Abstract
Amorphous composite powders are useful to fabricate ceramic nanocomposite. The nanostructure is formed by phase separation and crystallization during sintering. Si3N4-BN composite powder was prepared by a vapor phase reaction method and heated in N2 with and without Y2O3-Al2O3 sintering aid. Particle coarsening was observed above 1400°C in monolithic Si3N4, whereas the particle growth was retarded in Si3N4-BN composite. α-Si3N4 was detected above 1400°C in monolithic Si3N4, but Si3N4-BN composite was still amorphous even at 1600°C. When the sintering aid was used, β-Si3N4 was formed at 1600°C in monolithic Si3N4 and Si3N4-BN composite. The phase separation of BN was investigated by IR spectroscopy. The phase separation of Si3N4-BN composite powder became significant at 1600°C and the crystallization was stimulated by the sintering aid. It was confirmed from TEM observation that BN was segregated on the surface of Si3N4 particle.
