In situ synthesis mechanism of Al2O3-Mo nanocomposite by ball milling process

Al2O3-Mo nanocomposites were synthesized by ball milling of aluminum and molybdenum oxide powder mixtures. The structural evaluation of powder particles after different milling times was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and measurement of vial temperature. The molybdenum oxide and aluminum reaction appeared to occur through a rapid combustion reaction process. As a result, an alumina matrix nanocomposite containing molybdenum particulate was formed. In final stage of milling, Mo and alumina had a crystallite size of about 28 nm and 60 nm, respectively. After annealing at 800 deg. C for 60 min, Mo crystallite size remained constant. However, α-alumina crystallite size increased to 120 nm. After annealing a partial transformation of α-Al2O3 into different polymorphic, γ-Al2O3 with a crystallite size of 50 nm was observed.