Determination of structure in oxide sols and gels from neutron scattering and nitrogen adsorption measurements

Abstract

The structural changes which occur when silica and ceria sols (containing discrete and approximately spherical particles) are progressively concentrated and finally converted into porous gels have been investigated by small-angle neutron scattering. From an analysis of radial distribution functions it is shown that the particles in the sols have a pronounced short-range order, analogous to that found in simple liquids, which predetermines the particle packing and porous structure in the gels. Together with complementary results from nitrogen adsorption isotherms, measured on several gels composed of particles having different sizes (ca. 6–80 nm), it is concluded that this porous structure is similar to that obtained with a random close packing of uniform spheres.