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Observation of fluctuations in the order parameter of hydrogen in a quasi-2-dimensional V lattice
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
Manuscript (Other academic)
URN: urn:nbn:se:uu:diva-90821OAI: oai:DiVA.org:uu-90821DiVA: diva2:163303
Available from: 2003-09-04 Created: 2003-09-04 Last updated: 2010-01-13Bibliographically approved
In thesis
1. Phase Transitions and Phase Formation of Hydrogen in Quasi-2D Lattices
Open this publication in new window or tab >>Phase Transitions and Phase Formation of Hydrogen in Quasi-2D Lattices
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The role of the dimensionality and strain state of metallic lattices on the phase behavior of dissolved hydrogen was explored. Metallic superlattices with well defined hydrogen absorption potential on the nm scale, were utilized as test systems. The solubility isotherms of hydrogen in Fe/V(001), MoV/V(001), and Nb/W(110) superlattices were measured by a resistometric method, and the hydrogen-induced changes of the structures were measured by in-situ X-ray diffraction. In the V based superlattices, the long-ranged ordered bulk V hydride phase β-V2H is absent, which is attributed to the finite-size of V lattice. The intrinsic strain-state of the hydrogen dissolving layers was found to have a strong effect on the interaction between metal and hydrogen as well as on the hydrogen-hydrogen (H-H) interaction. For low hydrogen content in the V layers, the compressive strain resulted in a strong enhancement of the H-H interaction, while a tensile strain appeared to diminish the H-H interaction. This is due to different site occupancy of hydrogen for different strain states, which depending on the relation between the symmetries of hydrogen induced global and local strain fields, gives rise to different elastic H-H interaction. Moderately strained V layers exhibited a strong attractive H-H interaction over a broad concentration range. In the concentration ranges where attractive H-H interaction was established, the hydrogen atoms appeared to be strongly correlated on a microscopic length scale. In the Nb based superlattices, the critical temperature for the α–α’ transition was found to be suppressed as a result of the clamping of the film plane by the film-substrate coupling. An exception from this could be noticed when the intrinsic compressive strain were reduced.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2003. 47 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 887
Physics, hydrogen, finite-size effects, long-ranged interactions, superlattices, phase transitions, elastic interaction, Fysik
National Category
Physical Sciences
urn:nbn:se:uu:diva-3571 (URN)91-554-5732-0 (ISBN)
Public defence
2003-09-29, Room 801 01, Ångström Laboratory, Uppsala, 13:15
Available from: 2003-09-04 Created: 2003-09-04Bibliographically approved

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