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Dynamique et rhéologie des fluides complexes (gels, polymères, mousses, colloïdes)
(23) Production(s) de l'année 2023
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Front propagation in ultrastable glasses is dynamically heterogeneous 
Auteur(s): Herrero C., Ediger Mark, Berthier L.
(Article) Publié:
The Journal Of Chemical Physics, vol. 159 p.114504 (2023)
Texte intégral en Openaccess : 
Ref HAL: hal-04228257_v1
Ref Arxiv: 2304.12039
DOI: 10.1063/5.0168506
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: Upon heating, ultrastable glassy films transform into liquids via a propagating equilibration front, resembling the heterogeneous melting of crystals. A microscopic understanding of this robust phenomenology is, however, lacking because experimental resolution is limited. We simulate the heterogeneous transformation kinetics of ultrastable configurations prepared using the swap Monte Carlo algorithm, thus allowing a direct comparison with experiments. We resolve the liquid–glass interface both in space and in time as well as the underlying particle motion responsible for its propagation. We perform a detailed statistical analysis of the interface geometry and kinetics over a broad range of temperatures. We show that the dynamic heterogeneity of the bulk liquid is passed on to the front that propagates heterogeneously in space and intermittently in time. This observation allows us to relate the averaged front velocity to the equilibrium diffusion coefficient of the liquid. We suggest that an experimental characterization of the interface geometry during the heterogeneous devitrification of ultrastable glassy films could provide direct experimental access to the long-sought characteristic length scale of dynamic heterogeneity in bulk supercooled liquids.
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A double rigidity transition rules the fate of drying colloidal drops
Auteur(s): Milani M., Phou T., Ligoure C., Cipelletti L., Ramos L.
(Article) Publié:
Soft Matter, vol. 19 p.6968-6977 (2023)
Texte intégral en Openaccess :
Ref HAL: hal-04301565_v1
Ref Arxiv: 2307.08815
DOI: 10.1039/D3SM00625E
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: The evaporation of drops of colloidal suspensions plays an important role in numerous contexts, such as the production of powdered dairies, the synthesis of functional supraparticles, and virus and bacteria survival in aerosols or drops on surfaces. The presence of colloidal particles in the evaporating drop eventually leads to the formation of a dense shell that may undergo a shape instability. Previousworks propose that, for drops evaporating very fast, the instability occurs when the particles form a rigid porous solid, constituted of permanently aggregated particles at random close packing. To date, however, no measurements could directly test this scenario and assess whether it also applies todrops drying at lower evaporation rates, severely limiting our understanding of this phenomenon and the possibility of harnessing it in applications. Here, we combine macroscopic imaging and spaceand time-resolved measurements of the microscopic dynamics of colloidal nanoparticles in drying drops sitting on a hydrophobic surface, measuring the evolution of the thickness of the shell and the spatial distribution and mobility of the nanoparticles. We find that, above a threshold evaporationrate, the drop undergoes successively two distinct shape instabilities, invagination and cracking. While permanent aggregation of nanoparticles accompanies the second instability, as hypothesized in previous works on fast-evaporating drops, we show that the first one results from a reversible glass transition of the shell, unreported so far. We rationalize our findings and discuss their implicationsin the framework of a unified state diagram for the drying of colloidal drops sitting on a hydrophobic surface.
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Determination of pairwise interactions via the radial distribution function in equilibrium systems interacting with the Mie potential
Auteur(s): Tian Jianxiang, Berthier L.
(Article) Publié:
Results In Physics, vol. 52 p.106782 (2023)
Texte intégral en Openaccess : 
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The two faces of friction in the relaxation dynamics of granular systems
Auteur(s): Kob W.
Conférence invité: Komaba Mini-Workshop (Tokyo, JP, 2023-08-22)
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Granular materials under cyclic shear: No elastic regime and they always flow
Auteur(s): Kob W.
Conférence invité: 9th International Discussion Meeting on Relaxation in Complex Systems (Chiba, JP, 2023-08-12)
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Surface properties of alkali silicate glasses: Influence of the modifiers
Auteur(s): Zhang Z., Ispas S., Kob W.
(Article) Publié:
The Journal Of Chemical Physics, vol. 158 p.244504 (2023)
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On the medium-range order in silicate glass-formers: From standard two-body correlations to many-body correlations
Auteur(s): Kob W.
Conférence invité: 4th International Workshop on Challenges of MD simulations of Glasses and Amorphous Materials (Corning, US, 2023-07-13)
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