由分形结构引起的悬浮液粘性活化能的异常变化。
Anomalous variations in the viscous activation energy of suspensions induced by fractal structuring.
机构信息
Laboratory for the Chemistry of Construction Materials (LC(2)), Department of Civil and Environmental Engineering, University of California, Los Angeles, CA, USA; Department of Materials Science and Engineering, University of California, Los Angeles, CA, USA.
Department of Materials Science and Engineering, University of California, Los Angeles, CA, USA.
出版信息
J Colloid Interface Sci. 2018 Nov 15;530:603-609. doi: 10.1016/j.jcis.2018.07.008. Epub 2018 Jul 4.
HYPOTHESIS
In suspensions, the activation energy of viscous flow is an important property that controls the temperature dependence of the viscosity. However, the differentiated roles of the properties of the liquid phase and the structure of the solid particles in controlling the activation energy remain unclear. We propose here that particle fractal structuring yields an anomalous behavior in the activation energy of viscous flow.
EXPERIMENTS
The rheology of two series of suspensions consisting of glass beads suspended in poly(1-decene) was investigated over a wide range of solid volume fractions (0.00 ≤ φ ≤ 0.55). These suspensions were characterized by their viscosity (η, Pa∙s) via shear rate sweeps and by their yield stress (Pa) via oscillatory amplitude sweeps.
FINDINGS
Interestingly, for suspensions consisting of nominally smaller particles (d ≈ 5 µm), we observe an anomalous decrease in the activation energy (E, kJ/mol) of viscous flow with increasing solid fraction. Based on oscillatory rheology analyses, it is suggested that such anomalous behavior arises due to entropic effects that result from the formation of fractally-architected cooperatively rearranging regions (i.e., agglomerates) in the suspension.
假设
在悬浮液中，粘性流的活化能是控制粘度对温度依赖性的重要性质。然而，液相性质和固体颗粒结构在控制活化能方面的区别作用仍不清楚。我们在这里提出，颗粒分形结构导致粘性流的活化能出现异常行为。
实验
我们研究了由玻璃珠悬浮在聚（1-癸烯）中组成的两个系列悬浮液的流变性能，固体体积分数范围很宽（0.00≤φ≤0.55）。这些悬浮液的粘度（η，Pa·s）通过剪切率扫描进行表征，屈服应力（Pa）通过振荡幅度扫描进行表征。
发现
有趣的是，对于由名义上较小的颗粒（d≈5μm）组成的悬浮液，我们观察到粘性流的活化能（E，kJ/mol）随着固体分数的增加而异常降低。基于振荡流变学分析，这种异常行为是由于在悬浮液中形成了分形结构的协同重排区域（即团聚体）而导致的熵效应引起的。
Zotero 插件