Improvement of the mechanical properties of hot-pressed silicon-carbide-fiber-reinforced silicon carbide composites by polycarbosilane impregnation

Green sheets of SiC with Al2O3–Y2O3–CaO sintering additives prepared by the doctor-blade method and polycarbosilane (PCS)-impregnated Hi-Nicalon cloth with a BN coating were used for the fabrication of SiC-fiber-reinforced SiC (SiC/SiCf) composites by hot-pressing. Two kinds of SiC/SiCf composites with different fiber volume fractions were fabricated and their room-temperature mechanical properties were investigated. These composites showed non-brittle fracture behavior. The maximum strength of a composite with 52 vol.% of fibers was about twice as high as that of a composite with 40 vol.% of fibers, and the composite hot-pressed at 1700°C showed the highest maximum strength. In this fabrication process, PCS-impregnation into Hi-Nicalon cloth was an effective way of forming the matrix between fibers.