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Sample records for cathodes

  1. Cathodic Protection Model Facility

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: Performs Navy design and engineering of ship and submarine impressed current cathodic protection (ICCP) systems for underwater hull corrosion control and...

  2. Improved Dispenser Cathodes

    Science.gov (United States)

    Ives, R. Lawrence; Falce, Lou

    2006-01-01

    Variations in emission current from dispenser cathodes can be caused by variations in temperature and work function over the surface. This paper described research to reduce these variations using improved mechanical designs and controlled porosity cathodes made from sintered tungsten wires. The program goal is to reduce current emission variations to less than 5% over the surface of magnetron injection guns operating temperature limited.

  3. Nanostructured sulfur cathodes

    KAUST Repository

    Yang, Yuan

    2013-01-01

    Rechargeable Li/S batteries have attracted significant attention lately due to their high specific energy and low cost. They are promising candidates for applications, including portable electronics, electric vehicles and grid-level energy storage. However, poor cycle life and low power capability are major technical obstacles. Various nanostructured sulfur cathodes have been developed to address these issues, as they provide greater resistance to pulverization, faster reaction kinetics and better trapping of soluble polysulfides. In this review, recent developments on nanostructured sulfur cathodes and mechanisms behind their operation are presented and discussed. Moreover, progress on novel characterization of sulfur cathodes is also summarized, as it has deepened the understanding of sulfur cathodes and will guide further rational design of sulfur electrodes. © 2013 The Royal Society of Chemistry.

  4. Cathodes - Technological review

    International Nuclear Information System (INIS)

    Lithium cobalt oxide (LiCoO2) was already used in the first commercialized Li-ion battery by SONY in 1990. Still, it is the most frequently used cathode material nowadays. However, LiCoO2 is intrinsically unstable in the charged state, especially at elevated temperatures and in the overcharged state causing volume changes and transport limitation for high power batteries. In this paper, some technological aspects with large impact on cell performance from the cathode material point of view will be reviewed. At first it will be focused on the degradation processes and life-time mechanisms of the cathode material LiCoO2. Electrochemical and structural results on commercial Li-ion batteries recorded during the cycling will be discussed. Thereafter, advanced nanomaterials for new cathode materials will be presented

  5. Cathode materials review

    International Nuclear Information System (INIS)

    The electrochemical potential of cathode materials defines the positive side of the terminal voltage of a battery. Traditionally, cathode materials are the energy-limiting or voltage-limiting electrode. One of the first electrochemical batteries, the voltaic pile invented by Alessandro Volta in 1800 (Phil. Trans. Roy. Soc. 90, 403-431) had a copper-zinc galvanic element with a terminal voltage of 0.76 V. Since then, the research community has increased capacity and voltage for primary (nonrechargeable) batteries and round-trip efficiency for secondary (rechargeable) batteries. Successful secondary batteries have been the lead-acid with a lead oxide cathode and a terminal voltage of 2.1 V and later the NiCd with a nickel(III) oxide-hydroxide cathode and a 1.2 V terminal voltage. The relatively low voltage of those aqueous systems and the low round-trip efficiency due to activation energies in the conversion reactions limited their use. In 1976, Wittingham (J. Electrochem. Soc., 123, 315) and Besenhard (J. Power Sources 1(3), 267) finally enabled highly reversible redox reactions by intercalation of lithium ions instead of by chemical conversion. In 1980, Goodenough and Mizushima (Mater. Res. Bull. 15, 783-789) demonstrated a high-energy and high-power LiCoO2 cathode, allowing for an increase of terminal voltage far beyond 3 V. Over the past four decades, the international research community has further developed cathode materials of many varieties. Current state-of-the-art cathodes demonstrate voltages beyond any known electrolyte stability window, bringing electrolyte research once again to the forefront of battery research

  6. Highly Efficient Micro Cathode Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Busek Company, Inc. proposes to develop a micro thermionic cathode that requires extremely low power and provides long lifetime. The basis for the cathode is a...

  7. Advanced Cathode Electrolyzer (ACE) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed innovation is a static, cathode-fed, 2000 psi, balanced-pressure Advanced Cathode Electrolyzer (ACE) based on PEM electrolysis technology. It...

  8. Cathode material for lithium batteries

    Science.gov (United States)

    Park, Sang-Ho; Amine, Khalil

    2013-07-23

    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.

  9. Smart cathodic protection systems

    NARCIS (Netherlands)

    Polder, R.B.; Leggedoor, J.; Schuten, G.; Sajna, S.; Kranjc, A.

    2010-01-01

    Cathodic protection delivers corrosion protection in concrete structures exposed to aggressive environments, e.g. in de-icing salt and marine climates. Working lives of a large number of CP systems are at least more than 13 years and probably more than 25 years, provided a minimum level of maintenan

  10. Pipeline integrity through cathodic protection

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, N. [Gas Authority India Ltd., New Delhi (India); Khanna, A.S. [Indian Inst. of Technology, Bombay (India)

    2008-07-01

    Pipeline integrity management is defined as a process for assessing and mitigating pipeline risks in an effort to reduce both the likelihood and consequences of incidents. Defects on pipelines result in production losses, environmental losses, as well as loss of goodwill and subsequent financial losses. This presentation addressed pipeline integrity through cathodic protection. It noted that pipeline integrity can be strengthened by successfully controlling, monitoring and mitigating corrosion strategies. It can also be achieved by avoiding external and internal corrosion failures. A good coating offers the advantages of low current density; lower power consumption; low wear of anodes; larger spacing between cathodic protection stations; and minimization of interference problems. The presentation reviewed cathodic protection of cross-country pipelines; a sacrificial cathodic protection system; and an impressed current cathodic protection system. The efficiency of a cathodic system was shown to depend on the use of reliable power sources; proper protection criterion; efficient and effective monitoring of cathodic protection; proper maintenance of the cathodic protection system; and effective remedial measures. Selection criteria, power sources, and a comparison of cathodic protection sources were also presented. Last, the presentation addressed protection criteria; current interruption circuits; monitoring of the cathodic protection system; use of corrosion coupons; advantages of weightless coupons; checking the insulating flanges for shorted bolts; insulated/short casings; anodic and cathodic interference; common corridor problems; and intelligent pigging. tabs., figs.

  11. Arc cathode spots

    International Nuclear Information System (INIS)

    Arc spots are usually highly unstable and jump statistically over the cathode surface. In a magnetic field parallel to the surface, preferably they move in the retrograde direction; i.e., opposite to the Lorentzian rule. If the field is inclined with respect to the surface, the spots drift away at a certain angle with respect to the proper retrograde direction (Robson drift motion). These well-known phenomena are explained by one stability theory

  12. Emission from ferroelectric cathodes

    International Nuclear Information System (INIS)

    The authors have recently initiated an investigation of electron emission from ferroelectric cathodes. The experimental apparatus consisted of an electron diode and a 250 kV, 12 ohm, 70 ns pulsed high voltage power source. A planar triode modulator driven by a synthesized waveform generator initiates the polarization inversion and allows inversion pulse tailoring. The pulsed high voltage power source is capable of delivering two high voltage pulses within 50 μs of each other and is capable of operating at a sustained repetition rate of 5 Hz. The initial measurements indicate that emission current densities above the Child-Langmuir Space Charge Limit, JCL, are possible. They explain this effect to be based on a non-zero initial energy of the emitted electrons. They also determined that this effect is strongly coupled to relative timing between the inversion pulse and application of the main anode-cathode pulse. They also have initiated brightness measurements of the emitted beam and estimate a preliminary lower bound to be on the order of 109 A/m2-rad2 for currents close to JCL and factor of two less at currents over 4JCL. As in previous measurements at this Laboratory, they performed the measurement using a pepper pot technique. Beamlet profiles are recorded with a fast phosphor and gated cameras. They describe their apparatus and preliminary measurements

  13. Nanostructured lanthanum manganate composite cathode

    DEFF Research Database (Denmark)

    Wang, Wei Guo; Liu, Yi-Lin; Barfod, Rasmus;

    2005-01-01

    that the (La1-xSrx)(y)MnO3 +/-delta (LSM) composite cathodes consist of a network of homogenously distributed LSM, yttria-stabilized zirconia (YSZ), and pores. The individual grain size of LSM or YSZ is approximately 100 nm. The degree of contact between cathode and electrolyte is 39% on average. (c...

  14. Virtual cathode microwave devices -- Basics

    Energy Technology Data Exchange (ETDEWEB)

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

    1991-01-01

    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.

  15. Virtual cathode microwave devices: Basics

    Science.gov (United States)

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

    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 while in other designs 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.

  16. Miniature Reservoir Cathode: An Update

    Science.gov (United States)

    Vancil, Bernard K.; Wintucky, Edwin G.

    2002-01-01

    We report on recent work to produce a small low power, low cost reservoir cathode capable of long life (more than 100,000 hours) at high loading (> 5 A/sq cm). Our objective is a highly manufacturable, commercial device costing less than $30. Small highly loaded cathodes are needed, especially for millimeter wave tubes, where focusing becomes difficult when area convergence ratios are too high. We currently have 3 models ranging from .060-inch diameter to. 125-inch diameter. Reservoir type barium dispenser cathodes have a demonstrated capability for simultaneous high emission density and long life. Seven reservoir cathodes continue to operate on the cathode life test facility at NSWC, Crane, Indiana at 2 and 4 amps/sq cm. They have accumulated nearly 100,000 hours with practically no change in emission levels or knee temperature.

  17. Hollow Cathode With Multiple Radial Orifices

    Science.gov (United States)

    Brophy, John R.

    1992-01-01

    Improved hollow cathode serving as source of electrons has multiple radial orifices instead of single axial orifice. Distributes ion current more smoothly, over larger area. Prototype of high-current cathodes for ion engines in spacecraft. On Earth, cathodes used in large-diameter ion sources for industrial processing of materials. Radial orientation of orifices in new design causes current to be dispersed radially in vicinity of cathode. Advantageous where desireable to produce plasma more nearly uniform over wider region around cathode.

  18. Micro-hollow cathode dischargers

    International Nuclear Information System (INIS)

    In order to develop a hollow cathode discharge (HCD) with its increased current over planar electrode glow discharges, the cathode fall, which is on the order of the mean free path for ionization, must be comparable in length to the hole diameter. This indicates that the discharge parameters vary with pressure, p, times hole diameter, D. The pD product for stable operation of a hollow cathosde discharge was quoted to be on the order of one to ten Torr cm for noble gases, less for molecular gases. White (1959) observed the hollow cathode effect in a neon discharge at a pressure of 100 Torr when the hole dimensions were less than 1 mm. The cathode hole in his experiments changed from a cylindrical into a spherical cavity due to sputtering. The anode consisted in White's experiment of a pin on the axis of the discharge geometry. We have studied micro-hollow (submillimeter) cathode discharges between two electrodes with aligned cylindrical holes by determining the current-voltage characteristics and the visual appearance of the discharge in argon over a wide range of pressure and voltage. The cross-section of the discharge geometry. The cathode is made of molybdenum or barium oxide inserted into a tungsten matrix (dispenser-cathode), the anode of molybdenum, and the dielectric spacer is mica. The discharge was operated under dc conditions, with half-wave rectified ac voltage applied, and pulsed with a 400 μs rectangular voltage pulse. The lower limit in pressure was determined by the maximum voltage which could be applied to the discharge geometry without breakdown along insulators. The upper limit, in this study, is determined by the transition from cathode electrode emission due to ion-impact to thermal emission of electrons, which causes a dramatic increase in current and a drop in forward voltage to values on the order of 20 V

  19. Hollow cathode hydrogen ion source

    International Nuclear Information System (INIS)

    High current density ion sources have been used to heat plasmas in controlled thermonuclear reaction experiments. High beam currents imply relatively high emission currents from cathodes which have generally taken the form of tungsten filaments. This paper describes a hydrogen ion source which was primarily developed to assess the emission current capability and design requirements for hollow cathodes for application in neutral injection devices. The hydrogen source produced ions by electron bombardment via a single hollow cathode. Source design followed mercury ion thruster technology, using a weak magnetic field to enhance ionization efficiency. A 1.3-cm diameter hollow cathode using a low work function material dispenser performed satisfactorily over a discharge current range of 10 to 90 A. Cylindrical probe measurements taken without ion extraction indicate maximum ion number densities on the order of 1012 cm-3. Discharge durations ranged from 30 seconds to continuous operation. Tests with beam extraction at 2.5 keV and 30 A discharge current yield average ion beam current densities of 0.1 A cm-2 over a 5-cm extraction diameter. Results of this study can be used to supply the baseline information needed to scale hollow cathodes for operation at discharge currents of hundreds of amperes using distributed cathodes

  20. Reservoir Cathode for Electric Space Propulsion Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose a hollow reservoir cathode to improve performance in ion and Hall thrusters. We will adapt our existing reservoir cathode technology to this purpose....

  1. Reservoir Cathode for Electric Space Propulsion Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose a reservoir cathode to improve performance in both ion and Hall-effect thrusters. We propose to adapt our existing reservoir cathode technology to this...

  2. Hollow cathode arc: effect of the cathode material on the internal plasma

    International Nuclear Information System (INIS)

    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 lathanum hexaboride have been used. The parameters of the plasma generated into the cathode have been measured with electrostatic probes. (Auth.)

  3. Mechanistic Enhancement of SOFC Cathode Durability

    Energy Technology Data Exchange (ETDEWEB)

    Wachsman, Eric [Univ. of Maryland, College Park, MD (United States)

    2016-02-01

    Durability of solid oxide fuel cells (SOFC) under “real world” conditions is an issue for commercial deployment. In particular cathode exposure to moisture, CO2, Cr vapor (from interconnects and BOP), and particulates results in long-term performance degradation issues. Here, we have conducted a multi-faceted fundamental investigation of the effect of these contaminants on cathode performance degradation mechanisms in order to establish cathode composition/structures and operational conditions to enhance cathode durability.

  4. Cathodic protection to control microbiologically influenced corrosion

    International Nuclear Information System (INIS)

    Information about the cathodic protection performance in environments with microbiologically influenced corrosion (MIC) effects is very fragmented and often contradictory. Not enough is known about the microbial effects on cathodic protection effectiveness, criteria, calcareous deposits, corrosion rates and possible hydrogen embrittlement of titanium and some stainless steel condenser tubes. This paper presents a review of cathodic protection systems, describes several examples of cathodic protection in environments with MIC effects and provides preliminary conclusions about cathodic protection design parameters, criteria and effectiveness in MIC environments. 30 refs

  5. Synopsis of Cathode No.4 Activation

    International Nuclear Information System (INIS)

    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

  6. Hybrid microwave oscillators with a virtual cathode

    International Nuclear Information System (INIS)

    A review is given of the developments and theoretical investigations of a fundamentally new class of microwave devices, namely, hybrid microwave oscillators with a virtual cathode, which combine the useful properties of virtual cathodes with the advantages of those traditional microwave oscillators that operate with subcritical-current beams and have a high efficiency in generating ultrarelativistic electron beams. Among such devices are the following: a hybrid diffractional microwave oscillator with a virtual cathode, a hybrid gyro-device with a virtual cathode, a hybrid beam-plasma vircator, a hybrid gyrocon with a virtual cathode, a hybrid Cherenkov oscillator with a virtual cathode, a hybrid microwave oscillator of the 'vircator + traveling-wave tube' type, an original two-beam tube with a virtual cathode, and a klystron-like vircator

  7. LOW TEMPERATURE CATHODE SUPPORTED ELECTROLYTES

    Energy Technology Data Exchange (ETDEWEB)

    Harlan U. Anderson; Fatih Dogan; Vladimir Petrovsky

    2002-03-31

    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

  8. Barium-Dispenser Thermionic Cathode

    Science.gov (United States)

    Wintucky, Edwin G.; Green, M.; Feinleib, M.

    1989-01-01

    Improved reservoir cathode serves as intense source of electrons required for high-frequency and often high-output-power, linear-beam tubes, for which long operating lifetime important consideration. High emission-current densities obtained through use of emitting surface of relatively-low effective work function and narrow work-function distribution, consisting of coat of W/Os deposited by sputtering. Lower operating temperatures and enhanced electron emission consequently possible.

  9. Hollow cathode startup using a microplasma discharge

    Science.gov (United States)

    Aston, G.

    1981-01-01

    Attention is given to a microplasma discharge to initiate a hollow cathode discharge for such applications as plasma flow experiments, the electric propulsion of space vehicles, and as a replacement for filament cathodes in neutral beam injector ion sources. The technique results in a cathode that is easy to start, simple in design, and which does not require external RF exciters, inserts or heating elements. Future applications may include ion beam milling and ion implantation.

  10. Oxidation studies of impregnated dispenser cathodes

    International Nuclear Information System (INIS)

    We report on surface studies of the type M and type S impregnated dispenser cathode using synchrotron radiation photoemission spectroscopy. The results indicate the presence of two barium configurations on the room temperature type S surface, probably barium metal and BaO. The room-temperature type M cathode has about a monolayer of barium metal and about a monolayer of tungsten, apparently alloyed to the Os/Ru coating, on the surface. The barium-related features of the type S cathode are extremely sensitive to small oxygen exposures, while the tungsten-related features are more sensitive to oxygen in the type M cathode

  11. Cathode-follower power amplifier

    International Nuclear Information System (INIS)

    In circular accelerators and particularly in storage rings it is essential that the total impedance, as seen by the beam, be kept below some critical value. A model of the accelerating system was built using a single-ended cathode-follower amplifier driving a ferrite-loaded cavity. The system operated at 234.5 kHz with a peak output voltage of +-10 kV on the gap. The dynamic output impedance, as measured on the gap, was < 15 ohms

  12. Hollow cathode lamp-construction aspects

    International Nuclear Information System (INIS)

    The hollow cathode discharge is a source used for absorption and fluorescence atomic spectrophotometry. In this paper various aspect like construction, cleanliness and operation have been described. The life time of the hollow cathode discharge for specific current is about 500 hs. The range of current for the non significant self-absorption of the recommended wavelenght has been determinated. (Author)

  13. Field emission cathode for high power beams

    International Nuclear Information System (INIS)

    Field emission is identified as the mechanism responsible for high current emission (50 A/cm2 at 3000K) from a dispenser-type cathode. This cathode has advantages for high power operation, and should be suitable for practical applications. (author)

  14. Effects of a low work function cathode on electron beam generation in a hollow cathode discharge

    International Nuclear Information System (INIS)

    Recent simulations reveal that a large contribution to the formation of the hollow cathode discharge comes from secondary electron emission due to ion bombardment of the hollow cathode surface. The simulations suggest that a decrease in work function of the hollow cathode surface will lead to enhanced plasma formation during the initial and latter phases of the discharge. The use of this enhanced plasma to more efficiently generate beams (both ion and electron) was studied. A pulsed hollow cathode discharge was constructed using low work function dispenser cathode material as the hollow cathode. The electron beam characteristics of the discharge were investigated. Other hollow cathodes constructed with various materials (molybdenum, copper) were constructed and the results will be compared. Applications of the new source are discussed

  15. Klystron Amplifier Utilizing Scandate Cathode and Electrostatic Focusing Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to build an electrostatically focused klystron that exploits recent breakthroughs in scandate cathode technology. We have built cathodes with greater...

  16. Physics of thermionic dispenser cathode aging

    Science.gov (United States)

    Longo, R. T.

    2003-11-01

    A dispenser cathode life model (DCLM) was originally published in 1984. More recent life test data have substantiated the basic physics used in the DCLM. However, re-evaluation of the model with this latest data alters the numerical parameters used in the model. The most important modification is the incorporation of the shape factor, α, in the emission equation, so that accurate descriptions of the cathode activity curves (i.e., current versus temperature) can be made as a function of cathode age. The original model was fit only to the cathode current as a function of time for a fixed operating temperature. This revision fits the cathode activity curves as a function of both time and cathode temperature. Variation in cathode current as a function of temperature is quite dependent upon the underlying physics, and gives a better measure of how the internal parameters, such as work function and knee position and knee shape change with time. Knowing these details provides a more accurate measure of how the cathode current at the operating point will change over time. The modification made to the emission equation in this revision incorporates the shape factor, α, which is a single number that describes the shape of the cathode activity curves. The shape factor is found to be dependent on time: The knee softens and rounds with age. Even though the shape factor was originally introduced as an empirical factor, I will present a theoretical model for the shape factor that provides some insight into its physical interpretation. This theory will show that it can be related to the thermodynamics of the emitter surface. The re-evaluation of the DCLM, based on the latest life data, and including the theory for the shape factor yields a longer life expectancy for the M-type dispenser cathode then was predicted by the original more conservative life model. The DCLM matches the observed life data more accurately.

  17. Analysis of cathode geometry to minimize cathode erosion in direct current microplasma jet

    Energy Technology Data Exchange (ETDEWEB)

    Causa, Federica [Dipartimento di Scienze dell' Ambiente, della Sicurezza, del Territorio, degli Alimenti e della Salute, Universita degli studi di Messina, 98122 Messina (Italy); Ghezzi, Francesco; Caniello, Roberto; Grosso, Giovanni [Istituto di Fisica del Plasma, Consiglio Nazionale delle Ricerche, EURATOM-ENEA-CNR Association, Via R. Cozzi 53, 20125 Milano (Italy); Dellasega, David [Istituto di Fisica del Plasma, Consiglio Nazionale delle Ricerche, EURATOM-ENEA-CNR Association, Via R. Cozzi 53, 20125 Milano (Italy); Dipartimento di Energia, Politecnico di Milano, Via Ponzio 34/3, 20133 Milano (Italy)

    2012-12-15

    Microplasma jets are now widely used for deposition, etching, and materials processing. The present study focuses on the investigation of the influence of cathode geometry on deposition quality, for microplasma jet deposition systems in low vacuum. The interest here is understanding the influence of hydrogen on sputtering and/or evaporation of the electrodes. Samples obtained with two cathode geometries with tapered and rectangular cross-sections have been investigated experimentally by scanning electron microscopy and energy dispersion X-ray spectroscopy. Samples obtained with a tapered-geometry cathode present heavy contamination, demonstrating cathode erosion, while samples obtained with a rectangular-cross-section cathode are free from contamination. These experimental characteristics were explained by modelling results showing a larger radial component of the electric field at the cathode inner wall of the tapered cathode. As a result, ion acceleration is larger, explaining the observed cathode erosion in this case. Results from the present investigation also show that the ratio of radial to axial field components is larger for the rectangular geometry case, thus, qualitatively explaining the presence of micro-hollow cathode discharge over a wide range of currents observed in this case. In the light of the above findings, the rectangular cathode geometry is considered to be more effective to achieve cleaner deposition.

  18. Batteries: Overview of Battery Cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Doeff, Marca M

    2010-07-12

    The very high theoretical capacity of lithium (3829 mAh/g) provided a compelling rationale from the 1970's onward for development of rechargeable batteries employing the elemental metal as an anode. The realization that some transition metal compounds undergo reductive lithium intercalation reactions reversibly allowed use of these materials as cathodes in these devices, most notably, TiS{sub 2}. Another intercalation compound, LiCoO{sub 2}, was described shortly thereafter but, because it was produced in the discharged state, was not considered to be of interest by battery companies at the time. Due to difficulties with the rechargeability of lithium and related safety concerns, however, alternative anodes were sought. The graphite intercalation compound (GIC) LiC{sub 6} was considered an attractive candidate but the high reactivity with commonly used electrolytic solutions containing organic solvents was recognized as a significant impediment to its use. The development of electrolytes that allowed the formation of a solid electrolyte interface (SEI) on surfaces of the carbon particles was a breakthrough that enabled commercialization of Li-ion batteries. In 1990, Sony announced the first commercial batteries based on a dual Li ion intercalation system. These devices are assembled in the discharged state, so that it is convenient to employ a prelithiated cathode such as LiCoO{sub 2} with the commonly used graphite anode. After charging, the batteries are ready to power devices. The practical realization of high energy density Li-ion batteries revolutionized the portable electronics industry, as evidenced by the widespread market penetration of mobile phones, laptop computers, digital music players, and other lightweight devices since the early 1990s. In 2009, worldwide sales of Li-ion batteries for these applications alone were US$ 7 billion. Furthermore, their performance characteristics (Figure 1) make them attractive for traction applications such as

  19. Cathodic behavior of zirconium in aqueous solutions

    International Nuclear Information System (INIS)

    The electrochemical behavior of Zr was studied by polarization measurements. The surface oxide and zirconium hydride formed by cathodic polarization of Zr have been examined by X-ray, SEM, and a hardness tester. Zirconium hydride would form on Zr cathode after the surface oxide is reduced at the potential, which is several hundred mV more noble than the predicted value shown by the Pourbaix diagram. The parameters for the hydrogen evolution reaction on the hydride formed Zr cathode differs from that on the oxide covered surface, which means that hydrogen evolution takes place on both surfaces under a different mechanism, while details are still veiled at present

  20. Plasma distribution of cathodic ARC deposition system

    Energy Technology Data Exchange (ETDEWEB)

    Anders, S.; Raoux, S.; Krishnan, K.; MacGill, R.A.; Brown, I.G. [Lawrence Berkeley National Lab., CA (United States)

    1996-08-01

    The plasma distribution using a cathodic arc plasma source with and without magnetic macroparticle filter has been determined by depositing on a transparent plastic substrate and measuring the film absorption. It was found that the width of the distribution depends on the arc current, and it also depends on the cathode material which leads to a spatial separation of the elements when an alloy cathode is used. By applying a magnetic multicusp field near the exit of the magnetic filter, it was possible to modify the plasma distribution and obtain a flat plasma profile with a constant and homogeneous elemental distribution.

  1. Cyclotron resonance in a cathode ray tube

    International Nuclear Information System (INIS)

    Absorption of the RF energy by the electron beam in a cathode ray tube due to the cyclotron resonance is described. The cathode ray tube is placed within a Helmholtz coils system supplied by a sawtooth current generator. In order to generate RF field and to detect RF absorption a gate dip-meter equipped with a FET transistor is used. The bias voltage variations of the FET transistors as a function of the magnetic field are recorded. The operating point of the cathode ray tube has been chosen so that the relaxation oscillations of the detection system can be observed. (authors)

  2. High power microwave generation from coaxial virtual cathode oscillator using graphite and velvet cathodes

    Science.gov (United States)

    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

    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.

  3. Construction of cathode thermometry and emission test system

    International Nuclear Information System (INIS)

    A thermal cathode (Eimac Y-845) is used for an electron gun at the SPring-8 1-GeV linac. The gun can eject a 180 keV beam of 3 A from the cathode operated at a nominal heater voltage. As the discharge rate between the cathode and the grid becomes high along with the cathode driving time, we replace a cathode with a new one once a year. Before the cathode installation, we have definitely inspected new cathodes by means of a microscope to find defects in their cathodes and grids. However, the emission currents have been sometimes insufficient, or the cathode planes have contacted with the grids due to the heat distortion of the grids. We have suspected that the inadequate cathode temperature may have caused these cathode failures. To monitor the accurate cathode temperature and to reduce the cathode failures, we have constructed a measuring system of the cathode temperatures and the cathode emission currents at the test stand. We redesigned the whenelt and the anode to achieve a space-charge-limited current of 3 A at an acceleration voltage less than -70 kV. The cathode temperature at the nominal heater voltage is expected to be 854degC according to the Richardson-Dushman equation, whereas the actual temperature measured by an infrared thermometer was 813±5degC. This large disagreement is under investigation. (author)

  4. Hollow cathode ion source without magnetic field

    International Nuclear Information System (INIS)

    On the base of the IBM-4 ion source a hollow cathode source operating in the continuous regime is developed. The gas discharge chamber diameter equals 100 mm, chamber height - 50 mm. A hollow cathode represents a molybdenum tube with an internal diameter 13 mm and wall thickness 0,7-0,8 mm. An emitter is manufactured from zirconium carbide and lanthanum hexaboride. The investigations of the source operation have shown both cathodes operated efficiency. Electron emission density consitutes 25 A/cm2. At the 50 A discharge current ion current density in a center of plasma emitter constitutes 120 mA/cm2. As a result of the investigations carried out the compatibility of the hollow cathode and the IBM-type source is shown

  5. Short pulse photoemission from a dispenser cathode

    Science.gov (United States)

    Bergeret, H.; Boussoukaya, M.; Chehab, R.; Leblond, B.; Le Duff, J.

    1991-03-01

    Pulsed photoemission in the picosecond regime has been obtained from a standard thermionic dispenser cathode (WBaCa) at temperatures below the measurable thermoemission threshold. A picosecond Nd : YAG mode locked laser has been used at both green and UV light. Micropulse charges up to 0.5 nC have been measured on a wideband coaxial pickup located behind the anode. They correspond to an electron saturation limit from an approximately 20 mm 2 illuminated cathode area with a surface field of 3 MV/m. The effective cathode efficiency at small laser energies, defined as the number of electrons impinging on the coaxial pickup divided by the number of photons impinging on the cathode, is about 2 × 10 -5.

  6. Ion bombardment investigations of impregnated cathodes

    Science.gov (United States)

    Zhang, Xiaobing; Gaertner, Georg

    2003-06-01

    Ion bombardment is one of the important factors limiting the performance of impregnated cathodes (=Ba dispenser cathodes) in high end television tubes or in colour monitor tubes. Hence, when designing a new gun with, e.g. higher electron beam current density, it is important also to model the influence of ion bombardment. Therefore, relations between basic parameters as a function of temperature need to be known quantitatively. In this paper, the emission slump of impregnated cathodes has been analyzed in a diode configuration in UHV with a differentially pumped Ar ion gun. The emission degeneration during and regeneration periods after ion bombardment have been investigated as function of cathode temperature, ion current and ion energy. One of the important results is, that the degeneration time coefficient is only weakly dependent on ion energy. The data matrix obtained can be used to improve the ion bombardment model applied in new electron gun design.

  7. Short pulse photoemission from a dispenser cathode

    International Nuclear Information System (INIS)

    Pulsed photoemission in picosecond regime has been obtained from a standard thermionic dispenser cathode (W - Ba - Ca) at temperatures below measurable thermoemission threshold. A picosecond Nd: YAG mode locked laser has been used at both green and U.V. light. Micro-pulse charges up to 0.5 nC have been measured on a wideband coaxial pick up located behind the anode. They correspond to an electron saturation limit from an approximately 20 mm2 illuminated cathode area with a surface field of 3 MV/m. The effective cathode efficiency at small laser energies, defined as the number of electron impinging the coaxial pick up divided by the number of photons impinging the cathode, is about 2.10-5

  8. Ion bombardment investigations of impregnated cathodes

    International Nuclear Information System (INIS)

    Ion bombardment is one of the important factors limiting the performance of impregnated cathodes (=Ba dispenser cathodes) in high end television tubes or in colour monitor tubes. Hence, when designing a new gun with, e.g. higher electron beam current density, it is important also to model the influence of ion bombardment. Therefore, relations between basic parameters as a function of temperature need to be known quantitatively. In this paper, the emission slump of impregnated cathodes has been analyzed in a diode configuration in UHV with a differentially pumped Ar ion gun. The emission degeneration during and regeneration periods after ion bombardment have been investigated as function of cathode temperature, ion current and ion energy. One of the important results is, that the degeneration time coefficient is only weakly dependent on ion energy. The data matrix obtained can be used to improve the ion bombardment model applied in new electron gun design

  9. RF Electron Gun with Driven Plasma Cathode

    CERN Document Server

    Khodak, Igor

    2005-01-01

    It's known that RF guns with plasma cathodes based on solid-state dielectrics are able to generate an intense electron beam. In this paper we describe results of experimental investigation of the single cavity S-band RF gun with driven plasma cathode. The experimental sample of the cathode based on ferroelectric ceramics has been designed. Special design of the cathode permits to separate spatially processes of plasma development and electron acceleration. It has been obtained at RF gun output electron beam with particle energy ~500 keV, pulse current of 4 A and pulse duration of 80 ns. Results of experimental study of beam parameters are referred in. The gun is purposed to be applied as the intense electron beam source for electron linacs.

  10. Reservoir Scandate Cathode for Electric Propulsion Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to combine two revolutionary cathode technologies into a single device for use in electric space propulsion. This will overcome problems that both...

  11. High current density cathode for electrorefining in molten electrolyte

    Science.gov (United States)

    Li, Shelly X.

    2010-06-29

    A high current density cathode for electrorefining in a molten electrolyte for the continuous production and collection of loose dendritic or powdery deposits. The high current density cathode eliminates the requirement for mechanical scraping and electrochemical stripping of the deposits from the cathode in an anode/cathode module. The high current density cathode comprises a perforated electrical insulated material coating such that the current density is up to 3 A/cm.sup.2.

  12. Sodium expansion and creep of cathode carbon

    OpenAIRE

    Hop, Jørund Gimmestad

    2003-01-01

    An apparatus to measure compressive creep in carbon materials has been developed. Using the final experimental set-up five material properties could be measured in each electrolysis experiment. Creep, sodium expansion, compressive strength and E-modulus were measured for 3 commercial cathode materials at 25 and 980 °C with and without electrolysis. The sodium diffusion coefficient (D) was calculated from the sodium expansion results.Filler materials for cathode blocks, i.e., certain anthracit...

  13. Salt taste inhibition by cathodal current

    OpenAIRE

    Hettinger, Thomas P.; Frank, Marion E.

    2009-01-01

    Effects of cathodal current, which draws cations away from the tongue and drives anions toward the tongue, depend on the ionic content of electrolytes through which the current is passed. To address the role of cations and anions in human salt tastes, cathodal currents of −40 to −80 µA were applied to human subjects’ tongues through supra-threshold salt solutions. The salts were sodium chloride, sodium bromide, potassium chloride, ammonium chloride, calcium chloride, sodium nitrate, sodium su...

  14. Co-Flow Hollow Cathode Technology

    Science.gov (United States)

    Hofer, Richard R.; Goebel, Dan M.

    2011-01-01

    Hall thrusters utilize identical hollow cathode technology as ion thrusters, yet must operate at much higher mass flow rates in order to efficiently couple to the bulk plasma discharge. Higher flow rates are necessary in order to provide enough neutral collisions to transport electrons across magnetic fields so that they can reach the discharge. This higher flow rate, however, has potential life-limiting implications for the operation of the cathode. A solution to the problem involves splitting the mass flow into the hollow cathode into two streams, the internal and external flows. The internal flow is fixed and set such that the neutral pressure in the cathode allows for a high utilization of the emitter surface area. The external flow is variable depending on the flow rate through the anode of the Hall thruster, but also has a minimum in order to suppress high-energy ion generation. In the co-flow hollow cathode, the cathode assembly is mounted on thruster centerline, inside the inner magnetic core of the thruster. An annular gas plenum is placed at the base of the cathode and propellant is fed throughout to produce an azimuthally symmetric flow of gas that evenly expands around the cathode keeper. This configuration maximizes propellant utilization and is not subject to erosion processes. External gas feeds have been considered in the past for ion thruster applications, but usually in the context of eliminating high energy ion production. This approach is adapted specifically for the Hall thruster and exploits the geometry of a Hall thruster to feed and focus the external flow without introducing significant new complexity to the thruster design.

  15. Development of plasma cathode electron guns

    Science.gov (United States)

    Oks, Efim M.; Schanin, Peter M.

    1999-05-01

    The status of experimental research and ongoing development of plasma cathode electron guns in recent years is reviewed, including some novel upgrades and applications to various technological fields. The attractiveness of this kind of e-gun is due to its capability of creating high current, broad or focused beams, both in pulsed and steady-state modes of operation. An important characteristic of the plasma cathode electron gun is the absence of a thermionic cathode, a feature which leads to long lifetime and reliable operation even in the presence of aggressive background gas media and at fore-vacuum gas pressure ranges such as achieved by mechanical pumps. Depending on the required beam parameters, different kinds of plasma discharge systems can be used in plasma cathode electron guns, such as vacuum arcs, constricted gaseous arcs, hollow cathode glows, and two kinds of discharges in crossed E×B fields: Penning and magnetron. At the present time, plasma cathode electron guns provide beams with transverse dimension from fractional millimeter up to about one meter, beam current from microamperes to kiloamperes, beam current density up to about 100 A/cm2, pulse duration from nanoseconds to dc, and electron energy from several keV to hundreds of keV. Applications include electron beam melting and welding, surface treatment, plasma chemistry, radiation technologies, laser pumping, microwave generation, and more.

  16. Plasma processes inside dispenser hollow cathodes

    Science.gov (United States)

    Mikellides, Ioannis G.; Katz, Ira; Goebel, Dan M.; Polk, James E.; Jameson, Kristina K.

    2006-06-01

    A two-dimensional fluid model of the plasma and neutral gas inside dispenser orificed hollow cathodes has been developed to quantify plasma processes that ultimately determine the life of the porous emitters inserted in these devices. The model self-consistently accounts for electron emission from the insert as well as for electron and ion flux losses from the plasma. Two cathodes, which are distinctively different in size and operating conditions, have been simulated numerically. It is found that the larger cathode, with outer tube diameter of 1.5cm and orifice diameter of 0.3cm, establishes an effective emission zone that spans approximately the full length of the emitter when operated at a discharge current of 25A and a flow rate of 5.5sccm. The net heating of the emitter is caused by ions that are produced by ionization of the neutral gas inside the tube and are then accelerated by the sheath along the emitter. The smaller cathode, with an outer diameter of 0.635cm and an orifice diameter of 0.1cm, does not exhibit the same operational characteristics. At a flow rate of 4.25sccm and discharge current of 12A, the smaller cathode requires 4.5 times the current density near the orifice and operates with more than 6 times the neutral particle density compared to the large cathode. As a result, the plasma particle density is almost one order of magnitude higher compared to the large cathode. The plasma density in this small cathode is high enough such that the Debye length is sufficiently small to allow "sheath funneling" into the pores of the emitter. By accessing areas deeper into the insert material, it is postulated that the overall emission of electrons is significantly enhanced. The maximum emission current density is found to be about 1A/mm2 in the small cathode, which is about one order of magnitude higher than attained in the large cathode. The effective emission zone in the small cathode extends to about 15% of the emitter length only, and the power

  17. Plasma processes inside dispenser hollow cathodes

    International Nuclear Information System (INIS)

    A two-dimensional fluid model of the plasma and neutral gas inside dispenser orificed hollow cathodes has been developed to quantify plasma processes that ultimately determine the life of the porous emitters inserted in these devices. The model self-consistently accounts for electron emission from the insert as well as for electron and ion flux losses from the plasma. Two cathodes, which are distinctively different in size and operating conditions, have been simulated numerically. It is found that the larger cathode, with outer tube diameter of 1.5 cm and orifice diameter of 0.3 cm, establishes an effective emission zone that spans approximately the full length of the emitter when operated at a discharge current of 25 A and a flow rate of 5.5 sccm. The net heating of the emitter is caused by ions that are produced by ionization of the neutral gas inside the tube and are then accelerated by the sheath along the emitter. The smaller cathode, with an outer diameter of 0.635 cm and an orifice diameter of 0.1 cm, does not exhibit the same operational characteristics. At a flow rate of 4.25 sccm and discharge current of 12 A, the smaller cathode requires 4.5 times the current density near the orifice and operates with more than 6 times the neutral particle density compared to the large cathode. As a result, the plasma particle density is almost one order of magnitude higher compared to the large cathode. The plasma density in this small cathode is high enough such that the Debye length is sufficiently small to allow 'sheath funneling' into the pores of the emitter. By accessing areas deeper into the insert material, it is postulated that the overall emission of electrons is significantly enhanced. The maximum emission current density is found to be about 1 A/mm2 in the small cathode, which is about one order of magnitude higher than attained in the large cathode. The effective emission zone in the small cathode extends to about 15% of the emitter length only, and the

  18. Determination of Nd, Ho, Er, Tm and Y in solutions by hollow cathode discharge with copper cathodes

    International Nuclear Information System (INIS)

    A hollow cathode discharge has been applied to the determination of Nd, Ho, Er, Tm and Y in solutions using copper cathodes and argon as a carrier gas. The solutions were evaporated to dryness in the cathodes without a pretreatment. Absolute detection limit for the elements studied here were found to be lower in the copper cathode by about one order than those obtained in previous studies in graphite hollow cathodes

  19. Experimental Investigation of Thruster Cathode Physics

    Science.gov (United States)

    Crofton, Mark

    2004-11-01

    Advanced ion propulsion technologies are being developed under the Nuclear Electric Xenon Ion System (NEXIS) program for use in outer planet exploration. A revolutionary approach to thruster cathode design is dictated by the very high lifetime and propellant throughput requirements for nuclear electric applications. In conventional dispenser hollow cathodes used in thrusters, processes leading to depletion, inadequate transport, or insufficient production of barium are among those limiting the lifetime. A reservoir hollow cathode is being developed to address each of these failure mechanisms, exploiting four design variables - matrix material, source material, geometry, and thermal design - to essentially eliminate established failure modes. The very long anticipated lifetime necessitates new life validation methods to augment or replace the conventional lifetest approach. One important tool for quickly evaluating design changes is the ability to measure barium density inside a hollow cathode and/or in the plume. The dependence of barium density on temperature and other factors is an extremely important indicator of cathode health, particularly if the ratio Ba:BaO is also obtained. Comparison of barium production for reservoir and conventional cathodes will enable an assessment of the efficacy of reservoir designs and the goal of reducing barium consumption at a given emission current level. This study describes benchmark measurements made on a conventional cathode previously operated in a 20-kW NEXIS laboratory engine. Data on cathode operation and life-limiting processes were obtained through direct, real-time monitoring of atoms and molecules. A high-resolution, tunable laser system was employed to detect absorption of the low-density barium atoms inside the cathode. The plume was monitored also, using a quadrupole mass spectrometer to monitor multiple species and measure ion charge ratios. Data obtained with retarding potential analyzers or other means are

  20. Compact Rare Earth Emitter Hollow Cathode

    Science.gov (United States)

    Watkins, Ronald; Goebel, Dan; Hofer, Richard

    2010-01-01

    A compact, high-current, hollow cathode utilizing a lanthanum hexaboride (LaB6) thermionic electron emitter has been developed for use with high-power Hall thrusters and ion thrusters. LaB6 cathodes are being investigated due to their long life, high current capabilities, and less stringent xenon purity and handling requirements compared to conventional barium oxide (BaO) dispenser cathodes. The new cathode features a much smaller diameter than previously developed versions that permit it to be mounted on axis of a Hall thruster ( internally mounted ), as opposed to the conventional side-mount position external to the outer magnetic circuit ("externally mounted"). The cathode has also been reconfigured to be capable of surviving vibrational loads during launch and is designed to solve the significant heater and materials compatibility problems associated with the use of this emitter material. This has been accomplished in a compact design with the capability of high-emission current (10 to 60 A). The compact, high-current design has a keeper diameter that allows the cathode to be mounted on the centerline of a 6- kW Hall thruster, inside the iron core of the inner electromagnetic coil. Although designed for electric propulsion thrusters in spacecraft station- keeping, orbit transfer, and interplanetary applications, the LaB6 cathodes are applicable to the plasma processing industry in applications such as optical coatings and semiconductor processing where reactive gases are used. Where current electrical propulsion thrusters with BaO emitters have limited life and need extremely clean propellant feed systems at a significant cost, these LaB6 cathodes can run on the crudest-grade xenon propellant available without impact. Moreover, in a laboratory environment, LaB6 cathodes reduce testing costs because they do not require extended conditioning periods under hard vacuum. Alternative rare earth emitters, such as cerium hexaboride (CeB6) can be used in this

  1. Contactless monitoring of cathodic protection

    International Nuclear Information System (INIS)

    Cathodic protection is a very efficient and economical way for protecting underground structures from electrolytic corrosion. The protection is maintained when the potential between the structure surface and the surrounding electrolyte keeps the material in an immune state from corrosion. This means, that the potential on every spot of the protected pipeline should be checked and maintained. Checking the potential can be on few way. The classical way, measuring the pipe to soil potential on the test post spaced 1 - 2 km apart only 'potential samples' can be obtained while 'hot spots' can be left between the test post. The so called 'intensive measurements', when potential is surveyed along the pipeline by a moving electrode connected to a test post. By checking the magnetic field of the returning current along the pipeline, the same anomalies can be found, as by checking the potential distribution along the pipeline, so the places with contacts with foreign structures or coating damages can be located. This measurements can be done by one person walking along the pipeline route. If the pipe route is without obstacles, the measurements can be performed from a vehicle moving along the pipe route. By using a computer based recording device in the vehicle, the measured values can be combined with the location of the anomalies and the printout will show directly the sort and location of the anomalies. Using a helicopter, when up to several hundreds of km pipeline route can be checked daily, makes further improvements. This paper presents current situation on this field, and equipment in FZC I I Oktomvri in Kumanovo. (Author)

  2. Preparation of nanocomposite thoriated tungsten cathode by swaging technique

    Institute of Scientific and Technical Information of China (English)

    王发展; 诸葛飞; 张晖; 丁秉钧

    2002-01-01

    By using the high energy ball milling method,the nanosized ThO2 powders were obtained.Through mixing powders,sintering and hot swaging processing,a nanocomposite thoriated tungsten cathode was fabricated.The relative density of the nanocomposite material is near 100%.The microstructure of nanocomposite cathode is quite different from that of conventional thoriated tungsten cathode.Most of thoria particles are less than 100 nm in diameter,and distribute on the boundaries of tungsten grains.The nanocomposite cathode shows a much lower arc starting field than that of conventional cathode,which will improve the performance of the cathode significantly.

  3. Close cathode chamber: Low material budget MWPC

    International Nuclear Information System (INIS)

    Performance of asymmetric-type MWPC-s are presented. In this structure, referred to as Close Cathode Chamber in an earlier study, the material budget is significantly reduced on one hand by the elimination of external support frame, on the other hand by thin detector walls. In this paper it is demonstrated that the outline is compatible with large size detectors (1 m wire length), maintaining mechanical and operation stability, with total weight of 3 kg (including support structure) for a half square meter surface. The detection efficiency and response time is shown to be sufficient for L0 triggering in the ALICE VHMPID layout. Reduced sensitivity to cathode deformations (due to internal overpressure as mechanical strain) is directly demonstrated. On small sized chambers, improvement of position resolution with analog readout is evaluated, reaching 0.09 mm RMS with 2 mm wide cathode segments. Simulation results on signal time evolutions are presented. With the above studies, comparison of classical MWPC-s and the Close Cathode Chamber design is performed in all major aspects. -- Highlights: ► Asymmetric multi-wire proportional chamber, called the Close Cathode Chamber, is studied. ► Large size construction feasibility up to 1 m wire length is demonstrated in test beam and cosmic rays. ► Reduction of dependence of gas gain on chamber internal pressure is directly demonstrated. ► Position resolution and signal formation is shown to be compatible with classical MWPC.

  4. A model of dispenser cathode activity

    Science.gov (United States)

    Lamartine, B. C.; Eyink, K. G.; Czarnecki, J. V.; Lampert, W. V.; Haas, T. W.

    1985-12-01

    A semiquantitative model of dispenser cathode activity based on recent work on the co-adsorption of Ba and O onto W surfaces is presented. The co-adsorption studies have determined the shape of a three-dimensional surface of work function as a function of θO and θBa, the surface coverages of O and Ba, respectively. Compositions of a variety of pedigreed dispenser cathodes were fitted to this surface and their composition changes during lifetime were modeled. Changes of surface composition with temperature and of workfunction, φ, with temperature were also found to fit these curves. The concept of a patchy surface implied by the co-adsorption measurements was used to explain earlier results on the shape of the X-ray excited Ba MNN Auger feature. Finally, SIMS measurements under UHV conditions was found to provide an extremely sensitive measurement of surface composition in the region of surface coverages of interest in the study of cathode phenomena. Extensions of this work to other types of cathodes such as M-types, and rhenium substrate cathodes is also discussed.

  5. Sheet Plasma Produced by Hollow Cathode Discharge

    Institute of Scientific and Technical Information of China (English)

    张龙; 张厚先; 杨宣宗; 冯春华; 乔宾; 王龙

    2003-01-01

    A sheet plasma is produced by a hollow cathode discharge under an axial magnetic field.The plasma is about 40cm in length,4 cm in width and 1cm in thickness.The electron density is about 108cm-3.The hollow cathode is made to be shallow with a large opening,which is different from the ordinary deep hollow cathode.A Langmuir probe is used to detect the plasma.The electron density and the spatial distribution of the plasma change when voltage,pressure and the magnetic field vary.A peak and a data fluctuation at about 200 G-300 G are observed in the variation of electron density(or thickness of the sheet plasma)with the magnetic field.Our work will be helpful in characterizing the sheet plasma and will make the production of dense sheet plasma more controllable.

  6. Sheet plasma produced by hollow cathode discharge

    International Nuclear Information System (INIS)

    A sheet plasma is produced by a hollow cathode discharge under an axial magnetic field. The plasma is about 40 cm in length, 4 cm in width and 1 cm in thickness. The electron density is about 108 cm-3. The hollow cathode is made to be shallow with a large opening, which is different from the ordinary deep hollow cathode. A Langmuir probe is used to detect the plasma. The electron density and the spatial distribution of the plasma change when voltage, pressure and the magnetic field vary. A peak and a data fluctuation at about 200 G - 300 G are observed in the variation of electron density (or thickness of the sheet plasma) with the magnetic field. Our work will be helpful in characterizing the sheet plasma and will make the production of dense sheet plasma more controllable

  7. Advanced rechargeable sodium batteries with novel cathodes

    Science.gov (United States)

    Di Stefano, S.; Ratnakumar, B. V.; Bankston, C. P.

    1990-01-01

    Various high energy density rechargeable batteries are being considered for future space applications. Of these, the sodium-sulfur battery is one of the leading candidates. The primary advantage is the high energy density (760 W h/kg theoretical). Energy densities in excess of 180 W h/kg have been realized in practical batteries. More recently, cathodes other than sulfur are being evaluated. Various new cathode materials are presently being evaluated for use in high energy density sodium batteries for advanced space applications. The approach is to carry out basic electrochemical studies of these materials in a sodium cell configuration in order to understand their fundamental behaviors. Thus far, the studies have focussed on alternative metal chlorides such as CuCl2 and organic cathode materials such as TCNE.

  8. Cathodic protection in simulated geothermal environments

    Energy Technology Data Exchange (ETDEWEB)

    Bandy, R.; van Rooyen, D.

    1983-01-01

    The results of cathodic protection of carbon steel and AISI Type 316 stainless steel in simulated geothermal brines are described. Impressed current tests on carbon steel and stainless steel were conducted under controlled potential, and cathodic protection of carbon steel using zinc sacrificial anodes was studied by monitoring the galvanic current and potential of the couple with a zero-resistance ammeter. Weight-loss measurements and photomicrographs of test coupons were taken whenever necessary to determine the nature of attack and degree of protection. Tests were generally conducted at 90/sup 0/C. However, some tests on carbon steel were conducted up to 150/sup 0/C in a titanium autoclave. Results show that the weight loss of carbon steel can be reduced significantly and the pitting corrosion of the stainless steel can be prevented by shifting the potentials of the metals 60 to 80 mV cathodic to their respective open-circuit potentials.

  9. A porous metal cathode (a thermoemission converter)

    Energy Technology Data Exchange (ETDEWEB)

    Kozlov, V.I.; Avdeyev, V.Ye.

    1983-01-01

    The porous metallic cathode, which contains a body and the basic sponge attached to it with an active substance, made in the form of a base with an emitting projection, is distinguished by the fact that in order to increase the service life of the cathode, the based sponges on the side opposite the projection have a groove in which the replenishing chamber made of a difficulty fusible metal and filled with a mixture of tungsten and an active substance with a porosity of 35 to 80 percent which is open towards the projection is positioned, where the transverse cross section of the replenishing chamber intersects the transverse cross section of the projection, while the porosity of the basic sponge is 24 to 26 percent. The cathode is distinguished by the fact that a screen made of a difficultly fusible metal is installed on the facial surface with an opening for the projection and is connected with the body and with this surface.

  10. Improvements in cathodic protection using decoupling methods

    Energy Technology Data Exchange (ETDEWEB)

    Barreto, Mauro [IEC - Instalacoes e Engenharia de Corrosao Ltda., Rio de Janeiro, RJ (Brazil); Tachick, Michael [Dairyland Electrical Industries, Inc., Stoughton, WI (United States)

    2005-07-01

    Proper cathodic protection on a structure requires electrical isolation in order to minimize the CP current required, and to shift the voltage of the structure to acceptable levels. This can be difficult to achieve when bonds or grounds connect the structure to other metallic structures of a different galvanic potential. Electrical decoupling methods are available that can provide the needed DC isolation while conducting any AC components to ground, and therefore address the cathodic protection effects while mitigating AC, if present. Substantial improvements in cathodic protection levels, and a reduction in required current, are common results. If the decoupling methods used are rated for the system conditions and are of a fail-safe design, the system can safely address user concerns about AC fault and lightning effects, and can be used in electrical grounding systems. (author)

  11. Why palladium cathodes can bear resistance to methanol but not platinum cathodes

    International Nuclear Information System (INIS)

    Methanol crossover on the cathodes causes significant performance loss in direct methanol fuel cells, and the parasitic current induced by the electrochemical oxidation of methanol on the cathodes is believed to be the cause. Palladium cathodes are known to bear resistance to methanol but not platinum cathodes. By means of the density functional theory (DFT), the distorted molecular structure of the adsorbed methanol on platinum was revealed, and this distorted molecular structure indicates that platinum makes methanol has a tendency toward the elimination of the first hydrogen (involved in the first step of electrochemical oxidation of methanol) in electric neutrality, and loss of an electron can reinforce this tendency. However, palladium cannot distort the molecular structure of the adsorbed methanol, even in the loss of electron condition. The activation energies and the reaction energies calculated by means of DFT also show that after losing an electron, the elimination of the first hydrogen on platinum is more kinetically and thermodynamically favourable than that on palladium. These computational results can explain the experimental findings that no parasitic current is induced at palladium cathodes, but not at platinum cathodes; therefore, palladium cathodes have a methanol-resistance property

  12. Synchrotron Investigations of SOFC Cathode Degradation

    Energy Technology Data Exchange (ETDEWEB)

    Idzerda, Yves

    2013-09-30

    The atomic variations occurring in cathode/electrolyte interface regions of La{sub 1-x}Sr{sub x}Co{sub y}Fe{sub 1-y}O{sub 3-δ} (LSCF) cathodes and other SOFC related materials have been investigated and characterized using soft X-ray Absorption Spectroscopy (XAS) and diffuse soft X-ray Resonant Scattering (XRS). X-ray Absorption Spectroscopy in the soft X-ray region (soft XAS) is shown to be a sensitive technique to quantify the disruption that occurs and can be used to suggest a concrete mechanism for the degradation. For LSC, LSF, and LSCF films, a significant degradation mechanism is shown to be Sr out-diffusion. By using the XAS spectra of hexavalent Cr in SrCrO4 and trivalent Cr in Cr2O3, the driving factor for Sr segregation was identified to be the oxygen vacancy concentration at the anode and cathode side of of symmetric LSCF/GDC/LSCF heterostructures. This is direct evidence of vacancy induced cation diffusion and is shown to be a significant indicator of cathode/electrolyte interfacial degradation. X-ray absorption spectroscopy is used to identify the occupation of the A-sites and B-sites for LSC, LSF, and LSCF cathodes doped with other transition metals, including doping induced migration of Sr to the anti-site for Sr, a significant cathode degradation indicator. By using spatially resolved valence mapping of Co, a complete picture of the surface electrochemistry can be determined. This is especially important in identifying degradation phenomena where the degradation is spatially localized to the extremities of the electrochemistry and not the average. For samples that have electrochemical parameters that are measured to be spatially uniform, the Co valence modifications were correlated to the effects of current density, overpotential, and humidity.

  13. DARHT 2 kA Cathode Development

    International Nuclear Information System (INIS)

    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/cm2 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/cm2. 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 10-8 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

  14. Hollow-Cathode Source Generates Plasma

    Science.gov (United States)

    Deininger, W. D.; Aston, G.; Pless, L. C.

    1989-01-01

    Device generates argon, krypton, or xenon plasma via thermionic emission and electrical discharge within hollow cathode and ejects plasma into surrounding vacuum. Goes from cold start up to full operation in less than 5 s after initial application of power. Exposed to moist air between operations without significant degradation of starting and running characteristics. Plasma generated by electrical discharge in cathode barrel sustained and aided by thermionic emission from emitter tube. Emitter tube does not depend on rare-earth oxides, making it vulnerable to contamination by exposure to atmosphere. Device modified for use as source of plasma in laboratory experiments or industrial processes.

  15. DARHT 2 kA Cathode Development

    Energy Technology Data Exchange (ETDEWEB)

    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

    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

  16. Cathode architectures for alkali metal / oxygen batteries

    Energy Technology Data Exchange (ETDEWEB)

    Visco, Steven J; Nimon, Vitaliy; De Jonghe, Lutgard C; Volfkovich, Yury; Bograchev, Daniil

    2015-01-13

    Electrochemical energy storage devices, such as alkali metal-oxygen battery cells (e.g., non-aqueous lithium-air cells), have a cathode architecture with a porous structure and pore composition that is tailored to improve cell performance, especially as it pertains to one or more of the discharge/charge rate, cycle life, and delivered ampere-hour capacity. A porous cathode architecture having a pore volume that is derived from pores of varying radii wherein the pore size distribution is tailored as a function of the architecture thickness is one way to achieve one or more of the aforementioned cell performance improvements.

  17. Ferroelectric Cathodes in Transverse Magnetic Fields

    International Nuclear Information System (INIS)

    Experimental investigations of a planar ferroelectric cathode in a transverse magnetic field up to 3 kGs are presented. It is shown that the transverse magnetic field affects differently the operation of ferroelectric plasma cathodes in ''bright'' and ''dark'' modes in vacuum. In the ''bright'' mode, when the surface plasma is formed, the application of the transverse magnetic field leads to an increase of the surface plasma density. In the ''dark'' mode, the magnetic field inhibits the development of electron avalanches along the surface, as it does similarly in other kinds of surface discharges in the pre-breakdown mode

  18. Process For Patterning Dispenser-Cathode Surfaces

    Science.gov (United States)

    Garner, Charles E.; Deininger, William D.

    1989-01-01

    Several microfabrication techniques combined into process cutting slots 100 micrometer long and 1 to 5 micrometer wide into tungsten dispenser cathodes for traveling-wave tubes. Patterned photoresist serves as mask for etching underlying aluminum. Chemically-assisted ion-beam etching with chlorine removes exposed parts of aluminum layer. Etching with fluorine or chlorine trifluoride removes tungsten not masked by aluminum layer. Slots enable more-uniform low-work function coating dispensed to electron-emitting surface. Emission of electrons therefore becomes more uniform over cathode surface.

  19. Gas poisoning investigations of scandate and M-type dispenser cathodes

    Science.gov (United States)

    Shao, Wensheng; Zhang, Ke; Li, Ji; Yan, Suqiu; Chen, Qilue

    2003-06-01

    Gas poisoning tests of cathode emission were carried out with four kinds of thermal cathodes: W+Sc 2O 3 mixed matrix cathode, impregnated scandate cathode, Ir-coated cathode, Os-coated cathode. As a result, M-type cathodes are more sensitive to O 2, but can recover absolutely in a short time; scandate-type cathodes react slowly and recover partly after a long time. Compared to O 2, ambient air leaked into the vacuum chamber has a smaller influence on the cathode emission; H 2 has a little effect of activation on the four cathodes, especially on the Os-coated cathode.

  20. Nano-Particle Scandate Cathode for Space Communications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose an improved cathode based on our novel theory of the role of scandium oxide in enhancing emission in tungsten impregnate cathodes. Recent results have...

  1. Development of cathode material for lithium-ion batteries

    OpenAIRE

    Rustam Mukhtaruly Turganaly; Ivan Trussov; Andrey Petrovich Kurbatov

    2014-01-01

    The electrochemical characteristics of the cathode material coated with carbon layer has been developed. Various carbon coating methods. There  has been carried out a comparative electrochemical analysis of the coated and uncoated with carbon cathode material. 

  2. Long Life Cold Cathodes for Hall effect Thrusters Project

    Data.gov (United States)

    National Aeronautics and Space Administration — An electron source incorporating long life, high current density cold cathodes inside a microchannel plate for use with ion thrusters is proposed. Cathode lifetime...

  3. A new dispenser cathode with dual-layer

    Science.gov (United States)

    Li, Yutao; Zhang, Honglai; Liu, Pukun; Zhang, Mingchen

    2005-09-01

    The emission and surface characteristics of the dispenser cathode coated with Os-W alloy and that coated with Os-W/Re are studied and compared. The dispenser cathode coated with Os-W/Re has been applied in electron gun measurement system for making measurement of higher emission current and life test. We called the cathode coated with Os-W/Re as the cathode with dual-layer. It is found that the dispenser cathode coated with dual-layer has higher current density than that coated only with Os-W alloy. After being activated, the cathode coated with dual-layer presents ternary composition on the surface of it. The W surface composition does not rise with time comparing with that of the cathode coated with Os-W alloy. In electron gun, the dispenser cathode coated with dual-layer has pulse current density of 30 A/cm 2 and life of more than 800 h.

  4. A new dispenser cathode with dual-layer

    International Nuclear Information System (INIS)

    The emission and surface characteristics of the dispenser cathode coated with Os-W alloy and that coated with Os-W/Re are studied and compared. The dispenser cathode coated with Os-W/Re has been applied in electron gun measurement system for making measurement of higher emission current and life test. We called the cathode coated with Os-W/Re as the cathode with dual-layer. It is found that the dispenser cathode coated with dual-layer has higher current density than that coated only with Os-W alloy. After being activated, the cathode coated with dual-layer presents ternary composition on the surface of it. The W surface composition does not rise with time comparing with that of the cathode coated with Os-W alloy. In electron gun, the dispenser cathode coated with dual-layer has pulse current density of 30 A/cm2 and life of more than 800 h

  5. Optimized high-temperature cathode-heating unit

    International Nuclear Information System (INIS)

    Description of structure and test results of cathode-heating unit for electron accelerators are presented. In the given cathode unit LaB6 cathode area is enlarged, efficient heat isolations are used, heating element stiffness and strength are increased. Compact shild packets are used in a cathode unit. The heating element is made in the form of concentric rings. The unit heat efficiency is >80%, nonisothermality ΔT2 emitter area at T=2050 K constituted 700 h

  6. Feature of "Cold" Fusion Reaction in a Deuterated Complex Cathode

    OpenAIRE

    ARATA, Yoshiaki; ZHANG, Yue-Chang

    1992-01-01

    [Abstract] In order to corroborate the evidence of "cold" fusion reaction, a new-type, complex cathode was developed, consisting of a Ni rod with a Pd layer applied by plasma spraying. High reproducibility of a "cold" fusion reaction was confirmed, using a deuterated complex cathode. The Pd layer showed to have activated the surface functions of the deuterated cathode, and a reliable evidence was obtained that a new type of heat generation occurred in the complex cathode.

  7. Photothermal cathode measurements at the Advanced Photon Source

    International Nuclear Information System (INIS)

    The Advanced Photon Source (APS) ballistic bunch compression (BBC) gun in the Injector Test Stand (ITS) presently uses an M-type thermionic dispenser cathode as a photocathode. This photothermal cathode offers substantial advantages over conventional metal photocathodes, including easy replacement and easy cleaning via the cathode's built-in heater. We present the results of photoemission measurements as a function of cathode heater power, laser pulse energy, and applied rf field strength.

  8. LOW TEMPERATURE CATHODE SUPPORTED ELECTROLYTES

    Energy Technology Data Exchange (ETDEWEB)

    Harlan U. Anderson

    2000-03-31

    . However, they have the potential of being useful as an interface on the anode side of the electrolyte. NexTech has focused much of its effort during the past few months on establishing tape casting methods for porous LSM substrates. This work, performed under a separate DOE-funded program, involved tape casting formulations comprising LSM powders with bi-modal particle size distributions and fugitive pore forming additives. Sintered LSM substrates with porosities in the 30 to 40 vol% range, and pore sizes of 10 {approx} 20 microns have been prepared. In addition, tape casting formulations involving composite mixtures of LSM and Sm-doped ceria (SDC) have been evaluated. The LSM/SDC cathode substrates are expected to provide better performance at low temperatures. Characterization of these materials is currently underway.

  9. Development of Magnetic Hollow Cold Cathode for Ion Source

    OpenAIRE

    Djamel Boubetra; Bouafia, M.

    2008-01-01

    The research presented in this study focuses on the development of ion source with hollow cold cathodes which supplies low-power and high ion-current density applications. The theoretical and experimental results were used to design a second-generation laboratory model, low-current hollow cathode. Present experiment is to design a hollow cold cathode with two application possibilities.

  10. High-voltage virtual-cathode microwave simulations

    Energy Technology Data Exchange (ETDEWEB)

    Thode, L.; Snell, C.M.

    1991-01-01

    In contrast to a conventional microwave tube, a virtual-cathode device operates above the space-charge limit where the depth of the space-charge potential is sufficiently large to cause electron reflection. The region associated with electron reflection is referred to as a virtual cathode. Microwaves can be generated through oscillations in the position of the virtual cathode and by reflexing electrons trapped in the potential well formed between the real and virtual cathodes. A virtual-cathode device based on the first mechanism is a vircator while one based on latter mechanism is a reflex diode. A large number of low-voltage virtual-cathode microwave configurations have been investigated. Initial simulations of a high-voltage virtual-cathode device using a self-consistent particle-in-cell code indicated reasonable conversion efficiency with no frequency chirping. The nonchirping character of the high-voltage virtual-cathode device lead to the interesting possibility of locking four very-high-power microwave devices together using the four transmission lines available at Aurora. Subsequently, in support of two high-voltage experiments, simulations were used to investigate the effect of field-emission threshold and velvet position on the cathode; anode and cathode shape; anode-cathode gap spacing; output waveguide radius; diode voltage; a cathode-coaxial-cavity resonator; a high-frequency ac-voltage drive; anode foil scattering and energy loss; and ion emission on the microwave frequency and power. Microwave

  11. Radial profiles of electron density and current components at cathode surface in LaB6 hollow cathode arc

    International Nuclear Information System (INIS)

    Experimental studies on a hydrogen-fed LaB6 hollow cathode arc have been pursued. The plasma parameter in the cathode has been measured by a Langmuir probe. The radial variation in the electron density inside the cathode was calculated using the continuity and momentum equations, showing good agreement with the experimental results. The electron density at the cathode surface was estimated to be 15 % - 20 % of that at the cathode axis. It was also found from the current balance that the arc current components at the cathode surface consist of a thermionic current which takes into account the Schottky effect, the ion current and the secondary electron current induced by ion bombardment. The ion current and the cathode surface is larger than the electron current emitted from the cathode. (author)

  12. The double sheath on cathodes of discharges burning in cathode vapour

    Energy Technology Data Exchange (ETDEWEB)

    Benilov, M S; Benilova, L G [Departamento de Fisica, Universidade da Madeira, Largo do MunicIpio, 9000 Funchal (Portugal)

    2010-09-01

    The model of a collisionless near-cathode space-charge sheath with ionization of atoms emitted by the cathode surface is considered. Numerical calculations showed that the mathematical problem is solvable and its solution is unique. In the framework of this model, the sheath represents a double layer with a potential maximum, with the ions which are produced before the maximum returning to the cathode surface and those produced after the maximum escaping into the plasma. Numerical results are given in a form to be readily applicable in analysis of discharges burning in cathode vapour, such as vacuum arcs. In particular, the results indicate that the ion backflow coefficient in such discharges exceeds 0.5, in agreement with values extracted from the experiment.

  13. Barium depletion in hollow cathode emitters

    International Nuclear Information System (INIS)

    Dispenser hollow cathodes rely on a consumable supply of Ba released by BaO-CaO-Al2O3 source material in the pores of a tungsten matrix to maintain a low work function surface. The examination of cathode emitters from long duration tests shows deposits of tungsten at the downstream end that appear to block the flow of Ba from the interior. In addition, a numerical model of Ba transport in the cathode plasma indicates that the Ba partial pressure in the insert may exceed the equilibrium vapor pressure of the dominant Ba-producing reaction, and it was postulated previously that this would suppress Ba loss in the upstream part of the emitter. New measurements of the Ba depletion depth from a cathode insert operated for 8200 h reveal that Ba loss is confined to a narrow region near the downstream end, confirming this hypothesis. The Ba transport model was modified to predict the depletion depth with time. A comparison of the calculated and measured depletion depths gives excellent qualitative agreement, and quantitative agreement was obtained assuming an insert temperature 70 °C lower than measured beginning-of-life values

  14. Renovation of the cathodic protection system

    NARCIS (Netherlands)

    Schuten, G.; Leggedoor, J.; Polder, R.B.; Peelen, W.H.A.

    2003-01-01

    The first system for Cathodic Protection of concrete in the Netherlands was applied to a one bicycle lane of a bridge suffering corrosion due to de-icing salt penetration in 1986. This CP system was based on the Ferex 100S conducting polymer cable anode in a cementitious overlay. Its functioning was

  15. Barium depletion in hollow cathode emitters

    Energy Technology Data Exchange (ETDEWEB)

    Polk, James E., E-mail: james.e.polk@jpl.nasa.gov; Mikellides, Ioannis G.; Katz, Ira [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States); Capece, Angela M. [Graduate Aerospace Laboratories, California Institute of Technology, Pasadena, California 91125 (United States)

    2016-01-14

    Dispenser hollow cathodes rely on a consumable supply of Ba released by BaO-CaO-Al{sub 2}O{sub 3} source material in the pores of a tungsten matrix to maintain a low work function surface. The examination of cathode emitters from long duration tests shows deposits of tungsten at the downstream end that appear to block the flow of Ba from the interior. In addition, a numerical model of Ba transport in the cathode plasma indicates that the Ba partial pressure in the insert may exceed the equilibrium vapor pressure of the dominant Ba-producing reaction, and it was postulated previously that this would suppress Ba loss in the upstream part of the emitter. New measurements of the Ba depletion depth from a cathode insert operated for 8200 h reveal that Ba loss is confined to a narrow region near the downstream end, confirming this hypothesis. The Ba transport model was modified to predict the depletion depth with time. A comparison of the calculated and measured depletion depths gives excellent qualitative agreement, and quantitative agreement was obtained assuming an insert temperature 70 °C lower than measured beginning-of-life values.

  16. Barium depletion in hollow cathode emitters

    Science.gov (United States)

    Polk, James E.; Mikellides, Ioannis G.; Capece, Angela M.; Katz, Ira

    2016-01-01

    Dispenser hollow cathodes rely on a consumable supply of Ba released by BaO-CaO-Al2O3 source material in the pores of a tungsten matrix to maintain a low work function surface. The examination of cathode emitters from long duration tests shows deposits of tungsten at the downstream end that appear to block the flow of Ba from the interior. In addition, a numerical model of Ba transport in the cathode plasma indicates that the Ba partial pressure in the insert may exceed the equilibrium vapor pressure of the dominant Ba-producing reaction, and it was postulated previously that this would suppress Ba loss in the upstream part of the emitter. New measurements of the Ba depletion depth from a cathode insert operated for 8200 h reveal that Ba loss is confined to a narrow region near the downstream end, confirming this hypothesis. The Ba transport model was modified to predict the depletion depth with time. A comparison of the calculated and measured depletion depths gives excellent qualitative agreement, and quantitative agreement was obtained assuming an insert temperature 70 °C lower than measured beginning-of-life values.

  17. Improved cathodes for a dense plasma focus

    International Nuclear Information System (INIS)

    A series of modified cathodes have been tested in our ultra-high vacuum dense plasma focus (DPF) device in an effort to improve both neutron output and shot-to-shot reproducibility. Inspiration for these modifications originated from time resolved photographs of the initial current sheet as it approaches the cathode. In particular, the current sheet develops a slight annular protrusion, or ''bump'', that contacts the inside wall of the cathode at a distance from the breach approximately coincident with the end of the insulator. In an attempt to take advantage of this protrusion, a series of modified cathodes was provided with a decreased waist diameter in the vicinity of the end of the insulator. As previously discussed, this DPF device is constructed from high vacuum components using metal-to-metal and ceramic (Al2O3)-to-metal seals; the entire assembly is given a vacuum bake at 2500C resulting in a pre-fill vacuum of approx. =5 x 10-9 Torr. The DPF is powered by a 7 μf capacitor bank. The short circuit ringing frequency is 412 kHz corresponding to a free circuit inductance of 21 nH. With the DPF in operation at 20 kV, a current peak of 200 kA occurs at 0.8 μs. Neutron output was measured side on with a silver activation counter, and end on with an arsenic activation counter

  18. Improved Rare-Earth Emitter Hollow Cathode

    Science.gov (United States)

    Goebel, Dan M.

    2011-01-01

    An improvement has been made to the design of the hollow cathode geometry that was created for the rare-earth electron emitter described in Compact Rare Earth Emitter Hollow Cathode (NPO-44923), NASA Tech Briefs, Vol. 34, No. 3 (March 2010), p. 52. The original interior assembly was made entirely of graphite in order to be compatible with the LaB6 material, which cannot be touched by metals during operation due to boron diffusion causing embrittlement issues in high-temperature refractory materials. Also, the graphite tube was difficult to machine and was subject to vibration-induced fracturing. This innovation replaces the graphite tube with one made out of refractory metal that is relatively easy to manufacture. The cathode support tube is made of molybdenum or molybdenum-rhenium. This material is easily gun-bored to near the tolerances required, and finish machined with steps at each end that capture the orifice plate and the mounting flange. This provides the manufacturability and robustness needed for flight applications, and eliminates the need for expensive e-beam welding used in prior cathodes. The LaB6 insert is protected from direct contact with the refractory metal tube by thin, graphite sleeves in a cup-arrangement around the ends of the insert. The sleeves, insert, and orifice plate are held in place by a ceramic spacer and tungsten spring inserted inside the tube. To heat the cathode, an insulating tube is slipped around the refractory metal hollow tube, which can be made of high-temperature materials like boron nitride or aluminum nitride. A screw-shaped slot, or series of slots, is machined in the outside of the ceramic tube to constrain a refractory metal wire wound inside the slot that is used as the heater. The screw slot can hold a single heater wire that is then connected to the front of the cathode tube by tack-welding to complete the electrical circuit, or it can be a double slot that takes a bifilar wound heater with both leads coming out

  19. Preparation and characterization of SOFC cathode films

    International Nuclear Information System (INIS)

    Solid Oxide Fuel Cells (SOFC) are being widely studied due to their possible utilization to produce electrical energy in a wide power range (from 1 kW up to few hundreds of kW).The principle of operation of this kind of fuel cells involves reduction of O2 in the cathode oxygen ions (O2-) diffusion of oxygen through the electrolyte and fuel oxidation in the anode.Commercial SOFC must work at temperature higher than to 1000 degree C to enable the O2- diffusion.Therefore, it is necessary to investigate new materials that enable to decrease the operation temperature, improving SOFC performance and cost. La1-xSrxCo1-yFeyO3-δ (LSCF) perovskites are good candidates for SOFC cathodes because these materials present high ionic and electronic conductivity. LSCF cathodes are adequate to fabricate Ce1-xGdxO2-δ electrolyte SOFC due to its low chemical reactivity with this material and its similar thermal expansion coefficient. In this work we present a study of microstructural and electrochemical characteristics of films for SOFC cathodes. La0.4Sr0.6Co0.8Fe0.2O3-δ compounds were prepared by the acetate reaction method.Then, cathodes were deposited onto a Ce0.9Gd0.1O2-δ electrolyte disk by dip coating and spray techniques.Structural characterization is made by X-ray diffraction XRD and scanning electron microscopy (SEM).Electrochemical properties are characterized by complex impedance measurements.Finally, the relation between structural characteristics and electrical properties is discussed

  20. Explosive emission cathode on the base of carbon plastic fibre

    International Nuclear Information System (INIS)

    A fabrication process for explosive emission cathodes on the base of carbon plastic fibre of practically any geometrical shape and dimensions is developed. Experimental studies of electron beam current collection from cathodes, 2cm in diameter, at voltages across the diode of 10 and 150-250kV. It is shown that the ignition voltage for cathode plasma is ∼2kV at the interelectrode diode gap of 5mm and residual gas pressure of ∼5x10-5Torr. The carbon-fibre cathode, fabricated in this way, provides more stable current collection of an electron beam (without oscillations) than other cathodes

  1. Polymer coatings as separator layers for microbial fuel cell cathodes

    Science.gov (United States)

    Watson, Valerie J.; Saito, Tomonori; Hickner, Michael A.; Logan, Bruce E.

    2011-03-01

    Membrane separators reduce oxygen flux from the cathode into the anolyte in microbial fuel cells (MFCs), but water accumulation and pH gradients between the separator and cathode reduces performance. Air cathodes were spray-coated (water-facing side) with anion exchange, cation exchange, and neutral polymer coatings of different thicknesses to incorporate the separator into the cathode. The anion exchange polymer coating resulted in greater power density (1167 ± 135 mW m-2) than a cation exchange coating (439 ± 2 mW m-2). This power output was similar to that produced by a Nafion-coated cathode (1114 ± 174 mW m-2), and slightly lower than the uncoated cathode (1384 ± 82 mW m-2). Thicker coatings reduced oxygen diffusion into the electrolyte and increased coulombic efficiency (CE = 56-64%) relative to an uncoated cathode (29 ± 8%), but decreased power production (255-574 mW m-2). Electrochemical characterization of the cathodes ex situ to the MFC showed that the cathodes with the lowest charge transfer resistance and the highest oxygen reduction activity produced the most power in MFC tests. The results on hydrophilic cathode separator layers revealed a trade off between power and CE. Cathodes coated with a thin coating of anion exchange polymer show promise for controlling oxygen transfer while minimally affecting power production.

  2. Emission current control system for multiple hollow cathode devices

    Science.gov (United States)

    Beattie, John R. (Inventor); Hancock, Donald J. (Inventor)

    1988-01-01

    An emission current control system for balancing the individual emission currents from an array of hollow cathodes has current sensors for determining the current drawn by each cathode from a power supply. Each current sensor has an output signal which has a magnitude proportional to the current. The current sensor output signals are averaged, the average value so obtained being applied to a respective controller for controlling the flow of an ion source material through each cathode. Also applied to each controller are the respective sensor output signals for each cathode and a common reference signal. The flow of source material through each hollow cathode is thereby made proportional to the current drawn by that cathode, the average current drawn by all of the cathodes, and the reference signal. Thus, the emission current of each cathode is controlled such that each is made substantially equal to the emission current of each of the other cathodes. When utilized as a component of a multiple hollow cathode ion propulsion motor, the emission current control system of the invention provides for balancing the thrust of the motor about the thrust axis and also for preventing premature failure of a hollow cathode source due to operation above a maximum rated emission current.

  3. Scenario for Hollow Cathode End-Of-Life

    Science.gov (United States)

    Sarver-Verhey, Timothy R.

    2000-01-01

    Recent successful hollow cathode life tests have demonstrated that lifetimes can meet the requirements of several space applications. However, there are no methods for assessing cathode lifetime short of demonstrating the requirement. Previous attempts to estimate or predict cathode lifetime were based on relatively simple chemical depletion models derived from the dispenser cathode community. To address this lack of predicative capability, a scenario for hollow cathode lifetime under steady-state operating conditions is proposed. This scenario has been derived primarily from the operating behavior and post-test condition of a hollow cathode that was operated for 28,000 hours. In this scenario, the insert chemistry evolves through three relatively distinct phases over the course of the cathode lifetime. These phases are believed to correspond to demonstrable changes in cathode operation. The implications for cathode lifetime limits resulting from this scenario are examined, including methods to assess cathode lifetime without operating to End-of- Life and methods to extend the cathode lifetime.

  4. Polymer coatings as separator layers for microbial fuel cell cathodes

    KAUST Repository

    Watson, Valerie J.

    2011-03-01

    Membrane separators reduce oxygen flux from the cathode into the anolyte in microbial fuel cells (MFCs), but water accumulation and pH gradients between the separator and cathode reduces performance. Air cathodes were spray-coated (water-facing side) with anion exchange, cation exchange, and neutral polymer coatings of different thicknesses to incorporate the separator into the cathode. The anion exchange polymer coating resulted in greater power density (1167 ± 135 mW m-2) than a cation exchange coating (439 ± 2 mW m-2). This power output was similar to that produced by a Nafion-coated cathode (1114 ± 174 mW m-2), and slightly lower than the uncoated cathode (1384 ± 82 mW m-2). Thicker coatings reduced oxygen diffusion into the electrolyte and increased coulombic efficiency (CE = 56-64%) relative to an uncoated cathode (29 ± 8%), but decreased power production (255-574 mW m-2). Electrochemical characterization of the cathodes ex situ to the MFC showed that the cathodes with the lowest charge transfer resistance and the highest oxygen reduction activity produced the most power in MFC tests. The results on hydrophilic cathode separator layers revealed a trade off between power and CE. Cathodes coated with a thin coating of anion exchange polymer show promise for controlling oxygen transfer while minimally affecting power production. © 2010 Elsevier B.V. All rights reserved.

  5. Cathode scraper system and method of using the same for removing uranium

    Energy Technology Data Exchange (ETDEWEB)

    Williamson, Mark A; Wiedmeyer, Stanley G; Willit, James L; Barnes, Laurel A; Blaskovitz, Robert J

    2015-02-03

    Embodiments include a cathode scraper system and/or method of using the same for removing uranium. The cathode scraper system includes a plurality of cathode assemblies. Each cathode assembly includes a plurality of cathode rods. The cathode scraper system also includes a cathode scraper assembly configured to remove purified uranium deposited on the plurality of cathode rods. The cathode scraper assembly includes a plurality of scrapers arranged in a lattice, and each scraper of the plurality of scrapers is arranged to correspond to a different cathode rod.

  6. Design of ANSYS-based Cathode with Complex Groove

    Institute of Scientific and Technical Information of China (English)

    范植坚; 赵刚刚; 张丽娟

    2012-01-01

    The profile of cathode with complex groove needs to be modified time after time during design of electrochemical machining (ECM) cathode.A design scheme using finite element method (FEM) for cathode with complex profile is put forward to shorten the period of cathode design.Based on Laplace equation,the potential distribution on parameter-transformation model was calculated by using ANSYS,which is compared to the potential distribution calculated by substituting conductivity and current efficiency into Laplace equation.According to the difference between the results calculated and simulated by ANSYS,the cathode profile was modified by adjusting the cathode boundary.The experiments show that the dimensions and shape of workpiece machined by numerically simulated cathode conform well with the blueprint.

  7. Emission mechanism in high current hollow cathode arcs

    International Nuclear Information System (INIS)

    Large (2 cm-diameter) hollow cathodes have been operated in a magnetoplasmadynamic (MPD) arc over wide ranges of current (0.25 to 17 kA) and mass flow (10-3 to 8 g/sec), with orifice current densities and mass fluxes encompassing those encountered in low current steady-state hollow cathode arcs. Detailed cathode interior measurements of current and potential distributions show that maximum current penetration into the cathode is about one diameter axially upstream from the tip, with peak inner surface current attachment up to one cathode diameter upstream of the tip. The spontaneous attachment of peak current upstream of the cathode tip is suggested as a criterion for characteristic hollow cathode operation. This empirical criterion is verified by experiment

  8. Cathode R&D for Future Light Sources

    Energy Technology Data Exchange (ETDEWEB)

    Dowell, D.H.; /SLAC; Bazarov, I.; Dunham, B.; /Cornell U., CLASSE; Harkay, K.; /Argonne; Hernandez-Garcia; /Jefferson Lab; Legg, R.; /Wisconsin U., SRC; Padmore, H.; /LBL, Berkeley; Rao, T.; Smedley, J.; /Brookhaven; Wan, W.; /LBL, Berkeley

    2010-05-26

    This paper reviews the requirements and current status of cathodes for accelerator applications, and proposes a research and development plan for advancing cathode technology. Accelerator cathodes need to have long operational lifetimes and produce electron beams with a very low emittance. The two principal emission processes to be considered are thermionic and photoemission with the photocathodes being further subdivided into metal and semi-conductors. Field emission cathodes are not included in this analysis. The thermal emittance is derived and the formulas used to compare the various cathode materials. To date, there is no cathode which provides all the requirements needed for the proposed future light sources. Therefore a three part research plan is described to develop cathodes for these future light source applications.

  9. The effect of cathode geometry on barium transport in hollow cathode plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Polk, James E., E-mail: james.e.polk@jpl.nasa.gov; Mikellides, Ioannis G.; Katz, Ira [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109 (United States); Capece, Angela M. [California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125 (United States)

    2014-05-14

    The effect of barium transport on the operation of dispenser hollow cathodes was investigated in numerical modeling of a cathode with two different orifice sizes. Despite large differences in cathode emitter temperature, emitted electron current density, internal xenon neutral and plasma densities, and size of the plasma-surface interaction region, the barium transport in the two geometries is qualitatively very similar. Barium is produced in the insert and flows to the surface through the porous structure. A buildup of neutral Ba pressure in the plasma over the emitter surface can suppress the reactions supplying the Ba, restricting the net production rate. Neutral Ba flows into the dense Xe plasma and has a high probability of being ionized at the periphery of this zone. The steady state neutral Ba density distribution is determined by a balance between pressure gradient forces and the drag force associated with collisions between neutral Ba and neutral Xe atoms. A small fraction of the neutral Ba is lost upstream. The majority of the neutral Ba is ionized in the high temperature Xe plasma and is pushed back to the emitter surface by the electric field. The steady state Ba{sup +} ion density distribution results from a balance between electrostatic and pressure forces, neutral Xe drag and Xe{sup +} ion drag with the dominant forces dependent on location in the discharge. These results indicate that hollow cathodes are very effective at recycling Ba within the discharge and therefore maintain a high coverage of Ba on the emitter surface, which reduces the work function and sustains high electron emission current densities at moderate temperatures. Barium recycling is more effective in the cathode with the smaller orifice because the Ba is ionized in the dense Xe plasma concentrated just upstream of the orifice and pushed back into the hollow cathode. Despite a lower emitter temperature, the large orifice cathode has a higher Ba loss rate through the orifice

  10. The effect of cathode geometry on barium transport in hollow cathode plasmas

    International Nuclear Information System (INIS)

    The effect of barium transport on the operation of dispenser hollow cathodes was investigated in numerical modeling of a cathode with two different orifice sizes. Despite large differences in cathode emitter temperature, emitted electron current density, internal xenon neutral and plasma densities, and size of the plasma-surface interaction region, the barium transport in the two geometries is qualitatively very similar. Barium is produced in the insert and flows to the surface through the porous structure. A buildup of neutral Ba pressure in the plasma over the emitter surface can suppress the reactions supplying the Ba, restricting the net production rate. Neutral Ba flows into the dense Xe plasma and has a high probability of being ionized at the periphery of this zone. The steady state neutral Ba density distribution is determined by a balance between pressure gradient forces and the drag force associated with collisions between neutral Ba and neutral Xe atoms. A small fraction of the neutral Ba is lost upstream. The majority of the neutral Ba is ionized in the high temperature Xe plasma and is pushed back to the emitter surface by the electric field. The steady state Ba+ ion density distribution results from a balance between electrostatic and pressure forces, neutral Xe drag and Xe+ ion drag with the dominant forces dependent on location in the discharge. These results indicate that hollow cathodes are very effective at recycling Ba within the discharge and therefore maintain a high coverage of Ba on the emitter surface, which reduces the work function and sustains high electron emission current densities at moderate temperatures. Barium recycling is more effective in the cathode with the smaller orifice because the Ba is ionized in the dense Xe plasma concentrated just upstream of the orifice and pushed back into the hollow cathode. Despite a lower emitter temperature, the large orifice cathode has a higher Ba loss rate through the orifice because the Xe

  11. The effect of cathode geometry on barium transport in hollow cathode plasmas

    Science.gov (United States)

    Polk, James E.; Mikellides, Ioannis G.; Capece, Angela M.; Katz, Ira

    2014-05-01

    The effect of barium transport on the operation of dispenser hollow cathodes was investigated in numerical modeling of a cathode with two different orifice sizes. Despite large differences in cathode emitter temperature, emitted electron current density, internal xenon neutral and plasma densities, and size of the plasma-surface interaction region, the barium transport in the two geometries is qualitatively very similar. Barium is produced in the insert and flows to the surface through the porous structure. A buildup of neutral Ba pressure in the plasma over the emitter surface can suppress the reactions supplying the Ba, restricting the net production rate. Neutral Ba flows into the dense Xe plasma and has a high probability of being ionized at the periphery of this zone. The steady state neutral Ba density distribution is determined by a balance between pressure gradient forces and the drag force associated with collisions between neutral Ba and neutral Xe atoms. A small fraction of the neutral Ba is lost upstream. The majority of the neutral Ba is ionized in the high temperature Xe plasma and is pushed back to the emitter surface by the electric field. The steady state Ba+ ion density distribution results from a balance between electrostatic and pressure forces, neutral Xe drag and Xe+ ion drag with the dominant forces dependent on location in the discharge. These results indicate that hollow cathodes are very effective at recycling Ba within the discharge and therefore maintain a high coverage of Ba on the emitter surface, which reduces the work function and sustains high electron emission current densities at moderate temperatures. Barium recycling is more effective in the cathode with the smaller orifice because the Ba is ionized in the dense Xe plasma concentrated just upstream of the orifice and pushed back into the hollow cathode. Despite a lower emitter temperature, the large orifice cathode has a higher Ba loss rate through the orifice because the Xe

  12. Erosion behaviour of composite Al-Cr cathodes in cathodic arc plasmas in inert and reactive atmospheres

    CERN Document Server

    Franz, Robert; Hawranek, Gerhard; Polcik, Peter

    2015-01-01

    Al$_{x}$Cr$_{1-x}$ composite cathodes with Al contents of x = 0.75, 0.5 and 0.25 were exposed to cathodic arc plasmas in Ar, N$_2$ and O$_2$ atmospheres and their erosion behaviour was studied. Cross-sectional analysis of the elemental distribution of the near-surface zone in the cathodes by scanning electron microscopy revealed the formation of a modified layer for all cathodes and atmospheres. Due to intermixing of Al and Cr in the heat-affected zone, intermetallic Al-Cr phases formed as evidenced by X-ray diffraction analysis. Cathode poisoning effects in the reactive N$_2$ and O$_2$ atmospheres were non-uniform as a result of the applied magnetic field configuration. With the exception of oxide islands on Al-rich cathodes, reactive layers were absent in the circular erosion zone, while nitrides and oxides formed in the less eroded centre region of the cathodes.

  13. Erosion behavior of composite Al-Cr cathodes in cathodic arc plasmas in inert and reactive atmospheres

    International Nuclear Information System (INIS)

    AlxCr1−x composite cathodes with Al contents of x = 0.75, 0.5, and 0.25 were exposed to cathodic arc plasmas in Ar, N2, and O2 atmospheres and their erosion behavior was studied. Cross-sectional analysis of the elemental distribution of the near-surface zone in the cathodes by scanning electron microscopy revealed the formation of a modified layer for all cathodes and atmospheres. Due to intermixing of Al and Cr in the heat-affected zone, intermetallic Al-Cr phases formed as evidenced by x-ray diffraction analysis. Cathode poisoning effects in the reactive N2 and O2 atmospheres were nonuniform as a result of the applied magnetic field configuration. With the exception of oxide islands on Al-rich cathodes, reactive layers were absent in the circular erosion zone, while nitrides and oxides formed in the less eroded center region of the cathodes

  14. The coated cathode conductive layer chamber

    International Nuclear Information System (INIS)

    We describe a gaseous detector consisting of thin anode strips vacuum-evaporated on one side of a 100 μ thick plastic layer, alternating on the back side of the same foil with wider parallel cathode strips. Ionizatin released in a drift space on the anode side is amplified and detected much in the same way as in the microstrip gas chamber; in our detector however spontaenous breakdown due to surface currents is completely avoided by the presence of the insulating layer between anodes and cathodes. To reduce surface and volume charging up, we have used polymer foils with a moderate volume resistivity. The first results show good efficiency, good plateaux and time resolution in detecting low-rate minimum ionizing electrons. Although not suited for high rate or good energy resolution applications, this kind of detector seems rather promising for realizing cheaply large active surfaces. (orig.)

  15. Barium Depletion in Hollow Cathode Emitters

    Science.gov (United States)

    Polk, James E.; Capece, Angela M.; Mikellides, Ioannis G.; Katz, Ira

    2009-01-01

    The effect of tungsten erosion, transport and redeposition on the operation of dispenser hollow cathodes was investigated in detailed examinations of the discharge cathode inserts from an 8200 hour and a 30,352 hour ion engine wear test. Erosion and subsequent re-deposition of tungsten in the electron emission zone at the downstream end of the insert reduces the porosity of the tungsten matrix, preventing the ow of barium from the interior. This inhibits the interfacial reactions of the barium-calcium-aluminate impregnant with the tungsten in the pores. A numerical model of barium transport in the internal xenon discharge plasma shows that the barium required to reduce the work function in the emission zone can be supplied from upstream through the gas phase. Barium that flows out of the pores of the tungsten insert is rapidly ionized in the xenon discharge and pushed back to the emitter surface by the electric field and drag from the xenon ion flow. This barium ion flux is sufficient to maintain a barium surface coverage at the downstream end greater than 0.6, even if local barium production at that point is inhibited by tungsten deposits. The model also shows that the neutral barium pressure exceeds the equilibrium vapor pressure of the impregnant decomposition reaction over much of the insert length, so the reactions are suppressed. Only a small region upstream of the zone blocked by tungsten deposits is active and supplies the required barium. These results indicate that hollow cathode failure models based on barium depletion rates in vacuum dispenser cathodes are very conservative.

  16. Cathodic Cage Plasma Nitriding: An Innovative Technique

    OpenAIRE

    de Sousa, R. R. M.; de Araújo, F. O.; da Costa, J. A. P.; A. de S. Brandim; de Brito, R. A.; Alves, C

    2012-01-01

    Cylindrical samples of AISI 1020, AISI 316, and AISI 420 steels, with different heights, were simultaneously treated by a new technique of ionic nitriding, entitled cathodic cage plasma nitriding (CCPN), in order to evaluate the efficiency of this technique to produce nitrided layers with better properties compared with those obtained using conventional ionic nitriding technique. This method is able to eliminate the edge effect in the samples, promoting a better uniformity of temperature, and...

  17. Reduction of promethium on a mercury cathode

    International Nuclear Information System (INIS)

    The authors observed the separation of radioactive promethium on a mercury cathode with samarium, which showed that it can be reduced to a bivalent state. Using radiochemically-pure Pm147, the authors made a detailed study of the influence of a series of factors on the extent to which promethium passes into an amalgam. It was shown that radioactive promethium only passes into the mercury cathode if the current is relatively dense (above 50 mA/cm2) and when rare-earth elements such as ytterbium and samarium, which have a stable bivalent state, are present in the electrolyte. Electrolytic separation of the promethium is not observable until formation of the mixed potassium and samarium amalgam. The promethium then passes into the amalgam up to 85%. When the current is denser (100 mA/cm2), a notable difference may be observed in the transition speed of the promethium and samarium. The promethium separation is mainly affected by the nature of the alkali metal contained in the electrolyte. With lithium, the degree of promethium transition does not depend on the presence of another rare-earth element or the citrate ion concentration. This confirms the occurrence of electrolytic reduction of promethium in electrolysis with a mercury cathode at high current densities. Separation of the promethium into the mercury cathode goes through the stage of its reduction to a bivalent state with formation of the amalgam with the alkali metal. The authors also studied the behaviour of cerium and erbium. From the results of this study and all the published data, the authors conclude that promethium and other elements of the cerium group can be reduced to a bivalent state under certain conditions of electrolysis. (author)

  18. Field Emission Cathodes for Electron Microscopes

    Czech Academy of Sciences Publication Activity Database

    Delong, Armin; Kolařík, V.

    Brno: Institute of Scientific Instruments AS CR, 2004 - (Müllerová, I.), s. 23 - 24 ISBN 80-239-3246-2. [Recent Trends /9./ in Charged Particle Optics and Surface Physics Instrumentation. Skalský Dvůr (CZ), 12.07.2004-16.07.2004] Institutional research plan: CEZ:AV0Z2065902 Keywords : field emission cathodes * electron microscopy Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  19. Cathode Ion Bombardment in RF Photoguns

    Energy Technology Data Exchange (ETDEWEB)

    Pozdeyev,E.; Kayran, D.; Litvinenko, V.

    2008-09-01

    In this paper, we use the method of rapid oscillating field to solve the equation of ion motion in an RF gun. We apply the method to the BNL 1/2-cell SRF photogun and demonstrate that a significant portion of ions produced in the gun can reach the cathode if no special precautions are taken. Also, the paper proposes a simple mitigation recipe that can reduce the rate of ion bombardment.

  20. Infrared photoelectron emission from Scandate dispenser cathodes

    Science.gov (United States)

    Jensen, Kevin L.; Feldman, Donald W.; Virgo, Matt; O'Shea, Patrick G.

    2003-08-01

    Nonlinear photoelectric emission from Scandate dispenser cathodes using 1.064-μm radiation in nanosecond-scale pulses has been observed. Unlike single-photon emission, the photocurrent is a strong function of both the initial lattice temperature and the applied electric field as well as laser intensity. The parametric data is compared to a theoretical model for the process, and the data is shown to be explicable in terms of laser heating of the electron gas and subsequent photoemission.

  1. The dependence of vircator oscillation mode on cathode material

    Science.gov (United States)

    Li, Limin; Liu, Lie; Cheng, Guoxin; Xu, Qifu; Wan, Hong; Chang, Lei; Wen, Jianchun

    2009-06-01

    This paper presents the effects of cathode materials on the oscillation mode of a virtual cathode oscillator (vircator). In the case of the stainless steel cathode, an oscillation mode hopping appeared with two separate frequencies. Interestingly, the vircator using the carbon fiber cathode exhibited an almost unchanged microwave frequency throughout the microwave pulse. To understand this phenomenon, several parameters are compared, including the diode voltage, accelerating gap, emitting area, and beam uniformity. It was found that a flat-top voltage and a relatively stable gap will provide a possibility of generating a constant microwave frequency. Further, the cathode operated in a regime where the beam current was between the space-charge limited current determined by Child-Langmuir law and the bipolar flow. On the cathode surface, the electron emission is initiated from discrete plasma spots and next from a continuing area, while there is a liberation process of multilayer gases on the anode surface. The changes in the emitting area of carbon fiber cathode showed a self-quenching process, which is not observed in the case of stainless steel cathode. The two-dimensional effect of microwave frequency is introduced, and the obtained results supported the experimental observations on the oscillation mode. By examining the cross section of electron beam, the electron beam for carbon fiber cathode was significantly centralized, while the discrete beam spots appeared for stainless steel cathode. These results show that the slowed diode closure, high emission uniformity, and stable microwave frequency tend to be closely tied.

  2. Cathode power distribution system and method of using the same for power distribution

    Energy Technology Data Exchange (ETDEWEB)

    Williamson, Mark A; Wiedmeyer, Stanley G; Koehl, Eugene R; Bailey, James L; Willit, James L; Barnes, Laurel A; Blaskovitz, Robert J

    2014-11-11

    Embodiments include a cathode power distribution system and/or method of using the same for power distribution. The cathode power distribution system includes a plurality of cathode assemblies. Each cathode assembly of the plurality of cathode assemblies includes a plurality of cathode rods. The system also includes a plurality of bus bars configured to distribute current to each of the plurality of cathode assemblies. The plurality of bus bars include a first bus bar configured to distribute the current to first ends of the plurality of cathode assemblies and a second bus bar configured to distribute the current to second ends of the plurality of cathode assemblies.

  3. Scanning optical pyrometer for measuring temperatures in hollow cathodes

    International Nuclear Information System (INIS)

    Life-limiting processes in hollow cathodes are determined largely by the temperature of the electron emitter. To support cathode life assessment, a noncontact temperature measurement technique which employs a stepper motor-driven fiber optic probe was developed. The probe is driven inside the hollow cathode and collects light radiated by the hot interior surface of the emitter. Ratio pyrometry is used to determine the axial temperature profile. Thermocouples on the orifice plate provide measurements of the external temperature during cathode operation and are used to calibrate the pyrometer system in situ with a small oven enclosing the externally heated cathode. The diagnostic method and initial measurements of the temperature distribution in a hollow cathode are discussed

  4. Rf Gun with High-Current Density Field Emission Cathode

    International Nuclear Information System (INIS)

    High current-density field emission from an array of carbon nanotubes, with field-emission-transistor control, and with secondary electron channel multiplication in a ceramic facing structure, have been combined in a cold cathode for rf guns and diode guns. Electrodynamic and space-charge flow simulations were conducted to specify the cathode configuration and range of emission current density from the field emission cold cathode. Design of this cathode has been made for installation and testing in an existing S-band 2-1/2 cell rf gun. With emission control and modulation, and with current density in the range of 0.1-1 kA/cm2, this cathode could provide performance and long-life not enjoyed by other currently-available cathodes

  5. Cathodic phosphate coating containing nano zinc particles on magnesium alloy

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A technology for preparation of a cathodic phosphate coating mainly containing nano metallic zinc particles and phosphate compounds on magnesium alloy was developed.The influence of cathodic current density on the microstructure of the cathodic phosphate coating Was investigated.The results show that the crystals of the coating are finer and the microstructures of the outer surface of the coatings are zigzag at the cathodic density of 0.2-0.5 A/dm2.The content of nano metallic zinc particles in the coating decreases with the increase of the thickness of the coatings and tends to be zero when the coating thickness is 4.14 μm.The cathodic phosphate coating was applied to be a transition coating for improving the adhesion between the paints and the magnesium alloys.The formation mechanism of the cathodic phosphate coating was investigated as well.

  6. Effect of cathodic protection on the state of steel reinforcement

    International Nuclear Information System (INIS)

    Damage of reinforced concrete structures is mainly caused by chloride or carbonation induced corrosion of steel. Cathodic protection is a very effective measure for corrosion control of steel in concrete, especially in chloride contaminated concrete. In this paper, effect of cathodic protection on the state of steel reinforcement is presented. Cathodic polarization of reinforcements in concrete was done under different submerged conditions. Cyclic potentiodynamic tests were used to determine the effect of cathodic protection on the behavior of the steel. Pitting appeared on the non-protected steel, but was not observed on the cathodically protected steel. microscopic photographs show that a close film exists on the protected steel, while the non-protected steel's film is loose. Investigated results have proved the effect of cathodic protection in restoring or strengthening passive film on the steel reinforcement

  7. NiF2 Cathodes For Rechargeable Na Batteries

    Science.gov (United States)

    Bugga, Ratnakumar V.; Distefano, Salvador; Halpert, Gerald

    1992-01-01

    Use of NiF2 cathodes in medium-to-high-temperature rechargeable sodium batteries increases energy and power densities by 25 to 30 percent without detracting from potential advantage of safety this type of sodium battery offers over sodium batteries having sulfur cathodes. High-energy-density sodium batteries with metal fluoride cathodes used in electric vehicles and for leveling loads on powerlines.

  8. Lighting sources with a cold cathode electron tube

    International Nuclear Information System (INIS)

    Lighting sources with a cold cathode are widely used in electronics. The lamps with a cold cathode are used primarily as sources of white light in optical scanners, digital indicators, display panels and signalling devices. In the paper the advantages of carbonaceous materials as emitters of cold electrons and the possibilities of using them to create a cathode in an electron lamp are discussed. (authors)

  9. Molten carbonate fuel cell cathode with mixed oxide coating

    Science.gov (United States)

    Hilmi, Abdelkader; Yuh, Chao-Yi

    2013-05-07

    A molten carbonate fuel cell cathode having a cathode body and a coating of a mixed oxygen ion conductor materials. The mixed oxygen ion conductor materials are formed from ceria or doped ceria, such as gadolinium doped ceria or yttrium doped ceria. The coating is deposited on the cathode body using a sol-gel process, which utilizes as precursors organometallic compounds, organic and inorganic salts, hydroxides or alkoxides and which uses as the solvent water, organic solvent or a mixture of same.

  10. Work function measurements of dispenser cathodes by retarding potential method

    Science.gov (United States)

    Khairnar, Rajendra S.; Chopra, A. K.

    1992-11-01

    The work function of dispenser cathode pellets has been determined by means of the retarding potential technique. A low-energy electron gun was fabricated which delivers a collimated beam of electrons on the pellet surface at normal incidence. The set up is calibrated by employing samples of known work function such as gold and tungsten, prior to determining the work function of the cathode pellets. This set up provides a rapid determination of the work function of cathode pellets.

  11. Scanning optical pyrometer for measuring temperatures in hollow cathodes

    OpenAIRE

    Polk, J. E.; Marrese-Reading, C. M.; Thornber, B.; Dang, L.; Johnson, L. K.; Katz, I

    2007-01-01

    Life-limiting processes in hollow cathodes are determined largely by the temperature of the electron emitter. To support cathode life assessment, a noncontact temperature measurement technique which employs a stepper motor-driven fiber optic probe was developed. The probe is driven inside the hollow cathode and collects light radiated by the hot interior surface of the emitter. Ratio pyrometry is used to determine the axial temperature profile. Thermocouples on the orifice plate provide measu...

  12. High current density pulsed cathode experiments at SLAC

    International Nuclear Information System (INIS)

    A 1.9 microperveance beam diode has been constructed to test high current density cathodes for use in klystrons. Several standard and specially coated dispenser cathodes are being tested. Results of tests to date show average cathode current densities in excess of 25 amps/cm, and maximum electric field gradients of more than 450 kV/cm for pulses of the order of 1μsec. 3 refs., 11 figs

  13. Surface Characterization of the LCLS RF Gun Cathode

    Energy Technology Data Exchange (ETDEWEB)

    Brachmann, Axel; /SLAC; Decker, Franz-Josef; /SLAC; Ding, Yuantao; /SLAC; Dowell, David; /SLAC; Emma, Paul; /SLAC; Frisch, Josef; /SLAC; Gilevich, Sasha; /SLAC; Hays, Gregory; /SLAC; Hering, Philippe; /SLAC; Huang, Zhirong; /SLAC; Iverson, Richard; /SLAC; Loos, Henrik; /SLAC; Miahnahri, Alan; /SLAC; Nordlund, Dennis; /SLAC; Nuhn, Heinz-Dieter; /SLAC; Pianetta, Piero; /SLAC; Turner, James; /SLAC; Welch, James; /SLAC; White, William; /SLAC; Wu, Juhao; /SLAC; Xiang, Dao; /SLAC

    2012-06-25

    The first copper cathode installed in the LCLS RF gun was used during LCLS commissioning for more than a year. However, after high charge operation (> 500 pC), the cathode showed a decline of quantum efficiency within the area of drive laser illumination. They report results of SEM, XPS and XAS studies that were carried out on this cathode after it was removed from the gun. X-ray absorption and X-ray photoelectron spectroscopy reveal surface contamination by various hydrocarbon compounds. In addition they report on the performance of the second installed cathode with emphasis on the spatial distribution of electron emission.

  14. Apparatuses for making cathodes for high-temperature, rechargeable batteries

    Energy Technology Data Exchange (ETDEWEB)

    Meinhardt, Kerry D.; Sprenkle, Vincent L.; Coffey, Gregory W.

    2016-09-13

    The approaches and apparatuses for fabricating cathodes can be adapted to improve control over cathode composition and to better accommodate batteries of any shape and their assembly. For example, a first solid having an alkali metal halide, a second solid having a transition metal, and a third solid having an alkali metal aluminum halide are combined into a mixture. The mixture can be heated in a vacuum to a temperature that is greater than or equal to the melting point of the third solid. When the third solid is substantially molten liquid, the mixture is compressed into a desired cathode shape and then cooled to solidify the mixture in the desired cathode shape.

  15. Measuring current emission and work functions of large thermionic cathodes

    International Nuclear Information System (INIS)

    As one component of the nations Stockpile Stewardship program, Los Alamos National Laboratory is constructing a 20 MeV, 2 kA (with a 4 kA upgrade capability), 3ps induction linac for doing x-ray radiography of explosive devices. The linac is one leg of a facility called the Dual-Axis Radiography Hydrodynamic Test Facility (DARHT). The electron gun is designed to operate at 3.2 MV. The gun is a Pierce type design and uses a 6.5' cathode for 2 kA operation and an 8' cathode for 4 kA operation. We have constructed a small facility called the Cathode Test Stand (CTS) to investigate engineering and physics issues regarding large thermionic dispenser-cathodes. In particular, we have looked at the issues of temperature uniformity on the cathode surface and cathode quality as measured by its work function. We have done thermal imaging of both 8' and 6.5' cathodes. Here we report on measurements of the cathode work function, both the average value and how it vanes across the face of the cathode.

  16. Characterization of Hollow Cathode Performance and Thermal Behavior

    Science.gov (United States)

    Polk, James E.; Goebel, Dan M.; Watkins, Ron; Jameson, Kristina; Yoneshige, Lance; Przybylowski, JoHanna; Cho, Lauren

    2006-01-01

    Hollow cathodes are one of the main life-limiting components in ion engines and Hall thrusters. Although state-of-the-art hollow cathodes have demonstrated up to 30,352 hours of operation in ground tests with careful handling, future missions are likely to require longer life, more margin and greater resistance to reactive contaminant gases. Three alternate hollow cathode technologies that exploit different emitter materials or geometries to address some of the limitations of state-of-the-art cathodes are being investigated. Performance measurements of impregnated tungsten-iridium dispenser cathodes at discharge currents of 4 to 15 A demonstrated that they have the same operating range and ion production efficiency as conventional tungsten dispenser cathodes. Temperature measurements indicated that tungsten-iridium cathodes also operate at the same emitter temperatures. They did not exhibit the expected reduction in work function at the current densities tested. Hollow cathodes with lanthanum hexaboride emitters operated over a wide current range, but suffered from lower ion production efficiency at currents below about 12.4 A because of higher insert heating requirements. Differences in operating voltages and ion production rates are explained with a simple model of the effect of cathode parameters on discharge behavior.

  17. Large area dispenser cathode applied to high current linac

    International Nuclear Information System (INIS)

    The paper introduced a dispenser cathode (411 M) which was 55 mm in diameter. A 200 kV long pulsed power generator with 2 μs flattop based on Marx-PEN and system with heat and voltage insulation were built. A 52 A space charge limited current was gained, when the temperature was 1165 degree C and the filament current was 18 A on the cathode and the voltage of the pulse was 75 kV at the cathode test stand. Experimental results show that the current values are consistent with the numerical simulation. The experiment reveals that the deflated gas will influence the cathode emission ability. (authors)

  18. Effects of three-dimensional cathode microstructure on the performance of lithium-ion battery cathodes

    International Nuclear Information System (INIS)

    Highlights: ► Segments of Li-ion battery cathodes are reconstructed from FIB-SEM experiments. ► The three-dimensional reconstructed cathode is discretized using a cut-cell approach. ► A Three-dimensional model of cathode performance is developed. ► Three-dimensional simulations reveal significant spatial variations in concentrations and voltage. -- Abstract: This paper develops a computational model that resolves the complex three-dimensional microstructure of Li-ion battery cathodes. The microstructural geometry is reconstructed from focused-ion-beam–scanning-electron-microscopy (FIB-SEM) experiments. Raw data from FIB-SEM experiments are processed into finite-volume discretizations that are directly suited for three-dimensional computational simulation. The model represents transport and electrochemistry within the solid phase of the electrode structure. The results predict the temporally and spatially varying Li concentrations and electrostatic potentials within the solid-phase electrode material (e.g., LiCoO2) as functions of discharge rate. The models predict global discharge characteristics that are consistent with experiment. Moreover, the results reveal significant three-dimensional spatial variations within the actual electrode structure that cannot be predicted with models based on idealized microstructures such as spherical electrode particles

  19. Organic Cathode Materials for Rechargeable Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Ruiguo; Qian, Jiangfeng; Zhang, Jiguang; Xu, Wu

    2015-06-28

    This chapter will primarily focus on the advances made in recent years and specify the development of organic electrode materials for their applications in rechargeable lithium batteries, sodium batteries and redox flow batteries. Four various organic cathode materials, including conjugated carbonyl compounds, conducting polymers, organosulfides and free radical polymers, are introduced in terms of their electrochemical performances in these three battery systems. Fundamental issues related to the synthesis-structure-activity correlations, involved work principles in energy storage systems, and capacity fading mechanisms are also discussed.

  20. Radioimmunological determination and characterization of cathodal trypsin-like immunoreactivity in normal human plasma

    International Nuclear Information System (INIS)

    A radioimmunological method for determination of human cathodal trypsin-like immunoreactivity is described. DFP-treated human cathodal trypsin is used as standard and tracer. Freshly drawn normal human plasma contains about 25μg/l of cathodal trypsin-like immunoreactivity measured as DFP-treated cathodal trypsin. The normally circulating cathodal trypsin-like immunoreactivity is shown to consist mainly of cathodal trypsinogen. (Auth.)

  1. Oxide diffusion in innovative SOFC cathode materials.

    Science.gov (United States)

    Hu, Y; Thoréton, V; Pirovano, C; Capoen, E; Bogicevic, C; Nuns, N; Mamede, A-S; Dezanneau, G; Vannier, R N

    2014-01-01

    Oxide diffusion was studied in two innovative SOFC cathode materials, Ba(2)Co(9)O(14) and Ca(3)Co(4)O(9)+δ derivatives. Although oxygen diffusion was confirmed in the promising material Ba(2)Co(9)O(14), it was not possible to derive accurate transport parameters because of an oxidation process at the sample surface which has still to be clarified. In contrast, oxygen diffusion in the well-known Ca(3)Co(4)O(9)+δ thermoelectric material was improved when calcium was partly substituted with strontium, likely due to an increase of the volume of the rock salt layers in which the conduction process takes place. Although the diffusion coefficient remains low, interestingly, fast kinetics towards the oxygen molecule dissociation reaction were shown with surface exchange coefficients higher than those reported for the best cathode materials in the field. They increased with the strontium content; the Sr atoms potentially play a key role in the mechanism of oxygen molecule dissociation at the solid surface. PMID:25407246

  2. Development of cathode material for lithium-ion batteries

    Directory of Open Access Journals (Sweden)

    Rustam Mukhtaruly Turganaly

    2014-08-01

    Full Text Available The electrochemical characteristics of the cathode material coated with carbon layer has been developed. Various carbon coating methods. There  has been carried out a comparative electrochemical analysis of the coated and uncoated with carbon cathode material. 

  3. Temperature controlled cathode heating in the electron gun

    Czech Academy of Sciences Publication Activity Database

    Horáček, Miroslav

    Brno: CSMS, 2002 - (Frank, L.), s. 69 - 70 ISBN 80-238-8749-1. [CSEM. Vranovská Ves (CZ), 08.02.2002-09.02.2002] Institutional research plan: CEZ:AV0Z2065902 Keywords : directly heated tungsten cathode * electron gun * temperature controlled cathode heating Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  4. The Cathode Ramper: Application for the Duoplasmatron Ion Source

    CERN Document Server

    Sánchez-Conejo, J

    2003-01-01

    The purpose of the Cathode Ramper Application is to heat the Linac 2 duoplasmatron ion source cathode up to a desired temperature selected by the user. The application has been developed in Java, making use of the Java Development Kit 1.4 and the PS Java environment.

  5. Effects of Humidity on Solid Oxide Fuel Cell Cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Hardy, John S. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Stevenson, Jeffry W. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Singh, Prabhakar [Univ. of Connecticut, Storrs, CT (United States); Mahapatra, Manoj K. [Univ. of Connecticut, Storrs, CT (United States); Wachsman, E. D. [Univ. of Maryland, College Park, MD (United States); Liu, Meilin [Georgia Inst. of Technology, Atlanta, GA (United States); Gerdes, Kirk R. [National Energy Technology Lab. (NETL), Morgantown, WV (United States)

    2015-03-17

    This report summarizes results from experimental studies performed by a team of researchers assembled on behalf of the Solid-state Energy Conversion Alliance (SECA) Core Technology Program. Team participants employed a variety of techniques to evaluate and mitigate the effects of humidity in solid oxide fuel cell (SOFC) cathode air streams on cathode chemistry, microstructure, and electrochemical performance.

  6. Cathodic disbonding of organic coatings on submerged steel

    Energy Technology Data Exchange (ETDEWEB)

    Knudsen, Ole oeystein

    1998-12-31

    In offshore oil production, submerged steel structures are commonly protected by an organic coating in combination with cathodic protection. The main advantage is that the coating decreases the current demand for cathodic protection. But the coating degrades with time. This thesis studies one of the most important mechanisms for coating degradation in seawater, cathodic disbonding. Seven commercial coatings and two model coatings with various pigmentations have been studied. Parameter studies, microscopy and studies of free films were used in the mechanism investigations. Exposure to simulated North Sea conditions was used in the performance studies. The effect of aluminium and glass barrier pigments on cathodic disbonding was investigated. The mechanism for the effect of the aluminium pigments on cathodic disbonding was also investigated. The transport of charge and oxygen to the steel/coating interface during cathodic disbonding was studied for two epoxy coatings. Cathodic disbonding, blistering and current demand for cathodic protection was measured for nine commercial coatings for submerged steel structures, using the ASTM-G8 standard test and a long term test under simulated North Sea conditions. The relevance of the ASTM-G8 test as a prequalification test was evaluated. 171 refs., 40 figs., 6 tabs.

  7. The Effect of Substrate Topography on Coating Cathodic Delamination

    DEFF Research Database (Denmark)

    Weinell, Claus E.; Sørensen, Per A.; Kiil, Søren

    2011-01-01

    This article describes the effect of steel substrate topography on coating cathodic delamination. The study showed that the surface preparation can be used to control and minimize the rate of cathodic delamination. The coating should have maximum wetting properties so that substrates with high...

  8. Tandem cathode for proton exchange membrane fuel cells

    DEFF Research Database (Denmark)

    Siahrostami, Samira; Björketun, Mårten E.; Strasser, Peter;

    2013-01-01

    The efficiency of proton exchange membrane fuel cells is limited mainly by the oxygen reduction reaction at the cathode. The large cathodic overpotential is caused by correlations between binding energies of reaction intermediates in the reduction of oxygen to water. This work introduces a novel...

  9. Cathodic protection -- Addition of 6 anodes to existing rectifier 31

    International Nuclear Information System (INIS)

    This Acceptance Test Procedure (ATP) has been prepared to demonstrate that the cathodic protection system additions are installed, connected, and function as required by project criteria. The cathodic protection system is for the tank farms on the Hanford Reservation. The tank farms store radioactive wastes

  10. Microbial Fuel Cell Performance with a Pressurized Cathode Chamber

    Science.gov (United States)

    Microbial fuel cell (MFC) power densities are often constrained by the oxygen reduction reaction rate on the cathode electrode. One important factor for this is the normally low solubility of oxygen in the aqueous cathode solution creating mass transport limitations, which hinder oxygen reduction a...

  11. High Performance Fe-Co Based SOFC Cathodes

    DEFF Research Database (Denmark)

    Kammer Hansen, Kent; Hansen, Karin Vels; Mogensen, Mogens Bjerg

    2010-01-01

    With the aim of reducing the temperature of the solid oxide fuel cell (SOFC), a new high-performance perovskite cathode has been developed. An area-specific resistance (ASR) as low as 0.12 Ωcm2 at 600 °C was measured by electrochemical impedance spectroscopy (EIS) on symmetrical cells. The cathode...

  12. Cathodes for Solid Oxide Fuel Cells Operating at Low Temperatures

    DEFF Research Database (Denmark)

    Samson, Alfred Junio

    . High performance cathodes were obtained from strontium-doped lanthanum cobaltite (LSC) infiltrated - Ce0.9Gd0.1O1.95 (CGO) ionic conducting backbone. Systematic tuning of the CGO and LSC firing temperatures and LSC loading resulted in a cathode with low polarization resistance, Rp = 0.044 cm2 at 600......+delta/CGO 50 vol % composite cathode at 600degreeC. A 1-dimensional model has been developed in order to understand and predict the the performance of cathodes prepared by LSC infiltration. With the model, it was possible to extract an expression for the area specific resistance associated with oxygen...... surface exchange for the infiltrated LSC. The extracted values are significantly lower than literature values suggesting that the performance of LSC-infiltrated cathodes could not be explained by downscaled microstructure alone. A series of microstructural parameter variations are presented and discussed...

  13. Hollow cathode ion source for application to an implanter

    International Nuclear Information System (INIS)

    A hollow cathode ion source has been studied in order to improve the life-time of an ion source for an ion implanter. Both volatile and refractory elements are shown to be ionized using two types of discharge state of the hollow cathode namely hot and cold cathode discharge. The life-time of LaB6 as the hot cathode is more than 150 h and the ion beam currents reach more than 10 mA cm-2 at the extraction voltage of 10 kV. For the cold cathode operation, stable currents of approx. 40 to 70 μA are extracted of refractory metal ions such as W and Mo. (author)

  14. High Performance Infiltrated Backbones for Cathode-Supported SOFC's

    DEFF Research Database (Denmark)

    Gil, Vanesa; Kammer Hansen, Kent

    2014-01-01

    The concept of using highly ionic conducting backbones with subsequent infiltration of electronically conducting particles has widely been used to develop alternative anode-supported SOFC's. In this work, the idea was to develop infiltrated backbones as an alternative design based on cathode-supported...... printed symmetrical cells. Samples with LSM/YSZ composite and YSZ backbones made with graphite+PMMA as pore formers exhibited comparable Rp values to the screen printed LSM/YSZ cathode. This route was chosen as the best to fabricate the cathode supported cells. SEM micrograph of a cathode supported cell...... with infiltrated LSM nanoparticles is shown in Fig. 1. Figure 1. Cross section of LSM infiltrated cathode supported cell. [Formula]...

  15. Investigation of Endurance Performance of Carbon Nanotube Cathodes

    Science.gov (United States)

    Saito, Nanako; Yamagiwa, Yoshiki; Ohkawa, Yasushi; Nishida, Shin-Ichiro; Kitamura, Shoji

    The Aerospace Research and Development Directorate of the Japan Aerospace Exploration Agency (JAXA) is considering a demonstration of electrodynamic tether (EDT) systems in low Earth orbit (LEO). Carbon nanotubes (CNTs) have some advantages as electron sources compared to conventional Spindt type emitters, and so are expected to be useful in EDT systems. Experiments to investigate the durability of CNT cathodes in a space environment had been conducted in a diode mode, but it was found that electron extraction tests, in which the cathode with a gate electrode is used, are necessary to evaluate the endurance of CNTs more accurately. In this paper, we conducted long duration operating tests of a cathode with a gate. It was found that there was almost no change in cathode performance at current densities below 100 A/m2 even after the cathode was operated for over 500 hours in the high vacuum environment.

  16. Work function distribution for W Ir mixed metal matrix cathodes

    Science.gov (United States)

    Santhosh Kumar, K.; Durga Devi, P.; Ravi, M.; Bhat, K. S.

    2006-06-01

    Mixed metal matrix cathodes have inherent non-uniformity and patchiness of emission due to the presence of two-alloy phase structure on the surface. I- V characteristics of cathode studied in a close spaced diode configuration is one of the easy and cost effective methods to estimate the variation of work function on the cathode surface. Tungsten iridium mixed metal matrix dispenser cathodes of Ø1.4 mm (80 wt.% W-20 wt.% Ir) have been fabricated in the laboratory and their I- V characteristics have been investigated in diode configuration. In this paper the model suggested by Tonnerre et al. has been used to find out the work function distribution of W-Ir cathodes from I- V characteristics. An attempt has been made to correlate the microstructure with the work function values.

  17. Barium depletion study on impregnated cathodes and lifetime prediction

    Science.gov (United States)

    Roquais, J. M.; Poret, F.; le Doze, R.; Ricaud, J. L.; Monterrin, A.; Steinbrunn, A.

    2003-06-01

    In the thermionic cathodes used in cathode ray-tubes (CRTs), barium is the key element for the electronic emission. In the case of the dispenser cathodes made of a porous tungsten pellet impregnated with Ba, Ca aluminates, the evaporation of Ba determines the cathode lifetime with respect to emission performance in the CRT. The Ba evaporation results in progressive depletion of the impregnating material inside the pellet. In the present work, the Ba depletion with time has been extensively characterized over a large range of cathode temperature. Calculations using the depletion data allowed modeling of the depletion as a function of key parameters. The link between measured depletion and emission in tubes has been established, from which an end-of-life criterion was deduced. Taking modeling into account, predicting accelerated life-tests were performed using high-density maximum emission current (MIK).

  18. Barium depletion study on impregnated cathodes and lifetime prediction

    International Nuclear Information System (INIS)

    In the thermionic cathodes used in cathode ray-tubes (CRTs), barium is the key element for the electronic emission. In the case of the dispenser cathodes made of a porous tungsten pellet impregnated with Ba, Ca aluminates, the evaporation of Ba determines the cathode lifetime with respect to emission performance in the CRT. The Ba evaporation results in progressive depletion of the impregnating material inside the pellet. In the present work, the Ba depletion with time has been extensively characterized over a large range of cathode temperature. Calculations using the depletion data allowed modeling of the depletion as a function of key parameters. The link between measured depletion and emission in tubes has been established, from which an end-of-life criterion was deduced. Taking modeling into account, predicting accelerated life-tests were performed using high-density maximum emission current (MIK)

  19. Design of Cathode Heater Assembly for High Power Gyrotron

    Science.gov (United States)

    Bhattacharya, Ranajoy; Khatun, Hasina; Singh, Narendra Kr.; Singh, Udaybir; Sinha, A. K.

    2013-04-01

    A 3D model of dispenser cathode with toroid shape heater assembly is simulated using simulation software, ANSYS Multi-physics. The reported design study of cathode heater assembly of 1 MW 120 GHz gyrotron helps to optimize the input heater power with respect to cathode surface temperature. The simulation study shows that the input power depends strongly on the heater dimension as well as material properties including the potting material. The optimum input power helps to achieve desired current density (10 A/cm2) and cathode surface temperature (1000 °C). Further, the thermal and structural analyses are carried out to study the temperature distribution on the cathode assembly due to the heat dissipation and mechanical strength of the assembly.

  20. Focused cathode design to reduce anode heating during vircator operation

    Science.gov (United States)

    Lynn, Curtis F.; Dickens, James C.; Neuber, Andreas A.

    2013-10-01

    Virtual cathode oscillators, or vircators, are a type of high power microwave device which operates based on the instability of a virtual cathode, or cloud of electrons, which forms when electron current injected into the drift tube exceeds the space charge limited current within the drift tube. Anode heating by the electron beam during vircator operation ultimately limits achievable pulse lengths, repetition rates, and the duration of burst mode operation. This article discusses a novel cathode design that focuses electrons through holes in the anode, thus significantly reducing anode heating by the electrons emitted from the cathode during the first transit through the A-K gap. Reflexing electrons continue to deposit energy on the anode; however, the discussed minimization of anode heating by main beam electrons has the potential to enable higher repetition rates as well as efficiency and longer diode lifetime. A simulation study of this type of cathode design illustrates possible advantages.

  1. Focused cathode design to reduce anode heating during vircator operation

    Energy Technology Data Exchange (ETDEWEB)

    Lynn, Curtis F.; Dickens, James C.; Neuber, Andreas A. [Center for Pulsed Power and Power Electronics, Department of Electrical and Computer Engineering, Texas Tech University, Lubbock, Texas 79409 (United States)

    2013-10-15

    Virtual cathode oscillators, or vircators, are a type of high power microwave device which operates based on the instability of a virtual cathode, or cloud of electrons, which forms when electron current injected into the drift tube exceeds the space charge limited current within the drift tube. Anode heating by the electron beam during vircator operation ultimately limits achievable pulse lengths, repetition rates, and the duration of burst mode operation. This article discusses a novel cathode design that focuses electrons through holes in the anode, thus significantly reducing anode heating by the electrons emitted from the cathode during the first transit through the A-K gap. Reflexing electrons continue to deposit energy on the anode; however, the discussed minimization of anode heating by main beam electrons has the potential to enable higher repetition rates as well as efficiency and longer diode lifetime. A simulation study of this type of cathode design illustrates possible advantages.

  2. Focused cathode design to reduce anode heating during vircator operation

    International Nuclear Information System (INIS)

    Virtual cathode oscillators, or vircators, are a type of high power microwave device which operates based on the instability of a virtual cathode, or cloud of electrons, which forms when electron current injected into the drift tube exceeds the space charge limited current within the drift tube. Anode heating by the electron beam during vircator operation ultimately limits achievable pulse lengths, repetition rates, and the duration of burst mode operation. This article discusses a novel cathode design that focuses electrons through holes in the anode, thus significantly reducing anode heating by the electrons emitted from the cathode during the first transit through the A-K gap. Reflexing electrons continue to deposit energy on the anode; however, the discussed minimization of anode heating by main beam electrons has the potential to enable higher repetition rates as well as efficiency and longer diode lifetime. A simulation study of this type of cathode design illustrates possible advantages

  3. New doped tungsten cathodes. Applications to power grid tubes

    International Nuclear Information System (INIS)

    Thermionic emission behavior of tungsten/tungsten carbide modified with rare earth (La, Ce, Y) oxides is examined on account of suitability to deliver important current densities in a thermo-emissive set up and for long lifetime. Work functions of potential cathodes have been determined from Richardson plots for La2O3 doped tungsten and for tungsten covered with variable compositions rare earth tungstates. The role of platinum layers covering the cathode was also examined. Given all cathodes containing mainly lanthanum oxides were good emitters, emphasis was put on service lifetime. Comparisons of lifetime in tungsten doped with rare earth oxides and with rare earth tungstates show that microstructure of the operating cathodes may play the major role in the research of very long lifetime cathodes. Based on these results, tests still running show lifetime compatible with power grid tubes applications. (author)

  4. Comparative simulation studies of plasma cathode electron (PCE) gun

    International Nuclear Information System (INIS)

    Pseudospark discharge based plasma cathode has capability to provide high current density electron beam during discharge process. In this paper an effort has been made to simulate the breakdown processes in the pseudospark discharge based plasma cathode electron gun. The two-dimensional plasma simulation codes VORPAL and OOPIC-Pro have been used and results are compared. The peak discharge current in the plasma cathode electron gun is found to be dependent on aperture size, hollow cathode dimensions, anode voltage and seed electrons energy. The effect of these design parameters on the peak anode current has been analysed by both the codes and results matches well within 10% variation. For the seed electron generation an electron beam trigger source is used to control the discharge process in the hollow cathode cavity. The time span of trigger source has been varied from 1-100 ns to analyze the effect on the peak anode current.

  5. Correlation of cathode parameters of high power grid tubes with material characteristics of cathode-grid units

    International Nuclear Information System (INIS)

    One way to increase the longevity of dispenser cathodes is based on reducing the Barium evaporation. This can be achieved by the decrease of the reaction 'activity' of the emitter impregnant with the porous tungsten (W) body, which supplies free Barium from the interior of the porous cathode to its surface

  6. Air humidity and water pressure effects on the performance of air-cathode microbial fuel cell cathodes

    KAUST Repository

    Ahn, Yongtae

    2014-02-01

    To better understand how air cathode performance is affected by air humidification, microbial fuel cells were operated under different humidity conditions or water pressure conditions. Maximum power density decreased from 1130 ± 30 mW m-2 with dry air to 980 ± 80 mW m -2 with water-saturated air. When the cathode was exposed to higher water pressures by placing the cathode in a horizontal position, with the cathode oriented so it was on the reactor bottom, power was reduced for both with dry (1030 ± 130 mW m-2) and water-saturated (390 ± 190 mW m-2) air. Decreased performance was partly due to water flooding of the catalyst, which would hinder oxygen diffusion to the catalyst. However, drying used cathodes did not improve performance in electrochemical tests. Soaking the cathode in a weak acid solution, but not deionized water, mostly restored performance (960 ± 60 mW m-2), suggesting that there was salt precipitation in the cathode that was enhanced by higher relative humidity or water pressure. These results showed that cathode performance could be adversely affected by both flooding and the subsequent salt precipitation, and therefore control of air humidity and water pressure may need to be considered for long-term MFC operation. © 2013 Elsevier B.V. All rights reserved.

  7. Correlation of cathode parameters of high power grid tubes with material characteristics of cathode-grid units

    Science.gov (United States)

    Melnikova, Irina P.; Polyakov, Igor V.; Usanov, Dmitry A.

    2005-09-01

    One way to increase the longevity of dispenser cathodes is based on reducing the Barium evaporation. This can be achieved by the decrease of the reaction "activity" of the emitter impregnant with the porous tungsten (W) body, which supplies free Barium from the interior of the porous cathode to its surface.

  8. Cationic fluorinated polymer binders for microbial fuel cell cathodes

    KAUST Repository

    Chen, Guang

    2012-01-01

    Fluorinated quaternary ammonium-containing polymers were used as catalyst binders in microbial fuel cell (MFC) cathodes. The performance of the cathodes was examined and compared to NAFION ® and other sulfonated aromatic cathode catalyst binders using linear sweep voltammetry (LSV), impedance spectroscopy, and performance tests in single chamber air-cathode MFCs. The cathodes with quaternary ammonium functionalized fluorinated poly(arylene ether) (Q-FPAE) binders showed similar current density and charge transfer resistance (R ct) to cathodes with NAFION ® binders. Cathodes containing either of these fluorinated binders exhibited better electrochemical responses than cathodes with sulfonated or quaternary ammonium-functionalized RADEL ® poly(sulfone) (S-Radel or Q-Radel) binders. After 19 cycles (19 d), the power densities of all the MFCs declined compared to the initial cycles due to biofouling at the cathode. MFC cathodes with fluorinated polymer binders (1445 mW m -2, Q-FPAE-1.4-H; 1397 mW m -2, Q-FPAE-1.4-Cl; 1277 mW m -2, NAFION ®; and 1256 mW m -2, Q-FPAE-1.0-Cl) had better performance than those with non-fluorinated polymer binders (880 mW m -2, S-Radel; 670 mW m -2, Q-Radel). There was a 15% increase in the power density using the Q-FPAE binder with a 40% higher ion exchange capacity (Q-FPAE-1.4-H compared to Q-FPAE-1.0-Cl) after 19 cycles of operation, but there was no effect on the power production due to counter ions in the binder (Cl -vs. HCO 3 -). The highest-performance cathodes (NAFION ® and Q-FPAE binders) had the lowest charge transfer resistances (R ct) in fresh and in fouled cathodes despite the presence of thick biofilms on the surface of the electrodes. These results show that fluorinated binders may decrease the penetration of the biofilm and associated biopolymers into the cathode structure, which helps to combat MFC performance loss over time. © 2012 The Royal Society of Chemistry.

  9. Cathodic Cage Plasma Nitriding: An Innovative Technique

    Directory of Open Access Journals (Sweden)

    R. R. M. de Sousa

    2012-01-01

    Full Text Available Cylindrical samples of AISI 1020, AISI 316, and AISI 420 steels, with different heights, were simultaneously treated by a new technique of ionic nitriding, entitled cathodic cage plasma nitriding (CCPN, in order to evaluate the efficiency of this technique to produce nitrided layers with better properties compared with those obtained using conventional ionic nitriding technique. This method is able to eliminate the edge effect in the samples, promoting a better uniformity of temperature, and consequently, a smaller variation of the thickness/height relation can be obtained. The compound layers were characterized by X-ray diffraction, optical microscopy, and microhardness test profile. The results were compared with the properties of samples obtained with the conventional nitriding, for the three steel types. It was verified that samples treated by CCPN process presented, at the same temperature, a better uniformity in the thickness and absence of the edge effect.

  10. Nanostructured cathode materials for rechargeable lithium batteries

    Science.gov (United States)

    Myung, Seung-Taek; Amine, Khalil; Sun, Yang-Kook

    2015-06-01

    The prospect of drastic climate change and the ceaseless fluctuation of fossil fuel prices provide motivation to reduce the use of fossil fuels and to find new energy conversion and storage systems that are able to limit carbon dioxide generation. Among known systems, lithium-ion batteries are recognized as the most appropriate energy storage system because of their high energy density and thus space saving in applications. Introduction of nanotechnology to electrode material is beneficial to improve the resulting electrode performances such as capacity, its retention, and rate capability. The nanostructure is highly available not only when used alone but also is more highlighted when harmonized in forms of core-shell structure and composites with carbon nanotubes, graphene or reduced graphene oxides. This review covers syntheses and electrochemical properties of nanoscale, nanosized, and nanostructured cathode materials for rechargeable lithium batteries.

  11. Catadioptric aberration correction in cathode lens microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Tromp, R.M. [IBM T.J. Watson Research Center, PO Box 218, Yorktown Heights, NY 10598 (United States); Kamerlingh Onnes Laboratory, Leiden Institute of Physics, Niels Bohrweg 2, 2333 CA Leiden (Netherlands)

    2015-04-15

    In this paper I briefly review the use of electrostatic electron mirrors to correct the aberrations of the cathode lens objective lens in low energy electron microscope (LEEM) and photo electron emission microscope (PEEM) instruments. These catadioptric systems, combining electrostatic lens elements with a reflecting mirror, offer a compact solution, allowing simultaneous and independent correction of both spherical and chromatic aberrations. A comparison with catadioptric systems in light optics informs our understanding of the working principles behind aberration correction with electron mirrors, and may point the way to further improvements in the latter. With additional developments in detector technology, 1 nm spatial resolution in LEEM appears to be within reach. - Highlights: • The use of electron mirrors for aberration correction in LEEM/PEEM is reviewed. • A comparison is made with similar systems in light optics. • Conditions for 1 nm spatial resolution are discussed.

  12. Catadioptric aberration correction in cathode lens microscopy

    International Nuclear Information System (INIS)

    In this paper I briefly review the use of electrostatic electron mirrors to correct the aberrations of the cathode lens objective lens in low energy electron microscope (LEEM) and photo electron emission microscope (PEEM) instruments. These catadioptric systems, combining electrostatic lens elements with a reflecting mirror, offer a compact solution, allowing simultaneous and independent correction of both spherical and chromatic aberrations. A comparison with catadioptric systems in light optics informs our understanding of the working principles behind aberration correction with electron mirrors, and may point the way to further improvements in the latter. With additional developments in detector technology, 1 nm spatial resolution in LEEM appears to be within reach. - Highlights: • The use of electron mirrors for aberration correction in LEEM/PEEM is reviewed. • A comparison is made with similar systems in light optics. • Conditions for 1 nm spatial resolution are discussed

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

    Science.gov (United States)

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

    2010-11-01

    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.

  14. Using cathode spacers to minimize reactor size in air cathode microbial fuel cells

    KAUST Repository

    Yang, Qiao

    2012-04-01

    Scaling up microbial fuel cells (MFCs) will require more compact reactor designs. Spacers can be used to minimize the reactor size without adversely affecting performance. A single 1.5mm expanded plastic spacer (S1.5) produced a maximum power density (973±26mWm -2) that was similar to that of an MFC with the cathode exposed directly to air (no spacer). However, a very thin spacer (1.3mm) reduced power by 33%. Completely covering the air cathode with a solid plate did not eliminate power generation, indicating oxygen leakage into the reactor. The S1.5 spacer slightly increased columbic efficiencies (from 20% to 24%) as a result of reduced oxygen transfer into the system. Based on operating conditions (1000ς, CE=20%), it was estimated that 0.9Lh -1 of air would be needed for 1m 2 of cathode area suggesting active air flow may be needed for larger scale MFCs. © 2012 Elsevier Ltd.

  15. Simulation of Filament Heater for Uniform Emission from Dispenser Cathode

    Science.gov (United States)

    Singh, Narendra Kr.; Bhattacharya, Ranojoy; Khatun, Hasina; Singh, Udaybir; Sinha, A. K.

    2012-06-01

    This paper presents the design study of toroid shape filament heater for dispenser cathode.The filament heater will be used in cathode assembly of 200 kW 42 GHz gyrotron. A 3 D model of cathode assembly is designed using electromagnetic and thermal simulation software, ANSYS. The simulations are performed for optimizing the input filament heater power with respect to cathode surface temperature. The parametric study shows that the input power and cathode surface temperature depends strongly on the potting material, diameter of filament, number of turns, position and height of the filament heater with respect to cathode pellet. The design analyses are also carried out for two different filament heater materials i.e. tungsten and molybdenum. Further, the thermal, structural and transient analyses are also carried out to study the mechanical strength of the filament heater. It is concluded that the input heater power should be greater than 200 W to achieve cathode surface temperature greater than 1,000°C.

  16. High Performance Cathodes for Li-Air Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Xing, Yangchuan

    2013-08-22

    The overall objective of this project was to develop and fabricate a multifunctional cathode with high activities in acidic electrolytes for the oxygen reduction and evolution reactions for Li-air batteries. It should enable the development of Li-air batteries that operate on hybrid electrolytes, with acidic catholytes in particular. The use of hybrid electrolytes eliminates the problems of lithium reaction with water and of lithium oxide deposition in the cathode with sole organic electrolytes. The use of acid electrolytes can eliminate carbonate formation inside the cathode, making air breathing Li-air batteries viable. The tasks of the project were focused on developing hierarchical cathode structures and bifunctional catalysts. Development and testing of a prototype hybrid Li-air battery were also conducted. We succeeded in developing a hierarchical cathode structure and an effective bifunctional catalyst. We accomplished integrating the cathode with existing anode technologies and made a pouch prototype Li-air battery using sulfuric acid as catholyte. The battery cathodes contain a nanoscale multilayer structure made with carbon nanotubes and nanofibers. The structure was demonstrated to improve battery performance substantially. The bifunctional catalyst developed contains a conductive oxide support with ultra-low loading of platinum and iridium oxides. The work performed in this project has been documented in seven peer reviewed journal publications, five conference presentations, and filing of two U.S. patents. Technical details have been documented in the quarterly reports to DOE during the course of the project.

  17. Plasma characterization on carbon fiber cathode by spectroscopic diagnostics

    International Nuclear Information System (INIS)

    This paper mainly investigates plasma characterization on carbon fiber cathodes with and without cesium iodide (CsI) coating powered by a ∼300 ns, ∼200 kV accelerating pulse. It was found that the CsI layers can not only improve the diode voltage, but also maintain a stable perveance. This indicates a slowly changed diode gap or a low cathode plasma expansion velocity. By spectroscopic diagnostics, in the vicinity of the cathode surface the average plasma density and temperature were found to be ∼3 × 1014 cm−3 and ∼5 eV, respectively, for an electron current density of ∼40 A/cm2. Furthermore, there exists a multicomponent plasma expansion toward the anode. The plasma expansion velocity, corresponding to the carbon and hydrogen ions, is estimated to be ∼1.5 cm/μs. Most notably, Cs spectroscopic line was obtained only at the distance ≤ 0.5 mm from the cathode surface. Carbon and hydrogen ions are obtained up to the distance of 2.5 mm from the cathode surface. Cs ions almost remain at the vicinity of the cathode surface. These results show that the addition of CsI enables a slow cathode plasma expansion toward the anode, providing a positive prospect for developing long-pulse electron beam sources. (general)

  18. Cathodic oxygen reduction catalyzed by bacteria in microbial fuel cells.

    Science.gov (United States)

    Rabaey, Korneel; Read, Suzanne T; Clauwaert, Peter; Freguia, Stefano; Bond, Philip L; Blackall, Linda L; Keller, Jurg

    2008-05-01

    Microbial fuel cells (MFCs) have the potential to combine wastewater treatment efficiency with energetic efficiency. One of the major impediments to MFC implementation is the operation of the cathode compartment, as it employs environmentally unfriendly catalysts such as platinum. As recently shown, bacteria can facilitate sustainable and cost-effective cathode catalysis for nitrate and also oxygen. Here we describe a carbon cathode open to the air, on which attached bacteria catalyzed oxygen reduction. The bacteria present were able to reduce oxygen as the ultimate electron acceptor using electrons provided by the solid-phase cathode. Current densities of up to 2.2 A m(-2) cathode projected surface were obtained (0.303+/-0.017 W m(-2), 15 W m(-3) total reactor volume). The cathodic microbial community was dominated by Sphingobacterium, Acinetobacter and Acidovorax sp., according to 16S rRNA gene clone library analysis. Isolates of Sphingobacterium sp. and Acinetobacter sp. were obtained using H(2)/O(2) mixtures. Some of the pure culture isolates obtained from the cathode showed an increase in the power output of up to three-fold compared to a non-inoculated control, that is, from 0.015+/-0.001 to 0.049+/-0.025 W m(-2) cathode projected surface. The strong decrease in activation losses indicates that bacteria function as true catalysts for oxygen reduction. Owing to the high overpotential for non-catalyzed reduction, oxygen is only to a limited extent competitive toward the electron donor, that is, the cathode. Further research to refine the operational parameters and increase the current density by modifying the electrode surface and elucidating the bacterial metabolism is warranted. PMID:18288216

  19. Neutral hydrophilic cathode catalyst binders for microbial fuel cells

    KAUST Repository

    Saito, Tomonori

    2011-01-01

    Improving oxygen reduction in microbial fuel cell (MFC) cathodes requires a better understanding of the effects of the catalyst binder chemistry and properties on performance. A series of polystyrene-b-poly(ethylene oxide) (PS-b-PEO) polymers with systematically varying hydrophilicity were designed to determine the effect of the hydrophilic character of the binder on cathode performance. Increasing the hydrophilicity of the PS-b-PEO binders enhanced the electrochemical response of the cathode and MFC power density by ∼15%, compared to the hydrophobic PS-OH binder. Increased cathode performance was likely a result of greater water uptake by the hydrophilic binder, which would increase the accessible surface area for oxygen reduction. Based on these results and due to the high cost of PS-b-PEO, the performance of an inexpensive hydrophilic neutral polymer, poly(bisphenol A-co-epichlorohydrin) (BAEH), was examined in MFCs and compared to a hydrophilic sulfonated binder (Nafion). MFCs with BAEH-based cathodes with two different Pt loadings initially (after 2 cycles) had lower MFC performance (1360 and 630 mW m-2 for 0.5 and 0.05 mg Pt cm-2) than Nafion cathodes (1980 and 1080 mW m -2 for 0.5 and 0.05 mg Pt cm-2). However, after long-term operation (22 cycles, 40 days), power production of each cell was similar (∼1200 and 700-800 mW m-2 for 0.5 and 0.05 mg Pt cm-2) likely due to cathode biofouling that could not be completely reversed through physical cleaning. While binder chemistry could improve initial electrochemical cathode performance, binder materials had less impact on overall long-term MFC performance. This observation suggests that long-term operation of MFCs will require better methods to avoid cathode biofouling. © 2011 The Royal Society of Chemistry.

  20. Explosive emission cathode plasmas in intense relativistic electron beam diodes

    International Nuclear Information System (INIS)

    An experimental study of cathode plasmas in planar diodes driven by a Sandia Nereus accelerator (270 kV, 60 kA, 70 ns), with particular attention devoted to plasma uniformity and expansion velocity, has been carried out. This diode current density was varied over a factor of ten and the rate of rise of the applied field dE/dt was varied over a factor of six. Different cathode materials, coatings, and surface roughnesses were used and the effects of glow discharge cleaning and in situ heating of the cathode were examined. Framing photography, electron beam dosimetry, perveance measurements, optical interferometry, and (spatially and temporally resolved) spectroscopy were used to diagnose the plasma uniformity, electron beam uniformity, plasma front motion, electron density, plasma composition, motion of distinct species, electron temperature, and ion (and neutral) densities. Electron beam uniformity is seen to be related to cathode plasma uniformity; this uniformity is enhanced by a high value of (the microscopic) dE/dt, which is determined both by the rise time of the applied field and by the cathode surface roughness. The significance of dE/dt is believed to be related to the screening effect of emitted electrons. The motion of the plasma front is seen to be affected by two phenomena. To begin with, all species of the cathode plasma are seen to expand at the same rate. The ions are believed to be accelerated to velocities on the order of 2 to 3 cm/μs in dense cathode spot regions at the cathode surface. Plasma expansion is also influenced by electric pressure effects, which are determined by the shape of the driving power pulse. A simple cathode plasma model, which explains the similarity of plasmas in diodes with greatly differing parameters, is proposed. The relevance of these results to inductively driven diodes, repetitively pulsed diodes, and magnetically insulated transmission lines is also discussed

  1. Iron phosphate materials as cathodes for lithium batteries

    CERN Document Server

    Prosini, Pier Paolo

    2011-01-01

    ""Iron Phosphate Materials as Cathodes for Lithium Batteries"" describes the synthesis and the chemical-physical characteristics of iron phosphates, and presents methods of making LiFePO4 a suitable cathode material for lithium-ion batteries. The author studies carbon's ability to increase conductivity and to decrease material grain size, as well as investigating the electrochemical behaviour of the materials obtained. ""Iron Phosphate Materials as Cathodes for Lithium Batteries"" also proposes a model to explain lithium insertion/extraction in LiFePO4 and to predict voltage profiles at variou

  2. Rep-rate explosive whisker emission cathode investigations

    Science.gov (United States)

    Litz, Marc S.; Golden, Jeffry

    1994-05-01

    An experiment is underway to study the performance of several materials as field-emission cathodes for low voltage (EQ 100 kV), repetitive (coatings, niobium wire nanocomposite, and poly-crystalline tungsten. Surface emission is monitored by an array of Faraday cups. The `turn-on' time, uniformity of emission, and gap closure time are measured as a function of the spatially averaged, macroscopic electric field at the cathode. The carbon fiber cathode produces the largest current density and has the lowest threshold voltage for emission.

  3. Lanthanum hexaboride hollow cathode for dense plasma production

    International Nuclear Information System (INIS)

    A hollow tube cathode using lanthanum hexaboride as the electron emitter has been designed and constructed. Tests in both argon and hydrogen indicate that this cathode is capable of producing over 800 A of electron current continuously, corresponding to over 25 A/cm2 from the LaB6. The cathode has been operated for over 300 h and exposed to air more than 100 times with no deterioration in emission. Projected lifetime is in excess of 3500 h for the sintered LaB6 piece tested in this configuration. Construction details, performance characteristics, and discussions of space charge limits on emission are described

  4. Resonant cavity operation of a virtual cathode oscillator

    International Nuclear Information System (INIS)

    Gigawatt level virtual cathode sources have been proposed for several applications. These include microwave weapons and drivers for high-energy particle accelerators. Both of these require a microwave source with very high power output that is controllable in frequency and phase. A conventional virtual cathode oscillator will not meet these requirements. The addition of a resonant cavity surrounding the oscillating virtual cathode either alone or pumped with a low-power injection signal, causing it to operate as an amplifier, could greatly influence the performance of this type of source making it more practical for accelerator and weapon applications. The progress on an experiment to test these concepts will be discussed

  5. The approach curve method for large anode-cathode distances

    Energy Technology Data Exchange (ETDEWEB)

    Mammana, Victor P.; Monteiro, Othon R.; Fonseca, Leo R.C.

    2003-09-20

    An important technique used to characterize field emission is the measurement of the emitted current against electric field (IxE). In this work we discuss a procedure for obtaining IxE data based on multiple approach curves. We show that the simulated features obtained for an idealized uniform surface matches available experimental data for small anode-cathode distances, while for large distances the simulation predicts a departure from the linear regime. We also discuss the shape of the approach curves for large anode-cathode distances for a cathode made of carbon nanotubes.

  6. Development of artificial surface layers for thin film cathode materials

    OpenAIRE

    Carrillo Solano, Mercedes Alicia

    2016-01-01

    The present work was based on the investigation of different thin film components of Li ion batteries. A first part was dedicated to the deposition of cathodes in thin film form of a known material, LiCoO2, and an alternative one, Li(NiMnCo)O2 employing physical vapor deposition (PVD) and chemical vapor deposition (CVD), respectively. A second part was focused on the cathode-electrolyte interface for three case studies: 1) as deposited LiCoO2 cathode thin film, 2) ZrO2 coated LiCoO2 thin...

  7. Poisoning studies of an osmium-coated dispenser cathode

    International Nuclear Information System (INIS)

    The results of our studies on the reduction of the emission current from an osmium-alloy-coated dispenser cathode (derivative of the M cathode) due to exposure to various gases or vapors are reported. The primary interest of these studies is poisoning by chemical agents that might be encountered in the vacuum system of an induction linear accelerator. Of the constituents normally found in a tight unbaked vacuum chamber, the cathode is most sensitive to partial pressures of water vapor. Of the vapors studied which might be encountered in an induction accelerator, Freon was the most virulent poison

  8. The cathode test stand for the DARHT second-axis

    International Nuclear Information System (INIS)

    The injector for the DARHT second-axis injector will use an 8-in. thermionic dispenser cathode. Because the cathode is relatively large and requires a large amount of heat (5 kW) there are certain engineering issues that need to be addressed, before the DARHT injector reaches the final design stage. The Cathode Test Stand (CTS) will be used to address those concerns. The CTS is a new facility, presently under construction. The CTS will consist of a high-voltage pulse modulator, a high-vacuum diode test-chamber, and a short beam-transport section with diagnostics. This paper discusses the status of the project

  9. Erosion behavior of composite Al-Cr cathodes in cathodic arc plasmas in inert and reactive atmospheres

    Energy Technology Data Exchange (ETDEWEB)

    Franz, Robert, E-mail: robert.franz@unileoben.ac.at; Mendez Martin, Francisca; Hawranek, Gerhard [Montanuniversität Leoben, Franz-Josef-Strasse 18, 8700 Leoben (Austria); Polcik, Peter [Plansee Composite Materials GmbH, Siebenbürgerstrasse 23, 86983 Lechbruck am See (Germany)

    2016-03-15

    Al{sub x}Cr{sub 1−x} composite cathodes with Al contents of x = 0.75, 0.5, and 0.25 were exposed to cathodic arc plasmas in Ar, N{sub 2}, and O{sub 2} atmospheres and their erosion behavior was studied. Cross-sectional analysis of the elemental distribution of the near-surface zone in the cathodes by scanning electron microscopy revealed the formation of a modified layer for all cathodes and atmospheres. Due to intermixing of Al and Cr in the heat-affected zone, intermetallic Al-Cr phases formed as evidenced by x-ray diffraction analysis. Cathode poisoning effects in the reactive N{sub 2} and O{sub 2} atmospheres were nonuniform as a result of the applied magnetic field configuration. With the exception of oxide islands on Al-rich cathodes, reactive layers were absent in the circular erosion zone, while nitrides and oxides formed in the less eroded center region of the cathodes.

  10. A series of tufted carbon fiber cathodes designed for different high power microwave sources

    Science.gov (United States)

    Liu, Lie; Li, Limin; Zhang, Jun; Zhang, Xiaoping; Wen, Jianchun; Liu, Yonggui

    2008-06-01

    We report the fabrication technique of tufted carbon fiber cathodes for different microwave sources. Three carbon fiber cathodes were constructed, including a planar cathode, an annular cathode, and a cylindrical cathode for radial emission. Experimental investigations on these cathodes were performed in a reflex triode virtual cathode oscillator (vircator), a backward wave oscillator (BWO), and a magnetically insulated transmission line oscillator (MILO), respectively. The pulse duration of microwave emission from the reflex triode vircator was lengthened by using the planar carbon fiber cathode. In the BWO with the annular carbon fiber cathode, the uniform electron beam with a kA /cm2 current density was observed. In addition, carbon fiber has great promise as field emitter for MILOs. These results show that the carbon fiber cathodes can be utilized for electron emission in high power diodes with different structures.

  11. A High Performance Cathode Heater for Hall Thrusters Project

    Data.gov (United States)

    National Aeronautics and Space Administration — High current hollow cathodes are the baseline electron source for next generation high power Hall thrusters. Currently for electron sources providing current levels...

  12. Intermetallics as cathode materials in the electrolytic hydrogen production

    Energy Technology Data Exchange (ETDEWEB)

    Stojic, D.L.; Maksic, A.D.; Kaninski, M.P.M. [Vinca Inst. of Nuclear Sciences, Belgrade (Serbia and Montenegro). Lab. of Physical Chemistry; Cekic, B.D. [Vinca Inst. of Nuclear Sciences, Belgrade (Serbia and Montenegro). Lab. of Physics; Miljanic, S.S. [Belgrade Univ. (Serbia and Montenegro). Faculty of Physical Chemistry

    2005-01-01

    The intermetallics of transition metals have been investigated as cathode materials for the production of hydrogen by electrolysis from water-KOH solutions, in an attempt to increase the electrolytic process efficiency. We found that the best effect among all investigated cathodes (Hf{sub 2}Fe, Zr-Pt, Nb-Pd(I), Pd-Ta, Nb-Pd(II), Ti-Pt) exhibits the Hf{sub 2}Fe phase. These materials were compared with conventional cathodes (Fe and Ni), often used in the alkaline electrolysis. A significant upgrade of the electrolytic efficiency using intermetallics, either in pure KOH electrolyte or in combination with ionic activators added in situ, was achieved. The effects of these cathode materials on the process efficiency were discussed in the context of transition metal features that issue from their electronic configuration. (Author)

  13. High-performance lanthanum-ferrite-based cathode for SOFC

    DEFF Research Database (Denmark)

    Wang, W.G.; Mogensen, Mogens Bjerg

    2005-01-01

    LSCF/CGO on YSZ, the Rs was the same as that of our best LSM samples, which indicates good adhesion between LSCF/CGO cathode and YSZ electrolyte. Aging experiment at 800 'C for the cathode of LSCF/CGO on YSZ electrolyte shows a degradation rate of 5 x 10(-4) Omega CM2/h in R-p, while the R-s has no...... degreesC were achieved. These results are roughly six times better than our typical LSM cathodes. Slightly higher R-s was observed in the samples with LSCF/CGO cathode on the YSZ electrolyte with CGO coating due to extra contribution from the thin CGO layer and the CGO/YSZ interface. For the samples with...

  14. Extended area cathode for transverse discharge gas lasers

    International Nuclear Information System (INIS)

    Laser cathodes of extended emission area are disclosed having a plurality of substantially aligned electrically conductive plates spaced from one another and disposed in respective planes perpendicular to the longitudinal axis of the laser housing. Adjacent plates are spaced by a spacing s selected to achieve the ''hollow'' cathode effect and satisfying the relation s = k/p where p is the laser gas pressure and k is a constant determined by the laser gas and lying in the range of from about 5 to about 20 torr-cm. In one embodiment the cathode plates are supported by and attached to a pair of longitudinally extending electrically conductive rods. In another embodiment the cathode consists of a laminated array of alternatively disposed aligned taller and shorter electrically conductive plates. (U.S.)

  15. 12Cao-7Al2o3 Electride Hollow Cathode

    Science.gov (United States)

    Rand, Lauren P. (Inventor); Williams, John D. (Inventor); Martinez, Rafael A. (Inventor)

    2016-01-01

    The use of the electride form of 12CaO-7Al.sub.2O.sub.3, or C12A7, as a low work function electron emitter in a hollow cathode discharge apparatus is described. No heater is required to initiate operation of the present cathode, as is necessary for traditional hollow cathode devices. Because C12A7 has a fully oxidized lattice structure, exposure to oxygen does not degrade the electride. The electride was surrounded by a graphite liner since it was found that the C12A7 electride converts to it's eutectic (CA+C3A) form when heated (through natural hollow cathode operation) in a metal tube.

  16. Verification of high efficient broad beam cold cathode ion source.

    Science.gov (United States)

    Abdel Reheem, A M; Ahmed, M M; Abdelhamid, M M; Ashour, A H

    2016-08-01

    An improved form of cold cathode ion source has been designed and constructed. It consists of stainless steel hollow cylinder anode and stainless steel cathode disc, which are separated by a Teflon flange. The electrical discharge and output characteristics have been measured at different pressures using argon, nitrogen, and oxygen gases. The ion exit aperture shape and optimum distance between ion collector plate and cathode disc are studied. The stable discharge current and maximum output ion beam current have been obtained using grid exit aperture. It was found that the optimum distance between ion collector plate and ion exit aperture is equal to 6.25 cm. The cold cathode ion source is used to deposit aluminum coating layer on AZ31 magnesium alloy using argon ion beam current which equals 600 μA. Scanning electron microscope and X-ray diffraction techniques used for characterizing samples before and after aluminum deposition. PMID:27587108

  17. High current density nanofilament cathodes for microwave amplifiers

    NARCIS (Netherlands)

    Schnell, J-P.; Minoux, E.; Gangloff, L.; Vincent, P.; Legagneux, P.; Dieumegard, D.; David, J.-F.; Peauger, F.; Hudanski, L.; Teo, K.B.K.; Lacerda, R.; Chhowalla, M.; Hasko, D.G.; Ahmed, H.; Amaratunga, G.A.J.; Milne, W.I.; Vila, L.; Dauginet-De Pra, L.; Demoustier-Champagne, S.; Ferain, E.; Legras, R.; Piraux, L.; Gröening, O.; Raedt, H. De; Michielsen, K.

    2004-01-01

    We study high current density nanofilament cathodes for microwave amplifiers. Two different types of aligned nanofilament array have been studied: first, metallic nanowires grown by electrodeposition into nanoporous templates at very low temperature (T

  18. Development of a cathode strip chamber for minimum ionizing particles

    International Nuclear Information System (INIS)

    A cathode strip chamber (CSC) capable of measuring position information for minimum ionizing particles (MIPS) has been developed. The chamber operates in the proportional or limited proportional region, where the avalanche on the anode wire is localised to a small region around the anode wire. The position of the avalanche can be obtained by the pulse heights induced on the cathode strips which run perpendicular to direction of the anode wire. The pulse height induced on the cathode strips is proportional directly to the strip width and inversely to the distance between the strip centre to the avalanche location. Thus by measuring the pulse heights on at least three cathode strips for every event, one can reconstruct the centroid that would give the location of the avalanche on the anode

  19. Dynamic Aspects of Solid Solution Cathodes for Electrochemical Power Sources

    DEFF Research Database (Denmark)

    Atlung, Sven; West, Keld; Jacobsen, Torben

    1979-01-01

    Battery systems based on alkali metal anodes and solid solution cathodes,i.e., cathodes based on the insertion of the alkali cation in a "host lattice,"show considerable promise for high energy density storage batteries. Thispaper discusses the interaction between battery requirements, in...... particularfor vehicle propulsion, and electrochemical and constructional factors. It isargued that the energy obtainable at a given load is limited by saturation ofthe surface layers of cathode particles with cations, and that the time beforesaturation occurs is determined by diffusion of cations and electrons...... diffusioncoefficient in the solid exceeds 10–10 cm2 sec–1. On the basis of an approximaterelation between cathode thickness and electrode spacing the specificenergy for the Li/TiS2 system with organic electrolyte is estimated to be 120–150W-hr/kg in agreement with published values. ©1979 The Electrochemical Society...

  20. The Properties of Normal Conducting Cathodes in FZD Superconducting Gun

    CERN Document Server

    Xiang, R; Buettig, H; Janssen, D; Justus, M; Lehnert, U; Michel, P; Murcek, P; Schamlott, A; Schneider, Ch; Schurig, R; Staufenbiel, F; Teichert, J

    2009-01-01

    The superconducting radio frequency photoinjector (SRF photoinjector) is one of the latest applications of SC technology in the accelerator field. Since superconducting cathodes with high QE are not available up to now, normal conducting cathode material is the main choice for the SRF photoinjectors. However, the compatibility between the cathode and the cavity is one of the challenges for this concept. The SRF gun with Cs2Te cathode has been successfully operated under the collaboration of BESSY, DESY, FZD, and MBI. In this paper, some experience gained in the gun commissioning will be concluded. The results of the properties of Cs2Te photocathode in the cavity will be presented, such as the Q.E., the life time, the dark current and the thermal emittance.

  1. Scandate Cathode for High Power Long Life Electric Propulsion Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Scandate cathodes are proposed as a way to boost performance and life for electric space propulsion systems. This company has recently demonstrated breakthrough...

  2. Temperature variation of a thermionic cathode during electron emission

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    It is necessary to know the actual temperature of a thermionic cathode that works as the electron source in a microwave tube. It has been found that the temperature of the cathode drops markedly during the thermionic emission. For example, the temperature could fall by about 30oC under a current density of 2.92 A/cm2. Using the molecular thermodynamics, the dependence of the cathode temperature on the emission current density has been obtained. It has been theoretically pointed out that several factors, such as heating model and temperature coefficient of resis-tance of heater, can influence the cathode temperature. These theoretical conclu-sions were supported by the experimental results.

  3. Développement de cathodes performantes pour batteries lithium/air

    OpenAIRE

    Berenger, Sophie

    2014-01-01

    In this thesis, high-performance cathodes for lithium/air batteries have been investigated. The main limitations for lithium/air batteries are oxygen diffusion into the cathode and in the electrolyte and the progressive clogging of cathode pores by lithium oxide. The development of the air cathode is strongly dependant on the organic electrolyte used, thus the nature of the electrolyte has been here considered. Electrode porosity and the kind of catalyst employed influence the cathode perform...

  4. Electrokinetic Treatment of Cr-, Cu-, and Zn-Contaminated Sediment: Cathode Modification

    OpenAIRE

    Rajić, Ljiljana; Dalmacija, Božo; Perović, Svetlana Ugarčina; Krčmar, Dejan; Rončević, Srđan; Tomašević, Dragana

    2013-01-01

    Enhanced electrokinetic (EK) removal of Cr, Cu, and Zn from sediment by using original and modified integrated ion exchange (IIX™) cathodes was investigated. IIX cathode design and EK device process modifications were made to improve performance: separation of IIX cathode components (IIXS), combination of modified IIX cathode with pulsed electric field (IIXSP), and separation of IIX cathode components with addition of an anion exchange resin compartment (IIXA). After using the IIXSP, overall ...

  5. Hot pressing and degradation of TiB inert cathodes

    OpenAIRE

    Jensen, Morten Sundheim

    2009-01-01

    Primary aluminium production is an energy intensive process, and the aluminiumindustry strives to lower the energy consumption. However, with the current technology a considerable reduction in the energy consumption is difficult to achieve. Implementation of an inert wettable drained cathode may reduce the energyconsumption for the process considerably. TiB2 is the inert cathode material which has been considered the most promising and has received most attention. Although TiB2 does not react...

  6. Influence of substrate topography on cathodic delamination of anticorrosive coatings

    OpenAIRE

    Sørensen, Per Aggerholm; Kiil, Søren; Dam-Johansen, Kim; Weinall, C.E.

    2009-01-01

    The cathodic delamination of a commercial magnesium silicate and titanium dioxide pigmented epoxy coating on abrasive cleaned cold rolled steel has been investigated. The rate of delamination was found to depend on interfacial transport from the artificial defect to the delamination front and thereby the substrate topography, whereas the coating thickness had little influence. The presence of a significant potential gradient between the anode and the cathode and the dependency of the delamina...

  7. Chromium (V) compounds as cathode material in electrochemical power sources

    Science.gov (United States)

    Delnick, F.M.; Guidotti, R.A.; McCarthy, D.K.

    A cathode for use in a thermal battery, comprising a chromium (V) compound. The preferred materials for this use are Ca/sub 5/(CrO/sub 4/)/sub 3/Cl, Ca/sub 5/(CrO/sub 4/)OH, and Cr/sub 2/O/sub 5/. The chromium (V) compound can be employed as a cathode material in ambient temperature batteries when blended with a suitably conductive filler, preferably carbon black.

  8. Cathodes for lithium-air battery cells with acid electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Xing, Yangchuan; Huang, Kan; Li, Yunfeng

    2016-07-19

    In various embodiments, the present disclosure provides a layered metal-air cathode for a metal-air battery. Generally, the layered metal-air cathode comprises an active catalyst layer, a transition layer bonded to the active catalyst layer, and a backing layer bonded to the transition layer such that the transition layer is disposed between the active catalyst layer and the backing layer.

  9. High-Current Cold Cathode Employing Diamond and Related Materials

    Energy Technology Data Exchange (ETDEWEB)

    Hirshfield, Jay L. [Omega-P, Inc., New Haven, CT (United States)

    2014-10-22

    The essence of this project was for diamond films to be deposited on cold cathodes to improve their emission properties. Films with varying morphology, composition, and size of the crystals were deposited and the emission properties of the cathodes that utilize such films were studied. The prototype cathodes fabricated by the methods developed during Phase I were tested and evaluated in an actual high-power RF device during Phase II. These high-power tests used the novel active RF pulse compression system and the X-band magnicon test facility at US Naval Research Laboratory. In earlier tests, plasma switches were employed, while tests under this project utilized electron-beam switching. The intense electron beams required in the switches were supplied from cold cathodes embodying diamond films with varying morphology, including uncoated molybdenum cathodes in the preliminary tests. Tests with uncoated molybdenum cathodes produced compressed X-band RF pulses with a peak power of 91 MW, and a maximum power gain of 16.5:1. Tests were also carried out with switches employing diamond coated cathodes. The pulse compressor was based on use of switches employing electron beam triggering to effect mode conversion. In experimental tests, the compressor produced 165 MW in a ~ 20 ns pulse at ~18× power gain and ~ 140 MW at ~ 16× power gain in a 16 ns pulse with a ~ 7 ns flat-top. In these tests, molybdenum blade cathodes with thin diamond coatings demonstrated good reproducible emission uniformity with a 100 kV, 100 ns high voltage pulse. The new compressor does not have the limitations of earlier types of active pulse compressors and can operate at significantly higher electric fields without breakdown.

  10. High-current carbon-epoxy capillary cathode

    Science.gov (United States)

    Gleizer, J. Z.; Queller, T.; Bliokh, Yu.; Yatom, S.; Vekselman, V.; Krasik, Ya. E.; Bernshtam, V.

    2012-07-01

    The results of experiments on the reproducible generation of an electron beam having a high current density of up to 300 A/cm2 and a satisfactorily uniform cross-sectional distribution of current density in a ˜200 kV, ˜450 ns vacuum diode with a carbon-epoxy capillary cathode are presented. It was found that the source of the electrons is the plasma formed as a result of flashover inside the capillaries. It is shown that the plasma formation occurs at an electric field ≤15 kV/cm and that the cathode sustains thousands of pulses without degradation in its emission properties. Time- and space-resolved visible light observation and spectroscopy analyses were used to determine the cathode plasma's density, temperature, and expansion velocity. It was found that the density of the cathode plasma decreases rapidly in relation to the distance from the cathode. In addition, it was found that the main reason for the short-circuiting of the accelerating gap is the formation and expansion of the anode plasma. Finally, it was shown that when an external guiding magnetic field is present, the injection of the electron beam into the drift space with a current amplitude exceeding its critical value changes the radial distribution of the current density of the electron beam because the inner electrons are reflected from the virtual cathode.

  11. Cathode erosion in high-current high-pressure arc

    CERN Document Server

    Nemchinsky, V A

    2003-01-01

    Cathode erosion rate was experimentally investigated for two types of arcs: one with tungsten cathode in nitrogen atmosphere and one with hafnium cathode in oxygen atmosphere. Conditions were typical for plasma arc cutting systems: gas pressure from 2 to 5 atm, arc current from 200 to 400 A, gas flow rate from 50 to 130 litre min sup - sup 1. It was found that the actual cathode evaporation rate G is much lower than G sub 0 , the evaporation rate that follows from the Hertz-Knudsen formula: G = nu G sub 0. The difference is because some of the evaporated particles return back to the cathode. For conditions of our experiments, the factor nu could be as low as 0.01. It was shown experimentally that nu depends strongly on the gas flow pattern close to the cathode. In particular, swirling the gas increases nu many times. To explain the influence of gas swirling, model calculations of gas flows were performed. These calculations revealed difference between swirling and non-swirling flows: swirling the gas enhances...

  12. Cathodic protection for the bottoms of above ground storage tanks

    Energy Technology Data Exchange (ETDEWEB)

    Mohr, John P. [Tyco Adhesives, Norwood, MA (United States)

    2004-07-01

    Impressed Current Cathodic Protection has been used for many years to protect the external bottoms of above ground storage tanks. The use of a vertical deep ground bed often treated several bare steel tank bottoms by broadcasting current over a wide area. Environmental concerns and, in some countries, government regulations, have introduced the use of dielectric secondary containment liners. The dielectric liner does not allow the protective cathodic protection current to pass and causes corrosion to continue on the newly placed tank bottom. In existing tank bottoms where inadequate protection has been provided, leaks can develop. In one method of remediation, an old bottom is covered with sand and a double bottom is welded above the leaking bottom. The new bottom is welded very close to the old bottom, thus shielding the traditional cathodic protection from protecting the new bottom. These double bottoms often employ the use of dielectric liner as well. Both the liner and the double bottom often minimize the distance from the external tank bottom. The minimized space between the liner, or double bottom, and the bottom to be protected places a challenge in providing current distribution in cathodic protection systems. This study examines the practical concerns for application of impressed current cathodic protection and the types of anode materials used in these specific applications. One unique approach for an economical treatment using a conductive polymer cathodic protection method is presented. (author)

  13. Reducing DRIFT Backgrounds with a Submicron Aluminized-Mylar Cathode

    CERN Document Server

    Battat, James B R; Dorofeev, Alexei; Ezeribe, Anthony C; Fox, Jennifer R; Gauvreau, Jean-Luc; Gold, Michael; Harmon, Lydia; Harton, John; Lafler, Randy; Lauer, Robert J; Lee, Eric R; Loomba, Dinesh; Lumnah, Alexander; Matthews, John; Miller, Eric H; Mouton, Frederic; Murphy, Alexander St J; Phan, Nguyen; Sadler, Stephen W; Scarff, Andrew; Schuckman, Fred; Snowden-Ifft, Daniel; Spooner, Neil J C; Walker, Daniel

    2015-01-01

    Background events in the DRIFT-IId dark matter detector, mimicking potential WIMP signals, are predominantly caused by alpha decays on the central cathode in which the alpha particle is completely or partially absorbed by the cathode material. We installed a 0.9 micron thick aluminized-mylar cathode as a way to reduce the probability of producing these backgrounds. We study three generations of cathode (wire, thin-film, and radiologically clean thin-film) with a focus on the ratio of background events to alpha decays. Two independent methods of measuring the absolute alpha decay rate are used to ensure an accurate result, and agree to within $10\\%$. Using alpha range spectroscopy, we measure the radiologically cleanest cathode version to have a contamination of $3.3\\pm0.1$ ppt $^{234}$U and $73\\pm2$ ppb $^{238}$U. This cathode reduces the probability of producing an RPR from an alpha decay by a factor of $70\\pm20$ % while reducing the overall background rate by $96.5\\pm0.5\\%$ compared to the original stainles...

  14. Dynamic behavior of thermionic dispenser cathodes under ion bombardment

    Science.gov (United States)

    Cortenraad, R.; van der Gon, A. W. Denier; Brongersma, H. H.; Gärtner, G.; Raasch, D.; Manenschijn, A.

    2001-04-01

    We have investigated the surface coverage and electron emission of thermionic dispenser cathodes during 3 keV Ar+ ion bombardment, thereby simulating the bombardment of the cathodes by residual gases that takes place in cathode-ray tubes as used in television sets. During the ion bombardment at the operating temperature of 1030 °C, a dynamic equilibrium is established between the sputter removal and resupply mechanisms of the Ba and O atoms that form the dipole layer on the cathode substrate. We demonstrated that the performance of the cathodes under ion bombardment is governed by the O removal and resupply rates. It was found that the Ba resupply rate is almost an order of magnitude higher than the O resupply rate, but that the Ba can only be present on the surface bound to O atoms. Therefore, the Ba/O ratio is approximately equal to unity during the ion bombardment. Based on the investigations of the removal and resupply processes, we proposed a model that accurately describes the surface coverage and electron emission during the ion bombardment, including the dependence of the ion flux and cathode temperature.

  15. A hollow cathode hydrogen ion source. [for controlled fusion

    Science.gov (United States)

    Sovey, J. S.; Mirtich, M. J.

    1977-01-01

    High current density ion sources have been used to heat plasmas in controlled thermonuclear reaction experiments. High beam currents imply relatively high emission currents from cathodes which have generally taken the form of tungsten filaments. This paper describes a hydrogen ion source which was primarily developed to assess the emission current capability and design requirements for hollow cathodes for application in neutral injection devices. The hydrogen source produced ions by electron bombardment via a single hollow cathode. Source design followed mercury ion thruster technology, using a weak magnetic field to enhance ionization efficiency. A 1.3-cm-diam hollow cathode using a low work function material dispenser performed satisfactorily over a discharge current range of 10-90 A. Cylindrical probe measurements taken without ion extraction indicate maximum ion number densities on the order of 10 trillion/cu cm. Discharge durations ranged from 30 sec to continuous operation. Tests with beam extraction at 2.5 keV and 30 A discharge current yield average ion beam current densities of 0.1 A/sq cm over a 5-cm extraction diameter. Results of this study can be used to supply the baseline information needed to scale hollow cathodes for operation at discharge currents of hundreds of amperes using distributed cathodes.

  16. Cathodic Protection of the Yaquina Bay Bridge

    Energy Technology Data Exchange (ETDEWEB)

    Bullard, Sophie J.; Cramer, Stephen D.; Covino, Bernard S., Jr.; Holcomb, Gordon R.; Russell, James H.; Laylor, H.M.; Cryer, C.B.

    2001-02-01

    The Yaquina Bay Bridge in Newport, Oregon, was designed by Conde B. McCullough and built in 1936. The 3,223-foot (982 m) structure is a combination of concrete arch approach spans and a steel through arch over the shipping channel. Cathodic protection is used to prevent corrosion damage to the concrete arches. The Oregon Department of Transportation (Oregon DOT) installed a carbon anode coating (DAC-85) on two of the north approach spans in 1985. This anode was operated at a current density of 6.6 mA/m2(0.6 mA/ft2). No failure of the conductive anode was observed in 1990, five years after application, or in 2000, 15 years after application. Thermal-sprayed zinc anodes 20 mils (0.5 mm) thick were applied to half the south approach spans beginning in 1990. Thermal-sprayed zinc anodes 15 mils (0.4 mm) thick were applied to the remaining spans in 1996. These anodes were operated at a current density of 2.2 mA/m2(0.2 mA/ft2). In 1999, four zones on the approach spans were included in a two-year field trial of humectants to improve zinc anode performance. The humectants LiNO3 and LiBr were applied to two zones; the two adjacent zones were left untreated as controls. The humectants substantially reduced circuit resistance compared to the controls.

  17. Lowering of the cathode fall voltage by laser exposure of the cathode in a high-pressure mercury discharge

    International Nuclear Information System (INIS)

    The effect of an additional electrode heating by laser light exposure of one electrode has been studied in a high-pressure mercury discharge. The exposed electrode operates as cathode or anode during the corresponding half-cycles of a square-wave current which has been used for driving the discharge. The additional heating influences the discharge voltage and the electrode tip temperatures in different ways during the cathode and anode phases. Only during the cathode phase is there a noticeable decrease in the discharge voltage connected with a moderate increase in the cathode tip temperature. The maximum absorbed laser power of 6.2 W causes a voltage decrease of about 3.5 V for a discharge current of 1.8 A. The exposure during the anode phase is characterized by a strong increase in the electrode tip temperature and a nearly unchanged discharge voltage. Theoretically determined parameters of the cathode boundary layer are given. For a constant discharge current the power balance at the cathode surface suggests a nearly linear dependence of the discharge voltage lowering on the laser input power, which has been verified experimentally

  18. Physical model and experimental results of cathode erosion related to power supply ripple

    Science.gov (United States)

    Harris, W. J.; O'Hair, E. A.; Hatfield, L. L.; Kristiansen, M.

    1992-01-01

    This paper discusses the physical effects of power supply ripple on cathode erosion and cathode arc attachment in a water-cooled, 30 kW nitrogen arcjet. Experimental results are presented for 2 percent thoriated tungsten, which show that the long-term cathode erosion rate is a decreasing function of current ripple over the range 1-13 percent. Above this range, the cathode discharge becomes unstable, and the erosion rate rapidly increases. A qualitative model of this effect is given in terms of a magnetically induced radial motion of the arc column, and an overall increase in the cathode spot radius due to the higher peak current associated with higher ripple. The most important effect of power supply ripple is therefore shown to be its ability to collectively drive the cathode attachment away from the cathode center. This leads to an increase in the cathode attachment area, and a subsequent decrease in the cathode erosion rate.

  19. Durability and performance optimization of cathode materials for fuel cells

    Science.gov (United States)

    Colon-Mercado, Hector Rafael

    The primary objective of this dissertation is to develop an accelerated durability test (ADT) for the evaluation of cathode materials for fuel cells. The work has been divided in two main categories, namely high temperature fuel cells with emphasis on the Molten Carbonate Fuel Cell (MCFC) cathode current collector corrosion problems and low temperature fuel cells in particular Polymer Electrolyte Fuel Cell (PEMFC) cathode catalyst corrosion. The high operating temperature of MCFC has given it benefits over other fuel cells. These include higher efficiencies (>50%), faster electrode kinetics, etc. At 650°C, the theoretical open circuit voltage is established, providing low electrode overpotentials without requiring any noble metal catalysts and permitting high electrochemical efficiency. The waste heat is generated at sufficiently high temperatures to make it useful as a co-product. However, in order to commercialize the MCFC, a lifetime of 40,000 hours of operation must be achieved. The major limiting factor in the MCFC is the corrosion of cathode materials, which include cathode electrode and cathode current collector. In the first part of this dissertation the corrosion characteristics of bare, heat-treated and cobalt coated titanium alloys were studied using an ADT and compared with that of state of the art current collector material, SS 316. PEMFCs are the best choice for a wide range of portable, stationary and automotive applications because of their high power density and relatively low-temperature operation. However, a major impediment in the commercialization of the fuel cell technology is the cost involved due to the large amount of platinum electrocatalyst used in the cathode catalyst. In an effort to increase the power and decrease the cathode cost in polymer electrolyte fuel cell (PEMFC) systems, Pt-alloy catalysts were developed to increase its activity and stability. Extensive research has been conducted in the area of new alloy development and

  20. Measurement of cathode surface temperature using the method of CCD imaging in arc discharge

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A two-wavelength pyrometry device using ordinary array CCD (charge coupled device) to collect the radiation data in the horizontal and vertical directions has been developed for measuring the cathode surface temperature during the arc discharge. Analyses of experimental results show that the device can make the measurement of the cathode surface temperature feasible. The cathode surface temperatures measured are lower than the melting point of tungsten (3653 K), and the arc current, cathode diameter, and the cathode length are the main influencing factors of the cathode surface temperature.

  1. Inert Anode/Cathode Program: Fiscal Year 1986 annual report. [For Hall-Heroult cells

    Energy Technology Data Exchange (ETDEWEB)

    Brenden, B.B.; Davis, N.C.; Koski, O.H.; Marschman, S.C.; Pool, K.H.; Schilling, C.H.; Windisch, C.F.; Wrona, B.J.

    1987-06-01

    Purpose of the program is to develop long-lasting, energy-efficient anodes, cathodes, and ancillary equipment for Hall-Heroult cells used by the aluminum industry. The program is divided into four tasks: Inert Anode Development, Cathode Materials Evaluation, Cathode Bonding Development, and Sensor Development. To devise sensors to control the chemistry of Hall-Heroult cells using stable anodes and cathodes. This report highlights the major FY86 technical accomplishments, which are presented in the following sections: Management, Materials Development, Materials Evaluation, Thermodynamic Evaluation, Laboratory Cell Tests, Large-Scale Tests, Cathode Materials Evaluation, Cathode Bonding Development, and Sensor Development.

  2. Electron and ion kinetics in a micro hollow cathode discharge

    Energy Technology Data Exchange (ETDEWEB)

    Kim, G J; Iza, F; Lee, J K [Electronics and Electrical Engineering Department, Pohang University of Science and Technology, Pohang, 790-784 (Korea, Republic of)

    2006-10-21

    Electron and ion kinetics in a micro hollow cathode discharge are investigated by means of two-dimensional axisymmetric particle-in-cell Monte Carlo collision simulations. Argon discharges at 10 and 300 Torr are studied for various driving currents. Electron and ion energy probability functions (IEPF) are shown at various times and locations to study the spatio-temporal behaviour of the discharge. The electron energy probability function (EEPF) evolves from the Druyvesteyn type in the early stages of the discharge into a two (or three) temperature distribution when steady state is reached. In steady state, secondary electrons accelerated across the cathode fall populate the high energy tail of the EEPF while the low energy region is populated by trapped electrons. The IEPF evolves from a Maxwellian in the negative glow (bulk) to a two temperature distribution on the cathode surface. The overpopulation of low energy ions near the cathode surface is attributed to a larger collision cross section for low energy ions and ionization within the cathode fall.

  3. A microwave plasma cathode electron gun for ion beam neutralization

    Science.gov (United States)

    Fusellier, C.; Wartski, L.; Aubert, J.; Schwebel, C.; Coste, Ph.; Chabrier, A.

    1998-02-01

    It is well known that there exist two distinct types of ion beam neutralization, viz., charge and current neutralization. We have designed and studied a versatile and compact microwave plasma (MP) cathode electron gun dedicated to charge as well as current neutralization. Unlike the conventional hot cathode neutralizer, this MP cathode allows operation of the electron gun in a reactive gaseous environment when it is eventually associated with an electron cyclotron resonance (ECR) ion gun. Charge neutralization can be easily carried out by extracting from the MP cathode through a 1 mm diameter hole, a 35 mA electron beam under a 20 V voltage; the MP cathode being fed with a 75 W microwave power at 2.45 GHz. Higher beam intensities could be obtained using a multiaperture thin plate. Electron beam intensities as high as 300 mA and energies of 2 keV needed for current neutralization, e.g., when an ion beam impinges onto a thick dielectric surface, are obtained via a two-stage arrangement including an anodic chamber associated with a set of three monoaperture plates for the electron beam extraction. Transport of 200-2000 eV electron beams is ensured using focusing optics composed of three aligned tubes 6 cm in diameter and unsymmetrically polarized.

  4. Trajectory control strategy of cathodes in blisk electrochemical machining

    Institute of Scientific and Technical Information of China (English)

    Zhu Dong; Zhu Di; Xu Zhengyang; Zhou Laishui

    2013-01-01

    A turbine blisk,which combines blades and a disk together,is one of the most important components of an aero engine.In the process of blisk electrochemical machining (ECM),the sheet cathode,which is usually used as a tool electrode,has a complicated structure.In addition to that,the channel between the adjacent blades is narrow and twisted,so interference is apt to happen when the sheet cathode feeds into the channel.Therefore,it is important to choose suitable trajectory control strategy.In this paper,a new trajectory control strategy of the sheet cathode is presented and corresponding simulation analysis is conducted on the basis of an actual blisk model.The simulation results demonstrate that the sheet cathode can feed into the channel by a spatial line trajectory without interference.Moreover,the verification experiments are carried out according to the simulation.The experimental results show that the cathode can move into the channel without interference.It is verified that the new trajectory control strategy is correct and can be used in the blisk ECM process successfully.

  5. A new large-scale plasma source with plasma cathode

    International Nuclear Information System (INIS)

    A new large-scale plasma source (200 mm diameter) with a plasma cathode has been investigated. The plasma has a good spatial uniformity, operates at low electron temperature, and is highly ionized under relatively low gas pressure of about 10-4 Torr. The plasma source consists of a plasma chamber and a plasma cathode generator. The plasma chamber has an anode which is 200 mm in diameter, 150 mm in length, is made of 304 stainless steel, and acts as a plasma expansion cup. A filament-cathode-like plasma ''plasma cathode'' is placed on the central axis of this source. To improve the plasma spatial uniformity in the plasma chamber, a disk-shaped, floating electrode is placed between the plasma chamber and the plasma cathode. The 200 mm diameter plasma is measure by using Langmuir probes. As a result, the discharge voltage is relatively low (30-120 V), the plasma space potential is almost equal to the discharge voltage and can be easily controlled, the electron temperature is several electron volts, the plasma density is about 1010 cm-3, and the plasma density is about 10% variance in over a 100 mm diameter. (Author)

  6. Blacking FTO by strongly cathodic polarization with enhanced photocurrent

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Yun; Lu, Xiaoqing; Huang, Wei, E-mail: hjhw9513@163.com; Li, Zelin, E-mail: lizelin@hunnu.edu.cn

    2015-08-30

    Graphical abstract: - Highlights: • Transparent FTO became blackish under strongly cathodic polarization. • Part of SnO{sub 2} coating on the FTO can be reduced into Sn nanoparticles. • The black FTO increased solar absorption and enhanced photocurrent responses. • Take care in photoelectrochemistry test while FTO is strongly cathodically polarized. - Abstract: Transparent fluorine-doped tin oxide (TFTO) coating on quartz glass is widely used as substrate in photoelectrochemistry for solar energy transformation, sensing and so on. We observed that the TFTO could become blackish by strongly cathodic polarization. Characterization of the black FTO (BFTO) by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy revealed that part of SnO{sub 2} on the TFTO was reduced into metal Sn nanoparticles during the cathodic polarization. The BFTO greatly increased solar absorption and enhanced photocurrent responses in comparison with TFTO. It might be necessary to take caution in photoelectrochemical measurements while the FTO is strongly cathodically polarized.

  7. Photoemission experiments of a large area scandate dispenser cathode

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Huang, E-mail: bamboobbu@hotmail.co [Institute of Fluid Physics, CAEP, P.O. Box 919-106, Mianyang 621900 (China); Liu Xingguang; Chen Yi; Chen Debiao; Jiang Xiaoguo; Yang Anmin; Xia Liansheng; Zhang Kaizhi; Shi Jinshui; Zhang Linwen [Institute of Fluid Physics, CAEP, P.O. Box 919-106, Mianyang 621900 (China)

    2010-09-21

    A 100-mm-diameter scandate dispenser cathode was tested as a photocathode with a 10 ns Nd:YAG laser (266 nm) on an injector test stand for linear induction accelerators. This thermionic dispenser cathode worked at temperatures ranging from room temperature to 930 {sup o}C (below or near the thermionic emission threshold) while the vacuum was better than 4x10{sup -7} Torr. The laser pulse was synchronized with a 120 ns diode voltage pulse stably and they were in single pulse mode. Emission currents were measured by a Faraday cup. The maximum peak current collected at the anode was about 100 A. The maximum quantum efficiency measured at low laser power was 2.4x10{sup -4}. Poisoning effect due to residual gas was obvious and uninterrupted heating was needed to keep cathode's emission capability. The cathode was exposed to air one time between experiments and recovered after being reconditioned. Photoemission uniformity of the cathode was also explored by changing the laser spot's position.

  8. Three Dimensional Effects on Virtual Cathode Formation in Electron Guns.

    Science.gov (United States)

    Valfells, Agust

    2001-10-01

    Recent experiments at the University of Maryland using photoemission from a dispenser cathode have yielded some interesting results regarding the effects of the area of emission and of the ratio between the pulse length and the gap transit time on the amount of current that may be drawn from an electron gun before a virtual cathode forms. The experiments show that a much higher current density may be drawn from a short pulse or limited emitter area than is anticipated by the Child-Langmuir limiting current. There is also evidence that the current may be increased even after virtual cathode formation, which leads one to distinguish between a limiting current density and a current density critical for virtual cathode formation. The experiments have also yielded some interesting results on the longitudinal structure of the current pulse passed through the anode. Some empirical and theoretical scaling laws regarding the formation of virtual cathodes in an electron gun will be presented. This work was motivated by the needs of the University of Maryland Electron Ring (UMER), where we wish to generate pulses that are well-localized in time and space.

  9. Photoemission experiments of a large area scandate dispenser cathode

    Science.gov (United States)

    Zhang, Huang; Liu, Xing-guang; Chen, Yi; Chen, De-biao; Jiang, Xiao-guo; Yang, An-min; Xia, Lian-sheng; Zhang, Kai-zhi; Shi, Jin-shui; Zhang, Lin-wen

    2010-09-01

    A 100-mm-diameter scandate dispenser cathode was tested as a photocathode with a 10 ns Nd:YAG laser (266 nm) on an injector test stand for linear induction accelerators. This thermionic dispenser cathode worked at temperatures ranging from room temperature to 930 °C (below or near the thermionic emission threshold) while the vacuum was better than 4×10 -7 Torr. The laser pulse was synchronized with a 120 ns diode voltage pulse stably and they were in single pulse mode. Emission currents were measured by a Faraday cup. The maximum peak current collected at the anode was about 100 A. The maximum quantum efficiency measured at low laser power was 2.4×10 -4. Poisoning effect due to residual gas was obvious and uninterrupted heating was needed to keep cathode's emission capability. The cathode was exposed to air one time between experiments and recovered after being reconditioned. Photoemission uniformity of the cathode was also explored by changing the laser spot's position.

  10. Photoemission experiments of a large area scandate dispenser cathode

    International Nuclear Information System (INIS)

    A 100-mm-diameter scandate dispenser cathode was tested as a photocathode with a 10 ns Nd:YAG laser (266 nm) on an injector test stand for linear induction accelerators. This thermionic dispenser cathode worked at temperatures ranging from room temperature to 930 oC (below or near the thermionic emission threshold) while the vacuum was better than 4x10-7 Torr. The laser pulse was synchronized with a 120 ns diode voltage pulse stably and they were in single pulse mode. Emission currents were measured by a Faraday cup. The maximum peak current collected at the anode was about 100 A. The maximum quantum efficiency measured at low laser power was 2.4x10-4. Poisoning effect due to residual gas was obvious and uninterrupted heating was needed to keep cathode's emission capability. The cathode was exposed to air one time between experiments and recovered after being reconditioned. Photoemission uniformity of the cathode was also explored by changing the laser spot's position.

  11. Durability and Performance of High Performance Infiltration Cathodes

    DEFF Research Database (Denmark)

    Samson, Alfred Junio; Søgaard, Martin; Hjalmarsson, Per; Hjelm, Johan; Bonanos, Nikolaos; Foghmoes, Søren Preben Vagn; Ramos, Tania

    2013-01-01

    The performance and durability of solid oxide fuel cell (SOFC) cathodes consisting of a porous Ce0.9Gd0.1O1.95 (CGO) infiltrated with nitrates corresponding to the nominal compositions La0.6Sr0.4Co1.05O3-δ (LSC), LaCoO3-δ (LC), and Co3O4 are discussed. At 600°C, the polarization resistance, Rp...... infiltrate but also from a better surface exchange property. A 450h test of an LSC-infiltrated CGO cathode showed an Rp with final degradation rate of only 11mΩcm2kh-1. An SOFC with an LSC-infiltrated CGO cathode tested for 1,500h at 700°C and 0.5Acm-2 (60% fuel, 20% air utilization) revealed no measurable...... degradation. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim....

  12. Anthraquinone-Based Polymer as Cathode in Rechargeable Magnesium Batteries.

    Science.gov (United States)

    Bitenc, Jan; Pirnat, Klemen; Bančič, Tanja; Gaberšček, Miran; Genorio, Boštjan; Randon-Vitanova, Anna; Dominko, Robert

    2015-12-21

    Mg batteries are a promising battery technology that could lead to safer and significantly less expensive non-aqueous batteries with energy densities comparable or even better than state-of-the-art Li-ion batteries. Although the first prototype Mg battery using stable Mo6S8 as cathode was introduced over fifteen years ago, major challenges remain to be solved. In particular, the design of high energy cathode materials and the development of non-corrosive electrolytes with high oxidative stability are issues that need to be tackled. Herein, we present a new, general, and robust approach towards achieving stable cycling of Mg batteries. The core of our approach is the use of stable polymer cathode and Mg powder anode coupled with non-nucleophilic electrolytes. Our systems exhibit an excellent rate capability and significant improvement in electrochemical stability. PMID:26610185

  13. Cyclic erosion of a cathode in high-pressure arcs

    Energy Technology Data Exchange (ETDEWEB)

    Nemchinsky, Valerian [ESAB Welding and Cutting Products and Francis Marion University, Florence, SC 29501 (United States)

    2003-07-07

    Erosion that occurred during arc shut down was investigated. The arc current was 200 A; the cathode was made of hafnium. Different gases were used: oxygen, nitrogen, and noble gases (argon, helium, and hydrogen-argon mixture). The gas pressure was 3 atm. It was shown that erosion in noble gases is higher compared to gases that create chemical compounds with hafnium (oxygen and nitrogen). The following model of arc-off erosion is suggested. An amount of plasma gas is diluted in the molten tip of the cathode. When the arc is terminated, the gas pressure in the cathode vicinity drops down. The diluted gas then leaves the molten puddle and carries some liquid material with it.

  14. An interchangeable-cathode vacuum arc plasma source

    International Nuclear Information System (INIS)

    A simplified vacuum arc design [based on metal vapor vacuum arc (MeVVA) concepts] is employed as a plasma source for a study of a 7Be non-neutral plasma. The design includes a mechanism for interchanging the cathode source. Testing of the plasma source showed that it is capable of producing on the order of 1012 charges at confinable energies using a boron-carbide disk as the cathode target. The design is simplified from typical designs for lower energy and lower density applications by using only the trigger spark rather than the full vacuum arc in high current ion beam designs. The interchangeability of the cathode design gives the source the ability to replace only the source sample, simplifying use of radioactive materials in the plasma source. The sample can also be replaced with a completely different conductive material. The design can be easily modified for use in other plasma confinement or full MeVVA applications.

  15. Thermionically electron emitting matrix cathodes for magnetohydrodynamic generators: Analytical model

    International Nuclear Information System (INIS)

    Current and voltage drop calculations have been made for matrix cathodes having a number of sharp pins projecting out from its surface in open-cycle magnetohydrodynamic plasmas. It is assumed that from the cathode surface to the cathode sheath edge, the current flows in current tubes formed around the projected pins. The effect of high electric field on the work function of the tip has been taken into account and calculations are made for a variable number of tips and tip area. Work functions of the tip and the slant surface are taken to be different. The current and voltage characteristics have been obtained by solving the current continuity and Poisson's equations in spherical coordinate geometry. It is observed that the current increases with an increase in the number of pins per unit area and tip area. The theoretical results have been compared with the experimental observations

  16. Wettable Ceramic-Based Drained Cathode Technology for Aluminum Electrolysis

    Energy Technology Data Exchange (ETDEWEB)

    J.N. Bruggeman; T.R. Alcorn; R. Jeltsch; T. Mroz

    2003-01-09

    The goal of the project was to develop the ceramic based materials, technology, and necessary engineering packages to retrofit existing aluminum reduction cells in order to reduce energy consumption required for making primary aluminum. The ceramic materials would be used in a drained cathode configuration which would provide a stable, molten aluminum wetted cathode surface, allowing the reduction of the anode-cathode distance, thereby reducing the energy consumption. This multi-tasked project was divided into three major tasks: (1) Manufacturing and laboratory scale testing/evaluation of the ceramic materials, (2) Pilot scale testing of qualified compositions from the first task, and (3) Designing, retrofitting, and testing the ceramic materials in industrial cells at Kaiser Mead plant in Spokane, Washington. Specific description of these major tasks can be found in Appendix A - Project Scope. Due to the power situation in the northwest, the Mead facility was closed, thus preventing the industrial cell testing.

  17. Measurement and analysis of thermal photoemission from a dispenser cathode

    Science.gov (United States)

    Jensen, Kevin L.; Feldman, Donald W.; Virgo, Matt; O'Shea, Patrick G.

    2003-08-01

    Photocathodes for free electron lasers (FELs) are required to produce nano-Coulomb pulses in picosecond time scales with demonstrable reliability, lifetime, and efficiency. Dispenser cathodes, traditionally a rugged and long-lived thermionic source, are under investigation to determine their utility as a photocathode and have shown promise. The present study describes theoretical models under development to analyze experimental data from dispenser cathodes and to create predictive time-dependent models to predict their performance as an FEL source. Here, a steady-state model of a dispenser cathode with partial coverage of a low work function coating and surface nonuniformity is developed. Quantitative agreement is found for experimental data, especially with regard to temperature, field, laser intensity, and quantum efficiency versus laser wavelength dependence. In particular, for long wavelength incident lasers of sufficient intensity, the majority of the absorbed energy heats the electron gas and background lattice, and photoemission from the heated electron distribution constitutes the emitted current.

  18. Microwave generator experiment at LLNL. [Virtual cathode oscillator (VIRCATOR)

    Energy Technology Data Exchange (ETDEWEB)

    Hofer, W.W.; Burkhart S.C.; Scarpetti, R.D.

    1983-02-14

    A high power microwave oscillator known as a Virtual Cathode Oscillator (VIRCATOR) is described here. It is basically a space charge limited field emission cathode injecting electrons through a thin foil into a 4.3 cm radius circular waveguide. The total injected current forms a potential which exceeds the electron energy at which point a virtual cathode forms, and the electrons are reflected back across the foil. This occurs cyclically, coupling energy into TM/sub on/ waveguide modes. The frequency and power of the oscillations are very dependent on geometry and driving voltage. The VIRCATOR is presented here in two parts. First, the VIRCATOR theory and experiment setup is discussed, then numerical analysis of various VIRCATOR geometries is shown.

  19. Back bombardment for dispenser and lanthanum hexaboride cathodes

    Science.gov (United States)

    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

    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 6μs 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.

  20. Comparative Spectroscopic Temperature Measurements In Hydrogen Hollow Cathode Glow Discharge

    Science.gov (United States)

    Majstorovic, G. Lj.; Šišovic, N. M.; Konjevic, N.

    2010-07-01

    We report results of optical emission spectroscopy measurements of rotational Trot and translational temperature Ttr of hydrogen molecules. The light source was hollow cathode glow discharge with titanium cathode operated in hydrogen at low pressure. The rotational temperature of excited electronic states of H2 was determined either from relative line intensities of the R branch of the GK ? B band or from the Q branch of the Fulcher-a diagonal band. The population of excited energy levels, determined from relative line intensities, was used to derive ro-vibronic temperature of the ground state of hydrogen molecule.

  1. Modulation transfer spectroscopy of ytterbium atoms in hollow cathode lamp

    International Nuclear Information System (INIS)

    We present the experimental study of modulation transfer spectroscopy of ytterbium atoms in a hollow cathode lamp. The dependences of its linewidth, slope and magnitude on the various experimental parameters are measured and fitted by the well-known theoretical expressions. The experimental results are in good agreement with the theoretical prediction. We have observed the Dicke narrowing effect by increasing the current of the hollow cathode lamp. It is also found that there are the optimal current and laser power to generate the better modulation transfer spectroscopy signal, which can be employed for locking the laser frequency to the atomic transition. (authors)

  2. NEW CATHODE MATERIALS FOR INERT AND OXIDIZING ATMOSPHERE PLASMA APPLICATION

    OpenAIRE

    Sadek, A; Kusumoto, K.; Ushio, M; Matsuda, F.

    1990-01-01

    This study has been carried out to develop new cathode materials for two types of thermionic cathode. First is concerning to the tungsten electrodes for the plasma furnace and welding torches. The second one is the electrodes for air plasma cutting torch. Tungsten electrodes activated with a single and combined additives of rare earth metal oxides, such as La2O3, Y2O3 and CeO2, are produced and pared with pure and thoriated tungsten electrode conventionally used, from the point of view of ele...

  3. Improved Cathode Structure for a Direct Methanol Fuel Cell

    Science.gov (United States)

    Valdez, Thomas; Narayanan, Sekharipuram

    2005-01-01

    An improved cathode structure on a membrane/electrode assembly has been developed for a direct methanol fuel cell, in a continuing effort to realize practical power systems containing such fuel cells. This cathode structure is intended particularly to afford better cell performance at a low airflow rate. A membrane/electrode assembly of the type for which the improved cathode structure was developed (see Figure 1) is fabricated in a process that includes brush painting and spray coating of catalyst layers onto a polymer-electrolyte membrane and onto gas-diffusion backings that also act as current collectors. The aforementioned layers are then dried and hot-pressed together. When completed, the membrane/electrode assembly contains (1) an anode containing a fine metal black of Pt/Ru alloy, (2) a membrane made of Nafion 117 or equivalent (a perfluorosulfonic acid-based hydrophilic, proton-conducting ion-exchange polymer), (3) a cathode structure (in the present case, the improved cathode structure described below), and (4) the electrically conductive gas-diffusion backing layers, which are made of Toray 060(TradeMark)(or equivalent) carbon paper containing between 5 and 6 weight percent of poly(tetrafluoroethylene). The need for an improved cathode structure arises for the following reasons: In the design and operation of a fuel-cell power system, the airflow rate is a critical parameter that determines the overall efficiency, cell voltage, and power density. It is desirable to operate at a low airflow rate in order to obtain thermal and water balance and to minimize the size and mass of the system. The performances of membrane/electrode assemblies of prior design are limited at low airflow rates. Methanol crossover increases the required airflow rate. Hence, one way to reduce the required airflow rate is to reduce the effect of methanol crossover. Improvement of the cathode structure - in particular, addition of hydrophobic particles to the cathode - has been

  4. Cathodic arc grown niobium films for RF superconducting cavity applications

    Science.gov (United States)

    Catani, L.; Cianchi, A.; Lorkiewicz, J.; Tazzari, S.; Langner, J.; Strzyzewski, P.; Sadowski, M.; Andreone, A.; Cifariello, G.; Di Gennaro, E.; Lamura, G.; Russo, R.

    2006-07-01

    Experimental results on the characterization of the linear and non-linear microwave properties of niobium film produced by UHV cathodic arc deposition are presented. Surface impedance Zs as a function of RF field and intermodulation distortion (IMD) measurement have been carried out by using a dielectrically loaded resonant cavity operating at 7 GHz. The experimental data show that these samples have a lower level of intrinsic non-linearities at low temperature and low circulating power in comparison with Nb samples grown by sputtering. These results make UHV cathodic arc deposition a promising technique for the improvement of RF superconducting cavities for particle accelerators.

  5. Cathodic arc grown niobium films for RF superconducting cavity applications

    Energy Technology Data Exchange (ETDEWEB)

    Catani, L. [INFN-Roma2, Rome (Italy); Cianchi, A. [INFN-Roma2, Rome (Italy); Lorkiewicz, J. [INFN-Roma2, Rome (Italy); Tazzari, S. [Universita di Roma ' Tor Vergata' and INFN-Roma2, Rome (Italy); Langner, J. [Soltan Institute for Nuclear Studies, Swierk (Poland); Strzyzewski, P. [Soltan Institute for Nuclear Studies, Swierk (Poland); Sadowski, M. [Soltan Institute for Nuclear Studies, Swierk (Poland); Andreone, A. [University of Napoli ' Federico II' and INFN-NA, Naples (Italy); Cifariello, G. [University of Napoli ' Federico II' and INFN-NA, Naples (Italy); Di Gennaro, E. [University of Napoli ' Federico II' and INFN-NA, Naples (Italy); Lamura, G. [University of Napoli ' Federico II' and INFN-NA, Naples (Italy); Russo, R. [Seconda Universita di Napoli, INFN-NA, Naples (Italy)

    2006-07-15

    Experimental results on the characterization of the linear and non-linear microwave properties of niobium film produced by UHV cathodic arc deposition are presented. Surface impedance Z {sub s} as a function of RF field and intermodulation distortion (IMD) measurement have been carried out by using a dielectrically loaded resonant cavity operating at 7 GHz. The experimental data show that these samples have a lower level of intrinsic non-linearities at low temperature and low circulating power in comparison with Nb samples grown by sputtering. These results make UHV cathodic arc deposition a promising technique for the improvement of RF superconducting cavities for particle accelerators.

  6. Impedance Modeling of Solid Oxide Fuel Cell Cathodes

    DEFF Research Database (Denmark)

    Mortensen, Jakob Egeberg; Søgaard, Martin; Jacobsen, Torben

    2010-01-01

    partial pressure range 0.028-1.00 atm. The recorded impedance spectra were successfully analyzed using the developed impedance model in the investigated temperature and oxygen partial pressure range. It is also demonstrated that the model can be used to predict how impedance spectra evolve with different......A 1-dimensional impedance model for a solid oxide fuel cell cathode is formulated and applied to a cathode consisting of 50/50 wt% strontium doped lanthanum cobaltite and gadolinia doped ceria. A total of 42 impedance spectra were recorded in the temperature range: 555-852°C and in the oxygen...

  7. Cathode Ray Research Leading to J.J. Thomson's Discovery

    Science.gov (United States)

    Mulligan, Joseph

    1997-04-01

    This paper reviews the research on the properties and nature of cathode rays that led to the discovery of the electron by J. J. Thomson in the years 1897 - 1899. During the period from about 1870 to 1897 important research on cathode rays was carried out by William Crookes and Arthur Schuster in England, by Eugen Goldstein, Heinrich Hertz, Philipp Lenard, Emil Wiechert and Walter Kaufman in Germany, and by Jean Perrin in France. This research was always tedious and often inexact because fast vacuum pumps and convenient vacuum gauges did not yet exist. Still a few of these earlier researchers narrowly missed beating J. J. Thomson to the discover of the electron.

  8. Emission nonuniformity due to profilimetry variation in thermionic cathodes

    Science.gov (United States)

    Jensen, Kevin L.; Lau, Y. Y.; Jordan, Nicholas

    2006-04-01

    A model is developed which shows that the micron-scale ridges, introduced by the surface machining of thermionic dispenser cathodes, may lead to significant angular variations in the macroscopic current density on ring-shaped cathodes commonly used in gyrotrons. An account of the local enhancement in the microscopic emission current density on the ridges is considered for a representative physical model, which shows that the angular variation in current may be pronounced and accounted for by variations in ridges as a consequence of large scale profilimetry variations resulting from machining.

  9. An RF excited plasma cathode electron beam gun design

    OpenAIRE

    Del Pozo, S.; Ribton, C; Smith, DR

    2014-01-01

    A plasma cathode electron beam (EB) gun is presented in this work. A radio frequency (RF) excited plasma at 84 MHz was used as the electron source to produce a beam power of up to 3.2 kW at -60 kV accelerating voltage. The pressure in the plasma chamber is approximately 1 mbar. The electrons are extracted from the plasma chamber to the vacuum chamber (at 10-5 mbar) through a diaphragm with a 0.5 mm diameter nozzle. Advantages over thermionic cathode guns were demonstrated empirically. Mainten...

  10. Virtual cathode oscillator with E-beam modulation

    International Nuclear Information System (INIS)

    A new type virtual cathode oscillator (VCO) with preliminary e-beam modulation was studied by numerical simulation and experimentally tested. It was shown that the variation of the beam modulation signal leaded to the change of character of vircator. In the vircator scheme, the microwave generated by virtual cathode oscillation was partially fed back to the beam acceleration region to modulate the injected e-beam and so as to improve the performance of the vircator. Changing the length of feedback waveguide resulted in a 8dB variation of the radiated microwave power

  11. QE data for Pb/Nb deposited photo cathode samples

    CERN Document Server

    Sekutowicz, J

    2010-01-01

    This report outlines progress in the development of photo-cathodes for a hybrid lead/niobium (Pb/Nb) superconducting SRF electron injector. We have coated eight Nb samples with lead to study and determine deposition conditions leading to high quality emitting area. The results show that the oxide layer significantly influences the quantum efficiency (QE) of all measured cathodes. In addition, we learned that although the laser cleaning enhanced the QE substantially, the film morphology was strongly modified. That observation convinced us to make the coatings thicker and therefore more robust.

  12. Web-Based Cathode Strip Chamber Data Display

    CERN Multimedia

    Firmansyah, M

    2013-01-01

    Cathode Strip Chamber (CSC) is a detector that uses gas and high electric field to detect particles. When a particle goes through CSC, it will ionize gas particles and generate electric signal in the anode and cathode of the detector. Analysis of the electric signal data can help physicists to reconstruct path of the particles and determine what happen inside the detector. Using data display, analysis of CSC data becomes easier. One can determine which data is interesting, unusual, or maybe only contain noise.\

  13. Axis-1 diode simulations I: standard 2-inch cathode

    Energy Technology Data Exchange (ETDEWEB)

    Ekdahl, Carl [Los Alamos National Laboratory

    2011-01-11

    The standard configuration of the DARHT Axis-I diode features a 5.08-cm diameter velvet emitter mounted in the flat surface of the cathode shroud. The surface of the velvet is slightly recessed {approx}2.5 mm. This configuration produces a 1.75 kA beam when a 3.8-MV pulse is applied to the anode-cathode (AK) gap. This note addresses some of the physics of this diode through the use of finite-element simulations.

  14. Titanium Dioxide as a Cathode Material in a Dry Cell

    OpenAIRE

    Duncan ALOKO; Eyitayo Amos AFOLABI

    2007-01-01

    Titanium dioxide was proposed as an alternative cathode material in place of Manganesse (IV) oxide. TiO2 was found to be highly polarized when in an electric field and its surface area of adsorption of solution determined to be 1070.32 m2/g. The adsorption of alkaline anions (i.e. SO42- , NO3-, Cl- and Br-) were investigated. The anions were adsorbed between the layers of the cathode material thereby altering its surface texture for a better performance. Increase in concentration of the anion...

  15. Methods and apparatus for using gas and liquid phase cathodic depolarizers

    Science.gov (United States)

    Murphy, Oliver J. (Inventor); Hitchens, G. Duncan (Inventor)

    1998-01-01

    The invention provides methods for using gas and liquid phase cathodic depolarizers in an electrochemical cell having a cation exchange membrane in intimate contact with the anode and cathode. The electrochemical conversion of cathodic depolarizers at the cathode lowers the cell potential necessary to achieve a desired electrochemical conversion, such as ozone evolution, at the anode. When gaseous cathodic depolarizers, such as oxygen, are used, a gas diffusion cathode having the cation exchange membrane bonded thereto is preferred. When liquid phase cathodic depolarizers are used, the cathode may be a flow-by electrode, flow-through electrode, packed-bed electrode or a fluidized-bed electrode in intimate contact with the cation exchange membrane.

  16. Compact High Current Rare-Earth Emitter Hollow Cathode for Hall Effect Thrusters

    Science.gov (United States)

    Hofer, Richard R. (Inventor); Goebel, Dan M. (Inventor); Watkins, Ronnie M. (Inventor)

    2012-01-01

    An apparatus and method for achieving an efficient central cathode in a Hall effect thruster is disclosed. A hollow insert disposed inside the end of a hollow conductive cathode comprises a rare-earth element and energized to emit electrons from an inner surface. The cathode employs an end opening having an area at least as large as the internal cross sectional area of the rare earth insert to enhance throughput from the cathode end. In addition, the cathode employs a high aspect ratio geometry based on the cathode length to width which mitigates heat transfer from the end. A gas flow through the cathode and insert may be impinged by the emitted electrons to yield a plasma. One or more optional auxiliary gas feeds may also be employed between the cathode and keeper wall and external to the keeper near the outlet.

  17. Nano-Particle Scandate Cathode for Space Communications Phase 2 Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose an improved cathode based on our novel theory of the role of scandium oxide in enhancing emission in tungsten-impregnated cathodes. Recent results have...

  18. Power generation using an activated carbon and metal mesh cathode in a microbial fuel cell

    KAUST Repository

    Zhang, Fang

    2009-11-01

    An inexpensive activated carbon (AC) air cathode was developed as an alternative to a platinum-catalyzed electrode for oxygen reduction in a microbial fuel cell (MFC). AC was cold-pressed with a polytetrafluoroethylene (PTFE) binder to form the cathode around a Ni mesh current collector. This cathode construction avoided the need for carbon cloth or a metal catalyst, and produced a cathode with high activity for oxygen reduction at typical MFC current densities. Tests with the AC cathode produced a maximum power density of 1220 mW/m2 (normalized to cathode projected surface area; 36 W/m3 based on liquid volume) compared to 1060 mW/m2 obtained by Pt catalyzed carbon cloth cathode. The Coulombic efficiency ranged from 15% to 55%. These findings show that AC is a cost-effective material for achieving useful rates of oxygen reduction in air cathode MFCs. © 2009 Elsevier B.V. All rights reserved.

  19. Numerical analysis of the rotating arc root on the cathode surface

    International Nuclear Information System (INIS)

    Three-dimensional heat transfer equation was used to discuss the circular region of high temperature formed on the surface of the tubular tungsten cathode, the cathode surface temperature in the region becomes uniform gradually (except that at the point of the cathode arc root) when the cathode arc root of the secondary arc is rotating on surface of the tungsten cathode and the rotating frequency of the secondary arc root is increasing. And the necessary condition of the cathode surface temperature is provided to form the model of the multi-arc-root or diffusive arc root. At the same time, the cathode surface temperature at the point of the cathode arc root decreases and reaches a constant when the rotating frequency increases

  20. A study of the microstructural distribution of cathodic hydrogen in austenitic stainless steels by hydrogen microprint

    International Nuclear Information System (INIS)

    The cathodic hydrogen distribution in austenitic stainless steel (304L; 316L) microstructure is shwon, at electron microscope scale, using the hydrogen microprint technique. Cathodic hydrogen induced cracking is analysed

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

    International Nuclear Information System (INIS)

    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. (paper)

  2. Enhanced Oxygen and Hydroxide Transport in a Cathode Interface by Efficient Antibacterial Property of a Silver Nanoparticle-Modified, Activated Carbon Cathode in Microbial Fuel Cells.

    Science.gov (United States)

    Li, Da; Qu, Youpeng; Liu, Jia; Liu, Guohong; Zhang, Jie; Feng, Yujie

    2016-08-17

    A biofilm growing on an air cathode is responsible for the decreased performance of microbial fuel cells (MFCs). For the undesired biofilm to be minimized, silver nanoparticles were synthesized on activated carbon as the cathodic catalyst (Ag/AC) in MFCs. Ag/AC enhanced maximum power density by 14.6% compared to that of a bare activated carbon cathode (AC) due to the additional silver catalysis. After operating MFCs over five months, protein content on the Ag/AC cathode was only 38.3% of that on the AC cathode, which resulted in a higher oxygen concentration diffusing through the Ag/AC cathode. In addition, a lower pH increment (0.2 units) was obtained near the Ag/AC catalyst surface after biofouling compared to 0.8 units of the AC cathode, indicating that less biofilm on the Ag/AC cathode had a minor resistance on hydroxide transported from the catalyst layer interfaces to the bulk solution. Therefore, less decrements of the Ag/AC activity and MFC performance were obtained. This result indicated that accelerated transport of oxygen and hydroxide, benefitting from the antibacterial property of the cathode, could efficiently maintain higher cathode stability during long-term operation. PMID:27441786

  3. Research and Development of a New Field Enhanced Low Temperature Thermionic Cathode that Enables Fluorescent Dimming and Loan Shedding without Auxiliary Cathode Heating

    Energy Technology Data Exchange (ETDEWEB)

    Feng Jin

    2009-01-07

    This is the final report for project entitled 'Research and development of a new field enhanced low temperature thermionic cathode that enables fluorescent dimming and load shedding without auxiliary cathode heating', under Agreement Number: DE-FC26-04NT-42329. Under this project, a highly efficient CNT based thermionic cathode was demonstrated. This cathode is capable of emitting electron at a current density two order of magnitude stronger then a typical fluorescent cathode at same temperatures, or capable of emitting at same current density but at temperature about 300 C lower than that of a fluorescent cathode. Detailed fabrication techniques were developed including CVD growth of CNTs and sputter deposition of oxide thin films on CNTs. These are mature technologies that have been widely used in industry for large scale materials processing and device fabrications, thus, with further development work, the techniques developed in this project can be scaled-up in manufacturing environment. The prototype cathodes developed in this project were tested in lighting plasma discharge environment. In many cases, they not only lit and sustain the plasma, but also out perform the fluorescent cathodes in key parameters such like cathode fall voltages. More work will be needed to further evaluate more detailed and longer term performance of the prototype cathode in lighting plasma.

  4. Testing a GaAs cathode in SRF gun

    Energy Technology Data Exchange (ETDEWEB)

    Wang, E.; Kewisch, J.; Ben-Zvi, I.; Burrill, A.; Rao, T.; Wu, Q.; Holmes, D.

    2011-03-28

    RF electron guns with a strained superlattice GaAs cathode are expected to generate polarized electron beams of higher brightness and lower emittance than do DC guns, due to their higher field gradient at the cathode's surface and lower cathode temperature. We plan to install a bulk GaAs:Cs in a SRF gun to evaluate the performance of both the gun and the cathode in this environment. The status of this project is: In our 1.3 GHz 1/2 cell SRF gun, the vacuum can be maintained at nearly 10{sup -12} Torr because of cryo-pumping at 2K. With conventional activation of bulk GaAs, we obtained a QE of 10% at 532 nm, with lifetime of more than 3 days in the preparation chamber and have shown that it can survive in transport from the preparation chamber to the gun. The beam line has been assembled and we are exploring the best conditions for baking the cathode under vacuum. We report here the progress of our test of the GaAs cathode in the SRF gun. Future particle accelerators, such as eRHIC and the ILC require high-brightness, high-current polarized electrons. Strained superlattice GaAs:Cs has been shown to be an efficient cathode for producing polarized electrons. Activation of GaAs with Cs,O(F) lowers the electron affinity and makes it energetically possible for all the electrons, excited into the conduction band that drift or diffuse to the emission surface, to escape into the vacuum. Presently, all operating polarized electron sources, such as the CEBAF, are DC guns. In these devices, the excellent ultra-high vacuum extends the lifetime of the cathode. However, the low field gradient on the photocathode's emission surface of the DC guns limits the beam quality. The higher accelerating gradients, possible in the RF guns, generate a far better beam. Until recently, most RF guns operated at room temperature, limiting the vacuum to {approx}10{sup -9} Torr. This destroys the GaAs's NEA surface. The SRF guns combine the excellent vacuum conditions of DC guns and

  5. Theory, Investigation and Stability of Cathode Electrocatalytic Activity

    Energy Technology Data Exchange (ETDEWEB)

    Ding, Dong; Liu, Mingfei; Lai, Samson; Blinn, Kevin; Liu, Meilin

    2012-09-30

    The main objective of this project is to systematically characterize the surface composition, morphology, and electro-catalytic properties of catalysts coated on LSCF, aiming to establish the scientific basis for rational design of high-performance cathodes by combining a porous backbone (such as LSCF) with a thin catalyst coating. The understanding gained will help us to optimize the composition and morphology of the catalyst layer and microstructure of the LSCF backbone for better performance. More specifically, the technical objectives include: (1) to characterize the surface composition, morphology, and electro-catalytic properties of catalysts coated on LSCF; (2) to characterize the microscopic details and stability of the LSCF-catalyst (e.g., LSM) interfaces; (3) to establish the scientific basis for rational design of high-performance cathodes by combining a porous backbone (such as LSCF) with a thin catalyst coating; and (4) to demonstrate that the performance and stability of porous LSCF cathodes can be enhanced by the application of a thin-film coating of LSM through a solution infiltration process in small homemade button cells and in commercially available cells of larger dimension. We have successfully developed dense, conformal LSM films with desired structure, composition, morphology, and thickness on the LSCF surfaces by two different infiltration processes: a non-aqueous and a water-based sol-gel process. It is demonstrated that the activity and stability of LSCF cathodes can be improved by the introduction of a thin-film LSM coating through an infiltration process. Surface and interface of the LSM-coated LSCF cathode were systematically characterized using advanced microscopy and spectroscopy techniques. TEM observation suggests that a layer of La and Sr oxide was formed on LSCF surfaces after annealing. With LSM infiltration, in contrast, we no longer observe such La/Sr oxide layer on the LSM-coated LSCF samples after annealing under similar

  6. Nano-structured textiles as high-performance aqueous cathodes for microbial fuel cells

    KAUST Repository

    Xie, Xing

    2011-01-01

    A carbon nanotube (CNT)-textile-Pt cathode for aqueous-cathode microbial fuel cells (MFCs) was prepared by electrochemically depositing Pt nanoparticles on a CNT-textile. An MFC equipped with a CNT-textile-Pt cathode revealed a 2.14-fold maximum power density with only 19.3% Pt loading, compared to that with a commercial Pt coated carbon cloth cathode. © 2011 The Royal Society of Chemistry.

  7. Oxygen transport in the internal xenon plasma of a dispenser hollow cathode

    OpenAIRE

    Capece, Angela M.; Polk, James E.; Mikellides, Ioannis G.; Shepherd, Joseph E.

    2014-01-01

    Reactive gases such as oxygen and water vapor modify the surface morphology of BaO dispenser cathodes and degrade the electron emission properties. For vacuum cathodes operating at fixed temperature, the emission current drops rapidly when oxygen adsorbs on top of the low work function surface. Previous experiments have shown that plasma cathodes are more resistant to oxygen poisoning and can operate with O_2 partial pressures one to two orders of magnitude higher than vacuum cathodes before ...

  8. Some results of Auger spectroscopy and emission spectroscopy applied to impregnated cathodes

    International Nuclear Information System (INIS)

    A study of impregnated cathodes using combined Auger spectroscopy and emission microscopy shows that a realistic pressures regions of thick-film coverage emit more strongly than monolayer regions. The presence of sulphur and phosphorus on the surface of dispenser cathodes has been correlated with poor emission. These contaminants may be removed by heating cathodes in oxygen, a process which increases substantially the emission available from poor cathodes. (orig.)

  9. Explosive emission cathodes for high power microwave devices: gas evolution studies

    OpenAIRE

    Schlise, Charles A.

    2004-01-01

    Approved for public release, distribution is unlimited Present-day high power microwave devices suffer from a lack of reliable, reproducible cathodes for generating the requisite GW-level electron beam in a vacuum. Standard explosive emission cathode pulse durations have been limited to 10's or 100's of ns due to the expansion of cathode-generated plasma and the ensuing impedance collapse that debilitates microwave output. Traditional thermionic cathodes do not suffer from this drawback of...

  10. SOFC LSM:YSZ cathode degradation induced by moisture: An impedance spectroscopy study

    DEFF Research Database (Denmark)

    Nielsen, Jimmi; Mogensen, Mogens Bjerg

    2011-01-01

    The cause of the degradation effect of moisture during operation of LSM cathode based SOFCs has been investigated by means of a detailed impedance characterization on LSM:YSZ composite cathode based SOFCs. Further the role of YSZ as cathode composite material was studied by measurements on SOFCs ...... thus eventually a decomposition of LSM....

  11. Pulse-Width Increase of Reflex Triode Vircator Using the Carbon Fibre Cathode

    Institute of Scientific and Technical Information of China (English)

    LIU Lie; LI Li-Min; ZHANG Xiao-Ping; WEN Jian-Chun; WAN Hong

    2006-01-01

    @@ We present the investigation on the reflex triode virtual cathode oscillator in which performances of carbonfibre and stainless-steel cathodes are compared with each other. The experimental results and analyses show that surface tracking induces the electron emission of the carbon fibre cathode.

  12. Relative work function, surface composition and topography of ``pedigreed'' impregnated tungsten dispenser cathodes

    Science.gov (United States)

    Tomich, D. H.; Mescher, J. A.; Wittberg, T. N.; Grant, J. T.

    1985-12-01

    A study has been made of the variation in work function, surface composition, and topography of 5:3:2 impregnated tungsten dispenser cathodes made under carefully controlled conditions (pedigreed cathodes). Despite these conditions several cathodes had unexpected deposits on their emitting surfaces, and one showed a variation in work function and composition across the surface during activation.

  13. Chromium poisoning of LSM/YSZ and LSCF/CGO composite cathodes

    DEFF Research Database (Denmark)

    Bentzen, Janet Jonna; Høgh, Jens Valdemar Thorvald; Barfod, Rasmus;

    2009-01-01

    from 300 to 2,970 h. Both LSM/YSZ and LSCF/CGO cathodes were sensitive to chromium poisoning; LSCF/CGO cathodes to a lesser extent than LSM/YSZ. Humid air aggravated the degradation of the cathode performance. Post-mortem electron microscopic investigations revealed several Cr-containing compounds...

  14. Extracellular electron transfer from cathode to microbes: application for biofuel production

    OpenAIRE

    Choi, Okkyoung; Sang, Byoung-In

    2016-01-01

    Extracellular electron transfer in microorganisms has been applied for bioelectrochemical synthesis utilizing microbes to catalyze anodic and/or cathodic biochemical reactions. Anodic reactions (electron transfer from microbe to anode) are used for current production and cathodic reactions (electron transfer from cathode to microbe) have recently been applied for current consumption for valuable biochemical production. The extensively studied exoelectrogenic bacteria Shewanella and Geobacter ...

  15. Fabrication and testing of a large area cathode pad chamber

    International Nuclear Information System (INIS)

    Saha Institute of Nuclear Physics (SINP) is participating in the Forward Muon Spectrometer collaboration of ALICE at CERN and is responsible in the design and fabrication of the second tracking station. The tracking detectors will be cathode pad chambers (CPC). Two small CPC prototypes have already been fabricated and tested at CERN

  16. Anodic or cathodic motor cortex stimulation for pain?

    NARCIS (Netherlands)

    Holsheimer, J.; Manola, L.

    2006-01-01

    Objective. In motor cortex stimulation (MCS) for central and trigeminal pain Resume leads are placed epidurally over the motor and sensory cortex. Several bipolar combinations are used to identify the cortical target corresponding to the painful body segment. The cathode giving the largest motor r

  17. Influence of substrate topography on cathodic delamination of anticorrosive coatings

    DEFF Research Database (Denmark)

    Sørensen, Per Aggerholm; Kiil, Søren; Dam-Johansen, Kim; Weinall, C.E.

    The cathodic delamination of a commercial magnesium silicate and titanium dioxide pigmented epoxy coating on abrasive cleaned cold rolled steel has been investigated. The rate of delamination was found to depend on interfacial transport from the artificial defect to the delamination front and...

  18. Bacterial corrosion in marine sediments: influence of cathodic protection

    International Nuclear Information System (INIS)

    In order to protect offshore structures from marine corrosion, cathodic protection is widely applied via sacrificial anodes (for example zinc or aluminium) or impressed current. In aerated seawater, steel is considered to be protected when a potential of -8050 mV/Cu.CuSO4 is achieved. In many cases, however this potential must be lowered, due to the activity of microorganisms and more specially sulfate-reducing bacteria (SRB). SRB are obligate anaerobes using sulphate as electron acceptor with resultant production of sulphide. Some of them are also able to use hydrogen as energy source, causing cathodic depolarization of steel surfaces. An experiment was performed to analyze the relation between SRB activity and use of different cathodic potentials applied to mild steel samples in marine sediments. Analytical techniques employed included lipid bio-markers and electrochemical methods. Results indicated an evolution of the bacterial community structure both on the steel and in the sediment, as a function of time and potential. The results also show that cathodically produced hydrogen promotes the growth of SRB (author)

  19. The hollow cathode in the quasi-steady MPD discharge

    Science.gov (United States)

    Von Jaskowsky, W. F.; Jahn, R. G.; Clark, K. E.; Krishnan, M.

    1973-01-01

    A large hollow cathode has been operated in a quasi-steady MPD discharge over a range of current from 7 to 30 kA and argon mass flow from 0.04 to 6.0 g/sec. The 1.3-cm-i.d. cathode cavity attains steady emission characteristics in some tens of microseconds without the assistance of auxiliary heating, low work function inserts, or external keeper electrodes. Measured current and potential distributions within the cavity reveal that the current attaches in a zone 1 to 2 cm long with a surface current density greater than 1000 A/sq cm and a local axial electric field less than 10 V/cm. Electron densities within the cavity, estimated from spectroscopic records, are above 10 to the 17th power per cu cm, at least one order of magnitude greater than has been reported for either ion engine hollow cathodes or conventional solid cathodes in similar arc discharges.

  20. Temperature Controlled Cathode Heating in Electron Beam Welding Machine

    Czech Academy of Sciences Publication Activity Database

    Horáček, Miroslav; Dupák, Jan

    2001-01-01

    Roč. 62, 2-3 (2001), s. 165-169. ISSN 0042-207X R&D Projects: GA AV ČR IBS2065015 Institutional research plan: CEZ:AV0Z2065902 Keywords : Electron beam welding machine * cathode heating * temperature control Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 0.541, year: 2001

  1. Cathodic protection in highly-aggressive geothermal environments

    Energy Technology Data Exchange (ETDEWEB)

    Bandy, R.; van Rooyen, D.

    1982-01-01

    The feasibility of cathodic protection in highly aggressive geothermal environments has been investigated in the laboratory using both impressed current and sacrificial anode techniques. Artificial brines simulating the hypersaline geothermal brines of the Imperial Valley of California and the less aggressive geothermal fluids found in some other parts of the US were used as test environments. Impressed current tests on carbon steel were conducted under controlled potential, and cathodic protection of carbon steel using zinc sacrificial anodes was studied by monitoring the galvanic current and potential of the couple with a zero resistance ammeter. Weight loss measurements were conducted in all cases to determine the amount of protection achieved. Results show that the weight loss generally follows a semi-logarithmic relationship with the amount of potential shift away from the corrosion potential as a result of the impressed current; significant cathodic protection can be achieved by shifting the potential of the order of only 70 to 80 mV. Under certain controlled cathodic conditions, electrocrystallization has been observed on the carbon steel surface, resulting in a small weight gain. For the carbon steel-zinc couple, the potential gradually drifts towards that of the open circuit potential of zinc, resulting in excellent protection for the steel and a relatively tolerable corrosion rate for zinc.

  2. The Cathode Strip Chamber Data Acquisition System for CMS

    CERN Document Server

    Bylsma, B G; Gilmore, J R; Gu, J H; Ling, T Y

    2007-01-01

    The Cathode Strip Chamber (CSC) [1] Data Acquisition (DAQ) system for the CMS [2] experiment at the LHC [3] will be described. The CSC system is large, consisting of 218K cathode channels and 183K anode channels. This leads to a substantial data rate of ~1.5GByte/s at LHC design luminosity (1034cm-2s-1) and the CMS first level trigger (L1A) rate of 100KHz. The DAQ system consists of three parts. The first part is on-chamber Cathode Front End Boards (CFEB)[4], which amplify, shape, store, and digitise chamber cathode signals, and Anode Front End Boards (AFEB)[5], which amplify, shape and discriminate chamber anode signals. The second part is the Peripheral Crate Data Acquisition Motherboards (DAQMB), which control the onchamber electronics and the readout of the chamber. The third part is the off-detector DAQ interface boards, which perform real time error checking, electronics reset requests and data concentration. It passes the resulting data to a CSC local DAQ farm, as well as CMS main DAQ [6]. All electron...

  3. Enhancement of Platinum Cathode Catalysis by Addition of Transition Metals

    Science.gov (United States)

    Duong, Hung Tuan

    2009-01-01

    The sluggish kinetics of oxygen reduction reaction (ORR) contributes significantly to the loss of cathode overpotential in fuel cells, thus requiring high loadings of platinum (Pt), which is an expensive metal with limited supply. However, Pt and Pt-based alloys are still the best available electrocatalysts for ORR thus far. The research presented…

  4. Research of characteristics of photo- and thermoemission cathodes

    International Nuclear Information System (INIS)

    A description of the stand for research of photo-and thermoemission cathodes for an electronic gun of the Linac-800 accelerator is given. The structure of the equipment and the basic characteristics of the stand are shown. The stand allows one to make tuning of control electronics, calibration of operating and measuring channels, debugging of the software. Introduction of the stand of mass spectrometers with the leaking subsystem into the structure of the equipment enables one to analyze gas structure of vacuum volume and to change its structure depending on a task in view. Application, at the stand of the laser with wavelengths of 1064, 532, 355 and 266 nm allows one to investigate a wide spectrum of materials for the photocathode. A description of a model of cathode assembly, results of simulation and their coordination with experimental data is given. Issue characteristics of the impregnated cathode (tungsten with 20% of oxides of barium, calcium and aluminium) are presented. Data on research of this cathode as the photocathode (with heating and without it) at a lasing wavelength of 532 nm are given

  5. Researching the characteristics of photo- and thermoemission cathodes

    Science.gov (United States)

    Balalykin, N. I.; Minashkin, V. Ph.; Nozdrin, M. A.; Shirkov, G. D.; Shabratov, V. G.

    2008-12-01

    The description of the stand for research photo-and thermoemission cathodes for an accelerator Linak-800 electronic gun is given. The structure of the equipment and the basic characteristics of the stand are described. The stand allows us to tune the control electronics, calibrate the operating and measuring channels, and debug the software. Introducing the structure of the equipment of the mass spectrometer stand with a leaking sub-system enables us to analyze the gas structure of vacuum volume and to change its structure, depending on the task at hand. Using the stand with a laser with 1064 nm, 532 nm, 355 nm, and 266 nm wavelengths allows us to investigate a wide spectrum of materials for photocathode. The cathode assembly model and the simulation results and their coordination with experimental data are described. Issue characteristics of the impregnated cathode (tungsten with 20% barium, calcium and aluminium oxides) are presented. Data on the research of this cathode as a photocathode (with heating and without it) with a 532 nm wavelength laser are given.

  6. Cathodic Arcs From Fractal Spots to Energetic Condensation

    CERN Document Server

    Anders, Andre

    2009-01-01

    Emphasizes the fractal character of cathode spots, and describes strongly fluctuating plasma properties such as the presence of multiply charged ions that move with supersonic velocity. This book also deals with issues, such as arc source construction, and macroparticle removal. It is intended for scientists, practitioners, and students alike

  7. Interaction between Cathodic Protection and Microbially Influenced Corrosion.

    OpenAIRE

    Bujang Masli, Azlan Bin

    2011-01-01

    The present work studied the interaction between cathodic protection and microbiallyinfluenced corrosion (MIC) on the surface of mild steel. Potential trending wasobserved when the currents were held constant, and current trending was observedwhen potentials were held constant. Scanning electron microscopy and energydispersive x-ray spectroscopy were used to study surface deposits on the samples andfurther understand the result of the interaction. Sul...

  8. The fractal nature of vacuum arc cathode spots

    Energy Technology Data Exchange (ETDEWEB)

    Anders, Andre

    2005-05-27

    Cathode spot phenomena show many features of fractals, for example self-similar patterns in the emitted light and arc erosion traces. Although there have been hints on the fractal nature of cathode spots in the literature, the fractal approach to spot interpretation is underutilized. In this work, a brief review of spot properties is given, touching the differences between spot type 1 (on cathodes surfaces with dielectric layers) and spot type 2 (on metallic, clean surfaces) as well as the known spot fragment or cell structure. The basic properties of self-similarity, power laws, random colored noise, and fractals are introduced. Several points of evidence for the fractal nature of spots are provided. Specifically power laws are identified as signature of fractal properties, such as spectral power of noisy arc parameters (ion current, arc voltage, etc) obtained by fast Fourier transform. It is shown that fractal properties can be observed down to the cutoff by measurement resolution or occurrence of elementary steps in physical processes. Random walk models of cathode spot motion are well established: they go asymptotically to Brownian motion for infinitesimal step width. The power spectrum of the arc voltage noise falls as 1/f {sup 2}, where f is frequency, supporting a fractal spot model associated with Brownian motion.

  9. Diagnostics of cathode material loss in cutting plasma torch

    Czech Academy of Sciences Publication Activity Database

    Gruber, Jan; Šonský, Jiří; Hlína, Jan

    2014-01-01

    Roč. 47, č. 29 (2014). ISSN 0022-3727 Institutional support: RVO:61388998 Keywords : plasma torch * plasma cutting * cathode wear Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.721, year: 2014 http://iopscience.iop.org/0022-3727/47/29/295201/

  10. Investigation of a Mercury-Argon Hot Cathode Discharge

    Science.gov (United States)

    Wamsley, Robert Charles

    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.

  11. Engineering analyses of large precision cathode strip chambers for GEM

    Energy Technology Data Exchange (ETDEWEB)

    Horvath, J.A.; Belser, F.C.; Pratuch, S.M.; Wuest, C.R. [Lawrence Livermore National Lab., CA (United States); Mitselmakher, G. [Superconducting Super Collider Lab., Dallas, TX (United States); Gordeev, A. [Institute of Theoretical and Experimental Physics, Moscow (Russian Federation); Johnson, C.V. [Lawrence Livermore National Lab., CA (United States)]|[Superconducting Super Collider Lab., Dallas, TX (United States); Polychronakos, V.A. [Brookhaven National Lab., Upton, NY (United States); Golutvin, I.A. [Joint Institute for Nuclear Research, Dubna (Russian Federation)

    1993-10-21

    Structural analyses of large precision cathode strip chambers performed up to the date of this publication are documented. Mechanical property data for typical chamber materials are included. This information, originally intended to be an appendix to the {open_quotes}CSC Structural Design Bible,{close_quotes} is presented as a guide for future designers of large chambers.

  12. Operational test report - Project W-320 cathodic protection systems

    International Nuclear Information System (INIS)

    Washington Administrative Code (WAC) 173-303-640 specifies that corrosion protection must be designed into tank systems that treat or store dangerous wastes. Project W-320, Waste Retrieval Sluicing System (WRSS), utilizes underground encased waste transfer piping between tanks 241-C-106 and 241-AY-102. Corrosion protection is afforded to the encasements of the WRSS waste transfer piping through the application of earthen ionic currents onto the surface of the piping encasements. Cathodic protection is used in conjunction with the protective coatings that are applied upon the WRSS encasement piping. WRSS installed two new two rectifier systems (46 and 47) and modified one rectifier system (31). WAC 173-303-640 specifies that the proper operation of cathodic protection systems must be confirmed within six months after initial installation. The WRSS cathodic protection systems were energized to begin continuous operation on 5/5/98. Sixteen days after the initial steady-state start-up of the WRSS rectifier systems, the operational testing was accomplished with procedure OTP-320-006 Rev/Mod A-0. This operational test report documents the OTP-320-006 results and documents the results of configuration testing of integrated piping and rectifier systems associated with the W-320 cathodic protection systems

  13. Low temperature and cold emission of scandate cathodes1

    Science.gov (United States)

    Gaertner, G.; Geittner, P.; Raasch, D.

    2002-11-01

    The unprecedented emission capability of top-layer scandate cathodes prepared by laser ablation deposition (LAD) was already reported [1,2] yielding 460 A cm -2 at 1030 °C true temperature, which is a factor of about 20 higher than for the best impregnated (I) cathodes. Therefore their emission behaviour has been investigated down to room temperature, yielding 0.5 A cm -2 at 500 °C and 0.001 A cm -2 at 300 °C. The measurements underline, that the work function (WF) remains about constant over a wide temperature range. The effective work function with the theoretical thermionic constant of 120.4 A (cm K) -2 amounted to 1.42 eV, a Richardson plot determination resulted in a Richardson WF of 1.16 eV and a Richardson constant of 8.5 A (cmK) -2. Field emission was observed at room temperature and at about 300 °C for LAD-top-layer scandate cathodes ('Sc'/Re-I) and was compared with other Ba dispenser cathodes. The threshold field strengths were 3.2 V μm -1 for 'Sc'/Re-I, 12.4 V μm -1 for Re-I and 15.7 V μm -1 for W-'I. The emission stability at low operating temperatures is dependent on residual gas pressure and composition.

  14. Experimental Optimization of a reflex triode virtual cathode oscillator

    International Nuclear Information System (INIS)

    Experimental findings on a high power Reflex Triode Virtual Cathode Oscillator (Vircator) are reported. The performance of a vircator are modified with the inclusion of reflecting strips. Motivation for this technique was driven by success of reflector inclusion to a coaxial vircator. A parametric experimental study was performed to optimize the performance of this geometry

  15. Interactions of alkali metals and electrolyte with cathode carbons

    Energy Technology Data Exchange (ETDEWEB)

    Naas, Tyke

    1997-12-31

    The Hall-Heroult process for electrolytic reduction of alumina has been the only commercial process for production of primary aluminium. The process runs at high temperature and it is important to minimize the energy consumption. To save energy it is desirable to reduce the operating temperature. This can be achieved by adding suitable additives such as LiF or KF to the cryolitic electrolyte. This may conflict with the objective of extending the lifetime of the cathode linings of the cell as much as possible. The thesis investigates this possibility and the nature of the interactions involved. It supports the hypothesis that LiF-additions to the Hall-Heroult cell electrolyte is beneficial to the carbon cathode performance because the diminished sodium activity reduces the sodium induced stresses during the initial period of electrolysis. The use of KF as an additive is more dangerous, but the results indicate that additions up to 5% KF may be tolerated in acidic melts with semigraphitic or graphitic cathodes with little risk of cathode problems. 153 refs., 94 figs., 30 tabs.

  16. Composite Cathodes for Dual-Rate Li-Ion Batteries

    Science.gov (United States)

    Whitacre, Jay; West, William; Bugga, Ratnakumar

    2008-01-01

    Composite-material cathodes that enable Li-ion electrochemical cells and batteries to function at both high energy densities and high discharge rates are undergoing development. Until now, using commercially available cathode materials, it has been possible to construct cells that have either capability for high-rate discharge or capability to store energy at average or high density, but not both capabilities. However, both capabilities are needed in robotic, standby-power, and other applications that involve duty cycles that include long-duration, low-power portions and short-duration, high-power portions. The electrochemically active ingredients of the present developmental composite cathode materials are: carbon-coated LiFePO4, which has a specific charge capacity of about 160 mA h/g and has been used as a high-discharge-rate cathode material and Li[Li(0.17)Mn(0.58)Ni(0.25)]O2, which has a specific charge capacity of about 240 mA h/g and has been used as a high-energy-density cathode material. In preparation for fabricating the composite material cathode described, these electrochemically active ingredients are incorporated into two sub-composites: a mixture comprising 10 weight percent of poly(vinylidine fluoride); 10 weight percent of carbon and 80 weight percent of carbon coated LiFePO4; and, a mixture comprising 10 weight percent of PVDF, and 80 weight percent of Li[Li(0.17)Mn(0.58)Ni(0.25)]O2. In the fabrication process, these mixtures are spray-deposited onto an aluminum current collector. Electrochemical tests performed thus far have shown that better charge/discharge performance is obtained when either 1) each mixture is sprayed on a separate area of the current collector or (2) the mixtures are deposited sequentially (in contradistinction to simultaneously) on the same current-collector area so that the resulting composite cathode material consists of two different sub-composite layers.

  17. Functionally Graded Cathodes for Solid Oxide Fuel Cells

    Energy Technology Data Exchange (ETDEWEB)

    Harry Abernathy; Meilin Liu

    2006-12-31

    One primary suspected cause of long-term performance degradation of solid oxide fuels (SOFCs) is the accumulation of chromium (Cr) species at or near the cathode/electrolyte interface due to reactive Cr molecules originating from Cr-containing components (such as the interconnect) in fuel cell stacks. To date, considerable efforts have been devoted to the characterization of cathodes exposed to Cr sources; however, little progress has been made because a detailed understanding of the chemistry and electrochemistry relevant to the Cr-poisoning processes is still lacking. This project applied multiple characterization methods - including various Raman spectroscopic techniques and various electrochemical performance measurement techniques - to elucidate and quantify the effect of Cr-related electrochemical degradation at the cathode/electrolyte interface. Using Raman microspectroscopy the identity and location of Cr contaminants (SrCrO{sub 4}, (Mn/Cr){sub 3}O{sub 4} spinel) have been observed in situ on an LSM cathode. These Cr contaminants were shown to form chemically (in the absence of current flowing through the cell) at temperatures as low as 625 C. While SrCrO{sub 4} and (Mn/Cr){sub 3}O{sub 4} spinel must preferentially form on LSM, since the LSM supplies the Sr and Mn cations necessary for these compounds, LSM was also shown to be an active site for the deposition of Ag{sub 2}CrO{sub 4} for samples that also contained silver. In contrast, Pt and YSZ do not appear to be active for formation of Cr-containing phases. The work presented here supports the theory that Cr contamination is predominantly chemically-driven and that in order to minimize the effect, cathode materials should be chosen that are free of cations/elements that could preferentially react with chromium, including silver, strontium, and manganese.

  18. Methanol-Tolerant Cathode Catalyst Composite For Direct Methanol Fuel Cells

    Science.gov (United States)

    Zhu, Yimin; Zelenay, Piotr

    2006-03-21

    A direct methanol fuel cell (DMFC) having a methanol fuel supply, oxidant supply, and its membrane electrode assembly (MEA) formed of an anode electrode and a cathode electrode with a membrane therebetween, a methanol oxidation catalyst adjacent the anode electrode and the membrane, an oxidant reduction catalyst adjacent the cathode electrode and the membrane, comprises an oxidant reduction catalyst layer of a platinum-chromium alloy so that oxidation at the cathode of methanol that crosses from the anode through the membrane to the cathode is reduced with a concomitant increase of net electrical potential at the cathode electrode.

  19. Field emission of electrons from cathodes made of carbon fibers with a nanostructured emitting surface

    Science.gov (United States)

    Lupekhin, S. M.; Ibragimov, A. A.

    2011-06-01

    Field electron emission from cathodes made of a bunch of carbon fibers under the condition of technical vacuum is studied experimentally. A model to optimize the field emission properties of the cathode by optimizing its macrogeometry with regard to the emitting surface structure is suggested. The current-voltage characteristics of the cathode are taken in the working voltage range 1-3 kV and for anode-cathode spacings varying from 1 to 10 mm. The current density from the cathode may reach 10 A/cm2 or more.

  20. Effect of thermionic cathode heating current self-magnetic field on gaseous plasma generator characteristics.

    Science.gov (United States)

    Lopatin, I V; Akhmadeev, Yu H; Koval, N N

    2015-10-01

    The performance capabilities of the PINK, a plasma generator with a thermionic cathode mounted in the cavity of a hollow cathode, depending for its operation on a non-self-sustained low-pressure gas discharge have been investigated. It has been shown that when a single-filament tungsten cathode 2 mm in diameter is used and the peak filament current is equal to or higher than 100 A, the self-magnetic field of the filament current significantly affects the discharge current and voltage waveforms. This effect is due to changes in the time and space distributions of the emission current density from the hot cathode. When the electron mean free path is close to the characteristic dimensions of the thermionic cathode, the synthesized plasma density distribution is nonuniform and the cathode is etched nonuniformly. The cathode lifetime in this case is 8-12 h. Using a cathode consisting of several parallel-connected tungsten filaments ∼0.8 mm in diameter moderates the effect of the self-magnetic field of the filament current and nearly doubles the cathode lifetime. The use of this type of cathode together with a discharge igniting electrode reduces the minimum operating pressure in the plasma generator to about one third of that required for the generator operation with a single-filament cathode (to 0.04 Pa). PMID:26520947

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

    Energy Technology Data Exchange (ETDEWEB)

    Benilov, M. S.; Cunha, M. D. [Departamento de Fisica, CCCEE, Universidade da Madeira, Largo do Municipio, 9000 Funchal (Portugal)

    2013-02-14

    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.

  2. Effect of thermionic cathode heating current self-magnetic field on gaseous plasma generator characteristics

    International Nuclear Information System (INIS)

    The performance capabilities of the PINK, a plasma generator with a thermionic cathode mounted in the cavity of a hollow cathode, depending for its operation on a non-self-sustained low-pressure gas discharge have been investigated. It has been shown that when a single-filament tungsten cathode 2 mm in diameter is used and the peak filament current is equal to or higher than 100 A, the self-magnetic field of the filament current significantly affects the discharge current and voltage waveforms. This effect is due to changes in the time and space distributions of the emission current density from the hot cathode. When the electron mean free path is close to the characteristic dimensions of the thermionic cathode, the synthesized plasma density distribution is nonuniform and the cathode is etched nonuniformly. The cathode lifetime in this case is 8–12 h. Using a cathode consisting of several parallel-connected tungsten filaments ∼0.8 mm in diameter moderates the effect of the self-magnetic field of the filament current and nearly doubles the cathode lifetime. The use of this type of cathode together with a discharge igniting electrode reduces the minimum operating pressure in the plasma generator to about one third of that required for the generator operation with a single-filament cathode (to 0.04 Pa)

  3. Development of alloy-film coated dispenser cathode for terahertz vacuum electron devices application

    International Nuclear Information System (INIS)

    High power terahertz vacuum electron devices demand high current density and uniform emission dispenser cathode. It was found that the coating of noble metals e.g., Os, Ir, and Re on the surface of tungsten dispenser cathodes enhances the emission capabilities and uniformity. Hence metal coated cathode might be the best candidate for terahertz devices applications. In this study, ternary-alloy-film cathode (2Os:2Re:1 W) and Os coated cathode have been developed and the results are presented. The cathodes made out of this alloy coating showed 1.5 times higher emission and 0.02 eV emission uniformity as compared to those of simply Os coated cathodes which can be used in terahertz devices application.

  4. Mercury vapor hollow cathode component studies. [emissive materials for ion thruster requirements

    Science.gov (United States)

    Zuccaro, D. E.

    1973-01-01

    An experimental study of starting and operating characteristics of conventional hollow cathodes and of hollow cathodes without alkaline earth emissive materials demonstrated that the emissive mix is essential to obtain the desired cathode operation. Loss of the emissive mix by evaporation and chemical reaction was measured. New insert designs consisting of emissive mix supported on nickel and of barium impregnated porous tungsten were studied. Cathodes with a modified orifice geometry operated in a low voltage, 'spot' mode over a broad range of discharge current. Thermal degradation tests on cathode heaters showed the flame sprayed SERT II type to be the most durable at high temperatures. Thermal shock was observed to be a significant factor in limiting cathode heater life. A cathode having a barium impregnated porous tungsten tip and a heater which is potted in sintered alumina was found to have favorable operating characteristics.

  5. Modular cathode assemblies and methods of using the same for electrochemical reduction

    Energy Technology Data Exchange (ETDEWEB)

    Wiedmeyer, Stanley G; Barnes, Laurel A; Williamson, Mark A; Willit, James L

    2014-12-02

    Modular cathode assemblies are useable in electrolytic reduction systems and include a basket through which fluid electrolyte may pass and exchange charge with a material to be reduced in the basket. The basket can be divided into upper and lower sections to provide entry for the material. Example embodiment cathode assemblies may have any shape to permit modular placement at any position in reduction systems. Modular cathode assemblies include a cathode plate in the basket, to which unique and opposite electrical power may be supplied. Example embodiment modular cathode assemblies may have standardized electrical connectors. Modular cathode assemblies may be supported by a top plate of an electrolytic reduction system. Electrolytic oxide reduction systems are operated by positioning modular cathode and anode assemblies at desired positions, placing a material in the basket, and charging the modular assemblies to reduce the metal oxide.

  6. Development of alloy-film coated dispenser cathode for terahertz vacuum electron devices application

    Science.gov (United States)

    Barik, R. K.; Bera, A.; Raju, R. S.; Tanwar, A. K.; Baek, I. K.; Min, S. H.; Kwon, O. J.; Sattorov, M. A.; Lee, K. W.; Park, G.-S.

    2013-07-01

    High power terahertz vacuum electron devices demand high current density and uniform emission dispenser cathode. It was found that the coating of noble metals e.g., Os, Ir, and Re on the surface of tungsten dispenser cathodes enhances the emission capabilities and uniformity. Hence metal coated cathode might be the best candidate for terahertz devices applications. In this study, ternary-alloy-film cathode (2Os:2Re:1 W) and Os coated cathode have been developed and the results are presented. The cathodes made out of this alloy coating showed 1.5 times higher emission and 0.02 eV emission uniformity as compared to those of simply Os coated cathodes which can be used in terahertz devices application.

  7. Emission and surface characteristic of ternary alloy Ir/Re/W-coated impregnated tungsten cathodes

    Science.gov (United States)

    Zhang, Honglai; Liu, Yanwen; Zhang, Mingchen; Li, Yutao

    2005-09-01

    In order to improve the activation characteristics and emission ability of the conventional Ir-coated impregnated tungsten cathodes, a new type of dispenser cathode with ternary alloy Ir/Re/W coating was developed. The improved cathodes show higher emission current density and faster activation characteristics than that of the conventional pure Ir-coated impregnated tungsten cathodes. X-ray photoelectron spectroscopy (XPS) was used to analyze the element compositions on the surface of the cathodes coated with pure Ir and Ir/Re/W alloy. The results show that for pure Ir coating cathode, binary alloy (Ir/W) is formed. The surface atom concentration is near 50/50 after full activation. For ternary alloy coating cathode, the surface atom concentration has changed from 35%Ir-25%Re-40%W to 33%Ir-19%Re-48%W before and after activation.

  8. Life-limiting mechanisms in Ba-oxide, Ba-dispenser and Ba-Scandate cathodes

    Science.gov (United States)

    Gaertner, G.; Barratt, D.

    2005-09-01

    Ba-oxide, Ba-dispenser and Ba-Scandate cathodes have been continuously improved in their emission performance in the past decades. Ba-oxide and Ba-dispenser cathodes are also the dominant types of thermionic cathodes used in most vacuum tube applications. When improvements in emissive properties are introduced, their impact on cathode life - where several years in a vacuum tube environment are typically required - also needs to be known. Hence, the investigation of cathode life-limiting effects is the basis of accelerated life predictions and of further cathode improvement. In this contribution, the main effects limiting the operating life of Ba/BaO-based thermionic cathodes are discussed, especially related to intrinsic dispensation and resupply to the emissive surface. Emission poisoning induced by adsorption of poisonous gases will not be addressed here. We will stress common points and point out the differences between the three types.

  9. Emission and surface characteristic of ternary alloy Ir/Re/W-coated impregnated tungsten cathodes

    International Nuclear Information System (INIS)

    In order to improve the activation characteristics and emission ability of the conventional Ir-coated impregnated tungsten cathodes, a new type of dispenser cathode with ternary alloy Ir/Re/W coating was developed. The improved cathodes show higher emission current density and faster activation characteristics than that of the conventional pure Ir-coated impregnated tungsten cathodes. X-ray photoelectron spectroscopy (XPS) was used to analyze the element compositions on the surface of the cathodes coated with pure Ir and Ir/Re/W alloy. The results show that for pure Ir coating cathode, binary alloy (Ir/W) is formed. The surface atom concentration is near 50/50 after full activation. For ternary alloy coating cathode, the surface atom concentration has changed from 35%Ir-25%Re-40%W to 33%Ir-19%Re-48%W before and after activation

  10. Pulse-Width Increase of Reflex Triode Vircator Using the Carbon Fibre Cathode

    Science.gov (United States)

    Liu, Lie; Li, Li-Min; Zhang, Xiao-Ping; Wen, Jian-Chun; Wan, Hong

    2006-04-01

    We present the investigation on the reflex triode virtual cathode oscillator in which performances of carbon-fibre and stainless-steel cathodes are compared with each other. The experimental results and analyses show that surface tracking induces the electron emission of the carbon fibre cathode. There are electron emission phenomena observed not only from the top of the carbon fibre but also from its side surface. Compared with the case of the stainless steel cathode, the plasma expansion velocity for the carbon fibre cathode is slower, and using the carbon fibre cathode can widen the pulse width of output microwave. The output microwave pulse width reaches an increase of about 20%. This mechanism is different from the conventional explosive emission of metal cathodes.

  11. Pulse-width increase of reflex triode vircator using the carbon fibre cathode

    International Nuclear Information System (INIS)

    The authors present the investigation on the reflex triode virtual cathode oscillator in which performances of carbon fibre and stainless-steel cathodes are compared with each other. The experimental results and analyses show that surface tracking induces the electron emission of the carbon fibre cathode. There are electron emission phenomena observed not only from the top of the carbon fibre but also from its side surface. Compared with the case of the stainless steel cathode, the plasma expansion velocity for the carbon fibre cathode is slower, and using the carbon fibre cathode can widen the pulse width of output microwave. The output microwave pulse width reaches an increase of about 20%. This mechanism is different from the conventional explosive emission of metal cathodes. (authors)

  12. Development of spark cathode electron guns for the CO2 laser fusion program. Final report, July 1978-December 1979

    International Nuclear Information System (INIS)

    Spark cathodes are designed and constructed to replace the bladed cold cathode structure in the electron guns of the Los Alamos Scientific Laboratory, Antares, prototype power amplifier and driver amplifier. Design work is described and data from cathode testing is reported. The spark cathode offers precise control of emission site location, design flexibility, and high reliability

  13. Using Multispectral Imaging to Measure Temperature Profiles and Emissivity of Large Thermionic Dispenser, Cathodes

    International Nuclear Information System (INIS)

    Thermionic dispenser cathodes are widely used in modern high-power microwave tubes. Use of these cathodes has led to significant improvement in performance. In recent years these cathodes have been used in electron linear accelerators (LINACs), particularly in induction LINACs, such as the Experimental Test Accelerator at Lawrence Livermore National Laboratory and the Relativistic Test Accelerator at Lawrence Berkeley National Laboratory. For induction LINACs, the thermionic dispenser cathode provides greater reproducibility, longer pulse lengths, and lower emittance beams than does a field emission cathode. Los Alamos National Laboratory is fabricating a dual-axis X-ray radiography machine called dual-axis radiograph hydrodynamic test (DARHT). The second axis of DARHT consists of a 2-kA, 20-MeV induction LINAC that uses a 3.2-MeV electron gun with a tungsten thermionic-dispenser cathode. Typically the DARHT cathode current density is 10 A/cm2 at 1050 C. Under these conditions current density is space-charge limited, which is desirable since current density is independent of temperature. At lower temperature (the temperature-limited regime) there are variations in the local current density due to a nonuniform temperature profile. To obtain the desired uniform current density associated with space-charge limited operation, the coolest area on the cathode must be at a sufficiently high temperature so that the emission is space-charge limited. Consequently, the rest of the cathode is emitting at the same space-charge-limited current density but is at a higher temperature than necessary. Because cathode lifetime is such a strong function of cathode temperature, there is a severe penalty for nonuniformity in the cathode temperature. For example, a temperature increase of 50 C means cathode lifetime will decrease by a factor of at least four. Therefore, we are motivated to measure the temperature profiles of our large-area cathodes

  14. Sputter deposition of BSCCO films from a hollow cathode

    International Nuclear Information System (INIS)

    High-Tc superconducting thin films were deposited onto MgO single crystal substrates from a hollow cathode onto ceramic targets with the nominal composition of Bi2Sr2CaCu2Ox. Films similar in composition to those used for the targets were deposited on MgO substrates by rf sputtering. The effects of sputtering time, rf power, and post-annealing on film microstructure and properties were studied in detail. Substrate temperature was found to have a significant influence on the film characteristics. Initial results show that deposition rates from a hollow cathode are an order of magnitude higher than those of a planar magnetron source at equivalent power levels. Large deposition rates allow for the coating of long lengths of wire

  15. Higher harmonics generation in relativistic electron beam with virtual cathode

    International Nuclear Information System (INIS)

    The study of the microwave generation regimes with intense higher harmonics taking place in a high-power vircator consisting of a relativistic electron beam with a virtual cathode has been made. The characteristics of these regimes, in particular, the typical spectra and their variations with the change of the system parameters (beam current, the induction of external magnetic field) as well as physical processes occurring in the system have been analyzed by means of 3D electromagnetic simulation. It has been shown that the system under study demonstrates the tendency to the sufficient growth of the amplitudes of higher harmonics in the spectrum of current oscillations in the VC region with the increase of beam current. The obtained results allow us to consider virtual cathode oscillators as promising high power mmw-to-THz sources

  16. Analysis of a diode with a ferroelectric cathode

    International Nuclear Information System (INIS)

    It has been shown experimentally that electron current densities of more than 30 A/cm2 can be achieved from a cathode made of ferroelectric ceramic, when applying a field of order 0.1 MV/m. This current exceeds the Child--Langmuir current by two orders of magnitude. The current in the diode varies linearly with the applied voltage, provided that the latter is positive. In this theoretical study we show that the ferroelectric material plays a crucial role in the emission process. When a voltage is applied to the ferroelectric, the internal polarization field varies and the amount of screening charge required decreases. As a result, the electrons distribution near the cathode changes, forming a cloud which fills part of the diode gap. If now a positive voltage is applied to the anode, electrons are readily transferred through the diode gap. The qualitative and quantitative results of the theory are in good accordance with the experiment

  17. Heterogeneous electrocatalysis in porous cathodes of solid oxide fuel cells

    CERN Document Server

    Fu, Y; Bertei, A; Qi, C; Mohanram, A; Pietras, J D; Bazant, M Z

    2014-01-01

    A general physics-based model is developed for heterogeneous electrocatalysis in porous electrodes and used to predict and interpret the impedance of solid oxide fuel cells. This model describes the coupled processes of oxygen gas dissociative adsorption and surface diffusion of the oxygen intermediate to the triple phase boundary, where charge transfer occurs. The model accurately captures the Gerischer-like frequency dependence and the oxygen partial pressure dependence of the impedance of symmetric cathode cells. Digital image analysis of the microstructure of the cathode functional layer in four different cells directly confirms the predicted connection between geometrical properties and the impedance response. As in classical catalysis, the electrocatalytic activity is controlled by an effective Thiele modulus, which is the ratio of the surface diffusion length (mean distance from an adsorption site to the triple phase boundary) to the surface boundary layer length (square root of surface diffusivity div...

  18. Analysis of the cathodic region of atmospheric pressure discharges

    International Nuclear Information System (INIS)

    The cathodic region of atmospheric pressure arcs is dominated by a number of different mechanisms. This makes a theoretical model extremely difficult. A description of this region based on fundamental physical principles is given. Using a previously published model of the inhomogeneous boundary layer of a Saha plasma (Schmitz H and Riemann K-U 2001 J. Phys. D: Appl. Phys. 34 1193), the description is set on a firm theoretical basis. A number of equations including the energy balances of plasma boundary and cathode body lead to a maximum closure of the system. The values for the boundary conditions toward the plasma column could be motivated by a simple minimum principle argument thus eliminating all arbitrary fitting parameters. Results are given for a variety of external parameters and three different discharge gases. The comparison with experimental results shows excellent agreement. (author)

  19. The tungsten powder study of the dispenser cathode

    International Nuclear Information System (INIS)

    The intercorrelation of tungsten powder properties, such as grain size, distribution and morphology, and porous matrix parameters with electron emission capability and longevity of Ba dispenser cathodes has been investigated for the different grain morphologies. It is shown that a fully cleaning step of the tungsten powder is so necessary that the tungsten powder will be reduction of oxide in hydrogen atmosphere above 700 deg. C. The porosity of the tungsten matrix distributes more even and the closed pore is fewer, the average granule size of the tungsten powder distributes more convergent. The porosity of the tungsten matrix and the evaporation of the activator are bigger and the pulse of the cathode is smaller when the granularity is bigger by the analysis of the electronic microscope and diode experiment

  20. The tungsten powder study of the dispenser cathode

    Science.gov (United States)

    Bao, Ji-xiu; Wan, Bao-fei

    2006-06-01

    The intercorrelation of tungsten powder properties, such as grain size, distribution and morphology, and porous matrix parameters with electron emission capability and longevity of Ba dispenser cathodes has been investigated for the different grain morphologies. It is shown that a fully cleaning step of the tungsten powder is so necessary that the tungsten powder will be reduction of oxide in hydrogen atmosphere above 700 °C. The porosity of the tungsten matrix distributes more even and the closed pore is fewer, the average granule size of the tungsten powder distributes more convergent. The porosity of the tungsten matrix and the evaporation of the activator are bigger and the pulse of the cathode is smaller when the granularity is bigger by the analysis of the electronic microscope and diode experiment.

  1. Higher harmonics generation in relativistic electron beam with virtual cathode

    Energy Technology Data Exchange (ETDEWEB)

    Kurkin, S. A., E-mail: KurkinSA@gmail.com; Badarin, A. A.; Koronovskii, A. A.; Hramov, A. E. [Saratov State Technical University, Politechnicheskaja 77, Saratov 410028, Russia and Saratov State University, Astrakhanskaja 83, Saratov 410012 (Russian Federation)

    2014-09-15

    The study of the microwave generation regimes with intense higher harmonics taking place in a high-power vircator consisting of a relativistic electron beam with a virtual cathode has been made. The characteristics of these regimes, in particular, the typical spectra and their variations with the change of the system parameters (beam current, the induction of external magnetic field) as well as physical processes occurring in the system have been analyzed by means of 3D electromagnetic simulation. It has been shown that the system under study demonstrates the tendency to the sufficient growth of the amplitudes of higher harmonics in the spectrum of current oscillations in the VC region with the increase of beam current. The obtained results allow us to consider virtual cathode oscillators as promising high power mmw-to-THz sources.

  2. Higher harmonics generation in relativistic electron beam with virtual cathode

    Science.gov (United States)

    Kurkin, S. A.; Badarin, A. A.; Koronovskii, A. A.; Hramov, A. E.

    2014-09-01

    The study of the microwave generation regimes with intense higher harmonics taking place in a high-power vircator consisting of a relativistic electron beam with a virtual cathode has been made. The characteristics of these regimes, in particular, the typical spectra and their variations with the change of the system parameters (beam current, the induction of external magnetic field) as well as physical processes occurring in the system have been analyzed by means of 3D electromagnetic simulation. It has been shown that the system under study demonstrates the tendency to the sufficient growth of the amplitudes of higher harmonics in the spectrum of current oscillations in the VC region with the increase of beam current. The obtained results allow us to consider virtual cathode oscillators as promising high power mmw-to-THz sources.

  3. High power microwave generation in virtual cathode systems

    International Nuclear Information System (INIS)

    Pulsed high-power microwave generation by means of high current accelerator system has recently become an intensive area of research, the most promising among them being virtual cathode devices or vircators. There are two mechanisms which lead to production of high-power microwaves in vircators. The first deals with electrons, oscillating near the anode and the second with virtual cathode (VC) oscillating as a whole. Generally both mechanisms are presented, but in a given device one may dominate the other. If the anode is thick enough to absorb reflected electrons thus preventing the authors from reentering the diode region, the first mechanism vanished. In this paper the authors discuss the second mechanism, which is realized, for example, in reditron. Anode plasma produced by high-current electron beam passing through the anode is taken into account

  4. The use of hollow cathodes in deposition processes: A critical review

    International Nuclear Information System (INIS)

    The first report of a discharge in a hollow cathode was by F. Paschen in 1916. That study showed that such a system was capable of producing a high electron flux and relatively low ion and neutral temperatures. About 40 years later, the work of Lidsky and others showed that hollow cathode arc discharges were one of the best plasma sources available at that time. The term “hollow cathode discharges” has commonly been used in reference to almost any discharge in a cathode with a cavity-like geometry, such that the plasma was enclosed or partially bound by the electrode walls that were at the cathode potential. Just as the magnetic field trapping of the electrons in a magnetron cathode results in an increase in the plasma density, in the hollow cathode, the reduced electron loss due to the geometry of the cathode also results in a higher plasma density. At least three types of discharge can be established in a hollow cathode. At low power and/or at relatively low gas pressures, the plasma is a “conventional” discharge characterized by low currents and medium to high voltages (we will call this a discharge in a hollow cathode or D-HC). Even this type of plasma has a higher density than a normal planar parallel-plate or magnetron system because the hollow geometry strongly reduces the loss of electrons. Using an adequate combination of gas pressure and applied power with a given hollow cathode diameter, or separation of the cathode surface, the negative glow of the plasma can expand to occupy the majority of the interior volume of the cathode. Under this condition the plasma current can, for the same voltage, be 100 to 1000 times the value of the “simple” D-HC discharge, and the plasma density is correspondingly larger (we call this a hollow cathode discharge or HCD). If the cathode is not cooled, the discharge can transform into a dispersed arc as the electrode temperature increases and thermal-field electron emission becomes an important additional source

  5. Position resolution studies of a cathode pad chamber

    International Nuclear Information System (INIS)

    Two prototype cathode pad chambers (CPC's) for muon tracking stations of ALICE were fabricated and tested at SPS, CERN. In order to achieve a mass resolution better than 100 MeV, required to resolve the Υ resonances, the large area tracking stations should have a position resolution of < 100 μm. In this paper, the in-beam position resolution of the CPC prototype has been reported

  6. New molybdenium chalcogenide cathodes for rechargeable lithium batteries

    International Nuclear Information System (INIS)

    The synthesis, characterization, and electrochemical study of novel molybdenum chalcogenides with application as secondary Li battery cathodes are described. These compounds include oxysulfides having the formula MoOS2 and MoO2S, the selenosulfide MoSe3S, and a rhenium substituted trisulfide Mo.94Re.06S3. The performance of these materials in secondary Li cells is compared to that of MoS3. MoS3 and MoSe3S

  7. Cathodic Protection of Pipeline Using Distributed Control System

    OpenAIRE

    Gopalakrishnan Jayapalan; Ganga Agnihotri; Deshpande, D. M.

    2014-01-01

    Distributed control system (DCS) is available in most of the compressor stations of cross-country pipeline systems. Programmable logic controller (PLC) is used in all the intermediate pigging (IP) stations/sectional valve (SV) stations to collect the field data and to control the remote actuated valves. This paper presents how DCS or PLC can be used for cathodic protection of gas pipelines. Virtual instrumentation (VI) software is used here for simulation and real-time implementation purpose....

  8. Modelling cathode catalyst degradation in polymer electrolyte fuel cells

    OpenAIRE

    Rinaldo, Steven Giordano

    2013-01-01

    Nano-sized Pt particles in the cathode catalyst layer of a polymer electrolyte fuel cell afford a high initial electrochemically active surface-area. However, the gain in active surface area for desired surface reactions is offset in part by enhanced rates of degradation processes that cause losses in catalyst mass, catalyst surface-area, and electrocatalytic activity. The loss of electrochemically active surface-area of the catalyst causes severe performance degradation over relevant lifetim...

  9. Application of mercury cathode electrolysis to fission-product separation

    International Nuclear Information System (INIS)

    A method involving controlled potential mercury cathode electrolysis has been developed to separate fission products. It allows the radiochemical determination of Ag, Cd, Pd, Rh, Ru, Sn, Te, Sb and Mo from solutions of fission products highly concentrated in mineral salts. The general procedure consists in three main steps: electrolytic amalgam generation, destruction of amalgams and ultimate purification of elements by other means. Electrolytic operations last about five hours. Chemical yields lie between 10 per cent and 70 per cent. (authors)

  10. Central tracking chamber with inflated cathode-strip foils

    International Nuclear Information System (INIS)

    A new cylindrical low-mass central drift chamber has been constructed for the K+ → π+νν experiment at BNL (E787). The chamber consists of 12 layers of axial wire cells and 6 layers of thin cathode-strip foils, four of which are supported by differential gas pressure. The momentum resolution (RMS) for muons and pions in the range 150 to 250 MeV is found to be about 0.9%. (authors)

  11. Transport properties of β-irradiated zeolite cathodes

    International Nuclear Information System (INIS)

    Full text : The interesting properties of zeolites such as the ion-exchange selectivity is their ability to spontaneously generate a free electron and hole in the zeolite by β-radiation that an electron transfer from the guest to the zeolite can occur leading to the desired nuclear applications. It is important to know the relation between the discharge generation in nanopores and plasma characteristics for unirradiated and irradiated cathode in terms of GDED optimization

  12. Plasma gun with coaxial powder feed and adjustable cathode

    Science.gov (United States)

    Zaplatynsky, Isidor (Inventor)

    1991-01-01

    An improved plasma gun coaxially injects particles of ceramic materials having high melting temperatures into the central portion of a plasma jet. This results in a more uniform and higher temperature and velocity distribution of the sprayed particles. The position of the cathode is adjustable to facilitate optimization of the performance of the gun wherein grains of the ceramic material are melted at lower power input levels.

  13. Unusual Cathode Erosion Patterns Observed for Steered Arc Sources

    OpenAIRE

    Kolbeck, Jonathan; Anders, André

    2014-01-01

    A cathodic arc source with a magnetron-type magnetic field was investigated for stability, erosion, and compatibility with a linear macroparticle filter. Here we report about unusual arc spot erosion patterns, which were narrow (~ 2 mm) with periodic pits when operating in argon, and broad (~ 10 mm) with periodic groves and ridges when operating in an argon and oxygen mixtures. These observations can be correlated with the ignition probability for type 2 and type 1 arc spots, respectively.

  14. Heat flux at the refractory cathode of a high-current, high-pressure arc (two modes of cathode spot attachment)

    Energy Technology Data Exchange (ETDEWEB)

    Nemchinsky, Valerian [ESAB Welding and Cutting Products and Francis Marion University, Florence SC 29501 (United States)

    2004-04-07

    Calorimetric measurements of a refractory (pure and thoriated tungsten) cathode in a high-current (100-500 A) high-pressure (1-5 atm) arc in nitrogen were performed. The measurements confirmed the existence of a 'high-current' mode of cathode spot (CS) operation-the mode we observed by a footprint method in our work (2003 J. Phys. D: Appl. Phys. 36 3007). In this mode, the heat load of a cathode does not depend on the pressure and is directly proportional to the arc current as opposed to the 'low current' mode where it is inversely proportional to the square root of pressure and directly proportional to the square root of current. The current density at the cathode surface calculated from the measured heat flux to the cathode is approximately half of the current density obtained by a footprint method. Both densities exhibit the same current and pressure dependences. The radial distribution of the cathode temperature inside the CS is discussed. We hypothesize that the temperature has its maximum at the spot periphery. In the case of the thoriated tungsten cathode, this maximum may be so high that, at this location, the cathode is virtually thorium free.

  15. Chromium impact on Strontium and Manganese-free cathode materials

    Energy Technology Data Exchange (ETDEWEB)

    Stodolny, M.K.; Rietveld, G.; Van Berkel, F.P.F. [Energy research Centre of the NetherlandsECN, Petten (Netherlands); Boukamp, B.A.; Blank, D.H.A. [Department of Science and Technology, MESA Institute for Nanotechnology, University of Twente, Enschede (Netherlands)

    2011-11-15

    The outline of the presentation shows (1) the aim: understanding degradation mechanisms of the Cr-poisoned LNF (the perovskite La(Ni,Fe))cathode; (2) Introduction: (2a) Cost-effective SOFC stack (cheap metallic interconnects), (2b) Cr-poisoning of SoA SOFC cathodes, and (2c) Promises of the La(Ni,Fe)O{sub 3} material; and (3) the subject of a PhD research: LNF stability in the presence of Cr species, focusing on (3a) Solid-state reactivity of LNF+Cr2O3 and (3b) Gas transport of Cr and impact on LNF for the Explanation of the Cr-poisoning mechanism. The Summary and Outlook slide shows Understanding of solid-state reactivity between LNF and Cr2O3, and Gas transport of Cr and its impact on the LNF {rho}properties established. It is concluded that Cr-poisoning is dependent on: LNF microstructure, Operating temperature, and Cr atmosphere. The Outlook shows: Impedance data deconvolution, In-depth explanation of Cr-poisoning on LNF, and Suggestions for Cr-resistant cathode.

  16. Accelerated life ac conductivity measurements of CRT oxide cathodes

    Science.gov (United States)

    Hashim, A. A.; Barratt, D. S.; Hassan, A. K.; Nabok, A.

    2006-07-01

    The ac conductivity measurements have been carried out for the activated Ba/SrO cathode with additional 5% Ni powder for every 100 h acceleration life time at the temperature around 1125 K. The ac conductivity was studied as a function of temperature in the range 300-1200 K after conversion and activation of the cathode at 1200 K for 1 h in two cathodes face to face closed configuration. The experimental results prove that the hopping conductivity dominate in the temperature range 625-770 K through the traps of the WO 3 associate with activation energy Ea = 0.87 eV, whereas from 500-625 K it is most likely to be through the traps of the Al 2O 3 with activation energy of Ea = 1.05 eV. The hopping conductivity at the low temperature range 300-500 K is based on Ni powder link with some Ba contaminants in the oxide layer stricture which indicates very low activation energy Ea = 0.06 eV.

  17. Performance of field emission cathodes prepared from diamond nanoparticles

    International Nuclear Information System (INIS)

    Nano-diamond field emission cathodes were fabricated using a two-step technique. A mixture of nano-diamond and nano-Ti powders was coated onto a Ti substrate using a spin-coating process, followed by the application of an annealing treatment to form a TiC phase. The effects of the annealing temperature and the number of coating layers on the electron field emission properties of the as-fabricated field emission cathodes were investigated. The samples fabricated under different conditions were analyzed by Raman spectroscopy, X-ray diffraction, and scanning electron microscopy. The differences in terms of the electron field emission properties were explained by a TiC network model. A higher temperature is necessary to form a continuous TiC network when a thicker coating is used on the field emission cathode. In contrast, for the thinner coating, a relatively low temperature is sufficient to form such a TiC network. Only a continuous TiC network coating can facilitate the passage of electrons through the coating and lead to emission. - Highlights: • The field emission properties of nano-diamond powder were investigated. • Nano-diamond powder was deposited by spin coating on titanium substrate. • Nano-titanium powder was mixed into the coating. • A titanium carbide network model was proposed to explain the samples' properties

  18. High-Capacity, High-Voltage Composite Oxide Cathode Materials

    Science.gov (United States)

    Hagh, Nader M.

    2015-01-01

    This SBIR project integrates theoretical and experimental work to enable a new generation of high-capacity, high-voltage cathode materials that will lead to high-performance, robust energy storage systems. At low operating temperatures, commercially available electrode materials for lithium-ion (Li-ion) batteries do not meet energy and power requirements for NASA's planned exploration activities. NEI Corporation, in partnership with the University of California, San Diego, has developed layered composite cathode materials that increase power and energy densities at temperatures as low as 0 degC and considerably reduce the overall volume and weight of battery packs. In Phase I of the project, through innovations in the structure and morphology of composite electrode particles, the partners successfully demonstrated an energy density exceeding 1,000 Wh/kg at 4 V at room temperature. In Phase II, the team enhanced the kinetics of Li-ion transport and electronic conductivity at 0 degC. An important feature of the composite cathode is that it has at least two components that are structurally integrated. The layered material is electrochemically inactive; however, upon structural integration with a spinel material, the layered material can be electrochemically activated and deliver a large amount of energy with stable cycling.

  19. Development of improved cathodes for solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, H.U.

    1991-03-01

    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.

  20. Optimization of cold cathode saddle field ion source

    Energy Technology Data Exchange (ETDEWEB)

    Abdelrahman, M.M., E-mail: moustafa82003@yahoo.co [Accelerators and Ion Sources Department, Nuclear Research Center, Atomic Energy Authority, Inchas, Cairo 13759 (Egypt); Abdelsalam, F.W. [Accelerators and Ion Sources Department, Nuclear Research Center, Atomic Energy Authority, Inchas, Cairo 13759 (Egypt)

    2010-02-01

    The modified cold cathode saddle field ion source operates at low gas pressure and requires neither magnetic field nor filament. We have designed a cold cathode saddle field ion source (cylindrical symmetry type) and characterized the discharge with nitrogen gas in the oscillating ('low pressure') mode. The distance between the two anode rods was optimized for maximum electrostatic confinement of the electrons. The discharge anisotropy was investigated and the discharge was found to be mainly an axial one in which the electrons oscillate near the axis at the discharge region. A high output beam current was measured on the Faraday cup at a distance of 1.5 cm from the cylindrical cathode, and was found to be dependent upon the operating pressure and the discharge current. An ion beam current of 220 muA was obtained at the optimum distance between the two anode rods of 6 mm for a nitrogen gas pressure of 8x10{sup -4} mbar and a discharge current of 2 mA.

  1. Cathode for tritium-forming exothermic reaction by electrolysis

    International Nuclear Information System (INIS)

    The present invention provides a cathode used for a reaction in which liquid containing heavy water is electrolyzed under a room temperature to generate energy greater than that required for electrolysis in the liquid. The cathode used in this electrolysis includes any of those described below. (a) metal uranium (U metal) coated with palladium (Pd), (b) U metal contained in porous aluminum (Al203) container and (c) an alloy of U metal and Pd metal contained in a porous aluminum container. According to the result of an experiment, the temperature of the electrolyte is elevated to 40degC at 50 min after the start of electric supply and tritium in the electrolyte is increased to about three times of background, by using any one of cathodes (a), (b) and (c). Based on the result of the experiment, it is assumed that a specific tritium-forming exothermic reaction like that a nuclear fusion reaction is caused in this reaction. (I.S.)

  2. Emission current from a single micropoint of explosive emission cathode

    International Nuclear Information System (INIS)

    Explosive emission cathodes (EECs) are widely used due to their large current. There has been much research on the explosive electron emission mechanism demonstrating that a current density of 108–109 A/cm2 is necessary for a micropoint to explode in several nanoseconds and the micropoint size is in micron-scale according to the observation of the cathode surface. This paper, however, makes an effort to research the current density and the micropoint size in another way which considers the space charge screening effect. Our model demonstrates that the relativistic effect is insignificant for the micropoint emission due to the small size of the micropoint and uncovers that the micron-scale size is an intrinsic demand for the micropoint to reach a space charge limited current density of 108–109 A/cm2. Meanwhile, our analysis shows that as the voltage increases, the micropoint emission will turn from a field limited state to a space charge limited state, which makes the steady-state micropoint current density independent of the cathode work function and much less dependent on the electric field and the field enhancement factor than that predicted by the Fowler-Nordheim formula

  3. Molecular beam sampling of a hollow cathode arc

    International Nuclear Information System (INIS)

    This thesis deals with the description of the process of molecular beam sampling of a Hollow Cathode Arc. The aim of the study is twofold, i.e. investigation of the applicability of molecular beam sampling as a plasma diagnostic and the use of a Hollow Cathode Arc as a high intensity beam source for ground state atoms and metastable state atoms in the superthermal energy range. Suitable models are introduced, describing the process of molecular beam sampling of both ground state atoms and metastable state atoms. Fast ground state atoms produced by ion-atom collisions. The experimental facilities, i.e. the Hollow Cathode Arc, the time-of-flight machine and the dye laser system are described. And an alternative detection scheme for ground state atoms is presented and experimental results on the molecular beam sampling of a low density plasma (densities 1019-1020 m-3) in the long arc configuration are reported. The results on the short arc configuration (densities 1021-1022 m-3) are discussed. (Auth.)

  4. Patterning of dispenser cathode surfaces to a controlled porosity

    Science.gov (United States)

    Garner, Charles E.; Deininger, William D.; Gibson, John; Thomas, Richard

    1989-01-01

    A process to pattern slots approximately 1.25 microns in width into 25-micron-thick W films that have been deposited onto flat or concave surfaces is discussed. A 25-micron-thick W film with a high degree of (100) orientation is chemically vapor deposited (CVD) onto a flat or concave Mo mandrel. A 5-micron-thick Al film is deposited onto the CVD W, followed by 2 microns of photoresist. On concave cathodes, XeCl2 laser ablation or X-ray lithography is used to pattern the photoresist, whereas on flat cathodes deep UV lithography can be used. The patterned photoresist serves as the mask in a Cl ion-beam-assisted etching (IBAE) process to pattern the Al. An alternative process is to deposit Al2O3 films onto the W and pattern the Al2O3 using laser ablation. The W film is then patterned to 3-6-micron slot widths using IBAE + ClF3 with the patterned Al or Al2O3 as the mask. Finally, a sputter deposition step is required to close up the slots to approximately 1 micron. The process described is capable of patterning concave dispenser cathodes to a controlled and precise porosity.

  5. X-Band Thermionic Cathode RF Gun at UTNL

    CERN Document Server

    Fukasawa, Atsushi; Dobashi, Katsuhiro; Ebina, Futaro; Hayano, Hitoshi; Higo, Toshiyasu; Kaneyasu, Tatsuo; Matsuo, Kennichi; Ogino, Haruyuki; Sakae, Hisaharu; Sakamoto, Fumito; Uesaka, Mitsuru; Urakawa, Junji

    2005-01-01

    The X-band (11.424 GHz) linac for compact Compton scattering hard X-ray source are under construction at Nuclear Engineering Research Laboratory, University of Tokyo. This linac designed to accelerate up to 35 MeV, and this electron beam will be used to produce hard X-ray by colliding with laser. It consists of a thermionic cathode RF gun, an alpha magnet, and a traveling wave tube. The gun has 3.5 cells (unloaded Q is 8250) and will be operated at pi-mode. A dispenser cathode is introduced. Since the energy spread of the beam from the gun is predicted to be broad due to the continuous emission from the thermionic cathode, a slit is placed in the alpha magnet to eliminate low energy electrons. The simulation on the injector shows the beam energy 2.9 MeV, the charge 23 pC/bunch, and the emittance less than 10 mm.mrad. The experiment on the gun is planed in the beginning of 2005, and the details will be discussed on the spot.

  6. High-power microwave emission by magnetized virtual cathode oscillator

    Energy Technology Data Exchange (ETDEWEB)

    Kostov, K.G.; Ferreira, J.L. [Univ. of Brasilia (Brazil). Dept. of Physics

    1996-12-31

    The results of computer simulation of an axially extracted virtual cathode oscillator with an external guide magnetic field are presented. The simulation was performed using the electromagnetic relativistic particle-in-cell (PIC) computer code KARAT. The foil diode parameters as accelerating voltage, cathode diameter and anode-cathode gap are chosen in such a way that the beam current injected through the anode foil into the output waveguide exceeds the space charge limited current but on the outer side it is below the critical current for beam pinching. In this case without using an external guide magnetic field the beam expands in radial direction until it hits the conductive wall. It is shown that the vircator can operate with and without magnetic field however in the case without guide magnetic field the vircator efficiency is small due to the current losses in radial direction. The emitted microwave power with guide magnetic field is bigger than in the case without magnetic field and the microwave frequency slightly increase with magnetic field intensity increasing. The results from computer simulation are compared with experimental results obtained in a similar vircator configuration.

  7. Ion velocities in a micro-cathode arc thruster

    International Nuclear Information System (INIS)

    Ion velocities in the plasma jet generated by the micro-cathode arc thruster are studied by means of time-of-flight method using enhanced ion detection system (EIDS). The EIDS triggers perturbations (spikes) on arc current waveform, and the larger current in the spike generates denser plasma bunches propagating along with the mainstream plasma. The EIDS utilizes double electrostatic probes rather than single probes. The average Ti ion velocity is measured to be around 2×104 m/s without a magnetic field. It was found that the application of a magnetic field does not change ion velocities in the interelectrode region while leads to ion acceleration in the free expanding plasma plume by a factor of about 2. Ion velocities of about 3.5×104 m/s were detected for the magnetic field of about 300 mT at distance of about 100–200 mm from the cathode. It is proposed that plasma is accelerated due to Lorentz force. The average thrust is calculated using the ion velocity measurements and the cathode mass consumption rate, and its increase with the magnetic field is demonstrated.

  8. Control led electron gun with a plasma cathode

    International Nuclear Information System (INIS)

    A description of a power electron gun with a plasma cathode is given. Its design is the development of gas-discharge sources of the duaplasmatron type. The basic elements of the gas-discharge source- the gun anode, the gun plasma cathode, the intermediate electrode of the source, and the tungsten thermocathode- are placed in side a high-voltage insulator. The diameter of the plasma cathode can be up to 2 cm, and the length of the accelerating gap- up to 0.3 cm. The discharge chamber is filled with Ar under 0.3 torr pressure. The electron beam focusing is carried out by means of two magnetic lenses, and displacement of the electron beam - by means of a deflecting coil. Experimental data are given on beam current control by modulating the discharge current and also by means of the electromagnetic system of the plasma gas-discharge source. The electron gun described shapes electron beams with a current up to 4.5 A under stationary operating conditions

  9. Cr(VI) reduction at rutile-catalyzed cathode in microbial fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yan; Lu, Anhuai; Ding, Hongrui; Yan, Yunhua; Wang, Changqiu; Zen, Cuiping; Wang, Xin [The Key Laboratory of Orogenic Belts and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871 (China); Jin, Song [MWH Americas, 3665 JFK Parkway, Suite 206, Fort Collins, CO 80525 (United States); Department of Civil and Architectural Engineering, University of Wyoming, Laramie, WY 82071 (United States)

    2009-07-15

    Cathodic reduction of hexavalent chromium (Cr(VI)) and simultaneous power generation were successfully achieved in a microbial fuel cell (MFC) containing a novel rutile-coated cathode. The selected rutile was previously characterized to be sensitive to visible light and capable of both non-photo- and photocatalysis. In the MFCs containing rutile-coated cathode, Cr(VI) was rapidly reduced in the cathode chamber in presence and absence of light irradiation; and the rate of Cr(VI) reduction under light irradiation was substantially higher than that in the dark. Under light irradiation, 97% of Cr(VI) (initial concentration 26 mg/L) was reduced within 26 h, which was 1.6 x faster than that in the dark controls in which only background non-photocatalysis occurred. The maximal potential generated under light irradiation was 0.80 vs. 0.55 V in the dark controls. These results indicate that photocatalysis at the rutile-coated cathode in the MFCs might have lowered the cathodic overpotential, and enhanced electron transfer from the cathode to Cr(VI) for its reduction. In addition, photoexcited electrons generated during the cathode photocatalysis might also have contributed to the higher Cr(VI) reduction rates when under light irradiation. This work assessed natural rutile as a novel cathodic catalyst for MFCs in power generation; particularly it extended the practical merits of conventional MFCs to cathodic reduction of environmental contaminants such as Cr(VI). (author)

  10. Effect of a cathode buffer layer on the stability of organic solar cells

    International Nuclear Information System (INIS)

    We present the effect of a cathode buffer layer on the performance and stability of organic photovoltaics (OPVs) based on a blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM). Six kinds of cathode buffer layers, i.e. lithium fluoride, sodium chloride, NaCl/Mg, tris-(8-hydroxy-quinoline) aluminum, bathocuproine and 1,3,5-tris(2-N-phenylbenzimidazolyl)benzene, were inserted between the photoactive layer and an Al cathode, which played a dominant role in the device’s performance. Devices with the cathode buffer layers above exhibited improved performance. The degradation of these devices with encapsulation was further investigated in an inert atmosphere. The results indicated that devices with inorganic cathode buffer layers exhibited better stability than those with organic cathode buffer layers. (paper)

  11. Note: Design and development of improved indirectly heated cathode based strip electron gun

    Energy Technology Data Exchange (ETDEWEB)

    Maiti, Namita; Patil, D. S.; Dasgupta, K. [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Bade, Abhijeet; Tembhare, G. U. [Department of Mechanical Engineering, Veermata Jijabai Technological Institute, Matunga, Mumbai 400 019 (India)

    2015-02-15

    An improved design of indirectly heated solid cathode based electron gun (200 kW, 45 kV, 270° bent strip type electron gun) has been presented. The solid cathode is made of thoriated tungsten, which acts as an improved source of electron at lower temperature. So, high power operation is possible without affecting structural integrity of the electron gun. The design issues are addressed based on the uniformity of temperature on the solid cathode and the single long filament based design. The design approach consists of simulation followed by extensive experimentation. In the design, the effort has been put to tailor the non-uniformity of the heat flux from the filament to the solid cathode to obtain better uniformity of temperature on the solid cathode. Trial beam experiments have been carried out and it is seen that the modified design achieves one to one correspondence of the solid cathode length and the electron beam length.

  12. Two-dimensional model of orificed micro-hollow cathode discharge for space application

    International Nuclear Information System (INIS)

    In this paper, we describe results of self-consistent two-dimensional (x-z) particle-in-cell simulations, with a Monte Carlo collision model, of an orificed micro-hollow cathode operating in a planar diode geometry. The model includes thermionic electron emission with Schottky effect, secondary electron emission due to cathode bombardment by the plasma ions, several different collision processes, and a non-uniform xenon background gas density in the cathode-anode gap. Simulated results showing behavior of the plasma density, potential distribution, and energy flux towards the hollow cathode and orifice walls, are discussed. In addition, results of simulations showing the effect of different Xe gas pressures, orifice size, and cathode voltage, on operation of the micro-hollow cathode are presented

  13. Characterization of Atomic and Electronic Structures of Electrochemically Active SOFC Cathode Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kevin Blinn; Yongman Choi; Meilin Liu

    2009-08-11

    The objective of this project is to gain a fundamental understanding of the oxygen-reduction mechanism on mixed conducting cathode materials by means of quantum-chemical calculations coupled with direct experimental measurements, such as vibrational spectroscopy. We have made progress in the elucidation of the mechanisms of oxygen reduction of perovkite-type cathode materials for SOFCs using these quantum chemical calculations. We established computational framework for predicting properties such as oxygen diffusivity and reaction rate constants for adsorption, incorporation, and TPB reactions, and formulated predictions for LSM- and LSC-based cathode materials. We have also further developed Raman spectroscopy as well as SERS as a characterization tool for SOFC cathode materials. Raman spectroscopy was used to detect chemical changes in the cathode from operation conditions, and SERS was used to probe for pertinent adsorbed species in oxygen reduction. However, much work on the subject of unraveling oxygen reduction for SOFC cathodes remains to be done.

  14. Note: Design and development of improved indirectly heated cathode based strip electron gun

    International Nuclear Information System (INIS)

    An improved design of indirectly heated solid cathode based electron gun (200 kW, 45 kV, 270° bent strip type electron gun) has been presented. The solid cathode is made of thoriated tungsten, which acts as an improved source of electron at lower temperature. So, high power operation is possible without affecting structural integrity of the electron gun. The design issues are addressed based on the uniformity of temperature on the solid cathode and the single long filament based design. The design approach consists of simulation followed by extensive experimentation. In the design, the effort has been put to tailor the non-uniformity of the heat flux from the filament to the solid cathode to obtain better uniformity of temperature on the solid cathode. Trial beam experiments have been carried out and it is seen that the modified design achieves one to one correspondence of the solid cathode length and the electron beam length

  15. Effect of cathode structure on neutron yield performance of a miniature plasma focus device

    International Nuclear Information System (INIS)

    In this Letter we report the effect of two different cathode structures - tubular and squirrel cage, on neutron output from a miniature plasma focus device. The squirrel cage cathode is typical of most DPF sources, with an outer, tubular envelope that serves as a vacuum housing, but does not carry current. The tubular cathode carries the return current and also serves as the vacuum envelope, thereby minimizing the size of the DPF head. The maximum average neutron yield of (1.82±0.52)x105 n/shot for the tubular cathode at 4 mbar was enhanced to (1.15±0.2)x106 n/shot with squirrel cage cathode at 6 mbar operation. These results are explained on the basis of a current sheath loading/mass choking effect. The penalty for using a non-transparent cathode negates the advantage of the smaller size of the DPF head.

  16. Electricity generation of microbial fuel cell with waterproof breathable membrane cathode

    Science.gov (United States)

    Xing, Defeng; Tang, Yu; Mei, Xiaoxue; Liu, Bingfeng

    2015-12-01

    Simplification of fabrication and reduction of capital cost are important for scale-up and application of microbial electrochemical systems (MES). A fast and inexpensive method of making cathode was developed via assembling stainless steel mesh (SSM) with waterproof breathable membrane (WBM). Three assemble types of cathodes were fabricated; Pt@SSM/WBM (SSM as cathode skeleton, WBM as diffusion layer, platinum (Pt) catalyst applied on SSM), SSM/Pt@WBM and Pt@WBM. SSM/Pt@WBM cathode showed relatively preferable with long-term stability and favorable power output (24.7 W/m3). Compared to conventional cathode fabrication, air-cathode was made for 0.5 h. The results indicated that the novel fabrication method could remarkably reduce capital cost and simplify fabrication procedures with a comparable power output, making MFC more prospective for future application.

  17. Hollow Cathode and Low-Thrust Extraction Grid Analysis for a Miniature Ion Thruster

    OpenAIRE

    Wirz, Richard; Sullivan, Regina; Przybylowski, JoHanna; Silva, Mike

    2008-01-01

    Miniature ion thrusters are well suited for future space missions that require high efficiency, precision thrust, and low contamination in the mN to sub-mN range. JPL’s miniature xenon Ion (MiXI) thruster has demonstrated an efficient discharge and ion extraction grid assembly using filament cathodes and the internal conduction (IC) cathode. JPL is currently preparing to incorporate a miniature hollow cathode for the MiXI discharge. Computational analyses anticipate that an axially upstream h...

  18. Cleaning of used cathode and board units of electrolytic cells by acid method

    International Nuclear Information System (INIS)

    Present article is devoted to cleaning of used cathode and board units of electrolytic cells by acid method. The studies results on setting of optimal parameters of extraction of extrinsic components remain after aqueous treatment of used cathode and board units of electrolytic cells of aluminium production were considered. It was defined that with using of 10% of hydrochloric acid solution from used cathode and board units of electrolytic cells it is possible to obtain the purified carbon-graphite material.

  19. The behaviour of amalgams of some d-metals during cathodic polarization in solutions

    International Nuclear Information System (INIS)

    Results of electrochemical investigation of rhenium, molybdenum and tungsten amalgams during cathodic polarization in alkali and acid solutions are presented. A variant of electrolysis with sodium amalgam as anode is used for the investigation. On the basis of experimental data on potentials of amalgam cathodes (under current and after switching off one), as well as redox-potentials of solutions near the cathode surface, formation of negative ions of metals (rhenium, molybdenum and tungsten) is established

  20. A dual pore carbon aerogel based air cathode for a highly rechargeable lithium-air battery

    OpenAIRE

    Wang, Fang; Xu, Yang-Hai; Luo, Zhong-Kuan; PANG, YAN; Liang, Chun-Sheng; Chen, Jing; Liu, Dong; Zhang, Xianghua

    2014-01-01

    International audience Cathode structure plays a vital role in lithium-air battery for that it can provide space for discharged products accommodation and free path for oxygen, e− and Li+ transport. However, pore blockage, cathode passivation and degradation all result in low discharge rates and poor cycling capability. To get rid of these predicaments, a novel highly conductive dual pore carbon aerogel based air cathode is fabricated to construct a lithium-air battery, which exhibits 18 t...

  1. Composite Organic Radical - Inorganic Hybrid Cathode for Lithium-ion Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Qian; Cosimbescu, Lelia; Koech, Phillip K.; Choi, Daiwon; Lemmon, John P.

    2013-07-01

    A new organic radical inorganic hybrid cathode comprised of PTMA/LiFePO4 composite system is developed and reported for the first time. The hybrid cathodes demonstrate high pulse power capability resulting in a significant improvement over the pure PTMA or LiFePO4 cathode which is very promising for transportation and other high pulse power applications that require long cycle life and lower cost.

  2. Cathode development for solid oxide electrolysis cells for high temperature hydrogen production

    OpenAIRE

    Yang, Xuedi

    2010-01-01

    This study has been mainly focused on high temperature solid oxide electrolysis cells (HT-SOECs) for steam electrolysis. The compositions, microstructures and metal catalysts for SOEC cathodes based on (La₀.₇₅Sr₀.₂₅)₀.₉₅Mn₀.₅Cr₀.₅O₃ (LSCM) have been investigated. Hydrogen production amounts from SOECs with LSCM cathodes have been detected and current-to-hydrogen efficiencies have been calculated. The effect of humidity on electrochemical performances from SOECs with cathodes ba...

  3. Emission characteristics of laser ablation-hollow cathode glow discharge spectral source

    OpenAIRE

    Karatodorov Stefan; Mihailov Valentin; Grozeva Margarita

    2014-01-01

    The emission characteristics of a scheme combining laser ablation as sample introduction source and hollow cathode discharge as excitation source are presented. The spatial separation of the sample material introduction by laser ablation and hollow cathode excitation is achieved by optimizing the gas pressure and the sample-cathode gap length. At these conditions the discharge current is maximized to enhance the analytical lines intensity.

  4. Materials Characterization of Impregnated W and W-Ir Cathodes after Oxygen Poisoning

    OpenAIRE

    Polk, James E.; Capece, Angela M.

    2015-01-01

    Electric thrusters use hollow cathodes as the electron source for generating the plasma discharge and for beam neutralization. These cathodes contain porous tungsten emitters impregnated with BaO material to achieve a lower surface work function and are operated with xenon propellant. Oxygen contaminants in the xenon plasma can poison the emitter surface, resulting in a higher work function and increased operating temperature. This could lead directly to cathode failure by preventing discharg...

  5. The influence of cathode material on electrochemical degradation of trichloroethylene in aqueous solution.

    Science.gov (United States)

    Rajic, Ljiljana; Fallahpour, Noushin; Podlaha, Elizabeth; Alshawabkeh, Akram

    2016-03-01

    In this study, different cathode materials were evaluated for electrochemical degradation of aqueous phase trichloroethylene (TCE). A cathode followed by an anode electrode sequence was used to support reduction of TCE at the cathode via hydrodechlorination (HDC). The performance of iron (Fe), copper (Cu), nickel (Ni), aluminum (Al) and carbon (C) foam cathodes was evaluated. We tested commercially available foam materials, which provide large electrode surface area and important properties for field application of the technology. Ni foam cathode produced the highest TCE removal (68.4%) due to its high electrocatalytic activity for hydrogen generation and promotion of HDC. Different performances of the cathode materials originate from differences in the bond strength between atomic hydrogen and the material. With a higher electrocatalytic activity than Ni, Pd catalyst (used as cathode coating) increased TCE removal from 43.5% to 99.8% for Fe, from 56.2% to 79.6% for Cu, from 68.4% to 78.4% for Ni, from 42.0% to 63.6% for Al and from 64.9% to 86.2% for C cathode. The performance of the palladized Fe foam cathode was tested for degradation of TCE in the presence of nitrates, as another commonly found groundwater species. TCE removal decreased from 99% to 41.2% in presence of 100 mg L(-1) of nitrates due to the competition with TCE for HDC at the cathode. The results indicate that the cathode material affects TCE removal rate while the Pd catalyst significantly enhances cathode activity to degrade TCE via HDC. PMID:26761603

  6. Osmium-tungsten alloys and their relevance to improved M-type cathodes

    International Nuclear Information System (INIS)

    Osmium/tungsten matrix impregnated cathodes and partially osmium coated B-type cathodes have been studied using numerous ananlytical techniques. A strong correlation between the formation of an osmium/tungsten alloy and reduced effective work function has been demonstrated. Using this result an improved dispenser cathode has been constructed with an effective work function 0.2 eV lower than conventional B-type emitters. (orig.)

  7. Study and characterization of dispenser cathode of 10 MeV Linac

    International Nuclear Information System (INIS)

    A dispenser cathode of pressed and sintered Ba-Ni powder is used as electron source in electron linac having 10 MeV beam energy and 10 kW beam power at RRCAT. This linac is planned for development of agricultural radiation processing facility. In this e-linac a triode type electron gun is used. This paper describes the cathode behavioural model during operation with addition of sparkle on materials characterization of diminished emission cathode surface. (author)

  8. Solid Oxide Fuel Cell Cathodes. Unraveling the Relationship Between Structure, Surface Chemistry and Oxygen Reduction

    Energy Technology Data Exchange (ETDEWEB)

    Gopalan, Srikanth [Boston Univ., MA (United States)

    2013-03-31

    In this work we have considered oxygen reduction reaction on LSM and LSCF cathode materials. In particular we have used various spectroscopic techniques to explore the surface composition, transition metal oxidation state, and the bonding environment of oxygen to understand the changes that occur to the surface during the oxygen reduction process. In a parallel study we have employed patterned cathodes of both LSM and LSCF cathodes to extract transport and kinetic parameters associated with the oxygen reduction process.

  9. On the actual cathode mixed potential in direct methanol fuel cells

    Science.gov (United States)

    Zago, M.; Bisello, A.; Baricci, A.; Rabissi, C.; Brightman, E.; Hinds, G.; Casalegno, A.

    2016-09-01

    Methanol crossover is one of the most critical issues hindering commercialization of direct methanol fuel cells since it leads to waste of fuel and significantly affects cathode potential, forming a so-called mixed potential. Unfortunately, due to the sluggish anode kinetics, it is not possible to obtain a reliable estimation of cathode potential by simply measuring the cell voltage. In this work we address this limitation, quantifying the mixed potential by means of innovative open circuit voltage (OCV) tests with a methanol-hydrogen mixture fed to the anode. Over a wide range of operating conditions, the resulting cathode overpotential is between 250 and 430 mV and is strongly influenced by methanol crossover. We show using combined experimental and modelling analysis of cathode impedance that the methanol oxidation at the cathode mainly follows an electrochemical pathway. Finally, reference electrode measurements at both cathode inlet and outlet provide a local measurement of cathode potential, confirming the reliability of the innovative OCV tests and permitting the evaluation of cathode potential up to typical operating current. At 0.25 A cm-2 the operating cathode potential is around 0.85 V and the Ohmic drop through the catalyst layer is almost 50 mV, which is comparable to that in the membrane.

  10. Fundamental Investigations and Rational Design of Durable High-Performance SOFC Cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yu [Georgia Inst. of Technology, Atlanta, GA (United States); Ding, Dong [Georgia Inst. of Technology, Atlanta, GA (United States); Wei, Tao [Georgia Inst. of Technology, Atlanta, GA (United States); Liu, Meilin [Georgia Inst. of Technology, Atlanta, GA (United States)

    2016-03-31

    The main objective of this project is to unravel the degradation mechanism of LSCF cathodes under realistic operating conditions with different types of contaminants, aiming towards the rational design of cathodes with high-performance and enhanced durability by combining a porous backbone (such as LSCF) with a thin catalyst coating. The mechanistic understanding will help us to optimize the composition and morphology of the catalyst layer and microstructure of the LSCF backbone for better performance and durability. More specifically, the technical objectives include: (1) to unravel the degradation mechanism of LSCF cathodes under realistic operating conditions with different types of contaminants using in situ and ex situ measurements performed on specially-designed cathodes; (2) to examine the microstructural and compositional evolution of LSCF cathodes as well as the cathode/electrolyte interfaces under realistic operating conditions; (3) to correlate the fuel cell performance instability and degradation with the microstructural and morphological evolution and surface chemistry change of the cathode under realistic operating conditions; (4) to explore new catalyst materials and electrode structures to enhance the stability of the LSCF cathode under realistic operating conditions; and (5) to validate the long term stability of the modified LSCF cathode in commercially available cells under realistic operating conditions. We have systematically evaluated LSCF cathodes in symmetrical cells and anode supported cells under realistic conditions with different types of contaminants such as humidity, CO2, and Cr. Electrochemical models for the design of test cells and understanding of mechanisms have been developed for the exploration of fundamental properties of electrode materials. It is demonstrated that the activity and stability of LSCF cathodes can be degraded by the introduction of contaminants. The microstructural and compositional evolution of LSCF

  11. Methods and apparatuses for making cathodes for high-temperature, rechargeable batteries

    Science.gov (United States)

    Meinhardt, Kerry D; Sprenkle, Vincent L; Coffey, Gregory W

    2014-05-20

    The approaches for fabricating cathodes can be adapted to improve control over cathode composition and to better accommodate batteries of any shape and their assembly. For example, a first solid having an alkali metal halide, a second solid having a transition metal, and a third solid having an alkali metal aluminum halide are combined into a mixture. The mixture can be heated in a vacuum to a temperature that is greater than or equal to the melting point of the third solid. When the third solid is substantially molten liquid, the mixture is compressed into a desired cathode shape and then cooled to solidify the mixture in the desired cathode shape.

  12. Simulations of multipacting in the cathode stalk and FPC of 112 MHz superconducting electron gun

    Energy Technology Data Exchange (ETDEWEB)

    Xin T.; Ben-Zvi, I.; Belomestnykh, S.; Chang, X.; Rao, T.; Skaritka, J.; Wu, Q.; Wang, E.; Liang, X.

    2012-05-20

    A 112 MHz superconducting quarter-wave resonator electron gun will be used as the injector of the Coherent Electron Cooling (CEC) proof-of-principle experiment at BNL. Furthermore, this electron gun can be used for testing of the performance of various high quantum efficiency photocathodes. In a previous paper, we presented the design of the cathode stalks and a Fundamental Power Coupler (FPC). In this paper we present updated designs of the cathode stalk and FPC. Multipacting in the cathode stalk and FPC was simulated using three different codes. All simulation results show no serious multipacting in the cathode stalk and FPC.

  13. Non-local model of hollow cathode and glow discharge - theory calculations and experiment comparison

    OpenAIRE

    Gorin, Vladimir V.

    2009-01-01

    General form of the non-local equation for an ionization source in glow discharge and hollow cathode 3D-simulation is formulated. It is a fundamental equation in a hollow cathode theory, which allows to make up a complete set of field equations for a self-consistent problem in a stationary glow discharge and a hollow cathode. It enables to describe adequately the region of negative glow and the hollow cathode effect. Here you can see first attempts to compare calculation results of electrical...

  14. Preliminary investigation of an improved metal-dielectric cathode for magnetically insulated transmission line oscillator

    International Nuclear Information System (INIS)

    In order to explore the cathode with good repetition quality for the magnetically insulated transmission line oscillators, an improved metal-dielectric cathode is proposed and investigated experimentally. The cathode is designed to be step-like shape, and thin copper plated boards are periodically and compactly arrayed on the surface of the cathode base, which ensures the uniformity of the electrons emitted from the cusps of the copper plated boards. According to the numerical simulation results, the step-like shape is beneficial to convert the kinetic energy of the magnetic insulating current partially and enhance the beam-wave interaction efficiency. Finally, a preliminary experiment of an L-band magnetically insulated transmission line oscillator (MILO) with the improved metal-dielectric cathode is carried out. A high power microwave (HPM) with an average power of 1.95 GW is generated from the MILO, with an efficiency of 13.5%. Under the same experiment condition, the output power and main frequency with the presented cathode are almost the same to those with the velvet cathode. Apart from that, metal-dielectric cathode has the merits of small outgassing and long lifetime, and all of these make the improved metal-dielectric cathode significantly promising for the MILO repetition operation

  15. The electrolysis of actinide chloride by a solid cathode surrounded with a ceramic container

    International Nuclear Information System (INIS)

    In Korea, the studies on partitioning have been focused on the development of a pyro-processing based on an electrorefining of actinides as it is a kind of proliferation-resistive technology, wherein all the transuranic metals are separated together as a mixture. Electrorefining is a key pyro-processing technology and is generally composed of two recovery steps deposit of uranium onto a solid cathode and the recovery of actinide elements by a liquid cadmium cathode. The liquid cadmium cathode has some disadvantages such as a cadmium volatilization and a complicated structure. The solid cathode could replace a liquid cadmium cathode if the detachment problem of the cathode deposit is solved. In this study, a solid cathode surrounded by a perforated ceramic container was employed and tested during the electrorefining experiments. Several anode materials including metal oxide were compared by the potential-current relation and their behaviour during the uranium deposition experiments. It was found that the solid cathode used in this study could be a potential candidate for replacing a liquid cadmium cathode. (authors)

  16. Synthesis and electrochemical characterization of pure and composite cathode materials for solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Sun, L.; Favreau-Perreault, M.; Brisard, G. [Universite de Sherbrooke, Departement de Chimie, Sherbrooke, PQ (Canada)

    2004-10-01

    A rare earth cathode composed of various combinations of lanthanum, strontium, copper, iron oxide, cesium and gadolinium oxide was synthesized by using glycine-nitrate combustion techniques, and the Pechini method. Pure and composite complexes composed of these same materials were used to synthesize eight mol per cent yttria-stabilized zirconia cathodes by scanning electron microscopy. Cathode resistances were evaluated by electrochemical impedance spectroscopy and galvanostatic current interruption techniques. Both techniques were found to give identical results in evaluating the total polarization resistance of the cathodes. 24 refs., 2 tabs., 9 figs.

  17. Multi-variable mathematical models for the air-cathode microbial fuel cell system

    Science.gov (United States)

    Ou, Shiqi; Kashima, Hiroyuki; Aaron, Douglas S.; Regan, John M.; Mench, Matthew M.

    2016-05-01

    This research adopted the version control system into the model construction for the single chamber air-cathode microbial fuel cell (MFC) system, to understand the interrelation of biological, chemical, and electrochemical reactions. The anodic steady state model was used to consider the chemical species diffusion and electric migration influence to the MFC performance. In the cathodic steady state model, the mass transport and reactions in a multi-layer, abiotic cathode and multi-bacteria cathode biofilm were simulated. Transport of hydroxide was assumed for cathodic pH change. This assumption is an alternative to the typical notion of proton consumption during oxygen reduction to explain elevated cathode pH. The cathodic steady state model provided the power density and polarization curve performance results that can be compared to an experimental MFC system. Another aspect considered was the relative contributions of platinum catalyst and microbes on the cathode to the oxygen reduction reaction (ORR). Simulation results showed that the biocatalyst in a cathode that includes a Pt/C catalyst likely plays a minor role in ORR, contributing up to 8% of the total power calculated by the models.

  18. R and D of the gun cathode for the SPring-8 linac

    International Nuclear Information System (INIS)

    The SPring-8 linac has used Y-845 cathodes (Eimac/CPI) as an electron gun cathode. However, its cathode emission current is not sufficient in some cases. We therefor started the development of a new type cathode for reinforcement of the emission current and for reduction of the grid emission current which increases along with the heater-on time. The target in terms of the cathode emission is to double that of Y-845. To produce a solid and reliable cathode, a thin metal plate with honeycomb etched holes was adopted as a grid mesh instead of a traditional wire mesh. Because the aperture ratio of such an etched plate is lower than that of a wire mesh, we decided to employ the cathode disk which has honeycomb micro dimples on its surface forming focused multi electron beams with the aligned grid plate to result in a very high beam transmission rate. The first test of the cathode assembly, whose cathode disk has the micro-dimple array structure, presented that the emission of 13 A was obtained. The detail of the development and the first test will be reported in this paper. (author)

  19. Realization of limited-area cathodes and their performance in an electron optical column

    International Nuclear Information System (INIS)

    Limited-area cathodes based upon impregnated dispenser cathod material have been investigated in an electron optical column at accelerating voltages of up to 30 kV. A peak axial brightness of about 6 X 105 A/cm2 sr was obtained at this voltage using a flat cathode. Brightness values greater by a factor of 10 were measured using a conical limited-area cathode with a tip radius of curvature of 0.075 mm. The latter measurements were affected by space-charge spreading in the beam. 7 refs., 6 figs., 1 tab

  20. Development and evaluation of carbon and binder loading in low-cost activated carbon cathodes for air-cathode microbial fuel cells

    KAUST Repository

    Wei, Bin

    2012-01-01

    Activated carbon (AC) air cathodes were constructed using variable amounts of carbon (43-171 mg cm-2) and an inexpensive binder (10 wt% polytetrafluoroethylene, PTFE), and with or without a porous cloth wipe-based diffusion layer (DL) that was sealed with PDMS. The cathodes with the highest AC loading of 171 mg cm-2, and no diffusion layer, produced 1255 ± 75 mW m-2 and did not appreciably vary in performance after 1.5 months of operation. Slightly higher power densities were initially obtained using 100 mg cm-2 of AC (1310 ± 70 mW m-2) and a PDMS/wipe diffusion layer, although the performance of this cathode decreased to 1050 ± 70 mW m-2 after 1.5 months, and 1010 ± 190 mW m-2 after 5 months. AC loadings of 43 mg cm-2 and 100 mg cm-2 did not appreciably affect performance (with diffusion layers). MFCs with the Pt catalyst and Nafion binder initially produced 1295 ± 13 mW m-2, but the performance decreased to 930 ± 50 mW m -2 after 1.5 months, and then to 890 ± 20 mW m-2 after 5 months. Cathode performance was optimized for all cathodes by using the least amount of PTFE binder (10%, in tests using up to 40%). These results provide a method to construct cathodes for MFCs that use only inexpensive AC and a PTFE, while producing power densities similar to those of Pt/C cathodes. The methods used here to make these cathodes will enable further tests on carbon materials in order to optimize and extend the lifetime of AC cathodes in MFCs. © 2012 The Royal Society of Chemistry.

  1. Ab initio investigation of the surface properties of dispenser B-type and scandate thermionic emission cathodes

    Science.gov (United States)

    Vlahos, Vasilios; Lee, Yueh-Lin; Booske, John H.; Morgan, Dane; Turek, Ladislav; Kirshner, Mark; Kowalczyk, Richard; Wilsen, Craig

    2009-05-01

    Scandate cathodes (BaxScyOz on W) are important thermionic electron emission materials whose emission mechanism remains unclear. Ab initio modeling is used to investigate the surface properties of both scandate and traditional B-type (Ba-O on W) cathodes. We demonstrate that the Ba-O dipole surface structure believed to be present in active B-type cathodes is not thermodynamically stable, suggesting that a nonequilibrium steady state dominates the active cathode's surface structure. We identify a stable, low work function BaxScyOz surface structure, which may be responsible for some scandate cathode properties and demonstrate that multicomponent surface coatings can lower cathode work functions.

  2. Advanced Measurement and Modeling Techniques for Improved SOFC Cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Stuart Adler; L. Dunyushkina; S. Huff; Y. Lu; J. Wilson

    2006-12-31

    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.

  3. Physics of Plasma Cathode Current Injection During LHI

    Science.gov (United States)

    Hinson, E. T.; Barr, J.; Bongard, M.; Burke, M. G.; Fonck, R.; Perry, J.

    2015-11-01

    Localized helicity injection (LHI) ST startup employs current sources at the tokamak edge. Max Ip in LHI scales with injection voltage Vinj, requiring an understanding of injector impedance. For the arc-plasma cathode electron injectors in Pegasus, impedance is plasma-determined, and typically Vinj>1kV for Iinj = 2kA. At low Iinj, Iinj Vinj3 / 2 , an indication of a double layer (DL) common to such devices. However, at Iinj> 1kA, Iinj Vinj1 / 2 occurs, a scaling expected for limited launched beam density, nb ≡Iinj / (e√{ 2eVinj /me }Ainj) Iinj /Vinj1 / 2 . An ohmic discharge injection target was created to test this hypothesis. Langmuir probe data showed Iinj/Vinj1 / 2 nedge at low nedge, consistent with a limit (nedge >=ne , b) imposed by quasineutrality. If edge fueling maintained nedge >=ne , b , spectroscopic measurements of source density narc indicated Iinj/Vinj1 / 2 narc , as expected from DL expansion. Thus nb established by narc or nedge determines Vinj up to the onset of cathode spot (CS) arcing. Technology development has increased obtainable Vinj and reduced CS damage using new ring shielding and a cathode design drawing CS's away from insulators. This involved a novel optimization of conical frustum geometry. Finally, consistent with NIMROD predictions of coherent streams in the edge during LHI, pairwise triangulation of outboard Mirnov data assuming beam m =1 motion has allowed an estimate of beam R(t), Z(t) location that is near the injector R, and consistent across the array. Supported by U.S. DOE Grant DE-FG02-96ER54375.

  4. Element- and charge-state-resolved ion energies in the cathodic arc plasma from composite AlCr cathodes in argon, nitrogen and oxygen atmospheres

    OpenAIRE

    Franz, Robert; Polcik, Peter; Anders, André

    2014-01-01

    The energy distribution functions of ions in the cathodic arc plasma using composite AlCr cathodes were measured as a function of the background gas pressure in the range 0.5 to 3.5 Pa for different cathode compositions and gas atmospheres. The most abundant aluminium ions were Al$^{+}$ regardless of the background gas species, whereas Cr$^{2+}$ ions were dominating in Ar and N$_2$ and Cr$^{+}$ in O$_2$ atmospheres. The energy distributions of the aluminium and chromium ions typically consist...

  5. Electrochemistry of metal chloride cathodes in sodium batteries

    Science.gov (United States)

    Ratnakumar, B. V.; Di Stefano, S.; Halpert, G.

    1990-01-01

    Fundamental electrochemical studies on three candidate materials, i.e., FeCl2, NiCl2, and CuCl2, were carried out using various techniques, such as cyclic voltammetry, linear polarization, potentiodynamic polarization, and ac impedance. These studies were aimed at identifying various rate processes in the reduction, elucidating the reaction mechanisms, and determining the kinetic parameters for the reduction. The limitations in the performance of these cathode materials in high power density applications were also examined. Finally, recommendations were made from these studies for the selection of a candidate system among these materials for future NASA applications.

  6. Large CMS cathode strip chambers: design and performance

    International Nuclear Information System (INIS)

    Presented are the main design features of the large Cathode Strip Chambers (CSCs) for the CMS Endcap Muon System as well as the performance results obtained with the two full-scale 3.4x1.5 m2 six-plane prototypes. The prototype performance was within the baseline requirements: (a) higher than 99% efficiency of muon track finding at the trigger level with more than 92% probability for bunch crossing identification and better than 2 mm spatial resolution, and (b) better than 150 μm spatial resolution in off-line

  7. Synthesis of tin oxide nanoparticle film by cathodic electrodeposition.

    Science.gov (United States)

    Kim, Seok; Lee, Hochun; Park, Chang Min; Jung, Yongju

    2012-02-01

    Three-dimensional SnO2 nanoparticle films were deposited onto a copper substrate by cathodic electrodeposition in a nitric acid solution. A new formation mechanism for SnO2 films is proposed based on the oxidation of Sn2+ ion to Sn4+ ion by NO+ ion and the hydrolysis of Sn4+. The particle size of SnO2 was controlled by deposition potential. The SnO2 showed excellent charge capacity (729 mAh/g) at a 0.2 C rate and high rate capability (460 mAh/g) at a 5 C rate. PMID:22630013

  8. Performance of the CMS Cathode Strip Chambers with Cosmic Rays

    CERN Document Server

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Bendavid, J; Busza, W; Butz, E; Cali, I A; Chan, M; D'Enterria, D; Everaerts, P; Gomez Ceballos, G; Hahn, K A; Harris, P; Jaditz, S; Kim, Y; Klute, M; Lee, Y J; Li, W; Loizides, C; Ma, T; Miller, M; Nahn, S; Paus, C; Roland, C; Roland, G; Rudolph, M; Stephans, G; Sumorok, K; Sung, K; Vaurynovich, S; Wenger, E A; Wyslouch, B; Xie, S; Yilmaz, Y; Yoon, A S; Bailleux, D; Cooper, S I; Cushman, P; Dahmes, B; De Benedetti, A; Dolgopolov, A; Dudero, P R; Egeland, R; Franzoni, G; Haupt, J; Inyakin, A; Klapoetke, K; Kubota, Y; Mans, J; Mirman, N; Petyt, D; Rekovic, V; Rusack, R; Schroeder, M; Singovsky, A; Zhang, J; Cremaldi, L M; Godang, R; Kroeger, R; Perera, L; Rahmat, R; Sanders, D A; Sonnek, P; Summers, D; Bloom, K; Bockelman, B; Bose, S; Butt, J; Claes, D R; Dominguez, A; Eads, M; Keller, J; Kelly, T; Kravchenko, I; Lazo-Flores, J; Lundstedt, C; Malbouisson, H; Malik, S; Snow, G R; Baur, U; Iashvili, I; Kharchilava, A; Kumar, A; Smith, K; Strang, M; Alverson, G; Barberis, E; Boeriu, O; Eulisse, G; Govi, G; McCauley, T; Musienko, Y; Muzaffar, S; Osborne, I; Paul, T; Reucroft, S; Swain, J; Taylor, L; Tuura, L; Anastassov, A; Gobbi, B; Kubik, A; Ofierzynski, R A; Pozdnyakov, A; Schmitt, M; Stoynev, S; Velasco, M; Won, S; Antonelli, L; Berry, D; Hildreth, M; Jessop, C; Karmgard, D J; Kolberg, T; Lannon, K; Lynch, S; Marinelli, N; Morse, D M; Ruchti, R; Slaunwhite, J; Warchol, J; Wayne, M; Bylsma, B; Durkin, L S; Gilmore, J; Gu, J; Killewald, P; Ling, T Y; Williams, G; Adam, N; Berry, E; Elmer, P; Garmash, A; Gerbaudo, D; Halyo, V; Hunt, A; Jones, J; Laird, E; Marlow, D; Medvedeva, T; Mooney, M; Olsen, J; Piroué, P; Stickland, D; Tully, C; Werner, J S; Wildish, T; Xie, Z; Zuranski, A; Acosta, J G; Bonnett Del Alamo, M; Huang, X T; Lopez, A; Mendez, H; Oliveros, S; Ramirez Vargas, J E; Santacruz, N; Zatzerklyany, A; Alagoz, E; Antillon, E; Barnes, V E; Bolla, G; Bortoletto, D; Everett, A; Garfinkel, A F; Gecse, Z; Gutay, L; Ippolito, N; Jones, M; Koybasi, O; Laasanen, A T; Leonardo, N; Liu, C; Maroussov, V; Merkel, P; Miller, D H; Neumeister, N; Sedov, A; Shipsey, I; Yoo, H D; Zheng, Y; Jindal, P; Parashar, N; Cuplov, V; Ecklund, K M; Geurts, F J M; Liu, J H; Maronde, D; Matveev, M; Padley, B P; Redjimi, R; Roberts, J; Sabbatini, L; Tumanov, A; Betchart, B; Bodek, A; Budd, H; Chung, Y S; de Barbaro, P; Demina, R; Flacher, H; Gotra, Y; Harel, A; Korjenevski, S; Miner, D C; Orbaker, D; Petrillo, G; Vishnevskiy, D; Zielinski, M; Bhatti, A; Demortier, L; Goulianos, K; Hatakeyama, K; Lungu, G; Mesropian, C; Yan, M; Atramentov, O; Bartz, E; Gershtein, Y; Halkiadakis, E; Hits, D; Lath, A; Rose, K; Schnetzer, S; Somalwar, S; Stone, R; Thomas, S; Watts, T L; Cerizza, G; Hollingsworth, M; Spanier, S; Yang, Z C; York, A; Asaadi, J; Aurisano, A; Eusebi, R; Golyash, A; Gurrola, A; Kamon, T; Nguyen, C N; Pivarski, J; Safonov, A; Sengupta, S; Toback, D; Weinberger, M; Akchurin, N; Berntzon, L; Gumus, K; Jeong, C; Kim, H; Lee, S W; Popescu, S; Roh, Y; Sill, A; Volobouev, I; Washington, E; Wigmans, R; Yazgan, E; Engh, D; Florez, C; Johns, W; Pathak, S; Sheldon, P; Andelin, D; Arenton, M W; Balazs, M; Boutle, S; Buehler, M; Conetti, S; Cox, B; Hirosky, R; Ledovskoy, A; Neu, C; Phillips II, D; Ronquest, M; Yohay, R; Gollapinni, S; Gunthoti, K; Harr, R; Karchin, P E; Mattson, M; Sakharov, A; Anderson, M; Bachtis, M; Bellinger, J N; Carlsmith, D; Crotty, I; Dasu, S; Dutta, S; Efron, J; Feyzi, F; Flood, K; Gray, L; Grogg, K S; Grothe, M; Hall-Wilton, R; Jaworski, M; Klabbers, P; Klukas, J; Lanaro, A; Lazaridis, C; Leonard, J; Loveless, R; Magrans de Abril, M; Mohapatra, A; Ott, G; Polese, G; Reeder, D; Savin, A; Smith, W H; Sourkov, A; Swanson, J; Weinberg, M; Wenman, D; Wensveen, M; White, A

    2010-01-01

    The Cathode Strip Chambers (CSCs) constitute the primary muon tracking device in the CMS endcaps. Their performance has been evaluated using data taken during a cosmic ray run in fall 2008. Measured noise levels are low, with the number of noisy channels well below 1%. Coordinate resolution was measured for all types of chambers, and fall in the range 47 microns to 243 microns. The efficiencies for local charged track triggers, for hit and for segments reconstruction were measured, and are above 99%. The timing resolution per layer is approximately 5 ns.

  9. Excimer emission from pulsed microhollow cathode discharges in xenon

    OpenAIRE

    Lee, B.-J.; Rahman, H.; Nam, S. H.; Iberler, M.; J. Jacoby; Frank, Klaus

    2014-01-01

    Direct current (dc) microhollow cathode discharge (MHCD) is an intense source for excimer radiation in vacuum ultraviolet at a wavelength of 172 nm in a high pressure xenon (Xe) gas. The concentration of precursors for the excimer formation, i.e., excited and ionized gas atoms, increases significantly by applying high voltage pulse onto the dc MHCD over the pulse duration range from 20 to 100 ns. The intensity of the excimer emission for the voltage pulse of 20 ns duration exceeds that of the...

  10. Synthesis, Characterization and Performance of Cathodes for Lithium Ion Batteries

    OpenAIRE

    Zhu, Jianxin

    2014-01-01

    Lithium ion batteries provide a high energy density, higher voltage as well as a long shelf life compared to traditionally used lead acid, NiMH and NiCd batteries. Thus, they are a very promising energy storage system for our daily life. As one of the most important components in a battery, cathode materials have been investigated intensively in recent years as they play a key role in determining the cell voltage and discharge capacity in a battery. Both layered Li(Ni1/3Co1/3Mn1/3)O2 (NCM) an...

  11. Corrosion induced by cathodic hydrogen in 2205 duplex stainless steel

    Science.gov (United States)

    Michalska, J.

    2011-05-01

    In this work new results about the influence of cathodic hydrogen on passivity and corrosion resistance of 2205 duplex stainless steel are described. The results were discussed by taking into account hydrogen charged samples and without hydrogen. The corrosion resistance to pitting was qualified with the polarization curves. The conclusion is that, hydrogen deteriorated the passive film stability and corrosion resistance to pitting of 2205 duplex stainless steel. The presence of hydrogen in passive films increases corrosion current density and decreases the potential of the film breakdown. It was also found that degree of susceptibility to hydrogen action was dependent on the hydrogen charging conditions.

  12. Corrosion induced by cathodic hydrogen in 2205 duplex stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Michalska, J, E-mail: joanna.k.michalska@polsl.pl [Department of Materials Science, Silesian University of Technology, Krasinskiego 8, 40-019 Katowice (Poland)

    2011-05-15

    In this work new results about the influence of cathodic hydrogen on passivity and corrosion resistance of 2205 duplex stainless steel are described. The results were discussed by taking into account hydrogen charged samples and without hydrogen. The corrosion resistance to pitting was qualified with the polarization curves. The conclusion is that, hydrogen deteriorated the passive film stability and corrosion resistance to pitting of 2205 duplex stainless steel. The presence of hydrogen in passive films increases corrosion current density and decreases the potential of the film breakdown. It was also found that degree of susceptibility to hydrogen action was dependent on the hydrogen charging conditions.

  13. Central tracking chamber with inflated cathode-strip foils

    Energy Technology Data Exchange (ETDEWEB)

    Blackmore, E.W.; Bryman, D.A.; Kuno, Y.; Lim, C.; Numao, T.; Padley, P.; Redlinger, G.; Soluk, R. [TRIUMF, Vancouver, BC (Canada); McPherson, R.A. [Joseph Henry Laboratories, Princeton University, Princeton, NJ 08544 (United States)

    1998-02-21

    A new cylindrical low-mass central drift chamber has been constructed for the K{sup +}{yields}{pi}{sup +}{nu} anti {nu} experiment at BNL (E787). The chamber consists of twelve layers of axial wire cells and six layers of thin cathode-strip foils, four of which are supported by differential gas pressure. The momentum resolution (RMS) for muons and pions in the range 150-250 MeV/c is found to be about 0.9%. (orig.). 16 refs.

  14. Fabrication of sacrificial anode cathodic protection through casting method

    International Nuclear Information System (INIS)

    Aluminum is one of the few metals that can be cast by all of the processes used in casting metals. These processes consist of die casting, permanent mold casting, sand casting (green sand and dry sand), plaster casting, investment casting, and continuous casting. Other processes such as lost foam, squeeze casting, and hot isostatic pressing are also used. Permanent mold casting method was selected in which used for fabricating of sacrificial anode cathodic protection. This product was ground for surface finished and fabricated in the cylindrical form and reinforced with carbon steel at a center of the anode. (Author)

  15. A thrust balance for low power hollow cathode thrusters

    International Nuclear Information System (INIS)

    A hanging thrust balance has been designed, manufactured and tested at the University of Southampton. The current design allows for direct steady thrust measurements ranging from 0.1 to 3 mN but this can be easily extended to measure thrust in a different range. Moreover the chosen balance design and the thrust measurement procedure allow for the cancellation of thermal drifts. The thrust balance was tested with a T6 hollow cathode thruster providing measurements with an uncertainty of about 9.7%. The thrust data were compared to those obtained with another direct thrust balance and they are in quantitative agreement—the maximum difference being only 6%. (paper)

  16. Petroleum porphyrins as electrocatalysts for cathodic oxygen reduction

    International Nuclear Information System (INIS)

    This paper examines the possibilities for obtaining active catalysts for cathodic oxygen reduction by subjecting concentrates of vanadyl porphyrins (VONP) extracted from crude oils with dimethylformamide and then purified chromatographically on aluminum oxide and silica gel to pyrolysis on carbon. Data obtained with synthetic vanadyl tetra(nmethoxyphenyl)porphyrin (VOTMPP) are reported for comparison. It is shown that VONP-1 and VONP-3 containing more than 80 wt.% of VONP are sufficiently active catalysts for O2 reduction in alkaline solution. The lower activity of VONP-2 is evidently due to its higher impurity content. Natural vanadyl porphyrins promise to be useful as electrocatalysts of the oxygen reaction in alkaline media

  17. Oscillating virtual cathode, large-orbit gyrotron and driver

    Energy Technology Data Exchange (ETDEWEB)

    VanHaaften, F.W.; Hoeberling, R.F.; Fazio, M.V.

    1986-01-01

    Studies using an oscillating virtual cathode (vircator) and a large-orbit gyrotron to generate microwave levels of several hundred megawatts are being conducted at the Los Alamos National Laboratory (LANL). A pulse level of approx.1 MV, with length approaching 1 ..mu..s at a repetition rate of a few hertz, is anticipated for extension of these studies from the present single-shot mode with 100-ns pulse width. The increased pulse width is needed to test longer pulse length microwave sources. Pulse forming network (PFN), transformer-coupled drivers have been studied and are part of the subject of this paper. The large-orbit gyrotron is discussed here.

  18. Studies on niobium triselenide cathode material for lithium rechargeable cells

    Science.gov (United States)

    Ratnakumar, B. V.; Ni, C. L.; Distefano, S.; Somoano, R. B.; Bankston, C. P.

    1988-01-01

    NbSe3 exhibits superior characteristics such as high capacity, high volumetric and gravimetric energy densities, and high discharge rate capability, as compared to other intercalating cathodes. This paper reports the preparation, characterization, and performance of NbSe3. Several electrochemical techniques, such as cyclic voltammetry, constant-current/constant-potential discharges, dc potentiodynamic scans, ac impedance, and ac voltammetry, have been used to give insight to the mechanisms of intercalation of three lithiums with NbSe3 and also into the rate determining process in the reduction of NbSe3.

  19. New secondary batteries utilizing electronically conductive polymer cathodes

    Science.gov (United States)

    Martin, Charles R.; White, Ralph E.

    1989-01-01

    The objectives of this project are to characterize the transport properties in electronically conductive polymers and to assess the utility of these films as cathodes in lithium/polymer secondary batteries. During this research period, progress has been made in a literature survey of the historical background, methods of preparation, the physical and chemical properties, and potential technological applications of polythiophene. Progress has also been made in the characterization of polypyrrole flat films and fibrillar films. Cyclic voltammetry and potential step chronocoulometry were used to gain information on peak currents and potentials switching reaction rates, charge capacity, and charge retention. Battery charge/discharge studies were also performed.

  20. Field electron emission from pencil-drawn cold cathodes

    Science.gov (United States)

    Chen, Jiangtao; Yang, Bingjun; Liu, Xiahui; Yang, Juan; Yan, Xingbin

    2016-05-01

    Field electron emitters with flat, curved, and linear profiles are fabricated on flexible copy papers by direct pencil-drawing method. This one-step method is free of many restricted conditions such as high-temperature, high vacuum, organic solvents, and multistep. The cold cathodes display good field emission performance and achieve high emission current density of 78 mA/cm2 at an electric field of 3.73 V/μm. The approach proposed here would bring a rapid, low-cost, and eco-friendly route to fabricate but not limited to flexible field emitter devices.

  1. Use of Both Anode and Cathode Reactions in Wastewater Treatment

    Science.gov (United States)

    Brillas, Enric; Sirés, Ignasi; Cabot, Pere LluíS.

    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

  2. Cathodic protection design of seawater pump by boundary element analysis

    International Nuclear Information System (INIS)

    A three-dimensional boundary element method (3D-BEM) was developed to quantitatively estimate cathodic protection and macro-cell corrosion. To confirm the validity and usefulness of the BEM for analysis of fluid machines handling seawater with complex 3D fields, experiments and analyses were performed. A cast iron vertical pump, with Zn anodes for cathodic protection, was submerged in seawater and operated. Potential distributions inside the pump and anodic currents on the Zn anodes were measured. The polarization curves of the pump material were measured as functions of flow rate, time and temperature, and the polarization characteristics were applied as boundary conditions in performing BEM analysis. Through analyses and experimental work, the following conclusions were obtained. By means of appropriate modelling that takes account of the symmetry of the object being analyzed, it is possible to apply the BEM effectively to corrosion problems of machines with complex 3D fields. Furthermore, extremely high accurate analysis on potential and current density distributions can be performed for fluid machines handling seawater, by precisely ascertaining the dependency of polarization curves on flow rate, time and temperature, and reflecting these dependencies in the boundary conditions. (author)

  3. VOCl as a Cathode for Rechargeable Chloride Ion Batteries.

    Science.gov (United States)

    Gao, Ping; Reddy, M Anji; Mu, Xiaoke; Diemant, Thomas; Zhang, Le; Zhao-Karger, Zhirong; Chakravadhanula, Venkata Sai Kiran; Clemens, Oliver; Behm, R Jürgen; Fichtner, Maximilian

    2016-03-18

    A novel room temperature rechargeable battery with VOCl cathode, lithium anode, and chloride ion transporting liquid electrolyte is described. The cell is based on the reversible transfer of chloride ions between the two electrodes. The VOCl cathode delivered an initial discharge capacity of 189 mAh g(-1) . A reversible capacity of 113 mAh g(-1) was retained even after 100 cycles when cycled at a high current density of 522 mA g(-1) . Such high cycling stability was achieved in chloride ion batteries for the first time, demonstrating the practicality of the system beyond a proof of concept model. The electrochemical reaction mechanism of the VOCl electrode in the chloride ion cell was investigated in detail by ex situ X-ray diffraction (XRD), infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The results confirm reversible deintercalation-intercalation of chloride ions in the VOCl electrode. PMID:26924132

  4. Cathodic Protection of Pipeline Using Distributed Control System

    Directory of Open Access Journals (Sweden)

    Gopalakrishnan Jayapalan

    2014-01-01

    Full Text Available Distributed control system (DCS is available in most of the compressor stations of cross-country pipeline systems. Programmable logic controller (PLC is used in all the intermediate pigging (IP stations/sectional valve (SV stations to collect the field data and to control the remote actuated valves. This paper presents how DCS or PLC can be used for cathodic protection of gas pipelines. Virtual instrumentation (VI software is used here for simulation and real-time implementation purpose. Analog input channels available in DCS/PLC can be used to measure pipe to soil potential (PSP with the help of half-cell and voltage transducer. Logic blocks available in DCS can be used as low selector switch to select the lowest PSP. Proportional-integral (PI controller available in DCS/PLC can be used for taking the controlling action. PI controller output varies the firing angle of AC phase controller. Phase controller output is rectified, filtered, and fed to the pipeline as cathodic protection current. Proposed scheme utilizes existing infrastructure to control pipeline corrosion.

  5. Realisation of 50% quantum efficiency from photomultiplier cathodes

    International Nuclear Information System (INIS)

    Standard trialkali red sensitive photomultiplier (PM) tubes have cathode quantum efficiencies which typically fall from ∼25% at 400 nm to ∼1% at 800 nm, partly because the material has lower optical absorption coefficients at long wavelengths. Increasing cathode thickness benefits long wavelength response but overall reduces electron extraction efficiency. In the present work modelling of the interaction of light within the dielectric materials of the windows indicates that considerably greater quantum efficiency (QE) is feasible under a variety of conditions. Some of these possibilities have been explored with standard PM tubes giving data where the blue response is increased by a factor of 2, to ∼50%. Much higher improvement factors, of more than 10 times, are realised at longer wavelengths. Current work suggests that the enhancement methods can be exploited further, and at least 50% performance obtained across most of the range of spectral response. A secondary feature of the enhancement is that the useful operating range of the tube is extended further into the near infrared

  6. Methods for batch fabrication of cold cathode vacuum switch tubes

    Science.gov (United States)

    Walker, Charles A.; Trowbridge, Frank R.

    2011-05-10

    Methods are disclosed for batch fabrication of vacuum switch tubes that reduce manufacturing costs and improve tube to tube uniformity. The disclosed methods comprise creating a stacked assembly of layers containing a plurality of adjacently spaced switch tube sub-assemblies aligned and registered through common layers. The layers include trigger electrode layer, cathode layer including a metallic support/contact with graphite cathode inserts, trigger probe sub-assembly layer, ceramic (e.g. tube body) insulator layer, and metallic anode sub-assembly layer. Braze alloy layers are incorporated into the stacked assembly of layers, and can include active metal braze alloys or direct braze alloys, to eliminate costs associated with traditional metallization of the ceramic insulator layers. The entire stacked assembly is then heated to braze/join/bond the stack-up into a cohesive body, after which individual switch tubes are singulated by methods such as sawing. The inventive methods provide for simultaneously fabricating a plurality of devices as opposed to traditional methods that rely on skilled craftsman to essentially hand build individual devices.

  7. Transparent white organic light emitting diodes with improved cathode transparency

    Science.gov (United States)

    Lee, Jeong-Ik; Lee, Jonghee; Lee, Joowon; Shin, Jae-Heon; Hwang, Chi-Sun; Chu, Hye Yong

    2009-08-01

    We have fabricated transparent white organic light emitting diode (WOLED) for lighting application based on a hybrid white OLED and a phosphorescence white OLED. For the hybrid WOLED, a blue fluorescence emitting layer (FLEML) and green and red phosphorescence emitting layers (PH-EMLs) have been used in the device structure of ITO/hole transporting layer (HTL)/PH-EMLs/interlayer/FL-EML/ETL/LiF/Al. The balanced emissions from the FLEML and the PH-EMLs have been obtained by using appropriate carrier (hole) trapping effects in the PH-EMLs, which resulted in external and power efficiencies of 15 % and 27 lm/W, respectively, at a luminance of 1000 cd/m2 without any out-coupling enhancement. The Commission Internationale de L'Eclairage (CIE) coordinates of this hybrid WOLED is (0.43,0.44) with color rendering index (CRI) of 80 and correlated color temperature (CCT) of 3200 K, respectively, in the bottom emission structure. Based on this hybrid WOLED, we established highly efficient transparent WOLED by introduction of a transparent cathode, and obtained over 19 lm/W of power efficiency at a total luminance of 1000 cd/m2 as well as over 60 % of transmittance at 550 nm with the conventional glass encapsulation. Moreover, when the phosphorescent white OLED was combined with a transparent cathode, the power efficiency was reached up to 24 lm/W of power efficiency at a total luminance of 1000 cd/m2.

  8. Aberrations of the cathode objective lens up to fifth order

    Energy Technology Data Exchange (ETDEWEB)

    Tromp, R.M., E-mail: rtromp@us.ibm.com [Thomas J. Watson Research Center, IBM Research Division, 1101 Kitchawan Road, P.O. Box 218, Yorktown Heights, NY 10598 (United States); Leiden University, Kamerlingh Onnes Laboratorium, P.O. Box 9504, NL-2300 RA Leiden (Netherlands); Wan, W. [Ernest Orlando Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Mailstop 80R0114, Berkeley, CA 94720 (United States); Schramm, S.M. [Leiden University, Kamerlingh Onnes Laboratorium, P.O. Box 9504, NL-2300 RA Leiden (Netherlands)

    2012-08-15

    In this paper we discuss a topic that was close to Prof. Gertrude Rempfer s interests for many years. On this occasion of her 100th birthday, we remember and honor Gertrude for her many outstanding contributions, and for the inspiring example that she set. We derive theoretical expressions for the aberration coefficients of the uniform electrostatic field up to 5th order and compare these with raytracing calculations for the cathode lens used in Low Energy Electron Microscopy and Photo Electron Emission Microscopy experiments. These higher order aberration coefficients are of interest for aberration corrected experiments in which chromatic (C{sub c}) and spherical (C{sub 3}) aberrations of the microscope are set to zero. The theoretical predictions are in good agreement with the results of raytracing. Calculations of image resolution using the Contrast Transfer Function method show that sub-nanometer resolution is achievable in an aberration corrected LEEM system. -- Highlights: Black-Right-Pointing-Pointer A theory is presented for the aberrations of the uniform electrostatic field up to fifth order. Black-Right-Pointing-Pointer Such aberrations are important for advanced LEEM and PEEM instruments. Black-Right-Pointing-Pointer Good agreement between theory and raytracing results for a full cathode objective lens. Black-Right-Pointing-Pointer Contrast Transfer Function calculations predict that spatial resolution below 1 nm is achievable.

  9. Gadolinia-Doped Ceria Cathodes for Electrolysis of CO2

    Science.gov (United States)

    Adler, Stuart B.

    2009-01-01

    Gadolinia-doped ceria, or GDC, (Gd(0.4)Ce(0.6)O(2-delta), where the value of delta in this material varies, depending on the temperature and oxygen concentration in the atmosphere in which it is being used) has shown promise as a cathode material for high-temperature electrolysis of carbon dioxide in solid oxide electrolysis cells. The polarization resistance of a GDC electrode is significantly less than that of an otherwise equivalent electrode made of any of several other materials that are now in use or under consideration for use as cathodes for reduction of carbon dioxide. In addition, GDC shows no sign of deterioration under typical temperature and gas-mixture operating conditions of a high-temperature electrolyzer. Electrolysis of CO2 is of interest to NASA as a way of generating O2 from the CO2 in the Martian atmosphere. On Earth, a combination of electrolysis of CO2 and electrolysis of H2O might prove useful as a means of generating synthesis gas (syngas) from the exhaust gas of a coal- or natural-gas-fired power plant, thereby reducing the emission of CO2 into the atmosphere. The syngas a mixture of CO and H2 could be used as a raw material in the manufacture, via the Fisher-Tropsch process, of synthetic fuels, lubrication oils, and other hydrocarbon prod

  10. The Best Arc Heater Regime for Minimum Copper Cathode Erosion

    International Nuclear Information System (INIS)

    On the basis of the experimental investigations and simple theoretical model, which regards electrode erosion as ablation of the electrode material under the action of intensive heat fluxes in the arc spot, we give estimations of the range of operating regimes of copper cathode with the minimum erosion. We show, that application of a magnetic field for displacing of arc over the electrodes surface has a number of specific limitations from point of view of electrode erosion. These limitations are related with a variation in the energy parameters of the arc spot and heat transfer between electric arc and the electrodes under the variation of magnetic field. As a result, an optimal magnetic field exists, which is a function of an electrode temperature θ0 and derivative dθ/ds. Here θ0=T/Tf; Tf - melting point of electrode material; s = v/I0.5; v - arc velocity; I - current. We give here relationships and diagrams, which make it possible to evaluate the range of the operation of copper cathode with the minimum erosion

  11. Microbial fuel cell with an azo-dye-feeding cathode

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Liang [Chinese Academy of Sciences, Guangzhou (China). Guangzhou Inst. of Geochemistry; Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou (China). Guangdon Key Lab. of Agricultural Environment Pollution Integrated Control; Graduate Univ. of Chinese Academy of Sciences, Beijing (China); Li, Fang-bai [Guangdong Institute of Eco-Environmental and Soil Sciences, Guangzhou (China). Guangdon Key Lab. of Agricultural Environment Pollution Integrated Control; Feng, Chun-hua [South China Univ. of Technology, Guangzhou (China). School of Chemistry and Chemical Engineering; Li, Xiang-zhong [Hong Kong Polytechnic Univ., Hong Kong (China). Dept. of Civil and Structural Engineering

    2009-11-15

    Microbial fuel cells (MFCs) were constructed using azo dyes as the cathode oxidants to accept the electrons produced from the respiration of Klebsiella pneumoniae strain L17 in the anode. Experimental results showed that a methyl orange (MO)-feeding MFC produced a comparable performance against that of an air-based one at pH 3.0 and that azo dyes including MO, Orange I, and Orange II could be successfully degraded in such cathodes. The reaction rate constant ({kappa}) of azo dye reduction was positively correlated with the power output which was highly dependent on the catholyte pH and the dye molecular structure. When pH was varied from 3.0 to 9.0, the k value in relation to MO degradation decreased from 0.298 to 0.016 {mu}mol min{sup -1}, and the maximum power density decreased from 34.77 to 1.51 mW m{sup -2}. The performances of the MFC fed with different azo dyes can be ranked from good to poor as MO > Orange I > Orange II. Furthermore, the cyclic voltammograms of azo dyes disclosed that the pH and the dye structure determined their redox potentials. A higher redox potential corresponded to a higher reaction rate. (orig.)

  12. Theoretical study of cathode surfaces and high-temperature superconductors

    Science.gov (United States)

    Mueller, Wolfgang

    1995-01-01

    Calculations are presented for the work functions of BaO on W, Os, Pt, and alloys of Re-W, Os-W, and Ir-W that are in excellent agreement with experiment. The observed emission enhancement for alloy relative to tungsten dispenser cathodes is attributed to properties of the substrate crystal structure and explained by the smaller depolarization of the surface dipole on hexagonal as compared to cubic substrates. For Ba and BaO on W(100), the geometry of the adsorbates has been determined by a comparison of inverse photoemission spectra with calculated densities of unoccupied states based on the fully relativistic embedded cluster approach. Results are also discussed for models of scandate cathodes and the electronic structure of oxygen on W(100) at room and elevated temperatures. A detailed comparison is made for the surface electronic structure of the high-temperature superconductor YBa2Cu3O7 as obtained with non-, quasi-, and fully relativistic cluster calculations.

  13. Electronic structure of BaO/W cathode surfaces

    Science.gov (United States)

    Muller, Wolfgang

    1989-01-01

    The local electronic structure of the emissive layer of barium dispenser thermionic cathodes is investigated theoretically using the relativistic scattered-wave approach. The interaction of Ba and O with W, Os, and W-Os alloy surfaces is studied with atomic clusters modeling different absorption environments representative of B- and M-type cathodes. Ba is found to be strongly oxidized, while O and the metal substrate are in a reduced chemical state. The presence of O enhances the surface dipole and Ba binding energy relative to Ba on W. Model results for W-Os alloy substrates show only relatively small changes in Ba and O for identical geometries, but very large charge redistributions inside the substrate, which are attributed to the electronegativity difference between Os and W. If Os is present in the surface layer, the charge transfer from Ba to the substrate and the Ba binding energy increase relative to W. Explanations are offered for the improved electron emission from alloy surfaces and the different emission enhancement for different alloy substrates.

  14. An investigation of energy balances in palladium cathode electrolysis experiments

    International Nuclear Information System (INIS)

    In recently publicized cold fusion experiments at the University of Utah, generation of excess heat was reported. To investigate mechanisms that may contribute to energy flows in electrolysis cells, a series of experiments was performed at the Idaho National Engineering Laboratory (INEL). Ordinary water (H2O), heavy water (D2O), and mixture of the two were used in the INEL experiments. Cathodes used include a 51-μm Pd foil and 1-mm diameter extruded wire Pd rods in two configurations. Energy balances in these experiments revealed that some of the required voltage to sustain a given current is due to irreversibilities associated with cell operation. Particularly significant are electrolyte resistance and activation energy polarization effects. Energy balances in the INEL experiments showed there was no significant net grain or net loss of energy. Cell overpotential curves were fit well with a Tafel equation, with parameters dependent on electrode configuration, electrolyte composition, and temperature. Water evaporation and interactions of hydrogen isotopes with the Pd cathode were evaluated and found not to be significant to energy balances. No ionizing radiation, tritium production, or other evidence of fusion reactions was seen in the INEL experiments. 4 refs., 6 figs., 2 tabs

  15. Production of neutron and tritium from D2O electrolysis with palladium cathode

    International Nuclear Information System (INIS)

    Anomalous neutron burst and an increase in tritium concentration were observed simultaneously from heavy water electrolysis with palladium cathode. Considered with previous experiment results, we presumed that production of neutron and tritium from D2O electrolysis depends heavily on the constitution and the state of each cathode. (author)

  16. Characterization of scandia doped pressed cathode fabricated by spray drying method

    International Nuclear Information System (INIS)

    Scandia doped pressed cathode was prepared by a new method of spray drying combined with two-step hydrogen reduction process. The Sc2O3 and barium-calcium aluminate co-doped powders have sub-micrometer size in the range of 0.1-1 μm and scandium oxide and barium-calcium aluminate are distributed evenly in the powders. The cathodes sintered by powder metallurgy at 1600 deg. Cb have a smooth surface and sub-micrometer grain structure with homogeneous distribution of scandium, barium, calcium and aluminum which are dispersed over and among the tungsten grains. This cathode has good emission, e.g., the current density of this cathode reaches 31.50 A/cm2 at 850 deg. Cb. After proper activation, the cathode surface is covered by a Ba-Sc-O active substances layer with a preferable atomic ratio, leading to its good emission property. The evaporation activation energy of SDP cathode with 4.58 eV is the highest among the Ba-W, M-type and SDP cathodes, and the average evaporation velocity vt of SDP cathode with 1.28 x 10-8 g cm-2 s-1 at 1150 deg. Cb is the lowest one.

  17. A Study on a Salt Clean-up with Solid Cathode- Perforated Ceramic Container

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, S.W.; You, Y.J.; Paek, S.W.; Kim, S.H.; Kim, K.R.; Shim, J.B.; Chung, H.; Ahn, D.H. [Korea Atomic Energy Research Institute, 150 Dukjin-dong, Yuseong, Daejeon 305-600 (Korea, Republic of)

    2008-07-01

    Electrorefining is a key technology of pyrochemical processing. The electrorefining is generally composed of two recovery steps: deposit of uranium onto a solid cathode and the recovery of actinide elements by a liquid cadmium cathode. After the operation of the liquid cadmium cathode, it is necessary to remove the remaining TRU (transuranic) elements from the molten salt before a treatment of waste salt or salt regeneration. In this study, we attempted to clean up a molten salt with a cathode of solid cathode-perforated ceramic container and a glassy carbon anode. LiCl-KCl eutectic salt was used as a medium of the electrolytic bath. Uranium and cerium were used as solutes, where uranium was used as a surrogate for the TRU elements. Initial contents of uranium and cerium in the salt were varied in the range of 0 to 5 wt. %. Electrolysis experiments were carried out by passing a constant current between the anode and the cathode at 500 deg. C. The solute contents were measured by using ICP (inductively coupled plasma-atomic emission) spectroscopy. The initial cathode potential was about -1.6 V. This value decreased with decreasing content of uranium in the salt. The electro-refiner was successfully operated and uranium in the molten salt was effectively recovered onto the cathode. (authors)

  18. Effect of A-site Non-stoichiometry on LSCF Cathodes

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-09-01

    LSCF Cathodes were explored when effected with A-site non-stoichiometry. At 700-800 C, the operating temperatures of intermediate temperature (IT-) SOFCs have enabled the use of stainless steels in the SOFC framework and current collectors, allowing significant reductions in cost. However, the lower operating temperatures of IT-SOFC's also result in significant decreases in power densities of cells with LSM cathodes due to their high activation energies. LSCF is a mixed ionic electronic conducting perovskite that exhibits higher performance than LSM/YSZ composites and shows potential as a replacement cathode. This study investigates the effect of A-site stoichiometry on the performance of LSCF cathodes. Cell tests showed that A-site and Sr-deficient LSCF cathodes consistently outperformed stoichiometric LSCF cathodes, exhibiting up to 10% higher cell power densities. It was also observed that all stoichiometric, A-site, and Sr-deficient LSCF cathodes degraded over time at similar rates. Contributions of ohmic and electrode polarization losses to cell degradation rates were similar regardless of cathode composition.

  19. High Current Density, Long Life Cathodes for High Power RF Sources

    Energy Technology Data Exchange (ETDEWEB)

    Ives, Robert Lawrence [Calabazas Creek Research,, Inc.; Collins, George [Calabazas Creek Research, Inc.; Falce, Lou [Consultant; Schwartzkopf, Steve [Ron Witherspoon, Inc.; Busbaher, Daniel [Semicon Associates

    2014-01-22

    This program was tasked with improving the quality and expanding applications for Controlled Porosity Reservoir (CPR) cathodes. Calabazas Creek Research, Inc. (CCR) initially developed CPR cathodes on a DOE-funded SBIR program to improve cathodes for magnetron injection guns. Subsequent funding was received from the Defense Advanced Research Projects Agency. The program developed design requirements for implementation of the technology into high current density cathodes for high frequency applications. During Phase I of this program, CCR was awarded the prestigious 2011 R&D100 award for this technology. Subsequently, the technology was presented at numerous technical conferences. A patent was issued for the technology in 2009. These cathodes are now marketed by Semicon Associates, Inc. in Lexington, KY. They are the world’s largest producer of cathodes for vacuum electron devices. During this program, CCR teamed with Semicon Associates, Inc. and Ron Witherspoon, Inc. to improve the fabrication processes and expand applications for the cathodes. Specific fabrications issues included the quality of the wire winding that provides the basic structure and the sintering to bond the wires into a robust, cohesive structure. The program also developed improved techniques for integrating the resulting material into cathodes for electron guns.

  20. Influence of NaCl on Cathode Performance of Solid Oxide Fuel Cells

    Institute of Scientific and Technical Information of China (English)

    LIU Run-ru; WANG De-jun; LENG Jing

    2013-01-01

    Degradation induced by sodium chloride in air was investigated for (La0.8Sr0.2)0.98MnO3(LSM) and La0.6Sr0.4Co0.2Fe0.8O3(LSCF) cathodes in solid oxide fuel cells(SOFC).Cell performance was measured by volatilizing NaCl to be supplied to the cathode at a constant current density of 200 mA/cm2 for up to 100 h.At 800 ℃,an exposure of the cathode to 30 mg/L NaCl caused negligible degradation of LSM at least for 100 h.Slight change in the composition of the cathode materials was observed which may imply the gradual degradation of cell performance for the long-term.In addition,cell performance degradation was compared between 700 ℃ and 900 ℃,being poisoned by 30 mg/L NaC1.Degradation was negligible for LSM cathode,while LSCF cathode showed slightly poor tolerance at 700 ℃ due to the decomposition of the cathode material.Further studies should be done to clarify the long-term influence of NaCl on cathode performance.

  1. Improved cathode assembly for electron gun of 7 MeV linac

    International Nuclear Information System (INIS)

    This Electron Beam Linear Accelerator (LINAC) of RPCD, BARC is the key component of the pulse radiolysis facility being used for radiation chemistry research. The heart of the LINAC is the electron gun, which generates electron from a tungsten cathode. Recently an improved cathode assembly is designed and fabricated for better performance of the linac. (author)

  2. On the mechanism of operation of a cathode spot cell in a vacuum arc

    Energy Technology Data Exchange (ETDEWEB)

    Mesyats, G. A.; Petrov, A. A. [P. N. Lebedev Physical Institute, RAS, 53 Leninsky Ave., Moscow 119991 (Russian Federation); Bochkarev, M. B. [Institute of Electrophysics, UB, RAS, 106 Amundsen St., Ekaterinburg 620016 (Russian Federation); Barengolts, S. A., E-mail: sb@nsc.gpi.ru [A. M. Prokhorov General Physics Institute, RAS, 38 Vavilov St., Moscow 119991 (Russian Federation)

    2014-05-05

    The erosive structures formed on a tungsten cathode as a result of the motion of the cathode spot of a vacuum arc over the cathode surface have been examined. It has been found that the average mass of a cathode microprotrusion having the shape of a solidified jet is approximately equal to the mass of ions removed from the cathode within the lifetime of a cathode spot cell carrying a current of several amperes. The time of formation of a new liquid-metal jet under the action of the reactive force of the plasma ejected by the cathode spot is about 10 ns, which is comparable to the lifetime of a cell. The growth rate of a liquid-metal jet is ∼10{sup 4} cm/s. The geometric shape and size of a solidified jet are such that a new explosive emission center (spot cell) can be initiated within several nanoseconds during the interaction of the jet with the dense cathode plasma. This is the underlying mechanism of the self-sustained operation of a vacuum arc.

  3. Quantifying the Water Content in the Cathode of Enzyme Fuel Cells via Neutron Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Aaron, D [Georgia Institute of Technology; Borole, Abhijeet P [ORNL; Hussey (NIST), Daniel [National Institute of Standards and Technology (NIST); Jacobson, David [National Institute of Standards and Technology (NIST); Yiacoumi, Sotira [Georgia Institute of Technology; Tsouris, Costas [ORNL

    2011-01-01

    Neutron imaging was used to study cathode water content over time in a three-dimensional-cathode enzyme fuel cell (EFC). A porous carbon felt cathode allowed air to flow through the electrode. A solution with laccase and a mediator formed an aqueous layer on the electrode surface. Water loss was observed in situ via neutron imaging for varying experimental conditions, including flow rates of hydrogen and air, cathode inlet humidity, volume of enzyme solution, and its composition. Cathode water loss occurred for all experimental conditions, but the loss rate was noticeably reduced when a high-salt-concentration enzyme solution was used in the cathode in conjunction with increased humidity in the air feed stream. Results from neutron imaging and power density analysis were used in analyzing the causes that could contribute to EFC water loss. An increase in temperature due to the exothermic cathode reaction is considered a plausible cause of cathode water loss via evaporation. This is the first reported application of neutron imaging as a technique to study EFC water management. The results suggest that neutron imaging can be employed to provide a better understanding of EFC phenomena and thereby contribute to design and operational improvements of EFCs.

  4. Asymmetric and double-cathode-pad wire chambers for the LHCb muon system

    CERN Document Server

    Kachtchouk, A; Riegler, W; Schmidt, B; Schneider, T; Souvorov, V

    2005-01-01

    We present results from two types of Multi-Wire Proportional Chambers (MWPCs) with wire pitch of 1.5 mm and cathode–cathode distance of 5 mm intended for triggering purposes in the LHCb experiment. Both prototypes use cathode readout because this allows arbitrary segmentation in order to achieve the required granularity. One MWPC prototype uses a symmetric wire–cathode distance (2.5/2.5 mm) with double cathode readout, which doubles the signal compared to reading only one cathode. The second prototype uses an asymmetric wire–cathode distance (1.25/3.75 mm) with single cathode readout which also doubles the signal and in addition reduces the width of the induced charge distribution and therefore reduces the crosstalk for small cathode pads. We also performed a dedicated optimization of readout traces and guard traces in order to reduce the pad–pad crosstalk. Both prototypes show a few hundred volts of operating plateau defined as the region with 99% efficiency in a 20 ns time window. Close to the plate...

  5. Cathode and interdigitated air distributor geometry optimization in polymer electrolyte membrane (PEM) fuel cells

    International Nuclear Information System (INIS)

    A steady-state single-phase three-dimensional electro-chemical model is combined with a nonlinear constrained optimization procedure to maximize the performance of the cathode and the interdigitated air distributor in a polymer electrolyte membrane (PEM) fuel cell. The cathode and the interdigitated air distributor design parameters considered include: the cathode thickness, the thickness of the interdigitated air distributor channels and the width of the interdigitated air distributor channels. A statistical sensitivity analysis is used to determine robustness of the optimal PEM fuel cell design. The results of the optimization analysis show that higher current densities at the membrane/cathode interface are obtained in the PEM cathode and the interdigitated air distributor geometries that promote convective oxygen transport to the membrane/cathode interface and reduce the thickness of the boundary diffusion layer at the same interface. The statistical sensitivity analysis results show that, while the predicted average current density at the membrane/cathode interface is affected by uncertainties in a number of model parameters, the optimal designs of the PEM cathode and the interdigitated air distributor are quite robust

  6. Novel anti-flooding poly(dimethylsiloxane) (PDMS) catalyst binder for microbial fuel cell cathodes

    KAUST Repository

    Zhang, Fang

    2012-11-01

    Poly(dimethylsiloxane) (PDMS) was investigated as an alternative to Nafion as an air cathode catalyst binder in microbial fuel cells (MFCs). Cathodes were constructed around either stainless steel (SS) mesh or copper mesh using PDMS as both catalyst binder and diffusion layer, and compared to cathodes of the same structure having a Nafion binder. With PDMS binder, copper mesh cathodes produced a maximum power of 1710 ± 1 mW m -2, while SS mesh had a slightly lower power of 1680 ± 12 mW m -2, with both values comparable to those obtained with Nafion binder. Cathodes with PDMS binder had stable power production of 1510 ± 22 mW m -2 (copper) and 1480 ± 56 mW m -2 (SS) over 15 days at cycle 15, compared to a 40% decrease in power with the Nafion binder. Cathodes with the PDMS binder had lower total cathode impedance than those with Nafion. This is due to a large decrease in diffusion resistance, because hydrophobic PDMS effectively prevented catalyst sites from filling up with water, improving oxygen mass transfer. The cost of PDMS is only 0.23% of that of Nafion. These results showed that PDMS is a very effective and low-cost alternative to Nafion binder that will be useful for large scale construction of these cathodes for MFC applications. © 2012 Elsevier B.V.

  7. Correlation of emission capability and longevity of dispenser cathodes with characteristics of tungsten powders

    International Nuclear Information System (INIS)

    The intercorrelation of tungsten powder properties, such as grain size, distribution and morphology, and porous matrix parameters with electron emission capability and longevity of Ba dispenser cathodes are investigated for three different grain morphologies. Best results of tungsten cathode life were found for isoaxis polyhedron morphology in combination with certain powder and matrix parameters

  8. Correlation of emission capability and longevity of dispenser cathodes with characteristics of tungsten powders

    Science.gov (United States)

    Melnikova, Irina P.; Vorozheikin, Victor G.; Usanov, Dmitry A.

    2003-06-01

    The intercorrelation of tungsten powder properties, such as grain size, distribution and morphology, and porous matrix parameters with electron emission capability and longevity of Ba dispenser cathodes are investigated for three different grain morphologies. Best results of tungsten cathode life were found for isoaxis polyhedron morphology in combination with certain powder and matrix parameters.

  9. Simulation optimization of the cathode deposit growth in a coaxial electrolyzer-refiner

    Science.gov (United States)

    Smirnov, G. B.; Fokin, A. A.; Markina, S. E.; Vakhitov, A. I.

    2015-08-01

    The results of simulation of the cathode deposit growth in a coaxial electrolyzer-refiner are presented. The sizes of the initial cathode matrix are optimized. The data obtained by simulation and full-scale tests of the precipitation of platinum from a salt melt are compared.

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

    KAUST Repository

    Cheng, Shaoan

    2011-03-01

    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. © 2010 Elsevier Ltd.

  11. Cathodic current enhancement via manganese and oxygen related reactions in marine biofilms

    Science.gov (United States)

    Strom, Matthew James

    Corrosion is a threat that has economic, and environmental impacts worldwide. Many types of corrosive attack are the subject of ongoing research. One of these areas of research is microbiologically influenced corrosion, which is the enhancement and/or initiation of corrosion events caused by microorganisms. It is well known that colonies of microorganisms can enhance cathodic currents through biofilm formation. The aim of the present work was to elucidate the role of manganese in enhancing cathodic currents in the presence of biofilms. Repeated polarizations conducted in Delaware Bay waters, on biofilm coated Cr identified potentially sustainable reduction reactions. The reduction of MnO2 and the enhancement of the oxygen reduction reaction (ORR) were proven to be factors that influence cathodic current enhancement. The removal of ambient oxygen during polarizations resulted in a shutdown of cathodic current enhancement. These field data led to an exploration of the synergistic relationship between MnO2 and the ORR. Laboratory studies of the catalysis of peroxide disproportionation by MnO2 were monitored using a hanging mercury drop electrode. Experiments were run at an ambient sweater pH of 8 and pH 9, which simulated the near-surface conditions typical of cathodes immersed in seawater. Rapid reoxidation at the more basic pH was shown to allow manganese to behave as a persistent catalyst under the typical electrochemical surface conditions of a cathode. As a result a mechanism for ORR enhancement by manganese was proposed as a unique mechanism for cathodic current enhancement in biofilms. A separate field study of Delaware biofilms on stainless steel coupled to a sacrificial Al anode was carried out to identify the ORR enhancement mechanism and sustainable redox reactions at the cathode. Chemical treatments of glutaraldehyde and formaldoxime were applied to cathodes with biofilms to distinguish between enzymatic and MnO2 related ORR enhancement. The results ruled

  12. Simulating different modes of current transfer to thermionic cathodes in a wide range of conditions

    Energy Technology Data Exchange (ETDEWEB)

    Benilov, M S; Cunha, M D; Faria, M J [Departamento de Fisica, Universidade da Madeira, Largo do MunicIpio, 9000 Funchal (Portugal)

    2009-07-21

    Changes in the pattern of steady-state modes of current transfer to thermionic cathodes induced by variations of the cathode geometry and temperature of the cooling fluid are studied numerically. For some combinations of control parameters, only one stable mode in a wide current range exists, which combines features of spot and diffuse modes. This mode, when attached to an elongated protrusion on the cathode surface, may be identified with the so-called super spot mode observed in experiments on low-current arcs. There is also reasonable agreement between the modelling and the experiment on cathodes of high-current arcs operating in the diffuse mode. The conclusions on existence under certain conditions of only one stable mode in a wide current range and of a minimum of the dependence of the temperature of the hottest point of the cathode on the arc current, manifested by this mode, may have industrial importance and admit a straightforward experimental verification.

  13. Diffuse and spot mode of cathode arc attachments in an atmospheric magnetically rotating argon arc

    International Nuclear Information System (INIS)

    A model including the cathode, near-cathode region, and arc column was constructed. Specifically, a thermal perturbation layer at the arc fringe was calculated in order to couple sheath/presheath modelling with typical arc column modelling. Comparative investigation of two modes of attachment of a dc (100, 150, 200 A) atmospheric-pressure arc in argon to a thermionic cathode made of pure tungsten was conducted. Computational data revealed that there exists two modes of arc discharge: the spot mode, which has an obvious cathode surface temperature peak in the arc attachment centre; and the diffuse mode, which has a flat cathode surface temperature distribution and a larger arc attachment area. The modelling results of the arc attachment agree with previous experimental observations for the diffuse mode. A further 3D simulation is obviously needed to investigate the non-axisymmetrical features, especially for the spot mode. (paper)

  14. Optical Interference Effects by Metal Cathode in Organic Light-Emitting Diodes

    Institute of Scientific and Technical Information of China (English)

    WU Zhao-Xin; WANG Li-Duo; QIU Yong

    2004-01-01

    The dependence of light intensities of organic light-emitting diodes (OLEDs) on the distance of emission zone to metal cathode is investigated numerically. The investigation is based on the half-space optical model that accounts for optical interference effects of metal cathode. We find that light intensities of OLEDs are functions of the distance of emission zone from the metal cathode because of the effect of interference of the metal cathode.This interference leads to an optimal location of emission zone in OLEDs for the maximum of light intensities.Optimal locations of emission zone are numerically shown in various emitting colour OLEDs with different metal cathodes and these results are expected to give insight into the preparation of high efficiency full colour or white light OLEDs.

  15. Emission characteristics of Y1Ba2Cu3O7-δ cathode

    International Nuclear Information System (INIS)

    The results are presented of experimental investigation of the electron beam in diode with cathode on the base of Y1Ba2Cu3O7-δ. After corresponding cathode training, the cathode made from Y1Ba2Cu3O7-δ material may be practicable of stable current electron beam yeild. It is shown experimentally that the voltage of diode of about 100-300 kV there exists an evident possibility of forming the electron beams with the current density of 70 A-380 A/cm2. The motion velicity of cathode plasma in the direction of anode for this material of a cathode amounts to (1-3)x 106 cm/s

  16. Emission characteristics of dispenser cathodes with a fine-grained tungsten top layer

    Science.gov (United States)

    Kimura, S.; Higuchi, T.; Ouchi, Y.; Uda, E.; Nakamura, O.; Sudo, T.; Koyama, K.

    1997-02-01

    In order to improve the emission stability of the Ir-coated dispenser cathode under ion bombardment, a fine-grained tungsten top layer was applied on the substrate porous tungsten plug before Ir coating. The emission characteristics were studied after being assembled in a CRT gun. Cathode current was measured under pulse operation in a range of 0.1-9% duty. Remarkable anti-ion bombardment characteristics were observed over the range of 1-6% duty. The improved cathode showed 1.5 times higher emission current than that of a conventional Ir-coated dispenser cathode at 4% duty. AES analysis showed that the recovering rates of surface Ba and O atoms after ion bombardment were 2.5 times higher. From these results it is confirmed that the Ir coated cathode with a fine-grained tungsten top layer is provided with a good tolerance against the ion bombardment.

  17. Thermionic properties of Mo-La2O3 cathode wires

    Institute of Scientific and Technical Information of China (English)

    张久兴; 周美玲; 周文元; 王金淑; 聂祚仁; 左铁镛

    2002-01-01

    The recent advances in Mo-La2O3 thermionic cathode materials were presented. It is shown that Mo-La2O3 cathode has better ductility, radioactive pollution-free, excellent thermionic electron-emission properties and lower operating temperature compared with W-ThO2 cathode. At operating temperature 1350~1400℃, the average saturation current of the Mo-La2O3 cathode is 118mA, the corresponding average current density is 367mA/cm2, and the average emission efficiency is 11.8mA/W. The lifetime of diode is more than 2000h when the stable emission current is 80mA. Moreover, the lifetime of practical 6T51-type triode is more than 1000h. These advances show that the Mo-La2O3 cathode electron tube is closer to industry application.

  18. Mechanism of cathode spot splitting in vacuum arcs in an oblique magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Beilis, I. I. [Electrical Discharge and Plasma Laboratory, School of Electrical Engineering, Fleischman Faculty of Engineering, Tel Aviv University, P.O. Box. 39040, Tel Aviv 69978 (Israel)

    2015-10-15

    Experiments in the last decade showed that for cathode spots in a magnetic field that obliquely intercepts the cathode surface, the current per spot increased with the transverse component of the magnetic field and decreased with the normal component. The present work analyzes the nature of cathode spot splitting in an oblique magnetic field. A physical model for cathode spot current splitting was developed, which considered the relation between the plasma kinetic pressure, self-magnetic pressure, and applied magnetic pressure in a current carrying cathode plasma jet. The current per spot was calculated, and it was found to increase with the tangential component of the magnetic field and to decrease with the normal component, which agrees well with the experimental dependence.

  19. Work function distribution for W-Ir mixed metal matrix cathodes

    International Nuclear Information System (INIS)

    Mixed metal matrix cathodes have inherent non-uniformity and patchiness of emission due to the presence of two-alloy phase structure on the surface. I-V characteristics of cathode studied in a close spaced diode configuration is one of the easy and cost effective methods to estimate the variation of work function on the cathode surface. Tungsten iridium mixed metal matrix dispenser cathodes of O1.4 mm (80 wt.% W-20 wt.% Ir) have been fabricated in the laboratory and their I-V characteristics have been investigated in diode configuration. In this paper the model suggested by Tonnerre et al. has been used to find out the work function distribution of W-Ir cathodes from I-V characteristics. An attempt has been made to correlate the microstructure with the work function values

  20. External Mass Injection to Reduce Energetic Ion Production in the Discharge Plume of High Current Hollow Cathodes

    OpenAIRE

    Chu, Emily

    2012-01-01

    Hollow cathode discharge studies have shown the existence of energetic ions at high discharge currents that are likely responsible for the high erosion rates and erosion patterns observed on the keeper electrode of the hollow cathode. This thesis uses experimental methods to study the effects of neutral gas injection in the xenon hollow cathode discharge plume on the production of energetic ions to determine the injection conditions that yield optimum hollow cathode operation and life. Para...

  1. Air-cathode structure optimization in separator-coupled microbial fuel cells

    KAUST Repository

    Zhang, Xiaoyuan

    2011-12-01

    Microbial fuel cells (MFC) with 30% wet-proofed air cathodes have previously been optimized to have 4 diffusion layers (DLs) in order to limit oxygen transfer into the anode chamber and optimize performance. Newer MFC designs that allow close electrode spacing have a separator that can also reduce oxygen transfer into the anode chamber, and there are many types of carbon wet-proofed materials available. Additional analysis of conditions that optimize performance is therefore needed for separator-coupled MFCs in terms of the number of DLs and the percent of wet proofing used for the cathode. The number of DLs on a 50% wet-proofed carbon cloth cathode significantly affected MFC performance, with the maximum power density decreasing from 1427 to 855mW/m 2 for 1-4 DLs. A commonly used cathode (30% wet-proofed, 4 DLs) produced a maximum power density (988mW/m 2) that was 31% less than that produced by the 50% wet-proofed cathode (1 DL). It was shown that the cathode performance with different materials and numbers of DLs was directly related to conditions that increased oxygen transfer. The coulombic efficiency (CE) was more affected by the current density than the oxygen transfer coefficient for the cathode. MFCs with the 50% wet-proofed cathode (2 DLs) had a CE of >84% (6.8A/m 2), which was substantially larger than that previously obtained using carbon cloth air-cathodes lacking separators. These results demonstrate that MFCs constructed with separators should have the minimum number of DLs that prevent water leakage and maximize oxygen transfer to the cathode. © 2011 Elsevier B.V.

  2. On the issue of reducing the effect of ionic bombardment of the cathode on the performance of microwave vacuum tubes

    International Nuclear Information System (INIS)

    A possibility of reducing the effect of ionic bombardment on the operation of cathodes in vacuum electron tubes has been considered. The improvement can be reached by modifying the geometry of the cathode - emitting surface. Results of experimental investigations of millimeter and submillimeter wave clinotrons with such cathodes are presented. Such clinotrons show improved performance characteristics

  3. Characteristics of Single Cathode Cascaded Bias Voltage Arc Plasma

    Science.gov (United States)

    Ou, Wei; Deng, Baiquan; Zeng, Xianjun; Gou, Fujun; Xue, Xiaoyan; Zhang, Weiwei; Cao, Xiaogang; Yang, Dangxiao; Cao, Zhi

    2016-06-01

    A single cathode with a cascaded bias voltage arc plasma source has been developed with a new quartz cathode chamber, instead of the previous copper chambers, to provide better diagnostic observation and access to the plasma optical emission. The cathode chamber cooling scheme is also modified to be naturally cooled only by light emission without cooling water to improve the optical thin performance in the optical path. A single-parameter physical model has been developed to describe the power dissipated in the cascaded bias voltage arc discharge argon plasmas, which have been investigated by utilizing optical emission spectroscopy (OES) and Langmuir probe. In the experiments, discharge currents from 50 A to 100 A, argon flow rates from 800 sccm to 2000 sccm and magnetic fields of 0.1 T and 0.2 T were chosen. The results show: (a) the relationship between the averaged resistivity and the averaged current density exhibits an empirical scaling law as \\barη \\propto \\bar {j}-0.63369 and the power dissipated in the arc has a strong relation with the filling factor; (b) through the quartz, the argon ions optical emission lines have been easily observed and are dominating with wavelengths between 340 nm and 520 nm, which are the emissions of Ar+‑434.81 nm and Ar+‑442.60 nm line, and the intensities are increasing with the arc current and decreasing with the inlet argon flow rate; and (c) the electron density and temperature can reach 2.0 × 1019 m‑3 and 0.48 eV, respectively, under the conditions of an arc current of 90 A and a magnetic field of 0.2 T. The half-width of the ne radial profile is approximatively equal to a few Larmor radii of electrons and can be regarded as the diameter of the plasma jet in the experiments. supported by the International Thermonuclear Experimental Reactor (ITER) Program Special of Ministry of Science and Technology (No. 2013GB114003), and National Natural Science Foundation of China (Nos. 11275135, 11475122)

  4. The cathode strip chamber data acquisition electronics for CMS

    International Nuclear Information System (INIS)

    Data Acquisition (DAQ) electronics for Cathode Strip Chambers (CSC) [CMS Collaboration, The Muon Project Technical Design Report, CERN/LHCC 97-32, CMS TDR3, 1997] in the Compact Muon Solenoid (CMS) [CMS Collaboration, The Compact Muon Solenoid Technical Proposal, CERN/LHCC 94-38, 1994] experiment at the Large Hadron Collider (LHC) [The LHC study group, The Large Hadron Collider: Conceptual Design, CERN/AC 1995-05, 1995] is described. The CSC DAQ system [B. Bylsma, et al., in: Proceedings of the Topical Workshop on Electronics for Particle Physics, Prague, Czech Republic, CERN-2007-007, 2007, pp. 195-198] includes on-detector and off-detector electronics, encompassing five different types of custom circuit boards designed to handle the high event rate at the LHC. The on-detector electronics includes Cathode Front End Boards (CFEB) [R. Breedon, et al., Nucl. Instr. and Meth. A 471 (2001) 340], which amplify, shape, store, and digitize chamber cathode signals; Anode Front End Boards (AFEB) [T. Ferguson, et al., Nucl. Instr. and Meth. A 539 (2005) 386], which amplify, shape and discriminate chamber anode signals; and Data Acquisition Motherboards (DAQMB), which controls the on-chamber electronics and the readout of the chamber. The off-detector electronics, located in the underground service cavern, includes Detector Dependent Unit (DDU) boards, which perform real time data error checking, electronics reset requests and data concentration; and Data Concentrator Card (DCC) boards, which further compact the data and send it to the CMS DAQ System [CMS Collaboration, The TriDAS Project Technical Design Report, Volume 2: Data Acquisition and High-level Trigger, CERN/LHCC 2002-26, 2002], and serve as an interface to the CMS Trigger Timing Control (TTC) [TTC system ] system. Application Specific Integrated Circuits (ASIC) are utilized for analogous signal processing on front end boards. Field Programmable Gate Arrays (FPGA) are utilized on all boards in the system to provide

  5. The cathode strip chamber data acquisition electronics for CMS

    Science.gov (United States)

    Bylsma, B. G.; Durkin, L. S.; Gilmore, J.; Gu, J.; Ling, T. Y.; Rush, C.

    2009-03-01

    Data Acquisition (DAQ) electronics for Cathode Strip Chambers (CSC) [CMS Collaboration, The Muon Project Technical Design Report, CERN/LHCC 97-32, CMS TDR3, 1997] in the Compact Muon Solenoid (CMS) [CMS Collaboration, The Compact Muon Solenoid Technical Proposal, CERN/LHCC 94-38, 1994] experiment at the Large Hadron Collider (LHC) [The LHC study group, The Large Hadron Collider: Conceptual Design, CERN/AC 1995-05, 1995] is described. The CSC DAQ system [B. Bylsma, et al., in: Proceedings of the Topical Workshop on Electronics for Particle Physics, Prague, Czech Republic, CERN-2007-007, 2007, pp. 195-198] includes on-detector and off-detector electronics, encompassing five different types of custom circuit boards designed to handle the high event rate at the LHC. The on-detector electronics includes Cathode Front End Boards (CFEB) [R. Breedon, et al., Nucl. Instr. and Meth. A 471 (2001) 340], which amplify, shape, store, and digitize chamber cathode signals; Anode Front End Boards (AFEB) [T. Ferguson, et al., Nucl. Instr. and Meth. A 539 (2005) 386], which amplify, shape and discriminate chamber anode signals; and Data Acquisition Motherboards (DAQMB), which controls the on-chamber electronics and the readout of the chamber. The off-detector electronics, located in the underground service cavern, includes Detector Dependent Unit (DDU) boards, which perform real time data error checking, electronics reset requests and data concentration; and Data Concentrator Card (DCC) boards, which further compact the data and send it to the CMS DAQ System [CMS Collaboration, The TriDAS Project Technical Design Report, Volume 2: Data Acquisition and High-level Trigger, CERN/LHCC 2002-26, 2002], and serve as an interface to the CMS Trigger Timing Control (TTC) [TTC system web.cern.ch/TTC/intro.html>] system. Application Specific Integrated Circuits (ASIC) are utilized for analogous signal processing on front end boards. Field Programmable Gate Arrays (FPGA) are utilized on all

  6. Optimized high-temperature cathode-heater unit

    International Nuclear Information System (INIS)

    In electrophysical apparatus and accelerators that form electron beams with a high current density, the most stringent requirements are imposed on the operating life, reliability, and thermal efficiency of the high-temperature cathode-heater units (CHU), the replacement of which involves great expenditures of time and prolonged shutdown of the apparatus. The shortcomings of existing CHUs with LaB6 emitters include, among others, the low optical transparency of the graphite heating element and inconstancy of the temperature field of the emitter owing to unavoidable thickening at the locations of the massive leads. All of this reduces the thermal efficiency of the CHU. The authors describe a CHU that is free of the above-mentioned shortcomings. The CHU has a thermal efficiency of > 80% and a temperature inconstancy ΔT 2, at temperature T = 2,050 K is 700 h

  7. Intense stationary H- ion source with a hollow cathode

    International Nuclear Information System (INIS)

    H- ion source with a cesium hollow cathode, operating in the stationary regime, is investigated for designing the thermonuclear device injector. The source is of an axial-symmetry geometry with the radial magnetic field. Ion extraction is being performed tranverse the magnetic field through the holes in the main anode. The movable magnetic analyzer has been used for controlling of the beam. The ion current of 109 mA and the energy of 5 keV is obtained in the stationary regime. The analysis of the ion source operation has shown: 1)the source preserves working capacity even without the magnetic field; 2)the largest H- current is in a small magnetic field (10-20 G) in the region of emission holes; 3)H- ion current increases at decreasing hydrogen consumption

  8. IBIS: A hollow-cathode multipole boundary ion source

    International Nuclear Information System (INIS)

    The plasma production and containment system for a high-power continuously operating magnetic multipole ion source has been designed and constructed. Preliminary tests on this system prior to high voltage extraction of large beams indicate advantageous performance for neutral-beam injection applications. The source has produced 80 A to the extractor region at 0.33 A/cm2 with a discharge of 330 A at 80 V. Density uniformity is better than 1% over a 16-cm diameter, dropping to -4% at 18 cm, with plasma noise of less than 3%. Gas utilizaion efficiency and atomic (H+) species output are anticipated to be high due to a source length of 40 cm. This quiet efficient performance is attributed to the use of a hollow-tube LaB6 cathode and an improved magnetic multipole confinement system

  9. The 'KATOD-1' strip readout ASIC for cathode strip chamber

    International Nuclear Information System (INIS)

    The 'KATOD-1', a 16-channels readout ASIC, has been designed to perform tests of P3 and P4 full-scale prototypes of the cathode strip chamber for the ME1/1 forward muon station of the Compact Muon Solenoid (CMS) experiment. The ASIC channel consists of two charge-sensitive preamplifiers, a three-stage shaper with cancellation, and an output driver. The ASIC is instrumented with control of gain, in the range of (-4.2 : +5.0) mV/fC, and control of output pulse-shape. The equivalent input noise is equal to 2400 e with the slope of 12 e/pF for detector capacity up to 200 pF. The peaking time is 100 ns for the chamber signal. The ASIC has been produced by a microwave Bi-jFET technology

  10. Carbon xerogels as catalyst supports for PEM fuel cell cathode

    International Nuclear Information System (INIS)

    Carbon xerogels with various pore textures were prepared by evaporative drying and pyrolysis of resorcinol-formaldehyde gels, and used as supports for Pt catalysts in PEM fuel cell cathodes. The goal of this study was to determine whether carbon xerogels could replace the carbon aerogels which were previously used as Pt catalyst supports in the same electrochemical system, and to determine how the pore texture influences the cell performances. Pt catalysts were prepared by impregnation of carbon supports with aqueous H2PtCl6 solution followed by reduction in aqueous phase with NaBH4. Fuel cell measurements show that the metal surface actually available for the oxygen reduction reaction and the voltage losses due to diffusion phenomena strongly depend on the carbon pore texture. Finally, some carbon xerogels yield similar performance than carbon aerogels

  11. Chemical and electrical properties of LSM cathodes prepared by mechanosynthesis

    Science.gov (United States)

    Moriche, R.; Marrero-López, D.; Gotor, F. J.; Sayagués, M. J.

    2014-04-01

    Mechanosynthesis of La1-xSrxMnO3 (x = 0, 0.25, 0.5, 0.75 and 1) was carried out at room temperature from stoichiometric mixtures of La2O3, Mn2O3 and SrO, obtaining monophasic powders with the perovskite structure. Physical properties of these materials and their chemical compatibility with the electrolyte yttria stabilized zirconia (YSZ), which depend strongly on the La/Sr ratio, were evaluated to corroborate availability to be implemented as cathode material in solid oxide fuel cells (SOFCs). Electrical conductivity values in air ranged between 100 and 400 S cm-1 in the temperature range of 25-850 °C. Samples presented low reactivity with YSZ in the working temperature range (600-1000 °C) maintaining the grain size small enough to preserve the catalytic activity for oxygen reduction.

  12. Cathodic electrodeposition of cobalt oxide films using polyelectrolytes

    International Nuclear Information System (INIS)

    Composite films consisting of cobalt hydroxide and polyelectrolytes, such as poly(diallyldimethylammonium chloride) (PDDA) and polyethylenimine (PEI), were obtained by electrodeposition. In the proposed method, electrophoretic deposition of PDDA macromolecules or PEI-Co2+ complexes has been combined with cathodic electrosynthesis of cobalt hydroxide. By varying the concentration of the polyelectrolytes in solutions, the deposition time and the current density, the amount of deposited material and its composition can be varied. The composite deposits have been studied by scanning, transmission and atomic force microscopy, X-ray diffraction and thermogravimetric analysis. The obtained results have been compared with the results of investigation of pure cobalt hydroxide films. Heat treatment of the deposits resulted in decomposition of the hydroxide precursor and burning out of polymer to form cobalt oxide films. This method enables the formation of thick nanostructured oxide films

  13. Applications of Cold Cathode PIG Ion Source in Lithography

    International Nuclear Information System (INIS)

    The cold cathode Penning ion source (PIG) of axial type could be modified to produce ion and electron beam with a considerable amount to use it in the lithography process. Lithography is a new applications of ion/electron beam at which one can use the ion/ or electron beam as a pencil to write and draw on a metal surface. The electron beam takes 1/3 the time needed for ion beam to make good picture. So that with the help of ion/or electron beam lithography one can mark tools, parts, instruments, and equipment with names, numbers, designs, trademark or brand name in few seconds. It is an easy process, quick and an inexpensive method. Firstly, operating characteristics of this ion source is studied. Lithography application of ion source with optimum conditions is done. Later, the hardness and the tensile strength is measured and each of them increases with increasing time

  14. High-pressure dc glow discharges in hollow diamond cathodes

    Science.gov (United States)

    Truscott, B. S.; Turner, C.; May, P. W.

    2016-04-01

    We report the generation and characterization of dc helium microdischarges at several times atmospheric pressure in monolithic diamond hollow-cathode devices having cavity diameters on the order of 100 μm. I-V characteristics indicated operation in the glow discharge regime even at nearly 10 atm, while spectroscopic measurements of the N2 C3Πu  →  B3Πg emission returned rotational temperatures always around 420 K, with a pressure-dependent vibrational population distribution. The variation of breakdown voltage with pressure closely followed Paschen’s law, but with offsets in both axes that we tentatively ascribe to strong diffusive loss and a partial thermalization of electron energies under the high pressures considered here.

  15. Atlas of uranium emission intensities in a hollow cathode discharge

    Energy Technology Data Exchange (ETDEWEB)

    Palmer, B.A.; Keller, R.A.; Engleman, R. Jr.

    1980-07-01

    The uranium emission spectrum from a hollow cathode discharge is displayed from 11,000 to 26,000 cm/sup -1/. This atlas lists 4928 spectral lines of uranium; 3949 are classified to the neutral spectrum and 431 are classified to the singly ionized spectrum. Listed wavenumbers are accurate to +-0.003 cm/sup -1/ and the listed relative intensities to +-8%. The richness of the spectrum makes this atlas useful for wavenumber calibration of lasers, spectrographs, and monochromators to an accuracy of 1 part in 10/sup 7/. This atlas is also useful as a guide to the uranium spectrum, and relative oscillator strengths (gf values) can be calculated from the intensities to a precision of +-20%.

  16. Impregnation of LSM Based Cathodes for Solid Oxide Fuel Cells

    DEFF Research Database (Denmark)

    Højberg, Jonathan; Søgaard, Martin

    2011-01-01

    Composites cathodes consisting of strontium doped lanthanum manganite (LSM) and yttria stabilized zirconia have been impregnated with the nitrates corresponding to the nominal compositions: La0.75Sr0.25Mn1.05O3 +/-delta (LSM25), Ce0.8Sm0.2O2 (SDC) and a combination of both (dual). The latter...... performed best with a polarization resistance (R-P) of 0.39 Omega cm(2) at 600 degrees C and 0.039 Omega cm(2) at 750 degrees C compared to 2.17 and 0.19 Omega cm(2) respectively for electrodes without impregnation. Furthermore the dual impregnation decreased the activation energy of R-P to 1.19 eV compared...

  17. Cathodic electrocrystallization and electrochromic properties of doped rechargeable oxotungstates

    International Nuclear Information System (INIS)

    We extend the technique of preparing oxotungstate thin films by cathodic electrocrystallization from metastable acidic solutions to fabricate vanadium- and molybdenum-doped films on platinum and fluorine-doped tin oxide (FTO). By means of cyclic voltammetry, we demonstrate a wider potential interval of highly reversible redox activity for these doped films, as compared to purely tungstate films. Electrochromic behavior in this region is dependent on the nature of the doping element. We characterize the microstructure of these films using scanning tunneling and atomic force microscopy. We also apply Raman and UV-vis spectroscopy to characterize the acidic deposition solutions. In tungstate-vanadate bath, we observe evidence of mixed isopolyanions. We also found some features of less stable mixed anions in the tungstate-molybdate bath, characterized phase composition of these films by means of XRD, and explain the results in the terms of parallel deposition from coexisting molecular precursors.

  18. Cathodic electrocrystallization and electrochromic properties of doped rechargeable oxotungstates

    Energy Technology Data Exchange (ETDEWEB)

    Laurinavichute, V.K. [Moscow State University, Leninskie Gory, 1-str. 3, Moscow 119991 (Russian Federation)], E-mail: nika@elch.chem.msu.ru; Vassiliev, S.Yu. [Moscow State University, Leninskie Gory, 1-str. 3, Moscow 119991 (Russian Federation); Plyasova, L.M.; Molina, I.Yu. [Boreskov Institute of Catalysis, Siberian Division of the Russian Academy of Sciences, Prosp. Lavrentieva 5, Novosibirsk 630090 (Russian Federation); Khokhlov, A.A. [Moscow State University, Leninskie Gory, 1-str. 3, Moscow 119991 (Russian Federation); Pugolovkin, L.V. [Moscow State University, Leninskie Gory, 1-str. 3, Moscow 119991 (Russian Federation); Boreskov Institute of Catalysis, Siberian Division of the Russian Academy of Sciences, Prosp. Lavrentieva 5, Novosibirsk 630090 (Russian Federation); Borzenko, M.I.; Tsirlina, G.A. [Moscow State University, Leninskie Gory, 1-str. 3, Moscow 119991 (Russian Federation)

    2009-09-30

    We extend the technique of preparing oxotungstate thin films by cathodic electrocrystallization from metastable acidic solutions to fabricate vanadium- and molybdenum-doped films on platinum and fluorine-doped tin oxide (FTO). By means of cyclic voltammetry, we demonstrate a wider potential interval of highly reversible redox activity for these doped films, as compared to purely tungstate films. Electrochromic behavior in this region is dependent on the nature of the doping element. We characterize the microstructure of these films using scanning tunneling and atomic force microscopy. We also apply Raman and UV-vis spectroscopy to characterize the acidic deposition solutions. In tungstate-vanadate bath, we observe evidence of mixed isopolyanions. We also found some features of less stable mixed anions in the tungstate-molybdate bath, characterized phase composition of these films by means of XRD, and explain the results in the terms of parallel deposition from coexisting molecular precursors.

  19. One-step electrodeposition process to fabricate cathodic superhydrophobic surface

    International Nuclear Information System (INIS)

    In this work, a rapid one-step process is developed to fabricate superhydrophobic cathodic surface by electrodepositing copper plate in an electrolyte solution containing manganese chloride (MnCl2·4H2O), myristic acid (CH3(CH2)12COOH) and ethanol. The superhydrophobic surfaces were characterized by means of scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The shortest electrolysis time for fabricating a superhydrophobic surface is about 1 min, the measured maximum contact angle is 163° and rolling angle is less than 3°. Furthermore, this method can be easily extended to other conductive materials. The approach is time-saving and cheap, and it is supposed to have a promising future in industrial fields.

  20. Development of fiber laser for photo cathode electron gun

    International Nuclear Information System (INIS)

    We develop L-band photocathode RF gun which is conducted by the collaborations with the groups of Osaka University, KEK and Hiroshima University. For the photocathode, we uniquely develop laser at Osaka University. At the first laser system, we have developed passive mode lock Yb fiber laser at repetition rate of 108MHz. on the other hand, thermionic cathode electron gun generates electron with sub harmonic buncher with the repetition of 27MHz now in addition to 108MHz. For this reason, we started to develop passive mode lock Yb fiber laser at repetition rate of 27MHz uniquely. The mean power at pulse is 35∼70mW, and Max energy at a pulse is 2.7nJ. (author)

  1. Theoretical and experimental studies of virtual cathode microwave devices

    Energy Technology Data Exchange (ETDEWEB)

    Alyokhin, B.V.; Dubinov, A.E.; Selemir, V.D.; Shamro, O.A.; Shibalko, K.V.; Stepanov, N.V.; Vatrunin, V.E. (Russia Federation Nuclear Center, Arzamas (Russian Federation). All-Russia Scientific Research Inst. of Experimental Physics)

    1994-10-01

    The results of theoretical and experimental studies of microwave devices with virtual cathodes (VCs) are reviewed. It is shown that the basic factors affecting operation efficiency of these devices are phase separation of electron flux, diode impedance matching with the high-voltage transmission line, and the availability of two characteristic features in the output spectrum. Using nonlinear theory, the authors have observed the evolution of the electron velocity distribution function in the vicinity of the VC, have found the VC effective temperature, and have studied the fractal indices for various functions in time. This report also describes a series of experiments where 2-D features of the electron dynamics in the vircator are rather important, and 11% generation efficiency with a pinch-vircator was achieved. The understanding of the physical processes occurring in VC microwave devices gained in this work supports the proposal of several new highly efficient concepts for such devices.

  2. Aberrations of the cathode objective lens up to fifth order.

    Science.gov (United States)

    Tromp, R M; Wan, W; Schramm, S M

    2012-08-01

    In this paper we discuss a topic that was close to Prof. Gertrude Rempfer s interests for many years. On this occasion of her 100th birthday, we remember and honor Gertrude for her many outstanding contributions, and for the inspiring example that she set. We derive theoretical expressions for the aberration coefficients of the uniform electrostatic field up to 5th order and compare these with raytracing calculations for the cathode lens used in Low Energy Electron Microscopy and Photo Electron Emission Microscopy experiments. These higher order aberration coefficients are of interest for aberration corrected experiments in which chromatic (C(c)) and spherical (C₃) aberrations of the microscope are set to zero. The theoretical predictions are in good agreement with the results of raytracing. Calculations of image resolution using the Contrast Transfer Function method show that sub-nanometer resolution is achievable in an aberration corrected LEEM system. PMID:22188906

  3. Atlas of uranium emission intensities in a hollow cathode discharge

    International Nuclear Information System (INIS)

    The uranium emission spectrum from a hollow cathode discharge is displayed from 11,000 to 26,000 cm-1. This atlas lists 4928 spectral lines of uranium; 3949 are classified to the neutral spectrum and 431 are classified to the singly ionized spectrum. Listed wavenumbers are accurate to +-0.003 cm-1 and the listed relative intensities to +-8%. The richness of the spectrum makes this atlas useful for wavenumber calibration of lasers, spectrographs, and monochromators to an accuracy of 1 part in 107. This atlas is also useful as a guide to the uranium spectrum, and relative oscillator strengths (gf values) can be calculated from the intensities to a precision of +-20%

  4. Hollow nanoparticle cathode materials for sodium electrochemical cells and batteries

    Energy Technology Data Exchange (ETDEWEB)

    Shevchenko, Elena; Rajh, Tijana; Johnson, Christopher S.; Koo, Bonil

    2016-07-12

    A cathode comprises, in its discharged state, a layer of hollow .gamma.-Fe.sub.2O.sub.3 nanoparticles disposed between two layers of carbon nanotubes, and preferably including a metallic current collector in contact with one of the layers of carbon nanotubes. Individual particles of the hollow .gamma.-Fe.sub.2O.sub.3 nanoparticles comprise a crystalline shell of .gamma.-Fe.sub.2O.sub.3 including cation vacancies within the crystal structure of the shell (i.e., iron vacancies of anywhere between 3% to 90%, and preferably 44 to 77% of available octahedral iron sites). Sodium ions are intercalated within at least some of the cation vacancies within the crystalline shell of the hollow .gamma.-Fe.sub.2O.sub.3 nanoparticles.

  5. Velocimetry of cathode particles in a magnetoplasmadynamic thruster discharge plasma

    Science.gov (United States)

    Walker, J.; Langendorf, S.; Walker, M.; Polzin, K.; Kimberlin, A.

    2015-07-01

    With high-speed imaging, it is possible to directly observe the time-evolution of the macroscopic behavior of the discharge plasma in a magnetoplasmadynamic thruster (MPDT). By utilizing direct high-speed imaging capable of capturing many images over the course of a single discharge, the velocity of the cathode erosion particles can be measured, opening the possibility of a novel, noninvasive technique for discharge plasma flow field velocimetry. In this work, an 8 kA argon MPDT discharge is imaged at 26 173 fps utilizing a 0.9 neutral density filter. The camera is aligned with thruster centerline 4 m downstream of the thruster exit plane. By tracking visible particles appearing in the multiple images, the particle motion in the radial and azimuthal directions is directly imaged. Through the use of traditional techniques in digital particle image velocimetry, the cathode particles emanating from the discharge are measured to have a mean radial velocity of 44.6 ± 6.0 m/s with a 95% confidence interval and a statistically insignificant azimuthal velocity. The setup and analysis employed permits measurement of the particle velocity in orthogonal direction to the image sensor plane using a single camera. By combining a background removal subtraction technique and knowledge of the optical focal plane, the estimated mean axial velocity of the particles is 1.59 km/s. This investigation ends with a discussion of important factors to consider for future MPDT high-speed imaging particle velocimetry, such as frame-rate, image size, spatial resolution, optics, and data handling selections.

  6. Understanding electrochemical potentials of cathode materials in rechargeable batteries

    Directory of Open Access Journals (Sweden)

    Chaofeng Liu

    2016-03-01

    Full Text Available Presently, sustainable energy as well as efficient and economical energy conversion and storage technologies has become important work in light of the rising environmental issues and dependence on portable and uninterrupted power sources. Increasingly more researchers are focusing on harvesting and converting solar energy, mechanical vibration, waste heat, and wind to electricity. Electrical energy storage technologies play a significant role in the demand for green and sustainable energy. Rechargeable batteries or secondary batteries, such as Li-ion batteries, Na-ion batteries, and Mg-ion batteries, reversibly convert between electrical and chemical energy via redox reactions, thus storing the energy as chemical potential in their electrodes. The energy density of a rechargeable battery is determined collectively by the specific capacity of electrodes and the working voltage of the cell, which is the differential potential between the cathode and the anode. Over the past decades, a significant number of studies have focused on enhancing this specific capacity; however, studies to understand and manipulate the electrochemical potential of the electrode materials are limited. In this review, the material characteristics that determine and influence the electrochemical potentials of electrodes are discussed. In particular, the cathode materials that convert electricity and chemical potential through electrochemical intercalation reactions are investigated. In addition, we summarize the selection criteria for elements or compounds and the effect of the local atomic environment on the discharge potential, including the effects of site energy, defects, crystallinity, and microstructure, using LiMn2O4, V2O5, Mo6S8, LiFePO4, and LiCoO2 as model samples for discussion.

  7. Lanthanum manganate based cathodes for solid oxide fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Juhl Joergensen, M.

    2001-07-01

    Composite cathodes for solid oxide fuel cells were investigated using electrochemical impedance spectroscopy and scanning electron microscopy. The aim was to study the oxygen reduction process in the electrode in order to minimise the voltage drop in the cathode. The electrodes contained a composite layer made from lanthanum strontium manganate (LSM) and yttria stabilised zirconia (YSZ) and a layer of pure LSM aimed for current collection. The performance of the composite electrodes was sensitive to microstructure and thickness. Further, the interface between the composite and the current collecting layer proved to affect the performance. In a durability study severe deg-radation of the composite electrodes was found when passing current through the electrode for 2000 hours at 1000 deg. C. This was ascribed to pore formation along the composite interfaces and densification of the composite and current collector microstructure. An evaluation of the measurement approach indicated that impedance spectroscopy is a very sensitive method. This affects the reproducibility, as small undesirable variations in for instance the microstructure from electrode to electrode may change the impedance. At least five processes were found to affect the impedance of LSM/YSZ composite electrodes. Two high frequency processes were ascribed to transport of oxide ions/oxygen intermediates across LSM/YSZ interfaces and through YSZ in the composite. Several competitive elementary reaction steps, which appear as one medium frequency process in the impedance spectra, were observed. A low frequency arc related to gas diffusion limitation in a stagnant gas layer above the composite structure was detected. Finally, an inductive process, assumed to be connected to an activation process involving segregates at the triple phase boundary between electrode, electrolyte and gas phase, was found. (au)

  8. Hydrogen production in single chamber microbial electrolysis cells with stainless steel fiber felt cathodes

    Science.gov (United States)

    Su, Min; Wei, Liling; Qiu, Zhaozheng; Wang, Gang; Shen, Jianquan

    2016-01-01

    Microbial electrolysis cell (MEC) is a promising technology for sustainable production of hydrogen from biodegradable carbon sources. Employing a low-cost and high efficient cathode to replace platinum catalyzed cathode (Pt/C) for hydrogen generation is a challenge for commercialization of MEC. Here we show that a 3D macroporous stainless steel fiber felt (SSFF) with high electrochemical active surface area has an excellent catalytic activity for hydrogen generation, which is comparable to Pt/C cathode and superior to stainless steel mesh (SSM) cathode in the single-chamber MEC. The SSFF cathode (mean filter rating 100 μm) produces hydrogen at a rate of 3.66 ± 0.43 m3 H2 m-3d-1 (current density of 17.29 ± 1.68 A m-2), with a hydrogen recovery of 76.37 ± 15.04% and overall energy efficiency of 79.61 ± 13.07% at an applied voltage of 0.9 V. The performance of SSFF cathode improves over time due to a decrease in overpotential which caused by corrosion. These results demonstrate that SSFF can be a promising alternative for Pt catalytic cathode in MEC for hydrogen production.

  9. Influence of the Iron Anisothermal Sintering on the Characteristic of the Hollow Cathode Discharge

    Institute of Scientific and Technical Information of China (English)

    BRUNATTO; Silvio Francisco; MUZART; Joel Louis Rene

    2004-01-01

    This work studies the influence of anisothermal iron sintering process on hollow cathode discharge characteristics. Two independent cathodes form an annular discharge. The pressed cylindrical iron powder sample, acting as central cathode, was placed concentrically in the interior of an external cathode. The external cathode, machined from an AISI 3 l0 steel bar, besides acting to confine the geometry of the plasma, can also acts as a source of alloying elements. The sample heating is a function of the ion bombardment energy and, so, of the discharge electrical parameters: current (or current density) and the effective potential applied to the cathode. Successive anisothermal sintering is performed in a same sample until the reproducibility of the electrical parameters being obtained. The heating experiments up to 1250 ℃, in a gas mixture of 80% Ar + 20% H2, at pressure of 133 Pa, at flow of 2xl0-6 m3s-1, with an inter-cathode radial space of 5.8 mm,were carried out. It was verified the metallurgical evolution of the iron sample sintering process influences the current-ton(time switched-on of the pulse) characteristics of the discharge.

  10. Ambient temperature cured TiB2 cathode coating for aluminum electrolysis

    Institute of Scientific and Technical Information of China (English)

    赖延清; 李庆余; 杨建红; 李劼

    2003-01-01

    The concept of ambient temperature curable TiB2 cathode coating was put forward, and the ambient temperature curable TiB2 cathode coating was prepared successfully. Differing from the previous TiB2 cathode coating solidified approximately at 200 ℃,the ambient temperature curable TiB2 cathode coating can be solidified at room temperature, so the heating equipment is not necessary, which simplifies the preparation process and facilitates the industrial application of TiB2 cathode coating. Many kinds of resin and curing agent were investigated. On the above-mentioned basis, the ambient temperature curable TiB2 cathode coating was prepared with furan resin 5 500 mixed with complex resins B as carbon binder and DXG1 as curing agent in 24 h. The results show that the properties of prepared coating are excellent, the electrical resistivity is 29.8 μΩ*m, the compressive strength is 33.6 MPa, which are all better than the relevant properties of partially graphitized cathode carbon block for aluminum electrolysis prescribed by the GB 8744-88. SEM morphologies show that the section morphology of the TiB2 coating is unaltered during the electrolysis test, the TiB2 coating can be used in aluminum electrolysis industry to save energy and prolong the life of aluminum electrolysis cell.

  11. Silver electrodeposition on the activated carbon air cathode for performance improvement in microbial fuel cells

    Science.gov (United States)

    Pu, Liangtao; Li, Kexun; Chen, Zhihao; Zhang, Peng; Zhang, Xi; Fu, Zhou

    2014-12-01

    The present work was to study silver electrodeposition on the activated carbon (AC) air cathode for performance improvement in microbial fuel cells (MFCs). The treated cathodes were proved to be effective to enhance the performance of MFCs. The maximum power density of MFC with silver electrodeposition time of 50 s (Ag-50) cathode was 1080 ± 60 mW m-2, 69% higher than the bare AC air cathode. X-ray photoelectron spectroscopy (XPS) results showed that zero-valent, monovalent and divalent silver were present to transform mutually, which illustrated that the oxygen reduction reaction (ORR) at the cathode took place through four-electron pathway. From electrochemical impedance spectroscopy (EIS) analysis, the electrodeposition method made the total resistance of the electrodes largely reduced. Meanwhile the deposited silver had no toxic effects on anode culture but inhibited the biofilm growth of the cathodes. This kind of antimicrobial efficient cathode, prepared with a simple, fast and economical method, was of good benefit to the performance improvement of MFCs.

  12. Electrokinetic Treatment of Cr-, Cu-, and Zn-Contaminated Sediment: Cathode Modification.

    Science.gov (United States)

    Rajić, Ljiljana; Dalmacija, Božo; Perović, Svetlana Ugarčina; Krčmar, Dejan; Rončević, Srđan; Tomašević, Dragana

    2013-12-01

    Enhanced electrokinetic (EK) removal of Cr, Cu, and Zn from sediment by using original and modified integrated ion exchange (IIX™) cathodes was investigated. IIX cathode design and EK device process modifications were made to improve performance: separation of IIX cathode components (IIXS), combination of modified IIX cathode with pulsed electric field (IIXSP), and separation of IIX cathode components with addition of an anion exchange resin compartment (IIXA). After using the IIXSP, overall Cr, Cu, and Zn removal efficacies were significantly improved compared with the other treatments investigated. No improvements in overall Cr, Cu, and Zn removal efficacies were achieved by utilization of IIXA. Nevertheless, significant removal efficacies occurred at the anode region since distribution of the alkaline front was prevented. However, metal accumulation in the cathode region occurred. This was a consequence of metal cation complexation with Cl(-) released from the anion exchange resin that changed the direction of metal migration. Enhancing EK remediation of Cr-, Cu-, and Zn-contaminated sediment can be achieved by using a modified IIX cathode. PMID:24381480

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

    Science.gov (United States)

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

    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, liquid water appears and a two-phase zone forms within the porous cathode. A two-phase, multicomponent mixture model in conjunction with a finite-volume-based computational fluid dynamics (CFD) technique is applied to simulate the cathode operation in this regime. The model is able to handle the situation where a single-phase region co-exists with a two-phase zone in the air cathode. For the first time, the polarization curve as well as water and oxygen concentration distributions encompassing both single- and two-phase regimes of the air cathode are presented. Capillary action is found to be the dominant mechanism for water transport inside the two-phase zone of the hydrophilic structure. The liquid water saturation within the cathode is predicted to reach 6.3% at 1.4 A cm -2 for dry inlet air.

  14. Improving lithium-ion battery performances by adding fly ash from coal combustion on cathode film

    International Nuclear Information System (INIS)

    A lithium battery is composed of anode, cathode and a separator. The performance of lithium battery is also influenced by the conductive material of cathode film. In this research, the use of fly ash from coal combustion as conductive enhancer for increasing the performances of lithium battery was investigated. Lithium iron phosphate (LiFePO4) was used as the active material of cathode. The dry fly ash passed through 200 mesh screen, LiFePO4 and acethylene black (AB), polyvinylidene fluoride (PVDF) as a binder and N-methyl-2-pyrrolidone (NMP) as a solvent were mixed to form slurry. The slurry was then coated, dried and hot pressed to obtain the cathode film. The ratio of fly ash and AB were varied at the values of 1%, 2%, 3%, 4% and 5% while the other components were at constant. The anode film was casted with certain thickness and composition. The performance of battery lithium was examined by Eight Channel Battery Analyzer, the composition of the cathode film was examined by XRD (X-Ray Diffraction), and the structure and morphology of the anode film was analyzed by SEM (Scanning Electron Microscope). The composition, structure and morphology of cathode film was only different when fly ash added was 4% of AB or more. The addition of 2% of AB on cathode film gave the best performance of 81.712 mAh/g on charging and 79.412 mAh/g on discharging

  15. In situ X-ray studies of film cathodes for solid oxide fuel cells

    International Nuclear Information System (INIS)

    Highlights: •Synchrotron X-rays are used to study in operando the structural and chemical changes of LSM and LSCF film cathodes during half-cell operations. •A-site and B-site cations actively segregate or desegregate on the changes of temperature, pO2, and electrochemical potential. •Chemical lattice expansions show that oxygen-cathode interface is the primary source of rate-limiting processes. •The surface and subsurface of the LSM and LSCF films have different oxidation-states due to vacancy concentration changes. •Liquid-phase infiltration and coarsening processes of cathode materials into porous YSZ electrolyte backbone were monitored by USAXS. -- Abstract: Synchrotron-based X-ray techniques have been used to study in situ the structural and chemical changes of film cathodes during half-cell operations. The X-ray techniques used include X-ray reflectivity (XR), total-reflection X-ray fluorescence (TXRF), high-resolution diffraction (HRD), ultra-small angle X-ray scattering (USAXS). The epitaxial thin film model cathodes for XR, TXRF, and HRD measurements are made by pulse laser deposition and porous film cathodes for USAX measurements are made by screen printing technique. The experimental results reviewed here include A-site and B-site segregations, lattice expansion, oxidation-state changes during cell operations and liquid-phase infiltration and coarsening of cathode to electrolyte backbone

  16. Improving lithium-ion battery performances by adding fly ash from coal combustion on cathode film

    Energy Technology Data Exchange (ETDEWEB)

    Dyartanti, Endah Retno; Jumari, Arif, E-mail: arifjumari@yahoo.com; Nur, Adrian; Purwanto, Agus [Research Group of Battery & Advanced Material, Department of Chemical Engineering, Sebelas Maret University, Jl. Ir. Sutami 36 A Kentingan, Surakarta Indonesia 57126 (Indonesia)

    2016-02-08

    A lithium battery is composed of anode, cathode and a separator. The performance of lithium battery is also influenced by the conductive material of cathode film. In this research, the use of fly ash from coal combustion as conductive enhancer for increasing the performances of lithium battery was investigated. Lithium iron phosphate (LiFePO{sub 4}) was used as the active material of cathode. The dry fly ash passed through 200 mesh screen, LiFePO{sub 4} and acethylene black (AB), polyvinylidene fluoride (PVDF) as a binder and N-methyl-2-pyrrolidone (NMP) as a solvent were mixed to form slurry. The slurry was then coated, dried and hot pressed to obtain the cathode film. The ratio of fly ash and AB were varied at the values of 1%, 2%, 3%, 4% and 5% while the other components were at constant. The anode film was casted with certain thickness and composition. The performance of battery lithium was examined by Eight Channel Battery Analyzer, the composition of the cathode film was examined by XRD (X-Ray Diffraction), and the structure and morphology of the anode film was analyzed by SEM (Scanning Electron Microscope). The composition, structure and morphology of cathode film was only different when fly ash added was 4% of AB or more. The addition of 2% of AB on cathode film gave the best performance of 81.712 mAh/g on charging and 79.412 mAh/g on discharging.

  17. Ion spectra of vacuum arc plasma with compound and alloy cathodes

    International Nuclear Information System (INIS)

    We have carried out an experimental investigation of the charge state distribution of ions produced in the vacuum arc plasma for the case when the cathode is a compound or alloy. The plasma was generated in a metal vapor vacuum arc ion source, and the charge state spectra were measured using a time-of-flight method. We have compared these spectra to the spectra obtained from cathodes of the constituent elements. The cathode materials used and reported on here were the following groups: SiC/Si/C [i.e., we have compared the spectra obtained using a cathode of silicon carbide with the spectra obtained using (a) a silicon cathode and (b) a carbon cathode], TiC/TiN/TiO2/Ti/C, WC/W/C, (UC-ZrC)/UN/U/Zr/C, brass/Cu/Zn, and stainless steel/Fe/Cr/Ni. The arc current employed throughout was approximately 100 A. We find that the charge state distributions change depending on the elemental composition of the alloy or compound of which the cathode is fabricated

  18. Enhanced stability of multilayer graphene-supported catalysts for polymer electrolyte membrane fuel cell cathodes

    Science.gov (United States)

    Marinkas, A.; Hempelmann, R.; Heinzel, A.; Peinecke, V.; Radev, I.; Natter, H.

    2015-11-01

    One of the biggest challenges in the field of polymer electrolyte membrane fuel cells (PEMFC) is to enhance the lifetime and the long-term stability of PEMFC electrodes, especially of cathodes, furthermore, to reduce their platinum loading, which could lead to a cost reduction for efficient PEMFCs. These demands could be achieved with a new catalyst support architecture consisting of a composite of carbon structures with significant different morphologies. A highly porous cathode catalyst support layer is prepared by addition of various carbon types (carbon black particles, multi-walled carbon nanotubes (MWCNT)) to multilayer graphene (MLG). The reported optimized cathodes shows extremely high durability and similar performance to commercial standard cathodes but with 89% lower Pt loading. The accelerated aging protocol (AAP) on the membrane electrode assemblies (MEA) shows that the presence of MLG increases drastically the durability and the Pt-extended electrochemical surface area (ECSA). In fact, after the AAP slightly enhanced performance can be observed for the MLG-containing cathodes instead of a performance loss, which is typical for the commercial carbon-based cathodes. Furthermore, the presence of MLG drastically decreases the ECSA loss rate. The MLG-containing cathodes show up to 6.8 times higher mass-normalized Pt-extended ECSA compared to the commercial standard systems.

  19. Improving lithium-ion battery performances by adding fly ash from coal combustion on cathode film

    Science.gov (United States)

    Dyartanti, Endah Retno; Jumari, Arif; Nur, Adrian; Purwanto, Agus

    2016-02-01

    A lithium battery is composed of anode, cathode and a separator. The performance of lithium battery is also influenced by the conductive material of cathode film. In this research, the use of fly ash from coal combustion as conductive enhancer for increasing the performances of lithium battery was investigated. Lithium iron phosphate (LiFePO4) was used as the active material of cathode. The dry fly ash passed through 200 mesh screen, LiFePO4 and acethylene black (AB), polyvinylidene fluoride (PVDF) as a binder and N-methyl-2-pyrrolidone (NMP) as a solvent were mixed to form slurry. The slurry was then coated, dried and hot pressed to obtain the cathode film. The ratio of fly ash and AB were varied at the values of 1%, 2%, 3%, 4% and 5% while the other components were at constant. The anode film was casted with certain thickness and composition. The performance of battery lithium was examined by Eight Channel Battery Analyzer, the composition of the cathode film was examined by XRD (X-Ray Diffraction), and the structure and morphology of the anode film was analyzed by SEM (Scanning Electron Microscope). The composition, structure and morphology of cathode film was only different when fly ash added was 4% of AB or more. The addition of 2% of AB on cathode film gave the best performance of 81.712 mAh/g on charging and 79.412 mAh/g on discharging.

  20. Pore geometry of dispenser cathode surface vs. emission characteristics, and Ba recovery characteristics after ion bombardment

    Science.gov (United States)

    Higuchi, Toshiharu; Nakamura, Osamu; Matsumoto, Sadao; Uda, Eiichirou

    1999-05-01

    A study was conducted to investigate the emission characteristics and barium recovery characteristics after ion bombardment of two types of Ir-coated dispenser cathodes having a pore density on the surface layer of the cathodes of 4×10 4 and 1.3×10 4 pores/mm 2. Cathode current was measured under pulse operation in a range of 0.1-9% duty cycle. When the duty cycle dependence of emissions was examined, the current densities of both cathodes were the same in the case of 0.1% duty cycle, delivering about 12 A/cm 2. The work functions also showed the same value. However, evaluations of 4% duty cycle and 9% duty cycle found that the cathode with a higher pore density showed emission characteristics higher by 50% and 70%. Regarding the recovery time of barium and oxygen after argon ion bombardment with Auger electron spectroscopy (AES), the low-pore-density cathode required as long as 3 min for recovery, whereas the high-pore-density cathode recovered in 1.1 min. From the above experiments, it was clarified that emission characteristics under high duty and barium recovery characteristics after ion bombardment can be improved by increasing the pore density of the surface layer. The basic mechanisms leading to these results were also theoretically considered by solving surface diffusion equations.

  1. The emission carbonate crystallite and oxide cathode performance in electron tubes

    Science.gov (United States)

    Shafer, Don; Turnbull, John

    Emission from an oxide cathode is dependent upon the ratio of alkaline earth carbonates present at the cathodes surface. The method by which each carbonate is made plays a key role in its function in a cathode. Other factors effecting the performance of the oxide cathode are the type of constituents in the base metal. These constituents play key roles in barium diffusion and evaporation. It has been found that the crystalline structure of the alkaline earth carbonates affects the life of oxide cathode tubes. The rates of diffusion and evaporation of alkaline earth oxides, were studied with the use of the SEM-electron beam probe and energy dispersive X-ray Edax. Cathode surfaces to the depths of 1000 Å (approximately 200 atomic layers) were scanned. Many cathodes were studied after conversion from carbonates to oxides. It was found that barium oxide evaporated to 1/3 of the original formulation at oxide conversion. This diffusion and evaporation reaction took place throughout tube life. This work has shown that the crystal size, structure, and composition may be modified to lengthen the BaO half life and therefore lengthen the overall life of the electron tube.

  2. Considerations of the Role of the Cathodic Region in Localized Corrosion

    International Nuclear Information System (INIS)

    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, Inet, 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

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

    KAUST Repository

    Luo, Yong

    2011-11-01

    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 density of 1355 ± 62 mW m -2 (normalized to the projected cathode area), which was similar to that obtained with a carbon cloth cathode (1390 ± 72 mW m-2). Carbon mesh with a PTFE diffusion layer produced only a slightly lower (6.6%) maximum power density (1303 ± 48 mW m-2). The Coulombic efficiencies were a function of current density, with the highest value for the carbon mesh and PDMS (79%) larger than that for carbon cloth (63%). The cost of the carbon mesh cathode with PDMS/Carbon or PTFE (excluding catalyst and binder costs) is only 2.5% of the cost of the carbon cloth cathode. These results show that low cost carbon materials such as carbon mesh can be used as the cathode in an MFC without reducing the performance compared to more expensive carbon cloth. © 2011 Elsevier B.V.

  4. Frequency study of microwave generation in an axially extracted virtual cathode oscillator

    Energy Technology Data Exchange (ETDEWEB)

    Yatsuzuka, M.; Nakayama, M.; Nobuhara, S. [Himeji Inst. of Tech., Hyogo (Japan). Dept. of Electrical Engineering; Hashimoto, Y. [Kobe City Coll. of Technology, Hyogo (Japan). Dept. of Electronic Engineering; Ishihara, O. [Texas Tech Univ., Lubbock, TX (United States). Dept. of Electrical Engineering

    1996-12-31

    In virtual cathode oscillators (vircators) the axial electric field, driven by either reflecting electrons between the real and virtual cathodes or oscillations of the virtual cathode, couples with axially symmetric transverse magnetic waveguide mode (TM{sub 0m}). To study this mechanism in detail the dependence of radiation frequency on cathode diameter, output waveguide diameter, and anode-cathode (A-K) gap spacing was studied experimentally in an axially-extracted vircator at Himeji Institute of Technology. The radiation frequency decreased with increasing A-K gap spacing for a constant cathode diameter. The maximum power emission was observed at the A-K gap spacing for which reflecting trapped electrons between the real and virtual cathodes determine the radiation frequency. The measurement of power density profile in the radial and azimuthal directions showed the radiation pattern of TM{sub 01} mode, in agreement with the observed frequency which satisfies the dispersion relation of TM{sub 01} mode in the circular output waveguide.

  5. A study on the mechanical and electrical reliability of individual carbon nanotube field emission cathodes

    International Nuclear Information System (INIS)

    Individual carbon nanotube (CNT) field emission characteristics present a number of advantages for potential applications in electron microscopy and electron beam lithography. Mechanical and electrical reliability of individual CNT cathodes, however, remains a challenge and thus device integration of these cathodes has been limited. In this work, we present an investigation into the reliability issues concerning individual CNT field emission cathodes. We also introduce and analyze the reliability of a novel individual CNT cathode. The cathode structure is composed of a multi-walled carbon nanotube (MWNT) attached by Joule heating to a nickel-coated Si microstructure. The junction of the CNT and the Si microstructure is mechanically and electrically robust to withstand the strong electric field conditions that are typical for field emission devices. An optimal Ni film coating of 25 nm on the Si microstructure is required for mechanical and electrical stability. Experimental current-voltage data for the new cathode structure definitively demonstrates carbon nanotube field emission. Additionally, we demonstrate that our new nanofabrication method is capable of producing sophisticated cathode structures that were previously not realizable, such as one consisting of two parallel MWNTs, with highly controlled CNT lengths with 40 nm accuracy and nanotube-to-nanotube separations of less than 10 μm

  6. A study on the mechanical and electrical reliability of individual carbon nanotube field emission cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Ribaya, Bryan P; Leung, Joseph; Brown, Philip; Nguyen, Cattien V [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Rahman, Mahmud [Electron Devices Laboratory, Santa Clara University, 500 El Camino Real, Santa Clara, CA 95053 (United States)], E-mail: Cattien.V.Nguyen@nasa.gov

    2008-05-07

    Individual carbon nanotube (CNT) field emission characteristics present a number of advantages for potential applications in electron microscopy and electron beam lithography. Mechanical and electrical reliability of individual CNT cathodes, however, remains a challenge and thus device integration of these cathodes has been limited. In this work, we present an investigation into the reliability issues concerning individual CNT field emission cathodes. We also introduce and analyze the reliability of a novel individual CNT cathode. The cathode structure is composed of a multi-walled carbon nanotube (MWNT) attached by Joule heating to a nickel-coated Si microstructure. The junction of the CNT and the Si microstructure is mechanically and electrically robust to withstand the strong electric field conditions that are typical for field emission devices. An optimal Ni film coating of 25 nm on the Si microstructure is required for mechanical and electrical stability. Experimental current-voltage data for the new cathode structure definitively demonstrates carbon nanotube field emission. Additionally, we demonstrate that our new nanofabrication method is capable of producing sophisticated cathode structures that were previously not realizable, such as one consisting of two parallel MWNTs, with highly controlled CNT lengths with 40 nm accuracy and nanotube-to-nanotube separations of less than 10 {mu}m.

  7. Power generation by packed-bed air-cathode microbial fuel cells

    KAUST Repository

    Zhang, Xiaoyuan

    2013-08-01

    Catalysts and catalyst binders are significant portions of the cost of microbial fuel cell (MFC) cathodes. Many materials have been tested as aqueous cathodes, but air-cathodes are needed to avoid energy demands for water aeration. Packed-bed air-cathodes were constructed without expensive binders or diffusion layers using four inexpensive carbon-based materials. Cathodes made from activated carbon produced the largest maximum power density of 676±93mW/m2, followed by semi-coke (376±47mW/m2), graphite (122±14mW/m2) and carbon felt (60±43mW/m2). Increasing the mass of activated carbon and semi-coke from 5 to ≥15g significantly reduced power generation because of a reduction in oxygen transfer due to a thicker water layer in the cathode (~3 or ~6cm). These results indicate that a thin packed layer of activated carbon or semi-coke can be used to make inexpensive air-cathodes for MFCs. © 2013 Elsevier Ltd.

  8. Different modes of arc attachment at HID cathodes: simulation and comparison with measurements

    International Nuclear Information System (INIS)

    Based on a model for the plasma boundary layer of high intensity discharge cathodes, simulations are performed and compared with experimental results. To solve the power balance of the cathode body different methods are used, namely a 1D integral solution as well as 1D, 2D and 3D finite-element calculations. The simulations are done for cylindrical tungsten cathodes operated in different pure noble gas discharges (0.1-1.0 MPa) and with currents between 0.5 and 10 A. Under these conditions different modes of arc attachment are found, both in simulations and experiments. For the diffuse mode of arc attachment an excellent quantitative agreement between measurements and the simulations is obtained, reflecting an improved accuracy of measurements and simulation. In addition, different spot modes are found. At least one of these modes is also observed in the experiment. Also for this spot mode the agreement between measurements and simulation for the integral quantities is good. There are still some open questions concerning the spot mode of cathodic arc attachment. Varying the geometric dimensions of the cathode, the proper simulation of the heat conduction problem of the cathode body is shown. Variations of the plasma properties, like gas type and pressure, prove the conceptional capability of the boundary layer model for the simulation of different modes of arc attachment. Evaluating the cathode fall characteristics, regions of existence for the different modes are found, which are similar to the experiments

  9. Diffusion layer characteristics for increasing the performance of activated carbon air cathodes in microbial fuel cells

    KAUST Repository

    Zhang, Xiaoyuan

    2016-01-01

    The characteristics of several different types of diffusion layers were systematically examined to improve the performance of activated carbon air cathodes used in microbial fuel cells (MFCs). A diffusion layer of carbon black and polytetrafluoroethylene (CB + PTFE) that was pressed onto a stainless steel mesh current collector achieved the highest cathode performance. This cathode also had a high oxygen mass transfer coefficient and high water pressure tolerance (>2 m), and it had the highest current densities in abiotic chronoamperometry tests compared to cathodes with other diffusion layers. In MFC tests, this cathode also produced maximum power densities (1610 ± 90 mW m−2) that were greater than those of cathodes with other diffusion layers, by 19% compared to Gore-Tex (1350 ± 20 mW m−2), 22% for a cloth wipe with PDMS (1320 ± 70 mW m−2), 45% with plain PTFE (1110 ± 20 mW m−2), and 19% higher than those of cathodes made with a Pt catalyst and a PTFE diffusion layer (1350 ± 50 mW m−2). The highly porous diffusion layer structure of the CB + PTFE had a relatively high oxygen mass transfer coefficient (1.07 × 10−3 cm s−1) which enhanced oxygen transport to the catalyst. The addition of CB enhanced cathode performance by increasing the conductivity of the diffusion layer. Oxygen mass transfer coefficient, water pressure tolerance, and the addition of conductive particles were therefore critical features for achieving higher performance AC air cathodes.

  10. Impact of salinity on cathode catalyst performance in microbial fuel cells (MFCs)

    KAUST Repository

    Wang, Xi

    2011-10-01

    Several alternative cathode catalysts have been proposed for microbial fuel cells (MFCs), but effects of salinity (sodium chloride) on catalyst performance, separate from those of conductivity on internal resistance, have not been previously examined. Three different types of cathode materials were tested here with increasingly saline solutions using single-chamber, air-cathode MFCs. The best MFC performance was obtained using a Co catalyst (cobalt tetramethoxyphenyl porphyrin; CoTMPP), with power increasing by 24 ± 1% to 1062 ± 9 mW/m2 (normalized to the projected cathode surface area) when 250 mM NaCl (final conductivity of 31.3 mS/cm) was added (initial conductivity of 7.5 mS/cm). This power density was 25 ± 1% higher than that achieved with Pt on carbon cloth, and 27 ± 1% more than that produced using an activated carbon/nickel mesh (AC) cathode in the highest salinity solution. Linear sweep voltammetry (LSV) was used to separate changes in performance due to solution conductivity from those produced by reductions in ohmic resistance with the higher conductivity solutions. The potential of the cathode with CoTMPP increased by 17-20 mV in LSVs when the NaCl addition was increased from 0 to 250 mM independent of solution conductivity changes. Increases in current were observed with salinity increases in LSVs for AC, but not for Pt cathodes. Cathodes with CoTMPP had increased catalytic activity at higher salt concentrations in cyclic voltammograms compared to Pt and AC. These results suggest that special consideration should be given to the type of catalyst used with more saline wastewaters. While Pt oxygen reduction activity is reduced, CoTMPP cathode performance will be improved at higher salt concentrations expected for wastewaters containing seawater. © 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

  11. Impact of the Usage of a Slotted Cathode Carbon Block on Thermoelectric Field in an Aluminum Reduction Cell

    Science.gov (United States)

    Tao, Wenju; Li, Tuofu; Wang, Zhaowen; Gao, Bingliang; Shi, Zhongning; Hu, Xianwei; Cui, Jianzhong

    2015-05-01

    The horizontal current in a metal pad of an aluminum reduction cell is critical because of its effect on the fluctuation of the metal pad. In this study, a novel cathode with a slotted cathode carbon block was proposed to decrease the horizontal current. The effects of the slotted cathode carbon block on the horizontal and vertical currents in the metal pad, cathode voltage, and temperature distribution in the cathode were calculated using the finite-element method. The results show that the slotted cathode carbon has great potential to decrease the horizontal current. When the length of slot b equals 400 mm, the maximum horizontal current density decreased by 50.4%. However, the cathode voltage in the cathode with the slotted cathode carbon was ~43 mV higher than that in a conventional cell, and the temperature in the slotted cathode carbon was slightly higher than that in a conventional carbon cell. Moreover, with increasing length of slot b, the maximum horizontal and vertical currents in the metal pad moved toward the cell center. The result of this study may provide the database in understanding the effect of the slotted cathode carbon on cell.

  12. Poly(vinyl alcohol) separators improve the coulombic efficiency of activated carbon cathodes in microbial fuel cells

    KAUST Repository

    Chen, Guang

    2013-09-01

    High-performance microbial fuel cell (MFC) air cathodes were constructed using a combination of inexpensive materials for the oxygen reduction cathode catalyst and the electrode separator. A poly(vinyl alcohol) (PVA)-based electrode separator enabled high coulombic efficiencies (CEs) in MFCs with activated carbon (AC) cathodes without significantly decreasing power output. MFCs with AC cathodes and PVA separators had CEs (43%-89%) about twice those of AC cathodes lacking a separator (17%-55%) or cathodes made with platinum supported on carbon catalyst (Pt/C) and carbon cloth (CE of 20%-50%). Similar maximum power densities were observed for AC-cathode MFCs with (840 ± 42 mW/m2) or without (860 ± 10 mW/m2) the PVA separator after 18 cycles (36 days). Compared to MFCs with Pt-based cathodes, the cost of the AC-based cathodes with PVA separators was substantially reduced. These results demonstrated that AC-based cathodes with PVA separators are an inexpensive alternative to expensive Pt-based cathodes for construction of larger-scale MFC reactors. © 2013 Elsevier B.V. All rights reserved.

  13. Crystal nucleus formation on the cathode under conditions of supersaturation of melt by lower valent forms

    International Nuclear Information System (INIS)

    Nucleation on the cathode of sodium-tungsten bronzes forom the Na2WO4-WO3 melt, containing 40 mol.% WO3 is studied. It has been found that in the initial period the cathode deposition of sodium-tungsten bronze is preceeded by the formation of tungsten soluble lower reduced forms, the concentration of which can considerably exceed the equilibrium one because of excessive overstress of oxide bronze crystal nucleation. The polarization of cathode and change of its potential at the crystal nucleation of sodium-tungsten bronze and switching-off of the electrolysis current has been studied

  14. Degradation Studies on LiFePO4 cathode

    OpenAIRE

    Scipioni, Roberto; Jørgensen, Peter Stanley; Hjelm, Johan; Norby, Poul; Rasmussen, Claus Nygaard; Jensen, Søren Højgaard

    2014-01-01

    Lithium-ion batteries are a promising technology for automotive application, but limited performance and lifetime is still a big issue. The aim of this work is to study and address degradation processes which affect LiFePO4 (LFP) cathodes - one of the most common cathodes in commercial Li-ion batteries. In order to evaluate how the LFP cathode is affected by C-rate a LFP working electrode, Lithium metal foil counter electrode and Lithium metal reference electrode was tested in a 3-electrode s...

  15. Outcoupling efficiency of OLEDs with 2D periodical corrugation at the cathode

    International Nuclear Information System (INIS)

    We study theoretically the optical performance of organic light-emitting diodes (OLEDs) with 2D periodical corrugation at the cathode. We show how emergence of radiative surface plasmon resonances at the 2D corrugated cathode leads to the enhancement of the outcoupling efficiency of the OLED, which is primarily due to the outcoupling of emission generated by vertically oriented emitting excitons in the emission layer. We analyze the outcoupling efficiency of the OLED as a function of geometrical parameters of the corrugation and establish design rules for optimal outcoupling enhancement with the 2D corrugation at the cathode. (paper)

  16. Negative hydrogen ion beam extraction from an AC heated cathode driven Bernas-type ion source

    Science.gov (United States)

    Okano, Y.; Miyamoto, N.; Kasuya, T.; Wada, M.

    2015-04-01

    A plasma grid structure was installed to a Bernas-type ion source used for ion implantation equipment. A negative hydrogen (H-) ion beam was extracted by an AC driven ion source by adjusting the bias to the plasma grid. The extracted electron current was reduced by positively biasing the plasma grid, while an optimum plasma grid bias voltage for negative ion beam extraction was found to be positive 3 V with respect to the arc chamber. Source operations with AC cathode heating show extraction characteristics almost identical to that with DC cathode heating, except a minute increase in H- current at higher frequency of cathode heating current.

  17. Effect of conductive additives in LiFePO4 cathode for lithium-ion batteries

    OpenAIRE

    Shim, J; Guerfi, A.; Zaghib, K.; Striebel, K.A.

    2003-01-01

    The electrochemical properties of LiFePO4 cathodes with different carbon contents were studied to find out the role of carbon as conductive additive. LiFePO4 cathodes containing from 0 percent to 12 percent of conductive additive (carbon black or mixture of carbon black and graphite) were cycled at different C rates. The capacity of LiFePO4 cathode increased, as conductive additive content increased. Carbon increased the utilization of active material and the electrical conductivity of e...

  18. Selection of high-brightness, laser-driven cathodes for electron accelerators and FELS

    International Nuclear Information System (INIS)

    Very intense, low emittance pulsed beams of electrons can be generated from laser-driven cathodes either by thermionic- or photo-emission. Several hundreds of amperes of electrons per square centimeter were observed for pulse lengths up to 50 ns. A normalized beam brightness of 107 A/cm2/rad2 has been measured. These beams can be emission-gated at the cathode surface by modulating the laser-beam. Such beam bunching will generate picosecond-to-microsecond-long pulses at the source. A variety of cathodes are described, and a method of selection for specific applications is presented

  19. Microstructure and properties of a Mo-CeO2 heated cathode material

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jiuxing; WAN Xiaofeng; LI Xiangbo; ZHOU Wenyuan; ZHOU Meiling

    2004-01-01

    The microstructure, mechanical properties, and electron-emission properties of a newly developed heated cath ode material Mo-CeO2 with 4.0% (mass fraction) of CeO2 were investigated. It is shown that the Mo-CeO2 cathode material possesses high tensile strength and good room-temperature ductility. After carbonized, the Mo-CeO2 cathode material has a higher zero field emission current density and a lower work function compared with the W-ThO2 cathode material.

  20. Cation-substituted spinel oxide and oxyfluoride cathodes for lithium ion batteries

    Science.gov (United States)

    Manthiram, Arumugam; Choi, Wongchang

    2014-05-13

    The present invention includes compositions and methods of making cation-substituted and fluorine-substituted spinel cathode compositions by firing a LiMn.sub.2-y-zLi.sub.yM.sub.zO.sub.4 oxide with NH.sub.4HF.sub.2 at low temperatures of between about 300 and 700.degree. C. for 2 to 8 hours and a .eta. of more than 0 and less than about 0.50, mixed two-phase compositions consisting of a spinel cathode and a layered oxide cathode, and coupling them with unmodified or surface modified graphite anodes in lithium ion cells.