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1

The use of double-sided cloth without diffusion layers as air-cathode in microbial fuel cells  

Microsoft Academic Search

The cost of electrode materials is one of the most important factors limiting the scale of microbial fuel cells (MFCs). In this study, a novel double-sided cloth (DC) without diffusion layer is using as air-cathode, which decreases the cost and simplifies electrode production process. Using Pt as catalyst, the maximum power density of MFC using DC cathode is 0.70±0.02Wm?2, which

Jia Liu; Yujie Feng; Xin Wang; Xinxin Shi; Qiao Yang; He Lee; Zhaohan Zhang; Nanqi Ren

2

Air cathode structure manufacture  

DOEpatents

An improved air cathode structure for use in primary batteries and the like. The cathode structure includes a matrix active layer, a current collector grid on one face of the matrix active layer, and a porous, nonelectrically conductive separator on the opposite face of the matrix active layer, the collector grid and separator being permanently bonded to the matrix active layer. The separator has a preselected porosity providing low IR losses and high resistance to air flow through the matrix active layer to maintain high bubble pressure during operation of the battery. In the illustrated embodiment, the separator was formed of porous polypropylene. A thin hydrophobic film is provided, in the preferred embodiment, on the current collecting metal grid.

Momyer, William R. (Palo Alto, CA); Littauer, Ernest L. (Los Altos Hills, CA)

1985-01-01

3

Investigation of the Gas-Diffusion-Electrode Used as Lithium/Air Cathode in Non-aqueous Electrolyte and the Importance of Carbon Material Porosity  

SciTech Connect

The gas-diffusion-electrode used in a Li-air cell has been studied in a unique homemade electrochemical cell. Three major obstacles for the development of a feasible Li-air system were discussed with a focus on the development of a functional gas-diffusion-electrode in non-aqueous electrolytes and the way of avoiding the passivation of gas-diffusion-electrodes caused by the deposition of the reduction products. It is the first time that the importance of establishing the 3-phase electrochemical interface in non-aqueous electrolyte is demonstrated by creating air-diffusion paths and an air saturated portion for an air cathode. A model mechanism of electrode passivation by the reaction products was also proposed. Lithium oxides formed during O{sub 2} reduction tend to block small pores, preventing them from further utilization in the electrochemical reaction. On the other hand, lithium oxides would accumulate inside the large pores during the reduction until the density of oxides becomes high enough to choke-off the mass transfer. Carbon materials with a high surface area associated with larger pores should be selected to make the gas-diffusion-electrode for Li-air battery. For the first time, a near linear relationship between the capacity of GDE in a non-aqueous electrolyte and the average pore diameter was demonstrated, which could be used to estimate the capacity of the GDE quantitatively.

Qu, D.; Yang, X.; Tran, C.

2010-04-02

4

Power generation using carbon mesh cathodes with different diffusion layers in microbial fuel cells  

Microsoft Academic Search

An inexpensive carbon material, carbon mesh, was examined to replace the more expensive carbon cloth usually used to make cathodes in air-cathode microbial fuel cells (MFCs). Three different diffusion layers were tested using carbon mesh: poly(dimethylsiloxane) (PDMS), polytetrafluoroethylene (PTFE), and Goretex cloth. Carbon mesh with a mixture of PDMS and carbon black as a diffusion layer produced a maximum power

Yong Luo; Fang Zhang; Bin Wei; Guangli Liu; Renduo Zhang; Bruce E. Logan

2011-01-01

5

Electro-fenton and photoelectro-fenton degradation of sulfanilic acid using a boron-doped diamond anode and an air diffusion cathode.  

PubMed

The mineralization of sulfanilic acid has been studied by electro-Fenton (EF) and photoelectro-Fenton (PEF) reaction with UVA light using an undivided electrochemical cell with a boron-doped diamond (BDD) anode and an air diffusion cathode able to generate H(2)O(2). Organics were then oxidized by hydroxyl radicals formed at the anode surface from water oxidation and in the bulk from Fenton's reaction between generated H(2)O(2) and added Fe(2+). The UVA irradiation in PEF enhanced the production of hydroxyl radicals in the bulk, accelerating the removal of organics and photodecomposed intermediates like Fe(III)-carboxylate complexes. Partial decontamination of 1.39 mM sulfanilic acid solutions was achieved by EF until 100 mA cm(-2) at optimum conditions of 0.4 mM Fe(2+) and pH 3.0. The increase in current density and substrate content led to an almost total mineralization. In contrast, the PEF process was more powerful, yielding almost complete mineralization in less electrolysis time under comparable conditions. The kinetics for sulfanilic acid decay always followed a pseudo-first-order reaction. Hydroquinone and p-benzoquinone were detected as aromatic intermediates, whereas acetic, maleic, formic, oxalic, and oxamic acids were identified as generated carboxylic acids. NH(4)(+) ion was preferentially released in both treatments, along with NO(3)(-) ion in smaller proportion. PMID:22404230

El-Ghenymy, Abdellatif; Garrido, José Antonio; Centellas, Francesc; Arias, Conchita; Cabot, Pere Lluís; Rodríguez, Rosa María; Brillas, Enric

2012-03-21

6

Investigation of the gas-diffusion-electrode used as lithium\\/air cathode in non-aqueous electrolyte and the importance of carbon material porosity  

Microsoft Academic Search

The gas-diffusion-electrode used in a Li–air cell has been studied in a unique homemade electrochemical cell. Three major obstacles for the development of a feasible Li–air system were discussed with a focus on the development of a functional gas-diffusion-electrode in non-aqueous electrolytes and the way of avoiding the passivation of gas-diffusion-electrodes caused by the deposition of the reduction products. It

Chris Tran; Xiao-Qing Yang; Deyang Qu

2010-01-01

7

Hot hollow cathode diffuse arc deposition of chromium nitride films  

Microsoft Academic Search

The hollow cathode in the diffuse arc regime (arc with hot thermionic cathode) was used for deposition of chromium and chromium nitride films. The chromium hollow cathode serving as a gas inlet was connected to a radio frequency (rf) generator with the rf power up to 350 W. The process of generation and performance of the hollow cathode discharge and

H. Baránková; L. Bárdos; L.-E. Gustavsson

2005-01-01

8

Nonaqueous Lithium-Air Batteries with an Advanced Cathode Structure  

Microsoft Academic Search

Lithium-air batteries consist of lithium anodes electrochemically coupled to atmospheric oxygen through an air cathode. Oxygen gas introduced into the battery through an air cathode is essentially an unlimited cathode reactant source. Theoretically with oxygen as an unlimited cathode reactant, the capacity of the battery is limited by the Li anode. The theoretical specific energy of the Li-oxygen cell is

Arthur Dobley; Joseph DiCarlo; K. M. Abraham

9

Diffusion-limited model for a lithium\\/air battery with an organic electrolyte  

Microsoft Academic Search

A diffusion-limited transient mathematical model for a lithium\\/air cell, with the air cathode pores flooded with an organic electrolyte, has been developed. During cell discharge, the cathode pore radius profile is reflective of the distribution of the lithium peroxide product in the cathode. The cathode pore radius profile has been predicted as a function of time, current density, oxygen gas

S. S. Sandhu; J. P. Fellner; G. W. Brutchen

2007-01-01

10

Dual electrodes oxidation of dye wastewater with gas diffusion cathode.  

PubMed

The high energy cost of an electrochemical method is the fatal drawback that hinders its large scale application in wastewater treatment. In traditional single-chamber electrolysis cell, only direct oxidation at an anode exists. Although a small amount of hydrogen peroxide is produced at the cathode by reduction, it is transferred to the anode and destroyed there without adding much benefit to organic decomposition. A two-chamber electrolytic cell, connected with an electrolyte bridge, was developed in this work. In this new reactor, direct oxidation at anode and indirect oxidation by hydrogen peroxide at cathode can occur simultaneously. Therefore "dual electrodes oxidation" in one electrochemical reactor was achieved successfully. Compared to a traditional one cell reactor, this reactor cuts the energy cost by 50%, and thus might lead to reconsideration of the electrochemical role in wastewater treatment. A Pt/C gas diffusion electrode (GDE) is fabricated and used as a cathode fed with oxygen-containing gases to produce hydrogen peroxide. When purified air diffuses through the active layer on the GDE, oxygen is reduced to hydrogen peroxide with a high yield to decompose organics. It has been found that the direct oxidation process at an anodic zone is slightly affected by factors such as pH variation, Fe(II) existence and aeration, while indirect oxidation at the cathodic zone is strongly affected. Dye used as a model pollutant was oxidized into small organic acids in both anode and cathode regions in this electrolytic reactor. GC-MS and IR spectrum were employed to analyze the intermediates formed during the degradation. Twenty intermediates have been detected, including 14 esters, 3 acids and 3 compounds with NO2 or N-OH groups. Thereafter, the degradation pathways of dye Acid Red B are proposed. PMID:15819242

Shen, Zhemin; Yang, Ji; Hu, Xiaofang; Lei, Yangming; Ji, Xiuling; Jia, Jinpin; Wang, Wenhua

2005-03-15

11

Hot hollow cathode diffuse arc deposition of chromium nitride films  

NASA Astrophysics Data System (ADS)

The hollow cathode in the diffuse arc regime (arc with hot thermionic cathode) was used for deposition of chromium and chromium nitride films. The chromium hollow cathode serving as a gas inlet was connected to a radio frequency (rf) generator with the rf power up to 350 W. The process of generation and performance of the hollow cathode discharge and its transition to the arc regime was examined for different gases. The comparison is also given with other target metals. The reactive process of CrN deposition was investigated. Films were deposited on unheated silicon and steel substrates. Highly oriented crystalline CrN films were deposited at rates up to 4.5 ?m/min. The effect of process parameters and their correlation to properties (microcrystalline structure, hardness, and deposition rate) of CrN is given.

Baránková, H.; Bárdoš, L.; Gustavsson, L.-E.

2005-07-01

12

Water-Electrolysis Cells Using Hydrogen-Diffusion Cathodes.  

National Technical Information Service (NTIS)

A matrix based on diamond powder was satisfactory for extended use over 200 C electrolyte temperature in oxygen-generating electrolysis cells using Pd-25Ag hydrogen diffusion cathodes and operating on a water-vapor feed. Over 2500 hours of essentially 100...

E. C. Kolic J. E. Clifford

1969-01-01

13

Battery with modular air cathode and anode cage  

SciTech Connect

A battery assembly of the consumable metal anode type has now been constructed for ready assembly as well as disassembly. In a non-conductive and at least substantially inert cell body, space is provided for receiving an open-structured, non-consumable anode cage. The cage has an open top for facilitating insertion of an anode. A modular cathode is used, comprising a peripheral current conductor frame clamped about a grid reinforced air cathode in sheet form. The air cathode may be double gridded. The cathode frame can be sealed, during assembly, with electrolyte-resistant-sealant as well as with adhesive. The resulting cathode module can be assembled outside the cell body and readily inserted therein, or can later be easily removed therefrom.

Niksa, Marilyn J. (Painesville, OH); Pohto, Gerald R. (Mentor, OH); Lakatos, Leslie K. (Mentor, OH); Wheeler, Douglas J. (Cleveland Heights, OH); Niksa, Andrew J. (Painesville, OH); Schue, Thomas J. (Huntsburg, OH)

1987-01-01

14

Battery with modular air cathode and anode cage  

SciTech Connect

A battery assembly of the consumable metal anode type has now been constructed for ready assembly as well as disassembly. In a non-conductive and at least substantially inert cell body, space is provided for receiving an open-structured, non-consumable anode cage. The cage has an open top for facilitating insertion of an anode. A modular cathode is used, comprising a peripheral current conductor frame clamped about a grid reinforced air cathode in sheet form. The air cathode may be double gridded. The cathode frame can be sealed, during assembly, with electrolyte-resistant-sealant as well as with adhesive. The resulting cathode module can be assembled outside the cell body and readily inserted therein, or can later be easily removed therefrom.

Niksa, Marilyn J. (Painesville, OH); Pohto, Gerald R. (Mentor, OH); Lakatos, Leslie K. (Mentor, OH); Wheeler, Douglas J. (Cleveland Heights, OH); Niksa, Andrew J. (Painesville, OH); Schue, Thomas J. (Huntsburg, OH); Turk, Thomas R. (Mentor, OH)

1988-01-01

15

Numerical modelling of stability limit of diffuse discharge on thermionic cathodes  

Microsoft Academic Search

Steady-state current transfer from arc plasmas to axially symmetric cathodes is treated. An approach is developed to calculation of the limit of stability of the diffuse mode (the current below which the diffuse mode becomes unstable). Effect produced on the stability limit by variations of control parameters (cathode dimensions, work function of the cathode material, plasma-producing gas and its pressure)

M. S. Benilov; M. D. Cunha

2003-01-01

16

Two types of diffusions at the cathode/electrolyte interface in IT-SOFCs  

SciTech Connect

Analytical transmission electron microscopy, in particular with the combination of energy dispersive X-ray spectroscopy (EDX) and electron energy-loss spectroscopy (EELS), has been performed to investigate the microstructure and microchemistry of the interfacial region between the cathode (La{sub 0.6}Sr{sub 0.4}Co{sub 0.8}Fe{sub 0.2}O{sub 3}, LSCF) and the electrolyte (Gd-doped ceria, GDC). Two types of diffusions, mutual diffusion between cathode and electrolyte as well as the diffusion along grain boundaries, have been clarified. These diffusions suggest that the chemical stability of LSCF and GDC are not as good as previously reported. The results are more noteworthy if we take into consideration the fact that such interdiffusions occur even during the sintering process of cell preparation. - Graphical Abstract: Two types of diffusions, the mutual diffusion and the diffusion along grain boundaries, occurred at the cathode/electrolyte interface of intermediate temperature solid state fuel cells, during cell preparation. The mutual diffusion is denoted by black arrows and the diffusion along grain boundaries assigned by pink arrows. Highlights: > All the cations in cathode (LSCF) and electrolyte (GDC) can mutually diffuse into each other. > Diffusing elements will segregate at grain boundaries or triple junctions around the cathode/electrolyte interface. > Two types of diffusions, the mutual diffusion and diffusion along grain boundaries, have been clarified thereafter.

Li Zhipeng, E-mail: LI.Zhipeng@nims.go.jp [Global Research Center for Environment and Energy based on Nanomaterials Science, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Mori, Toshiyuki [Global Research Center for Environment and Energy based on Nanomaterials Science, National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Auchterlonie, Graeme John [Centre for Microscopy and Microanalysis, University of Queensland, St. Lucia, Brisbane, Queensland 4072 (Australia); Zou Jin [Centre for Microscopy and Microanalysis, University of Queensland, St. Lucia, Brisbane, Queensland 4072 (Australia); Division of Materials, University of Queensland, St. Lucia, Brisbane, Queensland 4072 (Australia); Drennan, John [Centre for Microscopy and Microanalysis, University of Queensland, St. Lucia, Brisbane, Queensland 4072 (Australia)

2011-09-15

17

Performance of Carbon/Polytetrafluoroethylene (PTFE) Air Cathodes from pH 0 to 14 for Li-Air Batteries.  

National Technical Information Service (NTIS)

The purpose of this project was to construct an inexpensive air cathode free of catalyst that is capable of functioning in both acidic and basic electrolytes. The performance of an uncatalyzed air cathode for use in a Li-Air battery was evaluated over the...

J. A. Read M. B. Marx

2007-01-01

18

Diffusion of undecane (1); air (2)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) undecane; (2) air

Winkelmann, J.

19

Diffusion of air (1); cyanogen chloride (2)  

Microsoft Academic Search

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) cyanogen chloride

J. Winkelmann

2007-01-01

20

Diffusion of air (1); sulfur hexafluoride (2)  

Microsoft Academic Search

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) sulfur hexafluoride

J. Winkelmann

2007-01-01

21

Diffusion of air (1); aniline (2)  

Microsoft Academic Search

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) aniline

J. Winkelmann

2007-01-01

22

Diffusion of air (1); ammonia (2)  

Microsoft Academic Search

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) ammonia

J. Winkelmann

2007-01-01

23

Diffusion of air (1); carbon dioxide (2)  

Microsoft Academic Search

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) carbon dioxide

J. Winkelmann

2007-01-01

24

Diffusion of air (1); trichloronitromethane (2)  

Microsoft Academic Search

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) trichloro-nitro-methane

J. Winkelmann

2007-01-01

25

Diffusion of air (1); water (2)  

Microsoft Academic Search

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) water

J. Winkelmann

2007-01-01

26

Diffusion of air (1); bromine (2)  

Microsoft Academic Search

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) bromine

J. Winkelmann

2007-01-01

27

Diffusion of air (1); hydrogen cyanide (2)  

Microsoft Academic Search

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) hydrogen cyanide

J. Winkelmann

2007-01-01

28

Diffusion of air (1); methane (2)  

Microsoft Academic Search

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) methane

J. Winkelmann

2007-01-01

29

Diffusion of air (1); phosgene (2)  

Microsoft Academic Search

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) phosgene

J. Winkelmann

2007-01-01

30

Diffusion of air (1); biphenyl (2)  

Microsoft Academic Search

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) biphenyl

J. Winkelmann

2007-01-01

31

Diffusion of air (1); argon (2)  

Microsoft Academic Search

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) argon

J. Winkelmann

2007-01-01

32

Diffusion of air (1); chlorine (2)  

Microsoft Academic Search

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) chlorine

J. Winkelmann

2007-01-01

33

Diffusion of air (1); phosgene (2)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) phosgene

Winkelmann, J.

34

Diffusion of tricresyl phosphate (1); air (2)  

Microsoft Academic Search

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) tricresyl phosphate; (2) air

J. Winkelmann

2007-01-01

35

Diffusion of tricresyl phosphate (1); air (2)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) tricresyl phosphate; (2) air

Winkelmann, J.

36

Diffusion of air (1); furfural (2)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) furfural

Winkelmann, J.

37

Diffusion of propylbenzene (1); air (2)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) propylbenzene; (2) air

Winkelmann, J.

38

Chromium transport by solid state diffusion on solid oxide fuel cell cathode  

Microsoft Academic Search

Iron–chromium ferritic stainless steel is widely used in solid oxide fuel cell (SOFC) components. At 650–800°C, stainless steels form a protective chromia oxide scale. This low conductivity catalytic compound can degrade SOFC cathode performance. The migration of Cr species onto the cathode occurs through vapor transport and\\/or solid state diffusion, and electrochemical reactions may affect the migration.It is important to

Grace Yan Yi Lau; Michael C. Tucker; Craig P. Jacobson; Steven J. Visco; Stacy H. Gleixner; Lutgard C. DeJonghe

2010-01-01

39

Behavior of diffusing elements from an integrated cathode of an electrochemical reduction process  

Microsoft Academic Search

The electrochemical reduction process for spent oxide fuel is operated in a molten salt bath and adopts an integrated cathode\\u000a in which the oxides to be reduced act as a reactive cathode in the molten salt electrolyte cell. Heat-generating radioisotopes\\u000a in the spent oxide fuel such as cesium and strontium are dissolved in the molten salt and diffuse from the

Byung Heung Park; Jin-Mok Hur

2010-01-01

40

SOFC cathode\\/electrolyte interfaces. Part II: Study of NdAlO 3 diffusion barriers  

Microsoft Academic Search

The growth of La2Zr2O7 and SrZrO3 reaction layers at the cathode-electrolyte interface during the fabrication process and in operating conditions negatively affects the SOFC (solid oxide fuel cell) performance. In the present paper the effectiveness of diffusion barriers at the SOFC cathode-electrolyte interface is investigated. Thin layers of neodymium aluminate (NdAlO3) were evaporated onto yttria-stabilized zirconia (YSZ) substrates and characterized

C. Brugnoni; U. Ducati; C. Chemelli; M. Scagliotti; G. Chiodelli

1995-01-01

41

Anode-fall and cathode-fall voltages of air arc in atmosphere between silver electrodes  

Microsoft Academic Search

A method for estimating an anode-fall and a cathode-fall voltages of an arc discharge was proposed. By using this method, the separate estimation of the anode-fall and the cathode-fall voltages was performed for an air arc in atmosphere burning between silver electrodes. The derived anode-fall and cathode-fall voltages proved to be about 4.5 V and 14 V, respectively. It was

Rei Hemmi; Yasunobu Yokomizu; Toshiro Matsumura

2003-01-01

42

The transition from a filamentary dielectric barrier discharge to a diffuse barrier discharge in air at atmospheric pressure  

Microsoft Academic Search

A transparent plasma discharge reactor using air was used to investigate the transition from a filamentary dielectric barrier discharge (FDBD) operation regime into the diffuse barrier discharge regime. Recent results of other researchers indicate that the stability of diffuse barrier discharges in nitrogen may be attributed to the lack of a fully formed cathode fall layer when the discharge operates

Daniel M. Sherman

2005-01-01

43

Molecular Dynamics Study of Lithium Diffusion in Lithium-Manganese Spinel Cathode Materials  

SciTech Connect

A series of molecular dynamics computer simulations of the self-diffusion of lithium in pure and several doped lithium-manganese spinel materials has been completed. The theoretical approach is part of an effort to understand the mechanisms and rates of lithium diffusion, and to evaluate the structural control of the cathode materials upon lithium intercalation (charge-discharge) process. The molecular dynamics approach employs a fully ionic forcefield that accounts for electrostatic, repulsive, and dispersion interactions among all ions.

Cygan, R.T.; Westrich, H.R.; Dought, D.H.

1998-01-01

44

Evolution of Copper Vapor from the Cathode of a Diffuse Vacuum Arc  

Microsoft Academic Search

The metal-vapor evolution from the cathode of a diffuse vacuum arc is described by a model that starts from the expression for the collisionless expansion into vacuum of atoms originating from an instantaneous point source. The velocity distribution is assumed to be Maxwellian at the moment the atoms are released from the source. By convolution with the vapor generation rate,

G. Lins

1987-01-01

45

Study of azo dye decolorization and determination of cathode microorganism profile in air-cathode microbial fuel cells  

Microsoft Academic Search

Five textile azo dyes, as part of an artificial mixture, were treated in single-chamber air-cathode microbial fuel cells while simultaneously utilizing acetate for electricity production. Remazol Black, Remazol Brilliant Blue, Remazol Turquoise Blue, Reactive Yellow and Reactive Red at concentrations of 40 or 80 mg l were decolorized to a similar extent, at averages of 78, 95, 53, 93 and 74%, respectively,

Mert Kumru; Hilal Eren; Tunc Catal; Hakan Bermek; Alper Tunga Akarsuba??

2012-01-01

46

The use of air fuel cell cathodes to remove contaminants from spent chromium plating solutions.  

PubMed

Results from experiments using an impregnation-reduction (I-R) Pt / Nafion membrane electrode assembly (MEA) in an air fuel cell cathode to remove contaminants (Cu(II), Ni(II), and Fe(III)) from spent chromium electroplating baths are presented in this study. A platinum-carbon (Pt-C) / Nafion MEA and a Pb planar cathode were also used for comparison. The average removal rates of Cu(II) and Ni(II) were almost the same (0.39 and 0.40 mM hr(-1) (or 0.117 and 0.12 mmol hr(-1)), respectively) but higher than that of Fe(III) (0.16 mM hr(-1), or 0.048 mmol hr(-1)) in accordance with the Nernst-Planck flux equation. The removal rates for the same cation were independent of the cathode used. The average removal rate of each impurity was approximately proportional to the product of its initial concentration and separator area/anolyte volume ratio using Pb cathodes. Under constant current conditions the system using the Pt-C / Nafion cathode needed the highest cell voltage, about 3 V more than needed for the system with the Pt / Nafion cathode. The cell voltage required using the Pt / Nafion cathode was similar to that using the conventional planar Pb cathode. Analyses of cathode deposits by SEM/EDS and XPS techniques indicated they were minimal on the Pb and Pt / Nafion cathode and more apparent on the Pt-C / Nafion cathode. The primary deposits on the Pb cathode were chromium oxides (e.g., Cr2O3) with minor amount of lead chromate (lead dichromate or lead trichromate) and other chromium solids (Cr black). As expected, the dominant deposit on the lead anode surface was PbO2. PMID:15027648

Huang, K L; Holsen, T M; Chou, T C; Yang, M C

2004-01-01

47

Degradation of 4-chlorophenol by the anodic-cathodic cooperative effect with a Pd/MWNT gas-diffusion electrode.  

PubMed

Pd/multi-walled carbon nanotubes (MWNTs) catalyst used for the gas-diffusion electrode was prepared by ethylene glycol (EG) reduction and characterized by the X-ray diffraction (XRD) and scanning electron microscope (SEM). The results indicated that Pd particles with an average size of 8.0 nm were highly dispersed in the MWNTs with amorphous structure. In a diaphragm electrolysis system with a Ti/RuO(2)/IrO(2) anode and the Pd/MWNT gas diffusion cathode, the degradation of 4-chlorophenol was performed by a combination of electrochemical reduction and oxidation. The combined process was in favor of improving 4-chlorophenol degradation efficiency. The optimum reaction conditions were as following: initial pH 7, aeration with hydrogen and air. Under the optimized electrolysis conditions the removal of 4-chlorophenol in the anodic and cathodic compartments were 98.5 and 90.5%, respectively. Additionally, based on the analysis of electrolysis intermediates using high performance liquid chromatography (HPLC) and ion chromatography (IC), the electrolysis degradation of 4-chlorophenol was proposed containing the intermediates, such as phenol, hydroquinone, benzoquinone, maleic acid, fumaric acid, succinic acid, malonic acid, oxalic acid, acetic acid and formic acid. PMID:22592472

Wang, H; Wei, X J; Bian, Z Y

2012-01-01

48

A new double-cathode ionic air flowmeter for internal combustion engines  

Microsoft Academic Search

A very quick response air mass flowmeter for accurate measurement of intake air in internal combustion engines was developed. This flowmeter consists of a disk type anode surrounded by two coaxial cylinders which serve as the first and second cathodes, respectively. Steady state flow tests show this flowmeter has sufficient accuracy, linearity, and directivity and no hysteresis was observed. The

M. Tanaka; U. Kitajima; S. Doi; T. Sato

1988-01-01

49

Two-phase flow and transport in the air cathode of proton exchange membrane fuel cells  

Microsoft Academic Search

Two-phase flow and transport of reactants and products in the air cathode of proton exchange membrane (PEM) fuel cells is studied analytically and numerically. Single- and two-phase regimes of water distribution and transport are classified by a threshold current density corresponding to first appearance of liquid water at the membrane\\/cathode interface. When the cell operates above the threshold current density,

Z. H. Wang; C. Y. Wang; K. S. Chen

2001-01-01

50

A study of diffusion behavior of elements lanthanum and oxygen in Mo–La 2O 3 cathode  

Microsoft Academic Search

The diffusion behavior of elements lanthanum and oxygen in Mo–La2O3 cathode has been carried out by using Auger Electron Spectroscopy. Lanthanum and oxygen ions (La3+ and O2+) diffuse from the grain boundaries to the surface. The experimental results were analyzed by kinetics of grain boundary diffusion. In the temperature range 1123 K–1423 K, the diffusion coefficients of La3+ and O2+

Wang Jinshu; Zhou Meiling; Nie Zuoren; Zhang Jiuxing; Zuo Tieyong; Wang Yiman

2000-01-01

51

Portable power source based on air-hydrogen fuel cells with free-breathing cathodes  

NASA Astrophysics Data System (ADS)

Portable power source based on air-hydrogen fuel cells (FCs) operating in a free-breathing cathode regime has been developed. At a volume of 100 cm3, the source has a power capacity of 8.5 W h and generates a power of 2 W that is independent of the temperature within 5-40°C and the relative humidity of the ambient air within 40-98%. With respect to the specific energy characteristics, the proposed PTI type device exceeds other air-hydrogen FCs and in some respects is even superior to power sources based on air-methanol FCs.

Gurevich, S. A.; Terukov, E. I.; Kon'kov, O. I.; Tomasov, A. A.; Zelenina, N. K.; Kompan, M. E.; Gorokhov, M. V.; Astrova, E. V.; Andronikov, D. A.; Zabrodskii, A. G.

2011-05-01

52

Study of azo dye decolorization and determination of cathode microorganism profile in air-cathode microbial fuel cells.  

PubMed

Five textile azo dyes, as part of an artificial mixture, were treated in single-chamber air-cathode microbial fuel cells while simultaneously utilizing acetate for electricity production. Remazol Black, Remazol Brilliant Blue, Remazol Turquoise Blue, Reactive Yellow and Reactive Red at concentrations of 40 or 80 mg L(-1) were decolorized to a similar extent, at averages of 78, 95, 53, 93 and 74%, respectively, in 24 hours. During the process of decolorization, electricity generation from acetate oxidation continued. Power densities obtained in the presence of textile dyes ranged from 347 to 521 mW m(-2) at the current density range of 0.071 - 0.086 mA cm(-2). Microbial community analyses of cathode biofilm exhibited dynamic changes in abundant species following dye decolorization. Upon the addition of the first dye, a major change (63%) in microbial diversity was observed; however, subsequent addition of other dyes did not affect the community profile significantly. Actinobacteria, Aquamicrobium, Mesorhizobium, Ochrobactrum, Thauera, Paracoccus, Achromobacter and Chelatacoccus affiliated phylotypes were the major phylotypes detected. Our results demonstrate that microbial fuel cells could be a promising alternative for treatment of textile wastewaters and an active bacterial community can rapidly be established for simultaneous azo dye decolorization and sustainable electricity generation. PMID:23240212

Kumru, Mert; Eren, Hilal; Catal, Tunc; Bermek, Hakan; Akarsuba?i, Alper Tunga

2012-09-01

53

In situ Fourier transform infrared-diffuse reflection spectroscopy of direct methanol fuel cell anodes and cathodes  

Microsoft Academic Search

In situ Fourier transform infrared-diffuse reflection spectroscopy (FTIR-DRS) was used to study both the adsorbed and desorbed species produced on high surface area anodes and cathodes of direct methanol\\/oxygen fuel cells. The authors investigated platinum-ruthenium and platinum black as anodes. The cathodes studied were platinum black. The primary product detected on both Pt-black and Pt-Ru anodes at low methanol\\/water vapor

Qinbai Fan; C. Pu; E. S. Smotkin

1996-01-01

54

A single chamber stackable microbial fuel cell with air cathode.  

PubMed

A single chamber stackable microbial fuel cell (SCS-MFC) comprising four MFC units was developed. When operated separately, each unit generated a volumetric power density (P(max,V)) of 26.2 W/m(3) at 5.8 mA or 475 mV. The total columbic efficiency was 40% for each unit. Parallel connection of four units produced the same level of power output (P(max,V) of 22.8 W/m(3) at 27 mA), which was approximately four times higher than a single unit alone. Series connection of four units, however, only generated a maximum power output of 14.7 W/m(3) at 730 mV, which was less than the expected value. This energy loss appeared to be caused by lateral current flow between two units, particularly in the middle of the system. The cathode was found to be the major limiting factor in our system. Compared to the stacked operation of multiple separate MFCs, our single chamber reactor does not require a delicate water distribution system and thus is more easily implemented in pre-existing wastewater treatment facilities with serpentine flow paths, such as fixed-bed reactors, with minimal infrastructure changes. PMID:19034389

Wang, Bin; Han, Jong-In

2008-11-26

55

Pre-acclimation of a wastewater inoculum to cellulose in an aqueous-cathode MEC improves power generation in air-cathode MFCs.  

PubMed

Cellulose has been used in two-chamber microbial fuel cells (MFCs), but power densities were low. Higher power densities can be achieved in air-cathode MFCs using an inoculum from a two-chamber, aqueous-cathode microbial electrolysis cell (MEC). Air-cathode MFCs with this inoculum produced maximum power densities of 1070 mW m(-2) (cathode surface area) in single-chamber and 880 mW m(-2) in two-chamber MFCs. Coulombic efficiencies ranged from 25% to 50%, and COD removals were 50-70% based on total cellulose removals of 60-80%. Decreasing the reactor volume from 26 to 14 mL (while maintaining constant electrode spacing) decreased power output by 66% (from 526 to 180 mW m(-2)) due to a reduction in total mass of cellulose added. These results demonstrate that air-cathode MFCs can produce high power densities with cellulose following proper acclimation of the inoculum, and that organic loading rates are important for maximizing power densities from particulate substrates. PMID:20580223

Cheng, Shaoan; Kiely, Patrick; Logan, Bruce E

2010-06-26

56

Continuous electricity generation by a graphite granule baffled air-cathode microbial fuel cell  

Microsoft Academic Search

A baffled air-cathode microbial fuel cell (BAFMFC) was designed and operated under continuous flow. With glucose fed as substrate, an average voltage of 652 mV was obtained under the external resistance of 1000 X (30 C). The maximum power density was 15.2 W\\/m 3 with the chemical oxygen demand (COD) removal rate of 88.0%. The overall resistance was 13.7 X

Yujie Feng; He Lee; Xin Wang; Yaolan Liu; Weihua He

2010-01-01

57

A new double-cathode ionic air flowmeter for internal combustion engines  

SciTech Connect

A very quick response air mass flowmeter for accurate measurement of intake air in internal combustion engines was developed. This flowmeter consists of a disk type anode surrounded by two coaxial cylinders which serve as the first and second cathodes, respectively. Steady state flow tests show this flowmeter has sufficient accuracy, linearity, and directivity and no hysteresis was observed. The effects of temperature, pressure, and humidity of the air were studied. For pulsating air flow this flowmeter showed excellent dynamic response. Furthermore, this meter succeeded in measuring the intake air flow rate of a single cylinder spark ignition engine under firing conditions. Therefore, this flowmeter is very useful not only for analyzing the transient characteristics of internal combustion engines, but also for the accurate control of the fuel injection systems of gasoline engines.

Tanaka, M.; Kitajima, U.; Doi, S.; Sato, T.

1988-01-01

58

Diffusion of air (1); 2-methyl-tetrahydro-furan (2)  

Microsoft Academic Search

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) 2-methyl-tetrahydro-furan

J. Winkelmann

2007-01-01

59

Diffusion of air (1); furan-2-yl-methanethiol (2)  

Microsoft Academic Search

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) furan-2-yl-methanethiol

J. Winkelmann

2007-01-01

60

Diffusion of air (1); water (2); sodium chloride (3)  

Microsoft Academic Search

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) water; (3) sodium chloride

J. Winkelmann

2007-01-01

61

Diffusion of air (1); tetrahydrofuran-2-yl-methanol (2)  

Microsoft Academic Search

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) air; (2) tetrahydrofuran-2-yl-methanol

J. Winkelmann

2007-01-01

62

Diffusion of phosphorous acid tributyl ester (1); air (2)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) phosphorous acid tributyl ester; (2) air

Winkelmann, J.

63

Chemistry on the low field anodes and cathodes of air corona gaps  

NASA Astrophysics Data System (ADS)

Surface effects of electrical coronas have been studied on the low field electrodes of point-to-plane air gaps with discharges burning in negative and positive glow regimes, i.e., mainly producing chemical effects without significant sputtering or thermal effects. Most of these chemical effects are due to oxidation and reduction processes taking place in aqueous microdroplets formed by the discharge where oxides, nitrates, and cyanides, are mainly found. Generally oxidation prevails providing very high oxidation states, but using preoxidized gold samples as cathodes enabled the separate observation of reduction phenomena.

Séverac, C.; Jouve, G.; Goldman, A.; Goldman, M.

2004-04-01

64

Soot Formation in Hydrocarbon/Air Laminar Jet Diffusion Flames.  

National Technical Information Service (NTIS)

Soot processes within hydrocarbon/air diffusion flames are important because they affect the durability and performance of propulsion systems, the hazards of unwanted fires, the pollutant and particulate emissions from combustion processes, and the potent...

P. B. Sunderland G. M. Faeth

1994-01-01

65

The Diffusion of Air Through Monel Metal  

Microsoft Academic Search

The rate at which gases from the atmosphere diffuse through monel metal at various temperatures has been observed. An evacuated heavy-walled metal tube, a section of which was machined to a thin wall, was heated in a furnace. The rate at which the pressure inside the tube increased as a result of the diffusion of gases from the atmosphere was

H. S. Coleman; H. L. Yeagley

1943-01-01

66

Effect of electrolyte pH on the rate of the anodic and cathodic reactions in an air-cathode microbial fuel cell  

Microsoft Academic Search

The measurement of electricity generation from an air-cathode microbial fuel cell (MFC) with a mixed bacteria culture at different pH showed that this MFC could tolerate an initial (feed solution) pH as high as 10. The optimal initial pH was between 8 and 10 with higher current generation compared to lower or higher pH. The bacterial metabolism exhibited a buffer

Zhen He; Yuelong Huang; Aswin K. Manohar; Florian Mansfeld

2008-01-01

67

Atmospheric Diffusion and Air Pollution: Abstracts.  

National Technical Information Service (NTIS)

The abstracts cover a variety of areas in pollution. Included are diffusion of these pollutants, sampling, tall emission sources, the factor of wind direction, and characteristics of the change in pH in atmospheric precipitation in urban areas.

M. E. Berlyand

1971-01-01

68

Model of a diffuse column vacuum arc with cathode jets burning in parallel with a high-current plasma column  

Microsoft Academic Search

The behavior of the high-current diffuse columnar arc in vacuum is considered. A single cathode spot jet appearing to the side of a high-current plasma column is studied using a two-dimensional magnetohydrodynamic model. The plasma expansion and current flow in the jet are affected by the presence of the main column and the applied axial magnetic field (AMF). Increasing the

Michael Keidar; Michael Bruce Schulman; Erik D. Taylor

2004-01-01

69

Enhancement of diffuse reflectance using air tunnel structure.  

PubMed

Submicrometer air gap structure has formed on diffuse reflection structure to improve light reflectance. Covering polymer or liquid on a diffuse reflector to make optical components induces the severe decrease of the total reflectance, since the diffuse reflected angle of some light rays is larger than the critical angle and the rays travel to the medium until meeting a proper small incident angle. The reflectance drops to 68% of the original value with just a polymer coating on the diffuse reflector. The formation of an air tunnel structure between the polymer layer and the diffuse reflector makes a symmetrical reflective index matching state and recovers 95% of the original reflectance. Due to the simple fabrication process and the chemical stability, the structure can be applied to various optical components and reflective display devices. PMID:23381414

Jang, Jae Eun; Lee, Gae Hwang; Song, Byoung Gwon; Cha, Seung Nam; Jung, Jae Eun

2013-02-01

70

Survey on the air diffusion devices for air-conditioning systems in Hong Kong  

Microsoft Academic Search

Design data on the air diffusion systems for air-conditioned buildings in Hong Kong are surveyed to get a general picture of the current practice. Questionnaires were distributed to building services consultant engineers, contracting firms, and building operation and maintenance teams to collect information related to the geometry of the space, primary design objectives and criteria, types of air terminal devices

W. K. Chow; L. T. Wong

1998-01-01

71

Vortex dynamics and structures of methane\\/air jet diffusion flames with air coflow  

Microsoft Academic Search

In this paper, high speed direct\\/schlieren imaging system together with Particle Image Velocimetry (PIV) system is applied to investigate the vortex dynamics and structures of methane–air coflow diffusion flames. The schlieren and PIV images show that the dynamics of the vortices outside the visible flame are strongly affected by the coflow air velocity. The coflow air is observed to push

Q. Wang; H. Gohari Darabkhani; L. Chen; Y. Zhang

72

Diffusion barriers in modified air brazes  

DOEpatents

A method for joining two ceramic parts, or a ceramic part and a metal part, and the joint formed thereby. The method provides two or more parts, a braze consisting of a mixture of copper oxide and silver, a diffusion barrier, and then heats the braze for a time and at a temperature sufficient to form the braze into a bond holding the two or more parts together. The diffusion barrier is an oxidizable metal that forms either a homogeneous component of the braze, a heterogeneous component of the braze, a separate layer bordering the braze, or combinations thereof. The oxidizable metal is selected from the group Al, Mg, Cr, Si, Ni, Co, Mn, Ti, Zr, Hf, Pt, Pd, Au, lanthanides, and combinations thereof.

Weil, Kenneth Scott (Richland, WA); Hardy, John S. (Richland, WA); Kim, Jin Yong (Richland, WA); Choi, Jung-Pyung (Richland, WA)

2010-04-06

73

Diffusion barriers in modified air brazes  

DOEpatents

A method for joining two ceramic parts, or a ceramic part and a metal part, and the joint formed thereby. The method provides two or more parts, a braze consisting of a mixture of copper oxide and silver, a diffusion barrier, and then heats the braze for a time and at a temperature sufficient to form the braze into a bond holding the two or more parts together. The diffusion barrier is an oxidizable metal that forms either a homogeneous component of the braze, a heterogeneous component of the braze, a separate layer bordering the braze, or combinations thereof. The oxidizable metal is selected from the group Al, Mg, Cr, Si, Ni, Co, Mn, Ti, Zr, Hf, Pt, Pd, Au, lanthanides, and combinations thereof.

Weil, Kenneth Scott; Hardy, John S; Kim, Jin Yong; Choi, Jung-Pyung

2013-04-23

74

Temperature dependence of OH diffusion in air and He  

Microsoft Academic Search

Although accurate knowledge of OH diffusion under atmospheric conditions is important, only one experimental study has been carried out at room temperature. Here, we report laboratory measurements of the OH diffusion coefficient in He and in a mixture of He and air over the range 218–318 K, using a temperature-controlled flow tube coupled to a low-pressure chemical ionization mass spectrometer.

Yong Liu; Andrey V. Ivanov; Mario J. Molina

2009-01-01

75

Temperature dependence of OH diffusion in air and He  

Microsoft Academic Search

Although accurate knowledge of OH diffusion under atmospheric conditions is important, only one experimental study has been carried out at room temperature. Here, we report laboratory measurements of the OH diffusion coefficient in He and in a mixture of He and air over the range 218-318 K, using a temperature-controlled flow tube coupled to a low-pressure chemical ionization mass spectrometer.

Yong Liu; Andrey V. Ivanov; Mario J. Molina

2009-01-01

76

Mineralization of pentachlorophenol with enhanced degradation and power generation from air cathode microbial fuel cells.  

PubMed

The combined anaerobic-aerobic conditions in air-cathode single-chamber MFCs were used to completely mineralize pentachlorophenol (PCP; 5 mg/L), in the presence of acetate or glucose. Degradation rates of 0.140 ± 0.011 mg/L-h (acetate) and 0.117 ± 0.009 mg/L-h (glucose) were obtained with maximum power densities of 7.7 ± 1.1 W/m(3) (264 ± 39 W/m(2), acetate) and 5.1 ± 0.1 W/m(3) (175 ± 5 W/m(2), glucose). At a higher PCP concentration of 15 mg/L, PCP degradation rates increased to 0.171 ± 0.01 mg/L-h (acetate) and 0.159 ± 0.011 mg/L-h (glucose). However, power was inversely proportional to initial PCP concentration, with decreases of 0.255 W/mg PCP (acetate) and 0.184 W/mg PCP (glucose). High pH (9.0, acetate; 8.0, glucose) was beneficial to exoelectrogenic activities and power generation, whereas an acidic pH = 5.0 decreased power but increased PCP degradation rates (0.195 ± 0.002 mg/L-h, acetate; 0.173 ± 0.005 mg/L-h, glucose). Increasing temperature from 22 to 35°C enhanced power production by 37% (glucose) to 70% (acetate), and PCP degradation rates (0.188 ± 0.01 mg/L-h, acetate; 0.172 ± 0.009 mg/L-h, glucose). Dominant exoelectrogens of Pseudomonas (acetate) and Klebsiella (glucose) were identified in the biofilms. These results demonstrate that PCP degradation using air-cathode single-chamber MFCs may be a promising process for remediation of water contaminated with PCP as well as for power generation. PMID:22392229

Huang, Liping; Gan, Linlin; Wang, Ning; Quan, Xie; Logan, Bruce E; Chen, Guohua

2012-03-22

77

Electrochemical Performance and Stability of the Cathode for Solid Oxide Fuel Cells II. Role of Ni diffusion on LSM performance  

SciTech Connect

The sintering of a standard (La0.8Sr0.2)0.98MnO3 (LSM-20) solid oxide fuel cell cathode composition (in the temperature range of 1050-1200şC) on anode-supported cells utilizing a Ni-YSZ anode and thin YSZ electrolyte (<10 ?m thickness) has revealed the need for a protective ceria interlayer to prevent a detrimental interaction between the YSZ and the LSM. The interaction, however, is not the typically assumed formation of insulating La- and/or Sr-zirconate, but rather the result of Ni diffusion from the anode through the YSZ electrolyte and into the LSM resulting in coarsening and increased densification of the LSM microstructure. As an alternative to the use of a protective ceria interlayer, the presence of YSZ in the cathode material was able to suppress coarsening of LSM, thereby significantly improving the electrochemical performance.

Zhou, Xiao Dong; Simner, Steven P.; Templeton, Jared W.; Nie, Zimin; Stevenson, Jeffry W.; Gorman, B. P.

2010-03-26

78

Doped lanthanum nickelates with a layered perovskite structure as bifunctional cathode catalysts for rechargeable metal-air batteries.  

PubMed

Rechargeable metal-air batteries have attracted a great interest in recent years because of their high energy density. The critical challenges facing these technologies include the sluggish kinetics of the oxygen reduction-evolution reactions on a cathode (air electrode). Here, we report doped lanthanum nickelates (La2NiO4) with a layered perovskite structure that serve as efficient bifunctional electrocatalysts for oxygen reduction and evolution in an aqueous alkaline electrolyte. Rechargeable lithium-air and zinc-air batteries assembled with these catalysts exhibit remarkably reduced discharge-charge voltage gaps (improved round-trip efficiency) as well as high stability during cycling. PMID:24053465

Jung, Kyu-Nam; Jung, Jong-Hyuk; Im, Won Bin; Yoon, Sukeun; Shin, Kyung-Hee; Lee, Jong-Won

2013-09-23

79

Increasing power generation for scaling up single-chamber air cathode microbial fuel cells.  

PubMed

Scaling up microbial fuel cells (MFCs) requires a better understanding the importance of the different factors such as electrode surface area and reactor geometry relative to solution conditions such as conductivity and substrate concentration. It is shown here that the substrate concentration has significant effect on anode but not cathode performance, while the solution conductivity has a significant effect on the cathode but not the anode. The cathode surface area is always important for increasing power. Doubling the cathode size can increase power by 62% with domestic wastewater, but doubling the anode size increases power by 12%. Volumetric power density was shown to be a linear function of cathode specific surface area (ratio of cathode surface area to reactor volume), but the impact of cathode size on power generation depended on the substrate strength (COD) and conductivity. These results demonstrate the cathode specific surface area is the most critical factor for scaling-up MFCs to obtain high power densities. PMID:21273062

Cheng, Shaoan; Logan, Bruce E

2011-01-01

80

ANALYTICAL DIFFUSION MODEL FOR LONG DISTANCE TRANSPORT OF AIR POLLUTANTS  

EPA Science Inventory

A steady-state two-dimensional diffusion model suitable for predicting ambient air pollutant concentrations averaged over a long time period (e.g., month, season, or year) and resulting from the transport of pollutants for distances greater than about 100 km from the source is de...

81

Numerical Simulation Of Methane-air Turbulent Diffusion Flames  

Microsoft Academic Search

This study deals with the numerical investigation of a chemically reacting methane gas jet which issues into a quiescent atmosphere. Assuming fuel-air mixing to be the rate controlling process (Le. Infinite chemical kinetics) the Shvab Zel'dovich formulation has been employed for analysing the turbulent diffusion flame characteristics. A transient FEM scheme in terms of the primitive variables ( u ,

P. V. R. C. Sekhar; T. Sundararajan

1997-01-01

82

Toxic potency and effects of diffuse air pollution  

Microsoft Academic Search

Diffuse air pollution consists of an omnipresent complex mixture of pollutants that is emitted from many widely dispersed sources as traffic, industries, households, energy plants, waste incinerators, and agriculture. It can be deposited in relatively remote areas as a result of (long-range) airborne transport. It has a heterogeneous composition in time and space and consists of many known and unknown

Timo Hamers

2002-01-01

83

Field-based determination of air diffusivity using soil air and atmospheric pressure time series  

Microsoft Academic Search

Air diffusivity in two zones over a 4.6-m interval of the unsaturated zone was determined through analysis of atmospheric pressure and soil air pressure time series. Regression analysis was used to calculate the ratio of amplitudes (admittance) and phase lag between these series at diurnal and semidiurnal frequencies. The admittance for each of the monitoring zones was close to unity

Stuart Rojstaczer; John P. Tunks

1995-01-01

84

Electricity generation from fermented primary sludge using single-chamber air-cathode microbial fuel cells.  

PubMed

Single-chamber air-cathode microbial fuel cells (MFCs) were used to generate electricity from fermented primary sludge. Fermentation (30 °C, 9 days) decreased total suspended solids (26.1-16.5 g/L), volatile suspended solids (24.1-15.3g/L) and pH (5.7-4.5), and increased conductivity (2.4-4.7 mS/cm), soluble COD (2.66-15.5 g/L), and volatile fatty acids (1.9-10.1g/L). To lower the COD and increase pH, fermentation supernatant was diluted with primary effluent before being used in the MFCs. The maximum power density was 0.32 ± 0.01 W/m(2), compared to 0.24 ± 0.03 W/m(2) with only primary effluent. Power densities were higher with phosphate buffer added to the supernatant (1.03 ± 0.06 W/m(2)) or the solution (0.87 ± 0.05 W/m(2)). Coulombic efficiencies ranged from 18% to 57%, and sCOD removals from 84% to 94%. These results demonstrated that sludge can effectively be used for power generation when fermented and then diluted with only primary effluent. PMID:23186679

Yang, Fei; Ren, Lijiao; Pu, Yuepu; Logan, Bruce E

2012-10-16

85

Comparison of Electrode Reduction Activities of Geobacter sulfurreducens and an Enriched Consortium in an Air-Cathode Microbial Fuel Cell  

Microsoft Academic Search

An electricity-generating bacterium, Geobacter sulfurreducens PCA, was inoculated into a single-chamber, air-cathode microbial fuel cell (MFC) in order to determine the maximum electron transfer rate from bacteria to the anode. To create anodic reaction-limiting conditions, where electron transfer from bacteria to the anode is the rate-limiting step, anodes with electrogenic biofilms were reduced in size and tests were conducted using

S. Ishii; K. Watanabe; S. Yabuki; B. E. Logan; Y. Sekiguchi

2008-01-01

86

Advances and trends in primary and small secondary batteries with zinc anodes and manganese dioxide and\\/or air cathodes  

Microsoft Academic Search

Incremental improvements continue to be made year by year in the consumer carbon-zinc and alkaline zinc-manganese dioxide cells. In addition, primary and secondary zinc-air cells many with substantial amounts of manganese dioxide in the cathode are becoming more common in consumer use. The gain in the past fifteen years in the carbon zinc cells approaches fifteen percent and that in

Brooke Schumm

2000-01-01

87

Development of a cathode-directed streamer discharge in air at different pressures: Experiment and comparison with direct numerical simulation  

Microsoft Academic Search

The results are given of an experimental investigation of a cathode-directed streamer discharge in synthetic air in the pressure range from 760to300torr and their comparison with the results of direct numerical simulation in a 2D hydrodynamic approximation. The pattern of discharge branching upon variation of pressure is investigated experimentally. The results are given of comparison of the predicted and measured

S. Pancheshnyi; M. Nudnova; A. Starikovskii

2005-01-01

88

Calculation of diffusion coefficients in air-metal thermal plasmas  

Microsoft Academic Search

This paper presents the combined diffusion coefficients of metal vapours (silver, copper and iron) in air thermal plasmas for temperatures ranging from 300 to 30 000 K. The theory used to calculate these coefficients is remembered and validated by comparison with the literature values in several cases such as Ar-He, Ar-Cu and N2-O2 mixtures. The results are discussed showing the

Y. Cressault; A. Gleizes

2010-01-01

89

Characteristics of diffuse electrical discharges stabilized in flowing air, argon and nitrogen  

Microsoft Academic Search

In studying electrically augmented flames it has been found that the fuel flow to a burner can be reduced to zero, leaving an electrical discharge stabilized in axially flowing air at atmospheric pressure. An electrode configuration of axial anode and cylindrical cathode stabilized the discharge under conditions where it would be unstable in quiescent air. No ionizable seed material was

D A Allen; I Fells; F J Fletcher

1971-01-01

90

Exciton Diffusion in Air-Suspended Single-Walled Carbon Nanotubes  

Microsoft Academic Search

Direct measurements of the diffusion length of excitons in air-suspended single-walled carbon nanotubes are reported. Photoluminescence microscopy is used to identify individual nanotubes and to determine their lengths and chiral indices. Exciton diffusion length is obtained by comparing the dependence of photoluminescence intensity on the nanotube length to numerical solutions of diffusion equations. We find that the diffusion length in

S. Moritsubo; T. Murai; T. Shimada; Y. Murakami; S. Chiashi; S. Maruyama; Y. K. Kato

2010-01-01

91

Measurement of Diffusion Coefficients of Air in Silicone Oil and in Hydraulic Oil  

Microsoft Academic Search

A piston-cylinder apparatus was established to measure the solubility and diffusivity of air in dimethyl silicone oils and in hydraulic oils based on the PVT state equation of air and the solution of unsteady one-dimensional diffusion equation. The measured diffusivity-temperature relation can be well fitted by the Arrhenius equation for engineering applications. The correlation between the solute diffusivity D and

Chuan DING; Yurun FAN

2011-01-01

92

Spatial distribution of bacterial communities on volumetric and planar anodes in single-chamber air-cathode microbial fuel cells.  

PubMed

Pyrosequencing was used to characterize bacterial communities in air-cathode microbial fuel cells across a volumetric (graphite fiber brush) and a planar (carbon cloth) anode, where different physical and chemical gradients would be expected associated with the distance between anode location and the air cathode. As expected, the stable operational voltage and the coulombic efficiency (CE) were higher for the volumetric anode than the planar anode (0.57?V and CE?=?22% vs. 0.51?V and CE?=?12%). The genus Geobacter was the only known exoelectrogen among the observed dominant groups, comprising 57?±?4% of recovered sequences for the brush and 27?±?5% for the carbon-cloth anode. While the bacterial communities differed between the two anode materials, results showed that Geobacter spp. and other dominant bacterial groups were homogenously distributed across both planar and volumetric anodes. This lends support to previous community analysis interpretations based on a single biofilm sampling location in these systems. Biotechnol. Bioeng. 2013;110: 3059-3062. © 2013 Wiley Periodicals, Inc. PMID:23616357

Vargas, Ignacio T; Albert, Istvan U; Regan, John M

2013-05-29

93

Nitrogen-doped carbon nanotubes as cathode for lithium–air batteries  

Microsoft Academic Search

Nitrogen-doped carbon nanotubes (N-CNTs) were synthesized by a floating catalyst chemical vapor deposition (FCCVD) method. Various techniques including X-ray photoelectron spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Raman spectroscopy revealed the morphology and structure of CNTs and N-CNTs as well confirmed the existence of incorporated nitrogen (10.2at.%) in N-CNTs. N-CNTs were investigated as cathode material

Yongliang Li; Jiajun Wang; Xifei Li; Jian Liu; Dongsheng Geng; Jinli Yang; Ruying Li; Xueliang Sun

2011-01-01

94

Mineralization of desmetryne by electrochemical advanced oxidation processes using a boron-doped diamond anode and an oxygen-diffusion cathode  

Microsoft Academic Search

The mineralization of acidic aqueous solutions of the herbicide desmetryne has been studied by electrochemical advanced oxidation processes (EAOPs) such as anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF) with UVA light. Electrolyses were conducted in an open and cylindrical cell with a boron-doped diamond (BDD) anode and an O2-diffusion cathode for H2O2 generation. The main oxidizing

Núria Borrŕs; Conchita Arias; Ramon Oliver; Enric Brillas

2011-01-01

95

[Performance of microbial fuel cells with Fe/C catalyst carbon felt air-cathode for treating landfill leachate].  

PubMed

Ferric nitrate/activated carbon powder catalyst was obtained through impregnation and Fe/C catalyst was adsorbed on carbon felt as air cathode electrodes. Effects of activated carbon powder dosage and ferric nitrate concentration on electricity generation of MFC with landfill leachate as fuel were measured. Performances of cathodes obtained at different ferric nitrate concentrations were evaluated by cyclic voltammetry tests. The results showed that with the increase of activated carbon powder dosage or the iron nitrate concentration, MFC produce electrical properties showed a decreasing trend after the first rise. When the activated carbon powder dosage was 1 g and the iron nitrate concentration was 0.25 mol x L(-1), it was proved to be an optimum cell performance for 4199.8 mW x m(-3) output power and 465 omega apparent resistance. Under the optimal ratio rang between ferric nitrate and activated carbon powder, MFC apparent resistance decreased and the power density increased respectively with the increase of catalyst total dosage. The best produce electrical properties of MFC with Fe/C catalyst for 0.25 mol x L(-1) iron nitrate and 1 g activated carbon powder dosage was observed by cyclic voltammetry tests. The output power of MFC and the removal quantity increased with the concentration of inlet and the maximum values were respectively 5478.92 mW x m(-3) and 1505.2 mg x L(-1). the maximum removal rates of COD achieved at 89.1%. PMID:22946205

Tang, Yu-Lan; Peng, Man; Yu, Yan; He, Ya-Ting; Fu, Jin-Xiang; Zhao, Yu-Hua

2012-06-01

96

Comparison of Electrode Reduction Activities of Geobacter sulfurreducens and an Enriched Consortium in an Air-Cathode Microbial Fuel Cell? †  

PubMed Central

An electricity-generating bacterium, Geobacter sulfurreducens PCA, was inoculated into a single-chamber, air-cathode microbial fuel cell (MFC) in order to determine the maximum electron transfer rate from bacteria to the anode. To create anodic reaction-limiting conditions, where electron transfer from bacteria to the anode is the rate-limiting step, anodes with electrogenic biofilms were reduced in size and tests were conducted using anodes of six different sizes. The smallest anode (7 cm2, or 1.5 times larger than the cathode) achieved an anodic reaction-limiting condition as a result of a limited mass of bacteria on the electrode. Under these conditions, the limiting current density reached a maximum of 1,530 mA/m2, and power density reached a maximum of 461 mW/m2. Per-biomass efficiency of the electron transfer rate was constant at 32 fmol cell?1 day?1 (178 ?mol g of protein?1 min?1), a rate comparable to that with solid iron as the electron acceptor but lower than rates achieved with fumarate or soluble iron. In comparison, an enriched electricity-generating consortium reached 374 ?mol g of protein?1 min?1 under the same conditions, suggesting that the consortium had a much greater capacity for electrode reduction. These results demonstrate that per-biomass electrode reduction rates (calculated by current density and biomass density on the anode) can be used to help make better comparisons of electrogenic activity in MFCs.

Ishii, Shun'ichi; Watanabe, Kazuya; Yabuki, Soichi; Logan, Bruce E.; Sekiguchi, Yuji

2008-01-01

97

Thermionic Cathodes.  

National Technical Information Service (NTIS)

A study on lanthanum hexaboride cathodes for thermionic diodes is presented. Cathode designs, emitting properties of lanthanum hexaboride cathodes, activation and resistance to poisoning of a lanthanum hexaboride cathode, the effect of ion bombardment on ...

G. A. Kudintseva A. I. Mel'nikov A. V. Morozov B. P. Nikonov

1978-01-01

98

Diffusion of 1-chloro-1,1,2,2,2-pentafluoro-ethane (1); air (2)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) 1-chloro-1,1,2,2,2-pentafluoro-ethane; (2) air

Winkelmann, J.

99

Diffusion of 1,1,1,2,2-pentafluoro-ethane (1); air (2)  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of (1) 1,1,1,2,2-pentafluoro-ethane; (2) air

Winkelmann, J.

100

ESTIMATION OF THE MOISTURE DIFFUSION COEFFICIENT OF POTATO DURING HOT-AIR DRYING  

Microsoft Academic Search

The purpose of this work, is to evaluate the moisture diffusion coefficient of potato during convective drying. Two models of diffusion have been performed to evaluate that coefficient. The first one based on Fick's law, when a model fitting procedure was applied to experimental drying data. The diffusion coefficient was found to vary with air temperature and also increase with

L. Hassini; S. Azzouz; A. Belghith

2004-01-01

101

Effect of oxygen vacancy on Li-ion diffusion in a V2O5 cathode: a first-principles study  

NASA Astrophysics Data System (ADS)

The energy barriers of lithium-ion mobility in a V2O5 cathode are calculated using the nudged elastic band method. The low activation energy of the hopping pathway along the <0?1?0> direction (paralleling with the b-axis, the shortest lattice parameter) indicates that V2O5 has a one-dimensional diffusion pattern at the initial stage of charging and discharging. At a temperature of 300 K, the estimated diffusion coefficient is 2.520 × 10-8 cm2 s-1, which is consistent with the range of diffusivity of the previous reported fast ionic conductors. A systematic investigation of the effect of oxygen vacancy on Li-ion diffusion suggests that the bridging oxygen O(2) plays a very positive role in the Li-ion diffusion along the <0?1?0> direction and the activation energy is reduced from 0.340 to 0.215 eV, while the existence of O(1) and O(3) vacancies can hinder the lithium diffusion along this direction due to the increase in the activation energy, respectively. The oxygen vacancies make the energy barriers of the other two potential diffusion pathways reduced to some extent, which is still very large compared with the energy barrier of diffusion along the b-axis.

Ma, W. Y.; Zhou, B.; Wang, J. F.; Zhang, X. D.; Jiang, Z. Y.

2013-03-01

102

Behaviour of the Cathode Active Surface Temperature in the Steady-State Diffuse Mode of HID Lamps.  

National Technical Information Service (NTIS)

Generally, the topics of functioning model of high intensity discharge (HID) lamp electrode presents a big scientific interest. A lot of lamp properties and lamp efficient functioning are in strong relationship with the cathode operation. The non-linear e...

G. Zissis M. Cristea

2003-01-01

103

A study of the effects of air preheat on the structure of methane\\/air counterflow diffusion flames  

Microsoft Academic Search

The effects of air preheat on flame structure are studied in counterflow methane–air diffusion flames, considering air temperatures in the range 300 to 560 K. Species concentrations for H2, O2, N2, CH4, CO, CO2, C2H2, and C2H4 were measured using sampling and gas chromatography. Concentrations of NO were measured using sampling and chemiluminescence analysis. Results of numerical calculations using GRI-Mech

Jongmook Lim; Jay Gore; Raymond Viskanta

2000-01-01

104

Characteristics of Gaseous Diffusion Flames With High Temperature Combustion Air in Microgravity.  

National Technical Information Service (NTIS)

The characteristics of gaseous diffusion flames have been obtained using high temperature combustion air under microgravity conditions. The time resolved flame images under free fall microgravity conditions were obtained from the video images obtained. Th...

A. K. Gupta M. Ghaderi

2004-01-01

105

Temperature Measurements in an Ethylene-Air-Opposed Flow Diffusion Flame.  

National Technical Information Service (NTIS)

To support the advancement of chemical kinetic models for soot, temperature measurements were conducted on an ethylene (C2H4)/air-opposed flow diffusion flame at atmospheric pressure. This detailed study compares temperature measurements acquired from a s...

C. M. Kweon J. M. Densmore K. L. McNesby M. S. Kurman

2012-01-01

106

Experimental study of humid air reverse diffusion combustion in a turbulent flow field  

Microsoft Academic Search

Experiments were performed to investigate the differences between the propane\\/air turbulent diffusion reactive flows past\\u000a bluff-body and the propane\\/humid air turbulent diffusion reactive flows in the same conditions. The velocity distributions\\u000a of the non-humid reactive flow fields and the humid reactive flow fields were measured by particle image velocimetry (PIV)\\u000a techniques. The temperature fields were measured by high temperature thermocouples,

Bing Ge; Shusheng Zang; Xin Gu

2007-01-01

107

Study of sintered stainless steel fiber felt as gas diffusion backing in air-breathing DMFC  

Microsoft Academic Search

Adoption of a sintered stainless steel fiber felt was evaluated as gas diffusion backing in air-breathing direct methanol fuel cell (DMFC). By using a sintered stainless steel fiber felt as an anodic gas diffusion backing, the peak power density of an air-breathing DMFC is 24mWcm?2, which is better than that of common carbon paper. A 30-h-life test indicates that the

Jianguo Liu; Gongquan Sun; Fengliang Zhao; Guoxiong Wang; Gang Zhao; Likang Chen; Baolian Yi; Qin Xin

2004-01-01

108

A best fit approach to estimating multiple diffuse source terms using ambient air monitoring data and an air dispersion model.  

PubMed

Lawrence Livermore National Laboratory uses CAP88-PC Version 1.0 modeling software to demonstrate compliance with the Code of Federal Regulations Title 40 Part 61 Subpart H (National Emission Standards for Emissions of Radionuclides Other Than Radon From Department of Energy Facilities). Annual air emissions from both well characterized stack sources and difficult to characterize diffuse sources must be assessed. This paper describes a process that uses a mathematical optimization routine to find a set of estimated diffuse source terms that together with the measured stack source terms provides a best fit of modeled air concentrations to measured air concentrations at available sampling locations. The estimated and measured source terms may then be used in subsequent CAP88-PC modeling to estimate dose at the off-site maximally exposed individual. LLNL has found this process to be an effective way to deal with the required assessment of diffuse sources that have otherwise been difficult to assess. PMID:23803667

MacQueen, Donald; Bertoldo, Nicholas; Wegrecki, Anthony

2013-08-01

109

The Use of Passive Diffusion Tubes for Measuring Concentrations of Nitrogen Dioxide in Air  

Microsoft Academic Search

Passive diffusion tubes have been widely used in Europe for spatial and temporal measurement of NO2 concentrations. The method is cheap, simple, and provides concentration data in most circumstances that are sufficiently accurate for assessing exposure and compliance with air quality criteria. Tube-type diffusion samplers are prone to several sources of uncertainty, arising from the materials of construction, the absorbent

J. N. Cape

2009-01-01

110

Chemistry on the low field anodes and cathodes of air corona gaps  

Microsoft Academic Search

Surface effects of electrical coronas have been studied on the low field electrodes of point-to-plane air gaps with discharges burning in negative and positive glow regimes, i.e., mainly producing chemical effects without significant sputtering or thermal effects. Most of these chemical effects are due to oxidation and reduction processes taking place in aqueous microdroplets formed by the discharge where oxides,

C. Se´verac; G. Jouve; A. Goldman; M. Goldman

2004-01-01

111

Prediction of Air Mixing From High Sidewall Diffusers in Cooling Mode: Preprint  

SciTech Connect

Computational fluid dynamics modeling was used to evaluate the performance of high sidewall air supply in cooling mode. The research focused on the design, placement, and operation of air supply diffusers located high on a sidewall and return grilles located near the floor on the same sidewall. Parameters of the study are the supply velocity, supply temperature, diffuser dimensions and room dimensions. Thermal loads characteristic of high performance homes were applied at the walls and room temperature was controlled via a thermostat. The results are intended to provide information to guide the selection of high sidewall supply diffusers to provide proper room mixing for cooling of high performance homes.

Ridouane, E. H.; Gawlik, K.

2011-02-01

112

Sustainable design of high-performance microsized microbial fuel cell with carbon nanotube anode and air cathode.  

PubMed

Microbial fuel cells (MFCs) are a promising alternative energy source that both generates electricity and cleans water. Fueled by liquid wastes such as wastewater or industrial wastes, the microbial fuel cell converts waste into energy. Microsized MFCs are essentially miniature energy harvesters that can be used to power on-chip electronics, lab-on-a-chip devices, and/or sensors. As MFCs are a relatively new technology, microsized MFCs are also an important rapid testing platform for the comparison and introduction of new conditions or materials into macroscale MFCs, especially nanoscale materials that have high potential for enhanced power production. Here we report a 75 ?L microsized MFC on silicon using CMOS-compatible processes and employ a novel nanomaterial with exceptional electrochemical properties, multiwalled carbon nanotubes (MWCNTs), as the on-chip anode. We used this device to compare the usage of the more commonly used but highly expensive anode material gold, as well as a more inexpensive substitute, nickel. This is the first anode material study done using the most sustainably designed microsized MFC to date, which utilizes ambient oxygen as the electron acceptor with an air cathode instead of the chemical ferricyanide and without a membrane. Ferricyanide is unsustainable, as the chemical must be continuously refilled, while using oxygen, naturally found in air, makes the device mobile and is a key step in commercializing this for portable technology such as lab-on-a-chip for point-of-care diagnostics. At 880 mA/m(2) and 19 mW/m(2) the MWCNT anode outperformed the others in both current and power densities with between 6 and 20 times better performance. All devices were run for over 15 days, indicating a stable and high-endurance energy harvester already capable of producing enough power for ultra-low-power electronics and able to consistently power them over time. PMID:23899322

Mink, Justine E; Hussain, Muhammad Mustafa

2013-08-08

113

Transition of a diffuse discharge to a spark at nanosecond breakdown of high-pressure nitrogen and air in a nonuniform electric field  

NASA Astrophysics Data System (ADS)

The transition of a runaway-electron-induced diffuse discharge initiated in a nonuniform electric field under a high pressure of air and nitrogen to a spark is studied. High-voltage pulses with a rise time of 0.5 ns are applied to a discharge gap with a tubular cathode having a small radius of curvature. It is shown that the leader of the spark discharge propagates toward the tubular cathode along preproduced tracks and may pass from one track to another. For a pulse rise time of about 0.5 ns and a gap length of 12 mm or more, it is found that spark leaders originating at the cathode (which has a small radius of curvature) do not reach the anode and accordingly, do not cause the spark breakdown of the gap. It is confirmed that the spark breakdown of the gap is associated with a spark leader that moves away from the plane electrode after the appearance of a bright spot on it.

Tarasenko, V. F.; Baksht, E. Kh.; Lomaev, M. I.; Rybka, D. V.; Sorokin, D. A.

2013-08-01

114

Electrochemical Performance and Stability of the Cathode for Solid Oxide Fuel Cells II. Role of Ni diffusion on LSM performance  

Microsoft Academic Search

The sintering of a standard (La0.8Sr0.2)0.98MnO3 (LSM-20) solid oxide fuel cell cathode composition (in the temperature range of 1050-1200şC) on anode-supported cells utilizing a Ni-YSZ anode and thin YSZ electrolyte (<10 m thickness) has revealed the need for a protective ceria interlayer to prevent a detrimental interaction between the YSZ and the LSM. The interaction, however, is not the typically

Xiao Dong Zhou; Steven P. Simner; Jared W. Templeton; Zimin Nie; Jeffry W. Stevenson; B. P. Gorman

2010-01-01

115

Reduced energy requirement for air conditioning by using air diffusion with air flow from floor to ceiling  

Microsoft Academic Search

When supplying air from the ceiling in an air-conditioned room, there is a mixing all over the room; when supplying from the floor or from desks there is mixing region only in the lower area. Above is warm air from which the return air is drawn. For air supply from below, the cooling load can be decreased. In combination with

H. Bach; W. Dittes; R. Mangelsdorf; R. Detzer; E. Jungbaeck; K. Fitzner; W. Radtke; F. Soethout

1982-01-01

116

NITRIC ACID-AIR DIFFUSION COEFFICIENT: EXPERIMENTAL DETERMINATION  

EPA Science Inventory

Trace gaseous HNO3 in air is removed in a laminar flow nylon tube. The HNO3 deposition pattern was obtained by sectioning the tube, extracting with an aqueous solution, and measuring the concentration by ion chromatography. Mass transport analysis of the deposition pattern demons...

117

Scalar Dissipation Measurements in Turbulent Jet Diffusion Flames of Air Diluted Methane and Hydrogen  

Microsoft Academic Search

Simultaneous two-dimensional Rayleigh and fuel Raman images have been collected in air-diluted methane and hydrogen jet diffusion flames. Temperature, fuel mass fraction and mixture fraction images are derived by a two-scalar approach based on one-step chemistry and equal species diffusivities. This enables calculation of two components of the scalar dissipation rate x-The inherently weak Raman signal has been maximised by

S. H. STARNER; R. W. BILGER; M. B. LONG; J. H. FRANK; D. F. MARRAN

1997-01-01

118

Large-eddy simulation of a turbulent piloted methane\\/air diffusion flame (Sandia flame D)  

Microsoft Academic Search

The Lagrangian Flamelet Model is formulated as a combustion model for large-eddy simulations of turbulent jet diffusion flames. The model is applied in a large-eddy simulation of a piloted partially premixed methane\\/air diffusion flame (Sandia flame D). The results of the simulation are compared to experimental data of the mean and RMS of the axial velocity and the mixture fraction

H. Pitsch; H. Steiner

2000-01-01

119

Monitoring of hydrocarbon vapor diffusion in air using a thermal wave interferometer  

Microsoft Academic Search

A discussion on the use of thermal wave interference (TWI) for the monitoring of the transients of hydrocarbon in air is presented. The thermal wave signal was modeled using the logarithm-mixing model for the thermal diffusivity of a two-phase gas system in which the hydrocarbon vapor concentration in the air-filled TWI cell is a varying function of time. The time

J. A. P. Lima; M. G. da Silva; M. S. O. Massunaga; E. Mar?´n; H. Vargas; L. C. M. Miranda

2002-01-01

120

A correlation of air-coupled ultrasonic and thermal diffusivity data for CFCC materials  

SciTech Connect

An air-coupled (non contact) through-transmission ultrasonic investigation has been conducted on 2D multiple ply Nicalon{trademark} SiC fiber/SiNC CFCC panels as a function of number of processing cycles. Corresponding thermal diffusivity imaging was also conducted. The results of the air-coupled ultrasonic investigation correlated with thermal property variations determined via infrared methods. Areas of delaminations were detected and effects of processing cycles were also detected.

Pillai, T.A.K. [Univ. of Wisconsin, LaCrosse, WI (United States). Dept. of Physics; Easler, T.E.; Szweda, A. [Dow Corning Corp., Midland, MI (United States). Advanced Ceramics Program] [and others

1997-01-01

121

Impact of co-flow air on buoyant diffusion flames flicker  

Microsoft Academic Search

This paper describes experimental investigation of co-flow air velocity effects on the flickering behaviour of laminar non-lifted methane diffusion flames. Chemiluminescence, high-speed photography, schlieren and Particle Imaging Velocimetry (PIV), have been used to study the changes in the flame\\/vortex interactions as well as the flame flickering frequency and magnitude by the co-flow air. Four cases of methane flow rates at

H. Gohari Darabkhani; Q. Wang; L. Chen; Y. Zhang

2011-01-01

122

Effects of Coaxial Air on Nitrogen-Diluted Hydrogen Jet Diffusion Flame Length and NOx Emission  

SciTech Connect

Turbulent nitrogen-diluted hydrogen jet diffusion flames with high velocity coaxial air flows are investigated for their NOx emission levels. This study is motivated by the DOE turbine program’s goal of achieving 2 ppm dry low NOx from turbine combustors running on nitrogen-diluted high-hydrogen fuels. In this study, effects of coaxial air velocity and momentum are varied while maintaining low overall equivalence ratios to eliminate the effects of recirculation of combustion products on flame lengths, flame temperatures, and resulting NOx emission levels. The nature of flame length and NOx emission scaling relationships are found to vary, depending on whether the combined fuel and coaxial air jet is fuel-rich or fuel-lean. In the absence of differential diffusion effects, flame lengths agree well with predicted trends, and NOx emissions levels are shown to decrease with increasing coaxial air velocity, as expected. Normalizing the NOx emission index with a flame residence time reveals some interesting trends, and indicates that a global flame strain based on the difference between the fuel and coaxial air velocities, as is traditionally used, is not a viable parameter for scaling the normalized NOx emissions of coaxial air jet diffusion flames.

Weiland, N.T.; Chen, R.-H.; Strakey, P.A.

2007-10-01

123

Carbonate-mediated Fe(II) oxidation in the air-cathode fuel cell: a kinetic model in terms of Fe(II) speciation.  

PubMed

Due to the high redox activity of Fe(II) and its abundance in natural waters, the electro-oxidation of Fe(II) can be found in many air-cathode fuel cell systems, such as acid mine drainage fuel cells and sediment microbial fuel cells. To deeply understand these iron-related systems, it is essential to elucidate the kinetics and mechanisms involved in the electro-oxidation of Fe(II). This work aims to develop a kinetic model that adequately describes the electro-oxidation process of Fe(II) in air-cathode fuel cells. The speciation of Fe(II) is incorporated into the model, and contributions of individual Fe(II) species to the overall Fe(II) oxidation rate are quantitatively evaluated. The results show that the kinetic model can accurately predict the electro-oxidation rate of Fe(II) in air-cathode fuel cells. FeCO3, Fe(OH)2, and Fe(CO3)2(2-) are the most important species determining the electro-oxidation kinetics of Fe(II). The Fe(II) oxidation rate is primarily controlled by the oxidation of FeCO3 species at low pH, whereas at high pH Fe(OH)2 and Fe(CO3)2(2-) are the dominant species. Solution pH, carbonate concentration, and solution salinity are able to influence the electro-oxidation kinetics of Fe(II) through changing both distribution and kinetic activity of Fe(II) species. PMID:23662901

Song, Wei; Zhai, Lin-Feng; Cui, Yu-Zhi; Sun, Min; Jiang, Yuan

2013-05-22

124

The vapor diffusion resistance and air permeance of masonry and roofing systems  

Microsoft Academic Search

Several building parts contain layers composed of separate elements that are mortared together or simply interlock or overlap. Typical examples are masonry walls, brick veneers, tiled roofing systems and slated roofing systems. The mortar joints, the interlocks and overlaps should affect the water vapor diffusion resistance and the air permeance of the composite layer, at least in comparison with the

Hugo S. L. C. Hens

2006-01-01

125

Pulmonary surfactant layers accelerate O 2 diffusion through the air-water interface  

Microsoft Academic Search

During respiration, it is accepted that oxygen diffuses passively from the lung alveolar spaces through the respiratory epithelium until reaching the pulmonary capillaries, where blood is oxygenated. It is also widely assumed that pulmonary surfactant, a lipid–protein complex secreted into alveolar spaces, has a main surface active function, essential to stabilize the air–liquid interface, reducing in this way the work

Bárbara Olmeda; Laura Villén; Antonio Cruz; Guillermo Orellana; Jesus Perez-Gil

2010-01-01

126

Trajectory-grid: An accurate sign-preserving advection-diffusion approach for air quality modeling  

Microsoft Academic Search

We propose a new method, called the trajectory-grid (T-G) approach, which contains a fully Lagrangian advection scheme coupled with an Eulerian diffusion scheme, to remove the numerical problems associated with the advection equation in air quality modeling. This method is sign preserving, mass conserving, and very accurate. The method assigns the spatial locations of points on a given concentration profile

David P. Chock; Pu Sun; Sandra L. Winkler

1996-01-01

127

Influence of differential diffusion on maximum flame temperature in turbulent nonpremixed hydrogen\\/air flames  

Microsoft Academic Search

A turbulent nonpremixed H2\\/air flame is simulated using 2D direct numerical simulations coupled with a complete chemical scheme and a detailed transport model. The influence of differential diffusion is evidenced by comparing these results in terms of scatterplots and local flame structures with similar computations using a Lewis number unity hypothesis. The fast chemistry limit and thus the maximum flame

R. Hilbert; D. Thévenin

2004-01-01

128

Analysis of the structure and mechanisms of extinction of a counterflow methanol-air diffusion flame  

Microsoft Academic Search

Numerical calculations were performed to determine the structure and to clarify the extinction mechanisms of diffusion flames stabilized between counterflowing streams of methanol and air. The calculations were performed at a value of the thermodynamic pressure equal to 1 atmosphere, with different values for the rate of strain and with two different chemical kinetic mechanisms, mechanism a and mechanism b.

K. Seshadri; C. Trevino; M. D. Smooke

1989-01-01

129

Effects of plume spacing and flowrate on destratification efficiency of air diffusers  

Microsoft Academic Search

This study adopts techniques of computational fluid dynamics (CFD) to analyze the combined effect of adjacent plumes of an air-diffuser system on its destratification efficiency. Lab experiments were carried out to calibrate and verify the CFD models in thermally stratified freshwater. The CFD simulation and lab experiment results were analyzed to relate destratification efficiency with four non-dimensional variables. The results

Kyungtaek Yum; Sung Hoon Kim

2008-01-01

130

Characterization of bacterial and archaeal communities in air-cathode microbial fuel cells, open circuit and sealed-off reactors.  

PubMed

A large percentage of organic fuel consumed in a microbial fuel cell (MFC) is lost as a result of oxygen transfer through the cathode. In order to understand how this oxygen transfer affects the microbial community structure, reactors were operated in duplicate using three configurations: closed circuit (CC; with current generation), open circuit (OC; no current generation), and sealed off cathodes (SO; no current, with a solid plate placed across the cathode). Most (98 %) of the chemical oxygen demand (COD) was removed during power production in the CC reactor (maximum of 640?±?10 mW/m(2)), with a low percent of substrate converted to current (coulombic efficiency of 26.5?±?2.1 %). Sealing the cathode reduced COD removal to 7 %, but with an open cathode, there was nearly as much COD removal by the OC reactor (94.5 %) as the CC reactor. Oxygen transfer into the reactor substantially affected the composition of the microbial communities. Based on analysis of the biofilms using 16S rRNA gene pyrosequencing, microbes most similar to Geobacter were predominant on the anodes in the CC MFC (72 % of sequences), but the most abundant bacteria were Azoarcus (42 to 47 %) in the OC reactor, and Dechloromonas (17 %) in the SO reactor. Hydrogenotrophic methanogens were most predominant, with sequences most similar to Methanobacterium in the CC and SO reactor, and Methanocorpusculum in the OC reactors. These results show that oxygen leakage through the cathode substantially alters the bacterial anode communities, and that hydrogenotrophic methanogens predominate despite high concentrations of acetate. The predominant methanogens in the CC reactor most closely resembled those in the SO reactor, demonstrating that oxygen leakage alters methanogenic as well as general bacterial communities. PMID:23775270

Shehab, Noura; Li, Dong; Amy, Gary L; Logan, Bruce E; Saikaly, Pascal E

2013-06-18

131

Monitoring of gas diffusion in air using the TWI technique: Thermal diffusivity measurements made easy  

Microsoft Academic Search

The thermal wave interference technique (TWI) has been explored in recent years for the investigation of the thermal and transport properties of gases and liquids. In this article we address ourselves to the quantitative understanding of the transient thermal wave interference signal of air:hydrocarbon vapor mixtures. This is the situation one faces when placing a given portion of liquid hydrocarbon

J. A. P. Lima; M. G. da Silva; M. S. O. Masssunaga; S. L. Cardoso; H. Vargas; E. Mar?´n; L. C. M. Miranda

2003-01-01

132

Cathodic protection and cathodic prevention  

Microsoft Academic Search

Developments in cathodic protection for aerial concrete structures are described. The principles on which the technique is based and the various protecting effects induced by the cathodic polarization of reinforcement are illustrated; the differences between the cathodic protection applied to control corrosion rate of chloride contaminated constructions and that applied to improve the corrosion resistance of the reinforcement of new

Pietro Pedeferri

1996-01-01

133

Numerical study of the effects of pressure and air-dilution on no formation in laminar counterflow diffusion flames of methane in high temperature air  

Microsoft Academic Search

Flame structure, extinction characteristics, and nitric oxide (NO) formation in diffusion flames of methane and diluted air have been investigated numerically by adopting counterflow as a model. Effect of pressure on NO emission is emphasized in high-temperature and diluted-air conditions. With undiluted air, extinction strain rate and flame temperature at a specified strain rate increase with pressure. In this case,

C. H. SOHN; I. M. JEONG; S. H. CHUNG

2002-01-01

134

Modeling of a polymer electrolyte membrane fuel cell cathode  

NASA Astrophysics Data System (ADS)

Two models have been presented in this dissertation for an air cathode of a polymer electrolyte membrane fuel cell: a steady state impedance model and a steady state polarization model. Two impedance loops have been predicted on an air cathode by our steady state impedance model at a high steady state current density. The high frequency impedance loop is associated with the effective charge transfer resistance and double layer charging, and the low frequency impedance loop is associated with gas phase transport limitations. They are in agreement with the predictions by a similar impedance model in the literature. Several problems in the latter model have been addressed in our impedance model. By using the steady state polarization model presented in this dissertation, five parameters for an air cathode (the volume fraction of gas pores in the gas diffusion layer, the volume fraction of gas pores in the catalyst layer, the exchange current density for the O2 reduction reaction, the effective ionic conductivity in the catalyst layer, and the ratio of the effective diffusion coefficient of dissolved O2 in a spherical agglomerate particle to the square of the particle radius) have been determined by least square fitting of polarization curves of an air cathode. A decoupling method for calculating the model equations and the sensitivity equations has first been proposed to optimize the numerical efficiency in the estimation of parameters. The polarization curves of an air cathode have been obtained by correcting the experimental polarization curves of an air/H2 polymer electrolyte membrane fuel cell for the voltage drop across the membrane. The validity of the correction method for the voltage drop across the membrane has been justified. A more robust correction method has also been presented. The possible influence on the parameter estimation accuracy of the assumption that a H 2 anode was always at its equilibrium in our experiments has been discussed. The parameter estimates obtained in this dissertation indicate that ionic conduction in the catalyst layer and the gas phase transport in the gas diffusion layer are two processes influencing the polarization performance of an air cathode significantly. The goodness of our steady state polarization model has been demonstrated by comparing our model to a polarization model in the literature. An equation used in our polarization model to describe the O 2 reaction current density in the catalyst layer, which is capable of predicting a change of Tafel slope, has been noticed to be superior to a simple Tafel equation used in the literature.

Guo, Qingzhi

135

Extended reaction zone of La0.6Sr0.4Co0.2Fe0.8O3 cathode for solid oxide fuel cell  

SciTech Connect

The oxygen reduction reaction at the cathode of solid oxide fuel cell (SOFC) is a complicated process which involves the interaction of oxygen molecules, electrons, and oxygen ions. Therefore, it can only proceed at locations where gas, electronic conductor, and an oxygen ion conductor meet. Although the extension of the reaction zone beyond the traditional so-called triple-phase-boundary (TPB) is widely accepted for a mixed ionically and electronically conductive cathode, work in this area has yet to reach a consensus on how far the reaction zone can be extended. In this study, anode-supported fuel cells with a variety of LSCF cathode thicknesses were fabricated and tested in two cathode environments, flowing oxygen and flowing air. In flowing oxygen, the cell performance increased with LSCF cathode thickness over the entire range investigated (from 5 to 33 ?m). In flowing air, the cell performance also increased with the LSCF cathode thickness from 5 to 13 ?m, but then remained almost constant with further increase in cathode thickness. In flowing oxygen, since there was no concentration polarization related to oxygen diffusion, the polarization resistance of oxygen reduction decreased with the LSCF cathode thickness because of the increased number of reaction sites. A linear relationship was established between the reciprocal of the polarization resistance and the cathode thickness, which was explained by a model developed for aqueous gas diffusion electrodes.

Lu, Zigui; Hardy, John S.; Templeton, Jared W.; Stevenson, Jeffry W.

2012-01-03

136

Theory of the arc hollow cathode  

NASA Astrophysics Data System (ADS)

Cathode erosion is a problem in electric arcs. Hollow cathodes have been found to erode less due to more diffuse current attachment. A theoretical model explains several observed properties of hollow cathodes. This model is usually integrated numerically but an analytical solution is possible in some circumstances. The model allows the prediction of the cathode temperature and plasma properties. Results of the theory are compared to experimental data.

Kennedy, R. V.

2001-03-01

137

Hollow cathode conditioning and discharge initiation  

NASA Astrophysics Data System (ADS)

In the framework of developing a fast-starting hollow cathode, one must understand how a cathode is conditioned for operation. The desorption of known contaminates as a function of heater power was measured to quantify cathode conditioning characteristics. In addition to conditioning, a study of hollow cathode emission characteristics under vacuum conditions was performed. Results of these two studies are described herein along with measurements of the temperature of the cathode as a function of time and heater power. The data are used to validate a transient surface diffusion model that describes the migration and surface coverage fraction of low-work-function material from the interior of the hollow cathode to the orifice barrel and to the exterior surface of the orifice plate of the cathode. A sufficiency condition is presented for our cathode geometry of vacuum emission current level and the ability to start a hollow cathode discharge once gas flow is initiated.

Rubin, Binyamin; Williams, John D.

2008-09-01

138

Evaluation of alloy anodes for aluminum-air batteries. II. Delineation of anodic and cathodic partial reactions  

Microsoft Academic Search

The design, calibration, and operation of a source\\/collector electrochemical cell for delineating anodic and cathodic partial currents for reactive metals in aqueous media is described. This cell has been used to measure the hydrogen evolution current on aluminum and aluminum alloys in 4M KOH at 25°, 50°, and 80°C over a wide range of potential. These data were then combined

S. Real; M. Urquidi-Macdonald; D. D. Macdonald

1988-01-01

139

Molecular diffusion effects in LES of a piloted methane-air flame  

SciTech Connect

Molecular diffusion effects in LES of a piloted methane-air (Sandia D) flame are investigated on a series of grids with progressively increased resolution. The reacting density, temperature and chemical composition are modeled based on the mixture fraction approach combined with a steady flamelet model. With a rationale to minimize interpolation uncertainties that are routinely introduced by a flamelet table look-up, quadratic splines relationships are employed to represent thermochemical variables. The role of molecular diffusivity in effecting spatial transport is studied by drawing a comparison with the turbulent diffusivity and analyzing their statistics conditioned on temperature. Statistical results demonstrate that the molecular diffusivity in the near-field almost always exceeds the turbulent diffusivity, except at low temperatures (less than 500 K). Thus, by altering the jet near-field, molecular transport plays an important role in the further downstream jet development. Molecular diffusivity continues to dominate in the centerline region throughout the flow field. Overall, the results suggest the strong necessity to represent molecular transport accurately in LES studies of turbulent reacting flows. (author)

Kemenov, Konstantin A.; Pope, Stephen B. [Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY 14853 (United States)

2011-02-15

140

Effect of varied air flow on flame structure of laminar inverse diffusion flames.  

SciTech Connect

The structure of laminar inverse diffusion flames (IDFs) of methane and ethylene was studied using a cylindrical co-flowing burner. Several flames of the same fuel flow-rate yet various air flow-rates were examined. Heights of visible flames were obtained using measurements of hydroxyl (OH) laser-induced fluorescence (LIF) and visible images. Polycyclic aromatic hydrocarbon (PAH) LIF and soot laser-induced incandescence (LII) were also measured. In visible images, radiating soot masks the blue region typically associated with the flame height in normal diffusion flames (NDFs). Increased air flow-rates resulted in longer flames. PAH LIF and soot LII indicated that PAh and soot are present on the fuel side of the flame and that soot is located closer to the reaction zone than PAH. Ethylene flames produced significantly higher PAH LIF and soot LII signals than methane flames, which is consistent with the sooting propensity of ethylene.

Shaddix, Christopher R.; Williams, Timothy C.; Blevins, Linda Gail; Mikofski, Mark A. (University of California Berkeley)

2004-03-01

141

Influence of Strouhal number on pulsating methane-air coflow jet diffusion flames  

Microsoft Academic Search

Four periodically time-varying methane–air laminar coflow jet diffusion flames, each forced by pulsating the fuel jet's exit velocity Uj sinusoidally with a different modulation frequency wj and with a 50% amplitude variation, have been computed. Combustion of methane has been modeled by using a chemical mechanism with 15 species and 42 reactions, and the solution of the unsteady Navier–Stokes equations

M. Sanchez-Sanz; B. A. V. Bennett; M. D. Smooke; A. Linan

2010-01-01

142

A mechanistic study of Soret diffusion in hydrogen-air flames  

Microsoft Academic Search

The separate and combined effects of Soret diffusion of the hydrogen molecule (H) and radical (H) on the structure and propagation speed of the freely-propagating planar premixed flames, and the strain-induced extinction response of premixed and nonpremixed counterflow flames, were computationally studied for hydrogen-air mixtures using a detailed reaction mechanism and transport properties. Results show that, except for the conservative

F. Yang; C. K. Law; C. J. Sung; H. Q. Zhang

2010-01-01

143

A mechanistic study of Soret diffusion in hydrogen–air flames  

Microsoft Academic Search

The separate and combined effects of Soret diffusion of the hydrogen molecule (H2) and radical (H) on the structure and propagation speed of the freely-propagating planar premixed flames, and the strain-induced extinction response of premixed and nonpremixed counterflow flames, were computationally studied for hydrogen–air mixtures using a detailed reaction mechanism and transport properties. Results show that, except for the conservative

F. Yang; C. K. Law; C. J. Sung; H. Q. Zhang

2010-01-01

144

A diffusive sampler for the ion?chromatographic measurement of sulfur dioxide in ambient air  

Microsoft Academic Search

We have combined a diffusive sampler and ion chromatograph to determine SO2 in ambient air. The sampler is made of a three?piece cassette holder containing a triethanolamine?impregnated glass?fiber filter. We here describe the absorbent used, sample treatment, method of analysis and the assessment of the sampler in the laboratory and on site. We conclude that the samplers are satisfactory for

1993-01-01

145

Lift-off Heights and Visible Lengths of Vertical Turbulent Jet Diffusion Flames in Still Air  

Microsoft Academic Search

The lift-off heights and visible-flame lengths of jet diffusion flames in still air have been determined for hydrogen, propane, methane and ethylene.The flame lift-off height varies linearly with the jet exit velocity and is independent of the burner diameter for a given gas. The results support the assumption that if the burner exit flow is choked the burner can be

T. Gautam

1984-01-01

146

International Diffusion of Open Path FTIR Technology and Air Monitoring Methods: Taiwan (Republic of China)  

Microsoft Academic Search

International cooperation and diffusion of environmental technologies is a central goal of the U.S. EPA Environmental Technology Initiative, and is of great interest to many countries. One objective is to exchange knowledge and skills concerning new monitoring technologies. In this case, the technology was open path Fourier Transform Infrared Spectrometry (op-FTIR).Taiwan is a high-technology, newly industrialized country. Because of air

Steven P. Levine

1996-01-01

147

Performance of a thermally desorbable diffusion sampler for personal and indoor air monitoring  

Microsoft Academic Search

A diffusion passive sampler suitable for large-scale investigations of population exposure to volatile organic compounds (VOC) in indoor air has been developed and tested. The sampler consists of a glass tube (6Ă160 mm or 6Ă100 mm) containing an adsorbent (Tenax or Carbotrap) that collects vapours at a flow rate of 4 to 8 cmÂł\\/h, depending on the compound. This flow

M. De Bortoli; H. Knoeppel; E. Pecchio; H. Vissers

1989-01-01

148

Extinction of premixed H{sub 2}/air flames: Chemical kinetics and molecular diffusion effects  

SciTech Connect

Laminar flame speed has traditionally been used for the partial validation of flame kinetics. In most cases, however, its accurate determination requires extensive data processing and/or extrapolations, thus rendering the measurement of this fundamental flame property indirect. Additionally, the presence of flame front instabilities does not conform to the definition of laminar flame speed. This is the case for Le<1 flames, with the most notable example being ultralean H{sub 2}/air flames, which develop cellular structures at low strain rates so that determination of laminar flame speeds for such mixtures is not possible. Thus, this low-temperature regime of H{sub 2} oxidation has not been validated systematically in flames. In the present investigation, an alternative/supplemental approach is proposed that includes the experimental determination of extinction strain rates for these flames, and these rates are compared with the predictions of direct numerical simulations. This approach is meaningful for two reasons: (1) Extinction strain rates can be measured directly, as opposed to laminar flame speeds, and (2) while the unstretched lean H{sub 2}/air flames are cellular, the stretched ones are not, thus making comparisons between experiment and simulations meaningful. Such comparisons revealed serious discrepancies between experiments and simulations for ultralean H{sub 2}/air flames by using four kinetic mechanisms. Additional studies were conducted for lean and near-stoichiometric H{sub 2}/air flames diluted with various amounts of N{sub 2}. Similarly to the ultralean flames, significant discrepancies between experimental and predicted extinction strain rates were also found. To identify the possible sources of such discrepancies, the effect of uncertainties on the diffusion coefficients was assessed and an improved treatment of diffusion coefficients was advanced and implemented. Under the conditions considered in this study, the sensitivity of diffusion coefficients to the extinction response was found to be significant and, for certain species, greater than that of the kinetic rate constants.

Dong, Yufei; Holley, Adam T.; Andac, Mustafa G.; Egolfopoulos, Fokion N.; Wang, Hai [Department of Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, CA 90089-1453 (United States); Davis, Scott G. [Exponent, Natick, MA 01760 (United States); Middha, Prankul [Department of Mechanical Engineering, University of Delaware, Newark, DE 19716 (United States)

2005-09-01

149

Compact lanthanum hexaboride hollow cathode  

NASA Astrophysics Data System (ADS)

A compact lanthanum hexaboride hollow cathode has been developed for space applications where size and mass are important and research and industrial applications where access for implementation might be limited. The cathode design features a refractory metal cathode tube that is easily manufactured, mechanically captured orifice and end plates to eliminate expensive e-beam welding, graphite sleeves to provide a diffusion boundary to protect the LaB6 insert from chemical reactions with the refractory metal tube, and several heater designs to provide long life. The compact LaB6 hollow cathode assembly including emitter, support tube, heater, and keeper electrode is less than 2 cm in diameter and has been fabricated in lengths of 6-15 cm for different applications. The cathode has been operated continuously at discharge currents of 5-60 A in xenon. Slightly larger diameter versions of this design have operated at up to 100 A of discharge current.

Goebel, Dan M.; Watkins, Ronald M.

2010-08-01

150

Interstitial Air Pressure Dependence of Effective Thermal Conductivity and Diffusivity of Rajasthan Desert Sand Using Transient Hot-Strip Method  

Microsoft Academic Search

The transient hot strip (T H S) method used for the simultaneous measurement of effective thermal conductivity and diffusivity of loose granular two-phase materials at normal pressure and room temperature is now used for the measurement of effective thermal conductivity and diffusivity of Rajasthan Desert sand at different interstitial air pressure and room temperature. Experimental values of effective thermal conductivities

N. S. Saxena; M. A. Chohan; S. E. Gustafsson

1987-01-01

151

Turbulent Diffusion Combustion Model Using Chemical Equilibrium Combined with the Eddy Dissipation Concept for Reducing Detailed Chemical Mechanisms : An Application of H2-air Turbulent Diffusion Flame  

Microsoft Academic Search

This research aims at building a turbulent diffusion combustion model based on chemical equilibrium and kinetics for simplifying complex chemical mechanism. This paper presents the combustion model based on chemical equilibrium combined with an eddy dissipation concept model (CE-EDC); the model is validated by simulating a H2-air turbulent diffusion flame. In the CE-EDC model, the reaction rate of fuels and

Kazui Fukumoto; Yoshifumi Ogami

2010-01-01

152

Cathodic arcs  

SciTech Connect

Cathodic arc plasma deposition has become the technology of choice for hard, wear and corrosion resistant coatings for a variety of applications. The history, basic physics of cathodic arc operation, the infamous macroparticle problem and common filter solutions, and emerging high-tech applications are briefly reviewed. Cathodic arc plasmas standout due to their high degree of ionization, with important consequences for film nucleation, growth, and efficient utilization of substrate bias. Industrial processes often use cathodic arc plasma in reactive mode. In contrast, the science of arcs has focused on the case of vacuum arcs. Future research directions include closing the knowledge gap for reactive mode, large area coating, linear sources and filters, metal plasma immersion process, with application in high-tech and biomedical fields.

Anders, Andre

2003-10-29

153

Diffuse discharge produced by repetitive nanosecond pulses in open air, nitrogen, and helium  

NASA Astrophysics Data System (ADS)

Atmospheric-pressure gas discharge driven by high voltage pulses with fast rise-time and short duration has attracted significant attention for various plasma applications. In this paper, discharges were generated in a highly non-uniform electric field by point-plane gaps in open air by four repetitive nanosecond-pulse generators with repetition rate up to 1 kHz. The rise time of generators was 25 (generator #1), 15 (generator #2), 3 (generator #3), and 0.2 ns (generator #4) and a full width at half maximum was 40, 30-40, 5, and 1 ns, respectively. The experimental results show that there were typical discharge fashions, i.e., corona, diffuse, spark, or arc modes. The variables affecting the discharge characteristics, including the gap spacing and applied pulse parameters, were investigated. Especially, the diffuse discharges were investigated and discussed. With generator #1 at voltage 70-120 kV, characteristics of measured x-rays on the discharge modes were studied, and it indicates that counts of x-rays in a diffuse discharge are up to a peak value under the experimental conditions. With amplitude of voltage pulses in incident wave up to 18 (generator #3) and 12.5 kV (generator #4), runaway electron beam in low pressure helium, nitrogen, and air in a pulse-periodic mode of discharge with repetition rate up to 1 kHz was obtained. Electron beam was registered behind a thin foil in a pressure range from several to tens of Torr. X-ray radiation was obtained in a wide range of pressures, as well as at atmospheric pressure of helium, nitrogen, and air. Voltage pulses of positive and negative polarities were used. Generation of runaway electrons with pulses of positive polarity appeared because of reflected voltage pulses of reverse polarity.

Shao, Tao; Tarasenko, Victor F.; Zhang, Cheng; Baksht, Evgeni Kh.; Zhang, Dongdong; Erofeev, Mikhail V.; Ren, Chengyan; Shutko, Yuliya V.; Yan, Ping

2013-03-01

154

Diffuse scattering from hemispherical nanoparticles at the air-silicon interface  

NASA Astrophysics Data System (ADS)

There has been much recent interest in the application of plasmonics to improve the efficiency of silicon solar cells. In this paper we use finite difference time domain calculations to investigate the placement of hemispherical gold nanoparticles on the rear surface of a silicon solar cell. The results indicate that nanoparticles protruding into the silicon, rather than into air, have a larger scattering efficiency and diffuse scattering into the semiconductor. This finding could lead to improved light trapping within a thin silicon solar cell device.

Centeno, Anthony; Ahmed, Badar; Reehal, Haricharan; Xie, Fang

2013-10-01

155

Diffuse scattering from hemispherical nanoparticles at the air-silicon interface.  

PubMed

There has been much recent interest in the application of plasmonics to improve the efficiency of silicon solar cells. In this paper we use finite difference time domain calculations to investigate the placement of hemispherical gold nanoparticles on the rear surface of a silicon solar cell. The results indicate that nanoparticles protruding into the silicon, rather than into air, have a larger scattering efficiency and diffuse scattering into the semiconductor. This finding could lead to improved light trapping within a thin silicon solar cell device. PMID:24045859

Centeno, Anthony; Ahmed, Badar; Reehal, Haricharan; Xie, Fang

2013-09-17

156

Extinction of diffusion flames burning diluted methane and diluted propane in diluted air  

SciTech Connect

A theoretical and experimental investigation of the extinction limits of counterflow diffusion flames burning methane and propane is outlined. A diffusion flame is stabilized between counterflowing streams of a fuel diluted with nitrogen and air diluted with nitrogen. Extinction limits for such flames were measured over a wide parametric range. Results for methane and propane were found to be in appropriate agreement with previous measurements. The experimental results are interpreted by use of activation energy asymptotic theories developed previously. The gas-phase chemical reaction is approximated as a one step, irreversible process with a large value for the ratio of the activation energy characterizing the chemical reaction to the thermal energy in the flame. Equilibrium dissociation of products is neglected. The theoretical predictions are compared with experimental results, and the overall chemical kinetic rate parameters characterizing the gas-phase oxidation of methane and propane in a diffusion flame are deduced. The overall chemical kinetic rate parameters deduced by use of this procedure are valid only at flame temperatures where equilibrium dissociation is negligible. The scalar dissipation rate at extinction is predicted over a wide range.

Puri, I.K.; Seshadri, K.

1986-08-01

157

Laser-induced fluorescence measurements and modeling of nitric oxide in methane–air and ethane–air counterflow diffusion flames  

Microsoft Academic Search

Quantitative laser-induced fluorescence (LIF) measurements of nitric oxide concentrations [NO] have been obtained along the centerline in atmospheric pressure methane–air and ethane–air counterflow diffusion flames. These flames are highly diluted to avoid both soot formation and the influence of radiative heat losses on NO formation, thereby ensuring NO production mostly via the prompt mechanism. Linear LIF measurements of [NO] are

R. V. Ravikrishna; Normand M. Laurendeau

2000-01-01

158

Nanotube Cathodes.  

National Technical Information Service (NTIS)

Carbon nanotubes have shown promise for applications in many diverse areas of technology. In this report we describe our efforts to develop high-current cathodes from a variety of nanotubes deposited under a variety of conditions. Our goal was to develop ...

D. L. Overmyer M. P. Siegal P. A. Miller T. R. Lockner

2006-01-01

159

A physics-based drift-diffusion approach to model Li-air batteries with organic electrolyte  

Microsoft Academic Search

Drift diffusion models have been used extensively by the semiconductor device research community to provide a physics-based approach for the modeling and simulation of electronic devices under various bias conditions. In this article we develop a model based on the drift-diffusion equations for the simulation of Li-air batteries with organic electrolyte. The model is carefully calibrated and takes into consideration

P. Andrei; J. P. Zheng; M. Hendrickson; E. J. Plichta

2010-01-01

160

24-HOUR DIFFUSIVE SAMPLING OF TOXIC VOCS IN AIR ONTO CARBOPACK X SOLID ADSORBENT FOLLOWED BY THERMAL DESORPTION/GC/MS ANALYSIS - LABORATORY STUDIES  

EPA Science Inventory

Diffusive sampling of a mixture of 42 volatile organic compounds (VOCs) in humidified, purified air onto the solid adsorbent Carbopack X was evaluated under controlled laboratory conditions. The evaluation included variations in sample air temperature, relative humidity, and ozon...

161

Diffusion-weighted 19F-MRI of lung periphery: Influence of pressure and air-SF6 composition on apparent diffusion coefficients.  

PubMed

Lung functional magnetic resonance imaging (MRI) has become a reality using different inert hyperpolarized gases, such as 3He and 129Xe, which have provided an extraordinary boost in lung imaging and has also attracted interest to other chemically inert gaseous contrast agents. In this context, we have recently demonstrated the first diffusion-weighted images using thermally polarized inhaled sulfur hexafluoride (SF6) in small animals. The aim of this study was to evaluate whether or not the diffusion coefficient of this fluorinated gas is sensitive to pulmonary structure, gas concentration and air pressure in the airways. Diffusion coefficients of SF6 (both pure and in air mixtures) measured in vitro at different pressures and 20 degrees C showed an excellent agreement with theoretical values. Measurements of diffusion coefficients were also performed in vivo and post-mortem on healthy rats, achieving satisfactory signal-to-noise ratios (SNRs), and SF6 gas was found to be in an almost completely restricted diffusion regime in the lung, i.e., the transport by molecular diffusion is delayed by collisions with barriers such as the alveolar septa. This observed low diffusivity means that this gas will be less sensitive to structural changes in the lungs than other magnetic resonance sensitive gas such as 3He, particularly at human scale. However, it is still possible that SF6 plays a role since it opens a new structural window. Thus, the interest of researchers in delimiting the important limiting technical factors that makes this process very challenging is obvious. Among them, T2 relaxation is very fast, so gradient systems with very fast switching rate and probably large radiofrequency (RF) power and high field systems will be needed for hexafluoride to be used in human studies. PMID:16098469

Ruiz-Cabello, Jesús; Pérez-Sánchez, José Manuel; Pérez de Alejo, Rigoberto; Rodríguez, Ignacio; González-Mangado, Nicolás; Peces-Barba, Germán; Cortijo, Manuel

2005-08-25

162

Experimental investigation of characteristics of a diffusion flame established over liquid ethanol surface under opposed air flow  

SciTech Connect

A preliminary study of the shape and the extinction characteristics of a diffusion flame established over a circular liquid fuel surface under the influence of an opposed air flow, is presented. Renewable liquid fuel such as ethanol is employed. A simple heterogeneous combustion setup, which consists of a cylindrical tube containing ethanol located at the bottom, is exposed to an opposed air flow from a coaxial circular pipe of same size located at the top at a fixed separation distance. Axial and radial extents of flame for different air flow rates are qualitatively analyzed. Burning rates of ethanol for different separation distances and air flow rates are recorded. For a fixed separation distance, at a particular air flow rate the flame extinction takes place. Extinction air flow rates and corresponding strain rates for different separation distances are presented. (author)

Sen, Anirudh; Raghavan, Vasudevan; Shet, U.S.P. [Department of Mechanical Engineering, Indian Institute of Technology Madras, 206A TDCE Lab., Chennai 600036 (India)

2009-03-15

163

Influence of mass transport on the performance of carbon gas-diffusion air electrodes in alkaline solution  

Microsoft Academic Search

The effect of mass transport on the electrochemical behaviour of carbon gas-diffusion air electrodes in alkaline solution was investigated on the basis of ?E(i) curves. These curves are obtained by subtraction of potential values for an electrode operating with airEair(i) from potential values for the same electrode operating with pure oxygenEoxygen(i) at the same current densityi. Three different regions on

I. Iliev; S. Gamburzev; A. Kaisheva; J. Mrha

1975-01-01

164

Laser-induced fluorescence measurements and modeling of absolute CH concentrations in strained laminar methane\\/air diffusion flames  

Microsoft Academic Search

We have applied linear laser-induced fluorescence to obtain spatially resolved profiles of CH radicals in laminar methane\\/air and methane\\/nitric oxide\\/air counterflow diffusion flames at atmospheric pressure. Excitation and detection of transitions in the A–X band and calibrating the optical detection efficiency via Rayleigh scattering allowed the determination of absolute radical concentrations. Flames at strain rates from 59 to 269s?1 were

Christophe Gibaud; Jordan A. Snyder; Volker Sick; R. Peter Lindstedt

2005-01-01

165

The influence of fuel-air swirl intensity on flame structures of syngas swirl-stabilized diffusion flame  

Microsoft Academic Search

Flame structures of a syngas swirl-stabilized diffusion flame in a model combustor were measured using the OH-PLIF method\\u000a under different fuel and air swirl intensity. The flame operated under atmospheric pressure with air and a typical low heating-value\\u000a syngas with a composition of 28.5% CO, 22.5% H2 and 49% N2 at a thermal power of 34 kW. Results indicate that

Weiwei Shao; Yan Xiong; Kejin Mu; Zhedian Zhang; Yue Wang; Yunhan Xiao

2010-01-01

166

Gas diffusivity and air permeability of the firn from cold polar sites  

NASA Astrophysics Data System (ADS)

Recent field investigations of a megadunes region of East Antarctica provide evidence that differences in grain size, thermal conductivity, and permeability across a megadune are due to relative accumulation patterns in the absence of significant variations in microclimate. The differences in accumulation patterns include distinct areas of perceptible but low accumulation (less than 40 mm w.eq.a-1) and areas of accumulation hiatus within several kilometers proximity, as determined by remote sensing, surface feature classification, and GPR profiling. Near-surface firn properties are very sensitive to the amount of accumulation in low accumulation rate regions, with relatively small differences in accumulation rate (less than 40 mm w.eq.a -1) creating distinctive differences in grain size, thermal conductivity, and permeability, accompanied by variations in satellite-based microwave data from both passive and active sensors. Cores from the megadunes region exhibit variations in physical properties at depth due to temporal changes in local accumulation caused by dune migration. A new way of describing gas diffusivity and air permeability of polar firn is developed. Diffusivity-porosity and permeability-porosity power-law relationships vary from site to site with accumulation rate having the largest impact on the value of the exponent. The largest differences in firn properties occur between firn from hiatus sites compared to sites where any accumulation, from low to high values, occurs.

Courville, Zoe Renee

167

Multiple hollow cathode wear testing  

NASA Astrophysics Data System (ADS)

A hollow cathode-based plasma contactor has been baselined for use on the Space Station to reduce station charging. The plasma contactor provides a low impedance connection to space plasma via a plasma produced by an arc discharge. The hollow cathode of the plasma contactor is a refractory metal tube, through which xenon gas flows, which has a disk-shaped plate with a centered orifice at the downstream end of the tube. Within the cathode, arc attachment occurs primarily on a Type S low work function insert that is next to the orifice plate. This low work function insert is used to reduce cathode operating temperatures and energy requirements and, therefore, achieve increased efficiency and longevity. The operating characteristics and lifetime capabilities of this hollow cathode, however, are greatly reduced by oxygen bearing contaminants in the xenon gas. Furthermore, an optimized activation process, where the cathode is heated prior to ignition by an external heater to drive contaminants such as oxygen and moisture from the insert absorbed during exposure to ambient air, is necessary both for cathode longevity and a simplified power processor. In order to achieve the two year (approximately 17,500 hours) continuous operating lifetime requirement for the plasma contactor, a test program was initiated at NASA Lewis Research Center to demonstrate the extended lifetime capabilities of the hollow cathode. To date, xenon hollow cathodes have demonstrated extended lifetimes with one test having operated in excess of 8000 hours in an ongoing test utilizing contamination control protocols developed by Sarver-Verhey. The objectives of this study were to verify the transportability of the contamination control protocols developed by Sarver-Verhey and to evaluate cathode contamination control procedures, activation processes, and cathode-to-cathode dispersions in operating characteristics with time. These were accomplished by conducting a 2000 hour wear test of four hollow cathodes with different xenon gas purities and activation processes. The following will be presented: a description of the facility and test hardware, testing procedures and operating conditions, a discussion of test results, and conclusions.

Soulas, George C.

1994-06-01

168

Thermal and electrochemical decomposition of lithium peroxide in non-catalyzed carbon cathodes for Li-air batteries.  

PubMed

The decomposition of lithium peroxide during the charging process of lithium-air batteries is investigated. A novel preparation method for electrodes in the discharged state, i.e., prefilled with Li2O2 using polyethylene oxide as a binder, is presented. The composition and reactivity of Li2O2-prefilled electrodes are examined by thermal analysis coupled with on-line mass spectrometry. Voltage profiles and gas evolution during the charging process of Li2O2-prefilled electrodes in battery cells are correlated with the thermal decomposition process of Li2O2 and its impact on other electrode compounds. It is found that both thermal Li2O2 decomposition and the electrochemical decomposition of Li2O2 during charging enhance the oxidation of the electrolyte, the binder, and/or carbon, which is suggested to be due to the formation of "nascent" oxygen during Li2O2 decomposition into O2 and Li2O (thermally) or into O2 and lithium ions (electrochemically). PMID:23715054

Beyer, H; Meini, S; Tsiouvaras, N; Piana, M; Gasteiger, H A

2013-05-28

169

A high-performance cathode for the next generation of solid-oxide fuel cells  

NASA Astrophysics Data System (ADS)

Fuel cells directly and efficiently convert chemical energy to electrical energy. Of the various fuel cell types, solid-oxide fuel cells (SOFCs) combine the benefits of environmentally benign power generation with fuel flexibility. However, the necessity for high operating temperatures (800-1,000°C) has resulted in high costs and materials compatibility challenges. As a consequence, significant effort has been devoted to the development of intermediate-temperature (500-700°C) SOFCs. A key obstacle to reduced-temperature operation of SOFCs is the poor activity of traditional cathode materials for electrochemical reduction of oxygen in this temperature regime. Here we present Ba0.5Sr0.5Co0.8Fe0.2O3-?(BSCF) as a new cathode material for reduced-temperature SOFC operation. BSCF, incorporated into a thin-film doped ceria fuel cell, exhibits high power densities (1,010mWcm-2 and 402mWcm-2 at 600°C and 500°C, respectively) when operated with humidified hydrogen as the fuel and air as the cathode gas. We further demonstrate that BSCF is ideally suited to `single-chamber' fuel-cell operation, where anode and cathode reactions take place within the same physical chamber. The high power output of BSCF cathodes results from the high rate of oxygen diffusion through the material. By enabling operation at reduced temperatures, BSCF cathodes may result in widespread practical implementation of SOFCs.

Shao, Zongping; Haile, Sossina M.

2004-09-01

170

A Computational Study of the Soot Formation in Methane-Air Diffusion Flame During Early Transience Following Ignition  

Microsoft Academic Search

A CFD-based numerical model has been developed for the determination of the volume concentration and number density of soot in a laminar diffusion flame of methane in air, under transient condition following ignition of the flame. The transience is studied from the point of ignition till the final steady state is reached. The burner is an axi- symmetric co-flowing one

Bijan Kumar Mandal; Amitava Datta; Amitava Sarkar

2008-01-01

171

Effect of Ferrocene on Soot in a Prevaporized Iso-Octane/Air Diffusion Flame. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

Measurements were carried out to determine the effect on soot when ferrocene is added to a prevaporized isooctane/air diffusion flame. Data were obtained for operation of the flame above and below its smoke-point. Mile scattering was used to determine soo...

P. A. Bonczyk

1991-01-01

172

Effect of pressure on the extinction, acoustic pressure response, and NO formation in diluted hydrogen–air diffusion flames  

Microsoft Academic Search

Characteristics of extinction, acoustic response, and NO formation for diluted hydrogen–air diffusion flames at various pressures are investigated numerically by adopting a counterflow model. The results show that extinction can be classified into three regimes, where extinction strain rate increases with pressure at low pressures, decreases at moderate pressures, and increases again at high pressures. This behavior is caused by

C. H. SOHN; S. H. CHUNG

2000-01-01

173

POINT SOURCE TURBULENT DIFFUSION FOR AN AIR FLOW IN A DUCT. Technical Report No. 6 on EXPLORATION AND APPLICATION OF TURBULENCE THEORY  

Microsoft Academic Search

The turbulent diffusion process was examined by in jecting hydrogen at ; the center of a three inch pipe into turbulently flowing air and by taking ; concentration traverses at distances downstream. The air velocity in the pipe ; was varied to determine how the diffusion rate varied over a Reynolds' number ; range of from 5,700 to 87,000. The

T. J. Hanratty; D. L. Flint

1958-01-01

174

Opposed jet diffusion flames of nitrogen-diluted hydrogen vs air - Axial LDA and CARS surveys; fuel/air rates at extinction  

SciTech Connect

An experimental study of H-air counterflow diffusion flames (CFDFs) is reported. Coaxial tubular opposed jet burners were used to form dish-shaped CFDFs centered by opposing laminar jets of H2/N2 and air in an argon bath at 1 atm. Jet velocities for extinction and flame restoration limits are shown versus input H2 concentration. LDA velocity data and CARS temperature and absolute N2, O2 density data give detailed flame structure on the air side of the stagnation point. The results show that air jet velocity is a more fundamental and appropriate measure of H2-air CFDF extinction than input H2 mass flux or fuel jet velocity. It is proposed that the observed constancy of air jet velocity for fuel mixtures containing 80 to 100 percent H2 measure a maximum, kinetically controlled rate at which the CFDF can consume oxygen in air. Fuel velocity mainly measures the input jet momentum required to center an H2/N2 versus air CFDF. 42 refs.

Pellett, G.L.; Northam, G.B.; Wilson, L.G.; Jarrett, O. Jr.; Antcliff, R.R.

1989-01-01

175

Micro hollow cathode discharges  

Microsoft Academic Search

Summary form only given, as follows. Hollow cathode discharges are glow discharges with the cathode fall and negative glow confined in a cavity in the cathode. For the discharge to develop the cathode hole dimensions must be on the order of the mean free path. By reducing the cathode hole dimensions it is therefore possible to increase the pressure. Stable

K. H. Schoenbach; F. E. Peterkin; R. Verhappen

1995-01-01

176

Diffusion  

NSDL National Science Digital Library

Diffusion is the movement of particles from an area of high concentration to an area of low concentration. The molecules move until equilibrium is reached. If a perfume is sprayed on one side of the room, the perfume molecules will eventually spread out all over the room until there are equal concentrations of the molecules throughout the space.

Christopher Thomas (None;)

2006-11-09

177

Experimental Results for the Thermal Diffusion Sensitivity of 40Ar/36Ar in air: Calibration of the Ice Core Fossil-Air Paleothermometer.  

NASA Astrophysics Data System (ADS)

Greenland ice cores supply a detailed record of climate for the last ~100 kyrs. The conventional paleotemperature proxy, ?18O of the ice, displays persistent millennial-scale oscillations throughout the Last Glacial Period. Determination of the magnitudes of the associated abrupt climate warmings using the observed shifts in ?18Oice is ambiguous (Jouzel J., Science, vol.286, p.910, 1999). An alternative approach involves observing the amount of 29N2/28N2 and 40Ar/36Ar fractionation caused by thermal diffusion in the fossil air extracted from ice cores (Severinghaus J.P. and Brook E.J., ibid., p.930). This method makes use of the thermal diffusion constants of the respective isotopic pairs known from the laboratory experiments. We find that the thermal diffusion sensitivity value for 40Ar/36Ar in air is (40.5\\pm0.5)\\times10-3 per mil/oC at -30oC compared with the corresponding value in pure argon of (46.3\\pm0.4)\\times10-3 per mil/oC. The error translates into a ~0.1oC error for a ~10oC warming. The pure argon thermal diffusion constants are the only ones available in the literature and are unsuitable for paleoenvironmental applications, since values for air differ substantially. More careful and extensive experimentation allowed establishing the sensitivity values in air with greater precision than in our preliminary work (Grachev A.M. and Severinghaus J.P., EOS: Transactions, AGU, vol.80(46), p.F12).

Grachev, A. M.; Severinghaus, J. P.

2002-12-01

178

Microengineered cathode interface studies  

SciTech Connect

The overpotential at the cathode/electrolyte interface has been recognized as an important limitation on the performance of solid oxide fuel cells (SOFCs). This project is an effort to gain a scientific understanding of which interface features and conditions contribute to cathode polarization in SOFCs. The paper discusses three possible rate-limiting factors in the cathode reaction. The paper studies the electronic conductivity in the electrolyte, the ionic conductivity in the cathode, cathode geometry near the interface, and cathode surface area.

Kueper, T.; Doshi, R.; Krumpelt, M. [Argonne National Lab., IL (United States). Electrochemical Technology Program

1996-10-01

179

Soot formation and temperature field structure in laminar propane-air diffusion flames at elevated pressures  

SciTech Connect

The effect of pressure on soot formation and the structure of the temperature field was studied in coflow propane-air laminar diffusion flames over the pressure range of 0.1 to 0.73 MPa in a high-pressure combustion chamber. The fuel flow rate was selected so that the soot was completely oxidized within the visible flame and the flame was stable at all pressures. Spectral soot emission was used to measure radially resolved soot volume fraction and soot temperature as a function of pressure. Additional soot volume fraction measurements were made at selected heights using line-of-sight light attenuation. Soot concentration values from these two techniques agreed to within 30% and both methods exhibited similar trends in the spatial distribution of soot concentration. Maximum line-of-sight soot concentration along the flame centerline scaled with pressure; the pressure exponent was about 1.4 for pressures between 0.2 and 0.73 MPa. Peak carbon conversion to soot, defined as the percentage of fuel carbon content converted to soot, also followed a power-law dependence on pressure, where the pressure exponent was near to unity for pressures between 0.2 and 0.73 MPa. Soot temperature measurements indicated that the overall temperatures decreased with increasing pressure; however, the temperature gradients increased with increasing pressure. (author)

Bento, Decio S.; Guelder, OEmer L. [Institute for Aerospace Studies, University of Toronto, 4925 Dufferin Street, Toronto, ON M3H 5T6 (Canada); Thomson, Kevin A. [National Research Council, ICPET Combustion Technology, 1200 Montreal Road M-9, Ontario K1A 0R6 (Canada)

2006-06-15

180

Distributed-memory parallel computation of a forced, time-dependent, sooting, ethylene\\/air coflow diffusion flame  

Microsoft Academic Search

Forced, time-varying laminar flames help bridge the gap between laminar and turbulent combustion as they reside in an ever-changing flow environment. A distributed-memory parallel computation of a time-dependent sooting ethylene\\/air coflow diffusion flame, in which a periodic fluctuation (20 Hz) is imposed on the fuel velocity for four different amplitudes of modulation, is presented. The chemical mechanism involves 66 species,

S. B. Dworkin; J. A. Cooke; B. A. V. Bennett; B. C. Connelly; M. B. Long; M. D. Smooke; R. J. Hall; M. B. Colket

2009-01-01

181

Numerical Prediction of Air-preheating Effect on Soot Formation in Diffusion Flame During Early Transience Following Ignition  

Microsoft Academic Search

A CFD-based numerical model has been developed for the determination of the volume concentration and number density of soot in a laminar diffusion flame of methane in air, under transient condition following ignition of the flame. The transience is studied from the point of ignition till the final steady state is reached. The burner is an axi-symmetric co-flowing one with

Bijan Kumar Mandal; Amitava Datta; Amitava Sarkar

2007-01-01

182

Diffusion of VoIP in Chinese large enterprises: the cases of Air China and Harvest Fund  

Microsoft Academic Search

Purpose – This research paper aims to apply the technology-organization-environment (TOE) framework to describe and discuss the critical factors concerning the diffusion of voice over internet protocol (VoIP) innovations among Chinese large enterprises, in particular, Air China and Harvest Fund. Design\\/methodology\\/approach – The paper deploys a dual case study methodology and extensive triangulation, including review of archival data, in-depth interviews

Dimitris Assimakopoulos; Herman Wu

2010-01-01

183

Extinguishment of diffusion flames around a cylinder in a coaxial air stream with dilution or water mist  

Microsoft Academic Search

Extinguishment of methane and polymethylmethacrylate (PMMA) diffusion flames by gaseous and water-mist fire-extinguishing agents has been studied experimentally and computationally using a cylindrical burner inserted downwardly into an upward coaxial air stream. Transient computations were performed for methane flames with full chemistry and a simple water-mist model to reveal the flame structure and suppression processes. For methane, as a gaseous

Fumiaki Takahashi; Viswanath R. Katta

2009-01-01

184

NAREL (National Air and Standard Environmental Laboratory) standard operating procedures for radon-222 measurement using diffusion barrier charcoal canisters  

Microsoft Academic Search

Radon monitoring procedures for the National Air and Radiation Environment Laboratory (NAREL) are described. Radon is detected by sorption to activated charcoal, followed by detection of gamma ray emissions from the radon decay products lead-214 (295 KeV and 392 KeV) and bismuth-214 (609 KeV). The activated charcoal is held in an 8 ounce metal can, under a polyethylene diffusion barrier

D. J. Gray; S. T. Windham

1990-01-01

185

A New Insight into the Polaron--Li Complex Diffusion in Cathode Material LiFe1-yMnyPO4 for Li Ion Batteries  

NASA Astrophysics Data System (ADS)

Based on the Heyd--Scuseria--Ernzerhof hybrid density functionals study, we proposed a new insight into the diffusion of polaron--Li vacancy complexes in LiFe1-yMnyPO4 (y=0,1/2,1). It is found that the polaron migrates along a crossing or a parallel path relative to the Li moving direction. In LiFePO4, the complex diffusion along the zigzag pathway is favorable and has a barrier of 600 meV, while the diffusion along the parallel pathway with a barrier of 623 meV is favorable in LiMnPO4. For LiFe1/2Mn1/2PO4, since the polaron is formed within a single Fe layer, the diffusion proceeds along the parallel pathway with a barrier of 635 meV.

Dinh, Van An; Nara, Jun; Ohno, Takahisa

2012-04-01

186

Aromatic hydrocarbon and methyl tert-butyl ether measurements in ambient air of Helsinki (Finland) using diffusive samplers.  

PubMed

The diffusive sampling method was evaluated for measuring benzene, toluene, ethylbenzene, xylenes, styrene, propylbenzene, ethyltoluenes, trimethylbenzenes and methyl tert-butyl ether (MTBE) in the urban air of Helsinki, Finland. Concentrations were measured in 2-week periods at four different sites during the year 2000. Tube type adsorbent tubes were pre-packed with Carbopack-B (60/80). Analysis was conducted using thermal desorption and gas chromatograph coupled to a mass spectrometer. In different seasons, during five diffusive sampling periods, parallel measurements were conducted using pumped and online sampling. The compared techniques agreed reasonably well for other compounds than trimethylbenzenes. Based on comparisons, diffusive uptake rates for ethyltoluenes, styrene, propylbenzene and MTBE were determined, and for trimethylbenzenes, uptake rates were revised. The concentrations of aromatic compounds in Helsinki metropolitan area were also compared to the concentrations of a rural, forested site in Central Finland. PMID:12449329

Hellén, Heidi; Hakola, Hannele; Laurila, Tuomas; Hiltunen, Veijo; Koskentalo, Tarja

2002-10-21

187

Air  

MedlinePLUS

... do to protect yourself from dirty air . Indoor air pollution and outdoor air pollution Air can be polluted indoors and it can ... this chart to see what things cause indoor air pollution and what things cause outdoor air pollution! Indoor ...

188

Numerical study on rectangular microhollow cathode discharge  

SciTech Connect

Rectangular microhollow cathode discharge in argon is investigated by using two-dimensional time-dependent self-consistent fluid model. The electric potential, electric field, particle density, and mean electron energy are calculated. The results show that hollow cathode effect can be onset in the present configuration, with strong electric field and high mean electron energy in the cathode fall while high density and quasineutral plasma in the negative glow. The potential well and electric filed reversal are formed in the negative glow region. It is suggested that the presence of large electron diffusion flux necessitates the field reversal and potential well.

He Shoujie [School of Science, Beijing Institute of Technology, Beijing 100081 (China); College of Physics Science and Technology, Hebei University, Baoding 071002 (China); Ouyang Jiting; He Feng; Li Shang [School of Science, Beijing Institute of Technology, Beijing 100081 (China)

2011-03-15

189

New insights in the polarization resistance of anode-supported solid oxide fuel cells with La0.6Sr0.4Co0.2Fe0.8O3 cathodes  

SciTech Connect

In this study, the polarization resistance of the La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) solid oxide fuel cell (SOFC) cathode was investigated by I-V sweep and electrochemcial impedance spectroscopy under a series of dc bias voltages and cathode environments (i.e. stagnant air, flowing air, and flowing oxygen) at temperatures from 550 to 750 °C. In flowing oxygen, the polarization resistance of the fuel cell decreased considerably with the applied current density. A linear relationship was observed between the ohmic-free over-potential and the logarithm of the current density of the fuel cell at all the measuring temperatures. In stagnant or flowing air, a new arc related to the molecular oxygen diffusion in the pores of the cathode was identified at high temperatures and high current densities. The magnitude of this arc increased with the applied current density due to the decreased oxygen partial pressure at the interface of the cathode and the electrolyte. It is found that the performance of the fuel cell in air is mainly determined by the oxygen diffusion process. Elimination of this process by flowing oxygen to the cathode improved the cell performance significantly. At 750 °C, for a fuel cell with a laser-deposited Sm0.2Ce0.8O1.9 (SDC) interlayer, an extraordinarily high power density of 2.6 W cm-2 at 0.7 V was achieved in flowing oxygen, as a result of reduced ohmic and polarization resistance of the fuel cell, which were 0.06 ? cm2 and 0.03 ? cm2, respectively. The results indicate that optimization of the microstructure of the LSCF cathode or adoption of a new cell design which can mitigate the diffusion problem in the cathode might enhance cell performance significantly.

Lu, Zigui; Hardy, John S.; Templeton, Jared W.; Stevenson, Jeffry W.

2011-01-01

190

Nanotube cathodes.  

SciTech Connect

Carbon nanotubes have shown promise for applications in many diverse areas of technology. In this report we describe our efforts to develop high-current cathodes from a variety of nanotubes deposited under a variety of conditions. Our goal was to develop a one-inch-diameter cathode capable of emitting 10 amperes of electron current for one second with an applied potential of 50 kV. This combination of current and pulse duration significantly exceeds previously reported nanotube-cathode performance. This project was planned for two years duration. In the first year, we tested the electron-emission characteristics of nanotube arrays fabricated under a variety of conditions. In the second year, we planned to select the best processing conditions, to fabricate larger cathode samples, and to test them on a high-power relativistic electron beam generator. In the first year, much effort was made to control nanotube arrays in terms of nanotube diameter and average spacing apart. When the project began, we believed that nanotubes approximately 10 nm in diameter would yield sufficient electron emission properties, based on the work of others in the field. Therefore, much of our focus was placed on measured field emission from such nanotubes grown on a variety of metallized surfaces and with varying average spacing between individual nanotubes. We easily reproduced the field emission properties typically measured by others from multi-wall carbon nanotube arrays. Interestingly, we did this without having the helpful vertical alignment to enhance emission; our nanotubes were randomly oriented. The good emission was most likely possible due to the improved crystallinity, and therefore, electrical conductivity, of our nanotubes compared to those in the literature. However, toward the end of the project, we learned that while these 10-nm-diameter CNTs had superior crystalline structure to the work of others studying field emission from multi-wall CNT arrays, these nanotubes still had a thin coating of glassy carbon surrounding them in a sheath-like manner. This glassy carbon, or nano-crystalline graphite, is likely to be a poor conductor due to phonon scattering, and should actually be deleterious for extracting electrons with electric fields. While we did not achieve the field emission reported for single-wall carbon nanotubes that spurred the idea for this project, at the year's very end, we had a breakthrough in materials growth and learned to control the growth of very-small diameter nanotubes ranging from 1.4 to 7 nm. The 1.4-nm nanotubes are single-walled and grow at only 530 C. This is the lowest temperature known to result in single-wall carbon nanotubes, and may be very important for many applications that where certain substrates could not be used due to the high temperatures commonly used for CNT growth. Critically important for field emission, these small diameter nanotubes, consisting of only a few concentric graphene cylindrical walls, do not show the presence of a poorly-conductive sheath material. Therefore, these nanotubes will almost definitely have superior field emission properties to those we already measured, and it is possible that they could provide the necessary field emission to make this project successful. Controlled spacing and lengths of these single-wall nanotubes have yet to be explored, along with correlating their structures to their improved field emission. Unfortunately, we did not discover the methods to grow these highly-crystalline and small diameter CNTs until late in the year. Since we did not achieve the necessary emission properties by mid-year, the project was ''prematurely'' terminated prior to the start of the second year. However, it should be noted that with the late developments, this work has not hit the proverbial ''brick wall''. Clearly the potential still exists to reproduce and even exceed the high emission results reported for randomly-oriented and curly single-wall carbon nanotubes, both in terms of total field emitting currents and perhaps more importantly, in reproducibility.

Overmyer, Donald L.; Lockner, Thomas Ramsbeck; Siegal, Michael P.; Miller, Paul Albert

2006-11-01

191

Spiral cathodes for microwave heating magnetrons  

NASA Astrophysics Data System (ADS)

Cathodes have been developed for magnetrons for microwave heating using thermally stable alloys of an activator metal and a platinum group metal as a surface layer on the cathode. Metal alloy cathodes (MAC) utilizing Ir 5La or Re 2Th were tested and shown to be capable of operating at a lower temperature than carburized thoriated tungsten or pure tungsten cathodes. An alternative cathode configuration was developed and tested in which a spiral wound cathode had an additional source of activator metal installed as a bushing on a rod within the hollow interior of the winding and heated by radiation. When the spiral is heated the active metal evaporating from the source initially is adsorbed on the inner surface of the spiral and then migrates to the external surface via surface diffusion. Three variations of this cathode configuration were tested. At T = 1000°C brightness and with a collector current of 2 to 3 A/cm 2 the cathode life without replenishment is 3000 h and the provision of an activator replenishment source was found to permit a potential severalfold increase in life. A 6000 h operating life has been achieved to date and the life tests are presently still being continued.

Djubua, B. Ch.; Ilyin, B. N.; Polivnikova, O. V.; Zemchikhin, E. M.

1997-02-01

192

Implementation of REDIM reduced chemistry to model an axisymmetric laminar diffusion methane–air flame  

Microsoft Academic Search

The goal of this work is to analyze the use of automatically reduced chemistry by the Reaction–Diffusion Manifold (REDIM) method in simulating axisymmetric laminar coflow diffusion flames. Detailed chemical kinetic models are usually computationally prohibitive for simulating complex reacting flows, and therefore reduced models are required. Automatic reduction model approaches usually exploit the natural multi-scale structure of combustion systems. The

Pedro Henrique de Almeida Konzen; Thomas Richter; Uwe Riedel; Ulrich Maas

2011-01-01

193

COMPARISON OF 24H AVERAGE VOC MONITORING RESULTS FOR RESIDENTIAL INDOOR AND OUTDOOR AIR USING CARBOPACK X-FILLED DIFFUSIVE SAMPLERS AND ACTIVE SAMPLING - A PILOT STUDY  

EPA Science Inventory

Analytical results obtained by thermal desorption GC/MS for 24h diffusive sampling of 11 volatile organic compounds (VOCs) are compared with results of time-averaged active sampling at a known constant flow rate. Air samples were collected with co-located duplicate diffusive samp...

194

Tracer gas technique developed to study diffusive leakages of air pollutants from petrochemical complexes.  

National Technical Information Service (NTIS)

A tracer gas technique has been developed by NILU to study emission rates and diffusion of gases in industrial building complexes. This paper describes the technique and outlines the design and requirements for simulations and gives several examples of fi...

B. Sivertsen

1995-01-01

195

Small-angle neutron scattering study of soot particles in an ethylene-air diffusion flame  

SciTech Connect

Neutron scattering techniques have been applied to the study soot particles in an ethylene diffusion flame. Primary particle sizes have been determined as a function of height-above-the-burner. The practicality of the method has been demonstrated. (author)

Mitchell, J.B.A.; Le Garrec, J.L.; Florescu-Mitchell, A.I. [PALMS, UMR No. 6627 du CNRS, Universite de Rennes I, 35042 Rennes cedex (France); di Stasio, S. [Aerosol and Nanostructures Laboratory, Istituto Motori, National Research Council of Italy, Via Marconi 8, 80125 Naples (Italy)

2006-04-15

196

Bimodal Probability Law Model for Unified Description of Water Retention, Air and Water Permeability, and Gas Diffusivity in Variably Saturated Soil  

Microsoft Academic Search

Air and water permeabilities and gas diffusivity as functions of soil fluid phase (air or water) contents are governing chemical transport and fate processes in the vadose zone, and have frequently been iden- tified as the three main transport parameters determining time and ef- ficiency during soil vapor extraction (soil venting) at polluted soil sites. A mathematically flexible function that

Tjalfe G. Poulsen; Per Moldrup; Seiko Yoshikawa; Toshiko Komatsu

2006-01-01

197

Stochastic simulation of the gas diffusion in the air phase of the human lung  

Microsoft Academic Search

The solution of the diffusion equation in the gas phase of the human lung is very difficult because of the structure of the\\u000a bronchial tree. It is shown by means of physical arguments, how one can reduce the diffusion equation to a simple one-dimensional\\u000a form. The solution is then obtained by a stochastic simulation, which is easily realized on a

Manuel Paiva; Irina Paiva-Veretennicoff

1972-01-01

198

Study on Flows inside and outside an Air Diffuser for Membrane Bioreactor  

NASA Astrophysics Data System (ADS)

Effects of the total gas flow rate on the water level in a diffuser pipe for a membrane bioreactor, the gas flow rate from each aeration hole and the bubble diameter are investigated. The diffuser has evenly positioned five aeration holes on the top and a larger hole on the bottom for introducing the liquid into the pipe. The gas flow rate from each aeration hole is measured by capturing generated bubbles. The water level and gas velocity inside the diffuser are computed by processing video images. The bubble diameter is calculated using the gas flow rate and the bubble generation frequency measured from the video images. The conclusions obtained are as follows: (1) the gas flow rate from the aeration hole depends on the water level inside the diffuser and becomes constant for all the holes as the total gas flow rate increases since the high total gas flow rate make the water level uniform, which results in a constant gas pressure in the diffuser, (2) the onset of slugging in the diffuser is well correlated in terms of the local gas velocity and the Mishima-Ishii's slugging model, (3) the increase in the total gas flow rate decreases the water level, causing suppression of the onset of slugging, (4) the diameter of aeration hole strongly affects the gas flow rate from each aeration hole and water level, and (5) the Davidson-Schuler correlation gives reasonable estimations of the bubble diameter, provided that the influence of slugging is not significant.

Kira, Fumihiro; Furuno, Shinsuke; Hayashi, Kosuke; Sampei, Tomoyuki; Tomiyama, Akio

199

Surface tension, diffusion and kinetics studies of an air-stripping process  

Microsoft Academic Search

Volatile organic compounds (VOC) are among the most common wastewater pollutants and are often removed by the process of air-stripping. Since VOC molecules in solution must adsorb to the air–liquid interface before evaporating, it is possible to use surface tension measurement to monitor the change in interfacial properties. This paper demonstrates that axisymmetric drop shape analysis (ADSA) can be used

C Mak; E Cornu; C Moresoli; P Chen

2004-01-01

200

Imaging air quality evaluation based on Noise Brightness Ratio & Gompertz Type Diffusion Process  

Microsoft Academic Search

A novel air quality evaluation method, which only uses the surveillance image data, is presented in this paper. Since the intensity change of the Image Quality (IQ) can reflect the photography condition change of a CCD camera, the image can be used to evaluate the trend change of the air quality. In this paper, first a new IQ metric, which

Haoting Liu; Hanqing Lu

2010-01-01

201

Recent Advances in Thermionic Cathodes  

SciTech Connect

The latest advances in thermionic cathodes, including scandate and controlled porosity reservoir cathodes, are reviewed. These new cathodes provide improved performance over conventional cathodes for many applications. Advantages and disadvantages are presented.

Ives, R. Lawrence; Miram, George; Collins, George [Calabazas Creek Research, Inc., 690 Port Drive, San Mateo, CA 94404 (United States); Falce, Louis R. [Consultant, 16521 W. Pueblo Lane, Surprise AZ (United States)

2010-11-04

202

Sintered wire cathode  

DOEpatents

A porous cathode structure is fabricated from a plurality of wires which are placed in proximity to each other in elevated temperature and pressure for a sintering time. The sintering process produces the porous cathode structure which may be divided into a plurality of individual porous cathodes, one of which may be placed into a dispenser cathode support which includes a cavity for containing a work function reduction material such as BaO, CaO, and Al.sub.2O.sub.3. The work function reduction material migrates through the pores of the porous cathode from a work replenishment surface adjacent to the cavity of the dispenser cathode support to an emitting cathode surface, thereby providing a dispenser cathode which has a uniform work function and therefore a uniform electron emission.

Falce, Louis R. (San Jose, CA); Ives, R. Lawrence (Saratoga, CA)

2009-06-09

203

Cathodic protection -- Rectifier 47  

SciTech Connect

This Acceptance Test Procedure (ATP) has been prepared to demonstrate that the cathodic protection system functions as required by project criteria. The cathodic protection system is for the tank farms at the Hanford Reservation. The tank farms store radioactive waste.

Lane, W.M. [Westinghouse Hanford Co., Richland, WA (United States)

1995-06-14

204

Cathodic protection -- Rectifier 46  

SciTech Connect

This Acceptance Test Procedure (ATP) has been prepared to demonstrate that the cathodic protection system functions as required by project criteria. The cathodic protection system is for the tank farms on the Hanford Reservation. The tank farms store radioactive waste.

Lane, W.M. [Westinghouse Hanford Co., Richland, WA (United States)

1995-06-14

205

Improved cerebral protection through replacement of residual intracavital air by carbon dioxide: a porcine model using diffusion-weighted magnetic resonance imaging  

Microsoft Academic Search

BackgroundMajor risk of central or peripheral organ damage is attributed to air embolism from incompletely de-aired cardiac chambers after cardiac operations. Replacement of air by carbon dioxide insufflation into the thoracic cavity is widely used. Diffusion-weighted magnetic resonance imaging of the brain detects ischemia within minutes after onset. The reversibility of ischemia in cerebral tissue after massive gaseous emboli has

S Martens; A Theisen; J. O Balzer; M Dietrich; K Graubitz; M Scherer; C Schmitz; M Doss; A Moritz

2004-01-01

206

Interactions between arrayed hollow cathodes  

NASA Astrophysics Data System (ADS)

An array of novel hollow cathode plasma sources of 4 mm diameter and driven by up to 500 W of 13.56 MHz rf power was constructed. It was investigated using spatially resolved Langmuir probe measurements in the plasma expansion region. Initial results suggest the plasma observed downstream is the combination of a diffusion from the exit orifice of the 30 mm long cylindrical source region and a uniform plasma created in the expansion region. By measuring the ion density of the plasma plumes produced by two or more active hollow cathode sources, their mutual interaction has been inferred with the aim of determining whether a much larger array of sources could be envisioned. The effectiveness of the plasma in dissociating reactive species was tested using SF6 and measuring etch rates on unbiased silicon wafers. The results have been modelled and show that it is possible to produce a uniform spread of ±5%.

Dixon, Sam; Charles, Christine; Boswell, Rod; Cox, Wes; Holland, John; Gottscho, Richard

2013-04-01

207

Analysis of Turbulent Free Jet Hydrogen-Air Diffusion Flames with Finite Chemical Reaction Rates.  

National Technical Information Service (NTIS)

The nonequilibrium flow field resulting from the turbulent mixing and combustion of a supersonic axisymmetric hydrogen jet in a supersonic parallel coflowing air stream is analyzed. Effective turbulent transport properties are determined using the (K-epsi...

J. P. Sislian

1978-01-01

208

LAMINAR METHANE-AIR DIFFUSION FLAME WITH CHLORINE IMPURITIES: PRELIMINARY RESULTS  

EPA Science Inventory

The extended abstract gives preliminary results of exploratory tests, conducted by adding chlorine to the fuel side of a well characterized methane-air flame, to study the fundamental processes accompanying the combustion of chlorinated hydrocarbons. (NOTE: Formation of products ...

209

Numerical study on the influence of hydrogen addition on soot formation in a laminar ethylene-air diffusion flame  

SciTech Connect

The influence of hydrogen addition to the fuel of an atmosphere pressure coflow laminar ethylene-air diffusion flame on soot formation was studied by numerical simulation. A detailed gas-phase reaction mechanism, which includes aromatic chemistry up to four rings, and complex thermal and transport properties were used. The fully coupled elliptic governing equations were solved. The interactions between soot and gas-phase chemistry were taken into account. Radiation heat transfer from CO{sub 2}, CO, H{sub 2}O, and soot was calculated using the discrete-ordinates method coupled to a statistical narrow-band-correlated K-based wide-band model. The predicted results were compared with the available experimental data and analyzed. It is indicated that the addition of hydrogen to the fuel in an ethylene-air diffusion flame suppresses soot formation through the effects of dilution and chemistry. This result is in agreement with available experiments. The simulations further suggest that the chemically inhibiting effect of hydrogen addition on soot formation is due to the decrease of hydrogen atom concentration in soot surface growth regions and higher concentration of molecular hydrogen in the lower flame region. (author)

Guo, Hongsheng; Liu, Fengshan; Smallwood, Gregory J. [Institute for Chemical Process and Environmental Technology, National Research Council of Canada, 1200 Montreal Road, Building M-9, Ottawa, Ontario (K1A 0R6 Canada); Guelder, OEmer L. [Institute for Aerospace Studies, University of Toronto, 4925 Dufferin Street, Toronto, Ontario (M3H 5T6 Canada)

2006-04-15

210

Diffusion d'air humide avec condensation de vapeur d'eau en milieu poreux  

Microsoft Academic Search

This paper is devoted to the experimental and numerical investigations of the non-isothermal moisture diffusion with condensation in homogeneous isotropic non deformable capillary porous bodies. From the comparisons between experimental and numerical results it was possible: to justify, at least in part, the use of the Philip de Vries mathematical model as a predictive tool; to identify the reasons of

S Larbi; G Bacon; S. A Bories

1995-01-01

211

Combustion modeling of turbulent jet diffusion H 2\\/air flame with detailed chemistry  

Microsoft Academic Search

In the present paper, turbulent jet diffusion flames are investigated numerically using a finite volume method for the solution of the Navier–Stokes and reaction equations governing the problem. The method is based on a finite volume discretization and the SIMPLE approach for velocity and pressure coupling. For validation of the modeling of turbulence and numerical method, results are shown for

X. Zhou; Z. Sun; G. Brenner; F. Durst

2000-01-01

212

Technology diffusion and environmental regulation: Evidence from electric power plants under the Clean Air Act  

Microsoft Academic Search

Even though environmental policy can greatly affect the path of technology diffusion, the economics literature contains limited empirical evidence of this relationship. My research will contribute to the available evidence by providing insight into the technology adoption decisions of electric generating firms. Since policies are often evaluated based on the incentives they provide to promote adoption of new technologies, it

Elaine F. Frey

2008-01-01

213

Performance of a thermally desorbable type-tube diffusive sampler for very low air concentrations monitoring  

Microsoft Academic Search

Perkin-Elmer tubes packed with Tenax TA have been tested for the monitoring of low concentrations of aromatic compounds and linear alkanes using diffusive sampling. The uptake rates have been investigated for different exposure doses. A particular hexane and benzene behaviour has been observed: their uptake rates decrease rapidly in the lower exposure doses and so follow an exponential curve. The

A. Roche; R. Thevenet; V. Jacob; P. Kaluzny; C. Ferrari; P. Baussand; P. Foster

1999-01-01

214

Diffusion of metal in a confined nanospace of carbon nanotubes induced by air oxidation.  

PubMed

Air oxidation can result in the motion of metal confined in carbon nanotubes (CNTs). This can also be utilized to tailor various hybrid nanostructures. By controllable air-oxidation, as-prepared metal@CNT nanorods (a) can be converted first to core-shell-void nanorods (b), then to metal/metal oxide@CNT nanotubes (c), and finally to mesoporous metal oxide nanotubes (d). The metal/metal oxide@CNT nanotubes and mesoporous metal oxide nanotubes are expected to find many applications, such as in lithium ion batteries, catalysis, magnetic drug delivery, and gas sensing. PMID:20684548

Zhou, Jisheng; Song, Huaihe; Chen, Xiaohong; Huo, Junping

2010-08-25

215

Raman measurement of mixing and finite-rate chemistry in a supersonic hydrogen-air diffusion flame  

SciTech Connect

Ultraviolet (UV) spontaneous vibrational Raman scattering and laser-induced predissociative fluorescence (LIPF) from a KrF excimer laser are combined to simultaneously measure temperature, major species concentrations (H[sub 2], O[sub 2], N[sub 2], H[sub 2]O), and OH radical concentration in a supersonic lifted co-flowing hydrogen-air diffusion flame. The axisymmetric flame is formed when a sonic jet of hydrogen mixes with a Mach 2 annular jet of vitiated air. Mean and rms profiles of temperature, species concentrations, and mixture fraction are obtained throughout the supersonic flame. Simultaneous measurements of the chemical species and temperature are compared with frozen chemistry and equilibrium chemistry limits to assess the local state of the mixing and chemistry. Upstream of the lifted flame base, a very small amount of reaction occurs form mixing with hot vitiated air. Downstream of the lifted flame base, strong turbulent mixing leads to sub equilibrium values of temperature and OH concentration. Due to the interaction of velocity and temperature in supersonic compressible flames, the fluctuations of temperature and species concentrations are found to be higher than subsonic flames. Farther downstream, slow three-body recombination reactions result in super equilibrium OH concentrations that depress temperatures below their equilibrium values.

Cheng, T.S.; Wehrmeyer, J.A.; Pitz, R.W. (Vanderbilt Univ., Nashville, TN (United States). Dept. of Mechanical Engineering); Jarrett, O. Jr.; Northam, G.B. (NASA, Hampton, VA (United States). Langley Research Center)

1994-10-01

216

Discharge characteristics of lithium/molten nitrate thermal battery cells using silver salts as solid cathode materials  

NASA Astrophysics Data System (ADS)

Thermal battery cells using molten nitrate electrolytes and liquid lithium anodes have been evaluated using several silver salts with low solubility in molten nitrates as solid cathode materials. These cathode materials do not readily diffuse into the anolyte and, thus, do not have parasitic reactions with the lithium anode. Furthermore, the solid cathode materials have voltammetric characteristics as favorable as many soluble silver salt cathodes. This paper presents the effects of temperature, current density, and cathode material on cell discharge characteristics.

McManis, G. E.; Miles, M. H.; Fletcher, A. N.

1985-12-01

217

NOx Formation in CounterFlow Opposed-Jet Diffusion CH4\\/Air Flames  

Microsoft Academic Search

The present study focuses on the effect of pressure and strain rate on the formation of NOx and NO to NO2 conversion processes. The theoretical investigation was carried out using a stretched counter-flow opposed-jet diffusion flame code. The CHEMKIN thermodynamic and transport database were used in the model and a detailed reaction mechanism from GRI was employed. The fuel used

S. BONTURI; M. POURKASHANIAN; A. WILLIAMS; G. OSKAM; C. WILSON

1996-01-01

218

Effect of ferrocene on soot in a prevaporized iso-octane\\/air diffusion flame  

Microsoft Academic Search

This paper reports on ferrocene, or dicyclopentadienyl iron ((CâHâ)âFe) which is an organometallic compound of proven, considerable importance in relation to the control of soot resulting from the combustion of hydrocarbon fuels. Ferrocene as a fuel additive has been observed to suppress soot in oil-fired boilers and furnaces, jet engines, poly (vinyl chloride) combustion, acetylene pyrolysis, and laboratory-scale diffusion flames.

P BONCZYK

1991-01-01

219

Relationships between bifurcation and numerical analyses for ignition of hydrogen—air diffusion flames  

Microsoft Academic Search

Linear bifurcation and numerical techniques are employed to determine critical conditions for ignition in steady, counterflow, nonpremixed hydrogen-air systems, with varying degrees of nitrogen dilution of the fuel, at temperatures larger than the crossover temperature associated with the second explosion limit for hydrogen. Analysis of profiles of the radical pool at ignition reveals that, irrespective of the degree of dilution

A. L. Sánchez; G. Balakrishnan; A. Lińán; F. A. Williams

1996-01-01

220

Determination of Methyl tertButyl Ether in Air Using a Diffusive Sampler  

Microsoft Academic Search

United States production of methyl tert-butyl ether (MTBE) has risen more than 25% in the past decade. It is used in oxygenated fuel formulations as a response to mandates of the Clean Air Act. Recently, a method for the determination of MTBE in gasoline vapors was published by the National Institute for Occupational Safety and Health (NIOSH), which involves collection

Martin Harper; Amy A. Fiore

1995-01-01

221

Different K+-Na+ inter-diffusion kinetics between the air side and tin side of an ion-exchanged float aluminosilicate glass  

NASA Astrophysics Data System (ADS)

The difference between the inter-diffusion kinetics of K+-Na+ in the air and tin sides of an ion-exchanged float aluminosilicate glass was investigated as a function of the exchange temperature and time. The potassium concentration profiles of the ion-exchanged glass surface were experimentally measured by electron microprobe analysis, and the diffusion coefficient was calculated by the Boltzmann-Montano approach. On the tin side of the ion-exchanged glass, the diffusion of K+-Na+ ions is hindered by tin. The diffusion coefficient is also more sensitive to temperature and time on the tin than on the air sides. The results would be useful in guiding the strengthening process of float glass by one step ion-exchange or two step ion-exchange to obtain engineered stress profile (ESP) glasses.

Jiang, Liangbao; Guo, Xintao; Li, Xiaoyu; Li, Lei; Zhang, Guanli; Yan, Yue

2013-01-01

222

Simulation of CO-H2-air Turbulent Diffusion Flame by the Combustion Model Combined Chemical Equilibrium Method with the Eddy Dissipation Concept Model  

Microsoft Academic Search

This research aims at building a turbulent diffusion combustion model based on chemical equilibrium and kinetics for simplifying complex chemical mechanisms. This paper presents the combustion model based on chemical equilibrium combined with an eddy dissipation concept model (CE-EDC); the model is validated by simulating a CO-H2-air turbulent diffusion flame. In the CE-EDC model, the reaction rate of fuels and

Kazui Fukumoto; Yoshifumi Ogami

2010-01-01

223

Computational Modelling of Swirling Diffusion Flame in Air-Staged Burner  

Microsoft Academic Search

The present paper presents an application of computational fluid dynamics (CFD) to simulating an industrial-scale low NOx burner. The main aim of the performed research is to provide the experimentally validated computational prediction of turbulent, non-premixed swirling gas flame in an air-staged burner. Computations are performed using the k-?, k-? and Reynolds-stress turbulence models in order to examine the relative

P. B?lohradský; V. Kermes; P. Stehlík

224

Effect of ferrocene on soot in a prevaporized iso-octane/air diffusion flame  

SciTech Connect

This paper reports on ferrocene, or dicyclopentadienyl iron ((C{sub 5}H{sub 5}){sub 2}Fe) which is an organometallic compound of proven, considerable importance in relation to the control of soot resulting from the combustion of hydrocarbon fuels. Ferrocene as a fuel additive has been observed to suppress soot in oil-fired boilers and furnaces, jet engines, poly (vinyl chloride) combustion, acetylene pyrolysis, and laboratory-scale diffusion flames. This study of a well-defined laminar diffusion flame applies several complementary diagnostic approaches to clarify ferrocene's influence on soot particulates, their precursors, and flame temperature. Unlike most past work, the additive's intervention was evaluated with spatial precision throughout the luminous zone of the flame. To this end, light scattering measurements were made in order to determine the effect of ferrocene on particulate size, number density, and volume fraction. Sampling of the flame with a quartz microprobe was done as well to search for the perturbation of soot precursor and other gas-phase species by the additive; sample concentrations were analyzed via conventional gas chromatography.

Bonczyk, P.A. (United Technologies Research Center, East Hartford, CT (US))

1991-12-01

225

From pores to eddies - linking diffusion-based evaporative fluxes from porous surfaces with a turbulent air boundary layer  

NASA Astrophysics Data System (ADS)

Evaporation affects hydration and energy balance of terrestrial surfaces. Evaporation rates exhibit complex dynamics reflecting interactions between external conditions and internal transport properties of a the drying porous surface Motivated by recent progress in estimating evaporative fluxes from isolated pores across laminar air sublayer, we seek to expand the description and quantify evaporation across a turbulent boundary layer. We adopt concepts from surface renewal (SR) theory focusing on turbulent exchange with individual eddies and linking eddies surface footprint and their local boundary layer over patches of a drying surface. The model resolves diffusive exchange during limited residence time and integrates fluxes over the entire surface to quantify mean evaporative fluxes from drying surfaces into turbulent airflows accounting for subsurface internal transport processes and diffusive exchanges. Input parameters and model evaluation would be based on data from spatially and temporally resolved Infrared (IR) thermography of drying surfaces under prescribe turbulent regimes conducted in a wind-tunnel experiment. The study provides basic ingredients and building blocks essential for upscaling the results to estimation of evaporative fluxes at the field and landscape scales. Keywords: Evaporation; Turbulent Coupling; Surface Renewal; Infrared Imaging.

Haghighi, E.; Or, D.

2012-04-01

226

Diffuse radioactivity measurements and radionuclide identification in the air of the industrial area of Sindos?Thessaloniki before and after the arrival of the Chernobil “cloud”  

Microsoft Academic Search

A diffuse radioactivity measuring facility has been recording data since 1981. The mean daily values of air radioactivity for the time period February 1981?April 1986 were never found to exceed the level of 25 counts per minute (cpm). Values recorded during May 1986 were as high as 200cpm due to the arrival of the Chernobil radioactive cloud in the area

F. K. Vosniakos; K. S. Farmakis

1989-01-01

227

FIELD STUDY OF THE INFLUENCES OF ROADSIDE TREES AND MOVING AUTOMOBILES ON TURBULENT DIFFUSION OF AIR POLLUTANTS AND THERMAL ENVIRONMENT IN URBAN STREET CANYONS  

Microsoft Academic Search

This study aims to investigate and clarify the effects of roadside trees and moving automobiles on outdoor airflow distribution, turbulent diffusion of air pollutants and thermal environment within street canyons by means of the results obtained from field measurements in the central part of Sendai city, Japan. The detailed field measurements were carried out in the summer of 2006, at

A. Kikuchi; N. Hatay; A. Mochida; H. Yoshino; Y. Tabata; H. Watanabe; Y. Jyunimura

228

Effect of the thickness and porosity of carbon-black gas-diffusion air electrodes on the efficiency of hydrogen peroxide synthesis from atmospheric oxygen  

Microsoft Academic Search

Effect of the porosity and thickness of hydrophobized gas-diffusion air electrodes composed of A 437-E acetylene black or\\u000a its mixture with P 702 and P 701 furnace blacks on the efficiency of electroreduction of atmospheric oxygen to H2O2 in 0.5 M NaOH was studied.

G. V. Kornienko; N. V. Chaenko; I. S. Vasil’eva; G. A. Kolyagin; V. L. Kornienko

2010-01-01

229

Monitoring of workers exposed to a mixture of toluene, styrene and methanol vapours by means of diffusive air sampling, blood analysis and urinalysis  

Microsoft Academic Search

Summary Exposure of 34 male workers to combined toluene, styrene and methanol was monitored by personal diffusive sampling of solvent vapours in breathing zone air, analysis of shift-end blood for the 3 solvents and analysis of shift-end urine for hippuric, mandelic and phenylglyoxylic acids and methanol. The exposure of most of the workers was below current occupational exposure limits. Regression

Toshio Kawai; Tomojiro Yasugi; Kazunori Mizunuma; Shun'ichi Horiguchi; Ikuharu Morioka; Kazuhisa Miyashita; Yoko Uchida; Masayuki Ikeda

1992-01-01

230

Implementation of an advanced fixed sectional aerosol dynamics model with soot aggregate formation in a laminar methane\\/air coflow diffusion flame  

Microsoft Academic Search

An advanced fixed sectional aerosol dynamics model describing the evolution of soot particles under simultaneous nucleation, coagulation, surface growth and oxidation processes is successfully implemented to model soot formation in a two-dimensional laminar axisymmetric coflow methane\\/air diffusion flame. This fixed sectional model takes into account soot aggregate formation and is able to provide soot aggregate and primary particle size distributions.

Q. Zhang; H. Guo; F. Liu; G. J. Smallwood; M. J. Thomson

2008-01-01

231

The flame preheating effect on numerical modelling of soot formation in a two-dimensional laminar ethylene–air diffusion flame  

Microsoft Academic Search

Numerical modelling of soot formation is conducted for an axisymmetric, laminar, coflow diffusion ethylene–air flame by two different methods to investigate the effect of flame preheating. The first method cannot account for the preheating effect, while the second one can. A detailed gas-phase reaction mechanism and complex thermal and transport properties are used. The fully coupled elliptic equations are solved.

Hongsheng Guo; Fengshan Liu; Gregory J Smallwood; Ömer L Gülder

2002-01-01

232

Cesium Vapor Cathode Study.  

National Technical Information Service (NTIS)

Cesium-plasma cathodes have been studied as sources of very high-density electron beams. The commonemitter type of cathode using a highly directed cesiumvapor flow has been used to obtain a beam with a density of 800 A/sq cm. The beam was accelerated to 1...

A. E. Eichenbaum F. H. Norman H. Sobol S. Bloom

1965-01-01

233

A hybrid, infrared thermography: heat diffusion equation, method for the 3D air-temperature measurement  

NASA Astrophysics Data System (ADS)

The question of how to map the 3D indoor temperature by infrared thermography is solved by a hybrid method which is a combination of infrared thermography and the well known heat diffusion equation. The idea is to use infrared thermography to get the surface temperature of each frontier of the 3D domain of interest. A suitable procedure is devoted to this, allowing an automatic scanning of the whole frontier, the registration of data and computation. These surface temperatures constitute the boundary conditions of the heat equation solved in the domain of interest. The solution of the heat equation allows analyzing and controlling the temperature of every point belonging to the considered domain. This temperature distribution is controlled over the time with a period of the same order than the necessary time to obtain the frontier temperatures and at the end to contribute to the analysis of the thermal comfort. The study is done for the steady-state conditions under various weather situations. In this case the temperature depends only on space coordinates. With such procedure, we can have an idea about the time necessary to reach thermal equilibrium; time which has a great impact on the thermal comfort sensation. The results yielded by this method are compared with those given by others techniques used for temperature measurement. Finally, the method is used to access 3D temperature distribution for various geometric shapes.

Djupkep Dizeu, F. B.; Maldague, X.; Bendada, A.; Grinzato, E.; Bison, P.

2011-05-01

234

Separation of metals at vibrating cathodes  

SciTech Connect

The authors studies of vibrating electrodes for the cathodic deposition of metals showed that diffusional difficulties in the discharge of ions can be lowered by vibration. This induced them to examine the effect of cathode vibration on the separation of Zr from Hf or of Nb from Ta which are present as impurities during refining in chloride fluoride melts. It was shown in this work that an efficient separation of metals during electrolysis first of all depends on the difference between their conventional standard potentials. A difference between the diffusion coefficients of the metal species to be separated has marked effects when the conventional standard potentials are similar or when the impurity has a more positive potential. Vibration of the cathode can have important effects.

Khramov, A.P.; Ivanovskii, L.E.; Batukhtin, V.P.

1987-10-01

235

Improvement of Cathode Reaction of a Mediatorless Microbial Fuel Cell  

Microsoft Academic Search

Oxygen diffuses through the cation-specific membrane, reducing the coulomb yield of the fuel cell. In the present study, attempts were made to enhance current generation from the fuel cell by lowering the oxygen diffusion, including the uses of ferricyanide as a cathode mediator and of a platinum-coated graphite electrode. Ferricyanide did not act as a mediator as expected, but as

JAE KYUNG JANG; BYUNG HONG KIM

2004-01-01

236

Arc-Cathode Attachment Modes in High-Pressure Arcs  

NASA Astrophysics Data System (ADS)

Three different modes of attachment at the cathode are observed with high-pressure arcs: i) diffuse, ii) constricted (so-called hot spot), and iii) cathode spot-like. The exact form taken by the arc attachment depends mainly on the refractory character and electron emission properties of the cathode material, the geometry of the cathode, the arc current and gas fill composition and pressure. In this paper, the recent theoretical developments made in the field are discussed. First, the physical model self-consistently treating the near-cathode arc equations and the two-dimensional cathode thermal problem is described. Then, the existence of the two modes of arc attachment on a refractory cathode (diffuse and hot spot) is explained through the non-uniqueness of the thermal solution in the cathode when exposed to a nonlinear heat source (arc).^1 The predictions obtained with a pure Ar arc (3.75 atm) on a long cylindrical W cathode (1.5 mm-diameter) reveal that a diffuse mode solution typically exists for arc currents larger than ~3.5 A giving rise to a minimum cathode temperature of 3050 K, increasing monotonically with the arc current (roughly 60 K/A). For arc currents below ~3.5 A, only constricted solutions exist. For a 200 ?m-diameter attachment, the cathode surface temperatures range from 3600 to 3750 K for arc currents ranging respectively from 2 to 3 A. The theoretical analysis is then further extended to the arc attachment on non-refractory cathodes. A notable observation made from this analysis is that the strong erosion rates observed on such cathodes can no longer be seen only as a consequence of their non-refractory nature, but more importantly, as a necessarily condition for the self-sustaining attachment of the arc.^2,3 Indeed, high local metallic vapor pressures built up by the strong local thermal vaporization of the cathode are required for the maintenance of a high density of ions in the cathode sheath, which in turns, is responsible for maintaining high cathode surface temperatures and high surface electric fields. Both effects combined give rise to a copious thermo-field emission of electrons and a self-sustaining operation of the arc attachment. For a Cu cathode, the local metallic vapor pressure at the attachment point (cathode spot) is expected to fall in the 25--65 atm range. This pressure becomes lower as the cathode material becomes more refractory. The analysis of these different arc attachment modes allowed the introduction of a simple set of conditions needed to achieve a self-sustaining attachment. The principal ones are: i) The fraction of the incoming heat flux from the arc available for conduction in the cathode needs to be larger than zero. ii) The slope of the dependence of this conduction flux to the cathode surface temperature needs to be negative. iii) The ratio of the ion to electron emission currents at the cathode surface needs to be no larger than unity. ^1M. S. Benilov, Phys. Rev. E, 58, 6480 (1998). ^2J. -L. Meunier and S. Coulombe, Pure & Appl. Chem., 70 1175 (1998). ^3S. Coulombe and J. -L. Meunier, Plasma Sources Sci. Technol., 6 508 (1997).

Coulombe, Sylvain

2000-10-01

237

Increased performance of single-chamber microbial fuel cells using an improved cathode structure  

Microsoft Academic Search

Maximum power densities by air-driven microbial fuel cells (MFCs) are considerably influenced by cathode performance. We show here that application of successive polytetrafluoroethylene (PTFE) layers (DLs), on a carbon\\/PTFE base layer, to the air-side of the cathode in a single chamber MFC significantly improved coulombic efficiencies (CEs), maximum power densities, and reduced water loss (through the cathode). Electrochemical tests using

Shaoan Cheng; Hong Liu; Bruce E. Logan

2006-01-01

238

Understanding the degradation of Congo red and bacterial diversity in an air-cathode microbial fuel cell being evaluated for simultaneous azo dye removal from wastewater and bioelectricity generation.  

PubMed

We investigated the mechanism of Congo red degradation and bacterial diversity in a single-chambered microbial fuel cell (MFC) incorporating a microfiltration membrane and air-cathode. The MFC was operated continuously for more than 4 months using a mixture of Congo red and glucose as fuel. We demonstrated that the Congo red azo bonds were reduced at the anode to form aromatic amines. This is consistent with the known mechanism of anaerobic biodegradation of azo dyes. The MFC developed a less dense biofilm at the anode in the presence of Congo red compared to its absence indicating that Congo red degradation negatively affected biofilm formation. Denaturing gradient gel electrophoresis and direct 16S ribosomal DNA gene nucleotide sequencing revealed that the microbial communities differed depending on whether Congo red was present in the MFC. Geobacter-like species known to generate electricity were detected in the presence or absence of Congo red. In contrast, Azospirillum, Methylobacterium, Rhodobacter, Desulfovibrio, Trichococcus, and Bacteroides species were only detected in its presence. These species were most likely responsible for degrading Congo red. PMID:22678023

Sun, Jian; Li, Youming; Hu, Yongyou; Hou, Bin; Zhang, Yaping; Li, Sizhe

2012-06-08

239

Hollow-cathode arc discharge  

Microsoft Academic Search

An experimental study of a high-current hollow-cathode arc is presented. It is shown that the zone of current attachment to the internal surface of the cathode is significantly narrower than the hotter zone of the cathode; the plasma current to the cathode beyond this attachment zone is equal to zero. An equation is obtained for determining the position of the

V. S. Cherednichenko; V. A. Kosinov

1980-01-01

240

Microhollow Cathode Discharge Excimer Lamps  

Microsoft Academic Search

character. Reducing the diameter of the cathode hole in a hollow cathode discharge geometry to values on the order of 100 mum has allowed us to extend the pressure range of stable, direct current hollow cathode gas discharges up to atmospheric pressure. The large concentration of high-energy electrons generated in the cathode fall, in combination with the high neutral gas

K. H. Schoenbach

1999-01-01

241

NAREL (National Air and Standard Environmental Laboratory) standard operating procedures for radon-222 measurement using diffusion barrier charcoal canisters  

SciTech Connect

Radon monitoring procedures for the National Air and Radiation Environment Laboratory (NAREL) are described. Radon is detected by sorption to activated charcoal, followed by detection of gamma ray emissions from the radon decay products lead-214 (295 KeV and 392 KeV) and bismuth-214 (609 KeV). The activated charcoal is held in an 8 ounce metal can, under a polyethylene diffusion barrier and a stainless steel screen, 30--50% open. The polyethylene barrier reduces water absorption by the charcoal, and improves integration over the exposure period. The proper use of the container is described, as is the counting system and calibration of the detecting system. Fabrication of reference standards and background canisters is described. Equations and sample calculations to determine radon concentrations are given. All terms in the equation are defined, and all calibration factors are calculated. The minimal detectable amounts of radon as a function of detector exposure time are calculated. 5 refs., 7 figs., 1 tab. (MHB)

Gray, D.J.; Windham, S.T.

1990-11-01

242

Coaxial Virtual Cathode Enhancement.  

National Technical Information Service (NTIS)

Traditionally, the radiated microwave frequency in a coaxial vircator is considered to be determined primarily by the virtual cathode oscillation frequency and the electron reflection frequency. In this paper, some experiments showing different results ar...

M. Kristiansen J. Mankowski

2004-01-01

243

Cathodic Bridge Deck Protection.  

National Technical Information Service (NTIS)

Five systems of cathodic protection were installed on the US87 Missouri-Pacific Railroad overpass in Big Spring, Texas. The design and construction of the systems are summarized in this report. The Federal Highway Administration sponsored the demonstratio...

L. Smith

1990-01-01

244

Prediction of the cathodic arc root behaviour in a hollow cathode thermal plasma torch  

Microsoft Academic Search

The upper part of a well type cathode (WTC) plasma torch is modelled for several conditions in an air medium in the presence of an electric arc. The plasma flow created by the electric arc is described and the results compared with the data from the literature. Special attention is paid to the description of arc root attachment and to

Pierre Freton; Jean-Jacques Gonzalez; Gaelle Escalier

2009-01-01

245

Oxygen reduction sites and diffusion paths at La 0.9Sr 0.1MnO 3? x \\/yttria-stabilized zirconia interface for different cathodic overvoltages by secondary-ion mass spectrometry  

Microsoft Academic Search

Oxygen reduction active sites were investigated at the interface of O2\\/La0.9Sr0.1MnO3?x (LSM)\\/yttria-stabilized zirconia (YSZ) for three different overvoltages of cathodic polarization (?=?0.336 V, ?=?0.185 V, and ?=?0.090 V versus reference electrode). Isotopic oxygen (16O\\/18O) exchange under cathodic polarization and secondary ion mass spectrometry (SIMS) technique were examined to visualize the oxygen incorporation\\/reduction active sites. The LSM mesh pattern electrode was

Teruhisa Horita; Katsuhiko Yamaji; Natsuko Sakai; Harumi Yokokawa; Tatsuya Kawada; Tohru Kato

2000-01-01

246

Conditional diffusion: Smoke free air legislation and tobacco taxation policies in the United States 1970-2006 1  

Microsoft Academic Search

The notion of policy diffusion has recently come under closer scrutiny as researchers are trying to disentangle the various channels through which policies diffuse across jurisdictional boundaries (e.g.: learning vs. competition). At the same time, researchers became interested in the question of how to differentiate between genuine diffusion and common exogenous shocks. What has been largely overlooked so far is

Christian W. Martin

247

An Analysis of a Finite-Difference and a Galerkin Technique Applied to the Simulation of Advection and Diffusion of Air Pollutants from a Line Source  

Microsoft Academic Search

A finite-difference scheme and a Galerkin scheme are compared with respect to a very accurate solution describing time-dependent advection and diffusion of air pollutants from a line source in an atmosphere vertically stratified and limited by an inversion layer. The accurate solution was achieved by applying the finite-difference scheme on a very refined grid with a very small time step.

E. Runca; P. Melli; F. Sardei

1985-01-01

248

A NOVEL CFD CODE BASED ON METHOD OF LINES FOR REACTING fLOWS: VERIFICATION ON METHANE\\/AIR DIFFUSION FLAME  

Microsoft Academic Search

A novel parallel computational fluid dynamic (CFD) code based on method of lines (MOL) approach was developed for the numerical simulation of multi-component reacting flows using detailed transport and thermodynamic models. The code was applied to the prediction of a confined axi-symmetric laminar co-flowing methane-air diffusion flame for which experimental data were available in the literature. 1-, 5- and 10-step

TANIL TARHAN; NEVIN SELÇUK

2007-01-01

249

Effect of cathodic potential on corrosion fatigue crack growth rates of a Ni-Cr-Mo-V turbine disc steel in room temperature caustic environment. [Steel-ASTM-471  

SciTech Connect

Corrosion fatigue crack growth rates were measured on compact toughness specimens of ASTM A-471 turbine disc steel in room temperature 12M NaOH solution. The role of cathodic potentials on corrosion fatigue crack growth rates was investigated. Intergranular cracking was observed at cathodic potentials compared to transgranular cracking at open circuit potential and in air. The results suggest a hydrogen embrittlement mechanism of cracking at cathodic potentials. The results suggest that hydrogen diffusion into the material ahead of the crack tip is not rate controlling but is a necessary condition to accelerated cracking. Positive and negative sawtooth wave form results show that environmental effects are accelerated during loading part of the cycle when deformation is occurring. The results have also been analyzed with respect to the linear superposition model proposed by Wei and Landes.

Rungta, R. (Battelle-Columbus Labs., OH); Begley, J.A.

1980-05-01

250

Effect of dielectric material on bipolar nanosecond pulse diffuse dielectric barrier discharge in air at atmospheric pressure  

NASA Astrophysics Data System (ADS)

In this paper, dielectric plates made by ceramic, quartz and polytetrafluoroethylene (PTFE) respectively are employed to generate low gas temperature, diffuse dielectric barrier discharge plasma by using a needle-plate electrode configuration in air at atmospheric pressure. Both discharge images and the optical emission spectra are obtained while ceramic, quartz and PTFE are used as dielectric material. Plasma gas temperature is also calculated by comparing the experimental emission spectra with the best fitted spectra of N2 (C3?u ? B3?g 1-3) and N2 (C3?u ? B3?g 0-2). The effects of different pulse peak voltages and gas gap distances on the emission intensity of N2 (C3?u ? B3?g, 0-0, 337.1 nm) and the plasma area on dielectric surface are investigated while ceramic, quartz and PTFE are used as dielectric material. It is found that the permittivity of dielectric material plays an important role in the discharge homogeneity, plasma gas temperature, emission spectra intensity of the discharge, etc. Dielectric with higher permittivity i.e., ceramic means brighter discharge luminosity and stronger emission spectra intensity of N2 (C3?u ? B3?g, 0-0, 337.1 nm) among the three dielectric materials. However, more homogeneous, larger plasma area on dielectric surface and lower plasma gas temperature can be obtained under dielectric with lower permittivity i.e., PTFE. The emission spectra intensity and plasma gas temperature of the discharge while the dielectric plate is made by quartz are smaller than that while ceramic is used as dielectric material and bigger than that when PTFE is used as dielectric material.

Tang, Kai; Wang, Wenchun; Yang, Dezheng; Zhang, Shuai; Yang, Yang; Liu, Zhijie

2013-08-01

251

Influences of flame-vortex interactions on formation of oxides of nitrogen in curved methane-air diffusion flamelets  

SciTech Connect

To improve knowledge of production rates of nitrogen oxides in turbulent diffusion flames in reaction-sheet regimes, an analytical investigation is made of the structure of a parabolic flamelet. The mixture-fraction field, scalar dissipation rate and gas velocity relative to the flamelet in the vortex are related to flame curvature at the parabolic tip. Flame structure for major species and temperature is described by rate-ratio asymptotics based on two-step and three-step reduced chemical-kinetic mechanisms. Production rates by prompt, thermal and nitrous-oxide mechanisms are obtained from one-step reduced-chemistry approximations that employ steady states for all reaction intermediaries. For sufficiently large streamwise separation distances between isoscalar surfaces, it is found that equilibrium conditions are closely approached near the flame tip, and the thermal mechanism dominates there, but the prompt mechanism always dominates in the wings, away from the tip, where the highest rates of scalar dissipation occur. Increasing the tip curvature increases the Peclet number and the prompt contribution while decreasing the thermal contribution. At 1 atm and ambient temperatures of 300 K, the prompt mechanism always dominates the total production rate in the parabolic flamelet, and, perhaps surprisingly, the rate of the nitrous-oxide mechanism is faster than that of the thermal mechanism and varies with the tip curvature and with scalar dissipation in the same manner as that of the prompt mechanism, different from that of the thermal mechanism. Conclusion reached is that Zel`dovich NO is relatively insignificant in hydrocarbon-air mixtures in reaction-sheet regimes.

Card, J.M. [Sandia National Labs., Livermore, CA (United States); Ryden, R. [Volvo Flygmotor AB, Trollhaettan (Sweden); Williams, F.A. [California Univ., San Diego, La Jolla, CA (United States). Center for Energy and Combustion Research

1994-01-01

252

Cathodic protection current testing for large plant structures  

SciTech Connect

Design of cathodic protection (CP) for underground facilities in large plants is a problem. A method is described for performing data interpretation of field cathodic current requirement tests on large plant structures. It is possible to perform meaningful tests with small temporary current sources and arrive at a design where final requirements are many times larger. Examples of its use at a power plant and an air separation plant are given.

Maynard, R.J. [Aurora Corrosion Control, Calgary, Alberta (Canada)

1996-07-01

253

A Diffuse Interface Model for solid-liquid-air dissolution problems based on a porous medium theory  

NASA Astrophysics Data System (ADS)

The underground cavities may be dissolved by the flows of groundwater where the dissolution mainly happens at the liquid-solid interface. In many real cases, the cavities are not occupied only by the water, but also the gas phase, e.g., air, or other gases. In this case, there are solid-liquid-gas three phases. Normally, the air does not participate the dissolution. However, it may influence the dissolution as the position of the solid-liquid interface may gradually lower down with the dissolution process. Simulating the dissolution problems with multi- moving interfaces is a difficult task but rather interesting to study the evolution of the underground cavities. In this paper, we propose a diffuse interface model (DIM) to simulate the three-phase dissolution problem, based on a porous medium theory and a volume averaging theory te{Whitaker1999,Golfier2002,Quintard1994}. The interface is regarded as a continuous layer where the phase indicator (mainly for solid-liquid interface) and phase saturation (mainly for liquid-gas interface) vary rapidly but smoothly. The DIM equations enable us to simulate the moving interface under a fixed mesh system, instead of a deformed or moving mesh. Suppose we have three phases, solid, liquid and gas. The solid phase contains only species A. The gas phase contains only the air. The volume averaging theory is used to upscale the balance equations. The final DIM equations are presented below. The balance equation of solid phase can be written as {partialrho_{s}(1-\\varepsilon_{f})}/{partial t}=-K_{sl} where \\varepsilonf represents the volume fraction of the fluids (liquid+gas) and Ksl refers to the mass exchange between the solid phase and the liquid phase. Ksl cam be expressed as K_{sl}=rho_{l}alpha(omega_{eq}-Omega_{Al}). The balance equations of liquid phase can be written as {partialrho_{l}\\varepsilon_{f}S_{l}}/{partial t}+nabla\\cdot(rho_{l}{V}_{l})= K_{sl}. The balance equation of liquid phase can be written as {partialrho_{g}\\varepsilon_{f}(1-S_{l})}/{partial t}+nabla\\cdot(rho_{g}{V}_{g}) =0. The balance equations of species A can be written as rho_{l}\\varepsilon_{f}S_{l} {partialOmega_{Al}}/{partial t} +rho_{l}{V}_{l}\\cdotnablaOmega_{Al} =nabla\\cdot(rho_{l}{D}_{Al}^{*}nablaOmega_{Al})+K_{sl}. We introduce the multi-phase Darcy's Law to {V}l and {V}g, {V}_{l}=-{{K}k_{rl}}/{mu_{l}}(nabla P_{l}-rho_{l}{g}) {V}_{g}=-{K}k_{rg}}/{mu_{g}}(nabla P_{g}-rho_{g}{g}) Kozeny-Carman equation is introduced to calculate {K}, Capillary pressure theory can be used to calculate krl, krg, and the capillary pressure Pc, as a function of Sl.

Luo, H.; Quintard, M.; Debenest, G.; Laouafa, F.

2011-12-01

254

Hydrogen Diffusivities and Concentrations in 520M Carbon Steel under Cathodic Protection in 0.5M NaCl and the Effect of Added Sulphite, Dithionite, Thiosulphate, and Sulphide  

Microsoft Academic Search

Hydrogen diffusion experiments in 520M carbon steel were performed with the Devanathan- Statchurski permeation cell at 22şC in 0.5M NaCl at pH 7 and -800, -900 or -1050 mV SCE. The hydrogen diffusivity and subsurface concentration (C0) were evaluated by fitting a fourier series expansion of the diffusion equation to the permeation data. The hydrogen diffusivity in the steel was

E. Hörnlund; J. K. T. Fossen; S. Hauger; C. Haugen; T. Havn; T. Hemmingsen

2007-01-01

255

Cathode Research and the Threshold Cathode Test Facility.  

National Technical Information Service (NTIS)

This technical report discusses the parameters of the Threshold Cathode Test Facility (TCTF) and the use of the TCTF to perform cathode research. Experimental and simulation results are documented, as well as references to additional, more detailed, catho...

R. J. Umstattd T. A. Spencer

2002-01-01

256

A new composite cathode for high-performance lithium–polymer batteries  

Microsoft Academic Search

Low-molecular-weight poly(ethyleneglycol) was tested as lithium-ion conductive matrix in a crystalline V2O5-based composite cathode. To assess the feasibility of this composite cathode in solid-state rechargeable batteries, the ion transport properties, the chemical stability and the electrochemical stability were evaluated. The cathode exhibited fairly good electrochemical properties at a moderately high temperature. At 338K, a 7Li diffusion coefficient of about 6.8×10?8cm2s?1

P. P. Prosini; C. Capiglia; Y. Saito; T. Fujieda; R. Vellone; M. Shikano; T. Sakai

2001-01-01

257

Filtered cathodic arc source  

DOEpatents

Disclosed is a continuous, cathodic arc ion source coupled to a macro-particle filter capable of separation or elimination of macro-particles from the ion flux produced by cathodic arc discharge. The ion source employs an axial magnetic field on a cathode (target) having tapered sides to confine the arc, thereby providing high target material utilization. A bent magnetic field is used to guide the metal ions from the target to the part to be coated. The macro-particle filter consists of two straight solenoids, end to end, but placed at 45{degrees} to one another, which prevents line-of-sight from the arc spot on the target to the parts to be coated, yet provides a path for ions and electrons to flow, and includes a series of baffles for trapping the macro-particles.

Falabella, S.; Sanders, D.M.

1992-12-31

258

Synergetic effects of anodic–cathodic electrocatalysis for phenol degradation in the presence of iron(II)  

Microsoft Academic Search

A novel electrocatalysis method for phenol degradation was described using a ?-PbO2 anode modified with fluorine resin and a Ni–Cr–Ti alloy cathode. In case of air sparging at the cathodic zone, the techniques of anodic–cathodic electrocatalysis (ACEC) and ferrous ion catalyzed anodic–cathodic electrocatalysis (FACEC) in the presence of iron(II) were developed. Both of ACEC and FACEC were more effective than

Zucheng Wu; Minghua Zhou; Dahui Wang

2002-01-01

259

Cathodic protection and cathodic preventionin concrete: principles and applications  

Microsoft Academic Search

The paper deals with the principles of cathodic protection for atmospherically exposed concrete structures, the various protecting effects induced by the cathodic polarization and tests and field experience results. The differences between the cathodic protection applied for controlling the corrosion rate of chloride contaminated co nstructions and that applied to improve the corrosion resistance of the reinforcement of new structures

L. Bertolini; F. Bolzoni; P. Pedeferri; L. Lazzari; T. Pastore

1998-01-01

260

Discharge with a Hollow Cathode (Selected Chapters).  

National Technical Information Service (NTIS)

Contents: Determination and classification of various types of discharge with a hollow cathode; Experimental characteristics of glow discharge with a hollow cathode; The theory of glow discharge with a hollow cathode; Gas-discharge hollow cathode lasers.

B. I. Moskalev

1973-01-01

261

Applications of aluminum-air batteries  

Microsoft Academic Search

Advances in aluminum-air batteries are described. These include alloys that show higher efficiencies and therefore lower hydrogen evolution, low-cost air cathodes that can be fabricated in production quantities, and methods for handling the aluminum hydroxide reaction product. Emphasis is placed on the advances in air cathodes. The application of this technology to new products and the implications for electric vehicles

R. P. Hamlen; W. H. Hoge; J. A. Hunter; W. B. O'Callaghan

1991-01-01

262

Cathodic Protection System Inspection 6.  

National Technical Information Service (NTIS)

If the cathodic protection system is periodically inspected and maintained to provide continuous protection the condition of the protected structure can be inferred from the cathodic protection system records without the need for physical inspection of th...

J. Jenkins

1994-01-01

263

Miniaturized cathodic arc plasma source  

DOEpatents

A cathodic arc plasma source has an anode formed of a plurality of spaced baffles which extend beyond the active cathode surface of the cathode. With the open baffle structure of the anode, most macroparticles pass through the gaps between the baffles and reflect off the baffles out of the plasma stream that enters a filter. Thus the anode not only has an electrical function but serves as a prefilter. The cathode has a small diameter, e.g. a rod of about 1/4 inch (6.25 mm) diameter. Thus the plasma source output is well localized, even with cathode spot movement which is limited in area, so that it effectively couples into a miniaturized filter. With a small area cathode, the material eroded from the cathode needs to be replaced to maintain plasma production. Therefore, the source includes a cathode advancement or feed mechanism coupled to cathode rod. The cathode also requires a cooling mechanism. The movable cathode rod is housed in a cooled metal shield or tube which serves as both a current conductor, thus reducing ohmic heat produced in the cathode, and as the heat sink for heat generated at or near the cathode. Cooling of the cathode housing tube is done by contact with coolant at a place remote from the active cathode surface. The source is operated in pulsed mode at relatively high currents, about 1 kA. The high arc current can also be used to operate the magnetic filter. A cathodic arc plasma deposition system using this source can be used for the deposition of ultrathin amorphous hard carbon (a-C) films for the magnetic storage industry.

Anders, Andre (Albany, CA); MacGill, Robert A. (Richmond, CA)

2003-04-15

264

Updating Applied Diffusion Models.  

National Technical Information Service (NTIS)

Most diffusion models currently used in air quality applications are substantially out of date with understanding of turbulence and diffusion in the planetary boundary layer. Under a Cooperative Agreement with the Environmental Protection Agency, the Amer...

J. C. Weil

1985-01-01

265

A two-phase flow and transport model for the cathode of PEM fuel cells  

Microsoft Academic Search

A unified two-phase flow mixture model has been developed to describe the flow and transport in the cathode for PEM fuel cells. The boundary condition at the gas diffuser\\/catalyst layer interface couples the flow, transport, electrical potential and current density in the anode, cathode catalyst layer and membrane. Fuel cell performance predicted by this model is compared with experimental results

Lixin You; Hongtan Liu

2002-01-01

266

Soft X-Ray Spectroscopic Study of Dense Strontium-Doped Lanthanum Manganite Cathodes for Solid Oxide Fuel Cell Applications  

SciTech Connect

The modification of the Mn charge-state, chemical composition and electronic structure of La0.8Sr0.2MnO3 (LSMO) cathodes for solid oxide fuel cell (SOFC) applications remains an area of interest, due to the poorly understood enhanced catalytic activity (often referred to as the "burn-in" phenomenon) observed after many hours of operation. Using a combination of core-level X-ray photoemission spectroscopy (XPS), X-ray emission/absorption spectroscopy (XES/XAS), resonant inelastic X-ray scattering (RIXS) and resonant photoemission spectroscopy (RPES), we have monitored the evolution of these properties in LSMO at various stages of fabrication and operation. By rapidly quenching and sealing in vacuum, we were able to directly compare the pristine (as-fabricated) LSMO with both "heat-treated" (800°C in air, and no bias) and "burnt-in" (800°C in air, -1 V bias) LSMO cathodes i.e. before and after the activation observed in our electrochemical impendence spectroscopy measurements. Comparison between the O K-edge XAS/XES and Mn L3,2-edge XAS of pristine and “burnt-in” LSMO cathodes revealed a severe change in the oxygen environment along with a reduced Mn2+ presence near the surface following activation. The change in the oxygen environment is attributed to SrxMnyOz formation, along with possible passive SrO and Mn3O4 species. We present evidence from our “heat-treated” samples that SrxMnyOz regions form at elevated temperatures in air before the application of a cathodic bias. Our core-level XPS, Mn L3,2-edge RIXS and Mn L3 RPES studies of “heat-treated” and pristine LSMO determined that SOFC environments result in La-deficiency (severest near the surface) and stronger Mn4+ contribution, leading to the increased insulating character of the cathode prior to activation. The passive Mn2+ species near the surface and increased hole-doping (>0.6) of the LSMO upon exposure to the operating environment are considered responsible for the initially poor performance of the SOFC. Meanwhile, the improved oxygen reduction following the application of a cathodic bias is considered to be due to enhanced bulk oxygen-ion diffusion resulting from the migration of Mn2+ ions towards the LSMO/electrolyte interface and the SrxMnyOz regions facilitating enhanced bulk oxygen reduction reaction kinetics.

Piper, L.F.J.; Preston, Andrew R.H.; Cho, Sang Wan; DeMasi, Alexander; Chen, Bin; Laverock, J.; Smith, K. E.; Miara, Lincoln J.; Davis, Jacob N.; Basu, Soumendra; Pal, Uday B.; Gopalan, Srikanth; Saraf, Laxmikant V.; Kaspar, Tiffany C.; Matsuura, A. Y.; Glans, P.A.; Guo, Jianzhong

2010-12-02

267

Lifetime Modeling of Xenon Hollow Cathodes Used in Electric Propulsion  

NASA Astrophysics Data System (ADS)

Xenon hollow cathodes with barium calcium aluminate impregnated tungsten inserts are widely used in electric propulsion. These high current, low power cathodes are employed in ion thrusters, Hall thrusters, and on the International Space Station in plasma contactors. The entitlement lifetime of a thermionic emission cathode impregnated with barium-containing compounds is determined by the evolution and transport of barium away from the emitter surface. A model is being developed to study the process of barium transport and loss from the emitter insert in hollow cathodes. A thermodynamic model of the chemical process of barium evolution has been adapted from that of Lipeles and Kan^1. The model accounts for the diffusion of barium and barium oxide gas through the xenon expellant and loss of barium-containing gases through the cathode orifice as well as loss by condensation. Axial barium density profiles are presented and cathode lifetimes are estimated. Results of the model are compared with experimental results from the extensive hollow cathode life test database at the NASA Glenn Research Center. 1. Lipeles, R.A., Kan, H.K.A., Appl. Surf. Sci. 16, 189(1983).

Kovaleski, Scott

2001-10-01

268

Thermionically emitting copper cathode in contact with combustion plasmas  

NASA Astrophysics Data System (ADS)

Current density and electrode potential drops have been investigated using a copper cathode inserted in potassium seeded combustion products of liquefied-petroleum-gas and oxygen. The work fuction of the composite cathode surface, formed owing to enhanced seed deposition on the inserted electrode, is observed to be much lower than the work function of pure copper. This leads to large thermionic emission of electrons from the composite cathode surface and hence, a sharp decrease in cathode potential drop. Consequently, a high current density could be sustained in the diffusive mode of current conduction. The experimental observations are found to be in resonably good agreement with a theoretical model developed taking into account the thermionic emission of electrons.

Raju, G. V. R.; Dahiya, R. P.; Gupta, B.

1983-02-01

269

Cathode material for lithium batteries  

DOEpatents

A method of manufacture an article of a cathode (positive electrode) material for lithium batteries. The cathode material is a lithium molybdenum composite transition metal oxide material and is prepared by mixing in a solid state an intermediate molybdenum composite transition metal oxide and a lithium source. The mixture is thermally treated to obtain the lithium molybdenum composite transition metal oxide cathode material.

Park, Sang-Ho; Amine, Khalil

2013-07-23

270

Thermionic cathode heater  

Microsoft Academic Search

A heater is described for insertion into a thermionic cathode capable of providing a strip electron beam, the heater comprising: a first current carrying means extending in a predetermined direction; and a second current carrying means disposed in series with and substantially surrounding the first current carrying means along the predetermined direction. The means substantially prevents the creation of a

K. E. Williams; W. A. Frutiger; K. E. Hall

1987-01-01

271

Cathode erosion in a high-pressure high-current arc: calculations for tungsten cathode in a free-burning argon arc  

NASA Astrophysics Data System (ADS)

The motion of an evaporated atom of the cathode material in a near-cathode plasma is considered. It is shown that the evaporated atom is ionized almost instantly. The created ion, under the influence of a strong electric field existing in the cathode proximity, has a high probability of returning to the cathode. A small fraction of evaporated atoms are able to diffuse away from the cathode to the region where they are involved in plasma flow and lose their chance to return to the cathode. The fraction of the total evaporated atoms, which do not return to the cathode, the escape factor, determines the net erosion rate. In order to calculate this factor, the distributions of the plasma parameters in the near-cathode plasma were considered. Calculations showed that the escape factor is on the order of a few per cent. Using experimental data on the plasma and cathode temperatures, we calculated the net erosion rate for a free-burning 200 A argon arc with a thoriated tungsten cathode. The calculated erosion rate is close to 1 µg s-1, which is in agreement with available experimental data.

Nemchinsky, Valerian

2012-04-01

272

Joule heat generation in thermionic cathodes of high-pressure arc discharges  

NASA Astrophysics Data System (ADS)

The nonlinear surface heating model of plasma-cathode interaction in high-pressure arcs is extended to take into account the Joule effect inside the cathode body. Calculation results are given for different modes of current transfer to tungsten cathodes of different configurations in argon plasmas of atmospheric or higher pressures. Special attention is paid to analysis of energy balances of the cathode and the near-cathode plasma layer. In all the cases, the variation of potential inside the cathode is much smaller than the near-cathode voltage drop. However, this variation can be comparable to the volt equivalent of the energy flux from the plasma to the cathode and then the Joule effect is essential. Such is the case of the diffuse and mixed modes on rod cathodes at high currents, where the Joule heating causes a dramatic change of thermal and electrical regimes of the cathode. The Joule heating has virtually no effect over characteristics of spots on rod and infinite planar cathodes.

Benilov, M. S.; Cunha, M. D.

2013-02-01

273

Lattice Expansion of LSCF-6428 Cathodes Measured by In-situ XRD during SOFC Operation  

SciTech Connect

A new capability has been developed for analyzing solid oxide fuel cells (SOFCs). This paper describes the initial results of in-situ x-ray diffraction (XRD) of the cathode on an operating anode-supported solid oxide fuel cell. It has been demonstrated that XRD measurements of the cathode can be performed simultaneously with electrochemical measurements of cell performance or electrochemical impedance spectroscopy (EIS). While improvements to the technique are still to be made, the XRD pattern of a lanthanum strontium cobalt ferrite (LSCF) cathode with the composition La0.6Sr0.4Co0.2Fe0.8O3-? (LSCF-6428) was found to continually but gradually change over the course of more than 60 hours of operation in air under typical SOFC operating conditions. It was determined that the most significant change was a gradual increase in the cubic lattice parameters of the LSCF from 3.92502 Ĺ (as determined from the integration of the first 20 hours of XRD patterns) to 3.92650 Ĺ (from the integration of the last 20 hours). This analysis also revealed that there were several peaks from unidentified minor phases that increased in intensity over this timeframe. After a temporary loss of airflow early in the test, the cell generated between 225 and 250 mW/cm2 for the remainder of the test. A large low frequency arc in the impedance spectra suggests the cell performance was gas diffusion limited and that there is room for improvement in air delivery to the cell.

Hardy, John S.; Templeton, Jared W.; Edwards, Danny J.; Lu, Zigui; Stevenson, Jeffry W.

2012-01-03

274

DARHT 2 kA Cathode Development  

SciTech Connect

In the campaign to achieve 2 kA of electron beam current, we have made several changes to the DARHT-II injector during 2006-2007. These changes resulted in a significant increase in the beam current, achieving the 2 kA milestone. Until recently (before 2007), the maximum beam current that was produced from the 6.5-inch diameter (612M) cathode was about 1300 A when the cathode was operating at a maximum temperature of 1140 C. At this temperature level, the heat loss was dominated by radiation which is proportional to temperature to the fourth power. The maximum operating temperature was limited by the damage threshold of the potted filament and the capacity of the filament heater power supply, as well as the shortening of the cathode life time. There were also signs of overheating at other components in the cathode assembly. Thus it was clear that our approach to increase beam current could not be simply trying to run at a higher temperature and the preferred way was to operate with a cathode that has a lower work function. The dispenser cathode initially used was the type 612M made by SpectraMat. According to the manufacturer's bulletin, this cathode should be able to produce more than 10 A/cm{sup 2} of current density (corresponding to 2 kA of total beam current) at our operating conditions. Instead the measured emission (space charge limited) was 6 A/cm{sup 2}. The result was similar even after we had revised the activation and handling procedures to adhere more closely to the recommend steps (taking longer time and nonstop to do the out-gassing). Vacuum was a major concern in considering the cathode's performance. Although the vacuum gauges at the injector vessel indicated 10{sup -8} Torr, the actual vacuum condition near the cathode in the central region of the vessel, where there might be significant out-gassing from the heater region, was never determined. Poor vacuum at the surface of the cathode degraded the emission (by raising the work function value). We reexamined all the components in the cathode region and eliminated those parts that were suspected to be potential sources of contamination, e.g., feed-throughs with zinc coating. Finally, we considered a change in the cathode type, by using a different combination of impregnation and coating. Since the ETA-II accelerator at LLNL used a 12.5 cm diameter 311XW (barium oxide doped with scandium and coated with a osmium-tungsten thin film) cathode and emitted 2200A of beam current (i.e. 18 A/cm{sup 2}), it was reasonable to assume that DARHT can adopt this type of cathode to produce 2 kA (i.e., 10A/cm{sup 2}). However, it was later found that the 311XW has a higher radiation heat loss than the 612M and therefore resulted in a maximum operating temperature (as limited by filament damage) below that required to produce the high current. With the evidence provided by systematic emission tests using quarter-inch size cathodes, we confirmed that the 311XM (doped with scandium and has a osmium-ruthenium (M) coating) had the best combination of low work function and low radiation heat loss. Subsequently a 6.5-inch diameter 311XM cathode was installed in DARHT and 2 kA beam current was obtained on June 14, 2007. In testing the quarter-inch size cathode, we found that the beam current was sensitive to the partial pressure of various gases in the vacuum chamber. Furthermore, there was a hysteresis effect on the emission as a function of temperature. The phenomenon suggested that the work function of the cathode was dependent on the dynamic equilibrium between the diffusion of the impregnated material to the surface and the contamination rate from the surrounding gas. Water vapor was found to be the worst contaminant amongst the various gases that we have tested. Our data showed that the required vacuum for emitting at 10 A/cm{sup 2} is in the low 10{sup -8} Torr range.

Henestroza, E.; Houck, T.; Kwan, J.W.; Leitner, M.; Miram, G.; Prichard, B.; Roy, P.K.; Waldron, W.; Westenskow, G.; Yu, S.; Bieniosek, F.M.

2009-03-09

275

Synopsis of Cathode #4 Activation  

SciTech Connect

The purpose of this report is to describe the activation of the fourth cathode installed in the DARHT-II Injector. Appendices have been used so that an extensive amount of data could be included without danger of obscuring important information contained in the body of the report. The cathode was a 612 M type cathode purchased from Spectra-Mat. Section II describes the handling and installation of the cathode. Section III is a narrative of the activation based on information located in the Control Room Log Book supplemented with time plots of pertinent operating parameters. Activation of the cathode was performed in accordance with the procedure listed in Appendix A. The following sections provide more details on the total pressure and constituent partial pressures in the vacuum vessel, cathode heater power/filament current, and cathode temperature.

Kwan, Joe; Ekdahl, C.; Harrison, J.; Kwan, J.; Leitner, M.; McCruistian, T.; Mitchell, R.; Prichard, B.; Roy, P.

2006-05-26

276

NO{sub x} emissions of a jet diffusion flame which is surrounded by a shroud of combustion air  

SciTech Connect

The present work reports an experimental study on the behavior of a jet flame surrounded by a shroud of combustion air. Measurements focussed on the flame length and the emissions of NO{sub x}, total unburned hydrocarbons, CO{sub 2}, and O{sub 2}. Four different fuel flow rates (40.0, 78.33, 138.33, and 166.6 cm/s), air flow rates up to 2500 cm{sup 3}/s and four different air injector diameters (0.079 cm, 0. 158 cm, 0.237 cm, and 0.316 cm) were used. The shroud of combustion air causes the flame length to decrease by a factor proportional to 1/[p{sub a}/p{sub f} + C{sub 2}({mu}{sub a}Re,a/{mu}{sub f}Re,f){sup 2}]{sup {1/2}}. A substantial shortening of the flame length occurred by increasing the air injection velocity keeping fuel rate fixed or conversely by lowering the fuel flow rate keeping air flow rate constant. NO{sub x} emissions ranging from 5 ppm to 64 ppm were observed and the emission of NO{sub x} decreased strongly with the increased air velocity. The decrease of NO{sub x} emissions was found to follow a similar scaling law as does the flame length. However, the emission of the total hydrocarbons increased with the increased air velocity or the decreased fuel flow rate. A crossover condition where both NO{sub x} and unburned- hydrocarbon emissions are low, was identified. At an air-to-fuel velocity ratio of about 1, the emissions of NO{sub x} and the total hydrocarbons were found to be under 20 ppm.

Tran, P.X.; White, F.P.; Mathur, M.P.; Ekmann, J.M.

1996-08-01

277

Thermal sprayed titanium anode for cathodic protection of reinforced concrete bridges  

NASA Astrophysics Data System (ADS)

Stable operation of cobalt catalyzed thermal sprayed titanium anodes for cathodic protection (CP) of bridge reinforcing steel was maintained in accelerated tests for a period equivalent to 23 years service at Oregon Department of Transportation (Oregon DOT) bridge CP conditions with no evidence that operation would degrade with further aging. The cobalt catalyst dispersed into the concrete near the anodeconcrete interface with electrochemical aging to produce a more diffuse anode reaction zone. The titanium anode had a porous heterogeneous structure composed of ?-titanium containing interstitial oxygen and nitrogen, and a fee phase thought to be Ti(O,N). Splat cooling rates were 10 to 150 K/s, and microstructures were produced by equilibrium processes at the splat solidification front. Nitrogen gas atomization during thermal spraying produced a coating with more uniform composition, less cracking, and lower resistivity than using air atomization.

Cramer, S. D.; Covino, B. S.; Holcomb, G. R.; Bullard, S. J.; Collins, W. K.; Govier, R. D.; Wilson, R. D.; Laylor, H. M.

1999-03-01

278

Cathodic-arc deposition with boron-alloyed titanium cathodes  

Microsoft Academic Search

Titanium cathodes containing low boron concentrations were recently found to be important for (1) the reduction of droplet emission and (2) the formation of a denser structure of reactively deposited Ti–B–N hard coatings. Based on these results, detailed studies on the cathode behaviour and the Ti–B–N coating properties were performed using titanium cathodes containing 0–7.5at% boron and cemented carbides and

Martin Balzer; Herbert Kappl; Hermann A Jehn; Volker Güther

1999-01-01

279

A numerical study on the effect of hydrogen/reformate gas addition on flame temperature and NO formation in strained methane/air diffusion flames  

SciTech Connect

This paper investigates the effects of hydrogen/reformate gas addition on flame temperature and NO formation in strained methane/air diffusion flames by numerical simulation. The results reveal that flame temperature changes due to the combined effects of adiabatic temperature, fuel Lewis number and radiation heat loss, when hydrogen/reformate gas is added to the fuel of a methane/air diffusion flame. The effect of Lewis number causes the flame temperature to increase much faster than the corresponding adiabatic equilibrium temperature when hydrogen is added, and results in a qualitatively different variation from the adiabatic equilibrium temperature as reformate gas is added. At some conditions, the addition of hydrogen results in a super-adiabatic flame temperature. The addition of hydrogen/reformate gas causes NO formation to change because of the variations in flame temperature, structure and NO formation mechanism, and the effect becomes more significant with increasing strain rate. The addition of a small amount of hydrogen or reformate gas has little effect on NO formation at low strain rates, and results in an increase in NO formation at moderate or high strain rates. However, the addition of a large amount of hydrogen increases NO formation at all strain rates, except near pure hydrogen condition. Conversely, the addition of a large amount of reformate gas results in a reduction in NO formation. (author)

Guo, Hongsheng; Neill, W. Stuart [Institute for Chemical Process and Environmental Technology, National Research Council Canada, 1200 Montreal Road, Ottawa, Ontario, K1A 0R6 (Canada)

2009-02-15

280

Simulation of CO-H2-air Turbulent Diffusion Flame by the Combustion Model Combined Chemical Equilibrium Method with the Eddy Dissipation Concept Model  

NASA Astrophysics Data System (ADS)

This research aims at building a turbulent diffusion combustion model based on chemical equilibrium and kinetics for simplifying complex chemical mechanisms. This paper presents the combustion model based on chemical equilibrium combined with an eddy dissipation concept model (CE-EDC); the model is validated by simulating a CO-H2-air turbulent diffusion flame. In the CE-EDC model, the reaction rate of fuels and intermediate species are estimated by using the equations of the EDC model. Then, the reacted fuels and intermediate species are assumed to be in chemical equilibrium; the amounts of the other species are determined by the Gibbs free energy minimization method by using the amounts of the reacted fuels, intermediate species, and air as reactants. An advantage of the CE-EDC model is that the amounts of the combustion products can be determined without using detailed chemical mechanisms. Moreover, it can also predict the amounts of the intermediate species. The obtained results are compared with Correa's experimental data and Gran's computational data by using the EDC model, which uses the complex chemical mechanisms. The mole fractions of CO, H2, H2O, OH, temperature, and mixture fraction obtained by using our CE-EDC model were in good agreement with these reference data. Using the present CE-EDC model, amounts of combustion products can be calculated by using a reduced chemical mechanism and the Gibbs free energy minimization theory. The accuracy of this model is in the same order as that of the EDC model.

Fukumoto, Kazui; Ogami, Yoshifumi

281

Axially Extracted Virtual Cathode Oscillator with Annular Cathode  

NASA Astrophysics Data System (ADS)

A numerical simulation study of a virtual cathode oscillator withannular cathode has been performed by a 3 dimensionalparticle-in-cell (PIC) code called MAGIC. Also the experimentalstudies are performed for comparison of numerical results. Theannular diode consists of circular anode mesh and annular typecathode. The object for this investigation is to find theoptimized width and radius of the annular cathode in our highpower microwave pulser, “Chundoong". Both of simulation andexperimental results show that the output microwave power andfrequency depend on emission width and radius of annular cathode, and the dominant mode of output microwave is TM01 under theoptimized width 4 mm and radius of 20 mm.

Choi, Eun Ha; Sung, Kew Yong; Jeon, Wook; Jung, Yoon

282

Stereological estimation of the surface area and oxygen diffusing capacity of the respiratory stomach of the air-breathing armored catfish Pterygoplichthys anisitsi (Teleostei: Loricariidae).  

PubMed

The stomach of Pterygoplichthys anisitsi has a thin, translucent wall and a simple squamous epithelium with an underlying dense capillary network. In the cardiac and pyloric regions, most cells have short microvilli distributed throughout the cell surface and their edges are characterized by short, densely packed microvilli. The mucosal layer of the stomach has two types of pavement epithelial cells that are similar to those in the aerial respiratory organs. Type 1 pavement epithelial cells, resembling the Type I pneumocyte in mammal lungs, are flat, with a large nucleus, and extend a thin sheet of cytoplasm on the underlying capillary. Type 2 cells, resembling the Type II pneumocyte, possess numerous mitochondria, a well-developed Golgi complex, rough endoplasmic reticulum, and numerous lamellar bodies in different stages of maturation. The gastric glands, distributed throughout the mucosal layer, also have several cells with many lamellar bodies. The total volume (air + tissue), tissue, and air capacity of the stomach when inflated, increase along with body mass. The surface-to-tissue-volume ratio of stomach varies from 108 cm(-1) in the smallest fish (0.084 kg) to 59 cm(-1) in the largest fish (0.60 kg). The total stomach surface area shows a low correlation to body mass. Nevertheless, the body-mass-specific surface area varied from 281.40 cm(2) kg(-1) in the smallest fish to 68.08 cm(2) kg(-1) in the largest fish, indicating a negative correlation to body mass (b = -0.76). The arithmetic mean barrier thickness between air and blood was 1.52 +/- 0.07 microm, whereas the harmonic mean thickness (tau(h)) of the diffusion barrier ranged from 0.40 to 0.74 microm. The anatomical diffusion factor (ADF = cm(2) microm(-1) kg(-1)) and the morphological O(2) diffusion capacity (D(morphol)O(2) = cm(3) min(-1) mmHg(-1) kg(-1)) are higher in the smallest specimen and lower in the largest one. In conclusion, the structure and morphometric data of P. anisitsi stomach indicate that this organ is adapted for oxygen uptake from air. PMID:19107815

da Cruz, André Luis; Pedretti, Ana Carolina Elias; Fernandes, Marisa Narciso

2009-05-01

283

Annular diffusion denuder for simultaneous removal of gaseous organic compounds and air oxidants during sampling of carbonaceous aerosols.  

PubMed

A specially designed annular diffusion denuder for simultaneous removal of organic gaseous compounds and atmospheric oxidants in carbonaceous aerosol sampling is presented. Various kinds of denuder coatings were compared with respect to the collection efficiency of both organic gaseous compounds and NO(2) and ozone. The optimum sorbent is a mixture of activated charcoal and sulfite on molecular sieve. To ensure high collection efficiency over long-term field operation, two annular diffusion denuders are combined in series. The first half of the first denuder is filled with Na(2)SO(3) on molecular sieve (23 cm long layer) while the second half of the first denuder and the whole second denuder are filled with activated charcoal (the total length of the charcoal section is 67 cm). At a flow rate of 16.6 L min(-1), the collection efficiency of organic gaseous compounds and atmospheric oxidants in the annular diffusion denuder is better than 95%. Only small losses of aerosol particles (<3.6% in number concentration) were observed in the size range 0.12-2.26 ?m. The annular diffusion denuder is compatible with the collection of aerosols on 47-mm diameter quartz fiber filters at a flow rate of 16.6 L min(-1). The use of this denuder enables one to sample carbonaceous aerosols on filters without positive sampling artefacts from volatile organic compounds and interferences from atmospheric oxidants. The annular diffusion denuder has been applied successfully for the sampling of carbonaceous aerosols during field campaigns of typically 1 month each at urban and forested sites in Europe. PMID:22244138

Mikuška, Pavel; Ve?e?a, Zbyn?k; Bartošíková, Anna; Maenhaut, Willy

2011-12-03

284

Gas Fed Multichannel Hollow Cathode Arcs  

Microsoft Academic Search

A new type of gas fed hollow cathode (multichannel cathode) has been studied. Such cathodes operate with a lower voltage drop and higher maximum current density than conventional one-channel cathodes and have a longer lifetime as well. Moreover, multichannel cathodes allow operation within a wide range of discharge currents and with extremely low gas flow rates. A theoretical analysis clarifies

J. L. Delcroix; H. Minoo; A. R. Trindade

1969-01-01

285

Back bombardment for dispenser and lanthanum hexaboride cathodes  

NASA Astrophysics Data System (ADS)

The back bombardment (BB) effect limits wide usage of thermionic rf guns. The BB effect induces not only ramping-up of a cathode’s temperature and beam current, but also degradation of cavity voltage and beam energy during a macropulse. This paper presents a comparison of the BB effect for the case of dispenser tungsten-base (DC) and lanthanum hexaboride (LaB6) thermionic rf gun cathodes. For each, particle simulation codes are used to simulate the BB effect and electron beam dynamics in a thermionic rf gun cathode. A semiempirical equation is also used to investigate the stopping range and deposited heat power of BB electrons in the cathode material. A numerical simulation method is used to calculate the change of the cathode temperature and current density during a single macropulse. This is done by solving two differential equations for the rf gun cavity equivalent circuit and one-dimensional thermal diffusion equation. High electron emission and small beam size are required for generation of a high-brightness electron beam, and so in this work the emission properties of the cathode are taken into account. Simulations of the BB effect show that, for a pulse of 6?s duration, the DC cathode experiences a large change in the temperature compared with LaB6, and a change in current density 6 times higher. Validation of the simulation results is performed using experimental data for beam current beyond the gun exit. The experimental data is well reproduced using the simulation method.

Bakr, Mahmoud; Kinjo, R.; Choi, Y. W.; Omer, M.; Yoshida, K.; Ueda, S.; Takasaki, M.; Ishida, K.; Kimura, N.; Sonobe, T.; Kii, T.; Masuda, K.; Ohgaki, H.; Zen, H.

2011-06-01

286

Cathodes for molten salt batteries  

Microsoft Academic Search

Carbon-based chlorine cathodes were evaluated in molten-salt rechargeable lithium water-stack-type cells. Chlorine-based cathodes having open-circuit voltages (OCVs) of 2.8-3.3 V were investigated for their high rate capability. Carbon cathodes augmented with thermally and electrochemically stable additives demonstrated good performance with 2-in-diameter stacked-wafer configuration cells. Specific cathode capacities of 0.17-0.21 Ah\\/g at current densities of 124-248 mA\\/cm2 were observed. Pulse power

Shyam D. Argade

1992-01-01

287

Depression cathode structure for cathode ray tubes having surface smoothness and method for producing same  

SciTech Connect

Depression cathode structures for cathode ray tubes are produced by dispensing liquid cathode material into the depression of a metallic supporting substrate, removing excess cathode material by passing a doctor blade across the substrate surface and over the depression, and drying the cathode layer to a substantially immobile state. The cathode layer may optionally be further shaped prior to substantially complete drying thereof.

Rychlewski, T.V.

1984-10-23

288

Diffusive sampling of 25 volatile organic compounds in indoor air: Uptake rate determination and application in Flemish homes for the elderly  

NASA Astrophysics Data System (ADS)

Passive sampling of volatile organic compounds (VOCs) in air has received increasing attention in recent years. However, in order to use passive sampling as a reliable sampling technique a compound and sampler specific uptake rate is needed. Therefore, the scope of our study was threefold. First, uptake rates for 25 VOCs were determined under real indoor and outdoor conditions using axial-sampling tube-type samplers filled with Tenax TA, and active (pumped) sampling as a reference technique. Secondly, the mechanisms of passive sampling were investigated by comparing the experimentally determined uptake rates (0.13-0.46 ml min -1) to the ideal uptake rates, calculated based on Fick's first law of diffusion and sampler geometry. Sampling efficiency SE, defined as the ratio between the experimental and ideal uptake rate, was introduced as a correction factor and showed that ideal uptake rates may underestimate VOC concentrations by a factor up to 4. This compound dependent SE is explained in terms of the partitioning coefficient K, i.e. the compound's Tenax TA to air concentration equilibrium ratio. Compounds with a low K-value showed the most pronounced non-ideal sorptive behavior. Third, the experimentally determined uptake rates were used to determine VOC concentrations (between 12 and 311 ?g m -3) in 6 homes for the elderly in Antwerp (Belgium). This study provides unique data for indoor air quality at care centers in Flanders.

Walgraeve, C.; Demeestere, K.; Dewulf, J.; Van Huffel, K.; Van Langenhove, H.

2011-10-01

289

A hot Cathode Magnetron Discharge for Hollow Cathode Arc Ignition  

Microsoft Academic Search

An E X B discharge has been used to ignite a hollow cathode arc in a convenient and reliable manner.Voltage-current characteristics of this auxiliary high pressure magnetron discharge in argon have been measured in the pressure and magnetic field ranges of our usual hollow cathode arc operation parameters. Two stable branches of the characteristics can be distinguished, resembling arc and

P. J. Blaas; K. L. Buisman; H. de Kluiver

1970-01-01

290

Opposed jet burner studies of silane-methane, silane-hydrogen, and hydrogen diffusion flames with air  

Microsoft Academic Search

An atmospheric pressure tubular opposed jet burner technique was used to characterize certain diffusion-flame transitions and associated burning rates for N2-diluted mixtures of highly-reactive fuels. The paper presents: (1) details of the technique, with emphasis on features permitting the study of flames involving pyrophoric gases and particle-forming combustion reactions; (2) discoveries on the properties of these flames which correspond to

G. L. Pellett; R. Guerra; L. G. Wilson; G. B. Northam

1986-01-01

291

Novel Composite Materials for SOFC Cathode-Interconnect Contact  

Microsoft Academic Search

This report summarized the research efforts and major conclusions of our University Coal Research Project, which focused on developing a new class of electrically-conductive, Cr-blocking, damage-tolerant Ag-perovksite composite materials for the cathode-interconnect contact of intermediate-temperature solid oxide fuel cell (SOFC) stacks. The Ag evaporation rate increased linearly with air flow rate initially and became constant for the air flow rate

J. H. Zhu; L. T. Wilkinson; J. M. Shoulders

2009-01-01

292

Multiple hollow cathode wear testing  

Microsoft Academic Search

A hollow cathode-based plasma contactor has been baselined for use on the Space Station to reduce station charging. The plasma contactor provides a low impedance connection to space plasma via a plasma produced by an arc discharge. The hollow cathode of the plasma contactor is a refractory metal tube, through which xenon gas flows, which has a disk-shaped plate with

George C. Soulas

1994-01-01

293

Cathodic protection with parallel cylinders  

Microsoft Academic Search

This paper reports that anodes should be placed so as to supply a uniform current density to the surface of the protected cathode to maintain it within a specified potential range relative to the adjacent electrolytic medium. Analysis of two or more parallel circular cylinders is carried out by solving Laplace's equation with the uniform current density on the cathode.

John Newman

1991-01-01

294

Virtual cathode microwave devices -- Basics  

SciTech Connect

Unlike a conventional microwave tube, a virtual-cathode device operates above the space-charge limit where the depth of the space-charge potential can cause electron reflection. The region associated with this electron reflection is referred to as a virtual cathode. Microwaves can be generated through oscillations in the position of the virtual cathode and through the bunching of electrons trapped in a potential well between the real and virtual cathodes. These two mechanisms are competitive. There are three basic classes of virtual cathode devices: (1) reflex triode; (2) reditron and side-shoot vircator; and (3) reflex diode or vircator. The reflex diode is the highest power virtual-cathode device. For the reflex diode the energy exchange between the beam and electromagnetic wave occurs in both the axial and radial directions. In some designs the oscillating-virtual-cathode frequency exceeds the reflexing-electron frequency exceeds the oscillating-virtual-cathode frequency. For the flex diode a periodic disruption in magnetic insulation can modulate the high- frequency microwave power. Overall, particle-in-cell simulation predictions and axial reflex diode experiments are in good agreement. Although frequency stability and phase locking of the reflex diode have been demonstrated, little progress has been made in efficiency enhancement. 58 refs., 11 figs.

Thode, L.E.; Snell, C.M.

1991-01-01

295

Cathodic protection in deep water  

Microsoft Academic Search

A review of literature that addresses the application of cathodic protection (CP) in the oceans of depths greater than 300 meters is presented. The review discusses environmental factors encountered in deep water and their effect on cathodic polarization behavior of steel and calcareous deposit formation. Deep water field tests results and operating experiences are also presented. An evaluation of available

K. P. Fischer; W. H. Thomason

1989-01-01

296

Hot hollow cathode gun assembly  

DOEpatents

A hot hollow cathode deposition gun assembly includes a hollow body having a cylindrical outer surface and an end plate for holding an adjustable heat sink, the hot hollow cathode gun, two magnets for steering the plasma from the gun into a crucible on the heat sink, and a shutter for selectively covering and uncovering the crucible.

Zeren, J.D.

1983-11-22

297

Electrochemical studies on the cathodic reaction of marine atmospheric corrosion  

NASA Astrophysics Data System (ADS)

Electrochemical studies on the cathodic reaction of marine atmospheric corrosion using Kelvin probe as reference electrode showed that the rate of cathodic reaction-oxygen reduction first increases then decreases, with the reaction maximizing at a certain thickness as the electrolyte film decreases during evaporation. It was indicated that with decreasing electrolyte thickness by drying, the oxygen reduction rate was accelerated by the faster oxygen diffusion due to the thinner electrolyte layer on the metal surface. The results also revealed that although the oxygen salting out effect has great influence on the rate of oxygen reduction, it is not the main causative factor for the decrease in cathodic limiting current in the case of a very thin electrolyte layer.

Wang, Jia

1996-12-01

298

Linear air-fuel sensor development  

SciTech Connect

The electrochemical zirconia solid electrolyte oxygen sensor, is extensively used for monitoring oxygen concentrations in various fields. They are currently utilized in automobiles to monitor the exhaust gas composition and control the air-to-fuel ratio, thus reducing harmful emission components and improving fuel economy. Zirconia oxygen sensors, are divided into two classes of devices: (1) potentiometric or logarithmic air/fuel sensors; and (2) amperometric or linear air/fuel sensors. The potentiometric sensors are ideally suited to monitor the air-to-fuel ratio close to the complete combustion stoichiometry; a value of about 14.8 to 1 parts by volume. This occurs because the oxygen concentration changes by many orders of magnitude as the air/fuel ratio is varied through the stoichiometric value. However, the potentiometric sensor is not very sensitive to changes in oxygen partial pressure away from the stoichiometric point due to the logarithmic dependence of the output voltage signal on the oxygen partial pressure. It is often advantageous to operate gasoline power piston engines with excess combustion air; this improves fuel economy and reduces hydrocarbon emissions. To maintain stable combustion away from stoichiometry, and enable engines to operate in the excess oxygen (lean burn) region several limiting-current amperometric sensors have been reported. These sensors are based on the electrochemical oxygen ion pumping of a zirconia electrolyte. They typically show reproducible limiting current plateaus with an applied voltage caused by the gas diffusion overpotential at the cathode.

Garzon, F. [Los Alamos National Lab., NM (United States); Miller, C. [General Motors, Flint, MI (United States). GM/Delphi E. Division

1996-12-14

299

Transition from constricted to diffuse vacuum arc modes during high-current interruption  

Microsoft Academic Search

Modes of high current vacuum arc between butt contacts at a fixed gap of 10 mm during the decrease of current to zero were characterised. Three groups of arc modes were featured: (i) constricted-without a significant share of individual cathode spots; (ii) constricted-with a considerable number of cathode spots beyond the concentrated cathode root; and (iii) diffuse modes. It was

Z. Zalucki; J. Janiszewski

1998-01-01

300

Electrochemical impedance spectroscopy studies of lithium diffusion in doped manganese oxide.  

National Technical Information Service (NTIS)

Cathode performance is critical to lithium ion rechargeable battery performance; effects of doping lithium manganese oxide cathode materials on cathode performance are being investigated. In this paper, Li diffusion in Al-doped LiMn(sub 2)O(sub 4) was stu...

B. J. Johnson D. H. Doughty J. A. Voigt T. J. Boyle

1996-01-01

301

Hollow-cathode evaporators  

SciTech Connect

This paper describes devices for producing plasma from the vapor of a solid substance under vacuum and depositing films from the plasma. The plasma is produced by a discharge between a hollow cathode crucible and an anode, which are placed in a magnetic field longitudinal in relation to the vapor flow. The basic parameters are: film deposition rate 1-70 nm/sec, consumption of working substance 1-30 mg/sec, ionization factor for the working substance in the flow 1-10%, ion-current density at the substrate 0.1-10 mA/cm/sup 2/. Films of Cu, Au, Ag, Cr, and A1 have been made with parameters better than those of films deposited without ionization.

Saenko, V.A.; Kravatskii, V.A.; Veremeichenko, G.N.; Vladimirov, A.I.

1985-08-01

302

Electron emission from pseudospark cathodes  

SciTech Connect

The pseudospark cathode has the remarkable property of macroscopically homogeneous electron emission at very high current density ([gt]1 kA/cm[sup 2]) over a large area (some cm[sup 2]). The model of electron emission presented here is based on the assumption that the pseudospark microscopically utilizes explosive arc processes, as distinct from earlier models of anomalous emission in superdense glow discharges.'' Explosive emission similar to vacuum are cathode spots occurs rapidly when the field strength is sufficiently high. The plasma remains macroscopically homogeneous since the virtual plasma anode adapts to the cathode morphology so that the current is carried by a large number of homogeneously distributed cathode spots which are similar to type 1'' and type 2'' spots of vacuum arc discharges. The net cathode erosion is greatly reduced relative to spark gap-type'' emission. At very high current levels, a transition to highly erosive spot types occurs, and this arcing'' leads to a significant reduction in device lifetime. Assuming vacuum-arc-like cathode spots, the observed current density and time constants can be easily explained. The observed cathode erosion rate and pattern, recent fast-camera data, laser-induced fluorescence, and spectroscopic measurements support this approach. A new hypothesis is presented explaining current quenching at relatively low currents. From the point of view of electron emission, the superdense glow'' or superemissive phase'' of pseudosparks represents an arc and not a glow discharge even if no filamentation or arcing'' is observed.

Anders, A.; Anders, S. (Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720 (United States)); Gundersen, M.A. (Physics Department, University of Southern California, Los Angeles, California 90089-0484 (United States))

1994-08-01

303

Electron emission from pseudospark cathodes  

NASA Astrophysics Data System (ADS)

The pseudospark cathode has the remarkable property of macroscopically homogensous electron emission at very high current density (greater than 1 kA/sq cm) over a large area (some sq cm). The model of electron emission presented here is based on the assumption that the pseudospark microscopically utilizes explosive arc processes, as distinct from earlier models of 'anomalous emission in superdense glow discharges.' Explosive emission similar to vacuum are cathode spots occurs rapidly when the field strength is sufficiently high. The plasma remains macroscopically homogeneous since the virtual plasma anode adapts to the cathode morphology so that the current is carried by a large number of homogeneously distributed cathode spots which are similar to 'type 1' and 'type 2' spots of vacuum arc discharges. The net cathode erosion is greatly reduced relative to 'spark gap-type' emission. At very high current levels, a transition to highly erosive spot types occurs, and this 'arcing' leads to a significant reduction in device lifetime. Assuming vacuum-arc-like cathode spots, the observed current density and time constants can be easliy explained. The observed cathode erosion rate and pattern, recent fast-camera data, laser-induced fluorescence, and spectroscopic measurments support this apprach. A new hypothesis is presented explaining current quenching at relatively low currents. From the point of view of electron emission, the 'superdense glow' or 'superemissive phase' of pseudosparks represents an arc and not a glow discharge even if no filamentation or 'arcing' is observed.

Anders, Andre; Anders, Simone; Gundersen, Martin A.

1994-08-01

304

Cathodic protection in deep water  

SciTech Connect

A review of literature that addresses the application of cathodic protection (CP) in the oceans of depths greater than 300 meters is presented. The review discusses environmental factors encountered in deep water and their effect on cathodic polarization behavior of steel and calcareous deposit formation. Deep water field tests results and operating experiences are also presented. An evaluation of available data and an indentification of data needed for optimum cathodic protection design for deep water are included. Current CP design approaches and deep water CP studies are also discussed.

Fischer, K.P. (Norwegian Marine Techology Research Inst. A/S, P.O. Box 173, N-3201 Sandefjord (NO)); Thomason, W.H. (Conoco Inc., Ponca City, OK (US))

1989-01-01

305

RADC cathode life test program  

NASA Astrophysics Data System (ADS)

This brief is an update of RADC cathode life test program and includes details of evaluation procedures, progress, and future plans. A technique has been developed which permits repeatable temperature measurements on cathode test vehicles using a two-color pyrometer. The setup of the pyrometer for the cathode activity plot measurements is critical. The technique developed, when compared to the previously used measurement procedures, has several advantages: (1) an increase in the repeatability of the measurement data; (2) decreased instrumentation setup time; (3) adjustments eliminating any jarring or jolting of the instrumentation during setup positioning; and (4) different individuals can perform the measurements and obtain similar results.

Bussey, D.; Daniszewski, E.; Novak, M.; Ryan, J.; Wilkinson, J.

1990-12-01

306

Using the tabulated diffusion flamelet model ADF-PCM to simulate a lifted methane-air jet flame  

SciTech Connect

Two formulations of a turbulent combustion model based on the approximated diffusion flame presumed conditional moment (ADF-PCM) approach [J.-B. Michel, O. Colin, D. Veynante, Combust. Flame 152 (2008) 80-99] are presented. The aim is to describe autoignition and combustion in nonpremixed and partially premixed turbulent flames, while accounting for complex chemistry effects at a low computational cost. The starting point is the computation of approximate diffusion flames by solving the flamelet equation for the progress variable only, reading all chemical terms such as reaction rates or mass fractions from an FPI-type look-up table built from autoigniting PSR calculations using complex chemistry. These flamelets are then used to generate a turbulent look-up table where mean values are estimated by integration over presumed probability density functions. Two different versions of ADF-PCM are presented, differing by the probability density functions used to describe the evolution of the stoichiometric scalar dissipation rate: a Dirac function centered on the mean value for the basic ADF-PCM formulation, and a lognormal function for the improved formulation referenced ADF-PCM{chi}. The turbulent look-up table is read in the CFD code in the same manner as for PCM models. The developed models have been implemented into the compressible RANS CFD code IFP-C3D and applied to the simulation of the Cabra et al. experiment of a lifted methane jet flame [R. Cabra, J. Chen, R. Dibble, A. Karpetis, R. Barlow, Combust. Flame 143 (2005) 491-506]. The ADF-PCM{chi} model accurately reproduces the experimental lift-off height, while it is underpredicted by the basic ADF-PCM model. The ADF-PCM{chi} model shows a very satisfactory reproduction of the experimental mean and fluctuating values of major species mass fractions and temperature, while ADF-PCM yields noticeable deviations. Finally, a comparison of the experimental conditional probability densities of the progress variable for a given mixture fraction with model predictions is performed, showing that ADF-PCM{chi} reproduces the experimentally observed bimodal shape and its dependency on the mixture fraction, whereas ADF-PCM cannot retrieve this shape. (author)

Michel, Jean-Baptiste; Colin, Olivier; Angelberger, Christian [IFP, 1 et 4 avenue de Bois Preau, F92852, Rueil-Malmaison Cedex (France); Veynante, Denis [EM2C, CNRS et Ecole Centrale Paris, F92295, Chatenay-Malabry (France)

2009-07-15

307

Dispenser cathode high power gridded klystron gun  

Microsoft Academic Search

This paper describes the design and performance of a new shadow gridded gun useful for high power radar klystrons. The gun features an M-type dispenser cathode having heater power identical to a larger diameter cathode oxide cathode gun used in one application. It is known that dispenser cathodes are more tolerant of arcs, poisoning, and other effects that can ruin

R. B. True; M. F. Kirshner; L. Turek; G. R. Good; R. J. Hansen; T. M. Bemis; R. J. Bartkowski

2004-01-01

308

Spiral cathodes for microwave heating magnetrons  

Microsoft Academic Search

Cathodes have been developed for magnetrons for microwave heating using thermally stable alloys of an activator metal and a platinum group metal as a surface layer on the cathode. Metal alloy cathodes (MAC) utilizing Ir5La or Re2Th were tested and shown to be capable of operating at a lower temperature than carburized thoriated tungsten or pure tungsten cathodes. An alternative

B. Ch. Djubua; B. N. Ilyin; O. V. Polivnikova; E. M. Zemchikhin

1997-01-01

309

Theory of the hollow cathode arc  

Microsoft Academic Search

A theory of the hollow cathode arc is given which explains the physical mechanisms of operation of these discharges. The following basic phenomena are studied: the gas flow inside the cathode; the formation of the internal plasma column by ionization of the neutral gas by the primary electrons emitted by the cathode, which are accelerated in the cathode sheath; the

C. M. Ferreira; J. L. Delcroix

1978-01-01

310

Laser Micromachined, Monolithic Cathodes for Cathode Priming of a Relativistic Magnetron  

Microsoft Academic Search

Summary form only given. Experiments have been performed on a relativistic magnetron using innovative monolithic metal cathodes (Al). These new types of cathodes are fabricated utilizing KrF laser ablation of metal surfaces to enhance the local E field. Two new types of cathodes invented are: projection ablation lithography (PAL) and ablation line focused (ALF) cathodes. PAL cathodes are fabricated by

N. M. Jordan; M. C. Jones; R. M. Gilgenbach; V. B. Neculaes; W. M. White; B. W. Hoff; Y. Y. Lau; Y. Hidaka; T. A. Spencer; D. Price

2005-01-01

311

A simple mechano-thermal coating process for improved lithium battery cathode materials  

Microsoft Academic Search

A simple, economical and convenient mechano-thermal coating procedure for the production of LiCoO2 with improved cycling performance is described. The coating material was pre-formed nanoparticulate fumed silica. TEM studies with a 1.0wt.% silica-coated cathode suggested that the silica species partially diffused into the bulk of the cathode material. XRD studies showed a diminished lattice parameter c upon coating, indicating that

George Ting-Kuo Fey; Hao-Zhong Yang; T. Prem Kumar; Sajo P. Naik; Anthony S. T. Chiang; Dzu-Chi Lee; Jinn-Ren Lin

2004-01-01

312

The numerical modeling of near, cathode erosion processes in electric-arc plasma generators  

Microsoft Academic Search

An electric-arc plasma generator with high-current arc that burns in hydrocarbon-containing gas (methane) at atmosphere pressure is simulated. In a hydrocarbon plasma at the near cathode region two streams are always found. The first, ion stream is directed to the cathode surface and moves under the effect of the electric field. The second, backward stream, resulting from diffusion of the

A. Rychkov; V. Salomatov

2001-01-01

313

Seasonal, anthropogenic, air mass, and meteorological influences on the atmospheric concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs): Evidence for the importance of diffuse combustion sources  

SciTech Connect

Sampling programs were undertaken to establish air polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) concentrations at a semirural site on the northwest coast of England in autumn and summer and to investigate factors causing their variability. Changing source inputs, meteorological parameters, air masses, and the impact of a festival when it is customary to light fireworks and bonfires were investigated. Various lines of evidence from the study point to diffuse, combustion-related sources being a major influence on ambient air concentrations. Higher PCDD/F concentrations were generally associated with air masses that had originated and moved over land, particularly during periods of low ambient temperature. Low concentrations were associated with air masses that had arrived from the Atlantic Ocean/Irish Sea to the west of the sampling site and had little or no contact with urban/industrialized areas. Concentrations in the autumn months were 2 to 10 times higher than those found in the summer.

Lee, R.G.M.; Green, N.J.L.; Lohmann, R.; Jones, K.C. [Lancaster Univ. (United Kingdom)

1999-09-01

314

Cathodes for molten-salt batteries  

Microsoft Academic Search

Viewgraphs of the discussion on cathodes for molten-salt batteries are presented. For the cathode reactions in molten-salt cells, chlorine-based and sulfur-based cathodes reactants have relatively high exchange current densities. Sulfur-based cathodes, metal sulfides, and disulfides have been extensively investigated. Primary thermal batteries of the Li-alloy\\/FeS2 variety have been available for a number of years. Chlorine based rechargable cathodes were investigated

Shyam D. Argade

1993-01-01

315

Oxides of nitrogen emissions from turbulent hydrocarbon/air jet diffusion flames. Annual report, January - December 1990  

SciTech Connect

Measurements of oxides of nitrogen emission indices, flame radiant fractions, and visual flame dimensions were made for turbulent jet diffusion flames covering a wide range of flow conditions. Objectives of the study were to understand the interrelationships among NO{sub x} emissions, flow conditions, and flame radiation; and to provide a well-characterized data base to guide modeling efforts. A range of radiant fractions, and hence characteristic flame temperatures, were obtained by varying fuel type. The use of three fuels, CH{sub 4}, C{sub 3}H{sub 8}, and C{sub 2}H{sub 4}, with and without nitrogen dilution, resulted in a series of flames with widely varying sooting characteristics. Four burners with different jet diameters allowed independent variation of Reynolds and Froude numbers, while H{sub 2} pilot flame stabilization allowed a large range of jet exit velocities, and hence length and time scales, to be studied. Characteristic flame temperatures deduced from the measured radiant fractions were used to scale the normalized NO{sub x} emission rates from all flames. A simple result, consistent with Zeldovich kinetics, obtained at the higher temperatures when the flames were non-luminous, regardless of fuel type. At lower temperatures, fuel-type was important, with the normalized emission rates increasing in the same order as sooting tendencies. The results are consistent with, but do not prove, the view that the bulk of the NO{sub x} emitted by jet flames is formed in the high-temperature, nearly stoichiometric, large-scale eddies at the flame tip.

Turns, S.R.; Myhr, F.H.

1991-01-01

316

Geometrical aspects of a hollow-cathode planar magnetron  

NASA Astrophysics Data System (ADS)

A hollow-cathode planar magnetron (HCPM), built by surrounding a planar sputtering-magnetron cathode with a hollow-cathode structure (HCS) [Z. Wang and S. A. Cohen, J. Vac. Sci. Technol. A 17, 77 (1999)], is operable at substantially lower pressures than its planar-magnetron counterpart. HCPM operational parameters depend on the inner diameter D and length L of its cylindrical HCS. Only when L is greater than L0, a critical length, is the HCPM operable in the new low-pressure regime. The critical length varies with HCS inner diameter D. Explanations of the lower operational pressure regime, critical length, and plasma shape are proposed and compared with a one-dimension diffusion model for energetic electron transport. At pressures above 1 mTorr, Bohm diffusion (temperature?primary electron energy), with an ambipolar constraint, can explain the ion-electron pair creation required to sustain the discharge. At the lowest pressure, ~0.3 mTorr, collision-limited diffusion creates fewer ion-electron pairs than required for steady state and therefore cannot explain the experimental data. The critical length L0 is consistent with the magnetization length of the primary electrons.

Wang, Zhehui; Cohen, Samuel A.

1999-05-01

317

Geometrical aspects of a hollow-cathode planar magnetron  

SciTech Connect

A hollow-cathode planar magnetron (HCPM), built by surrounding a planar sputtering-magnetron cathode with a hollow-cathode structure (HCS) [Z. Wang and S. A. Cohen, J. Vac. Sci. Technol. A {bold 17}, 77 (1999)], is operable at substantially lower pressures than its planar-magnetron counterpart. HCPM operational parameters depend on the inner diameter {ital D} and length {ital L} of its cylindrical HCS. Only when {ital L} is greater than L{sub 0}, a critical length, is the HCPM operable in the new low-pressure regime. The critical length varies with HCS inner diameter {ital D}. Explanations of the lower operational pressure regime, critical length, and plasma shape are proposed and compared with a one-dimension diffusion model for energetic electron transport. At pressures above 1 mTorr, Bohm diffusion (temperature{congruent}primary electron energy), with an ambipolar constraint, can explain the ion{endash}electron pair creation required to sustain the discharge. At the lowest pressure, {approximately}0.3 mTorr, collision-limited diffusion creates fewer ion{endash}electron pairs than required for steady state and therefore cannot explain the experimental data. The critical length L{sub 0} is consistent with the magnetization length of the primary electrons. {copyright} {ital 1999 American Institute of Physics.}

Wang, Z.; Cohen, S.A. [Plasma Physics Laboratory, Princeton University, P.O. Box 451, Princeton, New Jersey 08543 (United States)

1999-05-01

318

Performance of Stainless Steel Mesh Cathode and PVDF-graphite Cathode in Microbial Fuel Cells  

NASA Astrophysics Data System (ADS)

Inexpensive and conductive materials termed as stainless steel mesh and polyvinylidene fluoride (PVDF)-graphite were currently used as the air cathode electrodes in MFCs for the investigation of power production. By loading PTFE (poly(tetrafluoroethylene)) on the surface of stainless steel mesh, electricity production reached 3 times as high as that of the naked stainless steel. A much high catalytic activity for oxygen reduction was exhibited by Pt based and PTFE loading stainless steel mesh cathode, with an electricity generation of 1144+/-44 mW/m2 (31+/-1 W/m3) and a Coulombic efficiency (CE) of 77+/-2%. When Pt was replaced by an inexpensive transition metal based catalyst (cobalt tetramethylphenylporphyrin, CoTMPP), power production and CE were 845+/-21 mW/m2 (23+/-1 W/m3) and 68+/-1%, respectively. Accordingly, power production from PVDF-graphite (hydrophobic) MFC and PVDF-graphite (hydrophile) MFC were 286+/-20 mW/m2(8+/-1 W/m3) and 158+/-13 mW/m2(4+/-0.4 W/m3), respectively using CoTMPP as catalyst. These results give us new insight into materials like stainless steel mesh and PVDF-graphite as low cost cathode for reducing the costs of MFCs for wastewater treatment applications.

Huang, Liping; Tian, Ying; Li, Mingliang; He, Gaohong; Li, Zhikao

2010-11-01

319

Numerical analysis of reaction-diffusion effects on species mixing rates in turbulent premixed methane-air combustion  

SciTech Connect

The scalar mixing time scale, a key quantity in many turbulent combustion models, is investigated for reactive scalars in premixed combustion. Direct numerical simulations (DNS) of three-dimensional, turbulent Bunsen flames with reduced methane-air chemistry have been analyzed in the thin reaction zones regime. Previous conclusions from single step chemistry DNS studies are confirmed regarding the role of dilatation and turbulence-chemistry interactions on the progress variable dissipation rate. Compared to the progress variable, the mixing rates of intermediate species is found to be several times greater. The variation of species mixing rates are explained with reference to the structure of one-dimensional premixed laminar flames. According to this analysis, mixing rates are governed by the strong gradients which are imposed by flamelet structures at high Damkoehler numbers. This suggests a modeling approach to estimate the mixing rate of individual species which can be applied, for example, in transported probability density function simulations. Flame-turbulence interactions which modify the flamelet based representation are analyzed. (author)

Richardson, E.S.; Grout, R.W.; Chen, J.H. [Reacting Flow Research Department, Combustion Research Facility, Sandia National Laboratories, P.O. Box 969 MS 9051, Livermore, CA 94551-0969 (United States); Sankaran, R. [National Center for Computational Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6008 (United States)

2010-03-15

320

Plasma Cathodes as Electron Sources for Large Volume, High-Pressure Glow Discharges  

NASA Astrophysics Data System (ADS)

A method to suppress the glow-to-arc transition in high pressure glow discharges is the use of a plasma cathode consisting of microhollow cathode discharges (MHCD) [1]. In our experiment a microhollow cathode discharge with a 100 micrometer diameter cathode hole and identical anode hole was used to provide electrons for a large volume main discharge, sustained between the hollow anode of the MHCD and a third electrode. Current and voltage characteristics, and the visual appearance of the main discharge and MHCD were studied in argon and air by using the micro plasma cathode as electron source. We are able to get stable dc operation in argon up to 1 atm and in air up to 600 torr. The main discharge is ignited when the current in the plasma cathode (MHCD), which is on the order of mA, reaches a threshold value. This threshold current increases with reduced applied voltage across the main gap. Above this transition the current in the main discharge is on the same order as the MHCD current and can be controlled by the MHCD current. Experiments with two MHCDs in parallel have indicated that large area high pressure stable glow discharges can be generated by using arrays of MHCDs as electron sources. [1] K. H. Schoenbach et al, Plasma Sources Sci. Techn. 6, 468 (1997). This work was solely funded by the Air Force Office of Scientific Research (AFOSR) in cooperation with the DDR&E Air Plasma Ramparts MURI program.

Stark, Robert H.; Schoenbach, Karl H.

1998-10-01

321

Generation Of Atmospheric Pressure Non-Thermal Plasma By Diffusive And Constricted Discharges In Rest And Flowing Gases (Air And Nitrogen)  

NASA Astrophysics Data System (ADS)

Weekly ionized non-thermal plasma (NTP) is of great interest for many applications because of its strong non-equilibrium state wherein an average electron energy Te exceeds markedly gas temperature Tg, i.e. electrons in the NTP are strongly overheated compared to neutral gas. Energetic electrons due to frequent collisions with the neutrals excite and dissociate effectively atoms and molecules of the plasma-forming gas that results in a creation of physically-, and bio-chemically active gaseous medium in a practically cold background gas. At present there are many kinds of plasma sources working at low and atmospheric pressure and using MW, RF, low frequency, pulsed and DC power supplies for NTP generation. The NTP at atmospheric pressure is of considerable interest for practice. A reason is that sustaining the NTP at atmospheric pressure at first allows us to avoid the use of expensive vacuum equipment and second gives opportunity to use the NTP for treatment of the exhausted gases and polluted liquids. The second opportunity cannot be realized at all with use of the NTP at low pressure. Main subject of this talk is low current atmospheric pressure gas discharges powering with DC power supplies. Plasma forming gases are air and nitrogen which are much cheaper compared to rare gases like He or Ar. Besides, great interest to molecular nitrogen as plasma forming gas is caused first of all its unique capability to accumulate huge energy in vibration, electron (metastables) and dissociated (atomic) states providing high chemical reactivity of the activated nitrogen. All active particles mentioned above have a long lifetime, and they can be therefore transported for a long distance away from place of their generation. Different current modes (diffusive and constricted) of these discharges are discussed. Experimental and numerical results on generation of chemically active species in the diffusive and constricted mode are presented. Some data on the usage of the atmospheric pressure NTP for gas cleanup, surface treatment and sterilization are given.

Akishev, Y.; Grushin, M.; Karalnik, V.; Kochetov, I.; Napartovich A.; Trushkin N.

2010-07-01

322

Oxygen mass transfer in PEM fuel cell gas diffusion layers  

Microsoft Academic Search

A simple two-dimensional model involving kinetics and mass transfer in a PEM fuel cell cathode is presented. In this model, the catalyst layer was simplified as an infinite thin film. The oxygen mass transfer in the gas diffusion layer (GDL) was described using a pure diffusion equation that introduced equivalent oxygen diffusivity. The PEM fuel cell performance under the influence

K. T. Jeng; S. F. Lee; G. F. Tsai; C. H. Wang

2004-01-01

323

An in-situ method to measure a soil`s undisturbed pore gas radon concentration, diffusion length for radon and air filled porosity  

SciTech Connect

Previous work has shown that for soils of insignificant permeability (soils with permeability less than about 10{sup {minus}12} m{sup 2}) the important soil parameters for characterizing radon mobility in the soil`s steady-state pore gas radon concentration at depth (C{sub s}), the soil`s bulk diffusion length for radon (L) and the soil`s air filled porosity (p{sub a}). Existing methods to measure these parameters have been based wholly or in part on measurements of soil samples taken to a laboratory for analysis. The drawbacks of this approach are twofold: (1) since soil structure can be quite heterogeneous, the sample may not have characteristics indicative of the site as a whole, and (2) since the parameters are dependent on soil structure and the soil structure of the sample may be changed in the process of acquiring the sample, one may be changing the parameters that one is trying to measure. These problems can be avoided by using a totally in-situ method to measure C{sub s}, L, and p{sub a}. This paper describes a totally in-situ method for simultaneously measuring the important soil parameters, based on measurements of the radon concentration as a function of time for the gas in a cavity in the soil. 7 refs., 3 figs., 3 tabs.

Jarzemba, M.S.; Blue, T.E. [Ohio State Univ., Columbus, OH (United States)

1996-04-01

324

A probability density function Eulerian Monte Carlo field method for large eddy simulations: Application to a turbulent piloted methane/air diffusion flame (Sandia D)  

SciTech Connect

The Eulerian stochastic field method is applied to the solution of the modeled evolution equation for the subgrid joint probability density function (JPDF) of the reacting scalars in a large eddy simulation (LES) of a piloted methane/air diffusion flame (Sandia Flame D). A simple model for subgrid scale (SGS) stresses and fluxes and a global four-step mechanism for combustion are combined in the formulation. Test cases with varying mesh sizes and numbers of stochastic fields were completed. The differences in the results obtained with the two grids were very small and this indicates that the mesh resolution was sufficient. However, incorporation of the JPDF, via the stochastic field solution method, improved the quality of predictions significantly, particularly those quantities related to reaction, such as temperature. Eight stochastic fields were shown to be enough to characterize the influence of SGS fluctuations on filtered species formation rate to reasonable accuracy and at moderate computational cost. With the exceptions of H{sub 2} and CO, good agreement between measured and computed mean and RMS profiles of velocity, composition, and temperature was achieved. The discrepancies in H{sub 2} and CO concentrations are attributable to limitations in the global chemistry mechanism used in the LES. Overall the results serve to highlight the potential of the Eulerian stochastic field method in LES. (author)

Mustata, Radu; Valino, Luis; Jimenez, Carmen [LITEC Consejo Superior de Investigaciones Cientificas, Maria de Luna 10, 50018, Zaragoza (Spain); Jones, W.P.; Bondi, S. [Department of Mechanical Engineering, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom)

2006-04-15

325

A 4 V lithium manganese oxide cathode for rocking-chair lithium-ion cells  

Microsoft Academic Search

Composite cathodes for lithium-ion rocking-chair cells have been fabricated based on LiMn[sub 2]O[sub 4] which was synthesized by a new solution route that may be carried out in air. These cathodes have been cycled in three-electrode cells at discharge and charging current densities of 1 and 0.5 mA cm[sup [minus]2], respectively (corresponding to a discharge rate of C\\/2), between limits

Haitao Huang; P. G. Bruce

1994-01-01

326

Cathode properties of amorphous and crystalline FePO 4  

Microsoft Academic Search

FePO4 is an attractive rare-metal-free cathode active material. Simple and inexpensive new synthesis routes obtained from solution were investigated. P2O5 and Fe metal powders, both of which react in water at room temperature, were selected as inexpensive starting materials. Amorphous powders obtained through ball milling were annealed at various temperatures (100–650°C) in air. IR spectra showed that PO4 tetrahedra units

Shigeto Okada; Takafumi Yamamoto; Yasunori Okazaki; Jun-ichi Yamaki; Masahiro Tokunaga; Tetsuaki Nishida

2005-01-01

327

Fundamentals of cathodic protection interference  

SciTech Connect

The primary cause of cathodic interference was initially related to operation of direct current (DC) traction systems, such as rail systems, mining carts, and the like. Nowadays the increased use of impressed current cathodic protection (ICCP) systems for pipelines and other underground and submerged metallic structures has become another major cause of cathodic interference. With the requirements of cathodic protection (CP) installations on some underground storage tanks (USTs) and the renewed interest by municipalities installing DC traction light rail systems, a higher level of cathodic interference can be expected. Although interference may be caused by stray earth currents from many different sources, this discussion only concerns interference caused by earth currents produced by the operation of ICCP systems. All forms of interference correction require considerable field work and testing by knowledgeable and experienced personnel. It can be time consuming and therefore very expensive. Much of this expense can be saved if careful planning is done in the design stage before a CP installation is made.

Lichtenstein, J. [Corrosion Control Specialist, Inc., Park City, UT (United States)

1999-09-01

328

Improved Sinterability and Performance of Lanthanum Ferrite SOFC Cathodes  

SciTech Connect

Strontium-doped lanthanum ferrite (LSF) materials have shown considerable promise as solid oxide fuel cell (SOFC) cathodes. When used in conjunction with an anode-supported yttria-stabilized zirconia (YSZ) electrolyte assembly, power densities of 0.7-0.9 W/cm2 at 750 C and 0.7V can be achieved. However, this performance relies on the incorporation of a doped ceria interlayer between the YSZ electrolyte and LSF cathode. In the case of Sr-doped lanthanum manganites and cobaltites the ceria interlayer acts as a reaction barrier and prevents the formation of poorly conducting Sr- and La- zirconate phases. LSF, on the other hand, does not appear to react with YSZ to form the aforementioned zirconate phases even if reacted at 1400 C ({approx}250 C above the typical firing temperature for LSF). Instead, when sintered in direct contact with YSZ, Zr4+ cations diffuse into the perovskite where they occupy B-site positions, and result in decreased electrical (and possibly ionic) conductivity of the cathode. As expected the Zr diffusion exhibits thermal dependence, and is typically observed at temperatures ?1000 C. The current cathode of choice, La0.8Sr0.2FeO3-? (LSF-20), has an optimized (in terms of adherence and microstructure) sintering temperature of {approx}1150 C. Therefore, application of this cathode directly on YSZ results in the aforementioned LSF-YSZ interaction, and subsequently relatively poor performance. Hence, the need for the protective ceria interlayer. Recently, the authors have considered changes in the LSF-20 chemistry to facilitate enhanced cathode sintering <1000 C in an attempt to avoid the LSF-YSZ reaction. Modifications must be subtle in nature since high cation dopant levels can result in the formation of poorly conducting zirconate phases, typically observed with manganites and cobaltites. A composition that appears somewhat promising is a slightly A-site deficient lanthanum ferrite with a marginal amount of Cu dopant on the B-site, (La0.8Sr0.2)0.98Fe0.98Cu0.02O3-?. This composition can be sintered onto YSZ at 950 C, and to date has indicated power densities of 1.3-1.8 W/cm2 at 750 C and 0.7V ({approx}1.5-2.0 times greater than the performance exhibited for a cell with an LSF-20 cathode and ceria interlayer). Other transition metal dopants and degrees of non-stoichiometry are also under investigation.

Simner, Steve P.; Anderson, Michael D.; Stevenson, Jeffry W.

2003-10-01

329

Investigation of a Mercury-Argon Hot Cathode Discharge  

NASA Astrophysics Data System (ADS)

Classical absorption and laser induced fluorescence (LIF) experiments are used to investigate processes in the cathode region of a Hg-Ar hot cathode discharge. The absorption and LIF measurements are used to test the qualitative understanding and develop a quantitative model of a hot cathode discharge. The main contribution of this thesis is a model of the negative glow region that demonstrates the importance of Penning ionization to the ionization balance in the negative glow. We modeled the excited argon balance equation using a Monte Carlo simulation. In this simulation we used the trapped radiative decay rate of the resonance levels and the Penning ionization rate as the dominant loss terms in the balance equation. The simulated data is compared to and found to agree with absolute excited argon densities measured in a classical absorption experiment. We found the primary production rate per unit volume of excited Ar atoms in the simulation is sharply peaked near the cathode hot spot. We used the ion production rate from this simulation and a Green's function solution to the ambipolar diffusion equation to calculate the contribution of Penning ionization to the total ion density. We compared the results of this calculation to our experimental values of the Hg ^+ densities in the negative glow. We found that Penning ionization is an important and possibly the dominant ionization process in the negative glow.

Wamsley, Robert Charles

330

Pyrometric cathode temperature measurements in metal halide lamps  

NASA Astrophysics Data System (ADS)

Time-averaged temperature distributions along the electrodes of vertically operated high-intensity discharge lamps with cylindrical quartz burners filled with mercury and additives of NaI, TlI and DyI3 have been measured. The lamps have been driven by 120 Hz switched-dc currents between 0.4 and 1.78 A and the measurements have been performed during the cathodic phase at the lower electrode. All considered currents are characterized by a diffuse arc attachment. For the correction of disturbing effects the measured distributions have been fitted with solutions of the quasi-one-dimensional and steady-state energy balance of a rod-shaped tungsten cathode. A model of the near-cathode layer in a multi-species plasma has been applied for the determination of the boundary layer characteristics where the work function has been treated as a free parameter. The required plasma component concentrations have been estimated from spectroscopic measurements in the arc column. The fit procedure includes the adjustment of the extension of the lateral arc attachment region which has a distinct impact on the determined tip temperature, power input from the plasma into the cathode and the work function. For the latter the tungsten value has been verified in the pure Hg lamp, but strong deviations result in the case of a TlI admixture. The lamp with DyI3 clearly shows the gas-phase emitter effect of lowering the work function induced by Dy.

Schmidt, M.; Schneidenbach, H.; Kettlitz, M.

2013-10-01

331

Effect of cathode microstructure on arc velocity and erosion rate of cold cathodes in magnetically rotated atmospheric pressure arcs  

NASA Astrophysics Data System (ADS)

Atmospheric pressure arc velocity and arc erosion measurements were performed on thermal sprayed copper cathodes having grain size distributions from submicrometre to a few micrometres in a continuous running arc system. Ultrahigh purity (UHP), 99.99% pure, argon and a mixture of UHP argon with 10% (volumetric) extra dry air were used as plasma forming gases. An external magnetic field of 0.10 T was used to rotate the arc which was operated at a constant power setting of 6 kW (150 A and 40 V). Cathodes having different microstructures were formed using high velocity oxygen fuel (HVOF) spraying and vacuum plasma spraying (VPS) methods with different annealing times. HVOF sprayed cathodes were tested for arc erosion and arc velocity in their as-sprayed state and also after annealing them at 300 and 600 °C for 1 and 8 h durations in an inert argon atmosphere. VPS sprayed coatings were tested as-sprayed. The effect of the initial coating thickness on erosion rates was investigated. Annealing HVOF coatings at 600 °C for 8 h produced near equi-axed grains with a 2-3 µm average size. These coatings showed 60% higher steady state arc velocities and up to 68% lower erosion rates compared with massive copper cathodes having a 20-23 µm average grain size. VPS coatings having a 0.9-1.5 µm average grain size gave up to 70% lower erosion rates when compared with massive copper cathodes. The results show a clear effect of the cathode microstructure on the arc velocity and the erosion rate.

Rao, Lakshminarayana; Munz, Richard J.

2008-08-01

332

Geometrical Aspects of a Hollow-cathode Magnetron (HCM)  

SciTech Connect

A hollow-cathode magnetron (HCM), built by surrounding a planar sputtering-magnetron cathode with a hollow-cathode structure (HCS), is operable at substantially lower pressures than its planar-magnetron counterpart. We have studied the dependence of magnetron operational parameters on the inner diameter D and length L of a cylindrical HCS. Only when L is greater than L sub zero, a critical length, is the HCM operable in the new low-pressure regime. The critical length varies with HCS inner diameter D. Explanations of the lower operational pressure regime, critical length, and plasma shape are proposed and compared with a one-dimension diffusion model for energetic or primary electron transport. At pressures above 1 mTorr, an electron-impact ionization model with Bohm diffusion at a temperature equivalent to one-half the primary electron energy and with an ambipolar constraint can explain the ion-electron pair creation required to sustain the discharge. The critical length L sub zero is determined by the magnetization length of the primary electrons.

Cohen, Samuel, A.; Wang, Zhehui

1998-11-01

333

Innovative Diffusion Driven Desalination Process  

Microsoft Academic Search

An innovative diffusion driven desalination (DDD) process is presented, and its performance based on thermodynamic considerations is thoroughly explored. The desalination is driven by water vapor saturating dry air flowing through a diffusion tower. Liquid water is condensed out of the air\\/vapor mixture in a direct contact condenser. The desalination process is suitable for operation at low temperatures and may

James F. Klausner; Mohamed Darwish; Renwei Mei

2004-01-01

334

Hollow cathode arc - Effect of the cathode material on the internal plasma  

Microsoft Academic Search

In discharges with hollow cathodes functioning in the arc regime, the cathode emits thermionic electrons which ionize the gas. To reduce the electrical power consumed by these discharges, cathodes made of thoriated tungsten and lanthanum hexaboride have been used. The parameters of the plasma generated into the cathode have been measured with electrostatic probes.

A. Brunet

1975-01-01

335

Prediction and analysis of the cathode catalyst layer performance of proton exchange membrane fuel cells using artificial neural network and statistical methods  

Microsoft Academic Search

A mathematical model was developed to investigate the cathode catalyst layer (CL) performance of a proton exchange membrane fuel cell (PEMFC). A numerous parameters influencing the cathode CL performance are implemented into the CL agglomerate model, namely, saturation and eight structural parameters, i.e., ionomer film thickness covering the agglomerate, agglomerate radius, platinum and carbon loading, membrane content, gas diffusion layer

N. Khajeh-Hosseini-Dalasm; S. Ahadian; K. Fushinobu; K. Okazaki; Y. Kawazoe

2011-01-01

336

Investigating Microbial Fuel Cell Bioanode Performance Under Different Cathode Conditions  

SciTech Connect

A compact, three-in-one, flow-through, porous, electrode design with minimal electrode spacing and minimal dead volume was implemented to develop a microbial fuel cell (MFC) with improved anode performance. A biofilm-dominated anode consortium enriched under a multimode, continuous-flow regime was used. The increase in the power density of the MFC was investigated by changing the cathode (type, as well as catholyte strength) to determine whether anode was limiting. The power density obtained with an air-breathing cathode was 56 W/m3 of net anode volume (590 mW/m2) and 203 W/m3 (2160 mW/m2) with a 50-mM ferricyanide- based cathode. Increasing the ferricyanide concentration and ionic strength further increased the power density, reaching 304 W/m3 (3220 mW/m2, with 200 mM ferricyanide and 200 mM buffer concentration). The increasing trend in the power density indicated that the anode was not limiting and that higher power densities could be obtained using cathodes capable of higher rates of oxidation. The internal solution resistance for the MFC was 5 6 X, which supported the improved performance of the anode design. A new parameter defined as the ratio of projected surface area to total anode volume is suggested as a design parameter to relate volumetric and area-based power densities and to enable comparison of various MFC configurations.

Borole, Abhijeet P [ORNL; Hamilton, Choo Yieng [ORNL; Aaron, D [Georgia Institute of Technology; Tsouris, Costas [ORNL

2009-01-01

337

Novel Cathodes Prepared by Impregnation Procedures  

SciTech Connect

(1) We showed that similar results were obtained when using various LSM precursors to produce LSM-YSZ cathodes. (2) We showed that enhanced performance could be achieved by adding LSCo to LSMYSZ cathodes. (3) We have preliminary results showing that there is a slow deactivation with LSFYSZ cathodes.

Eduardo Paz

2006-09-30

338

Erosion structures on cathodes arced in vacuum  

Microsoft Academic Search

An analysis is presented of the structural changes which occur on cathode surfaces arced in vacuum. Cadmium, copper, molybdenum and tungsten cathodes carrying currents up to a few hundred amps showed a variety of erosion patterns which have been interpreted as representing a number of stages with different degrees of erosion. Cathode spots moving either randomly or under the influence

J. E. Daalder

1979-01-01

339

Theory of the hollow cathode arc  

Microsoft Academic Search

The hollow cathode is characterized by a plasma column inside its cavity, and the field-enhanced thermionic effect constitutes the basic emission mechanism of the cathode. In this paper, the flow of the neutral gas inside the cathode is studied, and the variation of the gas pressure and gas density along the tube is determined. The plasma column produced by the

C. M. Ferreira; J. L. Delcroix

1978-01-01

340

Hollow cathode and hybrid plasma processing  

Microsoft Academic Search

Generation and features of the radio frequency (rf) hollow cathode discharge (HCD) and its transition into the hollow cathode arc (HCA) are described. Rf linear hollow cathodes for generation of plasma over large areas and suitable for further scale-up are presented. Examples of surface processing and coating by PVD, both by HCD and HCA, are given. The hybrid reactor, combining

Hana Baránková; Ladislav Bardos

2006-01-01

341

Cathodic protection for prestressed concrete structures  

Microsoft Academic Search

Recently, corrosion of prestressing steel in concrete has been reported. One of the effective countermeasures to stop corrosion is cathodic protection. Cathodic protection has been applied to reinforced concrete structures so far. However, there are several uncertainties especially associated with applicability to prestressed concrete structures. The authors conducted a series of experiments using cathodic protection system on prestressed concrete structures

K Ishii; H Seki; T Fukute; K Ikawa

1998-01-01

342

Field Emitter Cathodes and Electric Propulsion Systems  

Microsoft Academic Search

Replacing hollow and filament cathodes with field emitter (FE) cathodes could significantly improve the scalability, power, and performance of some meso- and microscale Electric Propulsion (EP) systems. This article discusses the motivation and challenges of integrating of FE and Electric Propulsion systems. The demands on cathode performance and lifetime and the propulsion system environments are described in this article. The

Colleen M. Marrese; James E. Polk; Juergen Mueller

2000-01-01

343

Latex-bound lead chloride cathodes  

Microsoft Academic Search

Cathodes were made from lead chloride mixed with a conductive carbon (graphite, preferably with small additions of Shawinigan black). These dry mixes were blended with various synthetic rubber latexes in aqueous suspension, spread on an expanded metal grid, dried, and ultimately compressed to form the cathode. Of 16 latexes examined, UCAR 891 proved particularly suitable. Cathodes so made were assembled

J. R. Coleman

1976-01-01

344

H+ diffusion and electrochemical stability of Li1+x+yAlxTi2-xSiyP3-yO12 glass in aqueous Li/air battery electrolytes  

SciTech Connect

It is well known that LATP (Li1+x+y AlxTi2?x SiyP3?yO12) glass is a good lithium ion conductor. However, the interaction between LATP glass and H+ ions (including its diffusion and surface adsorption) needs to be well understood before the long-term application of LATP glass in an aqueous electrolyte based Li-air batteries where H+ always present. In this work, we investigate the H+ ion diffusion properties in LATP glass and their surface interactions using both experimental and modeling approaches. Our analysis indicates that the apparent H+ related current observed in the initial cyclic voltammetry scan should be attributed to the adsorption of H+ ions on the LATP glass rather than the bulk diffusion of H+ ions in the glass. Furthermore, the density functional theory calculations indicate that the H+ ion diffusion energy barrier (3.21 eV) is much higher than that of Li+ ion (0.79 eV) and Na+ ion (0.79 eV) in NASICON type LiTi2(PO4)3 material. As a result, the H+ ion conductivity in LATP glass is negligible at room temperature. However, significant surface corrosion was found after the LATP glass was soaked in strong alkaline electrolyte for extended time. Therefore, appropriate electrolytes have to be developed to prevent the corrosion of LATP glass before its practical application for Li-air batteries using aqueous electrolyte.

Ding, Fei; Xu, Wu; Shao, Yuyan; Chen, Xilin; Wang, Zhiguo; Gao, Fei; Liu, Xingjiang; Zhang, Jiguang

2012-09-15

345

Air cell  

NASA Astrophysics Data System (ADS)

The present invention relates to an air cell. This air cell provides a compact light-weight power source for model aircraft permitting them to fly for an extended period so that they may be used for such practical purposes as crop dusting, surveying, and photographing. The cell is comprised of a current collector so disposed between a magnesium, zinc, or aluminum alloy cathode and a petroleum graphite anode that it is in contact with the anode. The anode is formed by adding polytetrafluoroethylene dispersion liquid in a mixture of active carbon and graphite powder, pouring the mixture into a mold and heating it to form the anode. It is fabricated by a plurality of anode sections and is formed with at least one hole so that it can provide a cell which is compact in size and light in weight yet is capable of generating a high output. The anode, the cathode, and a separator are wetted by an electrolytic liquid. The electrolyte is continuously supplied through the life of the cell.

Okamura, Okiyoshi; Wakasa, Masayuki; Tamanoi, Yoshihito

1991-04-01

346

A metal-dielectric cathode  

NASA Astrophysics Data System (ADS)

In order to improve the pulse repetition rate and the maintenance-free lifetime of an improved magnetically insulated transmission line oscillator (MILO) previously developed in our laboratory, a metal-dielectric cathode is investigated experimentally. It consists of three components: a stainless steel base, bronze foils, and double-sided printed boards. The experimental results show that the shot-to-shot reproducibility of the diode voltage and current is very good and the performances of the improved MILO are steady. In addition, no observable degradation could be detected in the emissive characteristic of the metal-dielectric cathode after 350 shots. The experimental results prove that the metal-dielectric cathode is a promising cathode for repetitively pulsed MILO operation. However, the leading edge of the radiated microwave pulse is gradually delayed during the repetition rate. A likely reason is that high pressure results in gas ionization in the beam-microwave interaction region, and plasma formation delays the time that the improved MILO achieves nonlinear steady state.

Fan, Yu-Wei; Zhong, Hui-Huang; Li, Zhi-Qiang; Yang, Han-Wu; Shu, Ting; Zhou, Heng; Yuan, Cheng-Wei; Zhang, Jun; Luo, Ling

2008-07-01

347

Cathodic protection system inspection 5  

NASA Astrophysics Data System (ADS)

The rectifier is the heart of an impressed current cathodic protection system. As it is subject to many adverse conditions including power surges, lightning strikes, vandalism, physical damage, and deterioration from atmospheric exposure, frequent inspections of rectifiers are vital to keeping an impressed current system operating so that it can provide nearly continuous protection of the underground, or submerged structures that are being protected.

Jenkins, Jim; Polly, Dan

1994-02-01

348

Offshore platform cathodic protection retrofits  

SciTech Connect

Cathodic protection (CP) is the primary technique used for underwater corrosion control on the majority of offshore steel structures. Offshore platforms are often kept in service far beyond their original design life. Refurbishment of the CP system is required when adequate protection can no longer be maintained. Various offshore platform CP retrofit designs are discussed.

Turnipseed, S.P. [Chevron Research and Technology Co., Richmond, CA (United States)

1996-10-01

349

Cathode for molten salt batteries  

DOEpatents

A molten salt electrochemical system for battery applications comprises tetravalent sulfur as the active cathode material with a molten chloroaluminate solvent comprising a mixture of AlCl.sub.3 and MCl having a molar ratio of AlCl.sub.3 /MCl from greater than 50.0/50.0 to 80/20.

Mamantov, Gleb (Knoxville, TN); Marassi, Roberto (Camerino, IT)

1977-01-01

350

Mechanistic modelling of a cathode-supported tubular solid oxide fuel cell  

Microsoft Academic Search

A two-dimensional mechanistic model of a tubular solid oxide fuel cell (SOFC) considering momentum, energy, mass and charge transport is developed. The model geometry of a single cell comprises an air-preheating tube, air channel, fuel channel, anode, cathode and electrolyte layers. The heat radiation between cell and air-preheating tube is also incorporated into the model. This allows the model to

R. Suwanwarangkul; E. Croiset; M. D. Pritzker; M. W. Fowler; P. L. Douglas; E. Entchev

2006-01-01

351

Diffusion, Osmosis, and Dialysis  

NSDL National Science Digital Library

Materials such as water, nutrients, dissolved gases, ions and waste are constantly moving across a cell's membrane. In this activity, students interact with models of diffusion and osmosis and observe the net flow of molecules in air, in cells, and across a cell's semi-permeable membrane. Students will be able to: Determine that diffusion results from random motion and/or collisions of particles; learn that particles diffuse from high concentration to low concentration; explore simple diffusion across a semi-permeable membrane; connect the process to dialysis.

Project, Molecular L.

352

High-emission cold cathode  

DOEpatents

A field-emission cathode having a multitude of field emission points for emitting a copious stream of electrons when subjected to a high field is described. The cathode is constructed by compressing a multitude of tungsten strips alternately arranged with molybdenum strips and copper ribbons or compressing alternately arranged copper plated tungsten and molybdenum strips, heating the arrangement to braze the tungsten and molybdenum strips together with the copper, machining and grinding the exposed strip edges of one side of the brazed arrangement to obtain a precisely planar surface, etching a portion of the molybdenum and copper to leave the edges of the tungsten strips protruding for electron emission, and subjecting the protruding edges of the tungsten strips to a high electric field to degas and roughen the surface to pnovide a large number of emitting points. The resulting structure is particularly useful as a cathode in a transversely excited gaseous laser where the cathode is mounted in a vacuum chamber for emitting electrons under the influence of a high electric field between the cathode and an extractor grid. The electrons pass through the extractor grid, a thin window in the wall of the laser chamber and into the laser chamber which is filled with a gaseous mixture of helium, nitrogen, and carbon dioxide. A second grid is mounted on the gaseous side of the window. The electrons pass into the laser chamber under the influence of a second electric field between the second grid and an anode in the laser chamber to raise selected gas atoms of the gaseous mixture to appropriately excited states so that a subsequent coherent light beam passing through the mixture transversely to the electron stream through windows in opposite ends of the laser chamber stimulates the excited atoms to amplify the beam. (Official Gazette)

Mancebo, L.

1974-01-29

353

New Cathode Materials for Intermediate Temperature Solid Oxide Fuel Cells  

SciTech Connect

Operation of SOFCs at intermediate temperatures (500-800 C) requires new combinations of electrolyte and electrode materials that will provide both rapid ion transport across the electrolyte and electrode-electrolyte interfaces and efficient electrocatalysis of the oxygen reduction and fuel oxidation reactions. This project concentrates on materials and issues associated with cathode performance that are known to become limiting factors as the operating temperature is reduced. The specific objectives of the proposed research are to develop cathode materials that meet the electrode performance targets of 1.0 W/cm{sup 2} at 0.7 V in combination with YSZ at 700 C and with GDC, LSGM or bismuth oxide based electrolytes at 600 C. The performance targets imply an area specific resistance of {approx}0.5 {Omega}cm{sup 2} for the total cell. The research strategy is to investigate both established classes of materials and new candidates as cathodes, to determine fundamental performance parameters such as bulk diffusion, surface reactivity and interfacial transfer, and to couple these parameters to performance in single cell tests. In this report, further measurements of the oxygen deficient double perovskite PrBaCo{sub 2}O{sub 5.5+{delta}} are reported. The high electronic conductivity and rapid diffusion and surface exchange kinetics of PBCO suggest its application as cathode material in intermediate temperature solid oxide fuel cells. Preliminary measurements in symmetric cells have shown low ASR values at 600 C. Here we describe the first complete cell measurements on Ni/CGO/CGO/PBCO/CGO cells.

Allan J. Jacobson

2006-06-30

354

New Cathode Materials for Intermediate Temperature Solid Oxide Fuel Cells  

SciTech Connect

Operation of SOFCs at intermediate temperatures (500-800 C) requires new combinations of electrolyte and electrode materials that will provide both rapid ion transport across the electrolyte and electrode--electrolyte interfaces and efficient electrocatalysis of the oxygen reduction and fuel oxidation reactions. This project concentrates on materials and issues associated with cathode performance that are known to become limiting factors as the operating temperature is reduced. The specific objectives of the proposed research are to develop cathode materials that meet the electrode performance targets of 1.0 W/cm{sup 2} at 0.7 V in combination with YSZ at 700 C and with GDC, LSGM or bismuth oxide based electrolytes at 600 C. The performance targets imply an area specific resistance of {approx}0.5 {Omega}cm{sup 2} for the total cell. The research strategy is to investigate both established classes of materials and new candidates as cathodes, to determine fundamental performance parameters such as bulk diffusion, surface reactivity and interfacial transfer, and to couple these parameters to performance in single cell tests. In this report, the oxygen exchange kinetics of a P2 composition are described in detail. The oxygen exchange kinetics of the oxygen deficient double perovskite LnBaCo{sub 2}O{sub 5.5+{delta}} (Ln=Pr and Nd) have been determined by electrical conductivity relaxation. The high electronic conductivity and rapid diffusion and surface exchange kinetics of PBCO suggest its application as cathode material in intermediate temperature solid oxide fuel cells.

Allan J. Jacobson

2005-11-17

355

Conflicting roles of nickel in controlling cathode performance in lithium ion batteries.  

PubMed

A variety of approaches are being made to enhance the performance of lithium ion batteries. Incorporating multivalence transition-metal ions into metal oxide cathodes has been identified as an essential approach to achieve the necessary high voltage and high capacity. However, the fundamental mechanism that limits their power rate and cycling stability remains unclear. The power rate strongly depends on the lithium ion drift speed in the cathode. Crystallographically, these transition-metal-based cathodes frequently have a layered structure. In the classic wisdom, it is accepted that lithium ion travels swiftly within the layers moving out/in of the cathode during the charge/discharge. Here, we report the unexpected discovery of a thermodynamically driven, yet kinetically controlled, surface modification in the widely explored lithium nickel manganese oxide cathode material, which may inhibit the battery charge/discharge rate. We found that during cathode synthesis and processing before electrochemical cycling in the cell nickel can preferentially move along the fast diffusion channels and selectively segregate at the surface facets terminated with a mix of anions and cations. This segregation essentially can lead to a higher lithium diffusion barrier near the surface region of the particle. Therefore, it appears that the transition-metal dopant may help to provide high capacity and/or high voltage but can be located in a "wrong" location that may slow down lithium diffusion, limiting battery performance. In this circumstance, limitations in the properties of lithium ion batteries using these cathode materials can be determined more by the materials synthesis issues than by the operation within the battery itself. PMID:22985059

Gu, Meng; Belharouak, Ilias; Genc, Arda; Wang, Zhiguo; Wang, Dapeng; Amine, Khalil; Gao, Fei; Zhou, Guangwen; Thevuthasan, Suntharampillai; Baer, Donald R; Zhang, Ji-Guang; Browning, Nigel D; Liu, Jun; Wang, Chongmin

2012-09-19

356

Study of Discharging Characteristics of Hollow Cathode Surge Protective Gap  

NASA Astrophysics Data System (ADS)

A hollow cathode surge protective gap (HCSPG) was designed, and the discharge characteristics was investigated in an air and nitrogen gas environment. For both the gap spacing D and the hole diameter varphi of HCSPG of 3 mm, the voltage protective value Up of HCSPG is about 3.5 kV and its converting time tc exceeds 100 ns at an air pressure from 10 Pa to 100 Pa. The maximum converting time tc from glow to arc discharging reaches 1600 ns at an air pressure of 100 Pa, while the minimum converting time tc is 120 ns at 10 Pa. For a triggered HCSPG, Up is reduced to about 1.6 kV while the converting time is 120 ns with a semiconductor trigger device and 50 ns with a dielectric porcelain trigger device under an air pressure of 100 Pa.

Yao, Xueling; Chen, Jingliang; Xu, Xiaowei; Liu, Yong; Zhao, Yong

2010-02-01

357

Electrical isolation method improves cathodic protection  

SciTech Connect

Cathodically protected structures often require seemingly incompatible requirements. Ideally, a cathodically protected system should be isolated; yet if the system contains electrical equipment, it must also be grounded. Isolation and grounding are conflicting demands inherent in any system that contains electrical equipment and uses cathodic protection (CP) to mitigate corrosion. Cathodic protection of many structures can be greatly simplified by the proper use of direct current (DC) isolating/alternate current (AC) coupling devices. An example is DC isolation of cathodically protected structures from electrical grounding systems while retaining AC continuity with those systems as required by electrical codes.

Tachick, H.N. [Dairyland Electrical Industries, Stoughton, WI (United States)

1997-08-01

358

Cathodes for ceria-based fuel cells  

SciTech Connect

Work is underway to develop a solid oxide fuel cell that has a ceria-based electrolyte and operates at lower temperatures (500-600{degrees}C) than conventional zirconia-based cells. At present the performance of this ceria-based solid oxide fuel cell is limited by the polarization of conventional cathode materials. The performance of alternative cathodes was measured by impedance spectroscopy and dc polarization. The performance was found to improve by using a thin dense interface layer and by using two-phase cathodes with an electrolyte and an electronic phase. The cathode performance was also found to increase with increasing ionic conductivity for single phase cathodes.

Doshi, R.; Krumpelt, M. [Argonne National Lab., IL (United States); Ricvhards, V.L. [Tri-State Univ., Angola, IN (United States). Dept. of Mech. & Aerospace Engr.

1997-08-01

359

Air Pollution.  

ERIC Educational Resources Information Center

|The purpose of this book is to describe the basic mechanisms whereby pollution is transported and diffused in the atmosphere. It is designed to give practitioners an understanding of basic mechanics and physics so they may have a correct basis on which to formulate their decisions related to practical air pollution control problems. Since many…

Scorer, Richard S.

360

Air Pollution.  

ERIC Educational Resources Information Center

The purpose of this book is to describe the basic mechanisms whereby pollution is transported and diffused in the atmosphere. It is designed to give practitioners an understanding of basic mechanics and physics so they may have a correct basis on which to formulate their decisions related to practical air pollution control problems. Since many…

Scorer, Richard S.

361

Considerations of the Role of the Cathodic Region in Localized Corrosion  

SciTech Connect

The ability of wetted cathodes of limited area to support localized corrosion sites on passive materials exposed to atmospheric conditions was studied computationally. The analysis pertains to conditions where metal surfaces are covered by thin layers of moisture in contrast to conditions of full immersion. The moisture may be a continuous layer or in patches with and without particulate on the surface. These conditions are of interest for the surfaces of the waste packages at the proposed Yucca Mountain Repository where waste packages are supported in air. The cathode capacity was characterized by the total net cathodic current, I{sub net}, which the surface surrounding a localized corrosion site (i.e., a pit or crevice) could supply. The cathode capacity increases with increasing cathode area, but it saturates at finite cathode sizes due to the resistance of the thin electrolyte layer. The magnitude of the capacity depends on the water layer thickness, the solution conductivity, and the electrochemical reaction kinetics. The presence of particulates is treated by considering both volume and surface coverage effects. The limited electrolyte volume under thin film conditions can lead to rapid pH changes which decrease the cathode capacity due to the slower electrochemical kinetics at elevated pH. These effects can make localized corrosion less likely to be sustained.

R.G. Kelly; A. Agarwal; F. Cui; X. Shan; U. Landau; J.H. Payer

2006-03-17

362

Air Dehydration Membranes for Nonaqueous Lithium-Air Batteries  

Microsoft Academic Search

In this paper, several types of new membranes were innovated and used as an O2-selective and H2O barrier films attached onto the cathode of non-aqueous Li-air batteries for continuous supplying of dry air into the batteries from ambient air. The membranes were prepared by depositing an O2\\/H2O selective coating layer on the exterior surface of a newly-invented thin porous Ni

Jian Zhang; Wu Xu; Xiaohong S. Li; Wei Liu

2010-01-01

363

LOW TEMPERATURE CATHODE SUPPORTED ELECTROLYTES  

SciTech Connect

This project has three main goals: Thin Films Studies, Preparation of Graded Porous Substrates and Basic Electrical Characterization and testing of Planar Single Cells. This period has continued to address the problem of making dense 1/2 to 5 {micro}m thick dense layers on porous substrates (the cathode LSM). Our current status is that we are making structures of 2-5 cm{sup 2} in area, which consist of either dense YSZ or CGO infiltrated into a 2-5 {micro}m thick 50% porous layer made of either nanoncrystalline CGO or YSZ powder. This composite structure coats a macroporous cathode or anode; which serves as the structural element of the bi-layer structure. These structures are being tested as SOFC elements. A number of structures have been evaluated both as symmetrical and as button cell configuration. Results of this testing indicates that the cathodes contribute the most to cell losses for temperatures below 750 C. In this investigation different cathode materials were studied using impedance spectroscopy of symmetric cells and IV characteristics of anode supported fuel cells. Cathode materials studied included La{sub 0.8}Sr{sub 0.2}Co{sub 0.2}Fe{sub 0.8}O{sub 3} (LSCF), La{sub 0.7}Sr{sub 0.2}MnO{sub 3} (LSM), Pr{sub 0.8}Sr{sub 0.2}Fe{sub 0.8}O{sub 3} (PSCF), Sm{sub 0.8}Sr{sub 0.2}Co{sub 0.2}Fe{sub 0.8}O{sub 3} (SSCF), and Yb{sub .8}Sr{sub 0.2}Co{sub 0.2}Fe{sub 0.8}O{sub 3} (SSCF). A new technique for filtering the Fourier transform of impedance data was used to increase the sensitivity of impedance analysis. By creating a filter specifically for impedance spectroscopy the resolution was increased. The filter was tailored to look for specific circuit elements like R//C, Warburg, or constant phase elements. As many as four peaks can be resolved using the filtering technique on symmetric cells. It may be possible to relate the different peaks to material parameters, like the oxygen exchange coefficient. The cathode grouped in order from lowest to highest ASR is LSCF < PSCF < SSCF < YSCF < LSM. The button cell results agree with this ordering indicating that this is an important tool for use in developing our understanding of electrode behavior in fuel cells.

Harlan U. Anderson; Fatih Dogan; Vladimir Petrovsky

2002-03-31

364

Symposium on multiple source urban diffusion models  

Microsoft Academic Search

The Meteorology Division of the National Air Pollution Control Administration and the North Carolina Air Pollution Consortium are sponsoring a symposium on Multiple Source Urban Diffusion Models scheduled for October 2730, 1969, at the University of North Carolina. The symposium will be devoted to the presentation and discussion of papers on mathematical models of transport and diffusion of air pollution

Anonymous

1969-01-01

365

Effect of formation of biofilms and chemical scale on the cathode electrode on the performance of a continuous two-chamber microbial fuel cell.  

PubMed

A two-chamber MFC system was operated continuously for more than 500 days to evaluate effects of biofilm and chemical scale formation on the cathode electrode on power generation. A stable power density of 0.57 W/m(2) was attained after 200 days operation. However, the power density decreased drastically to 0.2 W/m(2) after the cathodic biofilm and chemical scale were removed. As the cathodic biofilm and chemical scale partially accumulated on the cathode, the power density gradually recovered with time. Microbial community structure of the cathodic biofilm was analyzed based on 16S rRNA clone libraries. The clones closely related to Xanthomonadaceae bacterium and Xanthomonas sp. in the Gammaproteobacteria subdivision were most frequently retrieved from the cathodic biofilm. Results of the SEM-EDX analysis revealed that the cation species (Na(+) and Ca(2+)) were main constituents of chemical scale, indicating that these cations diffused from the anode chamber through the Nafion membrane. However, an excess accumulation of the biofilm and chemical scale on the cathode exhibited adverse effects on the power generation due to a decrease in the active cathode surface area and an increase in diffusion resistance for oxygen. Thus, it is important to properly control the formation of chemical scale and biofilm on the cathode during long-term operation. PMID:20923722

Chung, Kyungmi; Fujiki, Itto; Okabe, Satoshi

2010-05-23

366

Hydrothermal synthesis of cathode materials  

Microsoft Academic Search

A number of cathodes are being considered for the next generation of lithium ion batteries to replace the expensive LiCoO2 presently used. Besides the layered oxides, such as LiNiyMnyCo1?2yO2, a leading candidate is lithium iron phosphate with the olivine structure. Although this material is inherently low cost, a manufacturing process that produces electrochemically active LiFePO4 at a low cost is

Jiajun Chen; Shijun Wang; M. Stanley Whittingham

2007-01-01

367

Conservation in cathodic protection design  

SciTech Connect

Sacrificial anode cathodic protection offers cost-effective corrosion protection of submerged marine structures. The longevity of the protection systems can be estimated with a limited degree of accuracy. Some intentional overcapacity must be included in the design. Specific parameters are defined with an intrinsic conservatism, to provide adequate reliability, thereby avoiding high overcapacity and high potential costs associated with subsea retrofitting of anodes, if the design proves to be insufficient.

Sydberger, T.; Edwards, J.D.; Tiller, I.B. [Det Norske Veritas, Hovik (Norway)

1997-02-01

368

Cathodic phenomena in aluminum electrowinning  

NASA Astrophysics Data System (ADS)

Although aluminum is one of the world's highest production-volume primary metals, it is particularly costly to produce for a variety of factors, not the least of which are the expenses associated with electrolytic reduction. Based on the scale of global aluminum processing, even minor improvements in the electrowinning technology can result in significant savings of resources. Thus, from this perspective, the following reviews recent studies of cathodic phenomena in aluminum electrowinning.

Bouteillon, J.; Poignet, J. C.; Rameau, J. J.

1993-02-01

369

Arc-cathode interaction study  

NASA Astrophysics Data System (ADS)

Insufficient electrode life and uncertainties in that life are major problems hampering the development in many plasma application areas which make use of plasma torches, arc heaters, and arc jet thrusters. In spite of a considerable amount of work published dealing with arc-cathode phenomena, our present understanding is still incomplete because different physical phenomena dominate for different combinations of experimental parameters. The objective of our present research project is to gain a better understanding of the behavior of arc-cathode surface interaction over a wide range of parameters, and furthermore to develop guidelines for better thermal design of the electrode and the selection of materials. This report will present the research results and progress obtained on the arc-cathode interaction studies at the University of Minnesota. It includes results which have been obtained under programs other than the NASA funded program. Some of the results have been submitted in an informal interim progress report, and all of the results have been presented in a seminar during a visit to the NASA Lewis Research Center on October 16, 1992.

Zhou, X.; Heberlein, J.

1992-12-01

370

Prediction of the cathodic arc root behaviour in a hollow cathode thermal plasma torch  

NASA Astrophysics Data System (ADS)

The upper part of a well type cathode (WTC) plasma torch is modelled for several conditions in an air medium in the presence of an electric arc. The plasma flow created by the electric arc is described and the results compared with the data from the literature. Special attention is paid to the description of arc root attachment and to its movement due to the balance of forces. A fine description of the magnetic field produced by the external solenoid is reported. The model is based on the @Fluent software implemented with specific developments to be adapted to the thermal plasma domain. The paper shows the necessity to provide an accurate description of the external magnetic field due to the strong influence of the radial magnetic field component. Overall, we propose an original approach for arc root movement description which contributes to the understanding of the flow behaviour in the WTC torch.

Freton, Pierre; Gonzalez, Jean-Jacques; Escalier, Gaelle

2009-10-01

371

Conflicting Roles Of Nickel In Controlling Cathode Performance In Lithium-ion Batteries  

SciTech Connect

A variety of approaches are being made to enhance the performance of lithium ion batteries. Incorporating multi-valence transition metal ions into metal oxide cathodes has been identified as an essential approach to achieve the necessary high voltage and high capacity. However, the fundamental mechanism that limits their power rate and cycling stability remains unclear. The power rate strongly depends on the lithium ion drift speed in the cathode. Crystallographically, these transition metal-based cathodes frequently have a layered structure. In the classic wisdom, it is accepted that lithium ion travels swiftly within the layers moving out/in of the cathode during the charge/discharge. Here, we report the unexpected discovery of a thermodynamically driven, yet kinetically controlled, surface modification in the widely explored lithium nickel manganese oxide cathode material, which may inhibit the battery charge/discharge rate. We found that during cathode synthesis and processing before electrochemical cycling in the cell nickel can preferentially move along the fast diffusion channels and selectively segregate at the surface facets terminated with a mix of anions and cations. This segregation essentially blocks the otherwise fast out/in pathways for lithium ions during the charge/discharge. Therefore, it appears that the transition metal dopant may help to provide high capacity and/or high voltage, but can be located in a “wrong” location that blocks or slows lithium diffusion, limiting battery performance. In this circumstance, limitations in the properties of Li-ion batteries using these cathode materials can be determined more by the materials synthesis issues than by the operation within the battery itself.

Gu, Meng; Belharouak, Ilias; Genc, Arda; Wang, Zhiguo; Wang, Dapeng; Amine, Khalil; Gao, Fei; Zhou, Guangwen; Thevuthasan, Suntharampillai; Baer, Donald R.; Zhang, Jiguang; Browning, Nigel D.; Liu, Jun; Wang, Chong M.

2012-09-17

372

A pulsed cathodic arc spacecraft propulsion system  

NASA Astrophysics Data System (ADS)

We investigate the use of a centre-triggered cathodic arc as a spacecraft propulsion system that uses an inert solid as a source of plasma. The cathodic vacuum arc produces almost fully ionized plasma with a high exhaust velocity (>104 m s-1), giving a specific impulse competitive with other plasma or ion thrusters. A centre trigger design is employed that enables efficient use of cathode material and a high pulse-to-pulse repeatability. We compare three anode geometries, two pulse current profiles and two pulse durations for their effects on impulse generation, energy and cathode material usage efficiency. Impulse measurement is achieved through the use of a free-swinging pendulum target constructed from a polymer material. Measurements show that impulse is accurately controlled by varying cathode current. The cylindrical anode gave the highest energy efficiency. Cathode usage is optimized by choosing a sawtooth current profile. There is no requirement for an exhaust charge neutralization system.

Neumann, P. R. C.; Bilek, M. M. M.; Tarrant, R. N.; McKenzie, D. R.

2009-11-01

373

New Cathode Materials for Intermediate Temperature Solid Oxide Fuel Cells  

SciTech Connect

Operation of SOFCs at intermediate temperatures (500-800 C) requires new combinations of electrolyte and electrode materials that will provide both rapid ion transport across the electrolyte and electrode - electrolyte interfaces and efficient electrocatalysis of the oxygen reduction and fuel oxidation reactions. This project concentrates on materials and issues associated with cathode performance that are known to become limiting factors as the operating temperature is reduced. The specific objectives of the proposed research are to develop cathode materials that meet the electrode performance targets of 1.0 W/cm{sup 2} at 0.7 V in combination with YSZ at 700 C and with GDC, LSGM or bismuth oxide based electrolytes at 600 C. The performance targets imply an area specific resistance of {approx}0.5 {Omega}cm{sup 2} for the total cell. The research strategy is to investigate both established classes of materials and new candidates as cathodes, to determine fundamental performance parameters such as bulk diffusion, surface reactivity and interfacial transfer, and to couple these parameters to performance in single cell tests. The initial choices for study are perovskite oxides based on Sr substituted LaFeO{sub 3}, where significant data in single cell tests exists at PNNL for cathodes on both YSZ and CSO/YSZ, and Ln{sub 2}NiO{sub 4} compositions. A key component of the research strategy is to evaluate for each cathode material composition, the key performance parameters, including ionic and electronic conductivity, surface exchange rates, stability with respect to the specific electrolyte choice, and thermal expansion coefficients. Results on electrical conductivity relaxation measurements on additional compositions in the La{sub 2}NiO{sub 4+x} and Pr{sub 2}NiO{sub 4+x} series are presented in this report. Studies of the inter-diffusion of amorphous SrFeO{sub 3-x} and LaFeO{sub 3-x} bilayer films prepared by pulsed laser deposition are described. Such studies are a preliminary to the combinatorial synthesis approach discussed in previous reports.

Allan J. Jacobson

2004-07-23

374

Use of Air Diffusers to Improve Ambient Water Quality Parameters for Fish and Benthic Invertebrates in a Small Missouri Impoundment. Dingell-Johnson Project F-1-R-50.  

National Technical Information Service (NTIS)

A diffuser-style aeration system was installed in Perry County Community Lake (42 ha) during June 1997. The study objective was to examine the effectiveness, performance, and total benefits (i.e. fish growth, invertebrate production, zooplankton dynamics,...

S. A. Fischer

2001-01-01

375

Virtual Cathode Theory and Design of a Millimeter Wave VIRCATOR (Virtual Cathode Oscillator).  

National Technical Information Service (NTIS)

The theory of a virtual cathode oscillator and detailed experimental design of a millimeter wave virtual cathode oscillator (VIRCATOR) are presented. It is found that second order analytical approximations give an accurate value for the space-charge limit...

D. J. Sullivan D. E. Voss W. M. Bollen R. H. Jackson E. A. Coutsias

1983-01-01

376

Combustor air flow control method for fuel cell apparatus  

Microsoft Academic Search

A method for controlling the heat output of a combustor in a fuel cell apparatus to a fuel processor where the combustor has dual air inlet streams including atmospheric air and fuel cell cathode effluent containing oxygen depleted air. In all operating modes, an enthalpy balance is provided by regulating the quantity of the air flow stream to the combustor

Bruce J. Clingerman; Kenneth D. Mowery; Eugene V. Ripley

2001-01-01

377

Interrelationship between marine biofouling and cathodic protection  

SciTech Connect

Microorganisms colonize and form a gelatinous biofilm on all engineering materials exposed in natural marine environments, including cathodically protected surfaces. The impact of cathodic protection (CP) potentials on the chemical/biological composition of the biofilm and the impact of the biofilms on potentials required for CP have been the subject of many recent investigations. Literature on these subjects will be reviewed with emphasis on clarifying interactions between living and nonliving deposits on cathodically protected metal surfaces.

Little, B.J.; Wagner, P.A. (Naval Research Lab., Stennis Space Center, MS (United States))

1993-09-01

378

Cathodic casing protection using solar panels  

Microsoft Academic Search

A pilot system using solar cell panels for electrocorrosion protection of cathodic casings, installed on 11 well casings in August 1975, and consisting of 10 impressed-type groundbeds using solar panels and one sacrificial-type groundbed, is studied for effectiveness and expediting a combination of cathodic protection and solar cell technologies. The well casings require 1-2 amp to achieve cathodic protection. Soil

C. M. Wylie Jr.

1976-01-01

379

A direct density modulation cathode in magnetron  

NASA Astrophysics Data System (ADS)

A direct Density Modulation Cathode (DMC) in magnetron is proposed in this paper. By removing the velocity modulation process, electron spokes corresponding to the dominant operating mode can be quickly formed when the DMC is used. Based on theoretical analysis, particle-in-cell simulations and experimental investigations are carried out for demonstration. The final results show that compared with conventional solid cathode and transparent cathode, the DMC can increase 68% and even 146% of relative microwave widths, respectively.

Li, Wei; Zhang, Jun; Liu, Yong-gui; Yang, Han-wu; Shu, Ting

2013-09-01

380

Electrochemical impedance spectroscopy studies of lithium diffusion in doped manganese oxide  

Microsoft Academic Search

Cathode performance is critical to lithium ion rechargeable battery performance; effects of doping lithium manganese oxide cathode materials on cathode performance are being investigated. In this paper, Li diffusion in Al-doped LiMnâOâ was studied and found to be controlled by the quantity of Al dopant. Electrochemical cycling was conducted at 0.5mA\\/cmâ; electrochemical impedance spectra were taken at open circuit potential,

B. J. Johnson; D. H. Doughty; J. A. Voigt; T. J. Boyle

1996-01-01

381

Effect of gas and cathode material on the r.f. hollow cathode reactive PVD  

Microsoft Academic Search

The process of generation of the radio frequency (r.f.) hollow cathode discharge was examined for different gases and different materials of the r.f. electrode. The delivered r.f. power range used in the experiments enabled analysis of the hollow cathode discharge development together with the transition into the hollow cathode arc for selected combinations of cathode materials and gases. The results

H. Baránková; L. Bárdoš

1999-01-01

382

Emission properties of explosive field emission cathodes  

SciTech Connect

The research results of the explosive field emission cathode plasma expansion velocity and the initial emission area in the planar diode configuration with cathodes made of graphite, stainless steel, polymer velvet, carbon coated, and carbon fiber (needle type) cathodes are presented. The experiments have been performed at the electron accelerator LIA-200 (200 kV, 100 ns, and 4 kA). The diode voltage has been varied from 28-225 kV, whereas the current density has been varied from 86-928 A/cm{sup 2} with 100 ns pulse duration. The experimentally obtained electron beam diode perveance has been compared with the 1 dimensional Child-Langmuir- law. It was found that initially only a part of the cathode take part in the emission process. The plasma expands at 1.7-5.2 cm/{mu}s for 4 mm anode-cathode gap for various cathode materials. It was found that the plasma expansion velocity increases with the decrease in the cathode diameter. At the beginning of the accelerating pulse, the entire cathode area participates in the electron emission process only for the multiple needle type carbon fiber cathode.

Roy, Amitava; Patel, Ankur; Menon, Rakhee; Sharma, Archana; Chakravarthy, D. P. [Accelerator and Pulse Power Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Patil, D. S. [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

2011-10-15

383

Phthalocyanine cathode materials for secondary lithium cells  

SciTech Connect

Discharge and charge characteristics of various phthalocyanine cathodes coupled with lithium metal are studied. The best capacity based only on cathode active material weight is 1440 A-hr/kg in the lithium/iron phthalocyanine system, and the cycle life of the lithium/Cu phthalocyanine system is more than 100 times at the discharge depth of 157 A-hr/kg. The cathode reaction mechanism is supposed to be lithium intercalation between phthalocyanine molecules. The results indicate that these phthalocyanines are promising cathode active materials for lithium secondary batteries. 15 refs.

Yamaki, J.; Yamaji, A.

1982-01-01

384

Phthalocyanine cathode materials for secondary lithium cells  

SciTech Connect

Discharge and charge characteristics of various phthalocyanine cathodes coupled with lithium metal are studied. The best capacity based only on cathode active material weight is 1440 A-hr/kg in the lithium/iron phthalocyanine system, and the cycle life of the lithium/Cu phthalocyanine system is more than 100 times at the discharge depth of 157 A-hr/kg. The cathode reaction mechanism is supposed to be lithium intercalation between phthalocyanine molecules. The results indicate that these phthalocyanines are promising cathode active materials for lithium secondary batteries.

Tamaki, J.; Yamaji, A.

1982-01-01

385

Copper cathode erosion by an electric arc - the causes of the variations of the erosion rate with the electrode gap  

NASA Astrophysics Data System (ADS)

In this paper we present a study concerning the influence of the electrode gap on the erosion of a copper cathode under the sole action of an electric arc in air at atmospheric pressure. The causes of the variations of the erosion rate with this parameter are studied. It is shown that, certainly, the variations of the erosion rates with the electrode gap should be imputed to two factors: the arc mobility which changes strongly with the electrode gap and a `supplementary' heating of the cathode surface due to interactions that occur at small electrode gap values between the cathode surface and the anode plasma jets.

Teste, Ph; Leblanc, T.; Andlauer, R.; Chabrerie, J.-P.

2001-02-01

386

Annual summary report on thermionic-cathode project. Progress report No. 3, 1 September 1984-31 August 1985  

SciTech Connect

A planar-cathode, Pierce-type electron gun with a design perveance of .0000032 (Amps/volts to the 3/2 power) was operated with a lanthanum hexaboride (LaB/sub 6/) cathode. The cathode (useful diameter 1.9 cm) is heated by bombardment by electrons from a small tungsten filament. The bombardment heating system is stabilized by a feedback control circuit. The power required to heat the cathode is 315 W bombardment power and 200 W filament power. Heating power was reduced by careful heat shielding and reduction of heat-conduction losses. Significant additional reductions should be possible. The sintered LaB/sub 6/ cathode disk is 2.5 cm in diameter, 3.2 mm thick, and has a density of 94%. No problems have been encountered with cracking of the disk. Cathode emission is insensitive to repeated exposure to air after allowing the cathode to fully cool. The measured perveance and anode transmission of the gun are 3.2x10/sup -6/ and 94%, respectively. Current densities up to 6.5 A/sq cm have been reached with 5-micrometer pulses. Measurements were made at cathode temperatures of 1300 to 1600 C.

Getty, W.D.; Herniter, M.E.

1986-01-09

387

Micro-electromechanical systems and field emission array cathodes for high frequency RF sources  

Microsoft Academic Search

Summary form only given. Calabazas Creek Research, Inc is funded by the US Department of Energy (DOE), the National Aeronautics and Space Administration (NASA), and the US Air Force (USAF) to investigate applications for micro-electromechanical systems (MEMS) and field emission array (FEA) cathodes for vacuum electron devices. These include high power klystrons, traveling wave tubes (TWT's), and backward wave oscillators

R. L. Ives; C. Kory; M. Read; J. Booske; C. Spindt

2003-01-01

388

Monitoring DC anode current of a grounded-cathode photomultiplier tube  

Microsoft Academic Search

The Pierre Auger Observatories (PAO) for the highest energy cosmic rays will make use of both the Cherenkov and Air Fluorescence techniques. Surface Detectors (SD) and Fluorescence Detectors (FD) will have to operate in a desert-type environment during at least 15 years. In order to avoid dust deposition, due to electrostatics, and other practical inconveniences derived from biasing the cathode

S. Argirň; D. V. Camin; M. Destro; C. K Guérard

1999-01-01

389

Estimation of cathode temperature parameters by means of a rotating cathode spot mode  

NASA Astrophysics Data System (ADS)

A model for calculating three-dimensional temperature fields in a cathode and estimating the parameters of the melt hollow on the surface of a hafnium cathode is proposed. A qualitative comparison of the calculation data to the photographs of the end surface of the cathode has been made.

Shabunya, S. I.; Martynenko, V. V.; Richard, F.; Barthelemy, B.

2008-11-01

390

Model predictions of arc cathode erosion rate dependence on plasma gas and on cathode material  

Microsoft Academic Search

We have previously reported results of a theoretical study which predict that high current arc cathode erosion is predominantly dependent on the work function and the vapor pressure of the cathode material, and that the thermal design plays a secondary role. These results have been obtained with a newly developed self-consistent model of the cathode region including a realistic one-dimensional

X. Zhou; J. Heberlein; E. Pfender

1993-01-01

391

Development of improved cathodes for solid oxide fuel cells  

SciTech Connect

The University of Missouri-Rolla conducted a 17 month research program focused on the development and evaluation of improved cathode materials for solid oxide fuel cells (SOFC). The objectives of this program were: (1) the development of cathode materials of improved stability in reducing environments; and (2) the development of cathode materials with improved electrical conductivity. The program was successful in identifying some potential candidate materials: Air sinterable (La,Ca)(Cr,Co)O{sub 3} compositions were developed and found to be more stable than La{sub .8}Sr{sub .2}MnO{sub 3} towards reduction. Their conductivity at 1000{degrees}C ranged between 30 to 60 S/cm. Compositions within the (Y,Ca)(Cr,Co,Mn)O{sub 3} system were developed and found to have higher electrical conductivity than La{sub .8}Sr{sub .2}MnO{sub 3} and preliminary results suggest that their stability towards reduction is superior.

Anderson, H.U.

1991-03-01

392

Working conditions of a copper cathode with minimum erosion  

NASA Astrophysics Data System (ADS)

On the basis of experimental investigations and a simple theoretical model that regards electrode erosion as ablation of the electrode material under action of intensive heat fluxes generated by an arc spot, we give estimations of the domain of copper cathode operating regimes with minimum erosion. It is shown that the magnetic field, which is utilized for arc displacement along the electrode surface, has a number of specific limitations from the point of view of electrode erosion. These limitations are related to the variation of the arc spot energy parameters with the magnetic field, which results in a variation in heat transfer between the electric arc and the electrode. As a consequence, an optimal magnetic field exists. For a copper electrode in air, an increase in the magnetic field above 0.08 T makes no sense, because it can only decrease the reliability of the cathode operation by growing erosion. Experimental investigations carried out confirm the results of theoretical analysis. The relationships and diagrams, which make it possible to estimate the domain of the operational conditions of a copper cathode with minimum erosion, are given.

Essiptchouk, A. M.; Sharakhovsky, L. I.; Marotta, A.

2003-11-01

393

Layered Manganese Oxides as Cathodes  

Microsoft Academic Search

The first commercial lithium-ion batteries used LiCo02 as the cathode active material, and this material continues to be used in most lithium-ion batteries manufactured despite\\u000a the high cost and safety hazards associated with cobalt. Apart from LiCo02, only the isostructural nickelate LiNi02, and more particularly the Co-substituted nickelate LiCo\\u000a x\\u000a Ni1?x\\u000a 02, have been considered to have sufficient energy density

B. Ammundsen

394

Olivine-type nanosheets for lithium ion battery cathodes.  

PubMed

Olivine-type LiMPO4 (M = Fe, Mn, Co, Ni) has become of great interest as cathodes for next-generation high-power lithium-ion batteries. Nevertheless, this family of compounds suffers from poor electronic conductivities and sluggish lithium diffusion in the [010] direction. Here, we develop a liquid-phase exfoliation approach combined with a solvothermal lithiation process in high-pressure high-temperature (HPHT) supercritical fluids for the fabrication of ultrathin LiMPO4 nanosheets (thickness: 3.7-4.6 nm) with exposed (010) surface facets. Importantly, the HPHT solvothermal lithiation could produce monodisperse nanosheets while the traditional high-temperature calcination, which is necessary for cathode materials based on high-quality crystals, leads the formation of large grains and aggregation of the nanosheets. The as-synthesized nanosheets have features of high contact area with the electrolyte and fast lithium transport (time diffusion constant in at the microsecond level). The estimated diffusion time for Li(+) to diffuse over a [010]-thickness of <5 nm (L) was calculated to be less than 25, 2.5, and 250 ?s for LiFePO4, LiMnPO4, and LiCoPO4 nanosheets, respectively, via the equation of t = L(2)/D. These values are about 5 orders of magnitude lower than the corresponding bulk materials. This results in high energy densities and excellent rate capabilities (e.g., 18 kW kg(-1) and 90 Wh kg(-1) at a 80 C rate for LiFePO4 nanosheets). PMID:23713414

Rui, Xianhong; Zhao, Xiaoxu; Lu, Ziyang; Tan, Huiteng; Sim, Daohao; Hng, Huey Hoon; Yazami, Rachid; Lim, Tuti Mariana; Yan, Qingyu

2013-05-30

395

49 CFR 192.463 - External corrosion control: Cathodic protection.  

Code of Federal Regulations, 2010 CFR

... false External corrosion control: Cathodic protection. 192.463 Section 192.463 Transportation...192.463 External corrosion control: Cathodic protection. (a) Each cathodic protection system required by this subpart must...

2010-10-01

396

49 CFR 192.463 - External corrosion control: Cathodic protection.  

Code of Federal Regulations, 2010 CFR

... false External corrosion control: Cathodic protection. 192.463 Section 192.463 Transportation...192.463 External corrosion control: Cathodic protection. (a) Each cathodic protection system required by this subpart must...

2009-10-01

397

Formation and Decomposition of Sulfur Compounds in Dispenser Cathodes.  

National Technical Information Service (NTIS)

Formation of sulfur compounds during cathode processing and generation of sulfur during cathode operation were examined using thermodynamic data. Sulfur compounds can be formed in dispenser cathodes exposed to a source of hydrogen sulfide (such as stainle...

R. A. Lipeles

1987-01-01

398

49 CFR 192.463 - External corrosion control: Cathodic protection.  

Code of Federal Regulations, 2011 CFR

... false External corrosion control: Cathodic protection. 192.463 Section 192.463 Transportation...192.463 External corrosion control: Cathodic protection. (a) Each cathodic protection system required by this subpart must...

2011-10-01

399

49 CFR 192.463 - External corrosion control: Cathodic protection.  

Code of Federal Regulations, 2012 CFR

... false External corrosion control: Cathodic protection. 192.463 Section 192.463 Transportation...192.463 External corrosion control: Cathodic protection. (a) Each cathodic protection system required by this subpart must...

2012-10-01

400

IN SITU STUDIES ON THE CATALYTIC AND ELECTRONIC PROPERTIES OF MULTI-DIMENSIONAL CATHODE  

SciTech Connect

The overall objective of this program was to provide the fundamental background to enable SECA Industrial Team Members to select and develop oxide cathodes for the operation of solid oxide fuel cells in the intermediate temperature (500-700 C). A number of experimental techniques were used to address the specific obstacles within the program. The work expanded our existing experimental techniques to the use of in situ diffraction and spectroscopic techniques that are sensitive to the oxygen and iron structural and chemical environment. Such measurements were coupled with the evaluation and determination of the catalytic properties of potential cathode oxides. The scope of the work was to prepare carefully controlled cathode samples of various compositions and microstructure and perform fundamental measurements of their physical properties. The measurement of physical properties of the cathode materials systems were used to correlate those properties to the overall effectiveness of the material as a constituent of an SOFC cell. The measurements techniques of neutron scattering and Moessbauer are relatively unique capabilities which have significance to the LSCF cathode system. The unique ability to make thin film samples can provide special samples for surface science efforts to understand cathodic catalytic activity. The data obtained from neutron diffraction, Moessbauer Spectroscopy, electrical measurements and modeling show that the oxygen vacancy content at 500 C in air for La{sub 0.8}Sr{sub 0.2}MnO{sub 3}, La{sub 0.6}Sr{sub 0.4}FeO{sub 3} and La{sub 0.6}Sr{sub 0.4}Fe{sub 0.8}Co{sub 0.2}O{sub 3-{delta}} are 0, 1% and 5% respectively. This is a significant finding that should relate to performance as a cathode, and gives criteria for the selection of new cathode materials.

Harlan U. Anderson

2003-12-01

401

Aluminum-air batteries for military applications  

Microsoft Academic Search

The authors review the basic characteristics of aluminum-air batteries, describe some of the recent advances involving aluminum anodes and air cathodes, aluminum-air batteries and demonstrate certain potential military applications. They can be transported as lightweight, collapsible batteries and can be filled with water at the site of operation. The alkaline Al\\/air battery is advantageous when a high power is desired.

B. M. L. Rao; R. Cook; W. Kobasz; G. D. Deuchars

1992-01-01

402

Cathode priming of a relativistic magnetron using multi-emission zones on projection ablation lithography cathodes  

NASA Astrophysics Data System (ADS)

A novel priming technique of magnetrons, cathode priming, has been demonstrated experimentally and computationally to reduce microwave start-oscillation in The University of Michigan relativistic magnetron. In cathode priming, N/2 emission zones are constructed in discrete patches around the azimuth of the cylindrical cathode in an N-cavity magnetron. This emission geometry favors excitation of the pi-mode, the most efficient mode in the relativistic magnetron. Microwave oscillation builds-up from noise, therefore priming is advantageous. Advantages of priming include faster start-oscillation, potentially longer pulse-lengths, suppression of mode competition, and frequency locking. Relativistic magnetron experiments demonstrated that cathode priming reduced the start-oscillation times from 114 ns to 99 ns when compared to non-cathode priming shots. Generated magnetron frequencies operated in pi-mode range more frequently with priming (33%) than without priming (20%). Peak electronic efficiency yielded the highest average with cathode priming at 17%. Three-dimensional, electromagnetic, particle-in-cell simulations verified start-oscillation times were reduced with cathode priming, up to a factor of 3. In 3-D simulations, mode competition was suppressed in the startup phase with cathode priming. Without cathode priming the simulated relativistic magnetron initially operated in the 2pi/3-mode before transitioning into the pi-mode. The emission zones on the cathode have been fabricated by a new technique for explosive emission cathodes. This technique, denoted as Projection Ablation Lithography (PAL), involved micro-texturing of solid metal (Al 6061) cathodes by a KrF excimer laser to provide the electric field enhancement. Advantages to the PAL cathode compared to previously-used cotton cathode are: less out-gassing, resulting in lower base vacuum pressures; emission regions are heat-sinked to the cathode; and emission regions can be varied to provide the desired amount of electric field enhancement and cathode priming. PAL cathodes are capable of producing current densities of kA/cm2 with total crossed-field currents (for 6 cm2 area) between 2--10 kA. Experimentally, this all metal PAL cathode out-performed or was equal to the previously-used cotton fiber in every category (energy, pulselength, start-time) when used in the relativistic magnetron. Inferred plasma closure velocities were a factor of two lower with the PAL cathodes and in some shots exhibited zero plasma closure. Microwave pulselengths with PAL cathodes increased 57% to 212 ns, while microwave power averaged the same at 165 MW.

Jones, Michael Cameron

403

Cathodic Protection Developments for Prestressed Concrete Components.  

National Technical Information Service (NTIS)

This is the final report in a study that evaluated the feasibility of using cathodic protection of prestressed concrete bridge members. The interim report (FHWA-RD-92-056), published in February 1993, presented laboratory data showing that cathodic protec...

M. Funahashi J. Wagner W. T. Young

1994-01-01

404

Cathodic Protection for Reinforced Concrete Bridge Decks.  

National Technical Information Service (NTIS)

The first three cathodic protection systems installed on PennDOT decks are the focus of the report. PennDOT's first cathodic protection system was constructed in 1977 on U.S. Traffic Route 15 near Allenwood. It used high silicon-chromium iron anodes and a...

K. L. Highlands

1991-01-01

405

Hollow Cathode, Quasi-Steady Mpd Arc.  

National Technical Information Service (NTIS)

A quasi-steady MPD accelerator has been operated with four different hollow cathodes over a power range from 5 kilowatts to 5 megawatts. The absolute level of the argon mass flow, as well as the fractional division of the flow between the cathode and the ...

N. Parmentier R. G. Jahn

1971-01-01

406

Optimization of cathodic protection system by BEM  

Microsoft Academic Search

This paper presents a boundary element application to determine the optimum locations of electrodes and the optimum impressed current to each electrode in a cathodic protection system. The problem is reduced to minimizing the power supply under the protecting condition which is taken into account by the penalty function method. First, the cathodic protection system where the electrodes have to

Shigeru Aoki; Kenji Amaya

1997-01-01

407

Genetic algorithms for inverse cathodic protection problems  

Microsoft Academic Search

Cathodic protection (CP) is a corrosion prevention technique which uses electrochemical properties of metals to insure that the structure to be protected becomes the cathode of an electrolytic cell. The technique is commonly used for protecting metallic structures placed in aggressive environments, e.g. ship hulls, offshore structures and underground pipelines.Mathematical models of CP problems require appropriate boundary conditions given by

Luiz C Wrobel; Panayiotis Miltiadou

2004-01-01

408

Photovoltaic powered regulated cathodic protection system  

Microsoft Academic Search

The cathodic protection (CP) system objective is to protect metallic structures against corrosion caused by chemical reaction between metallic structures and surrounding mediums, such as soil or water. To overcome such a problem, a sacrificing anode is connected to the protected structure (which acts as a cathode) through a DC power supply. As a result, a current passes from the

Wagdy R. Anis; Hany A. Alfons

1994-01-01

409

Manganese oxide cathodes for rechargeable batteries  

Microsoft Academic Search

Manganese oxides are considered as promising cathodes for rechargeable batteries due to their low cost and low toxicity as well as the abundant natural resources. In this dissertation, manganese oxides have been investigated as cathodes for both rechargeable lithium and alkaline batteries. Nanostructured lithium manganese oxides designed for rechargeable lithium cells have been synthesized by reducing lithium permanganate with methanol

Dongmin Im

2002-01-01

410

Development of aqueous-lithium batteries with a focus on cathodes  

NASA Astrophysics Data System (ADS)

Topics dealing with the advancement of the aqueous-lithium battery technology are discussed. First, results are presented from the characterization of various cathode candidates for the aqueous-lithium systems: both water and oxygen reducing. Among the water reducing cathodes, nickel and ruthenium cathodes have proven to be the best candidates. Planar nickel and ruthenium electrodes have been studied in 8M KOH using electrochemical impedance spectroscopy (EIS) and equivalent circuits at -1.2, -1.25, -1.35, -1.45, and -1.7 VSCE. Aging characteristics based on EIS are presented for the nickel and ruthenium electrodes at -1.25 and -1.45 V SCE. Electrochemical rate constants are also reported from the EIS data, which are based on the Volmer-Heyrovsky mechanism of the hydrogen evolution reaction (HER). The kinetic parameters obtained from the mechanistic model agree with both the AC results obtained at all five cathodic overpotentials tested and the DC experimental results form nickel in 8M KOH. Among the oxygen reducing cathodes, four commercially available air cathodes form E-TEK, ERC, and Alupower were used to characterize the lithium-air system for a wide range of discharge rates. Secondly, a commercially available cation exchange membrane, NafionRTM 90209, has proven to be an effective means of controlling the electrolyte concentration of the battery if operating in an ocean environment. Finally, the characterization of aqueous-lithium single-celled batteries is presented for both lithium-air and lithium-water batteries. A novel idea for a lithium-water battery is also described, and results are presented for 8 days of continuous prototype operation. The specific energy density of the prototype, 4 kW-hr/kg, has almost doubled that of previous designed lithium-water systems, and the faradaic efficiency of the prototype exceeds 90%. The lithium-water prototype demonstrated that the system is promising, and efforts should continue for its development.

Vanvoorhis, Dewey J.

411

Cathode Effects in Cylindrical Hall Thrusters  

SciTech Connect

Stable operation of a cylindrical Hall thruster (CHT) has been achieved using a hot wire cathode, which functions as a controllable electron emission source. It is shown that as the electron emission from the cathode increases with wire heating, the discharge current increases, the plasma plume angle reduces, and the ion energy distribution function shifts toward higher energies. The observed effect of cathode electron emission on thruster parameters extends and clarifies performance improvements previously obtained for the overrun discharge current regime of the same type of thruster, but using a hollow cathode-neutralizer. Once thruster discharge current saturates with wire heating, further filament heating does not affect other discharge parameters. The saturated values of thruster discharge parameters can be further enhanced by optimal placement of the cathode wire with respect to the magnetic field.

Granstedt, E.M.; Raitses, Y.; Fisch, N. J.

2008-09-12

412

Cathode effects in cylindrical Hall thrusters  

SciTech Connect

Stable operation of a cylindrical Hall thruster has been achieved using a hot wire cathode, which functions as a controllable electron emission source. It is shown that as the electron emission from the cathode increases with wire heating, the discharge current increases, the plasma plume angle reduces, and the ion energy distribution function shifts toward higher energies. The observed effect of cathode electron emission on thruster parameters extends and clarifies performance improvements previously obtained for the overrun discharge current regime of the same type of thruster, but using a hollow cathode neutralizer. Once thruster discharge current saturates with wire heating, further filament heating does not affect other discharge parameters. The saturated values of thruster discharge parameters can be further enhanced by optimal placement of the cathode wire with respect to the magnetic field.

Granstedt, E. M.; Raitses, Y.; Fisch, N. J. [Plasma Physics Laboratory, Princeton University, P. O. Box 451, Princeton, New Jersey 08543 (United States)

2008-11-15

413

Adsorption of ions in the diffuse part of an electrical double layer at ionic surfactant solution-air interfaces in the presence of background electrolytes  

Microsoft Academic Search

The equations are derived for the calculation of adsorption values ?±d of coions and counterions in the diffuse part of an electrical double layer characterized by ?d potential in the presence of a background electrolyte. The case of arbitrary |?d| values is considered. Based on the known experimental data, the contributions of adsorption values ?±d to the surface excesses of

G. S. Aleiner; O. G. Us’yarov

2008-01-01

414

24-HOUR DIFFUSIVE SAMPLING OF 1,3-BUTADIENE IN AIR ONTO CARBOPACK X SOLID ADSORBENT FOLLOWED BY THERMAL DESORPTION/GC/MS ANALYSIS - FEASIBILITY STUDY  

EPA Science Inventory

Diffusive sampling of 1,3-butadiene for 24 hr onto the graphitic adsorbent Carbopack X packed in a stainless steel tube badge (6.3 mm o.d., 5 mm i.d., and 90 mm in length) with analysis by thermal desorption/gas chromatography (GC)/mass spectrometry (MS) has been evaluated in con...

415

Diffusion /Osmosis  

NSDL National Science Digital Library

This project is use to review the concepts of diffusion and osmosis 1. Watch the tutorials on diffusion and osmosis. Take the online quiz at the end of each one. Diffusion Animation Osmosis Animation 2. Do the interactive lab on diffusion. Stop when you get to the calculating water potential section. Diffusion/Osmosis Interactive Demo 3. Play the Quia review games. Quia Games- matching/concetration Quia Jeopardy 4. Check out the Elodea leaf cells. Be able to ...

Jensen

2007-11-26

416

Rapidly-refuelable 167-CM(2) aluminum-air power cell  

NASA Astrophysics Data System (ADS)

The rapidly-refuelable, 167-cm(2) aluminum-air power was tested both as a single cell and as a two cell stack. The electrolyte and is designed for rapid replacement of the anode and easy construction. A maximum power density of 4.2 kW/m(2) was measured. Cathode polarization is negligibly affected by air flow rate and air electrolyte differential pressure across the air cathode.

Homsy, R. V.

1981-11-01

417

NEW CATHODE MATERIALS FOR INTERMEDIATE TEMPERATURE SOLID OXIDE FUEL CELLS  

SciTech Connect

Operation of SOFCs at intermediate temperatures (500-800 C) requires new combinations of electrolyte and electrode materials that will provide both rapid ion transport across the electrolyte and electrode-electrolyte interfaces and efficient electrocatalysis of the oxygen reduction and fuel oxidation reactions. This project concentrates on materials and issues associated with cathode performance that are known to become limiting factors as the operating temperature is reduced. The specific objectives of the proposed research are to develop cathode materials that meet the electrode performance targets of 1.0 W/cm{sup 2} at 0.7 V in combination with YSZ at 700 C and with GDC, LSGM or bismuth oxide based electrolytes at 600 C. The performance targets imply an area specific resistance of {approx}0.5 {Omega}cm{sup 2} for the total cell. The research strategy is to investigate both established classes of materials and new candidates as cathodes, to determine fundamental performance parameters such as bulk diffusion, surface reactivity and interfacial transfer, and to couple these parameters to performance in single cell tests. The initial choices for study are perovskite oxides based on Sr substituted LaFeO{sub 3}, where significant data in single cell tests exists at PNNL for cathodes on both YSZ and CSO/YSZ, and of Ln{sub 2}NiO{sub 4} compositions. A key component of the research strategy is to evaluate for each cathode material composition, the key performance parameters, including ionic and electronic conductivity, surface exchange rates, stability with respect to the specific electrolyte choice, and thermal expansion coefficients. Results on electrical conductivity relaxation measurements on La{sub 2}NiO{sub 4+x} and Pr{sub 2}NiO{sub 4+x} samples are reported and compared with results from previous studies. Studies of the crystallization of amorphous SrFeO{sub 3-x} and LaFeO{sub 3-x} films prepared by pulsed laser deposition are reported. Such studies are a preliminary to the combinatorial synthesis approach described in the first report.

Allan J. Jacobson

2004-05-11

418

Use of Both Anode and Cathode Reactions in Wastewater Treatment  

NASA Astrophysics Data System (ADS)

Here, we describe the fundamentals, laboratory experiments, and environmental applications of indirect electrooxidation methods based on H2O2 electrogeneration such as electro-Fenton, photoelectro-Fenton and peroxicoagulation for the treatment of acidic wastewaters containing toxic and recalcitrant organics. These methods are electrochemical advanced oxidation processes that can be used in divided and undivided electrolytic cells in which pollutants are oxidized by hydroxyl radical (•OH) produced from anode and/or cathode reactions. H2O2 is generated from the two-electron reduction of O2 at reticulated vitreous carbon, graphite, carbon-felt, and O2-diffusion cathodes. The most usual method is electro-Fenton where Fe2 + added to the wastewater reacts with electrogenerated H2O2 to yield •OH and Fe3 + from Fenton's reaction. An advantage of this technique is that Fe2 + is continuously regenerated from cathodic reduction of Fe3 +. The characteristics of different electro-Fenton systems where pollutants are simultaneously destroyed by •OH formed in the medium from Fenton's reaction and at the anode surface from water oxidation are explained. The effect of the anode [Pt or boron-doped diamond (BDD)] and cathode (carbon-felt or O2-diffusion) on the degradation rate of persistent industrial by-products, herbicides, pharmaceuticals, dyes, etc. is examined. Initial pollutants react much more rapidly with •OH formed in the medium and their degradation sequences are discussed from aromatic intermediates and finally short aliphatic acids are detected. The synergetic positive catalytic effect of Cu2 + on the electro-Fenton process is evidenced. The photoelectro-Fenton method involves the irradiation of the wastewater with UVA light that rapidly photodecomposes complexes of Fe3 + with final carboxylic acids enhancing total decontamination. The peroxicoagulation method uses a sacrificial Fe anode that is continuously oxidized to Fe2 + and organics are either mineralized with •OH formed from both electrogenerated Fe2 + and H2O2 or removed by parallel coagulation with the FeOH3 precipitate formed from the excess of Fe3 + generated from Fenton's reaction.

Brillas, Enric; Sirés, Ignasi; Cabot, Pere LluíS.

419

Performance of Field Emission Cathodes in Xenon Electric Propulsion System Environments  

Microsoft Academic Search

Nomenclature Introduction FEA Cathode Performance Modeling Field Electron Emission Model Tip Sputtering Model Sputter Yield Model Cathode Experimental Performance Evaluations Experimental Apparatus Silicon FEA Cathodes Molybdenum FEA Cathodes Carbon-Film Cathodes Discussion Conclusions References

Colleen M. Marrese; James E. Polk; Kevin L. Jensen; Alec D. Gallimore; Capp A. Spindt; Richard L. Fink; W. Devereux Palmer

2000-01-01

420

Cathode for an electrochemical cell  

DOEpatents

Described is a thin-film battery, especially a thin-film microbattery, and a method for making same having application as a backup or primary integrated power source for electronic devices. The battery includes a novel electrolyte which is electrochemically stable and does not react with the lithium anode and a novel vanadium oxide cathode. Configured as a microbattery, the battery can be fabricated directly onto a semiconductor chip, onto the semiconductor die or onto any portion of the chip carrier. The battery can be fabricated to any specified size or shape to meet the requirements of a particular application. The battery is fabricated of solid state materials and is capable of operation between -15.degree. C. and 150.degree. C.

Bates, John B. (Oak Ridge, TN); Dudney, Nancy J. (Knoxville, TN); Gruzalski, Greg R. (Oak Ridge, TN); Luck, Christopher F. (Knoxville, TN)

2001-01-01

421

Weld techniques for reservoir cathodes  

NASA Astrophysics Data System (ADS)

We report improvements in weld technology in support of our efforts to produce a commercial, long-life, miniature reservoir cathode. We have found that the laser weld between sintered tungsten pellet and reservoir sleeve can be made reliably hermetic if we apply a subsequent coating of molybdenum-ruthenium brazing alloy to the sides of the pellet and especially to the weld region. The emissive material is then inserted in the open end of the reservoir sleeve, which is then closed by a secondary weld. This secondary weld is reliably hermetic without the Mo-Ru coating, because it does not involve the porous tungsten matrix. Moreover, we have discovered an inspection procedure that allows us to check weld hermeticity at each assembly step. Thermal cycling tests indicate good weld integrity. Emission life testing is proceeding.

Vancil, Bernard K.; Wintucky, Edwin G.

2005-09-01

422

Scanning thermionic emission imaging of cathode surfaces  

NASA Astrophysics Data System (ADS)

The evaluation of the thermionic emission characteristics of a variety of cathode technologies that may have application in the SCALPEL (Scattering with Angular Limitation Projection Electron-beam Lithography) instrument, has been conducted in a modified Scanning Electron Microscope. The thermionic emission image of the source, projected along the column axis by the electrostatic immersion lens of the gun, is analyzed by scanning this image across the entrance aperture of the column by driving the normal alignment coils with the scan drive electronics. The technique may be referred to as Scanning Thermionic Emission Electron Microscopy (STEEM). With this technique, the projected image of the cathode, the cross- over(s) and the cathode surface itself may be imaged by adjusting the focal length of the double condenser lens of the SEM. Images of 0.84 mm diameter cathodes in various forms, including polycrystalline Ta, coated polycrystalline cathodes and single crystal Ta have been examined at a range of magnifications. In addition to operation of the gun with a single large diameter Wehnelt aperture (2.5 mm), cathodes have been studied when located behind a fine mesh in the Wehnelt aperture. Multiple cross-overs with associated beams overlapping further along the axis of the instrument are observed. Single crystal Ta cathodes have been shown to provide the extremely uniform emission in the temperature limited mode, that is required for the effective operation of the SCALPEL technique.

Sewell, Peter B.; Katsap, Victor; Waskiewicz, Warren K.

1999-11-01

423

Cathodic oxygen consumption and electrically induced osteogenesis.  

PubMed

Small amounts of electric current stimulate bone formation in the region of a cathode. The purpose of this experiment is to compare changes in oxygen and hydroxyl ion concentration that occur at the cathode at current levels known to be capable of inducing osteogenesis (10-20 muamps) with those changes that occur at current levels known to be toxic to bone (100 muamps). An oxygen consumption chamber containing an oxygen electrode is fitted with two stainless steel electrodes which are connected to a constant current source. At the cathode, with a current of 100 muamps, oxygen is consumed at nearly stoichiometric rates. At higher current (100 muamps) levels, cathodic oxygen consumption gives way to hydrogen evolution. Cathodic hydroxyl ion production is directly proportional to current. It is concluded from these in vitro experiments that at 10-20 muamps the oxygen tension in the vicinity of the cathode is lowered and the pH is moderately increased. At 100 muamps the oxygen tension is not lowered, but the pH is increased dramatically. If these same changes occur in the vicinity of a cathode in vivo, then lowering the local tissue oxygen tension and raising the local pH may be mechanisms operative in electrically induced bone formation. PMID:236849

Brighton, C T; Adler, S; Black, J; Itada, N; Friedenberg, Z B

1975-01-01

424

Device lifetime improvement of polymer-based bulk heterojunction solar cells by incorporating copper oxide layer at Al cathode  

NASA Astrophysics Data System (ADS)

Organic solar cells are commonly susceptible to degradation in air. We present that insertion of a thin layer of thermally evaporated copper oxide (CuOx) between the organic active layer and the Al cathode can greatly extend the lifetime of P3HT:PCBM based bulk heterojunction solar cells. The performance can be further improved by applying an interfacial bilayer of CuOx/LiF. Our results suggest that the CuOx functions not only as a charge transport layer but also as a protection layer, which prevents formation of thick organic-Al interdiffusion area. This leads to a more air-resistive cathode/organic interface.

Wang, Mingdong; Xie, Fangyan; Xie, Weiguang; Zheng, Shizhao; Ke, Ning; Chen, Jian; Zhao, Ni; Xu, J. B.

2011-05-01

425

Stabilization mechanisms of aluminum-titanium bilayer cathodes in organic solar cells  

NASA Astrophysics Data System (ADS)

A major concern in organic solar cells today is to continue to improve their stability. Aluminum-titanium bilayer cathodes have been reported to prolong the shelf-lives of organic solar cells to be more than 3 months in air without encapsulation. However, the stabilization mechanism was unsolved, and further investigation into the mechanism was required. We probed the surface morphology of different cathodes with atomic force microscope and explored elemental depth profiles in different devices with time of flight-secondary ion mass spectrometry to analyze the mechanism, in addition to optimization of the cell structure. Based on the experimental observations, we attribute the improved shelf-lives to three functions of the bilayer cathodes, e.g., the elimination of large cracks, the suppression of interdiffusion, and the sustainable oxygen scavenging. These findings provide information useful for rationally designing efficient structures that stabilize organic solar cells.

Cao, Huanqi; Tanaka, Masaki; Ishikawa, Ken

2013-09-01

426

Experimental And Theoretical Studies On The Characteristics Of Low-Pressure Glow Discharge With Liquid Cathode  

NASA Astrophysics Data System (ADS)

The characteristics of low-pressure air glow discharge with liquid cathode (electrolytic cathode low-pressure discharge, ELCLPD) has been investigated. Distilled water was utilized as a cathode. The electric field strength, gas temperature as well as emission intensity of some bands of N2(C3?u?B3 ?g) were measured at pressure from 76 to 760 torr at fixed discharge current of 40 mA. Based upon these data, the reduced electric field strength, E/N, effective vibrational temperatures for N2(C3?u, X1Sg+) and rotational temperatures for N2(X1Sg+) were investigated. The electron energy distribution function (EEDF) and some electron parameters (average energy, electron density) were obtained on the base of numerical solution of the Boltzmann kinetic equation.

Shutov, D.; Ivanov, A.; Smirnov, S.; Rybkin v.

2010-07-01

427

Lithium batteries with organic slurry cathodes  

SciTech Connect

Electrical cells and batteries having lithium anodes and cathodes comprising an organic slurry of MnO/sub 2/ and carbon particles in an organic solvent in contact with a conductive plastic current collector, and a method of making the cathodes comprising the steps of heating MnO/sub 2/ to remove absorbed and adsorbed water and water of crystallization, cooling the dehydrated MnO/sub 2/, dispersing the cooled and dehydrated MnO/sub 2/ in an anhydrous solvent to form a slurry, depositing the slurry in discrete cathode patches on cell component substrates, and sealing the slurry patches into cells having substantially gas impervious cell enveloping boundaries.

Bruder, A.H.

1984-08-21

428

Molten carbonate fuel cell cathode development  

NASA Astrophysics Data System (ADS)

From the results obtained so far, Li2MnO3 and LiFeO3 look promising as cathode materials for the MCFC. The materials have low solubility in the molten electrolyte and do not migrate under cell operating conditions. However, further studies of their resistivity is required before they can be fully assessed. Zinc oxide does not appear to be a good cathode material candidate due to its high solubility and its incorporation into the LiAlO2 matrix, although the conductivity of doped ZnO is low enough for its application as a cathode.

Smith, J. L.; Kaun, T. D.; Minh, N. Q.; Vandeventer, E. H.; Mrazek, F. C.; Pierce, R. D.

429

Molten carbonate fuel cell cathode development  

SciTech Connect

From the results obtained so far, Li/sub 2/MnO/sub 3/ and LiFeO/sub 2/ look promising as cathode materials for the MCFC. The materials have low solubility in the molten electrolyte and do not migrate under cell operating conditions. However, further studies of their resistivity is required before they can be fully assessed. Zinc oxide does not appear to be a good cathode material candidate due to its high solubility and its incorporation into the LiAlO/sub 2/ matrix, although the conductivity of doped ZnO is low enough for its application as a cathode.

Smith, J.L.; Kaun, T.D.; Minh, N.Q.; VanDeventer, E.H.; Mrazek, F.C.; Pierce, R.D.

1984-01-01

430

Cathode for molten carbonate fuel cell  

DOEpatents

Disclosed are a porous sintered cathode for a molten carbonate fuel cell and method of making same. The cathode includes a skeletal structure of a first electronically conductive material slightly soluble in the electrolyte present in the molten carbonate fuel cell covered by fine particles of a second material of possibly lesser electronic conductivity insoluble in the electrolyte present in the molten carbonate fuel cell. The cathode has a porosity in the range of from about 60% to about 70% at steady-state cell operating conditions consisting of both macro-pores and micro-pores.

Kaun, T.D.; Mrazek, F.C.

1986-04-25

431

Plasma-based multistage virtual cathode radiation  

SciTech Connect

A plasma-based multistage virtual cathode radiation is proposed. Multistage virtual cathode can be formed as an electron beam passes through a high dense ion background. The reflected electrons can be coupled with transverse magnetic wave, and electromagnetic radiation is detected. Unlike the traditional virtual cathode devices, the beam current can be decreased greatly due to the effect of ions, and single mode operation can be achieved by adjusting the beam density. Besides, the radiation frequency, which is proportional to the beam density, covers from 10 to 100 GHz. The output power flux density reaches a magnitude of GWm{sup -2}.

Su Dong; Tang Changjian [Key Laboratory of High Energy Density Physics and Technology, Ministry of Education, Sichuan University, Chengdu 610064 (China)

2011-12-15

432

K2CsSb Cathode Development  

SciTech Connect

K{sub 2}CsSb is an attractive photocathode for high current applications. With a quantum efficiency of >4% at 532nm and >10% at 355nm, it is the only cathode to have demonstrated an average current of 35mA in an accelerator environment We describe ongoing cathode development work. for the energy recovery linac being constructed at BNL Several cathodes have been created on both copper and stainless steel substrates, and their spatial uniformity and spectral response have been characterized. Preliminary lifetime measurements have been performed at high average current densities (>1 mA/mm{sup 2}).

Smedley,J.; Rao, T.; Wang, E.

2008-10-01

433

Development of Lanthanum Ferrite SOFC Cathodes  

SciTech Connect

A number of studies have been conducted concerning compositional/microstructural modifications of a Sr-doped lanthanum ferrite (LSF) cathode and protective Sm-doped ceria (SDC) layer in an anode supported solid oxide fuel cell (SOFC). Emphasis was placed on achieving enhanced low temperature (700-800 degrees C) performance, and long-term cell stability. Investigations involved manipulation of the lanthanum ferrite chemistry, addition of noble metal oxygen reduction catalysts, incorporation of active cathode layer compositions containing Co, Fe and higher Sr contents, and attempts to optimize the ceria barrier layer between the LSF cathode and YSZ electrolyte.

Simner, Steve P.; Bonnett, Jeff F.; Canfield, Nathan L.; Meinhardt, Kerry D.; Shelton, Jayne P.; Sprenkle, Vince L.; Stevenson, Jeffry W.

2003-01-01

434

Fast Numerical Simulation of Two-Phase Transport Model in the Cathode of a Polymer Electrolyte Fuel Cell  

Microsoft Academic Search

In this paper, we apply streamline-diffusion and Galerkin-least-squares fi- nite element methods for 2D steady-state two-phase model in the cathode of polymer electrolyte fuel cell (PEFC) that contains a gas channel and a gas diffusion layer (GDL). This two-phase PEFC model is typically modeled by a modified Navier-Stokes equa- tion for the mass and momentum, with Darcy's drag as an

Pengtao Sun; Guangri Xue; Jinchao Xu

2009-01-01

435

Synthesis of zinc oxide by zinc–air system  

Microsoft Academic Search

An economical and environment friendly zinc–air system route is used for the synthesis of zinc oxide (ZnO) on a zinc (Zn) plate in room temperature. A Zn plate and a single air-cathode are used as the anode and cathode, respectively. It is found that the growth of ZnO increases with increasing electrolyte solution concentration until an optimum concentration is reached.

C. K. Yap; W. C. Tan; S. S. Alias; A. A. Mohamad

2009-01-01

436

Physics Of The Plasma-Cathode Interface Of Glow Discharge In Oxygen With Aluminium Cathode  

SciTech Connect

Glow discharge in oxygen with aluminium cathode has peculiar characteristics. It works at the product (p{center_dot}L{sub cf}) of gas pressure and the cathode space length, smaller than in other cases, e.g. even Ne/Al discharge. Numerical modelling of electrodynamic structure of the cathode region suggests low multiplication of electron fluxes and consequently high electron emission from the 'oxidised' cathode surface at relatively low anode-cathode voltages U{sub ac}. The above facts explain a low efficiency of the sputtering of 'oxidised' Al-cathodes when determined experimentally. Numerical modelling allows the quantitative explanation of the line emission intensity of oxygen molecules such as its 'linear 'dependence on both gas pressure and discharge current density, J{sub d}. However in the case of line emission of sputtered Al atoms and reflected 'free' O atoms we are able only to draw some qualitative conclusions.

Wronski, Z. [Instutute of Physics, M. Curie Sklodowsha University, 20-031 Lublin (Poland)

2008-03-19

437

High power microwave generation from coaxial virtual cathode oscillator using graphite and velvet cathodes  

NASA Astrophysics Data System (ADS)

High power microwave (HPM) generation studies were carried out in KALI-5000 pulse power system. The intense relativistic electron beam was utilized to generate HPMs using a coaxial virtual cathode oscillator. The typical electron beam parameters were 350 kV, 25 kA, and 100 ns, with a few hundreds of ampere per centimeter square current density. Microwaves were generated with graphite and polymer velvet cathode at various diode voltage, current, and accelerating gaps. A horn antenna setup with diode detector and attenuators was used to measure the microwave power. It was observed that the microwave power increases with the diode voltage and current and reduces with the accelerating gap. It was found that both the peak power and width of the microwave pulse is larger for the velvet cathode compared to the graphite cathode. In a coaxial vircator, velvet cathode is superior to the graphite cathode due to its shorter turn on time and better electron beam uniformity.

Menon, Rakhee; Roy, Amitava; Singh, S. K.; Mitra, S.; Sharma, Vishnu; Kumar, Senthil; Sharma, Archana; Nagesh, K. V.; Mittal, K. C.; Chakravarthy, D. P.

2010-05-01

438

Ultrathin V2O5 nanosheet cathodes: realizing ultrafast reversible lithium storage  

NASA Astrophysics Data System (ADS)

Few-layer V2O5 nanosheets with a thickness of 2.1-3.8 nm have been successfully synthesized in this work via a simple and scalable liquid exfoliation technique. The unique nanostructure allows the high-rate transportation of lithium ions and electrons due to very short diffusion paths provided by this ultrathin thickness, resulting in Li-ion cathodes with remarkable energy and power densities.Few-layer V2O5 nanosheets with a thickness of 2.1-3.8 nm have been successfully synthesized in this work via a simple and scalable liquid exfoliation technique. The unique nanostructure allows the high-rate transportation of lithium ions and electrons due to very short diffusion paths provided by this ultrathin thickness, resulting in Li-ion cathodes with remarkable energy and power densities. Electronic supplementary information (ESI) available: Experimental details and additional characterizations. See DOI: 10.1039/c2nr33422d

Rui, Xianhong; Lu, Ziyang; Yu, Hong; Yang, Dan; Hng, Huey Hoon; Lim, Tuti Mariana; Yan, Qingyu

2012-12-01

439

Hollow cathode plasma sources for large area surface treatment  

Microsoft Academic Search

Plasma generation over large areas using a hollow cathode discharge is described in this study. Radio frequency linear hollow cathodes in several arrangements, for operation at reduced gas pressure and suitable for scale-up, are presented. Examples of surface processing and coating by PVD, both by hollow cathode discharge (HCD) and hollow cathode arc (HCA), are given. A non-equilibrium atmospheric plasma

H Baránková; L Bárdoš

2001-01-01

440

Coated porous carbon cathodes for lithium ion batteries  

SciTech Connect

Coated porous carbon cathodes for automotive lithium batteries are being developed with the goal of overcoming the problems with capacity fade and poor thermal management in conventional polymer-bonded cathodes. The active cathode material (lithium iron phosphate nanoparticles) is carbon-bonded to the porous carbon support material. Cathodes have been developed with high specific energy and power and with good cycling behavior.

Kercher, Andrew K [ORNL; Dudney, Nancy J [ORNL; Kiggans, Jim [ORNL; Klett, James William [ORNL

2008-01-01

441

A stable cathode for the aprotic Li-O2 battery.  

PubMed

Rechargeable lithium-air (O2) batteries are receiving intense interest because their high theoretical specific energy exceeds that of lithium-ion batteries. If the Li-O2 battery is ever to succeed, highly reversible formation/decomposition of Li2O2 must take place at the cathode on cycling. However, carbon, used ubiquitously as the basis of the cathode, decomposes during Li2O2 oxidation on charge and actively promotes electrolyte decomposition on cycling. Replacing carbon with a nanoporous gold cathode, when in contact with a dimethyl sulphoxide-based electrolyte, does seem to demonstrate better stability. However, nanoporous gold is not a suitable cathode; its high mass destroys the key advantage of Li-O2 over Li ion (specific energy), it is too expensive and too difficult to fabricate. Identifying a suitable cathode material for the Li-O2 cell is one of the greatest challenges at present. Here we show that a TiC-based cathode reduces greatly side reactions (arising from the electrolyte and electrode degradation) compared with carbon and exhibits better reversible formation/decomposition of Li2O2 even than nanoporous gold (>98% capacity retention after 100 cycles, compared with 95% for nanoporous gold); it is also four times lighter, of lower cost and easier to fabricate. The stability may originate from the presence of TiO2 (along with some TiOC) on the surface of TiC. In contrast to carbon or nanoporous gold, TiC seems to represent a more viable, stable, cathode for aprotic Li-O2 cells. PMID:23995325

Ottakam Thotiyl, Muhammed M; Freunberger, Stefan A; Peng, Zhangquan; Chen, Yuhui; Liu, Zheng; Bruce, Peter G

2013-09-01

442

Neutral electrolyte aluminum air battery with open configuration  

Microsoft Academic Search

A kind of new long life aluminum air batteries with open configuration was developed, using aluminum alloy doped with Ga, In, Sn, Bi, Pb and Mn as anode, NaCl solution as electrolyte and air electrode as cathode. The polarization curves of aluminum electrode and air electrode were tested. And the cell's performance was tested to calculate the utilization of aluminum

Bin HAN; Guangchuan LIANG

2006-01-01

443

The development of aluminum-air batteries for electric vehicles  

Microsoft Academic Search

Progress made toward the development of a viable aluminum-air battery system is presented. The general aluminum\\/air reaction is discussed. Results from aluminum anode and air cathode experiments are presented. Solids separation technology, a heat exchanger unit, and cell design are also discussed. The projected specific energy and power of the battery can provide electric vehicle driving ranges comparable to those

A. S. Homa; E. J. Rudd

1989-01-01

444

Holographic diffusers  

NASA Astrophysics Data System (ADS)

Holographic diffusers are prepared using silver halide (Agfa 8E75 and Kodak 649F) and photopolymer (Polaroid DMP 128 and DuPont 600, 705, and 150 series) media. It is possible to control the diffusion angle in three ways: by selection of the properties of the source diffuser, by control of its subtended angle, and by selection of the holographic medium. Several conventional diffusers based on refraction or scattering of light are examined for comparison.

Wadle, Stephen; Wuest, Daniel; Cantalupo, John; Lakes, Roderic S.

1994-01-01

445

Advanced Measurement and Modeling Techniques for Improved SOFC Cathodes  

SciTech Connect

The goal of this project was to develop an improved understanding of factors governing performance and degradation of mixed-conducting SOFC cathodes. Two new diagnostic tools were developed to help achieve this goal: (1) microelectrode half-cells for improved isolation of cathode impedance on thin electrolytes, and (2) nonlinear electrochemical impedance spectroscopy (NLEIS), a variant of traditional impedance that allows workers to probe nonlinear rates as a function of frequency. After reporting on the development and efficacy of these tools, this document reports on the use of these and other tools to better understand performance and degradation of cathodes based on the mixed conductor La{sub 1-x}Sr{sub x}CoO{sub 3-{delta}} (LSC) on gadolinia or samaria-doped ceria (GDC or SDC). We describe the use of NLEIS to measure O{sub 2} exchange on thin-film LSC electrodes, and show that O{sub 2} exchange is most likely governed by dissociative adsorption. We also describe parametric studies of porous LSC electrodes using impedance and NLEIS. Our results suggest that O{sub 2} exchange and ion transport co-limit performance under most relevant conditions, but it is O{sub 2} exchange that is most sensitive to processing, and subject to the greatest degradation and sample-to-sample variation. We recommend further work that focuses on electrodes of well-defined or characterized geometry, and probes the details of surface structure, composition, and impurities. Parallel work on primarily electronic conductors (LSM) would also be of benefit to developers, and to improved understanding of surface vs. bulk diffusion.

Stuart Adler; L. Dunyushkina; S. Huff; Y. Lu; J. Wilson

2006-12-31

446

Efficiency Enhancement of Reflex Triode Virtual Cathode Oscillator Using the Carbon Fiber Cathode  

Microsoft Academic Search

This paper presents the investigation on the reflex triode (RT) virtual cathode oscillator (vircator) using a carbon fiber cathode. Experimental results show that the carbon fiber cathode can obviously improve the electron beam quality and dramatically enhance the beam-to-microwave efficiency of the RT vircator. It was found that the beam-to-microwave efficiency increased from about 4%-6% in the case of the

Lie Liu; Li-Min Li; Xiao-Ping Zhang; Jian-Chun Wen; Hong Wan; Ya-Zhou Zhang

2007-01-01

447

Cathode priming of a relativistic magnetron using multi-emission zones on projection ablation lithography cathodes  

Microsoft Academic Search

A novel priming technique of magnetrons, cathode priming, has been demonstrated experimentally and computationally to reduce microwave start-oscillation in The University of Michigan relativistic magnetron. In cathode priming, N\\/2 emission zones are constructed in discrete patches around the azimuth of the cylindrical cathode in an N-cavity magnetron. This emission geometry favors excitation of the pi-mode, the most efficient mode in

Michael Cameron Jones

2005-01-01

448

Study of lithium diffusion through vanadium pentoxide aerogel  

NASA Astrophysics Data System (ADS)

Good electrode materials play an important part in rechargeable Li batteries. In this paper, safe and inexpensive vanadium pentoxide (V2O5) aerogel materials were used as cathode materials. We discussed preparation of the films and lithium ion diffusion at the interface between the cathode and electrolyte by potential-step current transient technique and digital simulations. The results showed that diffusion coefficient (DLi) of the V2O5 aerogel film was 9.18×10-14cm2/s and exchange current was 12.5×10-6A at potential step 3.6~3.5VLi/Li+.

Wang, Airong; Wu, Guangming; Yang, Hui-yu; Zhang, Ming-xia; Fang, Xingmei; Yang, Xiao-yun; Zhou, Bin; Shen, Jun

2008-03-01

449

Low temperature aluminum reduction cell using hollow cathode  

SciTech Connect

A method of producing aluminum in an electrolytic cell containing alumina dissolved in an electrolyte. A plurality of non-consumable anodes are disposed substantially vertically in the electrolyte along with a plurality of monolithic hollow cathodes. Each cathode has a top and bottom and the cathodes are disposed vertically in the electrolyte and the anodes and the cathodes are arranged in alternating relationship. Each of the cathodes is comprised of a first side facing a first opposing anode and a second side facing a second opposing anode. The first and second sides are joined by ends to form a reservoir in the hollow cathode for collecting aluminum therein deposited at the cathode.

Brown, Craig W. (Seattle, WA); Frizzle, Patrick B. (Seattle, WA)

2002-08-20

450

Diffusion MRI  

NASA Astrophysics Data System (ADS)

Recent advances of magnetic resonance imaging have been described, especially stressed on the diffusion sequences. We have recently applied the diffusion sequence to functional brain imaging, and found the appropriate results. In addition to the neurosciences fields, diffusion weighted images have improved the accuracies of clinical diagnosis depending upon magnetic resonance images in stroke as well as inflammations.

Fukuyama, Hidenao

451

CO2 isotopes as tracers of firn air diffusion and age in an Arctic ice cap with summer melting, Devon Island, Canada  

Microsoft Academic Search

Firn air and ice have been sampled and analyzed for trace gases (CO2, N2O, CH4, and CO) and isotopes (14C, 13C, and 18O of CO2; 3H of ice) at 3 m intervals from the surface to the depth of closure at 60 m on the Devon Island Ice Cap, a low-elevation permanent glacier in the Canadian Arctic Islands, to investigate

Ian D. Clark; Lori Henderson; Jérôme Chappellaz; David Fisher; Roy Koerner; Douglas E. J. Worthy; Tom Kotzer; Ann-Lise Norman; Jean-Marc Barnola

2007-01-01

452

Design, construction, and initial operation of the BNL-coastal transport and diffusion, Air\\/Sea Interaction research buoy. Data report  

Microsoft Academic Search

Design features of the Brookhaven National Laboratory (BNL) Air\\/Sea Interaction (A\\/S-I) buoy are described, and construction, testing, and deployment experiences are related. This two-attitude buoy is similar to the MIT\\/Navy buoy which it replaces, but it accommodates more instruments and can be towed through shallower water. The BNL A\\/S-I buoy can be broken down into two, three, or four sections

D. Huszagh; W. Ripperger; S. Fink

1979-01-01

453

COMPUTATIONAL STUDY ON THE EFFECTS OF NON-PERIODIC FLOW PERTURBATIONS ON THE EMISSIONS OF SOOT AND NOX IN A CONFINED TURBULENT METHANE\\/AIR DIFFUSION FLAME  

Microsoft Academic Search

A computational investigation on the effects of fuel inlet perturbations in a confined turbulent CH4\\/air flame has been performed. Non-periodic fluctuations were characterised at the fuel inlet via a pair of sinusoidal harmonics of incommensurate periods with identical amplitude and frequency. Harmonic amplitudes of 2.5%, 7.5%, and 12.5% with respect to the time-averaged fuel inlet velocity have been simulated and

FERNANDO LOPEZ-PARRA; ALI TURAN

2007-01-01

454

Difference Between IR Radiation Spectra of Ethanol in Free Diffusion Combustion Regime and Regime Influenced by an Air Flow in Modeling of a Fire Tornado  

NASA Astrophysics Data System (ADS)

Results of experimental investigations of liquid fuel combustion in the regime of a twisted jet (model of a fire tornado) are presented. Flame radiation spectra were registered. In the chosen spectral range of registration (2.2-4.8 ?m), six spectral intervals were clearly traced in which the main portion of radiated energy was concentrated. Using the ratio of the sums of spectral intensities in the vicinities of the 6th and 3rd maxima, we successfully distinguished the regimes of modeled fire tornado and free diffusion fuel combustion.

Sherstobitov, M. V.; Tsvyk, R. Sh.

2013-06-01

455

Novel GaAs(AlGa)As Cold-Cathode Structure and Factors Affecting Extended Operation  

Microsoft Academic Search

A novel planar cold-cathode structure has been developed based on a GaAs&sngbnd;(AlGa)As heterojunction and a negative electron affinity GaAs surface. As an important feature of the device, the lateral confinement of the current flow to the desired area of the emitting surface is obtained by the selective diffusion of zinc. Under pulsed conditions, emission efficiencies as high as 4% and

H. Schade; H. Nelson; H. Kressel

1972-01-01

456

A microbial fuel cell with improved cathode reaction as a low biochemical oxygen demand sensor  

Microsoft Academic Search

Mediator-less microbial fuel cells (MFC) enriched with oligotrophic microbes were optimized through enhance- ment of cathode reaction and lowering O2 diffusion into the anode compartment as a low BOD sensor. The optimization of the MFC has greatly improved the maximum current and coulomb yield. The oligotroph-type MFC could be used as a low BOD sensor with high operational stability, good

Kui Hyun Kang; Jae Kyung Jang; Hyunsoo Moon; Byung Hong Kim

2003-01-01

457

Characteristics of cathodic polarization at Pt\\/YSZ interface without the effect of electrode microstructure  

Microsoft Academic Search

The characteristics of cathodic polarization at the Pt\\/yttria stabilized zirconia (YSZ) interface have been evaluated with different electrode microstructures by ac impedance analysis. The measurements were carried out at the temperatures of 873–1273K and oxygen partial pressure (PO2) in the range of 0.01–1atm. From the results of impedance analysis, it was found that gas phase diffusion can be involved in

Sung Pil Yoon; Suk Woo Nam; Seung-Goo Kim; Seong-Ahn Hong; Sang-Hoon Hyun

2003-01-01

458

Laser annealing of textured thin film cathode material for lithium ion batteries  

Microsoft Academic Search

The material development for advanced lithium ion batteries plays an important role in future mobile applications and energy storage systems. It is assumed that electrode materials made of nano-composited materials will improve battery lifetime and will lead to an enhancement of lithium diffusion and thus improve battery capacity and cyclability. Lithium cobalt oxide (LiCoO2) is commonly used as a cathode

R. Kohler; M. Bruns; P. Smyrek; S. Ulrich; M. Przybylski; W. Pfleging

2010-01-01

459

Ultrathin V2O5 nanosheet cathodes: realizing ultrafast reversible lithium storage.  

PubMed

Few-layer V(2)O(5) nanosheets with a thickness of 2.1-3.8 nm have been successfully synthesized in this work via a simple and scalable liquid exfoliation technique. The unique nanostructure allows the high-rate transportation of lithium ions and electrons due to very short diffusion paths provided by this ultrathin thickness, resulting in Li-ion cathodes with remarkable energy and power densities. PMID:23233048

Rui, Xianhong; Lu, Ziyang; Yu, Hong; Yang, Dan; Hng, Huey Hoon; Lim, Tuti Mariana; Yan, Qingyu

2012-12-12

460

The temporal development of hollow cathode discharges  

SciTech Connect

This paper reports the temporal development of hollow cathode discharges studied by means of electrical and optical diagnostic techniques. The results indicate that the discharge develops in two stages. The initial breakdown occurs along the longest straight path of the system; i.e., from the anode to the bottom of the cathode hole. This predischarge is confined to a narrow filament along the axis and carries a current of up to hundreds of mA. The resulting distortion of the electric field in the cathode hole is assumed to cause a radial breakdown from the filamentary plasma on the axis to the edge of the cathode hole. After this second breakdown, an increase in current by more than three orders of magnitude is observed. Measurements with axial magnetic fields support the two-stage model.

Ngo, M.T. (Advanced Plasma Physics Group, Mission Research Corp., Washington, DC (US)); Schoenbach, K.H.; Gerdin, G.A. (Old Dominion Univ., Norfolk, VA (USA). Dept. of Electrical Engineering); Lee, J.H. (NASA-Langley Research Center, Hampton, VA (US))

1990-06-01

461

Cathodic Protection Studies on Reinforced Concrete.  

National Technical Information Service (NTIS)

This report presents field and laboratory studies relating to monitoring techniques, materials, and instrumentation used on reinforced concrete bridge decks under cathodic protection. It provides followup data on Sly Park Bridge, the first known deck to b...

G. H. C. Chang J. A. Apostolos F. A. Myhres

1981-01-01

462

High brightness hollow cathode electron beam source  

SciTech Connect

An optically initiated hollow cathode electrode source has been demonstrated to produce high brightness electron beams in a low presssure background gas. Three phases of beam production have been identified, first a 3A, 20nsec, 45keV, 10[sup 10]A/m[sup 2]rad[sup 2] initial beam, second a 70A, 100nsec,20keV, 10[sup 11]A/m[sup 2]rad[sup 2] hollow cathode produced beam and third a 200A, steady state, 500eV superemissive cathode produced beam. A steady state hollow cathode produced beam of [similar to]100mA has also been observed. An experimental characterization of the electron beam source is presented.

Kirkman, G.; Reinhardt, N.; Jiang, B. (Integrated Applied Physics Inc. 50 Thayer Road, Waltham, MA 02154 (United States)); Gundersen, M.A.; Hsu, T.Y.; Liou, R.L. (University of Southern California, Los Angeles, CA 90089-0484 (United States)); Temkin, R.J. (Massachusetts Institute of Technology Cambridge, MA 02139 (United States))

1992-07-01

463

Interfacial phenomena on selected cathode materials  

SciTech Connect

We have carried out a series of surface studies of selected cathode materials. Instrumental techniques such as Raman microscopy, surface enhanced Raman spectroscopy (SERS), and atomic force microscopy were used to investigate the cathode surfaces. The goal of this study was to identify detrimental processes which occur at the electrode/electrolyte interface and can lead to electrode degradation and failure during cycling and/or storage at elevated temperatures.

Kostecki, Robert; Matsuo, Yoshiaki; McLarnon, Frank

2001-06-22

464

Anodes for Cathodic Protection of Reinforced Concrete  

Microsoft Academic Search

Consumable anodes were evaluated in the laboratory for use in cathodic protection systems for steel reinforced concrete bridges in coastal environments and in areas where de-icing salts are employed. The anode materials include Zn-hydrogel and thermal-sprayed Zn, Zn-15Al, and Al-12Zn-0.2In. These anodes were evaluated for service in both galvanic (GCP) and impressed current (ICCP) cathodic protection systems. ICCP anodes were

Sophie Bullard; C. B. Cryer; Gordon Holcomb; Stephen Cramer; H. M. Laylor; James Russell; Bernard Covino

2000-01-01

465

The hollow-cathode hot filament arc  

Microsoft Academic Search

A discharge system with a hot filament mounted inside a cylindrical hollow cathode designed to produce a low-pressure arc discharge is described together with the discharge characteristics. The combination of a hot filament and a hollow cathode allows a decrease in discharge operating voltage and a 3-4-fold increase in discharge current as compared to a configuration containing only a hot

D. P. Borisov; N. N. Koval; P. M. Schanin

1996-01-01

466

Characteristics of Hollow Cathode Arc Plasma as a Heat Source  

NASA Astrophysics Data System (ADS)

A feasibility study has been conducted to determine whether Hollow Cathode Arc (HCA) can be used for a welding heat source in space. The HCA method enables an arc discharge to ignite and maintain under low pressure conditions, where it is extremely difficult for the conventional Gas Tungsten Arc (GTA) method to form an arc discharge. In the previous paper, it has been demonstrated that the melting process by HCA under the condition that the gas flow rate is high (1.7ml/s) is significantly dominated by the diffuse anode and is characterized by shallow penetration, and that the electron temperature is about 1200018000K in arc space. In the present paper, the volt-ampere characteristics and the plasma property of HCA under the condition that the gas flow rate is low (0.17ml/s) have been made clear, and the melting phenomenon have been discussed. The results are summarized as follows, (1) The HCA under the condition that the gas flow rate is low is characterized by high voltage and high electron temperature, and the arc column is concentrated under the cathode.(2) The electron temperature is above 60000K near the arc axis.(3) The electrons with high temperature, that is high energy, contribute to the deep/huge penetration under the condition that the gas flowrate is low.

Nishikawa, Hiroshi; Maruyama, Toshikazu; Ohji, Takayoshi

467

Studies of contaminant diffusion in an aquitard and groundwater remediation by reactive metals at Dover Air Force Base, Delaware. Final report, October 1996--January 1998  

SciTech Connect

This project focused on analysis of in-situ concentrations of chlorinated hydrocarbons in an aquitard underlying the site of a prior field- scale investigation of pump-and-treat remediation in sheet-pile test cells at Dover AFB, DE. Another aspect was the conduct of exploratory long-term column investigations of zero-valent metal barrier technologies, as applied to contaminated groundwater taken from the aquifer surrounding the cells. During the post-pumping period, unique conditions of zero flow were maintained within the sheet-pile enclosures. Extensive soil coring was conducted at times corresponding to roughly seven and sixteen months after the termination of the prior project. New modeling approaches were developed both to: (1) apply concentration profile information toward more accurate estimation of plume history (inverse modeling for forensic interpretation); and (2) obtain predictions of the post-pumping contaminant movement (multi-layer diffusion modeling). Results were used to: (1) test the assumption that diffusion alone affected contaminant fate, and (2) conduct additional forensic interpretations and field-scale simulations. The column investigations provided long-term verification of halogenated alkene removal under essentially in situ groundwater conditions, including continuous removal of cis-1,2-dichloroethene. Results also confirmed that dichloromethane is not removed and showed apparent breakthrough of two other chemicals, tentatively identified as dichloroethanes.

Ball, W.P.; Chongxuan, L.; Wilson, R.D.; Mackey, D.M.

1998-01-23

468

Alternative cathodes for molten carbonate fuel cells  

SciTech Connect

Argonne National Laboratory (ANL) is developing advanced cathodes for pressurized operation of the molten carbonate fuel cell (MCFC). The present cathode, lithiated nickel oxide, tends to transport to the anode of the MCFC, where it is deposited as metallic nickel. The rate of transport increases with increasing CO{sub 2} pressure. This increase is due to an increased solubility of nickel oxide (NiO) in the molten carbonate electrolyte. An alternative cathode is lithium cobaltate (LiCoO{sub 2})-Solid solutions of LiCoO{sub 2} in LiFeO{sub 2} show promise for long-lived cathode materials. We have found that small additions of LiCoO{sub 2} to LiFeO{sub 2} markedly decrease the resistivity of the cathode material. Cells containing the LiCoO{sub 2}-LiFeO{sub 2} cathodes have stable performance for more than 2100 h of operation and display lower cobalt migration.

Bloom, I.; Lanagan, M.; Roche, M.F.; Krumpelt, M.

1996-02-01

469

Ir-coated dispenser cathode for CRT  

NASA Astrophysics Data System (ADS)

A compact dispenser cathode has been developed for application to CRTs. A cathode emitter, comprising BaO, CaO, and Al2O3 in a molar ratio of 4:1:1, was impregnated into a porous tungsten pellet. An intermetallic compound of tungsten and iridium was formed on the cathode pellet. Heater ratings were 6.3 V x 0.2 A. Emission characteristics were measured by using color CRTs. As a result, a cathode peak loading of 15 A/sq cm was ensured in the space-charge region. Furthermore, life tests with a peak loading of 7.5 A/sq cm were conducted over 10,000 h. The decrease in emission current after 10 000 h was within only 10 percent of the initial value. Reliability of cathode performance was assured in terms of breakdown potential between the heater and the cathode, emission characteristics, life performance, grid emission, and the drift in cutoff potential. In addition, the effects of the coating thickness on the emission characteristics are discussed.

Kimura, Sakae; Yakabe, Toru; Matsumoto, Sadao; Miyazaki, Daisuke; Yoshii, Tsuyoshi

1990-12-01

470

LOW TEMPERATURE CATHODE SUPPORTED ELECTROLYTES  

SciTech Connect

This report represents a summary of the work carried out on this project which started October 1999 and ended March 2003. A list of the publications resulting from the work are contained in Appendix A. The most significant achievements are: (1) Dense nanocrystalline zirconia and ceria films were obtained at temperatures < 400 C. (2) Nanocrystalline films of both ceria and zirconia were characterized. (3) We showed that under anodic conditions 0.5 to 1 micron thick nanocrystalline films of Sc doped zirconia have sufficient electronic conductivity to prevent them from being useful as an electrolyte. (4) We have developed a process by which dense 0.5 to 5 micron thick dense films of either YSZ or ceria can be deposited on sintered porous substrates which serve as either the cathode or anode at temperatures as low as 400 C. (5) The program has provided the research to produce two PhD thesis for students, one is now working in the solid oxide fuel cell field. (6) The results of the research have resulted in 69 papers published, 3 papers submitted or being prepared for publication, 50 oral presentations and 3 patent disclosures.

Harlan U. Anderson; Fatih Dogan; Vladimir Petrovsky

2003-03-31

471

DESCRIPTION OF ATMOSPHERIC TRANSPORT PROCESSES IN EULERIAN AIR QUALITY MODELS  

EPA Science Inventory

Key differences among many types of air quality models are the way atmospheric advection and turbulent diffusion processes are treated. Gaussian models use analytical solutions of the advection-diffusion equations. Lagrangian models use a hypothetical air parcel concept effecti...

472

Analysis of deformed palladium cathodes resulting from heavy water electrolysis  

SciTech Connect

Earlier experiments suggested that large differences in heat release between the two sides of a palladium electrode coated with gold on one side and manganese oxide on the other cause observed electrode deformation with high-pressure D{sub 2} gas loading in an electrolysis-like cell. Similar experiments were repeated using heavy water electrolysis. Palladium/titanium coatings on one side and gold coating on the other were made for the preparation of the palladium electrodes. Biaxial bending, partial discoloration, and microcracks of palladium electrodes were observed after 18 days of electrolysis. Analysis of the deformed palladium cathodes was performed. It was discovered that to convert this configuration to a practical energy-producing cell, a coating technique must be found to reduce outward diffusion of deuterium, i.e., to maintain a high D/Pd ratio over longer periods of time. 33 refs., 7 figs., 1 tab.

An, H.K.; Jeong, E.J.; Hong, J.H.; Lee, Y. [Research Inst. of Industrial Science and Technology, Kyoungbuk (Korea, Republic of)

1995-07-01

473

Diffusive exchange of polycyclic aromatic hydrocarbons across the air-water interface of the Patapsco River, an urbanized subestuary of the Chesapeake Bay  

SciTech Connect

Air-water exchange fluxes of 13 polycyclic aromatic hydrocarbons (PAHs) were determined along a transect in the Patapsco River from the Inner Harbor of Baltimore, MD, to the mainstem of the northern Chesapeake Bay. Sampling took place at six sites during three sampling intensives (June 1996, February 1997, and July 1997) and at one site every ninth day between March 1997 and March 1998 to measure spatial, daily, and annual variability in the fluxes. The direction and magnitude of the daily fluxes of individual PAHs were strongly influenced by the wind speed and direction, by the air temperature,