Phase diagrams for aggregates of thick colloidal platelets

• We developed a micromechanical model for aggregated clay platelet configurations.
• We derived stability conditions for face–edge, face–face and edge–edge aggregates.
• The stability of face–edge aggregates depends on the surface curvature of edge walls.
• Phase diagrams for different clay aggregates have been constructed.
• The locations of kaolin gel phases appearing after rapid coagulation are predicted.

The balance of van der Waals and electrostatic forces between the platelets in clay suspensions may lead to stable face–edge configurations. These configurations compete with face–face and edge–edge aggregates in clay gels. For clay platelets with thicknesses substantially larger than the interaction range, stability conditions for the different aggregates in terms of electric surface potentials, Debye-length, Hamaker constant and interface curvature in the edge region of the platelets are formulated. The stability conditions are useful to evaluate phase diagrams for mechanically and thermodynamically stable platelet aggregates.

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