| 摘要 |
PROBLEM TO BE SOLVED: To provide expansive graphite grains having less residual sulfuric acid group (sulfuric acid ions) and giving no adverse effect on the hardening of a resin used concurrently or for the corrosion of a molding die even when it is used as a molding material, provide a manufacturing method, provide a fuel cell separator securing excellent gas nonpermeability, mechanical strength, electric characteristics and lightness and having no possibility of hardening the resin or corroding the molding die, provide its manufacturing method, and provide a high-performance fuel cell using the separator. SOLUTION: The concentration of sulfuric acid ions (SO42-) in expansive graphite grains is set to 500 ppm or below. For the manufacturing method, expansive graphite powder is compressed, molded and pulverized into expansive graphite grains, and the expansive graphite grains are washed with water and dried, or the expansive graphite powder is compressed and molded, then it is heat-treated at 350 deg.C or above, and it is cooled and pulverized, or the expansive graphite powder is compressed, molded and pulverized into expansive graphite grains, then the graphite grains are heat-treated at 350 deg.C or above. |
