Abstract
Both single and binary inorganic oxides, and organic-inorganic hybrids have been successfully synthesised under mild reaction conditions using the non-hydrolytic sol-gel process. This alternative route to traditional hydrolytic sol-gel synthesis is based on the direct condensation reaction between metal and non-metal chlorides and various oxygen donors, such as alkoxides and ethers. Single oxides prepared were silica, alumina and titania. Combinations of the respective precursors were used to form the binary oxides, demonstrating both the generality and simplicity of this route. For the hybrid materials, the precursors were either organically-modified or an organic in-situ reaction was initiated within the inorganic system. Where necessary, iron(III) chloride was used as a catalyst and the use of volatile additives was avoided. Product yields were high (in excess of 70 wt.%) and the gels were characterised by thermogravimetric analysis (TGA), Fourier transform infra-red (IR) spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis, X-ray powder diffraction (XRD), scanning electron microscopy and solid-state 29Si nuclear magnetic resonance (NMR) spectroscopy. Studies of the calcined gels showed them to be amorphous up to at least 700°C. Clear evidence for the formation of true, crystalline binary systems was obtained only in the case of aluminosilicates. A titanium-silicon binary system gave only crystalline rutile and anatase following calcination, with no evidence for either crystalline silica or a binary oxide. BET studies on selected hybrids demonstrated the possibilities of organic templating in these materials.