Molybdenum disilicide intermetallic (MoSi 2 ) compound is one of the most important high temperature silicide compounds which features relatively high density, good electrical and thermal conduction and excellent high temperature oxidation resistance. Despite the excellent resistance to high temperature oxidation, low resistance to oxidation at intermediate temperatures have been reported for this compound. In the present study, self-propagating high temperature (SHS) and thermal explosive (TE) synthesis methods were used to fabricate MoSi 2 compound in the presence of zirconium with the aim to eliminate this problem. In continuation, to evaluate the effect of these methods, specimens with the appropriate stoichiometric ratios of silicon and molybdenum powders with 0, 2, 5, 7 and 10 wt% of zirconium powder were synthesized under air and argon atmospheres. Microstructural observations were made by using optical and scanning electron microscopes; in addition, X-ray diffraction (XRD) analysis and energy dispersive spectroscopy (EDS) were used for phase and chemical composition identification. In order to determine the effect of the zirconium on the mechanism of formation of MoSi 2 during combustion synthesis, fast cooling of burning sample (frozen combustion wave) was applied. Furthermore, temperature profile and propagation of combustion wave were investigated for specimen of synthesized by SHS method. Obtained results indicate that by increasing the zirconium content increases heat amount released during formation of ZrO 2 and ZrSi 2 and solution of zirconium in the structure of MoSi 2 and so that leading to an increase in the velocity of the combustion wave. However, this effect is less significant for specimens of synthesized under argon atmosphere. For explosively synthesized specimens, the ignition temperature decreases with increasing the zirconium content so that this temperature is 1395 o C in sample non zirconium and achieve 1050 o C in sample with 10 wt% zirconium under argon atmosphere. But, with regard to formation of SiO (g) by the endothermic reaction of silicon with SiO 2 , the ignition temperature was increased under air atmosphere in comparison to argon atmosphere. Finally, oxidation tests were performed on specimens of synthesized by SHS process under air atmosphere. A higher intermediate temperature oxidation resistance was obtained for specimens containing zirconium compared to that of zirconium free ones. Therefore, obtained results reveal that addition of zirconium not only results in reduction of ignition temperatures and increase in the velocity of the combustion wave, but also improves the intermediate temperature oxidation resistance. Keywords : Molybdenum disilicide, Zirconium, Self-propagating high temperature synthesis, Thermal explosive, Ignition temperature, oxidation resistance.
