Microstructural evolution and mechanical properties of Si₃N₄–SiC (nanoparticle)–Si₃N₄ (whisker) composites

The effects of SiC-nanoparticle and Si₃N₄-whisker additions on the microstructural evolution and mechanical properties of Si₃N₄ were investigated. The addition of SiC nanoparticles suppressed Si₃N₄ grain growth, leading to an improvement in the flexural strength. On the other hand, Si₃N₄ whiskers in the specimen promoted the formation of large elongated grains, which were found to be beneficial to the fracture toughness of the material. When both SiC nanoparticles and Si₃N₄ whiskers were added concurrently, large grains were formed in fine matrix grains. The microstructure of Si₃N₄ was controlled by adjusting the relative concentrations of SiC nanoparticles and the Si₃N₄ whiskers added. These compositional and microstructural variations of the Si₃N₄ had significant influence on the mechanical properties, such as strength, fracture toughness, R-curve behavior, and high-temperature strength.