焼結ＳｉＣ繊維強化ＳｉＯ２‐ムライト複合材料の作製と特性評価

Abstract

The sintered SiC fiber reinforced SiO2-mullite composites, which have three levels of added Al2O3 in the matrix, i.e., SiO2-3.7, 30, 50 mol%Al2O3, were synthesized by liquid state hot-pressing. Variation in the thermal residual stress fields in the composites caused by the difference in the thermo-mechanical mismatch between the fiber and matrices were investigated. The effects of the Al2O3 content in the matrix on the mechanical properties of the composites were then examined.The obtained composites had a very dense structure, and both the mullite and glassy SiO2 phases were found in the matrices. A higher Al2O3 content in the matrix lead to a higher mullite volume fraction. No chemical reaction among the constituents due to the fabrication process was observed.It was confirmed that the thermal residual stress field in the composites changed with an increase in the coefficient of thermal expansion of the matrix accompanied by an increasing Al2O3 content in the matrices.The network structure of the mullite crystals found in the SiC fiber/SiO2-30 mol%Al2O3 and SiC fiber/SiO2-50 mol%Al2O3 composites seemed to effectively prevent plastic deformation of the matrices during the flexural test at 1573 K.The SiC fiber/SiO2-30 mol%Al2O3 composite showed excellent mechanical properties up to 1573 K compared with previously reported ceramic matrix composites such as the SiC fiber/LAS composite or SiC fiber bonded ceramics in an inert atmosphere.