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 Al₃Ni 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 × 10⁴ W/cm³ was determined. The rapid succession of the two Al₃Ni formation stages was identified as the underlying mechanism for the self-sustaining reaction.

中文翻译：

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两阶段相形成对Al / Ni反应性多层体系中固态失控反应的作用

虽然对低于1.7 K / s和高于1000 K / s的加热速率进行了广泛研究，但尚未在100 K / s至1000 K / s的中间加热速率下检查Al / Ni反应性多层中的固态相变。结合纳米量热法和时间分辨同步加速器X射线衍射研究来解决总体组成为10 at.m的多层的加热速率范围。Ni％和双层厚度为220nm。发现Al ₃的两相形成Ni的加热速率高达1000 K / s。这两个生长阶段以固态发生，并且在动力学上是分开的。第一生长阶段的活化能确定为137 kJ / mol，这与文献中低加热速率下的数据非常吻合。以1000 K / s的速度观察到向失控反应的过渡。对于金属多层板，该反应完全在固态下进行，这也称为“固态火焰”。使用纳米量热法测定，点火的临界输入功率密度为5.8×10 ⁴ W / cm ³。Al ₃ Ni形成的两个阶段的快速连续被确定为自我维持反应的根本机制。