Investigation on Electromagnetic Wave Absorption of SiCw/Si₃N₄ Composites Exposed to Short-Time Oxidation

As oxidation is inevitable during application of microwave absorbing materials (MAM) exposed to oxygen-containing atmosphere at elevated temperatures. The investigations concerning influences of oxidation on microstructure and microwave absorption (MA) properties are of great significance. Aiming to better regulating MA for Si₃N₄-based ceramics serviced in high temperature environment, the evolution of MA properties of SiCw/Si₃N₄ composites (S_wSN) after oxidation at 1200 °C in ambient air for short time was studied. It was found that after oxidation for 7.5 h, both the real and imaginary permittivity of S_wSN showed only slight decrease due to good oxidation protection provided by dense SiO₂ layer formed on the surface. Moreover, S_wSN after short-time of oxidation also showed an almost negligible decline in MA properties. S_wSN which has good oxidation resistance and stable microwave attenuation abilities was subjected to oxidation at 1200 °C for short time. The results showed its favorable and potential applications in high-temperature microwave absorption fields.