Atmospheric Glow Discharge Research Articles

Diagnostics of Nitrogen-methane Atmospheric Glow Discharge Used for a Mimic of Prebiotic Atmosphere

The exploration of planetary atmosphere is being advanced by the exciting results of the Cassin-Huygens mission to Titan. The complex chemistry revealed in such atmospheres leading to the synthesis of bigger molecules is providing new insights into our understanding of how life on Earth developed. This work extends our previous investigation of nitrogen-methane (N<sub>2</sub>-CH<sub>4</sub>) atmospheric glow discharge for simulation chemical processes in prebiotic atmospheres. In presented experiments 2 % of water vapor were addet to nitrogen-methane gas mixture. Exhaust products of discharge in this gas mixture were in-situ analysed by Fourier Transform Infra Red spectroscopy (FTIR). The major products identified in spectra were: hydrogen cyanide, acetylene and acetonitrile.

Fabrication of Bioactive Fiber Reinforced Polyetheretherketone by the Function of Apatite Nuclei

We formed micropores on the surface of a carbon fiber reinforced polyetheretherketone (CFR-PEEK) and a glass fiber reinforced polyetheretherketone (GFR-PEEK) by immersing in sulfuric acid. In order to provide bioactivity to the CFR-PEEK and the GFR-PEEK, we treated the surfaces of the specimens with glow-discharge in oxygen gas atmosphere and precipitated apatite nuclei in the micropores. We evaluated apatite-forming ability of the specimens by using SBF and measured adhesive strength of formed apatite layer.

Ultratrace Determination of Tin, Germanium, and Selenium by Hydride Generation Coupled with a Novel Solution-Cathode Glow Discharge-Atomic Emission Spectrometry Method.

We herein describe a novel method of hydride generation (HG) coupled to a newly designed atmospheric pressure solution-cathode glow discharge (SCGD) spectrometric technique for the ultratrace determination of tin, germanium, and selenium. In this novel SCGD process, gas introduction was permitted using a hollow titanium tube as both the anode and sampling port. In these experiments, the analytes were converted into volatile hydrides upon passing through the hydride generator, and were introduced into the near-anode region of the SCGD system, where they were detected directly by atomic emission spectrometry (AES). A significant improvement in both selectivity and sensitivity was achieved, which was reflected in an improvement in the detection limits (DLs) by 3 orders of magnitude, in addition to successful valence analysis of Se without the requirement for chromatographic separation. In the absence of a strict sample pretreatment process and with a reduction in electrolyte consumption, the detection limits of Sn, Ge, and Se were determined to be 0.8, 0.5, and 0.2 μg·L-1. Moreover, our HG-SCGD-AES system demonstrated excellent repeatability (<3% peak height relative standard deviation) and more than 2 orders of linear dynamic range. The optimal operating conditions are outlined herein, and the analytical performance of the system is evaluated as described. Furthermore, our method was applied for the analysis of Sn, Ge, and Se in both environmental and biological samples, and the obtained results were in good agreement with reference values.

Operation Mode on Pulse Modulation in Atmospheric Radio Frequency Glow Discharges**supported by National Natural Science Foundation of China (Nos. 11475043 and 11375042)

The discharge operation regime of pulse modulated atmospheric radio frequency (RF) glow discharge in helium is investigated on the duty cycle and frequency of modulation pulses. The characteristics of radio frequency discharge burst in terms of breakdown voltage, alpha(α)-gamma(γ) mode transition voltage and current are demonstrated by the discharge current voltage characteristics. The minimum breakdown voltage of RF discharge burst was obtained at the duty cycle of 20% and frequency of 400 kHz, respectively. The α-γ mode transition of RF discharge burst occurs at higher voltage and current by reducing the duty cycle and elevating the modulation frequency before the RF discharge burst evolving into the ignition phase, in which the RF discharge burst can operate stably in the γ mode. It proposes that the intensity and stability of RF discharge burst can be improved by manipulating the duty cycle and modulation frequency in pulse modulated atmospheric RF glow discharge.

Ethanol conversion in a DC atmospheric pressure glow discharge

Conversion of ethanol-water mixture into syngas in a DC atmospheric pressure air glow discharge with a plasma cathode has been investigated experimentally and theoretically. The electric power of discharge was varied from 100 W up to 250 W. Novel diagnostics based on the absorption infrared spectroscopy was developed and used to determine the syngas composition and the conversion parameters. The main components of syngas were: hydrogen, carbon monoxide, methane, ethylene and acetylene. The achieved degree of conversion to hydrogen was about 90%, with hydrogen content in conversion products being equal to 40%. A method for numerical simulation of the conversion process has been developed under an assumption that the role of discharge in the conversion process is purely thermal in nature. The experimental and numerical data were found to be in a good agreement.

In situ coupling of chitosan onto polypropylene foils by an Atmospheric Pressure Air Glow Discharge with a liquid cathode

Atmospheric air plasma treatment of chitosan solutions leads to degradation of chitosan molecules by OH radicals and is accompanied by a predominant cleavage of glycosidic linkages and by a decrease of the molecular weight. The degradation proceeds via first order kinetics with the rate constant of (5.73±0.22)×10−6s−1 and the energetic yield of chitosan bond scission of (2.4±0.2)×10−8mol/J. Products of degradation together with intact chitosan molecules adsorb and form coatings on polypropylene foils immersed into the solution that is being plasma treated. The plasma treatment results in strong binding of chitosan to polypropylene due to the formation of covalent bonds between the activated polymer surface and chitosan molecules. Plasma-driven crosslinking is responsible for the accumulation of compressive stress which leads to the development of buckling instabilities in the chitosan coatings.

The Effect of pH on OH Radical Generation in Aqueous Solutions by Atmospheric Pressure Glow Discharge

Formation of hydroxyl radicals in aqueous solutions by atmospheric pressure DC glow discharge was investigated. The ferrocyanide was used as an OH scavenger at different pH. Experimental results indicated that pH effect on hydroxyl radical formation rate could be explained by particularities of [Fe(CN)6]4− and reactive species interaction in different media.

Modelling of an Atmospheric Pressure Nitrogen Glow Discharge Operating in High-Gas Temperature Regimes

Fil: Prevosto, Leandro. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina. Universidad Tecnologica Nacional. Facultad Regional Venado Tuerto; Argentina

Development of Bioactive PEEK by the Function of Apatite Nuclei

Micropores were formed on the surface of a polyetheretherketone (PEEK) by soaking in sulfuric acid. In order to provide bioactivity to PEEK, the surfaces of the specimens were treated with glow-discharge in O2 atmosphere and Apatite Nucleus (AN) was precipitated in the pores. The bioactivity of the specimens was evaluated by using SBF and adhesive strength of formed apatite layer was measured.

Manganese oxide octahedral molecular sieve K-OMS-2 as catalyst in post plasma-catalysis for trichloroethylene degradation in humid air

The total oxidation of trichloroethylene (TCE) in air at low relative humidity (RH=10%) in the presence of CO2 (520ppmv) was investigated in function of energy density using an atmospheric pressure negative DC luminescent glow discharge combined with a cryptomelane catalyst positioned downstream of the plasma reactor at a temperature of 150°C. When using Non-Thermal Plasma (NTP) alone, it is found a low COx (x=1–2) yield in agreement with the detection of gaseous polychlorinated by-products in the outlet stream as well as ozone which is an harmful pollutant. Introduction of cryptomelane enhanced trichloroethylene removal, totally inhibited plasma ozone formation and increased significantly the COx yield. The improved performances of the hybrid system were mainly ascribed to the total destruction of plasma generated ozone on cryptomelane surface to produce active oxygen species. Consequently these active oxygen species greatly enhanced the abatement of the plasma non-reacted TCE and completely destroyed the hazardous plasma generated polychlorinated intermediates. The facile redox of Mn species associated with oxygen vacancies and mobility as well as the textural properties of the catalyst might also contribute as a whole to the efficiency of the process.

The Influence of CO2 Admixtures on the Product Composition in a Nitrogen-Methane Atmospheric Glow Discharge Used as a Prebiotic Atmosphere Mimic.

This work extends our previous experimental studies of the chemistry of Titan's atmosphere by atmospheric glow discharge. The Titan's atmosphere seems to be similarly to early Earth atmospheric composition. The exploration of Titan atmosphere was initiated by the exciting results of the Cassini-Huygens mission and obtained results increased the interest about prebiotic atmospheres. Present work is devoted to the role of CO2 in the prebiotic atmosphere chemistry. Most of the laboratory studies of such atmosphere were focused on the chemistry of N2+CH4 mixtures. The present work is devoted to the study of the oxygenated volatile species in prebiotic atmosphere, specifically CO2 reactivity. CO2 was introduced to the standard N2+CH4 mixture at different mixing ratio up to 5% CH4 and 3% CO2. The reaction products were characterized by FTIR spectroscopy. This work shows that CO2 modifies the composition of the gas phase with the detection of oxygenated compounds: CO and others oxides. There is a strong influence of CO2 on increasing concentration other products as cyanide (HCN) and ammonia (NH3).

Use of Polyfuran/Chitosan Composite Films Deposited by Atmospheric Pressure Plasma Glow Discharge as Glucose Sensors

Use of Polyfuran/Chitosan Composite Films Deposited by Atmospheric Pressure Plasma Glow Discharge as Glucose Sensors

Non-linear macro evolution of a dc driven micro atmospheric glow discharge

We studied the macro evolution of the micro atmospheric glow discharge generated between a micro argon jet into ambient air and static water. The micro discharge behaves similarly to a complex ecosystem. Non-linear behaviors are found for the micro discharge when the water acts as a cathode, different from the discharge when water behaves as an anode. Groups of snapshots of the micro discharge formed at different discharge currents are captured by an intensified charge-coupled device with controlled exposure time, and each group consisted of 256 images taken in succession. Edge detection methods are used to identify the water surface and then the total brightness is defined by adding up the signal counts over the area of the micro discharge. Motions of the water surface at different discharge currents show that the water surface lowers increasingly rapidly when the water acts as a cathode. In contrast, the water surface lowers at a constant speed when the water behaves as an anode. The light curves are similar to logistic growth curves, suggesting that a self-inhibition process occurs in the micro discharge. Meanwhile, the total brightness increases linearly during the same time when the water acts as an anode. Discharge-water interactions cause the micro discharge to evolve. The charged particle bomb process is probably responsible for the different behaviors of the micro discharges when the water acts as cathode and anode.

Absolute OH density measurements in an atmospheric pressure dc glow discharge in air with water electrode by broadband UV absorption spectroscopy

Spatially resolved absolute OH radical density measurements are performed in an atmospheric pressure glow discharge generated in ambient air with water electrode by broadband UV absorption spectroscopy. The radial distributions of OH density and gas temperature are obtained for the positive column, anode and cathode regions both for water-cathode and water-anode discharges. It is found that for both polarities of the water electrode the radial profiles of the ground state OH density and gas temperature are significantly broader than the total discharge emission intensity and the emission intensity originating from OH() only. Exceptional large OH densities exceeding 1023 m−3 are found. The OH kinetics are discussed in detail.

Atmospheric pressure glow discharge generated in nitrogen-methane gas mixture: PTR-MS analyzes of the exhaust gas

This paper reports the results of an extensive study of with the in situ mass spectrometry analysis of gaseous phase species produced by an atmospheric plasma glow discharge in N 2 -CH 4 gas mixtures (with methane concentrations ranging from 1% to 4%). The products are studied using proton-transfer-reaction mass spectrometry (PTR-MS). HCN and CH 3 CN are identified as the main gaseous products. Hydrazine, methanimine, methyldiazene, ethylamine, cyclohexadiene, pyrazineacetylene, ethylene, propyne and propene are identified as minor compounds. All the detected compounds and their relative abundances are determined with respect to the experimental conditions (gas composition and applied power). The same molecules were observed by the Cassini-Huygens probe in Titan’s atmosphere (which has same N 2 -CH 4 gas mixtures). Such, experiments show that the formation of such complex organics in atmospheres containing C, N and H, like that of Titan, could be a source of prebiotic molecules.

Towards improving mechanical properties of basalt fiber/polylactic acid composites by fiber surface treatments

Attempting to improve reinforcement effect on basalt fiber/polylactic acid composites, this study evaluates the effects of silane treatment, atmospheric glow discharge plasma polymerization, desizing, and addition of maleic anhydride coupling agent. The treated fibers were characterized, in terms of surface morphology and existing molecular bonds, and the mechanical properties of the composites were tested (i.e. strength, stiffness, and elongation at yield). Among the fiber surface treatments and the addition of coupling agent, improved mechanical properties were only shown by the silane treated and the atmospheric plasma polymerized composites by having 26 and 22% higher strength, respectively, as compared with the untreated one.

Gas Chromatography Analysis of Discharge Products in N2‐CH4 Gas Mixture at Atmospheric Pressure: Study of Mimic Titan's Atmosphere

AbstractIn this paper, we report presence of various organic products formed in a flowing atmospheric glow discharge fed by gas mixture containing 1‐5 % of methane in nitrogen, which mimics the Titan's atmosphere. Gaseous products from the discharge exhaust were analysed by Gas Chromatography with Mass Spectrometry (GC‐MS). The experimental results revealed C2H2, HCN, and CH3CN as the major products. Various hydrocarbons and nitriles were the other determined gaseous products. Whilst many of these compounds have been predicted and/or observed in the Titan atmosphere, the present plasma experiments provide evidence of both the chemical complexity of Titan atmospheric processes and the mechanisms by which larger species grow prior to form the dust that should cover much of the Titan's surface. (© 2015 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Detection of some industrially relevant elements in water by electrolyte cathode atmospheric glow discharge optical emission spectrometry

An electrolyte cathode atmospheric glow discharge optical emission spectrometry (ELCAD-OES) method was developed for the detection of the industrially relevant In, Rh and Te in water samples. Acid/additive type, sample pH and flow rate were optimized. The UV–Vis spectrum was scanned for analytical lines, free from spectral overlap interferences, and sensitive enough for quantifying the analytes at mg L−1 or lower levels. In several cases, the background spectrum of the ELCAD hindered the use of conventional, resonant analytical lines in the UV due to overlaps with bands of molecular species (e.g., OH, NO, N2). Te and Rh showed lower emission intensities than In (determined at In I 451.1nm), even using the most sensitive, interference-free transitions (i.e., Te I 214.3nm, Te I 238.6nm and Rh I 437.5nm). The emission intensities were highly sample pH dependent, i.e., analytical signals could only be detected at pH levels lower than 2. Conversely, the use of acidity lower than pH1 caused lower plasma volume, due to its contraction into the sample introduction capillary, and discharge instability in terms of its frequent self-extinction. The detection limits for In, Rh and Te were 0.01, 0.5 and 2.4mgL−1, respectively. Calibration curves were linear up to 100–150mgL−1. The precision for In, Rh and Te in aqueous standards, expressed as relative standard deviation (RSD), was not higher than 4.6%, 6.4% and 7.4%, respectively. Samples with high salt content (e.g., well water) caused positive matrix effects (i.e., 2.0- to 3.6-fold signal enhancements), but also ~1.5 times higher RSDs.

On the physical processes ruling an atmospheric pressure air glow discharge operating in an intermediate current regime

Low-frequency (100 Hz), intermediate-current (50 to 200 mA) glow discharges were experimentally investigated in atmospheric pressure air between blunt copper electrodes. Voltage–current characteristics and images of the discharge for different inter-electrode distances are reported. A cathode-fall voltage close to 360 V and a current density at the cathode surface of about 11 A/cm2, both independent of the discharge current, were found. The visible emissive structure of the discharge resembles to that of a typical low-pressure glow, thus suggesting a glow-like electric field distribution in the discharge. A kinetic model for the discharge ionization processes is also presented with the aim of identifying the main physical processes ruling the discharge behavior. The numerical results indicate the presence of a non-equilibrium plasma with rather high gas temperature (above 4000 K) leading to the production of components such as NO, O, and N which are usually absent in low-current glows. Hence, the ionization by electron-impact is replaced by associative ionization, which is independent of the reduced electric field. This leads to a negative current-voltage characteristic curve, in spite of the glow-like features of the discharge. On the other hand, several estimations show that the discharge seems to be stabilized by heat conduction; being thermally stable due to its reduced size. All the quoted results indicate that although this discharge regime might be considered to be close to an arc, it is still a glow discharge as demonstrated by its overall properties, supported also by the presence of thermal non-equilibrium.

Influence of oxygen gas on characteristics of self-organized luminous pattern formation observed in an atmospheric dc glow discharge using a liquid electrode

Self-organized luminous pattern formation is observed in the liquid surface of an atmospheric dc glow discharge using a liquid electrode with a miniature helium flow. The factors affecting pattern formation are the gap length, discharge current, helium mass flow rate and polarity. The pattern shape depends on the conductivity and temperature of the liquid electrode. A variety of patterns were observed by changing the conductivity and temperature of the liquid. We clarified that the self-organized pattern formation depends on the amount of electronegative gas, such as oxygen, in the gas in the electrode gap. When an oxygen gas flow was fed to the liquid surface from the outside in an obliquely downward direction, namely, the amount of oxygen gas on the liquid surface was increased locally, self-organized pattern formation was observed in the region with the increased amount of oxygen gas. When the amount of oxygen in the gas in the gap was changed by using a sheath flow system, the appearance of the pattern changed. The presence of oxygen gas strongly affected the self-organized pattern formation of the atmospheric dc discharge using a liquid anode.