Stress Components and Shear Thickening of Concentrated Hard Sphere Suspensions

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• 作者：Vincent T. O'Brien and Michael E. Mackay
• 刊名：Langmuir
• 出版年：2000
• 出版时间：October 17, 2000
• 年：2000
• 卷：16
• 期：21
• 页码：7931 - 7938
• 全文大小：95K
• 年卷期：v.16,no.21(October 17, 2000)
• ISSN：1520-5827

文摘

The elastic-like and viscous-like viscosity components of model, Brownian hard sphere suspensions weredetermined. The elastic-like component, sometimes called the thermodynamic component, is due to Brownianmotion while the viscous-like component, sometimes called the hydrodynamic component, is due tohydrodynamic interaction between and drag on the particles. The three volume fractions tested were foundto be above the glass transition volume fraction due to the absence of a zero shear viscosity. The hydrodynamicviscosity component was approximately independent of shear rate, yet the suspension demonstrated alarge amount of shear thinning which was due to the elastic-like component. The measured stress componentsassociated with shear thickening were distinctly different in each sample. Continuous shear thickeningwas measured for the sample with 0.54 volume fraction while the samples with volume fractions 0.59 and0.63 showed discontinuous shear thickening. Shear thickening in these concentrated suspensions wasrelated to the effect of particle clustering increasing the effective volume fraction above maximum packingfraction. The type of shear thickening changed from being viscous-like for the two lower volume fractions,indicating the formation of particle clusters, to elastic-like for the highest volume fraction. Stress decayafter cessation of shear was found to follow a power law relation with time indicative of fractal-likemicrostructures.