Anomalous variations in the viscous activation energy of suspensions induced by fractal structuring

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:530

Article

Timmons, Jason^1,2  Falzone, Gabriel^1,2  Balonis, Magdalena²  Bauchy, Mathieu³  Sant, Gaurav^1,2,4 

[1] Univ Calif Los Angeles, Dept Civil & Environm Engn, Lab Chem Construct Mat LC2, Los Angeles, CA 90095 USA

[2] Univ Calif Los Angeles, Dept Mat Sci & Engn, Los Angeles, CA 90024 USA

[3] Univ Calif Los Angeles, Dept Civil & Environm Engn, Lab Phys Amorphous & Inorgan Solids PARISlab, Los Angeles, CA USA

[4] Univ Calif Los Angeles, Calif Nanosyst Inst, Los Angeles, CA USA

关键词: Suspension rheology;    Fractal structuring;    Activation energy;    Configurational entropy;   

DOI  :  10.1016/j.jcis.2018.07.008

来源: Elsevier

【 摘 要 】

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 <= phi <= 0.55). These suspensions were characterized by their viscosity (eta, 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(50) approximate to 5 mu m), we observe an anomalous decrease in the activation energy (E-a, 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. (C) 2018 Elsevier Inc. All rights reserved.

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