Carbon Nanotubes as Material in Electrical Engineering

There is also some benefit in employing carbon nanotubes in lithium ion batteries. They are a suitable additive to the anode material for several reasons. Firstly, their small diameter allows for an even distribution in the electrode. Secondly, their electric conductivity substantially contributes to that of the electrode material, and finally, they are able to absorb the stress arising from lithium intercalation. On the addition of a few percent of carbon nanotubes, the cycle efficiency remains close to 100% even after many charging cycles, whereas untreated electrodes show a decline here. 

Apart from the use in batteries, carbon nanotubes may also be added to materials employed in electric double layer capacitors. In this case, the nanotubes ensure 

Carbon nanotubes are one of the most important classes of new carbon materials. Distinctions are made between single- and multiwalled as well as between zig-zag, armchair, and chiral nanotubes. The structure is characterized by the descriptors n and m. These structural parameters allow for a prediction of the electric conductivity. Only armchair nano tubes n,n) and such species with m-n = iq are electric conductors. Any other nanotube is semiconducting. These statements have been established from symmetry considerations and from determining the band structure by way of the zone-folding method. There are different approaches to the production of single- and multiwalled nanotubes. Important methods of preparation are  

In the density of state function there are characteristic van Hove singularities. 

If a catalytic process has been appUed, residual catalyst must be removed from the crude nanotubes obtained. Further impurities include amorphous carbon and, in parts, fuUerenes. A customary purification comprises an acid treatment which, at the same time, removes the end caps of the formerly closed tubes. 

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