High-energy Capacitors Research Articles

Development of High Energy Capacitors Using La-Doped PbZrO3 Anti-Ferroelectric Thin Films

Chemical solution-derived anti-ferroelectric (AFE) thin films for energy storage devices were investigated. In order to evaluate dielectric properties(dielectric constant and loss, leakage current density), anti-ferroelectric properties(energy storage density and loss, energy storage efficiency) of anti-ferroelectric thin films with lanthanum (La) as a dopant, ∼1 μm-thick anti-ferroelectric (PbLa)ZrO3 (PLZO) films as a function of La doping concentration (0 ∼ 6 mol.%) were deposited on Pt/Ti/SiO2/Si substrate. With the increase of La-doping concentration, the energy storage loss was reduced from ∼8.8 J/cm3 to ∼6.6 J/cm3, and the efficiency was increased from ∼59.2% to ∼80.7%. In terms of the lowest leakage current density, the maximum energy storage performance was observed in La 2 mol.% doped PLZO thin film capacitor with the energy storage density ∼16.9 J/cm3, energy loss ∼8.4 J/cm3 and energy storage efficiency ∼66.8% at an applied electric field ∼1 MV/cm with frequency ∼1 kHz at room temperature.

Dielectric Response of Structured Multilayered Polyvinylidene Fluoride Films

To make clear the effect of thickness and layer number on the dielectric property of poly (vinylidenedi fluoride) (PVDF), the different multilayer films were prepared by spin coating. The relation between them has been explained by both experimental results and theoretical model. It is found the dielectric constant of multilayer increase linearly with the number of layers but decrease with the thickness. It is helpful to optimize the material structure and size parameters of polymer films for high energy capacitors.

An experimental research on single discharge machining of insulating ceramics efficiently with high energy capacitor

Insulating ceramics are applied to modern manufacturing industries for their improved material properties. But they are the difficult-to-machine materials because of their high rigidity, high brittleness and non-electrical conductivity. A new method which employs a high energy capacitor for electric discharge machining of insulating ceramics efficiently is presented in this paper, and the single discharge experiments have been carried out. The process uses the high voltage, large capacitor and high discharge energy, it is able to effectively machine insulating ceramics, and the single discharge crater volume of insulating ceramics can reach 17.63 mm3. The effects of polarity, peak voltage, capacitance, current-limiting resistance, tool electrode feed, tool electrode section area and assisting electrode thickness on the process performance such as the single discharge crater volume, the tool wear ratio and the assisting electrode wear ratio have been investigated. The microstructure of the discharge crater is examined with a scanning electron microscope (SEM). The results show that the discharge craters have sputtering appearance, the insulating ceramic materials are mostly removed by spalling, in the center region of the discharge some materials are removed by melting and vaporization, and the material removal is enhanced with the machining parameters increasing.

The role of nanomaterials in redox-based supercapacitors for next generation energy storage devices

The development of more efficient electrical storage is a pressing requirement to meet future societal and environmental needs. This demand for more sustainable, efficient energy storage has provoked a renewed scientific and commercial interest in advanced capacitor designs in which the suite of experimental techniques and ideas that comprise nanotechnology are playing a critical role. Capacitors can be charged and discharged quickly and are one of the primary building blocks of many types of electrical circuit, from microprocessors to large-sale power supplies, but usually have relatively low energy storage capability when compared with batteries. The application of nanostructured materials with bespoke morphologies and properties to electrochemical supercapacitors is being intensively studied in order to provide enhanced energy density without comprising their inherent high power density and excellent cyclability. In particular, electrode materials that exploit physical adsorption or redox reactions of electrolyte ions are foreseen to bridge the performance disparity between batteries with high energy density and capacitors with high power density. In this review, we present some of the novel nanomaterial systems applied for electrochemical supercapacitors and show how material morphology, chemistry and physical properties are being tailored to provide enhanced electrochemical supercapacitor performance.

Transportable high-energy high-power generator

High-power applications sometimes require a transportable, simple, and robust gigawatt pulsed power generator, and an analysis of various possible approaches shows that one based on a twin exploding wire array is extremely advantageous. A generator based on this technology and used with a high-energy capacitor bank has recently been developed at Loughborough University. An H-configuration circuit is used, with one pair of diagonally opposite arms each comprising a high-voltage ballast inductor and the other pair exploding wire arrays capable of generating voltages up to 300 kV. The two center points of the H configuration provide the output to the load, which is coupled through a high-voltage self-breakdown spark gap, with the entire autonomous source being housed in a metallic container. Experimentally, a load resistance of a few tens of Ohms is provided with an impulse of more than 300 kV, having a rise time of about 140 ns and a peak power of over 1.7 GW. Details of the experimental arrangement and typical results are presented and diagnostic measurements of the current and voltage output are shown to compare well with theoretical predictions based on detailed numerical modeling. Finally, the next stage toward developing a more powerful and energetic transportable source is outlined.

Molybdenum Carbide Derived Carbon Based Electrode Materials for High Energy and Power Density Electrochemical Double-Layer Capacitors

not Available.

Delayed Metabolic Activation of Oxidative Phosphorylation in Skeletal Muscle at Exercise Onset

In "normal" conditions (e.g., normoxia, absence of pathological conditions) convective and diffusive O(2) delivery to skeletal muscle fibers do not seem to represent important determinants for the kinetics of adjustment of oxidative phosphorylation following increases in metabolic demand. Whereas a limiting role by PDH has not been experimentally confirmed, inhibition of mitochondrial respiration by NO could be partially responsible for the delayed activation of oxidative phosphorylation at exercise onset. The main determinants of muscle VO(2) kinetics, however, likely reside in the intricate interplay between the various mechanisms of energy provision at exercise onset. By acting as high-capacitance energy buffers, PCr hydrolysis and anaerobic glycolysis would delay or attenuate the increase in [ADP] within the cell following rapid increases in ATP demand, thereby "buffering" a more rapid activation of oxidative phosphorylation. The "PCr-Cr shuttle" concept of a regulatory role of PCr or of the products of PCr hydrolysis on oxidative phosphorylation provides a mechanism that couples VO(2), which occurs in mitochondria, to PCr hydrolysis occurring in the cytoplasm.

Proton and Electron Conductivity in Hydrous Ruthenium Oxides Evaluated by Electrochemical Impedance Spectroscopy: The Origin of Large Capacitance

Electrochemical impedance spectroscopy was conducted on a series of hydrous ruthenium oxides, RuO(2).xH(2)O, (x = 0.5, 0.3, 0) and a layered ruthenic acid hydrate (H(0.2)RuO(2.1).nH(2)O) in order to evaluate their protonic and electronic conduction. The capacitor response frequency was observed at lower frequency for RuO(2).xH(2)O with higher water content, which was suggested to be due to electrolyte exhaustion within the film and/or utilization of hydrated interparticle micropores that have high ionic resistance. Analysis of the impedance data indicated that the charge-transfer resistance through the film is not significantly affected by the water content in RuO(2).xH(2)O, and the capacitor frequency response is dominated by the protonic conduction. The capacitor response frequency of layered H(0.2)RuO(2.1).nH(2)O was comparable to RuO(2).0.5H(2)O. The high specific capacitance at low frequency for layered H(0.2)RuO(2.1).nH(2)O is attributed to the utilization of the expandable hydrous interlayer, which accounts for the ionic conduction. The present results demonstrate the importance of hydrous regions (either interparticle or interlayer) to allow appreciable protonic conduction for high energy and high power electrochemical capacitors.

A pulsed magnetohydrodynamic generator for electric launcher

An invention scheme of pulsed magnetohydrodynamic generator (PMHDG) in milliseconds order of magnitude that can be used directly in electric launchers is presented for the first time. It is either different from ordinary small power dc MHD generators for power plants, or different from explosive MHD generators where its pulsed current width is in the microseconds order of magnitude. Operating principle of the PMHDG is as follows: fuels or oxidizing agents within two storage vessels are injected into a combustion chamber to combust by a pump and a valve, after waiting for the pressure (or density) of generated conductive electric MHD ascends some threshold value, a self-controlled valve in combustion chamber throat is opened automatically. As a result, conductive electric MHD passes into a generating channel in pulse to generate electric current. Obviously, by controlling the amount of the working substance entering into the combustion chamber with the injector valve, and adapting the spring pressure of the self-controlled valve, we can control the pulsewidth and obtain different values of high power to be used directly by the electric launcher. Besides, this paper gives a theory-mathematical model in which some characteristics of the generator were expressed. This helps us to understand the relationship between various physical quantities about the generator, and provides a basis to research their mutual influences. In addition, in physical design of the circuit, we adopted a proper high energy density capacitor as auxiliary energy storage. On one hand, the generator can realize the self-excited generation by using the capacitor; on the other hand, the high energy capacitor is charged directly by the generator and energy stored within the capacitor is realized, so as to form a generator-capacitor combined high power pulsed power supply that can be used by high energy electric launchers.

Critical components for high energy density capacitor modules

The application of electric guns in combat vehicles require pulsed power supply systems with a compact design and a high reliability. Other investigations show that capacitive pulsed power supply (PPS) systems will fulfil these requirements for electrothermal-chemical (ETC) guns. In these PPS systems, high energy density capacitors and high power switches are critical components that have yet to be realized. This paper gives an overview of the latest results obtained from Rheinmetall's investigations on high energy capacitors and optically activated semiconductor switches being developed for ETC PPS systems. The basic technical requirements to be fulfilled by these components are presented. The final setup and the design data of a 1.9-2 MJ/m/sup 3/ discharge capacitors and a 22 kV/40 kA closing switch are described. Results obtained from full scale testing are presented. Basic considerations on other applications of these components and their scaled performance data conclude the paper.

The destruction effect of a pulse discharge in water suspensions

A high-energy capacitor bank in a Blumlein circuit) was discharged over about through a 7 mm electrode gap in water suspensions of different materials - powder, wood materials (sawdust, needles) - and methylhydroxyethylcellulose dissolved in water. The Mach number of the compressional wave produced by the expanding discharge channel achieved a value of about 0.5. The destruction of added materials was tested using various methods: turbidity and covering ability of the -white, acid hydrolysis of beech sawdust, microbiological processes of spruce needles and molecular weight measurements of the cellulose derivative. In the used power conditions the physical destruction of materials dispersed in water (degassing and decomposition of physically bonded particles) is a dominant effect caused mainly by the compressional wave that can affect material in the whole volume. The chemical destruction probably occurs just in the vicinity or inside the plasma channel due to the action of plasma particles or energetic radiation.

High energy and high power density electrochemical capacitors

High energy density electrochemical capacitors were built with a newly discovered electrode material (amorphous RuO 2· xH 2O). Energy densities as high as 96 J/g (26 Wh/kg) were obtained based on the RuO 2· xH 2O electrode material alone. However, the power density of the capacitor is low. By mixing RuO 2· xH 2O powders with about 20% weight of carbon black, power densities greater than 10 kW/kg could be achieved at a delivered energy density of about 72 J/g (20 Wh/kg). Capacitance as a function of cycle life was studied for up to 60 000 cycles. The temperature dependence of capacitance and resistance of the capacitor are also reported in this paper.

Conducting polymers as active materials in electrochemical capacitors

Electronically conducting polymer represent an interesting clas of materials for use in electrochemical capacitors thanks to the combination of high capacitive energy density and low materials cost. Three generalized typed of electrochemical capacitors can be constructed using conducting polymers as active material, and in the third of these, which utilized conducting polymers that can be both n- and p-doped, energy densities of up to 39 Wh per kg of active material on both electrodes have been demonstrated. This energy density is obtained using poly-3-(4-fluorophenyl)-thiophene (PEPT) in an electrolyte of 1 M tetramethylammonium trifluoromethanesulfonate (TMATFMS) in acetonitrile. This unique system exhibits reversible n- and p-doping to high charge density in relatively thich films of the active polymer and a cell voltage exceeding 3 V in the fully charged state. Impedance data for both n- and p-doped PFPT suggest that high power densities can be obtained in electrochemical capacitors based on this active conducting polymer.

Analysis of experimental data from a 50-mm railgun driven by a 5-MJ capacitor power supply

The Compact High Energy Capacitor Module Advanced Test Experiment (CHECMATE) barrel coupled with a 5-MJ capacitor power supply has become a primary testbed for conducting armature research CHECMATE is a nominal 50-mm square-bore EM launcher that is 5 m in length. Recent testing on this hardware was conducted using molybdenum coated rails, G-9 insulators, and a plasma armature. Eight firings were performed at various charge voltages and with various power supply triggering schemes. Muzzle velocities achieved with the 93-g projectile ranged from 3.6 to 4.2 km/s. The analysis performed on this test series is summarized. The primary focus of this analysis was to identify and assess the potential mechanisms which lead to performance degradation at high velocities. Results presented indicate that the Electric Gun Circuit Analysis Code (EGCAC) demonstrates good agreement with experimental B-dot data up to approximately 3.5 km/s; however, on the higher voltage shots, EGCAC overpredicts the expected velocity.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Temporal Behaviors of Flash X-Ray Source Driven by a Low-Energy Capacitor Discharge

Temporal behaviors of a compact X-ray source driven by a low-energy capacitor discharge have been studied. X-rays are emitted only when the voltage appears between the anode and cathode at the beginning of the discharge, when the discharge current is small. The temporal X-ray emission profile has a significant correlation with the electrode voltage. Therefore, high discharge currents and high-energy capacitors are unnecessary. Spectral and spatial properties of the X-ray source are investigated by aluminum filters and thermoluminescent dosimetry. When the generator output voltage is 95 kV, the photon energy ranging from 15 to 30 keV is nearly 63% of the emitted X-ray and the maximum photon energy of 84.7 keV is obtained. Applying the experimental results, we propose a variable short-wavelength pulsed-light source.

Histologic changes and arrhythmogenicity after discharge through transseptal catheter electrode.

Ventricular tachycardia commonly arises within the intraventricular septum and successful catheter ablation of septal tachycardia might be enhanced by transseptal electrode placement. We have evaluated the safety of a transseptal ablation procedure. Arrhythmogenicity and histology were examined after high-energy capacitor discharges were delivered to an intracavitary cathode-anode pair placed on opposite sides of the interventricular septum in pentobarbital-anesthetized dogs. After two discharges of 200 or 100 J proved lethal, paired discharges of 30 or 50 J (10 dogs) or a single discharge of 100 J (four dogs) was used to induce 28 lesions. Acute rhythm changes and risk of induction of ventricular tachycardia by programmed stimulation were measures of arrhythmogenicity. Gross and histologic examination of the hearts after 20 min to 28 days allowed characterization of the evolution of lesions. The conduction system in nearby and remote locations was extensively examined in four dogs. Refractory ventricular fibrillation developed with paired shocks at 200 or 100 J. At lower energy levels, acute ventricular fibrillation occurred with 12 of 20 shocks (60%), but defibrillation was consistently achieved. After ablation, no dog had ventricular tachycardia or fibrillation induced with programmed stimulation. Matching anodal and cathodal lesions spanned the septum without perforation in 10 of 16 dogs, and the lesions were of similar histology. Each contained central areas of hemorrhage surrounded by a region of coagulation necrosis merging with normal myocytes peripherally. There was necrosis and edema without inflammation at 20 min, acute inflammatory cell infiltration at 1 to 2 days, and myocyte replacement by granulation tissue after 6 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Solid-state electric-double-layer elements using Cu + ion conductive solid electrolyte

The components for constructing a Cu-based double-layer element, high-energy-density capacitor and potential memory element were studied. The high-energy capacitor, which is constructed with a carbon polarization electrode and a polyphase counter electrode (Cu 60 wt%) exhibited nearly comparable performance to a Ag-based cell. The potential memory element constructed with three Cu 2S electrodes has ≈1000 times larger capacity; however, the practical potential range is about half that of a Ag-based one.