SWNT

Fig. 23. Experimental room temperature Raman spectrum from a sample consisting primarily of bundles or ropes of single-wall nanotubes with diameters near that of the (10,10) nanotube. The excitation laser wavelength is 514.5 nm. The inset shows the lineshape analysis of the vibrational modes near 1580 cm . SWNT refers to singlewall carbon nanotubes [195].

The yield strengths of defect-free SWNTs may be higher than that measured for Bacon s scroll structures, and measurements on defect-free carbon nanotubes may allow the prediction of the yield strength of a single, defect-free graphene sheet. Also, the yield strengths of MWNTs are subject to the same limitations discussed above with respect to tube slippage. All the discussion here relates to ideal nanotubes real carbon nanotubes may contain faults of various types that will influence their properties and require experimental measurements of their mechanical constants. 

Work on the production and oxidation of SWNT samples at SRI and other laboratories has led to the observation of very long bundles of these tubes, as can be seen in Fig. 2. In the cleanup and removal of the amorphous carbon in the original sample, the SWNTs self-assemble into aligned cable structures due to van der Waals forces. These structures are akin to the SW nanotube crystals discussed by Tersoff and Ruoff they show that van der Waals forces can flatten tubes of diameter larger than 2.5 nm into a hexagonal cross-sectional lattice or honeycomb structure[17]. 

Since most SWNTs have diameters in the range of 1 -2 nm, we can expect them to remain cylindrical when they form cables. The stiffness constant of the cable structures will then be the sum of the stiffness constants of the SWNTs. However, just as with MWNTs, the van der Waals binding between the tubes limits tensile strength unless the ends of all the tubes can be fused to a load. In the case of bending, a more exact... 

Fig. 2. Cables of parallel SWNTs thal have self-assembled during oxidative cleanup of arc-produced soot composed of randomly oriented SWNTs imbedded in amorphous carbon. Note the large cable consisting of several tens of SWNTs, triple and single strand tubes bent without kinks, and another bent cable consisting of 6 to 8 SWNTs.

The bulk modulus of an ideal SWNT crystal in the plane perpendicular to the axis of the tubes can also be calculated as shown by Tersoff and Ruoff and is proportional to for tubes of less than 1.0 nm diameter[17]. For larger diameters, where tube deformation is important, the bulk modulus becomes independent of D and is quite low. Since modulus is independent of D, close-packed large D tubes will provide a very low density material without change of the bulk modulus. However, since the modulus is highly nonlinear, the modulus rapidly increases with increasing pressure. These quantities need to be measured in the near future. 

Recently, TsHs has been encapsulated within single-walled (SWNTs) and multiwalled carbon nanotubes (MWNTs) with internal diameters of 0.8-8 nm. It was shown that the best results were obtained when the internal diameters (1.4—1.5 nm for SWNTs and 1.0-3.0 nm for MWNTs) slightly exceeded the diameter of TsHs (1.2 nm). T8H8 was introduced in the gas phase and reacted with the nanotubes through van der Waals interactions. ... 

Researchers [37] also compared the storage modulus of a 40 phr carbon black-filled compound and a 10 phr SWNT-NR nanocomposite. The different properties between carbon black- and SWNTs-filled NR nanocomposites can be explained in terms of two different filler morphology, particularly surface area, aspect ratio, and stmcture. It can be observed from Figure 28.22 that... 

In the near future, the possible synthesis of nanotubes with solid-gas potential will be more favorable to adsorption. The effect of hydrogen overpressure on the stability of adsorbed Ha needs to be verified in the near future. The high-purity nanotube produced by laser vaporization, catalytic decomposition, or other techniques should be investigated. It is noteworthy that the synthesis of the SWNT with defined diameters and distances between the walls is difficult to perform at present, but future synthesis routes will allow more... 

Fig. 4 shows the SEM images of SWNTs purified by the thermal oxidation and acid-treated. Fig. 4(a) shows a SEM image of the raw soot. In addition to the bundle of SWNTs, carbonaceous particles are shown in the figure. These stractural features mi t be causal by various in the arcing process because of an inhomogeneous distribution of catalysts in the anodes [7]. It can be seen that the appearance of SWNTs was curled and quite different fiom that of MWNTs. Fig. 4(b) shows a decrease of amorphous carbons after oxidation. The basic idea of the selective etching is that amorphous carbons can be etched away more easily than SWNTs due to the faster oxidation reaction rate [2]. Since the CNTs are etched away at the same time, the yield is usually low. The transition metals can be etched away by an add treatment. Fig. 4(c) shows the SEM image of the acid-treated sample, where the annealed sample was immersed in 10 % HCl. 

Fig. 5 shows typical Raman spectrum for SWNTs, the Raman spectra of SWNTs have fingerprint features, which is quite different fi om those of graphite, MWNTk and amorphous carbon. 

Fig. 5. FT-Raman spo of (a) the raw SWNTs sample and (b) the purifi sample Ni, Co and FeS were used as a catalysts)...

Magnetic Orientation and Organization of SWNTs or their Composite Materials Using Polymer Wrapping... 

Since the discovery of SWNTs, they have been expected to become the building blocks of the next generation of functional nanomaterials. However, their strong cohesive property and poor solubility have restricted the use of SWNTs for fundamental and applied research fields. One method to overcome these problems is to make the SWNTs more soluble by wrapping them with polymers [31]. At the same time, the fabrication of high-performance carbon nanotube (CNT)-based composites is driven by the ability to create anisotropy at the molecular level to obtain appropriate functions. 

In addition, SWNTs have been expected to act as acceptors or molecular wires in molecular photoelectric conversion since they have attractive electron-accepting... 

We examined the magnetic orientation or organization of the SWNTs or the polymer-wrapped SWNTs using MEHPPV by measurements of AFM images and polarized absorption spectra [46-48]. 

SWNTs (HiPco, Carbon Nanotechnologies Incorporated) were shortened by ultrasonication with a probe-type sonicator in mixed acids (H2SO4 and HNO3) under ice-cooling. After diluting the mixture with water (MiliQ), the shortened SWNTs were purified by filtration through a PTFE membrane filter (pore size 1 pm or 0.2 pm) or by chromatography (Sepadex G-50). 

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