Effect of Existence of Carbon Fiber on Carbonization of Coal-Tar Pitch under Pressure

Abstract

Carbon fiber/coal-tar pitch composite (51wt%carbon fiber) and a coal-tar pitch were carbonized up to 650°C in argon atmosphere at300kg/cm².The carbonization under pressure was carried out in sealed gold tube, which was set in a stellite bomb.The composite and the pitch thus carbonized were re-heated under normal pressure to investigate the effect of carbon fiber on the mesophase formation at the initial stage of carbonization, coke yield and graphitization of the pitch.
The mesophase formation in the pitch matrix of the composite was delayed under pressure.At the appearance of the mesophase spheres it was found to coalesce with each other, which seemed to accelerate by the presence of carbon fiber.Under pressure and with the presence of carbon fiber the coke yield from pitch increased.The stacking of lammelar molecules was oriented concentrically around the carbon fibers, when the bulk mesophase formed at 650°C.
The composite obtained at 650°C under pressure was re-heated from 1000°C to2500°C under normal pressure, formation of crack was observed in the coke matrix and also at the boundary of coke matrix and carbon fiber.The graphitizability of the coke matrix in the composite measured from the crystallite size and the interlayer spacing showed similar behaviour as the coke obtained from the pitch alone.