Marine Electric Field Research Articles

Marine Electric Field Observations With Variable Dielectric Polarization

Marine Electric Field Observations With Variable Dielectric Polarization

Influence of Double-Pulse Electrodeposition Parameters on the Performance of Ag/AgCl Electrochemical Electrode for Marine Electric Field.

This paper describes a Ag/AgCl electrochemical electrode for marine electric field measurements, which was prepared by depositing silver chloride on a silver foil substrate using double-pulse electrodeposition. The impact of positive direction peak current density and deposition time on electrode performance in the preparation of Ag/AgCl electrodes through double-pulse electrodeposition was investigated. Scanning electron microscopy and voltammetry have been used to study the properties of the prepared electrodes. This work reveals the correlation between the electrochemical behavior of electrodes and the physical properties of their surfaces, especially specific surface area and porosity. The study verified the characteristics of Ag/AgCl marine electric field electrodes obtained with different pulse parameters by analyzing the potential stability and noise level of the electrode in salt water. The study's results have positive significance for improving the accuracy of marine electric field measurements.

Ag/Reduced Graphene Oxide/Carbon Fiber Composites as Electrodes for Highly Stable and Responsive Marine Electric Field Sensors

The increasing demand for maintenance-free, cost-effective, and high-stability flexible electrodes is highly anticipated for the research of marine electric-field sensors, and various carbon fibers (CFs) are considered the most suitable carbon-based electrode for the purpose. Nevertheless, the conventional fabrication of acidified or nitrogenized CF electrodes did not attract great attention for commercial application, which has limitations in the case of simultaneous cost-effectiveness and long-term stability. In this study, with homemade reduced graphene oxide (rGO) load, the prepared double carbon substrate Ag-rGO-CF composite electrodes have a honeycomb rGO conductive skeleton and the dispersed Ag nanoparticles via a facile hermetic oxidation process and hydrothermal method. The prepared Ag-rGO-CF composite electrode demonstrated an outstanding electrode performance, including low resistance, high electrochemical reaction rate, and stable potential with long-term stability and low cost. The electric double-layer (EDL) structure theory from the Gouy–Chapman–Stern model and double carbon substrate mechanism between CFs and rGO with the help of Ag were clarified, whose principle is to strengthen the adsorption force and electrostatic attraction of the electrode and to offset the residual charge while reducing the thickness of the electric double layer to achieve the purpose of potential balance. The Ag-rGO-CF composite electrode has presented long-term stability and high sensitivity, especially a wide application bandwidth. The Ag-rGO-CF composite electrode made in this study is a competitive candidate material as a flexible marine electrode field sensor.

Controllable 3D Flower-Like Ag-CF Electrodes as Flexible Marine Electric Field Sensors with High Stability

Construction of three-dimensional (3D) flower-like nanostructures with controlled morphologies has emerged as an attractive tool by scientists in the marine electric field sensor research field due to their peculiar structural features. Herein, novel 3D flower-like Ag-CF capacitive composite electrodes have been created by an eco-friendly water-bath strategy via AgNO3 as a sliver source and subsequently compounded with carbon fibers (CFs) pretreated by thermal oxidation. A series of electrode samples with various morphologies obtained by modulating different reaction times and temperatures bring about the dominant formation mechanism of these nanostructures and the influence behavior on the CF electrode in detail. Especially, the 3D flower-like Ag-CF electrode shows a large surface area acquired under the conditions of 80 °C and 15 min, which can provide more electroactive sites in electrochemical analysis and exhibit a maximum areal specific capacitance of 619.75 mF·cm-2 at a scanning speed of 10 mV·s-1. This is mainly due to the synergistic behavior of the unique 3D flower-like morphology and the large specific surface area of CFs. Furthermore, a cylinder-shaped Ag-CF sensor is designed, which delivers a superior potential difference of 33.08 μV, a potential difference drift of 18.62 μV/24 h for 30 days, and a self-noise of 0.92 nV/rt (Hz)@1 Hz. In this work, the intriguing synthesis strategy can be a promising facile approach to manufacture the controllable 3D flower-like Ag-CF electrode for electric field sensor applications.

A preparation method of Ag/AgCl marine electric field electrode with sodium bicarbonate as foaming agent

• Using NaHCO 3 as foaming agen, an electrode with high porosity was prepared. • A two-stage temperature control method for NaHCO 3 -Ag/AgCl electrode is proposed. • The performances of NaHCO 3 -Ag/AgCl electrode were significantly improved. Using sodium bicarbonate (NaHCO 3 ) as foaming agent, an Ag/AgCl marine electric field electrode with high porosity was prepared. A two-stage temperature control method suitable for NaHCO 3 -Ag/AgCl electrode is proposed, that is, the sample is heated to 200 ℃ for 1 ∼ 2 h, then heated to 400 ℃, and then naturally cooled to room temperature. On the one hand, the two-stage temperature control method ensures the complete decomposition of sodium bicarbonate, on the other hand, it ensures that AgCl will not melt, and the electrode is formed and has a certain strength. The performance of NaHCO 3 -Ag/AgCl electrode prepared by this method is significantly improved.

Effect of Oxygen-Containing Groups on Electrochemical and Marine Electric Field Response Properties of Carbon Fiber Electrode

Electric field response of carbon fiber sensor in sea water can be tuned up through modification of molecules or groups on its surface, which plays an important role in its high sensitivity and stability. Herein, high performance carbon fiber electrodes with different oxygen-containing functional groups were prepared by electrochemical oxidation coupled with electrochemical reduction, and their electric field response and electrochemical performances of electrodes are investigated. The results show that the electrochemical oxidation and reduction obviously alter the dominant contents of carbonyl, hydroxyl and carboxyl groups. Among them, carbonyl group has positive effects for paired carbon fiber electrode on its electrode potential stability and its distortion rate of electric field response curves, hydroxyl group makes the paired carbon fiber electrode more sensitive to weak electric field. Carboxyl group has negative effects on the electrode potential stability due to its high activity, but its larger specific capacitance and smaller charge transfer resistance are simultaneously obtained. The detailed relationship between the dominant oxygen-containing carbon fiber electrode and its electric field response is first reported systematically, and it will shed some light on the design of fast-stable and highly sensitive marine electric field electrodes.

Reducing the Noise of Motion of a Marine Electric Field Sensor

Reducing the Noise of Motion of a Marine Electric Field Sensor

Flexible composite Ag-AgNWs-CF as low noise marine electric field sensor

Carbon fibers (CF) have triggered extensive interest with the progress of multifarious marine electric field sensor devices owing largely to their high flexibility, good conductivity and exceptional chemical/thermal stability. Herein, flexible Ag/sliver nanowires (AgNWs)/CF (Ag-AgNWs-CF) electrodes with extremely tiny potential difference drift of 67.22 μV/24 h have been successfully fabricated by a facile alcohol-thermal method with a reaction temperature of 170℃ for 120 min. The conductive AgNWs was introduced to the CF as a coating material. The AgNWs with three-dimensional (3D) network and silver particles accounts for superior areal specific capacitance and low Tafel slope for the composite electrodes (CEs). Using such flexible Ag-AgNWs-CF as a marine electric field sensor, the excellent self-noise was obtained, which signifies prospective ability to respond to weak signals.

Electrochemical performance of a new all solid-state ultra-low noise electrospray electrode as a marine electric field sensor.

A new type of Ag/AgCl electrode as a marine electric field sensor is prepared using electrospray. The surface of the electrode is porous, and the particle size of AgCl is small and uniform with an average particle size of 1.43 µm, which accelerated the speed of the oxidation-reduction reactions. Therefore, the electrode with large specific surface area has high stability and low noise. The impedance, sensitivity, self-noise, and stability of the electrode are measured to study the electrochemical performance of the electrode. The impedance of the electrode is 7.9 Ω, and the electrode shows resistance characteristics, meaning that the electrode can well receive the weak ocean electric field signals with low signal distortion. The sensitivity experiment result shows that the electrode can well restore the sinusoidal electric field signal of 1Hz (10 mV). The voltage drift is less than 5 µV/100 h, the self-potential is between -51 and 56 µV, and the self-noise of the electrode is 2.48 nV @ 1Hz. The AgCl layer on the surface of the electrode is porous and thick, and the particle size of AgCl is small and uniform. This makes the electrode have excellent electrochemical performance. All the experimental results show that the electrode has ultra-low noise and excellent response to low frequency weak electric field signals. The electrode is of great significance to the exploitation of marine resources as the marine electric field sensor.

Ocean Electric Field Tests of Carbon Fiber Electrodes Prepared by Nitric Acid Oxidation

The concentrated nitric acid oxidation was chosen as the surface treatments on carbon fibers in this paper. Treated carbon fibers were subjected to subsequent processing and forming, the electrodes applied in marine electric field detection were prepared. The electrochemical properties that related to practical application in marine electric field detection such as potential stability, polarization and cyclic voltammetry performance, the electrochemical impedance and the self-noise were characterized, thus an electrochemical evaluation system was formed to optimize the oxidation technology. Combining with the TGA and FTIR, the physical properties of carbon fibers were characterized and some oxidation laws were induced. The results indicate that the carbon fiber electrode prepared by oxidation 4 hours at 110 ℃ has the best electrochemical performance for detection.

Ag-modified carbon fiber as a stable sensor

Carbon Fiber (CF) electrode has a wide range of applications as an electric field sensor. However, its use is limited because of its poor stability. In this paper, the CF was pretreated by thermal oxidation (400 °C, 1 h) to remove surface impurities, resulting in 2.3% mass reduction, which means the increase of effective specific surface area. XRD and EDS confirmed the nano-silver coating was chemically modified on the surface of CF by electroplating. Charging current density differences and Tafel slope showed 6.19 mF cm−2 and 77 mV dec−1, respectively, which implied outstanding electrochemical performance. As a sensor, the Ag-modified CF electrode-pair has small potential difference drift of 29 μV/24 h and excellent response property to low frequency electric field signal, along with lower AC impedance (1.42 Ω@1 Hz) and electrochemical self-noise (1.38 nV/rt (Hz)@1 Hz). The novel Ag-modified CF electrodes provided a potential choice for the design of high-sensitivity marine electric field sensor.

Modified carbon fiber electrodes with enhanced impedance performance for marine sensor

At present, the use of carbon fiber electrodes as marine sensors for marine signal exploration has received much attention. AC impedance is the crucial factor affecting the performance of sensor. Unfortunately, the AC impedance performance of carbon fiber electrodes has been underappreciated up to date. In order to fully understand the influencing factors of AC impedance, the comprehensive and systematic study was carried out in terms of reference electrode type, encapsulated shell of electrode, immersion depth of electrode, obstacles between electrodes, electrode position, initial voltage electrolyte concentration and electrolyte type. Through analog equivalent circuits, the solution impedance R1, charge transfer impedance R2 and diffusion impedance W1 were found to be 1.485, 0.313 and 1.158 Ω, respectively. The smallest impedance of silver-plated carbon fiber electrodes is only 3.49 Ω at 1 Hz. Combined with different influencing factors, we can know that the modified carbon fiber electrodes performance was mainly controlled by diffusion and transfer processes. This study would contribute to the design and application of the silver-plated carbon fiber electrodes as marine electric field sensor.

Development and characterization of high-stability all-solid-state porous electrodes for marine electric field sensors

Marine electromagnetic (EM) methods can be used for marine geophysical exploration. We proposed an all-solid-state porous Ag/AgCl electrode with high stability and a long service life as a marine electric field sensor with the ability to withstand deep sea high pressures while improving the accuracy of electric field measurements for long-period marine EM method engineering projects. Compared with a plate electrode, the all-solid-state porous electrode has excellent polarization resistance in seawater. To avoid the short service life of the sensor used in marine EM method engineering, the all-solid-state porous Ag/AgCl electrodes were manufactured by a ball-milling and sintering process, and the electrochemical channel of the electrodes was observed under a scanning electron microscope. A sensor casing based on the porous electrodes used in the deep sea environment was designed. An experimental system for evaluation and characterization was designed to measure the polarization resistance, sensitivity, noise, self-potential and drift of the proposed electrodes, which are important properties and will affect the accuracy of marine electric field measurements. The results show that the source resistance of the electrode is 2.13 Ω/cm2, the electrode noise level is 1.57 nV/rt(Hz), the self-potential of the proposed electrode pair is less than 35 μV, and the potential drift is less than 10 μV/day. After more than 180 days of use, the electrodes showed outstanding stable drift potentials of below 15 μV/day. The proposed all-solid-state porous electrodes can ensure the measurement accuracy of marine electric field signals and promote the exploration of marine resources.

Fabrication of Ag/AgCl electrode for detection of electric field in marine environment

Underwater Electric Potential (UEP) and Extra Low Frequency Electric field (ELFE) measurement is very important and essential for defence and civilian applications. UEP signature is produced by an underwater vessel by corrosion currents in the ship or submarine hull and also from propeller or other dissimilar metallic material in contact with the salt / sea water. The hull of the ship and the propulsion also produces a modulation of the corrosion currents, which is called the ELFE signature. The underwater electric field detection is very important to find the presence or proximity of alien, or enemy underwater targets and their positioning by non-acoustic methods, in the defence sector. The electric field in the marine environment is measured usually with sensor electrodes that are either carbon fibre or silver/silver chloride (Ag/AgCl) based. The typical sensor system uses six electrodes, mounted on three orthogonal axes. By measuring the potential the potential difference between each pair of electrode, the electric field magnitude and the direction of source can be determined.In this study, Ag/AgCl electrodes have been fabricated by two different methods, thermal and thermal-electrolytic for the purpose of detection of marine electric field. Ag/AgCl electrodes, being reversible electrochemical electrodes, are ideal for measurement of marine electric field. Ag/AgCl electrodes have excellent electrochemical characteristics, such as very high ion exchange reaction current and lack of polarization at a low current density. The fabricated electrodes have been subjected to anodization by two different methods at constant potential and constant current, to increase the concentration of chloride ions for achieving fast equilibrium with chloride ions in sea water. The anodization process at constant potential is found comparatively more suitable in the study as it reduces the electrochemical noise associated with the electrode, the results of which are discussed. The electric field has been simulated in a tank and the characteristics of the fabricated electrodes are studied.

Preparation and Properties of Carbon Nanotube-Ag/AgCl Electrode for Marine Electric Field Test

The carbon dioxide was used as the material to modify the Ag/AgCl marine electric field electrode, and a new type of marine electric field detecting electrode was designed and manufactured. The surface morphology observation, electrochemical performance, electrode self-noise and range stability time were tested. The result shows that the specific surface area of the Ag/AgCl electrode increases greatly after the addition of carbon nanotubes and the range stability time is shortened. The range is small and the exchange current density become larger. It shows good electrochemical performance. Howeve, its electrode self-noise is too large, which is not suitable as a marine electric field detecting electrode.

Electrochemical and Electric Field Response Properties of Highly Sensitive Electrodes Based on Carbon Fiber With Oxygen and Nitrogen Surface Groups

In this paper, a high-sensitive carbon fiber electrode enriched oxygen and nitrogen groups were prepared using a method combining oxidation and graft modification. The surface compositions were analyzed by means of Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The electrochemical results show that the modified carbon fibers have a better electric double layer performance and a lower capacitive impedance at the lower frequency. The offset potential of the electrode pairs is typically below 1 mV with a drift of less than $40~\mu \text{V}$ /day. Typical measured noise level is below 2 nV/rt (Hz) at 1 Hz. The modified carbon fiber electrode pairs exhibit a good response to the ac sine signal of amplitude 1 mV and frequency 1 mHz. The sensitivity is increased by 82% and 59%, respectively, in comparison with Ag/AgCl electrode pair. The possible mechanism of the electric field response is discussed by the model of the electric double layer. This carbon fiber electrodes could provide the potential candidate and the theoretical basis for the design of high-sensitivity marine electric field sensor.

Fabrication of novel Ag/AgCl electrode pair on the template of carbon foam as marine electric field sensor and its electrochemical performances

A kind of novel Ag/AgCl electrode pair on the template of carbon foam is fabricated as electric field sensor for marine electric field test. The microstructure of AgCl layer and BET surface area are characterized and the electrochemical performances are tested, such as polarization resistance, stability of potential difference, signal response of electric field, and electrochemical self-noise. The results show the average diameter of AgCl grain is in the scale of 26 nm and the BET surface area of electrode is 1.40 m2/g. The polarization resistance is 21.17 Ω, meaning that the electrode has good anti-polarization property. The electrode pair has little potential difference drift (less than 0.02 mV/24 h) and excellent response property to low frequency electric field signal (1 mHz). Its electrochemical self-noise is about 1.60 $$ \mathrm{nV}/\sqrt{\mathrm{Hz}} $$ @ 1 Hz. All these results indicate that this electrode pair can offer a promising electric field sensor for marine oil-gas resources prospection.

Simulation Research of Direct Torque Control for Marine Permanent Magnet Synchronous Motor

The permanent magnet synchronous motors are more and more popular in marine electric propulsion field. Aiming to solve the problem of large torque ripple in traditional DTC system, this paper introduces the principle of space vector modulation and builds the electric propulsion system models based on direct torque control for permanent magnet synchronous motor in Simulink. Typical working condition experiments are designed to contrast the performances between traditional DTC and SVM-DTC. Simulation result proves that SVM-DTC can reduce ripples of both electromagnetic torque and stator flux effectively with the same dynamic response character as traditional DTC system.

Development and evaluation of an ultralow-noise sensor system for marine electric field measurements

In this paper, we describe the development of an ultralow-noise sensor system consisting of non-polarizable Ag/AgCl electrodes and a chopper amplifier for detecting marine electric field signals. Ag/AgCl electrodes were fabricated using a constant current density to clean the electrode cores and were then electrolytically chloridized by applying a constant potential. An amplifier was developed using the chopper stabilization (CHS) technique to reduce the 1/ƒ noise and the initial offset. To achieve ultralow-noise performance, we took advantage of newly developed materials in the fabrication of Ag/AgCl electrodes and proposed a residual ripple reduction loop to decrease the modulated noise and the offset of the chopper amplifier. Typical measured noise levels are 0.6nV/rt(Hz) for the Ag/AgCl electrodes and 0.55nV/rt(Hz) for the chopper amplifier at 1Hz. The source resistance between pairs of Ag/AgCl electrodes is approximately 5Ω. The offset potential is typically ±0.1mV with a drift of less than 5μV/day. The chopper amplifier had an offset voltage below 0.2μV with a −3dB bandwidth from 0.01Hz to 40Hz and a variable gain from 80dB to 120dB to achieve a large dynamic range. This sensor system is used for marine electric field measurements with high precision.