Satoshi Hayakawa

Porous titania films prepared from interactions of titanium with hydrogen peroxide solution

Abstract Anatase films with sub-micron porous structure were deposited homogeneously on Ti substrates by simply soaking in 15 wt.% hydrogen peroxide solution at 80 °C for 1 h followed by heating at 300 °C for 1 h in air. Deposition of the porous titania film was not sensitive to substrate morphology, whilst affected readily by the reaction rate.

In vitro bioactivity of anatase film obtained by direct deposition from aqueous titanium tetrafluoride solutions

Abstract Well-crystallized anatase films were deposited on commercially available pure titanium substrates from an acid titanium tetrafluoride aqueous solution kept at 60 °C for 24 h. The anatase films consisted of dual layers that were different in topography: a dense inner layer strongly adhered to the Ti substrate and a porous outer layer. In vitro bioactivity of such films was evaluated by soaking them in a simulated body fluid (SBF) of the Kokubo solution to observe their ability to induce apatite deposition. The anatase films with a subsequent thermal treatment at a temperature range of 300–700 °C induced apatite deposition within 5 days. Apatite particles were also found to deposit within 7 days on the anatase films being heated at 800 °C, which involved much rutile due to direct air oxidation of the titanium substrate. When the heating temperature is lower than 200 °C, no apatite deposited on the films even after 10 days of soaking in the SBF solution. The improved in vitro bioactivity of the films subsequently heated over 300 °C was attributed to the elimination of fluorine.

Soft solution approach to prepare crystalline titania films

Abstract Titania films with crystal structures of anatase or a mixture of anatase and rutile were prepared through a soft solution approach. The crystalline titania film resulted from crystallization of the previously deposited amorphous gel in an acidic solution. A low pH value of the solution favored the formation of rutile.

Low Temperature Deposition of Bioactive Crystalline Titania Films: Effects of Tantalum

Introduction Surface modification of commercially available pure titanium (cpTi) to induce apatite deposition when implanted in human body attracted continuous attention. Ohtsuki et al. reported that titania gel derived from interactions between titanium and H2O2 solutions containing TaCl5 initiated and formed apatite while soaked in a simulated body fluid (SBF) of Kokubo solution [1]. Wang et al. shortened successfully the apatite induction time through heating the amorphous titania gel at 400 °C for 1 h in air, which resulted in a layer with anatase as the predominant phase [2]. The apatite deposition ability of titania layers is ascribed to both the crystalline phase (anatase) and the abundant of Ti-OH groups. Thermal treatment applied to induce crystallization of the amorphous titania gel is supposed to cause loss of the Ti-OH groups and hence inhibit apatite deposition. We recently reported crystallization of the amorphous titania gel by hot water treating instead of hightemperature heating [3]. In this paper, we focus on effects of tantalum on the low-temperature crystallization process of the bioactive titania films.

Apatite Formation on Electrochemically Treated Titanium

A titanium oxide gel was electrochemically prepared on Ti with a cell consisting of Ti as the working electrode, Pt as the counter one, AgCl as the reference one, and an aqueous solution of 0.1 mol/L Ca(NO(3))(2) as the electrolyte solution. The Ti electrode was kept at 9.5V for 1 hr for oxidation and subsequently kept at-3.0V for 10 min (Ca9.5-3.0):calcium ions were expected to be adsorbed at the latter treatment. Other Ti specimen was kept at -3.0V for 10 min (Ca-3.0). Both specimens were found so bioactive as to deposit apatite in 12 hr (Ca9.5-3.0) and in 1 day (Ca-3.0) when soaked in a simulated body fluid (Kokubo solution). Calcium carbonate detected on the surface of Ca9.5-3.0 caused no harmful effects on spontaneous deposition of apatite in the fluid.