Evolution of particle-scale dynamics in an aging clay suspension

R. Bandyopadhyay; D. Liang; H. Yardimci; D. A. Sessoms; M. A. Borthwick; S. G. J. Mochrie; J. L. Harden; R. L. Leheny

doi:10.1103/PhysRevLett.93.228302

paper

Evolution of particle-scale dynamics in an aging clay suspension

arXiv:cond-mat/0410376 · doi:10.1103/PhysRevLett.93.228302

Abstract

Multispeckle x-ray photon correlation spectroscopy was employed to characterize the slow dynamics of a colloidal suspension formed by highly-charged, nanometer-sized disks. At scattering wave vectors $q$ corresponding to interparticle length scales, the dynamic structure factor follows a form $f (q, t) \sim exp [- (t / τ)^{β}$ ], where $β \approx$ 1.5. The characteristic relaxation time $τ$ increases with the sample age $t_{a}$ approximately as $τ \sim t_{a}^{1.8}$ and decreases with $q$ approximately as $τ \sim q^{- 1}$ . Such a compressed exponential decay with relaxation time that varies inversely with $q$ is consistent with recent models that describe the dynamics in disordered elastic media in terms of strain from random, local structural rearrangements. The amplitude of the measured decay in $f (q, t)$ varies with $q$ in a manner that implies caged particle motion at short times. The decrease in the range of this motion and an increase in suspension conductivity with increasing $t_{a}$ indicate a growth in the interparticle repulsion as the mechanism for internal stress development implied by the models.

4 pages, includes 4 postscript figures; accepted for publication in Phys Rev Lett

Evolution of particle-scale dynamics in an aging clay suspension

Abstract

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