Inhibition of hydrogen chemisorption on uranium surfaces by traces of water vapor |
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Authors: | E. Tiferet I. Jacob |
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Affiliation: | a Department of Nuclear Engineering, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84104, Israel b Nuclear Research Centre-Negev, P.O. Box 9001, Beer-Sheva 84190, Israel |
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Abstract: | 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”. |
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Keywords: | Adsorption kinetics Chemisorption Physical adsorption Surface diffusion Hydrogen Uranium Water |
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