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 stoichiometries and bilayer thicknesses. Al/CuO nanolaminates are deposited by a DC reactive magnetron sputtering method. Pure Al and Cu targets are used in argon-oxygen gas mixture 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 micrometer. 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 scanning calorimetry (DSC). Under stoichiometric conditions, the reactivity quickly increases with the decrease of Al/CuO bilayer thickness. The burning rate is 2 ms(-1) for bilayer thickness of 1.5 mm and reaches 80 ms(-1) for bilayer thickness 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 configuration was obtained for Al/CuO bilayer thickness of 150 nm.