Rheological Properties of PAN/DMF Spinning Solutions and Physical Properties of Conducting Carbon Nanofibers Prepared by Electrospinning and Carbonization

Abstract

Dynamic rheological properties of polyacrylonitrile (PAN)/dimethylformamide (DMF) solutions were measured at several different temperatures (25−55℃), and their electrospinning was conducted at corresponding temperatures to prepare PAN precursor fibers. The electrospun fibers were subsequently converted to carbon nanofibers through a carbonization process and their physical properties such as electrical conductivity, morphology and crystal structure were examined with regard to the electrospinning temperature. The dynamic viscosity of PAN/DMF solutions decreased with increasing temperature, exhibiting a lower Newtonian flow region followed by shear thinning. In the Cole-Cole plot, the initial slope decreased with decreasing temperature but a single master curve of constant slope above the inflection point was observed regardless of the temperature. FESEM images showed that the diameter of the PAN precursor fibers and resulting carbon nanofibers decreased as the electrospinning temperature increased. The diffraction peak of carbon nanofiber in the WAXD pattern was shifted from 22 to 24o. Further, Raman spectroscopy showed that the graphitic carbon peak at 1600 cm-1 increased with increasing electrospinning temperature. In addition, the electrical conductivity of the carbon nanofiber increased considerably from 2.95 to 6.15 S/cm with increasing electrospinning temperature from 25 to 55℃.