Observation of a shape-dependent density maximum in random packings and glasses of colloidal silica ellipsoids

Stefano Sacanna, L. Rossi, A. Wouterse, A. P. Philipse

Research output: Contribution to journalArticle

Abstract

We have measured the random packing density of monodisperse colloidal silica ellipsoids with a well-defined shape, gradually deviating from a sphere shape up to prolates with aspect ratios of about 5, to find for a colloidal system the first experimental observation for the density maximum (at an aspect ratio near 1.6) previously found only in computer simulations of granular packings. Confocal microscopy of ellipsoid packings, prepared by rapidly quenching ellipsoid fluids via ultra-centrifugation, demonstrates the absence of orientational order and yields pair correlation functions very much like those for random sphere packings. The density maximum, about 12% above the Bernal random sphere packing density, also manifests itself as a maximum in the hydrodynamic friction that resists the swelling osmotic pressure of the ellipsoid packings. The existence of the density maximum is also predicted to strongly effect the dynamics of colloidal non-sphere glasses: slightly perturbing the sphere shape in a sphere glass will cause it to melt.

Original languageEnglish (US)
Article number376108
JournalJournal of Physics: Condensed Matter
Volume19
Issue number37
DOIs
StatePublished - Sep 19 2007

Fingerprint

ellipsoids
Silicon Dioxide
Silica
silicon dioxide
Glass
glass
packing density
aspect ratio
Aspect ratio
Phosmet
osmosis
Confocal microscopy
swelling
friction
computerized simulation
quenching
hydrodynamics
Swelling
Quenching
microscopy

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Materials Science(all)

Cite this

Observation of a shape-dependent density maximum in random packings and glasses of colloidal silica ellipsoids. / Sacanna, Stefano; Rossi, L.; Wouterse, A.; Philipse, A. P.

In: Journal of Physics: Condensed Matter, Vol. 19, No. 37, 376108, 19.09.2007.

Research output: Contribution to journalArticle

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