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Understanding Degradation Phenomena in Solid-Oxide Fuel-Cell Anodes by Phase-Field Modeling and Analytics
The current work analyzes degradation effects in solid-oxide fuel cell anodes with the phase-field method. A model extension for interface diffusion is formulated and calibrated. Large-scale 3D-simulations provide interesting insights into phenomena at the microscale which are responsible for the degradation
High Performance Computing in Science and Engineering '19
This book presents the state-of-the-art in supercomputer simulation. It includes the latest findings from leading researchers using systems from the High Performance Computing Center Stuttgart (HLRS) in 2019. The reports cover all fields of computational science and engineering ranging from CFD to computational physics and from chemistry to computer science with a special emphasis on industrially relevant applications. Presenting findings of one of Europe’s leading systems, this volume covers a wide variety of applications that deliver a high level of sustained performance. The book covers the main methods in high-performance computing. Its outstanding results in achieving the best performance for production codes are of particular interest for both scientists and engineers. The book comes with a wealth of color illustrations and tables of results.
Mehrskalige Charakterisierung der Hochtemperatur-Brennstoffzelle (SOFC)
Die Hochtemperatur-Brennstoffzelle (SOFC) als Strom- und Wärmeproduzent der Zukunft stellt eine wichtige Schlüsseltechnologie für eine klimafreundliche Energieversorgung dar. Vorrangige Entwicklungsziele sind die Verbesserung der Lebensdauer und die Verringerung der Kosten der SOFC-Komponenten. In dieser Arbeit werden mikrostrukturelle Veränderungen, die während der Zellherstellung und im Betrieb (Alterungsverlauf) auftreten, durch den Einsatz mehrskaliger Untersuchungsmethoden identifiziert. - The solid oxide fuel cell (SOFC) as electricity and heat producer of the future represents a key technology in the context of a climate-friendly energy supply. Research focuses on the improvement of the lifetime and cost reduction of the SOFC components. In this work, microstructural changes that occur during cell production and operation (aging process) are identified by multiscale examination methods.
Diffusionseigenschaften von Nickel in einer Festoxid-Brennstoffzelle
In dieser Arbeit wurden Thermal Grooving Experimente an Anodenmikrostrukturen, Ni-Polykristallen sowie Ni-Bikristallen durchgeführt und die Korngrenzfurchen mittels eines AFM vermessen. Die Ergebnisse liefern erstmals zuverlässige Werte sowie die komplette Anisotropie der relevanten Materialparameter – der relativen Korngrenzenergien und der Oberflächendiffusionskoeffizienten – von Nickel unter realitätsnahen Betriebsbedingungen einer SOFC-Anode. - In this work, thermal grooving experiments were performed on anode microstructures, Ni polycrystals and Ni bicrystals. The grain boundary grooves were measured by means of an AFM. The results provide for the first time reliable values as well as the complete anisotropy of the relevant material parameters - the relative grain boundary energies and the surface diffusion coefficients - of nickel under realistic operating conditions of an SOFC anode.
Application of Data Mining and Machine Learning Methods to Industrial Heat Treatment Processes for Hardness Prediction
This work presents a data mining framework applied to industrial heattreatment (bainitization and case hardening) aiming to optimize processes and reduce costs. The framework analyses factors such as material, production line, and quality assessment for preprocessing, feature extraction, and drift corrections. Machine learning is employed to devise robust prediction strategies for hardness. Its implementation in an industry pilot demonstrates the economic benefits of the framework. - This work presents a data mining framework applied to industrial heattreatment (bainitization and case hardening) aiming to optimize processes and reduce costs. The framework analyses factors such as material, production line, and quality assessment for preprocessing, feature extraction, and drift corrections. Machine learning is employed to devise robust prediction strategies for hardness. Its implementation in an industry pilot demonstrates the economic benefits of the framework.
Consequences of hydroxyl generation by the silica/water reaction - Part I: Diffusion and Swelling
Water diffusing into silica surfaces gives rise for several effectson diffusion behaviour and mechanical properties. Water added to silica glass increases its specific volume so that the silica expands near the surface. Mechanical boundary conditions give rise for compressive “swelling stresses”. This fact provides a tool for the interpretation of many experimental observations from literature.
Modeling transport properties and electrochemical performance of hierarchically structured lithium-ion battery cathodes using resistor networks and mathematical half-cell models
Hierarchically structured active materials in electrodes of lithium-ion cells are promising candidates for increasing gravimetric energy density and improving rate capability of the system. To investigate the influence of cathode structures on the performance of the whole cell, efficient tools for calculating effective transport properties of granular systems are developed and their influence on the electrochemical performance is investigated in specially adapted cell models.
Dynamic Model-based Analysis of Oxygen Reduction Reaction in Gas Diffusion Electrodes
In this work, the first simulation model of oxygen depolarized cathodes (ODC), which are silver catalyst-based gas diffusion electrodes, is presented that considers the phase equilibrium of the gas-liquid interface and structure-related inhomogeneities in electrolyte distribution. By means of the model it has been identified that mass transport of water and ions in the liquid phase is a crucial factor for electrode performance and how it is influenced by the electrode structure.
Development of NbN based Kinetic Inductance Detectors on sapphire and diamond substrates for fusion plasma polarimetric diagnostics
This work aimed at designing, studying and producing the first prototypes of KIDs tailored for fusion plasma polarimetric diagnostics. Diamond was considered for the first time as substrate material for low-temperature superconducting detectors given its unmatched optical, radiation hardness and thermal qualities, properties necessary for working environments potentially saturated with radiation. This work represents a first step toward the optimization and final application of this technology.
Multiscale Modeling of Curing and Crack Propagation in Fiber-Reinforced Thermosets
During the production of fiber-reinforced thermosets, the resin material undergoes a reaction that can lead to damage. A two-stage polymerization reaction is modeled using molecular dynamics and evaluations of the system including a fiber surface are performed. In addition, a phase-field model for crack propagation in heterogeneous systems is derived. This model is able to predict crack growth where established models fail. Finally, the model is used to predict crack formation during curing.
