Investigation on the Mechanical Behavior and Fracture Mode of Ice-Templated NiO-YSZ Anode Electrode for Solid Oxide Fuel Cells Application

An aqueous slurry of nickel oxide (NiO) and yttria-stabilized zirconia powders mixture was freeze-cast to fabricate anisotropic porous-graded structures for solid oxide fuel cell anodes applications. The cooling rate and solid loading were controlled during the process. The porosity and compressive strength of the fabricated anodes were evaluated through Archimedes method and ring-on-ring compressive test, respectively. Scanning electron microscopy, aided by Fiji image analysis software, was used to characterize the pore morphology and lamella thickness. The recorded porosity and compressive strength were in the range of 59-75% and 2.7-14.02 MPa, respectively. It was proven that the amount of solid load controlled the overall porosity and lamella wall thickness, while the cooling rate greatly affected the microstructure of the freeze-casts. Weibull analysis showed that the Weibull modulus had a direct relationship with the cooling rate. The mode of fracture was related to porosity and lamella wall thickness and changed from cellular to brittle-like failure for a high-to-low pore volume regime.