Principles of structure formation and synthesis models produced by the sol–gel method SiO2–MexOy nanocomposites

Here we examine the essential features of the formation produced by the sol–gel method SiO2–MexOy nanostructured materials. The most perspective areas of application of these composites are revealed. A unified model, which allows analyzing the evolution of aggregates in the sol–gel is developed. It is based on the theory of fractals, the experimental data of the hydrolysis and the laws of coagulation. We have shown that in the early stages cluster formation processes are described by a model of diffusion-limited aggregation, the product of which are quasi-spherical fractal aggregates. In further aggregation of the sol, the possible formations are the labyrinthine structures, which are the products of spinodal decomposition and astringent percolation cluster. Spinodal decomposition can be achieved in both of the ways — by cooling the sol and by “chemical cooling”, meaning polycondensation. It is revealed that the functionality of the monomers derived from the hydrolysis process is one of the main factors affecting the nano-structure of the composites.