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|Author(s):||Fan Zhang; Andrew J. Allen; Lyle E. Levine; Jan Ilavsky; Gabrielle G. Long;|
|Title:||Structure and Dynamics Studies of Concentrated Micrometer-Sized Colloidal Suspensions|
|Published:||January 07, 2013|
|Abstract:||We present an experimental study of the structural and dynamical properties of concentrated suspensions of a series of different sized polystyrene microspheres dispersed in glycerol for volume fraction concentrations between 10 % and 20 %. The static structure, probed with ultra-small angle X-ray scattering, shows a behavior very similar to that of hard spheres. The equilibrium dynamics is probed with ultra-small angle X-ray scattering ‹ X-ray photon correlation spectroscopy, a new technique that overcomes the limits of visible light scattering techniques imposed by multiple scattering and is suitable for studies of optically opaque materials containing micrometer-sized structures. Contrary to a previous study of a similar, but much smaller nano-colloid system (Lurio et al., Phys. Rev. Lett. 84, 785, (2000)), we found that the intensity autocorrelation functions are better described by a stretched exponential function and microspheres in a concentrated suspension move collectively, rather than behaving as free particles in Brownian motion. We also found that the inverse of the effective diffusion coefficients display a peak with respect to the scattering vector that resembles the peaks in the static structure factors, which indicates that a long-lived, low free-energy state exists. The relaxation time is inversely related to scattering vector, a behavior consistent with models that describe the dynamics in terms of random, local structural arrangements in disordered elastic media.|
|Pages:||pp. 1379 - 1387|
|Keywords:||microstructure charaterization, small-angle X-ray scattering, X-ray photon correlation spectroscopy, colloidal dispersions, particle dynamics|
|Research Areas:||Characterization, Advanced Materials, Structures, Materials Science|
|PDF version:||Click here to retrieve PDF version of paper (3MB)|