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H/He interaction with vacancy-type defects in alpha-Al2O3 single crystals studied by positron annihilation

机译：H / H HI / HES-AL2O3单晶中的空位型缺陷相互作用，通过正电子湮灭研究

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摘要

To probe the interaction of H and He, produced by tritium decay, with vacancy-type defects of alpha-Al2O3 as a tritium permeation barrier (TPB) in fusion reactors, alpha-Al2O3 single crystals were treated in pure Ar gas, D-2 gas and T-2 gas with subsequent tritium aging, respectively, and then their positron annihilation lifetimes and the type of defects that may contribute to the observed positron lifetime components were studied, in combination with DFT results. More monovacancies and vacancy clusters were formed in the thermally hydrogenated samples when compared to the fresh and Ar-annealed samples, indicating the stabilizing effect of hydrogen; this was consistent with the Fermi level position of alpha-Al2O3 moving towards the conduction band minimum (CBM) in the presence of hydrogen impurities, resulting in V-Al(3-) and [V-Al(3-) - H+](2) becoming more stable, as observed by DFT calculations. The monovacancies were slightly eliminated when the samples were thermally annealed and then aged in T-2 gas at room temperature, indicating that He filled the vacancies. This was consistent with it being favourable for He atoms to occupy Al vacancies, with He-Al(3-) forming most readily, whilst more vacancy clusters were continuously induced, suggesting that Al-O bonds weakened and thus nano-hardness decreased with an external load. This study provides the first evidence that Al vacancies can be stabilized by H and filled with He, which will provide further novel TPB design opportunities.
机译：为了探测H和H的相互作用，通过氚衰减产生的，在熔融反应器中具有α-Al2O3作为氚渗透屏障（TPB）的空位型缺陷，在纯Ar气体，D-2中处理α-Al2O3单晶。对于随后的氚衰老的气体和T-2气体，然后研究了它们的正电子湮灭寿命和可能有助于观察到的正电子寿命组分的缺陷的类型，与DFT结果相结合。与新鲜和ar-an-an-un退火的样品相比，在热氢化样品中形成更多单涂层和空位簇，表明氢的稳定效果;这与α-Al2O3的费米水平位置一致地在存在氢杂质的情况下朝向导电带朝向导电带最小（CBM），得到V-Al（3-）和[V-Al（3-） - H +]（ 2）变得更稳定，如DFT计算所观察到。当样品热退火然后在室温下在T-2气体中老化时，单遗址略微消除，表明他填补了空缺。这是符合他占据Al职位空缺的占用，并且最容易形成的群体，而不断诱导簇，表明Al-O键减弱，因此纳米硬度随着纳米硬度降低外部负载。本研究提供了第一种证据，即AL空缺可以通过H稳定并充满他，这将提供进一步的新型TPB设计机会。

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  • 来源
    《RSC Advances》 |2016年第22期|共6页
  • 作者

    Zhang Guikai; Xiang Xin; Yang Feilong; Liu Lang; Tang Tao; Shi Yan; Wang Xiaolin;

  • 作者单位

    China Acad Engn Phys Inst Mat Jiangyou 621908 Peoples R China;

    China Acad Engn Phys Inst Mat Jiangyou 621908 Peoples R China;

    China Acad Engn Phys Inst Mat Jiangyou 621908 Peoples R China;

    China Acad Engn Phys Inst Mat Jiangyou 621908 Peoples R China;

    China Acad Engn Phys Inst Mat Jiangyou 621908 Peoples R China;

    China Acad Engn Phys Inst Mat Jiangyou 621908 Peoples R China;

    China Acad Engn Phys Inst Mat Jiangyou 621908 Peoples R China;

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  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 化学;
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