Research On Preparation,Properties And Application Of Cesium Tungsten Bronze Nano-powders

The application of a transparent heat-insulating coating on the glass of doors and windows is very promising in the energy conservation and emission reduction.This function could be realized by reasonably regulating the solar energy entering the building,and effectively reducing the energy consumption as well as the carbon dioxide emissions generated by the air-conditioning.The nano-tungsten bronze?M_xWO₃?material demonstrates excellent properties of transparence and heat-insulation because of its large forbidden band width and high concentration of carrier.This inexpensive material contains no toxic elements.It is expected to replace antimony tin oxide?ATO?and indium tin oxide?ITO?in transparent thermal insulation coatings.With W powder,H₂O₂ and CsCl as the raw materials,cesium tungsten bronze powders were synthesized by sol-gel method.Cesium tungsten bronzes were investigated for the impacts of different ratio of n?Cs?to n?W?,dispersants and different calcination conditions on the structures and properties.Cesium tungsten bronzes were characterized by the X-ray diffraction?XRD?,transmission electron microscopy?TEM?,scanning electron microscope?SEM?,energy-dispersive X-ray spectroscopy?EDS?,X-ray photoelectron spectroscopy?XPS?and ultraviolet-visible-near infrared spectrometers to determine the phase,microstructure,elemental composition and optical properties.The results show that the Cs_0.30WO₃ could be synthesized with good crystallinity,dispersibility and transparent thermal insulation properties when the ratio of n?Cs?and n?W?is 0.33,the dispersant is PEG-600,calcination temperature is 600?and calcination time is 2h.The Cs_0.30WO₃ is mainly a nanorods with a width of about50nm.The highest visible light transmittance and near-infrared shielding ratio of the Cs_0.30WO₃ film prepared initially are approximately 84%and 68%respectively.In addition,XPS indicates that the d-d electron transfer between W of different valence states provides some help for the near-infrared shielding performance of the Cs_0.30WO₃ powder.The study of the crystal growth kinetics of cesium tungsten bronze shows that the kinetics index of the crystal growth is 4.During the calcination process at 500?⁸00?,cesium tungsten bronze apparent activation energy of crystal growth is 143.17 kJ/mol.The Cs_0.30WO₃ slurry was obtained by physical-chemical method.In order to improve the stability of Cs_0.30WO₃ slurry,it was investigated for the impact of dispersion medium,mechanical dispersion method,dispersion time,dispersant type and dispersant dosage on the stability.The results show that the stability of Cs_0.30WO₃ slurry is better when the dispersion medium is water,the amount of PEG-400 is 5%and sand milling time is 6h.The particle size of Cs_0.30WO₃ in the slurry is about 124 nm.Cs_0.30WO₃ transparent thermal insulation coating was prepared by mechanical blending method with mixing the C_s0.30WO₃ slurry,organic resin and appropriate amount of auxiliary agent.The Cs_0.30WO₃ transparent thermal insulation film was prepared by spray coating method.The coating was investigated for the impact of the film former on the stability.The Cs_0.30WO₃ transparent thermal insulation film was investigated for the impacts of the content of Cs_0.30WO₃ slurry and the thickness of film on the mechanical properties,the optical properties and the thermal insulation properties.The results show that the coating stability and film performance are better when the film-forming agent is polycarbonate resin,the content of Cs_0.30WO₃ slurry is 40%and the film thickness is 1 layer?0.016mm?.In addition,the film adhesion level is 0,the hardness is 3H,the highest visible light transmittance and near-infrared blocking rate are about 77%and 83%respectively,the near-infrared absorption shifts toward the short wavelength direction,indicating that the wavelength range of near-infrared shielding becomes wider and the near-infrared shielding performance is better.The available temperature drop of the film measured by the self-made equipment is about16?and the thermal conductivity decreases from 0.9990 W/?m·K?to 0.6365 W/?m·K?,indicating that the film has a certain thermal insulation effect.In addition,comparing the optical properties of different functional film,it can be seen that the self-made nanocrystalline Cs_0.3WO₃ transparent thermal insulation film has better optical properties,a wider range of near-infrared shielding wavelengths and can shield the near-infrared light from 750 to 2500 nm.The self-made cesium tungsten bronzes transparent thermal insulation functional film has good mechanical properties and transparent thermal insulation effect,which leads to its good application value and market prospect.