AG3 battery.Graphene preparation technology is developing rapidly, and industrial production methods have not yet been formed.

　　Graphene preparation technology is developing rapidly. Graphene's excellent properties and wide application prospects have greatly promoted the rapid development of graphene preparation technology. Since Geim et al. first prepared graphene using micromechanical exfoliation in 2004, researchers have developed numerous methods for preparing graphene. Among the more mainstream methods are epitaxial growth method, chemical vapor deposition CVD method and graphite oxide reduction method.

　　The existing production methods cannot meet the requirements of graphene industrialization. Many preparation methods, including micromechanical exfoliation, epitaxial growth, chemical vapor deposition (CVD) and graphite oxide reduction, still cannot meet the requirements of industrialization. In particular, industrialization requires graphene preparation technology that can produce large-area, high-purity graphene stably and at low cost. This preparation technology problem has not yet been solved.

　　micromechanical exfoliation method

　　Graphene is first produced by micromechanical exfoliation. The micromechanical peeling method uses transparent tape to press highly oriented pyrolytic graphite sheets onto other surfaces and peel them off multiple times to finally obtain a single layer or several layers of graphene. In 2004, Geim, Novoselov and others obtained single-layer graphene for the first time in the world through this method, proving that the two-dimensional crystal structure can exist at room temperature.

　　The micromechanical peeling method is simple to operate and has high sample quality. It is currently the main method for producing single-layer high-quality graphene. However, its controllability is poor, the size of the graphene produced is small and there is great uncertainty. At the same time, the efficiency is low, the cost is high, and it is not suitable for large-scale production.

　　epitaxial growth method

　　Epitaxial growth methods include silicon carbide epitaxial growth and metal catalyzed epitaxial growth. The silicon carbide epitaxial growth method refers to heating SiC single crystal at high temperature, so that the Si atoms on the SiC surface are evaporated and separated from the surface, and the remaining C atoms are reconstructed through self-organization, thereby obtaining graphene based on the SiC substrate.

　　The metal catalytic epitaxial growth method is to pass hydrocarbons into the surface of a catalytically active transition metal substrate such as Pt, Ir, Ru, Cu, etc. under ultra-high vacuum conditions, and catalytically dehydrogenate the adsorbed gas through heating to produce graphene. . Gas can grow over the entire metal substrate during the adsorption process, and its growth process is a self-limiting process, that is, the substrate will not absorb the gas again after adsorbing it. Therefore, the graphene prepared is mostly a single layer and can be grown over a large area. Preparation of uniform graphene.

　　Chemical vapor deposition CVD method: the most potential large-scale production method

　　The CVD method is considered the most promising method for preparing high-quality, large-area graphene, and is the most promising method for industrial production of graphene films. The specific process of the chemical vapor deposition CVD method is: Pour hydrocarbons such as methane and ethanol into the Cu and Ni surfaces of metal substrates heated at high temperatures. The reaction lasts for a certain period of time and then is cooled. During the cooling process, several layers or layers will be formed on the surface of the substrate. For single-layer graphene, this process involves the dissolution and diffusion growth of carbon atoms on the substrate. This method is similar to the metal catalytic epitaxial growth method. Its advantage is that it can be carried out at a lower temperature, thereby reducing the energy consumption during the preparation process, and graphene and the substrate can be easily separated by chemical corrosion of metal, which is beneficial to The graphene is subsequently processed.

　　Samsung used this method to obtain a single layer of graphene with a diagonal length of 30 inches, showing the great potential of this method as an industrial production method. However, the thickness of the graphene produced by this process is difficult to control. Only a small part of the available carbon is converted into graphene during the precipitation process, and the transfer process of graphene is complicated.

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