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Specific Capacitance (specific + capacitance)
Selected AbstractsPrinted Sub-2 V Gel-Electrolyte-Gated Polymer Transistors and CircuitsADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Yu Xia Abstract The fabrication and characterization of printed ion-gel-gated poly(3-hexylthiophene) (P3HT) transistors and integrated circuits is reported, with emphasis on demonstrating both function and performance at supply voltages below 2,V. The key to achieving fast sub-2,V operation is an unusual gel electrolyte based on an ionic liquid and a gelating block copolymer. This gel electrolyte serves as the gate dielectric and has both a short polarization response time (<1,ms) and a large specific capacitance (>10,µF cm,2), which leads simultaneously to high output conductance (>2,mS mm,1), low threshold voltage (<1,V) and high inverter switching frequencies (1,10,kHz). Aerosol-jet-printed inverters, ring oscillators, NAND gates, and flip-flop circuits are demonstrated. The five-stage ring oscillator operates at frequencies up to 150,Hz, corresponding to a propagation delay of 0.7 ms per stage. These printed gel electrolyte gated circuits compare favorably with other reported printed circuits that often require much larger operating voltages. Materials factors influencing the performance of the devices are discussed. [source] Ordered Whiskerlike Polyaniline Grown on the Surface of Mesoporous Carbon and Its Electrochemical Capacitance Performance,ADVANCED MATERIALS, Issue 19 2006Y.-G. Wang Supercapacitor electrode materials must exhibit high specific capacitance and high-rate charge,discharge ability. The ordered whiskerlike polyaniline (PANI) reported here, which was synthesized in situ on the surface of mesoporous carbon by a novel process, is demonstrated to have these properties thanks to its ordered nanometer-sized "thorns" (see figure) and the V-shaped nanopores between them. [source] Activated carbon-polyethylenedioxythiophene composite electrodes for symmetrical supercapacitorsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008M. Selvakumar Abstract A symmetrical (p/p) supercapacitor has been fabricated by making use of activated carbon (AC)-polyethylenedioxythiophene (PEDOT)-composite electrodes for the first time. The composite electrodes have been prepared via electrochemical deposition of ,-napthalenesulphonate doped PEDOT onto AC electrodes. The characteristics of the electrodes and the fabricated supercapacitor have been investigated using cyclic voltammetry (CV) and AC impedance spectroscopy. The electrodes show a maximum specific capacitance of 158 Fg,1 at a scan rate of 10 mV s,1. This indicates that the in situ electro-polymerization of ethylenedioxythiophene (EDOT) onto AC could improve the performance of carbon electrodes for use in supercapacitors. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 [source] Supercapacitor studies of electrochemically deposited PEDOT on stainless steel substrateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2007S. Patra Abstract There has been increasing interest on various properties and applications of electronically conducting polymers. Polyethylenedioxythiophene (PEDOT) is an interesting polymer of this type as it exhibits very high ionic conductivity. In the present study, PEDOT has been electrochemically deposited on stainless steel (SS) substrate for supercapacitor studies. PEDOT/SS electrodes prepared in 0.1M H2SO4 in presence of a surfactant, sodium dodecylsulphate (SDS), have been found to yield higher specific capacitance (SC) than the electrodes prepared from neutral aqueous electrolyte. The effects of concentration of H2SO4, concentration of SDS, potential of deposition, and nature of supporting electrolytes used for capacitor studies on SC of the PEDOT/SS electrodes have been studied. SC values as high as 250 F/g in 1M oxalic acid have been obtained during the initial stages of cycling. However, there is a rapid decrease in SC on repeated charge-discharge cycling. Spectroscopic data reflect structural changes in PEDOT on extended cycling. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Preparation and Electrical Properties of an Anodized Al2O3,BaTiO3 Composite FilmJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2008Xianfeng Du A highly stable, water-based barium titanate BaTiO3, BT, sol was synthesized using a sol,gel route through a chelate lactate technique. Dried BT precursor powders were measured by thermal gravimetry,differential thermal analysis and X-ray diffraction. It was found that BT powders first converted into barium carbonate BaCO3, Ti complex, and intermediate phase Ba2Ti2O5CO3, and then transformed into perovskite phase BaTiO3. The crystallization temperature was about 550°C. The low-voltage etched aluminum foils were covered with BT sol by dip coating, and then annealed at 600°C for 30 min in air. After that, the samples were anodized in a 15 wt% aqueous solution of ammonium adipate. The voltage,time variations during anodizing were monitored, and the electrical properties of the anodic oxide film were examined. It was shown that the specific capacitance, the product of specific capacitance and withstanding voltage, and leakage current of samples with a BT coating were about 48.93%, 38.50%, and 167% larger than that without a BT coating, respectively. [source] Synthesis and Characterization of Nanostructured Manganese Dioxide Used as Positive Electrode Material for Electrochemical Capacitor with Lithium Hydroxide ElectrolyteCHINESE JOURNAL OF CHEMISTRY, Issue 1 2008An-Bao YUAN Abstract A nanostructured manganese dioxide electrode material was prepared using a solid-reaction route starting with MnCl2·4H2O and NH4HCO3, and its electrochemical performance as a positive electrode for MnO2/activated carbon hybrid supercapacitor with 1 mol·L,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 mol·L,1 LiOH electrolyte. The MnO2/AC hybrid capacitor with 1 mol·L,1 LiOH electrolyte presented excellent rate charge/discharge ability and cyclic stability. [source] High Power Density Electric Double Layer Capacitor with Improved Activated CarbonCHINESE JOURNAL OF CHEMISTRY, Issue 2 2003Yang 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] | ||||||||||