Melting and vaporization of Cu and Ni films during electron-beam heating
JA Sanchez and MP Menguc, JOURNAL OF APPLIED PHYSICS, 103, 054316 (2008).
In this paper, we present a study of the phase change processes that take place in Cu and Ni films when they are heated with an electron-beam produced by field emission from an array of carbon nanotubes. A Monte Carlo method is adapted to solve the electron-beam Boltzmann transport equation to determine the electron distribution inside these materials. A hybrid approach is implemented to couple the two-temperature model with molecular dynamics simulations. We consider an analysis based on an order parameter and a radial distribution function to characterize the transition point at which the materials change phase. Slower electron diffusion in Ni produces more pronounced temperature gradients in both the electron system and the lattice, whereas the temperature rise throughout the Cu film is more uniform due to the faster electronic diffusion. We found that the phase change process is a combination of speed of the energy diffusion into the materials accompanied by a concentration of tensile stresses that contribute to the expansion and breakage of the films. We calculated the velocity of melting and vaporization fronts for both films and found two melting fronts for Cu converging close to the center of film with high velocity and one for Ni reaching a maximum speed and then stabilizing at a constant magnitude. We also explored the heating effects of multiple carbon nanotubes acting on these films. (C) 2008 American Institute of Physics.
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