X-Ray Tomography and MRI Studies of Three-Dimensional Granular Materials: The Roles of Particle Geometry and Interactions

摘要CTS-0090490H。Jaeger，芝加哥大学建议联合使用两种诊断技术来阐明三维时间分辨颗粒流的性质分布。这些是磁共振成像(速度)和X射线断层成像(粒子密度、位置和方向)。到目前为止，PI可用的MRI系统已经产生了100微米分辨率(即1/10颗粒直径)的速度场。在此基础上，重建质量流量是可能的。然而，完整的说明(包括粒子自旋等)需要协同使用X射线层析成像，这也可用于美国能源部阿贡实验室新的先进光子源(550纳米分辨率)的PI。将特别关注颗粒形状、接触相互作用、超小(纳米)颗粒动力学和系统随时间的演化。这项研究的结果将提供一些对沉降过程的理解，以及体积排斥在最终达到非平衡分布(堵塞)中的作用。形状各向异性和星团形成对这种不太理想的粒子包的贡献，将与拟议的精确实验和最近可用的理论进行比较。重点将集中在三维几何、振荡剪切、粒子相互作用和混合物(例如棒状/球状)、超细粉末。

AbstractCTS-0090490H. Jaeger, University of ChicagoIt is proposed to operate jointly two diagnostic techniques to elucidate the property distribution of three-dimensional time-resolved granular flows. These are Magnetic Resonance Imaging (for velocity) and x-ray tomography (for particle density, position and orientation). So far, the MRI system available to the PI has yielded velocity fields with 100-micron resolution (i.e. 1/10-grain diameter). On that basis, it is possible to reconstruct mass flow rates. However, a full account (including particle spin, etc.) requires the synergistic use of X-ray tomography, which is also available to the PI from the new Advanced Photon Source at the DOE Argonne Laboratory (550-nm resolution). Special attention will be focussed on particle shape, contact interaction, ultrasmall ("nano") particle dynamics, and system evolution with time.The outcome of this research should provide some understanding of the settling process, and of the role of volume exclusion in reaching a final non-equilibrium distribution ("jamming"). The contribution of shape anisotropy and of cluster formation to this less-than-optimum package of particles, will be tested against the proposed accurate experiments and the recently available theories. Emphasis will be brought on three-dimensional geometry, oscillatory shear, particle interaction and mixtures (e.g. rod/spheres), ultrafine powders.