Biomedical Engineering Reference
In-Depth Information
intratube interactions further complicate the study of the properties
for the CNTs. CNTs with single atomic layer walls and diameters
of 1.2 ± 0.1 nm are ubiquitous in the TEM observations made by
Bethune
[45]. The tubules apparently crossed, aggregated, and
tangled before being encased. Figure 9.5a shows a bare nanotube
with several round objects, comparable in size to 60-100 carbon
atoms. Figure 9.5b shows CNTs grown by ENEA.
et al.
(b)
(a)
Figure 9.5
(a) TEM image of a SWCNT produced by arc discharge. This
is reprinted with permission [45]. (b) MWCNTs grown by RF-
PECVD at ENEA lab, by Penza
et al.
[249].
Figure 9.6a and b shows scanning electron micrograph (SEM)
of CNTs networked layers produced by radio frequency plasma-
enhanced chemical vapor deposition (RF-PECVD) method at ENEA
laboratories in Brindisi, Italy. Entangled network of bundles of CNTs
in the multiwalled format at high magnification are synthesized
onto alumina and silicon substrates, properly metal catalyzed. The
diameter of a single bundle of CNTs ranges from 10 to 40 nm. The
growth process was originally developed in order to decompose
gaseous precursors containing carbon atoms, e.g., acetylene (C
)
over transition metals catalysts, e.g., Co, Fe, Ni. A carpet of CNTs has
been observed by SEM analysis after their post-treatment in DMF
and chloroform solvents. Figure 9.6c and d show a carpet of CNTs
grown by CVD onto Fe-catalyzed silicon substrate at low and high
magnification, respectively. The effect of CNTs de-bundling with
DMF and chloroform solvents in ultrasonic agitation is very effective
to achieve higher surface area for gas adsorption.
H
2
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