Developing high photocatalytic antibacterial Zn electrodeposited coatings through Schottky junction with Fe3+-doped alkalized g-C_(3)N_(4) photocatalysts

Pure Zn coatings easily lose their protective performance after biofouling because they have no antibacterial effect under visible light.In this study,we fabricate a new antibacterial Zn composite coating using electrodeposition to couple Fe3+-doped alkalized g-C_(3)N_(4)(AKCN-Fe)into an existing Zn coating and show that the AKCN-Fe enhances antibacterial property of the Zn coating under visible light.We attribute this enhancement to the high photocatalytic performance,high loading content,and good dispersion of AKCN-Fe.In addition,the photocatalytic antibacterial mechanism of the composite coating is supported by scavenger experiments and electron paramagnetic resonance(EPR)measurements,suggesting that superoxide(·O_(2)^(-))and hydroxyl radical(·OH)play main and secondary roles,respectively.

Electroplated super-hydrophobic Zn−Fe coating for corrosion protection on magnesium alloy

A superhydrophobic Zn−Fe alloy coating was prepared on the surface of a reactive magnesium alloy using a simple,low-cost,eco-friendly method.Firstly,the Zn−Fe coating was obtained in a neutral glycerol Zn−Fe plating solution,which is green,compositionally stable,and non-corrosive to the equipment.And then the superhydrophobic surface with a flower-like microstructure was obtained by grafting myristic acid onto the Zn−Fe coating via a chelation reaction.The water contact angle was>150°and the rolling angle was 3°−4°.The corrosion rate of the two groups of superhydrophobic magnesium alloy samples with electrodeposition time of 30 and 50 min,respectively,was reduced by about 87%compared to that of the bare magnesium alloy.The prepared superhydrophobic coatings exhibit high performance in self-cleaning,abrasion resistance,and corrosion resistance.

ZnS coating of cathode facilitates lean‐electrolyte Li‐S batteries

Tremendous effort has been devoted to lithium‐sulfur batteries,where flooded electrolytes have been employed ubiquitously.The use of lean electrolytes albeit indispensable for practical applications often causes low capacity and fast capacity fading of the sulfur cathode;thus,the electrolyte/sulfur active mass ratios below 5μL/mg have been rarely reported.Herein,we demonstrate that ZnS coating transforms sulfur cathode materials electrolyte‐philic,which tremendously promotes the performance in lean electrolytes.The ZnS‐coated Li2S@graphene cathode delivers an initial discharge capacity of 944mAh/g at an E/S ratio of 2μL/mg at the active mass loading of 5.0 mg Li2S/cm^2,corresponding to an impressive specific energy of 500Wh/kg based on the mass of cathode,electrolyte,and the assumed minimal mass of lithium metal anode.Density functional theory calculations reveal strong binding between ZnS crystals and electrolyte solvent molecules,explaining the better wetting properties.We also demonstrate the reversible cycling of a hybrid cathode of ZnS‐coated Li2S@graphene mixed with VS2 as an additive at an E/AM(active mass)ratio of 1.1μL/mg,equivalent to the specific energy of 432 Wh/kg on the basis of the mass of electrodes and electrolyte.

Role of silicon in steels on galvanized coatings

In this article, five kinds of silicon-containing steel sheets have been electrodeposited, and then immersed in a pure molten zinc bath at 450℃ for various periods of time. The results by scanning electron microscopy （SEM） show that the coating of the sample （0.09 wt pct Si） with iron-electrodeposited pretreatment eliminates the reactive zones which are found in the coating without iron-electrodeposited pretreatment. The galvanized sample （0.28 wt pct Si） with iron-electrodeposited pretreatment exhibits a compact and coherent coating. The coating of the sample （0.37 wt pct Si） with the iron-electrodeposited pretreatment experiences a transition from a compact and coherent coating to a reactive one. The energy dispersive spectrum （EDS） results reveal that for the galvanized samples with iron-electrodeposited pretreatment, excessive silicon accumulates on the surface of the substrate due to the low solubility of silicon in the Г, after the iron layer is depleted by the increasing growth of the Fe-Zn intermetallics. With the movement of the substrate/Г interface toward the substrate, silicon-enriched α-Fe peels off from the substrate and breaks into the particles. The particles move toward the δ layer through the Г layer because silicon-enriched α-Fe cannot be absorbed in the F layer. When the particles reach the δ/Г interface, they are dissolved in the δ laver, making the F laver thin or even vanish.

INFLUENCE OF SILICON IN STEELS ON GALVANIZED COATINGS

After steel sheets （0.37wt%Si） pre-electroplated with a thin layer of pure Fe were immersed in molten zinc for various time, the change in the microstructure of the galvanized coating on the steel and the change of α-Fe/Г interface were studied. The EDS （energy dispersive sepectroscopy） resuits show that excessive silicon accumulates on the surface of the steel substrate due to the low solubility of silicon in the Г layer after the Fe layer is depleted by the increasing growth of the compound layers. With the movement of α-Fe/Г interface towards the substrate by the Fe/Zn reaction, silicon-rich α-Fe peels off from the substrate and breaks into particles. The particles, much like an inert marker in a Kirkendall effect experiment, move towards the δ layer through the Г layer because silicon-rich α-Fe can not be adsorbed in the Г layer. On reaching the 8/F interface, the particles quickly dissolve in the δ layer, and accelerate its growth, resulting in the gradual disappearance of the Г layer. At the same time, the normal coating is quickly changed into coatings typical of reactive steels as silicon dissolved in the δ layer soon diffuses toward the ζ layer. A similar process may happen in the initial stage of galvanizing reactive steels on a small scale, although it is hard to be observed.

Galvanic corrosion of AZ31B joined to dual-phase steel with and without Zn layer by ultrasonic and friction stir welding

Galvanic corrosion of AZ31B joined with bare or Zn-coated DP590 steel by ultrasonic spot welding or linear friction stir welding was quantitatively studied by pre-defining anode and cathode in the lap joint samples. Corrosion volume and depth from Mg anode surfaces exposed to 0.1 M sodium chloride solution was analyzed as functions of cathode surface type and welding method. Characterization of as-welded joints was performed to identify any microstructural feature of the bonding zone that could impact galvanic corrosion behavior.COMSOL modeling with modified user subroutine was conducted to simulate the progression of Mg corrosion in the same joint and electrode configurations used for the corrosion experiments. The experimental results indicated that Zn-coated cathode surface can reduce Mg galvanic corrosion significantly as galvanic polarization and cathodic current on Zn-coated surface remained relatively low for Mg in the weld joints.COMSOL modeling described the growth of Mg galvanic corrosion in a reasonable manner but showed limitation by underestimating the corrosion volume as it did not capture self-corrosion.

Coating highly lithiophilic Zn on Cu foil for high-performance lithium metal batteries

Lithium metal batteries(LMBs) are ideal candidates for next-generation high energy density energy storage systems.However,uncontrollable growth of Li dendrites due to uneven Li plating has restricted the practical application of the Li metal anode.Here,we develop a highly lithiophilic Zn coating on commercial Cu foil as a substrate for Li metal anode to settle above issues.We find that the lithiophilic nature of Zn can facilitate homogeneous nucleation and deposition of Li on Cu current collector surface.In addition,the uniform Zn coating can not only decrease the nucleation overpotential but also regulate the electric field distribution.Benefiting from the coated Zn layer,the designed anode for half-cell and full-cell tests shows better electrochemical performances compared with the untreated Cu foil.This work provides a simple and effective way to enable a promising dendrite-free lithium metal anode for large-scale industrial applications.

Understanding the efficient microwave absorption for Fe Co@ZnO flakes at elevated temperatures a combined experimental and theoretical approach

Considerable microwave absorption performance at elevated temperatures is highly demanded in both civil and military fields.Single dielectric or magnetic absorbers are difficult to attain efficient and broadband microwave absorption at the high temperature range of 373 K-573 K,and the evolution mechanism of the microwave absorption is still unclear especially for the magnetic absorbers.Herein,ZnO coated flaky-FeCo composite is proposed to break through the bottleneck,which possesses microwave absorption(RL<-10 dB)that covering the whole X band(8.2 GHz-12.4 GHz)at the temperature range of 298 K-573 K with a thickness of only~2 mm.Moreover,attenuation mechanism and evolution of the microwave absorption properties for the FeCo@ZnO flaky material at elevated temperature has been clearly disclosed by the composition and microstructure characterizations,electromagnetic performance measurements and first principles calculations for the first time.Moreover,the Poynting vector,volume loss density,magnetic field(H)and electric field(E)are simulated by HFSS to understand the interaction between EM waves and the samples at different temperatures,further elaborating the attenuation mechanism in high-temperature environment.This study provides guidance in designing and developing high-temperature microwave absorbers for the next generation.

Experimental observation of surface phonon absorption in Zn fine particles coated with ZnO

FINE particles have attracted much attention in the past few years due to their unique physical and chemical properties. For gas-evaporated fine metallic particles, a thin oxide layer is usually formed on their surface. According to Ruppin’s prediction, a dielectric coating on metallic particles should have a series of surface modes between ωTO and ωLO, the long-wavelength transverse and longitudinal optical phonon frequencies of the dielectric. The frequency of

Rare earth passivation and corrosion resistance of zinc coated NdFeB magnets

Rare earth passivation was conducted on Zn coated NdFeB magnets by chemical reaction to enhance the corrosion resistance performance.Morphologies,micro structures and compositions of different passivated coatings were studied by X-ray diffraction,field emission scanning electron microscopy,and X-ray photoelectron spectroscopy,respectively.The corrosion behavior was evaluated by electrochemical measurement and neutral salt spray test.The results show that the rare earth passivation can enhance the corrosion resistance of Zn coated NdFeB magnets.When the concentration of cerium nitrate is 5 g/L,the passivated specimens can achieve the longest NSS time of 360 h,which is 144 h longer than that of the pristine Zn/NdFeB magnets.The passivation layer on the Zn coating surface contributes to the enhancement of the magnets’corrosion resistance.