Corrosion behavior of carbon fibers and graphitized carbon fibers in hot phosphoric acid

It became clear that carbon fibers exhibited different graghitizability even treated at the same temperature depending on their precursor,and highly graphitized carbon fibers had high corrosion resisitibility in hot phosphoric acid. Therefore, it was concluded that the corrosion resisitibility of the PAFC electrode substrate in the hot phosphoric acid can be improved by use of highly graphitizable carbon fiber as a raw material. Under a mild corrosion condition, graghitizability of the fiber surface was important for improving corrosion resisitibility. Results showed that the corrosion of the carbon fiber occurred from a part of low graphitizability of the surface, and the carbon surface layer was converted to oxidized carbon compounds. In addition, specific surface area of the carbon fibers increased by corrosion to form micropores or surface roughness showing the extent of such changes depended greatly upon the graghitizability of the carbon fiber.