Preparation and characterization of super-hydrophobic surface through particle deposition by vacuum cold spray

Super-hydrophobic materials have broad application prospects in industry, agriculture and daily life. Not only the types of the materials but also the structure and the morphology of their surface have a significant impact on the hydrophobicity of materials. In this study, nano-structured TiO₂ coatings were deposited on glass surface by vacuum cold spray using agglomerated nano-TiO₂ powder and aggregated nanostructured TiO₂ powder to create nanostructured and micro-nano hierarchical structured TiO ₂ surface. The surface morphology of nanostructured TiO₂ deposited surface was characterized by scanning electron microscopy and 3D laser microscopy. The influences of the surface morphology, annealing and fluoroalkylsilane adsorption treatment on the wettability of the surfaces were investigated. The results showed that the nanostructured TiO₂ coatings in the as-sprayed and annealed states were hydrophilic. However, after adsorbing treatment by fluoroalkylsilane, the nanostructured TiO₂ deposited glass surface exhibited super-hydrophobicity. The contact angle of water drops on TiO₂ coating surfaces became greater than 120° up to 170° depending on the local surface morphology. Moreover, micro-nano hierarchical structured TiO₂ coatings obtained by VCS using aggregated nano-TiO₂ after fluoroalkylsilane adsorption exhibited excellent super-hydrophobic performance and the contact angle was greater than 170° and water droplets tended to roll on the surface with extremely low adhesion.