Carbon Nanotubes --> Carbon nanotubes structure

Carbon Nanotubes has been fortuitously discovered in 1991 by Sumio Iijima found out it between secondary products during fullerene synthesis.
In fact, Carbon nanotubes are fullerene-related structures which consist of graphene cylinders closed at either end with a sort of emi-fullerene.

Two category of carbon nanotubes are usually considered:
Single walled nanotubes (SWNT);
Multi walled nanotubes MWNT):concentric single walled nanotubes;

In the figures, at left Single walled Carbon Nanotubes whereas at right double walled carbon nanotubes with and without interaction between tubes.
Actually Carbon Nanotubes structure has imperfections that deform the structure (e.g octagonal or pentagonal rings).

Range of Single Walled carbon nanotubes diameter is from 1 nm to 10 nm, but the greater number of nanotubes are about 2 nm.

Nanotubes are characterized of high length/diameter ratio (10e4 10e5) gives typical great properties of this nanostructured materials.
Typical parameters of carbon nanotubes are: diameter and helicities characterized by the rolling vectors (n,m) see the figure:

From left (n,0) nanotubes, (n,n) nanotubes (n,m) nanotubes.

Between the tubes of multi walled carbon nanotubes there are weak interaction (lip-lip interaction) seem stabilize growth of nanotubes during synthesis process. Diameter is greater than single walled nanotubes as far as decine of nm.
Structure of multi walled carbon nanotubes has more imperfection than single walled carbon nanotubes.
For this reason single walled carbon nanotubes are considered products more valuable than multi walled carbon nanotubes and very difficult to synthetize.

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