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Matière Molle
(423) Articles dans des revues
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Saffman-Taylor instability for generalized Newtonian fluids ![doi link](plugins/aigle//images/ext_link.jpg)
Auteur(s): Mora S., Manna M.
(Article) Publié:
Physical Review E: Statistical, Nonlinear, And Soft Matter Physics, vol. 80 p.016308 (2009)
PMID 19658807
DOI: 10.1103/PhysRevE.80.016308
WoS: 000268616500052
21 Citations
Résumé: We study theoretically the linear Saffman-Taylor instability for non-Newtonian fluids in a Hele-Shaw cell. After introducing the notion of generalized Newtonian fluid we calculate the associated Darcy's law. We derive the relation governing the growth rate of normal modes for a large class of non-Newtonian flows. For shear-thinning fluids at high shear rate our theory provides Darcy's laws free of the nonphysical divergences appearing in the classical approaches. We characterize fluids which develop instabilities faster than Newtonian fluids under the same hydrodynamical conditions. Another primary result that this paper provides is that for some shear-thickening fluids, all normal modes are stable.
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Nanostructuring of Hybrid Silicas through a Self-Recognition Process ![doi link](plugins/aigle//images/ext_link.jpg)
Auteur(s): Arrachart Guilhem, Creff Gaëlle, Wadepohl Hubert, Blanc C., Bonhomme Christian, Babonneau Florence, Alonso Bruno, Bantignies J.-L., Carcel Carole, Moreau Joël J. E., Dieudonne-George P., Sauvajol J.-L., Massiot Dominique, Wong Chi Man Michel
(Article) Publié:
Chemistry - A European Journal, vol. 15 p.5002 (2009)
Ref HAL: hal-01224956_v1
PMID 19350601
DOI: 10.1002/chem.200802748
WoS: 000266292200007
Exporter : BibTex | endNote
13 Citations
Résumé: The hydrolysis and condensation of a silylated derivative of ureidopyrimidinone led to nanostructured hybrid silica, such as that depicted, as clearly shown by powder XRD studies. The nanostructuring was directly related to molecular recognition through hydrogen bonding. By combining FTIR, solution and solid-state NMR spectroscopic data, the transcription of the hydrogen-bonding networks from the precursor to the final product was clearly evidenced.
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Toward Organization of Cyano-Bridged Coordination Polymer Nanoparticles within an Ionic Liquid Crystal ![doi link](plugins/aigle//images/ext_link.jpg)
Auteur(s): Larionova Joulia, Guari Yannick, Blanc C., Dieudonne-George P., Tokarev Alexei, Guérin Christian
(Article) Publié:
Langmuir, vol. 25 p.1138 (2009)
Ref HAL: hal-01224941_v1
DOI: 10.1021/la803001x
WoS: 000262431100069
Exporter : BibTex | endNote
44 Citations
Résumé: Size controlled cyano-bridged coordination polymer nanoparticles Mn1.5[Cr(CN)6] have been synthesized and organized at the nanolevel by using the room temperature ionic liquid crystal (ILC) C12-MIMBF4. The as-obtained material was studied by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), optical microscopy, and X-ray diffraction. These analyses reveal the presence of a long-range organization of cyano-bridged nanoparticles at the nanoscale level within the ILC phase. The magnetic study of these nanoparticles reveals an appearance of a nanocluster-glass-like regime caused by magnetostatic interactions between neighboring nanoparticles. The properties of these organized nanoparticles have been compared with the properties of nanoparticles of the same composition and stoichiometry obtained and randomly dispersed into the isotropic IL C10-MIMBF4.
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Nonlinear Rheology of Surfactant Wormlike Micelles Bridged by Telechelic Polymers ![doi link](plugins/aigle//images/ext_link.jpg)
Auteur(s): Tabuteau Hervé, Ramos L., Nakaya-Yaegashi Kaori, Imai Masayuki, Ligoure C.
(Article) Publié:
Langmuir, vol. 25 p.2467-2472 (2009)
Ref HAL: hal-00514229_v1
PMID 19199743
DOI: 10.1021/la803304z
WoS: 000263373600083
Exporter : BibTex | endNote
20 Citations
Résumé: We have investigated the nonlinear rheology of a soft composite transient network made of a solution of surfactant wormlike micelles (WM) in the semidilute regime that are reversibly bridged by telechelic polymers. The samples are well described, in the linear regime, as two Maxwell fluids components blends, characterized by two markedly different characteristic times. The slow mode is mainly related to the transient network of entangled WM, and the fast mode to the network of telechelic chains. In this paper we investigate the nonlinear viscoelasticity and show that the nonlinear behavior reflects as well the behavior of two coupled networks. On one hand, stress relaxation experiments and time-resolved stress response following the application of a constant shear rate show that, in the weakly nonlinear regime, these novel composite networks stiffen. A fourfold increase of the elastic modulus with respect to the linear value is reached for strain amplitude of about 200%. This strain hardening is due to the nonlinear stretching of the telechelic polymer chains. On the other hand, the samples exhibit shear banding in the highly nonlinear regime, similarly to pure semidilute solutions of WM.
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Palladium Nanowires Synthesized in Hexagonal Mesophases: Application in Ethanol Electrooxidation ![doi link](plugins/aigle//images/ext_link.jpg)
Auteur(s): Ksar Faygal, Surendran Geetarani, Ramos L., Keita Bineta, Nadjo Louis, Prouzet Eric, Beaunier Patricia, Hagege Agnes, Audonnet Fabrice, Remita Hynd
(Article) Publié:
Chemistry Of Materials, vol. 21 p.1612-1617 (2009)
Ref HAL: hal-00514226_v1
DOI: 10.1021/cm803492j
WoS: 000265412400029
Exporter : BibTex | endNote
132 Citations
Résumé: Palladium nanowires (of length a few tens of nanometers) are synthesized in a hexagonal mesophase formed by a quaternary system (Pd-doped water, surfactant, cosurfactant, and oil) by electron beam irradiation. The mesophases can be doped by high concentrations of palladium (0.1 M) without any disturbance of the structure of the mesophases which allows the quantitative synthesis of 1D Pd nanostructures. We found an increase in the average length of the nanowires with the amount of cosurfactant (pentanol) that assists the reduction/growth processes. The electrocatalytic oxidation of ethanol was selected as a test reaction in alkaline medium where Pd is known to be among the best electrode materials. We found that the Pd nanowires exhibit both a very important electrocatalytic activity for ethanol oxidation and a very high stability.
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Bimetallic Palladium-Gold Nanostructures: Application in Ethanol Oxidation ![doi link](plugins/aigle//images/ext_link.jpg)
Auteur(s): Ksar Faycal, Ramos L., Keita Bineta, Nadjo Louis, Beaunier Patricia, Remita Hynd
(Article) Publié:
Chemistry Of Materials, vol. 21 p.3677-3683 (2009)
Ref HAL: hal-00514225_v1
DOI: 10.1021/cm901364w
WoS: 000268523300028
Exporter : BibTex | endNote
179 Citations
Résumé: Bimetallic Pd-Au nanostructures were synthesized in the soft templates provided by surfactant hexagonal mesophases. The nanostructures are constituted by a core rich in gold and a Pd porous shelf. The electrocatalytic activity of these nanostructures for ethanol oxidation in basic medium was compared with that of alloyed Pd-Au nanoparticles synthesized in solution. The Pd-Au alloy is active toward the oxidation of ethanol in an alkaline medium but is not durable in realizing this process. The Pd-shell-Au-core nanostructures synthesized in mesophases are promising for application in direct ethanol fuel cells as they exhibit a very good electrocatalytic activity and a high stability.
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Synthesis of Ultrathin Hexagonal Palladium Nanosheets ![doi link](plugins/aigle//images/ext_link.jpg)
Auteur(s): Siril Prem F., Ramos L., Beaunier Patricia, Archirel Pierre, Etcheberry Arnaud, Remita Hynd
(Article) Publié:
Chemistry Of Materials, vol. 21 p.5170-5175 (2009)
Ref HAL: hal-00514224_v1
DOI: 10.1021/cm9021134
WoS: 000271234300023
Exporter : BibTex | endNote
89 Citations
Résumé: Ultrathin palladium hexagonal nanosheets were synthesized in emulsions constituted of droplets of toluene containing Pd complexes in water and stabilized by CTAB as surfactant and in quaternary mesophases formed by water, toluene containing Pd complexes, CTAB, and a cosurfactant. We have identified slow reduction and nucleation provided by CO and adsorption at the CTAB interface as key factors for the formation of Pd nanosheets. These nanosheets exhibit a broad absorption band from the visible to the near-infrared region.
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