Measuring the concentration profiles induced by gravity settling is known to be an efficient route to obtain the equation of state of a colloidal suspension, to inspect the fine details of the phase diagram and to provide clues on the nature of metastable phases. Here we show that a careful analysis of the transient settling profiles may add valuable information for what concerns colloidal hydrodynamics. In particular, we show that a numerical inversion of a kinetic profile yields the full hydrodynamic factor K(Phi) up to the concentration of the original unsettled suspension, and that the dilute part of the profile yields a ‘dynamic’ gravitation length also related to K(Phi). These predictions are tested on a suspension of monodisperse hard and sticky spheres. Finally we describe and test a novel optical method, allowing us to measure sedimentation profiles on a wide class of colloidal systems, even in the presence of a noticeable turbidity.

Kinetics of sedimentation in colloidal suspensions

BUZZACCARO, STEFANO;RUSCONI, ROBERTO;VIGOLO, DANIELE;PIAZZA, ROBERTO
2008

Abstract

Measuring the concentration profiles induced by gravity settling is known to be an efficient route to obtain the equation of state of a colloidal suspension, to inspect the fine details of the phase diagram and to provide clues on the nature of metastable phases. Here we show that a careful analysis of the transient settling profiles may add valuable information for what concerns colloidal hydrodynamics. In particular, we show that a numerical inversion of a kinetic profile yields the full hydrodynamic factor K(Phi) up to the concentration of the original unsettled suspension, and that the dilute part of the profile yields a ‘dynamic’ gravitation length also related to K(Phi). These predictions are tested on a suspension of monodisperse hard and sticky spheres. Finally we describe and test a novel optical method, allowing us to measure sedimentation profiles on a wide class of colloidal systems, even in the presence of a noticeable turbidity.
sedimentation; disperse systems; colloids; equations of state
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11311/513339
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