SURFACE COMPOSITION OF CU-LI ALLOYS - THE INFLUENCE OF OXYGEN ON BOMBARDMENT AND SEGREGATION EFFECTS
Cu-Li alloys are considered as first-wall material in fusion devices because they may possibly reduce the sputtering of a high Z material (Cu) due to a segregated surface layer of Li. Reduced Cu sputtering rates have been found under certain conditions. The surface compositions of alloys ranging from 6 to 24 at % in Li content are analysed using ion scattering spectroscopy (ISS) and Auger electron spectroscopy (AES). The varying information depths of both techniques allow the analysis of the near surface depth distribution of Li. At room temperature Li segregation to the surface is observed, the segregation rate depending on the bulk composition. It is influenced by the bulk oxygen impurity concentration, which is detected by nuclear reaction analysis. Under ion bombardment the Li surface concentration is reduced and the steady state composition can be described by the balance between sputtering and segregation. A change from He(+) to Ar(+) ions results in increased Li depletion as expected from the increased sputtering yield. Some consequences for the usefulness of these alloys for first-wall material are discussed.
Bibliographic Reference: EXTRACT: JOURNAL OF NUCLEAR MATERIALS, VOL. 162-164 (1989) PP. 920-923, NORTH-HOLLAND, AMSTERDAM (NL)
Record Number: 1989128067800 / Last updated on: 1990-11-09
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