Nano tungsten trioxide is an infrared ultraviolet shielding material (thermal insulation material), which may be prepared by hydrothermal method using sodium tungstate and hydrochloric acid as main raw materials.
Preparing tungsten trioxide by hydrothermal method, pH and hydrothermal temperature of the system have greater impact on the structure, morphology and performance of tungsten trioxide:
1. If pH=1.0~1.5, the temperature is at the range of 80~140°C: The product is tungsten trioxide of hexagonal phase, whose particles are spherical of short needle shape.
2. If pH=2.0~2.5, the temperature range is between 160°C and 180°C, the product transforms from hexagonal phase to hydrated tungsten trioxide of cubic phase. And the synthesized particles are of irregular shape and size.
Compared with the cubic phase of tungsten trioxide and the hexagonal phase of tungsten trioxide, the hexagonal phase provides a channel for the photogenerated proton (H+) transport required for photochromism. As you may have known, photochromism is the basic principle of this kind of thermal insulation material.
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