Maximum Surface Charge Density Research Articles

Phase Dependence of Surface Charge Measurement on Epoxy Insulator in C4F7N/CO2 under AC Voltage.

The application of binary gas mixtures consisting of heptafluorobutyronitrile (C4F7N) and carbon dioxide (CO2) in AC GIS is currently attracting much attention. Therefore, the evaluation of the gas-solid interface charge distribution characteristics of epoxy resin is indispensable. Additionally, the phase-dependency of the charging behavior remains not fully understood. We simulated coaxial electrode structure in GIS and investigated the surface charge distribution on a down-scaled epoxy insulator. The influence of the truncated phase angle and duration of AC voltage on charge behavior were analyzed, and the charge transport mechanism under AC voltage was theoretically analyzed. The results showed that there was a noticeable negative charge speckle with the presence of the metal particle and the accumulated negative charge on the insulator surface far exceeded that of the positive charge. The maximum surface charge density and the amount of surface charge accumulated first increased and then decreased over time. It was found that the phase angle has a negligible influence on the surface charge distribution at the cut-off moment.

Fully‐Recyclable Green and Fire‐Resistant Triboelectric Elastomer via Geometrical Synergistic Fillers and Its Applications for Smart Firefighting Boots

AbstractWearable sensors for high temperatures (WSHT) applications pose a significant challenge in the electronics field due to the inherent inability of most electronics to function in harsh environments. Triboelectric nanogenerators (TENG) present a substantial potential for applications in such challenging conditions. Herein, a fully‐recyclable flame‐retardant triboelectric elastomer is developed, which exhibits superior charge stability under high temperature conditions and proposes the specially designed synergistic fillers that play a dual role by trapping more charges into the interface and stabilizing the char layers via layer‐ball‐layer structure. An efficient flame‐retardant system is presented, which exhibits a 31% lower fire growth index than the individual components. The maximum surface charge density of this triboelectric elastomer can reach 361 µC m−2, while this surface charge density can be preserved to 70.9% after 16 s of combustion (≈520 °C) and to 37.9% by continuously working at 130 °C. At last, utilizing this flame‐retardant triboelectric elastomer, smart firemen's boots featuring gait analysis for identification and second level early warning systems have been developed. This work paves the way for the development of triboelectric materials and intelligent wearable devices suitable for applications in harsh environments.

Triboelectric Nanogenerators Based on Nanostructured Layers of Zinc Oxide Deposited on Carbon Fabric

In this work, to obtain textile triboelectric layers for wearable flexible triboelectric nanogenerators (TENGs), we used two modes of growing nanostructured zinc oxide (ZnO) arrays on a carbon fabric (CF) using the automatic Successive Ionic Layer Adsorption and Reaction (SILAR) method. To produce a CF/ZnO_nr triboelectric textile with an array of intergrown short ZnO nanorods, we used a pre-coating of carbon fibers with ZnO seed layers. When the ZnO layer was fabricated by automatic SILAR on bare carbon fabric, we obtained the CF/ZnO_ns textile with an array of interconnected ZnO nanosheets 50–100 nm thick. As a proof of concept, we developed and tested two prototypes of flexible vertical contact–separation mode CF/ZnO_nr/PET/ITO and CF/ZnO_ns/PET/ITO TENGs, in which a gap was involuntarily formed between the smooth PET layer and the woven carbon textile coated with nanostructured ZnO films. In pressing tests with a force of ~5 N (pressure ~33 kPa), the CF/ZnO_ns/PET/ITO TENG created a higher open-circuit voltage up to 30 V and a higher maximum surface charge density of 1.3 μC/m2. In the successive press–release tests, this TENG showed an output voltage of 3.6 V, a current density of 1.47 μA/cm2, and a power density of 1.8 µW/cm2, confirming its effectiveness.

An enhanced distance-dependent electric field model for contact-separation triboelectric nanogenerator: Air-breakdown limit as a case study

Theoretical models have been proposed to bring an in-depth understanding of the working mechanisms of triboelectric nanogenerators (TENGs), aiming to enhance their output performance. This work proposes an enhanced distance-dependent electric field (EDDEF) model to predict triboelectric characteristics of TENGs more accurately. The model bridges the gap between the distance-dependent and distance-independent electric field models in terms of open-circuit (OC) voltage (VOC), short-circuit (SC) voltage (Vgap,SC), and SC surface charge density (σSC) at small separation distances by developing more accurate mathematical formulations of the electric potential. The EDDEF model was validated by finite element modeling (FEM) simulation. It introduced an accurate theoretical analysis of the air-breakdown boundary under the OC condition for the first time. The maximum surface charge density that can be obtained without air breakdown was predicted to be lateral size-dependent. It shows a monotonical decrease from 51.94 to 33.59 µC/m2 with a lateral size increase from 0.5 to 10 cm. Meanwhile, the corresponding separation distance increased from 0.915 to 12.48 mm, suggesting that improving CS-TENG’s performance by boosting the surface charge density is more effective at smaller lateral sizes and shorter separation distances. These findings serve as a guide towards the miniaturization of highly efficient CS-TENG technology. In addition, under SC condition, the EDDEF model showed great consistency with the distance-independent model in predicting the air-breakdown limit, supporting the distance-independent model applicability for predicting the air-breakdown under the CS condition.

Promotion of Epoxy Resin Surface Electrical Insulation Performance and Its Stability by Atmospheric Fluorocarbon Dielectric Barrier Discharge

This study investigates the promotion of epoxy resin (ER) surface electrical insulation and its stability by atmospheric fluorocarbon dielectric barrier discharge (DBD) plasma. Surface physicochemical and electrical properties of untreated and plasma treated samples are evaluated by scanning electron microscopy, X-ray photoelectron spectroscopy, surface and volume resistivity, surface charge accumulation, dissipation measurements, and flashover tests. Analysis shows that dusty-like fluorocarbon granules formed in plasma phase are deposited on ER samples and the concentration of fluorine groups is increased after plasma treatment. The surface withstand strength of epoxy resin in vacuum can be promoted up to 50%. Surface resistivity decreases by two orders of magnitude with treatment time while volume resistivity reduces slightly. The surface charge accumulation on treated ER samples is prohibited and the maximum surface charge density decreases from 77.84 to 1.42 pC/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The surface charge dissipation is accelerated with the central energy levels reducing to below 0.9eV and the density of electron traps increases from ~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sup> to ~10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">22</sup> eV <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> . Furthermore, the stability of surface flashover strength is tested. It is found that promotion of surface flashover strength of treated ER sample is stable after being kept in ambient air for a month. The physicochemical changes caused by plasma treatment prevents electrons from transferring to the surface which leads to a better surface insulation performance.

Effect of Insulator Bulk Conductivity Non-uniformity on Surface Charge Accumulation

In order to clarify the effect of insulator bulk conductivity non-uniformity, controlled by electric field, on surface charge accumulation under dc high voltage, a simulation model involving multi-physics, which includes transition from initial capacitive to stationary resistive field, is established. In terms of this, the characters of surface charge accumulation are obtained. It is found that non-uniformity of electric conductivity contributes to the change of surface charge distribution profile, but not to the increase of the maximum surface charge density when the applied voltage is less than 1000 kV. After voltage exceeds 1000 kV, the maximum charge density becomes smaller compared to the case with uniform conductivity. The results indicate that electric conductivity non-uniformity relating to electric field is a source contributing to surface charge accumulation through insulator bulk, and should not be neglected.

Synergistic Effects of BaTiO3/Multiwall Carbon Nanotube as Fillers on the Electrical Performance of Triboelectric Nanogenerator Based on Polydimethylsiloxane Composite Films

Herein, polydimethylsiloxane (PDMS) composite films containing BaTiO3 particles with an average size of 70 and 500 nm are prepared and characterized, respectively. Then, triboelectric nanogenerators (TENG) based on the composite films are designed at different BaTiO3 sizes and mass ratios. In addition, multiwall carbon nanotubes (MWCNTs) are also used for uniform dispersion of BaTiO3 particles in composite films for the TENG device. With the synergistic effects of BaTiO3/MWCNT fillers, discrete conductive micronetworks surrounded by BaTiO3 particles form, and then, the effective filler–matrix interface effect in the three‐phase composite is enhanced, leading to superior triboelectric output performance, supported by much higher dielectric permittivity and COMSOL simulation. Moreover, the triboelectric output performance of TENG changes with different‐sized BaTiO3 particles. As to BT‐70‐MWCNT/PDMS composites, with the same mass ratio of BT, the peak output current is always higher than that of BT‐500‐MWCNT/PDMS. Furthermore, the optimum BT mass ratio of BT‐70‐MWCNT/PDMS composites is also higher than that of BT‐500. With BaTiO3 of size 70 nm, the maximum surface charge density is about 160 μC m−2 under an optimized mass ratio, whereas it is about 110 μC m−2 for BaTiO3 of size 500 nm.

Evaluation of the antibacterial activity of a cationic polymer in aqueous solution with a convenient electrochemical method.

Quaternized chitosan is a cationic biopolymer with good antibacterial activity, biocompatibility, and biodegradability, and it has been widely applied in many fields. We have developed a convenient method to evaluate the antibacterial activity of hydroxypropyltrimethylammonium chloride chitosan (HACC) with a nonionic surfactant poloxamer in aqueous solution by monitoring the change of the oxidation peak current in cyclic voltammetry. Increasing values of the oxidation peak current were positively correlated with the antibacterial activity of HACC-poloxamer solutions. Optical microscope images, the zeta potential, and fluorescence spectroscopy showed that the aggregation state of HACC-poloxamer was related to the ratio of the two polymers and also to the antibacterial activity and oxidation peak current. At an HACC-to-poloxamer ratio of 1:0.75, the maximum surface charge density and the smooth edge of HACC-poloxamer aggregates can accelerate diffusion in aqueous solution. It is expected that this convenient method can be applied for a quick evaluation of the antibacterial activity of cationic biopolymers in aqueous solution. Graphical Abstract The cyclic voltammograms of MB in HACC/poloxamer solution, and the antibacterial efficiency against S. aureus after incubated with HACC (a) and 1/0.75 of HACC/poloxamer (b).

The Effect of PD Process on the Accumulation of Surface Charges

The distribution of surface charges at the interface between gas and insulating material relates to the partial discharge process in a void. In order to clarify this, a 2-D model is constructed in this paper. Based on this, the streamer development and the accumulating process of surface charges are obtained under both polarities of the applied voltage. It is found that the maximum surface charge density appears at the middle location of the interface, and monotonically decreases along the radial direction. As the drift velocity of the electron is higher than that of the positive ion, the accumulation of surface charges takes a much shorter time under the negative voltage than under the positive. Besides, the effect of the applied voltage amplitude and the void height on surface charge distribution is obtained. As the applied voltage or the void height becomes greater, the discharge process becomes more intense, leading to an increase of surface charge density and surface charge distribution area.

Hybrid nanogenerators based on triboelectrification of a dielectric composite made of lead-free ZnSnO3 nanocubes

Based on mixed piezoelectric and ferroelectric nanostructures with polymers in various architectural forms, the flexible triboelectric nanogenerators (TENGs) have been extensively investigated. In this study, we design and fabricate lead-free ZnSnO3 nanocubes @ polydimethylsiloxane (PDMS) based TENG by dispersing ZnSnO3 nanocubes into PDMS elastomer at different ratios. Finally, the TENG can attain a maximum electrical output signal up to 400V and 28μA at a current density of 7μAcm−2, and an effective power to 3mW at 6wt% mass ZnSnO3 mixed into PDMS. The harvested energy is utilized to drive 106 blue LEDs. In addition, this TENG generates stable electric power, even in the compressing-and-releasing process for over 500 cycles. Further investigation by electrostatic force microscopy shows clearly the maximum surface charge density appears at the optimal mixing ratio of ZnSnO3 piezoelectric nanostructures into PDMS. This demonstrates that the optimization of the mixing ration between ZnSnO3 piezoelectric nanostructures and PDMS is an effective method to increase the surface charges on the composite thin film and then improve the performance of the TENG. This TENG technology reveals a great candidate to be applied in large-scale device fabrications, flexible sensors and biological devices because of its easy fabrication process, high output power and biocompatibility.

Maximum surface charge density for triboelectric nanogenerators achieved by ionized-air injection: methodology and theoretical understanding.

For the maximization of the surface charge density in triboelectric nanogenerators, a new method of injecting single-polarity ions onto surfaces is introduced for the generation of surface charges. The triboelectric nanogenerator's output power gets greatly enhanced and its maximum surface charge density is systematically studied, which shows a huge room for the improvement of the output of triboelectric nanogenerators by surface modification.

Uranyl Adsorption at the Muscovite (Mica)/Water Interface Studied by Second Harmonic Generation

Uranyl adsorption at the muscovite (mica)/water interface was studied by second harmonic generation (SHG). Using the nonresonant χ(3) technique and the Gouy-Chapman model, the initial surface charge density of the mica surface was determined to be -0.022(1) C/m(2) at pH 6 and in the presence of dissolved carbonate. Under these same conditions, uranyl adsorption isotherms collected using nonresonant χ(3) experiments and resonantly enhanced SHG experiments that probe the ligand-to-metal charge transfer bands of the uranyl cation yielded a uranyl binding constant of 3(1) × 10(7) M(-1), corresponding to a Gibbs free energy of adsorption of -52.6(8) kJ/mol, and a maximum surface charge density at monolayer uranyl coverage of 0.028(3) C/m(2). These results suggest favorable adsorption of uranyl ions to the mica interface through strong ion-dipole or hydrogen interactions, with a 1:1 uranyl ion to surface site ratio that is indicative of monovalent cations ((UO(2))(3)(OH)(5)(+), (UO(2))(4)(OH)(7)(+), UO(2)OH(+), UO(2)Cl(+), UO(2)(CH(3)COO(-))(+)) binding at the interface, in addition to neutral uranyl species (UO(2)(OH)(2) and UO(2)CO(3)). This work provides benchmark measurements to be used in the improvement of contaminant transport modeling.

The inhibitory effects of carboxymethyl inulin on the seeded growth of calcium carbonate

Kinetics of precipitation of calcite (CaCO 3) from aqueous solution in the presence of carboxymethyl inulin (CMI) was investigated under strictly controlled temperature, pH, supersaturation ratio ( S = 4.8) and ionic strength ( I = 0.1 M). The highly reproducible constant composition technique was used to study the influence of biopolymers of crystal growth of CaCO 3, on CaCO 3 seed crystals at pH 8.5 and 25 °C. The crystal growth of calcium carbonate (CaCO 3) was inhibited in the presence of CMI at low concentration (2.5 × 10 −9 to 25 × 10 −9 mol/L). The larger number of negatively charged functional groups exhibited a 95% growth rate inhibition at a concentration of 15 × 10 −9 mol/L. The higher inhibition efficiency is related to the maximum surface charge density due to adsorbed polymer.

Inhibition of Calcium Oxalate Crystallization by Graft Copolymers

Influence of graft copolymers with different architecture on spontaneous batch crystallization of calcium oxalate was investigated. The series of water-soluble polyethyleneglycol methacrylate-vinylsulfonic acid graft copolymers [(PEG-MA)-co-VS] and homopolymer of vinylsulfonic acid have been made, by radical polymerization, with defined molecular weight and structure. The presence of polymers inhibited the crystal growth of calcium oxalate possibly through adsorption onto the active growth sites for crystal growth due to the charge and hydrophilic effects. The higher inhibition efficiency of vinylsulfonic acid homopolymer is related to the maximum surface charge density due to adsorbed polymer. The homopolymer influenced both the morphology and phase transformation of calcium oxalate crystals. Polyelectrolyte effects were interpreted in terms of the adsorption of inhibitors onto the active growth sites on the crystal surface.

Maximum mechanical energy harvesting strategy for a piezoelement

The electromechanical conversion capacity of a piezoelectric power generator is investigatedby considering a quasi-static work cycle. How the maximum energy can be harvested froma piezoelectric element limited by its maximum parameters such as the maximum strain,maximum field, maximum surface charge density and maximum stress is detailed in thispaper. The work cycle in which the electric field and the stress are controlled in a waydesigned to get the most energy is illustrated. A contrast has been made betweensynchronized switching harvesting with an inductor (SSHI) and the methods introducedhere, and it is pointed out theoretically that the proposed method yields more power thanSSHI.

Fundamental limits on energy transfer and circuit considerations for piezoelectric transformers

This work investigates fundamental limits on electromechanical energy conversion capacity of piezoelectric transformers by considering a work cycle analysis. Fundamental limitations in a lossless piezoelectric transformer are imposed by maximum electric field strength, maximum surface charge density, maximum stress and maximum strain. For the lossless case, the authors' analysis indicates that the mechanical stress limit is the effective constraint in typical PZT materials. For a specific PZT-5H sample considered, a mechanical stress-limited work cycle indicates that this material can handle 330 W/cm/sup 3/ at 100 kHz. A second direction this work has taken has been an investigation into a soft-switching drive and control circuit, that does not require any magnetic components. The theory of operation of soft-switching resonant drive circuitry is discussed, and experimental results on a soft-switching inverter incorporating no magnetic components are reported.

The influence of polyelectrolytes architecture on calcium sulfate dihydrate growth retardation

The retarding influence of acidic acrylate and methacrylate polymers made by group transfer polymerization on the growth of calcium sulfate dihydrate was examined in aqueous solution. The variations with polyelectrolyte charge, structure and molecular weight have been tested. The inhibition increases with the acid content of the polymers. Acrylates were much more effective than equivalent methacrylates. The higher inhibition efficiency is related to the maximum surface charge density due to adsorbed polymer.

Experimental discussion on maximum surface charge density of fine particles sustainable in normal atmosphere

The maximum surface charge density for large spherical particles in normal atmosphere is thought to be 27 μC/m 2, assuming that the electric breakdown field strength of air is 3 MV/m. For a given surface charge density, however, the layer of a very high electric field strength for electron avalanche in air around the particle becomes thin, when the particle size is small. As a result, a higher limit in the surface charge density is expected for small particles. In the present experiment, droplets with high surface charge density in the size range between 1 and 6 μm in diameter are prepared by evaporating negatively charged liquid particles of 45 μm. For a few kinds of liquids, the size and the charge of individual droplets are measured simultaneously by using an LDV system to obtain frequency histograms for the charges of droplets with several narrow size ranges. The results indicate that the maximum surface charge density sustainable in atmosphere for negatively charged particles depends mainly on the particle size and is inversely proportional to the square root of particle size to give very high surface charge density in micrometer order size range.

A Correlation Of Interfacial Charge With Various Interfacial Properties In Relation To Oil Recovery Efficiency During Waterflooding

Abstract The objective of this study was to correlate the interfacial charge with other properties of the crude oil/brine interface in relation to oil recovery efficiency. The dispersed droplets of Seeligson crude oil in brine solution exhibited a maximum in electrophonetic mobility at 3.5% NaCI concentration. At the same NaCI concentration, the drop volume of the crude oil in brine was minimum, which suggested that the interfacial tension was also minimum. Moreover, minimum interfacial viscosity between a thin crude oil film and brine occurred at 3.5% NaCI concentration. The surface-active components in the crude oil were eluted by chromatography in silica gel columns. The results showed that a maximum amount of surface-active material was eluted by 3.5% NaCI. We propose that the striking changes observed at 3.5% NaCI concentration are due to the maximum surface charge density at the crude oil/brine interface. Furthermore, we observed the maximum oil recovery efficiency in sandpacks and Berea cores when the crude oil-was displaced by 3.5% NaCI brine. Because contact angle measurements of crude oil droplets on quartz plates submerged in brine did not show a significant change at 3.5% NaCI the wettability alteration as a possible mechanism for enhanced oil recovery in this system is ruled out. The capillary number at 3.5% NaCI also remained below 10−6 and hence cannot account for the enhanced oil recovery. A possible explanation for the maximum oil recovery efficiency at a specific brine concentration is proposed in terms of interfacial charge at the crude oil/ brine interface and that at the sand/brine interface. It is further emphasized that surface charge is an important parameter which can influence interfacial tension and interfacial viscosity at the oil/brine interface. Introduction Since the first field application in 1865(1), the water- flooding process for oil recovery has evolved from plain water injection to the complicated processes involving the addition of solvents, chemicals, gas or heat. These additives change either one or several of factors such as water mobility (2,3), oil viscosity(4,5), rock wettability (6,7) and wateroil interfacial tension(8,9,10). The incorporation of these additives increases the oil displacement efficiency, the sweep efficiency, or both. Therefore, it is evident that in order to achieve a better oil recovery the physical and chemical properties of the injected brine are of the utmost importance. The main objective of this investigation was to elucidate the influence of salt concentration on the properties of the crude oil/brine interface and to correlate it with the oil displacement efficiency in sand packs and Berea cores. Experimental Materials and Methods Materials The crude oil used in all experiments was obtained from Seeligson Oil Field, Texas. It was collected at the wellhead prior to the addition of any agents and shipped directly to us from the field. The crude oil had 39.4 °API and a viscosity of 2.54 cp at 25 °C. The brine solutions were prepared by adding NaCI to deionized-distilled water on the weight per cent basis.

Charging of droplets by impulse corona

Experiments involving the production of impulse corona of both polarities within a cloud of droplets atomized from a solution of glycerin and water are described. The observed charging of droplets with radii in the range 2.5 to 15 μ is characterized by a maximum surface charge density that is nearly constant down to about 6 μ and increases for radii below that if other electric and geometric parameters are fixed. The largest surface charge densities observed for droplets with radii above 6 μ are approximately 4×10−6 coul m−2 for positive corona and −6×10−6 coul m−2 for negative corona. Our results suggest quite different charging mechanisms for the two corona polarities. With positive corona the droplet charging appears to result from direct interaction between the positive streamers and the droplets. These findings indicate a possible link between the lightning discharge and subsequent rapid cloud droplet growth.