The influence of an applied magnetic field on the formation of carbon materials from coal tar pitch is investigated. Under an applied magnetic field, crystallites in a mesophase resembling liquid crystals are magnetically oriented during the carbonization process. Compared with that under a nonmagnetic field, carbonized coal tar pitch under a strong magnetic field of 10 T, generated by a superconducting magnet, has a highly oriented structure of carbon crystallites. The orientation of samples prepared under 2 T, which can easily be supplied by an electromagnet, was insufficient. Activation by potassium hydroxide is effective for affording a precursor for activated carbon. The activated carbon obtained under a strong magnetic field has a unique adsorption ability, which arises from its increase in relative surface area and total pore volume compared with those of an activated carbon sample prepared from a precursor produced under zero magnetic field. The precursor carbonized under a magnetic field of 10 T contains a larger number of crystallites than that carbonized under a 0-T magnetic field, which leads to high-performance activated carbon.

Coal tar pitch was treated at 773 K in a constructed furnace system used under a magnetic flux density (B) of up to 10 T. The (002) X-ray diffraction peak intensity of the treated pitches increased with increasing B to approach a saturation value over 6 T. The magnetic-field dependence of the intensity was fitted by the order parameter calculated by assuming the cooperative orientation of several thousand carbon crystallites. This suggests that the hexagonal carbon layers should be oriented in parallel to the magnetic fields.