Single-walled 4 Å carbon nanotube arrays

Wang, N.; Tang, Zikang; Li, G. D.; Chen, J. S.

doi:10.1038/35040702

Cited by 377 publications

(295 citation statements)

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“…Separate from fullerenes, nanostructures have also been produced independently through arc-discharge vaporization [9][10][11], plasma-decomposition of benzene [29], pyrolysis of tripropylamine [12], and in a pyrolysis flame of carbon monoxide and hydrogen [30]. They have also been produced on large-scale by the catalytic decomposition of hydrocarbons at about 1200°C [31].…”

Section: Formation Offullerenes and Nanostructuresmentioning

confidence: 99%

“…These structures, which can be single-or multiple-shelled, consist of cylindrical walls composed entirely of hexagonal rings capped at each end by six pentagonal rings and the necessary hexagonal rings to close the structure. Nanotubes with diameters as small as 4 A have been observed [10][11][12] meaning that the fullerenic caps are smaller than C 60 molecules, which have a diameter of 7 A. Throughout the remainder of this work, to avoid confusion, buckyballs will be referred to simply as 'fullerenes', while onions and nanotubes will collectively be referred to as 'nanostructures'.…”

Section: Introductionmentioning

confidence: 99%

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Combustion synthesis of fullerenes and fullerenic nanostructures

Goel

Hebgen

Sande

et al. 2002

Carbon

117

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Fullerenes are molecules comprised entirely of sp 2 -bonded carbon atoms arranged in pentagonal and hexagonal rings to form a hollow, closed-cage structure. Buckyballs, a subset which contains C 60 and C 70 , are single-shell molecules while fullerenic nanostructures can contain many shells and over 300 carbon atoms. Both fullerenes and nanostructures have an array of applications in a wide variety of fields, including medical and consumer products. Fullerenes were discovered in 1985 and were first isolated from the products of a laminar low-pressure premixed benzene/oxygen/argon flame operating at fuel-rich conditions in 1991. Flame studies indicated that fullerene yields depend on operating parameters such as temperature, pressure, residence time, and equivalence ratio. High-resolution transmission electron microscopy (HRTEM) showed that the soot contains nanostructures, including onions and nanotubes.Although flame conditions for forming fullerenes have been identified, the process has not been optimized and many flame environments of potential interest are unstudied. Mechanistic characteristics of fullerene formation remain poorly understood and cost estimation of large-scale production has not been performed. Accordingly, this work focused on: 1) studying fullerene formation in diffusion and premixed flames under new conditions to identify optimal parameters; 2) investigating the reaction of fullerenes with soot; 3) positively identifying C 60 molecules in HRTEM by tethering them to carbon black; and 4) providing a cost estimation for industrial fullerenic soot production.Samples of condensable material from laminar low-pressure benzene/argon/oxygen diffusion flames were collected and analyzed by high-performance liquid chromatography (HPLC) and HRTEM. The highest concentration of fullerenes in a flame was always detected just above the height where the fuel is consumed. The percentage of fullerenes in condensable material increases with decreasing pressure and the fullerene content of flames with similar cold gas velocities shows a strong dependence on length. A shorter flame, resulting from higher dilution or lower pressure, favors the formation of fullerenes rather than soot, exhibited by the lower amount of soot and precursors in such flames. This indicates a stronger correlation of fullerene consumption to soot levels than of fullerene formation to precursor concentration. The maximum flame temperature seems to be of minor importance in formation. The overall highest amount of fullerenes was found for a surprisingly high dilution of fuel with argon. The HRTEM analysis showed an increase of the curvature of the carbon layers, and hence increased fullerenic character, with increasing distance from the burner up to the point of maximum fullerene concentration, after which it decreases, consistent with the HPLC analysis. The soot shows highly ordered regions that appear to have been cells of fullerenic nanostructure formation. The samples also included fullerenic nanostructures such as tubes and sp...

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Section: Formation Offullerenes and Nanostructuresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Combustion synthesis of fullerenes and fullerenic nanostructures

Goel

Hebgen

Sande

et al. 2002

Carbon

117

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“…22,23 The 4-Angstrom SWNTs are embedded in the linear channels of AlPO 4 -5 zeolite crystal (IUPA code: AFI), which is a member of the aluminophosphate zeolite family. As illustrated in Fig.…”

Section: Basic Characteristics Of 4-angstrom Carbon Nanotubes 21 Stmentioning

confidence: 99%

Superconductivity in 4-Angstrom carbon nanotubes—a short review

et al. 2012

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We give an up-to-date review of the superconducting phenomena in 4-Angstrom carbon nanotubes embedded in aligned linear pores of the AlPO 4 -5 (AFI) zeolite, first discovered in 2001 as a fluctuation Meissner effect. With the introduction of a new approach to sample synthesis around 2007, new data confirming the superconductivity have been obtained. These comprise electrical, specific heat, and magnetic measurements which together yield a consistent yet complex physical picture of the superconducting state, largely owing to the one-dimensional (1D) nature of the 4-Angstrom carbon nanotubes. For the electrical transport characteristics, two types of superconducting resistive behaviors were reproducibly observed in different samples. The first type is the quasi 1D fluctuation superconductivity that exhibits a smooth resistance drop with decreasing temperature, initiating at 15 K. At low temperatures the differential resistance also shows a smooth increase with increasing bias current (voltage). Both are unaffected by an applied magnetic field up to 11 Tesla. These manifestations are shown to be consistent with those of a quasi 1D superconductor with thermally activated phase slips as predicted by the Langer-Ambegaokar-McCumber-Halperin (LAMH) theory. The second type is the quasi 1D to 3D superconducting crossover transition, which was observed to initiate at 15 K with a slow resistance decrease switching to a sharp order of magnitude drop at $7.5 K. The latter exhibits anisotropic magnetic field dependence and is attributed to a Berezinskii-Kosterlitz-Thouless (BKT)-like transition that establishes quasi-long-range order in the plane transverse to the c-axis of the aligned nanotubes, thereby mediating a 1D to 3D crossover. The electrical data are complemented by magnetic and thermal specific heat bulk measurements. By using both the SQUID VSM and the magnetic torque technique, the onset of diamagnetism was observed to occur at $15 K, with a rapid increase of the diamagnetic moment below $7 K. The zero-field-cooled and field-cooled branches deviated from each other below 7 K, indicating the establishment of a 3D Meissner state with macroscopic phase coherence. The superconductivity is further supported by the specific heat measurements, which show an anomaly with onset at 15 K and a peak at 11-12 K. In the 3D superconducting state, the nanotube arrays constitute a type-II anisotropic superconductor with H c1 z 60 to 150 Oe, coherence length x z 5 to 15 nm, London penetration length l z 1.5 mm, and Ginzburg-Landau k z 100. We give a physical interpretation to the observed phenomena and note the challenges and prospects ahead.

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“…Due to their concentric double layer structures, ultra small diameter tubes can be encapsulated as the inner shell of DWNTs [13]. Nanotubes with diameters ∼ 4Å have already been observed in confined channels or as the inner shell of multiwall nanotubes [14,15,16]. The inner tubes in thin DWNTs usually feature high surface curvature and are shown to have large variations in work function [17].…”

Section: Introductionmentioning

confidence: 99%

First-principles study of work functions of double-wall carbon nanotubes

Shan

Cho

2006

Phys. Rev. B

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Using first-principles density functional calculations, we investigated work functions (WFs) of thin double-walled nanotubes (DWNTs) with outer tube diameters ranging from 1nm to 1.5nm.The results indicate that work function change within this diameter range can be up to 0.5 eV , even for DWNTs with same outer diameter. This is in contrast with single-walled nanotubes (SWNTs) which show negligible WF change for diameters larger than 1nm. We explain the WF change and related charge redistribution in DWNTs using charge equilibration model (CEM). The predicted work function variation of DWNTs indicates a potential difficulty in their nanoelectronic device applications. PACS numbers: 31.15.Ar, 72.80.Rj, 73.30.+y * Electronic address: kjcho@stanford.edu 1 Double-walled nanotubes (DWNTs) have attracted considerable attention due to their novel electronic and mechanical properties [1]. Compared to single-walled nanotubes (SWNTs), they have higher mechanical stiffness and greater thermal stability which may be of benefit in field emission devices [2]. Their double shell structure offers the possibility of shielding the inner tube from external perturbations [3]. Such advantages make them very interesting for certain device applications.Utilization of DWNTs in early days were largely hindered by the unwanted carbon nanomaterials generated at the same time with DWNTs during fabrication processes. Over past few years, substantial improvements have been achieved in fabrication and purification techniques of DWNTs. Synthesis of high-quality DWNTs in large scale has been realized using high temperature pulsed arc discharge technique [4] and catalytic chemical vapor deposition [5]. In a more recent experiment, production of DWNTs with experimental yields more than 95% has been reported [6]. Thin DWNTs has also been successfully fabricated by by filling C 60 molecules in SWNTs followed by electron beam irradiation, yielding DWNTs with diameter distribution around 13 ∼ 14Å [7]. In addition, it has now become possible to identify atomic correlations between adjacent graphene layers using high-resolution transmission electron microscopy [8], enabling an unambiguous classification of DWNTs. All these point toward a possible application of DWNTs in nanoelectronic devices.Recently, the potential use of DWNTs as channel materials for field-effect transistors (FETs) has been successfully demonstrated [9], with better subthreshold swing factor as compared to SWNTs. Also, due to different inner/outer tube combinations and inter-layer interactions, DWNTs-based FET yields richer transistor characteristics [10]. For further large-scale integration of DWNT-based FETs, an understanding of DWNT work function is essential, since even work function change on the order of 0.1eV may lead to substantial changes in device characteristics [11].The encapsulation of molecules such as C 60 inside SWNTs are known to modify the electronic properties of carbon nanotubes [12]. Due to their concentric double layer structures, ultra small diameter ...

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Single-walled 4 Å carbon nanotube arrays

Cited by 377 publications

References 10 publications

Combustion synthesis of fullerenes and fullerenic nanostructures

Combustion synthesis of fullerenes and fullerenic nanostructures

Superconductivity in 4-Angstrom carbon nanotubes—a short review

First-principles study of work functions of double-wall carbon nanotubes

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