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  • 501.
    Widenkvist, Erika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Quinlan, R.A.
    Akhtar, Sultan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Rubino, Stefano
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Boukhvalov, D.W.
    Katsnelson, M.I.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Eriksson, Olle
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Intercalation and Ultrasonic Treatment of Graphite: a New Synthetic Route to Graphene2008Conference paper (Refereed)
    Abstract [en]

    We will demonstrate that ultrasonic treatment of a graphite crystal in water can lead to the formation of small graphene-like flakes in solution. The delamination of the graphite can be increased dramatically by intercalation of bromine from a Br2-saturated water solution. After ultrasonic treatment, large amounts of graphene-like flakes with varying thickness are observed in SEM and TEM. They can be adsorbed onto a surface of a suitable substrate by a simple dipping technique. The effect of polar and non-polar solvents as well as adsorption of the graphene on hydrophobic and hydrophilic substrates will be demonstrated and compared. DFT calculations of the intercalation process have been carried out using the SIESTA package and the effect of bromine intercalation on cohesive energy and electronic structure will be discussed and compared with experimental data. Finally, the general approach of using ultrasonic treatment and intercalation as a facile route to graphene synthesis compared to other methods will be discussed.

  • 502.
    Widenkvist, Erika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Rubino, Stefano
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Akhtar, Sultan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Fabrication of graphene by sonochemical exfoliation of bromine-graphite2009In: UUCC 2009 - Uppsala University Chemistry Conference - Uppsala Sweden, 12 March 2009, 2009Conference paper (Other academic)
  • 503.
    Widenkvist, Erika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Rubino, Stefano
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Akhtar, Sultan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Sonochemical exfoliation of bromine-graphite2009Conference paper (Refereed)
  • 504.
    Widenkvist, Erika
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Rubino, Stefano
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Experimental Physics.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Fabrication of graphene by bromine-intercalation and sonochemical exfoliation2009Conference paper (Refereed)
    Abstract [en]

    We present a method of producing suspensions of graphene sheets by combining intercalation and mild sonication. Ultrasonic treatment of graphite leads to the formation of small graphene-like flakes in solution. The delamination of the graphite is dramatically increased by intercalation of bromine. After ultrasonic treatment, large amounts of graphene-like flakes with varying thickness are observed in SEM and TEM. They can be adsorbed onto a surface of a suitable substrate by a simple dipping technique. The effect of polar and non-polar solvents as well as adsorption of the graphene on hydrophobic and hydrophilic substrates will be demonstrated and compared. Finally, the general approach of using ultrasonic treatment and intercalation as a facile route to graphene synthesis compared to other methods will be discussed.

  • 505.
    Wikberg, J Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Knut, Ronny
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Audren, A
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ottosson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Linnarsson, M K
    Royal Institute of Technology, KTH-ICT, Electrum, Stockholm.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Hallén, A
    Royal Institute of Technology, KTH-ICT, Electrum, Stockholm.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Annealing effects on structural and magnetic properties of Co implanted ZnO single crystals2011In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 109, no 8, p. 083918-Article in journal (Refereed)
    Abstract [en]

    Single crystals of ZnO were implanted with 100 keV-Co ions at room temperature with a fluence of 4.8 x 10(16) cm(-2) and subsequently annealed at different temperatures up to 800 degrees C. The samples were analyzed by Rutherford backscattering spectrometry, secondary ion mass spectrometry, X-ray diffraction, X-ray photoemission spectroscopy and magnetometry. The as-implanted Co:ZnO crystal shows a homogeneous distribution of Co in the near surface region of the crystal. Upon annealing, clear evidence of secondary phases is found. At the highest annealing temperature (800 degrees C) a ferromagnetic behavior is observed at room temperature with a coercive field of 120 Oe assigned mainly to metallic fcc Co nano-crystallites. We find that for the annealed samples, the temperature dependent magnetization cannot be explained within a model containing only a paramagnetic contribution due to well dispersed Co ions and a ferromagnetic contribution due to Co nano-crystallites, at least one more ferromagnetic contribution is needed for a consistent explanation of the experimental results.

  • 506.
    Wikberg, J Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Knut, Ronny
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Bhandary, Sumanta
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Di Marco, Igor
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Ottosson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Sadowski, Janusz
    MAX-lab, Lund University.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Palmgren, Pål
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Tai, Cheuk W
    Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Magnetocrystalline anisotropy and uniaxiality of MnAs/GaAs(100) films2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 83, no 2, p. 024417-Article in journal (Refereed)
    Abstract [en]

    We present an investigation of the magnetic behavior of epitaxial MnAs films grown on GaAs(100). We address the dependence of the magnetic moment, ferromagnetic transition temperature (Tc), and magnetocrystalline anisotropy constants on epitaxial conditions. From thorough structural and magnetic investigations, our findings indicate a more complex relationship between strain and magnetic properties in MnAs films than a simple stretch/compression of the unit cell axes. While a small increase is seen in the anisotropy constants, the enhancement of the magnetic moment at saturation is significant. Results of x-ray magnetic circular dichroism show a behavior of the spin and orbital moment that is consistent with a structural transition at Tc. In particular, we find that the ratio of the orbital to the spin moment shows a marked increase in the coexistence region of the ferromagnetic α- and paramagnetic β-phases a result that is well in accord with the observed increase in the c/a ratio in the same temperature region. The ab initio density functional calculations reveal that the magnetic properties are more sensitive towards change in the ab-plane compared to change in the c-axis which is explained by the analysis of band structures. The effects of electron correlation in MnAs using ab initio dynamical mean field theory are also presented.

  • 507.
    Wilhelmsson, Ola
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Bijelovic, Stojanka
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lindquist, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    André, Benny
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Deposition and characterization of magnetic Ti–Fe–C nanocomposite thin films2010In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 518, no 10, p. 2607-2616Article in journal (Refereed)
    Abstract [en]

    Nanocomposite (Ti1−xFex)Cy films with different compositions have been deposited by dc magnetron sputtering at 450 °C. The sputtered films could dissolve as much as 20–30 at.% of Fe on the Ti sites which is far above the maximum solid solubility at equilibrium. The solubility was dependent on the carbon content and more carbon-rich films could dissolve more Fe without the formation of Fe-precipitates. The addition of Fe also reduced the grain size of the carbide particles. Upon annealing, α-Fe starts to precipitate and the amount and size of these precipitates can be controlled by the annealing procedure and from the total composition of the as-deposited films. Mechanical and tribological studies show that some compositions of the (Ti1−xFex)Cy films have very good wear-resistant properties. These results together with magnetization measurements suggest that Ti–Fe–C films can be used as a wear-resistant magnetic thin film material.

  • 508.
    Wilhelmsson, Ola
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Eklund, P
    Högberg, H
    Hultman, L
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Structural, electrical and mechanical characterization of magnetron-sputtered2008In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 56, no 11, p. 2563-2569Article in journal (Refereed)
    Abstract [en]

    V2GeC MAX-phase thin films were deposited by DC magnetron sputter epitaxy in the temperature range 450–850 °C. The MAX-phase nucleates directly on (0 0 0 l)-oriented sapphire-wafer substrates without the need for a seed layer. The films contain, however, a small fraction of binary vanadium carbide (VCx) inclusions. X-ray diffraction analysis furthermore shows that these inclusions partly consist of the ordered superstructure V8C7. The amount of Ge in the films decreases at higher temperatures, which can be attributed to Ge evaporation. At temperatures below 450 °C the films consist of polycrystalline Ge and an X-ray amorphous carbide phase attributed to VCx or V2C. No MAX-phase was observed in this temperature region. The electrical and mechanical properties of the films were characterized.

  • 509.
    Wilhelmsson, Ola
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Technology, Department of Engineering Sciences, Electronics. oorganisk kemi.
    Palmquist, Jens-Petter
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Technology, Department of Engineering Sciences, Electronics. oorganisk kemi.
    Nyberg, Tomas
    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, Electronics. Fasta tillståndets elektronik.
    Jansson, Ulf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Technology, Department of Engineering Sciences, Electronics. oorganisk kemi.
    Deposition of Ti2AIC and Ti3AIC2 epitaxial films by magnetron sputtering2004In: Applied Physics Letters, Vol. 85, no 6, p. 1066-1067Article in journal (Refereed)
  • 510.
    Williams, Kirk
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. ÅSTC.
    Eriksson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. ÅSTC.
    Thorslund, Robert
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. ÅSTC.
    Köhler, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. ÅSTC.
    Boman, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Stenmark, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. ÅSTC.
    Electrothermal feasibility of carbon microcoil heaters for cold/hot gas microthrusters2006In: Journal of Micromechanics and Microengineering, Vol. 16, p. 1154-1161Article in journal (Refereed)
    Abstract [en]

    With the miniaturization of spacecraft the need for efficient, accurate and low-weight attitude control systems is becoming evident. To this end, the cold/hot gas microthruster system of this paper incorporates carbon microcoils—deposited via laser-induced chemical vapor deposition—for heating the propellant gas (nitrogen) before the nozzle inlet. By increasing the temperature of the propellant gas for such a system, the specific impulse (Isp) of the microthruster will increase. The benefits of a higher Isp are lower propellant mass, higher thrust and shorter burning times. Therefore, the feasibility of achieving this increase with the carbon microcoils is investigated. The carbon microcoils have been characterized experimentally with respect to their electrothermal performance, i.e. resistance, temperature, parasitic heat losses and degradation in ambient. The resulting heat losses from the heater and the heated gas have been estimated through a combination of experiments, numerical simulation and approximate analytical expressions. At high powers, degradation of the carbon material leads to coil failure in ambient where trace oxygen was present. Thus, the next generation of carbon microcoils to be tested will have a protective coating to extend their lifetime. Theoretical modeling showed that an increase in the propellant gas temperature from 300 to 1200 K and a corresponding two-fold increase in the Isp can be achieved if 1.0 W of power is supplied to each coil in a three-coil thruster. These simulation results show that if the coils are capable of dissipating 1 W of heat at 1700 K coil temperature, the doubling of the Isp may be achieved. Comparing to the electrothermal characterization results we find that the carbon coils can survive at 1700 K if protected, and that they can be expected to reach 1700 K at power below 1 W.

  • 511.
    Williams, Kirk
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Köhler, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Boman, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Fabrication and Mechanical Characterization of LCVD-Deposited Carbon Micro-Springs2006In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 130-131, p. 358-364Article in journal (Refereed)
    Abstract [en]

    Carbon micro-springs were fabricated using laser-assisted chemical vapor deposition (LCVD) at laser powers and ethylene pressures ranging between 200 and 700 mW and 400 and 900 mbar, respectively. A scanning electron microscope was used to determine geometrical parameters such as wire diameter, outside coil diameter, spacing, and pitch. The spring rates for nine batches of springs – chosen from the extremes and middle of the processing ranges – were determined with values ranging between 0.0294 and 0.0604 mN/ m. With the spring rate values, trends regarding the shear modulus and the modulus elasticity of the carbon material as a function of laser power and precursor pressure were deduced. The shear moduli of the chosen batches had values between 13.6 and 733.5 MPa, and using a Poisson’s ratio value of 0.3 the moduli of elasticity ranged from 0.0353 to 1.9071 MPa.

  • 512. Wojcik, M
    et al.
    Sjöberg, S
    Hermansson, Kersti
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. strukturkemi.
    The dianions of o-, m-, p-carboranes from Ab initio calculations.2000In: Spec., Publ. - R.Soc. Chem.Article in journal (Other scientific)
  • 513. Yablonskikh, M. V.
    et al.
    Berger, Rolf
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Gelius, Ulrik
    Physics, Department of Physics. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Elektronspektroskopi.
    Lizárraga, R
    Physics, Department of Physics. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Teoretisk magnetism.
    Charikova, T. B.
    Kurmaev, E. Z.
    Moewes, A
    On the bonding situation in TlCo2Se22006In: Journal of Physics: Condensed Matter, Vol. 18, p. 1757-1768Article in journal (Refereed)
    Abstract [en]

    The electronic structure of TlCo2Se2 has been investigated by means of band structure calculations and x-ray photoelectron and emission spectroscopy (XPS and XES). The formation of the valence band is described in connection with calculations of partial densities of states of the valence band and Co Lα,β x-ray emission () aligned to the binding energy scale. The experimental results are in agreement with the calculated distribution of Co 3d states, which lie close to the Fermi level. The effect of Co–Se bonding is seen as satellite structures in the XPS Co 2p signals. Thermoelectric and Hall effect data as well as resistivity measurements show that TlCo2Se2 is metallic with electron holes as charge carriers with broadband mobility characteristics. The observed anisotropy of the resistivity in the ab plane and along c remains constant as a function of temperature, i.e. without signs of the magnetic ordering that occurs (TN~85 K). The results of local spin density functional calculations show ferromagnetic coupling within the cobalt plane as a result of direct magnetic interactions between the magnetic moments.

  • 514.
    Yang, Wenzhi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Widenkvist, Erika
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry.
    Stirring-induced aggregation of graphene in suspension2011In: New Journal of Chemistry, ISSN 1144-0546, E-ISSN 1369-9261, Vol. 35, no 4, p. 780-783Article in journal (Refereed)
    Abstract [en]

    Graphene in suspension undergoes stirring-induced aggregation that leads to reversible agglomeration and folding/scrolling, all of which affects the Raman spectra; the findings are of importance in all solution-based protocols for graphene preparation and processing.

  • 515. Zettersten, C
    et al.
    Bökman, C. F.
    Sjöberg, P. J. R.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    A Novel Set-Up for the Coupling of a Thin Layer Electrochemical Cell to Electrospray Mass Spectrometry2003In: presented at the 16th International Mass Spectrometry Conference (IMSC), Edinburgh, August 31 - September 5, 2003, 2003Conference paper (Refereed)
  • 516. Zettersten, C
    et al.
    Sjöberg, P. J. R.
    Nyholm, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    The Reaction Mechanism of 4-Chloroaniline studied by Cyclic Voltammetry and Electrochemistry coupled to Electrospray Ionisation Mass Spectrometry2008In: presented at the 18th Analysdagarna (The Analytical Days), Göteborg, 16-18 June, 2008., 2008Conference paper (Refereed)
  • 517.
    Zlotea, Claudia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Andersson, Yvonne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Microstructural modifications induced by hydrogen absorption in Mg5Ga2 and Mg6Pd2006In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 54, no 20, p. 5559-5564Article in journal (Refereed)
    Abstract [en]

    We have recently proposed a new method to design one-dimensional structures of MgH2 in the nano- and micrometer ranges by hydrogen-induced disproportionation of bulk Mg24Y5. The present study confirms the same behavior in hydrogenated Mg5Ga2 and Mg6Pd. Single-crystalline one-dimensional structures and microparticles of MgH2 are formed by hydrogen absorption and subsequent partial disproportionation of Mg5Ga2 and Mg6Pd. The MgH2 whiskers and particles grow with different morphologies for different alloying partners. Growth mechanisms are proposed in relation to the morphology and the chemical surface composition of original compounds.

  • 518.
    Zlotea, Claudia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Lu, Jun
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microstructure Laboratory.
    Andersson, Yvonne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Formation of one-dimensional MgH2 nano-structures by hydrogen induced disproportionation2006In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 426, no 1-2, p. 357-362Article in journal (Refereed)
    Abstract [en]

    Remarkable formation of one-dimensional single crystalline MgH2 structures in the nano- and micro-meters ranges is reported. These structures have been tailored by hydrogen absorption and subsequent disproportionation of bulk Mg24Y5. The MgH2 whiskers have been structurally and morphologically characterized by X-rays diffraction, scanning and transmission electron microcopies. A growth model is proposed for the early stage of the whiskers formation by combining surface chemical and morphological investigations. The formation of MgH2 whiskers opens new engineering explorations and challenges for further experimental and theoretical studies.

  • 519. Zlotea, Claudia
    et al.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Moretto, Pietro
    Andersson, Yvonne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Hydrogen sorption properties of a Mg-Y-Ti alloy2010In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 489, no 2, p. 375-378Article in journal (Refereed)
    Abstract [en]

    The catalytic effect of titanium on the hydrogen sorption properties of a Mg–Y–Ti alloy has been investigated. The alloy is formed by a majority phase Mg24+xY5, a minor phase of solid solution of Y in Mg and Ti clusters randomly dispersed in the sample. During the first hydrogen absorption cycle 5.6 wt.% hydrogen was absorbed at temperatures above 613 K. The alloy decomposed almost completely to MgH2 and YH3. After hydrogen desorption pure Mg and YH2 were formed. For further absorption/desorption cycles the material had a reversible hydrogen capacity of 4.8 wt.%. The MgH2 decomposition enthalpy was determined to −68 kJ/mol H2, and the calculated activation energy of hydrogen desorption of MgH2 was 150(±10) kJ/mol.

  • 520. Zlotea, Claudia
    et al.
    Sahlberg, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Özbilen, Sedat
    Moretto, Pietro
    Andersson, Yvonne
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Hydrogen desorption studies of the Mg24Y5–H system: Formation of Mg tubes, kinetics and cycling effects2008In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 56, no 11, p. 2421-2428Article in journal (Refereed)
    Abstract [en]

    The current study focuses on the hydrogen desorption properties of hydrogenated Mg24Y5. Recently, we have reported the formation of unidirectional MgH2 structures by hydrogen absorption and induced disproportionation of Mg24Y5. During hydrogen desorption, a complex voiding phenomenon produces Mg tubes and carved particles with nano-sized walls. The selected area electron diffraction patterns demonstrate that the Mg tubes are single crystals. A harmonized picture of the unidirectional growth based on different Mg vapor models is proposed. The kinetic properties of hydrogen desorption are improved as compared with commercial MgH2. Hydrogenation/dehydrogenation cycling lowers the thermal stability of the hydrogen desorption at the expense of the total desorbed hydrogen capacity. Both whiskers and microparticles are depleted into clusters of nanoparticles after extensive cyclin

  • 521.
    Ångström, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Hydrogen absorption/desorption properties of the Sc(AlxNi1-x)2 system2011Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Sc(AlxNi1-x)2 is a pseudobinary C14 Laves phase and a potential interstitial hydrogen storage material or anode in a Ni-MH battery. A previous study showed that Sc1Al1Ni1 can store hydrogen reversibly; both interstitially and trough decomposition into ScH2 and AlNi. It is also known that the exact composition is very important for the hydrogen storage properties of pseudobinary Laves phases. This thesis work is aimed at synthesising Sc(AlxNi1-x)2 and study the effect of the Ni/Al ratio on the hydrogen absorption/desorption process as well as the interstitial storage capacity. Compositions with high nickel content had the highest capacity (at least 0.67wt% for ScAl0.66Ni1.34) and ones with high aluminium content had the lowest total storage capacity (0wt% for ScAl1.28Ni0.62). The former composition was also shown to absorb and desorb hydrogen during multiple cycles. Desorption of interstitial hydrogen from ScAl0.66Ni1.34 requires 4.6kJ/mol in activation energy.

  • 522. Öberg, Å.
    et al.
    Kassman, Åsa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    André, Benny
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Lindquist, M.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Högberg, Hans
    Joelsson, T.
    Ljungcrantz, H.
    Conductive nanocomposite ceramics as tribological and electrical contact materials2010In: European Physical Journal: Applied physics, ISSN 1286-0042, E-ISSN 1286-0050, Vol. 49, no 2, p. 22902-Article in journal (Refereed)
    Abstract [en]

    Conductive ceramics have widespread use in many industrial applications. One important application for such materials is electrical contact technology. Over the last few years, a new class of nanocomposite ceramic thin film materials has been developed with contact coatings as one key objective. This family of materials has proven to combine the favorable contact properties of metals, such as low electrical and thermal resistivity, and high ductility, with those of ceramics such as low friction and wear rate, high chemical integrity and good high-temperature properties. Furthermore, it is also found that the tribological properties of such materials can be tailored by alloying thus creating a triboactive system. The technology is now industrialized, and a practical example of a contact system utilizing a nanocomposite coating for improved performance is given.

  • 523. Öberg, Åke
    et al.
    Kassman Rudolphi, Åsa
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Wiklund, Urban
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    André, Benny
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Conductive nanocomposite ceramics as tribological and electrical contact materials2008In: International Conference on Electrical Contacts, ICEC 2008, 2008Conference paper (Refereed)
  • 524. Östlund, L
    et al.
    Mattsson, A
    Leideborg, Mikael
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Westin, Gunnar
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. oorganisk kemi.
    Photodecomposition of acetone on ZrOx-TiO2 thin films in O2 excess and deficit conditions2007In: 31st Int. Conf. Adv. Ceram. Comp. s7, 2007, p. 175-186Conference paper (Refereed)
891011 501 - 524 of 524
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