Controlling Propagation Velocity in Al/Ni Reactive Multilayer Systems by Periodic 2D Surface Structuring

The chemical energy released as heat during the exothermic reaction of reactive multilayer systems has shown potential applications in various technological areas, e.g., in joining applications. However, controlling the heat release rate and the propagation velocity of the reaction is required to enhance their performance in most of these applications. Herein, a method to control the propagation velocity and heat release rate of the system is presented. The sputtering of Al/Ni multilayers on substrates with periodic 2D surface structures promotes the formation of growth defects into the system. This modification in the morphology locally influences the reaction characteristics. Tailoring the number of 2D structures in the substrate enables the control of the velocity and maximum temperature of the propagation front. The morphology of the produced reactive multilayers is investigated before and after reaction using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. In addition, the enthalpy of the system is obtained through calorimetric analysis. The self-sustained and self-propagating reaction of the systems is monitored by a high-speed camera and a high-speed pyrometer, thus revealing the propagation velocity and the temperatures with time resolution in the microsecond regime. Reactive multilayer systems are produced by physical vapor deposition on substrates with periodic 2D surface structures. The impact of these structures on the multilayer morphology is exploited to influence the dynamics of self-propagation. This enables the adjustment of the velocity of propagation and heat release behavior of the system by tailoring the number of structures on the substrate surface.image (c) 2024 WILEY-VCH GmbH