Freezing and melting transitions in mesoporous solids: From fundamental understanding to advanced characterization using thermoporometry
Final Report Abstract
Mesoporous solids used in various applications typically possess structural disorder, which makes their structural characterization an extremely challenging task. In this project, we have introduced the advanced NMR cryoporometry as an instrumental tool tackling these challenges. First of all, in analogue to the advanced gas sorption approaches, we have developed a set of microscopic kernels describing icewater equilibria in cylindrical and spherical mesopores with siliceous surfaces and different thermodynamic boundary conditions. Secondly, these kernels have been implemented into a novel framework including well-recognized in the literature network effects on the occurrences of phase transitions of confined matter. For this purpose, the problem of phase transitions with coupled nucleation-phase growth transition modes has been rigorously solved for a minimal pore network, statistically-disordered chain model (SDCM). The validity of the novel theoretical framework has been extensively tested against NMR cryoporometry experiments. By using a set of mesoporous materials with tubular pore structures (ordered and disordered) we have proven that SDCM accurately describes not only the boundary melting and freezing transitions, but also accurately reproduces any states within the hysteresis region. In materials with more complex 3-D pore networks, the application of SDCM allowed to explain self-consistently all features in the transition behaviors observed upon variation of their structural properties. The different patterns seen in the experiments were nicely correlated with the disorder parameter introduced in the frame of SDCM. In the context of NMR cryoporometry, it has been shown that the application of SDCM improves notably structural analysis of mesoporous solids with geometric disorder. In particular, structural analysis can now be based not only on a single transition, typically melting, but the entire behavior including melting, freezing and different types of scanning experiments may be included into analysis. Moreover, the work done in the project lays down a route for addressing complex physical phenomena depending on phase configurations of confined materials, which were not accessible so far. The methodology developed in this project may also be extended to similar approaches, such as gas sorption.
Publications
-
Capillary Condensation and Evaporation in Irregular Channels: Sorption Isotherm for Serially Connected Pore Model. The Journal of Physical Chemistry C, 123(26), 16239-16249.
Schneider, Daniel & Valiullin, Rustem
-
Comparative Gas Sorption and Cryoporometry Study of Mesoporous Glass Structure: Application of the Serially Connected Pore Model. Frontiers in Chemistry, 7.
Enninful, Henry R. N. B.; Schneider, Daniel; Hoppe, Antonia; König, Sandra; Fröba, Michael; Enke, Dirk & Valiullin, Rustem
-
A novel approach for advanced thermoporometry characterization of mesoporous solids: Transition kernels and the serially connected pore model. Microporous and Mesoporous Materials, 309, 110534.
Enninful, Henry R.N.B.; Schneider, Daniel; Kohns, Richard; Enke, Dirk & Valiullin, Rustem
-
Sorption Isotherm Reconstruction and Extraction of Pore Size Distributions for Serially Connected Pore Model (SCPM) Structures Employing Algorithmic and Statistical Models. The Journal of Physical Chemistry C, 124(39), 21591-21607.
Kikkinides, E. S.; Monson, P. A. & Valiullin, R.
-
Impact of Geometrical Disorder on Phase Equilibria of Fluids and Solids Confined in Mesoporous Materials. Langmuir, 37(12), 3521-3537.
Enninful, Henry R. N. B.; Schneider, Daniel; Enke, Dirk & Valiullin, Rustem
-
Nuclear Magnetic Resonance Cryoporometry Study of Solid–Liquid Equilibria in Interconnected Spherical Nanocages. The Journal of Physical Chemistry C, 125(48), 26916-26926.
Enninful, Henry R. N. B.; Schneider, Daniel; Rudolph, Benjamin; Meyer, Andreas; Mascotto, Simone & Valiullin, Rustem
-
Free energy landscape within the hysteresis regime for fluids confined in disordered mesoporous solids. The Journal of Chemical Physics, 157(15).
Alzaidi, A.; Kikkinides, E. S.; Schneider, D.; Monson, P. A. & Valiullin, R.
-
On the Comparative Analysis of Different Phase Coexistences in Mesoporous Materials. Materials, 15(7), 2350.
Enninful, Henry R. N. B.; Enke, Dirk & Valiullin, Rustem
