The structural evolution and mutation of graphite derived from coal under the influence of natural igneous plutonic intrusion

• Published in: Fuel (Guildford) Vol. 322; p. 124066
• Main Authors: Zhang, Hao, Li, Kuo, Sun, Junmin, Sun, Zhiming, Yuan, Liang, Liu, Qinfu
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.08.2022; Elsevier BV
• Subjects: Aromatic compounds; Carboniferous; Coal; Coal-derived graphite; Evolution; Fourier transforms; Free radicals; FTIR spectrometers; Graphene; Graphite; Graphitization; Growth stage; High resolution electron microscopy; Igneous plutonic intrusion; Immunoglobulins; Infrared analysis; Infrared spectrometers; Infrared spectroscopy; Intrusion; Meta-anthracite; Microcrystals; Multilayers; Mutation; Parameters; Photoelectron spectroscopy; Photoelectrons; Raman spectroscopy; Spectroscopy; Spectrum analysis; Stitching; Structural evolution; Transmission electron microscopy; X ray photoelectron spectroscopy; X-ray diffraction; Igneous plutonic intrusion; Structural evolution; Mutation; Meta-anthracite; Coal-derived graphite
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2022.124066

[Display omitted] •Structural evolution and mutation from meta-anthracite to graphite during the graphitization were studied.•A structural mutation of coal-derived graphite exists at semi-graphite stage.•Carbon-free radicals at the edges of polyaromatic rings play an important role in the stitching of La.•Conjugated π–π interaction force is crucial in the stacking of polyaromatic rings.•Lc growth is time lag behind than La during the graphitization process. Graphite can be formed from coal under the influence of a pluton intrusion. However, the mechanism by which polyaromatic rings of disordered structure extend laterally and stack vertically during graphitization from coal to graphite remains unknown. Therefore, proximate and ultimate analysis, X-ray diffraction (XRD), Raman spectroscopy, Fourier-transform infrared spectrometer (FTIR), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy were used to characterize a series of naturally graphitized coals collected from Lower Carboniferous strata in Xinhua county, Hunan province, China. The parameters derived from various analyses such as d002 and full width at half maximum (002) from XRD, ID/IG and I2D/ID + G from Raman spectroscopy, the proportion of sp2 and sp3 + Cvacancy from XPS, and the Aπ1 and Aπ2 from FTIR regularly change, indicating that the ordered graphite increased along with the removal of heteroatoms when approaching the pluton and the small condensed sp2–sp3 hybridized aromatic rings gradually transform to sp2 hybridized aromatic rings during graphitization. Furthermore, some parameters, such as ID/IG, La, Lc, and the proportion of sp2, changed dramatically in the semi-graphite stage, indicating that structural mutation of graphitized coal happens at the semi-graphite stage and the growth of Lc occurs slower than that of La during graphitization. The structural evolution can be divided into three stages: a. basic structural unit growth stage (<10 layers); b. fast growth stage of two-dimensional multilayer “ribbon-shaped” graphene (10–20 layers); c. three-dimensional-ordered microcrystal graphite growth stage (20–50 layers). The carbon-free radicals at layer edges and the conjugated π–π interaction force between graphite layers may be crucial in the stitching and stacking of polyaromatic rings.