Preparation, Structure And Properties Of Graphene/carbon Nanotube Composite Films

One-dimensional carbon nanotubes(CNTs)and two-dimensional graphene nanosheets are excellent carbon material with anisotropy.Selecting appropriate methods to prepare graphene/carbon nanotubes composite film can generate a synergistic effect between them with many physical and chemical properties enhanced.Now,spin-coating,chemical vapor deposition(CVD),electrophoretic deposition,vacuum filtration are the preparation methods of graphene/CNTs hybrid film.In consideration of our reserach mainly apply to transparent conductors and laser mode-locked,so the films must possess high conductivity and high transmittance.We prepared graphene by CVD because of CVD on metal substrates has been developed to achieve large area graphene films with high quality,few layers,high transmittance and uniformity across the whole area.However,graphene have its own drawbacks:Available grapene thin films have many grain-boundary defects,and easily broken in the process of transfer.In this paper,the free-standing,high conductivity and high transmittance hybrid thin films were prepared via a drop-coating method by using graphene prepared by CVD and carbon nanotube dispersed in 1,2-dichlorobenzene as crude materials.The research contents in this thesis mainly include the following parts:1)Graphene film was synthesized by an ambient pressure chemical vapor deposition process(APCVD).Graphene film with different layers,electrical conductivity and transmittance were prepared by controling experiment parameter.2)The dispersion effect of different solvent were Studied and compared,and the wettability of these solvent to graphene film were compared,the best dispersing agent of CNTs were confirmed;the composite methods of CNTs with graphene were studied,the best composite method were confirmed.3)The structure and morphology of graphene/CNTs hybrid thin films were characterized by scanning electron microscope(SEM),transmission electron microscopy(TEM),Raman spectroscopy and X-ray photoelectron spectroscopy(XPS).The nonlinear optical properties of films were measured by Z-scanning.The transmittance and sheet resistance of the hybrid thin films with diffrent concentration of the dispersed carbon nanotube were characterized by UV-visible spectroscope and four-point probe analyzer respectively.The transmittance and sheet resistance of Sandwiched graphene/CNTs hybrid films with diffrent layers were characterized by UV-visible spectroscope and four-point probe analyzer respectively,and the mechanical property of the graphene and hybrid thin films were studied with a nano-indenter.The structure and performance of graphene/CNTs hybrid film changed with different ?-ray irradiation dose were Studied,and their reaction mechanism were analyzed.From the study above,we have reached the following conclusions:1)large area and uniformity graphene film with high quality was synthesized by the method that graphene film was grown on muriatic acid pre-cleaned copper foil substrates with ethanol liquid as the precursor by an ambient pressure chemical vapor deposition process(APCVD).the layers and performance of the graphene films can be controlled by regulating the time and flow of inletting carbon source.2)1,2-dichlorobenzene was the best dispersing agent and wettability to graphene film;the better uniformity of hybrid thin films were prepared by drop-coating,and the surface density of carbon nanotube in the hybrid thin films were controlled.3)The transmittance and sheet resistance of the hybrid thin films can be controlled by regulating the concentration of carbon nanotube in the dispersion,showing significant decreases for both parameters when the concentration of the dispersed carbon nanotube increases.Sandwiched(graphene/CNTs)n hybrid films exhibit excellent electrical conductivities,the transmittance of hybrid thin films decreased linearly and sheet resistance of hybrid thin films rapidly decrease with the increase of layers.The nonlinear optical properties of graphene film and hybrid film were measured by Z-scanning,showing strong the third order nonlinear absorption,the absorption coefficient were found to be-7.08 × 10-4cm/W and-1.94 × 10-4cm/W respectively.The mechanical property of the thin films were measured by nano-indenter,it was found that mechanical strength of hybrid films better than graphene films,and mechanical strength of Sandwiched hybrid films enhancing with the increase of layers.The CNTs Welded to each other and cross-link with y-ray irradiation,forming network cross-linked structure on graphene film.The change rate of sheet resistance of hybrid films were found to be decreased after the first increased with the increase of irradiation dose.