The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Lisa D Pfefferle - One of the best experts on this subject based on the ideXlab platform.
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synthesis of uniform diameter single wall carbon nanotubes in co mcm 41 effects of the catalyst Prereduction and nanotube growth temperatures
Journal of Catalysis, 2004Co-Authors: Yuan Chen, Dragos Ciuparu, Sangyun Lim, Yanhui Yang, Gary L Haller, Lisa D PfefferleAbstract:Catalyst pretreatment and CO disproportionation reaction conditions were observed to strongly affect the diameter uniformity of single-wall carbon nanotubes (SWNT) grown on Co-MCM-41 catalysts. The Prereduction and CO disproportionation reaction temperatures were varied systematically while the carbon loading and the SWNT diameter uniformity were monitored by TGA, Raman spectroscopy, and TEM. The state of the catalyst during Prereduction and the size of the cobalt clusters formed during the SWNT growth process were monitored by in situ XANES during the Prereduction of the Co-MCM-41, and ex situ EXAFS of catalyst samples was performed after carbon deposition. These experiments allow development of correlations between the SWNT quality and the state of the catalyst. Control of the cobalt cluster size in the Co-MCM-41 catalyst is critical to the SWNT diameter control. The size of the cobalt cluster changes with both the Prereduction and the SWNT synthesis temperatures. SWNT with a very narrow diameter distribution can be grown in Co-MCM-41 by controlling both the Prereduction and the reaction temperatures.
T Sands - One of the best experts on this subject based on the ideXlab platform.
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dendrimer templated fe nanoparticles for the growth of single wall carbon nanotubes by plasma enhanced cvd
Journal of Physical Chemistry B, 2006Co-Authors: Placidus B Amama, Matthew R Maschmann, Timothy S Fisher, T SandsAbstract:A fourth-generation (G4) poly(amidoamine) (PAMAM) dendrimer (G4-NH2) has been used as a template to deliver nearly monodispersed catalyst nanoparticles to SiO2/Si, Ti/Si, sapphire, and porous anodic alumina (PAA) substrates. Fe2O3 nanoparticles obtained after calcination of the immobilized Fe3+/G4-NH2 composite served as catalytic “seeds” for the growth of single-wall carbon nanotubes (SWNTs) by microwave plasma-enhanced CVD (PECVD). To surmount the difficulty associated with SWNT growth via PECVD, reaction conditions that promote the stabilization of Fe nanoparticles, resulting in enhanced SWNT selectivity and quality, have been identified. In particular, in situ annealing of Fe catalyst in an N2 atmosphere was found to improve SWNT selectivity and quality. H2 Prereduction at 900 °C for 5 min was also found to enhance SWNT selectivity and quality for SiO2/Si supported catalyst, albeit of lower quality for sapphire supported catalyst. The application of positive dc bias voltage (+200 V) during SWNT growth...
Yuan Chen - One of the best experts on this subject based on the ideXlab platform.
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synthesis of uniform diameter single wall carbon nanotubes in co mcm 41 effects of the catalyst Prereduction and nanotube growth temperatures
Journal of Catalysis, 2004Co-Authors: Yuan Chen, Dragos Ciuparu, Sangyun Lim, Yanhui Yang, Gary L Haller, Lisa D PfefferleAbstract:Catalyst pretreatment and CO disproportionation reaction conditions were observed to strongly affect the diameter uniformity of single-wall carbon nanotubes (SWNT) grown on Co-MCM-41 catalysts. The Prereduction and CO disproportionation reaction temperatures were varied systematically while the carbon loading and the SWNT diameter uniformity were monitored by TGA, Raman spectroscopy, and TEM. The state of the catalyst during Prereduction and the size of the cobalt clusters formed during the SWNT growth process were monitored by in situ XANES during the Prereduction of the Co-MCM-41, and ex situ EXAFS of catalyst samples was performed after carbon deposition. These experiments allow development of correlations between the SWNT quality and the state of the catalyst. Control of the cobalt cluster size in the Co-MCM-41 catalyst is critical to the SWNT diameter control. The size of the cobalt cluster changes with both the Prereduction and the SWNT synthesis temperatures. SWNT with a very narrow diameter distribution can be grown in Co-MCM-41 by controlling both the Prereduction and the reaction temperatures.
Placidus B Amama - One of the best experts on this subject based on the ideXlab platform.
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dendrimer templated fe nanoparticles for the growth of single wall carbon nanotubes by plasma enhanced cvd
Journal of Physical Chemistry B, 2006Co-Authors: Placidus B Amama, Matthew R Maschmann, Timothy S Fisher, T SandsAbstract:A fourth-generation (G4) poly(amidoamine) (PAMAM) dendrimer (G4-NH2) has been used as a template to deliver nearly monodispersed catalyst nanoparticles to SiO2/Si, Ti/Si, sapphire, and porous anodic alumina (PAA) substrates. Fe2O3 nanoparticles obtained after calcination of the immobilized Fe3+/G4-NH2 composite served as catalytic “seeds” for the growth of single-wall carbon nanotubes (SWNTs) by microwave plasma-enhanced CVD (PECVD). To surmount the difficulty associated with SWNT growth via PECVD, reaction conditions that promote the stabilization of Fe nanoparticles, resulting in enhanced SWNT selectivity and quality, have been identified. In particular, in situ annealing of Fe catalyst in an N2 atmosphere was found to improve SWNT selectivity and quality. H2 Prereduction at 900 °C for 5 min was also found to enhance SWNT selectivity and quality for SiO2/Si supported catalyst, albeit of lower quality for sapphire supported catalyst. The application of positive dc bias voltage (+200 V) during SWNT growth...
Dragos Ciuparu - One of the best experts on this subject based on the ideXlab platform.
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synthesis of uniform diameter single wall carbon nanotubes in co mcm 41 effects of the catalyst Prereduction and nanotube growth temperatures
Journal of Catalysis, 2004Co-Authors: Yuan Chen, Dragos Ciuparu, Sangyun Lim, Yanhui Yang, Gary L Haller, Lisa D PfefferleAbstract:Catalyst pretreatment and CO disproportionation reaction conditions were observed to strongly affect the diameter uniformity of single-wall carbon nanotubes (SWNT) grown on Co-MCM-41 catalysts. The Prereduction and CO disproportionation reaction temperatures were varied systematically while the carbon loading and the SWNT diameter uniformity were monitored by TGA, Raman spectroscopy, and TEM. The state of the catalyst during Prereduction and the size of the cobalt clusters formed during the SWNT growth process were monitored by in situ XANES during the Prereduction of the Co-MCM-41, and ex situ EXAFS of catalyst samples was performed after carbon deposition. These experiments allow development of correlations between the SWNT quality and the state of the catalyst. Control of the cobalt cluster size in the Co-MCM-41 catalyst is critical to the SWNT diameter control. The size of the cobalt cluster changes with both the Prereduction and the SWNT synthesis temperatures. SWNT with a very narrow diameter distribution can be grown in Co-MCM-41 by controlling both the Prereduction and the reaction temperatures.