Environmental simulation experiments of 3D-C/SiC composites with different PyC interfacial layers

A series of 3D-C/SiC composites with different pyrolytic carbon (PyC) interfacial layers (about 20-300 nm thick) were prepared by the chemical vapor infiltration. Simulation experiments at different temperatures were performed by exposing C/SiC specimens in single and coupling gases partial pressure atmospheres, namely, O₂, H₂O vapor and molten salt (Na⁺) vapor. It was suggested that at an intermediate temperature range (about 600-800°C) a dramatic effect of PyC thickness on the weight and strength change of C/SiC was shown, which was mainly influenced by the O₂ partial pressure; at the high temperature range (about 1200-1300°C) the effect was not obvious relatively, which might be influenced by the H₂O vapor partial pressure; and finally at a very high temperature range (>1500°C) the molten salt vapor was the factor of most possibility affecting the weight change of C/SiC.