PREPARATION OF SNO2 SUPPORTED MEMBRANES WITH ULTRAFINE PORES

The colloidal route of the sol-gel process was used to prepare support ed SnO2 membranes. The influence of the sol and monoelectrolyte concen trations on the formation of the gel layer by sol-casting on the top o f macroporous alpha-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 wer e characterized by nitrogen adsorption-desorption isotherms and scanni ng electron microscopy. The set of results show that homogeneous membr ane layers containing the smallest quantity of cracks are formed in a critical interval of sol (1.01 less than or equal to[SnO2]less than or equal to 1.4 M) and electrolyte (2.O less than or equal to[Cl-]less t han or equal to 4.0 mM) concentrations. The samples prepared from conc entrated suspensions present a lot of interconnected cracks which favo rs the peeling of the coated layer. The membranes have pores of averag e diameter of about 1 nm.