Nonequilibrium behavior of dense suspensions of uniform particles: Volume fraction and size dependence of rheology and microstructure

Journal Article · Sun Jan 01 04:00:00 EST 1995 · Journal of Rheology; (United States)

DOI:https://doi.org/10.1122/1.550687· OSTI ID:6721187

Chow, M K; Zukoski, C F ^[1]

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1. Department of Chemical Engineering and Beckman Institute, University of Illinois, Urbana, Illinois 61801 (United States)

The rheological and microstructural properties of dense suspensions of uniform, charge stabilized colloidal spheres with diameters greater than 200 nm are investigated at volume fractions just below the ordering transition up to 0.6. Shear stresses marking static and dynamic yielding, discontinuous shear thinning, and shear thickening are weakly dependent on volume fraction and particle size when scaled on the crystal's elastic modulus [ital G][sub 0]. As shear stress is increased microstructures evolve through similar states independent of volume fraction. As rest, presheared suspensions exhibit long-range orientational order. Above the dynamic yield stress, the suspensions deform with a polycrystalline microstructure which, at intermediate shear rates, evolves to hexagonally close-packed planes lying parallel to the rheometer walls. At higher shear rates the suspensions melt. Thickening is only observed above a volume fraction of 0.4--0.5, depending on particle size and at shear rates above that where the hexagonal close packing has been degraded. Shear rates characteristic of changes in flow properties and microstructure increase exponentially with volume fraction in the same manner as [ital G][sub 0]. As a consequence, a volume fraction independent constitutive response is observed when stress is scaled on [ital G][sub 0] and the shear rate is scaled on [ital G][sub 0]/[mu]. Here [mu] is the continuous phase viscosity.

• DOE Contract Number: FG02-91ER45439
• OSTI ID: 6721187
• Journal Information: Journal of Rheology; (United States), Journal Name: Journal of Rheology; (United States) Vol. 39:1; ISSN JORHD2; ISSN 0148-6055
• Country of Publication: United States
• Language: English

Related Subjects

661300* -- Other Aspects of Physical Science-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COLLOIDS
CONFIGURATION
CRYSTALLIZATION
DISPERSIONS
HEXAGONAL CONFIGURATION
MECHANICAL PROPERTIES
MICROSTRUCTURE
PHASE TRANSFORMATIONS
RHEOLOGY
SCALING LAWS
SHEAR PROPERTIES
SUSPENSIONS
VISCOSITY