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Tintas y materiales compuestos anisotrópicos basados en nanotubos de carbono

Abstract : This thesis focus on the study of inks, composites and deposits of single-wall carbon nanotubes (SWNT). The control of dispersion and orientation of nanotubes in such nanostructured composites materials allows to optimize their properties, and especially their electrical and optical properties.The first part of the work is devoted to the optimization of dispersion of SWNT in aqueous suspensions stabilized by bile salts surfactants, and to the study of their optical properties, and especially their near infrared photoluminescence (PL). Dispersion of the nanotubes is probed by absorption spectroscopy. We show that their absorption coefficient is very sensitive to the individualization of the nanotubes. On the other hand, we revisit the interpretation of the PL spectra excited in the near infrared (especially at 1.17 and 1.58 eV), and we assign the different peaks to different mechanisms, namely direct excitonic transitions, exciton-phonon coupling, and energy transfer between nanotubes. We show that the evolution of PL intensity as a function of individualization allows to distinguish the different mechanisms.The second part of the work is dedicated to the preparation of aqueous suspensionsstabilized by hydrosoluble polymers (PVA and PVP), and SWNT/polymer composites, without surfactants. SWNT suspensions are mixed with polymer solutions, and then the surfactant is removed by dialysis. The yield, i.e. the relative concentration of SWNT in the dialyzed suspension, is ~75 times higher than for a suspension prepared directly with polymers. On the other hand, PL signatures are sensitive to the dielectric environment of the nanotubes which allows to evidence an exchange between the dispersing agents bile salts/PVA on the nanotube surface, such an exchange is not observed in the case of PVP.In the third part of the thesis, we use the inkjet printing technique to print continuous micrometric lines of SWNT, and we propose original methods to study their morphology and their anisotropy. The morphology of the deposits varies between two limit cases, an homogeneous deposit and a ‘‘pair of tracks'', by varying nanotube concentration in the inks, inter-drop distance and substrate temperature. The orientation of the nanotubes is very high at the edge of the deposits (orientational order parameter S between 0.6 y 0.9), the nanotubes are well-oriented as well in the tracks (S~0.5) and to a lesser extent in the homogeneous lines (S~0.3).
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Fernando José Torres-Canas. Tintas y materiales compuestos anisotrópicos basados en nanotubos de carbono. Physics [physics]. Université Montpellier; Instituto venezolano de investigaciones cientificas, 2015. Español. ⟨NNT : 2015MONTS142⟩. ⟨tel-02076359⟩

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