Study On Carbon Nanotube/Graphene Composite Fiber

Carbon nanotubes and graphene fibers are carbon-based one-dimensional materials with good electrical properties and high specific surface.Using covalent bonds to combine graphene and carbon nanotubes,the composite fibers can expand the properties of these one-dimensional materials into a three-dimensional space.Currently,how to realize the chemical combination of carbon nanotubes and graphene and optimize the preparation process of carbon nanotubes/graphene fibers has become an important challenge in this field.Graphene oxide(GO)and alginate acid were used to prepare GO fibers using dry-jet wet spinning technology.Owing to the complexing characteristics of alginate acid,transition metal ions were uniformly integrated to the GO fibers in the spinning process by "one-step" method.Carbon nanotubes were in situ grown by chemical vapor depositionto obtain composite materials with carbon nanotube seamlessly connected to the graphene fiber.The structure and electrochemical properties of the fibers were investigated.The main research results are as follows:1、Alginic acid successfully improved the spinnability of GO dispersion.Alginate/GO composite fibers were obtained using dry-jet wet spinning technique with alginate chains aligned to the GO sheets.The prepared alginic acid/graphene oxide fiber exhibited knottable characteristic,which indicated good mechanical properties of the fibers due to strong interaction between alginate and metal ions.2、During the spinning process,the metal catalyst was uniformly supported by alginate,and the carbon nanotubes were grown in situ after chemical vapor deposition.The carbon nanotubes/graphene composite fiber was successfully prepared with carbon nanotubes densely covered at the surface of the fiber.Electron microscope photos showed that the carbon nanotubes stood intact on the fiber surface after applying mechanical force,indicating that the carbon nanotubes were not simply physical adsorption,but combined to the fiber in the form of the covalent bond,which is a novel idea for making intelligent devices.3、The composite fiber exhibited large specific surface area and good electrical properties.Porous structures at fibers were formed as the oxygen containing fuctional groups pyrolysised at high temperature during chemical vapor deposition.The specific surface area of the composite fiber was closely related to the ratio of alginate and GO.When the mass ratio of alginate to GO was 5:2,the specific surface area of the composite fibers reached the highest value of 366.98 m2/g,which was 4.4 times higher than that of non-grown CNT fibers(82.99 m2/g).The composite fibers with large specific surface area showed large specific capacitance.At a scanning rate of 1 mV/s,the specific capacitance of the CNTs/graphene fiber reached 263 F/g.At the current density of 0.1 A/g,the specific capacitance was 49.3 F/g,that was 3-4 times of commercially available carbon nanotubes(14 F/g)and reduction of graphene oxide fiber(15.4 F/g)under the same test conditions.The low electrical resistance between carbon nanotubes and graphene was beneficial to the unimpeded transfer of electrons and increased the specific capacitance,which indirectly proved that carbon nanotubes are connected to the graphene matrix through covalent bonds.The method used in this thesis to prepare carbon nanotubes/graphene composite fibers combined the advantages of dry-jet wet spinning and chemical vapor deposition.The chemical bondation of carbon nanotubes to graphene sheets produced synergy and gave better performace t than a single material.As for the high specific surface area and capacitance,the CNTs/graphene fiber will have excellent application prospects in the field of supercapacitors,solar cells,displays,and fuel cells.