Deposition of metals into the porous structure of aluminum oxide
Authors:   North Caucasian Institute of Mining and  Metallurgy (State Technological University), Kozyrev Evgeniy , ASKEROV Roman ,   North Caucasian Institute of Mining and  Metallurgy (State Technological University), SABANOV Vladimir ,   North Caucasian Institute of Mining and  Metallurgy (State Technological University), GORDEEV Georgy ,   North Caucasian Institute of Mining and  Metallurgy (State Technological University)
Published: March 2024

Introduction. Nanostructured porous anodic aluminum oxide is used as a matrix, where it is often necessary to introduce impurities of various metals into its structure. In this case, an effective solution is the electrochemical deposition of metals into the pores of anodic aluminum oxide. However, metals can be deposited on the cathode from aqueous solutions of salts in which the electrode potential is electronegative and less than the potential for hydrogen evolution in solutions. Materials and methods. The anodizing process takes place in two stages: preliminary anodizing and anodizing itself. Before preliminary anodization, experimental samples were coated with a chemically resistant varnish for separation between the electrolyte and air. Then the samples prepared in this way were dried for 4–6 hours, after which the second stage of anodization was carried out. Results. It has been revealed that substrate inhomogeneities can be reduced by slowing down the oxide growth process or by using pore blanks. Using similar methods, a highly ordered structure can be achieved. A more dense arrangement of pores can be achieved through the use of strong acids, forming a barrier layer of thinner thickness with more penetration paths. It is worth noting that when using such acids, the number of inhomogeneities becomes not such an important parameter. Discussion. Films were obtained with greater chemical strength and a thickness of 84-100 microns, a pore diameter of 0.15-0.3 microns. By carrying out additional etching, the pore diameter was increased to 0.6 µm. Etching of PHA can be carried out in an alkali solution in an anhydrous solution of ethyl alcohol. Also, pores can be dissolved by reanodizing in a solution of phosphoric acid. The barrier layer grows to 100 A, removal is carried out with dilute hydrofluoric acid. The resulting PHAs have a fairly porous, homogeneous structure with an average effective pore size of 0.45-0.65 μm. Conclusion. Conditions have been developed for the joint deposition of two metals from aqueous solutions at close values of their electrode potentials, such as iron and cobalt. The conditions for the deposition of copper from copper sulfate into the pores of porous aluminum oxide have been established at 25 – 70 t/l of sulfate and 7÷12% sulfuric acid. Resume. The research results can be useful in obtaining films of porous anodic aluminum oxide, which can be used as substrates for creating solar-electric energy converters based on materials with a perovskite structure. This is especially true for the Republic of North Ossetia-Alania and for the mountainous territories of the North Caucasus. The use of solar energy converters will make it possible to more efficiently electrify populated areas in mountainous areas.