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A ceramic matrix composite (CMC) containing Si-Zr-C-O fibers with a surface carbon layer formed by heat treatment in CO atmosphere was studied. The thickness of surface carbon layer on Si-Zr-C-O fiber increased by adding 0.1% CO2 in CO atmosphere, compared with that formed in pure CO atmosphere. The flexural strength of the CMC containing the Si-Zr-C-O fibers with carbon layer increased with increasing the thickness of the carbon layer. This result indicated that the formation of a carbon layer by heat treatment on the Si-Zr-C-O fibers is a suitable way for modifying the interface structure of CMC.

A new type of continuous SiC-based, Si-M-C-O fiber, containing zirconium instead of titanium, has been developed. This new Si-Zr-C-O fiber exhibits improved thermal stability compared to a Si-Ti-C-O fiber. In this study, oxidation resistance of Si-Zr-C-O fiber was investigated in order to clarify the role of zirconium in the fiber. It was cleared that the oxidation resistance of Si-Zr-C-O fiber was better than that of Si-Ti-C-O fiber. Zirconium plays an important role in inhibiting of crystallization of the oxide material which forms on the surface of the fiber during oxidation.