Hydriding and dehydriding characteristics of mechanically alloyed mixtures Mg-xwt.%Ni (x = 5, 10, 25 and 55)

Song, Myoung Youp; Ivanov, E.; Darriet, B.; Pezat, M.; Hagenmuller, Paul

doi:10.1016/0022-5088(87)90502-9

Cited by 98 publications

(42 citation statements)

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“…In particular, a great number of alloy designs based on the Mg-Ni binary alloy have been investigated following the report by Reilly and Wiswall [12] that Ni could improve hydriding-dehydriding kinetics and decrease the working temperature dramatically compared to pure Mg. Many studies focused on the change in hydriding-dehydriding properties of Mg-Ni binary alloys with compositional change and change in processing variables [13][14][15][16]. However, there has been little research on the relationship between microstructure and the hydriding-dehydriding properties of Mg-Ni binary alloys.…”

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confidence: 98%

Microstructural change in gravity cast Mg−Ni alloys with Ni contents

et al. 2004

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The effects of Ni content on the microstructures of gravity cast Mg-Ni alloys were examined. Different shapes of primary solid particles and microstructures of the eutectic matrix were observed with varying Ni content. The eutectic matrix in the hypoeutectic alloy consisted of rod-like Mg2Ni phase with a small amount of α-Mg phase. The eutectic matrix in the near-eutectic and hypereutectic alloys consisted of eutectic cells oriented in different directions. A transition of lamellae to fiber occurred. The formation of cellular structure and transition of lamellae to fiber resulted from two-phase instability in the coupled region induced by constitutional undercooling.Keywords: Magnesium alloys, Casting, Interface structure, Microstructure, Eutectic solidification Magnesium has strong potential as a hydrogen storage material, because of low density, abundant supply, and low cost. Moreover, it has the highest hydrogen storage capacity among metallic materials. However, poor kinetic properties of hydriding and dehydriding and high working temperature have limited the practical application of Mg-based hydrogen storage materials. Consequently, numerous studies have been carried out in order to improve the hydriding and dehydriding properties of Mg-based materials. In this regard, several methods, including the addition of alloying elements [1][2][3][4][5], intermetallics [6][7][8], and oxides [9][10][11], have been introduced. In particular, a great number of alloy designs based on the Mg-Ni binary alloy have been investigated following the report by Reilly and Wiswall [12] that Ni could improve hydriding-dehydriding kinetics and decrease the working temperature dramatically compared to pure Mg. Many studies focused on the change in hydriding-dehydriding properties of Mg-Ni binary alloys with compositional change and change in processing variables [13][14][15][16]. However, there has been little research on the relationship between microstructure and the hydriding-dehydriding properties of Mg-Ni binary alloys. In this study, the microstructural change in gravity cast Mg-Ni binary alloys with varying Ni content was investigated parting terms of an analysis of change in the hydriding-dehydriding properties of Mg-Ni binary alloys.A pure Mg (99.9 %) ingot was charged into a carbon crucible and heated to 900 o C. After complete melting of the Mg ingot, Ni was added to the molten Mg in chip form in order to be dissolved as quickly as possible so as to minimize the evaporation of Mg at high temperature. Mechanical stirring was carried out in order to homogenize the melt and rapidly dissolve the Ni chips into the Mg melt. A protective gas comprised of CO2 and SF6 gases was blown to the melt surface to prohibit oxidation and ignition of Mg during heating and melting. The alloy melt was poured into a mold of 200 o C after the Ni chips were dissolved into the melt completely.Specimens for microstructural observation were cut into appropriate size from gravity cast Mg-Ni binary alloys and polished mechanically using emery papers ...

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confidence: 98%

Microstructural change in gravity cast Mg−Ni alloys with Ni contents

et al. 2004

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“…Song [15] studied the hydriding kinetics of a mechanically-alloyed mixture Mg-10 wt.%Ni, and reported that for its hydriding reaction at 575-615 K and 5.4-16.1 bar H 2 , the rate-controlling steps were the gas-phase mass transfer through the pores, cracks and interparticle channels, and the diffusion of hydrogen atoms through the growing hydride layer, which varied with the reacted fraction range. Song et al [14] also studied the dehydriding kinetics of a mechanically-alloyed mixture Mg-10 wt.%Ni and showed that, for its dehydriding reaction at 575-615K and 0.52-2.6 bar H 2 , the rate-controlling steps were the nucleation of an D-solid solution of hydrogen in Mg in the initial reacted fraction range, and the gas-phase mass transfer in the later reacted fraction ranges.…”

Section: Resultsmentioning

confidence: 99%

“…The hydriding and dehydriding kinetics of Mg can be improved, therefore, by a treatment such as mechanical alloying [14][15][16] which can facilitate nucleation by creating many defects on the surface and/or in the interior of Mg, or by the additive acting as active sites for nucleation, and shorten diffusion distances by reducing the effective particle sizes of Mg.…”

Section: Introductionmentioning

confidence: 99%

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Improvement of the hydrogen-storage kinetics of Mg by reactive mechanical grinding with 10 wt.% Fe2O3 and 5 wt.% Ni

et al. 2006

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The addition of Fe 2 O 3 to Mg is believed to be able to increase the hydriding rate of Mg, and the addition of Ni is thought to be able to increase the hydriding and dehydriding rates of Mg. A sample Mg-(10 wt.%Fe 2 O 3 , 5 wt.%Ni) was prepared by mechanical grinding under H 2 (reactive mechanical grinding). The as-milled sample absorbed 4.61 wt.% of hydrogen at 593 K under 12 bar H 2 for 60 min. Its activation was accomplished after two hydriding-dehydriding cycles. The activated sample absorbed 4.59 wt.% of hydrogen at 593 K under 12 bar H 2 for 60 min, and desorbed 3.83 wt.% hydrogen at 593 K under 1.0 bar H 2 for 60 min. The activated Mg-(10 wt.%Fe 2 O 3 , 5 wt.%Ni) had a slightly higher hydriding rate at the beginning of the hydriding reaction but a much higher dehydriding rate compared with the activated Mg-10 wt.%Fe 2 O 3 prepared via spray conversion. After hydriding-dehydriding cycling, Fe 2 O 3 was reduced, Mg 2 Ni was formed by the reaction of Mg with Ni, and a small fraction of Mg was oxidized.

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“…The hydriding apparatus has been described previously [19]. The absorbed or desorbed hydrogen quantity was measured as a function of time by a volumetric method.…”

Section: Methodsmentioning

confidence: 99%

Influences on the H2-sorption properties of Mg of Co (with various sizes) and CoO addition by reactive grinding and their thermodynamic stabilities

2004

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We attempted to improve the H 2 -sorption properties of Mg by mechanical grinding under H 2 (reactive grinding) with Co (with various particle sizes) and with CoO. The thermodynamic stabilities of the added Co and CoO were also investigated. CoO addition has the best influence and addition of smaller particles of Co (0.5-1.5 μm) has a better effect than the addition of larger particles of Co on the H 2 -sorption properties of Mg. The activated Mg+10 wt.%CoO sample has about 5.54 wt.% hydrogen-storage capacity at 598 K and the highest hydriding rate, showing an H a value of 2.39 wt.% after 60 min at 598 K, 11.2 bar H 2 . The order of the hydriding rates after activation is the same as that of the specific surface areas of the samples. The reactive grinding of Mg with Co or CoO and hydriding-dehydriding cycling increase the H 2 -sorption rates by facilitating nucleation of magnesium hydride or α solid solution of Mg and H (by creating defects on the surface of the Mg particles and by the additive), and by making cracks on the surface of Mg particles and reducing the particle size of Mg, thus shortening the diffusion distances of hydrogen atoms. The cobalt oxide is stable even after 14 hydriding cycles at 598 K under 11.2 bar H 2 . Discharge capacities are measured for the samples Mg+10 wt.%CoO and Mg+10 wt.%Co (0.5-1.5 μm) with good hydrogen-storage properties.

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Hydriding and dehydriding characteristics of mechanically alloyed mixtures Mg-xwt.%Ni (x = 5, 10, 25 and 55)

Cited by 98 publications

References 14 publications

Microstructural change in gravity cast Mg−Ni alloys with Ni contents

Microstructural change in gravity cast Mg−Ni alloys with Ni contents

Improvement of the hydrogen-storage kinetics of Mg by reactive mechanical grinding with 10 wt.% Fe2O3 and 5 wt.% Ni

Influences on the H2-sorption properties of Mg of Co (with various sizes) and CoO addition by reactive grinding and their thermodynamic stabilities

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