SiC反応焼結体の強度に及ぼす真空中の熱処理効果

概要

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A commercial reaction-sintered silicon carbide (RS-SiC) was heat-treated at 1600℃ in vacuum to remove the free Si, and the resulting SiC bulk with about 19% porosity was further heat-treated at 1600°-2000℃ for 0.2-20 h in vacuum of 0.65 Pa. Although the second heat-treatment did not significantly change the porosity, grain growth and oxygen content in the porous RS-SiC, the heat-treatment at 1780℃ for 2 h increased the bending strength of the porous RS-SiC from 205 MPa to 322 MPa and caused the transition from intergranular to transgraular fracture. The strengthening effect may be attributed to the increased bonding area between grains due to evaporation-condensation and surface diffusion, and to relaxation of stress concentration due to the change in pore shape. However, the strength decreased by heat-treatment at 1780℃ for 10 h or 2000℃ because of the decrease in the bonding area and the volume of SiC matrix due to the decomposition of the SiC invacuum.
社団法人日本セラミックス協会の論文
1989-12-01