Colloids and Surfaces A: Physicochem. Eng. Aspects 520 (2017) 9–16 Contents lists available at ScienceDirect Colloids and Surfaces A: Physicochemical and Engineering Aspects journa l h om epage: www.elsevier.com/locate/colsurfa Double layer electrical conductivity as a stability criterion for concentrated colloidal suspensions Robinson C.D. Cruz a , Ana M. Segadães b,∗ , Rainer Oberacker c , Michael J. Hoffmann c a University of Caxias do Sul, Instituto de Materiais Cerâmicos (IMC), 95765-000 Bom Princípio, Brazil b University of Aveiro, Department of Materials and Ceramics Engineering (CICECO), 3810-193 Aveiro, Portugal c Karlsruhe Institute of Technology, Institute for Applied Materials, Ceramics in Mechanical Engineering, 76131 Karlsruhe, Germany h i g h l i g h t s • Relationship between particle elec- trical conductivity and DLVO col- loidal stability. • Identified processing window for the stability control of concentrated sus- pensions. • DLVO secondary attractive minimum lies at 1.5 kT for the equilibrium con- ductivity. • At the minimum reversible dis- tance (∼7 nm) particles conductivity is zero. • More accurate measurement of static –potential at the isoconductivity point. g r a p h i c a l a b s t r a c t a r t i c l e i n f o Article history: Received 7 October 2016 Received in revised form 13 January 2017 Accepted 20 January 2017 Available online 23 January 2017 Keywords: Colloidal interactions Particle conductivity DLVO Electrokinetics Alumina a b s t r a c t The slightly attractive inter–particle equilibrium potential associated with electrostatically stabilized suspensions of minimum viscosity is described by the DLVO theory and commonly gauged by static -potential measurements, plagued with experimental uncertainties. In this work, the electrokinetic mobility of alumina particles was measured in suspensions prepared with selected solids content and ionic strength, as well as was the electrical conductivity of each suspension and suspending liquid. Par- ticles electrical conductivity was then calculated and related to the colloidal stability described by the DLVO theory, enabling the identification of a processing window for the stability control of concentrated suspensions. The maximum repulsive potential and distance between particles (∼46 nm) corresponds to the particles maximum conductivity. When the particles conductivity is zero, the diffuse layer is fully collapsed and they stand at the minimum reversible distance (∼7 nm). At the equilibrium conductivity, a potential curve is produced with a secondary attractive minimum of ∼1.5 kT at an inter–particle distance of ∼17 nm, as suggested by the DLVO theory and the Equipartition of Energy theorem. The condition for accurate measurement of static -potential occurs at the isoconductivity point between particles and suspending liquid. © 2017 Elsevier B.V. All rights reserved. ∗ Corresponding author. E-mail address: segadaes@ua.pt (A.M. Segadães). 1. Introduction The manipulation of nanoscale particles often requires the con- trol of the mobility of suspended particles, which is the underlying http://dx.doi.org/10.1016/j.colsurfa.2017.01.059 0927-7757/© 2017 Elsevier B.V. All rights reserved.