arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2004.11617cond-mat.soft
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毛细管力诱导凝胶的微观结构与屈服

Microstructure and yielding of capillary force induced gel

Sameer Huprikar, Saurabh Usgaonkar, Ashish K. Lele, Ashish V. Orpe

摘要:

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。颗粒在液体中的悬浮液在添加少量第二润湿液体时经历凝胶化,所述第二润湿液体在颗粒之间形成液体桥,导致样品跨越网络。该凝胶的流变学主要表现出在低剪切速率下的屈服应力,随后在高剪切速率下剪切应力的线性变化。从流动曲线中提取的表观屈服应力在饱和前随第二液体体积分数的增加而迅速增加,而随颗粒浓度的增加而单调增加。使用合适的移位因子的屈服应力曲线的重新缩放的结果在屈服应力的经验表达式中示出了对液体分数的平方依赖性,并且随着颗粒分数高于一定值而快速增加,两者以高度非线性的方式组合。利用三维X射线层析成像技术,获得了随二次液相含量和颗粒分数变化的微观结构变化。观察到的微观结构,以显示增加的局部致密性与液体含量和增加的空间均匀性与颗粒分数增加。从X射线断层扫描的图像进行分析,以获得在系统中的粒子-粒子键(配位数)的分布,用于解释所观察到的屈服应力行为在定性的方式。

英文摘要:

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 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 nonlinear 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 behavior in a qualitative manner.

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