Nanofiber yarns are introduced in this work, formed by PAN nanofibers electrospun from the dimethylformamide (DMF) solution via a novel process we recently developed. The fiber properties comparison at selected electrospinning parameters and different polymer concentrations are made in order to determine the influences of such parameters on the morphology and the cross-sectional shape of the nanofibers. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM), along with image processing technique are then conducted to investigate the profiles of these PAN nanofibers, in challenging the common conception of a circular cross-section for such fibers. Our results suggest that is nanofibers are in general with irregularity along the fiber longitudinal axis, it is overly simplistic to use diameter alone in describing the nanofiber thickness. So the cross-sectional shape and area are more desirable.
Keywords: Cross-sectional shape, electrospinning, polyacrylonitrile nanofiber, concentration, voltage, take up speed, Morphological investigation, twist, tip, diameter, orientation, TEM micrograph, cross-sectional area, oval shape
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