Si3N4/TiN composites produced from TiO2-Modified Si3N4 powders

Abstract

Si3N4/TiN composites have been produced by hot pressing at temperatures from 1600 to 1800°C in a nitrogen atmosphere, using silicon nitride powders prepared by self-propagating high-temperature synthesis and surface-modified with titanium dioxide nanoparticles. We examined the effect of TiO2 content on the microstructure, phase composition, and mechanical strength of the ceramics. It is shown that titanium nitride can be formed by the reaction Si3N4 + TiO2 → TiN + NO + N2O + 3Si. The Si3N4/TiN composites containing 5–20% TiN have a low density, high porosity, and a bending strength of 60 MPa or lower. In Si3N4/TiN ceramics produced using calcium aluminates as sintering aids, the silicon nitride grains are densely packed, which ensures an increase in strength to 650 MPa.