Morphological Change of Mesophase Pitch-based Carbon Fiber by Air Oxidation at High Temperature

Abstract

Morphological change by air oxidation at high temperature was investigated for some kinds of mesophase pitch-based carbon fibers with different microstructures and different graphitization degrees and was compared with that of PAN-based carbon fiber. By oxidation striations and pits appeared on the fiber surface and the surface appearance of the oxidized fibers suggested that oxidation behaviour was affected strongly by microstructure of the fiber. That is, the region where edges of carbon basal planes concentrated on the surface was preferentially oxidized. Pits generally formed in array along striation parallel to the fiber axis. Morphology of the pit was a little different between the fiber with radial structure and the one with onion structure. V shape crack observed for some of the fiber with radial structure changed to larger U shape crevasse by oxidation. The oxidation temperature at which morphological change appeared shifted to higher temperature for the fiber with higher graphitization degree. While, pits formed irregularly and diameter of the fiber decreased gradually by oxidation in the case of PAN-based carbon fiber.