Superhydrophobic surface fabricated by spraying hydrophobic R974 nanoparticles and the drag reduction in water

- Superhydrophobic surface with high bonding strength was achieved with epoxy layer.
- Industrialized R974 nanoparticles were used to prepare superhydrophobic surface.
- The “wet” and “dry” coatings were formed during R974-ethanol suspension spraying.
- The superhydrophobic coatings achieved a 12% drag reduction in water.

Based on the phenomena of the embedding dusts on the surface of fresh paint film, industrialized hydrophobic R974 nanoparticles were used as “dust”, and epoxy resin was used as “paint” to prepare the superhydrophobic film with high bonding strength. The superhydrophobic film was fabricated by spraying the R974-ethanol suspension onto the dip-coated epoxy resin film on glass slide. Because the epoxy resin acted as bonding layer between the R974 nanoparticles film and the glass slide, a combination of high bonding strength and superhydrophobicity was achieved. The superhydrophobic surface was characterized by water contact angle measurements and scanning electron microscopy (SEM). The water contact angle of the R974 coating could reach 154.7°, and the significant differences in the surface morphology of superhydrophobic coating were presented with different R974 concentrations. A flat, fractal-like texture was observed for coatings sprayed with low R974 concentration, and a rough, porous surface for coatings sprayed with high R974 concentration. The adhesion between the R974 coating and epoxy resin was evaluated by the adhesive-tape test. The interaction between fractal-like aggregated R974 with epoxy resin was large enough because of the surface-to-surface contact mode, and the interaction between microparticles of aggregated R974 with the epoxy resin was weak because of the point-to-surface contact mode. By comparing the skin friction drag on normal surface with the prepared superhydrophobic surface, the superhydrophobic coatings achieved a 12% drag reduction in water.

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