Plasma hydrogenation of Al, Mg and MgAl films under high-flux ion irradiation at elevated temperature

Milčius, D.; Pranevičius, L.; Thomas, George J.

doi:10.1016/j.jallcom.2003.10.029

Cited by 33 publications

(17 citation statements)

References 16 publications

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“…The synthesis of magnesium alanate is retarded. It was shown [6] that hydriding in pure H 2 plasma, when sputtering can be neglected, results in the complete transformation of Mg 17 Al 12 into magnesium alanate. Hydriding in H 2 +Ar plasma under floating potential results in Mg(AlH 4 ) 2 , MgH 2 , and Al phases.…”

Section: Discussionmentioning

confidence: 99%

“…The decomposition of magnesium alanate starts at temperature above 80 • C [6]. The decomposition reaction can be written as…”

Section: Simultaneous Deposition and Hydrogenationmentioning

confidence: 99%

“…Thin film physical vapour deposition technologies are emerging with nontraditional and new nanotechnology methods for designing high-performance storage materials [5,6].…”

Section: Introductionmentioning

confidence: 99%

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Hydrogenation of MgAl films in plasma

Pranevičius

Milčius²

2004

Lith. J. Phys.

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Dedicated to the 100th anniversary of Professor K. BaršauskasHydriding of MgAl films has been performed in two ways: (i) ion implantation of 100 eV hydrogen ions into the growing film, and (ii) hydrogenation of Mg17Al12 films under high-flux, low-energy hydrogen ion irradiation in H2+Ar plasma. The X-ray diffraction studies of phase transitions and structure modifications were carried out. The samples, which were hydrogenated by ion implantation during the deposition of MgAl film, show magnesium alanate, Mg(AlH4)2, phase. It decomposes at temperatures above 80• C. The samples hydrogenated in H2+Ar plasma show Mg(AlH4)2, Mg2Al3, MgH2, and Al phases. It is concluded that sputtering induced by Ar ion bombardment during hydrogenation in H2+Ar plasma limits the supply rate of hydrogen from the surface into the bulk. Experimentally registered synthesis of new phases and restructuring are explained on the basis of long-range transport of metal species, and the role of grain boundaries is emphasized in the mechanism of hydriding.

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Section: Discussionmentioning

confidence: 99%

“…The decomposition of magnesium alanate starts at temperature above 80 • C [6]. The decomposition reaction can be written as…”

Section: Simultaneous Deposition and Hydrogenationmentioning

confidence: 99%

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Hydrogenation of MgAl films in plasma

Pranevičius

Milčius²

2004

Lith. J. Phys.

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“…Nevertheless, a number of complex metal hydride materials of composition A m (MH x ) n , where A is an alkali or alkaline earth metal (Li, Na, Mg, K), and M is a group IIIb metal (B, Al), hold the promise of high weight percent, solid-state hydrogen storage. Examples of these materials under investigation for hydrogen storage properties are NaAlH 4 and Na 3 AlH 6 , LiAlH 4 and Li 3 AlH 6 , Na 2 LiAlH 6 , Mg(AlH 4 ) 2 , KAlH 4 and K 3 AlH 6 , and LiBH 4 [2][3][4][5][6]. Although none has emerged as a solid storage panacea, recent advances in transition metal doping have imparted attractive low temperature, reversible, solid-state hydrogen storage properties to these complex metal hydrides [1].…”

Section: Introductionmentioning

confidence: 99%

A general initial decomposition reaction for complex metal hydrides

Walters

Scogin

2006

Journal of Alloys and Compounds

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The initial thermally activated decomposition of several complex metal hydride compounds, to a binary alkali or alkaline hydride and a group IIIb metal hydride, appears to share a first step in their decomposition mechanisms. The application of this initial thermochemical decomposition step to several alanate compounds illustrates the generality of this approach. For LiAlH 4 , the decomposition data fall on the derived distribution plot calculated for NaAlH 4 . INTRODUCTIONMany enthusiastic efforts continue to contribute to a solid-state reversible hydrogen storage system that will enable an increased participation in an emerging hydrogen economy [1]. While the use of hydrogen as an energy carrier reduces our dependence on petroleum, solid-state hydrogen storage looms on the energy horizon as a major technical concern. Nevertheless, a number of complex metal hydride materials of composition A m (MH x ) n , where A is an alkali or alkaline earth metal (Li, Na, Mg, K), and M is a group IIIb metal (B, Al), hold the promise of high weight percent, solid-state hydrogen storage. Examples of these materials under investigation for hydrogen storage properties are NaAlH 4 and Na 3 AlH 6 , LiAlH 4 and Li 3 AlH 6 , Na 2 LiAlH 6 , Mg(AlH 4 ) 2 , KAlH 4 and K 3 AlH 6 , and LiBH 4 [2][3][4][5][6]. Although none has emerged as a solid storage panacea, recent advances in transition metal doping have imparted attractive low temperature, reversible, solid-state hydrogen storage properties to these complex metal hydrides [1].A key to deploying a solid-state hydrogen storage system lies in understanding the fundamental thermochemical processes intrinsic to hydride storage materials. Of late, we proposed a reversible solid-state hydrogen storage mechanism for NaAlH 4 [7]. Central to this mechanism is the initial production of a binary alkali hydride (NaH) and an intermediate alane (AlH 3 ) that migrates and delivers the evolved hydrogen gas upon decomposition at a titaniumaltered (catalytic) aluminum surface [8]. Then, by the application of high-pressure hydrogen, the same alane species seeks out NaH and produces the original alanate, thus accounting for the reformation of crystalline NaAlH 4 . The initial thermally activated decomposition step, producing a binary alkali or alkaline hydride and a group IIIb metal hydride, appears to be a general first step in the decomposition mechanism for this class of complex metal hydride compounds.The purpose of this short note is to point out that the application of this initial decomposition step to alkali and alkaline alanates demonstrates how some of the accumulating thermo-kinetic data now appearing in the literature for these potentially important solid-state hydrogen storage materials can begin to be rationalized. The proposed shared complex metal hydride initial decomposition step is reaction (1). This reaction initiates an autocatalytic reaction network that continues the decomposition. The reversible capacity of the complex metal hydride, therefore, derives from the decomposit...

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A General Initial Decomposition Reaction for Complex Metal Hydrides

Walters¹

2004

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Plasma hydrogenation of Al, Mg and MgAl films under high-flux ion irradiation at elevated temperature

Cited by 33 publications

References 16 publications

Hydrogenation of MgAl films in plasma

Hydrogenation of MgAl films in plasma

A general initial decomposition reaction for complex metal hydrides

A General Initial Decomposition Reaction for Complex Metal Hydrides

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