A study on mechanochemical behavior of MoO3–Mg–C to synthesize molybdenum carbide

Abstract The influence of Mg value in the MoO 3 –Mg–C mixture on the molybdenum carbide formation and the mechanism of reactions during mechanochemical process were investigated. In keeping with this aim, magnesium and carbon contents of the mixture were changed according to the following reaction: 2MoO 3 + (6 − x ) Mg + (1 + x ) C = (6 − x ) MgO + Mo 2 C + x CO. The value of x varied from 0 to 6. Differential thermal analysis (DTA) results for sample with stoichiometric ratio ( x = 0) revealed that in the early stage, carbon reduced the MoO 3 to MoO 2 and subsequently highly exothermic magnesiothermic MoO 2 reduction occurred after magnesium melting. Also, it was indicated that the exothermic reaction temperature shifted to before magnesium melting in the 11 h-milled sample ( x = 0) and all the exothermic reactions happened, simultaneously. According to the experimental findings, molybdenum carbide (Mo 2 C) was synthesized in the mixture powder with stoichiometric ratio ( x = 0) after 12 h milling process and the type of reactions was mechanically induced self-sustaining reaction (MSR). However, at lower Mg content in the MoO 3 –Mg–C mixture (0 x ≤ 2), the magnesiothermic reduction occurred in MSR mode and activated the carbothermal reaction. Further decrease in Mg value (2 x ≤ 3) resulted in MSR mode magnesiothermic reaction and gradual carbothermal reduction. In samples with lower magnesium contents, partial molybdenum oxide reduction proceeded through a gradual mode magnesiothermic reaction.