Correlating Microscopic Structures and Dynamics with Rheological Behavior in Charged Colloidal Suspensions

Energy materials in slurries and colloidal suspensions are important for technologies such as batteries, supercapacitors, and fuel cells. These systems typically contain nanoparticles, polymers, or functional additives dispersed in liquid media, forming complex fluids with adjustable properties. Their performance depends on rheological behavior, microscopic structures, and dynamic responses to external fields or mechanical stress. For example, lithium-ion battery electrodes use slurries containing active materials, binders, and conductive additives, where shear-thinning behavior and particle packing influence uniform film formation during coating. Similarly, proton-exchange membrane fuel cells rely on inks with optimized rheology to deposit catalyst layers with controlled porosity and thickness.

Energy materials often enter non-equilibrium states due to external factors such as temperature changes, mechanical forces, or chemical reactions. These conditions lead to transient behaviors, including metastable transitions, aging, rupture, avalanches, and phase re-entrance. Understanding these responses requires investigations into how microscopic dynamics influence macroscopic properties. Advanced characterization techniques, including X-ray photon correlation spectroscopy (XPCS), monitor structural dynamics in real time under shear and electric fields. Such studies reveal structural transitions, phase separation, and relaxation dynamics, providing insights into non-equilibrium processes.

This study applies a Markov chain framework to incorporate internal and external forces and introduces transport coefficients to describe non-equilibrium dynamics. Using XPCS, we capture subtle particle dynamics during yielding and stress relaxation, validating theoretical and simulation-based predictions of delayed yielding and resolidification. Our results show dynamical heterogeneity and cooperativity, providing data for artificial intelligence models. These findings link microscopic dynamics to macroscopic behavior, improve predictive models for transient processes, and support the design of optimized soft materials for industrial and natural applications.

Controlling yielding is key to maintaining structural stability. We examine yielding transitions in colloidal suspensions using Rheo-SAXS-XPCS and Fast Lubrication Dynamics simulations to track time-resolved particle dynamics and structural changes. In repulsive suspensions, yielding shows uniform flow and Andrade-like responses under deformation. In contrast, attractive suspensions show more complex behaviors, including shear banding, dynamic heterogeneity, delayed yielding, and resolidification. Attractive interactions promote shear band formation, leading to large dynamical heterogeneity and interface instability. The transient dynamics within the shear band interface dominate the macroscopic rheological response, affecting the yielding process.

These results highlight the role of interaction potentials in yielding transitions and suggest strategies for designing materials with targeted performance. A detailed understanding of rheological properties, microscopic structures, and dynamic responses supports the development of next-generation energy materials with improved performance and sustainability.