Preparation Of Three-dimensional Graphene By CVD Method

Graphene is a new kind of two-dimensional(2D) material and it has become a research focus owing to its excellent physicochemical properties and application potentialities in various fields. The two-dimensional plane structure of graphene makes it compatible with the architecture of traditional electrical devices. Recently, 3D graphene has become a research priority because of its 3D interconnected network, very high conductivity, large specific surface area,excellent mechanical flexibility, high thermal stablility and good chemical stablility. Therefore,2D graphene is usually needed to be assembled into 3D structure when applied to the field of energy, environment sensing and biology. As an common preparation method in preparing 2D graphene, chemical vapor deposition can also be used for 3D graphene.The main process of chemical vapor deposition is as follows. Carbon atoms which are obtained by decomposing a carbon source deposit in the 3D sacrifice template, nucleate and grow into graphene. Pure 3D graphene can be gained by etching the sacrifice template. Hydrogen and helium are main gas atmosphere in the preparation procedure and the growth temperature is in the range of 900-1100℃ which is the normal temperature range when 2D graphene is prepared.The 3D graphene after being etching will be transferred to the glass and silicon chip. The 3D graphene obtained will be characterized by the optical microscope, raman spectrometer, scanning electron microscope and four-probe resistivity measuring device in various aspects.Chemical vapor deposition is a kind of template-guided method and the structure of the 3D graphene which is prepared by this method can inherit its own template very well. However, the surface morphology of the 3D graphene often changes due to diverse factors during the preparation and it is mainly caused in the transfer process. Therefore, the research of the transfer method emphasizes on keeping the structure. Traditionally, gas carbon source is used in the method of chemical vapor deposition. Solid carbon source is used in this paper to investigate the regularity affected by different carbon sources. Besides finished nickel foam template, semifinished nickel foam template is also used in this research. Because of the obvious macro morphology change of 3D graphene made by the template, the influence of micro morphology caused by different templates is researched.This paper mainly focuses on the process of preparing 3D graphene by CVD. And the effects on the structure, surface morphology, component, quality and property of the 3D graphene,which caused by the transfer, carbon source and template, are elaborated in this paper. First, the paper discusses the important role of transfer method for the maintenance of three-dimensional morphology and structure. In exploring the preparation of 3D graphene using different carbon sources, it is found that the 3D graphene using solid carbon source has the same structure, surface morphology, component, quality and property as the one using gas carbon source. At last, this paper researches the finished product nickel foam template and the semifinished product reducing NiCl2·6H2O template. And it demonstrates that the 3D graphenes prepared by CVD have the macro-structure entirely inherited the template, but they are all made by self-supporting graphene sheets which connecting in different ways at the micro.The study of this paper demonstrates that excellent transfer methods can maintain the structure of three-dimensional graphene which inherited from the template well, and make it smaller defect, better quality and higher conductivity consequently. Compared with gas carbon source, the solid carbon source has high safety, and the generality of carbon source expands the range of applications of 3D graphenes prepared by CVD. By using the semifinished product template, the 3D graphene is able to freely change shape without machining and cutting. This paper further improves CVD method by preparing 3D graphene from the complex of polymer and nickel powder.In this paper, the factors on the preparation of 3D graphene by CVD have been researched from different aspects, and we greatly expands the scope of CVD method which has great significance in applications of 3D graphenes.