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Effect of Nonstoichiometry on Neutron-Irradiation-Behavior of Spinel

非化学计量对尖晶石中子辐照行为的影响

基本信息

批准号：
10480105
负责人：
YANO Toyohiko
金额：
$ 7.36万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

In this study, the effects of nonstoichiometry on neutron-induced damages of spinel were investigated by measuring length change, lattice parameter change, change in thermal diffusivity, changes in mechanical properties after neutron irradiation of synthetic spinel with different stoichiometry. The recovery of these properties was also evaluated. Furthermore, neutron-induced damages of other ceramics were observed for comparison. The main results obtained were summarized as follows. (1) Macroscopic length change and lattice parameter changes of spinel irradiated at lower temperatures corresponded well each other and increased with increasing n. The change in Vickers hardness was the same tendency. After annealing, the macroscopic length and lattice parameter shrunk gradually from the irradiation temperature to 550℃, then made small peak at 650℃, finally it was not changed above 800℃. From this results, it is suggested that the recombination of Frenkel pairs up to 800℃ and rearrangement in cations at around 650℃ are happened. (2) Knoop microhardness anisotropy of n=3 spinel was measured before and after irradiation, and after post-irradiation annealing. It was changed by neutron irradiation, but recovered to that of before irradiation after annealing. The anisotropy profile of n=3 spinel was different from that of stoichiometric spinel, due to the different degree of cation distribution. Change in Vicker's hardness by neutron irradiation was proportional to the square of volume change. (3) Cation distribution of spinel in tetrahedral sites and octahedral sites could not be detected by X-ray microprobe analysis coupled with profile analysis and temperature calibration on a present EPMA apparatus. By use of ALCHEMI analysis, it could be detected, and it was found that cation distribution in spinel changed toward more random distribution by neutron irradiation. (4) Physical property change in Al_2O_3, AlN, SiC and Si_3N_4 after heavy neutron irradiation was evaluated.

本研究通过测量不同化学计量合成尖晶石的长度变化、晶格参数变化、热扩散率变化以及中子辐照后力学性能的变化，研究了非化学计量对尖晶石中子损伤的影响。还评估了这些性能的恢复情况。此外，还观察了其他陶瓷的中子诱发损伤以进行比较。获得的主要结果总结如下。 (1) 较低温度下辐照尖晶石的宏观长度变化与晶格参数变化吻合较好，且随n的增加而增大。维氏硬度的变化也呈同样的趋势。退火后，宏观长度和晶格参数从辐照温度到550℃逐渐收缩，在650℃出现小峰，最后在800℃以上基本没有变化。由此结果表明，Frenkel对在800℃以下发生重组，阳离子在650℃左右发生重排。 (2)测量n=3尖晶石辐照前后以及辐照后退火后的努氏显微硬度各向异性。因中子照射而发生变化，但退火后恢复至照射前。由于阳离子分布程度不同，n=3尖晶石的各向异性分布与化学计量尖晶石的各向异性分布不同。中子照射引起的维氏硬度变化与体积变化的平方成正比。 (3)现有EPMA装置上的X射线微探针分析结合轮廓分析和温度校准无法检测尖晶石在四面体位点和八面体位点的阳离子分布。利用ALCHEMI分析进行检测，发现尖晶石中的阳离子分布因中子照射而变得更加随机分布。 (4)评价了重中子辐照后Al_2O_3、AlN、SiC和Si_3N_4的物性变化。