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Diplom- und Master-Arbeiten (eigene und betreute):

E. Lübke:
"Investigating Corrosion Processes in Ag-Cu Alloys";
Betreuer/in(nen): C. Gierl-Mayer, K. Hradil; X-Ray Center, 2021; Abschlussprüfung: 24.08.2021.



Kurzfassung englisch:
The Vienna Genesis, an artifact produced in the 6th century, is a manuscript written on parchment using silver ink and it has survived to this day. This silver ink corroded and partly damaged the parchment it was written on, threatening to destroy the manuscript. To understand the processes causing this damage, investigations using non-destructive X-ray methods were carried out.
It was attempted to reproduce the observed corrosion while measuring the reactions happening with in-situ powder X-ray diffraction using laboratory instruments. Silver-copper alloys matching the composition of the original inks were prepared in-situ by reducing an oxide-based precursor mixture with hydrogen gas. These alloys were corroded using pressurized air and brine spray at nonambient temperatures and the resulting diffraction patterns were refined using the Rietveld method.
While the corrosion products found did not match with the Vienna Genesis, oxygen induced segregation of the alloys above 200 °C was observed. This effect was investigated further by varying the composition of the alloy and corrosive agents as well as including an internal standard to obtain precise data on the lattice parameter of the segregated species.
It was found that in silver-copper alloys, the lattice parameter a of the fcc-silver phase increases during the segregation process to a larger value than pure silver. This result was confirmed by the addition of a standard reference material and measurements using parallel beam optics to circumvent the specimen displacement error.
No conclusive explanation for this effect was found, but a higher than predicted oxygen content was measured in segregated samples, which implies oxygen causing the observed lattice change. More research is required to fully explain the observed behaviour and its effects on the physical properties of the segregated material. This might offer new insights into the effects of oxygen induced segregation, which currently limit the application of Ag-Cu alloys as conductors, solders, etc.

Schlagworte:
Ag-Cu Legierung, Korrosion, XRD


Elektronische Version der Publikation:
https://publik.tuwien.ac.at/files/publik_296926.pdf


Erstellt aus der Publikationsdatenbank der Technischen Universität Wien.