Preparation of SnO2 supported membranes with ultrafine pores

The colloidal route of the sol-gel process was used to prepare supported SnO₂ membranes. The influence of the sol and monoelectrolyte concentrations on the formation of the gel layer by sol-casting on the top of macroporous α-Al₂O₃ support was described. The stability of the colloidal suspension as a function of the concentrations was analyzed from creep-recovery measurements. The calcined supported membranes were characterized by nitrogen adsorption-desorption isotherms and scanning electron microscopy. The set of results show that homogeneous membrane layers containing the smallest quantity of cracks are formed in a critical interval of sol (1.0<-[SnO₂]<-1.4 M) and electrolyte (2.0<-[Cl⁻]<-4.0 mM) concentrations. The samples prepared from concentrated suspensions present a lot of interconnected cracks which favors the peeling of the coated layer. The membranes have pores of average diameter of about 1 nm.