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 (TiB 2) compound from TiO 2-B 2 O 3-Mg mixtures. Thermodynamic evaluations of this system and its relevant subsystems revealed that TiB 2-MgO composite powder can be easily produced by a SHS reaction. However, experimental results of a TiO 2 : B 2 O 3 : 5Mg mixture heated in a domestic oven showed the formation of some intermediate compounds such as Mg 3 B 2 O 6 , presumably due to some degree of Mg loss. The optimum amount of Mg in TiO 2 : B 2 O 3 : xMg mixtures, yielding the highest amount of TiB 2 phase, was found to be around 7 mol, i.e., 40 mol% more than the stoichiometric amount. Experimental results revealed that a pure TiB 2 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 TiB 2 contains sub-micron (150-200 nm) particles, where each particle consists of a number of nanosized (32 nm) crystallites.