Cheung Cecilia S N, Weidner Donald J, Li Li, Meredith Philip G, Chen Haiyan, Whitaker Matthew, Chen Xianyin
Mineral Physics Institute, Department of Geoscience, Stony Brook University; Geological Engineering, Department of Civil and Environmental Engineering, University of Wisconsin-Madison;
Mineral Physics Institute, Department of Geoscience, Stony Brook University.
J Vis Exp. 2018 May 20(135):57555. doi: 10.3791/57555.
We report detailed procedures for performing compression experiments on rocks and mineral aggregates within a multi-anvil deformation apparatus (D-DIA) coupled with synchrotron X-radiation. A cube-shaped sample assembly is prepared and compressed, at room temperature, by a set of four X-ray transparent sintered diamond anvils and two tungsten carbide anvils, in the lateral and the vertical planes, respectively. All six anvils are housed within a 250-ton hydraulic press and driven inward simultaneously by two wedged guide blocks. A horizontal energy dispersive X-ray beam is projected through and diffracted by the sample assembly. The beam is commonly in the mode of either white or monochromatic X-ray. In the case of white X-ray, the diffracted X-rays are detected by a solid-state detector array that collects the resulting energy dispersive diffraction pattern. In the case of monochromatic X-ray, the diffracted pattern is recorded using a two-dimensional (2-D) detector, such as an imaging plate or a charge-coupled device (CCD) detector. The 2-D diffraction patterns are analyzed to derive lattice spacings. The elastic strains of the sample are derived from the atomic lattice spacing within grains. The stress is then calculated using the predetermined elastic modulus and the elastic strain. Furthermore, the stress distribution in two-dimensions allow for understanding how stress is distributed in different orientations. In addition, a scintillator in the X-ray path yields a visible light image of the sample environment, which allows for the precise measurement of sample length changes during the experiment, yielding a direct measurement of volume strain on the sample. This type of experiment can quantify the stress distribution within geomaterials, which can ultimately shed light on the mechanism responsible for compaction. Such knowledge has the potential to significantly improve our understanding of key processes in rock mechanics, geotechnical engineering, mineral physics, and material science applications where compactive processes are important.
我们报告了在与同步加速器X射线联用的多砧变形装置（D-DIA）中对岩石和矿物聚集体进行压缩实验的详细步骤。制备一个立方体形状的样品组件，并在室温下通过一组四个X射线透明烧结金刚石砧和两个碳化钨砧分别在横向和垂直平面上进行压缩。所有六个砧都安装在一台250吨的液压机内，并由两个楔形导向块同时向内驱动。一束水平能量色散X射线穿过样品组件并被其衍射。该束X射线通常处于白色或单色X射线模式。在白色X射线的情况下，衍射X射线由固态探测器阵列检测，该阵列收集产生的能量色散衍射图案。在单色X射线的情况下，使用二维（2-D）探测器，如成像板或电荷耦合器件（CCD）探测器记录衍射图案。对二维衍射图案进行分析以得出晶格间距。样品的弹性应变由晶粒内的原子晶格间距得出。然后使用预定的弹性模量和弹性应变计算应力。此外，二维应力分布有助于了解应力在不同方向上的分布情况。另外，X射线路径中的闪烁体产生样品环境的可见光图像，这使得能够在实验过程中精确测量样品长度变化，从而直接测量样品的体积应变。这种类型的实验可以量化地质材料内的应力分布，最终有助于揭示压实作用的机制。这些知识有可能显著提高我们对岩石力学、岩土工程、矿物物理学以及压实过程很重要的材料科学应用中的关键过程的理解。
