| The superhydrophobic materials,with special wettability characteristics,have shown great potential applications in various fields of self-cleaning,water/oil sepration,anti-corrosion,etc.In addition,hydrophobic or superhydrophobic surfaces are used to reduce the harzard of ice accumulation,which have been widely used in key technical fields such as aerospace,radar detection,transmission lines and high-speed trains.Therefore,this paper proposes to develop a superhydrophobic coating suitable for the bogie area of high-speed trains to obtain both anti-icing and ice-repellency properties to prolong the freezing time,lowering the adhesion of ice layers to the substrate,and reducing the ammount of ice accumulation.The WC-12 Co powders with different particle sizes(micro/nano scale)were deposited on the surface of weathering steel by High velocity oxy-fuel(HVOF)technology to obtain a base layer with a certain roughness.The scanning electron microscopy(SEM),three-dimensional contour(Laser Scanning Confocal Microscope,LSCM)of the surface and X-ray diffraction(XRD)were adopted to characterize the rationality of coating structure.Subsequently,polytetrafluoroethylene suspension and fumed silica acetone solution were prepared by spraying,brushing and soaking method,respectively to reduce the surface energy of the WC-12 Co coatings.After that,the roughness and wettability of modified coating were characterized.The results showed that the nano-WC-12 Co powder can be used to obtain a rough surface with a microstructure scale of 68-274 nm,and the coating had a surface roughness Ra of 3.32±0.23 ?m and Rz of 50.21±13.01 ?m.The static contact angle of the original steel substrate was increased from 82.7°±5.7° to 154.3°±3.0°,and the rolling angle was 4.1±0.1° after the hydrophobic nano-SiO2 was deposited on the surface of the rough WC-12 Co coating by a modified high-pressure spray method.The prepared superhydrophobic coating exhibited excellent mechanical and chemical stability in terms of self-cleaning,hydrophobic durability,abrasion resistance,acid pH resistance,corrosion resistance and weather resistance,etc.High speed camera technology was employed to capture the liquid drop condensation instantaneous form and recording the time of icing up,and the results showed that the average initial nucleation time of microdroplets on the superhydrophobic coating surface under the same low temperature conditions was 939.5s,which was about 6.6 times of the steel matrix.Further,a low temperature freezing model of microdroplets on different surfaces was used to explain the mechanism of delayed freezing time.In addition,the study also developed an ice adhesion test system to study the relationship between ice adhesion strength and temperature,icing time and surface roughness.The dynamic anti-icing performance of the material was tested by continuous water spraying in a low temperature environment.The results showed that the icing area fraction of the superhydrophobic coating was only 73.53% at the first 60 minutes,while the steel substrate was covered with ice layer completely within 10 min.A simplified impact model of micro-droplet indicated the droplet impacted the superhydrophobic coating with less contact time,smaller spreading area,and lower energy loss,which therefore,can resist the erosion of cold droplet and obstruct the accumulation of ice layer in a short time.Extending the dynamic ice time to 140 min,the ice weight gain rate of superhydrophobic coating was only 12.9% of the steel matrix,while only 30.0 % of the steel matrix at 180 min,showing an excellent anti-icing performance. |
PDF Full Text Request