Scientific questions surrounding the shear-dependent microstructure of carbon black suspensions are motivated by a desire to predict and control complex rheological and electrical properties encountered under shear. In this work, direct structural measurements over a hierarchy of length scales spanning from nanometers to tens of micrometers are used to determine the microstructural origin of the suspension viscosity measured at high shear rates. These experiments were performed on a series of dense suspensions consisting of high-structured carbon blacks from two commercial sources suspended in two Newtonian fluids, propylene carbonate and light mineral oil. The shear-induced microstructure was measured at a range of applied shear rates using Rheo-VSANS (very small angle neutron scattering) and Rheo-USANS (ultra-small angle neutron scattering) techniques. A shear-thinning viscosity is found to arise due to the self-similar break up of micrometer-sized agglomerates with increasing shear intensity. This self-similarity yields a master curve for the shear-dependent agglomerate size when plotted against the Mason number, which compares the shear force acting to break particle-particle bonds to the cohesive force holding bonds together. It is found that the agglomerate size scales as $R_{g,\mathrm{agg}}\sim M{n}^{-1}$. Inclusion of the particle stress contribution extends the relevance of the Mason number to concentrated suspensions such as those relevant to the processing of carbon black suspensions for various applications.

中文翻译：

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直接测量炭黑悬浮液中剪切稀化的微观结构起源

围绕预测和控制剪切下遇到的复杂流变学和电学特性的动机，引发了与碳黑悬浮液的剪切相关的微观结构有关的科学问题。在这项工作中，在跨度范围从纳米到数十微米的长度尺度的层次上的直接结构测量，被用来确定在高剪切速率下测得的悬浮液粘度的微观结构起源。这些实验是在一系列致密的悬浮液中进行的，这些悬浮液由悬浮在两种牛顿流体（碳酸亚丙酯和轻质矿物油）中的两种商业来源的高结构炭黑组成。使用Rheo-VSANS（超小角度中子散射）和Rheo-USANS（超小角度中子散射）技术在一定的剪切速率下测量了剪切诱导的微观结构。发现剪切稀化粘度的产生是由于随着剪切强度的增加，微米级团聚物的自相似破裂。当与梅森数作图时，这种自相似性产生了与剪切有关的团聚体尺寸的主曲线，该曲线比较了将颗粒间键断裂的剪切力与将键保持在一起的内聚力。发现附聚物的大小按比例缩放 当与梅森数作图时，这种自相似性产生了与剪切有关的团聚体尺寸的主曲线，该曲线比较了将颗粒间键断裂的剪切力与将键保持在一起的内聚力。发现附聚物的大小按比例缩放 当与梅森数作图时，这种自相似性产生了与剪切有关的团聚体尺寸的主曲线，该曲线比较了将颗粒间键断裂的剪切力与将键保持在一起的内聚力。发现附聚物的大小按比例缩放${\mathrm{[R}}_{G，\mathrm{gg}}〜\mathrm{中号}{ñ}^{-\mathrm{1个}}$。包含颗粒应力贡献可将梅森数的相关性扩展至浓缩悬浮液，例如与各种用途的炭黑悬浮液加工相关的悬浮液。