Tungsten trioxide, or WO3, is a main dingal material for preparing windshield thermal insulating film. There are a few methods for the preparation of tungsten trioxide powder such as electrochemical processes, solution-based colloidal approaches, bioligation processes and chemical vapor deposition techniques.
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For example, the experts prepared the oriented WO3 nanowires using a hydrothermal treatment in the presence of alkaline metal sulfates. And the experts also synthesized WO3 nanoparticles by a very simple, low temperature (95-98 °C) and low pressure (1bar) hydrothermal process. Therefore, the needs for a high pressure autoclave and highly acid-resistive liners in the reaction chamber are avoided, which present clear advantages for the industry. Moreover, it is possible to readily scale up this process for the production of large quantities of materials. A first reaction produces orthorhombic WO3·H2O followed by a hydrothermal process using a simple reflux system in the presence of oxalic acid as surfactant. Annealing at or above 300 °C in ambient air leads to a phase transformation to monoclinic WO3, where the morphology of the materials is preserved.
