Effect of Oxygen Partial Pressure in Heat Treatment Atmospheres on Wettability of Titanium Surface

The effects of heat treatment in different ambient pressures or oxygen concentration on the wettability of the titanium (Ti) surface were examined. Polished titanium plates were heat-treated at various temperatures and periods in the pressure-controlled or oxygen concentration-controlled atmospheres. The wettability was evaluated by water contact angle measurement. The X-ray photoelectron spectroscopy was performed on the heat-treated and stored Ti surface to analyze adsorbates and surface products. The heat-treated Ti in the atmospheric air became hydrophilic due to the desorption of hydrocarbons on the surface. Then, the adsorption of hydrocarbons during storage in the atmospheric air returned its wettability to that before heating. On the other hand, the heat-treated Ti in a vacuum (low ambient pressures) or low oxygen concentration became hydrophobic due to an increase in the CH/OH (hydrocarbon/hydroxyl group) ratio on the surface. The wettability of hydrophobized Ti retained its wettability during storage in the atmospheric air.