Design of a novel superhydrophobic F&Si-DLC film on the internal surface of 304SS pipes

Superhydrophobic surfaces are an effective measure to achieve drag reduction in the process of water transmission. A novel superhydrophobic F and Si incorporated DLC (F&Si-DLC) film with a micro/nanoscale structure was deposited on the internal surface of 304SS pipe by reducing the pumping speed (increasing the pressure), which combined hollow cathode discharge and plasma immersion implantation. The results indicate that the water contact angle and rolling angle of the as-deposited F&Si-DLC film are 151.6° and 9.4°, respectively. The water flow shed through the superhydrophobic F&Si-DLC film surface without adhesion and no sign of wetting was observed on the surface of the F&Si-DLC film, exhibiting a good and stable superhydrophobicity. Besides, the superhydrophobic F&Si-DLC film presents better mechanical properties (hardness ~ 7.1 GPa) than traditional organic superhydrophobic film. Compared with the pure DLC film, the DLC film containing only F atoms (F-DLC), and the DLC film containing only Si atoms (Si-DLC) deposited on the inner surface of the pipe under the same conditions, it is found that the incorporation of F or Si element is an effective way to reduce the surface energy of DLC films and improve their hydrophobicity. However, the F&Si-DLC film deposition a constant pressure (F&Si-DLC (one)) does not exhibit superhydrophobic properties (the water contact angle of 90°). Therefore, an important reason for obtaining superhydrophobic F&Si-DLC films by reducing the pressure is to generate more micro/nanoscale clusters, in other words, to obtain a rough surface with micro/nanoscale. The as-deposited superhydrophobic F&Si-DLC film offers the possibility of reducing drag in water transmission.