Precursors for the combustion synthesis of metal oxides from the sol–gel processing of metal complexes

Sol–gel processing of methanol solutions of Cu(II) acetylacetonates was used for obtaining controlled polymerization of the complex molecules. The resulting sols were evaporated and the resulting precipitate was heated until a self-sustaining combustion reaction took place. The simultaneous presence of nitrate ions and the acetylacetonato ligands resulted in a sharp combustion process, characterized by low activation temperature and intense exothermic feature. The same processing was applied to other metals and other ligands, showing that the sol–gel processing of transition metal complexes can be a simple, convenient, flexible generalization of the citrate–nitrate method for preparing precursors for the combustion synthesis of oxide powders. Moreover, the controlled sol–gel processing of the metal complex can be used as a tool for controlling the precursor structure and, hence, the morphology of the final product.