Preparation And Performance Of High Near-infrared Reflective Powdered Pigments

The global energy crisis and urban island effect can be relieved usefully by the environmentally benign and high near-infrared reflective pigments,and promote the development of green building energy-saving industries,which is of great significance to environmental significance and application value promote the development of green energy-saving industry.The increasing innovation of science and technology has also led to continuous improvement of building materials.It is difficult to meet the needs of people's better life by single-color or low-performance pigments.The development of a new class of non-toxic and color-controllable pigments with high reflectivity has become a domestic and international Hot topics for research.Ions doping is an important mean to achieve color diversity of high near-infrared reflective functional pigments.In order to improve the defects of traditional pigments contain toxic heavy metal elements.In this work,serial high near-infrared reflection Ba_1-xCu_xZr_1-yTb_yO₃ pigment powder co-doped with Cu²⁺and rare earth Tb³⁺,as well as Mg²⁺,Al³⁺double-doped Co_1-xMg_xCr_2-yAl_yO₄ was prepared by a sol-gel process.Meanwhile,high near infrared functional pigment[(Na_0.5Y_0.5)_xBi_1-x][Mo_xV_1-x]O₄ was prepared by solid phase method.The thermal decomposition of the prepared pigment precursor,thermal stability,phase structure,particle size,ultraviolet/visible/near-infrared reflectance,color parameters and chemistry durability of the synthesized pigment samples were investigated and characterized by thermogravimetric differential scanning calorimetry?TG-DSC?,X-ray diffraction?XRD?,scanning electron microscopy?SEM?,UV/vis/NIR spectroscopy?UV-vis-NIR?,and color CIE-L^*a^*b^*1976 color scales.The experimental results demonstrated that:?1?the optimum calcination temperature of Ba_1-xCu_xZr_1-yTb_yO₃ composite pigment particles is 1100°C.The doping of Cu²⁺and Tb³⁺ions do not change the cubic perovskite crystal structure of BaZrO₃ pigment matrix,and ion doping makes the unit cell volume of the pigment regularly reduce,which is mainly due to the difference of ionic radius;the uv-visible reflectance of the synthetic sample increases with the increase of the doping amount of copper and strontium ions;the transition metal ion Cu²⁺and the rare earth ion Tb³⁺are introduced to change the color of the pigment increasingly from white to gray,and to yellow,and the band gap Eg of the pigment decrease.The doping of Cu²⁺ion and Tb³⁺ions fully show the pigment color tunableness.In addition,the obtained pigments possess high near-infrared solar reflectance is up to 80.1%.Meanwhile,the synthesized pigment sample has good thermal stability,which can be applied to thermal insulation coating field.?2?The optimal sintering condition of Co_1-xMg_xCr_2-yAl_yO₄ composite particles is 900°C/6 h,and all obtained pigment samples behaved cubic spinel structure.The co-doping of Mg²⁺and Al³⁺was successfully introduced into the CoCrO₄ lattice,and substituted the Co²⁺and Cr³⁺sites in the matrix lattice,meanwhile the sample lattice is slightly distorted due to the difference in ionic radius.At the same time,the doping of Mg²⁺ion causes the sample color to change from atrovirens to blue-green,eventually show pale yellow color;and Al³⁺ion makes the green component in the sample color gradually decrease,the blue component gradually strengthen,and the pigment finally exhibit a bright blue color.The doping of the transition metal ions not only reduces the cost but also improves the near-infrared solar reflectance of the pigment.The prepared Co_1-xMg_xCr_2-yAl_yO₄ series pigments have high near-infrared solar reflectance?R^*>51%?;at the same time,the obtained pigment samples have good chemical stability and high temperature resistance,which have broadapplicationprospectsinheat-reflectingbuildingcoatingfield.?3?[(Na_0.5Y_0.5)_xBi_1-x][Mo_xV_1-x]O₄ pigment particles all have monoclinic scheelite vanadate structure,the space group is I 2/a?15?and no other peaks exist,which indicate that BiVO₄and?NaY?_1/2MoO₄ compounds eventually form an effective solid solution.Pigment sample particles have irregular shape and slight agglomeration,the doping ions make the pigment particle size more uniform.The pigment sample[(Na_0.5Y_0.5)_xBi_1-x][Mo_xV_1-x]O₄ exhibit orange-yellow to yellow color.The near-infrared solar reflectance R^*can reach up to 97.71%,and indicate that the pigment powder have excellent thermal insulation performance.In addition,the prepared pigment samples have good thermal stability and can be applied to heat-insulating coatings with low toxicity and plastic products fields.In conclusion,the synthesized composite pigment powder in this work have certain basic research value in the new building energy-saving and environmen-friendly materials fields,meanwhile provides a certain reference for better selection of materials in the fields of building decoration,chemical industry and automobile.