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Jansson, Ulf
Alternative names
Publications (10 of 183) Show all publications
Holmberg, M., Dancila, D., Rydberg, A., Hjörvarsson, B., Jansson, U., Marattukalam, J. J., . . . Andersson, J. (2018). On Surface Losses in Direct Metal Laser Sintering Printed Millimeter and Submillimeter Waveguides. Journal of Infrared, Millimeter and Terahertz Waves, 39(6), 535-545
Open this publication in new window or tab >>On Surface Losses in Direct Metal Laser Sintering Printed Millimeter and Submillimeter Waveguides
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2018 (English)In: Journal of Infrared, Millimeter and Terahertz Waves, ISSN 1866-6892, E-ISSN 1866-6906, Vol. 39, no 6, p. 535-545Article in journal (Refereed) Published
Abstract [en]

Different lengths of WR3 (220-330 GHz) and WR10 (75-110 GHz) waveguides are fabricated through direct metal laser sintering (DMLS). The losses in these waveguides are measured and modelled using the Huray surface roughness model. The losses in WR3 are around 0.3 dB/mm and in WR10 0.05 dB/mm. The Huray equation model is accounting relatively good for the attenuation in the WR10 waveguide but deviates more in the WR3 waveguide. The model is compared to finite element simulations of the losses assuming an approximate surface structure similar to the resulting one from the DMLS process.

Place, publisher, year, edition, pages
SPRINGER, 2018
Keywords
Millimeterwave, 3D-metal-printed, Waveguide loss
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-356385 (URN)10.1007/s10762-018-0470-x (DOI)000431255500005 ()
Funder
Swedish Foundation for Strategic Research
Available from: 2018-07-25 Created: 2018-07-25 Last updated: 2018-07-25Bibliographically approved
Karlsson, D., Ek, G., Cedervall, J., Zlotea, C., Moller, K. T., Hansen, T. C., . . . Sahlberg, M. (2018). Structure and Hydrogenation Properties of a HfNbTiVZr High-Entropy Alloy. Inorganic Chemistry, 57(4), 2103-2110
Open this publication in new window or tab >>Structure and Hydrogenation Properties of a HfNbTiVZr High-Entropy Alloy
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2018 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 57, no 4, p. 2103-2110Article in journal (Refereed) Published
Abstract [en]

A high-entropy alloy (HEA) of HfNbTiVZr was synthesized using an arc furnace followed by ball milling. The hydrogen absorption mechanism was studied by in situ X-ray diffraction at different temperatures and by in situ and ex situ neutron diffraction experiments. The body centered cubic (BCC) metal phase undergoes a phase transformation to a body centered tetragonal (BCT) hydride phase with hydrogen occupying both tetrahedral and octahedral interstitial sites in the structure. Hydrogen cycling of the alloy at 500 degrees C is stable. The large lattice strain in the HEA seems favorable for absorption in both octahedral and tetrahedral sites. HEAs therefore have potential as hydrogen storage materials because of favorable absorption in all interstitial sites within the structure.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-348913 (URN)10.1021/acs.inorgchem.7b03004 (DOI)000426014800044 ()29389120 (PubMedID)
Funder
Swedish Foundation for Strategic Research Danish National Research Foundation
Available from: 2018-04-25 Created: 2018-04-25 Last updated: 2018-04-25Bibliographically approved
Malinovskis, P., Fritze, S., Riekehr, L., von Fieandt, L., Cedervall, J., Rehnlund, D., . . . Jansson, U. (2018). Synthesis and characterization of multicomponent (CrNbTaTiW)C films for increased hardness and corrosion resistance. Materials & design, 149, 51-62
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: 2018-08-03Bibliographically approved
Malinovskis, P., Fritze, S., Riekehr, L., von Fieandt, L., Cedervall, J., Rehnlund, D., . . . Jansson, U. (2018). Synthesis and characterization of multicomponent (CrNbTaTiW)C filmsfor increased hardness and corrosion resistance. Materials and Design, 149, 51-62
Open this publication in new window or tab >>Synthesis and characterization of multicomponent (CrNbTaTiW)C filmsfor increased hardness and corrosion resistance
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2018 (English)In: Materials and Design, 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 depositedat 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 tetragonal distortion. X-ray diffraction results show 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 a lattice mismatch of about 11% along the Al2O3[110] direction. A segregation of Cr to the grain boundaries was observed in all films. The microstructure was found to be the most important factor for high hardness. Less dense Nb-rich and near-equimolar films deposited at low temperatures exhibited the lowest hardness (12 GPa), while very dense Ta/W-rich high temperature films were found to be the hardest (36 GPa). No correlation was found 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, in 1.0 M HCl.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
High entropy alloys, Multicomponent carbides, Epitaxial, CrNbTaTiW, Sputtering, Hardness
National Category
Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry; Chemistry with specialization in Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-355544 (URN)10.1016/j.matdes.2018.03.068 (DOI)
Funder
Swedish Research Council, 621-2012-4359Swedish Research Council, 622-2008-405Knut and Alice Wallenberg FoundationSwedish Foundation for Strategic Research , FunCase, RMA11-0029
Available from: 2018-07-01 Created: 2018-07-01 Last updated: 2018-10-04Bibliographically approved
Taher, M., Mao, F., Berastegui, P., Andersson, A. M. & Jansson, U. (2018). The Influence of Chemical and Phase Composition on Mechanical, Tribological and Electrical Properties of Silver-Aluminum alloys. Tribology International, 119, 680-687
Open this publication in new window or tab >>The Influence of Chemical and Phase Composition on Mechanical, Tribological and Electrical Properties of Silver-Aluminum alloys
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2018 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 119, p. 680-687Article in journal (Refereed) Published
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.

National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:uu:diva-320229 (URN)10.1016/j.triboint.2017.11.026 (DOI)000424960500066 ()
Funder
SweGRIDS - Swedish Centre for Smart Grids and Energy Storage
Available from: 2017-04-18 Created: 2017-04-18 Last updated: 2018-04-04Bibliographically approved
Taher, M., Mao, F., Berastegui, P., Andersson, A. M. & Jansson, U. (2018). Tuning tribological, mechanical and electrical properties of Ag-X (X=Al, In, Sn) alloys. Tribology International, 125, 121-127
Open this publication in new window or tab >>Tuning tribological, mechanical and electrical properties of Ag-X (X=Al, In, Sn) alloys
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2018 (English)In: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 125, p. 121-127Article in journal (Refereed) Published
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.

National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:uu:diva-320227 (URN)10.1016/j.triboint.2018.04.020 (DOI)000435747800014 ()
Funder
SweGRIDS - Swedish Centre for Smart Grids and Energy Storage, 38432-1
Available from: 2017-04-18 Created: 2017-04-18 Last updated: 2018-08-27Bibliographically approved
Kádas, K., Iusan, D., Hellsvik, J., Cedervall, J., Berastegui, P., Sahlberg, M., . . . Eriksson, O. (2017). AlM2B2 (M =Cr, Mn, Fe, Co, Ni): a group of nanolaminated materials. Journal of Physics: Condensed Matter, 29(15), Article ID 155402.
Open this publication in new window or tab >>AlM2B2 (M =Cr, Mn, Fe, Co, Ni): a group of nanolaminated materials
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2017 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 29, no 15, article id 155402Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2017
Keywords
nanolaminated ternary borides, phase stability, elastic constants, hardness, scanning electron microscopy
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-320624 (URN)10.1088/1361-648X/aa602a (DOI)000397921600002 ()28192279 (PubMedID)
Funder
Swedish Research Council
Available from: 2017-08-15 Created: 2017-08-15 Last updated: 2017-08-15Bibliographically approved
Johansson, F., Ahlberg, P., Jansson, U., Zhang, S.-L., Lindblad, A. & Nyberg, T. (2017). Minimizing sputter-induced damage during deposition of WS2 onto graphene. Applied Physics Letters, 110(9), Article ID 091601.
Open this publication in new window or tab >>Minimizing sputter-induced damage during deposition of WS2 onto graphene
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2017 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 110, no 9, article id 091601Article in journal (Refereed) Published
Abstract [en]

We demonstrate the sputter-deposition of WS2 onto a single-layer graphene film leaving the latter disorder-free. The sputtering process normally causes defects to the graphene lattice and adversely affects its properties. Sputtering of WS2 yields significant amounts of energetic particles, specifically negative S ions, and reflected neutral Ar, and it is therefore used as a model system in this work. The disorder-free sputtering is achieved by increasing the sputteringpressure of Ar thereby shifting the kinetic energy distribution towards lower energies for the impinging particle flux at the substrate. Raman spectroscopy is used to assess the amount of damage to the graphene film. Monte Carlo simulations of the sputteringprocess show that W is completely thermalized already at relatively low sputtering pressure, whereas Ar and S need a comparably higher pressure to thermalize so as to keep the graphene film intact. Apart from becoming completely amorphous at 2.3 mTorr, the graphene filmremains essentially disorder-free when the pressure is increased to 60 mTorr. The approach used here is generally applicable and readily extendable to sputter-deposition of other material combinations onto sensitive substrates. Moreover, it can be used without changing the geometry of an existing sputtering setup.

National Category
Other Physics Topics Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-316602 (URN)10.1063/1.4977709 (DOI)000397871600010 ()
Available from: 2017-03-04 Created: 2017-03-04 Last updated: 2018-04-11Bibliographically approved
Nygren, K., Samuelsson, M., Arwin, H. & Jansson, U. (2017). Optical methods to quantify amorphous carbon in carbide-based nanocomposite coatings. Thin Solid Films, 638, 291-297
Open this publication in new window or tab >>Optical methods to quantify amorphous carbon in carbide-based nanocomposite coatings
2017 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 638, p. 291-297Article in journal (Other academic) Published
Abstract [en]

We report how the total carbon content and the amorphous carbon (a-C) phase fraction in transition metal carbide/a-C nanocomposite coatings can be obtained using optical methods, which are much more practical for industrial use than conventional X-ray photoelectron spectroscopy. A large set of carbon-containing nanocomposite coatings deposited using different magnetron sputtering techniques were analyzed by X-ray photoelectron spectroscopy, reflectance spectrophotometry, and spectroscopic ellipsometry. The chemical composition and the a-C phase fraction were determined by X-ray photoelectron spectroscopy for each coating and results are presented for the Ti-C, Cr-C, and Nb-C systems. The composition and the a-C phase fraction are correlated to optical reflectance in the visible range, by parametrization in L*a*b* color space, and by ellipsometry primary data. Results show that it is possible to rapidly estimate the composition and the a-C fraction using these optical methods. We propose that optical methods have promising use in the industry as a cost-efficient technique for characterization of carbide-based coatings.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-302062 (URN)10.1016/j.tsf.2017.07.053 (DOI)000411775900038 ()
Available from: 2016-08-29 Created: 2016-08-29 Last updated: 2017-12-20Bibliographically approved
Nygren, K., Andersson, A. M., Eklund, P. & Jansson, U. (2017). Passive films on nanocomposite carbide coatings for electrical contact applications. Journal of Materials Science, 52(13), 8231-8246
Open this publication in new window or tab >>Passive films on nanocomposite carbide coatings for electrical contact applications
2017 (English)In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 52, no 13, p. 8231-8246Article in journal (Refereed) Published
Abstract [en]

Nanocomposite transition metal carbide/amorphous carbon coatings (Me-C/a-C) deposited by magnetron sputtering have excellent electrical contact properties. The contact resistance can be as low as that of noble metal coatings, although it is known to vary by several orders of magnitude depending on the deposition conditions. We have investigated a nanocrystalline niobium carbide/amorphous carbon (NbC (x) /a-C:H) model system aiming to clarify factors affecting the contact resistance for this group of contact materials. For the first time, the surface chemistry is systematically studied, by angle-resolved X-ray photoelectron spectroscopy, and in extension how it can explain the contact resistance. The coatings presented a mean oxide thickness of about 1 nm, which could be grown to 8 nm by annealing. Remarkably, the contact resistances covered four orders of magnitude and were found to be exponentially dependent on the mean oxide thickness. Moreover, there is an optimum in the amount of a-C:H phase where the contact resistance drops very significantly and it is thus important to not only consider the mean oxide thickness. To explain the results, a model relying on surface chemistry and contact mechanics is presented. The lowest contact resistance of a nanocomposite matched that of a gold coating at 1 N load (vs. gold), and such performance has previously not been demonstrated for similar nanocomposite materials, highlighting their useful properties for electrical contact applications.

National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-302061 (URN)10.1007/s10853-017-1039-0 (DOI)000399422000050 ()
Funder
Swedish Foundation for Strategic Research VINNOVASwedish Research Council, VR 2011-3492
Available from: 2016-08-29 Created: 2016-08-29 Last updated: 2017-05-23Bibliographically approved
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