Structure evolution of ZrB₂–SiC during the oxidation in air

The structure evolution and oxidation behavior of ZrB₂–SiC composites in air from room temperature to ultrahigh temperature were investigated using furnace testing, arc jet testing, and thermal gravimetric analysis (TGA). The oxide structure changed with the increasing temperature. SiC content has no apparent influence on the evolution of structure during the oxidation of ZrB₂–SiC below 1600 °C. However, the evolution of structure for ZrB₂–SiC above 1800 °C was significantly affected by the SiC content. The formation of the SiC depleted layer in the ZrB₂–SiC system not only depends on the surrounding conditions of pressure and temperature but also on the structure distribution of the SiC in the ZrB₂ matrix. The apparent recrystallization of the ZrO₂ occurred above 1800 °C. The SiC content should be controlled at ∼16% in the ZrB₂–SiC system for the ultrahigh-temperature application. The mechanisms of the structure evolution during oxidation in air were also analyzed.