Preparation And Drag Reduction Property Of Hydrophobic Coating And Ultra-slippery Coating Based On Modified Silica Dioxide

Drag reduction is a long-standing topic in maritime navigation,and the application of drag reduction coatings to ship surfaces can achieve drag reduction goals and improve energy efficiency.In this paper,the prepared modified silica particles and SiO₂/HLR-Si coating were analyzed and characterized by SEM,AFM,FTIR,TG and other analytical testing methods.At the same time,the wettability and drag reduction of the sample coating were investigated and analyzed by contact angle measuring instrument and rotating disc testing device.The hydrophilic silica particles were prepared by the traditional st（?）ber method,then the silica was modified with PFOTES.The hydrophobic SiO₂/HLR-Si coating was prepared by the silica and HLR-Si according to a certain proportion.A simple one-step spray deposition method was used to spray the mixture of hydrophobic silica,HLR-Si and solvent on the test sample to obtain a hydrophobic coating.The test results of SEM,AFM and contact angle measuring instrument show that the surface roughness increases with the increase of SiO₂ addition.When the addition amount is 25 wt.%,the surface of SiO₂/HLR-Si coating has obvious ridge structure.Its water contact angle is as high as 163°,and the rolling angle is 1.8°.The rotating disk test shows that the superhydrophobic SiO₂/HLR-Si coating has good drag reduction performance below 200 rpm,and the drag reduction rate is the largest at 90 rpm with a value of 23.4%.The artificial air replenishment method is used to verify that the superhydrophobic coating surface can capture the air film and form a solid-gas-liquid contact mode to achieve drag reduction.The SiO₂/HLR-Si coatings with water contact angles of 96°,123°,136°,152°and 163°were immersed in silicone oil.The retention rate and storage capacity tests of five silicone oil super-slip coatings show that the retention rate and storage capacity of the lubricating oil are the largest after the 163°coating is soaked with silicone oil,which are 16%and 24 mg/cm²,respectively.The SEM test shows that the larger the water contact angle,the better the surface lipophilicity.The rotating disc test shows that Slips-5 has good drag reduction performance below 600 rpm,and the drag reduction rate is the largest at 90 rpm wiith a value of 27.6%,which is better compared with the superhydrophobic coating.The SiO₂/HLR-Si coatings with water contact angles of 96°,123°,136°,152°and 163°were immersed in PFPE.The retention rate and storage capacity tests of five PFPE super-slip coatings show that the retention rate and storage capacity of lubricating oil are the largest after the 163°coating is soaked with PFPE,which are 22%and 18.1 mg/cm²,respectively.The SEM test shows that PFPE basically all is infiltrated.The surface oil film is very thin,so the microstructure of the substrate coating surface can be directly observed.The rotating disc test shows that Slips-10 has good drag reduction performance in the test range of 0-1000 rpm,and has significantly improved drag reduction effect compared with the superhydrophobic coating and silicone oil treated coating.