Cathode Glow Discharge Research Articles

Cathode failure behavior of ArF excimer laser glow discharge

Abstract In this paper, the failure behavior of the glow discharge cathode of the ArF excimer laser was investigated. The morphology and composition of the cathode were characterized by scanning electron microscopy, energy spectrometer and high resolution laser confocal microscope. The results show that Ar ions sputtering occurs in the cathode discharge area, resulting in sputtering pit, molten morphology and resolidified particles. Due to the thermal effect induced by sputtering, Zn element evaporates violently, which intensifies the cathode erosion. Argon ion sputtering experiments proved the influence of random sputtering on the generation of sputtering pits. The main failure form of the non-discharge region is the corrosion of F2 molecule, which is dominated by Cu and Zn fluoride, and the fluorination layer is not dense.

Solution Cathode Glow Discharge – Atomic Emission Spectrometry (SCGD-AES) With an Interference Filter for Spectral Discrimination for the Determination of Thallium in Surface Water

Solution cathode glow discharge atomic emission spectrometry (SCGD-AES) using wide-bandpass (10-nm) interference filters (IF) as a spectral discrimination device was used for the determination of thallium (Tl) in surface water. The use of wide-bandpass interference filters greatly reduces the cost of traditional detection instruments. The influence of solution flow rate, discharge current and pH on the detection limit was characterized. Moreover, matrix effect experiments were performed to study the effect of different concentrations of Na+, K+, Ca2+, and Mg2+ on the Tl signal intensity. Using a solution flow rate of 2.8 mL/min, a discharge current of 50 mA, and pH of 1.0 with HNO3 as the supporting electrolyte, SCGD coupled with an interference filter provided a detection limit of 7.76 μg/L for Tl in water samples, comparable to traditional SCGD-AES. Furthermore, the spiked recovery rate of Tl is quantitative in real water samples and comparable to the performance of inductive coupled plasma – optical emission spectrometry (ICP-OES).

Rapid Determination of Calcium, Iron, and Zinc in Gluconate Oral Solutions by Solution Cathode Glow Discharge – Atomic Emission Spectroscopy (SCGD-AES)

A novel solution cathode glow discharge atomic emission spectroscopy (SCGD-AES) system coupled with simplified sample preparation was developed for determining Ca, Fe, and Zn in gluconate oral solution. The preparation of the oral solution only involves diluting 1 g of the sample 100-fold and acidification with HNO3 to a concentration of 0.1 mol L−1. The preparation of each solution requires less than 5 min. Five oral solutions containing Ca, Fe, and Zn were analyzed. The results indicate that the optimal parameters are HNO3 of pH 1.0 as the electrolyte, a sample flow rate of 2.05 mL min−1, and a discharge current of 65 mA. The detection limits (DLs) of Ca, Fe, and Zn were 58.64, 64.29, and 15.92 µg L−1. The analyses by SCGD-AES for Ca, Fe, and Zn using direct dilution are in agreement with the values by ICP-OES and SCGD-AES with digestion. A t-test was conducted on the oral liquid samples, revealing that the majority of the obtained p-values exceeded .05. In addition, SCGD-AES reduces the time, energy, and quantity of concentrated HNO3 compared with previous studies, and the measurement time of each oral liquid sample was less than 2 min. These findings demonstrate the use of SCGD-AES as an expedited and dependable method for the determination of trace elements in health food products.

Solution cathode glow discharge coupled to atmospheric pressure chemical ionization for elemental detection of S and P in organic compounds

We report a post-plasma chemical ionization approach to evaluate solution cathode glow discharge (SCGD) for S and P elemental analysis. Here, the SCGD serves as a reactor to produce chemical vapors for S and P from organic compounds containing these elements, while a corona discharge operated in negative mode is used to ionize the products. The approach creates long-lived ions in atmospheric pressure, enabling direct investigation of chemical vapor products via mass spectrometric and ion mobility separations. The investigations indicate that SCGD converts S and P to H2SO4 and H3PO4, respectively. These species are then ionized as HSO4HNO3− and H3PO4NO3HNO3− via reactions with NO3HNO3− produced by corona discharge. The response factors for P among several small molecules varies within 10% of the average response from the compounds, suggesting a reasonable species-independent characteristic. The response factors for S show larger variations among compounds, indicating a higher dependence of chemical vapor generation efficiency on analytes' chemical structures. Detection limits of 15 and 29 ng/mL are achieved for P and S detection, respectively. These figures are limited by background equivalent concentrations and low ion flux in the utilized ion mobility-time of flight mass spectrometer, indicating potential for significant improvements. In particular, the specificity of clustering for S and P-containing ions produced in this approach suggest facile analysis of S and P using quadrupole-based mass spectrometers for improved analytical performance.

Sensitive and rapid determination of the iodine/calcium ratio in carbonate rock samples by ICP-MS based on solution cathode glow discharge sampling

A solution cathode glow discharge (SCGD) sampling technique coupled with ICP-MS for highly sensitive and accurate determination of I/Ca in low-iodine carbonate samples.

Construction and Application of a New Experimental Device for Determination of Alkaline Metal Elements by Plasma Atomic Emission Spectrometry Based on Solution Cathode Glow Discharge: An Alternative Approach for Fundamental Teaching Experiments in Emission Spectroscopy

Construction and Application of a New Experimental Device for Determination of Alkaline Metal Elements by Plasma Atomic Emission Spectrometry Based on Solution Cathode Glow Discharge: An Alternative Approach for Fundamental Teaching Experiments in Emission Spectroscopy

Development of a droplet cathode glow discharge excitation source for high throughput detection of Li, Ca and K in serum samples

Sensitive and high-throughput analysis of trace elements in biological samples with limited volume is of great significance for clinical studies.

(TiZrNbTaMo)N nanocomposite coatings embedded with silver nanoparticles: imparting mechanical, osteogenic and antibacterial traits to dental implants

Designing highly osteogenic and effective antibacterial biomaterials with a prolonged service life for oral implants remains an ongoing challenge. In this work, the multi-element (TiZrTaNbMo)N high entropy nitride (HEN), with different concentrations of Ag, was co-deposited onto surgical grade commercially pure titanium by a reactive sputter-deposition technique using a double cathode glow discharge plasma system. The effects of Ag concentration on the microstructure and mechanical properties of the HEN-Ag nanocomposite coatings were investigated by various testing methods. Potentiodynamic polarization measurements were used to evaluate the corrosion resistance of the coatings in simulated body fluid. The antibacterial activity of the HEN-Ag nanocomposite coatings against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Candida albicans (C. albicans) strains was examined based on the bacterial inhibitory zones and bacterial killing efficiency. The cytocompatibility and osteogenesis activity of the HEN nanocomposite coatings using MC3T3-E1 cells were evaluated by a CCK-8 assay and an alkaline phosphatase quantitative assay. These studies demonstrate that the Ag-free HEN coating was composed of a face-centered-cubic (FCC) nitride phase, which displays good mechanical properties, anti-corrosion performance and osteogenic function, but no antibacterial properties were observed. In contrast, the HEN0.9Ag0.1 coating, composed of amorphous/nanocrystalline high-entropy nitride embedded with silver nanoparticles ∼10 nm in diameter, displays good mechanical and anti-corrosion performance, together with the excellent cell compatibility and antibacterial performance, which offer potential for providing outstanding protective efficiency for dental implants. Although the HEN0.8Ag0.2 nanocomposite coating exhibited superior antibacterial efficacy, potential for in vitro cytotoxicity was identified.

Effects of nitrogen concentration on the microstructure and mechanical properties of nanocrystalline (TiZrNbTaMo)N high-entropy nitride coatings: Experimental investigations and first-principles calculations

Novel (TiZrTaNbMo)N high-entropy alloy nitride (HEAN) coatings were prepared by double cathode glow discharge method, at various nitrogen flow ratios (RN = N2/Ar), on to Ti-6Al-4V substrates. The effects of different nitrogen pressures, RN, on the microstructure and mechanical properties of these coatings were studied by X-ray diffraction, electron microscopy and nanoindentation. Over the range of RN values investigated, from 5% to 30%, these coatings exhibit a face centered cubic (FCC) structure and are composed of equiaxed nanocrystals between 8 and 12 nm in diameter. The thicknesses of the coatings range between 14.4 and 23.6 μm, far exceeding that of typical HEAN coatings prepared by magnetron sputtering. The (TiZrTaNbMo)N coating prepared at RN = 20% exhibits the highest values for both hardness and Young's modulus (39.7 GPa and 310.2 GPa, respectively), thus approaching the level of superhard coatings. Combined with the results of first-principles calculations, one of the most important factors governing the high hardness of these coatings is the existence of both covalent and ionic bonds between the N atom and the surrounding metal atoms. Moreover, compared with most HEAN coatings, the coatings prepared by this method exhibit an improved strength-toughness balance, which is essential for surface protection.

Comprehensive evaluation of matrix effect in the detection of Zn, Cd, Ni, Cu, Cr and Pb by solution cathode glow discharge optical emission spectrometry

Herein, the effect of different salt matrices on the signals of Zn, Cd, Ni, Cu, Cr, and Pb using solution cathode glow discharge optical emission spectrometry (SCGD-OES), was discussed at length. The cation interference test covered sodium, potassium, magnesium and calcium ions, while the anion interference test covered chloride and sulfate ions. Overall, the order of interference levels for the four cations was: Na+≈K+>Mg2+≈Ca2+. The emission of most elements was inhibited at Na+/K+/Mg2+/Ca2+ concentration exceeding 200 mg L-1. The impact of the two anions is not measurably different and almost no interference occurred when anion content reaching 200 mg L-1. The spectral interference caused by Na+ and K+ was also much greater than that of Mg2+ and Ca2+, which was reflected in the diminution of spectral bands of the two main molecules (OH and N2). The role of formic acid (HCOOH) has been reassessed at a salinity of 200 mg L-1 Na+. HCOOH was found to play a positive role on volatile species forming metals such as Pb, regardless of the presence of sodium salts. For elements (Cr) that are hard to evaporate and stimulate, HCOOH exhibited a strong inhibitory effect, possibly due to exacerbating the deterioration of the excitation state. For other transition metal elements in the fourth period, e.g., Zn, HCOOH demonstrated minor effects.

Antibacterial and corrosion resistant ANPs-TaC nanocomposite coating for biomedical applications

To improve the antibacterial properties of metallic implants to hinder the colonization of bacteria on their surfaces, an Ag nanoparticle (ANPs)/TaC nanocomposite coating was synthesized on a titanium alloy substrate by a double cathode glow discharge approach. The nanocomposite coating was composed of AgNPs (~13 nm in diameter) embedded in a nanoscale TaC matrix, with a mean grain size of 8 nm. The nanocomposite coating exhibited a bilayer structure, composed of a compact inner layer and a cauliflower-like outer layer. The corrosion resistance of the nanocomposite coating in both a 0.9 wt% NaCl solution and Ringer's solution was studied in comparison with both uncoated Ti-6Al-4V (TC4) and an Ag-free TaC coating by using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). These results showed that the incorporation of Ag nanoparticles slightly lowered the corrosion resistance of the TaC coating. The antibacterial activity of the ANPs-TaC nanocomposite coatings against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Salmonella Typhimurium (Salmonella) strains was examined based on the bacterial inhibitory zones and bacterial killing efficiency. The addition of ANPs markedly increased the antibacterial capacity of the TaC coating against all three types of microorganisms. Therefore, a unique combination of the electrochemically stable TaC phase, together with the antibacterial behavior of the ANPs, makes the ANPs-TaC nanocomposite coating an attractive choice in the design of next-generation biomedical implants.

Study of plasma characteristics of hollow cathode in glow discharge

In order to further investigate the conditions and the coupling mechanisms for generating the hollow cathode effect (HCE) for the process optimization in the field of surface modification, the plasma distribution and density in single glow and double glow hollow cathode discharge (HCD) were explored by experiments and simulations based on the two-dimensional fluid model. Additionally, we investigated the effects of the key parameters on the plasma density, the electron temperature and the potential field during the HCD. The experimental and simulation results showed that the high plasma density is owing to the HCE in the hollow cathode. It is found that there is a critical pore diameter for generating HCE, which is approximately the sum of the thickness of the plasma sheath and four times the electron-neutral mean free path in the single glow discharge while twice thickness of the plasma sheath and four times the electron-neutral mean free path in the double glow discharge. The HCE in the double glow discharge can be observed when the ignition voltage that the source cathode voltage be 250 V greater than the workpiece cathode voltage can be met while the PD value is about 1.5 ∼ 3.8 Torr mm. Consequently, we believe that our investigation on the plasma characteristics of hollow cathode in glow discharge will contribute to the development of the more optimal processing parameters for the application of the glow plasma discharge phenomena.

Synthesis of Ag nanoparticles by cathode glow discharge electrolysis using sacrificial Ag foil of anode

Synthesis of Ag nanoparticles by cathode glow discharge electrolysis using sacrificial Ag foil of anode

Influence of C2H2/N2 flow ratio on the microstructure, mechanical properties, and electrochemical behavior of TiCN composite coatings

The microstructure, mechanical properties, and electrochemical performances of TiCN composite coatings were investigated. Via the modification of the C2H2/N2 flow ratio, TiCN coatings with various C contents were synthesized by combining a cathodic arc and glow discharge technology. With a C2H2/N2 flow ratio of 1:8, TiCN coating mainly consisted of the TiC phase. As the C2H2/N2 flow ratio exceeded 1:4, the crystallinity of TiCN coatings deteriorated. The coexistence of the amorphous and crystalline phases was detected in TiCN coatings with a C2H2/N2 flow ratio of 3:8. The introduction of the C element into TiCN coatings could disturb the growth orientation and induce dislocation motion, leading to an enhancive toughness and a decrease in hardness and elastic modulus. Moreover, the precipitation of amorphous C or CNx was beneficial to the corrosion resistance of TiCN coatings. This finding indicates the potential application of TiCN composite coating in corrosive environments.

Determination of Metals by Portable Millisecond Pulsed Solution Cathode Glow Discharge (SCGD) Atomic Emission Spectroscopy (AES)

In order to determine metal ions in aqueous solution, a millisecond pulsed solution cathode glow discharge (SCGD) source coupled with a portable spectrometer was developed for atomic emission spectrometry (AES). The millisecond pulsed SCGD source was operated with two high-voltage DC power supplies and a high-voltage pulse switch, specifically boosting the analyte excitation and sustain the glow discharge. The method to excite the plasma discharge contrasts with traditional approaches that employ a single power source. The influence of operating parameters, including pulsed voltage, pulsed frequency, duty ratio, and sample flow rate, were optimized to construct a system having good stability and improved excitation of metal ions. The optimum detection limits for Na, K, Li, Mg, Ag, Cs, Rb, and Sr were 0.17, 0.32, 0.38, 0.50, 2.65, 1.30, 0.22, and 74.02 µg·L−1, respectively. Furthermore, mountain spring, Yangtze River, and reservoir water were spiked with Ag, Rb, and Cs; the recoveries ranged from 105% to 106%, 106% to 107%, and 107% to 108% indicating that the developed system has favorable analytical performance.

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.

Dynamic Impact Resistance and Scratch Adhesion of AlCrN Coatings Sputtered Using Cathodic Arc Glow Discharge

AlCrN coatings, which are characterized by high hardness and good wear resistance, are often used for drilling, milling, and punching tools. Therefore, the study of the behaviour of these coatings under cyclic impact loading is essential for their optimization. Our previous work has focused on the study of the composition and microstructure of AlCrN coatings prepared using a cathodic arc deposition system with a SCIL® controller that controls the average ion energy per deposited atom (Ed). Two sets of coatings were prepared in two different modes, with a metal target and with a poisoned target. The chemical compositions of the coatings were very similar regardless of their deposition conditions, but the structure and mechanical properties of the coatings depended strongly on Ed. The present work focused on the scratch adhesion and impact wear of these two sets of AlCrN coatings. The lifetimes of both sets of samples under repeated dynamic impacts were tested using a dynamic impact tester with a WC-Co ball. It was shown that the impact behaviour of the coatings prepared in the metallic regime does not depend on the deposition conditions. However, the impact behaviour of the coatings deposited in poisoned mode was improved by increasing Ed.

Tribo-Mechanical Behavior of Films and Modified Layers Produced by Cathodic Cage and Glow Discharge Plasma Nitriding Techniques

Two surface modification techniques, the glow discharge plasma nitriding (GDPN) and the cathodic cage plasma nitriding (CCPN), were compared regarding the mechanical and tribological behavior of layers produced on AISI 316 stainless-steel surfaces. The analyses were carried out at the micro/nanoscale using nanoindentation and nanoscratch tests. The nitriding temperature (°C) and time (h) parameters were 350/6, 400/6, and 450/6. Morphology, structure, and microstructure were evaluated by X-ray diffraction, scanning electron and optical interferometry microscopies, and energy-dispersive X-ray spectroscopy. GDPN results in stratified modified surfaces, solidly integrated with the substrate, with a temperature-dependent composition comprising nitrides (γ’-Fe4N, ε-Fe2+xN, CrN) and N-solid solution (γN phase). The latter prevails for the low treatment temperatures. Hardness increases from ~2.5 GPa (bare surface) to ~15.5 GPa (450 °C). The scratch resistance of the GDPN-modified surfaces presents a strong correlation with the layer composition and thickness, with the result that the 400 °C condition exhibits the highest standards against microwear. In contrast, CCPN results in well-defined dual-layers for any of the temperatures. A top 0.3–0.8 µm-thick nitride film (most ε-phase), brittle and easily removable under scratch with loads as low as 63 mN, covers a γN-rich case with hardness of 10 GPa. The thickness of the underneath CCPN layer produced at 450 °C is similar to that from GDPN at 400 °C (3 µm); on the other hand, the average roughness is much lower, comparable to the reference surface (Ra ~10 nm), while the layer formation involves no chromium depletion. Moreover, edge effects are absent across the entire sample´s surface. In conclusion, among the studied conditions, the GDPN 400 °C disclosed the best tribo-mechanical performance, whereas CCPN resulted in superior surface finishing for application purposes.

Hollow Cathode Glow Discharge Initiation in a Fore-Vacuum Plasma–Cathode Electron Source

In this article, we present the results of a study on the initiation of a hollow cathode discharge in the electrode system of a fore-vacuum plasma–cathode electron source. It is shown that the development of the hollow cathode effect is facilitated by the back-streaming ion flux of the high-voltage glow discharge (HGD) that arises in the accelerating gap of the electron source. The effect of the type of operating gas and the cathode hollow geometry on the value of the initiating accelerating voltage, which ensures the HGD back-streaming ion flux, have been studied. It is proposed to use an auxiliary pulsed surface flashover discharge to trigger the hollow cathode discharge. The two methods used jointly provide a stable discharge initiation in the entire operating pressure range of the source, including the ultimately low-pressure range where the operation of the hollow cathode discharge in its low-voltage form is still stable.

Determination of K, Na, and Mg in Brine by Liquid Cathode Glow Discharge—Optical Emission Spectrometry (LCGD-OES) with Interference Suppression

The determination of K, Na, and Mg in brine is important for its effective utilization. Liquid cathode glow discharge—optical emission spectrometry (LCGD-OES) is a successful approach for the determination of these elements in brine. However, matrix interferences reduce the accuracy using a standard curve. Here a correction method based upon the mutual interferences between K, Na, and Mg is reported to improve the accuracy of brine analysis. To verify the performance, LCGD-OES was employed to analyze four samples using the optimized operating voltage and sample flow rate. The results showed that the relative errors of the concentrations of K and Na in the brine were from 1.79% to 8.65% and 3.88% to 6.49% compared to inductively coupled plasma optical—emission spectrometry (ICP-OES). The reported correction method significantly reduced matrix interferences for the determination of K and Na. Additionally, Mg in brine was determined using Al as the internal standard.