Self-propagating exothermic reactions in nanoscale multilayer materials

This paper describes self-propagating, exothermic reactions in nanoscale, multilayer materials. It begins with a review of self-propagating reactions in powder-based materials and then focuses on similar exothermic reactions in multilayer foils. The multilayer foils consist of alternate layers of materials that have high heats of mixing, such as Al sind Ni. The individual layers (of Al or Ni) are only nanometers thick, but hundreds of these layers are sputter deposited to form one foil with a total thickness between 10 and 100 microns. The thick foils are easily removed from their substrates, and their exothermic mixing can be initiated at room temperature with a small spark. The exothermic reactions propagate at speeds greater than 10m/s and reach final temperatures as high as 1600 degrees C. Reaction velocities are presented for two different multilayer systems, and the chemical and structural parameters that control these velocities are addressed.