Design and fabrication of energetic Al/Ni exploding foil with enhanced energy efficiency and plasma density for direct ignition

In order to lower the firing voltage, an energetic Al/Ni exploding foil (Al/Ni-EF) with enhanced energy efficiency and plasma density was prepared in this study, to realize the direct ignition of pyrotechnics. An Al/Ni reactive multilayer foil (Al/Ni-RMF) was firstly synthesized by magnetron sputtering and wet etch method, and its structure and exothermic behavior were investigated. Scanning Electron Microscopy, Atomic Force Microscope and X-ray Diffraction characterizations confirmed the periodic layer structure of Al/Ni-RMF with a total thickness of 4 μm. The highest heat release in Al/Ni-RMF could be achieved theoretically when the ratio of Al and Ni was 1.5, and thus the thickness of single Al and Ni layer was determined to be 300 nm and 200 nm, respectively. The obtained Al/Ni-RMF was subsequently fabricated to be an exploding foil, and its electric explosion performance was further studied. Energy efficiency of the Al/Ni-EF was measured to be 85.9% during the electric explosion process, which was 30.9% higher than that of Cu exploding foil (Cu-EF). The plasma generated at Al/Ni-EF had larger volume, longer duration time and higher temperature than Cu-EF due to the intermetallic reaction between Al and Ni, which was beneficial for the direct ignition of Boron/Potassium Nitrate composition (B/KNO₃, BPN). Afterwards, a special Al/Ni-EF ignitor without slapper was constructed, and the fierce ignition of BPN at the minimum discharge voltage of 800 V was observed. Above results confirmed the feasibility of direct ignition, such a unique strategy was beneficial for the development of low-energy, low-cost and miniaturized ignitor.