Preparation of BaSO4 nanoparticles with self-dispersing properties

BaSO4 nanoparticles with an average particle size of 24.3 nm were prepared by the precipitation method using (NH4)(2)SO4 and BaCl2 as raw materials, and a water-alcohol solution as the reaction medium. The samples were characterized by photon correlation spectroscopy, transmission electron microscopy, X-ray diffraction, thermogravimetric analysis and infrared analysis. The results indicate that the BaSO4 powder sample has few mesopores and can self-diffuse in water, thus forming a suspension with enhanced stability and longevity. The preparation conditions that influenced the properties of the product were investigated and the mechanism of synthesis was also discussed. Adding ethanol during the preparation process can control the growth of the particles, and washing the precipitates in ethanol can prevent the particles from aggregating during the drying process. The powders are completely dried and treated at 200degreesC to get rid of any remaining water in order to avoid subsequent aggregation of the particles. The samples can then be preserved for a long period. Ethanol combined with BaSO4 forms a film through hydrogen bonding. The hydrogen bonds and mesopores trigger self-dispersal of the BaSO4 powder in water. (C) 2004 Elsevier B.V. All rights reserved.