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  • 1.
    Berastegui, Pedro
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Tai, Cheuk-Wai
    Stockholm University.
    Valvo, Mario
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Electrochemical reactions of AgFeO2 as negative electrode in Li- and Na-ion batteries2018In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 401, p. 386-396Article in journal (Refereed)
    Abstract [en]

    AgFeO2 nanoparticles synthesized via precipitation at room temperature are investigated in Li- and Na-ion cells through electrode coatings with an alginate binder. The electrochemical reactions of AgFeO2 with Li+ and Na+ions, as well as its role as alternative negative electrode in these cell systems are carefully evaluated. Initial Li uptake causes irreversible amorphization of the AgFeO2 structure with concomitant formation of Ag0 nanoparticles. Further Li incorporation results in conversion into Fe0 nanoparticles and Li2O, together with Li-alloying of these Ag0 clusters. Similar mechanisms are also found upon Na uptake, although such processes are hindered by overpotentials, the capacity and reversibility of the reactions with Na+ ions being not comparablewith those of their Li+ counterparts. The behaviour of AgFeO2 at low potentials vs. Li+/Li displays a synergic pseudo-capacitive charge storage overlapping Li-Ag alloying/de-alloying. This feature is exploited in full cells having deeply lithiated AgFeO2 and LiFePO4 as negative and positive electrodes, respectively. These environmentally friendly iron-based full cells exhibit attractive cycle performances with ≈80% capacity retention after 1000 cycles without any electrolyte additive, average round trip efficiency of ≈89% and operational voltage of 3.0 V combined with built-in pseudo-capacitive characteristics that enable high cycling rates up to≈25C.

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  • 2.
    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.

  • 3.
    Fang, Hailiang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Cedervall, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Casado, Francisco Javier Martinez
    Lund Univ, MAX IV Lab, Box 118, S-22100 Lund, Sweden..
    Matej, Zdenek
    Lund Univ, MAX IV Lab, Box 118, S-22100 Lund, Sweden..
    Bednarcik, Jozef
    Deutsch Elektronen Synchrotron DESY, Notkestr 85, D-22603 Hamburg, Germany..
    Ångstrom, Jonas
    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.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Insights into formation and stability of tau-MnAlZ(x) (Z = C and B)2017In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 692, p. 198-203Article in journal (Refereed)
    Abstract [en]

    The tau-phase MnAl alloys are promising candidate for rare earth free permanent magnets. In this study, In order to better understand the MnAl epsilon ->tau phase transition mechanism in a continuous cooling process and metastable MnAl tau-phase high temperature stability, Mn0.54Al0.46, Mn0.55Al0.45C0.02 and Mn0.55Al0.45B0.02 alloys were systematically studied by in situ synchrotron X-ray powder diffraction (SR-XRD). The relationship between tau-phase formation tendency and different cooling rates of Mn0.55Al0.45C0.02 was investigated. Besides, the high temperature stabilities of undoped tau-MnAl and carbon/boron doped tau-MnAl were studied. Differential thermal analysis (DTA) was also employed to study the phase transformation as well. The research results show that a high cooling rate of 600 degrees C/min leads to a 50/50 wt% mixture of epsilon- and tau-phase; almost pure tau-phase was obtained when cooled at a moderate cooling rate of 10 degrees C/min; while for a slow cooling rate of 2 degrees C/min, the tau-phase partially decomposed into beta and gamma(2) phases. No intermediate epsilon'-phase was observed during the epsilon ->tau phase transition during the experiments. For the boron and carbon doped tau-MnAl, the 800 degrees C high temperature stability experiments reveal that C stabilizes the tau-MnAl while doped B destabilises the tetragonal structure and it decomposes into beta- and gamma(2)-phases.

  • 4.
    Hedin, Allan
    et al.
    SKB, Swedish Nucl Fuel & Waste Management Co, SE-10124 Stockholm, Sweden.
    Johansson, Adam Johannes
    SKB, Swedish Nucl Fuel & Waste Management Co, SE-10124 Stockholm, Sweden.
    Lilja, Christina
    SKB, Swedish Nucl Fuel & Waste Management Co, SE-10124 Stockholm, Sweden.
    Boman, Mats
    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.
    Berger, Rolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Ottosson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Corrosion of copper in pure O2-free water?2018In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 137, p. 1-12Article in journal (Refereed)
    Abstract [en]

    Copper exposed to pure, O-2-free water for several months in glass- and metal-contained, well-controlled systems shows no evidence of corrosion, either through hydrogen evolution or through the occurrence of oxidized copper. The results contradict the interpretation of recent experiments where it has been claimed that copper corrodes in pure, O-2-free water far above the very limited extent predicted by established thermodynamic data. Reasons for the different experimental outcomes are discussed. Experimental and theoretical efforts to identify hitherto unknown, potentially corrosion driving species of the Cu-O-H system and studies of copper/water surface reactions are reviewed as background for the present study.

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  • 5.
    Kádas, Krisztina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Iusan, Diana
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Hellsvik, J.
    Royal Inst Technol KTH, Sch Informat & Commun Technol, Dept Mat & Nanophys, Elect 229, S-16440 Kista, Sweden..
    Cedervall, Johan
    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.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    AlM2B2 (M =Cr, Mn, Fe, Co, Ni): a group of nanolaminated materials2017In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 29, no 15, article id 155402Article in journal (Refereed)
    Abstract [en]

    Combining theory with experiments, we study the phase stability, elastic properties, electronic structure and hardness of layered ternary borides AlCr2B2, AlMn2B2, AlFe2B2, AlCo2B2, and AlNi2B2. We find that the first three borides of this series are stable phases, while AlCo2B2 and AlNi2B2 are metastable. We show that the elasticity increases in the boride series, and predict that AlCr2B2, AlMn2B2, and AlFe2B2 are more brittle, while AlCo2B2 and AlNi2B2 are more ductile. We propose that the elasticity of AlFe2B2 can be improved by alloying it with cobalt or nickel, or a combination of them. We present evidence that these ternary borides represent nanolaminated systems. Based on SEM measurements, we demonstrate that they exhibit the delamination phenomena, which leads to a reduced hardness compared to transition metal mono-and diborides. We discuss the background of delamination by analyzing chemical bonding and theoretical work of separation in these borides.

  • 6.
    Mockute, A.
    et al.
    Linkoping Univ, Dept Phys Chem & Biol IFM, Thin Film Phys Div, SE-58183 Linkoping, Sweden..
    Palisaitis, J.
    Linkoping Univ, Dept Phys Chem & Biol IFM, Thin Film Phys Div, SE-58183 Linkoping, Sweden..
    Alling, B.
    Linkoping Univ, Dept Phys Chem & Biol IFM, Thin Film Phys Div, SE-58183 Linkoping, Sweden.;Max Planck Inst Eisenforsch GmbH, D-40237 Dusseldorf, Germany..
    Berastegui, Pedro
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Broitman, E.
    Linkoping Univ, Dept Phys Chem & Biol IFM, Thin Film Phys Div, SE-58183 Linkoping, Sweden..
    Naslund, L. -A
    Nedfors, N.
    Linkoping Univ, Dept Phys Chem & Biol IFM, Thin Film Phys Div, SE-58183 Linkoping, Sweden..
    Lu, J.
    Linkoping Univ, Dept Phys Chem & Biol IFM, Thin Film Phys Div, SE-58183 Linkoping, Sweden..
    Jensen, J.
    Linkoping Univ, Dept Phys Chem & Biol IFM, Thin Film Phys Div, SE-58183 Linkoping, Sweden..
    Hultman, L.
    Linkoping Univ, Dept Phys Chem & Biol IFM, Thin Film Phys Div, SE-58183 Linkoping, Sweden..
    Patscheider, J.
    EMPA, Lab Nanoscale Mat Sci, Uberlandstr 129, CH-8600 Dubendorf, Switzerland..
    Jansson, U.
    Uppsala Univ, Angstrom Lab, Dept Chem Mat, POB 583, SE-75121 Uppsala, Sweden..
    Person, P. O. A.
    Linkoping Univ, Dept Phys Chem & Biol IFM, Thin Film Phys Div, SE-58183 Linkoping, Sweden..
    Rosen, J.
    Linkoping Univ, Dept Phys Chem & Biol IFM, Thin Film Phys Div, SE-58183 Linkoping, Sweden..
    Age hardening in (Ti1-xAlx)B2+Delta thin films2017In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 127, p. 122-126Article in journal (Refereed)
    Abstract [en]

    Thin films of (Ti0.71Al0.29)B2+1.08 have been deposited by magnetron sputtering. Post-deposition annealing at 1000 degrees C for 1 h results in increased hardness and elastic modulus, from 32 to 37 GPa and from 436 to 461 GPa, respectively. In both as-deposited and annealed states the films adhere well to the substrate, indicating no considerable internal stress. The initial high hardness is attributed to a columnar microstructure consisting of crystalline (Ti,Al)B-2 columns separated by an amorphous B matrix. The observed age hardening corresponds to phase separation within the (Ti,Al)B-2 columns including the formation of Ti-deficient crystallites within the grain interior upon annealing.

  • 7.
    Mockute, A.
    et al.
    Linkoping Univ, Thin Film Phys Div, Dept Phys Chem & Biol IFM, S-58183 Linkoping, Sweden.
    Palisaitis, J.
    Linkoping Univ, Thin Film Phys Div, Dept Phys Chem & Biol IFM, S-58183 Linkoping, Sweden.
    Nedfors, N.
    Linkoping Univ, Thin Film Phys Div, Dept Phys Chem & Biol IFM, S-58183 Linkoping, Sweden.
    Berastegui, Pedro
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Broitman, E.
    Linkoping Univ, Thin Film Phys Div, Dept Phys Chem & Biol IFM, S-58183 Linkoping, Sweden;SKF Res & Technol Dev Ctr, NL-3439 MT Nieuwegein, Netherlands.
    Alling, B.
    Linkoping Univ, Thin Film Phys Div, Dept Phys Chem & Biol IFM, S-58183 Linkoping, Sweden.
    Näslund, L-A
    Linkoping Univ, Thin Film Phys Div, Dept Phys Chem & Biol IFM, S-58183 Linkoping, Sweden.
    Hultman, L.
    Linkoping Univ, Thin Film Phys Div, Dept Phys Chem & Biol IFM, S-58183 Linkoping, Sweden.
    Patscheider, J.
    Evatec AG, Hauptstr 1a, CH-9477 Trubbach, Switzerland.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Persson, P. O. A.
    Linkoping Univ, Thin Film Phys Div, Dept Phys Chem & Biol IFM, S-58183 Linkoping, Sweden.
    Rosen, J.
    Linkoping Univ, Thin Film Phys Div, Dept Phys Chem & Biol IFM, S-58183 Linkoping, Sweden.
    Synthesis and characterization of (Ti1-xAlx)B2+Delta thin films from combinatorial magnetron sputtering2019In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 669, p. 181-187Article in journal (Refereed)
    Abstract [en]

    (Ti1-xAlx)B2+Delta films with a lateral composition gradient of x = [0.30-0.66] and Delta = [0.07-1.22] were deposited on an Al2O3 wafer by dual magnetron sputtering at 400 degrees C from sintered TiB2 and AlB2 targets. Composition analysis indicates that higher Ti:Al ratios favor overstoichiometry in B and a reduced incorporation of O. Transmission electron microscopy reveals distinctly different microstructures of Ti- and Al-rich compositions, with formation of characteristic conical growth features for the latter along with a lower degree of crystallinity and significantly less tissue phase from B segregation at the grain boundaries. For Al-rich films, phase separation into Ti- and Al-rich diboride nanometer-size domains is observed and interpreted as surface-initiated spinodal decomposition. The hardness of the films ranges from 14 to 28 GPa, where the higher values were obtained for the Ti-rich regions of the metal boride.

  • 8.
    Ottosson, Mikael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Boman, Mats
    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, Yvonne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Hahlin, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Korvela, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Berger, Rolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Response to the comments by P. Szakalos, T. angstrom kermark and C. Leygraf on the paper "Copper in ultrapure water, a scientific issue under debate"2018In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 142, p. 308-311Article in journal (Other academic)
  • 9.
    Ottosson, Mikael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Boman, Mats
    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, Yvonne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Hedlund, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Korvela, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Berger, Rolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Copper in ultrapure water, a scientific issue under debate2017In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 122, p. 53-60Article in journal (Refereed)
    Abstract [en]

    The corrosion properties of copper in ultrapure water have been studied experimentally by submerging copper samples (99.9999%) in pure water for up to 29 months. The surface was first electropolished at ambient temperature, then exposed to hydrogen gas treatment at 300-400 degrees C, thereby reducing the bulk hydrogen content to 0.03 ppm. These copper samples, the water and the glassware were all then subjected to precise chemical analysis. Great care was taken to avoid contamination. After exposure, only similar to 6 mu g/L copper had accumulated in the water phase. Electron spectroscopy could not detect Cu2O or any other oxidation products containing copper.

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  • 10.
    Pacheco, Victor
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lindwall, Greta
    KTH Royal Inst Technol, Dept Mat Sci & Engn, SE-10044 Stockholm, Sweden.
    Karlsson, Dennis
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Cedervall, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Fritze, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Ek, Gustav
    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.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Thermal Stability of the HfNbTiVZr High-Entropy Alloy2019In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 58, no 1, p. 811-820Article in journal (Refereed)
    Abstract [en]

    The multicomponent alloy HfNbTiVZr has been described as a single-phase high-entropy alloy (HEA) in the literature, although some authors have reported that additional phases can form during annealing. The thermal stability of this alloy has therefore been investigated with a combination of experimental annealing studies and thermodynamic calculations using the CALPHAD approach. The thermodynamic calculations show that a single-phase HEA is stable above about 830 degrees C. At lower temperatures, the most stable state is a phase mixture of bcc, hcp, and a cubic C15 Laves phase. Annealing experiments followed by quenching confirm the results from thermodynamic calculations with the exception of the Laves phase structure, which was identified as a hexagonal C14 type instead of the cubic C15 type. Limitations of the applied CALPHAD thermodynamic description of the system could be an explanation for this discrepancy. As-synthesized HfNbTiVZr alloys prepared by arc-melting form a single-phase bcc HEA at room temperature. In situ annealing studies of this alloy show that additional phases start to form above 600 degrees C. This indicates that the observed HEA is metastable at room temperature and stabilized by a slow kinetics during cooling. X-ray diffraction analyses using different cooling rates and annealing times show that the phase transformations in this HEA are slow and that completely different phase compositions can be obtained depending on the annealing procedure. In addition, it has been shown that the sample preparation method (mortar grinding, heat treatment, etc.) has a significant influence on the collected diffraction patterns and therefore on the phase identification and analysis.

  • 11.
    Rebrova, N. V.
    et al.
    Natl Acad Sci Ukraine, Inst Scintillat Mat, Nauky Ave 60, UA-61072 Kharkov, Ukraine.
    Grippa, A. Yu.
    Natl Acad Sci Ukraine, Inst Scintillat Mat, Nauky Ave 60, UA-61072 Kharkov, Ukraine.
    Boiaryntseva, I. A.
    Natl Acad Sci Ukraine, Inst Scintillat Mat, Nauky Ave 60, UA-61072 Kharkov, Ukraine.
    Berastegui, Pedro
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Gorbacheva, T. E.
    Natl Acad Sci Ukraine, Inst Scintillat Mat, Nauky Ave 60, UA-61072 Kharkov, Ukraine.
    Pedash, V. Yu.
    Natl Acad Sci Ukraine, Inst Scintillat Mat, Nauky Ave 60, UA-61072 Kharkov, Ukraine.
    Galkin, S. N.
    Natl Acad Sci Ukraine, Inst Scintillat Mat, Nauky Ave 60, UA-61072 Kharkov, Ukraine.
    Kononets, V. V.
    Natl Acad Sci Ukraine, Inst Scintillat Mat, Nauky Ave 60, UA-61072 Kharkov, Ukraine.
    Datsko, Yu. N.
    Natl Acad Sci Ukraine, Inst Scintillat Mat, Nauky Ave 60, UA-61072 Kharkov, Ukraine.
    Cherginets, V. L.
    Natl Acad Sci Ukraine, Inst Scintillat Mat, Nauky Ave 60, UA-61072 Kharkov, Ukraine.
    Crystal growth and characterization of Eu2+ doped Cs1-xRbxCaBr32020In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 816, article id 152594Article in journal (Refereed)
    Abstract [en]

    A series of Eu2+ doped Cs1-xRbxCaBr3 solid solutions were grown using the Bridgman-Stockbarger technique. Their photoluminescence and scintillation properties are studied. Upon optical and X-ray excitation, the Cs1-xRbxCaBr3 and Eu2+ activated samples show a band, which can be attributed to the 5d-4f transition in Eu2+. The decay time constants become shorter with increasing Rb content and lie in the range of 3-4 mu s. The scintillation performance of solid solutions Cs1-xRbxCa0. 95Eu0.05Br3 is improved compared with the end members (CsCa0.95Eu0.05Br3 and RbCa0.95Eu0.05Br3). The best energy resolution of 6.4% at 662 keV was determined for Cs0.2Rb0.8Ca0.95Eu0.05Br3 , and the best light yield, equal to 61.2% of Nal:TI, was demonstrated by Cs0.4Rb0.6Ca0.95Eu0.05Br3.

  • 12.
    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.

  • 13.
    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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