A simple and nonconventional electrospinning technique was employed for producing aligned polyacrylonitrile (PAN) nanofibers. A thermal zone was placed between syringe needles and collector in the electrospinning set up to obtain aligned and heat treated nanofibers. Suitable temperatures for heat treat process of PAN nanofibers was determined using differential scanning spectroscopy (DSC) technique. The influence of treatment temperature was investigated on morphology, internal structure and mechanical properties of collected PAN nanofibers. The average fiber diameter measured from SEM images exhibited decreasing trend at higher temperatures. FTIR spectra indicated no considerable difference between chemical structure of untreated and treated PAN nanofibers. Crystallization degree of PAN nanofibers calculated from WAXD patterns showed relatively low change with treatment temperature. Tenacity values of nanofiber bundles increased with increasing temperature while the extension values had an inverse trend. However, the modulus did not show a regular manner, but treated nanofibers had more modulus than untreated ones. The stress and modulus of PAN nanofibers increased to 112.9 MPa and 7.25 GPa at 270 degrees C, respectively. Nanofibers treated at the highest temperature had the largest amount of crystallinity and strength. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012