1,721,099 research outputs found
Simulation of phase explosion in the nanosecond laser ablation of aluminum
No full textVaporization, spallation and phase explosion are considered to be the main mechanisms contributing to the nanosecond laser ablation of metals. The theory of homogeneous nucleation, together with the dynamics of target heating, allows a space-time resolved simulation of the phase explosion mechanism. The thermal phenomena occurring at the target surface are studied within the framework of a thermodynamic continuum approach. A 20 ns laser pulse of variable fluence and Gaussian time dependence was assumed. The temperature profile in the target external layers is studied through the heat diffusion equation. The vaporization from the surface is modeled assuming unsteady adiabatic expansion (UAE) of the vapor and a Monte Carlo (MC) method is used to describe the formation of liquid nanodroplets through phase explosion. Liquid nanodroplets in the ablated material are studied at different laser fluences. The size distribution of the nanodroplets formed in the phase explosion process is here reported and connections with experiments are discussed
SODIUM PROFILES IN BETA'' ALUMINA CRYSTALS - MODIFICATIONS INDUCED BY ARGON BOMBARDMENT
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Dynamics of liquid nanodroplet formation in nanosecond laser ablation of metals
No full textThe laser ablation mechanisms of metallic targets leading to liquid nanodroplet ejection are of wide interest both from a fundamental point of view and for applications in various fields, especially when nanoparticle synthesis is required. The phase explosion process was recognized as the driving mechanism of the expulsion of a mixture of vapor and liquid nanodroplets in the short pulse laser ablation of metals. A model based on thermodynamics that links the theory of homogeneous vapor bubble nucleation to the size distribution of the generated liquid nanoclusters has been recently proposed. The present work aims to take a step ahead to remove some assumptions made in previous work. Here an improved computational approach allows us to describe time-dependent nucleation in a homogeneous system with no temperature spatial gradients under nanosecond laser irradiation. Numerical results regarding the size distribution of formed liquid clusters and the time evolution of the process are shown for aluminum, iron, cobalt, nickel, copper, silver and gold. Connections with experimental data and molecular dynamics simulations, when available from literature, are reported and discussed
Catalytic properties on the hydrogen desorption process of metallic additives dispersed in the MgH2 matrix
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