Vaterite Stability in the Presence of Chromate
| Autor: | Lurdes Fernández-Díaz, Alexander M. Gigler, J. A. Cruz, Nuria Sánchez-Pastor |
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| Rok vydání: | 2011 |
| Předmět: |
Calcite
Chromate conversion coating Precipitation (chemistry) Scanning electron microscope Silica gel Inorganic chemistry Atomic and Molecular Physics and Optics Analytical Chemistry chemistry.chemical_compound symbols.namesake chemistry Chemical engineering Vaterite symbols Raman spectroscopy Mineralogía Dissolution Spectroscopy |
| Zdroj: | E-Prints Complutense. Archivo Institucional de la UCM instname |
| ISSN: | 1532-2289 0038-7010 |
| Popis: | Vaterite aggregates grown in Cr(VI)-bearing silica gel were studied by combining scanning electron microscopy and Raman spectroscopy. All the vaterite samples were spherical aggregates consisting of lens-shaped individuals, and their morphology was distinctive for vaterite. Raman spectra corresponding to the aggregates grown in gels containing high Cr(VI) concentrations showed the typical bands of vaterite. However, in contrast to their morphology, the Raman spectra of the aggregates grown in the presence of lower Cr(VI) concentrations exclusively showed bands characteristic of calcite. These aggregates are interpreted as calcite pseudomorphs formed after vaterite through a replacement process. The replacement involves the interface coupling of the dissolution of vaterite and the precipitation of the stable polymorph calcite. The fact that only those vaterite aggregates formed in the presence of low Cr(VI) concentrations transformed into calcite indicates the presence of high Cr(VI) concentrations in the growth medium contributes to stabilize vaterite and prevents its transformation into calcite in the short term. |
| Databáze: | OpenAIRE |
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