Raman spectrum is a common method of evaluating the graphitization degree of carbon materials. However, there is still some controversy over its evaluation for coal graphitization, i.e., whether large I_D/I_G means a high graphitization degree of coal. This work uses an ultraviolet (UV) Raman spectrum to find a better index of graphitization degree. The T peak (sp³ sites) of coal was first directly detected. The I_T/I_G and I_D/I_G decrease after pyrolysis in UV Raman spectra at 266 nm, which shows that the sp³ site relative content decreases and the sp² site relative content increases. Moreover, the absolute value of the D band dispersion slopes as the excitation wavelength increases and the D peak width decreases, which shows that the coal gets more orderly after pyrolysis. The position difference (G–D) decreases and the G peak width increases after pyrolysis in UV–Vis Raman spectra, indicating the decomposition of vitrinite in coal. The 2D′ peak decreased after pyrolysis. These parameters in multi-wavelength Raman spectra can be used to evaluate the structure of coal.

中文翻译：

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紫外拉曼光谱：评估煤热解石墨化的合理方法

拉曼光谱是评估碳材料石墨化程度的常用方法。但是，其对煤石墨化的评价还存在争议，即大的I _D / I _G是否意味着煤的石墨化程度高。这项工作使用紫外线（UV）拉曼光谱来找到更好的石墨化程度指标。首先直接检测到煤的T峰（sp ³位）。在266 nm的UV拉曼光谱中热解后，I _T / I _G和I _D / I _G降低，这表明sp ³站点相对含量降低，sp ²站点相对含量增加。此外，随着激发波长的增加和D峰宽度的减小，D谱带色散的绝对值出现斜率，表明煤在热解后变得更有序。在UV-Vis拉曼光谱中热解后，位置差（G–D）减小，G峰宽增加，表明煤中的镜质石分解。热解后2D'峰降低。多波长拉曼光谱中的这些参数可用于评估煤的结构。