Mechanochemical preparation and investigation of properties of magnesium, calcium and lithium–magnesium alanates

Mamatha, M.; Bogdanović, Borislav; Felderhoff, Michael; Pommerin, A.; Schmidt, Wolfgang; Schüth, Ferdi; Weidenthaler, Claudia

doi:10.1016/j.jallcom.2005.06.069

Cited by 139 publications

(141 citation statements)

References 29 publications

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“…An enthalpy value of 1.7 kJ/mole for reaction 1 has been found by Mamatha et al [36], while Varin et al [37] reported a value close to zero. Iosub et al [39] estimated that the enthalpy of reaction 1 approached 2 kJ/mol.…”

Section: The Al-mg-h Systemmentioning

confidence: 74%

“…Decomposition of Mg(AlH 4 ) 2 has been investigated by different authors such as Mamatha et al [36] and Varin et al [37] using DSC and Kim et al [38] using TG/MS and DSC, and Iosub et al [39] using XRD, TPD (temperature programmed desorption), and DSC. It has been concluded that magnesium alanate, Mg(AlH 4 ) 2 , decomposes in two steps [38,40] according to the reactions:…”

Section: The Al-mg-h Systemmentioning

confidence: 99%

“…These results are in good agreement with the literature. In fact, Palumbo et al [34] calculated a temperature of 230°C for reaction (2), and values in the range 217-240°C have been reported using DSC experiments [36][37][38]. As mentioned in ''AlMg-H system'', Liu et al [41] expressed fcc-Al as Al 0.9-Mg 0.1 in Eq.…”

Section: The Al-mg-h Systemmentioning

confidence: 99%

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Understanding the hydrogen storage behavior of promising Al–Mg–Na compositions using thermodynamic modeling

Abdessameud

Medraj

2016

Mater Renew Sustain Energy

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Thermodynamic modeling of the Al-Mg-Na-H system is performed in this work to understand the phase relationships and reaction mechanisms in this system. The Al-Na system is reassessed using the modified quasichemical model for the liquid phase. All the terminal solid solutions were remodeled using the compound energy formalism. The thermodynamic properties of the ternary systems are estimated from the models of the binary systems and the ternary compound using the CALPHAD method. The reaction pathways for the systems MgH 2 / AlH 3 , MgH 2 /NaAlH 4 , and MgH 2 /Na 3 AlH 6 are calculated and compared to the experimental data from the literature. Details about the reaction mechanisms and temperatures, the amount of the products, and their composition are revealed and discussed in this work. The calculations show that in the composites MgH 2 /NaAlH 4 and MgH 2 /Na 3 AlH 6 , the components spontaneously destabilize mutually in specific relative amounts by forming NaMgH 3 , which may play only a catalytic role on the decomposition of (MgH 2 ? Al) mixture, NaAlH 4 , or Na 3 AlH 6 . Also, Al destabilizes MgH 2 and NaMgH 3 by forming b phase and reducing the decomposition temperatures of these hydrides by more than 50°C. The constructed database is successfully used to reproduce the pressure-composition isotherms (PCIs) for Mg-10 at% Al and Mg-4 at% Al alloys at 350°C. The results provide a better understanding of the reaction mechanisms in the PCIs found in the literature concerning the number of plateau pressures and their sloping. It is shown that the first plateau pressure observed during the PCIs of Al-Mg alloys depends on Al content and is higher than that of pure Mg. This difference is due to Al solubility in hcp-Mg.

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Section: The Al-mg-h Systemmentioning

confidence: 74%

Section: The Al-mg-h Systemmentioning

confidence: 99%

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Understanding the hydrogen storage behavior of promising Al–Mg–Na compositions using thermodynamic modeling

Abdessameud

Medraj

2016

Mater Renew Sustain Energy

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“…It decomposes to CaH 2 in a two-step process with the formation of a CaAlH 5 intermediate in the first step, as indicated in reactions ͑1͒ and ͑2͒. [3][4][5] Overall the decomposition can be described as reaction ͑3͒. The intermediate CaAlH 5 phase has been identified only recently.…”

Section: Introductionmentioning

confidence: 99%

Ca ( Al H 4 ) 2 , CaAlH5, and CaH2+6LiBH4: Calculated dehydrogenation enthalpy, including zero point energy, and the structure of the phonon spectra

Marashdeh

Frankcombe

2008

The Journal of Chemical Physics

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The dehydrogenation enthalpies of Ca͑AlH 4 ͒ 2 , CaAlH 5 , and CaH 2 + 6LiBH 4 have been calculated using density functional theory calculations at the generalized gradient approximation level. Harmonic phonon zero point energy ͑ZPE͒ corrections have been included using Parlinski's direct method. The dehydrogenation of Ca͑AlH 4 ͒ 2 is exothermic, indicating a metastable hydride. Calculations for CaAlH 5 including ZPE effects indicate that it is not stable enough for a hydrogen storage system operating near ambient conditions. The destabilized combination of LiBH 4 with CaH 2 is a promising system after ZPE-corrected enthalpy calculations. The calculations confirm that including ZPE effects in the harmonic approximation for the dehydrogenation of Ca͑AlH 4 ͒ 2 , CaAlH 5 , and CaH 2 + 6LiBH 4 has a significant effect on the calculated reaction enthalpy. The contribution of ZPE to the dehydrogenation enthalpies of Ca͑AlH 4 ͒ 2 and CaAlH 5 calculated by the direct method phonon analysis was compared to that calculated by the frozen-phonon method. The crystal structure of CaAlH 5 is presented in the more useful standard setting of P2 1 / c symmetry and the phonon density of states of CaAlH 5 , significantly different to other common complex metal hydrides, is rationalized.

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“…The reversibility of Na 2 LiAlH 6 is good but its hydrogen capacity is only 3.5 wt% under moderate conditions. K 2 LiAlH 6 and LiMg(AlH 4 ) 3 were synthesized, but they are not useful for reversible hydrogen storage [22,23]. [26].…”

mentioning

confidence: 99%

Thermodynamics study of hydrogen storage materials

Song

Wang

Jiao

et al. 2012

The Journal of Chemical Thermodynamics

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Mechanochemical preparation and investigation of properties of magnesium, calcium and lithium–magnesium alanates

Cited by 139 publications

References 29 publications

Understanding the hydrogen storage behavior of promising Al–Mg–Na compositions using thermodynamic modeling

Understanding the hydrogen storage behavior of promising Al–Mg–Na compositions using thermodynamic modeling

Ca ( Al H 4 ) 2 , CaAlH5, and CaH2+6LiBH4: Calculated dehydrogenation enthalpy, including zero point energy, and the structure of the phonon spectra

Thermodynamics study of hydrogen storage materials

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