Super grade violet tungsten oxide nanopowder may be prepared by calcining ammonium paratungstate with formula of 5(NH4)2O•12WO3•5H2O, APT for short.
The steps for calcining APT to prepare super grade violet tungsten oxide nanopowder are as follows:
Step one: Feed 5(NH4)2O•12WO3•5H2O from the feed inlet into the heated furnace tube with a feeding device, gradually moving from the low temperature zone to high temperature zone under the rotation of inclined furnace tube.
Step two: Calcine 5(NH4)2O•12WO3•5H2O to generate WO3, NH3 and water vapor;
Step three: NH3 in the furnace tube decomposed to generate reducing gas H2;
Step four: Material continues to move to high temperature zone under the rotation action of inclined furnace tube. When material temperature continues to rise, WO3 is gradually reduced by H2 to generate violet tungsten oxide WO2.72.
The preparation method of nano needle-shaped violet tungsten oxide described above is characterized in that:
1. The inclined furnace tube also introduces NH3 and/or H2 through the inlet.
2. The calcining temperature of ammonium paratungstate is 400°C or above.
3. Set the reaction temperature of WO2.72 to be above 600°C.
4. The end of the furnace tube is equipped with an air outlet. And the gas discharge speed in the furnace tube is controlled by controlling the amount of air suction of the suction fan installed outside the air outlet to ensure that the positive pressure in the furnace tube is 0mbar~5mbar.
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