Influence of Initial Temperature and Convective Heat Loss on the Self-Propagating Reaction in Al/Ni Multilayer Foils.

Mostafa Baloochi,Sebastian Matthes,Peter Schaaf,Isabella Gallino,Sascha Sebastian Riegler,Jörg Pezoldt,Marcus Glaser,Deepshikha Shekhawat,Jean Pierre Bergmann

doi:10.3390/ma14247815

Abstract

A two-dimensional numerical model for self-propagating reactions in Al/Ni multilayer foils was developed. It was used to study thermal properties, convective heat loss, and the effect of initial temperature on the self-propagating reaction in Al/Ni multilayer foils. For model adjustments by experimental results, these Al/Ni multilayer foils were fabricated by the magnetron sputtering technique with a 1:1 atomic ratio. Heat of reaction of the fabricated foils was determined employing Differential Scanning Calorimetry (DSC). Self-propagating reaction was initiated by an electrical spark on the surface of the foils. The movement of the reaction front was recorded with a high-speed camera. Activation energy is fitted with these velocity data from the high-speed camera to adjust the numerical model. Calculated reaction front temperature of the self-propagating reaction was compared with the temperature obtained by time-resolved pyrometer measurements. X-ray diffraction results confirmed that all reactants reacted and formed a B2 NiAl phase. Finally, it is predicted that (1) increasing thermal conductivity of the final product increases the reaction front velocity; (2) effect of heat convection losses on reaction characteristics is insignificant, e.g., the foils can maintain their characteristics in water; and (3) with increasing initial temperature of the foils, the reaction front velocity and the reaction temperature increased.

Highlights

The Nickel and Aluminum binary system in different forms such as particles, powder, flakes, nanorods, and foils, were under intensive investigation since the end of the 20th century [1,2,3,4,5,6,7,8,9,10,11,12,13]
Free-standing thin films were measured via Differential Scanning Calorimetry (DSC) to obtain the total reaction enthalpy during the reaction with slow heating rates
The obtained data were compared to the results of the simulations of the propagation velocity and the time–temperature dependence to adjust and validate the simulation model

Summary

Introduction

The Nickel and Aluminum binary system in different forms such as particles, powder, flakes, nanorods, and foils, were under intensive investigation since the end of the 20th century [1,2,3,4,5,6,7,8,9,10,11,12,13]. Fast and steady reaction and releasing a huge amount of energy on a very short time scale are the main beneficial aspects, applied in different fields of science and engineering. The chemical mixing rate increases, and in presence of external stimulation, the reaction occurs in the in-plane direction of the binary film in high-temperature self-propagating mode. In this case, theoretically, the temperature could increase up to 1912 K, which is the melting temperature of the NiAl B2 phase. The measured propagation velocity of the reaction front as reported in the literature is up to 15 m s−1 , depending on the bilayer thickness and the intermixing at the interfaces between the layers [21,22]

Methods

Results

Conclusion