Speaker
Description
In the context of energy- and climate-related challenges involving porous materials, understanding water dynamics across different states of porous matter, from reactive mineral solutions to consolidated colloidal gels, is essential for describing transport, aging, and stability in silicate-based and bio-inspired systems. However, capturing these processes under non-equilibrium conditions and across relevant length and time scales remains experimentally challenging. In this work, we develop and apply a dynamic low-field NMR relaxometry framework to investigate water dynamics and structural evolution in silicate systems, spanning the transition from alkaline silicate solutions to deformable porous gels.
We first investigate aqueous alkali silicate solutions using NMR relaxometry to quantify changes in water mobility and interfacial interactions as a function of hydroxide concentration and alkali nature. Transverse relaxation measurements reveal marked and systematic variations in relaxation behavior, reflecting modifications of solution speciation and mesoscale organization prior to gelation. These results demonstrate that NMR relaxometry provides a sensitive, non-destructive probe of structural evolution in reactive silicate solutions [1].
The approach is then extended to the drying of colloidal and aluminosilicate gels, where water transport is intrinsically coupled to deformation, gradient formation, and particle-network reconfiguration. Using a dynamic relaxometry methodology that follows transverse relaxation times (T₂) as a function of saturation rather than time, and combining global measurements with one-dimensional spatial water profiles, we identify robust power-law relationships linking relaxation efficiency to desaturation. These relationships reveal distinct drying regimes and allow a clear discrimination between ideal homogeneous drying and non-ideal scenarios governed by physical instabilities such as gradients and incomplete network reorganization [2].
To rationalize these observations, a minimal numerical framework is introduced, enabling the separation of the respective contributions of hydric gradients, macroscopic contraction, and particle-network reconfiguration. Additional relaxometry measurements performed at different magnetic fields further support the interpretation of relaxation mechanisms and interfacial water dynamics.
Overall, this work establishes dynamic NMR relaxometry as a unifying and quantitative methodology to continuously follow water dynamics from reactive solutions to porous gels, providing physically grounded descriptors relevant for transport, aging, and stability in porous materials, with direct implications for the understanding and control of water-related processes in energy-efficient and climate-resilient porous systems.
Keywords: Low-field NMR, NMR relaxometry, variable-field relaxometry, water dynamics, silicate solutions, colloidal gels, drying, porous media, non-equilibrium processes
References :
[1] Poulesquen, A.; Sidi-Boulenouar, R. et al. submitted — Comprehensive structural and dynamical study of alkali silicate solutions, Journal of Colloid And Interface Science, 2025.
[2] Maillet, B.; Sidi-Boulenouar, R.; Coussot, P. Dynamic NMR Relaxometry as a Simple Tool for Measuring Liquid Transfers and Characterizing Surface and Structure Evolution in Porous Media. Langmuir 2022, 38 (49), 15009–15025. https://doi.org/10.1021/acs.langmuir.2c01918.
| References | [1] Poulesquen, A.; Sidi-Boulenouar, R. et al. submitted — Comprehensive structural and dynamical study of alkali silicate solutions, Journal of Colloid And Interface Science, 2025. [2] Maillet, B.; Sidi-Boulenouar, R.; Coussot, P. Dynamic NMR Relaxometry as a Simple Tool for Measuring Liquid Transfers and Characterizing Surface and Structure Evolution in Porous Media. Langmuir 2022, 38 (49), 15009–15025. https://doi.org/10.1021/acs.langmuir.2c01918. |
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| Country | France |
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