DWCNT nanotube

CNTs may consist of just one layer (i.e. single-walled carbon nanotubes, SWCNTs), two layers (DWCNTs) or many layers (MWCNTs) and per definition exhibit diameters in the range of 0.7 < d < 2 nm, 1 < d < 3 nm, and 1. 4 < d < 150 nm, respectively. The length of CNTs depends on the synthesis technique used (Section 1.1.4) and can vary from a few microns to a current world record of a few cm [16]. This amounts to aspect ratios (i.e. length/diameter) of up to 107, which are considerably larger than those of high-performance polyethylene (PE, Dyneema). The aspect ratio is a crucial parameter, since it affects, for example, the electrical and mechanical properties of CNT-containing nanocomposites. 

Double-walled carbon nanotubes (DWCNTs) consist of two concentric graphene cylinders. DWCNTs, categorized different from both MWCNTs and SWCNTs, are expected to exhibit mechanical and electronic properties superior to SWCNTs. Endo et al. have suggested that... 

The most common method for the production of carbon nanotubes is hydrocarbon-based chemical vapor deposition (CVD) [97] and adaptations of the CVD process [98, 99], where the nanotubes are formed by the dissolution of elemental carbon into metal nanoclusters followed by precipitation into nanotubes [100]. The CVD method is used to produce multiwalled carbon nanotubes (MWCNTs) [101] and double-walled carbon nanotubes (DWCNTs) [102] as well as SWCNTs [103], The biomedical applications of CNTs have been made possible through surface functionalization of CNTs, which has led to drug and vaccine delivery applications [104,105],... 

CNTs are commonly classified into single-waUed (SWCNTs) and multi-walled (MWCNTs) nanotubes [28]. SWCNTs consist of a single graphene layer rolled up into a hollow cylinder and are either metallic or semiconducting, whereas MWCNTs are comprised of two, three, or more concentrically arranged cylinders and exhibit only metallic character. Double-wall carbon nanotubes (DWCNTs) are the most basic members of the MWCNT family. The special role of DWCNTs should be emphasized, as they are the link between SWCNTs and the more complex MWCNTs and, therefore, of great interest for a fundamental understanding of these novel nanostructures. 

The most noticeable effect during the in situ Raman studies was the near complete disappearance of the disorder-induced D band after oxidation (Fig. 12.3c). These results show that for the DWCNT sample, the D band originates mainly from amorphous carbon present in the sample and not from defects in the wall structure of the nanotubes. While the concentration of defects probably increases during the oxidation, disordered carbon and the associated D band disappear completely. However, it is well known that only metallic CNTs contribute to the D band intensity [57]. Therefore, the absence of any Raman signal... 

Carbon double-walled nanotubes (DWCNTs or DWNTs). These have been prepared by the Carbon Vapour Deposition (CVD) method with >90% carbon content and 50-80% DWCNT. They can be prepared with approximately the following dimension 5mn OD, 1.3-2.0nm ID and 50pm length and with 0.12-0.14g/ml bulk density and >600m2/g sirrface area. The rest (10-40%) consists of amorphoirs carbon and residtral metal catalysts which are deliberately placed in the original carbon in order to synthesise the carbon tubes. 

As compared to SWCNTs, the properties of capacitors based on double-wall carbon nanotubes (DWCNTs) were not published so frequently, as pure DWCNTs are very hard to obtain. Basically, DWCNTs and multiwall carbon nanotubes (MWCNTs) have a lower surface area for EDL formation as compared to SWCNTs. On the other hand, a variety of works on capacitive performance of MWCNTs has been published, as they are relatively easily synthesized and are much cheaper than SWCNTs. As dependent on the methods of synthesis and modifications, different types of MWCNTs with different specific surface area values were obtained. Their specific capacitance values obtained in aqueous and nonaqueous electrolytes are from 10 to 100 F/g. However, they are not so high as in the case of ACs. On the other hand, one must point out that bulk capacitance is relatively high because of high bulk density of MWCNTs. Synthesis of MWCNTs is often carried out by pyrolysis of ethylene using catalysts, for example, Fe-Co. 

Double-wall carbon nanotubes (DWCNT). Diameter is between 2 and 4 nm ... 

The spectroelectrochemistry of double-wall carbon nanotubes (DWCNTs) has also been investigated [2,90-97]. Nevertheless, the understanding of the effect of the doping is more difficult in DWCNTs. In general, the charge is located mostly on the outer tubes hence, there is a difference between the doping level of the inner and outer tubes. The distinct doping effects for inner and outer tubes are observed in the RBM modes and in the D and G bands as well. For doped DWCNTs, both the D and G bands split into two components upon electrochemical... 

FuUerene peapods represent another class of nanotube-based materials, which have been widely studied by spectroelectrochemistry [99-102]. The doping behavior of these materials is in general somewhat analogous to DWCNTs, but there are still some unexplained phenomena, such as the anomalous enhancement of the Ag(2) mode of CgQ SWCNT at high anodic potentials [103]. Hence, further investigation of these materials is needed. 

On the basis of the number of concentric walls, CNTs can be divided into single-walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs) [22]. SWCNTs consist of a single rolled graphite sheet defining a cylinder of 0.4-2 nm of diameter and up to several microns long. MWCNTs can be visualized as concentric and closed graphite tubules with two (double-walled carbon nanotubes, DWCNTs) or several layers of graphite sheet that define a... 

Compositematerialcontainingatleastonephasewithconstituentsofl-lOOmn in size can be termed nanocomposites. Nanoparticles commonly used in the nanocomposite include single-walled carbon nanotube (SWCNT), double-walled carbon nanotube (DWCNT), multi-walled carbon nanotubes (MWCNT), carbon nanofiber (CNF), graphite nanoplatelet (GNP), mont-morillonite (MMT), nanoclay and polyhedral oligomeric silsesquioxanes (POSS). Other nanoparticles, such as SiOj, AljOj, TiOj and nanosilica are also used in the nanocomposite. The potential benefits of the nanoparticles for structural and multifunctional nanocomposites are sunamarized below. 

Metal-free reactions represent a direct way to study the confinement effects induced by the nanotube itself. Few such reactions have been carried out within CNTs, but notable examples include the formation of linear structures, such as fuUerene [151] and fullerene epoxide oligomers [174], formation of DWCNTs from endohedral fiiUerenes encapsulated in SWCNTs [71,155,156], or from encapsulated ferrocene [165], graphene nanoribbons (GNR) [186,187], the transformation of [Fe(C6oMc5)Cp] into encapsulated C70 [157], or the transformation of adamantane [188] and functionalized diamantine [189] in carbon chains. 

The influence of different types of the CNTs, i.e., single-wall nanotubes (SWCNT), double-waU nanotubes (DWCNT) and multiwall nanotubes (MWCNT)) on the ORR catalytic activity of the M-N4 macrocycle modified CNT composites has been studied by Morozan et al. [134]. Their results show that the oxidized MWCNT supported MPc catalysts exhibit higher current density, lower onset potential and more electron transfer for ORR in alkaline and acid medium than the catalysts prepared with other types of CNTs [134]. 

CNT exist in a wide variety of forms and few of them are single-walled carbon nanotubes—SWCNT (Ma et al. 2010), multiwalled carbon nanotubes—MWCNT, and double walled carbon nanotubes—DWCNT (Stobinski et al. 2010 Sahoo et al. 2010). The aspect ratios of the types of carbon nanotubes are large since their lengths are in the range of several micrometers. Among them, two are the most widely used ... 

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