Rapid synthesis of MoSi2-Si3N4 nanocomposite via reaction milling of Si and Mo powder mixture

The nanocomposite of MoSi2-Si3N4 (molybdenum disilicide-silicon nitride) was synthesized by reaction milling of the Mo and Si powder mixture. Changing the processing parameters led to the formation of different products such as alpha- and beta-MoSi2, Si3N4, Mo2N, and Mo5Si3 at various milling times. A thermodynamic appraisal showed that the milling of Mo32Si68 powder mixture was associated with highly exothermic mechanically induced self-sustaining reaction (MSR) between Mo and Si. The MSR took place around 5 h of milling led to the formation of alpha-MoSi2 and the reaction between Si and N2 to produce Si3N4 under a nitrogen pressure of 1 MPa. By increasing the nitrogen pressure to 5 MPa, more heat is released, resulting in the dissociation of Si3N4 and the transformation of alpha-MoSi2 to beta-MoSi2. Heat treatment was also performed on the milled samples and led to the formation of Mo2N and the transformation of alpha-MoSi2 to beta-MoSi2 at the milling times of 10 and 40 h, respectively.