Preparation And Properties Of Composite Materials Of Carbon Fibers Based On Electrospinning Of Polyacrylonitrile

Carbon fibers with diameters in nano-scale could be obtained from ultrafine fibers of polyacrylonitrile (PAN) by electrospinning and followed heat treatment. Chemical vapor deposition (CVD) is a widely used method to produce carbon nanotubes (CNTs) due to the advantage of simple operation, low cost, controllable parameters and etc. Some transition metals and their oxides with the advantage of high specific capacitance are ideal electrode materials for supercapacitors. Application of carbon fibers can be improved in lithium ion batteries and supercapacitors through compounding with CNTs or transition metals.In this dissertation, PAN fiber mats were prepared using electrospinning method and then stabilization and carbonization were preformed researching the effect of different stabilization temperature and time on structure change of PAN. The optimal stabilization conditions at 300?C for 1.5h and carbonization at 1000?C for 0.5h were obtained according to characterization results of Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray diffraction (XRD).CNTs were grown on carbon fibers using the CVD method and the effect of different conditions on the growth of CNTs was studied. It was found that CNTs could be grown on the carbon fibers uniformly and continuously when the concentration of catalyst was 0.025g/mL, the growth temperature was 850?C and growth time was 40min. Thermogravimetry results showed that the content of CNTs in carbon fibers/CNTs composites was 7.41wt%. Cycle voltammetry (CV) results showed that the specific capacitance (SC) of carbon fibers was 0.034F/g, while the SC of CNTs was 1.22F/g without considering the contribution of cabon fibers matrix to capacitance which was 40 times higher than that of carbon fibers matrix. Carbon fibers/CNTs were used as anode materials in lithium ion batteries and the charge/discharge performance was tested. The results showed that when discharge rate was 20mA/g, the first-cycle discharge capacity was 580mAh/g and the second-cycle discharge capacity was 300mAh/g, after that the discharge capacity maintained at a relatively stable level.Sn nanoparticles embedded and surface adsorption carbon fibers matrix composite materials were prepared through co-electrospinning PAN/dibutyltion dilaurate (DBTDL) and DBTDL adsorbed onto the surface of carbon fibers, respectively, and their electrochemical properties were tested after heating treatment. The addition of Sn had no effect of electrochemical properties on Sn nanoparticle embedded carbon fibers composite materials because there was no contact between Sn nanoparticle and electrolyte. But Sn nanoparticle surface adsorption carbon fibers composite materials had very high SC value and cycle stability. According to the CV curves, when the sweep rate was 20mV/s, SC of carbon fibers/Sn was 777 times higher than carbon fibers matrix, reaching 69.96F/g.