PREPARATION AND SIZE DISTRIBUTION OF POROUS SILICA:THE ROLE OF CATALYSTS
多孔SiO2凝胶玻璃的制备及孔径控制

orous silica gel glass was prepared by sol-gel process from tetraethoxysilane (TEOS). The principal catalytic mechanisms and effects of different types of catalysts such as HCl, HF, HNO3, NH3.H2O on pore size distribution were studied. Ammonia catalyzed gel particles exhibited spherical shapes, while the glass had large pore size due to nucleophilicsubstitution of hydroxyl ions. Gels catalyzed by hydrochloride acid had smaller pore radius and the gel glass was condensed from irregular chain particles due to electrophilic reaction of hydroniums. Hydrofluoride acid catalyzed gels exhibited the largest pore radius due to nucleophilic reaction of fluorine ions. With the increase of fluorine ion concentration, pores changed from those with narrow necks and large abdomens to cylindrical pores, consequently gel particles varied from irregular chains to spherical particles.