Pressure Effects on the Thermal Stability of Silicon Carbide Fibers

Abstract

Commerically available polymer‐derived SiC fibers were treated at temperatures from 1000° to 2200°C under vacuum and at argon gas pressures of 0.1 and 138 MPa. Effects of increasing inert gas pressure on the thermal stability of the fibers were determined through studies of the fiber microstructure, weight loss, grain growth, and tensile strength. The 138‐MPa argon gas treatment was found to shift the onset of fiber weight loss from 1200° to above 1500°C. Grain growth and tensile strength degradation were correlated with weight loss and were thus also inhibited by high‐pressure treatments. Retreatment in 0.1 MPa of argon of the fibers initially treated in 138 MPa of argon caused further weight loss and tensile strength degradation, thus indicating that high‐pressure inert gas conditions were effective only in delaying fiber strength degradation and that no permanent microstructural changes were induced.