Numerical Investigation of the Self-Propagation of Intermetallic Reaction Waves in Nanoscale Aluminum/Nickel Reactive Multilayer Foils

Among several candidates for nanoenergetic materials and systems, nanoscale reactive multilayer foils (NRMF) or bimetallic nano-laminates are highly promising candidates. They provide the highly desirable pyrotechnical properties of high energy density and reaction sensitivity as well as flexible tunability. They could be useful in various fields of explosive and propellant ignition devices, in alternative heat sources, and for the precision joining of metal components in miniaturized forms. NRMF consists of many alternating nanosized layers of two different metals. It exhibits novel energetic performances, including a considerably short ignition delay and superfast reaction propagation with high exothermic heat release. This numerical study presents the computational modeling of self-propagating intermetallic reaction waves in aluminum and nickel based multilayer NRMF microsystems. The existence of atomic pre-mixing at the bimetallic interface was also carefully considered in the numerical model. The computational results of reaction wave speed in NRMF with Al-Ni bilayer spacing from 10 to 180 nm were found to be in excellent agreement with the corresponding measurements, which validates the present numerical model and predictions. The fundamental physical mechanism of self-sustaining reaction waves was also closely investigated. It was found that increasing the thickness of interface pre-mixing leads to a clear observation of periodic wave unsteadiness and hot spots in intermetallic reaction wave propagation in NRMF systems.