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Ti and its alloys have received wide attention in marine engineering. However, the limited anti-biofouling capability may hinder their wide application. In the present work, micro-arc oxidation (MAO) with and without the introduction of ultrasonic vibration (UV) has been conducted on metallic Ti substrate in an aqueous solution containing Na2Cu-EDTA to produce a Cu-modified TiO2 coating. Microstructural characterization reveals that the introduction of UV increased the thickness of the coating (ranging from ~13.5 μm to ~26.2 μm) compared to the coating (ranging from ~8.1 μm to ~12.8 μm) without UV. A relatively higher Cu content (~2.13 wt.%) of the coating with UV relative to the coating (~1.39 wt.%) without UV indicates that UV enhances the incorporation of Cu into TiO2. Further, both electrochemical properties and the response to sulfate-reducing bacteria (SRB) were evaluated, revealing that UV introduction endows Cu-modified TiO2 coating with enhanced corrosion resistance and antifouling capability. The present results suggest that ultrasound-auxiliary micro-arc oxidation (UMAO) obviously enhances the surface performance of Ti alloys for promising applications in marine engineering. [ABSTRACT FROM AUTHOR]

Surfaces with desirable cytocompatibility and bactericidal ability are favoured for orthopaedic implants to stimulate osteogenic activity and to prevent implant-associated infection. In this work, we creatively introduce ultrasonic vibration (UV) to micro-arc oxidation (MAO) process and explore its influence on the microstructure, corrosion property and biological responses of Zn-modified TiO 2 coating. With the introduction of UV, a uniform surface layer with homogeneously-distributed clusters could be produced as the outer layer, which possesses a fusion band with the underlying TiO 2. The microstructural modification associated with UV results in the enhanced corrosion resistance, increased adhesive strength and improved biological performances of the resultant coating relative to that with the absence of UV. Hence, the ultrasonic auxiliary micro-arc oxidation (UMAO) is regarded as a promising surface modification method to produce Ti-based orthopaedic implants of high quality. [Display omitted] • A uniform appearance is achieved by ultrasound-auxiliary micro-arc oxidation. • A fusion band enhance the adhesive strength of the coating. • Ultrasonic action benefits corrosion resistance and biological performance. • In vivo biocompatibility of Zn-modified TiO 2 coating is demonstrated. [ABSTRACT FROM AUTHOR]

As an effective antimicrobial element, the incorporation of Cu into the surface layer of metallic Ti substrate is regarded as a promising method to enhance its antifouling phenomenon. In this work, a micro-arc oxidation (MAO) process was conducted in an aqueous electrolyte containing Na 2 Cu-EDTA to produce a Cu-modified TiO 2 coating on metallic Ti. The influence of Na 2 Cu-EDTA concentrations on microstructural feature, corrosion resistance and antifouling capability of the Cu-modified TiO 2 coatings were examined. The results indicate that an increased amount of Cu could be incorporated into TiO 2 with a higher concentration of Na 2 Cu-EDTA, which also affects the micro-arc discharge events and, consequently, the morphological features of the coating. The content of incorporated Cu determines the antifouling performance of Cu-modified TiO 2 coating, which remains harmless to the corrosion resistance. • Na 2 Cu-EDTA tailors micro-arc discharge events to affect microstructure of Cu-modified TiO 2 coating. • Corrosion resistance of TiO 2 is insensitive to the content of incorporated Cu. • TiO 2 with a higher content of Cu exhibits an enhanced antifouling performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • A uniform appearance is achieved by the introduction of ultrasound. • Ultrasound stimulates the formation of an amorphous Ca, P, Cu and O-rich layer. • Ultrasound is beneficial for corrosion and biological properties of the coating. To achieve a uniform surface layer with enhanced corrosion resistance, antibacterial capability and cytocompatibility on the titanium (Ti)-based orthopaedic implant, ultrasound-auxiliary micro-arc oxidation (UMAO) was carried out on Ti substrate to fabricate a Cu-incorporated TiO 2 coating. Instead of the co-existence of central brown area and peripheral black area in the Cu-incorporated TiO 2 coating fabricated by conventional micro-arc oxidation, a uniform brownish appearance could be achieved after the introduction of ultrasonic vibration (UV). The introduction of UV also significantly modifies the elemental composition, phase component and chemical configuration of the coating, which exhibits a bi-layered structure with the porous TiO 2 as the inner layer and the amorphous Ca, P, O and Cu component as the outer layer. Finally, electrochemical measurement and in vitro biological tests indicate that the introduction of UV is conducive to corrosion resistance, antibacterial capability and cytocompatibility of the Cu-incorporated TiO 2 coating. [ABSTRACT FROM AUTHOR]

In the present work, the early-stage growth behaviour of titania on titanium (Ti) substrate during plasma electrolytic oxidation (PEO) process in an aqueous electrolyte rich in Ca and P was investigated. Microstructural characterization reveals the dramatic evolutions of morphology, porosity, phase component and chemical composition of titania during the early stage of PEO process. The PEO coating initially exhibits ultrafine pores with a completely amorphous structure after oxidation for 5 s, which displays a relatively low Ca/P ratio. With the extension of oxidation periods, titania gradually transforms to grooved morphology with an increased Ca/P ratio, which mainly consists of crystalline anatase phase. Finally, with the prolongation of oxidation period to 1 min, titania exhibits porous morphology typical for PEO coating, which comprises of both rutile and anatase crystals. Along with the prolongation of oxidation periods, the surface wettability of titania remains relatively stable whereas the corrosion resistance changes dramatically, which is closely associated with the combined effects of its porosity and thickness. The results of our present work advance the understanding of early-stage growth of titania during the PEO process, which offer theoretical guidance for the controllable synthesis of PEO coating on Ti and its alloys. • The growth behaviour of titania prior to dielectric breakdown was examined. • Titania initially displays ultrafine pores, transforms to grooved morphology and finally stabilizes as porous structure. • The initial titania is amorphous, which transforms to anatase and finally becomes the mixture of rutile and anatase. • The Ca/P ratio gradually increases with the prolongation of oxidation periods and finally reaches ~0.9. • The combined effect of porosity and thickness results in the dramatic modification of corrosion resistance in titania. [ABSTRACT FROM AUTHOR]

The hydroxyapatite (HA)-based/TiO 2 -based composite coating was produced through plasma electrolytic oxidation (PEO) method in the present work. The microstructural evolution of the composite coating was examined as a function of PEO duration. It was observed that Ca P phase initially appears at the cracks of TiO 2 -based layer in form of plates of micrometre scales after PEO duration of 5 min and then transforms to the hybrid of plates and floccules, which finally convert to clusters composed of nano-sized plates by self-assembly. After 15 min oxidation, a two-layered composite coating was revealed, including TiO 2 -based inner layer and HA-based outer layer. It is also noticed that the thickness of HA-based layer continuously increases as the oxidation period extends whereas both the thickness of TiO 2 -based layer beneath the HA-based layer and the coverage rate of Ca P phase on TiO 2 -based layer remain relatively stable at the late stage of PEO process. The microstructural variation inevitably affects the biocompatibilities and corrosion properties of the composition coatings. With the extension of oxidation periods, an increased amount of Ca P phase was produced in the composite coating, which thus results in an improved corrosion resistance due to its insulation property, hydrophobicity and physical barrier effect. Meanwhile, the enhanced biocompatibility of the composite coating could also be achieved with the prolongation of PEO duration, which is associated with the high bioactivity of Ca P phase. • The hydroxyapatite/TiO 2 composite coating has been successfully produced through plasma electrolytic oxidation. • The formation of hydroxyapatite is closely associated with cracks in the TiO 2 -based layer. • The presence of hydroxyapatite retards the growth of underlying TiO 2. • The coverage rate of hydroxyapatite initially increases dramatically and finally remains stable at approximately 80%. • An increased amount of hydroxyapatite results in an improved corrosion resistance and biocompatibility of the coating. [ABSTRACT FROM AUTHOR]