Preparation of SiOC/HfO2 fibers from silicon alkoxides and tetrachloride hafnium by a sol–gel process

• Novel SiOC/HfO2 fibers are successfully fabricated by the sol–gel process.
• SiOC/HfO2 fibers show high ceramic yield of 81 wt%.
• SiOC/HfO2 fibers exhibit good thermal stability and mechanical property.

This study presents fabrication and characterization of novel SiOC/HfO2 fibers by a sol–gel process. Polyhafnosiloxane (PHfSO) fibers have been drawn from silicon alkoxide solution consisting of tetraethoxylsilane (TEOS) and dimethyldiethoxylsilane (DMDES) using tetrachloride hafnium (HfCl4) as hafnium source. The spinnability of the solution has been optimized by varying the amount of HfCl4 and H2O. The Hf incorporation is confirmed by the formation of Hf–O–Si bridge through co-condensation of HfCl4, TEOS and DEDES. Subsequent pyrolysis treatment of the PHfSO gel fibers yields dense SiOC/HfO2 fibers with high ceramic yield of 81 wt%. The SiOC/HfO2 fibers exhibit good thermal stability up to 1500 °C and mechanical property with tensile strength of 930 MPa.