Structural characterization of water and ice in mesoporous SBA-15 silicas: II. The 'almost-filled' case for 86 angstrom pore diameter

Neutron diffraction measurements for D2O in SBA-15 silica of pore diameter 86 angstrom have been made in a temperature range from 300 to 100 K. The pore-filling factor for the liquid phase is 0.95, resulting in an `almost-filled' sample. The nucleation and transformation of the ice phase were determined for cooling and warming cycles at two different rates. The primary nucleation event at 258 K leads to a defective form of ice-I with predominantly cubic ice features. For temperatures below the main nucleation event, the data indicate the formation of an interfacial layer of disordered water/ice that varies with temperature and is reversible. The main diffraction peak for the water phase shows similar features to those observed in earlier studies, indicating enhanced hydrogen bonding and network correlations for the confined phase as the temperature is decreased. A detailed profile analysis of the triplet peak is presented in the accompanying paper (Seyed-Yazdi et al 2008 J. Phys.: Condens. Matter 20 205108).