Sintering Behaviour of Ultrafine Silicon Carbide Powders Obtained by a Vapor Phase Reaction

Abstract

The sintering behaviour of ultrafine β-SiC powder with the average particle size of 0.01∼0.06μm produced by a vapor phase reaction of the (CH₃)₄Si-H₂ system (1200∼1400°C) was investigated at the temperature range of 1400∼2050°C. In vacuum, a large weight loss of the compact owing to the vaporization of SiC was observed, whereas the introduction of Ar (300mmHg) suppressed the weight loss to a negligible extent even at 2050°C. The compact of un. doped SiC powders was hardly densified at 2050°C, although the grain grew up to ∼5μm. The additions of both boron and carbon powders by 1∼2 wt% promoted the densification and gave the sintered body with the ralative density of above 90% by the pressureless-sintering at -2050°C. When an adequate amount of carbon was deposited for the oxygen content of SiC powders in the course of vapor phase reaction, the powder showed a high sinterability, giving the sintered body with a relative density above 97% by the addition of boron powder alone. This indicates that the homogeneous dispersion of carbon on SiC particles is important to remove the surface oxide layer effectively. Boron and barbon had the inhibitive effet for the grain growth of SiC.