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Nucleation events in alumosilicate hydrogels of different density

Five alumosilicate hydrogels, having chemical composition adjusted for the synthesis of zeolite A, were prepared. Different density (viscosity) of the gels was obtained by changing the ratio SiO2/H2O, while the ratios Na2O/H2O and SiO2/Al2O3 remained constant. Freshly precipitated hydrogels were hydrothermally treated at 80 °C. The course of the reaction was monitored by XRD, chemical analysis, microscopy, and by thermogravimetry. Crystal size distribution curves of the end products were measured, while according curves of nuclei distribution within gel matrix and specific number of crystals were calculated. The obtained data about zeolite A nuclei formation, were commented from the viewpoint of the autocatalytic nucleation theory.

zeolite A; synthesis; hydrogel density; autocatalytic nucleation

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