Carbon Nanostructures
Mostrando 25-36 de 42 artigos, teses e dissertações.
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25. Compositos resina epóxi/nanotubos de carbono de paredes múltiplas: caracterização dos materiais de partida e avaliação das condutividades elétrica e térmica
Investigamos 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).
Publicado em: 2009
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26. Propriedades opticas de nanofios de InP / Optical properties of InP nanowires
Optical properties of InP nanowires grown by Vapor-Liquid-Solid (VLS) method in a Chemical Beam Epitaxy system were investigated by using micro-photoluminescence spectroscopy varying experimental parameters such as excitation power, emitted signal polarization and sample temperature. Due to polytypism (InP in cubic, zincblende (ZB), and hexagonal, wurtzite (
Publicado em: 2009
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27. Preparação, caracterização e avaliação de carbono funcionalizado para aplicações em células a combustível tipo PEM / Preparation, characterization and evaluation of electrocatalysts supported on functionalized carbon black for polymer exchange membrane fuel cell applications
A tecnologia de células a combustível associada à crescente exigência de baixo impacto ambiental tornou-se bastante promissora no cenário mundial de energia. As células a combustível são, em princípio, dispositivos que convertem energia química diretamente em energia elétrica e térmica, possuindo, entretanto, uma operação contínua, graças à
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 31/01/2008
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28. Estudo de Impurezas de Carbono em Nanoestruturas de BN
In this work, we performed an analysis of the structural and electronic stability of nanostructures of Boron Nitride (BN), such as layers, tubes and cones, when doped with Carbon, through first-principles calculations as implemented in code SIESTA. We found that substitutional doping of Carbon for either a single Boron or a single Nitrogen atom produces sign
Publicado em: 2008
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29. Purificação e caracterização de nanotubos de carbono produzidos pelo método de descarga em arco elétrico
The objective of this work was to study the purification of a sample of commercial carbon nanotubes (CNTs) produced by the Carbolex arc-discharge method using the catalyst mixture Ni/Y (4/1 at. %). Another objective of this work was to investigate an alternative functionalization route for the introduction of hydroxyl groups (-OH) onto CNT sidewalls and to e
Publicado em: 2008
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30. Casca de arroz processada via enzimólise como fonte de carbono para produção de celulose por Acetobacter xylinum / Rice husk processed with hidrolityc enzimes as source of carbon for the production of bacterial cellulose by Acetobacter xylinum
Bacterial cellulose (BC) has been applied in the electronic industry and in medicine as a wound dressing film. However, the high manufacturing cost limits its wide-scale use. To reduce the costs of the process and obtain a differentiated product, this work proposes the use of rice husk as a substrate for the production of BC, since it consists of minerals, c
Publicado em: 2008
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31. Caracterização óptica de dispersões aquosas de nanotubos de carbono
It has been demonstrated that the electronic and optical properties of single-wall carbon nanotubes (SWNT) are strongly affected by the environment. This strong environmental effect is very relevant in analyzing the composition of carbon nanotube samples using optical techniques, especially in the case of separation experiments, where the SWNT environments a
Publicado em: 2008
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32. Análise por impedância eletroquímica \"on-line\" de conjuntos eletrodo/membrana (MEA) de células a combustível a membrana polimérica (PEMFC) / Analysis for impedance electrochemistry \"on-line\" of membrane/electrode assemble (MEA) of protons exchange membrane fuel cells (PEMFC)
This work reports results of studies and characterization on Membrane Electrode Assemblies (MEAs) for Proton Exchange Membrane Fuel Cell (PEMFC). Some cell operation conditions and different processes of MEA production were investigated. The Electrochemical Impedance Spectroscopy Technique (EIS) (in situ - 0 to 16 A) was used \"on-line\" as a tool for diagno
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 15/08/2007
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33. Estudo estrutural e eletronico de fulerenos e diamondoides encapsulados em nanotubos de carbono / Structural and electronical study of encapsulated fullerenes and diamondoids in carbon nanotubes
This work presents a theoretical study of carbon nanostructures with great interest in nanoscience world. It is about the structural, electronic and mechanical study of hybrid structures that result from encapsulation of carbon molecules (fullerenes and diamondoids) introduced inside carbon nanotubes. Using classical methods of molecular dynamics we performe
Publicado em: 2007
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34. Nanoestruturas formadas por redes orgânicas covalentes
In this work we apply first-principles calculations based on the Density Functional Theory (DFT) to investigate structural and electronic properties of covalent organic frameworks (COF s). These structures were recently obtained experimentally and constitute a new class of porous nanostructures composed only of light elements (H, C, B and O atoms). The coval
Publicado em: 2007
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35. Interação de nanotubos de carbono com segmentos de DNA
Single- and double-stranded DNA (deoxyribonucleic acid) molecules can strongly bind to single-walled carbon nanotubes (SWNT) via non-covalent interactions. Under certain conditions, the DNA molecule spontaneously self-assembles into a helical wrapping around the tubular structure of the carbon nanotubes to form DNA/SWNT hybrids, which are both stable and sol
Publicado em: 2007
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36. Preparação e caracterização de nanoestruturas de carbono contendo nitrogenio / Synthesis and characterization of carbon nanostructires containing nitrogen
Nesta tese são apresentados os efeitos nas propriedades estruturais, eletrônicas e de emissão eletrônica por efeito de campo elétrico induzidos pela incorporação de nitrogênio em nanoestruturas de carbono. As nanoestruturas de carbono contendo nitrogênio foram preparadas por pulverização catódica (sputtering) de um alvo de grafite assistido, ou n
Publicado em: 2007