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Hydrogen storage properties of nitrogen- and halogen- containing materials

Du Plessis, Rachel Frances (2017)
Ph.D. thesis, University of Birmingham.

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Abstract

The Li−Mg−N−H system represents a promising system for a solid-state hydrogen store. Kinetic and thermodynamic improvements are required to bring the properties of this system to a suitable position. The effect of preparation conditions and the addition of dopant materials into this system were investigated by a variety of experimental techniques. The preparation method of the sample was found to be very important. The choice of initial preparation and desorption conditions can be used to control the phase of Li\(_2\)Mg(NH)\(_2\) formed. Pressurised milling conditions (under 100 bar H\(_2\)) appeared to be successful in reducing gas release during milling, but changed the reaction pathway.

The addition of 0.1 mole fraction of either calcium halide dopant, CaCl\(_2\) or CaBr\(_2\) lowered the peak hydrogen desorption temperature from this system. The activation energies of all the doped samples were reduced relative to the undoped samples prepared in the same manner.

The reactions between MgH\(_2\) and NH\(_4\)Cl at various temperatures and stoichiometry’s were also investigated using several techniques. Solid-state reactions between these two reagents have not been carried out before. An unknown set of peaks was observed by powder XRD and a new phase, Mg(NH\(_4\))\(_2\)Cl\(_4\) was identified which was found to be iso-structural with Mg(NH\(_4\))\(_2\)F\(_4\).

Type of Work:Ph.D. thesis.
Supervisor(s):Anderson, P.A. (Paul Alexander) (1965-) and Read, Mark S. D.
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Chemistry
Additional Information:

Publications arising from thesis:

R. F. Bill, D. Reed, D. Book, P.A. Anderson, Effect of the calcium halides, CaCl2 and CaBr2, on hydrogen desorption in the Li-Mg-N-H system, Journal of Alloys and Compounds. 2015, 645, S96-S99
http://dx.doi.org/10.1016/j.jallcom.2014.12.269



Subjects:QD Chemistry
Institution:University of Birmingham
ID Code:7862
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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