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  • 151.
    Boström, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Jensen, Jens
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Ion Physics.
    Valizadeh, Sima
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Westin, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    ERDA of Ni-Al2O3/SiO2 solar thermal selective absorbers2008In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 92, no 10, p. 1177-1182Article in journal (Refereed)
    Abstract [en]

    Thin film materials for the use in solar thermal absorbers have been investigated using time-of-flight energy elastic recoil detection analysis (ERDA). The ERDA measurements proved to be very efficient in detecting the elemental depth composition of a selective solar absorber. The three-layer absorber is composed of an 80% nickel-20% alumina film at the base, a 40% nickel-60% alumina layer in the middle and finally an AR film of silica or hybrid-silica film at the top. The difference between solution volume percent and actual volume percent could be investigated when studying individual nickel-alumina films with varying ratios coated on glass substrates. The result showed that there was a maximum difference of 3% between the calculated solution volume percent and the actual volume percentages in the solid films. The ERDA measurements also indicate that about 15% of the nickel found in the nickel-alumina composite films is bound in the form of NiO.

  • 152.
    Boström, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Westin, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Wäckelgård, Ewa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Optimization of a solution-chemically derived solar absorbing spectrally selective surface2007In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 91, no 1, p. 38-43Article in journal (Refereed)
    Abstract [en]

    A previously studied solution chemically derived two layer absorber has been improved by adding a third layer. Simulations done with a thin film program showed that the optimized three layer selective absorber should be composed of an 80% nickel-20% alumina film of 100 nm at the base, a 40% nickel-60% alumina film of 60 nm in the middle and finally a 100% silica film of 85 nm at the top. Experimental results confirmed the computer simulated three layer structure. Prepared absorber consisting of the theoretically found optimized layer structure achieved a solar absorptance, alpha(sol), of 0.97 and a thermal emittance, epsilon(therm), of 0.05.

  • 153.
    Boström, Tobias
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Wäckelgård, Ewa
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Westin, Gunnar
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. oorganisk kemi.
    Anti-reflection coatings for solution-chemically derived nickel—alumina solar absorbers2004In: Solar Energy Materials & Solar Cells, no 84, p. 183-191Article in journal (Refereed)
    Abstract [en]

    In order to suppress reflections from a solar absorber surface an anti-reflection (AR) layer is usually deposited on top of the solar absorbing coating. For the AR coating to function well it be made of a material with a lower refractive index than the underlying surface. Provided that the AR coating is sufficiently thin, it will not increase the thermal emittance value. Besides increasing the solar absorptance it is equally important that the AR layer is long term stable in order to create a successful solar selective coating. The objective was to create a highly efficient, flexible, inexpensive and durable AR coating for solar absorbers using simple techniques. Elastic properties are requested because it prohibits the formation of micro-cracks.

    Mumina, silica and hybrid silica AR coatings were synthesized using solution chemistry and )l-gel techniques. The AR coatings were deposited on the absorber surface using spin

    coating. The absorbers used without an AR layer had a normal solar absorptance of 0.79-0.81 and a normal thermal emittance of 0.03 The optimum anti-reflection coated sample acquired

    a normal solar absorptance of 0.93 while the thermal emittance remained unaltered. The study has shown that by adding a proper AR coating to a solar absorber the spectral selectivity can be considerably enhanced.

  • 154.
    Boström, Tobias
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Wäckelgård, Ewa
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Technology, Department of Engineering Sciences. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Westin, Gunnar
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Technology, Department of Engineering Sciences, Solid State Physics. oorganisk kemi.
    Solution-chemical derived nickel-alumina coatings for thermal solar absorbers2003In: Solar Energy, no 74, p. 497-503Article in journal (Refereed)
  • 155.
    Bowden, Tim
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Polymer Chemistry. polymerkemi.
    Hilborn, Jöns
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Polymer Chemistry. polymerkemi.
    Eriksson, Niklas
    A metal-free catalyst for the catalytic cationic ring opening polymerization of lactones2003In: PMSE Preprints (2003), 88, 2003, p. 535-536Conference paper (Refereed)
  • 156.
    Brandell, D
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Klintenberg, Mattias
    Aabloo, A
    Thomas, JO
    Calculation of the optical absorption spectrum of ErCl3 in poly(ethylene oxide) (PEO)2000In: INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, ISSN 0020-7608, Vol. 80, no 4-5, p. 799-806Article in journal (Refereed)
    Abstract [en]

    The optical absorption spectrum for the rare-earth ion Er3+ in a, amorphous polymer host poly(ethylene oxide) (PEO) has been calculated. A modified Judd-Ofelt theory has been exploited to calculate the oscillator strengths for the electric-dipole transiti

  • 157.
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Molecular Dynamics Modelling a 3D-MB Electrode/Electrolyte Interface2009Conference paper (Refereed)
    Abstract
  • 158.
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Molecular Dynamics Simulations of Li ion and H-conduction in polymer electrolytes2010In: Polymer electrolytes: Fundamentals and applications / [ed] César Sequeira and Diogo Santos, Woodhead Publishing , 2010, p. 314-339Chapter in book (Other academic)
  • 159.
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Multiscale Modelling 3D-Microbattery Materials2009Conference paper (Refereed)
    Abstract
  • 160.
    Brandell, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Understanding Ionic Conductivity in Crystalline Polymer Electrolytes2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Polymer electrolytes are widely used as ion transport media in vital applications such as energy storage devices and electrochemical displays. To further develop these materials, it is important to understand their ionic conductivity mechanisms.

    It has long been thought that ionic conduction in a polymer electrolyte occurs in the amorphous phase, while the crystalline phase is insulating. However, this picture has recently been challenged by the discovery of the crystalline system LiXF6∙PEO6 (X=P, As or Sb) which exhibits higher conductivity than its amorphous counterpart. Their structures comprise interlocking hemi-helical PEO-chain pairs containing Li+ ions and separating them from the XF6- anions.

    The first Molecular Dynamics (MD) simulation study of the LiPF6∙PEO6 system is presented in this thesis. Although its conductivity is too low for most applications at ambient temperature, it can be enhanced by iso- and aliovalent anion doping.

    It is shown that the diffraction-determined structure is well reproduced on simulating the system using an infinite PEO-chain model. The Li-Oet coordination number here becomes 6 instead of 5; minor changes also occur in the polymer backbone configuration. The crystallographic asymmetric unit and diffraction profiles are also reproduced. On simulating a shorter-chain system (n=22), more resembling the real material, the structure retains its double hemi-helices, but the polymer adopts a more relaxed conformation, facilitating the formation of Li+-PF6- pairs.

    Infinite-chain simulation shows the ionic conduction to be dominated by anion motion, in contrast to earlier NMR results. The effects of doping are also reproduced. Shortening the polymer chain-length has the effect of raising the transport number for lithium, thereby bring it into better agreement with experiment. It can be concluded that it is critical to take polymer chain-length and chain-termination into account when modelling ionic conductivity mechanisms in crystalline polymer electrolytes.

    List of papers
    1. Molecular Dynamics simulation of the LiPF6∙PEO6 structure
    Open this publication in new window or tab >>Molecular Dynamics simulation of the LiPF6∙PEO6 structure
    Show others...
    2005 (English)In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 15, no 14, p. 1422-1428Article in journal (Refereed) Published
    Abstract [en]

    Molecular dynamics (MD) simulations have been performed for the crystalline LiPF6·PEO6 system at ambient temperature in an effort to model the detail of its atomic-level structure and dynamics. Start coordinates were taken from the neutron powder diffraction analysis of Gadjourova et al., Chem. Mater., 2001, 13, 1282 (ref. ). Polymer-chain conformation, Li+-ion coordination and thermal displacement parameters are compared with experimentally determined values; the differences found are rationalised in terms of differences between the infinite-chain models investigated (both experimental and theoretical) and the finite chain-length material studied.

    National Category
    Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-92856 (URN)10.1039/b417232a (DOI)
    Available from: 2005-03-31 Created: 2005-03-31 Last updated: 2018-01-08Bibliographically approved
    2. Conduction mechanisms in crsytalline LiPF6∙PEO6 doped with SiF62- and SF6
    Open this publication in new window or tab >>Conduction mechanisms in crsytalline LiPF6∙PEO6 doped with SiF62- and SF6
    In: Chemistry of MaterialsArticle in journal (Refereed) Submitted
    Abstract
    Identifiers
    urn:nbn:se:uu:diva-92857 (URN)
    Available from: 2005-03-31 Created: 2005-03-31 Last updated: 2018-01-08Bibliographically approved
    3. Molecular Dynamics Simulation of the Crystalline Short-Chain Polymer System LiPF6PEO6 (Mw~1000)
    Open this publication in new window or tab >>Molecular Dynamics Simulation of the Crystalline Short-Chain Polymer System LiPF6PEO6 (Mw~1000)
    2005 In: Journal of Materials Chemistry, ISSN 0959-9428, Vol. 15, no 40, p. 4338-4345Article in journal (Refereed) Published
    Abstract
    Identifiers
    urn:nbn:se:uu:diva-95853 (URN)
    Available from: 2007-04-20 Created: 2007-04-20 Last updated: 2018-01-08Bibliographically approved
    4. A molecular dynamics study of ion-conduction mechanisms in crystalline low-Mw LiPF6·PEO6
    Open this publication in new window or tab >>A molecular dynamics study of ion-conduction mechanisms in crystalline low-Mw LiPF6·PEO6
    2007 (English)In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 17, no 37, p. 3938-3946Article in journal (Refereed) Published
    Abstract [en]

    Molecular dynamics (MD) simulation has been used to probe ion-conduction mechanisms in crystalline LiPF6.PEO6 for smectic- and nematic-ordered models of methyl-terminated short-chain monodisperse poly(ethylene oxide) chains with the formula CH3-(OCH2CH2)23-OCH3; Mw = 1059. The effect of aliovalent substitution of the PF6- anion by ca. 1% SiF62- has also been studied. External electric fields in the range 3-6 x 106 V m-1 have been imposed along, and perpendicular to, the chain direction in an effort to promote ion transport during the short timespan of the simulation. Ion-migration barriers along the polymer channel are lower for the nematic models than for the smectic, with anions migrating along the channels more readily than Li-ions. Ion mobility within the smectic interface could also be confirmed, but at a higher field-strength threshold than along the chain direction. Li-ion migration within the smectic plane appears to be suppressed by ion pairing, while Li-ion transport across the smectic gap is facilitated by uncoordinated methoxy end-groups. Interstitial Li-ions introduced into the PEO channel through SiF62- doping are also shown to enhance Li-ion conduction.

    Keywords
    Doping, Interstitials, Energy gap, Pairing, Diffusion, Interfaces, Ion mobility, Polymers, Diffusion barriers, Digital simulation, Electric field effects, External fields, Polyethylene glycols, Theoretical study, Ionic conduction, Molecular ions, Molecular dynamics method
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-92859 (URN)10.1039/b706938c (DOI)000249553200010 ()
    Available from: 2005-03-31 Created: 2005-03-31 Last updated: 2017-12-14Bibliographically approved
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  • 161.
    Brandell, Daniel
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. strukturkemi.
    Ainla, A
    Liivat, Anti
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. strukturkemi.
    Aabloo, A
    Molecular dynamics simulations of Li- and Na-Nafion membranes2006In: SPIE--The International Society for Optical Engineering Vol 61680G: Smart Structures and Materials 2006: Electroactive Polymer Actuators and Devices (EAPAD), 2006, p. 61680G-Conference paper (Refereed)
    Abstract [en]

    Molecular Dynamics (MD) techniques have been used to study the structure and dynamics of hydrated Li- and Na-Nafion membranes. The membranes were generated using a Monte Carlo-approach for Nafion 117 oligomers of Mw = 1100 and with water contents of 7.5 and 20 % by weight, equivalent to 5 and 15 water molecules per sulfonate group, respectively. After equilibration, local structural properties and dynamical features such as coordination, cluster stability, solvation and ion conductivity were studied. In a comparison between the two cationic systems, it is shown that the Na-Nafion system is more sensitive than Li-Nafion to the level of hydration, and also show higher ion conductivity. The ionic conductivity is shown to increase with higher level of hydration.

  • 162.
    Brandell, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Ainla, Alar
    Liivat, Anti
    Aabloo, Alvo
    Molecular Dynamics Simulations of Li- and Na-Nafion Membranes2006In: Proceedings of SPIE, the International Society for Optical Engineering, ISSN 0277-786X, E-ISSN 1996-756X, Vol. 6168, p. 61680G-Article in journal (Refereed)
    Abstract
  • 163. Brandell, Daniel
    et al.
    Karo, Jaanus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Liivat, Anti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Thomas, John
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Molecular dynamics studies of the Nafion®, Dow® and Aciplex® fuel-cell polymer membrane systems2007In: Journal of Molecular Modeling, ISSN 1610-2940, E-ISSN 0948-5023, Vol. 13, no 10, p. 1039-1046Article in journal (Refereed)
    Abstract [en]

    The Nafion, Dow and Aciplex systems – where the prime differences lies in the side-chain length – have been studied by molecular dynamics (MD) simulation under standard pressure and temperature conditions for two different levels of hydration: 5 and 15 water molecules per (H)SO3 end-group. Structural features such as water clustering, water-channel dimensions and topology, and the dynamics of the hydronium ions and water molecules have all been analysed in relation to the dynamical properties of the polymer backbone and side-chains. It is generally found that mobility is promoted by a high water content, with the side-chains participating actively in the H3O+/H2O transport mechanism. Nafion, whose side-chain length is intermediate of the three polymers studied, is found to have the most mobile polymer side-chains at the higher level of hydration, suggesting that there could be an optimal side-chain length in these systems. There are also some indications that the water-channel network connectivity is optimal for high water-content Nafion system, and that this could explain why Nafion appears to exhibit the most favourable overall hydronium/water mobility.

  • 164.
    Brandell, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Karo, Jaanus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Thomas, John O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    MD-assisted Design of PEMFC Electrolytes2009Conference paper (Refereed)
    Abstract
  • 165.
    Brandell, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Karo, Jaanus
    Thomas, John O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
     Modelling the Nafion® diffraction profile by molecular dynamics simulation2010In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 195, no 18, p. 5962-5965Article in journal (Refereed)
    Abstract [en]

    A diffraction profile is here derived from classical Molecular Dynamics (MD) simulation for the hydrated perfluorosulphonic acid fuel-cell membrane material Nafion at 363 K using a 76 angstrom x 76 angstrom x 76 angstrom box. The MD simulation reproduces the phase-separated nanoscale structure of Nafion and water channels. No specific structural features, such as a characteristic channel diameter, could be distinguished. Nevertheless, the envelope of the simulated diffraction profile based on 6000 MD "snapshots" reproduced well the key features of the experimental SAXS profile. This draws into questions previous interpretations of diffraction data for the Nafion (R) system which involve simplistic notions of channel- and cluster-diameter.

  • 166.
    Brandell, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Karo, Jaanus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Thomas, John O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    State-of-the art MD simulation of PEMFC Electrolytes2009Conference paper (Refereed)
    Abstract
  • 167.
    Brandell, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Kasemägi, Heiki
    Aabloo, Alvo
    Poly(ethylene oxide)-poly(butadiene) interpenetrated networks as electroactive polymers for actuators: a molecular dynamics study2010In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 55, no 4, p. 1333-1337Article in journal (Refereed)
    Abstract [en]

    Molecular dynamics (MD)techniques have been used to study ionic transport and coordination stability in an interpenetrating polymer (IPN) network used as electrolyte for actuator devices. The system consisted of poly(ethylene oxide) (PEO) and poly(butadiene) (PB) in a 80/20% weight ratio at a total polymer of 32%, immersed into propylene carbonate (PC) solutions of LiClO4. The system has been studied for five different concentrations of LiClO4 in PC: 0.25, 0.5, 0.75, 1.0 and 1.25 M, and with applied external electric fields of 0. 1 and 5 MV/m. It is shown that the polymer matrix has little involvement in the movement of ions and solvent, but that the polymer arrangement is important for the solvent phase nano-structure, and thereby influences the mobility. The mobility of PC is higher than of the other species in the system, but the charged species display higher mobility under external field. The field threshold level for conductivity processes is between 1 and 5 MV/m. It is argued that ion pairing, phase separation and coordination stability are important for the overall dynamic properties.

  • 168.
    Brandell, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Kasemägi, Heiki
    Citérin, Johann
    Vidal, Frédéric
    Chevrot, Claude
    Aabloo, Alvo
    Molecular Dynamics studies of interpenetrated polymer networks for actuator devices2008In: Proceedings of SPIE, the International Society for Optical Engineering, ISSN 0277-786X, E-ISSN 1996-756X, Vol. 6927Article in journal (Refereed)
  • 169.
    Brandell, Daniel
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. strukturkemi.
    Klintenberg, M
    Aabloo, A
    Thomas, John Oswald
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. strukturkemi.
    Calculation of the optical absorption spectrum of ErCl3 in poly(ethelylene oxide)(PEO).2000In: Int. J. Quant. Chem., Vol. 80, p. 799-Article in journal (Refereed)
  • 170.
    Brandell, Daniel
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. strukturkemi.
    Klintenberg, M
    Aabloo, A
    Thomas, John Oswald
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. strukturkemi.
    Optical absorption spectra from rare-earth ions in polymers: the effect of the polymer host2002In: Macromolecular Symposia, Vol. 186, p. 51-Article in journal (Refereed)
  • 171.
    Brandell, Daniel
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. strukturkemi.
    Klintenberg, M
    Aabloo, A
    Thomas, John Oswald
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. strukturkemi.
    The effect of the polymer host on optical absorption spectra for Er(CF3SO3)3 in poly(ethylene oxide)2002In: Journal of Materials Chemistry, Vol. 12, p. 565-Article in journal (Refereed)
  • 172.
    Brandell, Daniel
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. strukturkemi.
    Liivat, Anti
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. strukturkemi.
    Aabloo, A
    Thomas, John Oswald
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. strukturkemi.
    Conduction Mechanisms in Crystalline LiPF6·PEO6 Doped with SiF62- and SF62005In: Chem. Mater, Vol. 17, no 14, p. 3673-3680Article in journal (Refereed)
    Abstract [en]

    Molecular dynamics (MD) simulations have been made under imposed electric fields for crystalline LiPF6·PEO6, (LiPF6)1-x(Li2SiF6)x·PEO6, and (LiPF6)1-x(SF6)x·PEO6 for x = 0.01 under standard pressure and temperature conditions with the aim of identifying the conduction mechanisms in the systems. Contrary to the results of earlier experimental investigations where only cation mobility was observed, ionic transport is here found to occur in regions between the polymer hemi-helices, with a high transference number (0.9-1.0) for the PF6- anions.

  • 173.
    Brandell, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Liivat, Anti
    Aabloo, Alvo
    Thomas, Josh
    Conduction mechanisms in crsytalline LiPF6∙PEO6 doped with SiF62- and SF6In: Chemistry of MaterialsArticle in journal (Refereed)
    Abstract
  • 174. Brandell, Daniel
    et al.
    Liivat, Anti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Aabloo, Alvo
    Thomas, Josh
    Molecular Dynamics Simulation of the Crystalline Short-Chain Polymer System LiPF6PEO6 (Mw~1000)2005In: Journal of Materials Chemistry, ISSN 0959-9428, Vol. 15, no 40, p. 4338-4345Article in journal (Refereed)
    Abstract
  • 175.
    Brandell, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Liivat, Anti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Kasemägi, Heiki
    Aabloo, Alvo
    Thomas, Josh
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Molecular Dynamics simulation of the LiPF6∙PEO6 structure2005In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 15, no 14, p. 1422-1428Article in journal (Refereed)
    Abstract [en]

    Molecular dynamics (MD) simulations have been performed for the crystalline LiPF6·PEO6 system at ambient temperature in an effort to model the detail of its atomic-level structure and dynamics. Start coordinates were taken from the neutron powder diffraction analysis of Gadjourova et al., Chem. Mater., 2001, 13, 1282 (ref. ). Polymer-chain conformation, Li+-ion coordination and thermal displacement parameters are compared with experimentally determined values; the differences found are rationalised in terms of differences between the infinite-chain models investigated (both experimental and theoretical) and the finite chain-length material studied.

  • 176.
    Brandell, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Priimaegi, Priit
    Kasemaegi, Heiki
    Aabloo, Alvo
    Branched polyethylene/poly(ethylene oxide) as a host matrix for Li-ion battery electrolytes: A molecular dynamics study2011In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 57, p. 228-236Article in journal (Refereed)
    Abstract [en]

    This article discusses the structural and dynamic properties of a model polymer electrolyte system suitable for Li-ion batteries, investigated by Molecular Dynamics simulations at 293 K. It consists of a non-polar polyethylene backbone, onto which polar oligomeric polyethylene oxide side-chains of length 4-15 EO units are attached. LiPF(6) salt is dissolved into the matrix to a concentration corresponding to a Li:EO ratio of 1:12. It is found that the system display significantly higher mobility values that linear PEO using the same concentration, which is attributed to the high side-chain dynamics and the polar/non-polar topology of the system. An optimum side-chain length of 10 EO units is found for many properties, such as the dissolution of salt, although the Li(+) ion diffusion was found to be the highest for side-chain lengths of 15 EO units: 1.54 x 10(-13) m(2) s(-1).

  • 177.
    Brandell, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Zadin, Vahur
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Thomas, John O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    3DMicrobattery Design Limitations from MD/FEA Simulation2009Conference paper (Refereed)
    Abstract
  • 178.
    Brandell, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Zadin, Vahur
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Thomas, John O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    The Challenge of Modelling the 3D-Microbattery2009Conference paper (Refereed)
    Abstract
  • 179.
    Broddefalk, A
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Nordblad, P
    Berger, Rolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry. oorganisk kemi. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Structural and magnetic properties of TlCo2-xCuxSe2, 0 <= x <= 12000In: PHYSICA B, ISSN 0921-4526, Vol. 284, p. 1317-1318Article in journal (Refereed)
    Abstract [en]

    Structural and magnetic properties of single-crystal TlCo2-xCuxSe2, 0 less than or equal to x less than or equal to 1, have been investigated by means of X-ray diffraction experiments and magnetisation measurements. TlCo2Se2 and TlCu2Se2 are isostructural

  • 180.
    Brucas, R.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Hafermann, H.
    Institute of Theoretical Physics, University of Hamburg, 20355 Hamburg, Germany.
    Soroka, I. L.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Iusan, Diana
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Sanyal, B.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Katsnelson, M. I.
    Institute for Molecules and Materials, Radboud University, 6525 ED Nijmegen, The Netherlands.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Magnetic anisotropy and evolution of ground-state domain structures in bcc Fe81Ni19/Co(001) superlattices2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 78, no 2, p. 024421-Article in journal (Refereed)
    Abstract [en]

    The magnetic anisotropy and evolution of striped magnetic domain structures in bcc Fe81Ni19/Co(001) superlattices with the total thickness ranging from 85 to 1370 nm has been studied by magneto-optical Kerr effect and magnetic force microscopy. At a thickness of about 85 nm [25 bilayers (BL)] the domains appear as stripe domains, typical for perpendicular anisotropy films, with the weak cubic anisotropy of the in-plane magnetization component stabilizing the stripe direction. The magnetic domain period strongly depends on the thickness of the superlattice. As the thickness increases, the equilibrium magnetization orients at oblique angles with respect to the film plane and continuously varies with the thickness from in-plane to out-of-plane. We first apply a simple phenomenological model which correctly predicts the transition from in-plane to out-of-plane magnetization as well as increasing domain period and saturation field with increasing BL number. The results indicate the presence of partial flux-closure domains at the film surface with the tilt angle continuously varying with the superlattice thickness. By solving a linearized Landau–Lifshitz equation together with Maxwell’s equations in magnetostatic approximation for samples consisting of up to 1000 individual layers, we calculate the spin-wave dispersion and determine the stability conditions for the saturated ferromagnetic state. From these results the dependence of the saturation field on the number of layers is inferred and agrees well with the experiment. The uniaxial bulk anisotropy is attributed to distortions along the c axis and the results further show evidence for the presence of an easy-plane interface anisotropy in these samples.

  • 181.
    Bryngelsson, Hanna
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Insights into Stability Aspects of Novel Negative Electrodes for Li-ion Batteries2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Demands for high energy-density batteries have sharpened with the increased use of portable electronic devices, as has the focus global warming is now placing on the need for electric and electric-hybrid vehicles. Li-ion battery technology is superior to other rechargeable battery technologies in both energy- and power-density. A remaining challenge, however, is to find an alternative candidate to graphite as the commercial anode. Several metals can store more lithium than graphite, e.g., Al, Sn, Si and Sb. The main problem is the large volume changes that these metals undergo during the lithiation process, leading to degradation and pulverization of the anode with resulting limitations in cycle-life.

    The Li-ion battery is studied in this thesis with the goal of better understanding the critical parameters determining high and stable electrochemical performance when using a metal or a metal-alloy anode. Various antimony-containing systems will be presented. These represent different routes to circumvent the problems caused by volume change. Sb-compounds exhibit a high lithium storage capability. At most, three Li-ions can be stored per Sb atom, leading to a theoretical gravimetric capacity of 660 mAh/g. Model systems with stepwise increasing complexity have been designed to better understand the factors influencing lithium insertion/extraction.

    It is demonstrated that the microstructure of the anode material is crucial to stable cycling performance and high reversibility. The relative importance of the various factors controlling stability, such as particle-size, oxide content and morphology, varies strongly with the type of system studied. The cycling performance of pure Sb is improved dramatically by incorporating a second component, Sb2O3. With a critical oxide concentration of ~25%, a stable capacity close to the theoretical value of 770 mAh/g is obtained for over 50 cycles. Cu2Sb shows stable cycling performance in the absence of oxide. Cu9Sb2 has been presented for the first time as an anode material in a Li-ion battery context. Studies of the Solid Electrolyte Interphase (SEI) formed on AlSb composite electrodes show an SEI layer thinner than graphite, and with a clearly dynamic character.

    List of papers
    1. Electrodeposited Sb and Sb/Sb2O3 nanoparticle coatings as anode materials for Li-ion batteries
    Open this publication in new window or tab >>Electrodeposited Sb and Sb/Sb2O3 nanoparticle coatings as anode materials for Li-ion batteries
    Show others...
    2007 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 19, no 5, p. 1170-1180Article in journal (Refereed) Published
    Abstract [en]

    Galvanostatically electrodeposited coatings of pure Sb or co-deposited Sb and Sb2O3 nanoparticles, prepared from antimony tartrate solutions, were studied as anode materials in Li-ion batteries. It is demonstrated that the co-deposition of 20-25% (w/w) Sb2O3 results from a local pH increase at the cathode (due to protonation of liberated tartrate) in poorly buffered solutions. This causes precipitation of Sb2O3 nanoparticles and inclusion of some of the particles in the deposit where they become coated with a protecting layer of Sb. Chronopotentiometric cycling of the deposits, which also were characterized using, e.g., SEM, TEM, and XRD, clearly showed that the Sb2O3-containing deposits were superior as anode materials. While the Sb/Sb2O3 coatings exhibited a specific capacity close to the Sb theoretical value of 660 mA·h·g -1 during more than 50 cycles, the capacity for the Sb coatings gradually decreased to about 250 mA·h·g-1. This indicates that the influence of the significant volume changes present upon the formation and oxidation of Li3Sb was much smaller for the Sb/Sb2O3 nanoparticle coatings. The improved performance can be explained by significant formation of Sb2O3 during the reoxidation, the presence of smaller Sb particles in the Sb/Sb2O3 coatings, and the formation of buffering nanoparticles of Li2O in a matrix of Sb during the first reduction cycle for the Sb/Sb2O3 deposits.

    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-96156 (URN)10.1021/cm0624769 (DOI)000244467800034 ()
    Available from: 2007-09-07 Created: 2007-09-07 Last updated: 2022-01-28
    2. Electrodeposition and electrochemical characterisation of thick and thin coatings of Sb and Sb/Sb2O3 particles for Li-ion battery anodes
    Open this publication in new window or tab >>Electrodeposition and electrochemical characterisation of thick and thin coatings of Sb and Sb/Sb2O3 particles for Li-ion battery anodes
    2007 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, no 3, p. 1062-1073Article in journal (Refereed) Published
    Abstract [en]

    The possibilities to electrodeposit thick coatings composed of nanoparticles of Sb and Sb2O3 for use as high-capacity anode materials in Li-ion batteries have been investigated. It is demonstrated that the stability of the coatings depends on their Sb2O3 concentrations as well as microstructure. The electrodeposition reactions in electrolytes with different pH and buffer capacities were studied using chronopotentiometry and electrochemical quartz crystal microbalance measurements. The obtained deposits, which were characterised with XRD and SEM, were also tested as anode materials in Li-ion batteries. The influence of the pH and buffer capacity of the deposition solution on the composition and particle size of the deposits were studied and it is concluded that depositions from a poorly buffered solution of antimony-tartrate give rise to good anode materials due to the inclusion of precipitated Sb2O3 nanoparticles in the Sb coatings. Depositions under conditions yielding pure Sb coatings give rise to deposits composed of large crystalline particles with poor anode stabilities. The presence of a plateau at about 0.8V versus Li+/Li due to SEI forming reactions and the origin of another plateau at about 0.4 V versus Li+/Li seen during the lithiation of thin Sb coatings are also discussed. It is demonstrated that the 0.4 V plateau is present for Sb coatings for which the (0 1 2) peak is the main peak in the XRD diffractogram.

    Keywords
    Transition metal, Lithion ion batteries, Electrical characteristic, Morphology, Surface structure, Secondary cell, Electrochemical reaction, Specific capacity, Reaction mechanism, Electrode material, Nanoparticle, Anode, Nickel, Antimony Oxides, Thin film, Scanning electron microscopy, X ray diffraction, Antimony, Electrodeposition
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-96859 (URN)10.1016/j.electacta.2007.02.009 (DOI)000251305300004 ()
    Available from: 2008-03-19 Created: 2008-03-19 Last updated: 2022-01-28
    3. Thin films of Cu2Sb and Cu9Sb2 as anode materials in Li-ion batteries
    Open this publication in new window or tab >>Thin films of Cu2Sb and Cu9Sb2 as anode materials in Li-ion batteries
    2008 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, no 24, p. 7226-7234Article in journal (Refereed) Published
    Abstract [en]

    Thin Cu2Sb films have been prepared by heat-treating Sb films. electrodeposited on Cu substrates. The influence of the electrodeposition conditions and the heat-treatment period on composition and morphology of the films were investigated (SEM and XRD) and the obtained films were tested as anode materials for Li-ion batteries. The Cu2Sb material showed a stable capacity of 290 mAh g(-1) (close to the theoretical capacity of 323 mAh g-1) during more than 60 cycles. The presence of 9-11% (w/w) Sb2O3 in the electrodeposited films resulted in smaller particles but also slowed down formation of Cu2Sb during the heat-treatment step. The presence of Sb2O3 was found to decrease the cycling stability although structural reversibility of Cu2Sb was obtained both with and without Sb2O3. Longer heat-treatment of pure Sb films resulted in the formation of Cu9Sb2 which was shown to be reduced at a lower potential than Cu2Sb. The Cu9Sb2 was converted to Cu2Sb during repeated cycling and the capacity of the latter Cu2Sb material was found to be 230 mAh g(-1). While reduction of the materials was complicated by simultaneous formation of an SEI layer, three plateaus Could be identified during the oxidation of Li3Sb, indicating the presence of three separate one-electron oxidation reactions.

    Keywords
    Li-ion batteries, anode material, Cu2Sb, electrodeposition, Cu9Sb
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-96860 (URN)10.1016/j.electacta.2008.05.005 (DOI)000258977900027 ()
    Available from: 2008-03-19 Created: 2008-03-19 Last updated: 2022-01-28
    4. Surface chemistry of intermetallic AlSb-anodes for Li-ion batteries
    Open this publication in new window or tab >>Surface chemistry of intermetallic AlSb-anodes for Li-ion batteries
    Show others...
    2007 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 52, no 15, p. 4947-4955Article in journal (Refereed) Published
    Abstract [en]

    The solid electrolyte interphase (SEI) layer on AlSb electrodes has been studied in Li/AlSb cells containing a LiPF6 EC/DEC electrolyte using X-ray photoelectron spectroscopy (XPS). Data were collected before SEI-formation, during formation, and after formation at 0.01 V versus Li0/Li+, and at full delithiation in cycled cells at 1.20 V. The thickness of the SEI layer increases during lithiation and decreases during delithiation. This dynamic behaviour occurs continuously on cycling the cells. The growth of the SEI layer can be attributed predominantly to the deposition of carbonaceous species below 0.50 V versus Li0/Li+; these species disappear almost completely during delithiation. The extra surface-layer formation is a consequence of the additional charge that is needed to lithiate the remaining Sb component of the micrometer-sized AlSb particles at low potentials as seen by synchrotron-based X-ray diffraction. Aluminium is not reactive to lithium alloying in this electrolyte. Relatively small amounts of LiF were detected in the AlSb SEI layers compared to that commonly found in the SEI layers on graphite electrodes.

    Keywords
    SEI, AlSb, Intermetallic, Anode, Li-ion battery
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-96219 (URN)10.1016/j.electacta.2007.01.064 (DOI)000246160300012 ()
    Available from: 2007-09-07 Created: 2007-09-07 Last updated: 2022-01-28
    5. How dynamic is the SEI?
    Open this publication in new window or tab >>How dynamic is the SEI?
    2007 (English)In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 174, no 2, p. 970-975Article in journal (Refereed) Published
    Abstract [en]

    The surface chemistry of graphite and intermetallic AlSb has been studied by XPS (X-ray photoelectron spectroscopy) in a Li-ion battery context using LiPF6 in EC/DEC as electrolyte. The main results for graphite are as follows: the SEI (solid electrolyte interphase) is different for the lithiated state after 3 cycles (0.01 V) compared to the delithiated state (1.5 V); after 50 cycles the SEI is thicker; there are more Li2CO3 or semi-carbonates on the surface of the delithiated sample (1.5 V) than on the lithiated sample (0.01 V); LiF is continuously formed during the first cycles but a steady state is reached after 50 cycles; a new peak in the C 1s spectra indicating a fluorine-containing compound is found at high photon energies (292 eV). The main results for AlSb are as follows: the SEI is different for the lithiated state (0.01 V) compared to the delithiated state (1.2 V) after 3 cycles; after 50 cycles the surface layer thickness is slightly larger but significantly thinner than for graphite; contrary to graphite, more Li2CO3 or semi-carbonates are found on the surface of the lithiated sample; also here a new peak indicating a fluorine-containing compound is found in the C 1s spectra at 292 eV. The general result is that the SEI has many similar features between graphite and AlSb but also important differences. The carbonaceous layer is dynamically shifting in chemical composition during cycling for both samples.

    Keywords
    Li-ion battery, Intermetallic anode, SEI, Graphite, XPS, AlSb
    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-96220 (URN)10.1016/j.jpowsour.2007.06.050 (DOI)000252020500118 ()
    Available from: 2007-09-07 Created: 2007-09-07 Last updated: 2022-01-28
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  • 182.
    Bryngelsson, Hanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Eskhult, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Electrodeposition and electrochemical characterisation of thick and thin coatings of Sb and Sb/Sb2O3 particles for Li-ion battery anodes2007In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, no 3, p. 1062-1073Article in journal (Refereed)
    Abstract [en]

    The possibilities to electrodeposit thick coatings composed of nanoparticles of Sb and Sb2O3 for use as high-capacity anode materials in Li-ion batteries have been investigated. It is demonstrated that the stability of the coatings depends on their Sb2O3 concentrations as well as microstructure. The electrodeposition reactions in electrolytes with different pH and buffer capacities were studied using chronopotentiometry and electrochemical quartz crystal microbalance measurements. The obtained deposits, which were characterised with XRD and SEM, were also tested as anode materials in Li-ion batteries. The influence of the pH and buffer capacity of the deposition solution on the composition and particle size of the deposits were studied and it is concluded that depositions from a poorly buffered solution of antimony-tartrate give rise to good anode materials due to the inclusion of precipitated Sb2O3 nanoparticles in the Sb coatings. Depositions under conditions yielding pure Sb coatings give rise to deposits composed of large crystalline particles with poor anode stabilities. The presence of a plateau at about 0.8V versus Li+/Li due to SEI forming reactions and the origin of another plateau at about 0.4 V versus Li+/Li seen during the lithiation of thin Sb coatings are also discussed. It is demonstrated that the 0.4 V plateau is present for Sb coatings for which the (0 1 2) peak is the main peak in the XRD diffractogram.

  • 183.
    Bryngelsson, Hanna
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. strukturkemi.
    Eskhult, Jonas
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Nyholm, Leif
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Edström, Kristina
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. strukturkemi.
    Electrodeposited Nano-sized Thin Films of Sb and Sb2O3 as Anode Materials in Li-ion Batteries2006In: Presented at the 57th Annual Meeting of the International Society of Electrochemistry, Edinburgh, August 27 - September 1, 2006Conference paper (Refereed)
  • 184.
    Bryngelsson, Hanna
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. strukturkemi.
    Eskhult, Jonas
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Nyholm, Leif
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Edström, Kristina
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. strukturkemi.
    The role of the Oxide in Electrodeposited Nano-sized Thin Films of Sb2006In: Presented at the International Meeting on Lithium Batteries (IMLB2006) meeting in Biarritz, France, June 18-23, 2006Conference paper (Refereed)
  • 185.
    Bryngelsson, Hanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Eskhult, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Thin films of Cu2Sb and Cu9Sb2 as anode materials in Li-ion batteries2008In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 53, no 24, p. 7226-7234Article in journal (Refereed)
    Abstract [en]

    Thin Cu2Sb films have been prepared by heat-treating Sb films. electrodeposited on Cu substrates. The influence of the electrodeposition conditions and the heat-treatment period on composition and morphology of the films were investigated (SEM and XRD) and the obtained films were tested as anode materials for Li-ion batteries. The Cu2Sb material showed a stable capacity of 290 mAh g(-1) (close to the theoretical capacity of 323 mAh g-1) during more than 60 cycles. The presence of 9-11% (w/w) Sb2O3 in the electrodeposited films resulted in smaller particles but also slowed down formation of Cu2Sb during the heat-treatment step. The presence of Sb2O3 was found to decrease the cycling stability although structural reversibility of Cu2Sb was obtained both with and without Sb2O3. Longer heat-treatment of pure Sb films resulted in the formation of Cu9Sb2 which was shown to be reduced at a lower potential than Cu2Sb. The Cu9Sb2 was converted to Cu2Sb during repeated cycling and the capacity of the latter Cu2Sb material was found to be 230 mAh g(-1). While reduction of the materials was complicated by simultaneous formation of an SEI layer, three plateaus Could be identified during the oxidation of Li3Sb, indicating the presence of three separate one-electron oxidation reactions.

  • 186.
    Bryngelsson, Hanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Eskhult, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Herranen, Merja
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Alm, Oscar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Electrodeposited Sb and Sb/Sb2O3 nanoparticle coatings as anode materials for Li-ion batteries2007In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 19, no 5, p. 1170-1180Article in journal (Refereed)
    Abstract [en]

    Galvanostatically electrodeposited coatings of pure Sb or co-deposited Sb and Sb2O3 nanoparticles, prepared from antimony tartrate solutions, were studied as anode materials in Li-ion batteries. It is demonstrated that the co-deposition of 20-25% (w/w) Sb2O3 results from a local pH increase at the cathode (due to protonation of liberated tartrate) in poorly buffered solutions. This causes precipitation of Sb2O3 nanoparticles and inclusion of some of the particles in the deposit where they become coated with a protecting layer of Sb. Chronopotentiometric cycling of the deposits, which also were characterized using, e.g., SEM, TEM, and XRD, clearly showed that the Sb2O3-containing deposits were superior as anode materials. While the Sb/Sb2O3 coatings exhibited a specific capacity close to the Sb theoretical value of 660 mA·h·g -1 during more than 50 cycles, the capacity for the Sb coatings gradually decreased to about 250 mA·h·g-1. This indicates that the influence of the significant volume changes present upon the formation and oxidation of Li3Sb was much smaller for the Sb/Sb2O3 nanoparticle coatings. The improved performance can be explained by significant formation of Sb2O3 during the reoxidation, the presence of smaller Sb particles in the Sb/Sb2O3 coatings, and the formation of buffering nanoparticles of Li2O in a matrix of Sb during the first reduction cycle for the Sb/Sb2O3 deposits.

  • 187.
    Bryngelsson, Hanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Stjerndahl, Mårten
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Gustafsson, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    How dynamic is the SEI?2007In: Journal of Power Sources, ISSN 0378-7753, E-ISSN 1873-2755, Vol. 174, no 2, p. 970-975Article in journal (Refereed)
    Abstract [en]

    The surface chemistry of graphite and intermetallic AlSb has been studied by XPS (X-ray photoelectron spectroscopy) in a Li-ion battery context using LiPF6 in EC/DEC as electrolyte. The main results for graphite are as follows: the SEI (solid electrolyte interphase) is different for the lithiated state after 3 cycles (0.01 V) compared to the delithiated state (1.5 V); after 50 cycles the SEI is thicker; there are more Li2CO3 or semi-carbonates on the surface of the delithiated sample (1.5 V) than on the lithiated sample (0.01 V); LiF is continuously formed during the first cycles but a steady state is reached after 50 cycles; a new peak in the C 1s spectra indicating a fluorine-containing compound is found at high photon energies (292 eV). The main results for AlSb are as follows: the SEI is different for the lithiated state (0.01 V) compared to the delithiated state (1.2 V) after 3 cycles; after 50 cycles the surface layer thickness is slightly larger but significantly thinner than for graphite; contrary to graphite, more Li2CO3 or semi-carbonates are found on the surface of the lithiated sample; also here a new peak indicating a fluorine-containing compound is found in the C 1s spectra at 292 eV. The general result is that the SEI has many similar features between graphite and AlSb but also important differences. The carbonaceous layer is dynamically shifting in chemical composition during cycling for both samples.

  • 188.
    Brännvall, Karin
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Bergman, Kristoffer
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Wallenquist, Ulrika
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Svahn, Stefan
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Bowden, Tim
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Hilborn, Jöns
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Forsberg-Nilsson, Karin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Enhanced neuronal differentiation in a three-dimensional collagen-hyaluronan matrix2007In: Journal of Neuroscience Research, ISSN 0360-4012, E-ISSN 1097-4547, Vol. 85, no 10, p. 2138-2146Article in journal (Refereed)
    Abstract [en]

    Efficient 3D cell systems for neuronal induction are needed for future use in tissue regeneration. In this study, we have characterized the ability of neural stem/progenitor cells (NS/PC) to survive, proliferate, and differentiate in a collagen type I-hyaluronan scaffold. Embryonic, postnatal, and adult NS/PC were seeded in the present 3D scaffold and cultured in medium containing epidermal growth factor and fibroblast growth factor-2, a condition that stimulates NS/PC proliferation. Progenitor cells from the embryonic brain had the highest proliferation rate, and adult cells the lowest, indicating a difference in mitogenic responsiveness. NS/PC from postnatal stages down-regulated nestin expression more rapidly than both embryonic and adult NS/PC, indicating a faster differentiation process. After 6 days of differentiation in the 3D scaffold, NS/PC from the postnatal brain had generated up to 70% neurons, compared with 14% in 2D. NS/PC from other ages gave rise to approximately the same proportion of neurons in 3D as in 2D (9-26% depending on the source for NS/PC). In the postnatal NS/PC cultures, the majority of III-tubulin-positive cells expressed glutamate, -aminobutyric acid, and synapsin I after 11 days of differentiation, indicating differentiation to mature neurons. Here we report that postnatal NS/PC survive, proliferate, and efficiently form synapsin I-positive neurons in a biocompatible hydrogel.

  • 189. Bucur, R.V
    et al.
    Mecea, V.M
    Carlsson, Jan-Otto
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    EQCM with air-gap exitation electrode. Calibration tests with copper and oxygen coatings2003In: Electrochimica Acta, no 48, p. 3431-3438Article in journal (Refereed)
  • 190. Burba, Christopher M.
    et al.
    Frech, Roger
    Seidel, Agneta
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Häggström, Lennart
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Nytén, Anton
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Thomas, John O.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Detecting unalloyed tin in LiSn2(PO4)3-based anodes with Mössbauer spectroscopy2009In: Journal of Solid State Electrochemistry, ISSN 1432-8488, E-ISSN 1433-0768, Vol. 13, no 8, p. 1267-1272Article in journal (Refereed)
    Abstract [en]

    The first discharge of the Li+ ion anode material LiSn2(PO4)3 was investigated with Mössbauer spectroscopy and electrochemical techniques. Mössbauer spectroscopy provided insight into the structure of the tin atoms of the fully discharged anode materials. Spectra consist of overlapping peaks, which are assigned to noncrystalline β-Sn and Li–Sn alloy domains. An analysis of the relative intensities of the Mössbauer spectra shows the relative abundance of β-Sn increases at the expense of the Li–Sn alloy as the discharge rate increases. Cell polarization occurs at higher discharge rates, leading to inefficient electrode utilization and poor cycling performance. Sluggish Li+ ion diffusion through the amorphous Li3PO4 network that is formed early in the discharge process might be responsible for the poor electrochemical performance and the accumulation of unalloyed tin.

  • 191. Carbone, M
    et al.
    Larsson, Karin
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Carlsson, Jan-Otto
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorgansik kemi.
    Diamond Nucleation on Hexagonal Boron Nitride: A Theoretical Investigation of the Influence of CH3 and Na Substituents1998In: J. Phys. Chem., Vol. 102, no 30, p. 5866-Article in journal (Refereed)
    Abstract [en]

    The effect of CH3 and Na on diamond nucleation on hexagonal boron nitride (h-BN) was investigated theoretically by using the DFT method. The methyl and sodium species were used as substituents on zigzag edge atoms of the basal plane. Outgrowths correspon

  • 192. Carbone, M
    et al.
    Larsson, Karin
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Carlsson, Jan-Otto
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorgansik kemi.
    Diamond Nucleation on Hexagonal Boron Nitride: A Theoretical Investigation of the Influence of Nearest Substituents1997In: J. Phys. Chem., Vol. 101, no 9445Article in journal (Refereed)
  • 193. Carbone, Marilena
    et al.
    Larsson, Karin
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Methanol adsorption on the Si(100)-2 × 1 surface: a first-principles calculation2005In: Condens. Matter, Vol. 17, p. 1289-1300Article in journal (Refereed)
    Abstract [en]

    The process of adsorption of methanol on a Si(100)-2 × 1 surface has been investigated theoretically, using density functional theory and a periodic boundary condition. The methanol adsorption on Si(100)-2 × 1 is known to be dissociative, resulting in hydrogen(methanol)–oxygen(surface) and oxygen(methanol)–silicon(surface) bond formation. Adsorption energies have been calculated here for five different surface sites for the methoxy fragment (top, bridge, cave, valley-bridge and pedestal). The top site was found to be energetically most favourable. Surface sites bridging Si atoms from the first and second atomic layers were found to be energetically equivalent to the top site. The effects of the position of the hydrogen fragment on the methoxy adsorption energy for the various adsorption sites were also investigated. These various hydrogen positions only influenced the adsorption energies marginally

  • 194.
    Carlsson, Daniel O.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Mihranyan, Albert
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Strømme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Stability of Polypyrrole Cellulose Composites in Aqueous Solutions and Under Ambient Conditions.2011In: MRS Spring meeting 2011, 2011Conference paper (Refereed)
  • 195.
    Carlsson, Daniel O
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Nyström, Gustav
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Olsson, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Sjödin, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Mihranyan, Albert
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Strømme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Stability of Cladophora Cellulose/Polypyrrole Nanocomposites in Aqueous solutions2010Conference paper (Refereed)
  • 196.
    Carlsson, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Arteca, G. A.
    Sundberg, Jill
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Elvingson, Christer
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Off-equilibrium response of grafted polymer chains subject to a variable rate of compression2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 24, p. 11757-11765Article in journal (Refereed)
    Abstract [en]

    We present Brownian dynamics simulations of single grafted semiflexible chains (i.e., "polymer mushrooms'') with varying persistence lengths, intra-chain interactions, and subject to confinement. The results from different rates of compression are presented in the cases of an approaching infinite plane and a paraboloid tip. We discuss the different behaviour observed for grafted chains with strong and weak self-attraction (i.e., "hard'' and "soft'' polymer mushrooms). In both cases the effect on the size and shape is more pronounced for a slow compression rate, especially for "hard mushrooms''. We have also studied the relaxation of the chain while the compressing plane is maintained, and when it is removed suddenly. We find that the response depends strongly on the time allowed for relaxation in the compressed state. When using instead a paraboloid tip, the overall effects are similar yet less pronounced because the chain can dodge the confining object via an "escape transition.''

  • 197. Carrasco, J
    et al.
    Illas, F
    Lopez, N
    Kotomin, E.A.
    Zhukovskii, Yu.F.
    Piskunov, S
    Maier, J
    Hermansson, Kersti
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Structural Chemistry. strukturkemi.
    First principles simulations of F centers in cubic SrTiO32005In: physica status solidi (c), Vol. 2, no 1, p. 153-158Article in journal (Refereed)
    Abstract [en]

    Atomic and electronic structure of regular and O-deficient SrTiO3 have been studied. Several types of first principles atomistic simulations: Hartree-Fock method, Density Functional Theory, and hybrid HF-DFT functionals, have been applied to periodic models that consider supercells of different sizes (ranging between 40 and 240 atoms). We confirm the ionic character of the Sr-O bonds and the high covalency of the Ti-O2 substructure. For the stoichiometric cubic crystal; the lattice constant and bulk modulus correctly reproduce the experimental data whereas the band gap is only properly obtained by the B3PW functional. The relaxed geometry around the F center shows a large expansion of the two nearest Ti ions. Moreover, the vacancy formation energy is extremely sensitive to the size and the shape of the supercell as well as the calculation method. The electronic density map indicates the redistribution of two electrons of the missing O atom between the vacancy and 3d atomic orbitals of the two nearest Ti ions, in contrast to the F centers in ionic oxides where the charge centroid does not change.

  • 198. Carrot, G
    et al.
    Rutot-Houze, D
    Pottier, A
    Degee, P
    Hilborn, Jöns
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Polymer Chemistry. polymerkemi.
    Dubois, P
    Surface-initiated ring-opening polymerization: A versatile method for nanoparticle ordering.2002In: Macromolecules, Vol. 33, no 22, p. 8400-8404Article in journal (Refereed)
  • 199.
    Castleton, Christopher
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Kullgren, Jolla
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Hermansson, Kersti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Tuning LDA+U for electron localization and structure at oxygen vacancies in ceria2007In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 127, no 24, p. 244704-244704-11Article in journal (Refereed)
    Abstract [en]

    We examine the real space structure and the electronic structure (particularly Ce4f electron localization) of oxygen vacancies in CeO2 (ceria) as a function of U in density functional theory studies with the rotationally invariant forms of the LDA+U and GGA+U functionals. The four nearest neighbor Ce ions always relax outwards, with those not carrying localized Ce4f charge moving furthest. Several quantification schemes show that the charge starts to become localized at U~3 eV and that the degree of localization reaches a maximum at ~6 eV for LDA+U or at ~5.5 eV for GGA+U. For higher U it decreases rapidly as charge is transferred onto second neighbor O ions and beyond. The localization is never into atomic corelike states; at maximum localization about 80-90% of the Ce4f charge is located on the two nearest neighboring Ce ions. However, if we look at the total atomic charge we find that the two ions only make a net gain of (0.2-0.4)e each, so localization is actually very incomplete, with localization of Ce4f electrons coming at the expense of moving other electrons off the Ce ions. We have also revisited some properties of defect-free ceria and find that with LDA+U the crystal structure is actually best described with U=3-4 eV, while the experimental band structure is obtained with U=7-8 eV. (For GGA+U the lattice parameters worsen for U>0 eV, but the band structure is similar to LDA+U.) The best overall choice is U~6 eV with LDA+U and ~5.5 eV for GGA+U, since the localization is most important, but a consistent choice for both CeO2 and Ce2O3, with and without vacancies, is hard to find.

  • 200.
    Castleton, Christopher
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Nokbin, Somkiat
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Hermansson, Kersti
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry.
    Charge transfer and adhesion in Rh/MgO(001)2008In: Proceedings of the 17th international vacuum congress/13th international conference on surface science/international conference on nanoscience and technology / [ed] Johansson LSO; Andersen JN; Gothelid M; Helmersson U; Montelius L; Rubel M; Setina J; Wernersson LE, 2008, Vol. 100, no 8, p. 082027-Conference paper (Refereed)
    Abstract [en]

    Ab initio density functional calculations are reported for Rh adlayers on MgO(001) at coverages of 1, 1/2 and 1/8 monolayers. It is shown that charge is transferred from oxide surface to the Rh adatoms. The transfer ranges from 0.06 e to 0.27 e, depending upon adsorption site and coverage. In comparison, transfers of 0.08 e from adatom to surface and 0.32 e surface to adatom are found for monolayer coverages of Mg and O, respectively. With the Rh adatoms, significant charge polarization of both Rh and the surface are also seen, but it is never-the-less found that the adhesion energy is linearly related to the charge transfer, with the most stable adsorption site at any particular coverage being the one at which the charge transfer is a maximum.

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