抄録
Fine Si3N4 powder and Si3N4-TiN composite powder were prepared by vapor phase reaction method, and hot-pressed to investigate the effects of sintering condition and TiN inclusion on the microstructure and mechanical properties of sintered bodies. The prepared powders were fine with the size below 0.05μm. Hot-pressing was conducted at 1800-1850°C in N2 (1 atm) with 6wt% Y2O3 and 2wt% Al2O3 as sintering aid. When fine Si3N4 powder was sintered at 1800°C, the sintered body had a fine-grained microstructure. By increase in temperature to 1850°C, rod-like grains grew in the fine matrix, resulting in an increase in fracture toughness. Fine TiN particles were dispersed in Si3N4 matrix by sintering of Si3N4-TiN composite powder, indicating the formation of nanocomposite. In the composite system, the growth of rod-like grains was observed even at 1800°C. This suggests the acceleration of Si3N4 grain growth by TiN inclusion. The composite had a high fracture toughness.
