Effect of static pressure on ultrasonic liquid phase exfoliation of few-layer graphene

Review on the impacts of external pressure on sonochemistry

“…In [48] , a cyclic ultrasonication system (at 20 kHz, Acoustic power = 1400 W, Tliq = 40 °C) was designed to exfoliate expanded graphite (EG) by applying static pressure (0–0.6 MPa [0–5.92 atm]) to a flow chamber. The optimal processing conditions for producing graphene with the fewest layers and the largest lateral size were determined to be a 40-minute processing time under a static pressure of 0.6 MPa (5.92 atm).…”

“…As static pressure increases, large bubbles diminish while small bubbles tend to remain relatively stationary. Aa a result, high static pressure reduces kinetic energy loss by stabilizing bubbles, which enhances the efficiency of exfoliation by releasing energy through cavitation collapse [48] . Moreover, the small size of the collapsing bubble facilitates its penetration between the graphite layers, disrupting the van der Waals forces and thereby enhancing graphene exfoliation.…”

“…In contrast, as static pressure rises, large bubbles decrease in size, while smaller bubbles tend to remain relatively stationary. This stabilization of bubbles under high static pressure reduces the loss of kinetic energy, which enhances the sonochemical process by releasing energy through cavitation collapse [48] . Moreover, As static pressure increased, both the ultrasonic shielding and the volume of the bubble cloud decreased [49] .…”