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Isotropic/nematic and sol/gel transitions in aqueous suspensions of size selected nontronite NAu1

Published online by Cambridge University Press:  09 July 2018

L. J. Michot ,
E. Paineau ,
I. Bihannic ,
S. Maddi ,
J. F. L. Duval ,
C. Baravian ,
P. Davidson  and
P. Levitz
L. J. Michot*
Affiliation:
Laboratoire Interdisciplinaire des Environnements Continentaux, CNRS-Université de Lorraine UMR 7360, BP40, 54500 Vandoeuvre, France Physicochimie des Electrolytes, Colloïdes et Sciences Analytiques, CNRS-UPMC – ESPCI UMR 7195 - 4 place Jussieu, case courrier 51, 75005 Paris, France
E. Paineau
Affiliation:
Laboratoire Interdisciplinaire des Environnements Continentaux, CNRS-Université de Lorraine UMR 7360, BP40, 54500 Vandoeuvre, France Laboratoire de Physique des Solides, CNRS-Université Paris-Sud UMR 8502, Bât 510, 91405 Orsay Cedex, France
I. Bihannic
Affiliation:
Laboratoire Interdisciplinaire des Environnements Continentaux, CNRS-Université de Lorraine UMR 7360, BP40, 54500 Vandoeuvre, France
S. Maddi
Affiliation:
Laboratoire Interdisciplinaire des Environnements Continentaux, CNRS-Université de Lorraine UMR 7360, BP40, 54500 Vandoeuvre, France
J. F. L. Duval
Affiliation:
Laboratoire Interdisciplinaire des Environnements Continentaux, CNRS-Université de Lorraine UMR 7360, BP40, 54500 Vandoeuvre, France
C. Baravian
Affiliation:
Laboratoire d'Energétique et de Mécanique Théorique et Appliquée, CNRS-Université de Lorraine UMR 7563, 2, Avenue de la Forêt de Haye, BP160, 54504 Vandoeuvre Cedex, France
P. Davidson
Affiliation:
Laboratoire de Physique des Solides, CNRS-Université Paris-Sud UMR 8502, Bât 510, 91405 Orsay Cedex, France
P. Levitz
Affiliation:
Physicochimie des Electrolytes, Colloïdes et Sciences Analytiques, CNRS-UPMC – ESPCI UMR 7195 - 4 place Jussieu, case courrier 51, 75005 Paris, France
*
*E-mail: [email protected]
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Abstract

The phase behaviour of aqueous suspensions of NAu1 nontronite was studied on size-selected particles by combining osmotic pressure measurements, visual observations under polarized light, rheological experiments and Small Angle X-ray Scattering (SAXS). NAu1 suspensions display a liquid crystalline behaviour as they exhibit a Isotropic/Nematic (I/N) transition that occurs before the sol/gel transition for ionic strengths below 10–3 M/L. This I/N transition shifts towards lower volume fractions for increasing particle anisotropy and its position in the phase diagram agrees well with the theoretical predictions for platelets. SAXS measurements reveal the presence of characteristic interparticular distances in the isotropic, nematic and gel phases. In the gel phase a local lamellar order is observed which shows that the “house of cards” model is not appropriate for describing the gel structure in swelling clay materials at low ionic strength. Furthermore, by combining results from osmotic pressure measurements and X-ray scattering, it appears that the pressure of the system can be well described using a simple Poisson-Boltzmann treatment based on the repulsion between charged infinite parallel planes. In terms of rheological properties, even if the thermodynamical status of the sol/gel transition remains partially unclear, the yield stress and elasticity of the gels can be easily renormalized for all particle sizes on the basis of the volume of the particles. Furthermore, rheological modelling of the flow curves shows that for all the particles an approach based on excluded volume effects captures most features of nontronite suspensions.

Keywords

isotropic/nematic transitionsol/gel transitionrheologyelectrostaticsaqueous transitionsnontronite
Type
Research Article
Information
Clay Minerals , Volume 48 , Issue 5 , December 2013 , pp. 663 - 685
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2013

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Footnotes

§

Deceased

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