Controlled growth of superhydrophobic films without any low-surface-energy modification by chemical displacement on zinc substrates

Superhydrophobic surface was prepared via immersing the clean perpendicular zinc substrate into aqueous copper (II) chloride (CuCl₂) solution and followed by anneal under the humid condition. The prepared samples were characterized by powder X-ray diffraction analysis, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy (XPS), and scanning electron microscopy (SEM), and energy-dispersive X-ray spectrometry analysis (EDX). SEM images of the films showed that the resulted surfaces exhibit micro-nano binary structures. The resulting surfaces had a high water contact angle (CA) of larger than 150° as well as a small sliding angle (SA) of less than 6°. Cu-Zn alloy formed by chemical displacement. Crystal CuZn₅ formed via crystal transition via anneal treatment. Crystal ZnO formed in air or under the humid condition. The CuZn₅-ZnO micro-nano binary structures leads to the surface superhydrophobicity.