Deposition of dual-scale superhydrophobic coatings with uniform arrayed surface structures and controllable morphologies via plasma spray processes

In this work, dual-scale superhydrophobic Al 2 O 3 –13%TiO 2 coatings were deposited rapidly via the combination of atmospheric plasma spray (APS) process and suspension plasma spray (SPS) process. A wire mesh shielding method was employed in the APS process, which resulted in the formation of micron-sized conical bump surface structures with uniform morphologies. The SPS process was then applied to deposit submicron-sized particles on the conical bump-structured coatings, forming dual-scale surface structures. The effects of the mesh and its size on the formation of different surface structures were investigated. The dual-scale coatings deposited via the APS+SPS processes and mono-scale coatings deposited via the APS process were comparatively investigated via characterizations of the microstructures, element distribution, surface topographies, and wetting behaviors. The dual-scale coatings showed superhydrophobic behaviors with the largest water contact angles of ∼154° and smallest roll-off angles of ∼7° and complete droplet rebounding performance after chemical modification, while the mono-scale coatings showed high adhesion to water. The correlations between the wetting behaviors and morphological characteristics of the surface structures were elaborated by establishing a mathematical model.