Diffusion-driven growth of calcium carbonate polymorphs in microchannels.

We propose a novel approach to characterize the growth of individual crystals. Calcium chloride and sodium carbonate solutions have been injected into a Y-shaped microfluidic channel at various stoichiometric ratios, and the development of calcium carbonate has been monitored. The formation of calcite and vaterite depends not only on the stoichiometric ratio of the reactants but also on the region of the reactor where they form. From the crystal images, we have mapped the surface growth of the particles and have shown that closer to the confluence of the microchannel the crystal growth is significant. Both morphologies mainly form in the carbonate-rich zone, supported by numerical modeling. Moreover, the side growth of the calcite particles is diffusion-controlled and independent of the crystal orientation and the stoichiometric ratio of the reactants injected.