Anti-thixotropic dynamics in attractive colloidal dispersions: a shear restructuring driven by elastic stresses
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| Autores principales: | , , , , , |
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| Formato: | Preprint |
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2025
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| author | Bauland, Julien Legrand, Gauthier Manneville, Sébastien Divoux, Thibaut Poulesquen, Arnaud Gibaud, Thomas |
| author_facet | Bauland, Julien Legrand, Gauthier Manneville, Sébastien Divoux, Thibaut Poulesquen, Arnaud Gibaud, Thomas |
| contents | Due to rich rheological properties, dispersions of attractive colloidal particles are ubiquitous in industries. Specifically, upon experiencing a sudden reduction in shear rate, these dispersions may exhibit transient behaviors such as thixotropy-where viscosity increases over time-and anti-thixotropy, characterized by an initial viscosity decrease before reaching a steady state. While thixotropy has been described as a competition between structure buildup and disruption, the mechanisms of anti-thixotropy remain poorly understood. Here, we investigate the anti-thixotropic dynamics of carbon black particles dispersed in oil-a system known for exhibiting anti-thixotropy-through flow step-down experiments. Using a multi-technique approach combining rheology with velocimetry and structural characterizations, we show that viscosity decrease results from a decrease in wall slip concomitant to shear-induced structural rearrangements, indicating a transition from a dynamical network of fractal clusters into a network of loosely connected dense agglomerates. Additionally, after a characteristic anti-thixotropic time $τ$, a steady flow is reached. This time $τ$ diverges with increasing shear rate at a critical value corresponding to a Mason number of one, indicating that anti-thixotropy occurs only when colloidal attraction outweighs viscous forces. More precisely, we show that the structural rearrangement underpinning the viscosity decrease is mediated by elastic stresses $σ_e$, such that $τ\propto σ_e^{-3}$. Finally, on long time scales, the steady state is linked to a microstructure with nearly zero yield stress, indicating a loss of flow memory. These findings provide a mechanism for anti-thixotropy and suggest pathways for controlling viscosity and yield stress in attractive colloidal dispersions. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2501_16532 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Anti-thixotropic dynamics in attractive colloidal dispersions: a shear restructuring driven by elastic stresses Bauland, Julien Legrand, Gauthier Manneville, Sébastien Divoux, Thibaut Poulesquen, Arnaud Gibaud, Thomas Soft Condensed Matter Due to rich rheological properties, dispersions of attractive colloidal particles are ubiquitous in industries. Specifically, upon experiencing a sudden reduction in shear rate, these dispersions may exhibit transient behaviors such as thixotropy-where viscosity increases over time-and anti-thixotropy, characterized by an initial viscosity decrease before reaching a steady state. While thixotropy has been described as a competition between structure buildup and disruption, the mechanisms of anti-thixotropy remain poorly understood. Here, we investigate the anti-thixotropic dynamics of carbon black particles dispersed in oil-a system known for exhibiting anti-thixotropy-through flow step-down experiments. Using a multi-technique approach combining rheology with velocimetry and structural characterizations, we show that viscosity decrease results from a decrease in wall slip concomitant to shear-induced structural rearrangements, indicating a transition from a dynamical network of fractal clusters into a network of loosely connected dense agglomerates. Additionally, after a characteristic anti-thixotropic time $τ$, a steady flow is reached. This time $τ$ diverges with increasing shear rate at a critical value corresponding to a Mason number of one, indicating that anti-thixotropy occurs only when colloidal attraction outweighs viscous forces. More precisely, we show that the structural rearrangement underpinning the viscosity decrease is mediated by elastic stresses $σ_e$, such that $τ\propto σ_e^{-3}$. Finally, on long time scales, the steady state is linked to a microstructure with nearly zero yield stress, indicating a loss of flow memory. These findings provide a mechanism for anti-thixotropy and suggest pathways for controlling viscosity and yield stress in attractive colloidal dispersions. |
| title | Anti-thixotropic dynamics in attractive colloidal dispersions: a shear restructuring driven by elastic stresses |
| topic | Soft Condensed Matter |
| url | https://arxiv.org/abs/2501.16532 |