C/SiOC Composites by a Modified PIP Using Solid Polysiloxane: Fabrication, Microstructure and Mechanical Properties

A modified polymer infiltration and pyrolysis method (PIP) was developed to enhance the densification of C/SiOC composites, using molten MK resin (polymethylsilsesquioxane) as precursor. Organic sulfonic acid was added as cross-linking agent to lower the curing temperature. The cross-linking mechanism and ceramization behavior of MK resin was studied. A high ceramic yield of about 85wt% and low free carbon content below 3wt% are achieved, with excellent high-temperature stability of the derived SiOC. The modified PIP approach presents a high densification efficiency. After only 8 PIP cycles, the final C/SiOC composites possess a density of about 1.81 g/cm(3). Compared with those composites fabricated by conventional PIP process, the C/SiOC composites prepared by modified PIP process show a much denser microstructure with much more improved densification efficiency. Bending strength of the as-fabricated C/SiOC composites is of (312 +/- 25) MPa, showing obvious non-brittle fracture behavior.