Laser-assisted selective and localized surface transformation of titanium to anatase, rutile, and mixed phase nanostructures

Titanium dioxide (TiO₂) has been a key material in a wide range of applications such as catalysis, energy harvesting, and antibacterial surfaces. Typically, different TiO₂ phases are first synthesized and then coated onto the test parts. Here, the authors demonstrate a direct method for the formation of TiO₂ nanostructures and patterns with rutile, anatase, and mixed phases by a controlled laser-assisted surface modification approach on additive manufacturing titanium parts. A tunable nanosecond fiber laser coupled to a galvo scanner was employed to regulate the laser material for a controlled and localized transformation process in an oxygen environment. The influence of processing conditions such as scanning speed, laser power, laser pulse duration, frequency, and gas flow rate on the selective formation of rutile, anatase, and mixed phases was studied. The structural evolutions and morphology have been investigated using different characterization techniques, including scanning electron microscopy and Raman spectroscopy methods. The main advantage of this laser-assisted process is its ability to create selective TiO₂ phases on complex titanium parts such as implants.