METHOD FOR PRODUCING SIC FIBER-REINFORCED SIC COMPOSITE MATERIAL HAVING EXCELLENT FRACTURE TOUGHNESS

摘要

Polymeric slurry is prepared by uniformly dispersing fine SiC particles in polyvinyl-silane (PVS), which comprises the structural units (a) and (b) at an a/b ratio of 1, at a ratio of 50-70 mass %. A SiC fiber preform is impregnated with the polymeric slurry and preheat-treated at 300-400°C in an argon atmosphere to moderate PVS to a viscous or semi-cured state. Thereafter, the preheat-treated SiC fiber preform is pyrolyzed at a temperature of 1000°C or higher in an argon atmosphere under application of a unidirectional pressure of 2-10 MPa. Since internal stress is relaxed during pressurized pyrolysis, a product is dense SiC fiber-reinforced SiC-matrix composite good of mechanical strength and toughness with large fracture work. The SiC composite may be further densified and improved in fracture toughness by repetition of impregnation with sole PVS and pressure-less pyrolysis.