Sub-micron carbon fibres prepared from electrospun precursors

Electrospinning is a method that can be use to prepare polymeric or composite fibres having diameters typically sub-micron range. In electrospinning electrostatic field stretches the polymer solution into interconnected nanofiber web. Electrospun fibres can be prepared from wide variety of polymers. Metal containing nanofibres, for example, can be pyrolysed to ceramic nanofibres, and organic nanofibres graphitized to carbon nanofibres. Electrospun fibres can be utilized in many applications, such as filtration, reinforcement, filtration, tissue engineering, sensors, fuel cells and nanoelectronics. Carbon nanotubes (CNTs) are widely used as filler in electrospun fibres as reinforcement component in electrospun polymeric fibres, but they are also used in order to modify electrical properties of fibres. In this work electrospinning method was used for production of sub-micron sized precursor fibres for carbon fibre production. Fibres were prepared using from neat polymeric polyacrylontirile (PAN) solution as well as PAN solutions containing CNTs. Obtained fibrous web had fibre diameters on sub-micron range. Increment of CNTs into fibres changed their appearance as well as their tensile properties. Appearance of PAN and PAN/CNT fibres is presented in figure 1 a) and b), respectively. Force-strain curve illustrates the chance in tensile properties. Elongation of the polymeric fibre is higher, while composite fibres often had higher modulus. These fibrous webs were stabilized in temperatures around 300 °C and carbonization was conducted typically in temperatures above 1000 °C. Heat treatments were conducted as continuous processes. FTIR analysis showed that nitrile bonds were disappeared from the structure and new peaks related to the stabile structure were emerged during stabilization. Fibre diameters as well as web dimensions were reduced in both heat treatments. Tensile properties were also affected.