Properties of water adsorbed in porous silica aerogels

Silica aerogels have been prepared by hydrolysis and condensation of sols of composition TMOS-methanol-H 2 O with molar ratio TMOS:H 2 O=4:1 and volume ratio TMOS:methanol=0.2; 0.3; 0.4 and 0.6. Their true and apparent densities, BET surface area, total pore volume and pore size distribution have been systematically investigated as a function of densification heat treatment. The relaxation properties of water adsorbed on the highly reactive surface have been studied by dielectric and nuclear magnetic resonance techniques as a function of the H 2 O coverage (0 < ϑ H 2 O < 6) and temperature.