Surface-structure dependence of healing radiation-damage mechanism in nanoporous tungsten
Surface-structure dependence of healing radiation-damage mechanism in nanoporous tungsten
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DOI：
10.1016/j.jnucmat.2017.11.002
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发表时间：
2018
影响因子：
3.1
通讯作者：
Guohua Duan;Xiang-yan Li;Jingjing Sun;Congyu Hao;Yichun Xu;Yange Zhang;Wei Liu;C. S. Liu
中科院分区：
文献类型：
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作者：
Guohua Duan;Xiang-yan Li;Jingjing Sun;Congyu Hao;Yichun Xu;Yange Zhang;Wei Liu;C. S. Liu
在核聚变环境下，中子辐照钨（W）通常会产生大量空位（Vs）和自填隙原子（SIAs），从而引起位移损伤。这些缺陷不仅影响W的力学性能，而且作为注入氢同位素和氦的陷阱位置。具有高自由表面分数的纳米多孔W被开发用于减轻辐射损伤。然而，表面减少缺陷积累的机制还没有得到很好的理解。利用多尺度模拟方法，我们研究了SIA和V与不同表面的相互作用在不同的长度和时间尺度上。我们发现，在一个典型的操作温度为1000 K，表面（1 1 0）优先愈合的辐射损伤的W相比，表面（1 0 0）和边界（3 1 0）。在表面（110）上，SIA的扩散势垒仅为0.68eV。SIA-V的湮灭是通过V从体相向表面的偏聚和SIA在表面的二维扩散的耦合运动而发生的。这种机制使得表面（110）具有更好的愈合能力。在（100）面上，SIA的扩散能垒为2.48eV，高于体相V的扩散能垒。SIA-V的湮灭通过V的偏析和复合发生。SIA被发现迁移一维沿着边界（3 1 0）与0.21 eV的势垒，导致在边界的愈合效率较低。这项研究表明，除了表面增强扩散和表面附近的湮灭，在修复NP W的辐射损伤的表面过程中起着重要的作用。一定的表面结构使得纳米结构的W更耐辐射。
Under nuclear fusion environments, displacement damage in tungsten (W) is usually caused by neutrons irradiation through producing large quantities of vacancies (Vs) and self-interstitial atoms (SIAs). These defects not only affect the mechanical properties of W, but also act as the trap sites for implanted hydrogen isotopes and helium. Nano-porous (NP) W with a high fraction of free surfaces has been developed to mitigate the radiation damage. However, the mechanism of the surface reducing defects accumulation is not well understood. By using multi-scale simulation methods, we investigated the interaction of the SIA and V with different surfaces on across length and time scales. We found that, at a typical operation temperature of 1000 K, surface (1 1 0) preferentially heals radiation damage of W compared with surface (1 0 0) and boundary (3 1 0). On surface (1 1 0), the diffusion barrier for the SIA is only 0.68 eV. The annihilation of the SIA–V happens via the coupled motion of the V segregation towards the surface from the bulk and the two-dimensional diffusion of the SIA on the surface. Such mechanism makes the surface (1 1 0) owe better healing capability. On surface (1 0 0), the diffusion energy barrier for the SIA is 2.48 eV, higher than the diffusion energy barrier of the V in bulk. The annihilation of the SIA–V occurs via the V segregation and recombination. The SIA was found to migrate one-dimensionally along a boundary (3 1 0) with a barrier of 0.21 eV, leading to a lower healing efficiency in the boundary. This study suggested that the on-surface process plays an important role in healing radiation damage of NP W in addition to surface-enhanced diffusion and annihilation near the surface. A certain surface structure renders nano-structured W more radiation-tolerant.