Nanotube Synthesis and Characterization

Observed in 1991 by lijima [72] by transmission electron microscopy as a by-product of the reaction of the synthesis of fullerenes, carbon nanotubes can be described as a rolling-up of graphite planes. Because of its relation to graphite as well as its nanometer size and one dimensionality, this new material is expected to present unique properties. Several applications have been envisaged for electronics [73-75], for energy storage [76,77] or in medicine [78]. They also present unique mechanical properties [79] and many studies are presently being performed with the aim to use them as reinforcements in polymers [80-82]. 

Two main categories of synthesis methods of carbon nanotubes can be distinguished high-temperature methods and average-temperature methods. 

In the average-temperature methods, a carbonaceous gas is decomposed on a metal catalyst. These techniques are named chemical vapour deposition (CVD). The temperature of the furnace is between 800 and 1100 °C and gases used are carbon monoxide, methane or acetylene. The metal catalyst used is a transition metal, such as iron, nickel or cobalt. It is difficult to remove these metal catalysts after the synthesis without damaging the structure of the nanotubes because they are imprisoned in the nanotubes or are surrounded by amorphous carbon. They are therefore present in the nanotube samples after synthesis. 

Until now, the macroscopic tribological properties of the nanotubes had not been studied. The only studies carried out used the nanotubes as reinforcement in various matrices diamond thin film [87], polyimide [88], Ni [89], Ni-P [90], carbon/carbon composites [91] and alumina [92, 93]. These composite coatings present a better wear resistance and a lower friction. In nanotribology, Ohmae et al. studied friction of a gold tip on a nanotube forest. The friction coefficient obtained was high (1.2 to 1.5) and independent of humidity [94]. A very weak adhesion of the tip on the nanotubes was observed. During friction, no distortion of the nanotubes intervenes and there is no transfer of nanotubes on the tip. Recently, Miyoshi et al. 

Several kinds of nanotubes were studied to highhght the influence of different parameters on fribological properties of nanotubes the number of walls, the presence and the nature of a catalyst. Thereafter, acronyms will be used to describe the various samples of nanotubes (single-walled or multiwalled) studied  

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N. Li, Q. Xu, M. Zhou, W. Xia, X. Chen, M. Bron, W. Schuhmann, M. Muhler, Ethylenediamine-anchored gold nanoparticles on multi-walled carbon nanotubes synthesis and characterization, Electrochem. Commun. 12 (2010) 939-943. 

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