Comparative study of herringbone and stacked-cup carbon nanofibers

Kim, Yoong Ahm; Hayashi, T.; Naokawa, Satoru; Yanagisawa, Takashi; Endo, Morinobu

doi:10.1016/j.carbon.2005.06.037

Cited by 34 publications

(26 citation statements)

References 19 publications

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“…While the type of catalyst (Fe vs Ni) does not seem important for producing this type of CNFs, the presence of sulfur seems to be indispensable to produce of this unique structure. Kim et al [24] suggested that the catalyst particle must be molten, and according to Tibbetts et al [38], the presence of sulfur causes the catalyst particles to melt due to an eutectic in the Fe-S system at 1271 K and at a 42 at.% of S. This molten state increases the catalytic activity, which allows to reduce the residence time considerably and, in turn, mitigates the non-catalytic CVD coating (or soot) formation. The quantity of sulfur in the feedstock cannot be random and must be on a similar atomic ratio to iron.…”

Section: Discussionmentioning

confidence: 99%

“…1h. Although these nanofibers were previously described as either a Pd catalyzed product [22] with small diameters around 20 nm or a Fe derived nanofiber with a huge hollow space [23], Kim et al [24] recently stated that the stackedcup nanofibers have a circular cross-section and are different to fishbone nanofibers even though the TEM pictures look like the same. These authors also stated that stacked-cup carbon nanofibers, with a huge hollow space, are catalyzed with a molten particle.…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, Tibbetts and Balogh [39] reported that together to the role of sulfur, a liquid Fe-C intermediate in the catalytic particle is also necessary. Most of the carbon nanofibers produced with iron by the floating catalyst method with sulfur were thickened MWNTs until it was recently communicated that stacked-cup nanofibers [23,24] and fishbone nanofibers [40] can also be produced by the floating catalyst method with an iron organometallic and a sulfurhydrocarbon source. Consequently, the literature is not clear when differentiating between when each type of carbon nanofiber is produced.…”

Section: Introductionmentioning

confidence: 99%

“…There are also thickened carbon nanofibers whose base structures are another of the previously listed nanofiber types. For example, Kim et al [24] reported the stacked-cup nanofiber covered by a CVD coating.…”

Section: Introductionmentioning

confidence: 99%

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Differences between carbon nanofibers produced using Fe and Ni catalysts in a floating catalyst reactor

Martı́n-Gullón

Vera

Conesa

et al. 2006

Carbon

198

103

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Carbon nanofibers were produced by the catalytic CVD process by the floating catalyst method, in semi-industrial systems at temperatures above 1350 K. Iron-derived carbon nanofibers were produced from natural gas and xylene, using ferrocene as catalyst source, yielding a thickened submicron vapor grown carbon fibers with a core of multi-wall nanotubes. For the production of Ni derived nanofibers, natural gas was used as the carbon feedstock, and the Ni was added in a nickel compound solution. When no sulfur is used, only soot was obtained, but when sulfur is added to the reactive feedstock, a highly graphitic and very nice stacked-cup-type nanofibers with no free-CVD thickened layer were produced. TEM-EDS analysis confirms that this type of stacked-cup carbon nanofiber is produced only with a partially molten catalyst and methane as hydrocarbon source. In fact, very few fibers have either a particle tip at the end or trapped metal particle inside the wide hollow core of this type of produced carbon material.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Differences between carbon nanofibers produced using Fe and Ni catalysts in a floating catalyst reactor

Martı́n-Gullón

Vera

Conesa

et al. 2006

Carbon

198

103

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“…Cup-stacked carbon nanotubes are excellent as supports for Pt-Ru catalysts [77] and have been synthesized with a diameter of 80-120 nm and a hollow channel of 60-100 nm along the nanotube axis [78]. This configuration is shown in Figure 4 [79]. For carbon peapods, however, stability is probably compromised since it was shown that the axial stability is less than that of a carbon nanotube under identical conditions [80].…”

Section: Categories Of Carbon Nanotubesmentioning

confidence: 99%

The Separation Power of Nanotubes in Membranes: A Review

Bruggen

2012

ISRN Nanotechnology

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Research on mixed matrix membranes in which nanoparticles are used to enhance the membrane's performance in terms of flux, separation, and fouling resistance has boomed in the last years. This review probes on the specific features and benefits of one specific type of nanoparticles with a well-defined cylindrical structure, known as nanotubes. Nanotube structures for potential use in membranes are reviewed. These comprise mainly single-wall carbon nanotubes (SWCNTs) and multiwall carbon nanotubes (MWCNTs), but also other structures and materials, which are less studied for membrane applications, can be used. Important issues related to polymer-nanotube interactions such as dispersion and alignment are outlined, and a categorization is made of the resultant membranes. Applications are reviewed in four different areas, that is, gas separation, water filtration, drug delivery, and fuel cells.

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Single Negative Metamaterials in Unstructured Polymer Nanocomposites Toward Selectable and Controllable Negative Permittivity

2009

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Negative permittivity is one of the key characteristics of the unique metamaterials, a novel class of artificial materials with special structures that simultaneously exhibit negative permittivity and permeability. In metamaterials, adherence to the right-hand rule, which is obligatory for all other materials working in an electromagnetic field (electric field E, magnetic field H), does not apply. The wave vector k in metamaterials is consistent with a left-handed rule, and, hence, this special class of materials is also called left-handed materials (LHM), first theoretically proposed by Veselago in 1960s.[1] The negative permittivity and negative permeability endow LHM with several special properties, such as negative refractive index, reversed Doppler Effect, and reversed Cherenkov radiation, [2] none of which exist in natural materials. Metamaterials can be applied in sub-wavelength imaging, cloaking, wave filter, super lens, and band-gap design. [3][4][5] Since 2000, when investigations of metamaterials were experimentally performed by double-slit-ring resonator and linear vibrator, [6] research on the construction and application of metamaterials in optical and microwave frequencies range have attracted great interest, and much theoretical work has been published; however, the realization of their promise still requires great effort.It is well recognized that the unusual properties of metamaterials are determined by their specially designed structures, rather than their compositions. In other words, the permittivity and/or permeability are not, or are just weakly, dependent on chemical structures and constituent compositions, or interactions among different components in the materials. Various structures have been designed by physicists and electrical engineers to obtain negative permittivity and negative permeability, including double-split-ring resonators, [3] S-shaped resonators, [7] multilevel dendritic structures, [2] nano/small apertures, [8,9] metallic nanoclusters, [5] among others. In all of these, resonance was considered to be the main mechanism of the realization of both negative permittivity and negative permeability, while the phase changes close to the resonant frequency.[10] In contrast, the exploration of metamaterials from the point of view of materials (chemistry and properties) has not attracted substantive attention from material researchers. Among the very limited work reported, almost all research in this field focused on metals and ceramics, which contain metallic elements and can consequentially realize negative permittivity and/or permeability under certain conditions. In particular, ferromagnetic materials were the subject of considerable interests in realization of metamaterials, owing to the resultant negative permittivity of metallic materials below plasma frequency as well as negative permeability of some ferromagnetic metals and metallic alloys in the vicinity of the ferromagnetic resonance frequency. [11][12][13] However, to the best of our knowledge, research has been rarely...

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Comparative study of herringbone and stacked-cup carbon nanofibers

Cited by 34 publications

References 19 publications

Differences between carbon nanofibers produced using Fe and Ni catalysts in a floating catalyst reactor

Differences between carbon nanofibers produced using Fe and Ni catalysts in a floating catalyst reactor

The Separation Power of Nanotubes in Membranes: A Review

Single Negative Metamaterials in Unstructured Polymer Nanocomposites Toward Selectable and Controllable Negative Permittivity

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