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The structural parameters of six coals were determined by X-ray diffraction (XRD), scanning electron microscope (SEM), and Raman and FTIR spectroscopy. The results reveal that the derivative coals prepared by calcination and HF acidification contain much crystalline carbon like graphite structure and are improved significantly in aromaticity, coal rank, and hydroxyl concentration. The increase of hydroxyl (OH) bonds is very beneficial to the surface modification of coal crystalline layers. In addition, the derivative coals have an obvious decrease of the aliphatic C–H content and a significant increase of the aromatic C–H content in FTIR spectra compared to that for the raw coal (AY). They are consistent with the changes of aromaticity and crystalline carbon measured by XRD and Raman spectra. With the increase of coal rank, the content of defect crystalline carbon and amorphous carbon decreases gradually from AY to the coal prepared by calcination and HF acidification (AY-C-HF). The particles of AY-C-HF with about 20 nm in thickness have better dispersibility with simultaneously a lot of pore space. The process of first calcination and then acidification can help us delaminate the aromatic layers in the coals and obtain the superfine crystalline carbon materials like graphite structure.

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