Influence of the Carbon Allotropes on Dilatometric Properties …
669
associated with boundary effects and it is in Raman—the spectra of any carbon material indicating the presence and number of violations of its structure [67, 68]. The
increased intensity and the considerable width of this band may be due to the high
content of defective tubes or a large number of shortened nanotubes in which the
boundary effects are more pronounced, high concentration of the amorphous phase,
etc. The intensity of this band is determined by defect, that is, the degree of violation of sp
2 —the hybridization of carbon atoms (e.g., the carbon in the state of sp
3
hybridization). The ratio of the values of the intensity of the bands D and G (I D /I G )
to a certain degree characterizes the relationship between the number of materials
in the sample with a disordered and ordered structure [69]. The widths of the D and
G bands also increase with structure disorder increasing, and the positions of these
bands in a complicated manner depend on the structure and content of the carbon
material components [63–68].
The range of the D and G bands in the macro-Raman spectra of the studied
nanocomposites is shown in Fig. 17. It should be noted that the intensity of the
D and G bands on these spectra (indicated by wide arrows) are located on a broad
continuous background, which is probably due to the luminescence of functionalized,
in particular oxidized, carbon forms [69]. (Its contribution to the Fe–Cu-CNT(1.0)
spectrum is separated by a direct dashed line.) The wing of the observed D and G
bands in the range 900–1200 cm
−1 partially overlap with bands of lower intensity.
Up to now, their origin remains under question. It is believed that these bands can
be reflected by the vibration of the bonds of the methyl C–CH 3 (preferably) and
methylene (-CH 2 -) groups on the CNT surface [63, 67, 69]. At the same time, the
mention is that, in particular, the band in the vicinity of 1100–1160 cm
−1 (half-width
is 50–130 cm
−1 ), should be attributed to the manifestation of sp
3 states in amorphous
and glassy-like carbon and in other forms containing deformed carbon layers [70,
71]. Therefore, the manifestation of this so-called T band, and characteristics of
its contour (intensity, half-width) can also be an indicator of the CNT disordered
structure.
Analysis of the macro-Raman spectra of Fe–Cu-CNT composites in the range of
frequencies of the CNT vibrations was carried out by removing the contribution of
the above-noted background and the breakdown of the remainder to the components
of the Gaussian form. The breakdown variant for the Fe–Cu-CNT composite (1.0),
e.g., is shown in Fig. 17 and the breakdown parameters for all spectra are given in
Table 2. It is easy to see that the basic, in intensity, bands have characteristics of the
D and G bands, and the characteristics of less intensive bands in the vicinity ~960,
~1080 and ~1160 cm
−1 correspond to the bands of the methyl groups and T bands
of the CNT, respectively. It should be noted here that usually as I D and I G values
are either intensity of the bands at their maximum (I peak ) or their integral intensity,
which is proportional to the area of the spectrum under the corresponding band:
I Integr . Therefore, the values of the ratio of intensity, found both in the first, and in
the second definition are presented in Table 2.
The manifestation of the bands in the ~960 and ~1080 cm
−1 vicinity once again
points to the role of different types of molecular functional groups in the discussed
phenomena of composites expanding in this paper, while the reevaluation of the band
669
associated with boundary effects and it is in Raman—the spectra of any carbon material indicating the presence and number of violations of its structure [67, 68]. The
increased intensity and the considerable width of this band may be due to the high
content of defective tubes or a large number of shortened nanotubes in which the
boundary effects are more pronounced, high concentration of the amorphous phase,
etc. The intensity of this band is determined by defect, that is, the degree of violation of sp
2 —the hybridization of carbon atoms (e.g., the carbon in the state of sp
3
hybridization). The ratio of the values of the intensity of the bands D and G (I D /I G )
to a certain degree characterizes the relationship between the number of materials
in the sample with a disordered and ordered structure [69]. The widths of the D and
G bands also increase with structure disorder increasing, and the positions of these
bands in a complicated manner depend on the structure and content of the carbon
material components [63–68].
The range of the D and G bands in the macro-Raman spectra of the studied
nanocomposites is shown in Fig. 17. It should be noted that the intensity of the
D and G bands on these spectra (indicated by wide arrows) are located on a broad
continuous background, which is probably due to the luminescence of functionalized,
in particular oxidized, carbon forms [69]. (Its contribution to the Fe–Cu-CNT(1.0)
spectrum is separated by a direct dashed line.) The wing of the observed D and G
bands in the range 900–1200 cm
−1 partially overlap with bands of lower intensity.
Up to now, their origin remains under question. It is believed that these bands can
be reflected by the vibration of the bonds of the methyl C–CH 3 (preferably) and
methylene (-CH 2 -) groups on the CNT surface [63, 67, 69]. At the same time, the
mention is that, in particular, the band in the vicinity of 1100–1160 cm
−1 (half-width
is 50–130 cm
−1 ), should be attributed to the manifestation of sp
3 states in amorphous
and glassy-like carbon and in other forms containing deformed carbon layers [70,
71]. Therefore, the manifestation of this so-called T band, and characteristics of
its contour (intensity, half-width) can also be an indicator of the CNT disordered
structure.
Analysis of the macro-Raman spectra of Fe–Cu-CNT composites in the range of
frequencies of the CNT vibrations was carried out by removing the contribution of
the above-noted background and the breakdown of the remainder to the components
of the Gaussian form. The breakdown variant for the Fe–Cu-CNT composite (1.0),
e.g., is shown in Fig. 17 and the breakdown parameters for all spectra are given in
Table 2. It is easy to see that the basic, in intensity, bands have characteristics of the
D and G bands, and the characteristics of less intensive bands in the vicinity ~960,
~1080 and ~1160 cm
−1 correspond to the bands of the methyl groups and T bands
of the CNT, respectively. It should be noted here that usually as I D and I G values
are either intensity of the bands at their maximum (I peak ) or their integral intensity,
which is proportional to the area of the spectrum under the corresponding band:
I Integr . Therefore, the values of the ratio of intensity, found both in the first, and in
the second definition are presented in Table 2.
The manifestation of the bands in the ~960 and ~1080 cm
−1 vicinity once again
points to the role of different types of molecular functional groups in the discussed
phenomena of composites expanding in this paper, while the reevaluation of the band