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 mu m with the optimized spinning parameter T=337 degrees C, 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 mu m to 9.5 mu m. 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 distribution and enhanced flexibility.