Numerical modeling of self-propagating reactions in Ru/Al nanoscale multilayer foils

Abstract

The Ru/Al system integrates high energy density and high product ductility and serves as an alternative for utilization as nanoscale reactive multilayer. We present a modeling study that relates the Ru-Al phase transformations occurring during self-propagating reactions with macroscopic reaction parameters such as net front velocity and reaction temperature. We coupled equations for mass and thermal transport and used a numerical scheme to solve the differential equations. We calculated the temporal evolution of the temperature distribution in the reaction front as a function of the multilayer bilayer thickness. The calculated net velocities were between 4.2 m/s and 10.8 m/s, and maximal reaction temperatures were up to 2171 K, in good agreement with measured data. Interfacial premixing, estimated to be around 4 nm, had a large influence on reaction velocities and temperature at smaller bilayer thicknesses. Finally, the theoretical results of the present study help to explain the experimental findings and guide tailoring of reactive properties of Ru/Al multilayers for applications.

Effects of Ultrashort Pulsed Direct Laser Writing on Ni/Al Reactive Multilayer Foils

“…An example of such sensitive materials is reactive metallic multilayers built from at least two alternating metallic layers with individual layer thicknesses of ~5-200 nm and total film thicknesses of up to some tens of microns [14]. These materials are known for exhibiting exothermic self-propagating reactions upon local ignition with reaction front velocities of up to 100 m/s [15] and are capable of achieving reaction temperatures of well above 2000 • C. The best-studied reactive multilayer system is the Ni/Al system, though other material combinations such as Co/Al, Ru/Al, Nb/Si, Ti/Si, Pd/Al, and others have been identified and characterized over the past 30 years [16][17][18][19][20][21][22]. Reactions can be ignited in multiple ways, including direct heating, spark discharge, laser irradiation, and mechanical shock [23].…”