Violet tungsten oxide powder may be used to prepare near-infrared shielding material (heat insulating material), which has been gradually applied to the heat insulation fields of building and automobile.
The violet tungsten oxide has unique fine needle-like crystal morphology, and its polymer resembles a loose sponge. Compared with yellow tungsten oxide (YTO) and blue tungsten oxide (BTO), the bulk density of violet tungsten oxide is much smaller than that of YTO and BTO. The BET of violet tungsten oxide is the smallest, the chemical activity is the largest, and the production rate of tungsten powder is the fastest during hydrogen reduction. Also, violet tungsten oxide has the finest particle size, and the tungsten powder produced by such tungsten oxide has a fairly stable particle size and particle size distribution.
The same batch of APT raw materials can obtain tungsten oxides such as violet tungsten oxide (W18O49), yellow tungsten oxide (WO3), blue tungsten oxide and ammonium tungsten bronze at different temperatures and different atmospheres. In the phase transformation of the hydrogen reduction process, it was found that the reduction of violet tungsten oxide by dry hydrogen can directly produce β-W and α-W without providing an intermediate stage of the formation of WO2. That provides the basis for the reduction of violet tungsten oxide to obtain uniform fine tungsten powder.
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