Constant Potential Difference Research Articles

Water molecules mute the dependence of the double-layer potential profile on ionic strength.

We present the results of molecular dynamics simulations of a nanoscale electrochemical cell. The simulations include an aqueous electrolyte solution with varying ionic strength (i.e., concentrations ranging from 0-4 M) between a pair of metallic electrodes held at constant potential difference. We analyze these simulations by computing the electrostatic potential profile of the electric double-layer region and find it to be nearly independent of ionic concentration, in stark contrast to the predictions of standard continuum-based theories. We attribute this lack of concentration dependence to the molecular influences of water molecules at the electrode-solution interface. These influences include the molecular manifestation of water's dielectric response, which tends to drown out the comparatively weak screening requirement of the ions. To support our analysis, we decompose water's interfacial response into three primary contributions: molecular layering, intrinsic (zero-field) orientational polarization, and the dipolar dielectric response.

Mung Seeds Under Constant Low Potential Difference During Post-Germination When Sprout Length Grows

Low potential difference 𝟎.𝟎𝑽𝒐𝒍𝒕 𝟏.𝟓𝑽𝒐𝒍𝒕, 𝟑.𝟎𝑽𝒐𝒍𝒕, 𝟒.𝟓𝑽𝒐𝒍𝒕, and 𝟔.𝟎𝑽𝒐𝒍𝒕 are applied during the growth of sprout length after germination and post-germination of mung seeds in open-air conditions. The sprout length decreases with an increase in potential difference and graphs show non-linear variations. Thus, this potential difference produces a negative impact on the sprout length elongation of seeds. The decrease in the sprout length may be due to lesser diffusion through the cell wall or due to the weakening of the activity of the other cell components leading to a slower rate of cell division. This may have an impact on the process of preservation of seeds.

A Multifunctional Asymmetric Fabric for Sustained Electricity Generation from Multiple Sources and Simultaneous Solar Steam Generation.

Harvesting electrical energy from water and moisture has emerged as a novel ecofriendly energy conversion technology. Herein, a multifunctional asymmetric polyaniline/carbon nanotubes/poly(vinyl alcohol) (APCP) that can produce electric energy from both saline water and moisture and generate fresh water simultaneously is developed. The constructed APCP possesses a negatively charged porous structure that allows continuous generation of protons and ion diffusion through the material, and a hydrophilicity-hydrophobic interface which results in a constant potential difference and sustainable output. A single APCP can maintain stable output for over 130h and preserve a high voltage of 0.61V, current of 81µA, and power density of 82.4 µW cm-3 with 0.15 cm3 unit size in the water-induced electricity generation process. When harvesting moisture energy, the APCP creates dry-wet asymmetries and triggers the spontaneous development of electrical double layer with a current density of 1.25mA cm-3 , sufficient to power small electronics. A device consisting of four APCP can generate stable electricity of 3.35V and produce clean water with an evaporation rate of 2.06kg m-2 h-1 simultaneously. This work provides insights into the fabrication of multifunctional fabrics for multisource energy harvesting and simultaneous solar steam generation.

Insights into the electrolyte changes during the electro-deoxidation of niobium oxide cathode

In the last two decades, tremendous work has been investigating the electro-reduction of metal oxide cathodes in what is known as the FFC-Cambridge process. This paper explores the electrolyte changes that occur during the electro-deoxidation of metal oxides. The investigation takes niobium oxide as a case study and subjects a Nb2O5 cathode to a constant potential difference of 2.5V between the cathode and carbon anode during the in-situ recording of the cyclic voltammetry of the electrolyte on a glassy carbon electrode. The deoxidation of the cathode supplies oxygen ions that increase the oxygen content of the electrolyte, even in the very early stage of the process. We could detect many non-Faradic processes and increase the electrolyte electronic and ionic conductivity a few hours after starting the electro-deoxidation due to the reduction of CaO. It was also possible to detect partial dissolution of the cathode in the electrolyte and back deposition of Nb on the current collector. The dissolved niobium ions can combine with the oxide ion in the melt to form a negatively charged complex which can be discharged on the anode to form a thick ceramic layer. The electrolyte changes were also investigated using electrochemical impedance spectroscopy.

Pulsed Electrophoretic Deposition of Nanocarbons and Their Optical, Thermal, and Electrical Applications

Electrophoretic deposition (EPD) is a well-established, scalable industrial manufacturing technology for depositing a wide variety of coatings across a broad range of substrates, geometries and sizes. Conventional electrophoretic deposition (EPD) is the migration of small, suspended particles in a liquid driven by a constant electrical potential difference. As a subset of electrodeposition, EPD has been used to deposit layers on various conducting and semiconducting surfaces from polar, aqueous, and non-polar suspensions. On the other hand, state of the art developments within nanoscience and nanotechnology has opened a new vista for the field of nanocarbon materials. Nanostructured carbon materials, such as carbon nanotubes, graphene, carbon quantum dots, etc., exhibit excellent physical and chemical properties, and have been gaining attention in both fundamental research and technological applications.In this invited presentation, Faraday Technology will discuss an innovative electrophoretic deposition (EPD) manufacturing process, based on the use of pulsed electric fields, for controlled, reproducible, scalable deposition of a wide variety of nanocarbon based coatings across a broad range of substrates, geometries and sizes (Figure 1). The effects of waveforms, electrolytes, substrates, etc. on the formation of robust and uniform coating will be discussed in this talk. The optical and electrical properties, and environmental survivability of nanocarbon coatings will be demonstrated via a variety of testing or characterizations. Faraday will also introduce their applications ranging from low-reflective coatings, solar absorber, high emissivity coatings, to thin film electrodes for energy storage.In summary, a scalable EPD manufacturing process for fabricating nanocarbon based coatings have been developed at Faraday for various applications ranging from optical, thermal, to electrical fields. Acknowledgements: The financial support from NASA SBIR program through contracts No. 80NNSC18P2062 & 80NSSC19C0177, DOD DMEA STTR program through grant No. HQ0727-21-P-0029, DARPA SBIR program through grant No. W31P4Q-22-C-0014, DOD MDA STTR program through grant No. HQ0147-19-C-7065, DOD Air Force SBIR program through grant No. FA9453-19-P-0573, NASA SBIR program through contracts No. 80NSSC20C0287 are acknowledged. Figure 1

Phase-field model of ion transport and intercalation in lithium-ion battery

The unified 3D phase-field model for description of the lithium-ion cell as a whole is developed. The model takes into account the realistic distribution of particles in electrodes, percolative transport of ions, and difference in size of solute and solvent molecules. The model is based on the Cahn–Hilliard equation with spatially dependent interaction and dynamic parameters. The spatial dependences are determined through the order parameter field describing distribution of matter in nanostructured electrodes. The process of charging/discharging of a battery is simulated for constant chemical potential difference across the electrode/electrolyte interface, which naturally determines the electrochemical reaction. The proposed model is applied to study charging and discharging process in 3D lithium-ion cell with nanostructured electrodes. The current density over the cell depends linearly on the chemical potential difference. The obtained results indicate non-diffusive propagation of the concentration front during charging/discharging, nonuniform intercalation flux over the surface of electrode particles and violation of the equipartition of electric current density over the electrode surface. All these facts are not taken into account by most commonly used models.

The temperature state of a plane dielectric layer at constant voltage and fixed temperature of one of the surfaces of this layer

The paper formulates the nonlinear problem of steady‐state heat conduction at the constant electric potential difference on the surfaces of a plane dielectric layer with the temperature‐dependent heat conduction coefficient and electrical resistivity. A fixed temperature value is set on one of the layer surfaces, and the convective heat exchange with the ambient medium occurs on the opposite surface. The formulation of the problem is transformed to integral ratios, which allows the calculation of the temperature distribution over the layer thickness, governed by the monotonic and nonmonotonic functions. The quantitative assay of the temperature state of a layer of a polymer dielectric made of amorphous polycarbonate is given as an example and the analysis of nonuniformity of the absolute value of electric field intensity over the thickness of this layer.

Preliminary Study on The Effect of Time on Hydrogen Production from Electrolysis of The Seawater

To know the effect of electrode type on the production of hydrogen gas through the electrolysis of sea water, this research was conducted. At a constant potential difference of 12 Volt, the electrolysis process is carried out by alternately using graphite and copper as electrodes. The electrolysis process time was varied from 10 to 55 minutes with increments every 5 minutes for each electrode. The results showed that the use of copper in the electrolysis of sea water produced a maximum of 82 ml of hydrogen gas better than 76 ml of graphite with a total processing time of 5 hours and 25 minutes. The results also show that the production of hydrogen gas in graphite has the largest hydrogen production rate in the first 10 minutes, but continues to decline, while the copper electrode has the largest hydrogen production rate at 220 minutes and decreases when the electrolysis process reaches 270 minutes when the electric current experiences drop. This can be understood due to the corrosion of the electrode by chlorine, which causes the electrode life to be limited. Meanwhile, the water displacement measurement method is used to determine the volume of hydrogen gas produced from the electrolysis of seawater in this study.

Температурное состояние слоя электроизоляции сверхпроводящего кабеля постоянного тока при двустороннем охлаждении

For the reliable operation of a high-voltage DC cable with high-temperature superconducting current-carrying conductors with a sufficiently high difference in electrical potentials, it is necessary to maintain a fixed temperature state not only of the conductors but also of other cable elements, including the electrical insulation layer. In this layer, despite the high electrical resistivity of its material, which can be polymer dielectrics, Joule heat is released. The purpose of this study was to build a mathematical model that describes the temperature state of an electrical insulation layer made in the form of a long hollow circular cylinder, on the surfaces of which a constant potential difference of the electric field is set. Within the study, we consider an alternative design of a cable with central and external annular channels for cooling liquid nitrogen. Using a mathematical model, we obtained integral relations that connect the parameters of the temperature state of this layer, the conditions of heat transfer on its surfaces, and the temperature-dependent coefficient of thermal conductivity and electrical resistivity of an electrical insulating material with a given difference in electrical potentials. A quantitative analysis of integral relations is carried out as applied to the layer of electrical insulation of the superconducting cable. The results of the analysis make it possible to assess the possibilities of using specific electrical insulating materials in cooled high-voltage DC cables under design, including superconducting cables cooled with liquid nitrogen

Experimental Investigation on The Effect of Electrical Current Flow on The Coefficient of Friction between Two Dry Rubbing Surfaces.(Dept.M)

The main object of this paper is to determine experimentally the effect of electrical current flow on the coefficient of friction between two dry rubbing surfaces. The tests were performed utilizing a pin-disc machine (Tribometer) with a pin having a diameter of 6 mm and 200 mm diameter disc. The current was be varied from 0 to 8 amperes with a constant potential difference of 12 volts. The coefficient of friction was calculated, at different loading and electrical current, based on the measured friction force. The measurement was carried out via strain gauge and FFT analyzer. A parametric study was carried out to highlight the effect of material, velocity and load on the coefficient of friction with the electrical current flow. Three sets of materials were used; steel-steel, copper-copper and aluminum-aluminum. Sliding velocity was increased up to 700 r.p.m., while the load changed from 1 to 8 Newton. As a result of this investigation, it was found that the coefficient of friction is depending strongly on the electrical current flow at all operating conditions.

Effect of electric field on push-out strength of cemented steel pipes

<abstract> Cement-steel interfacial strength is an important measure for estimating the robustness and hydraulic sealing ability of wells. In this paper, laboratory experiments were performed in which small steel pipes (10 mm in diameter) were cemented in place within a Portland cement slurry under application of constant electrical potential difference between the pipes. The objective was to investigate whether there might be an observable difference between push-out strengths obtained with the pipes of different polarity (anode vs. cathode vs. reference nonpolarized pipe). The duration of the potential application and the magnitude of the potential difference were varied between the tests. The experiments demonstrated that at the higher potential difference (4 V), the duration of potential application had a noticeable effect on interfacial bonding. Application of 4 V for 24 h resulted in loss of bonding at cement-cathode interface, which could be attributed to massive water transportation to the cathode region by small radii cations. At the lower applied potential difference (1 V), there is an improvement in push-out strength at anode at short duration of potential application. This could be due to pore filling by precipitation of expansive minerals in pores and cement particles migration toward anode. The effect of potential on push-out strength in a hardened cement suggests that low potential difference applied for a short period of time might improve cement-steel interfacial strength. </abstract>

Electro-thermo-mechanical stress analysis of smart sandwich cylindrical shell

In this paper, stress analysis of a multi-walled hollow cylinder made from a functionally graded material (POLYMER) sandwiched between two piezoelectric layers is investigated. This system is subjected to internal and external pressure, a distributed temperature field due to steady state heat conduction with convective boundary condition, and a constant potential difference imposed on piezoelectric layers between its inner and outer surfaces or combination of these loadings. All mechanical and thermal properties except for the Poisson's ratio of Polymer layer are assumed to be power functions of the radial position. Using equilibrium equations, stress-strain relations and electromechanical coupling of piezoelectric layer, the constitutive differential equation in term of radial displacement is obtained. Considering electro-mechanical boundary conditions, this differential equation is analytically solved. The electro-thermo-mechanical stresses, electric potential and radial displacement distributions in three layers are obtained.

A Bidirectional DC–DC Converter With High Voltage Conversion Ratio and Zero Ripple Current for Battery Energy Storage System

In this article, a novel bidirectional dc-dc converter (BDC) consisting of an active switched-inductor (A-SL) cell, a zero current ripple cell and an auxiliary capacitor cell is proposed for the battery energy storage system. The proposed BDC integrates with the advantages of high voltage conversion ratio, low power switch voltage stresses, zero ripple current on the low voltage side (LVS), and constant potential difference between the grounds of LVS and high voltage side. Thanks to the use of synchronous rectification technology, the efficiency of the proposed BDC is increased. The operating principles, the characteristics analysis and the parameter design of the proposed BDC are given. In addition, to show the merits of the proposed BDC, a comparison study involves the proposed converter and other BDCs is demonstrated. Finally, some experimental results obtained using a 1000 W prototype are presented to valid the effectiveness of the proposed BDC. 96.43% and 96.67% maximum conversion efficiencies can be achieved in the step-up and step-down modes, respectively.

A Comparative Study of MPPT and PWM Solar Charge Controllers and their Integrated System

The most popular renewable energy system today which is getting implemented is the solar energy system. The reason is that solar energy can be implemented at an individual house or industry level fulfilling the small energy requirements and also at large scale fulfilling the commercial requirements in megawatts. In most cases, solar energy is used to store the energy in battery backup along with the energy utilization to the load. The energy storage needs a variation in the flow of current as required and a constant potential difference between the two terminals. But the solar panel generates a current flow as well as the potential difference purely depending on the sunlight. To convert the solar energy generation to the required format different types of charge controllers used. There are various methods of charge controllers which will convert the solar energy into the format that is required to the storage devices. Among them, the most popular charge controllers are PWM based as well as MPPT technology based. This paper highlights the benefits of PWM and MPPT technology. The paper also highlights the differences between the two types and gives a conceptual model of integration of both MPPT as well as the PWM solar charge controllers. The conceptual model shows how to balance the storage backup as well as the load so as to utilize the complete solar energy thus produced. The merits and demerits of the integrated system are also discussed.

A New SEPIC-Based Step-Up DC-DC Converter With Wide Conversion Ratio for Fuel Cell Vehicles: Analysis and Design

In this article, a new single-ended primary-inductor converter (SEPIC)-based step-up dc-dc converter which integrates discontinuous-current quasi-Z-source (qZS) and switched-capacitor networks is proposed. The proposed converter has a low input current ripple, wide voltage gain range, low voltage stress on the semiconductor devices, and a constant potential difference between the grounds of its input and output ports. These features make the proposed converter an excellent interface between the fuel cell and the dc-link bus inside the electric vehicle. The analysis of the proposed converter for steady-state operations in continuous conduction mode and discontinuous conduction mode are given. Finally, a 3-kW/800-V scaled-down prototype was built using a gallium nitride power switch and silicon carbide diodes to validate the feasibility of the proposed converter and its theoretical analysis.

A New Hybrid Structure of a Bidirectional DC-DC Converter With High Conversion Ratios for Electric Vehicles

In this paper, a new bidirectional dc-dc converter that is based on the quadratic and switched-capacitor structures is proposed for Electric Vehicle applications. The proposed converter has high voltage conversion ratios, low voltage stress on the semiconductor devices, constant potential difference between the grounds of its low voltage and high voltage ports, and continuous current at its low voltage port. Synchronous rectification is utilized to enhance the efficiency of the converter. In addition, an extended version of the proposed converter is discussed in this paper. Finally, the experimental results obtained from a 2-kW/800-V scaled-down prototype validate the feasibility of the proposed topology and the correctness of its theoretical analysis.

Electrification mechanism of corona charged organic electrets

This paper developed a comprehensive model which can fully explain the surface potential behavior of corona charged organic dielectric electrets. Compared to previous studies, both sides of the corona charged films were measured while they were grounded or free-standing. All films showed surface potential with the same magnitude, but opposite polarity on each side while they were measured with the other side grounded. This indicates that in contrast to the previous incomplete model, believing only the corona side containing injected charges, both sides should contain injected charges with the same magnitude but opposite polarity. This dipolar charge distribution is relatively stable and leads to a constant and controllable potential difference ΔVf between each side of the free-standing measured film. Interestingly, free-standing surface potential varied dramatically for films charged with the same parameters. This large variation is caused by the minor number of free charges, which is only ~0.1% of the corona induced dipolar charges. Therefore, in this model, dipolar charges control the surface potential difference between each side and the minor charges control the absolute value on a certain side. By manipulating them together, the surface potential on both sides can be precisely controlled.

Reduction of Carbon Dioxide to Carbon Nanostructures in Molten Salt: The Effect of Electrolyte Composition

The effect of the composition of the molten salt electrolyte on the morphology of carbon produced via reduction of carbon dioxide has been studied. Three different molten salt compositions (CaCl2-CaO-Na2Co3, CaCl2-Na2Co3, and CaCl2-CaO) were applied at constant potential difference of 3.0 V and carbon dioxide flow of ~ 1 mL/s for 120 min, and the current was recorded at 10-s intervals. The powder products obtained from the solidified electrolyte and cathode surface were then characterized by scanning electron microscopy and energy-dispersive spectroscopy. Rod-like structures with diameter of 120 nm formed on the surface of the steel cathode after electrolysis using CaCl2-0.5% M CaO-2% M Na2CO3 or CaCl2-2% M Na2CO3.

Diffuse arc discharge with a hot cathode in a magnetic field as a plasma source of lead and silver mixture for the problem of spent nuclear fuel reprocessing

Conversion of a solid substance mixture into a low-energy (≈ 10 eV) plasma stream with stable parameters is a one of the important tasks for the developing nowadays method of plasma separation. The study of plasma stream characteristics of Pb and Ag mixture was carried out. The evaporation of the substances was realized using induction crucible heating. The discharge was initiated by an electron beam. A variation of the thermionic cathode (LaB6) temperature and the crucible heater power allowed us to control the parameters of the discharge. It was shown, that maintaining a constant potential difference in the cathode-anode gap, in spite of the substantial difference in the saturated vapor pressure of model substances, is possible due to control of the thermionic current from the cathode and constant voltage power supply parameters. Measurements of the spectral composition of plasma radiation made it possible to determine the discharge burning regimes in which ions of multiplicity 2 were absent. The obtained results indicate a possibility of using this type of discharge for testing the method of plasma separation of spent nuclear fuel.

Multifunctional polyaniline hybrid nanofiber with YVO4 (Er2%;Yb8%)

We synthesized electrospun nanofibers based on polyaniline (PAni) and orthovanadate from Yttrium co-doped with Erbium and Ytterbium [YVO4 (Er2%, Yb8%)]. We evaluated the association of the electrical and thermal properties of PAni with the upconversion (UC) effect due to the orthovanadate. We characterized the material by UV–Vis Spectroscopy, Fourier transform infrared (FTIR), Impedance Spectroscopy and Photoluminescence. Initially, we obtained polyaniline by emulsion polymerization in presence of surfactant, sodium dodecyl sulfate, yttrium orthovanadate and polyvinyl alcohol, resulting in a homogeneous dark green color solution. When we subjected the solution to a 14 kV constant electric potential difference applied between a 12 mm diameter needle (cathode) and a collecting plate (anode) 12 cm apart, the material deposited in the form of fibers. SEM results show that these fibers presented an average diameter of (89 ± 40) nm. On the other hand, when excited with radiation of wavelength λ = 980 nm (2.5 W) the material emitted radiation in the visible region with characteristic peaks at 525, 543 and 553 nm. The emission of intense green light is characteristic of UC effect. Due to photothermal characteristic of PAni the sample was heated, reaching temperatures close to 100 °C without suffering degradation. Measurements of photoluminescence showed that when exposed to HCl vapor, the material presented an increase of almost 100% in the intensity of light emitted in the UC effect, as well as a reduction of its electrical impedance from the order of GΩ to 900 KΩ, in a reversible process. These results are suggestive that these composite fibers appear as a promising active material for the sensing of acid vapors.