CONTROLLING MICROMORPHOLOGY OF SILICA GELSBY UNIDIRECTIONAL FREEZING AND FREEZE DRYING

摘要

Unidirectional freezing and freeze drying were applied to a wide variety of silica gelprecursors: from hydrosols to thoroughly aged hydrogels. Porous silica gels with 3 kindsof morphologies (lamella, flat fiber and microhoneycomb) were prepared fromunidirectional freezing of hydrosols. On the other hand, porous silica gels prepared byunidirectional freezing of hydrogels had 3 kinds of morphologies (microhoneycomb,fiber with polygonal cross-section and powder). The morphologies of silica gels preparedwere mapped for the gelation time, the aging time and the delay time determined fromdynamic light scattering (DLS) measurements of silica hydrosols. The morphology ofsilica gel can be controlled by using the proposed map.