A series of Cu films with different surface structures were fabricated by an improved electric brush-plating technique. In the absence of surface chemical modification, the Cu films exhibited ...hydrophobic and even superhydrophobic behaviors due to their three-level hierarchical structures. Based on the classical Wenzel and Cassie models, the effects of two dimensionless geometrical parameters (the aspect ratio and the spacing factor of micro-scale structure) on the wetting behaviors of the Cu films were investigated. It was demonstrated that to obtain the stable Cassie superhydrophobic state, the aspect ratio and the water contact angle on the basal surface should be as large as possible and the spacing factor should be limited within a specific range for given aspect ratio and water contact angle on the basal surface.
► A Mg–2Dy–0.5Zn (at.%) alloy was prepared by extrusion and ageing treatment. ► This alloy exhibits the excellent tensile strengths at 300
°C, i.e.,
σ
0.2
=
245
MPa;
σ
b
=
260
MPa. ► The excellent ...strengths are attributed to the high volume fraction of LPSO phase.
A Mg–2Dy–0.5Zn (at.%) alloy was prepared by casting, heat treating at 525
°C for 10
h, extruding at 360
°C and ageing at 180
°C for 90
h. Microstructure characterization revealed that this alloy consists of the fine-grained α-Mg matrix composed nearly of the 14H long period stacking ordered (LPSO) phase and a small amount of (Mg, Zn)
x
Dy precipitations. Tensile tests showed that the yield and ultimate tensile strengths of this alloy can reach 245
MPa and 260
MPa at 300
°C, which are only slightly lower than those at room temperature (287
MPa and 321
MPa), the elongation of this alloy is 36% at 300
°C, which is far higher than that at room temperature (11.6%). The high volume fraction of the 14H LPSO phase in the fine-grained α-Mg grains and the high thermal stability of the microstructure during elevated temperature deformation are responsible for the excellent elevated temperature properties observed for this alloy.
Deformed coarse-grained polycrystalline metals always unload elastically where permanent dislocation network well-developed in the loading regime hinders the movement of dislocations and allows only ...the elastic relaxation of stress. Such elastic unloading behavior is, however, unexpected in nanocrystalline metals because the dislocation network cannot effectively form inside nanometer-scale grains. In this work, we report the experimental finding of significant plastic deformation that emerges in the unloading regime in the compressive cyclic test at room temperature of nanocrystalline Cu. The magnitude of plastic strain produced during unloading depends strongly on loading and unloading rates. This plastic unloading behavior arises from the rapid absorption of dislocations accumulated during loading, which was quantitatively interpreted by performing the incremental unloading test and developing a relationship between the dislocation density and the loading and unloading rates based on the models of the statistical absorption of dislocations by grain boundaries and the dislocation emission from grain boundary ledges. Concurrently, the evolution of deformation structures during the cyclic deformation was also analyzed in terms of the interactions of gliding dislocation–twin boundaries.
Nanocrystalline (nc) Ni coating was direct-current electrodeposited on the AZ91D magnesium alloy substrate aimed to improve its corrosion resistance using a direct electroless plating of nickel as ...the protective layer. As comparison, two electroless Ni coatings on the magnesium alloy with different thickness were also presented in the paper. The surface morphologies of the coatings were studied by SEM and FESEM. The nc Ni coating had an average grain size of about 40 nm and an evident {200} preferred texture revealed by XRD. The hardness of the nc Ni coating was about 580 VHN, which was far higher than that (about 100 VHN) of the AZ91D magnesium alloy substrate. The electrochemical measurements showed that the nc Ni coating on the magnesium alloy had the lowest corrosion current density and most positive corrosion potential among the studied coatings on the magnesium alloy. Furthermore, the nc Ni coating on the AZ91D magnesium alloy exhibited very high corrosion resistance in the rapid corrosion test illustrated in the paper. The reasons for an increase in the corrosion resistance of the nc Ni coating on the magnesium alloy should be attributable to its fine grain structure and the low porosity in the coating.
Rational nanostructure design is the key point to prepare catalysts with superior catalytic performance, and tedious preparation method limits them large-scale application. Here, a Cu2Se with fluffy ...intersected-nanosheets decorating nanotubes structure were prepared by a simple and rapid solution-immersion method at room temperature. The hollow hierarchical structure on a good conductor Cu foam (CF) enlarges surface available sites, enhances the conductivity of electrode materials, then endowing the catalyst with quick charge/mass transportation and favorable oxygen evolution reaction (OER) performance. In alkaline medium, our as-prepared Cu2Se/CF electrode demonstrates high OER performance, especially for lower overpotential (200 mV at 10 mA cm−2) compared with the previously reported Cu-based catalysts. Moreover, the Cu2Se catalyst could afford galvanostatic test of 10 mA cm−2 test over 12 h and present superior OER tolerance. These results indicate that the Cu2Se catalyst via cost efficiency and efficient solution-immersion method could be applied to large-scale efficient OER.
•Cu2Se/CF was prepared via a simple and rapid solution-immersion method.•Cu2Se/CF displayed intersected-nanosheets decorating nanotubes structure.•Cu2Se/CF presented lower overpotential than previous reported Cu-based catalysts.
Tensile properties of an electric brush-plated nanocrystalline Cu with an average grain size of 59nm were investigated at different strain rates. This nanocrystalline Cu exhibits an excellent ...combination of strength and ductility with its ultimate tensile strength increasing from 635MPa to 1000MPa and total elongation decreasing from 15.8% to 9.9% as strain rate increases from 10−4s−1 to 1s−1. Analysis based on the characterization results of transmission electron microscopy (TEM), scanning electron microscopy (SEM) and general area detector diffraction detection system (GADDS) on the as-brush-plated and deformed NC specimens revealed that the excellent combination of strength and ductility arises from the enhanced dislocation strain hardening ability and the improved deformation accommodation role played by GB sliding.
Bioactive calcium phosphate coatings were prepared on AZ91D magnesium alloy in phosphating solution in order to improve the corrosion resistance of the magnesium alloy in Simulated Body Fluid (SBF). ...The surface morphologies and compositions of the calcium phosphate coatings deposited in the phosphating bath with different compositions were investigated by Scanning Electron Microscopy (SEM) with Energy Dispersive Spectrometer (EDS) and X-ray Diffraction (XRD). Results showed that the calcium phosphate coating was mainly composed of dicalcium phosphate dihydrate (CaHPO4•2H2O, DCPD), with Ca/P ratio of approximately 1:1. The corrosion resistance was evaluated by acid drop, electrochemical polarization, electrochemical impedance spectroscopy and immersion tests. The dense and uniform calcium phosphate coating obtained from the optimal phosphating bath can greatly decrease the corrosion rate and hydrogen evolution rate of AZ91D magnesium alloy in SBF.
We designed a novel Ru-doped NiO/Co3O4 heterostructure as the catalyst to achieve superior OER, ORR, and HER activity. The synergistic interaction of Ru doping and NiO/Co3O4 heterostructure could ...substantially optimize the overall electrochemical active area, conductivity and activation energy of the catalyst, resulting in excellent catalytic performance.
Display omitted
•Ru-doped NiO/Co3O4 owns multiple active centers and strong synergistic effect.•The adjustment of electronic energy states by Ru doping and thus the influence of catalytic performance is revealed.•Such features allow Ru-doped NiO/Co3O4 with superior OER/ORR/HER catalytic activity in alkaline media.•Ru-doped NiO/Co3O4 catalyst has an ultralow overpotential for OER and a high half-wave potential for ORR.•Ru-doped NiO/Co3O4 based water-splitting device only needs 1.555 V and 1.650 V to reach 10 and 100 mA cm−2.
The development of cheap and efficient OER/ORR/HER electrocatalysts is important to promote green energy conversion and storage technologies. Experimental results show that the synergistic effect of Ru doping and NiO/Co3O4 heterostructure can significantly improve the catalytic activity. The existence of NiO/Co3O4 heterostructure, the appropriate proportion of Ru (only 2%) and the proper electronic energy state tuning are determined by electronic detection and elemental analysis, which enhanced the activation energy, electrical conductivity and electrochemical active surface area of the catalyst. Thus, the Ru-doped NiO/Co3O4 heterostructure exhibits superior OER/ORR/HER performance, reaching 100 mA cm−2 in alkaline electrolytes at only 138 mV (HER) and 269 mV (OER) overpotential, and a high half-wave potential of 0.88 V (ORR). The water-splitting device assembled by the catalyst can operate stably for a long time (>40 h), better than Pt/C and RuO2 at high current densities.
Water splitting is a sustainable and clean hydrogen-production technology, but driven either by solar energy with natural intermittent, or by power grid with high cost, which is not conductive to ...sustainable development. Additionally, the sluggish anodic oxygen evolution reaction (OER) remains a huge obstacle for efficient hydrogen production. Herein, an intersected nanosheets decorating micro-walls structure nickel-cobalt phosphide grown on Ni foam electrode (NiCoP/NF) is prepared, and displays good hydrogen evolution reaction (HER), excellent hydrazine oxidation reaction (HzOR) and enhanced NiCoP/NF//Zn battery capacity performance. Based on the trifunctional NiCoP/NF electrode, a continuous solar-driven energy-saving hydrogen generation is constructed. The solar cells drive the efficient hydrogen production and hydrazine degradation plus simultaneously charge the NiCoP/NF//Zn battery during the day; then the charged NiCoP/NF//Zn battery provide high output voltage to drive hydrogen generation and hydrazine degradation at night. The continuous solar-driven energy-saving hydrogen generation plus sewage treatment strategy exhibits a new way for clean and sustainable energy supply plus curbing environmental pollution.
•The nanosheets decorating micro-walls structure NiCoP was prepared.•The NiCoP exhibited superior HER and excellent HzOR performance.•The NiCoP achieved the unprecedented low potential for hydrogen generation.•Trifunctional NiCoP demonstrated the uninterrupted efficient hydrogen generation.
Electroless Ni-P alloy coating was deposited on carbon fibers (CFs) reinforced polyether ether ketone (PEEK), and a transparent passive film was formed on it. Effects of passivation on the oxidation ...behavior and electromagnetic interference shielding effectiveness (EMI SE) of Ni-P alloy coatings were investigated. The phase structure of the Ni-P coating was investigated by X-ray diffractometry (XRD). Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) showed that dense and uniform nodules presented in the coating, and chromate (VI) passive film formed onto Ni-P alloy coating. Electrochemical tests showed that passivation improved the corrosion resistance and delayed the oxidation of the Ni-P alloy coating. The EMI SE test proved that the passivation enhanced EMI SE greatly because passive film effectively restrained the oxidation of the Ni-P alloy coating. All the data proved that the passivated Ni-P alloy coating to be potential shielding material under oxidation environment.
•A passive Ni-P coating was electrolessly formed on PEEK.•Passivated coating exhibits better corrosion resistance than as-plated coating.•The oxidation resistance was improved after passivation.•Passivated coating presents superior EMI SE after oxidation.
