Navegando por Palavras-chave "carbon nanotubes"
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- ItemSomente MetadadadosAg Ion Decoration for Surface Modifications of Multi-walled Carbon Nanotubes(Univ Fed Sao Carlos, Dept Engenharia Materials, 2014-05-01) Travessa, Dilermando Nagle [UNIFESP]; Silva, Fabio S. da; Cristovan, Fernando H. [UNIFESP]; Jorge Junior, Alberto Moreira; Cardoso, Katia Regina [UNIFESP]; Universidade Federal de São Paulo (UNIFESP); Empresa Brasileira Aeronaut SA Embraer; Universidade Federal de São Carlos (UFSCar)The production of high performance metal matrix composites depends on a proper design of the surface of the reinforcing phase, ensuring a good contact with a metal phase. in the present work, two Ag decorating procedures to modify the surface of multi-walled carbon nanotubes (MWCNT) were evaluated for further production of aluminum matrix composites. the procedures consisted in a two steps route based on acid oxidation of carbon nanotubes (CNT) followed by suspension in an Ag ion solution; and a single step route, based on the effect of n-dimethylformamide (DMF) as an activation agent of CNT surface, in presence of Ag ions. Transmission and scanning-transmission electron microscopy, Raman and Fourier-transformed infrared spectroscopy were employed in order to characterize the results. the two steps route resulted in Ag nano-particles homogeneously deposited over the CNT surface. the mechanism for the deposition is based on carboxyl and probably hydroxyl functional groups formed in the first step, acting as nucleation sites for Ag precipitation in the second step. the single step route resulted in the formation of sub-micrometric Ag particles heterogeneously mixed to CNT bundles.
- ItemSomente MetadadadosCarbon Nanotube-Reinforced Aluminum Matrix Composites Produced by High-Energy Ball Milling(Springer, 2017) Travessa, Dilermando N. [UNIFESP]; da Rocha, Geovana V. B. [UNIFESP]; Cardoso, Katia R. [UNIFESP]; Lieblich, MarcelaAlthough multiwall carbon nanotubes (MWCNT) are promising materials to strengthen lightweight aluminum matrix composites, their dispersion into the metallic matrix is challenge. In the present work, MWCNT were dispersed into age-hardenable AA6061 aluminum alloy by high-energy ball milling and the blend was subsequently hot-extruded. The composite bars obtained were heat-treated by solution heat treatment at 520 A degrees C and artificially aged at 177 A degrees C for 8 h, in order to reach the T6 temper. Special attention was given to the integrity of the MWCNT along the entire composite production. The microstructure of the obtained bars was evaluated by optical and scanning electron microscopy, and the mechanical properties were evaluated by Vickers microhardness tests. Raman spectroscopy, x-ray diffraction and transmission electron microscopy were employed to evaluate the structural integrity of MWCNT. It was found that milling time is critical to reach a proper dispersion of the reinforcing phase. The composite hardness increased up to 67% with the dispersion of 2% in weight of MWCNT, when comparing with un-reinforced bars produced by similar route. However, age hardening was not observed in composite bars after heat treatment. It was also found that MWCNT continuously degraded along the process, being partially converted into Al4C3 in the final composite.
- ItemSomente MetadadadosCarbon Nanotubes Arranged As Smart Interfaces in Lipid Langmuir-Blodgett Films Enhancing the Enzymatic Properties of Penicillinase for Biosensing Applications(Amer Chemical Soc, 2017) Scholl, Fabio A. [UNIFESP]; Morais, Paulo V.; Gabriel, Rayla C.; Schoening, Michael J.; Siqueira, Jose R., Jr.; Caseli, Luciano [UNIFESP]In this paper, carbon nanotubes (CNTs) were incorporated in penicillinase-phospholipid Langmuir and Langmuir-Blodgett (LB) films to enhance the enzyme catalytic properties. Adsorption of the penicillinase and CNTs at dimyristoylphosphatidic acid (DMPA) monolayers at the air-water interface was investigated by surface pressure-area isotherms, vibrational spectroscopy, and Brewster angle microscopy. The floating monolayers were transferred to solid supports through the LB technique, forming mixed DMPA-CNTs-PEN films, which were investigated by I quartz crystal microbalance, vibrational spectroscopy, and atomic force microscopy. Enzyme activity was studied with UV-vis spectroscopy and the feasibility of the supramolecular device nanostructured as ultrathin films were essayed in a capacitive electrolyte-insulator-semiconductor (EIS) sensor device. The presence of CNTs in the enzyme-lipid LB film not only tuned the catalytic activity of penicillinase but also helped conserve its enzyme activity after weeks, showing increased values of activity. Viability as penicillin sensor was demonstrated with capacitance/voltage and constant capacitance measurements, exhibiting regular and distinctive output signals over all concentrations used in this work. These results may be related not only to the nanostructured system provided by the film, but also to the synergism between the compounds on the active layer, leading to a surface morphology that allowed a fast analyte diffusion because of an adequate molecular accommodation, which also preserved the penicillinase activity. This work therefore demonstrates the feasibility of employing LB films composed of lipids, CNTs, and enzymes as EIS devices for biosensing applications.
- ItemAcesso aberto (Open Access)Nanocompósitos formados por nanotubos de carbono verticalmente alinhados e polidimetilsiloxano (desenvolvimento e caracterização elétrica)(Universidade Federal de São Paulo (UNIFESP), 2015-09-03) Gonzatto Neto, Alfredo [UNIFESP]; Corat, Evaldo Jose [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Nanocomposites formed by polydimethylsiloxane and carbon nanotubes were produced. Some relationships have been established between mechanical deformation and piezoresistive and capacitive effects through experiments involving deformation analysis and electrical characterizations. This study also allowed us to understand the probable piezoresistividade mechanisms responsible for the electrical characteristics of polymer nanocomposites of carbon nanotubes. Films of vertically aligned multi-walled carbon nanotubes were produced by microwave plasma on Ti substrate / TiN and subsequently integrated and transferred into a polymer matrix made in films form. Electrical DC analysis and AC impedance spectroscopy revealed two distinct contributions: from the physical contact of the carbon nanotubes, and from the no contact between the carbon nanotubes separated by small silicone fills. The second one, gives capacitive effects and especially the tunneling effect. Tunneling effect dependencies were found in relation to the density of the carbon nanotube film, to the applied voltage and range of deflection to which the membrane was subjected, thus influencing the response sensitivity. The nanocomposite behaved regularly under large deformations (910 μԐ to μԐ 90900), presenting Gauge factor between 8.6 and 0.8 in the respective order. In small deformations (10.4 μԐ to 41.6 μԐ) demonstrated good sensitivity, presenting Gauge Factor of 689, attributed to the use of the film in the relaxed state, benefiting from tunneling effect. The results were relevant and of considerable contribution to the study and development of new elastic and flexible sensors.
- ItemSomente MetadadadosProduction of rotary jet spun ultrathin fibers of poly-butylene adipate-co- terephthalate (PBAT) filled with nanocomposites(Spie-Int Soc Optical Engineering, 2017) Andrade, P. O. [UNIFESP]; Santo, A. M. E. [UNIFESP]; Costa, M. M.; Lobo, A. O.Composite fibers of bioabsorbable poly-butylene adipate-co-terephthalate (PBAT) reinforced with superhydrophilic carbon nanotubes and hydroxyapatite nanocrystals were obtained by rotary jet spinning technique (RJS). The fibers were morphologically and biologically analyzed and found of potential use as scaffold for hard tissue engineering.
- ItemSomente MetadadadosRedox-enzymes, cells and micro-organisms acting on carbon nanostructures transformation: A mini-review(Wiley-Blackwell, 2013-01-01) Seabra, Amedea B. [UNIFESP]; Paula, Amauri J.; Duran, Nelson; Universidade Federal de São Paulo (UNIFESP); Universidade Estadual de Campinas (UNICAMP); Universidade Federal do ABC (UFABC)Carbon nanotubes, graphene and fullerenes are actual nanomaterials with many applications in different industrial areas, with increasing potentialities in the field of nanomedicine. Recently, different proactive approaches on toxicology and safety management have become the focus of intense interest once the industrial production of these materials had a significant growth in the last years, even though their short- and long-term behaviors are not yet fully understood. the most important concerns involving these carbon-based nanomaterials are their stability and potential effects of their life cycles on animals, humans, and environment. in this context, this mini review discuss the biodegradability of these materials, particularly through redox-enzymes, micro-organisms and cells, to contribute toward the design of biocompatible and biodegradable functionalized carbon nanostructures, in order to use these materials safely and with minimum impact on the environment. (c) 2013 American Institute of Chemical Engineers Biotechnol. Prog. 29:1-10, 2013.