Effects of the total thickness of multilayer thermite materials Al/CuO on the combustion mode and morphology of reaction products

Abstract The multilayer thermite material Al/CuO is an outstanding representative of metastable intermolecular composites characterized by excellent energy and combustible properties. However, the combustion of such a material is accompanied by intensive release of gas and spraying products. In this work, it is demonstrated that in a certain thickness range (2–3 μ m) of the multilayer thermite material (Al/CuO) n formed on the surface of Sitall substrates, the reaction products remain on the surface of the substrate in the form of composite entities, in some cases resembling ladybugs. By means of high-speed video shooting from different angles, the propagation velocity of the combustion front was measured and the intensity of gas release was visually assessed depending on the thickness of the multilayer structure (Al/CuO) n . The spraying products effect becomes significant for multilayer structures (Al/CuO) 40 with a total thickness of 4 μ m. It was found that the propagation velocity of the combustion front increases with the thickness of the multilayer structure (Al/CuO) n until the effect of spraying products intensifies. The morphology and composition of the combustion products of multilayer structures were studied using scanning electron microscopy in combination with focused ion beam and energy-dispersive x-ray spectroscopy. In particular, it was found that in many cases, the composite entities are hollow inside and consist of an aluminum oxide framework, rounded fuses of metallic copper, and fragments of unreacted film multilayers. As a result of the analysis of experimental data, two combustion modes of multilayer thermocomposite materials on a substrate were described depending on the temperature of the combustion front, which are related to the thickness of the multilayer structure.