Evolution of particle-scale dynamics in an aging clay suspension |
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Authors: | Bandyopadhyay R Liang D Yardimci H Sessoms D A Borthwick M A Mochrie S G J Harden J L Leheny R L |
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Institution: | Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA. |
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Abstract: | Multispeckle x-ray photon correlation spectroscopy was employed to characterize the slow dynamics of a suspension of highly charged, nanometer-sized disks. At wave vectors q corresponding to interparticle length scales, the dynamic structure factor follows a form f(q,t) approximately exp(-(t/tau)(beta)], where beta approximately 1.5. The relaxation time tau increases with the sample age t(a) approximately as tau approximately t(1.8)(a) and decreases with q as tau approximately q(-1). Such behavior is consistent with models that describe the dynamics in disordered elastic media in terms of strain from random, local structural rearrangements. The measured amplitude of f(q,t) varies with q in a manner that implies caged particle motion. The decrease in the range of this motion and an increase in suspension conductivity with increasing t(a) indicate a growth in interparticle repulsion as the mechanism for internal stress development implied by these models. |
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