SANS of ZrO2 center dot SiO2 gels

Small angle neutron scattering (SANS) measurements have been performed to investigate the nanoscale structure of materials of the system xZrO(2) . SiO2 with x less than or equal to 10 mol%, at different processing stages. The materials were prepared by sol-gel using the alkoxides method, in strong acidic conditions. Samples studied as xerogels were heat-treated at 120 degrees C and 850 degrees C; as wet gels at the gel point; and after 4 h aging at 60 degrees C. The samples showed extended linear chains ca. 10 nm long at the gel point. The aged gel has a mass fractal structure with fractal dimension of ca. 1.8. The 120 degrees C heat-treated xerogel shows homogeneous oxide regions with 16 nm average diameter and mass fractal nature. For the 850 degrees C heat-treated xerogel the oxide regions average diameter reduced to about 13 nm and presented a sharp and smooth surface, obeying the Porod law.