Ultrasonic dispersion is a reliable method to produce graphene layers from graphite flakes or particles. Other common dispersion technologies (e.g., ball mills, roller mills, or high-shear mixers) are susceptible to the use of aggressive reagents and solvents. Ultrasonic dispersion technology can overcome this problem and prepare graphene materials efficiently.

Ultrasonic dispersion transforms graphene in liquid into a dispersed state, that is, fine or ultra-fine ultrasonic grinding of solids or fluids due to ultrasonic vibration effects. Due to the special nature of the ultrasonic field generated in liquid media, ultrasonic dispersion provides a highly dispersed uniform, chemically pure suspension (particle size less than 1μm).

Principle of graphene preparation by ultrasonic wave
Graphene produced by ultrasound is based on cavitation effects and therefore does not destroy the quantum structure inside the graphene. Ultrasonic cavitation can generate high frequency amplitudes through high power ultrasound. High power ultrasound can be used for liquid processing, such as mixing, emulsifying, dispersing and depolymerizing, or grinding. When a liquid is ultrasonic processed at high intensity, sound waves propagating into the liquid medium cause alternating high pressure (compression) and low pressure (reflection) cycles, with rates depending on the frequency. High intensity ultrasonic waves in low pressure circulation produce small vacuum bubbles or voids in the liquid. When bubbles reach a volume that cannot absorb energy, they collapse violently in a high-pressure cycle. This phenomenon is called cavitation.

Spalling and dispersion of graphene
If graphene is to be used as a material, it must first be evenly dispersed into the formula. Due to the hydrophobicity of graphene, it is difficult to obtain a high concentration of graphene dispersions without stabilizing them with surfactants or dispersants.

Graphene nanosheets (GNP) can be made by stripping graphite in a solvent through high-power ultrasonic processing. Ultrasonics - stripped graphene can be functionalized with biopolymers to obtain water-dispersed graphene. The synthesized graphene can be further processed into a stable water-based dispersion by ultrasonic cavitation. When graphene nanoparticles are mixed into liquid, agglomeration is easy to occur. Ultrasonic dispersion can break the graphene aggregates in water and non-water suspensions, which can exert the full potential of nanomaterials.

Go is water-soluble and can be easily dispersed into stable colloids. Ultrasonic spalling and dispersion is a very effective, fast and cost-effective method for synthesizing, dispersing and functionalizing go on an industrial scale. In order to control the size of GO nanosheets, the peeling method plays a key role. Due to its precise and controllable process parameters, ultrasonic stripping is the most widely used layering technique for the production of high-quality graphene and go.