Grade 1 violet tungsten oxide nanopowder adopts tungstic acid (mWO3•nH2O, m≥1, n≥1) as raw material. And the VTO may be produced by calcinating and reducing mWO3•nH2O in a hydrogen reducing atmosphere.
Hydrogen Reduction Method to Prepare Nano Needle-shaped Violet Tungsten Oxide
Step one: By using feeding device, feed tungstic acid from the feed end into the heated furnace tube, and gradually move it from low temperature zone to high temperature zone under the rotation of inclining furnace tube;
Step two: Heat tungstic acid to generate WO3 and water vapor;
Step three: Material continues to move to high temperature zone by rotating the inclining furnace tube. When temperature of the material continues to rise, WO3 is gradually reduced by H2 to generate violet tungsten oxide WO2.72.
This producing method is characterized in that:
1. NH3 is introduced through the air inlet into the inclining furnace tube, and it is decomposed by calcination to generate the reducing gas H2.
2. H2 or a mixed gas of NH3 and H2 is also introduced into the inclining furnace tube through the air inlet.
3. The heating temperature of mWO3•nH2O is 100°C or above.
4. The temperature of generation of WO2.72 controlled above 600°C.
5. An outlet port is set at the end of the furnace tube to ensure the positive pressure inside the furnace tube is at the range of 0mbar~5mbar.
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