title: Elementary surface chemistry during CuO/Al nanolaminate-thermite synthesis: copper and oxygen deposition on aluminum (111) surfaces.
abstract: The surface chemistry associated with the synthesis of energetic nanolaminates controls the formation of the critical interfacial layers that dominate the performances of nanothermites. For instance, the interaction of Al with CuO films or CuO with Al films needs to be understood to optimize Al/CuO nanolaminates. To that end, the chemical mechanisms occurring during early stages of molecular CuO adsorption onto crystalline Al(111) surfaces are investigated using density functional theory (DFT) calculations, leading to the systematic determination of their reaction enthalpies and associated activation energies. We show that CuO undergoes dissociative chemisorption on Al(111) surfaces, whereby the Cu and O atoms tend to separate from each other. Both Cu and O atoms form islands with different properties. Copper islanding fosters Cu insertion (via surface site exchange mechanism) into the subsurface, while oxygen islands remain stable at the surface. Above a critical local oxygen coverage, aluminum atoms are extracted from the Al surface, leading to oxygen-aluminum intermixing and the formation of aluminum oxide (γ-alumina). For Cu and O co-deposition, copper promotes oxygen-aluminum interaction by oxygen segregation and separates the resulting oxide from the Al substrate by insertion into Al and stabilization below the oxide front, preventing full mixing of Al, Cu, and O species.
authors.affiliation: Laboratory of Analysis and Architecture of Systems, Centre National de la Recherche Scientifique , 7 Avenue du Colonel Roche, F-31400 Toulouse, France.
authors.forename: Cloé
authors.initials: C
authors.lastname: Lanthony
authors.forename: Mathilde
authors.initials: M
authors.lastname: Guiltat
authors.forename: Jean Marie
authors.initials: JM
authors.lastname: Ducéré
authors.forename: Agnes
authors.initials: A
authors.lastname: Verdier
authors.forename: Anne
authors.initials: A
authors.lastname: Hémeryck
authors.forename: Mehdi
authors.initials: M
authors.lastname: Djafari-Rouhani
authors.forename: Carole
authors.initials: C
authors.lastname: Rossi
authors.forename: Yves J
authors.initials: YJ
authors.lastname: Chabal
authors.forename: Alain
authors.initials: A
authors.lastname: Estève
keywords: Al/CuO nanolaminates; Al/CuO nanothermites; Cu and O co-deposition on Al(111); Cu on Al(111); DFT calculations; aluminum oxidation