热应变导致的脉冲激光诱导金微粒碎裂
Pulsed-laser induced gold microparticle fragmentation by thermal strain
AI总结：
本研究针对悬浮微粒激光碎裂机制不明的问题，采用超快X射线散射结合双温模型模拟，揭示了金微粒在不同激光注量下的碎裂机理与动力学过程，为该技术优化提供了结构层面的依据。
摘要：
悬浮微粒的激光碎裂是一种新兴的可替代液相激光烧蚀（LAL）的技术，能够简化输送流程并优化辐照条件以实现最佳效率。但迄今为止，该过程的结构基础尚未得到充分理解。本文中，我们对悬浮在液体中的金微粒进行皮秒激光激发，采用超快X射线散射技术来探究碎裂后的热动力学及结构演化过程。我们还结合双温模型开展模拟，以验证时空温度分布。研究发现，在注量阈值高于750 J/m²时，微粒会在1纳秒内碎裂为数个大块，其驱动力一方面来自高度不均匀热分布引发的应变，另一方面来自超快加热（相较于应力传播）导致的应力约束。在注量为2700 J/m²时，微粒正面的光热分解会额外产生少量小团簇。
英文摘要：
Laser fragmentation of suspended microparticles is an upcoming alternative to laser ablation in liquid (LAL) that allows to streamline the the delivery process and optimize the irradiation conditions for best efficiency. Yet, the structural basis of this process is not well understood to date. Herein we employed ultrafast x-ray scattering upon picosecond laser excitation of a gold microparticle suspension in order to understand the thermal kinetics as well as structure evolution after fragmentation. The experiments are complemented by simulations according to the two-temperature model to verify the spatiotemporal temperature distribution. It is found that above a fluence threshold of 750 J/m$^2$ the microparticles are fragmented within a nanosecond into several large pieces where the driving force is the strain due to a strongly inhomogenous heat distribution on the one hand and stress confinement due to the ultrafast heating compared to stress propagation on the other hand. The additional limited formation of small clusters is attributed to photothermal decomposition on the front side of the microparticles at the fluence of 2700 J/m$^2$.
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