Raman Spectra of Carbon-Based Materials (from Graphite to Carbon Black) and of Some Silicone Composites

Abstract

Carbon-based nanomaterials have emerged as a subject of enormous scientific attention due to their outstanding mechanical, electrical and thermal properties. Incorporated in a polymeric matrix, they are expected to significantly improve physical properties of the host medium at extremely small filler content. In this work, we report a characterization of various carbonaceous materials by Raman spectroscopy that has become a key technique for the analysis of different types of sp 2 nanostructures, including one-dimensional carbon nanotubes, two-dimensional graphene and the effect of disorder in their structures. The dispersion behavior of the D and G' Raman bands, that is, their shift to higher frequencies with increasing laser excitation energy, is used to assess the interfacial properties between the filler and the surrounding polymer in the composites.

Raman Micro-Spectroscopy Identifies Carbonaceous Particles Lying on the Surface of Crocidolite, Amosite, and Chrysotile Fibers

“…Fitting process applied to it revealed two bands: one, more intense, at 1596 cm −1 , corresponding to G band and another one at 1624 cm −1 (D band, Figure 1d). Also, the G band, corresponding to the second order Raman scattering is detected at 2658 cm −1 [51]. Noteworthy, in the 3000-2900 cm −1 spectral range, Raman νCH stretching mode diagnostic peaks account for different C-H aliphatic groups embedded in carbon substrates.…”

“…Other four minor bands at 2658, 2916, 3617, and 3633 cm −1 were detected. By literature data, specific bands in the spectral region 3500-1200 cm −1 are produced by carbonaceous phases, which may be characterized by different degrees of reticular order-disorder [48][49][50][51][52][53][54][55][56]. Fitting program has been applied on the band at 1600 cm −1 , which appears large and formed by more than one component.…”

“…Considering the Raman spectra recorded in dark regions, for the spectral range corresponding to lattice vibrations of the crocidolite, amosite, and chrysotile minerals 1200-100 cm −1 , the observed data (Table 1) [5,6,57], except for the band at 1120 cm −1 on chrysotile spectra, Figure 1b, Figure 2b and Figure 3b. New bands were observed in the spectral range of 4000-1200 cm −1 , where bands produced by carbonaceous phases occur [48][49][50][51][52][53][54][55][56]. In fact, these phases exhibit on the Raman spectra a mixture of D bands (diamond-like), provided by defective graphitic layers and by different sp 3 C-bonds, and G bands (graphite-like), due to sp 2 C-frameworks.…”

“…The different wavenumbers observed for the same vibrational mode are related to different order-disorder combinations in the lattice and higher wavenumbers corresponding to higher disorder degree [52]. Also, the relative intensities of the D and G bands are related to the reticular characteristics: higher intensity of the D band with respect to the G band indicates a higher degree of disorder in the structure of the carbonaceous phases, with the D vibrational modes Raman active only in defective graphitic samples [50,51]. In the Raman spectra recorded on crocidolite samples studied during this work, the D band, detected at 1333 cm −1 , showed higher intensity than the G band observed at 1600 cm −1 , Figure 1c.…”

“…Nevertheless, a certain degree of disorder could yet be hypothesized by the presence of the satellite D band at 1613 cm −1 and by the weak CH-aliphatic broad band at 2914 cm −1 [58]. The band lying at 3235 cm −1 , harmonic 2D band [51], is peculiar for carbonaceous materials on amosite, and the three bands at 3613, 3635 and 3650 cm −1 are assigned to crystalline stretching vibrations of OH − groups, values matching with the data reported in Bard et al, 1997, and Lewis et al, 1996 [61,62].…”