熔融纺丝过程优化制备细直径碳化硅纤维及其对力学性能的影响

强度、模量和柔顺性作为碳化硅(SiC)纤维重要的力学性能受到纤维直径大小的影响, 而制备工艺中的熔融纺丝过程对纤维直径起决定作用。本工作研究了纺丝温度、纺丝压力和卷绕速度对聚碳硅烷(Polycarbosilane, PCS)原纤维直径的影响, 分析了纺丝过程中纤维断裂的原因, 并初步探究了SiC纤维直径与力学性能的关系。结果表明, 在一定范围内降低纺丝温度、降低纺丝压力和提高卷绕速度均能显著减小原纤维的直径。在连续纺丝的前提下, 最优纺丝工艺下得到的PCS原纤维直径为13.5 μm。随着PCS纤维直径由18.3 μm减小至13.5 μm, SiC纤维直径则由13.8 μm减小至9.5 μm, 而SiC纤维的强度与模量分别由1.7、181 GPa提高至2.9、233 GPa, 强度分布更为集中, 柔顺性得到显著提高。

Enhancing Mechanical Property of SiC Fiber by Decreasing Fiber Diameter through a Modified Melt-spinning Process

Strength, modulus and flexibility as three important mechanical properties for silicon carbide (SiC) fibers can be affected by diameter of SiC fiber, which is controled by specific melt-spinning process. In this study, effects of spinning temperature (T), spinning pressure (P) and winding speed (V) on diameter of polycarbosilane (PCS) fiber were studied. Mechanisms for the fiber breakage during spinning process was explored, and relationship between diameter and mechanical properties of SiC fiber was also analyzed. The results show that diameter of the PCS fiber is significantly reduced either by decreasing spinning temperature, or decreasing spinning pressure or increasing winding speed. The finest diameter of PCS fiber is 13.5 μm with the optimized spinning parameter T=337℃, P=0.2 MPa and V=240 m/min. After high-temperature pyrolysism, diameter of the obtained PCS fiber can be reduced from 13.8 μm to 9.5 μm. Meanwhile, tensile strength of SiC fibers increases from 1.7 GPa to 2.9 GPa, and Young’s modulus increases from 181 GPa to 233 Gpa, respectively, with less dispersed strength distnbution and enhanced flexibility.