Understanding the electrochemical behavior of bulk-synthesized MgZn2 intermetallic compound in aqueous NaCl solutions as a function of pH

A multifunctional quasi-solid-state polymer electrolyte with highly selective ion highways for practical zinc ion batteries

The uncontrolled dendrite growth and detrimental parasitic reactions of Zn anodes currently impede the large-scale implementation of aqueous zinc ion batteries. Here, we design a versatile quasi-solid-state polymer electrolyte with highly selective ion transport channels via molecular crosslinking of sodium polyacrylate, lithium magnesium silicate and cellulose nanofiber. The abundant negatively charged ionic channels modulate Zn2+ desolvation process and facilitate ion transport. Moreover, an in-situ formed Zn-Mg-Si medium-entropy alloy on Zn anode allows for an improved Zn nucleation kinetics and homogeneous Zn deposition. These combined advantages of the polymer electrolyte enable Zn anodes to achieve an average Coulombic efficiency of 99.7 % over 2400 cycles and highly reversible cycling up to 600 h with large depth of discharge of 85.6%. The resultant Zn | |V2O5 offers a stable long-term cycling performance and its pouch cell achieves a cycling capacity of 1.13 Ah at industrial-level loading mass of 31.3 mg.

The effect of Desulfovibrio caledoniensis and Pseudomonas aeruginosa on the corrosion behaviour of 70Cu-30Ni alloy

This work investigated the effect of Desulfovibrio caledoniensis (D. caledoniensis) and Pseudomonas aeruginosa (P. aeruginosa) on the microbiologically influenced corrosion (MIC) behaviour of 70Cu-30Ni alloy using surface analysis and electrochemical techniques. The results demonstrated that the mixed medium containing D. caledoniensis and P. aeruginosa further accelerated the MIC of 70Cu-30Ni alloy compared to the single species medium. The addition of exogenous pyocyanin (PYO) to the D. caledoniensis medium increased the maximum pit depth on 70Cu-30Ni alloy from 5.40 μm to 6.59 μm, and the corrosion current density (icorr) increased by one order of magnitude. From the perspective of bioenergetics and extracellular electron transfer (EET), the comprehensive MIC mechanism of 70Cu-30Ni alloy induced by D. caledoniensis and P. aeruginosa was proposed.

A review of the electrochemical and galvanic corrosion behavior of important intermetallic compounds in the context of aluminum alloys

Aluminum alloys are widely sought for different applications due to their high strength-to-weight ratio. Most often this increased strength of the alloy is achieved by specific alloying elements and heat treatment processes which give rise to second phases intermetallic particles (IMPs) also known as intermetallic compounds (IMCs). These second phases play a dominant role in the corrosion susceptibility of aluminum alloys. This review provides a systematic survey of the electrochemical, and galvanic corrosion behavior of IMPs in the context of aluminum alloys. A discussion of the electrochemical/galvanic corrosion behavior of selected/important intermetallic compounds that are commonly found in aluminum alloys such as the Q-phase (Al4Cu2Mg7Si8), π-phase (Al8Mg3FeSi6), θ-phase (Al2Cu), S-phase (Al2CuMg), the β-phase (Mg2Si), β-phase (Al3Mg2), δ (Al3Li), η-phase (MgZn2), and β-phase (Al3Fe) is provided. In addition, the limitations in the electrochemical characterization of intermetallic compounds, the research gap, and prospects are also provided in addition to the phenomenon of galvanic polarity reversal and self-dissolution of IMPs.

Characteristics of Mg-Based Sintered Alloy with Au Addition

The magnesium-based alloys produced by mechanical alloying (MA) are characterized by specific porosity, fine-grained structure, and isotropic properties. In addition, alloys containing magnesium, zinc, calcium, and the noble element gold are biocompatible, so they can be used for biomedical implants. The paper assesses selected mechanical properties and the structure of the Mg₆₃Zn₃₀Ca₄Au₃ as a potential biodegradable biomaterial. The alloy was produced by mechanical synthesis with a milling time of 13 h, and sintered via spark-plasma sintering (SPS) carried out at a temperature of 350 °C and a compaction pressure of 50 MPa, with a holding time of 4 min and a heating rate of 50 °C∙min^-1 to 300 °C and 25 °C∙min^-1 from 300 to 350 °C. The article presents the results of the X-ray diffraction (XRD) method, density, scanning electron microscopy (SEM), particle size distributions, and Vickers microhardness and electrochemical properties via electrochemical impedance spectroscopy (EIS) and potentiodynamic immersion testing. The obtained results reveal the compressive strength of 216 MPa and Young's modulus of 2530 MPa. The structure comprises MgZn₂ and Mg₃Au phases formed during the mechanical synthesis, and Mg₇Zn₃ that has been formed during the sintering process. Although MgZn₂ and Mg₇Zn₃ improve the corrosion resistance of the Mg-based alloys, it has been revealed that the double layer formed because of contact with the Ringer's solution is not an effective barrier; hence, more data and optimization are necessary.

Environmentally Friendly Layered Double Hydroxide Conversion Layers: Formation Kinetics on Zn-Al-Mg-Coated Steel

Phosphate- or chromate-based industrially produced conversion layers, while effectively increasing adhesion for organic coatings and corrosion resistance, come at the cost of environmentally problematic and harmful treatment solutions and waste. In this respect, layered double hydroxide (LDH)-based conversion layers offer an environmentally benign alternative without toxicologically concerning compounds in the treatment solution. Here, we study an LDH conversion layer on Zn-Al-Mg-coated steel (ZM-coated steel), which was produced by immersion into a carbonate- and magnesium-containing alkaline solution. The mechanism and kinetics of the conversion layer formation were investigated with in situ open circuit potential measurements, cyclic voltammetry (CV), and scanning electron microscopy (SEM). Acceleration of the LDH layer formation through high convection in the treatment solution was found. This was attributed to a higher oxygen availability at the metal/solution interface because no diffusion-limited state during the layer formation is reached due to high convection. The importance of oxygen within the kinetics indicates a corrosion-like mechanism, with cathodic and anodic sites on the steel sample. The LDH formation happens by co-precipitation of ions present in the treatment solution and dissolved ions from the ZM-coated steel. With CV, SEM, and X-ray diffraction, the growth of the LDH conversion layer was investigated with respect to the immersion time. It was found that after 30 s, the sample surface was almost fully covered with an LDH layer, and with the increasing immersion time, the layer grows in thickness. Increased understanding on the kinetics and mechanism of the LDH conversion layer formation on ZM-coated steel gives rise to a targeted optimization of the treatment solution and process parameters.

Why are Zn-rich Zn-Mg nanoalloys optimal protective coatings against corrosion? A first-principles study of the initial stages of the oxidation process

ZnMg alloys of certain compositions in the Zn-rich side of the phase diagram are particularly efficient, and widely used, as anticorrosive coatings, but a sound understanding of the physico-chemical properties behind such quality is still far from being achieved. The present work focuses on the first stage of the corrosion process, namely the initial growth of a sacrificial surface oxide layer, whose characteristics will condition the next stages of the corrosion. A comprehensive ab initio study, based on density functional theory, is carried out on ZnMg nanoalloys with 20 atoms and different compositions, which serve as model systems to simulate the complex processes that occur in extended granular surfaces. The structural and electronic properties, when progressive oxidation of the nanoalloys takes place, are analyzed in detail with the help of structural descriptors, energetic descriptors such as the oxygen adsorption energies and excess adsorption energies, as well as with electronic ones based on the topological analysis of the electron density and the electron localization function, from which a detailed analysis of the bonding patterns is extracted. We explain why small amounts of Mg create a very positive synergy between Zn and Mg that increases the reactivity to oxygen while reducing, at the same time, the stress induced on the cluster substrate, both facts working in favor of promoting the growth of the oxide crust whilst protecting the core. Moreover, we also show that stoichiometries close to the Mg₂Zn₁₁ and MgZn₂ compositions are the best candidates to optimize the protection against corrosion in Zn-Mg alloys, in agreement with the experimental observations.