Growth mechanism of subsurface hydrogen cavities in tungsten exposed to low-energy high-flux hydrogen plasma
Growth mechanism of subsurface hydrogen cavities in tungsten exposed to low-energy high-flux hydrogen plasma
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DOI：
10.1016/j.actamat.2020.04.012
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发表时间：
2020-07-01
期刊：
影响因子：
9.4
通讯作者：
Liu, W.
中科院分区：
文献类型：
--
作者：
Chen, W. Q.;Wang, X. Y.;Liu, W.
由于缺乏直接的实验结果，控制核聚变中暴露于ITER相关条件下的钨（W）起泡行为的详细机制仍不清楚。氢（H）气泡的生长机制就是一个例子。在这项工作中，再结晶的W暴露于50 eV，1.5 x 10（26）m（-2）和573 K的H等离子体。采用等离子体聚焦离子束（FIB）制备透射电子显微镜（TEM）样品，然后进行快速抛光以有效去除FIB引起的表面损伤。TEM图像显示，在暴露表面上观察到的一般水泡与下面的空腔相关。在空洞附近发现了大量的位错。观察到棱柱位错环阵列，包括小尺寸的“咖啡豆”棱柱环和大尺寸的棱柱环。在空穴尖端附近，还发现了剪切环的发射，并根据实验结果提出了H空穴的多阶段生长机制。环冲压机制是非常小的空腔和空腔的尺寸大于几百纳米的操作。而在中等尺寸时，空腔通过从空腔尖端发射剪切环而生长。(C)2020 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
Due to a lack of direct experimental results, the detailed mechanisms that govern the blistering behavior of tungsten (W) exposed to ITER-relevant condition in nuclear fusion remain unclear. The growth mechanism of hydrogen (H) blisters is one example. In this work, recrystallized W was exposed to H plasma at 50 eV, 1.5 x 10(26) m(-2), and 573 K. Transmission electron microscopy (TEM) samples were prepared using plasma-focused ion beam (FIB) followed by flash-polishing to effectively remove surface damages induced by FIB. The TEM images revealed that the general blisters observed on the exposed surface are associated with underlying cavities. A considerable amount of dislocations were found in the vicinity of the cavities. Prismatic dislocation loop arrays were observed, including small size 'coffee-bean' prismatic loops and large size prismatic loops. Near the tip of surfaces cavities, evidences for the emission of shear loops were also found. Based on the experimental findings, a multi-stage growth mechanism of H cavities was proposed. The loop-punching mechanism is operative for both very small cavities and cavities with sizes larger than several hundreds of nanometers. Whereas at intermediate sizes, cavities grow by emitting shear loops from the cavity tip. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.