Positronium annihilation study of surface modified silica gel particles

Positron annihilation in powder silica gel-based materials studies are presented throughout this work. The principal aim was to investigate sizes and contents of nanoporosity based on the knowledge of positronium lifetime spectra. The groups of advanced materials analyzed by Positron Annihilation Lifetime Spectroscopy (PALS) are well-proven to be excellent media to investigate positron annihilation from intermolecular meso- and nano- pores. One group is formed by a set of silica (SiO2) gel-based powders and. the other group is based on silica-alumina (SiO2- Al2O3), both of which have shown the presence of a complex combined nanoporosity of close and interconnected spaces, leading to interesting correlations among nanoporosity proper-ties, surface area and catalytic activity.