Fabrication And Electrical Properties Of PAN Aligned Carbon Nanofibers

In this paper, we use polyacrylonitrile (PAN) and N, N-dimethylformamide (DMF) asprecursor to prepare PAN nanofibers by the method of electrospinning.Then through stabilizationand carbonization to prepare carbon nanofibers. And we measured the electric conductivity ofthese carbon nanofibers.We study the effect of concentration and rotating speed for the electricconductivity of carbon nanofibers membrane. Besides, we create the conductive model of carbonnanofibers membrane.Because the carbon nanofibers which based on the current processparameters are twisted seriously,in order to fabricate the carbon nanofibers membrane that havegood formability and excellent electrical properties, we study the process parameters ofstabilization and carbonization through a variety of tests.Finally, we pick out the best processparameters of stabilization and carbonization. These work will provide experimental basis forfabricate good formability, excellent electrical properties of carbon nanofibers materials in thefuture.We used flat collector to prepared different concentrations of PAN nanofibersmembrane.The concentrations of the mixed solutions are8%,10%,12%and14%. Theelectrospinning parameters:high voltage power supply:12kv,the distance of the spinnerets and thereceiving plate is12cm,spinning rate:0.01ml/min. Stabilization process parameters is270℃,1h,carbonization process parameters is800℃,1h. Through the texts of FE-SEM, XRD, four pointprobes and others to character non-aligned carbon nanofibers membrane. The results showed thatwith increasing of concentrations of the solution, the electrical resistivity of carbon nanofibersmembrane decreases first and then increases, when the concentration of the solution is12%, theelectrical resistivity of carbon nanofibers membrane is least. These is improved that in a certainrange, increase the concentration of the solution can improve the electrical properties ofnon-aligned carbon nanofibers membrane.We used rotating drum to prepared aligned carbon nanofibers. The rotating speeds of thedrum are800rpm,1000rpm,1500rpm,2000rpm and2500rpm. The concentration of the solutionis10%, and the spinning parameters are not changed, the stabilization and carbonization processparameters remains:270℃,1h,800℃,1h. Using FE-SEM, TEM, XRD, four point probes to text and analysis different rotating speeds of ailgned carbon nanofibers, and according to theelectrical properties of the carbon nanofibers membrane,we established the conductive models.Itcan be concluded:(1) when the rotating speed reaches2500rpm, the aligned carbon nanofibersform a significant internal lattice structure. So it can be said that rotating speed can improve thecrystallinity of aligned carbon nanofibers.(2) in a certain range, increase the rotating speed canimprove the electrical conductivity of aligned carbon nanofibers, but when the rotating speed outof range,it will reduce the electrical conductive of aligned carbon nanofibers.(3) the alignedcarbon nanofibers membrane that in the orientation direction have better electrical conductivitythan which perpendicular to the orientation direction.(4) the electrical conductivity of alignedcarbon nanofibers membrane are greater than non-aligned carbon nanofibers membrane.By the method of orthogonal test to study the process parameters of stabilization.We usedstabilization temperature, stabilization time, and stabilization heating rate as orthogonal factors.By the texts of FE-SEM, FT-IR, XRD, and uniaxially stretched to text and analysis the alignedstabilization nanofibers at different stabilization conditions. Finally we get the best stabilizationconditions:230℃,1h. Then, on the basis of the best stabilization conditions, we study thecarbonization temperature in the carbonization process.The aligned carbon nanofibers membranewere prepared by the carbonization temperature of800℃,1000℃,1200℃and1400℃. By thetexts of FE-SEM, TEM, and four point probe to text and analysis the morphology, internalstructure and electrical properties of carbon nanofibers membrane which at differentcarbonization temperature. It can be drawn: When the carbonization temperature is1000℃, thealigned carbon nanofibers membrane not only have good morphology, but also have excellentelectrical properties.