Thesis (Ph.D.)--Københavns universitet, 1996. / Ph.d. afhandling, Københavns Universitet Med litteraturhenvisninger Title from title screen (viewed on July 9, 2008). Title from document title page. Includes bibliographical references. Available in PDF format via the World Wide Web.

Thesis (M. S.)--Materials Science and Engineering, Georgia Institute of Technology, 2005. / Ready, Jud, Committee Co-Chair ; Carter, Brent, Committee Co-Chair ; Snyder, Bob, Committee Member ; Wang, Zhong Lin, Committee Member. Includes bibliographical references.

Thesis (Ph. D.)--State University of New York at Binghamton, Materials Science and Engineering Program, 2009. / Includes bibliographical references.

Made available in DSpace on 2018-06-27T18:55:56Z (GMT). No. of bitstreams: 3 Paulo Inacio Obregon do Carmo.pdf: 2602281 bytes, checksum: 7b94441337f178869475a9dda7ce86a5 (MD5) Paulo Inacio Obregon do Carmo.pdf.txt: 111751 bytes, checksum: 0fc962a4e4b8838558177bcf7859a818 (MD5) Paulo Inacio Obregon do Carmo.pdf.jpg: 3913 bytes, checksum: 6352e7404ddd8978e5632801dda2b544 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Carbon Nanotubes (CNTs) they are object of intense theoretical and experimental researches, tends in view the extreme sensibility of their electronic properties, deformations and to defects in the hexagonal net to alterations in the structural parameters. The structural and electronic properties of CNTs have been considered the base for the development of coverings nanoestruturados destined to the research space, sensor and fotovoltaics devices, among others. A better knowledge of the properties of these materials is necessary so that we can project more efficient and durable devices, besides assisting to crescent it disputes of the market of technological innovation. In this work analyses of the elastic and electronic properties of single-walled nanotubes carbon (SWCNT) and multi-walled with two (DWCNT) and three (TWCNT) shells deformed by axial traction were accomplished. The structural and energy properties of CNTs studied were obtained through calculations of first beginnings, with base in the Theory of the Functional of the Density, that one find implemented in the program SIESTA (Spanish Initiative goes Electronic Simulations with Thousand of Atoms). Considering CNTs discreet shells and making use of the mechanics solids continuous, we obtained that the elasticity modulus varies of 0,65TPa - for the nanotubo (4,4), to 0,95 TPa - for NTC (10,10). It was verified that the mechanical resistance increases with the diameter of CNT, except for CNT (15,15) that presents smaller mechanical resistance than CNT (10,10). We determined with base in the variation of the elastic energy and of the connection length the modulus of young. We observed that the nanotubos with different layers have behaviors differentiated front to the tensions, so much in points of rupture of the chemical structure, when to the electronic properties. Nanotubes of carbon of the type armchair are metallic, however starting from certain deformations, they become semiconductors and their energy gap varies in agreement with the intensity of the applied tension. / Nanotubos de carbono (NTCs) são objeto de intensas pesquisas teóricas e experimentais, tendo em vista a extrema sensibilidade das suas propriedades eletrônicas a alterações nos parâmetros estruturais, deformações e a defeitos na rede hexagonal. As propriedades estruturais e eletrônicas dos NTCs têm sido consideradas a base para o desenvolvimento de revestimentos nanoestruturados destinados à pesquisa espacial, sensores, dispositivos fotovoltaicos, entre outros. Um melhor conhecimento das propriedades destes materiais é necessário para que se possa projetar dispositivos mais eficientes e duráveis, além de atender a crescente demanda do mercado de inovação tecnológica. Neste trabalho foram realizadas análises das propriedades elásticas e eletrônicas de nanotubos de carbono de uma (SWCNT), duas (DWCNT) e três (TWCNT) camadas deformados por tração axial. As propriedades estruturais e energéticas dos NTCs estudados foram obtidas através de cálculos de primeiros princípios, com base na Teoria do Funcional da Densidade, que se encontra implementada no programa SIESTA (Spanish Initiative for Electronic Simulations with Thousand of Atoms). Considerando os NTCs cascas discretas e fazendo uso da mecânica dos sólidos contínuos, obtivemos que o módulo de elasticidade varia de 0,65TPa - para o nanotubo (4,4), a 0,95 TPa para o NTC (10,10). Constatou-se que a resistência mecânica aumenta com o diâmetro do NTC, com exceção do NTC (15,15) que apresenta resistência mecânica menor que o NTC (10,10). Determinamos com base na variação da energia elástica e do comprimento de ligação o módulo de Young. Observamos que os nanotubos com diferentes camadas têm comportamentos diferenciados frente às tensões, tanto em pontos de ruptura da estrutura química, quanto às propriedades eletrônicas. Nanotubos de carbono do tipo armchair são metálicos, porém a partir de determinadas deformações, tornam-se semicondutores e seus gaps de energia variam de acordo com a intensidade da tensão aplicada.

Orientador: Leonilda Maria Barbosa dos Santos / Dissertação (Mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-21T19:55:43Z (GMT). No. of bitstreams: 1 Paula_RosemeireFlorencadeOliveirade_M.pdf: 1324085 bytes, checksum: 46d777e0734d49f399f5275c0ef511c3 (MD5) Previous issue date: 2012 / Resumo: A capacidade dos nanotubos de carbono penetrar nas células abriu a possibilidade da utilização dessas nanopartículas no diagnóstico e tratamento das neoplasias malignas. Contudo, pouco se conhece sobre o efeito dessas partículas não funcionalizadas, ou seja, sem moléculas acopladas, sobre a resposta imune. Nesse estudo demonstramos que nanotubos de carbono de paredes múltiplas (MWCNT) corados com substância fluorescente penetram nas células de carcinoma de pulmão (LLC) de camundongos. A internalização dessas partículas foi avaliada utilizando-se microscopia confocal e citometria de fluxo. Uma vez dentro das células o MWCNT inibiu a resposta proliferativa das LLC in vitro. A inoculação dos nanotubos de carbono in vivo também reduziu a velocidade de crescimento do tumor. A redução da velocidade de crescimento foi acompanhada de aumento da resposta proliferativa dos linfócitos estimulados por mitógeno inespecífico e pela expressão de IFN. O IFN está envolvido na resposta contra os tumores e esses resultados indicam que os nanotubos de carbono estimulam a resposta imune. Por outro lado, verificou-se significativa redução da expressão citocinas como TNF, IL-17, IL-10 e TFG, que estão envolvidas na resposta imunes pró-tumor. Esses resultados indicam que, mesmo na ausência de funcionalização, os nanotubos de carbono ativam a resposta imune e que conseqüentemente a resposta imune altera o crescimento desse tumor / Abstract: The ability of carbon nanotube to penetrate cells opens the possibility for using these particles on diagnosis and treatment of malignant neoplasms. However, little is known about the effect of the non functionalized carbon nanotube, in other words, without attached molecules, on the immune response. In this study, we demonstrate that the multi-walled carbon nanotubos (MWCNT) stained with a fluorescent dye can penetrate mouse lung carcinoma (LLC) cells. These particles internalization was evaluated by confocal microscopy and flow cytometry. Once inside the cells, the MWCNT inhibited the LLC proliferative response in vitro. The in vivo inoculation of MWCNT in tumor-bearing mice also resulted in the reduction of tumor growth. The growth speed reduction was accompanied by mitogen nonspecific stimulation of T lymphocyte proliferative response and IFN expression. The IFN is involved on response against tumor and these results show that the carbon nanotubes stimulate the immune response. On the other hand, a significant reduction on cytokines like TNF, IL-17, IL-10 e TFG that are involved on pro- tumoral immune response was verified. These results show that, even without functionalization, the carbon nanotubos activate the immune response and consequently the immune response changes the tumoral growth / Mestrado / Clinica Medica / Mestra em Clínica Médica

Pb(II) removal is imperative due to its inherent toxicity at low levels and its tendency to accumulate in ecosystems. Conductive carbonaceous nanomaterials (CCNs), such as carbon nanotubes (CNTs) and carbon nanofibers (CNFs), have recently gained the interest of researchers due to their superior properties and ease of functionalization. The aim of this study is to utilize CCNs for Pb(II) removal within membrane technology and bioremediation strategies. Membranes have shown promise in their treatment abilities, producing excellent effluent quality while reducing plant footprints. The integration of CNTs within membrane technology provides an opportunity to couple its removal capacity with Pb(II) removal that exhibits regeneration capabilities. However, membrane fouling can be problematic for membrane longevity and regeneration. CNTs have also shown to be capable of mitigating fouling via electrostatic repulsion and pollutant degradation. However, little work has been conducted on its fabrication. In this work, CNTs were incorporated with poly(vinyl) alcohol (PVA) in thin film composites, where the effects of PVA chain length and degree of crosslinking were investigated. It was found that a pseudo-optimal coating can be obtained using 31-50kDa PVA with 10% crosslinking. This combination lead to a highly permeable, hydrophilic surface with good electrical conductivity that exhibited a molecular weight cut off of 2000kDa. Biosorption has shown promise in Pb(II) removal in the lab scale but its large-scale use is hindered from rapid saturation of binding sites and low regeneration abilities. Exoelectrogens were proposed as reactive biosorbents to couple biosorption with bioreduction in an attached growth configuration. CCNs were investigated as bacterial scaffolds, where their efficacy and Pb(II) dosage concentration was studied. It was found that CNFs were superior in removing Pb(II), exhibiting Pb(II) concentrations ≤0.10 ppm where removal increased when Pb(II) dosage increased from 0.5 to 5ppm. SEM-EDX analysis provided evidence that bioreduction dominated Pb(II) removal. A long-term study was further conducted using CNFs, revealing its robustness in long term removal over suspended growth reactors with a sustained removal of ≈ 80%. A numerical model was further proposed which exhibited a goodness of fit with an R-squared of 0.92. This model confirmed that bioreduction dominated Pb(II) removal and revealed biofilm thickness and Monod kinetics to be the main influential parameters on Pb(II) removal. / Thesis / Master of Applied Science (MASc)

Indiana University-Purdue University Indianapolis (IUPUI) / Recent theoretical and experimental studies, suggest that Carbon nanotubes are 10-100 times higher than the strongest steel at a fraction of the weight. There are two main types of CNTs that can have high structural perfection. Single-walled nanotubes (SWNTs) consist of a single graphite sheet seamlessly wrapped into a cylindrical tube. Multi-walled carbon nanotubes (MWNTs) comprise an array of such nanotubes concentrically nested like rings of a tree trunk. Denture base acrylics have been reinforced with different materials with limited success. No single reinforced material has showed a great statistical difference in mechanical improvement. The goal of this investigation was to study the effects of Single Walled Carbon Nanotubes reinforcement on the mechanical properties of commercially available denture base PMMA. Denture Base material was reinforced with Single-walled Carbon Nanotubes (SWNTs) at dispersion of 0.25 wt % (group 1), 0.50 wt % (group 2), 0.75 wt % (group 3) and 0.0 wt % (group 4, control). Samples from each group were evaluated for microhardness, flexural strength, flexural modulus, and fracture toughness. The samples were tested in two conditions, as manufactured (dry) and after storing at 37 C for 7 days (wet). Data from four experiments was analyzed by ANOVA. All control sample values were in the range of acceptance compared with previous studies. Higher values were obtained for the control groups for flexural strength and modulus compared with the experimental samples. (p < 0.05) There was no statistical difference regarding fracture toughness between control and experimental groups. A statistical difference was observed in Hardness. The experimental group showed higher values under compression.

Dans cette dissertation nous présentons une étude expérimentale et théorique sur les propriétés optiques de nanotubes de carbone mono-parois (SWNTs) semi-conducteurs. Nous nous concentrons sur les aspects et phénomènes typiquement quantiques dont la description nécessite de sortir du cadre de la physique classique et des équations de Maxwell. Notre résultat experimental le plus important est l'observation du dégroupement des photons dans la photoluminescence (FL) émise par les SWNTs. Tenant compte des particularités de notre échantillon qui consiste de SWNTs enrobés dans un surfactant et déposés sur un substrat fonctionalisé, nous montrons que l'absence d'émission simultanée de plusieurs photons est dûe à la localisation des excitons dans des pièges de quelques nanomètres de long sur nanotube. L'annihilation exciton-¬exciton rapide et efficace résultant de la dimension réduite des nanotubes de carbone joue un role déterminant pour éviter l'émission de paires de photons. La fidèle reproduction des larges lignes asymétriques en FL par un model physique reposant sur le confinement des excitons supporte cette vision. Nous calculons le spectre d'une boîte quantique (QD) formée sur un SWNT et démontrons que le couplage de l'exciton avec les phonons acoustiques de faible énergie du nanotube cause un déphasage ultra-rapide et non-markovien de l'état optiquement excité. Dans le domaine spectral, la force d'oscillateur est transférée de la transition sans phonon (ZFL) vers des ailes associées aux phonons et présentant une forte asymétrie aux températures cryogéniques. Nous prouvons que nos données sont des preuves directes de la réalisation expérimentale du modèle spin-boson dans le régime (sous-)ohmique. Ceci est une conséquence de l'uni-dimensionnalité du bain de phonons se réfléchissant dans la densité spectrale gouvernant les dissipations. Nous soulignons les différences qua-litatives par rapport aux boîtes quantiques traditionnels dans une matrice à trois dimensions, et discutons brièvement les conséquences pour l'utilisation des SWNT¬QDs dans le traitement d'information quantique. Une possibilité passionnante ouverte par le fort couplage exciton-phonon dans les nanotubes de carbone est leur utilisation comme résonateurs mécaniques pour le refroidissement assisté par laser. Nous proposons un dispositif basé sur un SWNT suspendu où le confinement de l'exciton est contrôlé par de fines pointes servant de grilles. Le potentiel appliqué aux pointes peut en outre être utilisé pour induire le couplage de l'exciton au mode de flexion du SWNT et pour régler sa force. La diffusion inélastique d'un faible laser désaccordé vers le rouge permet alors de réduire le nombre d'occupation du mode fondamental de flexion jusqu'àl'état fondamental quantique. Dans une tentative de donner une image unifiée pour l'ensemble de nos obser-vations expérimentales, nous proposons aussi une origine physique à la formation de SWNT-QDs dans notre échantillon. Nous considérons la présence d'une impureté h chargée dans les environs du nanotube et démontrons que le champ électrique qui en résulte piège les excitons du SWNT. Les caractéristiques particulières de ce potentiel confinant pourraient expliquer la plupart des caractéristiques expérimentales. Enfin, nous montrons comment le couplage spin-orbite non-nul récemment me-surédans des expériences de transport permet la manipulation purement optique du spin dans des nanotubes de carbone. Nous effectuons des simulations numériques basées sur les équations de Bloch pour démontrer que la préparation du spin avec haute fidélitéest réalisable. La manipulation optique cohérente du spin et de pos¬sibles utilisations du spin des nanotubes de carbone dans le traitement quantique de l'information sont également discutées. Alliant de nouveaux résultats expérimentaux surprenants et de diverses études théoriques et numériques, ce travail met l'accent sur le potentiel fascinant des nano-tubes de carbone dans l'étude de la physique quantique des matériaux de dimension réduite.

Kohlenstoffnanoröhren besitzen eine Reihe von einzigartigen strukturellen, mechanischen und elektronischen Eigenschaften. Sie können in Abhängigkeit von der Chiralität metallisches oder halbleitendes Verhalten zeigen, hohe mechanische, thermische und chemische Stabilität aufweisen, können chemisch funktionalisiert werden und sind hervorragende Elektronenemitter. Vor dem Hintergrund dieser vielversprechenden Eigenschaften wurde schnell die Frage von möglichen technischen Anwendungen von Kohlenstoffnanoröhren gestellt. Vor einer umfassenden kommerziellen Umsetzung sind allerdings noch grundlegende Untersuchungen, sowohl zu den Eigenschaften als auch zu einer gezielten Herstellung und Manipulation, erforderlich. Der Mechanismus des gerichteten Wachstums der Kohlenstoffnanoröhren ist äußerst komplex, weshalb er bis heute nicht völlig aufgeklärt werden konnte. Der Grund liegt in der Vielfalt der möglichen Reaktionen zwischen den Molekülen in der Gasphase, der Wechselwirkung zwischen Gasphase und verwendeten Unterlagen und den Reaktionsmechanismen auf diesen Substratoberflächen. Bislang fehlt es an einem einheitlichen Verständnis des Entstehungsprozesses von Kohlenstoffnanoröhren bzw. –nanostrukturen. Der Schwerpunkt dieser Arbeit liegt in der Abscheidung von Kohlenstoffnanostrukturen mittels plasmaaktivierter und hitzdrahtgestützter chemischen Gasphasenabscheidung -„Plasma enhanced hot filament chemical vapor deposition“ (PE-HF-CVD). Es sollen Abscheidungsbedingungen für die Synthese von unterschiedlichen Kohlenstoffnanostrukturen gefunden und optimiert werden. Die Darstellung und Charakterisierung von „phasenreinen“, mehrwandigen, tubularen Röhren auf unterschiedlichen metallbeschichteten Substraten steht im Vordergrund der Arbeit. Das Interesse besteht in einer Abscheidung bei niedrigen Substrattemperaturen, damit temperaturempfindliche Werkstoffe wie z.B. Glas, als Substratmaterialien eingesetzt werden können. Mittels der PE-HF-CVD Methode, die als vielversprechende Technologie zur Darstellung gerichteter Kohlenstoffnanoröhren gilt, sollen Erkenntnisse zum Einfluss einzelner Abscheidungsparameter auf den Wachstumsprozess von Nanoröhren gewonnen werden, wozu auch die plasmadiagnostische Langmuirsondentechnik und die optische Emissionsspektroskopie (OES) eingesetzt werden. Dadurch soll der Zusammenhang zwischen inneren Plasmaparametern und Wachstumsprozessen der Kohlenstoffnanoröhren oder –fasern definiert werden, um eine Prozesskontrolle während der Abscheidungsphase zu ermöglichen.

<p>U ovom radu, izvr&scaron;ena je sinteza i karakterizacija bionanokompozitnih materijala na osnovu poli(laktida) i vi&scaron;eslojnih ugljeničnih nanocevi. Ispitivan je uticaj različitih tehnika funkcionalizacije nanocevi, kao i izbor uslova sinteze i odnosa polaznih komponenti sistema, na svojstva dobijenih kompozitnih materijala na osnovu poli(L-laktida). Radi postizanja uniformne raspodele nanopunila u kompozitima, vi&scaron;eslojne ugljenične nanocevi su modifikovane hemijskom i radijacionom funkcionalizacijom. Izvr&scaron;ena je karakterizacija ugljeničnih nanocevi, sa ciljem utvrđivanja uspe&scaron;nosti primenjenih tehnika modifikacije na njihova svojstva i stepen funkcionalizacije. Metodom in situ polimerizacije L-laktida sa povr&scaron;ina modifikovanih nanocevi, pripremljene su serije uzoraka kompozitnih materijala sa različitim sadrţajem funkcionalizovanih nanocevi. Detaljno je ispitan uticaj funkcionalizovanih nanocevi na toplotna, kristalna, morfolo&scaron;ka, mehanička i električna svojstva sintetisanih kompozitnih materijala. Postignuta homogena disperzija nanocevi unutar biorazgradive, biokompatibilne matrice polimera koji se dobija iz obnovljivih sirovina, uticala je na pobolj&scaron;anje svojstava, kao i na uspostavljanje novih funkcionalnosti dobijenih materijala. Značajno pobolj&scaron;anje toplotnih i mehaničkih svojstva sintetisanih materijala, zajedno sa postignutom električnom provodljivo&scaron;ću, omogućava pro&scaron;irenje oblasti primene kompozita na osnovu poli(laktida) i ugljeničnih nanocevi.</p> / <p>In this thesis, bionanocomposites based on poly(lactide) and multi-walled carbon nanotubes were synthesized and characterised. Poly(L-lactide) was used as a matrix for the composite synthesis; the influence of nanofillers content, the methods of their functionalization, as well as the synthesis parameters, on the properties of obtained materials were investigated. In order to achieve a uniform dispersion of nanofillers in composite materials, multi-walled carbon nanotubes were modified using chemical and radiation functionalization. Characterization of carbon nanotubes was performed in order to determine the influence of applied modification techniques on their properties and degree of functionalization. A series of composite materials with different content of modified nanotubes were prepared by in situ polymerization of L-lactide from the surface of functionalized nanotubes. The influence of functionalized nanotubes on the thermal, crystal, morphological, mechanical and electrical properties of synthesized composites was investigated in detail. The homogeneous dispersion of carbon nanotubes within the biodegradable, biocompatible, biobased polymer matrix, has influenced the improvement of the properties, as well as the acquiring of new functionalities of synthesized materials. The significant improvement of thermal and mechanical properties of composites, and the achievement of its electrical conductivity, allow the field of application of composites based on poly(lactide) and carbon nanotubes to be expanded.</p>