High Resolution Transmission Electron Microscopy of Mesoporous MCM-41 TypeMaterials

摘要

The mesoporous silica based materials invented by scientists of the MobilCorporation have attracted considerable interest since the first scientific publications appeared in 1992. Recently a detailed mechanism was suggested how these materials can be formed via a layered intermediate. Although already in the first publications transmission electron micrographs have been published, it is yet not clear whether the pore shape is hexagonal or round. A model describing the intensities of the X-ray diffraction patterns is favoring a hexagonal pore shape. This was, however, not confirmed by other techniques. Here we present for the first time a direct observation of the transition between the layered and the hexagonal phase which also allows to discriminate between two possible mechanisms for this transformation, as well as direct evidence of the hexagonal pore shape.