Tungsten Bronze Nano-Powder for Thermal Insulation Coating

Near-infrared light accounts for about 46% of the solar spectrum. In many countries, building energy consumption accounts for about 30-40% of national energy consumption, while energy consumed through glass doors and windows accounts for over 50% of building energy consumption. Building window glass energy-saving and insulation is of great significance for energy saving and emission reduction. Therefore, the development of thermal insulation coatings, especially architectural thermal insulation coatings closely related to human life, and has great practical significance.

It has been reported that a transparent insulating material (tungsten bronze powder: MxWO3-yAy) can be added to the coating to produce a transparent heat-insulating coating having high visible light transmittance and high infrared absorption rate, and a transparent heat insulating material. In recent years, the research and application of transparent heat-insulating film has also received wide attention. Transparent heat-insulating film is widely used in automobile film and building door and window film. However, whether it is a film or a coating, the performance of the nano-scale transparent heat-insulating powder added is undoubtedly the focus.

In the case of tungsten bronze powder, the small and uniform particle size not only facilitates the dispersion of the tungsten bronze powder in the coating, but also contributes to the improvement of the visible light transmittance and the near-infrared shielding rate. Therefore, it is very necessary to find a low-cost, simple process to prepare tungsten bronze nano-powder with uniform particle size and small size. Some scholars have published a process for preparing Cs0.32WO3 hexagonal germanium tungsten bronze nano-short rod particles, the specific contents are as follows:

1) Weigh 6.3503g of sodium tungstate, add 30ml of deionized water, fully dissolve, and quickly add 5mol/L hydrochloric acid under stirring to make the pH ≤1. After stirring for 30min, we will get the yellow pigmented colloidal tungsten. The acid colloid suspension is filtered to obtain a milky yellow solid tungstic acid having a certain volume; the solid colloidal tungstic acid is added to 120 ml of deionized water, and the mixture is uniformly stirred under ultrasonic vibration assisting conditions to be redispersed into suspension. The solution was further filtered by suction, and repeated three times; the above operation was repeated using 120 ml of absolute ethanol, and the mixture was filtered three times. The obtained block gel was taken out and added with an appropriate amount of absolute ethanol to make a total volume of 77 ml, and stirred and dispersed under ultrasonic shaking conditions. Suspending liquid to obtain a solid colloidal tungstic acid ethanol dispersion;

2) Preparation of reaction precursor solution and powder synthesis

Weigh 0.6g of barium sulfate, add it to 40ml solid colloidal tungstic acid ethanol dispersion, measure and add 70ml of acetylacetone, and finally add 8.356g of oxalic acid, 1g of P123 inducer, stir for 2h, and obtain the reaction precursor liquid; The reaction precursor liquid was transferred into a 200 ml autoclave, and continuously reacted at 190 ° C for 72 h. The precipitate after the reaction was washed with water and alcohol three times in sequence, and after centrifugation, dried at 60 ° C for 10 h, according to XRD and EDS. It was judged that the synthesized blue powder was Cs0.32WO3 hexagonal germanium tungsten bronze.

The solid colloidal tungstic acid ethanol dispersion prepared under the above conditions can synthesize Cs0.32WO3 hexagonal germanium tungsten bronze nano short rod particles, and CsxWO3 powder synthesized under similar hydrothermal conditions using tungstic acid solution or sol. In the body, usually containing a large number of abnormally grown micron-sized long rod particles, the long rod particles are not conducive to its uniform dispersion in the coating, and to some extent affect its visible light transmittance and near-infrared absorption / shielding performance.

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