Preparation And Application Of Carbon Nanofiber Composite Materials Based On Polyacrylonitrile

Electrospinning is a facile and versatile technology to produce fibers,whose diameter can vary from a few tens of nanometers to several microns.Carbon nanofibers originating from electrospun polymer nanofibers have advantages of large specific surface area,high electrical conductivity and extremely high length-diameter ratio.Therefore,the fabrication of carbon nanofiber and its composite is high of importance in theory study and practical application.In this thesis,we focus on the preparation of carbon nanofiber and its composites and their application in the fields of superamphiphobicity,electromagnetic shielding and supercapacitors.The detailed research work was divided into three parts,which are shown as follows:?1?Polyacrylonitrile?PAN?composite fibers containing different amount of Mn precursors were prepared by electrospinning.And then,pre-oxidation and carbonization of the as-prepared PAN nanofiber composite were carried out to obtain the resultant flexible carbon nanofibers.Finally,the as-obtained carbon nanofiber composite became super-amphiphobic after fluorination modification,and the influence of the concentration of POTS and the fluorinated time on the super-amphiphobicity of the composite mat were investigated in detail.The nanofibers and their composites were characterized by scanning electron microscopy,transmission electron microscopy,Raman spectrum and X-ray photoelectron spectroscopy.The results show that the addition of manganese acetylacetonate was finally transformed to MnO₂,which can significantly increase the surface roughness of the carbon fiber and also endow the carbon nanofiber composite flexibility.According to the mapping analysis,Mn was evenly distributed on the fibers surface and inside the fibers.The prepared manganese-doped carbon nanofiber membrane showed superamphiphobicity after surface treatment of the fluorine-containing molecules.The water contact angle was about 155°,which could be maintained at different pH;the contact angles for different oils were around 152°.?2?Polyacrylonitrile nanocomposite fibers with different amount of Ni precursors were prepared by electrospinning.Carbon nanofibers containing Ni nanoparticles were finally obtained by pre-oxidation and subsequent carbonization of as prepared PAN composite fibers.The resultant flexible carbon nanofiber composite membrane was used for electromagnetic interference shielding.The morphology and microstructure of the nanofiber materials were characterized by Scanning electron microscopy,transmission electron microscopy and Raman spectrum.The results show that the introduction of nickel Ni nanoparticles could effectively improve the flexibility of the carbon nanofiber membrane.It was found that the Ni nanoparticles were uniformly distributed on both the nanofiber surface and inside the nanofibers,based on the element mapping measurement.The X-ray diffraction pattern shows that the Ni existed mainly in the form of nickel substance.The result of electromagnetic shielding test shows that the nickel nanoparticle decorated carbon nanofiber membrane possessed an excellent electromagnetic interference shielding performance with a maximum shielding effect of nearly 30 dB.Furthermore,the carbon nanofiber composite mat could gain superior superamphiphobicity after surface fluorination,and the shielding effect could still maintain around 25 dB.?3?Polyacrylonitrile nanocomposite fibers with different ratios of Ni were prepared by electrospinning.Pre-oxidation and carbonization of the electrospun polyacrylonitrile nanofiber composite were carried out to obtain the resultant flexible carbon nanofiber mat.And then,the as-obtained flexible carbon fibers were used as electrode material of supercapacitor.Through X-ray photoelectron spectroscopy analysis,which shows that the carbon fiber mainly possessed the elements of carbon,nitrogen,oxygen and nickel.In addition,the Ni element on the fiber surface also existed with the form of NiO.The electrochemical tests show that the carbon fiber doped with heteroatom had a specific capacitance of 202.7 F g^-1 at a current density of 1A g^-1 in a 3 M KOH electrolyte,because of the specific property of the nanofiber surface.