Research On The Preparation And Properties Of Smart Coatings Based On Thermochromic Vanadium Dioxide Nanoparticles

Ordinary glass has problems such as large heat loss coefficient and high radiation transmittance,which can easily cause a large amount of heat to flow in and out leading to a substantial increase of energy consumption for cooling and heating in the buildings.Vanadium dioxide(VO₂)is a material that intelligently responds to the ambient temperature to adjust the transmittance of radiation.When applied to the glass surfaces,it could maintain a comfortable indoor environment without consuming energy.However,key issues hinder the commercial application of VO₂ smart windows including high phase transition temperature,insufficient luminous transmittance and poor thermal insulating effect.According to this,based on VO₂ crystal structure,atomic doping was used to reduce the phase transition temperature.Then,through modification of VO₂ particles and structure design of the coatings,optical performance and stability were improved.Furthermore,near-infrared absorption material was introduced to make up for the poor thermal insulating effect of VO₂ material.The main research contents and results can be concluded as follows:In hydrothermal environment,low-temperature phase transition W_xV_1-xO₂ particles were synthesized by W atom doping.W_xV_1-xO₂@TiO₂ nanoparticles were prepared by using hydrolyzed TiO₂ as the shell and modified with SEFS-61.The obtained W_xV_1-xO₂@TiO₂ nanoparticles with good crystallinity occurred phase transition at room temperature when the W doping amount was 1.5-2at%.Under the combined function of the TiO₂ shell and surfactant SEFS-61,the modified VO₂nanoparticles could not only have small particle size and stable dispersion ability,but also possess a lower refractive index.Compared with VO₂ particle coating,the luminous transmittance(T_lum)of W_xV_1-xO₂@TiO₂ coating increased by 12.6%to 66.0%.However,the W_xV_1-xO₂@TiO₂ coating cannot achieve near-infrared modulating ability(?T_IR)enhancement by LSPR,and the adhesion between the particles and the substrate was insufficient so that it exhibited unsatisfactory performance with?T_IR of 11%,hardness of HB and adhesion of level 4.The modified VO₂ nanoparticles were compounded with polymer matrixs to fabricate VO₂coatings.Through optimizing particle concentration,thickness and polymer matrix of the coatings,the oil-based and water-based VO₂ coatings displayed excellent performance with?T_IR greater than15%,hardness higher than 3H,adhesion of level 0,and solution(water,acid,alkali)resistant more than 168h.The experiment confirmed that the core-shell structure,grafting surfactant and polymer matrix played an important role in increasing the?T_IR and stability of the coatings.In order to improving the T_lum,the superhydrophilic SiO₂ coating with anti-reflection property was used to design and fabricate SiO₂/VO₂@TiO₂/SiO₂ coating.The T_lum and?T_IR of the coating were as high as72.5%and 16.3%,respectively.Thermal insulating test showed that the SiO₂/VO₂@TiO₂/SiO₂coating obtained thermal insulating effect only 7.7°C.To improve the near-infrared shielding(T_IRS)of SiO₂/VO₂/SiO₂ coating under low and high temperature and thermal insulating effect,the cesium tungsten bronze(Cs_0.33WO₃)with excellent near-infrared absorption property was introduced to construct a multilayer coating.Cs_0.33WO₃nanoparticles,having high crystallinity,were synthesized by solvothermal method.After modifying the Cs_0.33WO₃ nanoparticles,Cs_0.33WO₃ coating was achieved by optimizing the preparation process and structure of the coating,which exhibited high T_lum and T_IRS.Owing to the outstanding near-infrared absorption characteristic of Cs_0.33WO₃ nanoparticles,the SiO₂/VO₂/Cs_0.33WO₃/SiO₂ coating showed appealing performances with enhanced T_IRS-20°C of 53.1%,T_IRS-90°C of 62.5%,and thermal insulating effect of 9.9°C.