High pressure Raman and neutron scattering study on structure of carbon black particles (original) (raw)
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Raman spectroscopy of closed-shell carbon particles
Chemical Physics Letters, 1993
Raman spectra of annealed carbon soot reveal strong structural changes. Downshifts of the graphite-like phonon bands to lower energies after annealing are suggested to be related to strained or curved graphitic planes. The effect of curvature on the energy of the in-plane optical phonon mode is quantitatively estimated by applying the semi-empirical interatomic Tersoff potential. A weighted average curvature corresponding to a bond bending of 2.1' is deduced for spherical shells with 20.6 A radius. These findings are consistent with high-resolution electron microscopy images which reveal closed-shell carbon particles in the same size
Raman spectroscopic characterization of some commercially available carbon black materials
Carbon, 1995
Some commercially available carbon black materials were characterized by Raman spectroscopy. The Raman spectra were recorded between 1000 and 1800 cm-', which corresponds to the spectral region that provides the most valuable data on the microstructure of carbons. A comparative study of the intensity, bandwidth and frequency shifts of the D and G bands, as well as the broad amorphous feature, is presented here. A curve fitting method is also proposed in order to improve the accuracy in determining the spectroscopic parameters of the main Raman bands. Correlations between the Raman spectra and the structure were established. The samples were found to correspond to low order sp' bonded carbons, but cannot be considered as truly amorphous since they have some degree of order in the basal plane.
Raman spectroscopy of carbon materials: Structural basis of observed spectra
Chemistry of Materials, 2009
The first-and second-order Raman spectral features of graphite and related sp2 carbon materials were examined with laser wavelengths ranging from 293 to 1064 nm. A wide range of carbon materials was considered, including highly ordered pyrolytic graphite (HOPG), powdered and randomly oriented graphite, and glassy carbon prepared at different heat-treatment temperatures. Of particular interest is boron-doped highly ordered pyrolytic graphite (BHOPG), in which boron substitution decreases local lattice symmetry but does not disrupt the ordered structure. New second-order bands at 2950,3654, and -4300 cm-' are reported and assigned to overtones and combinations. The D band at 1360 cm-l, which has previously been assigned to disordered carbon, was observed in ordered boronated HOPG, and its overtone is strong in HOPG. The observed Raman shift of the D band varies with laser wavelength, but these shifts are essentially independent of the type of carbon involved. It is concluded that the D band results from symmetry breaking occurring at the edges of graphite planes in sp2 carbon materials or at boron atoms in BHOPG. The observations are consistent with the phonon density of states predicted for graphitic materials, and the fundamental and higher order Raman features are assignable to theoretically predicted lattice vibrations of graphite materials. The laser wavelength dependence of the D band frequency appears to result from scattering from different populations of phonons, perhaps through a resonance enhancement mechanism. However, the results are inconsistent with resonance enhancement of graphite microcrystallites of varying size.
Determination of crystallite size in polished graphitized carbon by Raman spectroscopy
Physical Review B, 2012
A series of polished and unpolished sp 2-nanostructured carbons "nanographites" obtained from the pyrolysis of various precursor types have been systematically studied by both Raman spectroscopy and x-ray diffraction. The ratio between the intensities of the disorder-induced D band and the first-order graphite G band (I D /I G) commonly used up to now to estimate the "crystallite" diameter L a displays, in the case of polished graphitized sp 2 carbons, clear spatial heterogeneities and can lead to the overestimation of the intrinsic structural disorder. The full width at half maximum of the G band, which is shown to be insensitive to the polishing process, exhibits a linear dependence on the mean "crystallite" diameter [FWHM(G) = 14 + 430/L a ] and therefore can be used for an accurate structural characterization of these nanographites.
Microstructure of carbon blacks determined by X-ray diffraction profile analysis
Carbon, 2002
The microstructure of carbon blacks is investigated by X-ray diffraction peak profile analysis. Strain anisotropy is accounted for by the dislocation model of the mean square strain in terms of average dislocation contrast factors. Crystallite shape anisotropy is modeled by ellipsoids incorporated into the size profile function. Different grades of carbon blacks, N990, N774 and N134, untreated, heat-treated and compressed at 2.5 GPa have been investigated. The microstructure is characterized in terms of crystallite size-distribution, dislocation density and crystallite shape anisotropy. Heat treatment results in increased vertical and lateral sizes of graphitic crystallites. Postproduction pressure treatment has little effect on the average sizes of the crystallites, however, it affects the crystallite size distribution function. The average sizes of the crystallites obtained by X-ray diffraction agree with those estimated from Raman spectra. Applied pressure affects the magnitude of strain within the crystallites.
Raman spectroscopy of carbon nano-particles synthesized by laser ablation of graphite in water
Revista Mexicana De Fisica, 2017
Carbon nanoparticles (CNPs) have been synthesized by laser ablation of polycrystalline graphite in water using a pulsed Nd:YAG laser (1064 nm) with a width of 8 ns. Structural and mesoscopic characterization of the CNPs in the supernatant by Raman spectroscopy provide evidence for the presence of mainly two ranges of particle sizes: 1-5 nm and 10-50 nm corresponding to amorphous carbon and graphite NPs, respectively. These results are corroborated by complementary characterization using atomic force microscopy (AFM) and transmission electron microscopy (TEM). In addition, large (10-100 µm) graphite particles removed from the surface are essentially unmodified (in structure and topology) by the laser as confirmed by Raman analysis.
Size and shape of crystallites and internal stresses in carbon blacks
Composites Part A: Applied Science and Manufacturing, 2005
The effect of graphitization and pressure treatment on the microstructure and internal stresses of carbon blacks is studied by X-ray diffraction peak profile analysis. The Fourier transforms of the experimental line profiles are fitted by theoretical functions based on the model of the microstructure. In this model the crystallites are ellipsoids with log-normal size distribution. It was found that in raw carbon blacks crystallites have lateral dimensions twice the size in the hexagonal c direction. During graphitization process caused by heat treatment the crystallites grow and their shapes becomes more spherical. The pressure has no effect on the size and shape of crystallites. The internal strains and stresses in the crystallites are determined from the X-ray diffraction profiles by the Griffith model. It was established that the internal stresses increase due to pressure treatment while they are reduced by graphitization. q
Carbon, 2004
CO 2 laser vaporization of graphite was carried out in the presence of high pressure Ar gas up to 0.8 MPa. We compared transmission electron microscope images and Raman spectra of deposited particles and luminous laser plumes of vaporized and clustered carbon species. We discuss the growth mechanisms of three graphitic carbon particles, a single-wall carbon nanohorn aggregate, a platelet graphite particle, and a polyhedral graphite particle, grown depending on the confinement of the Ar atmosphere. The formation of graphitic sheet or shell structures, dependent on resident carbon densities and their temperature gradient, is thought to begin from supersaturated hot carbon vapor up to about 3000°C and leads to the growth of the three graphitic particles.