Slow defluorination of graphite fluoride fibers during nitrogen heating produces both graphitized carbon fibers having high defect density and a yellow film which may contain fullerenerelated materials. The carbon fibers thus obtained can pick up some copper and form aluminum composite during direct molten metal exposure. Explosion of graphite fluoride fibers during quick nitrogen heating produced amorphous carbon containing very little fluorine. They cannot be wetted by copper, but pick up some aluminum during direct molten metal exposure. By either spreading the graphite fluoride fibers apart or adding a small amount of bromoform into the graphite fluoride fibers before the quick nitrogen heating, the possibility of explosion can be reduced.