Influence of the chemical composition of precursors and reduction conditions on the properties of magnesiothermic tungsten powders

Resumo

We have studied tungsten powders prepared by reducing the tungsten oxide compounds WO₃, MgWO₄, CaWO₄, and Ca₃WO₆ with magnesium vapor in the temperature range 700–800°C. In the case of the reduction of WO₃ and MgWO₄, we observed segregation of reaction products: removal of most of the forming magnesium oxide from the reaction zone. The powders prepared by reducing WO₃, MgWO₄, and CaWO₄ consisted of α-W, whereas the reduction of Ca₃WO₆ at temperatures below 740°C led to the formation of both α-W and β-W. The use of tungsten precursors containing refractory oxides (MgWO₄, CaWO₄, and Ca₃WO₆) allowed us to obtain tungsten powders with specific surface areas at a level of 20 m²/g and mesoporous structures.