Control of calcium carbonate particle size and shape by precipitation from CTAB/alcohol/hexadecane mixtures

 When used as a precipitation media, emulsified mixtures of cetyltrimethylammonium bromide/n-butanol (E), hexadecane (O) and water (W), controls the size and shape of calcium carbonate particles. Monodisperse 2-micron spherical-calcite particles were obtained in a water-rich region of the mixture, while 2-micron rhombohedral-calcite particles with an aspect ratio near one were obtained in the middle region of the mixture. Replacing n-butanol with i-butanol led to consistent formation of monodisperse spherical particles, while using n-propanol in place of n-butanol limited the number of spherical particles produced in the water-rich region. Received: 17 March 1997 Accepted: 2 May 1997