The interaction of hydrogen with metallic glass

• 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.    The real-space correlations in the form of the pair distribution functions in thin metallic films have primarily only been accessible through synchrotron radiation. An effective methodological procedure using laboratory-based x-ray sources is here brought forth, which, for the first time, can produce accessible and accurate pair distribution functions from thin films down to a thickness of 80 nm.    The underpinning mechanisms behind the hydrogen-induced volume expansion of metallic glasses in the form of the dipole force tensor and an elastic hydrogen-hydrogen interaction were examined using in situ neutron reflectometry and first-principles calculations of expanding V80Zr20 amorphous structures. The dipole force tensor was concluded to be similar in magnitude to a mole-fraction-weighted sum of the ones found in hydrogen-contained vanadium and zirconium crystals, and the theoretical calculations demonstrated that it and the interaction energy varies with hydrogen concentration.   The electronic structure of the metallic glass V80Zr20 was determined via hard x-ray photoemission spectrometry and confirmed by first-principles calculations to be modified by the presence of hydrogen, in which a collection of s-d hybridized states 7 eV below the Fermi level was formed. The changes closer to the Fermi level, together with the volume expansion, were via experiments and ab initio calculations established to cause a parabolic change in resistance and a strong wavelength dependence on the optical transmission.   The thermal stability of amorphous VxZr1-x metals, investigated via ab initio calculations of the thermodynamic driving force towards crystallization, was found to affirm the observed hydrogen-induced enhancement in thermal stability. 

Ämnesord

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

Nyckelord

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

Publikations- och innehållstyp

vet (ämneskategori)

dok (ämneskategori)