Capacitors

Distribution by Scientific Domains
Distribution within Engineering

Kinds of Capacitors

  • electrochemical capacitor
  • interdigital capacitor
  • layer capacitor
  • mim capacitor

  • Terms modified by Capacitors

  • capacitor application

  • Selected Abstracts


    Joining Strategies for Open Porous Metallic Foams on Iron and Nickel Base Materials,

    ADVANCED ENGINEERING MATERIALS, Issue 8 2007
    S. Longerich
    Within the Collaborative Research Centre (SFB) 561 "Thermally highly loaded, porous and cooled multilayer systems for combined cycle power plants" open porous Ni-based structures are developed for the requirements of an effusion cooling. A two-dimensional cooling strategy for the walls of combustion chambers, that allows the outflow of the cooling medium over the complete wall area of the combustion chamber, could be realized by an open porous metallic foam structure. The challenge is to join the porous foam structure with the solid substrate material. Capacitor discharge welding and laser beam welding/-brazing methods seems to be promising methods due to a minimum input of energy and, connected with this, a small joining zone. [source]


    Synthesis of Microporous Carbon Nanofibers and Nanotubes from Conjugated Polymer Network and Evaluation in Electrochemical Capacitor

    ADVANCED FUNCTIONAL MATERIALS, Issue 13 2009
    Xinliang Feng
    Abstract One-dimensional fibers and tubes are constructed through the oriented carbon-carbon cross-linking reactions towards rigid conjugated polymer networks. As the result, a template-free and one-step synthesis of CNTs and CNFs is achieved through a simple carbonization of the as-formed carbon-rich tubular and fiberlike polyphenylene precursors under argon. Microporous CNTs and CNFs with a surface area up to 900 m2 g,1 are obtained, together with HR-TEM characterizations indicating the formation of intrinsic microporous structure in these rigid carbon-rich networks. The primary electrochemical experiments reveal their promising applications as advanced electrodes in electrochemical double-layered capacitor (EDLC). [source]


    Grafted 2D Assembly of Colloidal Metal Nanoparticles for Application as a Variable Capacitor,

    ADVANCED MATERIALS, Issue 13 2007
    N. Lidgi-Guigui
    A combination of sputtering and colloidal chemistry is employed to prepare [Co/Al2O3//Ru nanoparticles//Al2O3/Co] junctions (see figure). These junctions are applied as variable capacitors relying on Coulomb blockades in a 2D assembly of nanoparticles. AC measurements show a significant capacitance variation as a function of applied DC voltage with a maximum of relative variation value that is proportional to the particle density embedded in the dielectric layer and is in good agreement with the theoretical model. [source]


    Failure Mechanism of a Low-Temperature-Cofired Ceramic Capacitor with an Inner Ag Electrode

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2010
    Yi-Ting Shih
    Failure mechanism of a multilayer ceramic capacitor (MLCC) made of a low-fire BaNd2Ti4O12(BNT)+ZnO,B2O3 (ZB) dielectric with an inner pure silver electrode at elevated temperatures and voltages has been investigated. A nonlinear current,voltage leakage characteristic is found when the degradation of MLCC occurs, and the time to failure decreases with increasing either the temperature or the voltage. Results of microstructure, composition, and impedance analyses reveal that the failure is caused by silver diffusion in the ZB glass during sintering and highly accelerated life test. [source]


    A Pilot Study of a Low-Tilt Biphasic Waveform for Transvenous Cardioversion of Atrial Fibrillation: Improved Efficacy Compared with Conventional Capacitor-Based Waveforms in Patients

    PACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 8 2008
    BENEDICT M. GLOVER M.D.
    Background:The optimal waveform tilt for defibrillation is not known. Most modern defibrillators used for the cardioversion of atrial fibrillation (AF) employ high-tilt, capacitor-based biphasic waveforms. Methods:We have developed a low-tilt biphasic waveform for defibrillation. This low-tilt waveform was compared with a conventional waveform of equivalent duration and voltage in patients with AF. Patients with persistent AF or AF induced during a routine electrophysiology study (EPS) were randomized to receive either the low-tilt waveform or a conventional waveform. Defibrillation electrodes were positioned in the right atrial appendage and distal coronary sinus. Phase 1 peak voltage was increased in a stepwise progression from 50 V to 300V. Shock success was defined as return of sinus rhythm for ,30 seconds. Results:The low-tilt waveform produced successful termination of persistent AF at a mean voltage of 223 V (8.2 J) versus 270 V (6.7 J) with the conventional waveform (P = 0.002 for voltage, P = ns for energy). In patients with induced AF the mean voltage for the low-tilt waveform was 91V (1.6 J) and for the conventional waveform was 158 V (2.0 J) (P = 0.005 for voltage, P = ns for energy). The waveform was much more successful at very low voltages (less than or equal to 100 V) compared with the conventional waveform (Novel: 82% vs Conventional 22%, P = 0.008). Conclusion:The low-tilt biphasic waveform was more successful for the internal cardioversion of both persistent and induced AF in patients (in terms of leading edge voltage). [source]


    Surface Modification of Carbon Electrode for Electric Double Layer Capacitor

    PLASMA PROCESSES AND POLYMERS, Issue S1 2007
    Daisuke Tashima
    Abstract In this research, spatio-temporal profiles of positive and negative charges in an electric double layer capacitor (EDLC) which consists of activated carbon, treated by plasma discharges were measured. The plasma type was a high frequency glow discharge and the sample of activated carbon is set in the center of glow discharge. Optimal conditions for plasma surface treatment of activated carbon was examined from 0 to 60 min at 150,C in nitrogen gas. As a result, nitrogen atom was doped onto the surface layer of the activated carbon. In addition, electron spectroscopy for chemical analysis (ESCA) spectra of nitrogen in the activated carbon was examined. By etching the surface layer of carbon electrode exposed to the plasma, the doped nitrogen atom penetrated about 3 nm of the surface layer of carbon electrode after 60 min of plasma surface treatment. [source]


    Synthesis and Characterization of Nanostructured Manganese Dioxide Used as Positive Electrode Material for Electrochemical Capacitor with Lithium Hydroxide Electrolyte

    CHINESE JOURNAL OF CHEMISTRY, Issue 1 2008
    An-Bao YUAN
    Abstract A nanostructured manganese dioxide electrode material was prepared using a solid-reaction route starting with MnCl24H2O and NH4HCO3, and its electrochemical performance as a positive electrode for MnO2/activated carbon hybrid supercapacitor with 1 molL,1 LiOH electrolyte was reported. The material was proved to be a mixture of nanostructured , -MnO2 and , -MnO2 containing some bound water in the structure, which was characterized by X-ray diffraction analysis, infrared spectrum analysis, and transmission electron microscope observation. Electrochemical properties of the MnO2 electrode and the MnO2/AC capacitor were investigated by cyclic voltammetry, ac impedance and galvanostatic charge/discharge methods. Experimental results showed that the MnO2 electrode exhibited faradaic pseudocapacitance behavior and higher specific capacitance in 1 molL,1 LiOH electrolyte. The MnO2/AC hybrid capacitor with 1 molL,1 LiOH electrolyte presented excellent rate charge/discharge ability and cyclic stability. [source]


    High Power Density Electric Double Layer Capacitor with Improved Activated Carbon

    CHINESE JOURNAL OF CHEMISTRY, Issue 2 2003
    Yang Hui
    Abstract The improvement on commercial activated carbon (AC) through the reactivation under steam in the presence of NiCl2 catalyst leads to the increases of both energy and power densities of electric double layer (dl) capacitors. When AC was treated at 875 C for 1 h, its discharge specific capacitance increases up to 53.67 F g,1, an increase of about 25% compared to the as-received AC. Moreover, a significant increase in high rate capability of electric dl capacitor was found after the improvements. Surprisingly, both the treated and untreated AC samples showed similar specific surface area and pore size distribution, but some changes in the surface groups and their concentrations after reactivation were verified by X-photoelectron spectra. Thus, it is reasonable to conclude that the decrease in the surface concentration of the carbonyl-containing species for the improved AC results in an increase of accessibility of the pores to the organic electrolyte ion, causing the enhancements of both the specific capacitance and high rate capability. [source]


    Capacitors with an Equivalent Oxide Thickness of <0.5 nm for Nanoscale Electronic Semiconductor Memory

    ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010
    Seong Keun Kim
    Abstract The recent progress in the metal-insulator-metal (MIM) capacitor technology is reviewed in terms of the materials and processes mostly for dynamic random access memory (DRAM) applications. As TiN/ZrO2 -Al2O3 -ZrO2/TiN (ZAZ) type DRAM capacitors approach their technical limits, there has been renewed interest in the perovskite SrTiO3, which has a dielectric constant of >100, even at a thickness ,10 nm. However, there are many technical challenges to overcome before this type of MIM capacitor can be used in mass-production compatible processes despite the large advancements in atomic layer deposition (ALD) technology over the past decade. In the mean time, rutile structure TiO2 and Al-doped TiO2 films might find space to fill the gap between ZAZ and SrTiO3 MIM capacitors due to their exceptionally high dielectric constant among binary oxides. Achieving a uniform and dense rutile structure is the key technology for the TiO2 -based dielectrics, which depends on having a dense, uniform and smooth RuO2 layer as bottom electrode. Although the Ru (and RuO2) layers grown by ALD using metal-organic precursors are promising, recent technological breakthroughs using the RuO4 precursor made a thin, uniform, and denser Ru and RuO2 layer on a TiN electrode. A minimum equivalent oxide thickness as small as 0.45 nm with a low enough leakage current was confirmed, even in laboratory scale experiments. The bulk dielectric constant of ALD SrTiO3 films, grown at 370 C, was ,150 even with thicknesses ,15 nm. The recent development of novel group II precursors made it possible to increase the growth rate largely while leaving the electrical properties of the ALD SrTiO3 film intact. This is an important advancement toward the commercial applications of these MIM capacitors to DRAM as well as to other fields, where an extremely high capacitor density and three-dimensional structures are necessary. [source]


    High K Capacitors and OFET Gate Dielectrics from Self-Assembled BaTiO3 and (Ba,Sr)TiO3 Nanocrystals in the Superparaelectric Limit

    ADVANCED FUNCTIONAL MATERIALS, Issue 4 2010
    Limin Huang
    Abstract Nanodielectrics is an emerging field with applications in capacitors, gate dielectrics, energy storage, alternatives to Li-ion batteries, and frequency modulation in communications devices. Self-assembly of high k dielectric nanoparticles is a highly attractive means to produce nanostructured films with improved performance,namely dielectric tunability, low leakage, and low loss,as a function of size, composition, and structure. One of the major challenges is conversion of the nanoparticle building block into a reliable thin film device at conditions consistent with integrated device manufacturing or plastic electronics. Here, the development of BaTiO3 and (Ba,Sr)TiO3 superparaelectric uniform nanocrystal (8,12,nm) films prepared at room temperature by evaporative driven assembly with no annealing step is reported. Thin film inorganic and polymer composite capacitors show dielectric constants in the tunable range of 10,30, dependent on composition, and are confirmed to be superparaelectric. Organic thin film transistor (TFT) devices on flexible substrates demonstrate the readiness of nanoparticle-assembled films as gate dielectrics in device fabrication. [source]


    Hard Macrocellular Silica Si(HIPE) Foams Templating Micro/Macroporous Carbonaceous Monoliths: Applications as Lithium Ion Battery Negative Electrodes and Electrochemical Capacitors

    ADVANCED FUNCTIONAL MATERIALS, Issue 19 2009
    Nicolas Brun
    Abstract By using Si(HIPEs) as hard, exotemplating matrices, interconnected macro-/microporous carbon monolith-type materials with a surface area of around 600,m2 g,1 are synthesized and shaped. The carbonaceous foams exhibit a conductivity of 20,S cm,1, addressed with excellent mechanical properties (Young's modulus of 0.2,GPa and toughness of 13,J g,1, when the carbon core is optimized). The above-mentioned specificities, combined with the fact that the external shape and size can be easily designed on demand, are of primary importance for applications. The functionality of these carbonaceous monoliths is tested as both an electrochemical capacitor and a lithium ion negative electrode. The electrochemical capacitors' voltage,current profiles exhibit a non-ideal rectangular response, confirming the double-layer behavior of the carbon studied, while the charge-discharge current profile of the electric double-layer capacitor is directly proportional to the scan where the current response during charge and discharge exhibits high reversibility. When acting as a lithium ion negative electrode, after initial irreversibility, a good cyclability is obtained, associated with a stable capacity of 200,mA h g,1 during the first 50 cycles at a reasonable current density (C/10). [source]


    Settling the "Dead Layer" Debate in Nanoscale Capacitors

    ADVANCED MATERIALS, Issue 48 2009
    Li-Wu Chang
    Permittivity peaks in single crystal thin film capacitors are strongly suppressed compared to bulk in the case of Pt/SrTiO3/Pt, but are relatively unaffected in Pt/BaTiO3/Pt structures. This is consistent with the recent suggestion that subtle variations in interfacial bonding between the dielectric and electrode are critical in determining the presence or absence of inherent dielectric "dead layers". [source]


    Fabrication and Tunable Dielectric Properties of (Ba0.7Sr0.3)TiO3 -Glass-Based Thick-Film Capacitors

    INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 2 2009
    Pulipparambil Vasu Divya
    Ferroelectric glass,ceramics of composition 0.90 (Ba0.7Sr0.3) TiO3,0.10(B2O3:SiO2) (0.90 BST:0.10 BS) synthesized by sol,gel method have been used for the preparation of dielectric thick-film inks. The particle dispersion of the glass,ceramic powders in the thick-film ink formulations have been studied through rheological measurements for fabricating thick-film capacitors by screen printing technique. The thick films derived from such glass,ceramics are found to sinter at considerably lower temperatures than the pure ceramic, and exhibit good dielectric characteristics with a tunability of 32% at 1 MHz under a dc bias field of 35 kV/cm. [source]


    New Approach to Biphasic Waveforms for Internal Defibrillation:

    JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2000
    Fully Discharging Capacitors
    Internal Defibrillation with Fully Discharging Capacitors. Introduction: The use of two independent, fully discharging capacitors for each phase of a biphasic defibrillation waveform may lead to the design of a simpler, smaller, internal defibrillator. The goal of this study was to determine the optimal combination of capacitor sizes for such a waveform. Methods and Results: Eight full-discharge (95/95% tilt), biphasic waveforms produced by several combinations of phase-1 capacitors (30, 60, and 90 ,F) and phase-2 capacitors (1/3, 2/3, and 1.0 times the phase-1 capacitor) were tested and compared to a single-capacitor waveform (120 ,F, 65/65% tilt) in a pig ventricular fibrillation model (n = 12, 23 2 kg). In the full-discharge waveforms, phase-2 peak voltage was equal to phase-1 peak voltage. Shocks were delivered between a right ventricular lead and a left pectoral can electrode. E50s and V50s were determined using a ten-step Bayesian process. Full-discharge waveforms with phase-2 capacitors of ,40 ,F had the same E50 (6.7 1.7 J to 7.3 3.9 J) as the single-capacitor truncated waveform (7.3 3.7 J), whereas waveforms with phase-2 capacitors of ,60 ,F had an extremely high E50 (14.5 10.8 J or greater, P < 0.05). Moreover, of the former set of energy-efficient waveforms, those with phase-1 capacitors of ,60 ,F additionally exhibited V50s that were equivalent to the V50 of the single-capacitor waveform (344 65 V to 407 50 V vs 339 83 V). Conclusion: Defibrillation efficacy can be maintained in a full-discharge, two-capacitor waveform with the proper choice of capacitors. [source]


    Intragranular Voids and dc Degradation in (CaO+MgO) Codoped BaTiO3 Multilayer Ceramic Capacitors

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2009
    Hwan-Wen Lee
    The microstructure of multilayer ceramic capacitors (MLCC) based on BaTiO3 and nickel electrode, have been analyzed using the scanning and the transmission electron microscopy. In order to investigate how MgO improves MLCC against dc degradation, both CaO doped and (CaO+MgO) codoped chips, pristine as well as highly accelerated life-tested, are studied. BaTiO3 grains are characterized by both the types I and II core shell structure, which is typical of MLCC exhibiting the X7R dielectric behavior. Intragranular voids are found in BaTiO3 grains in the vicinity of the electrode,dielectric interface. Void-containing grains are more frequently observed and voids are more abundant in (CaO+MgO) codoped chips than in CaO doped ones. Higher concentration of oxygen vacanciesis induced extrinsically from both MgO codoping and Ni diffusion into BaTiO3 grains along the electrode,dielectric interface during sintering. Such oxygen vacancies have reacted with both cation vacanciesandby an inverse Schottky defect reaction and condensed to form voids. This reaction requiring cation and oxygen vacancies in the stoichiometric BaTiO3 composition of 1:1:3 has significantly decreased the randomly distributed mobile oxygen vacancies, and contributes to improve against dc degradation. [source]


    Role of Length Scale on Pressure Increase and Yield of Poly(vinyl butyral),Barium Titanate,Platinum Multilayer Ceramic Capacitors during Binder Burnout

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2000
    Leo C.-K.
    The binder-burnout kinetics of poly(vinyl) butyral from BaTiO3 multilayer ceramic capacitors with platinum metal electrodes were analyzed by combining thermogravimetric analysis with infrared spectroscopy. The rate of weight loss was accelerated when both BaTiO3 and platinum metal were present, and the presence of both metal and ceramic enhanced the production of CO2. The activation energy and pre-exponential factor were determined by analysis of the weight-loss data with a first-order kinetics model. Then, the decomposition kinetics were incorporated into a coupled heat- and mass-transport model to predict pressure increases as a function of the heating cycle. The heating cycles determined in this manner then were used to evaluate the yield of capacitors 1.3,3.8 cm long and 0.3,1.3 cm high. The optimum yield was realized at an aspect ratio (height:length) of 1:3. [source]


    Effects of Calcination Temperature and A/B Ratio on the Dielectric Properties of (Ba,Ca)(Ti,Zr,Mn)O3 for Multilayer Ceramic Capacitors with Nickel Electrodes

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2000
    Wen-Hsi Lee
    The electrical performance of multilayer ceramic capacitors (MLCCs) with Ni inner electrodes, made from (Ba,Ca)(Ti,Zr,Mn)O3 (BCTZM), is closely related to the calcination temperature and the A/B ratio of the powder. For materials showing A/B = 1.000, the lifetime, the breakdown voltage, and the RC increase with higher calcination temperatures. No significant effect of the calcination temperature on RC and lifetime was found for materials showing A/B = 0.991. The isoelectric point of BCTZM is shifted toward higher pH values when the calcination temperature is decreased. The above results are attributed to the colloidal stability of aqueous BCTZM suspensions and the resulting green density of powder compacts. [source]


    Investigation of top gate electrode options for high-k gate dielectric MOS capacitors

    PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2008
    D. C. Moschou
    Abstract Capacitors with a high-k HfO2 film as gate dielectric were fabricated, using three different variations for the top gate electrode. This way it was possible to acquire important information on which kind of gate material should be used in combination with HfO2 as a gate insulator for optimum performance of possible low temperature applications, such as high-k TFTs. The variations of gate electrode were e-gun evaporated Al, sputtered W and CVD polysilicon followed by ion implantation and annealing. The capacitors were then characterized with capacitance-voltage measurements and current-voltage measurements. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Electrical Properties of MIS Capacitors with AlN Films Synthesized by Pulsed Laser Deposition

    PLASMA PROCESSES AND POLYMERS, Issue 2 2006
    Silvia Bakalova
    Abstract Summary: We manufactured for the first time MIS capacitors based on aluminium nitride (AlN) thin films synthesized by Pulsed Laser Deposition (PLD). AlN films were deposited on Si substrates by PLD from AlN targets in nitrogen ambient by multi-pulse ablation using a UV KrF excimer laser source (,,=,248 nm, ,,=,7 ns). The structures we prepared were electrically characterized by C-V and I-V complementary measurements. Our studies evidence the formation of good interfaces, and of defects into the film bulk which are electrically active. This justifies further developments in view of future applications of PLD synthesized AlN thin films as a dielectric alternatives to SiO2. The distribution of the interface trap densities (Dit) in Si bandgap for AlN/Si structures synthesized at different N2 pressures. [source]


    In situ Chemical Deposition of Polyaniline on Activated Carbon for Electrochemical Capacitors

    CHINESE JOURNAL OF CHEMISTRY, Issue 1 2006
    Zhang-Hua Zhou
    Abstract Polyaniline (PA) film was chemically deposited onto the surface of activated carbon (AC) uniformly. Chemical deposition was carried out in 0.1 mol/L aniline plus 0.5 mol/L H2SO4 solution adopting V2O5nH2O coated on the surface of activated carbon as oxidant. The surface morphologies and structures of the composite materials were characterized by scanning electron microscopy and FT-IR spectra. The electrochemical properties of the composite material electrodes were studied by cyclic voltammetry and constant current charge/discharge tests in 1 mol/L H2SO4 solutions. The specific capacitance of composite materials was exhibited as high as 237.5 F/g at a current density of 1.0 A/g compared with a value of 120 F/g for pure carbon electrode. Good power characteristic and good stability of composite electrodes were also demonstrated. [source]


    Spectroscopic Diagnostics of Pulsed arc Plasmas for Particle Generation

    CONTRIBUTIONS TO PLASMA PHYSICS, Issue 8 2008
    K. Behringer
    Abstract Pulsed arc plasmas were diagnosed by means of emission spectroscopy. A capacitor was discharged through argon and hydrogen leading to a few cycles of damped current oscillation with ,120 ,s period and 5-12 kA maximum current. Spectroscopic measurements in the visible range were carried out in order to characterise the electron temperature and density in the arc channel as well as electron and gas temperatures in the afterglow plasmas. Spectra were integrated over 10 ,s time windows and shifted in time from pulse to pulse. The plasmas also contained substantial fractions of electrode material (brass), namely copper and zinc. The electron density was measured in the conventional way from the broadening of H, or from the Ar I Stark width. In the arc channel, it ranged from about 3 1022 to 2 1023 m,3. The broadening of Zn II lines could also be used. Ratios of Ar I to Ar II and of Zn I to Zn II line intensities were analysed for the electron temperature. Line pairs were found which lay conveniently close in one frame of the spectrometer allowing automatic on-line analysis without relying on reproducibility. Atomic physics models including opacity were developed for Ar II and Zn II in order to check the existence of a Boltzmann distribution of their excited states. These calculations showed that the observed levels were in fact close to thermodynamic equilibrium, in particular, if the resonance lines were optically thick. Electron temperature measurements yielded values between 14000 K and 21000 K. The gas temperature in the afterglow, where particles should have formed, was derived from the rotational and vibrational temperatures of C2 molecular bands. Ratios between Cu I line intensities yielded the electron temperatures. Both were found to be a few 1000 K. ( 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Estimation of backward impedance on low-voltage distribution system using measured resonant current

    ELECTRICAL ENGINEERING IN JAPAN, Issue 3 2010
    Toru Miki
    Abstract Two estimation methods for a backward impedance of a power distribution system are proposed in this paper. According to the first method, the backward impedance is estimated based on information obtained from the frequency response of a transient current flowing into a capacitor connected to a distribution line. The backward impedance is determined from the attenuation constant and the resonant frequency calculated using the capacitance and the impedance of the power distribution system. These parameters can be reliably obtained from a frequency response of the transient current using the least square method. The accuracy of the method strongly depends on the origin on the time axis for Fourier transform. An additional estimate of the time-origin is required for an accurate estimation of the backward impedance. The second method estimates the backward impedance using two transient current waveforms obtained by alternately connecting different capacitors to a distribution line. The backward impedance can be represented as a function of the frequency responses of these currents. Since this method is independent from the time-origin, it is suitable for automatic measurements of the backward impedance. Proposed methods are applicable to the estimation of harmonic currents in distribution systems. In this paper, harmonic currents flowing through a distribution line are calculated based on the estimated backward impedance and on the measured values of voltage harmonics obtained by the instrument developed by the authors. 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(3): 28,40, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20900 [source]


    Voltage fluctuation compensator for Shinkansen

    ELECTRICAL ENGINEERING IN JAPAN, Issue 4 2008
    Tetsuo Uzuka
    Abstract In AC electric railways, three-phase voltage is changed into the single-phase circuit of two circuits with the Scott-connected transformer. If unbalancing of the load between single-phase circuits becomes large, voltage fluctuation becomes large on the three-phase side. Railway static power conditioner (RPC) was developed for the purpose of controlling voltage fluctuation on the three-phase side. An RPC is comprised of a pair of self-commutated PWM inverters. These inverters connect the main phase and teaser feeding buses, coupled with a DC side capacitor such as a back-to-back (BTB) converter. In this way, the two self-commutated inverters can act as a static var compensator (SVC) to compensate for the reactive power and as an active power accommodator from one feeding bus to another. 20 MVA/60 kV RPCs started commercial operation in 2002 at each two substations on the newly extended Tohoku Shinkansen for compensating voltage fluctuation on the three-phase side caused by traction loads, absorbing harmonic current. The results of operational testing indicate that an RPC can accommodate single-phase loads such as those of PWM-controlled Shinkansen and thyristor phase-controlled Shinkansen, and handle the exciting rush current of transformers, as well as compensate for harmonics successfully. 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(4): 25,34, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20397 [source]


    A 3-D dielectrophoretic filter chip

    ELECTROPHORESIS, Issue 7 2007
    Ciprian Iliescu Dr.
    Abstract The paper presents a 3-D filter chip employing both mechanical and dielectrophoretic (DEP) filtration, and its corresponding microfabrication techniques. The device structure is similar to a classical capacitor: two planar electrodes, made from a stainless steel mesh, and bonded on both sides of a glass frame filled with round silica beads. The solution with the suspension of particles flows through both the mesh-electrodes and silica beads filter. The top stainless steel mesh (with openings of 60,,m and wires of 30,,m-thickness) provides the first stage of filtration based on mechanical trapping. A second level of filtration is based on DEP by using the nonuniformities of the electric field generated in the capacitor due to the nonuniformities of the dielectric medium. The filter can work also with DC and AC electric fields. The device was tested with yeast cells (Saccharomyces cerevisae) and achieved a maximal trapping efficiency of 75% at an applied AC voltage of 200,V and a flow rate of 0.1,mL/min, from an initial concentration of cells of 5105 cells/mL. When the applied frequency was varieted in the range between 20 and 200,kHz, a minimal value of capture efficiency (3%) was notticed at 50,kHz, when yeast cells exhibit negative DEP and the cells are repelled in the space between the beads. [source]


    Dielectric Properties of a Printed Sol,Gel Matrix Composite,

    ADVANCED ENGINEERING MATERIALS, Issue 5 2010
    Tobias Lehnert
    Low temperature processable materials with high dielectric constants are required for application on flexible organic substrates, for example, in printed electronics. To date, mainly organic polymers with embedded functional particles have been investigated for this purpose. For the first time, we present a printable dielectric composite material composed of ferroelectric high permittivity particles (BaTiO3) bonded by a mainly inorganic sol,gel derived network. The exemplary optimization of the properties by varying the sol,gel precursor illustrates the potential of sol,gel chemistry for printable functional materials. An operational gravure printed capacitor including printed silver electrodes is presented. The measured dielectric constants are among the highest reported in literature for low temperature cured films with moderate dissipation factors. Besides these promising dielectric properties, this composite film shows a ferroelectric response. [source]


    Interactions and co-ordination of multiple-function FACTS controllers

    EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 1 2001
    H. F. Wang
    This paper presents two study cases of interaction analysis of multiple-function FACTS (flexible AC transmission systems) controllers: - the contradiction between the voltage and the damping control of a SVC (static VAr compensator); - the interaction between the voltage control of the DC link capacitor and the damping control of a UPFC (unified power-flow controller). In the paper, an algorithm is proposed for the co-ordinated design of these two multiple-function FACTS controllers. Examples are presented to confirm the analytical conclusions obtained and to demonstrate the effectiveness of the algorithm of the co-ordination proposed. [source]


    Capacitors with an Equivalent Oxide Thickness of <0.5 nm for Nanoscale Electronic Semiconductor Memory

    ADVANCED FUNCTIONAL MATERIALS, Issue 18 2010
    Seong Keun Kim
    Abstract The recent progress in the metal-insulator-metal (MIM) capacitor technology is reviewed in terms of the materials and processes mostly for dynamic random access memory (DRAM) applications. As TiN/ZrO2 -Al2O3 -ZrO2/TiN (ZAZ) type DRAM capacitors approach their technical limits, there has been renewed interest in the perovskite SrTiO3, which has a dielectric constant of >100, even at a thickness ,10 nm. However, there are many technical challenges to overcome before this type of MIM capacitor can be used in mass-production compatible processes despite the large advancements in atomic layer deposition (ALD) technology over the past decade. In the mean time, rutile structure TiO2 and Al-doped TiO2 films might find space to fill the gap between ZAZ and SrTiO3 MIM capacitors due to their exceptionally high dielectric constant among binary oxides. Achieving a uniform and dense rutile structure is the key technology for the TiO2 -based dielectrics, which depends on having a dense, uniform and smooth RuO2 layer as bottom electrode. Although the Ru (and RuO2) layers grown by ALD using metal-organic precursors are promising, recent technological breakthroughs using the RuO4 precursor made a thin, uniform, and denser Ru and RuO2 layer on a TiN electrode. A minimum equivalent oxide thickness as small as 0.45 nm with a low enough leakage current was confirmed, even in laboratory scale experiments. The bulk dielectric constant of ALD SrTiO3 films, grown at 370 C, was ,150 even with thicknesses ,15 nm. The recent development of novel group II precursors made it possible to increase the growth rate largely while leaving the electrical properties of the ALD SrTiO3 film intact. This is an important advancement toward the commercial applications of these MIM capacitors to DRAM as well as to other fields, where an extremely high capacitor density and three-dimensional structures are necessary. [source]


    Hard Macrocellular Silica Si(HIPE) Foams Templating Micro/Macroporous Carbonaceous Monoliths: Applications as Lithium Ion Battery Negative Electrodes and Electrochemical Capacitors

    ADVANCED FUNCTIONAL MATERIALS, Issue 19 2009
    Nicolas Brun
    Abstract By using Si(HIPEs) as hard, exotemplating matrices, interconnected macro-/microporous carbon monolith-type materials with a surface area of around 600,m2 g,1 are synthesized and shaped. The carbonaceous foams exhibit a conductivity of 20,S cm,1, addressed with excellent mechanical properties (Young's modulus of 0.2,GPa and toughness of 13,J g,1, when the carbon core is optimized). The above-mentioned specificities, combined with the fact that the external shape and size can be easily designed on demand, are of primary importance for applications. The functionality of these carbonaceous monoliths is tested as both an electrochemical capacitor and a lithium ion negative electrode. The electrochemical capacitors' voltage,current profiles exhibit a non-ideal rectangular response, confirming the double-layer behavior of the carbon studied, while the charge-discharge current profile of the electric double-layer capacitor is directly proportional to the scan where the current response during charge and discharge exhibits high reversibility. When acting as a lithium ion negative electrode, after initial irreversibility, a good cyclability is obtained, associated with a stable capacity of 200,mA h g,1 during the first 50 cycles at a reasonable current density (C/10). [source]


    Printable Ferroelectric PVDF/PMMA Blend Films with Ultralow Roughness for Low Voltage Non-Volatile Polymer Memory

    ADVANCED FUNCTIONAL MATERIALS, Issue 17 2009
    Seok Ju Kang
    Abstract Here, a facile route to fabricate thin ferroelectric poly(vinylidene fluoride) (PVDF)/poly(methylmethacrylate) (PMMA) blend films with very low surface roughness based on spin-coating and subsequent melt-quenching is described. Amorphous PMMA in a blend film effectively retards the rapid crystallization of PVDF upon quenching, giving rise to a thin and flat ferroelectric film with nanometer scale , -type PVDF crystals. The still, flat interfaces of the blend film with metal electrode and/or an organic semi-conducting channel layer enable fabrication of a highly reliable ferroelectric capacitor and transistor memory unit operating at voltages as low as 15,V. For instance, with a TIPS-pentacene single crystal as an active semi-conducting layer, a flexible ferroelectric field effect transistor shows a clockwise I,V hysteresis with a drain current bistability of 103 and data retention time of more than 15,h at 15,V gate voltage. Furthermore, the robust interfacial homogeneity of the ferroelectric film is highly beneficial for transfer printing in which arrays of metal/ferroelectric/metal micro-capacitors are developed over a large area with well defined edge sharpness. [source]


    Synthesis of Microporous Carbon Nanofibers and Nanotubes from Conjugated Polymer Network and Evaluation in Electrochemical Capacitor

    ADVANCED FUNCTIONAL MATERIALS, Issue 13 2009
    Xinliang Feng
    Abstract One-dimensional fibers and tubes are constructed through the oriented carbon-carbon cross-linking reactions towards rigid conjugated polymer networks. As the result, a template-free and one-step synthesis of CNTs and CNFs is achieved through a simple carbonization of the as-formed carbon-rich tubular and fiberlike polyphenylene precursors under argon. Microporous CNTs and CNFs with a surface area up to 900 m2 g,1 are obtained, together with HR-TEM characterizations indicating the formation of intrinsic microporous structure in these rigid carbon-rich networks. The primary electrochemical experiments reveal their promising applications as advanced electrodes in electrochemical double-layered capacitor (EDLC). [source]