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Permanent link (DOI): https://doi.org/10.7939/R3VD6PD0P

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Study of the hydrogenation of Mg alloy thin film multilayers by Neutron Refraction Open Access

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Other title
Subject/Keyword
thin-film
neutron reflectometry
hydrogen storage
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Harrower, Christopher
Supervisor and department
Mitlin, Dave (Chemical and Materials Engineering)
Tsui, Ying (Electrical and Computer Engineering)
Examining committee member and department
Tun, Zin (National Research Council Canada)
Pramanik, Sandipan (Electrical and Computer Engineering)
Fedosejevs, Robert (Electrical and Computer Engineering)
Brett, Michael (Electrical and Computer Engineering)
Department
Department of Electrical and Computer Engineering
Specialization
Microsystems & Nanodevices
Date accepted
2014-01-31T08:26:58Z
Graduation date
2014-06
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Magnesium is a promising material for solid state hydrogen storage applications owing to its high theoretical capacity of 8.2 wt% (H/Mg). Unfavourable thermodynamics coupled with poor kinetics leads to unacceptably slow sorption rates at modest temperatures and pressures. Approaches to increasing the sorption rates include using various formulations of catalytic additions on magnesium surface or using alloy additions within magnesium. The aim of these additions is to increase the kinetics while altering the thermodynamics by making the hydride less stable relative to the metal phase. In this thesis magnetron co-sputtering and sequential sputtering are used to introduce the destabilizing or nanocrystalline catalytic phases. In particular, this thesis shows the hydrogen sorption stages of several binary surface catalysts with particular attention to the superior sorption behaviour of a Pd-Ta binary surface catalyst. The results show that the addition of a Ta layer between the Pd and Mg layers lowers the required sorption pressure by a factor of 10 as compared to a simple Pd-catalysed sample. The sorption behaviour is compared to other bi-layer catalysts that also show promise for increased sorption. (e.g. Pd-Ti bilayer catalyst). Next, the sorption behaviour of the Mg-Al samples is compared to the sorption behaviour of a pure Mg sample. The result show that Mg-Al tends to absorb homogenously throughout the thin film whereas pure Mg sample tends to absorb from the surface downwards (in a core-shell type of absorption). Finally, absorption kinetics are increased through catalytic additions within the Mg bulk alloy. This increased sorption behaviour and absorption character is observed through neutron reflectometry measurements of multilayer thin film multilayer structures. The results show that the absorption occurs within the catalysts layers prior to absorption within the Mg layers; however this observation is not widely seen due to typical instrumentation limitations.
Language
English
DOI
doi:10.7939/R3VD6PD0P
Rights
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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2014-06-15T07:09:01.011+00:00
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File size: 3385503
Last modified: 2015:10:12 16:00:32-06:00
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File title: Text1
File author: Christopher Harrower
Page count: 175
File language: en-CA
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