Research on structure of Al-Pt composites obtained by thermal oxidation of Al-Pt nano layers

What is it about?

The article presents the methodology for the Pt/Al and Pt/Al nanolaminates production as well as Pt + Al composites using two magnetrons by preparing the oxide-metal composites through high temperature oxidation of nanofilms deposited by PVD method on a metal substrate. In the paper were described the nanostructures obtained as a result of that technology. The applied layers were oxidized at a temperature of 860°C under Ar + O2 for 48 hours. SEM surface analysis of the obtained nanolamines showed that the base of the oxidized laminates was covered with a fine wafer and whisker structure with an anisotropic growth orientation. Oxidation of composite layers provided the growth of chaotically oriented and mutually penetrable whiskers and small crystals. Analysis of nanolayers by the TEM technique indicated that the growth of oxide crystals leads to the dissipation of Pt particles. The comparison of oxide layers obtained with the Pt/Al system with oxide layers obtained with Pt + Al composite nanofilms indicates that those obtained through the oxidation of nanofilms shows a greater surface development. This is due to the partial covering of Pt particles through the Al layer, which causes a very strong fragmentation of the Pt nanofilm occurring during oxidation. During the oxidation in the entire volume of nanofilms, strong stresses are created that cause numerous nano-cracks, which promotes the expansion of the surface and its high activity.

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Why is it important?

1. Tests on FeCrAl steel oxidation kinetics have shown that there is an optimal fraction of oxygen in the Ar/O2 atmosphere, which should not exceed 70% vol and where the greatest oxide weight gains for certain temperature-time conditions were found. 2. Tests on steel additionally coated with Al, Pt nanolayers, Pt/Al laminate and nanolayers of Pt+Al composite have revealed that the direct presence of Pt nanolayers on steel promotes the growth of the oxide layer so that it is comparable with the growth obtained for the Al layer. The catalytic effect of Pt on the oxide weight gain occurred clearly in the case of oxidation of the Pt/Al laminate layer, and to a lesser extent in the case of oxidation of the Pt+Al composite layer. This is due to the synergistic action of Pt and Al in the process of oxidation.