Effect of oxidation on the compressive strength of sintered SiC-fiber bonded ceramics

The compressive strength of SiC-fiber bonded ceramics obtained from hot-pressed amorphous Si–Al–C–O fibers and its degradation by high temperature exposure to an oxidizing environment was studied. Compressive strength was measured at room temperature as a function of strain rate, orientation, and oxidation temperature. Weight loss was monitored as a function of exposure time in atmospheric air at temperatures ranging from 800 to 1600 °C, for times ranging from 0.5 to 5 h. Room-temperature compressive strength had a moderate decrease after exposures at 800 °C associated to carbon burnout; increased for exposures in the range 1000–1500 °C due to a defect-blunting action of the silica scale; and decreased significantly at 1600 °C due to extensive surface recession.

► Carbon oxidation in SiC-fiber bonded ceramic monoliths is diffusion limited at 800 °C.
► Strength decrease after exposure to atmospheric air at 800 °C.
► At 1000–1500 °C formation of silica scale halt oxidation and increases strength.
► Significant surface recession is due to silica volatilization at 1600 °C.
► Surface recession and residual porosity caused marked decrease in strength at 1600 °C.