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Non-equilibrium Interface and Surface Dynamics

Phase field Modeling of Reactive Wetting

James A. Warren

National Institute of Standards and Technology


Recent experimental studies [1-3] of molten metal droplets wetting high temperature reactive substrates have established that the majority of triple-line motion occurs when inertial effects are dominant. In light of these studies, this talk investigates wetting and spreading on dissolving substrates when inertial effects are dominant using a thermodynamically derived, diffuse interface model of a binary, three-phase material. The liquid-vapor transition is modeled using a van der Waals diffuse interface approach, while the solid-fluid transition is modeled using a phase field approach. The results from the simulations demonstrate an O(t1/2) spreading rate during the inertial regime and oscillations in the triple-line position when the metal droplet transitions from inertial to diffusive spreading. It is found that the extent of spreading extent is reduced if dissolution is enhanced through a manipulation of the initial liquid composition. The results from the model exhibit good qualitative and quantitative agreement with a number of recent experimental studies of high-temperature droplet spreading, particularly experiments of copper droplets spreading on silicon substrates. Analysis of the numerical data suggests that the extent and rate of spreading is regulated by a contact angle calculated from a force balance based on a plausible definition of the instantaneous interface energies. Lastly, to investigate hypotheses in the existing contemporary literature, we examine the sources of dissipation using the entropy-production field, and find that dissipation primarily occurs in the locality of the triple-line region during the inertial stage, but extends along the solid-liquid interface region during the diffusive stage.

[1] E. Saiz and A. Tomsia, Nature Materials, 3, 903 (2004))
[2] P. Protsenko, O. Kozova, R. Voytovych, and N. Eustathopoulos, J. Mat. Sci. 43, 5669 (2008)
[3] L. Yin, B. T. Murray, S. Su, Y. Sun, Y. Efraim, H. Taitelbaum, and T. J. Singler, J. Phys-Cond. Mat. 21 (2009))

Joint work with D. Wheeler and W. J. Boettinger