文摘
This work reported the synthesis of submicrometric TaB2 powders by reduction of Ta2O5 using B4C in vacuum. The starting mixture with a molar ratio of B4C/Ta2O5=1.57 completely converted to a mixture of TaB2 and B2O3 at 1100 °C, whereas that converted to a mixture of TaB2, Ta3B4 and minor TaB at 1550 °C due to the boron loss resulting from the formation of gaseous boron-rich oxides. Microstructure observation showed the TaB2 and Ta3B4 particles had small equiaxed and large plate-like shapes, respectively. Excess B4C should be added to compensate for the boron loss. Phase-pure TaB2 powders with equiaxed shape were synthesized at 1550 °C with a molar ratio of B4C/Ta2O5=1.90. The particle size and oxygen content of TaB2 powders were ~0.7 µm and ~0.80 wt%, respectively.