Preparation And Properties Of Ti-based Surface Micro-/Nanostructures By Femtosecond Laser Etching And Thermal Oxidation

Titanium is a very important structural metal developed in the middle of last century.It is not only widely used in aerospace because of its low density,high strength and heat resistance,but also widely used in mechanical manufacturing,chemical industry,biomedical and other fields because of its excellent properties such as high tensile strength,good chemical stability and biocompatibility.The surface properties of titanium can be modified by some traditional surface treatment techniques to improve its application value.In recent decades,as a new surface treatment technology,ultrafast laser has attracted extensive attention of researchers.Femtosecond laser microfabrication can significantly reduce the heat-affected zones when interacting with materials,thus improving the quality and accuracy of the processing because of its short pulse durations and high peak power.Femtosecond laser etching or thermal oxidation can be used to fabricate titanium surface to form micro-/nanostructures,which can improve the reflectivity,corrosion resistance,hydrophobicity and other functional properties.It has important research value for expanding the application of titanium in solar energy utilization,optoelectronic devices,anticorrosion,antifouling,aerospace and other fields.The main contents of this paper include:1.Two typical surface structures,periodic ripple structure overlapped with grooves and micro-bump array structure,were obtained by femtosecond laser etching of titanium sheets in anhydrous ethanol and deionized water environments.The formation mechanism of surface micro-/nanostructures in different media is explained by the surface plasma wave theory and the remodulation effect of initial structure on the subsequent light field.It is found that the shock wave released by bubble breakdown in liquid microfabrication plays an important role in the formation of clear structure.The anti-reflectivity,corrosion resistance and hydrophobicity of micro/ nanostructured surface were tested.The results show that laser-etched Ti surfaces in liquid have excellent surface properties.2.Thermal oxidation of Ti sheets deposited by magnetron sputtering was carried out in box furnace.The results show that nanospheres and nanowires loaded with gold particles at the top can be obtained on the surface of titanium sheets after thermal oxidation in air with Ti substrate as titanium source under the catalysis of gold particles.With the increase of thermal oxidation temperature and time,nanospheres tend to be formed.On the contrary,nanowires are easy to be formed.After thermal oxidation,the surface composition of titanium sheets changed,and all of them were transformed into Rutile titanium dioxide.3.Two kinds of micro-bump arrays covered with nanowires or nanospheres were fabricated on the surface of titanium sheets by femtosecond laser etching combined with thermal oxidation.With the increase of the laser fluence of femtosecond laser,the hierarchy of the composite structure is more obvious.With the increase of thermal oxidation temperature and time,the composite structures with nanospheres tend to be formed.On the contrary,it is more likely to generate micro-bump arrays with nanowires.Performance tests of the surface treated by the composite process show that the hydrophobicity and corrosion resistance of the micro-/nanostructures with obviously hierarchical structure have been further improved,although the anti-reflectivity of the surface treated by the composite process is weakened compared with that of the surface only etched by laser.