| Abstrakt: |
In this work, we present a simple, low cost, reproducible, scalable, and environmentally friendly approach to fabricate superhydrophobic hierarchical surfaces composed of micro- and nanostructured features. We utilized a combination of sandblasting and hot water treatment (HWT) techniques to introduce micro-roughness and nano-roughness, respectively, on copper sheets. Bare copper sheets were sandblasted by using AlO abrasive particles. HWT step simply involved immersing samples in DI water at 75 °C for 24 h. The process resulted in copper oxide nanostructures formed by the HWT coated on the micro-structured copper surface produced by sandblasting. Nanostructures were observed to have CuO stoichiometry and had the shapes of leaves with thicknesses ∼15 nm and widths ∼250 nm. Such nano-leaves located especially at the sidewalls of micro-hills are believed to provide a re-entrant (overhang) topography that is critical to achieve superhydrophobic property. Then, hierarchically, rough samples were coated with PFDTS (1H, 1H, 2H, 2H-perfluorodecyltrichlorosilane), which is a fluorination process to reduce the surface energy. As a result, we achieved water contact angles as high as ∼164° for our hierarchical micro-nano-rough copper sheets, which reveal the superhydrophobic property. However, fluorinated control (flat), nano-rough (only HWT), and micro-rough (only sandblasting) samples had contact angles of ∼132°, ∼137°, and ∼149°, respectively. On the other hand, non-fluorinated control, nano-rough, micro-rough, and hierarchically rough Cu sheets showed a hydrophilic behavior with contact angles of ∼78°, ∼73°, ∼60°, and ∼50°, respectively. Therefore, sandblasting and HWT methods can be useful to produce a wide spectrum of wetting behavior ranging from highly hydrophilic to superhydrophobic surfaces. Therefore, sandblasting and HWT methods can be useful to produce a wide spectrum of wetting behavior ranging from highly hydrophilic to superhydrophobic surfaces. In addition, durability tests of our samples show that morphology and crystal structure of HWT copper oxide nanostructures are stable at elevated temperatures. Results also show that superhydrophobic surfaces can provide a superior wetting stability, which is believed to originate from their intrinsic self-cleaning property. [ABSTRACT FROM AUTHOR] |
