Bioactive titania gel layers formed by chemical treatment of Ti substrate with a H2O2/HCl solution

An amorphous titania gel layer was formed on the titanium surface after the titanium specimen was treated with a H2O2/0.1 HCl solution at 80°C. The thickness of the gel layer increased almost linearly with the period of the treatment. A subsequent heat treatment above 300°C transformed gradually the amorphous gel to the anatase crystal structure and the rutile started to appear after heat treatment at 600°C. Meanwhile, the densification of the gel occurred significantly after heat treatment above 700°C. Similar to the sol–gel derived titania gel coatings, titania gel layers obtained in the present study exhibited in vitro apatite deposition ability after the gel layers exceeded a minimum thickness (0.2 μm) and was subsequently heated in a proper temperature range (400–600°C).