Synthesis, characterization and hydrogen storage properties of Mg-Ti-Ni system, produced by different ball milling techniques

Ana V. Borissova ,  Stefano Deledda ,  Bjørn C. Hauback 

Physics Department, Institute for Energy Technology, P.O. Box 40, Kjeller NO-2027, Norway

Abstract

Magnesium is considered as one of the most promising material for hydrogen storage, because of its high theoretical hydrogen capacity (7,6wt.% in MgH2), low price and low specific energy. The poor sorption kinetics, fast oxidation as well as high thermodynamic stability of MgH2 (∆H = 75kJ/mol), decrease its maximum capacity, cycle life and therefore make practical utilization very difficult. Improvement in hydrogen absorption properties have been achieved by different approaches, mainly by (i) surface modification of Mg by fluoride treatment, nanocrystalline/amorphous microstructures, (ii) addition of alloying elements and (iii) formation of composite materials with different catalyst such as metals and oxides or another hydride forming alloy or intermetallic compound. Hydrogen storage properties of composite materials mainly depend on the interaction between the different components present in the system. Mechanical milling leads to improvement of the sorption kinetics and thermodynamic properties by reducing the crystalline size. Hydrogen storage in the Mg-Ti-Ni system is presented here. Low temperature desorption and high hydrogen capacity have been found and reported for this system. Here (Mg0,8Ti0,2)2Ni powders were ball milled under low and high hydrogen pressures using different milling conditions as duration of the milling process and ball to powder ratio. Cryomilling was performed in argon atmosphere as well. Powder X-ray diffraction analysis was carried out to investigate the structural changes as a function of the milling time. The microstructure, particle size and chemical composition were characterized with SEM and EDX analysis. Hydrogen absorption/desorption behavior as well as the cycling stability of the composites were examined using the Sieverts method at different temperatures. Financial support from the NANOMAT program in the Research Council of Norway is acknowledged.

 

Presentation: Oral at E-MRS Fall Meeting 2007, Symposium D, by Ana V. Borissova
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-05-14 13:40
Revised:   2009-06-07 00:44