Preparation of high near-infrared reflectance mica/(Ni, Sb)-co-doped rutile yellow composite pigment via mechanochemical pretreatment and sintering

摘要

Mica/(Ni, Sb)-co-doped rutile yellow composite pigment with a high near-infrared reflectance was prepared via mechanochemical pretreatment and subsequent sintering. (Ni, Sb)-co-doped rutile yellow pigment was synthesized by a solid-phase method in the presence of sodium fluoride (NaF) as a mineralizer, and mica was peeled by ultrafine grinding. The pigment, mica and mica/pigment composite were characterized by X-ray diffraction, laser diffraction particle size analysis, nitrogen gas adsorption method, scanning electron microscopy, energy dispersive spectroscopy, ultraviolet-visible-near-infrared spectroscopy, CIEL*a*b* color scales, and infrared irradiation image, respectively. The results show that the temperature of synthesizing a pure rutile pigment in solid-phase reaction is reduced by 100 degrees C due to the addition of mineralizer NaF. (Ni, Sb)-co-doped rutile pigment has better color rendering performance and near-infrared (NIR) reflectance. Ultrafine grinding produces the finer flatty mica particles with fresh reflective surfaces, thus improving NIR reflectance of peeled mica. In mica/ pigment composite prepared via mechanochemical pretreatment and subsequent sintering, peeled mica has a synergistic effect on (Ni, Sb)-co-doped rutile pigment particles to further scatter near-infrared radiation through the multiple layer reflections, leading to a better heat insulation. The high near-infrared reflectance of composite pigment increases to 97.72%, and the b* value of the pigment synthesized with 1 wt% NaF is 37.77. For the irradiation infrared lamp, the surface temperature of aluminum plate coated with mica/(Ni, Sb)-co-doped rutile yellow composite pigment is 40.1 +/- 0.2 degrees C, which is lower than that of aluminum plate uncoated determined by thermal camera and thermocouple. When aluminum plate coated with mica/(Ni, Sb)-co-doped rutile yellow composite pigment is under sunshine, its surface temperature is 38.6 +/- 0.2 degrees C. In addition, the mechanism of preparing the composite pigment via mechanochemical pretreatment and subsequent sintering and the multiple structure reflection effect on peeled mica surface coated with (Ni, Sb)-co-doped rutile yellow pigment particles were also discussed.

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