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In this study, nanotube morphology changes of Ti- x Ta-Ag-Pt alloys with Ta content for biomaterials were researched using various experimental instruments. Ti- x Ta-Ag-Pt alloys were manufactured in an Ar atmosphere using a vacuum arc-melting furnace with Ta contents of 10 and 50, and then heat-treated at 1100 °C for 1 hr. Nanotube formation of Ti- x Ta-Ag-Pt ( x = 10, 50 wt%) alloys were performed using a DC power of 30 V in 1.0 M H₃PO₄ + 0.8 wt% NaF electrolyte solution. Surface characteristics were investigated using an optical microscope, X-ray diffractometer, field-emission scanning electron microscope, energy-dispersive X-ray spectroscopy, and Image analyzer (Image J). Ti-10Ta-Ag-Pt alloy had a needle-like structures, and Ti-Ti-50Ta-Ag-Pt showed the mixed structure (equiaxed and needle-like structures). As the Ta content increased, the α -phase decreased and the β -phase increased. The highly ordered nanotubes were formed on the β -phase, whereas disordered nanotubes were formed on needle-like structure of α -phase in Ti-10Ta-Ag-Pt alloy. As the Ta content increases, large and small nanotube diameters became smaller in size. Anatase and rutile phases were formed on the alloy surface. Ta, Ag, and Pt elements were uniformly distributed over the entire surface and at the edge or inside of the nanotube.

Surface modification of dental implants or orthopedic implants is important for biocompatibility, and Ti-6Al-4 V alloy is mainly used as implant material for clinical use. In particular, research on the formation of nanotubes for drug doping to improve biocompatibility is in progress. For the control of nanotube shape, in this study, nanotube shape changes on Ti-6Al-4 V alloy via various applied potential for bio-implants were researched using various instruments. The formation of nanotubes on the surface of the Ti-6Al-4 V alloy was performed using a DC power source as a two-electrode system, and platinum as a counter electrode and a working electrode as an anode. The electrolyte was 0.8 wt. % NaF solution and 1.0 M H3PO4 were used and mixed using a magnetic bar during anodization. At this time, the voltage applied when forming the nanotubes was varied as (10 → 20 → 30 V), (30 → 10 → 30 V), and (10 → 30 → 30 V), respectively, and these voltages were applied for 30 min for each step. After the formation of nanotubes, the surface morphology and structural properties of the samples were observed using field-emission scanning electron microscope, X-ray diffractometer, Fourier transform infrared spectroscopy, and nanoindentation tester. The higher the voltage applied during the formation of nanotubes, the larger is the diameter. In the case of the nanotube (10 → 20 → 30 V), the top of the nanotube was narrow and the diameter increased toward the bottom, forming a cone shape. In the case of the nanotube (30 → 10 → 30 V), a narrow waist shape was formed, and in the case of the nanotube (10 → 30 → 30 V), a jar shape was formed with anatase and rutile phases. From the FT-IR results, when nanotubes are formed, TiO2 anatase was detected and showed the tendency to change from crystallization to amorphous state. The indentation hardness and elastic modulus decreased for the nanotube surface compared with those of the bulk Ti alloy. [ABSTRACT FROM AUTHOR]

In general, Ti alloys are commonly used as biomaterials for implants. However, in the case of such alloys, the high elastic modulus causes stress shielding effects and bacterial growth, reducing their biocompatibility. In order to improve it, new alloys composed of Ti–Nb–Ag–Pt were developed in this study because it is possible to reduce the elastic modulus by adding an alloying element, such as Nb, and to reduce the bacterial activity by adding Ag and Pt elements. The following studies were conducted with the aim of manufacturing and forming nanotubes on the surface to greatly improve the biocompatibility. Ti–xNb–Ag–Pt alloys were manufactured using a vacuum arc furnace in an Ar atmosphere, homogenized for 1 h at 1050 °C, and then quenched at 0 °C. The formation of nanotubes on the surfaces of the alloys was performed using the anodization method with an applied voltage of 30 V in 1 M H3PO4 + 0.8 wt% NaF for 1 h at 25 °C. The formed nanotube surfaces were analyzed by optical microscopy, field emission scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, nanoindentation tests, and antibacterial tests. Antibacterial activity was evaluated according to the ISO 22196:2007 method, for which S. aureus (NBRC122135) was used. The microstructure of Ti–10Nb–Ag–Pt was a needle-like structure, and Ti–50Nb–Ag–Pt presented both an equiaxed structure and a needle-like structure. The size of the nanotube diameter decreased as the Nb content increased. The Ag and Pt elements were evenly distributed on the nanotube-formed alloy surfaces. The Vickers hardness and the elastic modulus value decreased as the Nb content increased. Following the nanotube formation, the Vickers hardness and elastic modulus values decreased by thrice, and only the nanotube-formed Ti–xNb alloys containing Ag and Pt showed the antibacterial activity effect. [ABSTRACT FROM AUTHOR]

• Dental implant showed the scratches in the vertical direction made by machine. • Sandblasted surface showed the indented trace instead of mechanical scratch. • In surface by plasma electrolytic oxidation, the pore shape was different on implant parts. • Nanotubes were uniformly well-formed in the α-phase but not well in the β-phase. • The surface with pores showed low corrosion potential and high current density. In this study, the corrosion behaviors of macro/micro/nano-scale surface modifications of Ti-6Al-4V dental implant for bio-implants were investigated. For this purpose, macro/micro/nano-scale surface roughness was formed on the surface of Ti-6Al-4V alloy using plasma electrolytic oxidation (PEO), anodization, and sandblasting. Potentiodynamic and potentiostatic methods were used to investigate the corrosion behavior of the samples. The surface properties of the alloy were observed using field-emission scanning electron microscopy and X-ray diffractometry. The bulk sample exhibited scratches in the vertical direction created by the machine. The sandblasted sample showed an indented trace instead of a machined scratch. The PEO-treated sample showed different pore shapes in the screw valley, screw flank, and screw top. Nanotubes were uniformly formed in the α phase but not well formed in the β phase. In the case of nanotubes on sandblasting, the nanotubes were not well formed in the defect areas formed during the sandblasting process. In a corrosion test, the corrosion potential significantly increased with no surface treatment, whereas it significantly decreased when defects or pores were formed on the surface. The current density–time curves revealed that the sandblasted specimen showed the most unstable film behavior and in the case of the nanotube and nanotube-on-sandblasting specimens, the current density increased with time. [ABSTRACT FROM AUTHOR]

• Needle-like structure of Ti-40Nb-xZr alloys changed to equiaxed structure as Zr content increased. • Nanoindentation hardness and elastic modulus of Ti-alloys decreased as the Zr content increased. • Irregular pores were formed on the alloy surface as the applied voltage increased in the PEO process. • Surface roughness of the PEO-treated Ti-alloys increased as the applied voltage and Zr content increased. • Contact angle of the PEO-treated Ti-alloys decreased as the applied voltage and Zr content increased. In this study, the formation of micro-scale morphology on Ti-40Nb-xZr alloys was investigated under plasma electrolytic oxidation (PEO) treatment. By varying the Zr content to 0, 3, 7, and 15 wt.%, non-toxic, low-modulus alloys were prepared. PEO was then performed using a direct current power source with the sample as the anode and a carbon rod as the cathode in an electrolyte solution of 0.15 M calcium acetate monohydrate + 0.02 M calcium glycerophosphate. The applied voltage was varied from 180–380 V at a current density of 75 mA for 3 min. In the Ti-40Nb-xZr alloys, as the Zr content increased, the microstructure changed from a needle-like structure to an equiaxed structure, and the elastic modulus and hardness in nanoindentation tests decreased (from 120 to 67 GPa and 4.55 to 2.00 GPa, respectively). As the applied voltage increased during the PEO process, the pore size increased. The TiO 2 layer formed on the alloy surface contained Ca and P from the electrolyte. The surface roughness obtained from atomic force measurements was the lowest in the bulk samples (0.133 to 0.024 μm), and it gradually increased as the applied voltage increased and decreased as the Zr content increased. As the applied voltage increased, the contact angle decreased, whereas as the Zr content increased, the contact angle increased. [ABSTRACT FROM AUTHOR]