Raman Spectroscopic Characterization and Surface Graphitization Degree of Coal-Based Graphite With the Number of Aromatic Layers
LI Huan-tong1, 2, CAO Dai-yong3, ZOU Xiao-yan3, ZHU Zhi-rong1, ZHANG Wei-guo1, XIA Yan4
1. College of Geology and Environment, Xi’an University of Science and Technology, Xi’an 710054, China
2. Shaanxi Provincial Key Laboratory of Geological Support for Coal Green Exploitation, Xi’an 710054, China
3. College of Geoscience and Surveying Engineering，China University of Mining and Technology (Beijing)，Beijing 100083，China
4. Coal Geology Survey of Ningxia Hui Autonomous Region, Yinchuan 750011, China
Abstract：Comparison of Raman spectra at multi-excitation wavelengths (325, 405, 514, 633 and 785 nm) for coal-based graphite, and evolution of the spectra at 514 nm with the number of aromatic layers were detail studied. Moreover, the Raman mapping test studied the surface defects distribution of coal-based graphite block. The results show disordered graphite has a smaller size and arbitrary orientation than graphite crystallites. With the increase of stacking degree and average stacking layers, the Raman spectrum characteristics of graphite microcrystal edge appear. When the disordered structure of coal-based graphite transforms to order, the defects gradually disappear, and the D3 and D4 peaks in the first-order gradually become invisible or disappear, but the overtone peaks appear weakly, especially as the intensity of the 2D1 peak increases. Further extending the meaning of ID1/ID2 parameter to defect type and average orientation, the ID1/ID2 ratio of anthracite is the largest. With the increase in crystallite size (d002<0.344 nm), the ID1/ID2 of 3D ordered graphite was the smallest. The FWHM of the G peak always decreases with the decrease of disorder at different excitation wavelengths. D1 peak and 2D1 peak show a strong dispersion effect, and the intensity of each peak grows with the increase of excitation energy. Under UV excitation, the peak position difference of D1 and G peaks is significantly smaller than that under visible light excitation. With the increase of excitation wavelength, the D1 peak moves towards the low wavenumber direction, and the dispersion of the 2D1 peak is about twice the intensity of the D1 peak. During the graphitization process of high rank coal, the non-oriented aromatic carbon experienced a series of physical and chemical structure evolution to produce various intermediate phases, and the residual coal macerals (vitrinite and inertinite) and new graphite components (pyrolytic carbon, etc.) coexist. (IG-ID1)/(PG-D1)≥0.3, ID1/IG<0.4, AD1/A(D1+G)<0.45 were used as the boundaries of graphite and semi-graphite. The surface uniformity of the sample was characterized by planar scanning area imaging. The confidence interval of the frequency distribution of 0.9 was used to comprehensively determine the surface graphitization degree of the sample, which was 84.16%~86.40%, and the average was 85.49%, which was similar to the estimated value of XRD parameters.
李焕同，曹代勇，邹晓艳，朱志蓉，张卫国，夏 炎. 不同堆砌层数煤系石墨的拉曼光谱表征及其表面石墨化均匀程度[J]. 光谱学与光谱分析, 2022, 42(08): 2616-2623.
LI Huan-tong, CAO Dai-yong, ZOU Xiao-yan, ZHU Zhi-rong, ZHANG Wei-guo, XIA Yan. Raman Spectroscopic Characterization and Surface Graphitization Degree of Coal-Based Graphite With the Number of Aromatic Layers. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2022, 42(08): 2616-2623.
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