Analysis of neutron-irradiation-induced defects using nanometer-sensitive dilatometry : Recovery rate study

不同晶体结构的陶瓷材料在中子辐照下的辐照响应是不同的。在本研究中，利用高精度膨胀仪在高温下精确测量了热处理后引起小体积变化的缺陷的恢复行为。(1)首先对膨胀仪的性能进行了校核。利用该膨胀计将试样加热至指定温度，保存6 h，连续监测试样长度变化。然后，将试样温度再升高50℃，测量其长度变化。这些测量依次进行，直到试样长度成为辐照前的原始长度。(2)通过分析两种中子辐照SiC试样在不同温度下的长度变化，明确了每次等温退火时的长度恢复曲线由两部分组成，如果由一级反应组成，则时间越短，时间越长。得到了这些回收率。根据各温度下反应速率的阿伦尼乌斯图，得到了表观活化能。(3)对中子辐照后的单晶硅进行了相似度测量，晶体结构与碳化硅相似。虽然辐照引起的变化很小，但可以成功地测量恢复阶段。(4)对辐照和退火后的碳化硅进行了高分辨率电镜观察，明确了在较高温度下辐照至20 dpa的样品中，退火至1400℃后形成空洞。在这些试样中，晶格参数的增加小于宏观长度的增加，并且包含许多微小的间隙环。(5)在本研究结果的基础上，结合前人的研究，讨论了晶体结构与辐照响应和恢复行为的关系。少

Irradiation response of ceramics induced by neutron irradiation varies material to material with different crystal structure. In this research, recovery behavior of defects, which induce small volume change, by heat-treatment was precisely measured using a high-precision dilatometer at high temperature.(1) At first, performance of the dilatometer was checked. Using this dilatometer, the specimen was heated up to a designated temperature, and then it was kept for 6 h, and length change of the specimen was continuously monitored. Then, the temperature of the specimen was increased 50℃ higher temperature, and the length change was measured. These measurement was conducted sequentially up to the specimen length became the original length before irradiation.(2) Based on the analysis of the length change of the two kind of neutron-irradiated SiC specimens obtained at each temperature, it was clarified that length recovery curves at each isothermal annealing consisted from two components, for … More shorter time and for longer time, if the process composed from the first order reactions. These recovery rates were obtained. From the Arrhenius plots of the rate at each temperature, apparent activation energies were obtained.(3) Resemble measurement was conducted on neutron-irradiated single crystal silicon, that crystal structure is similar with silicon carbide. Whereas the change induced by irradiation was very small, the recovery stage could be measured successfully.(4) High-resolution electron microscope observation on irradiated and annealed SiC was performed, and it was clarified that the void was formed after annealing up to 1400℃ in the specimen neutron-irradiated up to 20 dpa at relatively higher temperature. In these specimens, lattice parameter increased less than that of the macroscopic length, and included many tiny interstitial loops.(5) Based on the results obtained in this study and previous studies, the relation between crystal structures and irradiation response and recovery behavior was discussed. Less