[SY-F4] Symposium F-4

[SY-F4] Coarsening and grain-growth in an SOFC-anode under surface and grain boundary self-diffusion: A Multiphase-field approach

^○Paul Hoffrogge¹, Daniel Schneider^1,2, Britta Nestler^1,2, Patricia Haremski^2,3, Matthias Wieler³, Piero Lupetin³ (1.Karlsruhe University of Applied Sciences, Germany, 2.Karlsruhe Institute of Technology, Germany, 3.Robert Bosch GmbH, Germany)

Solide oxide fuel cells (SOFCs) convert chemical energy stored in form of a gaseous fuel into electrical energy. Due to the typically high energy-conversion efficiencies achieved, SOFCs are a very promising technology to reduce carbon emission. One of the critical parameters to be economically competitive is the lifetime of an SOFC device. In order to improve the SOFCs long-term performance it is essential to obtain a better understanding of the underlying physical processes leading to a decrease in SOFC performance during operation.
The present study focuses on the evolution of a polycrystalline and porous 3D microstructure of an Ni-YSZ (yttria-stabilized zirconia) SOFC-anode during isothermal coarsening. We employ a multiphase-field model which incorporates self-diffusion of nickel by a grand-chemical formulation to simulate grain-boundary and surface diffusion coupled with simultaneous growth of the inherent Ni-grains. We validate the model by 2D thermal-grooving simulations under surface-diffusion and by a quantitative comparison with analytical results. A comprehensive study of several input parameters such as grain-size on the coarsening behavior of the SOFC-anode is performed. The detailed investigation includes an analysis of the microstructure as a function of particle size, tortuosity and triple-phase boundary length.