Surface characteristics of anodized and hydrothermally treated titatnium with an increasing concentration of calcium ion

Abstract

Titanium is widely used as an implant material due to its good mechanical properties and the excellent biocompatibility of the oxide film on the surface. To modify the unstable oxide surface of pure titanium, plasma electrolytic oxidation was applied in this study. The electrolyte used for anodizing was a mixture of GP (glycerophosphate disodium salt) and CA (calcium acetate). In addition, a hydrothermal treatment was performed to precipitate a calcium phosphate crystal on the titanium oxide layer for bioactivity. The effect of the CA concentration of the electrolyte on the surface of titanium was investigated, with CA concentrations at 0.1 M, 0.2 M, and 0.3 M. A high concentration of CA results in a low breakdown voltage; hence many large micropores were formed on the anodized surface. Moreover, the size of the HA crystals was more minute in proportion to the increasing concentration of CA. The crystal phase of titanium dioxide was mainly anatase, and a rutile phase was also observed. As the size and/or amount of HA crystals increased, the surface roughness increased. However, the surface roughness could be decreased by fully and uniformly covering the surface with HA crystals. The corrosion resistance in the saline solution was increased by anodic spark oxidation. In addition, it was slightly increased by a hydrothermal treatment. It is considered that a more stable and thicker titanium oxide layer is formed by anodic oxidation and a hydrothermal treatment.

Bioactive and electrochemical characterization of TiO2 nanotubes on titanium via anodic oxidation

“…In the case of AN, a low voltage anodic oxidation process was used to form a thin nanotube oxide layer (under m size, as shown in Fig. 2) to increase the surface area and promote cell growth instead of the high-voltage anodic oxidation process that is normally used to enhance the corrosion resistance [20,23]. Therefore, the thin nanotube structure formed by the AN process has an unstable amorphous structure due to the formation of a TiO 2 oxide layer and its dissolution by F − ions as the anodizing time increases [23][24][25][26][27][28][29].…”

“…F − ions then continuously attack the pits to form pores. Eventually, the pores are converted into tubes [20,[23][24][25][26][27]. In other words, breakdown sites formed randomly on the oxide layer in the early anodizing stage form a porous structure due to dissolution by F − ions.…”

Processing Ti-25Ta-5Zr Bioalloy via Anodic Oxidation Procedure at High Voltage

“…Several studies have shown that the use of a voltage higher than the breakdown voltage can result in the formation of micropores several micrometers in diameter on the surface of materials, and ions contained in the electrolyte solution can be adsorbed onto the inside of the porous oxide layer. [30][31][32] The thickness of the titanium alloys oxidized layer increased with increasing anodic oxidation voltage. [33] Sul et al [34] performed anodic oxidation for titanium with sulfuric acid, acetic acid, phosphoric acid, calcium hydroxide, sodium hydroxide, and other electrolyte solutions, and they found that the thickness of the oxide layer differed according to the type and composition of electrolyte solution.…”

Effects of anodic spark oxidation by pulse power on titanium substrates

“…The purpose of most surface modification methods is to increase the mechanical binding ability with the bone after implantation in the body or to change the chemical components on the surface to induce stable binding with the in vivo biochemical components and to improve osseointegration 2–6. Among the many surface modification methods, anodic spark oxidation can satisfy simultaneously the above‐mentioned advantages; therefore, many researchers have been carrying out studies on anodic oxidation 7–19. Anodic oxidation is a type of electrochemical treatment method using titanium, aluminum, and other base metals, such as the anode, and forms an oxide layer on the surface of the substrate metal electrically.…”

“…Park et al reported that the concentration of electrolyte solution affected the breakdown voltage on using GP (glycerophosphate disodium salt hydrate) and CA as the electrolyte solution. In addition, the surface morphology was also changed at the different breakdown voltages owing to varied concentrations of the electrolyte, even if anodic spark oxidation was performed at the same anodizing voltage 17. Moreover, it was reported that the surface characteristics and the thickness of the oxide film became different during anodic oxidation using a constant electrolyte solution with a varying anodic oxidation voltage 18.…”