Synthesis of silicon carbide fibers by sol-gel processing

Abstract

Silica-phenolic resin hybrid fibers with carbon-to-silicon atomic ratios of 2.6 to 5.4 have been prepared from ethanol solutions of tetraethoxysilane, phenolic resins, water, and hydrochloric acid with a tetraethoxysilane-H2O−HCl molar ratio of 1:2:0.01 by sol-gel processing. The hybrid fibers have been heated at 1500°C in Ar for carbothermal reduction to convert them into silicon carbide fibers. The effects of the holding time at 1500°C and the carbon-to-silicon atomic ratio of the hybrid fibers on the free carbon content in the silicon carbide fibers have been investigated. It has been found that the conversion is complete by the heat-treatment for more than 2 h. The silicon carbide fibers with a free carbon content of ca. 2 wt% have been obtained from the hybrid fibers with the ratios of 2.6 to 4.3.