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Structural modifications of smectites mechanically deformed under controlled conditions

Christidis Georgios, Francesco Dellisanti , G. Valdre, Pagona Makri

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Year 2005
Type of Item Peer-Reviewed Journal Publication
Bibliographic Citation G.E. Christidis ,F. Dellisanti, G. Valdre , P. Makri , "Structural modifications of smectites mechanically deformed under controlled conditions ",Cl. Min., vol. 40,no.4,pp.511-522 ,2005.doi :10.1180/0009855054040188
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SWy-1 and SAz-1 smectites and an Italian bentonite from Sardinia weremechanically deformed via high-energy ball milling for 20 h, in a controlled thermodynamicenvironment at constant temperature (25ëC) under vacuum. The deformed smectites have a lowercation exchange capacity (CEC) and form thicker particles than the original ones, due toagglomeration of smectite crystallites. The 001 diffraction maximum shifted to lower d spacings, theintensity of the 060 reflection decreased and the background at 20ÿ30ë2y increased, suggestingpartial amorphization of the smectite. Moreover, the layer charge of the smectites decreased. Theintensity of the complex stretching band at 3625 cmÿ1, and the AlAlOH, and AlFe3+OH bendingbands at 916 cmÿ1 and 886 cmÿ1, respectively, decreased, while the band at AlMgOH bending at849 cmÿ1, disappeared. Deformation mainly disrupted the octahedral sheet and preferentiallydestroyed those sites occupied by Mg cations, thus explaining the observed decrease in layer charge.Octahedral sites occupied by Fe were least affected. The disruption of the octahedral sheet issubstantiated further by the almost total disappearance of the dehydroxylation peak, which is morepronounced in the Mg-rich SAz-1 smectite.

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