Positron and Positronium Annihilation Lifetime Studies of Pores and Free Volumes in Silica Xerogels Prepared by Sol-Gel Process

Silica gels were prepared from alcoholic solutions of tetramethyl ortho-silicate (TMOS) using an ordinary one-step hydrolysis process and positron annihilation lifetime method were applied to investigate the influences of synthetic conditions to gel structures by probing nano-pores generated in the gels. The long lifetimes associated to pore sizes are discussed in detail.