Melting Of Ice In Mesoporous Silica

Melting of solids into liquids is a common and important phase transition. With regard to water, because of its importance in materials science, biology, geology, meteorology and so on, melting of ice and its size dependence are of specific interests. Intensive efforts have been devoted to the size-dependent melting of ice. However, on the one hand, reported results in different works showed significant discrepancies and, on the other hand, understandings to the size effect on melting remain quite controversial.The invention of new families of mesoporous materials, particularly MCM-41and SBA-15, offers new possibilities for studying the size effect on ice melting. In this paper, SBA-15samples with different pore diameters were synthesized and, in combination of silica gel samples, were used. Pore diameters were characterized by two different methods namely nitrogen desorption and small-angle X-ray scattering. Melting of pore ice was investigated by differential scanning calorimetry measurement.Pore diameters of the12samples used here were found to vary between1.7nm and11.5nm; the melting point depression△T showed a linear dependence on the inverse pore diameter1/d; with regard to melting enthalpy depression, of several competing theoretical models, our results favor the "excluded volume" analysis by S. L. Lai et al in which the contribution of the liquid-like-layer to melting enthalpy was negligible.Since silica is hydrophilic, mesoporous polymer/carbon FDU-15samples are being synthesized and characterized in order to study the influence of interface properties on ice melting and its size dependence.