Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 3 of 3
Full-Text Articles in Physics
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
Browse all Theses and Dissertations
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 …
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
Browse all Theses and Dissertations
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 …
Evanescent Microwave Characterization Of Carbon Nanotube Films Grown On Silicon Carbide Substrate, Kineshma Munbodh
Evanescent Microwave Characterization Of Carbon Nanotube Films Grown On Silicon Carbide Substrate, Kineshma Munbodh
Browse all Theses and Dissertations
The electromagnetic characterization of carbon nanotube films (CNT) grown by the surface decomposition of silicon carbide (SiC) has been performed. The CNT films formed on the carbon and silicon terminated face of the SiC substrate were uncapped by an annealing process at a temperature of 4000 C with dwelling time up to 60 minutes in oxygen or carbon dioxide atmosphere. X-Y scans of the quality factor were used to deduce the local conductive properties of the films measured by evanescent microwave microscopy. Real and imaginary permittivity values, as determined by these electromagnetic measurements, provided valuable information for future field emission …