Attractive and Repulsive Particles: Relations Between Microstructure Formation and Yield Behavior of 2D Jammed Clays

To advance predictive models of bulk behavior of naturally occurring materials, such as clay or mud, it is important to understand the dynamics and structural properties of the material constituents (i.e. particles). Here, we investigate the flow and microstructure of clay suspensions using a custom made interfacial stress rheometer. This device measures suspension rheology (e.g. G’, G”) while simultaneously characterizing the fluid microstructure.

We find the development of system-spanning networks of attractive particles that cause jamming at lower concentrations as compared to repulsive systems. The role of reversibility in yielding of naturally occurring, complex materials is elucidated by studying a system of clay. Kaolinite, a non-swelling plate shaped clay is chosen because these particles have opposite charges on faces as edges, creating bulk attraction. We observe evolution of the microstructure in the form of system-spanning aggregates and persistent voids. Inter-particle attraction is believed to create these aggregates, which in turn impede shear. It is expected that elasticity grows steadily with shear frequency, but at a critical amplitude loss due to viscosity sets in.