Regensburg 2022 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 24: New Methods and Developments: Spectroscopies, Diffraction and Others (joint session O/KFM)

KFM 24.3: Vortrag

Donnerstag, 8. September 2022, 11:15–11:30, H6

Advanced Kernel-Based NMR Cryoporometry Characterization of Mesoporous Solids — •Henry R.N.B. Enninful, Daniel Schneider, Richard Kohns, Dirk Enke, and Rustem Valiullin — Leipzig University, Leipzig, Germany

NMR cryoporometry is a pore space characterization technique for industrial and natural materials such as catalysts, gas storage materials, cartilage, bones, rocks and many more. While gaining wide use, the fundamental phenomena underlying solid-liquid phase transitions in geometrically disordered porous materials is still not fully understood. This may lead to inaccurate pore size distributions from the NMR cryoporometry technique.

In this work, we have developed a new approach to NMR cryoporometry. Herein, it takes account of cooperativity effects in pores, the existence of a variable non-frozen layer (NFL) thickness between the frozen core and pore wall and the effect of curvature on thermal fluctuations in pores which hitherto are missing in the current approach. In the first place, we compile a family of transition curves characterizing the phase state in pores with different pore sizes, so called kernels. Thereafter, we apply a general framework for predicting phase equilibria in a collection of pores. Specifically, the proposed kernel-based approach is coupled with the serially-connected pore model (SCPM) to be able to predict phase behavior in independent pore systems as well as in pore networks. We demonstrate the new approach by applying it to ordered porous materials such as MCM-41 and SBA-15. Consequently, a more accurate pore size distribution (PSD) is obtained.