Controllable preparation of novel Fe2O3/flake α-Al2O3 pearlescent pigments with high coating ratio

Novel Fe2O3/flake α-Al2O3 pearlescent pigments with a high coating ratio and regular hexagonal shape were successfully prepared by liquid phase deposition for the first time. Through the design of an orthogonal test, the effects of pH, FeCl3 dose, sintering temperature, and holding time on the coating ratio of Fe2O3 were systematically studied. Additionally, the phase structures, surface topographies, and elements distribution were evaluated using X-ray diffractometry (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The range analysis demonstrated that the coating ratio of the Fe2O3/α-Al2O3 pearlescent pigment was affected in the following order of influence strength: pH > FeCl3 dose > holding time > sintering temperature. With the increase of pH, the coating ratio increased. When the FeCl3 dose was moderate, samples with better coating ratio and dispersion could be obtained. Moreover, the coating ratio reached 28% under a pH of 4, an FeCl3 dose of 4.5 mL, a holding time of 10 min, and a sintering temperature of 950 °C. Finally, the possible coating mechanism was discussed. The results of the present research provide an effective way to optimize the coating ratio and process.