Structural and Phase Evolution in the Mg-Al System Leading to Lower Hydrogen Desorption Temperature
Miniyazov A.Z. Mukhamedova N.M. Sokolov I.A. Tulenbergenov T.R. Ospanova Z.N. Uazyrkhanova G.K. Bekmagambetova B.Y. Oken O. Zhakiya R.Y.
December 2025Multidisciplinary Digital Publishing Institute (MDPI)
Hydrogen (Switzerland)
2025#6Issue 4
A comprehensive study of the structural–phase transformations and hydrogen desorption kinetics in the Mg56Al44 system was conducted using a multistage approach combining thermodynamic modeling CALPHAD, Thermo-Calc 2025a, mechanical synthesis (MS), spark plasma sintering (SPS), and subsequent dispersion treatment. Thermodynamic modeling revealed a stable existence region of the intermetallic compound Mg17Al12, exhibiting Cp-T anomalies at 303 and 351 °C that closely corresponded to the experimental DSC/TGA results. Microstructural analysis showed that varying the ball-to-powder ratio BPR 20:1 and BPR 30:1 determines the defect density, crystallite size 25–45 nm, and lattice strain 1.5–3.0 × 10−3, all of which directly influence the hydrogen desorption kinetics. For the samples synthesized at BPR 30:1, the onset temperature of hydrogen release decreased to 180–200 °C while maintaining a hydrogen storage capacity of 4.9 wt.%, accompanied by a reduction in the apparent activation energy of desorption from 92 to 74 kJ·mol−1 according to the Kissinger method. The dispersion stage partially disrupted and redistributed the surface MgO layer, leading to a reduction in its overall contribution and improvement in structural homogeneity, rather than complete oxide removal. The combined MS-SPS-dispersion processing route enabled controlled nanostructure formation, reduced the hydrogen desorption temperature by approximately 100 °C compared to conventional MgH2-based materials, and significantly enhanced the thermokinetic performance. These findings demonstrate that Mg-Al alloys are promising candidates for solid-state hydrogen storage systems with improved desorption kinetics and reduced activation barriers.
desorption temperature , hydrogen sorption kinetics , magnesium intermetallides , mechanical synthesis , phase transformations , solid-state hydrogen storage , spark plasma sintering , thermodynamic modeling
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The National Nuclear Center of the Republic of Kazakhstan, The Institute of Atomic Energy, Kurchatov, 071100, Kazakhstan
Department of Technical Physics and Heat Power Engineering, Shakarim University, Semey, 071410, Kazakhstan
Center of Excellence “VERITAS”, D. Serikbayev East Kazakhstan Technical University, Ust-Kamenogorsk, 070004, Kazakhstan
The National Nuclear Center of the Republic of Kazakhstan
Department of Technical Physics and Heat Power Engineering
Center of Excellence “VERITAS”
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