Hollow ammonium metatungstate sphere may be prepared by spray drying method. The average diameter of the hollow ammonium metatungstate ball is 1.03μm, and the wall thickness is about 100nm.
The preparation process is divided into 3 stages: atomization, shell formation during flash evaporation and hollow structure formation. The initial temperature in hot air drying tower is 130°C, which is far higher than the boiling point of water, leading to rapid evaporation of droplet surface water. The fast evaporation speed leads to the droplet surface crystallization and the shell formation, thus the hollow structure forms.
Ammonium metatungstate is widely applied for preparing WO3 dingal materials due to its large solubility in water and low cost. Nano-WO3 based materials have many properties, such as photodegradation, water splitting, electrochromism, thermochromism and photochromism, etc. Therefore, nanostructured WO3 based materials are potentially used in the fields of photocatalysis, new energy resources preparation, smart windows, sensors and flat-panel display. It means that the demand for AMT, one of the raw materials of the preparation of WO3, is strong.
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