Preparation of rhenium powder by redox method
Ammonium perrhenate or potassium perrhenate is placed in a tubular reduction furnace for hydrogen reduction, and the reduction is usually carried out twice. The first reduction temperature of ammonium perrhenate is 573-623K, and the second reduction temperature is 1073-1223K. The first reduction temperature of potassium perrhenate is 773-823K, and the second reduction temperature is 1173-1273K. The purity of the rhenium powder depends on the purity of the raw material. When the purity of ammonium perrhenate reaches more than 99.99%, the purity of the obtained rhenium powder can reach 99.99%. The particle size can be less than 2.5 μm.

The rhenium powder prepared with potassium perrhenate contains a large amount of potassium, that is, after washing with water and dilute hydrochloric acid, it still contains a few dry parts of potassium, and the purity is only 99%. This kind of rhenium powder should not be used as a raw material for deep processing. Therefore, the method of reducing potassium perrhenate raw materials with hydrogen has been eliminated. Pure rhenium powder can also be obtained by reducing the raw material of rhenium heptaoxide with hydrogen, but the cost is higher.