Meeting challenges in nanomaterials for sustainable energy applications using high‐resolution positron methods

Eijt, S.W.H.

doi:10.1002/pssc.200982146

Cited by 4 publications

(5 citation statements)

References 30 publications

(62 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The change in S-parameter is similar in magnitude as for the Mg to MgH 2 transformation in Mg [5][6][7] and Mg 0.90 Ti 0.10 films [7]. Our previous studies [5,15] demonstrated that such a large reduction in S-parameter is a direct result of the metal-insulator transition upon hydrogenation to the MgH 2 phase. Mg metal, namely, has a freeelectron-like electronic structure with a Fermi momentum cut-off at p F ∼ 5.3 × 10 −3 m o c [5], leading to a relatively sharp valence electron momentum distribution (EMD) [5].…”

Section: Doppler Depth Profiling Of Metal Hydride Thin Filmssupporting

confidence: 52%

“…2) show similar clear and large shifts upon hydrogenation, typical for the Mg to MgH 2 metal-to-insulator transition [5,15]. In Refs.…”

Section: Double Layer Behavior Of Mg 90 Ti 10 H X Filmsmentioning

confidence: 58%

“…Rutile phase MgH 2 , on the other hand, is an insulator with primarily ionic Mg-H bonds with more localized valence electron orbitals. This leads to a substantial broadening of the electron momentum distribution upon transition to the insulator phase, resulting in the observed strong reduction in S-parameter [15].…”

Section: Doppler Depth Profiling Of Metal Hydride Thin Filmsmentioning

confidence: 94%

See 2 more Smart Citations

Layer-resolved study of the Mg to MgH2 transformation in Mg–Ti films with short-range chemical order

Eijt¹,

Leegwater²,

Schüt³

et al. 2011

Journal of Alloys and Compounds

View full text Add to dashboard Cite

Section: Doppler Depth Profiling Of Metal Hydride Thin Filmssupporting

confidence: 52%

“…2) show similar clear and large shifts upon hydrogenation, typical for the Mg to MgH 2 metal-to-insulator transition [5,15]. In Refs.…”

Section: Double Layer Behavior Of Mg 90 Ti 10 H X Filmsmentioning

confidence: 58%

Section: Doppler Depth Profiling Of Metal Hydride Thin Filmsmentioning

confidence: 94%

See 1 more Smart Citation

Layer-resolved study of the Mg to MgH2 transformation in Mg–Ti films with short-range chemical order

Eijt¹,

Leegwater²,

Schüt³

et al. 2011

Journal of Alloys and Compounds

View full text Add to dashboard Cite

“…The transition from the free-electronlike Mg metal to the insulator metal hydride phase leads to a substantial broadening of the electron momentum distribution. 15 A remarkable feature of the S-W diagram is that the cluster points for Mg 70 Ti 30 and Mg 90 Ti 10 lie very close to those of well-annealed ͑defect-free͒ Mg and of sputterdeposited Mg layers. 10 Despite the high Ti-fractions of up to 30%, the cluster points remain surprisingly far from the S-W point of well-annealed Ti.…”

mentioning

confidence: 81%

“…10 The S-W cluster point characteristic for the metal Mg 70 Ti 30 phase shows a clear and large shift to the S-W point for the fluorite Mg 70 Ti 30 H x phase upon hydrogenation of the layer. Our previous studies 10,15 demonstrated that such a large reduction in S-parameter is a direct result of the metalinsulator transition occurring during the transition from the Mg to the MgH 2 phase. The transition from the free-electronlike Mg metal to the insulator metal hydride phase leads to a substantial broadening of the electron momentum distribution.…”

mentioning

confidence: 95%

Divacancies and the hydrogenation of Mg-Ti films with short range chemical order

Leegwater

Schüt

Egger

et al. 2010

Applied Physics Letters

Self Cite

View full text Add to dashboard Cite

We obtained evidence for the partial chemical segregation of as-deposited and hydrogenated Mg 1−y Ti y films ͑0 Յ y Յ 0.30͒ into nanoscale Ti and Mg domains using positron Doppler-broadening. We exclusively monitor the hydrogenation of Mg domains, owing to the large difference in positron affinity for Mg and Ti. The electron momentum distribution broadens significantly upon transformation to the MgH 2 phase over the whole compositional range. This reveals the similarity of the metal-insulator transition for rutile and fluorite MgH 2 . Positron lifetime studies show the presence of divacancies in the as-deposited and hydrogenated Mg-Ti metal films. In conjunction with the relatively large local lattice relaxations we deduce to be present in fluorite MgH 2 , these may be responsible for the fast hydrogen sorption kinetics in this MgH 2 phase. © 2010 American Institute of Physics. ͓doi:10.1063/1.3368698͔Mg-Ti alloys are promising materials for application as hydrogen storage media, metal hydride rechargeable batteries, hydrogen sensors, and smart solar collectors. 1,2 Hydrogenation of Mg-Ti films with Ti-concentrations larger than ϳ15% ͑Mg 0.85 Ti 0.15 ͒ leads to the formation of a fluorite Mg 1−y Ti y H x phase with substantially faster hydrogenation kinetics than the common rutile MgH 2 phase. At the same time, a high hydrogen storage capacity of up to 6.5 wt % capacity is reached for Mg 0.80 Ti 0.20 . 1 The Mg-Ti͑-H͒ films have an intriguing microstructure. While Ti and Mg are immiscible metals on a macroscopic scale, codeposition of Mg and Ti by magnetron sputtering leads to Mg-Ti films with a coherent structure, as indicated by x-ray and electron diffraction studies, 3-5 and a very high degree of intermixing of the Mg and Ti. Extended x-ray absorption fine structure ͑EXAFS͒ studies, in contrast, indicated that atomically mixed alloys are not formed. Instead, a partial chemical segregation into Mg and Ti domains on a length scale of the order of less than 10 nm was suggested. 4 The stabilization of the cubic fluorite phase is thought to occur via elastic coupling of MgH 2 to the nanoscale TiH 2 domains. This coupling remains effective during the full ͑de-͒hydrogenation cycle because of the similarity of the unit cell volumes of cubic TiH 2 and hexagonal closed packed Mg in the intermediate state. 4 A direct observation of these phase segregated domains, however, is currently lacking.Furthermore, the fast hydrogen kinetics of these types of films-especially in the cubic hydride phase formed at Ti concentrations larger than 15%-is not well understood. The metal hydride lattice contracts upon increased incorporation of Ti, leading to reduced space for hydrogen mobility. 3,4 It was suggested that the unoccupied octahedral positions in the fluorite MgH 2 structure could aid the hydrogen mobility. 6 Ab initio studies indicate that vacancies form a key factor in the hydrogen diffusion of both the rutile and fluorite MgH 2 phases. [7][8][9] Further insight into the occurrence of vacancies and their possible role in t...

show abstract

In-situ Hydrogen Sorption 2D-ACAR Facility for the Study of Metal Hydrides for Hydrogen Storage

et al. 2012

View full text Add to dashboard Cite

Meeting challenges in nanomaterials for sustainable energy applications using high‐resolution positron methods

Cited by 4 publications

References 30 publications

Layer-resolved study of the Mg to MgH2 transformation in Mg–Ti films with short-range chemical order

Layer-resolved study of the Mg to MgH2 transformation in Mg–Ti films with short-range chemical order

Divacancies and the hydrogenation of Mg-Ti films with short range chemical order

In-situ Hydrogen Sorption 2D-ACAR Facility for the Study of Metal Hydrides for Hydrogen Storage

Contact Info

Product

Resources

About