Carbon nanotubes-induced in-situ crystallization of silicon carbide fibers for promoted high temperature resistance

Abstract

SiC fibers, widely used in the aerospace and nuclear fields, have been researched primarily for their high-temperature resistance. However, SiC_xO_y composite phase thermal decomposition primarily contributes to SiC fiber corrosion and degeneration. To address this problem, we proposed a novel strategy based on multi-walled carbon nanotubes (MWCNTs) inducing in-situ crystallization of SiC during the pyrolysis of SiC_xO_y. We performed theoretical calculations to analyze the SiC_xO_y composite phase thermal decomposition process and investigated the impact of bonding between different sites on the MWCNTs and SiC_xO_y. Calculations showed that the sp³ site on the MWCNTs could induce SiC_xO_y phase conversion to SiC grains and in-situ crystallization to enable the improved high-temperature resistance of SiC fibers. Through experiments, the number of SiC grains was increased considerably, and their size was effectively suppressed. As a result, the strength retention of the 0.05 %-MWCNTs/SiC composite fibers rose from 15.7 % to 50.3 %, representing a 220 % increase after annealing at 1600 °C. Significantly, 0.05 %-MWCNTs/SiC composite fibers could still maintain their original morphology even after annealing at 1800 °C. Consequently, MWCNTs-induced SiC in-situ crystallization exhibits significant potential for improving the high temperature resistance of ceramic fibers.