Preparation Of Antimony Doped Tin Oxide Transparent Heat-insulating Coatings

With the progress of energy conservation, building glasses are required to have both high transparency in visible region and effective heat-insulating performance in infrared region. Energy-saving glasses like coated glass, filmed glass and vacuum glass may have the ability of heat insulation. But their low transparency in visible region may affect architectural lighting. Thus, coatings with high transparency and excellent heat-insulating performance must be developed. Antimony doped tin oxide (ATO) coatings is an ideal transparent heat-insulating coatings, which has both the high transparency in visible region and effective heat-insulating performance in infrared region. However, ATO nanopowders may agglomerate easily due to their large specific surface area and high surface activity. Therefore, ATO nanopowders must be dispersed firstly to prepare the transparent heat-insulating coatings.In this thesis, ATO nanopowders of small grain size were prepared by solvothermal method. ATO heat-insulating slurry of good dispersivity was successfully prepared with ATO nanopowders via surface modification. Transparent heat-insulating coatings was prepared, using aqueous ATO slurry as coating filler and waterborne polyurethane as coating substrate. Films of well optical performance were prepared through spin-coating method. It is a new preparation method for energy-saving glasses. The main achievements are as follows:1. Preparation and structure of ATO nanopowdersATO nanopowders were prepared by hydrothermal method, using inorganic salts SnCl4·5H2O and SbCl3as raw material. Effects of doping amount, reaction temperature and reaction time on structures of ATO nanopowders were investigated. The results show that antimony is doped into SnO2crystal lattice after being reacted at180℃for16hours. The distribution of antimony in nanopowders is uniform. Nanopowders’ average grain size is about10nm. With the increase of Sb content, average grain size of ATO nanopowders reduced, interplanar crystal spacing reduced initially then increased, and it reaches a minimum when the doping amount is10at.%. The structure of obtained powders changes from amorphous to crystalline as the hydrothermal temperature turns higher. The increase of reaction time may lead to larger grain size. Interplanar crystal spacing reduced initially then increased with the increase of reaction time, reaching a minimum when the reaction time is16h. 2. Modification of ATO and preparation of waterborne ATO heat-insulating slurryWaterborne ATO heat-insulating slurry was successfully prepared with ATO nanopowders via surface modification by vinyl triethoxy silane (VTES). The dispersibility, stability and modification mechanisms of the slurries before and after surface modification were studied. The effects of the amount of VTES, reaction temperature and reaction time on the grafting degree of VTES were investigated. The results show that the best dispersing agent for ATO nanopowders is VTES. After surface modification by VTES, the dispersibility and stability of the slurry are improved, its average particle size of ATO nanoparticles decreases from221nm to121.1nm, and the relative sedimentation heights still keeps as high as96.3%after sedimentation for24h. The transmittance of the visual light range and blocking ability of the near infrared light range of the ATO film obviously enhance, after surface modification. The optimal amount of VTES, reaction temperature and reaction time for modification are0.4ml,30℃and2h, respectively.3. Preparation and properties of ATO transparent heat-insulating coatingsTransparent heat-insulating coatings were prepared through compounding method, using waterborne ATO heat-insulating slurry and waterborne polyurethane as raw materials. Films were prepared by spin-coating method. Effects of spin speed, amount of ATO slurry and times of coating on optical properties of films were investigated. The results show that the surfaces of the films are uniformly dense, adhesion between film and glass is strong, meaning that the coatings are easily film-forming. ATO nanoparticles disperse uniformly in the films. Transparency in visual light region of the film prepared with25vol%ATO slurry is best, as high as84.7%. With the increase of coating times, the films’ thickness increases and the thickness of each layer is about1.01μm. The transmittances of films in ultra violet, visual and infrared regions decrease gradually at the same time with the increase of coating times. The biggest drop in transmittance is infrared region, while the drop of visual region is of the minimum. The optical performance of coating sample coated with6times is the best.Film’s transparency in infrared region is21.6% and the number in visual region is as high as70.7%.