串联谐振CCPS电路结构研究

分析了高压串联谐振电容器充电电源(CCPS)中升压整流单元的等效电路,从而将实际的串联谐振CCPS等效成一个串并联谐振CCPS,有助于对串联谐振CCPS充电特性进行分析和设备调试.     

Solid state synthesis of hydrous ruthenium oxide for supercapacitors

A novel solid state route has been successfully developed for the synthesis of nano-scale hydrous ruthenium oxide (denoted as RuO₂·xH₂O). The procedure involves directly mixing RuCl₂·xH₂O with alkali to form RuO₂·xH₂O in a mortar at room temperature. Transmission electron microscopy (TEM) and N₂ adsorption–desorption measurement indicate that the RuO₂·xH₂O particle is approximately 30–40 nm with mesoporous structure. The crystalline structure and the electrochemical properties of RuO₂·xH₂O have been systematically explored as a function of annealing temperature. At lower temperatures, the RuO₂·xH₂O powder was found in an amorphous phase and the maximum capacitance of 655 F g⁻¹ was obtained by annealing at 150 °C. Higher temperatures (exceeding 175 °C) presumably converted amorphous phase into crystalline one and the corresponding specific capacitance dropped rapidly from 547 F g⁻¹ at 175 °C to 87 F g⁻¹ at 400 °C. Also, the dependence of electrochemical performance on annealing conditions of RuO₂·xH₂O was investigated by electrical impedance spectroscopy (EIS) study.     

Effect of treatment of activated carbon fiber cloth electrodes with cold plasma upon performance of electric double-layer capacitors

Charge/discharge behavior of electric double-layer capacitors composed of activated carbon fiber cloth (ACFC) electrodes and an organic electrolyte was investigated. The modification of the ACFC electrodes was performed using cold plasma generated in argon-oxygen atmosphere. The effect of the cold plasma treatment of the ACPC electrodes on the capacitor performance was discussed on the basis of the physical and chemical properties of the ACFC surface such as pore radius distribution and surface atom concentration.     

采用特高压隔离开关切合固定串补平台的电容式电压互感器的快速暂态试验

采用特高压(UHV)隔离开关切合串补平台时会产生隔离开关的重复击穿和快速暂态过程,可能导致邻近的电容式电压互感器(CVT)发生故障。为系统研究该暂态过程,通过特高压隔离开关切合串补平台模拟试验,测量了CVT上的过电压水平、快速暂态电压和电流波形,并分析了在CVT高压端上加装保护电阻和保护电感对快速暂态的抑制效果。试验结果表明:隔离开关操作时,CVT端口最大过电压约为1.54倍工频试验电压峰值,远小于其雷电冲击耐受电压,不会对CVT造成严重威胁。快速暂态电流振荡主频为500 k Hz,幅值可达2.2 k A,高幅值和高陡度的快速暂态电流可能会导致CVT内部元件局部过热,并产生局部过电压,进而导致CVT损坏。在CVT高压端加装保护电阻和保护电感能有效限制快速暂态电流的幅值和陡度,对CVT具有较好的保护效果。     

Preparation and properties of sol-gel derived PZT thin films for decoupling capacitor applications

Abstract

The use of ceramic thin films as decoupling capacitors offers the possibility of capacitor integration within the integrated circuit (IC) package, and potentially, directly onto the IC itself. Since these configurations minimize series inductance, higher operational speeds are possible. In the present study we have investigated the dielectric and leakage characteristics of sol-gel PZT films. For compositions near the morphotropic phase boundary, dielectric constants of 1000, and loss tangents of about 0.02, were observed. The current-voltage behavior of the capacitors was characterized by a non-linear response, and significant asymmetry in both the leakage and breakdown characteristics as a function of bias sign was observed. Breakdown fields for PZT 53/47 thin films were typically ～800 kV/cm at 25°C. We have also studied the effects of La and Nb dopant additions and alternate firing strategies on film leakage characteristics. Donor doping at 2–5 mol% lowered leakage currents by a factor of 10³ For films prepared by a multilayering approach, firing each layer to crystallization resulted in leakage currents that were a factor of 10² lower than films prepared by the standard process.     

Challenges for plasma etch integration of ferroelectric capacitors in FeRAM's and DRAM's

Abstract

The plasma etch process requirements are different for etching 2μm ferroelectric capacitor structures in FeRAM's (SRAM) vs. the smaller capacitor sizes (0.2–0.5 μm) of DRAM's. Plasma etch integration of ferroelectric capacitors presents three major differences between FeRAM's and DRAM's. The first difference is in the ferroelectric capacitor structure. FeRAM's use planar capacitors with top side metal contacts to vias while DRAM's use vertical capacitor structures with bottom side contact to a poly post structure. The second major difference is in material selected and thickness of layers. FeRAM's use thicker electrodes of Pt or Ir and a thicker PZT or Y1 dielectric layer. FeRAM's use a thick bottom electrode (and a thin top electrode) consisting of Pt, Ru or Ir and a thin BST dielectric layer. The third major difference is the plasma etch process requirements for the two devices. FeRAM's require a clean etch process and no corrosion. Profile is not critical but should be maintained at greater than 60° for 2μm bottom post electrode. An HRe^? (Highly Density Reflected Electron) etch system is used to develop process trends for ferroelectric capacitor applications.     

石墨烯电极材料的制备及其在双电层电容器中的应用

综述了目前石墨烯基电极材料的最新研究进展,介绍了化学还原法、活化法、热还原法、凝胶法、插入法等制备双电层电容器用石墨烯基电极材料的物理及化学方法,并对其良好的应用前景及今后的研究方向进行了展望。     

离子液体在片式铝电解电容器中的应用研究

利用离子液体具有的高热稳定性、高离子电导率的特点,选用了几种离子液体用作片式铝电解电容器工作电解液。性能测试结果表明,以马来酸或邻苯二甲酸的1,3-二烷基取代的咪唑盐或四氢吡咯盐的离子液体为电解质,所制成的电容器能通过105℃1000h寿命试验和耐回流焊接热试验。但电解液的闪火电压与传统电解液相比较低,一般只能做50V以下的低压电容器产品。     

Energy Storage in Ceramic Dielectrics

Historically, multilayer ceramic capacitors (MLC's) have not been considered for energy storage applications for two primary reasons. First, physically large ceramic capacitors were very expensive and, second, total energy density obtainable was not nearly so high as in electrolytic capacitor types. More recently, the fabrication technology for MLC's has improved significantly, permitting both significantly higher energy density and significantly lower costs. Simultaneously, in many applications, total energy storage has become smaller, and the secondary requirements of very low effective series resistance and effective series inductance (which, together, determine how efficiently the energy may be stored and recovered) have become more important. It is therefore desirable to reexamine energy storage in ceramics for contemporary commercial and near-commercial dielectrics. Stored energy is proportional to voltage squared only in the case of paraelectric insulators, because only they have capacitance that is independent of bias voltage. High dielectric constant materials, however, are ferroics (that is ferroelectric and/or antiferroelectric) and display significant variation of effective dielectric constant with bias voltage. The common ferroelectric materials, whether based upon barium titanate or lead manganese niobate (PMN), in the high-field limit, exhibit an energy storage which increases linearly with bias voltage. Mixed phase, ferroelectric plus antiferroelectric, dielectrics from the lead lanthanum zirconate titanate (PLZT) system, as predicted theoretically, show the best energy density at low to moderate fields. Surprisingly, maximum energy storage is not obtained in high dielectric constant materials but in those materials which display intermediate dielectric constant and the highest ultimate breakdown voltages.     

Studies on Me/Al-layered double hydroxides (Me = Ni and Co) as electrode materials for electrochemical capacitors

Me/Al-layered double hydroxides (Me=Ni and Co) prepared by the chemical co-precipitation method have been shown to be outstanding novel materials for electrochemical capacitors. The crystalline structure and the electrochemical properties of the electrodes have been studied by considering the effect of the mole ratio of nickel/cobalt. X-ray diffraction analysis shows that the materials belong to hexagonal system with layered structure. Cyclic voltammetric measurements indicate that Me/Al-layered double hydroxides with the Ni/Co mole ratio of 4:6 exhibit excellent capacitive properties within the potential range of 0.0-0.6 V versus Hg/HgO in 6 mol/L KOH electrolyte. Charge/discharge behaviors have been observed with the highest specific capacitance values of 960 F/g at the current density of 400 mA/g. Impedance studies show that the enhanced electrical properties and high frequency response are attributed to the presence of Co oxides.