Uniform and aligned nanofibers have been obtained by eletrospinning. Activated carbon nanofibers (ACNFs) have been used as electrode materials for battery and electric double layer due to its porous properties. A high value of surface area can be attained (1000 - 3000 nm) by activation, due to the presence of micropores on the surface of nanofibers. A series of nanofibers have been prepared using different polymer precursors and concentrations by electrospinning in this study. Morphological study by SEM reveals a uniform and aligned fibrous structure for the PAN-based CNF (11 wt%) and a curved and twisted fibrous structure for the PAN-based CNF (8 wt%) and the acrylic-based CNF (9 wt%). Thus, the microstructure of CNF can be greatly influenced by the concentration of polymer precursor; high quality of nanofibers can be produced with higher polymer concentration and higher viscosity. The diameter of PAN-based nanofibers is gradually decreased from 400 to 200 nm during stabilization, carbonization, and activation, due mainly to the degradation and condensation. Surface of CNF becomes rough after activation due to the etching by potassium ions at high temperatures. Microstructural study by X-ray diffraction and Raman spectroscopy indicates a discernible diffraction peak at d002 = 0.356 nm and the ratio ID/IG = 1.83 of ACNFs, showing an amorphous and disordered structure, and leading to a low conductivity. Adsorption/desorption isotherms obtained from BET measurements under nitrogen atmosphere suggests a relatively small surface area of 8-10 m2/g, indicating that there might be no adsorption on the porous ACNF or the porous structure has been destroyed after carbonization. This leads to a relatively low conductance of 17 Faraday/g measured from the cyclic voltammetry.

In this study, we developed the manufacturing pathways of carbon nanofibers (CNF) and activated carbon nanofibers (ACNF) via the ¡§melt-spinning¡¨ method. A novel route based on the solvent-free core/sheath melt-spinning of polypropylene/ (phenol formaldehyde-polyethylene) (PP/(PF-PE)) to prepare CNF. The approach consists of three main steps: co-extrusion of PP (core) and a polymer blend of PF and PE (sheath), followed by melt-spinning, to form the core/sheath fibers; stabilization of core/sheath fibers to form the carbon fiber precursors; and carbonization of carbon fiber precursors to form the final CNF. Both scanning electron microscopy and transmission electron microscopy images reveal long and winding CNF with diameter 100 - 600 nm and length greater than 80 £gm. With a yield of ~ 45 % based on its raw material PF, the CNF exhibits regularly oriented bundles which curl up to become rolls of wavy long fibers with clean and smooth surface. Results from X-ray diffractometry, energy dispersive X-ray, Raman spectroscopy, and selected area electron diffraction patterns further reveal that the CNF exhibits a mixed phase of carbon with graphitic particles embedded homogeneously in an amorphous carbon matrix. The carbon atoms in CNF are evenly distributed in a matrix having a composition of 90 % carbon element and 10 % in oxygen element. A series of ACNF have also been prepared based on the chemical activation on the thus-prepared CNF; their morphological and microstructure characteristics were analyzed by scanning electron microscopy, atomic force microscopy (AFM), Raman spectroscopy, and X-ray diffractometry, with particular emphasis on the qualitative and quantitative AFM analysis. The effect of activating agent, potassium hydroxide and phosphorous acid, is compared; factors affecting the surface morphology and microstructure of ACNF are analyzed. The ACNF also exhibits a mixed phase of carbon with graphitic particles embedded homogeneously in an amorphous carbon matrix. The resulting ACNF consists of 73 % C element and 27 % O element. The total pore volume of the all activated ACNF is larger than that of un-activated CNF. It can be inferred that chemical activation by KOH results in increased micropore volume in carbon nanofibers; while the micropores produced by the chemical activation of H3PO4 may further be activated and then enlarged to become the mesopores at the expense of micropore volume. For the concentration effect of KOH on ACNF, it can be inferred that high concentration KOH activation results in increased SBET and micropore volume in carbon nanofibers. The average pore diameter of ACNF gradually decreases as the KOH concentration increases.