Controlling the Diameter of Carbon Nanotubes in Chemical Vapor Deposition Method by Carbon Feeding

Lu, Chenguang; Liu, Jie

doi:10.1021/jp0632283

Cited by 183 publications

(182 citation statements)

References 32 publications

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“…17 We speculate that the few size distributions available in the literature [37][38][39][40][41][42][43][44] are not representative of the ones that have been used in the production of the percolating networks in CNT composites. Although a speculation, we feel it is plausible because sonication and, in some preparation procedures, screw extrusion 54 causes a larger skewness toward short lengths.…”

Section: Discussionmentioning

confidence: 99%

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Connectivity percolation of polydisperse anisotropic nanofillers

Otten¹,

Schoot²

2011

The Journal of Chemical Physics

127

168

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We present a generalized connectedness percolation theory reduced to a compact form for a large class of anisotropic particle mixtures with variable degrees of connectivity. Even though allowing for an infinite number of components, we derive a compact yet exact expression for the mean cluster size of connected particles. We apply our theory to rodlike particles taken as a model for carbon nanotubes and find that the percolation threshold is sensitive to polydispersity in length, diameter, and the level of connectivity, which may explain large variations in the experimental values for the electrical percolation threshold in carbon-nanotube composites. The calculated connectedness percolation threshold depends only on a few moments of the full distribution function. If the distribution function factorizes, then the percolation threshold is raised by the presence of thicker rods, whereas it is lowered by any length polydispersity relative to the one with the same average length and diameter. We show that for a given average length, a length distribution that is strongly skewed to shorter lengths produces the lowest threshold relative to the equivalent monodisperse one. However, if the lengths and diameters of the particles are linearly correlated, polydispersity raises the percolation threshold and more so for a more skewed distribution toward smaller lengths. The effect of connectivity polydispersity is studied by considering nonadditive mixtures of conductive and insulating particles, and we present tentative predictions for the percolation threshold of graphene sheets modeled as perfectly rigid, disklike particles.

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Section: Discussionmentioning

confidence: 99%

“…However, in practice m remains close to unity because for both SWCNTs and MWCNTs, we estimate it to be at most 0.2. 37,38 As to the influence of a length polydispersity, the fact that a large value of s leads to a low PT is an important issue that we return to in the discussion.…”

Section: Tetradisperse Distributionmentioning

confidence: 99%

Connectivity percolation of polydisperse anisotropic nanofillers

Otten¹,

Schoot²

2011

The Journal of Chemical Physics

127

168

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“…Based on the VLS mechanism, many methods have been developed to grow SWNTs in a controlled manner. For example, the size distribution of catalyst nanoparticles can strongly influence the distribution of nanotube diameters [3,4]; special catalysts can grow SWNTs with narrow chirality distributions [5,6]; site-controlled catalyst nanoparticles determine the growth position of carbon nanotubes [7]; the carbon feeding rate during the growth can be used to control the diameter distribution of SWNTs [8]; the growth of SWNTs Nano Res (2009) 2: 768 773 Áoating in the gas phase [9,10] can afford ultra-long Á carbon nanotubes (up to centimeters in length); and on single-crystal substrates, such as sapphire [11,12] and quartz [13,14], SWNTs with extremely high alignment can be grown. However, for an individual carbon nanotube, it is difÀ cult to control its growth, À because the active growth time and growth rate depend on the activity of the catalyst, which is uncontrollable.…”

Section: Introductionmentioning

confidence: 99%

Nanobarrier-terminated growth of single-walled carbon nanotubes on quartz surfaces

et al. 2009

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Using carbon nanotubes as nanobarriers, the growth of single-walled carbon nanotubes (SWNTs) on a quartz surface can be terminated. First, carbon nanotube nanobarriers were grown on a quartz surface by the gas Áow-Á directed growth mode. Then, the SWNTs were grown on the quartz surface via the lattice-oriented growth mode, in which growth of SWNTs can be terminated by hitting the nanotube nanobarriers. Moreover, using the carbon nanotube nanobarrier as a marker, the mechanism of the growth of SWNTs on the quartz surface can be studied; a base-growth mechanism is indicated. Based on this termination process and the base-growth mechanism, SWNT arrays with controlled lengths can be grown on a quartz surface by Àxing the sites of both À catalysts and nanobarriers.

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“…This condition is due to nanoparticles activated by their diameter under a given carbon feeding rate where large particles are underfed and not nucleating growth, while smaller particles are cutoff from carbon supplies in consequence of carbon poisoning. [29,30] In this work, Co catalyst has a better role in growing CNTs as compared with Ni due to the effect of catalytic activity. The growth rate of nanotube appears to be more prominent in Co catalyst due to broader particle size distribution that allows further absorption of carbon feedstock, thereby resulting in a much thicker nanotube formation and higher growth rate.…”

Section: Resultsmentioning

confidence: 97%

Effect of Co and Ni nanoparticles formation on carbon nanotubes growth via PECVD

Lee

Haniff

Teh

et al. 2015

Journal of Experimental Nanoscience

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The effect of cobalt (Co) and nickel (Ni) nanoparticle catalysts on the growth of carbon nanotubes (CNTs) were studied, where the CNTs were vertically grown by plasma enhanced chemical vapour deposition (PECVD) method. The growth conditions were fixed at a temperature of 700 C with a pressure of 1000 mTorr for 40 minutes with various thicknesses of sputtered metal catalysts. Only multiwalled carbon nanotubes are present from the growth as large average diameter of outer tube (»10À30 nm) were measured for both of the catalysts used. Experimental results show that high density of CNTs was observed especially towards thicker catalysts layers where larger and thicker nanotubes were formed. The nucleation of the catalyst with various thicknesses was also studied as the absorption of the carbon feedstock is dependent on the initial size of the catalyst island. The average diameter of particle size increases from 4 to 10 nm for Co and Ni catalysts. A linear relationship is shown between the nanoparticle size and the diameter of tubes with catalyst thicknesses for both catalysts. The average growth rate of Co catalyst is about 1.5 times higher than Ni catalyst, which indicates that Co catalyst has a better role in growing CNTs with thinner catalyst layer. It is found that Co yields higher growth rate, bigger diameter of nanotube and thicker wall as compared to Ni catalyst. However, variation in Co and Ni catalysts thicknesses did not influence the quality of CNTs grown, as only minor variation in I G /I D ratio from Raman spectra analysis. The study reveals that the catalysts thickness strongly affects not only nanotube diameter and growth rate but also morphology of the nanoparticles formed during the process without influencing the quality of CNTs.

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Controlling the Diameter of Carbon Nanotubes in Chemical Vapor Deposition Method by Carbon Feeding

Cited by 183 publications

References 32 publications

Connectivity percolation of polydisperse anisotropic nanofillers

Connectivity percolation of polydisperse anisotropic nanofillers

Nanobarrier-terminated growth of single-walled carbon nanotubes on quartz surfaces

Effect of Co and Ni nanoparticles formation on carbon nanotubes growth via PECVD

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