Abstract
Ultrasound-assisted liquid-phase exfoliation is a promising method for manufacturing two-dimensional materials. Understanding the effect of ultrasonication parameters such as the temperature and input power on the developed pressure field is pivotal for optimization of the process. Limited research has been carried out to determine the optimal temperature for exfoliation, with some data generating disputed results. Simply maximizing the sonication power does not necessarily produce a higher yield because of shielding. In this study, a high-temperature calibrated cavitometer was used to measure the acoustic pressure generated in different graphite solutions in deionized water at various temperatures (from 10°C to 70°C) and input power conditions (from 20% to 100%). In addition, high-speed optical imaging provided insight on the shock wave generation from transient bubble collapses under different sonication conditions. The optimal sono-exfoliation parameters were determined to be 20% input power at 10°C for graphite flake solution, and 100% input power at 40°C to 50°C for graphite powder solution.
Highlights
Since the revolutionary discovery of graphene, a panoply of research into two-dimensional (2D) layered material (LM) exfoliation has been conducted.[1]
We focused on the effects of the liquid temperature and input power on the generation of cavitation to promote exfoliation based on the developed pressure field
The acoustic pressure for the graphite flakes (GF) solution and DI water gradually decreased with increasing temperature, while for the Graphite powder (GP) solution there was a slight increase in pressure above 40°C
Summary
Since the revolutionary discovery of graphene, a panoply of research into two-dimensional (2D) layered material (LM) exfoliation has been conducted.[1]. The implosion of cavitation bubbles and the associated high-pressure shock waves and high-velocity (up to several 100 m sÀ1) liquid jets[11,12] generate strong shear forces that are responsible for the exfoliation. Despite the complementary shear forces, adverse effects deleterious to LMs such as edge defects and holes can be produced by prolonged ultrasonic treatment.[15] It has been shown that the temperature increase during sonication can result in inconsistent exfoliation.[16] the implementation of a temperature control strategy is essential. Graphite powder (GP) and graphite flakes (GF) were sonicated in deionized (DI) water, which was previously identified as an ideal medium for exfoliation due to its low cost and nontoxic nature.[14] High-speed shadow-graphic imaging was applied for different amplitudes to observe the shock wave generation alongside the acoustic pressure measurements. The results reveal that the use of specific combinations of solution temperature and acoustic power generates favorable conditions for LM exfoliation
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