Search Results (3,722)

This study investigates the time-dependent corrosion behavior of 6060 aluminum profiles subjected to three industrially relevant surface treatments: clear anodizing, black anodizing, and pre-anodizing followed by polyester powder coating during 30 days of immersion in NaCl solution. Electrochemical Impedance Spectroscopy combined with equivalent electrical circuit modeling was used to monitor corrosion evolution and identify the governing degradation mechanisms. Black-anodized specimens exhibited the highest initial corrosion resistance during the first 4 days of immersion, while clear-anodized specimens provided superior protection between 7 and 15 days due to the formation of a more protective inner oxide layer. Both anodized systems showed evidence of repassivation during prolonged exposure through corrosion product accumulation within the porous oxide structure. The pre-anodized/powder-coated system delayed corrosion initiation beyond 15 days, demonstrating the highest long-term barrier performance. Dynamic perpendicular impact loading after corrosion exposure revealed significant differences in mechanical durability: clear-anodized specimens maintained coating integrity up to 15 days, whereas black-anodized specimens experienced complete coating removal, associated with corrosion-induced microcracks and void formation observed by SEM. Overall, clear anodizing provided the best balance between corrosion resistance and post-corrosion mechanical durability, while the pre-anodized/powder-coated system offered the greatest long-term corrosion protection, demonstrating that the optimum surface treatment depends on the intended service conditions. Full article

This study investigates the electrochemical properties of polymer-based microelectrode arrays (pMEAs) and their performance in measuring oxygen (O₂) and hydrogen peroxide (H₂O₂). Morphological characterization by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) revealed a uniform, fine-grained platinum surface with nanoscale roughness, consistent with the Ti/Pt/Au/Pt multilayer stack architecture. The electrochemical behavior of the pMEAs was assessed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which demonstrated favorable responses for both O₂ reduction and H₂O₂ oxidation, together with low impedance (41.1 kΩ at 1 kHz). For O₂ detection, amperometric measurements at −0.6 V vs. Ag/AgCl indicated a sensitivity of −0.25 ± 0.04 nA μM⁻¹ and a detection limit of 5.4 ± 1.4 nM. For H₂O₂ detection, application of +0.7 V vs. Ag/AgCl resulted in a sensitivity of 88.13 ± 7.61 nA mM⁻¹ and a detection limit of 41.9 ± 5.6 nM. Selectivity evaluation showed effective interferent exclusion following m-phenylenediamine electrodeposition, without compromising analytical performance. Overall, these findings indicate the suitability of pMEAs for real-time, in vivo monitoring of O₂ and H₂O₂ in brain tissue with high spatial and temporal resolution, supporting applications in oxidative stress research and neurometabolic sensing. Full article

Accurate electrochemical impedance spectroscopy (EIS) characterization of low-impedance (<1 mΩ) lithium-ion battery cells used in electric vehicles is challenging because resistance and inductance in the measurement pathway can be comparable to the intrinsic cell impedance. This study investigates an EV-grade, large-format commercial lithium-ion pouch cell using a four-terminal EIS configuration and a custom connection fixture designed to maintain low and consistent contact resistance and reduce measurement-pathway effects. The EIS measurements shows good repeatability, and their linearity was confirmed using the Kramers–Kronig validity test. Impedance spectra acquired under selected state-of-charge (SOC) and temperature conditions were interpreted using an equivalent circuit model comprising an effective series inductance, an ohmic resistance, a constant phase element, a charge-transfer resistance, and a generalized Warburg element. Bayesian optimization followed by Nelder–Mead refinement was applied for parameter identification. The selected model represents the measured inductive, interfacial, and diffusion-related features as effective lumped responses rather than as a unique mechanistic decomposition. Across the SOC conditions investigated, the fitted ohmic resistance and charge-transfer resistance generally decreased as the temperature increased from 25 °C to 40 °C. By reducing the measurement errors related to the connection method rather than relying solely on instrument-side accuracy improvements, this work provides a practical approach for EIS measurements of milliohm-scale battery cells. These results establish a foundation for future temperature-compensated impedance diagnostics and further investigation of interfacial and transport behavior in EV battery cells. Full article

In recent years, alternative recycling approaches such as melt quenching and electrochemical evaluation methods have been investigated to assess the quality and performance of recovered lead materials. In this study, several samples obtained from the recycling process were analyzed electrochemically. The objective was to compare their electrochemical parameters and identify the samples with better electrochemical performance. The main methods used in this paper are X-ray diffraction analysis and voltammetric investigations using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). Electrochemical characterization provides valuable information about the behavior of recycled lead materials. Parameters such as half-wave potential (E_1/2), anodic current density (I_a), and solution or bulk resistance (R_b) are commonly used to evaluate electrochemical activity and conductivity. The electrochemical analysis reveals noticeable differences among the samples studied. The analysis of CV, LSV, and EIS indicates that the samples P2 (doped with CuO and Sb₂O₃) and P3N (doped with CaO/Fe₂O₃/Fe) exhibit the most favorable electrochemical behavior for lead acid battery applications, with the highest current response and smallest peak separation, suggesting efficient Pb/PbSO₄ redox reactions and minimal polarization. Full article

The growing demand for wearable and Internet of Medical Things (IoMT) devices is driving the development of compact, low-power platforms for continuous physiological monitoring. Bioimpedance analysis represents a versatile non-invasive technique for the assessment of tissue properties, body composition, and respiratory dynamics. This work presents a comprehensive experimental validation of a compact bioimpedance measurement platform based on the SENSIPLUS chip, a CMOS sensor interface integrating a frequency-programmable lock-in amplifier for Electrochemical Impedance Spectroscopy in the 10 kHz–1 MHz range. The platform was validated at three complementary levels: (i) electrical characterization on Debye tissue-equivalent circuits using a three-point bilinear calibration, with analysis of the electrode–skin contribution and repeatability assessment; (ii) in vivo multi-frequency bioimpedance spectroscopy (BIS) with Cole–Cole model fitting and hook-effect correction; and (iii) single-frequency thoracic impedance plethysmography for respiratory monitoring. Results were compared against an Agilent E4980A precision Inductance (L), Capacitance (C), and Resistance (R) meter and a calibrated spirometer. The presented device achieved a maximum resistance error below 5.7% and reactance deviation under 6 $\mathsf{\Omega }$ across the investigated frequency range, Cole–Cole parameters consistent with reference values, and strong linear correlation ($R^2=0.97$) between thoracic impedance variations and tidal volume, with respiratory rate estimation errors below 2% across the ten sessions, specifically 1.43% during normal breathing and 1.96% during deep breathing. These results demonstrate that the SENSIPLUS-based platform achieves metrological performance compatible with the requirements of wearable IoMT applications, here demonstrated in a single-subject proof-of-concept study, while relying for all critical analog functions on a compact ($1.5\times 1.5$) mm² system-on-chip with low power consumption (1.5 mW). Full article

Pitting corrosion is a more insidious and dangerous failure mode than uniform corrosion for protective coatings in marine environments, especially when sulfide ions (S²⁻) are present. In this work, Inconel 625 (IN625) and IN625-5 wt.% yttria-stabilized zirconia (YSZ) composite coatings were fabricated on 20G steel by laser-directed energy deposition (LDED) using optimized parameters. The coatings exhibit dense microstructures, with porosities of 1.87% ± 0.10% and 1.67% ± 0.10%, respectively. The pitting resistance was systematically evaluated by cyclic potentiodynamic polarization (CPP) and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl solution without and with 20 ppm Na₂S. The CPP results show that the addition of YSZ decreases the pitting potential (E_pit) and protection potential (E_prot), indicating reduced resistance to pit initiation, while the smaller hysteresis loop suggests an improved tendency for repassivation. S²⁻ induces a notable drop in E_prot and impairs repassivation for both coatings, yet the IN625-YSZ coating retains a slightly higher E_prot than IN625. EIS analysis reveals that the IN625-YSZ coating in S²⁻-containing solution shows an increased R_ct of 2.738 × 10⁵ Ω·cm² compared with its counterpart in 3.5 wt.% NaCl solution, while the corresponding R_L decreases to 2.513 Ω·cm², suggesting a weakened outer barrier layer despite partial interfacial blocking. Post-corrosion morphology shows that YSZ particles act as preferential pitting nucleation sites; in sulfide-free solution they produce numerous shallow pits, whereas in S²⁻-containing solution they lead to larger and deeper pits. The results may provide a reference for the future design and evaluation of LDED-manufactured composite coatings under sulfide-containing marine environments. Full article

The sustainable bio-activated carbon platelets were synthesized from tamarind (tamarind indicia) fruit seed shells (TFSs) by a pyrolysis approach with an inert gas atmosphere. The carbonization process was carried out at 800 °C under an inert argon atmosphere, yielding both pure TFS-AC and chemically activated TFS-AC (KOH) carbon materials. Microscopic surface morphological analysis confirmed the formation of thin, interconnected porous carbon platelet nanosheets with enhanced surface structural uniformity. Raman spectroscopy revealed characteristic D- and G-bands, signifying the presence of graphitic domains and partial structural disorder. BET surface area analysis indicated a significant improvement from 48.54 m²/g in TFS-AC to 124.72 m²/g in TFS-AC (KOH), suggesting enhanced pore development and surface accessibility due to KOH activation. Electrochemical two-electrode performance was evaluated in symmetric device configurations using 3M KOH aqueous electrolyte. The TFS-AC (KOH) device exhibited a remarkable specific capacitance, which delivered 129.03 F/g at 0.5A/g, compared to the pure TFS-AC device. Electrochemical impedance spectroscopy (EIS) further confirmed low internal resistance and favorable ion transport. These findings confirm that KOH-activated TFS-derived carbon nanosheets have higher electrochemical stability, retaining 98.2% capacitance over 10,000 cycles. These results are promising electrode materials for high-performance supercapacitor applications, owing to their superior electrochemical symmetric device performance of bio-mass carbon Tamarind seed shell platelet nanosheets for future energy storage symmetric device applications. Full article

In this study, an electrochemical immunosensor based on polyaniline/nano-Fe₃O₄ (PANI/Nano-Fe₃O₄) nanocomposite (PANI/Nano-Fe₃O₄/Anti-FLA/BSA/GCE) was developed for the highly sensitive and selective detection of trace levels of fluoranthene (FLA) in marine environments. Fluoranthene antibodies (Anti-FLA) were covalently immobilized on a glassy carbon electrode (GCE) modified with PANI/Nano-Fe₃O₄ via an EDC/NHS activation strategy, enabling specific recognition of FLA based on the antigen–antibody binding mechanism. The performance of the sensor was systematically optimized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV), and differential pulse voltammetry (DPV). The results demonstrated a linear inverse relationship between peak current (I_p) and FLA concentration in the range of 0.5~80 ng/mL, with a regression equation of I = −1.55C + 174.602 (R² = 0.996). The limit of detection (LOD) was as low as 0.354 ng/mL (S/N = 3). In real seawater sample analysis, spiked recovery tests at three representative sites in the Maowei Sea, Guangxi, yielded recoveries of 95.44%~97.51%, with RSDs below 3%, confirming the sensor’s resistance to matrix interference. The synergistic effect of the porous conductive network of PANI and the high specific surface area of Nano-Fe₃O₄ significantly amplified the electrochemical signal, while the molecular specificity of the antibody ensured targeted recognition. This sensor provides a novel and effective approach for the on-site rapid detection of polycyclic aromatic hydrocarbon (PAH) pollutants in complex marine environments, offering both high sensitivity and selectivity. Full article

Copper and its alloys are extensively employed in a broad range of industrial applications owing to their outstanding mechanical, electrical, and thermal properties. However, their susceptibility to corrosion in aggressive environments remains a major challenge, making corrosion inhibitors one of the most practical and cost-effective strategies for extending their service life. Nevertheless, conventional synthetic inhibitors are often limited by their high cost and adverse environmental and health impacts resulting from their toxicity. In this context, the present work provides a comprehensive experimental and theoretical assessment of the corrosion inhibition performance of Furosemide as an environmentally friendly inhibitor for copper in 3.5 wt.% NaCl solution. The corrosion inhibition performance was evaluated experimentally through gravimetric measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS), while the adsorption behavior of Furosemide was investigated using density functional theory (DFT) calculations. The results demonstrated that expired Furosemide effectively reduced the corrosion rate of copper, with the inhibition efficiency increasing as the inhibitor concentration increased and decreased with increasing temperature. A maximum inhibition efficiency of 90% was achieved at an inhibitor concentration of 400 ppm. The calculated Gibbs free energy of adsorption indicated that Furosemide adsorbs onto the copper surface through a mixed physisorption–chemisorption mechanism, following the Langmuir adsorption isotherm. Potentiodynamic polarization measurements further revealed that Furosemide predominantly suppresses the anodic dissolution reaction, indicating that it behaves as an anodic-type corrosion inhibitor. In addition, the presence of Furosemide significantly decreased the passive current density and shifted the breakdown potential toward more positive values, demonstrating an enhancement in the stability and protective character of the passive film. Electrochemical impedance spectroscopy showed that the corrosion process was governed by diffusion-controlled kinetics in the uninhibited solution, whereas the addition of Furosemide changed the corrosion mechanism to a charge-transfer-controlled process. Density functional theory (DFT) calculations provided additional insight into the inhibition mechanism of Furosemide. The calculated E_HOMO) and E_LUMO values indicate that the molecule can both donate and accept electrons, reflecting its nucleophilic and electrophilic character and its strong affinity for adsorption on the copper surface. Furthermore, the relatively small energy gap (4.631 eV) suggests high molecular reactivity and facilitates electronic interactions with the metal surface. The estimated fraction of electrons transferred further supports the electron-donating ability of Furosemide during the adsorption process. Differences between the Fukui functions and the molecular electrostatic potential (MEP) maps are attributed to the distinct chemical information provided by each descriptor. Whereas the Fukui functions identify the most reactive atomic sites involved in soft donor–acceptor interactions, the MEP maps describe the molecular charge distribution governing electrostatic (hard–hard) interactions. Full article

Anodic corrosion of Al alloy electrodes limits their use as anodes in alkaline aluminum–air batteries. Na₂SO₄- and Al₂(SO₄)₃-containing formulations were compared at matched nominal sulfate-group inputs but different formulation-derived Na and Al inputs. Aqueous 2 M NaOH was mixed with 0.3 M Na₂SO₄ or 0.1 M Al₂(SO₄)₃ solution at NaOH:additive-solution volume ratios of 7:3, 5:5, and 3:7, and Al–Mg–Sn–Gd–P alloy electrodes were evaluated in a three-electrode configuration. All galvanostatic tests passed the same external charge of 160 mAh. Mass-loss-normalized anodic charge (Q_Δm) is reported as an operational metric normalized by the net post-discharge electrode mass decrease, not as conventional battery capacity or efficiency. The Al₂(SO₄)₃-containing formulations showed higher Q_Δm values; at the 3:7 ratio, Q_Δm increased from 917 to 1894 mAh g⁻¹. Potentiodynamic polarization yielded lower polarization-derived apparent corrosion current densities and higher polarization resistances, while potentiostatic electrochemical impedance spectroscopy showed larger interfacial impedance responses in the Al₂(SO₄)₃-containing series. Scanning electron microscopy showed electrolyte-dependent post-discharge morphologies. These results establish sulfate-source-dependent differences in anodic, polarization, impedance, and morphological responses under matched nominal sulfate-group input without isolating the effect of a single Na- or Al-containing species, establishing the presence or chemical identity of a distinct interfacial film, or demonstrating improved full-cell performance. Full article

The inferior electronic conductivity, sluggish bulk Li⁺ transport, and Jahn–Teller distortion intrinsic to Mn³⁺ collectively impede the practical application of LiMn_0.6Fe_0.4PO₄ (LMFP) as a high-performance cathode for lithium-ion batteries. Herein, a series of W-doped Li(Mn_0.6Fe_0.4)_1−xW_xPO₄/C (x = 0, 0.005, 0.010, 0.015) cathode materials were synthesized via spray-drying combined with carbothermal reduction. Rietveld refinement indicated decreases in the fitted lattice parameters and unit-cell volume with increasing nominal W content, and no crystalline secondary phases were detected within the laboratory XRD detection limit. Although the structural evolution is consistent with W incorporation, direct determination of the occupation site requires further local structural characterization. X-ray photoelectron spectroscopy indicated that the detectable near-surface W species are predominantly present as W⁶⁺, and the semi-quantitative Mn 2p peak-area fitting showed that the fitted relative Mn³⁺ contribution decreased from 70.4% in LMFP-0 to 58.3% in LMFP-2. The optimal composition (LMFP-2, x = 0.010) delivers an initial discharge capacity of 160.2 mAh g⁻¹ at 0.1 C, retains 98.1% capacity after 100 cycles at 1 C, and achieves 126.3 mAh g⁻¹ at 5 C. Electrochemical impedance spectroscopy reveals that LMFP-2 possesses the lowest charge-transfer resistance (195.4 Ω) and the highest Li⁺ diffusion coefficient (5.3 × 10⁻¹⁵ cm² s⁻¹). These improvements may be attributed to the synergistic effects of enhanced bulk electronic conductivity, accelerated Li⁺ diffusion kinetics, and improved structural stability induced by moderate W incorporation. This work establishes W doping as a viable compositional engineering strategy for olivine-based cathode materials. Full article

The corrosion inhibition performance of a ternary inhibitor based on alkyl phosphate esters was investigated in environments simulating geothermal CO₂ systems at 60 °C and 80 °C using AISI 1018 steel as the test material. The inhibition efficiency was evaluated using mass loss method and electrochemical techniques, including linear polarization resistance (LPR), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). Structural and surface characterization of the samples were performed using Fourier transform infrared spectroscopy (FTIR) and intermittent contact–alternating current scanning electrochemical microscopy (IC-AC-SECM). The results demonstrated a significant reduction in the corrosion rate in the presence of the inhibitor at both investigated temperatures, accompanied by an increase in polarization resistance and a decrease in corrosion current density. Electrochemical measurements indicated that the investigated inhibitor acts as a mixed-type corrosion inhibitor. FTIR analysis supported the presence of inhibitor-related species at the steel interface, while IC-AC-SECM measurements indicated a relatively homogeneous and electrochemically protected surface under the investigated conditions. The concentration–surface-coverage relationship was close to the Langmuir-type form at 60 °C, whereas greater deviations were observed at 80 °C, together with a lower apparent adsorption parameter, suggesting temperature-dependent changes in the interfacial layer. The results demonstrate the strong corrosion-protection performance of the investigated commercial ternary inhibitor formulation under the tested conditions. Full article

In this study, the inhibition efficiency (IE) of symmetrical bis(imino)pyridines (BIPs) used in corrosion protection for zinc and iron was investigated in 0.5 M NaCl (pH 3 and pH 7) and an acidic (1 M HCl) medium using linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS). Three derivatives, BIP-9, BIP-14 and BIP-16, exhibited the most relevant inhibition performance and acted as mixed-type corrosion inhibitors. In a neutral medium, BIP-16 exhibited the highest IE calculated from EIS, reaching 74.8% on iron and 61.2% on zinc. In 1 M HCl, the highest IE inhibition efficiency was obtained for BIP-9 on iron (93.7%), while BIP-16 and BIP-14 reached 78.8% and 75.1%, respectively. The IE increased with concentration up to an optimum value, while time- and temperature-dependent studies indicated partial loss of protection for individual inhibitor systems and improved long-term protection for the Ce(III) acetate + BIP-16 system, particularly on iron. The highest IE was observed at 25 °C, likely due to inhibitor desorption at higher temperatures. Ce(III) acetate also showed the highest IE for iron in 0.5 M NaCl at pH 3. Adsorption of inhibitors followed the Langmuir model, and calculated parameters indicated spontaneous adsorption with dominant physisorption. DFT calculations supported a medium-dependent inhibition mechanism. Environmental hazard assessment identified BIP-16 as the least hazardous compound with promising eco-friendly potential. Full article

The corrosion of metallic biomaterials under physiological conditions remains a critical challenge due to the risk of ion release affecting biocompatibility. In this study, the time-dependent electrochemical behavior of a poly(vinyl alcohol) (PVA)/chitosan biopolymer coating applied to biomedical-grade steel was evaluated to assess its protective performance. The coating was prepared via dip-coating using a 9.9:0.1 PVA/chitosan formulation and characterized by FTIR and Raman spectroscopy to confirm intermolecular interactions and film formation. Electrochemical impedance spectroscopy was employed over 216 h of immersion in Hanks’ Balanced Salt Solution to monitor coating degradation and corrosion mechanisms. The coated system exhibited a significant increase in the low-frequency impedance modulus from approximately 1200–1400 to 5000–6000 Ω·cm², indicating enhanced barrier properties and interfacial stability compared to uncoated steel. Equivalent circuit analysis revealed a transition from a predominantly capacitive, barrier-controlled response at early immersion stages to diffusion-influenced behavior at longer exposure times, associated with electrolyte penetration and interfacial processes. Overall, the PVA/chitosan coating effectively delays corrosion reactions and maintains high impedance under simulated physiological conditions, demonstrating its potential as a protective and biocompatible surface modification for metallic biomedical applications. Full article

Laser powder bed fusion (LPBF) produces microstructural anisotropy that influences hydrogen transport and passive film stability, yet the mechanistic relationship between build orientation, passive film chemistry, and corrosion behavior remains insufficiently understood. This study investigates how LPBF build orientation governs hydrogen-assisted passive film degradation by correlating electrochemical behavior with passive film chemistry. Additively manufactured 316L stainless steel specimens were fabricated in two build orientations, horizontal (0°) and vertical (90°), and subjected to electrochemical hydrogen charging for durations ranging from 2 to 36 h. Corrosion behavior was evaluated using open-circuit potential (OCP), electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR), and potentiodynamic polarization (PDP), while X-ray photoelectron spectroscopy (XPS) was employed to characterize hydrogen-induced changes in passive film chemistry. The electrochemical response showed that hydrogen charging progressively reduced the corrosion resistance of both build orientations. However, the degradation exhibited a non-monotonic dependence on charging duration, with intermediate charging durations suggesting transient repassivation before renewed deterioration during prolonged hydrogen exposure. EIS analysis revealed a substantial decrease in the fitted total resistance (R_total = R_ct + R_po), from 1.44 to 0.27 kΩ cm² for the 0° specimens and from 4.23 to 0.55 kΩ cm² for the 90° specimens. Potentiodynamic polarization showed that prolonged hydrogen charging increased the corrosion current density from 20.99 to 98.91 μA cm⁻² for the 0° specimens and from 0.79 to 46.86 μA cm⁻² for the 90° specimens. XPS analysis revealed progressive depletion of protective oxide species (Fe₂O₃, Cr₂O₃, Mo oxides, and lattice oxygen) together with enrichment of hydroxide-rich species, resulting in a lower O²⁻/OH⁻ ratio and transformation of the passive film into a more porous and less protective surface layer. These chemical changes were more pronounced in the 90° build orientation and were consistent with the greater reduction in passive film stability observed from the electrochemical measurements. The combined electrochemical and XPS analyses establish that LPBF build orientation governs hydrogen-assisted corrosion through its influence on microstructural anisotropy, hydrogen transport, passive film chemistry, and the resulting electrochemical response, providing mechanistic insight into the corrosion behavior of additively manufactured 316L stainless steel in hydrogen-containing environments. Full article