Tungsten trioxide applying for thermal insulation dispersion liquid may be synthesized by hydrothermal method using Na2SO4 as an additive. And the influence of the concentration of Na2SO4 on the morphology of WO3 crystals was investigated. It was found that the concentration of Na2SO4 had a certain influence on the grain size of the WO3 product.
Influence of Additive Na2SO4 Concentration on Morphology of WO3 Crystals
The SEM pattern of tungsten trioxide prepared at different concentrations of Na2SO4 is shown in the picture below. 
You can see it in the picture that the morphology of the WO3 products obtained under different concentrations of Na2SO4 are all clustered nanowire structure, but the thickness and length of the WO3 nanowires are different. Moreover, the smaller the concentration of additive Na2SO4, the finer and shorter the WO3 nanowires. It shows that the concentration of additive has a certain influence on the grain size of the WO3 product. In addition, the results also show that when Na2SO4 is used as an additive, hexagonal WO3 nanowires cluster structure can be formed, indicating that Na+ may play an important structural directing role in the formation of nanowires, whose in-depth exploration is still in progress.
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