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arXiv · 1202.6474

Equilibrium concentration profiles and sedimentation kinetics of colloidal gels under gravitational stress

Stefano Buzzaccaro·Eleonora Secchi·Giovanni Brambilla·R. Piazza·Luca Cipelletti
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Abstract

We study the sedimentation of colloidal gels by using a combination of light scattering, polarimetry and video imaging. The asymptotic concentration profiles $φ(z,t\rightarrow \infty)$ exhibit remarkable scaling properties: profiles for gels prepared at different initial volume fractions and particle interactions can be superimposed onto a single master curve by using suitable reduced variables. We show theoretically that this behavior stems from a power law dependence of the compressive elastic modulus \textit{vs} $φ$, which we directly test experimentally. The sedimentation kinetics comprises an initial latency stage, followed by a rapid collapse where the gel height $h$ decreases at constant velocity, and a final compaction stage characterized by a stretched exponential relaxation of $h$ towards a plateau. Analogies and differences with previous works are briefly discussed.

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Stefano Buzzaccaro, Eleonora Secchi, Giovanni Brambilla, R. Piazza, Luca Cipelletti. 2012-02-29. Equilibrium concentration profiles and sedimentation kinetics of colloidal gels under gravitational stress. https://doi.org/10.1088/0953-8984%2F24%2F28%2F284103

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