Blue nano tungsten oxide may not only be applied to prepare window heat insulation film for applying in building glass such as office buildings, hotels, villas, high-end apartments, exhibition halls, galleries and indoor swimming pools, but also to produce medium grain size tungsten powder by cyclic redox process. The so-called cyclic redox method is a recycling process in which blue tungsten oxide is reduced to tungsten powder, and then the tungsten powder is oxidized to tungsten trioxide and then reduced.
The steps of preparing medium grain size tungsten powder by the cyclic redox process are as follows:
1.0 Ultrapure ammonium paratungstate was raised to 600°C in a slow heating rate in argon, and was kept at a temperature of 600°C for 10min to prepare blue tungsten oxide powder.
2.0 The first reduction of the blue tungsten oxide powder obtained in 1.0 was carried out in hydrogen to obtain tungsten powder, and the reduction temperature curve is shown in Figure 1.
3.0 The tungsten powder of 2.0 was slowly heated in air to 500°C for the first oxidation, and the temperature was maintained at 500°C for 10min to obtain tungsten trioxide.
4.0 A second reduction was carried out with tungsten trioxide of 3.0 in hydrogen. The reduction temperature curve is shown in Figure 1.
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