Adsorption of O-2 and C2Hn (n=2, 4, 6) on the Al9Co2(001) and o-Al13Co4(100) complex metallic alloy surfaces - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Applied Surface Science Année : 2015

Adsorption of O-2 and C2Hn (n=2, 4, 6) on the Al9Co2(001) and o-Al13Co4(100) complex metallic alloy surfaces

Résumé

Oxidation of the Al9CO2( 0 0 1) and Al13Co4(1 0 0) surfaces has been performed in a wide range of temperatures at 2 x 10(-8) or 1 x 10(-7) mbar oxygen pressure. Only Al-O bonding is observed. The oxidation kinetics are controlled by the quantity of oxygen sticking on the surface. Oxidation results from a competition between several effects: formation of an oxide film, dissolution of the film, oxygen desorption and oxygen dissolution into the bulk. For temperatures lower than 710 K for the Al9Co2(0 0 1) surface and 925 K for the Al13Co4(1 0 0) surface, a similar to 5 angstrom thick oxide film is formed which does not show any long-range order and desorbs upon annealing. When oxidation is performed at higher temperatures, oxygen diffusion into the bulk is observed. A poorly ordered oxide film having a sixton structure is formed on the Al9Co2(0 0 1) surface when oxidation is performed at 775 K, which is dissolved when annealing at higher temperatures. On the Al13Co4(1 0 0) surface, only a weak streaky polar circle is observed following annealing at 925 K the film formed at room temperature, which corresponds to an hexagonal network of O atoms into small ultrathin oxide layers domains. The oxidation behaviour of the Al9Co2(0 0 1) and Al13Co4(1 0 0) surfaces has been ascribed to the strong covalent character of bonds present in these Al-Co phases, which prevents aluminium diffusion. C2Hn molecules (n = 2, 4, 6) do not adsorb on the Al13Co4(1 0 0) surface in the experimental conditions used in this study, thus suggesting that this surface might not be the active one in the semi-hydrogenation of acetylene.
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Dates et versions

hal-01288102 , version 1 (14-03-2016)

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M. Warde, M. Herinx, J. Ledieu, L. N. Serkovic Loli, Vincent Fournée, et al.. Adsorption of O-2 and C2Hn (n=2, 4, 6) on the Al9Co2(001) and o-Al13Co4(100) complex metallic alloy surfaces. Applied Surface Science, 2015, 357 (B), pp.1666-1675. ⟨10.1016/j.apsusc.2015.10.001⟩. ⟨hal-01288102⟩
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