Oxidation kinetics of hot-pressed ZrB2–SiC ceramic matrix composites

The isothermal oxidation of ZrB2 ceramics with different content of SiC was carried out in air up to 1700 °C, and the effect of chemical composition on the oxidation kinetics of ZrB2–SiC ceramics was analyzed. As indicated by the experimental results, both ceramics with 20 vol% and 30 vol% SiC particles followed near parabolic oxidation kinetics. And higher concentration of SiC led to better oxidation resistance performance due to the formation of more silica glass on the surface of the specimens and formation of zircon phase ZrSiO4. In addition, the oxidation of the ceramic composites is diffusion controlled and the activation energies for the diffusion of oxygen in the oxide scale of the ceramics oxidized at temperatures below 1500 °C were 5134 J/mol and 5960 J/mol for ZS2 and ZS3, respectively. Then the oxidation of the ceramics transformed to reaction controlled under elevated temperature due to evaporation of the protective silica glass. Furthermore, the evolution process of the surface morphology and oxide scale of the ceramic during initial oxidation stage was given detailed investigation.