Middle stage heat treatment for microstructure control of reaction-bonded silicon nitride-silicon carbide composite

Abstract

A silicon nitride-silicon carbide composite was fabricated from silicon and carbon powders by reaction-bonding and post-hot-pressing procedures. The fabricated specimens had a nanocomposite-like microstructure with β-silicon nitride and β-silicon carbide. For some specimens, middle-stage heat treatment was applied before hot-pressing, which resulted in microstructure formation with large and elongated silicon nitride grains. With this microstructure, the specimens subjected to the middle stage heat treatment exhibited much higher fracture toughness than those not subjected to it.