We have investigated the rheology and structure of a gel formed from a mixture of non-Brownian particles and two immiscible liquids. The suspension of particles in a liquid undergoes gelation upon the addition of a small content of second, wetting liquid which forms liquid bridges between particles leading to a sample spanning network. The rheology of this gel primarily exhibits a yield stress at low shear rates followed by a linear variation of shear stress at high shear rates. The apparent yield stress extracted from the flow curves increases rapidly with volume fraction of the second liquid before saturation, while it exhibits a monotonic increase with increasing particle concentration. Rescaling of the yield stress curves using suitable shift factors results in an empirical expression for the yield stress showing squared dependence on liquid fraction and a rapid increase with particle fraction above a certain value, both combined in a highly non-linear manner. The microstructural variations with changing secondary liquid content and particle fractions are captured using three-dimensional X-ray tomography technique. The microstructure is observed to show increased local compactness with increased liquid content and increased spatial homogeneity with increased particle fractions. The images from X-ray tomography are analysed to obtain the distributions of particle-particle bonds (coordination number) in the system which serve to explain the observed yield stress behaviour in a qualitative manner.

中文翻译：

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毛细力诱导凝胶的微观结构和屈服

我们研究了由非布朗粒子和两种不混溶液体的混合物形成的凝胶的流变学和结构。在加入少量第二种润湿液体后，液体中的颗粒悬浮液会发生凝胶化，从而在颗粒之间形成液桥，从而形成样品跨越网络。这种凝胶的流变性主要在低剪切速率下呈现屈服应力，然后在高剪切速率下呈现线性变化。从流动曲线中提取的表观屈服应力随着饱和前第二种液体的体积分数而迅速增加，而随着颗粒浓度的增加，它表现出单调增加。使用合适的移位因子重新调整屈服应力曲线会导致屈服应力的经验表达式显示出对液体分数的平方依赖性和粒子分数超过某个值时的快速增加，两者都以高度非线性的方式结合。使用三维 X 射线断层扫描技术捕获随二次液体含量和颗粒分数变化的微观结构变化。观察到微观结构显示出随着液体含量增加而增加的局部致密性和随着颗粒分数增加而增加的空间均匀性。分析来自 X 射线断层扫描的图像，以获得系统中粒子 - 粒子键（配位数）的分布，用于以定性方式解释观察到的屈服应力行为。