Preparation Method for Uniform Mixing Sodium in Tungsten Trioxide

The main process for preparing coarse grain carbide crystal in China is adding alkali metals such as sodium in tungsten trioxide to generate coarse grain tungsten powder after hydrogen reduction, and carbonization at high temperature to get coarse tungsten carbide powder, and then grinding, forming, sintering process to prepare coarse grain carbide. Conventional methods of preparation sodium doped WO₃ are spray, artificial doping method, the defects of the two methods is sodium distributing not uniform in WO₃ thus affects the subsequent production, and leading particle growing not uniform, products of great difference in properties. Besides, the manufactures may have to buy equipments by using the spray method, thus resulting cost increased. So, is there any way to make the sodium mixed uniform, and do no need to purchase any other equipment? This paper we will provide a method for preparation of WO₃ uniform doped sodium.

Steps are as bellows:
1. Take the ammonium tungstate of WO3 concentrate 200~300 g/L as raw material, and Na+ mass concentration of PPM 10~40;
2. Add solid sodium salt according to the requirements of subsequent products, Na/WO₃ about 0.05%~0.25%, mix the solution;
3. Evaporate and crystallize, temperature controlled in 80~100℃ with the stirring speed of 50~200 r/min;
4. The end of crystallization when pH reaches 6.4~7.0, then stop heating and cooling down to 20~50℃;
5. Filter the liquid by vacuum filtration, dry to generate APT powder with uniform sodium;
6. Calcine APT in the claining furnace at 680~740℃to obtain tungsten trioxide powder with uniform sodium.

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