Abstract
Solid Oxide Fuel Cell (SOFC) can generate high efficiency electric power using H_2 and O_2 gases without environmental pollution. SOFC is expected to become a major electric power source in the future. Under normal operating conditions, fuel is supplied at the anode (Ni-YSZ) and Ni is kept in its reduced state. However, the Ni may be re-oxidized due to factors such as high fuel utilization, accidental interruption of fuel gas supply, and leakage of air. Re-oxidation of Ni-YSZ causes a change in the volume of the anode, and this change causes degradation of SOFC. We study the relationship between the porosity and mechanical properties with Ni-YSZ under the reducing environment and the oxidizing environment for reliable SOFCs. We evaluated the mechanical properties of Ni-YSZ by using an in-situ Small Punch (SP) test method. Experimental results obtained from the SP tests demonstrated that there are weak relationship between porosity and mechanical properties with Ni-YSZ under reducing environment (at an oxygen partial pressure of 10^<-2>5atm, 800℃). Then re-oxidation of Ni-YSZ cermets resulted in residual stress in the anode itself. But these stress can be reduced with increasing porosity. It is suggested that higher porosity Ni-YSZ can avoid the degradation of the mechanical properties.
