mA Discharge Current Research Articles

Sustainable Solution Anode Glow Discharge-Atomic Emission Spectroscopy (SAGD-AES) with Semiconductor Cathode Cooling for Elemental Analysis

A long-term sustainable tungsten cathode-solution anode glow discharge (SAGD) source for atomic emission spectrometry was developed for the determination of heavy metal elements. The tungsten cathode of this source was cooled by a compact refrigeration semiconductor, which is simple in design and able to operate at atmospheric pressure for long periods. When the equipment operates at its optimal conditions (75 mA discharge current, 2.0 mm discharge gap, 3.8 mL min−1 flow rate, and solution pH value of 2.0), the detection limits of Ag (338.24 nm), Cd (228.80 nm), Hg (253.66 nm), Pb (368.28 nm), Tl (337.52 nm), and Zn (213.79 nm) were explored, and the values were 0.030, 1.7, 7.2, 17, 0.24, and 25 μg L−1, respectively. The interference of coexisting ions in water, such as K+, Ca2+, Na+, Mg2+, and Li+, on the analytical performance of the solution anode glow discharge-atomic emission spectrometry (SAGD-AES) for Cd, Hg, Pb, and Zn were investigated. The results showed that coexisting metal ions’ interferences are insignificant. The SAGD-AES system was successfully applied for analyzing water samples from the Yangtze River and Baixi River, and its accuracy and practicality were verified by comparison with inductively coupled plasma-optical emission spectrometry (ICP-OES) results.

Determination of Metals in Environmental Waters by Solution Cathode Glow Discharge -Atomic Emission Spectroscopy (SCGD-AES) with a Syringe Pump for Sample Introduction

This study reports a syringe injection pump for sample introduction for solution cathode glow discharge (SCGD) atomic emission spectroscopy (AES). The experimental conditions are optimized at 60 mA discharge current, 2.5 mm gap spacing, 2.0 mm distance from the glass capillary to cathode, 1.60 mL/min flow rate, and pH 1.0 based on the detection limits (DLs) obtained for Li, Cd, Cu, Ag, Mn, Pb, Cr, and Zn. The detection limits for Li, Cd, Cu, Ag, Mn, Pb, Cr, and Zn were 0.24, 12.26, 12.08, 1.09, 46.42, 25.81, 183.05, and 29.01 µg/L, respectively, significantly lower than using the traditional peristaltic pump. The detection limits decreased by 1.4, 1.8, 2.2, 5.0, 1.4, 1.4, 1.4, 1.6, and 2.2-fold for these elements. The flow rate and the solution consumed per unit time were significantly reduced using this design. The spectral detection revealed stable and practical operation of the system with relative standard deviations <0.85%. Water samples from Yangtze River, Baixi River, and Baiyun Reservoir are analyzed using the modified SCGD system and its evaluation is based upon comparison to inductively coupled plasma—optical emission spectroscopy (ICP-OES). The modified device operates at atmospheric pressure without inert gas and integrates a syringe injection pump and a compact spectrometer to optimize solution utility, analytical performance, and operation size for industrial and environmental monitoring applications.

Radar cross-section reduction by tunable low-pressure gas discharge plasma

In this experimental research, the effect of tunable low-pressure gas discharge plasma was examined on radar cross-section (RCS) reduction. A quintet array of plasma tubes (PAr = 10 torr, PHg ≈ 2–6 × 10−3 torr, Rin = 18 mm) next to each other was used to reduce the RCS of a planar metallic target. Plasma columns were optimized to have minimum axial and temporal inhomogeneity. The plasma electron density, plasma frequency, and collision frequency of the plasma tubes were measured by fast time-resolved microwave interferometry with simultaneous measurement of current and voltage. The influence of the discharge current (Irms = 50–1500 mA) as a regulator of the plasma parameters was investigated. RCS reduction changes were observed by tuning plasma parameters at a frequency range of 2–18 GHz for the normal and oblique incidence of TE and TM polarizations. The assembled plasma tubes depicted broadband RCS reduction (<−10 dB) in TM polarization for a 300 mA discharge current (42.5% total bandwidth) and in TE polarization for a 1400 mA discharge current (34% total bandwidth) for normal incidence. It was shown that the measurement is in good agreement with the simulation. It was concluded that by performing bistatic measurements, the plasma cylinders behave as a wave absorber and scattering object in the TE and TM polarizations, respectively.

A Novel Graphene Based Cathode for Metal–Air Battery

The design and optimization of air-electrode structure play a prominent role in metal–air battery which is one of the most promising technologies among various electrochemical energy storage systems. Graphene offers porous path for the reactant transport in an electrode than conventional Carbon black powder, which helps in achieving high capacity metal/air battery. In house designed air diffusing substrate has been used in making the cathode of zinc–air battery. Flow Porometry technique also reveals that Graphene based air diffusion cathode had larger pore sizes, when compared to Vulcan XC Carbon based cathodes. A single cell was constructed with graphene based air diffusion cathode, alkaline electrolyte and bulk zinc sheet as anode. The single cell open circuit voltage was found to be 1.43 V. Open circuit voltage tests show that graphene based air diffusion cathode are more stable and could be operated for longer hours than carbon based air diffusion cathode. It has been observed that the static behavior of graphene based cathodes was better with higher durability compared to carbon based cathodes. The discharge characteristics show that the zinc/air battery with graphene based air cathode performs several folds longer than that of carbon based air cathode at 50 mA discharge current. The capacity of the constructed zinc/air battery was found to be 250 mA h.

The application of a non-aqueous bis(acetylacetone)ethylenediamine cobalt electrolyte in redox flow battery

A single-metal redox flow battery employing bis(acetylacetone)ethylenediamine cobalt(II) as the active species and tetrabutylammonium hexafluorophosphate as the supporting electrolyte with acetonitrile as the solvent has been examined. Cyclic voltammetry is used to measure the electrode kinetics of the anodic and cathodic reactions. Three redox couples are observed in the stable potential window, these electrode reactions are quasi-reversible and together yield a cell potential of 2.0 V. The disproportion reactions of active species are controlled by the diffusion coefficient. The effect of the environmental factors, such as temperature, oxygen and water, has been tested in the experiment. The charge–discharge characteristics of this system are evaluated in an H-type glass cell. The coulombic efficiencies 90.24% and 87.88% in cycle 5 and cycle 8 are obtained, respectively, with 1 mA charge 0.5 mA discharge current.

Microplasmas as vacuum ultraviolet source for Cl-atom density measurements by resonance absorption spectroscopy

A micro-hollow cathode discharge was used to generate radiation on the chlorine atom resonance lines. Such radiation could be used to measure, by resonance absorption spectroscopy, the density of chlorine atoms in either ground state (3p5 2P3/2) or in the fine structure metastable state (3p5 2P1/2), which is located at 882.35 cm−1. Among the nine analysed lines in the 132–142 nm spectral region, only those at 137.953 and 139.653 nm, which are strong enough and are not affected by the self-absorption, can be used for the resonance absorption diagnostic of the ground state and the metastable state, respectively. The best operating conditions of the lamp source are 0.5% of Cl2 in argon at 150 mbar and 4 mA discharge current. The measured 800 ± 30 K gas temperature of the microplasma, indicates that under these specific conditions, these two lines are dominantly Doppler broadened. So their profile is Gaussian shaped with full widths at half maximum of (4.7 ± 0.1) × 10−4 nm.

Evaluating the corrosion resistance of UBM-deposited Cr/CrN multilayers

This work was aimed at evaluating the corrosion resistance of multilayer Cr/CrN coatings deposited by the unbalanced magnetron sputtering (UBM) technique. Coatings were produced at room temperature using 400 mA discharge current, 9 sccm argon flow and 3 sccm nitrogen flow. The total thickness of coatings deposited on AISI 304 stainless steel and silicon (100) varied between 0.2 a 3 μm as bilayer period varied between 20 and 200 nm. Coating microstructure and chemical composition was studied through scanning electron microscopy (SEM) and texture and crystalline phases were analysed by X-ray diffraction (XRD) before and after corrosion tests which were carried out by potentiodynamic polarisation using 0.5 M H2SO4 + 0.05M KSCN solution. Lower bilayer period coatings presented better corrosion resistance and their corrosion mechanism is discussed in this article.

A comparative study of corrosion resistance in CrN and CrN/Cr coatings, electrodeposited chromium and epoxy paints

This work was aimed at comparing the corrosion resistance of CrN and CrN/Cr coatings deposited through unbalanced magnetron sputtering (UBM), Cr industrial coatings and epoxy paints. UBM coatings were optimised and produced at room temperature, using 400 mA discharge current. Ar and N2 flow rates were set at 9 standard cubic centimetres per minute (SCCM) and 3 SCCM, respectively. Deposition times were set to produce CrN monolayers and nanometric multilayers having 1μm total thickness and 100 nm period. Coating microstructure was determined through scanning electron microscopy as texture and crystalline phases were determined using x-ray diffraction and infrared spectroscopy. Corrosion resistance was studied with anodic polarisation tests using 0.5M H2SO4 and 0.05M KSCN solution. Nanometric multilayers improved stainless steel corrosion resistance and it was observed that coated CrN steel A36 could be an alternative for replacing stainless steel in acid environments. Corrosion mechanisms for the coatings so deposited are discussed.

The effects of carbon nanotubes on the hydrogen storage performance of the alloy electrode for high-power Ni–MH batteries

The multi-walled carbon nanotubes (MWNTs) were added to the nickel hydrogen battery negative electrode to prepare high-power CNTs compound nickel hydrogen battery. Their capacity, large-current discharging performance of high-power battery and the cycle life were investigated. It's found that adding carbon nanotubes was greatly advantageous for enhancing the electrochemical performance of the battery as a whole, especially the large-current discharge performance and cycle life. When the weight ratio of the MWNTs in the compound electrode was 0.8%, the overall performance of the battery was the best, which has a highest capacity of 3369 mAh under the condition of 3000 mA charge current and 6000 mA discharge current (2C-rate discharge), and the cycle life surpassed 600 times (97% discharge depth). Especially under the 10C-rate large-current discharge condition (3000 mA charge current and 30000 mA discharge current), its cycle life still surpassed 100 times (75% discharge depth). In 600th cycle, the inner electric resistance of battery without MWNTs is 5 times more than adding 8% MWNTs. The adding of MWNTs can prevent inner resistance from rising, and therefore improve the cycle life of the Ni–MH batteries.

Influence of Addition of Carbon Nanotubes in the Hydrogen Storage Alloy Electrode on the Performance of SC High Power Batteries

The carbon nanotubes were added to the cathode to prepare SC high-power Ni/MH batteries. The capacity, large-current discharging performance and cycle life were investigated. It was found that adding carbon nanotubes was greatly advantageous to enhance the batteries′ overall performance, especially the large-rate discharge performance and cycle life. When the weight ratio of the MWNTs in the compound electrode was 0.8%(w), the overall performance of the battery was the best, which showed a highest capacity of 3369 mAh in the condition of 3000 mA charge current and 6000 mA discharge current (2C-rate discharge), and the cycle life surpassed 600 times, the capacities passed 3280 mAh (97%DOD (depth of discharge)). Especially in the condition of 5C-rate large-current discharge (3000 mAh charge current and 15000 mA discharge current), its cycle life surpassed 180 times (89.1%DOD).

Infrared emission spectra of BeH2 and BeD2

High resolution infrared emission spectra of beryllium dihydride and dideuteride have been recorded with a Fourier transform spectrometer. The molecules were generated in a discharge-furnace source, at 1500 °C and 333 mA discharge current, with beryllium metal and a mixture of helium and hydrogen or deuterium gases. The antisymmetric stretching modes (ν3) of BeH2 and BeD2, as well as several hot bands involving ν1, ν2, and ν3, were rotationally analyzed and spectroscopic constants were determined. The equilibrium rotational constant (Be) of BeH2 was found to be 4.753 66(2) cm−1, and the equilibrium bond distance (Re) of 1.326 407(3) Å was determined for BeH2.

Infrared emission spectra of BeH and BeD

High resolution infrared emission spectra of beryllium monohydride and monodeuteride have been recorded. The molecules were generated in a furnace-discharge source, at 1500 °C and 333 mA discharge current, with beryllium metal and a mixture of helium and hydrogen or deuterium gases. Approximately 160 BeH lines and 167 BeD lines for the vibrational bands v=1→0 to v=4→3 were observed in the spectra and spectroscopic constants were determined. The Dunham constants (Yl,m) and Born–Oppenheimer breakdown constants were obtained in a combined fit of the BeH and BeD data. The equilibrium rotational constants (Be) for BeH and BeD were found to be 10.319 59(3) cm−1 and 5.688 29(2) cm−1, respectively, while the equilibrium vibrational constants (ωe) are 2061.416(3) and 1529.956(3) cm−1. The equilibrium distance (Re) was determined to be 1.342 436(2) Å for BeH.

Electron Kinetics of Ionization Waves in Helium Positive Columns

Electron kinetics related to ionization waves is discussed using the results of temporally and radial-spatially resolved Langmuir probe measurements during propagation of an artificially excited ionization wave packet along a helium positive column at 0.55 Torr pressure and 200 mA discharge current. The results show a strong interdependence between the axial and radial electric field fluctuations and the electron energy distribution fluctuations. Fluctuations in the electron energy distribution function related to the ionization waves revealed a complex energy spectrum whose low (0–10 eV) and high (10–25 eV) energy regions oscillate with opposite phases.

Studies of jet configurations for jet-enhanced sputtering devices

A modified gas, jet-enhanced glow discharge device for atomic spectrometry has been developed. Three types of jet configurations were constructed and investigated: six-jet, conejet and cylinder-jet. The discharge current, pressure and gas flow rate were studied for optimum discharge conditions. The sample mass loss for a Cu sample increases three-fold using a six-jet and cone-jet configuration, with a gas flow rate increase of 0–200 sccm. However, the sample mass loss increases from 0.8 to 1.5 mg as the gas flow rate increases from 0 to 200 sccm with a cylinder-jet configuration. The maximum absorbance was obtained with a cone-jet configuration at 1.7 mbar, 150 sccm and 30 mA discharge current.

Direct Method of Laser Parameter Analysis Using Laser Oscillator

A new method of laser parameter analysis is proposed in which gain parameter G0, saturation irradiance Is and a measure of partially homogeneous broadening m are readily determined by measuring the output powers of a traveling-wave-type laser oscillator twice for different intracavity losses without using any probe laser. Applying this scheme to a He–Ne 3.39 µm laser oscillator with a CH4 gas cells as a variable attenuator, G0=0.417 m-1, Is=1.36 mW/mm2 and |m|=0.710 (the ratio of the Lorentzian to Doppler line widths, i.e. ΔνL/ΔνD≃0.604) are obtained under 14 mA discharge current of the laser.

Determination of Rotational Temperatures in a Transitional Type Hollow Cathode Glow Discharge

AbstractRotational temperatures were measured in a transitional type hollow cathode, operating at 60 ‐ 150 mA discharge current under 260 ‐ 1060 Pa helium or argon pressure. A method using rotational lines in the 2Σ ‐ 2Σ (0, 0) CN 3883 Å band and the 2Σ ‐ 2Σ (0, 0) N+2 3914 Å band, is described. The dependence of measured rotational temperatures (800 ‐ 1700°K) on gas pressure, discharge current and cathode temperature is discussed.

Species composition in a CO2laser discharge

Recent experimental studies have shown that small quantities of nitrogen oxides can seriously effect discharge stability and power output in flowing CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> discharge lasers. In the present study, the formation of these oxides was measured in a sealed-off discharge tube under operating conditions similar to those in CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> lasers. The gas composition was sampled with a modulated molecular beam, low-voltage ionizer, quadrupole mass spectrometer. The combined use of low ionizer voltage and phase sensitive detection eliminated extraneous mass peaks caused by background gases and dissociative ionization in the analyzer itself. Equilibrium and time-varying measurements were made of neutral and ionix species. Two initial gas compositions were used 1) 71.8 percent He, 15.5 percent N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , 12.7 percent CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , and 2) 87.2 percent He, 12.8 percent CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> . Measurements were made in a discharge tube 2.2 cm inside diameter, 26 cm between electrodes. The system was pumped to approximately 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> mm Hg between data runs. Total pressure was varied from 1 to 8 mm Hg and discharge current from 0 to 80 mA. Typical CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> dissociation data at 40 mA and 4 mm Hg indicate an initial rate of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7(\pm0.5) \times 10^{-2}</tex> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> with an equilibrium value of approximately 65 percent dissociation in the He/ N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> /CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> mixture and slightly lower vatues in the He/CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> mixture. Under the same conditions, nitric oxide (NO) exhibited a buildup rate of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8(\pm1) \times 10^{-2}</tex> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> with an equilibrium value of approximately 0.1 percent of total gas composition. Nitrogen diozide (NO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> ) was detected by comparing the relative amounts of mass numbers 45 and 46. Data indicate that in the He/N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> / CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> mixture the NO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> component of mass 46 can be as high as 0.12 percent of total mixture with an initial buildup rate of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7(\pm2) \times 10^{-2}</tex> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> at 80 mA discharge current. Measurement of the ion spectra at the cathode indicate that CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> + is the major initial ion in the He/N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> /CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> mixture, but decays with a rate of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.5 (\pm.5) \times 10^{-1}</tex> s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> and is replaced by NO <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> at approximately the same rate. In the He/CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> mixture CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> + is replaced as the major ion by O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> + , with with slightly lower rates than those measured in the mixtures containing N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> .