Oxidation Behaviors of SiCf/SiC Composites Tested at High Temperature in Air by an Ablation Method

Using the thermal ablation method, the oxidation behavior of SiC f /SiC composites was investigated in air and in the temperature range of 1,300 o C to 2,000 o C. At the relatively low temperature of 1,300 o C, passive oxidation, which formed amorphous phase, predominantly occurred in the thermal ablation test.When the oxidation temperature increased, SiO (g) and CO (g) were formed by active oxidation and the dense oxide layer changed to a porous one by vaporization of gas phases.In the higher temperature oxidation test, both active oxidation due to SiO 2 decomposition on the surface of the oxide layer and active/passive oxidation transition due to interfacial reaction between oxide and base materials such as SiC fiber and matrix phase simultaneously occurred.This was another cause of high temperature degradation of SiC f /SiC composites.