A mechanism-based study of the wettability transition of surface vaporization of nanosecond laser-treated titanium under various storage conditions

Surface vaporization of metals is currently receiving significant attention as a wastewater treatment technique. This article examined the wettability transition of a treated titanium surface (so-called an evaporator) under varied storage conditions. Several aspects of the transition mechanism were evaluated, including contact angles, surface chemistry, and wetting dynamics. The titanium treated surface changed significantly in wettability when exposed to ambient air, going from highly water-attracting to ultra-hydrophobic after only 40 days of storage. The experiments conducted proved that the contaminants in the air absorbed on the Ti surface are responsible for this wettability shift. We found an increase in C/Ti ratios and C-C(H) (at. %) over time, which implied a nonpolar nature and showed a hydrophobic tendency. The samples kept in nitrogen and water, on the other hand, remained in their original state. In contrast, the sample stored in an open water environment increased its contact angles slowly over time, which could have been influenced by organic matter in the air. The results of this research are not only helpful in understanding the transition mechanism of nanosecond laser-treated titanium but also provide information that the wastewater industry can implement to store evaporators to avoid the rapid transition of wettability and produce super-hydrophilic surfaces with stability and durability.