Ellipsoid ultramarine blue pigment with high near-infrared reflectance

Abstract In this work, an ultramarine blue pigment with high near-infrared (NIR) reflectance is achieved by adjusting the content of Na2CO3 during the preparation process. The acquired pure ultramarine blue (PU) pigment has a relatively uniform ellipsoid morphology with a narrow size distribution ranging from 1 to 3 μm. More importantly, the PU pigment shows a NIR reflectance of 80.67 %, which is higher as compared to those previously reported (∼72 %). The thermal stability of the sample is also evaluated by thermogravimetric-differential scanning calorimeter (TG-DSC), and the result shows that the PU pigment is relatively stable when the temperature does not exceed 800℃. In addition, the effectiveness of its ability to cooling the substrate is investigated by applying the PU pigment onto an Al plate. Interestingly, the inner surface temperature of the Al plate coated with the PU pigment reveals 0.8∼2℃ lower than its counterpart coated with the commercial pigment. Thus, this result shows the potential of using the PU pigment as a high NIR reflective material for thermal management.