Heat treatment effects on the surface chemisorption behavior of strained uranium: The H2O/U reaction

Tiferet, Eitan; Mintz, M.H.; Zalkind, S.; Jacob, I.; Shamir, N.

doi:10.1016/j.jallcom.2006.10.103

Cited by 7 publications

(5 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…5-7 illustrate the inhibition effect of water on the H 2 chemisorption process. For the pure water adsorption [9,14,15], the hydrogen atoms, originating from the full dissociation of water on the metallic surface can be shadowed by neighboring oxygen atoms, an effect that increases with increasing exposure, accounting for the minimum, observed in the H(DR)/O(DR) ratio [14,15]. At a more progressive stage, when an oxide layer is formed, only partial dissociation of water occurs, with non shadowed OH groups, located on top of the oxide, which accounts for the increase of the H(DR)/O(DR) ratio, for this stage.…”

Section: Inhibition Of Hydrogen Chemisorption On Uranium Surfaces By Traces Of Water Vapormentioning

confidence: 99%

“…As mentioned in the introduction a study was conducted on water adsorption [9] and hydrogen inhibition [17] on a series of samples, with successive steps of strain relief.…”

Section: Inhibition Of Hydrogen Chemisorption On Uranium Surfaces By Traces Of Water Vapormentioning

confidence: 99%

“…It is well known that most conventional surface analysis techniques are either not capable of probing directly surface hydrogen, or (e.g. SIMS) have some limitations in interpreting H surface concentrations [9][10][11][12]. A complementary powerful technique for such studies is the direct recoils spectrometry (DRS) previously reviewed [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

“…Exposing a UHV chamber to water vapor increases instantly hydrogen presence at the residual gas phase due to water dissociation on the interior surface of the vacuum chamber. In the study of reaction of H 2 O with various uranium surfaces [9], it was evident that there was no effect of background hydrogen in the vacuum chamber, for various H 2 O/H 2 ratios (even for ratios <1). On the other hand, exposure of uranium to "clean" hydrogen (the actual amount of residual water vapor was not measured but estimated to be negligible) yielded clear, Langmuir like hydrogen chemisorption on the surface [13].…”

Section: Introductionmentioning

confidence: 99%

“…The initial strain was created during hot-worked rolling of the metallic uranium. Wider studies of water vapor dissociation, adsorption and initial oxidation [9], presented the strain effects on the adsorption and initial oxidation mechanisms of water products on uranium surfaces, as well as the effects of the strain on the inhibition of hydrogen adsorption by water vapor [16].…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

The interaction of water vapor and hydrogen water mixtures with a polycrystalline uranium surface

Tiferet¹,

Mintz²,

Zalkind³

et al. 2008

Annales UMCS, Chemistry

Self Cite

View full text Add to dashboard Cite

The initial room-temperature interactions of water vapor with polycrystalline bulk annealed uranium surfaces were studied by combined measurements utilizing Direct Recoil Spectrometry (DRS) and X-ray Photoelectron Spectroscopy (XPS). It was found that the water goes through a complete dissociation into oxidic oxygen and two neutral H atoms throughout the whole exposure range. The process proceeds by two consecutive stages: (i) below about 80% monolayer coverage, the dissociation products chemisorb mainly on the remaining non-reacted metallic surface by a simple Langmuir-type process; (ii) Between about 80% and full coverage, three dimensional oxide islands (that start to form at 50-60% coverage) cover most of the surface and full dissociation continues on top of them, with part of the hydrogen staying on top of the oxide. It was also found that traces of about 2% water vapor are sufficient to inhibit hydrogen dissociation and chemisorption on uranium surfaces, under low pressure exposures, at room temperature. The efficiency of the inhibition increases with temperature in the range of 200 -400 K. The inhibition effect is also influenced by the extent of residual strain of the sample, with increasing inhibition efficiencies exhibited by a less strained surface. O2, in contrast to H2O, is not an inhibitor to surface adsorption and dissociation of hydrogen. Three types of mechanisms are discussed in order to account for the above inhibition effect of water. It is concluded that the most probable mechanism involves the reversible adsorption of water molecules on hydrogen dissociation sites causing their ''blocking''.

show abstract

Section: Inhibition Of Hydrogen Chemisorption On Uranium Surfaces By Traces Of Water Vapormentioning

confidence: 99%

“…As mentioned in the introduction a study was conducted on water adsorption [9] and hydrogen inhibition [17] on a series of samples, with successive steps of strain relief.…”

Section: Inhibition Of Hydrogen Chemisorption On Uranium Surfaces By Traces Of Water Vapormentioning

confidence: 99%