Electrical explosions of Al, Ti, Fe, Ni, Cu, Nb, Mo, Ag, Ta, W, W-Re, Pt, and Au wires in water: A comparison study

In this paper, an experimental study was performed to document the characteristics of underwater electrical explosions involving different wires made from 15 different metals/alloys. Experiments were undertaken with those wires (4 cm in length; 100-300 μm in diameter) driven by a pulsed current source with 500 J initial stored energy. The results indicated that the electrical and thermophysical properties of the metal were critical in the explosion process. Non-refractory metals, such as Al, Cu, Ag, and Au, absorbed about twice as much energy as their enthalpy of atomization before the voltage peak, while for refractory metals, such as Nb, Mo, Ta, and W, the deposited energy before the peak was close to their atomization enthalpy. Accordingly, the strongest measured shock wave for non-refractory metals was 12.4 MPa (peak pressure) while that for refractory metals was only 8.5 MPa (peak pressure). By contrast, the light intensities of non-refractory metals were at least an order of magnitude lower than those of refractory metals. From 100 to 300 μm, the estimated average temperature at the plasma-water interface decreased from ∼10 000 K to ∼4000 K. It was also found that, as evidenced from the time-integrated spectra, obvious chemical reactions occurred between water and relatively active metals such as Al, Ti, and Fe. In addition, Pt and Au, which have high first ionization energies, exhibited longer current pauses (>50 μs) or vaporization phases relative to the other metals.