XRD and Raman Spectroscopy Characterization of Graphitization Trajectories of High-Rank Coal
LI Huan-tong1, 2, CAO Dai-yong3*, ZHANG Wei-guo1, 2, WANG Lu4
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. Chongqing Institute of Geology and Mineral Resources, Chongqing 401120, China
Abstract：In order to the interpretation of ordering and crystallinity of natural graphitized coal, nineteen kinds of different deformation-metamorphism degree high-rank coal from Hunan Province and Shaanxi Province were studied with proximate and ultimate analysis, X-ray diffraction (XRD), Raman spectrum and curve-fitting analysis. The graphitization, crystal size (La and Lc), interplanar spacing (d002) were calculated with XRD. The parameters of PG (G band position), P1 (G and D1 band separation), R1=ID1/IG, the peak height ratio, R2=AD1/(AG+AD1), peak area ratio were calculated with Raman. The results showed that the H/C decreases gradually with the increase of metamorphic degree during the coalification stage, but during the graphitization stage, the change was primarily physical, and the trend was slow or not significant. The parameters of d002, La, Lc, N and La/Lc had shown that the crystalline structure of natural graphitized coal presented nonlinear continuous (step) change with metamorphism degree. The inflection point corresponds roughly to Rm=7.0% and d002=0.338 nm. Before the inflection point, La, Lc and N changed little (or increase steadily), and the graphite crystal structure formed rapidly after the inflection point, the stacking effect begins and gradually increases, as the crystallite size increases. La/Lc variation reflected that the graphitization process changed from condensation to overlap. The graphitization trajectory of high-rank coal can be given in a three-stage model of orderly increase. During the stage from amorphous carbon (anthracite) to meta-anthracite, the parameters of PG and P1 changed significantly, and ID1/IG did not obey the TK relation when expressing the degree of disorder. During the stage from meta-anthracite to semi-graphitization showed different directions, R1 presented an opposite trajectory with the increase of order, the evolution of some graphite components followed the TK relation, and R2 showed a completely contradictory trajectory when the graphitization degree was 45%. The temperature and pressure in the graphite stage led to a sharp increase in crystal size (step evolution), and the decrease of ID1/IG obeying the TK relation. As neogenesis-associated components in different graphitized coals, d002 cannot reflect the largest metamorphic degree of graphitized coal. However, it was still a superior choice to consider d002 as an average scaling of the graphitized coals in the process of graphitization. Moreover, full width at half maximum of the (002) and (γ) band are reliable indicators for distinguishing and classifying of metamorphism type of nature graphitized coals. H/C, and ID1/IG also evolved over d002 trajectory was altered, needed to use d002＜0.344 nm, R1＜2.0, H/C＜0.12 and other comprehensive indicators to identify the beginning of graphitization. From this, it could be seen that XRD and Raman spectral analysis techniques could be used to characterize the graphitization track stages and structural differences of high rank coal.
李焕同，曹代勇，张卫国，王 路. 高煤级煤石墨化轨迹阶段性的XRD和Raman光谱表征[J]. 光谱学与光谱分析, 2021, 41(08): 2491-2498.
LI Huan-tong, CAO Dai-yong, ZHANG Wei-guo, WANG Lu. XRD and Raman Spectroscopy Characterization of Graphitization Trajectories of High-Rank Coal. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2021, 41(08): 2491-2498.
[1] CAO Dai-yong, LI Xiao-ming, DENG Jue-mei(曹代勇，李小明，邓觉梅). Earth Science Frontiers(地学前缘), 2009, 16(4): 52.
[2] LI Huan-tong, WANG Nan, ZHU Zhi-rong, et al(李焕同，王 楠，朱志蓉, 等). Acta Geologica Sinica(地质学报), 2020, 94(11): 3503.
[3] Wang L, Cao D, Peng Y, et al. Minerals (Basel), 2019, 9(10): 617.
[4] LI Jiu-qing, QIN Yong, CHEN Yi-lin(李久庆，秦 勇，陈义林). Coal Geology & Exploration(煤田地质与勘探), 2020, 48(1): 27.
[5] QIN Yong(秦 勇). Earth Science Frontiers(地学前缘), 1999，(S1): 29.
[6] Grew E S. Journal of Geology, 1974, 82(1): 50.
[7] Landis C A. Contributions to Mineralogy and Petrology, 1971, 30(1): 34.
[8] Wada H, Tomita T, Matsuura K, et al. Contributions to Mineralogy and Petrology, 1994, 118(3): 217.
[9] Franklin R E. Acta Crystallographica, 1951, 4(3): 253.
[10] Li K, Rimmer S M, Liu Q. International Journal of Coal Geology, 2018, 195: 267.
[11] Ferrari A C, Robertson J. Physical Review B, 2000, 61(20): 14095.
[12] ZHU Ya-ming, ZHAO Xue-fei, GAO Li-juan, et al(朱亚明，赵雪飞，高丽娟, 等). Spectroscopy and Spectral Analysis(光谱学与光谱分析), 2017, 37(6): 1919.
[13] XIANG Jian-hua, ZENG Fan-gui, LIANG Hu-zhen, et al(相建华，曾凡桂，梁虎珍, 等). Journal of China Coal Society(煤炭学报), 2016, 41(6): 1498.
[14] Sonibare O O, Haeger T, Foley S F. Energy (Oxford), 2010, 35(12): 5347.
[15] Yui T F, Huang E, Xu J. Journal of Metamorphic Geology, 1996, 14(2): 115.
[16] Tuinstra F, Koenig J L. The Journal of Chemical Physics, 1970, 53(3): 1126.
