Multiple-walled carbon nanotube

Since the 1970s, patch-clamp electrodes (electrodes placed inside a borosilicate glass pipet that is then heated and pulled, with its contents, to submicron-size diameters) have been used as micron-sized probes in elec-trophysiology experiments. Since 2000, single-walled and multiple-walled carbon nanotubes have been used as nanoelectrodes. 

Rolf Landauer proved that the minimum resistance of any single-channel wire (composed of atoms or molecules or polymers), measured between any two macroscopic electrodes, is the quantum of resistance R = (h/2e ) = 12.91 kQ, where h is Planck s constant, and e is the electronic charge. In Milestone Two, this Landauer quantum of resistance was measured by Walt de Heer and coworkers at room temperature between a multiple-walled carbon nanotube (MWCNT), glued to a conducting AFM tip, and a pool of liquid... 

Fig. 3.4 Multiple-wall carbon nanotube (CNT) acting as an anchoring support for PVPfOsfbipylJ Cl (Reproduced fiom Ref. [32] with the permission of Elsevier)...

Huang, H.M. Liu, I.C. Chang, C.Y. Tsai, H.C. Hsu, C.H. Tsiang, R.C.C. (2004). Preparing a polystyrene-functionalized multiple-walled carbon nanotubes via covalently linking acyl chloride functionalities with living polystyryllithium. Journal of Polymer Science, Part A Polymer Chemistry, 42, 5802-5810. 

At the present time, important nanofillers include certain nanoclays (montmorillonite, hydrotalcite in platelet form), nanofibers (single- and multiple-wall carbon nanotubes), and nanosized particulate metal oxides. Several technological advances will undoubtedly contribute to additional growth in the usage of these fillers. Examples of such advances include [45]... 

It has to be taken into consideration that a great variety of materials is included under the same name. For example, CNTs can be present in different forms and therefore properties and applications could be diverse [144], Apart from variations in diameter or length, two main classes can be distinguished multiple-wall carbon nanotubes (MWCNTs) and... 

A number of methods have been developed to produce single- and multiple-wall carbon nanotubes. The most prominent are laser ablation, arc discharge, and catalytic growth (vapor deposition (CVD) and high pressure carbon monoxide (HipCO) process). 

Figure 5, Transmission electron micrograph of catalytically grown multiple-wall carbon nanotubes with less impurities, but with a higher defect density and strongly entangled.

Figure 6. Scanning electron micrograph of catalytically grown multiple-wall carbon nanotubes. The cotton-like appearance is due to the manufacturing CVD process, where CNT grow onto a catalyst-covered substrate plate and, in addition to the strong entanglement, a generally parallel orientation of the tubes can be achieved. ...

Our studies aimed at the improvement of the mechanical properties of epoxies by the addition of multiple-wall carbon nanotubes. The quality of the dispersion and the possible interaction between the CNT and the epoxy were investigated by light microscopy. For the homogeneous distribution of carbon black in an epoxy matrix, it was sufficient to use a high-speed disperser (Ultraturrax T-25), but for the dispersion of nanotubes this approach was not optimal (Figure 10a). The nanometer-scale size of the CNT and their aspect ratio make it necessary to develop new dispersion techniques in order to brake up the intermolecular bonds, leading to the formation of agglomerates. 

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