SGER: Demonstration of Local Lattice Strain Measurement Associated with Metal Hydride Particles using Coherent X-Ray Diffraction

技术支持：将用相干X射线衍射（CXD）直接测量嵌入基质中的单个金属氢化物颗粒的局部晶格应变。通过量化局部应变状态来分离单个第二相粒子并直接研究相干性损失的能力将代表材料表征的显著进步。相干X射线衍射是一种相对较新的技术，仅适用于第三代同步加速器X射线源，如先进光子源。原则上，这种技术可以直接测量单个粒子特有的晶格应变。然而，迄今为止，还没有人尝试过这样的实验。有两个原因导致原理验证实验没有被执行。首先，CXD是一种新兴技术，其需要非常高的光束强度，仅可从第三代源的插入装置获得。第二，难以充分控制固态沉淀，使得可以在相对于生长和相干性损失的平衡下原位研究单个颗粒。在这里将使用两种金属-氢系统Pd-H和Nb-H进行这样的原理实验的证明。与这项工作相关的风险很高，因为它通常是使用相对较新的技术进行的新实验。由于这些实验是第一个用CXD研究嵌入粒子的实验，因此不存在存档出版物的基础来作为进一步工作的基础，简而言之，基础尚未奠定。然而，局部晶格应变对嵌入颗粒的CXD响应的影响的理论框架已经开发，这将作为研究的出发点。此外，在CXD数据的图像反演过程中取得了非常新的进展。另一个风险是足够的敏感性。实验的成功取决于单个氢化物粒子的分离。这将是困难的，即使在APS，将需要一个系统的搜索。最后，从倒置CXD图像中提取应变信息还有待完成。这样做的程序可能不会完全成功，并且可能取决于CXD图像的质量。非技术性：这项研究涉及使用一种重要的实验技术，X射线衍射。参与这项工作的学生将获得与新颖的CXD技术相关的宝贵培训，以及与图像反演相关的数值算法。这项培训将包括在两个大型国家用户设施，即阿贡国家实验室的高级光子源和伊利诺伊大学的弗雷德里克塞茨材料研究实验室的研究经验。

TECHNICAL: The direct measurement of local lattice strain associated with a single metal hydride particle embedded in a host matrix with coherent x-ray diffraction (CXD) will be done. The ability to isolate a single second phase particle and study coherency loss directly by quantifying local strain states would represent a significant advancement in materials characterization. Coherent x-ray diffraction is a relatively new technique that is only practical at 3rd generation synchrotron x-ray sources like the Advanced Photon Source. This technique can, in principle, provide a direct measurement of lattice strain specific to a single particle. To date, however, such an experiment has not been attempted. There are two reasons why a proof of principle experiment has not been performed. First, CXD is an emerging technique that requires very high beam intensity only available from insertion devices at 3rd generation sources. Second, it is difficult to sufficiently control solid-state precipitation so that individual particles can be studied in situ under equilibrium with respect to growth and coherency loss. Such a proof of principle experiment will be conducted here using two metal-hydrogen systems, Pd-H and Nb-H. The risk associated with the work is high, as it often is with novel experiments using a relatively new technique. Since the experiments are the first to study embedded particles with CXD, a foundation of archived publications does not exist from which to base further work, in short, the groundwork has yet to be laid. However, the theoretical framework of the effect of local lattice strain on the CXD response of embedded particles has been developed and this will serve as the starting point for the research. In addition, very recent advances in the image inversion procedure specific to CXD data have been made. Another risk is one of adequate sensitivity. Success of the experiments depends on the isolation of a single hydride particle. This will be difficult even at the APS and will require a systematic search. Finally, the extraction of strain information from inverted CXD images has yet to be accomplished. It is possible that the procedure to do this may not be entirely successful and will likely depended on the quality of the CXD images. NON-TECHNICAL: The research involves the use of an important experimental technique, x-ray diffraction. The student participating in this work will gain valuable training associated the novel CXD technique, as well as the numerical algorithms related to image inversion. This training will include research experiences at two large national user facilities, the Advanced Photon Source at Argonne National Laboratory and the Frederick Seitz Materials Research Laboratory at the University of Illinois.