A versatile TiO2/ZrO2 nanocomposite coating produced on Ti-6Al-4V via plasma electrolytic oxidation process

Abstract

In this work, ZrTiO4/TiO2 composite coatings were synthesized via plasma electrolytic oxidation process, representing multifunctional applications ranging from corrosion resistance to photocatalytic performance. We produced ceramic coatings on Ti-6Al-4V alloy under different current density conditions (2, 4, and 6 A/dm2) with an electrolyte containing Na3PO4.12H2O and ZrO2 nanoparticles. Prepared coatings were analyzed through SEM, XRD, AFM, and the sessile drop technique to measure contact angle. The cytotoxicity, electrochemical, and photocatalysis behavior of coatings were evaluated using MG63 cell, Hank's physiological, and methylene blue solution, respectively. The apatite forming ability in SBF (bioactivity behavior) and the release of Ti, Al, V, and Zr of composite coating were examined for optimum coating. The pore size, thickness, roughness, and porosity percentage increased with ascending the current density from 2 to 6 A/dm2, whereas the wettability of oxide coatings decreased moderately. ZrO2 nanoparticles were experienced reactive incorporation to the coating during PEO process, resulting in the formation of ZrTiO4 phases. The in vitro corrosion resistance and MG63 cell response indicated that the increment in current density has detrimental effects on electrochemical behavior and cell attachment of PEO-treated coatings. The apparent constant rate of MB photodegradation in the presence of the Zr3CD2 coating was about 3.15 times faster than the PEO coating without ZrO2 nanoparticles produced with 2 A/dm2 current density. Moreover, although the microstructure of PEO coating produced at the current density of 2 A/dm2 was fruitful for the apatite phase deposition, it accelerated the Al and V ion release rather than untreated sample.