Synthesis of nanocrystalline TiB$_2$ powder from TiO$_2$, B$_2$O$_3$ and Mg reactants through microwave-assisted self-propagating high-temperature synthesis method

[摘要] 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$_2$â€�?�B$_2$O$_3$â€�?�Mg mixtures. Thermodynamicevaluations of this system and its relevant subsystems revealed that TiB$_2$â€�?�MgO composite powder can be easily produced by a SHS reaction. However, experimental results of a TiO$_2$ : B$_2$O$_3$ : 5 Mg 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 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 thata 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 (150â€�??200 nm) particles, where each particle consists of a number of nanosized (32 nm) crystallites.

[学科分类] 材料工程

[关键词] Titanium diboride;thermodynamic calculations;microwave processing;combustion synthesis.