2012/08/01 by Q. Hu, Qiaona Hu, J. Zhang +5 · 7 citations
Chemistry · Earth and Planetary Sciences · Engineering · Materials Science · #Bone Tissue Engineering Materials #Calcium Carbonate Crystallization and Inhibition #Calcium carbonate #Chemical engineering #Chemistry #Composite material #Crystallite #Crystallography #Lamellar structure #Materials science #Nanotechnology #Paleontology and Stratigraphy of Fossils #Transmission electron microscopy #Vaterite
paper · doi:10.2138/am.2012.3983
openalex publication_date 2012/08/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Metastable vaterite crystals were synthesized by increasing the pH and consequently the saturation states of Ca 2+ - and CO 2- 3 -containing solutions using an ammonia diffusion method. SEM and TEM analyses indicate that vaterite grains produced by this method are polycrystalline aggregates with a final morphology that has a sixfold-symmetry. The primary structure develops within an hour and is almost a spherical assemblage of nanoparticles (5-10 nm) with random orientation, followed by the formation of hexagonal platelets (1-2 μm), which are first composed of nanoparticles and that develop further into single crystals. As determined using transmission electron microscopy, these hexagonal crystallites are terminated by (001) surfaces and are bounded by 110 edges. The hexagonal crystals subsequently stack to form the “petals” (20 μm wide, 1 μm thick) of the final “flower-like” vaterite morphology. The large flakes gradually tilt toward the center as growth progresses so that their positions become more and more vertical, which eventually leads to a depression in the center. Since this sequence encompasses several morphologies observed in previous studies (spheres, hexagons, flowers etc.), they may actually represent different stages of growth rather than equilibrium morphologies for specific growth conditions.