Controlling the reaction path of Ni/Al reactive multilayer on substrates

In this study, we explore the transferability of the exothermic reaction between structured Ni/Al multilayers elements. Two systems were prepared with and without Sn as an adhesive layer between substrates and multilayers to investigate the effect on the reaction front. To achieve this, obstacles of varying sizes were integrated into Ni/Al multilayer foils using a combination of photolithography and lift-off techniques. They were systematically positioned along the path of the self-sustained reaction in Ni/Al multilayers on substrates, with different spacing configurations between them. The advancement of the reaction front was monitored using a high-speed camera, while time-resolved pyrometer measurements provided insights into the maximum temperature attained during the self-propagating reaction. X-ray diffraction analysis confirmed the formation of the NiAl phase formed in both systems, while scanning electron microscopy revealed morphological changes induced by the reaction in both the Ni/Al multilayers and the quenching zone. Notably, the reaction front halted at various intervals between obstacles. Our findings suggest several key observations: (I) Minimal spacing between obstacles can effectively quench the reaction front; (II) The modification of the heat loss by the adhesive layer and subsequently impacts the reaction front; (III) To determine the condition to tailor the heat release of the reactive Ni/Al multilayer systems; (IV) The observation revealed that Sn initiates compressive stress during the deposition of the Ni/Al multilayers. Additionally, it aids in decreasing the cooling rate after the reaction and facilitates grain growth in the Ni/Al multilayers afterward. • Control the reaction propagation front of reactive Ni/Al multilayers become possible. • Find the critical distances between obstacles that can quench the reaction front. • Positive impact of reactive Ni/Al multilayer structuring on substrate in MEMS joining applications. • The reaction front can be guided between obstacle rows with a specific dimension.