Sedimentation of an attractive colloidal gel : time dependence of concentration and velocity profiles and local dynamics
- Paper number
IAC-08.A2.1.6
- Author
Prof. luca cipelletti, UM2 and CNRS, France
- Coauthor
Prof. Roberto Piazza, Italy
- Coauthor
Mr. Giovanni Brambilla, France
- Year
2008
- Abstract
We use space and time-resolved depolarized light scattering to investigate the evolution of a gel made by attractive colloidal particles. In comparison with previous works where only the total height of the gel could be measured, our technique allows us to follow the evolution of the concentration profile, the velocity profile, and the local dynamics. Initially, small clusters of particles are formed and fall due to gravity. The size of these clusters is most likely limited by the shear flow experienced during settling. Once the clusters deposit on the bottom of the cell, they form a gel phase. We focus on the evolution of the gel phase once no free clusters are present anymore in solution. The gel height decreases exponentially toward a plateu. We find that during this compaction process, the sedimentation velocity increases linearly with height in the gel, i.e. that the compaction follows an affine law, with the same strain rate at all heights. The local internal dynamics appears to be independent of the local volume fraction and the local settling velocity. By contrast, the characteristic time of the local dynamics is highly correlated with the (time dependent) strain rate, in analogy with what found for other glassy materials.
- Abstract document
- Manuscript document
IAC-08.A2.1.6.pdf (🔒 authorized access only).
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