用慢正电子束研究金属多层膜的微结构

Nuclear energy has become more and more important in the energy constituents of the future world. However, the various materials in the nuclear reactor are always subjected to severe radiation. This leads to the change of structure and degradation of the performance of materials, and affects safety of nuclear reactors. Design of materials with superior radiation resistance has become an urgent problem. It was revealed by experiment that the metallic nano-scaled multilayer can improve the radiation tolerance. In this project, we will use slow positron beam as the primary technique to study the microstructure of some typical metal multilayer. The research contents include: 1)Study the positron states in various multilayer with different structure, clarify the positron annihilation in metal layers and the interface between metal layers; 2)Study the microstructure of the interface between metal layers, the effect of layer thickness on the interface structure, and the thermal stability of interface; 3)Study the irradiation induced defects in metal layers and also the interface area, and make a comparison with the single metal films to study the radiation resistance of multilayer; 4)Analyze the evolution of defects during thermal annealing, find the role of interface on the recovery of defects. The results of our project will provide underlying mechanism of the radiation resistance of multilayer, and are significant for the understanding of the reaction between defects and interface, and also the design of new generation radiation resistant materials.

核能在未来的能源结构中将起着越来越重要的作用。然而，核反应堆中的各种材料长期处于核辐射环境中，导致材料的结构变化和性能恶化，影响了反应堆的安全。设计和制备具有优异抗辐照性能的材料已成为当前急剧解决的问题。实验证明，金属纳米多层膜材料能够有效提高抗辐照性能。本项目将以慢正电子束技术为主，系统研究几种典型的金属多层膜材料的微观结构，主要内容包括：1）研究各种不同结构的多层膜中正电子的湮没状态，区分正电子在各个金属层中及界面中的湮没；2）系统研究金属层间界面的微观结构，金属层厚度对界面的影响，界面的热稳定性等；3）研究经过辐照后的多层膜内部及界面区域产生的缺陷，并与单层金属进行比较，研究抗辐照性能的变化；4）分析缺陷在退火过程中的变化，了解界面在缺陷恢复过程中的作用。本项目的研究结果将揭示多层膜材料抗辐照性能的微观机制，对于了解界面与缺陷的相互作用以及设计新一代抗辐照材料都有重要的指导意义。

本项目以慢正电子束技术为主，配合TEM等实验手段，结合理论计算，系统研究了V/Ag、Cu/V等几种典型的金属多层膜材料的微观结构，摸索出一套制备性能优质纳米金属多层膜的方法，制备出系列优质金属多层膜；研究了不同结构的多层膜中正电子的湮没状态，区分正电子在各个金属层中及界面中的湮没，发现纳米金属多层膜中的Ag层或Cu层对e+有选择性捕获的特点；观测了经过辐照后的多层膜内部及界面区域产生的缺陷，并与单层金属进行比较，分析了材料的抗辐照性能及层厚对其影响；采用中性原子叠加方法(ATSUP)探究了V/Ag多层膜正电子湮没特性, 发现正电子波函数在多层结构中主要局域在Ag层中，且V/Ag多层结构中正电子湮没寿命与Ag 单质的正电子湮没寿命一致，即正电子主要在Ag层中被捕获。本项目的研究证实了正电子对多层膜材料微观结构变化极为灵敏，所得结果有助于揭示纳米金属多层膜材料抗辐照性能的微观机制，对于了解界面与缺陷的相互作用以及设计新一代抗辐照材料有较为重要的指导意义。