Cesium Tungsten Bronze Nanopowder in Transparent Insulation Coating

To make the thin, transparent external material like glass, plastic not only insulated and not blocking light, but also energy-saving, the most effective way is to add nanoparticles with the ability to absorb infrared light to resin, such as antimony-doped tin oxide (ATO), indium tin oxide (ITO), lanthanum hexaboride, and cesium tungsten bronze nanoparticles, and made transparent thermal insulation coatings directly onto the glass or shade cloth, or pre-coated on PET (polyester) film, and then stuck the PET film to the glass (such as car film), or made into a sheet of plastic, such as PVB (polyvinyl butyral), EVA (ethylene-vinyl acetate copolymer) plastic, then composite the plastic sheet and tempered glass, which also play a role in blocking the infrared, so as to achieve the effect of transparent insulation.

In the above nanoparticles that are capable of absorbing infrared rays and to achieve transparent insulation , the cesium tungsten bronze nanoparticles(also known as cesium tungstate) has the best near-infrared absorption properties that usually 2 g of addition per square meter coating can reach transmittance of 10% at 950 nm (this data indicates the near infrared absorption), while it can reach transmittance of more than 70% at 550 nm (70% is the majority basic indicators of high levels of transparency film). Although the cesium tungsten bronze nanoparticles have excellent transparent insulation properties, high temperature solid state reaction of raw materials tungsten and cesium is the mainly existing production process. For example, firstly form a tungsten bronze crystal structure at about 600 ℃, and then restore at about 800 ℃ reducing atmosphere, thereby form cesium tungsten bronze nanoparticles with a high carrier concentration (cesium tungsten bronze infrared absorption derived from the carrier).

The process is simple and have stable batch, but the problem is particles being too large, usually in the micron level. To meet the transparent coating requirements, grinding by high-dispersion device for a long time is needed to make the particle size less than 100 nm, which greatly increases the cost, and the presence of large particles increases the coating haze and affects the optical effect of the coating. In addition, using hydrogen reduction at high risk in the production process also increased production costs. Many studies have reported the use of wet chemical liquid phase process, such as the preparation of cesium tungsten bronze nanoparticles by hot water method, hot solvent method and high temperature thermal pyrolysis, but the problems that the high cost of the equipment or severe corrosion, high pressure and low safety factors still exist, and there is still not reports of completely liquid-phase production of small particles cesium tungsten bronze powders.