Preparation And Properties Of W-F Co-Doped VO₂ Powders

The ordinary glass of general architecture always has no permselectivity to the sunlight which could result a vast waste of energy. The heat will be transferred into room via the glass with the irradiation under sunlight in summer, which result in a warming indoor temperature,so it is inevitably that the energy consumption of air-conditions are increased. Meanwhile, the indoor heat is easily emitting out in winter, and that dramatically enhanced the consumption of heating units, naturally. Smart materials has become the mainstream of today's new materials development, due to its excellent structural properties, controllable exchange process of energy with outside, so as to achieve the rational use of energy and reducing the energy consumption finally. The application of VO2 powders, with low-temperature phase transition properties, on the glass as a heat insulation coating, could change the optical properties of ordinary glass, and adjust the transmittance and reflectivity of glass under sunlight intelligently, so as to control the indoor temperature effectively.In this present paper, the VO2 powders were prepared by hydrothermal synthetic method.The optimizing parameters including hydrothermal conditions, calcination conditions, doping ratio, water kettle polyure filling degrees were discussed in details. The properties of VO2 powders were characterized by XRD, SEM, EDS, DSC and dynamic light scattering. The optimum conditions of VO2 powders prepared by hydrothermal synthetic method were determined: using V2O5 as raw materials, C2H2CO4·2H2O as reductant, Na2WO4·2H2O as the W dopant, NH4·F as the F dopant, 0.15 mol L-1 H2NCONH2 as the precipitant, hydrothermal reaction was performed 3 days under 190?. And the V_1-mW_mO_2-nF_n powders were obtained by calcination at 800? under nitrogen atmosphere with 5 hours, and the minimum phase transition temperature was about 27.5?.The V_1-mW_mO_2-nF_n water-soluble slurry were prepared by the method of mechanical polishing-ultrasonic dispersion, which distilled water as dispersion medium. The obtained slurry had exhibited an improved dispersive property after surface modification. And the stability effects of dispersant and dispering time to slurry were systematically studied. These results revealed that the optimum prepared conditions are identified, the content of KH560 modifiers and PVP dispersant were 1.8 % and 1.5%, respectively, and sanding time is 1.5h.The glass heat insulation coating were prepared by coated with V_1-mW_mO_2-nF_n to the surface,and the UV-VIS-IR was performed. It is indicated that the slurry contents and thickness could affect the optical characteristic evidently, and 30% slurry content with 1² coating layer were select as optimum conditions according to visible light transmittance and infrared rejection analysis.