Mossbauer Diffraction From Polycrystalline Ordered Alloys

本研究将穆斯堡尔衍射应用于粉末结构表征。超精细相互作用导致57铁原子的散射因子随着伽马射线能量的轻微不同而发生强烈变化。这为衍射实验中独特的化学选择性提供了基础。化学选择性可以用来将伽马射线调谐到特定的铁原子化学环境中，并仅从该化学环境中确定特定的衍射模式。实验工作试图测量do3有序57铁铝化物中两个铁位的面心立方和简单立方衍射图样。初步实验结果令人鼓舞，为这项工作提供了实用参数。如果第一次实验成功，将对部分有序的57铁铝化物和B2 57铁铑中的反位原子的排列进行测量。同时，将测试位置敏感探测器的定时能力。如果探测器可以同时操作时间和正电子分辨率，以后的实验可以在同步辐射设备上进行。到目前为止，材料科学主要依靠x射线、电子和中子衍射来表征粉末的结构。穆斯堡尔衍射是由原子核的伽马射线散射而产生的，它是粉末衍射的另一种有用的技术。＊＊＊

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. ***