Combustion synthesis of tungsten powder from sodium tungstate

Tungsten powders were prepared by Self-propagating High-temperature Synthesis (SHS) method directly from hitherto unreported system: sodium tungstate (Na₂WO₄) and magnesium (Mg). The adiabatic temperatures of self-propagating combustion reactions with different amount of Mg in Na₂WO₄ + Mg system were calculated. The influences of different starting conditions (molar ratios of Mg/Na₂WO₄ and relative densities of samples) on the compositions and microstructure of reaction products were investigated. It shown that, the complete reduction of WO₃ required a 60% excess of magnesium over the stoichiometric molar ratio Mg/Na₂WO₄ of 3. The amount of the impurities is minimal at appropriate relative density. At last, tungsten powders can be obtained after the acid enrichment and distilled water washing.