Biomedical Engineering Reference
In-Depth Information
Figure 9.6
(a) Low-magnification and (b) high-magnification SEM
micrograph of the carbon nanotubes produced by RF-PECVD
method by using acetylene as precursor and Co as metal
catalyst at ENEA laboratories in Brindisi, Italy. SEM images at
(c) low-magnification and (d) high-magnification of a CNTs
carpet, grown by CVD technology with Fe-catalyst at ENEA
laboratories, and de-bundled with DMF and CHCl
solvents.
3
Raman spectroscopy [41, 46-48] is one of the most powerful
tools and nondestructive analysis technique to characterize the
allotropic forms of the carbon, in particular the CNTs. A typical
Raman spectrum showing the structural characteristics in the CNTs
is reported in Fig. 9.7. Generally, the position, width, and relative
intensity of the bands are modified according to the carbon forms.
The main features of the spectra are the following:
−1
(i) A low-frequency peak (<200 cm
) characteristic of the
SWCNTs assigned to A
“breathing” mode of the tubes,
whose frequency depends essentially on the diameter of the
nanotube. This mode is called
1g
radial breathing mode
(
RBM
)
.
−1
(ii) A large structure (1340 cm
) assigned to residual disordered
(D: disorder).
(iii) A high-frequency band (1500-1600 cm
graphite, the so-called
D-line
or
D-band
−1
), called
G-band
,
corresponding to a splitting of the E
stretching mode of the
2g
graphite.
