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(24) Production(s) de l'année 2017
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Off-equilibrium surface tension in miscible fluids
Auteur(s): Truzzolillo D., Cipelletti L.
(Article) Publié:
Soft Matter, vol. 13 p.13-21 (2017)
Ref HAL: hal-01499947_v1
DOI: 10.1039/c6sm01026a
WoS: WOS:000395374100002
Exporter : BibTex | endNote
14 Citations
Résumé: The interfacial tension between immiscible fluids is responsible for a wealth of every-day phenomena, from the spherical shape of small drops and bubbles to the ability to walk on water of many insects.More than a century ago, physicist and mathematician D. Korteweg postulated the existence of an effective interface tension for miscible fluids, whenever a composition gradient exists, as encountered, e.g., in many flow geometries. In this mini-review, we discuss experimental work performed in the last decades that demonstrates the existence of a positive effective interface tension in a variety of systems, from molecular, near-critical liquids to complex fluids such as polymer solutions and colloidal suspensions. The various experimental strategies that have been deployed are discussed, together with their advantages and limitations. Finally, some of the key theoretical questions still open are outlined.
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Impact of solid and liquid balls on a solid surface: an unified description
Auteur(s): Arora S., Fromental J.-M., Mora S., Phou T., Ramos L., Ligoure C.
Conference: APS March meeting 2017 (La Nouvelle-Orléans, US, 2017-03-12)
Ref HAL: hal-01495935_v1
Exporter : BibTex | endNote
Résumé: We study experimentally the impact of ultra soft spherical gel balls of millimetric size d0 on a rigid substrate covered by a thin layer of liquid nitrogen to avoid viscous dissipation. The balls largely deform like a pancake at high impact velocities. We measure the maximally deformed size dmax and the the time needed to reach this maximal size after impact τmax, versus the impact velocity ui for various elastic moduli. We do the same type of experiments with liquid droplets of various surface tensions. The experiments reveal a universal scaling behavior of the maximum deformation dmax/d0 of both solid balls and liquid drops provided that both bulk and surface elasticity are properly taken into account. Moreover, we show that, in absence of viscous dissipation, the dynamics of the system can be understood as a conventional spring-mass system with a stiffness given by a combination of surface tension and bulk elasticity and a mass given by that of the ball (or drop); the deformation of the small ball (drop) during the impact linearly depends on the impact velocity, and the contact time scales as the period of this spring-mass system.
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Highly active poly(3-hexylthiophene) nanostructures for photocatalysis under solar light
Auteur(s): Floresyona Dita, Goubard Fabrice, Aubert Pierre-Henri, Lampre Isabelle, Mathurin Jeremie, Dazzi Alexandre, Ghosh Srabanti, Beaunier Patricia, Brisset Francois, Remita Samy, Ramos L., Remita Hynd
(Article) Publié:
Applied Catalysis B-Environmental, vol. 209 p.23-32 (2017)
Ref HAL: hal-01553454_v1
DOI: 10.1016/j.apcatb.2017.02.069
WoS: WOS:000400584900003
Exporter : BibTex | endNote
31 Citations
Résumé: Conjugated polymer nanostructures have recently emerged as a new class of very active photocatalysts under solar light. Poly(3-hexylthiophene) (P3HT) is one of the commonly used conjugated polymers for photovoltaics applications. P3HT nanostructures synthesized in soft templates provided by hexagonal mesophases show high photocatalytic activity for degradation of pollutants under both UV and visible light. These photocatalysts are very stable even after repeated cycling. Addition of scavengers and mechanistic studies show that O2•−is the main radical responsible for degradation of phenol taken as a model pollutant. P3HT nanostructures can be easily deposited on flat supports such as quartz for photocatalytic applications avoiding a separation step by centrifugation. Most interestingly, the photocatalytic activityof these P3HT nanostructures is highly enhanced when they are supported on a solid surface opening new perspectives in photocatalytic reactors and self-cleaning surfaces.
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