Joining C/C to C/C-SiC composites by Si infiltration reaction bonding and their thermal behaviors

This paper develops a novel adhesive for in-situ joining C/C composites to C/C-SiC composites using a phenolic resin modified with inert fillers (SiC and graphite powders). The primary phase of the reaction bonding joint layer is SiC, which matches the thermal expansion coefficient of the matrix better than metallic phases, making it an improvement over traditional brazing. The effect of filler content on joint strength, oxidation resistance, and thermal shock resistance has been systematically investigated. The results show that increasing the filler content from 0 to 50 wt% increases shear strength up to a maximum of 25.97 MPa at 15 wt% SiC and 15 wt% graphite powder. The oxidation and thermal shock tests reveal that the joints exhibit a decrease in shear strength due to oxidation at temperatures above 600 °C, with a significant reduction occurring between 600 °C and 700 °C. After seven thermal shock cycles at 800 °C, the shear strength of the joints remains relatively high, indicating the good thermal shock resistance of the bonding layer. The method proposed in this study provides a new approach for controlling residual silicon and enhancing the properties of C/C-SiC joints.