Electrochemical Impedance Spectroscopy Methods Research Articles

Synthesis and evaluation of Schiff base as corrosion inhibitor for carbon steel in 1 M HCl solution

Purpose The main purpose of the present study is to introduce new Schiff bases as corrosion inhibitor for carbon steel in 1 M HCl. The inhibitory activity of Schiff base was also assessed. Design/methodology/approach 2,2′-((1Z,1′Z)-((2,2-dimethylpropane-1,3-diyl)bis(azanylylidene))bis(methanylylidene))diphenol was synthesized and it’s performance as an inhibitor was then investigated in 1 M HCl. The inhibition of this compound was studied and evaluated by the chemical methods of electrochemical impedance spectroscopy, electrochemical potential dynamic polarization and Atomic Force microscopy (AFM) method. The thermodynamics parameters were investigated for corrosion of carbon steel in both the absence and presence of Schiff base. Findings The results of the tests showed that this compound has a good performance as an inhibitor and the percentage of inhibition on steel corrosion will increase with increasing concentration and it will reach 70% in the presence of 2 × 10−3 M of this inhibitor. Polarization tests indicated that this compound will act as a mixed inhibitor. Nyquist curves showed that the addition of this substance to the solution increased the charge transfer resistance and decreased the capacity of the double layer. The absorption of the new Schiff base on steel follows Langmuir adsorption isotherm, and the amount of free energy of adsorption indicates the spontaneous adsorption of this inhibitor. Using AFM investigations, the results of electrochemical methods were confirmed. Originality/value Incorporation of a new Schiff base into 1 M HCl is a promising approach for protecting the carbon steel against corrosive solution.

One-step facile synthesis of the photocatalyst using pyrolyzed terephthalic acid and m-phenylenediamine composite for Cr(VI) reduction in aqueous solutions

Discharging heavy metals into water bodies presents a serious environmental risk. Hexavalent chromium (Cr(VI)) is one of the harmful substances that pose substantial health hazards to humans. The aim of this research is to synthesize an organic composite photocatalyst by polymerizing m-phenylenediamine (mPD) and Terephthalic acid (TA) at high temperatures. TA and mPD interact and result in the formation of a polymerized-mPD-TA photocatalyst to reduce Cr(VI) under visible light. Field Emission Scanning Electron Microscopic (FESEM), Energy-Dispersive X-ray (EDX), Dynamic Light Scattering (DLS), Fourier-transform Infrared spectroscopic (FT-IR), Brunauer-Emmett-Teller (BET), UV–Vis Diffuse Reflectance Spectra (UV–vis-DRS), Electrochemical Impedance Spectroscopy (EIS) and Mott-Schottky methods were used to characterize the produced photocatalyst. The effect of operational parameters including pH, volume of hole scavenger, photocatalyst mass, and Cr(VI) initial concentration was investigated, and the optimum conditions were clarified. To investigate the adsorptive characteristics of the prepared photocatalyst, Isotherm, and Kinetic investigations were carried out. The adsorption studies revealed that the Freundlich and pseudo-second-order (PSO) models offered a better suitable match to the experimental data. In order to investigate the practicality of the photocatalyst, reusability, and sunlight tests were carried out, and it was shown that the prepared composite possessed great durability and could perform under sunlight to reduce Cr(VI).

The Influence of Catalyst Loading on Electrocatalytic Activity and Hydrogen Production in PEM Water Electrolysis

The climate change caused by the widespread and continuous use of fossil fuels is a problem that needs to be addressed urgently. One of the solutions offered is through an energy transition towards the use of new or renewable and low-carbon fuels. Hydrogen gas as a carrier of energy is an alternative solution that has attracted the attention of researchers, due to its high combustion energy and environmental friendliness. The production of hydrogen gas using the Proton Exchange Membrane Water Electrolysis (PEMWE) method is considered effective for large-scale production. This study investigates the impact of catalyst loading and various current densities on hydrogen production in the PEM water electrolysis process, utilizing the Cu2O/C catalyst. This study investigates the impact of catalyst loading and different current densities on hydrogen production in the PEM water electrolysis process, utilizing the Cu2O/C catalyst. The electrode catalytic properties were evaluated using the Cyclic Voltammetry (CV) method to determine the Electrochemical Surface Area (ECSA) and the Electrochemical Impedance Spectroscopy (EIS) method to determine the electrical conductivity. The ECSA and EIS measurements demonstrated that the best results were obtained at a higher catalyst loading of 2 mg/cm2 with an ECSA value of 0.21 m2/g and electrical conductivity of 3.04 × 10−6 S/cm. The production of hydrogen results showed that the highest hydrogen production rate was 3.75 mL/s with a catalyst loading of 2.5 mg/cm2, indicating that increasing the load could lead to a higher rate of hydrogen gas production, but this is highly dependent on the surface area utilized. Additionally, at higher current densities, the cell resistance in the electrolysis process may decrease, leading to reduced electrode efficiency for hydrogen production. Thus, the use of high currents may not always be advantageous in hydrogen production using the PEM water electrolysis method.

Multi-cell sensorless internal temperature estimation based on electrochemical impedance spectroscopy with Gaussian process regression for lithium-ion batteries safety

Recently, fire incidents due to electrical vehicle (EV) lithium-ion battery (LIB)-based energy storages have been increasingly occurring. Preemptive diagnosis of the thermal runaway is essential for preventing such fires. However, precise and accurate temperature monitoring at the single cell level is required for all the batteries present in the EV pack. Electrochemical impedance spectroscopy (EIS) closely correlates with the battery's internal temperature (Tint) for sensorless temperature estimation, but is limited for multi-cell use because of the effect of the cell-to-cell differences on the EIS impedance values, causing inaccuracies in the use case of predefined models. This study developed a framework combining the EIS method with Gaussian process regression (GPR) machine learning for multiple LIBs cell temperature estimation. The intrinsic relationship linking the temperature, state of charge, state of health and temperature sensitivity with the impedance properties of the batteries at different frequencies was investigated. The results showed that from 51 extracted frequencies only single-point frequency measurements at 10 Hz were necessary to develop the temperature estimation model. The data at this frequency was subsequently utilized to train the GPR model. Five kernel functions were studied, trained, and validated experimentally. The root means square error (RMSE) for the most accurate kernel was 0.2 °C at the validation step, and the test RMSE for the estimation of a new cell was 0.79 °C, confirming the high accuracy of the model.

Investigation of phosphoric acid influence on the oxygen reduction reaction on carbon-supported platinum electrocatalyst via rotating disk electrodes

Phosphoric acid (PA), utilized as an electrolyte in high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs), has been observed to exert a detrimental effect on oxygen reduction reaction (ORR) electrocatalyst, consequently compromising cell performance. To comprehensively elucidate the impact of phosphoric acid on ORR, this study employs a range of electrochemical techniques, including electrochemical impedance spectroscopy and voltammetry method. The negative influence of PA on commercial Pt/C electrocatalyst manifests differently under various potentials and PA concentrations. Upon the introduction of PA, the decay rate and amplitude of ECSA, as calculated by Hupd adatoms, are notably smaller compared to the kinetic current density generated by the oxygen reduction reaction. Particularly, in the kinetic-controlled potential range, the negative impact of PA becomes more pronounced at higher electrode potentials, accompanied by a significantly steeper Tafel slope. Additionally, the EIS results suggest that phosphoric acid may gradually transform into polyphosphoric acid at a high concentration, accentuating the poisoning effect of PA under steady-state conditions. However, a high PA concentration can substantially alter the electrolyte properties, potentially leading to an inaccurate assessment of PA tolerance in electrocatalysts. Hence, it is imperative to consider the appropriate PA concentration when evaluating PA tolerance and to discern the poisoning mechanism under different electrode potentials.

ZnO Nanorods on POPD/GCN/TCFP with Ternary Synergy for Promoting Electro-Oxidation of Furfuryl Alcohol

In this work, Poly(o-phenylenediamine) (POPD) and zinc oxide (ZnO) nanoparticles were electrochemically deposited on GCN (graphitic carbon nitride) coated TCFP (Toray carbon fiber paper) electrode. The modified electrode ZnO-POPD-GCN-TCFP was assessed by Field emission scanning electron microscopy (FESEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS) studies. The electrochemical studies were carried out via cyclic voltammetry (CV) and electrochemical impedance spectroscopic (EIS) methods. The developed electrode was employed for the oxidation of furfuryl alcohol (FA) using 4-ACT (4-acetamido TEMPO) as a mediator in an alkaline medium via bulk electrolysis. Proton nuclear magnetic resonance (1H NMR) spectroscopy was used to characterize the final product. The oxidation of FA to furfural was accelerated by the heterogeneous catalyst ZnO-POPD-GCN-TCFP electrode owing to its good electrocatalytic activity and stability. Hence, a sustainable electrochemical method for synthesizing furfural, with significance in the realm of green chemistry, was developed. The Electro-oxidation of FA offers a clean alternative to traditional methods utilizing electricity, potentially from renewable sources, to drive the reaction, reducing reliance on harsh chemicals and minimizing environmental impact. By adjusting parameters like electrode potential and electrolyte composition, it is possible to optimize the reaction conditions for furfural production with optimal yield, which has several applications in daily life.

Electrochemical impedance spectroscopy: Effects of stray current and sulfate exposure on rubber powder mortar

Stray current induced by the subway power supply system can significantly accelerate the external sulfate attack of cement-based materials, leading to severe degradation. In this work, two rubber powders with different particle sizes were used to improve the performance of cement-based materials against the detrimental effects of stray current and sulfate. The electrochemical impedance spectroscopy (EIS) method was applied to investigate the effect of rubber powder on the electrochemical properties of cement-based materials exposed to stray current and sulfate. The electrochemical parameters of mortar incorporating rubber powder were obtained by fitting a novel equivalent circuit (Rs + Q1/(Rct1+W1) + Q2/(Rct2+W2)). The effects of rubber powde dosage and fineness on EIS parameters were analyzed. The results revealed that the compressive strength of mortar incorporating rubber powder decreased, but both the pore solution resistance (Rs) and charge transfer process resistance (Rct1) of the specimens significantly increased. Furthermore, the increase in Rs and Rct1 values correlated with the dosage of rubber powder, and the 74 μm rubber powder demonstrating a more pronounced effect compared to the 180 μm rubber powder. After exposure for 30 days, it was observed that rubber powder could effectively improve the performance of mortar against the deteriorated effects of stray current and sulfate. Specifically, the 74 μm of rubber powder exhibited superior performance compared to the 180 μm rubber powder. Additionally, it was found that Rs and Rct1 values positively correlated with the compressive strength after exposure. Therefore, the EIS parameters Rs and Rct1 could be used to predict the variation trend of the compressive strength of mortar incorporating rubber powder.

Electrochemical development and characterisation of nanostructured Ni–Fe alloy coatings for corrosion protection

ABSTRACT Nanostructured Ni–Fe alloy coatings were developed galvanostatically using a new low-concentration bath. The composition and operating parameters of the bath were optimised by taking the benefit of the conventional Hull cell method. Ni–Fe alloy coatings were developed at different current densities (2.0 to 5.0 A dm−2), keeping pH = 2.5. The corrosion behaviour of electrodeposited alloy coatings was evaluated in 3.5% NaCl solution, using Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarisation methods. Ni–Fe alloy coating, deposited at 2.0 A dm−2 exhibited a lesser corrosion rate (14.71 × 10−2 mm y−1) than those at higher current densities. The lowest corrosion rate was attributed to its least crystallite size (10.4 nm), evidenced by an X-Ray Diffraction (XRD) study. The corrosion performance of Ni–Fe alloy coatings was discussed in the light of their surface morphology and composition, evidenced by SEM and Energy-Dispersive X-ray spectroscopy (EDS) analysis, respectively.

Synergistic corrosion inhibition of rubber seed extract with KI on cold rolled steel in sulfuric acid solution

BackgroundPlant-based inhibitor has emerged an important topic owing to the combing merits of eco-friendly, low cost, rich natural resources as well as easy preparation. Rubber seed is the agricultural waste, and is mainly composed of oil and fatty acids those contain many polar oxygen atoms, and so it can be extracted to prepare the potential corrosion inhibitor. MethodsRubber seed extract (RSE) is prepared using reflux extraction method with the extracting solvent of ethanol aqueous solution. The synergistic inhibition effect of RSE and potassium iodide (KI) on the corrosion of cold rolled steel (CRS) in 0.50 M H2SO4 solution is firstly studied by weight loss, potentiodynamic polarization (PDP) curves and electrochemical impedance spectroscopy (EIS) methods. CRS surface was thoroughly characterized using metallographic microscope, scanning electron microscope (SEM), atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements. FTIR, UV–vis and liquid chromatography mass spectrometry (LC-MS) compositional analysis of RSE were used to analyze the efficient components in RSE. Significant findingsThe results indicate that individual RSE or KI cannot function as a successful inhibitor to prevent CRS corrosion, but the mixture of RSE/KI performs better at inhibiting, with a maximal inhibition efficacy of up to 96.4% of 200 mg L−1 RSE/100 mg L−1 KI. The synergistic coefficient of the mixture is larger than 1, indicating that a true synergism. RSE/KI can drastically retard both cathodic and anodic processes, and interfacial capacitance falls as the charge transfer resistance of CRS/solution rises. It exhibits remarkable inhibition properties when the capacitor arc grows. There is only a small corrosion response in the inhibited media, as evidenced by the variations in electrical conductivity and ultraviolet spectrum before and after immersion. The hydrophilicity and surface roughness of CRS surface is dropped as a result of the introduction of RSE/KI. A series of metallurgical microscopy, AFM, SEM or contact angle tests indicate a synergistic inhibition effect is more pronounced for RSE/KI. XPS results clearly demonstrate that elements including Fe, S, N, and I are bonded to the surface of CRS. The primary ingredients of oleic acid, polyphenols, phenylpropanoids can also produce a strong synergism with KI.

A novel method for improving the electrochemical properties by modifying conductive polymer on 3D printed nanocarbon electrode

The technology of 3D printing has emerged as a potent tool for the preparation of 3D-printed electrode. Using commercial graphene/polylactic acid (PLA) composite filaments as printed materials, fused deposition modeling as 3D-printed technique, 3D printed electrodes (3DEs) were created in this work. Gold nanoparticles (AuNPs) and the composites of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) were used to modify the activated 3DEs for constructing a novel electrode (SACP@Au@3DE), and in this work chlorogenic acid (CGA) was regarded as a probe for testing the performance of SACP@Au@3DE. The surface physicochemical properties of the prepared 3DEs were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The electrochemical properties of the prepared 3DEs were investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) methods. The constructed SACP@Au@3DE can be used to determine CGA at concentrations ranging from 10 to 400 μM with a limit of detection (LOD) of 4.13 μM. Ultimately, the SACP@Au@3DE sensor was used for CGA detection in coffee powder sample to explore the potential for real sample analysis. This work opens the novel avenue of using conductive polymer modified 3D-printed electrode in the field of sensor.

Exploring Impact of Various Operating Parameters on the Specific Capacitance at the Glassy Carbon/H2SO4 Interface: A Comparative Analysis Using Electrochemical Characterization

AbstractThe aim of this study is to investigate the influence of scanning rate, electrolyte concentration, temperature and electrode rotation speed on the capacitance of glassy carbon electrode in sulfuric acid solution using cyclic voltammetry (CV). The results show that they have a significant influence on the capacitance with varying experimental conditions. In addition, the electrochemical impedance spectroscopy (EIS) method was employed to conduct a more thorough analysis of the ways in which hydrodynamic circumstances resulting from a rotating electrode affect the electrode capacity and the charge storage process. Step potential electrochemical spectroscopy (SPECS) was used to identify the various charge storage mechanisms involved. It was shown that the voltammograms measured by the CV method and determined from the SPECS method have a quasi‐rectangular shape, revealing a predominantly capacitive behavior and that capacitance decreases with increasing scanning rate. Furthermore, both methods confirm that the contribution of the diffusion process is the main factor influencing the charge storage mechanism when the sweep rate is taken into account. However, the SPECS approach provides more accurate and detailed information regarding the kinetic characteristics of the electrode.

Pore size, conductivity and surface area effects of rGO/ZnO/PTh hybrid nanocomposite for supercapacitors

This paper presents an easy and low-cost synthesis of reduced graphene oxide (rGO) and Zinc oxide (ZnO) as binary nanocomposite (rGO/ZnO) and rGO, ZnO and polythiophene (PTh) as ternary hybrid nanocomposite (rGO/ZnO/PTh). Firstly, graphene oxide (GO) was synthesized from modified Hummers method. And it was reduced by microwave-assisted method to form as reduced graphene oxide (rGO). Polythiophene (PTh) was chemically synthesized to comparison with nanocomposites. Secondly, binary nanocomposite of rGO/ZnO were synthesized by probe-sonication method. Thirdly, rGO/ZnO/PTh hybrid nanocomposite was chemically synthesized using FeCl3 as an oxidant. All these materials were examined by many different techniques, such as FTIR-ATR, SEM-EDX, TGA-DTA, BET, Four-point probe analysis, cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) analysis. The average pore width, conductivity and specific capacitance values were comparatively investigated to understand these effects on electrochemical performances of supercapacitor devices.The highest specific capacitance (Csp) was obtained as Csp = 430 F/g for rGO/ZnO nanocomposite at a scan rate of 2 mV/s. Moreover, it also shows a good charge/discharge performance (up to 1000 cycles) with 98.43 % capacitance retention at a scan rate of 100 mV/s by CV method. However, GCD and EIS methods have showed the highest specific capacitances as Csp = 85.6 F/g at 10 A/g, and Csp = 25.8 F/g for both hybrid rGO/ZnO/PTh nanocomposites, respectively. In addition, a new equivalent circuit model [R1(C1(Rct(C2R2)))] was suggested to interpret the EIS data for supercapacitor devices. As a results, both binary and ternary nanocomposites may be recognized as electrode materials with three different methods (CV, GCD and EIS) in supercapacitor applications.

Study of Resistance Extraction Methods for Proton Exchange Membrane Fuel Cells Based on Static Resistance Correction

Accurate extraction of polarization resistance is crucial in the application of proton exchange membrane fuel cells. It is generally assumed that the steady-state resistance obtained from the polarization curve model is equivalent to the AC impedance obtained from the electrochemical impedance spectroscopy (EIS) when the frequency approaches zero. However, due to the low-frequency stability and nonlinearity issues of the EIS method, this dynamic process leads to an additional rise in polarization resistance compared to the steady-state method. In this paper, a semi-empirical model and equivalent circuit models are developed to extract the steady-state and dynamic polarization resistances, respectively, while a static internal resistance correction method is proposed to represent the systematic error between the two. With the correction, the root mean square error of the steady-state resistance relative to the dynamic polarization resistance decreases from 26.12% to 7.42%, indicating that the weighted sum of the static internal resistance and the steady-state resistance can better correspond to the dynamic polarization resistance. The correction method can also simplify the EIS procedure by directly generating an estimate of the dynamic polarization resistance in the full current interval.

Densification and corrosion properties of graphite reinforced binderless TiC70N30 ceramic composites

In this study, binderless TiC70N30 ceramic composites with varying graphite (TiC70N30–Gr) reinforcements were fabricated via spark plasma sintering and their effect on densification was assessed. Subsequently, the electrochemical behaviour of TiC70N30–Gr composites was evaluated in 0.5 mol/L hydrochloric acid (HCl), 0.5 mol/L sulphuric acid (H2SO4) and 0.5 mol/L nitric acid (HNO3) solutions using open circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. The corrosion behaviour of TiC70N30-based ceramic composites with and without graphite reinforcement exhibited high corrosion resistance in the acidic electrolytes. Composites with 0.5 and 1.0 wt% graphite content showed lower Icorr values of 0.452 µA and 0.081 µA in 0.5 mol/L HCL and 0.5 mol/L HNO3, respectively, while specimen without graphite addition showed better corrosion resistance in 0.5 mol/L H2SO4 (0.041 µA). Based on the corrosion results, the corrosion properties of TiC70N30 ceramic composites in HCl and HNO3 solutions were significantly enhanced upon the incorporation of graphite reinforcements. However, the corrosion test results conducted in H2SO4 solution showed that the addition of graphite had a negligible influence on the corrosion resistance of the titanium carbonitride (TiCN) composites.

Elucidating the Role of Electrochemically Formed LiF in Discharge and Aging of Li-CFx Batteries.

Fifty years after its introduction, the lithium-carbon monofluoride (Li-CFx) battery still has the highest cell-level specific energy demonstrated in a practical cell format. However, few studies have analyzed how the main electrochemical discharge product, LiF, evolves during the discharge and cell rest periods. To fill this gap in understanding, we investigated molecular-level and interfacial changes in CFx electrodes upon the discharge and aging of Li-CFx cells, revealing the role of LiF beyond that of a simple discharge product. We reveal that electrochemically formed LiF deposits on the surface of the CFx electrode and subsequently partially disperses into the electrolyte to form a colloidal suspension during cell aging, as determined from galvanostatic electrochemical impedance spectroscopy (EIS), solid-state 19F nuclear magnetic resonance (NMR), dynamic light scattering (DLS), and operando optical light microscopy measurements. Electrochemical LiF formation and LiF dispersion into the electrolyte are distinct competing rate processes that each affect the cell impedance differently. Using knowledge of LiF dispersion and saturation, an in-line EIS method was developed to compute the depth of discharge of CFx cells beyond coulomb counting. Solid-state 19F NMR measurements quantitatively revealed how LiF and CF moieties evolved with discharge. Covalent CF bonds react first, followed by a combination of covalent and ionic CF bonds. Quantitively correlating NMR and electrochemical measurements reveals not only how LiF formation affects cell impedance but also that CF bonds with the most ionic character remain unreacted, which limits realization of the full theoretical specific capacity of the CFx electrode. The results reveal new insights into the electrochemical discharge mechanism of Li-CFx cells and the unique role of LiF in cell discharge and aging, which suggest pretreatment strategies and methods to improve and measure the performance of Li-CFx batteries.

Investigation of the Electrochemical Corrosion Property of 2xxx Series Cast Aluminium Alloy in 0.3 M, 0.6 M NaCl, and Seawater Environments

The electrochemical corrosion activities of 2xxx series Al alloys were investigated in NaCl of 0.3 M, and 0.6 M concentrations and seawater environments. Both Tafel polarization and electrochemical impedance spectroscopy (EIS) methods were followed to analyze the corrosion behavior. These results implied that corrosive attack is more aggressive in sodium chloride solution compared to seawater, as additional elements present in seawater are involved in forming various protective layers. Again, a higher concentration of NaCl solution damaged the alloy surface more drastically. The open circuit potential moved towards the nobler direction in the case of seawater environment, and 0.3 M solution for NaCl. The corrosion rate and corrosion current showed higher values in NaCl solution than in seawater. The surface morphologies of the alloys were characterized not only with an optical microscope but with a scanning electron microscope also. The scratch marks from polishing were removed after corrosion. Extensive damage to the surface was found in the NaCl environment, where 0.6 M solution created the most damage, which is evident by both optical and scanning electron micrography. A higher level of pitting corrosion occurred in NaCl than in seawater, identified by SEM images.

Data-driven internal temperature estimation methods for sodium-ion battery using electrochemical impedance spectroscopy

As sodium-ion batteries (SIBs) move towards commercialization, safety monitoring of SIBs has become the next key issue, and how to avoid thermal runaway is one of the toughest challenges. The electrochemical impedance spectroscopy (EIS) method for the internal temperature estimation of lithium-ion batteries has received considerable attention due to its non-invasive detection and high accuracy. However, research on the impedance-temperature characteristics of commercial SIBs remains limited, and EIS methods suitable for estimating the internal temperature of SIBs require further investigation. In this study, four commercial 26,700 SIBs were tested, the EIS results of the batteries in various state-of-charge (SoC) states and at different temperatures were systematically investigated, and a method for estimating the internal temperature of SIBs on the basis of the combination of EIS and machine learning (ML) is proposed. Seven component parameters were extracted as features from the raw EIS data using equivalent circuit model fitting, and four features, which were found to be highly correlated with temperature, were further selected by correlation analysis. The mapping relationship between the extracted features and the internal temperature of the battery was established based on three ML regression models. Results demonstrate that the average estimation error of the multi-layer perceptron models for the internal temperature of the battery with unknown SoC states is only 1.086 °C. This paper fills the gap in the temperature characterization of EIS for SIBs and proposes an effective method for overcoming the cross-coupling of the battery EIS with the SoC and temperature within the framework of mechanical learning to estimate the internal temperature of SIBs.

CORROSION EVALUATION OF LPBF-MANUFACTURED DUPLEX STAINLESS STEEL

In this study, the effect of as built and heat-treated additively manufactured 2507 super duplex stainless steel (SDSS) on electrochemical corrosion performance was examined. The corrosion was studied by Tafel polarization and electrochemical impedance spectroscopy (EIS) methods in a 3.5% NaCl solution. For this purpose, the as-built and heat-treated printed samples (solution annealed and stress-relieved) were examined by LOM/SEM and X-ray diffraction to evaluate the phase changes of steel at different processing stages. The correlation between corrosion resistance, structure, and heat treatment was assessed. As a result of the very fast cooling rate of the LPBF process, SDSS reveals ferrite as the major phase in the printed samples. To enhance the corrosion resistance of LPBF-produced duplex stainless steel, it's crucial to balance its two-phase structure and minimize residual stresses. The ferrite grains are elongated in the build direction, with some austenite precipitation along the grain boundaries or as Widmanstatten laths. The stress-relieved and as-printed SDSS exhibits reduced corrosion characteristics by around 20% compared to the solution-annealed SDSS, according to anodic polarization curves. Based on EIS results, the solution-annealed SDSS revealed an almost double increase in corrosion resistance (based on charge transfer resistance values) compared to the as-printed and stress-relieved conditions.

Investigation on chloride migration behavior of metakaolin-quartz-limestone blended cementitious materials with electrochemical impedance spectroscopy method

Calcined clay and limestone powder composites offer a viable solution for reducing carbon emissions in building materials by allowing significant cement replacement. However, there is a need for further investigation into their impact on durability, especially for low-grade clays. In this study, different ratios of metakaolin and quartz powder are utilized to simulate various grades of calcined clay, while limestone powder is incorporated as a partial cement substitute. Initially, the influence of metakaolin content on rapid chloride migration was analyzed. Subsequently, various analytical techniques such as free water content, Mercury Intrusion Porosimetry (MIP), X-ray diffraction (XRD)/Rietveld method, and electrochemical impedance spectroscopy (EIS) test were employed to investigate the effects of metakaolin contents on the pore structure, phase assemblage, and electrochemical parameters of the blended cementitious system. The relationship between chloride migration coefficient and free water content, critical pore size, and impedance parameters was established to determine the key indicators for chloride migration. The study revealed that systems with partial metakaolin content demonstrate improved chloride resistance in the blended system, which could be predicted using Rct1 from the EIS test. Furthermore, the inclusion of metakaolin and limestone powder facilitated the formation of Monocarboaluminate (Mc) and Hemicarboaluminate (Hc), leading to the refinement of the pore structure and inhibition of chloride transport within the blended material. This study indicates the potential of low-grade calcined clay to enhance the overall durability of the blended cementitious system while contributing to carbon emissions reduction.

The Inhibition Action of Some Brij-Type Nonionic Surfactants on the Corrosion of OLC 45 in Various Aggressive Environments.

The corrosion protection property of three Brij-type surfactants, namely, Brij 35, Brij 56 and Brij 58P, was considered on OLC 45 carbon steel in a 0.5 M H2SO4 medium. The efficacy for these organic compounds was examined using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods, scanning electron microscopy (SEM) procedures, and Fourier transform infrared (FT-IR) spectroscopy. We hypothesized that these surfactants hinder the corrosion for OLC 45 samples through a protecting mechanism owing to the adsorption of organic molecules that form an inhibitive film or through the formation of complex oxides. These surfactants exhibited an appreciable protective effect against OLC 45 corrosion, operating as mixed inhibitors, as could be demonstrated by their influence on the electrochemical characteristics of the metallic substrates. The adsorption of surfactants over the substrates zone conformed to the representation of the Langmuir isotherm. The effect of temperature on the electrochemical comportment of the OLC 45 specimens in H2SO4 without and with Brij at 800 ppm was examined in the temperature interval of 293 to 333 K. The negative estimate of thermodynamic attributed as Gibbs free energy of adsorption presented the spontaneity of the adsorption activity. The investigation with FT-IR and SEM established the adsorption of Brij and the constitution of the corrosive components on the OLC 45 surface. Electrochemical determinations of these surfactants indicated its anticorrosion inhibition performance and the highest inhibition of 96% was reached when the Brij 35 concentration was at 800 or 1000 ppm, while for Brij 56 and Brij 58P, the highest inhibition was obtained when their concentrations were 500, 800, or 1000 ppm.