Wettability modification of titanium sheets induced by activated surface treatment

In this work, wettability properties of titanium sheets have been largely modified and controlled by a chemical activated surface treatment. The first step of surface modification, performed by a hydrogen and methane fluxing mixture activated by a hot tantalum filament, led to titanium sheets that were completely amphiphilic. Then wettability properties evolved toward different behaviors according to the post-treatment: no difference was observed if samples were put in an inert atmosphere such as N-2 or a vacuum, while a high hydrophobicity was developed if samples were exposed to air. Hydrophilicity and oleophilicity properties have been determined by water and alpha-bromonaphthalene contact angle measurements, respectively. Modifications induced have been characterized by X-ray photoelectron spectroscopy and have shown that our treatment induces a carburization of the titanium surface. Moreover, we found that the hydrophobic character, developed only in the presence of oxygen, is due to a partial reoxidation of the surface, which probably makes the surface less polar with respect to the untreated surface.