In situ formation of dual amorphous phases for the joining and repair of SiC ceramics: Microstructural evolution and mechanical properties

SiC ceramics are promising candidates for high-temperature pipeline applications as alternatives to conventional alloys. However, the reliable joining of SiC ceramic pipelines with total lengths exceeding 10 m remains a critical challenge. In this study, a high-performance composite adhesive was developed by incorporating polycarbosilane with SiC, B₄C, Al₂O₃, and Y₂O₃ fillers. After heat treatment at 1200 °C in air under pressureless conditions, the resulting SiC joints exhibited a shear strength of 62 MPa at 1000 °C. These results indicate that the proposed adhesive system has significant potential for the joining and repair of SiC pipelines of arbitrary length. The joining mechanism is attributed to chemical reactions occurring within the adhesive during heat treatment, leading to the in situ formation of B-Si-O and B-Si-Al-Y-O amorphous phases. The B-Si-Al-Y-O amorphous phase imparts excellent high-temperature resistance and mechanical properties to the interlayer, whereas the B-Si-O amorphous phase, owing to its low viscosity at elevated temperatures, facilitates the filling of pores and cracks, thereby promoting interlayer densification. The synergistic effects of these amorphous phases result in a dense, high-temperature-resistant, and high-strength SiC joint.