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Pach, Elzbieta. "Electron microscopy studies on functional carbon nanotubes." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/456581.
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La presente tesis doctoral se centra en el estudio exhaustivo de nanotubos de carbono funcionales por medio de técnicas de microscopía electrónica. Los nanotubos de carbono (CNTs) funcionales están atrayendo una creciente atención debido a su potencial uso para aplicaciones biomédicas, incluyendo para la adquisición de imágenes in vivo, acumulación selectiva en tumores y sistemas de administración de fármacos. Una ventaja intrínseca de los nanotubos de carbono es que su cavidad interna puede llenarse con una carga útil de interés mientras que la superficie externa puede modificarse para mejorar su dispersabilidad y biocompatibilidad.
Debido a su potencial aplicación en el campo biomédico, es esencial una caracterización detallada de las muestras en todas las etapas de su proceso de preparación (purificación, acortamiento, llenado y funcionalidad externa). Para lograr este objetivo, en esta tesis doctoral hemos empleado tanto los análisis ya establecidos que incluye microscopía electrónica de transmisión de alta resolución para estudiar la estructura del material de relleno o espectroscopia de dispersión de energía de rayos X para evaluar su composición, pero también hemos explorado el uso de otras técnicas para ampliar las posibilidades de caracterización de las muestras.
En este sentido, hemos optimizado las condiciones para el estudio de las longitudes de CNTs monocapa purificados por microscopía electrónica de barrido de alta resolución (HRSEM) con sensibilidad superficial. Además, la microscopía electrónica de transmisión y barrido (STEM) a bajos voltajes se ha demostrado como una técnica eficiente y rápida para evaluar el rendimiento del rellenado y la pureza del material. De hecho, la combinación de alta resolución espacial y el trabajo a bajos voltajes de esta técnica la ha hecho particularmente adecuada para el estudio de la interacción de nanotubos de carbono funcionales con muestras biológicas, como por ejemplo células.
Algunos de los compuestos con interés para aplicaciones biomédicas empleados en este trabajo tienen una estructura laminar. Se sabe que los materiales laminares forman monocapas que pueden tener propiedades mejoradas o nuevas debido a efectos de confinamiento. Los CNT pueden actuar como plantillas para guiar los materiales laminares a formar nanotubos monocapa. Este es el caso de los haluros de lutecio y el yoduro de plomo. En esta tesis de doctorado hemos conseguido la formación de nanotubos de haluros de lutecio de tamaño subnanométrico, y su naturaleza tubular se ha demostrado mediante STEM con corrector de aberraciones y simulaciones de imagen. Además, se ha logrado el crecimiento con alto rendimiento de nanotubos de PbI2 en el exterior de CNTs. La estructura de los híbridos se ha revelado mediante STEM con aberración corregida y tomografía electrónica. Cabe destacar que las propiedades ópticas de los híbridos difieren de las del PbI2 en masa. El desplazamiento azul observado por fotoluminiscencia se ha confirmado mediante análisis en híbridos PbI2-CNT individuales por catodoluminiscencia-STEM.
En conclusión, durante este proyecto de doctorado la gama de técnicas de microscopía electrónica utilizadas para el estudio de CNT funcionales se ha ampliado para obtener una caracterización exhaustiva de las muestras.The present PhD thesis focuses on the thorough study of functional carbon nanotubes by means of electron microscopy techniques. Functional carbon nanotubes (CNTs) are attracting an increased attention due to their potential use for biomedical applications, including in vivo imaging, tumour targeting and drug delivery systems. An intrinsic advantage of carbon nanotubes is that their inner cavity can be filled with a chosen payload whilst the outer surface can be modified to improve their dispersability and biocompatibility. Being the envisaged application in the biomedical field, a detailed characterization of the samples in all the steps of the preparation process (namely purification, shortening, filling and external functionalization) is mandatory. To achieve this goal, in this PhD thesis we have employed already established analysis including high resolution transmission electron microscopy to study the structure of the filling material, or energy dispersive X-ray spectroscopy to assess their composition, but also we have explored the use of other techniques to expand the possibilities of characterization of the samples. In this sense, we have optimized the conditions for the study of the lengths of as-purified single-walled CNTs by surface sensitive high resolution scanning electron microscopy (HRSEM). Besides, low voltage scanning transmission electron microscopy (STEM) has been demonstrated as a time-efficient technique for assessment of filling yield and purity. Indeed, the combination of high spatial resolution and low voltage operation of this technique has made it particularly suitable for the study of the interaction of functional carbon nanotubes with biological samples such as cells. Some of the employed compounds with interest for biomedical applications have a layered structure in their bulk form. Layered materials are known to form monolayers which may exert enhanced or novel properties due to the confinement effects. CNTs may act as templates to guide those layered materials to form single-layered nanotubes. This is the case of lutetium halides and lead iodide. In this PhD thesis we have succeeded in the formation of lutetium halide subnanometer-sized nanotubes, and proved their tubular nature by aberration corrected STEM and image simulations. Additionally, the high yield growth of PbI2 nanotubes on the exterior of CNTs has been achieved. Thanks to aberration corrected HAADF STEM and electron tomography, the structure of the hybrids has been revealed. Remarkably, the optical properties of the hybrids differ from those of the bulk PbI2. The blue shift observed by photoluminescence has been further confirmed by cathodoluminescence STEM analysis detected on individual PbI2-CNT hybrids. In conclusion, during this PhD project the range of electron microscopy techniques used for the study of functional CNTs has been expanded to get a thorough characterisation of the samples.
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Brunner, Eric W. "Bioapplications of carbon nanotubes and carbon nanotube assemblies." Thesis, University of Surrey, 2010. http://epubs.surrey.ac.uk/2858/.
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As new materials are discovered, their potential and applications are investigated widely across the various scientific disciplines for general or highly specialized applications. While new nanomaterials such as carbon nanotubes have received the greatest interest for electronics, optics, and structural composites, their applications have also been explored for biological applications such as sensing, selective cell destruction, cellular growth scaffolds, and intracellular delivery of bioactive cargos. Carbon nanotubes are unique materials particularly suited for these applications as they possess characteristic optical and electronic properties in conjunction with large aspect ratios and massive surface areas. The work of this thesis explores the use of carbon nanotubes for cellular growth scaffolds in Chapters 3, tailoring the various properties of these scaffolds in Chapter 4, and their cellular internalization and intracellular locations in Chapter 5. The aim of Chapters 3 and 4 are to create a surface that mimics a cell's natural environment by varying characteristics such as roughness, pore size distribution, wettability, and chemical functionalization of the carbon nanotubes surface. Such variations can have beneficial, detrimental or abnormal effects on the tested cell line as a cell's natural environment within the body consists of a three dimensional mesh of extracellular matrix proteins which is not at all replicated by the commonly used polystyrene tissue culture flask. Carbon nanotubes possess diameters ranging from 0.7 to several nanometers and lengths that can range up to several microns thereby allowing certain types of CNTs to scale with these extracellular matrix proteins and thus impart a nanoscale textured topology that more closely resembles a cell's in vivo environment. Additionally, the replacement of extracted extracellular matrix proteins for coating cellular growth surfaces with synthetic carbon nanotubes eliminates any risk of pathogen contamination and batch-to-batch variability of biological specimens. Fundamental understanding of the interactions between carbon nanotube surfaces and adhered cell cultures will provide a foundation for carbon nanotube applications in 3- dimensional cellular growth scaffolds and tissue implantation devices. Chapter 5 explores the interactions between designed peptides with slight variations in their amino acid sequences and the consequential effects of these peptide interactions with carbon nanotubes for cellular internalization and intracellular location. The efficacy of pharmaceutical drugs and the cellular responses to biomacromolecules depends heavily upon their abilities to transverse the cellular plasma membranes, and exploring the interactions with designed biomolecules such as synthetic peptides provides simple methods for increasing the cellular internalization of carbon nanotubes and altering the intracellular delivery location. The results and methods investigated within these chapters can then be easily applied to other carbon nanotube transporter schemes.,
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Fifield, Leonard S. "Functional materials based on carbon nanotubes : carbon nanotube actuators and noncovalent carbon nanotube modification /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/11560.
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PRADHAN, NIHAR R. "Thermal Conductivity of Nanowires, Nanotubes and Polymer-Nanotube Composites." Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-dissertations/112.
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Ever rising power densities and smaller transistor dimensions are increasing the challenge of thermal management within integrated-circuit chips and their surrounding packaging. In addition, the need for sustainable energy has placed urgent emphasis on energy conversion. Thermoelectric phenomena, involving the conversion of heat to electrical current, provide a central focus for both needs. Specifically, there is a need to engineer materials or composites with low thermal conductivity and high electrical conductivity for energy conversion and the opposite for heat management. In this presentation, experimental results will be presented of the specific heat and thermal conductivity of cobalt nanowires (CoNW), carbon nanotubes (CNT) and polymer-carbon nanotubes, in various composite arrangements with our high precession Calorimetric technique. Due to the nature of these samples, boundary and defect scattering of phonons in nanomaterials can dominate. This scattering phenomena shows decreasing thermal conductivity in metal nanowires, turns to be good for thermoelectric application. For the CNT, and possibly due to the high volume per atom leading to ballistic phonon propagation, the observed thermal conductivity along the nanotube direction, which leads to manage the heat dissipation problem in integrated circuits (ICs) and microprocessors. The thermal conductivity of a single Single-Wall Carbon Nanotube (SWCNT) was found to be 6600 W/mK, theoretically, twice that of diamond. When such high thermal conductivity materials are dispersed in a low thermal conducting polymer (PMMA), the effective thermal conductivity and thermal stability of the composite can change dramatically. The experimental results show good agreement with theoretical model proposed by Nelsen, Hamilton, Crosse, Geometric, and Xue. The thermal relaxation phenomena such as glass transition temperature (Tg) and dynamics of the molecules in the polymer-nanotubes composites, changes significantly different than the pure polymers during thermal treatment and is one of the focusing point of this presentation. Liquid crystalline materials confined to restrictive nano-channels are of great interest in many potential applications of electro-optics and display technology. This part of the presentation investigates the unexplored phenomenon of the coating and filling of 8CB and 10CB liquid crystals inside ~200nm diameter Multi-Wall Carbon nanopipes. The phase transition characteristics of the confined liquid crystal films were studied using MDSC technique and will be the last part of this presentation.
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Jayaraman, Karthik. "Solvent behavior in hydrophobic silica nanotubes and nanotube membranes." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/3284.
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Thesis (M.S.)--University of Maryland, College Park, 2005.Thesis research directed by: Dept. of Chemistry and Biochemistry. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Willey, Anthony D. "Thin Films of Carbon Nanotubes and Nanotube/Polymer Composites." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3540.
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A method is described for ultrasonically spraying thin films of carbon nanotubes that have been suspended in organic solvents. Nanotubes were sonicated in N-Methyl-2-pyrrolidone or N-Cyclohexyl-2-pyrrolidone and then sprayed onto a heated substrate using an ultrasonic spray nozzle. The solvent quickly evaporated, leaving a thin film of randomly oriented nanotubes. Film thickness was controlled by the spray time and ranged between 200-500 nm, with RMS roughness of about 40 nm. Also described is a method for creating thin (300 nm) conductive freestanding nanotube/polymer composite films by infiltrating sprayed nanotube films with polyimide.
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Bahmach, M. V., and D. V. Bychko. "Nanotubes." Thesis, Sumy State University, 2014. http://essuir.sumdu.edu.ua/handle/123456789/45446.
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Carbon nanotubes are long structures of cylindrical shape with a diameter from one to several tens of nanometers. They consist of one or several rolled into a tube hexagonal graphite planes. Sumio Iijima synthesized them by the method of arc evaporation. In the mid-twentieth century there were two research teams from the USA and New Zealand.
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Eberhardt, Oliver, and Thomas Wallmersperger. "Molecular mechanics methods for individual carbon nanotubes and nanotube assemblies." SPIE, 2015. https://tud.qucosa.de/id/qucosa%3A35032.
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Since many years, carbon nanotubes (CNTs) have been considered for a wide range of applications due to their outstanding mechanical properties. CNTs are tubular structures, showing a graphene like hexagonal lattice. Our interest in the calculation of the mechanical properties is motivated by several applications which demand the knowledge of the material behavior. One application in which the knowledge of the material behavior is vital is the CNT based fiber. Due to the excellent stiffness and strength of the individual CNTs, these fibers are expected to be a promising successor for state of the art carbon fibers. However, the mechanical properties of the fibers fall back behind the properties of individual CNTs. It is assumed that this gap in the properties is a result of the van-der-Waals interactions of the individual CNTs within the fiber. In order to understand the mechanical behavior of the fibers we apply a molecular mechanics approach.
The mechanical properties of the individual CNTs are investigated by using a modified structural molecular mechanics approach. This is done by calculating the properties of a truss-beam element framework representing the CNT with the help of a chemical force field.
Furthermore, we also investigate the interactions of CNTs arranged in basic CNT assemblies, mimicking the ones in a simple CNT fiber. We consider the van-der-Waals interactions in the structure and calculate the potential surface of the CNT assemblies.
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Castro, Célia. "Mécanismes de croissance de nanotubes de carbone alignés : relation catalyseur-nanotube." Paris 11, 2009. http://www.theses.fr/2009PA112273.
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Dans le domaine des nanosciences qui est actuellement en plein essor, les nanotubes de carbone (NTC) suscitent un fort intérêt en raison de leurs propriétés originales qui résulte de leur structure particulière. Pour maîtriser et optimiser les procédés de fabrication, il est essentiel de comprendre les mécanismes qui régissent leur croissance. Parmi les techniques de synthèse des NTC, la CCVD (Catalytic Chemical Vapour deposition) d’aérosol, développée au laboratoire Francis Perrin, permet la croissance rapide et continue de NTC multi-feuillets alignés et propres par l’injection simultanée de précurseur carboné liquide (toluène) et catalytique (métallocène). Notre principal objectif a été de comprendre comment le métallocène donne naissance à la particule catalytique, quelle est la nature exacte de celle-ci, quels sont les paramètres qui contrôlent son activité et enfin comment les espèces catalytiques cheminent pour permettre la croissance des NTC. Grâce à une approche expérimentale faisant intervenir une étude systématique des produits le long du four pour différentes conditions thermodynamiques (flux et mode de refroidissement) et chimiques (concentration en précurseurs, introduction de gaz réducteur), nous avons mis en évidence une germination homogène des particules de fer en phase gazeuse se produisant en amont de la zone isotherme suivie de leur dépôt graduel le long du four. Les particules catalytiques à la base du tapis de NTCs alignés seraient un fer semi-fondu sursaturé en carbone qui est alimenté en continu par les espèces catalytiques qui diffusent le long du tapis de NTC jusqu’à sa baseThe field of nanoscience which is developing intensively, carbon nanotubes (CNTs) are attracting strong interest because of their particular properties resulting of their special structure. To control and optimize manufacturing processes, it is important to understand the mechanisms governing their growth. Among the synthesis methods of CNTs, the aerosol-assisted CCVD (Catalyst Chemical Vapor Deposition) process, developed in Laboratoire Francis Perrin, allows the continuous and rapid growth of aligned and clean Multi-Walled CNT by the simultaneous injection of liquid carbonaceous precursor (toluene) and catalyst precursor (metallocene). Our main objective was to understand how the chemical transformation of metallocene into catalyst particles, what is the exact nature of catalyst particles, what are the parameters controlling their activity and finally how the catalytic species progress to enable the growth of CNTs. From an experimental approach involving a systematic study of products all along the furnace for different thermodynamic (flow and cooling step) and chemical (concentration of precursors, introduction of reducing gas) conditions, we demonstrate a homogeneous nucleation of particles of iron in the gas phase occurring before the isothermal area followed by their gradual deposition along the furnace. The catalytic particles located at the base of the aligned nanotube carpet are semi-molten iron saturated with carbon that is fed continuously by the catalytic species which diffuse all along the CNT carpet to its base
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Choi, Yongho. "Growth, fabrication, and characterization of carbon nanotubes, nanotube films, and nanowires." [Gainesville, Fla.] : University of Florida, 2008. http://purl.fcla.edu/fcla/etd/UFE0022789.
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Castro, Celia. "Mécanismes de croissance de nanotubes de carbone alignés : relation catalyseur - nanotube." Phd thesis, Université Paris Sud - Paris XI, 2009. http://tel.archives-ouvertes.fr/tel-00508509.
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Dans le domaine des nanosciences qui est actuellement en plein essor, les nanotubes de carbone (NTC) suscitent un fort intérêt en raison de leurs propriétés originales qui résulte de leur structure particulière. Pour maîtriser et optimiser les procédés de fabrication, il est essentiel de comprendre les mécanismes qui régissent leur croissance. Parmi les techniques de synthèse des NTC, la CCVD (Catalytic Chemical Vapour deposition) d'aérosol, développée au laboratoire Francis Perrin, permet la croissance rapide et continue de NTC multi-feuillets alignés et propres par l'injection simultanée de précurseur carboné liquide (toluène) et catalytique (métallocène). Notre principal objectif a été de comprendre comment le métallocène donne naissance à la particule catalytique, quelle est la nature exacte de celle-ci, quels sont les paramètres qui contrôlent son activité et enfin comment les espèces catalytiques cheminent pour permettre la croissance des NTC. Grâce à une approche expérimentale faisant intervenir une étude systématique des produits le long du four pour différentes conditions thermodynamiques (flux et mode de refroidissement) et chimiques (concentration en précurseurs, introduction de gaz réducteur), nous avons mis en évidence une germination homogène des particules de fer en phase gazeuse se produisant en amont de la zone isotherme suivie de leur dépôt graduel le long du four. Les particules catalytiques à la base du tapis de NTCs alignés seraient un fer semi-fondu sursaturé en carbone qui est alimenté en continu par les espèces catalytiques qui diffusent le long du tapis de NTC jusqu'à sa base.
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Kang, Dun-Yen. "Single-walled metal oxide nanotubes and nanotube membranes for molecular separations." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44715.
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Synthetic single-walled metal oxide (aluminosilicate) nanotubes (SWNTs) are emerging materials for a number of applications involving molecular transport and adsorption due to their unique pore structure, high surface reactivity, and controllable dimensions. In this thesis, I discuss the potential for employing SWNTs in next generation separation platforms based upon recent progress on synthesis, interior modification, molecular diffusion properties, transport modeling and composite membrane preparation of metal oxide SWNTs. First, I describe the structure, synthesis, and characterization of the SWNTs. Thereafter, chemical modification of the nanotube interior is described as a means for tuning the nanotube properties for molecular separations. Interior functionalization of SWNTs (e.g. carbon nanotubes and metal oxide nanotubes) is a long-standing challenge in nanomaterials science. After controlled dehydration and dehydroxylation of the SWNTs, I then demonstrate that the SWNT inner surface can be functionalized with various organic groups of practical interest via solid-liquid heterogeneous reactions. Finally, I describe a mass transport modeling and measurements for composite membranes composed of SWNTs as fillers. This work demonstrates the use of SWNTs for novel scalable separation units from both a nanoscale and a macroscale point of view.
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Pantoja, Suárez Luis Fernando. "Carbon nanotubes grown on stainless steel for supercapacitor applications." Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/667708.
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The ability of humans to study, manipulate and understand matter at the nanoscale has enabled us to develop materials that can combine physical, chemical, optical, magnetic and mechanical properties that bulk materials do not possess. One of the materials that triggered interest in the world of Nanoscience and Nanotechnology was carbon nanotubes (CNTs). These nanostructures had already been reported more than forty years ago, but it is not until the beginning of the 90s that Dr. Sumio Iijima manages to produce them under stable conditions in his laboratory. From that time onwards, the resources devoted to the research and production of these carbon-based materials were on the rise. Although today they do not capture the same scientific interest as they did until 2010, their importance in the scientific world and especially in the market is relevant. In fact, since the technology for the production of CNTs on an industrial scale has matured, they are found in an infinite number of applications, such as reinforcing polymers, acting as scaffolds for the growth of artificial tissue, in the manufacture of conductive inks or as part of new generation battery electrodes and supercapacitors. It is precisely in this last application that scientific interest has been focused with special attention. Together with other carbon-based materials, such as graphene, they are excellent support materials for materials with high capacitance. Research groups and companies around the world are spending a lot of resources to obtain electrodes that have a three-dimensional architecture at the nanoscale and whose specific surface is high.
In that sense, the objective of this work was to synthesize CNTs on the surface of a flexible and conductive material: 304 stainless steel. We focused on optimizing the growth processes by plasma enhanced chemical vapor Deposition (PECVD) and water assisted chemical vapor deposition (WACVD) with and without the contribution of external catalyst material. In addition, as will be seen in the development of this work there is an important effort to understand the effects that thermal processes, necessary for CNTs growth, produced on the properties of steel. Especially the influence on corrosion resistance, since the final use of stainless steel CNTs is the manufacture of electrodes exposed to corrosive environments.La capacidad de los seres humanos para estudiar, manipular y comprender la materia a escala nanométrica nos ha permitido desarrollar materiales que pueden combinar propiedades físicas, químicas, ópticas, magnéticas y mecánicas que los materiales a granel no poseen. Uno de los materiales que despertó el interés en el mundo de la Nanociencia y la Nanotecnología fueron los nanotubos de carbono (CNTs por sus siglas en inglés). Estas nanoestructuras ya habían sido reportadas hace más de cuarenta años, pero no es hasta principios de los años 90 que el Dr. Sumio Iijima logra producirlas en condiciones estables en su laboratorio. A partir de ese momento, los recursos dedicados a la investigación y producción de estos materiales basados en el carbono fueron en aumento. Aunque hoy en día no captan el mismo interés científico que hasta 2010, su importancia en el mundo científico y especialmente en el mercado es relevante. De hecho, ya que la tecnología para la producción de CNTs a escala industrial ha madurado, estos se encuentran en un gran número de aplicaciones, tales como en el refuerzo de polímeros, actuando como andamiajes para el crecimiento de tejidos artificiales, en la fabricación de tintas conductoras o como parte de los electrodos para baterías y de los supercondensadores de nueva generación. Es precisamente en esta última aplicación donde el interés científico se ha centrado con especial atención. Junto con otros materiales a base de carbono, como el grafeno, son excelentes materiales de soporte para materiales con alta capacitancia. Los grupos de investigación y las empresas de todo el mundo están invirtiendo muchos recursos en la obtención de electrodos que tienen una arquitectura tridimensional a nanoescala y cuya superficie específica es elevada. En ese sentido, el objetivo de este trabajo fue sintetizar CNTs sobre la superficie de un material flexible y conductor: el acero inoxidable 304. Nos centramos en la optimización de los procesos de crecimiento mediante el depósito químico en fase de vapor asistido por plasma (PECVD por sus siglas en inglés) y el depósito químico en fase de vapor asistido por agua (WACVD por sus siglas en inglés) con y sin la contribución de material de catalizador externo. Además, como se verá en el desarrollo de este trabajo, hubo un esfuerzo importante para entender los efectos que los procesos térmicos, necesarios para el crecimiento de CNTs, producen sobre las propiedades del acero. Especialmente la influencia en la resistencia a la corrosión, ya que el uso final de los CNTs en acero inoxidable es la fabricación de electrodos expuestos a ambientes corrosivos.
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Міхно, Світлана Василівна, Свитлана Васильевна Михно, Svitlana Vasylivna Mikhno, and M. Sergienko. "Carbon nanotubes." Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/13469.
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Vishnubhatla, Kapil Bharadwaj. "Catalyst Immobilization for Patterned Growth of Carbon Nanotubes." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1282053821.
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Maestro, Luis Fernando. "Aperfeiçoamentos na obtenção de nanotubos de carbono com paredes simples (NTCPS) e possíveis aplicações na estocagem de energia." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277457.
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Orientador: Carlos Alberto LuengoDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
Made available in DSpace on 2018-08-04T03:18:18Z (GMT). No. of bitstreams: 1 Maestro_LuisFernando_M.pdf: 1958027 bytes, checksum: cb56dc89c2faea48a95f3fa1350d5666 (MD5) Previous issue date: 2005
Resumo: Desde a sua descoberta em 1991, os Nanotubos de Carbono (NTC) têm atraído muito a atenção da comunidade científica, devido as suas propriedades. Neste trabalho é apresentada uma breve revisão das pesquisas em NTC e algumas definições básicas relevantes para a sua estrutura e propriedades. Em vista da utilização deste material em uma futura aplicação e devido ao interesse do grupo na área de energia, é apresentado o estado da arte do armazenamento de Hidrogênio e, em particular, no armazenamento em sólidos de grande área superficial, classe a qual os NTC pertencem. Apresentam-se as modificações realizadas em um Reator de Arco Elétrico (Forar II) para se realizar a Síntese de NTC, são relatadas as experiências e a caracterização das amostras obtidas utilizando-se Microscopia Eletrônica de Varredura e Espectroscopia Raman.
Abstract: Since their discovery in 1991 Carbon Nanotubes (CNT) have received increasing attention by the scientific community due to their properties. Here is presented a brief review of ongoing CNT research, and basic definitions useful to understand their structure and significant properties. Because of future applications in the energy area, are presented developments in Hydrogen storage, more specifically its adsorption in solids with large internal surface areas, a characteristic of CNT materials. Modifications of the existing FORAR II to obtain CNT by the electric arc method are presented, and a description of the routines employed to obtain CNT. The characterization of catalysts and CNT by Scanning Electron Microscopy and Raman Spectroscopy are presented and discussed.
Mestrado
Física da Matéria Condensada
Mestre em Física
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Maguer, Aude. "Manipulation et fonctionnalisation de nanotube : Application aux nanotubes de nitrure de bore." Phd thesis, Paris 11, 2007. http://www.theses.fr/2007PA112215.
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Cette thèse se divise en deux parties autour des nanotubes de nitrure de bore (NTBN) et de carbone. La première partie concerne la synthèse, la purification et la fonctionnalisation chimique des NTBN. Des NTBN monofeuillets sont synthétisés par vaporisation LASER d’une cible de hBN. L’amélioration des paramètres de la synthèse a d’abord permis de limiter les sous-produits (hBN, acide borique). Un procédé de purification des échantillons a ensuite été développé pour les enrichir en nanotubes. Les échantillons purifiés ont été ensuite utilisés pour développer deux nouvelles voies de fonctionnalisation chimique des NTBN impliquant des molécules possédant une affinité marquée pour le réseau de BN. L’utilisation d’une quinuclidine et d’une borazine greffées par des chaînes alkyles a ainsi permis la solubilisation des NTBN en milieu organique. La purification et la fonctionnalisation développées pour les NTBN monofeuillets ont été appliquées avec succès à des NTBN multifeuillets. La sensibilité du bore aux neutrons thermiques a enfin servi de point de départ à l’étude des possibilités de fonctionnalisation covalente du réseau. La seconde partie de cette thèse concerne la séparation des nanotubes de carbone en fonction de leurs propriétés. L’irradiation microondes de nanotubes de carbone a d’abord permis l’enrichissement d’échantillons initialement polydisperses en nanotubes de grand diamètre. Une seconde stratégie impliquant une interaction sélective entre un type de tubes et des micelles de fullérènes fonctionnalisés a enfin été envisagée pour solubiliser sélectivement des nanotubes de carbone de propriétés électroniques donnéesThis PhD work is divided into two parts dealing with boron nitride (BNNT) and carbon nanotubes. The first part is about synthesis, purification and chemical functionalization of BNNT. Single-walled BNNT are synthesized by LASER ablation of a hBN target. Improving the synthesis parameters first allowed us to limit the byproducts (hBN, boric acid). A specific purification process was then developed in order to enrich the samples in nanotubes. Purified samples were then used to develop two new chemical functionalization methods. They both involve chemical molecules that present a high affinity towards the BN network. The use of long chain-substituted quinuclidines and borazines actually allowed the solubilization of BNNT in organic media. Purification and functionalization were developed for single-walled BNNT and were successfully applied to multi-walled BNNT. Sensibility of boron to thermic neutrons finally gave birth to a study about covalent functionalization possibilities of the network. The second part of the PhD work deals with separation of carbon nanotubes depending on their properties. Microwave irradiation of carbon nanotubes first allowed the enrichment of initially polydisperse samples in large diameter nanotubes. A second strategy involving selective interaction between one type of tubes and fullerene micelles was finally envisaged to selectively solubilize carbon nanotubes with specific electronic properties
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Martinčić, Markus. "Encapsulation of inorganic payloads into carbon nanotubes with potential application in therapy and diagnosis." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/458136.
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Los nanotubos de carbono representan un grupo de materiales relativamente nuevo con potencial aplicación en diferentes áreas científicas. Esta tesis se centra en beneficiarse de sus cavidades internas para encapsular compuestos biomédicamente relevantes. Los nanotubos de carbono permiten el confinamiento de materiales en su interior impidiendo su fuga y, en consecuencia, reduciendo los efectos secundarios, no deseados, de estos materiales en el medio circundante. Esto hace que los nanotubos de carbono sean unos vectores elegantes para el diagnóstico y tratamiento de enfermedades.
Se ha demostrado que el proceso utilizado para purificar muestras de nanotubos de carbono permite no sólo la reducción de impurezas, que podrían causar citotoxicidad, sino también acortar la longitud de los nanotubos. Teniendo en cuenta que el análisis termogravimétrico es una técnica ampliamente utilizada para evaluar la pureza de muestras de nanotubos de carbono, se ha investigado la influencia que tienen diferentes parámetros que controlan este análisis para asegurar que los resultados obtenidos son lo más precisos y representativos posible. El proceso de purificación también ha sido reajustado para minimizar la cantidad de catalizador en muestras de nanotubos de carbono. También hemos desarrollado un protocolo que permite determinar el contenido de catalizador en muestras de nanotubos de carbono mediante espectroscopía ultravioleta-visible de una manera precisa y fiable.
Se ha investigado la preparación de cloruro de samario(III) anhidro a partir de óxido de samario(III), así como la capacidad que ofrece el material preparado para el llenado de nanotubos de carbono, ya que éste tiene interés para el desarrollo de radiotrazadores. El proceso de llenado de nanotubos de carbono resulta en muestras que contienen grandes cantidades de material externo, no encapsulado, lo cual puede comprometer el rendimiento del material en el contexto biológico. Hemos desarrollado un protocolo para monitorizar la eliminación del material no encapsulado a través de espectroscopía de ultravioleta-visible, que a la vez permite mejorar el procedimiento de lavado.
El uso de nanotubos de carbono multicapa tiene algunos beneficios sobre sus homólogos monocapa debido a la presencia de una cavidad interna más grande que puede contener más material. Se ha investigado el cierre espontáneo de las puntas de nanotubos de carbono multicapa a través de su calentamiento térmico a diferentes temperaturas, así como la encapsulación de distintos materiales en el mismo rango de temperaturas. Finalmente, distintas muestras de nanotubos de carbono multicapa llenos han sido examinadas in-vitro con el fin de evaluar su citotoxicidad y la captación celular de los nanosistemas desarrollados.Carbon nanotubes present a relatively novel group of materials with potential application in different scientific fields. The scope of this Thesis is to benefit from their inner cavities to encapsulate biomedically relevant payloads. Carbon nanotubes allow the confinement of selected materials within their walls, preventing their leakage and, as a consequence, undesired effects of such materials to the surrounding media. This makes filled carbon nanotubes very elegant vectors for the diagnosis and therapy of diseases. The process used to purify samples of carbon nanotubes proved to be a valuable asset, not only in the reduction of impurities which might cause cytotoxicity, but also for shortening the length of nanotubes. Thermogravimetric analysis is a widely-used technique in evaluating the purity of carbon nanotube samples. The role of different parameters that control the analysis has been investigated to assure that the most appropriate and representative results are obtained. The purification process has also been readjusted to assure the presence of the lowest amount of catalyst possible in the carbon nanotube samples with the employed purification strategy. We have also introduced a simple UV-Vis spectrophotometric assertion of the catalyst content in samples of nanotubes in a precise and reliable manner. The preparation of dry samarium(III) chloride from samarium(III) oxide was investigated, together with the nanotube filling-ability of the prepared material, of interest for the development of radiotracers. Bulk filling of carbon nanotubes results in samples that contain a large amount of external, non-encapsulated material, which can compromise the performance of the material in the biological context. We have developed a protocol to monitor the removal of the non-encapsulated material by means of UV-Vis, which in turn allows improving the washing procedure. The usage of multi-walled carbon nanotubes has some benefits over their single-walled counterparts, due to the presence of a bigger cavity which can host more material. The spontaneous closure of the tips of multi-walled carbon nanotubes by thermal annealing was investigated at different temperatures, along with the encapsulation of different materials. The prepared filled multi-walled samples were tested in-vitro to assess cytotoxicity and cellular uptake of the developed nanosystems.
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Durán, Valdeiglesias Elena. "Study of optical and optoelectronic devices based on carbon nanotubes." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS100/document.
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La photonique silicium est reconnue comme la technologie à même de répondre aux nouveaux défis des interconnexions optiques. Néanmoins, la photonique silicium doit faire face à d'importants défis. En effet, le Si ne peux pas émettre ou détecter de la lumière dans la plage de longueurs d'onde des télécom (1,3 µm à 1,5 µm). Par conséquent, les sources et les détecteurs sont mis en œuvre avec du Ge et des matériaux III-V. Cette approche multi-matériaux complique la fabrication des dispositifs et augmente le coût final du circuit. Cependant, les nanomatériaux ont été identifiés comme alternative pour la mise en œuvre d’émetteurs-récepteurs moins chers et plus petits.Cette thèse est dédiée à l'étude et au développement de dispositifs optiques et optoélectroniques sur la plateforme photonique silicium basés sur l’utilisation de nanotubes de carbone mono paroi (SWCNT). L’objectif principal est de démontrer les blocs fonctionnels de base qui ouvriront la voie à une nouvelle technologie photonique dans laquelle les propietés actives proviennent des nanotubes de carbone.Les nanotubes de carbone ont été étudiés comme matériaux pour la nanoélectronique avec la démonstration de transistors ultra-compacts à hautes performances. De plus, les SWCNTs semi-conducteurs (s-SWCNTs) sont également des matériaux très intéressants pour la photonique. Les s-SWCNTs présentent une bande interdite directe qui peut être ajustée dans la gamme de longueurs d'onde du proche infrarouge en choisissant le bon diamètre. Les s-SWCNT présentent une photoluminescence et une électroluminescence, pouvant être exploitées pour la mise en œuvre de sources de lumière. Ils présentent également diverses bandes d’absorption pour la réalisation de photodétecteurs. Ces propriétés font que les nanotubes de carbone sont des candidats très prometteurs pour le développement de dispositifs optoélectroniques pour la photonique.Le premier objectif de la thèse était l'optimisation des solutions de nanotubes de carbone. Une technique de tri par ultra-centrifugation assistée par polymère a été optimisée, donnant des solutions de haute pureté en s-SWCNT. Sur cette base, plusieurs solutions de s-SWCNTs ont été élaborées pour obtenir des SWCNTs émettant dans les longueurs d'onde comprise entre 1µm et 1,6µm.Le deuxième objectif était d’étudier l'interaction des s-SWCNT avec des guides d'onde silicium et des résonateurs optiques. Plusieurs géométries ont été étudiées dans le but de maximiser l'interaction des s-SWCNT avec le mode optique en exploitant la composante transverse du champ électrique. D'autre part, une approche alternative a été proposée et démontrée en utilisant la composante longitudinale du champ électrique. En utilisant la composante longitudinale, une amélioration de la photoluminescence, un seuil d’émission avec la puissance de pompe ainsi qu’un rétrécissement de la largeur spectrale des résonances dans les microdisques ont été observés. Ces résultats sont un premier pas très prometteur vers la démonstration d’un laser intégré à base de SWNTs.Le troisième objectif était d'étudier les dispositifs optoélectroniques à base de s-SWCNTs. Plus spécifiquement, une diode électroluminescente (DEL) et un photodétecteur ont été développés, permettant la démonstration du premier lien optoélectronique sur puce basé sur les s-SWCNT.Le dernier objectif de la thèse était d'explorer le potentiel de s-SWCNT pour l’optique non linéaire. Il a été démontré expérimentalement, qu’en choisissant la chiralité des s-SWCNTs, le signe du coefficient Kerr pouvait être soit positif ou négatif. Cette capacité unique ouvre un nouveau degré de liberté pour contrôler les effets non linéaires sur puce, permettant de compenser ou d'améliorer les effets non linéaires pour des applications variéesSilicon photonics is widely recognized as an enabling technology for next generation optical interconnects. Nevertheless, silicon photonics has to address some important challenges. Si cannot provide efficient light emission or detection in telecommunication wavelength range (1.3μm-1.5μm). Thus sources and detectors are implemented with Ge and III-V compounds. This multi-material approach complicates device fabrication, offsetting the low-cost of Si photonics. Nanomaterials are a promising alternative route for the implementation of faster, cheaper, and smaller transceivers for datacom applications.This thesis is dedicated to the development of active silicon photonics devices based on single wall carbon nanotubes (SWCNTs). The main goal is to implement the basic building blocks that will pave the route towards a new Si photonics technology where all active devices are implemented with the same technological process based on a low-cost carbon-based material, i.e. SWCNT.Indeed, carbon nanotubes are an interesting solution for nanoelectronics, where they provide high-performance transistors. Semiconducting SWCNT exhibit a direct bandgap that can be tuned all along the near infrared wavelength range just by choosing the right tube diameter. s-SWCNTs provide room-temperature photo- and electro- luminescence and have been demonstrated to yield intrinsic gain, making them an appealing material for the implementation of sources. SWCNTs also present various absorption bands, allowing the realization of photodetectors.The first objective of this thesis was the optimization of the purity of s-SWCNT solutions. A polymer-sorting technique has been developed and optimized, yielding high-purity s-SWCNT solutions. Based on this technique, several solutions have been obtained yielding emission between 1µm and 1.6µm wavelengths.The second objective was the demonstration of efficient interaction of s-SWCNT with silicon photonics structures. Different geometries have been theoretically and experimentally studied, aiming at maximizing the interaction of s-SWCNT with optical modes, exploiting the electric field component transversal to light propagation. An alternative approach to maximize the interaction of s-SWCNT and the longitudinal electric field component of waveguide modes was proposed. Both, a power emission threshold and a linewidth narrowing were observed in several micro disk resonators. These results are a very promising first step to go towards the demonstration of an integrated laser based on CNTs.The third objective was to study optoelectronic SWCNT devices. More specifically, on-chip light emitting diode (LED) and photodetector have been developed, allowing the demonstration of the first optoelectronic link based on s-SWCNT. s-SWCNT-based LED and photodetector were integrated onto a silicon nitride waveguide connecting them and forming an optical link. First photodetectors exhibited a responsivity of 0.1 mA/W, while the complete link yielded photocurrents of 1 nA/V.The last objective of the thesis was to explore the nonlinear properties of s-SWCNT integrated on silicon nitride waveguides. Here, it has been experimentally shown, for the first time, that by choosing the proper s-SWCNT chirality, the sign of the nonlinear Kerr coefficient of hybrid waveguide can be positive or negative. This unique tuning capability opens a new degree of freedom to control nonlinear effects on chip, enabling to compensate or enhancing nonlinear effects for different applications
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Woods, Richard David. "Functionalised Flagellar Nanotubes." Thesis, University of Nottingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489968.
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This project investigated the Potential for using the bacterial flagellar filament as a functionalized protein nanotube. A varied approach to flagellin engineering was taken using the flagella of E. coli and R. sphaeroides, with engineered flagellar flilaments from E. coli proving successful. A variety ofepitopes were inserted into the E. coli flagellin, resulting in filaments which displayed adhesive peptides or cleaveable sites. His-tagged filaments allowed the binding of metal ions and nanoparticles, and the biotin-avidin system was empl~yed to allow more specific binding of ligands. Cys-tagged filaments were 'made to order' for a collaborator to allow improved binding of gold to flagellar filaments. The TEV protease recognition site was used to allow specific cleavage of the surface displayed portion of the flagellin within the intact filament structure. Other proteases allowed further digestion ofthis surface displayed region. By combining the adhesive epitope with flanking TEV protease sites selective excision of the tag was possible, allowing the potential for directed whole filament removal from a surface or scaffold in applications such as nanolithography. An in trans expression system was developed to allow assembly of different flagellins into the same filament, with expression levels varied to result in specific ratios of each functionalised monomer. This allowed the creation of bi-functional protein nanotubes, which could bind more than one ligand.
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Monet, Geoffrey. "Nanotubes géo-inspirés : structure atomique, transformation en température et dynamiques corrélées nanotube-eau moléculaire." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS388/document.
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Ce travail de thèse est consacré à l’étude de nanotubes géo-inspirés des nanotubes d’imogolite naturels présents dans certains sols et à celle des propriétés dynamiques de l’eau dans ces objets. Les objets étudiés, de stoechiométrie Ge(Si)Al₂O₇H₄ et Ge(Si)Al₂O₆CH₆, sont des nanotubes d’aluminosilicate et d’aluminogermanate dont la paroi interne est tapissée soit de groupements hydroxyles, hydrophiles, soit de groupements méthyles, hydrophobes. Dans le premier chapitre de ce manuscrit, nous présentons un état des connaissances sur ces nanotubes et nous introduisons la thématique de l’eau confinée. Le second chapitre est consacré à l’analyse de la structure des nanotubes sur la base d’expériences de diffusion des rayons X sur poudre. Nous y introduisons une nouvelle méthodologie, fondée sur l’utilisation des symétries hélicoïdales et la minimisation d’une énergie semi-empirique, permettant de réduire la détermination d’une structure tubulaire complexe à l’évaluation de quelques paramètres géométriques. Grâce à cette procédure, nous déterminons la structure des nanotubes d’aluminosilicate et d’aluminogermanate méthylés et hydroxylés. En particulier, un mode d’enroulement différent pour les nanotubes méthylés et hydroxylés est mis en évidence. Dans le troisième chapitre, nous présentons l’étude expérimentale des transformations en température des nanotubes d’aluminogermanate hydroxylés, jusqu’à 1000°C, grâce à une approche multitechnique associant la spectroscopie d’absorption X in situ aux seuils K de l’aluminium et du germanium, la spectroscopie RMN, la spectroscopie infrarouge et la diffusion des rayons X. Le quatrième chapitre est consacré à l’étude de la dynamique de l’eau dans les nanotubes d’aluminogermanate hydroxylés et méthylés, par diffusion inélastique des neutrons. Dans le cas des nanotubes hydroxylés, les expériences sont analysées à la lumière de simulations de dynamique moléculaire. Nous montrons que l’eau liée à la paroi interne des nanotubes présente une structuration originale et que les dynamiques de l’eau et du nanotube sont fortement corréléesThis thesis focuses on the investigation of nanotubes geo-inspired from natural imogolite nanotubes present in some soils and on the dynamical properties of water confined in these objects. These objects with nominal stoichiometry Ge(Si)Al₂O₇H₄ and Ge(Si)Al₂O₆CH₆, are aluminosilicate and aluminogermanate nanotubes whose inner wall is covered with either hydrophilic hydroxyl groups or hydrophobic methyl groups. In the first chapter of this manuscript, we present a state of knowledge on these nanotubes and introduce the topic of confined water. The second chapter is dedicated to the analysis of the structure of nanotubes thanks to X-ray powder scattering experiments. We introduce a new methodology, based on the use of helical symmetries and on the minimization of semi-empirical energy, which reduces the determination of a complex tubular structure to the evaluation of some geometric parameters. With this procedure, we solve the structure of both methylated and hydroxylated aluminosilicate and aluminogermanate nanotubes. In particular, a different rolling mode is highlighted for methylated and hydroxylated nanotubes. In the third chapter, we present the experimental study of the thermal transformations of hydroxylated aluminogermanate nanotubes, up to 1000°C. This work is the result of a multi-technical approach combining in situ X-ray absorption spectroscopy at the K thresholds of aluminium and germanium, NMR spectroscopy, infrared spectroscopy and X-ray scattering. The fourth chapter focuses on the study of water dynamics in hydroxylated and methylated aluminogermanate nanotubes by inelastic neutron scattering. For hydroxylated nanotubes, experiments are analyzed in the light of molecular dynamics simulations. We show that the water layer bound to the inner wall of the nanotubes presents an original structure and that the dynamics of water molecules and of the nanotube are strongly correlated
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Sippel-Oakley, Jennifer A. "Charge induced actuation in carbon nanotubes and resistance changes in carbon nanotube networks." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0010052.
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Liu, Ying-Chun, Joshua D. Moore, Qu Chen, Thomas J. Roussel, Qi Wang, and Keith E. Gubbins. "Crossover from single-file to fickian diffusion in carbon nanotubes and nanotube bundles." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-188932.
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The diffusion mechanism of pure component Ar and binary mixtures of Ar/Kr and Ar/Ne confined in single-walled carbon nanotubes (SWNTs) and bundles was investigated by a combined Grand Canonical Monte Carlo and molecular dynamics study.
For Ar confined in SWNTs, a crossover from single-file to Fickian diffusion existed when the density of Ar was a minimum as a function of the SWNT diameter. Argon diffused by a single-file mechanism in SWNTs smaller than an accessible diameter of 1.76σAr, corresponding to (7,7), (12,0) and (8,6) SWNTs but by a Fickian mechanism for SWNTs larger in diameter. Both components in Ar/Kr mixtures had a single-file diffusional mechanism in (6,6) and (7,7) SWNTs and a Fickain mechanism for SWNTs larger in diameter. Likewise, both components in a Ar/Ne mixtures had a single-file diffusional mechanism in a (6,6) CNT, and Ar had a single-file diffusional mechanism in a (7,7) SWCNT. However, Ne in the Ar/Ne mixture exhibited Fickian diffusion in the (7,7) SWNT , which
indicated bi-modal diffusion. Larger diameters of SWNTs provided Fickian diffusion for both components in an Ar/Ne mixture. Argon diffused in a (25,0) SWNT bundle (with a bimodal pore size distribution) in a bimodal mechanism, with Ar diffusing in single-file in interstitial sites and in a Fickian mechanism in inner nanotube channels.
In all cases of single-file diffusion the mean-squared displacement (MSD) of the fluid molecules had a square root of time dependence, while molecules diffusing by a Fickian mechanism had a MSD with a linear time dependence.
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Casanova, Cháfer Juan. "Gas Sensing with Modified Carbon Nanotubes, Graphene and Diamondoids." Doctoral thesis, Universitat Rovira i Virgili, 2020. http://hdl.handle.net/10803/669791.
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Aquesta tesi està centrada en el desenvolupament de diferents sensors de gasos mitjançant la modificació de nanomaterials de carboni. Concretament, al llarg d’aquest treball s’han modificat nanotubs de carboni (CNT), grafè i nanodiamants, amb diferents aproximacions. Per exemple, s’ha procedit a la seva decoració amb nanopartícules d’òxids metàl·lics, la formació de monocapes auto-assemblades o la seva funcionalització amb diferents molècules o àtoms, entre altres estratègies. Malgrat que els nanomaterials de carboni presenten extraordinàries propietats electròniques, fisico-químiques, i mecàniques, encara no s’han pogut desenvolupar sensors a escala comercial basats en el seu ús. Açò és a causa de problemes intrínsecs en la detecció de molècules gasoses, com per exemple la seva baixa especificitat i limitada reactivitat. Per tant, en aquesta tesi s’han desenvolupat diversos sensors modificant els diferents nanomaterials de carboni amb la finalitat de millorar paràmetres clau en el sensat de gasos, com poden ser la selectivitat, sensibilitat i temps de resposta. A més a més, s’ha dut a terme una exhaustiva caracterització dels nous nanomaterials desenvolupats mitjançant tècniques espectroscòpiques i microscòpiques. Així mateix, s’han proposat detallats mecanismes de sensat, és a dir, s’han estudiat les interaccions fisico-químiques entre els nanomaterials i els gasos. Per tant, aquest treball ofereix una visió integral per al desenvolupament de nous sensors, des del seu disseny i caracterització, fins als seus principis de funcionament a escala atòmica. A més a més, considerant les inquietuds de la nostra societat, els sensors desenvolupats solen treballar a temperatura ambient, amb la conseqüent dràstica reducció del consum energètic. Com a conclusió, els nanomaterials de carboni desenvolupats són capaços de detectar gasos tòxics, com per exemple el diòxid de nitrogen, a concentracions traça, molt per sota dels límits establerts per la legislació.Esta tesis está centrada en el desarrollo de distintos sensores de gases mediante la modificación de nanomateriales de carbono. Concretamente, a lo largo de este trabajo se han modificado nanotubos de carbono (CNT), grafeno y nanodiamantes, con distintas aproximaciones. Por ejemplo, se ha procedido a su decoración con nanopartículas de óxidos metálicos, la formación de monocapas autoensambladas o su funcionalización con distintas moléculas o átomos, entre otras estrategias. A pesar de las extraordinarias propiedades electrónicas, físico-químicas y mecánicas de los nanomateriales de carbono, todavía no se han podido desarrollar sensores a nivel comercial basados en su uso. Esto es debido a sus problemas intrínsecos en la detección de moléculas gaseosas, como por ejemplo su baja especificidad y limitada reactividad. Por tanto, en esta tesis se han desarrollado diversos sensores modificando los nanomateriales de carbono con la finalidad de mejorar parámetros clave en la monitorización de gases, como puede ser la selectividad, sensibilidad y tiempos de respuesta. Además, se ha llevado a cabo una exhaustiva caracterización de los nuevos nanomateriales desarrollados mediante técnicas espectroscópicas y microscópicas. Asimismo, se han propuesto detallados mecanismos de detección, es decir, se han estudiado las interacciones físico-químicas entre los nanomateriales y los gases. Por tanto, este trabajo ofrece una visión integral para el desarrollo de nuevos sensores, desde su diseño y caracterización, hasta sus principios de funcionamiento a nivel atómico. Además, considerando las inquietudes de nuestra sociedad, los sensores desarrollados suelen trabajar a temperatura ambiente, con la consiguiente drástica reducción del consumo energético. Como conclusión, los nanomateriales de carbono desarrollados son capaces de detectar gases tóxicos, como por ejemplo el dióxido de nitrógeno, a concentraciones traza, muy por debajo de los límites establecidos por la legislación.
This thesis focuses in the development of different gas sensors through the modification of carbon nanomaterials. In particular, we employed carbon nanotubes (CNT), graphene and diamondoids, with different approaches. For instance, these nanomaterials were either decorated with metal oxide nanoparticles, modified of self-assembled monolayers of thiols or functionalized with different molecules or atoms, among other strategies. Despite the outstanding properties of carbon nanomaterials, such as their electronic, physicochemical and mechanical properties, it has not been possible so far to develop commercial sensors based on these nanomaterials. The main reason is derived from their inherent problems in the gas molecule detection process, such as low specificity and limited reactivity. Thus, we developed new gas sensors by modifying carbon nanomaterials to improve essential gas sensing parameters, such as selectivity, sensitivity and response time. Furthermore, an exhaustive material characterization was carried out through spectroscopic and microscopic techniques. Also, detailed gas sensing mechanisms were proposed, ergo, the physicochemical interactions between nanomaterials and gases were studied. In consequence, this thesis provides a comprehensive vision for the development of new gas sensors employing carbon nanomaterials, from their design and characterization to their working principles at to the atomic scale. In consideration of the social concerns, the sensors developed usually work at room temperature. Therefore, the device power-consumption was drastically reduced. In summary, the modified carbon nanomaterials employed in this thesis can detect harmful gases, such as nitrogen dioxide, at trace concentration, even at lower levels than those established by law as threshold limit values.
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Parlapalli, Rohit. "Effect of twist on load transfer and tensile strength in carbon nanotube bundles." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1382372894.
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Miranda, Reyes Cesar Alejandro. "Thermoelectric properties of carbon nanotube films." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/289715.
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Thermoelectric generators are solid state machines used to convert temperature gradients into electrical energy. They are formed by several thermoelectric units connected electrically in series and thermally in parallel. These units are made by creating a junction between a p-type and an n-type conductor. This investigation documents the characterisation of the thermoelectric properties of carbon nanotube (CNT) films and the fabrication process of carbon nanotube-based thermoelectric devices. The Seebeck coefficient is a intrinsic property of a thermoelectric material that correlates the voltage produced by a conductor and the temperature gradient applied to it. To measure the Seebeck coefficient of films, an experimental set-up was fabricated and calibrated using constantan as standard material. CNT films of aligned nanotubes fabricated using a chemical vapour deposition method were analysed. The Seebeck coefficient along and across the samples did not show significant variations, with values between 40$\mu$V/K and 80$\mu$V/K. Using these CNT films, thermoelectric cells were fabricated with the CNT as the p-type conductor and constantan as the n-type. As a proof of concept, two hand-made thermoelectric generators were assembled by connecting hundreds of these thermoelectric cells. These devices were subjected to a temperature gradient of $\approx$200K, which was enough to produce enough power to light an LED. Other analytical techniques were used to characterise the materials used in this work. Electrical conductivity measurements, thermogravimetric analysis, Raman spectroscopy and scanning electron microscopy were performed. Using a deposition technique, films of nanotubes were produced from a liquid phase. The impact of the production method on their properties was evaluated. Characterisation equipment was developed to measure the Seebeck coefficient and thermal conductivity. Thermoelectric devices made with the carbon nanotube films were fabricated and characterised. The values of thermal conductivity of the CNT films analysed in this work are between 0.86Wm$^{-1}$K$^{-1}$. The electrical conductivity of these materials is between 3500Sm$^{-1}$ and 14100Sm$^{-1}$. The maximum figure of merit of the carbon nanotube thermoelectric devices fabricated in this work is $ZT$=0.35.
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Papadopoulos, Christo. "Nanotube engineering and science, synthesis and properties of highly ordered carbon nanotube arrays and Y-junction carbon nanotubes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0018/MQ53443.pdf.
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Sattari, Andrea Poopak. "Field emission of carbon nanotubes and electroless silver deposition in carbon nanotubes, utilizing carbon nanotubes formed in porous aluminum oxide." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0004/MQ45626.pdf.
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Monereo, Cuscó Oriol. "Gas sensors based on carbon nanofibers: a low power consumption approach." Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/400488.
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Gas sensors can be found in many activities ranging from environment protection, risk prevention, agriculture and even in food, chemical, and petrochemical industries. There exist different technologies for gas sensors depending on the transduction mechanism: mass-sensitive, optical, calorimetric, magnetic, electrochemical and conductometric. In this work, conductometric (or resistive) gas sensors are studied. Conductometric devices base its operating principle on the variation of the electrical conductivity (resistivity) or conductance (resistance) of a reactive (active) material interacting with gas. A chemical reaction between the active material (surface or bulk) and the gas occurs. This reaction induces a variation on some electrical property of the material resulting in a change on the electrical signal (conductivity or resistivity of the active material) of the sensor. Therefore, the sensor material should be compatible with the mentioned properties above. A carbon based material was chosen to be the reactive compound for the conductometric sensors. This material, a specific type of carbon nanofibers (CNFs), shares some suitable properties with other trendy carbon based materials such as carbon nanotubes or graphene. Conductometric gas sensors usually are composed of two main parts: the already mentioned reactive material and the heater device. The heater is required in order to stabilize the temperature of operation and to activate a desired chemical reaction. Unfortunately, despite the efforts to improve the heater technology, this component is still the most power demanding part of the overall device. The here studied sensors have been characterized with a heater device, but also alternative energy sources and other sensing strategies have been tested in order to reduce the energy cost. Among these, the use of ultraviolet and visible light sources were tested in order to modulate the sensor properties. In addition, another non-common strategy was used to operate the sensor: the so called self-heating effect (or Joule effect). To obtain the electrical signal of a sensor, the reactive material have to be scanned, usually a current (or voltage) is applied to the sensor, then, the voltage (or current) is read. If the probing magnitude is increased, the power dissipation through the sensing material, and its temperature, also increases. Therefore, the sensor could be operated without a heater device with a considerable reduction of its power consumption. Moreover, the self-heating also allows reducing the fabrication complexity, as there is no need of the heater element.
In summary, the main objective of this work was to characterize the CNFs as a reactive material for conductometric sensors for low cost applications. First, the CNFs properties (electrical,
mechanical, response to light and gases) were screened with the aim to assess the applicability of the sensing material (O. Monereo et al., 2013, Flexible sensor based on carbon nanofibers with multifunctional sensing features). Then, the sensor was tested with the use of temperature modulation (S. Claramunt et al., 2013, Flexible gas sensor array with an embedded heater based on metal decorated carbon nanofibres). At this point, a more detailed characterization of the gas sensing properties with O2, H2O, NO2 and NH3 was conducted. Then, the use of continuous self-heating operation (O. Monereo et al., 2015, Self-heating effects in large arrangements of randomly oriented carbon nanofibers: Application to gas sensors) and pulsed self-heating application (O. Monereo et al., 2016, Self-heating in pulsed mode for signal quality improvement: application to carbon nanostructures-based sensors) were found to be efficient methodologies to modulate the sensing characteristics of sensor devices, based on large arrays of nanostructures. Among the benefits achieved, the sensor presented improvements on stability, specificity, the detection time modulation, all along the simplification of device fabrication and the reduction of the power consumption. Finally, the phenomenon of self-heating in carbon nanofibers and its origin was studied (O. Monereo et al., 2016, Localized self-heating in large arrays of 1D nanostructures). In addition, the use of ultraviolet and visible light as alternative energy sources was also assessed and compared with the self-heating operation. Finally, the applicability of self-heating was also tested in graphene based (reduced graphene oxide) and metal oxide based (ZnO) devices to test the applicability of self-heating in other relevant sensing materials.El objetivo principal de esta tesis es la caracterización de las nanofibras de carbono (CNFs) como material reactivo para sensores resistivos de gas para aplicaciones de bajo consumo. Primero, las propiedades eléctricas, mecánicas y respuesta a luz y gases de las CNFs fueron evaluadas para comprobar la aplicabilidad del material sensor (O. Monereo et al., 2013, Flexible sensor based on carbon nanofibers with multifunctional sensing features). Posteriormente, la respuesta del sensor a gases fue estudiada con modulación de temperatura (S. Claramunt et al., 2013, Flexible gas sensor array with an embedded heater based on metal decorated carbon nanofibres). En este punto, una caracteritzación más detallada de la respuesta del sensor a gases modulados con temperatura se realizó con O2, H2O, NO2 y NH3. A continuación, el uso de la metodología de auto-calentamiento continuo (O. Monereo et al., 2015, Self-heating effects in large arrangements of randomly oriented carbon nanofibers: Application to gas sensors) y pulsado (O. Monereo et al., 2016, Self-heating in pulsed mode for signal quality improvement: application to carbon nanostructures-based sensors) han sido probados como formas energéticamente eficientes para modular la respuesta de sensores basados en grandes matrices de CNFs. Entre los beneficios encontrados, consta una mejora de la estabilidad, especificidad, la modulación del tiempo de detección; todo añadiendo la simplificación de la fabricación. Finalmente, el origen del fenómeno de auto-calentamiento en CNFs fue estudiado en detalle (O. Monereo et al., 2016, Localized self-heating in large arrays of 1D nanostructures). Además, la aplicabilidad de la metodología fue también probada en nanotubos de carbono, óxido de grafeno reducido y nanohilos de óxido de zinc. Finalmente, el uso de luz ultraviolada y visible ha sido estudiado como a energías alternativas para la modulación de los sensores de gases de CNFs.
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Benoit, Jean-Michel. "Transport et propriétés vibrationnelles des nanotubes de carbone et composites polymère - nanotubes." Nantes, 2001. http://www.theses.fr/2001NANT2045.
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Les nanotubes de carbone, nouvelle forme allotropique du carbone, sont promis à un bel avenir grâce à leurs propriétés exceptionnelles (électroniques, mécaniques. . . ), notamment pour les applications dans les nanotechnologies. L'objectif de cette thèse vise à élucider les mécanismes de transport électrique et les propriétés vibrationnelles de ces nanotubes de carbone. Dans un premier temps, l'étude des nanotubes multifeuillets par spectroscopie Raman a permis de mettre en évidence des modes de phonons de basse énergie, modes de vibration déjà observés pour les nanotubes monofeuillets. Nous montrons que ces modes sont intrinsèques à chacun des feuillets constituant le nanotube et que leur énergie de vibration résulte du couplage entre les différents feuillets. .
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Abraham, Jürgen. "Functionalization of carbon nanotubes." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=97712293X.
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Nordlinder, Sara. "Nanotubes for Battery Applications." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5870.
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Korneva, Guzeliya Gogotsi IU G. Schweitzer-Stenner Reinhard. "Functionalization of carbon nanotubes /." Philadelphia, Pa. : Drexel University, 2008. http://hdl.handle.net/1860/2797.
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Samsonidze, Georgii G. "Photophysics of carbon nanotubes." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38921.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references (leaves 213-233).
This thesis reviews the recent advances made in optical studies of single-wall carbon nanotubes. Studying the electronic and vibrational properties of carbon nanotubes, we find that carbon nanotubes less than 1 nm in diameter exhibit dramatic changes in their electron and phonon dispersion relations due to the curvature of the nanotube sidewall and the enhanced electron correlation effects associated with one dimensionality. The optical transition energies in small-diameter carbon nanotubes show a strong dependence on their geometrical structure, as was first observed in the photoluminescence experiments. The frequencies of the Raman-active phonon modes also become very sensitive to the geometrical structure of small-diameter carbon nanotubes. In particular, certain phonon modes exhibit anomalous behavior that significantly affects resonance Raman spectra of small-diameter carbon nanotubes. We have developed the extended tight-binding and advanced force-constant models that properly take into account the curvature effects in the small-diameter limit. The many-body corrections are fitted to the photoluminescence and resonance Raman spectroscopy data.
(cont.) The resulting extended tight-binding model with semiempirical many-body corrections shows a good agreement with the experimental results. The electron-photon and electron-phonon transition matrix elements are calculated within the framework of the extended tight-binding model. Finally, the photoluminescence and Raman intensities in the graphene sheet and carbon nanotubes are calculated. The calculated intensities show a reasonable agreement with the experimental results and allow structural characterization of carbon nanotubes by their spectroscopic signatures.
by Georgii G. Samsonidze.
Ph.D.
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Singh, Charanjeet. "Synthesis of carbon nanotubes." Thesis, University of Cambridge, 2002. https://www.repository.cam.ac.uk/handle/1810/272043.
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Chauveau, Anne. "Cellules NK et nanotubes." Aix-Marseille 2, 2009. http://www.theses.fr/2009AIX22083.
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Mon travail de thèse s'est attaché à décrire et comprendre le rôle des nanotubes formés par les cellules Natural Killer (NK). Nous avonx observé que la formation de nanotubes par les cellules NK est consécutif à un contact initial prolongé avec leurs cibles et qu'elle est en partie contrôlée par le nombre d'intreractions récepteurs/ligands ainsi que par l'état d'activation des cellules NK. De plus, nous avons démontré que des protéines s'accumulent à la jonction formée par le nanotube et le coprs cellulaire de la cellule cible, dont DAP10, la protéine adaptatrice associée au récepteur activateur NKG2D, ainsi que son ligand, MICA. Cette accumulation de récepteurs/ligands au niveau de ce petit contact synaptique est associée à l'initiation d'événements de singalisation déterminés par la présence à cette jonction de protéines phosphorylées et par le recrutement de Vav-1, protéine de signalisation. Enfin, la connexion dec cellules NK avec leurs cibles via les nanotubes est corrélée à l'apparition d'un phénotype de mort cellulaire des cellules cibles. Nous avons ainsi pu mettre en évidence que les cellules NK forment des nanotubes membranaires qui leur permettent de communiquer à distance avec leurs ciblesMembrane nanotubes are menbranous tethers that commonly connect cells over long-distances. Here, we report that chen human Natural Killer (NK) cells make contact with target cells and subsequently depart ; up to 20% of NK cells remain connected by a membrane nanotube. The frequency of nanotube formation is controlled, at least in part, by the number of receptor/ligrand interactions between cells and by the activation status of the NK cells. Importantly, NK cell nanotubes are not open-ended tunnels but instead contain a small synaptic contact or junction. At this small synapse,, proteins accumulate that include the signalling adaptator protein DAP10, associated with the activating receptor NKG2D, and the NKG2D ligand MICA. This micrometer-scale immune synapse is active in signalling as avidenced by a large accumulation of tyrosine-phosphorylated proteins and the recruitment of Vav-1 proteins. Moreover, these nanotubular conncections can aid NK cells in lysing distant target cells either directly or by pulling back target cells into close contact to be killed via a conventional synapse. Together, our data suggest that membrane nanotubes allow NK cells to functionally interact with target cells over long distances
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Проценко, Олена Борисівна, Елена Борисовна Проценко, Olena Borysivna Protsenko, and N. V. Bondar. "Application of carbon nanotubes." Thesis, Сумський державний університет, 2013. http://essuir.sumdu.edu.ua/handle/123456789/33511.
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During the last years carbon nanotubes have attracted a great interest of world scientists. Nowadays researchers study their properties, perform the experiment in the laboratories anddevelop a set of theories about their practical application.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/33511
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Borghi, Nicolas. "Nanotubes membranaires : extrusion hydrodynamique." Paris 6, 2006. http://www.theses.fr/2006PA066556.
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Afshari, R., S. Mazinani, M. Abdouss, E. Asadi, and A. Haji. "Carbon Nanotubes-Chitosan-Molecularly Imprinted Polymer Nano-Carriers Synthesis for Nanomedicine Application." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35211.
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Carbon nanotube-natural biopolymer nanovectors have important potential applications in delivery system for drugs and biomolecules. In this work, the use of multi-wall CNTs as nanoreserviors for drug loading and controlled release is demonstrated .We synthesized CNT-based Drug delivery systems; MWCNT-CS nanoparticles based on an ionotropic gelation method as a sustained-release systems for the delivery of Tenofovir (hydrophilic anti-retroviral drug).
Molecularly imprinted polymer used as shell for encapsulating the synthesized polymer to reduce the toxicity of CNT and improved theit application in Drug Delivery System. The prepared nanoparticles were characterized by FTIR spectroscopy. TGA was applied to study the thermal stabilities, and SEM to investi-gate the morphology.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35211
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Pereira, Aline Cristina [UNESP]. "Estudo da cinética de cura e das propriedades térmicas da resina benzoxazina e de seus compósitos nanoestruturados." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/94420.
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As resinas polibenzoxazinas constituem uma nova classe de resinas fenólicas termorrígidas que surgiram nas últimas décadas, superando as propriedades das tradicionais resinas epóxi e fenólicas aplicadas na indústria aeroespacial. A incorporação de baixa concentração em massa de nanotubo de carbono (NTC) em matrizes poliméricas pode produzir materiais estruturais com propriedades superiores. Nesse sentido, o presente trabalho tem como objetivo a preparação de compósitos nanoestruturados de resina benzoxazina/NTC, bem como o estudo da cinética de cura da resina benzoxazina e de seus compósitos nanoestruturados. Além disso, objetiva-se, ainda, a caracterização térmica da resina benzoxazina curada e de seus compósitos nanoestruturados também curados pelo mesmo ciclo de cura. O estudo da cinética de cura foi realizado por meio da técnica de calorimetria exploratória diferencial (DSC) sob condições não-isotérmicas (dinâmicas). A caracterização térmica foi realizada por meio do uso de termogravimetria, da análise dinâmico-mecânica, da análise termomecânica, do DSC e por análises de espectroscopia de infravermelho com transformada de Fourier e microscopia eletrônica de varredura. A partir destas análises, concluiu-se, de maneira geral, que os nanotubos de carbono agem como catalisadores da cura da matriz de benzoxazina sem afetar suas temperaturas iniciais e finais de polimerização. A adição de NTC não modifica a estabilidade térmica da resina benzoxazina e nem a temperatura de transição vítrea (Tg) dos compósitos nanoestruturados, com exceção da adição de 0,1% em massa de NTC na matriz polimérica que gera um aumento na Tg
Polibenzoxazine resins are a new class of thermosetting phenolic resins that have emerged in recent decades, overcoming the traditional properties of epoxy and phenolic resins applied in the aerospace industry. The addition of small amount of carbon nanotube in polymeric matrices can produce superior structural materials. Thus, this work aims to prepare nanostructured composite benzoxazine resin/NTC as well the study of the cure kinetic of neat benzoxazine resin and their nanostructured composites produced. Moreover, the objective is also the thermal characterization of cured neat benzoxazine resin and their composites nanostructured also cured by the same cure cycle. The study of cure kinetics was performed using the technique of differential scanning calorimetry (DSC) under non-isothermal (dynamic). The thermal characterization was performed by using thermogravimetry, dynamic mechanical analysis, thermomechanical analysis, DSC analysis and infrared spectroscopy with Fourier transformed and scanning electron microscopy. From these tests, it can be concluded, in general, that the carbon nanotubes act as catalysts for curing the benzoxazine matrix without affecting the initial and final temperatures of polymerization. The addition of CNT does not change neither the thermal stability of the benzoxazine resin nor the glass transition temperature (Tg) of nanostructured composites, except for the addition of 0.1 wt% of CNT in polymer matrix that generates a slight increase in Tg
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Bondi, Scott Nicholas. "LCVD synthesis of carbon nanotubes and their characterization." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-08112004-143541/unrestricted/bondi%5Fscott%5Fn%5F200412%5Fphd.pdf.
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Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2005.Z.L. Wang, Committee Member ; Thomas Starr, Committee Member ; Mostafa Ghiaasiaan, Committee Member ; W. Jack Lackey, Committee Chair; Shreyes Melkote, Committee Member. Vita. Includes bibliographical references.
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Sowani, Anshuman A. "Exploration of Electromagnetic Assisted Spinning and Electrical Annealing of Carbon Nanotubes." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1367924864.
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Wang, Genwei. "Stabilité du nanotube de carbone : fabrication et comportement mécanique du composite à base des nanotubes." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2006. http://tel.archives-ouvertes.fr/tel-00136102.
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Dans les premières parties, le flambage du nanotube de carbone sous ses poids propres a été analysé sous hypothèse de mécanique des milieux continus. Cela montre que le rapport critique de longueur/diamètre peut aller jusqu'à 106. On utilise aussi un modèle de poutre pour étudier la valeur critique de longueur pour que les deux nanotubes se collent sous action des forces de van der Waals. Ceci dans le but d'une guide de conception de nano interrupteur. La suite de la thèse est consacrée à la fabrication des composites à base de résine avec les renforts des particules de sic mais avec les nanotubes poussées dessus. Différents tests sous chargement statique et dynamique ont été utilisés pour étudier l'effet de ces renforts. L'observations microscopiques montrent par ailleurs que ces charges ont été dispersées de façon homogène.
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Wang, Genwei. "Stabilité du nanotube de carbone : fabrication et comportement mécanique du composites à base des nanotubes." Cachan, Ecole normale supérieure, 2006. http://tel.archives-ouvertes.fr/tel-00136102.
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Dans les premières parties, le flambage du nanotube de carbone sous ses poids propres a été analysé sous hypothèse de mécanique des milieux continus. Cela montre que le rapport critique de longueur/diamètre peut aller jusqu'à 106. On utilise aussi un modèle de poutre pour étudier la valeur critique de longueur pour que les deux nanotubes se collent sous action des forces de van der Waals. Ceci dans le but d'une guide de conception de nano interrupteur. La suite de la thèse est consacrée à la fabrication des composites à base de résine avec les renforts des particules de sic mais avec les nanotubes poussées dessus. Différents tests sous chargement statique et dynamique ont été utilisés pour étudier l'effet de ces renforts. L'observations microscopiques montrent par ailleurs que ces charges ont été dispersées de façon homogèneThe stability of carbon nanotube under self weight is analyzed by continuum method. Research results show that the critical aspect ratio can reach to 106. Double cantileveled beam model is used to study the pull in instability of two carbon nanotubes under van der waals forces. The obtained results are useful for the critical design of carbon nanotube based nanoswitch. Carbon nanotube/sic (cnt/sic) hybrid structure are fabricated by chemical vapor despositon. Different loadings of cnt/sic are added into epoxy resin to make micro/nanoscale hybrid composites. The static and dynamic compressive tests are first made to study the renforcement of different filler. Sem observation on the facture surfaces shows that both carbon nanotube and sic particle are dispersed homogeneously
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Li, Zhaoming. "Electronic and vibrational properties of ultrasmall single-walled carbon nanotubes /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202004%20LIZ.
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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 112-123). Also available in electronic version. Access restricted to campus users.
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Cleuziou, Jean-Pierre. "Propriétés de transport électronique de nanotubes de carbone: des nanotubes hybrides au nano-SQUID." Phd thesis, Université Paul Sabatier - Toulouse III, 2007. http://tel.archives-ouvertes.fr/tel-00342549.
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L'électronique moléculaire et la spintronique moléculaire sont deux domaines émergeant de la nanophysique, prometteurs pour réaliser de nouveaux types de dispositifs utiles tant pour le stockage d'information que pour l'information quantique. Ce travail de thèse a pour objet de contribuer à ces deux domaines de recherche par la réalisation de jonctions moléculaires à base de nanotubes de carbone, faisant intervenir des nanostructures magnétiques. Nous avons choisi deux approches: (i) le transport électronique à travers des nanotubes de carbone remplis de matériaux magnétiques (nanotubes hybrides) et (ii) le développement du nano-SQUID composé de jonctions supraconductrices à nanotube de carbone. Ce magnétomètre devrait être suffisamment sensible pour étudier les propriétés magnétiques de molécules individuelles attachées au nanotube de carbone.
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Metenier, Karine. "Intercalation et stockage electrochimique dans les nanotubes de carbone : evolution thermique des nanotubes monoparoi." Orléans, 1999. http://www.theses.fr/1999ORLE2053.
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Depuis 1991, les nanotubes de carbone font l'objet de nombreux travaux de recherche, depuis leur elaboration jusqu'a l'exploitation de leurs proprietes dans des domaines aussi varies que les nanotechnologies, l'electronique moleculaire, le renforcement des composites, le stockage de l'energie leur diametre est de quelques nanometres et leur longueur peut atteindre le millimetre. Les nanotubes multiparois sont constitues de feuillets carbones arranges en couches concentriques (jusqu'a plusieurs dizaines). Les nanotubes monoparoi, d'un diametre compris entre 1 et 2 nanometres, s'associent par faisceaux de plusieurs centaines de tubes. Dans ce travail, nous nous sommes interesses aux transformations thermiques et aux reactivites chimique et electrochimique de nanotubes multiparois et monoparoi. Les nanotubes multiparois ont ete synthetises par decomposition catalytique ou thermique d'hydrocarbures et les nanotubes monoparoi par la methode de l'arc electrique. Les echantillons ont ete caracterises principalement au moyen de la microscopie electronique par transmission. 1) lors d'un traitement thermique jusqu'a 2800\c, le diametre des nanotubes monoparoi augmente des 1600\c. A 2000\c, ils perdent definitivement leur arrangement bidimensionnel en faisceaux. Au-dela de 2400\c, ils sont integralement transformes en nanotubes multiparois. Cette etude a mis en evidence des mecanismes de coalescence ainsi qu'une metastabilite des nanotubes monoparoi. 2) la deuxieme partie de ce travail traite des modifications structurales et electroniques induites par des reactions d'intercalation de metaux alcalins lourds (k, rb et cs) dans les nanotubes. Avec les nanotubes multiparois, le stade, la periode d'identite, la surstructure de l'intercalat et l'evolution des largeurs de raies en rpe en fonction du stade et du numero atomique de l'alcalin rappellent ceux des composes d'intercalation du graphite. Dans le cas des nanotubes monoparoi, nous montrons que l'intercalation se produit entre les tubes, modifiant le parametre du reseau et dans certains cas, cela va jusqu'a detruire l'arrangement periodique au sein des faisceaux. 3) la troisieme partie est consacree au stockage electrochimique de l'energie par des nanotubes multiparois de structure et microtexture variees. Deux applications sont etudiees : les batteries au lithium et les supercondensateurs. Nous montrons en particulier que si la mesoporosite des nanotubes -bien mise en evidence par les mesures d'adsorption physique d'azote a 77k- apparait nefaste dans les batteries lithium-ion du fait de l'importante irreversibilite et de la polarisation entre les courbes de charge-decharge, en revanche, elle permet d'assurer un bon stockage de charges dans le cas des supercondensateurs.
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Yi, Yan. "Ballistic conduction in multiwalled carbon nanotubes." Diss., Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-05102004-103121/unrestricted/yi%5Fyan%5F200407%5Fphd.pdf.
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Thesis (Ph. D.)--School of Physics, Georgia Institute of Technology, 2005. Directed by Walt A. de Heer.Whetten, Robert L., Committee Member ; Conrad, Edward H., Committee Member ; First, Phillip N., Committee Member ; de Heer, Walt A., Committee Chair ; Gaylord, Thomas K., Committee Member. Includes bibliographical references.
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Aitkaliyeva, Assel. "Irradiation Stability of Carbon Nanotubes." [College Station, Tex. : Texas A&M University, 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-08-3251.
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Motavas, Saloome. "Optical absorption in carbon nanotubes." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/50121.
Full textAbstract:
Due to their unique optical properties, carbon nanotubes have been widely investigated for use in photonic and optoelectronic devices and optical absorption and emission with nanotubes have been achieved in experiments. On the other hand, the structural characteristics of nanotubes, e.g. the chirality, diameter, and length, as well as other factors such as the polarization of the incident light, presence of a magnetic field and mechanical deformation can significantly affect the optical properties of these structures. Some of these effects have been theoretically studied at the tight-binding approximation level. However, a systematic first-principles-based study of nanotubes that addresses these effects did not exist in the literature prior to the present work. This thesis aims at performing such a fundamental study. We first describe a method for calculating the dipole moments and transition rates in nanotubes. This also enables the study of selection rules, based on which a modified set of rules is defined. The probability of absorption is studied in the full range of infrared-visible-ultraviolet. We show that π-σ*, σ-π*, and σ-σ* transitions that are neglected in previous works are allowed and can lead to high probabilities of transition. We then investigate several effects caused by the curvature of the nanotube sidewall and their impacts on the optical properties. The overall effect is shown to not only depend on the diameter, but also on the chirality of the nanotube. Through the study of the light polarization effect, we show that the overall transition rate spectrum of the perpendicularly polarized light is suppressed for smaller-diameter nanotubes in the IR/VIS range. In the UV region, however, perpendicular polarization is generally absorbed at a higher rate compared to parallel polarization. Finally, we show how the absorption spectra of short nanotube segments can be different from those of long nanotubes. We examine the effect of length on individual absorption peaks and also investigate the effect of spin on the optical properties of nanotube segments. The calculation method described in this thesis and the results can be used to estimate the effects of structural and environmental factors on the optical absorption properties of nanotubes.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate