Novel Non-Hydrolytic Sol-Gel Route to Metal Oxides

Monolithic alumina and aluminosilicate gels have been prepared using a novel sol-gel process based on the non-hydrolytic condensation reaction between a metal halide and a metal alkoxide. XRD indicated that the alumina gel remained amorphous at 750 degrees C; solid state Al-27 NMR indicated the presence in the dried gel and in the amorphous calcined sample of a large amount of pentacoordinated aluminum atoms. A study of the sol formation using liquid state Al-27 NMR suggested that the gel structure was reminiscent of the oligomeric structure of the chloroisopropoxide precursors. Differential thermal analysis and XRD indicated that the aluminosilicate gels were converted to mullite below 1000 degrees C, suggesting a high degree of homogeneity in these precursors.