An Attempt to Produce Electrical Discharges in Acoustic Cavitation Bubbles

Abstract

It is widely known that cavitation bubbles are not static bubbles but have the dynamics of the expansion, the shrinkage, and the collapse. In this work, we produced electrical discharges in acoustic cavitation bubbles for the first time with the intension of enhancing the reactivity of sonochemical processes. Glow-like discharges were observed in cavitation bubbles on the bottom surface of the cylindrical electrode which was connected to a pulsed high-voltage power supply. Bright optical emission was observed from the region corresponding to the cloud of expanded cavitation bubbles, while we also observed electrical discharges even in the shrinking phase of cavitation bubbles. If discharge-produced reactive species have lifetimes that are longer than the interval between the discharge and the collapse of the cavitation bubble, the species composition in the collapsed cavitation bubble becomes different from that in conventional cavitation bubble, which may result in the enhancement of reactivity in sonochemical processes.

Highly Efficient Piezocatalytic Activity of Poly(tetrafluoroethylene) for Large-Scale Organic Wastewater Purification

“…In this work, the catalytic reaction of PTFE was carried out under ultrasonic vibration, which provides the required conditions for the formation of polarized PTFE electret with catalytic activity. Under ultrasonic vibration, the generated acoustic cavitation bubbles instantaneously break, which can produce high pressure (0.2–2 GPa) to PTFE. − The pressure deforms the PTFE particles and structural defects are generated, while charges result from the electric field and get trapped in the defects of PTFE particles. , Thus, a polarized piezoelectric PTFE electret is formed. The local piezoelectric response of PTFE particles was confirmed by PFM, and the amplitude butterfly loop (red) and phase hysteresis loop (black) of PTFE powders were observed with a bias voltage (−8 to 8 V), as shown in Figure a.…”

On Adaptive Control for Electrical Discharge Machining Using Vibroacoustic Emission

“…The blanks were fastened on the worktable of EDM machine tool. The processing was done with the immersion of the blanks in a dielectric for 10 min before machining; it was done according to the EDM standards for high precision processing to exclude the thermal shrinkage of the materials [37]. The level of the dielectric was 1-2 mm above the blanks.…”