Microstructure and Properties of Porous Ni50Cr50-Al2O3 Cermet Support for Solid Oxide Fuel Cells

Porous metal or cermet are used as the support of solid oxide fuel cells. Microstructure and properties of cermet support, which require high electrical conductivity, necessary permeability, good match of thermal expansion with other functional layers and high temperature strength, influence significantly the performance and the stability of solid oxide fuel cells (SOFCs). In this study, a porous Ni50Cr50-Al₂O₃ cermet was designed. The porous cermet was deposited by flame spraying with a powder mixture of 30vol.% Al₂O₃ powder and 70vol.% composite powder containing 40vol.% Ni50Cr50 and 60vol.% polyester. The effect of microstructure on the gas permeability was investigated. The electrical conductivity, thermal expansion coefficient and bending strength were also studied. The cermet stability at high temperature and SOFCs performance were discussed. The results showed that the gas leakage rate of the cermet supports increased with the increase of polyester content in the starting powder. The linear expansion coefficient of the composite cermet decreased with the increase of volume fraction of Al₂O₃. Moreover, the electric conductivity of the cermet increased significantly after high temperature sintering, and reached 1000 S/cm after sintering at 1000°C for 15 hours. The three point bending strength of the Ni50Cr50-based cermet support reached 170 MPa. The cermet support exhibited good high temperature stability, which can fulfil the requirement of SOFCs application.