Abstract
Anthracite and coal-based graphite (CBG) samples were collected at varying distances from a granite intrusion. Optical microscopy, X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM) were used to characterize the structural evolution of CBG at different scales. The results indicated differences in the graphitization rates of coal macerals and crystallization degree of different graphite-like particles. Differentiated graphitization of coal was caused by deformation, which led to the discontinuous distribution of CBG. This indicates that samples located at the same distance from the intrusion were graphitized to different degrees or that CBG with a similar graphitization degree occurred at varying distances from the intrusion. A possible mechanism for graphitization is strain-induced graphitization, where the local stress concentration leads to preferred orientations of the basic structure units (BSUs), as well as the motion and rearrangement of structural defects, resulting in the formation of a locally ordered structure. The graphitization degree is enhanced as the local graphite structure spreads.
Highlights
Graphite, as a raw material for the production of new carbon materials, has been listed as a strategic resource by countries around the world [1,2,3,4,5]
Based on the microstructure observations, we summarize the three types of carbonaceous particles we identified in Coal-based graphite (CBG), including coal macerals, pyrolytic carbons, and graphite-like particles
Coal macerals are graphitized at different rates, producing different graphite-like particles with various degrees of crystallization
Summary
As a raw material for the production of new carbon materials, has been listed as a strategic resource by countries around the world [1,2,3,4,5]. Coal-based graphite (CBG) is formed by the metamorphism of coal seams under the effects of magmatic intrusion and tectonic stress [3,4,5,6,7]. Anthracite, semi-graphite, and graphite are progressively formed [11,12,13,14,15]. Optical analysis, X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM) have been applied to characterize coal and CBG [11,16,17,18,19,20]. Marques et al [10] investigated the correlations between optical, chemical, and microstructural properties in anthracite and CBG. Deurbergue et al [14]
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