Monodisperse Calcium Carbonate Microtablets Forming at 70°C in Prerefrigerated CaCl2–Gelatin–Urea Solutions

Calcium carbonate particles with a unique tablet shape were produced by simply aging the prerefrigerated (at 41C for 24 h) CaCl2–gelatin–urea solutions at 701C for 24 h in ordinary glass media bottles. Gelatin is known to be the denatured collagen. The thermal decomposition of dissolved urea was exploited to provide the Ca ion and gelatin-containing solutions with aqueous carbonate ions. Monodisperse CaCO3 microtablets formed in solution had a mean particle size of 472.5mm. CaCO3 microtablets were biphasic in nature and comprised of about 93% vaterite and 7% calcite. Identical solutions used without prerefrigeration yielded only trigonal prismatic calcite crystals upon aging at 701C for 24 h. Prerefrigeration of CaCl2– gelatin–urea solutions was thus shown to have a remarkable effect on the particle morphology. Samples were characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, and powder X-ray diffraction.