as a copolymer obtained from japan exlan co was dried under vacuum at 80 u00b0 c before being used carbon nanotubes multi wall carbon nanotubes were obtained from iljin nanotech co of korea the pan powder was dissolved in dimethylformamide dmf obtained from sigma aldrich co using an impeller at 90 u00b0 c and the cnt powder was dispersed in dmf using a bath sonicator branson 3510 mt the cnt dmf dispersion was subsequently mixed with the pan solution for fiber spinning and the pan cnt composite fibers were fabricated using a dry jet wet spinning unit obtained from the bradford university research uk with a spinneret of 250 u03bcm diameter and two coagulation dmf water baths the fibers were subsequently drawn in boiling water and dried in an oven at 50 u00b0 c for 7 days the joule heating effect was induced by applying electrical current using a source meter unit keithley 2400 sourcemeter the fiber structure was measured by real time wide angle x ray equipment during joule heating process wide angle x ray diffraction waxd using cuk u03b1 u03bb 0 1542 nm was conducted with an x ray generator rigaku micromax 002 with 45 kv operating voltage and 0 65 ma current diffraction patterns were recorded by a detection system rigaku r axis iv and analyzed by areamax version 1 00 and mdi jade version 9 0 from the waxd data pan crystallinity pan crystal size and the herman 39 s orientation factors of the polymer and of.