Easy conversion process of titanium surface covered with passive film into functional surface

摘要

abstract_textpSurface functionalization of titanium metal is of great interest, especially as the conversion of the surface passive film into objective functional film can be widely used in bio- and environmental applications. However, since the surface passive film is very stable, the functionalization (such as conversion into photocatalytic anatase-TiO2) has been performed using relatively complicated processes, for example, hydrothermal reaction and anodic oxidation. This is because direct oxidation of titanium metal only leads to thermodynamic formation of octahedral-rutile-TiO2 in the entire temperature region, while chemical synthesis using precursors can easily produce tetrahedral-anatase-TiO2 at 600 degrees C or less. Here, we report a simple process for the direct formation of photocatalytic anatase-TiO2 on titanium by simple oxidation. In the first step in our process, titanium is treated with a reducing agent to create a surface titaniumhydride layer. After that, the treated titanium covered with titaniumhydride is immerged in aqueous silica; subsequent calcination at 900 degrees C (specific temperature) in air effectively generates the surface anatase-TiO2 layer. This is because the covered tetrahedral-silica stabilizes the anatase structure that is formed. The covered silica is easily removed by quenching in water to reveal the photocatalytic surface layer composed of anatase-TiO2./p/abstract_text