Evolution of catalyst particle size during carbon single walled nanotube growth and its effect on the tube characteristics

Harutyunyan, Avetik R.; Tokune, Toshio; Mora, Elena; Yoo, Jae Cheal; Epstein, Arthur J.

doi:10.1063/1.2335396

Cited by 24 publications

(16 citation statements)

References 46 publications

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“…In the AFM images there are clear examples of NPs at the end of SWNTs where the particles are much larger than the SWNTs, providing direct evidence that larger NPs can catalyze the growth of smaller SWNTs. This observation is in line with previous studies that found indirect evidence that for larger catalyst particles there appeared to be no direct correlation between the catalyst size and nanotube diameter 41. It is also interesting that the SWNT network density is so insensitive to catalyst concentration.…”

Section: Resultssupporting

confidence: 92%

Controlled Growth and Characterization of Two‐Dimensional Single‐Walled Carbon‐Nanotube Networks for Electrical Applications

Edgeworth

Wilson

Macpherson

2007

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We demonstrate the reproducible fabrication of single-walled carbon nanotube (SWNT) networks, via catalyzed chemical vapor deposition (cCVD). Fe nanoparticles are employed as the catalyst, with methane as the carbon-containing gas. cCVD growth under these conditions results in the formation of multiply interconnected, random, two-dimensional networks of SWNTs. Investigation of the effect of parameters such as methane flow rate and temperature on the growth process enables control over the density of the network, which controls the network conductivity. Low-density networks demonstrate p-type semiconductor behavior, whilst high-density networks exhibit semimetallic behavior. In both cases conductance is demonstrated over macroscopic length scales, up to millimeters, much longer than the individual SWNTs, despite the surface coverage being <1 %. The networks can be defined in regions of a surface by photolithography before or after growth. Controlled growth of SWNT networks thus enables the application of SWNTs as macroscale conductors with controllable, predictable, and reproducible characteristics.

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Section: Resultssupporting

confidence: 92%

Controlled Growth and Characterization of Two‐Dimensional Single‐Walled Carbon‐Nanotube Networks for Electrical Applications

Edgeworth

Wilson

Macpherson

2007

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“…Consequently, if liquefaction was a prerequisite for catalytic activity, the small particles would begin to produce nanotubes earlier. Experimental verification of this hypothesis is challenging: very small catalyst nanoparticles (d ∼ =1 nm) have a fast rate of coalescence during the reaction and coagulate to form bigger clusters [100,101]. Following the VLS model, the growth of very small nanotubes using metallic catalyst would be possible only if the reaction temperature were above T eut (to liquefy the particle) and below the temperature at which particles begin to coalesce.…”

Section: Phase Diagram Of Free and Supported Fe-c Nanoparticlesmentioning

confidence: 99%

Theoretical study of the thermal behavior of free and alumina-supported Fe-C nanoparticles

et al. 2007

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The thermal behavior of free and alumina-supported iron-carbon nanoparticles is investigated via molecular dynamics simulations, in which the effect of the substrate is treated with a simple Morse potential fitted to ab initio data. We observe that the presence of the substrate raises the melting temperature of medium and large Fe1−xCx nanoparticles (x = 0 − 0.16, N = 80 − 1000, nonmagic numbers) by 40-60 K; it also plays an important role in defining the ground state of smaller Fe nanoparticles (N = 50 − 80). The main focus of our study is the investigation of Fe-C phase diagrams as a function of the nanoparticle size. We find that as the cluster size decreases in the 1.1-1.6-nm-diameter range the eutectic point shifts significantly not only toward lower temperatures, as expected from the Gibbs-Thomson law, but also toward lower concentrations of C. The strong dependence of the maximum C solubility on the Fe-C cluster size may have important implications for the catalytic growth of carbon nanotubes by chemical vapor deposition.

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“…In our experiments, Fe catalysts supported on alumina powder were prepared using a the common impregnation method [14]. To find the minimum synthesis temperature, T min synth , as a function of catalyst size, different particles' dimensions were obtained by varying the Fe:Al 2 O 3 molar ratio 1:15, 1:25, 1:50 and 1:100, [24] corresponding to particles of diameters ∼ 3 ± 0.6, ∼ 2 ± 0.8, ∼ 1.4 ± 0.7, and ∼ 1.3 ± 0.7 nm, respectively. The growth of SWC-NTs was performed with CCVD at temperatures between 650-900 • C, for 90 min over the pre-reduced catalysts [25].…”

mentioning

confidence: 99%

Reduced Carbon Solubility in Fe Nanoclusters and Implications for the Growth of Single-Walled Carbon Nanotubes

et al. 2008

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Fe nanoclusters are becoming the standard catalysts for growing single-walled carbon nanotubes via chemical vapor decomposition. Contrary to the Gibbs-Thompson model, we find that the reduction of the catalyst size requires an increase of the minimum temperature necessary for the growth. We address this phenomenon in terms of solubility of C in Fe nanoclusters and, by using first-principles calculations, we devise a simple model to predict the behavior of the phases competing for stability in Fe-C nanoclusters at low temperature. We show that, as a function of particle size, there are three scenarios compatible with steady state growth, limited growth, and no growth of single-walled carbon nanotubes, corresponding to unaffected, reduced, and no solubility of C in the particles.

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Evolution of catalyst particle size during carbon single walled nanotube growth and its effect on the tube characteristics

Cited by 24 publications

References 46 publications

Controlled Growth and Characterization of Two‐Dimensional Single‐Walled Carbon‐Nanotube Networks for Electrical Applications

Controlled Growth and Characterization of Two‐Dimensional Single‐Walled Carbon‐Nanotube Networks for Electrical Applications

Theoretical study of the thermal behavior of free and alumina-supported Fe-C nanoparticles

Reduced Carbon Solubility in Fe Nanoclusters and Implications for the Growth of Single-Walled Carbon Nanotubes

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