H-1 nmr analysis of nuclear relaxation mechanisms in Pd-H and Pd-Ag-H alloys

Bokor, Mónika Zsuzsanna and Bánki, Péter and Lasanda, György and Tompa, Kálmán (2005) H-1 nmr analysis of nuclear relaxation mechanisms in Pd-H and Pd-Ag-H alloys. JOURNAL OF ALLOYS AND COMPOUNDS, 404. pp. 238-242. ISSN 0925-8388

Text 1245805.pdf Restricted to Registered users only Download (174kB) | Request a copy

Abstract

Crystalline Pd1-xAgx-H-y (x = 0-0.35) alloys were studied as model systems representing a chemically disordered system for hydrogen-storage materials. Extensive H-1 relaxation rate (R-1, R-1p and R-2) measurements were carried out in a wide temperature range of 2.4-400 K. Palladium-silver alloys of silver concentration as high as 35 at.% were studied by NMR spectroscopy for the first time. The relaxation mechanisms magnetic dipolar relaxation (hydrogen diffusion), Korringa relaxation, relaxation by paramagnetic impurity ions and cross-relaxation to quadrupolar metal nuclei were identified and characterized. The presence of cross-relaxation between H-1 and quadrupolar Pd-105 nuclear spins was assumed and demonstrated for the first time in Pd-H andPd(1-x)Ag(x)-H systems. More than one jump processes of diffusing hydrogen were found to be present in the studied palladium-silver alloys. Only lower estimated limit values of Korringa constants could be obtained since no frequency independent R, versus T region was found. These values are significantly higher than the ones reported by others. (c) 2005 Elsevier B.V. All rights reserved.

Actions (login required)

Edit Item