Biomedical Engineering Reference
In-Depth Information
14.13
An Ar + N
2
microwave discharge sustained by a surface wave
launched on the quartz tube. A high quantity of atomic nitrogen is
produced in this plasma discharge (Ruelle, 2009).
the density of functionalization. Khare et al. studied the exposition of
SWNTs to microwave-generated N
2
plasma, by placing CNTs at different
distances from discharge (Khare et al., 2005). At the shortest distance
(1 cm), they observed the highest concentration in nitrogen groups but also a
loss of integrity of SWNTs due to highly reactive species, like N
2
+
.At
intermediate distances, the incorporation of nitrogen, but also a high
quantity of oxygen, onto the CNTs is obtained while functionalization was
not observed for the maximal distance of 7 cm due to total recombination of
atomic nitrogen before arriving at the CNT surface. It is thus important to
place CNTs outside the glow discharge zone at an optimal distance to avoid
interaction with highly reactive ions and UV photons. In this treatment
configuration, radicals become the most important reactive species for the
grafting of functional groups onto carbon nanotubes. The efficiency of this
approach depends on the density of the radicals produced.
In this context, a surface wave discharge set-up was developed (Godfroid
et al., 2003). The microwave-induced plasmas present a higher density of
electrons in comparison with other type of plasmas, such as RF plasmas, for
instance, because electrons are more easily created with microwaves (at the
same power).
The high electron density of the
-wave-induced plasmas is the key
parameter in the creation of atomic nitrogen in Ar+N
2
microwave plasma
(Fig. 14.13). Godfroid et al. have demonstrated that production of atomic
nitrogen in Ar+N
2
μ
μ
-wave discharge is achieved through two electronic
