Divisive effect of alcohol-water mixed solvents on growth morphology of calcium carbonate crystals

Controlling the process of crystal growth is of importance to the biomineralization and materials science. In this work, some novel morphology of calcium carbonate (CaCO3) was precipitated in an ethanol-water binary solvent (EWBS) with a CaCl2/Na2CO3 reaction system. For the solutions of CaCl2/Na2CO3 in EWBS, the alcoholization and hydration of Ca2+ and CO32- were discussed from the radial distribution functions by molecular dynamics simulations, and the number density profiles of water molecules around and similar to 15 angstrom away from CO32- were employed to reveal the distribution of water molecules. It is found that EWBS has a divisive effect on Ca2+ and CO32-, and the local inhomogeneity of EWBS would be enhanced by adding some Na2CO3 into it. This inhomogeneity results in an aqueous two-phase system as x(E) goes up to 0.7. In addition, the novel morphology of CaCO3 under different molar ratios of Ca2+/CO32- and in different mixed solvents were confirmed by XRD and SEM, and the relationships between the morphology of CaCO3 and the structural properties of mixed solvents were further explored.