Low-cost C/SiC composites prepared by CVI+pressure-PIP hybrid process

Low-cost C/SiC composites were prepared by CVI+PIP combined process. A silicone impregnant with fillers was used in the PIP process. The pyrolysis mechanism of the impregnant and the properties of the composites were investigated. The results show that silicone impregnant with fillers has high pyrolysis yield and its pyrolysis product is dense, pressure can enhance the PIP efficiency of the tillered impregnant. CVI+P-PIP hybrid process makes use of the densification advantages of CVI process and PIP process, which can shorten the process cycle. C/SiC/C multilayered coating can decrease the bonding strength of the fiber/matrix interface, and it reduces the diffusing velocity of oxygen to the surface of carbon fibers. Hence the mechanical properties and anti-oxidation properties are improved. The flexural strength and fracture toughness (K_IC) of the C/SiC composites are 455 MPa and 15.7 MPa·m^-1/2 respectively. The weight loss of the C/SiC composites is merely 8.5% after heated at 1300°C in air 3 h.