Growth of vaterite with novel morphologies directed by a collodion membrane

Calcium carbonate (CaCO3) crystals were synthesized by a simple CO2-diffusion method. A collodion membrane was employed to direct growth of CaCO3 crystals. Polymorphs transformation was obtained at different temperatures, in which the vaterite transferred to the calcite, and the calcite transferred to the aragonite with increase of the experimental temperature. Dissolution-recrystallization processes can be used to explain these changes. At 28 °C, hexagonal slices of vaterite were firstly produced, for which the membrane was thought to be the main reason. In order to decrease surface energy, these slices assembled into various superstructures, in which hexagonal cake-like particles were the most stable among these superstructures. The cake-like vaterite transferred to the calcite through dissolution-recrystallization processes with increase of the aging time. The interested phenomenon is that the inside of the cake-like vaterite was dissolved firstly, in which the cake-like vaterite with inner hollow was determined. The membrane may induce this change.