HIGH-TEMPERATURE OXIDATION OF ZrB₂–MoSi₂–AlN COMPOSITE CERAMICS

Abstract

The oxidation mechanism for ZrB₂–MoSi₂–AlN composite ceramics has been studied in the range 1550–1680 °C. The oxidation stages and scale structure and phase composition have been established. Two main scale layers have been found to form. The outer layer forms at ~1550 °C. It consists of SiO₂ (β-cristobalite) and Al₂O₃–SiO₂ solid solution in which MoO₃ is present. At 1680 °C, a layer of crystal zirconium dioxide colonies forms at the boundary with the initial ceramic surface. This layer is an effective protective barrier for oxygen diffusion into the sample.