Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.9/2103
Título: Natural nanomaterials : reappraising the elusive structure of the nano-sized mineral ferrihydrite through X-Ray absorption spectroscopy at the iron K-edge
Autor: Figueiredo, M. Ondina
Silva, Teresa Pereira
Veiga, João Pedro
Palavras-chave: Nanominerais
Ferrohidrite
XANES
K-edge
Data: 2013
Citação: Figueiredo, M. O.; Silva, T. P.; Veiga, J. P. - Natural nanomaterials : reappraising the elusive structure of the nano-sized mineral ferrihydrite through X-Ray absorption spectroscopy at the iron K-edge. In: Materials Science Forum, vols. 730-732, (2013), p. 931-935
Resumo: Ferrihydrite is natural ferric oxyhydroxide occurring exclusively nanocrystalline. With ideal formula 5 Fe2 O3 . 9 H2 O, ferrihydrite is quite abundant in sediments, weathering crusts and mine wastes, being characteristic of red pre-soils formed by loose weathered rock plus mineral debris (regoliths) and commonly designated as “2-line” or “6-line” on the basis of the broadened maxima observed in the X-ray diffraction pattern. Synthetic nanocrystalline “6-line” ferrihydrite was recently studied through methods based on atomic-pair distribution functions disclosing the possible occurrence of icosahedral clusters formed by twelve octahedra centred by an inner tetrahedron, all filled by Fe 3+ ions. However, Mössbauer studies were inconclusive about the existence of 4-coordinated iron, thus suggesting that the tetrahedral cation may well be Si4+. In view of such structural uncertainty, a XANES study at the Fe K-edge was undertaken on ferrihydrite from a regolith to ascertain the occurrence of tetrahedral iron. Comparison with data collected from well crystallized iron oxide and hydroxide minerals where Fe 3+/2+ ions occur in octahedral and tetrahedral coordination is described and the results so far obtained are discussed, showing that supplementary study is needed on the elusive structure of ferrihydrite.
URI: http://hdl.handle.net/10400.9/2103
Versão do Editor: http://dx.doi.org/10.4028/www.scientific.net/MSF.730-732.931
Aparece nas colecções:RM - Artigos em revistas internacionais

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