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

中子辐照引起的陶瓷材料的辐照响应因材料的晶体结构而异。在本研究中，通过热处理，诱导小体积变化的缺陷的恢复行为，使用高精度的电阻率计在高温下精确测量。(1)首先，对温度计的性能进行了检查。使用该温度计，将试样加热至指定温度，然后保持6小时，并连续监测试样的长度变化。然后，将试样的温度升高50℃以上，并测量长度变化。这些测量依次进行，直到试样长度变为照射前的原始长度。(2)通过对两种中子辐照SiC试样在不同温度下长度变化的分析，阐明了在不同温度下的长度恢复曲线由两个分量组成： 关于我们 如果过程由一级反应组成，则时间更短，时间更长。获得了这些回收率。从在每个温度下的速率的Arrhenius图，获得表观活化能。(3)对中子辐照单晶硅进行了相似性测量，晶体结构与碳化硅相似。而辐射引起的变化是非常小的，恢复阶段可以成功地测量。(4)对辐照和退火后的SiC样品进行了高分辨电镜观察，结果表明，在较高温度下，中子辐照20 dpa的样品在1400℃退火后形成了空洞。在这些样品中，晶格参数的增加小于宏观长度的增加，并包括许多微小的间隙环。(5)在此基础上，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