The Preparation and Some Properties of Magnesium Hydride<sup>1</sup>

Ellinger, F.H.; Holley, Charles E.; McInteer, B.B.; Pavone, D.; Potter, Robert; Staritzky, Eugene.; Zachariasen, W. H.

doi:10.1021/ja01614a094

Cited by 192 publications

(64 citation statements)

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“…There is a substantial scattering of the reported desorption bulk enthalpies of MgH 2 [11,[14][15][16][17][18][19][20][21], ranging from −67.0 kJ/molH 2 [11] to −81.3 kJ/molH 2 [20,21]. The thermodynamic properties of our Mg films in desorption are in a very good agreement with few bulk references [15] and, in general, fall within the experimental spread.…”

Section: Hydrogenography Experiments On Mg/ta/pd Filmssupporting

confidence: 81%

Thermodynamic Properties, Hysteresis Behavior and Stress-Strain Analysis of MgH2 Thin Films, Studied over a Wide Temperature Range

2012

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Using hydrogenography, we investigate the thermodynamic parameters and hysteresis behavior in Mg thin films capped by Ta/Pd, in a temperature range from 333 K to 545 K. The enthalpy and entropy of hydride decomposition, ∆H des = −78.3 kJ/molH 2 , ∆S des = −136.1 J/K molH 2 , estimated from the Van't Hoff analysis, are in good agreement with bulk results, while the absorption thermodynamics, ∆H abs = −61.6 kJ/molH 2 , ∆S abs = −110.9 J/K molH 2 , appear to be substantially affected by the clamping of the film to the substrate. The clamping is negligible at high temperatures, T > 523 K, while at lower temperatures, T < 393 K, it is considerable. The hysteresis at room temperature in Mg/Ta/Pd films increases by a factor of 16 as compared to MgH 2 bulk. The hysteresis increases even further in Mg/Pd films, most likely due to the formation of a Mg-Pd alloy at the Mg/Pd interface. The stress-strain analysis of the Mg/Ta/Pd films at 300-333 K proves that the increase of the hysteresis occurs due to additional mechanical work during the (de-)hydrogenation cycle. With a proper temperature correction, our stress-strain analysis quantitatively and qualitatively explains the hysteresis behavior in thin films, as compared to bulk, over the whole temperature range. OPEN ACCESSCrystals 2012, 2 711

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Section: Hydrogenography Experiments On Mg/ta/pd Filmssupporting

confidence: 81%

Thermodynamic Properties, Hysteresis Behavior and Stress-Strain Analysis of MgH2 Thin Films, Studied over a Wide Temperature Range

2012

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“…[50][51][52] Magnesium hydride, whose crystal structure is simple tetragonal, is a highly stable hydride with strong Mg-H bond, which is a mixture of ionic and covalent bonding. 53 The calculated bulk lattice constants are a MgH2 = b MgH2 = 4.452 Å, c MgH2 = 2.992 Å with the c/a value of 0.672, which agree well with the previous experimental [54][55][56] and theoretical [57][58][59] results.…”

Section: A the Bulk Properties Of Magnesium And Magnesium Hydridesupporting

confidence: 87%

Modeling and stabilities of Mg/MgH2 interfaces: A first-principles investigation

et al. 2014

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We have theoretically investigated the modeling and the structural stabilities of various Mg/MgH2 interfaces, i.e. Mg($10\bar 10$101¯0)/MgH2(210), Mg(0001)/MgH2(101) and Mg($10\bar 10$101¯0)/MgH2(101), and provided illuminating insights into Mg/MgH2 interface. Specifically, the main factors, which impact the interfacial energies, are fully considered, including surface energies of two phases, mutual lattice constants of interface model, and relative position of two phases. The surface energies of Mg and MgH2, on the one hand, are found to be greatly impacting the interfacial energies, reflected by the lowest interfacial energy of Mg(0001)/MgH2(101) which is comprised of two lowest energy surfaces. On the other hand, it is demonstrated that the mutual lattice constants and the relative position of two phases lead to variations of interfacial energies, thus influencing the interface stabilities dramatically. Moreover, the Mg-H bonding at interface is found to be the determinant of Mg/MgH2 interface stability. Lastly, interfacial and strain effects on defect formations are also studied, both of which are highly facilitating the defect formations. Our results provide a detailed insight into Mg/MgH2 interface structures and the corresponding stabilities.

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“…% Mg is added as was shown already by Van der Molen et al 16 Thus, both YH x and LaH x stay fcc between xϭ2 and xϭ3 and their optical properties change gradually with hydrogen concentration. 19 Magnesium however, is hcp in the metallic phase and tetragonal ͑rutile͒ 43,44 or orthorhombic 44,45 in the insulating MgH 2 phase. Thus, magnesium forms MgH 2 grains ͑with a structural phase transition͒, whose volume fraction increases with increasing H uptake.…”

Section: Re-mg Filmsmentioning

confidence: 99%

Highly absorbing black Mg and rare-earth-Mg switchable mirrors

2004

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Apart from a reflecting and a transparent state, rare-earth-Mg alloys ͑RE-Mg͒ exhibit also a highly absorbing, black state during loading with hydrogen. The occurrence of such a black state is due to the disproportionation into subwavelength size REH 2ϩ⑀ and Mg grains during the first hydrogen loading. While the optical properties of REH x change continuously with a further increase in hydrogen concentration x, Mg changes abruptly from a good reflector to a transparent insulator (MgH 2 ). Thin pure Mg films also show this black state when ͑un͒loaded carefully at elevated temperatures. By using the Bruggeman effective medium approximation in combination with the transfer matrix method it is shown that the coexistence of Mg and MgH 2 grains is the cause of this high absorption. Furthermore, we compare this phenomenon to the high absorption of light observed in metal-dielectric composites.

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The Preparation and Some Properties of Magnesium Hydride¹

Cited by 192 publications

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Thermodynamic Properties, Hysteresis Behavior and Stress-Strain Analysis of MgH2 Thin Films, Studied over a Wide Temperature Range

Thermodynamic Properties, Hysteresis Behavior and Stress-Strain Analysis of MgH2 Thin Films, Studied over a Wide Temperature Range

Modeling and stabilities of Mg/MgH2 interfaces: A first-principles investigation

Highly absorbing black Mg and rare-earth-Mg switchable mirrors

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The Preparation and Some Properties of Magnesium Hydride1

Cited by 192 publications

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Thermodynamic Properties, Hysteresis Behavior and Stress-Strain Analysis of MgH2 Thin Films, Studied over a Wide Temperature Range

Thermodynamic Properties, Hysteresis Behavior and Stress-Strain Analysis of MgH2 Thin Films, Studied over a Wide Temperature Range

Modeling and stabilities of Mg/MgH2 interfaces: A first-principles investigation

Highly absorbing black Mg and rare-earth-Mg switchable mirrors

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The Preparation and Some Properties of Magnesium Hydride¹