M.T. Mehran, R-H Song, T-H Lim, S-B Lee, J-W Lee, S-J Park
Korea Institute of Energy Research,
Keywords: solid oxide fuel cell, degradation, anode support, mechanical strength, Al2O3
Summary:Solid oxide fuel cells are well known to be highly efficient and clean energy conversion devices for stationary and portable power generation. The ceramics based SOFC’s operate at high temperatures (>700 °C) and the durability of SOFC is critical for the early commercialization of SOFC based systems. Anode support of the SOFC becomes vulnerable to severe degradation during the long-term operation due the thermal stresses, humid and reducing environment, and the threat of redox-cycling. The mechanical strength of the nickel-yttria-stabilized zirconia (Ni-YSZ) anode supports needs to be assessed and improved for a durable SOFC. In this study, we developed a highly durable Ni-3YSZ based anode support material for SOFC with higher mechanical strength and stability. At first, the strength and mechanical properties of the typical Ni-3mol% yttria-stabilized zirconia (Ni-3YSZ) and Ni-8mol% yttria-stabilized zirconia (Ni-8YSZ) were assessed during 1000h long-term degradation test. It was found that after 1000 h, the flexural strength of the Ni-3YSZ anode support cermet was decreased up to 57%. Therefore, the mechanical properties of Ni-3YSZ anode support were improved by the addition of dispersed nano-particles of Al2O3. Different amounts of nano-Al2O3 were added and their effect on long-term stability was studied. The anode support with 3wt. % nano-Al2O3 dispersed Ni-3YSZ (Al-Ni-3YSZ) showed only 18% degradation in the mechanical strength. Further analysis by SEM and XRD before and after the long-term degradation test showed that the tetragonal to monoclinic phase transformation in zirconia was reduced due to the addition of nano-Al2O3 in Ni-3YSZ cermet, resulting into an improved long-term stability and higher mechanical strength. The nano-oxide dispersed Ni-3YSZ anode support showed superior mechanical strength after 1000h long-term test and can be used to fabricate a durable SOFC promising structural integrity to fuel cell stack over the lifetime.