High-Temperature Oxidation Behavior of 10 vol% AlN/Al₂O₃ Composites

Abstract

Alumina composites dispersed with 10 vol% AlN particles are prepared by commercial α-Al₂O₃ and AlN powder. The pulsed electric current sintering is used to densify the bulk samples. The high-temperature oxidation experiments are conducted at temperatures ranging from 1200 to 1350°C for 6, 12 and 24 h in the air environment. The internally oxidized zone (IOZ) is developed from the sample surface to consist of the Al₂O₃ matrix with small closed pores. The growth of IOZ obeys the parabolic law, which means the rate-controlling process is mass transport in IOZ. The high-temperature oxidation behavior of 10 vol% AlN/Al₂O₃ is compared with the 10 vol% Ni/Al₂O₃ composites. The differences in the microstructure at IOZ and the diffusion of oxygen through the Al₂O₃ matrix grain boundaries dependence on the oxygen partial pressure are discussed for understanding the high-temperature oxidation behavior of both composites.

Fig. 6 Fractured surface after oxidation at 1350°C for 12 h with their microstructure at IOZ and non-oxidized zone respectively, (a)–(c) for 10 vol% AlN/Al₂O₃ and (d)–(f) for 10 vol% Ni/Al₂O₃ composites.