Kinetics and modeling study of magnesium hydride with various additives at constant pressure thermodynamic driving forces

In this research a comparison was made of the reaction kinetics of MgH 2 ball milled with 4 mol% of TiH 2, Nb 2O 5 or Mg 2Ni. This comparison was made using a novel procedure in which the ratio of the equilibrium plateau pressure ( P m) to the opposing pressure ( P op) was the same in all cases. TPD...

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Bibliographic Details
Published in:Journal of alloys and compounds 2011-09, Vol.509, p.S588-S591
Main Authors: Sabitu, S.T., Fagbami, O., Goudy, A.J.
Format: Article
Language:English
Subjects:
Alloys
Ball milling
Boundaries
Diffusion
Hydrides
Hydrogen absorbing materials
Magnesium
Magnesium hydride
Metal hydride
Nucleation
Reaction kinetics
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Summary:In this research a comparison was made of the reaction kinetics of MgH 2 ball milled with 4 mol% of TiH 2, Nb 2O 5 or Mg 2Ni. This comparison was made using a novel procedure in which the ratio of the equilibrium plateau pressure ( P m) to the opposing pressure ( P op) was the same in all cases. TPD analysis showed that the addition of 4 mol% of the various additives to MgH 2 resulted in a reduction of the onset temperature of MgH 2 by as much as 120 °C. Kinetic data showed that the reaction rates with additives are in the order: TiH 2 < Mg 2Ni < Nb 2O 5. These data were fitted to models for a moving boundary mechanism, a diffusion-controlled process, and nucleation and growth. It was found that a moving boundary mechanism best fit the data and most likely controlled the reaction rates. Kissinger plots showed that the activation energies for the mixtures were in the order: TiH 2 > Mg 2Ni > Nb 2O 5.
ISSN:0925-8388
1873-4669
DOI:10.1016/j.jallcom.2010.11.174