Abstract
The precipitation of barium and strontium carbonate in alkaline silica gels or silica solutions produces nanocrystalline self-assembled composite materials displaying biomimetic shapes and textures. We have crystallized concomitantly in time and space two anhydrous polymorphs of calcium carbonate, under similar conditions at different temperatures. The orthorhombic phase aragonite produces nanocrystalline aggregates exhibiting non-crystallographic morphologies and complex textures characteristic of silica biomorphs. Conversely, the simultaneously forming trigonal phase, calcite, yields rhombohedral crystals that experience fibrous growth and that maintain memory of the point symmetry group of the crystalline structure. Experiments performed at different temperatures (room temperature, 45, 60 and 80 °C) revealed that the higher the temperature the higher the aragonite/calcite precipitation ratio, but the crystallization of calcite was never fully inhibited. We have studied the growth mechanism, the growth texture and the morphogenesis for both cases. We have found that the dramatic difference between the crystallization behaviours of the two mineral phases is due to the difference in the growth mechanism at the nanoscale.
Highlights
The ability of inorganic matter to mimic the morphology and texture of mineral or organic structures of living organisms is of both academic and technological interest
We have found that the dramatic difference between the crystallization behaviours of the two mineral phases is due to the difference in the growth mechanism at the nanoscale
By studying at different length scales the texture of both types of structures we reveal the growth mechanism and the morphogenesis of these structures
Summary
The ability of inorganic matter to mimic the morphology and texture of mineral or organic structures of living organisms is of both academic and technological interest. Silica biomorphs are purely inorganic nanocrystalline selforganized composite materials, displaying non-crystallographic morphologies and complex hierarchical textures that are strongly. In this study we report the simultaneous precipitation of aragonite and calcite crystals in silica gel under ambient conditions at different temperatures. Aragonite displays fascinating complex biomorphic morphologies including diabolo-like, flower-like and helicoids, while calcite exhibits single-crystal rhombohedra and skeletal morphologies that withhold the symmetry of the crystallographic structure. Experiments performed at different temperatures reveal that the higher the temperature the higher the aragonite/calcite precipitation ratio, complete inhibition of calcite has not been observed
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