691 ISSN 2075-1133, Inorganic Materials: Applied Research, 2021, Vol. 12, No. 3, pp. 691–699. © Pleiades Publishing, Ltd., 2021. Russian Text © The Author(s), 2020, published in Fizika i Khimiya Obrabotki Materialov, 2020, No. 3, pp. 19–30. Effect of Boehmite Nanoparticles on the Structural, Corrosion, and Diffusion Properties of Microarc Biocoatings V. V. Chebodaev a, b, *, N. N. Nazarenko a, **, M. B. Sedelnikova a, ***, S. V. Gnedenkov c, *****, V. S. Egorkin c, ******, S. L. Sinebryukhov c, *******, and Yu. P. Sharkeev a, b, **** a Institute of Strength Physics and Materials Science, Siberian Branch, Russian Academy of Sciences, Tomsk, 634055 Russia b National Research Tomsk Polytechnical University, Tomsk, 634050 Russia c Institute of Chemistry, Far Eastern Branch, Russian Academy of Sciences, Vladivostok, 690022 Russia *e-mail: vtina5@mail.ru **e-mail: nnelli@ispms.tsc.ru ***e-mail: smasha5@yandex.ru ****e-mail: sharkeev@ispms.tsc.ru *****e-mail: svg21@hotmail.com ******e-mail: egorkin@ich.dvo.ru *******e-mail: sls@ich.dvo.ru Received June 4, 2019; revised August 5, 2019; accepted January 13, 2020 Abstract—The results of studying the morphology, porous structure, and corrosion and diffusion properties of boehmite-containing calcium phosphate coatings formed by microarc oxidation on titanium substrates are presented. Boehmite nanoparticles obtained as a result of the AlN hydrolysis were deposited on the surface of microarc coatings with a developed relief. With an increase in the duration of the preliminary ultrasonic treatment (UST) of the AlN suspension in the interval of 20–60 min, the size of agglomerates of boehmite nanoparticles on the coating surface is decreased from 200 to 40 μm. The surface porosity of the modified coatings and the area occupied by boehmite particles are decreased from 36 to 33% and from 27 to 10%, respectively. Agglomerates with boehmite nanoparticles after 60 min of UST of an AlN powder suspension are distributed in the coating more uniformly than after 20 min of treatment. When the duration of UST of the initial suspensions is increased, the effective diffusion coefficients of the model biological f luid in porous coatings is decreased from 7.98 × 10 –11 to 7.25 × 10 –11 m 2 /s. Modification of calcium phosphate coatings with boehmite nanoparticles by varying the duration of UST of AlN powder increases the corrosion resistance of the surface layers. Keywords: boehmite, ultrasonic treatment, effective diffusion coefficient, porosity, microarc oxidation, cal- cium phosphate coating, commercially pure titanium VT1-0 DOI: 10.1134/S2075113321030072 INTRODUCTION Currently, there is a need in medicine to create bio- materials capable of replacing lost or damaged tissues in the human body. When developing materials for bone implants, special attention is paid not only to the mechanical properties of replacing fragments of the bone skeleton but also to the interaction of the implant material with the surrounding biological tissues and fluids [1]. Therefore, it is necessary to take into account the morphological features of the surface lay- ers of the introduced biomaterial, their chemical com- position, wettability, and electrochemical and electro- physical properties [2, 3]. Owing to its good biocom- patibility and acceptable mechanical properties, commercially pure titanium, for example, VT1-0, is a promising and widely used material for implantation. To enhance the interaction between biomaterial and living tissue, bioactive calcium phosphate (CaP) coat- ings similar in mineral composition to bone tissue are applied to titanium implants [1, 2, 4–7]. The method of microarc oxidation (MAO), as well as the method of plasma electrolytic oxidation (PEO), allows the for- mation of coatings with a developed morphological structure, into the pores of which various modifying additives can be impregnated [2, 6–11]. Thus, using MAO, it is possible to obtain composite coatings of various compositions with a given thickness, struc- ture, and functional properties and use them as corro- sion-resistant, antifriction, and biocompatible (bioac- tive) coatings [1, 2, 4–9, 11]. It is known that the surface of living cells has a neg- ative zeta potential [12, 13]; therefore, to enhance cell FUNCTIONAL COATINGS AND SURFACE TREATMENT