Microwave-assisted synthesis of spheroidal vaterite CaCO 3 in ethylene glycol–water mixed solvents without surfactants

Abstract

Spheroidal vaterite CaCO 3 composed of irregular nanoparticals have been synthesized by a fast microwave-assisted method. The structures are fabricated by the reaction of Ca(CH 3COO) 2 with (NH 4) 2CO 3 at 90 °C in ethylene glycol–water mixed solvents without any surfactants. The diameters of the spheroidal vaterite CaCO 3 range from 1 to 2 μm, and the average size of the nanoparticals is about 70 nm. Bundle-shaped aragonite and rhombohedral calcite are also obtained by adjusting the experimental parameters. Our experiments show that the ratio of ethylene glycol to water, microwave power, reaction time, and two sources of ammonium ions and acetate anions are key parameters for the fabrication of spheroidal vaterite CaCO 3. A possible growth mechanism for the spheroidal structures has been proposed, which suggests that the spheroidal vaterite CaCO 3 is formed by an aggregation mechanism.