Search Results (70)

By modulating the mass ratio of hydrothermal agents to cobalt/iron precursors, Co₃O₄ nanowires were successfully integrated into spinel-type Co/Fe@NF, forming a heterojunction anode for alkaline water electrolysis (AWE) hydrogen production. This Co₃O₄ nanowire-assembled CoFe₂O₄ nanosheet anode (Co/Fe(5:1)@NF) exhibits exceptional electrochemical oxygen evolution reaction (OER) performance, requiring only 221 mV overpotential to achieve 10 mA cm⁻². Sulfamethoxazole (SMX) was employed as a model pollutant to investigate the anode sacrificial material; it achieved approximately 95% SMX degradation efficiency, reducing the OER potential of 50 mV/10 mA cm⁻². SMX oxidation coupled with Co/Fe heterojunction structure partially substitutes the OER. Co/Fe heterojunction generates an internal magnetic field, which induces the formation of novel active species within the system. ·O₂⁻ is the newly formed active oxygen species, which enhanced the proportion of indirect SMX oxidation. Quantitative analysis reveals that superoxide radical-mediated indirect oxidation of SMX accounts for approximately 38.5%, Fe(VI) for 9.4%, other active species for 6.1%, and direct oxidation for 46.0%. The nanowire–nanosheet assembly stabilizes a high-spin configuration on the catalyst surface, redirecting oxygen intermediate pathways toward triplet oxygen (³O₂) generation. Subsequent electron transfer from nanowire tips facilitates rapid ³O₂ reduction, forming superoxide radicals (·O₂⁻). This study effectively driven by indirect oxidation, with cathodic hydrogen production, providing a novel strategy for utilizing renewable electricity and reducing OER while offering insights into the design of Co/Fe-based catalyst. Full article

This study systematically investigated the effects of biologically relevant microalloying elements—calcium (Ca), strontium (Sr), manganese (Mn), and zirconium (Zr)—on the electrochemical behavior of Mg-Y-Zn alloys containing long-period stacking ordered (LPSO) phases. The alloys were prepared by casting and characterized using X-ray diffraction (XRD), optical microscopy (OM), and scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS). Electrochemical properties were assessed through potentiodynamic polarization in Hank’s solution, and corrosion rates were determined by hydrogen evolution and weight loss methods. Microalloying significantly enhanced the corrosion resistance of the base Mg-Y-Zn alloy, with corrosion rates decreasing from 2.67 mm/year (unalloyed) to 1.65 mm/year (Ca), 1.36 mm/year (Sr), 1.18 mm/year (Zr), and 1.02 mm/year (Mn). Ca and Sr additions introduced Mg₂Ca and Mg₁₇Sr₂, while Mn and Zr refined the existing LPSO structure without new phases. Sr refined the LPSO phase and formed a uniformly distributed Mg₁₇Sr₂ network, promoting uniform corrosion and suppressing deep localized attacks. Ca-induced Mg₂Ca acted as a temporary sacrificial phase, with corrosion eventually propagating along LPSO interfaces. The Mn-containing alloy exhibited the lowest corrosion rate; this is attributed to the suppression of both anodic and cathodic reaction kinetics and the formation of a stable protective surface film. Zr improved general corrosion resistance but increased susceptibility to localized attacks due to dislocation-rich zones. These findings elucidate the corrosion mechanisms in LPSO-containing Mg alloys and offer an effective strategy to enhance the electrochemical stability of biodegradable Mg-based implants. Full article

The influence of multiwall carbon nanotube (MWCNT) reinforcements on electrochemical corrosion investigations at varying NaCl concentrations (0.4 M, 0.6 M, 0.8 M, 1 M) of Mg-Zn-Ce nanocomposites is studied in this work. The Mg-Zn-Ce/MWCNT nanocomposites were developed by using an ultrasonication-assisted hybrid stir–squeeze (UHSS) casting method with different MWCNT concentrations (0, 0.4, 0.8, 1.2 wt.%) in a Mg-Zn-Ce magnesium alloy matrix. The microstructural characterizations shown using X-ray diffraction revealed the presence of secondary phases (MgZn₂, Mg₁₂Ce), T-phase (Mg₇Zn₃RE), α-Mg, and MWCNT peaks. Optical microscopy results showed grain refinement in the case of nanocomposites. Transmission electron microscope studies revealed well-dispersed MWCNT, indicating the good selection of processing parameters. The uniform dispersion of MWCNTs was achieved due to a hybrid stirring mechanism along with transient cavitation, ultrasonic streaming, and squeeze effect. The higher E_corr value of −1.39 V, lower I_corr value (5.81 µA/cm²), and lower corrosion rate of 0.1 mm/Yr (↑77%) were obtained by 0.8% nanocomposite at 0.4 M NaCl concentration, when compared to the monolithic alloy. The Mg(OH)₂ passive film formation on 0.8 wt.% nanocomposite was denser, attributed to the refined grains. At higher NaCl concentration, the one-dimensional morphological advantage of MWCNT helped to act as a barrier for further Mg exposure to excessive Cl⁻ attack, which reduced the formation of MgCl₂. Therefore, the UHSS-casted Mg-Zn-Ce/MWCNT nanocomposites present a good potential as sacrificial anodes for use in a wide range of industrial applications. Full article

To solve the problem of the boundary condition of the electrochemical field for a cathodic protection system of a steel offshore platform jacket, a new concept for the real electrochemical boundary condition was first proposed. The new idea considers that different points on the steel surface have different surface states and different polarization processes. The new method involved using sixteen sets of measurement equipment and a small test jacket to obtain different polarization processes at different points. A new test device was designed to obtain the relationship curves of potential/current density at different points. The polarization processes at different points were obtained. We first found that all polarization processes had four stages: rapid polarization, data jumping, polarization with middle speed, and slow polarization. At the end of the measurement, the current density interval exhibited a convergence phenomenon. The fitting curve based on the endpoint of the fourth stage of each relationship curve was regarded as the real boundary condition. The boundary condition was verified by the small test jacket and the real jacket. The comparison between the calculation and the measurement proved that the boundary condition was correct. The real boundary condition based on the new method reflected the real state and polarization process of the jacket and provided the correct incoming data for electrochemical field. Full article

In the field of degradable metals, Zn-based implants have gradually gained more attention. However, the relatively slow degradation rate compared with the healing rate of the damaged bone tissue, along with the excessive Zn²⁺ release during the degradation process, limit the application of Zn-based implants. The use of intermetallic compounds with more negative electrode potentials as sacrificial anodes of Zn-based implants is likely to be a feasible approach to resolve this contradiction. In this work, three intermetallic compounds, MgZn₂, CaZn₁₃, and Ca₂Mg₆Zn₃, were prepared. The phase structures, microstructures, and relevant properties, such as thermal stability, in vitro degradation properties, and cytotoxicity of the compounds, were investigated. The XRD patterns indicate that the MgZn₂ and CaZn₁₃ specimens contain single-phase MgZn₂ and CaZn₁₃, respectively, while the Ca₂Mg₆Zn₃ specimen contains Mg₂Ca and Ca₂Mg₆Zn₃ phases. After purifying treatment in 0.9% NaCl solution, high purity Ca₂Mg₆Zn₃ phase was obtained. Thermal stability tests suggest that the MgZn₂ and CaZn₁₃ specimens possess good thermal stability below 773 K. However, the Ca₂Mg₆Zn₃ specimen melted at around 739.1 K. Polarization curve tests show that the corrosion potentials of MgZn₂, CaZn₁₃, and Ca₂Mg₆Zn₃ in simulated body fluid (SBF) were −1.063 V_SCE, −1.289 V_SCE, and −1.432 V_SCE, which were all more negative than that of the pure Zn specimen (−1.003 V_SCE). Clearly, these compounds can act as sacrificial anodes in Zn-based implants. The immersion tests indicate that these compounds were degraded according to the atomic ratio of the elements in each compound. Besides that, the compounds can efficiently induce Ca-P deposition in SBF. Cytotoxicity tests demonstrate that the 10% extracts prepared from these compounds exhibit good cell activity on MC3T3-E1 cells. Full article

Iron and iron-nickel alloy electrodeposits synthesized from sulfate-based electroplating baths were applied to a mild carbon steel substrate. Coated specimens were immersed in an oxygen-saturated, weak ammonium hydroxide solution (pH 9.5–10.0), and their corrosion performance was evaluated using electrochemical techniques. Galvanic and general corrosion behaviors were analyzed to assess the sacrificial protection provided by Fe and Fe-Ni coatings relative to uncoated steel. The influence of anode-to-cathode (A/C) surface area ratios (1:1, 10:1, and 100:1) on the occurrence of plating-induced surface cracks was also examined. Surface morphology and elemental composition of the deposits were characterized. Results of the study indicated that increasing the Ni²⁺/Fe²⁺ molar ratio of the electroplating bath from 0 to 0.167 led to (1) reduced surface porosity and cracking, (2) decreased galvanic corrosion rates between the electrodeposit and substrate, and (3) a progressive increase in the temperature dependence of the general corrosion rate between 20 °C and 60 °C. The development of Fe and Fe-Ni alloy electrodeposits as protective coatings is of particular interest in water-tube power boiler applications, where production of corrosion products must be controlled. Further research is needed to develop coatings that perform predictably under elevated pressures and temperatures typical of operating boiler environments. Full article

Epitaxial layers of water-soluble Sr₃Al₂O₆ were fabricated as sacrificial layers on SrTiO₃ (100) single-crystal substrates using the Pulsed Laser Deposition technique. This approach envisages the possibility of developing a new generation of micro-Solid Oxide Fuel Cells and micro-Solid Oxide Electrochemical Cells for portable energy conversion and storage devices. The sacrificial layer technique offers a pathway to engineering free-standing membranes of electrolytes, cathodes, and anodes with total thicknesses on the order of a few nanometers. Furthermore, the ability to etch the SAO sacrificial layer and transfer ultra-thin oxide films from single-crystal substrates to silicon-based circuits opens possibilities for creating a novel class of mixed electronic and ionic devices with unexplored potential. In this work, we report the growth mechanism and structural characterization of the SAO sacrificial layer. Epitaxial samarium-doped ceria films, grown on SrTiO3 substrates using Sr₃Al₂O₆ as a buffer layer, were successfully transferred onto silicon wafers. This demonstration highlights the potential of the sacrificial layer method for integrating high-quality oxide thin films into advanced device architectures, bridging the gap between oxide materials and silicon-based technologies. Full article

The development of environmentally friendly materials is a subject of increasing interest in corrosion protection research. The objective of the present investigation is to propose the preparation procedure of chitosan–alginate (CHI/ALG) nanocontainers loaded with zinc oxide (ZnO) nanoparticles or combining ZnO nanoparticles with corrosion inhibitor caffeine (CAF), both suitable for incorporation into the matrix of ordinary zinc coatings on mild steel substrates. The nanocontainers were synthesized through spontaneous polysaccharide complexation in the presence of ZnO nanoparticles and CAF using a cross-linking agent, namely tripolyphosphate (TPP). Dynamic light scattering and laser Doppler velocimetry measurements are used for evaluation of the size distribution and zeta potentials of the nanocontainers, both loaded or unloaded with CAF. Using UV-spectroscopy, entrapment efficiency and release amounts of CAF are quantitatively evaluated. The nanocontainers thus obtained were incorporated into the matrices of ordinary zinc coatings via co-electrodeposition with zinc from zinc sulfate solution, aiming to improve the corrosion protection of steel in corrosive environments containing chloride ions. The surface morphology and elemental composition of the electrodeposited hybrid coatings before and after treating in the model corrosive medium of 3.5% NaCl is studied by scanning electron microscopy (SEM). The cyclic voltammetry method (CVA) is applied to characterize the cathodic (electrodeposition) and anodic (dissolution) processes. The protective characteristics of the hybrid coatings are investigated by application of potentiodynamic polarization (PDP) curves and polarization resistance (Rp) measurements after a time interval of 40 days. The obtained results indicate that both hybrid coating types could prolong the life time of mild steel in aggressive Cl⁻ ion-containing solution, combining the protection effect of sacrificial zinc with barrier (ZnO) and active (CAF) protective effects. Full article

The synergistic effect of CNT and three-dimensional N-doped graphene foam (3DNG) on improving corrosion resistance of zinc-reinforced epoxy (ZRE) composite coatings was studied in this work. Although CNT itself was demonstrated to be effective to promote the anti-corrosion performance of the ZRE coating, the incorporation of additional 3DNG leads to further enhancement of its corrosion resistance under the synergistic effect of the hybrid carbon nanofillers with different dimensions. Both the content of the carbonaceous fillers and the ratio between them affected the performance of the coating. The optimal content of hybrid filler in the coating was determined to be only 0.1% with 3DNG:CNT = 1:3. With the modification of hybrid fillers, the corrosion current of the coating could be reduced by more than six orders of magnitude. Additionally, the immersion test of the pre-scratched coating directly demonstrated the evident contribution of the hybrid fillers to the sacrificial anode-based surface protection mechanism of the coating. These results confirmed the synergistic effect of the hybrid 1D and 3D carbonaceous fillers on promoting the corrosion inhibition of their coating, which could be promising for application in other functional composites. Full article

The Cu undercut is a recently discovered new defect generated in the wet stripping process of MoNb/Cu gate stacked electrodes for thin-film transistors (TFTs). The formation mechanism and preventive strategy of this defect were identified and investigated in this paper. The impact of stripper concentration and stripping times on the morphology and the corrosion potential (E_corr) of Cu and MoNb were studied. It is observed that the undercut is Cu tip-deficient, not the theoretical MoNb indentation, and the undercut becomes severer with the increase in stripping times. The in-depth mechanism analysis revealed that the abnormal Cu undercut was not ascribed to the galvanic corrosion between MoNb and Cu but to the local crevice corrosion caused by the corrosive medium intruding along the MoNb/Cu interface. Based on this newly found knowledge, three possible prevention schemes (MoNiTi (abbreviated as Mo technology development (MTD) layer/Cu), MoNb/Cu/MTD, and MoNb/Cu/MoNb) were proposed. The experimental validation shows that the Cu undercut can only be completely eliminated in the MoNb/Cu/MTD triple-stacked structure with the top MTD layer as a sacrificial anode. This work provides an effective and economical method to avoid the Cu undercut defect. The obtained results can help ensure TFT yield and improve the performance of TFT devices. Full article

This study compared the advantages and disadvantages of various corrosion protection methods for steel rebars and clarified the advantages of the cathodic protection (CP) method in the application of corrosion protection in marine structures. The advantages and disadvantages of sacrificial anodes and impressed current technology for the CP of steel rebars in marine structures were further discussed in detail, and the feasibility of CP applications in practical engineering was evaluated. Full article

This article compares chemical coagulation with electrocoagulation, two popular methods for the primary treatment of wastewater generated in the process of underground coal gasification (UCG). The primary aim was to determine which method is more effective in the removal of cyanide and sulphide ions, metals and metalloids, as well as organic compounds. In both cases, experiments were conducted in batch 1 dm³ reactors and using iron ions. Four types of coagulants were tested during the chemical coagulation study: FeCl₂, FeSO₄, Fe₂(SO₄)₃, and FeCl₃. In the electrocoagulation experiments, pure iron Armco steel was used to manufacture the sacrificial iron anode. Both processes were tested under a wide range of operating conditions (pH, time, Fe dose) to determine their maximum efficiency for treating UCG wastewater. It was found that, through electrocoagulation, a dose as low as 60 mg Fe/dm³ leads to >60% cyanide reduction and >98% sulphide removal efficiency, while for chemical coagulation, even a dose of 307 mg Fe/dm³ did not achieve more than 24% cyanide ion removal. Moreover, industrial chemical coagulants, especially when used in very high doses, can be a substantial source of cross-contamination with trace elements. Full article

Steel monopile support structures for offshore wind turbines require protection from corrosion and consideration with respect to biofouling on their external and internal surfaces. Cathodic protection (CP) works effectively to protect the external surfaces of monopiles, but internally, byproducts from aluminum sacrificial anode CP (SACP) and impressed current CP (ICCP) induce acidification that accelerates steel corrosion. Through an 8-week sea water deployment of four steel pipes, this project investigated the effect of perforations on internal CP systems. Additionally, marine growth on the internal and external surfaces of the pipes was assessed. SACP and ICCP systems inside perforated pipes performed similarly to external systems at a lower current demand relative to internal systems in sealed pipes. The organisms that grew inside of the perforated SACP and ICCP pipes were similar, suggesting that the CP systems did not affect organism recruitment. The results of this study demonstrate the potential benefits of designing perforated monopiles to enable corrosion control while providing an artificial reef structure for marine organisms to develop healthy ecosystems. Full article

Vinasse is acidic, dark brown wastewater obtained as a residue from the alcohol distillation process, the main component of which is water, in addition to mineral nutrients and a high organic load. Electrocoagulation (EC) is a technology that generates coagulating substances in situ by oxidizing sacrificial anodes through an electric current applied to the electrodes. During the last decade, the electrocoagulation process has been intensively investigated in several reviews, due to its ease of operation, versatility, sustainability and low environmental impact. The objective of the present work has been to make a general review of the EC process, its principle, reaction mechanism and operating parameters involved in the electrocoagulation process. In this research, the PRISMA method was used for the analysis of articles from different databases such as Scopus, ScienceDirect and Google Scholar. This review collects numerous studies of the EC process in stillage wastewater treatment and makes a comparison between these experimental results mainly in terms of chemical oxygen demand removal. In addition, this review makes a comprehensive analysis of EC coupled to other processes, taking into account their operating parameters and stillage contaminant removal efficiency. The conclusion of this research points out that electrocoagulation coupled with other treatment processes is very necessary because it reduces energy consumption and increases the rate of pollutant removal from wastewater. Full article

Phosphorus, P, is a vital element of paramount importance for both humans and for the Environment. Wastewater contains often relatively high concentrations of P which can be recovered as crystalline struvite (MgNH₄PO₄·6H₂O, MAP). This option is quite attractive in assisting sustainable development because struvite can be used as a slow-release fertilizer. Domestic wastewater is usually high in P and nitrogen, N, but relatively poor in magnesium, Mg. It is necessary to develop low-cost solutions for the enrichment of wastewater with Mg. In the present work, sacrificial magnesium anodes were used, which dissolve upon anodic polarization, releasing sufficient magnesium for the selective precipitation of MAP. The application of constant current between two electrodes of which the anode is a low-cost magnesium cylindrical rod (4 cm² exposed surface area) and the other a platinum cathode electrode, both immersed in ammonium phosphate solutions, without adjustment of the solution pH, was investigated. Constant current density over the range 10–100 A·m⁻², between the Mg- Pt electrodes immersed in solutions of ammonium hydrogen phosphate of exactly known initial concentration, was applied using a potentiostat. In the presence of sodium chloride solutions, on the magnesium anode and in the bulk solution, Mg(OH)₂ (brucite) formed because of the passivation of the Mg electrode. In dilute ammonium hydrogen phosphate solutions, the magnesium anode dissolution resulted in struvite precipitation, even at a low applied current (10 mA). Struvite crystals with an average size of 20 μm were precipitated. The behavior of the cell for the electrolyte solutions used was Faradaic as long as the surface coverage of the anode was relatively low. The anodic dissolution of Mg resulted in high pH values (pH 11) eliminating the need for alkali addition. Full article