Surface morphology regulates the sorption-induced deformation of mesoporous media

MY Chen and LL Ke, MICROPOROUS AND MESOPOROUS MATERIALS, 335, 111822 (2022).

DOI: 10.1016/j.micromeso.2022.111822

Sorption in mesoporous media can induce either solid expansion or contraction, with the governing mechanism at molecular scale still unclear. The coupling between sorption and deformation is studied by an atomistic slit pore model with the help of molecular simulations. It is found that the sorption-induced deformation can shift between expansion and contraction by simply tuning the surface morphology. The underlying mechanism is revealed by a theoretical analysis conducted on a simplified two-dimensional model. It shows that the change in surface morphology alters the directions of atomistic forces between solid and fluid atoms, resulting in the change of sign of the strain. The theoretical analysis predicts that contraction happens on relatively smooth solid surfaces while expansion on corrugated surfaces, which is validated by molecular simulations. Moreover, roles of different solid- fluid interaction parameters on the coupling behavior are characterized. The interaction strength parameter influences the magnitude of the strain but has no effect on the sign, while the interaction distance parameter takes effect on both the magnitude and the sign. The current research explains both sorption-induced expansion and contraction and paves ways to material design for targeted sorption-induced deformation behavior.

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