Mechanical Properties and Microstructure of Si3N4-TiC Nanocomposites
摘要
Si3 N4/TiC nanocomposite ceramics have been fabricated by hot pressing technique with Al2O3 and Y2O3 as additives.The results showed that well dispersed composite powder was carried out by adding dispersant and adjusting pH values of suspensions. Remarkable increase in flexural strength at room temperatures was obtained by adding nanoparticles in Si3N4 matrix with 10% (wt pct) of nano-Si3N4 and 15% of nano-TiC. The flexural strength, fracture toughness and hardness were 1025 MPa,7.5 MPa·1/2 and 15.6 GPa,respectively.The microstructures of materials were analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), which indicated that TiC nanoparticles distribute in the matrix and at the grain boundaries. According to the fracture form, low contents of nano particles could refine matrix grains and lead to the crack deflection as well as crack pinning. The multiplex microstructure was formed by mixing nano-Si3N4 particles. The crack trajectories exhibited crack deflection, rod-like grain bridging and pull-out.