rheo-VSANS和rheo-USANS测定的连续剪切增稠胶体悬浮液的微观结构,Soft Matter

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rheo-VSANS和rheo-USANS测定的连续剪切增稠胶体悬浮液的微观结构
Soft Matter ( IF 3.4 ) Pub Date : 2022-05-20 , DOI: 10.1039/d2sm00215a
Yu-Fan Lee ₁ , Yimin Luo ₁ , Tianyi Bai ₁ , Scott C Brown ₂ , Norman J Wagner ₁

Affiliation

对剪切增稠胶体悬浮液的研究表明，微观结构的测量可以阐明剪切增稠状态下流变材料特性的来源，以及基于增强润滑流体动力学、弹性流体动力学和接触等多种机制的严格测试模拟和理论摩擦。先前关于具有明确剪切增稠状态的连续剪切增稠分散体的工作将水团簇的形成确定为该状态的特征，确定最近邻分布中的各向异性，并使用该信息来测试流行的理论和模拟。然而，关于中尺度的重要问题仍然存在（即, 粒子簇尺度) 剪切增稠状态的微观结构。在这里，我们采用中子散射方法应用于剪切具有两个极端摩擦和润滑表面特性的球形颗粒的胶体分散体，以解决剪切增厚状态下的较长尺度微观结构。Hydroclusters 被证明是高度局部化的，与先前的中子散射和直接光学测量一致，但与预测更远距离结构形成的最新模拟不一致。

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Microstructure of continuous shear thickening colloidal suspensions determined by rheo-VSANS and rheo-USANS

Research on shear thickening colloidal suspensions demonstrates that measurements of the microstructure can elucidate the source of the rheological material properties in the shear thickened state as well as critically test simulations and theory based on a variety of mechanisms such as enhanced lubrication hydrodynamics, elastohydrodynamics, and contact friction. Prior work on continuous shear thickening dispersions with a well-defined shear thickened state identified the formation of hydroclusters as characteristic of this state, determined the anisotropy in the nearest neighbor distribution, and used this information to test prevailing theories and simulations. However, important questions remain about the mesoscale (i.e., particle cluster scale) microstructure of the shear thickened state. Here we employ neutron scattering methods applied to shearing colloidal dispersions of spherical particles with two extremes of friction and lubrication surface properties to resolve the longer-length scale microstructure in the shear thickened state. Hydroclusters are shown to be highly localized, in agreement with prior neutron scattering and direct optical measurements, but in disagreement with the most recent simulations that predict a longer-range structure formation. These results combined with prior measurements provide experimental evidence about the length scale of microstructure formation in continuous shear thickening suspensions necessary to improve our understanding of the phenomenon as well as guide theoretical investigations that quantitatively link nanoscale forces to macroscopic properties in the shear thickened state.

更新日期：2022-05-20

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