Linear Impedance Research Articles

A flow loop study on the effect of Ca2+ ions on the CO2 corrosion of 1Cr carbon steel in a CaCO3-saturated solution

ABSTRACT This paper investigates the effect of calcium on the CO2 corrosion behaviour of 1Cr carbon steel under the effect of flow. The experiments were performed in a flow loop system in 1 wt-% NaCl solution at 80°C, pH = 6.34 with initial S CaCO3 = 2 and pCO2 = 0.53 bar. The flow velocity was kept at 3 m s−1 and the system was pressurised to 3 bar. The corrosion process was monitored with linear polarisation resistance and electrochemical impedance spectroscopy (EIS). Phase analysis of the corrosion products was obtained using X-ray powder diffraction and surface morphology was characterised with scanning electron microscopy. Results show that the flow delayed the precipitation of substitutional solid solution of Fe0.31Ca0.69CO3, deferring the pseudo-passivation stage. The flow did not cause Mesa attack or localised corrosion. The protectiveness of this film was not affected by the presence of calcium and was comparable to the one of pure FeCO3.

Humidity sensor based on Gallium Nitride for real time monitoring applications

Gallium Nitride (GaN) remarkably shows high electron mobility, wide energy band gap, biocompatibility, and chemical stability. Wurtzite structure makes topmost Gallium atoms electropositive, hence high ligand binding ability especially to anions, making it usable as humidity sensor due to water self-ionization phenomenon. In this work, thin-film GaN based humidity sensor is fabricated through pulse modulated DC magnetron sputtering. Interdigitated electrodes (IDEs) with 100 μm width and spacing were inkjet printed on top of GaN sensing layer to further enhance sensor sensitivity. Impedance, capacitance, and current response were recorded for humidity and bio-sensing applications. The sensor shows approximate linear impedance response between 0 and 100% humidity range, the sensitivity of 8.53 nF/RH% and 79 kΩ/RH% for capacitance and impedance, and fast response (Tres) and recovery (Trec) time of 3.5 s and 9 s, respectively. The sensor shows little hysteresis of < 3.53% with stable and wide variations for accurate measurements. Especially, it demonstrates temperature invariance for thermal stability. Experimental results demonstrate fabricated sensor effectively evaluates plant transpiration cycle through water level monitoring by direct attachment onto leaves without causing any damage as well as freshness level of meat loaf. These properties of the proposed sensor make it a suitable candidate for future electronics providing a low-cost platform for real time monitoring applications.

A novel current-controlled memristor-based chaotic circuit

In this paper, a novel third-order autonomous memristor-based chaotic circuit is proposed. The circuit has simple topology and contains only four elements including one linear negative impedance converter-based resistor, one linear capacitor, one linear inductor, and one nonlinear current-controlled memristor. Firstly, the voltage-current characteristic analysis of the memristor emulator for different driving amplitudes and frequencies are presented. With dimensionless system, the symmetry, equilibrium point and its stability are analysed. It is shown that the system has two unstable saddle-foci and one unstable saddle. A set of typical parameters are chosen for the generation of chaotic attractor. Differing from the common period-doubling bifurcation route in smooth dynamical systems, this memristive system shows abrupt transition from the coexisting period-1 limit cycles to robust chaos when varying system parameters. Various dynamical behaviors are analysed using the numerical simulations and circuit verifications.

Efficiency Evaluation of Anti-corrosion Treatment of Carbon Steel by Extracts of Red Algae Collected from Mediterranean Coast

The paper presents the assessment of inhibition effectiveness of biomolecules extracted from red seaweed against biocorrosion in the petroleum industry. The first objective of this study was to obtain extracts (A, B and C, prepared respectively from red algae species: Corallina ellongata, Gymnogongrus crenulatus and Pterocladia capillacea) by ethanol extraction method. The infrared spectra of the three extracts confirmed the presence of amine derivatives molecules known by their anti-corrosion inhibiting powers. The second objective was based on the identification of physico-chemical characteristics of the extracts and thus revealing their inhibitory and / or bactericidal power in bacterial corrosion of carbon steel in injection water contaminated with sulfato-reducing bacteria. Biological test of all extracts gave a concentration upto 10 germs/mL in contaminated water by sulfato-reducing bacteria during 28 days of incubation at 37�C. Evolution in time of the open-circuit potential showed a longer incubation time for electrolyte with extracts, whereas the stabilization time was shorter. Current corrosion density, polarization resistance, charge transfer resistance and double layer capacity were determined by using linear polarizarion resistance technique and electrochemical impedance spectroscopy. The corrosion protection efficiency of extract obtained from Gymnogongrus crenulatus (extract B) reached a maximum protective capacity of 99.69% at 5 ppm in the injection water.

Selective Enhancement of Electrochemical Signal Based on the Size of Alcohols Using Nanoporous Platinum

AbstractNanoporous electrodes are representative electrode materials for diverse applications, such as energy conversion devices and sensors. Recently, selectivity based on the size of ions arising from nanoporous structures has been applied to capacitive deionization, electrochemical supercapacitors, and conductometry. Herein, we explored the selectivity based on the size of the redox molecules on the electrochemical reaction at the nanoporous Pt electrode with extremely small (1–2 nm) and uniform pores by linear sweep voltammetry and AC impedance spectroscopy. Among primary alcohols with sizes smaller than that of the pores, we observed exceptional selective enhancement in the case of methanol due to its smallest size, despite all the alcohols having a similar reaction mechanism. These findings may provide an insight into electrochemical analysis and electrocatalysis based on nanoporous structures.

Topology Automatic Identification Method for Low-Voltage Stations Based on Line Impedance Analysis

Aiming at the problems of high cost, low real-time performance of manual identification of low-voltage station topological structure, automatic identification methods such as instantaneous power failure method and voltage correlation analysis method, which affect residents’ electricity consumption, and the success rate is limited by application scenarios, this paper proposes a method based on multiple linear regression Line impedance analysis method for automatic identification of the topology of low-voltage stations. Based on the relationship between voltage, current, and impedance, multiple linear regression analysis is used to derive the upstream topology step by step from the bottom up to the top of the topology and then determine the station membership by voltage correlation. The cloud platform based on Docker technology and Hadoop technology is used for data distributed storage calculation, and an identification model in the context of big data is established to effectively improve the efficiency of the algorithm. Finally, the correctness of the algorithm verification is judged based on the results of manual field verification.

Synergistic inhibition effect of novel counterion-coupled surfactant based on rice bran oil and halide ion on the C-steel corrosion in molar sulphuric acid: Experimental and computational approaches

The counterion-coupled surfactant (RBOS-12) based on rice bran oil is synthesized, characterized, and evaluated as a new inhibitor for carbon steel corrosion. The inhibition, and synergistic effect performance of individual RBOS-12, and that is combined with chloride ions on the corrosion of carbon steel in a molar sulphuric acid medium at 30–60 ± 1 °C has been examined using open circuit potential-time, linear polarization resistance (LPR) corrosion rate, impedance spectroscopy (EIS), potentiodynamic polarization (PDP), surface topology (Field emission-scanning electron microscopy/Energy dispersive X-ray analysis (FE-SEM/EDS), X-ray diffraction (XRD) and UV–vis spectroscopic studies), density functional theory (DFT) and molecular dynamics (MD) simulations. Experimental findings exhibited that the inhibition capacity of individual RBOS-12 is 95.5% at the concentration of 1.0 × 10−3 M. Synergistic inhibition effect was observed between the RBOS-12 surfactant and the Cl- ion additives, with the maximum corrosion inhibition capacity as high as ~99.1% at 1 × 10–5 M RBOS-12 + 0.1 M Cl- ions. The individual RBOS-12 and RBOS-12/Cl− system get adsorbed onto the metal interface through mixed categories of adsorption mainly with the chemisorption. Meanwhile, the adsorption mode follows the Langmuir isotherm model. FE-SEM/EDS and XRD investigates approve the protective and adsorption capabilities of the individual RBOS-12 and RBOS-12/Cl− inhibitor systems. UV–vis spectroscopic analysis display that the additive interacts with metal in H2SO4 medium to form Fe-inhibitor complexes. DFT calculations and MD simulations further support the empirical outcomes. The findings exhibited that the prepared RBOS-12/Cl- system can be used as economic, eco-friendly, and efficient corrosion inhibitor with good anticorrosion properties for metals in acidic environments.

Sweet Drinks as Fuels for an Alkaline Fuel Cell with Nonprecious Catalysts

Sugar has the potential to create enough energy to power mobile electronics. Various sugar-powered fuel cells have been reported, however, most of them used pure glucose as substrate and enzymes/noble metals as catalysts. In this work, an alkaline fuel cell with cheap catalysts were constructed, and different sweet drinks were used as fuels for power generation. The influence of different substrates on the electrochemical performance was characterized under the controlled conditions. Our experimental results showed that the fuel cell fueled with carbonated soft drinks had the best performance under the conditions of 99.95 g/L chemical oxygen demand and 3M KOH. The power densities of the fuel cell fueled with different substrates decreased in the order of Pepsi (33.41 W/m2) &gt; Sprite (28.38 W/m2) &gt; apple juice (20.63 W/m2) &gt; Coca (16.31 W/m2) &gt; pear juice (15.31 W/m2) &gt; orange juice (12.75 W/m2), which was consistent with linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) analysis. This is the first report on alkaline fuel cell (AFC) performance using different sweet drinks as substrate. These values are more than 10 times higher than those of reported microbial fuel cells. Our findings demonstrated that sweet drinks fueled alkaline fuel cells can be a promising energy source for low-power electronics.

Complementary Stability of Markovian Systems: Series Elastic Actuators and Human-Robot Interaction

Abstract This paper presents an extension of the complementary stability analysis for discrete-time Markovian systems applied in interaction control. The control strategy considers an internal loop force control for Series Elastic Actuators based on the Robust Regulator for Discrete-time Markov Jump Linear systems and extern loop impedance control to regulate the interaction between the human and robot. Two examples show the complementary stability analysis of the human-robot interaction system, where is regarded as different values of the virtual impedances, different levels for the robustness of the force control, uncertainties, and abrupt changes for human parameters. Simulation results show the capacity of control strategy to deal with active interaction models, where the Mean Square Stability guarantees safe for the user. Additionally, from results it is understood the transmissibility of impedance achieved is a consequence of the robust performance given by the force controller.

Effect of the sample form on the corrosion behavior of steels for concrete in 3% NaCl medium

Corrosion of steel constitutes a major preoccupation in the field of civil engineering and the building sector. In this paper, we investigated the electrochemical behavior of two steel specimens with different forms (latched steel and smooth steel) in a 3 wt.% NaCl solution. For this purpose, we studied the steel samples by linear polarization, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The surface morphologies of the substrates were examined by scanning electron microscopy coupled with energy diffraction spectroscopy (SEM/EDS). Results of linear polarization, Tafel polarization curves and EIS show that latched steel (LS) is more susceptible to corrosion than smooth steel (SS) in saline solution. Gravimetric and SEM/EDS analysis after 10 days of immersion confirmed the results obtained by electrochemical methods. All of our results are in agreement and demonstrate that the sample form plays a key role in corrosion resistance.

The Role of PEG 6000 and PVP as Stabilizing and Surfactant Agents in the Photoelectrochemical Properties of BiVO4 Monoclinic Structure

Nanocrystalline BiVO4 on monoclinic phase was obtained by a modified-solution combustion synthesis (SCS) using poly(ethylene glycol) (PEG 6000) and polyvinylpyrrolidone (PVP) as stabilizing and surfactant agents, respectively. An active photoanode was built using a simple procedure by dip-coating deposition process on fluorine-doped tin dioxide (FTO). The structure, morphology and optical properties of FTO/BiVO4 photoanode were evaluated by means of X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and diffuse reflectance UV-Vis spectroscopy. The photoelectrochemical performance measurements were carried out by linear sweep voltammetry (LSV), chronoamperometry and electrochemical impedance spectroscopy (EIS) under InGaN blue light emitting diode (LED) illumination condition (about 450 nm). In Na2SO4 electrolyte solution, the electrode has presented better photoelectroactivity than in NaNO3 solution, as evidenced by photoelectrochemical parameters such as: the highest photocurrent density (js) value, cathodic shifts of the onset potential (OP) and lower charge-transfer resistence (Rct). In the methyl orange (MO) degradation reaction the FTO/BiVO4 electrode has presented high photoelectroactivity, where the estimated kinetic constant rate (kobs) is 4.74 × 10−3 and 7.54 × 10−3 min−1 in NaNO3 and Na2SO4 solutions, respectively. This remarkable performance of the as-prepared electrode is due to the morphological BiVO4 structure,with elongated-shape nano-sized domain particles, besides the considerable porosity and roughness levels on electrode surface.

Synthesis, Characterization and Investigation of Hydrogen Evolution Activity of Ni‐Mo/Al2O3 Composite

AbstractIn the present study, the hydrogen evolution activity of the Ni−Mo/Al2O3 catalyst was investigated. This catalyst was produced by milling of oxide precursors of nickel oxide (NiO) and molybdenum trioxide (MoO3) with aluminum as a reducing agent. So that oxide precursors with 100 % excess aluminum on stoichiometric composition at different times were milled to perform complete reduction operations. Subsequently, X‐ray diffraction (XRD) analysis was performed for phase analysis and scanning electron microscopy (SEM) was used to investigate the microstructure. It was found that oxide precursors with 100 % excess aluminum on stoichiometric composition were reduced after 50 h of milling and nickel molybdenum/alumina composite was produced. On the other hand, to compare the activity of Ni−Mo/Al2O3 two different catalysts (57 NiMo, 80 NiMo) were also produced by the milling method. The specimens were transformed into pills of 10 mm in diameter and 3 mm in height at 900 MPa pressure. A furnace under an argon atmosphere at a temperature of 1400 °C was used to sinter the produced pills. Finally, the hydrogen evolution activity of this sample was investigated by linear polarization tests and impedance spectroscopy in 1 M KOH solution. The sample reduced with 100 % excess aluminum showed higher activity than the stoichiometric combination, with −62 mV cathodic‐Tafel slope, −70 mV over‐potential at a current density of −10 mA cm−2 and a charge transfer resistance of 126.6 ohms.

Dry Hydrogen Production in a Tandem Critical Raw Material-Free Water Photoelectrolysis Cell Using a Hydrophobic Gas-Diffusion Backing Layer

A photoelectrochemical tandem cell (PEC) based on a cathodic hydrophobic gas-diffusion backing layer was developed to produce dry hydrogen from solar driven water splitting. The cell consisted of low cost and non-critical raw materials (CRMs). A relatively high-energy gap (2.1 eV) hematite-based photoanode and a low energy gap (1.2 eV) cupric oxide photocathode were deposited on a fluorine-doped tin oxide glass (FTO) and a hydrophobic carbonaceous substrate, respectively. The cell was illuminated from the anode. The electrolyte separator consisted of a transparent hydrophilic anionic solid polymer membrane allowing higher wavelengths not absorbed by the photoanode to be transmitted to the photocathode. To enhance the oxygen evolution rate, a NiFeOX surface promoter was deposited on the anodic semiconductor surface. To investigate the role of the cathodic backing layer, waterproofing and electrical conductivity properties were studied. Two different porous carbonaceous gas diffusion layers were tested (Spectracarb® and Sigracet®). These were also subjected to additional hydrophobisation procedures. The Sigracet 35BC® showed appropriate ex-situ properties for various wettability grades and it was selected as a cathodic substrate for the PEC. The enthalpic and throughput efficiency characteristics were determined, and the results compared to a conventional FTO glass-based cathode substrate. A throughput efficiency of 2% was achieved for the cell based on the hydrophobic backing layer, under a voltage bias of about 0.6 V, compared to 1% for the conventional cell. For the best configuration, an endurance test was carried out under operative conditions. The cells were electrochemically characterised by linear polarisation tests and impedance spectroscopy measurements. X-Ray Diffraction (XRD) patterns and Scanning Electron Microscopy (SEM) micrographs were analysed to assess the structure and morphology of the investigated materials.

Development of novel electrochemical sensor for the detection of biological warfare agents: enzyme, antibody, and DNA free

There is an urgent need to develop a novel sensor that can quickly and accurately detect biological warfare agents (BWAs). A novel electrochemical sensor was specially designed and developed for Staphylococcus aureus as a potential BWAs without using any enzyme, antibody, or genetic material. Cyclic voltammetry (CV), linear resistance polarization (LRP), chronoamperometry, impedance spectroscopy, and Differential Pulse Voltammetry (DPV) techniques were used for fast and accurate detection of BWAs. Co-precipitation technique was used for the synthesis of CuO nanoparticles (NPs) for their use in the electrochemical sensor. The effect of temperature, stirring and addition of CuO NPs was thoroughly investigated. The storage, stability, and performance of electrochemical sensor was tested for 45 days. The current response of the electrochemical sensor was found linear with the correlation coefficient, R2 = 0.991. The major advantage of this novel electrochemical sensor is that immobilization of enzyme, antibody, or DNA is not required in sensing technology as the immobilization process makes biosensors a highly specific. The novel electrochemical sensor was very quick, accurate, non-specific, and provide reliable results in the qualitative and quantitative estimation of pathogenic bacteria as a potential BWAs. A novel electrochemical sensor was specially designed and developed for the detection of Staphylococcus aureus pathogenic bacteria as a potential BWAs without using any enzyme, antibody, or genetic material. Cyclic voltammetry, linear resistance polarization, chronoamperometry, impedance spectroscopy, and Differential Pulse Voltammetry (DPV) experiments were carried out for fast and accurate detection of BWAs. Storage, stability, and reusability of the electrochemical sensor was tested for continuous 45 days. The current response of the electrochemical sensor was found to be linear with the correlation coefficient, R2 = 0.991. The major advantage of this novel sensor is that immobilization of enzyme, antibody, or DNA is not required in sensing technology as the immobilization process makes biosensor a highly specific. The novel electrochemical sensor was proved to be very quick, accurate, non-specific, and provide reliable results in the qualitative and quantitative estimation of pathogenic bacteria as a potential BWAs.

Evaluating the Effect of Varying the Metal Precursor in the Colloidal Synthesis of MoSe2 Nanomaterials and Their Application as Electrodes in the Hydrogen Evolution Reaction.

Herein we report on the use of different metal precursors in the synthesis of MoSe2 nanomaterials in order to control their morphology. The use of Mo(CO)6 as the metal precursor resulted in the formation of wrinkled few-layer nanosheets, while the use of H2MoO4 as the metal precursor resulted in the formation of nanoflowers. To investigate the effect of the morphologies on their performance as catalysts in the hydrogen evolution reaction, electrochemical characterization was done using linear sweep voltammetry (LSV), cyclic voltammetry (CV), and electrical impedance spectroscopy (EIS). The MoSe2 nanoflowers were found to have superior electrochemical performance towards the hydrogen evolution reaction with a lower Tafel slope, on-set potential, and overpotential at 10 mA/cm2 compared to the wrinkled few-layer nanosheets. This was found to be due to the higher effective electrochemical surface area of the nanoflowers compared to the nanosheets which suggests a higher number of exposed edge sites in the nanoflowers.

Spatially-Adaptive Variational Reconstructions for Linear Inverse Electrical Impedance Tomography

The inverse electrical impedance tomography (EIT) problem involves collecting electrical measurements on the smooth boundary of a region to determine the spatially varying electrical conductivity distribution within the bounded region. Effective applications of EIT technology emerged in different areas of engineering, technology, and applied sciences. However, the mathematical formulation of EIT is well known to suffer from a high degree of nonlinearity and severe ill-posedness. Therefore, regularization is required to produce reasonable electrical impedance images. Using difference imaging, we propose a spatially-variant variational method which couples sparsity regularization and smoothness regularization for improved EIT linear reconstructions. The EIT variational model can benefit from structural prior information in the form of an edge detection map coming either from an auxiliary image of the same object being reconstructed or automatically detected. We propose an efficient algorithm for minimizing the (non-convex) function based on the alternating direction method of multipliers. Experiments are presented which strongly indicate that using non-convex versus convex variational EIT models holds the potential for more accurate reconstructions.

Detection of Single-Phase to Ground Faults in Low-Resistance Grounded MV Systems

The Conventional zero-sequence (ZS) overcurrent protection method exhibits poor performance for single-phase to ground faults (SPGFs) with high impedance in low-resistance grounded systems (LRGSs), a type of medium-voltage (MV) distribution system. Hence, in this study, a novel SPGF detection methodology, designed specifically for LRGSs, is proposed. Considering the effects of system imbalance, a crucial limitation to the method based on ZS components, the concept of the Δ-circuit is first utilized to suppress such effects, maintaining the independence of the ZS network. Based on this, the proposed method computes the ZS power factor of a line to discriminate the line state, with the assistance of single-phase instantaneous reactive power theory (SIP) and the 4th-order components of the instantaneous active power. Not only the arcing features, but also the inherent characteristics brought by the unique grounding mode are subtly involved. Multiple simulations conducted in PSCAD software verify the good performance of the proposed detection method for various SPGFs, including those with low or high impedance and those with linear fault impedance or nonlinear arcs.

Electrocatalytic performance of cobalt doped copper bismuth oxide for glucose sensing and photoelectrochemical applications

Copper bismuth oxide (CBO), modified with cobalt as dopant has been prepared by coprecipitation and the electrode was prepared by doctor blade method. The cobalt doped copper bismuth oxide (Co-CBO) has been extensively used for selective glucose sensing and photoelectrochemical activity. Physical characterizations like X-ray diffraction, field-emission scanning electron microscopy are studied to confirm the formation of desired electrode. Linear sweep voltammetry, chronoamperometric and impedance studies explain about the electrocatalytic nature of cobalt doped CBO. Oxidation peak for glucose was observed for CBO at 0.54 V while for Co-CBO it occurred at 0.46 V. The reduction in potential is explained through synergistic catalytic enhancement due to cobalt doping. Further, Co-CBO was used for photoelectrochemical application, the electrode has shown current density of −0.80 mA cm−2 while that for CBO is −0.20 mA cm−2. Therefore, CBO has formed a desirable phase with cobalt which resulted in the enhancement of electrocatalytic performance.

Enhanced corrosion resistance of atmospheric plasma-sprayed zirconia–GNP composite by graphene oxide nanoplatelet encapsulation

The unique natural diffusion barrier property of graphene plays a crucial role in protecting the carbon steel substrates from corrosion, particularly using graphene oxide nanoplatelets (GNP)–zirconia (ZrO2) composites. In the present work, atmospheric plasma spraying (APS) technique has been used to coat both the spray-dried pristine ZrO2 and ZrO2–(0.5, 1.0, 1.5 and 2) wt% GNP composite on the carbon steel substrate. The retention of GNPs in the coating was confirmed using XRD, Raman spectroscopy, TEM, FE-SEM, and EDAX techniques. The corrosion properties of the coatings in 3.5 wt%NaCl electrolyte were studied using linear polarization resistance and electrochemical impedance spectroscopy technique. This reveals the enhanced charge transfer resistance, decreased corrosion current density and corrosion rate of ZrO2–GNP composite. Further, the corrosion rate of ZrO2–2 wt% GNP coating is 130 times less than the plasma-sprayed ZrO2. Compared to 0.5, 1.0 and 1.5 wt% GNP added zirconia coatings, ZrO2–2 wt% GNP displayed the highest stability up to 14 days in 3.5% NaCl electrolyte.

Post‐stack impedance blocky inversion based on analytic solution of viscous acoustic wave equation

ABSTRACTThe conventional impedance inversion method ignores the attenuation effect, transmission loss and inter‐layer multiple waves; the smooth‐like regularization approach makes the corresponding impedance solution excessively smooth. Both fundamentally limit the resolution of impedance result and lead to the inadequate ability of boundary characterization. Therefore, a post‐stack impedance blocky inversion method based on the analytic solution of viscous acoustic equation is proposed. Based on the derived recursive formula of reflections, the 1D viscous acoustic wave equation is solved analytically to obtain zero‐offset full‐wave field response. Applying chain rule, the analytical expression of the Fréchet derivative is derived for gradient‐descent non‐linear inversion. Combined with smooth constraints, the blocky constraints can be introduced into the Bayesian inference framework to obtain stable and well‐defined inversion results. According to the above theory, we firstly use model data to analyse the influence of incompleteness of forward method on seismic response, and further verify the effectiveness of the proposed method. Then the Q‐value sensitivity analysis of seismic trace is carried out to reduce the difficulty of Q‐value estimation. Finally, the real data from Lower Congo Basin in West Africa indicate that the proposed approach provide the high‐resolution and well‐defined impedance result. As a supplement and development of linear impedance inversion method, the non‐linear viscous inversion could recover more realistic and reliable impedance profiles.