Nano violet tungsten oxide for producing near-infrared shielding material can be prepared by APT hydrogen reduction method in an industrial rotary kiln under wet hydrogen and high temperature conditions.
APT decomposes at a higher temperature to produce water vapor and NH3. And NH3 can be decomposed into N2 and H2 at high temperature. At the same time, H2 can lightly reduce and decompose APT to produce W18O49 phase. Since the volume of NH3 increases after decomposition, a large amount of water vapor generated by the reaction can be taken away. But the NH3 flow rate is too high, so the partial pressure of H2 in the furnace atmosphere is increased. And it leads to an increase in the content of WO2 phase in the product, thereby affecting product quality.
Through the verification test, the best process parameters of violet tungsten oxide powder can be obtained: the temperature is in the range of 790~805°C; the feeding speed is 0.55kg/min; the furnace tube speed is 2.0r/min; the NH3 flow rate is 0.7m3/h.
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