Tunable coloring via post-thermal annealing of laser-processed metal surface

Abstract

Thermal annealing is performed as a post treatment to tune the color generated by pulsed laser processing of a titanium substrate surface. A comparison of the reflectance spectra before and after thermal annealing shows the peak shift, as well as an increase in overall reflectance, which demonstrates that the color hue changes and the lightness of color increases. Microscope image shows that additional blue and yellow colors on the titanium surfaces are generated through the thermal annealing treatment. Further analyses show that the rate and area of the color shift depend on the annealing temperature and duration. Chemical composition analyses reveal that a TiO2 layer is generated after the laser processing of the titanium surface. Post-thermal annealing causes further oxidation and generates Ti2O3. The tuning process and mechanism behind it are discussed.