Imaging structural transitions of a non-Newtonian fluid using time-resolved X-ray diffraction computed tomography

Non-Newtonian fluids change viscosity under the application of stress, and understanding the properties and phase transitions of these fluids are important to create models of their flow behaviour in porous media. Certain non-Newtonian fluids crystallize in the absence of stress, and behave like an approximate Bingham fluid. When sufficient stress is applied, the viscosity drops significantly so that the material flows like a fluid with minimal shear forces. The spatial dynamic behaviour of these complex fluids in complicated geometries is surprisingly unknown. Here, we propose time-resolved X-ray diffraction computed tomography to spatially and chemically map the interplay between flow regimes, crystallization, and the local geometrical constraints on complex fluids in several distinct sample environments, to better understand the physical behaviour of complex fluids flowing in complex porous media.

非牛顿流体（Non-Newtonian fluids）在应力作用下会改变黏度，理解这类流体的性质与相变对于构建其在多孔介质中的流动行为模型至关重要。部分非牛顿流体在无应力状态下会发生结晶，表现近似于宾汉流体（Bingham fluid）。当施加足够应力时，其黏度显著降低，使得材料能以极小的剪切力像流体一样流动。这类复杂流体在复杂几何结构中的空间动态行为却鲜为人知，这一点颇为意外。在此，我们提出采用时间分辨X射线衍射计算机断层扫描（time-resolved X-ray diffraction computed tomography）技术，在多种不同的样品环境中，对复杂流体的流动状态、结晶过程与局部几何约束之间的相互作用进行空间与化学映射，以期更深入地理解复杂流体在复杂多孔介质中的流动物理行为。