Atomic Defects and Their Relationship to Aragonite鈥揅alcite Transformation in Portlandite Nanocrystal Carbonation

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• 作者：L. S. Gomez-Villalba ; P. L贸pez-Arce ; M. Alvarez de Buergo ; R. Fort
• 刊名：Crystal Growth & Design
• 出版年：2012
• 出版时间：October 3, 2012
• 年：2012
• 卷：12
• 期：10
• 页码：4844-4852
• 全文大小：651K
• 年卷期：v.12,no.10(October 3, 2012)
• ISSN：1528-7505

文摘

The defects in calcium carbonate polymorphs forming when portlandite nanocrystals are exposed to high relative humidity were directly observed and analyzed under high-resolution transmission electron microscopy. The findings provided significant insight into aragonite to calcite phase transformation mechanisms. The aragonite lattice exhibited stacking faults, the insertion of extra atomic planes into its normal sequence, and vacancies. These defects were shown to generate minor lattice translation of around 1/3d_111aragonite or nanovoids 2d_111aragonite or 3/2d_020aragonite in size. The presence of both extra atoms and nanovoids suggests the involvement of crystallization/dissolution processes. Calcite phase nucleation transformation mechanisms were observed as a result of the rearrangement of CO₃^{2鈥?/sup> anions in areas characterized by the disorder resulting from aragonite lattice dislocations. A series of dislocations, stacking faults, and modulated microstructures were identified in the neoformed calcite nanocrystals, more intensely after shorter than after longer exposure times.}