Phase-targeted X-ray diffraction.
Phase-targeted X-ray diffraction.
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DOI：
10.1107/s1600576716011936
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发表时间：
2016-10-01
影响因子：
6.1
通讯作者：
Hansford GM
中科院分区：
文献类型：
--
作者：
Hansford GM
提出了一种增强样品内特定目标结晶相的X射线衍射信号的方法。该技术可以以手持或在线仪器格式实现。首次提出了一种增强混合物中特定晶相信号的粉末X射线衍射（XRD）方法。对目标相的特异性依赖于找到晶体d间距的比率和元素特征X射线能量的比率的重合。可以利用这种重合，使得两个晶体平面在两个不同的X射线能量下通过相同的散射角相互作用。如果目标矿物或相存在于样品中，则以适当散射角放置的能量分辨检测器将在这些能量下检测到显著增强的信号。当使用高散射角（例如2θ > 150°）实施时，该方法对样品形态和102 mm尺度上的距离具有耐受性。 用PdL α1和PdL β1发射线增强石英衍射信号的方法，从实验上证明了该方法的原理。用纯石英粉颗粒和未经处理的泥岩岩样进行了试验，并发展了相靶法。利用InL β1和Ti Kβ发射线的组合，对钢样中残余奥氏体的灵敏检测进一步证实了该技术。对于这两个例子，它也示出了如何使用衰减箔，具有接近和高于较高能量的特征X射线线的吸收边缘，可以在一定程度上隔离的重合信号从其他荧光和衍射峰在检测到的光谱。相靶向XRD技术适合于使用手持或在线仪器格式的低成本现成组件来实现。
A method to enhance the X-ray diffraction signal of a specific targeted crystalline phase within a sample is presented. This technique can be implemented in a handheld or in-line instrument format. A powder X-ray diffraction (XRD) method to enhance the signal of a specific crystalline phase within a mixture is presented for the first time. Specificity to the targeted phase relies on finding coincidences in the ratios of crystal d spacings and the ratios of elemental characteristic X-ray energies. Such coincidences can be exploited so that the two crystal planes diffract through the same scattering angle at two different X-ray energies. An energy-resolving detector placed at the appropriate scattering angle will detect a significantly enhanced signal at these energies if the target mineral or phase is present in the sample. When implemented using high scattering angles, for example 2θ > 150°, the method is tolerant to sample morphology and distance on the scale of ∼2 mm. The principle of the method is demonstrated experimentally using Pd Lα1 and Pd Lβ1 emission lines to enhance the diffraction signal of quartz. Both a pure quartz powder pellet and an unprepared mudstone rock specimen are used to test and develop the phase-targeted method. The technique is further demonstrated in the sensitive detection of retained austenite in steel samples using a combination of In Lβ1 and Ti Kβ emission lines. For both these examples it is also shown how the use of an attenuating foil, with an absorption edge close to and above the higher-energy characteristic X-ray line, can serve to isolate to some degree the coincidence signals from other fluorescence and diffraction peaks in the detected spectrum. The phase-targeted XRD technique is suitable for implementation using low-cost off-the-shelf components in a handheld or in-line instrument format.