MECHANISM OF HIGH-TEMPERATURE OXIDATION OF ZrB₂-BASED COMPOSITE CERAMIC OF ZrB₂–SiC–AlN SYSTEM

Abstract

In this paper the process of oxidation under high temperatures (1170–1550 °C) of ZrB₂–SiC–AlN composite material structure and scale composition have been investigated. Hereby it has been established the two-stage- mechanism of oxide layer formation, the latter at the low temperature stage (1170–1250 °C) the main interval ZrB₂–based layer is formed, the latter being the solid solutions of xAl₂O₃–ySiO₂ and also colonies of zirconium oxide crystals. The latters are placed at the borders of the mullite phase grains. The oxide layer which is formed on the sample surface is the effective potencial barrier which prevents to oxygen diffusion into the sample volume mulite solid solution of xAl₂O₃–ySiO₂ system and colonies of ZrO-crystals. The latter are disposed at the borders of mullite phase. It has been established that the oxide film, formed at the oxidation, is the potential barrier which prevents from the oxygen diffusion to the specimen volume.