Preparation and characterization of continuous SiZrOC fibers by polyvinyl pyrrolidone-assisted sol-gel process

Continuous PZSO-PVP gel fibers have been drawn from polyzirconosiloxane (PZSO) solution consisting of two-component silicon alkoxides (tetraethoxysilane and dimethyldiethoxylsilane) and ZrOCl2, utilizing polyvinyl pyrrolidone (PVP) as spinning reagent and ethanol as solvent. The PVP addition significantly improves the solution spinnability and stability by adjusting the solution viscosity, the coordination with Zr atom, and the steric hindrance effect. The PZSO-PVP fibers are composed of smooth dense surface and elliptical-shaped cross section due to nonhomogeneous shrinkage during gelation and drying. Fourier transform infrared and X-ray photoelectron spectroscopy analysis on the PZSO-PVP fibers suggest a structure of mixed SiO4 and SiC2O2 units with incorporated Zr in the form of Zr-O-Zr and Zr-O-Si. SiZrOC ceramic fibers are obtained through subsequent drying and pyrolysis treatment, with good thermal stability up to 1500 A degrees C. The fibers are of mixed silicon oxycarbide phase embraced with ZrO2 phase and free carbon but no SiC phase.