Micro-porous silica-yttria membrane by sol-gel method: Preparation and characterization

Micro-porous yttria doped silica membrane, fabricated on alpha-alumina substrate and gamma-alumina interlayer, has been prepared via the polymeric sol-gel method. In order to investigate the hydrothermal stability of the membrane, silica sols with different amounts of 5, 15 and 25 wt% yttria were prepared. These sols showed particle size distributions in the range of 0.6-3 nm. It was found that the hydrothermal stability of the unsupported silica-15% yttria membrane heat treated at 500 °C is the highest according to the results of FTIR analysis showing the formation of Si-O-Y bonds. XRD data showed thermal stability up to around 800 °C for the unsupported silica membrane with 15% yttria. N2 adsorption-desorption isotherm confirmed the existence of micro-porous structure for this membrane as BET surface area and average pore size of the unsupported membrane was 286 m2g−1 and 1.9 nm, respectively. Modified substrate surface reduced average roughness and a layer with similar roughness and pore size was achieved. Cross sectional images by FESEM showed the thickness of 680 nm for the obtained membrane.