Graphite can be classified into natural graphite from mines and artificial graphite. Due to its outstanding properties such as light weight, thermal resistance, electrical conductivity, thermal conductivity, chemical stability, and high-temperature strength, artificial graphite is used across various industries in powder form and bulk form. Artificial graphite of powder form is usually used as anode materials for secondary cells, while artificial graphite of bulk form is used in steelmaking electrode bars, nuclear reactor moderators, silicon ingots for semiconductors, and manufacturing equipment. This study defines artificial graphite as bulk graphite, and provides an overview of bulk graphite manufacturing, including isotropic and anisotropic materials, molding methods, and heat treatment.

Isotropic synthetic graphite scrap and phenolic resin were mixed, and the mixed powder was formed at 300 MPa to produce a green body. New bulk graphite was produced by carbonizing the green body at 700°C, and the bulk graphite thus produced was impregnated with resin and re-carbonized at 700°C. The bulk density of the bulk graphite was 1.29 g/cm 3 , and the porosity of the open pores was 29.8%. After one impregnation, the density increased to 1.44 g/cm 3 while the porosity decreased to 25.2%. Differences in the pore distribution before and after impregnation were easily confirmed by observing the microstructure. In addition, by using an X-ray diffractometer, the degrees-of-alignment (Da) were obtained for one side perpendicular to the direction of compression molding of the bulk graphite (the "top-face"), and one side parallel to the direction of compression molding (the "side-face"). The anisotropy ratio calculated from the Da-values obtained was 1.13, which indicates comparatively good isotropy.

When manufacturing bulk graphite, pores develop within the bulk during the carbonization process due to the volatile components of the fillers and the binders. As a result, the physical properties of bulk graphite are inferior to the theoretical values. Impregnants are impregnated into the pores generated in the carbonization process through pressurization and/or depressurization. The physical properties of bulk graphite that has undergone impregnation and re-carbonization processes are outstanding. In the present study, a green body was manufactured by molding with natural graphite flakes and phenolic resin at 45 MPa. Bulk graphite was manufactured by carbonizing the green body at 700 and it was subsequently impregnated with impregnants having viscosity of 25.0 cP, 10.3 cP, and 5.1 cP, and the samples were re-carbonized at 700°C. The above process was repeated three times. The open porosity of bulk graphite after the final process was 22.25%, 19.86%, and 18.58% in the cases of using the impregnant with viscosity of 25.0 cP, 10.3 cP, and 5.1 cP, respectively.

The development of hollow carbon balls by CO 2 oxidation of two types of carbon blacks was studied. Super P (SP) and Denka Black (DB) were used for this study. Specific surface area (SSA), structural parameters, and microstructures were examined using Brunauer, Emmett and Teller apparatus, X-ray diffraction spectroscopy, and transmission electron microscope (TEM), respectively. The SSAs of both oxidized carbon blacks increased after oxidation. The SSAs of raw DB and SP were 73 m /g) after 3 h oxidation compared with the original carbon blacks. Through TEM observation the outer parts of the oxidized carbon blacks showed a rigid shell structure and the inner parts looked empty. Generally it looked like an angular soccer ball, so we named it 'hollow carbon ball.' It is expected that the hollow carbon ball can be used as catalyst supports.

This study investigated a developed process for producing a composite bipolar plate having excellent conductivity by using coal tar pitch and phenol resin as binders. We used a pressing method to prepare a compact of graphite powder mixed with binders. Resistivity of the impregnated compact was observed as heat treatment temperature was increased. It was observed that pore sizes of the GCTP samples increased as the heat treatment temperature increased. There was not a great difference between the flexural strengths of GCTP-IM and CPR-IM as the heat treatment temperature was increased. The resistivity of GPR700-IM, heat treated at 700°C using phenolic resin as a binder, was 4829 µΩ·cm which was best value in this study. In addition, it is expected that with the appropriate selection of carbon powder and further optimization of process we can produce a composite bipolar plate which has excellent properties.