Galvanic Sensor Research Articles

Anisotropic magnetoresistance probed by non-resonant microwave absorption in exchange-biased NiFe/IrMn structures

Sharp change of non-resonant microwave absorption was found in exchange-biased NiFe/IrMn and NiFe/Cu/IrMn structures possessing anisotropic magnetoresistance (AMR) and planar Hall effect (PHE). Angular dependence of the microwave detected AMR and contribution of the domain expansion to AMR microwave signal were analyzed. Decrease in the microwave absorption signal caused by Cu spacer between ferromagnetic NiFe and antiferromagnetic IrMn layers was observed, when NiFe and IrMn layers become exchange decoupled. Additional characterization of the electric transport was proved by asymmetry of resonant line. Sensitivity of the microwave AMR method is enough high to detect magnetic fields of microTesla level, that provides remote detection with a sensitivity corresponding to standard galvanic sensors. Developed technique is promising for wireless AMR sensor technology providing coordinate and angular field measurements through remote microwave absorption.

Designing advanced 0D/2D heterojunctions of N, S-co-doped carbon dots/Ti3C2Tx MXene nanosheets in electrochemical sensor applications

Ti3C2Tx MXene has demonstrated well-established sensitivity in electrochemical sensing but is susceptible to oxidation. Nitrogen-sulfur doped carbon dots (N, S-CDs) were functionalized on Ti3C2Tx MXene nanosheets via a surface modification strategy, leading to significant enhancement in the performance of Ti3C2Tx MXene. The incorporation of N, S-CDs into Ti3C2Tx MXene nanosheets effectively prevents the aggregation of Ti3C2Tx MXene flakes, resulting in improvement of the interlayer spacing to 1.578 nm and a threefold expansion of the specific surface area. Furthermore, the N, S-CDs contribute to increase the effective active surface area of the Ti3C2Tx MXene electrode, facilitating accelerated the electron transfer rates and providing additional active sites. On this basis, a galvanic sensor for dopamine (DA) detection was attained through loading N, S-CDs/Ti3C2Tx on glassy carbon electrodes. The optimized sensor achieved a linear detection range of 1 μM–1000 μM for DA, with a detection limit of 0.91 μM (S/N = 3). This work presents a promising approach for the utilization of chemically stable Ti3C2Tx MXene and MXene-based sensors, offering a new avenue for quantitative detection of DA that holds potential for application in real sample analysis.

Influence of the working surface roughness of the pulsed X-ray radiation galvanic sensor on its performance

A new design of a galvanic sensor of pulsed X-ray radiation is proposed, which is a flat electric capacitor with a window in one metal lining and a solid dielectric made of a single-crystal sapphire with a thickness of 200-300 μm inside. The influence of the surface roughness of the sapphire in the window area on the galvanic linear sensor of X-ray radiation has been established. Tests have shown that, with ultra-smooth polishing of the sapphire plate working surface in the window area to a roughness of Rq≤ 0.2 nm, it is possible to provide the galvanic linear detection of X-rays with an energy in the range of 0.1-1 keV and power density of 1-2 MW· cm-2 with a sensor response time of about 8 ns. Sensors of this type can be used in studies of inertial nuclear fusion processes. Keywords: X-ray radiation, galvanic sensor, sapphire, dielectric, flat capacitor.

Влияние состояния рабочей поверхности гальванического датчика импульсного рентгеновского излучения на его быстродействие

A new design of a galvanic sensor of pulsed X-ray radiation is proposed, which is a flat electric capacitor with a window in one metal lining and a solid dielectric made of the single crystal sapphire with a thickness of 200-300 µm inside. The influence of the surface roughness of the sapphire in the window area on the galvanic linear sensor of X-ray radiation has been established. Tests have shown that with ultra-smooth polishing of the sapphire plate working surface in the window area to a roughness of Rq≤ 0.2 nm, it is possible to provide the galvanic linear detection of X-rays with an energy in the range of 0.1-1 keV and a power density of 1-2 MW•cm-2 with a sensor response time of about 8 ns. Sensors of this type can be used in studies of inertial nuclear fusion processes

Self-Powered Galvanic Vibration Sensor.

The development of the IoT demands small, durable, remote sensing systems that have energy harvesters and storage. Various energy harvesters are developed, including piezoelectric, triboelectric, electromagnetic, and reverse-electrowetting-on-dielectric. However, integrating energy storage and sensing functionality receives little attention. This paper presents an electrochemical vibration sensor with a galvanic cell (Zn-Cu cell) as energy storage and a vibration transducer. The frequency response, scale factor, long-term response, impedance study, and discharge characteristics are given. This study proved the possibility of integrating energy storage and vibration sensing functionality with promising performance. The performance of the sensor halved within 74 min. The longevity of the sensor is short due to the spontaneous reactions and ions drained. The sensitivity can be restored after refilling the electrolyte. The sensor could be rechargeable by changing to a reversible electrochemical system such as a lead–acid cell in the future.

Relation between resistivity of concrete and corrosion rate of reinforcing bars caused by galvanic cells in the presence of chloride

The article presents the experimental study and theoretical analysis of the relationship between the resistivity of the concrete (ρ) and the reinforcement corrosion rate. The corrosion process was simulated using a galvanic sensor. The distance between the galvanic sensor plates and the sizes of the plates are selected in such a way as to simulate the functioning of microcells in the case of corrosion in the presence of chlorides. Tests carried out on bimetallic galvanic sensor embedded in mortar have corroborated a direct proportionality between the rate of corrosion and resistivity of concrete. The role of ohmic resistance in the corrosion process have been estimated by comparing model calculations and experimental results. The hypothesis of ohmic control the corrosion process in case of microcells was rule out. It was suggested that the process of corrosion is governed by the fraction of metallic surface wetted by porous liquid. A form of the equation for the current in a galvanic cell is proposed, taking into account the above model representations. The proposed approach can be used to simulate the corrosion process of reinforcement in concrete and to assess the effect of the saturation of concrete with moisture on the corrosion rate.

Galvanic Sensor for Detecting Corrosion during Acid Cleaning of Magnetite in Steam Boilers

A simple galvanic sensor was developed to determine the onset of iron corrosion under conditions similar to those used for removing the iron oxide (magnetite) layer from steam boilers with a hy-drochloric acid solution. Since the potentials of magnetite and iron are different, the initiation of the dissolution of the magnetite layer without corroding the base metal can be determined by moni-toring the potential of a sensor made of magnetite layers of different thicknesses that can be placed directly on the iron surface. Moreover, the time at which the addition of corrosion inhibitors is required to protect the base metal can be specified using this sensor. It has been shown that the time required for the iron base metal to start was dependent on the magnetite layer thickness in the sensor. With this sensor, the onset of the steel corrosion during the cleaning can be detected in re-al-time which makes the oxide removal process less harmful to the base metal.

Toward more realistic time of wetness measurement by means of surface relative humidity

Temperature difference between metallic surfaces and surrounding bulk air caused by sun heating and nocturnal radiation cooling challenges the accuracy of the time of wetness (TOW) determined from meteorological data. In this paper, the importance of measuring surface relative humidity (SRH) in preference to air relative humidity (RH) for determination of TOW and corrosivity is demonstrated. The TOW established from SRH data was from 33 to 40 % higher than that based on air RH data obtained during outdoor monitoring for a year, depending on the surface colour. Measurements with a galvanic sensor ascertained the correctness of the new procedure.

Corrosion Rate Estimation Based on Sensor Monitoring: Field Test Validation in Transmission Towers

A quantitative evaluation of corrosion rate was conducted by analyzing the data obtained from monitoring with galvanic sensors. Using humidity data, a new methodology was established to extract out...

Implementation of Nondestructive Testing of Massive Products in Measuring the Diffusivity of Solvents

Consideration is given to the problem of determination of the range of variation of the regime parameters of the process of measuring the diffusivity of solvents in massive products manufactured from capillary-porous materials with the aim of improving the efficiency and accuracy of the employed nondestructive-testing method. The order of implementation of measurement operations of the developed method is determined as a result of the performed investigations. The accuracy in determining the sought diffusivity is improved due to the concentration maximum of the solvent falling within the rational range of the static characteristics of a galvanic sensor used to monitor the local concentration of solvents. Reduction in the expenditure of time and funds is ensured by eliminating the need for individual calibration of the measure of concentration of solvents of the analyzed materials in a solid phase for each new system ″capillary-porous material–solvent,″ and also for numerous trial experiments with different volumes of a pulsed-action dose to improve the accuracy of the method.

Experimental Study on Rebar Corrosion Using the Galvanic Sensor Combined with the Electronic Resistance Technique.

In this paper, a new kind of carbon steel (CS) and stainless steel (SS) galvanic sensor system was developed for the study of rebar corrosion in different pore solution conditions. Through the special design of the CS and SS electronic coupons, the electronic resistance (ER) method and zero resistance ammeter (ZRA) technique were used simultaneously for the measurement of both the galvanic current and the corrosion depth. The corrosion processes in different solution conditions were also studied by linear polarization resistance (LPR) and the measurements of polarization curves. The test result shows that the galvanic current noise can provide detailed information of the corrosion processes. When localized corrosion occurs, the corrosion rate measured by the ER method is lower than the real corrosion rate. However, the value measured by the LPR method is higher than the real corrosion rate. The galvanic current and the corrosion current measured by the LPR method shows linear correlation in chloride-containing saturated Ca(OH)2 solution. The relationship between the corrosion current differences measured by the CS electronic coupons and the galvanic current between the CS and SS electronic coupons can also be used to evaluate the localized corrosion in reinforced concrete.

Experimental Investigation on the Corrosivity of Atmosphere through the Atmospheric Corrosion Monitoring (ACM) Sensors

Atmospheric corrosion is an essential problem to industrial and infrastructure engineering. The abundant concerned of the problem is the lifetime service of metal structure and equipment which result in the safety operation and economic loss. Atmospheric corrosion is a very complicated process that causes deterioration of metallic materials by chemical or electrochemical reaction between the metal and its environment. The corrosion parameters like relative humidity, time of wetness, and numerous pollutant substances which involve species deposited from atmosphere and species from the metal resulting from corrosion itself, affect to the atmospheric corrosion. A common method for atmospheric corrosion investigation is the long-term exposure test under natural environment, but this method requires time-consuming and high-cost expanse. To investigate the corrosivity of atmosphere, in this research, several chemical species such as NaCl, KCl, Na2SO4, NaNO3, KNO3, MgCl2.6H2O, and Mg(NO3)2.6H2O were used as artificial rainfall solution with the variation of concentration. Four types of ACM sensors which consist of Fe-Ag, Zn-Ag, Al-Ag, and Cu-Ag galvanic couple were used to define the correlation between sensor output and Corrosion Rate (CR), which affected by the chemical concentration of individual and mixed solutions. The 1 mm thick of low-carbon steel sheet specimens, with the size of 70 × 150 mm, were exposed to the artificial rainfall test. The CRs were calculated by measuring weight loss after removing corrosion products, or rust layer, by immersing the samples into Hydrochloric Acid (HCl) solution ( ISO/DIS 8403.3). In water, the molecules of the species are separated into cation and anion. The results reveal that the corrosivity of the cation is negligible compared to the anion. In term of the concentration, the SO4 2- anion is more corrosive than Cl- and NO3 - anion respectively. For a low chemical concentration, the CRs affected by each ion are small and similar to the CR of Deionize-water. This is the result of the spontaneously formed of the oxide film which provides some degree of protection, and the breakdown of the film is usually required higher aggressivity of the electrolyte. For further increasing the molar concentration, the CR raises up to reach a steady state. The signal output of Fe-Ag and Zn-Ag couple give a good relation for determining the corrosion rate in both individual and mixed solutions. Al-Ag couple, however, is unable to forecast the CR in the unknown pollution species, especially the mixed solution, because it is more sensitive with Cl- and NO3 - ions and less so with SO4 2- ions. Nonetheless, Al-Ag galvanic sensor offers a great advantage to predict the chemical species in the environment. For instance, if the CR is high, and the Al-Ag sensor output is low, the SO4 2- ions is assumed as the major contain in the solution or the environment. The lifetime service of Fe-Ag galvanic sensor is much lower than those of Zn-Ag, Al-Ag, and Cu-Ag, respectively. The results of the research indicate that the ACM sensors are capable of estimating corrosivity of the atmosphere; the research methods discussed in this paper proves that the CRs are dependent on the atmospheric composition and can be forecasted through ACM sensors.

Oxygen Optical Sensing in Gas and Liquids with Nanostructured ZnO Thin Films Based on Exciton Emission Detection

Transparent nanocolumnar porous ZnO thin films have been prepared by plasma-enhanced chemical vapor deposition. By controlling the H2/O2 ratio in the plasma gas, the deposition conditions were optimized to obtain an intense exciton emission at around 381 nm and virtually no luminescence in the visible region associated with electronic states in the gap. The intensity of the exciton band varied significantly and reversibly with the partial pressure of oxygen in the environment. This behavior and its variations with temperature and water vapor sustain the use of these thin films as photonic sensors of oxygen. Further experiments in liquid water show that fluorescence intensity also varies with the amount of dissolved oxygen even for concentrations lower than 0.02 mg/L where commercial oxygen galvanic sensors show limited sensitivity. These results and the use of ZnO as photonic sensor of oxygen are discussed by assuming a classical mechanism involving the photoactivated adsorption of oxygen when this oxide is irradiated with UV light during its fluorescence interrogation.

Setup of galvanic sensors for the monitoring of gilded bronzes.

Traditional electrochemical techniques, such as linear polarization resistance (Rp), and electrochemical impedance spectroscopy (EIS), cannot be applied to gilded bronzes, as it may not be possible to interpret the results obtained due to the bimetallic nature of the studied material. The measurement of the macrocouple current generated by the gold/bronze galvanic couple can be used as an indicator of degradation processes. Nevertheless, this measurement cannot be performed directly on the original artifacts due to the systematic presence of short-circuits between the two metals. In the present work the use of galvanic sensors is proposed as a possible solution for the monitoring of gilded bronze artefacts. The sensors have been designed to simulate real gilded bronze surfaces in terms of composition and stratigraphy and have proved to be a reliable diagnostic tool for the in situ monitoring of the rates of deterioration of gilded bronze surfaces and to test new conservation treatments. Their set-up and application is reported and their performances discussed.

Galvanic type sensor for determination of hydrogen sulfide in air

The polarization properties of different materials suitable as an auxiliary electrode to create a galvanic sensor of hydrogen sulfide. The results of the research developed a two-electrode galvanic sensor for hydrogen sulfide air monitoring on the basis of the gas diffusion manganese oxide catalytically active electrode as a working electrode and auxiliary electrode based on manganese oxide (IV) brand EDM-2. Metrological characteristics are determined and conducted laboratory tests of the developed sensors that are highly selective in the oxidation of hydrogen sulfide in the presence of other renewable gases such as CO, H2, carbonyl compounds. In the range of measured concentrations, resolution, speed, stability characteristics over time developed a sensor responds sensors that are part of a unified series of range of NTUU «KPI».

Smart Electrochemical Oxygen Sensor for Personal Protective Equipment

Self contained closed circuit rebreathers are life supporting breathing systems, where the exhaled gas is recycled by filtering CO2 and replacing metabolized O2. For the O2 injection control galvanic O2 sensors are used to measure the partial pressure of O2. A malfunction of the sensors can lead to a gas mixture beyond life supporting limits which is life threatening. Galvanic O2 sensors are often used in anaesthetic machines in hospitals. Also in this case, a malfunction of the sensors can cause severe injury to a person. It is obvious that such sensors are key elements in life supporting equipment and as such must be designed in order to achieve high functional safety. However these sensors are consuming sensors, and with that, will fail at a certain time. Failure modes include current limitation, non linearity, electrolyte evaporation or leakage, etc. Within this paper a novel low cost read out electronic circuit for galvanic O2 sensors is presented, which allows not only digital readout, digital temperature compensation, on board storage of calibration and manufacturing data, but also can be used for performing voltammetry cycles to test the Pb anode for exhaustion. First measurements are presented and compared to data from a Solartron SI 1287 impedance analyzer, which is state-of-the-art in electrochemical sensor characterization.

A galvanic sensor system for detecting the corrosion damage of the steel embedded in concrete structures: Laboratory tests to determine the cathodic protection and stray-current

In order to evaluate the possible application of a galvanic sensor for cathodic protection (CP) and straycurrent monitoring of steel embedded in concrete structures, the correlation of sensor current to protection abilities (protection potential/current) and stray-current was investigated by galvanostatic tests that simulated the CP and stray-current. The results revealed a good correlation between the sensor current and the protection abilities or stray-current in terms of the sign as well as magnitude. Thus, the galvanic sensor is proposed as an effective tool for the quantitative determination of the effectiveness of CP or of the interference effect of stray-current.

A Galvanic Sensor for Monitoring the Corrosion Condition of the Concrete Reinforcing Steel: Relationship Between the Galvanic and the Corrosion Currents

This work reports a study carried out on the design and performance of galvanic and polarization resistance sensors to be embedded in concrete systems for permanent monitoring of the corrosion condition of reinforcing steel, aiming to establish a correlation between the galvanic currents, Igal, and the corrosion currents, Icorr, estimated from the polarization resistance, Rp. Sensors have been tested in saturated Ca(OH)2 aqueous solutions, under a variety of conditions, simulating the most important parameters that can accelerate the corrosion of concrete reinforcing steel, such as carbonation, ingress of chloride ions, presence or absence of O2. For all the conditions, the influence of temperature (20 to 55 °C) has also been considered. From this study, it could be concluded that the galvanic currents are sensitive to the various parameters following a trend similar to that of the Rp values. A relationship between the galvanic and the corrosion current densities was obtained and the limiting values of the Igal, indicative of the state condition of the reinforcing steel for the designed sensor, were established.

Experimental study on seawater-pipeline internal corrosion monitoring system

In this paper, a Cu–Zn galvanic sensor is developed for the internal-pipeline corrosion on-line monitoring system, in which the internal-pipeline corrosion state is grasped based on monitoring the corrosion capability of the internal electrolyte environment. The galvanic corrosion behaviors of the sensor in a simulated seawater environment are investigated using a 50-m-long pipeline in the laboratory. After long-term test and analysis, the effective working period of the sensor is confirmed, and the influence caused by the oxidative film on the electrode working face is eliminated by an amendatory correlation coefficient relating to the electrolyte flow rate and the temperature. A complex and non-linear relationship, among the electric current of the galvanic sensor, flow rate and temperature of the electrolyte, the concentration of dissolved oxygen (DO) in pipeline, is acquired. Finally, back-propagation artificial neural network (BP-ANN) is employed to estimate the concentration of DO of the electrolyte according to the measured factors such as the electric current of the galvanic sensor, flow rate and temperature of the internal electrolyte. Based on the comparison between corrosion coupons test and monitoring system, it is affirmed that a more reasonable evaluation of internal-pipeline corrosion can be proposed in the monitoring system.

Comparison of Galvanic and Chemi‐Luminescent Sensors for Detecting Soil Air Oxygen in Flood‐Irrigated Pecans

Low soil O2 levels have been shown to limit growth in pecan [Carya illinoinensis (Wangenh.) K. Koch] seedlings and may limit yield in mature trees. To assess changes in the gas‐phase O2 concentration in a pecan orchard soil in response to flood irrigations throughout a growing season, two types of O2 sensor were field tested: a galvanic O2 sensor and a spectrometer‐coupled chemical sensor (FOXY sensor). Galvanic sensors, housed in diffusion chambers, were buried at four depths and a datalogger recorded continuous voltage output. The FOXY O2 sensor was utilized as part of a mobile O2 detection system to field analyze gas samples withdrawn periodically from buried diffusion chambers. The FOXY sensor was found to be unstable, however, and difficult to calibrate under conditions of changing temperature and humidity. Laboratory experiments simulating submersion of the galvanic sensor indicated that voltage outputs were comparable to the range observed in the field, but the absence of diurnal concentration fluctuations, typically found in soil measurements, provided a way to discriminate between normal and aberrant output. The responsiveness of the galvanic sensor and its capability to continuously gather hourly data makes it superior to methods dependent on manual sample collection. Galvanic sensors were adequately suited for long‐term in situ use in agricultural soil when housed in appropriate diffusion chambers. Higher costs, limited access to diffusion chambers during flood periods, and high variability associated with manually collected data make the FOXY mobile O2 detection system comparatively less optimal for use in agricultural settings.