Improvement of hydrogen storage properties of melt-spun Mg–Ni–RE alloys by nanocrystallization

Tanaka, Kazuhide; Kanda, Yoshisada; Furuhashi, Masaki; Saito, Kensuke; Kuroda, Kotaro; Saka, Hiroyasu

doi:10.1016/s0925-8388(99)00477-6

Cited by 96 publications

(53 citation statements)

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“…The former corresponds to a reversible reaction Mg + H 2 ⇔ MgH 2 , while the latter to Mg 2 Ni + 2H 2 ⇔ Mg 2 NiH 4 , of the coexisting phases in the sample. 8,9) Since both reactions are expected to proceed independently in the alloy, their equilibrium pressures inevitably reflect those of Mg and Mg 2 Ni single phases. The presence of a strongly curved region in the first stage of PCT is a characteristic of a nanostructured Mg-based alloy, and it probaly reflects an enhanced hydrogen solution in the grain-boundary region of the nanosized Mg grains.…”

Section: Resultsmentioning

confidence: 99%

“…In our former works, [8][9][10] we presented a simpler and more efficient method for preparing massive Mg-Ni and Mg-Pd alloys added with a catalytic component of Nd. A Mg-rich MgNi-Nd alloy prepared by full melting and subsequent rapid cooling showed substantially enhanced H/D rates at relatively low temperatures (<573 K) without reducing the high hydrogen capacity of Mg appreciably.…”

Section: Introductionmentioning

confidence: 99%

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Hydriding-Dehydriding Properties of Mg-Rich Mg-Ni-Nd Alloys with Refined Microstructures

Yin

Tanaka

2002

Mater. Trans.

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The hydriding/dehydriding characteristics, pressure-composition isotherms and X-ray diffractographs of Mg-rich Mg-Ni-Nd alloys fabricated by different solidifying processes (mold-casting, water-quenching, or melt-spinning) are compared and discussed in relation with their microstructures observed by SEM. Among them, the alloy prepared by melt-spinning and subsequent annealing presents best hydrogen-storage properties. It can quickly absorb hydrogen up to ∼5.0 mass% above 423 K and can wholly desorb it above 453 K with moderate speeds. These enhanced absorption/desorption kinetics are exclusively caused by a refined microstructure of the alloy involving Mg 2 Ni and Nd 2 H 5 precipitates in a Mg matrix as well as by a catalytic action of the Nd-hydride.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hydriding-Dehydriding Properties of Mg-Rich Mg-Ni-Nd Alloys with Refined Microstructures

Yin

Tanaka

2002

Mater. Trans.

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“…The effectiveness of refining the microstructures for improving the reaction kinetics has really been proved for Mg-based alloys fablicated by mechanical alloying 3,8,9) and melt-spinning. 4,10) The objective of the present study is firstly to examine the hydrogen-storage characteristics of a Mg-rich Mg-Ni alloy added with a small amount of Nd and subjected to melt-spinning and annealing, and secondly to characterize its microstructure by high-resolution transmission electron microscopy (HRTEM) and electron diffraction (ED) for discussing a possible H/D mechanism in the alloy.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3] The addition of a catalyst appears to be a simple and effective method to overcome these problems. In our previous works, we have shown that certain Mg-rich Mg-Ni-RE and Mg-Pd-RE alloys (RE: rare earth) exhibit high H-capacities and excellent kinetics, [4][5][6][7] where a rare-earth element such as La and Nd is considered to act as an efficient catalyst for dissociating H 2 molecules and transferring the H atoms to the surrounding Mg matrix. In addition, reducing the grains of the matrix is thought to be another efficient way to improve the reaction kinetics because it may enhance the inward transport of H atoms along the grain boundaries and thereby reduce the depth of the hydride layer.…”

Section: Introductionmentioning

confidence: 99%

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Hydrogen-Storage Properties and Structure Characterization of Melt-Spun and Annealed Mg-Ni-Nd Alloy

Yin

Tanaka

2002

Mater. Trans.

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The hydriding/dehydriding characteristics of a Mg-rich Mg-Ni-Nd alloy produced by melt-spinning and subsequent annealing have been investigated. This alloy absorbs ∼ 4.7 mass% hydrogen (H/M∼ 1.5) quickly between 423 and 573 K and wholly desorbs it at moderate speeds above 453 K. Transmission electron microscope observations and selected-area electron diffraction analyses of this alloy before and after hydriding demonstrate that it consists of multiple phases of Mg 2 Ni and Nd-hydride precipitated uniformly in a nano-structured Mg matrix. The fast reaction kinetics is caused by an interplay between a catalytic action of the Nd-hydrides and the surrounding nano-sized Mg grains which quickly store or evolve hydrogen across the interfaces.

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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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Improvement of hydrogen storage properties of melt-spun Mg–Ni–RE alloys by nanocrystallization

Cited by 96 publications

References 1 publication

Hydriding-Dehydriding Properties of Mg-Rich Mg-Ni-Nd Alloys with Refined Microstructures

Hydriding-Dehydriding Properties of Mg-Rich Mg-Ni-Nd Alloys with Refined Microstructures

Hydrogen-Storage Properties and Structure Characterization of Melt-Spun and Annealed Mg-Ni-Nd Alloy

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

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