# The role of two-stage phase formation for the solid-state runaway reaction in Al/Ni reactive multilayers

Neuhauser, T.; Tinti, G.; Leiste, H.; Casati, N.; Ulrich, S.; Stüber, M.; Woll, K.

##### Abstract:
While extensively studied for heating rates below 1.7 K/s and above 1000 K/s, the solid-state phase transformations in Al/Ni reactive multilayers have not been examined at intermediate heating rates between 100 K/s and 1000 K/s. Combined nanocalorimetry and time-resolved synchrotron x-ray diffraction studies are utilized to address this range of heating rates for multilayers with an overall composition of 10 at. % Ni and a bilayer thickness of 220 nm. It was found that a two-stage phase formation of Al$_{3}$Ni proceeds up to a heating rate of 1000 K/s. The two growth stages occur in the solid-state and are kinetically separated. The activation energy of the first growth stage is determined to be 137 kJ/mol, which agrees well with the literature data at low heating rates. At 1000 K/s, a transition to a runaway reaction is observed. Unusual for metallic multilayers, the reaction proceeds completely in the solid-state which is also known as “solid flame.” Using nanocalorimetry, a critical input power density for ignition of 5.8 x 10$^{4}$ W/cm$^{3}$ was determined. The rapid succession of the two Al$_{3}$Ni formation stages was identified as the underlying mechanism for the self-sustaining reaction.

 Zugehörige Institution(en) am KIT Institut für Angewandte Materialien - Werkstoff- und Biomechanik (IAM-WBM)Institut für Angewandte Materialien - Angewandte Werkstoffphysik (IAM-AWP) Publikationstyp Zeitschriftenaufsatz Publikationsjahr 2020 Sprache Englisch Identifikator ISSN: 0003-6951, 1077-3118, 1520-8842 KITopen-ID: 1000122792 Erschienen in Applied physics letters Band 117 Heft 1 Seiten Art. Nr.: 011902 Vorab online veröffentlicht am 08.07.2020 Nachgewiesen in Web of ScienceScopus
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