Effect of fiber splitting on the catalytic graphitization of electroless Ni–B-coated polyacrylonitrile-based carbon fibers

The catalytic graphitization of split polyacrylonitrile (PAN) -based carbon fibers in the presence of Ni–B is investigated. The carbon fibers are split by electrochemically oxidization of carbon fibers in a 0.1 M H2SO4 electrolyte solution and a following fast heat treatment at 900 °C for 30 s, with formation of cracks and fissures on the fibers, which thereby increases the fiber surface area favoring the following chemical deposition of Ni–B. Both the splitting treatment and the Ni–B catalyst can accelerate the graphitization of PAN-based carbon fibers; 86.7% graphitization degree with a d002 of 0.3362 nm is achieved at a heat treatment temperature of 2400 °C.