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Institute of Energy and Climate Research

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Modeling

The modeling team develops mathematical and numerical descriptions of the physical processes governing manufacturing and the later operation of the produced components.

The thus acquired understanding supports the development of modern processing technologies and allows us to design components with optimal functional properties. We mainly use macro-scale simulation methods (mechanical and multi physics finite element analyses, computation fluid dynamics – CFD), analytical-numerical models (e.g. for life-time calculations), but also mesoscopic methods resolving the material’s microstructure (Monte Carlo, diffusion). In addition to different workstations, we own a computing cluster with 320 cores and 3.2 TB RAM to run the simulations. The most important thermo-mechanical material properties (Young’s modulus, viscosity, sintering strains etc.) we can measure with our own equipment. Some examples of our work follow.

Thermal Spraying: Plasma Jets and Coating Microstructures

Thermal Spraying: Plasma Jets and Coating MicrostructuresLeft: Simulation of the temperature distribution during atmospheric plasma spraying; right: simulated microstructure of a PS-PVD coating

Using CFD, we model the flow field, the temperature distribution, and the trajectories of injected particles during atmospheric and suspension plasma spraying, plasma-spray physical vapor deposition (PS-PVD), and aerosol spraying. Thereby, we obtain an understanding of the experimentally hard-to-access processes. In addition, we simulate the microstructure in particular of the coatings applied by PS-PVD with aid of Monte-Carlo calculations for the transport of the material clusters as a function of the process parameters.

Life-Time of Thermal Barrier Coatings

Life-Time of Thermal Barrier CoatingsLeft: stress distribution in a thermal barrier coating at the interface to the bond coat for a real surface topography; right: life-time calculation for a simplified surface topography

We complement the time-consuming experimental investigation of the failure of coating systems by the modelling of the failure mechanism. Thermal barrier coatings for gas turbines contribute much to both their reliability and their safety. We thus developed a statistical model of the life-time and its variance for this multilayer system which includes the changes in the layer structure and the material properties under operation. The mechanical stresses are calculated as a function of time, that weaken the material by an subcritical crack growth and ultimately lead to failure of the coating.

Process Simulation of Field Assisted Sintering

Process Simulation of Field Assisted SinteringLeft: Temperature field calculated during field assisted sintering; Right: Microstructural development simulated with the Monte Carlo method

In the field of sintering of ceramics, we conduct simulations of innovative fabrication processes, such as Field Assisted Sintering (FAST/SPS) and Flash Sintering. In order to develop a strategy to control and enhance the process, finite element analysis are carried out that predict the temperature field and its transient development. The resulting microstructures are simulated with the help of the Monte Carlo method, which allows us to observe the dynamics of densification, grain growth, and pore coarsening.

Gas Transport in Gas Separation Membranes

Gas Transport in Gas Separation MembranesSimulated flow field in a real porous support of a oxygen conduction membrane

The structure of membrane supports for gas separation of membrane reactors decisively affect the overall performance of the complete membrane assemblage. The flux through the multi-layered membrane is calculated using e.g. the Binary Friction model as a function of operating configurations (pressure, gas composition, with/without sweep gas, orientation of the support). The necessary transport parameters we either measure experimentally or obtain them by simulations carried out on real microstructures (e.g. computed tomography). With help of the obtained relations we developed strategies to optimize the microstructure that are now transferred to practise.

Mechanical Loads in All-Solid-State Batteries

Mechanical Loads in All-Solid-State BatteriesElastic stress state in a reconstructed three dimensional microstructure of a composite cathode made from LiCoO2 (LCO) / Li7La3Zr2O12 (LLZ) after charging the all-solid-state battery

In contrast to batteries with liquid electrolytes, dense-grained electrodes of all-solid-state batteries provide only a very small strain tolerance required for the volume change of the storage material during charging and discharging. This causes large mechanical stresses and material failure. Based on stress calculations in real microstructures (obtained at high resolution by scanning electron microscope sectional imaging, FIB-SEM), we design microstructures that are significantly more strain tolerant and thus generate almost no mechanical stresses while still fulfilling all prerequisites of electrode materials (conductivity and capacity).


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