Effect of Composition and Structures on the Elastic Modulus of SiC Fibers

High modulus SiC fibers can be used in complex working environment with alternating heat and cold. In this paper, SiC fibers with various oxygen contents and crystal size were fabricated by polymer-derived ceramics routes. The effects of oxygen content and crystal size on the elastic modulus of SiC fibers were studied in detail. It was found that the elastic modulus of SiC fibers can be improved by reducing the oxygen content and increasing the crystal size of SiC fibers when the crystal size was less than 2 nm. When the oxygen content decreased from 21.5 wt.% to 11.7 wt.%, the elastic modulus of SiC fibers was increased from 131 GPa to 167 GPa. Particularly, the highest elastic modulus of CVC treated hypoxic SiC fibers is close to 200 GPa when the crystallite size is about 2 nm.