[Introduction]Barium sulfate (BaSO4) is not only low-cost and abundant,but also has a high solar reflectance and hemispherical emittance. However,its thermal insulation performance as a filler in coating is inferior to that of rutile-type titania (TiO2) and silica (SiO2). Therefore,modifications are needed to enhance the thermal insulation performance of BaSO4.[Method]Using BaSO4 and zirconia (ZrO2) as raw materials,BaSO4/ZrO2 composite powder was obtained through calcination at high temperature. A thermal insulation coating was then prepared with the BaSO4/ZrO2 composite powder as filler and pure acrylic emulsion as binder. The chemical structure and morphology of the powders were characterized by X-ray diffraction (XRD),Fourier-transform infrared spectroscopy (FTIR),scanning electron microscopy (SEM),and energy-dispersive spectroscopy (EDS). The effect of ZrO2 dosage on properties of the coating was discussed.[Result]With the increasing of ZrO2 dosage,the solar reflectance,near-infrared reflectance,and hemispherical emissivity of the coating was increased initially and then decreased,while the thermal insulation temperature difference followed a similar trend. At an optimal ZrO2 dosage of 5％ by mass,the coating exhibited the best thermal insulation performance,with a solar reflectance of 0.809,near-infrared reflectance of 0.785,and hemispherical emissivity of 0.92. The thermal insulation temperature difference of the coating prepared with BaSO4/ZrO2 composite powder reached 11.29 ℃,which was 3.12 ℃ higher than that with only BaSO4 powder,and 4.52 ℃ higher than that with uncalcined BaSO4/ZrO2 powder.[Conclusion]This study provides a scientific basis for the development of thermal insulation coating technologies and products based on modified BaSO4.
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