ERA

Download the full-sized PDF of Microstructure-property correlation in magnesium-based hydrogen storage systems- The case for ball-milled magnesium hydride powder and Mg-based multilayered compositesDownload the full-sized PDF

Analytics

Share

Permanent link (DOI): https://doi.org/10.7939/R3G04Q

Download

Export to: EndNote  |  Zotero  |  Mendeley

Communities

This file is in the following communities:

Graduate Studies and Research, Faculty of

Collections

This file is in the following collections:

Theses and Dissertations

Microstructure-property correlation in magnesium-based hydrogen storage systems- The case for ball-milled magnesium hydride powder and Mg-based multilayered composites Open Access

Descriptions

Other title
Subject/Keyword
Hydrogen storage
Ball milling
Accumulative roll bonding
Magnesium
Transmission electron microscopy
Magnesium hydride
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Danaie, Mohsen
Supervisor and department
Mitlin, David (Chemical and Materials Engineering)
Examining committee member and department
Nychka, John (Chemical and Materials Engineering)
Zhang, Hao (Chemical and Materials Engineering)
Cadien, Ken (Chemical and Materials Engineering)
Elias, Anastasia (Chemical and Materials Engineering)- Chair
Brett, Michael (Electrical and Computer Engineering)
Botton, Gianluigi (Materials Science and Engineering- McMaster University)
Department
Department of Chemical and Materials Engineering
Specialization

Date accepted
2010-12-02T18:20:18Z
Graduation date
2011-06
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
The main focus of this thesis is the characterization of defects and microstructure in high-energy ball milled magnesium hydride powder and magnesium-based multilayered composites. Enhancement in kinetics of hydrogen cycling in magnesium can be achieved by applying severe plastic deformation. A literature survey reveals that, due to extreme instability of α-MgH2 in transmission electron microscope (TEM), the physical parameters that researchers have studied are limited to particle size and grain size. By utilizing a cryogenic TEM sample holder, we extended the stability time of the hydride phase during TEM characterization. Milling for only 30 minutes resulted in a significant enhancement in desorption kinetics. A subsequent annealing cycle under pressurized hydrogen reverted the kinetics to its initial sluggish state. Cryo-TEM analysis of the milled hydride revealed that mechanical milling induces deformation twinning in the hydride microstructure. Milling did not alter the thermodynamics of desorption. Twins can enhance the kinetics by acting as preferential locations for the heterogeneous nucleation of metallic magnesium. We also looked at the phase transformation characteristics of desorption in MgH2. By using energy-filtered TEM, we investigated the morphology of the phases in a partially desorbed state. Our observations prove that desorption phase transformation in MgH2 is of “nucleation and growth” type, with a substantial energy barrier for nucleation. This is contrary to the generally assumed “core-shell” structure in most of the simulation models for this system. We also tested the hydrogen storage cycling behavior of bulk centimeter-scale Mg-Ti and Mg-SS multilayer composites synthesized by accumulative roll-bonding. Addition of either phase (Ti or SS) allows the reversible hydrogen sorption at 350°C, whereas identically roll-bonded pure magnesium cannot be absorbed. In the composites the first cycle of absorption (also called “activation”) kinetics improve with increased number of fold and roll (FR) operations. With increasing FR operations the distribution of the Ti phase is progressively refined, and the shape of the absorption curve no longer remains sigmoidal. Up to a point, increasing the loading amount of the second phase also accelerates the kinetics. Microscopy analysis performed on 1-2 wt.% hydrogen absorbed composites demonstrates that MgH2 formed exclusively on various heterogeneous nucleation sites. During activation, MgH2 nucleation occurred at the Mg-hard phase interfaces. On the subsequent absorption cycles, heterogeneous nucleation primarily occurred in the vicinity of “internal” free surfaces such as cracks.
Language
English
DOI
doi:10.7939/R3G04Q
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.
Citation for previous publication

File Details

Date Uploaded
Date Modified
2014-04-25T00:01:17.064+00:00
Audit Status
Audits have not yet been run on this file.
Characterization
File format: pdf (Portable Document Format)
Mime type: application/pdf
File size: 8642006
Last modified: 2015:10:12 18:40:27-06:00
Filename: Danaie_Mohsen_Spring2011.pdf
Original checksum: b0eb5791fb7560864d897947efcac8ff
Well formed: true
Valid: true
Status message: File header gives version as 1.4, but catalog dictionary gives version as 1.3
File title: Microsoft Word - MainBody.docx
File author: Mohsen Danaie
Page count: 121
Activity of users you follow
User Activity Date