Influences of Al₂O₃ grain size on high-temperature oxidation of nano-Ni/Al₂O₃ composites

Two 5 vol% Ni/Al2O3 composites with the difference in Al2O3 grain size were fabricated by pulsed electric current sintering technique to investigate the influence of Al2O3 grain size on oxidation behavior of the composites. Average Al2O3 grain sizes of two fabricated composites were 1.1 μm and 0.5 μm after sintering. Oxidation tests were conducted at temperatures ranging from 1100 to 1350 °C for 1–48 h in air. A thin NiAl2O4 layer was observed in exposed surface of samples after oxidation. An oxidized zone that consisted of Al2O3 matrix and NiAl2O4 grains was defined. Growth of the oxidized zone obeyed the parabolic law. Influences of Al2O3 grain size on high-temperature oxidation of the composites were discussed.