A novel low-cost solvent-thermal method was proposed for the preparation of cobalt blue (CoAl 2 O 4 ) pigments. The effects of solvent composition , reaction time, reactant molar ratio, and reaction temperature on the structure and tone of the synthesized pigments were investigated. The results revealed that the optimal process conditions for the synthesis of uniform, vibrant cobalt blue pigments were obtained when the volume ratio of alcohol-water was 1:1, the molar ratio of Co 2+ to Al 3+ was 1:3, the reaction time was 4 h, and the reaction temperature was 200 °C. This solvothermal synthesis method is mild, cost-effective, and easily controllable, thus making it highly suitable for industrial applications.
Weiran Zhang,Jieqin Li,Fan Zhong,Guohua Wu,Haiyun Jiang,Weili Zhang,Qilong Liu
Cobalt blue pigments, which mainly comprise CoAl2O4, are widely synthesized as nano-scale particles using the coprecipitation method. Such ultrafine powders are necessary for the ceramics industry because of their significant effect on the color of glaze and bulk tiles. In this paper, cobalt blue pigments have been prepared using the coprecipitation method and then subjected to supercritical fluid drying. The differences in their physicochemical and optical properties are characterized using a series of analysis including X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive spectrometer (EDS), and CIE-L*a*b*colorimetry analysis. The results indicate that the CoAl2O4 pigments subjected to supercritical fluid drying exhibit a fine-scale structure, a crystallite size of approximately 52 nm at 1400°C, and an excellent stability at high temperatures. They also present a vivid blue color, with improved brightness and hue than those of other cobalt blue pigments. Furthermore, this study elucidates the promising potential of supercritical fluid drying for fabricating nano-sized CoAl2O4 pigments with excellent optical and physicochemical properties.