聚碳硅烷纤维在1-己炔气氛中不熔化处理制备低氧含量SiC纤维

将聚碳硅烷(PCS)纤维在1-己炔气氛中进行化学气相交联不熔化处理, 与空气不熔化相比, 能大大降低纤维的氧含量。PCS纤维在1-己炔气氛中反应, 其组成和结构都发生了变化。结果表明, 在1-己炔气氛中, PCS分子的Si—H键的反应程度和纤维的凝胶含量随温度的升高而逐渐增加。反应机制为1-己炔受热引发PCS分子中的Si—H和Si—CH₃键断裂生成Si自由基和Si—CH₂自由基, 促进PCS分子间形成Si—CH₂—Si交联结构, 最终实现不熔化。反应中有少量己基引入到PCS分子结构中。制得的SiC纤维拉伸强度达到2.79 GPa, 氧含量降低到5wt%~6wt%, 并且纤维的耐高温性能明显优于Nicalon纤维。在Ar气中处理至1300℃, 纤维强度保留率约为80%, 处理至1400℃, 纤维的强度保留率为60%, 并且在1300~1600℃的处理过程中, 纤维中β-SiC微晶的晶粒尺寸变化只有2.18nm。 

SiC fiber with a low oxygen content prepared by polycarbosilane fiber cured in 1 hexyne vapor

Polycarbosilane (PCS) fibers cured in 1-hexyne vapor have much less oxygen than those cured by air. The composition and structure of PCS fibers transform during 1-hexyne curing process. The results show that the reaction degree of Si—H bond and gel content of PCS fibers rapidly increase when the curing temperature increases. Si—H and Si—CH3 bonds in PCS are induced by 1-hexyne to cleavage and form Si-central radicals. Fully developed crosslinking fibers come into being through the combination of these radicals. And a small amount of hexyl is introduced to PCS structure during the reaction. The tensile strength of SiC fibers prepared is 2.79GPa and the oxygen content is 5wt%~6wt%. The fibers show better high temperature resistance than Nicalon fibers. After being exposed in Ar to 1300℃, the SiC fibers maintain 80% of the initial strength; after being exposed in Ar to 1400℃, they maintain 60% of the initial strength. And during the heat treatment from 1300℃ to 1600℃, the change of β-SiCs grain size is only 2.18nm.