Nanocomposites alumina/Pt produced by PVD and thermal oxidation methods used in catalytic applications

The work was focused on the deposition of Al₂O₃+Pt composite in the form of a nanofilm adherent to the substrate with good surface development and catalytic properties on the surface of 0H20J5 foil. With this end in view, a special carousel fixture for fixing the corrugated and flat foil and then coating with Al and Pt from two magnetron sources, in order to obtain a nanofilm of Al+Pt composite, was designed. A Pt/Al laminate layer was also produced by depositing Pt first and then Al, and the other way round. The layer systems obtained this way were subject to oxidation for 48 h at 860 °C and under Ar+O₂. The surface examined has shown that the process of oxidation produces the compact sublayer of columnar crystals (whiskers) well adherent to the substrate from which the needle-like whiskers are growing. Structures of whiskers form a laminar system with a catalytic element having a very-well developed surface. Structure analyses revealed that the films obtained comprised mostly α and θ Al₂O₃ phases and missed a Pt crystalline phase. The film morphology on the basis of oxide-film sections examined by TEM showed that the α Al₂O₃ structure was generated mostly deep in oxide films and was integrated with the foil. A microanalysis showed that it was uniformly distributed in its entirety in the Pt-composite based layers; however, in the case of laminate the surface of whiskers was coated. It was found from the comparison of the laminar system activity that the composite layers revealed much better catalytic properties at lower temperature than the laminate layers.