The Preparation And Performance Characterization Of Ordered Pan Hollow Micro/Nano Fibers

Electrospinning technology, with its low cost, simple device, controllable process conditions etc., has become one of the main methods which can fabricate continuous micro/nano fibers. Due to the unstable whip move of the jet, the electrospun fibers usually arrange disorderly into mats on flat collecting device, which makes them with low mechanical property, optical property, and so on. In this paper, ordered PAN hollow micro/nano fibers were prepared via Wire Drum Collector, and the performance of the fibers was studied.Firstly, the technological parameters were studied to prepare the ordered PAN hollow fibers. The continuous micro/nano fibers could be fabricated with smooth surface when the concentration of PAN solution was15%, spinning voltage was15kv, and receiving distance was20cm. Using multiple electrospinning technology, the hollow fibers with different hole diameter were prepared through adjusting the How rate of inner solution. When the flow rate was0.08ml/h (single hole) or0.06ml/h (two holes), the PAN hollow fibers were produced with average diameter being914nm and hole diameter being382nm (single hole fibers), or with average diameter being997nm, hole diameter being266nm (two holes fibers). Moreover, controlling the speed of the roller was2.0m/s, the fibers with best arrangement were fabricated. The fibers strength increased firstly and then decreased, and elongation at break decreased and then increased along with the roller speed increase, and both reached to the extreme at2.0m/s.In this paper, the influence of additives (MWCNTs and ZnCl2) was researched on the order degree, diameters, the crystallization and mechanical properties of composite fibers. The ordered fibers could be obtained when additives were added and it would affect the stability of the spinning if the content of the additives was in excess. The influence of different additives on the structure and properties of fibers was different. The crystallinity of PAN/MWCNTs fibers increased to27.6%when adding1.0%MWCNTs. With the content of MWCNTs increasing, the diameters of PAN/MWCNTs fibers increased, the strength increased firstly and then decreased, and elongation at break decreased; the crystallinity of PAN/ZnCl2fibers decreased to23.5%when adding10%ZnCl2. With the content of ZnCl2increasing, the diameters of PAN/MWCNTs fibers increased firstly and then decreased, the strength and elongation at break decreased; for PAN/MWCNTs/ZnCl2fibers, the strength and elongation at break decreased with the content of ZnCl2increasing when fixing the content of MWCNTs.Finally, the electrochemical property of porous PAN based carbon fibers was discussed in the paper. Though pre-oxidation, carbonization and acidification process, the ordered porous PAN/MWCNTs carbon fibers with two holes in the cross section were produced ultimately. The surface morphology was characterized using the field emission scanning electron microscopy (FESEM). The specific surface areas increased when additives were added, which adding MWCNTs could increase the surface roughness of the fibers and adding ZnCl2could increase the porous structure of fibers after acidification. The specific surface area of porous PAN/MWCNTs carbon fibers (two holes) reached to356.8cm2/g, which was three times as much as the PAN carbon fibers. According to the Cyclic voltammetry (CV) curve, compared with PAN carbon fibers, the porous PAN/MWCNTs carbon fibers (two holes) had great integral area of discharge, and showed capacitance properties in wide voltage range. The specific capacitance of the porous PAN/MWCNTs carbon fibers (two holes) was247.3F/g at the scanning speed of5mv/s, which demonstrates the electrospun fibers for use as electrode material have great potential applications in super capacitor.