STUDY OF STRUCTURAL TRANSFORMATION OF HIGH-SULFUR CARBON MATERIALS DURING GRAPHITIZATION BY RAMAN SPECTROSCOPY AND X-RAY DIFFRACTION ANALYSIS

Raman spectroscopy is widely used in studying the structural transformations of carbon materials during high-temperature processing, as well as during mechanical dispersion. In particular, by analyzing Raman spectra, it is possible to assess the spatial homogeneity of carbon materials and the degree of disorder, as well as determine the size of coherent scattering regions in the basal plane. In this work, using Raman spectroscopy with a spatial resolution of up to ~20 μm (EnSpectr spectrometer with a wavelength of 532 nm, equipped with an Olympus microscope and a motorized stage for moving the sample), the features of structural transformations of high-sulfur carbon materials during the graphitization process are examined. And the data obtained are compared with X-ray diffraction analysis. The influence of the addition of iron oxide on this process was traced. The objects of the study were samples of high-sulfur coke (sulfur content 1.3 wt.%), some of which contained the addition of dispersed iron oxide in an amount of 0.75 wt.%. It was shown that the formation of sp2-carbon occurs unevenly throughout the entire volume of the sample. At a temperature of 1400 °C, the highest value of the degree of disorder calculated from the ratio of the intensities of spectral lines D and G (ID/IG) and the dispersion σ(ID/IG) of this value of the materials under study are observed. A further increase in the processing temperature activates graphitization. The material becomes more homogeneous in its dispersed composition. After heat treatment of samples above 2000 °C, the ID/IG value and the dispersion σ(ID/IG) change insignificantly. To calculate the average sizes of coherent scattering regions L100 based on X-ray diffraction analysis data, the profile was divided in the range of Bragg angles from 40 to 50° into two maxima 100 and 101 graphite, described by the Pearson function. As the processing temperature increases, the average size of L100 increases to ~50 nm. These data are in fairly good agreement with the results of calculations of the average sizes of coherent scattering regions (Lа) obtained by Raman spectroscopy. More active recrystallization is observed in carbon material that does not contain dispersed iron oxide. For citation: Fazlitdinova A.G., Tyumentsev V.A. Study of structural transformation of high-sulfur carbon materials during graphitization by Raman spectroscopy and X-ray diffraction analysis. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 10. P. 114-121. DOI: 10.6060/ivkkt.20246710.6981.