Mechanochemical behavior of magnesium–boron oxide–melamine ternary system in the synthesis of h-BN nanopowder

Abstract

Hexagonal boron nitride (h-BN) nanopowder was synthesized by the mechanochemical method using mixtures of magnesium, boron oxide and pure melamine as raw materials. X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the synthesized powder. According to the results, the reaction starts with the magnesiothermic reduction of boron oxide after about 3.5h of milling in a mechanically induced Self-sustaining Reaction (MSR). The significant amount of heat generated from reduction reaction caused to decompose melamine to nitrogen-based active radicals, which reacted with elemental B to form h-BN compound. The formation of BN during the thermal treatment was also investigated by simultaneous thermal analysis (STA) technique. It was found that melamine decomposition took place at a temperature around 350°C; meanwhile, no boron nitride phase was achieved even up to 1100°C. Based on the morphological evolutions, it is evident that the mechanosynthesized BN is made up of nanometric particles.