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  • 1.
    Braceras, Inigo
    et al.
    Tecnalia Res & Innovat, Mikeletegi Pasealekua 2, San Sebastian, Spain.
    Ibanez, Inigo
    Tecnalia Res & Innovat, Mikeletegi Pasealekua 2, San Sebastian, Spain.
    Taher, Mamoun
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Mao, Fang
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    del Barrio, Andres
    Tecnalia Res & Innovat, Mikeletegi Pasealekua 2, San Sebastian, Spain.
    Saenz De Urturi, Saioa
    Tecnalia Res & Innovat, Mikeletegi Pasealekua 2, San Sebastian, Spain.
    Berastegui, Pedro
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Anna M.
    ABB AB, Corp Res, Insulat & Mat Technol, SE-72178 Vasteras, Sweden.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    On the electro-tribological properties and degradation resistance of silver-aluminum coatings2018In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 414, p. 202-211Article in journal (Refereed)
    Abstract [en]

    Contact materials in sliding electrical applications must possess low electrical contact resistance, low friction and wear coefficients, and high degradation resistance to the surrounding media. Silver coatings are commonly used in such applications despite their shortcomings. This work has focused on the study of alternative silver-aluminum coatings deposited by PVD. The main findings include the strong dependence of the tribological performance on the concentration of Al and hence the phases present in the coatings. Besides, the wear mechanism was found to be affected by the working media, either on air or insulating oil. Results have shown that for full HCP phase coatings (Ag67Al33), wear rates are lowest, with no adhesive wear and good surface sulphidation resistance, though with some proclivity to oxidation, coupled with a moderate increase in the electrical contact resistance.

  • 2.
    Kryshtal, O.
    et al.
    AGH Univ Sci & Technol, Int Ctr Electron Microscopy Mat Sci, Comp Sci, Al Mickiewicza 30, PL-30059 Krakow, Poland;AGH Univ Sci & Technol, Fac Met Engn & Ind, Comp Sci, Al Mickiewicza 30, PL-30059 Krakow, Poland.
    Kruk, A.
    AGH Univ Sci & Technol, Int Ctr Electron Microscopy Mat Sci, Comp Sci, Al Mickiewicza 30, PL-30059 Krakow, Poland;AGH Univ Sci & Technol, Fac Met Engn & Ind, Comp Sci, Al Mickiewicza 30, PL-30059 Krakow, Poland.
    Mao, Fang
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Taher, Mamoun
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Corp Res, Insulat & Mat Technol, Abb Ab, Vasteras, Sweden.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Czyrska-Filemonowicz, A.
    AGH Univ Sci & Technol, Int Ctr Electron Microscopy Mat Sci, Comp Sci, Al Mickiewicza 30, PL-30059 Krakow, Poland;AGH Univ Sci & Technol, Fac Met Engn & Ind, Comp Sci, Al Mickiewicza 30, PL-30059 Krakow, Poland.
    Microstructure and phase composition of the Ag-Al film wear track: Through-thickness characterization by advanced electron microscopy2019In: Archives of Metallurgy and Materials, ISSN 1733-3490, E-ISSN 2300-1909, Vol. 64, no 1, p. 251-256Article in journal (Refereed)
    Abstract [en]

    Analytical transmission electron microscopy has been applied to characterize the microstructure, phase and chemical composition of the Ag-Al wear track throughout its thickness down to the atomic level. Microscopy findings have been correlated with Ag-Al film tribological properties to understand the effect of the hexagonal solid solution phase on the tribological properties of this film. Ag-25Al (at.%) films have been produced by simultaneous magnetron sputtering of components in Ar atmosphere under 1 mTorr pressure and subjected to pin-on-disc tribological tests. It has been shown that hcp phase with (001) planes aligned parallel to the film surface dominates both in as-deposited and in tribofilm areas of the Ag-Al alloy film. Possible mechanisms of reduced friction in easily oxidized Ag-Al system are discussed and the mechanism based on readily shearing basal planes of the hcp phase is considered as the most probable one.

  • 3.
    Mao, Fang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Taher, Mamoun
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Kryshtal, Oleksandr
    AGH Univ Sci & Technol, Int Ctr Electron Microscopy Mat Sci, Al A Mickiewicza 30, PL-30059 Krakow, Poland.;AGH Univ Sci & Technol, Fac Met Engn & Ind Comp Sci, Al A Mickiewicza 30, PL-30059 Krakow, Poland..
    Kruk, Adam
    AGH Univ Sci & Technol, Int Ctr Electron Microscopy Mat Sci, Al A Mickiewicza 30, PL-30059 Krakow, Poland.;AGH Univ Sci & Technol, Fac Met Engn & Ind Comp Sci, Al A Mickiewicza 30, PL-30059 Krakow, Poland..
    Czyrska-Filemonowicz, Aleksandra
    AGH Univ Sci & Technol, Int Ctr Electron Microscopy Mat Sci, Al A Mickiewicza 30, PL-30059 Krakow, Poland.;AGH Univ Sci & Technol, Fac Met Engn & Ind Comp Sci, Al A Mickiewicza 30, PL-30059 Krakow, Poland..
    Ottosson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Anna M.
    ABB AB, Corp Res, SE-72178 Vasteras, Sweden..
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Combinatorial Study of Gradient Ag-Al Thin Films: Microstructure, Phase Formation, Mechanical and Electrical Properties2016In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 8, no 44, p. 30635-30643Article in journal (Refereed)
    Abstract [en]

    A combinatorial approach is applied to rapidly deposit and screen Ag-Al thin films-to evaluate the mechanical, tribological, and electrical properties as a function of chemical composition. Ag-Al thin films with large continuous composition gradients (6-60 atom % Al) were deposited by a custom-designed combinatorial magnetron sputtering system. X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning and transmission electron microscopy (SEM and TEM), X-ray photoelectron spectroscopy (XPS), nanoindentation, and four-point electrical resistance screening were employed to characterize the chemical composition, structure, and physical properties of the films in a time-efficient way. For low Al contents (<13 atom %), a highly (111)-textured fcc phase was formed. At higher Al contents, a (002)-textured hcp solid solution phase was formed followed by a fcc phase in the most At-rich regions. No indication of a mu phase was observed. The Ag-Al films with fcc-Ag matrix is prone to adhesive material transfer leading to a high friction coefficient (>1) and adhesive wear, similar to the behavior of pure Ag. In contrast, the hexagonal solid solution phase (from ca. 15 atom %Al) exhibited dramatically reduced friction coefficients (about 15% of that of the fcc phase) and dramatically reduced adhesive wear when tested against the pure Ag counter surface. The increase in contact resistance of the Ag Al films is limited to only 50% higher than a pure Ag reference sample at the low friction and low wear region (19-27 atom %). This suggests that a hcp Ag Al alloy can have a potential use in sliding electrical contact applications and in the future will replace pure Ag in specific electromechanical applications.

  • 4.
    Taher, Mamoun
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. ABB AB, Corp Res, Insulat & Mat Technol, SE-72178 Vasterdas, Sweden.
    Mao, Fang
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Berastegui, Pedro
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Anna M.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    The Influence of Chemical and Phase Composition on Mechanical, Tribological and Electrical Properties of Silver-Aluminum alloys2018In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 119, p. 680-687Article in journal (Refereed)
    Abstract [en]

    Ag1-xAlx alloys were investigated as potential sliding electrical contact materials. Seven Ag1-xAlx alloys, covering the different phase regions on the Ag-Al phase diagram, were prepared by arc melting. X-ray diffraction (XRD), scanning electron microscopy coupled with X-ray spectroscopy (SEM/EDX), X-ray photoelectron spectroscopy (XPS), nano- and microindentation, and four-point electrical contact resistance measurements were employed to characterize the composition, structure, and physicochemical properties of the alloys. The hardness of Ag1-xAlx alloys increases with Al content. The Ag1-xAlx alloys with hexagonal close-packed (hcp) structure exhibit better tribological properties than pure Ag and other phase compositions. The wear mechanisms change from adhesive, for the alloys with low Al content (<= 20 at. %) to oxidative and abrasive wear for the alloys with high Al content (>= 25 at. %). The Ag1-xAlx alloys with hcp structure exhibit the highest wear resistance. Depth-profile XPS data reveal that the oxide layer grows during the triboprocess and that its thickness increases with number of sliding cycles. Ag/Ag1-xAlx contact pairs exhibit higher contact resistance than the Ag/Ag pair and the contact resistance increases with Al content.

  • 5.
    Taher, Mamoun
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Mao, Fang
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Berastegui, Pedro
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Andersson, Anna M.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Tuning tribological, mechanical and electrical properties of Ag-X (X=Al, In, Sn) alloys2018In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 125, p. 121-127Article in journal (Refereed)
    Abstract [en]

    A new design concept for silver based alloys with a hexagonal structure as electrical contact materials with enhanced tribological properties has been investigated. The correlations between the phase composition and the tribological properties have been investigated in the Ag-Al, Ag-In and Ag-Sn systems. In each system, alloys with different chemical compositions were prepared by melting in evacuated ampoules. Characterisation techniques such as: optical microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning and transmission electron microscopies (SEM and TEM) have been used to evaluate the microhardneas, tribological properties and contact resistance of the samples. The phase compositions of the synthesized Ag-Al and Ag-Sn alloys were in agreement with the phase diagrams and the metastable hcp phase was observed in the Ag-In system. The friction coefficients and wear rates of all the hcp-Ag-X (X = Al, In, Sn) alloys were considerably lower than pure Ag or fcc-Ag alloys. This is attributed mainly to easily shearing basal planes in the hcp structure. The Ag-Sn alloys showed high contact resistances, making them less suitable for a sliding electrical contacts. In contrast, the Ag-In alloys showed much lower contact resistance, making them better alternatives for practical applications.

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