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Rochdale, United Kingdom

Ali N.,CNC Coatings | Chipara M.,University of Texas-Pan American | Bai J.B.,Ecole Centrale Paris
Journal of Nanoscience and Nanotechnology | Year: 2011

Room temperature electron spin resonance spectra of epoxy resins loaded with various concentrations of multiwalled carbon nanotubes of various lengths are analyzed. The resonance spectrum near the free electron line position is dominated by a single almost symmetric line assigned to delocalized electrons residing on multiwalled carbon nanotubes. The experimental research shown that: (1) The dependence of the g-factor on nanotubes length is controlled by the distortions of multiwalled carbon nanotubes. (2) The dependence of the g-factor on the concentration of multiwalled nanotubes reflects the interactions between electrons localized on different nanotubes. In insulating composites, the resonance line width broadens as the length and the concentration of multiwalled carbon nanotubes is increased. (3) For conducting composites, the dependence of the electron spin resonance line width on the length and concentration of multiwalled carbon nanotubes is controlled by Elliott contribution and exchange interactions, respectively. (4) The concentration of conduction electrons increases as the length and the concentration of multiwalled carbon nanotubes are increased. Copyright © 2011 American Scientific Publishers. All rights reserved. Source


Chipara M.,University of Texas-Pan American | Vaia R.A.,Air Force Research Lab | Nasar A.,CNC Coatings
Vacuum | Year: 2014

Electron Spin Resonance investigations on polyurethane - vapor grown carbon nanofiber composites are reported. The research focuses on the free radicals generated during the processing step and on the ESR spectrum of the conducting electrons delocalized over the carbon nanofiber. The deactivation of free radicals due to their interaction with the electrons residing on carbon nanofiber was analyzed and related to the enhanced stability of these composites. The dependence of the resonance line parameters on the concentration of the nanofiller is studied in detail. Experimental data indicates that the electrical conductivity is due to uncoupled electrons delocalized over the conducting domains of the nanofiller and suggests that the electrical conductivity is dominated by polarons. The percolation of the electrical conductivity is also reflected in the ESR data. The interactions between uncoupled electronic spins, as revealed by the line width dependence on the concentration of carbon nanofibers are discussed in detail. © Published by Elsevier Ltd. Source


Wei X.,University of Nebraska - Lincoln | Georgescu R.,Romanian National Institute for Lasers, Plasma and Radiation Physics | Ali N.,CNC Coatings | Morjan I.,Romanian National Institute for Lasers, Plasma and Radiation Physics | And 6 more authors.
Journal of Nanoscience and Nanotechnology | Year: 2012

The synthesis of iron doped tin oxide by pulsed laser pyrolysis is reported. The as obtained nanoparticles have a dominant SnO2 phase (as revealed by Wide Angle X-ray Scattering), with particles of the order of 10 nm. The doping with iron or iron oxide triggers magnetic properties as confirmed by SQUID experiments. EDX measurements supported the presence of Fe while Wide Angle X-ray Scattering failed to sense any iron or iron-oxide phase. It is concluded that Fe is well dispersed within the tin-oxide nanoparticles. The coercitive field has a complex dependence on the Fe/Sn content suggesting that the magnetization is not controlled solely by the amount of Fe dispersed within the nanoparticles. Copyright © 2012 American Scientific Publishers All rights reserved. Source


Popescu B.M.,Ovidius University | Ali N.,CNC Coatings | Basturea G.,University of Miami | Comsa G.I.,Ovidius University | And 2 more authors.
Applied Surface Science | Year: 2013

A critical review of the biological and medical effects of one dimensional nanoparticles is presented. The review focuses on the toxicity of carbon nanotubes-a subject under strong debate and discusses briefly the most important concepts. It is tentatively suggested that the huge aspect ratio and the high Young modulus of carbon nanotubes are playing an important role in the biological, medical, and toxicological aspects of carbon nanotubes despite their low intrinsic biochemical activity. The most suitable biomedical model for the biological and medical effects of carbon nanotubes is described by the so-called impaling mode which appears to be qualitatively consistent with partial phagocytosis. © 2013 Elsevier B.V. Source

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