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  • 1.
    Abbasi, M.
    et al.
    KTH Royal Inst Technol, Stockholm.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Cornell, A.
    KTH Royal Inst Technol, Stockholm.
    Fabrication of Spin-Coated Ti/TiHx/Ni-Sb-SnO2 Electrode: Stability and Electrocatalytic Activity2018Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 165, nr 9, s. H568-H574Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel three-layer anode having the composition Ti/TiHx/Ni-Sb-SnO2 (Ti/TiHx/NATO) was successfully prepared by a spin-coating and pyrolysis process aiming at a long service lifetime and good electrocatalytic properties for ozone formation. The TiHx as an interlayer was produced by electrochemical cathodic reduction of a coated layer of the TiOx on the titanium substrate. Spin coating and thermal decomposition were used to deposit the Sn-Sb-Ni precursor on the surface of the prepared Ti/TiHx electrode. Cyclic and linear scanning voltammetry, Raman spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to reveal the electrode performance and morphology. Results show that the onset potential for the oxygen evolution reaction (OER) of Ti/TiHx /NATO is higher than for Ti/NATO. They also indicate that the service lifetime of the Ti/TiHx/NATO is twice as long as the Ti/NATO at a current density of 50 mA.cm(-2) at room temperature. Electrochemical ozone generation and degradation of the methylene blue were investigated to confirm selectivity and activity of the electrodes. After 5 min electrolysis, a current efficiency for ozone generation of 56% was obtained the electrode with TiHx while 38% was obtained on Ti/NATO under same conditions. The results also confirm that the Ti/TiH x /NATO has a higher kinetic rate constant and decolorization efficiency for removal of the methylene blue compare to the Ti/NATO. The rate constant for the pseudo-first ordered reaction of methylene blue degradation showed high values of 350 x 10(-3) min(-1) for Ti/NATO and 440 x 10(-3) min(-1) for Ti/TiHx/NATO. 

  • 2. Abrashev, M. V.
    et al.
    Bäckström, Joakim
    Borjesson, L.
    Pissas, M.
    Kolev, N.
    Iliev, M. N.
    Raman spectroscopy of the charge- and orbital-ordered state in La0.5Ca0.5MnO32001Inngår i: Physical Review B, Vol. 64, nr 14Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polarized Raman spectra from microcrystals of La0.5Ca0.5MnO3 were studied as a function of temperature, excitation photon energy, and scattering configuration. At temperatures below the transition from ferromagnetic metallic phase to antiferromagnetic insulating charge- and orbital-ordered (COO) phase, several lines appear in Raman spectra excited with photon energies (h) over bar omega (L)<2.5 eV. We argue that their appearance signals ordering and freezing of the Jahn-Teller distortions at this transition temperature into a superstructure with a doubled elementary cell. We suggest a simplified structural model based on an analysis of the normal phonon modes in the COO phase, neglecting the octahedral tilts and containing ordered Mn4+O6 (undistorted) and Mn3+O6 (Jahn-Teller distorted) octahedra. The symmetries of the experimentally observed Raman lines are determined by comparing their relative intensities to those predicted by the polarization selection rules for a finely twinned quasicubic crystal. The most intensive Raman lines are assigned to definite normal modes in close comparison with corresponding modes in COO layered manganites and undoped RMnO3 (R=La, Y).

  • 3. Abrashev, M. V.
    et al.
    Bäckström, Joakim
    Borjesson, L.
    Popov, V. N.
    Chakalov, R. A.
    Kolev, N.
    Meng, R. L.
    Iliev, M. N.
    Raman spectroscopy of CaMnO(3): Mode assignment and relationship between Raman line intensities and structural distortions2002Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 65, nr 18, s. 1-9Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polarized Raman spectra of oriented finely twinned CaMnO(3) thin films and nonpolarized Raman spectra of CaMnO(3) ceramics were studied at room temperature using several excitation laser wavelengths. The selection rules for the polarized Raman spectra, obtained from samples consisting of finely twinned orthorhombic domains, were calculated and the symmetry of all observed Raman lines was determined. The relationship between the intensity of the Raman lines and the distortions in the ABO(3) perovskites with GdFeO(3)-type structure is discussed. These distortions can be described as superposition of four simple basic distortions: two MnO(6) octahedral tilts, Jahn-Teller deformation of Mn(3+) O(6) octahedra, and shift of the A ions from their sites in the ideal perovskite. Twenty of the 24 Raman-allowed modes in the real GdFeO(3)-type structure have counterparts in only one of the four simpler structures, obtained by a single basic distortion. The assignment of the Raman lines of CaMnO(3) to definite atomic vibrations, most of them activated by a single basic distortion, was made in close comparison with the results of lattice dynamical calculations and the Raman spectra of isostructural LaMnO(3) and CaGeO(3).

  • 4.
    Andersson, Henrik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Andres, Britta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Manuilskiy, Anatoliy
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Forsberg, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Contacting paper-based supercapacitors to printed electronics on paper substrates2012Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, nr 2, s. 476-480Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hybrid printed electronics, in which printed structures and silicon-based components co-exist will likely be among the first commercial solutions. In this case the paper substrate acts much in the same way as circuit boards, containing conductive tracks and acting as a carrier for the electrical components. It is important to consider the contacting of the components to be able to produce low resistance electrical contacts to the conductive tracks. Supercapacitors are able to deliver a large amount of current in a short time and are a good option for short term energy storage and if the printed product is to be used only one, or a few times, it can be the only power source needed. When manufacturing printed electronics, the overall resistance of the printed tracks as well as the contact resistance of the mounted components will add up to the total resistance of the system. A high resistance will cause a voltage drop from the power source to the component. This will waste power that goes to Joule heating and also the voltage and current available to components may be too low to drive them. If the intention is to use a power supply such as batteries or solar cells this becomes a limitation. In this article have been tested several conductive adhesives used to contact paper based supercapacitors to ink jet printed silver tracks on paper. The best adhesive gives about 0.3 Ω per contact, a factor 17 better compared to the worst which gave 5 Ω. The peak power that is possible to take out from a printed system with a flexible battery and super capacitors is about 10 times higher than compared with the same system with only the battery.

  • 5. Andreasson, Jakob
    et al.
    Holmlund, Joakim
    Knee, Christopher S.
    Kall, Mikael
    Borjesson, Lars
    Naler, Stefan
    Bäckström, Joakim
    Ruebhausen, Michael
    Azad, Abul Kalam
    Eriksson, Sten- G.
    Franck-Condon higher order lattice excitations in the LaFe1-xCrxO3 (x=0, 0.1, 0.5, 0.9, 1.0) perovskites due to Fe-Cr charge transfer effects2007Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 75Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    First and higher order lattice excitations in the B-site disordered perovskites LaFe1-xCrxO3 (x=0, 0.1, 0.5, 0.9, and 1) and La0.835Sr0.165Fe0.5Cr0.5O3-delta are investigated using temperature dependent and polarized inelastic light scattering [lambda=515 nm (2.41 eV) and 676 nm (1.83 eV)] on oriented crystallites. A peak at approximately 2.4 eV in the imaginary part of the dielectric function of LaFe0.5Cr0.5O3 is assigned to a charge transfer from Fe3+ (d(5)) to Cr3+ (d(3)) ions, coupled with the appearance of an intense A(g)-like mode at approximately 700 cm(-1) in the Raman data. This excitation is identified as a symmetric oxygen breathing mode activated by the Fe-Cr charge transfer through an orbital coupling mechanism. Higher order scattering (up to seventh order) of the intrinsic Raman active symmetric breathing mode is also explained by an orbital-mediated electron-phonon coupling, similar to the Franck-Condon effect observed in the Jahn-Teller active-perovskite-structured manganite LaMaO(3). These results show that the Franck-Condon mechanism is a more common mechanism for resonant higher order scattering in solids than previously believed and propose the LaFe1-xCrxO3 system as a model system for electron-phonon coupling and higher order Raman scattering in solids.

  • 6.
    Andres, Britta
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Forsberg, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Vilches, Ana Paola
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Andersson, Henrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Supercapacitors with graphene coated paper electrodes2012Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 27, nr 2, s. 481-485Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Paper based supercapacitors are prepared by stacking a paper between two graphene electrodes and soaking these in an aqueous electrolyte. We demonstrate that supercapacitors can easily be manufactured by using proven paper technologies. Several different electrode materials were compared and two types of contacting material, silver and graphite foil were tested. The influence of the paper used as separator was also investigated. The supercapacitors with a graphene-gold nanoparticle composite as electrodes showed a specific capacitance of up to 100 F/g and an energy density of 1.27 Wh/kg. The energy density can further be increased by using other electrolytes. The silver contacts showed a pseudo capacitance, which the graphite contacts did not. The papers tested had a minor effect on the capacitance, but they have an influence on the weight and the volume of the supercapacitor.

  • 7. Bjornsson, P.
    et al.
    Rubhausen, M.
    Bäckström, Joakim
    Kall, M.
    Eriksson, S.
    Eriksen, J.
    Borjesson, L.
    Lattice and charge excitations in La1-xSrxMnO32000Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 61, s. 1193-1197Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We employ inelastic Light scattering to study the dependence of the lattice and charge excitations in La1-xSrxMnO3 compounds on doping and temperature. The phonons reveal strong local lattice distortions in the paramagnetic state, which gradually vanish below the ferromagnetic transition. We identify charge excitations in the metallic state. They exhibit a dependence on the doping level and symmetry selection rules typical for a plasmonlike excitation. Their energy scale of 100 meV requires a low-carrier-density component of the plasma outlining the importance of electronic interactions in La1-xSrxMnO3.

  • 8.
    Blomquist, Nicklas
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap. STT Emtec AB, Sundsvall.
    Wells, Thomas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Andres, Britta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Forsberg, Sven
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Metal-free supercapacitor with aqueous electrolyte and low-cost carbon materials2017Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, artikkel-id 39836Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electric double-layer capacitors (EDLCs) or supercapacitors (SCs) are fast energy storage devices with high pulse efficiency and superior cyclability, which makes them useful in various applications including electronics, vehicles and grids. Aqueous SCs are considered to be more environmentally friendly than those based on organic electrolytes. Because of the corrosive nature of the aqueous environment, however, expensive electrochemically stable materials are needed for the current collectors and electrodes in aqueous SCs. This results in high costs for a given energy-storage capacity. To address this, we developed a novel low-cost aqueous SC using graphite foil as the current collector and a mix of graphene, nanographite, simple water-purification carbons and nanocellulose as electrodes. The electrodes were coated directly onto the graphite foil by using casting frames and the SCs were assembled in a pouch cell design. With this approach, we achieved a material cost reduction of greater than 90% while maintaining approximately one-half of the specific capacitance of a commercial unit, thus demonstrating that the proposed SC can be an environmentally friendly, low-cost alternative to conventional SCs.

  • 9. Budelmann, D.
    et al.
    Holmlund, J.
    Andreasson, J.
    Rodriguez, H.
    Bäckström, Joakim
    Borjesson, L.
    Adrian, H.
    Merkt, U.
    Rubhausen, M.
    Antiferromagnetic and superconducting proximity effects in YBa2Cu3O7-delta/PrBa2Cu3O7-delta superlattices2003Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 67Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigate the interplay between the antiferromagnetic and superconducting order parameters in YBa2Cu3O7-delta/PrBa2Cu3O7-delta superlattices by inelastic light scattering. The ratio of superconducting to antiferromagnetic order is varied through different modulations 4/6, 4/9, and 4/12 of (Y/Pr)Ba2Cu3O7-delta layers. This allows us to identify the proximity effect of the superconducting order parameter into the antiferromagnetic barrier as signified, e.g., by the sharpening of the two-magnon excitation. This proximity effect as well as gap feature and phonon anomalies reveals the delicate interplay between superconducting and antiferromagnetic order parameters.

  • 10. Bäckström, Joakim
    et al.
    Budelmann, D.
    Rauer, R.
    Rübhausen, M.
    Rodríguez, H.
    Adrian, H.
    Optical properties of YBa$_2$Cu$_3$O$_7 - \delta$ and PrBa$_2$Cu$_3$O$_7 - \delta$ films: High-energy correlations and metallicity2004Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 70, nr 17Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have investigated the temperature dependence of the dielectric functions of a high-Tc superconducting YBa2Cu3O7-- (Y-123) and a nonsuperconducting PrBa2Cu3O7-- (Pr-123) thin film using spectral ellipsometry. We evaluate the data by means of thermal-difference and sum-rule analysis techniques. We find that a spectral-weight transfer into the bands between 4 and 5 eV takes place before Y-123 becomes superconducting. We identify an anomaly around 1 eV that can be explained by a sudden plasma-frequency drop of the order of an meV around Tc. The absence of any sudden effects in the dielectric properties of Pr-123 suggests that both observations are intimately related to the superconducting state. Our findings point out that high-energy degrees of freedom must be considered for the understanding of high-temperature superconductivity.

  • 11. Bäckström, Joakim
    et al.
    Rubhausen, M.
    Kall, M.
    Borjesson, L.
    Litvinchuk, A. P.
    Kakihana, M.
    Osada, M.
    Dabrowski, B.
    Raman scattering in YBa2Cu4O8 and PrBa2Cu4O8 - indications of pseudogap effects in non-superconducting PrBa2Cu4O82000Inngår i: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 341, s. 2251-2252Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    By analysis of the temperature evolution of Raman spectra, we connect an observed supression in low-energy electronic density of states to an anomalous sharpening of the Ba-phonon mode in superconducting YBa2Cu4O8 (Y-124) at around T=150 K. We link the supression of electronic excitations to an opening of a pseudogap. Similar effects observed for the Ba-phonon mode at roughly the same temperature in non-superconducting PrBa2Cu4O8 (Pr-124) suggests that a pseduogap opens up around 150 K also in this material.

  • 12. Bäckström, Joakim
    et al.
    Rübhausen, M.
    Käll, M.
    Börjesson, L.
    Litvinchuk, A. P.
    Kakihana, M.
    Osada, M.
    Dabrowski, B.
    Raman scattering in \RmYBa$_2$Cu$_4$O$_8$ and PrBa$_2$Cu$_4$O$_8$: Indications of pseudogap effects in non-superconducting \RmPrBa$_2$Cu$_4$O$_8$2000Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 61, s. 7049-7054Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    By analysis of the Raman spectra of superconducting YBa2Cu4O8 (Y-124), we observe a suppression of low-energy electronic density of states that we link to changes in the linewidth of the Ba-phonon mode. These effects occur at a temperature below 150 K, where also anomalies in resistivity and other physical properties take place. We argue that these changes in the Raman spectra of Y-124 are connected to the opening of a pseudogap. Analogous anomalies in resistivity and the Ba-phonon width in the nonsuperconducting homologue PrBa2Cu4O8 (Pr-124) below 150 K suggest that similar pseudogap effects can occur without a following transition to a superconducting state at a lower temperature.

  • 13.
    Eivazihollagh, Alireza
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Dahlström, Christina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Carlsson, Fredrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Ibrahem, Ismail
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Lindman, Björn
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    One-pot synthesis of cellulose-templated copper nanoparticles with antibacterial properties2017Inngår i: Materials letters (General ed.), ISSN 0167-577X, E-ISSN 1873-4979, Vol. 187, s. 170-172Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report a facile in situ synthesis of spherical copper nanoparticles (NPs) templated by a gelled cellulose II matrix under alkaline aqueous reaction conditions. In under 20 min, the hybrid material could be obtained in a one-pot reaction. Field-emission scanning electron microscopy (FE-SEM) revealed that the polycrystalline NPs of 200–500 nm were well distributed in the regenerated cellulose matrix. The average Cu crystallite size was of the order of 20 nm, as estimated from both X-ray diffraction (XRD) and FE-SEM. XRD data also indicated that the composite contained up to approximately 20% Cu2O. In suspensions containing the hybrid material, growth of Escerichia coli and Staphylococcus aureus strains was inhibited by 80% and 95%, respectively, after 72 h. The synthesis procedure offers a general approach to designing various low-cost hybrid materials of almost any shape, and the concept could be extended to utilization areas such as catalysis, functional textiles, and food packaging as well as to electronic applications.

  • 14.
    Eivazihollagh, Alireza
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Electrochemical recovery of copper complexed by DTPA and C12-DTPA from aqueous solution using a membrane cell2018Inngår i: Journal of chemical technology and biotechnology (1986), ISSN 0268-2575, E-ISSN 1097-4660, Vol. 93, nr 5, s. 1421-1431Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    BACKGROUND

    The electrochemical recovery of copper from DTPA and C12-DTPA (a surface-active derivative of DTPA) complex solutions was investigated in a membrane flow cell. Electrolysis time, solution flow rate, applied current density, and solution pH were evaluated.

    RESULTS

    The chelating surfactant C12-DTPA can promote the kinetics of copper electrodeposition more than DTPA depending on the experimental conditions. At a current density of 30 A m–2, a solution flow rate of 0.6 L min–1, and pH 10 after 180 min treatment, the copper recovery and current efficiency were 50% and 43.3%, respectively, in the Cu(II)-DTPA system and about 65% and 53.6%, respectively, in the Cu(II)-C12-DTPA system. The differences in the amount of recovery could be explained in terms of differences in the diffusion of copper complexes with DTPA and C12-DTPA to the cathode, as well as their solution behavior and pH-dependent conditional stability constants (log10 K’CuDTPA3-).

    CONCLUSION

    Electrochemical methods could be effectively combined with foam flotation for the chelating surfactant C12-DTPA, to recover copper and C12-DTPA. This makes the overall treatment more sustainable, and can be helpful in complying with the increasingly stringent environmental regulations

  • 15.
    Eivazihollagh, Alireza
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Edlund, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Influences of the operational variables on electrochemical treatment of chelated Cu(II) in alkaline solutions using a membrane cell2017Inngår i: Journal of chemical technology and biotechnology (1986), ISSN 0268-2575, E-ISSN 1097-4660, Vol. 92, nr 6, s. 1436-1445Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    BACKGROUND

    The electrochemical recovery of copper and chelating agent from their complex solution using a membrane flow cell was investigated. The parameters electrolysis time, solution pH, current density, and temperature were investigated.

    RESULTS

    Electrochemical investigation indicated that chelating ligands can be recovered by the electrodeposition of copper ions on the cathode. For copper and EDTA recovery, the results indicated that recovery efficiency was affected by time, current density, and temperature. The recovery process was not influenced by pH in the range studied (pH 8–12), which can be explained by the low variation in the conditional stability constant, i.e. Δlog10 K' ≤ 0.7, over the pH range. However, when NTA, EDTA, and DTPA were compared, the results indicated that the recovery efficiency decreased as the conditional stability constant of the chelating agent–Cu(II) complex increased. The maximum current efficiency of copper and EDTA recovery after 5 h of treatment was approximately 85%, whereas the recovery was 80% of the initial concentration (0.05 mol L−1) at a current density of 1 A dm−2, temperature of 333 K, and pH of 10.

    CONCLUSION

    Relatively high recovery efficiency makes the process fairly sustainable and hinders the discharge of copper ions and chelating ligands as pollutants into the environment. 

  • 16.
    Forsberg, Viviane
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Andersson, Henrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Dahlström, Christina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Andres, Britta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Liquid Exfoliation of Layered Materials in Water for Inkjet Printing2016Inngår i: Printing for Fabrication 2016: Materials, Applications, and Processes, USA: Curran Associates, Inc., 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    MoS2 is a layered material which is abundant and non-toxic and has been increasingly studied during the last few years as a semiconducting alternative to graphene. While most studies have been performed on single MoS2 nanosheets, for example to demonstrate high-performance electronic transistors, more work is needed to explore the use of MoS2 in printed electronics. The importance of using MoS2 as a printed electronic material could be understood by considering the several orders higher electron mobility in MoS2, even in several nanometer thick layers, compared to the organic and other materials used today. In the few studies performed so far on printing MoS2, the developed dispersions used mainly organic solvents that might be detrimental for the environment. Here, we show an environmentally friendly liquid-based exfoliation method in water where the solution was stabilized by sodium dodecyl sulfate (SDS) surfactant. The dispersions consisted of very thin MoS2 nanosheets with average lateral size of about 150 nm, surface tension of 28 mN m-1 and a shelf life of a year. Although both the concentration and viscosity was less than optimal, we were able to inkjet print the MoS2 solution on paper and on PET films, using multiple printing passes. By tuning the concentration/viscosity, this approach might lead to an environmentally friendly MoS2 ink suitable for printed electronics.

  • 17.
    Forsberg, Viviane
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Andersson, Henrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Dahlström, Christina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Andres, Britta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Liquid Exfoliation of Layered Materials in Water for Inkjet Printing2016Inngår i: Journal of Imaging Science and Technology, ISSN 1062-3701, E-ISSN 1943-3522, Vol. 60, nr 4, s. 1-7, artikkel-id 040405Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    MoS2 is a layered material which is abundant and non-toxic and has been increasingly studied during the last few years as a semiconducting alternative to graphene. While most studies have been performed on single MoS2 nanosheets, for example to demonstrate high-performance electronic transistors, more work is needed to explore the use of MoS2 in printed electronics. The importance of using MoS2 as a printed electronic material could be understood by considering the several orders higher electron mobility in MoS2, even in several nanometer thick layers, compared to the organic and other materials used today. In the few studies performed so far on printing MoS2, the developed dispersions used mainly organic solvents that might be detrimental for the environment. Here, we show an environmentally friendly liquid-based exfoliation method in water where the solution was stabilized by sodium dodecyl sulfate (SDS) surfactant. The dispersions consisted of very thin MoS2 nanosheets with average lateral size of about 150 nm, surface tension of 28 mN m(-1), and a shelf life of a year. Although both the concentration and viscosity was less than optimal, we were able to inkjet print the MoS2 solution on paper and on PET films, using multiple printing passes. By tuning the concentration/viscosity, this approach might lead to an environmentally friendly MoS2 ink suitable for printed electronics.

  • 18.
    Forsberg, Viviane
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Zhang, Renyun
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Joakim, Bäckström
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Dahlström, Christina
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Andres, Britta
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Norgren, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för kemiteknik.
    Andersson, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Exfoliated MoS2 in Water without Additives2016Inngår i: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, nr 4, artikkel-id 0154522Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Many solution processing methods of exfoliation of layered materials have been studied during the last few years; most of them are based on organic solvents or rely on surfactants andother funtionalization agents. Pure water should be an ideal solvent, however, it is generallybelieved, based on solubility theories that stable dispersions of water could not be achievedand systematic studies are lacking. Here we describe the use of water as a solvent and thestabilization process involved therein. We introduce an exfoliation method of molybdenumdisulfide (MoS2) in pure water at high concentration (i.e., 0.14±0.01 g L−1). This was achieved by thinning the bulk MoS2by mechanical exfoliation between sand papers and dis-persing it by liquid exfoliation through probe sonication in water. We observed thin MoS2nanosheets in water characterized by TEM, AFM and SEM images. The dimensions of thenanosheets were around 200 nm, the same range obtained in organic solvents. Electropho-retic mobility measurements indicated that electrical charges may be responsible for the sta-bilization of the dispersions. A probability decay equation was proposed to compare thestability of these dispersions with the ones reported in the literature. Water can be used as asolvent to disperse nanosheets and although the stability of the dispersions may not be ashigh as in organic solvents, the present method could be employed for a number of applications where the dispersions can be produced on site and organic solvents are not desirable.

  • 19. Gustafsson, John
    et al.
    Hummelgård, Christine
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Odnevall Wallinder, Inger
    Habibur Rahman, Seikh Muhammad
    Lindbergh, Göran
    Eriksson, Sten
    Cornell, Ann
    In-situ activated hydrogen evolution by molybdate addition to neutral and alkaline electrolytes2012Inngår i: Journal of electrochemical science and engineering, ISSN 1847-9286, Vol. 2, nr 3, s. 105-120Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Activation of the hydrogen evolution reaction (HER) by in-situ addition of Mo(VI) to the electrolyte has been studied in alkaline and pH neutral electrolytes, the latter with the chlorate process in focus. Catalytic molybdenum containing films formed on the cathodes during polarization were investigated using scanning electron microscopy (SEM), energy-dispersive X ray analysis (EDS), X-ray photoelectron spectroscopy (XPS), and X ray fluorescence (XRF). In-situ addition of Mo(VI) activates the HER on titanium in both alkaline and neutral electrolytes and makes the reaction kinetics independent of the substrate material. Films formed in neutral electrolyte consisted of molybdenum oxides and contained more molybdenum than those formed in alkaline solution. Films formed in neutral electrolyte in the presence of phosphate buffer activated the HER, but were too thin to be detected by EDS. Since molybdenum oxides are generally not stable in strongly alkaline electrolyte, films formed in alkaline electrolyte were thinner and probably co-deposited with iron. A cast iron molybdenum alloy was also investigated with respect to activity for HER. When polished in the same way as iron, the alloy displayed a similar activity for HER as pure iron.

  • 20. Gustafsson, John
    et al.
    Li, Gongzhuo
    Hummelgård, Christine
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för tillämpad naturvetenskap och design.
    Cornell, Ann
    On the suppression of cathodic hypochlorite reduction by electrolyte additions of molybdate and chromate ions2012Inngår i: Journal of electrochemical science and engineering, ISSN 1847-9286, Vol. 2, nr 4, s. 185-198Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The goal of this study was to gain a better understanding of the feasibility of replacing Cr(VI) in the chlorate process by Mo(VI), focusing on the cathode reaction selectivity for hydrogen evolution on steel and titanium in a hypochlorite containing electrolyte. To evaluate the ability of Cr(VI) and Mo(VI) additions to hinder hypochlorite reduction, potential sweep experiments on rotating disc electrodes and cathodic current efficiency (CE) measurements on stationary electrodes were performed. Formed electrode films were investigated with scanning electron microscopy and energy-dispersive X-ray spectroscopy. Cathodic hypochlorite reduction is hindered by the Mo-containing films formed on the cathode surface after Mo(VI) addition to the electrolyte, but much less efficient compared to Cr(VI) addition. Very low levels of Cr(VI), in the mM range, can efficiently suppress hypochlorite reduction on polished titanium and steel. Phosphate does not negatively influence the CE in the presence of Cr(VI) or Mo(VI) but the Mo-containing cathode films become thinner if the electrolyte during the film build-up also contains phosphate. For a RuO2-TiO2 anode polarized in electrolyte with 40 mM Mo(VI), the anode potential increased and increased molybdenum levels were detected on the electrode surface

  • 21. Hadjiev, V. G.
    et al.
    Bäckström, Joakim
    Popov, V. N.
    Iliev, M. N.
    Meng, R. L.
    Xue, Y. Y.
    Chu, C. W.
    Symmetry of phonon, magnetic, and spin-phonon excitations in GdSr2RuCu2O8 single crystals2001Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 64Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a polarized Raman scattering study of GdSr2RuCu2O8 single crystals. In this compound, the RuO6 octahedra are rotated around the c axis that in turn gives some Raman activity of the oxygen (O-Ru) vibrations at 265 cm(-1) (A(1g)), 411 cm(-1) (B-2g) and 607 cm(-1) (B-1g). These vibrations, as well as those of the apical oxygen of RuO6, at 654 cm(-1) (A(1g)) and the Cu-plane oxygen at 318 cm(-1) (B-2g), clearly respond to the onset of magnetic ordering at T-m approximate to 140 K. In particular, the 265 cm(-1) mode hardens anomalously with decreasing temperature below T-m. Notably, the corresponding phonon line is absent in the Raman spectra of GdSr2NbCu2O8 (Nb5+:4d(0)), a compound isomorphic to GdSr2RuCu2O8 (Ru5+:4d(3)). We argue that the eigenvector of the 265 cm(-1) phonon (rotational mode) facilitates efficient modulation of the Ru(t(1g))-O-Ru (p) bands. This modulation gives both Raman scattering strength to the 265 cm(-1) mode and strong spin-phonon coupling.

  • 22.
    Hedenstedt, Kristoffer
    et al.
    Göteborgs Universitet; AkzoNobel.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap. Göteborgs Universitet.
    Ahlberg, Elisabet
    Göteborgs Universitet.
    In-Situ Raman Spectroscopy of α- and γ-FeOOH during Cathodic Load2017Inngår i: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, nr 9, s. H621-H627Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Water reduction on corroded iron surfaces is technologically and fundamentally important. Here, the technological interest originatesfrom the chlorate process where water reduction is the main cathodic process. Fundamentally, water reduction on oxide surfaces raisesquestions on the stability of the oxide and the nature of electrocatalytic surface sites. Two iron oxyhydroxides,α-andγ-FeOOH,were electrodeposited on titanium substrate and their reduction processes were followed in detail with in-situ Raman spectroscopy,using low incident laser power to avoid sample damaging. Polarization to negative potentials show two reduction peaks forγ-FeOOHand one peak forα-FeOOH prior to hydrogen evolution. The characteristic Raman peaks gradually disappear as the potential ismade more negative but no new peaks can be observed.δ-FeOOH was detected as an intermediate phase upon oxidation of thereduced surface layer. This indicates that Fe(OH)2is formed during cathodic polarization and initially re-oxidized to the isostructuralδ-FeOOH. Characteristic Raman signals of the original phases appear upon further oxidation in air.

  • 23. Holmlund, Joakim
    et al.
    Andreasson, Jakob
    Knee, Christopher S.
    Bäckström, Joakim
    Kall, Mikael
    Osada, Minoru
    Noji, Takashi
    Koike, Yoji
    Kakihana, Masato
    Borjesson, Lars
    Resonant two-phonon Raman scattering as a probe of hole crystal formation in Sr14-xCaxCu24O412006Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The charge dynamics of the spin ladder compound Sr14-xCaxCu24O41 with x=0,6,13.6 has been investigated using wavelength- and temperature-dependent phonon Raman scattering on single crystals. In the unsubstituted, x=0, compound, a set of sharp two-phonon lines shows a strong increase in intensity below T similar to 200 K for light polarized along the ladder layer and with excitation energy close to the charge transfer gap similar to 1.9 eV. The temperature dependence of the strongly enhanced two-phonon bands below 200 K closely follows the recently reported formation of a standing charge density wave in the ladders [P. Abbamonte , Nature 431, 1078 (2004)]. Upon calcium substitution the polarized resonant Raman response rapidly decreases, signaling an increase of hole mobility in the ladder units. Temperature-dependent measurements of the x=13.6 sample indicate mobility of holes down to < 8 K.

  • 24.
    Hummelgård, Christine
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Karlsson, Rasmus
    Applied Electrochemistry, School of Chemical Science and Engineering, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden .
    Cornell, Ann
    Applied Electrochemistry, School of Chemical Science and Engineering, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden .
    Habibur Rahman, S.M.
    Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 gothenburg, Sweden .
    Eriksson, Sten
    Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 gothenburg, Sweden .
    Physical and electrochemical properties of cobalt doped (ti,ru)O2 electrode coatings2013Inngår i: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 178, nr 20, s. 1515-1522Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The physical and electrochemical properties of ternary oxides Ti 0.7Ru0.3-xCoxO2 (x = 0.093 and x = 0) have been investigated and compared. Samples of three different thicknesses were prepared by spin-coating onto polished titanium to achieve uniform and well-defined coatings. The resulting electrodes were characterized with a variety of methods, including both physical and electrochemical methods. Doping with cobalt led to a larger number of micrometer-sized cracks in the coating, and coating grains half the size compared to the undoped samples (10 instead of 20 nm across). This is in agreement with a voltammetric charge twice as high, as estimated from cyclic voltammetry. There is no evidence of a Co 3O4 spinel phase, suggesting that the cobalt is mainly incorporated in the overall rutile structure of the (Ti,Ru)O2. The doped electrodes exhibited a higher activity for cathodic hydrogen evolution compared to the undoped electrodes, despite the fact that one third of the active ruthenium was substituted with cobalt. For anodic chlorine evolution, the activity was similar for both electrode types.

  • 25.
    Hummelgård, Christine
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Gustafsson, John
    Applied Electrochemistry, School of Chemical Science and Engineering, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden .
    Cornell, Ann
    Applied Electrochemistry, School of Chemical Science and Engineering, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden .
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Spin coated titanium-ruthenium oxide thin films2013Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 536, s. 74-80Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    Substrates of different roughness spin coated with Ti0.7Ru 0.3O2 films have been evaluated as model system for fundamental studies of the industrially and scientifically interesting (Ti,Ru)O2 based electrodes. The approach allowed for much more accurate control over the material synthesis than the traditionally used brush-, dip-, or spray-coating, on titanium-metal substrates. It moreover yielded well-defined samples suitable for basic studies of the surface properties that are of fundamental importance for understanding the electrochemical functionality of the electrode. We have compared the films on silicon substrates to films prepared by spin coating the same material on titanium-metal substrates. Samples have been characterized using atomic force microscopy (AFM), X-ray diffraction, scanning electron microscopy (SEM), and cyclic voltammetry. The samples displayed a uniformity of the films appropriate for AFM characterization. The smoother the substrate the less cracks in the coating. Using easily broken silicon wafers as substrate, a straightforward sample preparation technique was demonstrated for cross-section SEM. In addition, using high spinning velocities we have deposited the oxide films directly on silicon-nitride grids, thin enough to allow for studies with transmission electron microscopy without further sample preparation.

  • 26. Iliev, M. N.
    et al.
    Popov, V. N.
    Litvinchuk, A. P.
    Abrashev, M. V.
    Bäckström, Joakim
    Sun, Y. Y.
    Meng, R. L.
    Chu, C. W.
    Comparative Raman studies of Sr$_2$RuO$_4$, Sr$_3$Ru$_2$O$_7$ and Sr$_4$Ru$_3$O$_10$2005Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 358, nr 1--4Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The polarized Raman spectra of layered ruthenates of the Srn+1RunO3n+1 (n=1,2,3) Ruddlesden-Popper series were measured between 10 and 300 K. The phonon spectra of Sr3Ru2O7 and Sr4Ru3O10 confirmed earlier reports for correlated rotations of neighboring RuO6 octahedra within double or triple perovskite blocks. The observed Raman lines of Ag or B1g symmetry were assigned to particular atomic vibrations by considering the Raman modes in simplified structures with only one double or triple RuO6 layer per unit cell and by comparison to the predictions of lattice dynamical calculations for the real Pban and Pbam structures. Along with discrete phonon lines, a continuum scattering, presumably of electronic origin, is present in the zz, xx and xy, but not in the x'y' and zx spectra. Its interference with phonons results in Fano shape for some of the lines in the xx and xy spectra. The temperature dependences of phonon parameters of Sr3Ru2O7 exhibit no anomaly between 10 and 300 K where no magnetic transition occur. In contrast, two B1g lines in the spectra of Sr4Ru3O10, corresponding to oxygen vibrations modulating the Ru-O-Ru bond angle, show noticeable hardening with ferromagnetic ordering at 105 K, thus indicating strong spin-phonon interaction.

  • 27. Kakihana, M.
    et al.
    Kato, S.
    Petrykin, V.
    Bäckström, Joakim
    Borjesson, L.
    Osada, M.
    A simple and reproducible way to synthesize PrBa2Cu4O8 under 1 atm of oxygen by amorphous citrate method1999Inngår i: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 321, s. 74-80Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A simple aqueous solution technique utilizing citric acid (CA) as a complexant was applied to prepare PrBa2Cu4O8 (Pr124) at ambient oxygen pressure. Heating of a mixed-solution of CA, water (H2O) and ions of Pr, Ba and Cu with a molar ratio of [CA]:[H2O]:[Pr + Ba + Cu] = 3.6:40:1 on a hot-plate set at 200 degrees C produced a transparent amorphous citrate "gel" without any precipitation, which after heat-treatment at 450 degrees C was converted to a precursor for Pr124. The Pr124 compound with only minor traces of BaCuO2, PrBaO3 and CuO formed after heat-treating the precursor twice at 850 degrees C for 60 h under 1 atm oxygen pressure. The amount of impurities in the citrate-derived Pr124 was approximately half of that in the best sample previously prepared by the more elaborate high-pressure technique. (C) 1999 Elsevier Science B.V. All rights reserved.

  • 28. Kall, M.
    et al.
    Osada, M.
    Bäckström, Joakim
    Kakihana, M.
    Borjesson, L.
    Frello, T.
    Madsen, J.
    Andersen, N. H.
    Liang, R.
    Dosanjh, P.
    Hardy, W. N.
    Resonance Raman scattering as a probe of oxygen dynamics in YBa2Cu3Ox1998Inngår i: Journal of Physics and Chemistry of Solids, ISSN 0022-3697, E-ISSN 1879-2553, Vol. 59, s. 1988-1990Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the metastable photo-bleaching of the 2.15 eV yellow Raman resonance in oxygen deficient YBa2Cu3Ox (x = 6.35-6.87), extending investigations by Wake ct al. (Phys. Rev. Lett., 1991,67, 3728) for x approximate to 7. Polarization, x dependence and phonon spectra indicate that the resonance is localized at oxygen vacancies in long CuO-chains. The resonance is thermally reactivated from the metastable bleached state with a relaxation time tau similar to exp[Delta/k(B)T] with Delta approximate to 1 eV. The resulting temperature dependent equilibrium resonance intensity essentially miners the oxygen superstructure disordering around T* approximate to 100 degrees C observed in the same crystals by hard X-ray diffraction, thus offering a new effective probe of chain-oxygen dynamics in YBa2Cu3Ox. (C) 1998 Elsevier Science Ltd. All rights reserved.

  • 29. Kruger, R.
    et al.
    Schulz, B.
    Naler, S.
    Rauer, R.
    Budelmann, D.
    Bäckström, Joakim
    Kim, K. H.
    Cheong, S. W.
    Perebeinos, V.
    Rubhausen, M.
    Orbital ordering in LaMnO3 investigated by resonance Raman spectroscopy2004Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 92Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Orbital ordering leads to an unconventional excitation spectrum that we investigate by resonance Raman scattering using incident photon energies between 1.7 and 5.0 eV. We use spectral ellipsometry to determine the corresponding dielectric function. Our results show resonant behavior of the phonon Raman cross section when the laser frequency is close to the orbiton-excitation energy of 2 eV in LaMnO3. We show an excellent agreement between theoretical calculations based on the Franck-Condon mechanism activating multiphonon Raman scattering in first order of the electron-phonon coupling and the experimental data of phonons with different symmetries.

  • 30. Kunze, J.
    et al.
    Naler, S.
    Bäckström, Joakim
    Rubhausen, M.
    Mitchell, J. F.
    Optical study of competition between ordering and metallicity in La(2-2x)Sr(1+2x)Mn(2)O(7)2003Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 67Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study by spectroscopic ellipsometry the optical in-plane anisotropies in La(2-2x)Sr(1+2x)Mn(2)O(7) with 0.32less than or equal toxless than or equal to0.40 above and below the metal to insulator (MI) transition. Spectral-weight changes in the optical conductivity occur at a cross-over temperature T(’)=280 K for all dopings. Local ordering of orbital and charge degrees of freedom sets in doping dependently at temperatures of 145 Kless than or equal toT(*)less than or equal to310 K. Below the MI transition we observe for all dopings except x=0.36 a vanishing of the charge ordering and an isotropic and metallic state at low frequencies, whereas the local orbital ordering persists. For x=0.36 we observe two different characteristic developments of the ordering processes, one being compatible with the parabolic doping dependence on T(*) established by the other doping levels and the second showing ordering at a temperature slightly above the MI transition. We argue that our observations are compatible with a phase separation scenario.

  • 31.
    Malmgren, Christine
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Towards nanopatterned DSA2007Konferansepaper (Annet vitenskapelig)
  • 32.
    Malmgren, Christine
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Eriksson, A K
    Cornell, A
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Eriksson, S
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Nanocrystallinity in RuO2 coatings - influence of precursor and preparation temperature2010Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 518, nr 14, s. 3615-3618Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The effects of precursor and calcination temperature on the nano morphology of ruthenium dioxide on titanium, prepared from thermal decomposition of aqueous salt solutions were investigated. Transmission electron microscopy. X-ray diffraction, gas porosimetry and cyclic voltammetry showed that lower calcination temperature yielded smaller crystallites. The crystallites were between 6 and 22 nm in diameter. When using ruthenium nitrosyl nitrate the firing temperature had a large impact on the grain size, but for chloride there was only a minor effect in the temperature range 350-550 degrees C.

  • 33.
    Malmgren, Christine
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Cornell, Ann
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Nanoscale characterisation of crystallinity in DSA coating2008Inngår i: PROCEEDINGS OF THE 17TH INTERNATIONAL VACUUM CONGRESS/13TH INTERNATIONAL CONFERENCE ON SURFACE SCIENCE/INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY, Institute of Physics (IOP), 2008, Vol. 100, nr 052026, s. 4-4Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Dimensionally Stable Anodes (DSA (R)) are used for industrial production of e. g. chlorine and chlorate. It is known that the superior electrocatalytical properties of DSA (R) is due to the large effective area of the porous coating. However, this knowledge is mainly found from in situ electrochemical measurements. Here, we used ex situ methods, AFM, TEM and gas porosimetry, for characterization at the nanoscale. The DSA (R) coating was found to consist of mono-crystalline grains with a size of 20-30 nm and with pores of about 10 nm in diameter. Using a simple geometrical model an effective area was calculated. For a typical coating thickness, an increase of about 1000 times in the effective surface area was found, which is consistent with in situ estimations. These results suggest that the dominating source of surface enlargement is due to nano-crystallinity.

  • 34.
    Malmgren, Christine
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Cornell, A
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Eriksson, S
    Behavioural effects of production parameters on DSA®.: 2008Inngår i: 59:th Annual Meeting of the International Society of Electrochemistry, Sevilla, Spain, 7-12 September 2008., 2008Konferansepaper (Annet vitenskapelig)
  • 35. Neuber, G.
    et al.
    Rauer, R.
    Kunze, J.
    Bäckström, Joakim
    Rubhausen, M.
    Generalized magneto-optical ellipsometry in ferromagnetic metals2004Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 455, s. 39-42Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present spectral generalized magneto-optical ellipsometry as an optical tool to investigate magnetic and electronic properties of ferromagnetic materials. The advantage of the simultaneous observation of the dielectric and the magnetic responses within one measurement procedure is crucial for materials with coupled degrees of freedom near a phase transition or during annealing procedures to improve the film quality by removing grain boundaries. Moreover, we show the implementation of this technique within an UHV-cryostat for a temperature range between 4.2 and 800 K and fields up to 40 mT. Examplary measurements on iron and Permalloy demonstrate the comfortable application of this technique. (C) 2003 Elsevier B.V. All rights reserved.

  • 36. Neuber, G.
    et al.
    Rauer, R.
    Kunze, J.
    Korn, T.
    Pels, C.
    Meier, G.
    Merkt, U.
    Bäckström, Joakim
    Rubhausen, M.
    Temperature-dependent spectral generalized magneto-optical ellipsometry2003Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 83, s. 4509-4511Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a setup for temperature-dependent spectral generalized magneto-optical ellipsometry (SGME). This technique gives access to the electronic as well as the magnetic properties of ferromagnetic materials within one single magneto-optical measurement. It also allows the determination of the orientation of the magnetization. We show spectra of the real and the imaginary part of the refractive index N as well as the magneto-optical coupling parameter Q of permalloy and iron films for in-plane magnetization. Our findings demonstrate the relevance of SGME for the understanding of the interplay between electronic and magnetic properties of ferromagnetics. (C) 2003 American Institute of Physics.

  • 37.
    Näslund, Lars-Åke
    et al.
    Department of Physics, Chemistry, and Biology (IFM), Linköping University,.
    Sánchez-Sánchez, Carlos M.
    Instituto Universitario de Electroquímica, Universidad de Alicante.
    Ingason, Árni S.
    Uppsala universitet Fysiska sektionen Institutionen för fysik och astronomi Materialfysik .
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Herrero, Enrique
    Instituto Universitario de Electroquímica, Universidad de Alicante.
    Rosen, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Holmin, Susanne
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik.
    The Role of TiO2 Doping on RuO2-Coated Electrodes for the Water Oxidation Reaction2013Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, nr 12, s. 6126-6135Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Electrochemical water splitting into H2 and O2 presents a significant and challenging energy loss due to the high overpotential required at the anode. Today, in industrially relevant applications, dimensionally stable anodes (DSA) based on the electrocatalytic active RuO2 are conventionally utilized. To enhance the resistance against corrosion, incorporation of TiO2 in the RuO2-coated electrodes is widely employed. In the present work we have used scanning electrochemical microscopy (SECM) to demonstrate that TiO2-doped RuO2-coated electrodes, in addition to being more durable, also show an electrocatalytic activity that is, on average, 13% higher as compared to the pure RuO2-coated electrodes. We also demonstrate that cracks in the pure RuO2 coating are the most active zones, probably because Ti from the Ti support has diffused into the first applied layer of the RuO2 coating. To reveal the nature of this enhanced activity for water oxidation displayed on TiO2-doped RuO2 electrodes, we have employed X-ray photoelectron spectroscopy (XPS) for material characterization. The results show that the electrocatalytic activity enhancement displayed on the mixed (Ru1−x:Tix)O2 coating is promoted through a charge transfer from the RuO2 to the TiO2, which provides new and more reactive sites designated as activated RuO2δ+.

  • 38. Osada, M.
    et al.
    Kakihana, M.
    Bäckström, Joakim
    Kall, M.
    Borjesson, L.
    Resonant Raman scattering and photoinduced metastability in oxygen-deficient YBa2Cu3Ox2000Inngår i: Physica C, Vol. 338, s. 157-160Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We studied the photoinduced metastable states in oxygen-deficient YBa2Cu3Ox (Y123) (x = 6.35-6.87). The states are identified by the intensity dependences of CuO-chain resonance on photo irradiation and temperature. Below room temperature (RT) the CuO-chain resonance can be completely suppressed by irradiation with visible light polarized along the CuO chains, indicating photo-assisted oxygen ordering. Above RT, the resonance intensity returns and saturates at T > 100 degrees C. This behavior exactly reflects the temperature dependence of chain oxygen ordering in the same crystals observed by hard X-ray diffraction. The stability of the photo-induced state is in agreement with reported persistent photo-induced superconductivity effects. (C) 2000 Elsevier Science B.V. All rights reserved.

  • 39. Osada, M.
    et al.
    Kakihana, M.
    Kall, M.
    Bäckström, Joakim
    Borjesson, L.
    Andersen, N. H.
    Photoinduced effects and oxygen dynamics in YBa2Cu3Ox2001Inngår i: Physica. C, Superconductivity, ISSN 0921-4534, E-ISSN 1873-2143, Vol. 364, s. 545-548Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Oxygen-deficient YBa2Cu3Ox (Y123) exhibits persistent photoconductivity when illuminated by visible light. We have investigated resonant Raman spectra as a function of excitation wavelength and temperature, which shed new light on photoinduced effects and chain oxygen dynamics in Y123. Experimental evidence suggests that the mechanism behind the unusual photoinduced effects primary involves photoinduced oxygen ordering. Our Raman data also constitute the non-diffraction observations of the superstructure phase transition in Y123. (C) 2001 Elsevier Science B.V. All rights reserved.

  • 40. Osada, M.
    et al.
    Kall, M.
    Bäckström, Joakim
    Kakihana, M.
    Andersen, N. H.
    Borjesson, L.
    In situ resonant Raman scattering and reversible photoinduced structural change in YBa2Cu3O6+x2005Inngår i: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 71Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on bidirectional photoswitching associated with the CuO chains in oxygen-deficient YBa2Cu3O6+x single crystals. By varying the wavelength of light polarized along the CuO chains, the material can be reversibly switched between two metastable states characterized by the existence or absence of a specific Raman scattering resonance. A comparison of the spectral efficiencies for this photoswitching with analogous data for the persistent photoconductivity and photoconductivity quenching effects suggests that the two phenomena have the same microscopic origin. We argue that the effects are due to photoinduced Cu-O charge-transfer excitations, which destabilize chains of different length depending on wavelength, and promote the growth of thermally inaccessible oxygen ordering configurations.

  • 41. Rauer, R.
    et al.
    Bäckström, Joakim
    Budelmann, D.
    Kurfiss, M.
    Schilling, M.
    Rubhausen, M.
    Walter, T.
    Dorr, K.
    Cooper, S. L.
    Thickness dependent phase separation in La0.7Ca0.3MnO3 films2002Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 81, s. 3777-3779Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The complex dielectric function of La0.7Ca0.3MnO3 films with various thicknesses and on different substrates was determined by the analysis of measured ellipsometric parameters. The temperature-dependent redistribution of low-energy spectral weight shows that the metallicity is developed gradually below an onset temperature that is found to depend strongly on global and local strain properties, not on film thickness alone. Importantly, the 2 nm film shows no metallic conduction but an optical charge-carrier response below 240 K. This suggests that ultrathin films are characterized by phase separation and a percolation-type transition. (C) 2002 American Institute of Physics.

  • 42. Rauer, R.
    et al.
    Neuber, G.
    Kunze, J.
    Bäckström, Joakim
    Rubhausen, M.
    Temperature-dependent spectral generalized magneto-optical ellipsometry for ferromagnetic compounds2005Inngår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 76Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Spectral generalized magneto-optical ellipsometry is presented as an optical tool for the simultaneous measurement of the complex index of refraction n=n+ik, the complex magneto-optical coupling parameter Q=Q(r)+iQ(i) (i.e., the Voigt-parameter), and the orientation of the saturation magnetization M-s of isotropic ferromagnetic bulk materials. For wavelengths between 220 nm and 790 nm and at temperatures between 4.2 K and 800 K measurements on iron and permalloy demonstrate the comfortable application of this technique in order to resolve the spectral response of spin-polarized carriers and bands, which can provide valuable insight about the formation of the ferromagnetic state. (C) 2005 American Institute of Physics.

  • 43. Rauer, R.
    et al.
    Neuber, G.
    Kunze, J.
    Bäckström, Joakim
    Rubhausen, M.
    Walter, T.
    Dorr, K.
    Magneto-optical investigation of spin polarisation of La0.71Ca0.3MnO3 and La0.7Sr0.3MnO32005Inngår i: Journal of Magnetism and Magnetic Materials, Vol. 290, s. 948-951Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We investigate the ferromagnetic phase of thin epitaxial films of the CMR manganites La0.7Ca0.3MnO3 and La0.7Sr0.3MnO3 by temperature-dependent spectral generalised magneto-optical ellipsometry (SGME). The phase transitions from a paramagnetic insulator to a ferromagnetic metal take place at T-C &AP; 265 K and T-C &AP; 335 K, respectively. The measurements covering a spectral range of 0.5-5eV are performed in the temperature range of 25-425 K. SGME allows a complete magneto-optical characterisation consisting of the determination of the diagonal components as well as the off-diagonal components ε(xx) of the dielectric tensor within a single measurement. Upon cooling through the Curie temperature, we observe the development of a Drude-like free-carrier response in ε(xx), indicating the release of previously bound charges. Meanwhile, ε(xx) exhibits a rising magneto-optical response. This reflects, via the increasing degree of spin polarisation of the bands involved in optical transitions, the emergence of ferromagnetism. We tentatively assign spectral features between 2.5 and 4.5 eV to transitions involving the Mn-d shell, especially the e(g) and t(2g) levels. © 2004 Elsevier B.V. All rights reserved.

  • 44.
    Sandin, Staffan
    et al.
    KTH.
    Cheritat, Alicia
    KTH.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Cornell, Ann
    KTH.
    Deposition efficiency in the preparation of ozone-producing nickel and antimony doped tin oxide anodes2017Inngår i: Journal of Electrochemical Science and Engineering, ISSN 1847-9286, Vol. 7, nr 1, s. 51-64Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The influence of precursor salts in the synthesis of nickel and antimony doped tin oxide (NATO) electrodes using thermal decomposition from dissolved chloride salts was investigated. The salts investigated were SnCl45H2O, SnCl22H2O, SbCl3and NiCl26H2O. It was shown that the use of SnCl45H20 in the preparation process leads to a tin loss of more than 85 %. The loss of Sb can be as high as 90 % while no indications of Ni loss was observed. As a consequence, theconcentration of Ni in the NATOcoating will be much higher than in the precursor solution. This high and uncontrolled loss of precursors during the preparation process will lead to an unpredictable composition in the NATOcoating and will have negative economic and environmental effects. It was found that using SnCl22H20 instead of SnCl45H2Ocan reduce the tin loss to less than 50 %. This tin loss occurs at higher temperatures than when using SnCl45H2Owhere the tin loss occurs from 56–147°C causingthe composition to change both during the drying (80–110°C) and calcination (460 -550 °C) steps of the preparation process. Electrodes coated with NATObased on the two different tin salts were investigated for morphology, composition, structure, and ozone electrocatalytic properties.

  • 45. Schulz, B.
    et al.
    Bäckström, Joakim
    Budelmann, D.
    Maeser, R.
    Rubhausen, M.
    Klein, M. V.
    Schoeffel, E.
    Mihill, A.
    Yoon, S.
    Fully reflective deep ultraviolet to near infrared spectrometer and entrance optics for resonance Raman spectroscopy2005Inngår i: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 76Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present the design and performance of a new triple-grating deep ultraviolet to near-infrared spectrometer. The system is fully achromatic due to the use of reflective optics. The minimization of image aberrations by using on- and off- axis parabolic mirrors as well as elliptical mirrors yields a strong stray light rejection with high resolution over a wavelength range between 165 and 1000 nm. The Raman signal is collected with a reflective entrance objective with a numerical aperture of 0.5, featuring a Cassegrain-type design. Resonance Raman studies on semiconductors and on correlated compounds, such as LaMnO3, highlight the performance of this instrument, and show diverse resonance effects between 1.96 and 5.4 eV. (c) 2005 American Institute of Physics.

  • 46. Schulz, B.
    et al.
    Chan, D.
    Bäckström, Joakim
    Rubhausen, M.
    Spectroscopic ellipsometry on biological materials - investigation of hydration dynamics and structural properties2004Inngår i: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 455, s. 731-734Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We demonstrate that spectral ellipsometry is a suitable optical tool to investigate biological samples such as liver tissue, human nails, and human skin. We have performed ex-vivo as well as in-vivo measurements to obtain via the measured optical parameters psi and Delta information’s such as layer thicknesses or hydration conditions. As an example for in-vivo studies, a tape stripping study of human skin is shown. Furthermore, we present a hydration study of nails over 48 h following a hydration schedule. The dehydration behavior of the nail is compared with the dehydration behavior of liver tissue. By investigating the change of (n) over tilde upon hydration and dehydration, we reveal three different time domains, corresponding to ’free’ and ’bound’ water and their respective rate changes. (C) 2004 Elsevier B.V. All rights reserved.

  • 47. Schulz, B.
    et al.
    Chan, D.
    Bäckström, Joakim
    Rubhausen, M.
    Wittern, K. P.
    Wessel, S.
    Wepf, R.
    Williams, S.
    Hydration dynamics of human fingernails: An ellipsometric study2002Inngår i: Physical Review E, Vol. 65Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We use spectroscopic ellipsometry to obtain the complex refractive index, (n) over tilde =n+ik, of human fingernails. By studying the change of (n) over tilde upon hydration and dehydration, we reveal three different time domains with typical time constants of 4, 150, and 3200 min. A simple model that takes into account the presence of one fast and one slow process is fully consistent with the observed hydration and dehydration dynamics. We attribute these processes to "free" water incorporated between the keratin filaments and water more tightly "bound" in keratin complexes, respectively. From our model we determine the hydration profiles of "free" and "bound" water during, both, hydration and dehydration.

  • 48. Sveningsson, M.
    et al.
    Morjan, R. E.
    Nerushev, O. A.
    Sato, Y.
    Bäckström, Joakim
    Campbell, E. E. B.
    Rohmund, F.
    Raman spectroscopy and field-emission properties of CVD-grown carbon-nanotube films2001Inngår i: Applied Physics a-Materials Science & Processing, Vol. 73, s. 409-418Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Carbon-nanotube films are very efficient cathodes for field-emission devices. This study presents a comprehensive comparison between structural, spectroscopic and field-emission properties of films of aligned and non-aligned multi-wall nanotubes (MWNTs) which are grown by thermal chemical vapour deposition. Three types of films are investigated: vertically aligned MWNTs with clean and coated nanotube side walls as well as non-aligned MWNT films. Raman spectra taken on the aligned MWNT films consist of many lines of first-, second- and third-order signals. Several lines are reported here far the first time for MWNTs. The presence of the surface coating leads to a decrease and broadening of the higher-order signals as well as an increase in the disorder-induced contributions in the first-order regime. The aligned MWNT films have excellent field-emission properties with very high emission current densities and low turn-on and threshold fields. The presence of a surface coating has no impact on the efficiency of the field-emission process. Films of non-aligned MWNTs show considerably reduced electron-emission current densities and larger critical fields.

  • 49.
    Volpati, Diogo
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap. Sol Voltaics AB, Lund, Sweden.
    Mårtensson, Niklas
    Sol Voltaics AB, Lund, Sweden.
    Anttu, Nicklas
    Sol Voltaics AB, Lund, Sweden.
    Viklund, Per
    Sol Voltaics AB, Lund, Sweden.
    Sundvall, Christian
    Sol Voltaics AB, Lund, Sweden.
    Åberg, Ingvar
    Sol Voltaics AB, Lund, Sweden.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Björk, Mikael
    Sol Voltaics AB, Lund, Sweden.
    Castillo-Leon, Jaime
    Sol Voltaics AB, Lund, Sweden.
    Spectroscopic investigations of arrays containing vertically and horizontally aligned silicon nanowires2016Inngår i: Materials Research Express, ISSN 2053-1591, Vol. 3, nr 12, artikkel-id 125021Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The properties of nanowire arrays have been investigated mainly in comparison with isolated nanowires or thin films, owing to the difficulty in controlling the nanowire alignment. In this study, we report on arrays containing vertically or horizontally aligned silicon nanowires, whose alignment and structure were determined using x-ray diffraction and scanning electron microscopy. The Raman spectra of the nanowire arrays differ from those of isolated nanowires because of distinct heat dissipation rates of the absorbed energy from the laser, in agreement with recent theoretical calculations. The tailored alignment of the nanowires on solid substrates up to 1 inch of diameter also enabled the observation of resonance modes associated with light trapped into the nanowires. This was proven by comparing the light absorbed and scattered by the arrays, and may be exploited to enhance light harvesting in tandem solar cells. Significantly, the control of the assembly of nanowire arrays may have a direct impact on bottom-up technologies of high anisotropy nanomaterials.

  • 50.
    Öhlund, Thomas
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Schuppert, Anna
    Institut Charles Gerhardt de Montpellier, France.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Bäckström, Joakim
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för naturvetenskap.
    Inkjet Fabrication of Copper Patterns for Flexible Electronics: Using Paper with Active Precoatings2015Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, nr 33, s. 18273-18282Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Low-cost solution-processing of highly conductive films is important for the expanding market of printed electronics. For roll-to-roll manufacturing, suitable flexible substrates and compatible postprocessing are essential. Here, custom-developed coated papers are demonstrated to facilitate the inkjet fabrication of high performance copper patterns. The patterns are fabricated in ambient conditions using water-based CuO dispersion and intense pulsed light (IPL) processing. Papers using a porous CaCO3 precoating, combined with an acidic mesoporous absorption coating, improve the effectiveness and reliability of the IPL process. The processing is realizable within 5 ms, using a single pulse of light. A resistivity of 3.1 ± 0.12 μΩ·cm is achieved with 400 μm wide conductors, corresponding to more than 50% of the conductivity of bulk copper. This is higher than previously reported results for IPL-processed copper.

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