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Matière molle pour l’agronomie et l’environnement
(20) Production(s) de l'année 2020
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Microplastiques : d’une pollution invisible à un défi planétaire
Auteur(s): Fabre P.
Conférence invité: Conférence au Centre de Recherche Paul Pascal (Bordeaux) (Bordeaux, FR, 2020-03-12)
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Polypyrrole nanostructures modified with mono- and bimetallic nanoparticles for photocatalytic H2 generation
Auteur(s): Yuan Xiaojiao, Dragoe Diana, Beaunier Patricia, Uribe Daniel Bahena, Ramos L., Méndez-Medrano Maria Guadalupe, Remita Hynd
(Article) Publié:
Journal Of Materials Chemistry A, vol. 8 p.268-277 (2020)
Texte intégral en Openaccess :
Ref HAL: hal-03437340_v1
DOI: 10.1039/C9TA11088G
Exporter : BibTex | endNote
Résumé: Conjugated polymer polypyrrole nanostructures modified with bimetallic (Pt–Ni) nanoparticles are very active for hydrogen generation and a synergetic effect is obtained by alloying Pt with Ni.
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Role of Normal Stress in the Creep Dynamics and Failure of a Biopolymer Gel
Auteur(s): Pommella A., Cipelletti L., Ramos L.
(Article) Publié:
Physical Review Letters, vol. 125 p.268006 (2020)
Texte intégral en Openaccess :
Ref HAL: hal-03139495_v1
DOI: 10.1103/PhysRevLett.125.268006
WoS: WOS:000604249900023
Exporter : BibTex | endNote
Résumé: We investigate the delayed rupture of biopolymer gels under a constant shear load by simultaneous dynamic light scattering and rheology measurements. We unveil the crucial role of normal stresses built up during gelation: All samples that eventually fracture self-weaken during the gelation process, as revealed by a partial relaxation of the normal stress concomitant to a burst of microscopic plastic rearrangements.Upon applying a shear stress, weakened gels exhibit in the creep regime distinctive signatures in their microscopic dynamics, which anticipate macroscopic fracture by up to thousands of seconds. The dynamics in fracturing gels are faster than those of nonfracturing gels and exhibit large spatiotemporal fluctuations. A spatially localized region with significant plasticity eventually nucleates, expands progressively, and finally invades the whole sample, triggering macroscopic failure.
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Chemical-Physical Characterization of a Binary Mixture of a Twist Bend Nematic Liquid Crystal with a Smectogen
Auteur(s): Aouini A., Nobili M., Chauveau E., Dieudonne-George P., Dameme Gauthier, Stoenescu Daniel, Dozov I., Blanc C.
(Article) Publié:
Crystals, vol. 10 p.1110 (2020)
Texte intégral en Openaccess :
Ref HAL: hal-03113887_v1
DOI: 10.3390/cryst10121110
WoS: WOS:000601985600001
Exporter : BibTex | endNote
Résumé: Nematic twist-bend phases (N-TB) are new types of nematic liquid crystalline phases with attractive properties for future electro-optic applications. However, most of these states are monotropic or are stable only in a narrow high temperature range. They are often destabilized under moderate cooling, and only a few single compounds have shown to give room temperature N-TB phases. Mixtures of twist-bend nematic liquid crystals with simple nematogens have shown to strongly lower the nematic to N-TB phase transition temperature. Here, we examined the behaviour of new types of mixtures with the dimeric liquid crystal [4 ',4 '-(heptane-1,7-diyl)bis(([1 ',1 ''-biphenyl]4 ''-carbo-nitrile))] (CB7CB). This now well-known twist-bend nematic liquid crystal presents a nematic twist-bend phase below T approximate to 104 degrees C. Mixtures with other monomeric alkyl or alkoxy -biphenylcarbonitriles liquid crystals that display a smectic A (SmA) phase also strongly reduce this temperature. The most interesting smectogen is 4 '-Octyl-4-biphenylcarbonitrile (8CB), for which a long-term metastable N-TB phase is found at room and lower temperatures. This paper presents the complete phase diagram of the corresponding binary system and a detailed investigation of its thermal, optical, dielectric, and elastic properties.
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Pollution des océans par les plastiques et les microplastiques Pollution of oceans by plastics and microplastics
Auteur(s): Francois Galgani, Stéphane Bruzaud, Guillaume Duflos, Fabre P., Emmanuelle Casdaldi, Jeff Ghiglione, Régis Grimaud, George M., Arnaud Huvet, Fabienne Lagarde, Ika Paul-Pont, Alexandra Halle
(Article) Publié:
Techniques De L'ingenieur, vol. p. (2020)
Texte intégral en Openaccess :
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Role of normal stress in the creep dynamics and failure of a biopolymer gel
Auteur(s): Pommella A., Cipelletti L., Ramos L.
(Document sans référence bibliographique) 2020-12-17Texte intégral en Openaccess :
Ref HAL: hal-03081334_v1
Ref Arxiv: 2012.09827
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: We investigate the delayed rupture of biopolymer gels under a constant shear load by simultaneous dynamic light scattering and rheology measurements. We unveil the crucial role of normal stresses built up during gelation: all samples that eventually fracture self-weaken during the gelation process, as revealed by a partial relaxation of the normal stress concomitant to a burst of microscopic plastic rearrangements. Upon applying a shear stress, weakened gels exhibit in the creep regime distinctive signatures in their microscopic dynamics, which anticipate macroscopic fracture by up to thousands of seconds. The dynamics in fracturing gels are faster than those of non-fracturing gels and exhibit large spatio-temporal fluctuations. A spatially localized region with significant plasticity eventually nucleates, expands progressively, and finally invades the whole sample triggering macroscopic failure.
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Microstructure Characterization of Oceanic Polyethylene Debris
Auteur(s): Rowenczyk Laura, Dazzi Alexandre, Deniset-Besseau Ariane, Beltran Victoria, Goudounèche Dominique, Wong-Wah-Chung Pascal, Boyron Olivier, George M., Fabre P., Roux C., Mingotaud Anne-Françoise, ter Halle Alexandra
(Article) Publié:
Environmental Science And Technology, vol. 54 p.4102-4109 (2020)
Texte intégral en Openaccess :
Ref HAL: hal-02990067_v1
DOI: 10.1021/acs.est.9b07061
Exporter : BibTex | endNote
Résumé: Plastic pollution has become a worldwide concern. It was demonstrated that plastic breaks down to nanoscale particles in the environment, forming so-called nanoplastics. It is important to understand their ecological impact, but their structure is not elucidated. In this original work, we characterize the microstructure of oceanic polyethylene debris and compare them to the nonweathered objects. Cross-sections are analysed by several emergent mapping techniques. We highlight deep modifications of the debris within a layer a few hundred microns thick. The most 2 intense modifications are macromolecule oxidation and a considerable decrease in the molecular weight. The adsorption of organic pollutants and trace metals is also confined to this outer layer. Fragmentation of the oxidized layer of the plastic debris is the most likely source of nanoplastics. Consequently nanoplastic chemical nature differ greatly from plastics.
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