Effect of Y(NO3)3 additive on morphologies and size of metallic W particles produced by hydrogen reduction.

• Shape-controlled synthesis of W particles via salt-assisted reduction was proposed. • Large powders disappeared and were degraded under the influence of Y(NO 3) 3. • Temperature and additive greatly affected the morphology and size of W particles. • The added salt improved the crystallization of particles. • The reaction mechanism was discussed as well. Tungsten, one of the refractory metals, has lots of excellent properties, making tungsten powders become a choice of raw material for many applications. This work reported a simple method (the salt-assisted hydrogen reduction of WO 3 powders) for preparing tungsten powders with desired morphologies and size. By adjusting the amount of additive (Y(NO 3) 3) and reduction temperature, metallic tungsten particles with different morphologies and size were obtained. It was found that both temperature and additive had apparent effects on the morphology and size of metallic W particles, and the large parallelepiped-shaped powders disappeared and large irregular blocky-shaped powders were degraded under the influence of additive. With the increase of temperature and amount of salt, particles became more dispersed and the size increased at higher temperatures, and the shape of particles was changed from spherical to polyhedral as well. On the contrary, the size of sub-particles became smaller as increasing amount of Y(NO 3) 3 at lower temperatures. Based on the results, the reaction and refining mechanisms for preparing tungsten were proposed as well. [ABSTRACT FROM AUTHOR]