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Osmotic compression and expansion ofhighly ordered clay dispersions

Martin, Céline and Pignon, Frédéric and Magnin, Albert and Meireles, Martine and Lelièvre, Vincent and Lindner, Peter and Cabane, Bernard Osmotic compression and expansion ofhighly ordered clay dispersions. (2006) Langmuir, 2 (9). 4065-1075. ISSN 0743-7463

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Official URL: http://dx.doi.org/10.1021/la052605k


Aqueous dispersions of nanometric clay platelets (Laponite) have been dewatered through different techniques: centrifugation, mechanical compression, and osmotic stress (dialysis against a polymer solution). The positional and orientational correlations of the particles have been determined through small-angle neutron scattering. Uniaxial compression experiments produce concentrated dispersions (volume fraction > 0.03) in which the platelets have strong orientational and positional correlations. The orientational correlations cause the platelets to align with their normal along a common axis, which is the axis of compression. The positional correlations cause the platelets to be regularly spaced along this direction, with a spacing that matches the average volume per particle in the dispersion. The swelling law (volume fraction versus separation distance) is one-dimensional, as in a layered system. Changes in the applied osmotic pressure cause the water content of the dispersion to either rise or decrease, with time scales that are controlled by interparticle friction forces and by hydrodynamic drag. At long times, the dispersions approach osmotic equilibrium, which can be defined as the common limit of swelling and deswelling processes. The variation of the equilibrium water content with the applied osmotic pressure has been determined over 1 decade in volume fractions (0.03 < < 0.3) and 3 decades in pressures. This equation of state matches the predictions made from the knowledge of the forces and thermal agitation for all components in the dispersion (particles, ions, and water).

Item Type:Article
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Other partners > Institut Laue-Langevin - ILL (FRANCE)
Other partners > Ecole Supérieure de Physique et de Chimie Industrielles - ESPCI (FRANCE)
Other partners > Institut polytechnique de Grenoble (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Other partners > Université Pierre et Marie Curie, Paris 6 - UPMC (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
Other partners > Université de Paris Diderot - Paris 7 (FRANCE)
Laboratory name:
Deposited On:03 Nov 2008 11:35

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