How to dispersion the graphene by ultrasonic homogenizer machine?

How to dispersion the graphene by ultrasonic homogenizer machine?

Since the special properties of graphite are known, several methods for its preparation have been developed. In addition to the chemical production of graphene from graphene oxide in a multi-step process, very strong oxidizing and reducing agents are required. In addition, graphene prepared under these harsh chemical conditions often contains a large number of defects even after reduction compared to graphene obtained from other methods. However, ultrasound is a proven alternative method that can produce large amounts of high-quality graphene. The methods developed by researchers using ultrasound vary slightly, but in general, graphene production can be completed in just one step.

01 Direct exfoliation of graphene
Ultrasound can prepare graphene in organic solvents, surfactant/aqueous solutions or ionic liquids. This means that the use of strong oxidizing or reducing agents can be avoided. Stankovich et al. (2007) produced graphene by exfoliation under ultrasound. Ultrasonic treatment of a solution of graphene oxide with a concentration of 1mg/ml, AFM images show that there are always flakes with uniform thickness (1nm), and there are no graphene flakes with a thickness greater than 1nm or less than 1nm in these good graphene oxide exfoliation samples. It is concluded that under these conditions, complete exfoliation of graphene oxide to obtain single graphene oxide flakes is achieved.

02 Ultrasonic graphene treatment ...

To give an example of a specific graphene production process: Graphite is added to a mixture of dilute organic acid, alcohol and water, and the mixture is then exposed to ultrasonic radiation. The acid acts as a "molecular wedge" to separate the graphene sheets from the parent graphite. Through this simple process, a large amount of undispersed, high-quality graphene dispersed in water is produced.

03 Preparation of Graphene Sheets
A large amount of pure graphene sheets were successfully prepared in the production process of non-stoichiometric TiO2 graphene nanocomposites by thermally hydrolyzing a suspension of graphene nanosheets and titanium dioxide peroxide complexes. The pure graphene nanosheets were made from natural graphite using a high-intensity cavitation field generated by an ultrasonic processor in a high-pressure ultrasonic reactor at 5 bar. The resulting graphene sheets have a high specific surface area and unique electronic properties and can be used as a good carrier for TiO2 to improve photocatalytic activity. The quality of ultrasonically prepared graphene is much higher than that obtained by the Hummer method, in which graphite is exfoliated and oxidized. Since the physical conditions inside the ultrasonic reactor can be precisely controlled and by assuming that the concentration of graphene as a dopant will vary in the range of 1-0.001%, it is possible to produce graphene in a continuous system on a commercial scale.

04 Ultrasonic treatment of graphene oxide
Preparation process of graphene oxide (GO) layers using ultrasonic irradiation. Twenty-five milligrams of graphene oxide powder were suspended in 200 milliliters of deionized water. A heterogeneous brown suspension was obtained by stirring. The resulting suspension was ultrasonically treated (30 minutes, 1.3×105J) and after drying (373K), ultrasonically treated graphene oxide was prepared. FTIR spectroscopy showed that ultrasonic treatment did not change the functional groups of graphene oxide.

05 Functionalization of graphene sheets
Xu and Suslick (2011) described a one-step method for the preparation of polystyrene functionalized graphite. In their study, they used graphite flakes and styrene as basic raw materials. By ultrasonicating graphite flakes in styrene (reactive monomer), ultrasonic irradiation led to mechanochemical exfoliation of graphite flakes into single-layer and few-layer graphene flakes. At the same time, functionalization of graphene sheets with polystyrene chains was achieved. The same functionalization process can also be carried out with other graphene-based composite materials vinyl monomers.

06 Preparation of Carbon Nanoscrolls
Carbon nanoscrolls are similar to multi-walled carbon nanotubes. The difference with multi-walled carbon nanotubes is the open tips and the full accessibility of the inner surface to other molecules. They are wet-chemically synthesized by intercalation of graphite with potassium, exfoliation in water and ultrasonic treatment of the colloidal suspension. Ultrasound-assisted rolling up of graphene monolayers into carbon nanotubes with a conversion efficiency of up to 80% makes the production of nanotubes a hot topic for commercial applications.

07 Graphene Dispersions
The dispersion grade of graphene and graphene oxide is extremely important to exploit the full potential of graphene and its specific properties. If graphene is not dispersed under controlled conditions, the polydispersity of the graphene dispersion can lead to unpredictable or non-ideal effects once incorporated into a device, as the properties of graphene vary with its structural parameters. Sonication is a proven treatment method that can weaken interlayer forces and allows precise control of important processing parameters. "For graphene oxide (GO), which is typically exfoliated as single-layer sheets, one of the main polydispersity challenges is due to the variation in the lateral area of ​​the flakes. By varying the graphene feedstock and sonication conditions, the average lateral size of GO can be shifted from 400nm to 20μm. Ultrasonic dispersion of graphene has been demonstrated in many other studies to produce fine and even colloidal slurries."