Densification and microstructure of Si 3 N 4 -TiN ceramic composites

Abstract

Silicon nitride is a ceramic material widely used in various structural applications at high temperatures owing to its excellent combination of mechanical and thermal properties. To increase the application of Si 3 N 4 , many researches have been developed to improve its fracture toughness and processing conditions. In this study, the sintering and microstructure of Si 3 N 4 -TiN composites, containing Al 2 O 3 and Y 2 O 3 as sintering aids, were studied. Samples were obtained by the conventional method of mixing powders and sintered at 1750 ºC/1 h and 1815 ºC/1 h under nitrogen atmosphere. Density values of the samples were determined by the Archimedes method, reaching values between 96.9% and 98.0% of theoretical density, with a porosity of less than 0.5%. The sintered samples were analyzed by X-ray powder diffraction and scanning electron microscopy. The results showed the materials reached high fracture toughness, low hardness and a microstructure with TiN grains dispersed in a β-Si 3 N 4 matrix containing an amorphous intergranular phase.