Influence of Impurities on the Front Velocity of Sputter Deposited Al/CuO Thermite Multilayers.

Altangerel Dulmaa,Diederik Depla

doi:10.3390/ma14237224

Abstract

CuO and Al thin films were successively deposited using direct current (reactive) magnetron sputter deposition. A multilayer of five bilayers was deposited on glass, which can be ignited by heating a Ti resistive thin film. The velocity of the reaction front which propagates along the multilayer was optically determined using a high-speed camera. During the deposition of the aluminum layers, air was intentionally leaked into the vacuum chamber to introduce impurities in the film. Depositions at different impurity/metal flux ratios were performed. The front velocity reaches a value of approximately 20 m/s at low flux ratios but drops to approximately 7 m/s at flux ratios between 0.6 and 1. The drop is rather abrupt as the front velocity stays constant above flux ratios larger than 1. This behavior is explained based on the hindrance of the oxygen transport from the oxidizer (CuO) to the fuel (Al).

Highlights

Velocity of Sputter DepositedFor many applications, energy storage and harvesting should be down-scaled to the nano- and microscale [1,2]
Reactive multilayers are composed of alternating layers of two materials, which are involved in an oxidation/reduction reaction or in a compound formation reaction
We investigate the role of intentionally added impurities during the deposition of the aluminum layers, which act as fuel in the sputter-deposited Al/CuO

Summary

Introduction

Energy storage and harvesting should be down-scaled to the nano- and microscale [1,2]. Thin-film batteries and reactive multilayers are examples of chemical energy storage approaches in this field [3]. Reactive multilayers are composed of alternating layers of two materials, which are involved in an oxidation/reduction reaction or in a compound formation reaction. The multilayer is in a metastable state, with excess chemical energy [4]. When the multilayer is locally activated by an external energy source, the two materials mix or react, transform to a stable state, and release heat. The heat is partially transferred to the non-reacted part of the sample, which can result in a selfsustained system where the reaction propagates through the sample without additional external input [5]

Results

Discussion

Conclusion