Ceramic nanofilters is nowadays exposed to great attention in different industrial applications.In this work, the combind alumina-titania nanofilters were produced with sol-gel method. Different parameters affecting the of substrate characteristics and nanometer coating were studied. Alumina substrates were produced with slip casting method using different amounts of alumina powder, binder, dispersant and sintering temperature. The effect of slip milling on the quality and size of substrate particles and pores were studied. Taguchi method was used in this study to reduce the number of required experiments. The optimum substrate produced was coated with titania by sol-gel process and dip coating. In this step, the effects of ratio of hydrolyze (water to alkoksid ratio); pH, dip coating time and the number of layers were studied. Characterization of substrate and coating samples was performed by SEM, XRD, XRF, laser particle size analyser and mercury porosimetry. The primary results showed that slip milling before casting resulted in a considerable reduction in the average size of particles and pores of alumina substrate. It was found that the suitable conditions for producing the alumina substrate were 20% powder, 300 ml poly vinyl alcohol binder for 100 gr alumina, slip milling for 30 minutes and sintering temperature at 1500 ? C. Under these conditions a substrate without any crack with the average pore size of 268 nm, 8% surface porosity and 36% open porosity was produced. Also a stable Titania sol was produced with hydrolyze ratio of 30 and pH = 1.9. The best dip coating conditions were recognized as having two steps, with the entering and with drawling velocity of 18 mm/min and the dip coating times of 1 minute for the first stage and 30 seconds for the second one. Under such conditions, a uniform coating without any crack with the average size of 4-7 nm and a thickness of 600 nm on the alumina substrate was prepared. The combined alumina-titania nanofilter can be successfully nead as a proper membrane for industrial application.
