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HRTEM study of freeze-dried and untreated synthetic ferrihydrites: consequences of sample processing

Published online by Cambridge University Press:  09 July 2018

C. Greffié*
Affiliation:
BRGM, Ressources Minérales, B.P. 6009, 45060 Orléans Cedex 02
M. Amouric
Affiliation:
CRMCC, Campus de Luminy, 13288, Marseille
C. Parron
Affiliation:
CEREGE, UMR CNRS 6635, B.P. 80, 13545 Aix en Provence Cedex 04, France
*

Abstract

Two-line ferrihydrite samples were synthesized following conventional procedure. Detailed characterizations of freeze-dried and untreated samples – prepared from direct inclusion of the fresh precipitates in hydrophilic resin – were made by high resolution transmission electron microscopy to investigate in detail their structural organization and to compare the two types of preparations.

Only highly disordered chain-like aggregates of 2 5 nm diameter size nano-particles were revealed within the untreated samples. Conversely, in freeze-dried samples, domains with different degrees of order were recognized, from poorly ordered 2-line ferrihydrite to 3-line ferrihydrite particle aggregates that revealed lattice fringes. Associated with these aggregates, a goethite phase with a modified crystal morphology was also observed.

These HRTEM observations revealed that freeze-drying techniques induce artifacts by disturbing ferrihydrite aggregates while direct inclusion in hydrophilic resin preserves the primary organization of such poorly ordered phases.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2001

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