Mossbauer Diffraction From Polycrystalline Ordered Alloys

9415331富尔茨在本研究中，穆斯堡尔衍射被应用于粉末结构的表征。超精细相互作用导致57Fe原子的散射因数随伽马射线能量略有不同而发生强烈变化。这为在衍射实验中实现独特的化学选择性提供了依据。化学选择性可以用来将伽马射线调谐到57Fe原子的特定化学环境，并仅根据该化学环境确定特定的衍射图。实验工作试图测量DO_3有序的57铁铝化物中两个铁位的面心立方和简单立方衍射图。初步的实验结果令人鼓舞，为这项工作提供了实用的参数。如果第一次实验成功，将对偏序57铁铝化物和B_2 57铁-Rh中的反位原子排列进行测量。同时，还将测试位置敏感探测器的定时能力。如果探测器可以同时在时间分辨率和正电子分辨率下工作，以后的实验可能会在同步辐射设施中进行。到目前为止，材料科学很大程度上依赖于X射线、电子和中子衍射来表征粉末的结构。穆斯堡尔衍射是通过伽马射线与原子核的散射而发生的，作为另一种有用的粉末衍射技术被探索出来。***

9415331 Fultz In this research, Mossbauer diffraction is applied to powder structure characterization. Hyperfine interactions cause the scattering factor of an 57iron atom to change strongly for slightly different gamma ray energies. This could provide a basis for unique chemical selectivity in diffraction experiments. The chemical selectivity could be used to tune a gamma ray to the specific chemical environment of an 57iron atom and determine a specific diffraction pattern from that chemical environment alone. The experimental work attempts to measure the face-centered cubic and simple cubic diffraction patterns from two iron sites in DO3-ordered 57iron aluminide. Preliminary experimental results have been encouraging and have provided practical parameters for the this work. If these first experiments are successful, measurement will be made on the arrangements of antisite atoms in partially-ordered 57iron aluminide and in a B2 57iron - rhodium. In a parallel effort, the timing capabilities of the position-sensitive detector will be tested. If the detector can be operated with both time and positron resolution, later experiments may be performed at a synchrotron radiation facility. %%% To date, materials science has relied heavily on x-ray, electron, and neutron diffraction to characterize the structure of powders. Mossbauer diffraction, which occurs by scattering of gamma rays from nuclei, is explored as an additional useful technique for powder diffractometry. ***