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Dense colloidal fluids form denser amorphous sediments

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Original languageEnglish
Pages (from-to)5769-5773
Number of pages5
JournalProceedings of the National Academy of Sciences
Volume110
Issue number15
Early online date25 Mar 2013
DOIs
StatePublished - 9 Apr 2013

Abstract

We relate, by simple analytical centrifugation experiments, the density of colloidal fluids with the nature of their randomly packed solid sediments. We demonstrate that the most dilute fluids of colloidal hard spheres form loosely packed sediments, where the volume fraction of the particles approaches in frictional systems the random loose packing limit, φRLP=0.55. The dense fluids of the same spheres form denser sediments, approaching the so-called random
close packing limit, φRCP = 0.64. Our experiments, where particle sedimentation in a centrifuge is sufficiently rapid to avoid crystallization, demonstrate that the density of the sediments varies monotonically with the volume fraction of the initial suspension. We reproduce our experimental data by simple computer simulations, where structural reorganizations are prohibited, such that the rate of sedimentation is irrelevant. This suggests that in colloidal systems, where viscous forces dominate, the structure of randomly
close-packed and randomly loose-packed sediments is determined by the well-known structure of the initial fluids of simple hard spheres, provided that the crystallization is fully suppressed.

    Research areas

  • amorphous solids, colloids, microscopy, glass, granular matter

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