Synthesis of mullite-MoSi2 nano-composite through a mechanochemical processing

Nano-composite mullite-MoSi2 with 40wt.% MoSi2 was produced from the raw materials of MoO3, Al and Si by mechanochemical processing. Different Al amounts (stoichiometric amounts of 1, 1.5 and 2mol) and milling times (15, 23, 30, 60, 180, 300min) were applied to obtain this composite. A planetary ball mill with a rotation speed of 250rpm and a ball-to-powder ratio (BPR) of 40:1 was employed. The composite was formed using 1.5mol of Al and occurrence of mechanically induced self-propagating reaction (MSR) in 23-30min. The evolutions of phases and their microstructure were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM) with an energy dispersive X-ray spectrometer (EDX). By means of transmission electron microscopy (TEM) the particle size and morphology of the obtained powders were examined. The mean crystallite size of the composite changed from 60nm in 30min to 20nm in 5h; the average particle size was about 155nm in 5h.