Fabrication of micro-/nano-structured super-hydrophobic fluorinated polymer coatings by cold-spray

• Published in: Surface & coatings technology 2019-09, Vol.373, p.17-24
• Main Authors: Ravi, Kesavan, Sulen, Wesley Lock, Bernard, Chrystelle, Ichikawa, Yuji, Ogawa, Kazuhiro
• Format: Article
• Language: English
• Subjects: Alkanes; Bridges; Cold spray; Contact angle; Fluorination; Fluoropolymers; Hydrophobic surfaces; Hydrophobicity; Interlayers; Laser beam texturing; Mechanics; Mechanics of materials; Morphology; Mountains; Papillae; PFA; Physics; Polymer; Polymer coatings; Spray deposition; Stainless steel; Stainless steels; Structural mechanics; Substrates; Superhydrophobic coating; Texturing
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2019.05.078

A fabrication of superhydrophobic Perfluoroalkoxy Alkane (PFA) coatings on stainless steel surfaces by cold-spray technique has been demonstrated in this work. The in-situ supersonic impact deposition and consolidation of finely divided 20–40 μm powder material yielded hydrophobic thin coatings of PFA which exhibited contact angles of 125° but high roll off angles of 60°. The deposition efficiencies were less than 0.5%, coating was mechanically very fragile and non-uniform. However, the cold-spray deposition efficiency was subsequently increased to almost 15% by performing simple modification of particle surface morphology by introducing organosilane coated nanoceramic layers on the PFA particles and by laser texturing the stainless steel substrate surfaces to form mountain-valley micro-structures. The nanoceramic interlayers formed bridge bonds at the particle-particle interface and laser texturing achieved efficient coating-substrate interlock. The improved coatings exhibited super-hydrophobic character with 160° contact angle and 6° roll-off angle. The superhydrophobicity was seen to be as a result of micro-/nano-structured surface consisting of papillae like structures capped by a layer of hydrophobic nanoceramic. The coating also exhibited excellent water repellency. [Display omitted] •Superhydrophobic fluoropolymer coatings were fabricated by cold spray.•High deposition efficiency when nanoceramics dispersed polymer particles were sprayed on laser patterned surfaces.•Double structures with micron/nano-sized structures were formed on coating surface.•High water contact angle, low roll-off angles and excellent water repellency.