Effect of rare earth elements and alloy composition on hydrogenation properties and crystal structures of hydrides in Mg 2- x RE xNi 4

K. Sakaki, N. Terashita, S. Tsunokake, Y. Nakamura, E. Akiba

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

The effect of the rare earth elements and alloy composition on the hydrogenation properties and crystal structures of hydrides in Mg 2-xRE xNi 4 (RE = La, Pr, Nd, Sm, and Gd; x = 0.6 and 1.0) was investigated. All Mg 2-xRE xNi 4 alloys had a C15b Laves phase before hydrogenation. Mg 1.4RE 0.6Ni 4 (RE = Pr, Sm, and Gd) alloys were hydrogenated through one plateau to form Mg 1.4RE 0.6Ni 4H ∼3.6 while maintaining the C15b structure. Mg 1.0RE 1.0Ni 4 (RE = La, Pr, and Nd) alloys were hydrogenated to ∼1.0 H/M proceeding through two plateaus, and Mg 1.0RE 1.0Ni 4 (RE = Sm and Gd) alloys were hydrogenated to 0.6-0.7 H/M through one plateau. Mg 1.0RE 1.0Ni 4 alloys initially transformed into Mg 1.0RE 1.0Ni 4H ∼4 with an orthorhombic structure. In addition it was experimentally confirmed that Mg 1.0RE 1.0Ni 4H ∼4 with La, Pr, and Nd transformed into Mg 1.0RE 1.0Ni 4H ∼6 with a C15b structure, while no formation of Mg 1.0RE 1.0Ni 4H ∼6 (RE = Sm and Gd) was observed at 40 MPa at 250 K. Theoretical calculations suggest that Mg 1.0RE 1.0Ni 4H ∼4 with Sm and Gd also transform to Mg 1.0RE 1.0Ni 4H ∼6 at higher pressures than those used in our experiments (264 MPa for Mg 1.0Sm 1.0Ni 4 and 8.5 GPa for Mg 1.0Gd 1.0Ni 4 at 253 K). It was found that the hydrogenation properties and crystal structure of the hydrides in Mg 2-xRE xNi 4 are dependent on the alloy composition, i.e., the ratio of Mg to RE in the alloy phase, but independent of the choice of rare earth element.

Original languageEnglish
Pages (from-to)19156-19163
Number of pages8
JournalJournal of Physical Chemistry C
Volume116
Issue number36
DOIs
Publication statusPublished - Sep 13 2012

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

Fingerprint Dive into the research topics of 'Effect of rare earth elements and alloy composition on hydrogenation properties and crystal structures of hydrides in Mg <sub>2- x</sub> RE <sub>x</sub>Ni <sub>4</sub>'. Together they form a unique fingerprint.

  • Cite this