Fluid phase transitions in pores offer an important tool for pore space characterization. Alterations in the properties of fluids under confinement
provide markers for the quantitative analysis of pore sizes. By the well-known Gibbs-Thomson and Kelvin equation, the thermodynamic condition responsible for a fluid phase transition in a pore reveals the structural properties of the mesoporous solid. While this works well in ordered pore spaces, the interplay of both nucleation (metastable) and phase growth (equilibrium) thermodynamic processes accompanying phase equilibria processes in disordered pore systems render current characterization approaches inaccurate.
The recently developed serially-connected pore model (SCPM), modeled as a statistically linear chain of pores, incorporates both metastable and
thermodynamic processes to reveal the complexities in the disordered pore landscape. In this work, we present solid-liquid and gas-liquid phase equilibria studies in a strongly disordered silica mesoporous material. We show that, though the SCPM is modeled as statistical linear chains of pores, it is able to reproduce all phase states in our highly disordered porous material of very small mean pore size and provide a more accurate pore size distribution.
References
[1] Schneider D.; Kondrashova D.; Valiullin R., 2017, “Phase transitions in disordered mesoporous solids”, Scientific Reports, 7, 7216.
[2] Schneider, D. and Valiullin R., 2019, “Capillary condensation and evaporation in irregular channels: Sorption isotherm for serially connected pore model”, Journal of Physical Chemistry C, 123, 16239.
[3] Enninful H.R.N.B., Schneider D., Hoppe A., König S., Fröba M., Enke D. and Valiullin R., 2019, “Comparative gas sorption and cryoporometry study of mesoporous glass structure: Application of the serially connected pore model”, Frontiers in Chemistry, doi: 10.3389/fchem.2019.00230.
[4] Enninful H.R.N.B., Schneider D., Kohns R., Enke D. and Valiullin R., 2020, “A novel approach for advanced thermoporometry characterization of mesoporous solids: Transition kernels and the serially connected pore model”, Microporous and Mesoporous Materials 309, 110534.
[5] Enninful H.R.N.B., Schneider D., Enke D. and Valiullin R., 2021, “Impact of Geometrical Disorder on Phase Equilibria of Fluids and Solids Confined in Mesoporous Materials”, Langmuir, 37, 3521-3537