Optimization of stabilization conditions for electrospun polyacrylonitrile nanofibers

Polyacrylonitrile (PAN) precursor nanofibers with average diameter of 400 nm were synthesized by electrospinning. They were stabilized at 250-280 degrees C for 1-3 h, followed by carbonization at 1000 degrees C to fabricate CNFs with a diameter of 200 nm. The morphology, thermal properties, and chemical structure of the precursor nanofibers, the stabilized fibers and the final CNFs, were characterized by SEM, TEM, DSC, TG, XRD and XPS. It was found that the optimum stabilization conditions involved thermally treating them from 30 to 280 degrees C at a heating rate of 2 degrees C/min under a constant load of 1 kN, and keeping them at 280 degrees C for 2 h. Under these conditions, dehydrogenation and intra-cyclization reactions were almost completed; the PAN crystal structure was almost completely destroyed, and a thermally-stable ladder-like polymeric structure was formed. Nanofibers carbonized at 1000 degrees C were electrically conductive, and the conductivity was highly dependent on the stabilization conditions. The best electrical conductivity of similar to 20.2 +/- 1.2 S cm(-1) was obtained under the conditions described. (C) 2012 Elsevier Ltd. All rights reserved.