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

Jason Timmons¹, Gabriel Falzone¹, Magdalena Balonis², Mathieu Bauchy³, Gaurav Sant⁴

Affiliations

¹ 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.
² Department of Materials Science and Engineering, University of California, Los Angeles, CA, USA.
³ Laboratory for the Physics of Amorphous and Inorganic Solids (PARISlab), Department of Civil and Environmental Engineering, University of California, Los Angeles, CA, USA. Electronic address: bauchy@ucla.edu.
⁴ 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; California Nanosystems Institute, University of California, Los Angeles, CA, USA. Electronic address: gsant@ucla.edu.

PMID: 30005237
DOI: 10.1016/j.jcis.2018.07.008

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

Jason Timmons et al. J Colloid Interface Sci. 2018.

. 2018 Nov 15:530:603-609.

doi: 10.1016/j.jcis.2018.07.008. Epub 2018 Jul 4.

Authors

Jason Timmons¹, Gabriel Falzone¹, Magdalena Balonis², Mathieu Bauchy³, Gaurav Sant⁴

Affiliations

¹ 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.
² Department of Materials Science and Engineering, University of California, Los Angeles, CA, USA.
³ Laboratory for the Physics of Amorphous and Inorganic Solids (PARISlab), Department of Civil and Environmental Engineering, University of California, Los Angeles, CA, USA. Electronic address: bauchy@ucla.edu.
⁴ 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; California Nanosystems Institute, University of California, Los Angeles, CA, USA. Electronic address: gsant@ucla.edu.

PMID: 30005237
DOI: 10.1016/j.jcis.2018.07.008

Abstract

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 (d₅₀ ≈ 5 µm), 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.

Keywords: Activation energy; Configurational entropy; Fractal structuring; Suspension rheology.

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

Affiliations

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

Authors

Affiliations

Abstract

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