To see the other types of publications on this topic, follow the link: Nanotubes. Nanostructured materials. Carbon composites.
Dissertations / Theses on the topic 'Nanotubes. Nanostructured materials. Carbon composites'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Nanotubes. Nanostructured materials. Carbon composites.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Yao, Yanli. "Development of amperometric biosensors with carbon nanotube composite materials." HKBU Institutional Repository, 2008. http://repository.hkbu.edu.hk/etd_ra/895.
Full text
2
Kim, Il Tae. "Carbon-based magnetic nanohybrid materials for polymer composites and electrochemical energy storage and conversion." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45876.
Full textAbstract:
The role of nanohybrid materials in the fields of polymer composites and electrochemical energy systems is significant since they affect the enhanced physical properties and improved electrochemical performance, respectively. As basic nanomaterials, carbon nanotubes and graphene were utilized due to their outstanding physical properties. With these materials, hybrid nanostructures were generated through a novel synthesis method, modified sol-gel process; namely, carbon nanotubes (CNTs)-maghemite and reduced graphene oxide (rGO)-maghemite nanohybrid materials were developed. In the study on polymer composities, developed CNTs-maghemite (magnetic carbon nanotbues (m-CNTs)) were readily aligned under an externally applied magnetic field, and due to the aligned features of m-CNTs in polymer matrices, it showed much enhanced anisotropic electrical and mechanical properties. In the study on electrochemical energy system (Li-ion batteries), rGO-maghemite were used as anode materials; as a result, they showed improved electrochemical performance for Li-ion batteries due to their specific morphology and characteristics.
3
Zhang, Xiefei. "Studies on Single Wall Carbon Nanotube and Polymer Composite Films and Fibers." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7610.
Full textAbstract:
Single wall carbon nanotubes (SWNT) have been extensively studied over the last decade due to their excellent comprehensive properties for a variety of applications. This study is focused on the applications of SWNTs as reinforcement for polymer matrices. Due to van der Waal interactions, SWNTs form bundles of about 30 nm diameters. In order to take full advantage of the SWNT mechanical properties, SWNT must exfoliate or at least disperse in small diameter bundle size. Optical microscopy and SEM only give qualitative information of dispersion. Quantitative characterization through TEM or AFM can be time consuming in order to get statistical result. In this study, simple method is developed to quantitatively estimate the size of SWNT bundle in dispersion based on the geometry controlled electrical percolation behavior. The SWNTs can be dispersed /exfoliated via PVP wrapped SWNT aqueous dispersion assisted by surfactants such as sodium dodycel sulfate. PVA / SWNT composite films prepared through PVP wrapped SWNTs exhibit improved mechanical properties as well as the evidence of load transfer from the polymer matrix to the SWNT as monitored by the Raman spectroscopy. SWNT can also be well dispersed into PVA/DMSO/H2O solution. Gel spinning of PVA/SWNT composite fiber has been successfully carried out with improved mechanical properties. Functionalized tubes can be used to enhance SWNT dispersion and exfoliation. Oxidation in strong acids is one method used for functionalizing nanotubes. SWNTs have been functionalized in nitric acid. The structure and properties of films (buckypaper) processed from nitric acid functionalized tubes have been studied exhibiting high tensile strength and high electrical conductivity. Nitric acid treatment results in selective degradation of the small diameter tubes.
4
Zhu, Ronghua (Richard). "Atomistic Simulation of Nanostructured Materials." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1164059775.
Full text
5
Ford, Ericka N. J. "Carbon nanotubes as structural templates within poly(vinyl alcohol) composite fibers." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45921.
Full textAbstract:
Because the gel-spinning process has the potential to yield fibers of high strength and high modulus, this technique was employed to process continuous filaments of PVA/CNT, having CNTs at ¡Ü1 weight percent of polymer. A gel aging technique was employed with the goal of increasing the draw ratio for composite fibers and for promoting the development of crystalline PVA. Since residual solvent can lower the mechanical properties of drawn fibers, solvent phases of water and dimethyl sulfoxide (DMSO) within the drawn fibers were also characterized. As embedded SWNTs were uniaxially aligned along the drawn fiber axis, they were found to induce preferential alignment in the PVA side groups as well as for the residual solvent. This was attributed to charge transfer between SWNT and the respective functional groups. This orientation behavior has been characterized using Raman spectroscopy and infra-red dichroism. The behaviors of gel crystallization and solvent freezing within PVA/CNT dispersions were studied using thermal analysis and rheology. Carbon nanotubes were found to nucleate PVA crystallization in the gel state. PVA/CNT gel aging behavior was characterized by structural, thermal, and mechanical, and dynamic mechanical means. Gel aging was shown to increase the draw ratio of PVA/CNT fibers, and the development of the higher temperature melting peak was attributed to the draw induced ordering of PVA along CNTs. The scanning electron micrographs of fractured PVA/CNT fibers showed fibrils having an average diameter of about 22 nm. The storage modulus of aged gel was a function of solvent diffusion, which changed with aging time. CNTs were shown to have stabilized the gel network, as characterized by the dynamic mechanical properties, and to provide nucleation sites for the ordering of PVA chains, as characterized by WAXD.
6
Oubenali, Mustapha. "Synthèse par dépôt chimique en phase vapeur catalytique (C-CVD) de nanostructures de carbone et leurs applications en catalyse et pour des matériaux composites." Thesis, Toulouse, INPT, 2011. http://www.theses.fr/2011INPT0058/document.
Full textAbstract:
Dans ce travail, nous décrivons les différentes formes, la structure, les propriétés et la croissance catalytique de nanotubes et nanofibres de carbone (Chapitre I). L'hydroxyapatite a été utilisée comme support de la phase active pour la synthèse de nanotubes de carbone multi-feuillet (MWCNTs) et de nanofibres de carbone (CNFs-H) par la technique de dépôt chimique en phase de vapeur catalytique (C-CVD) en lit fluidisé (Chapitre II). Après l'élimination du support par un simple lavage à l'acide chloridrique dilué, une étude théorique et expérimentale de l'oxydation de la surface de nanotubes de carbone par un traitement à l'acide nitrique a permis d'une part d'identifier et de quantifier les groupes formés à la surface de nanostructures carbonées et d'autre part de proposer un mécanisme pour la formation de ces groupes (Chapitre III). Les matériaux résultants après génération des fonctions carboxyliques de surface ont été utilisés comme support de catalyseur. L'hydrogénation du p-halogénonitrobenzène a été choisit comme réaction modèle pour comparer les performances catalytiques de catalyseurs à base de ruthénium en fonction de la nature du support utilisé, MWCNTs ou CNFs-H. L'influence de certains paramètres tels que la température, la nature du substrat et un traitement thermique du catalyseur (activation) est présentée. Une explication des performances catalytiques est proposée après caractérisation du catalyseur par MET, TPD, TPR et PZC (Chapitre IV). Les nanostructures carbonnées produites et caractérisées ont été utilisées comme charge de renforcement d'hydroxyapatites connue comme biomatériaux. Nous avons étudié en particulier la capacité de germination du phosphate octocalcique par la méthode de croissance cristalline à composition constante (C4) (Chapitre V)In this work, we describe the different forms, the catalytic growth, the structure and properties of carbon nanotubes and nanofibres (Chapter I). Hydroxyapatite was used as catalyst support for the synthesis of multi-walled carbon nanotubes (MWCNTs) and nanofibres (CNFs) by catalytic chemical vapour deposition (C-CVD) in a fluidized bed reactor (Chapter II). After support removal by washing with diluted hydrochloric acid, a theoretical and experimental study of surface oxidation of carbon nanotubes by nitric acid treatment has been performed. It allows to identify and quantify the groups formed on the surface of carbon nanostructures and also to propose a mechanism for the formation of these groups (Chapter III). The functionalized nanotubes and nanofibers have been used as supports for heterogeneous catalysis. The hydrogenation of p-halonitrobenzene was used as model reaction to compare the catalytic performances of ruthenium supported on MWCNTs or CNFs-H catalysts. The influence of experimental parameters such as temperature, nature of the substrate and prior heat treatment (activation) of the catalyst on the catalytic activity and selectivity is presented. The catalytic performances have been correlated to the structure of the catalyst as determined from TEM, TPD, TPR and PZC analysis (Chapter IV). The carbon nanostructures produced have also been used as reinforcement fillers for hydroxyapatite-nanotube composites. We have studied in particular, the germination of octacalcium phosphate crystals under conditions of constant solution composition on the surface of the composite (Chapter V)
7
Steiner, Stephen Alan III. "Engineering carbon nanostructures : development of novel aerogel-nanotube composites and optimization techniques for nanotube growth." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36216.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.Includes bibliographical references (leaves 219-233).
Carbon aerogels offer several unique advantages which make them ideal for evaluating a metal's ability to catalyze nanotube growth, including in situ carbothermic reduction of oxidized nanoparticles to their catalytic metallic phase as they form and production of a bulk quantity of nanoparticles which can be easily characterized. In this work, metal-doped carbon aerogels of seven transition metals were synthesized, characterized, and evaluated for their ability to catalyze growth of carbon nanotubes by thermal chemical vapor deposition (CVD). It was found that carbon aerogels doped with Fe, Rh, Re, Au, and Nb all catalyzed the formation of nanotubes in moderate to high yields, resulting in a direct growth of nanotubes on the exterior surfaces of aerogel monoliths. Ta was found to grow nanotubes only after thorough reduction of its oxides. Growth with W was inconclusive. CVD growth of nanotubes throughout the interior porosity of metal-doped carbon aerogels was also achieved by templating a network of interconnected macropores into the monoliths. Surface-based nanoparticles composed of rhenium, gold, and varying combinations of gold and rhenium were investigated for their ability to catalyze carbon nanotube growth.
(cont.) Nanoparticles of these metals were nucleated onto silicon wafers from solutions of anhydrous ReCI5 and AuC13. After deposition, the nanoparticles were reduced under hydrogen for 10 min and then oxidized in air for 4 min. The samples were then processed by CVD employing hydrogen and ethanol-saturated Ar for 10 min. Nanoparticles deposited from metal chloride solutions with a 1:1 molar ratio of gold to rhenium or higher were found to result in high yields of single-walled nanotubes, where nanoparticles deposited from solutions with less than a 1:4 gold-to-rhenium ratio resulted in no nanotube growth. Lastly, a new low-pressure CVD system specialized for nanotube growth was developed. The objectives of the system are to provide a flexible architecture for developing new nanotube growth techniques and to lower the minimum temperature required for nanotube growth. The system features a separate sample heating plate for thermally activating nanoparticles and hot filament for carbon feedstock cracking. The system also features the ability to easily install or remove modules for electric field- and plasma-assisted growths.
by Stephen Alan Steiner, III.
S.M.
8
Naguib, Nevin N. Gogot︠s︡i I︠U︡ G. "Filling and chemical modification of carbon nanotubes /." Philadelphia, Pa. : Drexel University, 2004. http://dspace.library.drexel.edu/handle/1860/343.
Full text
9
Tahhan, May. "Carbon nanotubes and conducting polymer composites." Intelligent Polymers Research Institute - Faculty of Science, 2004. http://ro.uow.edu.au/theses/407.
Full textAbstract:
A nanocomposite is defined as a material of more than one solid phase, where at least one dimension falls in the nanometer range. The combination of carbon nanotubes (CNT) and conducting polymers offers an attractive route for the production of novel compounds that can be used in a variety of application such as sensors, actuators, and molecular scale electronic devices. The ultimate goal of this work is to develop and investigate CNT composites that provide a structural functionality together with one or more other key functions. A variety of novel CNT dispersions were prepared using commercially available CNT systems such as Rice single-walled carbon nanotubes (RCNT), HiPco single-walled carbon nanotubes (HCNT), and Multi-walled carbon nanotube (MWCNT). This study explored the application of novel functional dispersing agents. Deoxyribose Nucleic Acid (DNA) a biological molecule, N- sopropylacrylamide 2-acrylamido-2-methyl-1-propanesulfonic acid (NIPPAm-AMPS) a polyelectrolyte, Didodecyldimethyl ammonium bromide (DDAB) a polymerizable compound, Poly(methoxyaniline-5-sulfonic acid) (PMAS) an inherently conducting polymer, and PVA an insulating polymer were some of the agents used to disperse the CNT. These dispersions were then evaluated in term of their stability and ability to effectively disperse the CNT. Solid-state CNT composites (mats) were then prepared by means of pressure filtration of the CNT/dispersant solutions. These mats were characterized using a variety of different techniques to determine their viability to be used as mechanical actuators or electrochemical devices. The characterization methods included cyclic voltammetry, conductivity, capacitance, atomic force microscopy, scanning electron microscopy, Young’s modulus, and actuation measurements. Abstract RCNT/conducting polymer composites were prepared by the electropolymerization of Pyrrole with a range of different dopant anions in the presence of different RCNT dispersions. In these composites, the RCNT were completely covered by the polymer, consequently the electrochemical responses of these composites were dominated by the electrochemistry of the polymers with the CNT functioning as a conductor element. Polypyrrole was also electropolymerized using functionalized multi-walled carbon nanotubes (FMWCNT) as dopant. Electropolymerization was carried out using galvanostatic and potentiostatic techniques on gold-coated Mylar and ITO-glass. It was determined that PPy/FMWCNT composites deposited on either electrode using potentiostatic deposition exhibited redox peaks. This redox behavior was not observed when the galvanostatic deposition was employed. HCNT/Polyaniline (PAn) composites were prepared by either casting a film from a solution of HCNT and PAn in 1,2-Dichlorobenzene, or by casting a film of PAn onto an existing HCNT mat. The latter exhibited the highest conductivity. The actuation behavior of these CNT composites was investigated and it was determined that the PAn component contributes to the actuation strain while the HCNT component contributes to Young’s modulus. The combination of the HCNT (with their mechanical properties) and PAn (with its actuator behavior) offers and attractive route not only to reinforce the polymer film but also to introduce new electronic properties based on morphological modifications or electronic interactions between the two components giving a robust blend of optimum properties. These results open the door for these composites to be used in a variety of applications that require a combination of the above characteristics such as mechanically reinforced actuator devices, robotics, optical fiber switches, prosthetic devices, and anti-vibration systems. In addition, PPy with a range of dopant anions was electrodeposited galvanostatically, potentiostatically, and potentiodynamically on the surface of four different carbon electrodes, RCNT mat (unannealed), RCNT mat (annealed), glassy carbon, and carbon foil. It was found that the method of electrodeposition was crucial to the electroactivity of the deposited polymers, particularly when deposited onto a RCNT mat due to the different interaction between the deposited polymer and the RCNT mat. Finally, HCNT/SDS, HCNT/PMAS, and HCNT/DNA fibers were prepared using the Particle Coagulating Spinning method (PCS). The annealing process resulted in a dramatic increase in conductivity of up to 2600 times higher compared to the unannealed fibers. However, the annealing process did not play any role in keeping the fibers together or modifying the alignment of the carbon nanotubes ropes within the fibers. The HCNT/DNA fibers, with their biocompatibility, high conductivity, and good mechanical properties can be used as artificial muscles, bioelectronic sensors, or even as platforms to support the growth of nerve cells. This thesis delineates the methods of successful production of solid sate CNT mats and fibers, utilizing traditional polymeric and more novel multi- functional dispersant materials. Thereby, providing a series of new framework for which future device structures can be fabricated.
10
Botelho, Edson Cocchieri. "Processamento e caracterização de compósitos de resina fenólica com nanotubos de carbono com aplicações aeroespaciais /." Guaratinguetá : [s.n.], 2011. http://hdl.handle.net/11449/106719.
Full textAbstract:
Banca: Luis Rogério de Oliveira HeinBanca: Waldek Wladimir BaseFilho
Banca: Ailton de Souza Gomes
Banca: Durval Rodrigues Junior
Banca: Maysa Furlan
Resumo: Este trabalho de pesquisa consistiu na obtenção de compósitos nanoestruturados utilizando matrizes poliméricas termorrígidas e nanotubos de carbono (CNT) e posterior caracterização de suas propriedades mecânicas, térmicas, elétricas, reológicas e demais características físico-químicas para aplicações aeroespaciais. As atividades experimentais para a realização deste trabalho foram, em sua maioria, conduzidas na Alemanha. Durante o desenvolvimento deste trabalho de pesquisa, foi possível entender melhor como deve ser realizada a purificação, funcionalização e dispersão de CNT em compósitos poliméricos. Desta forma, CNT foram caracterizados e utilizados como reforços para a obtenção de compósitos nanoestruturados em matrizes termorrígidas (resina fenólica). Estes compósitos foram processados, por meio de cura em autoclave e avaliados com relação aos seus desempenhos mecânicos, físico-químicos e morfológicos. Duas metodologias foram utilizadas para permitir a dispersão dos CNT: dispersão em solução aquosa e por calandragem (TRC). Os resultados obtidos mostram que a metodologia mais adequada para dispersar os CNT em resina fenólica é a partir do processo por calandragem e que teores superiores a 0,5% em massa de CNT não resultam em melhorias significativas quanto aos desempenhos viscoelástico, térmico, elétrico e mecânico destes compósitos. Ainda, a partir dos ensaios reológicos e elétricos, foi observado que teores abaixo de 0,2% em massa de CNT já são suficientes para promover a percolação dos CNT na resina fenólica, gerando mudanças significativas no comportamento físico-químico do compósito nanoestruturado. A partir deste trabalho de pesquisa... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: This researcher work concerning about the nanostructured composite obtaining by using thermoset polymeric matrix and carbon nanotubes and posterior characterization of their mechanical, thermal, electrical, rheological and others physical-chemical properties for aerospace application. The experimental activities in order to perform this work, in its majority, have been done in Germany. During the development of this researcher work, it was possible to understand better how should be done the purification, functionalization and dispersion of CNT into polymeric composites. This way, CNT were characterized and used as reinforcement in order to obtain nanostructured composite materials in thermoset matrix (phenolic resin). These composites were processed by using autoclave cure processing and they were evaluated concerning about its mechanical, physical-chemical and morphological behavior. Two methodologies were used in order to allow the CNT dispersion: in aqueous solution and in three roll calender (TRC). The obtained results show that the TRC methodology is more adequate in order to disperse the CNT reinforcement and that the content higher than 0.5wt%CNT not result in significant gain in viscoelastic, thermal, rheological and electrical properties in these composites. Still, from the rheological and electrical tests, it was observed that loads below than 0.2wt%CNT are enough to promote the CNT percolation in phenolic resin, generating significant changes in physical-chemical properties of nanostructured composites. From this researcher work... (Complete abstract click electronic access below)
11
Li, Jing. "Electrical conducting polymer nanocomposites containing graphite nanoplatelets and carbon nanotubes /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?MECH%202006%20LI.
Full text
12
Ribeiro, Bruno [UNESP]. "Obtenção e caracterização de compósitos nanoestruturados de poli(sulfeto de fenileno) reforçados com nanotubos de carbono." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/123284.
Full textAbstract:
Made available in DSpace on 2015-05-14T16:53:17Z (GMT). No. of bitstreams: 0
Previous issue date: 2015-01-30Bitstream added on 2015-05-14T16:59:05Z : No. of bitstreams: 1
000825248.pdf: 2617755 bytes, checksum: d33b1e0e24ef50f07023fc78c225d13e (MD5)Neste trabalho, compósitos de poli(sulfeto de fenileno) reforçados com nanotubos de carbono (MWCNT) puros e funcionalizados foram obtidos a partir da técnica de mistura em fusão. Os compósitos nanoestruturados foram caracterizados através de ensaios elétricos, térmicos, mecânicos reológicos e morfológicos. A condutividade elétrica do PPS apresentou um aumento de 11 e 9 ordens de magnitude quando 3,0 e 4,0% em massa de MWCNT puros e funcionalizados foram incorporados na matriz polimérica, respectivamente. Além disso, os limites de percolação elétrica encontrado para esses sistemas foram de 2,1 e 3,6 m/m%, o que sugere a formação de uma rede tridimensional condutora no interior da matriz polimérica. A temperatura máxima de cristalização do PPS apresentou aumentos de 19°C e 13°C devido a incorporação dos reforços puros (p-MWCNT) e funcionalizados (f-MWCNT), respectivamente, evidenciando o efeito nucleante das nanopartículas. A análise dinâmico mecânica mostrou um aumento no módulo de armazenamento e na temperatura de transição vítrea a partir do aumento da concentração de MWCNT, com um incremento maior para o sistema p-MWCNT/PPS. A temperatura máxima de degradação do PPS aumentou 14°C e 6°C devido a incorporação de 4,0 e 2,0% em massa de p-MWCNT e f-MWCNT, respectivamente, sugerindo a formação de sistemas termicamente mais estáveis. O módulo de armazenamento (G’) do PPS apresentou um aumento de 2 ordens de magnitude quando 2,0 e 3,0% em massa de MWCNT puros e funcionalizados foram considerados, com a formação de uma estrutura interconectada de nanotubos, destacando o comportamento pseudoplástico das amostras. A formação de uma rede percolada de nanotubos foi atingida para concentrações de 1,5 e 2,3, m/m% em compósitos de p-MWCNT/PPS e f-MWCNT/PPS, respectivamente. As análises de microscopia ... (Resumo completo, clicar acesso eletrônico abaixo)
In this work, pristine and functionalized multiwalled carbon nanotubes reinforced poly (phenylene sulfide) composites were successfully obtained by melt mixing technique. The nanostructured composites were characterized by means of electrical, thermal, mechanical, rheological, and morphological methods. The electrical conductivity of neat PPS showed an increase by 11 and 9 orders of magnitude when 3.0 and 4.0 wt% of pristine MWCNT and functionalized MWCNT were incorporated in polymeric matrix, respectively. Moreover, the electrical percolation thresholds found on these systems were 2.1 and 3.6 wt%, suggesting the formation of three-dimensional conductive network within the polymeric matrix. The maximum crystallization temperature of PPS increased by about 19°C and 13°C due the incorporation of pristine (p-MWCNT) and functionalized filler (f- MWCNT), demonstrating the nucleating effect of the nanoparticles. Dynamic mechanical analysis showed an increase in storage modulus and glass transition temperature, due the incorporation of p-MWCNT and f-MWCNT in PPS matrix. However, it is worth to mention that the increment was bigger in p-MWCNT/PPS system. The maximum degradation temperature of PPS increased by about 14°C and 6°C due to the incorporation of 4,0 and 2,0 wt% of p-MWCNT and f-MWCNT, respectively, suggesting the formation of more thermally stable systems. The storage modulus (G’) of neat PPS presented an increase by 2 orders of magnitude when 2.0 and 3.0 wt% of pristine MWCNT and functionalized MWCNT were considered, with the formation of an interconnected nanotube structure, indicative of ‘pseudo-solid-like’ behavior. Percolation networks formed when the loading levels achieve up to 1.5 and 2.3 wt% for the composites with pristine MWCNT (p-MWCNT/PPS) and functionalized MWCNT (f-MWCNT/PPS), respectively. In addition, for ... (Complete abstract click electronic access below)
13
Malkovskiy, Andrey Victorovich. "Light Scattering of Nanostructured Materials." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1303760576.
Full text
14
Wong, Chi-yan. "Electronic characterization of individual single-walled carbon nanotubes." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B39557042.
Full text
15
Sirdeshmukh, Ranjani. "Biological functionalization of single-wall carbon nanotubes." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 0.97Mb, 59 p, 2005. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:1428206.
Full text
16
Wong, Chi-yan, and 王志仁. "Electronic characterization of individual single-walled carbon nanotubes." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39557042.
Full text
17
Liu, Gang. "Electrical transport in carbon nanotubes and graphene." Diss., [Riverside, Calif.] : University of California, Riverside, 2010. http://proquest.umi.com/pqdweb?index=0&did=2019837031&SrchMode=2&sid=1&Fmt=2&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1274282934&clientId=48051.
Full textAbstract:
Thesis (Ph. D.)--University of California, Riverside, 2010.Includes abstract. Title from first page of PDF file (viewed May 18, 2010). Includes bibliographical references. Issued in print and online. Available via ProQuest Digital Dissertations.
18
Silva, Wellington Marcos da. "Compositos resina epóxi/nanotubos de carbono de paredes múltiplas: caracterização dos materiais de partida e avaliação das condutividades elétrica e térmica." CNEN - Centro de Desenvolvimento da Tecnologia Nuclear, Belo Horizonte, 2009. http://www.bdtd.cdtn.br//tde_busca/arquivo.php?codArquivo=106.
Full textAbstract:
NenhumaInvestigamos neste trabalho as propriedades elétricas e térmicas de 1)compositos resina epóxi/nanotubos de carbono de paredes múltiplas concêntricas (MWNT) manufaturados com 0,1, 0,5 e 1% em massa de MWNT dispersos aleatoriamente na resina; 2)de compósitos reina/buckpaper; 3) de buckpaper (tecido de MWNT).
19
PAMMI, SRI LAXMI. "CARBON NANOCOMPOSITE MATERIALS." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1069881274.
Full text
20
LEBRAO, GUILHERME W. "Processamento e caracterização de material compósito polimérico obtido com nanotubo de carbono funcionalizado." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/23595.
Full textAbstract:
Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-03-17T10:45:40Z
No. of bitstreams: 0Made available in DSpace on 2015-03-17T10:45:40Z (GMT). No. of bitstreams: 0
Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
21
Liu, Jing. "Carbon nanotube/polymer composites and novel micro- and nano-structured electrospun polymer materials." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/22673.
Full textAbstract:
Thesis (Ph. D.)--Textile and Fiber Engineering, Georgia Institute of Technology, 2007.Committee Chair: Kumar, Satish; Committee Member: Carr, Wallace; Committee Member: Graham, Samuel; Committee Member: Griffin, Anselm; Committee Member: Yao, Donggang.
22
Zhang, Qiuhong. "Carbon Nanotubes on Carbon Fibers: Synthesis, Structures and Properties." Dayton, Ohio : University of Dayton, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1272515887.
Full textAbstract:
Thesis (Ph.D. in Materials Engineering) -- University of Dayton.Title from PDF t.p. (viewed 06/23/10). Advisor: Liming Dai. Includes bibliographical references (p. 136-162). Available online via the OhioLINK ETD Center.
23
Cummings, Aron William. "Molecular dynamics simulation of the thermal properties of Y-junction carbon nanotubes." Online access for everyone, 2004. http://www.dissertations.wsu.edu/Thesis/Summer2004/a%5Fcummings%5F072304.pdf.
Full text
24
Assfour, Bassem. "Hydrogen Storage In Nanostructured Materials." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-65858.
Full textAbstract:
Hydrogen is an appealing energy carrier for clean energy use. However, storage of hydrogen is still the main bottleneck for the realization of an energy economy based on hydrogen. Many materials with outstanding properties have been synthesized with the aim to store enough amount of hydrogen under ambient conditions.
Such efforts need guidance from material science, which includes predictive theoretical tools.
Carbon nanotubes were considered as promising candidates for hydrogen storage applications, but later on it was found to be unable to store enough amounts of hydrogen under ambient conditions. New arrangements of carbon nanotubes were constructed and hydrogen sorption properties were investigated using state-of-the-art simulation methods. The simulations indicate outstanding total hydrogen uptake (up to 19.0 wt.% at 77 K and 5.52wt.% at 300 K), which makes these materials excellent candidates for storage applications. This reopens the carbon route to superior materials for a hydrogen-based economy.
Zeolite imidazolate frameworks are subclass of MOFs with an exceptional chemical and thermal stability. The hydrogen adsorption in ZIFs was investigated as a function of network geometry and organic linker exchange. Ab initio calculations performed at the MP2 level to obtain correct interaction energies between hydrogen molecules and the ZIF framework. Subsequently, GCMC simulations are carried out to obtain the hydrogen uptake of ZIFs at different thermodynamic conditions. The best of these materials (ZIF-8) is found to be able to store up to 5 wt.% at 77 K and high pressure.
We expected possible improvement of hydrogen capacity of ZIFs by substituting the metal atom (Zn 2+) in the structure by lighter elements such as B or Li. Therefore, we investigated the energy landscape of LiB(IM)4 polymorphs in detail and analyzed their hydrogen storage capacities. The structure with the fau topology was shown to be one of the best materials for hydrogen storage. Its total hydrogen uptake at 77 K and 100 bar amounts to 7.8 wt.% comparable to the total uptake reported of MOF-177 (10 wt.%), which is a benchmark material for high pressure and low temperature H2 adsorption.
Covalent organic frameworks are new class of nanoporous materials constructed solely from light elements (C, H, B, and O). The number of adsorption sites as well as the strength of adsorption are essential prerequisites for hydrogen storage in porous materials because they determine the storage capacity and the operational conditions. Currently, to the best of our knowledge, no experimental data are available on the position of preferential H2 adsorption sites in COFs. Molecular dynamics simulations were applied to determine the position of preferential hydrogen sites in COFs. Our results demonstrate that H2 molecule adsorbed at low temperature in seven different adsorption sites in COFs. The calculated adsorption energies are about 3 kJ/mol, comparable to that found for MOF systems. The gravimetric uptake for COF-108 reached 4.17 wt.% at room temperature and 100 bar, which makes this class of materials promising for hydrogen storage applications.
25
Bardash, Liubov, and Liubov Bardash. "Synthesis and investigation of nanostructured polymer composites based on heterocyclic esters and carbon nanotubes." Phd thesis, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00821160.
Full textAbstract:
The thesis relates to synthesis and investigation of nanostructured polymer composites based on oligomers of cyanate esters of bisphenol a (DCBA) or cyclic butylene terephthalate (CBT) and multiwalled carbon nanotubes (MWCNTS). Catalytic effect of mwcnts in process of DCBA polycyclotrimerization as well as in cbt polymerization has been observed. Significant increase in crystallization temperature of nanocomposites based on polybutylene terephthalate (cPBT) with adding of MWCNTS is observed. The effect of processing method of cpbt/mwcnts nanocomposites on its electrical properties has been found. It has been established that the additional heating of the samples (annealing) at temperatures above melting of cPBT leads to reagglomeration of MWCNTS in the system. It is established that reagglomeration of MWCNTS results in increase of conductivity values of nanocomposites due to formation of percolation pathways of MWCNTS through polymer matrix. In the case of polycyanurate matrix (PCN), it is found that addition of small mwcnts contents (0.03-0.06 weight percents) provides increasing tensile strength by 62-94 percents. It has been found that addition of even 0.01 weight percents of MWCNTS provides significant increase in storage modulus of cPBT matrix. This is explained by effective dispersing of small amount of the nanofiller during in situ synthesis of pcn or cpbt matrix that is confirmed by microscopy techniques. It has been established that the properties of the nanocomposites based on heterocyclic esters and MWCNTS can be varied from isolator to conductor and has low percolation thresholds (0.22 and 0.38 weight percents for cPBT and PCN nanocomposites respectively). The conductivity of samples is particularly stable on a very large range of temperature from 300 to 10 degrees Kelvin that make these materials perspective for practical applications in microelectronics, as parts of aircraft and space constructions.
26
Bardash, Liubov. "Synthesis and investigation of nanostructured polymer composites based on heterocyclic esters and carbon nanotubes." Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10174/document.
Full textAbstract:
La thèse concerne les synthèse et caractérisation de composites polymères nanostructurés à base d’esters de cyanates de bisphénol a (DCBA) ou à base d’oligomères cycliques de butylène téréphtalate (CBT) et de nanotubes de carbone multi-parois (MWCNTS). L’effet catalytique des nanotubes de carbone sur la polycyclotrimerisation de DCBA et aussi sur la polymérisation du CBT est observé. L’augmentation de la température de cristallisation a été fixée pour tous les échantillons de nanocomposites à base de polybutylène téréphtalate (cPBT). L’effet de la méthode de mise en forme de cPBT/MWCNTS sur ses propriétés thermiques et électriques a été établi. Il est observé que le traitement thermique additionnel des échantillons (recuit) à des températures inférieures à celle de la fusion du cPBT cause la réagglomération des MWCNTS dans le système. Il est établi que l’ajout de très bas taux de MWCNTS (0.03-0.06 pour cent en masse) dans la matrice de polycyanurate (PCN) augmente les valeurs de résistance à la flexion (64-94 pour cent). De même l’ajout de 0.01 pourcent de MWCNTS en masse dans le CBT augmente considérablement le module d'élasticité des nanocomposites cPBT. Cet effet a été expliqué par la dispersion efficace de cette faible quantité de nanocharges pendant la synthèse in situ de la matrice de cPBT et est confirmée par les clichés en microscopie. Il est déterminé que les propriétés électriques des nanocomposites à base d’esters hétérocycliques et MWCNTS peuvent varier de matériaux isolants aux matériaux conducteurs. Les seuils de percolation des deux systèmes sont très bas (0.22 et 0.38 pourcent pour nanocomposites à base de cPBT et PCN respectivement). La conductivité des composites conducteurs est particulièrement stable sur un large domaine de température ce qui laisse présager des applications intéressantes dans le domaine de la microélectronique et pour des pièces d’avion et de navettes spatialesThe thesis relates to synthesis and investigation of nanostructured polymer composites based on oligomers of cyanate esters of bisphenol a (DCBA) or cyclic butylene terephthalate (CBT) and multiwalled carbon nanotubes (MWCNTS). Catalytic effect of mwcnts in process of DCBA polycyclotrimerization as well as in cbt polymerization has been observed. Significant increase in crystallization temperature of nanocomposites based on polybutylene terephthalate (cPBT) with adding of MWCNTS is observed. The effect of processing method of cpbt/mwcnts nanocomposites on its electrical properties has been found. It has been established that the additional heating of the samples (annealing) at temperatures above melting of cPBT leads to reagglomeration of MWCNTS in the system. It is established that reagglomeration of MWCNTS results in increase of conductivity values of nanocomposites due to formation of percolation pathways of MWCNTS through polymer matrix. In the case of polycyanurate matrix (PCN), it is found that addition of small mwcnts contents (0.03-0.06 weight percents) provides increasing tensile strength by 62-94 percents. It has been found that addition of even 0.01 weight percents of MWCNTS provides significant increase in storage modulus of cPBT matrix. This is explained by effective dispersing of small amount of the nanofiller during in situ synthesis of pcn or cpbt matrix that is confirmed by microscopy techniques. It has been established that the properties of the nanocomposites based on heterocyclic esters and MWCNTS can be varied from isolator to conductor and has low percolation thresholds (0.22 and 0.38 weight percents for cPBT and PCN nanocomposites respectively). The conductivity of samples is particularly stable on a very large range of temperature from 300 to 10 degrees Kelvin that make these materials perspective for practical applications in microelectronics, as parts of aircraft and space constructions
27
Hu, Hui. "PURIFICATION, CHEMISTRY AND APPLICATION OF CARBON NANOTUBES." Lexington, Ky. : [University of Kentucky Libraries], 2004. http://lib.uky.edu/ETD/ukychem2004d00156/huihudis.pdf.
Full textAbstract:
Thesis (M.S.)--University of Kentucky, 2004.Title from document title page (viewed Oct. 12, 2004). Document formatted into pages; contains xv, 263 p. : ill. Includes abstract and vita. Includes bibliographical references (p. 250-258).
28
Wang, Wenju. "Amperometric biosensors based on carbon nanotubes with different polymer coatings." HKBU Institutional Repository, 2011. http://repository.hkbu.edu.hk/etd_ra/1220.
Full text
29
Lu, Qiang. "Influence of random defects on the mechanical behavior of carbon nanotubes through atomistic simulation." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 3.14Mb, 205 p, 2005. http://wwwlib.umi.com/dissertations/fullcit/3181887.
Full text
30
Hsieh, Ching-Wen. "A simplified approach to produce carbon nanotubes using alumina substrate." abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1446421.
Full text
31
Johnson, Ryan David. "Adhesion and deformation during thermocompression bonding of vertically aligned carbon nanotube turfs to metallized substrates." Pullman, Wash. : Washington State University, 2008. http://www.dissertations.wsu.edu/Thesis/Fall2008/r_johnson_120808.pdf.
Full textAbstract:
Thesis (M.S. in materials science and engineering)--Washington State University, December 2008.Title from PDF title page (viewed on Mar. 3, 2009). "Department of Mechanical and Materials Engineering." Includes bibliographical references.
32
Al-khedher, Mohammad Abdelfatah. "Carbon nanotubes characterization and quality analysis using artificial intelligence." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Dissertations/Spring2007/m_al-khedher_041907.pdf.
Full text
33
Santos, Luis Felipe de. "Avaliação da resistência à fadiga de compósitos nanoestruturados de PEI/nanotubos de carbono/fibras de carbono com aplicação aeronáutica." Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/153435.
Full textAbstract:
Submitted by LUIS FELIPE DE PAULA SANTOS null (luiss9406@gmail.com) on 2018-04-07T14:17:57Z
No. of bitstreams: 1
Luis_dissertação_vfinal.pdf: 2915392 bytes, checksum: 7d6ba891adc68c5a6d0ae35e884f554e (MD5)Approved for entry into archive by Pamella Benevides Gonçalves null (pamella@feg.unesp.br) on 2018-04-09T13:53:51Z (GMT) No. of bitstreams: 1 santos_lfp_me_guara.pdf: 2915392 bytes, checksum: 7d6ba891adc68c5a6d0ae35e884f554e (MD5)
Made available in DSpace on 2018-04-09T13:53:51Z (GMT). No. of bitstreams: 1 santos_lfp_me_guara.pdf: 2915392 bytes, checksum: 7d6ba891adc68c5a6d0ae35e884f554e (MD5) Previous issue date: 2018-02-27
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Os avanços tecnológicos na área dos compósitos poliméricos criaram novas oportunidades para estruturas de alto desempenho e com baixo peso, favorecendo o desenvolvimento de sistemas estratégicos em diversos setores, principalmente o aeronáutico. Dentro deste contexto os compósitos poliméricos nanoestruturados encontram-se em uma posição vantajosa em relação a outros materiais, pois seus constituintes podem agregar melhorias nos desempenhos mecânico, térmico e elétrico. Neste trabalho, compósitos nanoestruturados de poli(éter-imida) e nanotubos de carbono de paredes múltiplas (PEI/MWCNT) foram obtidos a partir da técnica de mistura em solução. Posteriormente, foi realizada a consolidação do compósito nanoestruturado reforçado com fibra de carbono (PEI/MWCNT/FC) via moldagem por compressão a quente. A partir das análises térmicas de termogravimetria (TGA) e dinâmico-mecânica (DMA) realizadas no compósito PEI/MWCNT, verificou-se uma melhoria na resistência térmica e nas propriedades viscoelásticas do material. Além disso, as melhorias nas propriedades físicas ocasionadas pela adição de MWCNT a matriz polimérica, influenciaram positivamente na qualidade de processamento dos laminados. Após os ensaios de ILSS e CST observou-se que a adição do nanoreforço gerou um incremento de 16% e 58%, respectivamente, sugerindo uma melhoria na adesão interfacial do compósito. O comportamento em tração não sofreu influência significativa a partir da adição de MWCNT, levando apenas uma melhoria de 5% na resistência a tração e 2% no módulo de elasticidade do material. A adição de MWCNT não influenciou significativamente a resistência a fadiga dos laminados quando analisada em temperatura ambiente e em temperatura elevada, sendo possível observar uma pequena redução nas mesmas. Por outro lado, quando submetido a temperatura sub-ambiente, a adição favoreceu e gerou uma melhoria na resistência a fadiga dos materiais. Por fim, após as análises fractográficas observou-se macroscopicamente que o material PEI/MWCNT/FC possui um aspecto mais dúctil da fratura e microscopicamente há diferenças nos aspectos da fratura do material quando comparado ao laminado PEI/FC
Technological advances in polymer composites area have been created new opportunities for high-performance and lightweight structures, promoting the development of strategic systems in several sectors of industry, especially on the aerospace field. In this context, the nanostructured polymer composites are in an advantageous position compared to other materials, since its constituents may add improvements in mechanical, thermal and electrical performance. In this work, PEI/MWCNT nanostructured composites were obtained from solution mixing technique. Subsequently, the consolidation of the composite reinforced with carbon fiber, was performed by hot compression molding. TGA and DMA analyzes performed on PEI/MWCNT composite film revealed that there was an improvement in the thermal resistance and the viscoelastic properties of the material. In addition, the enhancement in physical properties due to the incorporation of MWCNT in polymer matrix had a positive role in the quality of the laminates. After ILSS and CST tests, it was observed that the addition of the nanofiller led to an increment of 16% and 58%, respectively, suggesting an improvement in the interfacial adhesion of the composite. The tensile behavior did not present a significant influence from the addition of MWCNT, leading to only a 5% improvement in tensile strength and 2% in the modulus of elasticity of the material. The addition of MWCNT did not significantly influence the fatigue strength of the laminates when analyzed at room and high temperature, being possible to observe a small reduction in these temperatures. On the other hand, when performed at sub-ambient temperature, the incorporation of the nanofiller led to an improvement in the fatigue resistance of the materials. Finally, after the fractographic analysis it was observed macroscopically that the PEI/MWCNT/FC composite has a more ductile aspect of the fracture and microscopically there are differences in the fracture aspects of the material when compared to the PEI/FC laminate
2016/12810-5
2017/09344-5
Demanda Social
34
Wang, Huan. "Synthesis, purification and applications of carbon nanomaterials and their polymer nanocomposites /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?CBME%202008%20WANG.
Full text
35
Hsieh, Yu-Yun. "Nanostructured Carbon-Based Composites for Energy Storage and Thermoelectric Applications." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin157322525150617.
Full text
36
Ruan, Shilun. "Multi-walled carbon nanotube reinforced ultra-high molecular weight polyethylene composites /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?MECH%202006%20RUAN.
Full text
37
Cheng, Hoi Sing. "Synthesis and characterization of carbon nanotubes by liquid-phase deposition at low temperature." HKBU Institutional Repository, 2007. http://repository.hkbu.edu.hk/etd_ra/868.
Full text
38
Karumuri, Anil Kumar. "Interfacial Modification of Microcellular Carbon: Influence of Ceramic and Carbon Nanotube Coatings." Wright State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=wright1262043697.
Full text
39
Périé, Thomas. "Dispersion de nanotubes de carbone dans les polymères : de la nanostructuration aux composites hautes performances." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2011. http://pastel.archives-ouvertes.fr/pastel-00634552.
Full textAbstract:
Nous avons synthétisé des composites nanostructurés de nanotubes de carbone (CNT) par deux approches différentes. La première approche se base sur la dispersion dans une matrice d'intérêt d'un masterbatch de polymère fortement chargé en CNT optimisé pour d'une part aider à la dispersion des CNT et d'autre part pour induire une nanostructuration de la matrice. Un masterbatch de poly(styrene-b-butadiene-b-methyl methacrylate) et de CNT re-dispersé dans une matrice de polymère fluoré a permis d'obtenir des composites chargés et néanmoins ductiles. Nous avons aussi utilisé un masterbatch réactif à base de polyamide-6 (PA6). La morphologie co-continue réalisée après ajout de polyéthylène maléisé (PE*) permet d'obtenir des composites cumulant : rigidité, ductilité, résistance aux solvants et conductivité. Dans la deuxième partie de ce mémoire, nous avons démontré une interaction spécifique entre la phase PA6 et les CNT de composites à matrice PE*/PA6 nanostructurée. Le PA6 s'adsorbe sur les CNT ce qui conduit (au dessus d'un seuil de percolation) à des composites possédant comme microstructure un réseau de nanotubes consolidé à ses jonctions par du PA6. Ce réseau " brasé " permet d'obtenir des composites avec des propriétés uniques de tenue haute température. De manière surprenante, nous avons démontré qu'après extraction de la matrice PE* le réseau de nanotubes consolidé se comporte comme un gel. Ces gels originaux peuvent être gonflés par différents solvants de manière parfaitement réversible et possèdent des propriétés électriques dépendantes de leurs taux de gonflement.
40
Paramguru, Kamrakali. "Growth of carbon nanotubes on anodized titanium oxide templates by catalytic chemical vapor deposition technique." abstract and full text PDF (free order & download UNR users only), 2005. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1433346.
Full text
41
Gilbank, Alexander. "Ceramic nanostructured catalysts." Thesis, University of Bath, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648952.
Full textAbstract:
Catalysis has an effect on almost every aspect of our lives. They are used to help grow the food we eat, clean the water we drink and produce the fuels our civilisation is so dependent upon. Homogeneous catalysts, those in the same phase as the reaction medium, are highly selective as a result of their tuneable nature, for example through changes to ligands in a metal complex. However, their separation from the reaction medium can become a problematic, costly, non-green issue, overcome through the use of heterogeneous catalysts which can be removed and recycled by simple separation techniques such as filtering and sedimentation. A major limitation on understanding the behaviour of heterogeneous catalysts is the presence of different active sites due to different exposed crystal surface, concentration of defects and morphological variations. With such considerations, the first section of this thesis focuses on the synthesis of discrete and well-defined nanostructured materials (ceria and titanate) using a single-step hydrothermal method. Nanostructured ceria with different morphologies (particles, rods and cubes), present a high oxygen storage capacity and thermal stability. Their oxidation catalytic activity was assessed using CO oxidation as a model reaction as a function of their physical and chemical properties, tuned by morphological control at the nanoscale. An inverse relationship is observed between crystallite size and rates of reaction normalised per surface area. Smaller crystallites present a constrained geometry resulting in a higher concentration of defects, highly active catalytically due to their unsatisfied coordination and high surface energy. The surface to bulk oxygen ratio generally increased as the surface area increased, however, ceria nanorods present a higher surface oxygen content than that which would be predicted according to their surface area, likely due to the selective exposure of the (110) and (100) dominating crystal surfaces presenting more facile oxygen atoms in their surface. Additionally a relationship between surface to bulk oxygen ratios and activation energies was also ascribed to the more facile nature of oxygen atoms on these surfaces and their more readily formed oxygen vacancies as a result. This activity is as a result of the formation of oxygen vacancies being the rate-controlling step. The thermal stability of nanostructured ceria (particles, rods and cubes) was also studied to investigate their performance under cyclic high temperature applications. For this, the materials were pre-treated at 1000 °C under different atmospheres (inert, oxidative and reducing). In all cases, the materials sinter, consequently resulting in a dramatic decrease in surface area. Interestingly, their catalytic activity per surface area towards CO oxidation, seems to be maintained, although those materials pre-treated under inert and oxidising atmospheres became inactive in consecutive catalytic runs. However, nanostructured ceria pre-treated at 1000 °C under hydrogen appeared to maintain its activity per surface area. The presence of hydrogen during thermal treatment does not only facilitate the removal of surface oxygen, but also the bulk oxygen, resulting in a rearrangement of the structure that facilitates its catalytic stability. Titanate nanotubes were shown to be inactive for CO oxidation and thus were used in the second part of this thesis as a support for platinum nanoparticles to study the effect of the structure and metal-support interaction on the resulting catalytic activity. The study focuses on the effect of different loading methods (ion exchange and incipient wetness impregnation) of platinum nanoparticles on the resulting metal particle size, dispersion, metal-support interaction and consequently their resulting catalytic activity. Ion exchange consistently resulted in smaller nanoparticles with a lower dispersion of sizes and more active catalyst, both in terms of turnover frequency values and activation energy, compared with incipient wetness impregnation. The catalytic activity of the platinum supported on titanate nanotubes increases as the metal particle size decreases to a size value (between 1 and 2.5 nm) below which a dramatic decrease in activity is observed. Despite initial differences in catalytic activity between the different catalysts, it was observed that after initial reactions to 400 °C, the activation energy was independent of metal loading weight and was instead inherent of the loading method, suggesting the presence of similar active sites.
42
Pillai, Pradeep G. "Growth of carbon nanotubes on nanotubular titanium dioxide template and electrochemical hydrogen storage thereof." abstract and full text PDF (free order & download UNR users only), 2006. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1436015.
Full text
43
Saluja, Amandeep S. "A parametric study of gas sensing response of ZnO nanostructures and carbon nanotubes /." Online version of thesis, 2009. http://hdl.handle.net/1850/11388.
Full text
44
Yeoh, Wai Kong. "Processing and characterisation of nano carbon doped MgB2 in form of wire and bulk." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20061121.122622/index.html.
Full text
45
Searle, Andrew. "Application of nanostructured emitters for high efficiency lighting." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:81731b64-c40b-4c76-9c90-dae7c956e29f.
Full textAbstract:
This is the first study comparing morphologies of CNT films on Kanthal wire, with their field emission properties, and as such offers ways to design better cylindrical emitter devices. A low turn-on field was achieved (0.35 V/µm), the field emission results have been explained using a simple model, and a fluorescent lamp was fabricated. Whilst previous work has been done on the link between “as grown” CNT films and their respective field emission properties on flat substrates, very little work has been done on linking morphology to emission performance on wire substrates, where the morphology can be very different. Microscopic structures such as towers, ridges and clumps consisting of many aligned or entangled CNTs were grown using an aerosol chemical vapour deposition (a-CVD) technique. Hydrogen added to the carrier gas resulted in a decrease in defect density in the growth of undoped CNTs, and an increase in defect density in the growth of nitrogen doped CNTs (N-CNTs) and boron doped CNTs (BCNTs). In-situ transmission electron microscopy (TEM) studies show that damage to CNT tips results in a significantly higher turn-on field compared to undamaged tips. This can be recovered by making the CNT emit current for several minutes which makes the tip recrystallize due to heat caused by the Nottingham effect. The field emission properties of the “as grown” CNT films are dominated by protruding CNTs found at the edges of ridge and tower microscopic structures. The field emission properties are also related to the dimensions of these structures with the longest ridges (hence those with the longest protruding CNTs) resulting in the lowest turn-on electric field. The ridge and tower structures act to accommodate protruding CNTs at their edges and their physical dimensions (mainly width) act to separate these emitters so that screening is minimised. This work shows that efficient emitters can be fabricated effectively from simple a-CVD techniques and microscopic structures act to improve, not degrade, field emission properties.
46
Tran, Hoang Anh. "One-Dimensional Nanostructure and Sensing Applications: Tin Dioxide Nanowires and Carbon Nanotubes." PDXScholar, 2016. http://pdxscholar.library.pdx.edu/open_access_etds/2689.
Full textAbstract:
The key challenge for a nanomaterial based sensor is how to synthesize in bulk quantity and fabricate an actual device with insightful understanding of operational mechanisms during performance. I report here effective, controllable methods that exploit the concepts of the "green approach" to synthesize two different one-dimensional nanostructures, including tin oxide nanowires and carbon nanotubes. The syntheses are followed by product characterization and sensing device fabrications as well as sensor performance understanding at the molecular level. Sensor-analyte response and recovery kinetics are also presented.
The first part of the thesis describes bulk-scale synthesis and characterization of tin oxide nanowires by the molten salt synthetic method and the nanowire doping with antimony (n-types) and lithium. The work builds on the success of using n-doped SnO2 nanoparticles to selectively detect chlorine gas at room temperature. Replacing n-doped nanoparticles with n-doped nanowires reduces the number of inter-particle electron hops between sensing electrodes. The nanowire based sensors show unprecedented 5 ppb detectability of corrosive Cl2 gas concentration in air. At the higher range, 10 ppm of Cl2 gas leads to a 250 fold increase in the device resistance. During sensor recovery, FT-IR studies show that dichlorine monoxide (Cl2O) and chlorine dioxide (ClO2) are the desorbing species. Long term stability of devices is affected by lattice oxygen vacancies replaced by chlorine atoms.
Bulk-scale synthesis of multiwall carbon nanotube (MWCNTs) was achieved by a novel inexpensive synthetic method. The green chemistry method uses the non-toxic and easy to handle solid carbon source naphthalene. The synthesis is carried out by simply heating naphthalene and organometallic precursors as catalysts in a sealed glass tube. Synthesis at 610º C leads to MWCNTs of 50 nm diameter and lengths exceeding well over microns. MWCNT doping is attempted with nitrogen (n-type) and boron (p-type) precursors. Palladium nanoparticles decorated on as-synthesized MWCNTs are employed for specific detection of explosive hydrogen gas with concentrations far below the explosive concentration limits. During performance, the sensor exhibits abnormal response behaviors at hydrogen gas concentrations higher than 1%. A model of charge carrier inversion, brought about by reduction of MWCNT by hydrogen molecules dissociated by Pd nanoparticles is proposed.
47
Gao, Xiang. "Ultrasound Assisted Extrusion and Properties of Polycarbonate/Carbon Nanotubes Composites and Cast Films." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1493394163570255.
Full text
48
Lewis, Todd M. "Carbon Nanotube Composites Prepared by Ultrasonically Assisted Twin Screw Extrusion." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1405330978.
Full text
49
Axel, Salinier. "Préparation d’un composite hybride par co-malaxeur : influence des paramètres de mise en oeuvre sur les propriétés." Thesis, Pau, 2014. http://www.theses.fr/2014PAUU3047/document.
Full textAbstract:
Ce travail de thèse porte sur les relations entre les paramètres de mise en œuvre à l’état fondu et les propriétés d’un composite hybride à matrice thermoplastique. Les charges étudiées sont les fibres de verre courtes (échelle micrométrique) et les nanotubes de carbone (NTC) (échelle nanométrique) dispersées dans une matrice thermoplastique thermostable, le poly(éther imide) (PEI). Nous avons montré que les fibres de verre participent fortement à la structuration du réseau de NTC et que la conductivité électrique du composite hybride est plus élevée que celle des nanocomposites. Les paramètres de mise en œuvre et notamment le paramètre Energie Mécanique Spécifique (EMS) a une forte influence sur les propriétés des composites hybrides et notamment sur la conductivité électrique. Il a été montré que les variations de conductivité électrique sont la conséquence d’un changement d’état de dispersion des NTC. Le taux de fibres de verre introduit dans le nanocomposite PEI/NTC a une forte influence sur la conductivité du composite hybride. Il est possible de contrôler la conductivité électrique du composite multi-échelles en modifiant le taux de fibres de verre introduit notamment pour des concentrations en NTC proche du seuil de percolationThis PhD work deals with the relationship between the processing parameters at the melt state and the polymer matrix hybrid composite material’s properties. The fillers studied are short glass fibres (micrometric scale) and carbon nanotubes (CNT) (nanometric scale) dispersed in a high temperature polymer matrix, the poly(etherimide) (PEI). We showed that glass fibres strongly participate in the CNT network structuration and that electrical conductivity of multiscale composite materials is higher than the one of nanocomposite materials. The combination of the two fillers allows obtaining a synergy effect for the mechanical properties especially for the elongation at break which is due to a preferential localization of CNT at the PEI/glass fibres interfaces. The study of the influence of processing parameters on the properties of nanocomposite materials and hybrid composite materials showed that Specific Mechanical Energy (SME) has a strong influence on the hybrid composite material properties and especially on the electrical conductivity. These variations are the consequences of CNT network modifications. Glass fibres concentration has also a strong influence on the electrical conductivity of the hybrid composite materials. It is possible to adjust the electrical conductivity with modifying the concentration of glass fibres especially for the CNT amount closed to the electrical percolation threshold
50
ZHAO, JIAN. "LIGHT SCATTERING CHARACTERIZATION OF CARBON NANOTUBE DISPERSIONS AND REINFORCEMENT OF POLYMER COMPOSITES." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1153886150.
Full text