Preparation of mono-dispersed aragonite microspheres via a carbonation crystallization pathway

Monodispersed calcium carbonate microspheres were prepared by carbonating a calcium acetate aqueous solution with CO gas at a high pressure of 40 bar and a high temperature of 80 degrees C after 60 minutes of reaction. The products were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM), respectively. The XRD pattern showed that the crystal polymorph of the as-prepared monodispersed microspheres was aragonite. The SEM images also displayed needle-like aragonite self-organized into microsphere superstructure with diameters ranging from 5 to 15 mu m. Analysis of the formation mechanism of the calcium carbonate microsphere superstructure revealed that the rod-dumbbell-sphere morphogenesis mechanism along with the phase transformation of vaterite to aragonite was responsible for the growth of the monodispersed aragonite microspheres. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim