| In our countory,building energy consumption accounts for about 30%of the total social energy consumption.More than 50%of building energy consumption is lost through doors and windows.Therefore,energy-saving technologies of building glass have been widely concerned.In energy-saving technologies field,transparent coating glass has the advantages of simple production process and low cost,which has been widely studied.Vanadium dioxide stands out for the significantly and intelligently change of transmittance in infrared wave range according to different temperatures,which could reduce the solar radiation and air conditioning energy consumption.In this paper,W doped vanadium dioxide(WVO)nano dispersions were synthesized by the hydrothermal methods,and WVO/caesium tungsten bronze(CsxWO3)/polyurethane nanocomposite films were prepared by mixing the WVO dispersions with oil-based resin solution.Then it was coated on polyethylene terephthalate(PET)substrate and the other side was coated on glass to form nanocomposite energy-saving glass.Influences of preparation,modification and blending process conditions on the morphology,crystal form,morphology,dispersion of WVO nanoparyicles and properties of WVO/CsxWO3/oil-based resin and glass were investigated.The main conclusions of this paper are shown as follows:WVO nano dispersions were prepared by hydrothermal methods,and oxalic acid was used as the reducing agent and tungstic acid as the dopant.Then WVO/N-methyl pyrrolidone(NMP)nano dispersions were acquired by ball milling and surface modification.Influences of dopant concentration,mole ratio of raw materials,hydrothermal time,hydrothermal temperature on the morphology of WVO nanoparticles,the dispersity and properties of MST were investigated.Influences of ball milling time and solvent types of ball milling process on the morphology of WVO nanoparticles,particle sizes and properties of MST were investigated.Influences of modifying agents,modifying time and modifying temperatures on the morphology of WVO nanoparticles and particle sizes were investigated.Suitable preparing conditions were obtained:tungstic acid dosage of 0.5 at.%,mol ratio of H2C2O4 to V2O5 of 1:3,the hydrothermal pH value of 1.27,the precursor stirring time of 3 h,the hydrothermal temperature of 280 ?,the hydrothermal time of 24 h.The solvent of ball milling is ethanol/butanol,mole ratio of 1:1,the ball milling time of 20 min,concentration of 5 g·L-1.The modifying agent is modifying agent E,the modifying agent concentratioin of 50 wt%,the liquid medium of methanol,the modifying time of 2 h,the modifying temperature of 60?.The prepared WVO nanoparticles showed 5-20 nm primary particle size,27 nm average size,narrow size distribution and remarkable dispersity in NMP.The grafting rate of the modifying agent was 13.1 wt%.The phase transition temperature of WVO nanoparticles is 55.2?,with high latent heat of 33.5 W·g-1.The WVO and CsxW03 dispersions which were sold in market,were mixed with oil-based resin and coated on PET substrate,then the transparent nano composite films with obvious properties of MST were obtained.Influences of oil-based substrate materials,dosage of WVO and CsxW03 nanoparticles,filming thickness on the optical properties,mechanical properties and properties of MST of the transparent composite film were investigated.The results showed that under the process conditions of that polyurethane(TPU)as the oil based resin,mass ratio of WVO to TPU of 20 wt%,mass ratio of CsxW03 to TPU of 10 wt%,and coating thickness of 15 pm,that the prepared WVO/CsxWO3/TPU composite coating has high transparency,good properties of MST.The visible light transmitted of composite film is 78%at 550 nm and the near infrared ray transmitted of composite film changed from 59%to 18%with the temperature changing from 20? to 90?,the change reached 41%.Nanocomposite films were coated on glass to prepare nanocomposite glass.The results of heat insulation test results are as follows:The WVO/CsxWO3/TPU nanocomposite glass materials showed the excellent heat insulation and properties of MST.And the temperature of air on the other side of the composite glass is 6? lower than that of the blank glass under the same light irradiation in the time of 60 s.The WVO/Cs,W03/TPU composite glass went a phase transition in the time of 35 s,and the heating rate droped from 0.103?/s to 0.016?/s,while the glass coated with WVO/TPU film didn't go a phase change under the light irradiation in the time of 60 s,and the heating rate of air was 0.15?/s.The results showed that the addition of CsxW03 improved the temperature of the glass in a short time,so the problem of high MST temperature could be solved and the heat insulation performance of the composite glass could be improved after the combination with CsxWO3. |
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