DWNTS Double Walled Carbon

Ceo = Fullerene SWNTs = Single-walled carbon nanotubes MWNTs = Multiwalled carbon nanotubes DWNTs = Double-walled carbon nanotubes CNTs = carbon nanotubes TEM = Transmission electron microscopy HRTEM = High-resolution transmission electron microscopy SEM = Scanning electron microscopy AFM = Atomic force microscopy Ch = Chiral vector CVD = Chemical vapor deposition HiPco process = High-pressure disproportionation of CO RBM = Radical breathing vibration modes DOS = Electronic density of states. 

Depending on the amount of rolled sheets, the CNTs can be divided into two categories those with only one wall, called single wall (SWNT—Single-Wall Nanotubes) or multi-wall (MWNT— Multi-WaU Carbon Nanotnbes). The latter is the result of several coaxial cylinders with a distance similar to the distance between the walls of graphene sheets that make np graphite (0.335 nm [34]).The number of sheets or walls of MWNTs can vary widely, from two (also eaUed DWNT, Double-Wall Carbon Nanotubes) to dozens of walls [35, 36]. MWNTs are usually isolated in synthesis products, while SWNTs are usually produced in the form of bundles of nanotubes [37]. 

A single-walled carbon nanotube (S WNT) is a single graphene sheet rolled up in a seamless cylinder, whose diameter is of the order of few nanometers (Fig. 4.12). A double-walled carbon nanotube (DWNT) consists of rolled two graphene layers, and a multiwall carbon nanotube (MWNT) exhibits several co-axial rolls of graphene sheets, one sitting in each other and separated by about 0.35 nm. 

SWNTs single-walled nanotubes DWNTs double-walled nanotubes MWNTs multi-walled nanotubes CNTs carbon nanotubes not purified... 

Double-walled carbon nanotubes (DWNTs), first observed in 1996, constitute a unique family of carbon nanotubes (CNTs). -2 DWNTs occupy a position between the single-walled carbon nanotubes (SWNTs) and the multiwalled carbon nanotubes (MWNTs), as they consist of two concentric cylinders of rolled graphene. DWNTs possess useful electrical and mechanical properties with potential applications. Thus, DWNTs and SWNTs have similar threshold voltages in field electron emission, but the DWNTs exhibit longer lifetimes.3 Unlike SWNTs, which get modified structurally and electronically upon functionalization, chemical functionalization of DWNTs surfaces would lead to novel carbon nanotube materials where the inner tubes are intact. The stability of DWNTs is controlled by the spacing of the inner and outer layers but not by the chirality of the tubes 4 therefore, one obtains a mixture of DWNTs with varying diameters and chirality indices of the inner and outer tubes. DWNTs have been prepared by several techniques, such as arc discharge5 and chemical vapor depo-... 

Figure 11.1. Crystallinity of PVA-nanotubes composites versus carbon nanotube volume fraction, for various types of nanotubes (DWNT= double-walled nanotubes, OHMWNT= hydroxyled MWNTs, NMWNT= catalytic Nanocyl S.A. MWNTs, OMWNT=catalytic MWNTs from Orleans, AMWNT=Arc grown MWNTs produced in the author s laboratory. Reprinted with permission from reference (23)).

Fig. 8 (A) Coexistence of a VGCF and an SWNT (with a diameter of about 20 nm) obtained by the catalytic decomposition of benzene. (From Ref l) The deposition of a partial carbon layer on a carbon nanotube during the thickening process is observed. (B) Double-walled carbon nanotube (obtained by benzene decomposition) and subsequently heat treated at 2800 °C, yielding the same structure as nanotubes prepared by the arc method. (From Ref l) Insert is a schematic diagram of DWNTs. (From Ref (C) Fligh-resolution transmission electron microscope image of two crossing SWNTs coated with amorphous carbons indicates that the structure consists of an individual graphene cylinder in projection. (From Ref. . )...

Figure 3.42 Growth mechanism for double-walled carbon nanotubes (DWNT).

Double-Walled Carbon Nanotubes (DWNT), 462 Multiwalled Carbon Nanotubes (MWNT), 463 Graphene, 464 Nanohoms, 465... 

Figure 13.9 Raman spectra of the RBM-band (left) and G -band (right) regions measured with a laser energy of 1.96 eV of three different samples (a) sample containing more than 90% DWNTs with outer and inner diameter of 1.85 0.15 and 1.15 + 0.15 nm, respectively (b) sample containing about 30% DWNTs and 70% SWNTs with similar outer diameter of 1.85 nm and (c) SWNTs with average diameter of 1.85 nm. (Reproduced with permission from W. Ren and H. M. Cheng, in Raman Spectroscopy on Double-Walled Carbon Nanotubes. Springer, New York, 2008.)...

Carbon nanotube is classified as single walled nanotubes (SWNTs), multiwalled nanotubes (MWNTs) and Double walled carbon nanotubes (DWNTs). 

Double-walled carbon nanotubes consist of a particular set of nanotubes because their morphology and properties are comparable to those of SWNT but they have considerably superior chemical resistance. Prominently, it is important when grafting of chemical functions at the surface of the nanotubes is required to achieve new properties of the CNT. In this processing of SWNT, some C=C double bonds will be broken by covalent functionalization, and thus, both mechanical and electrical properties of nanotubes will be modified. About of DWNT, only the outer shell is modified. 

Carbon nanotubes are one-dimensional carbon nanostructures with tubular morphology. Depending on the number of walls present in carbon nanotubes, these are named as single-walled carbon nanotubes (SWNTs), double-walled carbon nanotubes (DWNTs), and multi-walled carbon nanotubes (MWNTs). Each of these types have slightly different properties. For example, the electrical conductivity of pure SWNT is higher than that of DWNT and MWNT. Carbon nanotubes can be synthesized by arc discharge [11], laser ablation [12], catalytic CVD [13,14], etc. 

Rg. 1.8 Schematic diagrams of (a) a single-wall carbon nanotube (SWNT), (b) a multiwall carbon nanotube (MWNT), (c) a double-wall carbon nanotube (DWNT), and (d) a peapod nanotube consisting of an SWNT filled with fuUerenes (e.g., C ) (Reprinted with permission firom Dresselhaus et al. 2003, Copyright 2003 Elsevier)... 

Dense, vertically aligned double-walled carbon nanotubes (DWNTs) were grown on the surface of a sihcon tip by catalytic chemical vapor deposition (Step... 

Finally, Eklund s group has described double-walled nanotubes (DWNT), with ca. 0.7 nm inner diameter and 1.4 nm outer diameter, that can form a three-layer cylindrical capacitor with a shell of bromine anions forming the outer electrode. Holes segregate on the outer nanotube, and saturation bromine doping creates 1 hole per 26 carbon atoms in the DWNT [135]. 

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