Uniform Preparation And Superhydrophobic Modification Of Nanotubes Coating On The Titanium U-tube Surface

With the advancement of technology,various materials surface treatment methods have also been greatly developed.The general material surface treatment method is for flat or block materials.By improving the surface properties of the material,it can better adapt to the service requirements of various working environments.Compared with the open processing environment of flat materials,tube materials have limited surface treatment methods due to factors such as narrow internal space and complicated shape.In this thesis,the electrochemical anodizing process applied to the inner and outer surfaces of titanium U-tubes was studied,and the homogenization preparation and functional application of the inner and outer surface super-wetting coatings were realized,which provided a new idea for the surface treatment of tube components.Titanium and titanium alloy tubes have the advantages of high specific strength,good corrosion resistance and non-magnetic properties,and are widely used in seawater desalination,marine equipment,heat collecting and other fields.In this paper,a coaxial anodization method was established for the inner surface treatment of titanium U-tubes,which achieved uniform preparation of the inner surface coating.And the fluid drag reduction performance of the U-tube was studied.The flexible carbon fiber and insulating rigid balls were used as the cathode to realize coaxial anodization.and uniform titanium dioxide?TiO₂?nanotube arrays were prepared on the inner surface of the U-tube.The reaction was carried out for 8 hours under the conditions of a dynamic circulating electrolyte speed of 75 mL/min and a constant voltage of 20 V,and the resulting TiO₂ nanotube arrays showed the average length of5.8?m.The micro-nano composite structure with superhydrophobic effect was prepared by electrochemical etching and anodization with this coaxial anodization method.After low surface energy treatment,the structure can achieve superhydrophobic effect with the static apparent contact angle of 157°and the rolling angle of less than 10°.Compared with the original titanium tube,the super-hydrophobic titanium tube showed obvious fluid drag reduction effect in many tests,the water flow with an initial velocity of 27.4 mL/min could maintain a large kinetic energy after being turned 180°along the U-tube anti-gravity,and rushed out along the tube.This has a very broad application prospect in the future.A tube-in-tube coaxial anodization method was established to achieve uniform preparation of TiO₂ nanotube coating on the outer surface of titanium U-tubes,and the anti-icing performance was studied.A coaxial stainless steel tube was employed as the cathode to ensure coaxial anodization configuration.The reaction was carried out for 8 hours under the condition of static electrolyte and a constant voltage of 20 V,the resulting nanotube arrays showed the average length of 4.6?m.The micro-nano composite structure was prepared on the outer surface of the titanium tube by sequential electrochemical etching and anodization to realize superhydrophobic modification of the outer surface of the titanium U-tube.Compared to the original titanium tube,the super-hydrophobic titanium U-tube exhibits delayed frosting performance in the temperature range of -10??-20?.And after the melting cycle,it can still maintain its anti-frost effect,which has great application prospects in the field of low temperature antifreeze and frost resistance.