Cr Effect on Hydrogen Interactions with Intrinsic Point Defects and Hydrogen Diffusion in α-Al2O3 as Tritium Permeation Barriers

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• 作者：Xin Xiang ; Guikai Zhang ; Feilong Yang ; Xiaolin Wang ; Tao Tang ; Yan Shi
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：May 5, 2016
• 年：2016
• 卷：120
• 期：17
• 页码：9535-9544
• 全文大小：602K
• 年卷期：0
• ISSN：1932-7455

文摘

Hydrogen transport in the outer Al₂O₃ scale is the rate-limiting step for H-permeation resistance of FeAl/Al₂O₃-type aluminide tritium permeation barriers (TPBs) in fusion reactors. With first-principle calculations, the effects of Cr, a main impurity element in the Al₂O₃ scale, on intrinsic point defect formation, hydrogen interactions with intrinsic point defects, and hydrogen diffusion in α-Al₂O₃ have been investigated under the working conditions of aluminide TPBs. It is found that Cr addition is favorable for the formation of V_O, yet unfavorable for V_Al formation in α-Al₂O₃. Compared with the α-Al₂O₃–H case, Cr is beneficial for the formation of H-related defects in α-Al₂O₃, whereas it is unfavorable for the H_i trapping ability of V_Al and V_O. H_O^– will dominate among H_i^–, V_Al^3–, V_O⁰, and [V_Al^3––H⁺]^2–, and only one step of H_i reorientation will be involved for the H_i diffusion in Cr-doped α-Al₂O₃. H_i is the dominant diffusion species in both pure and Cr-doped α-Al₂O₃, whereas the activation energy of H diffusion in Cr-doped α-Al₂O₃ is sharply reduced, which is unfavorable for H-permeation resistance of aluminide TPBs. The Cr effect on hydrogen behaviors in α-Al₂O₃ can be attributed to the chemically unstable electron structure of Cr³⁺ and a relatively stronger bonding interaction between H and Cr than that between H and Al or O atoms.