Influence of Si-Doping of Nano-Ni Dispersed Al₂O₃ Composites on High-Temperature Oxidation

Abstract

The oxidation kinetics of 5 vol% nano-Ni dispersed Al₂O₃ with Si-doping (nano-Ni/Al₂O₃-Si) was studied in the present paper. The starting powder mixture was prepared by drying aqueous slurry consisting of alumina with nickel nitrate and Si (OCH₃)₄. The powder mixture was reduced at 600°C for 12 h in a stream of Ar-1%H₂ gas mixture. Nano-Ni/Al₂O₃-Si was densified by pulsed electric current sintering. The oxidation test was conducted at 1200–1350°C for 1–14 d in air. Oxidized zone consisted of Al₂O₃ matrix and NiAl₂O₄ as the oxidation product. Growth of the oxidized zone followed a parabolic manner. A thin NiAl₂O₄ layer was also observed on the sample surface. Si-doping decreases growth rate of oxidized zone effectively at lower temperatures such 1200°C.