Spray-coating of superhydrophobic aluminum alloys with enhanced mechanical robustness.
A superhydrophobic aluminum alloy was prepared by one-step spray coating of an alcohol solution consisting of hydrophobic silica nanoparticles (15-40 nm) and methyl silicate precursor on etched aluminum alloy with pitted morphology. The as-sprayed metal surface showed a water contact angle of 155° and a roll-off angle of 4°. The coating was subjected to repeated mechanical tests, including high-pressure water jetting, sand particles impacting, and sandpaper shear abrasion. It remained superhydrophobic with a roll-off angle <10° up to three cycles of water jetting (25 kPa for 10 min) and sand particle impinging. After five cycles, the roll-off angle increased, but no more than 19° while the water contact angle remained greater than 150°. The superhydrophobic state was also maintained after three cycles of sandpaper abrasion. It was found that the micro-protrusion structures on the etched aluminum alloy played an important role to enhance the coating mechanical robustness, where the nanoparticles could grab on the rough surface, specifically in the groove structures, in comparison with the smooth glass substrates spray coated with the same materials. Further, we showed that the superhydrophobicity could be restored by spray a new cycle of the nanocomposite solution on the damaged surface.
School of Materials Science and Engineering, Southeast University, Nanjing 211189, PR China; Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA 19104, United States.
Youfa
Y
Zhang
Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA 19104, United States.
Dengteng
D
Ge
Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA 19104, United States. Electronic address: shuyang@seas.upenn.edu.
Shu
S
Yang
D000497:Alloys / Q000737:chemistry*; D000535:Aluminum / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008422:Materials Testing; D053758:Nanoparticles / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D012828:Silicones / Q000737:chemistry; D013499:Surface Properties
D000497:Alloys; D012828:Silicones; C078211:polymethylsiloxane; D012822:Silicon Dioxide; D000535:Aluminum
Mechanical robustness; Polymethylsiloxane; Silica nanoparticles; Spray coating; Superhydrophobic surfaces