This work examines the initial growth and collapse stages of bubbles induced by laser ablation in liquids. First, the bubble shape and size are tracked using an ultrafast camera in a shadowgraph imaging setup. The use of an ultrafast camera ensures a high control of the reproducibility, because a thorough measurement of each bubble lifetime is performed. Next, an analytical cavitation-based model is developed to assess the thermodynamic bubble properties. This study demonstrates that the bubble evolution is adiabatic and driven by inertial forces. Surprisingly, it is found that the bubbles consist of significantly more solvent molecules than ablated matter. These results are valuable to the field of nanoparticle synthesis as they provide insight into the mechanics of laser ablation in liquids.
We report on the formation and growth of nanobubbles around laser-heated gold nanoparticles in water. Using a hydrodynamic free-energy model, we show that the temporal evolution of the nanobubble radius is asymmetrical: the expansion is found to be adiabatic, while the collapse is best described by an isothermal evolution. We unveil the critical role of the thermal boundary resistance in the kinetics of formation of the nanobubbles: close to the vapor production threshold, nanobubble generation is very long, yielding optimal conditions for laser-energy conversion. Furthermore, the long appearance times allow nanoparticle melting before the onset of vaporization.
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