Abstract
The fabrication process and microstructure of Si3N4-based nanocomposites were investigated for the improvement in fracture toughness. The fine Si3N4 powders containing metal nitride particles such as VN, NbN, TaN and TiN were synthesized by heating the mixtures of Si3N4 and corresponding metal oxide powders in a N2 atmosphere. The obtained VN/Si3N4 and TiN/Si3N4 powders were confirmed to be very fine (20 to 30 nm in diameter). These composite powders were sintered with sintering aids. No improvement in fracture toughness for the VN/Si3N4 composites. For the TiN/Si3N4 composites, in which nano-sized TiN grains were dispersed within the Si3N4 matrix Brains, the fracture toughness was increased. This was probably due to crack propagation through intragrains of the Si3N4 matrix.
