Highly efficient densification of carbon fiber-reinforced SiC-matrix composites by melting infiltration and pyrolysis using polycarbosilane

Carbon fiber-reinforced SiC-matrix composites (Cf/SiC) were fabricated via a precursor infiltration and pyrolysis (PIP) process. A polycarbosilane (PCS) precursor was used, with a halogen element (iodine) for curing. The effects of high-temperature polycarbosilane infiltrate melting and iodine-based curing on the efficiency of the PIP process, as well as the physical characteristics of the fabricated Cf/SiC composites, were investigated. Highly dense Cf/SiC composites with strong fiber/matrix interfacial bonding were fabricated. By melting the infiltrate and using iodine-based preform curing, the ceramic yield of polycarbosilane increased drastically from 38 wt% to 82 wt%. This increase, which is due to pyrolysis, resulted in a low degree of shrinkage in the polycarbosilane-derived matrix. This shrinkage, in turn, increased the density of the Cf/SiC composites and improved the interfacial bonding between the matrix and fibers. As a result, the fabricated Cf/SiC composites exhibited a density of 1.75 g/cm3. This was much higher than the 0.38 g/cm3 density of bare carbon fiber preforms after 6 iterations of the PIP process.