Sökning: "Gunnar Pálsson"

Visar resultat 1 - 5 av 6 avhandlingar innehållade orden Gunnar Pálsson.

  1. 1. Influence of Self-trapping, Clamping and Confinement on Hydrogen Absorption

    Författare :Gunnar Karl Pálsson; Björgvin Hjörvarsson; Keith Ross; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; hydrogen diffusion; thin films; superlattices; phase transitions; confinement; clamping; self-trapping; finite-size effect; Surfaces and interfaces; Ytor och mellanytor; Physics with spec. in Atomic; Molecular and Condensed Matter Physics; Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik;

    Sammanfattning : The dissociation of hydrogen molecules at surfaces is the first step in the absorption process. If the absorbing material is covered by an oxide, this layer will determine the effective uptake rate of an underlying absorbing material. LÄS MER

  3. 2. The interaction of hydrogen with metallic glass

    Författare :Johan Bylin; Gunnar K. Pálsson; Ralph H. Scheicher; Gabriella Andersson; Astrid Pundt; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; metallic glass; hydrogen; thin film; density functional theory; stochastic quenching; molecular dynamics; x-ray diffraction; pair distribution function; neutron reflectometry; volume expansion; elastic hydrogen-hydrogen interaction; dipole force tensor; electronic structure; optical conductivity; resistivity; optical transmission; x-ray photoelectron spectroscopy; thermodynamic driving force; Gibbs free energy; Physics with spec. in Atomic; Molecular and Condensed Matter Physics; Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik;

    Sammanfattning : Combining theoretical ab initio calculations with high-purity thin film sample synthesis and in situ measurements is a compelling way to bridge the gap in our understanding concerning hydrogen in metallic glasses, which is the primary work of this dissertation thesis. The main emphasis has been on how hydrogen affects the structure of metallic glasses, and how those changes influence not only the electronic properties of the amorphous metals but also their thermal stability. LÄS MER

  4. 3. The effect of nano-confinement on hydrogen uptake in metallic superlattices

    Författare :Sotirios A. Droulias; Max Wolff; Gunnar K. Pálsson; Björgvin Hjörvarsson; Daniel Azofeifa; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

    Sammanfattning : The absorption of hydrogen is exothermic in vanadium whereas it is endothermic in iron and chromium. Investigations of the hydrogen uptake within Fe/V(001) and Cr/V(001) superlattices allow therefore a detailed exploration of finite size effects and the influence of boundaries on hydrogen absorption. LÄS MER

  5. 4. Designing metallic glasses : Alloying, properties, and degrees of freedom

    Författare :Maciej Kaplan; Björgvin Hjörvarsson; Gunnar Pálsson; Jochen Schneider; Susanne Norgren; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; amorphous alloys; enthalpy of mixing; glass formation; thermal stability; thermodynamics; mechanical properties; corrosion resistance; hydrogen;

    Sammanfattning : The present design rules for metallic glasses with respect to glass formation, thermal stability (resistance to crystallisation), and material properties can still be improved. A main design rule is to use thermodynamic calculations to determine the composition of eutectic points in the phase space. LÄS MER

  7. 5. Order and interfaces in epitaxial heterostructures : Structure and magnetism

    Författare :Anna L. Ravensburg; Vassilios Kapaklis; Björgvin Hjörvarsson; Gunnar K. Pálsson; Martina Müller; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES;

    Sammanfattning : The work in this dissertation is devoted to investigating order and interfaces in epitaxial heterostructures. To achieve that the software tool box GenL was developed for simulating and fitting x-ray diffraction patterns from epitaxial thin films, which is used to access structural information on the length scales of interfaces and atomic bonds. LÄS MER