TEM原位研究元素掺杂改善氚化铒固氦性能的基本机制

The material degradation caused by the helium bubble is not only an important scientific issue, but also one of the key issues to be resolved in developing the nuclear energy technique. All the studies on the mechanism of helium bubble nucleation, bubble evolution and the effective method to improve the ability of helium retention are active research fields. Theoretical and experimental studies have shown that alloying element can be incorporated into the materials to control the helium trapping position, improve the diffusion barrier of helium atom migration, and delay the helium critical release from the erbium tritide. Rare earth element erbium is considered as candidate material for tritium storage due to the high storage capacity as well as the low equilibrium plateau pressure at room temperature. This proposal is focused on the effects of alloying element on the helium bubble evolution using a in-situ technique. In situ transmission electron microscopy study of impurity elements on the helium bubble evolution of doped erbium tritide films. Based on the experimental results, comprehensive analyzing the basic mechanism of improving the helium retention of material by alloying element.

氦泡引发的材料性能下降是重要的基础科学问题，也是发展核能工程亟待解决的关键问题之一。认识氦泡的形核机理、演化过程，探索提升材料固氦能力的有效方法及其固氦机理研究是目前材料科学的研究热点。理论及实验研究表明，合理掺入合金元素可调控材料中氦的捕陷位置、提高氦原子的迁移扩散势垒、延缓氚化铒中氦的临界释放阈值，是有效改善材料固氦性能的重要途径。金属铒因贮氚量大、平衡压低等优点被作为贮氚候选材料。本项目拟以氚化铒为研究对象，在透射电子显微镜(TEM)下定期、定位观察氦泡的演化过程，原位研究掺杂元素对氚化铒中氦泡的迁移合并机制的影响，在纳米尺度上获得元素掺杂改善氚化铒固氦性能的基本机制。

采用SEM和XRD研究了基片类型和沉积温度对磁控法制备的铒膜的膜基结合力的影响，调控磁控镀膜的工艺参数，获得了掺入不同含量Ti和Hf杂质元素的铒膜试样，实现了替位型掺杂铒膜的制备。采用TEM原位加热研究了铒膜和氘化铒膜中氦泡的形状和生长过程，铒膜和氘化铒膜中氦泡分别呈现球形和扁平状，随温度升高氦泡尺寸均呈现增大和贯通趋势。铒膜中离子注入的氦会使铒膜晶粒尺寸减小，但会使其硬度明显增大，杨氏模量逐渐减小。掺杂氚化铒中氦泡均呈现为球形，时效过程中氦泡尺寸缓慢增大，静态氦释放结果表明氚化铒中引入Ti和Hf杂质元素后，氦释放系数明显降低，这可能与掺杂后氚化铒晶格常数增大有直接关系，以及杂质原子作为氦原子的捕陷位置，阻碍了氦原子的迁移和释放过程。以上结果表明，掺杂Ti和Hf后增强了氚化铒的固氦性能，结合XRD和TEM技术对其影响机制进行了详细分析，达到了本项目的预期研究目标。