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

技术：将用相干X射线衍射(CXD)直接测量镶嵌在基质中的单个金属氢化物颗粒的局部晶格应变。分离单个第二相粒子并通过量化局部应变状态直接研究相干损失的能力将代表着材料表征方面的重大进步。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，这项技术可以直接测量特定于单个粒子的晶格应变。然而，到目前为止，还没有人尝试过这样的实验。没有进行原则性证明实验有两个原因。首先，CXD是一种新兴的技术，它需要非常高的束流强度，只有在第三代源的插入设备上才能获得。其次，很难充分控制固相沉淀，以便在平衡的情况下原位研究单个粒子的生长和凝聚性损失。这种原理验证实验将在这里使用Pd-H和Nb-H两个金属-氢系统进行。与这项工作相关的风险很高，就像使用相对较新的技术进行新实验一样。由于这些实验是第一次用CXD研究嵌入的粒子，因此没有存档出版物的基础来为进一步的工作奠定基础，简而言之，基础还没有奠定。然而，局域晶格应变对嵌入粒子CXD响应的影响的理论框架已经形成，这将作为研究的起点。此外，在针对CXD数据的图像反演过程中取得了非常新的进展。另一个风险是足够敏感的风险。实验的成功取决于能否分离出单一的氢化物颗粒。即使在APS，这也将是困难的，需要进行系统的搜索。最后，从CXD倒置图像中提取应变信息尚未完成。这样做的过程可能并不完全成功，很可能取决于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。这次培训将包括在两个大型国家用户设施--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.