ルテチアを焼結助剤とする配向組織窒化ケイ素の作製と機械特性

Abstract

Porous anisotropic silicon nitrides exhibiting superior mechanical properties at elevated temperatures were successfully fabricated. The silicon nitrides containing lutetia (Lu2O3) as sintering additive were fabricated using a partial sinter-forging technique in which uniaxial pressure was applied after heating up to the sinter-forging temperature. Rod-like silicon nitride grains were formed during the heating, and they were aligned by the subsequent forging. Strength of a specimen with porosity of about 23% was more than 600 MPa at room temperature (R.T.), which was achieved by choosing a suitable sinter-forging condition. It maintained more than 450 MPa even at 1500°C. Fracture energies at R.T. and 1500°C were 110 and 150 J•m-2, respectively. The concurrent achievement of high strength and fracture energy is very likely the result of the combined effects of grain alignment, presence of pores between grains, and the lutetia sintering additive. High strength at elevated temperatures is caused by the lutetia sintering additive.