POLYMER-DERIVED SILICON-CARBIDE FIBERS WITH LOW-OXYGEN CONTENT AND IMPROVED THERMOMECHANICAL STABILITY

Continuous silicon carbide fibers (UF fibers) with low oxygen content (approximately 1-2 wt%) were prepared in a range of diameters (approximately 8-50 mum) by the dry spinning of organosilicon polymer solutions and subsequent pyrolysis of the polymer fibers. Room-temperature mechanical properties were similar to commercially available Nicalon(TM) fibers, as average tensile strengths almost-equal-to 3 GPa were obtained for some batches with fiber diameters in the range of approximately 10 mum. Furthermore, UF fibers showed significantly better thermomechanical stability compared to Nicalon, as indicated by lower weight losses, lower specific surface areas, and improved strength retention after heat treatment at temperatures up to 1700-degrees-C. The structure and composition of UF fibers were also characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Auger depth profiling analysis, neutron activation analysis, and atomic absorption.