Sol-gel mono- and poly-component nanosized powders in the Al2O3-TiO2-SiO2-MgO system

Sol-gel processes allow for the synthesis of powders with a more elaborate structure from the point view of composition, purity, size, and size distribution. In the powder case, sol-gel refers to processing in a liquid medium to obtain a solid, which does not settle under gravity due to the formation of a diffuse network structure (the gel) comprising interparticle contacts. In the presence of water, the precursors undertake the following succession of transformations: hydrolysis --> polymerisation --> nucleation --> growth. Sol-gel monocomponent Al2O3, TiO2, MgO, and SiO2 powders as well as polycomponent powders in the Al2O3-TiO2-SiO2-MgO system have been obtained and have been characterized by x-ray diffraction (XRD), IR-spectroscopy, DTA/TG analysis, transmission electron microscopy (TEM), and BET specific surface area methods. Amorphous and nanosized powders with a tendency towards aggregation have been obtained. In the case of binary and ternary powders the dimension of the particles decreases and the specific surface area increases. The great value of specific surface area and the tendency towards crystallization underlines the high reactivity of these powders. Such powders may be used as pigments, catalysts, supports in chromatography or as raw materials for advanced polycrystalline ceramics.