Preparation method of Graphene

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Submitted by admin on Wed, 12/26/2018 - 09:03


Mechanical peeling
The mechanical peeling method is a method of obtaining a thin layer of graphene material by utilizing friction and relative motion between an object and graphene. This method is simple to operate and the resulting graphene typically maintains a complete crystal structure.

Redox method
The redox method is to oxidize natural graphite by using a chemical reagent such as sulfuric acid or nitric acid, an oxidizing agent such as potassium permanganate or hydrogen peroxide, to increase the spacing between the graphite layers, and to insert an oxide between the graphite layer and the layer to obtain graphite oxide. (Graphite Oxide). Then, the reactant was washed with water, and the washed solid was dried at a low temperature to obtain a graphite oxide powder. The graphite oxide powder is peeled off by a method such as physical peeling or high-temperature expansion to obtain graphene oxide. Finally, the graphene oxide is reduced by a chemical method to obtain graphene (RGO).

The graphene prepared by the redox method contains a rich oxygen-containing functional group and is easy to be modified. However, due to the reduction of graphene oxide, it is difficult to control the oxygen content of graphene after reduction, and at the same time, graphene oxide is continuously reduced under the influence of each external element such as sunlight irradiation and high temperature in transportation, so the redox method The quality of the produced graphene batch products is often inconsistent and it is difficult to control the quality.

Orientation epiphysis
The orientation epitaxy method uses the growth matrix atomic structure to "speculate" graphene. First, the carbon atoms are infiltrated into the crucible at 1150 ° C, and then cooled. After cooling to 850 ° C, a large amount of carbon atoms absorbed before will float to the surface of the crucible. The single layer of carbon atoms in the final lens shape will grow into a complete layer of graphene. After the first layer is covered, the second layer begins to grow. The underlying graphene will have a strong interaction with the ruthenium, while the second layer will be almost completely separated from the ruthenium, leaving only weak electrical coupling.

Silicon carbide epitaxy
The SiC epitaxial method is to sublimate silicon atoms out of the material in a high-temperature environment of ultra-high vacuum, and the remaining C atoms are reconstructed by an independent form to obtain graphene based on SiC substrate.

Herm
The graphite oxide is prepared by the Hummer method; the graphite oxide is ultrasonically dispersed in water to form a uniformly dispersed, graphene oxide solution having a mass concentration of 0.25 g/L to 1 g/L, and the mass is added dropwise to the graphene oxide solution. The concentration is 28% ammonia water; the reducing agent is dissolved in water to form an aqueous solution having a mass concentration of 0.25 g/L to 2 g/L; the prepared graphene oxide solution and the reducing agent aqueous solution are uniformly mixed, and the obtained mixed solution is placed in oil. The mixture was stirred under a bath condition, and after completion of the reaction, the mixture was filtered, washed, and dried to obtain graphene.

Chemical vapor deposition
Chemical vapor deposition (CVD) is a method in which a graphene film is obtained by vapor phase deposition using a carbon-containing organic gas as a raw material. This is currently the most effective method for producing graphene films.

 

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