Significant enhancement on creep resistance of the near stoichiometric SiC fibers by ultrafast Joule heating

Abstract

Heat treating is effective to enhance the thermal stability of the polymer derived SiC fibers through increasing the grain size and purifying the grain boundary. However, a long-term heat treatment usually causes serious damages to the fibers and finally sacrifices the tensile strength. In this work, we apply an ultrafast (5–30 s) and high temperature (1900–2100 °C) heat treatment on the near stoichiometric SiC fibers (namely C3) by Joule heating. As compared with the conventional heating techniques, the ultrafast Joule heating yields evident grain growth but less fiber damage. At above 2000 °C, an instantaneous decomposition of the surface SiC grains leading to grain size reduction and a non-monotonically grain size distribution along the fiber diameter, which also contributes to decrease the surface roughness. The C3 fibers heat treated at 2100 °C for 15 s show excellent creep resistance when compared to some other commercial SiC fibers, and also keeps high tensile strength.