Characterization of the Heterogeneous Evolution of the Nanostructure of Coal-Based Graphite

Abstract

The graphitization of coal is complicated due to multiple factors, such as magmatic intrusions, tectonic stresses and the catalysis of minerals. Heterogeneous graphitization was found based on the nanostructural characterization of anthracite and coal-based graphite. It was determined that the graphitization of coal is not only the rearrangement of carbon layers but also the extinction of structural defects, as revealed by the evolution of XRD and Raman spectra and structural parameters (i.e., the interlayer spacing d002 and R2). Based on a comprehensive analysis of the nonstructural evolution of coal, the graphitization of coal could be divided into four stages at the nanoscale. The first stage (d002 > 0.344 nm and R2 < 0.7) is the transition process from coalification to graphitization, the second (0.337 nm < d002 ≤ 0.344 nm and R2 > 0.65) is the crystallization of carbon layers, the third stage (0.337 nm < d002 ≤ 0.344 nm and R2 ≤ 0.65) is characterized by the elimination of structural defects and straightness of carbon layers, and the fourth stage (d002 ≤ 0.337 nm and R2 ≤ 0.6) shows that the locally ordered graphite structure expanded to the whole sample.

Study on the Formation Mechanism of a Core–Shell Structure during Graphitization of Anthracite

“…In recent years, the study of synthetic graphite and its applications has become a hot topic in the research field. , A range of carbon sources with high carbon content and fewer impurities, e.g., petroleum coke, coal tar pitch, anthracite, and bituminous coal, , were taken to prepare the synthetic graphite. Specifically, anthracite is one of the favorable resources for preparing synthetic graphite owing to its lower ash content and oxygen-containing functional groups. ,− Studies regarding coal-based synthetic graphite suggested that, with a lower rising rate of temperature and a higher final temperature, the obtained synthetic graphite tends to have a higher graphitization degree and perfect crystalline structure. , More importantly, the thermodynamics and kinetics of chemical reactions during the graphitization process of anthracite were investigated .…”

“…6−8 Furthermore, graphite is an important precursor for the preparation of graphene, which is a new material with epochmaking significance. 9,10 However, the continuous increase in graphite consumption leads to a growing shortage of its natural resource, and the supply-demand mismatch will be a future challenge. 1 Hence, finding an efficient method to prepare synthetic graphite is in great demand and could potentially make up for the shortage of natural graphite resources in the long run.…”

“…In recent years, the study of synthetic graphite and its applications has become a hot topic in the research field. 11 , 12 A range of carbon sources with high carbon content and fewer impurities, e.g., petroleum coke, 13 coal tar pitch, 14 anthracite, 15 and bituminous coal, 12 , 16 were taken to prepare the synthetic graphite. Specifically, anthracite is one of the favorable resources for preparing synthetic graphite owing to its lower ash content and oxygen-containing functional groups.…”