Study of Various Properties of Silica Gel by Positron Annihilation

摘要

The lifetimes ofohyphen;positronium in silica gel adsorbed with various amounts of water,nhyphen;hexane, or nitromethane were measured. The fraction ofohyphen;positronium escaping the condensed phase can be related to the specific area and the pore volume of the silica gel. The mean life ofohyphen;positronium in the pores is found to be very sensitive to the surface properties of silica gel. The formation of free radicals on the surface of silica and the reactions between these free radicals andohyphen;positronium are suggested as the explanations.