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Article Dans Une Revue Journal of Rheology Année : 2024

Attractive carbon black dispersions: structural and mechanical responses to shear

Résumé

The rheological behavior of colloidal dispersions is of paramount importance in a wide range of applications, including construction materials, energy storage systems and food industry products. These dispersions consistently exhibit non-Newtonian behaviors, a consequence of intricate interplays involving colloids morphology, volume fraction, and inter-particle forces. Understanding how colloids structure under flow remains a challenge, particularly in the presence of attractive forces leading to clusters formation. In this study, we adopt a synergistic approach, combining rheology with ultra small-angle X-ray scattering (USAXS), to probe the flow-induced structural transformations of attractive carbon black (CB) dispersions and their effects on the viscosity. Our key findings can be summarized as follow. First, testing different CB volume fractions, in the high shear rate hydrodynamic regime, CB particles aggregate to form fractal clusters. Their size conforms to a power law of the shear rate, ξc ∝ γ˙ −m, with m ≃ 0.5. Second, drawing insights from the fractal cluster structure, we compute an effective volume fraction φeff and find that the microstructural Krieger-Dougherty model adeptly accounts for the hydrodynamic stress contributions. We identify a critical shear rate γ˙∗ and a critical volume fraction φ ∗ eff, at which the clusters percolate to form a dynamical networks. Third, we show that the apparent yield stress measured at low shear rates inherits its properties from the percolation point. Finally, through data scaling and the integration of the Einstein’s viscosity equation, we revisit and discuss the CaggioniTrappe-Spicer model, revealing a significant connection between its empirical parameters and the structural properties of CB dispersions under flow.
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Dates et versions

cea-04574608 , version 1 (14-05-2024)

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Julien Bauland, Louis-Vincent Bouthier, Arnaud Poulesquen, Thomas Gibaud. Attractive carbon black dispersions: structural and mechanical responses to shear. Journal of Rheology, 2024, 68 (3), pp.429-443. ⟨10.1122/8.0000791⟩. ⟨cea-04574608⟩
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