False capacitance of supercapacitors

OpenAIRE

Ragoisha, G. A.; Aniskevich, Y. M.

2016-01-01

Capacitance measurements from cyclic voltammetry, galvanostatic chronopotentiometry and calculation of capacitance from imaginary part of impedance are widely used in investigations of supercapacitors. The methods assume the supercapacitor is a capacitor, while real objects correspond to different equivalent electric circuits and show various contributions of non-capacitive currents to the current which is used for calculation of capacitance. Specific capacitances which are presented in F g-1...

A Review of High Voltage Drive Amplifiers for Capacitive Actuators

DEFF Research Database (Denmark)

Huang, Lina; Zhang, Zhe; Andersen, Michael A. E.

2012-01-01

This paper gives an overview of the high voltage amplifiers, which are used to drive capacitive actuators. The amplifiers for both piezoelectric and DEAP (dielectric electroactive polymer) actuator are discussed. The suitable topologies for driving capacitive actuators are illustrated in detail...

In-situ polymerization of polyaniline on the surface of graphene oxide for high electrochemical capacitance

International Nuclear Information System (INIS)

Li, Xinlu; Zhong, Qineng; Zhang, Xinlin; Li, Tongtao; Huang, Jiamu

2015-01-01

Conducting polymer polyaniline (PANI) was in-situ polymerized on the surface of graphene oxide (GO) to form PANI encapsulating GO nanocomposites. The morphology and microstructure were examined by scanning electron microscopy, X-ray diffraction and N 2 absorption/desorption analysis. Electrochemical properties were tested by cyclic voltammetry, galvanostatic charge/discharge cycles and electrochemical impedance spectroscopy. Experimental results showed that ethanol assisted the dispersion of GO in water and facilitated the diffusion of polymer monomers on GO. GO as a support material can provide sufficient reaction sites for the deposition of aniline to form the film-like GO/PANI composites. Capacitive performance illustrated that the in-situ polymerization of PANI on GO was effective in improving the specific capacitance and cycling stability. - Highlights: • GO/PANI nanocomposites were achieved by in-situ polymerization. • PANI was uniformly coated on the surface of GO with addition of ethanol. • GO/PANI show high specific capacitance and cycling stability

High capacity and high rate capability of nitrogen-doped porous hollow carbon spheres for capacitive deionization

International Nuclear Information System (INIS)

Zhao, Shanshan; Yan, Tingting; Wang, Hui; Chen, Guorong; Huang, Lei; Zhang, Jianping; Shi, Liyi; Zhang, Dengsong

2016-01-01

Graphical abstract: - Highlights: • The nitrogen-doped porous hollow carbon spheres were prepared. • The obtained materials have a good capacitive deionization performance. • The electrodes show high salt adsorption rate and good regeneration performance. - Abstract: In this work, nitrogen-doped porous hollow carbon spheres (N-PHCS) were well prepared by using polystyrene (PS) spheres as hard templates and dopamine hydrochloride as carbon and nitrogen sources. Field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images demonstrate that the N-PHCS have a uniform, spherical and hollow structure. Nitrogen adsorption–desorption analysis shows that the N-PHCS have a high specific area of 512 m 2 /g. X-ray photoelectron spectroscopy result reveals that the nitrogen doping amount is 2.92%. The hollow and porous structure and effective nitrogen doping can contribute to large accessible surface area, efficient ion transport and good conductivity. In the electrochemical tests, we can conclude that the N-PHCS have a high specific capacitance value, a good stability and low inner resistance. The N-PHCS electrodes present a high salt adsorption capacity of 12.95 mg/g at a cell voltage of 1.4 V with a flow rate of 40 mL/min in a 500 mg/L NaCl aqueous solution. Moreover, the N-PHCS electrodes show high salt adsorption rate and good regeneration performance in the CDI process. With high surface specific area and effective nitrogen doping, the N-PHCS is promising to the CDI and other electrochemical applications.

High capacity and high rate capability of nitrogen-doped porous hollow carbon spheres for capacitive deionization

Energy Technology Data Exchange (ETDEWEB)

Zhao, Shanshan; Yan, Tingting; Wang, Hui; Chen, Guorong; Huang, Lei; Zhang, Jianping; Shi, Liyi; Zhang, Dengsong, E-mail: dszhang@shu.edu.cn

2016-04-30

Graphical abstract: - Highlights: • The nitrogen-doped porous hollow carbon spheres were prepared. • The obtained materials have a good capacitive deionization performance. • The electrodes show high salt adsorption rate and good regeneration performance. - Abstract: In this work, nitrogen-doped porous hollow carbon spheres (N-PHCS) were well prepared by using polystyrene (PS) spheres as hard templates and dopamine hydrochloride as carbon and nitrogen sources. Field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images demonstrate that the N-PHCS have a uniform, spherical and hollow structure. Nitrogen adsorption–desorption analysis shows that the N-PHCS have a high specific area of 512 m{sup 2}/g. X-ray photoelectron spectroscopy result reveals that the nitrogen doping amount is 2.92%. The hollow and porous structure and effective nitrogen doping can contribute to large accessible surface area, efficient ion transport and good conductivity. In the electrochemical tests, we can conclude that the N-PHCS have a high specific capacitance value, a good stability and low inner resistance. The N-PHCS electrodes present a high salt adsorption capacity of 12.95 mg/g at a cell voltage of 1.4 V with a flow rate of 40 mL/min in a 500 mg/L NaCl aqueous solution. Moreover, the N-PHCS electrodes show high salt adsorption rate and good regeneration performance in the CDI process. With high surface specific area and effective nitrogen doping, the N-PHCS is promising to the CDI and other electrochemical applications.

Hierarchical TiN nanoparticles-assembled nanopillars for flexible supercapacitors with high volumetric capacitance.

Science.gov (United States)

Qin, Ping; Li, Xingxing; Gao, Biao; Fu, Jijiang; Xia, Lu; Zhang, Xuming; Huo, Kaifu; Shen, Wenli; Chu, Paul K

2018-05-10

Titanium nitride (TiN) is an attractive electrode material in fast charging/discharging supercapacitors because of its excellent conductivity. However, the low capacitance and mechanical brittleness of TiN restricts its further application in flexible supercapacitors with high energy density. Thus, it is still a challenge to rationally design TiN electrodes with both high electrochemical and mechanical properties. Herein, the hierarchical TiN nanoparticles-assembled nanopillars (H-TiN NPs) array as binder free electrodes were obtained by nitriding of hierarchical titanium dioxide (TiO2) nanopillars, which was produced by a simple hydrothermal treatment of anodic TiO2 nanotubes (NTs) array in water. The porous TiN nanoparticles connected to each other to form ordered nanopillar arrays, effectively providing larger specific surface area and more active sites for charge storage. The H-TiN NPs delivered a high volumetric capacitance of 120 F cm-3 at 0.83 A cm-3, which is better than that of TiN NTs arrays (69 F cm-3 at 0.83 A cm-3). After assembling into all-solid-state devices, the H-TiN NPs based supercapacitors exhibited outstanding volumetric capacitance of 5.9 F cm-3 at 0.02 A cm-3 and a high energy density of 0.53 mW h cm-3. Our results reveal a new strategy to optimize the supercapacitive performance of metal nitrides.

Scalable Approach to Highly Efficient and Rapid Capacitive Deionization with CNT-Thread As Electrodes.

Science.gov (United States)

Moronshing, Maku; Subramaniam, Chandramouli

2017-11-22

A scalable route to highly efficient purification of water through capacitive deionization (CDI) is reported using CNT-thread as electrodes. Electro-sorption capacity (q e ) of 139 mg g -1 and average salt-adsorption rate (ASAR) of 2.78 mg g -1 min -1 achieved here is the highest among all known electrode materials and nonmembrane techniques, indicating efficient and rapid deionization. Such exceptional performance is achieved with feedstock concentrations (≤1000 ppm) where conventional techniques such as reverse osmosis and electrodialysis prove ineffective. Further, both cations (Na + , K + , Mg 2+ , and Ca 2+ ) and anions (Cl - , SO 4 2- and NO 3 - ) are removed with equally high efficiency (∼80%). Synergism between electrical conductivity (∼25 S cm -1 ), high specific surface area (∼900 m 2 g -1 ), porosity (0.7 nm, 3 nm) and hydrophilicity (contact angle ∼25°) in CNT-thread electrode enable superior contact with water, rapid formation of extensive electrical double layer and consequently efficient deionization. The tunable capacitance of the device (0.4-120 mF) and its high specific capacitance (∼27.2 F g -1 ) enable exceptional performance across a wide range of saline concentrations (50-1000 ppm). Facile regeneration of the electrode and reusability of the device is achieved for several cycles. The device demonstrated can desalinate water as it trickles down its surface because of gravity, thereby eliminating the requirement of any water pumping system. Finally, its portable adaptability is demonstrated by operating the device with an AA battery.

Surfactant free nickel sulphide nanoparticles for high capacitance supercapacitors

Science.gov (United States)

Nandhini, S.; Muralidharan, G.

2018-04-01

The surfactant free nickel sulphide nanoparticles were synthesized via facile hydrothermal method towards supercapacitor applications. The formation of crystalline spherical nanoparticles was confirmed through structural and morphological studies. Electrochemical behaviour of the electrode was analyzed using cyclic voltammetry (CV), galvanostatic charge-discharge studies (GCD) and electrochemical impedance spectroscopy (EIS). The CV studies imply that specific capacitance of the electrode arises from a combination of surface adsorption and Faradic reaction. The NiS electrode delivered a specific capacitance of about 529 F g-1 at a current density of 2 A g-1 (GCD measurements). A profitable charge transfer resistance of 0.5 Ω was obtained from EIS. The 100 % of capacity retention even after 2000 repeated charge-discharge cycles could be observed in 2 M KOH electrolyte at a much larger rate of 30 A g-1. The experimental results suggest that nickel sulphide is a potential candidate for supercapacitor applications.

Investigation of capacitance characteristics in metal/high-k

Indian Academy of Sciences (India)

Keywords. C − V characteristic; high-k dielectric; interface state density; MIS structure; nanotechnology; TCAD simulation. Abstract. Capacitance vs. voltage ( C − V ) curves at AC high frequency of a metal–insulator–semiconductor (MIS) capacitorare investigated in this paper. Bi-dimensional simulations with Silvaco TCAD ...

Specific methodology for capacitance imaging by atomic force microscopy: A breakthrough towards an elimination of parasitic effects

Energy Technology Data Exchange (ETDEWEB)

Estevez, Ivan [Laboratoire de Génie Électrique de Paris (LGEP), UMR 8507 CNRS-Supélec, Paris-Sud and UPMC Paris 06 Universities, 11 rue Joliot-Curie, Plateau de Moulon, 91192 Gif-sur-Yvette Cedex (France); Concept Scientific Instruments, ZA de Courtaboeuf, 2 rue de la Terre de Feu, 91940 Les Ulis (France); Chrétien, Pascal; Schneegans, Olivier; Houzé, Frédéric, E-mail: houze@lgep.supelec.fr [Laboratoire de Génie Électrique de Paris (LGEP), UMR 8507 CNRS-Supélec, Paris-Sud and UPMC Paris 06 Universities, 11 rue Joliot-Curie, Plateau de Moulon, 91192 Gif-sur-Yvette Cedex (France)

2014-02-24

On the basis of a home-made nanoscale impedance measurement device associated with a commercial atomic force microscope, a specific operating process is proposed in order to improve absolute (in sense of “nonrelative”) capacitance imaging by drastically reducing the parasitic effects due to stray capacitance, surface topography, and sample tilt. The method, combining a two-pass image acquisition with the exploitation of approach curves, has been validated on sets of calibration samples consisting in square parallel plate capacitors for which theoretical capacitance values were numerically calculated.

Vertically aligned BCN nanotubes with high capacitance.

Science.gov (United States)

Iyyamperumal, Eswaramoorthi; Wang, Shuangyin; Dai, Liming

2012-06-26

Using a chemical vapor deposition method, we have synthesized vertically aligned BCN nanotubes (VA-BCNs) on a Ni-Fe-coated SiO(2)/Si substrate from a melamine diborate precursor. The effects of pyrolysis conditions on the morphology and thermal property of grown nanotubes, as well as the nanostructure and composition of an individual BCN nanotube, were systematically studied. It was found that nitrogen atoms are bonded to carbons in both graphitic and pyridinic forms and that the resultant VA-BCNs grown at 1000 °C show the highest specific capacitance (321.0 F/g) with an excellent rate capability and high durability with respect to nonaligned BCN (167.3 F/g) and undoped multiwalled carbon nanotubes (117.3 F/g) due to synergetic effects arising from the combined co-doping of B and N in CNTs and the well-aligned nanotube structure.

Electropolymerized Star-Shaped Benzotrithiophenes Yield π-Conjugated Hierarchical Networks with High Areal Capacitance

KAUST Repository

Ringk, Andreas

2016-03-30

High-surface-area π-conjugated polymeric networks have the potential to lend outstanding capacitance to supercapacitors because of the pronounced faradaic processes that take place across the dense intimate interface between active material and electrolytes. In this report, we describe how benzo[1,2-b:3,4-b’:5,6-b’’]trithiophene (BTT) and tris-EDOT-benzo[1,2-b:3,4-b’:5,6-b’’]trithiophene (TEBTT) can serve as 2D (trivalent) building blocks in the development of electropolymerized hierarchical π-conjugated frameworks with particularly high areal capacitance. In comparing electropolymerized networks of BTT, TEBTT, and their copolymers with EDOT, we show that P(TEBTT/EDOT)-based frameworks can achieve higher areal capacitance (e.g., as high as 443.8 mF cm-2 at 1 mA cm-2) than those achieved by their respective homopolymers (PTEBTT and PEDOT) in the same experimental conditions of electrodeposition (PTEBTT: 271.1 mF cm-2 (at 1 mA cm-2) and PEDOT: 12.1 mF cm-2 (at 1 mA cm-2)). For example, P(TEBTT/EDOT)-based frameworks synthesized in a 1:1 monomer-to-comonomer ratio show a ca. 35x capacitance improvement over PEDOT. The high areal capacitance measured for P(TEBTT/EDOT) copolymers can be explained by the open, highly porous hierarchical morphologies formed during the electropolymerization step. With >70% capacitance retention over 1,000 cycles (up to 89% achieved), both PTEBTT- and P(TEBTT/EDOT)-based frameworks are resilient to repeated electrochemical cycling and can be considered promising systems for high life cycle capacitive electrode applications.

Electropolymerized Star-Shaped Benzotrithiophenes Yield π-Conjugated Hierarchical Networks with High Areal Capacitance

KAUST Repository

Ringk, Andreas; Lignie, Adrien; Hou, Yuanfang; Alshareef, Husam N.; Beaujuge, Pierre

2016-01-01

High-surface-area π-conjugated polymeric networks have the potential to lend outstanding capacitance to supercapacitors because of the pronounced faradaic processes that take place across the dense intimate interface between active material and electrolytes. In this report, we describe how benzo[1,2-b:3,4-b’:5,6-b’’]trithiophene (BTT) and tris-EDOT-benzo[1,2-b:3,4-b’:5,6-b’’]trithiophene (TEBTT) can serve as 2D (trivalent) building blocks in the development of electropolymerized hierarchical π-conjugated frameworks with particularly high areal capacitance. In comparing electropolymerized networks of BTT, TEBTT, and their copolymers with EDOT, we show that P(TEBTT/EDOT)-based frameworks can achieve higher areal capacitance (e.g., as high as 443.8 mF cm-2 at 1 mA cm-2) than those achieved by their respective homopolymers (PTEBTT and PEDOT) in the same experimental conditions of electrodeposition (PTEBTT: 271.1 mF cm-2 (at 1 mA cm-2) and PEDOT: 12.1 mF cm-2 (at 1 mA cm-2)). For example, P(TEBTT/EDOT)-based frameworks synthesized in a 1:1 monomer-to-comonomer ratio show a ca. 35x capacitance improvement over PEDOT. The high areal capacitance measured for P(TEBTT/EDOT) copolymers can be explained by the open, highly porous hierarchical morphologies formed during the electropolymerization step. With >70% capacitance retention over 1,000 cycles (up to 89% achieved), both PTEBTT- and P(TEBTT/EDOT)-based frameworks are resilient to repeated electrochemical cycling and can be considered promising systems for high life cycle capacitive electrode applications.

Electrochemical and Capacitive Properties of Carbon Dots/Reduced Graphene Oxide Supercapacitors.

Science.gov (United States)

Dang, Yong-Qiang; Ren, Shao-Zhao; Liu, Guoyang; Cai, Jiangtao; Zhang, Yating; Qiu, Jieshan

2016-11-14

There is much recent interest in graphene-based composite electrode materials because of their excellent mechanical strengths, high electron mobilities, and large specific surface areas. These materials are good candidates for applications in supercapacitors. In this work, a new graphene-based electrode material for supercapacitors was fabricated by anchoring carbon dots (CDs) on reduced graphene oxide (rGO). The capacitive properties of electrodes in aqueous electrolytes were systematically studied by galvanostatic charge-discharge measurements, cyclic voltammetry, and electrochemical impedance spectroscopy. The capacitance of rGO was improved when an appropriate amount of CDs were added to the material. The CD/rGO electrode exhibited a good reversibility, excellent rate capability, fast charge transfer, and high specific capacitance in 1 M H₂SO₄. Its capacitance was as high as 211.9 F/g at a current density of 0.5 A/g. This capacitance was 74.3% higher than that of a pristine rGO electrode (121.6 F/g), and the capacitance of the CD/rGO electrode retained 92.8% of its original value after 1000 cycles at a CDs-to-rGO ratio of 5:1.

Electrochemical and Capacitive Properties of Carbon Dots/Reduced Graphene Oxide Supercapacitors

Directory of Open Access Journals (Sweden)

Yong-Qiang Dang

2016-11-01

Full Text Available There is much recent interest in graphene-based composite electrode materials because of their excellent mechanical strengths, high electron mobilities, and large specific surface areas. These materials are good candidates for applications in supercapacitors. In this work, a new graphene-based electrode material for supercapacitors was fabricated by anchoring carbon dots (CDs on reduced graphene oxide (rGO. The capacitive properties of electrodes in aqueous electrolytes were systematically studied by galvanostatic charge-discharge measurements, cyclic voltammetry, and electrochemical impedance spectroscopy. The capacitance of rGO was improved when an appropriate amount of CDs were added to the material. The CD/rGO electrode exhibited a good reversibility, excellent rate capability, fast charge transfer, and high specific capacitance in 1 M H2SO4. Its capacitance was as high as 211.9 F/g at a current density of 0.5 A/g. This capacitance was 74.3% higher than that of a pristine rGO electrode (121.6 F/g, and the capacitance of the CD/rGO electrode retained 92.8% of its original value after 1000 cycles at a CDs-to-rGO ratio of 5:1.

A novel capacitive micro-accelerometer with grid strip capacitances and sensing gap alterable capacitances

International Nuclear Information System (INIS)

Dong Linxi; Chen Jindan; Huo Weihong; Li Yongjie; Sun Lingling; Yan Haixia

2009-01-01

The comb capacitances fabricated by deep reactive ion etching (RIE) process have high aspect ratio which is usually smaller than 30: 1 for the complicated process factors, and the combs are usually not parallel due to the well-known micro-loading effect and other process factors, which restricts the increase of the seismic mass by increasing the thickness of comb to reduce the thermal mechanical noise and the decrease of the gap of the comb capacitances for increasing the sensitive capacitance to reduce the electrical noise. Aiming at the disadvantage of the deep RIE, a novel capacitive micro-accelerometer with grid strip capacitances and sensing gap alterable capacitances is developed. One part of sensing of inertial signal of the micro-accelerometer is by the grid strip capacitances whose overlapping area is variable and which do not have the non-parallel plate's effect caused by the deep RIE process. Another part is by the sensing gap alterable capacitances whose gap between combs can be reduced by the actuators. The designed initial gap of the alterable comb capacitances is relatively large to depress the effect of the maximum aspect ratio (30 : 1) of deep RIE process. The initial gap of the capacitance of the actuator is smaller than the one of the comb capacitances. The difference between the two gaps is the initial gap of the sensitive capacitor. The designed structure depresses greatly the requirement of deep RIE process. The effects of non-parallel combs on the accelerometer are also analyzed. The characteristics of the micro-accelerometer are discussed by field emission microscopy (FEM) tool ANSYS. The tested devices based on slide-film damping effect are fabricated, and the tested quality factor is 514, which shows that grid strip capacitance design can partly improve the resolution and also prove the feasibility of the designed silicon-glass anodically bonding process.

Investigation of capacitance characteristics in metal/high-k ...

Indian Academy of Sciences (India)

MS received 4 May 2016; accepted 10 January 2017; published online 21 August 2017. Abstract. Capacitance vs. ... with high-k materials is the prime technological challenge. [2]. ... reliability of MOS devices are strongly dependent on the for-.

Robust and conductive two-dimensional metal-organic frameworks with exceptionally high volumetric and areal capacitance

Science.gov (United States)

Feng, Dawei; Lei, Ting; Lukatskaya, Maria R.; Park, Jihye; Huang, Zhehao; Lee, Minah; Shaw, Leo; Chen, Shucheng; Yakovenko, Andrey A.; Kulkarni, Ambarish; Xiao, Jianping; Fredrickson, Kurt; Tok, Jeffrey B.; Zou, Xiaodong; Cui, Yi; Bao, Zhenan

2018-01-01

For miniaturized capacitive energy storage, volumetric and areal capacitances are more important metrics than gravimetric ones because of the constraints imposed by device volume and chip area. Typically used in commercial supercapacitors, porous carbons, although they provide a stable and reliable performance, lack volumetric performance because of their inherently low density and moderate capacitances. Here we report a high-performing electrode based on conductive hexaaminobenzene (HAB)-derived two-dimensional metal-organic frameworks (MOFs). In addition to possessing a high packing density and hierarchical porous structure, these MOFs also exhibit excellent chemical stability in both acidic and basic aqueous solutions, which is in sharp contrast to conventional MOFs. Submillimetre-thick pellets of HAB MOFs showed high volumetric capacitances up to 760 F cm-3 and high areal capacitances over 20 F cm-2. Furthermore, the HAB MOF electrodes exhibited highly reversible redox behaviours and good cycling stability with a capacitance retention of 90% after 12,000 cycles. These promising results demonstrate the potential of using redox-active conductive MOFs in energy-storage applications.

Designing a robust high-speed CMOS-MEMS capacitive humidity sensor

International Nuclear Information System (INIS)

Lazarus, N; Fedder, G K

2012-01-01

In our previous work (Lazarus and Fedder 2011 J. Micromech. Microeng. 21 0650281), we demonstrated a CMOS-MEMS capacitive humidity sensor with a 72% improvement in sensitivity over the highest previously integrated on a CMOS die. This paper explores a series of methods for creating a faster and more manufacturable high-sensitivity capacitive humidity sensor. These techniques include adding oxide pillars to hold the plates apart, spin coating polymer to allow sensors to be fabricated more cheaply, adding a polysilicon heater and etching away excess polymer in the release holes. In most cases a tradeoff was found between sensitivity and other factors such as response time or robustness. A robust high-speed sensor was designed with a sensitivity of 0.21% change in capacitance per per cent relative humidity, while dropping the response time constant from 70 to 4s. Although less sensitive than our design, the sensor remains 17% more sensitive than the most sensitive interdigitated designs successfully integrated with CMOS. (paper)

In situ fabrication of Ni(OH){sub 2} nanofibers on polypyrrole-based carbon nanotubes for high-capacitance supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Fan, Jianzhang [School of Chemistry and Chemical Engineering, Xinjiang University, Urumqi 830046 (China); Mi, Hongyu, E-mail: mmihongyu@163.com [School of Chemistry and Chemical Engineering, Xinjiang University, Urumqi 830046 (China); Xu, Youlong, E-mail: ylxuxjtu@mail.xjtu.edu.cn [Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education, Xi’an Jiaotong University, Xi’an 710049 (China); Gao, Bo [Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi 830011 (China)

2013-03-15

Highlights: ► Facile surface decoration approach to highly porous Ni(OH){sub 2}/CNT composites. ► Polypyrrole-based CNTs form three-dimensional electron-transport channels. ► A high capacitance of 1118 F g{sup −1} at 50 mA cm{sup −2} is delivered. ► Ni(OH){sub 2}/CNT composites exhibit high discharge capability. - Abstract: Large-scale nickel hydroxide–carbon [Ni(OH){sub 2}/CNT] networks with three-dimensional electron-transport channels are synthesized via a facile and general surface-decoration approach, using polypyrrole-derived CNTs as the support. Flexible Ni(OH){sub 2} nanofibers with a diameter of 5–10 nm and a length of 50–120 nm are intertwined and wrapped homogenously on carbon networks, leading to the formation of more complex networks. When used as supercapacitor electrodes, this designed architecture with large surface area, abundant pores and good electrical conductivity is very important in technology. It can promote the bulk accessibility of electrolyte OH{sup −} and diffusion rate within the redox phase. Consequently, an unusual specific capacitance of 1745 F g{sup −1} can be obtained for Ni(OH){sub 2}/CNT composite at 30 mA cm{sup −2}. Even at a high rate (50 mA cm{sup −2}), the composite can also deliver a specific capacitance as high as 1118 F g{sup −1}, exhibiting the potential application for supercapacitors.

Layout Capacitive Coupling and Structure Impacts on Integrated High Voltage Power MOSFETs

DEFF Research Database (Denmark)

Fan, Lin; Knott, Arnold; Jørgensen, Ivan Harald Holger

2016-01-01

The switching performances of the integrated high voltage power MOSFETs that have prevailing interconnection matrices are being heavily influenced by the parasitic capacitive coupling of on-chip metal wires. The mechanism of the side-byside coupling is generally known, however, the layer-to-layer......The switching performances of the integrated high voltage power MOSFETs that have prevailing interconnection matrices are being heavily influenced by the parasitic capacitive coupling of on-chip metal wires. The mechanism of the side-byside coupling is generally known, however, the layer...... extraction tool shows that the side-by-side coupling dominated structure can perform better than the layer-to-layer coupling dominated structure, in terms of on-resistance times input or output capacitance, by 9.2% and 4.9%, respectively....

Three-dimensional activated reduced graphene oxide nanocup/nickel aluminum layered double hydroxides composite with super high electrochemical and capacitance performances

International Nuclear Information System (INIS)

Lin, Yan; Ruiyi, Li; Zaijun, Li; Junkang, Liu; Yinjun, Fang; Guangli, Wang; Zhiguo, Gu

2013-01-01

The paper reported a three-dimensional activated reduced graphene oxide nanocup/nickel aluminum layered double hydroxides composite (3D-ARGON/NiAl-LDH) with super high electrochemical and capacitance performances. Graphene oxide was reduced by hydrazine in ammonia medium to form three-dimensional reduced graphene oxide nanocup using polystyrene colloidal particle as sacrificial template. The nanocup was then activated by the alkali corrosion and thermal annealing. The 3D-ARGON/NiAl-LDH was finally fabricated by the hydrothermal synthesis via in situ growth of ultrathin NiAl-LDH nanoflakes on the 3D-ARGON in an ethanol medium. The study demonstrated that the composite offers special 3D architecture with a macropore on the rim of a cup and large mesoporous structure on the wall of a cup, which will greatly boost the electron transfer and mass transport during the faradaic redox reaction, and displays excellent electrochemical and capactance performances, including high specific capacitance and rate capability, good charge/discharge stability and long-term cycling life. Its maximum specific capacitance was found to be 2712.7 F g −1 at the current density of 1 A g −1 , which is more than 7-fold that of pure NiAl-LDH, 3-fold that of common reduced graphene oxide/NiAl-LDH and 1.8-fold that of two-dimensional activated reduced graphene oxide/NiAl-LDH. The specific capacitance can remain 1174 F g −1 when the current density increases up to 50 A g −1 . After 5000 cycles at the current density of 30 A g −1 , the capacitance can keep at least 98.9%. This study provides a promising approach for the design and synthesis of graphene-based materials with largely enhanced supercapacitor behaviors, which can be potentially applied in energy storage/conversion devices

High resolution capacitance detection circuit for rotor micro-gyroscope

Directory of Open Access Journals (Sweden)

Ming-Yuan Ren

2014-03-01

Full Text Available Conventional methods for rotor position detection of micro-gyroscopes include common exciting electrodes (single frequency and common sensing electrodes (frequency multiplex, but they have encountered some problems. So we present a high resolution and low noise pick-off circuit for micro-gyroscopes which utilizes the time multiplex method. The detecting circuit adopts a continuous-time current sensing circuit for capacitance measurement, and its noise analysis of the charge amplifier is introduced. The equivalent output noise power spectral density of phase-sensitive demodulation is 120 nV/Hz1/2. Tests revealed that the whole circuitry has a relative capacitance resolution of 1 × 10−8.

Large area, low capacitance Si(Li) detectors for high rate x-ray applications

International Nuclear Information System (INIS)

Rossington, C.S.; Fine, P.M.; Madden, N.W.

1992-10-01

Large area, single-element Si(Li) detectors have been fabricated using a novel geometry which yields detectors with reduced capacitance and hence reduced noise at short amplifier pulse-processing times. A typical device employing the new geometry with a thickness of 6 mm and an active area of 175 mm 2 has a capacitance of only 0.5 pf, compared to 2.9 pf for a conventional planar device with equivalent dimensions. These new low capacitance detectors, used in conjunction with low capacitance field effect transistors, will result in x-ray spectrometers capable of operating at very high count rates while still maintaining excellent energy resolution. The spectral response of the low capacitance detectors to a wide range of x-ray energies at 80 K is comparable to typical state-of-the-art conventional Si(Li) devices. In addition to their low capacitance, the new devices offer other advantages over conventional detectors. Detector fabrication procedures, I-V and C-V characteristics, noise performance, and spectral response to 2-60 keV x-rays are described

One-step synthesis of layered CuS/multi-walled carbon nanotube nanocomposites for supercapacitor electrode material with ultrahigh specific capacitance

International Nuclear Information System (INIS)

Huang, Ke-Jing; Zhang, Ji-Zong; Xing, Ke

2014-01-01

In this work, hierarchical-structured copper sulfide/multi-walled carbon nanotubes (CuS/MWCNTs) are synthesized via a one-step hydrothermal process. The chemical composition and microstructure of CuS-MWCNTs are characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy and research as electrode matericals for high-performance supercapacitors by cyclic voltammogram, galvanostatic charge-discharge and electrochemical impedance spectroscopy. As expected, the CuS-MWCNTs exhibit a much higher specific capacitance up to 2831 F g −1 , compared with 925.1 F g −1 for CuS and 555.6 F g −1 for MWCNTs. Furthermore, the CuS-MWCNTs hybrids also exhibit good cycling stability with more than 90% capacitance retention over 600 cycles. The enhancement of CuS/MWCNTs in supercapacitor performance not only attribute to their unique 3D structures with large specific surface area, but also their excellent conductivity, which facilitate efficient charge transport and promotes electrolyte diffusion

A new interface weak-capacitance detection ASIC of capacitive liquid level sensor in the rocket

Science.gov (United States)

Yin, Liang; Qin, Yao; Liu, Xiao-Wei

2017-11-01

A new capacitive liquid level sensing interface weak-capacitance detection ASIC has been designed. This ASIC realized the detection of the output capacitance of the capacitive liquid level sensor, which converts the output capacitance of the capacitive liquid level sensor to voltage. The chip is fabricated in a standard 0.5μm CMOS process. The test results show that the linearity of capacitance detection of the ASIC is 0.05%, output noise is 3.7aF/Hz (when the capacitance which will be detected is 40 pF), the stability of capacitance detection is 7.4 × 10-5pF (1σ, 1h), the output zero position temperature coefficient is 4.5 uV/∘C. The test results prove that this interface ASIC can meet the requirement of high accuracy capacitance detection. Therefore, this interface ASIC can be applied in capacitive liquid level sensing and capacitive humidity sensing field.

Study on photoelectric parameter measurement method of high capacitance solar cell

Science.gov (United States)

Zhang, Junchao; Xiong, Limin; Meng, Haifeng; He, Yingwei; Cai, Chuan; Zhang, Bifeng; Li, Xiaohui; Wang, Changshi

2018-01-01

The high efficiency solar cells usually have high capacitance characteristic, so the measurement of their photoelectric performance usually requires long pulse width and long sweep time. The effects of irradiance non-uniformity, probe shielding and spectral mismatch on the IV curve measurement are analyzed experimentally. A compensation method for irradiance loss caused by probe shielding is proposed, and the accurate measurement of the irradiance intensity in the IV curve measurement process of solar cell is realized. Based on the characteristics that the open circuit voltage of solar cell is sensitive to the junction temperature, an accurate measurement method of the temperature of solar cell under continuous irradiation condition is proposed. Finally, a measurement method with the characteristic of high accuracy and wide application range for high capacitance solar cell is presented.

Electrical Capacitance Volume Tomography with High-Contrast Dielectrics

Science.gov (United States)

Nurge, Mark

2010-01-01

The Electrical Capacitance Volume Tomography (ECVT) system has been designed to complement the tools created to sense the presence of water in nonconductive spacecraft materials, by helping to not only find the approximate location of moisture but also its quantity and depth. The ECVT system has been created for use with a new image reconstruction algorithm capable of imaging high-contrast dielectric distributions. Rather than relying solely on mutual capacitance readings as is done in traditional electrical capacitance tomography applications, this method reconstructs high-resolution images using only the self-capacitance measurements. The image reconstruction method assumes that the material under inspection consists of a binary dielectric distribution, with either a high relative dielectric value representing the water or a low dielectric value for the background material. By constraining the unknown dielectric material to one of two values, the inverse math problem that must be solved to generate the image is no longer ill-determined. The image resolution becomes limited only by the accuracy and resolution of the measurement circuitry. Images were reconstructed using this method with both synthetic and real data acquired using an aluminum structure inserted at different positions within the sensing region. The cuboid geometry of the system has two parallel planes of 16 conductors arranged in a 4 4 pattern. The electrode geometry consists of parallel planes of copper conductors, connected through custom-built switch electronics, to a commercially available capacitance to digital converter. The figure shows two 4 4 arrays of electrodes milled from square sections of copper-clad circuit-board material and mounted on two pieces of glass-filled plastic backing, which were cut to approximately square shapes, 10 cm on a side. Each electrode is placed on 2.0-cm centers. The parallel arrays were mounted with the electrode arrays approximately 3 cm apart. The open ends

Aspheric surface measurement using capacitive probes

Science.gov (United States)

Tao, Xin; Yuan, Daocheng; Li, Shaobo

2017-02-01

With the application of aspheres in optical fields, high precision and high efficiency aspheric surface metrology becomes a hot research topic. We describe a novel method of non-contact measurement of aspheric surface with capacitive probe. Taking an eccentric spherical surface as the object of study, the averaging effect of capacitive probe measurement and the influence of tilting the capacitive probe on the measurement results are investigated. By comparing measurement results from simultaneous measurement of the capacitive probe and contact probe of roundness instrument, this paper indicates the feasibility of using capacitive probes to test aspheric surface and proposes the compensation method of measurement error caused by averaging effect and the tilting of the capacitive probe.

Electrochemical capacitance performance of titanium nitride nanoarray

Energy Technology Data Exchange (ETDEWEB)

Xie, Yibing, E-mail: ybxie@seu.edu.cn [School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189 (China); Suzhou Research Institute of Southeast University, Suzhou 215123 (China); Wang, Yong [School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189 (China); Du, Hongxiu [School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189 (China); Suzhou Research Institute of Southeast University, Suzhou 215123 (China)

2013-12-01

Highlights: • TiN nanoarray is formed by a nitridation process of TiO{sub 2} in ammonia atmosphere. • TiN nanoarray exhibits much higher EDLC capacitance than TiO{sub 2} nanoarray. • The specific capacitance of TiN nanoarray achieves a high level of 99.7 mF cm{sup −2}. • A flexible solid-state supercapacitor is constructed by TiN nanoarray and PVA gel. -- Abstract: In this study, titanium nitride (TiN) nanoarrays with a short nanotube and long nanopore structure have been prepared by an anodization process of ultra thin titanium foil in ethylene glycol (EG) solution containing ammonium fluoride, subsequent calcination process in an air atmosphere, and final nitridation process in an ammonia atmosphere. The morphology and microstructure characterization has been conducted using field emission scanning electron microscope and X-ray diffraction. The electrochemical properties have been investigated through cyclic voltammetry and electrochemical impedance spectrum measurements. The electrochemical capacitance performance has been investigated by galvanostatic charge–discharge measurements in the acidic, neural and alkali electrolyte solution. Well-defined TiN nanoarrays contribute a much higher capacitance performance than titania (TiO{sub 2}) in the supercapacitor application due to the extraordinarily improved electrical conductivity. Such an electrochemical capacitance can be further enhanced by increasing aspect ratio of TiN nanoarray from short nanotubes to long nanopores. A flexible supercapacitor has been constructed using two symmetrical TiN nanoarray electrodes and a polyvinyl alcohol (PVA) gel electrolyte with H{sub 2}SO{sub 4}–KCl–H{sub 2}O–EG. Such a supercapacitor has a highly improved potential window and still keeps good electrochemical energy storage. TiN nanoarray with a high aspect ratio can act well as an ultra thin film electrode material of flexible supercapacitor to contribute a superior capacitance performance.

Exceptionally High Electric Double Layer Capacitances of Oligomeric Ionic Liquids.

Science.gov (United States)

Matsumoto, Michio; Shimizu, Sunao; Sotoike, Rina; Watanabe, Masayoshi; Iwasa, Yoshihiro; Itoh, Yoshimitsu; Aida, Takuzo

2017-11-15

Electric double layer (EDL) capacitors are promising as next-generation energy accumulators if their capacitances and operation voltages are both high. However, only few electrolytes can simultaneously fulfill these two requisites. Here we report that an oligomeric ionic liquid such as IL4 TFSI with four imidazolium ion units in its structure provides a wide electrochemical window of ∼5.0 V, similar to monomeric ionic liquids. Furthermore, electrochemical impedance measurements using Au working electrodes demonstrated that IL4 TFSI exhibits an exceptionally high EDL capacitance of ∼66 μF/cm 2 , which is ∼6 times as high as those of monomeric ionic liquids so far reported. We also found that an EDL-based field effect transistor (FET) using IL4 TFSI as a gate dielectric material and SrTiO 3 as a channel material displays a very sharp transfer curve with an enhanced carrier accumulation capability of ∼64 μF/cm 2 , as determined by Hall-effect measurements.

Synthesis and Characterization of “Ravine-Like” BCN Compounds with High Capacitance

Directory of Open Access Journals (Sweden)

Dongping Chen

2018-01-01

Full Text Available A series of “ravine-like” boron carbonitrides (abbreviation: BCN were synthesized by a green precursor pyrolysis method at different temperatures (about 700–1100 °C. The highest electrochemical performance of BCN-800 (Named BCN-temperature electrode was observed, because the “ravine-like” structure can significantly increase the contact area and improve the wettability between electrode and electrolyte. The BCN electrode exhibited ultrahigh specific capacitance 805.9 F/g (at a current density of 0.2 A/g, excellent rate capability, and good cycling stability (91% after 3000 cycles at a current density of 8 A/g, showing high potential applications in supercapacitors.

Varying carbon structures templated from KIT-6 for optimum electrochemical capacitance

Energy Technology Data Exchange (ETDEWEB)

Li Fujun; Laak, Nicole van der; Ting, S.-W. [Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong (Hong Kong); Chan, K.-Y., E-mail: hrsccky@hku.h [Department of Chemistry, University of Hong Kong, Pokfulam Road, Hong Kong (Hong Kong)

2010-03-01

Bicontinuous ordered mesoporous carbons (OMCs), fabricated from a KIT-6 template using aluminosilicate as catalyst and furfuryl alcohol as carbon source, were successfully prepared and studied as electrodes in supercapacitors. Their structures were characterized by transmission electron microscopy (TEM), small-angle X-ray diffraction (SAXD) and N{sub 2} cryosorption methods. Using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), the capacitive performance of the OMCs was found to be strongly dependent on the mesostructure. Specific capacitance value greater than 130 F g{sup -1} at 20 mV s{sup -1} were obtained from an OMC that featured high surface area with the existence of additional large pores to enhance the specific capacitance at high discharge rate. For the OMC with the best performance, we found that a power density as high as 4.5 kW kg{sup -1} at an energy density of 6.1 Wh kg{sup -1} can be delivered when the discharge current density is 20 A g{sup -1} and can also be continuously charged and discharged with little variation in capacitance after 2500 cycles. These results indicate that this OMC with optimized structure has potential to be used as a power component in electric vehicles.

Novel High Temperature Capacitive Pressure Sensor Utilizing SiC Integrated Circuit Twin Ring Oscillators

Science.gov (United States)

Scardelletti, M.; Neudeck, P.; Spry, D.; Meredith, R.; Jordan, J.; Prokop, N.; Krasowski, M.; Beheim, G.; Hunter, G.

2017-01-01

This paper describes initial development and testing of a novel high temperature capacitive pressure sensor system. The pressure sensor system consists of two 4H-SiC 11-stage ring oscillators and a SiCN capacitive pressure sensor. One oscillator has the capacitive pressure sensor fixed at one node in its feedback loop and varies as a function of pressure and temperature while the other provides a pressure-independent reference frequency which can be used to temperature compensate the output of the first oscillator. A two-day repeatability test was performed up to 500C on the oscillators and the oscillator fundamental frequency changed by only 1. The SiCN capacitive pressure sensor was characterized at room temperature from 0 to 300 psi. The sensor had an initial capacitance of 3.76 pF at 0 psi and 1.75 pF at 300 psi corresponding to a 54 change in capacitance. The integrated pressure sensor system was characterized from 0 to 300 psi in steps of 50 psi over a temperature range of 25 to 500C. The pressure sensor system sensitivity was 0.113 kHzpsi at 25C and 0.026 kHzpsi at 500C.

The Design of Phase-Locked-Loop Circuit for Precision Capacitance Micrometer

Directory of Open Access Journals (Sweden)

Li Shujie

2016-01-01

Full Text Available High precision non-contact micrometer is normally divided into three categories: inductance micrometer, capacitance micrometer and optical interferometer micrometer. The capacitance micrometer is widely used because it has high performance to price ratio. With the improvement of automation level, precision of capacitance micrometer is required higher and higher. Generally, capacitance micrometer consists of the capacitance sensor, capacitance/voltage conversion circuit, and modulation and demodulation circuits. However, due to the existing of resistors, capacitors and other components in the circuit, the phase shift of the carrier signal and the modulated signal might occur. In this case, the specific value of phase shift cannot be determined. Therefore, error caused by the phase shift cannot be eliminated. This will reduce the accuracy of micrometer. In this design, in order to eliminate the impact of the phase shift, the phase-locked-loop (PLL circuit is employed. Through the experiment, the function of tracking the input signal phase and frequency is achieved by the phase-locked-loop circuit. This signal processing method can also be applied to tuber electrical resistance tomography system and other precision measurement circuit.

Experimental observation of the inductive electric field and related plasma nonuniformity in high frequency capacitive discharge

International Nuclear Information System (INIS)

Ahn, S. K.; Chang, H. Y.

2008-01-01

To elucidate plasma nonuniformity in high frequency capacitive discharges, Langmuir probe and B-dot probe measurements were carried out in the radial direction in a cylindrical capacitive discharge driven at 90 MHz with argon pressures of 50 and 400 mTorr. Through the measurements, a significant inductive electric field (i.e., time-varying magnetic field) was observed at the radial edge, and it was found that the inductive electric field creates strong plasma nonuniformity at high pressure operation. The plasma nonuniformity at high pressure operation is physically similar to the E-H mode transition typically observed in inductive discharges. This result agrees well with the theories of electromagnetic effects in large area and/or high frequency capacitive discharges

Synthesis of NiMn-LDH Nanosheet@Ni3S2 Nanorod Hybrid Structures for Supercapacitor Electrode Materials with Ultrahigh Specific Capacitance.

Science.gov (United States)

Yu, Shuai; Zhang, Yingxi; Lou, Gaobo; Wu, Yatao; Zhu, Xinqiang; Chen, Hao; Shen, Zhehong; Fu, Shenyuan; Bao, Binfu; Wu, Limin

2018-03-27

One of the key challenges for pseudocapacitive electrode materials with highly effective capacitance output and future practical applications is how to rationally construct hierarchical and ordered hybrid nanoarchitecture through the simple process. Herein, we design and synthesize a novel NiMn-layered double hydroxide nanosheet@Ni 3 S 2 nanorod hybrid array supported on porous nickel foam via a one-pot hydrothermal method. Benefited from the ultrathin and rough nature, the well-defined porous structure of the hybrid array, as well as the synergetic effect between NiMn-layered double hydroxide nanosheets and Ni 3 S 2 nanorods, the as-fabricated hybrid array-based electrode exhibits an ultrahigh specific capacitance of 2703 F g -1 at 3 A g -1 . Moreover, the asymmetric supercapacitor with this hybrid array as a positive electrode and wood-derived activated carbon as a negative electrode demonstrates high energy density (57 Wh Kg -1 at 738 W Kg -1 ) and very good electrochemical cycling stability.

RF capacitance-voltage characterization of MOSFETs with high-leakage dielectric

NARCIS (Netherlands)

Schmitz, Jurriaan; Cubaynes, F.N; Cubaynes, F.N.; Havens, R.J.; de Kort, R.; Scholten, A.J.; Tiemeijer, L.F.

2003-01-01

We present a MOS Capacitance-Voltage measurement methodology that, contrary to present methods, is highly robust against gate leakage current densities up to 1000 A/cm/sup 2/. The methodology features specially designed RF test structures and RF measurement frequencies. It allows MOS parameter

Electrostatic Self-Assembly of Sandwich-Like CoAl-LDH/Polypyrrole/Graphene Nanocomposites with Enhanced Capacitive Performance.

Science.gov (United States)

Zhang, Yu; Du, Dongfeng; Li, Xuejin; Sun, Hongman; Li, Li; Bai, Peng; Xing, Wei; Xue, Qingzhong; Yan, Zifeng

2017-09-20

A novel sandwich-like composite with ultrathin CoAl-layered double hydroxide (LDH) nanoplates electrostatically assembled on both sides of two-dimensional polypyrrole/graphene (PG) substrate has been successfully fabricated using facile hydrothermal techniques. The PG not only serves as an excellent conductive and structural scaffold to enhance the transmission of electrons and prevent aggregation of CoAl-LDH nanoplates but also contributes to the enhancement of the specific capacitance. Owing to the homogeneous dispersion of CoAl-LDH nanoplates and its intimate interaction with PG substrate, the resulting CoAl-LDH/PG nanocomposite material exhibits excellent capacitive performance, for example, enhanced gravimetric specific capacitance (864 F g -1 at 1 A g -1 ), high rate performance (75% retention at 20 A g -1 ), and excellent cycle life (almost no degradation in supercapacitor performance after 5000 cycles) in aqueous KOH solution. Furthermore, the assembled asymmetric capacitor is able to deliver a superhigh energy density of 46.8 Wh kg -1 at 1.2 kW kg -1 and maintain 90.1% of its initial capacitance after 10 000 cycles. These results indicate a rational assembly strategy toward a high-performance pseudocapacitive electrode material with excellent rate performance, high specific capacitance, and outstanding cycle stability.

Binder-free activated graphene compact films for all-solid-state micro-supercapacitors with high areal and volumetric capacitances

DEFF Research Database (Denmark)

Wu, Zhong Shuai; Yang, Sheng; Zhang, Lili

2015-01-01

Micro-supercapacitors (MSCs) hold great promise as highly competitive miniaturized power sources satisfying the increased demand in microelectronics; however, simultaneously achieving high areal and volumetric capacitances is still a great challenge. Here we demonstrated the designed construction...... of binder-free, electrically conductive, nanoporous activated graphene (AG) compact films for high-performance MSCs. The binder-free AG films are fabricated by alternating deposition of electrochemically exfoliated graphene (EG) and nanoporous AG with a high specific surface area of 2920 m2/g, and then dry...

Bivariate quadratic method in quantifying the differential capacitance and energy capacity of supercapacitors under high current operation

Science.gov (United States)

Goh, Chin-Teng; Cruden, Andrew

2014-11-01

Capacitance and resistance are the fundamental electrical parameters used to evaluate the electrical characteristics of a supercapacitor, namely the dynamic voltage response, energy capacity, state of charge and health condition. In the British Standards EN62391 and EN62576, the constant capacitance method can be further improved with a differential capacitance that more accurately describes the dynamic voltage response of supercapacitors. This paper presents a novel bivariate quadratic based method to model the dynamic voltage response of supercapacitors under high current charge-discharge cycling, and to enable the derivation of the differential capacitance and energy capacity directly from terminal measurements, i.e. voltage and current, rather than from multiple pulsed-current or excitation signal tests across different bias levels. The estimation results the author achieves are in close agreement with experimental measurements, within a relative error of 0.2%, at various high current levels (25-200 A), more accurate than the constant capacitance method (4-7%). The archival value of this paper is the introduction of an improved quantification method for the electrical characteristics of supercapacitors, and the disclosure of the distinct properties of supercapacitors: the nonlinear capacitance-voltage characteristic, capacitance variation between charging and discharging, and distribution of energy capacity across the operating voltage window.

Nickel oxide film with open macropores fabricated by surfactant-assisted anodic deposition for high capacitance supercapacitors.

Science.gov (United States)

Wu, Mao-Sung; Wang, Min-Jyle

2010-10-07

Nickel oxide film with open macropores prepared by anodic deposition in the presence of surfactant shows a very high capacitance of 1110 F g(-1) at a scan rate of 10 mV s(-1), and the capacitance value reduces to 950 F g(-1) at a high scan rate of 200 mV s(-1).

Flexible graphene/carbon nanotube hybrid papers chemical-reduction-tailored by gallic acid for high-performance electrochemical capacitive energy storages

Science.gov (United States)

Yao, Lu; Zhou, Chao; Hu, Nantao; Hu, Jing; Hong, Min; Zhang, Liying; Zhang, Yafei

2018-03-01

Mechanically robust graphene papers with both high gravimetric and volumetric capacitances are desired for high-performance energy storages. However, it's still a challenge to tailor the structure of graphene papers in order to meet this requirement. In this work, a kind of chemical-reduction-tailored mechanically-robust reduced graphene oxide/carbon nanotube hybrid paper has been reported for high-performance electrochemical capacitive energy storages. Gallic acid (GA), as an excellent reducing agent, was used to reduce graphene oxide. Through vacuum filtration of gallic acid reduced graphene oxide (GA-rGO) and carboxylic multiwalled carbon nanotubes (MWCNTs) aqueous suspensions, mechanically robust GA-rGO/MWCNTs hybrid papers were obtained. The resultant hybrid papers showed high gravimetric capacitance of 337.6 F g-1 (0.5 A g-1) and volumetric capacitance of 151.2 F cm-3 (0.25 A cm-3). In addition, the assembled symmetric device based on the hybrid papers exhibited high gravimetric capacitance of 291.6 F g-1 (0.5 A g-1) and volumetric capacitance of 136.6 F cm-3 (0.25 A cm-3). Meanwhile, it exhibited excellent rate capability and cycling stability. Above all, this chemical reduction tailoring technique and the resultant high-performance GA-rGO/MWCNTs hybrid papers give an insight for designing high-performance electrodes and hold a great potential in the field of energy storages.

Enhanced Capacitance of Hybrid Layered Graphene/Nickel Nanocomposite for Supercapacitors

Science.gov (United States)

Mohd Zaid, Norsaadatul Akmal; Idris, Nurul Hayati

2016-08-01

In this work, Ni nanoparticles were directly decorated on graphene (G) nanosheets via mechanical ball milling. Based on transmission electron microscopy observations, the Ni nanoparticles were well dispersed and attached to the G nanosheet without any agglomerations. Electrochemical results showed that the capacitance of a G/Ni nanocomposite was 275 F g-1 at a current density of 2 A g-1, which is higher than the capacitance of bare G (145 F g-1) and bare Ni (3 F g-1). The G/Ni electrode also showed superior performance at a high current density, exhibiting a capacitance of 190 F g-1 at a current density of 5 A g-1 and a capacitance of 144 F g-1 at a current density of 10 A g-1. The equivalent series resistance for G/Ni nanocomposites also decreased. The enhanced performance of this hybrid supercapacitor is best described by the synergistic effect, i.e. dual charge-storage mechanism, which is demonstrated by electrical double layer and pseudocapacitance materials. Moreover, a high specific surface area and electrical conductivity of the materials enhanced the capacitance. These results indicate that the G/Ni nanocomposite is a potential supercapacitor.

Microwave Assisted Synthesis of Porous NiCo2O4 Microspheres: Application as High Performance Asymmetric and Symmetric Supercapacitors with Large Areal Capacitance

Science.gov (United States)

Khalid, Syed; Cao, Chuanbao; Wang, Lin; Zhu, Youqi

2016-01-01

Large areal capacitance is essentially required to integrate the energy storage devices at the microscale electronic appliances. Energy storage devices based on metal oxides are mostly fabricated with low mass loading per unit area which demonstrated low areal capacitance. It is still a challenge to fabricate supercapacitor devices of porous metal oxides with large areal capacitance. Herein we report microwave method followed by a pyrolysis of the as-prepared precursor is used to synthesize porous nickel cobaltite microspheres. Porous NiCo2O4 microspheres are capable to deliver large areal capacitance due to their high specific surface area and small crystallite size. The facile strategy is successfully demonstrated to fabricate aqueous-based asymmetric & symmetric supercapacitor devices of porous NiCo2O4 microspheres with high mass loading of electroactive materials. The asymmetric & symmetric devices exhibit maximum areal capacitance and energy density of 380 mF cm−2 & 19.1 Wh Kg−1 and 194 mF cm−2 & 4.5 Wh Kg−1 (based on total mass loading of 6.25 & 6.0 mg) respectively at current density of 1 mA cm−2. The successful fabrication of symmetric device also indicates that NiCo2O4 can also be used as the negative electrode material for futuristic asymmetric devices. PMID:26936283

CMOS capacitive biosensors for highly sensitive biosensing applications.

Science.gov (United States)

Chang, An-Yu; Lu, Michael S-C

2013-01-01

Magnetic microbeads are widely used in biotechnology and biomedical research for manipulation and detection of cells and biomolecules. Most lab-on-chip systems capable of performing manipulation and detection require external instruments to perform one of the functions, leading to increased size and cost. This work aims at developing an integrated platform to perform these two functions by implementing electromagnetic microcoils and capacitive biosensors on a CMOS (complementary metal oxide semiconductor) chip. Compared to most magnetic-type sensors, our detection method requires no externally applied magnetic fields and the associated fabrication is less complicated. In our experiment, microbeads coated with streptavidin were driven to the sensors located in the center of microcoils with functionalized anti-streptavidin antibody. Detection of a single microbead was successfully demonstrated using a capacitance-to-frequency readout. The average capacitance changes for the experimental and control groups were -5.3 fF and -0.2 fF, respectively.

Percoll gradient-centrifuged capacitated mouse sperm have increased fertilizing ability and higher contents of sulfogalactosylglycerolipid and docosahexaenoic acid-containing phosphatidylcholine compared to washed capacitated mouse sperm.

Science.gov (United States)

Furimsky, Anna; Vuong, Ngoc; Xu, Hongbin; Kumarathasan, Premkumari; Xu, Min; Weerachatyanukul, Wattana; Bou Khalil, Maroun; Kates, Morris; Tanphaichitr, Nongnuj

2005-03-01

Although Percoll gradient centrifugation has been used routinely to prepare motile human sperm, its use in preparing motile mouse sperm has been limited. Here, we showed that Percoll gradient-centrifuged (PGC) capacitated mouse sperm had markedly higher fertilizing ability (sperm-zona pellucida [ZP] binding and in vitro fertilization) than washed capacitated mouse sperm. We also showed that the lipid profiles of PGC capacitated sperm and washed capacitated sperm differed significantly. The PGC sperm had much lower contents of cholesterol and phospholipids. This resulted in relative enrichment of male germ cell-specific sulfogalactosylglycerolipid (SGG), a ZP-binding ligand, in PGC capacitated sperm, and this would explain, in part, their increased ZP-binding ability compared with that of washed capacitated sperm. Analyses of phospholipid fatty acyl chains revealed that PGC capacitated sperm were enriched in phosphatidylcholine (PC) molecular species containing highly unsaturated fatty acids (HUFAs), with docosahexaenoic acid (DHA; C22: 6n-3) being the predominant HUFA (42% of total hydrocarbon chains of PC). In contrast, the level of PC-HUFAs comprising arachidonic acid (20:4n-6), docosapentaenoic acid (C22:5n-6), and DHA in washed capacitated sperm was only 27%. Having the highest unsaturation degree among all HUFAs in PC, DHA would enhance membrane fluidity to the uppermost. Therefore, membranes of PGC capacitated sperm would undergo fertilization-related fusion events at higher rates than washed capacitated sperm. These results suggested that PGC mouse sperm should be used in fertilization experiments and that SGG and DHA should be considered to be important biomarkers for sperm fertilizing ability.

Electrochemical capacitive performances of nanoporous carbon derived from sunflower seed shell

Energy Technology Data Exchange (ETDEWEB)

Li, X; Xing, W.; Zhuo, S.; Zhou, J. [Shandong Univ. of Technology, Zibo (China). School of Chemical Engineering

2010-07-01

Electrochemical double-layer capacitances (EDLCs) are used in applications were high power density and long cycle life are required. Nanoporous materials are typically used to prepare EDLC electrodes due to their high surface area, good physicochemical stability, and high conductivity. In this study, nanoporous carbon materials were prepared from sunflower seed shells and used as an electrode material for an EDLC. The surface and structural properties of the carbon materials were analyzed using N{sub 2} adsorption and scanning electron microscopy (SEM) techniques. The study showed that AC-X-Y carbons prepared using the impregnation-activation process had a better capacitive behaviour and higher capacitance retention ratio at fast charge-discharge rates than carbons made using the carbonization-activation process. The improved electrochemical performance of the carbons was attributed to the abundant macroscopic pores and decreased interior micropore surface. The specific capacitances of the carbon was approximately twice that of a hard-templated mesoporous carbon in all current densities ranging from 0.25 to 10 A per g. Results indicated that sunflower seed shells can be used to prepare EDLCs. 2 refs., 1 fig.

Assembly of polypyrrole nanotube@MnO{sub 2} composites with an improved electrochemical capacitance

Energy Technology Data Exchange (ETDEWEB)

Ji, Jiayou; Zhang, Xiaoya; Liu, Jingya; Peng, Linfeng; Chen, Changlang; Huang, Zhiliang [School of Materials Science and Engineering, Wuhan Institute of Technology, Wuhan 430073 (China); Li, Liang, E-mail: msell08@163.com [School of Materials Science and Engineering, Wuhan Institute of Technology, Wuhan 430073 (China); Yu, Xianghua [School of Materials Science and Engineering, Wuhan Institute of Technology, Wuhan 430073 (China); Shang, Songmin, E-mail: shang.songmin@polyu.edu.hk [Institute of Textiles and Clothing, The Hong Kong Polytechnic University, Hong Kong (China)

2015-08-15

Graphical abstract: - Highlights: • PPy nanotube@MnO{sub 2} composites have been prepared. • The thickness of MnO{sub 2} coating can be tuned by the concentration of KMnO{sub 4}. • Synergistic effect between PPy and MnO{sub 2} generates better capacitance performance. • The composites exhibit high specific capacitance and good cycle stability. - Abstract: A facile strategy is presented to fabricate polypyrrole nanotube@manganese dioxide (PPy@MnO{sub 2}) composites. The effect of KMnO{sub 4} concentration on the morphology and property of PPy@MnO{sub 2} composites is investigated. The microstrucutres and properties of the resulting PPy@MnO{sub 2} composites are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray diffraction (EDX), X-ray diffraction (XRD), thermo-gravimetric analysis (TGA) and electrochemical measurements. The results indicate that the PPy@MnO{sub 2} composites possess high specific capacitance and good cyclic stability due to the coating of MnO{sub 2} onto PPy nanotubes. The specific capacitance of 403 F/g for the PPy@MnO{sub 2} composite is obtained from galvanostatic charge–discharge experiment at a current density of 1 A/g, exhibiting the potential application for supercapacitors.

Effects of electrochemical-deposition method and microstructure on the capacitive characteristics of nano-sized manganese oxide

International Nuclear Information System (INIS)

Shinomiya, Takuya; Gupta, Vinay; Miura, Norio

2006-01-01

The amorphous nano-structured manganese oxide was electrochemically deposited onto a stainless-steel electrode. The structure and surface morphology of the obtained manganese oxide were studied by means of X-ray diffraction analysis and scanning electron microscopy. The capacitive characteristics of the manganese oxide electrodes were investigated by means of cyclic voltammetry and constant current charge-discharge cycling. The morphological and capacitive characteristics of the hydrous manganese oxide was found to be strongly influenced by the electrochemical deposition conditions. The highest specific capacitance value of ca. 410 F g -1 and the specific power of ca. 54 kW kg -1 were obtained at 400 mV s -1 sweep rate of potentiodynamic deposition condition. The cyclic-life data showed that the specific capacitance was highly stable up to 10,000 cycles examined. This suggests the excellent cyclic stability of the obtained amorphous hydrous manganese oxide for supercapacitor application

Effects of electrochemical-deposition method and microstructure on the capacitive characteristics of nano-sized manganese oxide

Energy Technology Data Exchange (ETDEWEB)

Shinomiya, Takuya; Gupta, Vinay; Miura, Norio [Art, Science and Technology Center for Cooperative Research, Kyushu University, Kasuga-shi, Fukuoka 816-8580 (Japan)

2006-06-01

The amorphous nano-structured manganese oxide was electrochemically deposited onto a stainless-steel electrode. The structure and surface morphology of the obtained manganese oxide were studied by means of X-ray diffraction analysis and scanning electron microscopy. The capacitive characteristics of the manganese oxide electrodes were investigated by means of cyclic voltammetry and constant current charge-discharge cycling. The morphological and capacitive characteristics of the hydrous manganese oxide was found to be strongly influenced by the electrochemical deposition conditions. The highest specific capacitance value of ca. 410Fg{sup -1} and the specific power of ca. 54kWkg{sup -1} were obtained at 400mVs{sup -1} sweep rate of potentiodynamic deposition condition. The cyclic-life data showed that the specific capacitance was highly stable up to 10,000 cycles examined. This suggests the excellent cyclic stability of the obtained amorphous hydrous manganese oxide for supercapacitor application. (author)

A Ni-P@NiCo LDH core-shell nanorod-decorated nickel foam with enhanced areal specific capacitance for high-performance supercapacitors.

Science.gov (United States)

Xing, Jiale; Du, Jing; Zhang, Xuan; Shao, Yubo; Zhang, Ting; Xu, Cailing

2017-08-14

Recently, transition metal-based nanomaterials have played a key role in the applications of supercapacitors. In this study, nickel phosphide (Ni-P) was simply combined with NiCo LDH via facile phosphorization of Ni foam and subsequent electrodeposition to form core-shell nanorod arrays on the Ni foam; the Ni-P@NiCo LDH was then directly used for a pseudocapacitive electrode. Owing to the splendid synergistic effect between Ni-P and NiCo LDH nanosheets as well as the hierarchical structure of 1D nanorods, 2D nanosheets, and 3D Ni foam, the hybrid electrode exhibited significantly enhanced electrochemical performances. The Ni-P@NiCo LDH electrode showed a high specific capacitance of 12.9 F cm -2 at 5 mA cm -2 (3470.5 F g -1 at a current density of 1.3 A g -1 ) that remained as high as 6.4 F cm -2 at a high current density of 100 mA cm -2 (1700 F g -1 at 27 A g -1 ) and excellent cycling stability (96% capacity retention after 10 000 cycles at 40 mA cm -2 ). Furthermore, the asymmetric supercapacitors (ASCs) were assembled using Ni-P@NiCo LDH as a positive electrode and activated carbon (AC) as a negative electrode. The obtained ASCs delivered remarkable energy density and power density as well as good cycling performance. The enhanced electrochemical activities open a new avenue for the development of supercapacitors.

A High Resolution Capacitive Sensing System for the Measurement of Water Content in Crude Oil

Science.gov (United States)

Aslam, Muhammad Zubair; Tang, Tong Boon

2014-01-01

This paper presents the design of a non-intrusive system to measure ultra-low water content in crude oil. The system is based on a capacitance to phase angle conversion method. Water content is measured with a capacitance sensor comprising two semi-cylindrical electrodes mounted on the outer side of a glass tube. The presence of water induces a capacitance change that in turn converts into a phase angle, with respect to a main oscillator. A differential sensing technique is adopted not only to ensure high immunity against temperature variation and background noise, but also to eliminate phase jitter and amplitude variation of the main oscillator that could destabilize the output. The complete capacitive sensing system was implemented in hardware and experiment results using crude oil samples demonstrated that a resolution of ±50 ppm of water content in crude oil was achieved by the proposed design. PMID:24967606

A High Resolution Capacitive Sensing System for the Measurement of Water Content in Crude Oil

Directory of Open Access Journals (Sweden)

Muhammad Zubair Aslam

2014-06-01

Full Text Available This paper presents the design of a non-intrusive system to measure ultra-low water content in crude oil. The system is based on a capacitance to phase angle conversion method. Water content is measured with a capacitance sensor comprising two semi-cylindrical electrodes mounted on the outer side of a glass tube. The presence of water induces a capacitance change that in turn converts into a phase angle, with respect to a main oscillator. A differential sensing technique is adopted not only to ensure high immunity against temperature variation and background noise, but also to eliminate phase jitter and amplitude variation of the main oscillator that could destabilize the output. The complete capacitive sensing system was implemented in hardware and experiment results using crude oil samples demonstrated that a resolution of ±50 ppm of water content in crude oil was achieved by the proposed design.

Amphiphilic ligand exchange reaction-induced supercapacitor electrodes with high volumetric and scalable areal capacitances

Science.gov (United States)

Nam, Donghyeon; Heo, Yeongbeom; Cheong, Sanghyuk; Ko, Yongmin; Cho, Jinhan

2018-05-01

We introduce high-performance supercapacitor electrodes with ternary components prepared from consecutive amphiphilic ligand-exchange-based layer-by-layer (LbL) assembly among amine-functionalized multi-walled carbon nanotubes (NH2-MWCNTs) in alcohol, oleic acid-stabilized Fe3O4 nanoparticles (OA-Fe3O4 NPs) in toluene, and semiconducting polymers (PEDOT:PSS) in water. The periodic insertion of semiconducting polymers within the (OA-Fe3O4 NP/NH2-MWCNT)n multilayer-coated indium tin oxide (ITO) electrode enhanced the volumetric and areal capacitances up to 408 ± 4 F cm-3 and 8.79 ± 0.06 mF cm-2 at 5 mV s-1, respectively, allowing excellent cycling stability (98.8% of the initial capacitance after 5000 cycles) and good rate capability. These values were higher than those of the OA-Fe3O4 NP/NH2-MWCNT multilayered electrode without semiconducting polymer linkers (volumetric capacitance ∼241 ± 4 F cm-3 and areal capacitance ∼1.95 ± 0.03 mF cm-2) at the same scan rate. Furthermore, when the asymmetric supercapacitor cells (ASCs) were prepared using OA-Fe3O4 NP- and OA-MnO NP-based ternary component electrodes, they displayed high volumetric energy (0.36 mW h cm-3) and power densities (820 mW cm-3).

Response to capacitating stimuli indicates extender-related differences in boar sperm function.

Science.gov (United States)

Schmid, S; Henning, H; Petrunkina, A M; Weitze, K F; Waberski, D

2013-10-01

Spermatozoa, especially those of the porcine species, are highly susceptible to in vitro chilling and ageing. Extenders are continuously developed to protect boar spermatozoa from chilling injury. New semen extenders and other modified preservation strategies require sensitive testing for essential sperm functions. The key process on the pathway of fertilization is capacitation. The aim of the present study was to examine whether the specific response to capacitating stimuli is sensitive enough to indicate different preservation capacities of extenders during hypothermic storage of boar spermatozoa. Semen was diluted in Beltsville Thawing Solution (BTS) and Androstar Plus and kept for 3 h at 22°C or stored at 17°C, 10°C, and 5°C. Semen was analyzed at 24 and 96 h of storage. Motility and membrane integrity remained at high levels, except for lower values when stored in BTS at 5°C. Washed subsamples were incubated in capacitating medium (Tyrode) and control medium and were assessed for intracellular calcium concentration and integrity of plasma membranes using a flow cytometer. On the basis of the loss of low-calcium live cells in a kinetic approach, the specific response to capacitation stimuli was determined. There was a higher loss of response in semen stored hypothermically in the standard extender BTS compared to Androstar Plus. Assessment of the extent of phospholipid disorder under capacitating and control conditions by use of merocyanine staining did not reveal any significant extender-related differences. A field insemination trial with 778 sows was performed to relate in vitro results to fertility. Fertility parameters did not differ in semen stored up to 48 h at 10°C in Androstar Plus compared to controls stored at 17°C in BTS. In conclusion, assessment of specific reactivity to capacitating stimuli appears to be a sensitive tool for detection of extender-dependent alterations in functionality of chilled boar spermatozoa.

Isolating the effect of pore size distribution on electrochemical double-layer capacitance using activated fluid coke

Science.gov (United States)

Zuliani, Jocelyn E.; Tong, Shitang; Kirk, Donald W.; Jia, Charles Q.

2015-12-01

Electrochemical double-layer capacitors (EDLCs) use physical ion adsorption in the capacitive electrical double layer of high specific surface area (SSA) materials to store electrical energy. Previous work shows that the SSA-normalized capacitance increases when pore diameters are less than 1 nm. However, there still remains uncertainty about the charge storage mechanism since the enhanced SSA-normalized capacitance is not observed in all microporous materials. In previous studies, the total specific surface area and the chemical composition of the electrode materials were not controlled. The current work is the first reported study that systematically compares the performance of activated carbon prepared from the same raw material, with similar chemical composition and specific surface area, but different pore size distributions. Preparing samples with similar SSAs, but different pores sizes is not straightforward since increasing pore diameters results in decreasing the SSA. This study observes that the microporous activated carbon has a higher SSA-normalized capacitance, 14.1 μF cm-2, compared to the mesoporous material, 12.4 μF cm-2. However, this enhanced SSA-normalized capacitance is only observed above a threshold operating voltage. Therefore, it can be concluded that a minimum applied voltage is required to induce ion adsorption in these sub-nanometer micropores, which increases the capacitance.

Green Synthesis of Boron Carbonitride with High Capacitance

Directory of Open Access Journals (Sweden)

Dongping Chen

2018-03-01

Full Text Available Boron carbonitrides (BCN have attracted great interest in superhard or energy storage materials. In this work, thin BCN sheets were synthesized at 250 °C by a facile and green solvothermal method. The structure and morphology were characterized by X-ray diffraction (XRD, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS, scanning electron microscopy (SEM, and transmission electron microscopy (TEM. Based on the results of electrochemical experiments, the thin BCN sheet exhibited excellent capacitance performance (343.1 F/g at a current density of 0.5 A/g and cycling stability (90%, which showed high potential applications in supercapacitors.

Capacitive performance of molybdenum nitride/titanium nitride nanotube array for supercapacitor

Energy Technology Data Exchange (ETDEWEB)

Xie, Yibing, E-mail: ybxie@seu.edu.cn; Tian, Fang

2017-01-15

Highlights: • MoN{sub x}/TiN NTA is fully converted from MoO{sub 2}/TiO{sub 2} NTA by one-step nitridation process. • MoN{sub x}/TiN NTA is used as feasible electrode material of high-performance supercapacitor. • MoN{sub x}/TiN NTA shows high capacitance, rate capability and cycling stability. - Abstract: Molybdenum nitride (MoN{sub x}) depositing on titanium nitride nanotube array (TiN NTA) was designed as MoN{sub x}/TiN NTA for supercapacitor electrode material. MoN{sub x}/TiN NTA was fabricated by electrodepositing molybdenum oxide onto titanium dioxide NTA and one-step nitridation treatment in ammonia. MoN{sub x}/TiN NTA involved top-surface layer of MoN{sub x} nanoparticles and underlying layer of TiN NTA, which contributed to electric double layer capacitance in aqueous lithium-ion electrolyte solution. The specific capacitance was increased from 69.05 mF cm{sup −2} for TiN NTA to 121.50 mF cm{sup −2} for MoN{sub x}/TiN NTA at 0.3 mA cm{sup −2}, presenting the improved capacitance performance. MoN{sub x} exhibited the capacitance of 174.83 F g{sup −1} at 1.5 A g{sup −1} and slightly declined to 109.13 F g{sup −1} at 30 A g{sup −1}, presenting high rate capability. MoN{sub x}/TiN NTA exhibited the capacitance retention ratio of 93.8% at 3.0 mA cm{sup −2} after 1000 cycles, presenting high cycling stability. MoN{sub x}/TiN NTA could act as a promising electrode material of supercapacitor.

Determination of specific capacitance of modified candlenut shell based carbon as electrode material for supercapacitor

Science.gov (United States)

Zakir, M.; Budi, P.; Raya, I.; Karim, A.; Wulandari, R.; Sobrido, A. B. J.

2018-03-01

Surface modification of candlenut shell carbon (CSC) using three chemicals: nitric acid (HNO3), hydrogen peroxide (H2O2), and sulfuric acid (H2SO4) has been carried out. Activation of CSC was performed using H3PO4 solution with different ratio between CSC and activator. Carbon surface area was determined by methylene blue adsorption method. Surface characterization was performed using FTIR spectroscopy and Boehm titration method. Specific capacitance of electrode prepared from CSAC (candlenuts shell activated carbon) materials was quantified by Cyclic Voltammetry (CV) measurement. The surface area before and after activation are 105,127 m2/g, 112,488 m2/g, 124,190 m2/g, and 135,167 m2/g, respectively. Surface modification of CSAC showed the improvement in the chemical functionality of CSAC surface. Analyses using FTIR spectroscopy and Boehm titration showed that modifications with HNO3, H2SO4 and H2O2 on the surface of the CSAC increased the number of oxygen functional groups. As a consequence, the specific capacitance of CSAC modified with 65% HNO3 attained the highest value (127 μF/g). There is an incredible increase by a factor of 298% from electrode which was constructed with un-modified CSAC material. This increase correlates to the largest number of oxygen functional groups of CSAC modified with nitric acid (HNO3).

Two-step electrodeposition construction of flower-on-sheet hierarchical cobalt hydroxide nano-forest for high-capacitance supercapacitors.

Science.gov (United States)

Yang, Wanlu; Gao, Zan; Ma, Jing; Wang, Jun; Zhang, Xingming; Liu, Lianhe

2013-11-28

A novel flower-on-sheet hierarchical morphology of α-Co(OH)2 nanostructures was achieved via an easy two-step synthesis strategy. The method is based on first a galvanostatic electrodeposition (GE) of vertically aligned interconnected Co(OH)2 nanosheets to form a branch layer and second a potentiostatic electrodeposition (PE) of Co(OH)2 microflowers on the obtained branch layer from the secondary growth of their sheet-like precursors. The formation mechanism of this special PE time-dependent nanostructure was proposed and their morphology-dependent supercapacitor properties were also investigated. For a given areas mass loading, high specific capacitances of 1822 F g(-1) have been achieved for the electrode obtained after 200 s GE followed by a 300 s PE in a three-electrode configuration, and it maintained 91% of its initial capacity after 1000 constant-current charge/discharge cycles. Even when the discharge current density was increased from 1 to 50 mA cm(-2), the capacitance was still as high as 1499 F g(-1), indicating an excellent rate performance of the fabricated electrodes. The high performances of the electrodes are attributed to the special porous structure, 3D hierarchical morphology, vertical aligned orientation, and low contact resistance between active material and charge collector.

Ternary manganese ferrite/graphene/polyaniline nanostructure with enhanced electrochemical capacitance performance

Science.gov (United States)

Xiong, Pan; Hu, Chenyao; Fan, Ye; Zhang, Wenyao; Zhu, Junwu; Wang, Xin

2014-11-01

A ternary manganese ferrite/graphene/polyaniline (MGP) nanostructure is designed and synthesized via a facile two-step approach. This nanostructure exhibits outstanding electrochemical performances, such as high specific capacitance (454.8 F g-1 at 0.2 A g-1), excellent rate capability (75.8% capacity retention at 5 A g-1), and good cycling stability (76.4% capacity retention after 5000 cycles at 2 A g-1), which are superior to those of its individual components (manganese ferrite, reduced-graphene oxide, polyaniline) and corresponding binary hybrids (manganese ferrite/graphene (MG), manganese ferrite/polyaniline (MP), and graphene/polyaniline (GP)). A symmetric supercapacitor device using the as-obtained hybrid has been fabricated and tested. The device exhibits a high specific capacitance of 307.2 F g-1 at 0.1 A g-1 with a maximum energy density of 13.5 W h kg-1. The high electrochemical performance of ternary MGP can be attributed to its well-designed nanostructure and the synergistic effect of the individual components.

Synthesis and super capacitance of goethite/reduced graphene oxide for supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Xu, Huan; Hu, Zhongai, E-mail: zhongai@nwnu.edu.cn; Lu, Ailian; Hu, Yingying; Li, Li; Yang, Yuying; Zhang, Ziyu; Wu, Hongying

2013-08-15

We report a one-step fabrication of α-iron oxyhydroxide/reduced graphene oxide (α-FeOOH/rGO) composites, in which the ferrous sulfate (FeSO{sub 4}·7H{sub 2}O) are used as the iron raw and reducing agent to grow goethite (α-FeOOH) and reduce graphite oxide (GO) to rGO in the same time. The morphology, composition and microstructure of the as-obtained samples are systematically characterized by thermogravimetric (TG) analysis, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and FT-IR. Moreover, their electrochemical properties are investigated using cyclic voltammetry and galvanostatic charge/discharge techniques. The specific capacitance of 452 F g{sup −1} is obtained at a specific current of 1 A g{sup −1} when the mass ratio of α-FeOOH to rGO is up to 80.3:19.7. In addition, the α-FeOOH/rGO composite electrodes exhibit the excellent rate capability (more than 79% retention at 10 A g{sup −1} relative to 1 A g{sup −1}) and well cycling stability (13% capacitance decay after 1000 cycles). These results suggest the importance and great potential of α-FeOOH/rGO composites in the applications of high-performance energy-storage. - Graphical abstract: α-FeOOH loaded on rGO sheets reveals excellent super-capacitive performance. Display Omitted - Highlights: • A one-step synthesis of the environmentally friendly electrode material is designed. • Ferrous sulfate is used as both iron raw source of goethite and reductant of GO. • α-FeOOH nanorods loaded on rGO sheets arrange into a raft-like array. • The resultant composite exhibits high specific capacitance and long cycling stability.

Synthesis and super capacitance of goethite/reduced graphene oxide for supercapacitors

International Nuclear Information System (INIS)

Xu, Huan; Hu, Zhongai; Lu, Ailian; Hu, Yingying; Li, Li; Yang, Yuying; Zhang, Ziyu; Wu, Hongying

2013-01-01

We report a one-step fabrication of α-iron oxyhydroxide/reduced graphene oxide (α-FeOOH/rGO) composites, in which the ferrous sulfate (FeSO 4 ·7H 2 O) are used as the iron raw and reducing agent to grow goethite (α-FeOOH) and reduce graphite oxide (GO) to rGO in the same time. The morphology, composition and microstructure of the as-obtained samples are systematically characterized by thermogravimetric (TG) analysis, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and FT-IR. Moreover, their electrochemical properties are investigated using cyclic voltammetry and galvanostatic charge/discharge techniques. The specific capacitance of 452 F g −1 is obtained at a specific current of 1 A g −1 when the mass ratio of α-FeOOH to rGO is up to 80.3:19.7. In addition, the α-FeOOH/rGO composite electrodes exhibit the excellent rate capability (more than 79% retention at 10 A g −1 relative to 1 A g −1 ) and well cycling stability (13% capacitance decay after 1000 cycles). These results suggest the importance and great potential of α-FeOOH/rGO composites in the applications of high-performance energy-storage. - Graphical abstract: α-FeOOH loaded on rGO sheets reveals excellent super-capacitive performance. Display Omitted - Highlights: • A one-step synthesis of the environmentally friendly electrode material is designed. • Ferrous sulfate is used as both iron raw source of goethite and reductant of GO. • α-FeOOH nanorods loaded on rGO sheets arrange into a raft-like array. • The resultant composite exhibits high specific capacitance and long cycling stability

The mechanism of specific capacitance improvement of supercapacitors based on MnO{sub 2} at an elevated operating temperature

Energy Technology Data Exchange (ETDEWEB)

Xu Juliang; Li Zhao; Han Dong; Deng Bo; Li Jin; Jiang Yiming, E-mail: corrosion@fudan.edu.cn

2012-07-01

Amorphous nanostructured MnO{sub 2} film was anodically deposited onto economical duplex stainless steel substrate. The obtained MnO{sub 2} film was characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy for microstructural, morphological, and compositional studies. The capacitive behavior was systematically investigated by cyclic voltammetry, charge-discharge cycling and electrochemical impedance spectroscopy (EIS) in 1 M Na{sub 2}SO{sub 4} electrolyte at different operating temperatures ranging from 20 to 60 Degree-Sign C. The specific capacitance (SC) was improved with an increase of operating temperature, and the highest SC of 398 F/g was achieved at a scan rate of 10 mV/s and operating temperature of 60 Degree-Sign C. The mechanism of SC improvement at elevated operating temperature was investigated using EIS. With an increase of operating temperature, the conductivity of electrolyte was improved, and the charge-transfer resistance (R{sub ct}) was decreased. The temperature dependence of 1/R{sub ct} follows an Arrhenius equation. The MnO{sub 2} film was electrochemically activated at 60 Degree-Sign C due to the formation of Na{sub y}MnO{sub 2} after discharging. - Highlights: Black-Right-Pointing-Pointer MnO{sub 2} was anodically deposited onto duplex stainless steel substrate. Black-Right-Pointing-Pointer The effect of operating temperature on the performance of MnO{sub 2} was studied. Black-Right-Pointing-Pointer The mechanism of specific capacitance improvement was investigated.

Synthesis and electrochemical capacitive properties of nitrogen-doped porous carbon micropolyhedra by direct carbonization of zeolitic imidazolate framework-11

Energy Technology Data Exchange (ETDEWEB)

Hao, Fei; Li, Li; Zhang, Xiaohua, E-mail: mickyxie@hnu.edu.cn; Chen, Jinhua, E-mail: chenjinhua@hnu.edu.cn

2015-06-15

Highlights: • Nitrogen-doped porous carbon micropolyhedra (N-PCMPs) were prepared from ZIF-11. • The activated N-PCMPs with fused KOH (N-PCMPs-A) have high specific surface area. • N-PCMPs-A exhibits high specific capacitance. • N-PCMPs-A reveals good cycling performance even at a high current density. - Abstract: Nitrogen-doped porous carbon micropolyhedra (N-PCMPs) were successfully prepared by direct carbonization of ZIF-11 polyhedra and further activated with fused KOH to obtain N-PCMPs-A. The morphology and microstructure of samples were examined by scanning electron microscopy, X-ray diffraction, and micropore and chemisorption analyzer. Electrochemical properties were characterized by cyclic voltammetry and galvanostatic charge/discharge method in 1.0 M H{sub 2}SO{sub 4} aqueous solution on a standard three-electrode system. Results show that, compared with N-PCMPs, N-PCMPs-A has higher specific surface area (2188 m{sup 2} g{sup −1}) and exhibits improved electrochemical capacitive properties (307 F g{sup −1} at 1.0 A g{sup −1}). The mass specific capacitance of N-PCMPs-A is also higher than that of most MOF-derived carbons, some carbide-derived carbons and carbon aerogel-derived carbons. In addition, the capacitance of the N-PCMPs-A retains 90% after 4000 cycles even at a high current density of 10 A g{sup −1}. These imply that N-PCMPs-A is the promising materials for the construction of a high-performance supercapacitor.

An impedance bridge measuring the capacitance ratio in the high frequency range up to 1 MHz

International Nuclear Information System (INIS)

Kim, Dan Bee; Lee, Hyung Kew; Kim, Wan-Seop

2017-01-01

This paper describes a 2-terminal-pair impedance bridge, measuring the capacitance ratio in the high frequency range up to 1 MHz. The bridge was configured with two voltage sources and a phase control unit which enabled the bridge balance by synchronizing the voltage sources with an enhanced phase resolution. Without employing the transformers such as inductive voltage divider, injection and detection transformers, etc, the bridge system is quite simple to set up, and the balance procedure is quick and easy. Using this dual-source coaxial bridge, the 1:1 and 10:1 capacitance ratios were measured with 1 pF–1 nF capacitors in the frequency range from 1 kHz to 1 MHz. The measurement values obtained by the dual-source bridge were then compared with reference values measured using a commercial precision capacitance bridge of AH2700A, the Z -matrix method developed by ourselves, and the 4-terminal-pair coaxial bridge by the Czech Metrological Institute. All the measurements agreed within the reference uncertainty range of an order of 10 −6 –10 −5 , proving the bridge ability as a trustworthy tool for measuring the capacitance ratio in the high frequency range. (paper)

Capacitive sensor for continuous monitoring of high-volume droplet microfluidic generation

KAUST Repository

Conchouso Gonzalez, David

2016-12-19

This paper presents a capacitive sensor for monitoring parallel microfluidic droplet generation. The great electric permittivity difference between common droplet microfluidic fluids such as air, oil and water (ϵoil ≈ 2–3 and ϵwater ≈ 80.4), allows for accurate detection of water in oil concentration changes. Capacitance variations as large as 10 pF between a channel filled with water or dodecane, are used to continuously monitor the output of a parallelization system producing 150 µl/min of water in dodecane emulsions. We also discuss a low cost fabrication process to manufacture these capacitive sensors, which can be integrated to different substrates.

A Study of Dip-Coatable, High-Capacitance Ion Gel Dielectrics for 3D EWOD Device Fabrication

Directory of Open Access Journals (Sweden)

Carlos E. Clement

2017-01-01

Full Text Available We present a dip-coatable, high-capacitance ion gel dielectric for scalable fabrication of three-dimensional (3D electrowetting-on-dielectric (EWOD devices such as an n × n liquid prism array. Due to the formation of a nanometer-thick electric double layer (EDL capacitor, an ion gel dielectric offers two to three orders higher specific capacitance (c ≈ 10 μF/cm2 than that of conventional dielectrics such as SiO2. However, the previous spin-coating method used for gel layer deposition poses several issues for 3D EWOD device fabrication, particularly when assembling multiple modules. Not only does the spin-coating process require multiple repetitions per module, but the ion gel layer also comes in risks of damage or contamination due to handling errors caused during assembly. In addition, it was observed that the chemical formulation previously used for the spin-coating method causes the surface defects on the dip-coated gel layers and thus leads to poor EWOD performance. In this paper, we alternatively propose a dip-coating method with modified gel solutions to obtain defect-free, functional ion gel layers without the issues arising from the spin-coating method for 3D device fabrication. A dip-coating approach offers a single-step coating solution with the benefits of simplicity, scalability, and high throughput for deposition of high-capacitance gel layers on non-planar EWOD devices. An ion gel solution was prepared by combining the [EMIM][TFSI] ionic liquid and the [P(VDF-HFP] copolymer at various wt % ratios in acetone solvent. Experimental studies were conducted to fully understand the effects of chemical composition ratios in the gel solution and how varying thicknesses of ion gel and Teflon layers affects EWOD performance. The effectiveness and potentiality of dip-coatable gel layers for 3D EWOD devices have been demonstrated through fabricating 5 × 1 arrayed liquid prisms using a single-step dip-coating method. Each prism module has

RF-MEMS capacitive switches with high reliability

Science.gov (United States)

Goldsmith, Charles L.; Auciello, Orlando H.; Carlisle, John A.; Sampath, Suresh; Sumant, Anirudha V.; Carpick, Robert W.; Hwang, James; Mancini, Derrick C.; Gudeman, Chris

2013-09-03

A reliable long life RF-MEMS capacitive switch is provided with a dielectric layer comprising a "fast discharge diamond dielectric layer" and enabling rapid switch recovery, dielectric layer charging and discharging that is efficient and effective to enable RF-MEMS switch operation to greater than or equal to 100 billion cycles.

Towards ultrahigh volumetric capacitance: graphene derived highly dense but porous carbons for supercapacitors

Science.gov (United States)

Tao, Ying; Xie, Xiaoying; Lv, Wei; Tang, Dai-Ming; Kong, Debin; Huang, Zhenghong; Nishihara, Hirotomo; Ishii, Takafumi; Li, Baohua; Golberg, Dmitri; Kang, Feiyu; Kyotani, Takashi; Yang, Quan-Hong

2013-10-01

A small volumetric capacitance resulting from a low packing density is one of the major limitations for novel nanocarbons finding real applications in commercial electrochemical energy storage devices. Here we report a carbon with a density of 1.58 g cm-3, 70% of the density of graphite, constructed of compactly interlinked graphene nanosheets, which is produced by an evaporation-induced drying of a graphene hydrogel. Such a carbon balances two seemingly incompatible characteristics: a porous microstructure and a high density, and therefore has a volumetric capacitance for electrochemical capacitors (ECs) up to 376 F cm-3, which is the highest value so far reported for carbon materials in an aqueous electrolyte. More promising, the carbon is conductive and moldable, and thus could be used directly as a well-shaped electrode sheet for the assembly of a supercapacitor device free of any additives, resulting in device-level high energy density ECs.

A capacitive level shifter for high voltage (2.5kV)

DEFF Research Database (Denmark)

Andersen, Thomas; Andersen, Michael A. E.; Thomsen, Ole Cornelius

2012-01-01

with focus on low power consumption as well as low capacitive load between the floating half-bridge node and ground (output capacitance). The operation of the level-shifter is tested and verified by measurements on a prototype half-bridge gate driver. Results conclude stabile operation at 2.44kV, 50k...

Novel high-frequency energy-efficient pulsed-dc generator for capacitively coupled plasma discharge

Science.gov (United States)

Mamun, Md Abdullah Al; Furuta, Hiroshi; Hatta, Akimitsu

2018-03-01

The circuit design, assembly, and operating tests of a high-frequency and high-voltage (HV) pulsed dc generator (PDG) for capacitively coupled plasma (CCP) discharge inside a vacuum chamber are reported. For capacitive loads, it is challenging to obtain sharp rectangular pulses with fast rising and falling edges, requiring intense current for quick charging and discharging. The requirement of intense current generally limits the pulse operation frequency. In this study, we present a new type of PDG consisting of a pair of half-resonant converters and a constant current-controller circuit connected with HV solid-state power switches that can deliver almost rectangular high voltage pulses with fast rising and falling edges for CCP discharge. A prototype of the PDG is assembled to modulate from a high-voltage direct current (HVdc) input into a pulsed HVdc output, while following an input pulse signal and a set current level. The pulse rise time and fall time are less than 500 ns and 800 ns, respectively, and the minimum pulse width is 1 µs. The maximum voltage for a negative pulse is 1000 V, and the maximum repetition frequency is 500 kHz. During the pulse on time, the plasma discharge current is controlled steadily at the set value. The half-resonant converters in the PDG perform recovery of the remaining energy from the capacitive load at every termination of pulse discharge. The PDG performed with a high energy efficiency of 85% from the HVdc input to the pulsed dc output at a repetition rate of 1 kHz and with stable plasma operation in various discharge conditions. The results suggest that the developed PDG can be considered to be more efficient for plasma processing by CCP.

Novel high-frequency energy-efficient pulsed-dc generator for capacitively coupled plasma discharge.

Science.gov (United States)

Mamun, Md Abdullah Al; Furuta, Hiroshi; Hatta, Akimitsu

2018-03-01

The circuit design, assembly, and operating tests of a high-frequency and high-voltage (HV) pulsed dc generator (PDG) for capacitively coupled plasma (CCP) discharge inside a vacuum chamber are reported. For capacitive loads, it is challenging to obtain sharp rectangular pulses with fast rising and falling edges, requiring intense current for quick charging and discharging. The requirement of intense current generally limits the pulse operation frequency. In this study, we present a new type of PDG consisting of a pair of half-resonant converters and a constant current-controller circuit connected with HV solid-state power switches that can deliver almost rectangular high voltage pulses with fast rising and falling edges for CCP discharge. A prototype of the PDG is assembled to modulate from a high-voltage direct current (HVdc) input into a pulsed HVdc output, while following an input pulse signal and a set current level. The pulse rise time and fall time are less than 500 ns and 800 ns, respectively, and the minimum pulse width is 1 µs. The maximum voltage for a negative pulse is 1000 V, and the maximum repetition frequency is 500 kHz. During the pulse on time, the plasma discharge current is controlled steadily at the set value. The half-resonant converters in the PDG perform recovery of the remaining energy from the capacitive load at every termination of pulse discharge. The PDG performed with a high energy efficiency of 85% from the HVdc input to the pulsed dc output at a repetition rate of 1 kHz and with stable plasma operation in various discharge conditions. The results suggest that the developed PDG can be considered to be more efficient for plasma processing by CCP.

In situ synthesized heteropoly acid/polyaniline/graphene nanocomposites to simultaneously boost both double layer- and pseudo-capacitance for supercapacitors.

Science.gov (United States)

Cui, Zhiming; Guo, Chun Xian; Yuan, Weiyong; Li, Chang Ming

2012-10-05

It is challenging to simultaneously increase double layer- and pseudo-capacitance for supercapacitors. Phosphomolybdic acid/polyaniline/graphene nanocomposites (PMo(12)-PANI/GS) were prepared by using PMo(12) as a bifunctional reagent for not only well dispersing graphene for high electrochemical double layer capacitance but also in situ chemically polymerizing aniline for high pseudocapacitance, resulting in a specific capacitance of 587 F g(-1), which is ~1.5 and 6 times higher than that of PANI/GS (392 F g(-1)) and GS (103 F g(-1)), respectively. The nanocomposites also exhibit good reversibility and stability. Other kinds of heteropolyacids such as molybdovanadophosphoric acids (PMo(12-x)V(x), x = 1, 2 and 3) were also used to prepare PMo(12-x)V(x)-PANI/GS nanocomposites, also showing enhanced double layer- and pseudo-capacitance. This further proves the proposed concept to simultaneously boost both double layer- and pseudo-capacitance and demonstrates that it could be a universal approach to significantly improve the capacitance for supercapacitors.

Computation of Dielectric Response in Molecular Solids for High Capacitance Organic Dielectrics.

Science.gov (United States)

Heitzer, Henry M; Marks, Tobin J; Ratner, Mark A

2016-09-20

The dielectric response of a material is central to numerous processes spanning the fields of chemistry, materials science, biology, and physics. Despite this broad importance across these disciplines, describing the dielectric environment of a molecular system at the level of first-principles theory and computation remains a great challenge and is of importance to understand the behavior of existing systems as well as to guide the design and synthetic realization of new ones. Furthermore, with recent advances in molecular electronics, nanotechnology, and molecular biology, it has become necessary to predict the dielectric properties of molecular systems that are often difficult or impossible to measure experimentally. In these scenarios, it is would be highly desirable to be able to determine dielectric response through efficient, accurate, and chemically informative calculations. A good example of where theoretical modeling of dielectric response would be valuable is in the development of high-capacitance organic gate dielectrics for unconventional electronics such as those that could be fabricated by high-throughput printing techniques. Gate dielectrics are fundamental components of all transistor-based logic circuitry, and the combination high dielectric constant and nanoscopic thickness (i.e., high capacitance) is essential to achieving high switching speeds and low power consumption. Molecule-based dielectrics offer the promise of cheap, flexible, and mass producible electronics when used in conjunction with unconventional organic or inorganic semiconducting materials to fabricate organic field effect transistors (OFETs). The molecular dielectrics developed to date typically have limited dielectric response, which results in low capacitances, translating into poor performance of the resulting OFETs. Furthermore, the development of better performing dielectric materials has been hindered by the current highly empirical and labor-intensive pace of synthetic

Capacitance and surface of carbons in supercapacitors

OpenAIRE

Lobato Ortega, Belén; Suárez Fernández, Loreto; Guardia, Laura; Álvarez Centeno, Teresa

2017-01-01

This research is focused in the missing link between the specific surface area of carbons surface and their electrochemical capacitance. Current protocols used for the characterization of carbons applied in supercapacitors electrodes induce inconsistencies in the values of the interfacial capacitance (in F m−2), which is hindering the optimization of supercapacitors. The constraints of both the physisorption of N2 at 77 K and the standard methods used for the isotherm analysis frequently lead...

3D printed stretchable capacitive sensors for highly sensitive tactile and electrochemical sensing

Science.gov (United States)

Li, Kai; Wei, Hong; Liu, Wenguang; Meng, Hong; Zhang, Peixin; Yan, Chaoyi

2018-05-01

Developments of innovative strategies for the fabrication of stretchable sensors are of crucial importance for their applications in wearable electronic systems. In this work, we report the successful fabrication of stretchable capacitive sensors using a novel 3D printing method for highly sensitive tactile and electrochemical sensing applications. Unlike conventional lithographic or templated methods, the programmable 3D printing technique can fabricate complex device structures in a cost-effective and facile manner. We designed and fabricated stretchable capacitive sensors with interdigital and double-vortex designs and demonstrated their successful applications as tactile and electrochemical sensors. Especially, our stretchable sensors exhibited a detection limit as low as 1 × 10-6 M for NaCl aqueous solution, which could have significant potential applications when integrated in electronics skins.

Na/K-ATPase regulates bovine sperm capacitation through raft- and non-raft-mediated signaling mechanisms.

Science.gov (United States)

Rajamanickam, Gayathri D; Kastelic, John P; Thundathil, Jacob C

2017-11-01

Highly dynamic lipid microdomains (rafts) in the sperm plasma membrane contain several signaling proteins that regulate sperm capacitation. Na/K-ATPase isoforms (testis-specific isoform ATP1A4 and ubiquitous isoform ATP1A1) are abundant in bovine sperm plasma membrane. We previously reported that incubation of bovine sperm with ouabain, a specific Na/K-ATPase ligand, induced tyrosine phosphorylation of several sperm proteins during capacitation. The objective of this study was to investigate the roles of lipid rafts and non-rafts in Na/K-ATPase enzyme activity and signaling during bovine sperm capacitation. Content of ATP1A4 and, to a lesser extent, ATP1A1 was increased in raft and non-raft fractions of capacitated sperm, although non-raft enzyme activities of both isoforms were higher than the corresponding activities in rafts from capacitated sperm. Yet, ATP1A4 was the predominant isoform responsible for total Na/K-ATPase activity in both rafts and non-rafts. A comparative increase in phosphorylation of signaling molecules was observed in both raft (CAV1) and non-raft (EGFR and ERK1/2) membrane fractions during capacitation. Although SRC was phosphorylated in both membrane fractions, the non-raft fraction possessed more of this activated form. We also inferred, by immunoprecipitation, that ATP1A4 interacted with CAV1 and EGFR in the raft fraction, whereas interactions of ATP1A4 with SRC, EGFR, and ERK1/2 occurred in the non-raft fraction of ouabain-capacitated sperm; conversely, ATP1A1 interacted only with CAV1 in both fractions of uncapacitated and capacitated sperm. In conclusion, both raft and non-raft cohorts of Na/K-ATPase isoforms contributed to phosphorylation of signaling molecules during bovine sperm capacitation. © 2017 Wiley Periodicals, Inc.

Non-aqueous nanoporous gold based supercapacitors with high specific energy

International Nuclear Information System (INIS)

Hou, Ying; Chen, Luyang; Hirata, Akihiko; Fujita, Takeshi; Chen, Mingwei

2016-01-01

In this study, we report that the supercapacitor performance of polypyrrole (PPy) in non-aqueous electrolytes can be dramatically improved by highly conductive nanoporous gold which acts as both the support of active PPy and the current collector of supercapacitors. The excellent electronic conductivity, rich porous structure and large surface area of the nanoporous electrodes give rise to a high specific capacitance and low internal resistance in non-aqueous electrolytes. Combining with a wide working potential window of ~ 2 V, the non-aqueous PPy-based supercapacitors show an extraordinary energy density and power density.

Density Functional Theory Calculations of the Quantum Capacitance of Graphene Oxide as a Supercapacitor Electrode.

Science.gov (United States)

Song, Ce; Wang, Jinyan; Meng, Zhaoliang; Hu, Fangyuan; Jian, Xigao

2018-03-31

Graphene oxide has become an attractive electrode-material candidate for supercapacitors thanks to its higher specific capacitance compared to graphene. The quantum capacitance makes relative contributions to the specific capacitance, which is considered as the major limitation of graphene electrodes, while the quantum capacitance of graphene oxide is rarely concerned. This study explores the quantum capacitance of graphene oxide, which bears epoxy and hydroxyl groups on its basal plane, by employing density functional theory (DFT) calculations. The results demonstrate that the total density of states near the Fermi level is significantly enhanced by introducing oxygen-containing groups, which is beneficial for the improvement of the quantum capacitance. Moreover, the quantum capacitances of the graphene oxide with different concentrations of these two oxygen-containing groups are compared, revealing that more epoxy and hydroxyl groups result in a higher quantum capacitance. Notably, the hydroxyl concentration has a considerable effect on the capacitive behavior. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Phosphorization boosts the capacitance of mixed metal nanosheet arrays for high performance supercapacitor electrodes.

Science.gov (United States)

Lan, Yingying; Zhao, Hongyang; Zong, Yan; Li, Xinghua; Sun, Yong; Feng, Juan; Wang, Yan; Zheng, Xinliang; Du, Yaping

2018-05-01

Binary transition metal phosphides hold immense potential as innovative electrode materials for constructing high-performance energy storage devices. Herein, porous binary nickel-cobalt phosphide (NiCoP) nanosheet arrays anchored on nickel foam (NF) were rationally designed as self-supported binder-free electrodes with high supercapacitance performance. Taking the combined advantages of compositional features and array architectures, the nickel foam supported NiCoP nanosheet array (NiCoP@NF) electrode possesses superior electrochemical performance in comparison with Ni-Co LDH@NF and NiCoO2@NF electrodes. The NiCoP@NF electrode shows an ultrahigh specific capacitance of 2143 F g-1 at 1 A g-1 and retained 1615 F g-1 even at 20 A g-1, showing excellent rate performance. Furthermore, a binder-free all-solid-state asymmetric supercapacitor device is designed, which exhibits a high energy density of 27 W h kg-1 at a power density of 647 W kg-1. The hierarchical binary nickel-cobalt phosphide nanosheet arrays hold great promise as advanced electrode materials for supercapacitors with high electrochemical performance.

Electrodeposition and Capacitive Behavior of Films for Electrodes of Electrochemical Supercapacitors

Directory of Open Access Journals (Sweden)

Shi C

2010-01-01

Full Text Available Abstract Polypyrrole films were deposited by anodic electropolymerization on stainless steel substrates from aqueous pyrrole solutions containing sodium salicylate and tiron additives. The deposition yield was studied under galvanostatic conditions. The amount of the deposited material was varied by the variation of deposition time at a constant current density. SEM studies showed the formation of porous films with thicknesses in the range of 0–3 μm. Cyclic voltammetry data for the films tested in 0.5 M Na2SO4 solutions showed capacitive behavior and high specific capacitance (SC in a voltage window of 0.9 V. The films prepared from pyrrole solutions containing tiron showed better capacitive behavior compared to the films prepared from the solutions containing sodium salicylate. A highest SC of 254 F g−1 was observed for the sample with a specific mass of 89 μg cm−2 at a scan rate of 2 mV s−1. The SC decreased with an increasing film thickness and scan rate. The results indicated that the polypyrrole films deposited on the stainless steel substrates by anodic electropolymerization can be used as electrodes for electrochemical supercapacitors (ES.

Electrodeposition and Capacitive Behavior of Films for Electrodes of Electrochemical Supercapacitors

Science.gov (United States)

Shi, C.; Zhitomirsky, I.

2010-03-01

Polypyrrole films were deposited by anodic electropolymerization on stainless steel substrates from aqueous pyrrole solutions containing sodium salicylate and tiron additives. The deposition yield was studied under galvanostatic conditions. The amount of the deposited material was varied by the variation of deposition time at a constant current density. SEM studies showed the formation of porous films with thicknesses in the range of 0-3 μm. Cyclic voltammetry data for the films tested in 0.5 M Na2SO4 solutions showed capacitive behavior and high specific capacitance (SC) in a voltage window of 0.9 V. The films prepared from pyrrole solutions containing tiron showed better capacitive behavior compared to the films prepared from the solutions containing sodium salicylate. A highest SC of 254 F g-1 was observed for the sample with a specific mass of 89 μg cm-2 at a scan rate of 2 mV s-1. The SC decreased with an increasing film thickness and scan rate. The results indicated that the polypyrrole films deposited on the stainless steel substrates by anodic electropolymerization can be used as electrodes for electrochemical supercapacitors (ES).

Graphene and maghemite composites based supercapacitors delivering high volumetric capacitance and extraordinary cycling stability

International Nuclear Information System (INIS)

Zhang, Haitao; Zhang, Xiong; Lin, He; Wang, Kai; Sun, Xianzhong; Xu, Nansheng; Li, Chen; Ma, Yanwei

2015-01-01

Metal oxides (like MnO 2 , Fe 2 O 3 , and Co 3 O 4 , etc) based supercapacitors have disadvantages, such as low volumetric capacitance for thick-film electrodes, or short cycling life because a Faradaic process involves chemical changes of state of the reactant species. In the present work, we report that supercapacitors based on reduced graphene oxide and maghemite (γ-Fe 2 O 3 ) composites (GγM) exhibit superior performance. GγM electrodes with average electrode thickness up to ∼60 μm have a high volumetric capacitance of 230 F cm −3 , together with an outstanding electrode package density of 1.44 g cm −3 . Particularly, the GγM electrodes have excellent cycling performance of ∼90% capacitance retention over 100,000 galvanostatic charge–discharge cycles or voltage floating at 0.9 V for 300 h. No detectable change in phase and an effective inhibition of γ-Fe 2 O 3 refinement after cycle-life test are confirmed by X-ray diffraction and transmission electron microscopy

A High-Efficient Low-Cost Converter for Capacitive Wireless Power Transfer Systems

Directory of Open Access Journals (Sweden)

Il-Oun Lee

2017-09-01

Full Text Available Growth of the Internet of Things (IoT spurs need for new ways of delivering power. Wireless power transfer (WPT has come into the spotlight from both academia and industry as a promising way to power the IoT devices. As one of the well-known WPT techniques, the capacitive power transfer (CPT has the merit of low electromagnetic radiation and amenability of combined power and data transfer over a capacitive interface. However, applying the CPT to the IoT devices is still challenging in reality. One of the major issues is due to the small capacitance of the capacitive interface, which results in low efficiency of the power transfer. To tackle this problem, we present a new step-up single-switch quasi-resonant (SSQR converter for the CPT system. To enhance the CPT efficiency, the proposed converter is designed to operate at low frequency and drive small current into the capacitive interfaces. In addition, by eliminating resistor-capacitor-diode (RCD snubber in the converter, we reduce the implementation cost of the CPT system. Based on intensive experimental work with a CPT system prototype that supports maximum 50 W (100 V/0.5 A power transfer, we demonstrate the functional correctness of the converter that achieves up to 93% efficiency.

Novel graphene-like electrodes for capacitive deionization.

Science.gov (United States)

Li, Haibo; Zou, Linda; Pan, Likun; Sun, Zhuo

2010-11-15

Capacitive deionization (CDI) is a novel technology that has been developed for removal of charged ionic species from salty water, such as salt ions. The basic concept of CDI, as well as electrosorption, is to force charged ions toward oppositely polarized electrodes through imposing a direct electric field to form a strong electrical double layer and hold the ions. Once the electric field disappears, the ions are instantly released back to the bulk solution. CDI is an alternative low-energy consumption desalination technology. Graphene-like nanoflakes (GNFs) with relatively high specific surface area have been prepared and used as electrodes for capacitive deionization. The GNFs were synthesized by a modified Hummers' method using hydrazine for reduction. They were characterized by atomic force microscopy, N2 adsorption at 77 K and electrochemical workstation. It was found that the ratio of nitric acid and sulfuric acid plays a vital role in determining the specific surface area of GNFs. Its electrosorption performance was much better than commercial activated carbon (AC), suggesting a great potential in capacitive deionisation application. Further, the electrosorptive performance of GNFs electrodes with different bias potentials, flow rates and ionic strengths were measured and the electrosorption isotherm and kinetics were investigated. The results showed that GNFs prepared by this process had the specific surface area of 222.01 m²/g. The specific electrosorptive capacity of the GNFs was 23.18 µmol/g for sodium ions (Na+) when the initial concentration was at 25 mg/L, which was higher than that of previously reported data using graphene and AC under the same experimental condition. In addition, the equilibrium electrosorption capacity was determined as 73.47 µmol/g at 2.0 V by fitting data through the Langmuir isotherm, and the rate constant was found to be 1.01 min⁻¹ by fitting data through pseudo first-order adsorption. The results suggested that the

Enhanced performance in capacitive force sensors using carbon nanotube/polydimethylsiloxane nanocomposites with high dielectric properties

Science.gov (United States)

Jang, Hyeyoung; Yoon, Hyungsuk; Ko, Youngpyo; Choi, Jaeyoo; Lee, Sang-Soo; Jeon, Insu; Kim, Jong-Ho; Kim, Heesuk

2016-03-01

Force sensors have attracted tremendous attention owing to their applications in various fields such as touch screens, robots, smart scales, and wearable devices. The force sensors reported so far have been mainly focused on high sensitivity based on delicate microstructured materials, resulting in low reproducibility and high fabrication cost that are limitations for wide applications. As an alternative, we demonstrate a novel capacitive-type force sensor with enhanced performance owing to the increased dielectric properties of elastomers and simple sensor structure. We rationally design dielectric elastomers based on alkylamine modified-multi-walled carbon nanotube (MWCNT)/polydimethylsiloxane (PDMS) composites, which have a higher dielectric constant than pure PDMS. The alkylamine-MWCNTs show excellent dispersion in a PDMS matrix, thus leading to enhanced and reliable dielectric properties of the composites. A force sensor array fabricated with alkylamine-MWCNT/PDMS composites presents an enhanced response due to the higher dielectric constant of the composites than that of pure PDMS. This study is the first to report enhanced performance of capacitive force sensors by modulating the dielectric properties of elastomers. We believe that the disclosed strategy to improve the sensor performance by increasing the dielectric properties of elastomers has great potential in the development of capacitive force sensor arrays that respond to various input forces.Force sensors have attracted tremendous attention owing to their applications in various fields such as touch screens, robots, smart scales, and wearable devices. The force sensors reported so far have been mainly focused on high sensitivity based on delicate microstructured materials, resulting in low reproducibility and high fabrication cost that are limitations for wide applications. As an alternative, we demonstrate a novel capacitive-type force sensor with enhanced performance owing to the increased

Improved capacitance characteristics of electrospun ACFs by pore size control and vanadium catalyst.

Science.gov (United States)

Im, Ji Sun; Woo, Sang-Wook; Jung, Min-Jung; Lee, Young-Seak

2008-11-01

Nano-sized carbon fibers were prepared by using electrospinning, and their electrochemical properties were investigated as a possible electrode material for use as an electric double-layer capacitor (EDLC). To improve the electrode capacitance of EDLC, we implemented a three-step optimization. First, metal catalyst was introduced into the carbon fibers due to the excellent conductivity of metal. Vanadium pentoxide was used because it could be converted to vanadium for improved conductivity as the pore structure develops during the carbonization step. Vanadium catalyst was well dispersed in the carbon fibers, improving the capacitance of the electrode. Second, pore-size development was manipulated to obtain small mesopore sizes ranging from 2 to 5 nm. Through chemical activation, carbon fibers with controlled pore sizes were prepared with a high specific surface and pore volume, and their pore structure was investigated by using a BET apparatus. Finally, polyacrylonitrile was used as a carbon precursor to enrich for nitrogen content in the final product because nitrogen is known to improve electrode capacitance. Ultimately, the electrospun activated carbon fibers containing vanadium show improved functionality in charge/discharge, cyclic voltammetry, and specific capacitance compared with other samples because of an optimal combination of vanadium, nitrogen, and fixed pore structures.

Nonlinear Parasitic Capacitance Modelling of High Voltage Power MOSFETs in Partial SOI Process

DEFF Research Database (Denmark)

Fan, Lin; Knott, Arnold; Jørgensen, Ivan Harald Holger

2016-01-01

: off-state, sub-threshold region, and on-state in the linear region. A high voltage power MOSFET is designed in a partial Silicon on Insulator (SOI) process, with the bulk as a separate terminal. 3D plots and contour plots of the capacitances versus bias voltages for the transistor summarize...

Conductive MOF electrodes for stable supercapacitors with high areal capacitance

Science.gov (United States)

Sheberla, Dennis; Bachman, John C.; Elias, Joseph S.; Sun, Cheng-Jun; Shao-Horn, Yang; Dincă, Mircea

2017-02-01

Owing to their high power density and superior cyclability relative to batteries, electrochemical double layer capacitors (EDLCs) have emerged as an important electrical energy storage technology that will play a critical role in the large-scale deployment of intermittent renewable energy sources, smart power grids, and electrical vehicles. Because the capacitance and charge-discharge rates of EDLCs scale with surface area and electrical conductivity, respectively, porous carbons such as activated carbon, carbon nanotubes and crosslinked or holey graphenes are used exclusively as the active electrode materials in EDLCs. One class of materials whose surface area far exceeds that of activated carbons, potentially allowing them to challenge the dominance of carbon electrodes in EDLCs, is metal-organic frameworks (MOFs). The high porosity of MOFs, however, is conventionally coupled to very poor electrical conductivity, which has thus far prevented the use of these materials as active electrodes in EDLCs. Here, we show that Ni3(2,3,6,7,10,11-hexaiminotriphenylene)2 (Ni3(HITP)2), a MOF with high electrical conductivity, can serve as the sole electrode material in an EDLC. This is the first example of a supercapacitor made entirely from neat MOFs as active materials, without conductive additives or other binders. The MOF-based device shows an areal capacitance that exceeds those of most carbon-based materials and capacity retention greater than 90% over 10,000 cycles, in line with commercial devices. Given the established structural and compositional tunability of MOFs, these results herald the advent of a new generation of supercapacitors whose active electrode materials can be tuned rationally, at the molecular level.

Conductive MOF electrodes for stable supercapacitors with high areal capacitance.

Science.gov (United States)

Sheberla, Dennis; Bachman, John C; Elias, Joseph S; Sun, Cheng-Jun; Shao-Horn, Yang; Dincă, Mircea

2017-02-01

Owing to their high power density and superior cyclability relative to batteries, electrochemical double layer capacitors (EDLCs) have emerged as an important electrical energy storage technology that will play a critical role in the large-scale deployment of intermittent renewable energy sources, smart power grids, and electrical vehicles. Because the capacitance and charge-discharge rates of EDLCs scale with surface area and electrical conductivity, respectively, porous carbons such as activated carbon, carbon nanotubes and crosslinked or holey graphenes are used exclusively as the active electrode materials in EDLCs. One class of materials whose surface area far exceeds that of activated carbons, potentially allowing them to challenge the dominance of carbon electrodes in EDLCs, is metal-organic frameworks (MOFs). The high porosity of MOFs, however, is conventionally coupled to very poor electrical conductivity, which has thus far prevented the use of these materials as active electrodes in EDLCs. Here, we show that Ni 3 (2,3,6,7,10,11-hexaiminotriphenylene) 2 (Ni 3 (HITP) 2 ), a MOF with high electrical conductivity, can serve as the sole electrode material in an EDLC. This is the first example of a supercapacitor made entirely from neat MOFs as active materials, without conductive additives or other binders. The MOF-based device shows an areal capacitance that exceeds those of most carbon-based materials and capacity retention greater than 90% over 10,000 cycles, in line with commercial devices. Given the established structural and compositional tunability of MOFs, these results herald the advent of a new generation of supercapacitors whose active electrode materials can be tuned rationally, at the molecular level.

A core–shell structured nanocomposite of NiO with carbon nanotubes as positive electrode material of high capacitance for supercapacitors

International Nuclear Information System (INIS)

Wen, Z.B.; Yu, F.; You, T.; Zhu, L.; Zhang, L.; Wu, Y.P.

2016-01-01

Highlights: • A core–shell structured NiO@CNTs nanocomposite is synthesized by a simple hydrothermal method. • The CNTs core effectively improves the capacitance, rate and cycling performance of NiO. • A supercapacitor is assembled when activated carbon is used as the negative electrode. • The supercapacitor presents an energy density up to 52.6 Wh kg"−"1. - Abstract: A nanocomposite of carbon nanotubes coated with nickel oxide was prepared by a simple hydrothermal method. The structure, morphology and electrochemical performance of the nanocomposite were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy, electrochemical tests including cyclic voltammogram, galvanostatic charge–discharge and electrochemical impedance spectroscopy, respectively. It presents the highest specific capacitance of 1844 F g"−"1 at 1 A g"−"1 and 1145 F g"−"1 at current density of 10 A g"−"1 with 88.9% (at 1 A g"−"1) capacitance retention after 1000 cycles. The specific capacitance of the nanocomposite is almost double of that of the virginal NiO (972 F g"−"1 at 1 A g"−"1). Its cycling behavior is also very good. When combined with activated carbon as the negative electrode, the energy density can be up to 52.6 Wh kg"−"1. Such good electrochemical behavior indicates that the nanocomposite is a promising electrode material for supercapacitors.

One-Dimensional Assembly of Conductive and Capacitive Metal Oxide Electrodes for High-Performance Asymmetric Supercapacitors.

Science.gov (United States)

Harilal, Midhun; Vidyadharan, Baiju; Misnon, Izan Izwan; Anilkumar, Gopinathan M; Lowe, Adrian; Ismail, Jamil; Yusoff, Mashitah M; Jose, Rajan

2017-03-29

A one-dimensional morphology comprising nanograins of two metal oxides, one with higher electrical conductivity (CuO) and the other with higher charge storability (Co 3 O 4 ), is developed by electrospinning technique. The CuO-Co 3 O 4 nanocomposite nanowires thus formed show high specific capacitance, high rate capability, and high cycling stability compared to their single-component nanowire counterparts when used as a supercapacitor electrode. Practical symmetric (SSCs) and asymmetric (ASCs) supercapacitors are fabricated using commercial activated carbon, CuO, Co 3 O 4 , and CuO-Co 3 O 4 composite nanowires, and their properties are compared. A high energy density of ∼44 Wh kg -1 at a power density of 14 kW kg -1 is achieved in CuO-Co 3 O 4 ASCs employing aqueous alkaline electrolytes, enabling them to store high energy at a faster rate. The current methodology of hybrid nanowires of various functional materials could be applied to extend the performance limit of diverse electrical and electrochemical devices.

Capacitive-discharge-pumped copper bromide vapour laser

International Nuclear Information System (INIS)

Sukhanov, V B; Fedorov, V F; Troitskii, V O; Gubarev, F A; Evtushenko, Gennadii S

2007-01-01

A copper bromide vapour laser pumped by a high-frequency capacitive discharge is developed. It is shown that, by using of a capacitive discharge, it is possible to built a sealed off metal halide vapour laser of a simple design allowing the addition of active impurities into the working medium. (letters)

Molybdenum oxide nanowires based supercapacitors with enhanced capacitance and energy density in ethylammonium nitrate electrolyte

Energy Technology Data Exchange (ETDEWEB)

Sarfraz, Mansoor; Aboud, Mohamed F.A.; Shakir, Imran, E-mail: shakir@skku.edu

2015-11-25

Orthorhombic molybdenum trioxide (α-MoO{sub 3}) nanowires as an electrode for electrochemical supercapacitors in ethylammonium nitrate (EAN) electrolyte exhibits a high specific capacitance of 288 Fg{sup −1}, which is 8 times higher than the specific capacitance obtained from MoO{sub 3} nanowires in water based electrolyte. MoO{sub 3} nanowires in EAN electrolyte exhibit energy density of 46.32 Wh kg{sup −1} at a power density of 20.3 kW kg{sup −1} with outstanding cycling stability with specific capacitance retention of 96% over 3000 cycles. We believe that the superior performance of the MoO{sub 3} nanowires in EAN based electrolyte is primarily due to its relatively low viscosity (0.28 P at 25 °C), high electrical conductivity (20 mS cm{sup −1} at 25 °C) and large working voltage window. The results clearly demonstrate that EAN as electrolyte is one of the most promising electrolyte for high performance large scale energy storage devices. - Highlights: • Synthesis of single crystalline molybdenum oxide nanowires. • Ethylammonium Nitrate as an electrolyte for high performance large scale psuedocapacitor based energy storage devices. • Molybdenum oxide nanowires based electrodes shows 8 fold enhancement in Ethylammonium Nitrate electrolyte as compared to water based electrolytes. • The devices in Ethylammonium Nitrate exhibit excellent stability, retaining 96% of its initial capacity after 3000 cycles.

In Situ High-Level Nitrogen Doping into Carbon Nanospheres and Boosting of Capacitive Charge Storage in Both Anode and Cathode for a High-Energy 4.5 V Full-Carbon Lithium-Ion Capacitor.

Science.gov (United States)

Sun, Fei; Liu, Xiaoyan; Wu, Hao Bin; Wang, Lijie; Gao, Jihui; Li, Hexing; Lu, Yunfeng

2018-05-02

To circumvent the imbalances of electrochemical kinetics and capacity between Li + storage anodes and capacitive cathodes for lithium-ion capacitors (LICs), we herein demonstrate an efficient solution by boosting the capacitive charge-storage contributions of carbon electrodes to construct a high-performance LIC. Such a strategy is achieved by the in situ and high-level doping of nitrogen atoms into carbon nanospheres (ANCS), which increases the carbon defects and active sites, inducing more rapidly capacitive charge-storage contributions for both Li + storage anodes and PF 6 - storage cathodes. High-level nitrogen-doping-induced capacitive enhancement is successfully evidenced by the construction of a symmetric supercapacitor using commercial organic electrolytes. Coupling a pre-lithiated ANCS anode with a fresh ANCS cathode enables a full-carbon LIC with a high operating voltage of 4.5 V and high energy and power densities thereof. The assembled LIC device delivers high energy densities of 206.7 and 115.4 Wh kg -1 at power densities of 0.225 and 22.5 kW kg -1 , respectively, as well as an unprecedented high-power cycling stability with only 0.0013% capacitance decay per cycle within 10 000 cycles at a high power output of 9 kW kg -1 .

Capacitance of a highly ordered array of nanocapacitors: Model and microscopy

Science.gov (United States)

Cortés, A.; Celedón, C.; Ulloa, P.; Kepaptsoglou, D.; Häberle, P.

2011-11-01

This manuscript describes briefly the process used to build an ordered porous array in an anodic aluminum oxide (AAO) membrane, filled with multiwall carbon nanotubes (MWCNTs). The MWCNTs were grown directly inside the membrane through chemical vapor deposition (CVD). The role of the CNTs is to provide narrow metal electrodes contact with a dielectric surface barrier, hence, forming a capacitor. This procedure allows the construction of an array of 1010 parallel nano-spherical capacitors/cm2. A central part of this contribution is the use of physical parameters obtained from processing transmission electron microscopy (TEM) images, to predict the specific capacitance of the AAOs arrays. Electrical parameters were obtained by solving Laplace's equation through finite element methods (FEMs).

A core–shell structured nanocomposite of NiO with carbon nanotubes as positive electrode material of high capacitance for supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Wen, Z.B., E-mail: zbwen@jxnu.edu.cn [College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang 330022 (China); Yu, F. [College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang 330022 (China); College of Energy, Nanjing Tech University, Nanjing 211816, Jiangsu Province (China); New Energy and Material Laboratory (NEML), Department of Chemistry & Shanghai Key Laboratory of Molecular Catalysis and Innovative Material, Fudan University, Shanghai 200433 (China); You, T.; Zhu, L. [College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang 330022 (China); Zhang, L., E-mail: lzhang@jxnu.edu.cn [College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang 330022 (China); Wu, Y.P., E-mail: wuyp@fudan.edu.cn [College of Energy, Nanjing Tech University, Nanjing 211816, Jiangsu Province (China); New Energy and Material Laboratory (NEML), Department of Chemistry & Shanghai Key Laboratory of Molecular Catalysis and Innovative Material, Fudan University, Shanghai 200433 (China)

2016-02-15

Highlights: • A core–shell structured NiO@CNTs nanocomposite is synthesized by a simple hydrothermal method. • The CNTs core effectively improves the capacitance, rate and cycling performance of NiO. • A supercapacitor is assembled when activated carbon is used as the negative electrode. • The supercapacitor presents an energy density up to 52.6 Wh kg{sup −1}. - Abstract: A nanocomposite of carbon nanotubes coated with nickel oxide was prepared by a simple hydrothermal method. The structure, morphology and electrochemical performance of the nanocomposite were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy, electrochemical tests including cyclic voltammogram, galvanostatic charge–discharge and electrochemical impedance spectroscopy, respectively. It presents the highest specific capacitance of 1844 F g{sup −1} at 1 A g{sup −1} and 1145 F g{sup −1} at current density of 10 A g{sup −1} with 88.9% (at 1 A g{sup −1}) capacitance retention after 1000 cycles. The specific capacitance of the nanocomposite is almost double of that of the virginal NiO (972 F g{sup −1} at 1 A g{sup −1}). Its cycling behavior is also very good. When combined with activated carbon as the negative electrode, the energy density can be up to 52.6 Wh kg{sup −1}. Such good electrochemical behavior indicates that the nanocomposite is a promising electrode material for supercapacitors.

A high-capacitance solid-state supercapacitor based on free-standing film of polyaniline and carbon particles

International Nuclear Information System (INIS)

Khosrozadeh, A.; Xing, M.; Wang, Q.

2015-01-01

Highlights: • The solid-state supercapacitor has high energy density and good cyclic stability. • The electrode is a freestanding composite film of polyaniline and carbon particles. • The impregnation of electrodes with gel electrolyte facilitates high capacitance. • The supercapacitor is lightweight, thin, flexible, and environmental friendly. - Abstract: Polyaniline tends to degrade with cycling in aqueous electrolytes and it can be alleviated using gel electrolytes. A low-cost solid-state supercapacitor of high energy density and good cyclic stability is fabricated with a facile method. The electrodes of the supercapacitor are made of a freestanding composite film of polyaniline and acid-treated carbon particles using phytic acid as a crosslinker, and the gel electrolyte is composed of sulfuric acid and polyvinyl alcohol. The electrochemical performances of the as-fabricated supercapacitor are investigated with cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. Our results show that a maximum capacitance of 272.6 F/g (3.63 F/cm 2 ) at a current density of 0.63 A/g can be achieved by the supercapacitor, which is significantly higher than most solid-state ones reported in the literature. The ability to achieve a high-capacitance supercapacitor with good cyclic stability is mainly attributed to excellent infiltration of the gel electrolyte into the electrodes. The developed lightweight, thin, flexible, and environmental friendly supercapacitor would have potential applications in various energy storage devices, such as wearable electronics and hybrid electric vehicles

Facile synthesis of NiWO4/reduced graphene oxide nanocomposite with excellent capacitive performance for supercapacitors

International Nuclear Information System (INIS)

Xu, Xiaowei; Pei, Liyuan; Yang, Yang; Shen, Jianfeng; Ye, Mingxin

2016-01-01

NiWO 4 /reduced graphene oxide (NWG) nanocomposite was successfully synthesized through a facile one-pot solvothermal method for the first time. The resulting nanocomposite is composed of NiWO 4 nanoparticles that are uniformly attached on graphene sheets by in situ reducing. The as-prepared NWG composite has been systematically characterized by Powder X-ray diffraction, Fourier transform infrared spectra, Raman spectroscopy, Thermogravimetric analysis, Scanning electron microscopy, Transmission electron microscopy, X-ray photoelectron spectra, and Brunauer–Emmett–Teller analysis. The capacitive performances of the as-prepared NWG composite as electrode material are investigated. It is found that the NWG composite exhibits a high specific capacitance up to 1031.3 F g −1 at a current density of 0.5 A g −1 . The greatly enhanced capacitive performance of the NWG electrode can be attributed to the synergetic effect of NiWO 4 nanoparticles and RGO, which provides conducting channels and active sites. The cyclic stability tests demonstrated no decreases of its initial values after 5000 cycles, suggesting that such hybrid electrode possesses a great potential application in energy-storage devices. - Highlights: • NiWO 4 /RGO composite was successfully prepared through a facile solvothermal method. • The NiWO 4 /RGO composite shows a high specific capacitance of 1031.3 F g −1 . • Enhanced electrical conductivity leads to superior electrochemical performance.

Capacitive divider for output voltage measurement of intense electron beam accelerator

International Nuclear Information System (INIS)

Ding Desheng; Yi Lingzhi; Yu Binxiong; Hong Zhiqiang; Liu Jinliang

2012-01-01

A kind of simple-mechanism, easy-disassembly self-integrating capacitive divider used for measuring diode output voltage of intense electron beam accelerator (IEBA) is developed. The structure of the capacitive divider is described, and the capacitance value of the capacitive divider is calculated by theoretical analysis and electromagnetic simulation. The dependence of measurement voltage on electrical parameters such as stray capacitance, earth capacitance of front resistance is obtained by PSpice simulation. Measured waveforms appear overshoot phenomenon when stray capacitance of front resistance is larger, and the wavefront will be affected when earth capacitance of front resistance is larger. The diode output voltage waveforms of intense electron beam accelerator, are measured by capacitive divider and calibrated by water resistance divider, which is accordance with that measured by a resistive divider, the division ratio is about 563007. The designed capacitive divider can be used to measure high-voltage pulse with 100 ns full width at half maximum. (authors)

Interdigitated electrodes as impedance and capacitance biosensors: A review

Science.gov (United States)

Mazlan, N. S.; Ramli, M. M.; Abdullah, M. M. A. B.; Halin, D. S. C.; Isa, S. S. M.; Talip, L. F. A.; Danial, N. S.; Murad, S. A. Z.

2017-09-01

Interdigitated electrodes (IDEs) are made of two individually addressable interdigitated comb-like electrode structures. IDEs are one of the most favored transducers, widely utilized in technological applications especially in the field of biological and chemical sensors due to their inexpensive, ease of fabrication process and high sensitivity. In order to detect and analyze a biochemical molecule or analyte, the impedance and capacitance signal need to be obtained. This paper investigates the working principle and influencer of the impedance and capacitance biosensors. The impedance biosensor depends on the resistance and capacitance while the capacitance biosensor influenced by the dielectric permittivity. However, the geometry and structures of the interdigitated electrodes affect both impedance and capacitance biosensor. The details have been discussed in this paper.

Polyaniline nanofibers with a high specific surface area and an improved pore structure for supercapacitors

Science.gov (United States)

Xu, Hailing; Li, Xingwei; Wang, Gengchao

2015-10-01

Polyaniline (PANI) with a high specific surface area and an improved pore structure (HSSA-PANI) has been prepared by using a facile method, treating PANI nanofibers with chloroform (CHCl3), and its structure, morphology and pore structure are investigated. The specific surface area and pore volume of HSSA-PANI are 817.3 m2 g-1 and 0.6 cm3 g-1, and those of PANI are 33.6 m2 g-1 and 0.2 cm3 g-1. As electrode materials, a large specific surface area and pore volume can provide high electroactive regions, accelerate the diffusion of ions, and mitigate the electrochemical degradation of active materials. Compared with PANI, the capacity retention rate of HSSA-PANI is 90% with a growth of current density from 5.0 to 30 A g-1, and that of PANI is 29%. At a current density of 30 A g-1, the specific capacitance of HSSA-PANI still reaches 278.3 F g-1, and that of PANI is 86.7 F g-1. At a current density of 5.0 A g-1, the capacitance retention of HSSA-PANI is 53.1% after 2000 cycles, and that of PANI electrode is only 28.1%.

Experimental study on capacitance void fraction meters for high temperature and high pressure conditions

International Nuclear Information System (INIS)

Watanabe, Hironori; Mitsutake, Toru; Shibata, Mitsuhiko; Takase, Kazuyuki

2010-01-01

The electro-void fraction meter (Capacitance type meter) was applied to higher pressure conditions of 18 MPa than BWR operating conditions of 7 MPa. The void fraction measurement system has been developed including the electrodes of void fraction measurement, instrumentation cables with mineral insulation and simplified electric circuit to provide good signal-to-noise ratio. It satisfied the performance of thermal and pressure resistance and electric insulating capacity. Calibration function for high temperature and high pressure conditions was confirmed through calibration test with 37-rod bundle against datum 19-rod bundle by the quick-shut valve method respectively under 2 MPa conditions. It was confirmed that the measured data were consistent with those measured by the quick-shut valve method. (author)

The critical role of point defects in improving the specific capacitance of δ-MnO₂ nanosheets

Energy Technology Data Exchange (ETDEWEB)

Gao, Peng; Metz, Peter; Hey, Trevyn; Gong, Yuxuan; Liu, Dawei; Edwards, Doreen D.; Howe, Jane Y.; Huang, Rong; Misture, Scott T.

2017-02-23

3D porous nanostructures built from 2D δ-MnO₂ nanosheets are an environmentally friendly and industrially scalable class of supercapacitor electrode material. While both the electrochemistry and defects of this material have been studied, the role of defects in improving the energy storage density of these materials has not been addressed. In this work, δ-MnO₂ nanosheet assemblies with 150 m² g^-1 specific surface area are prepared by exfoliation of crystalline K_xMnO₂ and subsequent reassembly. Equilibration at different pH introduces intentional Mn vacancies into the nanosheets, increasing pseudocapacitance to over 300 F g^-1, reducing charge transfer resistance as low as 3 Ω, and providing a 50% improvement in cycling stability. X-ray absorption spectroscopy and high-energy X-ray scattering demonstrate a correlation between the defect content and the improved electrochemical performance. The results show that Mn vacancies provide ion intercalation sites which concurrently improve specific capacitance, charge transfer resistance and cycling stability.

Programmable differential capacitance-to-voltage converter for MEMS accelerometers

Science.gov (United States)

Royo, G.; Sánchez-Azqueta, C.; Gimeno, C.; Aldea, C.; Celma, S.

2017-05-01

Capacitive MEMS sensors exhibit an excellent noise performance, high sensitivity and low power consumption. They offer a huge range of applications, being the accelerometer one of its main uses. In this work, we present the design of a capacitance-to-voltage converter in CMOS technology to measure the acceleration from the capacitance variations. It is based on a low-power, fully-differential transimpedance amplifier with low input impedance and a very low input noise.

Electrochemical capacitance of nanocomposite films formed by loading carbon nanotubes with ruthenium oxide

Energy Technology Data Exchange (ETDEWEB)

Lee, Jae-Kyung [Department of Chemical Engineering, University of Seoul, 90 Chonnong-dong, Tongdaemun-gu, Seoul (Korea, Republic of); Pathan, Habib M.; Jung, Kwang-Deog; Joo, Oh-Shim [Eco-Nano Research Center, Korea Institute of Science and Technology (KIST), P.O. Box 131, Cheongryang, Seoul (Korea, Republic of)

2006-09-22

This work reports the supercapacitive properties of composite films of multiwalled carbon nanotubes (MWNT) and ruthenium oxide (RuO{sub 2}). Transmission and scanning electron microscopy, cyclic voltammetry, and electrochemical studies revealed that the nanoporous three-dimensional arrangement of RuO{sub 2}-coated MWNT in these films facilitated the improvement of electron and ion transfer relative to MWNT films. The capacitance was measured for films of different RuO{sub 2} loading, revealing specific capacitances per mass as high as 628Fg{sup -1}. The energy storage density of the electrode has increased about three times as compared to MWNT treated with piranha solution. (author)

Capacitive chemical sensor

Science.gov (United States)

Manginell, Ronald P; Moorman, Matthew W; Wheeler, David R

2014-05-27

A microfabricated capacitive chemical sensor can be used as an autonomous chemical sensor or as an analyte-sensitive chemical preconcentrator in a larger microanalytical system. The capacitive chemical sensor detects changes in sensing film dielectric properties, such as the dielectric constant, conductivity, or dimensionality. These changes result from the interaction of a target analyte with the sensing film. This capability provides a low-power, self-heating chemical sensor suitable for remote and unattended sensing applications. The capacitive chemical sensor also enables a smart, analyte-sensitive chemical preconcentrator. After sorption of the sample by the sensing film, the film can be rapidly heated to release the sample for further analysis. Therefore, the capacitive chemical sensor can optimize the sample collection time prior to release to enable the rapid and accurate analysis of analytes by a microanalytical system.

Voltage Dependence of Supercapacitor Capacitance

Directory of Open Access Journals (Sweden)

Szewczyk Arkadiusz

2016-09-01

Full Text Available Electronic Double-Layer Capacitors (EDLC, called Supercapacitors (SC, are electronic devices that are capable to store a relatively high amount of energy in a small volume comparing to other types of capacitors. They are composed of an activated carbon layer and electrolyte solution. The charge is stored on electrodes, forming the Helmholtz layer, and in electrolyte. The capacitance of supercapacitor is voltage- dependent. We propose an experimental method, based on monitoring of charging and discharging a supercapacitor, which enables to evaluate the charge in an SC structure as well as the Capacitance-Voltage (C-V dependence. The measurement setup, method and experimental results of charging/discharging commercially available supercapacitors in various voltage and current conditions are presented. The total charge stored in an SC structure is proportional to the square of voltage at SC electrodes while the charge on electrodes increases linearly with the voltage on SC electrodes. The Helmholtz capacitance increases linearly with the voltage bias while a sublinear increase of total capacitance was found. The voltage on SC increases after the discharge of electrodes due to diffusion of charges from the electrolyte to the electrodes. We have found that the recovery voltage value is linearly proportional to the initial bias voltage value.

High precision capacitive beam phase probe for KHIMA project

Energy Technology Data Exchange (ETDEWEB)

Hwang, Ji-Gwang, E-mail: windy206@hanmail.net [Korea Institute of Radiological and Medical Sciences, 215–4, Gongneung-dong, Nowon-t, Seoul 139–706 (Korea, Republic of); Yang, Tae-Keun [Korea Institute of Radiological and Medical Sciences, 215–4, Gongneung-dong, Nowon-t, Seoul 139–706 (Korea, Republic of); Forck, Peter [GSI Helmholtz Centre for Ion Research, Darmstadt 64291, German (Germany)

2016-11-21

In the medium energy beam transport (MEBT) line of KHIMA project, a high precision beam phase probe monitor is required for a precise tuning of RF phase and amplitude of Radio Frequency Quadrupole (RFQ) accelerator and IH-DTL linac. It is also used for measuring a kinetic energy of ion beam by time-of-flight (TOF) method using two phase probes. The capacitive beam phase probe has been developed. The electromagnetic design of the high precision phase probe was performed to satisfy the phase resolution of 1° (@200 MHz). It was confirmed by the test result using a wire test bench. The measured phase accuracy of the fabricated phase probe is 1.19 ps. The pre-amplifier electronics with the 0.125 ∼ 1.61 GHz broad-band was designed and fabricated for amplifying the signal strength. The results of RF frequency and beam energy measurement using a proton beam from the cyclotron in KIRAMS is presented.

Study of the capacitance technique for measuring high-temperature blade tip clearance on ceramic rotors

Science.gov (United States)

Barranger, John P.

1993-01-01

Higher operating temperatures required for increased engine efficiency can be achieved by using ceramic materials for engine components. Ceramic turbine rotors are subject to the same limitations with regard to gas path efficiency as their superalloy predecessors. In this study, a modified frequency-modulation system is proposed for the measurement of blade tip clearance on ceramic rotors. It is expected to operate up to 1370 C (2500 F), the working temperature of present engines with ceramic turbine rotors. The design of the system addresses two special problems associated with nonmetallic blades: the capacitance is less than that of a metal blade and the effects of temperature may introduce uncertainty with regard to the blade tip material composition. To increase capacitance and stabilize the measurement, a small portion of the rotor is modified by the application of 5-micron-thick platinum films. The platinum surfaces on the probe electrodes and rotor that are exposed to the high-velocity gas stream are coated with an additional 10-micron-thick protective ceramic topcoat. A finite-element method is applied to calculate the capacitance as a function of clearance.

Fabrication and Characteristics of High Capacitance Al Thin Films Capacitor Using a Polymer Inhibitor Bath in Electroless Plating Process.

Science.gov (United States)

Cho, Young-Lae; Lee, Jung-Woo; Lee, Chang-Hyoung; Choi, Hyung-Seon; Kim, Sung-Su; Song, Young Il; Park, Chan; Suh, Su-Jeong

2015-10-01

An aluminum (Al) thin film capacitor was fabricated for a high capacitance capacitor using electrochemical etching, barrier-type anodizing, and electroless Ni-P plating. In this study, we focused on the bottom-up filling of Ni-P electrodes on Al2O3/Al with etched tunnels. The Al tunnel pits were irregularly distributed on the Al foil, diameters were in the range of about 0.5~1 μm, the depth of the tunnel pits was approximately 35~40 μm, and the complex structure was made full filled hard metal. To control the plating rate, the experiment was performed by adding polyethyleneimine (PEI, C2H5N), a high molecular substance. PEI forms a cross-link at the etching tunnel inlet, playing the role of delaying the inlet plating. When the PEI solution bath was used after activation, the Ni-P layer was deposited selectively on the bottoms of the tunnels. The characteristics were analyzed by adding the PEI addition quantity rate of 100~600 mg/L into the DI water. The capacitance of the Ni-P/Al2O3 (650~700 nm)/Al film was measured at 1 kHz using an impedance/gain phase analyzer. For the plane film without etch tunnels the capacitance was 12.5 nF/cm2 and for the etch film with Ni-P bottom-up filling the capacitance was 92 nF/cm2. These results illustrate a remarkable maximization of capacitance for thin film metal capacitors.

Effects of electrolytic composition on the electric double-layer capacitance at smooth-surface carbon electrodes in organic media

International Nuclear Information System (INIS)

Kim, In-Tae; Egashira, Minato; Yoshimoto, Nobuko; Morita, Masayuki

2010-01-01

As a fundamental research on the optimization of electrolyte composition in practical electrochemical capacitor device, double-layer capacitance at Glassy Carbon (GC) and Boron-doped Diamond (BDD), as typical smooth-surface carbon electrodes, has been studied as a function of the electrolyte composition in organic media. Specific capacitance (differential capacitance: F cm -2 ) determined by an AC impedance method, in which no contribution of mass-transport effects is included, corresponded well to integrated capacitance evaluated by conventional cyclic voltammetry. The specific capacitance at the GC electrode varied with polarized potential and showed clear PZC (potential of zero charge), while the potential dependence of the capacitance at BDD was very small. The effects of the solvent and the electrolytic salt on the capacitance behavior were common for both electrodes. That is, the sizes of the solvent molecule and the electrolytic ion (cation) strongly affected the capacitance at these smooth-surface carbon electrodes.

2D fluid-analytical simulation of electromagnetic effects in low pressure, high frequency electronegative capacitive discharges

International Nuclear Information System (INIS)

Kawamura, E; Lichtenberg, A J; Lieberman, M A; Marakhtanov, A M

2016-01-01

A fast 2D axisymmetric fluid-analytical multifrequency capacitively coupled plasma (CCP) reactor code is used to study center high nonuniformity in a low pressure electronegative chlorine discharge. In the code, a time-independent Helmholtz wave equation is used to solve for the capacitive fields in the linearized frequency domain. This eliminates the time dependence from the electromagnetic (EM) solve, greatly speeding up the simulations at the cost of neglecting higher harmonics. However, since the code allows up to three driving frequencies, we can add the two most important harmonics to the CCP simulations as the second and third input frequencies. The amplitude and phase of these harmonics are estimated by using a recently developed 1D radial nonlinear transmission line (TL) model of a highly asymmetric cylindrical discharge (Lieberman et al 2015 Plasma Sources Sci. Technol. 24 055011). We find that at higher applied frequencies, the higher harmonics contribute significantly to the center high nonuniformity due to their shorter plasma wavelengths. (paper)

Instrumentation to Measure the Capacitance of Biosensors by Sinusoidal Wave Method

Directory of Open Access Journals (Sweden)

Pavan Kumar KATHUROJU

2009-09-01

Full Text Available Micro Controller based instrumentation to measure the capacitance of biosensors is developed. It is based on frequency domain technique with sinusoidal wave input. Changes in the capacitance of biosensor because of the analyte specific reaction are calculated by knowing the current flowing through the sample. A dedicated 8-bit microcontroller (AT89C52 and its associated peripherals are employed for the hardware and application specific software is developed in ‘C’ language. The paper describes the methodology, instrumentation details along with a specific application to glucose sensing. The measurements are conducted with glucose oxidase based capacitance biosensor and the obtained results are compared with the conventional method of sugar measurements using the UV-Visible spectroscopy (Phenol-Sulphuric acid assay method. Measurement accuracy of the instrument is found to be ± 5 %. Experiments are conducted on glucose sensor with different bias voltages. It is found that for bias voltages varying from 0.5 to 0.7 Volt, the measurements are good for this application.

Solvent evaporation induced graphene powder with high volumetric capacitance and outstanding rate capability for supercapacitors

Science.gov (United States)

Zhang, Xiaozhe; Raj, Devaraj Vasanth; Zhou, Xufeng; Liu, Zhaoping

2018-04-01

Graphene-based electrode materials for supercapacitors usually suffer from poor volumetric performance due to the low density. The enhancement of volumetric capacitance by densification of graphene materials, however, is usually accompanied by deterioration of rate capability, as the huge contraction of pore size hinders rapid diffusion of electrolytes. Thus, it is important to develop suitable pore size in graphene materials, which can sustain fast ion diffusion and avoid excessive voids to acquire high density simultaneously for supercapacitor applications. Accordingly, we propose a simple solvent evaporation method to control the pore size of graphene powders by adjusting the surface tension of solvents. Ethanol is used instead of water to reduce the shrinkage degree of graphene powder during solvent evaporation process, due to its lower surface tension comparing with water. Followed by the assistance of mechanical compression, graphene powder having high compaction density of 1.30 g cm-3 and a large proportion of mesopores in the pore size range of 2-30 nm is obtained, which delivers high volumetric capacitance of 162 F cm-3 and exhibits outstanding rate performance of 76% capacity retention at a high current density of 100 A g-1 simultaneously.

Effect of cation nature of zeolite on carbon replicas and their electrochemical capacitance

International Nuclear Information System (INIS)

Zhou, Jin; Li, Wen; Zhang, Zhongshen; Wu, Xiaozhong; Xing, Wei; Zhuo, Shuping

2013-01-01

Graphical abstract: Cation nature of zeolite influences the porosity, surface chemical properties of carbon replicas of zeolite, resulting in different electrochemical capacitance. Highlights: ► The porosity of carbon replica strongly depends on zeolite's effective pore size. ► The surface chemical properties influence by the cation nature of zeolite. ► The N-doping introduces large pseudo-capacitance. ► The HYC800 carbon showed a high capacitance of up to 312 F g −1 in 1 M H 2 SO 4 . ► The prepared carbons show good durability of galvanostatic cycle. -- Abstract: N-doped carbon replicas of zeolite Y are prepared, and the effect of cation nature of zeolite (H + or Na + ) on the carbon replicas is studied. The morphology, structure and surface properties of the carbon materials are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N 2 adsorption, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The pore regularity, pore parameter and surface chemical properties of the carbons may strongly depend on the cation nature of the zeolite Y. The carbon replicas of zeolite HY (H-form of zeolite Y) possesses higher pore regularity and much larger surface area than those of zeolite NaY (Na-form of zeolite Y), while the latter carbons seem to possess higher carbonization degrees. Electrochemical measurements show a large faradaic capacitance related to the N- or O-containing groups for the prepared carbons. Owing to the large specific surface area, high pore regularity and heteroatom-doping, the HYC800 sample derived from zeolite HY presents very high gravimetric capacitance, up to 312.4 F g −1 in H 2 SO 4 electrolyte, and this carbon can operate at 1.2 V with good retention ratio in the range of 0.25 to 10 A g −1

Preparation and electrochemical capacitance performances of super-hydrophilic conducting polyaniline

Energy Technology Data Exchange (ETDEWEB)

Li, Xingwei; Li, Xiaohan; Dai, Na; Wang, Gengchao; Wang, Zhun [Shanghai Key Laboratory of Advanced Polymeric Materials, Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Meilong Road 130, Shanghai 200237 (China)

2010-08-15

Super-hydrophilic conducting polyaniline was prepared by surface modification of polyaniline using tetraethyl orthosilicate in water/ethanol solution, whereas its conductivity was 4.16 S cm{sup -1} at 25 C. And its electrochemical capacitance performances as an electrode material were evaluated by the cyclic voltammetry and galvanostatic charge/discharge test in 0.1 M H{sub 2}SO{sub 4} aqueous solution. Its initial specific capacitance was 500 F g{sup -1} at a constant current density of 1.5 A g{sup -1}, and the capacitance still reached about 400 F g{sup -1} after 5000 consecutive cycles. Moreover, its capacitance retention ratio was circa 70% with the growth of current densities from 1.5 to 20 A g{sup -1}, indicating excellent rate capability. It would be a promising electrode material for aqueous redox supercapacitors. (author)

Low Capacitive Inductors for Fast Switching Devices in Active Power Factor Correction Applications

DEFF Research Database (Denmark)

Hernandez Botella, Juan Carlos; Petersen, Lars Press; Andersen, Michael A. E.

2014-01-01

This paper examines different winding strategies for reduced capacitance inductors in active power factor correction circuits (PFC). The effect of the parasitic capacitance is analyzed from an electro magnetic compatibility (EMI) and efficiency point of views. The purpose of this work is to inves......This paper examines different winding strategies for reduced capacitance inductors in active power factor correction circuits (PFC). The effect of the parasitic capacitance is analyzed from an electro magnetic compatibility (EMI) and efficiency point of views. The purpose of this work...... is to investigate different winding approaches and identify suitable solutions for high switching frequency/high speed transition PFC designs. A low parasitic capacitance PCB based inductor design is proposed to address the challenges imposed by high switching frequency PFC Boost converters....

Characterising thermal resistances and capacitances of GaN high-electron-mobility transistors through dynamic electrothermal measurements

DEFF Research Database (Denmark)

Wei, Wei; Mikkelsen, Jan H.; Jensen, Ole Kiel

2014-01-01

This study presents a method to characterise thermal resistances and capacitances of GaN high-electron-mobility transistors (HEMTs) through dynamic electrothermal measurements. A measured relation between RF gain and the channel temperature (Tc) is formed and used for indirect measurements...

Capacitance-Power-Hysteresis Trilemma in Nanoporous Supercapacitors

Directory of Open Access Journals (Sweden)

Alpha A. Lee

2016-06-01

Full Text Available Nanoporous supercapacitors are an important player in the field of energy storage that fill the gap between dielectric capacitors and batteries. The key challenge in the development of supercapacitors is the perceived trade-off between capacitance and power delivery. Current efforts to boost the capacitance of nanoporous supercapacitors focus on reducing the pore size so that they can only accommodate a single layer of ions. However, this tight packing compromises the charging dynamics and hence power density. We show via an analytical theory and Monte Carlo simulations that charging is sensitively dependent on the affinity of ions to the pores, and that high capacitances can be obtained for ionophobic pores of widths significantly larger than the ion diameter. Our theory also predicts that charging can be hysteretic with a significant energy loss per cycle for intermediate ionophilicities. We use these observations to explore the parameter regimes in which a capacitance-power-hysteresis trilemma may be avoided.

Measurement of gas-liquid two-phase flow in micro-pipes by a capacitance sensor.

Science.gov (United States)

Ji, Haifeng; Li, Huajun; Huang, Zhiyao; Wang, Baoliang; Li, Haiqing

2014-11-26

A capacitance measurement system is developed for the measurement of gas-liquid two-phase flow in glass micro-pipes with inner diameters of 3.96, 2.65 and 1.56 mm, respectively. As a typical flow regime in a micro-pipe two-phase flow system, slug flow is chosen for this investigation. A capacitance sensor is designed and a high-resolution and high-speed capacitance measurement circuit is used to measure the small capacitance signals based on the differential sampling method. The performance and feasibility of the capacitance method are investigated and discussed. The capacitance signal is analyzed, which can reflect the voidage variation of two-phase flow. The gas slug velocity is determined through a cross-correlation technique using two identical capacitance sensors. The simulation and experimental results show that the presented capacitance measurement system is successful. Research work also verifies that the capacitance sensor is an effective method for the measurement of gas liquid two-phase flow parameters in micro-pipes.

Approaching the theoretical capacitance of graphene through copper foam integrated three-dimensional graphene networks

DEFF Research Database (Denmark)

Dey, Ramendra Sundar; Hjuler, Hans Aage; Chi, Qijin

2015-01-01

We report a facile and low-cost approach for the preparation of all-in-one supercapacitor electrodes using copper foam (CuF) integrated three-dimensional (3D) reduced graphene oxide (rGO) networks. The binderfree 3DrGO@CuF electrodes are capable of delivering high specific capacitance approaching...

Decrease in the cytosolic NADP+-dependent isocitrate dehydrogenase activity through porcine sperm capacitation.

Science.gov (United States)

Katoh, Yuki; Tamba, Michiko; Matsuda, Manabu; Kikuchi, Kazuhiro; Okamura, Naomichi

2018-02-26

In order to understand the molecular mechanisms involved in the sperm capacitation, we have identified the proteins tyrosine-phosphorylated during the capacitation especially in conjunction with the regulation of the levels of reactive oxygen species (ROS) in sperm. In the present study, the effects of the tyrosine phosphorylation of cytosolic NADP + -dependent isocitrate dehydrogenase (IDPc) on its catalytic activity and on the levels of ROS in sperm have been studied. The tyrosine phosphorylated IDPc showed a significantly lowered enzymatic activity. The immunocytochemical analyses using the highly specific antisera against IDPc revealed that IDPc was mainly localized to the principal piece of the porcine sperm flagellum. As IDPc is one of the major NADPH regenerating enzymes in porcine sperm, it is strongly suggested that the decrease in IDPc activity is involved in the increased levels of ROS, which results in the induction of hyperactivated flagellar movement and capacitation. Copyright © 2018 Elsevier Inc. All rights reserved.

3D capacitive tactile sensor using DRIE micromachining

Science.gov (United States)

Chuang, Chiehtang; Chen, Rongshun

2005-07-01

This paper presents a three dimensional micro capacitive tactile sensor that can detect normal and shear forces which is fabricated using deep reactive ion etching (DRIE) bulk silicon micromachining. The tactile sensor consists of a force transmission plate, a symmetric suspension system, and comb electrodes. The sensing character is based on the changes of capacitance between coplanar sense electrodes. High sensitivity is achieved by using the high aspect ratio interdigital electrodes with narrow comb gaps and large overlap areas. The symmetric suspension mechanism of this sensor can easily solve the coupling problem of measurement and increase the stability of the structure. In this paper, the sensor structure is designed, the capacitance variation of the proposed device is theoretically analyzed, and the finite element analysis of mechanical behavior of the structures is performed.

3D MnO2-graphene composites with large areal capacitance for high-performance asymmetric supercapacitors

Science.gov (United States)

Zhai, Teng; Wang, Fuxin; Yu, Minghao; Xie, Shilei; Liang, Chaolun; Li, Cheng; Xiao, Fangming; Tang, Renheng; Wu, Qixiu; Lu, Xihong; Tong, Yexiang

2013-07-01

In this paper, we reported an effective and simple strategy to prepare large areal mass loading of MnO2 on porous graphene gel/Ni foam (denoted as MnO2/G-gel/NF) for supercapacitors (SCs). The MnO2/G-gel/NF (MnO2 mass: 13.6 mg cm-2) delivered a large areal capacitance of 3.18 F cm-2 (234.2 F g-1) and good rate capability. The prominent electrochemical properties of MnO2/G-gel/NF are attributed to the enhanced conductivities and improved accessible area for ions in electrolytes. Moreover, an asymmetric supercapacitor (ASC) based on MnO2/G-gel/NF (MnO2 mass: 6.1 mg cm-2) as the positive electrode and G-gel/NF as the negative electrode achieved a remarkable energy density of 0.72 mW h cm-3. Additionally, the fabricated ASC device also exhibited excellent cycling stability, with less than 1.5% decay after 10 000 cycles. The ability to effectively develop SC electrodes with high mass loading should open up new opportunities for SCs with high areal capacitance and high energy density.In this paper, we reported an effective and simple strategy to prepare large areal mass loading of MnO2 on porous graphene gel/Ni foam (denoted as MnO2/G-gel/NF) for supercapacitors (SCs). The MnO2/G-gel/NF (MnO2 mass: 13.6 mg cm-2) delivered a large areal capacitance of 3.18 F cm-2 (234.2 F g-1) and good rate capability. The prominent electrochemical properties of MnO2/G-gel/NF are attributed to the enhanced conductivities and improved accessible area for ions in electrolytes. Moreover, an asymmetric supercapacitor (ASC) based on MnO2/G-gel/NF (MnO2 mass: 6.1 mg cm-2) as the positive electrode and G-gel/NF as the negative electrode achieved a remarkable energy density of 0.72 mW h cm-3. Additionally, the fabricated ASC device also exhibited excellent cycling stability, with less than 1.5% decay after 10 000 cycles. The ability to effectively develop SC electrodes with high mass loading should open up new opportunities for SCs with high areal capacitance and high energy density. Electronic

Fabrication of nickel hydroxide electrodes with open-ended hexagonal nanotube arrays for high capacitance supercapacitors.

Science.gov (United States)

Wu, Mao-Sung; Huang, Kuo-Chih

2011-11-28

A nickel hydroxide electrode with open-ended hexagonal nanotube arrays, prepared by hydrolysis of nickel chloride in the presence of hexagonal ZnO nanorods, shows a very high capacitance of 1328 F g(-1) at a discharge current density of 1 A g(-1) due to the significantly improved ion transport.

Capacitive MEMS-based sensors : thermo-mechanical stability and charge trapping

OpenAIRE

van Essen, M.C.

2009-01-01

Micro-Electro Mechanical Systems (MEMS) are generally characterized as miniaturized systems with electrostatically driven moving parts. In many cases, the electrodes are capacitively coupled. This basic scheme allows for a plethora of specifications and functionality. This technology has presently matured and is widely employed in industry. A voltage across the electrodes will attract the movable part. This relation between electric field and separation (or capacitance) can be conveniently em...

Measurement Error Estimation for Capacitive Voltage Transformer by Insulation Parameters

Directory of Open Access Journals (Sweden)

Bin Chen

2017-03-01

Full Text Available Measurement errors of a capacitive voltage transformer (CVT are relevant to its equivalent parameters for which its capacitive divider contributes the most. In daily operation, dielectric aging, moisture, dielectric breakdown, etc., it will exert mixing effects on a capacitive divider’s insulation characteristics, leading to fluctuation in equivalent parameters which result in the measurement error. This paper proposes an equivalent circuit model to represent a CVT which incorporates insulation characteristics of a capacitive divider. After software simulation and laboratory experiments, the relationship between measurement errors and insulation parameters is obtained. It indicates that variation of insulation parameters in a CVT will cause a reasonable measurement error. From field tests and calculation, equivalent capacitance mainly affects magnitude error, while dielectric loss mainly affects phase error. As capacitance changes 0.2%, magnitude error can reach −0.2%. As dielectric loss factor changes 0.2%, phase error can reach 5′. An increase of equivalent capacitance and dielectric loss factor in the high-voltage capacitor will cause a positive real power measurement error. An increase of equivalent capacitance and dielectric loss factor in the low-voltage capacitor will cause a negative real power measurement error.

A Self-Templating Scheme for the Synthesis of Nanostructured Transition Metal Chalcogenide Electrodes for Capacitive Energy Storage

KAUST Repository

Xia, Chuan

2015-06-11

Due to their unique structural features including well-defined interior voids, low density, low coefficients of thermal expansion, large surface area and surface permeability, hollow micro/nanostructured transition metal sulfides with high conductivity have been investigated as new class of electrode materials for pseudocapacitor applications. Herein, we report a novel self-templating strategy to fabricate well-defined single and double-shell NiCo2S4 hollow spheres, as a promising electrode material for pseudocapacitors. The surfaces of the NiCo2S4 hollow spheres consist of self-assembled 2D mesoporous nanosheets. This unique morphology results in a high specific capacitance (1257 F g-1 at 2 A g-1), remarkable rate performance (76.4% retention of initial capacitance from 2 A g-1 to 60 A g-1) and exceptional reversibility with a cycling efficiency of 93.8% and 87% after 10,000 and 20,000 cycles, respectively, at a high current density of 10 A g-1. The cycling stability of our ternary chalcogenides is comparable to carbonaceous electrode materials, but with much higher specific capacitance (higher than any previously reported ternary chalcogenide), suggesting that these unique chalcogenide structures have potential application in next-generation commercial pseudocapacitors.

High Capacitive Storage Performance of Sulfur and Nitrogen Codoped Mesoporous Graphene.

Science.gov (United States)

Ma, Xinlong; Gao, Daowei

2018-03-22

Mesoporous graphene is synthesized based on the chemical vapor deposition methodology by using heavy MgO flakes as substrates in a fluidized-bed reactor. Subsequently, sulfur and nitrogen coincorporation into graphene frameworks is realized by the reaction between carbon atoms and thiourea molecules. The as-obtained sulfur and nitrogen codoped mesoporous graphene (SNMG) exhibits remarkable capacitive energy-storage behavior, as a result of well-developed pore channels, in terms of that in a symmetric supercapacitor and lithium-ion hybrid capacitor (LIHC). The ultrahigh durability of the SNMG/SNMG symmetric supercapacitor is demonstrated by long-term cycling, for which no capacitance decay is found after 20 000 cycles. A LIHC constructed from commercial Li 4 Ti 5 O 12 (LTO) as the anode and SNMG as the cathode is capable of delivering much enhanced lithium-storage ability and better rate capability than that of activated carbon (AC)/LTO LIHC. Moreover, SNMG/LTO LIHC exhibits maximum energy and power densities of 86.2 Wh kg -1 and 7443 W kg -1 and maintains 87 % capacitance retention after 2000 cycles. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

An approach to evaluate capacitance, capacitive reactance and resistance of pivoted pads of a thrust bearing

Science.gov (United States)

Prashad, Har

1992-07-01

A theoretical approach is developed for determining the capacitance and active resistance between the interacting surfaces of pivoted pads and thrust collar, under different conditions of operation. It is shown that resistance and capacitive reactance of a thrust bearing decrease with the number of pads times the values of these parameters for an individual pad, and that capacitance increases with the number of pads times the capacitance of an individual pad. The analysis presented has a potential to diagnose the behavior of pivoted pad thrust bearings with the angle of tilt and the ratio of film thickness at the leading to trailing edge, by determining the variation of capacitance, resistance, and capacitive reactance.

Titanium nitride films for micro-supercapacitors: Effect of surface chemistry and film morphology on the capacitance

Science.gov (United States)

Achour, Amine; Porto, Raul Lucio; Soussou, Mohamed-Akram; Islam, Mohammad; Boujtita, Mohammed; Aissa, Kaltouma Ait; Le Brizoual, Laurent; Djouadi, Abdou; Brousse, Thierry

2015-12-01

Electrochemical capacitors (EC) in the form of packed films can be integrated in various electronic devices as power source. A fabrication process of EC electrodes, which is compatible with micro-fabrication, should be addressed for practical applications. Here, we show that titanium nitride films with controlled porosity can be deposited on flat silicon substrates by reactive DC-sputtering for use as high performance micro-supercapacitor electrodes. A superior volumetric capacitance as high as 146.4 F cm-3, with an outstanding cycling stability over 20,000 cycles, was measured in mild neutral electrolyte of potassium sulfate. The specific capacitance of the films as well as their capacitance retentions were found to depend on thickness, porosity and surface chemistry of electrodes. The one step process used to fabricate these TiN electrodes and the wide use of this material in the field of semiconductor technology make it promising for miniaturized energy storage systems.

A Flexible Capacitive Sensor with Encapsulated Liquids as Dielectrics

Directory of Open Access Journals (Sweden)

Yasunari Hotta

2012-03-01

Full Text Available Flexible and high-sensitive capacitive sensors are demanded to detect pressure distribution and/or tactile information on a curved surface, hence, wide varieties of polymer-based flexible MEMS sensors have been developed. High-sensitivity may be achieved by increasing the capacitance of the sensor using solid dielectric material while it deteriorates the flexibility. Using air as the dielectric, to maintain the flexibility, sacrifices the sensor sensitivity. In this paper, we demonstrate flexible and highly sensitive capacitive sensor arrays that encapsulate highly dielectric liquids as the dielectric. Deionized water and glycerin, which have relative dielectric constants of approximately 80 and 47, respectively, could increase the capacitance of the sensor when used as the dielectric while maintaining flexibility of the sensor with electrodes patterned on flexible polymer substrates. A reservoir of liquids between the electrodes was designed to have a leak path, which allows the sensor to deform despite of the incompressibility of the encapsulated liquids. The proposed sensor was microfabricated and demonstrated successfully to have a five times greater sensitivity than sensors that use air as the dielectric.

Design of electrical capacitance tomography sensors

International Nuclear Information System (INIS)

Yang, Wuqiang

2010-01-01

Electrical capacitance tomography (ECT) has been developed since the late 1980s for visualization and measurement of a permittivity distribution in a cross section using a multi-electrode capacitance sensor. While the hardware and image reconstruction algorithms for ECT have been published extensively and the topics have been reviewed, few papers have been published to discuss ECT sensors and the design issues, which are crucial for a specific application. This paper will briefly discuss the principles of ECT sensors, but mostly will address key issues for ECT sensor design, with reference to some existing ECT sensors as a good understanding of the key issues would help optimization of the design of ECT sensors. The key issues to be discussed include the number and length of electrodes, the use of external and internal electrodes, implications of wall thickness, earthed screens (including the outer screen, axial end screens and radial screens), driven guard electrodes, dealing with high temperature and high pressure, twin planes for velocity measurement by cross correlation and limitations in sensor diameter. While conventional ECT sensors are circular with the electrodes in a single plane or in twin planes, some non-conventional ECT sensors, such as square, conical and 3D sensors, will also be discussed. As a practical guidance, the procedure to fabricate an ECT sensor will be given. In the end are summary and discussion on future challenges, including re-engineering of ECT sensors. (topical review)

cLite – A Capacitive Signal Conditioning IC

Directory of Open Access Journals (Sweden)

Krauss Gudrun

2009-12-01

Full Text Available The ZMD31210 cLite™ – a new member of the ZMDI’s Lite™ family of low-cost sensor signal conditioner (SSC integrated circuits – is described in this paper. The cLite™ is the first conditioner for capacitive sensors. Supporting sensor capacitances from 2 pF up to 260 pF, the new sensor signal conditioner covers a wide range of applications. An important aspect of conditioning a capacitance sensor input signal is the adaptation of the capacitive-to-digital converter (CDC input range to the sensor signal span and offset values in order to maximize accuracy. All typical features of the Lite™ family including the digital calibration math based on EEPROM-stored coefficients and a variety of outputs (I2C™, SPI, PDM, and programmable alarms are integrated in the cLite™ as well. Additional features including a sleep mode and low supply voltage range (down to 2.3 V support the low power concept. The paper focuses in particular on the capacitance sensor adaptation and high precision sensor conditioning.

Ultrahigh Temperature Capacitive Pressure Sensor

Science.gov (United States)

Harsh, Kevin

2014-01-01

Robust, miniaturized sensing systems are needed to improve performance, increase efficiency, and track system health status and failure modes of advanced propulsion systems. Because microsensors must operate in extremely harsh environments, there are many technical challenges involved in developing reliable systems. In addition to high temperatures and pressures, sensing systems are exposed to oxidation, corrosion, thermal shock, fatigue, fouling, and abrasive wear. In these harsh conditions, sensors must be able to withstand high flow rates, vibration, jet fuel, and exhaust. In order for existing and future aeropropulsion turbine engines to improve safety and reduce cost and emissions while controlling engine instabilities, more accurate and complete sensor information is necessary. High-temperature (300 to 1,350 C) capacitive pressure sensors are of particular interest due to their high measurement bandwidth and inherent suitability for wireless readout schemes. The objective of this project is to develop a capacitive pressure sensor based on silicon carbon nitride (SiCN), a new class of high-temperature ceramic materials, which possesses excellent mechanical and electric properties at temperatures up to 1,600 C.

3D self-supported hierarchical Ni−Co architectures with integrated capacitive performance and enhanced electronic conductivity for supercapacitors

International Nuclear Information System (INIS)

Tang, YanRu; Cheng, Baohai

2016-01-01

3D self-supported hierarchical Ni and Co co-hydroxide architectures are promising electrode materials for supercapacitor application attributed to their prominent properties such as binder-free electrode fabrication process and high power density. However, the intrinsic conductivity of Ni and Co co-hydroxide is poor. How to develop a new type of supercapacitors exhibiting enhanced electronic conductivity and involving pseudocapacitive performance and electric double-layer capacitive performance is still challenging. Herein, we present a facile co-electrodeposition method to fabricate self-standing Ni_xCo_2_x(OH)_y@Ni/ITO monolithic electrode by growing a layer of Ni_xCo_2_x(OH)_y with layered structure on surface of conductive Ni nanotube, which increases specific surface area and prompts fast ion adsorption/de-adsotption (electrochemical double layer capacitance performance) and fast surface redox reactions (pseudo-capacitance performance). With the conductive Ni nanotube as current collector and electronic conductor, the binder-free Ni_xCo_2_x(OH)_y@Ni/ITO electrode exhibits high specific capacitance (92.4 mF cm"−"2 at 0.1 mA cm"−"2, the mass of active material per cm"−"2 is typically in 100 s μg). Moreover, Ni_xCo_2_x(OH)_y@Ni/ITO hybrids display excellent cycling stability with 93.3% capacitance retention after 5000 cycles. The results suggest Ni_xCo_2_x(OH)_y@Ni/ITO nanostructure constructed based on integrated features of pseudocapacitive performance and electric double-layer capacitive performance and enhanced electronic conductivity is expected to be a type of excellent electrode material for supercapacitor. - Highlights: • Ni−Co electrode is fabricated by growing layered structure on Ni nanotube surface. • The layered structure prompts fast ion adsorption/de-adsotption and redox reactions. • The Ni nanotube serves as nanostructured current collector and electronic conductor. • The Ni−Co hybrids display 93.3% capacitance retention

Ferroelectric negative capacitance domain dynamics

Science.gov (United States)

Hoffmann, Michael; Khan, Asif Islam; Serrao, Claudy; Lu, Zhongyuan; Salahuddin, Sayeef; Pešić, Milan; Slesazeck, Stefan; Schroeder, Uwe; Mikolajick, Thomas

2018-05-01

Transient negative capacitance effects in epitaxial ferroelectric Pb(Zr0.2Ti0.8)O3 capacitors are investigated with a focus on the dynamical switching behavior governed by domain nucleation and growth. Voltage pulses are applied to a series connection of the ferroelectric capacitor and a resistor to directly measure the ferroelectric negative capacitance during switching. A time-dependent Ginzburg-Landau approach is used to investigate the underlying domain dynamics. The transient negative capacitance is shown to originate from reverse domain nucleation and unrestricted domain growth. However, with the onset of domain coalescence, the capacitance becomes positive again. The persistence of the negative capacitance state is therefore limited by the speed of domain wall motion. By changing the applied electric field, capacitor area or external resistance, this domain wall velocity can be varied predictably over several orders of magnitude. Additionally, detailed insights into the intrinsic material properties of the ferroelectric are obtainable through these measurements. A new method for reliable extraction of the average negative capacitance of the ferroelectric is presented. Furthermore, a simple analytical model is developed, which accurately describes the negative capacitance transient time as a function of the material properties and the experimental boundary conditions.

Solar Cell Capacitance Determination Based on an RLC Resonant Circuit

Directory of Open Access Journals (Sweden)

Petru Adrian Cotfas

2018-03-01

Full Text Available The capacitance is one of the key dynamic parameters of solar cells, which can provide essential information regarding the quality and health state of the cell. However, the measurement of this parameter is not a trivial task, as it typically requires high accuracy instruments using, e.g., electrical impedance spectroscopy (IS. This paper introduces a simple and effective method to determine the electric capacitance of the solar cells. An RLC (Resistor Inductance Capacitor circuit is formed by using an inductor as a load for the solar cell. The capacitance of the solar cell is found by measuring the frequency of the damped oscillation that occurs at the moment of connecting the inductor to the solar cell. The study is performed through simulation based on National Instruments (NI Multisim application as SPICE simulation software and through experimental capacitance measurements of a monocrystalline silicon commercial solar cell and a photovoltaic panel using the proposed method. The results were validated using impedance spectroscopy. The differences between the capacitance values obtained by the two methods are of 1% for the solar cells and of 9.6% for the PV panel. The irradiance level effect upon the solar cell capacitance was studied obtaining an increase in the capacitance in function of the irradiance. By connecting different inductors to the solar cell, the frequency effect upon the solar cell capacitance was studied noticing a very small decrease in the capacitance with the frequency. Additionally, the temperature effect over the solar cell capacitance was studied achieving an increase in capacitance with temperature.

Verification of high voltage rf capacitive sheath models with particle-in-cell simulations

Science.gov (United States)

Wang, Ying; Lieberman, Michael; Verboncoeur, John

2009-10-01

Collisionless and collisional high voltage rf capacitive sheath models were developed in the late 1980's [1]. Given the external parameters of a single-frequency capacitively coupled discharge, plasma parameters including sheath width, electron and ion temperature, plasma density, power, and ion bombarding energy can be estimated. One-dimensional electrostatic PIC codes XPDP1 [2] and OOPD1 [3] are used to investigate plasma behaviors within rf sheaths and bulk plasma. Electron-neutral collisions only are considered for collisionless sheaths, while ion-neutral collisions are taken into account for collisional sheaths. The collisionless sheath model is verified very well by PIC simulations for the rf current-driven and voltage-driven cases. Results will be reported for collisional sheaths also. [1] M. A. Lieberman, IEEE Trans. Plasma Sci. 16 (1988) 638; 17 (1989) 338 [2] J. P. Verboncoeur, M. V. Alves, V. Vahedi, and C. K. Birdsall, J. Comp. Phys. 104 (1993) 321 [3] J. P. Verboncoeur, A. B. Langdon and N. T. Gladd, Comp. Phys. Comm. 87 (1995) 199

Capacitance-voltage characteristics of GaAs ion-implanted structures

Directory of Open Access Journals (Sweden)

Privalov E. N.

2008-08-01

Full Text Available A noniterative numerical method is proposed to calculate the barrier capacitance of GaAs ion-implanted structures as a function of the Schottky barrier bias. The features of the low- and high-frequency capacitance-voltage characteristics of these structures which are due to the presence of deep traps are elucidated.

Whole-tree water transport scales with sapwood capacitance in tropical forest canopy trees.

Science.gov (United States)

F.C. Meinzer; S.A. James; G. Goldstein; D. Woodruff

2003-01-01

The present study examines the manner in which several whole-tree water transport properties scale with species specific variation in sapwood water storage capacity. The hypothesis that constraints on relationships between sapwood capacitance and other water relations characteristics lead to predictable scaling relationships between intrinsic capacitance and whole-tree...

Investigation of the capacitive performance of tobacco solution reduced graphene oxide

Energy Technology Data Exchange (ETDEWEB)

Jana, Milan [Surface Engineering and Tribology Division, Council of Scientific and Industrial Research – Central Mechanical Engineering Research Institute, Durgapur 713209 (India); Academy of Scientific and Innovative Research (AcSIR), Anusandhan Bhawan, 2 Rafi Marg, New Delhi 110001 (India); Saha, Sanjit; Samanta, Pranab; Murmu, Naresh Chandra [Surface Engineering and Tribology Division, Council of Scientific and Industrial Research – Central Mechanical Engineering Research Institute, Durgapur 713209 (India); Lee, Joong Hee, E-mail: jhl@jbnu.ac.kr [Advanced Materials Research Institute for BIN Fusion Technology (BK Plus Global, Program), Department of BIN Fusion Technology, Chonbuk National University, Jeonju, Jeonbuk 561-756 (Korea, Republic of); Kuila, Tapas, E-mail: tkuila@gmail.com [Surface Engineering and Tribology Division, Council of Scientific and Industrial Research – Central Mechanical Engineering Research Institute, Durgapur 713209 (India)

2015-02-01

A facile and green approach for the reduction of graphene oxide (GO) using tobacco leaves solution was reported. The benefits of this approach were the use of green and cheap reducing agent as compared to the commercially available toxic and hazardous chemicals. Moreover, the purification of reduced GO (rGO) sheets can be avoided by using naturally occurring reducing agents. The obtained rGO sheets were characterised by Ultra violet visible, Fourier transform infrared, Raman and X-ray photo electron spectroscopy analysis. The morphologies were recorded by transmission electron and field emission scanning electron microscopy analysis and these showed the formation of a few layer rGO sheets. The electrical conductivity of rGO was found to be ∼410 S m{sup −1} at room temperature. Electrochemical performances were characterised by cyclic voltammetry, charge–discharge and electrochemical impedance spectroscopy analysis. A two electrode symmetric supercapacitor device was designed using nickel foam as current collector. The specific capacitance of the two-electrode device reached to 206 F g{sup −1} at a current density of 0.16 A g{sup −1}. The retention in specific capacitance was found to be ∼112% after 1000 charge–discharge cycles. - Highlights: • Reduced graphene has been prepared by bio-reduction of graphene oxide. • Few layers of graphene has been synthesised as observed by Raman spectra. • Two electrode based supercapacitors are fabricated. • Highest specific capacitance is found to be 206 F g{sup −1}. • Retention in specific capacitance is 112% after 1000 charge–discharge cycles.

Capacitive sensing of droplets for microfluidic devices based on thermocapillary actuation

OpenAIRE

Chen, Jian Z.; Darhuber, Anton A.; Troian, Sandra M.; Wagner, Sigurd

2004-01-01

The design and performance of a miniaturized coplanar capacitive sensor is presented whose electrode arrays can also function as resistive microheaters for thermocapillary actuation of liquid films and droplets. Optimal compromise between large capacitive signal and high spatial resolution is obtained for electrode widths comparable to the liquid film thickness measured, in agreement with supporting numerical simulations which include mutual capacitance effects. An interdigitated, variable wi...

116 dB dynamic range CMOS readout circuit for MEMS capacitive accelerometer

International Nuclear Information System (INIS)

Long Shanli; Liu Yan; He Kejun; Tang Xinggang; Chen Qian

2014-01-01

A high stability in-circuit reprogrammable technique control system for a capacitive MEMS accelerometer is presented. Modulation and demodulation are used to separate the signal from the low frequency noise. A low-noise low-offset charge integrator is employed in this circuit to implement a capacitance-to-voltage converter and minimize the noise and offset. The application-specific integrated circuit (ASIC) is fabricated in a 0.5 μm one-ploy three-metal CMOS process. The measured results of the proposed circuit show that the noise floor of the ASIC is −116 dBV, the sensitivity of the accelerometer is 66 mV/g with a nonlinearity of 0.5%. The chip occupies 3.5 × 2.5 mm 2 and the current is 3.5 mA. (semiconductor integrated circuits)

Radical covalent organic frameworks: a general strategy to immobilize open-accessible polyradicals for high-performance capacitive energy storage.

Science.gov (United States)

Xu, Fei; Xu, Hong; Chen, Xiong; Wu, Dingcai; Wu, Yang; Liu, Hao; Gu, Cheng; Fu, Ruowen; Jiang, Donglin

2015-06-01

Ordered π-columns and open nanochannels found in covalent organic frameworks (COFs) could render them able to store electric energy. However, the synthetic difficulty in achieving redox-active skeletons has thus far restricted their potential for energy storage. A general strategy is presented for converting a conventional COF into an outstanding platform for energy storage through post-synthetic functionalization with organic radicals. The radical frameworks with openly accessible polyradicals immobilized on the pore walls undergo rapid and reversible redox reactions, leading to capacitive energy storage with high capacitance, high-rate kinetics, and robust cycle stability. The results suggest that channel-wall functional engineering with redox-active species will be a facile and versatile strategy to explore COFs for energy storage. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Opening of K+ channels by capacitive stimulation from silicon chip

Science.gov (United States)

Ulbrich, M. H.; Fromherz, P.

2005-10-01

The development of stable neuroelectronic systems requires a stimulation of nerve cells from semiconductor devices without electrochemical effects at the electrolyte/solid interface and without damage of the cell membrane. The interaction must rely on a reversible opening of voltage-gated ion channels by capacitive coupling. In a proof-of-principle experiment, we demonstrate that Kv1.3 potassium channels expressed in HEK293 cells can be opened from an electrolyte/oxide/silicon (EOS) capacitor. A sufficient strength of electrical coupling is achieved by insulating silicon with a thin film of TiO2 to achieve a high capacitance and by removing NaCl from the electrolyte to enhance the resistance of the cell-chip contact. When a decaying voltage ramp is applied to the EOS capacitor, an outward current through the attached cell membrane is observed that is specific for Kv1.3 channels. An open probability up to fifty percent is estimated by comparison with a numerical simulation of the cell-chip contact.

Efficiency of Capacitively Loaded Converters

DEFF Research Database (Denmark)

Andersen, Thomas; Huang, Lina; Andersen, Michael A. E.

2012-01-01

This paper explores the characteristic of capacitance versus voltage for dielectric electro active polymer (DEAP) actuator, 2kV polypropylene film capacitor as well as 3kV X7R multi layer ceramic capacitor (MLCC) at the beginning. An energy efficiency for capacitively loaded converters...... is introduced as a definition of efficiency. The calculated and measured efficiency curves for charging DEAP actuator, polypropylene film capacitor and X7R MLCC are provided and compared. The attention has to be paid for the voltage dependent capacitive load, like X7R MLCC, when evaluating the charging...... polypropylene film capacitor can be the equivalent capacitive load. Because of the voltage dependent characteristic, X7R MLCC cannot be used to replace the DEAP actuator. However, this type of capacitor can be used to substitute the capacitive actuator with voltage dependent property at the development phase....

Ion flux nonuniformities in large-area high-frequency capacitive discharges

International Nuclear Information System (INIS)

Perret, A.; Chabert, P.; Booth, J.-P.; Jolly, J.; Guillon, J.; Auvray, Ph.

2003-01-01

Strong nonuniformities of plasma production are expected in capacitive discharges if the excitation wavelength becomes comparable to the reactor size (standing-wave effect) and/or if the plasma skin depth becomes comparable to the plate separation (skin effect) [M. A. Lieberman et al., Plasma Sources Sci. Technol. 11, 283 (2002)]. Ion flux uniformity measurements were carried out in a large-area square (40 cmx40 cm) capacitive discharge driven at frequencies between 13.56 MHz and 81.36 MHz in argon gas at 150 mTorr. At 13.56 MHz, the ion flux was uniform to ±5%. At 60 MHz (and above) and at low rf power, the standing-wave effect was seen (maximum of the ion flux at the center), in good quantitative agreement with theory. At higher rf power, maxima of the ion flux were observed at the edges, due either to the skin effect or to other edge effects

A New Wide Frequency Band Capacitance Transducer with Application to Measuring Metal Fill Time

Directory of Open Access Journals (Sweden)

Wael DEABES

2009-01-01

Full Text Available A novel low cost, high frequency circuit for measuring capacitance is proposed in this paper. This new capacitance measuring circuit is able to measure small coupling capacitance variations with high stray-immunity. Hence, it could be used in many potential applications such as measuring the metal fill time in the Lost Foam Casting (LFC process and Electrical Capacitive Tomography (ECT system. The proposed circuit is based on differential charging/discharging method using current feedback amplifier and a synchronous demodulation stage. The circuit has a wide high frequency operating range with zero phase shift; hence multiple circuits can work at different frequencies simultaneously to measure the capacitance. The non-ideal characteristic of the circuit has been analyzed and the results verified through LTSpice simulation. Results from the tests on a prototype and a simulation elucidate the practicality of the proposed circuit.

Capacitance of circular patch resonator

International Nuclear Information System (INIS)

Miano, G.; Verolino, L.; Naples Univ.; Panariello, G.; Vaccaro, V.G.; Naples Univ.

1995-11-01

In this paper the capacitance of the circular microstrip patch resonator is computed. It is shown that the electrostatic problem can be formulated as a system of dual integral equations, and the most interesting techniques of solutions of these systems are reviewed. Some useful approximated formulas for the capacitance are derived and plots of the capacitance are finally given in a wide range of dielectric constants

High capacitance density MIS capacitor using Si nanowires by MACE and ALD alumina dielectric

Energy Technology Data Exchange (ETDEWEB)

Leontis, I.; Nassiopoulou, A. G., E-mail: A.Nassiopoulou@inn.demokritos.gr [INN, NCSR Demokritos, Patriarchou Grigoriou and Neapoleos, Aghia Paraskevi, 153 10 Athens (Greece); Botzakaki, M. A.; Georga, S. N. [Department of Physics, University of Patras, 26 504 Rion (Greece)

2016-06-28

High capacitance density three-dimensional (3D) metal-insulator-semiconductor (MIS) capacitors using Si nanowires (SiNWs) by metal-assisted chemical etching and atomic-layer-deposited alumina dielectric film were fabricated and electrically characterized. A chemical treatment was used to remove structural defects from the nanowire surface, in order to reduce the density of interface traps at the Al{sub 2}O{sub 3}/SiNW interface. SiNWs with two different lengths, namely, 1.3 μm and 2.4 μm, were studied. A four-fold capacitance density increase compared to a planar reference capacitor was achieved with the 1.3 μm SiNWs. In the case of the 2.4 μm SiNWs this increase was ×7, reaching a value of 4.1 μF/cm{sup 2}. Capacitance-voltage (C-V) measurements revealed that, following a two-cycle chemical treatment, frequency dispersion at accumulation regime and flat-band voltage shift disappeared in the case of the 1.3 μm SiNWs, which is indicative of effective removal of structural defects at the SiNW surface. In the case of the 2.4 μm SiNWs, frequency dispersion at accumulation persisted even after the two-step chemical treatment. This is attributed to a porous Si layer at the SiNW tops, which is not effectively removed by the chemical treatment. The electrical losses of MIS capacitors in both cases of SiNW lengths were studied and will be discussed.

High capacitance density MIS capacitor using Si nanowires by MACE and ALD alumina dielectric

International Nuclear Information System (INIS)

Leontis, I.; Nassiopoulou, A. G.; Botzakaki, M. A.; Georga, S. N.

2016-01-01

High capacitance density three-dimensional (3D) metal-insulator-semiconductor (MIS) capacitors using Si nanowires (SiNWs) by metal-assisted chemical etching and atomic-layer-deposited alumina dielectric film were fabricated and electrically characterized. A chemical treatment was used to remove structural defects from the nanowire surface, in order to reduce the density of interface traps at the Al_2O_3/SiNW interface. SiNWs with two different lengths, namely, 1.3 μm and 2.4 μm, were studied. A four-fold capacitance density increase compared to a planar reference capacitor was achieved with the 1.3 μm SiNWs. In the case of the 2.4 μm SiNWs this increase was ×7, reaching a value of 4.1 μF/cm"2. Capacitance-voltage (C-V) measurements revealed that, following a two-cycle chemical treatment, frequency dispersion at accumulation regime and flat-band voltage shift disappeared in the case of the 1.3 μm SiNWs, which is indicative of effective removal of structural defects at the SiNW surface. In the case of the 2.4 μm SiNWs, frequency dispersion at accumulation persisted even after the two-step chemical treatment. This is attributed to a porous Si layer at the SiNW tops, which is not effectively removed by the chemical treatment. The electrical losses of MIS capacitors in both cases of SiNW lengths were studied and will be discussed.

Energy-Efficient Capacitance-to-Digital Converters for Smart Sensor Applications

KAUST Repository

Alhoshany, Abdulaziz

2017-12-01

One of the key requirements in the design of wireless sensor nodes and miniature biomedical devices is energy efficiency. For a sensor node, which is a sensor and readout circuit, to survive on limited energy sources such as a battery or harvested energy, its energy consumption should be minimized. Capacitive sensors are candidates for use in energy-constrained applications, as they do not consume static power and can be used in a wide range of applications to measure different physical, chemical or biological quantities. However, the energy consumption is dominated by the capacitive interface circuit, i.e. the capacitance-to-digital converter (CDC). Several energy-efficient CDC architectures are introduced in this dissertation to meet the demand for high resolution and energy efficiency in smart capacitive sensors. First, we propose an energy-efficient CDC based on a differential successive-approximation data converter. The proposed differential CDC employs an energy-efficient operational transconductance amplifier (OTA) based on an inverter. A wide capacitance range with fine absolute resolution is implemented in the proposed coarse-fine DAC architecture which saves 89% of silicon area. The proposed CDC achieves an energy efficiency figure-of-merit () of 45.8fJ/step, which is the best reported energy efficiency to date. Second, we propose an energy efficient CDC for high-precision capacitive resolution by using oversampling and noise shaping. The proposed CDC achieves 150 aF absolute resolution and an energy efficiency of 187fJ/conversion-step which outperforms state of the art high-precision differential CDCs. In the third and last part, we propose an in-vitro cancer diagnostic biosensor-CMOS platform for low-power, rapid detection, and low cost. The introduced platform is the first to demonstrate the ability to screen and quantify the spermidine/spermine N1 acetyltransferase (SSAT) enzyme which reveals the presence of early-stage cancer, on the surface of a

Capacitive sensing of droplets for microfluidic devices based on thermocapillary actuation

NARCIS (Netherlands)

Chen, J.-Z.; Darhuber, A.A.; Troian, S.M.; Wagner, S.

2004-01-01

The design and performance of a miniaturized coplanar capacitive sensor is presented whose electrode arrays can also function as resistive microheaters for thermocapillary actuation of liquid films and droplets. Optimal compromise between large capacitive signal and high spatial resolution is

Measurement of Line-to-Ground Capacitance in Distribution Network Considering Magnetizing Impedance’s Frequency Characteristic

Directory of Open Access Journals (Sweden)

Qing Yang

2017-04-01

Full Text Available Signal injection method (SIM is widely applied to the insulation parameters’ measurement in distribution network for its convenience and safety. It can be divided into two kinds of patterns: injecting a specific frequency signal or several frequencies’ groups, and scanning frequency in a scheduled frequency scope. In order to avoid the disadvantages in related researches, improved signal injection method (ISIM, in which the frequency characteristic of the transformer magnetizing impedance is taken into consideration, is proposed. In addition, optimization for signal injection position has been accomplished, and the corresponding three calculation methods of line-to-ground capacitance has been derived. Calculations are carried out through the vector information (vector calculation method, the amplitude information (amplitude calculation method, the phase information (phase calculation method of voltage and current in signal injecting port, respectively. The line-to-ground capacitance is represented by lumped parameter capacitances in high-voltage simulation test. Eight different sinusoidal signals are injected into zero-sequence circuit, and then line-to-ground capacitance is calculated with the above-mentioned vector calculation method based on the voltage and the current data of the injecting port. The results obtained by the vector calculation method show that ISIM has a wider application frequency range compared with signal injection method with rated parameters (RSIM and SIM. The RSIM is calculated with the rated transformer parameters of magnetizing impedance, and the SIM based on the ideal transformer model, and the relative errors of calculation results of ISIM are smaller than that for other methods in general. The six groups of two-frequency set are chosen in a specific scope which is recommended by vector calculation results. Based on ISIM, the line-to-ground capacitance calculations through the amplitude calculation method and

Transition metal sulfides grown on graphene fibers for wearable asymmetric supercapacitors with high volumetric capacitance and high energy density

Science.gov (United States)

Cai, Weihua; Lai, Ting; Lai, Jianwei; Xie, Haoting; Ouyang, Liuzhang; Ye, Jianshan; Yu, Chengzhong

2016-06-01

Fiber shaped supercapacitors are promising candidates for wearable electronics because they are flexible and light-weight. However, a critical challenge of the widespread application of these energy storage devices is their low cell voltages and low energy densities, resulting in limited run-time of the electronics. Here, we demonstrate a 1.5 V high cell voltage and high volumetric energy density asymmetric fiber supercapacitor in aqueous electrolyte. The lightweight (0.24 g cm-3), highly conductive (39 S cm-1), and mechanically robust (221 MPa) graphene fibers were firstly fabricated and then coated by NiCo2S4 nanoparticles (GF/NiCo2S4) via the solvothermal deposition method. The GF/NiCo2S4 display high volumetric capacitance up to 388 F cm-3 at 2 mV s-1 in a three-electrode cell and 300 F cm-3 at 175.7 mA cm-3 (568 mF cm-2 at 0.5 mA cm-2) in a two-electrode cell. The electrochemical characterizations show 1000% higher capacitance of the GF/NiCo2S4 as compared to that of neat graphene fibers. The fabricated device achieves high energy density up to 12.3 mWh cm-3 with a maximum power density of 1600 mW cm-3, outperforming the thin-film lithium battery. Therefore, these supercapacitors are promising for the next generation flexible and wearable electronic devices.

Capacitive Biosensors and Molecularly Imprinted Electrodes.

Science.gov (United States)

Ertürk, Gizem; Mattiasson, Bo

2017-02-17

Capacitive biosensors belong to the group of affinity biosensors that operate by registering direct binding between the sensor surface and the target molecule. This type of biosensors measures the changes in dielectric properties and/or thickness of the dielectric layer at the electrolyte/electrode interface. Capacitive biosensors have so far been successfully used for detection of proteins, nucleotides, heavy metals, saccharides, small organic molecules and microbial cells. In recent years, the microcontact imprinting method has been used to create very sensitive and selective biorecognition cavities on surfaces of capacitive electrodes. This chapter summarizes the principle and different applications of capacitive biosensors with an emphasis on microcontact imprinting method with its recent capacitive biosensor applications.

Electrolyte Engineering: Optimizing High-Rate Double-Layer Capacitances of Micropore- and Mesopore-Rich Activated Carbon.

Science.gov (United States)

Chen, Ting-Hao; Yang, Cheng-Hsien; Su, Ching-Yuan; Lee, Tai-Chou; Dong, Quan-Feng; Chang, Jeng-Kuei

2017-09-22

Various types of electrolyte cations as well as binary cations are used to optimize the capacitive performance of activated carbon (AC) with different pore structures. The high-rate capability of micropore-rich AC, governed by the mobility of desolvated cations, can outperform that of mesopore-rich AC, which essentially depends on the electrolyte conductivity. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Aloe vera Derived Activated High-Surface-Area Carbon for Flexible and High-Energy Supercapacitors.

Science.gov (United States)

Karnan, M; Subramani, K; Sudhan, N; Ilayaraja, N; Sathish, M

2016-12-28

Materials which possess high specific capacitance in device configuration with low cost are essential for viable application in supercapacitors. Herein, a flexible high-energy supercapacitor device was fabricated using porous activated high-surface-area carbon derived from aloe leaf (Aloe vera) as a precursor. The A. vera derived activated carbon showed mesoporous nature with high specific surface area of ∼1890 m 2 /g. A high specific capacitance of 410 and 306 F/g was achieved in three-electrode and symmetric two-electrode system configurations in aqueous electrolyte, respectively. The fabricated all-solid-state device showed a high specific capacitance of 244 F/g with an energy density of 8.6 Wh/kg. In an ionic liquid electrolyte, the fabricated device showed a high specific capacitance of 126 F/g and a wide potential window up to 3 V, which results in a high energy density of 40 Wh/kg. Furthermore, it was observed that the activation temperature has significant role in the electrochemical performance, as the activated sample at 700 °C showed best activity than the samples activated at 600 and 800 °C. The electron microscopic images (FE-SEM and HR-TEM) confirmed the formation of pores by the chemical activation. A fabricated supercapacitor device in ionic liquid with 3 V could power up a red LED for 30 min upon charging for 20s. Also, it is shown that the operation voltage and capacitance of flexible all-solid-state symmetric supercapacitors fabricated using aloe-derived activated carbon could be easily tuned by series and parallel combinations. The performance of fabricated supercapacitor devices using A. vera derived activated carbon in all-solid-state and ionic liquid indicates their viable applications in flexible devices and energy storage.

Effects of heat treatment on the hierarchical porous structure and electro-capacitive properties of RuO2/activated carbon nanofiber composites

International Nuclear Information System (INIS)

Jun, Ye Ri; Kim, Bo Hye

2016-01-01

Electrochemical capacitors based on hierarchical porous activated carbon nanofiber (RuO 2 /ACNF) composites are fabricated by one-step electrospinning, and then stabilized at different activation temperatures. The effect of the activation temperature on the structural properties and electrochemical behavior of the RuO 2 /ACNF composites is intensively investigated in 6 M KOH electrolyte. The RuO 2 /ACNF-800 composites activated at high temperature possess abundant mesopores and larger pores, which improve the electrochemical performance, especially at high charge–discharge rates. The energy storage capabilities of the RuO 2 /ACNF-800 electrode prepared at high temperature are as follows: a maximum specific capacitance of 150 F/g and an energy density of 14–20 Wh/kg in the respective power density range of 400 to 10 000 W/kg in an aqueous solution. Furthermore, this electrode exhibits high-rate electrochemical performance with a specific capacitance reduction of less than 28% of the initial value at a discharge current of 20 mA/cm 2 . Therefore, the hierarchical porous RuO 2 /ACNF composites with well-developed mesoporous structure provide low resistance for charge diffusion and a short pathway for ion transportation, yielding good capacitive behavior

Development of an Intelligent Capacitive Mass Sensor Based on Co-axial Cylindrical Capacitor

Directory of Open Access Journals (Sweden)

Amir ABU AL AISH

2009-06-01

Full Text Available The paper presents a linear, robust and intelligent capacitive mass sensor made of a co-axial cylindrical capacitor. It is designed such that the mass under measurement is directly proportional to the capacitance of the sensor. The average value of the output voltage of a capacitance to voltage converter is proportional to the capacitance of the sensor. The output of the converter is measured and displayed, as mass, with the help of microcontroller. The results are free from the effect of stray capacitances which cause errors at low values of capacitances. Developed sensor is linear, free from errors due to temperature and highly flexible in design. The proto-type of the mass sensor can weigh up to 4 kilogram only.

Particle size analysis on density, surface morphology and specific capacitance of carbon electrode from rubber wood sawdust

Science.gov (United States)

Taer, E.; Kurniasih, B.; Sari, F. P.; Zulkifli, Taslim, R.; Sugianto, Purnama, A.; Apriwandi, Susanti, Y.

2018-02-01

The particle size analysis for supercapacitor carbon electrodes from rubber wood sawdust (SGKK) has been done successfully. The electrode particle size was reviewed against the properties such as density, degree of crystallinity, surface morphology and specific capacitance. The variations in particle size were made by different treatment on the grinding and sieving process. The sample particle size was distinguished as 53-100 µm for 20 h (SA), 38-53 µm for 20 h (SB) and < 38 µm with variations of grinding time for 40 h (SC) and 80 h (SD) respectively. All of the samples were activated by 0.4 M KOH solution. Carbon electrodes were carbonized at temperature of 600oC in N2 gas environment and then followed by CO2 gas activation at a temperature of 900oC for 2 h. The densities for each variation in the particle size were 1.034 g cm-3, 0.849 g cm-3, 0.892 g cm-3 and 0.982 g cm-3 respectively. The morphological study identified the distance between the particles more closely at 38-53 µm (SB) particle size. The electrochemical properties of supercapacitor cells have been investigated using electrochemical methods such as impedance spectroscopy and charge-discharge at constant current using Solatron 1280 tools. Electrochemical properties testing results have shown SB samples with a particle size of 38-53 µm produce supercapacitor cells with optimum capacitive performance.

Lightweight linear alternators with and without capacitive tuning

Science.gov (United States)

Niedra, Janis M.

1993-06-01

Permanent magnet excited linear alternators rated tens of kW and coupled to free-piston Stirling engines are presently viewed as promising candidates for long term generation of electric power in both space and terrestrial applications. Series capacitive cancellation of the internal inductive reactance of such alternators was considered a viable way to both increase power extraction and to suppress unstable modes of the thermodynamic oscillation. Idealized toroidal and cylindrical alternator geometries are used for a comparative study of the issues of specific mass and capacitive tuning, subject to stability criteria. The analysis shows that the stator mass of an alternator designed to be capacitively tuned is always greater than the minimum achievable stator mass of an alternator designed with no capacitors, assuming equal utilization of materials ratings and the same frequency and power to a resistive load. This conclusion is not substantially altered when the usually lesser masses of the magnets and of any capacitors are added. Within the reported stability requirements and under circumstances of normal materials ratings, this study finds no clear advantage to capacitive tuning. Comparative plots of the various constituent masses are presented versus the internal power factor taken as a design degree of freedom. The explicit formulas developed for stator core, coil, capacitor, and magnet masses and for the degree of magnet utilization provide useful estimates of scaling effects.

Nanoscale capacitance: A quantum tight-binding model

Science.gov (United States)

Zhai, Feng; Wu, Jian; Li, Yang; Lu, Jun-Qiang

2017-01-01

Landauer-Buttiker formalism with the assumption of semi-infinite electrodes as reservoirs has been the standard approach in modeling steady electron transport through nanoscale devices. However, modeling dynamic electron transport properties, especially nanoscale capacitance, is a challenging problem because of dynamic contributions from electrodes, which is neglectable in modeling macroscopic capacitance and mesoscopic conductance. We implement a self-consistent quantum tight-binding model to calculate capacitance of a nano-gap system consisting of an electrode capacitance C‧ and an effective capacitance Cd of the middle device. From the calculations on a nano-gap made of carbon nanotube with a buckyball therein, we show that when the electrode length increases, the electrode capacitance C‧ moves up while the effective capacitance Cd converges to a value which is much smaller than the electrode capacitance C‧. Our results reveal the importance of electrodes in modeling nanoscale ac circuits, and indicate that the concepts of semi-infinite electrodes and reservoirs well-accepted in the steady electron transport theory may be not applicable in modeling dynamic transport properties.

Capacitive Sensing of Glucose in Electrolytes Using Graphene Quantum Capacitance Varactors.

Science.gov (United States)

Zhang, Yao; Ma, Rui; Zhen, Xue V; Kudva, Yogish C; Bühlmann, Philippe; Koester, Steven J

2017-11-08

A novel graphene-based variable capacitor (varactor) that senses glucose based on the quantum capacitance effect was successfully developed. The sensor utilizes a metal-oxide-graphene varactor device structure that is inherently compatible with passive wireless sensing, a key advantage for in vivo glucose sensing. The graphene varactors were functionalized with pyrene-1-boronic acid (PBA) by self-assembly driven by π-π interactions. Successful surface functionalization was confirmed by both Raman spectroscopy and capacitance-voltage characterization of the devices. Through glucose binding to the PBA, the glucose concentration in the buffer solutions modulates the level of electrostatic doping of the graphene surface to different degrees, which leads to capacitance changes and Dirac voltage shifts. These responses to the glucose concentration were shown to be reproducible and reversible over multiple measurement cycles, suggesting promise for eventual use in wireless glucose monitoring.

In-situ space-confined catalysis for fabricating 3D mesoporous graphene and their capacitive properties

Science.gov (United States)

Qin, Jian; Zhu, Shan; Feng, Chao; Zhao, Naiqin; Shi, Chunsheng; Liu, En-Zuo; He, Fang; Ma, Liying; Li, Jiajun; He, Chunnian

2018-03-01

A one-step strategy for preparing 3D mesoporous graphene networks (3DMGNs) based on the concepts of space-confined effect, catalytic effect and chemical activation is reported in this work. The soluble salts act as the in-situ templates to confine the thickness of 3D graphene layers. Meanwhile, the Fe-catalysts greatly improve the graphitization of the graphene matrix, which are easy to be removed by acid treatment. In addition, the KOH activation introduces abundant mesopores into the graphene networks, which facilities the electrolyte permeation. Thus, when using as electrode materials for supercapacitor, the as-obtained 3DMGNs with high electron conductivity, large surface area and hierarchical porous structure exhibit excellent capacitive properties, including high specific capacitance (215 F g-1 at 0.5 A g-1) and superior rate performance (168 F g-1 at 50 A g-1).

Rapid capacitive detection of femtomolar levels of bisphenol A using an aptamer-modified disposable microelectrode array

International Nuclear Information System (INIS)

Cui, Haochen; Wu, Jayne; Eda, Shigetoshi; Chen, Jiangang; Chen, Wei; Zheng, Lei

2015-01-01

A label-free and single-step method is reported for rapid and highly sensitive detection of bisphenol A (BPA) in aqueous samples. It utilizes an aptamer acting as a probe molecule immobilized on a commercially available array of interdigitated aluminum microelectrodes. BPA was quantified by measuring the interfacial capacitance change rate caused by the specific binding between bisphenol A and the immobilized aptamer. The AC signal also induces an AC electrokinetic effect to generate microfluidic motion for enhanced binding. The capacitive aptasensor achieves a limit of detection as low as 10 fM(2.8 fg ⋅ mL −1 ) with a 20 s response time. The method is inexpensive, highly sensitive, rapid and therefore provides a promising technology for on-site detection of BPA in food and water samples. (author)

Protein phosphatases decrease their activity during capacitation: a new requirement for this event.

Directory of Open Access Journals (Sweden)

Janetti R Signorelli

Full Text Available There are few reports on the role of protein phosphatases during capacitation. Here, we report on the role of PP2B, PP1, and PP2A during human sperm capacitation. Motile sperm were resuspended in non-capacitating medium (NCM, Tyrode's medium, albumin- and bicarbonate-free or in reconstituted medium (RCM, NCM plus 2.6% albumin/25 mM bicarbonate. The presence of the phosphatases was evaluated by western blotting and the subcellular localization by indirect immunofluorescence. The function of these phosphatases was analyzed by incubating the sperm with specific inhibitors: okadaic acid, I2, endothall, and deltamethrin. Different aliquots were incubated in the following media: 1 NCM; 2 NCM plus inhibitors; 3 RCM; and 4 RCM plus inhibitors. The percent capacitated sperm and phosphatase activities were evaluated using the chlortetracycline assay and a phosphatase assay kit, respectively. The results confirm the presence of PP2B and PP1 in human sperm. We also report the presence of PP2A, specifically, the catalytic subunit and the regulatory subunits PR65 and B. PP2B and PP2A were present in the tail, neck, and postacrosomal region, and PP1 was present in the postacrosomal region, neck, middle, and principal piece of human sperm. Treatment with phosphatase inhibitors rapidly (≤1 min increased the percent of sperm depicting the pattern B, reaching a maximum of ∼40% that was maintained throughout incubation; after 3 h, the percent of capacitated sperm was similar to that of the control. The enzymatic activity of the phosphatases decreased during capacitation without changes in their expression. The pattern of phosphorylation on threonine residues showed a sharp increase upon treatment with the inhibitors. In conclusion, human sperm express PP1, PP2B, and PP2A, and the activity of these phosphatases decreases during capacitation. This decline in phosphatase activities and the subsequent increase in threonine phosphorylation may be an important

A novel 3D detector configuration enabling high quantum efficiency, low crosstalk, and low output capacitance

International Nuclear Information System (INIS)

Aurola, A.; Marochkin, V.; Tuuva, T.

2016-01-01

The benefits of pixelated planar direct conversion semiconductor radiation detectors comprising a thick fully depleted substrate are that they offer low crosstalk, small output capacitance, and that the planar configuration simplifies manufacturing. In order to provide high quantum efficiency for high energy X-rays and Gamma-rays such a radiation detector should be as thick as possible. The maximum thickness and thus the maximum quantum efficiency has been limited by the substrate doping concentration: the lower the substrate doping the thicker the detector can be before reaching the semiconductor material's electric breakdown field. Thick direct conversion semiconductor detectors comprising vertical three-dimensional electrodes protruding through the substrate have been previously proposed by Sherwood Parker in order to promote rapid detection of radiation. An additional advantage of these detectors is that their thickness is not limited by the substrate doping, i.e., the size of the maximum electric field value in the detector does not depend on detector thickness. However, the thicker the substrate of such three dimensional detectors is the larger the output capacitance is and thus the larger the output noise is. In the novel direct conversion pixelated radiation detector utilizing a novel three dimensional semiconductor architecture, which is proposed in this work, the detector thickness is not limited by the substrate doping and the output capacitance is small and does not depend on the detector thickness. In addition, by incorporating an additional node to the novel three-dimensional semiconductor architecture it can be utilized as a high voltage transistor that can deliver current across high voltages. Furthermore, it is possible to connect a voltage difference of any size to the proposed novel three dimensional semiconductor architecture provided that it is thick enough—this is a novel feature that has not been previously possible for semiconductor

Capacitive properties of PANI/MnO2 synthesized via simultaneous-oxidation route

International Nuclear Information System (INIS)

Zhang Jie; Shu Dong; Zhang Tianren; Chen Hongyu; Zhao Haimin; Wang Yongsheng; Sun Zhenjie; Tang Shaoqing; Fang Xueming; Cao Xiufang

2012-01-01

Highlights: ► PANI/MnO 2 composite was synthesized by the simultaneous-oxidation route. ► Good contact in inter-molecule level between PANI and MnO 2 improves the conductivity. ► The separation between PANI and MnO 2 prevents the aggregation of nano-composite. ► The maximum specific capacitance of the PANI/MnO 2 electrode is 320 F/g. ► The as-prepared PANI/MnO 2 exhibits excellent cycle stability of 84% capacitance retention after 10,000 cycles. - Abstract: Polyaniline (PANI) and manganese dioxide (MnO 2 ) composite (PANI/MnO 2 ) was synthesized via a simultaneous-oxidation route. In this route, all reactants were dispersed homogenously in precursor solution and existed as ions and molecules, and involved reactions of ions and molecules generating PANI and MnO 2 simultaneously. In this way, PANI molecule and MnO 2 molecule contact each other and arrange alternately in the composite. The inter-molecule contact improves the conductivity of the composite. The alternative arrangement of PANI molecules and MnO 2 molecules separating each other, and prevents the aggregation of PANI and cluster of MnO 2 so as to decrease the particle size of the composite. The morphology, structure, porous and capacitive properties are characterized by scanning electron microscopy, X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, Branauer–Emmett–Teller test, thermogravimetric analysis, Fourier transform infrared spectroscopy, cyclic voltammetry, charge–discharge test and the electrochemical impedance measurements. The results show that MnO 2 is predominant in the PANI/MnO 2 composite and the composite exhibits larger specific surface area than pure MnO 2 . The maximum specific capacitance of the composite electrode reaches up to 320 F/g by charge–discharge test, 1.56 times higher than that of MnO 2 (125 F/g). The specific capacitance retains approximately 84% of the initial value after 10,000 cycles, indicating the good cycle stability.

Influence of nonelectrostatic ion-ion interactions on double-layer capacitance

Science.gov (United States)

Zhao, Hui

2012-11-01

Recently a Poisson-Helmholtz-Boltzmann (PHB) model [Bohinc , Phys. Rev. EPLEEE81539-375510.1103/PhysRevE.85.031130 85, 031130 (2012)] was developed by accounting for solvent-mediated nonelectrostatic ion-ion interactions. Nonelectrostatic interactions are described by a Yukawa-like pair potential. In the present work, we modify the PHB model by adding steric effects (finite ion size) into the free energy to derive governing equations. The modified PHB model is capable of capturing both ion specificity and ion crowding. This modified model is then employed to study the capacitance of the double layer. More specifically, we focus on the influence of nonelectrostatic ion-ion interactions on charging a double layer near a flat surface in the presence of steric effects. We numerically compute the differential capacitance as a function of the voltage under various conditions. At small voltages and low salt concentrations (dilute solution), we find out that the predictions from the modified PHB model are the same as those from the classical Poisson-Boltzmann theory, indicating that nonelectrostatic ion-ion interactions and steric effects are negligible. At moderate voltages, nonelectrostatic ion-ion interactions play an important role in determining the differential capacitance. Generally speaking, nonelectrostatic interactions decrease the capacitance because of additional nonelectrostatic repulsion among excess counterions inside the double layer. However, increasing the voltage gradually favors steric effects, which induce a condensed layer with crowding of counterions near the electrode. Accordingly, the predictions from the modified PHB model collapse onto those computed by the modified Poisson-Boltzmann theory considering steric effects alone. Finally, theoretical predictions are compared and favorably agree with experimental data, in particular, in concentrated solutions, leading one to conclude that the modified PHB model adequately predicts the diffuse

Insight into capacitive performance of polyaniline/graphene oxide composites with ecofriendly binder

Science.gov (United States)

Bilal, Salma; Fahim, Muhammad; Firdous, Irum; Ali Shah, Anwar-ul-Haq

2018-03-01

The behaviour of gold electrode modified with polyaniline/graphene oxide composites (PGO) was studied for electrochemical and charge storage properties in aqueous acidic media. The surface of gold electrode was modified with aqueous slurry of PGO by using Carboxymethyl cellulose (CMC) as binder. The intercalation of polyaniline in the GO layers, synthesized by in situ polymerization was confirmed by scanning electron microscopy (SEM). The electrochemical behaviour and charge storing properties were investigated using cyclic voltammetry (CV), galvanostatic charge discharge (GCD) and electrochemical impedance spectroscopy (EIS). A high specific capacitance of 1721 F g-1 was obtained for PGO with 69.8% retention of capacitance even after 1000 voltammetric cycles in the potential range of 0-0.9 V at 20 mV s-1. EIS indicated low charge transfer resistance (Rct) and solution resistance (Rs) values of 0.51 Ω and 0.07 Ω, respectively. This good performance of PGO coated electrode is attributed to the use of CMC binder which generate a high electrode/ electrolyte contact area and short path lengths for electronic transport and electrolyte ion.

Nonlinear dynamics of capacitive charging and desalination by porous electrodes

Science.gov (United States)

Biesheuvel, P. M.; Bazant, M. Z.

2010-03-01

The rapid and efficient exchange of ions between porous electrodes and aqueous solutions is important in many applications, such as electrical energy storage by supercapacitors, water desalination and purification by capacitive deionization, and capacitive extraction of renewable energy from a salinity difference. Here, we present a unified mean-field theory for capacitive charging and desalination by ideally polarizable porous electrodes (without Faradaic reactions or specific adsorption of ions) valid in the limit of thin double layers (compared to typical pore dimensions). We illustrate the theory for the case of a dilute, symmetric, binary electrolyte using the Gouy-Chapman-Stern (GCS) model of the double layer, for which simple formulae are available for salt adsorption and capacitive charging of the diffuse part of the double layer. We solve the full GCS mean-field theory numerically for realistic parameters in capacitive deionization, and we derive reduced models for two limiting regimes with different time scales: (i) in the “supercapacitor regime” of small voltages and/or early times, the porous electrode acts like a transmission line, governed by a linear diffusion equation for the electrostatic potential, scaled to the RC time of a single pore, and (ii) in the “desalination regime” of large voltages and long times, the porous electrode slowly absorbs counterions, governed by coupled, nonlinear diffusion equations for the pore-averaged potential and salt concentration.

Ultrahigh volumetric capacitance and cyclic stability of fluorine and nitrogen co-doped carbon microspheres

Science.gov (United States)

Zhou, Junshuang; Lian, Jie; Hou, Li; Zhang, Junchuan; Gou, Huiyang; Xia, Meirong; Zhao, Yufeng; Strobel, Timothy A.; Tao, Lu; Gao, Faming

2015-09-01

Highly porous nanostructures with large surface areas are typically employed for electrical double-layer capacitors to improve gravimetric energy storage capacity; however, high surface area carbon-based electrodes result in poor volumetric capacitance because of the low packing density of porous materials. Here, we demonstrate ultrahigh volumetric capacitance of 521 F cm-3 in aqueous electrolytes for non-porous carbon microsphere electrodes co-doped with fluorine and nitrogen synthesized by low-temperature solvothermal route, rivaling expensive RuO2 or MnO2 pseudo-capacitors. The new electrodes also exhibit excellent cyclic stability without capacitance loss after 10,000 cycles in both acidic and basic electrolytes at a high charge current of 5 A g-1. This work provides a new approach for designing high-performance electrodes with exceptional volumetric capacitance with high mass loadings and charge rates for long-lived electrochemical energy storage systems.

Capacitive sensing of droplets for microfluidic devices based on thermocapillary actuation.

Science.gov (United States)

Chen, Jian Z; Darhuber, Anton A; Troian, Sandra M; Wagner, Sigurd

2004-10-01

The design and performance of a miniaturized coplanar capacitive sensor is presented whose electrode arrays can also function as resistive microheaters for thermocapillary actuation of liquid films and droplets. Optimal compromise between large capacitive signal and high spatial resolution is obtained for electrode widths comparable to the liquid film thickness measured, in agreement with supporting numerical simulations which include mutual capacitance effects. An interdigitated, variable width design, allowing for wider central electrodes, increases the capacitive signal for liquid structures with non-uniform height profiles. The capacitive resolution and time response of the current design is approximately 0.03 pF and 10 ms, respectively, which makes possible a number of sensing functions for nanoliter droplets. These include detection of droplet position, size, composition or percentage water uptake for hygroscopic liquids. Its rapid response time allows measurements of the rate of mass loss in evaporating droplets.

Electric double-layer capacitance between an ionic liquid and few-layer graphene.

Science.gov (United States)

Uesugi, Eri; Goto, Hidenori; Eguchi, Ritsuko; Fujiwara, Akihiko; Kubozono, Yoshihiro

2013-01-01

Ionic-liquid gates have a high carrier density due to their atomically thin electric double layer (EDL) and extremely large geometrical capacitance Cg. However, a high carrier density in graphene has not been achieved even with ionic-liquid gates because the EDL capacitance CEDL between the ionic liquid and graphene involves the series connection of Cg and the quantum capacitance Cq, which is proportional to the density of states. We investigated the variables that determine CEDL at the molecular level by varying the number of graphene layers n and thereby optimising Cq. The CEDL value is governed by Cq at n 4. This transition with n indicates a composite nature for CEDL. Our finding clarifies a universal principle that determines capacitance on a microscopic scale, and provides nanotechnological perspectives on charge accumulation and energy storage using an ultimately thin capacitor.

Compensation of the detector capacitance presented to charge-sensitive preamplifiers using the Miller effect

Energy Technology Data Exchange (ETDEWEB)

Kwon, Inyong, E-mail: iykwon@umich.edu [University of Michigan, Ann Arbor, MI (United States); Kang, Taehoon, E-mail: thnkang@umich.edu [University of Michigan, Ann Arbor, MI (United States); Wells, Byron T., E-mail: wells@galtresearch.com [Galt LLC, Ypsilanti, MI (United States); D’Aries, Lawrence J., E-mail: lawrence.j.daries.civ@mail.mil [Picatinny Arsenal, Rockaway Township, NJ (United States); Hammig, Mark D., E-mail: hammig@umich.edu [University of Michigan, Ann Arbor, MI (United States)

2015-06-01

This paper describes an integrated circuit design for a modified charge-sensitive amplifier (CSA) that compensates for the effect of capacitance presented by nuclear radiation detectors and other sensors. For applications that require large area semiconductor detectors or for those semiconductor sensors derived from high permittivity materials such as PbSe, the detector capacitance can degrade the system gain and bandwidth of a front-end preamplifier, resulting in extended rise times and attenuated output voltage signals during pulse formation. In order to suppress the effect of sensor capacitance, we applied a bootstrap technique into a traditional CSA. The technique exploits the Miller effect by reducing the effective voltage difference between the two sides of a radiation detector which minimizes the capacitance presented to the differential common-source amplifier. This new configuration is successfully designed to produce effective gain even at high detector capacitance. The entire circuit, including a core CSA with feedback components and a bootstrap amplifier, are implemented in a 0.18 μm CMOS process with a 3.3 V supply voltage. - Highlights: • A modified CSA was implemented for detector capacitance compensation. • Increasing detector capacitance degrades gain and rise time. • A bootstrap amplifier exploiting the Miller effect is described. • It allows using large area radiation sensors for high radiation-interaction rates. • Intensive noise analyses show that SNR is much better with the technique.

Capacitive sensor for continuous monitoring of high-volume droplet microfluidic generation

KAUST Repository

Conchouso Gonzalez, David; Carreno, Armando Arpys Arevalo; Castro, David; Kavaldzhiev, Mincho; Foulds, Ian G.

2016-01-01

for accurate detection of water in oil concentration changes. Capacitance variations as large as 10 pF between a channel filled with water or dodecane, are used to continuously monitor the output of a parallelization system producing 150 µl/min of water

Effects of heat treatment on the hierarchical porous structure and electro-capacitive properties of RuO{sub 2}/activated carbon nanofiber composites

Energy Technology Data Exchange (ETDEWEB)

Jun, Ye Ri; Kim, Bo Hye [Div. of Science Education, Chemistry Education Major, Daegu University, Daegu (Korea, Republic of)

2016-11-15

Electrochemical capacitors based on hierarchical porous activated carbon nanofiber (RuO{sub 2} /ACNF) composites are fabricated by one-step electrospinning, and then stabilized at different activation temperatures. The effect of the activation temperature on the structural properties and electrochemical behavior of the RuO{sub 2} /ACNF composites is intensively investigated in 6 M KOH electrolyte. The RuO{sub 2} /ACNF-800 composites activated at high temperature possess abundant mesopores and larger pores, which improve the electrochemical performance, especially at high charge–discharge rates. The energy storage capabilities of the RuO{sub 2} /ACNF-800 electrode prepared at high temperature are as follows: a maximum specific capacitance of 150 F/g and an energy density of 14–20 Wh/kg in the respective power density range of 400 to 10 000 W/kg in an aqueous solution. Furthermore, this electrode exhibits high-rate electrochemical performance with a specific capacitance reduction of less than 28% of the initial value at a discharge current of 20 mA/cm{sup 2}. Therefore, the hierarchical porous RuO{sub 2} /ACNF composites with well-developed mesoporous structure provide low resistance for charge diffusion and a short pathway for ion transportation, yielding good capacitive behavior.

Carbon flow electrodes for continuous operation of capacitive deionization and capacitive mixing energy generation

NARCIS (Netherlands)

Porada, S.; Hamelers, H.V.M.; Bryjak, M.; Presser, V.; Biesheuvel, P.M.; Weingarth, D.

2014-01-01

Capacitive technologies, such as capacitive deionization and energy harvesting based on mixing energy (“capmix” and “CO2 energy”), are characterized by intermittent operation: phases of ion electrosorption from the water are followed by system regeneration. From a system application point of view,

Simultaneous Characterization of Instantaneous Young’s Modulus and Specific Membrane Capacitance of Single Cells Using a Microfluidic System

Directory of Open Access Journals (Sweden)

Yang Zhao

2015-01-01

Full Text Available This paper presents a microfluidics-based approach capable of continuously characterizing instantaneous Young’s modulus (Einstantaneous and specific membrane capacitance (Cspecific membrane of suspended single cells. In this method, cells were aspirated through a constriction channel while the cellular entry process into the constriction channel was recorded using a high speed camera and the impedance profiles at two frequencies (1 kHz and 100 kHz were simultaneously measured by a lock-in amplifier. Numerical simulations were conducted to model cellular entry process into the constriction channel, focusing on two key parameters: instantaneous aspiration length (Linstantaneous and transitional aspiration length (Ltransitional, which was further translated to Einstantaneous. An equivalent distribution circuit model for a cell travelling in the constriction channel was used to determine Cspecific membrane. A non-small-cell lung cancer cell line 95C (n = 354 was used to evaluate this technique, producing Einstantaneous of 2.96 ± 0.40 kPa and Cspecific membrane of 1.59 ± 0.28 μF/cm2. As a platform for continuous and simultaneous characterization of cellular Einstantaneous and Cspecific membrane, this approach can facilitate a more comprehensive understanding of cellular biophysical properties.

Anomalous or regular capacitance? The influence of pore size dispersity on double-layer formation

Science.gov (United States)

Jäckel, N.; Rodner, M.; Schreiber, A.; Jeongwook, J.; Zeiger, M.; Aslan, M.; Weingarth, D.; Presser, V.

2016-09-01

The energy storage mechanism of electric double-layer capacitors is governed by ion electrosorption at the electrode surface. This process requires high surface area electrodes, typically highly porous carbons. In common organic electrolytes, bare ion sizes are below one nanometer but they are larger when we consider their solvation shell. In contrast, ionic liquid electrolytes are free of solvent molecules, but cation-anion coordination requires special consideration. By matching pore size and ion size, two seemingly conflicting views have emerged: either an increase in specific capacitance with smaller pore size or a constant capacitance contribution of all micro- and mesopores. In our work, we revisit this issue by using a comprehensive set of electrochemical data and a pore size incremental analysis to identify the influence of certain ranges in the pore size distribution to the ion electrosorption capacity. We see a difference in solvation of ions in organic electrolytes depending on the applied voltage and a cation-anion interaction of ionic liquids in nanometer sized pores.

Improved capacitance sensor with variable operating frequency for scanning capacitance microscopy

International Nuclear Information System (INIS)

Kwon, Joonhyung; Kim, Joonhui; Jeong, Jong-Hwa; Lee, Euy-Kyu; Seok Kim, Yong; Kang, Chi Jung; Park, Sang-il

2005-01-01

Scanning capacitance microscopy (SCM) has been gaining attention for its capability to measure local electrical properties in doping profile, oxide thickness, trapped charges and charge dynamics. In many cases, stray capacitance produced by different samples and measurement conditions affects the resonance frequency of a capacitance sensor. The applications of conventional SCM are critically limited by the fixed operating frequency and lack of tunability in its SCM sensor. In order to widen SCM application to various samples, we have developed a novel SCM sensor with variable operating frequency. By performing variable frequency sweep over the band of 160 MHz, the SCM sensor is tuned to select the best and optimized resonance frequency and quality factor for each sample measurement. The fundamental advantage of the new variable frequency SCM sensor was demonstrated in the SCM imaging of silicon oxide nano-crystals. Typical sensitivity of the variable frequency SCM sensor was found to be 10 -19 F/V

Highly electroconductive mesoporous graphene nanofibers and their capacitance performance at 4 V.

Science.gov (United States)

Cui, Chaojie; Qian, Weizhong; Yu, Yuntao; Kong, Chuiyan; Yu, Bo; Xiang, Lan; Wei, Fei

2014-02-12

We report the fabrication of one-dimensional highly electroconductive mesoporous graphene nanofibers (GNFs) by a chemical vapor deposition method using MgCO3·3H2O fibers as the template. The growth of such a unique structure underwent the first in situ decomposition of MgCO3·3H2O fibers to porous MgO fibers, followed by the deposition of carbon on the MgO surface, the removal of MgO by acidic washing, and the final self-assembly of wet graphene from single to double layer in drying process. GNFs exhibited good structural stability, high surface area, mesopores in large amount, and electrical conductivity 3 times that of carbon nanotube aggregates. It, used as an electrode in a 4 V supercapacitor, exhibited high energy density in a wide range of high power density and excellent cycling stability. The short diffusion distance for ions of ionic liquids electrolyte to the surface of GNFs yielded high surface utilization efficiency and a capacitance up to 15 μF/cm(2), higher than single-walled carbon nanotubes.

Overview of capacitive couplings in windings

NARCIS (Netherlands)

Djukic, N.; Encica, L.; Paulides, J.J.H.

2015-01-01

The use of electrical machines (EMs) with variable-frequency drives (VFDs) results in electromagnetic interference (EMI). At high frequencies (HFs) of conducted EMI, the impedance of an EM insulation system fed from a VFD is small due to the parasitic capacitive couplings. Thus, the conducted EMI

Electrode Mass Balancing as an Inexpensive and Simple Method to Increase the Capacitance of Electric Double-Layer Capacitors

Science.gov (United States)

Andres, Britta; Engström, Ann-Christine; Blomquist, Nicklas; Forsberg, Sven; Dahlström, Christina; Olin, Håkan

2016-01-01

Symmetric electric double-layer capacitors (EDLCs) have equal masses of the same active material in both electrodes. However, having equal electrode masses may prevent the EDLC to have the largest possible specific capacitance if the sizes of the hydrated anions and cations in the electrolyte differ because the electrodes and the electrolyte may not be completely utilized. Here we demonstrate how this issue can be resolved by mass balancing. If the electrode masses are adjusted according to the size of the ions, one can easily increase an EDLC’s specific capacitance. To that end, we performed galvanostatic cycling to measure the capacitances of symmetric EDLCs with different electrode mass ratios using four aqueous electrolytes— Na2SO4, H2SO4, NaOH, and KOH (all with a concentration of 1 M)—and compared these to the theoretical optimal electrode mass ratio that we calculated using the sizes of the hydrated ions. Both the theoretical and experimental values revealed lower-than-1 optimal electrode ratios for all electrolytes except KOH. The largest increase in capacitance was obtained for EDLCs with NaOH as electrolyte. Specifically, we demonstrate an increase of the specific capacitance by 8.6% by adjusting the electrode mass ratio from 1 to 0.86. Our findings demonstrate that electrode mass balancing is a simple and inexpensive method to increase the capacitance of EDLCs. Furthermore, our results imply that one can reduce the amount of unused material in EDLCs and thus decrease their weight, volume and cost. PMID:27658253

High energy density supercapacitors from lignin derived submicron activated carbon fibers in aqueous electrolytes

Science.gov (United States)

Hu, Sixiao; Zhang, Sanliang; Pan, Ning; Hsieh, You-Lo

2014-12-01

Highly porous submicron activated carbon fibers (ACFs) were robustly generated from low sulfonated alkali lignin and fabricated into supercapacitors for capacitive energy storage. The hydrophilic and high specific surface ACFs exhibited large-size nanographites and good electrical conductivity to demonstrate outstanding electrochemical performance. ACFs from KOH activation, in particular, showed very high 344 F g-1 specific capacitance at low 1.8 mg cm-2 mass loading and 10 mV s-1 scan rate in aqueous electrolytes. Even at relatively high scan rate of 50 mV s-1 and mass loading of 10 mg cm-2, a decent specific capacitance of 196 F g-1 and a remarkable areal capacitance of 0.55 F cm-2 was obtained, leading to high energy density of 8.1 Wh kg-1 based on averaged electrodes mass. Furthermore, over 96% capacitance retention rates were achieved after 5000 charge/discharge cycles. Such excellent performance demonstrated great potential of lignin derived carbons for electrical energy storage.

Verification of alternative dew point hygrometer for CV-LRT in MONJU. Short- and long-term verification of capacitance-type dew point hygrometer (Translated document)

International Nuclear Information System (INIS)

Ichikawa, Shoichi; Chiba, Yusuke; Ono, Fumiyasu; Hatori, Masakazu; Kobayashi, Takanori; Uekura, Ryoichi; Hashiri, Nobuo; Inuzuka, Taisuke; Kitano, Hiroshi; Abe, Hisashi

2017-03-01

To reduce the influence of maintenance of dew point hygrometers on the plant schedule at the prototype fast-breeder reactor MONJU, Japan Atomic Energy Agency examined a capacitance-type dew point hygrometer as an alternative to the lithium-chloride dew point hygrometer being used in the containment vessel leak rate test. As verifications, a capacitance-type dew point hygrometer was compared with a lithium-chloride dew point hygrometer under a containment vessel leak rate test condition. And the capacitance-type dew point hygrometer was compared with a high-precision-mirror-surface dew point hygrometer for long-term (2 years) in the containment vessel as an unprecedented try. A comparison of a capacitance-type dew point hygrometer with a lithium-chloride dew point hygrometer in a containment vessel leak rate test (Atmosphere: nitrogen, Testing time: 24 h) revealed no significant difference between the capacitance-type dew point hygrometer and the lithium-chloride dew point hygrometer. A comparison of the capacitance-type dew point hygrometer with the high-precision-mirror-surface dew point hygrometer for long-term verification (Atmosphere: air, Testing time: 24 months) revealed that the capacitance-type dew point hygrometer satisfied the instrumental specification (synthesized precision of detector and converter: ±2.04°C) specified in the Leak Rate Test Regulations for Nuclear Reactor Containment Vessel. It was confirmed that the capacitance-type dew point hygrometer can be used as a long-term alternative to the lithium-chloride dew point hygrometer without affecting the dew point hygrometer maintenance schedule of the MONJU plant. (author)

Negative quantum capacitance induced by midgap states in single-layer graphene.

Science.gov (United States)

Wang, Lin; Wang, Yang; Chen, Xiaolong; Zhu, Wei; Zhu, Chao; Wu, Zefei; Han, Yu; Zhang, Mingwei; Li, Wei; He, Yuheng; Xiong, Wei; Law, Kam Tuen; Su, Dangsheng; Wang, Ning

2013-01-01

We demonstrate that single-layer graphene (SLG) decorated with a high density of Ag adatoms displays the unconventional phenomenon of negative quantum capacitance. The Ag adatoms act as resonant impurities and form nearly dispersionless resonant impurity bands near the charge neutrality point (CNP). Resonant impurities quench the kinetic energy and drive the electrons to the Coulomb energy dominated regime with negative compressibility. In the absence of a magnetic field, negative quantum capacitance is observed near the CNP. In the quantum Hall regime, negative quantum capacitance behavior at several Landau level positions is displayed, which is associated with the quenching of kinetic energy by the formation of Landau levels. The negative quantum capacitance effect near the CNP is further enhanced in the presence of Landau levels due to the magnetic-field-enhanced Coulomb interactions.

High-capacitance supercapacitors using nitrogen-decorated porous carbon derived from novolac resin containing peptide linkage

OpenAIRE

Kim, Yong Jung; Jang, In Young; Park, Ki Chul; Jung, Yong Chae; Oka, Takuyuki; Iinou, Satoshi; Komori, Yasuhiro; Kozutsumi, Toshihiko; Hashiba, Takashi; Kim, Yoong Ahm; Endo, Morinobu

2010-01-01

We fabricated nitrogen-decorated porous carbon exhibiting high capacitance per unit volume and unit weight via chemical activation of novolac resin containing peptide linkage. The porosity and the amount of nitrogen atoms were controlled by changing the molecular weight of novolac resin, the added amount of potassium hydroxide, or both. After chemical activation, positively charged nitrogen atoms (i.e., pyridine/pyrrole) at 400.3 eV in photoemission spectra contributed to both a shift in the ...

Design and analysis of optimised class E power amplifier using shunt capacitance in the output structure

Science.gov (United States)

Hayati, Mohsen; Roshani, Sobhan; Zirak, Ali Reza

2017-05-01

In this paper, a class E power amplifier (PA) with operating frequency of 1 MHz is presented. MOSFET non-linear drain-to-source parasitic capacitance, linear external capacitance at drain-to-source port and linear shunt capacitance in the output structure are considered in design theory. One degree of freedom is added to the design of class E PA, by assuming the shunt capacitance in the output structure in the analysis. With this added design degree of freedom it is possible to achieve desired values for several parameters, such as output voltage, load resistance and operating frequency, while both zero voltage and zero derivative switching (ZVS and ZDS) conditions are satisfied. In the conventional class E PA, high value of peak switch voltage results in limitations for the design of amplifier, while in the presented structure desired specifications could be achieved with the safe margin of peak switch voltage. The results show that higher operating frequency and output voltage can also be achieved, compared to the conventional structure. PSpice software is used in order to simulate the designed circuit. The presented class E PA is designed, fabricated and measured. The measured results are in good agreement with simulation and theory results.

Capacitance enhancement via electrode patterning

International Nuclear Information System (INIS)

Ho, Tuan A.; Striolo, Alberto

2013-01-01

The necessity of increasing the energy density in electric double layer capacitors to meet current demand is fueling fundamental and applied research alike. We report here molecular dynamics simulation results for aqueous electrolytes near model electrodes. Particular focus is on the effect of electrode patterning on the structure of interfacial electrolytes, and on the potential drop between the solid electrodes and the bulk electrolytes. The latter is estimated by numerically integrating the Poisson equation using the charge densities due to water and ions accumulated near the interface as input. We considered uniform and patterned electrodes, both positively and negatively charged. The uniformly charged electrodes are modeled as graphite. The patterned ones are obtained by removing carbon atoms from the top-most graphene layer, yielding nanoscopic squares and stripes patterns. For simplicity, the patterned electrodes are effectively simulated as insulators (the charge remains localized on the top-most layer of carbon atoms). Our simulations show that the patterns alter the structure of water and the accumulation of ions at the liquid-solid interfaces. Using aqueous NaCl solutions, we found that while the capacitance calculated for three positively charged electrodes did not change much, that calculated for the negatively charged electrodes significantly increased upon patterning. We find that both water structure and orientation, as well as ion accumulation affect the capacitance. As electrode patterning affects differently water structure and ion accumulation, it might be possible to observe ion-specific effects. These results could be useful for advancing our understanding of electric double layer capacitors, capacitive desalination processes, as well as of fundamental interfacial electrolytes properties

Wireless Capacitive Pressure Sensor With Directional RF Chip Antenna for High Temperature Environments

Science.gov (United States)

Scardelletti, M. C.; Jordan, J. L.; Ponchak, G. E.; Zorman, C. A.

2015-01-01

This paper presents the design, fabrication and characterization of a wireless capacitive pressure sensor with directional RF chip antenna that is envisioned for the health monitoring of aircraft engines operating in harsh environments. The sensing system is characterized from room temperature (25 C) to 300 C for a pressure range from 0 to 100 psi. The wireless pressure system consists of a Clapp-type oscillator design with a capacitive MEMS pressure sensor located in the LC-tank circuit of the oscillator. Therefore, as the pressure of the aircraft engine changes, so does the output resonant frequency of the sensing system. A chip antenna is integrated to transmit the system output to a receive antenna 10 m away.The design frequency of the wireless pressure sensor is 127 MHz and a 2 increase in resonant frequency over the temperature range of 25 to 300 C from 0 to 100 psi is observed. The phase noise is less than minus 30 dBcHz at the 1 kHz offset and decreases to less than minus 80 dBcHz at 10 kHz over the entire temperature range. The RF radiation patterns for two cuts of the wireless system have been measured and show that the system is highly directional and the MEMS pressure sensor is extremely linear from 0 to 100 psi.

Capacitive MEMS-based sensors : thermo-mechanical stability and charge trapping

NARCIS (Netherlands)

van Essen, M.C.

2009-01-01

Micro-Electro Mechanical Systems (MEMS) are generally characterized as miniaturized systems with electrostatically driven moving parts. In many cases, the electrodes are capacitively coupled. This basic scheme allows for a plethora of specifications and functionality. This technology has presently

Polyaniline/single-wall carbon nanotube (PANI/SWCNT) composites for high performance supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Gupta, Vinay; Miura, Norio [Art, Science and Technology Center for Cooperative Research, Kyushu University, Kasuga-shi, Fukuoka 816-8580 (Japan)

2006-12-01

PANI/SWCNT composites were prepared by electrochemical polymerisation of polyaniline onto SWCNTs and their capacitive performance was evaluated by means of cyclic voltammetry and charge-discharge cycling in 1M H{sub 2}SO{sub 4} electrolyte. The PANI/SWCNT composites single electrode showed much higher specific capacitance, specific energy and specific power than pure PANI and SWCNTs. The highest specific capacitance, specific power and specific energy values of 485F/g, 228Wh/kg and 2250W/kg were observed for 73wt.% PANI deposited onto SWCNTs. PANI/SWCNT composites also showed long cyclic stability. Based upon the variations in the surface morphologies and specific capacitance of the composite, a mechanism is proposed to explain enhancement in the capacitive characteristics. The PANI/SWCNT composites have demonstrated the potential as excellent electrode materials for application in high performance supercapacitors. (author)

Synthesis and capacitance properties of N-doped porous carbon/NiO nanosheet composites using coal-based polyaniline as carbon and nitrogen source

Science.gov (United States)

Wang, Xiaoqin; Li, Qiaoqin; Zhang, Yong; Yang, Yufei; Cao, Zhi; Xiong, Shanxin

2018-06-01

A novel synthesis approach of N-doped porous carbon (NPC)/NiO composites possessing some honeycomb-shaped nanoporous carbon and plentiful NiO nanosheets is exploited. First NPC/Ni composites are achieved with NPC yield of 52.9% through a catalytic pyrolysis method, using coal-based polyaniline particles prepared by an in-situ polymerization method as a carbon and nitrogen source, and nickel particles as a catalyst, respectively. Next NPC/NiO composites are achieved unexpectedly with plentiful NiO nanosheets and N content of 1.00 wt% after a liquid oxidation process. In NPC/NiO composites, porous carbon mainly presents in the amorphous state, while the incorporated nitrogen mainly presents in the form of pyrrolic N (92.9 at.%) and oxidized N (7.1 at.%). Plentiful NiO nanosheets are embedded in the pores or on the NPC surface. 33.3 at.% Ni2O3 components exist in the surface of NiO nanosheets. NPC/NiO composites possess not only rich micropores, but also significant mesopores and nanoscale macropores. The BET specific surface area, BET average pore width and BJH adsorption average pore diameter are 627.5 m2/g, 2.0 nm and 5.1 nm, respectively. NPC/NiO composites demonstrate a high specific capacitance of 404.1 F/g at 1 A/g, and a good cycling stability maintaining high specific capacitance of 212.4 F/g (84.3% of the initial capacitance) at 5 A/g after 5000 cycles of charge and discharge, attributed to some honeycomb-shaped nanopores of carbon and large specific surface area of NiO nanosheets, and the synergistic effects between electric double-layer capacitance of NPC and pseudocapacitance of NiO. This study may provide a novel approach for the value-added applications of low-rank coal.

High Temperature Capacitive Pressure Sensor Employing a SiC Based Ring Oscillator

Science.gov (United States)

Meredith, Roger D.; Neudeck, Philip G.; Ponchak, George E.; Beheim, Glenn M.; Scardelletti, Maximilian; Jordan, Jennifer L.; Chen, Liang-Yu; Spry, David J.; Krawowski, Michael J.; Hunter, Gary W.

2011-01-01

In an effort to develop harsh environment electronic and sensor technologies for aircraft engine safety and monitoring, we have used capacitive-based pressure sensors to shift the frequency of a SiC-electronics-based oscillator to produce a pressure-indicating signal that can be readily transmitted, e.g. wirelessly, to a receiver located in a more benign environment. Our efforts target 500 C, a temperature well above normal operating conditions of commercial circuits but within areas of interest in aerospace engines, deep mining applications and for future missions to the Venus atmosphere. This paper reports for the first time a ring oscillator circuit integrated with a capacitive pressure sensor, both operating at 500 C. This demonstration represents a significant step towards a wireless pressure sensor that can operate at 500 C and confirms the viability of 500 C electronic sensor systems.

A transimpedance amplifier for excess noise measurements of high junction capacitance avalanche photodiodes

International Nuclear Information System (INIS)

Green, James E; David, John P R; Tozer, Richard C

2012-01-01

This paper reports a novel and versatile system for measuring excess noise and multiplication in avalanche photodiodes (APDs), using a bipolar junction transistor based transimpedance amplifier front-end and based on phase-sensitive detection, which permits accurate measurement in the presence of a high dark current. The system can reliably measure the excess noise factor of devices with capacitance up to 5 nF. This system has been used to measure thin, large area Si pin APDs and the resulting data are in good agreement with measurements of the same devices obtained from a different noise measurement system which will be reported separately. (paper)

The Capacitive Magnetic Field Sensor

Science.gov (United States)

Zyatkov, D. O.; Yurchenko, A. V.; Balashov, V. B.; Yurchenko, V. I.

2016-01-01

The results of a study of sensitive element magnetic field sensor are represented in this paper. The sensor is based on the change of the capacitance with an active dielectric (ferrofluid) due to the magnitude of magnetic field. To prepare the ferrofluid magnetic particles are used, which have a followingdispersion equal to 50 brand 5BDSR. The dependence of the sensitivity of the capacitive element from the ferrofluid with different dispersion of magnetic particles is considered. The threshold of sensitivity and sensitivity of a measuring cell with ferrofluid by a magnetic field was determined. The experimental graphs of capacitance change of the magnitude of magnetic field are presented.

Virtual electrical capacitance tomography sensor

International Nuclear Information System (INIS)

Li, Y; Yang, W Q

2005-01-01

Electrical capacitance tomography (ECT) is an effective technique for elucidating the distribution of dielectric materials inside closed pipes or vessels. This paper describes a virtual electrical capacitance tomography (VECT) system, which can simulate a range of sensor and hardware configurations and material distributions. A selection of popular image reconstruction algorithms has been made available and image error and capacitance error tools enable their performance to be evaluated and compared. Series of frame-by-frame results can be stored for simulating real-time dynamic flows. The system is programmed in Matlab with DOS functions. It is convenient to use and low-cost to operate, providing an effective tool for engineering experiment

Intrinsic Low Hysteresis Touch Mode Capacitive Pressure Sensor

DEFF Research Database (Denmark)

Fragiacomo, Giulio; Pedersen, Thomas; Hansen, Ole

2011-01-01

Hysteresis has always been one of the main concerns when fabricating touch mode capacitive pressure sensors (TMCPS). This phenomenon can be fought at two different levels: during fabrication or after fabrication with the aid of a dedicated signal conditioning circuit. We will describe...... a microfabrication step that can be introduced in order to reduce drastically the hysteresis of this type of sensors without compromising their sensitivity. Medium-high range (0 to 10 bar absolute pressure) TMCPS with a capacitive signal span of over 100pF and less than 1 % hysteresis in the entire pressure range...

Flexible PVDF ferroelectric capacitive temperature sensor

KAUST Repository

Khan, Naveed

2015-08-02

In this paper, a capacitive temperature sensor based on polyvinylidene fluoride (PVDF) capacitor is explored. The PVDF capacitor is characterized below its Curie temperature. The capacitance of the PVDF capacitor changes vs temperature with a sensitivity of 16pF/°C. The linearity measurement of the capacitance-temperature relation shows less than 0.7°C error from a best fit straight line. An LC oscillator based temperature sensor is demonstrated based on this capacitor.

Excellent capacitive performance of a three-dimensional hierarchical porous graphene/carbon composite with a superhigh surface area.

Science.gov (United States)

Li, Xue Jin; Xing, Wei; Zhou, Jin; Wang, Gui Qiang; Zhuo, Shu Ping; Yan, Zi Feng; Xue, Qing Zhong; Qiao, Shi Zhang

2014-10-06

Three-dimensional hierarchical porous graphene/carbon composite was successfully synthesized from a solution of graphene oxide and a phenolic resin by using a facile and efficient method. The morphology, structure, and surface property of the composite were investigated intensively by a variety of means such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption, Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). It is found that graphene serves as a scaffold to form a hierarchical pore texture in the composite, resulting in its superhigh surface area of 2034 m(2) g(-1), thin macropore wall, and high conductivity (152 S m(-1)). As evidenced by electrochemical measurements in both EMImBF4 ionic liquid and KOH electrolyte, the composite exhibits ideal capacitive behavior, high capacitance, and excellent rate performance due to its unique structure. In EMImBF4 , the composite has a high energy density of up to 50.1 Wh kg(-1) and also possesses quite stable cycling stability at 100 °C, suggesting its promising application in high-temperature supercapacitors. In KOH electrolyte, the specific capacitance of this composite can reach up to an unprecedented value of 186.5 F g(-1), even at a very high current density of 50 A g(-1), suggesting its prosperous application in high-power applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The correlation of the results of capacitance mapping and of sheet resistance mapping in semi-insulating 6H-SiC

International Nuclear Information System (INIS)

Lin Shenghuang; Chen Zhiming; Liang Peng; Jiang Dong; Xie Huajie; Yang Ying

2010-01-01

A combination of complex surface capacitance mapping and sheet resistance mapping is applied to establish the origin of resistance variations on semi-insulating (SI) 6H-SiC substrates. The direct correlation between the capacitance quadrature and the sheet resistance is found in vanadium-doped SI samples. Regions with low capacitance quadrature show high sheet resistance. This indicates, associated with the nonhomogeneity of sheet resistance on the substrate, that the quality of crystallization is not good enough, which also leads to resistivity nonhomogeneity when comparing with different types of deep defects. According to the capacitance mapping, the region with bad crystallization quality has a high radio absorption coefficient. Another correlation is established between the capacitance in-phase and sheet resistance for the vanadium-doped sample. In this sample, the capacitance in-phase map shows not only the surface topography, but also the same distribution trend as the sheet resistance, namely, regions of high capacitance in-phase reveal high sheet resistance.

Triboelectricity in capacitive biopotential measurements.

Science.gov (United States)

Wartzek, Tobias; Lammersen, Thomas; Eilebrecht, Benjamin; Walter, Marian; Leonhardt, Steffen

2011-05-01

Capacitive biopotential measurements suffer from strong motion artifacts, which may result in long time periods during which a reliable measurement is not possible. This study examines contact electrification and triboelectricity as possible reasons for these artifacts and discusses local triboelectric effects on the electrode-body interface as well as global electrostatic effects as common-mode interferences. It will be shown that most probably the triboelectric effects on the electrode-body interface are the main reason for artifacts, and a reduction of artifacts can only be achieved with a proper design of the electrode-body interface. For a deeper understanding of the observed effects, a mathematical model for triboelectric effects in highly isolated capacitive biopotential measurements is presented and verified with experiments. Based on these analyses of the triboelectric effects on the electrode-body interface, different electrode designs are developed and analyzed in order to minimize artifacts due to triboelectricity on the electrode-body interface. © 2011 IEEE

Effect of Plasma Membrane Semipermeability in Making the Membrane Electric Double Layer Capacitances Significant.

Science.gov (United States)

Sinha, Shayandev; Sachar, Harnoor Singh; Das, Siddhartha

2018-01-30

Electric double layers (or EDLs) formed at the membrane-electrolyte interface (MEI) and membrane-cytosol interface (MCI) of a charged lipid bilayer plasma membrane develop finitely large capacitances. However, these EDL capacitances are often much larger than the intrinsic capacitance of the membrane, and all of these capacitances are in series. Consequently, the effect of these EDL capacitances in dictating the overall membrane-EDL effective capacitance C eff becomes negligible. In this paper, we challenge this conventional notion pertaining to the membrane-EDL capacitances. We demonstrate that, on the basis of the system parameters, the EDL capacitance for both the permeable and semipermeable membranes can be small enough to influence C eff . For the semipermeable membranes, however, this lowering of the EDL capacitance can be much larger, ensuring a reduction of C eff by more than 20-25%. Furthermore, for the semipermeable membranes, the reduction in C eff is witnessed over a much larger range of system parameters. We attribute such an occurrence to the highly nonintuitive electrostatic potential distribution associated with the recently discovered phenomena of charge-inversion-like electrostatics and the attainment of a positive zeta potential at the MCI for charged semipermeable membranes. We anticipate that our findings will impact the quantification and the identification of a large number of biophysical phenomena that are probed by measuring the plasma membrane capacitance.

Structure-based capacitance modeling and power loss analysis for the latest high-performance slant field-plate trench MOSFET

Science.gov (United States)

Kobayashi, Kenya; Sudo, Masaki; Omura, Ichiro

2018-04-01

Field-plate trench MOSFETs (FP-MOSFETs), with the features of ultralow on-resistance and very low gate–drain charge, are currently the mainstream of high-performance applications and their advancement is continuing as low-voltage silicon power devices. However, owing to their structure, their output capacitance (C oss), which leads to main power loss, remains to be a problem, especially in megahertz switching. In this study, we propose a structure-based capacitance model of FP-MOSFETs for calculating power loss easily under various conditions. Appropriate equations were modeled for C oss curves as three divided components. Output charge (Q oss) and stored energy (E oss) that were calculated using the model corresponded well to technology computer-aided design (TCAD) simulation, and we validated the accuracy of the model quantitatively. In the power loss analysis of FP-MOSFETs, turn-off loss was sufficiently suppressed, however, mainly Q oss loss increased depending on switching frequency. This analysis reveals that Q oss may become a significant issue in next-generation high-efficiency FP-MOSFETs.

Direct growth of cobalt aluminum double hydroxides on graphene nanosheets and the capacitive properties of the resulting composites

International Nuclear Information System (INIS)

Kim, Yuna; Kim, Seok

2015-01-01

We synthesized graphene nanosheets (GNs)/cobalt aluminum (CoAl) double hydroxide composites through a layer-by-layer deposition process while varying the concentration of the graphene precursor used. The CoAl layered double hydroxide particles were uniformly distributed on the surfaces of the graphene layers and effectively prevented the agglomeration of the GNs, resulting in a higher reactive surface area and easier ion transport. We employed X-ray diffraction analysis, energy-dispersive X-ray spectroscopy, field-emission scanning electron microscopy, and field-emission transmission electron microscopy to investigate the microstructures and morphologies of the composites. In addition, cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge measurements were performed to analyze the electrochemical behaviors of the composites. The as-prepared composites showed desirable electrochemical characteristics, including high specific capacitances, low resistances, and high cycling stabilities. In particular, the composite formed by optimizing the GNs/CoAl ratio (the electrolyte used was a 6 M aqueous KOH solution) exhibited the maximum specific capacitance, which was 974 F g −1

Resonant frequency detection and adjustment method for a capacitive transducer with differential transformer bridge

Energy Technology Data Exchange (ETDEWEB)

Hu, M.; Bai, Y. Z., E-mail: abai@mail.hust.edu.cn; Zhou, Z. B., E-mail: zhouzb@mail.hust.edu.cn; Li, Z. X.; Luo, J. [MOE Key Laboratory of Fundamental Physical Quantities Measurement, School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)

2014-05-15

The capacitive transducer with differential transformer bridge is widely used in ultra-sensitive space accelerometers due to their simple structure and high resolution. In this paper, the front-end electronics of an inductive-capacitive resonant bridge transducer is analyzed. The analysis result shows that the performance of this transducer depends upon the case that the AC pumping frequency operates at the resonance point of the inductive-capacitive bridge. The effect of possible mismatch between the AC pumping frequency and the actual resonant frequency is discussed, and the theoretical analysis indicates that the output voltage noise of the front-end electronics will deteriorate by a factor of about 3 due to either a 5% variation of the AC pumping frequency or a 10% variation of the tuning capacitance. A pre-scanning method to determine the actual resonant frequency is proposed followed by the adjustment of the operating frequency or the change of the tuning capacitance in order to maintain expected high resolution level. An experiment to verify the mismatching effect and the adjustment method is provided.

Resonant frequency detection and adjustment method for a capacitive transducer with differential transformer bridge

International Nuclear Information System (INIS)

Hu, M.; Bai, Y. Z.; Zhou, Z. B.; Li, Z. X.; Luo, J.

2014-01-01

The capacitive transducer with differential transformer bridge is widely used in ultra-sensitive space accelerometers due to their simple structure and high resolution. In this paper, the front-end electronics of an inductive-capacitive resonant bridge transducer is analyzed. The analysis result shows that the performance of this transducer depends upon the case that the AC pumping frequency operates at the resonance point of the inductive-capacitive bridge. The effect of possible mismatch between the AC pumping frequency and the actual resonant frequency is discussed, and the theoretical analysis indicates that the output voltage noise of the front-end electronics will deteriorate by a factor of about 3 due to either a 5% variation of the AC pumping frequency or a 10% variation of the tuning capacitance. A pre-scanning method to determine the actual resonant frequency is proposed followed by the adjustment of the operating frequency or the change of the tuning capacitance in order to maintain expected high resolution level. An experiment to verify the mismatching effect and the adjustment method is provided

Morphological reason for enhancement of electrochemical double layer capacitances of various acetylene blacks by electrochemical polarization

International Nuclear Information System (INIS)

Kim, Taegon; Ham, Chulho; Rhee, Choong Kyun; Yoon, Seong-Ho; Tsuji, Masaharu; Mochida, Isao

2008-01-01

Enhancement of electrochemical capacitance and morphological variations of various acetylene blacks caused by electrochemical polarization are presented. Acetylene blacks of different mean particle diameters were modified by air-oxidation and heat treatment to diversify the morphologies of the acetylene blacks before electrochemical polarization. The various acetylene blacks were electrochemically oxidized at 1.6 V (vs. Ag/AgCl) for 10 s and the polarization step was repeated until the capacitance values did not change any longer. These polarization steps enhanced the capacitances of the acetylene blacks and the specific enhancement factors range from 2 to 5.5. Such an enhancement is strongly related to morphological modification as revealed by transmission electron microscopic observations. The electrochemical polarization resulted in formation of tiny graphene sheets on the wide graphitic carbon surfaces, which were most responsible for the observed capacitive enhancement. Although the pseudo-capacitance increased after polarization by forming oxygenated species on the surfaces, its contribution to the total capacitance was less than 10%. The mechanism of the formation of the tiny graphene sheets during the electrochemical oxidation is described schematically

A Multifunction Low-Power Preamplifier for MEMS Capacitive Microphones

DEFF Research Database (Denmark)

Jawed, Syed Arsalan; Nielsen, Jannik Hammel; Gottardi, Massimo

2009-01-01

A multi-function two-stage chopper-stabilized preamplifier (PAMP) for MEMS capacitive microphones (MCM) is presented. The PAMP integrates digitally controllable gain, high-pass filtering and offset control, adding flexibility to the front-end readout of MCMs. The first stage of the PAMP consists...... of a source-follower (SF) while the second-stage is a capacitive gain stage. The second-stage employs chopper-stabilization (CHS), while SF buffer shields the MCM sensor from the switching spurs. The PAMP uses M poly bias resistors for the second-stage, exploiting Miller effect to achieve flat audio...

Paper-like N-doped graphene films prepared by hydroxylamine diffusion induced assembly and their ultrahigh-rate capacitive properties

International Nuclear Information System (INIS)

Chang, Yunzhen; Han, Gaoyi; Fu, Dongying; Liu, Feifei; Li, Miaoyu; Li, Yanping; Liu, Cuixian

2014-01-01

An approach as “hydroxylamine diffusion induced assembly” has been developed to fabricate N-doped graphene paper-like films (NG-P) and composite films containing multiwalled carbon nanotubes (NG-MWCNT-P). The obtained films have been characterized by using X-ray photoelectron spectroscopy, X-ray diffraction spectroscopy and scanning electron microscopy. The results indicate that the N atoms have doped into the graphene sheets and the interplanar distance between the graphene sheets decreases with the increment of the thermally treated temperature. The films of NG-P prepared at 100 °C are flexible and exhibit a maximum tensile stress of about 70.5 MPa and a Young's modulus of about 17.7 GPa, and the films of NG-P thermally treated at 300 °C (NG-P300) have high thermal conductivity of about 3403 W m -1 K −1 . However, the NG-MWCNT-P film exhibits a relatively weaker tensile stress compared with NG-P. The electrochemical measurements show that the NG-P300 possesses excellent ultrahigh-rate capacitive properties, and that the specific capacitance and the impedance phase angle of the capacitor can reach to about 318 μF cm −2 and -77.1° respectively at frequency of 120 Hz. Simple measurements on NG-MWCNT-P show that it has specific capacitance of about 90 F g −1 based on one electrode and the capacitor possesses the high-rate capability

A new normalization method based on electrical field lines for electrical capacitance tomography

International Nuclear Information System (INIS)

Zhang, L F; Wang, H X

2009-01-01

Electrical capacitance tomography (ECT) is considered to be one of the most promising process tomography techniques. The image reconstruction for ECT is an inverse problem to find the spatially distributed permittivities in a pipe. Usually, the capacitance measurements obtained from the ECT system are normalized at the high and low permittivity for image reconstruction. The parallel normalization model is commonly used during the normalization process, which assumes the distribution of materials in parallel. Thus, the normalized capacitance is a linear function of measured capacitance. A recently used model is a series normalization model which results in the normalized capacitance as a nonlinear function of measured capacitance. The newest presented model is based on electrical field centre lines (EFCL), and is a mixture of two normalization models. The multi-threshold method of this model is presented in this paper. The sensitivity matrices based on different normalization models were obtained, and image reconstruction was carried out accordingly. Simulation results indicate that reconstructed images with higher quality can be obtained based on the presented model

Capacitive properties of PANI/MnO{sub 2} synthesized via simultaneous-oxidation route

Energy Technology Data Exchange (ETDEWEB)

Zhang Jie [School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); Shu Dong, E-mail: dshu@scnu.edu.cn [School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); Tianneng Group, Changxing 313100, Zhejiang Province (China); Base of Production, Education and Research on Energy Storage and Power Battery of Guangdong Higher Education Institutes, Guangzhou 510006 (China); Key Laboratory of Electrochemical Technology on Energy Storage and Power Generation of Guangdong Higher Education Institutes, South China Normal University, Guangzhou 510006 (China); Zhang Tianren [Tianneng Group, Changxing 313100, Zhejiang Province (China); Chen Hongyu [School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); Base of Production, Education and Research on Energy Storage and Power Battery of Guangdong Higher Education Institutes, Guangzhou 510006 (China); Key Laboratory of Electrochemical Technology on Energy Storage and Power Generation of Guangdong Higher Education Institutes, South China Normal University, Guangzhou 510006 (China); Zhao Haimin; Wang Yongsheng [Tianneng Group, Changxing 313100, Zhejiang Province (China); Sun Zhenjie; Tang Shaoqing [School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China); Fang Xueming [Tianneng Group, Changxing 313100, Zhejiang Province (China); Cao Xiufang [School of Chemistry and Environment, South China Normal University, Guangzhou 510006 (China)

2012-08-15

Highlights: Black-Right-Pointing-Pointer PANI/MnO{sub 2} composite was synthesized by the simultaneous-oxidation route. Black-Right-Pointing-Pointer Good contact in inter-molecule level between PANI and MnO{sub 2} improves the conductivity. Black-Right-Pointing-Pointer The separation between PANI and MnO{sub 2} prevents the aggregation of nano-composite. Black-Right-Pointing-Pointer The maximum specific capacitance of the PANI/MnO{sub 2} electrode is 320 F/g. Black-Right-Pointing-Pointer The as-prepared PANI/MnO{sub 2} exhibits excellent cycle stability of 84% capacitance retention after 10,000 cycles. - Abstract: Polyaniline (PANI) and manganese dioxide (MnO{sub 2}) composite (PANI/MnO{sub 2}) was synthesized via a simultaneous-oxidation route. In this route, all reactants were dispersed homogenously in precursor solution and existed as ions and molecules, and involved reactions of ions and molecules generating PANI and MnO{sub 2} simultaneously. In this way, PANI molecule and MnO{sub 2} molecule contact each other and arrange alternately in the composite. The inter-molecule contact improves the conductivity of the composite. The alternative arrangement of PANI molecules and MnO{sub 2} molecules separating each other, and prevents the aggregation of PANI and cluster of MnO{sub 2} so as to decrease the particle size of the composite. The morphology, structure, porous and capacitive properties are characterized by scanning electron microscopy, X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, Branauer-Emmett-Teller test, thermogravimetric analysis, Fourier transform infrared spectroscopy, cyclic voltammetry, charge-discharge test and the electrochemical impedance measurements. The results show that MnO{sub 2} is predominant in the PANI/MnO{sub 2} composite and the composite exhibits larger specific surface area than pure MnO{sub 2}. The maximum specific capacitance of the composite electrode reaches up to 320 F/g by charge-discharge test, 1.56 times

Calculation of secondary capacitance of compact Tesla pulse transformer

International Nuclear Information System (INIS)

Yu Binxiong; Liu Jinliang

2013-01-01

An analytic expression of the secondary capacitance of a compact Tesla pulse transformer is derived. Calculated result by the expression shows that two parts contribute to the secondary capacitance, namely the capacitance between inner and outer magnetic cores and the attached capacitance caused by the secondary winding. The attached capacitance equals to the capacitance of a coaxial line which is as long as the secondary coil, and whose outer and inner diameters are as large as the inner diameter of the outer magnetic and the outer diameter of the inner magnetic core respectively. A circuital model for analyzing compact Tesla transformer is built, and numeric calculation shows that the expression of the secondary capacitance is correct. Besides, a small compact Tesla transformer is developed, and related test is carried out. Test result confirms the calculated results by the expression derived. (authors)

Effect of different nickel precursors on capacitive behavior of electrodeposited NiO thin films

Energy Technology Data Exchange (ETDEWEB)

Kore, R. M.; Ghadge, T. S.; Ambare, R. C.; Lokhande, B. J., E-mail: bjlokhande@yahoo.com [School of Physical Sciences, Solapur University, Solapur-413 255, M.S. (India)

2016-04-13

In the present study, the effect of nickel precursors containing different anions like nitrate, chloride and sulphate on the morphology and pseudocapacitance behavior of NiO is investigated. The NiO samples were prepared by using a potentiondynamic electrodeposition technique in the three electrode cell. Cyclic voltammetry technique was exploited for potentiodynamic deposition of the films. The obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), etc. The XRD reveals the cubic crystal structure for all samples. The SEM micrograph shows nanoflakelike, up grown nanoflakes and honeycomb like nanostructured morphologies for nitrate, chloride and sulphate precursors respectively. The capacitive behavior of these samples was recorded using cyclic voltammetry (CV), charge-discharge and electrochemical impedance spectroscopy (EIS) in 1 M KOH electrolyte. The specific capacitance values of NiO samples obtained using CV for nitrate, chloride and sulphate precursors were 136, 214 and 893 Fg{sup −1} respectively, at the scan rate of 5 mVs{sup −1}. The charge discharge study shows high specific energy for the sample obtained from sulphate (23.98 Whkg{sup −1}) as compared to chloride (9.67 Whkg{sup −1}) and nitrate (4.9 Whkg{sup −1}), whereas samples of cholride (13.9 kWkg{sup −1} and nitrate (10.5 kWkg{sup −1}) shows comparatively more specific power than samples obtained from sulphate (7.6 kWkg{sup −1}). The equivalent series resistance of NiO samples observed from EIS study are 1.34, 1.29 and 1.27 Ω respectively for nitrate, chloride and sulphate precursors. These results emphasizes that the samples obtained from sulphate precursors provides very low impedance through honeycomb like nanostructured morphology which supports good capacitive behavior of NiO.

Quantum capacitance of the armchair-edge graphene nanoribbon

Indian Academy of Sciences (India)

Home; Journals; Pramana – Journal of Physics; Volume 81; Issue 2. Quantum capacitance of the ... Abstract. The quantum capacitance, an important parameter in the design of nanoscale devices, is derived for armchair-edge single-layer graphene nanoribbon with semiconducting property. The quantum capacitance ...

A binder-free NiCo2O4 nanosheet/3D elastic N-doped hollow carbon nanotube sponge electrode with high volumetric and gravimetric capacitances for asymmetric supercapacitors.

Science.gov (United States)

Tong, Hao; Yue, Shihong; Lu, Liang; Jin, Fengqiao; Han, Qiwei; Zhang, Xiaogang; Liu, Jie

2017-11-09

To increase the volumetric and gravimetric capacitances of supercapacitors, a new class of electrode materials with high electrochemical activity and favorable structures is extremely desired. In this work, a hollow novel nitrogen-doped 3D elastic single-walled carbon nanotube sponge (NSCS) which is ultra lightweight with the lowest density of 0.8 mg cm -3 , and has a high open surface structure for electrolyte accessibility and excellent compressible properties as the electrode scaffold has been successfully fabricated by the pyrolysis method which could produce the carbon nanotube sponge easily on a large scale without high-cost and time-consuming processes. Moreover, a NiCo 2 O 4 nanosheet supported on the NSCS has been successfully fabricated. The highest volumetric and gravimetric capacitance of this electrode is 790 F cm -3 at 1.43 g cm -3 and 1618 F g -1 at 0.54 g cm -3 with excellent cycling stability. The density of NiCo 2 O 4 /NSCS electrode was adjusted by mechanical compression and the most favorable density of the film for both high volumetric and gravimetric capacitances obtained was 1.21 g cm -3 . The thick NiCo 2 O 4 /NSCS film of 72 μm has been fabricated at this favorable density, presenting both high volumetric and gravimetric capacitances of 597 F cm -3 and 1074 F g -1 at 1 A g -1 , respectively, indicating that the structure of the NSCS is extremely feasible for obtaining a thick film electrode with excellent volumetric and gravimetric capacitances. Furthermore, an asymmetric supercapacitor of NiCo 2 O 4 /NSCS//NGN/CNTs was fabricated, exhibiting a high gravimetric energy density of 47.65 W h kg -1 at 536 W kg -1 and a volumetric energy density of 33.44 W h L -1 at 376.16 W L -1 .

Energy consumption in membrane capacitive deionization for different water recoveries and flow rates, and comparison with reverse osmosis

NARCIS (Netherlands)

Zhao, R.; Porada, S.; Biesheuvel, P.M.; Wal, van der A.

2013-01-01

Membrane capacitive deionization (MCDI) is a non-faradaic, capacitive technique for desalinating brackish water by adsorbing ions in charged porous electrodes. To compete with reverse osmosis, the specific energy consumption of MCDI needs to be reduced to less than 1 kWh per m3 of freshwater

Facile preparation of polypyrrole/graphene oxide nanocomposites with large areal capacitance using electrochemical codeposition for supercapacitors

Science.gov (United States)

Zhou, Haihan; Han, Gaoyi; Xiao, Yaoming; Chang, Yunzhen; Zhai, Hua-Jin

2014-10-01

A simple and low-cost electrochemical codeposition method has been introduced to fabricate polypyrrole/graphene oxide (PPy/GO) nanocomposites and the areal capacitance of conducting polymer/GO composites is reported for the first time. Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) are implemented to determine the PPy/GO nanocomposites are successfully prepared and the interaction between PPy and GO. The as-prepared PPy/GO nanocomposites show the curly sheet-like morphology, superior capacitive behaviors and cyclic stability. Furthermore, the varying deposition time is implemented to investigate the impact of the loading amount on electrochemical behavior of the composites, and a high areal capacitance of 152 mF cm-2 is achieved at 10 mV s-1 CV scan. However, the thicker films caused by the long deposition time would result in larger diffusion resistance of electrolyte ions, consequently exhibit the relatively lower capacitance value at the high current density. The GCD tests indicate moderate deposition time is more suitable for the fast charge/discharge. Considering the very simple and effective synthetic process, the PPy/GO nanocomposites with relatively high areal capacitance are competitive candidate for supercapacitor application, and its capacitive performances can be easily tuned by varying the deposition time.

Resistive and Capacitive Based Sensing Technologies

Directory of Open Access Journals (Sweden)

Winncy Y. Du

2008-04-01

Full Text Available Resistive and capacitive (RC sensors are the most commonly used sensors. Their applications span homeland security, industry, environment, space, traffic control, home automation, aviation, and medicine. More than 30% of modern sensors are direct or indirect applications of the RC sensing principles. This paper reviews resistive and capacitive sensing technologies. The physical principles of resistive sensors are governed by several important laws and phenomena such as Ohm’s Law, Wiedemann-Franz Law; Photoconductive-, Piezoresistive-, and Thermoresistive Effects. The applications of these principles are presented through a variety of examples including accelerometers, flame detectors, pressure/flow rate sensors, RTDs, hygristors, chemiresistors, and bio-impedance sensors. The capacitive sensors are described through their three configurations: parallel (flat, cylindrical (coaxial, and spherical (concentric. Each configuration is discussed with respect to its geometric structure, function, and application in various sensor designs. Capacitance sensor arrays are also presented in the paper.

Capacitance of carbon-based electrical double-layer capacitors.

Science.gov (United States)

Ji, Hengxing; Zhao, Xin; Qiao, Zhenhua; Jung, Jeil; Zhu, Yanwu; Lu, Yalin; Zhang, Li Li; MacDonald, Allan H; Ruoff, Rodney S

2014-01-01

Experimental electrical double-layer capacitances of porous carbon electrodes fall below ideal values, thus limiting the practical energy densities of carbon-based electrical double-layer capacitors. Here we investigate the origin of this behaviour by measuring the electrical double-layer capacitance in one to five-layer graphene. We find that the capacitances are suppressed near neutrality, and are anomalously enhanced for thicknesses below a few layers. We attribute the first effect to quantum capacitance effects near the point of zero charge, and the second to correlations between electrons in the graphene sheet and ions in the electrolyte. The large capacitance values imply gravimetric energy storage densities in the single-layer graphene limit that are comparable to those of batteries. We anticipate that these results shed light on developing new theoretical models in understanding the electrical double-layer capacitance of carbon electrodes, and on opening up new strategies for improving the energy density of carbon-based capacitors.

Chemical splitting of multiwalled carbon nanotubes to enhance electrochemical capacitance for supercapacitors

Science.gov (United States)

Li, Xinlu; Li, Tongtao; Zhang, Xinlin; Zhong, Qineng; Li, Hongyi; Huang, Jiamu

2014-06-01

Multiwalled carbon nanotubes (MWCNTs) were chemically split and self-assembled to a flexible porous paper made of graphene oxide nanoribbons (GONRs). The morphology and microstructure of the pristine MWCNTs and GONRs were analyzed by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Raman spectroscopy and Fourier transform infrared spectroscopy. And the specific surface area and porosity structure were measured by N2 adsorption-desorption. The longitudinally split MWCNTs show an enhancement in specific capacitance from 21 F g-1 to 156 F g-1 compared with the pristine counterpart at 0.1 A g-1 in a 6 M KOH aqueous electrolytes. The electrochemical experiments prove that the chemical splitting of MWCNTs will make inner carbon layers opened and exposed to electrochemical double layers, which can effectively improve the electrochemical capacitance for supercapacitors.

Novel RF-MEMS capacitive switching structures

NARCIS (Netherlands)

Rottenberg, X.; Jansen, Henricus V.; Fiorini, P.; De Raedt, W.; Tilmans, H.A.C.

2002-01-01

This paper reports on novel RF-MEMS capacitive switching devices implementing an electrically floating metal layer covering the dielectric to ensure intimate contact with the bridge in the down state. This results in an optimal switch down capacitance and allows optimisation of the down/up

The Pyramidal Capacitated Vehicle Routing Problem

DEFF Research Database (Denmark)

Lysgaard, Jens

This paper introduces the Pyramidal Capacitated Vehicle Routing Problem (PCVRP) as a restricted version of the Capacitated Vehicle Routing Problem (CVRP). In the PCVRP each route is required to be pyramidal in a sense generalized from the Pyramidal Traveling Salesman Problem (PTSP). A pyramidal...

The pyramidal capacitated vehicle routing problem

DEFF Research Database (Denmark)

Lysgaard, Jens

2010-01-01

This paper introduces the pyramidal capacitated vehicle routing problem (PCVRP) as a restricted version of the capacitated vehicle routing problem (CVRP). In the PCVRP each route is required to be pyramidal in a sense generalized from the pyramidal traveling salesman problem (PTSP). A pyramidal...

High-capacitance supercapacitors using nitrogen-decorated porous carbon derived from novolac resin containing peptide linkage

Energy Technology Data Exchange (ETDEWEB)

Kim, Yong Jung [Institute of Carbon Science and Technology, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553 (Japan); Jang, In Young; Park, Ki Chul; Jung, Yong Chae; Oka, Takuyuki [Department of Electric and Electronic Engineering, Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553 (Japan); Iinou, Satoshi [MEFS, Co. Ltd. Choei Nagano, Higasiguchi Bldg, 2F, 1000-1 Gentakubo, Kurita, Nagano 380-0921 (Japan); Komori, Yasuhiro; Kozutsumi, Toshihiko; Hashiba, Takashi [SHOWA HIGHPOLYMER, Co., Ltd. 1021 Tomizuka-cho, Isesaki-City, Gunma 372-0833 (Japan); Kim, Yoong Ahm, E-mail: yak@endomoribu.shinshu-u.ac.j [Department of Electric and Electronic Engineering, Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553 (Japan); Endo, Morinobu [Institute of Carbon Science and Technology, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553 (Japan)] [Department of Electric and Electronic Engineering, Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553 (Japan)

2010-08-01

We fabricated nitrogen-decorated porous carbon exhibiting high capacitance per unit volume and unit weight via chemical activation of novolac resin containing peptide linkage. The porosity and the amount of nitrogen atoms were controlled by changing the molecular weight of novolac resin, the added amount of potassium hydroxide, or both. After chemical activation, positively charged nitrogen atoms (i.e., pyridine/pyrrole) at 400.3 eV in photoemission spectra contributed to both a shift in the point of zero charge toward negative potential and the generation of pseudocapacitance. Suitably developed pores and the positively charged nitrogen atoms make nitrogen-decorated novolac resin-derived porous carbon a promising material for electrodes in high-performance supercapacitors.

CMOS based capacitance to digital converter circuit for MEMS sensor

Science.gov (United States)

Rotake, D. R.; Darji, A. D.

2018-02-01

Most of the MEMS cantilever based system required costly instruments for characterization, processing and also has large experimental setups which led to non-portable device. So there is a need of low cost, highly sensitive, high speed and portable digital system. The proposed Capacitance to Digital Converter (CDC) interfacing circuit converts capacitance to digital domain which can be easily processed. Recent demand microcantilever deflection is part per trillion ranges which change the capacitance in 1-10 femto farad (fF) range. The entire CDC circuit is designed using CMOS 250nm technology. Design of CDC circuit consists of a D-latch and two oscillators, namely Sensor controlled oscillator (SCO) and digitally controlled oscillator (DCO). The D-latch is designed using transmission gate based MUX for power optimization. A CDC design of 7-stage, 9-stage and 11-stage tested for 1-18 fF and simulated using mentor graphics Eldo tool with parasitic. Since the proposed design does not use resistance component, the total power dissipation is reduced to 2.3621 mW for CDC designed using 9-stage SCO and DCO.

Application of the SRISM approach to the study of the capacitance of the double layer of a high density primitive model electrolyte

Directory of Open Access Journals (Sweden)

S. Woelki

2011-12-01

Full Text Available In this study the Singlet Reference Interaction Site Model (SRISM is employed to the study of the electrode charge dependence of the capacitance of a planar electric double layer using the primitive model of the double layer for a high density electrolyte that mimics an ionic liquid. The ions are represented by charged hard spheres and the electrode is a uniformly charged flat surface. The capacitance of this model fluid is calculated with the SRISM approach with closures based on the hypernetted chain (HNC and Kovalenko-Hirata (KH closures and compared with simulations. As long as the magnitude of the electrode charge is not too great, the HNC closure shows the most promise. The KH results are reasonably good for a high density electrolyte but are poor when applied at low densities.

Capacitive Feedthroughs for Medical Implants.

Science.gov (United States)

Grob, Sven; Tass, Peter A; Hauptmann, Christian

2016-01-01

Important technological advances in the last decades paved the road to a great success story for electrically stimulating medical implants, including cochlear implants or implants for deep brain stimulation. However, there are still many challenges in reducing side effects and improving functionality and comfort for the patient. Two of the main challenges are the wish for smaller implants on one hand, and the demand for more stimulation channels on the other hand. But these two aims lead to a conflict of interests. This paper presents a novel design for an electrical feedthrough, the so called capacitive feedthrough, which allows both reducing the size, and increasing the number of included channels. Capacitive feedthroughs combine the functionality of a coupling capacitor and an electrical feedthrough within one and the same structure. The paper also discusses the progress and the challenges of the first produced demonstrators. The concept bears a high potential in improving current feedthrough technology, and could be applied on all kinds of electrical medical implants, even if its implementation might be challenging.

Scanning Capacitance Microscopy | Materials Science | NREL

Science.gov (United States)

obtained using scanning capacitance microscopy. Top Right: Image of p-type and n-type material, obtained 'fingers' of light-colored n-type material on a yellow and blue background representing p-type material material, obtained using scanning capacitance microscopy, in a sample semiconductor device; the image shows

Capacitance-voltage characterization of fully silicided gated MOS capacitor

International Nuclear Information System (INIS)

Wang Baomin; Ru Guoping; Jiang Yulong; Qu Xinping; Li Bingzong; Liu Ran

2009-01-01

This paper investigates the capacitance-voltage (C-V) measurement on fully silicided (FUSI) gated metal-oxide-semiconductor (MOS) capacitors and the applicability of MOS capacitor models. When the oxide leakage current of an MOS capacitor is large, two-element parallel or series model cannot be used to obtain its real C-V characteristic. A three-element model simultaneously consisting of parallel conductance and series resistance or a four-element model with further consideration of a series inductance should be used. We employed the three-element and the four-element models with the help of two-frequency technique to measure the Ni FUSI gated MOS capacitors. The results indicate that the capacitance of the MOS capacitors extracted by the three-element model still shows some frequency dispersion, while that extracted by the four-element model is close to the real capacitance, showing little frequency dispersion. The obtained capacitance can be used to calculate the dielectric thickness with quantum effect correction by NCSU C-V program. We also investigated the influence of MOS capacitor's area on the measurement accuracy. The results indicate that the decrease of capacitor area can reduce the dissipation factor and improve the measurement accuracy. As a result, the frequency dispersion of the measured capacitance is significantly reduced, and real C-V characteristic can be obtained directly by the series model. In addition, this paper investigates the quasi-static C-V measurement and the photonic high-frequency C-V measurement on Ni FUSI metal gated MOS capacitor with a thin leaky oxide. The results indicate that the large tunneling current through the gate oxide significantly perturbs the accurate measurement of the displacement current, which is essential for the quasi-static C-V measurement. On the other hand, the photonic high-frequency C-V measurement can bypass the leakage problem, and get reliable low-frequency C-V characteristic, which can be used to

Capacitance densitometer for flow regime identification

International Nuclear Information System (INIS)

Shipp, R.L. Jr.

1978-01-01

This invention relates to a capacitance densitometer for determining the flow regime of a two-phase flow system. A two-element capacitance densitometer is used in conjunction with a conventional single-beam gamma densitometer to unambiguously identify the prevailing flow regime and the average density of a flowing fluid

Fluidized bed electrodes with high carbon loading for water desalination by capacitive deionization

NARCIS (Netherlands)

Doornbusch, G.J.; Dykstra, J.E.; Biesheuvel, P.M.; Suss, M.E.

2016-01-01

The use of carbon flow electrodes has significantly impacted electrochemical energy storage and capacitive deionization (CDI), but device performance is limited as these electrodes cannot surpass ∼20 wt% carbon while maintaining flowability. We here introduce flowable fluidized bed electrodes

Label-free detection of sex determining region Y (SRY) via capacitive biosensor

KAUST Repository

Sivashankar, Shilpa

2016-10-20

In this work, we present for the first time, the use of a simple fractal capacitive biosensor for the quantification and detection of sex-determining region Y (SRY) genes. This section of genetic code, which is found on the Y chromosome, finds importance for study as it causes fetuses to develop characteristics of male sex-like gonads when a mutation occurs. It is also an important genetic code in men, and disorders involving the SRY gene can cause infertility and sexual malfunction that lead to a variety of gene mutational disorders. We have therefore designed silicon-based, label-free fractal capacitive biosensors to quantify various proteins and genes. We take advantage of a good dielectric material, Parylene C for enhancing the performance of the sensors. We have integrated these sensors with a simple microchannel for easy handling of fluids on the detection area. The read-out value of an Agilent LCR meter used to measure capacitance of the sensor at a frequency of 1 MHz determined gene specificity and gene quantification. These data revealed that the capacitance measurement of the capacitive biosensor for the SRY gene depended on both the target and the concentration of DNA. The experimental outcomes in the present study can be used to detect DNA and its variations in crucial fields that have a great impact on our daily lives, such as clinical and veterinary diagnostics, industrial and environmental testing and forensic sciences.

Ferroelectric Negative Capacitance Domain Dynamics

OpenAIRE

Hoffmann, Michael; Khan, Asif Islam; Serrao, Claudy; Lu, Zhongyuan; Salahuddin, Sayeef; Pešić, Milan; Slesazeck, Stefan; Schroeder, Uwe; Mikolajick, Thomas

2017-01-01

Transient negative capacitance effects in epitaxial ferroelectric Pb(Zr$_{0.2}$Ti$_{0.8}$)O$_3$ capacitors are investigated with a focus on the dynamical switching behavior governed by domain nucleation and growth. Voltage pulses are applied to a series connection of the ferroelectric capacitor and a resistor to directly measure the ferroelectric negative capacitance during switching. A time-dependent Ginzburg-Landau approach is used to investigate the underlying domain dynamics. The transien...

Distribution of coronary arterial capacitance in a canine model.

Science.gov (United States)

Lader, A S; Smith, R S; Phillips, G C; McNamee, J E; Abel, F L

1998-03-01

The capacitative properties of the major left coronary arteries, left main (LM), left anterior descending (LAD), and left circumflex (LCX), were studied in 19 open-chest isolated dog hearts. Capacitance was determined by using ramp perfusion and a left ventricular-to-coronary shunt diastolic decay method; both methods gave similar results, indicating a minimal systolic capacitative component. Increased pericardial pressure (PCP), 25 mmHg, was used to experimentally alter transmural wall pressure. The response to increased PCP was different in the LAD vs. LCX; increasing PCP decreased capacitance in the LCX but increased capacitance in the LAD. This may have been due to the different intramural vs. epicardial volume distribution of these vessels and a decrease in intramural tension during increased PCP. Increased PCP decreased LCX capacitance by approximately 13%, but no changes in conductance or zero flow pressure intercept occurred in any of the three vessels, i. e., evidence against the waterfall theory of vascular collapse at these levels of PCP. Coronary arterial capacitance was also linearly related to perfusion pressure.

The capacitance of Pt/Pb0.65La0.28Ti0.96O3/Pt structures

International Nuclear Information System (INIS)

Shaw, T.M.; Laibowitz, R.B.; Beach, D.; Duncombe, P.R.

1996-01-01

The capacitance/voltage characteristics of thin paraelectric lead lanthanum titanate films are measured using platinum electrodes. The films have a maximum capacitance when either a small positive or negative bias voltage is applied. This characteristic is consistent with the electrode interfaces acting as Schottky-like barriers. The voltage at which the capacitance maxima occur increases linearly with film thickness indicating that the film is highly resistive. On the basis of the high apparent film resistance it is proposed that the voltage dependence of the capacitance of the electrode interfaces arises from the ionization of deep level traps within the film and not from depletion layers associated with shallow donor or acceptor states. Application of voltages larger than about 2 endash 3 V results in the disappearance of the capacitance maxima indicating that irreversible changes in the electrode interfaces occur at higher electric fields. copyright 1995 American Institute of Physics

Few-layered Ni(OH)2 nanosheets for high-performance supercapacitors

Science.gov (United States)

Sun, Wenping; Rui, Xianhong; Ulaganathan, Mani; Madhavi, Srinivasan; Yan, Qingyu

2015-11-01

Few-layered Ni(OH)2 nanosheets (4-5 nm in thickness) are synthesized towards high-performance supercapacitors. The ultrathin Ni(OH)2 nanosheets show high specific capacitance and good rate capability in both three-electrode and asymmetric devices. In the three-electrode device, the Ni(OH)2 nanosheets deliver a high capacitance of 2064 F g-1 at 2 A g-1, and the capacitance still has a retention of 1837 F g-1 at a high current density of 20 A g-1. Such excellent performance is by far one of the best for Ni(OH)2 electrodes. In the two-electrode asymmetric device, the specific capacitance is 248 F g-1 at 1 A g-1, and reaches 113 F g-1 at 20 A g-1. The capacitance of the asymmetric device maintains to be 166 F g-1 during the 4000th cycle at 2 A g-1, suggesting good cycling stability of the device. Besides, the asymmetric device exhibits gravimetric energy density of 22 Wh kg-1 at a power density of 0.8 kW kg-1. The present results demonstrate that the ultrathin Ni(OH)2 nanosheets are highly attractive electrode materials for achieving fast charging/discharging and high-capacity supercapacitors.

Improved electronic interfaces for AT-cut quartz crystal microbalance sensors under variable damping and parallel capacitance conditions.

Science.gov (United States)

Arnau, A; García, J V; Jimenez, Y; Ferrari, V; Ferrari, M

2008-07-01

A new configuration of automatic capacitance compensation (ACC) technique based on an oscillatorlike working interface, which permits the tracking of the series resonant frequency and the monitoring of the motional resistance and the parallel capacitance of a thickness-shear mode quartz crystal microbalance sensor, is introduced. The new configuration permits an easier calibration of the system which, in principle, improves the accuracy. Experimental results are reported with 9 and 10 MHz crystals in liquids with different parallel capacitances which demonstrate the effectiveness of the capacitance compensation. Some frequency deviations from the exact series resonant frequency, measured by an impedance analyzer, are explained by the specific nonideal behavior of the circuit components. A tentative approach is proposed to solve this problem that is also common to previous ACC systems.

Improved electronic interfaces for AT-cut quartz crystal microbalance sensors under variable damping and parallel capacitance conditions

International Nuclear Information System (INIS)

Arnau, A.; Garcia, J. V.; Jimenez, Y.; Ferrari, V.; Ferrari, M.

2008-01-01

A new configuration of automatic capacitance compensation (ACC) technique based on an oscillatorlike working interface, which permits the tracking of the series resonant frequency and the monitoring of the motional resistance and the parallel capacitance of a thickness-shear mode quartz crystal microbalance sensor, is introduced. The new configuration permits an easier calibration of the system which, in principle, improves the accuracy. Experimental results are reported with 9 and 10 MHz crystals in liquids with different parallel capacitances which demonstrate the effectiveness of the capacitance compensation. Some frequency deviations from the exact series resonant frequency, measured by an impedance analyzer, are explained by the specific nonideal behavior of the circuit components. A tentative approach is proposed to solve this problem that is also common to previous ACC systems

Some applications of capacitance technology in nuclear reactor components inspections

International Nuclear Information System (INIS)

Walton, H.

1985-01-01

The paper considers application of a capacitance measuring system that has overcome many of the original contraints, such as sensitivity to cable length, induced electric field and high acoustic noise, and illustrates the ease of use with examples of proven capability in severe environments of high temperature or high radiation. The Capacitance Displacement Transducer (CDT) measuring principle was originally developed as a working technique during the early years of full-scale, on-load refuelling trials performed in the Windscale Civil Advanced Gas-Cooled Reactor (CAGR) test rig where it was necessary to measure the vibrational behaviour of fuel components in simulated reactor conditions. At that time, 1968-1969, no instrumentation existed that would measure displacement in the range 0 to 100 mms to an accuracy of 25x10 -3 mms, without physical contact, at temperatures of 600 0 C in high velocity gas, in high acoustic noise fields of 150 db's over cable lengths approaching 100 metres. The principles incorporated in the CDT overcome all these problems. The advantages inherent in this system have been extended to metrology applications in more recent years by the further development of the electronics to enable linear displacement measurement to be obtained between two capacitance plates whose separation varies, either by plate movement or by surface irregularity. This principle has been used to good effect in novel applications associated with the inspection of nominally inaccessible internal tube surfaces

3D simulations and modeling of new low capacitance silicon pixel detectors

Energy Technology Data Exchange (ETDEWEB)

Xiong, Bo; Li, Yu Yun [School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105 (China); Center for Semiconductor Particle and photon Imaging Detector Development and Fabrication, Xiangtan University, Xiangtan 411105 (China); Li, Zheng, E-mail: zhengli58@gmail.com [School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105 (China); Center for Semiconductor Particle and photon Imaging Detector Development and Fabrication, Xiangtan University, Xiangtan 411105 (China)

2016-09-21

With signal to noise ratio (S/N) being a key parameter of a high performance detector, reducing the detector noise has been one of the main tasks in detector development. A new low capacitance silicon pixel detector is proposed, which is based on a new electrode geometry with reduced effective electrode area while keeping the sensitive volume unchanged. Detector electrical characteristics including electrostatic potential, electric field, full depletion voltage, and capacitance have been simulated in detail using a 3D TCAD tool. From these simulations and calculations, we confirm that the new detector structure has a much reduced capacitance (by a factor of 3) as compared to the traditional pixel detectors with the same sensitive volume. This reduction in detector capacitance can certainly improve the detector signal to noise ratio. However, the full depletion voltage for the new structure is larger than that of the traditional one due to the small electrode effect.

Nano-aggregates of cobalt nickel oxysulfide as a high-performance electrode material for supercapacitors

Science.gov (United States)

Liu, Lifeng

2013-11-01

Nano-aggregates of cobalt nickel oxysulfide (CoNi)OxSy have been synthesized by hydrothermal processing and exhibited specific and areal capacitance as high as 592 F g-1 and 1628 mF cm-2, respectively, at a current density of 0.5 A g-1/1.375 mA cm-2. They also show high capacitance retention upon extended cycling at high rates.Nano-aggregates of cobalt nickel oxysulfide (CoNi)OxSy have been synthesized by hydrothermal processing and exhibited specific and areal capacitance as high as 592 F g-1 and 1628 mF cm-2, respectively, at a current density of 0.5 A g-1/1.375 mA cm-2. They also show high capacitance retention upon extended cycling at high rates. Electronic supplementary information (ESI) available: Experimental details; supplementary tables. See DOI: 10.1039/c3nr03533f

Switchless charge-discharge circuit for electrical capacitance tomography

International Nuclear Information System (INIS)

Kryszyn, J; Smolik, W T; Radzik, B; Olszewski, T; Szabatin, R

2014-01-01

The main factor limiting the performance of electrical capacitance tomography (ECT) is an extremely low value of inter-electrode capacitances. The charge-discharge circuit is a well suited circuit for a small capacitance measurement due to its immunity to noise and stray capacitance, although it has a problem associated with a charge injected by the analogue switches, which results in a dc offset. This paper presents a new diode-based circuit for capacitance measurement in which a charge transfer method is realized without switches. The circuit was built and tested in one channel configuration with 16 multiplexed electrodes. The performance of the elaborated circuit and a comparison with a classic charge-discharge circuit are presented. The elaborated circuit can be used for sensors with inter-electrode capacitances not lower than 10 fF. The presented approach allows us to obtain a similar performance to the classic charge-discharge circuit, but has a simplified design. A lack of the need to synchronize the analogue switches in the transmitter and the receiver part of this circuit could be a desirable feature in the design of measurement systems integrated with electrodes. (paper)

Two-Dimensional Micro-/Nanoradian Angle Generator with High Resolution and Repeatability Based on Piezo-Driven Double-Axis Flexure Hinge and Three Capacitive Sensors.

Science.gov (United States)

Tan, Xinran; Zhu, Fan; Wang, Chao; Yu, Yang; Shi, Jian; Qi, Xue; Yuan, Feng; Tan, Jiubin

2017-11-19

This study presents a two-dimensional micro-/nanoradian angle generator (2D-MNAG) that achieves high angular displacement resolution and repeatability using a piezo-driven flexure hinge for two-dimensional deflections and three capacitive sensors for output angle monitoring and feedback control. The principal error of the capacitive sensor for precision microangle measurement is analyzed and compensated for; so as to achieve a high angle output resolution of 10 nrad (0.002 arcsec) and positioning repeatability of 120 nrad (0.024 arcsec) over a large angular range of ±4363 μrad (±900 arcsec) for the 2D-MNAG. The impact of each error component, together with the synthetic error of the 2D-MNAG after principal error compensation are determined using Monte Carlo simulation for further improvement of the 2D-MNAG.

Development and analysis of a capacitive touch sensor using a liquid metal droplet

International Nuclear Information System (INIS)

Baek, Seungbum; Won, Dong-Joon; Kim, Joong Gil; Kim, Joonwon

2015-01-01

In this paper, we introduce a small-sized capacitive touch sensor with large variations in its capacitance. This sensor uses the changes in capacitance caused by the variation of the overlap area between a liquid metal (LM) droplet and a flat electrode while keeping the gap between the droplet and the bottom electrode at a small constant value (i.e. thickness of dielectric layer). Initially, the droplet is placed inside a polydimethylsiloxane (PDMS) chamber, and a thin silicon dioxide film separates the droplet and the electrode. Owing to the high surface tension of the LM, the droplet retains its spherical shape and the overlap area remains small, which means that the capacitance between the droplet and the electrode also remains small. When normal force is applied, the pressure on the membrane pushes the droplet downward, thus spreading the droplet to the bottom of the chamber and increasing the capacitance. To verify our concept, we performed theoretical analyses and experiments using a 2 mm  ×  2 mm  ×  2 mm 1-cell touch sensor. Finally, we obtained a capacitance variation of ∼30 pF by applying forces between 0 N and 1 N. (paper)

DNA Nucleotides Detection via capacitance properties of Graphene

Science.gov (United States)

Khadempar, Nahid; Berahman, Masoud; Yazdanpanah, Arash

2016-05-01

In the present paper a new method is suggested to detect the DNA nucleotides on a first-principles calculation of the electronic features of DNA bases which chemisorbed to a graphene sheet placed between two gold electrodes in a contact-channel-contact system. The capacitance properties of graphene in the channel are surveyed using non-equilibrium Green's function coupled with the Density Functional Theory. Thus, the capacitance properties of graphene are theoretically investigated in a biological environment, and, using a novel method, the effect of the chemisorbed DNA nucleotides on electrical charges on the surface of graphene is deciphered. Several parameters in this method are also extracted including Electrostatic energy, Induced density, induced electrostatic potential, Electron difference potential and Electron difference density. The qualitative and quantitative differences among these parameters can be used to identify DNA nucleotides. Some of the advantages of this approach include its ease and high accuracy. What distinguishes the current research is that it is the first experiment to investigate the capacitance properties of gaphene changes in the biological environment and the effect of chemisorbed DNA nucleotides on the surface of graphene on the charge.

Capacitance and voltage matching between MnO2 nanoflake cathode and Fe2O3 nanoparticle anode for high-performance asymmetric micro-supercapacitors

Institute of Scientific and Technical Information of China (English)

Zehua Liu; Xiaocong Tian; Xu Xu; Liang He; Mengyu Yan; Chunhua Han; Yan Li; Wei Yang; Liqiang Mai

2017-01-01

Planar micro-supercapacitors show great potential as the energy storage unit in miniaturized electronic devices.Asymmetric structures have been widely investigated in micro-supercapacitors,and carbon-based materials are commonly applied in the electrodes.To integrate different metal oxides in both electrodes in micro-supercapacitors,the critical challenge is the pairing of different faradic metal oxides.Herein,we propose a strategy of matching the voltage and capacitance of two faradic materials that are fully integrated into one high-performance asymmetric micro-supercapadtor by a fadle and controllable fabrication process.The fabricated micro-supercapacitors employ MnO2 as the positive active material and Fe2O3 as the negative active material,respectively.The planar asymmetric micro-supercapacitors possess a high capacitance of 60 F·cm-3,a high energy density of 12 mW·h·cm-3,and a broad operation voltage range up to 1.2 V.

Electrosorption capacitance of nanostructured carbon-based materials.

Science.gov (United States)

Hou, Chia-Hung; Liang, Chengdu; Yiacoumi, Sotira; Dai, Sheng; Tsouris, Costas

2006-10-01

The fundamental mechanism of electrosorption of ions developing a double layer inside nanopores was studied via a combination of experimental and theoretical studies. A novel graphitized-carbon monolithic material has proven to be a good electrical double-layer capacitor that can be applied in the separation of ions from aqueous solutions. An extended electrical double-layer model indicated that the pore size distribution plays a key role in determining the double-layer capacitance in an electrosorption process. Because of the occurrence of double-layer overlapping in narrow pores, mesopores and micropores make significantly different contributions to the double-layer capacitance. Mesopores show good electrochemical accessibility. Micropores present a slow mass transfer of ions and a considerable loss of double-layer capacitance, associated with a shallow potential distribution inside pores. The formation of the diffuse layer inside the micropores determines the magnitude of the double-layer capacitance at low electrolyte concentrations and at conditions close to the point of zero charge of the material. The effect of the double-layer overlapping on the electrosorption capacitance can be reduced by increasing the pore size, electrolyte concentration, and applied potential. The results are relevant to water deionization.

A 45.8fJ/Step, energy-efficient, differential SAR capacitance-to-digital converter for capacitive pressure sensing

KAUST Repository

Alhoshany, Abdulaziz

2016-05-03

An energy-efficient readout circuit for a capacitive sensor is presented. The capacitive sensor is digitized by a 12-bit energy efficient capacitance-to-digital converter (CDC) that is based on a differential successive-approximation architecture. This CDC meets extremely low power requirements by using an operational transconductance amplifier (OTA) that is based on a current-starved inverter. It uses a charge-redistribution DAC that involves coarse-fine architecture. We split the DAC into a coarse-DAC and a fine-DAC to allow a wide capacitance range in a compact area. It covers a wide range of capacitance of 16.14 pF with a 4.5 fF absolute resolution. An analog comparator is implemented by cross-coupling two 3-input NAND gates to enable power and area efficient operation. The prototype CDC was fabricated using a standard 180 nm CMOS technology. The 12-bit CDC has a measurement time of 42.5 μs, and consumes 3.54 μW and 0.29 μW from analog and digital supplies, respectively. This corresponds to a state-of-the-art figure-of-merit (FoM) of 45.8 fJ/conversion-step. © 2016 Elsevier B.V. All rights reserved.

A 45.8fJ/Step, energy-efficient, differential SAR capacitance-to-digital converter for capacitive pressure sensing

KAUST Repository

Alhoshany, Abdulaziz; Omran, Hesham; Salama, Khaled N.

2016-01-01

An energy-efficient readout circuit for a capacitive sensor is presented. The capacitive sensor is digitized by a 12-bit energy efficient capacitance-to-digital converter (CDC) that is based on a differential successive-approximation architecture. This CDC meets extremely low power requirements by using an operational transconductance amplifier (OTA) that is based on a current-starved inverter. It uses a charge-redistribution DAC that involves coarse-fine architecture. We split the DAC into a coarse-DAC and a fine-DAC to allow a wide capacitance range in a compact area. It covers a wide range of capacitance of 16.14 pF with a 4.5 fF absolute resolution. An analog comparator is implemented by cross-coupling two 3-input NAND gates to enable power and area efficient operation. The prototype CDC was fabricated using a standard 180 nm CMOS technology. The 12-bit CDC has a measurement time of 42.5 μs, and consumes 3.54 μW and 0.29 μW from analog and digital supplies, respectively. This corresponds to a state-of-the-art figure-of-merit (FoM) of 45.8 fJ/conversion-step. © 2016 Elsevier B.V. All rights reserved.

Holey nickel-cobalt layered double hydroxide thin sheets with ultrahigh areal capacitance

Science.gov (United States)

Zhi, Lei; Zhang, Wenliang; Dang, Liqin; Sun, Jie; Shi, Feng; Xu, Hua; Liu, Zonghuai; Lei, Zhibin

2018-05-01

Strong coupling of electroactive components on conductive carbonaceous matrix to fabricate flexible hybrid electrodes represents a promising approach towards high performance supercapacitors. This work reports the fabrication of holey nickel cobalt layered double hydroxide (NiCo-LDH) nanosheets that are vertically grown on the cotton cloth-derived activated textile carbon (aTC). The abundant nanoholes on the thin-sheet NiCo-LDH not only enhance the electrode efficiency for efficient Faradaic redox reactions but also facilitate access of electrolyte to the electrode surface, thus giving rise to 70% capacitance arising from their outer surface. As a result, the aTC-NiCo hybrid electrode is capable of simultaneously achieving extremely high areal capacitance (6.37 F cm-2), mass capacitance (525 F g-1) and volumetric capacitance (249 F cm-3) at a practical level of mass loading (6.72 mg cm-2). Moreover, a solid-state asymmetric capacitor built with aTC-NiCo as positive electrode and active carbon-coated on aTC as negative electrode can deliver a volumetric energy density of 7.4 mWh cm-3 at a power density of 103 mW cm-3, while preserving a superior power performance, satisfying cycling stability and good mechanical flexibility.

Enhancement of Capacitive Performance in Titania Nanotubes Modified by an Electrochemical Reduction Method

Directory of Open Access Journals (Sweden)

Nurul Asma Samsudin

2018-01-01

Full Text Available Highly ordered titania nanotubes (TNTs were synthesised by an electrochemical anodization method for supercapacitor applications. However, the capacitive performance of the TNTs was relatively low and comparable to the conventional capacitor. Therefore, in order to improve the capacitive performance of the TNTs, a fast and facile electrochemical reduction method was applied to modify the TNTs (R-TNTs by introducing oxygen vacancies into the lattice. X-ray photoelectron spectroscopy (XPS data confirmed the presence of oxygen vacancies in the R-TNTs lattice upon the reduction of Ti4+ to Ti3+. Electrochemical reduction parameters such as applied voltage and reduction time were varied to optimize the best conditions for the modification process. The electrochemical performance of the samples was analyzed in a three-electrode configuration cell. The cyclic voltammogram recorded at 200 mV s−1 showed a perfect square-shaped voltammogram indicating the excellent electrochemical performance of R-TNTs prepared at 5 V for 30 s. The total area of the R-TNTs voltammogram was 3 times larger than the unmodified TNTs. A specific capacitance of 11.12 mF cm−2 at a current density of 20 μA cm−2 was obtained from constant current charge-discharge measurements, which was approximately 57 times higher than that of unmodified TNTs. R-TNTs also displayed outstanding cycle stability with 99% capacity retention after 1000 cycles.

CAPACITANCE OF SUPERCAPACITORS WITH ELECTRODES BASED ON CARBON NANOCOMPOSITE MATERIAL

OpenAIRE

S.L Revo; B.I Rachiy; S Hamamda; T.G Avramenko; K.O Ivanenko

2012-01-01

This work presents the results of our research of the structure and practically important characteristics of a nanocomposite material on the basis of nanoporous carbon and thermally exfoliated graphite. This work shows that the use of the abovementioned composition in electrodes for supercapacitors allows to attain the level of their specific electrical capacitance at (155...160) F/g.

Reduction of parasitic capacitance in 10 kV SiC MOSFET power modules using 3D FEM

DEFF Research Database (Denmark)

Jørgensen, Asger Bjørn; Christensen, Nicklas; Dalal, Dipen Narendrabhai

2017-01-01

The benefits of emerging wide-band gap semiconductors can only be utilized if the semiconductor is properly packaged. Capacitive coupling in the package causes electromagnetic interference during high dv/dt switching. This paper investigates the current flowing in the parasitic capacitance between...... the output node and the grounded heat sink for a custom silicon carbide power module. A circuit model of the capacitive coupling path is presented, using parasitic capacitances extracted from ANSYS Q3D. Simulated values are compared with experimental results. A new iteration of the silicon carbide power...

Developments of capacitance stabilised etalon technology

Science.gov (United States)

Bond, R. A.; Foster, M.; Thwaite, C.; Thompson, C. K.; Rees, D.; Bakalski, I. V.; Pereira do Carmo, J.

2017-11-01

This paper describes a high-resolution optical filter (HRF) suitable for narrow bandwidth filtering in LIDAR applications. The filter is composed of a broadband interference filter and a narrowband Fabry-Perot etalon based on the capacitance stabilised concept. The key requirements for the HRF were a bandwidth of less than 40 pm, a tuneable range of over 6 nm and a transmission greater than 50%. These requirements combined with the need for very high out-of-band rejection (greater than 50 dB in the range 300 nm to 1200 nm) drive the design of the filter towards a combination of high transmission broadband filter and high performance tuneable, narrowband filter.

Highly sensitive and selective SO2 MOF sensor: the integration of MFM-300 MOF as a sensitive layer on a capacitive interdigitated electrode

KAUST Repository

Chernikova, Valeriya; Yassine, Omar; Shekhah, Osama; Eddaoudi, Mohamed; Salama, Khaled N.

2018-01-01

We report on the fabrication of an advanced chemical capacitive sensor for the detection of sulfur dioxide (SO2) at room temperature. The sensing layer based on an indium metal–organic framework (MOF), namely MFM-300, is coated solvothermally on a functionalized capacitive interdigitated electrode. The fabricated sensor exhibits significant detection sensitivity to SO2 at concentrations down to 75 ppb, with the lower detection limit estimated to be around 5 ppb. The MFM-300 MOF sensor demonstrates highly desirable detection selectivity towards SO2 vs. CH4, CO2, NO2 and H2, as well as an outstanding SO2 sensing stability.

Highly sensitive and selective SO2 MOF sensor: the integration of MFM-300 MOF as a sensitive layer on a capacitive interdigitated electrode

KAUST Repository

Chernikova, Valeriya

2018-03-05

We report on the fabrication of an advanced chemical capacitive sensor for the detection of sulfur dioxide (SO2) at room temperature. The sensing layer based on an indium metal–organic framework (MOF), namely MFM-300, is coated solvothermally on a functionalized capacitive interdigitated electrode. The fabricated sensor exhibits significant detection sensitivity to SO2 at concentrations down to 75 ppb, with the lower detection limit estimated to be around 5 ppb. The MFM-300 MOF sensor demonstrates highly desirable detection selectivity towards SO2 vs. CH4, CO2, NO2 and H2, as well as an outstanding SO2 sensing stability.

Self-sacrifice Template Formation of Hollow Hetero-Ni7S6/Co3S4 Nanoboxes with Intriguing Pseudo-capacitance for High-performance Electrochemical Capacitors

Science.gov (United States)

Hua, Hui; Liu, Sijia; Chen, Zhiyi; Bao, Ruiqi; Shi, Yaoyao; Hou, Linrui; Pang, Gang; Hui, Kwun Nam; Zhang, Xiaogang; Yuan, Changzhou

2016-02-01

Herein, we report a simple yet efficient self-sacrifice template protocol to smartly fabricate hollow hetero-Ni7S6/Co3S4 nanoboxes (Ni-Co-S NBs). Uniform nickel cobalt carbonate nanocubes are first synthesized as the precursor via solvothermal strategy, and subsequently chemically sulfidized into hollow heter-Ni-Co-S NBs through anion-exchange process. When evaluated as electrode for electrochemical capacitors (ECs), the resultant hetero-Ni-Co-S NBs visually exhibit attractive pesudo-capacitance in KOH just after continuously cyclic voltammetry (CV) scanning for 100 cycles. New insights into the underlying energy-storage mechanism of the hollow hetero-Ni-Co-S electrode, based on physicochemical characterizations and electrochemical evaluation, are first put forward that the electrochemically induced phase transformation gradually occurrs during CV sweep from the hetero-Ni-Co-S to bi-component-active NiOOH and CoOOH, which are the intrinsic charge-storage phases for the appealing Faradaic capacitance (~677 F g-1 at 4 A g-1) of hollow Ni-Co-S NBs at high rates after cycling. When further coupled with negative activated carbon (AC), the AC//hetero-Ni-Co-S asymmetric device with extended electrochemical window of 1.5 V demonstrates high specific energy density of ~31 Wh kg-1. Of significance, we strongly envision that hollow design concept and new findings here hold great promise for enriching synthetic methodologies, and electrochemistry of complex metal sulfides for next-generation ECs.

Design of double capacitances infrasonic receiver

International Nuclear Information System (INIS)

Wang Changhai; Han Kuixia; Wang Fei

2003-01-01

The article introduces the theory of infrasonic generation and reception of nuclear explosion. An idea of the design of double capacitances infrasonic receiver using CPLD technology is given in it. Compare with the single capacitance infrasonic receiver, sensitivity of the improved receiver can be improved scores of times, dynamic range can be improved largely, and the whole performance gets improvement a lots

Design of a High Voltage Bidirectional DC-DC Converter for Driving Capacitive Incremental Actuators usable in Electric Vehicles (EVs)

DEFF Research Database (Denmark)

Thummala, Prasanth; Zhang, Zhe; Andersen, Michael A. E.

2014-01-01

the converter for efficiently charging and discharging the capacitive actuator from 0 V to 2.5 kV and vice versa, respectively. The converter is used to drive a dielectric electro active polymer (DEAP) based capacitive incremental actuator, which has the potential to be used in automotive (e.g., EVs), space...

Capacitive VAr requirements for wind driven self-excited induction generators

International Nuclear Information System (INIS)

Singaravelu, S.; Velusami, S.

2007-01-01

This paper presents the capacitive VAr requirements of a three phase pole changing self-excited induction generator and a single phase self-excited induction generator, used as isolated power sources by a constant speed or a variable speed prime mover, to obtain the desired voltage regulation at various values of load and speed. Different performance criteria such as constant terminal voltage or constant air gap flux have been considered. The developed mathematical model using nodal analysis based on graph theory is quite general in nature and can be used for any combination of the unknown variables such as magnetizing reactance (X M ) and frequency (F) or capacitive reactance (X C ) and frequency (F) or capacitive reactance (X C ) and speed (υ). The proposed model completely avoids the tedious and erroneous manual work of segregating the real and imaginary components of the complex impedance of the machine for deriving the specific model for each operating modes. Moreover, any element, like the core loss component, can be included or excluded from the model if required. Next, to obtain the capacitive VAr requirements of a three phase pole changing self-excited induction generator and a single phase self-excited induction generator, a fuzzy logic approach is used for the first time to find the unknown variables using the above model. The results are presented in a normalized form so that they are valid for a wide range of machines and would be useful for the design of voltage regulators for such generators

Multi-Channel Capacitive Sensor Arrays

Directory of Open Access Journals (Sweden)

Bingnan Wang

2016-01-01

Full Text Available In this paper, multi-channel capacitive sensor arrays based on microstrip band-stop filters are studied. The sensor arrays can be used to detect the proximity of objects at different positions and directions. Each capacitive sensing structure in the array is connected to an inductive element to form resonance at different frequencies. The resonances are designed to be isolated in the frequency spectrum, such that the change in one channel does not affect resonances at other channels. The inductive element associated with each capacitive sensor can be surface-mounted inductors, integrated microstrip inductors or metamaterial-inspired structures. We show that by using metamaterial split-ring structures coupled to a microstrip line, the quality factor of each resonance can be greatly improved compared to conventional surface-mounted or microstrip meander inductors. With such a microstrip-coupled split-ring design, more sensing elements can be integrated in the same frequency spectrum, and the sensitivity can be greatly improved.

Bioenergetics of mammalian sperm capacitation.

Science.gov (United States)

Ferramosca, Alessandra; Zara, Vincenzo

2014-01-01

After ejaculation, the mammalian male gamete must undergo the capacitation process, which is a prerequisite for egg fertilization. The bioenergetics of sperm capacitation is poorly understood despite its fundamental role in sustaining the biochemical and molecular events occurring during gamete activation. Glycolysis and mitochondrial oxidative phosphorylation (OXPHOS) are the two major metabolic pathways producing ATP which is the primary source of energy for spermatozoa. Since recent data suggest that spermatozoa have the ability to use different metabolic substrates, the main aim of this work is to present a broad overview of the current knowledge on the energy-producing metabolic pathways operating inside sperm mitochondria during capacitation in different mammalian species. Metabolism of glucose and of other energetic substrates, such as pyruvate, lactate, and citrate, is critically analyzed. Such knowledge, besides its obvious importance for basic science, could eventually translate into the development of novel strategies for treatment of male infertility, artificial reproduction, and sperm selection methods.

A robust parasitic-insensitive successive approximation capacitance-to-digital converter

KAUST Repository

Omran, Hesham

2014-09-01

In this paper, we present a capacitive sensor digital interface circuit using true capacitance-domain successive approximation that is independent of supply voltage. Robust operation is achieved by using a charge amplifier stage and multiple comparison technique. The interface circuit is insensitive to parasitic capacitances, offset voltages, and charge injection, and is not prone to noise coupling. The proposed design achieves very low temperature sensitivity of 25ppm/oC. A coarse-fine programmable capacitance array allows digitizing a wide capacitance range of 16pF with 12.5-bit quantization limited resolution in a compact area of 0.07mm2. The fabricated prototype is experimentally verified using on-chip sensor and off-chip MEMS capacitive pressure sensor. © 2014 IEEE.

A robust parasitic-insensitive successive approximation capacitance-to-digital converter

KAUST Repository

Omran, Hesham; Arsalan, Muhammad; Salama, Khaled N.

2014-01-01

In this paper, we present a capacitive sensor digital interface circuit using true capacitance-domain successive approximation that is independent of supply voltage. Robust operation is achieved by using a charge amplifier stage and multiple comparison technique. The interface circuit is insensitive to parasitic capacitances, offset voltages, and charge injection, and is not prone to noise coupling. The proposed design achieves very low temperature sensitivity of 25ppm/oC. A coarse-fine programmable capacitance array allows digitizing a wide capacitance range of 16pF with 12.5-bit quantization limited resolution in a compact area of 0.07mm2. The fabricated prototype is experimentally verified using on-chip sensor and off-chip MEMS capacitive pressure sensor. © 2014 IEEE.

Design and test of a capacitance detection circuit based on a transimpedance amplifier

International Nuclear Information System (INIS)

Mu Linfeng; Zhang Wendong; He Changde; Zhang Rui; Song Jinlong; Xue Chenyang

2015-01-01

This paper presents a transimpedance amplifier (TIA) capacitance detection circuit aimed at detecting micro-capacitance, which is caused by ultrasonic stimulation applied to the capacitive micro-machined ultrasonic transducer (CMUT). In the capacitance interface, a TIA is adopted to amplify the received signal with a center frequency of 400 kHz, and finally detect ultrasound pressure. The circuit has a strong anti-stray property and this paper also studies the calculation of compensation capacity in detail. To ensure high resolution, noise analysis is conducted. After optimization, the detected minimum ultrasound pressure is 2.1 Pa, which is two orders of magnitude higher than the former. The test results showed that the circuit was sensitive to changes in ultrasound pressure and the distance between the CMUT and stumbling block, which also successfully demonstrates the functionality of the developed TIA of the analog-front-end receiver. (paper)

Nitrogen-doped two-dimensional porous carbon sheets derived from clover biomass for high performance supercapacitors

Science.gov (United States)

Wang, Cunjing; Wu, Dapeng; Wang, Hongju; Gao, Zhiyong; Xu, Fang; Jiang, Kai

2017-09-01

Highly porous carbon sheets were prepared from fresh clover stems under air atmosphere via a facile potassium chloride salt-sealing technique, which not only avoids using the high cost inert gas protection but also spontaneously introduce multi-level porosity into the carbon structure taking advantage of the trace of oxygen in the molten salt system. The as-obtained porous carbon sheets possess high specific surface area of 2244 m2 g-1 and interconnected hierarchical pore structures from micro-to macro-scale, which provide abundant storage active sites and fast ion diffusion channels. In addition, the spontaneously formed N (2.55 at%) and O (6.94 at%) doping sites not only improve the electron conductivity of the electrode but also enhance the specific capacitance by introducing pseudocapacitance. When employed as supercapacitor electrodes, a high specific capacitance of 436 F g-1 at 1 A g-1 and an excellent rate capacity with capacitance remaining 290 F g-1 at 50 A g-1 are demonstrated. Furthermore, the assembled symmetric supercapacitor delivers a high specific capacitance of 420 F g-1 at 0.5 A g-1, excellent energy density of 58.4 Wh kg-1 and good cycling stability which retains 99.4% of the initial capacitance at 5 A g-1 after 30,000 cycles.

A reciprocity-based formula for the capacitance with quadrupolar electrodes

Energy Technology Data Exchange (ETDEWEB)

Cho, Sungbo [Gachon University of Medicine and Science, Incheon (Korea, Republic of)

2011-11-15

A new capacitance formula for the practical design and characterization of quadrupolar electrode arrays with capacitive structures was derived based on the reciprocal theorem. The reciprocity-based capacitance formula agreed with the empirical equations established to estimate the capacitance of a single strip line or disk electrode compensating for the fringing field effect that occurs at the electrode edge. The reciprocity-based formula was applied to compute the capacitance measurable by using a quadrupolar square electrode array with a symmetric dipole-dipole configuration and was compared with the analytical equation established based on the image method assuming that the electrodes were points. The results showed that the capacitance of the quadrupolar electrodes was determined by the size of the quadrupolar electrodes relative to the separation distance between the electrodes and that the reciprocity-based capacitance formula was in agreement with the established analytical equation if the separated distance between the electrodes relative to the electrode size was large enough.

A reciprocity-based formula for the capacitance with quadrupolar electrodes

International Nuclear Information System (INIS)

Cho, Sungbo

2011-01-01

A new capacitance formula for the practical design and characterization of quadrupolar electrode arrays with capacitive structures was derived based on the reciprocal theorem. The reciprocity-based capacitance formula agreed with the empirical equations established to estimate the capacitance of a single strip line or disk electrode compensating for the fringing field effect that occurs at the electrode edge. The reciprocity-based formula was applied to compute the capacitance measurable by using a quadrupolar square electrode array with a symmetric dipole-dipole configuration and was compared with the analytical equation established based on the image method assuming that the electrodes were points. The results showed that the capacitance of the quadrupolar electrodes was determined by the size of the quadrupolar electrodes relative to the separation distance between the electrodes and that the reciprocity-based capacitance formula was in agreement with the established analytical equation if the separated distance between the electrodes relative to the electrode size was large enough.

Analysis of a Segmented Annular Coplanar Capacitive Tilt Sensor with Increased Sensitivity.

Science.gov (United States)

Guo, Jiahao; Hu, Pengcheng; Tan, Jiubin

2016-01-21

An investigation of a segmented annular coplanar capacitor is presented. We focus on its theoretical model, and a mathematical expression of the capacitance value is derived by solving a Laplace equation with Hankel transform. The finite element method is employed to verify the analytical result. Different control parameters are discussed, and each contribution to the capacitance value of the capacitor is obtained. On this basis, we analyze and optimize the structure parameters of a segmented coplanar capacitive tilt sensor, and three models with different positions of the electrode gap are fabricated and tested. The experimental result shows that the model (whose electrode-gap position is 10 mm from the electrode center) realizes a high sensitivity: 0.129 pF/° with a non-linearity of design.

Characteristics Study of In-Situ Capacitive Sensor for Monitoring Lubrication Oil Debris.

Science.gov (United States)

Han, Zhibin; Wang, Yishou; Qing, Xinlin

2017-12-08

As an essential part of engine health monitoring (EHM), online lubrication oil debris monitoring has recently received great attention for the assessment of rotating and reciprocating parts in aero-engines, due to its high integration, low cost and safe characteristics. However, it is be a challenge to find a suitable sensor operating in such a complex environment. We present an unconventional novel approach, in which a cylinder capacitive sensor is designed and integrated with the pipeline of an engine lubrication system, so that the capacitive sensor can effectively detect changes in the lubrication oil condition. In this paper, an attempt to illustrate the performance characteristics of the developed cylinder capacitive sensor is made, through an experiment system that simulates a real scenario of a lubrication oil system. The main aim of the research was to qualitatively describe the relationship between the sensor parameter and the lubrication oil debris. In addition, the effect of the temperature and flow rate of the lubrication oil on capacitance change was performed by several experiments and we figured out a compensation method. The experimental results demonstrated that the cylinder capacitive sensor can potentially be used for lubrication oil debris monitoring of the health condition of an aero-engine.

Nitrogen-doped porous carbon derived from biomass waste for high-performance supercapacitor.

Science.gov (United States)

Ma, Guofu; Yang, Qian; Sun, Kanjun; Peng, Hui; Ran, Feitian; Zhao, Xiaolong; Lei, Ziqiang

2015-12-01

High capacitance property and low cost are the pivotal requirements for practical application of supercapacitor. In this paper, a low cost and high capacitance property nitrogen-doped porous carbon with high specific capacitance is prepared. The as-prepared nitrogen-doped porous carbon employing potato waste residue (PWR) as the carbon source, zinc chloride (ZnCl2) as the activating agent and melamine as nitrogen doping agent. The morphology and structure of the carbon materials are studied by scanning electron microscopy (SEM), N2 adsorption/desorption, X-ray diffraction (XRD) and Raman spectra. The surface area of the nitrogen-doped carbon which prepared under 700°C is found to be 1052m(2)/g, and the specific capacitance as high as 255Fg(-1) in 2M KOH electrolyte is obtained utilize the carbon as electrode materials. The electrode materials also show excellent cyclability with 93.7% coulombic efficiency at 5Ag(-1) current density of for 5000cycles. Copyright © 2015 Elsevier Ltd. All rights reserved.

Oxygen source-oriented control of atmospheric pressure chemical vapor deposition of VO2 for capacitive applications

Directory of Open Access Journals (Sweden)

Dimitra Vernardou

2016-06-01

Full Text Available Vanadium dioxides of different crystalline orientation planes have successfully been fabricated by chemical vapor deposition at atmospheric pressure using propanol, ethanol and O2 gas as oxygen sources. The thick a-axis textured monoclinic vanadium dioxide obtained through propanol presented the best electrochemical response in terms of the highest specific discharge capacity of 459 mAh g-1 with a capacitance retention of 97 % after 1000 scans under constant specific current of 2 A g-1. Finally, the electrochemical impedance spectroscopy indicated that the charge transfer of Li+ through the vanadium dioxide / electrolyte interface was easier for this sample enhancing significantly its capacitance performance.

Compressed magnetic flux amplifier with capacitive load

International Nuclear Information System (INIS)

Stuetzer, O.M.

1980-03-01

A first-order analysis is presented for a compressed magnetic flux (CMF) current amplifier working into a load with a capacitive component. Since the purpose of the investigation was to gain a general understanding of the arrangement, a number of approximations and limitations were accepted. The inductance of the transducer varies with time; the inductance/resistance/capacitance (LRC) circuit therefore is parametric and solutions are different for the stable regime (high C), the oscillation regime (low C), and the transition case. Solutions and performance depend strongly on circuit boundary conditions, i.e., energization of the circuit by either an injected current or by an applied capacitor charge. The behavior of current and energy amplification for the various cases are discussed in detail. A number of experiments with small CMF devices showed that the first-order theory presented predicts transducer performance well in the linear regime

Two-Dimensional Micro-/Nanoradian Angle Generator with High Resolution and Repeatability Based on Piezo-Driven Double-Axis Flexure Hinge and Three Capacitive Sensors

Directory of Open Access Journals (Sweden)

Xinran Tan

2017-11-01

Full Text Available This study presents a two-dimensional micro-/nanoradian angle generator (2D-MNAG that achieves high angular displacement resolution and repeatability using a piezo-driven flexure hinge for two-dimensional deflections and three capacitive sensors for output angle monitoring and feedback control. The principal error of the capacitive sensor for precision microangle measurement is analyzed and compensated for; so as to achieve a high angle output resolution of 10 nrad (0.002 arcsec and positioning repeatability of 120 nrad (0.024 arcsec over a large angular range of ±4363 μrad (±900 arcsec for the 2D-MNAG. The impact of each error component, together with the synthetic error of the 2D-MNAG after principal error compensation are determined using Monte Carlo simulation for further improvement of the 2D-MNAG.

CMOS MEMS capacitive absolute pressure sensor

International Nuclear Information System (INIS)

Narducci, M; Tsai, J; Yu-Chia, L; Fang, W

2013-01-01

This paper presents the design, fabrication and characterization of a capacitive pressure sensor using a commercial 0.18 µm CMOS (complementary metal–oxide–semiconductor) process and postprocess. The pressure sensor is capacitive and the structure is formed by an Al top electrode enclosed in a suspended SiO 2 membrane, which acts as a movable electrode against a bottom or stationary Al electrode fixed on the SiO 2 substrate. Both the movable and fixed electrodes form a variable parallel plate capacitor, whose capacitance varies with the applied pressure on the surface. In order to release the membranes the CMOS layers need to be applied postprocess and this mainly consists of four steps: (1) deposition and patterning of PECVD (plasma-enhanced chemical vapor deposition) oxide to protect CMOS pads and to open the pressure sensor top surface, (2) etching of the sacrificial layer to release the suspended membrane, (3) deposition of PECVD oxide to seal the etching holes and creating vacuum inside the gap, and finally (4) etching of the passivation oxide to open the pads and allow electrical connections. This sensor design and fabrication is suitable to obey the design rules of a CMOS foundry and since it only uses low-temperature processes, it allows monolithic integration with other types of CMOS compatible sensors and IC (integrated circuit) interface on a single chip. Experimental results showed that the pressure sensor has a highly linear sensitivity of 0.14 fF kPa −1 in the pressure range of 0–300 kPa. (paper)

Development trends of combined inductance-capacitance electromechanical energy converters

Directory of Open Access Journals (Sweden)

Karayan Hamlet

2018-01-01

Full Text Available In the article the modern state of completely new direction of electromechanical science such as combined inductive-capacitive electromechanics is considered. The wide spectra of its possible practical applications and prospects for further development are analyzed. A new approach for mathematical description of transients in dualcon jugate dynamic systems is proposed. On the basis of the algorithm differential equations for inductive-capacitive compatible electromechanical energy converters are derived. The generalized Lagrangian theory of combined inductively-capacitive electric machines was developed as a union of generalized Lagrangian models of inductive and capacitive electro-mechanical energy converters developed on the basis of the basic principles of binary-conjugate electrophysics. The author gives equations of electrodynamics and electromechanics of combined inductive-capacitive electric machines in case there are active electrotechnical materials of dual purpose (ferroelectromagnets in the structure of their excitation system. At the same time, the necessary Lagrangian for combined inductive-capacitive forces was built using new technologies of interaction between inductive and capacitive subsystems. The joint solution of these equations completely determines the dynamic behavior and energy characteristics of the generalized model of combined machines of any design and in any modes of interaction of their functional elements

Nanoporous Activated Carbon Derived from Rice Husk for High Performance Supercapacitor

Directory of Open Access Journals (Sweden)

Huaxing Xu

2014-01-01

Full Text Available Nanoporous activated carbon material was produced from the waste rice husks (RHs by precarbonizing RHs and activating with KOH. The morphology, structure, and specific surface area were investigated. The nanoporous carbon has the average pore size of 2.2 nm and high specific area of 2523.4 m2 g−1. The specific capacitance of the nanoporous carbon is calculated to be 250 F g−1 at the current density of 1 A g−1 and remains 80% for 198 F g−1 at the current density of 20 A g−1. The nanoporous carbon electrode exhibits long-term cycle life and could keep stable capacitance till 10,000 cycles. The consistently high specific capacitance, rate capacity, and long-term cycle life ability makes it a potential candidate as electrode material for supercapacitor.

A p-nitroaniline redox-active solid-state electrolyte for battery-like electrochemical capacitive energy storage combined with an asymmetric supercapacitor based on metal oxide functionalized β-polytype porous silicon carbide electrodes.

Science.gov (United States)

Kim, Myeongjin; Yoo, Jeeyoung; Kim, Jooheon

2017-05-23

A unique redox active flexible solid-state asymmetric supercapacitor with ultra-high capacitance and energy density was fabricated using a composite comprising MgCo 2 O 4 nanoneedles and micro and mesoporous silicon carbide flakes (SiCF) (SiCF/MgCo 2 O 4 ) as the positive electrode material. Due to the synergistic effect of the two materials, this hybrid electrode has a high specific capacitance of 516.7 F g -1 at a scan rate of 5 mV s -1 in a 1 M KOH aqueous electrolyte. To obtain a reasonable matching of positive and negative electrode pairs, a composite of Fe 3 O 4 nanoparticles and SiCF (SiCF/Fe 3 O 4 ) was synthesized for use as a negative electrode material, which shows a high capacitance of 423.2 F g -1 at a scan rate of 5 mV s -1 . Therefore, by pairing the SiCF/MgCo 2 O 4 positive electrode and the SiCF/Fe 3 O 4 negative electrode with a redox active quasi-solid-state PVA-KOH-p-nitroaniline (PVA-KOH-PNA) gel electrolyte, a novel solid-state asymmetric supercapacitor device was assembled. Because of the synergistic effect between the highly porous SiCF and the vigorous redox-reaction of metal oxides, the hybrid nanostructure electrodes exhibited outstanding charge storage and transport. In addition, the redox active PVA-KOH-PNA electrolyte adds additional pseudocapacitance, which arises from the nitro-reduction and oxidation and reduction process of the reduction product of p-phenylenediamine, resulting in an enhancement of the capacitance (a specific capacitance of 161.77 F g -1 at a scan rate of 5 mV s -1 ) and energy density (maximum energy density of 72.79 Wh kg -1 at a power density of 727.96 W kg -1 ).

Graphene/MnO2 hybrid nanosheets as high performance electrode materials for supercapacitors

International Nuclear Information System (INIS)

Mondal, Anjon Kumar; Wang, Bei; Su, Dawei; Wang, Ying; Chen, Shuangqiang; Zhang, Xiaogang; Wang, Guoxiu

2014-01-01

Graphene/MnO 2 hybrid nanosheets were prepared by incorporating graphene and MnO 2 nanosheets in ethylene glycol. Scanning electron microscopy and transmission electron microscopy analyses confirmed nanosheet morphology of the hybrid materials. Graphene/MnO 2 hybrid nanosheets with different ratios were investigated as electrode materials for supercapacitors by cyclic voltammetry (CV) and galvanostatic charge–discharge in 1 M Na 2 SO 4 electrolyte. We found that the graphene/MnO 2 hybrid nanosheets with a weight ratio of 1:4 (graphene:MnO 2 ) delivered the highest specific capacitance of 320 F g −1 . Graphene/MnO 2 hybrid nanosheets also exhibited good capacitance retention on 2000 cycles. - Highlights: • Graphene/MnO 2 hybrid nanosheets with different ratios were fabricated. • The specific capacitance is strongly dependent on graphene/MnO 2 ratios. • The graphene/MnO 2 hybrid electrode (1:4) exhibited high specific capacitance. • The electrode retained 84% of the initial specific capacitance after 2000 cycles

A capacitive ECG array with visual patient feedback.

Science.gov (United States)

Eilebrecht, Benjamin; Schommartz, Antje; Walter, Marian; Wartzek, Tobias; Czaplik, Michael; Leonhardt, Steffen

2010-01-01

Capacitive electrocardiogram (ECG) sensing is a promising technique for less constraining vital signal measurement and close to a commercial application. Even bigger trials testing the diagnostic significance were already done with single lead systems. Anyway, most applications to be found in research are limited to one channel and thus limited in its diagnostic relevance as only diseases coming along with a change of the heart rate can be diagnosed adequately. As a consequence the need for capacitive multi-channel ECGs combining the diagnostic relevance and the advantages of capacitive ECG sensing emerges. This paper introduces a capacitive ECG measurement system which allows the recording of standardized ECG leads according to Einthoven and Goldberger by means of an electrode array with nine electrodes.

Negative capacitance in a ferroelectric capacitor.

Science.gov (United States)

Khan, Asif Islam; Chatterjee, Korok; Wang, Brian; Drapcho, Steven; You, Long; Serrao, Claudy; Bakaul, Saidur Rahman; Ramesh, Ramamoorthy; Salahuddin, Sayeef

2015-02-01

The Boltzmann distribution of electrons poses a fundamental barrier to lowering energy dissipation in conventional electronics, often termed as Boltzmann Tyranny. Negative capacitance in ferroelectric materials, which stems from the stored energy of a phase transition, could provide a solution, but a direct measurement of negative capacitance has so far been elusive. Here, we report the observation of negative capacitance in a thin, epitaxial ferroelectric film. When a voltage pulse is applied, the voltage across the ferroelectric capacitor is found to be decreasing with time--in exactly the opposite direction to which voltage for a regular capacitor should change. Analysis of this 'inductance'-like behaviour from a capacitor presents an unprecedented insight into the intrinsic energy profile of the ferroelectric material and could pave the way for completely new applications.

Membrane capacitive deionization

NARCIS (Netherlands)

Biesheuvel, P.M.; Wal, van der A.

2010-01-01

Membrane capacitive deionization (MCDI) is an ion-removal process based on applying an electrical potential difference across an aqueous solution which flows in between oppositely placed porous electrodes, in front of which ion-exchange membranes are positioned. Due to the applied potential, ions

Global Model for Asymmetric, Diode-Type Dual Frequency Capacitive Discharge

Science.gov (United States)

Kim, Jisoo; Lieberman, M. A.; Lichtenberg, A. J.

2003-10-01

Dual frequency capacitive reactors can have desirable properties for dielectric etch: low cost, robust uniformity over large areas, and control of dissociation. In the ideal case, the high frequency power controls the plasma density (ion flux) and the low frequency voltage controls the ion bombarding energy. Typical operating conditions are: discharge radius 15-30 cm, length 1-3 cm, pressure 30-200 mTorr, high frequency 27.1-160 MHz, low frequency 2-13.6 MHz, and powers of 500-3000 W for both high and low frequencies. The decoupling of the high and low frequencies is an important feature of dual frequency capacitive discharges. In this work, we describe a global (volume-averaged) model having different top and bottom plate areas that incorporates particle balance, and ohmic and stochastic heating for high and low frequencies. The model is used to obtain the decoupling of high and low frequencies and to investigate limitations to ideal decoupling. Support provided by Lam Research, NSF Grant ECS-0139956, California industries, and UC-SMART Contract SM99-10051.

Ionic Liquid-Assisted Synthesis of a NiO/CNTs Composite and Its Electrochemical Capacitance

Directory of Open Access Journals (Sweden)

Yitong Chen

2014-01-01

Full Text Available A novel solid-state method has been developed for synthesizing nickel oxide (NiO/carbon nanotubes (CNTs composite using an ionic liquid (IL, 1-butyl-3-methylimidazolium chloride as the reaction medium. Ultraviolet-visible (UV-vis absorbance spectroscopy, infrared spectroscopy (IR, and scanning electron microscopy (SEM were employed to investigate the structure, morphology, and formation mechanism of the synthesized sample. The results demonstrated that the IL is effective for dispersing CNTs, which allows the tethering of nickel (II ions onto the surfaces of the CNTs and facilitates the subsequent chemical deposition of NiO to obtain the NiO/CNTs composite. The electrochemical properties of the composite were determined using cyclic voltammetry and galvanostatic charge/discharge measurements in 6 M KOH. Because of its unique structure, the prepared NiO/CNTs electrode exhibited good capacitive behavior and cyclability. The high specific capacitance (521 F g−1 and good rate capability (91% capacity retention at 0.5 A g−1 of the NiO/CNTs composite enable its use as a practical supercapacitor electrode material.

On the correlation between the porous structure and the electrochemical response of powdered and monolithic carbon aerogels as electrodes for capacitive deionization

Energy Technology Data Exchange (ETDEWEB)

Macías, C., E-mail: carlosmacias@nanoquimia.com [Nanoquimia S.L., PCT Rabanales 21, Ed. Aldebarán M.4.3., 14014 Córdoba (Spain); Lavela, P. [Laboratorio de Química Inorgánica, Universidad de Córdoba, Marie Curie, Campus de Rabanales, 14071 Córdoba (Spain); Rasines, G. [Nanoquimia S.L., PCT Rabanales 21, Ed. Aldebarán M.4.3., 14014 Córdoba (Spain); Zafra, M.C.; Tirado, J.L. [Laboratorio de Química Inorgánica, Universidad de Córdoba, Marie Curie, Campus de Rabanales, 14071 Córdoba (Spain); Ania, C.O. [ADPOR Group, Instituto Nacional del Carbón (INCAR), CSIC, Apdo. 73, 33080 Oviedo (Spain)

2016-10-15

The combined effect of resorcinol/catalyst (100≤R/C≤800) and resorcinol/water (0.04≤R/W≤0.13) molar ratio on the textural and capacitive properties of carbon aerogels with potential application for capacitive deionization has been evaluated. Activated and pyrolyzed aerogels were synthesized by the sol-gel polymerization of resorcinol-formaldehyde mixtures and dried in supercritical conditions. Data show that high R/C and R/W molar ratios lead to materials with large pores in the mesopore range, whereas the surface area and micropore volumes remain somewhat the same. The activation of the aerogels increased the differences in the specific surface and micropore volumes due to the development of microporosity. This effect was more remarkable for the samples with low R/C whatever the R/W ratio, indicating that the carbon aerogel obtained using high amounts of catalyst are more prone to be activated. Regarding the electrochemical features of the aerogels, low capacitance values were measured in aerogels combining low R/W and high R/C and reciprocally low R/C and high R/W molar ratios, due to their higher resistance. Polarization resistances were found to be slightly higher for the pyrolyzed than for activated aerogels, and followed a decreasing trend with the mesoporosity, indicating the outstanding contribution of the mesoporous network to provide a good kinetic response. The desalting capacity of monolithic aerogels showed a simultaneous dependence with the surface area and the resistivity of the electrodes, pointing out the importance of performing electrochemical measurements in adequate cell configurations (i.e., desalting units) upon the intended application. - Graphical abstract: The textural properties of carbon aerogels are strongly influenced by the synthesis parameters precursor to catalyst (R/C) and water (R/C) ratios. The volumetric capacitance measured in a symmetric cell with monolithic electrodes of carbon aerogel strongly correlates with both

Study on effective MOSFET channel length extracted from gate capacitance

Science.gov (United States)

Tsuji, Katsuhiro; Terada, Kazuo; Fujisaka, Hisato

2018-01-01

The effective channel length (L GCM) of metal-oxide-semiconductor field-effect transistors (MOSFETs) is extracted from the gate capacitances of actual-size MOSFETs, which are measured by charge-injection-induced-error-free charge-based capacitance measurement (CIEF CBCM). To accurately evaluate the capacitances between the gate and the channel of test MOSFETs, the parasitic capacitances are removed by using test MOSFETs having various channel sizes and a source/drain reference device. A strong linear relationship between the gate-channel capacitance and the design channel length is obtained, from which L GCM is extracted. It is found that L GCM is slightly less than the effective channel length (L CRM) extracted from the measured MOSFET drain current. The reason for this is discussed, and it is found that the capacitance between the gate electrode and the source and drain regions affects this extraction.

Reducing the capacitance of piezoelectric film sensors

Energy Technology Data Exchange (ETDEWEB)

González, Martín G., E-mail: mggonza@fi.uba.ar [Grupo de Láser, Óptica de Materiales y Aplicaciones Electromagnéticas (GLOMAE), Departamento de Física, Facultad de Ingeniería, Universidad de Buenos Aires, Paseo Colón 850, C1063ACV Buenos Aires (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), C1425FQB Buenos Aires (Argentina); Sorichetti, Patricio A.; Santiago, Guillermo D. [Grupo de Láser, Óptica de Materiales y Aplicaciones Electromagnéticas (GLOMAE), Departamento de Física, Facultad de Ingeniería, Universidad de Buenos Aires, Paseo Colón 850, C1063ACV Buenos Aires (Argentina)

2016-04-15

We present a novel design for large area, wideband, polymer piezoelectric sensor with low capacitance. The large area allows better spatial resolution in applications such as photoacoustic tomography and the reduced capacitance eases the design of fast transimpedance amplifiers. The metalized piezoelectric polymer thin film is segmented into N sections, electrically connected in series. In this way, the total capacitance is reduced by a factor 1/N{sup 2}, whereas the mechanical response and the active area of the sensor are not modified. We show the construction details for a two-section sensor, together with the impedance spectroscopy and impulse response experimental results that validate the design.

Reducing the capacitance of piezoelectric film sensors

International Nuclear Information System (INIS)

González, Martín G.; Sorichetti, Patricio A.; Santiago, Guillermo D.

2016-01-01

We present a novel design for large area, wideband, polymer piezoelectric sensor with low capacitance. The large area allows better spatial resolution in applications such as photoacoustic tomography and the reduced capacitance eases the design of fast transimpedance amplifiers. The metalized piezoelectric polymer thin film is segmented into N sections, electrically connected in series. In this way, the total capacitance is reduced by a factor 1/N"2, whereas the mechanical response and the active area of the sensor are not modified. We show the construction details for a two-section sensor, together with the impedance spectroscopy and impulse response experimental results that validate the design.

A versatile method to grow localized arrays of nanowires for highly sensitive capacitive devices

DEFF Research Database (Denmark)

Antohe, V.A.; Radu, A.; Yunus, S.

2008-01-01

We propose a new approach to increase the detection efficiency of the capacitive sensing devices, by growing vertically aligned nanowires arrays, localized and confined on small interdigited electrodes structures. The metallic tracks are made using optical lithography, and the nanowires are reali...

The split delivery capacitated team orienteering problem

NARCIS (Netherlands)

Archetti, C.; Bianchessi, N.; Speranza, M. G.; Hertz, A.

2014-01-01

In this article, we study the capacitated team orienteering problem where split deliveries are allowed. A set of potential customers is given, each associated with a demand and a profit. The set of customers to be served by a fleet of capacitated vehicles has to be identified in such a way that the

Porous hollow Co3O4 with rhombic dodecahedral structures for high-performance supercapacitors

Science.gov (United States)

Zhang, Yi-Zhou; Wang, Yang; Xie, Ye-Lei; Cheng, Tao; Lai, Wen-Yong; Pang, Huan; Huang, Wei

2014-11-01

Porous hollow Co3O4 with rhombic dodecahedral structures were prepared by the calcination of ZIF-67 ([Co(mim)2; mim = 2-methylimidazolate]) rhombic dodecahedral microcrystals. A supercapacitor was successfully constructed by adopting the resulting porous hollow Co3O4 rhombic dodecahedral structure as the electrode material, which showed a large specific capacitance of 1100 F g-1 and retained more than 95.1% of the specific capacitance after 6000 continuous charge-discharge cycles. The excellent capacitive properties and stability mark the porous hollow Co3O4 with the rhombic dodecahedral structure as one of the most promising electrode materials for high-performance supercapacitors.Porous hollow Co3O4 with rhombic dodecahedral structures were prepared by the calcination of ZIF-67 ([Co(mim)2; mim = 2-methylimidazolate]) rhombic dodecahedral microcrystals. A supercapacitor was successfully constructed by adopting the resulting porous hollow Co3O4 rhombic dodecahedral structure as the electrode material, which showed a large specific capacitance of 1100 F g-1 and retained more than 95.1% of the specific capacitance after 6000 continuous charge-discharge cycles. The excellent capacitive properties and stability mark the porous hollow Co3O4 with the rhombic dodecahedral structure as one of the most promising electrode materials for high-performance supercapacitors. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04782f

Fabrication and electrochemical capacitance of hierarchical graphene/polyaniline/carbon nanotube ternary composite film

International Nuclear Information System (INIS)

Lu Xiangjun; Dou Hui; Yang Sudong; Hao Liang; Zhang Luojiang; Shen Laifa; Zhang Fang; Zhang Xiaogang

2011-01-01

Graphical abstract: A hierarchical film with coaxial polyaniline/carbon nanotube (PANI/CNT) nanocables uniformly sandwiched between graphene (GN) sheets was prepared by filtration of the complex dispersion of graphite oxide (GO) and PANI/CNT. Highlights: → A film composed of GN sheets, PANI and CNTs was fabricated. → The coaxial PANI/CNT nanocables uniformly sandwiched between the GN sheets. → The unique structure facilitates contact between electrolyte and electrode materials. → Each component provides unique function to achieve superior electrochemical properties. - Abstract: A film composed of graphene (GN) sheets, polyaniline (PANI) and carbon nanotubes (CNTs) has been fabricated by reducing a graphite oxide (GO)/PANI/CNT precursor prepared by flow-directed assembly from a complex dispersion of GO and PANI/CNT, followed by reoxidation and redoping of the reduced PANI in the composite to restore the conducting PANI structure. Scanning electron microscope images indicate that the ternary composite film is a layered structure with coaxial PANI/CNT nanocables uniformly sandwiched between the GN sheets. Such novel hierarchical structure with high electrical conductivity perfectly facilitates contact between electrolyte ions and PANI for faradaic energy storage and efficiently utilizes the double-layer capacitance at the electrode-electrolyte interfaces. The specific capacitance of the GN/PANI/CNT estimated by galvanostatic charge/discharge measurement is 569 F g -1 (or 188 F cm -3 for volumetric capacitance) at a current density of 0.1 A g -1 . In addition, the GN/PANI/CNT exhibits good rate capability (60% capacity retention at 10 A g -1 ) and superior cycling stability (4% fade after 5000 continuous charge/discharge cycles).

A novel heuristic algorithm for capacitated vehicle routing problem

Science.gov (United States)

Kır, Sena; Yazgan, Harun Reşit; Tüncel, Emre

2017-09-01

The vehicle routing problem with the capacity constraints was considered in this paper. It is quite difficult to achieve an optimal solution with traditional optimization methods by reason of the high computational complexity for large-scale problems. Consequently, new heuristic or metaheuristic approaches have been developed to solve this problem. In this paper, we constructed a new heuristic algorithm based on the tabu search and adaptive large neighborhood search (ALNS) with several specifically designed operators and features to solve the capacitated vehicle routing problem (CVRP). The effectiveness of the proposed algorithm was illustrated on the benchmark problems. The algorithm provides a better performance on large-scaled instances and gained advantage in terms of CPU time. In addition, we solved a real-life CVRP using the proposed algorithm and found the encouraging results by comparison with the current situation that the company is in.

Evaluating and enhancing quantum capacitance in graphene-based electrodes from first principles

Science.gov (United States)

Ogitsu, Tadashi; Otani, Minoru; Lee, Jonathan; Bagge-Hansen, Michael; Biener, Juergen; Wood, Brandon

2013-03-01

Graphene derivatives are attractive as supercapacitor electrodes because they are lightweight, chemically inert, have high surface area and conductivity, and are stable in electrolyte solutions. Nevertheless, devising reliable strategies for improving energy density relies on an understanding of the specific factors that control electrode performance. We use density-functional theory calculations of pristine and defective graphene to extract quantum capacitance, as well as to identify specific limiting factors. The effect of structural point defects and strain-related morphological changes on the density of states is also evaluated. The results are combined with predicted and measured in situ X-ray absorption spectra in order to give insight into the structural and chemical features present in synthesized carbon aerogel samples. Performed under the auspices of the U.S. DOE by LLNL under Contract DE-AC52-07NA27344.

Electromagnetic effects in high-frequency capacitive discharges used for plasma processing

International Nuclear Information System (INIS)

Chabert, P

2007-01-01

In plasma processing, capacitive discharges have classically been operated in the electrostatic regime, for which the excitation wavelength λ is much greater than the electrode radius, and the plasma skin depth δ is much greater than the electrode spacing. However, contemporary reactors are larger and excited at higher frequencies which leads to strong electromagnetic effects. This paper gives a review of the work that has recently been carried out to carefully model and diagnose these effects, which cause major uniformity problems in plasma processing for microelectronics and flat panel displays industries. (topical review)

Can root electrical capacitance be used to predict root mass in soil?

Science.gov (United States)

Dietrich, R C; Bengough, A G; Jones, H G; White, P J

2013-07-01

Electrical capacitance, measured between an electrode inserted at the base of a plant and an electrode in the rooting substrate, is often linearly correlated with root mass. Electrical capacitance has often been used as an assay for root mass, and is conventionally interpreted using an electrical model in which roots behave as cylindrical capacitors wired in parallel. Recent experiments in hydroponics show that this interpretation is incorrect and a new model has been proposed. Here, the new model is tested in solid substrates. The capacitances of compost and soil were determined as a function of water content, and the capacitances of cereal plants growing in sand or potting compost in the glasshouse, or in the field, were measured under contrasting irrigation regimes. Capacitances of compost and soil increased with increasing water content. At water contents approaching field capacity, compost and soil had capacitances at least an order of magnitude greater than those of plant tissues. For plants growing in solid substrates, wetting the substrate locally around the stem base was both necessary and sufficient to record maximum capacitance, which was correlated with stem cross-sectional area: capacitance of excised stem tissue equalled that of the plant in wet soil. Capacitance measured between two electrodes could be modelled as an electrical circuit in which component capacitors (plant tissue or rooting substrate) are wired in series. The results were consistent with the new physical interpretation of plant capacitance. Substrate capacitance and plant capacitance combine according to standard physical laws. For plants growing in wet substrate, the capacitance measured is largely determined by the tissue between the surface of the substrate and the electrode attached to the plant. Whilst the measured capacitance can, in some circumstances, be correlated with root mass, it is not a direct assay of root mass.

Carbon nanofiber supercapacitors with large areal capacitances

KAUST Repository

McDonough, James R.

2009-01-01

We develop supercapacitor (SC) devices with large per-area capacitances by utilizing three-dimensional (3D) porous substrates. Carbon nanofibers (CNFs) functioning as active SC electrodes are grown on 3D nickel foam. The 3D porous substrates facilitate a mass loading of active electrodes and per-area capacitance as large as 60 mg/ cm2 and 1.2 F/ cm2, respectively. We optimize SC performance by developing an annealing-free CNF growth process that minimizes undesirable nickel carbide formation. Superior per-area capacitances described here suggest that 3D porous substrates are useful in various energy storage devices in which per-area performance is critical. © 2009 American Institute of Physics.

Electrochemical capacitance characteristics of patterned ruthenium dioxide-carbon nanotube nanocomposites grown onto graphene

International Nuclear Information System (INIS)

Shih, Yi-Ting; Lee, Kuei-Yi; Huang, Ying-Sheng

2014-01-01

Highlights: • Graphene was grown on Cu foil by mobile thermal chemical vapor deposition system. • CNT was synthesized on graphene for RuO 2 nanostructure growth by thermal chemical vapor deposition system. • The CNT growth location was fixed through the use of photolithography technique, thereby increasing the specific area. • RuO 2 nanostructures were coated onto CNT bundle arrays through metal organic chemical vapor deposition, in order to utilize its pseudo capacitive property. - Abstract: In this study, graphene was used as a conductive substrate for vertically aligned carbon nanotube (CNT) bundle arrays growth, to be used as an electrode for electrochemical double layer capacitor (EDLC), as graphene and CNT exhibit good conductivity and excellent chemical stability. Both of them are composed of carbon, therefore making a superior adhesion between them. The configuration of bundle arrays provided a relatively higher specific surface area in contact with electrolyte, thereby resulting in demonstratively higher capacitance. Moreover, as the RuO 2 nanostructures have good pseudocapacitance characteristics, they were coated onto vertically aligned CNT bundle arrays in order to effectively enhance the EDLC performances. The characteristics of CNT/graphene, CNT bundle/graphene, and RuO 2 /CNT bundle/graphene electrodes were examined with the use of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. Furthermore, their electrochemical properties were investigated by an electrochemical analyzer. The specific capacitances of CNT/graphene, CNT bundle/graphene, and RuO 2 /CNT bundle/graphene were 4.64, 6.65, and 128.40 F/g at the scan rate of 0.01 V/s, respectively

A capacitively coupled dose-rate-dependent transient upset mechanism in a bipolar memory

International Nuclear Information System (INIS)

Turfler, R.M.; Pease, R.L.; Dinger, G.; Armstrong, B.

1992-01-01

This paper reports on a pattern sensitivity that was observed in the threshold dose rate response of a bipolar 16K PROM for radiation pulse widths of 20-100 ns. For the worst case pattern, the upset threshold was a factor of three lower than for the commonly used checkerboard pattern. The mechanism for this pattern sensitivity was found to be a capacitively coupled voltage transient on a sensitive node which caused a low-to-high transition at the output. A design fix was implemented to significantly alter the ratio of the two parasitic capacitances in a capacitive divider which reduced the amplitude of the voltage transient at the sensitive node. It was demonstrated that in the redesign, the pattern sensitivity was eliminated

Oxygen- and nitrogen-co-doped activated carbon from waste particleboard for potential application in high-performance capacitance

International Nuclear Information System (INIS)

Shang, Tong-Xin; Ren, Ru-Quan; Zhu, Yue-Mei; Jin, Xiao-Juan

2015-01-01

Graphical abstract: All electrodes showed excellent capacitance and retention versus discharge current density from 0.05 to 5 A/g. - Abstract: Oxygen- and nitrogen-co-doped activated carbons were obtained from phosphoric acid treated nitrogen-doped activated carbons which were prepared from waste particleboard bonded with urea-formaldehyde resin adhesives. The activated carbon samples obtained were tested as supercapacitors in two-electrode cell and extensive wetting 7 M KOH electrolytes. Their structural properties and surface chemistry, before the electrical testing, were investigated using elemental analysis, X-ray photoelectron spectroscopy, scanning electron microscopy, X-ray diffraction, Raman spectra, and adsorption of nitrogen. Activated carbon treated by 4 M phosphoric acid of the highest capacitance (235 F/g) was measured in spite of a relatively lower surface (1360 m 2 /g) than that of the activated carbon treated by 2 M phosphoric acid (1433 m 2 /g). The surface chemistry, and especially oxygen- and nitrogen-containing functional groups, was found of paramount importance for the capacitive behavior and for the effective pore space utilization by the electrolyte ions

Mode transition of power dissipation and plasma parameters in an asymmetric capacitive discharge

International Nuclear Information System (INIS)

Lee, Soo-Jin; Lee, Hyo-Chang; Bang, Jin-young; Oh, Seung-Ju; Chung, Chin-Wook

2013-01-01

Electrical characteristics and plasma parameters were experimentally investigated in asymmetric capacitively coupled plasma with various argon gas pressures. At a low discharge current region, the transferred power to the plasma was proportional to the current, while the transferred power increased proportionally to square of the current at a high discharge current region. The mode transition of power dissipation occurred at the lower discharge current region with the high gas pressure. At the low radio-frequency power or low discharge current, the plasma density increased linearly with the discharge current, while at the high power or high discharge current, the rate of an increase in the plasma density depended on the gas pressures. A transition of the discharge resistance was also found when the mode transition of the power dissipation occurred. These changes in the electrical characteristics and the plasma parameters were mainly caused by the power dissipation mode transition from the plasma bulk to the sheath in the capacitive discharge with the asymmetric electrode, which has extremely high self-bias voltages. - Highlights: • Mode transition of the power dissipation in an asymmetrical capacitive discharge • Evolution of the discharge power, electrode voltage, and discharge impedance • Electron temperature and plasma density on the power dissipation mode transition

High-efficiency super capacitors based on hetero-structured α-MnO2 nanorods

International Nuclear Information System (INIS)

Ghouri, Zafar Khan; Shaheer Akhtar, M.; Zahoor, Awan; Barakat, Nasser A.M.; Han, Weidong; Park, Mira; Pant, Bishweshwar; Saud, Prem Singh; Lee, Cho Hye; Kim, Hak Yong

2015-01-01

Highlights: • Hetero-structured α-MnO 2 nanorods are prepared by a facile hydrothermal route. • It is applied as active electrode materials for supercapacitor. • A high specific capacitance of 298 Fg −1 with a superior long term cyclic stability is achieved. • Supercapacitor shows high specific capacitance retention 94% after 1000 cycles. - Abstract: Hetero-structured manganese dioxide nanorods with α phase (α-MnO 2 ) were prepared by a facile hydrothermal route at low temperature. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption–desorption measurements were used to characterize the prepared hetero-structured α-MnO 2 nanorods. Supercapacitive performance of the hetero-structured α-MnO 2 nanomaterials as active electrode material was evaluated by cyclic voltammetry (CV) in alkaline medium. The MnO 2 hetero-structure with 2 × 2 tunnels constructed from double chains of octahedral [MnO 6 ] structure yield a significantly high specific capacitance of 298 Fg −1 at 5 mV s −1 and demonstrated a superior long term cyclic stability, with specific capacitance retention about 94% after 1000 cycles. The superior supercapacitive performance of the hetero-structured α-MnO 2 electrode is due to its high specific surface area and unique hierarchy architecture which facilitate fast electron and ion transport

A porous ceramic membrane tailored high-temperature supercapacitor

Science.gov (United States)

Zhang, Xin; He, Benlin; Zhao, Yuanyuan; Tang, Qunwei

2018-03-01

The supercapacitor that can operate at high-temperature are promising for markedly increase in capacitance because of accelerated charge movement. However, the state-of-the-art polymer-based membranes will decompose at high temperature. Inspired by solid oxide fuel cells, we present here the experimental realization of high-temperature supercapacitors (HTSCs) tailored with porous ceramic separator fabricated by yttria-stabilized zirconia (YSZ) and nickel oxide (NiO). Using activated carbon electrode and supporting electrolyte from potassium hydroxide (KOH) aqueous solution, a category of symmetrical HTSCs are built in comparison with a conventional polymer membrane based device. The dependence of capacitance performance on temperature is carefully studied, yielding a maximized specific capacitance of 272 F g-1 at 90 °C for the optimized HTSC tailored by NiO/YSZ membrane. Moreover, the resultant HTSC has relatively high durability when suffer repeated measurement over 1000 cycles at 90 °C, while the polymer membrane based supercapacitor shows significant reduction in capacitance at 60 °C. The high capacitance along with durability demonstrates NiO/YSZ membrane tailored HTSCs are promising in future advanced energy storage devices.

The interfacial tension of the mercury —1 M HClO4− solution interface at high potentials; comparison with double-layer capacitance measurements

NARCIS (Netherlands)

Sluyters-Rehbach, M.; Woittiez, W.J.A.; Sluyters, J.H.

Interfacial tension values have been measured in order to calculate the electrical charge density as a function of potential. The results are in accordance with those obtained from double-layer capacitance data reported earlier2,3, also at highly positive potentials.

Preparing two-dimensional microporous carbon from Pistachio nutshell with high areal capacitance as supercapacitor materials

Science.gov (United States)

Xu, Jiandong; Gao, Qiuming; Zhang, Yunlu; Tan, Yanli; Tian, Weiqian; Zhu, Lihua; Jiang, Lei

2014-07-01

Two-dimensional (2D) porous carbon AC-SPN-3 possessing of amazing high micropore volume ratio of 83% and large surface area of about 1069 m2 g-1 is high-yield obtained by pyrolysis of natural waste Pistachio nutshells with KOH activation. The AC-SPN-3 has a curved 2D lamellar morphology with the thickness of each slice about 200 nm. The porous carbon is consists of highly interconnected uniform pores with the median pore diameter of about 0.76 nm, which could potentially improve the performance by maximizing the electrode surface area accessible to the typical electrolyte ions (such as TEA+, diameter = ~0.68 nm). Electrochemical analyses show that AC-SPN-3 has significantly large areal capacitance of 29.3/20.1 μF cm-2 and high energy density of 10/39 Wh kg-1 at power of 52/286 kW kg-1 in 6 M KOH aqueous electrolyte and 1 M TEABF4 in EC-DEC (1:1) organic electrolyte system, respectively.

Fabrication of a thin-film capacitive force sensor array for tactile feedback in robotic surgery.

Science.gov (United States)

Paydar, Omeed H; Wottawa, Christopher R; Fan, Richard E; Dutson, Erik P; Grundfest, Warren S; Culjat, Martin O; Candler, Rob N

2012-01-01

Although surgical robotic systems provide several advantages over conventional minimally invasive techniques, they are limited by a lack of tactile feedback. Recent research efforts have successfully integrated tactile feedback components onto surgical robotic systems, and have shown significant improvement to surgical control during in vitro experiments. The primary barrier to the adoption of tactile feedback in clinical use is the unavailability of suitable force sensing technologies. This paper describes the design and fabrication of a thin-film capacitive force sensor array that is intended for integration with tactile feedback systems. This capacitive force sensing technology could provide precise, high-sensitivity, real-time responses to both static and dynamic loads. Capacitive force sensors were designed to operate with optimal sensitivity and dynamic range in the range of forces typical in minimally invasive surgery (0-40 N). Initial results validate the fabrication of these capacitive force-sensing arrays. We report 16.3 pF and 146 pF for 1-mm(2) and 9-mm(2) capacitive areas, respectively, whose values are within 3% of theoretical predictions.

Doping effect of polyaniline/MWCNT composites on capacitance and cyclic stability of supercapacitors.

Science.gov (United States)

Karthikeyan, G; Sahoo, S; Nayak, G C; Das, C K

2012-03-01

Polyaniline doped by Zn2+ ions was synthesized as nanocomposites with multiwalled carbon nanotubes (MWCNT) by in-situ oxidative polymerization and investigated as electrode material for supercapacitors. The uniform coating of polyaniline on MWCNT was characterized by field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). The effect of Zn2+ ions on nanocomposites were characterized by Fourier transform infrared (FTIR) spectroscopy. The electrochemical performances were investigated by cyclic voltammetry (CV), constant current charging/discharging cyclic test (CC) and electrochemical impedance spectroscopy (EIS) using a three-electrode system. The doped polyaniline composites show higher specific capacitance and better cyclic stability.

Carrier Statistics and Quantum Capacitance Models of Graphene Nanoscroll

Directory of Open Access Journals (Sweden)

M. Khaledian

2014-01-01

schematic perfect scroll-like Archimedes spiral. The DOS model was derived at first, while it was later applied to compute the carrier concentration and quantum capacitance model. Furthermore, the carrier concentration and quantum capacitance were modeled for both degenerate and nondegenerate regimes, along with examining the effect of structural parameters and chirality number on the density of state and carrier concentration. Latterly, the temperature effect on the quantum capacitance was studied too.

Circuit and Measurement Technique for Radiation Induced Drift in Precision Capacitance Matching

Science.gov (United States)

Prasad, Sudheer; Shankar, Krishnamurthy Ganapathy

2013-04-01

In the design of radiation tolerant precision ADCs targeted for space market, a matched capacitor array is crucial. The drift of capacitance ratios due to radiation should be small enough not to cause linearity errors. Conventional methods for measuring capacitor matching may not achieve the desired level of accuracy due to radiation induced gain errors in the measurement circuits. In this work, we present a circuit and method for measuring capacitance ratio drift to a very high accuracy (<; 1 ppm) unaffected by radiation levels up to 150 krad.

Human body capacitance: static or dynamic concept? [ESD

DEFF Research Database (Denmark)

Jonassen, Niels M

1998-01-01

A standing human body insulated from ground by footwear and/or floor covering is in principle an insulated conductor and has, as such, a capacitance, i.e. the ability to store a charge and possibly discharge the stored energy in a spark discharge. In the human body, the human body capacitance (HBC...... when a substantial part of the flux extends itself through badly defined stray fields. Since the concept of human body capacitance is normally used in a static (electric) context, it is suggested that the HBC be determined by a static method. No theoretical explanation of the observed differences...

High-efficiency super capacitors based on hetero-structured α-MnO{sub 2} nanorods

Energy Technology Data Exchange (ETDEWEB)

Ghouri, Zafar Khan [Department of BIN Fusion Technology, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Department of Organic materials and Fiber Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Shaheer Akhtar, M. [New & Renewable Energy Material Development Center (NewREC), Chonbuk National University, Jeonbuk (Korea, Republic of); Zahoor, Awan [Department of Chemical Engineering, NED University of Engineering & Technology, University Road, Karachi 75270 (Pakistan); Barakat, Nasser A.M., E-mail: nasser@jbnu.ac.kr [Department of Organic materials and Fiber Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Department of Chemical Engineering, Faculty of Engineering, El-Minia University, El-Minia (Egypt); Han, Weidong [Department of BIN Fusion Technology, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Park, Mira [Department of Organic materials and Fiber Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Pant, Bishweshwar; Saud, Prem Singh; Lee, Cho Hye [Department of BIN Fusion Technology, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Kim, Hak Yong, E-mail: khy@jbnu.ac.kr [Department of BIN Fusion Technology, Chonbuk National University, Jeonju 561-756 (Korea, Republic of)

2015-09-05

Highlights: • Hetero-structured α-MnO{sub 2} nanorods are prepared by a facile hydrothermal route. • It is applied as active electrode materials for supercapacitor. • A high specific capacitance of 298 Fg{sup −1} with a superior long term cyclic stability is achieved. • Supercapacitor shows high specific capacitance retention 94% after 1000 cycles. - Abstract: Hetero-structured manganese dioxide nanorods with α phase (α-MnO{sub 2}) were prepared by a facile hydrothermal route at low temperature. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption–desorption measurements were used to characterize the prepared hetero-structured α-MnO{sub 2} nanorods. Supercapacitive performance of the hetero-structured α-MnO{sub 2} nanomaterials as active electrode material was evaluated by cyclic voltammetry (CV) in alkaline medium. The MnO{sub 2} hetero-structure with 2 × 2 tunnels constructed from double chains of octahedral [MnO{sub 6}] structure yield a significantly high specific capacitance of 298 Fg{sup −1} at 5 mV s{sup −1} and demonstrated a superior long term cyclic stability, with specific capacitance retention about 94% after 1000 cycles. The superior supercapacitive performance of the hetero-structured α-MnO{sub 2} electrode is due to its high specific surface area and unique hierarchy architecture which facilitate fast electron and ion transport.

Flexible supercapacitors with high areal capacitance based on hierarchical carbon tubular nanostructures

Science.gov (United States)

Zhang, Haitao; Su, Hai; Zhang, Lei; Zhang, Binbin; Chun, Fengjun; Chu, Xiang; He, Weidong; Yang, Weiqing

2016-11-01

Hierarchical structure design can greatly enhance the unique properties of primary material(s) but suffers from complicated preparation process and difficult self-assembly of materials with different dimensionalities. Here we report on the growth of single carbon tubular nanostructures with hierarchical structure (hCTNs) through a simple method based on direct conversion of carbon dioxide. Resorting to in-situ transformation and self-assembly of carbon micro/nano-structures, the obtained hCTNs are blood-like multichannel hierarchy composed of one large channel across the hCTNs and plenty of small branches connected to each other. Due to the unique pore structure and high surface area, these hCTN-based flexible supercapacitors possess the highest areal capacitance of ∼320 mF cm-2, as well as good rate-capability and excellent cycling stability (95% retention after 2500 cycles). It was established that this method can control the morphology, size, and density of hCTNs and effectively construct hCTNs well anchored to the various substrates. Our work unambiguously demonstrated the potential of hCTNs for large flexible supercapacitors and integrated energy management electronics.

Vertically Aligned Carbon Nanotube Arrays as Efficient Supports for Faradaic Capacitive Electrodes

Science.gov (United States)

Oguntoye, Moses; Holleran, Mary-Kate; Roberts, Katherine; Pesika, Noshir

Supercapacitors are notable for their ability to deliver energy at higher power (compared to batteries) and store energy at higher density (compared to capacitors) as well as exhibit a long cycle life. In our efforts to further the development of supercapacitors, our focus is on using vertically aligned carbon nanotubes (VACNT) as supports for faradaic capacitive electrode materials. The objective is to develop electrodes functioning in an inexpensive aqueous environment with small potential windows, that store energy at a higher density than carbon materials alone. We describe the different approaches explored to overcome the challenges of non-uniform deposition, poor wetting and array collapse. Materials that are electrochemically anchored to VACNT supports include NiCo2O4, VOx, Fe2O3 and Co-Mn mixed oxides. In each case, the specific capacitance obtained using the VACNT arrays as supports is significantly more than that obtained by direct deposition onto current collectors or by using VACNT alone. The ease of VACNT growth and the degree of coating control achievable using electrodeposition means there is much potential in exploring them as supports for capacitive electrode materials.

Zinc oxide nanowire-poly(methyl methacrylate) dielectric layers for polymer capacitive pressure sensors.

Science.gov (United States)

Chen, Yan-Sheng; Hsieh, Gen-Wen; Chen, Shih-Ping; Tseng, Pin-Yen; Wang, Cheng-Wei

2015-01-14

Polymer capacitive pressure sensors based on a dielectric composite layer of zinc oxide nanowire and poly(methyl methacrylate) show pressure sensitivity in the range of 2.63 × 10(-3) to 9.95 × 10(-3) cm(2) gf(-1). This represents an increase of capacitance change by as much as a factor of 23 over pristine polymer devices. An ultralight load of only 10 mg (corresponding to an applied pressure of ∼0.01 gf cm(-2)) can be clearly recognized, demonstrating remarkable characteristics of these nanowire-polymer capacitive pressure sensors. In addition, optical transmittance of the dielectric composite layer is approximately 90% in the visible wavelength region. Their low processing temperature, transparency, and flexible dielectric film makes them a highly promising means for flexible touching and pressure-sensing applications.

Novel designs for application specific MEMS pressure sensors.

Science.gov (United States)

Fragiacomo, Giulio; Reck, Kasper; Lorenzen, Lasse; Thomsen, Erik V

2010-01-01

In the framework of developing innovative microfabricated pressure sensors, we present here three designs based on different readout principles, each one tailored for a specific application. A touch mode capacitive pressure sensor with high sensitivity (14 pF/bar), low temperature dependence and high capacitive output signal (more than 100 pF) is depicted. An optical pressure sensor intrinsically immune to electromagnetic interference, with large pressure range (0-350 bar) and a sensitivity of 1 pm/bar is presented. Finally, a resonating wireless pressure sensor power source free with a sensitivity of 650 KHz/mmHg is described. These sensors will be related with their applications in harsh environment, distributed systems and medical environment, respectively. For many aspects, commercially available sensors, which in vast majority are piezoresistive, are not suited for the applications proposed.

Trade-off between quantum capacitance and thermodynamic stability of defected graphene: an implication for supercapacitor electrodes

Science.gov (United States)

Srivastava, Anurag; SanthiBhushan, Boddepalli

2018-03-01

Defects are inevitable most of the times either at the synthesis, handling or processing stage of graphene, causes significant deviation of properties. The present work discusses the influence of vacancy defects on the quantum capacitance as well as thermodynamic stability of graphene, and the nitrogen doping pattern needs to be followed to attain a trade-off between these two. Density Functional Theory (DFT) calculations have been performed to analyze various vacancy defects and different possible nitrogen doping patterns at the vacancy site of graphene, with an implication for supercapacitor electrodes. The results signify that vacancy defect improves the quantum capacitance of graphene at the cost of thermodynamic stability, while the nitrogen functionalization at the vacancy improves thermodynamic stability and quantum capacitance both. It has been observed that functionalizing all the dangling carbons at the defect site with nitrogen is the key to attain high thermodynamic stability as well as quantum capacitance. Furthermore, the results signify the suitability of these functionalized graphenes for anode electrode of high energy density asymmetric supercapacitors.

Porous carbon spheres via microwave-assisted synthesis for capacitive deionization

International Nuclear Information System (INIS)

Liu, Yong; Pan, Likun; Chen, Taiqiang; Xu, Xingtao; Lu, Ting; Sun, Zhuo; Chua, Daniel H.C.

2015-01-01

Highlights: • Porous carbon spheres were fabricated through a fast microwave-assisted approach. • The capacitive deionization performance of Porous carbon spheres was studied. • Porous carbon spheres exhibit a high NaCl removal with good regeneration ability. - Abstract: Porous carbon spheres (PCSs) were fabricated through a fast microwave-assisted approach using sucrose as the precursor in a microwave system and subsequent thermal treatment at 600, 800 and 1000 °C. The morphology, structure and electrochemical performance of the PCSs were characterized by scanning electron microscopy, Raman spectroscopy, nitrogen adsorption-desorption, cyclic voltammetry and electrochemical impedance spectroscopy. Their electrosorption performance in NaCl solution was studied and compared with activated carbon, carbon nanotubes, reduced graphene and carbon aerogels. The results show that due to their high specific surface area and low charge transfer resistance, PCSs treated at 1000 °C exhibit high electrosorption capacity of 5.81 m g g −1 when the initial solution concentration is 500 mg l −1 , which is higher than those of other carbon materials

Preparatory research for development of a capacitance sensor monitoring the liquid fraction in an inclined pipe

International Nuclear Information System (INIS)

Ko, Min Seok; Lee, Bo An; Kim, Sin; Yun, Byong Jo

2012-01-01

Two phase flow is a highly general phenomenon in various engineering fields including thermal hydraulic systems of the nuclear power plant. In particular, the liquid fraction in two phase system is one of the most important parameters to be considered for efficient system design and analysis. There have been various methods for the liquid fraction measurement. Wojtan et al. employed an optical fiber for liquid fraction measurement. Elbow and Rezkallah adopted the capacitance signal, Tsochatzidis et al. and Fossa used the conductance response in order to monitor the liquid fraction in various two phase flow regimes. The electrical methods are based on the fact that the liquid and gas have different conductivity and permittivity values, and these electrical properties directly correspond to phase distributions. In the capacitance method, in particular, one or more pairs of electrodes attached inside or outside the pipe wall measure the capacitance between electrode pairs and this measured capacitance signal is directly converted to the liquid fraction. In this work, as a preparatory research for development of a capacitance sensor monitoring the liquid fraction in an inclined pipe whose diameter and inclination angle are 45mm and 3rad, respectively, a capacitance is designed. Also, data evaluation procedures of a wire mesh sensor which would be employed for the verification of capacitance sensor performance are verified by comparing static experiments

Carrier accumulation and depletion in point-contact capacitance-voltage measurements

Science.gov (United States)

Naitou, Yuichi

2017-11-01

Scanning capacitance microscopy (SCM) is a variation of atomic force microscopy in which a conductive probe tip detects the bias modulated capacitance for the purpose of measuring the nanoscale semiconductor carrier concentration. SCM can be regarded as a point-contact capacitance-voltage system, and its capacitance-voltage properties are different from those of a conventional parallel-plate capacitor. In this study, the charge accumulation and depletion behavior of a semiconductor sample were closely investigated by SCM. By analyzing the tip-sample approach curve, the effective probe tip area and charge depletion depth could be quantitatively determined.

Capacitance-based frequency adjustment of micro piezoelectric vibration generator.

Science.gov (United States)

Mao, Xinhua; He, Qing; Li, Hong; Chu, Dongliang

2014-01-01

Micro piezoelectric vibration generator has a wide application in the field of microelectronics. Its natural frequency is unchanged after being manufactured. However, resonance cannot occur when the natural frequencies of a piezoelectric generator and the source of vibration frequency are not consistent. Output voltage of the piezoelectric generator will sharply decline. It cannot normally supply power for electronic devices. In order to make the natural frequency of the generator approach the frequency of vibration source, the capacitance FM technology is adopted in this paper. Different capacitance FM schemes are designed by different locations of the adjustment layer. The corresponding capacitance FM models have been established. Characteristic and effect of the capacitance FM have been simulated by the FM model. Experimental results show that the natural frequency of the generator could vary from 46.5 Hz to 42.4 Hz when the bypass capacitance value increases from 0 nF to 30 nF. The natural frequency of a piezoelectric vibration generator could be continuously adjusted by this method.

Capacitance-Based Frequency Adjustment of Micro Piezoelectric Vibration Generator

Directory of Open Access Journals (Sweden)

Xinhua Mao

2014-01-01

Full Text Available Micro piezoelectric vibration generator has a wide application in the field of microelectronics. Its natural frequency is unchanged after being manufactured. However, resonance cannot occur when the natural frequencies of a piezoelectric generator and the source of vibration frequency are not consistent. Output voltage of the piezoelectric generator will sharply decline. It cannot normally supply power for electronic devices. In order to make the natural frequency of the generator approach the frequency of vibration source, the capacitance FM technology is adopted in this paper. Different capacitance FM schemes are designed by different locations of the adjustment layer. The corresponding capacitance FM models have been established. Characteristic and effect of the capacitance FM have been simulated by the FM model. Experimental results show that the natural frequency of the generator could vary from 46.5 Hz to 42.4 Hz when the bypass capacitance value increases from 0 nF to 30 nF. The natural frequency of a piezoelectric vibration generator could be continuously adjusted by this method.

Exponential model normalization for electrical capacitance tomography with external electrodes under gap permittivity conditions

International Nuclear Information System (INIS)

Baidillah, Marlin R; Takei, Masahiro

2017-01-01

A nonlinear normalization model which is called exponential model for electrical capacitance tomography (ECT) with external electrodes under gap permittivity conditions has been developed. The exponential model normalization is proposed based on the inherently nonlinear relationship characteristic between the mixture permittivity and the measured capacitance due to the gap permittivity of inner wall. The parameters of exponential equation are derived by using an exponential fitting curve based on the simulation and a scaling function is added to adjust the experiment system condition. The exponential model normalization was applied to two dimensional low and high contrast dielectric distribution phantoms by using simulation and experimental studies. The proposed normalization model has been compared with other normalization models i.e. Parallel, Series, Maxwell and Böttcher models. Based on the comparison of image reconstruction results, the exponential model is reliable to predict the nonlinear normalization of measured capacitance in term of low and high contrast dielectric distribution. (paper)

Measurements of time average series resonance effect in capacitively coupled radio frequency discharge plasma

International Nuclear Information System (INIS)

Bora, B.; Bhuyan, H.; Favre, M.; Wyndham, E.; Chuaqui, H.; Kakati, M.

2011-01-01

Self-excited plasma series resonance is observed in low pressure capacitvely coupled radio frequency discharges as high-frequency oscillations superimposed on the normal radio frequency current. This high-frequency contribution to the radio frequency current is generated by a series resonance between the capacitive sheath and the inductive and resistive bulk plasma. In this report, we present an experimental method to measure the plasma series resonance in a capacitively coupled radio frequency argon plasma by modifying the homogeneous discharge model. The homogeneous discharge model is modified by introducing a correction factor to the plasma resistance. Plasma parameters are also calculated by considering the plasma series resonances effect. Experimental measurements show that the self-excitation of the plasma series resonance, which arises in capacitive discharge due to the nonlinear interaction of plasma bulk and sheath, significantly enhances both the Ohmic and stochastic heating. The experimentally measured total dissipation, which is the sum of the Ohmic and stochastic heating, is found to increase significantly with decreasing pressure.

Graphene/MnO{sub 2} hybrid nanosheets as high performance electrode materials for supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Mondal, Anjon Kumar, E-mail: Anjon.K.Mondal@student.uts.edu.au [Centre for Clean Energy Technology, School of Chemistry and Forensic Science, University of Technology, Sydney, Broadway, Sydney, NSW 2007 (Australia); Wang, Bei; Su, Dawei; Wang, Ying; Chen, Shuangqiang [Centre for Clean Energy Technology, School of Chemistry and Forensic Science, University of Technology, Sydney, Broadway, Sydney, NSW 2007 (Australia); Zhang, Xiaogang [College of Materials Science and Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing (China); Wang, Guoxiu, E-mail: Guoxiu.wang@uts.edu.au [Centre for Clean Energy Technology, School of Chemistry and Forensic Science, University of Technology, Sydney, Broadway, Sydney, NSW 2007 (Australia)

2014-01-15

Graphene/MnO{sub 2} hybrid nanosheets were prepared by incorporating graphene and MnO{sub 2} nanosheets in ethylene glycol. Scanning electron microscopy and transmission electron microscopy analyses confirmed nanosheet morphology of the hybrid materials. Graphene/MnO{sub 2} hybrid nanosheets with different ratios were investigated as electrode materials for supercapacitors by cyclic voltammetry (CV) and galvanostatic charge–discharge in 1 M Na{sub 2}SO{sub 4} electrolyte. We found that the graphene/MnO{sub 2} hybrid nanosheets with a weight ratio of 1:4 (graphene:MnO{sub 2}) delivered the highest specific capacitance of 320 F g{sup −1}. Graphene/MnO{sub 2} hybrid nanosheets also exhibited good capacitance retention on 2000 cycles. - Highlights: • Graphene/MnO{sub 2} hybrid nanosheets with different ratios were fabricated. • The specific capacitance is strongly dependent on graphene/MnO{sub 2} ratios. • The graphene/MnO{sub 2} hybrid electrode (1:4) exhibited high specific capacitance. • The electrode retained 84% of the initial specific capacitance after 2000 cycles.

Solving the Capacitive Effect in the High-Frequency sweep for Langmuir Probe in SYMPLE

International Nuclear Information System (INIS)

Pramila; Patel, J J; Rajpal, R; Hansalia, C J; Anitha, V P; Sathyanarayana, K

2017-01-01

Langmuir Probe based measurements need to be routinely carried out to measure various plasma parameters such as the electron density (n e ), the electron temperature (T e ), the floating potential (V f ), and the plasma potential (V p ). For this, the diagnostic electronics along with the biasing power supplies is installed in standard industrial racks with a 2KV isolation transformer. The Signal Conditioning Electronics (SCE) system is populated inside the 4U-chassis based system with the front-end electronics, designed using high common mode differential amplifiers which can measure small differential signal in presence of high common mode dc- bias or ac ramp voltage used for biasing the probes. DC-biasing of the probe is most common method for getting its I-V characteristic but method of biasing the probe with a sweep at high frequency encounters the problem of corruption of signal due to capacitive effect specially when the sweep period and the discharge time is very fast and die down in the order of μs or lesser. This paper presents and summarises the method of removing such effects encountered while measuring the probe current. (paper)

Solving the Capacitive Effect in the High-Frequency sweep for Langmuir Probe in SYMPLE

Science.gov (United States)

Pramila; Patel, J. J.; Rajpal, R.; Hansalia, C. J.; Anitha, V. P.; Sathyanarayana, K.

2017-04-01

Langmuir Probe based measurements need to be routinely carried out to measure various plasma parameters such as the electron density (ne), the electron temperature (Te), the floating potential (Vf), and the plasma potential (Vp). For this, the diagnostic electronics along with the biasing power supplies is installed in standard industrial racks with a 2KV isolation transformer. The Signal Conditioning Electronics (SCE) system is populated inside the 4U-chassis based system with the front-end electronics, designed using high common mode differential amplifiers which can measure small differential signal in presence of high common mode dc- bias or ac ramp voltage used for biasing the probes. DC-biasing of the probe is most common method for getting its I-V characteristic but method of biasing the probe with a sweep at high frequency encounters the problem of corruption of signal due to capacitive effect specially when the sweep period and the discharge time is very fast and die down in the order of μs or lesser. This paper presents and summarises the method of removing such effects encountered while measuring the probe current.

Porous hollow Co₃O₄ with rhombic dodecahedral structures for high-performance supercapacitors.

Science.gov (United States)

Zhang, Yi-Zhou; Wang, Yang; Xie, Ye-Lei; Cheng, Tao; Lai, Wen-Yong; Pang, Huan; Huang, Wei

2014-11-06

Porous hollow Co₃O₄ with rhombic dodecahedral structures were prepared by the calcination of ZIF-67 ([Co(mim)2; mim = 2-methylimidazolate]) rhombic dodecahedral microcrystals. A supercapacitor was successfully constructed by adopting the resulting porous hollow Co₃O₄ rhombic dodecahedral structure as the electrode material, which showed a large specific capacitance of 1100 F g(-1) and retained more than 95.1% of the specific capacitance after 6000 continuous charge-discharge cycles. The excellent capacitive properties and stability mark the porous hollow Co₃O₄ with the rhombic dodecahedral structure as one of the most promising electrode materials for high-performance supercapacitors.

Dopant density from maximum-minimum capacitance ratio of implanted MOS structures

International Nuclear Information System (INIS)

Brews, J.R.

1982-01-01

For uniformly doped structures, the ratio of the maximum to the minimum high frequency capacitance determines the dopant ion density per unit volume. Here it is shown that for implanted structures this 'max-min' dopant density estimate depends upon the dose and depth of the implant through the first moment of the depleted portion of the implant. A a result, the 'max-min' estimate of dopant ion density reflects neither the surface dopant density nor the average of the dopant density over the depletion layer. In particular, it is not clear how this dopant ion density estimate is related to the flatband capacitance. (author)

The Comparative Study of Electrochemical Capacitance Performance between Sulphur-Doped Co3O4 and CoS Anodes

Directory of Open Access Journals (Sweden)

Wei Xu

2016-01-01

Full Text Available Anode materials with high capacitance performance are highly desirable for supercapacitors (SCs. In this work, nanomaterials cobalt sulfide (CoS, sulphur-doped Co3O4 (S-Co3O4, and Co3O4 were fabricated on a carbon cloth substrate by hydrothermal method. The composition and morphology of the material were characterized by X-ray diffraction (XRD patterns and Scanning Electron Microscope (SEM. The electrochemical measurements were performed in a three-electrode system. The result shows that CoS nanomaterial as anode is of the best electrochemical performance, achieving areal capacitance of 1.98 F/cm2 at 2 mA/cm2 in a 5 M LiCl solution. Moreover, the CoS anode has long-term cycling stability with more than 85.7% capacitance retention after 10000 cycles, confirming its larger capacitance, good redox activity, and electrochemical stability.

Modelling and design of a capacitive touch sensor for urinary tract infection detection at the point-of-care.

Science.gov (United States)

Barbosa, Cátia; Dong, Tao

2014-01-01

Due to great use of touchscreens in mobile telephones and other electronic devices, there has been great evolution in this technology. Its wide applicability makes the touch sensor technology suitable for detection of specific components in urine, responsible for urinary tract infection (UTI). Integration of a touch sensor in a disposable probe tip to be used in UTI detection represents a powerful tool to develop new point-of-care testing (POCT) devices. The simplified structure of an electrodes array touch screen was simulated using the software COMSOL Multiphysics to prove that capacitive based touch screens can be used for detection of UTI. Besides we assumed presence of E.coli, one of the major causes of UTI urine. Results show that global capacitance increases if an E.coli sphere is present near the active electrodes, remaining approximately constant when further apart electrodes are excited. The output simulated voltage varies according to the capacitance value, decreasing when the capacitance is increased.

Electrochemical capacitance characteristics of patterned ruthenium dioxide-carbon nanotube nanocomposites grown onto graphene

Energy Technology Data Exchange (ETDEWEB)

Shih, Yi-Ting [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Lee, Kuei-Yi, E-mail: kylee@mail.ntust.edu.tw [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Department of Electronic Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Huang, Ying-Sheng [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Department of Electronic Engineering, National Taiwan University of Science and Technology, No. 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China)

2014-03-01

Highlights: • Graphene was grown on Cu foil by mobile thermal chemical vapor deposition system. • CNT was synthesized on graphene for RuO{sub 2} nanostructure growth by thermal chemical vapor deposition system. • The CNT growth location was fixed through the use of photolithography technique, thereby increasing the specific area. • RuO{sub 2} nanostructures were coated onto CNT bundle arrays through metal organic chemical vapor deposition, in order to utilize its pseudo capacitive property. - Abstract: In this study, graphene was used as a conductive substrate for vertically aligned carbon nanotube (CNT) bundle arrays growth, to be used as an electrode for electrochemical double layer capacitor (EDLC), as graphene and CNT exhibit good conductivity and excellent chemical stability. Both of them are composed of carbon, therefore making a superior adhesion between them. The configuration of bundle arrays provided a relatively higher specific surface area in contact with electrolyte, thereby resulting in demonstratively higher capacitance. Moreover, as the RuO{sub 2} nanostructures have good pseudocapacitance characteristics, they were coated onto vertically aligned CNT bundle arrays in order to effectively enhance the EDLC performances. The characteristics of CNT/graphene, CNT bundle/graphene, and RuO{sub 2}/CNT bundle/graphene electrodes were examined with the use of scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. Furthermore, their electrochemical properties were investigated by an electrochemical analyzer. The specific capacitances of CNT/graphene, CNT bundle/graphene, and RuO{sub 2}/CNT bundle/graphene were 4.64, 6.65, and 128.40 F/g at the scan rate of 0.01 V/s, respectively.

A comparison of the microstructures and electrochemical capacitive properties of 2 graphenes prepared by arc discharge method and chemical method

Energy Technology Data Exchange (ETDEWEB)

Zhang, H.; Yang, Y. [Research Inst. of Chemical Defense, Beijing (China); Univ. of Science and Technology, Beijing (China); Cao, G.; Xu, B. [Research Inst. of Chemical Defense, Beijing (China)

2010-07-01

In this study, 2 kinds of graphene materials were prepared using both arc discharge and chemical methods. The pore structures and electrochemical capacitive properties of the materials were investigated. A mesopore structure was obtained for the graphene prepared using the arc discharge method, with a capacitance of 12.9 F/g and a high rate capability when used in electrochemical applications. The graphene prepared with the chemical method demonstrated a more highly developed micropore structure and capacitances greater than 70 F/g. However, rate performance for the graphene was normal. 2 figs.

Biopolymer-nanocarbon composite electrodes for use as high-energy high-power density electrodes

Science.gov (United States)

Karakaya, Mehmet; Roberts, Mark; Arcilla-Velez, Margarita; Zhu, Jingyi; Podila, Ramakrishna; Rao, Apparao

2014-03-01

Supercapacitors (SCs) address our current energy storage and delivery needs by combining the high power, rapid switching, and exceptional cycle life of a capacitor with the high energy density of a battery. Although activated carbon is extensively used as a supercapacitor electrode due to its inexpensive nature, its low specific capacitance (100-120 F/g) fundamentally limits the energy density of SCs. We demonstrate that a nano-carbon based mechanically robust, electrically conducting, free-standing buckypaper electrode modified with an inexpensive biorenewable polymer, viz., lignin increases the electrode's specific capacitance (~ 600-700 F/g) while maintaining rapid discharge rates. In these systems, the carbon nanomaterials provide the high surface area, electrical conductivity and porosity, while the redox polymers provide a mechanism for charge storage through Faradaic charge transfer. The design of redox polymers and their incorporation into nanomaterial electrodes will be discussed with a focus on enabling high power and high energy density electrodes. Research supported by US NSF CMMI Grant 1246800.

The capacitated team orienteering problem with incomplete service

NARCIS (Netherlands)

Archetti, Claudia; Bianchessi, Nicola; Speranza, M. Grazia

2013-01-01

In this paper we study the capacitated version of the Team Orienteering Problem (TOP), that is the Capacitated TOP (CTOP) and the impact of relaxing the assumption that a customer, if served, must be completely served. We prove that the profit collected by the CTOP with Incomplete Service (CTOP-IS)

Highly-wrinkled reduced graphene oxide-conductive polymer fibers for flexible fiber-shaped and interdigital-designed supercapacitors

Science.gov (United States)

Li, Bo; Cheng, Jianli; Wang, Zhuanpei; Li, Yinchuan; Ni, Wei; Wang, Bin

2018-02-01

Flexible supercapacitors have attracted great interest due to outstanding flexibility and light weight. Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) fibers have the great potential in using as electrodes for flexible supercapacitors due to the good flexibility. However, the reported conductivity and specific capacitance of these PEDOT: PSS fibers are not very high, which limit their electrochemical performances. In this work, composite fibers of reduced graphene oxide(rGO)-PEDOT: PSS with a highly-wrinkled structure on the surface and pores inside are prepared by wet spinning. The fibers with different ratios of graphene to PEDOT:PSS show a distinctly enhanced conductivity up to ca. 590 S·cm-1 and high strength up to ca. 18.4 MPa. Meanwhile, the composite fibers show an improved electrochemical performances, including a high specific areal capacitance of 131 mF cm-2 and high specific areal energy density of 4.55 μWh·cm-2. The flexible supercapacitors including fiber-shaped supercapacitors and interdigital designed supercapacitors not only could work in different bending states without obvious capacitance decay, but also have small leakage current. The interdigital design can further improve the performances of composite fibers with high capacitance and high utilization compared with traditional parallel connected structure.

Capacitance for carbon capture

International Nuclear Information System (INIS)

Landskron, Kai

2018-01-01

Metal recycling: A sustainable, capacitance-assisted carbon capture and sequestration method (Supercapacitive Swing Adsorption) can turn scrap metal and CO 2 into metal carbonates at an attractive energy cost. (copyright 2018 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Three-dimensional skeleton networks of graphene wrapped polyaniline nanofibers: an excellent structure for high-performance flexible solid-state supercapacitors

Science.gov (United States)

Hu, Nantao; Zhang, Liling; Yang, Chao; Zhao, Jian; Yang, Zhi; Wei, Hao; Liao, Hanbin; Feng, Zhenxing; Fisher, Adrian; Zhang, Yafei; Xu, Zhichuan J.

2016-01-01

Thin, robust, lightweight, and flexible supercapacitors (SCs) have aroused growing attentions nowadays due to the rapid development of flexible electronics. Graphene-polyaniline (PANI) hybrids are attractive candidates for high performance SCs. In order to utilize them in real devices, it is necessary to improve the capacitance and the structure stability of PANI. Here we report a hierarchical three-dimensional structure, in which all of PANI nanofibers (NFs) are tightly wrapped inside reduced graphene oxide (rGO) nanosheet skeletons, for high-performance flexible SCs. The as-fabricated film electrodes with this unique structure showed a highest gravimetric specific capacitance of 921 F/g and volumetric capacitance of 391 F/cm3. The assembled solid-state SCs gave a high specific capacitance of 211 F/g (1 A/g), a high area capacitance of 0.9 F/cm2, and a competitive volumetric capacitance of 25.6 F/cm3. The SCs also exhibited outstanding rate capability (~75% retention at 20 A/g) as well as excellent cycling stability (100% retention at 10 A/g for 2000 cycles). Additionally, no structural failure and loss of performance were observed under the bending state. This structure design paves a new avenue for engineering rGO/PANI or other similar hybrids for high performance flexible energy storage devices. PMID:26795067

Automatic Power Factor Correction Using Capacitive Bank

OpenAIRE

Mr.Anant Kumar Tiwari,; Mrs. Durga Sharma

2014-01-01

The power factor correction of electrical loads is a problem common to all industrial companies. Earlier the power factor correction was done by adjusting the capacitive bank manually [1]. The automated power factor corrector (APFC) using capacitive load bank is helpful in providing the power factor correction. Proposed automated project involves measuring the power factor value from the load using microcontroller. The design of this auto-adjustable power factor correction is ...

Plasma Treated Active Carbon for Capacitive Deionization of Saline Water

Directory of Open Access Journals (Sweden)

Aiping Zeng

2017-01-01

Full Text Available The plasma treatment on commercial active carbon (AC was carried out in a capacitively coupled plasma system using Ar + 10% O2 at pressure of 4.0 Torr. The RF plasma power ranged from 50 W to 100 W and the processing time was 10 min. The carbon film electrode was fabricated by electrophoretic deposition. Micro-Raman spectroscopy revealed the highly increased disorder of sp2 C lattice for the AC treated at 75 W. An electrosorption capacity of 6.15 mg/g was recorded for the carbon treated at 75 W in a 0.1 mM NaCl solution when 1.5 V was applied for 5 hours, while the capacity of the untreated AC was 1.01 mg/g. The plasma treatment led to 5.09 times increase in the absorption capacity. The jump of electrosorption capacity by plasma treatment was consistent with the Raman spectra and electrochemical double layer capacitance. This work demonstrated that plasma treatment was a potentially efficient approach to activating biochar to serve as electrode material for capacitive deionization (CDI.

Electrostatic capacitance and Faraday cage behavior of carbon nanotube forests

Energy Technology Data Exchange (ETDEWEB)

Ya' akobovitz, A. [Mechanosynthesis Group, Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States); Department of Mechanical Engineering, Faculty of Engineering Sciences, Ben-Gurion University, Beer-Sheva (Israel); Bedewy, M. [Mechanosynthesis Group, Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States); Hart, A. J. [Mechanosynthesis Group, Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109 (United States); Department of Mechanical Engineering and Laboratory for Manufacturing and Productivity, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2015-02-02

Understanding of the electrostatic properties of carbon nanotube (CNT) forests is essential to enable their integration in microelectronic and micromechanical devices. In this study, we sought to understand how the hierarchical geometry and morphology of CNT forests determines their capacitance. First, we find that at small gaps, solid micropillars have greater capacitance, yet at larger gaps the capacitance of the CNT forests is greater. The surface area of the CNT forest accessible to the electrostatic field was extracted by analysis of the measured capacitance, and, by relating the capacitance to the average density of CNTs in the forest, we find that the penetration depth of the electrostatic field is on the order of several microns. Therefore, CNT forests can behave as a miniature Faraday cage. The unique electrostatic properties of CNT forests could therefore enable their use as long-range proximity sensors and as shielding elements for miniature electronic devices.

Electrostatic capacitance and Faraday cage behavior of carbon nanotube forests

International Nuclear Information System (INIS)

Ya'akobovitz, A.; Bedewy, M.; Hart, A. J.

2015-01-01

Understanding of the electrostatic properties of carbon nanotube (CNT) forests is essential to enable their integration in microelectronic and micromechanical devices. In this study, we sought to understand how the hierarchical geometry and morphology of CNT forests determines their capacitance. First, we find that at small gaps, solid micropillars have greater capacitance, yet at larger gaps the capacitance of the CNT forests is greater. The surface area of the CNT forest accessible to the electrostatic field was extracted by analysis of the measured capacitance, and, by relating the capacitance to the average density of CNTs in the forest, we find that the penetration depth of the electrostatic field is on the order of several microns. Therefore, CNT forests can behave as a miniature Faraday cage. The unique electrostatic properties of CNT forests could therefore enable their use as long-range proximity sensors and as shielding elements for miniature electronic devices

Electrostatic capacitance and Faraday cage behavior of carbon nanotube forests

Science.gov (United States)

Ya'akobovitz, A.; Bedewy, M.; Hart, A. J.

2015-02-01

Understanding of the electrostatic properties of carbon nanotube (CNT) forests is essential to enable their integration in microelectronic and micromechanical devices. In this study, we sought to understand how the hierarchical geometry and morphology of CNT forests determines their capacitance. First, we find that at small gaps, solid micropillars have greater capacitance, yet at larger gaps the capacitance of the CNT forests is greater. The surface area of the CNT forest accessible to the electrostatic field was extracted by analysis of the measured capacitance, and, by relating the capacitance to the average density of CNTs in the forest, we find that the penetration depth of the electrostatic field is on the order of several microns. Therefore, CNT forests can behave as a miniature Faraday cage. The unique electrostatic properties of CNT forests could therefore enable their use as long-range proximity sensors and as shielding elements for miniature electronic devices.

EFFECT OF DIESEL CONTAMINATION ON CAPACITANCE VALUES OF CRUDE PALM OIL

Directory of Open Access Journals (Sweden)

C. H. FIZURA

2014-06-01

Full Text Available Measurement of crude palm oil (CPO contamination is a major concern in CPO quality monitoring. In this study, capacitive sensing technique was used to monitor diesel contamination levels in CPO. A low cost capacitive sensing system was developed by using AD7746 capacitance to digital converter. The capacitance value of CPO samples with different contamination levels (v/v% ranged from 0% to 50% was collected at a room temperature (25°C. The objective of this study is to find a relationship between capacitance values and diesel contamination levels in CPO. The results showed that capacitance value decreased as the diesel contamination levels increased. For the 0% to 50% contamination range, the regression equation was y = 0.0002x2 - 0.0125x + 0.936 with R2 value of 0.96. For the 0% to 10% contamination range (where the percentage was the representative of potential contaminations levels found in CPO the correlation equation was y = -0.02x + 0.95 with R2 value of 0.95. These results indicated that capacitive sensing technique has potential for CPO quality monitoring.

Easy fabrication and high electrochemical capacitive performance of hierarchical porous carbon by a method combining liquid-liquid phase separation and pyrolysis process

International Nuclear Information System (INIS)

Fan, Hui-li; Ran, Fen; Zhang, Xuan-xuan; Song, Hai-ming; Jing, Wen-xia; Shen, Kui-wen; Kong, Ling-bin; Kang, Long

2014-01-01

A hierarchical porous carbon membrane was designed and prepared through a method combining liquid-liquid phase separation and then pyrolysis process using polyacrylonitrile (PAN) as precursor. The results of scan electron microscopy, transmission electron microscope and Brunauer-Emmett-Teller characterization reveal that the 3D nanoscaled architecture with hierarchical porous structure was achieved, which not only provide a continuous electron pathway to ensure good electrical contact, but also facilitate ion transport by shortening diffusion pathways. The effect of PAN concentration in casting solution on structure feature of carbon membrane was also studied, indicating that the membrane thickness with different porous structure can be mediated by PAN concentration. As the electrode material for supercapacitor, a high specific capacitance of 277.0 F g −1 was attained at a current density of 5 mA cm −2 and long cycle life of 90.0% capacity retention was obtained after 2000 charge-discharge cycles in 2 mol L −1 KOH solution

Preparation of the Lentinus edodes-based porous biomass carbon by hydrothermal method for capacitive desalination

Science.gov (United States)

Yan, Junbin; Zhang, Hexuan; Xie, Zhengzheng; Liu, Jianyun

2017-08-01

Biomass carbon materials were prepared by hydrothermal method using Lentinus edodes, followed by activation by ZnCl2 at high carbonization temperature. SEM and contact angle test show that ZnCl2 has a significant effect on the surface morphology and properties of porous carbon materials. Using the porous carbon as electrodes of the capacitor, the specific capacitance of the porous carbon material was found to be 247.6 F/g. The desalination amount of porous carbon material in capacitor cell was 12.9 mg/g, being the 1.9 times of that of the commercial activated carbon.

High-performance Supercapacitors Based on Electrochemical-induced Vertical-aligned Carbon Nanotubes and Polyaniline Nanocomposite Electrodes

Science.gov (United States)

Wu, Guan; Tan, Pengfeng; Wang, Dongxing; Li, Zhe; Peng, Lu; Hu, Ying; Wang, Caifeng; Zhu, Wei; Chen, Su; Chen, Wei

2017-03-01

Supercapacitors, which store electrical energy through reversible ion on the surface of conductive electrodes have gained enormous attention for variously portable energy storage devices. Since the capacitive performance is mainly determined by the structural and electrochemical properties of electrodes, the electrodes become more crucial to higher performance. However, due to the disordered microstructure and low electrochemical activity of electrode for ion tortuous migration and accumulation, the supercapacitors present relatively low capacitance and energy density. Here we report a high-performance supercapacitor based on polyaniline/vertical-aligned carbon nanotubes (PANI/VA-CNTs) nanocomposite electrodes where the vertical-aligned-structure is formed by the electrochemical-induction (0.75 V). The supercapacitor displays large specific capacitance of 403.3 F g-1, which is 6 times higher than disordered CNTs in HClO4 electrolyte. Additionally, the supercapacitor can also present high specific capacitance (314.6 F g-1), excellent cycling stability (90.2% retention after 3000 cycles at 4 A g-1) and high energy density (98.1 Wh kg-1) in EMIBF4 organic electrolyte. The key to high-performance lies in the vertical-aligned-structure providing direct path channel for ion faster diffusion and high electrochemical capacitance of polyaniline for ion more accommodation.

High-performance Supercapacitors Based on Electrochemical-induced Vertical-aligned Carbon Nanotubes and Polyaniline Nanocomposite Electrodes.

Science.gov (United States)

Wu, Guan; Tan, Pengfeng; Wang, Dongxing; Li, Zhe; Peng, Lu; Hu, Ying; Wang, Caifeng; Zhu, Wei; Chen, Su; Chen, Wei

2017-03-08

Supercapacitors, which store electrical energy through reversible ion on the surface of conductive electrodes have gained enormous attention for variously portable energy storage devices. Since the capacitive performance is mainly determined by the structural and electrochemical properties of electrodes, the electrodes become more crucial to higher performance. However, due to the disordered microstructure and low electrochemical activity of electrode for ion tortuous migration and accumulation, the supercapacitors present relatively low capacitance and energy density. Here we report a high-performance supercapacitor based on polyaniline/vertical-aligned carbon nanotubes (PANI/VA-CNTs) nanocomposite electrodes where the vertical-aligned-structure is formed by the electrochemical-induction (0.75 V). The supercapacitor displays large specific capacitance of 403.3 F g -1 , which is 6 times higher than disordered CNTs in HClO 4 electrolyte. Additionally, the supercapacitor can also present high specific capacitance (314.6 F g -1 ), excellent cycling stability (90.2% retention after 3000 cycles at 4 A g -1 ) and high energy density (98.1 Wh kg -1 ) in EMIBF 4 organic electrolyte. The key to high-performance lies in the vertical-aligned-structure providing direct path channel for ion faster diffusion and high electrochemical capacitance of polyaniline for ion more accommodation.

Biasing of Capacitive Micromachined Ultrasonic Transducers.

Science.gov (United States)

Caliano, Giosue; Matrone, Giulia; Savoia, Alessandro Stuart

2017-02-01

Capacitive micromachined ultrasonic transducers (CMUTs) represent an effective alternative to piezoelectric transducers for medical ultrasound imaging applications. They are microelectromechanical devices fabricated using silicon micromachining techniques, developed in the last two decades in many laboratories. The interest for this novel transducer technology relies on its full compatibility with standard integrated circuit technology that makes it possible to integrate on the same chip the transducers and the electronics, thus enabling the realization of extremely low-cost and high-performance devices, including both 1-D or 2-D arrays. Being capacitive transducers, CMUTs require a high bias voltage to be properly operated in pulse-echo imaging applications. The typical bias supply residual ripple of high-quality high-voltage (HV) generators is in the millivolt range, which is comparable with the amplitude of the received echo signals, and it is particularly difficult to minimize. The aim of this paper is to analyze the classical CMUT biasing circuits, highlighting the features of each one, and to propose two novel HV generator architectures optimized for CMUT biasing applications. The first circuit proposed is an ultralow-residual ripple (generator that uses an extremely stable sinusoidal power oscillator topology. The second circuit employs a commercially available integrated step-up converter characterized by a particularly efficient switching topology. The circuit is used to bias the CMUT by charging a buffer capacitor synchronously with the pulsing sequence, thus reducing the impact of the switching noise on the received echo signals. The small area of the circuit (about 1.5 cm 2 ) makes it possible to generate the bias voltage inside the probe, very close to the CMUT, making the proposed solution attractive for portable applications. Measurements and experiments are shown to demonstrate the effectiveness of the new approaches presented.

Microwave-assisted ionothermal synthesis of nanostructured anatase titanium dioxide/activated carbon composite as electrode material for capacitive deionization

International Nuclear Information System (INIS)

Liu, Po-I; Chung, Li-Ching; Shao, Hsin; Liang, Teh-Ming; Horng, Ren-Yang; Ma, Chen-Chi M.; Chang, Min-Chao

2013-01-01

The nanostructured anatase titanium dioxide/activated carbon composite material for capacitive deionization electrode was prepared in a short time by a lower temperature two-step microwave-assisted ionothermal (sol–gel method in the presence of ionic liquid) synthesis method. This method includes a reaction and a crystallization step. In the crystallization step, the ionic liquid plays a hydrothermal analogy role in driving the surface anatase crystallization of amorphous titanium dioxide nanoparticles formed in the reaction step. The energy dispersive spectroscopic study of the composite indicates that the anatase titanium dioxide nanoparticles are evenly deposited in the matrix of activated carbon. The electrochemical property of the composite electrode was investigated. In comparison to the pristine activated carbon electrode, higher specific capacitance was observed for the nanostructured anatase titanium dioxide/activated carbon composite electrode, especially when the composite was prepared with a molar ratio of titanium tetraisopropoxide/H 2 O equal to 1:15. Its X-ray photoelectron spectroscopic result indicates that it has the highest amount of Ti-OH. The Ti-OH group can enhance the wetting ability and the specific capacitance of the composite electrode. The accompanying capacitive deionization result indicates that the decay of electrosorption capacity of this composite electrode is insignificant after five cycle tests. It means that the ion electrosorption–desorption becomes a reversible process

Analysis of a Segmented Annular Coplanar Capacitive Tilt Sensor with Increased Sensitivity

Directory of Open Access Journals (Sweden)

Jiahao Guo

2016-01-01

Full Text Available An investigation of a segmented annular coplanar capacitor is presented. We focus on its theoretical model, and a mathematical expression of the capacitance value is derived by solving a Laplace equation with Hankel transform. The finite element method is employed to verify the analytical result. Different control parameters are discussed, and each contribution to the capacitance value of the capacitor is obtained. On this basis, we analyze and optimize the structure parameters of a segmented coplanar capacitive tilt sensor, and three models with different positions of the electrode gap are fabricated and tested. The experimental result shows that the model (whose electrode-gap position is 10 mm from the electrode center realizes a high sensitivity: 0.129 pF/° with a non-linearity of <0.4% FS (full scale of ±40°. This finding offers plenty of opportunities for various measurement requirements in addition to achieving an optimized structure in practical design.

Changes in exposed membrane proteins during in vitro capacitation of boar sperm

International Nuclear Information System (INIS)

Berger, T.

1990-01-01

Exposed plasma membrane proteins were labeled with 125 I before and after incubation of boar sperm under capacitating conditions. Labeled protein profiles were compared to the ability of the sperm to penetrate zona-free hamster ova. Quantitatively, the labeled sperm membrane proteins were primarily low Mr prior to capacitation. The majority of the labeled seminal plasma protein was also low Mr. After capacitation, two new proteins (64,000 Mr and 78,000 Mr) were labeled. Sperm did not exhibit these exposed membrane proteins when incubated under noncapacitating conditions. Appearance of these proteins was not correlated to the percentage of acrosome-reacted sperm. Although the 64,000 Mr protein was not consistently observed, the relative labeling of the 78,000 Mr protein was highly correlated with the ability of sperm to fuse with zona-free hamster ova. The 78,000 Mr protein may be a sperm protein involved in fusion with the egg plasma membrane

Capacitive Micro Pressure Sensor Integrated with a Ring Oscillator Circuit on Chip

Directory of Open Access Journals (Sweden)

Cheng-Yang Liu

2009-12-01

Full Text Available The study investigates a capacitive micro pressure sensor integrated with a ring oscillator circuit on a chip. The integrated capacitive pressure sensor is fabricated using the commercial CMOS (complementary metal oxide semiconductor process and a post-process. The ring oscillator is employed to convert the capacitance of the pressure sensor into the frequency output. The pressure sensor consists of 16 sensing cells in parallel. Each sensing cell contains a top electrode and a lower electrode, and the top electrode is a sandwich membrane. The pressure sensor needs a post-CMOS process to release the membranes after completion of the CMOS process. The post-process uses etchants to etch the sacrificial layers, and to release the membranes. The advantages of the post-process include easy execution and low cost. Experimental results reveal that the pressure sensor has a high sensitivity of 7 Hz/Pa in the pressure range of 0–300 kPa.

Capacitance for carbon capture

Energy Technology Data Exchange (ETDEWEB)

Landskron, Kai [Department of Chemistry, Lehigh University, Bethlehem, PA (United States)

2018-03-26

Metal recycling: A sustainable, capacitance-assisted carbon capture and sequestration method (Supercapacitive Swing Adsorption) can turn scrap metal and CO{sub 2} into metal carbonates at an attractive energy cost. (copyright 2018 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Nanoscale capacitance imaging with attofarad resolution using ac current sensing atomic force microscopy

International Nuclear Information System (INIS)

Fumagalli, L; Ferrari, G; Sampietro, M; Casuso, I; MartInez, E; Samitier, J; Gomila, G

2006-01-01

Nanoscale capacitance imaging with attofarad resolution (∼1 aF) of a nano-structured oxide thin film, using ac current sensing atomic force microscopy, is reported. Capacitance images are shown to follow the topographic profile of the oxide closely, with nanometre vertical resolution. A comparison between experimental data and theoretical models shows that the capacitance variations observed in the measurements can be mainly associated with the capacitance probed by the tip apex and not with positional changes of stray capacitance contributions. Capacitance versus distance measurements further support this conclusion. The application of this technique to the characterization of samples with non-voltage-dependent capacitance, such as very thin dielectric films, self-assembled monolayers and biological membranes, can provide new insight into the dielectric properties at the nanoscale

Nanoscale capacitance imaging with attofarad resolution using ac current sensing atomic force microscopy

Energy Technology Data Exchange (ETDEWEB)

Fumagalli, L [Dipartimento di Elettronica e Informazione, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 (Italy); Ferrari, G [Dipartimento di Elettronica e Informazione, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 (Italy); Sampietro, M [Dipartimento di Elettronica e Informazione, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133 (Italy); Casuso, I [Departament d' Electronica, Universitat de Barcelona, C/MartIi Franques 1, 08028 Barcelona (Spain); MartInez, E [Plataforma de Nanotecnologia, Parc Cientific de Barcelona, C/ Josep Samitier 1-5, 08028-Barcelona (Spain); Samitier, J [Departament d' Electronica, Universitat de Barcelona, C/MartIi Franques 1, 08028 Barcelona (Spain); Gomila, G [Departament d' Electronica, Universitat de Barcelona, C/MartIi Franques 1, 08028 Barcelona (Spain)

2006-09-28

Nanoscale capacitance imaging with attofarad resolution ({approx}1 aF) of a nano-structured oxide thin film, using ac current sensing atomic force microscopy, is reported. Capacitance images are shown to follow the topographic profile of the oxide closely, with nanometre vertical resolution. A comparison between experimental data and theoretical models shows that the capacitance variations observed in the measurements can be mainly associated with the capacitance probed by the tip apex and not with positional changes of stray capacitance contributions. Capacitance versus distance measurements further support this conclusion. The application of this technique to the characterization of samples with non-voltage-dependent capacitance, such as very thin dielectric films, self-assembled monolayers and biological membranes, can provide new insight into the dielectric properties at the nanoscale.

Capacitance probe for detection of anomalies in non-metallic plastic pipe

Science.gov (United States)

Mathur, Mahendra P.; Spenik, James L.; Condon, Christopher M.; Anderson, Rodney; Driscoll, Daniel J.; Fincham, Jr., William L.; Monazam, Esmail R.

2010-11-23

The disclosure relates to analysis of materials using a capacitive sensor to detect anomalies through comparison of measured capacitances. The capacitive sensor is used in conjunction with a capacitance measurement device, a location device, and a processor in order to generate a capacitance versus location output which may be inspected for the detection and localization of anomalies within the material under test. The components may be carried as payload on an inspection vehicle which may traverse through a pipe interior, allowing evaluation of nonmetallic or plastic pipes when the piping exterior is not accessible. In an embodiment, supporting components are solid-state devices powered by a low voltage on-board power supply, providing for use in environments where voltage levels may be restricted.

Combined resonant tank capacitance and pulse frequency modulation control for ZCS-SR inverter-fed high voltage DC power supply

International Nuclear Information System (INIS)

Lee, S S; Iqbal, S; Kamarol, M

2011-01-01

Conventional pulse frequency modulated (PFM) zero current switching (ZCS) series resonant (SR) inverter fed high voltage dc power supplies have nearly zero switching loss. However, they have limitations of poor controllability at light loads and large output voltage ripple at low switching frequencies. To address these problems, this paper proposes a combined resonant tank capacitance and pulse frequency modulation based control approach. For the realization of the proposed control approach, the tank circuit of the resonant inverter is made up of several resonant capacitors that are switched into or out of the tank circuit by electromechanical switches. The output voltage of the converter is regulated by digitally modulating the resonant tank capacitance and narrowly varying the switching frequency. The proposed control scheme has several features, namely a wide range of controllability even at light loads, less output voltage ripple, and less current stress on the inverter's power switches at light loads. Therefore, the proposed control approach alleviates most of the problems associated with conventional PFM. Experimental results obtained from a scaled down laboratory prototype are presented to verify the effectiveness of the proposed system.

Influence of oxidation level on capacitance of electrochemical capacitors fabricated with carbon nanotube/carbon paper composites

International Nuclear Information System (INIS)

Hsieh, C.-T.; Chen, W.-Y.; Cheng, Y.-S.

2010-01-01

Gaseous oxidation of carbon papers (CPs) decorated with carbon nanotubes (CNTs) with varying degrees of oxidation was conducted to investigate the influence of surface oxides on the performance of electrochemical capacitors fabricated with oxidized CNT/CP composites. The oxidation period was found to significantly enhance the O/C atomic ratio on the composites, and the increase in oxygen content upon oxidation is mainly contributed by the formation of C=O and C-O groups. The electrochemical behavior of the capacitors was tested in 1 M H 2 SO 4 within a potential of 0 and 1 V vs. Ag/AgCl. Both superhydrophilicity and specific capacitance of the oxidized CNT/CP composites were found to increase upon oxidation treatment. A linearity increase of capacitance with O/C ratio can be attributed to the increase of the population of surface oxides on CNTs, which imparts excess sites for redox reaction (pseudocapacitance) and for the formation of double-layer (double-layer capacitance). The technique of ac impedance combined with equivalent circuit clearly showed that oxidized CNT/CP capacitor imparts not only enhanced capacitance but also a low equivalent series resistance.

High conductivity graphene-like MoS2/polyaniline nanocomposites and its application in supercapacitor

International Nuclear Information System (INIS)

Wang, Jin; Wu, Zongchao; Hu, Kunhong; Chen, Xiangying; Yin, Huabing

2015-01-01

Highlights: • A facile synthesis method of MoS 2 /PANI intercalated nanocomposites is developed. • There is synergistic effect between PANI and MoS 2 layer in the MoS 2 /PANI composites. • Intercalation is benefit for electrons transportation and conductivity increase. • The well-defined MoS 2 /PANI have good specific capacitances and long cyclic life. - Abstract: High conductivity nanocomposites of molybdenum disulfide (MoS 2 )/polyaniline (PANI) were prepared via direct intercalation of aniline monomer and doped with dodecyl benzene sulfonic acid (DBSA). The intercalated interaction between PANI and MoS 2 improves the conductivity and thermal stability of MoS 2 /PANI nanocomposites with the increasing fraction of MoS 2 . The conductivity and maximum weight loss velocity temperature of PANI/MoS 2 -38 sample are 2.38 S cm −1 and 353 °C, respectively. This architecture is also advantageous for enhancing the capacitance properties and cyclic stabilities of MoS 2 /PANI electrodes. In comparison to the specific capacitance of 131 F/g and 42% retained capacitance over 600 cycles of PANI electrode, the MoS 2 /PANI-38 electrode provides a specific capacitance up to 390 F/g and 86% retained capacitance over 1000 cycles. Thus it provides an improved capacitance method which synergistically combines pseudocapacitance and double-layer capacitance for supercapacitor electrodes

Low Power/Low Voltage Interface Circuitry for Capacitive Sensors

DEFF Research Database (Denmark)

Furst, Claus Efdmann

This thesis focuses mainly on low power/low voltage interface circuits, implemented in CMOS, for capacitive sensors. A brief discussion of demands and possibilities for analog signal processing in the future is presented. Techniques for low power design is presented. This is done by analyzing power...... power consumption. It is shown that the Sigma-Delta modulator is advantageous when embedded in a feedback loop with a mechanical sensor. Here a micro mechanical capacitive microphone. Feedback and detection circuitry for a capacitive microphone is presented. Practical implementations of low power....../low voltage interface circuitry is presented. It is demonstrated that an amplifier optimized for a capacitive microphone implemented in a standard 0.7 micron CMOS technology competes well with a traditional JFET amplifier. Furthermore a low power/low voltage 3rd order Sigma-Delta modulator is presented...

One-step electroplating porous graphene oxide electrodes of supercapacitors for ultrahigh capacitance and energy density.

Science.gov (United States)

Wang, Yongjie; Zhu, Jiaqi

2015-02-06

An electroplating method was used for the first time to synthesize 3D porous graphene oxide (PGO) architectures, exhibiting ultrahigh capacitance and energy density as electrodes of supercapacitors. Scanning electron microscopy illustrated the porous structures which promoted the stability and alleviated the stacking of the graphene oxide layers. As investigated in a three-electrode supercapacitor cell, PGO electrodes exhibited the maximum capacitance and energy of 973 F · g(-1) and 98.4 Wh · Kg(-1), which are better than current reports and comparable to batteries. At 4 A · g(-1) for high-power applications, PGO electrodes reached a capacitance, energy, and power density of 493 F · g(-1), 49.9 Wh · Kg(-1), and 1700 W · Kg(-1), and they retained ∼97.83% of capacitance after 10 000 charge/discharge processes. Furthermore, when the PGO was bent exaggeratedly, it still displayed identical properties, which is of important significance for supporting wearable devices.

Development of electrical capacitance sensor for tomography

International Nuclear Information System (INIS)

Rasif Mohd Zain; Jaafar Abdullah; Ismail Mustapha; Sazrol Azizee Ariff; Susan Maria Sipaun; Lojius Lombigit

2004-01-01

Electrical capacitance tomography (ECT) is one of the successful methods for imaging 2-phase liquid/gas mixture in oil pipelines and solids/gas mixture in fluidized bed and pneumatic conveying system for improvement of process plants. This paper presents the design development of an electrical capacitance sensor for use with an ECT system. This project is aimed at developing a demonstration ECT unit to be used in the oil pipe line. (Author)

Capacitance-Power-Hysteresis Trilemma in Nanoporous Supercapacitors

OpenAIRE

Lee, Alpha A; Vella, Dominic; Goriely, Alain; Kondrat, Svyatoslav

2015-01-01

Nanoporous supercapacitors are an important player in the field of energy storage that fill the gap between dielectric capacitors and batteries. The key challenge in the development of supercapacitors is the perceived trade-off between capacitance and power delivery. Current efforts to boost the capacitance of nanoporous supercapacitors focus on reducing the pore size so that they can only accommodate a single layer of ions. However, this tight packing compromises the charging dynamics and he...

TMEM16A inhibition impedes capacitation and acquisition of hyperactivated motility in guinea pig sperm.

Science.gov (United States)

Cordero-Martínez, Joaquín; Reyes-Miguel, Tania; Rodríguez-Páez, Lorena; Garduño-Siciliano, Leticia; Maldonado-García, Deneb; Roa-Espitia, Ana L; Hernández-González, Enrique O

2018-07-01

Ca 2+ -activated Cl - channels (CaCCs) are anionic channels that regulate many important physiological functions associated with chloride and calcium flux in some somatic cells. The molecular identity of CaCCs was revealed to be TMEM16A and TMEM16B (also known as Anoctamin or ANO1 and ANO2, respectively) in all eukaryotes. A recent study suggests the presence of TMEM16A in human sperm and a relationship with the rhZP-induced acrosome reaction. However, to the best of our knowledge, little is known about the role of TMEM16A in other spermatic processes such as capacitation or motility. In this study, we evaluated the effects of two TMEM16A antagonists on capacitation, acrosome reaction, and motility in guinea pig sperm; these antagonists were T16Ainh-A01, belonging to a second generation of potent antagonists of TMEM16A, and niflumic acid (NFA), a well-known antagonist of TMEM16A (CaCCs). First of all, we confirmed that the absence of Cl - in the capacitation medium changes motility parameters, capacitation, and the progesterone-induced acrosome reaction. Using a specific antibody, TMEM16A was found as a protein band of ∼120 kDa, which localization was in the apical crest of the acrosome and the middle piece of the flagellum. Inhibition of TMEM16A by T16Ainh-A01 affected sperm physiology by reducing capacitation, blocking the progesterone-induced acrosome reaction under optimal capacitation conditions, inhibiting progressive motility, and the acquisition of hyperactivated motility, diminishing [Ca 2+ ]i, and increasing [Cl - ]i. These changes in sperm kinematic parameters provide new evidence of the important role played by TMEM16A in the production of sperm capable of fertilizing oocytes. © 2018 Wiley Periodicals, Inc.

Digital Control of a High Voltage (2.5 kV) Bidirectional Flyback DC-DC Converter for Driving a Capacitive Incremental Actuator

DEFF Research Database (Denmark)

Thummala, Prasanth; Maksimovic, Dragan; Zhang, Zhe

2016-01-01

This paper presents a digital control technique to achieve valley switching in a bidirectional flyback converter used to drive a dielectric electro-active polymer based capacitive incremental actuator. The paper also provides the design of a low input voltage (24 V) and variable high output voltage...... on the output high-voltage (HV) side. Experimental results verifying the bidirectional operation of a high voltage flyback converter are presented, using a 3 kV polypropylene film capacitor as the load. The energy loss distributions of the converter when 4 kV and 4.5 kV HV MOSFETs are used on HV side...

Novel Designs for Application Specific MEMS Pressure Sensors

Directory of Open Access Journals (Sweden)

Erik V. Thomsen

2010-10-01

Full Text Available In the framework of developing innovative microfabricated pressure sensors, we present here three designs based on different readout principles, each one tailored for a specific application. A touch mode capacitive pressure sensor with high sensitivity (14 pF/bar, low temperature dependence and high capacitive output signal (more than 100 pF is depicted. An optical pressure sensor intrinsically immune to electromagnetic interference, with large pressure range (0–350 bar and a sensitivity of 1 pm/bar is presented. Finally, a resonating wireless pressure sensor power source free with a sensitivity of 650 KHz/mmHg is described. These sensors will be related with their applications in  harsh environment, distributed systems and medical environment, respectively. For many aspects, commercially available sensors, which in vast majority are piezoresistive, are not suited for the applications proposed.

Dispersion capacitive de l'interface H2SO4/Pt Capacitive dispersion ...

African Journals Online (AJOL)

Administrateur

Département de Physique, Faculté des Sciences Exactes. Université des .... d'un comportement idéal de la capacité. Au vu .... Figure 2 : Photographie de la cellule Pt/0,5 MH2SO4 (fabriquée par Verre-Lab Constantine) plongée dans un bain.

Three-dimensional hierarchical porous flower-like nickel-cobalt oxide/multi-walled carbon nanotubes nanocomposite for high-capacity supercapacitors

Energy Technology Data Exchange (ETDEWEB)

Liu, Peipei; Hu, Zhonghua, E-mail: huzh@tongji.edu.cn; Liu, Yafei; Yao, Mingming; Zhang, Qiang

2015-02-15

Highlights: • 3D hierarchical porous flower-like Ni-Co oxide/MWCNTs was synthesized. • The electrode shows a large specific surface area and desirable mesoporosity. • High specific capacitances and outstanding stability were obtained. • The content of MWCNTs affects the electrochemical properties of the electrode. - Abstract: Three-dimensional (3D) hierarchical porous flower-like nickel-cobalt oxide/multi-walled carbon nanotubes (Ni-Co oxide/MWCNTs) nanocomposites were fabricated by a facile and template-free hydrothermal method as electrodes for high-capacity supercapacitors. The samples were characterized by energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption-desorption and thermal gravimetric analysis (TGA). The electrochemical performance was investigated by cyclic voltammetry (CV), galvanostatic charge-discharge, and cycle life. It was found that Ni-Co oxide/MWCNTs nanocomposites displayed a high specific capacitance (1703 F g{sup −1} at a discharge current density of 1 A g{sup −1}) and, additionally, an excellent cycling performance, retaining 97% of the maximum capacitance after 2000 cycles at 10 A g{sup −1}. Even at a high current density (20 A g{sup −1}), the specific capacitance was still up to 1309 F g{sup −1}. This outstanding capacitive performance may be attributed to the ideal composition of the material and to its unique 3D hierarchical porous flower-like architecture.

Three-dimensional hierarchical porous flower-like nickel-cobalt oxide/multi-walled carbon nanotubes nanocomposite for high-capacity supercapacitors

International Nuclear Information System (INIS)

Liu, Peipei; Hu, Zhonghua; Liu, Yafei; Yao, Mingming; Zhang, Qiang

2015-01-01

Highlights: • 3D hierarchical porous flower-like Ni-Co oxide/MWCNTs was synthesized. • The electrode shows a large specific surface area and desirable mesoporosity. • High specific capacitances and outstanding stability were obtained. • The content of MWCNTs affects the electrochemical properties of the electrode. - Abstract: Three-dimensional (3D) hierarchical porous flower-like nickel-cobalt oxide/multi-walled carbon nanotubes (Ni-Co oxide/MWCNTs) nanocomposites were fabricated by a facile and template-free hydrothermal method as electrodes for high-capacity supercapacitors. The samples were characterized by energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption-desorption and thermal gravimetric analysis (TGA). The electrochemical performance was investigated by cyclic voltammetry (CV), galvanostatic charge-discharge, and cycle life. It was found that Ni-Co oxide/MWCNTs nanocomposites displayed a high specific capacitance (1703 F g −1 at a discharge current density of 1 A g −1 ) and, additionally, an excellent cycling performance, retaining 97% of the maximum capacitance after 2000 cycles at 10 A g −1 . Even at a high current density (20 A g −1 ), the specific capacitance was still up to 1309 F g −1 . This outstanding capacitive performance may be attributed to the ideal composition of the material and to its unique 3D hierarchical porous flower-like architecture

Capacitance level probe, Type FSK 88

International Nuclear Information System (INIS)

Vogt, W.

2001-01-01

The aim of the capacitive level probe, Type FSK 88, is to supervise the level within vessels continuously and to signalize alterations immediately. Since 1987 the level probe is installed in the pool for burn up fuel elements and in the reactor containment sump of BWRs, PWRs and WWERs. The capacitive level probe of type FSK 88 was qualified for Loss of Coolant Accidents and seismic events according to international rules. The measuring principle takes credit from the fact that the dielectric with different dielectric constants in a condensator changes the capacity of the condensator. (Authors)

PERBEDAAN SKIN CAPACITANCE DAN TRANSEPIDERMAL WATER LOSS PADA KULIT NON-LESI PASIEN PITIRIASIS VERSIKOLOR DENGAN NON-PITIRIASIS VERSIKOLOR

Directory of Open Access Journals (Sweden)

Satya Wydya Yenny

2008-09-01

Full Text Available AbstrakPada pitiriasis versikolor sering timbul kekambuhan, diduga salah satu penyebabnya adalah kelembaban kulit yang tinggi. Kelembaban kulit dipengaruhi oleh skin capacitance dan transepidermal water loss.Mengetahui skin capacitance dan transepidermal water loss kulit pasien pitiriasis versikolor dan perbedaannya dengan non-pitiriasis versikolor.Penelitian ini merupakan studi potong lintang perbandingan antar kelompok, yang dilakukan pada bulan September sampai dengan Nopember 2004 di Rumah Sakit Dr. Cipto Mangunkusumo. Subyek penelitian pasien pitiriasis versikolor dan kontrol non-pitiriasis versikolor yang dipasangkan dalam hal umur dan jenis kelamin dan dilakukan pemeriksaan skin capacitance dan transepidermal water loss pada kulit yang tampak normal di punggung menggunakan alat Tewameter/Corneometer 350.Dalam kurun waktu tersebut telah diperiksa sebanyak 32 pasien pitiriasis versikolor dan 32 kontrol non-pitiriasis versikolor. Skin capacitance pasien pitiriasis versikolor secara statistik tidak berbeda dengan kontrol non-pitiriasis versikolor (p = 0,730. Transepidermal water loss pasien pitiriasis versikolor secara bermakna lebih rendah dari pada kelompok kontrol non-pitiriasis versikolor (p = 0,000.Tidak ada perbedaan skin capacitance kulit pasien pitiriasis versikolor dengan non-pitiriasis versikolor. Transepidermal water loss kulit pasien pitiriasis versikolor lebih rendah daripada non-pitiriasis versikolor.Kata kunci: pitiriasis versikolor, skin capacitance, transepidermal water lossAbstractThe recurrence of pityriasis versicolor is high, it could be caused by high skin hydration. Skin hydration was influenced by skin capacitance and transepidermal water loss.ARTIKEL PENELITIAN168The purpose of this study was to compare the differences of the skin capacitance and transepidermal water loss between the pityriasis versicolor skin and healthy non-pityriasis versicolor skin.The design of this study was comparative cross-sectional study

Clean energy generation using capacitive electrodes in reverse electrodialysis

NARCIS (Netherlands)

Vermaas, David; Bajracharya, S.; Bastos Sales, B.; Saakes, Michel; Hamelers, B.; Nijmeijer, Dorothea C.

2013-01-01

Capacitive reverse electrodialysis (CRED) is a newly proposed technology to generate electricity from mixing of salt water and fresh water (salinity gradient energy) by using a membrane pile as in reverse electrodialysis (RED) and capacitive electrodes. The salinity difference between salt water and

Volume Recovery of Polymeric Glasses: Application of a Capacitance-based Measurement Technique

Science.gov (United States)

Sakib, Nazam; Simon, Sindee

Glasses, including polymeric glasses, are inherently non-equilibrium materials. As a consequence, the volume and enthalpy of a glass evolve towards equilibrium in a process termed structural recovery. Several open questions and new controversies remain unanswered in the field. Specifically, the presence of intermediate plateaus during isothermal structural recovery has been reported in recent enthalpy work. In addition, the dependence of the relaxation time on state variables and thermal history is unclear. Dilatometry is particularly useful for structural recovery studies because volume is an absolute quantity and volumetric measurements can be done in-situ. A capillary dilatometer, fitted with a linear variable differential transducer, was used previously to measure volume recovery of polymeric glass formers in our laboratory. To improve on the limitations associated with that methodology, including competition between the range of measurements versus the sensitivity, a capacitance-based technique has been developed following the work of Richert, 2010. The modification is performed by converting the glass capillary dilatometer into a cylindrical capacitor. For precision in capacitance data acquisition, an Andeen-Hagerling ultra-precision capacitance bridge (2550A, 1 kHz) is used. The setup will be tested by performing the signatures of structural recovery as described by Kovacs, 1963. Experiments are also planned to address the open questions in the field.

Accurate sizing of supercapacitors storage system considering its capacitance variation.

OpenAIRE

Trieste , Sony; Bourguet , Salvy; Olivier , Jean-Christophe; Loron , Luc; Le Claire , Jean-Claude

2011-01-01

International audience; This paper highlights the energy errors made for the design of supercapacitors used as a main energy source. First of all, the paper presents the two definitions of capacitance of a capacitance-voltage dependent material. The number of supercapacitors is important for the application purchasing cost. That is why the paper introduces an analytical model and an electrical model along with an identification method for the capacitance variation. This variation is presented...

Microstructural modification of NiAl layered double hydroxide electrodes by adding graphene nanosheets and their capacitative property

International Nuclear Information System (INIS)

Kim, Yuna; Kim, Seok

2015-01-01

NiAl layered double hydroxide (LDH) composite electrodes containing various contents of graphene nanosheets (GNS) were prepared by a hydrothermal method. The microstructure and morphological properties were examined by FE-SEM, FE-TEM, XRD, and FTIR. Electrochemical analysis was also carried out by cyclic voltammetry, impedance, and cycle life measurement. The as-prepared composite that contained 500 mg of graphene (denoted as NiAl/G-50) achieved the highest specific capacitance of 1147 F/g among the various NiAl LDH/GNS composites. Besides, the NiAl LDH/GNS composite exhibited the lower diffusion resistance, improved rate capability, and good cyclic stability (83% of initial capacitance after 2000 cycles). Considering the morphological data and the improved capacitative properties together, we concluded the synthesized NiAl LDH/GNS composites would be a promising electrode material for supercapacitors

Microstructural modification of NiAl layered double hydroxide electrodes by adding graphene nanosheets and their capacitative property

Energy Technology Data Exchange (ETDEWEB)

Kim, Yuna; Kim, Seok [School of Chemical and Biomolecular Engineering, Pusan National University, Busan (Korea, Republic of)

2015-02-15

NiAl layered double hydroxide (LDH) composite electrodes containing various contents of graphene nanosheets (GNS) were prepared by a hydrothermal method. The microstructure and morphological properties were examined by FE-SEM, FE-TEM, XRD, and FTIR. Electrochemical analysis was also carried out by cyclic voltammetry, impedance, and cycle life measurement. The as-prepared composite that contained 500 mg of graphene (denoted as NiAl/G-50) achieved the highest specific capacitance of 1147 F/g among the various NiAl LDH/GNS composites. Besides, the NiAl LDH/GNS composite exhibited the lower diffusion resistance, improved rate capability, and good cyclic stability (83% of initial capacitance after 2000 cycles). Considering the morphological data and the improved capacitative properties together, we concluded the synthesized NiAl LDH/GNS composites would be a promising electrode material for supercapacitors.

Highly Compressible Carbon Sponge Supercapacitor Electrode with Enhanced Performance by Growing Nickel-Cobalt Sulfide Nanosheets.

Science.gov (United States)

Liang, Xu; Nie, Kaiwen; Ding, Xian; Dang, Liqin; Sun, Jie; Shi, Feng; Xu, Hua; Jiang, Ruibin; He, Xuexia; Liu, Zonghuai; Lei, Zhibin

2018-03-28

The development of compressible supercapacitor highly relies on the innovative design of electrode materials with both superior compression property and high capacitive performance. This work reports a highly compressible supercapacitor electrode which is prepared by growing electroactive NiCo 2 S 4 (NCS) nanosheets on the compressible carbon sponge (CS). The strong adhesion of the metallic conductive NCS nanosheets to the highly porous carbon scaffolds enable the CS-NCS composite electrode to exhibit an enhanced conductivity and ideal structural integrity during repeated compression-release cycles. Accordingly, the CS-NCS composite electrode delivers a specific capacitance of 1093 F g -1 at 0.5 A g -1 and remarkable rate performance with 91% capacitance retention in the range of 0.5-20 A g -1 . Capacitance performance under the strain of 60% shows that the incorporation of NCS nanosheets in CS scaffolds leads to over five times enhancement in gravimetric capacitance and 17 times enhancement in volumetric capacitance. These performances enable the CS-NCS composite to be one of the promising candidates for potential applications in compressible electrochemical energy storage devices.

Experimental Validation of Topology Optimization for RF MEMS Capacitive Switch Design

DEFF Research Database (Denmark)

Philippine, Mandy Axelle; Zareie, Hosein; Sigmund, Ole

2013-01-01

In this paper, we present 30 distinct RF MEMS capacitive switch designs that are the product of topology optimizations that control key mechanical properties such as stiffness, response to intrinsic stress gradients, and temperature sensitivity. The designs were evaluated with high-accuracy simul...

Asymmetric Electrodes Constructed with PAN-Based Activated Carbon Fiber in Capacitive Deionization

Directory of Open Access Journals (Sweden)

Mingzhe Li

2014-01-01

Full Text Available Capacitive deionization (CDI method has drawn much attention for its low energy consumption, low pollution, and convenient manipulation. Activated carbon fibers (ACFs possess high adsorption ability and can be used as CDI electrode material. Herein, two kinds of PAN-based ACFs with different specific surface area (SSA were used for the CDI electrodes. The CDI performance was investigated; especially asymmetric electrodes’ effect was evaluated. The results demonstrated that PAN-based ACFs showed a high electrosorption rate (complete electrosorption in less than half an hour and moderate electrosorption capacity (up to 0.2 mmol/g. CDI experiments with asymmetric electrodes displayed a variation in electrosorption capacity between forward voltage and reverse voltage. It can be attributed to the electrical double layer (EDL overlap effect and inner pore potential; thus the ions with smaller hydrated ionic radius can be adsorbed more easily.

Three-dimensional cross-linked carbon network wrapped with ordered polyaniline nanowires for high-performance pseudo-supercapacitors

Science.gov (United States)

Hu, Huan; Liu, Shuwu; Hanif, Muddasir; Chen, Shuiliang; Hou, Haoqing

2014-12-01

The polyaniline (PANI)-based pseudo-supercapacitor has been extensively studied due to its good conductivity, ease of synthesis, low-cost monomer, tunable properties and remarkable specific capacitance. In this work, a three-dimensional cross-linked carbon network (3D-CCN) was used as a contact-resistance-free substrate for PANI-based pseudo-supercapacitors. The ordered PANI nanowires (PaNWs) were grown on the 3D-CCN to form PaNWs/3D-CCN composites by in-situ polymerization. The PaNWs/3D-CCN composites exhibited a specific capacitance (Cs) of 1191.8 F g-1 at a current density of 0.5 A g-1 and a superior rate capability with 66.4% capacitance retention at 100.0 A g-1. The high specific capacitance is attributed to the thin PaNW coating and the spaced PANI nanowire array, which ensure a higher utilization of PANI due to the ease of diffusion of protons through/on the PANI nanowires. In addition, the unique 3D-CCN was used as a high-conductivity platform (or skeleton) with no contact resistance for fast electron transfer and facile charge transport within the composites. Therefore, the binder-free composites can process rapid gains or losses of electrons and ions, even at a high current density. As a result, the specific capacitance and rate capability of our composites are remarkably higher than those of other PANI composites.

Design of capacitance measurement module for determining critical cold temperature of tea leaves

Directory of Open Access Journals (Sweden)

Yongzong Lu

2016-12-01

Full Text Available Critical cold temperature is one of the most crucial control factors for crop frost protection. Tea leaf's capacitance has a significant response to cold injury and appears as a peak response to a typical low temperature which is the critical temperature. However, the testing system is complex and inconvenient. In view of these, a tea leaf's critical temperature detector based on capacitance measurement module was designed and developed to measure accurately and conveniently the capacitance. Software was also designed to measure parameters, record data, query data as well as data deletion module. The detector utilized the MSP430F149 MCU as the control core and ILI9320TFT as the display module, and its software was compiled by IAR5.3. Capacitance measurement module was the crucial part in the overall design which was based on the principle of oscillator. Based on hardware debugging and stability analysis of capacitance measurement module, it was found that the output voltage of the capacitance measurement circuit is stable with 0.36% average deviation. The relationship between capacitance and 1/Uc2 was found to be linear distribution with the determination coefficient above 0.99. The result indicated that the output voltage of capacitance measurement module well corresponded to the change in value of the capacitance. The measurement error of the circuit was also within the required range of 0 to 100 pF which meets the requirement of tea leaf's capacitance. Keywords: Tea leaves, Critical cold temperature, Capacitance peak response, Frost protection, Detector

Electric field theory and the fallacy of void capacitance

DEFF Research Database (Denmark)

McAllister, Iain Wilson

1991-01-01

The concept of the capacitance of a gaseous void is discussed as applied to electrical insulation science. The most pertinent aspect of the capacitance definition is that of reference to a single-valued potential difference between surfaces. This implies that these surfaces must be surfaces...

Capacitive Coupling in Double-Circuit Transmission Lines

Directory of Open Access Journals (Sweden)

Zdenka Benesova

2004-01-01

Full Text Available The paper describes an algorithm for calculation of capacitances and charges on conductors in systems with earth wires and in double-circuit overhead lines with respect to phase arrangement. A balanced voltage system is considered. A suitable transposition of individual conductors enables to reduce the electric and magnetic fields in vicinity of overhead lines and to limit the inductive and capacitive linkage. The procedure is illustrated on examples the results of which lead to particular recommendations for designers.

Optimizing the fabrication of carbon nanotube electrode for effective capacitive deionization via electrophoretic deposition strategy

Directory of Open Access Journals (Sweden)

Simeng Zhang

2018-04-01

Full Text Available In order to obtain superior electrode performances in capacitive deionization (CDI, the electrophoretic deposition (EPD was introduced as a novel strategy for the fabrication of carbon nanotube (CNT electrode. Preparation parameters, including the concentration of slurry components, deposition time and electric field intensity, were mainly investigated and optimized in terms of electrochemical characteristic and desalination performance of the deposited CNT electrode. The SEM image shows that the CNT material was deposited homogeneously on the current collector and a non-crack surface of the electrode was obtained. An optimal preparation condition of the deposited CNT electrode was obtained and specified as the Al (NO33 M concentration of 1.3 × 10−2 mol/L, the deposition time of 30 min and the electric field intensity of 15 V/cm. The obtained electrode performs an increasing specific mass capacitance of 33.36 F/g and specific adsorption capacity of 23.93 mg/g, which are 1.62 and 1.85 times those of the coated electrode respectively. The good performance of the deposited CNT electrode indicates the promising application of the EPD methodology in subsequent research and fabrication of the CDI electrodes for CDI process. Keywords: Carbon nanotube, Water treatment, Desalination, Capacitive deionization, Electrode fabrication, Electrophoretic deposition

Hierarchically porous nitrogen-doped carbon derived from the activation of agriculture waste by potassium hydroxide and urea for high-performance supercapacitors

Science.gov (United States)

Zou, Kaixiang; Deng, Yuanfu; Chen, Juping; Qian, Yunqian; Yang, Yuewang; Li, Yingwei; Chen, Guohua

2018-02-01

Nitrogen-doped carbon with an ultra-high specific surface area and a hierarchically interconnected porous structure is synthesized in large scale from a green route, that is, the activation of bagasse via a one-step method using KOH and urea. KOH and urea play a synergistic effect for the enhancement of the specific surface area and the modification of pore size of the as-prepared material. Benefiting from the multiple synergistic roles originated from an ultra-high specific area (2905.4 m2 g-1), a high porous volume (2.05 mL g-1 with 75.6 vol% micropores, which is an ideal proportion of micropores for obtaining high specific capacitance), a suitable nitrogen content (2.63 wt%), and partial graphitization, the hierarchically interconnected porous N-doped carbon exhibits an excellent electrochemical performance with a high specific capacitance (350.8, 301.9, and 259.5 F g-1 at 1.0 A g-1 in acidic, alkaline, and neutral electrolytes, respectively), superior rate capability and excellent cycling stability (almost no capacitance loss up to 5000 cycles). Furthermore, the symmetric device assembled by this material achieves high energy densities of 39.1 and 23.5 Wh kg-1 at power densities of 1.0 and 20 kW kg-1, respectively, and exhibits an excellent long-term cycling stability (with capacitance retention above 95.0% after 10 000 cycles).

Ni nanoparticles@Ni-Mo nitride nanorod arrays: a novel 3D-network hierarchical structure for high areal capacitance hybrid supercapacitors.

Science.gov (United States)

Ruan, Yunjun; Lv, Lin; Li, Zhishan; Wang, Chundong; Jiang, Jianjun

2017-11-23

Because of the advanced nature of their high power density, fast charge/discharge time, excellent cycling stability, and safety, supercapacitors have attracted intensive attention for large-scale applications. Nevertheless, one of the obstacles for their further development is their low energy density caused by sluggish redox reaction kinetics, low electroactive electrode materials, and/or high internal resistance. Here, we develop a facile and simple nitridation process to successfully synthesize hierarchical Ni nanoparticle decorated Ni 0.2 Mo 0.8 N nanorod arrays on a nickel foam (Ni-Mo-N NRA/NF) from its NiMoO 4 precursor, which delivers a high areal capacity of 2446 mC cm -2 at a current density of 2 mA cm -2 and shows outstanding cycling stability. The superior performance of the Ni-Mo-N NRA/NF can be ascribed to the metallic conductive nature of the Ni-Mo nitride, the fast surface redox reactions for the electrolyte ions and electrode materials, and the low contacted resistance between the active materials and the current collectors. Furthermore, a hybrid supercapacitor (HSC) is assembled using the Ni-Mo-N NRA/NF as the positive electrode and reduced graphene oxide (RGO) as the negative electrode. The optimized HSC exhibits excellent electrochemical performance with a high energy density of 40.9 W h kg -1 at a power density of 773 W kg -1 and a retention of 80.1% specific capacitance after 6000 cycles. These results indicate that the Ni-Mo-N NRA/NF have a promising potential for use in high-performance supercapacitors.

Transparent Flexible Active Faraday Cage Enables In Vivo Capacitance Measurement in Assembled Microsensor.

Science.gov (United States)

Ahmadi, Mahdi; Rajamani, Rajesh; Sezen, Serdar

2017-10-01

Capacitive micro-sensors such as accelerometers, gyroscopes and pressure sensors are increasingly used in the modern electronic world. However, the in vivo use of capacitive sensing for measurement of pressure or other variables inside a human body suffers from significant errors due to stray capacitance. This paper proposes a solution consisting of a transparent thin flexible Faraday cage that surrounds the sensor. By supplying the active sensing voltage simultaneously to the deformable electrode of the capacitive sensor and to the Faraday cage, the stray capacitance during in vivo measurements can be largely eliminated. Due to the transparency of the Faraday cage, the top and bottom portions of a capacitive sensor can be accurately aligned and assembled together. Experimental results presented in the paper show that stray capacitance is reduced by a factor of 10 by the Faraday cage, when the sensor is subjected to a full immersion in water.

An integrated energy-efficient capacitive sensor digital interface circuit

KAUST Repository

Omran, Hesham

2014-06-19

In this paper, we propose an energy-efficient 13-bit capacitive sensor interface circuit. The proposed design fully relies on successive approximation algorithm, which eliminates the need for oversampling and digital decimation filtering, and thus low-power consumption is achieved. The proposed architecture employs a charge amplifier stage to acheive parasitic insensitive operation and fine absolute resolution. Moreover, the output code is not affected by offset voltages or charge injection. The successive approximation algorithm is implemented in the capacitance-domain using a coarse-fine programmable capacitor array, which allows digitizing wide capacitance range in compact area. Analysis for the maximum achievable resolution due to mismatch is provided. The proposed design is insensitive to any reference voltage or current which translates to low temperature sensitivity. The operation of a prototype fabricated in a standard CMOS technology is experimentally verified using both on-chip and off-chip capacitive sensors. Compared to similar prior work, the fabricated prototype achieves and excellent energy efficiency of 34 pJ/step.

Concentration Fluctuations and Capacitive Response in Dense Ionic Solutions.

Science.gov (United States)

Uralcan, Betul; Aksay, Ilhan A; Debenedetti, Pablo G; Limmer, David T

2016-07-07

We use molecular dynamics simulations in a constant potential ensemble to study the effects of solution composition on the electrochemical response of a double layer capacitor. We find that the capacitance first increases with ion concentration following its expected ideal solution behavior but decreases upon approaching a pure ionic liquid in agreement with recent experimental observations. The nonmonotonic behavior of the capacitance as a function of ion concentration results from the competition between the independent motion of solvated ions in the dilute regime and solvation fluctuations in the concentrated regime. Mirroring the capacitance, we find that the characteristic decay length of charge density correlations away from the electrode is also nonmonotonic. The correlation length first decreases with ion concentration as a result of better electrostatic screening but increases with ion concentration as a result of enhanced steric interactions. When charge fluctuations induced by correlated ion-solvent fluctuations are large relative to those induced by the pure ionic liquid, such capacitive behavior is expected to be generic.

Conjugate Image Theory Applied on Capacitive Wireless Power Transfer

Directory of Open Access Journals (Sweden)

Ben Minnaert

2017-01-01

Full Text Available Wireless power transfer using a magnetic field through inductive coupling is steadily entering the market in a broad range of applications. However, for certain applications, capacitive wireless power transfer using electric coupling might be preferable. In order to obtain a maximum power transfer efficiency, an optimal compensation network must be designed at the input and output ports of the capacitive wireless link. In this work, the conjugate image theory is applied to determine this optimal network as a function of the characteristics of the capacitive wireless link, as well for the series as for the parallel topology. The results are compared with the inductive power transfer system. Introduction of a new concept, the coupling function, enables the description of the compensation network of both an inductive and a capacitive system in two elegant equations, valid for the series and the parallel topology. This approach allows better understanding of the fundamentals of the wireless power transfer link, necessary for the design of an efficient system.

Quantifying the thickness of the electrical double layer neutralizing a planar electrode: the capacitive compactness.

Science.gov (United States)

Guerrero-García, Guillermo Iván; González-Tovar, Enrique; Chávez-Páez, Martín; Kłos, Jacek; Lamperski, Stanisław

2017-12-20

The spatial extension of the ionic cloud neutralizing a charged colloid or an electrode is usually characterized by the Debye length associated with the supporting charged fluid in the bulk. This spatial length arises naturally in the linear Poisson-Boltzmann theory of point charges, which is the cornerstone of the widely used Derjaguin-Landau-Verwey-Overbeek formalism describing the colloidal stability of electrified macroparticles. By definition, the Debye length is independent of important physical features of charged solutions such as the colloidal charge, electrostatic ion correlations, ionic excluded volume effects, or specific short-range interactions, just to mention a few. In order to include consistently these features to describe more accurately the thickness of the electrical double layer of an inhomogeneous charged fluid in planar geometry, we propose here the use of the capacitive compactness concept as a generalization of the compactness of the spherical electrical double layer around a small macroion (González-Tovar et al., J. Chem. Phys. 2004, 120, 9782). To exemplify the usefulness of the capacitive compactness to characterize strongly coupled charged fluids in external electric fields, we use integral equations theory and Monte Carlo simulations to analyze the electrical properties of a model molten salt near a planar electrode. In particular, we study the electrode's charge neutralization, and the maximum inversion of the net charge per unit area of the electrode-molten salt system as a function of the ionic concentration, and the electrode's charge. The behaviour of the associated capacitive compactness is interpreted in terms of the charge neutralization capacity of the highly correlated charged fluid, which evidences a shrinking/expansion of the electrical double layer at a microscopic level. The capacitive compactness and its first two derivatives are expressed in terms of experimentally measurable macroscopic properties such as the

Current source enhancements in Electrical Impedance Spectroscopy (EIS) to cancel unwanted capacitive effects

Science.gov (United States)

Zarafshani, Ali; Bach, Thomas; Chatwin, Chris; Xiang, Liangzhong; Zheng, Bin

2017-03-01

Electrical Impedance Spectroscopy (EIS) has emerged as a non-invasive imaging modality to detect and quantify functional or electrical properties related to the suspicious tumors in cancer screening, diagnosis and prognosis assessment. A constraint on EIS systems is that the current excitation system suffers from the effects of stray capacitance having a major impact on the hardware subsystem as the EIS is an ill-posed inverse problem which depends on the noise level in EIS measured data and regularization parameter in the reconstruction algorithm. There is high complexity in the design of stable current sources, with stray capacitance reducing the output impedance and bandwidth of the system. To confront this, we have designed an EIS current source which eliminates the effect of stray capacitance and other impacts of the capacitance via a variable inductance. In this paper, we present a combination of operational CCII based on a generalized impedance converter (OCCII-GIC) with a current source. The aim of this study is to use the EIS system as a biomedical imaging technique, which is effective in the early detection of breast cancer. This article begins with the theoretical description of the EIS structure, current source topologies and proposes a current conveyor in application of a Gyrator to eliminate the current source limitations and its development followed by simulation and experimental results. We demonstrated that the new design could achieve a high output impedance over a 3MHz frequency bandwidth when compared to other types of GIC circuits combined with an improved Howland topology.

Resonant gravimetric immunosensing based on capacitive micromachined ultrasound transducers

KAUST Repository

Viržonis, Darius

2014-04-08

High-frequency (40 MHz) and low-frequency (7 MHz) capacitive micromachined ultrasound transducers (CMUT) were fabricated and tested for use in gravimetric detection of biomolecules. The low-frequency CMUT sensors have a gold-coated surface, while the high-frequency sensors have a silicon nitride surface. Both surfaces were functionalized with bovine leukemia virus antigen gp51 acting as the antigen. On addition of an a specific antibody labeled with horseradish peroxidase (HRP), the antigen/antibody complex is formed on the surface and quantified by HRP-catalyzed oxidation of tetramethylbenzidine. It has been found that a considerably smaller quantity of immuno complex is formed on the high frequency sensor surface. In parallel, the loading of the surface of the CMUT was determined via resonance frequency and electromechanical resistance readings. Following the formation of the immuno complexes, the resonance frequencies of the low-frequency and high-frequency sensors decrease by up to 420 and 440 kHz, respectively. Finite element analysis reveals that the loading of the (gold-coated) low frequency sensors is several times larger than that on high frequency sensors. The formation of the protein film with pronounced elasticity and stress on the gold surface case is discussed. We also discuss the adoption of this method for the detection of DNA using a hybridization assay following polymerase chain reaction.

Improving accuracy of electrochemical capacitance and solvation energetics in first-principles calculations

Science.gov (United States)

Sundararaman, Ravishankar; Letchworth-Weaver, Kendra; Schwarz, Kathleen A.

2018-04-01

Reliable first-principles calculations of electrochemical processes require accurate prediction of the interfacial capacitance, a challenge for current computationally efficient continuum solvation methodologies. We develop a model for the double layer of a metallic electrode that reproduces the features of the experimental capacitance of Ag(100) in a non-adsorbing, aqueous electrolyte, including a broad hump in the capacitance near the potential of zero charge and a dip in the capacitance under conditions of low ionic strength. Using this model, we identify the necessary characteristics of a solvation model suitable for first-principles electrochemistry of metal surfaces in non-adsorbing, aqueous electrolytes: dielectric and ionic nonlinearity, and a dielectric-only region at the interface. The dielectric nonlinearity, caused by the saturation of dipole rotational response in water, creates the capacitance hump, while ionic nonlinearity, caused by the compactness of the diffuse layer, generates the capacitance dip seen at low ionic strength. We show that none of the previously developed solvation models simultaneously meet all these criteria. We design the nonlinear electrochemical soft-sphere solvation model which both captures the capacitance features observed experimentally and serves as a general-purpose continuum solvation model.

Contribution of Dielectric Screening to the Total Capacitance of Few-Layer Graphene Electrodes.

Science.gov (United States)

Zhan, Cheng; Jiang, De-en

2016-03-03

We apply joint density functional theory (JDFT), which treats the electrode/electrolyte interface self-consistently, to an electric double-layer capacitor (EDLC) based on few-layer graphene electrodes. The JDFT approach allows us to quantify a third contribution to the total capacitance beyond quantum capacitance (CQ) and EDL capacitance (CEDL). This contribution arises from the dielectric screening of the electric field by the surface of the few-layer graphene electrode, and we therefore term it the dielectric capacitance (CDielec). We find that CDielec becomes significant in affecting the total capacitance when the number of graphene layers in the electrode is more than three. Our investigation sheds new light on the significance of the electrode dielectric screening on the capacitance of few-layer graphene electrodes.

Calculating and optimizing inter-electrode capacitances of charge division microchannel plate detectors

Energy Technology Data Exchange (ETDEWEB)

Xing, Yan [Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Chen, Bo, E-mail: chenb@ciomp.ac.cn [Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Zhang, Hong-Ji; Wang, Hai-Feng; He, Ling-Ping [Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Jin, Fang-Yuan [Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); University of Chinese Academy of Sciences, Beijing 100049 (China)

2016-04-01

Based on the principle of charge division microchannel plate detectors, the inter-electrode capacitances of charge division anodes which are related to electronic noise of the charge sensitive amplifier and crosstalk effect of the anode are presented. Under all the requirements of charge division microchannel plate detectors such as the imaging linearity and spatial resolution, decreasing the inter-electrode capacitances is one way to improve the imaging performance. In this paper, we illustrate the simulation process of calculating the inter-electrode capacitances. Moreover, a Wedge and Strip (WSZ) anode is fabricated with the picosecond laser micromachining process. Comparing the simulated capacitances and measured capacitances, the three-dimensional finite element method is proved to be valid. Furthermore, by adjusting the design parameters of the anode, the effects of the substrate permittivity, insulation width and the size of pitch on the inter-electrode capacitances have been analysed. The structure of the charge division anode has been optimized based on the simulation data.

Microfabricated pseudocapacitors using Ni(OH)2 electrodes exhibit remarkable volumetric capacitance and energy density

KAUST Repository

Kurra, Narendra

2014-09-10

Metal hydroxide based microfabricated pseudocapacitors with impressive volumetric stack capacitance and energy density are demonstrated. A combination of top-down photolithographic process and bottom-up chemical synthesis is employed to fabricate the micro-pseudocapacitors (μ-pseudocapacitors). The resulting Ni(OH)2-based devices show several excellent characteristics including high-rate redox activity up to 500 V s-1 and an areal cell capacitance of 16 mF cm-2 corresponding to a volumetric stack capacitance of 325 F cm-3. This volumetric capacitance is two-fold higher than carbon and metal oxide based μ-supercapacitors with interdigitated electrode architecture. Furthermore, these μ-pseudocapacitors show a maximum energy density of 21 mWh cm-3, which is superior to the Li-based thin film batteries. The heterogeneous growth of Ni(OH)2 over the Ni surface during the chemical bath deposition is found to be the key parameter in the formation of uniform monolithic Ni(OH)2 mesoporous nanosheets with vertical orientation, responsible for the remarkable properties of the fabricated devices. Additionally, functional tandem configurations of the μ-pseudocapacitors are shown to be capable of powering a light-emitting diode.

3-Axis Fully-Integrated Capacitive Tactile Sensor with Flip-Bonded CMOS on LTCC Interposer.

Science.gov (United States)

Asano, Sho; Muroyama, Masanori; Nakayama, Takahiro; Hata, Yoshiyuki; Nonomura, Yutaka; Tanaka, Shuji

2017-10-25

This paper reports a 3-axis fully integrated differential capacitive tactile sensor surface-mountable on a bus line. The sensor integrates a flip-bonded complementary metal-oxide semiconductor (CMOS) with capacitive sensing circuits on a low temperature cofired ceramic (LTCC) interposer with Au through vias by Au-Au thermo-compression bonding. The CMOS circuit and bonding pads on the sensor backside were electrically connected through Au bumps and the LTCC interposer, and the differential capacitive gap was formed by an Au sealing frame. A diaphragm for sensing 3-axis force was formed in the CMOS substrate. The dimensions of the completed sensor are 2.5 mm in width, 2.5 mm in length, and 0.66 mm in thickness. The fabricated sensor output coded 3-axis capacitive sensing data according to applied 3-axis force by three-dimensional (3D)-printed pins. The measured sensitivity was as high as over 34 Count/mN for normal force and 14 to 15 Count/mN for shear force with small noise, which corresponds to less than 1 mN. The hysteresis and the average cross-sensitivity were also found to be less than 2% full scale and 11%, respectively.

One-step electroplating porous graphene oxide electrodes of supercapacitors for ultrahigh capacitance and energy density

International Nuclear Information System (INIS)

Wang, Yongjie; Zhu, Jiaqi

2015-01-01

An electroplating method was used for the first time to synthesize 3D porous graphene oxide (PGO) architectures, exhibiting ultrahigh capacitance and energy density as electrodes of supercapacitors. Scanning electron microscopy illustrated the porous structures which promoted the stability and alleviated the stacking of the graphene oxide layers. As investigated in a three-electrode supercapacitor cell, PGO electrodes exhibited the maximum capacitance and energy of 973 F · g −1 and 98.4 Wh · Kg −1 , which are better than current reports and comparable to batteries. At 4 A · g −1 for high-power applications, PGO electrodes reached a capacitance, energy, and power density of 493 F · g −1 , 49.9 Wh · Kg −1 , and 1700 W · Kg −1 , and they retained ∼97.83% of capacitance after 10 000 charge/discharge processes. Furthermore, when the PGO was bent exaggeratedly, it still displayed identical properties, which is of important significance for supporting wearable devices. (paper)

Nitrogen doped activated carbon from pea skin for high performance supercapacitor

Science.gov (United States)

Ahmed, Sultan; Ahmed, Ahsan; Rafat, M.

2018-04-01

In this work, nitrogen doped porous carbon (NDC) has been synthesized employing a facile two-step process. Firstly, carbon precursor (pea skin) was heated with melamine (acting as nitrogen source) followed by activation with KOH in different ratios. The dependence of porosity and nitrogen content on impregnation ratio was extensively studied. Other textural properties of prepared NDC sample were studied using standard techniques of material characterization. The electrochemical performance of NDC sample as an electrode was studied in two-electrode symmetric supercapacitor system. 1 M LiTFSI (lithium bis-trifluoromethanesulfonimide) solution in IL EMITFSI (1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide), was used as electrolyte. It was found that the fabricated supercapacitor cell offers high values of specific capacitance (141.1 F g‑1), specific energy (19.6 Wh kg‑1) and specific power (25.4 kW kg‑1) at current density of 1.3 A g‑1. More importantly, the fabricated supercapacitor cell shows capacitance retention of ∼75%, for more than 5000 cycles. The enhanced performance of NDC sample is primarily due to large surface area with favorable surface structure (contributing to double layer capacitance) and presence of nitrogen functionalities (contributing to pseudo-capacitance). Such important features make the synthesized NDC sample, an attractive choice for electrode material in high performance supercapacitor.

Extrinsic and Intrinsic Frequency Dispersion of High-k Materials in Capacitance-Voltage Measurements

Directory of Open Access Journals (Sweden)

S. Taylor

2012-06-01

Full Text Available In capacitance-voltage (C-V measurements, frequency dispersion in high-k dielectrics is often observed. The frequency dependence of the dielectric constant (k-value, that is the intrinsic frequency dispersion, could not be assessed before suppressing the effects of extrinsic frequency dispersion, such as the effects of the lossy interfacial layer (between the high-k thin film and silicon substrate and the parasitic effects. The effect of the lossy interfacial layer on frequency dispersion was investigated and modeled based on a dual frequency technique. The significance of parasitic effects (including series resistance and the back metal contact of the metal-oxide-semiconductor (MOS capacitor on frequency dispersion was also studied. The effect of surface roughness on frequency dispersion is also discussed. After taking extrinsic frequency dispersion into account, the relaxation behavior can be modeled using the Curie-von Schweidler (CS law, the Kohlrausch-Williams-Watts (KWW relationship and the Havriliak-Negami (HN relationship. Dielectric relaxation mechanisms are also discussed.

Nitrogen-doped mesoporous carbons for high performance supercapacitors

Science.gov (United States)

Wu, Kai; Liu, Qiming

2016-08-01

The mesoporous carbons have been synthesized by using α-D(+)-Glucose, D-Glucosamine hydrochloride or their mixture as carbon precursors and mesoporous silicas (SBA-15 or MCF) as hard templates. The as-prepared products show a large pore volume (0.59-0.97 cm3 g-1), high surface areas (352.72-1152.67 m2 g-1) and rational nitrogen content (ca. 2.5-3.9 wt.%). The results of electrochemical tests demonstrate that both heteroatom doping and suitable pore structure play a decisive role in the performance of supercapacitors. The representative sample of SBA-15 replica obtained using D-Glucosamine hydrochloride only exhibits high specific capacitance (212.8 F g-1 at 0.5 A g-1) and good cycle durability (86.1% of the initial capacitance after 2000 cycles) in 6 M KOH aqueous electrolyte, which is attributed to the contribution of double layer capacitance and pseudo-capacitance. The excellent electrochemical performance makes it a promising electrode material for supercapacitors.

Technical evaluation of vehicle ignition systems: conduct differences between a high energy capacitive system and a standard inductive system

Directory of Open Access Journals (Sweden)

Bruno Santos Goulart

2014-09-01

Full Text Available An efficient combustion depends on many factors, such as injection, turbulence and ignition characteristics. With the improvement of internal combustion engines the turbulence intensity and internal pressure have risen, demanding more efficient and powerful ignition systems. In direct injection engines, the stratified charge resultant from the wall/air-guided or spray-guided system requires even more energy. The Paschen’s law shows that spark plug gap and mixture density are proportional to the dielectric rupture voltage. It is known that larger spark gaps promote higher efficiency in the internal combustion engines, since the mixture reaction rate rises proportionally. However, the ignition system must be adequate to the imposed gap, not only on energy, but also on voltage and spark duration. For the reported study in this work two test benches were built: a standard inductive ignition system and a capacitive discharge high energy ignition system, with variable voltage and capacitance. The influence of the important parameters energy and ignition voltage on the spark duration, as well as the electrode gap and shape were analyzed. It was also investigated the utilization of a coil with lower resistance and inductance values, as well as spark plugs with and without internal resistances.

Rough-Surface-Enabled Capacitive Pressure Sensors with 3D Touch Capability.

Science.gov (United States)

Lee, Kilsoo; Lee, Jaehong; Kim, Gwangmook; Kim, Youngjae; Kang, Subin; Cho, Sungjun; Kim, SeulGee; Kim, Jae-Kang; Lee, Wooyoung; Kim, Dae-Eun; Kang, Shinill; Kim, DaeEun; Lee, Taeyoon; Shim, Wooyoung

2017-11-01

Fabrication strategies that pursue "simplicity" for the production process and "functionality" for a device, in general, are mutually exclusive. Therefore, strategies that are less expensive, less equipment-intensive, and consequently, more accessible to researchers for the realization of omnipresent electronics are required. Here, this study presents a conceptually different approach that utilizes the inartificial design of the surface roughness of paper to realize a capacitive pressure sensor with high performance compared with sensors produced using costly microfabrication processes. This study utilizes a writing activity with a pencil and paper, which enables the construction of a fundamental capacitor that can be used as a flexible capacitive pressure sensor with high pressure sensitivity and short response time and that it can be inexpensively fabricated over large areas. Furthermore, the paper-based pressure sensors are integrated into a fully functional 3D touch-pad device, which is a step toward the realization of omnipresent electronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Temperature-dependent electrochemical capacitive performance of the α-Fe2O3 hollow nanoshuttles as supercapacitor electrodes.

Science.gov (United States)

Zheng, Xin; Yan, Xiaoqin; Sun, Yihui; Yu, Yinsheng; Zhang, Guangjie; Shen, Yanwei; Liang, Qijie; Liao, Qingliang; Zhang, Yue

2016-03-15

The design and optimization of supercapacitors electrodes nanostructures are critically important since the properties of supercapacitors can be dramatically enhanced by tunable ion transport channels. Herein, we demonstrate high-performance supercapacitor electrodes materials based on α-Fe2O3 by rationally designing the electrode microstructure. The large solid-liquid reaction interfaces induced by hollow nanoshuttle-like structures not only provide more active sites for faradic reactions but also facilitate the diffusion of the electrolyte into electrodes. These result in the optimized electrodes with high capacitance of 249 F g(-1) at a discharging current density of 0.5 A g(-1) as well as good cycle stability. In addition, the relationship between charge storage and the operating temperature has been researched. The specific capacitance has no significant change when the working temperature increased from 20 °C to 60 °C (e.g. 203 F g(-1) and 234 F g(-1) at 20 °C and 60 °C, respectively), manifesting the electrodes can work stably in a wide temperature range. These findings here elucidate the α-Fe2O3 hollow nanoshuttles can be applied as a promising supercapacitor electrode material for the efficient energy storage at various potential temperatures. Copyright © 2015 Elsevier Inc. All rights reserved.

A flexible capacitive tactile sensing array with floating electrodes

International Nuclear Information System (INIS)

Cheng, M-Y; Huang, X-H; Ma, C-W; Yang, Y-J

2009-01-01

In this work, we present the development of a capacitive tactile sensing array realized by using MEMS fabrication techniques and flexible printed circuit board (FPCB) technologies. The sensing array, which consists of two micromachined polydimethlysiloxane (PDMS) structures and a FPCB, will be used as the artificial skin for robot applications. Each capacitive sensing element comprises two sensing electrodes and a common floating electrode. The sensing electrodes and the metal interconnect for signal scanning are implemented on the FPCB, while the floating electrode is patterned on one of the PDMS structures. This special design can effectively reduce the complexity of the device structure and thus makes the device highly manufacturable. The characteristics of the devices with different dimensions are measured and discussed. The corresponding scanning circuits are also designed and implemented. The tactile images induced by the PMMA stamps of different shapes are also successfully captured by a fabricated 8 × 8 array

In situ fabrication of nickel based oxide on nitrogen-doped graphene for high electrochemical performance supercapacitors

Science.gov (United States)

Pan, Denghui; Zhang, Mingmei; Wang, Ying; Yan, Zaoxue; Jing, Junjie; Xie, Jimin

2017-10-01

In this article, we synthesize Ni(OH)2 homogeneous grown on nitrogen-doped graphene (Ni(OH)2/NG), subsequently, small and uniform nickel oxide nanoparticle (NiO/NG) is also successfully obtained through tube furnace calcination method. The high specific capacitance of the NiO/NG electrode can reach to 1314.1 F/g at a charge and discharge current density of 2 A/g, meanwhile the specific capacitance of Ni(OH)2/NG electrode is also 1350 F/g. The capacitance of NiO/NG can remain 93.7% of the maximum value after 1000 cycles, while the Ni(OH)2/NG electrode losses 16.9% of the initial capacitance after 1000 cycles. It can be attributed to nickel hydroxide instability during charge-discharge cycles.

3D printed biomimetic whisker-based sensor with co-planar capacitive sensing

NARCIS (Netherlands)

Delamare, John; Sanders, Remco G.P.; Krijnen, Gijsbertus J.M.

2016-01-01

This paper describes the development of a whisker sensor for tactile purposes and which is fabricated by 3D printing. Read-out consists of a capacitive measurement of a co-planar capacitance which is affected by a dielectric that is driven into the electric field of the capacitance. The current

Synergistically Active NiCo2 S4 Nanoparticles Coupled with Holey Defect Graphene Hydrogel for High-Performance Solid-State Supercapacitors.

Science.gov (United States)

Tiruneh, Sintayehu Nibret; Kang, Bong Kyun; Kwag, Sung Hoon; Lee, YoungHun; Kim, MinSeob; Yoon, Dae Ho

2018-03-02

Nickel cobalt sulfide nanoparticles embedded in holey defect graphene hydrogel (HGH) that exhibit highly porous structures and uniform nickel cobalt sulfide nanoparticle sizes are successfully prepared by a facile solvothermal-hydrothermal method. As an electrode material for supercapacitors, the as-prepared NiCo 2 S 4 @HGH shows ultra-high specific capacitances of 1000 F g -1 and 800 F g -1 at 0.5 and 6 A g -1 , respectively, owing to the outstanding electrical conductivity of HGH and high specific capacitance of NiCo 2 S 4 . After 2100 charge/discharge cycles at a current density of 6 A g -1 , 96.6 % of the specific capacitance was retained, signifying the superb durability of NiCo 2 S 4 @HGH. Moreover, remarkable specific capacitance (312.6 F g -1 ) and capacity retention (87 % after 5000 cycles) at 6 A g -1 were displayed by the symmetric solid-state supercapacitor fabricated by using NiCo 2 S 4 @HGH electrodes. These auspicious supercapacitor performances demonstrate that the as-developed solvothermal-hydrothermal approach can be widely used to prepare graphene-coupled binary metal sulfides for high-performance supercapacitor applications. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Facile synthesis of NiS anchored carbon nanofibers for high-performance supercapacitors

Science.gov (United States)