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Titolo:
Non-equilibration of nanostructured Mg2Ni by bulk mechanical alloying
Autore:
Aizawa, T; Kuji, T; Nakano, H;
Indirizzi:
Res Ctr Adv Sci & Technol, Tokyo 1538904, Japan Res Ctr Adv Sci & TechnolTokyo Japan 1538904 hnol, Tokyo 1538904, Japan Mitsui & Smelting Co Ltd, Corp R&D Ctr, Ageo 3620021, Japan Mitsui & Smelting Co Ltd Ageo Japan 3620021 R&D Ctr, Ageo 3620021, Japan Tokai Univ, Sch High Technol & Human Welf, Numazu 4100395, Japan Tokai Univ Numazu Japan 4100395 hnol & Human Welf, Numazu 4100395, Japan
Titolo Testata:
MATERIALS TRANSACTIONS
fascicolo: 7, volume: 42, anno: 2001,
pagine: 1284 - 1292
SICI:
1345-9678(200107)42:7<1284:NONMBB>2.0.ZU;2-9
Fonte:
ISI
Lingua:
ENG
Keywords:
non-equilibrium Mg2Ni; bulk mechanical alloying; nano-structured Mg2Ni; low temperature phase of Mg2NiH4; self-constraint in nanograins;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Engineering, Computing & Technology
Citazioni:
25
Recensione:
Indirizzi per estratti:
Indirizzo: Aizawa, T Res Ctr Adv Sci & Technol, Tokyo 1538904, Japan Res Ctr Adv Sci & Technol Tokyo Japan 1538904 o 1538904, Japan
Citazione:
T. Aizawa et al., "Non-equilibration of nanostructured Mg2Ni by bulk mechanical alloying", MATER TRANS, 42(7), 2001, pp. 1284-1292

Abstract

Bulk mechanical alloying was successfully applied to solid-state synthesisof Mg2Ni, which is a promising hydro gen storage alloy. Through XRD, TEM and PCT measurement, the synthesized product was characterized to be a single-phase Mg2Ni, excluding co-synthesized MgNi2 or residuals of nickel or magnesium as in conventional processing. The synthesized Mg2Ni has a fine microstructure with the grain size of 10-20nm. Thermodynamic data for hydride formation are coincident with reference data, so that nano-structuring in the solid-state synthesized, stoichiometric Mg2Ni has little role to make essential change in hydrogen storage capacity and mechanism. Physical modification by enrichment of nickel via the bulk mechanical alloying enables us toobtain the nickel-enriched, nano-structured Mg2Ni and to demonstrate the phase transformation of Mg2NiH4 takes place from high temperature phase (HT-phase) to low temperature phase (LT-phase) with decreasing the holding temperature. Negative shift of formation entropy of Mg2NiH4 from HT-phase to LT-phase is corresponding to the hydrogen ordering, where a part of octahedral vacancy sites in Mg Ni structure is only occupied by hydrogen atoms. Formation of LT-phase is also verified by XRD analysis working together with PC7 measurement. Positive shift of formation enthalpy of Mg2NiH4 from HT-phase to LT-phase drives a significant increase of plateau pressure in the PCT diagram. Non-equilibration of nano-structured Mg2Ni leads to control of hydride formation process. Use of these non-equilibrium phase materials helps us to understand various unknown properties of metal hydrides.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 29/09/20 alle ore 23:56:30