celebrated on October 25 by a nice gathering with our Chancellor Dr. Manfred Efinger. In the meantime, all groups of the Institute, after having been separated for nearly one year, moved back into the fully renovated building and are now located in their familiar environment. We are very excited about the modern and inspiring working environment. Our consecutive Bachelor and Masters program ‘Angewandte Geowissenschaften’ is fully implemented and proves to be very attractive for prospective students. In October 2013, The total number presently enrolled at the Institute of Applied Geosciences is 370 students. In the focus of the 8th deep geothermal energy forum, held by the research group of Prof. Ingo Sass on October 1st 2013 at the Institute of Applied Geosciences, were presentations of the recent Hessian deep geothermal energy power plant projects and their public participation campaigns. 158 Institute of Applied Geosciences – Preface The strongly discussed topic of induced seismicity and the area of conflict between energy exploitation and technological impact assessment were addressed in a public presentation series focused on different aspects of man-made seismicity. The presentations took place from June 2013 till February 2014 and were funded by the BUND Hesse and house of clean energy. The hydrogeology group of Prof. Christoph Schüth coordinates the EU FP 7 project ‘MARSOL – Managed Aquifer Recharge as a Solution to Water Scarcity and Drought’ with 21 partners from 7 countries. With a total budget of 8 Mio €, the main objective of MARSOL is to demonstrate that MAR is a sound, safe and sustainable strategy which can be applied with great confidence. Therefor, 8 field sites are operated in southern Europe using different waters (treated waste water, desalinated water, and river water) while applying different techniques to replenish depleted groundwater resources. As it is a long standing tradition in Geosciences to conclude the academic year with the ‘Barbara Fest’, all faculty, staff and students got together to discuss the events of the year as well as the future in a very friendly and positive atmosphere. Due to the high number of freshmen, the welcome ceremony of the new students, who were babtized during this event, was rather crowded but, finally, everyone was finally officially accepted as a new member of the Institute of Applied Geosciences. Institute of Applied Geosciences – Preface 159 Physical Geology and Global Cycles In the solar system, Earth is a unique rocky planet with an ocean and an atmosphere. It is inhabited by bacteria since about 4 billion years and by higher life – plants and animals – since ca. 600 million years. Organisms, air, water, and rocks are interconnected in a never ending cycle of matter and energy: The Earth System. The crustal plates of Earth are driven by radioactive heat. This causes creation of new crust at mid-oceanic ridges at rates of several centimeters per year. On the other side, plate margins become subducted into the mantle again or fold up vast mountain ranges, like the Alps and the Himalayas, combining rocks of very different origin. During subduction the basaltic crust is partially melted, generating more felsic magmas which rise to form plutons and to cause lines of andesitic volcanoes such as occurring around the entire Pacific Rim. This is called the endogenic cycle of rocks. At the same time Earth receives solar radiation which moves air and water in gigantic cycles around the planet. Specifically the water cycle causes the denudation of mountains by mechanical erosion and the leveling of plains by chemical weathering, the latter aided tremendously by vegetation and its CO2-input to soils. This is called the exogenic cycle of rocks. This exogenic cycle is increasingly impacted by mankind. The radiation balance of the atmosphere has been upset by the emission of carbon dioxide, methane, and other trace gases. Earth is warming. Industrially produced chlorinated hydrocarbons have risen to the stratosphere, weakening the protective ozone layer. Dust from traffic, industry and agriculture produces reagents which alter air chemistry, causing unprecedented interactions with the marine realm, vegetation and even rocks through acidification, excessive deposition of nutrients and salts. Dry and wet deposition of anthropogenic (i.e. produced by humans) particles can be measured world-wide. The population explosion caused the intensification of agriculture and an alarming loss of topsoil while reducing the extent of natural ecosystems at the same time. Artificial fertilization of soils causes wide-spread nitrate pollution of shallow ground waters. Urbanization alters the water cycle above and below ground. Local leakage of chemicals impacts soil, rivers and ground water. Civil engineering causes alterations in almost all rivers world-wide, and even coastal oceans show increasing eutrophication, siltation and ecosystem changes in the water column and in their shallow sediments. Scars left by mining of minerals and fossil energy are visible everywhere and cause increasing problems. Throughout the globe man has changed the rate of natural processes. He spreads ever further into the landscape, utilizing regions and building in areas which are not suitable for construction, considering their natural risks. Thus, damage of natural catastrophes rise each year, endangering the world insurance system. These processes and their consequences are topics in Environmental Geology. Understanding Global Change and accepting the responsibility of mankind to conserve the planet and its resources for future generations are prerequisites for ensuring a sustainable development. The division of Physical Geology and Geological Cycles at the Institute for Applied Geosciences addresses questions important to environmental geology both in the present and in the geological past. 160 Institute of Applied Geosciences – Physical Geology and Global Cycles Staff Members Head Prof. Dr. Stephan Kempe Research Associates Dr. Günter Landmann Technical Personnel Ingrid Hirsmüller Secretaries Kirsten Herrmann / Pia Cazzonelli PhD Students Ingo Bauer, Christina Bonanati Diploma Students Sven Philipp Student research projects Jan Will Hans-Peter Hubrich Research Projects 3D Scanning of caves and speleogenetic process studies Pyroducts (Lava Tunnels) in the Kahuku Ranch area, Hawaii Volcanoes National Park Desert Kites in the Harrat of Jordan Dekapolis Tunnel, a presumably >100 km long Roman aqueduct system in Northern Jordan Tectonic structure of the southern boundary of the Harz Mountain and its development since the Permian Paleoclimate of the Lake Van region (Eastern Anatolia) in the period 20-15 ka BP Past climate reconstruction on sediment of the Layla Lake, Saudi Arabia Publications Articles and book chapters: [1] Lauerwald, R., Hartmann, J., Moosdorf, N., Kempe, S., & Raymond, P.A. 2013: What controls the spatial patterns of the riverine carbonate system? A case study for North America. - Chemical Geology, 337-338: 114–127. DOI:10.1016/j.chemgeo. 2012.11.011 [2] Kempe, S., 2013: Morphology of speleothems in primary (lava-) and secondary caves. - In: Shroder, J. (Editor in Chief), Frumkin, A. (Ed.), Treatise on Geomorphology. Academic Press, San Diego, CA, vol. 6, Karst Geomorphology, pp. 267–285. [3] Kempe, S., & Al-Malabeh, A., 2013: Desert kites in Jordan and Saudi Arabia: Structure, statistics and function, a Google Earth study. – Quaternary International, 297: 126-146. http://dx.doi.org/10.1016/j.quaint.2013.02.013, Institute of Applied Geosciences – Physical Geology and Global Cycles 161 [4] Lauerwald, R., Hartmann, J., Moosdorf, N., Dürr, H.H., & Kempe, S., 2013: Retention of dissolved silica within the fluvial systems oft he cconterminous USA. – Biogeochemistry 112(1-3): 637-659. DOI: 10.1007/s1 0533-012-9754-8 [5] Kempe, S., & Al-Malabeh, A., 2013: New geoglyphs of the Jordanian Harrat. - Past Horizons. May 10, http://www.pasthorizonspr.com/index.php/archives/05/2013/ new-geoglyphs-of-the-jordanian-harrat [6] Kempe, S., Naumann, G., & Dunsch, B., 2013: Athanasius Kircher’s chapter XX „About caves, fractures and the innumerable passages of the earth“ and the Grotto of Antiparos from „Mundus subterraneus“, 1678, translated from Latin. – In: Filippi, M. & Bosák, P. (eds.), Proceedings 16th Intern. Congr. Speleology, Brno, July 21 -28, 2013, Vol. 1: 59-64. [7] Knolle, F., Kempe, S., & Travassos L.E.P., 2013: Nazi military use of German caves, Dr. Benno Wolf and the world cave registry project. – In: Filippi, M. & Bosák, P. (eds.), Proceedings 16th Intern. Congr. Speleology, Brno, July 21 -28, 2013, Vol. 1: 65-70. [8] Bonanati, C., Bauer, I., & Kempe, S., 2013: Radon measurements in Austrian and Slovenian caves with an Alphaguard instrument. – In: Filippi, M. & Bosák, P. (eds.), Proceedings 16th Intern. Congr. Speleology, Brno, July 21 -28, 2013, Vol. 2: 479-484. [9] Bauer, I., Kempe, S., & Bosted, P., 2013: Kahuenaha Nui (Hawaii): A cave developed in four different lava flows. – In: Filippi, M. & Bosák, P. (eds.), Proceedings 16th Intern. Congr. Speleology, Brno, July 21 -28, 2013, Vol. 3: 231-236. [10] Bosted, P., Gracanin, T., Hackell, V., Bosted, A., Bauer, I., & Kempe, S., 2013: The Keokeo lava tube system in Hawaii. – In: Filippi, M. & Bosák, P. (eds.), Proceedings 16th Intern. Congr. Speleology, Brno, July 21 -28, 2013, Vol. 3: 243-246. 162 Institute of Applied Geosciences – Physical Geology and Global Cycles Radon measurements in Austrian and Slovenian Caves with an AlphaGuard Instrument Christina Bonanati, Ingo Bauer, Stephan Kempe In September 2012, radon and CO2 measurements were carried out in Lipiška jama and Mačkovica in Slovenia and Austria’s Dachstein-Mammuthöhle. The AlphaGUARD proved to be a suitable device for long- and short-term radon measurements in caves. Values ranged from undetectable in some locations of Dachstein-Mammuthöhle to 4920 ± 549 Bq m-3 in Mačkovica, presumably correlating with ventilation, material and size of the caves. A longterm measurement in Mačkovica revealed no diurnal variation pattern. In the old parts of Dachstein-Mammuthöhle there is no threat for workers or tourists from radiation. Overview Radon is a tracer for cave climate and air circulation and can be a potential threat for workers, speleologists or tourists. 222Rn is an inert noble gas, a naturally occurring radioactive daughter product of 226Ra from the 238U decay chain with a half-life of only 3.82 days. It has a diffusion coefficient of around 1*10-6 m2s-1 2,3; the diffusivity of .Rn is limited and dependent on the porosity and moisture of the material Various parameters affect the radon concentration in cave air and its release from rocks, cave sediments and water: Its emanation coefficient depends on mineralogy, density and porosity, grain-size and shape – moisture1 and the spatial occurrence of radon in the mineral grains2. Diffusive and advective transport processes in the cave and mixing with ambient atmospheric air. Ventilation is governed by the specific shape of the cave and can be caused by pressure and temperature differences, the drag force from changes of water levels, or harmonic movements which can occur due to compression of air. Method The measurement setup consists of an AlphaPUMP and the AlphaGUARD PQ 2000 PRO (Genitron Instruments GmbH). Cave air was pumped into the ionisation chamber of the AlphaGUARD. In order to determine the radon concentration in the air the ionisation chamber was kept closed for a minimum of 11 minutes after it was filled, by connecting the hoses with each other to produce a closed cycle. For the long-term measurement, the hoses were taken off and the AlphaGUARD was put into diffusive mode in which every hour one average value is documented. The AlphaGUARD measures and records simultaneously atmospheric pressure, temperature and humidity with integrated sensors. CO2 concentration in the cave air was measured with a handheld DRÄGER Multi Gas Detector. Measurements were carried out in September 2012 in Dachstein-Mammuthöhle (Austria) and Mackovica and Lipiška jama (Slovenia). Results and Discussion • The Dachstein Mammut Höhle revealed the lowest Radon activity concentration in the cave air. It ranged from undetectable (error bigger than value) to 233 ± 44 Bq m-3. The generally low radon concentration reflects the strong ventilation and connection to outside air. Furthermore it might be possible that the wet cave loam has an influence on a general low exhalation rate of the cave material as water in the pore-space can decrease the exhalation of radon 3,5. Institute of Applied Geosciences – Physical Geology and Global Cycles 163 • In Lipiška jama the measurements reveal a general increase of the radon and CO2 concentration with depth (Fig. 1). The strong ventilation occurring between the two entrances gives rise to low radon concentrations at 340 ± 145 Bq m -3 in the “Drca” (L1). A very high radon level at 3644 ± 500 Bq m-3 in the artificial passage at the end of the cave (L8) reflects the impeded ventilation resulting in radon accumulation. High values were also measured in the narrow passages of the “Labirint” (L8) which does not contain much fine sediment and is not well ventilated. Low values which were measured in the “Kozinski Rov” and the “Suhi Izvir” suggests a connection with outside air through fissures. CO2 concentrations ranged from 3000 ppm near the entrance (L1) to 15 000 ppm in front of the entrance to the loamy passage (L9). Local, however non-locatable CO2 sources and impeded ventilation can give rise to the high CO2 concentrations in the lower parts of the cave. Figure 1. Longitudinal cross-section6 of Lipiška jama with measurement locations. • In Mackovica, measurements were done at two sites, M1 at the end of “Mala Dvorana” and M2 below the entrance to “Velika Dvorana”. The average radon activity concentration was 4585 Bq m-3. At site M2 the CO2 concentration was 0.15 Vol %. At this site, a long-term diffusive measurement was run for 32 hours. During the measurement the air pressure ranged from 969 to 965 mbar. In the first hours the radon values were around 4000 Bq m-3. Then they constantly dropped down to 3104 ± 189 Bq m-3 until 5 p.m.. The drop is coherent with a slight drop in pressure. However, even though air pressure rose again, the radon level stayed constant until the next morning. The long-term radon measurement shows no correlation with ambient atmospheric air temperature (Fig. 2). At the time of the measurement campaign water levels were low everywhere. Thus it is unlikely that there was a change in water level in the siphon at the back of the cave, influencing the measurement results. The student group visiting the cave at the beginning of the long-term measurement might have affected the air movement. Figure 2. Mackovica long-term radon monitoring. 164 Institute of Applied Geosciences – Physical Geology and Global Cycles Conclusion • • • • • The AlphaGUARD proves to be a suitable device for long- and short-term radon measurements in caves. The measured radon activity concentrations in the cave air are at least one order of magnitude lower than the specific activities of the potential source material. Radioactive equilibrium has not been reached. Reasons are the ventilation or impeded radon exhalation due to moisture or low effective porosity of the material. The highest radon levels were measured in Mackovica, the smallest of all three caves with the least ventilation. The long-term measurements suggest that air temperature outside the cave is not a driving force in ventilating the cave with outside air in summer. In Lipišca jama, radon levels were also high, but lower values in deeper parts of the cave suggest the existence of unknown pathways, enhancing the air circulation. Variation in moisture or textural and chemical properties of the sediments may influence the differences in radon levels in the less ventilated parts of the caves. The measurement results from Dachstein-Mammuthöhle suggest a strong air circulation and thus frequent mixing of cave air with ambient atmospheric air. The radon levels are too low in order to be used for any study on air circulation within the cave. There is no threat for workers or tourists from radiation. References 1. Adler, PM, Perrier F, 2008. Radon emanation in partially saturated porous media. Transport in porous media, 78(2), 149-159. 2. Washington JW, Rose W, 1990. Regional and temporal relations of radon in soil gas to soil temperature and moisture. Geophysical Research Letters, 17(6), 829-832. 3. Tanner AB, 1964. Radon migration in the ground: a review. In: Adams JAS, Lowder WM (Eds.), Natural Radiation Environment, University of Chicago Press, Chicago, 161-190. 4. Vaupoti J, 2010. Radon levels in carst caves in Slovenia. Acta Carsologica, 39(3), 503-512. 5. Fleischer RL, 1987. Moisture and 222Rn-emanation. Health Phys. 52: 797–799. 6. Jakofcic J, 2006. Longitudinal cross-section of Lipiška jama, cited in Cerkvenik R, 2012: Impacts of visitors on cave’s physical environment and its protection, Dissertation, 405. Institute of Applied Geosciences – Physical Geology and Global Cycles 165 Proposed paleoclimate study on sediments of the Layla Lakes, Saudi Arabia: First Results Günter Landmann, Stephan Kempe, Cristoph Schüth The Layla Lakes in the Centre of Saudi Arabia fell dry in the beginning of the 1990’s due to groundwater mining. The lakes, fed by ascending groundwater, filled a series of sinkholes that formed by hypogene karstification of the underlying Upper Jurassic anhydrite Hith Formation. The lake sediment, here named ‘The Layla Formation’, is now accessible in profiles at the sinkhole walls. XRD-, XRF- and CNS-Analyses of 19 samples taken from such a profile show good correlation between the different methods used and allow classification of the samples (Fig. 1). The samples from 2; 5; 6; 8.7; 8.95; 9.5 m depth contain mainly sparitic gypsum with some calcite and trace elements. They form hard crust and are interpreted to represent periods of drought. Fig. 1. Comparison between concentrations determined by CNS- and XRF-analyses (filled circles) and intensity of the main peaks of calcite (cc), gypsum (gy) and quartz (qz) measured by XRD-analyses (open circles) reveal good correlation between the different methods. Samples with high SO3-content consist almost entirely of gypsum, those with high CO2-content contain 60-85 % calcite. Vertical error bars give standard deviation of double CNS-determinations. 166 Institute of Applied Geosciences – Physical Geology and Global Cycles Micritic calcite, with up to 3 % Mg in samples close to gypsum layers, precipitated due to degassing of CO2 at times with a positive water balance when the lakes overflow (Fig. 1). The changes in the composition of these cyclic series of chemical sediments therefore carries paleoclimatic information. The hydraulically powered direct push device Geoprobe was used close to the sinkhole profile to obtain a continuous sediment profile. Due to compaction caused during coring, the former 10.8 m long sediment column was reduced to 8.47 m (78 %), with highest porosities occurring in the gypsum layers. An XRF-scan was done with a resolution of 1 cm providing the relative concentration of the elements Al, Si, S, K, Ti, Sr, Zr, Br, Pb, Rb and Ba. The core reveals a good stratigraphic correlation with the sinkhole profile (Fig. 2). Fig. 2. The correlation between the XRF-Analyses of the sinkhole profile (black) and the XRF-scan of the core (red) is based on element concentrations higher than mean values (given by dotted vertical lines). The elements Si and Ti represent the clastic sediment corresponding to the blue areas, which mark the more humid periods. Yellow areas indicate the gypsum layers, representing arid periods. Arrows at the depth axis give theposition of dated materials (see text). Institute of Applied Geosciences – Physical Geology and Global Cycles 167 So far only one 14C-Analyses of a gastropod shell and one U/Th-date on carbonate is available (Fig. 2). The old age of the shell collected from surface sediment is assumed to be caused by the hard water effect of the ascending and old groundwater that fed the lake. The proposal aims to date the sediments in more detail (14C and U/Th) and to validate the preliminary hypotheses by correlating other profiles by sampling, and mineralogical and geochemical analysis. Micropaleontological investigations (pollen, spores, diatoms and other algae, thekamoeba, ostracods) are planed to reconstruct the climate and geochemical environment in the center of Saudi Arabia, a region so far lacking upper Holocene climate records. 168 Institute of Applied Geosciences – Physical Geology and Global Cycles 3D-Scanning of Underground Cavities, Case Study: Entdeckungshalle, Segeberger Höhle Stephan Kempe1, Ingo Bauer1 1 Institute of Applied Geosciences, University of Technology Darmstadt, Schnittspahnstr. 9, D-64287 Darmstadt, Germany, The Segeberger Höhle, Bad Segeberg, is the northern-most show cave in Germany, situated in the “gypsum hat” of a salt dome in central Schleswig Holstein. The maze-like cave developed in the shallow ground water body during the Holocene. It fell dry rather recently, probably during the 19th century when salt mining was attempted at Segeberg. The cave was discovered in 1913 during anhydrite and gypsum quarrying. The former quarry serves today as an open air theater for the famous Karl May festival at Segeberg. The festival today is a major economic factor for Bad Segeberg. The cave, in part, is very near to the stage and the stability of its largest hall, the „Entdeckungshalle“ („Discovery Hall“), may be of importance for the safety of the staff and visitors of the festival. We therefore scanned the Entdeckungshalle with a Faro 3D 120 Scanner in order to document all tectonic elements and assess the cave’s stability. Between the Entrance (St. 1) and the weather doors at the southern end of the Hall (St.19) 19 scans were recorded. Station 06 on the „Asselberg“ was recorded in high resolution to document the Hall for later comparative scans in ordert o assess small alterations by breakdown. St. 07 was deleted and replaced by St. 08. At nine places marks were mounted (iron plates of 40 mm diameter) in order to place the magnetic reference spheres (14 cm) at exactly the same locations for later scans. Scans 01-05 und 08-19 were combined into one 3D-Model with the Faro Software SCENE (Fig. 1). The model contains 745 Mio. data points. Depending on the distance of the scanner to the wall the resolution is between 1 and ca. 10 mm. All stationen can be viewed individually and appear almost as black-and-white 360° panomara photos because the Faro Scanner records not only X,Y, and Z data but also a reflection value for each point. Due to this fact, differences in rock reflectivity and therefore stratification are visible in the scans. Fig. 1: View of the Entedeckungshalle, Segeberger Höhle, from above. Length of the section shown is ca. 100 m. The lines show the strike of the strata which are tilted here tot he vertical. X points East, Y North and Z upward. Institute of Applied Geosciences – Physical Geology and Global Cycles 169 Results The Entdeckungshalle is 98 m long (Fig. 2). Its highest point at the discovery hole is 12.5 m above the cave’s floor. At this site the hall has a cross-section similar to a tipi with a floor width of 9 m. 11.8 m south of the back wall (right on Fig. 2), the ceiling comes down to 5.8 m and then keeps more or less at a hight of 3.5 m. Fig. 2: View of the entire length of the Entdeckungshalls in direction 189° from the outside. Pertinent features are marked. The Entdeckungshalle follows the NW-SE oriented strike of the strata that are tilted to the vertical due to the upward movement of the saltdome (Fig. 1). Similarly, the passages near the entrance and the columns that carry the SW wall of the Entdeckungshalle are composed of vertically tilted strata. Along one of the stratification planes a vertical fault has evolved that marks the crest of the hall in the NW and disappears into the cave’s wall about 10 m SE of the passage leading to the cave’s entrance. In some places slick’n-sides are preserved, showing vertical displacement. The anhydrite/gypsum strata show fine to coarse lamination, affecting the form and width of the blocks that can detach from the ceiling. A third, prominent tectonic element is joints that dip ca. 70° to the NW (Fig. 3, joints A to H plus some smaller joints). Joints A and B form the back wall of the hall. In between them they define a large, upward tapering, triangular block (green in Fig. 3) that is detached on one side by the semi-vertical fault. Furthermore it is missing its foot support and could potentially collapse. Nevertheless no recent collapse blocks are noticed. The explanation may be that this block is still gypsyfying and expanding, therefore wedging itself into position. Gypsification (hydration of anhydrite) causes a volume increase of 26 % (according to density difference of the two minerals). Further investigation may substantiate these conclusions. 3D-underground scanning proves to be a valueable tool to investigate tectonic structure and hence stability of underground cavities. 170 Institute of Applied Geosciences – Physical Geology and Global Cycles Fig. 3: View from the outside at the NW-End of the Entdeckungshalle with major joints marked. Institute of Applied Geosciences – Physical Geology and Global Cycles 171 Hydrogeology The Hydrogeology Group focuses on three main research areas, (I) the fate of organic contaminants in the environment, (II) the development of novel methods to remediate soil and groundwater contaminations, and (III), on water resources management from a local to a regional scale. In all three research areas externally funded projects are currently running, some as part of larger joint projects with national and international pertners. Our water resources management project in Saudi Arabia, which was part of the BMBF funded joined project IWAS, was phased out this year. However, we continue to focus on water management in arid regions. We started a project on water quality in northern Africa with partners from the Helmholtz Center for Envionmental Research in Leipzig (UFZ), from the Federal Institute of Geosciences and Natural Resources (BGR) and others. Here we focus on naturally occurring radioactivity in the fossil groundwaters in the large sandstone aquifers in northern Africa that is of major concern. We have been also successful in applying for a project in the 7th framework program of the EU as coordinator. MARSOL (Managed Aquifer Recharge as a Solution to Water Scarcity and Drought) has 20 partners in southern Europe and will operate 8 field sites in the Mediterranean to demonstrate that Managed Aquifer recharge (MAR) is a sound, safe and sustainable method to increase water resources in areas with dwindling water availability. We are very excited to be in a key position to promote this technology. Together with partners from our Institute and from the Civil- and Environmental Engineering Department we submitted, as coordinators, a proposal in the LOEWE program of the state of Hesse. The topic of the planned center is ‘Urban H2O’, dealing with all aspects of water management in cities. We have been invited to submit a full proposal and advanced to the final stage. A decision will be made in summer 2014 and we are very much looking forward to have the chance to work on this relevant topic as a team of geoscientists and engineers. Staff Members Head Prof. Dr. Christoph Schüth Research Associates Dr. Laura Foglia Dr. Thomas Schiedek Dr. Annette Wefer-Roehl PhD Students Abidur Khan Nils Michelsen Layth Sahib Christoph Kludt Mustafa Yasin Stefan Schulz Anja Wolf Layth Latai Master Students Christian Adam Eunice Agyare Brago Haftay Gebrehivot Tanuja Gorele Pamela LaForce Asanka Thilakerathne Indriani Preiß Jannes Winnacker Andreas Androulakakis Suraya Fatema Beatrice Kanyamuna Terence Ngole Anja Tögl Sehab Uddin Secretary Pamela Milojevic 172 Institute of Applied Geosciences – Hydrogeology Technical Personnel Zara Neumann Rauiner Branolte Claudia Cosma Research Projects MARSOL - Managed Aquifer Recharge as a Solution to Water Scarcity and Droughts (EU2013-2015) RADAQUA - Pilotstudie zur Einschätzung erhöhter Radionuklidkonzentrationen in Grundwässern der Arabischen Halbinsel und Nord-Afrikas (BMBF 2013-2014) Prozessorientierte Untersuchung zum Nitratabbauvermögen der Grundwasserkörper im Hessischen Ried (HLUG: 2012-2014) Heavy metal contamination of surface water and groundwater resources in the industrial area of Dhaka City, Bangladesh (BMBF-IPSWAT, 2011-2014) Detection of oil spills and water contamination in the Kirkuk area, Irak, using remote sensing data (DAAD 2011-2014) Publications [1] El Haddad, E., Ensinger, W., Schüth, C. (2013): Untersuchungen zur Sorptionsreversibilität von organischen Schadstoffen in Aktivkohle, Holzkohle und Zeolith Y-200. Grundwasser, 18, 197-203. [2] Engelhardt, I., Rausch, R., Lang, U., Al-Saud, M., Schüth, C. (2013): Impact of Preboreal to Subatlantic shifts in climate on groundwater resources on the Arabian Peninsula. Environmental Earth Sciences, 69, 557-570. [3] Engelhardt, I., Rausch, R., Keim, M., Al-Saud, M., Schüth, C. (2013): Surface and subsurface conceptual model of an arid environment with respect to mid- and late Holocene climate changes. Environmental Earth Sciences, 69, 537-555. [4] Engelhardt, I., Prommer, H., Moore, C., Schulz, M., Schüth, C., Ternes, T. (2013): Suitability of temperature, hydraulic heads, and acesulfame to quantify wastewater-related fluxes in the hyporheic and riparian zone. Water Resources Research, 49, 426-440. [5] Foglia, L., McNally, A., Harter, T. (2013): Coupling a spatiotemporally distributed soil water budget with stream-depletion functions to inform stakeholder-driven management of groundwater-dependent ecosystems. Water Resources Research, 49, 7292-7310. [6] Foglia, L., Mehl, S.W., Hill, M.C., Burlando, P. (2013): Evaluating model structure adequacy: The case of the Maggia Valley groundwater system, southern Switzerland. Water Resources Research, 49, 260-282. [7] Rasa, E., Foglia, L., Mackay, D.M., Skow, K. (2013): Effect of different transport observations on inverse modeling results: case study of a long-term groundwater tracer test monitored at high resolution. Hydrogeology Journal, 21, 1539-1554. [8] Wolf, A., Bergmann, A., Wilken, R.D., Xu G., Bi, Y., Chen, H., Schüth, C. (2013): Occurrence and distribution of dissolved organic trace substances in waters from the Three Gorges Reservoir, China. Environmental Science and Pollution Research, 20, 7124-7139. Institute of Applied Geosciences – Hydrogeology 173 Occurrence and distribution of trace substances in the waters from the Treee Gorges Reservoir, China Anja Wolf, Axel Bergmann, Rolf-Dieter Wilken, Xu Gao, Yonghong Bi, Hao Chen, Christoph Schüth With a length of 6,300 km, the Yangtze River is the third largest river in the world Its catchment covers 1,810,000 km2, about 20%of the area of China with a population of 450 million people. The Three Gorges Dam (TGD) impounds the Yangtze River for the world's largest project for hydroelectric power generation in terms of installed capacity (18.2 million kW). The TGD also provides additional benefits, such as flood control, enhanced navigability, or stimulation of tourism. However, there is an ongoing controversial debate about the social and environmental impacts of the TGD. The impoundment of the 630-kmlong Three Gorges Reservoir (TGR) had a significant impact on the hydrological regime and ecology up- and downstream of the TGD (Xu and Milliman 2009; Xu et al. 2011). Upstream, huge industrial, residential, and agricultural areas were flooded. Hence, considerable amounts of organic and inorganic pollutants were released into the reservoir. Currently, there are additional anthropogenic pollutant sources, such as household sewage, industrial discharge, wastewater treatment plant (WWTP) effluents, garbage dumping, and agricultural runoff (Chang et al. 2010). Water quality in TGR is of major concern since surface water is commonly used as raw water source for public water supply (Luo et al. 2011). Furthermore, the water from TGR is considered for the provision of freshwater to the dryer northern part of China as part of the south to north water diversion project (Liang 2013). Fig. 1: Sampling points in the TGR area. Map source: Yangtze-Hydro Project In this study the water quality of the TGR) was evaluated in order to assess its suitability as a raw water source for drinking water production Wolf et al. 2013). Therefore, water samples from (1) surface water, (2) tap water, and (3) wastewater treatment plant 174 Institute of Applied Geosciences – Hydrogeology effluents were taken randomly in 2011–2012 in the area of the TGR (Fig. 1) and analyzed for seven different organic contaminant groups (207 substances in total), applying nine different analytical methods. In the three sampled water sources, typical contaminant patterns were found (Fig. 2), i.e., pesticides and polycyclic aromatic hydrocarbons (PAH) in surface water with concentrations of 0.020–3.5 μg/L and 0.004–0.12 μg/L, disinfection by-products in tap water with concentrations of 0.050–79 μg/L, and pharmaceuticals in wastewater treatment plant effluents with concentrations of 0.020–0.76 μg/L, respectively. The most frequently detected organic compounds in surface water (45 positives out of 57 samples) were the pyridine pesticides clopyralid and picloram. The concentrations might indicate that they are used on a regular basis in the area of the TGR. Three- and four-ring PAH were ubiquitously distributed, while the poorly soluble five- and six-ring members, perfluorinated compounds, polychlorinated biphenyls, and polybrominated diphenyl ethers, were below the detection limit. In general, the detected concentrations in TGR are in the same range or lower compared to surface waters in western industrialized countries, although contaminant loads can still be high due to a high discharge. With the exception of the two pesticides, clopyralid and picloram, concentrations of the investigated organic pollutants in TGR meet the limits of the Chinese Standards for Drinking Water Quality GB 5749 (Ministry of Health of China and Standardization Administration of China 2006) and the European Union (EU) Council Directive 98/83/EC on the quality of water intended for human consumption (The Council of the European Union 1998), or rather, the EU Directive on environmental quality standards in the field of water policy (The European Parliament and The Council of the European Union 2008). Therefore, the suggested use of surface water from TGR for drinking water purposes is a valid option. Current treatment methods, however, do not seem to be efficient since organic pollutants were detected in significant concentrations in purified tap water. Fig. 2: Boxplot of the concentrations of the 24 detected organic compounds, sum of pesticides, sum of THM, and sum of PAH in samples from a surface water, b tap water, and c WWTP effluents. The triangles in a and b illustrate the limit values given by the Chinese Surface Water Standards and Drinking Water Quality Standards; the squares are those given by the EU Environmental Quality Standards Directive and Drinking Water Directive. Institute of Applied Geosciences – Hydrogeology 175 References [1] Chang X, MeyerMT, Liu X, Zhao Q, ChenH, Chen JA, Qiu Z, Yang L, Cao J, Shu W (2010): Determination of antibiotics in sewage from hospitals, nursery and slaughter house, wastewater treatment plant and source water in Chongqing region of Three Gorge Reservoir in China. Environ Pollut 158(5):1444–1450. [2] Liang SM (2013): A joint water diversion plan for China. American Water Works Association 105(5):E264–E277 [3] Luo H, Fu G, Peng M, Gong R, Xiang W, Wang H (2011): Centralized water supply in rural villages of Three Gorges Reservoir. Chinese Rural Health Service Administration 31(9) [4] Wolf, A., Bergmann, A., Wilken, R.D., Xu G., Bi, Y., Chen, H., Schüth, C. (2013): Occurrence and distribution of dissolved organic trace substances in waters from the Three Gorges Reservoir, China. Environmental Science and Pollution Research, 20, 7124-7139. [5] Xu KH, Milliman JD (2009): Seasonal variations of sediment discharge from the Yangtze River before and after impoundment of the Three Gorges Dam. Geomorphology 104(3–4):276–283 [6] Xu XB, Tan Y, Yang GS, Li HP, SuWZ (2011): Impacts of China's Three Gorges Dam Project on net primary productivity in the reservoir area. Sci Total Environ 409(22):4656–4662. 176 Institute of Applied Geosciences – Hydrogeology Engineering Geology Engineering Geology is a branch of geology that deals with the characterization of soil, rock and rock masses for the location, design, construction and operation of engineering works. Typical tasks relate to foundation of roads and buildings, but also to underground excavations like tunnels and caverns. The special focus of the Engineering Geology group at Technische Universität Darmstadt is on reservoir geomechanics, i.e., the application of rock mechanics as well as of techniques for stress and fracture characterization to depth of up to 5 km. In particular, numerical (finite element) models are used to predict the corresponding subsurface conditions prior to drilling operations. Such predictive tools are of great value not only for the optimal exploration and efficient use of hydrocarbon and geothermal reservoirs, but also for CO2 sequestration sites as well as radioactive waste repositories. The present research activities of the group comprise several case studies applying geomechanical modeling techniques to oil and gas reservoirs in the North German basin and the Rhine Graben area as well as to a demonstration site in Australia. There the safe subsurface storage of CO2 (CCS) is investigated. Other studies focus on the analysis of surface outcrops which serve as analogs to subsurface reservoirs. Such outcrop analogs provide a broader data base than the limited well data which usually is available for reservoirs. Thus, they are ideal to test and validate the general modeling concepts used for subsurface modeling later-on. For research as well as teaching various software packages and powerful computing facilities are available which allow to run 3D geomechanical reservoir models with several millions of elements. In addition, new rock mechanical lab facilities like uniaxial, triaxial and ultrasonic measurement devices have been established which allow to derive the necessary reservoir-specific mechanical properties for input into the numerical simulations. For field work and outcrop analog studies a terrestrial laser scanner allows for rapid detection of fracture networks and determination of their geometrical and statistical properties. Staff Members Head Prof. Dr. Andreas Henk Research Associates M.Sc. Karsten Fischer Dipl. Geol. Christian Heinz M.Sc. Dennis Laux Dipl. Geol. Christoph Wagner Technical Personnel Reimund Rosmann Secretary Dipl. Kffr. Stefanie Kollmann Ph.D. students M.Sc. Chiara Aruffo Institute of Applied Geosciences – Engineering Geology M.Sc. Bastian Weber 177 Research Projects Prediction of tectonic stresses and fracture networks with geomechanical reservoir models (DGMK Projekt 721, ExxonMobil, GDF SUEZ, RWE Dea) PROTECT - PRediction Of deformation To Ensure Carbon Traps (BMBF) Buidling and populating geomechanical reservoir models – a case study from the Upper Rhine Graben (GDF SUEZ) LIDAR-based analysis of fracture networks (PhD thesis) Fracture prediction in fold-and-thrust belts – a worked example from the southern Pyrenees (PhD thesis) Publications [1] Aruffo, C. M., Henk, A. and PROTECT Research Group, 2013: Seismo-mechanic workflow to ensure CO2 storage in the Otway Basin, Australia. Extended Abstracts 75th EAGE Conference and Exhibition, London. [2] Aruffo, C.M. and PROTECT Research Group, 2013: Workflow for geomechanical modeling to ensure CO2 storage in the Otway Basin, Australia – joint project PROTECT. Proceedings 4th IGSC Conference, Berlin. [3] Aruffo, C.M., Henk, A., 2013: Geomechanical workflow to ensure CO2 storage in Otway Basin, Australia. Abstract volume CO2CRC Research Symposium, Hobart, Australia. [4] Fischer, K., Henk, A., 2013: A workflow for building and calibrating 3-D geomechanical models – a case study for a gas reservoir in the North German Basin. Solid Earth, 4: 1–9. [5] Fischer, K., Henk, A., 2013: Field-scale geomechanical modeling of an intensely faulted gas reservoir. Conference Proceedings ARMA 13-219, 47th US Rock Mechanics / Geomechanics Symposium, San Francisco. [6] Fischer, K., Henk, A., 2013: Generating and Calibrating 3D Geomechanical Reservoir Models. Conference Proceedings, Extended Abstracts 75th EAGE Conference & Exhibition, London. [7] Fischer, K., Henk, A., 2013: Constructing Reservoir-Scale 3D Geomechanical FE-models – A Refined Workflow for Model Generation and Calculation. DGMK-Tagungsbericht 20131, DGMK-ÖGEW Frühjahrstagung, Celle. [8] Fischer, K., Henk, A., 2013: Geomechanical reservoir models for the prediction of tectonic stress fields in deep geothermal reservoirs. Conference Proceedings, 19. Tagung für Ingenieurgeologie, München. 178 Institute of Applied Geosciences – Engineering Geology [9] Laux, D., Henk, A., 2013: LIDAR in Geosciences – A quantitative analysis of fracture networks in outcrops to improve input parameters for DFN modelling. Conference Proceedings, Riegl LIDAR 2013 International User Conference, Wien. [10] Laux, D., Henk, A., 2013: Charakterisierung von Trennflächengefügen in Oberflächenaufschlüssen durch terrestrisches Laserscanning zur Erzeugung eines Discrete Fracture Network Modells. DGMK-Tagungsbericht 2013-1, DGMK-ÖGEW Frühjahrstagung, Celle. [11] Laux, D., Henk, A., 2013: Erfassung von Trennflächengefügen mit dem terrestrischen Laserscanner (TLS) als Eingabedaten für Discrete Fracture Network (DFN-) Modelle. Conference Proceedings, 19. Tagung für Ingenieurgeologie, München. [12] Wagner, C., Henk, A., 2013: Seismische Interpretation und Erstellung eines geomechanischen Reservoirmodells – eine Fallstudie aus dem Oberrheingraben. DGMKTagungsbericht 2013-1, DGMK-ÖGEW Frühjahrstagung, Celle. Institute of Applied Geosciences – Engineering Geology 179 Geomechanical reservoir modeling – workflow and case study from the North German Basin Fischer, K. There is an increasing importance for the optimal exploitation of conventional hydrocarbon reservoirs to have detailed knowledge of the specific state of stress in a reservoir and to gain clarity on the corresponding geomechanical implications. This knowledge is even becoming mandatory for most unconventional plays. The local stress field directly affects, for instance, wellbore stability, the orientation of hydraulically induced fractures, and – especially in fractured reservoirs – permeability anisotropies. Robust information on the locally prevailing stresses is thus ideally required prior to drilling. Numerical models based on the finite element (FE) method are able to cope with the complexity of real reservoirs. Acting as predictive tools, these models not only provide quantitative information on the stress distribution, but also a process-based understanding of geomechanical reservoir behavior. This study evaluates the potential of geomechanical FE models for the prediction of local in situ stress distribution and fracture networks in faulted reservoirs. The work of this study was conducted in cooperation with three major operators in the E&P industry and comprises two main parts. In the first methodological part, a generally applicable workflow is developed for building geomechanical FE models and calibrating them to field data. These models focus on spatial variations of in situ stress resulting from faults and contrasts in mechanical rock properties. Special techniques are elaborated regarding the transfer of the reservoir geometry from geological subsurface models to the numerical model and for the most effective application of boundary conditions. Complex fault geometries and the detailed topology of lithostratigraphic horizons can be considered on reservoir scale. In combination with reservoir-specific material parameters the incorporated horizons establish a mechanical stratigraphy inside the model. Faults are implemented as discrete planes by 2D interface elements. This allows fault-specific stresses and corresponding fault behavior to be analyzed. The resulting geomechanical models comprise high spatial resolution and several million elements. They are calculated in reasonable time spans by using highperformance computing. In addition, submodels resolving a detailed mechanical stratigraphy can be integrated into the reservoir-wide modeling for local focus. In the second part of the study, the workflow was successfully applied to an intensively faulted gas reservoir in the North German Basin. Comprehensive datasets are provided by the field operators and project partners for building and calibrating a detailed and truly field-scale geomechanical model covering more than 400km². It incorporates a network of 86 faults and a mechanical stratigraphy of three layers comprising reservoir-specific material parameters. For the static modeling approach, the present-day regional stress field is applied as boundary condition. Static modeling results are compared to local stress measurements, e.g. orientations from borehole breakouts and magnitudes from frac data. After iterative calibration, the best-fit model reveals the recent in situ stress distribution and individual fault behavior throughout the reservoir. The results show significant local perturbations of stress magnitudes (max. ±10MPa over 1-2km distance) and only minor deviations in stress orientation from the regional trend (max. ±25°). The strong 180 Institute of Applied Geosciences – Engineering Geology dependency on the specific fault trace, offset and interactions precludes the derivation of generally valid rules for estimating stress variations and underlines the necessity of numerical modeling. Analysis of fault-specific results indicates that critical stress states occur most likely on NW-SE trending faults in the present-day stress field. Fracture information is inferred from a (geo-)dynamic model focusing on the major stages in the tectonic history of the reservoir and the respective past in situ stresses. Consequently, paleo-stress fields are applied as boundary condition and material parameters are adjusted. Correlation of fracture orientations and modeled paleo-stresses in the reservoir allows the formation of fracture sets to be assigned to Triassic and Late Jurassic to Early Cretaceous times. Increased perturbation intensity in the Late Jurassic to Early Cretaceous is related to potential reactivation of NW-SE trending faults and explains the variability of the corresponding fracture set. These results elucidate how stress perturbations can explain fracture variability without the need for complex tectonic histories. Furthermore, the dynamic model sheds light on fault zone permeability. Modeling indicates that if cataclasis is responsible for a reduced fault permeability, then it will most likely occur along E-W and NNE-SSW trending faults due to the high slip tendency values they experienced in the tectonic past. Modeling results show no such increased geomechanical exposure for NW-SE oriented faults. However, high dilation tendencies support the possibility of activity of these faults in Late Jurassic times – as proposed by fracture correlation. Low permeability of NW-SE trending faults is thus most likely the result of fluid entry and illitization, which is also observed at a wellbore close to such a fault set. The combination of static and dynamic modeling results suggests no significant impact of critically stressed natural fractures on the recent hydraulic behavior of the entire reservoir. Additionally tests of fault block refinements and submodels demonstrate their capability to provide further increased spatial resolution in areas of particular interest. The submodel generated for the northwestern part of the case study underlines the impact of the specific connections of the fault network on the modeling results. The outcome of this study confirms the high potential of geomechanical FE models to reveal the specific in situ stress and fault behavior, and to infer fracture characteristics from paleo-stresses. Beside the case study specific insights, the successfully applied and approved workflow can be used for future modeling of stress-sensitive reservoirs. Furthermore, the geomechanical models are not limited in application to the hydrocarbon industry. As general tools for stress prediction in undrilled rock formations, they can also be applied to deep geothermal reservoirs and underground engineering, for instance. The possibility of characterizing fault behavior makes the models additionally valuable in the fields of carbon capture and storage (CCS) and nuclear waste disposal. Acknowledgements This work has been funded by ExxonMobil Production Deutschland GmbH, Gaz de France Suez E&P Deutschland GmbH and RWE Dea AG within the frame of the DGMK (Deutsche Wissenschaftliche Gesellschaft für Erdöl, Erdgas und Kohle e.V.) project 721. Institute of Applied Geosciences – Engineering Geology 181 Fault stability assessment of the CO2CRC Otway Project, Australia – a geomechanical approach Aruffo, C.M., Henk, A. & PROTECT Research Group Introduction In the past years geosequestration reached the interest of public opinion as a technology that can significantly reduce greenhouse emissions from the burning of fossil fuels. The Australian government, through the CO2CRC (Cooperative Research Centre for Greenhouse Gas Technologies), launched a pilot project for carbon dioxide storage in 2005 (Jenkins et al. 2011). The CO2CRC Otway Project is located in Nirranda South, Victoria, Australia and it is the first CO2 storage project of the southern hemisphere. CO2 sequestration utilizes an existing depleted natural gas field, the Naylor Field. Gas used for storage contains about 80% CO2 and is produced from the adjacent Buttress Field. The CO2CRC Otway Project aims to demonstrate that carbon capture and storage (CCS) is technically and environmentally safe. Potential risks that could arise due to the subsurface injection of CO 2 are, among others, potential reactivation of faults and leakage of CO2 along them. This risk can be addressed by an accurate analysis of stresses and fractures within the injection area. Geomechanical modeling based on numerical methods provides a tool to understand the state of stress in the reservoir and in the surrounding area and the changes that can occur in response to CO2 sequestration. Fault stability and potential fault reactivation under reservoir pressure and temperature changes can be also assessed through geomechanical studies. Two different approaches have been followed in the present study both using Finite Element (FE) techniques to provide a comprehensive geomechanical analysis of the injection area. A structural analysis has been performed in order to describe the present-day state of stress and the slip tendency of the faults under this stress condition. A one-way coupled simulation allows to estimate the potential reactivation of the faults in response to CO2 injection in the subsurface, using history matching techniques. Geomechanical modelling approach A geomechanical study of the injection site is required in order to ensure safe CO2 storage. Two complementary modelling approaches have been followed to describe geomechanical features that are relevant to geosequestration, with a particular interest on fault stability. A 3D geological model derived from a 3D seismic interpretation (Ziesch et al., in prep.) of a public database of Otway basin (Urosevic et al. 2011) is the common basis for both models. Area of interest surrounds the injection site and has a maximum width of 8x5 km. An analysis of the tectonic stress field acting in the area of injection and its surrounding is provided using the commercial software Ansys®. Based on the FE method, this software allows to compute the in situ stresses for boundary conditions representing the regional stresses in order to study the local stress perturbations related to changes in mechanical properties as well as the presence of faults. Stability of faults is analysed from a structural point of view, estimating the slip and dilation tendency of each fault under the present-day stress conditions. The second geomechanical approach is a one-way coupled flow and geomechanics simulation that takes into account also the influence of CO2 injection on the 182 Institute of Applied Geosciences – Engineering Geology local stresses. Flow model has been computed with the Finite Difference software Eclipse®, while the geomechanical simulation has been performed using the Finite Element software Visage®, both from Schlumberger. The aim in this case is to assess fault stability and caprock integrity in relation to changes in pressure due to injection of CO2 in the subsurface. Structural geomechanical modelling The build-up of a 3D geomechanical model using the Finite Element (FE) software Ansys® requires the generation of a new volume model. The geometry is transferred from the original 3D geological model through a series of horizon lines and auxiliary lines. Horizon lines represent intersection between lithostratigraphic horizons and faults, while auxiliary lines are necessary in order to better reproduce the topology of surface patches used for reconstructing reservoir geometry (Henk and Fischer 2011). The model extends from the earth’s surface to the underburden layer of the reservoir and comprises 5 lithostratigraphic horizons and 10 faults (Fig. 1). Faults are modelled using contact elements, defined at both sides of the fault surfaces. Contact elements are able to reproduce frictional sliding that could occur between hanging wall and footwall. Mechanical properties from well logs and a literature review (Bérard et al. 2008, Vidal-Gilbert et al. 2010) are incorporated in the model through a layer-cake population process (Fig.1). Top 2800 m Dilwyn Fm Timboon Fm/ Paaratte Fm Skull Creek/Belfast Mudstone Waarre Fm Eumeralla Fm Figure 1: Layer-cake model for 3D structural geomechanical simulation. Each colour corresponds to a different lithostratigraphic unit. Boundary conditions derived from regional tectonic stresses are applied to the model by calibrated displacements. Results of this modelling approach include the description of the tectonic stresses acting in the reservoir and its surrounding, and the local stress perturbation related to the presence of faults and changes in mechanical parameters. Furthermore this 3D geomechanical model contributes to provide answers to fault stability issues through the estimation of slip and dilation tendency of faults under the in situ stress conditions computed. Institute of Applied Geosciences – Engineering Geology 183 One-way coupled flow and geomechanics simulation A one-way coupled flow and geomechanics simulation allows studying the response of reservoir and surrounding rock to changes in pore pressure due to production/injection of oil and gas. Although the same 3D geological model has been used, area of interest has been modified after some preliminary geomechanical studies. For this second modelling approach the 3D model has a width of 4x4 km, having its centre at the injection well (Aruffo and Henk 2013). The reservoir model for the flow simulation is even smaller, as injection of CO2 affects only the area immediately around the injection well. Flow model has been computed using the Finite Difference software Eclipse® using a history matching approach, constraining the model with injection data available. Simulation of CO2 injection into the subsurface provides as results changes in pressure inside the reservoir. These pressure data are used to couple the flow model with the geomechanical model, being used as input inside the Finite Element (FE) software Visage®. The coupling scheme involves 5 time steps at which pressure data are passed to the geomechanical simulator as pressure loads, so that effective stresses can be computed taking into account these pressure variations. Population of the mechanical properties in this case follows a moving average algorithm, taking into account vertical and lateral variation within the same lithostratigraphic unit. Faults are modelled as discontinuities, represented by a list of grid cells which intersect with the fault. Different material properties are assigned to each cell of the faults, such as dip value, dip direction, normal stiffness, shear stiffness, cohesion, friction angle, dilation angle and tensile strength. Regional tectonic stresses are again used to provide boundary conditions for the simulation. Results from the one-way coupled simulation comprise, among others, description of stress and strain in response to CO2. In particular, effective stresses can be used to assess fault stability at each time step. MohrCoulomb failure criterion has been chosen for this analysis, and for each cell belonging to a fault the distance to the failure envelope is calculated. The equation of the failure envelope for the Mohr-Coulomb criterion is: where σs is the shear stress, σn is the normal stress, C0 is the cohesion of the fault and μ is the friction coefficient of the fault. Assumptions for the Otway Project site lead to assign a value of 0.001MPa for cohesion, thus considering them almost cohesionless, and a friction coefficient of 0.6 (van Ruth et al. 2007). Fault analysis conducted in this way revealed that under these assumptions none of the fault cells reach the failure envelope for both linear and non-linear analysis (Fig. 2). Results from numerical simulation have been compared with previous analytical studies (Van Ruth et al., 2006 and 2007, Vidal-Gilbert et al., 2010) and also with an analytical model which uses exactly the same mechanical parameters and assumptions as the numerical study. 184 Institute of Applied Geosciences – Engineering Geology Figure 2: Mohr-Coulomb failure plot for faults (friction coefficient = 0.6) at the end of the injection stage. No failure is computed for each time step. Conclusions Geomechanical aspects of CO2 storage in the Otway area have already been investigated by van Ruth et al. (2006 and 2007) and Vidal-Gilbert (2010) during the assessment of the area undertaken by CO2CRC. Their analytical analyses focused on the immediate area of injection. The present work integrates these previous studies into a larger 3D geomechanical model for the CO2CRC Otway Project. Among others, fault stability and potential fault reactivation are considered to be critical factor of risk during geosequestration. Furthermore the expansion of the model up to the earth’s surface, allows to investigate also the stresses acting on the entire overburden, not only on the reservoir. A 3D structural geomechanical model describes the in situ stress and perturbations that may occur locally near faults or due to changes in mechanical properties. This first model covers an area of about 40 km2 and can assess fault stability under the present-day stress conditions, computing slip and dilatation tendency of faults. Additionally, a one-way coupled simulation model has been set up to study the impact of changes in pore pressure on the effective stresses acting in the reservoir and its surrounding. The area of interested has been restricted to 16 km2, following indications from preliminary geomechanical simulations. A fault stability analysis in this second case has been performed for each time step of the coupled simulation i.e. for different pressures acting on the reservoir. Modeling results suggest that fault failure is not a factor of risk under the calculated present-day stress conditions and the current assumptions regarding fault properties and the MohrCoulomb failure criterion. Acknowledgments This work was sponsored in part by the Australian Commonwealth Government through the Cooperative Research Centre for Greenhouse Gas Technologies (CO2CRC). PROTECT Institute of Applied Geosciences – Engineering Geology 185 (PRediction Of deformation To Ensure Carbon Traps) is funded through the Geotechnologien Programme (grant 03G0797) of the German Ministry for Education and Research (BMBF). The PROTECT research group consists of Leibniz Institute for Applied Geophysics in Hannover, Technical University Darmstadt, Helmholtz-Zentrum für Umweltforschung in Leipzig, Trappe Erdöl Erdgas Consultant in Isernhagen (all Germany) and Curtin University in Perth, Australia. C.M.A. would like to thank the Applied Geomechanics Team of Schlumberger based in Bracknell (UK) for their hospitality during a 3 month-internship. They provided invaluable support for C.M.A’s work and gave her the opportunity to use their technology. References [1] Aruffo, C. M. and Henk, A. [2013] Fault stability and potential fault reactivation analysis in Otway Basin, Australia. Fourth EAGE CO2 Geological Storage Workshop. [2] Bérard, T., Sinha, B. K., van Ruth, T., John, Z. and Tan, C. [2008] Stress Estimation at the Otway CO2 Storage Site, Australia. SPE Asia Pacific Oil and Gas Conference and Exhibition, 26, Perth, Australia. [3] Henk, A. and Fischer, K. [2013] Building and calibrating 3D geomechanical reservir models - a worked rd example. 73 EAGE Conference & Exhibition. [4] Jenkins, C. R., Cook, P. J., Ennis-King, J., Undershultz, J., Boreham, C., Dance, T., de Caritat, P., Etheridge, D. M., Freifeld, B. M., Hortle, A., Kirste, D., Paterson, L., Pevzner, R., Schacht, U., Sharma, S., Stalker, L. and Urosevic, M. [2011] Safe storage and effective monitoring of CO2 in depleted gas fields. Proceedings of the National Academy of Sciences 109(2), E35-E41. [5] Urosevic, M., Pevzner, R., Shulakova, V., Kepic, A., Caspari, E. and Sharma, S. [2011] Seismic monitoring of CO2 injection into a depleted gas reservoir–Otway Basin Pilot Project, Australia. Energy Procedia 4(0), 3550-3557. [6] van Ruth, P. and Rogers, C. [2006] Geomechanical analysis of the Naylor structure, Otway Basin Australia. CO2CRC (RPT06-0039), 26. [7] van Ruth, P., Tenthorey, E. and Vidal-Gilbert, S. [2007] Geomechanical Analysis of the Naylor structure, Otway Basin, Australia - Pre-injection. CO2CRC (RPT07-0966), 27. [8] Vidal-Gilbert, S., Tenthorey, E., Dewhurst, D., Ennis-King, J., Van Ruth, P. and Hillis, R. [2010] Geomechanical analysis of the Naylor Field, Otway Basin, Australia: Implications for CO2 injection and storage. International Journal of Greenhouse Gas Control 4(5), 827-839. [9] Ziesch, J., Aruffo, C. M., Tanner, D. C., Beilecke, T., Weber, B., Dance, T., Tenthorey, E., Henk, A. and Krawczyk, C. M. [in prep.] Structural evolution of the CO2CRC Otway Project pilot site, Australia: fault dynamics based on quantitative 3D seismic intepretation. Basin Research. 186 Institute of Applied Geosciences – Engineering Geology Geothermal Science and Technology Geothermal Energy is defined as the heat of the accessible part of the earth crust. It contains the stored energy of the earth which can be extracted and used and is one part of the renewable energy sources. Geothermal Energy can be utilized for heating and cooling by applying heat pumps as well as it can be used to generate electricity or heat and electricity in a combined heat and power system. The field of Geothermal Science has natural scientific and engineering roots. Geothermal Science connects the basic knowledge with the requirements of practical industry applications. Geothermal Science is in interdisciplinary exchange with other applied geological subjects such as hydrogeology and engineering geology and therefore is a logic and proper addition to the research profile of the Technische Universität Darmstadt. The broad implementation of geothermal energy applications and the utilization of the underground as a thermal storage will help to reduce CO2 emissions and meet the according national and international climate protection objectives. Furthermore, the utilization of geothermal energy will strengthen the independency on global markets and the utilization of domestic resources. Geothermal Energy will be an essential part of the decentralized domestic energy supply and will contribute an important share of the desired future renewable energy mix. Regarding the worldwide rising importance of renewable energy resources, Geothermal Science is one of the future's most important field in Applied Geosciences. In 2009, the industry-funded Chair for Geothermal Science and Technology was established at the TU Darmstadt – the first foundation professorship in energy science of the university. The Chair of Geothermal Science and Technology deals with the characterization of geothermal reservoirs, starting from basic analyses of thermo-physical rock properties, which lead to sophisticated calculation of the reservoir potential of distinct rock units. Reliable reservoir prognosis and future efficient reservoir utilisation is addressed in outcrop analogue studies world-wide. Organisation of a highly qualified geothermal lab and experimental hall (TUDA HydroThermikum) started already in 2007 and was continued in 2013. Field courses and excursions in 2013 focused on geothermal energy in New Zealand, Jordan, Germany and Austria. Staff Members Head Prof. Dr. Ingo Sass Research Associates M.Sc. Achim Aretz M.Sc. Swaroop Chauhan Dipl.-Ing. M.Sc. Sebastian Homuth Dipl.-Ing. Robert Priebs (until 31.03.2013) Dr. Wolfram Rühaak Dipl.-Ing. Johannes Stegner Dr. Kristian Bär M.Sc. Claus-Dieter Heldmann Dipl.-Geol. Philipp Mielke Dipl.-Ing. Mathias Nehler (until 31.05.2013) Dipl.-Ing. M.Sc. Johanna Rüther Dipl.-Ing. Rafael Schäffer Dipl.-Ing. Bastian Welsch Technical Personnel Gabriela Schubert Rainer Seehaus Secretaries Simone Roß-Krichbaum Dunja Sehn (until 30.03.2013) Institute of Applied Geosciences – Geothermal Science and Technology 187 PhD Students Dipl.-Ing. Hauke Anbergen Dipl.-Geol. Ulf Gwildis Dipl.-Geol. Clemens Lehr M.Sc. Daniel Schulte Dipl.-Ing. Christoph Drefke M.Sc. Yixi Gu M.Sc. Liang Pei Students Bemmlott, Juliane Brauner, Sebastian Dönges, Florian Hochstein, Tim Hofheinz, Andreas Jensen, Benjamin Lewang, Alexander Orendt, Robert Ratz, Konstantin Rybak, Thomas Schmidt, Stefanie Schmitz, Thomas Schwalb,jörn Sikora, Christiane Trojanowski, Dominik Weinert, Sebastian Wiesner, Peter Zimmermann, Philipp Brand, Paul Brettreich, Frank Hesse, Jan Hoffmann, Hellmuth Hubert, Michel Kappas, Jan-Dominik Matzikanides, Damianos Philipp, Alexej Rautenberg, Stefan Schedel, Markus Schmitt, Tobias Schreiter, Inga Torres Melo Santos Craizer, Rafaela Weber, Jan Niklas Weis, Julian Yenna, Divya Sai Sri Guest Scientists Prof. Dr. Michael Alber (Ruhr-Universität Bochum, Ingenieurgeologie/Felsbau) Dr. Jörg Baumgärtner (BESTEC GmbH) Prof. Dr. Victor Bense (University of East Anglia, Norwich/ England) JProf. Dr. Andreas Englert (Ruhr-Universität Bochum) Prof. Dr. Jens Hartmann (Universität Hamburg) Prof. Dr. Michael Himmelsbach (Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Hannover) Prof. Dr. Michael Kersten (Johannes-Gutenberg Universität Mainz) Prof. Dr. Michael Kühn (Deutsches Geoforschungszentrum (GFZ) Potsdam/Universität Potsdam) Dr. Christian Lerch (Geschäftsführer der Pfalzwerke geofuture Geofuture GmbH) Dr. Naser Meqbel (Deutsches Geoforschungszentrum (GFZ) Potsdam) Prof. Dr. Horst Rüter (Geschäftsführer der HarbourDom GmbH, Vizepräsident der Geothermischen Vereinigung) Prof. Dr. Eva Schill (Université de Neuchâtel) B.Sc. Chiranth Hedge, National Institute of Technology Karnataka, Surathkal, Indien; 11 week Internship in Fracture Flow Modelling 188 Institute of Applied Geosciences – Geothermal Science and Technology Guest Lecturers Dr.-Ing. Ulrich Burbaum, CDM Consult Alsbach Dr. Thomas Nix, LBEG Hannover Prof. Dr. Christoph Spötl, Universität Insbruck Dr. Thomas Kölbel, EnBW Karlsruhe Dipl.-Geol. Stefan Knopf, Krebs und Kiefer Ingenieure, Karlruhe Dipl.-Ing. Jörn Müller, CDMSmith Consult GmbH, Alsbach Research Projects started in 2013 Simulation und Evaluierung von Kopplungs- und Speicherkonzepten regenerativer Energieformen zur Heizwärmeversorgung Funding: 1.5 years, Energietechnologieoffensive Hessen, HA Hessen Agentur GmbH Entwicklung von numerischen Simulations- und Parameterschätzerverfahren zur ThermoHydro-Mechanisch gekoppelten Simulation des Untergrunds - Kurztitel: THM-Modul BMU/PTH Research proposal, Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit Integrated Methods for Advanced Geothermal Exploration - IMAGE Geldgeber: EU - Seventh Framework Programme (FP7) - ENERGY.2013.2.4.1: Exploration and assessment of geothermal reservoirs Research Projects continued and finalized in 2013 Geothermische Untersuchungen an den Tiefbohrungen des Geothermieprojektes Geretsried Funding: 2012-2013, ENEX Power Germany GmbH, ongoing Market Report Study on Deep Geothermal Energy in Europe Funding 2013, Ed. Züblin AG, finalized Quantitativer Einfluss des Wasserhaushalts, der Umwelttemperatur und der geothermischen Kennwerte auf die Wärmeableitung erdverlegter Starkstromkabel Funding: 2 years, E.ON Bayern AG Experimentelle Untersuchungen zur Verifizierung eines Mehrphasenmodells Wärmetransportverhalten im Untergrund Funding: 3 Years, Bundesministerium für Wirtschaft und Technologie für das Machbarkeitsstudie „Machbarkeit und Nutzung von tiefer geothermischer Energie am Flughafen Frankfurt Funding: 2010-2013, FRAPORT AG Charakterisierung des Geothermischen Reservoirpotenzials des Permokarbons in Hessen und Rheinland-Pfalz Funding: 3 Years, Bundesministeriums für Umwelt, Naturschutz und Reaktorsicherheit Institute of Applied Geosciences – Geothermal Science and Technology 189 Entwicklung von wartungsarmen PEHD-Filterelementen für oberflächennahe geothermische Brunnenanlagen Funding: 3 Years, Deutsche Bundesstiftung Umwelt Scientific consulting and supervision of enhanced hydrothermal power plant systems, Upper Rhine Valley Private clients, confidential. Evaluation of thermal response tests using a cylinder source approach (Type Curve Fitting Method) – Industry-funded project (Geotechnisches Umweltbüro Lehr). Development of a thermal conductivity measuring device for soil or cuttings In collaboration with DIN-Innovation of normalisation and standardization. Untersuchungen zur Radon-Emanation im Bereich der Heilquellen und Heilbrunnen Bad Soden-Salmünsters Funding: 6 months, Spessart-Therme Kur- und Freizeit GmbH Wiss. Beratung Sanierung Spruedelfassungen Sprudelhof Bad Nauheim, Funding: 18 months, Stiftung Sprudelhof Bad Nauheim Quellbeweissicherung der Erdwärmebohrungen des Sporthotel Stock, Finkenberg, Tirol, Österreich Funding: 2 months, Sporthotel Stock GmbH Publications Anbergen, H. & Sass, I. (2013): Freeze-Thaw-Behaviour: Observations in Grouted Borehole Heat Exchangers. - In: Thirty-Eighth Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, California, February 11 - 13, SGP-TR-198. Aretz, A., Bär, K., Sass, I. (2013): Charakterisierung des geothermischen Reservoirpotenzials des Permokarbons in Hessen und Rheinland-Pfalz – thermophysikalische und hydraulische Gesteinskennwerte. Swiss Bulletin für angewandte Geologie, Vol. 18/1, 2013, S. 33-41. Arndt, D. & Bär, K. (2013): Geologische 3D-Modellierung und multikriterielle Potenzialbestimmung. Geothermie.ch - Zeitschrift der Schweizerischen Vereinigung für Geothermie SVG, 54: 22-24. Chauhan, S., Rühaak, W., Enzmann, F., Khan, F., Mielke, P., Kersten, M., Sass, I. (2013): Comparison of Micro X-ray Computer Tomography Image Segmentation Methods: Artificial Neural Networks Verses Least Square Support Vector Machine'', Mathematics of Planet Earth, Lecture Notes in Earth System Sciences, pp 141-143; DOI: 10.1007/978-3-642-32408-6_34. Hegde, C., Rühaak, W, Sass, I. (2013) Evaluation of Modelling of Flow in Fractures. Proc. of Int. Conf. on Advances in Civil Engineering, AETACE. DOI: 02.AETACE.2013.4.24 Homuth, S., Hamm, K., Sass, I. (2013): BHE logging and cement hydration heat analyses for the determination of thermo-physical parameters. Bulletin of Engineering Geology and the Environment, Volume 72, Issue 1, Page 93-100, Springer Verlag Berlin Heidelberg. DOI 10.1007/s10064-012-0455-2 190 Institute of Applied Geosciences – Geothermal Science and Technology Rühaak, W., & Sass, I., (2013): Applied Thermo-Hydro-Mechanical Coupled Modeling of Geother-mal Prospection in the Northern Upper Rhine Graben. - In: Thirty-Eighth Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, California, February 11 - 13, SGP-TR-198. Rüther, J. & Sass, I. (2013): Entwicklung poröser Filterelemente aus hochdichtem Polyethylen für geothermale Brunnenanlagen, bbr- Fachmagazin für Wasser und Leitungsbau, 04/2013, 64-69. Sass, I. (2013, Gelbdruck): Empfehlungen des Arbeitskreises Geothermie. Oberflächennahe Geother-mie „Planung, Bau, Betrieb und Qualitätssicherung“. FH-DGG und FI-DGGT/DGG. Berlin, Germany, Ernst & Sohn. Schäffer, R. & Sass, I. (2013): The Thermal Springs of Jordan. - Environmental Earth Sciences. DOI 10.1007/s12665-013-2944-4. Institute of Applied Geosciences – Geothermal Science and Technology 191 Optimizing High Temperature Borehole Thermal Energy Storage Systems Daniel O. Schulte, Bastian Welsch Due to its seasonal changes, solar energy presents a suitable source to setup a storage system with borehole heat exchangers (BHE). Excess heat is fed in during summer and extracted in winter. A couple of requirements have to be met by such a system: the stored heat must remain in place and the working fluid must maintain an extraction temperature sufficiently high for the specific heating purpose at all times. Storing heat at temperature levels of up to 90 °C has a key benefit, compared to low temperature energy storage, because higher loading temperatures in the summer season result in higher unloading temperatures during the heating period in winter. This makes the high temperature storages suitable for applications in existing building stock with radiator heating systems. Furthermore, a higher overall efficiency of the heating system can be achieved. However, higher temperature levels in the storage system increase the heat losses, due to a higher temperature gradient with respect to the surrounding subsurface. As ground temperature increases with depth, the installation of deep borehole heat exchanger systems at depths of 400 m up to 1500 m is considered to minimize these thermal losses. In this study the potential of High Temperature Borehole Thermal Energy Storages (HT-BTES) is presented. The most important rock properties for HT-BTES are a high specific heat capacity, a medium thermal conductivity and a low hydraulic conductivity. Igneous rocks from the Paleozoic Odenwald Crystalline Basement seem to match all of these requirements. As part of an outcrop analogue study 76 rock samples from the crystalline basement were collected in the vicinity of Darmstadt. Further samples of the crystalline basement were taken from two research boreholes close to the Messel Pit. Porosities and thermal conductivities were determined from the collected samples to gain input parameters for numerical underground models. Figure 2: Numerical model of an exemplary borehole thermal energy storage. The storage consists of 4 BHEs with a length of 1000 m and a distance of 10 m between the boreholes. The window on the right side shows the positions of the BHEs on the model surface. 192 Institute of Applied Geosciences – Geothermal Science and Technology First calculations were made, using the finite element program FEFLOW [1] for modeling the heat transport processes in the BHE and in the crystalline rocks. The initial results indicate, that there is a strong dependence of the performance of such storage systems on the alignment and the depth of the BHEs. Since drilling is the most critical cost factor, the required number of BHE and the respective BHE length, need to be optimized. Thus, various BTES configurations are compared. The previously optimized shape and parameters of the BHEs, the overall length of the BHEs as well as the flow rate and the inlet temperatures are kept constant, whereas the number of boreholes, the length of the boreholes and the distance between the boreholes are varied, to identify the system designs with the highest heat recovery rate possible. As a second step, possible variations of the operational mode and other technical parameters are taken into account as well. However, this “try-and-error-scheme” of parameter alteration in FEFLOW is very time consuming. Thus, an efficient solution to this problem requires mathematical optimization techniques, which minimize the number of required iterations. A simplified MATLAB model is developed to simulate the thermal behavior of a HT-BTES. Our approach goes beyond the problems discussed in Beck et al. [2013]: a more detailed physical description of the underlying processes is applied. The BHE storage system is simulated with a set of MATLAB functions, which dynamically calculate the conductive heat transport within the subsurface, employing a finite element method algorithm [3] and also the heat transfer within the BHE [4]. To allow the computation of large numbers of models to test different BHE set-ups, Fig. 3: Underground temperature distribution the code uses a fully unstructured tetrahedron in 400 m depth with four BHE after 10 years mesh, which is specifically refined around the BHE. of constant loading with 90°C in each BHE. For the meshing TetGen [5] is used. For solving the optimization problem, a Monte-Carlo technique [6] is applied as a comparably simple approach. Additionally mathematical optimization algorithms will be applied to evaluate their potential to solve these problems in a more efficient way: genetic algorithms [7], which mimic natural selection in the process of developing an optimal solution as well as simulated annealing [8], which iteratively improves a candidate solution with respect to a quality threshold. [1] [3] [4] [5] [6] [7] [8] Diersch, H.-J., 2014. FEFLOW Finite Element Modeling of Flow, Mass and Heat Transport in Porous and Fractured Media. Springer-Verlag Berlin Heidelberg, 384 p. Alberty, J.,Carstensen, C. and Funken, S.A., 1999. Remarks around 50 lines of Matlab: short finite element implementation, Numerical Algorithms, 20(2-3): 117-137. Eskilson, P. and Claesson, J, 1988. Simulation model for thermally interacting heat extraction boreholes, Numerical Heat Transfer, 13: 149-165. Si, H., 2011. Constrained Delaunay tetrahedral mesh generation and refinement. Finite elements in Analysis and Design, 46 (1-2): 33-46. Sabelfeld, K.K.: Monte Carlo Methods in Boundary Value Problems, 1991. Springer Series in Computational Physics: Springer-Verlag, Printed in the United States of America 281 p. Goldberg, D.E., 1989. Genetic Algorithms in Search, Optimization and Machine Learning (1st ed.). Addison-Wesley Longman Publishing Co., Inc., Boston, MA, USA, 372 p. Kirkpatrick, S., Gelatt Jr., C.D., and Vecchi, M.P., 1983. Optimization by Simulated Annealing. Science, 220 (4598), 671-680. Institute of Applied Geosciences – Geothermal Science and Technology 193 Investigation of hydrothermal springs and geothermal exploration of an Alpine Marble Karst, Tuxertal, Tirol, Austria Claus-Dieter Heldmann, Ingo Sass, Rafael Schäffer The thermal springs in Hintertux are probably the highest of Europe in 1500 m above sea level. More than 20 outlets originate with 20 °C in an alluvial fan at the foot of Schmittenberg Mountain. For more than 150 years they are used for balneological and medicinal purposes. Although they are well-known, no comprehensive genetic explanation of the temperature anomaly’s origin is given yet. Since 2012 these and other sources of the valley are under hydrochemical investigation. The hydrochemical characteristics are used to identify the hydrogeochemical signatures of every geological unit and so associated with the origin of every spring (fig. 1). The Tuxertal is a sport region with energy-intensive tourism and a huge demand for heating and water in spa attractions. The unique geology of an alpine karst aquifer, reaching over the whole valley, bearing thermal springs and its geothermal potential is under research now. The high solubility of the carbonates in the late Jurassic Hochstegen Marble is the reason for the karstification. The first geothermal systems in these rocks was installed in 2013 in the form of a 400 m deep borehole heat storage under a large hotel complex for 1 GWh heating and 0.3 GWh cooling per year [1]. Before a sustainable, feasible exploration can be started, investigations must deliver more data about geothermal properties and explain dependencies between the aquifers and the thermal springs. The hydrochemical field parameters temperature, electrical conductivity, pH value, redox potential, oxygen saturation and the carbonate concentration were determined in-situ. The concentrations of iron, manganese and the major ions were analyzed by atomic absorption spectrometry and ion gas chromatography. Non-published hydrochemical data of measurements from 1969 to 1974 and 1993 to 2008 were evaluated for showing annual and seasonal trends and for correlation purposes. The study includes 6 thermal springs and 15 non-thermal springs. Borehole loggings of the Hochstegen Marble in Finkenberg and an Enhanced Geothermal Response Test detected karst structures and high ground water velocities below 200 m below surface. The previous hypothesis of meteoric water seeping into the crevices of the gneisses followed by local rising in fault zones during the Hochstegen Marble cannot explain the composition of the thermal water. Although water can migrate in transregional faults like the Olperer Shear Zone, their steep falling and distance does not fit to the hypothesis. However the alpine geothermal gradient is so low that this scenario is difficult considering hydraulic situations. The increased sodium and magnesium content shown in the analyses remain unnoticed in hypothesis. The high Mg/Ca ratio results from magnesium enrichment in dolomitized areas or maybe formations which are not considered in this area (e.g. Aigerbach formation). In the new hypothesis a mixed origin is be assumed. If the origin of the temperature anomaly is a crystalline reservoir, this can explain the contents of sulfate, sodium and potassium. Due to concentrations approximately 50 % of the water volume could originate from such a reservoir. Accordingly, higher reservoir temperatures must be assumed, what is even underpinned by the magnesium corrected Na-K-Ca chemical geothermometer giving 90 °C [2]. Because currently only little amount of the water is used and only with the surface temperature of 20 °C, drilling wells into the heat plume will provide more hot water. 194 Institute of Applied Geosciences – Geothermal Science and Technology Figure 1: Tectonic units and characteristic hydrochemical signatures attributed by Stiff diagrams, Tux Valley, Tyrol, Austria. of the geothermal heat exchangers and surrounding springs at Finkenber [3]. Karst aquifers can affect advantageously the efficiency of geothermal systems due to its elevated permeabilities. However, karst aquifer properties require special exploration and exploitation. The marble karst aquifer of the Hochstegenformation was investigated to construct a middle deep borehole heat exchange storage at Finkenberg, Austria. Investigations of streams and springs all over the Tuxertal led to an attribution of characteristic hydrochemical signatures to each tectonic unit in accordance to its lithology Institute of Applied Geosciences – Geothermal Science and Technology 195 (Fig. 1). Determining the surroundings of Finkenberg it became evident, that the geological catchment of the Hochstegenformation reaches there from 840 to 2650 m above sea level. Results of geological mapping and an exploration well showed that the tectonic situation is much more complex than described in the official geologic map. The Hochstegenformation can reach locally significant higher thicknesses than estimated before. In addition, the layer sequence is more unconformable as supposed. Karstified zones till 400 m depth could be detected within the boreholes (Fig. 2). Groundwater flow velocities up to 14 m/d were measured. The drilling operations were accompanied by a conservation of evidences at neighbouring springs. Thereby collected data allow the calculation of gap flow velocities. A total number of nine 400 m deep boreholes were drilled. The borehole heat exchange storage system has an abstraction performance of 1 GWh/a and 400 MWh/a storage performance. The successful conclusion of this project and gathered knowledge up to now led to the idea to explore the Hochstegenformation for extensive geothermal use. Exploration of a 1200 m deep well for hydrothermal use is in process now. Figure 2: a): Geological map of the drilling site and location of the boreholes. b): Results of the logging in borehole 6. References [1] [2] [3] 196 SASS, I. & LEHR, C. (2013): Design Parameter Acquisition of an Underground Heat Storage and Extraction System. – Proc. Thirty-Eigth Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California. FOURNIER R. O. & POTTER R. W. (1979): Magnesium correction to the Na-K-Ca chemical geothermometer, Geochimica and Cosmochimica, Vol. 43, pp 1543–1550. SASS, I., HELDMANN, C.-D. & SCHÄFFER, R. (2014, submitted): Geothermische Erschließung und hydrogeologische Beweissicherung des Hochstegenmarmors, Tuxertal. Grundwasser. Institute of Applied Geosciences – Geothermal Science and Technology Applied Sedimentology Sedimentary rocks cover about 75% of the earth’s surface and host the most important oil and water resources in the world. Sedimentological research and teaching at the Darmstadt University of Technology focus on applied aspects with specific emphasis on hydrogeological, engineering and environmental issues. One key issue in this context is the quantitative prediction of subsurface reservoir properties which is essential in modelling of regional groundwater hydrology, oil and gas exploration, and geothermal exploitation. However, also basic sedimentological research is carried out, e.g. the use of sediments as archives in earth history to reconstruct geodynamic, climatic and environmental processes and conditions in the past. To predict groundwater movement, pollutant transport or foundations of buildings in sedimentary rocks a detailed knowledge about the hydraulic, geochemical or geotechnical properties is needed which often vary about several magnitudes. This kind of subsurface heterogeneity can be related to distinct sedimentological patterns of various depositional systems. In addition, changes of depositional systems with time can be explained by specific controlling parameters e.g. changes in sea level, climate, sediment supply and are nowadays described by the concept of sequence stratigraphy. The research in applied sedimentology also includes modelling of erosion and sediment transport and its implication for the management of rivers and reservoirs with the help of GIS. For any subsurface management a quantitative 3D model is a prerequisite, either related to water and geothermal energy or to gas, oil, and CO2 storage. Together with the groups of Prof. Schüth (Hydrogeology), Prof. Sass (Geothermics), and Prof. Henk (Engineering Geology) the sedimentology group focusses on detecting the large to meso-scale sedimentary architecture and permeabilities of sedimentary reservoir rocks in order to achieve an optimized subsurface management of water and renewable energy resources. Dr. Hornung received a grant from Shell to analyse small-scale heterogeneities of porosities and permeabilities of sedimentary rocks and their link to microfacies patterns. To detect subsurface heterogeneities at a high resolution, the sedimentology group hosts a georadar equipment for field measurements. This geophysical device is composed of various antennas and a receiver unit. Sophisticated computer facilities are provided to process the data and construct real 3D subsurface models. The group shares their equipment and facilities with the Universities of Frankfurt (Applied geophysics), Tübingen (Applied sedimentology), the RWTH Aachen and industrial partners. These institutions founded the Georadar-Forum which runs under the leadership of Dr. Jens Hornung (http://www.georadarforum.de/). Thanks to funding via a DFG research grant we could invest into a shear wave measuring unit, which will extent our abilities for subsurface surveys down to several hundred meters and through materials, weakly penetrable by electromagnetic waves. Here we cooperate with the Leibniz Institute for Applied Geophysics in Hannover. For quantification of reservoir properties a self-constructed facility for permeability measurements of soil and rock materials exists which is further developed. This lab is also fundamental to geothermal research. In 2013, the group participated in the DFG Research Unit RiftLink (www.riftlink.de) and two European Research Groups within the EUCORES Programme (TOPOEurope, SedyMONT). The topic of these research projects are in the context of earth surface Institute of Applied Geosciences – Applied Sedimentology 197 processes, palaeoenvironmental reconstructions and georisk assessments. For the DFG Research Unit RiftLink we received an additional funding for one year from DFG. Furthermore, a project in Saud Arabia runs in the context of exploring deep water resources together with Prof. Schüth (Hydrogeology) and in cooperation with the GIZ (Gesellschaft für I(nternational Zusammenarbeit), the UFZ (Umweltforschungszentrum Halle-Leipzig), and the Ministry of Water and Energy of Saudi Arabia (MOEWE). The aim is to investiate the storage properties of large sedimentary aquifers and their relation to the amount and quality of substracted groundwater in a hyperarid area suffering from water scarcity. A Saudi Arabian student from the MOEWE received his PhD from TU Darmstadt in 2013. This forms the basis for further cooperation and future projects in the region. One outcome is the submission of a DFG proposal in order to elucidate the provenance of the widespread sandstones on the Arabian Peninsula which host most water resources of Saudi Arabia but whose quality partly suffer from increased radioactivity. At the moment a second proposal to MOEWE is prepared. Based on previous work of the group several research initiatives are running at the moment, e.g. past environmental pollution in Central Europe as reconstructed from lake sediments, Mesozoic palaeoenvironmental evolution in NW China (initiative together with University of Bonn and Jilin University, China), and high-resolution palaeoclimatic studies in Messel and similar maar lakes (DFG). Jianguang Zhang continued his PhD with a Chinese grant. Dr. Dorthe Pflanz joined the sedimentology group and prepared a DFG proposal about palaeoclimatic implications of loess and sand dune deposits in southern Hessen. Thanks to constructing a new gas pipeline from Gernheim to Hercherode she could sample a complete transect from the Rhine plain to the central Odenwald. Several BSc and MSc theses could be attached to this project. Based on this unique sample collection, Dr. Pflanz could establish the first absolute chronology of these eolian deposits in southern Hessen. The results have been presented on a conference and are now going to be published. Prof. Hinderer is still member and speaker of the "Wissenschaftlicher Beirat Beschleunigungsmassenspektrometer, DFG University of Cologne” and was nominated by the DFG senat commission of common geoscientific research (DFG-Senatkommission Zukunftsaufgaben der Geowissenschaften). He is also the representative of the Germanspeaking sedimentologists (Section of Sedimentology in Geologische Vereinigung and SEPM-CES) and co-organized the SEDIMENT conference in Tübingen 2013. He keeps on being a member of the editorial board of the International Journal of Earth Sciences. In 2013, the vacant position for the technical personnel could be filled with Reimund Rosmann who works part time also in the Engineering Geology group of Prof. Henk. Staff Members Head Prof. Dr. Matthias Hinderer Research Associates Dr. Jens Hornung Postdoctoral Students Dorthe Pflanz 198 Dr. Olaf Lenz Institute of Applied Geosciences – Applied Sedimentology PhD Students Hussain Al-Ajmi Alexander Bassis Dennis Brüsch Daniel Franke Technical Personnel Reimund Rosmann Secretary Kirsten Herrmann Inge Neeb Frank Owenier Sandra Schneider Jianguang Zhang Research Projects Linking source and sink in the Ruwenzori Mountains and adjacent rift basins, Uganda: landscape evolution and the sedimentary record of extreme uplift: Subproject B3 of DFG Research Group RIFT-LINK “Rift Dynamics, Uplift and Climate Change: Interdisciplinary Research Linking Asthenosphere, Lithosphere, Biosphere and Atmosphere” (DFG HI 643/72). Spatial distribution of modern rates of denudation from cosmogenic Nuclides and Sediment Yields throughout the Alps (EUCORES programme TOPOEurope, Research Unit TOPO Alps, IP 3, DFG HI 643/9-1). High resolution 3D architectural analysis and chronology of alluvial fan deposits in mountain landscapes: A case study of the Illgraben fan, Switzerland (EUCORES programme TOPOEurope, Research Unit SedyMONT, IP 6, DFG HI 643/10-1). Monitoring of soil water content with ground penetrating radar (PhD thesis). Climatic and tectonic interplay in central Asian basins and its impact on paleoenvironment and sedimentary systems during the Mesozoic (1 PhD thesis). Sedimentology, dynamic stratigraphy and hydrofacies model of Paleozoic and Mesozoic aquifers in Saudi Arabia. (PhD thesis financed by Umweltforschungszentrum Leipzig-Halle, GIZ Eschborn, and the Ministry of Water and Energy in Riyadh, Saudi Arabia). Provenance of Paleozoic clastic sediments and reasons for radioactive anomalies in groundwaters on the Arabian Platform (PhD thesis) Aggradation of alluvial fans in the Eastern Cordillera in response to humidity changes and a climate gradient from the Altiplano to theAmazon Basin (two Master theses and preparation of a DFG project) Periglacial eolian sediments in southern Hessia, their chornology, and their genesis (Diploma und BSc theses and preparation of a DFG project) 2-D heterogeneities of poroperm, ultrasonic and resistivity on sub-meter scale (funded by Shell) Institute of Applied Geosciences – Applied Sedimentology 199 Publications [1] Arp, G., Blumenberg, M., Hansen, B.T., Jung, D., Kolepka, C., Lenz, O.K., Nolte, N., Poschlod, K., Reimer, A., Thiel, V. (2013): Chemical and ecological evolution of the Miocene Ries impact crater lake, Germany: a reinterpretation based on the Enkingen (SUBO 18) drill core. GSA Bulletin, doi: 10.1130/B3073.1. [2] Hinderer, M., Kastowski, M., Kamelger, A., Bartolini, C., Schlunegger, F., (2013): River loads and modern denudation of the Alps – a review, Earth Science Reviews. [3] Hinderer, M., Pflanz, D., Schneider, S. (2013): Chemical denudation rates in the humid tropics of East Africa and comparison with 10Be-derived erosion rates. WRI-14 Avignon 2013. Procedia Earth and Planetary Science. [4] Lenhardt, N., Böhnel, H., Hinderer, M. & Hornung, J. (2013): Paleocurrent direction measurements in volcanic settings by means of anisotropy of magnetic susceptibility: A case study from the Lower Miocene Tepoztlán Formation (Transmexican Volcanic Belt, Central Mexico). J. of Sedimentology [5] Lenhardt, N., Herrmann, M. & Götz, A.E. (2013): Palynomorph preservation in volcaniclastic rocks oft he Miocene Tepoztlan Formation (Central Mexico) and implications for palaeoenvironmental reconstruction. Palaios 28(10): 710-723. 200 Institute of Applied Geosciences – Applied Sedimentology OSL- Dating of a glacial dune field in the upper Rhine valley: a transect study Dorthe Pflanz1, Alexander Kunz2, Matthias Hinderer1 1 TU Darmstadt, Institute of Applied Geosciences, Schnittspahnstr. 9 D-64287 Darmstadt National Taiwan University, Department of Geosciences,Luminescence Dating Laboratory, No.1 Sec.4, Roosevelt Road, Taipei 106, Republic of China (Taiwan) 2 In this study aeolian sands are investigated which are largely extend in the Upper Rhine Valley. Especially in the area of Darmstadt/Zwingenberg they form thick dune fields covering the upper Lower Terrace of the Rhine River. The aeolian sands are subdivided into different units by paleosoil horizons, gravel layers or unconformities indicating periods of non-deposition. Transport and deposition of aeolian sands could only take place when the flood plain of the Rhine river was dry (Löscher 1994). In this area, the sand forms parabolic dune fields. This gives us a hint of dry climate with a steppe vegetation cover during sedimentation. It is generally supposed that the main deposition of the sand happened during the LGM and terminated during the Younger Dryas (Becker 1967). Several studies show that the dunes were very likely reactivated during the Holocene (e.g. Baray & Zöller 1993; Semmel 1980). So far, however, no absolute ages for these dune deposits (“Bergsträsser Flugsande”) were available. We took the opportunity to sample the dune belt between Bickenbach and Seeheim-Jugenheim south of Darmstadt along a trench which was shortly excavated for constructing a new gas pipeline. Besides Samples for OSL dating we analysed grain sizes, carbonate content, and magnetic susceptibility. Fig. 1: Position of the Gas- pipeline in the Northern Upper Rhine Graben. Institute of Applied Geosciences – Applied Sedimentology 201 OSL dating was done on quartz with a grain size of 100-150 µm using the SAR protocol following Wintle and Murray (2006). Standard tests as preheat-dose recovery and dose recovery test have been done to find the optimum parameters for the SAR protocol. Linear modulated optical stimulated luminescence (LM-OSL) has been done for all samples. The LM-OSL signal curves were analyzed using curve fitting procedures introduced by Choi et al. (2006). Results show that the quartz OSL signal from all samples is dominated by the fast component. Interestingly there are regional differences in the amount of medium and slow components. This could indicate different source areas of the dune sands but needs further investigation. Fig. 2: Cross section of the investigated dune field and OSL dating results. Preliminary OSL ages generally confirm that the major accumulation of the dune sands happened during the LGM and lastest until the Younger Dryas, i.e. until 11600 years BP. Moreover, Holocene reactiviation could be proved by two ages. Dating and further sedimentological analysis is going on and a publication is under preparation. One diploma thesis and one BSs thesis was attached to this study. The first author was appointed as a temporal postdoc (Dr. Dorthe Pflanz) and prepared a DFG proposal for an own position. This opportunity is highly acknowledged. The submission of the proposal is delayed because of this unique chance to sample continuously a transect. It is now ready for submission. References 1. 2. 3. 4. 5. 6. 202 Choi, J. H., Duller, G. A. T., and Wintle, A. G. (2006): Analysis of quartz LM-OSL curves. Ancient TL 24, 9-20. Baray, M. & Zöller, L. (1993): Aspekte der Thermolumineszenz-Datierung an spätglazialholozänen Dünen im Oberrheingraben und in Brandenburg. – Berliner geogr. Arb., 78(1):1-33. Becker, E. (1967): Zur stratigraphischen Gliederung der jungpleistozänen Sedimente im nördlichen Oberrheintalgraben. – Eiszeitalter Gegenw., 18: 5-50. Löscher, M. (1994): Zum Alter der Dünen auf der Niederterrasse im nördlichen Oberrheingraben.– Beih. Veröff. Natursch. Landschaftspfl. Baden-Württemberg, 80: 17-22. Semmel, A. (1980): Quartär. – In: Golwer, A. & Semmel, A.: Erläuterungen zur Geologischen Karte von Hessen 1:25 000, Bl. 5917 Kelsterbach. – 3., neu bearb. Aufl.: 25-49. Wintle, A. G., and Murray, A. S. (2006): A review of quartz optically stimulated luminescence characteristics and their relevance in single-aliquot regeneration dating protocols. Radiation Measurements 41, 369-391. Institute of Applied Geosciences – Applied Sedimentology Geo-Resources and Geo-Hazards Mes of rapid population growth and the resulting strain of the resilience of natural systems, geosciences in particular have become an increasingly important research area. However, geoscientific knowledge about material flows from and back into the environment and about the prevention of catastrophic consequences of big natural phenomena is often not understood by decision makers, who were not able to spend long years on understanding the four-dimensional space-time-development of our earth. On the other hand, the metabolism of cities, its growing needs for clean water and raw material for constructions while simultaneously egesting waste into its neighbourhood, require a thorough understanding of its undergrounds and peripheries as well as safe construction sites. Computer based Geo Information Systems and 3 to 4D-techniques are powerful tools to qualify and to quantify resources and hazards in the peripheries of urban areas. They enable the aggregation of complex geological and spatial data to thematic maps for a better understanding and interpretation by local decision makers. Staff Members Head Prof. Dr. Andreas Hoppe Research Associates Dipl.-Geoökol. Monika Hofmann Dr. Rouwen Lehné Dipl.-Geol. Ina Lewin Technical Personnel Dipl.-Kartogr. (FH) Ulrike Simons Secretaries Pia Cazzonelli PhD students Hannah Budde (MSc Geowiss.) Dipl.-Geogr. Constanze Bückner Ingram Haase (Mag. Gesch./Geogr.) Dipl.-Geol. Marie Luise Mayer Students Tobias Faißt (MSC), Shirin Gomez (MSc), Georg Kuhn (BSc), Marie Mohr (BSc), Narmada Maheshani Rathnayake (MSc), Shaojuan Xu (MSc), Stefan Wewior (BSc), Student apprentices Arola Moreras (Universidad de Catalunya in Barcelona, during July-August 2013) Guest Scientist Prof. Dr. Prem B. Thapa (Tribhuvan University Kathmandu, Nepal, during June 2013) Prof. Dr. Joachim Karfunkel (Universidade Federal de Minas Gerais in Belo Horizonte, Brazil, during November 2013) Institute of Applied Geosciences – Geo-Resources and Geo-Hazards 203 Research Projects Focus was still laid on the analysis and evaluation of geopotentials in the surroundings of urban areas as well as on hazards based on mass movements. Tools do achieve these goals were geoinformation systems (GIS) and 3D modelling (GOCAD). First results have been compiled by Andreas Hoppe and Rouwen Lehné in a special volume of the German Journal of Geosciences (ZDGG) on Urban Geology. Monika Hofmann defended successfully her dissertation about the geopotentials in the north of the Brazilian megalopolis Belo Horizonte. Hannah Budde continued to elaborate a 3D model for the RheinMain area in cooperation with the Hessian Geological Survey (HLUG). Constanze Bückner investigates the relations between natural framework conditions and development of German major cities. Ina Lewin elaborated a high resolution model of Quaternary sediments in a test area east of the Odenwald and investigated the water exchange between a dredging lake and a groundwater well in cooperation with the local water distributor (ZVG Dieburg) 3D modelling of the Quaternary of the Northern Upper Rhine Graben was intensified by Rouwen Lehné. Together with HLUG, he also started a GIS supported data base on geohazards in Hesse. Mass movements in the Lesser Himalayas were analysed in two master theses co-orientated by Prem Thapa (Katmandu). First steps to model future hazards in the Eastern Alps by retreating ice and permafrost were done by Ingram Haase in cooperation with the University of Natural Resources and Life Sciences in Vienna. Distribution and quality of geopotentials in Estonia (i.e. oil shale and black shale) have been investigated with GIS and GOCAD techniques by Rouwen Lehné and master students in cooperation with the Estonian Land Board. Andreas Hoppe served as Chief Editor of the ZDGG and evaluated in April the education in geology and mineral prospecting at the Siberian University in Yakutsk. Rouwen Lehné served as speaker of the Section Geoinformatics within the German Geological Society (DGG). Publications [1] Bückner, C. (2013): Local Agenda 21: Natural resources in German urban sustainability strategies. - Z. dt. Ges. Geowiss. 164/4: 535-539, Stuttgart. [2] Hofmann, M., Hoppe, A., Karfunkel, J. & Büchi, A. (2013): Regionalizing hydrological soil properties in the Brazilian cerrado region using a semantic import model approach. – In E.C. Lannon, ed., Drainage Basins and Catchment Management: Classification, Modelling and Environmental Assessment, 50 pp., New York (Nova Science Publ.) [ISBN: 978-1-62618-368-1] [3] Hoppe, A. (2013): Cities and geology. - Z. dt. Ges. Geowiss. 164/4: 517-524, Stuttgart. 204 Institute of Applied Geosciences – Geo-Resources and Geo-Hazards [4] Hoppe, A. & Lehné, R., eds. (2013): Urban Geology.– Z. dt. Ges. Geowiss. 164/4: 515-603, Stuttgart (Schweizerbart). [5] Hoselmann, C. & Lehné, R. (2013): Neue Lithostratigraphie und ein geologisches 3DModell des nördlichen Oberrheingrabens. – Jahresbericht 2012 des Hessischen Landesamtes für Umwelt und Geologie, 77-87, Wiesbaden. [6] Lamelas, M.T., Marinoni, O.T., de la Riva, J. & Hoppe, A. (2013): Spatial decision support for sustainable land-use decision making: An application for industry site planning and irrigation use in the surroundings of Zaragoza (Spain). – In J.M. PradoLorenzo & I.M. Garcia Sanchez, eds., Sustainable Development – New Research, 65-79, 7 figs., 1 table, New York (Nova Science Publ.) [ISBN 978-1-62081-903-6]. [7] Lehné, R., Hoselmann, C., Heggemann, H., Budde, H. & Hoppe, A. (2013): Geological 3D modelling in the densely populated metropolitan area Frankfurt/Rhine-Main. - Z. dt. Ges. Geowiss. 164/4: 591-609, Stuttgart. [8] Panteleit, B., Jensen, S., Seiter, K., Budde, H. & McDiarmid, J. (2013): A regional and geological groundwater flow model of Bremen (Germany): an example management tool for resource administration.- Z. dt. Ges. Geowiss. 164/4: 569-580, Stuttgart. Institute of Applied Geosciences – Geo-Resources and Geo-Hazards 205 Multi-criteria approach for 3D-modelling of geological horizons in the Lower Main Plain, Germany Hannah Budde(1), Christian Hoselmann(2), Rouwen Lehné(1), Heiner Heggemann(2), Andreas Hoppe(1) (1) Technische Universität Darmstadt, Angewandte Geowissenschaften, Schnittspahnstr. 9, D-64287 Darmstadt (2) Hessisches Landesamt für Umwelt und Geologie (HLUG), Rheingaustr. 186, D-65203 Wiesbaden Introduction: The availability of near-surface geo-resources such as groundwater or sand and gravel deposits plays a key role in urban development. Due to the increasing demand for land, particularly in metropolitan areas, conflicts of utilization between different economic and environmental interests often arise. Therefore, in cooperation with the Hessian Agency for the Environment and Geology (HLUG), a 3D geological model for a part of the metropolitan region of Frankfurt / RheinMain will be created to evaluate geo-potentials, model usage scenarios and to work out criteria for the evaluation of land use conflicts. In the process, the model should always be transparent concerning to its input data and thus easy comprehensible to third parties. The aim of the model is to visualize important stratigraphic units like the Base Quaternary and Tertiary. Depending on data availability, the space between will be further differentiated stratigraphically. The 2,700 km² large project area focusses the subsidence sites of the Lower Main Plain (Hanau Basin, Upper Rhine Graben, Mainz Basin, Wetterau Tertiary depression) and is bounded by the Rhenish Slate Mountains (Rheinisches Schiefergebirge) in the northwest and the Odenwald in the southeast (Fig. 1). Frankfurt am Main Wiesbade n Darmstad t Fig. 1: Elevation model of the project area from SRTM data. Scale in [m]. Colormap shows height above sea level in [m]. Data source: Jarvis et al. (2008) 206 Institute of Applied Geosciences – Geo-Resources and Geo-Hazards Methodology and data background: Within the preparation of well data, a large number of inconsistent entries in the borehole database were observed. Especially in the field of stratigraphy, differences in the interpretation of layers depending on the processor and drilling year occur. Therefore, a multi-criteria approach for the derivation of the horizons has been developed to avoid model errors due to incorrect entries from the borehole database, to objectify the stratigraphic classification, and to specify a size for the reliability of model areas. In this process, each entry will be evaluated by its petrographic description and under specification of the probability and with geological expert knowledge and regional experiences semiautomatically assigned to one stratigraphic unit (Fig. 2). Fig. 2: Workflow. Evaluation of each borehole entry in terms of belonging to a specified stratigraphic unit based on defined characteristic parameters. Quaternary Main terrace Pliocene Fig. 3: Results of the classification of the layers entries in Quaternary terrace sediments and Pliocene deposits using the evaluation matrix shown in relation to their spatial position Institute of Applied Geosciences – Geo-Resources and Geo-Hazards 207 Characteristics and descriptive information about the lithology of each stratigraphic unit in the project area have been derived based on publications that address the geology of the Rhein-Main area (e.g. Gabriel et al. 2012, Hoselmann 2008), results from two projects, i.e.3D_NORG (Hoselmann & Lehné 2012) and the Hanau Basin (Lang 2007), as well as geological maps (scale 1:25,000) and river seismic (e.g. Haimberger et al. 2005). The different parameters, such as color, carbonate content, grain size etc. will be weighted and for each stratigraphic unit combined in a specific matrix. In addition to the development of classification criteria from the literature, the definition of relevant keys and the query criteria in a project-specific GIS is an essential part of the methodology. Results: First test runs are implemented for the layers Pliocene and Quaternary Rhine terrace sediments and give consistent results (Fig. 3). About 3,000 out of the total 200,000 entries comply with the defined criteria for Quaternary terrace sediments in the Lower Main Plain to at least 70% and can therefore be used as markers for horizon modeling. Throughout the area, they are spatially located above of the 500 entries that were classified as Pliocene. The capacity of the information derived by this approach is verified semi-automatic as well as visually by quality control and expert knowledge. Next steps will be the extension of the matrix to more criteria like heavy minerals, as well as the deviation of point data sets for all project relevant stratigraphic layers, e.g. the Untermain-Basalt-Formation or the Arvernensis Gravels. References: [1] [2] [3] [4] [5] [6] [7] 208 Gabriel, G., Ellwanger, D., Hoselmann, C., Weidenfeller, M., Wielandt-Schuster, U. (2013): The Heidelberg Basin, Upper Rhine Graben (Germany): a unique archive of Quaternary sediments in Central Europe. Quaternary International, 292: 43-58. Grimm, M.C., Wielandt-Schuster ,U., Hottenrott, M., Grimm, K.I. & Radtke,G. (2011): Oberrheingraben. – In: Lange, J.-M. & Röhling, H.-G.[Hrsg.]: Stratigraphie von Deutschland IX Tertiär, Teil 1: Oberrheingraben und benachbarte Tertiärgebiete. – Schriftenreihe dt. Ges. Geowiss., 75, 57 132; Hannover. Haimberger, R., Hoppe, A., Schäfer, A. (2005):High-resolution seismic survey on the Rhine River in the northern Upper Rhine Graben.Int. J. Earth Sci., 94: 657–668 Hoselmann, C. (2008): The Pliocene and Pleistocene fluvial evolution in the northern Upper Rhine Graben based on results of the reasearch borehole at Viernheim (Hessen, Germany). Quaternary Science Journal (Eiszeitalter und Gegenwart), 57/3-4: 286–315. Hoselmann, C. & Lehné., R.J. (2012): Neue Lithostratigraphie und ein geologisches 3D-Modell des nördlichen Oberrheingrabens – Hessisches Landesamt für Umwelt und Geologie – Jahresbericht 2012, 77-87. Jarvis, A., Reuter, H.I., Nelson, A., Guevara E. (2008): Hole-filled seamless SRTM data V4. International Centre for Tropical Agriculture (CIAT) http://srtm.csi.cgiar.org Lang, S. (2007): Die geologische Entwicklung der Hanau-Seligenstädter Senke (Hessen, Bayern). Dissertation an der Technischen Universität Darmstadt. (http://elib.tu-darmstadt.de/diss/000782). Institute of Applied Geosciences – Geo-Resources and Geo-Hazards Radon measurements in soil and ambient air in and around Darmstadt – an investigation in a geological context Georg Kuhn, Rouwen Lehné, Andreas Hoppe Institute of Applied Geosciences, Technische Universität Darmstadt Introduction Radon is a radioactive noble gas which originates in decay series. Its natural occurrence in soil as well as ambient air strongly is depending on the local mineralogical composition of rocks and soil. High radon concentrations in and around Darmstadt are given due the crystalline rocks of the Odenwald Mts. and migration paths (natural such as tectonic faults and anthropogenic, e.g. openings in foundations) which enable radon to overcome larger distances and accumulate into radon anomalies. They can be an indicator for recent tectonic activities. High concentrations of radon, e.g. in poorly ventilated cellars, may also pose a health hazards related alpha-emitting is supposed to be the second most reason for lung cancer. In Darmstadt, radon concentrations in soil air have been measured on the university´s campus at Lichtwiese and Botanischer Garten as well as along the eastern master fault of the Upper Rhine Graben in the city center accompanied by measurements of room air in order to find possible connections to migration paths from the underground In addition, radon measurements are currently under way along newly discovered faults in the northern Upper Rhine Graben near Groß-Gerau in order to verify recent activities. Measurements are embedded in works for setting up a geothermal power plant. Actually, the measuring method described by Kemski et al. (1998) is widely used. However, it measures the activity of radon only, without determining the quantity of soil air flowing through the measurement chamber. Consequently, it is difficult to compare soils with different permeabilities, so that it is intended to develop a standardised method which combines the measurement of radon with the detection of CO2 in soil air. Furthermore, a flow-meter will be installed in the measurement setup to log the actual air flow. This is necessary to compare the different results of measurements in several soil types. Field measurements of soil samples are complemented by analyses with gamma ray spectrometry in order to determine the concentration of radium, the parent nuclide of radon. This is necessary to differentiate between radon which is formed in situ and the radon which migrates along the fault zones. Darmstadt Radon concentrations in the city are high due to its geological underground. While under campus Lichtwiese and Botanischer Garten it is related to Permian volcanic rocks, the center lies on gabbro in the east and is dissected by the eastern master fault of the Upper Rhine Graben. Institute of Applied Geosciences – Geo-Resources and Geo-Hazards 209 Campus Botanischer Garten Several measurements of radon in the soil air show concentrations of > 50.000 Bq/m³, one measurement exceeds 100.000 Bq/m³ (Fig. 1), very likely related to Permian basalts. Therefore, radon concentration in room air has been measured in several campus buildings. Results show uncritical concentrations. However, varying concentrations in different parts, i.e. the Institute of Applied Geosciences, describe different modernity of one building (Fig. 1). Fig. 1: Concentrations of radon in both soil and ambient air in the area of the campus Botanischer Garten of Technische Universität Darmstadt (left) in the vicinity of the eastern master fault of the Upper Rhine Graben (right) While part B2/01 of the building erected in the 1960ies shows higher radon concentrations in the room air, the concentrations in the recently modernized part B2/02 are very low, indicating that either old migration paths have been closed or ventilation is effective in the reduction of radon concentration. In building B2/01 both average radon concentrations of 136 Bq/m³ and maximum radon concentrations of more than 300 Bq/m³ exceed the average concentration of radon in the air of closed rooms in Germany (49 Bq/m³, Menzler et al. 2006) significantly. Therefore it is recommended (i) to ensure regular ventilation and (ii) to repeat measurements because staff should not be exposed to concentrations of more than 150 Bq/m³ over a longer period. 210 Institute of Applied Geosciences – Geo-Resources and Geo-Hazards Darmstadtium The darmstadtium is the city´s congress center and city palace. It is placed immediately on the eastern master fault of the Upper Rhine Graben which separates fluvial Tertiary in the west from gabbros in the east (Hoppe & Lang 2007). Here measurements of radon in soil air have not been conducted. Ambient air in the building though shows very high concentrations of radon in two of three rooms. The reason can be seen in favourable migration conditions along the master fault (Fig. 1). Groß-Gerau Planning for a geothermal power plant near Trebur posed the question if tectonic faults in the vicinity might be active recently and thus enable migration paths. In the frame of a running co-operation with the local energy supplier (Überlandwerke Groß-Gerau) therefore radon in soil air is currently measured. To increase the reliability of detected concentrations, in addition CO2 and the flow rate are considered. Furthermore, soil samples for every single measuring point will be analyzed for the presence of radium, the parent nuclide of radon, in order to differentiate between radon that developed in situ and radon that migrated to the measuring environment. The project thus progressively leads to both a deeper understanding of the geological inventory and an improved methodology for analyzing and interpreting soil gases. Results are expected for summer 2014. References: [1] [2] [3] Hoppe, A. & Lang, S. (2007): The eastern master fault of the Upper Rhine Graben below the Science and Conference Centre in Darmstadt (Germany). Z. dt. Ges. Geowiss. 158/1: 113-117, Stuttgart. Kemski, J., Siehl, A, Stegemann, R., Valdivia-Manchego, M. (1998): Geogene Faktoren der Strahlenexposition unter besonderer Berücksichtigung des Radonpotentials. Abschlussbericht zum Forschungsvorhaben ST. Sch. 4106. Geologisches Institut der Universität Bonn. Menzler S., Schaffrath-Rosario A., Wichman H.E., Kreienbrock, L. (2006): Abschätzung des attributablen Lungenkrebsrisikos in Deutschland durch Radon in Wohnungen. Ecomed-Verlag, Landsberg. Institute of Applied Geosciences – Geo-Resources and Geo-Hazards 211 Geomaterial Science The research group of Prof. Hans-Joachim Kleebe is active in the field of Geomaterial Science (formerly Applied Mineralogy) and explores the formation/processing conditions, composition, microstructure and properties of minerals and rocks in addition to material science relevant compounds. The study of the latter material group focuses on both basic science and potential industrial applications. Research activities include a comprehensive characterization of natural and synthetic materials, their performance for example at elevated temperature, local chemical variations as well as tailored synthesis experiments for high-tech materials. The experimental studies comprise the crystal chemistry of minerals and synthetic materials, in particular, their crystal structure, phase assemblage and, in particular, microstructure evolution. The microstructure variation (e.g., during exposure to high temperature) has an essential effect on the resulting material properties, which is true for synthetic materials as well as for natural minerals. Therefore, the main focus of most research projects is to understand the correlation between microstructure evolution and resulting material properties. An important aspect of the Fachgebiet Geomaterial Science is the application of transmission electron microscopy (TEM/STEM) techniques for the detailed micro/nanostructural characterization of solids. STEM in conjunction with spectroscopic analytical tools such as energy-dispersive X-ray spectroscopy (EDS) and electron energy-loss spectroscopy (EELS) are employed for detailed microstructure and defect characterization down to the atomic scale. High-resolution imaging of local defects in addition to chemical analysis with high lateral resolution is similarly applied to natural minerals as well as to high-performance materials. Recent research projects involve topics such as fatigue of ferroelectrics, re-calibration of the clinopyroxene-garnet geothermometer with respect to small variations in the Fe2+/Fe3+ratio, defect structure in Bixbyite single crystals (and their corresponding exaggerated grain growth), morphology of In2O3 nanocrystals, transparent ceramics (Mg-Al spinel), interface structures in polycrystals, high-temperature microstructures, fatigue of ferroelectrics, and the study of biomineralisation and biomaterials. Staff Members Head Prof. Dr. Hans-Joachim Kleebe Associated Professors Prof. Dr. Ute Kolb – Electron Crystallography Prof. Dr. Peter van Aken, MPI Stuttgart, TEM/HRTEM/EELS Research Associates Dr. Stefan Lauterbach Dr. Leopold Molina-Luna Postdoctoral Students Dr. Ana Ljubomira Schmitt 212 Dr. Ingo Sethmann Institute of Applied Geosciences – Geomaterial Science PhD Students Stefania Hapis Cigdem Özsoy Keskinbora Marc Rubat du Merac Xiaoke Mu Mathis M. Müller Katharina Nonnenmacher Scientific Assistant Dr. Gerhard Miehe Senior Scientist Prof. Dr. Wolfgang F. Müller Diploma Students Angela P. Moissl Sven Schild Technical Personnel Bernd Dreieicher Secretary Angelika Willführ Michael Scherrer Ekin Simsek Stefanie Schultheiß Dmitry Tyutyunnikov Marina Zakhozheva Leoni Wilhelm Research Projects Polymer-derived SiCO/HfO2 and SiCN/HfO2 Ceramic Nanocomposites for Ultrahightemperature Applications, SPP-1181 (DFG 2009-2014) Investigation of Strengthened Hydroxylapatit/ß-Tricalcium Phosphate Composites with Tailored Porosity (DFG 2008-2013) Structural Investigations of Fatigue in Ferroelectrics, Characterization of Lead-Free Ferroelectrics (DFG 2007-2014) SFB-595, detailed TEM TEM Characterization of Various Materials/Composites in the LOEWE Excellence Initiative AdRIA (Adaptronik – Research, Innovation, Application 2011-2014) Investigation of the Atomic and Electronic Structure of Perovskite-MultilayerHeterojunctions (in collaboration with the MPI Stuttgart, Prof. P. van Aken) Phase Developments and Phase Transformations of Crystaline Non-Equilibrium Phases (in collaboration with the MPI Stuttgart, Prof. P. van Aken) Precipitation mechanisms of Ca-oxalate in the presence of Ca-phosphates and osteopontin molecules related to kidney stone formation (DFG 2011-2013) Microstructure Characterization and Correlation with Corresponding Properties, in particular Hardness und Fracture Toughness, of Boron Suboxide Materials (DFG 20122015) Microstructure Characterization of Polycrystalline Transparent Mg-Al-Spinel Samples; The Effect of LiF Doping (Industry 2012-14) Antibacterial Properties of Ag-modified Ca-Phosphate Scaffolds for Bone Replacement Materials (DFG 2012-2013) Microstructucure and Defect Control of Thin Film Solar Cells (Helmholtz Virtual Institute 2012-2018). Institute of Applied Geosciences – Geomaterial Science 213 Publications F. Muench, A. Fuchs, E. Mankel, M. Rauber, S. Lauterbach, H.-J. Kleebe, W. Ensinger, “Synthesis of nanoparticle/ligand composite thin films by sequential ligand self assembly and surface complex reduction”, Journal of Colloid and interface Science, 389 (2013) 2330. B. Papendorf, E. Ionescu, H.-J. Kleebe, C. Linck, O. Guillon, K. Nonnenmacher, R. Riedel, “High-Temperature Creep Behavior of Dense SiOC-Based Ceramic Nanocomposites: Microstructural and Phase Composition Effects”, Journal of the American Ceramic Society, 96 [1] (2013) 272-280. G. Mera, A. Navrotsky, S. Sen, H.-J. Kleebe, R. Riedel, “Polymer-deviced SiCN ceramics – structure and energetic at the nanoscale”, Journal of Materials Chemistry A, 12 [1] (2013) 3826-3836. M.F. Bekheet, M.R. Schwarz, M.M. Müller, S. Lauterbach, H.-J. Kleebe, R. Riedel, A. Gurlo, “Phase segregation in Mn-doped In2O3: in situ high-pressure high-temperature synchrotron studies in multi-anvil assemblies”, RSC Advances, 16 [3] (2013) 5357-5360. S. Hayakawa, T. Kanaya, K. Tsuru, Shirosaky, A. Osaka, E. Fujii, K. Kawabata, G. Gasqueres, C. Bonhomme, F. Babonneau, C. Jager, H.-J. Kleebe, “Heterogeneous structure and in vitro degradation behavior of wet-chemically derived nanocrystalline siliconcontaining hydroxyapatite particles”, ACTA Biomaterialia, 1 [9] (2013) 4856-4867. I. Levin, I.M. Reaney, E.M. Anton, W. Jo, J. Rodel, J. Pokorny, L.A. Schmitt, H.-J. Kleebe, M. Hinterstein, J.L. Jons, “Local structure, pseudosymmetry, and phase transitions in Na1/2Bi1/2TiO3-K1/2Bi1/2TiO3 ceramics”, Physical Review B, 2 [87] (2013) 024113. M. Schlosser, S. Frols, U. Hauf, I. Setmann, S. Schultheiss, F. Pfeifer, H.-J. Kleebe, “Combined Hydrothermal Conversion and Vapor Transport Sintering of Ag-Modified Calcium Phosphate Scaffolds”, Journal of the American Ceramic Society, 2 [96] (2013) 4212-419. G. Miehe, S. Lauterbach, H.-J. Kleebe, A. Gurlo, “Indium hydroxide to oxide decomposition observed in one nanocrystal during in situ transmission electron microscopy studies”, Journal of Solid State Chemistry, (2013) 364-370. U. Sydow, K. Sempf, M. Herrmann, M. Schneider, H.-J. Kleebe, A. Michaelis, “Electrochemical corrosion of liquid phase sintered silicon carbide ceramics”, Material and Corosion-Werkstoffe und Korrosion, 3 [64] (2013) 218-224. H. Purwin, S. Lauterbach, G.P. Brey, A.B. Woodland, H.-J. Kleebe, „An experimental study of the Fe oxidation states in garnet and clinopyroxene as a function of temperature in the system CaO-FeO-Fe2O3-MgO-Al2O3-SiO2: implications for garnet-clinopyroxene geothermometry”, Contr. to Mineralogy and Petrology, 4 [165] (2013) 623-639. 214 Institute of Applied Geosciences – Geomaterial Science M.F. Bekheet, MR. Schwarz, S. Lauterbach, H.-J. Kleebe, P. Kroll, R. Riedel, A. Gurlo, “Orthorhombic In2O3: A Metastable Polymorph of Indium Sesquioxide”, Angewandte Chemie-International Edition, 25, (2013) 6531-6535. M. Herrmann , I. Sigalas, M. Thiele, MM. Muller, H.-J. Kleebe, A. Michaelis, „Boron suboxide ultrahard materials“ Int. J. of Refractory Metals & Hard Materials, SI, [39] (2013) 53-60. S. Schultheiss, I. Sethmann I., M. Schlosser, H.-J. Kleebe, “Pseudomorphic transformation of Ca/Mg carbonates into phosphates with focus on dolomite conversion” Mineralogical Magazine, 6, [77] [2013) 2725-2737. M. Rubat du Merac, IE. Reimanis, C. Smith, H-J. Kleebe, MM. Müller, “Effect of Impurities and LiF Additive in Hot-Pressed Transparent Magnesium Aluminate Spinel”, International Journal of Applied Ceramic Technology, SI, [10] (2013) E33-E48. K. Morita, G. Mera, K. Yoshida, Y. Ikuhara, A. Klein, H.-J. Kleebe, R. Riedel, “Thermal stability, morphology and electronic band gap of Zn(NCN)”, Solid State Sciences, [23] (2013) 50-57. B. Lyson-Sypien, A. Czapla, M. Lubecka, A. Zakrzewska, M. Radecka, A. Kusior, A.G. Balogh, S. Lauterbach, H.-J. Kleebe, “Gas sensing properties of TiO2-SnO2 nanomaterials”, Sensors and Actuators B-Chemical, SI, [187] (2013) 445-454. MT. Uddin, Y. Nicolas, C. Olivier, T. Toupance, M.M. Muller, H.-J. Kleebe, K. Rachut, J. Ziegler, A. Klein, W. Jaegermann, “Preparation of RuO2/TiO2 Mesoporous Heterostructures and Rationalization of Their Enhanced Photocatalytic Properties by Band Alignment Investigations”, Journal of Physical Chemistry C, 42 [117] (2013) 22098-22100. L. Molina-Luna, Leopoldo, R. Egoavil, S.Turner, T. Thersleff, J. Verbeeck, B. Holzapfel, O. Eibl, G. Van Tendeloo, “Interlayer Structure in YBCO-coated Conductors Prepared by Chemical Solution Deposition”, Supercond. Sci. & Tech., 26 [7] (2013) 075016-24. T.T.D. Nguyen, L. Dimesso, G. Cherkashinin, J.C. Jaud, S. Lauterbach, R. Hausbrand, W. Jaegermann, “Synthesis and characterization of LiMn1-xFe(x)PO4 carbon nanotubes composites as cathodes for Li-ion batteries, ” Ionics 19 [9] 1229-1240. M.F. Bekheet, M.R. Schwarz, S. Lauterbach, H.-J. Kleebe, P. Kroll, A. Stewart, U. Kolb, R. Riedel, A. Gurlo, “In situ high pressure high temperature experiments in multi-anvil assemblies with bixbyite-type In2O3 and synthesis of corundum-type and orthorhombic In2O3 polymorphs,” High Pressure Research 33 [3] (2013) 697-711. M.R. du Merac, H.-J. Kleebe, M.M. Muller, I.E. Reimanis, “Fifty Years of Research and Development Coming to Fruition; Unraveling the Complex Interactions during Processing of Transparent Magnesium Aluminate (MgAl2O4) Spinel”, Journal of the American Ceramic Society, 11 [96] (2013) 3341-3365. Institute of Applied Geosciences – Geomaterial Science 215 Sintering mechanisms of LiF-doped Mg-Al-Spinel M.M. Müller, M. Rubat du Merac and H.-J. Kleebe MgAl2O4 is considered a promising material for optical applications and hence object to research for more than 40 years worldwide [1-4]. The densification mechanism of MgAl2O4 (hereafter termed spinel) doped with lithium fluoride (LiF) as transparent ceramic has been intensively studied [5]. Optical transparency requires densification to a value near the theoretical density since residual porosity, which acts as scattering source, has to be eliminated. In addition, impurities and secondary phases have to be removed to avoid scattering or absorption of the transmitted radiation (i.e. visible or IR light). LiF greatly reduces the sintering temperature and facilitates densification at low temperatures. However, the basic mechanisms behind the sintering process are still not fully understood, as neither LiF nor an additional secondary phase is detectable in the final product. Based on individual studies Reimanis, Kleebe and Rozenburg [6-8] postulated three major processes during sintering of spinel with LiF including (i) Enhanced volume diffusion by incorporation of O-vacancies: It is postulated that LiF can be incorporated into the spinel structure as described by Kröger-Vinck notation as follows: MgAl 2O4 3 LiF LiMg 2 Li Al 3 FO VO / // Due to the necessary charge compensation, oxygen vacancies are predicted which enhance volume diffusion in the spinel lattice, strongly promoting grain growth. (ii) Dissolution – Reprecipitation: At 840°C, molten LiF partially reacts with spinel by the formation of liquid MgF2 and solid LiAlO2. MgAl 2O4 3 LiF(l) LiF : MgF2 (l) 2LiAlO 2 (s) In the temperature range between 840°C and 1000°C, both the remaining LiF and the MgF 2 become gaseous, LiF : MgF2 (l) LiF(g) MgF2 (g) which is seen as the origin of the dewetting process. This enables the back reaction above 1050°C to form a second generation of spinel and gaseous LiF which can now the leave the system. MgF2 (g) 2LiAlO 2 (s) MgAl 2 O 4 (s) 2 LiF(g) and (iii) Wetting – Dewetting: At this early stage of sintering, the densification mechanism can be described by a classical liquid phase sintering process facilitating particle rearrangement. At temperatures above 1000°C, no secondary phase is detectable along grain boundaries. Since conventional sinter regimes for this material system are pressure supported the geometry of sintered devises is limited. Therefore, the overall aims of the present study are 216 Institute of Applied Geosciences – Geomaterial Science (i) to verify the postulated mechanisms and (ii) to transfer this knowledge to a pressure less sinter process. In a recent work it was shown that these mechanisms occur simultaneously interacting with each other [9], however, the verification was made by indirect methods as for example the double fringe technique introduced by D.R. Clark [10] for the wetting-dewetting mechanism as shown in Figure 1. Fig. 1: Defocus series of a spinel-spinel grain boundary. The material was sintered at 900°C [a,b,c] and 1100°C [d]. The double fringes occurring at 900°C indicate a twice changing mean inner potential which was interpreted as a wetting of the grain boundary. At higher temperatures no wetting was observed.[9] Recent experiments showed the reason for the twice changing mean inner potential creating the double Fresnel fringes as an example of the high potential of probe-corrected microscopes in the applied transmission electron microscopy and material science. Using an ARM 200F operating at 200kV a series of high resolution STEM-EELS investigations were performed at a polycrystalline spinel sample, sintered at 900°C, consistently showing an incorporation of fluorine close to the grain boundaries as depicted in Figure 2. Fig. 2: HR-STEM image of a spinel-spinel grain boundary. When applying the defocus technique double Fresnel fringes occurred but even in highest magnification no wetting could be shown. Instead, by using STEM EELS techniques, an incorporation of fluorine in the first two atomic layers was observed at a sintering temperature of 900°C. Institute of Applied Geosciences – Geomaterial Science 217 This means that a) the double Fresnel fringes cannot only be created by an amorphous layer of a secondary phase but also by additional incorporated elements and b) the wetting mechanism occurs much earlier in the sintering process then postulated. Furthermore, based on dedicated model experiments and a characterisation using e.g. state-of-the-art electron microscopy it was shown for the first time that (a) a dissolutionreprecipation process occurs at significantly lower temperatures by the formation of a variety of transient phases (Figure 3), (b) a vapour transport mechanism leads to a notable mass transport involving the magnesium and (c) an exaggerated grain growth of a second generation of spinel hinders the densification process. Fig. 3: HR-SEM micrograph of MgO and LiAlO2 as transient phases observed in a model experiment at a sintering temperature of 900°C. References 1. R.J. Bratton. Characterization and Sintering of Active MgAl2O4 Spinel, Am Ceram Soc Bull, 47 [9] (1968) pp. 883-887. 2. M. Rubat du Merac, Marc, H.-J. Kleebe, M.M. Mueller and I.E. Reimanis, “Fifty Years of Research and Development Coming to Fruition; Unraveling the Complex Interactions during Processing of Transparent Magnesium Aluminate (MgAl2O4) Spinel” J. Am. Ceram. Soc., 96 [11] (2013) 3341-3365. 3. D.W. Roy, Hot-Pressed MgAl2O4 for Ultraviolet (UV), Visible and Infrared (IR) Optical Requirements, P. Soc. Photo.-Opt. Inst., 297 (1981) pp. 13-18. 4. M. Shimada, T. Endo, T. Saito, and T. Sato, Fabrication of transparent spinel polycrystalline materials, Mat. Let., 28 [4-6] (1996) pp. 413-15. 5. M. Rubat du Merac, I.E. Reimanis, C. Smith, H.-J. Kleebe and M.M. Mueller “Effect of Impurities and LiF Additive in Hot-Pressed Transparent Magnesium Aluminate Spinel”, Int. J. App. Ceram. Tech. 10 [1] (2013) pp. E33-E48. 6. I.E. Reimanis and H.-J. Kleebe, Reactions in the sintering of MgAl2O4 spinel doped with LiF. Int. J. Mat. Res., 98 [12] (2007) pp. 1273-78. 7. K. Rozenburg, I.E. Reimanis, H.-J. Kleebe, and R.L. Cook, Chemical interaction between LiF and MgAl 2O4 spinel during sintering. J. Am. Ceram. Soc. 90 [7] (2007) pp. 2038-2042. 8. I.E. Reimanis and H.-J. Kleebe, A Review on the Sintering and Microstructure Development of Transparent Spinel (MgAl2O4). J. Am. Ceram. Soc. 92 [7] (2009) pp.1472-1480. 9. M.M. Müller and H.-J. Kleebe, Sintering Mechanisms of LiF-Doped Mg-Al-Spinel, J. Am. Ceram. Soc., 95 [10] (2013) pp. 3022-3024. 10. D.R. Clarke, On the detection of thin intergranular films by electron microcopy, Ultramicroscopy 4 (1979) pp. 33-44. 218 Institute of Applied Geosciences – Geomaterial Science Electron Microscopy Studies of {100} Faults in Bixbyite Crystals from the Thomas Range Rhyolite (Utah) Stefan Lauterbach and Hans-Joachim Kleebe Despite its simple composition, bixbyite is a rather uncommon manganese-iron oxide with a general formula (Mn,Fe)2O3. It crystallises in the Ia3 cubic symmetry and is known as the type mineral for the so-called bixbyite structure. It forms black cubic crystals with metallic lustre that are occasionally truncated by small icositetrahedral faces at corners. The best specimens of bixbyite are found at Thomas Range (Utah), where it occurs in the cavities of the rhyolite host rock in association with topaz, pseudobrookite, braunite, hematite, hausmannite, spessartine, beryl and quartz. Most of the bixbyite crystals from Thomas Range with developed icositetrahedral forms show distinct reentrant facets at the halfway of every edge of the cube, whereas such reentrants are absent on simple cubic crystals. On the lustrous surfaces of the crystal, it is frequently observed that pairs of adjacent reentrant pitches are linked by a band of parallel notches, crossing at the centres of each face of the cube. According to the morphological features these crystals convincingly appear to be {100} twins and are as such recognised in the mineralogical community. However, any twinning operation on {100} planes of the centrosymmetric bixbyite structure would produce an identical crystal, suggesting that {100} twins in bixbyite are crystallographically not possible, and that these defects could be some yet unknown type of polytypic faults. This fact attracted our attention to study the structure and chemistry of {100} planar faults in bixbyite crystals from the Thomas Range locality. Fig. 1: 20 mm large bixbyite crystal from Thomas Range (Utah) with many reentrant facets, causing a jigsaw appearance of the crystal edges. Each reentrant pitch (arrows) is followed by slender notches that indicate the presence of braunite-type {100} polytypic faults. In order to disclose the nature of these defects we used different methods of electron microscopy. Scanning electron microscopy combined with quantitative energy dispersive Xray spectroscopy was used to determine the chemical composition of bulk bixbyite, while high-resolution transmission electron microscopy was employed to study the atomic structure of the polytypic lamellae. Line analysis over a band of polytypic faults showed an increase in Mn and decrease in Fe content in these areas. To prepare the TEM specimens the crystals were cut parallel to [001] orientation from the fault-rich areas. HRTEM images of these areas show clusters of polytypic faults running along {100} planes of the bixbyite structure. The interfaces are atomically sharp and planar over large areas of the crystal. Occasionally the faults make rectangular steps to the equivalent planes of the {100} family. Phase contrast on the polytypic faults shows special features, which imply a periodic occupancy or chemistry fluctuations in the fault planes. TEM/EDS analyses using for example the multiple beam diameter method, which is particularly suited for determination of atomicscale composition of planar faults, clearly showed a presence of Si in the fault-rich areas with a simultaneous increase of the Mn/Fe ratio (see inset in Figure 2). The composition of Institute of Applied Geosciences – Geomaterial Science 219 the polytypic faults closely corresponds to a manganese silicate braunite, which is also present in the paragenesis of the rhyolite vugs. Fig. 2: HRTEM image of the host crystal bixbyite with a polytypic planar fault of braunite Mn6SiO12. The local enrichment in Si can be seen from the EDS spectrum included as inset. Our study showed that the bixbyite crystals from the Thomas Range in Utah are in fact not twinned, but contain braunite-like polytypic lamellae coherently intergrown along the {100} planes of the host bixbyite single crystal [1]. Such defect structures incorporated in the crystal act as fast diffusion paths, promoting exaggerated grain growth, as observed in [100] the bixbyite samples from that very bixbyite location, similarly observed in different systems [2]. bixbyite (Mn,Fe)2O3 Si-rich polytypic faults braunite (Mn6SiO12) Most recent studies focus on the observed phenomena that small bixbyite precipitations are located precicely at the interface between braunite lamella and bixbyite (large) host crystal, as shown in Figure 3. It is assumed that such precipitates can only be incorporated into the host crystal via the formation of a new surface (of braunite), acting as nucleation site. Fig. 3: HR-STEM image of the host crystal bixbyite with a polytypic planar fault of braunite and a small bixbyite precipitate. The still open question is whether the braunite lamella indeed runs completely along the precipitate inter-face. References 1. H.-J. Kleebe and S. Lauterbach, "Exaggerated Grain Growth in Bixbyite via Fast Diffusion Along Planar Defects," Cryst. Res. Technol., 43 [11] (2008) 1143-49. 2. Recnik, M. Ceh and D. Kolar, "Polytype Induced Exaggerated Grain Growth in Ceramics“, J. Eur. Ceram. Soc. 21 (2001) 2117-2121. 220 Institute of Applied Geosciences – Geomaterial Science Electron Crystallography Electron crystallography uses electron radiation to characterize the structure of matter by imaging, diffraction and spectroscopy from fully crystalline over highly disordered to amorphous materials. One of the most potential tools for solid state investigation in the nano regime are transmission electron microscopes (TEM). Apart from imaging techniques in parallel illumination, scanning methods, based on a sequential data collection, are becoming more and more popular. The scientific approach of this group lies mainly on the development of electron diffraction techniques. The Automated Diffraction Tomography (ADT) method, invented by this group, consists of a new data collection concept and is applicable to nano particles down to a size of some tens of nanometer. Using ADT, nearly kinematical 3D electron diffraction data can be collected from a selected nano crsytal being suitable for „ab-initio“ structure solution, i.e. based only on electron diffraction data. In contrast to high resolution imaging this approach is applicable to material even highly sensitive tot he electron beam (e.g. drugs, MOFs, zeolites, hybrid materials) Fig. 1: Structural Sketch of the bismuth sulfate with the new „zeolite-like“ structure found at Alfenza mine and solved from a 50nm crystal. Projection down a) [010] and b) [001]. Note the presence of channels with a diameter of ~0.7 nm filled with disulfide anions. (Ref. 6) Apart from the structure determination of highly crystalline nano particles even with complicated structural features, a quantitative approach to describe disordered structures is under development. It is planned to use approaches (e.g. pair distribution funktion) already successfull are becoming applied to X-ray data. Application as well as development of the above described ADT method has a high demand for cooperation within the Materials- and Geosciences but also with other departments such as chemistry, mathematics and informatics. Prof. Kolb started to build up the group in the Institute of Applied Geosciences in November 2012. In addition she has been assigned as Equal Opportunities Officer. Institute of Applied Geosciences – Electron Crystallography 221 Staff Members Head Prof. Dr. Ute Kolb Diploma Students Angela Patricia Moissl (MSc) Secretary Angelika Willführ Publications 1) Applications of Automated Diffraction Tomography (ADT) on nanocrystalline porous materials Enrico Mugnaioli and Ute Kolb*, Microporous and Mesoporous Materials, 166 93-101 (2013) 2) Using FOCUS to solve zeolite structures from 3D electron diffraction data Stef Smeets, L. B. McCusker, Ch. Baerlocher, E. Mugnaioli and U. Kolb, Applied Crystallography, 46 1017-1023 (2013) 3) Application of delta recycling to electron ADT data from inorganic crystalline nanovolumes J. Rius, E. Mugnaioli, O. Vallcorba and U. Kolb, Acta Cryst A, 69 396-407 (2013) highlighted article 4) In situ high pressure high temperature experiments in multi-anvil assemblies with bixbyite-type In2O3 and synthesis of corundum-type and orthorhombic In2O3 polymorphs M. F. Bekheet, M. Schwarz, S. Lauterbach, H.-J. Kleebe, P. Kroll, A. Stewart, U. Kolb, R. Riedel and A. Gurlo, High Pressure Research, 33(3), 697-711 (2013) 5) Snapshots of the Formation of NaTi3O6(OH)x2H2O Nanowires: A Time-Resolved XRD/HRTEM Study Zeitschrift für Anorganische und Allgemeine Chemie, 639(14) 2521-2526 (2013) 222 Institute of Applied Geosciences – Electron Crystallography Technical Petrology with Emphasis in Low Temperature Petrology Petrology is devoted to study the genesis and the mineralogical evolution of a rock with a specific bulk composition at various physical and chemical conditions. The scientific and educational fields of this branch within the applied geosciences are based on crucial knowledge in magmatic-, metamorphic-, hydrothermal petrology, mineralogy, structural geology, tectonophysics, geothermal geology, sediment petrography, thermodynamics/ kinetics and geochemistry. Technical Petrology aims to assess the physical and chemical properties of natural or synthetic rocks for applied purposes at various physical and chemical conditions (e.g. pressure, temperature, chemical composition). The Technical Petrology group is in particular devoted to study the low temperature domain. These low temperature studies serve as an aid to qualify and quantify processes occurring in hydrocarbon prospecting, geothermal system, and geodynamic study. The principal motivation of our Low-Temperature Petrology research group is to understand and to quantify low temperature petrologic processes. For this purpose, an effort is addressed to innovate new tools to calibrate and to model the metamorphic P-T-Xd-t conditions in low-grade rocks. A multidisciplinary approach is necessary because crystallization and recrystallisation are not obvious at low temperature. Hence, our work links field and experimental petrology, analytical methods, thermodynamic and kinetic modelling. Similar approaches are easily applied in archaeometry in order to characterise a range of firing temperatures and to describe recrystallisation processes of starting clay material. Opposite to prograde diagenetic to metamorphic processes, presented working philosophy is employed to describe the reverse cycles of destruction and weathering of rocks and the formation of clays and techno soils. The main research interests of the Technical Petrology Group are focussed on the following topics: Experimental Petrology (will be closed in 2014) Synthesis and characterisation of the coalification processes by means of optical parameters that are used to determine kinetics of maturation. Synthesis and characterisation of mineral reactions as well as firing structures and textures in ceramic materials. This aims to enhance knowledge on the ancient pottery production technology and to assess its socially embedded impacts. Coal Petrology (will be closed in 2014) The application of vitrinite reflectance and other coal petrological parameters to determine a grade of diagenesis and incipient metamorphism. Development of geothermobarometers based on the maturation kinetics of vitrinite. For the first time it will be possible to use barometric as well as thermometric models to establish geothermal gradients. These can be used in orogenic researches, sediment basin analyses, hydrocarbon exploration, geothermic prospections and energy researches. Institute of Applied Geosciences – Technical Petrology 223 o Improvement of methods related to hydrocarbon exploration. o Improvement of methods related to the low-grade metamorphism characterisation. o Application of the bituminate reflectance in the kerogene research, palaeogeothermics, and in the external orogens investigation. Clay Mineralogy The application of Kübler Index and other clay mineral parameters to determine a grade of diagenesis and incipient metamorphism. Development of Geothermobarometers based on the reaction kinetics in the reaction progress and aggradation of clay minerals to micas. These can be used in orogenic researches, sediment basin analyses, hydrocarbon exploration, and geothermic prospections. o Improvement of methods related to hydrocarbon exploration. o Improvement of methods related to the low-grade metamorphism characterisation. Archaeometry and Clay Mineralogy (will be closed in 2014) Determination and investigation on the production technology of the Iron Age, Hellenistic and Roman pottery fineware. o Determination of firing conditions and duration of peak ceramic firing. o Characterisation of applied raw material. o Provenance of exploited raw material. o Reconstruction of ancient trade routes by characterisation of nonlocal clayey raw and temper material. Environmental Geology Reaction processes reconstruction that take place in the mining damps, recognition of soil alteration via acid rock drainage, quantification of clay mineral degradation and clay-rock-water interactions. Determination of water-rock interaction and water chemistry in the basement crystalline ground waters and their usage as potable water. Low-Temperature Petrology s.l. Orogen and palaeogeothermal researches in foreland basins of the Alps, Vosges, Dinarides, Carpathians, Stara Planina (Bulgaria), Balkanides, Variscides of the Bosporus and Turkey. A broad analytical spectrum must be applied in low-temperature petrology due to very small grain-size. Technical Petrology group maintains a Microscopy Laboratory (CCA coalreflection microscopy, MPV coal-reflection microscopy, fluorescence microscopy, transmitted light microscopy). The former XRD laboratories (Clay and XRD Laboratory and a research XRD Laboratory) had to be moved and merged with the awkward geochemical laboratory. The ICP-AES, TOC, AOX and gas chromatography together with the Organic Geochemical Laboratory was closed in 2012. A non-completed refurbishment of the 224 Institute of Applied Geosciences – Technical Petrology Geoscience Institute and missing financial support forced us to accept an adverse decision. Due to the adjournment of the refurbishment of the building and the infrastructure the situation did not change in 2013. On photographs of the laboratories the iniquitous situation depended on development is documented on the wep page to testify the need to get back ideal working conditions. A XRF laboratory (Wave-dispersive BRUKER S8-Tiger) is maintained together with the groups of Chemical Analytics and Environmental Mineralogy. Staff Members Head Prof. Dr. Rafael Ferreiro Mählmann Research Associates Dr. Lan Nguyen Technical Personnel Dr. Norbert Laskowski Secretary Natali Vakalopoulou Buffet BSc-MSc Students Tobias Necke Research Projects Please see information on the web page and the annual report 2012. No new projects were funded and case of the head caused a dramatic scientific and third-party funds raid. Due to internal evaluation rules the coal petrology research associate position was cut and employment rules for research associates (12 years of temporary engagement) forced the pullout of the second assistant, leaving in 2013 the health-threat head allone. Recent projects in 2013 without funding: The Zlatitsa para-series group, a new Palaeozoic lithostratigraphic member determined in the Kashana section at the southern Stara Planina mountain range (Central Balkanides, Bulgaria). Cooperation with the Universität Freiburg (D), Université de Genève (CH), University of Sofia "St. Kl. Ohridski" (Bg). Characterization of Fe-smectites from Nui Nua clay, Thanh Hoa province, Viet Nam and its alteration potential considering for HLW repositories. Cooperation with the Ernst-MoritzArndt-Universität, Greifswald (D), Hanoi University of Science (Vietnam), Gesellschaft für Anlagen- und Reaktorsicherheit mbH, Braunschweig (D), Vietnamese Academy of Science and Technology. Fossil Multiphase Normal Faults - Prime Targets for Geothermal Drilling in the Bavarian Molasse Basin. Cooperation with the University of Alberta (Canada), GeoTec Consult, Markt Schwaben (D), Loske Geosciences, Essen (D), GFZ - Helmholtz Centre Potsdam (D), Exorca, Grünwald (D). Determination of rock maturity using vitrinite like bituminite kinetics. A field and laboratory study including liptinite and vitrinite reflectances. Implications for prospection and engeneering geology in meta-sedimentary rocks. Cooperation with GFZ - Helmholtz Centre Potsdam (D). Institute of Applied Geosciences – Technical Petrology 225 Environmental Mineralogy Environmental mineralogy focuses its research on the characterization of individual aerosol particles by electron beam techniques (high-resolution scanning electron microscopy, transmission electron microscopy, environmental scanning electron microscopy). We study individual aerosol particles in order to derive the physical and chemical properties (e.g., complex refractive index, deliquescence behavior, ice nucleation) of the atmospheric aerosol. These data are of great importance for modeling the global radiation balance and its change due to human activities. We are also interested in studying particle exposure in urban environments and at working places. As aerosol particles may have adverse effects on human health, the knowledge of the particle size distribution and the chemical and mineralogical composition of the particles is of prime importance in order to derive the exact mechanisms of the adverse health effects. In addition, we also investigate particles as carriers of pollutants into Nordic and Arctic ecosystems. Our research is carried out in cooperation with the following national and international partners: Max Planck Institute for Chemistry in Mainz, Institute for Atmosphere and Environmental Sciences (University of Frankfurt) Institute for Atmospheric Physics (University of Mainz), Institut für Steinkonservierung (IFS) in Mainz, Institute for Meteorology and Climate Research (Karlsruhe Institute of Technology), Institute for Tropospheric Research in Leipzig, Institute of Atmospheric Physics (German Aerospace Center DLR) in Oberpfaffenhofen, Paul Scherrer Institute (Laboratory of Atmospheric Chemistry) in Villigen (Switzerland), National Institute of Occupational Health (STAMI) in Oslo (Norway), and the Norwegian University of Life Science (NMBU) in Ås (Norway). Staff Members Head Prof. Dr. Stephan Weinbruch Research Associates APL Prof. Dr. Martin Ebert Dr. Nathalie Benker Postdocs PD Dr. Konrad Kandler Dr. Annette Worringen Dr. Dirk Scheuvens Technical Personnel Thomas Dirsch Secretary Astrid Zilz PhD Students Dipl.-Met. Dörthe Müller-Ebert Dipl.-Ing. Katharina Schütze Diploma Students Katharina Schütze Master Students Markus Hartmann Bachelor Students Patrick Marschall 226 Dipl.-Ing. Thomas Herrmann MSc Mark Scerri Angela Moissl Institute of Applied Geosciences – Environmental Mineralogy Research Projects Environmental scanning electron microscopical studies of ice-forming nuclei (DFG Forschergruppe INUIT). Electron microscopy of long-range transported mineral dust. Source apportionment of rural and urban aerosols. Sources of soot at work places (National Institute of Occupational Health, Oslo, Norway). Influence of traffic on the surface of monuments. Particle and organic pollutant emissions of coal burning in the Arctics. Publications Lieke, K.I., Kristensen, T.B., Korsholm, U.S., Sørensen, J.H., Kandler K. Weinbruch S., Ceburnis D., Ovadnevaite J., O’Dowd C.D., and Bilde M. (2013): Characterization of volcanic ash from the 2011 Grímsvötn eruption by means of single-particle analysis. Atmospheric Environment 79, 411-420. Von Hobe M., Bekki S., Borrmann S., Cairo F., D’Amato F., Di Donfrancesco G., Dörnbrack A., Ebersoldt A., Ebert M., Emde C., Engel I., Ern M., Frey W., Genco S., Griessbach S., Grooß J.-U., Gulde T., Günther G., Hösen E., Hoffmann L., Homonnai V., Hoyle C. R., Isaksen I.S.A., Jackson D.R., Jánosi I.M., Jones R.L., Kandler K., Kalicinsky C., Keil A., Khaykin S.M., Khosrawi F., Kivi R., Kuttippurath J., Laube J.C., Lefèvre F., Lehmann R., Ludmann S., Luo B.P., Marchand M., Meyer J., Mitev V., Molleker S., Müller R., Oelhaf H., Olschewski F., Orsolini Y., Peter T., Pfeilsticker K., Piesch C., Pitts M.C., Poole L.R., Pope F.D., Ravegnani F., Rex M., Riese M., Röckmann T., Rognerud B., Roiger A., Rolf C., Santee M.L., Scheibe M., Schiller C., Schlager H., Siciliani de Cumis M., Sitnikov N., Søvde O.A., Spang R., Spelten N., Stordal F., Sumińska-Ebersoldt O., Ulanovski A., Ungermann J., Viciani S., Volk C.M., vom Scheidt M., von der Gathen P., Walker K., Wegner T., Weigel R., Weinbruch S., Wetzel G., Wienhold F.G., Wohltmann I., Woiwode W., Young I.A.K., Yushkov V., Zobrist B., and Stroh F. (2013): Reconciliation of essential process parameters for an enhanced predictability of Arctic stratospheric ozone loss and its climate interactions (RECONCILE): activities and results. Atmospheric Chemistry and Physics 13 (18), 9233-9268. Auras, M., Beer, S., Bundschuh, P., Eichhorn, J., Mach, M., Scheuvens D., Schorling M., von Schumann J., Snethlage R., and Weinbruch S. (2013): Traffic-related immissions and their impact on historic buildings: implications from a pilot study at two German cities. Environmental Earth Sciences 69 (4), 1135-1147. Scheuvens, D., Schütz, L., Kandler, K., Ebert, M., Weinbruch, S. (2013): Bulk composition of northern African dust and its source sediments—A compilation. Earth-Science Reviews 116, 170-194. Fries, E., Dekiff, J.H., Willmeyer, J. Willmeyer, J., Nuelle, M.-T., Ebert, M., Remy, D. (2013): Identification of polymer types and additives in marine microplastic particles using pyrolysis-GC/MS and scanning electron microscopy, Environmental Science-Processes & Impacts 15, 1949-1956. Weinbruch S., Nordby, K.C. (2013): Fatalities in High Altitude Mountaineering: A Review of Quantitative Risk Estimates. High altitude medicine & biology 14 (4), 346-359. Institute of Applied Geosciences – Environmental Mineralogy 227 Chemical composition, mixing state, size and morphology of ice nucleating particles at the Jungfraujoch research station, Switzerland Martin Ebert1, Annette Worringen1, Konrad Kandler1, Ludwig Schenk2, Stephan Mertes2, Susan Schmidt3, Johannes Schneider3, Fabian Frank4, Björn Nillius4 and Stephan Weinbruch1 1 Institute of Applied Geosciences, Environmental Mineralogy, Darmstadt 2 Leibniz-Institute for Tropospheric Research, Leipzig 3 Max Planck Institute for Chemistry, Mainz 4 Frankfurt Institute for Atmospheric and Environmental Sciences Goethe-University Frankfurt am Main An intense field campaign from the Ice Nuclei Research Unit (INUIT) was performed in January and February of 2013 at the High-Alpine Research Station Jungfraujoch (3580 m a.s.l., Switzerland). Main goal was the assessment of microphysical and chemical properties of free-tropospheric ice-nucelating particles. The ice-nucleating particles were discriminated from the total aerosol with the ‘Fast Ice Nucleation CHamber’ (FINCH; University Frankfurt) and the ‘Ice-Selective Inlet’ (ISI, Paul Scherer Institute) followed by a pumped counter-stream virtual impactor. The separated ice-nucleating particles were then collected with a nozzle-type impactor. Finally, with the ICE Counter-stream Virtual Impactor (ICE-CVI) atmospheric ice crystals are separated from the total aerosol and their water content is evaporated to retain the ice residual particles, which are then also collected by impactor sampling. All samples were analyzed in a high-resolution scanning electron microscope. By this technique, the size, morphology, mixing-state and chemical composition are obtained for each particle. In total 2838 ice nucleating particles were analyzed. silicate Ca - rich soot aged sea salt carbonaceous Pb metal oxide Figure 1: Secondary electron images of ice nuclei/residuals (IN/IR): a) alumosilcate; b) Ca-rich; c) soot; d) metal oxide; e) aged sea salt; f) carbonaceous particle. 228 Institute of Applied Geosciences – Environmental Mineralogy Originally more than 5000 potential IN/IR were analyzed in the samples from the three IN/IR-selective pathways. SEM-EDX analysis revealed that in ICE-CVI samples about 60% of the particles were aluminiumoxides, in the ISI samples ~75% of all detected particles were silicon oxide spheres and in FINCH samples ~15% were alloy particles (Fe,Cr,Ni). These particles were identified as instrumental artifacts and were not considered further. Based on their chemical composition, the remaining particles were classified into seven groups: silicates, metal oxides, Ca-rich particles, (aged) sea-salt, soot, sulphates and carbonaceous material. Figure 2: Average relative particle group number abundance of IN/IR at the Jungfraujoch station measured by ISI, FINCH, and ICE-CVI. The most frequent ice nucleating particles/ice residuals at the Jungfraujoch station are silicates > carbonaceous particles > metal oxides. Calcium-rich particles and soot play a minor role. Similar results are obtained by quasi-parallel measurements with an online single particle laser ablation mass spectrometer (ALABAMA). All the tested techniques for measuring ice nucleating particles perform similar from a chemical point of view within the range of their uncertainties and low counting statistics due to the low particle concentrations in free-tropospheric air. Thus, for the first time most of the existing ice nucleation measurement techniques could be compared side by side under real-world atmospheric conditions. Acknowledgment This project is founded by the DFG (INUIT, FOR 1525) Institute of Applied Geosciences – Environmental Mineralogy 229 Diploma Theses in Applied Geosciences Adam, Christian; Ermittlung von Chlorisotopen-Fraktionierungsfaktoren beim Abbau von chlorierten Schadstoffen in wässriger Phase, 1.10.13 Brauner, Sebastian; Bemessung einer Rigole zur Reinfiltration Grundwasser einer Altlastensanierung, 27.09.2013 von gereinigtem Helm, Johannes; Äolische Sedimente in Südhessen, 28.06.2013 Hesse, Jan; Untersuchung der thermophysikalischen Eigenschaften von Bettungsmaterialien für Nieder- und Mittelspannungskabel, 05.11.2013 Schütze, Katharina; Organic pollutant and particle characterization from primary atmospheric emission sources in the Arctic, 10.05.2013 Tunon Vettermann, Gabino; Outcrop analogue study of the Minjur Formation, Kingdom of Saudi Arabia, 09.08.2013 Winicker, Jannes; Massenbilanzierung von persistenten organischen Schadstoffen in einem urban belasteten Gewässer, 29.04.2013 Master Theses in Applied Geosciences Dönges, Florian; Einsatz von Nanotechnologie zur Qualitätssicherung bei der Errichtung von Erdwärmesonden, 20.12.2013 Faißt, Tobias; GIS-based landslide susceptibility modeling in the Lesser Himalaya of Central Nepal, 15.08.2013 Heldmann, Claus; Die hydrothermalen Vorkommen im Zillertal, 11.01.2013 Preiß, Indriani; Anwendbarkeit einer Screeningmethode zur Bestimmung des Nitratabbaupotentials mittels Redoxprofilmessungen in Grundwasserstellen im Hessischen Ried, 28.02.2013 230 Diploma- and Master Theses in Applied Geosciences Master Theses TropHEE in Applied Geosciences Agyare, Eunice Brago; Influence of small scale mining operations on surface water quality and possible treatment options in the Tarkwa area, 27.09.2013 Androulakakis, Andreas; Characterization of chromium species in surface and groundwater samples for the Olatha area, Bangladesh, 10.12.2013 Fatema, Suraiya; Chlorine Isotope Effects During Sorption Of Organic Compounds On Carbonaceous Materials, 11.01.2013 Gebrehiwot, Haftay Hailu; Assessing the Groundwater potential in Tigray region, Ethiopia, using hydraulic and hydro-chemical methods, 07.10.2013 Gomez, Shirin; 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Hydraulische und hydrochemische Untersuchungen der Vernässungsproblematik im Bereich der Weidsiedlung bei Weinheim, 19.07.2013 Krepp, Robin; Kompilation von boden- und felsmechanischen Kennwerten für das Quartär und Tertiär des nördlichen bis mittleren Oberrheingrabens, 21.05.2013 Kuhn, Georg; Messung von Radonkonzentration in Boden- und Raumluft im Stadtgebiet Darmstadt zur Beurteilung von Radonmigration im geodynamischem Kontext, 06.08.2013 Kurka, Sebastian; Standsicherheitsberechnungen von Böschungen auf der Grundlage von Triaxialversuchen an Großproben, 31.03.2013 Kusch, Ramona; Entwicklung von Methoden zur Probenvorbereitung für geothermische Laboruntersuchungen, 23.03.2013 Marshall, Patrick; Zusatzkonzentrationsanalyse bei industriell beeinflussten Messstellen, 08.07.2013 Mentges, Simon; Erste palynologische Bearbeitung der lakustrinen Sedimente aus dem mitteleozänen Maar-See von Offenthal (Sprendlinger Horst, Süd-Hessen), 27.04.2013 Schildt, Sven; TEM Characterization of Electron Beam Irradiated Cu-Nanotubes, 01.11.13 Schröder, Daniel; Lithofazies und Architekturelementanalyse spätpleistozäner bis rezenter Sedimente im NW Fuerteventuras (Kanarische Inseln), 10.02.2013 Schumacher, Christina; Sedimentological detailed modeling of an alluvial fan (Illgraben, Switzerland) with GOCAD® based on ground penetrating radar data, 13.11.2013 Werner, Melanie; Ableitung homogener Sedimentkörper mit Hilfe von Bohrverzeichnissen am Westrand des Oberrheingrabens, 05.07.2013 Wewior, Stefan; Messung von Radonkonzentrationen in der Bodenluft zur Beurteilung der Aktivität von tektonischen Störungen im Raum Darmstadt, 14.05.2013 Zahn, Florian; Stratigraphie und ökologische Bewertung der Forschungsbohrung Messel 2004 A (Sprendlinger Horst, Nordhessen) mit Hilfe palynologischer Methoden, 30.09.2013 232 Bachelor Theses in Applied Geosciences PhD Theses in Applied Geosciences Hussain Al Ajmi: Sedimentology, stratigraphy and reservoir quality of the Paleozoic Wajid Sandstone in SW Saudi Arabia, 15.03.2013 – Betreuer: Prof. Hinderer Karsten Fischer: Geomechanical reservoir modeling – workflow and case study from the North German Basin, 18.10.2013 – Betreuer: Prof. Henk Monika Barbara Hofmann: GIS-based analysis of Geo-Potentials in the Northern Periphery of Belo Horizonte, MG, Brazil, 15.11.2013 – Betreuer: Prof. Hoppe Xiaoke Mu: TEM study of the structural evolution of ionic solids from amorphous to polycrystalline phases in the case of alkaline earth difluoride systems – Experimental exploration of energy landscape, 20.08.2013 – Betreuer: Prof. Kleebe Stefanie Schultheiß; Pseudomorphe Mineralumwandlung von Calcit, Dolomit, Magnesit und Witherit, 31.10.2013 – Betreuer: Prof. Kleebe PhD Theses in Applied Geosciences 233 Materials Science: Alarich-Weiss-Straße 2 L2/01 64287 Darmstadt Applied Geosciences: Schnittspahnstraße 9 B2 01/02 64287 Darmstadt Phone: +49(0)6151/16-5377 Fax: +49(0)6151/16-5551 www.mawi.tu-darmstadt.de Phone: +49(0)6151/16-2171 Fax: +49(0)6151/16-6539 www.iag.tu-darmstadt.de For further information contact: Dr. Joachim Brötz, Phone: +49(0)6151 / 16-4392; eMail: [email protected] Dipl.-Ing.(BA) Andreas Chr. Hönl, Phone: +49(0)6151 / 16-6325, eMail: [email protected] 234 Bachelor Theses in Applied Geosciences
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