Pore surface fractal dimension of sol–gel-derived Al2O3–SiO2 membranes

Pore surface roughness change in composite Al2O3–SiO2 membranes induced by chemical composition and sintering process has been investigated by the analysis of surface fractal dimension. Fractal features are analyzed from N2 adsorption–desorption measurements. It was found that an increase in the surface fractal dimension occurs while silica content increases at the composite membranes with different molar ratio of alumina to silica sintering at 600 °C. The surface fractal dimension of membrane with 40 mol% silica content slightly increases while sintering from 200 to 600 °C due to shrinkage and increase of mass fractal dimension of silica clusters, but decreases at the temperature of 800 °C, attributable to the smoothing of clusters and the collapse of pores located between clusters.