Graphene nanosheets, with their excellent mechanical properties, extremely high electron mobility, and good chemical stability, have become a research hotspot in materials science. Among numerous preparation methods, ultrasonic exfoliation has become one of the core technologies for the large-scale preparation of high-quality graphene nanosheets due to its advantages such as mild process and controllable cost.
The core principle of ultrasonic exfoliation is to utilize the cavitation effect of ultrasound to achieve interlayer exfoliation of graphite. When high-frequency sound waves propagate in a liquid, they induce intense compaction-sparse vibrations, forming a large number of tiny cavitation bubbles. These bubbles rapidly expand and then collapse instantaneously, generating high-speed microjets pointing towards the graphite surface. The impact force effectively breaks the weak van der Waals forces between graphite layers, causing the graphite to be gradually exfoliated into single-layer or few-layer nanosheets. Simultaneously, ultrasonic vibration also promotes the uniform dispersion of nanosheets in the solvent, preventing agglomeration.
The parameter control during the preparation process directly determines the product quality. Solvent selection is fundamental. Polar solvents such as N-methylpyrrolidone and dimethylnitrosamine can reduce the surface energy of graphite and improve exfoliation efficiency; a mixture of water and surfactants enables environmentally friendly preparation. Precise matching of ultrasonic power and time is crucial. Typically, processing at 500-1000W power for 0.5-6 hours yields good results; excessively long processing times or high power can lead to excessively small nanosheet sizes and increased defects.
Compared to other preparation techniques, ultrasonic exfoliation exhibits unique advantages. Compared to the high-temperature, high-pressure conditions of chemical vapor deposition, it can be performed at room temperature and pressure, reducing equipment investment costs by more than 50%. Compared to redox methods, it requires no strong oxidizing or reducing agents throughout the process, maximizing the preservation of the complete graphene lattice structure and avoiding the introduction of chemical defects. Experimental data shows that the number of graphene nanosheets prepared by this method can be controlled to below 10 layers, with a carbon content of up to 98.1% and excellent crystal quality.
In application fields, graphene nanosheets prepared by ultrasonic exfoliation have shown broad potential. In composite materials, their composite systems with resins can increase material strength by over 30%; in energy storage, as electrode materials, they can significantly improve the charging and discharging efficiency of supercapacitors; in environmental protection, graphite tailings resource recovery technology based on this method can achieve the recycling of over 80% of graphite in tailings, possessing both economic and ecological value.
With the development of technologies such as composite solvent systems and intelligent parameter control, ultrasonic exfoliation is moving towards higher efficiency and precision. In the future, combining it with technologies such as high-pressure microfluidics is expected to further overcome the bottleneck of balancing yield and quality, propelling graphene nanosheets from the laboratory to large-scale industrial applications.
