Person:
Pérez Garrido, Carlos

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First Name
Carlos
Last Name
Pérez Garrido
URI
https://hdl.handle.net/20.500.14352/75245
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Mineralogía y Petrología
Area
Cristalografía y Mineralogía
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2007 - 20092
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Subject: 548.5 ×

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    In situ AFM study of the interaction between calcite {101¯ 4} surfaces and super saturated Mn2+–CO3 2- aqueous solutions
    (Journal of Crystal Growth, 2009) Pérez Garrido, Carlos; Astilleros García-Monge, José Manuel; Fernández Díaz, María Lourdes; Prieto Rubio, Manuel
    Growth of rhodochrosite(MnCO3) on calcite(101¯ 4) substrates from supersaturated aqueous solutions was observed in situ using anatomic force microscope (AFM). The supersaturation with respectto rhodochrosite (expressed as βrhod=a[Mn2+]a[CO3 2-]/Ksp, rhod.; where a[Mn2+] and a[CO3 2-] are the activities of Mn2+ and CO3 2- in the aqueous solution)ranged from 48.89 to 338.04. After an induction period, nuclei of the new phase are forme don the calcite substrate. These nuclei readily reach a significan the ight (2.270.2 nm), which remained approximately constant during their lateral spread. The characteristics of the growth pattern of islands of the newly for med phase i ndicate that the reexists an epitaxial relation ship bet ween the new phase and the calcite substrate. The islands showa highly anisotropic growth, preferentiallys preading along [421¯ ] on the calcite substrate at a rate up to 15 times faster than along [010]. As a result, the islands develop needle and sword blade-like morphologies, elongated along [421¯ ] and showing different truncated ends. This unusual elongation is interpreted as the result from a kinetic effect, which is controlled by both the structural characteristic of the calcite (101¯ 4) surface and the structure and elastic properties of the over growing phase. The lateral growth of islands leads to their coalescence and the formation of aquite homogeneous nanometric layer. The characteristics of the epitaxial growth are in a reement with a Volmer–Weber growth mechanism controlling the formation of the epitaxy. The results obtained in the se experiment sare compared with those obtained in several similar systems.
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    In situ AFM observations of the interaction between calcite (1014) surfaces and Cd-bearing aqueous solutions
    (Surface science, 2007) Pérez Garrido, Carlos; Fernández Díaz, María Lourdes; Pina Martínez, Carlos Manuel; Prieto Rubio, Manuel
    In situ atomic force microscopy (AFM) observations of the interaction between calcite ð1014Þ surfaces and Cd-bearing aqueous solutions have been carried out, by maintaining the solutions static in the AFM fluid cell. The interaction involves the dissolution of the original surface and the simultaneous epitaxial growth of multilayer three-dimensional islands 2.75 nm in height of Cd-rich members of the CdxCa1xCO3 solid solution. Dissolution occurs by the retreating of steps and the formation and growth of etch pits. Both the etch pits and the multilayer islands are elongated along the [421] direction. Such an unusual elongation direction is interpreted as a kinetic effect controlled by both the structural characteristics of the calcite (1014) surface and the structure and elastic properties of the overgrowth. Using aqueous solutions highly concentrated in cadmium, the formation of ~ 2.75 nm thick islands occurs after the initial growth of a solid solution monolayer ~ 0.3 nm thick, which finally dissolves as the islands grow. This effect seems to be a result of the coherent strain energy accumulated in the substrate–monolayer interface. Significantly, the dissolution rate of the calcite surface decreases when the concentration of Cd2+ in the aqueous solution increases, suggesting that, together with co-precipitation, Cd adsorption plays an important role in the interaction process. During co-precipitation, the progressive coalescence of the Cd-rich islands results in formation of a nanometric epitaxial layer on the calcite (1014)surface. This layer armours the substrate from further dissolution and determines the end of the process at a ‘‘partial’’ pseudo-equilibrium endpoint.