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Influence of irradiation-induced point defects on the dissolution and diffusion properties of hydrogen in α-Al2O3: a first-principles study
Nuclear Fusion ( IF 3.3 ) Pub Date : 2021-01-27 , DOI: 10.1088/1741-4326/abcf8c
Xin-Dong Pan 1, 2 , Yu-Ping Xu 1 , Tao Lu 3 , Hai-Shan Zhou 1 , Xiao-Chun Li 1 , Fei Gao 4 , Guang-Nan Luo 1, 2
Affiliation  

Alpha-alumina (α-Al2O3) is considered to be an ideal candidate material for the tritium permeation barrier (TPB) with excellent tritium resistance properties. However, in a fusion reactor, the irradiation-induced defects could sum up on fabrication-induced defects so to reduce drastically the barrier performance. The underlying mechanism is still not settled. In this paper, the first-principles density functional theory (DFT) approach is used to explore the influence of irradiation-induced point defects on the dissolution and diffusion properties of hydrogen (H) in α-Al2O3. $\left[{\mathrm{H}}^{+}-{V}_{\mathrm{A}\mathrm{l}}^{-3}\right]$ and $\left[{\mathrm{H}}^{+}-{V}_{\mathrm{O}}^{0}\right]$ defects have much lower formation energies at E G/2 in both Al-rich and O-rich growth environments that H atoms are easily captured by vacancy-type irradiation-induced point defects. As a result, higher H retention can be expected, which is consistent with the experimental results. Moreover, by calculating several different diffusion pathways of H-defect complexes and the corresponding diffusion coefficient, it can be inferred that H atoms and vacancy-type point defects can hardly diffuse as a bound entity. Therefore, isolated vacancy-type irradiation-induced point defects can trap multiple H atoms to form H-defect complexes and impede the diffusion process of H, which can enhance the efficiency of protection against H permeation through α-Al2O3 TPB. However, the minimum diffusion barrier for O i H migration to the first nearest neighbor O interstitial site is 0.44eV, which is so low that O i H can migrate quickly at room temperature. This fast diffusion pathway for H could be the underlying mechanism for the low efficiency in preventing H permeation through irradiated α-Al2O3. Our results provide a sound theoretical explanation for recent experimental results of H permeation in α-Al2O3 under irradiation environment.



中文翻译:

在氢的溶解和扩散性辐射诱导的点缺陷的影响的α-Al 2 ö 3:第一原理研究

α-氧化铝(α-Al系2 ö 3)被认为是用于氚渗透阻挡(TPB)具有优良的氚阻力性质的理想候选材料。但是,在聚变反应堆中,辐照引起的缺陷可以归结为制造引起的缺陷,从而大大降低了阻隔性能。底层机制仍未解决。在本文中,第一原理密度泛函理论(DFT)方法被用于探索辐射诱导的点缺陷对氢(H)中的α-Al的溶解和扩散性能的影响2 Ó 3$ \ left [{\ mathrm {H}} ^ {+}-{V} _ {\ mathrm {A} \ mathrm {l}} ^ {-3} \ right] $并且$ \ left [{\ mathrm {H}} ^ {+}-{V} _ {\ mathrm {O}} ^ {0} \ right] $缺陷在E G / 2处具有更低的形成能在富铝和富氧的生长环境中,空位型辐照引起的点缺陷很容易捕获H原子。结果,可以预期更高的H保留,这与实验结果一致。此外,通过计算H-缺陷络合物的几种不同的扩散途径和相应的扩散系数,可以推断出H原子和空位型点缺陷很难作为结合实体扩散。因此,分离的空位型辐射诱导的点缺陷可以陷阱多个H原子以形成H-缺陷络合物和阻碍H的扩散过程,这可以增强对ħ渗透保护的通过的α-Al效率2 Ó 3 TPB。但是,O i H的最小扩散势垒 迁移至第一个最近的O间质位点为0.44eV,该值非常低,以至于O i H 可以在室温下快速迁移。为H该快速扩散路径可能是用于预防ħ渗透通过照射的α-Al低效率的基本机制2 ö 3。我们的研究结果在的α-Alħ渗透的最近的实验结果提供了完善的理论解释2 ö 3照射环境下。

更新日期:2021-01-27
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