The effect of heat treatment on the interplanar spacing of the mesostructure during the synthesis of mesoporous MCM-41 silica

The effect of the heat treatment temperature on the interplanar spacing of mesostructures during the synthesis of mesoporous MCM-41 silica particles was investigated. The results of X-ray diffraction (XRD)-differential scanning calorimetry (DSC) simultaneous measurements and Fr-IR measurements clearly show that during the heat treatment from room temperature to 773 K the interplanar spacing of the mesostructures of the silica particles synthesized using CTAB as a template decreases slightly below 373 K and significantly at around 473 K. The former decrease is related to the disordering of CTAB in the molecular self-assemblies accompanied by an increase in the fraction of gauche conformers and the latter to the thermal decomposition of the hydrocarbon chains of the CTAB molecules. The combustion of CTAB did not affect the interplanar spacing of the mesostructures. When the heat treatment temperature was above 823 K, the sintering of silica frameworks resulted in a decrease of the interplanar spacing of mesoporous MCM-41 silica particles. (C) 2009 Elsevier B.V. All rights reserved.