Tensile and oxidation behavior of SiC fibers

In support of the development of SiC/SiC composite materials for fuel cladding in a Gas-cooled Fast Reactor, micrometric silicon carbide-based fibers with low residual oxygen were investigated in the reactor operating environment. A dedicated machine enabled to slow tensile strain single fibers from room temperature up to 1700 degrees C under secondary vacuum. It was observed that fibers are brittle and their mechanical properties drop when the temperature is increased. In addition, thermogravimetric analysis was performed at 1100 degrees C under helium with an oxygen partial pressure of 20 Pa. Fibers oxidized and the reaction rate appeared to be globally parabolic after about 60 h. Electronic microscopy confirmed that a thin silicon-oxide scale has been formed on the fiber surface. Future work includes studying the effect of oxidation on the fiber tensile behavior.