Preparation for Cesium Tungsten Bronze by Resin Exchange and Sol Gel Method

Energy conservation is a problem that must be considered in the sustainable development of every country's economy. In the energy consumption of many countries, building energy consumption accounts for about 30 ~ 40% of the national energy consumption, while the energy consumed through glass doors and windows accounts for more than 50% of the energy consumption of the building. If the transmission of near infrared light is reduced, the heat shielding effect will be greatly improved. Transparent heat insulation coating and transparent heat insulation film have bright prospects for economic, convenient use and good insulation effect.

Cesium tungsten bronze can also be called caesium tungstate. It is a good transparent insulating material. The near infrared shielding mechanism of cesium tungsten bronze heat insulation particles is mainly due to the strong absorption of MxWO3 to near infrared. The nanosesium tungsten bronze has a strong near infrared absorption capacity, and can effectively convert it into heat energy, which shows great application value in the treatment of cancer. In the future, photothermal therapy is a new method for the treatment of tumors. It has great potential for development. Cesium tungsten bronze is expected to become an excellent tumor marker.

The preparation technology of cesium tungsten bronze is complex. So far, no effective method has been found for mass production. A cesium tungsten bronze preparation method includes the following steps:

(1) Solid state colloidal tungstic acid was prepared by resin exchange sol gel method or rapid acidification method. Tungstate solution with a concentration of 0.1 to 2mol/L was dissolved in water, and tungstate solution was converted to tungstate solution by cation exchange resin.

(2) The excess citric acid solution was quickly added to the tungstate solution under the stirring condition, making pH less than 1; continuous stirring to produce floc colloidal tungstic acid suspension, stirring time more than 5min, making solid colloidal tungstic acid precipitated from liquid phase, completely converted to solid colloidal tungstic acid and suspended in solution. Finally, flocculated tungstic acid was formed. After filtration, solid colloidal tungstic acid was obtained.

(3) The precursor solution containing A salt, M salt and solid colloidal tungstic acid is prepared with appropriate solvents and inducers. The atomic molar ratio of A: M: W in the precursor solution is (0.0001~0.9): (0.1~1): 1, and the molar concentration of the inducer in the reaction precursor is 0.1 ~5.0mol/L, and the concentration of solid state colloidal tungstate in the reaction precursor is 0.001~5mol/L, specific. M salt and inducer were accurately called and dissolved in the solvent. After mixing, the solid colloidal tungstic acid was mixed under mixing conditions, and then added into the solid state gelatinous tungstic acid, then A salt or A salt solution was added, and 1~5h was stirring to obtain the reaction precursor. (A salt was the salt of Co, Ni, Pd, Pt, Au, Ge, Se, Sn, Sb, Te, Pb, Bi, In.  A mixture of A/W atoms with a molar ratio of 0.0001 to 0.9:1, a M salt containing Cs and a M/W atom molar ratio of 0.1~1:1).

(4) The prepared reaction precursor was reacted at 151~400°C for 5~72 hours, and the precipitates after the reaction were washed, centrifuged and dried, and the CsxWO₃ nano powders were obtained.

The above method uses solid state colloidal tungstic acid as the tungsten source. Solid colloidal tungstic acid provides physical nucleation in the process of high temperature reaction. It is beneficial to increase the number of crystal nuclei, and the particle size of the synthetic powder is easy to control. It can ensure that the length of the nanorods over 95% is 10 ~ 100nm, small and highly uniform grain size is beneficial to it. With the enhancement of light transmittance and excellent dispersity and stability, the coating has excellent visibility and so on.

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