液态聚碳硅烷的结构及固化行为对其陶瓷化的影响

Liquid polycarbosilane, as a new precursor of ceramics, can be used to prepare ceramic matrix composites (CMC) by precursor infiltration and pyrolysis (PIP) process, and to improve the ablative resistance of flexible insulation layer by coating organic fibers. The structures of three liquid polycarbosilane precursors (VHPCS, VHPCs-S and AHPCS) were characterized by IR and NMR. The curing reaction before 150 ℃ was mainly carried out by various ways of C=C bond. Compared with the AHPCS, the mole ratio of double bond to hydrogen silicon bond in the VHPCS and VHPCS-S is increased by about 18.2%. The curing kinetics of three precursors in the system of dicumyl peroxide (DCP) was studied by non- isothermal DSC. The curing temperature and apparent activation energy of the precursors are decreased, and the precursors could achieve rapid crosslinking reaction at low temperature. The ceramization process of precursor and crystallization behavior of its pyrolysis products were analyzed by STA and XRD. The ceramic yield of VHPCS-S at 1200 ℃ is higher than that of the other two precursors (VHPCS and AHPCS). For the DCP/VHPCS-S crosslinking system, the ceramic yield reaches 89.82% after curing at 150 ℃. In addition, the addition of DCP can effectively inhibit β-SiC crystallization.