64 / 2021-06-30 10:42:11

Fabrication of Superhydrophobic Ceramic Coatings with Reversible Wetting Behaviors via Solution Precursor Plasma Spray Process

superhydrohobic coatings,solution precursor plasma spray,reversible wettability

Superhydrophobic coatings show excellent non-wettability with water contact angles larger than 150° and roll-off angles smaller than 10°. The engineering applications of superhydrophobic coatings are severely limited and impeded by the complex fabrication processes and low durability of the coatings. In this work, a novel solution precursor plasma spray (SPPS) process was developed and used to deposit durable superhydrophobic rare earth oxide coatings. Yb(NO₃)₃ solution was used as feedstock and injected into the plasma jet in the SPPS process forming crystalline Yb₂O₃ coatings, which exhibited hierarchical structures with nano-scale splats/particles superimposed on micron-sized columnar structures. The coating showed a water contact angle of ~163°, a roll-off angle of ~3°, and multiple complete droplet rebound behavior. A series of tests were conducted including particle contamination, long-term water immersion, water flushing and water jetting, which further demonstrated the highly durable hydrophobicity of the coatings. In addition to the excellent superhydrophobicity, the coatings showed unique reversible wetting behaviors. The superhydrophobic coatings became superhydrophilic after long-term thermal exposure, while the superhydrophobicity was recovered after vacuum treatment, showing reversible wettability. The vacuum treatment and thermal exposure processes served as a switch to turn on and off the superhydrophobicity. The surface concentrations of Yb, O, and C for coatings with different wettability were investigated, which showed that the reversible wetting behaviors could be attributed to the adsorption and desorption of hydrocarbon species on the coating surface.