Title: U-Zr alloy: XPS and TEM study of surface passivation
Citation: APPLIED SURFACE SCIENCE vol. 441 p. 113-119
Publication Year: 2018
JRC N°: JRC111412
ISSN: 0169-4332
URI: http://publications.jrc.ec.europa.eu/repository/handle/JRC111412
DOI: 10.1016/j.apsusc.2018.01.319
Type: Articles in periodicals and books
Abstract: Surface reactivity of Uranium metal is an important factor limiting its practical applications. Bcc alloys of U with various transition metals are much less reactive than pure Uranium. So as to specify the mechanism of surface protection, we have been studying the U-20 at.% Zr alloy by photoelectron spectroscopy and transmission electron microscopy. The surface was studied in as-obtained state, in various stages of surface cleaning, and during an isochronal annealing cycle. The analysis based on U-4f, Zr-3p, and O-1 s spectra shows that a Zr-rich phase segregates at the surface at temperatures exceeding 550 K, which provides a self-assembled coating. The comparison of oxygen exposure of the stoichiometric and coated surfaces shows that the coating is efficiently preventing the oxidation of uranium even at elevated temperatures. The coating can be associated with the UZr2+x phase. TEM study indicated that the coating is about 20 nm thick. For the clean state, the U-4f core-level lines of the bcc alloy are practically identical to those of α-U, revealing similar delocalization of the 5f electronic states.
JRC Directorate:Nuclear Safety and Security

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