Phase diagram for mesoporous CTAB–silica films prepared under dynamic conditions

Abstract

Using θ–2θ and grazing incidence synchrotron X-ray diffraction experiments, the domain of existence of the different phases is established for spin-coated mesoporous silica films as a function of the surfactant/Si molar ratio and the condensation rate of the initial silica sol. These phases derive from three different micellar structures: the 3D-hexagonal structure (P6₃/mmc), formed from spherical micelles, the cubic structure (Pm3n), made up of ellipsoidal micelles, and the 2D-hexagonal structure (p6m), composed of cylindrical micelles. Electron microscopy investigations show that the organization of films is generally maintained after removal of the surfactant by calcination. However, structural distortions take place in mesoporous films as a consequence of the usual contraction during drying and calcination of films.