Fabrication Of Superamphiphobic Surfaces On Titanium Substrates And Research On Wettability Control

Superhydrophobic surfaces have many special properties, such as self-cleaning, drag reduction, corrosion resistance, anti-icing, vapour film collapse suppression in nuclear power plants and so on. However, superhydrophobic surfaces may lose the self-cleaning ability in oily circumstances, which hinder their applications. To overcome this problem, superamphiphobic surface was proposed. Superamphiphobic surfaces can not only be used in oily conditions, but also have almost all the properties of superhydrophobic surfaces. Titanium, the so-called aerospace metal, is widely used in aerospace, automobile, information engineering, biomedicine, nuke industry, and shipbuilding industry for its various advantages, including good corrosion resistance, high specific strength, and low density. Therefore, fabrication of superamphiphobic surfaces on titanium substrates has considerable potential values in fundamental research and industrial applications.To date, there are many methods to fabricate superamphiphobic surfaces, however, most of these methods are either at a high cost or contaminative to the environment. Based on the problems, we proposed an electrochemical method using neutral electrolyte to prepare superamphiphobic surfaces.Economical, environmental, and neutral sodium bromide (NaBr) electrolyte was used for electrochemical etching to create the micro morphologies that required by superamphiphobic surfaces and superhydrophobic surfaces. Ethanol solution of fluoroalkylsilane (FAS) was used to reduce surface energy of etched titanium surfaces. After that, superamphiphobic surface and superhydrophobic surfaces can be obtained, respectively. Scanning electron microscopy (SEM) was used to characterize surface micro morphologies. The surface that has re-entrant structures on it would become superamphiphobic after FAS modification; the one which has nanoflakes on it would be superhydrophobic. X-ray diffraction (XRD)was used to characterize the crystal structures. It shows that superamphiphobic surface, superhydrophobic surface and untreated surface do not have apparent difference in crystal structures, indicating crystal structures do not affect wettability of titanium surfaces. Fourier transform infrared spectrophotometry (FTIR) and energy-dispersive spectroscopy (EDS) were used to characterize the surface chemical compositions. It indicates that superamphiphobic surface and superhydrophobic surface have FAS on them, while the untreated surface does not. The analysis of electrolyte, reaction process, and products of the electrochemical processing shows that during the reaction, the solution remained neutral, which resulted in less harm to the environment than acid or alkali solution could cause. In terms of the reaction products, H2and Ti(OH)4are also environmentally friendly.In addition, we studied the effects of electrochemical parameters, which could affect titanium surface wettability through impacting the surface micro morphologies. Among those parameters, current density and electrochemical etching time affect the surface wettability a lot; electrolyte temperature only has an effect on oleophobicity but not hydrophobicity; electrolyte concentration has nearly no effect on surface wettability. Titanium surface wettability can be controlled and selective using this parameter law, resulting superamphiphobic surfaces, superamphiphilic surfaces, superhydrophobic-oleophilic surfaces, superhydrophobic-oleophobic surfaces can be obtained. respectively.