Magnetron Sputtered Al-CuO Nanolaminates: Effect of Stoichiometry and Layers Thickness on Energy Release and Burning Rate

This paper reports on the reaction characteristic of Al/CuO reactive nanolaminates for different stoichiome- tries and bilayer thicknesses. Al/CuO nanolaminates are de- posited by a DC reactive magnetron sputtering method. Pure Al and Cu targets are used in argon-oxygen gas mix- ture plasma and an oxygen partial pressure of 0.13 Pa. This process produces low stress multilayered materials, each layer being in the range of 25 nanometers to one microme- ter. Their structural, morphological, and chemical properties were characterized by high resolution transmission electron microscopy (HR-TEM), X-ray Diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The heat of reaction and onset temperature were measured using differential scan- ning calorimetry (DSC). Under stoichiometric conditions, the reactivity quickly increases with the decrease of Al/CuO bilayer thickness. The burning rate is 2 m s � 1 for bilayer thickness of 1.5 mm and reaches 80 m s � 1 for bilayer thick- ness of 150 nm. At constant heating rate, the Al/CuO heat of reaction depends on both stoichiometry and bilayer thickness. When the bilayer thickness exceeds 300 nm, the heat of reaction decreases; it seems that only the region near the interface reacts. The best nanolaminate configura- tion was obtained for Al/CuO bilayer thickness of 150 nm.