Abstract

The microstructure and mechanical properties of Si_3N_4/BN nanocomposites synthesized by chemical processing were investigated. The nanocomposites containing 15 vol% hexagonal BN (h-BN) were fabricated by hot-pressing alpha-Si_3N_4powders covered with turbostratic BN (t-BN). The t-BN coating on alpha-Si_3N_4particles was prepared by heating alpha-Si_3N_4 particles covered with a mixture of boric acid and urea in hydrogen gas. TEM observations of this nanocomposite revealed that nano-sized h-BN particles were homogeneously dispersed within Si_3N_4grains as well as at grain boundaries. The strength and thermal shock resistance were significantly improved in comparison with the Si_3N_4/BN microcomposites.

• Keywords: Nanocomposite;Si_3N_4/BN;Powder synthesis;Thermal shock resistance;