Evolution of particle-scale dynamics in an aging clay suspension.
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.
Bandyopadhyay
R
R
Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA.
Liang
D
D
Yardimci
H
H
Sessoms
D A
DA
Borthwick
M A
MA
Mochrie
S G J
SG
Harden
J L
JL
Leheny
R L
RL
D000538:Aluminum Silicates / Q000737:chemistry*; D000077215:Clay; D003102:Colloids / Q000737:chemistry*; D003198:Computer Simulation; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D015233:Models, Statistical; D008968:Molecular Conformation; D043942:Nanotubes / Q000737:chemistry*; D010316:Particle Size; D055672:Static Electricity; D013997:Time Factors
D000538:Aluminum Silicates; D003102:Colloids; D000077215:Clay