Tungsten trioxide powder applying for thermal insulation film may be prepared by hydrothermal synthesis method. For example, the Na2WO4 solution is acidified with HCl and hydrothermally reacted at 130~200°C for 1~5 days. Eventually, tungsten trioxide with uniform particle size distribution can be obtained. The obtained tungsten trioxide can be used for the preparation of a variety of heat-insulating materials, such as film, coating, and so on, thereby being applied to heat-insulating glasses and the like.
What is hydrothermal synthesis?
Hydrothermal synthesis includes various techniques of crystallizing substances from high-temperature aqueous solutions at high vapor pressures. Hydrothermal synthesis can be defined as a method of synthesis of single crystals that depends on the solubility of minerals in hot water under high pressure. The crystal growth is performed in an apparatus consisting of a steel pressure vessel called an autoclave, in which a nutrient is supplied along with water. A temperature gradient is maintained between the opposite ends of the growth chamber. At the hotter end the nutrient solute dissolves, while at the cooler end it is deposited on a seed crystal, growing the desired crystal.
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