Streak spectrograph temperature analysis from electrically exploded Ni/Al nanolaminates

We report on electrically-induced heating and mixing of multilayered nickel/aluminum (Ni/Al) laminates observed by streak camera emission spectroscopy. Past experiments probing the kinetic energy of material ejected from the reaction zone indicate that additional kinetic energy originates from Ni/Al samples, presumably from exothermic mixing between the two metals. Here we examine streak spectrographs of similar experiments to determine the presence of expected elements and their temperatures. We conducted these experiments in rough vacuum, but found the emission to be dominated by argon (Ar) and nitrogen (N) lines in addition to the expected emission of Al and Ni, which were also present. Using the spectral information of Ar, we analyzed the relative intensities of four Ar peaks between 425 and 455 nm, with respect to their expected Boltzmann distributions to yield temperatures as a function of time. These temperatures were 2.24–2.59 eV for Al samples, and 2.93–3.27 eV for both Ni and Ni/Al samples, and were within estimates based on the measured electrical energy delivered to each device. The higher Ni/Al sample temperatures seemed to validate our past measurements of increased kinetic energy and the apparent rapid exothermic mixing between Ni and Al, although Ni samples yielded surprisingly high temperatures as well. These results may be important for future nanomanufacturing techniques involving localized heating from reactive Ni/Al multilayers, where the precise control of spatial temperatures may necessitate an equally precise temporal control of the reaction.