Engineering of Al/CuO Reactive Multilayer Thin Films for Tunable Initiation and Actuation

Sputter-deposited Al/CuO multilayers represent the state-of-the-art of energetic nanomaterials. As such, they offer an opportunity for tunable ignition and actuation because their theoretical energy densities are significantly higher than most conventional secondary explosives while being less sensitive to undesired initiation. Both the sensitivity and combustion properties (temperature, rate and products released) can be manipulated via the layering, reactant spacing and stoichiometry of the multilayer and, to a lesser extent, via interface engineering. In this article, we first describe the technology of deposition of Al/CuO multilayers focusing on direct current sputter deposition followed by a comprehensive review of the materials structural characteristics. Next, experimental and theoretical works performed on these reactive multilayered materials to date is presented in terms of methods used, the results acquired on ignition and combustion properties, and conclusions drawn. Emphasis is placed on several studies elucidating the fundamental processes that underlie propagating combustion reactions. We examine the influence of the « ceiling » temperature that traduces the multilayer disintegration when reaching high temperatures (e.g., vaporization temperatures). This paper provides a good support for engineers to safely propose Al/CuO multilayers structure to regulate the energy release rates and ignition threshold in order to manufacture high performance and tunable initiator devices.