晶体材料纳米缺陷的电子显微学

The properties of solid state materials are controlled largely by defects. In order to investigate the effects of the defects to materials properties, we have to gain a thorough understanding of the nature of the defects inside the materials. It is relatively a routine work to characterize defects bigger than 5 nanometers using conventional TEM amplitude-contrast imaging techniques. However, there has no suitable mature technique to characterize the defects of the size beyond this limit. These kinds of extremely small defects are of significance in the mechanical, thermal and electromagnetic properties of the materials. For example, in fusion materials, the structural components of fusion reactors are bombarded with high-energy neutrons, leading to the formation of very small defect clusters. However, there is an issue needs to be underpinned in the design, selection and failure analysis of fusion materials, that is how to characterize such small defects. In this project, breakthroughs will be made on the TEM imaging theories，computational methods and experimental techniques of characterizing extremely small defects, We are going to advance the conventional TEM amplitude-contrast imaging techniques and develop further the new technique based on electron elastic diffuse scattering. As the byproduct of the project, a comprehensive computer programs for TEM amplitude-contrast imaging and diffuse scattering pattern simulation will be developed based on the computer programs namely TEMACI and DynaDS written by the applicant. Advanced data treatment, imaging analysis, database-building functions as well as graphic-user interface will be integrated into the programs to form a sophisticated software platform for the purpose of charactreization of defects.

凝聚态材料的性能极大地依赖于其中的缺陷。为了阐明缺陷对材料性能的影响，我们必须首先充分掌握材料中缺陷的形态。晶体材料中尺寸大于5纳米的缺陷，可利用传统的电子显微衍衬成像技术来表征。但对于更细微缺陷的表征，到目前为止还没有切实可行的成熟方法。而这些非常微小的缺陷对材料的力学、热学及电磁等性能均有极大的影响，如核聚变反应器的结构材料受高能中子的辐照会产生大量的非常微小的缺陷团簇，如何表征这些细微缺陷团簇是一个在进行核材料设计、遴选以及时效评价时必须解决难题。 本项目将在细微缺陷电子显微学理论、电子显微成像模拟方法和实验技术上取得突破，通过完善传统电子衍衬像技术并开发新的基于电子弹性散射的表征方法来解决这一问题。同时作为项目的副产品，将在申请人过去开发的模拟软件TEMACI以及DynaDS的基础上，增加新的数据处理、图像分析、图形数据库功能以及图形用户界面，形成一个功能完备的工具软件。

本项目拓展了纳米缺陷电子显微学的理论基础；完善了利用透射电镜传统衍衬像成像的理论体系，解决了前人的理论与模拟方法对于纳米缺陷的弱束成像无法准确实现的不足，在程序上克服了纳米缺陷，主要是位错环与层错四面体的应变场的计算难题，实现了缺陷与成像几何的准确控制。最终使得系统模拟微小缺陷的电子衍衬像成为可能。..本项目最主要的工作在于系统地完成了缺陷致电子弹性散射的理论体系的建立，不仅在X射线弹性散射的运动学理论的基础上推导了电子弹性散射的运动学方程，并首次系统了动力学的理论体系，建立了模型和编写了程序实现了分别基于运动学和动力学理论的模拟，和早期的实验结果进行了对比，取得了该领域零的突破。..所形成的软件有望拓展为模拟在正空间和倒易空间下纳米缺陷的电镜成像的辅助系统。本项目的这些结果对于研究晶体材料中的纳米缺陷的形态、演变，进而对材料性能的影响有辅助作用。也可作为电子显微教学的辅助工具使用。