The Structure And Properties Of PAN Nanofibers Facribated By Electrospinning

The definition of nanomaterial is that at least one of three dimension of the material is in nano-scale. With the development of science and technology. The interests of researchers is more and more focus on one dimension material, nanofiber. The method of producing nanofiber contains static electricity spinning, island form reunites spinning, catalyst extrudes, member sprays etc. The electrospinning is a direct method to continuously prepare the polymeric nanofibers and to be further developed for mass production of one-by-one nanofibers.In our work, Based on the development of collecting setup, PAN naonofibers were obtained by collecting on a rotating take-up wheel. and the naonofibers were hot stretched at 135℃for 5 minute. Then it was oxidative stabilization under tention and carbonized by fixing the two endso。The effect to the nanofibers was investigated by adjusting the main process parameters including solution concentration(8wt%～14wt%),electrostatic voltage( 10～15Kv),surface velocity(6．28 m/s～14．65m/s.) of a take-up wheel rotating collection. Based on the experiment result.The optimized process parameters was: solution concentration(10wt%),electrostatic voltage(10Kv),surface velocity( 10．47 m/s). And the average diameters of nanofibers were 250nm.PAN/MWNT nanofibers were made by electrospinning. SEM and TEM observation indicated that the MWNTs were parallel and oriented along the axes of the nanofibers. With the increase of the MWNT content. The nanofibers became rougher and the diameter distribution got non-uniform because of the variety in MWNT shapes. The tensile properties of PAN Nanofibers were promoted by the addition of MWNT filler. However, as the MWNT content is 10%, the tensile strength of composite nanofibers dramatically decreased. DSC and TG results showed that the addition of MWNT accelerated the thermal decomposition and cryclization of PAN-based nanofibers. and it was of benefit to the oxidation and carbonization.The nanofibers were hot-stretched to improve the mechanical properties.After hot-stretching, the average diameter of nanofibers was decreased from 250nm to 220nm. The crystallinity was increased from 7．92% to 31．76%.the Orientation coefficient was increased from 45．57% to 55．41%. the strain at break was increased from 85±18MPa to 210±23MPa.Preoxidation is key process of making carbon nanofibers.With the increasing of temperature. the color of the nanofibers was conversed from white to gold,brown,black. The IR characteristic (2243cm) peak and XRD characteristic (17．100°) peak of PAN gradually decreased. and new characteristic peak ((IR 1591cm),(XRD25．212°)) appeared. It indicated that the structure of pan began to become ladder structure from line structure by the chemical reactions associated with oxidation, dehydrogenation and crylization。At last the Preoxidation naonofibers were carbonized at 1000℃.The average diameter of the typical carbon nanofibers was 140 nanometers. And the surface of nanofibers was smooth. The the strain at break of the ultimate carbon nanofibers was up to a maximum of 2243 +230 MPa and 170±15．8GPa.