Preparation and characterization of a homogeneous joint of SiC ceramics based on a novelpolycarbosilane cross-linking network

Silicon carbide (SiC) ceramics exhibit outstanding properties; however, their inherent difficulty in machining and welding has severely restricted their practical applications. In this study, a straightforward and highly efficient method for joining SiC ceramics was developed. Initially, a novel organosilicon polymer (POSS-VHPCS) with a high ceramic yield was synthesized by Vinylhydridopolycarbosilane (VHPCS) with octavinyl-substituted polyhedral oligomeric silsesquioxane (POSS). SiC and B₄C powders were subsequently added as fillers to the liquid VHPCS to produce a high-performance adhesive (PVSB-adhesive) for bonding SiC ceramics. The joining process involves applying the adhesive, curing it at 200 °C, and subjecting it to heat treatment at 1200 °C in an air atmosphere, without the application of external pressure. The resulting adhesive demonstrates an exceptional bonding performance, achieving an ambient shear strength of 11.4 MPa after curing at 200 °C, and reaching 88 MPa following heat treatment at 1200 °C. Furthermore, the high-temperature shear strength of joint was averaged 66 MPa at 600 °C following 1200 °C heat treatment. The bonding mechanism is primarily attributed to the formation of a unique interfacial structure and a dense, highly robust homogenized joining layer. The primary advantage of this approach lies in its ability to eliminate the need for complex or expensive joining equipment, offering a convenient and efficient solution for bonding SiC ceramics.