采用辐射氧化联合热交联技术制备碳化硅(SiC)纤维,利用红外光谱研究辐照及热处理前后纤维的化学结构变化,并对它们及SiC纤维中的氧含量进行测定;采用强度变化评估SiC纤维的热稳定性,通过X射线衍射和扫描电镜等手段研究其微观结构变化。结果表明:辐射氧化主要引入了Si—OH活性基团,该基团在热交联过程中参与反应。SiC纤维中的氧含量可通过调节剂量得到控制,最低仅为6%,吸收剂量仅为200kGy;热稳定性与氧含量密切相关,氧含量降低,耐温性能得到提升,1400℃热处理后强度保留率为75%,1500℃处理后强度损失与晶粒增大及氧化物高温分解相关。
Sillicon carbide fibers were prepared from polycarbosilane(PCS) fibers by radiation oxidation & thermal curing technique.The chemical structure of PCS fibers after radiation oxidation and thermal curing process was studied using FT-IR,and the oxygen content of all the fibers was determined.The thermal stability of SiC fiber was evaluated via the loss of strength and the microstructure changes was shown using XRD and SEM.It was found that Si—OH was introduced onto PCS fibers molecular chains by radiation oxidation and then consumed in thermal curing reaction.The oxygen content of SiC fibers with a minimum of 6% at 200kGy could be controlled by adjusting dose.Thermal stability of SiC fiber was closely related to oxygen content and the retention rate of strength at 1400℃ was 75% for SiC fibers with lower oxygen content.The strength loss at 1500℃ was found to be related to crystal growth and decomposition of oxidation product.
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基金资助
国家自然科学基金(11505268和11575279);上海市自然科学基金(15ZR1448600)
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