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.

Graphical abstractThe nano-grains on the micro-pillars are formed at the most thermodynamically active sites for saturation, precipitation of the zinc atoms and the surface effect of the micro structure in the process of heat treatment. The micro sized pillars and the nano sized grain composed a micro–nano binary structure, which is analogous to that of the lotus leaf.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Cu–Zn alloy formed via chemical displacement at a perpendicular way. ► Crystal CuZn5 and ZnO formed via anneal treatment in humidity. ► Micro-pillars and nano-grain composed a micro–nano binary structure. ► Micro–nano surfaces prepared exhibited good superhydrophobicity.