Mechanism and characteristics on the electric explosion of Al/Ni reactive multilayer foils

Abstract

Al/Ni multilayer foils were integrated with high voltage initiators using conventional microelectronic processing techniques and electrically exploded at an extremely high heating rate. In order to increase the knowledge about the electric explosion process of Al/Ni foils, several samples with different bilayer thicknesses, bridge dimensions, and capacitor voltages were tested. Time dependent voltage and current waveforms, energy depositions, and average flier velocities were measured and compared. The application of Al/Ni multilayers significantly increased the flier velocity and energy deposition of the device. The stored chemical energy of Al/Ni multilayer foils indeed contributed to the flier velocity increase, according to the experimental observations that the 225 nm bilayer bridges with the largest heat of reaction resulting in the highest flier velocities of all. Analysis of the experimental results allows us to prove that the electric explosion process of Al/Ni foils consisted of three stages. First, the Al layers were heated to vaporize. Then, the condensed AlNi grains started to nucleate due to exothermic mixing and subsequently evaporated with continuous energy deposition. Finally, the metal vapors ionized and formed plasma. These results provide fundamental understanding about electric explosion of Al/Ni reactive multilayer foils, and also enable us to improve the reliability and energy efficiency of electrically exploded Al/Ni multilayers for specific applications.