Synthesis of novel vinyl preceramic polymer (PBSZ) adhesives and their performances in ceramic joints

It is a challenge to bind ceramics for aeronautical and astronautical engineering applications at ultrahigh temperature. In this work, a novel preceramic polymer (polyborosilazane, PBSZ) was synthesized by modifying polysilazane (PSZ) with n-butyllithium, vinylchloride and m-carborane. Furthermore, a high-temperature organic adhesive (PBSZ-based adhesive) was prepared with no pressure applied using PBSZ as a matrix and B4C powder as a filler. The ceramic yield of PBSZ-based adhesive increased to 86 wt%, and the binding strength between PBSZ-based adhesive and ceramic substrate could reach to 12.9 MPa after treatment at 800 degrees C. Also, the finite element analysis of PBSZ-based adhesive joint exhibited that the failure of joints occurred as the cohesion failure inside of the adhesive accompanied by the breakage of the substrate adjacent to the adhesive, which further confirmed good binding strength of the joint. The analysis of binding mechanism showed that the introduction of boron could generate strong chemical bonds (such as B-C, B-N, C-N, Si-B) in the adhesive, as well as intermolecular forces and B-C chemical bonds could be formed between the adhesive and the SiBON ceramic substrate. The high performance of the adhesive enables the application to the joining of ceramic materials for aerospace applications.