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Dynamique du séchage unidirectionnel de dispersions colloïdales

publié le , mis à jour le

We investigate the dynamics of unidirectional drying of silica dispersions within glass capillary.
Evaporation induces a flow towards the open end, which continuously convects the colloids at the air-dispersion
interface, up to forming a dense incompressible solid which invades the capillary.

In the case of small nanoparticles (radii < 20 nm), a slowing down of the evaporation rate has been often reported in the literature.

We first propose that Kelvin’s effect, i.e. the reduction of the partial pressure of water in the
presence of highly curved nanomenisci at the drying air-dispersion interface, has to be taken into
account in the existing models explaining the slowing down.

We also performed careful
measurements of the dynamics of solidification, which clearly demonstrate that the existing models (taking into
account or not Kelvin’s effect) do not fit correctly the slowing down. This is consistent with a brief review
of similar recent measurements.

We suggest that these discrepancies may come from
the polydispersity of the suspensions and from the inhomogeneity of the flow within the fracturated
solid region.

Ces travaux ont été publiés dans la revue Soft Matter
- Article en ligne