Fabrication And Characterization Of Superhydrophobic Titanium Surface By Chemical Etching

Titanium and its alloys are widely used in aerospace, naval and biomedical industry due to their high specific strength, good corrosion resistance, excellent biocompatibility etc. Although many studies of super-hydrophobic performance on titanium surface have been reported, the existing fabrication methods still need further to be improved due to the requirements of specific instruments, high the experimental cost, and complicated operation etc. To this end, we proposed two simple and effective methods to fabricate superhydrophobic titanium surfaces, and investigated their anti-icing behavior and mechanical durability, the main content are as follows:(1) Superhydrophobic surface was prepared on Titanium substrate by combining hydrogen peroxide etching with surface modification. The change of hydrophobic performance strongly depends on etching time, i.e., the hydrophobic performance is promoted firstly and reaches a stable with an increase of the etching time. Considering the relationship between hydrophobic properties and experimental periods, we found that two days of etching is the best reaction time. Meanwhile, we found that the superhydrophobic surface presents a good self-cleaning effect. Furthermore, by using the freezer to simulate low temperature environment of real condition, we conducted anti-freezing test on the super-hydrophobic surface. The result shows that the freezing time of the droplets in superhydrophobic surface can be prolonged suspension by 55.6 minutes compared with re-prepared surface under the same condition(-9.5℃, relative humidity 45%, for the volume of 30 micro-liters tap water).(2) Superhydrophobic surface was prepared Titanium substrate by using combination sulfuric acid etching and surface modification. Phase composition of titanium surface after etching was analyzed, and then the effect of different experimental steps on the properties of superhydrophobic surface were discussed. Comparing the contact angle of hydrophobic surface under different etching condition, we can conclude that the best experimental parameters for fabricating superhydrophobic surface by sulfuric acid etching is sulfuric acid concentration of 72%, etching temperature of 120 ℃, etching time of 30 minutes. By analyzing the microstructure of samples after different etching time, we can find that the sample surface after 30 minutes etching possesses farmland-like structures, and the morphology of their inner structures are a little different, such as honeycomb-like structure and wave-like structure etc, these structures in the surface are helpful to produce the larger roughness, which could contribute to better super-hydrophobic performance. Meanwhile, the wear resistance of the superhydrophobic surface and the dynamic behavior of water droplet on this surface were studied. Moreover, we checked their anti-freezing behavior by using the freezer to simulate low-temperature natural environmental condition, which was conducted under the condition of-9.5 ℃, relative humidity 45%, for the volume of 30 micro-liters tap water. Compared with re-preparing surface, the super-hydrophobic surface prepared by sulfuric acid etching exhibits more freezing time of the droplets, which is about 67.2 minutes.(3) In order to investigate the mechanical durability for superhydrophobic Titanium surface, tensile test was conducted on superhydrophobic specimen. The results show that the contact angle and rolling angle of superhydrophobic surface decrease and increase gradually with an increase of pre-strain, which means that the performance of superhydrophobic becomes slight degradation. By analyzing the microstructure of tensile samples with different pre-strain, we can reveal that both the boundary of farmland-like structure and the interval of its inner structure are wider with an increase of pre-strain, resulting in the reduced roughness and giving rise to degradation of hydrophobic performance.