Preparation And Properties Of Pitch Derived Carbon Nanofibers

Pitch has the advantages of wide source,rich aromatics and high carbonization yield as a by-product of coal/petroleum chemical industry,which is an excellent carbonaceous precursor for preparing high-performance carbon materials.Among them,pitch derived carbon nanofibers(CNFs)has become the research focus in the field of preparation and application of carbon materials due to their high conductivity,good flexibility and high specific surface area.However,the preparation of pitch derived CNFs by electrospinning has been facing great challenges due to poor solvent solubility and wide molecular weight distribution of pitch.In this thesis,pitch derived nanofibers(SNFs)were prepared by electrospinning using pitch and polyacrylonitrile(PAN)blends as precursors,and pitch derived CNFs were prepared by stabilization and carbonization process.The structure and properties of CNFs derived from isotropic pitch(IP)and mesophase pitch(MP)were compared;The electrospinning behavior of MP components and the process of stabilization and carbonization of MP components derived fibers were investigated;The effects of Lignin addition on the structure and properties of pitch derived CNFs were studied.The results showed that the excessive proportion of aliphatic components in pitch leads to the rapid occurrence of SNFs stabilization.However,the insufficient proportion will lead to the insufficient stabilization of SNFs,both of which are difficult to maintain the morphology of SNFs fibers.Among them,the toluene insoluble tetrahydrofuran soluble(TI-THFS)component of MP shows potential advantages in the preparation of CNFs with good fiber distribution and excellent properties.The conclusions are as follows:(1)MP is composed of high content of aromatic molecules and many aliphatic components,its derived SNFs show slow and enough stabilization,which effectively maintain the morphology of SNFs,exhibit high specific surface area(387 m²g^-1),and exhibit good electrical and thermal conductivity.There are too abundant aliphatic components in IP,which make the stabilization process of SNFs exothermic,and the corresponding CNFs fiber fusion is serious,resulting in poor performance.(2)Both n-hexane insoluble-toluene soluble(HI-TS)and TI-THFS have narrow molecular weight distributions and show good spinning performance.However,the wide molecular weight distribution and insolubility of tetrahydrofuran insoluble(THFI)lead to the presence of many beads or nodes on SNFs.The SNFs of HI-TS with the most aliphatic branched chains showed the fastest oxidation rate during the stabilization process,which led to the fusion of SNFs.The excessively aromatic THFI exhibits the lowest oxidation activity during the stabilization process,causing its SNFs to melt and deform severely during the subsequent carbonization process.At the same time,TI-THFS-derived CNFs have excellent fiber morphology and porous structure characteristics.As a self-supporting supercapacitor electrode material,it shows certain electrochemical performance(0.5 A g^-1,167 F g^-1).(3)The addition of lignin can reduce the cyclization activation energy of SNFs,promote their stabilization process,form a dense three-dimensional fiber lap structure,and improve the flexibility and electrical and thermal conductivity of the CNFs.while the addition of lignin reduces the pore structure of CNFs,and its performance decreases when it is used as the ethyl acetate adsorption material and the electrode material of self-supporting supercapacitor.Therefore,this paper studies the molecular composition and structure of pitch,as well as the preparation and the evolution of stabilization and carbonization of pitch derived SNFs.The influence mechanism of pitch and its components on the structure and performance of pitch derived CNFs is clarified,which provides a theoretical basis and technical support for the regulation and preparation of pitch derived CNFs and the application development.