Studying carbonisation with raman spectroscopy (original) (raw)
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Raman Spectroscopy of Carbon Materials
Spectroscopy, 1996
Use of carbon materials is no longer limited to diamond jewelry or graphite pencils and lubricants. The last decade has witnessed an explosion of technological applications driven by the development of fabrication methods and the discovery of several new classes of pure carbon. Structural diversity exhibited by the carbon atoms, from local chemical order to long-range crystalline order, is key to understanding their physical and chemical properties and in future materials development. This article summarizes the use of Raman spectroscopy as a principal tool to investigate the vibrational dynamics of carbon materials and to provide indirect structural characterization of their short-, medium-and long-range order.
Use of Raman Spectroscopy to Qualify Carbon Materials
Spectroscopy
In the last 30 to 40 years, various new types of carbon materials have been engineered for multiple industrial uses. It is now well-known that the Raman spectrum is sensitive to the structure, even though the spectrum is rather uncomplicated. Because Raman spectroscopy now has a reputation for providing good information, potential users of Raman equipment can request information on the quality of their sample. However, they are often not able to define clearly what they mean by “quality.” If they are growing diamond films, they may or may not want interstitial sp2 carbon to glue polycrystalline diamond together. If they are growing hard diamond-like carbon (DLC) films, they may want to correlate the spectral characteristics with physical characteristics of the film. In this column, I explain how the Raman characteristics can aid in characterization of carbon materials.
Raman spectroscopy of carbon-containing particles
Vibrational Spectroscopy, 2001
Raman spectroscopy has been used to study a number of carbon-containing particles: commercial graphite of various compositions, Candle soot (CS) and Diesel soot (DS), and ambient particles. The spectra show the known D, G, D H and 2D bands with varying characteristics. An analysis of the spectra allows the inference of internal physical characteristics of the samples such as the size or degree of disorder of the carbon microcrystalline domains on a nanometer scale. The samples are also analyzed using a scanning electron microscope, revealing their structure in the 1±20 mm scale. #
Raman spectroscopy of selected carbonaceous samples
International Journal of Coal Geology, 2010
This paper presents the results of Raman spectra measured on carbonaceous materials ranging from greenschist facies to granulite-facies graphite (Anchimetamorphism and Epimetamorphism zones). Raman spectroscopy has come to be regarded as a more appropriate tool than X-ray diffraction for study of highly ordered carbon materials, including chondritic matter, soot, polycyclic aromatic hydrocarbons and evolved coal samples. This work demonstrates the usefulness of the Raman spectroscopy analysis in determining internal crystallographic structure (disordered lattice, heterogeneity). Moreover, this methodology permits the detection of differences within the meta-anthracite rank, semi-graphite and graphite stages for the samples included in this study. In the first order Raman spectra, the bands located near to c.a. 1350 cm − 1 (defects and disorder mode A 1g) and 1580 cm − 1 (in plane E 2g zone-centre mode) contribute to the characterization and determination of the degree of structural evolution and graphitization of the carbonaceous samples. The data from Raman spectroscopy were compared with parameters obtained by means of structural, chemical and optical microscopic analysis carried out on the same carbonaceous samples. The results revealed some positive and significant relationships, although the use of reflectance as a parameter for following the increase in structural order in natural graphitized samples was subject to limitations.
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.
Carbon, 2015
The aim of this paper is to describe carbonisation and partial graphitization of carbon blacks (CB). Raman spectrometry is used to investigate a series of five CB grades during heat treatment (up to 2600°C). Obtained results are discussed by comparing Raman data with Xray diffraction and High-Resolution Transmission Electron Microscopy (HRTEM) observations. For Raman spectra interpretation, the usual curve fitting method proposed by Sadezky et al. for soot and disordered carbonaceous material is applied. As the same procedure can be applied over all the heat-treatment temperature range, the determination of band parameters from five band decompositions appears to be the most convenient to follow the CB's structural improvement. We demonstrate that only a partial graphitization takes place and the graphitizability is limited by the diameter of the primary particles. Our observations generalize the results obtained for cokes: graphitization degree of carbonaceous materials after the heat-treatment is limited by the diameter of the volumes within polyaromatic layers are oriented in parallel.
Raman Spectroscopy of Amorphous Carbon
1998
Amorphous carbon is an elemental form of carbon with low hydrogen content, which may be deposited in thin films by the impact of high energy carbon atoms or ions. It is structurally distinct from the more well-known elemental forms of carbon, diamond and graphite. It is distinct in physical and chemical properties from the material known as diamond-like carbon, a form which is also amorphous but which has a higher hydrogen content, typically near 40 atomic percent. Amorphous carbon also has distinctive Raman spectra, whose patterns depend, through resonance enhancement effects, not only on deposition conditions but also on the wavelength selected for Raman excitation. This paper provides an overview of the Raman spectroscopy of amorphous carbon and describes how Raman spectral patterns correlate to film deposition conditions, physical properties and molecular level structure.
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
C, 2015
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.