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Ultraviolet and X-ray photoelectron spectroscopies (UPS and XPS respectively) were used to study the CO adsorption on U, UNi(2) and UNi(5) in the temperature range from 73 to 573 K. At 73 K both dissociative adsorption and molecular chemisorption were observed at CO dosages below 6L (L = Langmuir). The role of the Ni surface atoms as sites for the molecular chemisorption was demonstrated, while U surface atoms were sites for the dissociative adsorption of CO. However, Ni atoms lose this property with increasing U surface concentration, which is attributed to a change of their electronic structure. At dosages above 6L, CO is physisorbed on all samples. At temperatures at and above 300 K, only dissociative CO adsorption was observed. A surface oxidic compound which is not a simple uranium oxide (UO(y), y = 2 to 3) is formed. It is characterised by an emission at the Fermi level with a predominant U 5f character. It is believed to be a uranium oxycarbide UO(x)C(l-x).

Additional information

Authors: GOUDER T, JRC Karlsruhe (DE);NAEGELE J R, JRC Karlsruhe (DE);SPIRLET J C, JRC Karlsruhe (DE);VERBIST J, JRC Karlsruhe (DE);COLMENARES C A, University of California, Lawrence Livermore National Laboratory, Livermore (US)
Bibliographic Reference: Article: Surface Science, Vol. 264 (1992) pp. 354-364
Record Number: 199210744 / Last updated on: 1994-12-02
Original language: en
Available languages: en