| Window glass is identified to be one of the most important channels for energy exchange between architecture and the environment,and contributes a considerable amount of building energy consumption.Transparent heat-insulating coatings on glass can selectively cut off the ultraviolet and near-infrared(NIR)light,while simultaneously ensure visible transparency.In recent years,they have received extensive research attention in the field of building energy-saving.So far,a variety of transparent insulating materials have already found.Among them,indium tin oxide(ITO)as well as antimony tin oxide(ATO)is a typical representative of transparent conductive oxide.However,the distribution of indium and antimony elements is uneven and the cost is high.LaB6 has high energy consumption in the synthesis process and La is expensive.What is worse,the insulation effect is limited.Compared with them,tungsten bronzes(MxWO3),selective light transmitting materials,usethe local surface plasmon resonance effect between incident light and the material surface free electrons or small polaron absorption mechanism.It has caused widespreading concern because of excellent shielding ability in infrared area(780-2500 nm),especially transmittance down to 10 % in900-1200 nm.In addition,it have many advantages,such as high reserve,low price,non-toxic raw materials,and become one of ideal transparent insulation coatings.Among alkali metal elements,Cs,Rb with large radius are beneficial to improve the structural stability and provide more free electrons,leading to the increasing of near-infrared shielding performance.In addition,Cs,F co-doping CsxWO3-y Fy was prepared to achieve F part replacement O by the similarity of O and F,and finally tested its near infrared shielding performance.In this paper,the effects of different molar ratios of Cs/Rb and F/W on the phase,microstructure and near infrared shielding properties of(Cs,Rb)xWO3 and CsxWO3-yFy were systematically discussed.The products were characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM),thermogravimetry(TG),Zeta potential-particle size,UV-vis-NIR spectrophotometer.The main conclusions are as follows:(1)Using tungsten acid,CsCl and RbCl as raw materials,ethylene glycol as reducing agent and reaction solvent,respectively,Cs,Rb co-doped(Cs,Rb)xWO3 were prepared by solvothermal method.Theeffects of different molar ratios of Cs/Rb on the phase,morphology and near-infrared shielding properties of the products were investigated.The results showed that the morphology of the products was dominated by nanorods(about 100 nm in diameter and several hundred nanometers in length).The optical properties of the coated films showed that the transmittance of the coated films increased firstly,then decreased and finally increased slightly at 300-2600 nm.When the molar ratio of Cs/Rb =1:2,the best near infrared shielding performance was obtained,the visible light transmittance peak(Tvis-max),the transmittance at 950 nm(T950 nm)and near infrared rate(TNIR-min)were 74.9 %,20.9 %,8.6 %,respectively.(2)Cs,F co-doped Cs0.33WO3-xFx was prepared by sol-gel method using tungstic acid,CsCl and Cs F as raw materials(Cs/W = 0.33).The influence of different F doping amount on the phase,morphology and near infrared shielding properties of the product were discussed.The results showed that with the increase of F doping amount,the diffraction peak of the product was obviously broadened.The products gradually changed from nanorods(diameter about 30-50 nm,length from 20 to several hundred nanometers)into nanoparticles(about 10 nm in diameter).When F/W = 0.22,Cs0.33WO3-xFx exhibited the best near-infrared shielding performance(Tvis-max = 76.3 %,T950 nm = 25.7 %,TNIR-min = 10.5 %)... |
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