Phase Transformation and Characterization of 3D Reactive Microstructures in Nanoscale Al/Ni Multilayers

Yesenia Haydee Sauni Camposano,Christian Schäfer,Heike Bartsch,Sascha Sebastian Riegler,Konrad Jaekel,Frank Mücklich,Peter Schaaf,Jörg Schmauch,Christoph Pauly,Isabella Gallino

doi:10.3390/app11199304

Yesenia Haydee Sauni Camposano, Christian Schäfer + Show 8 more

Open Access

https://doi.org/10.3390/app11199304

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Abstract

Reactive multilayer systems represent an innovative approach for potential usage in chip joining applications. As there are several factors governing the energy release rate and the stored chemical energy, the impact of the morphology and the microstructure on the reaction behavior is of great interest. In the current work, 3D reactive microstructures with nanoscale Al/Ni multilayers were produced by alternating deposition of pure Ni and Al films onto nanostructured Si substrates by magnetron sputtering. In order to elucidate the influence of this 3D morphology on the phase transformation process, the microstructure and the morphology of this system were characterized and compared with a flat reactive multilayer system on a flat Si wafer. The characterization of both systems was carried out before and after a rapid thermal annealing treatment by using scanning and transmission electron microscopy of the cross sections, selected area diffraction analysis, and differential scanning calorimetry. The bent shape of multilayers caused by the complex topography of silicon needles of the nanostructured substrate was found to favor the atomic diffusion at the early stage of phase transformation and the formation of two intermetallic phases Al0.42Ni0.58 and AlNi3, unlike the flat multilayers that formed a single phase AlNi after reaction.

Highlights

3D-Reactive multilayer systems (RMS) were characterized by scanning and transmission electron microscopy before and after rapid thermal annealing (RTA) and compared with standard RMS
The difference in the morphology of these two systems was attributed to the shadow effect generated by the topography of nanostructured black silicon
X-ray diffraction analysis (XRD) and selected area electron diffraction (SAED) patterns revealed that the novel morphology of 3D reactive multilayers (3D-RMS) during RTA promotes the formation of the two stable phases Al0.42 Ni0.58 and

Summary

Introduction

Reactive multilayer systems (RMS), typically forming binary or ternary intermetallic phases, have been thoroughly investigated due to their energetic properties and potential applications [1]. Due to the high amount of stored chemical energy and the large energy release rate of RMS, they can be used in technological applications such as welding, brazing, or in thermal batteries [3,4,5,6]. Al/Ni RMS were used as an ultrafast heat source to produce high entropy alloy films [7]. Much effort has been made in order to study the influence of different RMS characteristics, such as bilayer thickness, intermixing thickness, and chemical composition, on its energetic properties [4,8,9,10,11]. During a self-propagating reaction, the formation of AlNi intermetallic phase occurs directly from a semi liquid–solid state [13]

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