三氯环硼氮烷改性聚碳硅烷的合成及陶瓷转化

Synthesis of polycarbosilane modified by B-trichloroborazine and its ceramic conversion

为研究三氯环硼氮烷(TCB)对聚碳硅烷(PCS)性能及陶瓷转化的影响,将一定量的TCB加入PCS中制备TCB改性PCS聚合物,分析了TCB与PCS的反应性及TCB用量对改性PCS结构、陶瓷收率、可加工性和SiC产物微结构的影响,并采用红外光谱、热重、X射线衍射等测试技术对相应产物进行表征.结果表明,PCS中的Si-H键可部分地与TCB中的-Cl反应生成HCl;随着TCB质量分数的增加,PCS中Si—H键相对于Si-CH3的浓度比呈下降趋势.TCB的加入可显著提高PCS的陶瓷收率,TCB质量分数大于8%时,陶瓷收率质量分数约增加10%.TCB质量分数为5%～8%时,可在提高PCS收率的同时使其保持较好的可加工性能,TCB质量分数大于8%时,可加工性能变差.B、N的引入对SiC的微结构有影响:在氩气保护下,经1000℃热处理时,TCB的加入促进SiC晶粒的生长;经1400℃热处理时,TCB的加入抑制SiC晶粒的长大.

To study the effect of B-trichloroborazine（TCB） on the basic properties of polycarbosilane（PCS） and its ceramic conversion,TCB modified PCS polymers were synthesized by adding TCB to PCS at ambient temperature.Reactivity of TCB and PCS as well as the effect of TCB contents on the PCS structure,ceramic yield,processability and SiC microstructure was investigated by IR,TG-DSC,XRD and so on.The results revealed that Si—H bonds in PCS partly reacted with —Cl in TCB at room temperature to generate the gas HCl and the content of Si—H bond decreased with the increase of TCB content.When the TCB content was more than 8 wt%,TCB markedly increased the ceramic yield by about 10 wt%.And with the TCB content about 5wt%-8wt%,modified PCS showed higher ceramic yield and good processability in harmony.With the TCB content about 10wt%-15wt%,the processability became poor.The addition of TCB influenced the growth of β-SiC crystal grain.The crystal grain of SiC obtained from TCB modified PCS at 1000 ℃ in Ar was higher than that obtained from pure PCS,while the addition of TCB inhibited the grain growth at 1400 ℃.