Biomedical Engineering Reference
In-Depth Information
14.11 The emission current density and fluorescent photos of the
CNT films at 6.4 V/
μ
m after various N
2
plasma treatment times
(Feng
et al.
, 2007).
creation of vacancies and interstitials in CNTs; the superficial structure,
including the amorphous carbon that was produced, is thus lost. In a second
step, the ion beams continue to react with amorphous carbon until they are
peeled totally away from the CNTs. Finally, the oxidation of amorphous
carbon in CO
2
occurs, inducing the decrease of the CNT's average diameter.
Plasma-oxidized CNTs were reported to present improved dispersion in
epoxy resin in comparison with non-treated CNTs (Kim et al., 2006). The
epoxy nanocomposites filled with plasma-modified CNTs exhibited higher
storage and loss moduli than CNT/epoxy nanocomposites as well as
improved tensile strength and elongation at break due to better dispersion
and stronger interaction between the CNTs and the polymer matrix.
Felten et al. showed that cluster dispersion on thermal evaporation
coating of CNTs with various metals can be tuned by increasing the cluster
nucleation density through the formation of interaction sites when CNTs
are treated in an O
2
RF plasma (Felten et al., 2007). The same effect was
also observed when the CNTs were exposed to an NH
3
RF plasma before
the metal coating.
The nitrogen-containing groups can be grafted through plasma treatment
if gases, such as N
2
,N
2
/H
2
or NH
3
, are used. The treatment of multi-walled
CNTs in an N
2
/Ar RF plasma was shown to be an effective procedure to
enhance the field emission characteristics of CNTs due to the doping of the
CNT structure with N atoms (Gohel et al., 2005). The N1s core level peak
was fitted with components at 398.2, 398.6, 399.7 and 400.8eV, which
corresponds to C-N, C
N (sp
3
bonding), C=N (sp
2
bonding) and NO. The
field emission properties of screen-printed CNT films were also improved
after NH
3
or N
2
RF plasma treatment (Feng et al., 2007). For the CNT
≡
