Oxidation resistance of Ni-toughened Al2O3

Adding nickel inclusions into alumina can enhance its strength and toughness. However, the oxidation resistance of alumina is degraded due to the presence of metallic nickel. In the present study, the oxidation kinetics of Ni-toughened Al2O3 in the temperature region from 1000 to 1300 °C are investigated. In the Al2O3/Ni composites, the Ni inclusions are isolated to each other within the Al2O3 matrix as the Ni content is less than 15 vol.%. The oxidation of the composites is mainly a diffusional process, nickel ions diffuse out and oxygen ions diffuse in. A dense NiAl2O4 spinel is formed on the surface of the composite after oxidation. The oxidation rate constants of the alumina incorporated with isolated Ni inclusions are in a comparable range with those of hot-pressed silicon nitride.