From Nanometer Aggregates to Micrometer Crystals: Insight into the Coarsening Mechanism of Calcite

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• 作者：L. N. Schultz ; K. Dideriksen ; L. Lakshtanov ; S. S. Hakim ; D. Müter ; F. Hau?er ; K. Bechgaard ; S. L. S. Stipp
• 刊名：Crystal Growth & Design
• 出版年：2014
• 出版时间：February 5, 2014
• 年：2014
• 卷：14
• 期：2
• 页码：552-558
• 全文大小：481K
• ISSN：1528-7505

文摘

Grain size increases when crystals respond to dynamic equilibrium in a saturated solution. The pathway to coarsening is generally thought to be driven by Ostwald ripening, that is, simultaneous dissolution and reprecipitation, but models to describe Ostwald ripening neglect solid鈥搒olid interactions and crystal shapes. Grain coarsening of calcite, CaCO₃, is relevant for biomineralization and commercial products and is an important process in diagenesis of sediments to rock during geological time. We investigated coarsening of pure, synthetic calcite powder of sub-micrometer diameter crystals and aged it in saturated solutions at 23, 100, and 200 掳C for up to 261 days. Scanning electron microscopy (SEM) and Brunauer鈥揈mmett鈥揟eller (BET) surface area analysis showed rapid coarsening at 100 and 200 掳C. Evidence of particle growth at 23 掳C was not visible by SEM, but high resolution X-ray diffraction (XRD) data demonstrated steady growth of nanometer crystallites. The results can be described by theory where grains coarsen preferentially by aggregation at early times and high temperatures and by Ostwald ripening at later stages. Crystal form and dimension are influenced by the transition from one growth mechanism to the other. This has been poorly described by mean field coarsening models and offers predictive power to grain coarsening models.