Dynamics of cavitation bubbles formed by pulsed-laser ablation plasmas near the critical point of CO2

Abstract

The realization of superior reaction fields for the synthesis of nanomaterials with pulsed-laser ablation (PLA) in high-density media, such as liquids, high pressure gases, and supercritical fluids (SCFs), especially near the critical point (CP), and the important role of the formation and evolution of cavitation bubbles for tuning the properties of the nanomaterials have been reported. In this study, to further elucidate the dynamics of the fluid in the stages following PLA, the characteristic behavior of cavitation bubbles formed by PLA plasmas near the CP of CO2 has been investigated using shadowgraph imaging. The time evolution of the cavitation bubbles can be divided into six phases. These include a double-layer structure and a long-time stagnation of the cavitation bubbles, which are peculiar to experimental conditions near the CP. Both spatial and time scale of the cavitation bubbles are at maximum 4-5 times larger near the CP compared to high-pressure liquid and liquid-like SCF far from the CP.