Tungsten Trioxide by Thermal Decomposition

Different synthesis methods have a significant impact on the physical and chemical properties of tungsten trioxide. Because of the different synthesis methods, will directly affect the synthesis of tungsten trioxide crystal structure, particle size and so on. Currently there are a variety of ways to prepare tungsten trioxide, but according to the nature of raw materials and the reaction process can be divided into: solid phase method, gas phase method and liquid phase method.

Solid phase method that is thermal decomposition method is a method using tungsten oxide or tungsten tungstate and other tungsten oxide directly heated decomposition decomposition method to prepare tungsten trioxide. According to the different materials and heating methods, the thermal decomposition method can be divided into the direct thermal decomposition of solid powder, spray thermal decomposition and gas phase thermal decomposition of compounds. The direct heating of solid powder as thermal decomposition method is the use of thermal decomposition of ammonium tungstate can be inserted into the nitrogen trioxide tungsten photoelectrode, and its application in water oxidation. Its principle is to dissolve the tungstic acid solution in ammonia water, then evaporate the solvent. The resulting ammonium tungstate is heated under oxygen to finally decompose ammonium tungstate into tungsten trioxide with nitrogen gas inserted.

Spray pyrolysis method is obtained by controlling the time of thermal decomposition of tungstic acid solution precursor tungsten trioxide, tungstic acid composite photocatalyst. In the composite photocatalyst obtained by this method, the content of tungsten trioxide is 1.89%, 15.95%, 51.04% and 93.23% respectively. The thermal decomposition of gaseous compounds is tungsten trioxide dissolved in ammonia, and add citric acid as morphology regulator, the use of spray pyrolysis method to prepare tungsten oxide hollow spheres. The preparation system consists of three parts, namely drop generators, quartz tube reactor and particle collector. The drop generator was a supersonic instrument. The supershorted Fog overloaded gas entered a quartz tube with an inner diameter of 55 mm and a temperature of 700 ºC. The thermal decomposition process gave the final product. Thermal decomposition method has the characteristics of simple synthesis, but due to high temperature calcination process, often easy to synthesize samples with larger particle size and reduce the photocatalytic properties of the sample.

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