| Since 2004,Professor A.Geim from the University of Manchester in the United Kingdom has used the micro-mechanical lift-off method to separate single-layered graphene sheets.Graphene has attracted widespread attention from all the world,because of its excellent performance.And the excellent electrical properties of graphene open up a new perspective for the development of next-generation electrical devices.Graphene is a two-dimensional material with a hexagonal honeycomb lattice structure composed of carbon atoms of the sp2 hybrid orbital.There are three strong a bonds and one ? bond between carbon atoms in the lattice structure of graphene,which permeate the entire graphene structure.And each carbon atom will provide a ?-electron to form a ?-orbital,which can shuttle freely in the graphene without hindrance,which is the reason for the excellent electrical properties of graphene.Studies have shown that different sizes,geometries,and egde types will cause graphene to exhibit different electrical properties.Changing the graphene structure by nanocutting process can improve the performance of graphene.This paper mainly studied that nanocutting of graphene by metal particles as "scissors" to obtain graphene with different shapes and sizes and different edge types.At the same time,the carbon nanotubes are grown on cutting channels,so the directional growth of the carbon nanotubes is controlled.The nanocutting technology by metal particle is applicable not only to two-dimensional graphenes such as highly-oriented pyrolytic graphite and single-crystal graphene,but also can modify the three-dimensional graphene.On this basis,we can further expand our research by compounding or synthesizing other materials.The content of our work is as follows:1.The nanocutting of highly oriented pyrolytic graphite by metallic nickel particles was studied,and a method for the controllable modification of graphene structure was provided.By scanning electron microscopy,transmission electron microscopy,and atomic force microscopy,we found that after nickel nanoparticles were deposited on the surface of HOPG,catalytic hydrogenation reactions was in progress,nickel particles as catalysts etched carbon atoms and formed cutting channels on the surface of graphene.Nickel particles are located at the end of the channel,and the width of the channel was consistent with the nickel particle diameter.The edge type of the channel formed along the[1120]lattice direction is zig-zag,and the edge type of channel formed along the[1100]lattice direction is an armchair.In addition,when the metal particles encountered defects or free boundaries during the cutting process,the cutting direction would change.If the cutting direction occurred a 60° or 120° transition,it means that the direction is still along the same lattice direction;if the cutting direction occurred a 90° transition,it means that the direction of the lattice has changed in the cutting direction..Because the channels crossed each other,graphene sheets with different size,morphology and edge types can be obtained,thereby improving the electrical properties of the graphene.2.To expand the previous part of the study,carbon nanotubes were grown in the nanocutting channels of highly oriented pyrolytic graphite surface,which is of great significance for the directional growth of carbon nanotubes.The carbon source for carbon nanotube growth is HOPG,and the catalyst is nickel particles.To characterize the carbon nanotubes in the channels,we found that the CNTs were multi-walled carbon nanotubes,which growing strictly within inner wall of the channels,and CNTs can be bent with direction of channels.The diameters of carbon nanotubes synthesized in different edge type channels are also different,which means,the(n,m)index and number of layers of CNT may be different.By adjusting the size of the nickel metal particles,the direction of the nanocutting and the width of the channels can be adjusted to control the growth of carbon nanotubes with different structural features.In addition,carbon nanotubes which growing on the surface of HOPG were different from that inside channels.Due to the unrestricted of domains,carbon nanotubes on the surface can form a variety of structural shapes such as "octopus" structure,spiral structure,etc.3.Mainly studied the nanocutting of single-crystal graphene by metallic nickel particles,single-crystal graphene overcomes the difficulty of HOPG transfer operation,making sample characterization is easier to perform.Through characterization,the nanocutting of single crystal graphene by metallic nickel particles was along a straight direction.When nickel particles encountered vacancy or graphene defect during the cutting process,the cutting direction occurred changing.In addition,the starting points of channels were mostly located at the breakage edge of graphene.We can produce monocrystalline graphene sheets with different size and different edge type by nanocutting,such as nano-sized triangles,quadrilateral single-crystal graphene sheets,single-crystal graphene nanoribbons,etc.This is of great significance to the modification of monocrystalline graphene,and it has expanded a new idea for the application in electrical devices.4.Nickel particles were used to nano-cut 3D graphene composites,and the electrochemical properties,energy storage properties were characterized.Studies have shown that increasing the porosity of three-dimensional graphene and preparing three-dimensional graphene composites are the most common methods to increase the specific surface area and capacitance of 3D graphene.Through the nanocutting process,the pores inside 3D graphene composite material increased,and the specific surface area increased too.This material was used as a cathode electrode material for lithium ion battery.Due to its large porosity and specific surface area,the internal ion transmission distance of the graphene became shorter and the number of ion attachment sites increased,thereby further improving the specific capacity and other properties of the lithium ion battery. |
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