Effect of Al- and Si-containing precursors on the structures formed by sol–gel methods

Abstract

The main aim of the present work was to study the effect of various Al- and Si-containing precursors on the gel structures prepared by sol–gel methods. The purpose of the investigations of the effect of aluminum nitrate, chloride, and isopropoxide was to form a homogeneous aluminosilicate gel structure with high Al incorporation and to get optically clear, bulk gel samples. The selection of aluminum acetate and sodium metasilicate has been realized considering the point of view of environmental protection and industry. The chemical bond systems have been investigated by 27>Al and 29>Si (cross-polarization) magic-angle spinning nuclear magnetic resonance spectroscopy and Fourier transform IR spectroscopy. Small-angle X-ray scattering measurements were used for the study of supramolecular structures. The high Al content and the special structure of the samples provide the aluminosilicate systems prepared by new sol–gel methods with new, unique properties (e.g. piezoelectricity, high porosity, low density, and low thermal conductivity) that are not obtainable with conventional Al- and Si-containing ceramics or glasses.