Anode Space Research Articles

Regeneration by Membrane Electrolysis of an Etching Solution Based on Copper Chloride

Regeneration of an acid solution for copper etching, based on copper(II) chloride, hydrochloric acid, and ammonium chloride, by membrane electrolysis was studied. The concentrations of copper(I, II) ions in the cathode and anode spaces, current efficiency, degree of copper recovery, and specific consumption of electric power at different quantities of electricity passed through the electrolyzer were measured. The influence exerted by the current density on the electric power expenditure for recovery of metallic copper was examined. The anode current efficiency by chlorine was determined with a spent etching solution and an H2SO4 solution used as anolyte.

Diamond vacuum field emission devices

This article reports the development of (a) vertical and (b) lateral diamond vacuum field emission devices with excellent field emission characteristics. These diamond field emission devices, diode and triode, were fabricated using a self-aligning gate formation technique from silicon-on-insulator wafers using conventional silicon micropatterning and etching techniques. High emission current >0.1 A was achieved from the vertical diamond field emission diode with an indented anode design. The gated diamond triode in vertical configuration displayed excellent transistor characteristics with high DC gain of ∼800 and large AC output voltage of ∼100 V p–p. Lateral diamond field emission diodes with cathode–anode spacing less than 2 μm were fabricated. The lateral diamond emitter exhibited a low turn-on voltage of ∼5 V and a high emission current of 6 μA. The low turn-on voltage (field ∼3 V/μm) and high emission characteristics are the best of reported lateral field emitter structures.

Stable field emission from W tips in poor vacuum conditions

We report a stable field emission (FE) current from sharp tungsten (W) tips in relatively poor vacuum (up to 10−2 mbar) conditions. We use small tip–anode spacing to keep the extraction voltage low. A simple current regulator circuit, with a bandwidth of ∼1.6 kHz, was designed, which controls the voltage applied according to the emission current measured. Without a current regulator circuit, an uncleaned W tip in unbaked 6×10−7 mbar system pressure cannot emit stable FE current and short-term fluctuations at a few nA current were found to be more than 300%. The current regulator circuit improves the FE current stability dramatically. It was observed that at current level of ∼3.5 nA and regulation voltage of ∼120 V the short-term fluctuations in the current were ∼5% at 6×10−7 mbar unbaked system pressure. Subsequently, the system pressure was increased in steps up to 10−3 mbar of argon gas and it was observed that the current regulator circuit worked at almost the same efficiency. Around 10−2 mbar of Ar gas pressure larger short-term fluctuations started appearing and around 10−1 mbar of Ar gas pressure the current regulator circuit failed to regulate the current. In another experiment, at 10−3 mbar of Ar gas pressure, at ∼1.5 and 25 nA current levels long-term FE current stability was recorded. Our results show that the FE current stability in our experiments is much better than that reported in the literature with feedback on the tip–anode distance. This study may find applications in focused electron beam systems as well as in electron impact ion sources.

The characteristics of a wire–plane corona streamer detector when an α-particle source is moved in a plane parallel to the cathode

The operation characteristics of a wire–plane corona streamer detector (WPCSD) in open air were investigated for broad side irradiation. Investigations were made on the counting characteristics in relation to their dependence on various anode diameters and source–anode spacing. The onset voltages for the corona mode V o as well as for the spark mode V p were determined. For each wire diameter a streamer mode ( V p− V o) was found. The sensitivity of the WPCSD was studied when a collimated beam of α-particles was moved parallel to the plane of the cathode from the anode-wire toward the cathode. In addition, the pulse height spectra of α-particles incident on the detector for different values of the anode voltage, V a, were determined and studied. A qualitative interpretation of the experimental data was given.

Direct Electrochemical Synthesis of Diaziridines

The possibility of direct electrosynthesis of mono- and bicyclic diaziridines is studied using, respectively, 1,2-dimethyldiaziridine and 1,5-diazobicyclo[3,1,0]hexane as an example. In either case the process is realized in a galvanostatic electrolysis in the anodic space of a diaphragm cell and proceeds through intermediate formation of alkylchloramines; other electrosynthesis conditions depend on the structure of the source aminoalkane. In the synthesis of monocyclic diaziridines, for the electrolyte, a 4 M solution of NaCl in water was used, which contained high concentrations of 0.5 and 2.0 M of, respectively, CH2O and MeNH2, and the amine excess served, in particular, for binding protons in the reaction of diaziridine synthesis. The process occurs in a homogeneous phase, and the current efficiency for 1,2-dimethyldiaziridine amounted to 40–50% in optimum conditions. In the synthesis of bicyclic diaziridines, the electrolyte was a 4 M solution of NaCl in a 20-% aqueous methanol, containing a low—0.1 M concentration of H2N(CH2)3NH2 and an equimolar quantity of CH2O, and additives of NaHCO3 were used for binding protons in the reaction of diaziridine synthesis. The process occurs in a heterophase environment because of an incomplete dissolution in the conditions of experiment of NaCl and intermediately-formed chloraminoalkane. The current efficiency for 1,5-diazobicyclo[3,1,0]hexane reached 80–85% in optimum conditions, but the loads of the source aminoalkane were 20 times lower than in the synthesis of monocyclic diaziridines. Compared are the results of a direct and an earlier-described indirect method of electrosynthesis of mono- and bicyclic diaziridines.

Applicability of the Slope Parameter Method to the Design of Cathodic Protection Systems for Marine Pipelines

Abstract This paper reviews the generalized approach to marine cathodic protection design, as applied to petroleum production jackets and to pipelines. It is demonstrated that the existing method in the case of pipelines can be interfaced with a newly proposed attenuation equation for evaluation of the range of applicability and calculation error. Accordingly, a modification to the existing protocol for galvanic cathodic protection system design is presented that quantitatively interrelates design life; anode size, weight, and properties; pipe size, current demand, and coating quality; seawater resistivity; magnitude of polarization; and anode spacing. An example cathodic protection (CP) system design is presented, and the utility of the method is discussed.

Planar field emitters fabricated by sulfur-doped boron nitride

Boron nitride (BN) films are grown on sapphire substrates by plasma-assisted chemical vapor deposition. BN films are doped with sulfur (S). The electrical resistivity of the S-doped BN film is reduced to 103 Ω cm, while the electrical resistivity of the undoped BN film is 1011 Ω cm. It is demonstrated that the negative electron affinity appears on the BN surface. Insertion of a GaN layer between the BN film and sapphire leads to a tight adhesion of the BN film. Cathode and anode electrons are formed on the BN film and the sapphire substrate, respectively, by evaporating Ti and Au. An emission current of 1 μA is obtained at an electric-field strength of 16 V/μm for the planar field emitter. An emission current density as high as 0.1 A/cm2 is detected. It is expected that the planar field emitters can be operated at several tens V with a decreased cathode–anode spacing and that the present field emitter structure is applicable to a field-emission panel display.

Electron field emission from diamond grown by a multiple pulsed laser process

Among wide-band-gap materials, diamond has been tested extensively in many laboratories for its applicability as an electron emission material. The results are encouraging but also point out the necessity of modifying the diamond films with respect to their chemical composition and/or atomic structure. This article reports on electron emission measurements conducted on diamond coatings deposited on WC/Co alloy by a multiple pulsed laser process. The electron emission has been measured in a diode configuration with a diamond surface–anode spacing of 20 and 50 μm in vacuum at P=10−7 Torr. Current densities of 6 mA/cm2 have been calculated at an applied voltage of 3000 V (for 20 μm). We propose an explanation for electron emission.

Effect of majority carrier space charges on minority carrier injection in dye doped polymer light-emitting devices

By blending suitable dyes into poly(N-vinylcarbazole) we have fabricated devices which emit light in the whole visible spectrum. Their current–voltage characteristics can be described by space-charge limited currents with effective trapping of the charge carriers by the dye molecules, while the light intensity shows a Fowler–Nordheim-like behavior as a function of the external electric field. However, the anodic space charge changes the field distribution inside the device and leads to a cathodic field enhancement which has to be considered in the Fowler–Nordheim equation. We were able to model the electroluminescence characteristics by assuming tunneling of the minority charge carriers through a triangular barrier. The obtained barrier heights showed a strong dependence on the dye molecules, suggesting that the injection of minority charge carriers takes place directly into the lowest unoccupied molecular orbital of the chromophors. Using poly(p-phenylenevinylene) and an oxadiazole starburst molecule as additional hole and electron transport layers, respectively, luminance of 250 cd/m2 and external quantum efficiency of 1% could be achieved.

Two-dimensional modeling of Cd(Zn)Te strip detectors

Although there has been significant recent progress in the development of CdTe and CdZnTe radiation detectors, these materials are still plagued by charge trapping and recombination problems. Recent work has shown that fabrication of arrays with small anodes can overcome these problems to some extent. The purpose of this simulation study was to investigate this small anode effect in relatively large strip detectors of various geometries. Unlike previous simulations, the current study includes the effects of both trapping and detrapping, significant inter-pixel spacing, and non-linear electric field profiles. In addition, the methods have the potential to account efficiently for spatial variations in trapping behavior and for multiple trapping levels. The results of the simulation predict that 8 mm thick strip detectors with 1 mm anode thickness and 0.3 mm anode spacing will provide adequate performance for our medical imaging application.

Cathodic Protection of a Plane with Parallel Cylindrical Anodes

To prevent corrosion of the circular bottom of a storage tank, several small cylindrical anodes are placed beneath and parallel to the tank bottom, and parallel to each other. A design strategy is presented for determining the anode spacing and depth for proper cathodic protection. For a uniform flux density of oxygen to the tank bottom, the maximum potential variation on the tank bottom (made dimensionless with the average cathode current density, the soil conductivity, and the anode spacing) is reported along with estimates of the potential drop in the soil between the cathode and the anodes and the potential drop within the anodes themselves.

Selective Oxidation of Ethane Using the Au|YSZ|Ag Electrochemical Membrane System

The catalytic conversion of ethane to acetaldehyde on an inert gold electrode has been studied using the electrochemical membrane reactor with yttria‐stabilized zirconia (YSZ) solid electrolyte at 475°C. On applying a direct current to the reaction cell, 5% ethane in Au|YSZ|Ag, 100% acetaldehyde was formed and the formation rate increased linearly with increasing current. Selectivities to acetaldehyde and carbon dioxide were 45 and 55%, respectively. The addition of oxygen to the ethane‐mixed gas in the anode space did not affect the acetaldehyde formation. The use of YSZ powder as a fixed bed catalyst under the mixed gas flow of ethane and oxygen at 450 to 600°C resulted in the formation of carbon monoxide, carbon dioxide, and ethene. Even the use of instead of oxygen resulted in no formation of acetaldehyde. Hence, it is likely that partial oxidation of ethane to acetaldehyde was carried out by the oxygen species transferred electrochemically through the YSZ which appeared at the gold‐YSZ‐gas triple‐phase boundary. From the results of ethanol oxidation over the Au|YSZ|Ag system, the following mechanism was proposed: ethane is dehydrogenated to an ethyl radical, then converted to ethoxide, and finally to acetaldehyde by the oxygen species transferred through the YSZ.

Selective Oxidation of Propene Using an Electrochemical Membrane Reactor with CeO2‐Based Solid Electrolyte

The partial oxidation of propene to acrylaldehyde on an inert gold electrode has been studied at 350 to 450°C over an electrochemical membrane reactor using as a solid electrolyte. This material has a high ionic conductivity at low temperatures. On applying a direct current to the reaction cell, acrylaldehyde was formed at the gold anode, and the formation rate of acrylaldehyde increased linearly with increasing current density. The addition of oxygen to the propene‐mixed gas at the anode space did not affect the acrylaldehyde production. Hence, it is likely that partial oxidation of propene was carried out by the oxygen species produced electrochemically through the electrolyte, and appearing at the gold‐electrolyte gas‐phase triple‐phase boundary. From the dependence of the acrylaldehyde selectivity on the amount and the type of dopants, it was found that the complete oxidation of propene with lattice oxygen from the rare‐earth‐doped surface was significant, and that the reactivity of lattice oxygen in with hydrocarbons decreased with increasing ionic conduction of the oxide.

Study of space-charge characteristics in polyethylene for power cable insulation by laser-induced pressure-pulse technique

By utilizing the laser induced pressure-pulse (LIPP) technique, the behavior of space charge in low-density polyethylene (LDPE) and crosslinked polyethylene (XLPE) films in contact with metal or carbon-loaded semiconducting layers was studied quantitatively to clarify the space-charge characteristics in power cables. Negative heterospace charge near the anode and positive space charge in the bulk were observed in unoxidized LDPE under the fields above 120 kV/mm. The amount of negative space charge increased with applied field, while positive space charge in the bulk disappeared with increasing applied field. This indicates that electron injection and ionization are enhanced by applied field. Prominent negative homospace charge was formed near the cathode in oxidized LDPE, which indicates that oxidation enhanced electron injection. The depth of charge centroid from the cathode became larger with increasing temperature. This indicates that the effective electron mobility increases with temperature. Negative space charge also was formed in the bulk in XLPE films with metal electrodes, which indicates that crosslinking enhanced electron injection. XLPE films with a carbon-loaded semiconducting layer showed both negative and positive homospace charges near the semiconducting layers, which indicates that both electrons and holes were injected from the semiconducting layer.

レーザ誘起圧力パルス法による電力ケーブル絶縁用ポリエチレンの空間電荷特性の検討

By utilizing the laser induced pressure-pulse (LIPP) technique, the behavior of space charge in low-density polyethylene (LDPE) and crosslinked polyethylene (XLPE) films in contact with metal or carbon-loaded semiconducting layers was studied quantitatively to clarify the space-charge characteristics in power cables. Negative heterospace charge near the anode and positive space charge in the bulk were observed in unoxidized LDPE under the fields above 120 kV/mm. The amount of negative space charge increased with applied field, while positive space charge in the bulk disappeared with increasing applied field. This indicates that electron injection and ionization are enhanced by applied field. Prominent negative homospace charge was formed near the cathode in oxidized LDPE, which indicates that oxidation enhanced electron injection. The depth of charge centroid from the cathode became larger with increasing temperature. This indicates that the effective electron mobility increases with temperature. Negative space charge also was formed in the bulk in XLPE films with metal electrodes, which indicates that crosslinking enhanced electron injection. XLPE films with a carbon-loaded semiconducting layer showed both negative and positive homospace charges near the semiconducting layers, which indicates that both electrons and holes were injected from the semiconducting layer.

Potential and velocity measurements in a magnetized hollow cathode discharge by means of electric probes and laser induced fluorescence

By means of electric probes, surfaces of equal electrical potential are measured in the plasma of a magnetized hollow cathode arc burning in argon. At moderate distances between the cathode and the anode the potential increases nearly linearly in proceeding in the axial direction from the cathode to the anode. In the radial direction a potential growth can be observed up to a plateau regime near the plasma edge. If the cathode–anode distance exceeds a critical length, the situation changes insofar as a voltage jump of nearly a factor of 2 occurs near the anode where higher voltage values are reached than on the anode surface. There the voltage drops in the radial direction to the outside plateau value. This voltage distribution is produced by a (positive) anodic space charge cloud, which accelerates the electrons. The voltage jump guarantees the transport of the arc current even in the case of a long arc. This space charge decelerates the ions flying in the axial direction and creates the possibility of ions rotating around the cathode–anode axis in the anode regime. This latter possibility was examined by monitoring the frequency resolved Doppler shift of the argon ion line at λ=611.49 nm measured by laser induced scattering. The flow field of the ions can be quantitatively understood from the spatial distribution of the electrical potential.

Electron-optical zooming using a modified image tube configuration

An electrostatic image converter tube geometry (model 6914) has been modified as a four-electrode configuration to provide electron-optical zooming. The zoom lens action is effected by the principle of anode space zooming. A zooming factor of 2.8 has been achieved using an image tube assembly with a resolution of about 30 line-pairs/mm, in an electron-optical demountable system. Gold photocathodes with a printed resolution pattern were used for this study. An interpretation of the observed electron-optical zooming action has been given in terms of gaussian optics. The results of some zoom image tubes having patterned cathode substrates on which Cs3Sb photocathodes has been processed are also presented.

Xenon Short Arc Lamps for Film Projection: The State of the Art after 20 Years

Xenon short arc lamps were developed in Europe over thirty years ago, but were not used in the United States until twenty years ago. The first major applications of these lamps were with developments associated with the New York World's Fair, and later serious applications were found in studios and theaters in the mid-1960's. Since that time, growth in the use of xenon arc lamps has been rapid and widespread. Unfortunately, with only half-a-dozen factory sources, the various short arc bulbs were often introduced in noninterchangeable designs by manufacturers using a variety of lengths and pin fittings. This tends to complicate the various applications, but there are a limited number of lamp designs between 500 and 5000 W which fit all studio and theater applications. The various types and sizes are outlined and reviewed here. Over the past thirty years, a number of cathode, anode, and arc space designs have been developed, with varying degrees of success and different lamp lives.

Effect of Caro's acid in electrolytic preparation of peroxodisulphates

Measurements of the current yield of oxygen and of the anode potential during electrolytic preparation of peroxodisulphates in a continually operating flow-through model electrolyser both in the stationary state and after the beginning of anolyte feeding with an increased content of Caro's acid into the anode space proved that this acid is preferentially oxidised at the anode under evolution of oxygen, whereby the current yield of peroxo compounds is lowered. Owing to this reaction taking place preferentially on the anode, the anode potential is lowered at constant current density, which is denoted as depolarization effect of Caro's acid in persulphate electrolysis.

A Charged Particle Detector System for High Rate Experiments

A charged particle detector system under development at BNL for use at the Multiparticle Spectrometer (MPS) and eventually at ISABELLE is described. The object is to take full advantage of the position accuracy, resolving time and instantaneous rate capabilities of narrow anode spacing drift-proportional chambers. The system will have position resolution sigma approximately equal to 100..mu.., time resolution approximately equal to 8 ns, detector sensitive time approximately equal to 50 ns, and consecutive particle resolving power of 40 ns per wire. It is planned to implement this system in a large system of 30,000 wires at the MPS and greater than 100,000 wires in ISABELLE experiments. Central to the development of this detector system is the production of two custom integrated circuits.