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Description
Large-scale use of hydrogen is limited by storage and transport constraints due to its very low volumetric density as a diatomic gas at ambient conditions. Compression and cryogenic liquefaction increase density, but liquefaction requires cooling to ~20 K, consumes a notable fraction of the energy content, and is prone to boil-off and leakage. Metal hydrides offer solid-state storage by allowing hydrogen to diffuse into metal lattices, occupy interstitial sites or induce phase changes, and form a hydride via a solid–gas reaction
Magnesium-based hydrides offer high gravimetric hydrogen capacity, but their practical deployment is limited by slow sorption kinetics and high operating temperatures. In this work, we investigated the hydrogen storage performance of Mg-based materials by forming Mg–Al intermetallics and refining the microstructure.
Hydrogenation at 350°C and 50 bars using a homemade Sievert apparatus produced a hydride with a hydrogen capacity of 2.97 wt%. X-ray diffraction after hydrogenation confirmed the formation of MgH2 and the Mg2Al3 intermetallic phase. To introduce additional lattice defects and reduce kinetic barriers, β-Mg₁₇Al₁₂ was further processed by ball milling.
After 15 min of ball milling, the crystallite size decreased from 26.0 ± 0.5 nm to 11.7 ± 0.3 nm. Hydrogen absorption kinetics were accelerated after ball milling, and analysis of the kinetic data yielded a lower apparent hydrogenation activation energy, consistent with increased fresh surfaces as pathways for hydrogen atoms to diffuse. On the other hand, we observed that the absorbed hydrogen content of the ball-milled material, increased from 3.72 wt% in the first absorption cycle to 4.2 wt% in the second cycle. In addition, DSC results for ball-milled samples showed a decrease in desorption temperature. These results underscore the critical influence of mechanical processing on hydrogen storage performance.
| Keyword-1 | Hydrogen Storage |
|---|---|
| Keyword-2 | Metal Hydrides |
| Keyword-3 | Solid state hyrdogen storage |