The hydrogen reduction of tungsten trioxide and ammonium para-tungstate was studied by means of a high pressure type thermobalance in the range of 1 to 20 atm and X-ray analysis. Owing to the formation of intermediate oxides, the feature of the reduction curve was complicated. Therefore, analysis of the reduction curve by using a topochemical reaction model was difficult. The initiation temperature for the reduction of WO3 was about 400°C. The effect of pressured hydrogen was observed mainly in the reduction from WO3 to WO2 at lower temperatures such as 500 and 600°C. At a high temperature, 700°C, the reduction rate of WO2 to W was also increased and the complete reduction time was shortened to a half of the time obtained in the atmospheric pressure.Para-tungstate began to decompose at about 50°C and changed to WO3 at around 400°C. Since then, the reduction from WO3 to W occurred. The reduction under high pressure has a merit to decrease the sublimation loss at about 800°C. Furthermore, the change of the particle shape in the reduction process was observed by scanning electron micrography, and the experimental results were discussed on the basis of an equilibrium diagram.
Any feendback or inquiry of Ammonium Paratungstate(APT) please feel free to contact us: