Surface segregation of Cu and S in Ni-Cu(S) ternary alloy

The Ni_xCu_1-x alloy system has been extensively investigated due to its applications in catalysis and metallurgy. It has a simple phase diagram and forms a solid solution in the entire compositional range [1, 2]. The surface segregation of Cu and S in a Ni-21.3 at.% Cu alloy with 0.0007at.% S was measured by using Auger electron spectroscopy (AES) coupled with a linear programmed heater. The results showed that the Cu and S surface coverage reached maximum values of 41 at.% and 17 at.%, respectively. Once the Cu reached the maximum surface coverage, it started to desegregate until Cu was replaced by S. The measured segregation data were fitted by Fick’s and Guttmann’s ternary segregation models, yielding the segregation energy (ΔG), the interaction parameter (Ω), the pre-exponential factor (D₀) and the activation energy (Q) for both Cu and S elements. Based on these obtained segregation parameters, the whole segregation data were reevaluated by the modified Darken model.

References:

[1] T. Sakurai, T. Hashizume, A. Kobayashi, A. Sakai, S. Hyodo, Y. Kuk, H.W. Pickering, Surface segregation of Ni-Cu binary alloys studied by an atom-probe, Phys. Rev. B 34 (1986) 8379.

[2] X. L. Yan, J. Y. Wang, Size effects on surface segregation in Ni–Cu alloy thin films, Thin Solid Films 529 (2013) 483-487.