In recent years, graphene has received more and more attention. The country also advocates the development of graphene industry. However, the method of preparing graphene also restricts the pace of most manufacturers. The common oxidation methods include Brodie method, Staudemanaier method and The Hummers method is based on the principle of treating graphite with a strong acid and then adding a strong oxidizing agent for oxidation. The oxidized graphite is formed by ultrasonication to obtain a graphene dispersion device to form graphene oxide, and then a reducing agent is added for reduction to obtain graphene.
Ultrasonic dispersion of graphene
Because of its surface inertness, graphene is incompatible with many substances and has poor dispersibility. It is easy to agglomerate to form larger agglomerates, and the agglomerates are irreversible, so that the nanoparticles cannot be uniformly dispersed by a single particle, reducing At the same time, its own adsorption capacity can not exert its nano characteristics. It has a very adverse effect on the application properties of nano-powders and the improvement of the properties of graphene-reinforced composites.
The use of surfactants or dispersants to prepare stable and highly concentrated graphene is a challenging task. In order to overcome the van der Waals forces between the graphene layers, the strong shear forces generated by ultrasonic cavitation are the most advanced methods for preparing such stable dispersions. The propagation of ultrasonic waves in a liquid state produces powerful pressure waves that form numerous microscopic bubbles that undergo rapid growth and closure. When the bubble is closed, a strong shock wave is generated due to the collision between the liquids, and a pressure of thousands of atmospheres is generated at the periphery thereof, thereby generating a strong shearing activity.
As the ultrasonic power is increased, the instantaneous release pressure of the ultrasonic waves destroys the van der Waals force between the graphene layer and the layer, effectively expanding the graphite layer spacing. Larger layer spacing is not only beneficial to the formation of graphite intercalation composites between other molecules, atoms and other intercalation layers, but also easier to be stripped, laying the foundation for the next step of preparing single-layer graphene. In addition, by precisely controlling the process parameters of the ultrasonic treatment, the ultrasonic dispersion technique can avoid chemical effects and damage to the crystal structure, thereby obtaining the original, defect-free graphene sheets.