Preparation and characterization of Si3N4/TiC nanocomposite ceramics

By adding nano-sized Si3N4 and nano-sized TiC particles into the submicro-sized Si3N4 matrix, Si3N4/TiC nanocomposite ceramics were fabricated by means of hot pressing technique with Al2O3 and Y2O3 as sintering aids. The experimental results showed that optimal mechanical properties were achieved for the composite with the addition of 10 wt.% nano-sized Si3N4 particles and 15 wt.% nano-sized TiC particles, with the flexural strength, fracture toughness and Vicker's hardness being 1090 MPa, 7.5 MPa·m1/2 and 17 GPa respectively. The microstructure and phase composition of the composites were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). It was found that the rod-like β-Si3N4 grains were characterized by an obvious duplex distribution, with small β-Si3N4 grains embedded in the matrix of large β-Si3N4 grains. The fracture surface of the composite was observed to exhibit a mix of intergranular and transgranular fracture as a probable result of the presence of both intergranular and intragranular TiC nanoparticles.