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Consolidation de suspensions colloidales chargées

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We investigate the dynamics of solidification of a
charged colloidal dispersion using an original microfluidic technique
referred to as micropervaporation. This technique exploits pervaporation
within a microfluidic channel to extract the solvent of a dilute
colloidal dispersion. Pervaporation concentrates the colloids in a
controlled way up to the tip of the channel until a wet solid made of
closely packed colloids grows and invades the microfluidic channel.
For the charged dispersion under study, we however evidence a liquid
to solid transition (LST) preceding the formation of the solid, owing
to the presence of long-range electrostatic interactions. This LST is
associated with the nucleation and growth of domains confined in the channel. These domains are then compacted
anisotropically up to forming a wet solid of closely packed colloids. This solid then invades the whole channel as in directional
drying with a growth rate which depends on the microfluidic geometry. In the final steps of the solidification, we observed the
occurrence of cracks and shear bands, the delamination of the wet solid from the channel walls, and its invasion by a receding air
front. Interestingly, this air front follows specific patterns within the solid which reveal different microscopic colloidal
organizations.

Ces travaux ont été publiés dans la revue Langmuir
- [Article en ligne-
>http://pubs.acs.org/doi/abs/10.1021/acs.langmuir.5b01563