Microstructural Characteristics of Graphite Microcrystals in Graphitized Coal: Insights from Petrology, Mineralogy and Spectroscopy

Graphite microcrystals are the product of coal graphitization and widely exist in graphitized Yongan Coalfield, Fujian Province, China, which is direct mineralogical evidence for transformation to graphite. Optical microscopy, scanning electron microscopy (SEM) micro-Raman spectroscopy were used detect morphology microstructure situ graphite microcrystals. The results show that volume proportion samples between 2.39% 7.32%, optical anisotropy stronger than macerals. occurrence attached microcrack inner walls or infilling cell cavity, with several forms flakes, needles aggregates. Under polarized light a retarder plate 1?, color primary yellow secondary blue, two kinds colors appear alternately when microscope rotating. Additionally, flake-like an isochromatic zone diameter 10?50 ?m most distributed coal. SEM, rough irregular edge characterized by flow bubble film structures along pores, cooling crystallization after softening melting carbon-containing substances. Moreover, developed interlayer pores clear outline loose stacking almost entirely composed pure carbon; small amount oxygen related oxygen-containing functional groups structural defects. spectra first-order region low-intensity D1 D2 bands high-intensity G band, parameters R1 R2 vary from 0.21–0.39 0.60–0.74, respectively. second-order higher intensity 2D1 band lower other three bands. parameter R3, derived area ratio all region, was proposed. value R3 ranges 0.78 0.86, both them indicate percentage graphene plane highly internal crystallographic structure. Similar spectrum, effective characterize ordering degree microstructure, may be evaluate