The Fabrication Of Carbon Nanofibers And The Study On Its Dispersion Morphology

Electrospinning is a novel method to produce nanofibers. It is a process by which polymer fibers (with diameter lower than 100nm and lengths up to kilometers) can be produced using static electricity of high-voltage which compel polymer solution (or polymer melt) to jet.The diameter of fibers produced by conventional spinning technology (wet spinning,dry spinning, melt spinning, gel spinning etc.) is from several to several hundred microns, however, the diameter of efectrospinning fibers can be less than 100 nm. Because of its small diameter, the fiber has large specific surface area. It can be used as filtration and film materials. Furthermore it has many potential applications in biomaterials and composite materials.The work in this paper included:First, in order to learn electrospinning process comprehensively, poly(ethylene oxide)(PEO)/water solutions were electrospun under different technological parameters to prepare nanofiber. Dispersion morphology of electrospun fibers was characterized by scanning electron microscopy(SEM). Crystallization property of electrospun fibers was characterized by differential scanning calorimetry(DSC) and X-ray diffraction(XRD). Dispersing morphology of electrospun fibers was affected by the solution concentration, the voltage and the distance between two electrodes. In all parameters, the concentration and voltage were the key factors. When the concentration was reduced, the voltage was increased and the distance between two electrodes was boosted, electrospinning fibers gradually became fine. Compared with PEO powder, electrospinning fibers crystallinity declined, and the possible mechanism was analysed theoretically.Second, synthetical A-stage resol and PVA solution at different mass ratio were electrospun into fibers. After solidified at 150℃ for an hour, phenol formaldehyde (PF) fibers were obtained. When the PF fibers(mass ratio of PF and PVA were 1:2) were calcined at different temperature, the fibers sized less than 200 nm in diameters based on PF were obtained. By field emission scanning electron microscopy(FESEM), the diameter and morphology of the fibers were observed and compared. The infrared(IR) spectra showed that the fibers calcined at 600℃ werecarbon fibers and it was found that morphology of the fibers were the best.Third, the fiber of polyacrylonitrile(PAN) were fabricated by means of electrospinning.With the help of FESEM, the morphology of PAN fiber were investigated. The influence of electrospinning parameters on diameter and morphology of fiber ware discussed. It was found that the diameter of the fiber increased with the increasing of solution concentration and decreasing of electrospinning voltage, and other factors have few influences on fiber diameter. The best fibers were calcined at 240 °C in air and then calcined in nitrogen at higher temperatures. The transformation of fiber diameter and morphology was observed by means of FESEM. The chemical structure of the fibers was analyzed by IR, and it was conformed that the fiber calcined at 900 °C were carbon fiber.