There has been first established improvement in strength and electrical conductivity following cyclic redox treatment (redox cycling) of NiO-containing anodes. Such a combination of physical and mechanical properties is caused by formation of continuous sceleton of nickel phase and more fine 10Sc1CeSZ–Ni cermet structure comparing to reduced in hydrogen. A new redox cycling regime has been developed: heating of NiO-containing ceramics up to the fixed temperature in vacuum or inert environment to avoid structure degradation caused by nickel hydride formation, reduction in hydrogenous environment at the temperature mentioned, intermediate degassing between reduction and oxidation half-cycles promoting more fine nickel phase formation.
Taking into account physical, mechanical and economic indexes it was shown that after redox cycling 8YSZ–50Ni cermet becomes the best anode material. Using such a treatment for 8YSZ–50NiO and 10Sc1CeSZ–50NiO ceramics the improvement in strenth by 100…160% and the decrease in specific electrical resistance by 40…80% comparing to the materials reduced in hydrogen can be reached.
It was confirmed that start and stop stages of solid oxide fuel cell (SOFC) operation should be performed in inert environment at 3–20°С/min to provide service reliability of the anodes.
Based on the results obtained and the literature data it was concluded that redox cycling effect on 10Sc1CeSZ–Ni and 8YSZ–Ni cermets structures depends on the treatment temperature: after redox cycling at 800–1000°C anode substrate material strength decreases substantially while at 600–650°C increases. This predetermines investigation of various factors (quantitative and qualitative content of cermets; sintering temperature, porosity; concentrations of reducing and oxidizing environments; reducing and oxidizing temperature) that influence mechanical behaviour of anode substrate material of SOFC.
Keywords: Porous ceramic and metallic materials, microstructure, electrical conductivity, strength, crack growth resistance, high temperature, hydrogen.