In Situ Synchrotron Small-Angle X-ray Scattering/X-ray Diffraction Study of the Formation of SBA-15 Mesoporous Silica

Abstract

The initial stages of the formation of SBA-15 have been studied by in situ SAXS/XRD using synchrotron radiation. Modeling of both the diffuse scattering and the X-ray diffraction patterns obtained at different stages of the reaction results in a detailed description of the different reaction steps. The first step in the formation is the liquid-liquid phase separation of spherical P123-silicate hybrid micelles after which nucleation and growth of the 2D hexagonal phase occurs. Two-dimensional electron density maps calculated on the basis of the intensities of the Bragg reflections suggest that changes in the degree of intermicellar condensation are responsible for the time-dependent observations. The silica source (alkoxysilanes) may be partially unhydrolyzed long after formation of the hexagonal structure, since the kinetics of the mesophase evolution is notably slower when TEOS is used as the silica precursor as compared to TMOS. The results obtained for SBA-15 are compared with other published data on the formation ofSBA-15 and of the smaller pore MCM-41 materials.

Three-dimensional periodic complex structures in soft matter: investigation using scattering methods

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Expanding mesoporosity of triblock-copolymer-templated silica under weak synthesis acidity

“…Several events occurred during the induction period, including individual aggregate formation, floc formation and precipitation [49][50][51]. From the beginning, the silica species begin to adsorb on the hydrated PEO shell of the Pluronic micelles, forming individual micelles coated with silica [52].…”

Time-Resolved in Situ Raman and Small-Angle X-ray Diffraction Experiments: From Silica-Precursor Hydrolysis to Development of Mesoscopic Order in SBA-3 Surfactant-Templated Silica

“…Short acquisition times and adaptable experimental setup made it the most-used technique in time-resolved [8][9] and even temperature-resolved 10-11 in-situ experiments. Nevertheless, acquisition times obtained with low energetic X-ray sources are not compatible with time-resolved requirements, as it was already shown in 1998 by Lindén et al 12 ;…”