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Electron Probe and Auger Electron Microprobe Characterization of Modified Cu-Based Amorphous Alloys

Published online by Cambridge University Press:  01 August 2003

A. Szummer
Affiliation:
Faculty of Materials Science and Engineering, Technical University, Woloska 141, 02-507 Warsaw, Poland
M. Janik-Czachor
Affiliation:
Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
P. Mack
Affiliation:
Thermo VG Scientific, East Grinstead, West Sussex RH19 1UB, England
M. Pisarek
Affiliation:
Faculty of Materials Science and Engineering, Technical University, Woloska 141, 02-507 Warsaw, Poland
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Abstract

Changes in morphology and local chemical composition due to various methods of modification of surfaces of Cu-Zr, Cu-Hf, and Cu-Ti amorphous alloys (caused by aging in air/dry corrosion or hydrogen charging) were investigated. These modification/activation procedures transform the original amorphous ribbons of low surface area into efficient and stable catalysts, due to the segregation of a distinct amount of Cu and the development of a large specific surface area of Cu on a ZrOx or HfOx support. It was found that aging in air resulted in the formation of a bilayer of rough copper (containing small Cu particles indispensable for catalysis) on top of a rather smooth oxide underlayer (ZrOx, HfOx). Careful examination of the cross sections of the modified Cu-based ribbons revealed that, even after prolonged aging in air, only the first few microns of the surface layer was modified. Cu-Ti alloy was stable in air and did not undergo the expected modification. Hydrogenation followed by air exposure resulted in a disintegration of the ribbons into small pieces. Each piece was covered with many small Cu clusters 0.1–0.5 μm in diameter formed on an oxide underlayer. High-energy resolution Auger spectroscopy allowed identification of the underlayers (ZrO2, HfO2, or TiOx), identification of small Cu clusters, determination of the degree of surface oxidation of them, and mapping of the surface to identify the Cu-covered and “naked” heavy metal.

Type
Fifth EMAS Regional Workshop: Electron Probe Microanalysis Today—Practical Aspects
Copyright
© 2003 Microscopy Society of America

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