Flexible ultrafine nearly stoichiometric polycrystalline SiC fibers with excellent oxidation resistance and superior thermal stability up to 1900 °C

Flexible ultrafine SiC fibers with superior high-temperature stability and excellent oxidation resistance are regarded as one of the most promising materials for high-temperature applications. However, excess oxygen and carbon in the ultrafine SiC fibers limit their thermal stability due to decomposition of the SiCxOy phase. In the present work, flexible ultrafine nearly stoichiometric polycrystalline SiC fibers were fabricated by combining the electrospinning technique and polymer-derived ceramic method. The ultrafine SiC fibers exhibited superior high-temperature stability and oxidation resistance. The retention rates of tensile strength were 90.0 %, 94.2 % and 86.4 % after heat treatment in argon at 1800 °C, 1900 °C and 2000 °C, respectively. TG results of the fibers showed little weight loss of only 1.52 % at 1900 °C in Ar and the weight gain of only 4.1 % up to 1500 °C in air. Such improved thermal stability was achieved through sintering at high temperature for elimination of excess oxygen and carbon with Al doped as the sintering aid to restrain the grain coarsening. The ultrafine SiC fibers still exhibited excellent flexibility without obvious damage when they were heated by the butane blowtorch flame of about 1100 °C in air. Furthermore, the infrared thermography illustrated that the ultrafine SiC fiber membrane also had good thermal insulation performance. The outstanding mechanical properties and thermal stability of ultrafine SiC fibers suggest their potential applications at the high temperature and harsh environment.