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

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.