Synthesis of Polytitanocarbosilane and Preparation of Si-C-Ti-B Fibers

Continuous SiC fiber is a kind of high-performance ceramic fiber that combines many advantages, such as high strength, high modulus, high hardness and low density. It has excellent mechanical properties, high-temperature and oxidation resistance, which could be applied as essential reinforcement in advanced ceramic matrix composites (CMCs) in the fields of aerospace and advanced weaponry. Melt-spinnable polytitanocarbosilane (PTCS) is an important precursor, which can be used to prepare continuous SiC fibers through a precursor-derived method. In this work, low-softening-point polycarbosilane (LPCS) and tetrabutyl titanate were used to prepare polytitanocarbosilane with a ceramic yield of 67.5 wt% at 1000 degrees C. FT-IR, TGA, GPC, H-1 NMR, Si-29 NMR, and elemental analysis were used to analyze the composition and structure of the PTCS precursor. Finally, Si-C-Ti-B fibers with an average tensile strength of 1.93 GPa were successfully prepared by melt spinning, pre-oxidation, pyrolysis, and high-temperature sintering of the PTCS precursor. The strength retention rates were 71.5% and 79.8% after heat treatment at 1900 degrees C and 2000 degrees C under an argon atmosphere for 1 h, respectively. The strength retention rates of Si-C-Ti-B fibers are higher than those of commercial Hi-Nicalon fibers, Tyranno ZMI fibers and Hi-Nicalon S fibers. This work can lay a theoretical foundation and technical support for developing high-performance SiC ceramic fibers containing titanium and their ceramic matrix composites.