Biomedical Engineering Reference
In-Depth Information
impurities of the CNTs [41]. Diameters and chiralities distribution are
also observed as well as a different number of layers for nanotubes
when the X-ray incident beam is directed toward samples under
investigation. The interlayer spacing can be obtained from angular
position of the reflected beam by using the Bragg law with a family
of (
) peaks due to the honeycomb lattice of the single graphene
sheet. Usually, the peak position shifted from 26.5° for graphite to
~
h k l
q
[50] demonstrated by XRD
analysis that an array of aligned CNTs can be filled with nickel
nanowire by electrodeposition for reliable technological application
in nanoelectronic devices. The XRD spectrum proved the effective
filling of the CNTs array with Ni nanowires. Moreover, Bougrine
et al.
26° in 2
for SWCNT layers. Bao
et al.
[51] demonstrated by XRD analysis that the two-step purification
process (oxidation and acid treatment) of the CNTs consisting in the
removal of the amorphous carbon and the metal impurities from
the CNTs networks results to be very effective. Additionally, a mean
diameter of CNTs can be calculated through the use of the Debye-
Scherrer relation on the (002) peak, measured by the powder XRD
method and compared to computational X-ray diffraction simulated
patterns [41]. Also, Pichot
[52] studied the structural properties
from X-ray scattering measurements performed on a CNTs carpet,
grown by aerosol pyrolysis method. Nanotube alignment of
et al.
5.5°
with respect to the average growth axis is achieved. In addition, CNTs
are partially filled with iron, mainly one phase (
±
-Fe) encapsulated
inside nanotubes and exhibiting a preferential crystallographic
(110) axis along the nanotubes.
Scanning tunnelling microscopy (STM) can resolve
simultaneously both the atomic structure and the electronic
density of state in the CNTs. Therefore, this technique is suitable
for the CNTs characterization. Recent STM studies of the intrinsic
electronic properties of SWCNTs have been overviewed [53, 54].
Using STM atomically resolved images, the chiral angle of CNTs can
be determined. The effects of finite curvature and broken symmetry
on electronic properties, and the atomic structure and the electronic
properties of the intramolecular junctions can be described by STM
technique.
X-ray photoelectron spectroscopy (XPS) technique can give
information on the chemical structure of CNTs, therefore it is used
to characterize the structure modifications of the CNTs walls due
to the chemical interaction with organic compounds adsorbed.
g
