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  • 1.
    Casillas-Trujillo, Luis
    et al.
    Linköping Univ, Dept Phys Chem & Biol IFM, SE-58183 Linköping, Sweden..
    Osinger, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Karlsson, Dennis
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Abrikosov, Alexei I.
    Linköping Univ, Dept Sci & Technol, SE-58183 Norrköping, Sweden..
    Fritze, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    von Fieandt, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Alling, Björn
    Linköping Univ, Dept Phys Chem & Biol IFM, SE-58183 Linköping, Sweden..
    Hotz, Ingrid
    Linköping Univ, Dept Sci & Technol, SE-58183 Norrköping, Sweden..
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Abrikosov, Igor A.
    Linköping Univ, Dept Phys Chem & Biol IFM, SE-58183 Linköping, Sweden.;Natl Univ Sci & Technol MISIS, Mat Modelling & Dev Lab, Moscow 119049, Russia..
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Experimental and theoretical evidence of charge transfer in multi-component alloys: how chemical interactions reduce atomic size mismatch2021In: Materials Chemistry Frontiers, E-ISSN 2052-1537, Vol. 5, no 15, p. 5746-5759Article in journal (Refereed)
    Abstract [en]

    Ab initio simulations of a multi-component alloy using density functional theory (DFT) were combined with experiments on thin films of the same material using X-ray photoelectron spectroscopy (XPS) to study the connection between the electronic and atomic structures of multi-component alloys. The DFT simulations were performed on an equimolar HfNbTiVZr multi-component alloy. Structure and charge transfer were evaluated using relaxed, non-relaxed, as well as elemental reference structures. The use of a fixed sphere size model allowed quantification of charge transfer, and separation into different contributions. The charge transfer was generally found to follow electronegativity trends and results in a reduced size mismatch between the elements, and thus causes a considerable reduction of the lattice distortions compared to a traditional assumption based on tabulated atomic radii. A calculation of the average deviation from the average radius (i.e. the so-called δ-parameter) based on the atomic Voronoi volumes gave a reduction of δ from ca. 6% (using the volumes in elemental reference phases) to ca. 2% (using the volumes in the relaxed multi-component alloy phase). The reliability of the theoretical results was confirmed by XPS measurements of a Hf22Nb19Ti18V19Zr21 thin film deposited by sputter deposition. The experimentally observed core level binding energy shifts (CLS), as well as peak broadening due to a range of chemical surroundings, for each element showed good agreement with the calculated DFT values. The single solid solution phase of the sample was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) including energy dispersive spectroscopy (EDS) with nm-resolution. These observations show that the HfNbTiVZr solid solution phase is non-ideal, and that chemical bonding plays an important part in the structure formation, and presumably also in the properties. Our conclusions should be transferable to other multi-component alloy systems, as well as some other multi-component material systems, and open up interesting possibilities for the design of material properties via the electronic structure and controlled charge transfer between selected metallic elements in the materials.

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  • 2.
    Fritze, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Microstructure and Mechanical Properties of Magnetron Sputtered Refractory Metal Thin Films2020Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The design and development of new multifunctional materials that exhibit a combination of high hardness and ductility, as well as a high corrosion resistance and thermal stability, is one of the key challenges in the field of material science. The focus of this thesis is on the development of novel multifunctional magnetron sputtered CrNbTaTiW–C based thin films. Carbon was selected as an alloying element to investigate if it could modify the microstructure (via grain refinement) and improve the properties (e.g. the hardness and ductility).

    TaW-rich and near-equimolar high entropy alloys in the CrNbTaTiW system were selected as starting points for this study. The latter alloys were predicted, based on empirical design rules, to form a single-phase solid solution. In contrast, thermodynamic calculations showed that the films at equilibrium should be composed of a mixture of several phases at temperatures below 1100 °C.  Experimentally, however, a single-phase bcc structure was observed for the deposited films and it was concluded that the films were kinetically and not entropy stabilised. A hypothesis is that the kinetics during sputtering allow a ’direct’ phase selection by tuning the process parameters and evidence of this was found in the HfNbTiVZr alloy system.

    The CrNbTaTiW–C system is, however, complex and additional studies were carried out on the W–C and TaW–C systems. All metallic films crystallised in a bcc structure with a <110> texture and the column width of these films varied between 25 nm and 80 nm. The films were very hard (~ 13 GPa), which was explained by the small grain size. A single-phase bcc structure was also obtained upon the addition of 5-10 at.% carbon for all compositions except the near-equimolar CrNbTaTiW. X-ray diffraction indicated a unit cell expansion, which was attributed to the formation of a supersaturated solid solution. Additional atom probe tomography (APT) studies on selected samples confirmed the formation of such solid solutions. The supersaturated solid solution is not thermodynamically stable and an annealing study showed that heat treatment yielded segregation and clustering of carbon at the grain boundaries. The addition of carbon had a grain refining effect in the W–C system and the multicomponent CrNbTaTiW–C system. In general, the addition of carbon increased the hardness, which was mainly caused by a reduced grain size in line with the Hall-Petch relationship. Excellent mechanical properties of carbon supersaturated films were further confirmed in pillar tests on W–C films, which showed very high yield strength (~ 9 GPa) and no brittle fracture. The results show that carbon can be used as a chemical approach to control the grain size and properties of these films. 

    Multicomponent carbides with a B1 structure were formed at high carbon concentrations (~ 40 at.%). The microstructure of these films depended strongly on the process parameters and a higher deposition temperature was found to increase the film density and hardness. The TaW-rich carbide exhibited a very high hardness of ~ 35 GPa and excellent corrosion resistance.

    List of papers
    1. Magnetron Sputtering of Carbon Supersaturated W Films - A Chemical Approach to Increase Strength and Ductility
    Open this publication in new window or tab >>Magnetron Sputtering of Carbon Supersaturated W Films - A Chemical Approach to Increase Strength and Ductility
    (English)Manuscript (preprint) (Other academic)
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-404772 (URN)
    Available from: 2020-02-26 Created: 2020-02-26 Last updated: 2020-02-28
    2. Influence of Carbon on Microstructure and Mechanical Properties of Magnetron Sputtered TaW Coatings
    Open this publication in new window or tab >>Influence of Carbon on Microstructure and Mechanical Properties of Magnetron Sputtered TaW Coatings
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    2020 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 196, article id 109070Article in journal (Refereed) Published
    Abstract [en]

    (Ta,W) and (Ta,W):C films with-5 at.% C were deposited by non-reactive magnetron sputtering. They crystallised in a bcc structure with a columnar microstructure. The solid solubility of C in (Ta,W) alloys is very low, which suggests that the (Ta,W):C films are supersaturated with respect to carbon. This was confirmed by diffraction and atom probe tomography (APT) showing that carbon is in the as-deposited (Ta,W):C films homogeneously distributed in the structure without carbide formation or carbon segregation. Annealing at 900 degrees C for 2 h showed no significant column coarsening but an increased defect density at the column boundaries in the (Ta,W):C films. The films were still supersaturated with respect to carbon but APT showed a partial segregation of carbon presumably to defect-rich column boundaries after annealing. The (Ta,W) films exhibited a hardness of-12-13 GPa. Alloying with carbon increased the hardness to-17 GPa. The hardness increased to-19 GPa for the annealed (Ta,W):C films. This annealing-induced hardness increase was explained by C segregation to the more defect-rich column boundaries, which restricts dislocation movements. (Ta,W):C coatings may be a potential alternative to ceramic coatings, worth exploring further by small scale mechanical testing to investigate if these materials are ductile.

    Place, publisher, year, edition, pages
    Elsevier, 2020
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:uu:diva-404744 (URN)10.1016/j.matdes.2020.109070 (DOI)000588267900006 ()
    Funder
    Swedish Research Council, 2018-04834Swedish Research Council, 821-2012-5144Swedish Research Council, 2017-00646_9Swedish Foundation for Strategic Research , RIF14-0053
    Available from: 2020-02-26 Created: 2020-02-26 Last updated: 2020-12-02Bibliographically approved
    3. Hard and crack resistant carbon supersaturated refractory nanostructured multicomponent coatings
    Open this publication in new window or tab >>Hard and crack resistant carbon supersaturated refractory nanostructured multicomponent coatings
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    2018 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 8, article id 14508Article in journal (Refereed) Published
    Abstract [en]

    The combination of ceramic hardness with high crack resistance is a major challenge in the design of protective thin films. High entropy alloys have shown in earlier studies promising mechanical properties with a potential use as thin film materials. In this study, we show that small amounts of carbon in magnetron-sputtered multicomponent CrNbTaTiW films can lead to a significant increase in hardness. The film properties were strongly dependent on the metal composition and the most promising results were observed for TaW-rich films. They crystallised in a bcc structure with a strong (110) texture and coherent grain boundaries. It was possible to deposit films with 8 at.% C in a supersaturated solid-solution into the bcc structure without carbide formation. A major effect of carbon was a significant grain refinement, reducing the column diameter from approximately 35 to 10 nm. This resulted in an increase in hardness from 14.7 to 19.1 GPa while the reduced E-modulus stayed constant at 322 GPa. The carbon-containing films exhibited extremely little plastic deformation around the indent and no cracks were observed. These results show that supersaturation of carbon into high entropy films can be a promising concept to combine superior hardness with high crack resistance.

    Place, publisher, year, edition, pages
    NATURE PUBLISHING GROUP, 2018
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:uu:diva-368107 (URN)10.1038/s41598-018-32932-y (DOI)000445894500011 ()30266967 (PubMedID)
    Funder
    Swedish Research Council, 621-2012-4359Swedish Research Council, 622-2008-405Swedish Foundation for Strategic Research , RMA11-0029
    Available from: 2018-12-05 Created: 2018-12-05 Last updated: 2022-09-15Bibliographically approved
    4. Elemental Distribution in CrNbTaTiW-C High Entropy Alloy Thin Films
    Open this publication in new window or tab >>Elemental Distribution in CrNbTaTiW-C High Entropy Alloy Thin Films
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    2019 (English)In: Microscopy and Microanalysis, ISSN 1431-9276, E-ISSN 1435-8115, Vol. 25, no 2, p. 489-500Article in journal (Refereed) Published
    Abstract [en]

    The microstructure and distribution of the elements have been studied in thin films of a near-equimolar CrNbTaTiW high entropy alloy (HEA) and films with 8 at.% carbon added to the alloy. The films were deposited by magnetron sputtering at 300 degrees C. X-ray diffraction shows that the near-equimolar metallic film crystallizes in a single-phase body centered cubic (bcc) structure with a strong (110) texture. However, more detailed analyses with transmission electron microscopy (TEM) and atom probe tomography (APT) show a strong segregation of Ti to the grain boundaries forming a very thin Ti-Cr rich interfacial layer. The effect can be explained by the large negative formation enthalpy of Ti-Cr compounds and shows that CrNbTaTiW is not a true HEA at lower temperatures. The addition of 8 at.% carbon leads to the formation of an amorphous structure, which can be explained by the limited solubility of carbon in bcc alloys. TEM energy-dispersive X-ray spectroscopy indicated that all metallic elements are randomly distributed in the film. The APT investigation, however, revealed that carbide-like clusters are present in the amorphous film.

    Place, publisher, year, edition, pages
    CAMBRIDGE UNIV PRESS, 2019
    Keywords
    atom probe tomography, carbon clustering, high entropy alloy, segregation, thin film
    National Category
    Materials Chemistry
    Identifiers
    urn:nbn:se:uu:diva-385570 (URN)10.1017/S1431927618016264 (DOI)000466756600025 ()30712522 (PubMedID)
    Conference
    Atom Probe Tomography and Microscopy (APT and M) Conference, JUN 10-15, 2018, Gaithersburg, MD
    Funder
    Swedish Research Council, 621-2012-4359Swedish Research Council, 622-2008-405Knut and Alice Wallenberg FoundationSwedish Foundation for Strategic Research , RMA11-0029
    Available from: 2019-06-19 Created: 2019-06-19 Last updated: 2020-02-28Bibliographically approved
    5. Synthesis and characterization of multicomponent (CrNbTaTiW)C films for increased hardness and corrosion resistance
    Open this publication in new window or tab >>Synthesis and characterization of multicomponent (CrNbTaTiW)C films for increased hardness and corrosion resistance
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    2018 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 149, p. 51-62Article in journal (Refereed) Published
    Abstract [en]

    Multicomponent carbide thin films of (CrNbTaTiW)C (30–40 at.% C) with different metal contents were depos-ited at different temperatures using non-reactive DC magnetron sputtering. The lattice distortion for the metallattice was estimated to vary from about 3 to 5%. Most films crystallized in the cubic B1 structure but Ta/W-rich films deposited at 600 °C exhibited a tetra gonal distortion. X-ray diffraction results sh ow that near-equimolar films exhibited a strong (111) texture. In contrast, Ta/W-rich films exhibited a shift from (111) to(100) texture at 450 °C. The in-plane relationship was determined to MC(111)[-12-1]//Al2O3(001)[110] with alattice mismatch of about 11% along the Al2O3[110] direction. A segregation of Cr to the grain boundaries was ob-served in all films. The microstructure was found to be the most important factor for high hardness. Less denseNb-rich and near-equimolar films deposited at low tem peratures exhib ited the low est hardnes s (12 GPa),while very dense Ta/W-rich high temperature films were found to be the hardest (36 GPa). No correlation wasfound between the lattice distortion and the hardness. Corrosion studies revealed that the multicomponentfilms exhibited excellent corrosion resistance, superior to that of a reference hyper-duplex stainless steel, in1.0 M HCl.

    National Category
    Inorganic Chemistry
    Research subject
    Chemistry with specialization in Inorganic Chemistry; Chemistry with specialization in Materials Chemistry
    Identifiers
    urn:nbn:se:uu:diva-335985 (URN)10.1016/j.matdes.2018.03.068 (DOI)000431007500006 ()
    Funder
    Swedish Research Council, 621-2012-4359Swedish Research Council, 622-2008-405Knut and Alice Wallenberg FoundationSwedish Foundation for Strategic Research , RMA11-0029
    Available from: 2017-12-12 Created: 2017-12-12 Last updated: 2020-02-28Bibliographically approved
    6. Influence of Deposition Temperature on the Phase Evolution of HfNbTiVZr High-Entropy Thin Films
    Open this publication in new window or tab >>Influence of Deposition Temperature on the Phase Evolution of HfNbTiVZr High-Entropy Thin Films
    Show others...
    2019 (English)In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 4, article id 587Article in journal (Refereed) Published
    Abstract [en]

    In this study, we show that the phase formation of HfNbTiVZr high-entropy thin films is strongly influenced by the substrate temperature. Films deposited at room temperature exhibit an amorphous microstructure and are 6.5 GPa hard. With increasing substrate temperature (room temperature to 275 degrees C), a transition from an amorphous to a single-phased body-centred cubic (bcc) solid solution occurs, resulting in a hardness increase to 7.9 GPa. A higher deposition temperature (450 degrees C) leads to the formation of C14 or C15 Laves phase precipitates in the bcc matrix and a further enhancement of mechanical properties with a peak hardness value of 9.2 GPa. These results also show that thin films follow different phase formation pathways compared to HfNbTiVZr bulk alloys.

    Place, publisher, year, edition, pages
    MDPI, 2019
    Keywords
    high-entropy alloys, physical vapour deposition (PVD), metallic glass
    National Category
    Metallurgy and Metallic Materials Materials Chemistry
    Identifiers
    urn:nbn:se:uu:diva-380494 (URN)10.3390/ma12040587 (DOI)000460793300037 ()30781407 (PubMedID)
    Funder
    Swedish Research Council, 2018-04834
    Available from: 2019-03-28 Created: 2019-03-28 Last updated: 2020-02-28Bibliographically approved
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  • 3.
    Fritze, Stefan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Chen, M.
    Swiss Fed Inst Technol, Lab Nanomet, Vladimir Prelog Weg 5, CH-8093 Zurich, Switzerland..
    Riekehr, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Osinger, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Sortica, Mauricio A.
    Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Tandem Laboratory.
    Srinath, Aishwarya
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Menon, Ashok S.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Primetzhofer, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Tandem Laboratory. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Wheeler, J. M.
    Swiss Fed Inst Technol, Lab Nanomet, Vladimir Prelog Weg 5, CH-8093 Zurich, Switzerland..
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Magnetron sputtering of carbon supersaturated tungsten films-A chemical approach to increase strength2021In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 208, article id 109874Article in journal (Refereed)
    Abstract [en]

    Tungsten (W)-based materials attract significant attention due to their superior mechanical properties. Here, we present a chemical approach based on the addition of carbon (C) for increased strength via the combination of three strengthening mechanisms in W thin films. W:C thin films with C concentrations up to-4 at.% were deposited by magnetron sputtering. All films exhibit a body-centred-cubic structure with strong texture and columnar growth behaviour. X-ray and electron diffraction measurements suggest the formation of supersaturated W:C solid solution phases. The addition of C reduced the average column width from-133 nm for W to-20 nm for the film containing-4 at.% C. The column refinement is explained by a mechanism where C acts as re-nucleation sites. The W film is-13 GPa hard, while the W:C films achieve a peak hardness of-24 GPa. The W:C films are-11 GPa harder than the W film, which is explained by a combination of grain refinement strengthening, solid solution strengthening and increased dislocation density. Additional micropillar compression tests showed that the flow stress increased upon C addition, from-3.8 to-8.3 GPa and no brittle fracture was observed.

  • 4.
    Fritze, Stefan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Hahn, R.
    Institute of Materials Science and Technology, TU Wien, Vienna, Austria.
    Aboulfadl, H.
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Johansson, Fredrik O.L.
    Division of Applied Physical Chemistry, Department of Chemistry, KTH – Royal Institute of Technology, SE-100 44 Stockholm, Sweden; Institute Methods and Instrumentation for Synchrotron Radiation Research PS-ISRR, Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Straße 15, 12489 Berlin, Germany; Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, 14476 Potsdam, Germany.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Böör, Katalin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lindblad, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Berggren, Elin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Condensed Matter Physics of Energy Materials.
    Kühn, D.
    Institute Methods and Instrumentation for Synchrotron Radiation Research PS-ISRR, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany.
    Leitner, T.
    Institute Methods and Instrumentation for Synchrotron Radiation Research PS-ISRR, Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin, Germany.
    Osinger, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lewin, Erik
    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.
    Mayrhofer, P.H.
    Institute of Materials Science and Technology, TU Wien, Vienna, Austria.
    Thuvander, M.
    Department of Physics, Chalmers University of Technology, Göteborg, Sweden.
    Elemental distribution and fracture properties of magnetron sputtered carbon supersaturated tungsten films2024In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 477, article id 130326Article in journal (Refereed)
    Abstract [en]

    The combination of strength and toughness is a major driving force for alloy design of protective coatings, and nanocrystalline tungsten (W)-alloys have shown to be promising candidates for combining strength and toughness. Here we investigate the elemental distribution and the fracture toughness of carbon (C) alloyed W thin films prepared by non-reactive magnetron sputtering. W:C films with up to ~4 at.% C crystallize in a body-centered-cubic structure with a strong 〈hh0〉texture, and no additional carbide phases are observed in the diffraction pattern. Atom probe tomography and X-ray photoelectron spectroscopy confirmed the formation of such a supersaturated solid solution. The pure W film has a hardness ~13 GPa and the W:C films exhibit a peak hardness of ~24 GPa. In-situ micromechanical cantilever bending tests show that the fracture toughness decreases from ~4.5 MPa·m1/2 for the W film to ~3.1 MPa·m1/2 for W:C films. The results show that C can significantly enhance the hardness of W thin films while retaining a high fracture toughness.

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  • 5.
    Fritze, Stefan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Hans, M.
    Materials Chemistry, RWTH Aachen University, Aachen, Germany.
    Riekehr, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Osinger, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Schneider, J.M.
    Materials Chemistry, RWTH Aachen University, Aachen, Germany.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Influence of Carbon on Microstructure and Mechanical Properties of Magnetron Sputtered TaW Coatings2020In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 196, article id 109070Article in journal (Refereed)
    Abstract [en]

    (Ta,W) and (Ta,W):C films with-5 at.% C were deposited by non-reactive magnetron sputtering. They crystallised in a bcc structure with a columnar microstructure. The solid solubility of C in (Ta,W) alloys is very low, which suggests that the (Ta,W):C films are supersaturated with respect to carbon. This was confirmed by diffraction and atom probe tomography (APT) showing that carbon is in the as-deposited (Ta,W):C films homogeneously distributed in the structure without carbide formation or carbon segregation. Annealing at 900 degrees C for 2 h showed no significant column coarsening but an increased defect density at the column boundaries in the (Ta,W):C films. The films were still supersaturated with respect to carbon but APT showed a partial segregation of carbon presumably to defect-rich column boundaries after annealing. The (Ta,W) films exhibited a hardness of-12-13 GPa. Alloying with carbon increased the hardness to-17 GPa. The hardness increased to-19 GPa for the annealed (Ta,W):C films. This annealing-induced hardness increase was explained by C segregation to the more defect-rich column boundaries, which restricts dislocation movements. (Ta,W):C coatings may be a potential alternative to ceramic coatings, worth exploring further by small scale mechanical testing to investigate if these materials are ductile.

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  • 6.
    Fritze, Stefan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Koller, Christian M.
    TU Wien, Inst Mat Sci & Technol, A-1060 Vienna, Austria.
    von Fieandt, Linus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Malinovskis, Paulius
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Johansson, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Mayrhofer, Paul H.
    TU Wien, Inst Mat Sci & Technol, A-1060 Vienna, Austria.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Influence of Deposition Temperature on the Phase Evolution of HfNbTiVZr High-Entropy Thin Films2019In: Materials, ISSN 1996-1944, E-ISSN 1996-1944, Vol. 12, no 4, article id 587Article in journal (Refereed)
    Abstract [en]

    In this study, we show that the phase formation of HfNbTiVZr high-entropy thin films is strongly influenced by the substrate temperature. Films deposited at room temperature exhibit an amorphous microstructure and are 6.5 GPa hard. With increasing substrate temperature (room temperature to 275 degrees C), a transition from an amorphous to a single-phased body-centred cubic (bcc) solid solution occurs, resulting in a hardness increase to 7.9 GPa. A higher deposition temperature (450 degrees C) leads to the formation of C14 or C15 Laves phase precipitates in the bcc matrix and a further enhancement of mechanical properties with a peak hardness value of 9.2 GPa. These results also show that thin films follow different phase formation pathways compared to HfNbTiVZr bulk alloys.

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  • 7.
    Fritze, Stefan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Malinovskis, Paulius
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Riekehr, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    von Fieandt, Linus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lewin, Erik
    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.
    Hard and crack resistant carbon supersaturated refractory nanostructured multicomponent coatings2018In: Scientific Reports, E-ISSN 2045-2322, Vol. 8, article id 14508Article in journal (Refereed)
    Abstract [en]

    The combination of ceramic hardness with high crack resistance is a major challenge in the design of protective thin films. High entropy alloys have shown in earlier studies promising mechanical properties with a potential use as thin film materials. In this study, we show that small amounts of carbon in magnetron-sputtered multicomponent CrNbTaTiW films can lead to a significant increase in hardness. The film properties were strongly dependent on the metal composition and the most promising results were observed for TaW-rich films. They crystallised in a bcc structure with a strong (110) texture and coherent grain boundaries. It was possible to deposit films with 8 at.% C in a supersaturated solid-solution into the bcc structure without carbide formation. A major effect of carbon was a significant grain refinement, reducing the column diameter from approximately 35 to 10 nm. This resulted in an increase in hardness from 14.7 to 19.1 GPa while the reduced E-modulus stayed constant at 322 GPa. The carbon-containing films exhibited extremely little plastic deformation around the indent and no cracks were observed. These results show that supersaturation of carbon into high entropy films can be a promising concept to combine superior hardness with high crack resistance.

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  • 8.
    Glechner, T.
    et al.
    TU Wien, Inst Mat Sci & Technol, A-1060 Vienna, Austria.
    Mayrhofer, P. H.
    TU Wien, Inst Mat Sci & Technol, A-1060 Vienna, Austria.
    Holec, D.
    Univ Leoben, Dept Mat Sci, A-8700 Leoben, Austria.
    Fritze, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Paneta, Valentina
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Primetzhofer, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Kolozsvari, S.
    Plansee Composite Mat GmbH, D-86983 Lechbruck, Germany.
    Riedl, H.
    TU Wien, Inst Mat Sci & Technol, A-1060 Vienna, Austria.
    Tuning structure and mechanical properties of Ta-C coatings by N-alloying and vacancy population2018In: Scientific Reports, E-ISSN 2045-2322, Vol. 8, article id 17669Article in journal (Refereed)
    Abstract [en]

    Tailoring mechanical properties of transition metal carbides by substituting carbon with nitrogen atoms is a highly interesting approach, as thereby the bonding state changes towards a more metallic like character and thus ductility can be increased. Based on ab initio calculations we could prove experimentally, that up to a nitrogen content of about 68% on the non-metallic sublattice, Ta-C-N crystals prevail a face centered cubic structure for sputter deposited thin films. The cubic structure is partly stabilized by non-metallic as well as Ta vacancies-the latter are decisive for nitrogen rich compositions. With increasing nitrogen content, the originally super-hard fcc-TaC0.71 thin films soften from 40 GPa to 26 GPa for TaC0.33N0.67, accompanied by a decrease of the indentation modulus. With increasing nitrogen on the non-metallic sublattice (hence, decreasing C) the damage tolerance of Ta-C based coatings increases, when characterized after the Pugh and Pettifor criteria. Consequently, varying the non-metallic sublattice population allows for an effective tuning and designing of intrinsic coating properties.

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  • 9.
    Johansson, Kristina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala Univ, Angstrom Lab, Dept Chem, Inorgan Res Programme, Box 538, SE-75121 Uppsala, Sweden.
    Riekehr, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Fritze, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Multicomponent Hf-Nb-Ti-V-Zr nitride coatings by reactive magnetron sputter deposition2018In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 349, p. 529-539Article in journal (Refereed)
    Abstract [en]

    Multicomponent nitride coatings of the Hf-Nb-Ti-V-Zr system with different Hf content (0-18 at.%) were deposited using reactive dc magnetron sputtering. Coatings with lower Hf content (0-7 at.%) were found to consist of a single solid solution phase with NaCl-type structure (space group Fm-3m). Coatings with higher Hf content (10-18 at.%) showed a two-phase material consisting of cubic Fm-3m and tetragonal I4/m:run solid solution phase. The lattice distortion, estimated by calculating the delta-parameter under the assumption of a single solid solution phase, varied between 3.8 and 4.0% and slightly decreased with increasing Hf content. SEM and TEM cross section images showed a columnar microstructure with columns that were frayed on the surface or throughout the whole column. The column size decreased as Hf content increased. The hardness increased from 8 to 19 GPa with increased Hf content, which most probably is related to the change in microstructure rather than change in lattice distortion. The electrical resistivity for all samples ranged between 231 and 286 mu Omega cm.

  • 10.
    Kaplan, Maciej
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Srinath, Aishwarya
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Riekehr, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Fritze, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Combinatorial design of amorphous TaNiSiC thin films with enhanced hardness, thermal stability, and corrosion resistance2022In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 220, article id 110827Article in journal (Refereed)
    Abstract [en]

    Amorphous TaNiSiC and TaNiC films (with varying Ta/Ni and Si/C ratios) were deposited using combinatorial magnetron sputtering. The TaNiSiC films remained X-ray amorphous after four hour-long annealings up to 700 °C, while TaNiC alloys with high Ni and C contents crystallized. These differences were attributed to a strong driving force for separation of Ni and C in TaNiC, whereas the addition of Si, due to its solubility in the other elements, reduced the elemental segregation in TaNiSiC. The as-deposited TaNiSiC films exhibited hardnesses of 9–12 GPa. Annealing led to an increase in hardness by 2–4 GPa, due to decreases in average atomic distance, as evidenced by X-ray diffraction measurements. Potentiodynamic polarizations from –0.7 to +1.5 V vs. Ag/AgCl (3 M NaCl) in 10 mM sodium borate showed lower current densities by up to 2 orders of magnitude with increasing Ta content (28–52 at.%). Changes in Si/C content (7–13 at.% Si) had no effect. However, optical microscopy showed that TaNiSiC films with high Si/low C contents (13/10 at.%) suffered much less localized etching compared to TaNiC films. Thus, Si had a significant role in increasing the mechanical strength, corrosion resistance, and thermal stability of the TaNiSiC films.

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  • 11.
    Malinovskis, Paulius
    et al.
    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.
    Palisaitis, Justinas
    Linköping Univ, Thin Film Phys Div, Dept Phys Chem & Biol IFM, SE-58183 Linköping, Sweden..
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Patscheider, Jörg
    Evatec AG, Hauptst 1a, CH-9477 Trubbach, Switzerland..
    Persson, Per O. Å.
    Linköping Univ, Thin Film Phys Div, Dept Phys Chem & Biol IFM, SE-58183 Linköping, Sweden..
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Synthesis and characterisation of nanocomposite Mo-Fe-B thin films deposited by magnetron sputtering2021In: Materials, E-ISSN 1996-1944, Vol. 14, no 7, article id 1739Article in journal (Refereed)
    Abstract [en]

    Several ternary phases are known in the Mo-Fe-B system. Previous ab initio calculations have predicted that they should exhibit a tempting mix of mechanical and magnetic properties. In this study, we have deposited Mo-Fe-B films with a Fe-content varying from 0-37 at.% using non-reactive DC (direct current) magnetron sputtering. The phase composition, microstructure, and mechanical properties were investigated using X-ray diffraction, scanning transmission electron microscopy, and nanoindentation measurements. Films deposited at 300 degrees C and with >7 at.% Fe are nanocomposites consisting of two amorphous phases: a metal-rich phase and a metal-deficient phase. Hardness and elastic modulus were reduced with increasing Fe-content from similar to 29 to similar to 19 GPa and similar to 526 to similar to 353 GPa, respectively. These values result in H-3/E-2 ratios of 0.089-0.052 GPa, thereby indicating brittle behaviour of the films. Also, no indication of crystalline ternary phases was observed at temperatures up to 600 degrees C, suggesting that higher temperatures are required for such films to form.

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  • 12.
    Malinovskis, Paulius
    et al.
    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.
    Riekehr, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    von Fieandt, Linus
    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.
    Rehnlund, David
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lewin, Erik
    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.
    Synthesis and characterization of multicomponent (CrNbTaTiW)C films for increased hardness and corrosion resistance2018In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 149, p. 51-62Article in journal (Refereed)
    Abstract [en]

    Multicomponent carbide thin films of (CrNbTaTiW)C (30–40 at.% C) with different metal contents were depos-ited at different temperatures using non-reactive DC magnetron sputtering. The lattice distortion for the metallattice was estimated to vary from about 3 to 5%. Most films crystallized in the cubic B1 structure but Ta/W-rich films deposited at 600 °C exhibited a tetra gonal distortion. X-ray diffraction results sh ow that near-equimolar films exhibited a strong (111) texture. In contrast, Ta/W-rich films exhibited a shift from (111) to(100) texture at 450 °C. The in-plane relationship was determined to MC(111)[-12-1]//Al2O3(001)[110] with alattice mismatch of about 11% along the Al2O3[110] direction. A segregation of Cr to the grain boundaries was ob-served in all films. The microstructure was found to be the most important factor for high hardness. Less denseNb-rich and near-equimolar films deposited at low tem peratures exhib ited the low est hardnes s (12 GPa),while very dense Ta/W-rich high temperature films were found to be the hardest (36 GPa). No correlation wasfound between the lattice distortion and the hardness. Corrosion studies revealed that the multicomponentfilms exhibited excellent corrosion resistance, superior to that of a reference hyper-duplex stainless steel, in1.0 M HCl.

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  • 13. Mukhamedov, B.O.
    et al.
    Fritze, Stefan
    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.
    Osinger, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Alling, B.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Abrikosov, I.A.
    Tetragonal distortion in magnetron sputtered bcc-W films with supersaturated carbon2022In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 214, article id 110422Article in journal (Refereed)
    Abstract [en]

    Carbon has a low solid solubility in bcc tungsten at equilibrium. However, metastable supersaturated solid solutions can be synthesized with magnetron sputtering. Here, we present a systematic study on the phase stability and mechanical properties of such supersaturated W–C solid solutions. Θ–2θ scans show a split of the 200/020 and the 002 peaks for supersaturated films which is explained by a tetragonal distortion of the bcc structure. This split increases with increasing C content and is maximized at 4 at.% C, where we observe an a/b axis of 3.15–3.16 Å and a c-axis of 3.21–3.22 Å. We performed first-principles calculations of lattice parameters, mixing enthalpies, elastic constants and polycrystalline elastic moduli for cubic and tetragonal W–C solid solutions. Calculations show that tetragonal structure is more stable than the bcc supersaturated solid solution and the calculated lattice parameters and Young’s moduli follow the same trends as the experimental ones as a function of C concentration. The results suggest that supersaturated films with lattice distortion can be used as a design approach to improve the properties of transition metal films with a bcc structure.

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  • 14.
    Osinger, Barbara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Donzel-Gargand, Olivier
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Solar Cell Technology.
    Fritze, Stefan
    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.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Structural and mechanical properties of magnetron sputtered (NbxMo1-x)C thin films2024In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 224, article id 113146Article in journal (Refereed)
    Abstract [en]

    While transition metal carbides (TMCs) exhibit favourable mechanical properties, alloying according to the valence electron concentration (VEC) has the potential to further enhance the properties of these hard but inherently brittle materials. This study investigates the influence of alloying on the microstructure and mechanical properties of (NbxMo1-x)C carbide films, including binary references and ternary compositions with varying metal ratios (x between 0.35 and 0.53). Furthermore, the influence of various substrate materials is studied by comparing films deposited on Al2O3, MgO and SiO2. All films exhibit a NaCl-type carbide structure and X-ray photoelectron spectroscopy revealed the presence of small amounts of an additional amorphous carbon (a-C) phase. Hardness values around 20 ± 2 GPa were obtained for the films on Al2O3 and MgO, whereas a reduced hardness of 11 ± 1 GPa was observed for the films on SiO2 which is attributed to larger crystallite size and more polycrystalline structure. Overall no clear trend as a function of composition can be noted, indicating that microstructure effects dominate the mechanical properties in this study overshadowing the effect of varying the metal content.

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  • 15.
    Osinger, Barbara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Mao, Huahai
    KTH Royal Inst Technol, Stockholm, Sweden.;Thermo Calc Software AB, Solna, Sweden..
    Fritze, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Riekehr, Lars
    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.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Investigation of the phase formation in magnetron sputtered hard multicomponent (HfNbTiVZr)C coatings2022In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 221, article id 111002Article in journal (Refereed)
    Abstract [en]

    Multicomponent carbides have gained interest especially for ultra-high temperature applications, due to their ceramic hardness, good oxidation resistance and enhanced strength. In this study the phase forma-tion, stability and mechanical properties of (HfNbTiVZr)C multicomponent carbide coatings were inves-tigated. Phase stability was predicted by the CALPHAD (CALculation of PHAse Diagrams) methods. This revealed that the multicomponent solid solution phase is only stable at elevated temperatures, namely above 2400 degrees C. At lower temperatures a phase mixture was predicted, with a particular tendency for V to segregate. Magnetron sputtered thin films deposited at 300 degrees C exhibited a single NaCl-type multicom-ponent carbide phase, which attributes to the kinetic stabilisation of simple structures during thin film growth. Films deposited at 700 degrees C, or exposed to UHV annealing at 1000 degrees C, however, revealed the decom-position of the single-phase multicomponent carbide by partial elemental segregation and formation of additional phases. Thus, confirming the CALPHAD predictions. These results underscore the importance of explicitly considering temperature when discussing the stability of multicomponent carbide materials, as well as the applicability of CALPHAD methods for predicting phase formation and driving forces in these materials. The latter being crucial for designing materials, such as carbides, that are used in appli-cations at elevated temperatures.

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  • 16.
    Osinger, Barbara
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Tunes, Matheus A.
    Chair of Non-Ferrous Metallurgy, Montanuniversität Leoben, 8700 Austria.
    Willenshofer, Patrick
    Chair of Non-Ferrous Metallurgy, Montanuniversität Leoben, 8700 Austria.
    Greaves, Graeme
    School of Computing and Engineering, University of Huddersfield, Huddersfield HD1 3DH, United Kingdom .
    Ström, Petter
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Malinovskis, Paulius
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics. School of Computing and Engineering, University of Huddersfield, Huddersfield HD1 3DH, United Kingdom .
    Vishnyakov, Vladimir M.
    Lewin, Erik
    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.
    Probing the high entropy concept through the irradiation response of near-equimolar (CrTiTaWNb)C ceramic coatingsManuscript (preprint) (Other academic)
  • 17.
    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.

  • 18.
    Shinde, Deodatta
    et al.
    Chalmers Univ Technol, Dept Phys, SE-41296 Gothenburg, Sweden.
    Fritze, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Thuvander, Mattias
    Chalmers Univ Technol, Dept Phys, SE-41296 Gothenburg, Sweden.
    Malinovskis, Paulius
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Riekehr, Lars
    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.
    Stiller, Krystyna
    Chalmers Univ Technol, Dept Phys, SE-41296 Gothenburg, Sweden.
    Elemental Distribution in CrNbTaTiW-C High Entropy Alloy Thin Films2019In: Microscopy and Microanalysis, ISSN 1431-9276, E-ISSN 1435-8115, Vol. 25, no 2, p. 489-500Article in journal (Refereed)
    Abstract [en]

    The microstructure and distribution of the elements have been studied in thin films of a near-equimolar CrNbTaTiW high entropy alloy (HEA) and films with 8 at.% carbon added to the alloy. The films were deposited by magnetron sputtering at 300 degrees C. X-ray diffraction shows that the near-equimolar metallic film crystallizes in a single-phase body centered cubic (bcc) structure with a strong (110) texture. However, more detailed analyses with transmission electron microscopy (TEM) and atom probe tomography (APT) show a strong segregation of Ti to the grain boundaries forming a very thin Ti-Cr rich interfacial layer. The effect can be explained by the large negative formation enthalpy of Ti-Cr compounds and shows that CrNbTaTiW is not a true HEA at lower temperatures. The addition of 8 at.% carbon leads to the formation of an amorphous structure, which can be explained by the limited solubility of carbon in bcc alloys. TEM energy-dispersive X-ray spectroscopy indicated that all metallic elements are randomly distributed in the film. The APT investigation, however, revealed that carbide-like clusters are present in the amorphous film.

  • 19.
    Srinath, Aishwarya
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    von Fieandt, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lindblad, Rebecka
    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.
    Korvela, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Pettersson, Jean
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Analytical Chemistry.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Influence of the nitrogen content on the corrosion resistances of multicomponent AlCrNbYZrN coatings2021In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 188, article id 109557Article in journal (Refereed)
    Abstract [en]

    In this study, the relationship between the nitrogen content and the corrosion resistances of non-equimolar multicomponent AlCrNbYZrN films (N = 13-49 at.%) is probed. While there was no linear relationship between nitrogen content and corrosion resistance, the results clearly show that the corrosion resistances of the films were instead determined by their nitrogen-induced porosities i.e. the less porous the sample, the higher the corrosion resistance. The 23, 30 and 37 at.% N samples were denser while the 13 at.% N sample was porous and the 49 at.% N film had an underdense nanocrystalline columnar cross section permitting the ingress of electrolyte.

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  • 20. Tunes, Matheus A.
    et al.
    Fritze, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Osinger, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Willenshofer, Patrick
    Alvarado, Andrew M.
    Martinez, Enrique
    Menon, Ashok S.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Ström, Petter
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Greaves, Graeme
    Lewin, Erik
    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.
    Pogatscher, Stefan
    Saleh, Tarik A.
    Vishnyakov, Vladimir M.
    El-Atwani, Osman
    From high-entropy alloys to high-entropy ceramics: The radiation-resistant highly concentrated refractory carbide (CrNbTaTiW)C2023In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 250, article id 118856Article in journal (Refereed)
    Abstract [en]

    High-entropy materials represent the state-of-the-art on the alloy design strategy for future applications in extreme environments. Recent data indicates that high-entropy alloys (HEAs) exhibit outstanding radiation resistance in face of existing diluted alloy counterparts due to suppressed damage formation and evolution. An extension of the HEA concept is presented in this paper towards the synthesis and characterization of novel high-entropy ceramics as emergent materials for application in environments where energetic particle irradiation is a major concern. A novel carbide within the quinary refractory system CrNbTaTiW has been synthesized using magnetron-sputtering. The material exhibited nanocrystalline grains, single-phase crystal structure and C content around 50 at.%. Heavy-ion irradiation with in-situ Transmission Electron Microscopy was used to assess the irradiation response of the new high-entropy carbide (HEC) at 573 K and a comparison with the HEA within the system is made. No displacement damage effects appear within the microstructures of both HEA and HEC up to a dose of 10 displacements-per-atom. Surprisingly, the HEC has not amorphized under the investigated conditions. Xe was implanted in both materials and bubbles nucleated, but smaller sizes compared with conventional nuclear materials shedding light they are potential candidates for use in nuclear energy.

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  • 21.
    von Fieandt, Kristina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Pilloud, David
    Univ Lorraine, Campus ARTEM, UMR 7198, CNRS,Inst Jean Lamour, FR-54011 Nancy, France..
    Fritze, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Osinger, Barbara
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Pierson, Jean-Francois
    Univ Lorraine, Campus ARTEM, UMR 7198, CNRS,Inst Jean Lamour, FR-54011 Nancy, France..
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Optical and electrical properties of hard (Hf,Nb,Ti,V,Zr)N-x thin films2021In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 193, article id 110517Article in journal (Refereed)
    Abstract [en]

    (Hf,Nb,Ti,V,Zr)N-x coatings with nitrogen content between 0 and 49 at.% were deposited by sputter deposition, and thoroughly characterised. Nitrogen-free coatings were found to have a bcc structure, low hardness (8 GPa), and an electrical resistivity of 144 mu Omega cm. The nitride coatings (43-49 at.% N) had NaCl-type structure, consistent with a multi-component solid solution phase. Photoelectron core level binding energies indicate that the electronic structure of the multi-component nitride differs from that of the binary nitrides, probably a result of charge transfer between the metal atoms. The nitride coatings exhibited a dense microstructure and a hardness between 29 and 33 GPa, and electrical resistivities of 141-254 mu Omega cm. They also exhibited a minimum in the optical reflectance, similar to that of TiN, indicating plasmonic properties. The position of this minimum was found to be shifted to smaller wavelengths (272-339 nm) compared to a TiN reference (428 nm) and varied with nitrogen content. The tuneability of the optical properties, in combination with the potential to influence the electronic structure through charge transfer between metal atoms point to new interesting routes to design optical materials, and a new class of optical materials based on the concept of multi-component nitrides.

  • 22.
    von Fieandt, Kristina
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Riekehr, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Osinger, Barbara
    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.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Influence of N content on structure and mechanical properties of multi-component Al-Cr-Nb-Y-Zr based thin films by reactive magnetron sputtering2020In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 389, article id 125614Article in journal (Refereed)
    Abstract [en]

    Al-Cr-Nb-Y-Zr-N films have been deposited with reactive dc magnetron sputtering at various N-2 flow ratios to achieve films with different nitrogen content, from purely metallic to fully nitrided films. The structure evolved from mainly amorphous with a minor crystalline intermetallic phase for the film without nitrogen, to nanocomposites with a cubic crystalline phase in an amorphous matrix for intermediate nitrogen content (15-41 at.% N), and at higher nitrogen content (46-51 at.% N) to crystalline solid solution nitrides with a NaCl-type structure. Partial elemental segregation on the nanoscale was found in all studied samples and the films exhibited different segregation behaviour depending on the nitrogen content, implying that the structural evolution on the nanoscale of films in this material system complex and highly composition-dependent. The hardness increased with increasing nitrogen content, reaching a maximum at about 30 GPa at for the nitride films with 50 at.% N. Deformation behaviour, studied by indentation measurements, of the nitride films was found to be ductile, where no sign of crack formation could be observed. This can be attributed to a metallic phase in the columnar boundaries caused by partial elemental segregation of mainly yttrium. Hence, films within in this material system, although the nanostructure is found to be relatively complex, show very promising mechanical properties and the structural complexity can be used as a guide for designing nitride materials that combine high hardness with ductility.

  • 23.
    Zendejas Medina, León
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Tavares da Costa, Marcus V.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    Paschalidou, E. Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Lindwall, Greta
    Royal Inst Technol KTH, Dept Mat Sci & Engn, Brinellvägen 23, SE-10044 Stockholm, Sweden.
    Riekehr, Lars
    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.
    Fritze, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Kolozsvári, Szilárd
    Plansee Composite Mat GmbH, Siebenburgerstr 23, DE-86983 Lechbruck, Germany.
    Gamstedt, E. Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Applied Mechanics.
    Nyholm, Leif
    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.
    Enhancing corrosion resistance, hardness, and crack resistance in magnetron sputtered high entropy CoCrFeMnNi coatings by adding carbon2021In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 205, article id 109711Article in journal (Refereed)
    Abstract [en]

    This study explores carbon addition as a materials design approach for simultaneously improving the hardness, crack resistance, and corrosion resistance of high entropy thin films. CoCrFeMnNi was selected as a starting point, due to its high concentration of weak carbide formers. The suppression of carbides is crucial to the approach, as carbide formation can decrease both ductility and corrosion resistance. Films with 0, 6, and 11 at.% C were deposited by magnetron co-sputtering, using a graphite target and a sintered compound target. The samples with 0 at.% C crystallized with a mixture of a cubic closed packed (ccp) phase and the intermetallic χ-phase. With 6 and 11 at.% C, the films were amorphous and homogenous down to the nm-scale. The hardness of the films increased from 8 GPa in the carbon-free film to 16 GPa in the film with 11 at.% C. Furthermore, the carbon significantly improved the crack resistance as shown in fragmentation tests, where the crack density was strongly reduced. The changes in mechanical properties were primarily attributed to the shift from crystalline to amorphous. Lastly, the carbon improved the corrosion resistance by a progressive lowering of the corrosion current and the passive current with increasing carbon concentration.

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