The early stage of the thermal pulse explosions of aluminum nanowires under different energy deposition levels

Molecular dynamics simulations are performed to study the initial stage of the electrical explosions of Al nanowires in vacuum. The radial difference of wire expansion rate was observed in the early stages of the explosions. It is found that the wire radial expansion rate and the thermodynamic parameters interact with each other. We studied the time-varying thermodynamic parameters in the matched mode expansions, obtained the phase trajectories of wire material. Our results proved that the energy deposition levels dominate the explosion regime: when the energy ratio is less than 0.208, wire expansion will not develop into an explosion; phase explosion occurs under an underheated condition; supercritical explosion generally happens when the energy deposition is greater than the sublimation energy. We tracked the transformation trajectory of the deposited energy and found it is not preferentially transformed into the internal energy but simultaneously transformed into the explosion kinetic energy. As a result, even for the deposited energy reaching or exceeding the sublimation energy, material cannot be fully gasified. Finally, the deposition energy consumed by the internal energy has an upper limit: the sublimation energy.