The improvement in thermal and mechanical properties of TiB₂ modified adhesive through the polymer-derived-ceramic route

An air stable high temperature adhesive synthesized via the polymer-derived-ceramic route had received increased attention in the last two decades. To improve the thermal stability and adhesion strength of a polysilazane (PSNB) adhesive, TiB₂ was added as active filler to join SiC ceramic discs. The thermal stability, phase composition and microstructure were investigated by using TGA, XRD, FT-IR, BSE and SEM measurements. Effects of the pyrolysis temperature and active filler TiB₂ on the microstructure and adhesion strength have been investigated. After curing and heat-treating at 120 °C and 1000 °C in air for 2 h, respectively, the adhesion strength of the modified adhesive reached up to 10.07 MPa (3 times higher than that of pure PSNB) at room temperature, and, more importantly, retained a strength of 8.0 MPa at 800 °C in air. It should be noted that the formation of a glass comprised of SiO₂-B₂O₃-TiO₂ and the emergence of the hexagonal and granular TiB₂ in the adhesive layer are mainly responsible for the enhanced high temperature strength.