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(28) Production(s) de AZNAR R.
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Bridging interactions due to telechelic linkers balanced by screened Coulombic repulsions
Auteur(s): Porte Grégoire, Ligoure C., Appell Jacqueline, Aznar R.
(Article) Publié:
Journal Of Statistical Mechanics: Theory And Experiment, vol. P05005 p. (2006)
Résumé: When telechelic polymers (poly-ethyleneoxide grafted at both ends with an aliphatic chain) are added to a microemulsion of decane droplets in water stabilized by a surfactant film they can link the droplets and thus introduce an effective attractive interaction between the droplets, eventually leading to a phase separation. Starting from a neutral microemulsion we show that this attractive interaction can be offset by adding minute quantities of an ionic surfactant, thus introducing a repulsive Coulombic interaction. This opens up the possibility of 'weighting' an unknown effective attraction against a well known repulsion. The phase behaviour and the small angle neutron scattering spectra of different samples illustrate this point. The spectra are simulated assuming the interaction potentials to be the sum of attractive and repulsive contributions and a good agreement is found between the experimental and simulated spectra in the neutral microemulsion, in the charged microemulsion and in the charged and connected microemulsion.
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Structural selective charge transfer in iodine-doped carbon nanotubes 
Auteur(s): Michel T., Alvarez L., Sauvajol J.-L., Almairac Robert, Aznar R., Mathon O., Bantignies J.-L., Flahaut Emmanuel
(Article) Publié:
Journal Of Physics And Chemistry Of Solids, vol. vol. 67 n° 5-6. p.1190-1192 , available on http://oatao.univ-toulouse.fr/744/1/flahaut_744.pdf (2006)
Ref HAL: hal-00474864_v1
Exporter : BibTex | endNote
Résumé: We have investigated iodine intercalated carbon nanostructures by extended X-ray absorption fine structure (EXAFS) and Raman spectroscopies. We discuss here the charge transfer and the iodine–carbon interaction as a function of the carbon nanostructures (graphite, multi-walled, double-walled and single walled nanotubes). The results show that iodine is weakly adsorbed on the surface of all multi-walled nanotubes. By contrast, a charge transfer between iodine and single walled nanotubes is evidenced.
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EXAFS investigations of iodine-doped carbon nanotubes
Auteur(s): Michel T., Alvarez L., Sauvajol J.-L., Almairac Robert, Aznar R., Bantignies J.-L., Mathon O.
(Article) Publié:
Physical Review B, vol. 73 p.195419 (2006)
Ref HAL: hal-00498071_v1
Exporter : BibTex | endNote
Résumé: We report an x-ray absorption fine structure study at the iodine-K edge of the local structure in iodine-doped carbon nanotubes. The iodine-carbon host interaction is shown to be weaker in multiwalled carbon nanotubes (MWNTs) than in single-walled carbon nanotubes (SWNTs). Iodine species are only localized at the surface of the external tube for MWNTs, whereas iodine species enter inside SWNTs. For doped SWNTs, both the experimental and the theoretical EXAFS spectra allow us to establish the structure of the iodine chain as disordered pentaiodide at the saturation level.
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Etude par spectroscopie d'absorption des rayons X du dopage des fagos de nanotubes monoparois
Auteur(s): Bantignies J.-L., Aznar R., Alvarez L.
(Affiches/Poster)
GFECI 2006 (Autrans, France, FR), 2006-03-28 |
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Insertion (adsorption) dans les nanotubes de carbone
Auteur(s): Abou hamad Edy, Almairac Robert, Alvarez C., Anglaret E., Aznar R., Bantignies J.-L., Bendiab Nicolas, Cambedouzou Jean, Dragin Fabienne, Firlej L., Goze-Bac C., Michel T., Rols Stéphane, Sauvajol J.-L.
(Affiches/Poster)
Comité d'Evaluation du LCVN (Montpellier, France, FR), 2006-02-23 |
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EXAFS study of rubidium-doped single-wall carbon nanotube bundles
Auteur(s): Bantignies J.-L., Alvarez L., Aznar R., Almairac Robert, Sauvajol J.-L., Duclaux L., Villain F.
(Article) Publié:
Physical Review B, vol. 71 p.195419 (2005)
Ref HAL: hal-00498755_v1
Exporter : BibTex | endNote
Résumé: The local structure around the rubidium ions inserted in single-wall carbon nanotube bundles (Rb-doped SWCNT) is studied by Rb K-edge extended x-ray-absorption fine structure (EXAFS). The dependence of the local order around the rubidium ions is investigated as a function of the time of doping (i.e., as a function of the stoichiometry of the sample). The first coordination shell of the rubidium ions, related to the distance between rubidium and the first nearest-neighboring carbon atoms, has a clear time doping dependence. Comparison between ab initio simulations of the EXAFS spectra and experimental data questions the interstitial site (between three tubes) as the preferential insertion site in SWCNT bundles. The results indicate that the rubidium ions are mainly located inside the tubes and around the bundles. The results are in good agreement with combined x-ray and neutron diffraction experiments performed on the same samples.
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