Reducing thermal treatment energy during carbonization in graphite preparation by optimizing magnetic orientation

Abstract

The production of graphite often requires temperatures as high as 3000 K and is, therefore, energy-intensive. Reducing this energy demand while maintaining material quality is essential for sustainable graphite production. Previously, we reported that energy consumption was previously reduced by ∼10% by applying a magnetic field to a part of the graphite preparation process. In this process, carbon crystallites—the building blocks of the graphite precursors—were effectively oriented during the initial stage, which enhanced crystallite interconnection during graphite formation above 1000 K. This behavior suggested that the amount of energy required for graphite preparation decreased. Herein, we aimed to accelerate the orientation of carbon crystallites under a magnetic field. During the carbonization of coal tar pitch, low-molecular-weight hydrocarbons (LMwHCs) melt, and the carbon crystallites aggregate into spherical domains behaving as single units. Magnetic alignment of spherical domains occurred readily in the liquid phase, and its solidification afforded a highly oriented graphite precursor. By optimizing the amounts of carbon crystallites and LMwHCs in the coal tar pitch during carbonization at 600–800 K, we increased the sphere size, thereby enhancing the orientation of carbon crystallites under the influence of a magnetic field. The increased size enhanced the magnetic torque exerted on these domains, making them more responsive to the applied magnetic field and easier to align. Carbonization upon thermal treatment at up to 1523 K achieved using the highly oriented precursor reduced the energy consumption by >25%, which illustrated the possibility of graphite preparation at even lower energies.