In situ synthesis and microstructure characterization of TiC-TiB_2-SiC ultrafine composites from hybrid precursor

摘要

TiC-TiB_2-SiC ceramics with enhanced yield and microstructure homogeneity were synthesized from hybrid polymer precursors. The polymer reactions and phase evolution were characterized through a variety of techniques. It had been found that the ceramic yield of allylhydridopolycarbosilane was increased after introduction of borazine and was further enhanced by subsequently adding proper amount of tetrabutyl titanate. The borazine favored cross-linking and induced B containing phases to facilitate the densification, while the Ti source was competent to fix B and excess C (which was redundant for the formation of SiC) as uniformly distributed TiB_2 and TiC through sintering, respectively. An optimally thermal-stable TiC-TiB_2-SiC structure was constructed by consuming the excess C as the Ti content rose to 5 wt.%, at the cost of a slightly reduced ceramic yield.