Nano tungsten trioxide for thermal insulation dispersion liquid may be synthesized using Na2SO4 as an additive, by hydrothermal method. And then, analyzing the Raman spectrum of WO3 to reveal whether the product contains crystal water or not.
Raman spectra analysis of WO3 prepared using different concentrations of Na2SO4 additive was done, and the results were shown in the picture below. The concentration of Na2SO4 in “a” was 0.5M, the concentration of Na2SO4 in “b” was 0.25M, and the concentration of Na2SO4 in “c” was 0.125M.
As can be seen from the picture, the positions of peak and absorption peaks of the three Ramam images were approximately unchanged, and there were more prominent Raman peaks near the centers of 59cm-1, 675cm-1, 790cm-1, and 900cm-1. With the decrease of Na2SO4 concentration, the intensity of the characteristic absorption peaks at 59cm-1, 675cm-1, and 900cm-1 gradually increased, but the characteristic peak at 790cm-1 first increased and then weakened. When the Na2SO4 concentration was 0.25M, the intensity was the largest (b). With the decrease of Na2SO4 concentration, each Raman peak shifted slightly to low wave, but the half width of spectrum peak did not change substantially. The absorption peak around 270cm-1 corresponds to the O-W-O characteristic vibration mode, and no absorption peak was observed at 600cm-1, indicating that no crystal water was contained in the product.
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