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.