Formation and Growth Mechanism of Calcium Carbonate Nanoparticles via a Bubbling Method

The mechanism of formation and growth of calcium carbonate (CaCO₃) nanoparticles by bubbling carbon dioxide in aqueous suspensions of calcium hydroxide was investigated using time-resolved in situ synchrotron small-angle X-ray scattering (SAXS) and transmission electron microscopey (TEM). In situ SAXS showed a significant change in the particles size in the primary reaction. This suggests that the nucleus forms CaCO₃ at in this period. After the nucleation, the crystal grow with the reaction time to yield 40 nm CaCO₃ nanoparticles. TEM showed fibrous or chain-like intermediates formed by aggregation of fine particles of CaCO₃ as calcite. We propose that CaCO₃ crystal nuclei generated in the primary reaction grow to yield fibrous or chain-like CaCO₃ which then separates into individual particles to form CaCO₃ nanoparticles.