Microstructure of surface cerium hydride growth sites

Journal Article · Thu May 15 00:00:00 EDT 2014 · Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films

DOI:https://doi.org/10.1116/1.4867475· OSTI ID:22258628

Brierley, Martin ^[1]; Knowles, John; Montgomery, Neil ^[2]; Preuss, Michael ^[3]

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1. Atomic Weapons Establishment, Aldermaston, Berkshire, RG7 4PR, United Kingdom and The School of Materials, University of Manchester, Manchester, M13 9PL (United Kingdom)
2. Atomic Weapons Establishment, Aldermaston, Berkshire, RG7 4PR (United Kingdom)
3. The School of Materials, University of Manchester, Manchester, M13 9PL (United Kingdom)

Samples of cerium were exposed to hydrogen under controlled conditions causing cerium hydride sites to nucleate and grow on the surface. The hydriding rate was measured in situ, and the hydrides were characterised using secondary ion mass spectrometry, scanning electron microscopy, and optical microscopy. The results show that the hydriding rate proceeded more quickly than earlier studies. Characterisation confirmed that the hydrogen is confined to the sites. The morphology of the hydrides was confirmed to be oblate, and stressed material was observed surrounding the hydride, in a number of cases lathlike features were observed surrounding the hydride sites laterally with cracking in the surface oxide above them. It is proposed that during growth the increased lattice parameter of the CeH{sub 2} induces a lateral compressive stress around the hydride, which relieves by the ca. 16% volume collapse of the γ-Ce to α-Ce pressure induced phase transition. Cracking of the surface oxide above the laths reduces the diffusion barrier to hydrogen reaching the metal/oxide interface surrounding the hydride site and contributes to the anisotropic growth of the hydrides.

• OSTI ID: 22258628
• Journal Information: Journal of Vacuum Science and Technology. A, Vacuum, Surfaces and Films, Vol. 32, Issue 3; Other Information: (c) 2014 Crown; Country of input: International Atomic Energy Agency (IAEA); ISSN 0734-2101
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANISOTROPY
CERIUM
CERIUM HYDRIDES
CRACKING
DIFFUSION BARRIERS
HYDRIDATION
HYDROGEN
LATTICE PARAMETERS
MASS SPECTROSCOPY
MICROSTRUCTURE
MORPHOLOGY
OPTICAL MICROSCOPY
OXIDES
PHASE TRANSFORMATIONS
SCANNING ELECTRON MICROSCOPY
STRESSES
SURFACES