Three dimensional stress analysis of solid oxide fuel cell anode micro structure
Özet
One of the most common problems in solid oxide fuel cells (SOFCs) is the delamination and
thus the degradation of electrode/electrolyte interface which occurs in the consequences
of the stresses generated within the different layers of the cell. Nowadays, the modeling of
this problem under certain conditions is one of the main issues for the researchers. The
structural and thermo-physical properties of the cell materials (i.e. porosity, density,
Young's modulus etc.) are usually assumed to be homogenous in the mathematical
modeling of solid oxide fuel cells at macro-scale. However, during the real operation, the
stresses created in the multiphase porous layers might be very different than those at
macro-scale. Therefore, micro-level modeling is required for an accurate estimation of the
real stresses and the performance of SOFCs. This study presents a microstructural characterization and a finite element analysis of the delamination and the degradation of
porous solid oxide fuel cell anode and electrode/electrolyte interface under various operating temperatures, compressing forces and material compositions by using the synthetically generated microstructures. A multi physics computational package (COMSOL) is
employed to calculate the Von Misses stresses in the anode microstructures. The
maximum thermal stress in the electrode/electrolyte interface and three phase boundaries
is found to exceed the yield strength at 900 C while 800 C is estimated as a critical
temperature for the delamination and micro cracks due to thermal stress generated. The
thermal stress decreases in the grain boundaries with increasing content of one of the
phases (either Ni or YSZ) and the porosity of the electrode. A clamping load higher than
5 kg cm2 is also found to exceed the shear stress limit.
