Ultrasonic cavitation refers to the phenomenon that when the ultrasonic energy is high enough, the tiny bubbles (cavitation nuclei) existing in the liquid vibrate, grow and continuously accumulate the acoustic field energy under the action of the ultrasonic field. When the energy reaches a certain threshold, the cavitation bubbles collapse and close rapidly.
The life of cavitation bubble is about 0.1 μ s. It can release huge energy when it collapses sharply, and generate a micro jet with a speed of about 110m / s and a strong impact force, making the collision density as high as 1.5kg/cm2. The cavitation bubble generates local high temperature and high pressure (5000K, 1800atm) at the moment of rapid collapse, and the cooling rate can reach 109K / s. The cavitation effect of ultrasonic wave greatly improves the heterogeneous reaction rate, realizes the uniform mixing between heterogeneous reactants, accelerates the diffusion of reactants and products, promotes the formation of new solid phase, and controls the size and distribution of particles.