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Full-Text Articles in Physical Sciences and Mathematics
Temperature And Frequency Dependent Conduction Mechanisms Within Bulk Carbon Nanotube Materials, John Simmons Bulmer
Temperature And Frequency Dependent Conduction Mechanisms Within Bulk Carbon Nanotube Materials, John Simmons Bulmer
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The resistance of three types of bulk carbon nanotube (CNT) materials (floating catalyst CNT yarn, forest grown CNT yarn, and super acid spun CNT fiber) was measured from room temperature to 900 C. Fitting the curves to established conduction equations for disordered materials, competing conduction mechanisms pertaining to the material could be determined. Floating catalyst CNT yarn displayed both semiconductive and metallic isotropic behavior with a resistance minimum, similar to the behavior of crystalline graphite. It was found that, at room temperature, the semiconducting contribution-most likely junctions between CNTs-accounted for 99.99% of the overall resistance. The resistance of forest grown …
Ostwald Ripening Of Iron (Fe) Catalyst Nanoparticles On Aluminum Oxide Surfaces (Al2O3) For The Growth Of Carbon Nanotubes, Roberto I. Acosta
Ostwald Ripening Of Iron (Fe) Catalyst Nanoparticles On Aluminum Oxide Surfaces (Al2O3) For The Growth Of Carbon Nanotubes, Roberto I. Acosta
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Theoretical models have proposed that the nucleation and growth mechanism of carbon nanotubes (CNTs) has been affected by the catalytic activity of transition metals. The catalyst behavior during growth has been mainly associated as the responsible mechanism for the termination of CNT growth. Although several hypotheses have been developed to explain this mechanism, is still today an unresolved phenomenon. It was recently shown that the Ostwald ripening of iron (Fe) nanoparticles played a dominant role in the termination of CNT growth. The Ostwald ripening mechanism was further investigated as a function of thermal annealing in Hydrogen (H2) for …