Nano tungsten trioxide powder, for preparing thermal insulation dispersion liquid, has many different preparation methods. At present, there are mainly hydrothermal method, sol-gel method, microemulsion method, and precipitation method, etc. Among them, the hydrothermal method is commonly used to synthesize WO3 nanowires, WO3 nanorods, WO3 nanotubes, WO3 nanobelts, WO3 nanoparticles and WO3 nanofilms.
By adopting hydrothermal method, using Na2WO4 as raw material and K2SO4 as an auxiliary agent, WO3 nanowires with a diameter of 10nm can be synthesized (The length is in the micron range.). And it was found that, under the hydrothermal environment, the main factors affecting the morphology and crystal form of WO3 were pH value, hydrothermal temperature, additives and hydrothermal time. Then, the influence of different additives (KNO3, NaNO3, Na2SO4 and K2SO4) on the crystal form was investigated using sodium tungstate and HCl as raw materials. It was found that the orthorhombic phase WO3 was generated when the additive was KNO3, while other additives produced the hexagonal phase WO3.
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