Anti-reflective and anticorrosive properties of laser-etched titanium sheet in different media

The effects of femtosecond laser etching in different media (air, deionized water, and anhydrous ethanol) on the morphology, anti-reflection, and anticorrosion of titanium sheet surface were studied. Ripples, ripples overlapped by grooves and micro-bumps, were, respectively, obtained by laser etching in the air, ethanol, and water. Compared to the untreated titanium, on the surface of titanium sheet, Ti6O and Ti3O are obtained by laser etching in water, but Ti6O was obtained by laser etching in ethanol. The reflectivity of laser-etched Ti surface in ethanol or water is reduced to less than 17% within the 200 nm–1200 nm spectral range. The etched surface in ethanol shows better reflectivity in the ultraviolet–visible range with a minimum value of 3%, and the etched surface in water exhibits better anti-reflection performance in the near-infrared spectral range 800 nm–1200 nm with the lowest value of 7.6%. The differences of anti-reflection are ascribed to the competition between the light trapping effects and the effective medium effect. Furthermore, the anticorrosion property of titanium is also improved by laser etching in water or ethanol. Ecorr of the laser-etched samples is about 0.05 v higher than that of untreated Ti, while Icorr is reduced by about 0.5 order of magnitude. The better anticorrosion is mainly due to the improved hydrophobicity in 3.5% NaCl solution. The improvement of these properties allows titanium to have more important application value in solar collector panels, optoelectronic devices, thermal photovoltaic power generation, and so on.