Influence of the interdependency between matrix material and pore system on the small angle X-ray scattering in ordered mesoporous materials

An in-depth analysis of the development of small angle X-ray scattering (SAXS) data of ordered mesoporous materials (OMM) upon continuous modification of the material is presented. Two cases are considered here: in situ SAXS pattern of the decomposition of MCM-41 with a 1 M solution of NaOH and the calcination of Pd/TiO2 nanocomposite material at different temperatures. In both cases the modification of the pore shapes lead to a reduction of the intensity of the mesoporous Bragg-reflection and to an increase of statistical scattering. In the latter case the crystallite size of the matrix material is the decisive factor for the order of the pore system. The results obtained here are important for the estimation of the degree of ordering of OMMs.

In situ SAXS measurements of the reaction of MCM-41 with 1M solution of NaOH: Increasing reaction time leads to an increase of statistical scattering and a loss of orderFigure optionsDownload as PowerPoint slideHighlights
► Increasing statistical scattering indicates decreasing homogeneity of pore shapes.
► Missing Bragg reflections do not necessarily indicate total destruction of the pores.
► A complete pore system description by SAXS needs Bragg and statistical scattering.
► TiO2 materials calcined at elevated temperatures show porosity and crystallinity.