Controllable Preparation And Its Application Of Carbon Nanofibers

Carbon nanofibers(CNFs)has been used in area of composite materials,supercapacitor materials,field emission devices,catalyst carriers,environmental protection and biological medicine due to their excellent properties such as high strength,high specific surface area and high chemical stability.However,the technology for large scaled preparation CNFs with high purity is not available now,fine structure control and bulk production for CNFs not only play a key role on basic research and industrial application,but also a challenging and critical issues of the further development of CNFs faced.Therefore,the preparation of CNFs decides the future of it,and the development of bulk production for CNFs growth technology and continuous preparation equipment is important for the industrialization of CNFs.The helical carbon nanofibers(HCNFs)have attracted the attention of researchers.Many overlapping pores will be formed in the process of forming helical structure.The helical structure can also cross link more molecular chains when reinforcing composite materials.However,the strong van der Waals force between fibers makes them entangle each other,which limits their practical application.The preparation and application of CNFs determine its future development.It is of great significance for the industrialization of CNFs to carry out the preparation process of high yield CNFs and the development of continuous preparation devices,and develop their irreplaceable applications.This paper focuses on the preparation technology,preparation equipment and irreplaceable applications of high yield CNFs and HCNFs.The main research content and results of this paper are shown as following:(1)When using the substrate method to prepare CNFs,only a single preparation is possible,and the heating and cooling time during the preparation process is longer,which affects the production efficiency.Designed and developed a set of continuous CNFs preparation system,which is mainly composed of growth chamber,lofting chamber,sampling chamber heating furnace,lofting transmission device,sampling transmission device,cooling device,vacuum control device and other parts.In the preparation process,the continuous operation of lofting,reaction and sampling is realized,so as to achieve the purpose of continuous preparation,shorten the production cycle,and improve production efficiency.It has important scientific research value and practical value for promoting the industrialization of CNFs and HCNFs.(2)Macroscopic CNFs sponge and CNFs powder were synthesized by one-step chemical vapor deposition method at 230?and 260?respectively.The growth mechanism is a coordination polymerization mechanism,and the macrostructure of CNFs can be controlled and controlled by the preparation temperature.The length of a single carbon nanofiber sponge exceeds 10?m,which is the key to in-situ growth and self-assembly into a three-dimensional sponge structure.(3)Three kinds of(Fe,Co,Ni)tartaric acid complexes were prepared and used as catalyst precursors,and CNFs were prepared by one-step chemical vapor deposition(CVD)method.The effects of carbon source flow rate,reaction time and preparation temperature on yield were investigated.There is no need to pass in reducing gas and additives during the process.When cobalt tartrate was used as the catalyst precursor,the acetylene flow rate was200 m L/min,the growth time was 60 min,and the preparation temperature was 650°C,the yield of the linear CNFs prepared was 1025.81%.When nickel tartrate was used as the catalyst precursor,the acetylene flow rate was 100 m L/min,the growth time was 120 min,and the preparation temperature was 480°C,the yield of the linear CNFs prepared was1252.39%.When ferrous tartrate is used as the catalyst precursor,the acetylene flow rate is200 m L/min,the growth time is 600 min,and the preparation temperature is 500?,the yield of the prepared HCNFs is 907.83%.The experiment uses a one-step CVD method,simple operation,no other additives,and provides industrial support for the preparation of low-cost and high-yield CNFs and HCNFs.(4)The HCNFs/sodium alginate composite hydrogel is prepared by the blending method,when the mass concentration of sodium alginate is 1%,the mass concentration of Ca Cl₂ is 0.03 mol/L,and the mass concentration of HCNFs is 0.5 mg/m L,The prepared HCNFs/sodium alginate hydrogel has a equilibrium swelling degree of 30.12 and a compressive strength of 7.84 k Pa.(5)Acid oxidation modification can effectively improve the dispersibility of HCNFs,thereby increasing the specific capacitance of the material.Using HNO₃ oxidation method and improved Hummers oxidation method to modify the HCNFs can increase the surface oxygen-containing functional groups and specific surface area.When the scan rate is 1 A/g,the specific capacitance of HCNFs-2(143.6 F/g)is much higher than the original HCNFs(10.7 F/g)and HCNFs-1(65.5 F/g),and the content of oxygen-containing functional groups is higher,the greater the specific capacitance.The actual contribution of oxidation modification to the double-capacitance layer and pseudo-capacitance of HCNFs is also studied.At a scanning rate of 10 m V/s,the double layer capacitance of HCNFs-1 and HCNFs-2 accounted for 64.5%and 53.5%of the total capacitance,respectively.(6)Sodium dodecylbenzene sulfonate itself has incomparable capacitance performance.In order to improve the wettability of the electrolyte on the surface of the HCNFs electrode,a simple one-step non-covalent bond polymerization method was used to successfully modify the surface of HCNFs(SHCNFs).The surface modification amount of sodium dodecylbenzene sulfonate on SHCNFs,SHCNFs-1 and SHCNFs-2 is about 3.41%,9.38%,24.22%.When the current density is 1A/g,the specific capacitance of HCNFs-2modified with sodium dodecylbenzene sulfonate increases from 143.9 F/g to 212.5 F/g,which can effectively increase the specific capacitance of HCNFs.