Generation of nanoparticles by laser ablation of metal microparticles and plume dynamics

摘要

This paper describes the process of nanoparticle synthesis by laser ablation of consolidated microparticles, focusing on the dynamics of ablation plume. We have generated nanoparticles by high-power pulsed laser ablation of Al and Cu microparticles using a Q-switched Nd:YAG laser (wavelength 355 nm, FWHM 10 ns, fluence 0.8 ～ 2.0 J/cm~2). Microparticles of mean diameter 18 ～ 80 μm are ablated in the ambient air. The generated nanoparticles are collected on a glass substrate and the scanning electron micrographs of the samples are examined for characterizing the particles. The effect of laser fluence and collector position on the distribution of particle size is investigated. Optical diagnostics and numerical simulations are conducted to study the flow field and plume dynamics. The dynamics of ablation plume and shock wave is analyzed by monitoring the photoacoustic probe-beam deflection signal. Nanosecond time-resolved images of the ablation process are also obtained by laser flash shadowgraphy. Based on the results of experiment and numerical simulation, discussions are made on the dynamics of ablation plume.