https://doi.org/10.1140/epjb/e2005-00023-9
Hydrogen desorption from ball milled MgH2 catalyzed with Fe
1
Department of Physics, University of Bologna and INFM, Bologna, Italy
2
Materials and Technology Unit, ENEA C.R. Casaccia, Roma, Italy
Corresponding author: a luca.pasquini@bo.infm.it
Received:
5
October
2004
Revised:
23
November
2004
Published online:
11
February
2005
In order to obtain faster hydrogen sorption kinetics, MgH2-Fe nanocomposites were prepared by high-energy ball milling. The MgH2 decomposition was studied in samples obtained by changing in a systematic way both the catalyst amount and the degree of microstructural refinement. To this purpose, blends containing increasing Fe concentration have been ball milled in processing conditions able to impart different amount of structural defects. The resulting samples have been characterized by X-ray diffraction to investigate the microstructural features and the phase composition, while the powder morphology and the degree of catalyst dispersion were analyzed by scanning electron microscopy. Differential scanning calorimetry was carried out to characterize the hydrogen desorption behavior of these nanocomposites. Experimental results clearly show that the characteristics of the desorption process are dominated, among other factors, by the morphology of the catalyst dispersion, which in turns depends on the processing conditions and blend composition. In order to achieve low desorption temperatures the homogeneous catalyst dispersion in micron-size particles throughout the structure is required. This condition can be achieved by suitable tuning of the milling conditions and of the catalyst amount.
PACS: 61.72.-y – Defects and impurities in crystals; microstructure / 64.70.Hz – Solid-vapor transitions / 66.30.Pa – Diffusion in nanoscale solids / 81.07.Bc – Nanocrystalline materials
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2005