Water confined in silica gel and in vycor glass at low and room temperature, x-ray diffraction study

X-ray diffraction experiments on water confined in silica gel powder hydrated at 22% and 50% and in vycor glass hydrated at 25% are presented and analyzed at room temperature and down to 77 K. At room temperature, the molecular packing at the level of the first neighbors is found similar to that in bulk water, but a distortion is observed at the level of the second neighbors. At low temperature, the intensity of water confined in silica gel powder show evidence for the simultaneous presence of cubic ice and uncrystallized water. (C) 2002 American Institute of Physics.