Preparation of Ultrafine W Powder via Carbothermic Prereduction of Tungsten Oxide Followed by Deep Reduction with Hydrogen
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A two-step reduction method to synthesize tungsten powder with controllable size is proposed. Firstly, precursors composed of W and WO2 were synthesized via carbothermic prereduction of tungsten trioxide with different C/WO3 ratios at 1323 K, then the precursors were completely reduced by hydrogen to remove residual oxygen at 1023 K and 1223 K, respectively. It was observed that increasing the C/WO3 molar ratio in the prereduction stage was beneficial to decrease the particle size of the W powder. In the subsequent hydrogen reduction stage, the presence of the gaseous intermediate phase W-O-H had a great influence on the morphology of the final product. Tungsten powders with particle size ranging from micron to nanometer range could be prepared by controlling the C/WO3 ratio and hydrogen reduction temperature.
This work was supported by the National Natural Science Foundation of China (51734002).