Oxidation protection of C/Si–C–N composite by a mullite interphase

The polymer impregnation and pyrolysis (PIP) process was used to prepare a mullite interphase of C/Si–C–N composites in order to provide an acceptable oxidation protection of these composites. The comparison of oxidation behaviors of C/Si–C–N with a mullite interphase and C/Si–C–N without interphase was made to analyze the role of mullite interphase during the oxidation process. The results indicate that the oxidation resistance of C/Si–C–N with a mullite interphase was significantly improved as compared to C/Si–C–N without interphase. The increase of oxidation resistance was attributed to the low oxygen diffusivity through the mullite interphase, strong bonding between the interphase and fibers, and low thermal stress in matrix caused by the mullite interphase.