Spray synthesis of monodisperse sub-micron spherical silica particles

A novel spray approach has been developed for the synthesis of controlled size oxide microparticles and the technique is illustrated by the preparation of ca. 250 nm silica particles. Stöber-type spherical silica of uniform particle size is formed by spraying a tetraethoxysilane precursor solution onto the surface of a stirred ammoniacal hydrolysis medium. Particle size characteristics are determined through selection of reaction conditions, with solvent, temperature, reagent concentrations and mixing contributing to the particle size and dispersity. The silica products have been characterized by particle size distribution measurements, electron microscopy and nitrogen adsorption studies. The mechanism of particle formation under differing experimental conditions is discussed.