Neutron diffraction studies of water in porous silica

Neutron diffraction measurements have been made on D2O water dispersed in the porous silicas Spherisorb (pore diameter = 90 Å) and Gasil (pore diameter = 20 Å) in the liquid and supercooled liquid region (20°C to -22°C). The structural features of water in Spherisorb are found to be essentially identical to those of bulk water and the temperature variation behaves in an analogous manner until nucleation occurs at -13°C. The diffraction pattern at -15°C indicated the presence of cubic ice (I c) together with some unfrozen water. Results for water in Gasil silica show evidence for an enhanced hydrogen-bonding compared with that of bulk water. These enhanced interactions were maintained into the supercooled region which extended to -22°C.