Optimization of the synthesis of a nano-sized mica-hematite pearlescent pigment

Abstract

The present paper attempts as how the pigments comprising of nano-sized hematite particles deposited on mica surfaces in optimum conditions offer an excellent pearlescent properties. It has applied homogeneous hydrolysis method in order to produce red mica-hematite pearlescent pigments. To record the influencing parameters on the synthesis process, response surface methodology (RSM) technique was used where temperature of reaction, synthesis time and concentration of urea were selected as variable parameters. Some 17 experiments with various conditions were designed following RSM technique. Taking into account colorimetric parameters, the whole process was then analyzed by “Design Expert” software that finally gave following optimum factors: reaction temperature = 82.02 °C, synthesis time = 11.98 h and urea concentration = 37.5 g l −1. The results clearly reveal that excessive increase of temperature and urea concentration influence pearlescent effect negatively whereas, increased synthesis time improves the pearlescent effect. Once the above optimum parameters selected, seemingly, the spherical hematite particles of about 60 nm in diameter are deposited uniformly on mica surfaces.