皮芯结构碳化硅陶瓷纤维的制备及性能

Preparation and Properties of Skin–core Structure Silicon Carbide Ceramic Fibers

采用空气与真空气氛脉冲的方法对聚碳硅烷(PCS)纤维进行气氛脉冲热氧化处理,然后在惰性气氛中热解制备出具有皮芯结构的碳化硅陶瓷(Si C)纤维,研究了脉冲次数对PCS纤维热氧化质量增加率、化学结构、Si–H键反应程度、氧元素分布及烧成SiC纤维晶体结构与力学性能的影响。结果表明:气氛脉冲处理可实现PCS的热氧化不熔化,且热氧化反应主要发生在PCS纤维的外表层,外表层形成了大量的Si–OH、Si–O–Si和C=O含氧结构,氧在PCS纤维径向上呈现梯度分布特性,表层富氧芯部低氧,脉冲热氧化使得PCS纤维凝胶出现时对应的热氧化质量增长和Si–H键反应程度都较低,分别为7.03%和25.37%;烧成得到的Si C陶瓷纤维仍保持了同样的氧梯度分布特性,且具有β-SiC晶体结构,是一种典型的皮芯结构,抗拉强度可达(1.74±0.21) GPa。

Polycarbosilane(PCS) fibers were heat treated via atmosphere pulse in pulsing air and vacuum atmosphere. The skin–core structure silicon carbide(SiC) ceramic fibers were prepared via the pyrolysis of PCS fibers in inert atmosphere. The effect of pulse oxidation time on the weight gain, chemical structure, Si—H reaction degree, oxygen element distribution of the PCS fibers, crystal structure and mechanical properties of the SiC fibers was investigated. The results show that the PCS fibers are thermal oxidation curing in atmosphere pulse treatment. The thermal oxidation reaction mainly occurs on the outside-surface of the PCS fibers, forming the oxygen-containing structures such as Si—OH, Si—O—Si and C=O. The oxygen element presents a gradient distribution characteristic. The surface is rich in oxygen and the core has a lower oxygen content. When the gel appears, the PCS fibers have a lower thermal oxidation mass fraction and Si—H reaction degree due to pulse thermal oxidation, i.e., 7.03% and 25.37%. The sintered SiC fibers have the same oxygen element distribution in the cross-section and with β-SiC crystal structure. The SiC ceramic fibers obtained by this method are a skin–core structure, having a preferable tensile strength of(1.74±0.21) GPa.