Stress response of coalcondensed aromatic ring:Inspiration for graphitization of anthracite

The discovery of scabbard fold in shallow(< 5 km)detachment structure indicates that the coal seam ductile shear zone could also be developed in the brittle deformation domain，whose structural characteristics and associat⁃ ed graphite mineralization have been recognized internationally. However，the research on the evolution mechanism of ultra⁃fine structure order in the process of coal ductile rheology is still not sufficient，and there is a lack of experimen⁃ tal demonstration and theoretical analysis. In this study， the high⁃temperature and high⁃pressure deformation experiment on primary structure anthracite，high⁃resolution transmission electron microscope(HRTEM)，and X⁃ray dif⁃ fraction(XRD)are used as the main research methods to simulate the effects of stress and strain rate on the structural alignment of the condensed aromatic ring(CAR). It is supposed to reveal the structural order evolution of coal CAR under different stress states and strain rates and its enlightenment on the graphitization of anthracite. The results indi⁃ cate that the high tectonic stress and low strain rate enhance the length and directionality of anthracite macromolecular CAR. Both have the most significant effect on the order of CARs. The curvature of coal CARs increases with the en⁃ hancement of differential stresses and hydrostatic pressure，however，it decreases with the decreasing strain rate. The stacking extent slightly increases with the enhancement of differential stresses and decreasing strain rate，where the stacking extent is insensitive to the hydrostatic pressures. The XRD results show that the spacing of CAR networks de⁃ creases with the increase of tectonic stress and the decrease of strain rate，which is consistent with the HRETM results. The experimental results show that besides temperature，high differential stress，and low strain rate are the key factors for the enhancement of CAR structural alignment for anthracite. The study on the stress response characteristics of CAR within coal macromolecules has an important implication for anthracite graphitization mineralization.