High Temperature Performance of Modified Cf/SiC Composites with LPVCS

Three dimensional and four directional carbon fiber reinforced SiC matrix (C-f/SiC) composites were fabricated by precursor infiltration and pyrolysis process employing a new precursor, liquid polyvinylcarbosilane (LPVCS). LPVCS is a novel precursor with active Si-H and -CH=CH2 groups with relatively high oxygen content (similar to 7.3 wt%). The mechanical properties improvement caused by ameliorated interface and low porosity was researched. Samples with ameliorated interface employing LPVCS show better mechanical properties than those employing polycarbosilane (PCS). The flexural strength and fracture toughness of the C f /SiC composites fabricated with PCS are 301 MPa and 11.2 MPa.m(1/2), respectively, whereas those of the samples fabricated with ameliorated interface are 442 MPa and 26.1 MPa.m(1/2), respectively. Employing LPVCS for the first infiltration and pyrolysis cycle forms suitable interface, employing PCS as precursor for the left several cycles forms relatively low oxygen content matrix, and then employing LPVCS for the last several cycles forms low porosity, which is the main reason of mechanical properties improvement.