Flow of colloidal aqueous silica dispersions

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Abstract
Concentrated dispersions of colloidal silica particles in water behave as soft solids. Under low stresses they show viscoelastic behavior, i.e., elastic response at short times and viscous creep at long times. Visualization of the deformation field shows that in this case the shear is homogeneous throughout the sample. Under large stresses they yield and accommodate any rate of shear; the dynamic yield stress follows the osmotic pressure of the dispersion. Visualization of the flow field shows that in this case the shear localizes in internal slip layers. The mechanism for localization results from release of water into fractures which let the solid regions flow past each other. At rest the solid regions reabsorb this water and heal the fractures. In this sense the flow is self‐lubricating.

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