Surface segregation and oxidation studies on Cu-Ni-Sn and Ag-Cu-Ge ternary alloys

Abstract

Surface segregation and oxidation of Cu-9.7at%Ni-2.3at%Sn and Ag-39at%Cu-1.6at%Ge ternary alloys have been carried out employing XPS and AES techniques. Segregation of both Ni and Sn have been observed on the surface of Cu-Ni-Sn alloy. On oxidation of this alloy at 500 K, Cu₂O, NiO and SnO have been observed and on heating the oxidized alloy in vacuum to 600 K, Cu₂O was reduced to Cu through a displacement reaction involving Ni. Further heating to 750 K showed only SnO₂ along with the reduction of NiO to Ni. The Ag-Cu-Ge alloy showed segregation of both Ag and Ge to the surface. On oxidation at 500 K, only Cu₂O and GeO have been observed. Heating of the oxidized surface to 700 K in vacuum showed desorption of GeO, coupled with the reduction of Cu₂O to Cu, thereby leaving the alloy surface clean.