Modeling of the shrinking process of a bubble induced by laser metal ablation in water and experimental verification

Abstract

Laser ablation of a solid target immersed in liquid (such as water) has many important applications such as laser synthesis of nanoparticles, laser micromachining in water, and laser shock peening. Laser ablation of a solid target in water involves complicated physical processes. One important process often involved is the generation and evolution of a bubble in water and attached to the target surface, which may have significant effects on the target and the ambient water, and hence may greatly affect the relevant practical applications. Some experimental studies were reported in the literature on bubble evolutions induced by laser ablation of a solid target in water. However, the reported previous relevant physics-based modeling work is not sufficient. A physics-based model may help improve the process fundamental understanding and generate valuable information to related applications. In this paper, physics-based modeling work has been performed on the shrinking process of a bubble induced by laser metal ablation in water, together with time-resolved shadowgraph imaging experiments to verify the model. The model-predicted bubble evolution agrees reasonably well with the experimental measurement shown in the paper. Under the studied conditions, it has been found that near the bubble collapse moment (i.e., the moment when the bubble shrinks to a minimum size): (1) the bubble shrinks very fast, and the peak fluid velocity magnitude occurs inside the bubble and can exceed ∼550 m/s; (2) the temperature inside the bubble increases very quickly and approaches ∼2000 K; and (3) the pressure inside the bubble becomes very high, and can reach a peak magnitude of ∼380 MPa at the collapse moment at the bubble center. During the shrinking process, a high-pressure region outside and near the bubble wall is generated near the collapse moment, but the temperature of the region outside the bubble mostly remains low.

Early appearance of crystalline nanoparticles in pulsed laser ablation in liquids dynamics

“…47 A reasonable modelling can be done by the Rayleigh-Plesset (RP) equation, although it is known that RP does not well reproduce the collapse phase, and in particular the size of the bubble rebound. 48,49 The Gilmore equation incorporates water compressibility and condensation to reach a better agreement with bubble dynamics. [50][51][52] Nevertheless, we are mostly interested in the expanding bubble, where virtually no differences between the RP and Gilmore equations can be found with appropriate fitting parameters.…”

Dynamics of laser-induced cavitation bubbles at a solid–liquid interface in high viscosity and high capillary number regimes

“…Tomko et al reported an asymmetric shrinking 35 . Contact angle hysteresis and bell-shaped bubbles in water have been observed 39 .…”

“…An early laser-induced plasma is quickly quenched a few microseconds after the impact, leading to a vapour bubble [27][28][29][30][31][32] containing nanoparticles [33][34][35][36] . The bubble grows and collapses for first within a few hundreds of microseconds and finally leads to the release of the nanoparticles into the liquid 34,35 when the bubble fully collapses and disappears after a few oscillations 26,[37][38][39] . Persistent microbubbles are released during the collapse phase, which may shield a large portion of subsequent laser pulse in particular at high liquid viscosities 40 , and consist of chemical reaction products of the solvent and target, such as volatile carbohydrates 40 , hydrogen, oxygen and hydrogen peroxide 41 .…”

“…The dynamics of the cavitation bubble and its influence on the nanoparticle formation has been investigated by many researchers 28,[37][38][39][42][43][44] . Surprisingly, there is a lack of literature investigating cavitation bubbles in highly viscous liquids, although viscous liquids are becoming more and more interesting for LAL applications in oils 45,46 or monomers 47 through offering the possibility for one-step synthesis of colloids.…”

Opportunities and Challenges for Laser Synthesis of Colloids

“…These calculations supported the experimental evidence about the formation of oligoatomic clusters and also give possible explanations for wide size distributions observed for some LAL configurations. Also, finite element methods are being applied to study the cavitation bubble dynamics and, in particular, its collapse …”