Morphology and size control of barium carbonate in ethanol–water mixed solvents

Abstract

Barium carbonate (BaCO3) particles have been obtained by the precipitation reaction of CO2 bubbles to barium hydroxide [Ba(OH)2] in the ethanol–water mixed solvents. Various morphologies, from rounded peanut, leaf-like, rod, and needle particles, were controlled by the precipitation step, where CO2 gas was fed to Ba(OH)2 in ethanol–water mixed solvent. The CO2 gas as a carbonate source and Ba(OH)2 slurry as a barium ion source are dissolved in the mixed solvents, within the solubility limit, to precipitate. The reactants dissolve progressively while they precipitate to BaCO3. Ba(OH) 2 slurry becomes translucent and opaque while the reaction proceeds. It becomes more opaque, upon which the dissolution of Ba(OH)2 proceeds and BaCO3 precipitates. The opaqueness of the products depends on the particle size of BaCO3 in the product. The characteristics of BaCO3 were confirmed by the X-ray diffraction (XRD), transmission electron microscope (TEM), and electrophoretic light scattering methods. The amount of water in the mixed solvents and of Ba(OH) 2 in the reaction batch is related to the reaction rate in the nucleation and growing step, so that it was possible to control the shape of particles. Based on the understanding of the size and morphology of BaCO3 in the solid/liquid–gas system, it was possible to obtain a well-dispersed average 40-nm BaCO3 colloid.