Interpreting rheology and electrical conductivity: It all boils down to which particle size


Hypothesis: The electrical charges that develop on the surface of the ceramic particles upon contact with water, due to the interaction with ions in solution, result in a liquid-solid interface, which utterly modifies the properties of individual particles and the way they interact with each other to form a structure. This work explores a new approach to the relationships between structure and stability of suspensions. Experiments: For this purpose, suspensions with a constant 0.35 volume fraction of alpha-alumina particles, neither spherical nor smooth, and controlled ionic strength (0-90 mM KCl) were prepared and characterized in terms of flow behaviour, electrical conductivity and particle's electrokinetic mobility. Findings: Electrical conductivity (132 mu S/cm < conductivity < 5730 mu S/cm) and rheology measurements (10(-2) Pa s < viscosity < 10(4) Pa s) were found to complement each other to produce a more accurate picture of the suspension's structure. Deviations of experimental data from well-accepted behavioural models were elucidated when the surface area equivalent particle size was used. With the electrical double layer thickness obtained from electrical conductivity measurements, this enabled the interpretation of the relationship between the suspension's viscosity and the particles electrical conductivity, which provides a criterion for the stability of concentrated colloidal suspensions. (C) 2020 Elsevier Inc. All rights reserved.



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Cruz, RCD; Segadaes, AM; Mantas, PQ; Oberacker, R; Hoffmann, MJ

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Authors appreciate the financial support received from the Brazilian Research Agency CAPES (R.C.D. Cruz, Ph.D. grant) and from Deutsche Forschungsgemeinschaft (DFG Research Unit FOR 371).

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