Preceramic metallocarbosilanes: synthesis, properties, thermal transformation

Ceramic-forming metallocarbosilanes {Ta(Zr)PCS and Ta(Hf)PCS} with a specified molar ratio of refractory metal atoms Ta/Zr (Ta/Hf) were synthesized by co-condensation of oligodimethylsilylenemethylenes and alkylamides of refractory metals (simultaneously Ta and Zr or Ta and Hf). The physicochemical properties of Ta(Zr)PCS and Ta(Hf)PCS were studied. It was determined that the metallocarbosilanes are soluble in hydrocarbon solvents and may possess fiber-forming properties. Polymer fibers based on Ta(Zr)PCS with a molar ratio Ta/Zr = 4 were prepared, then underwent curing and ceramization. The surface morphology and chemical composition of SiC fibers modified with mixed carbides Ta₄ZrC₅ after carbidization at 1250, 1500, and 1900 °C under argon were studied. The process of thermal transformation of metallocarbosilanes into ceramic phases at temperatures of 1250 and 1500 °C was investigated. It was shown that the synthesized metallocarbosilanes are precursors of SiC ceramics modified with mixed carbides Ta_xZr_yC_z or Ta_xHf_yC_z and can be used to obtain components (fibers, matrices, protective coatings) of ceramic composite materials with an ultrafine homogeneous stabilized structure.