The effects of MoSi₂ on the oxidation behavior of carbon/carbon composites

PAN-based carbon fibers impregnated with phenolic resin used as a precursor of carbonized matrix were modified by addition of molybdenum disilicide (MoSi₂) in different concentrations i.e., 0, 4, 12 and 20% by weight for improving anti-oxidation properties of the composites. In this work, the oxidation behavior of carbon-carbon composites made with MoSi₂ as an oxidation inhibitor in flowing air, has been studied in the temperature range of 600-1000°C. The results showed that the oxidation behavior of the composites made without MoSi₂ differs from those of the composites made with MoSi₂ and involves a degradation mechanism of its own, resulting in the highest oxidation rate during the initial phase of the oxidation. And the composites made with MoSi₂ led to a significantly improved oxidation resistance owing to both the reduction of the crack in composites and the formation of a mobile diffusion barrier for oxygen when compared to those made without MoSi₂. Hence, carbon active sites were blocked and oxidation of carbon was limited. This is probably due to the effect of the inherent MoSi₂ properties, resulted from a formation of the protective layer against oxygen attack, in the above of 800°C.