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Effect of Ageing in Air/Corrosion on Morphology and Catalytic Properties of Cu-Based Amorphous Alloy Ribbons

Investigations of the surfaces of Cu-based amorphous alloy ribbons exposed to air at room temperature for various periods of time in a laboratory atmosphere (ageing in air/corrosion) are reported. Various methods of analysis like X-ray electron microanalysis, SEM, XRD, electrochemistry and surface analysis (AES), with various lateral resolutions and different information depth, were used. It was found for the Cu-Zr and Cu-Hf ribbons that the corrosion processes start on the wheel side of the ribbon, where the original surface oxide layer is defective. As a result of ageing and devitrification a multilayer of Cu/XO 2 (X=Zr or Hf), encompassing of ∼ 10% of the ribbon thickness is formed. In contrast, the Cu-Ti alloy retains its metallic luster, with no distinct Cu segregation and morphological changes. The present investigations point to the role of oxidation/corrosion of the amorphous alloys in the initiation of the devitrification process and in the development of the resulting morphology. Catalytic tests revealed that only the Cu-Zr and Cu-Hf ribbons with a distinct segregation of Cu on the surface are catalytically active materials.