Metal hydride electrodes prepared by mechanical alloying of ZrV2-type materials

Jurczyk, M.; Rajewski, W.; Wójcik, Grażyna; Majchrzycki, W.

doi:10.1016/s0925-8388(98)01045-7

Cited by 30 publications

(10 citation statements)

References 12 publications

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“…It was confirmed that the discharge capacity of electrodes prepared by application of MA ZrV 2 material with 10 wt% of Ni powder addition could not be estimated because of extremely high polarization. The same result was reported earlier for high-energy ball milled ZrV 2 alloy [9]. Electrodes prepared from ZrV 1.5 Ni 0.5 alloy powder show improved discharge capacity.…”

Section: Compositionsupporting

confidence: 89%

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Nanocrystalline Hydrogen Storage Alloys Formed by Mechanical Alloying

Jurczyk

Rajewski

2000

Interface Controlled Materials

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The structural and electrochemical properties of a range of alloys, including: ZrV 2 , ZrV 1.5 Ni 0.5 , which have the cubic MgCu 2 structure, Zr 0.35 Ti 0.65 V 0.85 Cr 0.26 Ni 1.30 , which has the hexagonal MgZn 2 structure and MmNi 5 , MmNi 4.2 Al 0.8 , MmNi 3.5 Co 0.7 Al 0.8 , which have the hexagonal CaCu 5 type structure, have been investigated. These alloys have been prepared using mechanical alloying (MA) followed by annealing. The amorphous phase forms directly from the starting mixture of the elements, without other phase formation. Heating the MA samples at 1070 K for 1 h resulted in the creation of ordered alloys. For some nanocrystalline materials discharge capacities of 210 mAh g -1 were obtained.

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Section: Compositionsupporting

confidence: 89%

“…Mechanical alloying was performed under argon atmosphere using a SPEX 8000 Mixer Mill [9]. The purity of the starting materials was at least 99.5 % and the composition of the starting powder mixture corresponded to the stoichiometry of the "ideal" reactions.…”

Section: Methodsmentioning

confidence: 99%

Nanocrystalline Hydrogen Storage Alloys Formed by Mechanical Alloying

Jurczyk

Rajewski

2000

Interface Controlled Materials

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“…The mean crystallite sizes of MA and ammaled nmterial were less than 80 nm. The annealing results in grain growth, as was reported earlier in the case of other nanocrystalline ZrV2-type materials [5]. The mean crystallite sizes of the arc melted and homogenised sample were less than 1000 nm.…”

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confidence: 77%

“…Fornmtion of the nanocrystalline alloy was achieved by annealing the amorphous material in high purity argon atmosphere at 1020 K for 0.5 h. All diffraction peaks were assigned to those of the hexagonal crystal structure of CaCus-type with cell parameters a = 0.5056 mn and c = 0.4007 nm. The powder particles during the MA process are deformed, fractured and cold-welded [5,6]. The microstructure that forms during MA consists of layers of the starting material.…”

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confidence: 99%

Segregation effect on nanocrystalline La(Ni,Al)5 surface

et al. 2002

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Nanocrystalline La(Ni,A1)5 alloys were prepared by mechanical alloying (MA) followed by annealing. Results showed that the surface segregation of La atoms in the MA nanocrystalline samples is stronger compared to that of polycrystalline materials from re'c-melted ingots. Small amounts of Fe impurities, which strongly segregate to the surface, could influence on the hydrogenation properties of the MA nanocrystalline alloys. PACS: 71.20.BeLaNih-based materials combine a high reversible energy storage capacity with fast electrochemical activation, excellent long term cycling stability and good chargedischarge kinetics [1]. Tile partial respective replacement of Ni in LaNi5 by small amounts of AI resulted in a increase in the cycle lifetime without causing much decrease in capacity [2]. Photoemission studies conlbined with measurements of tile magnetic susceptibility [3] showed that La segregates to the surface of the LaNi5 alloy and binds the impurities as 02 or H20 keeping tile Ni subsurface layer metallic, which then is able to split the H2 molecule. In this paper we study tile influence of surface chemical composition and microstructure on the hydrogenation properties of nanocrystalline and polycrystalline La(Ni,AI)5 alloys prepared by mechanical alloying (MA) followed by annealing and arc melting, respectively.MA and arc melting were performed under high purity argon (99.999 vol.%) atmosphere. Tile purity of the starting metallic elements La, Ni, and A1 was 99.9 wt.% or better. The bulk chemical composition of the samples was measured by Xray fluorescence (XRF) method. The surface chemical composition of the smnples was measured by Auger photoelectron spectroscopy (AES) combined with 3 keV argon ion beam sputtering [4]. The MA process of the La-Ni-Al mLxture was studied by X-ray diffraction (XRD) and by scmming electron microscopy (SEM). Pressurecomposition isotherms in the dehydriding process of the hydrogenated material were determined by the Sieverts method at room temperature.Alloy of the La(Ni,Al)5-type was produced by mechanical alloying from crystalline powders. Using LaNi4.2'A10.s as a representative alloy example, the MA pro-*) Presented at ll

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“…However, it is now possible to avoid the inherent difficulties of the fusion technique by using mechanical alloying [3,[12][13][14]. This is so because the reaction between Mg and Ni takes place in solid state and, more importantly, the compound obtained possesses microstructural characteristics such as nanocrystallinity [4,15,16] that are more suitable for hydrogen absorption [17][18][19].…”

Section: Introductionmentioning

confidence: 99%