Yuanyuan Cheng

Fabrication of superhydrophobic Au–Zn alloy surface on a zinc substrate for roll-down, self-cleaning and anti-corrosion properties

Superhydrophobic Au–Zn alloy surfaces have been fabricated successfully on a zinc substrate via chemical substitution deposition and subsequent annealing treatment. The resulting surfaces exhibited remarkable superhydrophobicity with a WCA of 170 ± 2° and a WSA smaller than 1° without any organic modification. The surface morphologies and chemical compositions were investigated using field emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), and the surface roughness was analyzed by atomic force microscopy (AFM). The theoretical mechanism for superhydrophobicity and wettability were also analyzed. The surface wettability changed from superhydrophilicity to superhydrophobicity with a stable Cassie–Baxter state via thermal treatment, which caused the generation of Au–Zn alloys (including AuZn3 and AuZn) and ZnO, and the formation of micro-/nano-binary architectures. The resulting superhydrophobic Au–Zn alloy surfaces exhibited exquisite roll-down, self-cleaning, and excellent anti-corrosion properties, and also had a firm mechanical property about 10 N, and this might have important values for more potential applications. The corrosion current density was reduced by more than 2 orders of magnitude for the resulting superhydrophobic surface in comparison with the untreated zinc surface and this should be ascribed to the contribution of Au–Zn alloys on the surface.

Controllable wettability of micro- and nano-dendritic structures formed on aluminum substrates

A superhydrophilic surface with a static water contact angle of 4° ± 2° via two-step immersion process and a superhydrophobic surface with a static water contact angle of 169° ± 2° and a sliding angle of almost 0° via successive thermal treatment have been successfully fabricated on aluminum substrates. Surface morphologies and chemical compositions were investigated using field emission scanning electron microscopy, X-ray powder diffraction and X-ray photoelectron spectroscopy, and the formation mechanism was also analyzed. The thermal treatment, which causes the generation of oxides and the appearance of nano-sized particles, is very important for the surface characteristic transformation from superhydrophilicity to superhydrophobicity. The effects of various experimental parameters on wettability, corrosion resistance, anti-icing and deicing properties, stability and large-area preparation were also studied. The corrosion rate of the as-prepared superhydrophobic surface decreases by about 57.6 times compared with that of the untreated aluminum surface and about 34.8 times compared with that of the pure copper surface. These excellent properties of the superhydrophobic surface may be favorable for its potential applications and industrialization.

Fabrication of Au–AlAu4–Al2O3 superhydrophobic surface and its corrosion resistance

Superhydrophobic Au–AlAu4–Al2O3 surfaces have been successfully fabricated on aluminum substrate via immersion in chloroauric acid (HAuCl4) aqueous solution and subsequent annealing treatment. The morphologies of the surfaces exhibit dendritic structures. The surface with remarkable superhydrophobic properties has a water contact angle of 171 ± 2° and a sliding angle of approximately 0°. The effects of the immersion time, immersion concentration, annealing time and annealing temperature on surface wettability were investigated in detail. The corrosion resistance of the untreated aluminum surface and the resulting Au–AlAu4–Al2O3 surface were also investigated via the Tafel extrapolation method. The corrosion current densities are reduced by more than 1 order of magnitude for the resulting surface in comparison with the untreated aluminum surface. The anticorrosion properties of the surfaces get better over the immersion time and this may be due to the generation of corrosion products, which can prevent the corrosion process and protect the substrates. Moreover, the low current density of the resulting superhydrophobic surface demonstrates its excellent corrosion resistance.

Fabrication of Cu–CuO–Fe2O3/Fe anti-sticky and superhydrophobic surfaces on an iron substrate with mechanical abrasion resistance and corrosion resistance

Herein, Cu–CuO–Fe2O3/Fe superhydrophobic surfaces (SHSs) were successfully fabricated on an iron substrate via chemical substitution deposition and subsequent annealing treatment. The resulting surfaces exhibit remarkable superhydrophobicity with a water CA of 165 ± 2° and an SA of approximately 0° without any organic modification. The surface morphology and chemical compositions were investigated using field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS); moreover, the surface roughness was analyzed via atomic force microscopy (AFM). The thermal treatment, which caused generation of a new chemical substance and formation of micro-/nano-binary architectures, was important for superhydrophobicity and also enhanced the affinity of the iron substrate for the coatings. The annealing temperature and time were further investigated to explain the significance of the surface morphology and chemical composition in the fabrication of the optimal SH samples under appropriate conditions. The resulting SHSs exhibit roll-down, anti-abrasion, and anti-corrosion properties, which may have significant potential value for more applications.

A robust and repairable superhydrophobic Co5Zn21 alloy surface on a zinc substrate

Herein, on a zinc substrate, a superhydrophobic Co5Zn21 alloy surface with a nanometer needle structure was fabricated by immersing processed Zn sheets perpendicularly into a cobalt(II) nitrate aqueous solution followed by the annealing treatment. This alloy surface exhibited not only outstanding superhydrophobicity with a water contact angle of 160° but also excellent mechanical durability and corrosion resistance. The morphology and chemical composition of the superhydrophobic surface (SHS) were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction pattern (XRD), energy-dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of the samples was characterized via polarization, Nyquist, and bode modulus plots. The SHS endures mechanical stretch for more than 800 mm of abrasion using sandpaper with different grit sizes (P1200, P800, and P400) and shows abrasion resistance. When the superhydrophobic surface lost its superhydrophobicity after a long-term damage, the superhydrophobicity could be easily regenerated again by immersion and annealing treatment. The surface after repair can still maintain its superhydrophobicity after anti-friction, anti-ice, and UV irradiation tests.

Fabrication of graphene/copper–nickel foam composite for high performance supercapacitors

A three dimensional (3D) composite electrode of graphene/copper–nickel foam (CNF) was fabricated by successively immersing commercial CNF into polydopamine (PDA) aqueous solution and graphene oxide (GO) suspension solution, followed by an annealing process. CNF acted as a substrate for the composite film, as well as the copper and nickel source, and the formation of reduced graphene oxide (rGO) and nitrogen doping were achieved simultaneously during the annealing process. The novel rGO/PDA/CNF composite electrode exhibited an ultrahigh specific capacitance of 2427.3 F g−1 at 2 A g−1, a superior rate capability of 52.1% capacitance retention at 50 A g−1vs. 1 A g−1, an excellent cycling stability that meant the specific capacitance reached its maximum value after being fully activated and retained 99.5% of the value even after 5000 cycles, a maximum energy density of 92.9 W h kg−1 and a power density of 9.6 kW kg−1 in 1 M KOH electrolyte. The synthesis method and excellent properties offer an effective strategy for fabricating various composites and exhibit promising applications in energy storage devices.