Tungsten Trioxide Applied for Kitchen Thermal Insulating Glass Coating

Tungsten trioxide for the production of kitchen thermal insulating glass coating can be prepared using sodium tungstate dehydrates (Na2WO4·2H2O, 99.99%,) powder as the starting material, and hydrochloric acid (HCl, 37%) as well as nitric acid (HNO3, 68%) as the chemical materials for ion exchange reaction. Oxalic acid dihydrate powder (H2C2O4·2H2 O, 99.99%) and polyethylene glycol with a chain length of 200 (PEG 200, 99.99%) were used as the complexing agent and polymeric source, respectively. Deionized water was used for solution preparation and washing steps. All the chemicals and solvents were used without further purifications.

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The Na2WO4·2H2O powder was dissolved in water, then heated at 80 °C. Next, a mixture of HCl and HNO3 (molar ratio of 1:1) was added to the solution at the same temperature, while it was being stirred, to adjust the pH to 1-2 and enhance ion exchange process. After a while, the yellow precipitate was formed and converted into a soft gel through aging. Then the gel was washed by the addition of hot distilled water or 0.1 N HCl solution to the gel followed by stirring and aging the soft gel at the same temperature. Several washing steps were applied to remove residual acid and by-products of the reaction. Oxalic acid and PEG were then added as chelating and resin agents, respectively. Finally, the WO3 nanoparticles were synthesized by heat treatment of resin precursor prepared from hydrated tungstic precipitates. The samples were first heated at 150 °C to remove residual water, then heated to 550 °C, and kept at this temperature for 90 min followed by cooling to room temperature.

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