Rapid mechanochemical synthesis of nickel-vanadium carbide nanocomposite powder by magnesiothermic reaction

Abstract

In the present study, in-situ production of Ni-VC nanocomposite powder synthesized from several raw materials including NiO, V2O5, Mg and C, was carried out through mechanochemical approach by means of magnesiothermic reaction. Due to high adiabatic temperature (T = 3964K), this reaction is known as a self-propagating reaction or MSR. Raw materials were mixed at 1:1:6:2 stoichiometric ratios of nickel oxide, vanadium oxide, magnesium and graphite, respectively. Milling process was carried out in a high-energy planetary ball mill under argon atmosphere with various ball-to-powder weight ratios (15:1, 20:1 and 25:1) for the aim of obtaining the optimum ball-to-powder weight ratio to reduce the synthesis time. After milling for 30min and 40min, combustion occurred in the milling vial for 25:1 and 20:1 ball-to-powder weight ratios, respectively. The microscopic properties of milled nanocomposite powders were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). According to XRD patterns, after combustion reaction, anticipated products including nickel, vanadium carbide (VC) and magnesium oxide (MgO) were totally produced. To remove undesirable MgO phase, leaching process (1M HCl at 80°C for 1h) was used. According to XRD and X-ray-mapping analyses before and after the leaching process, HCl dissolved MgO phase thoroughly. Additionally, crystallite size and lattice strain were calculated based on Williamson-Hall method; these values were calculated 54nm and 0.00615 for VC, while they were 40nm and 0.00595 for nickel, respectively. Moreover, according to TEM micrograph, the morphology of the particles after leaching process was found to be spherical with the size of 50 ± 5nm.