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Näslund, Lars-Åke
Publications (10 of 15) Show all publications
Magnuson, M., Halim, J. & Näslund, L.-Å. (2018). Chemical bonding in carbide MXene nanosheets. Journal of Electron Spectroscopy and Related Phenomena, 224, 27-32
Open this publication in new window or tab >>Chemical bonding in carbide MXene nanosheets
2018 (English)In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 224, p. 27-32Article in journal (Refereed) Published
Abstract [en]

tThe chemical bonding in the carbide core and the surface chemistry in a new group of transition-metalcarbides Tin+1Cn-Tx(n = 1,2) called MXenes have been investigated by surface-sensitive valence bandX-ray photoelectron spectroscopy. Changes in band structures of stacked nano sheets of different thick-nesses are analyzed in connection to known hybridization regions of TiC and TiO2that affect elastic andtransport properties. By employing high excitation energy, the photoelectron cross-section for the C 2s– Ti 3d hybridization region at the bottom of the valence band is enhanced. As shown in this work, theO 2p and F 2p bands strongly depend both on the bond lengths to the surface groups and the adsorptionsites. The effect of surface oxidation and Ar+sputtering on the electronic structure is also discussed.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
MXene, 2D materials, Valence band, X-ray photoelecton spectroscopy, XPS, Chemical bonding, Termination species
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-145690 (URN)10.1016/j.elspec.2017.09.006 (DOI)000428825400006 ()2-s2.0-85030792688 (Scopus ID)
Available from: 2018-03-16 Created: 2018-03-16 Last updated: 2018-06-04Bibliographically approved
Goyenola, C., Lai, C.-C., Näslund, L.-Å., Lu, J., Högberg, H., Hultman, L., . . . Gueorguiev, G. K. (2016). Theoretical prediction and synthesis of CSxFy thin films. The Journal of Physical Chemistry C, 120(17), 9527-9534
Open this publication in new window or tab >>Theoretical prediction and synthesis of CSxFy thin films
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2016 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 17, p. 9527-9534Article in journal (Refereed) Published
Abstract [en]

A new carbon-based compound: CSxFy was addressed by density functional theory calculations and synthesized by reactive magnetron sputtering. Geometry optimizations and energy calculations were performed on graphene-like model systems containing sulfur and fluorine atoms. It is shown that [S+F] concentrations in the range of 0−10 at.%, structural ordered characteristics similar to graphene pieces containing ring defects are energetically feasible. The modeling predicts that CSxFy thin films with graphite and fullerene-like characteristics may be obtained for the mentioned concentration range. Accordingly, thin films were synthesized from a graphite solid target and sulfur hexafluoride as reactive gas. In agreement with the theoretical prediction, transmission electron microscopy characterization and selected area electron diffraction confirmed the presence of small ordered clusters with graphitic features in a sample containing 0.4 at.% of S and 3.4 at.% of F.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-121470 (URN)10.1021/acs.jpcc.6b02718 (DOI)000375631100060 ()
Note

funding agencies: Swedish Foundation for Strategic Research (SSF) [RMA11-0029]; Carl Trygger Foundation for Scientific Research; Swedish Research Council [642-2013-8020]; ERC [258509]; Knut and Alice Wallenberg Foundation; Swedish Government Strategic Research Area in Materials at Linkoping University 

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Available from: 2015-09-21 Created: 2015-09-21 Last updated: 2017-12-04Bibliographically approved
Schroeder, J., Thomson, W., Howard, B., Schell, N., Näslund, L.-Å., Rogström, L., . . . Birch, J. (2015). Industry-relevant magnetron sputtering and cathodic arc ultra-high vacuum deposition system for in situ x-ray diffraction studies of thin film growth using high energy synchrotron radiation. Review of Scientific Instruments, 86(9), 095113
Open this publication in new window or tab >>Industry-relevant magnetron sputtering and cathodic arc ultra-high vacuum deposition system for in situ x-ray diffraction studies of thin film growth using high energy synchrotron radiation
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2015 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 86, no 9, p. 095113-Article in journal (Refereed) Published
Abstract [en]

We present an industry-relevant, large-scale, ultra-high vacuum (UHV) magnetron sputtering and cathodic arc deposition system purposefully designed for time-resolved in situ thin film deposition/annealing studies using high-energy (greater than50 keV), high photon flux (greater than10(12) ph/s) synchrotron radiation. The high photon flux, combined with a fast-acquisition-time (less than1 s) two-dimensional (2D) detector, permits time-resolved in situ structural analysis of thin film formation processes. The high-energy synchrotron-radiation based x-rays result in small scattering angles (less than11 degrees), allowing large areas of reciprocal space to be imaged with a 2D detector. The system has been designed for use on the 1-tonne, ultra-high load, high-resolution hexapod at the P07 High Energy Materials Science beamline at PETRA III at the Deutsches Elektronen-Synchrotron in Hamburg, Germany. The deposition system includes standard features of a typical UHV deposition system plus a range of special features suited for synchrotron radiation studies and industry-relevant processes. We openly encourage the materials research community to contact us for collaborative opportunities using this unique and versatile scientific instrument. (C) 2015 AIP Publishing LLC.

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2015
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-122441 (URN)10.1063/1.4930243 (DOI)000362573300065 ()26429486 (PubMedID)
Note

Funding Agencies|Swedish Research Council via the Rontgen Angstrom Cluster (RAC) Frame Program [2011-6505]; German Federal Ministry of Education and Research (BMBF) [05K12CG1]

Available from: 2015-11-03 Created: 2015-11-02 Last updated: 2018-01-03
Lai, C.-C., Meshkian, R., Dahlqvist, M., Lu, J., Näslund, L.-Å., Rivin, O., . . . Rosén, J. (2015). Structural and chemical determination of the new nanolaminated carbide Mo2Ga2C from first principles and materials analysis. Acta Materialia, 99, 157-164
Open this publication in new window or tab >>Structural and chemical determination of the new nanolaminated carbide Mo2Ga2C from first principles and materials analysis
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2015 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 99, p. 157-164Article in journal (Refereed) Published
Abstract [en]

Following our recent discovery of a new nanolaminated carbide, Mo2Ga2C, we herein present a detailed structural and chemical analysis of this phase based on ab initio calculations, X-ray photoelectron spectroscopy, high resolution scanning transmission electron microscopy, and neutron powder diffraction. Calculations suggest an energetically and dynamically stable structure for C in the octahedral sites between the Mo layers, with Ga bilayers - stacked in a simple hexagonal arrangement - between the Mo2C layers. The predicted elastic properties are below those of the related nanolaminate Mo2GaC. The predicted structure, including lattice parameters and atomic positions, is experimentally confirmed. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2015
Keywords
First principles; Phase stability; Nanolaminated material; Crystal structure; Mo2Ga2C
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-122193 (URN)10.1016/j.actamat.2015.07.063 (DOI)000362145400017 ()
Note

Funding Agencies|Swedish Research Council [621-2011-4420, 642-2013-8020, 621-2014-4890]; Swedish Foundation for Strategic Research through the Synergy Grant FUNCASE Functional Carbides for Advanced Surface Engineering; Future Research Leaders 5 Program; ERC [258509]; Knut and Alice Wallenberg Foundation

Available from: 2015-10-26 Created: 2015-10-23 Last updated: 2018-05-24
Meshkian, R., Näslund, L.-Å., Halim, J., Lu, J., Barsoum, M. W. & Rosén, J. (2015). Synthesis of two-dimensional molybdenum carbide, Mo2C, from the gallium based atomic laminate Mo2Ga2C. Scripta Materialia, 108, 147-150
Open this publication in new window or tab >>Synthesis of two-dimensional molybdenum carbide, Mo2C, from the gallium based atomic laminate Mo2Ga2C
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2015 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 108, p. 147-150Article in journal (Refereed) Published
Abstract [en]

We report on the synthesis of a two-dimensional transition metal carbide, Mo2C, (MXene) obtained by immersing Mo2Ga2C thin films in hydrofluoric acid. Experimental evidences for neither synthesis of a Mo-based MXene nor selective etching of Ga from an atomic nanolaminate have previously been presented. MXene formation is verified through X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray spectroscopy. This discovery unlocks new potential applications for Mo-based MXenes in a host of applications, from thermoelectrics to catalysis and energy storage.

Place, publisher, year, edition, pages
Elsevier, 2015
Keywords
2D materials, Layered structures, MXene, Transmission electron microscopy (TEM), Energy dispersive X-ray spectroscopy (EDS)
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-121255 (URN)10.1016/j.scriptamat.2015.07.003 (DOI)000360250700035 ()
Available from: 2015-09-10 Created: 2015-09-10 Last updated: 2018-05-24Bibliographically approved
Zhirkov, I., Petruhins, A., Näslund, L.-Å., Kolozsvari, S., Polcik, P. & Rosén, J. (2015). Vacuum arc plasma generation and thin film deposition from a TiB2 cathode. Applied Physics Letters, 107(18), 184103
Open this publication in new window or tab >>Vacuum arc plasma generation and thin film deposition from a TiB2 cathode
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2015 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 107, no 18, p. 184103-Article in journal (Refereed) Published
Abstract [en]

We have studied the utilization of TiB2 cathodes for thin film deposition in a DC vacuum arc system. We present a route for attaining a stable, reproducible, and fully ionized plasma flux of Ti and B by removal of the external magnetic field, which leads to dissipation of the vacuum arc discharge and an increased active surface area of the cathode. Applying a magnetic field resulted in instability and cracking, consistent with the previous reports. Plasma analysis shows average energies of 115 and 26 eV, average ion charge states of 2.1 and 1.1 for Ti and B, respectively, and a plasma ion composition of approximately 50% Ti and 50% B. This is consistent with measured resulting film composition from X-ray photoelectron spectroscopy, suggesting a negligible contribution of neutrals and macroparticles to the film growth. Also, despite the observations of macroparticle generation, the film surface is very smooth. These results are of importance for the utilization of cathodic arc as a method for synthesis of metal borides. (C) 2015 AIP Publishing LLC.

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2015
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-123139 (URN)10.1063/1.4935152 (DOI)000364580800071 ()
Note

Funding Agencies|European Research Council under the European Community Seventh Framework Program (FP7)/ERC [258509]; Swedish Research Council (VR) [642-2013-8020]; Knut and Alice Wallenberg Foundation; SSF synergy grant FUNCASE

Available from: 2015-12-07 Created: 2015-12-04 Last updated: 2017-12-01
Holmin, S., Näslund, L.-Å., Sigurdur Ingason, A., Rosén, J. & Zimmerman, E. (2014). Corrosion of ruthenium dioxide based cathodes in alkaline medium caused by reverse currents. Electrochimica Acta, 146, 30-36
Open this publication in new window or tab >>Corrosion of ruthenium dioxide based cathodes in alkaline medium caused by reverse currents
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2014 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 146, p. 30-36Article in journal (Refereed) Published
Abstract [en]

A reverse current obtained during power shutdowns in industrial processes, such as chlor-alkali production or alkaline water electrolysis, is deleterious for hydrogen evolving ruthenium dioxide (Ru02) based cathodes. It has been observed that RuO2 coatings after a power shutdown, necessary for e.g. maintenance, are severely damaged unless polarization rectifiers are employed. In this work we show why these types of cathodes are sensitive to reverse currents, i.e. anodic currents, after hydrogen evolution. RuO2 coatings deposited on nickel substrates were subjected to different electrochemical treatments such as hydrogen evolution, oxygen evolution, or reverse currents in 8 M NaOH at 90 degrees C. Polarity inversion was introduced after hydrogen evolution to simulate the effect of reverse currents. Because of chemical interaction with hydrogen, a significant amount of the RuO2 coating was transformed into hydroxylated species during cathodic polarization. Our study shows that these hydroxylated phases are highly sensitive to electrochemical corrosion during anodic polarization after extended hydrogen evolution.

Place, publisher, year, edition, pages
Elsevier, 2014
Keywords
Hydrogen evolution; RuO2 coatings; Phase transformation; Polarity inversion; Corrosion
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-113016 (URN)10.1016/j.electacta.2014.09.024 (DOI)000345226100005 ()
Note

Funding Agencies|Swedish Research Council [2007-5059]; European Research Council under the European Communities/ERC [258509]; Swedish Research Council (VR) [642-2013-8020]; KAW Fellowship program

Available from: 2015-01-12 Created: 2015-01-08 Last updated: 2017-12-05
Tucker, M., Czigany, Z., Broitman, E., Näslund, L.-Å., Hultman, L. & Rosén, J. (2014). Filtered pulsed cathodic arc deposition of fullerene-like carbon and carbon nitride films. Journal of Applied Physics, 115(14), 144312
Open this publication in new window or tab >>Filtered pulsed cathodic arc deposition of fullerene-like carbon and carbon nitride films
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2014 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 14, p. 144312-Article in journal (Refereed) Published
Abstract [en]

Carbon and carbon nitride films (CNx , 0 ≤ x ≤ 0.26) were deposited by filtered pulsed cathodic arc and were investigated using transmission electron microscopy and X-ray photoelectron spectroscopy. A “fullerene-like” (FL) structure of ordered graphitic planes, similar to that of magnetron sputtered FL-CNx films, was observed in films deposited at 175 °C and above, with N2 pressures of 0 and 0.5 mTorr. Higher substrate temperatures and significant nitrogen incorporation are required to produce similar FL structure by sputtering, which may, at least in part, be explained by the high ion charge states and ion energies characteristic of arc deposition. A gradual transition from majority sp3-hybridized films to sp2 films was observed with increasing substrate temperature. High elastic recovery, an attractive characteristic mechanical property of FL-CNx films, is evident in arc-deposited films both with and without nitrogen content, and both with and without FL structure.

Place, publisher, year, edition, pages
AIP Publishing, 2014
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-105946 (URN)10.1063/1.4871179 (DOI)000334680400059 ()
Available from: 2014-04-15 Created: 2014-04-15 Last updated: 2017-12-05Bibliographically approved
Näslund, L.-Å., Ingason, A. S., Holmin, S. & Rosén, J. (2014). Formation of RuO(OH)(2) on RuO2-Based Electrodes for Hydrogen Production. The Journal of Physical Chemistry C, 118(28), 15315-15323
Open this publication in new window or tab >>Formation of RuO(OH)(2) on RuO2-Based Electrodes for Hydrogen Production
2014 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 28, p. 15315-15323Article in journal (Refereed) Published
Abstract [en]

The catalytic and durable electrode coating of ruthenium dioxide (RuO2), applied on nickel (Ni) substrates, is today utilized as electrocatalytic cathodes for hydrogen production, e.g., in the chlor-alkali process and alkaline water electrolysis. The drawback is, however, the sensitivity to reverse currents obtained during power shutdowns, e.g., at maintenance, where the RuO2-based electrodes can be severely damaged unless polarization rectifiers are employed. Through the material characterization techniques X-ray diffraction and X-ray photoelectron spectroscopy, we can now reveal that RuO2 coatings, when exposed to hydrogen evolution at industrially relevant conditions, transforms into ruthenium oxyhydroxide (RuO(OH)(2)). The study further shows that as the hydrogen evolution proceeds the formed RuO(OH)(2) reduces to metallic ruthenium (Ru).

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2014
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-109369 (URN)10.1021/jp503960q (DOI)000339368700026 ()
Available from: 2014-08-15 Created: 2014-08-15 Last updated: 2017-12-05Bibliographically approved
Näslund, L.-Å. (2014). Hydrogenation of O and OH on Pt(111): A comparison between the reaction rates of the first and the second hydrogen addition steps. Journal of Chemical Physics, 140(10), 104701
Open this publication in new window or tab >>Hydrogenation of O and OH on Pt(111): A comparison between the reaction rates of the first and the second hydrogen addition steps
2014 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 140, no 10, p. 104701-Article in journal (Refereed) Published
Abstract [en]

The formation of water through hydrogenation of oxygen on platinum occurs at a surprisingly low reaction rate. The reaction rate limited process for this catalytic reaction is, however, yet to be settled. In the present work, the reaction rates of the first and the second hydrogen addition steps are compared when hydrogen is obtained through intense synchrotron radiation that induces proton production in a water overlayer on top of the adsorbed oxygen species. A substantial amount of the produced hydrogen diffuses to the platinum surface and promotes water formation at the two starting conditions O/Pt(111) and (H 2O+OH)/Pt(111). The comparison shows no significant difference in the reaction rate between the first and the second hydrogen addition steps, which indicates that the rate determining process of the water formation from oxygen on Pt(111) is neither the first nor the second H addition step or, alternatively, that both H addition steps exert rate control. © 2014 AIP Publishing LLC.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2014
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-116405 (URN)10.1063/1.4867535 (DOI)000334120300046 ()24628190 (PubMedID)2-s2.0-84896327894 (Scopus ID)
Available from: 2015-03-27 Created: 2015-03-26 Last updated: 2017-12-04
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