Thermal Evolution of Hydrogen Following Water Adsorption on Defective UO2(100)
Thermal Evolution of Hydrogen Following Water Adsorption on Defective UO2(100)
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DOI：
10.1021/jp031066u
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发表时间：
2004-01
影响因子：
3.3
通讯作者：
J. Stultz;and M. T. Paffett;S. Joyce
中科院分区：
文献类型：
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作者：
J. Stultz;and M. T. Paffett;S. Joyce
本文用程序升温脱附方法研究了水蒸气作用下UO_2（100）表面分子氢的析出。从良好退火的原始表面没有观察到析氢。然而，大量的氢从高度缺陷的离子溅射表面在400 K下解吸。退火研究表明，大部分缺陷在加热到750 K后愈合。连续的水暴露也可以修复这些缺陷。这些结果表明，该缺陷可能是氧空位（还原铀位点）。在退火时，氧从近表面区域扩散以填充表面空位。水的解离吸附也填补了氧空位。由于离子溅射造成的损伤类似于放射性衰变过程中形成的反冲原子造成的损伤，缺陷处的热化学可能是α发射材料上吸附物质的辐射化学中的间接但重要的因素。
The evolution of molecular hydrogen from UO2(100) surfaces exposed to water vapor has been studied using temperature programmed desorption. No hydrogen evolution is observed from well-annealed, pristine surfaces. Significant amounts of hydrogen, however, desorb from highly defected, ion-sputtered surfaces at ∼400 K. Annealing studies show that the most of the defects are healed after heating to 750 K. Successive water exposures also heal these defects. These results indicate that the defect is likely an oxygen vacancy (reduced uranium site). On annealing, oxygen diffuses from the near-surface region to fill the surface vacancy. The dissociative adsorption of water also fills the oxygen vacancy. As the damage resulting from ion sputtering is similar to that caused by the recoil atom formed during radioactive decay, the thermal chemistry at defects may be an indirect, but significant, factor in the radiation chemistry of adsorbed species on alpha-emitting materials.