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

Robinson C D Cruz; Ana M Segadães; Pedro Q Mantas; Rainer Oberacker; Michael J Hoffmann

doi:10.1016/j.jcis.2020.04.046

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

J Colloid Interface Sci. 2020 Aug 15:574:97-109. doi: 10.1016/j.jcis.2020.04.046. Epub 2020 Apr 11.

Authors

Robinson C D Cruz¹, Ana M Segadães², Pedro Q Mantas³, Rainer Oberacker⁴, Michael J Hoffmann⁴

Affiliations

¹ University of Caxias do Sul, IMC-Instituto de Materiais Cerâmicos, Bom Princípio, Brazil.
² University of Aveiro, Department of Materials and Ceramics Engineering, Aveiro, Portugal; University of Aveiro, CICECO-Aveiro Institute of Materials, Aveiro, Portugal. Electronic address: segadaes@ua.pt.
³ University of Aveiro, Department of Materials and Ceramics Engineering, Aveiro, Portugal.
⁴ Karlsruhe Institute of Technology, Institute for Applied Materials, Ceramics in Mechanical Engineering, Karlsruhe, Germany.

PMID: 32305732
DOI: 10.1016/j.jcis.2020.04.046

Abstract

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 α-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 µS/cm < conductivity < 5730 µS/cm) and rheology measurements (10^-2 Pa s < viscosity < 10⁴ 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.

Keywords: Alumina particle; Colloidal interactions; DLVO; Rheology; Suspension electrical conductivity; Viscosity; Zeta-potential.