Nanomechanical properties of anthracite and graphite: The role of heteroatom functional groups and structural evolution

Abstract

This study investigates the anthracite and graphite samples from the Hanpoao mining area in Hunan Province, China, to understand their structural deformation characteristics in relation to tectonic stress and magmatic intrusion. Despite previous research highlighting the influence of tectonic stress on the microcrystalline structure of organic matter, there remains a gap in comprehensively understanding how these factors interact and affect the mechanical properties of coal and graphite. To address this, the research employed a combination of optical microscopy, reflectance measurements, Raman spectroscopy, and high-resolution atomic force microscopy, along with powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. Studies have shown that the Young's modulus of anthracite and graphite exhibits a certain correlation with both coal rank and the degree of graphitization. Notably, the presence of heteroatom functional groups, particularly sulfur-containing groups, plays a crucial role in modulating the Young's modulus. The study reveals an inverse correlation between thiophene sulfur content and Young's modulus, and a positive correlation with sulfone and sulfoxide sulfur content, suggesting that these groups significantly influence the mechanical properties of anthracite and graphite. We have done comprehensive investigation of the interplay between coal rank, microcrystalline structure, and heteroatom functional groups on the nanomechanical properties of anthracite and graphite. These studies provide a novel perspective for the assessment of the mechanical properties of coal and coal-based graphite, while also offering important theoretical foundations for the efficient utilization and advanced processing technologies of coal resources.