Thermal annealing of nuclear graphite during in-situ electron irradiation
Thermal annealing of nuclear graphite during in-situ electron irradiation
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DOI：
10.1016/j.carbon.2017.01.057
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发表时间：
2017-05
期刊：
影响因子：
10.9
通讯作者：
H. Freeman;A. Scott;R. Brydson
中科院分区：
文献类型：
--
作者：
H. Freeman;A. Scott;R. Brydson
我们研究了在83K到473K温度范围内，在200KV的透射电子显微镜中对核级堆A级石墨样品进行的电子辐照。在每个温度下，核级堆A级石墨样品受到大约1022个电子cm−~2的注量，并在电子束辐照过程中采集了透射电子显微照片和选定的区域衍射图。通过考虑石墨(002)d间距增加10%的临界注量，确定了损伤的温度阈值。在约420K以下，电子辐照造成了显著的净结构损伤：使基面碎裂并产生曲折的纳米结构。在此温度以上，热退火的影响变得更加普遍，即使在更高的通量下也保持了结构。我们推导了在这两个温度范围内工作的退火过程的活化能，并通过与理论预测的比较，首次将它们与特定的恢复过程联系在一起。
We have investigated the in-situ electron irradiation of nuclear graphite within a 200 kV transmission electron microscope at temperatures between 83 K and 473 K. For each temperature, nuclear grade Pile Grade A graphite specimens were subject to a fluence of ca. 1022electrons cm−2, and transmission electron micrographs and selected area diffraction patterns were collected during electron beam exposure. By considering a critical fluence, at which the graphite (002)d-spacing increased by 10%, a temperature threshold for damage has been determined. Below ca. 420 K, electron irradiation caused significant net structural damage: fragmenting basal planes and producing a tortuous nanotexture. Above this temperature the effects of thermal annealing became more prevalent, maintaining the structure even at much higher fluences. We have derived activation energies for the annealing processes operative in these two temperature regimes and, via a comparison with theoretical predictions have, for the first time, associated these with specific recovery processes.