Carbon nanotube general properties

Carbon nanotubes, generally in the form of multiwalled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs), may exhibit specific adsorption and electronic properties in comparison with activated carbon, due primarily to their peculiar morphology, the role of defects, the probability of opening or closing of the tubes, and so on [5], which are believed to induce cooperative or synergetic interactions between metal or metal oxide... 

In general, nanotechnology MBBs are distinguished for their unique properties. They include, for example, graphite, fullerene molecules made of various numbers of carbon atoms (C60, C70, C76, C240, etc.), carbon nanotubes, nanowires, nanocrystals, amino acids, and diamondoids [97]. All these molecular building blocks are candidates for various applications in nanotechnology. 

Nonconjugated hydrocarbon polymers could also be combined with carbon nanotubes, with polystyrene being the most studied example. The composites are generally prepared by solution or shear mixing techniques, resulting in materials with improved mechanical properties [60]. 

Pyrotechnics will take an important step forward by making use of several nanosized fuels and oxidizers for pyrotechnic formulations in the near future. As a result, the performance of such pyrotechnic formulations will become considerably better and thus the problem of availability of space for pyrotechnic devices will not remain as critical as it is now, because several metal powders and oxidizers are commercially available at the nanoscale these days. Before we discuss nanosized fuels, oxidizers and their formulations, it is considered essential to describe in brief nanomaterials (NMs)including carbon nanotubes (CNTs), their methods of preparation, their properties in general, and some important applications. 

On the other hand, forty years ago a lot of properties of carbon based materials coming from pyrolytic processes were well known [10-14] but it was in the last years where new kinds of CMS, fullerenes and carbon nanotubes [15-17] were discovered and studied These materials have the limitation of their small open pore size, which in general is near 10 A diameter, and then, diffusional and esteric problems may be present when they must interact with molecules of equal or bigger size within the mentioned pore diameter. 

As carbon nanotubes present exceptional mechanical, superior thermal and electrical properties in general, by using them as reinforcing elements there are high expectations for improvement of quality of nano- and microcomposites [14-18]. As shown from earlier measurements, through carbon nanotube addition a 15-37% improvement of mechanical properties (elastic modulus and strength) can be achieved in comparison to other carbon-filled samples [19]. 

Generally, a carbon nanotube FET device is constructed by a substrate (gate), two microelectrodes (source and drain), and bridging material between the electrodes, which is typically an individual SWNT or a SWNT network. A SWNT FET is usually fabricated by casting a dispersion of bulk SWNTs or directly growing nanotubes on the substrate by chemical vapor deposition (C VD) either before or after the electrodes are patterned.64 Due to the diffusive electron transport properties of semiconducting SWNTs, the current flow in SWNT FET is extremely sensitive to the substance adsorption or other related events on which the sensing is based. 

Similar issues were raised by Beguin et al. [97] regarding the capacitance properties of carbons in general and nanotubes in particular, because the higher the... oxygen content of the nanotubes, the higher the capacitance value, whereas after a few cycles, the capacitance of nanotubular materials rich in surface groups noticeably decreases the authors did not discuss the reasons for such behavior. 

Globally, carbon nanotubes have a positive effect on the mechanical properties of all the composites with PVA matrices described in the previous sections. However, the enhancement of mechanical properties differs substantially from a material to another, depending on the type of nanotubes, or on the process used to manufacture the composite. The Young s modulus and the strength are deduced from usual tensile experiments. As depicted in Figure 11.4, PVA/nanotube composites generally follow the same tensile behavior, with a short elastic regime on the first percent strain, followed by a more or less extended plastic behavior. 

The properties of carbon nanotubes, in general, are strongly dependent on the orientation of their honeycomb lattice with respect to the tube The electronic band structure... 

The stmctural diversity of carbon at the nanoscale exceeds that of all other materials [1]. Detailed information on the nature of the material and the structure-dependency of the oxidation kinetics is thus crucial for providing the required selectivity. While some nanomaterials, such as carbon nanotubes, have been studied extensively and are generally well understood, other nanostructures such as nanodiamond (ND) have received much less attention. However, in order to study their properties and open avenues for new applications, one has to provide a material of high purity and defined composition. 

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