Preparation of monodisperse and spherical powders by heating of alcohol-aqueous salt solutions

A method for the preparation of monodisperse and spherical powders from salt solution with a mixed solvent of alcohol and water is demonstrated. The volume ratio of alcohol to water (R/H ratio) in the alcohol-aqueous salt solutions greatly influenced the behavior of the precipitation and the morphology of the resulting particles. The precipitation, by heating an alcohol-aqueous salt solution, occurs by the decrease of dielectric constant of the solvent and thus a decrease in the salt solubility. The morphology and size variation of the resulting particles was explained by considering the parameters determining the colloidal stability in the DLVO theory; the zeta potential and the dielectric constant. During the preparation of the powders by heating of the alcohol-aqueous salt solution, the effect of heating methods on the characteristics of the resulting particles is also demonstrated. A microwave heating, as a uniform and rapid heating method, induced the uniform and rapid precipitation to produce monodisperse and spherical particles.