Examination of Multiphase (Zr,Ti)(V,Cr,Mn,Ni)2 Ni-MH Electrode Alloys: Part I. Dendritic Solidification Structure

Boettinger, William J.; Newbury, Dale E.; Wang, Ke; Bendersky, Leonid A.; Chiu, Chun; Kattner, Ursula R.; Kim, Young; Chao, B. S.

doi:10.1007/s11661-010-0237-z

Cited by 49 publications

(36 citation statements)

References 50 publications

(49 reference statements)

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“…In the microstructures of Mg-containing alloys, a C15 phase (judging from its relatively higher e/a value) with a slightly brighter contrast and an Mg-predominated phase with a darker contrast start to appear. The TiNi phase is usually surrounded by the C15 phase, since the cooling sequence is C14-C15-TiNi [59,60]. According to the EDS results shown in Table 4, the Mg-content in the C14 phase is very small (0.2-0.3 at%), while that of the C15 phase is slightly higher (0.3-0.7 at%).…”

Section: X-ray Diffractometer Analysismentioning

confidence: 98%

Studies on Incorporation of Mg in Zr-Based AB2 Metal Hydride Alloys

Chang

Kim

Ouchi³

et al. 2016

Batteries

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Abstract:Mg, the A-site atom in C14 (MgZn 2 ), C15 (MgCu 2 ), and C36 (MgNi 2 ) Laves phase alloys, was added to the Zr-based AB 2 metal hydride (MH) alloy during induction melting. Due to the high melting temperature of the host alloy (>1500˝C) and high volatility of Mg in the melt, the Mg content of the final ingot is limited to 0.8 at%. A new Mg-rich cubic phase was found in the Mg-containing alloys with a small phase abundance, which contributes to a significant increase in hydrogen storage capacities, the degree of disorder (DOD) in the hydride, the high-rate dischargeability (HRD), and the charge-transfer resistances at both room temperature (RT) and´40˝C. This phase also facilitates the activation process in measurement of electrochemical discharge capacity. Moreover, through a correlation study, the Ni content was found to be detrimental to the storage capacities, while Ti content was found to be more influential in HRD and charge-transfer resistance in this group of AB 2 metal hydride (MH) alloys.

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Section: X-ray Diffractometer Analysismentioning

confidence: 98%

Studies on Incorporation of Mg in Zr-Based AB2 Metal Hydride Alloys

Chang

Kim

Ouchi³

et al. 2016

Batteries

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“…The TiNi phase further transforms into Zr7Ni10, Zr9Ni11, and ZrNi phases via solid-state reactions [106][107][108][109] (Figure 14). When other modifiers are present, additional secondary phases are also formed.…”

Section: Non-laves Secondary Phasesmentioning

confidence: 99%

C14 Laves Phase Metal Hydride Alloys for Ni/MH Batteries Applications

2017

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C14 Laves phase alloys play a significant role in improving the performance of nickel/metal hydride batteries, which currently dominate the 1.2 V consumer-type rechargeable battery market and those for hybrid electric vehicles. In the current study, the properties of C14 Laves phase based metal hydride alloys are reviewed in relation to their electrochemical applications. Various preparation methods and failure mechanisms of the C14 Laves phase based metal hydride alloys, and the influence of all elements on the electrochemical performance, are discussed. The contributions of some commonly used constituting elements are compared to performance requirements. The importance of stoichiometry and its impact on electrochemical properties is also included. At the end, a discussion section addresses historical hurdles, previous trials, and future directions for implementing C14 Laves phase based metal hydride alloys in commercial nickel/metal hydride batteries.

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“…The composition of several representative areas (identified by Roman numerals) in the SEM micrographs were studied by EDS, and the results are summarized in Table 6. SEM micrographs of the C14 alloy shows a very typical multi-phase C14-C15-Zr x Ni y microstructure, which has been extensively studied with transmission electron microscopy (TEM) [76,77] and electron backscattering diffraction (EBSD) [75]. Occasional ZrO 2 inclusions are also seen in the C14 alloy and act as oxygen scavengers [78], which may contribute positively to the bulk diffusion of hydrogen and provide surface protection against oxidation by the electrolyte [79].…”

Section: Scanning Electron Microscope/energy Dispersive Spectroscopy mentioning

confidence: 99%

Comparison of C14- and C15-Predomiated AB2 Metal Hydride Alloys for Electrochemical Applications

Kim

Nei²,

Wan

et al. 2017

Batteries

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Abstract:Herein, we present a comparison of the electrochemical hydrogen-storage characteristics of two state-of-art Laves phase-based metal hydride alloys (Zr 21.5 (V and Cr) in the first composition results in an average electron density below the C14/C15 threshold ( e/a ∼ 6.9) and produces a C14-predominated structure, while the average electron density of the second composition is above the C14/C15 threshold and results in a C15-predominated structure. From a combination of variations in composition, main phase structure, and degree of homogeneity, the C14-predominated alloy exhibits higher storage capacities (in both the gaseous phase and electrochemical environment), a slower activation, inferior high-rate discharge, and low-temperature performances, and a better cycle stability compared to the C15-predominated alloy. The superiority in high-rate dischargeability in the C15-predominated alloy is mainly due to its larger reactive surface area. Annealing of the C15-predominated alloy eliminates the ZrNi secondary phase completely and changes the composition of the La-containing secondary phase. While the former change sacrifices the synergetic effects, and degrades the hydrogen storage performance, the latter may contribute to the unchanged surface catalytic ability, even with a reduction in total volume of metallic nickel clusters embedded in the activated surface oxide layer. In general, the C14-predominated alloy is more suitable for high-capacity and long cycle life applications, and the C15-predominated alloy can be used in areas requiring easy activation, and better high-rate and low-temperature performances.

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Examination of Multiphase (Zr,Ti)(V,Cr,Mn,Ni)2 Ni-MH Electrode Alloys: Part I. Dendritic Solidification Structure

Cited by 49 publications

References 50 publications

Studies on Incorporation of Mg in Zr-Based AB2 Metal Hydride Alloys

Studies on Incorporation of Mg in Zr-Based AB2 Metal Hydride Alloys

C14 Laves Phase Metal Hydride Alloys for Ni/MH Batteries Applications

Comparison of C14- and C15-Predomiated AB2 Metal Hydride Alloys for Electrochemical Applications

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