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

Graphite is a revolutionary material, and the development of synthetic graphite could potentially solve the shortage of natural graphite in the future. In this paper, the formation of core-shell-structured synthetic graphite prepared from an anthracite-FeO mixture was systematically investigated by a two-step method. First, heat treatment was performed on a layer of almandine (3FeO·AlO·3SiO) particles to obtain a large quantity of uniform-sized glass-phase spheroids. Second, the deashed anthracite was graphitized on the surface of the obtained spheroids to prepare core-shell-structured graphite. Furthermore, the obtained graphite products were systematically characterized by XRD, Raman spectroscopy, SEM-EDS, and TEM. Finally, a model was proposed to illustrate the formation mechanism of the core-shell structure during graphitization of the anthracite-almandine mixture. Under lower temperatures, almandine started to melt into spheroids. Under higher temperatures, the volatile components in the anthracite turned into the gas phase, and the carbon matrix started to bend on the surface of the core material and deposit layer by layer, thus forming the core-shell-structured graphite. The findings could provide theoretical guidance for the synthetic graphite industry and have meaningful implications for the coal chemistry field.