Study The Peparation And Properties Of Near Infrared Reflectance Color Pigments

Near-infrared reflective pigments generally exhibit certain colors in the visible light region.Pigments with a high reflectivity in the near-infrared region have a very broad market prospect because of their rich colors and excellent thermal insulation properties.However,pigments with rich colors tend to have poor near-infrared reflection properties,such as cobalt blue pigments;while pigments with good near-infrared reflection properties are not rich in colors,such as aluminum phosphate pigments,this resulted it is difficult to meet market demand.This paper intends to use ion doping technology to improve the near-infrared reflectivity of ordinary cobalt blue pigments and enrich the color of white aluminum phosphate pigments,so as to develop new synthesis processes for a series of environmentally friendly color pigments with high near-infrared reflection.In this paper,one kind of composite titanium-cobalt green pigments doped with metal elements zinc,magnesium and nickel and another kind of aluminum phosphate pigments doped with metal elements cobalt and nickel were prepared by the sol-gel method.The prepared composite titanium-cobalt green pigment was characterized to explore its physical phase,morphology,chromaticity,particle size,particle size distribution and near-infrared reflection,and the prepared pigments were made into heat-reflective coating for investigating their insulation performance.The effects of process conditions such as raw material molar ratio,pH value,calcination temperature and calcination time on the crystal structure and properties of the composite titanium cobalt green pigment and doped aluminum phosphate pigment were discussed,and the optimized conditions of the preparation process were obtained.In the titanium butyl acid,cobalt nitrate,aluminum nitrate,doped metal nitrate as the main raw materials,the use of sol-gel method to prepare titanium cobalt green pigment.The experimental results show that the titanium-cobalt green pigment CoTi1.2Al0.4O4 prepared under the optimal process has a near-infrared reflectance about 70.3%,by which composite titanium-cobalt green pigments Co1-xMxTiyAl2-1.33yO4(M=Zn,Mg,Ni)were prepared with doping zinc,magnesium,nickel metal ions,respectively.As the increase of doping ion content,the color of the pigments was reduced,but the reflectivity was greatly improved.Among them,ZnTi1.2Al0.4O4 doped with Zn had the highest near infrared reflectance,which could reach 117.8%.In the heat insulation performance experiment of this paper,the equilibrium temperature of ZnTi1.2Al0.4O4 heat insulation coating was 16.5?lower than that of ordinary cobalt blue pigment.In the main raw material synth of aluminum nitrate,phosphoric acid,doped metal nitrate,the sol-gel method was used to prepare the doped cobalt,nickel phosphate aluminum pigment MxAl1-xPO4(M=Co,Ni;x=0.0,0.01,0.05,0.1,0.2).The research results show that with the increase of ion doping content,the near-infrared reflectance of cobalt-doped pigments and nickel-doped pigments had decreased from 108.9%to 50.9%and 59.6%,respectively,this is due to the decrease of their forbidden width caused by dopping metal ions.However,the color of cobalt-doped aluminum phosphate changed from white to purple,and the color saturation of pigment color increased from 1.29 to 37.98,the color of nickel-doped aluminum phosphate changed from white to yellow,and the color saturation of pigment increased from 1.29 to 37.37.As the content of doped cobalt and nickel increases,the thermal insulation effect of the pigment becomes poor,but it is still better than the thermal insulation performance of commercial pigments with similar colors.Compared with the cobalt-doped series,the nickel-doped series has a higher near-infrared reflectivity and the chroma is almost the same.