Nano grain size tungsten trioxide may be used in thermal insulating glass. And nano tungsten trioxide with good dispersibility may be prepared by hydrothermal synthesis method using sodium tungstate as a tungsten source and formaldehyde as an organic inducer. In this process, the pH value is adjusted with hydrochloric acid (HCl).
Under the irradiation of 3W UV lamp, the color difference of formaldehyde-induced tungsten trioxide nanopowder was 20, while the color difference of tungsten trioxide powder without formaldehyde inducer was less than 2. The results showed that formaldehyde significantly increased the photochromic property of tungsten trioxide powder. And the synthesized powder had the following characteristics: the nanometer size was smaller than the ultraviolet wavelength; the quantum size effect was remarkable; the electron excited by the WO3 was more easily transitioned by the valence band guide band; the specific surface area was larger; the reactivity was higher; and the absorption capacity of excitation light was stronger.
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