an improved process for producing carbon fibers from pitch which has been transformed , in part , to a liquid crystal or so - called &# 34 ; mesophase &# 34 ; state . according to the process , pitch of a given mesophase content , suitable for producing carbon fibers , is produced in substantially shorter periods of time than heretofore possible , at a given temperature , by passing an inert gas through the pitch during formation of the mesophase .