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Many studies have proven that elastic properties of fluids confined in nanopores deviate from the values observed in bulk [1]. Interactions between the solids (pore wall) and fluids, and pore geometry are the key factors that determine the deviation in the elasticity of nanoconfined fluids. Therefore, experimental measurements of elastic properties of confined fluids can provide information about the porous solids themselves. In this work, we studied the elasticity of carbon xerogels when they are gradually saturated with water. Here, a novel adsorption-ultrasonic experimental setup [2] was employed to measure the ultrasonic wave speeds through the water-saturated carbon xerogel sample while measuring its water sorption isotherm. The measured water sorption isotherm follows type V isotherm [3], which describes the mechanisms of fluid adsorption to the nanopores. Elastic moduli of the xerogel-water composite, derived from the measured ultrasonic wave speeds, were then used to calculate the bulk modulus of the confined water using the Gassmann theory. The resulting elastic properties differ noticeably from those measured on water-saturated Vycor glass [2]. We found that the measured elastic properties of the water saturated carbon xerogels are strongly affected by adsorption-induced deformation [4].
References:
1. C. D. Dobrzanski, B. Gurevich, G. Y. Gor, Elastic properties of confined fluids from molecular modeling to ultrasonic experiments on porous solids, Applied Physics Review 8, 021317 (2021)
2. J. Ogbebor, J. J. Valenza, P. I. Ravikovitch, A. Karunarathne, G. Muraro, M. Lebedev, B. Gurevich, A. F. Khalizov, G. Y. Gor, Ultrasonic study of water adsorbed in nanoporous glasses, Physical Review E 108, 024802 (2023)
3. M. Thommes, K. Kaneko, A.V. Neimark, J.P. Olivier, F. Rodriguez-Reinoso, J. Rouquerol, K.S.W. Sing, Physisorption of gases, with special reference to the evaluation of surface area and pore size distribution (IUPAC Technical Report), Pure and Applied Chemistry, 87 (2015) 1051-1069
4. C. Balzer, S. Braxmeier, A. V. Neimark, Gudrun Reichenauer, Deformation of microporous carbon during adsorption of nitrogen, argon, carbon dioxide, and water studied by in situ dilatometry, Langmuir 2015, 31, 12512−12519
Acknowledgements:
A. K, A. F. K. and G. Y. G. thank the support from NSF CBET-2128679 grant.
