Search Results (101)

Titanium alloys are frequently subjected to surface treatments to enhance their biocompatibility and corrosion resistance in biological environments. Plasma electrolytic oxidation (PEO) is an environmentally friendly electrochemical technique capable of forming oxide layers characterized by high corrosion resistance, biocompatibility, and strong adhesion to the substrate. In this study, the PEO process was performed using a low-melting-point ternary eutectic electrolyte composed of Ca(NO₃)₂–NaNO₃–KNO₃ (41–17–42 wt.%) with the addition of ammonium dihydrogen phosphate (ADP). The use of this electrolyte system enables a reduction in the operating temperature from 280 to 160 °C. The effects of applied voltage from 200 to 400V, current frequency from 50 to 1000 Hz, and ADP concentrations of 0.1, 0.5, 1, 2, and 5 wt.% on the growth of titanium oxide composite coatings on a Ti-6Al-4V substrate were investigated. The incorporation of Ca and P was confirmed by phase and chemical composition analysis, while scanning electron microscopy (SEM) revealed a porous surface morphology typical of PEO coatings. Corrosion resistance in Hank’s solution, evaluated via Tafel plot fitting of potentiodynamic polarization curves, demonstrated a substantial improvement in electrochemical performance of the PEO-treated samples. The corrosion current decreased from 552 to 219 nA/cm², and the corrosion potential shifted from −102 to 793 mV vs. the Reference Hydrogen Electrode (RHE) compared to the uncoated alloy. These findings indicate optimal PEO processing parameters for producing composite oxide coatings on Ti-6Al-4V alloy surfaces with enhanced corrosion resistance and potential bioactivity, which are attributed to the incorporation of Ca and P into the coating structure. Full article

This paper investigates an integrable spin system known as the Myrzakulov-XIII (M-XIII) equation through geometric and gauge-theoretic methods. The M-XIII equation, which describes dispersionless dynamics with curvature-induced interactions, is shown to admit a geometric interpretation via curve flows in three-dimensional space. We establish its gauge equivalence with the complex coupled dispersionless (CCD) system and construct the corresponding Lax pair. Using the Sym–Tafel formula, we derive exact soliton surfaces associated with the integrable evolution of curves and surfaces. A key focus is placed on the role of geometric and gauge symmetry in the integrability structure and solution construction. The main contributions of this work include: (i) a commutative diagram illustrating the connections between the M-XIII, CCD, and surface deformation models; (ii) the derivation of new exact solutions for a fractional extension of the M-XIII equation using the Kudryashov method; and (iii) the classification of these solutions into trigonometric, hyperbolic, and exponential types. These findings deepen the interplay between symmetry, geometry, and soliton theory in nonlinear spin systems. Full article

In this study, the effect of plastic residual strain on the corrosion behavior of ZK60 magnesium alloy was systematically revealed using a research method combining experimental characterization and numerical simulation. Based on the multiphysical field coupling theory, a numerical model containing deformation field, corrosion phase field, and material transfer field was constructed, and the dynamic simulation of plastic residual strain-induced corrosion damage was successfully realized. Tafel polarization curves obtained from electrochemical tests were fitted to the key parameters of the secondary current distribution. The kinetic parameter L controlling the corrosion rate in the phase-field model was innovatively determined by the inverse calibration method, and a quantitative relationship between the kinetics of electrochemical corrosion and the phase-field theory was established. The corrosion depth distribution of the pre-strained specimens is quantitatively characterized and the results are in agreement with the finite element simulation results. The coupled strain-corrosion analysis method proposed in this study provides a theoretical basis for the design and life prediction of corrosion resistance of components under complex stress states. Full article

In the past ten years, many coal mines have encountered the problem of a premature failure of anchor rod materials. Through field investigation and laboratory research, it was found that the premature failure of these bolt materials is mostly caused by mine water corrosion. In this paper, a Zn-Y₂O₃-Al₂O₃ composite coating was prepared by an electrodeposition method for the corrosion protection of underground anchors. Through the single-factor experiment method, the co-deposition process of Zn²⁺ nano-Y₂O₃ and nano-Al₂O₃ particles was studied. Microhardness was used as the index to determine the optimum preparation process for the composite coatings. Combined with FSEM and XRD tests, the results showed that the synergistic effect of nano-Y₂O₃ and nano-Al₂O₃ particles made the coating grain refined and reduced the coating defects. The hardness of the coating increased from 98.7 Hv to 347.9 Hv, and the hardness and wear resistance of the coating were improved. The hydrophobicity of the Zn-Y₂O₃-Al₂O₃ composite coating was improved, and its static contact angle was 93.28°. The corrosion resistance of the composite coating was studied through electrochemical impedance spectroscopy, the Tafel curve, corrosion morphology, and weight loss. Under the synergistic effect of nano-Y₂O₃ and nano-Al₂O₃ particles, the self-corrosion current density decreased from 4.21 × 10⁻⁴ A/cm² to 1.06 × 10⁻⁵ A/cm², which confirmed that the Zn-Y₂O₃-Al₂O₃ composite coating had better corrosion resistance and durability. After soaking in mine water for 63 days, the Zn-Y₂O₃-Al₂O₃ composite coating had no obvious shedding on the surface and was well preserved. The practical application results show that it has excellent corrosion resistance and durability. The Zn-Y₂O₃-Al₂O₃ nano-composite coating material has significant potential advantages in the field of corrosion resistance of underground anchor rods. Full article

This study is based on the strategies of composite and element doping. Herein, P-MoS₂/rGO materials were synthesized using a solvent-assisted hydrothermal method. The MoS₂ nanosheets were uniformly and vertically grown on rGO; meanwhile, the optimized structure of MoS₂ was achieved by P doping, resulting in improved catalytic performance and structural stability. Under alkaline conditions, the P-MoS₂/rGO catalyst exhibits good electrocatalytic activity, demonstrating a Tafel slope of 70.7 mV dec⁻¹ and an overpotential of 172.8 mV at 10 mA/cm². Notably, even after 3000 consecutive LSV tests, the curves still show a high degree of overlap, indicating exceptional stability. Full article

The electrocatalyst layers (ECLs) in polymer electrolyte membrane (PEM) electrolyzers are fundamentally comprised of IrOx catalysts, support material, and an ionomer. Their stability is critically dependent on structure and composition, necessitating a thorough understanding of ionization potential and work function. We employ Density Functional Theory (DFT) to determine the ionization states of ECLs and to optimize their electronic properties. Furthermore, advanced deep learning simulations (DLSs) significantly enhance the kinetic and transport behaviors of these layers. This work integrates DFT and DLS to elucidate the characteristics of ECLs within PEM electrolyzer cells. We strategically utilize DFT to refine catalyst molecules and assess their electronic properties, while DLS is employed to predict the potential energy of support molecules in the catalyst layers. We establish a clear relationship between the energy and geometry of IrOx molecules. The DFT-DLS framework robustly calculates potential energy and reaction coordinates, effectively bridging theoretical computations with the dynamic behavior of molecules in catalyst layers. We validate our model by comparing it with the experimental polarization curve of the IrOx-based anode catalyst layer in a functioning electrolyzer. The observed Tafel slope and exchange current density unequivocally confirm that the oxygen evolution reaction (OER) occurs through a well-defined electrochemical pathway, with oxygen generation proceeding according to the charge transfer mechanism predicted by the DFT-DLS framework. Full article

The low corrosion resistance of aluminum alloy materials in chloride environments limits their application in light metal structural components. In this study, 434 stainless steel (SS) powders with different numbers of scan layers were deposited on T6061 aluminum using high-velocity oxygen fuel (HVOF). Tafel curve, electrochemical impedance spectroscopy (EIS), salt spray, and galvanic corrosion tests were employed to investigate the comprehensive corrosion behavior of the SS coatings in a chlorine environment. The results showed that the porosity of the SS coatings decreased as the scanning layer increased. A lower porosity slowed the penetration of the corrosive solution and led to an enhanced long-term resistance to chloride attacks in immersion and salt spray corrosion. On this basis, the preferred SS4 sample and iron screw composition system was subjected to galvanic corrosion, and its electric current intensity (5.11 × 10⁻⁵ A) was two orders of magnitude lower than that of T6061 aluminum (9.14 × 10⁻³ A), as well as presenting better anti-corrosion behavior. Full article

The changes in the inclusions in 316L stainless steel before and after Ce addition were studied by adding different contents of Ce. The effects of rare earth Ce treatment on the modification of MnS inclusions in steel and the pitting corrosion resistance of 316L stainless steel are studied by field-emission scanning electron microscopy, laser confocal microscopy, the 6% FeCl₃ corrosion weight loss test, and Tafel polarization curve test. The results show that the addition of Ce reduces the corrosion rate of stainless steel in 6% FeCl₃ solution, and reduces the number and size of corrosion pits. The corrosion resistance is the best at a 0.0082% Ce content. In addition, the addition of Ce reduced the corrosion current density of stainless steel in 3.5% NaCl solution and increased the corrosion potential. The corrosion potential increased from −329 mV to −31.4 mV. Through Ce treatment, the grain is refined and the inclusions in the experimental steel are modified. With the increase in rare earth content, Mn S gradually transforms into Ce₂O₂ S inclusions. The morphology of the inclusions gradually change from the original long strips to a spherical shape, and the average size is significantly reduced, which improves the corrosion resistance of the stainless steel. The addition of rare earth Ce plays modifies the inclusions and purifies molten steel. Full article

Using electrocatalytic water reduction to produce hydrogen fuel offers significant potential for clean energy, yet its large-scale adoption depends on developing cost-effective, non-precious, and efficient catalysts to replace expensive Pt-based state-of-the-art HER catalysts. The catalytic HER performance of an active catalyst largely depends on the available catalytic active sites, conductivity, and intrinsic electrochemical kinetics, all of which can be altered by incorporating a heteroatom into the active catalyst structure. Herein, we synthesized a unique nitrogen-doped CuO@CuS (NCOS) core–shell-structured catalyst through a facile hydrothermal process followed by an efficacious nitrogenation process, and its electrochemical performance for the HER was systematically analyzed. The NCOS core–shell-structured catalyst exhibits a reduced overpotential (55 mV) and Tafel slope (107 mV dec⁻¹) compared to the pure CuS (CS; 179 mV and 201 mV dec⁻¹) catalyst at a current density of 10 mA cm⁻². Moreover, the NCOS core–shell-structured catalyst demonstrates excellent endurance for up to 50 h of chronopotentiometric testing at a driving current density rate of 10 and 100 mA cm⁻². This excellent catalytic HER activity is a result of an increased electron transfer rate and a greater number of accessible active sites, attributed to a change in structural properties and the high electronic conductivity aroused from nitrogen incorporation, as evidenced from the TOF and EIS curve analyses. Full article

In order to obtain electronic contacts with good performance, Au-Cu alloy coatings with different gold contents were prepared on copper substrates by direct current electrodeposition and were tested against electrochemical corrosion and arc corrosion. The experimental results showed that the hardness of the Au-Cu alloy was in the range of 115.2 HV~171.6 HV, which meets the requirements of electronic contact materials. The polarization curve (Tafel) test and electrochemical impedance spectroscopy (EIS) test results indicated that the electrochemical corrosion resistance of Au-Cu alloy plating was much better than pure copper. With the rise of gold content in the alloy coatings, the corrosion resistance of the alloy coatings enhanced gradually. Compared with pure copper, the Au-Cu alloy coatings showed more stable contact resistance. After 1000 contacts, the resistivity of the alloy with 75% gold varied from 72 mΩ to 78 mΩ, whereas under the same conditions, the resistivity of copper changed from 14 mΩ to 78 mΩ. Anode-type material transfer occurred after 1000 contacts with a reduction in the total mass of each contact element. The mass loss of Au₇₅Cu₂₅ and Au₈₆Cu₁₄ contact elements was lower than that of pure copper. The Au-Cu alloy coatings displayed excellent arc corrosion resistance when the gold content in the alloy plating was higher than 75%. Full article

Pyrite is one of the most abundant metal sulfide tailings and is susceptible to oxidation, yielding acidic mine drainage (AMD) that poses significant environmental risks. Consequently, the exploration of pyrite surface oxidation and the kinetic influencing factors remains a pivotal research area. Despite the oxidation of pyrite producing a significant amount of sulfate (SO₄²⁻), a comprehensive investigation into its influence on the oxidation process is lacking. Leveraging pyrite’s semiconducting nature and the electrochemical intricacies of its surface oxidation, this study employs electrochemical techniques—cyclic voltammetry (CV), Tafel polarization, and electrochemical impedance spectroscopy (EIS)—to assess the effect of SO₄²⁻ on pyrite surface oxidation. The CV curve shows that SO₄²⁻ does not change the fundamental surface oxidation mechanism of pyrite, but its redox peak current density decreases with the increase in SO₄²⁻, and the surface oxidation rate of pyrite decreases. The possible reason is attributed to SO₄²⁻ adsorption onto pyrite surfaces, blocking active sites and impeding the oxidation process. Furthermore, Tafel polarization curves indicate an augmentation in polarization resistance with elevated SO₄²⁻ concentrations, signifying heightened difficulty in pyrite surface reactions. EIS analysis underscores an increase in Weber diffusion resistance with increasing SO₄²⁻, indicating that the diffusion of Fe³⁺ to the pyrite surface and the diffusion of oxidized products to the solution becomes more difficult. These findings will improve our understanding of the influence of SO₄²⁻ on pyrite oxidation and have important implications for deepening the understanding of surface oxidation of pyrite in the natural environment. Full article

Nickel–tungsten (Ni-W) alloys are gaining significant attention due to their superior hardness, wear resistance, anti-corrosion and electrochemical hydrogen evolution reaction (HER) activity. In this work, porous and crack Ni-W alloys with different W contents were prepared in a pyrophosphate bath. The key to forming a porous structure is a very high current density over 300 mA cm⁻². The HER activity of porous and crack Ni-W alloys was studied by means of electrochemical technologies of linear sweep voltammetry (LSV), Tafel curves (Taf) and electrochemical impedance spectroscopy (EIS). Compared with the crack Ni-W alloy, the porous Ni-W alloy exhibits improved alkaline electrochemical HER performances, which can deliver a current density of 10 mA cm⁻² at 166 mV (η10) vs. RHE (reversible hydrogen electrode). Full article

Analyzing PEM electrolyzer polarization curves via voltage breakdown analysis involves decomposing contributions from underlying processes, typically based on the assumption of reaction kinetics that may be expressed by means of the Tafel equation. When extrapolating the corresponding straight line to high current densities, there is a discrepancy between the measurement and model, which is often attributed to mass transport resistance. In addition to the qualitative description of this mass transport resistance, a consistent quantification is difficult to obtain from the measurement results. Accordingly, the approach to the breakdown analysis of the polarization curves is strongly based on assumptions that evade experimental verification. In this study, an alternative statistical method is introduced that permits the falsifiability of the standard approach. By means of experiments at different hydrogen partial pressures and a subsequent data fit, it is possible to extract the kinetic behavior without prior specification. The results indicate that behavior corresponding to the Tafel equation cannot be proven wrong. In addition, transport coefficients can be evaluated that fall between those of membranes and porous transport layers, indicating that the catalyst layer predominantly contributes to the mass transport resistance. Full article

The exceptional corrosion resistance and combined physical and chemical self-cleaning capabilities of superhydrophobic photocatalytic coatings have sparked significant interest among researchers. In this paper, we propose an economical and eco-friendly superhydrophobic epoxy resin coating that incorporates SiO₂@CuO/HDTMS nanoparticles modified with Hexadecyltrimethoxysilane (HDTMS). The application of superhydrophobic coatings effectively reduces the contact area between the metal surface and corrosive media, leading to a decreased corrosion rate. Additionally, the incorporation of nanomaterials, exemplified by SiO₂@CuO core–shell nanoparticles, improves the adhesion and durability of the coatings on aluminum alloy substrates. Experimental data from Tafel curve analysis and electrochemical impedance spectroscopy (EIS) confirm the superior corrosion resistance of the superhydrophobic modified aluminum alloy surface compared to untreated surfaces. Estimations indicate a significant reduction in corrosion rate after superhydrophobic treatment. Furthermore, an optical absorption spectra analysis of the core–shell nanoparticles demonstrates their suitability for photocatalytic applications, showcasing their potential contribution to enhancing the overall performance of the coated surfaces. This research underscores the promising approach of combining superhydrophobic properties with photocatalytic capabilities to develop advanced surface modification techniques for enhanced corrosion resistance and functional properties in diverse industrial settings. Full article

The rational design of a heterostructure electrocatalyst is an attractive strategy to produce hydrogen energy by electrochemical water splitting. Herein, we have constructed hierarchically structured architectures by immobilizing nickel–cobalt oxide nanowires on/beneath the surface of reduced graphene aerogels (NiCoO₂/rGAs) through solvent–thermal and activation treatments. The morphological structure of NiCoO₂/rGAs was characterized by microscopic analysis, and the porous structure not only accelerates the electrolyte ion diffusion but also prevents the agglomeration of NiCoO₂ nanowires, which is favorable to expose the large surface area and active sites. As further confirmed by the spectroscopic analysis, the tuned surface chemical state can boost the catalytic active sites to show the improved oxygen evolution reaction performance in alkaline electrolytes. Due to the synergistic effect of morphology and composition effect, NiCoO₂/rGAs show the overpotential of 258 mV at the current density of 10 mA cm⁻². Meanwhile, the small values of the Tafel slope and charge transfer resistance imply that NiCoO₂/rGAs own fast kinetic behavior during the OER test. The overlap of CV curves at the initial and 1001st cycles and almost no change in current density after the chronoamperometric (CA) test for 10 h confirm that NiCoO₂/rGAs own exceptional catalytic stability in a 1 M KOH electrolyte. This work provides a promising way to fabricate the hierarchically structured nanomaterials as efficient electrocatalysts for hydrogen production. Full article