Thermal stability of low-SiC fiber (Hi-Nicalon) treated in a hot isostaticpress

The low-oxygen SiC fiber fabricated by the electron-beam irradiation curing method, Hi-Nicalon, was heated at 1773 to 2273 K in a hot isostatic press (800 MPa of argon) and was subsequently reheated at 1873 K at 1 atm (101 kP a) of argon. The hot isostatic press treatment delayed the onset of fiber d eterioration to higher temperature. The fiber strength remained almost unch anged by subsequent reheating at 1873 K in 101 kPa of argon. The thermal st ability of Hi-Nicalon, as a consequence of the permanent change in surface structure, can be greatly improved by treating in the hot isostatic press.