Synthesis of nanocrystalline TiB2 powder from TiO2, B2O3 and Mg reactants through microwave-assisted self-propagating high-temperature synthesis method

Abstract

In this research work, microwave-assisted self-propagating high-temperature synthesis (SHS) process was employed for the fabrication of titanium diboride (TiB2) compound from TiO2–B2O3–Mg mixtures. Thermodynamic evaluations of this system and its relevant subsystems revealed that TiB2–MgO composite powder can be easily produced by a SHS reaction. However, experimental results of a TiO2 : B2O3 : 5Mg mixture heated in a domestic oven showed the formation of some intermediate compounds such as Mg3B2O6, presumably due to some degree of Mg loss. The optimum amount of Mg in TiO2 : B2O3 : xMg mixtures, yielding the highest amount of TiB2 phase, was found to be around 7 mol, i.e., 40 mol% more than the stoichiometric amount. Experimental results revealed that a pure TiB2 compound could be obtained by leaching the unwanted by-products in an HCl acid solution. Scanning electron microscopic observations and Scherrer calculations showed that the produced TiB2 contains sub-micron (150–200 nm) particles, where each particle consists of a number of nanosized (32 nm) crystallites.