Shear behavior and microstructures of confined colloidal suspensions
Hug, John Eric
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https://hdl.handle.net/2142/20124
Description
Title
Shear behavior and microstructures of confined colloidal suspensions
Author(s)
Hug, John Eric
Issue Date
1995
Doctoral Committee Chair(s)
Zukoski, Charles F.
Department of Study
Chemical and Biomolecular Engineering
Discipline
Chemical Engineering
Engineering, Materials Science
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Chemical
Engineering, Materials Science
Language
eng
Abstract
Rheological properties and microstructures of concentrated charge-stabilized suspensions confined to gap sizes on the order of a few particle diameters are investigated by molecular dynamics computer simulations. Suspensions of uniform spheres at volume fractions ranging from 0.28 to 0.53 covering the crystalline phase are studied. The suspensions are modeled as spheres interacting via a repulsive short-ranged electrostatic potential. Stress versus shear rate behavior is examined as a function of particle volume fraction, gap size, and shear history. Microstructures for systems at equilibrium and under shear are investigated by direct observation of particle configurations and by scattering patterns generated from structure factor calculations.
The observed shear behavior and microstructures compare favorably with experimental shear studies of bulk colloidal suspensions. The shear response and stresses marking rheological transitions scale on the equilibrium modulus in a universal manner. Small changes in gap size result in significant differences in the equilibrium properties which in turn can affect the observed rheological response. Gap size also plays an important role at shear rates where catastrophic shear thinning and shear thickening occur. Qualitative differences in shear behavior between experiments and simulations are observed at high shear rates suggesting that particle interactions dominate the shear behavior at low shear rates and hydrodynamics becomes important at high shear rates.
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