Lower Impedance Values Research Articles

Ensemble LVQ Model for Photovoltaic Line-to-Line Fault Diagnosis Using K-Means Clustering and AdaGrad

Line-to-line (LL) faults are one of the most frequent short-circuit conditions in photovoltaic (PV) arrays which are conventionally detected and cleared by overcurrent protection devices (OCPDs). However, OCPDs are shown to face challenges when detecting LL faults under critical detection conditions, i.e., low mismatch levels and/or high fault impedance values. This occurs due to insufficient fault current, thus leaving the LL faults undetected and leading to power losses and even catastrophic fire hazards. To compensate for OCPD deficiencies, recent studies have proposed modern artificial intelligence (AI)-based methods. However, various limitations can still be witnessed even in AI-based methods, such as (i) most of the models requiring a massive training dataset, (ii) critical fault detection conditions not being taken into consideration, (iii) models not being accurate enough when dealing with critical conditions, etc. To this end, the present paper proposes a learning vector quantization (LVQ)-based ensemble learning model in which three LVQs are individually trained to detect and classify LL faults in PV arrays. The initial LVQ vectors are determined using the k-means clustering method, and the learning rate is optimized by the adaptive gradient (AdaGrad) optimizer. The training and testing datasets are collected according to the PV array’s current–voltage (I–V) characteristic curve, and several features are extracted based on the Canberra and chi-squared distance techniques. The model utilizes a small training dataset, considers various critical detection conditions for LL faults—such as different mismatch levels and fault impedance values—and the final experimental results show that the model achieves an impressive average accuracy of 99.26%.

Effect of fruit ripeness on electrical impedance spectrum parameters

This study aimed to reveal the mechanisms underlying changes in the electrical parameters of fruit during ripening. Plums and blueberries were selected as research objects, and their electrical parameters, firmness, water state, and microstructure with different maturities were measured. The observed relationships between fruit ripeness and electrical parameters were as follows: as fruit ripeness increased, the cell structure loosened, the number of gaps increased, membrane permeability increased, the distribution of free water became more scattered, and firmness gradually decreased. These factors led to increased cell fluid fluidity, shorter current flow paths, and lower impedance values. This study reveals the changes in various physiological indicators and electrical parameters of fruits during ripening and provides theoretical support for detecting fruit maturity using electrical parameters. These results are significant for the detection and grading of fruit maturity, extending the fruit preservation period, and developing rational fruit storage strategies.

Constructing p-n heterojunctions of Cl-Cu2O and PANI on three-dimensional nanofiber networks for enhanced photocatalytic degradation of oxytetracycline

A p-n heterojunction was constructed on a bacterial cellulose (BC) film by combining n-type semiconductor chlorine-doped Cu2O (Cl-Cu2O) and p-type semiconductor polyaniline (PANI), creating a ternary composite flexible film of Cl-Cu2O/PANI/BC. The chemical structure, microscopic morphology, and photoelectrochemical properties of Cl-Cu2O/PANI/BC were characterized and analyzed. Compared with pure Cl-Cu2O, the Cl-Cu2O/PANI/BC composite flexible film exhibited a broader response range to visible and near-infrared light, higher carrier concentration, lower impedance value, and substantial reduction in the recombination probability of photogenerated carriers. The process conditions for the photocatalytic degradation of oxytetracycline (OTC) were optimized using the response surface method, and the degradation rate of OTC caused by the Cl-Cu2O/PANI/BC was 96.3 %. In the degradation process of OTC, superoxide radical is the main active species. It was found that OTC molecules degraded via demethylation, secondary alcohol oxidation, decarboxylation, and deamination reactions, finally being degraded into H2O, CO2, and other small organic molecules. Thirteen major intermediates and possible degradation pathways were speculated. The photocatalytic performance of the Cl-Cu2O/PANI/BC was improved owing to the successful construction of the p-n heterojunction. The built-in electric field generated at the interface between the two semiconductors promoted the diffusion of photogenerated holes from the n-type Cl-Cu2O particles to the PANI coating layer on the BC chain, whereas the photogenerated electrons from PANI diffused toward Cl-Cu2O, accelerating the separation efficiency of photoinduced electrons and holes in the two semiconductors and thereby improving the efficiency of photocatalytic degradation. In addition, the three-dimensional network structure of a composite flexible film can help recover the photocatalyst. After performing seven experiments for recovery and reuse, the photocatalytic degradation rate of OTC still remained above 90 %.

Formation of heterogeneous microstructure and its effect on corrosion properties of high-silicon stainless steel S38815 weldment

This study aims to clarify the formation of heterogeneous microstructure and its effect on corrosion properties of high-silicon stainless steel (high-Si SS) S38815 weldment. A series of tests about microstructure and electrochemical characteristics were performed, including the electron backscatter diffraction (EBSD) analysis, Mott-Schottky tests, electrochemical impedance spectroscopy (EIS) tests, potentiodynamic and potentiostatic polarization tests. The formation mechanism of heterogeneous microstructure related to high-silicon and its correlation on corrosion was discussed extensively. The results show that the significantly deformed and recrystallised grains were observed at the low temperature heat affected zone (LT-HAZ) and high temperature heat affected zone (HT-HAZ) respectively. The metastable pitting and low impedance values were formed in the above region, despite their low donor density. The deterioration in corrosion resistance of S38815 weldment as a result of high-angle grain boundaries (HAGBs) and carbides is more pronounced than the beneficial impact of Cr and Si oxidation. This study provides valuable references to the manufacturing and enhancing the anti-corrosion properties of this high-Si SS.

Hydrocarbon prospective study using seismic inversion and rock physics in an offshore field, Niger Delta

This study integrates seismic inversion and rock physics techniques to evaluate the hydrocarbon potential of an offshore field in the Niger Delta. Five wells revealed three reservoir sands with favourable reservoir properties, including gross thickness (49.2–81.4 m), porosity (0.18–0.2), permeability (565–1481 mD), and water saturation (0.16–0.54). A robust wavelet extraction process was implemented to guide seismic inversion, and a well log-centric approach was employed to validate the resulting acoustic impedance data. Rock physics analysis established correlations between acoustic impedance (Zp), porosity, fluid content, and lithology, enabling the identification of hydrocarbon-filled sands, brine-saturated sands, and shales. These relationships enabled the discrimination of hydrocarbon-filled sands [5000–8000 (m/s)(g/cc)], from brine-saturated sands [5600–8400 (m/s)(g/cc)], and shales [5000–9000 (m/s)(g/cc)] within the inverted seismic data. The inverted acoustic impedance section showed a general increase with depth, reflecting the typical compaction effects in the Niger Delta. Analysis of the impedance distribution across horizon time slices revealed prospective zones with low impedance values [below 6300 (m/s)(g/cc)], particularly in horizons 1 and 2. These newly identified zones exhibit the strongest potential for hydrocarbon accumulation and warrant further investigation. This study demonstrates the effectiveness of using well log and rock physics constrained seismic inversion for hydrocarbon exploration in an offshore field in the Niger Delta.

Direct (D)-Wave Monitoring Enhancement With Subdural Electrode Placement: A Case Series.

Direct-wave (D-wave) neuromonitoring is a direct measure of corticospinal tract integrity that detects potential injury during spinal cord surgery. Epidural placement of electrodes used for D-wave measurements can result in high electrical impedances resulting in substantial signal noise that can compromise signal interpretation. Subdural electrode placement may offer a solution. Medical records for consecutive patients with epidural and subdural D-wave monitoring were reviewed. Demographic and clinical information including preoperative and postoperative motor strength were recorded. Neuromonitoring charts were reviewed to characterize impedances and signal amplitudes of D-waves recorded epidurally (before durotomy) and subdurally (following durotomy). Nonparametric statistics were used to compare epidural and subdural D-waves. Ten patients (50% women, median age 50.5 years) were analyzed, of which five patients (50%) were functionally independent (modified McCormick grade ≤ II) preoperatively. D-waves were successfully acquired by subdural electrodes in eight cases and by epidural electrodes in three cases. Subdural electrode placement was associated with lower impedance values ( P = 0.011) and a higher baseline D-wave amplitude ( P = 0.007) relative to epidural placement. No association was observed between D-wave obtainability and functional status, and no adverse events relating to subdural electrode placement were encountered. Subdural electrode placement allows successful D-wave acquisition with accurate monitoring, clearer waveforms, and a more optimal signal-to-noise ratio relative to epidural placement. For spinal surgeries where access to the subdural compartment is technically safe and feasible, surgeons should consider subdural placement when monitoring D-waves to optimize clinical interpretation.

Cochlear Implantation: Long-Term Effect of Early Activation on Electrode Impedance.

Objectives: The growing adoption of cochlear implants (CIs) necessitates understanding the factors influencing long-term performance and improved outcomes. This work investigated the long-term effect of early activation of CIs on electrode impedance in a large sample of CI users at different time points. Methods: A retrospective study on 915 ears from CI patients who were implanted between 2015 and 2020. According to their CI audio processor activation time, the patients were categorized into early activation (activated 1 day after surgery, n = 481) and classical activation (activated 4 weeks after surgery, n = 434) groups. Then, the impact of the activation times on the electrode impedance values, along the electrode array contacts, at different time points up to two years was studied and analyzed. Results: The early activation group demonstrated lower impedance values across all the electrode array sections compared to the classical activation at 1 month, 1 year, and 2 years post-implantation. At 1 month, early activation was associated with a reduction of 0.34 kΩ, 0.46 kΩ, and 0.37 kΩ in the apical, middle, and basal sections, respectively. These differences persisted at subsequent intervals. Conclusions: Early activation leads to sustained reductions in the electrode impedance compared to classical activation (CA), suggesting that earlier activation might positively affect long-term CI outcomes.

Acoustic impedance prediction based on extended seismic attributes using multilayer perceptron, random forest, and extra tree regressor algorithms

Acoustic impedance is the product of the density of a material and the speed at which an acoustic wave travels through it. Understanding this relationship is essential because low acoustic impedance values are closely associated with high porosity, facilitating the accumulation of more hydrocarbons. In this study, we estimate the acoustic impedance based on nine different inputs of seismic attributes in addition to depth and two-way travel time using three supervised machine learning models, namely extra tree regression (ETR), random forest regression, and a multilayer perceptron regression algorithm using the scikit-learn library. Our results show that the R2 of multilayer perceptron regression is 0.85, which is close to what has been reported in recent studies. However, the ETR method outperformed those reported in the literature in terms of the mean absolute error, mean squared error, and root-mean-squared error. The novelty of this study lies in achieving more accurate predictions of acoustic impedance for exploration.

Light-Based 3D Multi-Material Printing of Micro-Structured Bio-Shaped, Conducting and Dry Adhesive Electrodes for Bioelectronics.

In this work, a new method of multi-material printing in one-go using a commercially available 3D printer is presented. The approach is simple and versatile, allowing the manufacturing of multi-material layered or multi-material printing in the same layer. To the best of the knowledge, it is the first time that 3D printed Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) micro-patterns combining different materials are reported, overcoming mechanical stability issues. Moreover, the conducting ink is engineered to obtain stable in-time materials while retaining sub-100µm resolution. Micro-structured bio-shaped protuberances are designed and 3D printed as electrodes for electrophysiology. Moreover, these microstructures are combined with polymerizable deep eutectic solvents (polyDES) as functional additives, gaining adhesion and ionic conductivity. As a result of the novel electrodes, low skin impedance values showed suitable performance for electromyography recording on the forearm. Finally, this concluded that the use of polyDES conferred stability over time, allowing the usability of the electrode 90 days after fabrication without losing its performance. All in all, this demonstrated a very easy-to-make procedure that allows printing PEDOT:PSS on soft, hard, and/or flexible functional substrates, opening up a new paradigm in the manufacturing of conducting multi-functional materials for the field of bioelectronics and wearables.

Intense interaction between biochar/g-C3N4 promotes the photocatalytic performance of heterojunction catalysts.

In recent decades, environmental protection and energy issues have gained significant attention, and the development of efficient, environmentally friendly catalysts has become especially crucial for the advancement of photocatalytic technology. This study employs the sintering method to produce biochar. A hybrid photocatalyst for the degradation of RHB under visible light was prepared by loading varying proportions of biochar onto g-C3N4 using ultrasonic technology. Among them, 2% CGCD (2% biochar/g-C3N4) achieved a degradation rate of 91.3% for RHB after 30 minutes of visible light exposure, which was more than 25% higher than GCD (g-C3N4), and exhibited a higher photocurrent intensity and lower impedance value. The enhancement in photocatalytic activity is primarily attributed to the increased utilization efficiency of visible light and the electron transfer channel effect from a minor amount of biochar, effectively reducing the recombination of photo-generated charge carriers on the g-C3N4 surface, thereby significantly improving photocatalytic activity. The degradation of RHB is synergistically mediated by O2 -, h+ (photo-generated holes), and ˙OH. The free radical capture experiment indicates that O2 - and ˙OH are the primary active components, followed by h+.

Lateral Rock Characteristic Evidence of Hydrocarbon Restoration from Post-Stack Impedance Inversion: A Case Study of ZED-field Offshore Niger Delta

Lateral predictions of rock properties that are descriptive of a reservoir have been studied using a model-established seismic inversion approach that was used to convert input seismic data into an acoustic impedance structure to optimize hydrocarbon restoration in the field. This was actualized by integrating wireline logs and 3D post stack seismic data procured from ZED-Field offshore Niger Delta. The inversion system employed in this study comprises of forward modelling of reflection coefficients starting with a low-frequency impedance model induced from well logs and convolution of the reflection coefficients with the source wavelet extracted from the seismic input. P-impedance analysis at reservoir C5000 delineated from the control well gave a near perfect correlation of 0.998109 (≈ 99.8 %) between the original P-impedance log, initial P-impedance model log and inverted P-impedance log with an estimated error of 0.0616932 which is about (6.16%). Seismic inversion analysis realized an acoustic impedance structure with P-impedance values ranging from 3801 to 11073.0m/s*g/cc and having an overall increase with depth tendency. Specifically, a low-impedance structure was observed at the reservoir window that can be profiled laterally elsewhere from the existing wells. Impedance slices extracted from the impedance volume at the top and base of reservoir C5000 clearly showed low impedance values away from the existing wells which are evidence of new hydrocarbon prospects (hydrocarbon-charged sands) in the field that can be explored for improved hydrocarbon recovery and field development. Therefore, the realized attribute could supply litho-fluids knowledge inside the current reservoirs, and likewise aid in defining probable hydrocarbon regions of low impedance that can be tested with the input seismic to boost the interpretation of reservoir attributes with feasible integration to seismic stratigraphy for improved reservoir prediction away from the extant wells. This information can be invaluable in delineating more prospective reservoir zones in the field, and thereby enhancing optimum field development which aids in reservoir management decisions.

Does severe and chronic esophageal distension by air (observed in SGB and GB) affect the esophageal mucosa integrity (MNBI).

Supragastric belching (SGB) and aerophagia are behavioral disorders characterized by air induced esophageal distension. SGB is known to be associated with Gastro Esophageal Reflux Disease (GERD). Low Mean Nocturnal Baseline Impedance (MNBI) values support GERD diagnosis. We aimed to assess if chronic esophageal distension by air affects the esophageal mucosa integrity by assessing changes in MNBI. In a single-center database study, we searched retrospectively for patients with a diagnosis of pathological SGB (n = 146) or aerophagia (n = 34) based on impedance-pH reflux monitoring. During the examined period, patients with a conclusive negative diagnosis of SGB and no evidence of aerophagia were used as a control cohort (n = 191). MNBI at 3, 5, and 17 cm over Lower Esophageal Sphincter (LES) was evaluated. GERD was diagnosed if acid exposure time (AET) >6%. All impedance studies of included patients were prospectively reevaluated. GERD was diagnosed in 31.7% patients with SGB, a rate not different in comparison to patients without SGB (30.8%, p = 0.906). MNBI at 3 and 5 cm above the LES was significantly decreased among patients with SGB. SGB was not correlated with MNBI at 3 cm over the LES, (p: 0.086 OR: 1.000 95% CI: 0.999-1.001) when using multivariate analysis. Moreover no difference was spotted as far as MNBI at 3, 5, and 17 cm over the LES is concerned among patients with or without aerophagia. Even if patients with SGB do show lower MNBI values, esophageal distention due to excessive air movement does not directly lead to impairment of esophageal mucosa integrity.

Electrochemical detection of oxytetracycline employing sugarcane carbon modified graphite electrode.

The present study used CeO2-Co3O4 quantum dots@porous carbon/multiwalled carbon nanotube (CeO2-Co3O4 QDs@PC/MWCNT/GE) composites to modify graphite electrodes to fabricate high-sensitivity electrochemical sensors to detect the presence of oxytetracycline (OTC). The quantum dots were made from waste sugarcane bagasse. The electrochemical analysis demonstrated the superior electrochemical performance of CeO2-Co3O4 QDs@PC/MWCNT/GE, with a peak current density of 1.276mA/cm2. Electrochemical impedance spectroscopy (EIS) revealed lower impedance values for CeO2-Co3O4 QDs@PC/MWCNT/GE compared to other electrodes, indicating enhanced conductivity. The modified electrode exhibited an enlarged electrochemically active area, with values of 0.602 cm2, almost seven times that of the bare graphite electrode (0.079 cm2). The results showed that the CeO2-Co3O4 QDs@PC/MWCNT/GE had excellent performance for OTC detection, and its linear calibration range was 1.007 × 10-8 to 2.04 × 10-7M (i.e., 0.005-0.1ppm) and 1.007 × 10-6 to 1.209 × 10-4M (i.e., 0.5-60ppm). The limit of detection and limit of quantification were 1.23nM (0.61ppb) and 4.09nM (2.03ppb) (S/N = 3), respectively. The electrode demonstrated long-term stability for up to 7weeks. This method provides a new way to prepare electrochemical sensors for OTC detection.

A novel high-performance coating with hybrid nanofiller reinforcement for superior self-cleaning, anti-icing, and corrosion resistance properties

A novel self-cleaning superamphiphobic nanocomposite coating with excellent corrosion protection, anti-icing, and mechanical properties has been developed through the integration of hybrid graphene nanoplate (GNP) and silica nanoparticle (NS) reinforcement, coupled with surface modification using fluorinated particles and polydimethylsiloxane (PDMS). The GNP/NS hybrid nanofiller imparts superior corrosion barrier performance and mechanical strength to the coating. The surface modification led to impressive contact angles of 168° for water and 150° for hexadecane. While sliding angle consistently displayed less than 10° for both fluids, signifying the coating's exceptional superamphiphobic characteristics. The coating demonstrates exceptional anti-icing performance, with significantly delayed ice formation and reduced ice adhesion. Moreover, the coating exhibits remarkable stability and durability, even after long-term exposure to corrosive and harsh weathering environments. Electrochemical impedance spectroscopy (EIS) measurements confirmed the coating's superior corrosion resistance; the impedance plot of developed coating remained unchanged and exceeded 1010 Ω/cm2 across various exposure durations, whereas the neat epoxy started with a lower impedance value that progressively diminished over the exposure period. Tensile tests revealed a 75% increase in tensile strength, 63% improvement in failure strain, and an 11% increase in Young's modulus compared to the neat epoxy. Additionally, to comprehensively elucidate the mechanisms underpinning the developed nanocomposite coating, this study utilized a range of advanced analytical methods, including SEM, EDX, XRD, FTIR, and hardness tests. The developed nanocomposite coating shows promising potential as a reliable, long-lasting protective solution for metal structures in civil, mechanical, and aerospace engineering applications.

Titania Nanoparticle-Stimulated Ultralow Frequency Detection and High-Pass Filter Behavior of a Flexible Piezoelectric Nanogenerator: A Self-Sustaining Energy Harvester for Active Motion Tracking.

A significant driving force for the fabrication of IoT-compatible smart health gear integrated with multifunctional sensors is the growing trend in fitness and the overall wellness of the human body. In this work, we present an autonomous motion and activity-sensing device based on the efficacious nucleation of the polar β-phase in an electroactive polymer. Representatively, we investigate the nucleating effect of TiO2 nanoparticles on weight-modulated PVDF-HFP films (PT-5, PT-10, and PT-15) and subsequently prototype a sensing device with the film that demonstrates superior β-phase nucleation. The PT-10 film, with an optimal polar β-phase, shows the highest remnant polarization (2Pr) and energy density of 0.36 μC/cm2 and 22.3 mJ/cm3, respectively, at 60 kV/cm. The films mimic a high pass filter at frequencies above 10 KHz with very low impedance and high ac conductivity values. The frequency-dependent impedance studies reveal an effective interfacial polarization between TiO2 nanoparticles and PVDF-HFP, explicitly observed in the low-frequency region. Consequently, the sensor fabricated with PT-10 as the sensing layer exhibits ultralow frequency detection (25 Hz) resulting from the blood flow muscle oxygenation. The device successfully senses voluntary joint movements of the human body and actively tracks a range of motions, from brisk walking to running. Additionally, through repetitive human finger-tapping motion, the nanogenerator lights up multiple light-emitting diodes in series and charges capacitors of varying magnitudes under 50 s. The real-time human motion sensing and movement tracking modalities of the sensor hold promise in the arena of smart wearables, sports biomechanics, and contact-based medical devices.

Effect of aging and obesity on esophageal mucosal integrity as measured by baseline impedance.

Low mean nocturnal baseline impedance (MNBI) values support gastroesophageal reflux disease (GERD) diagnosis. Recent data denote that age and obesity may affect MNBI. We aimed to evaluate diagnostic MNBI cutoffs as also the effect of aging and body mass index (BMI) on MNBI. In total 311 patients (M/F: 139/172, mean age: 47 ± 13) referred for typical GERD symptoms that have undertaken both high-resolution manometry (HRM) and pH-Impedance studies off PPI were evaluated. MNBI at 3, 5, and 17 cm over lower esophageal sphincter (LES) were evaluated. GERD was diagnosed if acid exposure time (AET) >6%. Mean BMI was 26.6 ± 5.9 kg/cm2 . GERD was diagnosed in 39.2% and 13.5% had inconclusive GERD. MNBI was correlated to patients' age, BMI, AET, and the length of LES-CD separation and at 3 cm also to the total number of reflux and LES hypotension. In the multivariate analysis MNBI at 3 and 5 cm was independently correlated only to age, BMI, and AET. Patients with definite GERD showed lower MNBI at 3 cm compared with inconclusive GERD though both showed lower values when compared with GERD absence. At 3 cm MNBI ability for diagnosing GERD was good (0.815, p < 0.001 95% CI: 0.766-0.863) with an optimal cutoff point of 1281 Ohm. According to our study findings age and BMI affect independently lower esophageal MNBI values in patients evaluated for GERD. MNBI significantly aids toward GERD diagnosis though in a real-life setting MNBI values much lower than the one previously proposed should be used.

Delineating tidal channel feature using integrated post-stack seismic inversion and spectral decomposition applications of the Upper Cretaceous reservoir Abu Roash C: A case study from Abu-Sennan oil field, Western Desert, Egypt

Delineating tidal channels that bear hydrocarbons in fluvial systems is crucial to minimize drilling risks, and raise the hydrocarbon potential. Therefore, we performed an integrated workflow that combines/compares the outcomes of a pair of post-stack inversion techniques (model-based inversion and colored inversion) and the spectral decomposition attribute to delineate (vertically and horizontally) the hydrocarbon-bearing tidal channel contained in the Upper Cretaceous Abu Roash (AR)/C reservoir in the South West Abu-Sennan (SWS) area in Abu-Gharadig basin in the Northern Egyptian Western Desert (NEWD). We used a dataset consisting of twenty seismic reflection profiles and borehole geophysical data of four wells. Data conditioning was performed in detail for the whole dataset that was used in this study. The application of the absolute impedance (model-based inversion) produced better results relative to the band-limited acoustic impendence (colored inversion). The model-based inverted sections gave an improved subsurface image of seismic data and delineated the reservoir properly. The low-frequency range detected through the use of seismic inversion techniques and the spectral decomposition attribute analysis showed a good fit with the low impedance values corresponding to hydrocarbons. The study results showed a correlation of roughly 0.99 exists between the generated synthetic impedance, original seismic, and the borehole geophysical data characterizing the tidal channel confined within the AR/C reservoir. The match between the post-stack inversion techniques and the spectral decomposition analysis results is considered a visual validation of the delineated tidal channel. The performed workflow can be applied and impact the understanding of comparable reservoirs with similar settings in near areas.

Microbe-induced pitting of Fe-based amorphous coating

It is well known that Fe-based amorphous coatings demonstrate excellent performance against marine corrosion, but the corrosion resistance is significantly reduced in the presence of ocean-microbes. However, the mechanism of microbe-induced corrosion, named as microbiologically influenced corrosion (MIC), has yet to be understood. In this paper, the MIC mechanism of an Fe-based amorphous coating (with the composition of Fe43.7Co7.3Cr14.7Mo12.6C15.5B4.3Y1.9) in the presence of Pseudomonas aeruginosa (one of the typical ocean-microbes) was elaborately investigated by electrochemical impedance spectroscopy (EIS), electrochemical noise analysis (EN), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The electrochemical results show that P. aeruginosa reduced the corrosion resistance of the amorphous coating, manifested by the lower impedance values and higher metastable pitting initiation rate compared to those in a sterile medium. XPS analysis indicates the enrichment of soluble high-valent metal oxides in the passive film formed in the P. aeruginosa medium. In addition, TEM observation reveals pitting initiated exactly beneath P. aeruginosa cells, rather than defect regions (i.e., intersplat) as expected. In the pitting region, a thick biofilm was formed, which resulted in thinning of the underlying passive film. Based on these results, an MIC mechanism based on the inward extracellular electron transfer (EET) effect was proposed, and a potential strategy to relieve MIC was examined.

Calibrated Electrochemical Impedance Spectroscopy and Time‐Domain Measurements of a 7 kWh Automotive Lithium‐Ion Battery Module with 396 Cylindrical Cells

AbstractA 7 kWh automotive battery module with 396 interconnected cells was tested with electrochemical impedance spectroscopy (EIS) and time‐domain pulsing over 260 charge‐discharge cycles. An EIS calibration workflow was developed for low complex impedance values in a frequency range of 1 kHz to 50 mHz. Significant corrections on the resistance and the reactance were obtained from the calibration, particularly at frequencies above 100 Hz. Equivalent circuit parameters were extracted from the EIS spectra and the pulse response and investigated with respect to the cycle number and state‐of‐charge (SoC). Fit parameters were robustly extracted including Rsol, Rct, and L from EIS, and R0, τ1 and τ2 from time‐domain pulsing. The ohmic resistance decreased over the cycling number indicating an enhanced wetting of the electrodes. Charge transfer resistance Rct showed a monotonic increase over the cycles related to cell ageing. From the charge and discharge pulses, the ohmic resistance R0 was determined from the instantaneous voltage step of the recovery pulse, while the two time constants τ1 and τ2 correspond to the slower exponential recovery phase. R0 from the time‐domain showed a similar trend as Rsol plus a contribution of Rct from EIS. Overall, we show that calibrated EIS and time‐domain pulsing are efficient methods to gain insights into the electrochemical processes related to different SoCs and the cycling ageing of battery modules and packs.

EFFECT OF ELECTRIC PULSE TREATMENT ON MICROSTRUCTURE, ELECTROCHEMICAL AND DISCHARGE PROPERTIES OF AZ61 ANODES FOR Mg-AIR BATTERIES

In this work, the effects of electric pulse treatment on the discharge and electrochemical properties of rolled and extruded AZ61 as anode of Mg-air battery were studied. The microstructure, electrochemical behavior and surface morphology after discharge were discussed to relate the discharge performance. The experimental results show that compared with the original magnesium anode (rolled and extruded), the magnesium anode treated by electric pulse has more negative corrosion potential, lower impedance value, higher discharge voltage and better specific energy. This is because electric pulse treatment can cause the coarse second phase in magnesium anode to dissolve and the grains to become more uniform. In particular, in the discharge process, the surface of magnesium anode after electric pulse treatment will form micro cracks, which is beneficial to promote the self-stripping of discharge products. It is worth noting that the effect of electric pulse treatment on rolled anode is better than that of extruded anode. It may be due to the different dislocation density in the two anodes. During the electric pulse treatment, the dislocation density in the alloy is highly correlated with the dissolution rate of β-Mg17Al12, which ultimately affects the volume fraction of the second phase in the alloy.