Dark blue nano tungsten oxide for heat insulation agricultural film can be prepared by hydrogen reduction using ammonium paratungstate (APT) as a raw material. The process of APT hydrogen reduction to blue tungsten oxide undergoes dehydration, deamination, and phase transformation processes. During this process, a large amount of water vapor and ammonia gas are discharged from the inside of the raw material APT particles. Due to the combined action of gas evolution and phase transition, a large number of cracks are generated in the APT powder particles, and the flower-like agglomerated particles split and spread.
The obtained blue tungsten oxide powder using such APT as raw material substantially retains the hexahedral characteristics of the raw material APT particles, but the shape of the reduced product is not as regular and coarse as APT due to cracking of powder particles upon reduction. The surface of blue tungsten oxide reduced by the rough surface APT has more cracks and the powder particles are thicker. Obviously, the shape of APT is hereditary.
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