Suggestions for new Master's theses

Where can you do research in a motivating environment? Implement your own ideas? In the field of Material Physics of course. Below are several current topic possibilities for your Master thesis:


 ______________ 

Fundamental materials physics and mechanical properties

Molecular dynamics simulation of hetero-phase interfacesThe role of grain boundary segregation in the stabilization of nanocrystalline materials

Energy storage and conversion materials

Micro-gravimetry of de-/intercalation in LiFePO4 thin film electrodes
Nanoanalysis of interface chemistry in LiNiF conversion electrodes (in cooperation with J. Maier, MPI-FKF)
Nanochemistry of the Half Heusler TiNiSn (collaboration with A. Weidenkaff)
Phase transformation in ultra-thin LiFePO4 electrodes

Nanostructured materials

         Phase separation in wire structures

High resolution material analysis

Atom probe analysis of polymer/ceramic compounds
Organic molecules and biological structures in atom probe tomography
Catalysis by metallic wiresPhase separation and solubility in the Cu/Ni and Pd/Pt phase diagram

(As of 12.12.2016)

Information and consulting:
Prof. Dr. Guido Schmitz (Tel: (0711) 685 61902, )

________________

Fundamental materials physics and mechanical properties

Molecular dynamics simulation of hetero-phase interfaces. The chemical structure and thickness of the interface in Ag/Cu or Ni/Au bilayers at different temperatures will be calculated by simulations based on embedded atom potentials. The aim is to determine the width of the chemical transition and also the interfacial energy and, if possible, the entropy. Direct comparison with atom probe measurements should reveal the characteristic of the coefficient of the gradient energy in thermodynamics of inhomogeneous systems. (Supervisors: Sebastian Eich, Guido Schmitz)

The role of grain boundary segregation in the stabilization of nanocrystalline materials. Nanocrystalline materials are promising for their good combination of strength and ductility. However, fast grain growth prevents application. In emulsions, it is well known that small droplets can be stabilized by surface-active substances. Does this principle also work for solid materials? In this project, nano-crystalline Cu(Ta) will be sputter-deposited. The grain size is determined as a function of temperature is characterized by X-ray diffraction. The segregation of Ta to the grain boundaries is quantified by atom probe tomography. (Supervisors: Guido Schmitz/Patrick Stender)

 
Energy storage and conversion materials


Micro-gravimetry of de-/intercalation in LiFePO4 thin film electrodes.
Solid electrolyte interface (SEI) layers play an important role for the cycle stability and degeneration of secondary batteries. Their exact composition and mechanisms of formation are practically unknown. By innovative simultaneous micro-gravimetry and electro-chemistry, we characterize SEI layer formation at the example cathode material LiFePO4 in detail. (Supervisors: Guido Schmitz/Susann Nowak)

Nanoanalysis of interface chemistry in LiNiF conversion electrodes (in cooperation with J. Maier, MPI-FKF). Battery anodes by the conversion principle promise high storage capacity. During electrochemical cycling a refinement of the microstructure appears that increases the density of internal interfaces enormously. Thus Li storage at the interfaces may become dominant. We will try to investigate the interfaces and the local Li concentration by latest atom probe tomography. Layer materials are deposited by ion beam sputtering, electrochemically cycled in half cells, cut by focused ion beams (FIB) and analyzed by Atom Probe tomography. (Supervisors: Guido Schmitz/Jianshu Zheng)

Nanochemistry of the Half Heusler TiNiSn (collaboration with A. Weidenkaff). The half Heusler alloy TiNiSn has a promising figure of merit in high temperature thermoelectric cells. The electrical and thermal conductivity is possibly controlled by nanometric precipitates. In a joint project with Anke Weidenkaff, we will produce thin films of this material and investigate their chemical homogeneity and decomposition on smallest length scales by latest atom probe tomography. (Supervisors: Guido Schmitz/Patrick Stender)

Phase transformation in ultra-thin LiFePO4 electrodes. LiFePO4 is a preferred cathode material, which shows an interesting phase separation during Li intercalation. It has been postulated that the miscibility gap is strongly affected by mechanical stress appearing in the battery cathodes. We will measure and hopefully confirm the stress dependency by reducing the thickness of thin film cathodes down to a few nanometers (Supervisors: Guido Schmitz/Patrick Stender)

Nanostructured materials

Phase separation in wire structures. Nanowires are intensively studied, because they may form design elements of future improved microelectronics. We would like to go a step further and elaborate internal structures within the nanowires themselves. Owing to the 1D structure of wires (long, very thin cylinder), we do expect a periodic stacking of decomposing phases. What is the periodicity of this stacking? The project will anneal alloyed nanowires in order to induce phase separation. TEM investigation will determine the influence of the 1D geometry on the atomic transport and the developing phase morphology. (Supervisor: Guido Schmitz)

 

High resolution material analysis

Atom probe analysis of polymer/ceramic compounds. Just a few years ago, only metallic samples could be analyzed by atom probe tomography (APT). By the innovative assistance of femto-second laser pulses, the method now can investigate also semiconductors and ceramics – and most recently shown by us – polymers. Now we want to go a step further: analyzing polymer/ceramic compounds as a model for biological materials which often represent ceramic-protein compounds. V2O5/poly-electrolyte multi-layers will be deposited in cooperation with the team of Prof. Bill. The structure of the inner interfaces will be analyzed for the first time with APT. (Supervisor: Patrick Stender)

Organic molecules and biological structures in atom probe tomography. By introducing laser-assisted field evaporation, we could recently demonstrate the analysis of polymeric materials even with atom probe tomography. In this project we want to embed interesting organic units (e.g. hemoglobin, ferritin or similar proteins) into a polymer matrix and then to evaporate both in a controlled fashion. The project has a pioneering character since on success, a microscopic chemical analysis of proteins or even DNA chains might become possible in future. (Supervisor: Patrick Stender)

Catalysis by metallic wires. In today’s catalytic converters, platinum is a key catalytic component to oxidize hazardous gases like CO and CxHx. To reduce the costs of the catalytic converters, it would be beneficial to use a Palladium/Platinum alloy instead of pure Pt. The addition of Pd will change the properties of the catalytic process and the stability of the catalytic component. Our goal is to investigate the oxidation of Pt/Pd alloy particles by atom probe tomography and to get an insight into the material changes during the catalytic process. (Supervisor: Patrick Stender)

Phase separation and solubility in the Cu/Ni and Pd/Pt phase diagram. Often binary alloys reveal a miscibility gap to lower temperature. But sometimes this temperature is so low that the equilibrium solubility is hard to establish. That is why in exceptional cases the miscibility gap could not be determined yet, although technological important (e.g. Pd/Pt in catalysis). We will try to measuring for the first time the equilibria by atom probe tomography on the nanoscale. Methods: Sputter deposition, Focussed Ion beam preparation, atom probe tomography. (Supervisors: Rüya Duran, Patrick Stender)