Oxidation behavior of three dimensional C/SiC composites in air and combustion gas environments

A three dimensional C/SiC composite was prepared and flexural strengths dur ing combustion atmosphere and weight changes in air were investigated. When oxidized in air, the C/SiC composite gained weight above the cracking temp erature, and lost weight below the cracking temperature. The weight loss re ached its maxumum value at about 700 degreesC. When oxidized during combust ion atmosphere, the composite always lost weight due to the large temperatu re gradient along the specimen. The strengths were lowest at the area close to the nozzle wall where the flame temperature was about 700 degreesC. The re were four oxidation zones along the specimens. There was an unoxidized z one (1) at the surporting end. Close to this was the cracking-oxidation zon e (II). At the high-temperature end was the coating-oxidation zone (IV). Be tween the coating oxidation and cracking-oxidation zones was the transition zone (III). Uniform, non-uniform and superficial oxidation regimes were ob served which were considered to be responsible for the weight changes in ai r and strength changes during combustion atmosphere. (C) 2000 Elsevier Scie nce Ltd. All rights reserved.