Hydrogen sorption properties of magnesium-based thin films

Hughes, Luke J.R (2016). Hydrogen sorption properties of magnesium-based thin films. University of Birmingham. Ph.D.

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Abstract

Magnesium hydride is a promising material for hydrogen storage. However, the thermodynamic stability of the hydride coupled with slow reaction kinetics means that it is currently infeasible for application as mobile hydrogen storage media.

Thin films of magnesium have been investigated to ascertain the influence of stress on the effects of the sorption thermodynamics and kinetics. It was found that:

• The intrinsic stress state can be heavily influenced by deposition conditions.
• The influence of the underlying microstructure heavily influences hydrogen sorption mechanics. A model has been proposed which shows regimes dominated by porosity, elastic and plastic contributions and their likely effects on sorption thermodynamics.
• Stress analysis using different film thicknesses has been used to model the diffusion behaviour within the films, demonstrating how differential rates and directionality of absorption also affect both kinetic and thermodynamic properties of the films.
• A novel approach to tailor thin film stress using flexible substrates was used to investigate and tune thermodynamics. The use of an opto-mechanical hydrogen sensor based on this system design.
• Y/Mg multilayer systems were investigated for the first time. The characterisation of these shows that hcp/fcc yttrium occurs at different layer thicknesses, altering the lattice spacings at coherent interfaces with Mg.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):