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.
This work has been published in Soft Matter (View online)