The morphology of calcite crystals grown in a porous medium doped with divalent cations
Calcite crystals were grown in the presence of small concentrations (50, 200, and 600 ppm) of divalent cations (Ba2+, Sr2+, Co2+ and Mn2+) in a silica hydrogel medium. The calcite crystals grown in the presence of cations larger than Ca2+ (Ba2+ or Sr2+) developed rhombohedral habits defined by {101¯...
| Autores: | , , |
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| Formato: | artículo |
| Fecha de publicación: | 2006 |
| País: | España |
| Recursos: | Universidad Complutense de Madrid (UCM) |
| Repositorio: | Docta Complutense |
| Idioma: | inglés |
| OAI Identifier: | oai:docta.ucm.es:20.500.14352/49801 |
| Acesso em linha: | https://hdl.handle.net/20.500.14352/49801 |
| Access Level: | acceso abierto |
| Palavra-chave: | 548.5 Calcite Crystal morphology Gel crystal growth method Impurities Cristalografía (Geología) |
| Resumo: | Calcite crystals were grown in the presence of small concentrations (50, 200, and 600 ppm) of divalent cations (Ba2+, Sr2+, Co2+ and Mn2+) in a silica hydrogel medium. The calcite crystals grown in the presence of cations larger than Ca2+ (Ba2+ or Sr2+) developed rhombohedral habits defined by {101¯4} form, similar to the morphology of calcite grown in a pure gel. SEM images show that growth on {101¯4} occurs by lateral advancement of layers founded by macroscopic dendritic or jagged steps. In the case of calcite crystals grown in a gel doped with cations smaller than Ca2+ (Co2+ or Mn2+), a variety of morphologies was obtained, ranging from blocky crystals (at lower concentrations: 50 and 200 ppm) to peanut-like aggregates, spheres and spherulites (at 600 ppm). The macroscopic morphological characteristics of such doped calcite crystals reflect closely the growth behaviour of calcite {101¯4} surface at a nanoscale, reported by previous AFM studies. Morphological features have been interpreted on the basis of the modification of growing steps characteristics as a consequence of asymmetrical cation incorporation. The use of such morphologies as a criterion of biological activity is, therefore, unreliable. |
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