TY - JOUR
T1 - Dense colloidal fluids form denser amorphous sediments
AU - Liber, Shir R.
AU - Borohovich, Shai
AU - Butenko, Alexander V.
AU - Schofield, Andrew B.
AU - Sloutskin, Eli
PY - 2013/4/9
Y1 - 2013/4/9
N2 - 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, φfRLP = 0.55. Thedensefluidsofthe same spheres form denser sediments, approaching the so-called random close packing limit, φfRCP = 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.
AB - 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, φfRLP = 0.55. Thedensefluidsofthe same spheres form denser sediments, approaching the so-called random close packing limit, φfRCP = 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.
KW - Amorphous solids
KW - Colloids
KW - Glass
KW - Granular matter
KW - Microscopy
UR - http://www.scopus.com/inward/record.url?scp=84876067157&partnerID=8YFLogxK
U2 - 10.1073/pnas.1214945110
DO - 10.1073/pnas.1214945110
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C2 - 23530198
SN - 0027-8424
VL - 110
SP - 5769
EP - 5773
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 15
ER -