Microstructural evolution and mechanical properties of Si 3 N 4 –SiC (nanoparticle)–Si 3 N 4 (whisker) composites

The effects of SiC-nanoparticle and Si 3 N 4 -whisker additions on the microstructural evolution and mechanical properties of Si 3 N 4 were investigated. The addition of SiC nanoparticles suppressed Si 3 N 4 grain growth, leading to an improvement in the flexural strength. On the other hand, Si 3 N 4 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 Si 3 N 4 whiskers were added concurrently, large grains were formed in fine matrix grains. The microstructure of Si 3 N 4 was controlled by adjusting the relative concentrations of SiC nanoparticles and the Si 3 N 4 whiskers added. These compositional and microstructural variations of the Si 3 N 4 had significant influence on the mechanical properties, such as strength, fracture toughness, R-curve behavior, and high-temperature strength.