Mechanical properties of SiC/SiC composites with a treatment of the fiber/matrix interfaces by metal-organic chemical vapor co-deposition of C and SixC1-x

Thin films of pyrolytic carbon and silicon carbide have been prepared under low pressure by thermal decomposition of cumene and SiEt4, respectively. The simultaneous pyrolysis of these precursors leads to C-rich SixC1-x films in which the carbon content can be controlled by monitoring the gas phase composition. Representative interphases have been deposited on Nicalon fibers prior to infiltration by the SiC matrix. The degree of fiber pull-out increases with the C content of the interphase and has been found comparable for the pyrolytic carbon and a compositional gradient layer (CGL) in which the composition changes continuously from C (fiber interface) to SiC (matrix interface). The mechanical behavior after heat treatment at 1300 C in air have revealed the superiority of the fiber treatment with the CGL layer. (orig.)