共查询到20条相似文献,搜索用时 31 毫秒
1.
Ying Tian Jingwang Yan Liping Huang Rong Xue Lixing Hao Baolian Yi 《Materials Chemistry and Physics》2014
Nickel hydroxide consisting of loosely packed nanospheres was synthesized as positive electrode material for an asymmetric capacitor based on Ni(OH)2 and activated carbon (AC). Two series of supercapacitors were fabricated to investigate the effects of the single electrodes of Ni(OH)2 and AC on the electrochemical performance of asymmetric Ni(OH)2–AC capacitor. Parameters including cell voltage window, specific capacitance and cyclic stability were assessed. In one series of supercapacitors, mass of Ni(OH)2 was excessive while mass of AC was varied, the AC electrode thus constrained both the capacitance and the upper limit of cell voltage. Deficiency of AC resulted in lower specific capacitance and narrower cell voltage window but benefited to cyclic stability. In the other series of supercapacitors, the mass of AC was excessive whereas the mass of Ni(OH)2 was changeable in each cell, Ni(OH)2 electrode thus dominated both the capacitance and the lower limit of cell voltage. As a consequence, deficiency of Ni(OH)2 led to higher specific capacity and wider cell voltage window as well as lower cyclic stability. These results can contribute to improving understanding of and optimizing performance of asymmetric Ni(OH)2–AC capacitor. 相似文献
2.
A. M. Bechasnov V. L. Bratman N. G. Kolganov S. V. Mishakin S. V. Samsonov 《Technical Physics Letters》2010,36(2):140-143
A relativistic backward wave oscillator for the 10-GHz range with the oscillation frequency tuned within about 5% by changing
the accelerating voltage from 600 to 350 kV has been developed. Discrete variations in the voltage and the corresponding frequency
tuning from pulse to pulse is rapidly performed by changing the anode-cathode distance in the vacuum diode without breaking
vacuum in the working volume. During this, the electron beam power remains almost constant, while the output microwave power
varies within 0.4–0.8 GW. The introduction of a dielectric cylinder into the accelerating gap provides a smooth voltage drop
from 600 to 350 kV with the corresponding frequency tuning during a 20-ns pulse. 相似文献
3.
C. Lämmel M. Schneider M. Weiser A. Michaelis 《Materialwissenschaft und Werkstofftechnik》2013,44(7):641-649
A comparison between various methods for determining the capacitance and resistance of electrochemical double layer capacitors (EDLC) with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), galvanostatic charge‐discharge methods and cell voltage jump experiments are presented. Therefore, a commercially available electrochemical double layer capacitor was used. For the validation of the screw cell measurements the electrode foils were isolated and extracted from the commercial capacitor. The results support the adequacy of the screw cell tests for electrode materials on a laboratory scale. The comparison of methods shows in part strong differences. The reasons will therefore be discussed. Consequently, the determination of specific values requires methods which respect the influence of the actual tests or measurement frequency and exhibit the importance of an internationally accepted specification for electrochemical double layer capacitors material investigation. 相似文献
4.
A. L. Freidman S. I. Popkov S. V. Semenov P. P. Turchin 《Technical Physics Letters》2018,44(2):123-125
We describe a capacitive dilatometer for measuring the magnetostriction, piezoelectric effect, and linear thermal-expansion coefficient in the temperature range from 1.85 to 350 K in external magnetic fields of up to 90 kOe under a voltage of 1 kV, which operates on the basis of a Quantum Design PPMS commercial facility for studying the properties of solids. 相似文献
5.
世界钽粉生产工艺的发展 总被引:11,自引:1,他引:10
论述了国内外电容器级高压钽粉、中压钽粉、高比容钽粉的生产工艺发展过程。在钽粉生产工艺发展过程中,各种先进的装备被应用,各钽粉生产厂家围绕着钽粉比容的提高,杂质含量的降低,物理性能的优化等综合性能的改善,不断开发出新工艺、新技术,使钽粉适应并推动着钽电容器的发展。 相似文献
6.
D.S. Choi Jung-Rae Park T. Hahn N. Presser G.W. Stupian Fahad Khalid 《Thin solid films》2010,518(17):5007-5009
This paper describes the development of micro-capacitors with electrodes based on electrochemically grown vertical gold nanowire arrays. A high aspect-ratio anodized aluminum oxide template integrated on silicon dioxide/silicon substrates was exploited for fabricating a vertical array of nanowires with a high surface to volume ratio. Bismuth ferric oxide thin films were deposited to create high dielectric material between the electrodes using room temperature electrodeposition. This nanofabrication process may be compatible with a complementary metal-oxide-semiconductor (CMOS) process, therefore, this capacitor can be used for protecting and regulating the surge voltage biased to the CMOS circuits. This capacitor achieved a high density capacitance of 3.1 μF/m2 at 1 MHz, which was measured using a parallel plate set-up. 相似文献
7.
In this paper, an alternative method for measuring the voltage dependent capacitance variation (VDCV) of compressed-gas capacitors is described. In the proposed method, the VDCV of the capacitor under test is measured by comparing it with a capacitor standard supplied with the secondary (low) voltage of a potential transformer. This transformer has its primary parallel connected with the capacitor under test. The paper presents and criticizes the test results obtained in which an uncertainty of at least 0.5 ppm is achieved 相似文献
8.
XiaofengWANG DazhiWANG JiLIANG 《材料科学技术学报》2003,19(3):265-269
The electrochemical storage of energy in a special kind of active carbon materials used as capacitor electrodes is considered. Petroleum coke was used for preparation of carbons with different porosities by KOH and vapor etching with catalysis of FeCl3 in turn. Carbon electrodes were fabricated and used as electrodes of double layer capacitors.Nitrogen adsorption was used to characterize the porous structure of the carbons. The electrochemical performance of the capacitors in 6mol/L KOH was investigated with constant current charge and discharge experiments. A specific capacitance larger than 160F/g was achieved with an electrode composed of 75% active carbon with a specific surface area of 1180m^2/g and 20% graphite as conductive agent. Evaluation of capacitor performance was conducted by different techniques, e.g. voltammetry and impedance spectroscopy. Characteristics of the capacitor were also discussed. A hybrid power source consisting of nickel-hydrogen and double layer capacitor was demonstrated by powering successfully a simulated power load encountered in communication equipment. 相似文献
9.
水下等离子体声源在民用和军用领域都有广泛的应用,其发声机理和系统最优化设计是当前的研究热点。为了使声源的输出峰值压力y尽可能大,设计了放电电极间距(2mm,3mm,4mm)、储能电容容量(1uF,2uF,5uF)和充电电压(12kV,16kV,20kV)的三因素三水平正交试验方案,严格按照正交试验安排表进行试验,并用直观分析法对试验结果进行分析。结果表明:最优化的试验组合方案为A1B3C2,即放点电极间距2mm,储能电容容量5uF,充电电压16kV,估计出其峰值压力为9.864MPa,并通过试验验证了平均峰值压力为10.165MPa,与正交试验结论相符。该研究成果为水下离子体声源性能试验研究和最优化设计提供了依据。 相似文献
10.
A microprocessor-based, switched-battery capacitance meter has been developed. It consists of an analog part, based on a previously designed capacitance meter, and a digital part in which a microprocessor and a timer perform the main functions. The capacitance is measured indirectly by means of a time constant measurement. Two phases of the measurement process are involved in measuring the capacitance. The first phase, when a capacitor is charged, is based on the software counter-timer measurements. The second phase, when the capacitor is discharged, requires a hardware timer controlled by the microprocessor. The digital hardware reflects a different approach than used for the previous construction 相似文献
11.
fF量级高频微小电容测量在军工电子产品领域有着重要作用,针对微小电容测量仪500fF/1MHz点无法溯源的现状,研制了惰性气体封装的500fF高频标准电容器作为传递标准。建立高频小电容测量模型,基于“反算法”估算出500fF高频标准电容器分布参数,称作“理论推导”溯源方案,不确定度优于0.15%;利用3台同等量级的高频微小电容测量传递标准,称作“计量比对”溯源方案,不确定度优于0.07%。利用以上2种方案对同1台仪器开展溯源,实验数据结果基本一致,能够满足用户使用要求,为更低容值、更高频率的微小电容的溯源提供了可参考的路径。 相似文献
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14.
Himani Sharma Kanika Sethi P. Markondeya Raj Rao Tummala 《Journal of Materials Science: Materials in Electronics》2012,23(2):528-535
System integration and miniaturization demands are driving component technologies towards integrated thin films with higher
volumetric efficiencies and component densities. Among the various system components, achieving higher densities with capacitors,
integrated in thin film form has been a major challenge for the past few decades. This paper reports the first proof-of-concept
demonstration of a novel silicon-compatible high-density capacitor technology. The key novelty stems from the tremendous enhancement
in surface area from thin and porous copper nanoelectrodes and conformal alumina dielectric on such nanoelectrodes. Atomic
Layer Deposition was chosen as the dielectric process because of its self-limiting, defect-free and conformal deposition on
3-D structures. Alumina with its moderate permittivity and superior dielectric properties over large voltage ranges was employed
as the representative dielectric. Thin copper particulate electrodes with conformal counter electrodes showed 10 times higher
capacitance density compared to the planar devices, with similar leakage properties. Thicker electrodes showed enormous enhancement
in surface area but inferior leakage properties. Combination of compositional and morphological techniques was used to show
alumina conformality on complex 3-D structures of copper particulate electrode. Capacitance–Voltage and Current–Voltage characterizations
were carried out to confirm the feasibility of the novel high density 3-D capacitor structure. 相似文献
15.
A transformation formula for the standard screened capacitor with additional electrodes, which forms part of the GéT 158-96
State Standard, is derived and analyzed. The formula connects the voltage applied to the capacitor with the electric-field
strength at the center of the capacitor, and enables the voltage applied to the additional electrodes to be chosen in the
optimum way, and ensures that the electric field at the center of the capacitor is uniform.
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Translated from Izmeritel’naya Tekhnika, No. 7, pp. 37–39, July, 2007. 相似文献
16.
引述了Ta电容器与Al电容器、多层陶瓷电容器相比突出的性能与应用特征,分析了Ta电容器片式化、小型化促进电容器级Ta粉高比容化发展的新趋势,叙述了航空、航天和军工领域对高压电容器高可靠性能的需求,以及对中高压Ta粉向更高电压、更低SER方向发展的引领,回顾了电容器用高比容Ta粉、中高压Ta粉发展应用进程,介绍了经典氟钽酸钾(K2TaF7)金属Na还原法、电子束熔炼法、球磨片式化法生产的高比容Ta粉、高压Ta粉、中压(片状)Ta粉的性能、产品品级及关键技术,分析了30~80kμFV/gTa粉耐压性能影响因素,介绍了Ta粉高比容化、高压化新技术、装置、产品形貌、性能及优缺点,在此基础上提出了电容器级Ta粉高比容化、高压化创新进步的思路。 相似文献
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18.
A. L. Grokhol'skii 《Measurement Techniques》1961,4(3):242-244
Conclusions The above disc capacitor can be used for various purposes as a reference single-valued effective capacitance, or as a many-valued capacitance set at will to any value within its range, for testing or research purposes.The KVCh-8M capacitors are particularly convenient for determining the frequency characteristic of effective capacitances of other capacitors by the substitution method. In this method the measured capacitor is replaced at the high frequency by the KVCh-8M capacitor, which is set to the appropriate value by adjusting the distance between its plates.The preliminary adjustment is made with the capacitor screen removed, and the final adjustment through the opening in the screen.The actual capacitance of the disc trimmer is then calculated from (4) having measured its capacitance on a low-frequency bridge. Such a method of checking capacitors is very simple, since it does not require any accurate high-frequency capacity measuring devices. It is quite sufficient to have any type of Q-meter. 相似文献
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20.
《IEEE transactions on instrumentation and measurement》1968,17(4):226-231
A cross capacitor is a calculable one whose capacitance is ideally determinable from one length measurement of its electrodes. In the Electrotechnical Laboratory of Japan (ETL), a horizontal cross capacitor was constructed. In this model, ease of checking alignment of the horizontal electrode bars, and a simple driving mechanism to move the guard electrode, were emphasized. Because the movable guard electrode rests on, and is guided by, the horizontal electrode bars no special supporting mechanism is necessary. The displacement, which defines the length of the capacitor, is observed by interference fringes using a Hg198 source. The sensitivity obtained for electrical measurement is better than 0.01 aF and for length measurement better than 1/30 fringe. The errors of this capacitor are examined in detail and confirmed by experimental tests. The absolute capacitance was determined as 0.1 pF with an accuracy better than 1 ppm. 相似文献