Europhys. Lett.
Volume 74, Number 3, May 2006
Page(s) 438 - 444
Section Condensed matter: structural, mechanical and thermal properties
Published online 22 March 2006
Europhys. Lett., 74 (3), pp. 438-444 (2006)
DOI: 10.1209/epl/i2005-10541-0

Intercalation-enhanced electric polarization and chain formation of nano-layered particles

J. O. Fossum1, Y. Méheust1, K. P. S. Parmar1, K. D. Knudsen2, K. J. Måløy3 and D. M. Fonseca1

1  Department of Physics, NTNU - Hoegskoleringen 5, NO-7491 Trondheim, Norway
2  Physics Department, IFE - P.O. Box 40, NO-2027 Kjeller, Norway
3  Physics Department, UiO - Postboks 1048 Blindern, NO-0316 Oslo, Norway

received 21 December 2005; accepted in final form 28 February 2006
published online 22 March 2006

Microscopy observations show that suspensions of synthetic and natural nano-layered smectite clay particles submitted to a strong external electric field undergo a fast and extended structuring. This structuring results from the interaction between induced electric dipoles, and is only possible for particles with suitable polarization properties. Smectite clay colloids are observed to be particularly suitable, in contrast to similar suspensions of a non-swelling clay. Synchrotron X-ray scattering experiments provide the orientation distributions for the particles. These distributions are understood in terms of competing i) homogenizing entropy and ii) interaction between the particles and the local electric field; they show that clay particles polarize along their silica sheet. Furthermore, a change in the platelet separation inside nano-layered particles occurs under application of the electric field, indicating that intercalated ions and water molecules play a role in their electric polarization. The resulting induced dipole is structurally attached to the particle, and this causes particles to reorient and interact, resulting in the observed macroscopic structuring. The macroscopic properties of these electro-rheological smectite suspensions may be tuned by controlling the nature and quantity of the intercalated species, at the nanoscale.

61.10.Eq - X-ray scattering (including small-angle scattering).
82.70.Dd - Colloids.
83.80.Gv - Electro- and magnetorheological fluids.

© EDP Sciences 2006