Chemistry Reference
In-Depth Information
9.3.2 CNT PROPERTIES
9.3.2.1 STRENGTH
In terms of strength, tensile strength and elastic modulus are explained
and it has not been discovered any material as strong as carbon nanotubes
yet. CNTs due to containing the single carbon atoms, having the covalent
sp
2
bonds formed between them and they could resist against high tensile
stress. Many studies have been done on tensile strength of carbon nano-
tubes and totally it was included that single CNT shells have strengths of
about 100 GPa. Since density of a solid carbon nanotubes is around of 1.3
to 1.4 g/cm
3
, specific strength of them is up to 48,000 kN·m·kg
−1
which
it causes to including carbon nanotube as the best of known materials,
compared to high carbon steel that has specific strength of 154 kN·m·kg
−1
.
Under extreme tensile strain, the tubes will endure plastic deformation,
which means the deformation is invariable. This deformation commences
at strains of around 5% and can enhance the maximum strain the tubes
undergo before breakage by releasing strain energy.
Despite of the most high strength of single CNT shells, weak shear in-
teractions between near shells and tubes leads to considerable diminutions
in the effective strength of multiwalled carbon nanotubes, while crosslink
in inner shells and tubes, included the strength of these materials is about
60 GPa for multiwalled carbon nanotubes and about 17 GPa for double-
walled carbon nanotube bundles.
Almost, hollow structure and high aspect ratio of carbon nanotubes
lead to their tendency to suffer bending when placed under compressive,
torsion stress.
9.3.2.2 HARDNESS
The regular single-walled carbon nanotubes have ability to undergo a
transformation to great hard phase and therefore, they can endure a pres-
sure up to 25 GPa without deformation. The bulk modulus of great hard
phase nanotubes is around 500 GPa, which is higher than that of diamond
(420 GPa for single diamond crystal).
