Copper surface enrichment of AgCu alloys

Abstract

We summarise the X-ray electron spectroscopy (XPS) study of changing surface composition of polycrystalline Ag-2.2 mass% Cu and Ag-5.1 mass% Cu alloys during in situ annealing at chosen temperatures ranging from 300 to 600• C. The results show obvious surface enrichment by copper, which is different for individual alloys. The contradiction of this result to general knowledge on preferential silver segregation can be explained on basis of attractive interaction of copper with oxygen and of accelerated diffusion of copper to the surface resulting in final copper surface enrichment.

Technical Analysis, Laser Cleaning and Numismatic Study of Tarnished Abbasid Silver Dirham from the 4th C A.H. (10th A.D)

“…With LIPS analysis, a semi-quantitative evaluation of the bulk composition, in correspondence of the last fifty laser pulses, can be performed assuming a binary alloy (Ag-Cu) composition (neglecting other minor components) and using previously calculated LIPS calibration curves where the calculated copper concentration amounts to 4.4 (0.4 wt%). The absence of lead in the chemical composition of the coin may indicate improvement of the production process and deliberate removal to avoid longterm embrittlement of the silver alloy 3 .…”

“…Different cleaning methods have been tested for cleaning tarnished and corroded silver 2 . Mechanical, chemical, and electrochemical cleaning methods showed moderate and inhomogeneous cleaning effectiveness and aggressiveness on silver objects with need of special set up 3 . Laser, comparing to other traditional techniques, could be more controllable, non-contact, very selective and self-limiting cleaning technique, when optimized can provide a satisfactory cleaning of the archaeological delicate and sensitive silver surfaces without involvement of mechanical actions 4 .…”

Kinetics of surface enrichment: A molecular dynamics study

“…However, the surface becomes enriched in the preferred component, resulting in a time-dependent surface-enrichment (SE) profile, which propagates into the bulk. This phenomenon of SE is well known in the context of polymer blends [17,18,19,20,21,22] and biopolymer mixtures [23], binary alloys [24,25], and the wetting of surfaces of fluids [4,26].…”

Non-destructive handheld XRF study of archaeological composite silver objects—the case study of the late Roman Seuso Treasure

“…Surface enrichment of silver alloys is a well-known phenomenon, during which base metals (e.g. copper and lead) are leached out from the surface, while silver and gold are enriched towards the surface (Hall 1961;Lejček et al 2010), artificially exaggerating the silver and gold content at the expense of copper. Therefore, non-destructive surface analytical results, like hXRF data, may not represent the core metal composition.…”