Nuclear Magnetic Resonance Cryoporometry Study of Solid-Liquid Equilibria in Interconnected Spherical Nanocages

In this work, a combined experimental and theoretical study of solid-liquid phase equilibria confined in mesoporous solids composed of spherical cages connected via smaller-sized cylindrical irregular channels is presented. The experimental data on phase equilibria obtained using nuclear magnetic resonance (NMR) cryoporometry with water as a probe liquid are analyzed using transition kernels developed for the spherical pores. They accurately predict the variation of the non-frozen water layer thickness with temperature as well as the positions of the solid-liquid and liquid-solid transition temperatures. By analyzing the melting and freezing transitions as well as scanning freezing transitions in materials with different properties of the interconnecting pore network achieved by different synthesis conditions, an accurate information on the textural properties and phase transition processes is obtained. The results obtained are compared to the structural information obtained using other experimental techniques such as small-angle X-ray scattering and gas sorption.