Harti R P, Valsecchi J, Trtik P, Mannes D, Carminati C, Strobl M, Plomp J, Duif C P, Grünzweig C
Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, Zurich, Switzerland.
Niels Bohr Institute, Copenhagen, Denmark.
Sci Rep. 2018 Dec 14;8(1):17845. doi: 10.1038/s41598-018-35845-y.
Structural properties of cohesive powders are dominated by their microstructural composition. Powders with a fractal microstructure show particularly interesting properties during compaction where a microstructural transition and a fractal breakdown happen before compaction and force transport. The study of this phenomenon has been challenging due to its long-range effect and the subsequent necessity to characterize these microstructural changes on a macroscopic scale. For the detailed investigation of the complex nature of powder compaction for various densification states along with the heterogeneous breakdown of the fractal microstructure we applied neutron dark-field imaging in combination with a variety of supporting techniques with various spatial resolutions, field-of-views and information depths. We used scanning electron microscopy to image the surface microstructure in a small field-of-view and X-ray tomography to image density variations in 3D with lower spatial resolution. Non-local spin-echo small-angle neutron scattering results are used to evaluate fitting models later used as input parameters for the neutron dark-field imaging data analysis. Finally, neutron dark-field imaging results in combination with supporting measurements using scanning electron microscopy, X-ray tomography and spin-echo small angle scattering allowed us to comprehensively study the heterogeneous transition from a fractal to a homogeneous microstructure of a cohesive powder in a quantitative manner.
粘性粉末的结构特性主要由其微观结构组成决定。具有分形微观结构的粉末在压实过程中表现出特别有趣的特性，在压实和力传递之前会发生微观结构转变和分形破坏。由于这种现象的长程效应以及随后在宏观尺度上表征这些微观结构变化的必要性，对这一现象的研究一直具有挑战性。为了详细研究各种致密化状态下粉末压实的复杂性质以及分形微观结构的非均匀破坏，我们将中子暗场成像与各种具有不同空间分辨率、视场和信息深度的支持技术相结合。我们使用扫描电子显微镜在小视场中对表面微观结构进行成像，并使用X射线断层扫描以较低的空间分辨率对三维密度变化进行成像。非局部自旋回波小角中子散射结果用于评估拟合模型，该模型随后用作中子暗场成像数据分析的输入参数。最后，中子暗场成像结果与使用扫描电子显微镜、X射线断层扫描和自旋回波小角散射的支持测量相结合，使我们能够以定量方式全面研究粘性粉末从分形微观结构到均匀微观结构的非均匀转变。
