Oxidation behavior of three-dimensional SiC/SiC composites in air and combustion environment

A three-dimensional Hi-Nicalon/SiC composite was prepared, the mechanical properties and weight changes before and after oxidation in air and combustion environment were investigated and compared in the present paper. The combustion gas with a high flow rate and a larger amount of H₂O accelerated the silica formation on the fibers and matrix, the oxidation channel could be sealed much earlier in combustion than in air, and the PyC interlayer was oxidized less. Weight loss of the composite in air was larger than that in combustion. The flexural strength did not decrease remarkably, in both air and combustion. Oxidation took place along and weakened the two interfaces of the interlayer with the fibers and matrix besides removal of the interlayer, the fracture displacement was greatly increased after oxidation in combustion compared with those before and after oxidation in air. It was shown that the composite had an excellent oxidation resistance in a short period of exposure. This result was of very important significance in the development of a self-adaptable interlayer.