An understanding of lattice strain, defects and disorder in nuclear graphite
An understanding of lattice strain, defects and disorder in nuclear graphite
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DOI：
10.1016/j.carbon.2017.08.070
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发表时间：
2017-11-01
期刊：
影响因子：
10.9
通讯作者：
Marsden, Barry J.
中科院分区：
文献类型：
--
作者：
Krishna, Ram;Wade, James;Marsden, Barry J.
本研究利用X射线衍射仪的衍射谱和拉曼光谱的散射谱，对不同中子辐照等级的石墨样品的晶格尺寸、微观应变和位错密度等微观结构参数进行了研究。利用900℃~6.6和10.2 dpa中子辐照的第四代候选石墨样品(PCEA级，GrafTech)，以及从英国实验堆零堆堆芯中取出的、在100~120℃~1.60 dpa辐照后，具有相似晶粒度和微观结构的石墨样品，研究了辐照剂量和温度对上述微观结构参数的影响。利用两种互补的拉曼光谱和X射线衍射谱技术，得到了一致的结果，发现两种石墨的平均横向微晶尺寸随着快中子辐照的增加或较低的辐照温度而减小。相反，随着辐照条件的改变，位错密度和微观应变也随之增加。使用高分辨率电子显微镜进行的直接观察为所获得的微观结构信息提供了佐证。这些图像显示了辐射诱导的棱柱状边缘位错的存在，以及表明存在基底位错的特征。它们还提供了文献中提出的通过损伤机制使石墨晶面逐渐恶化的证据。(C)2017爱思唯尔有限公司。保留所有权利。
In this study, microstructural parameters, such as lattice dimension, micro-strain and dislocation density, of different neutron-irradiated graphite grades have been evaluated using the diffraction profiles of X-ray diffraction (XRD) and the scattering profiles of Raman spectroscopy. Using Generation-IV candidate graphite samples (grade PCEA, GrafTech), subjected to neutron irradiation at 900 degrees C to 6.6 and 10.2 dpa, and graphite samples of similar grain size and microstructure taken from the core of the British Experimental Pile Zero reactor, which have been irradiated at 100-120 degrees C to 1.60 dpa, an investigation is presented on the effect of irradiation dose and temperature on the aforementioned microstructural parameters. Using two complementary techniques in Raman spectroscopy and XRD, which produced agreeable results, the average lateral crystallite size of the two graphites tested was found to decrease with increasing exposure to fast-neutron irradiation or at lower irradiation temperatures. Conversely, dislocation densities and micro-strains were found to increase following the same changes in irradiation conditions. Supporting evidence for the microstructural information obtained is provided by direct observations made using high-resolution transmission electron microscopy. These images demonstrate the presence of irradiation-induced prismatic edge dislocations as well as features that indicate the presence of basal dislocations. They also provide supporting evidence for the progressive deterioration of the graphitic planes via damage mechanisms as proposed in the literature. (C) 2017 Elsevier Ltd. All rights reserved.