Thermal stability of low-oxygen silicon carbide fiber (Hi-Nicalon) subjected to selected oxidation treatment

Low-oxygen silicon carbide fibers (Hi-Nicalon) were oxidized at temperature s from 1073 to 1773 K under an oxygen partial pressure of 0.25 atm. The str ength of the unoxidized core was practically unaffected by the oxidation te mperatures. The strength of the as-oxidized fibers with an SiO2 film decrea sed markedly with increasing oxidation temperature. When exposed subsequent ly to 1773 K in argon, the fibers with a SiO2 film of 0.3-0.5 mu m thicknes s had the best thermal stability.