Accelerated aqueous nano-film rupture and evaporation induced by electric field: A molecular dynamics approach

The interfacial heat and mass transfer at nano-scale are the key procedure of various phase changes phenomena, and are of significant importance for both science and engineering applications. In the present work, molecular dynamics simulations were applied to investigate the influence of external electric field on the rupture and evaporation of aqueous thin films, which is crucial for bubble coalescence within the context of flotation. The properties of pure water and saline liquid thin films at the absence and presence of parallel electric fields were examined with field intensity ranging from 0.1 to 10 V/nm. It was observed that for relatively thick film, which is very stable (4 × 4 × 1.45 nm) with infinite life time under the electric-field free condition, by incorporating an electric field, the rupture process was significantly accelerated with increases in the field strength. With the field strength reaches up to a threshold at 2-2.5 V/nm, the rupture occurred nearly instantly and temperature increased due to molecular friction, a further increase of strength resulted in thermostat's improper working and the evaporation of molecules. The surface tension exhibits a decreasing trend when the field strength is below 1 V/nm, surface tension cannot be correctly measured when the field intensity is above 2 V/nm due to the influence of rupture and evaporation. This result provides a theoretical guidance with external electric field for nano-electric transfer, regarding the potential of electro-coalescence between bubbles during flotation process.