Corrosion Resistance of the Superhydrophobic Mg(OH)2/Mg-Al Layered Double Hydroxide Coatings on Magnesium Alloys

Electrochemiluminescent resonance energy transfer between amino-modified g-C3N4/Bi2MoO6 composite and carboxyl CoS2 nanoboxes for sensitive detection of alpha fetoprotein

This work demonstrates an effective quenching electrochemiluminescent (ECL) immunosensor based on resonance energy transfer for the sensitive detection of alpha fetoprotein (AFP). In this strategy, graphitic carbon nitride (g-C3N4) was coupled with bismuth molybdenum oxide (Bi2MoO6) to form a g-C3N4/Bi2MoO6 nanocomposite as a novel type of ECL immunosensor. The as-synthesized amino-modified g-C3N4/Bi2MoO6 nanocomposite presents strong and stable cathodic ECL activity compared to pristine g-C3N4. One plausible reason is that the synergistic effect between the g-C3N4 and Bi2MoO6 could facilitate charge transfer process and thereby enhancing the separation efficiency of electron-hole pairs. The other functional part of the immunosensor, carboxyl CoS2 nanoboxes with a broad absorption range, was rationally designed and introduced. The evidence that the absorption spectra of carboxyl CoS2 NBs overlap with ECL spectra of g-C3N4/Bi2MoO6 nanocomposite holds accountable for exceptionally weakened ECL signal. This sandwich-type immunosensor was setup based on quenching mechanism concerning amino-modified g-C3N4/Bi2MoO6 as an ECL donor and carboxyl CoS2 NBs as an ECL accepter. The strategy was optimized to achieve a convincible and sensitive detection goal for AFP with a wide quantifiable range of 0.5 pg/mL-10 ng/mL whilst a sufficiently low detection limit of 0.04 pg/mL (S/N = 3). This immunosensor shows great potential for real sample analysis with reasonable recoveries ranging from 95.5 to 99.0 %, demonstrating its high precision for AFP determination.

Dipole Coupling Accelerated H2 O Dissociation by Magnesium-Based Intermetallic Catalysts

The water (H2 O) dissociation is critical for various H2 O-associated reactions, including water gas shift, hydrogen evolution reaction and hydrolysis corrosion. While the d-band center concept offers a catalyst design guideline for H2 O activation, it cannot be applied to intermetallic or main group elements-based systems because Coulomb interaction was not considered. Herein, using hydrolysis corrosion of Mg as an example, we illustrate the critical role of the dipole of the intermetallic catalysts for H2 O dissociation. The H2 O dissociation kinetics can be enhanced using Mgx Mey (Me=Co, Ni, Cu, Si and Al) as catalysts, and the hydrogen generation rate of Mg2 Ni-loaded Mg reached 80 times as high as Ni-loaded Mg. The adsorbed H2 O molecules strongly couple with the Mg-Me dipole of Mgx Mey , lowering the H2 O dissociation barrier. The dipole-based H2 O dissociation mechanism is applicable to non-transition metal-based systems, such as Mg2 Si and Mg17 Al12 , offering a flexible catalyst design strategy for controllable H2 O dissociation.

Bio-inspired and metal-derived superwetting surfaces: Function, stability and applications

Due to their exceptional anti-icing, anti-corrosion, and anti-drag qualities, biomimetic metal-derived superwetting surfaces, which are widely employed in the aerospace, automotive, electronic, and biomedical industries, have raised significant concern. However, further applications in other domains have been hampered by the poor mechanical and chemical durability of superwetting metallic surfaces, which can result in metal fatigue and corrosion. The potential for anti-corrosion, anti-contamination, anti-icing, oil/water separation, and oil transportation on surfaces with superwettability has increased in recent years due to the advancement of research in biomimetic superwetting interface theory and practice. Recent developments in functionalized biomimetic metal-derived superwetting surfaces were summarized in this paper. Firstly, a detailed presentation of biomimetic metal-derived superwetting surfaces with unique capabilities was made. The problems with the long-term mechanical and chemical stability of biomimetic metal-derived superwetting surfaces were then examined, along with potential solutions. Finally, in an effort to generate fresh concepts for the study of biomimetic metal-derived superwetting surfaces, the applications of superwetting metallic surfaces in various domains were discussed in depth. The future direction of biomimetic metal-derived superwetting surfaces was also addressed.

Chromate-Free Corrosion Protection Strategies for Magnesium Alloys-A Review: PART I-Pre-Treatment and Conversion Coating

Corrosion protection systems based on hexavalent chromium are traditionally perceived to be a panacea for many engineering metals including magnesium alloys. However, bans and strict application regulations attributed to environmental concerns and the carcinogenic nature of hexavalent chromium have driven a considerable amount of effort into developing safer and more environmentally friendly alternative techniques that provide the desired corrosion protection performance for magnesium and its alloys. Part I of this review series considers the various pre-treatment methods as the earliest step involved in the preparation of Mg surfaces for the purpose of further anti-corrosion treatments. The decisive effect of pre-treatment on the corrosion properties of both bare and coated magnesium is discussed. The second section of this review covers the fundamentals and performance of conventional and state-of-the-art conversion coating formulations including phosphate-based, rare-earth-based, vanadate, fluoride-based, and LDH. In addition, the advantages and challenges of each conversion coating formulation are discussed to accommodate the perspectives on their application and future development. Several auspicious corrosion protection performances have been reported as the outcome of extensive ongoing research dedicated to the development of conversion coatings, which can potentially replace hazardous chromium(VI)-based technologies in industries.

Insight into synergetic effects of serum albumin and glucose on the biodegradation behavior of WE43 alloy in simulated body fluid

The biodegradation rate of Mg alloy medical devices, such as screws and plates for temporary bone fracture fixation or coronary angioplasty stents, is an increasingly important area of study.In vitromodels of the corrosion behavior of these devices use revised simulated body fluid (m-SBF) based on a healthy individual's blood chemistry. Therefore, model outputs have limited application to patients with altered blood plasma glucose or protein concentrations. This work studies the biodegradation behavior of Mg alloy WE43 in m-SBF modified with varying concentrations of glucose and bovine serum albumin (BSA) to (1) mimic a range of disease states and (2) determine the contributions of each biomolecule to corrosion. Measurements include the Mg ion release rate, electrolyte pH, the extent of hydrogen evolution (as a proxy for corrosion rate), surface morphology, and corrosion product composition and effects. BSA (0.1 g l^-1) suppresses the rate of hydrogen evolution (about 30%) after 24 h and-to a lesser degree-Mg²⁺release in both the presence and absence of glucose. This effect gets more pronounced with time, possibly due to BSA adsorption on the Mg surface. Electrochemical studies confirm that adding glucose (2 g l^-1) to the solution containing BSA (0.1 g l^-1) caused a decrease in corrosion resistance (by around 40%), and concomitant increase in the hydrogen evolution rate (from 10.32 to 11.04 mg cm^-2d^-1) to levels far beyond the tolerance limits of live tissues.

A Review on LDH-Smart Functionalization of Anodic Films of Mg Alloys

This review presents an overview of the recent developments in the synthesis of layered double hydroxide (LDH) on the anodized films of Mg alloys prepared by either conventional anodizing or plasma electrolytic oxidation (PEO) and the applications of the formed composite ceramics as smart chloride traps in corrosive environments. In this work, the main fabrication approaches including co-precipitation, in situ hydrothermal, and an anion exchange reaction are outlined. The unique structure of LDH nanocontainers enables them to intercalate several corrosion inhibitors and release them when required under the action of corrosion-relevant triggers. The influences of different variables, such as type of cations, the concentration of salts, pH, and temperature, immersion time during the formation of LDH/anodic film composites, on the electrochemical response are also highlighted. The correlation between the dissolution rate of PEO coating and the growth rate of the LDH film was discussed. The challenges and future development strategies of LDH/anodic films are also highlighted in terms of industrial applications of these materials.

Zn-contained mussel-inspired film on Mg alloy for inhibiting bacterial infection and promoting bone regeneration

Infection and insufficient osteointegration are the main causes of orthopedic implant failure. Furthermore, activating favorable inflammation response is vital to the fast osteointegration of implants. Therefore, endowing the implants with multifunctions (antibacterial, anti-inflammation, and pro-osteointegration) is a promising strategy to improve the performance of orthopedic implants. In this study, a Zn-contained polydopamine (PDA) film was fabricated on AZ31 alloy. The film possessed a stable Zn ion release in 14 days. The results of electrochemical analysis implied the favorable corrosion protection of the film, and thus, leading to a suitable hemolysis ratio (below 1%). The in vitro antibacterial assessment revealed that the film exhibited excellent resistance against Staphylococcus aureus (nearly 100%), which can be ascribed to the release of Zn ions. The cell-culture evaluation revealed that the extract of Zn-contained PDA-coated sample can activate RAW264.7 polarization to an anti-inflammatory phenotype, as well as enhance the osteogenic differentiation ability of MC3T3-E1. Additionally, the femoral osteomyelitis model indicated that the as-prepared film had a high antibacterial capability at early stage of the implantation, and showed better osteogenesis and osteointegration after 8 weeks of implantation. With favorable antibacterial, anti-inflammation, and pro-osteogenesis abilities, the novel designed Zn-contained PDA film is promising to be used in Mg-based orthopedic implants.

Synthesis of ultrathin metal oxide and hydroxide nanosheets using formamide in water at room temperature

Here, 6 different ultrathin (<5 nm) 2D metal oxides and hydroxides have been successfully synthesized via a simple precipitation route in formamide aqueous solution at room temperature.

Stearic Acid/Layered Double Hydroxides Composite Thin Films Deposited by Combined Laser Techniques

We report on the investigation of stearic acid-layered double hydroxide (LDH) composite films, with controlled wettability capabilities, deposited by a combined pulsed laser deposition (PLD)-matrix-assisted pulsed laser evaporation (MAPLE) system. Two pulsed lasers working in IR or UV were used for experiments, allowing the use of proper deposition parameters (wavelength, laser fluence, repetition rate) for each organic and inorganic component material. We have studied the time stability and wettability properties of the films and we have seen that the morphology of the surface has a low effect on the wettability of the surfaces. The obtained composite films consist in stearic acid aggregates in LDH structure, exhibiting a shift to hydrophobicity after 36 months of storage.

In vitro and in vivo studies of Mg-30Sc alloys with different phase structure for potential usage within bone

Proper alloying magnesium with element scandium (Sc) could transform its microstructure from α phase with hexagonal closed-packed (hcp) structure into β phase with body-cubic centered (bcc) structure. In the present work, the Mg-30 wt% Sc alloy with single α phase, dual phases (α + β) or β phase microstructure were developed by altering the heat-treatment routines and their suitability for usage within bone was comprehensively investigated. The β phased Mg-30 wt% Sc alloy showed the best mechanical performance with ultimate compressive strength of 603 ± 39 MPa and compressive strain of 31 ± 3%. In vitro degradation test showed that element scandium could effectively incorporate into the surface corrosion product layer, form a double-layered structure, and further protect the alloy matrix. No cytotoxic effect was observed for both single α phased and β phased Mg-30 wt% Sc alloys on MC3T3 cell line. Moreover, the β phased Mg-30 wt%Sc alloy displayed acceptable corrosion resistance in vivo (0.06 mm y^-1) and maintained mechanical integrity up to 24 weeks. The degradation process did not significantly influence the hematology indexes of inflammation, hepatic or renal functions. The bone-implant contact ratio of 75 ± 10% after 24 weeks implied satisfactory integration between β phased Mg-30 wt%Sc alloy and the surrounding bone. These findings indicate a potential usage of the bcc-structured Mg-Sc alloy within bone and might provide a new strategy for future biomedical magnesium alloy design. STATEMENT OF SIGNIFICANCE: Scandium is the only rare earth element that can transform the matrix of magnesium alloy into bcc structure, and Mg-30 wt%Sc alloy had been recently reported to exhibit shape memory effect. The aim of the present work is to study the feasibility of Mg-30 wt%Sc alloy with different constitutional phases (single α phase, single β phase or dual phases (α + β)) as biodegradable orthopedic implant by in vitro and in vivo testings. Our findings showed that β phased Mg-30 wt%Sc alloy which is of bcc structure exhibited improved strength and superior in vivo degradation performance (0.06 mm y^-1). No cytotoxicity and systematic toxicity were shown for β phased Mg-30 wt%Sc alloy on MC3T3 cell model and rat organisms. Moreover, good osseointegration, limited hydrogen gas release and maintained mechanical integrity were observed after 24 weeks' implantation into the rat femur bone.

Three-dimensional nickel vanadium layered double hydroxide nanostructures grown on carbon cloth for high-performance flexible supercapacitor applications

This study reports the synthesis of ultrathin Ni-V layered double hydroxide nanosheets on carbon cloth (NVL@CC) through adopting a facile and cost-effective method for flexible supercapacitor applications. The as-synthesized NVL@CC possesses a uniform, mechanically strong and highly ordered porous network with connected pores, ensuring high specific capacitance and enhanced cyclability. A high specific capacity of 1226 C g^-1 (2790 F g^-1) was obtained at 1 A g^-1, and it remained at 430 C g^-1 (1122 F g^-1) even at a higher current density of 10 A g^-1. A hybrid supercapacitor (HSC) was assembled with the NVL@CC electrode as the positive electrode and activated carbon coated carbon cloth as the negative electrode (NVL@CC//AC HSC). The devices showed an excellent energy density of 0.69 mW h cm^-3 at a power density of 2.5 mW cm^-3 with 100% of the original capacitance being retained at a current density of 5 mA cm^-2. Furthermore, the devices exhibited an energy density of 0.24 mW h cm^-3 even at a higher power density of 214.4 mW cm^-3, surpassing the performances observed for many recently reported flexible supercapacitors. Importantly, the electrochemical performance of the solid-state flexible supercapacitors showed a negligible change upon bending and twisting of the devices. The devices showed no decay in specific capacitance and coulombic efficiency up to 5000 charge-discharge cycles, confirming the excellent cycle life of the HSC device. The performance of NVL@CC indicates the great potential of the material for future flexible energy storage devices.

Hydrothermally Tailored Three-Dimensional Ni-V Layered Double Hydroxide Nanosheets as High-Performance Hybrid Supercapacitor Applications

Here, we report a facile and easily scalable hydrothermal synthetic strategy to synthesize Ni-V layered double hydroxide (NiV LDH) nanosheets toward high-energy and high-power-density supercapacitor applications. NiV LDH nanosheets with varying Ni-to-V ratios were prepared. Three-dimensional curved nanosheets of Ni_0.80V_0.20 LDH showed better electrochemical performance compared to other synthesized NiV LDHs. The electrode coated with Ni_0.80V_0.20 LDH nanosheets in a three-electrode cell configuration showed excellent pseudocapacitive behavior, having a high specific capacity of 711 C g^-1 (1581 F g^-1) at a current density of 1 A g^-1 in 2 M KOH. The material showed an excellent rate capability and retained the high specific capacity of 549 C g^-1 (1220 F g^-1) at a current density of 10 A g^-1 and low internal resistances. Owing to its superior performance, Ni_0.80V_0.20 LDH nanosheets were used as positive electrode and commercial activated carbon was used as negative electrode for constructing a hybrid supercapacitor (HSC) device, having a working voltage of 1.5 V. The HSC device exhibited a high specific capacitance of 98 F g^-1 at a current density of 1 A g^-1. The HSC device showed a higher energy density of 30.6 Wh kg^-1 at a power density of 0.78 kW kg^-1 and maintained a high value of 24 Wh kg^-1 when the power density was increased to 11.1 kW kg^-1. The performance of NiV LDHs nanosheets indicates their great potential as low-cost electrode material for future energy-storage devices.

New Method for the Corrosion Resistance of AZ31 Mg Alloy with a Porous Micro-Arc Oxidation Membrane as an Ionic Corrosion Inhibitor Container

This work introduces a new composite anticorrosion coating for the AZ31 magnesium alloy, based on the synergistic effect of an organic/inorganic composite coating with a micro- and nanoporous micro-arc oxidation (MAO) membrane as the container of ionic corrosion inhibitor (M-16). The surface morphologies and size of the micro/nanocontainers in the porous MAO membrane before and after filling with M-16 corrosion inhibitor are examined by scanning electron microscopy (SEM). The effectiveness of M-16 for corrosion suppression on AZ31 Mg alloy with and without epoxy coating as the top sealing layer is demonstrated by electrochemical impedance spectroscopy (EIS) and salt spray tests. The potentiodynamic polarization and electrochemical impedance spectroscopy measurements show that, compared with the bare AZ31 Mg alloys, the composite coating has superior corrosion resistance with the a lower corrosion current (9.7 × 10^-9 A/cm²) and a higher protection efficiency (99.3%) after immersion in 3.5 wt % NaCl solution and, meanwhile, has stronger salt spray resistance within 30 days. The results demonstrate the synergistic effect of the isolation protection of the micro-arc oxidation layer and the inhibition of M-16 and that the epoxy coating contributed to the protection for AZ31 Mg substrate to some extent. Therefore, it is anticipated that the composite coating has a potential application in the protection of metals and their alloys.