Experimental and computational investigation into the hydrodynamics and chemical dynamics of laser ablation aluminum plasmas
Experimental and computational investigation into the hydrodynamics and chemical dynamics of laser ablation aluminum plasmas
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激光烧蚀铝等离子体的流体动力学和化学动力学的实验和计算研究
DOI：
10.1039/d3cp01586f
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发表时间：
2023
影响因子：
3.3
通讯作者：
Hartig, Kyle C.
中科院分区：
文献类型：
--
作者：
Kwapis, Emily H.;Posey, Jacob W.;Medici, Enrique;Berg, Kira;Houim, Ryan W.;Hartig, Kyle C.
激光烧蚀等离子体化学受到流体动力学等离子体-气体混合过程、热力学和快速高温化学反应之间复杂的相互作用的控制。在这项工作中，我们利用光谱学与先进的多物理场建模相结合，研究了空气中纳秒激光烧蚀铝等离子体的气相氧化化学。实验测量表明，早在 1 μs 时，等离子体羽流中就形成了 Al2O3，而计算结果表明，在存在大温度梯度和强冲击波的情况下，甚至更早的时间（<20 ns），几种 AlxOy 物质就分布在羽流的外围。研究表明，羽流快速膨胀过程中与烧蚀坑的相互作用会引发涡流形成，随后发生混合动力学，将 Al2O 拉入涡流，与气相 Al 反应形成 Al2O。氧气和几种氧化铝同时通过火球的茎被拉上来，促进反应物质之间的进一步混合并增强分子形成。这项工作的结论是，激光烧蚀等离子体中的化学动力学是由扩散过程、浓度梯度和羽流流体动力学驱动的，而激光烧蚀过程中产生的强冲击波不会阻碍化学反应。
Laser ablation plasma chemistry is governed by a complex interplay between hydrodynamic plasma-gas mixing processes, thermodynamics, and rapid high-temperature chemical reactions. In this work, we investigate the gas-phase oxidation chemistry of ns-laser ablation aluminum plasmas in air using optical spectroscopy combined with advanced multi-physics modeling. Experimental measurements demonstrate the formation of AlO in the plasma plume as early as 1 μs while computational results reveal that several AlxOy species are distributed in the periphery of the plume at even earlier times (<20 ns) in the presence of large temperature gradients and strong shockwaves. Interactions with the ablation crater during rapid plume expansion are shown to initiate vortex formation, followed by mixing dynamics that work to pull AlO into the vortices to react with gas-phase Al to form Al2O. Oxygen and several aluminum oxides are simultaneously pulled up through the stem of the fireball, encouraging further intermixing between reacting species and enhanced molecular formation. This work concludes that chemical dynamics in laser ablation plasmas is driven by diffusion processes, concentration gradients, and plume hydrodynamics while strong shockwaves generated during laser ablation do not impede chemical reactions.