Oxidation of MoSi2 and MoSi2-based materials

Oxidation experiments, at 500 degrees C, of MoSi2 and MoSi2-based compounds such as Mo(Al,Si)(2) and MoSi2 + 1 wt% C compacts have been carried out. T hese compacts were prepared by in situ synthesis and a compaction method, s tarting from the elemental powders. For comparison, commercial MoSi2 and Mo (Al,Si)(2) infiltrated into SiC preform were also studied under similar con ditions. It was found that the synthesized high density MoSi2 and Mo(Al,Si) (2) infiltrated into SiC preform did not show any oxidation even after 100 h of heating in air. The colour of the polished surfaces of commercial MoSi 2, Mo(Al,Si)(2) and MoSi2 + 1 wt% C had changed. The SEM of Mo(Al,Si)(2) sh owed open blisters with rods of MoO3 in them whereas MoSi2 + 1 wt% C surfac e had MoO3 rods but no blisters and the oxidation was superficial with no p enetration into the compact. It is suggested that in compounds, the presenc e of small amounts of impurities is not as detrimental to pesting as presen ce of defects like open pores or cracks. Hence, high density of the compact is essential for the prevention of complete disintegration of the compact.