Some recent developments in aqueous sol-gel processing

In this overview we describe the recent use of aqueous sol-gel processing f or the preparation of ceramics that have very different end-uses. Zirconia nanofiltration membranes with 50% rejection of solutes at a molecular weigh t of about 1000 have been produced using zirconia sols containing inorganic polymeric "particles" and evaluated on the pilot-plant scale. Microporous alumina- and zirconia-pillared clays having a large and hydrothermally stab le interlayer spacing (2 nm) and specific surface area (approximately 400 m (2) g(-1)) have been prepared using similar polymeric sols. These have been produced on the 20 kg scale and evaluated for catalytic applications. Cath odoluminescent phosphor powders, based on the doped-yttrium aluminium galli um oxide system, have been synthesized for high resolution displays using a combination of aqueous sol-gel precursors and aerosol techniques to produc e particles of controlled size and shape. Finally, ceramic stains for decor ating ceramic bodies have been synthesized using this method, not only in p owder form but also for direct application to ceramic ware by ink-jet print ing. These examples illustrate the versatility of aqueous sol-gel processin g for the preparation of a wide range of ceramic compositions and forms.