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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
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PhD Thesis: Syntheses and characterisations of nanostructural magnesium based hydrides for hydrogen storage applications

Author: YANG, Weina

Year: 2008

Supervisor(s): Mike Reece, Xiao Guo

Magnesium hydride is a promising compound for hydrogen storage, but suffers from a high desorption temperature and slow desorption kinetics. This project focuses on the improvements of these properties by modifications to the size, structure and phases of the material using mechanical milling and selected chemical additions.

The hydrogen release temperature of MgH2 is lowered to 305°C after enhanced mechanical refinement by B4C, compared with 440°C of the as-received MgH2. The transition metals, Ru and Hf, do not seem to influence hydrogen desorption of MgH2 due to the formation of Mg2RuH6 and HfH2. The addition of In to MgH2 leads to a small amount of hydrogen release at ~160°C, possibly due to the melting of In catalyses the surface of MgH2 particles facilitating hydrogen evolution. The addition of hcp-BN shows some positive effect on the dehydrogenation properties of MgH2 by reducing the adhesion and agglomerates of MgH2. The addition of nano-catalysts, 10 at.%Ninano or (2 at.%Ninano+2 at.%Fenano), reduces the hydrogen release onset temperature of MgH2 to 160°C. Further combined effects of size reduction, solid solutioning and catalysis by the addition of (B4C+A1+Ninano) largely improve the dehydrogenation properties of MgH2, lowering the hydrogen release peak temperature to 250°C.