One-Pot Synthesis of Alumina-Titanium Diboride Composite Powder at Low Temperature

Alumina-titanium diboride (Al(2)O(3)-TiB(2)) composite powders were synthesised via aluminothermic reduction of TiO(2) and B(2)O(3), mediated by a molten chloride salt (NaCl, KCl, or MgCl(2)). The effects of salt type, initial batch composition, and firing temperature/time on the phase formation and overall reaction extent were examined. Based on the results and equilibrium thermodynamic calculations, the mechanisms underpinning the reaction/synthesis processes were clarified. Given their evaporation losses at test temperatures, appropriately excessive amounts of Al and B(2)O(3) are needed to complete the synthesis reaction. Following this, phase-pure Al(2)O(3)-TiB(2) composite powders composed of 0.3–0.6 μm Al(2)O(3) and 30–60 nm TiB(2) particles were successfully fabricated in NaCl after 5 h at 1050 °C. By increasing the firing temperature to 1150 °C, the time required to complete the synthesis reaction could be reduced to 4 h, although the sizes of Al(2)O(3) and TiB(2) particles in the resultant phase pure composite powder increased slightly to 1–2 μm and 100–200 nm, respectively.