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International Journal of Energy for a Clean Environment

ISSN Print: 2150-3621
ISSN Online: 2150-363X

International Journal of Energy for a Clean Environment

Formerly Known as Clean Air: International Journal on Energy for a Clean Environment

DOI: 10.1615/InterJEnerCleanEnv.2015013543
pages 1-25

ULTRASHORT LASER MELTING OF COPPER NANOPARTICLES: A MOLECULAR DYNAMICS STUDY

Yingbin Hu
Department of Manufacturing Engineering, The University of Texas-Pan American, 1201 W University Dr, Edinburg, TX 78539, USA
Jianzhi Li
Department of Manufacturing Engineering, The University of Texas-Pan American, 1201 W University Dr, Edinburg, TX 78539, USA

ABSTRACT

Based on the simulation result of a model that combines two-temperature and molecular dynamic methods and takes both electrons conduction band and atomic-level equilibration procedure between the electrons and the lattice into account, an ultrashort laser mechanism of melting copper nanoparticles has been investigated. To be more precise, the effect of inner defect (grain boundary) on the melting process is considered in this paper. It can be expected that the inner defect has a positive impact on the laser melting because the atoms at defects with higher free energy are comparatively disordered and unsteady compared to those within the perfect lattice. Besides, the size effect is another major concern for nanoparticles on account of their relatively large specific surface area which makes them reactive to the laser pulse. Hence, nanoparticles of two different sizes of10 nm and 20 nm have been created and simulated to study their influence on the kinetics of melting process and on the respective physical and thermal properties with different laser fluences. For monocrystalline nanoparticles at low laser fluence, the surface melting phenomenon is remarkable compared to polycrystalline nanoparticles at both low and high laser fluences. In addition, the size of nanoparticle not only affects the microscopic mechanisms of laser melting, but also plays a dominant role in density decreasing degree and speed.