Precursor derived Si-B-C-N ceramic is a kind of amorphous materials with high hardness, low density, durability at extremely high temperature. The materials show a great potential to be used in the field of the Thermal Protective System (TPS). The physical states and chemical properties of the amorphous materials greatly depend on the starting materials. The effect of degree of polymerization (DP) of the precursor on the pyrolysis process and the characteristics of the amorphous Si-B-C-N materials are studied. The SiBCN-based preceramic polymer synthesized by dichloromethylvinylsilane, ammonia and BH3•SMe2. Dichloromethylvinylsilane reacted with ammonia and BH3•SMe2 in toluene or tetrahydrofuran (THF) as solvent in the presence of catalytic amounts of pyridine. The polymeric precursors were cured at low temperature to obtain solid-state precursors. Pyrolysis process of the solid-state precursors under various temperatures and carried out in nitrogen atmosphere. The results showed that DP of the precursor influences the pyrolysis process and the high temperature stability of the Si-B-C-N amorphous ceramics.

Amorphous Si–B–C–N ceramics synthesized by polymer thermolysis possess excellent chemical, thermal and mechanical stability at high temperature. Many attentions have been devoted to study the crystallization and stability of Si–B–C–N ceramics. The SiC nanocrystallite reinforced amorphous Si–B–C–N ceramics have been fabricated by pyrolysis of single-source precursors at high temperature. The heat-treatment at high temperature commonly impaired the thermal stability of the composites. Crack and pore limit the development of the composites. New processing routes that overcome those problems are desirable. Here we reported the thermolysis of binary-source precursors mixed by polycarbosilane and boron-modified polyvinylsilazanen to fabricate Si–B–C–N composites with relative densities up to 96%. Green bodies were obtained by compaction of precursors using warm pressing at different temperature. The obtained composites were characterized by Scanning Electron Microscope and X-ray Diffraction.