The development research to toughness of SiC/SiC composites by the interface control.

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It was examined that the strength of the fiber was effectively manifested in order to improve the strength characteristic of SiC/SiC composite. Therefore, the interface between fiber and matrix was coated with carbon and BN, and the research which controlled the interface combination was carried out. The SiC fiber used the Hi- Nicalon fiber of the filament. The CVI method was used in the material manufacture. The SiC/SiC composite material was produced using CィイD22ィエD2HィイD25ィエD2ClィイD23ィエD2Si in the raw material gas at about 1000℃. Though the material produced at the initial stage was a shape of the 40mm diameter, it was possible that it was the 120mm diameter afterwards and produces the large material of the 2mm thickness.The result got in this study in the following is shown.(1)Fiber volume fraction of produced SiC/SiC composite material was 35%, and the volume density was about 2.4g/cmィイD13ィエD1, and the material of which the uniform thickness was good was got.(2)It became possible that the carbon coat was made from number 10μm to number 1000μm in the fiber surface.(3)The interface between fiber and carbon coat was analyzed in high resolution electron microscope observation and EPMA analysis. As the result, it was proven that the crack progressed the interface.(4)The value which was the highest in the carbon 1.0μm coating thickness time was obtained the material bending strength which coated the carbon. It was possible to understand this from the relationship between interfacial shear sliding strength and strength of the matrix.(5)Formation of the carbon coat is necessary for the strengthening of the SiC/SiC composite. And, it was proven that the ductility also increased.From the above fact, the development of the SiC/SiC composite was possible. In the future, further developability is desired the SiC/SiC composite as a high temperature high-intense material.