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In this work, we investigated non-equilibrium plasma produced by nanosecond repetitively pulsed glow discharges applied across a lean premixed methane-air flame. The flame is stationary, axisymmetric, and laminar. The discharges are applied on the symmetry axis crossing the reactant gases, flame front, and product gases, allowing phase-locked averaged measurements and comparisons with axisymmetric numerical simulations. The thermal effect and methyl radical production are quantified in the discharge in the reactant gas region. One-dimensional, two-beam, hybrid, femtosecond-picosecond, coherent anti-Stokes Raman scattering is used to acquire spatial and temporal profiles of temperature and oxygen-to-nitrogen concentration ratio. Photo-fragmentation laser-induced fluorescence is used to acquire quantitative two-dimensional profiles of methyl radicals in the discharge providing the first quantitative imaging of methyl produced ahead of a flame by plasma-induced methane dissociation. The spatial profiles of temperature and oxygen-to-nitrogen concentration ratio are in steady state, indicating that individual discharges have an insignificant heating effect. Upper and lower bounds of the produced mole fraction of methyl radicals in the plasma are obtained due to uncertainties in the collisional quenching rates of excited state methylidyne radicals in the plasma. The discharges produce a maximum of 600–1100 ppm of methyl radicals upstream of the flame front within 25 ns. This amount is similar to the predicted methyl mole fraction for the flame without plasma and thus represents a significant chemical perturbation to the reactants upstream of the flame front. The produced methyl follows an exponential decay in the first microsecond after the discharge with a decay constant of 8 µs close to the flame, and 0.8 µs further from the flame. The decay then deviates from the exponential curve and the methyl persists for tens of microseconds. The results suggest that for the tested configuration, the thermal effect of individual discharges through fast gas heating is negligible, while active chemical species are produced in large quantities in the reactant gases, upstream of the flame front. [ABSTRACT FROM AUTHOR]

A negative DC high voltage is used to generate plasma at ambient condition. Self‐organized patterns (SOPs) are formed on the surfaces of the liquid anodes. With increased current or gap distance or reduced gas flow rate, the diameters of SOPs increase and SOPs become more complex, coinciding along with an increases of gas temperature and plasma radius and a decrease of electron density. Both plasma expansion and liquid evaporation in terms of gas temperature, lead to a drop of electron density and pattern formation. Our research elucidates the correlation between SOPs evolution and plasma properties and clarifies the physical process of SOPs formation based on the interaction between atmospheric pressure plasma and liquid anodes. [ABSTRACT FROM AUTHOR]

Surface recombination in an oxygen DC glow discharge in a Pyrex (borosilicate glass) tube is studied via mesoscopic modelling and comparison with measurements of recombination probability. A total of 106 experimental conditions are assessed, with discharge current varying between 10 and 40 mA, pressure values ranging between 0.75 and 10 Torr, and fixed outer wall temperatures ( T w ) of −20, 5, 25 and 50 ∘ C . The model includes O+O and O+O2 surface recombination reactions and a T w dependent desorption frequency. The model is validated for all the 106 studied conditions and intends to have predictive capabilities. The analysis of the simulation results highlights that for T w = − 20 ∘ C and T w = 5 ∘ C the dominant recombination mechanisms involve physisorbed oxygen atoms ( O F ) in Langmuir–Hinshelwood (L-H) recombination O F + O F and in Eley–Rideal (E-R) recombination O 2 + O F , while for T w = 25 ∘ C and T w = 50 ∘ C processes involving chemisorbed oxygen atoms ( O S ) in E-R O + O S and L-H O F + O S also play a relevant role. A discussion is taken on the relevant recombination mechanisms and on ozone wall production, with relevance for higher pressure regimes. [ABSTRACT FROM AUTHOR]

In this study, the use of nanosecond repetitively pulsed (NRP) glow discharges to mitigate thermoacoustic fluctuations was investigated. Two strategies in applying the discharges were compared: continuous forcing and closed-loop gated forcing. It was found that NRP glow discharges could mitigate thermoacoustic fluctuations in a wall-stabilized methane-air flame either by applying the discharges continuously or using a closed-loop control scheme. A parametric study was done to investigate the role of the forcing phase, the applied voltage (6.3–6.8 kV), the pulse repetition frequency (15–30 kHz), the duty cycle (24–50%), and the forcing frequency on the performance of the plasma actuator. The most effective control of the thermoacoustic fluctuations was obtained when using the closed-loop control scheme with an applied voltage of 6.8 kV, a forcing frequency matching the instability frequency, close to phase opposition with the instability, and a power input of 0.8% of the flame thermal power. It was also found that the duty cycle in the tested range did not have a significant effect on the performance of the scheme when the number of discharges per cycle was constant. Phase-locked imaging of the flame was employed and showed that the flame's base location, surface area, and surface area gradient oscillated over the thermoacoustic period. For the best discharge forcing, the oscillations in the flame's base location and surface area were suppressed making the flame temporally and spatially stable. [ABSTRACT FROM AUTHOR]

Pulsed discharge nozzles (PDNs) have been successfully used for decades to produce rotationally cold (Trot ∼ 20 K) radicals and ions of astrophysical interest and to characterize these species spectroscopically. In this work, an evolution of the PDN, the piezostack pulsed discharge nozzle (P2DN), is used for the first time to investigate the characteristics of the still poorly understood supersonic plasma expansion. The P2DN allows for a better control of the reservoir pressure of which an accurate measurement is required to characterize the plasma expansion. This new source, thus, gives the opportunity to further optimize the plasma conditions and extend its use to new target species. The spatial distribution of an argon plasma and the effect of the supersonic flow for different pressures are studied by combining a two-dimensional extended fluid model (extFM) and a direct simulation Monte Carlo (DSMC) method. The combined simulation is validated with experimental results obtained through emission spectroscopy associated with a group-code collisional-radiative model to retrieve the plasma parameters. The validated numerical approach (DSMC-extFM) allows for an accurate characterization of the plasma structure in our typical experimental conditions (a reservoir pressure ranging from 90 to 905 mbar). Thus, this simulation will be used in future studies to improve the plasma conditions to favor the synthesis of (transient) hydrocarbon species as found in space, by seeding the argon gas with a suitable precursor, such as acetylene. [ABSTRACT FROM AUTHOR]

We report a study of the cathode sheath (CS) space of the argon glow discharges in the abnormal DC regime by means of the iterative kinetic model. By matching the model shapes of the side-on spectra with the experimental data for the Ar II 460.954 nm line obtained via optical emission spectroscopy, we have estimated the thickness of the CS space and the distributions of the electric field strength and gas temperature over the entire CS space of discharge. [ABSTRACT FROM AUTHOR]

This paper presents experimental results of the characteristics appearance and the mechanism of self-oscillation in a parallel-plate glow discharge with argon as the discharge gas at 266 Pa. The cathode and anode are molybdenum plates with a diameter of 3 cm. The distance between the electrodes is 1 cm. Discharge average voltage and current vary between 300 V and 500 μA, respectively. Light emission from the electrode gap is measured by a charge coupled device camera and argon spectra are recorded of emission lines at 650–800 nm. Results show that self-oscillations exist in the negative differential resistance region in the static V–I curve. An obvious negative differential resistance also can be observed in the dynamic of the V–I curve for the self-oscillations. The appearance and disappearance of the self-oscillating phenomenon are companied with an obvious change in all of the discharge current, discharge images, and electron excited temperature. It can be determined that the self-oscillation is a mode transition between low-current stage of Townsend discharge and high-current stage of glow discharge. The frequency range of self-oscillations starts with 0.4 k Hz up to 24 k Hz in dependence of the average discharge current and the external capacitors. When the self-oscillation disappears, the luminescence shows a significant radial contraction, the electron excitation temperature rise obviously. The frequency of oscillations exhibits a substantial linear increase with the average discharge current and decreases with the increase in the external capacitance from 0 pF up to 250 pF. A resistance–capacitance circuit model is used to simulate the self-oscillation discharge in this experimental glow discharge. Results show that the waveforms simulated by this circuit model are well consistent with those obtained experimentally at different average discharge currents and external parallel capacitances. The equivalent plasma resistance decreases with an increase in the average discharge current. The theory of charge and discharge of a capacitor provides good insights into the characteristics and mechanism of self-oscillations in parallel-plate discharges. [ABSTRACT FROM AUTHOR]

An approach for evaluation of plasma parameters and conversion factor in glow discharges in CO2â€"N2 mixtures at low pressures is presented. In the framework of this approach, analytical expressions relating plasma characteristics (the electric field, the gas temperature) in discharges in the mixtures with those in pure CO2 have been obtained. It is shown that dissociation of CO2 molecules in collisions with electronically excited N2 molecules gives substantial contribution to the conversion rate. Obtained dependences of the plasma parameters and conversion factor on the nitrogen molar fraction agree with available experimental data. [ABSTRACT FROM AUTHOR]

A one-dimensional self-consistent fluid model was employed to comparatively investigate the influence of pre-ionization on the helium direct-current glow discharge in the large gap and the small gap at atmospheric pressure. For the large-gap and small-gap discharges, the negative glow space and the cathode fall layer are both offset to the cathode with the increase in pre-ionization, which is mainly ascribed to the decrease in charged particle density in the original negative glow space as a result of the increased probability of collision and recombination between ions and electrons, and the new balance between the positive and negative charges established at the distance closer to the cathode. The electron density tends to grow in the negative glow space due to the elevated pre-ionization, while the ion density exhibits an overall downward tendency in the cathode fall layer because the increase in secondary electrons produces more newly born electrons that neutralize more ions via the recombination reaction. Thanks to the pre-ionization, a significant reduction of sustaining voltage and discharge power is obtained in both the large-gap and small-gap discharges. A remarkable characteristic is that the absent positive column in the small-gap discharge comes into being again due to the pre-ionization. Moreover, with the increase in the pre-ionization level, the potential fall shifts from the cathode fall layer to the positive column in the large-gap discharge, while it is always concentrated in the cathode fall layer in the small-gap discharge. [ABSTRACT FROM AUTHOR]

The solution-cathode glow discharge (SCGD) is a low-power, atmospheric-pressure, ambient-atmosphere microplasma that is proving to be a proficient excitation source for atomic emission spectroscopy (AES). The analytical figures of merit [...]

Hollow cathodes are an integral part of ion, and Hall thrusters are used for electric propulsion in deep space missions and in commercial communications satellites. Hollow cathodes are known to operate in a quiescent "spot mode" and in a noisy "plume mode" in which plasma instabilities generate erosive energetic ions. The onset of the plume mode in hollow cathodes has been defined historically as when the keeper voltage oscillation values exceed 5 Vpp (peak-to-peak). Using a LaB6 hollow cathode in a vacuum chamber setup that simulates operation in ion and Hall thrusters, a set of emissive and Langmuir probes have been used to investigate the plasma properties associated with plume mode onset as a function of discharge current and gas flow rate. We find that the plume mode onset occurs at even less than 2 Vpp of the keeper voltage for the 5–75 A hollow cathode investigated here and starts at higher gas flow rates than expected from the traditional 5 Vpp metric used by those in the field. Mode competition and coupling between three different instabilities observed in the near-cathode plume affect the overall plasma oscillation levels that are correlated to energetic ion production. We find that the plasma oscillation levels measured by in situ plasma diagnostics are more indicative of the presence of oscillations and the generation of energetic ions than indirect keeper voltage measurements. [ABSTRACT FROM AUTHOR]

A reduced pressure glow discharge is produced by passing a high-power pulsed DC source of 0–500 W with a frequency of 50 Hz across two parallel disk electrodes. A hydrogen peroxide aqueous solution is used as a flowing gas for discharge generation. Optical emission spectroscopy is employed to diagnose the discharge generated at a reduced pressure of 0.2 mbar with an electrode gap of 4 cm. The spectra are recorded at a power density of 9.4 mW/cm3 and typically lie in the visible wavelength range of 380–880 nm. The spectra are analyzed using the line intensity ratio method to estimate electron temperature and density. The results indicated that the electron temperature and density are, respectively, 0.87 eV and 6.4 × 1014 cm−3. [ABSTRACT FROM AUTHOR]

Self-consistent numerical modeling was performed of a micro-glow discharge in helium self-organizing into 3D symmetrical patterns over a metallic cathode in the range of pressures of 600 to 800 Torr, for a constant gas temperature of 300 K. The 3D model employed comprised of Poisson's equation, equations of conservation of flux density, transport, and reactions, for a single ion species and electrons, assuming the drift-diffusion and local-field approximations. Multiple solutions to the model were found for the same range of discharge current, describing modes with different configurations of cathode spots. Stable transitions from the fundamental mode to the modes corresponding with self-organized patterns were identified as current was reduced from a discharge in the abnormal glow. At 600 Torr, the self-organized patterns comprised of symmetrically ordered, similarly sized, circular spots of current density that closely resembled patterns already identified in experiments and by modeling at lower pressures (in, e.g., xenon). At atmospheric pressure and above, the patterns emerged with one large central circular spot with small spots emerging uniformly around its periphery, resembling the shape of a gear. Modeling was also performed at atmospheric pressure for two constant temperatures above 300 K, of 600 and 1150 K. Qualitative changes to the patterns of current density on the cathode were observed. At 600 K, the first stable self-organized mode manifested similarly sized circular spots of current density on the cathode. At 1150 K, no self-organized patterns of spots emerged. The results indicate that self-organized patterns may emerge in atmospheric pressure micro-glow discharges but that gas temperature should be considered in an experiment attempting to characterize the phenomenon. [ABSTRACT FROM AUTHOR]

In recent years, pulse-modulated radio frequency (RF) plasmas have gained considerable interest in applications due to the advantages in reducing gas temperature and power consumption. In this article, the optimizations of operation mode in atmospheric pulse modulation RF discharges are investigated by a 1-D fluid model. From simulation data, the breakdown voltage and ${{\alpha -{\gamma }}}$ mode transition voltage both decrease as the duty cycle increases; however, a minimum breakdown voltage can be observed while altering the modulation frequency at a constant duty cycle, and the transition voltage always increases with the modulation frequency. The underpinning physics of the operation regime in pulsed RF discharges is discussed in detail by investigating the effects of the duration of the power-on phase based on the computational results. Increasing the number of applied RF cycles during the power-on phase contributes greatly to the breakdown and mode transition. This study can effectively deepen the understanding of the effects of pulse modulation in RF discharges and suggest ways to further optimize the pulse-modulated RF discharges. [ABSTRACT FROM AUTHOR]

The soft ionization mechanism of helium-based plasma seems to be understood while it still remains challenging in argon-based plasma, although many studies have used argon plasmas as a soft ionization source with good ionization efficiencies. In this study, helium, argon, krypton, and xenon were fed into the same discharge geometry, a flexible micro-tube plasma (FµTP), to determine the ionization mechanisms. The FµTPs operated with the named noble gases obtained comparable ionization efficiencies by MS measurements. The optical emission results showed that N2+ were the dominant ions within the helium-FµTP and noble gas ions were dominant for the other plasmas. These ions support the development of excitation and eventually stop at the end of the capillary. Therefore, Penning ionization and charge transfer between plasma and ambient air/analytes in the open atmosphere have been proven not to be the primary soft ionization mechanism. Furthermore, it was found that photoionization played a minor role in soft ionization. Using helium as a diagnosis gas in front of the discharge capillary nozzle of the FµTP, where the sample is usually positioned, shows that helium can be ignited by all of these FµTPs. This demonstrates that the excitation of a diagnosis gas as well as the ionization of analytes is independent of the type of the discharge gas. An alternative mechanism that a transient potential created by the ions is responsible for the soft ionization is subsequently proposed. [ABSTRACT FROM AUTHOR]

Eight kinds of patterned discharges are obtained by changing the discharge parameters in a dielectric barrier discharge with modulated gas gaps, which are applicable to materials patterned treatment. A square superlattice pattern consisting of two dot sublattices and one ring sublattice is studied and used to treat a PI film. The formation mechanism is studied by intensified charge coupled device. The spatial distribution of the plasma parameters is measured using optical emission spectra. The gas temperatures as well as the electron densities of the three sublattices are significantly different from each other. The physical and chemical properties of the treated film are measured using a surface profiler, x-ray photoelectron spectroscopy, and scanning electron microscope. The transmissivity, wettability, and etching depth of the treated PI film demonstrate square superlattice pattern distribution, which verifies the predictions based on plasma parameter measurements. The dielectric barrier discharge device reported here is also applicable to materials' patterned growth. [ABSTRACT FROM AUTHOR]

A solution anode glow discharge (SAGD) was established as a miniaturized excitation source of atomic emission spectrometry (AES) for the detection of Cd in rhizosphere soil, carrot, and carrot leaf samples. The working conditions, such as electrolyte pH, discharge voltage, support electrolyte, solution flow rate, and discharge distance, were systematically optimized. The effect of 31 foreign ions on the Cd determination was investigated. In addition, the influences of matrix modifiers on the Cd signal intensity and interference elimination were examined in detail. The results showed that under the optimal operating parameters, the presence of Fe3+, Co2+, Pb2+, Cu2+, Cr3+, and Tl3+ ions at 30 mg/L causes severe depression effects for the detection of Cd, and adding ascorbic acid as a matrix modifier can reduce the matrix interference, improve sensitivity, and lower the limit of detection (LOD). The LOD of Cd is 4.4 μg/L, and power is below 8 W using SAGD without any matrix modifier. Compared with the solution cathode glow discharge–atomic emission spectrometry (SCGD-AES), the sensitivity is improved about 11-fold, and the power is consumed only about one-sixth. The analysis results of SAGD-AES are in agreement with the Cd-certified reference material and verification values measured by inductively coupled plasma atomic emission spectroscopy, suggesting that proposed method has high accuracy and reliability. [ABSTRACT FROM AUTHOR]

Author affiliations *Corresponding authors n this work, a highly sensitive procedure for the determination of mercury in flue gas was developed, based on direct-current atmospheric pressure glow discharge in hydrogen and helium (H2-He) atomic emission spectroscopy (APGD-AES) coupled with gold amalgam enrichment (GA). Calibration mercury vapors generated by the cold vapor generation (CVG) system were sent to the GA system for enrichment. Subsequently, mercury was thermally desorbed and transmitted to APGD for excitation, and at the same time, the signal at 253.6 nm was recorded using a micro-spectrometer. The parameters of GA and APGD systems were optimized, including the type and flow rate of the carrier gas, discharge current and discharge gap. Under the optimum operating conditions, when the sampling volume of the flue gas was 10 L, the detection limit (DL) of Hg was 0.1 μg m-3, which met the actual measurement requirements, and the relative standard deviation (RSD) was 2% (n = 11), the linear correlation coefficient was better than 0.999. The accuracy and practicality of GA-APGD-AES were verified by the analysis of flue gas. The results were consistent with those of a direct mercury analysis (DMA) system (n = 3, relative deviation was less than 3%). [ABSTRACT FROM AUTHOR]

This study explores the impact of varying discharge gas compositions on the etching performance of silicon carbide (SiC) in a heptafluoroisopropyl methyl ether (HFE-347mmy)/O2/Ar plasma. SiC is increasingly favored for high-temperature and high-power applications due to its wide bandgap and high dielectric strength, but its chemical stability makes it challenging to etch. This research explores the use of HFE-347mmy as a low-global-warming-potential (GWP) alternative to the conventional high-GWP fluorinated gasses that are typically used in plasma etching. By examining the behavior of SiC etch rates and analyzing the formation of fluorocarbon films and Si-O bonds, this study provides insights into optimizing plasma conditions for effective SiC etching, while addressing environmental concerns associated with high-GWP gasses. [ABSTRACT FROM AUTHOR]

This study examined the impact of mixed probiotic inclusion in a reduced crude protein (CP) diet on production performance, nutrient retention, gas emissions, faecal score and meat quality of finishing pigs. In total, 150 pigs (body weight [BW] of 49.9 ± 2.80 kg and 6‐week trial) were arbitrarily distributed to one of three dietary treatments (10 replications per treatment, five pigs including three gilts and two barrows per replication). The dietary treatments were Positive Control/standard diet, 17.5% CP (PC); Negative Control/reduced (2.5%) CP diet, 15% CP (NC); and NC + 0.1% probiotic mix (NCP). Pigs fed the NCP diet exhibited tendency to increase BW gain at Week 6, increased the average daily gain (ADG) of pigs during Weeks 3–6 and showed tendency to increase ADG during the overall period than the NC diet. The CP digestibility decreased at Week 6 and presented a tendency to decrease at Week 3 in pigs fed the NC diet compared with the PC diet. However, CP digestibility increased with the NCP diet at Weeks 3 and 6 compared with the NC diet. A tendency in the reduction of H2S emissions from pig's faeces at Weeks 3 and 6 was observed by the NCP diet compared with NC and PC diets. Pigs fed the NC diet showed a lower faecal score than the PC diet at Week 6. The NC diet resulted in lower cooking loss and drip loss to the PC diet. Moreover, longissimus muscle area showed tendency to increase, cooking loss exhibited tendency to decrease and drip loss decreased in the meat samples of pigs receiving the NCP diet compared with the NC diet alone. The NCP diet exhibited great promise in maintaining performance by enhancing the growth performance, digestibility, mitigating gas emissions and improving the quality of meat in finishing pigs. [ABSTRACT FROM AUTHOR]

The study presents and analyzes the experimental results of geological and geomorphological observations in some marine areas with active gas emission from bottom sediments. The study was carried out using an instrumental complex of geophysical sonar equipment, which included a subbottom profiler and side scan bathymetric sonar that uses an interferometric method for measuring depths in the field of view. The results confirm the possibility of using the complex to classify the seabed morphology and control the processes of gas unloading. The use of sonar equipment for remote seabed mapping during satellite observations can be used to interpret the results of satellite remote sensing of the atmosphere. [ABSTRACT FROM AUTHOR]

Changes in the composition of the surface layer of a polyethylene film after treatment in the positive column of a direct current glow discharge in a stream of oxygen and argon have been studied. The possibility of copolymerization of a diallyldimethylammonium chloride monomer and a plasma-modified polyethylene surface is demonstrated. [ABSTRACT FROM AUTHOR]

This paper presents research on the development history as well as on the materials and techniques of technical installations with gas discharge lamps, colloquially known as ‘neon’ systems, in the former German Democratic Republic (GDR). Taking into account changes in materials, design, and technology between the 1950s and the 1980s, the findings also form the basis for the practical art-technological examination and evaluation of the examples still in existence. The majority of these objects have disappeared since the 1990s; the remainder are still acutely endangered today, due to progress in lighting technology and the current highly invasive repair practices. In this paper, a systematic examination case study is presented and discussed for the first time. The Poliklinik lettering under consideration is located on the façade of today's Medical Centre in the Hanseatic city of Stralsund and dates back to the second half of the 1950s. After more than 60 years of exposure to the elements, it appeared as an authentically aged, completely original example of the object group. A substance-careful concept for in situ examination was developed that did not require the fragile structure to be dismantled. The concept presented here is generally applicable to other objects with gas discharge lamps. [ABSTRACT FROM AUTHOR]

The commonly utilized nitriding steel 38CrMoAl is employed for components subjected to low-impact loads but high wear. In this investigation, 38CrMoAl underwent plasma nitrocarburizing using a hollow cathode plasma source, with variations in gas ratios aimed at process optimization. The findings revealed a noteworthy influence of the NH3 to CO2 ratio on the phase composition and properties of the nitrocarburizing layers. Two distinct surface types were observed: one composed of ɛ-Fe2–3(N, C) and γ'-Fe4N and the other consisting of nitrogen-containing martensite with a small quantity of nitride. The surface comprising iron nitride was formed via downslope diffusion, leading to increased surface hardness through nitride formation. Nitrogen-containing martensite was formed via uphill diffusion due to spinodal decomposition, reinforced by mechanisms including fine-grain strengthening, solid-solution strengthening, secondary hardening during tempering, and the pinning effect of metal nitrides precipitated at the grain boundaries. The spinodal structure exhibited superior properties, with a wear rate of 1.26e − 8 mm3/Nm. Thermodynamic calculations confirmed that nitrogen diffusion facilitated spinodal decomposition by expanding the spinodal gap and reducing system energy. This study successfully overcame the performance constraints associated with such nitrided layers, which holds promise for applications to other nitride materials. [ABSTRACT FROM AUTHOR]

Ceramic filler modified polymer blends are more in demand due to their excellent compatibility, easy processing and cost‐effectiveness. In the present work, we modified Polymethyl methacrylate (PMMA)/Polystyrene (PS) blends using solution blending with untreated (UT) and DC glow discharge plasma‐treated (air plasma treated‐APT) potassium hexatitanate (K2Ti6O13). Chemical bonding of virgin and modified blends was confirmed by Fourier transform infrared spectrophotometer (FTIR). Decreased structural defects and imperfections of KTO were confirmed by Raman spectroscopy. Modified surface morphology and elemental analysis were detected by scanning electron microscopy (SEM) and energy‐dispersive X‐ray analysis (EDAX). The quantification of particle size distribution has been determined by Zetasizer. Increased degree of crystallinity and decreased average crystallite size after plasma treatment were determined by X‐ray diffraction. Increased dielectric constant from ~22–200 and decreased loss up to 0.7 were analyzed by impedance analyzer. Lee's disc probe was deployed to confirm the optimized thermal conductivity of the modified blend system. By Differential Scanning Calorimetry, glass transition temperature of modified polymer blends was investigated. The change in surface from hydrophobic to hydrophilic by plasma exposure was confirmed by surface goniometer. However, the enhanced dielectric performance of modified PMMA/PS/KTO polymer blends may be suitable for flexible energy storage devices and gadgets. [ABSTRACT FROM AUTHOR]

In the present work, analyses have been performed to determine spectroscopic parameters, including transition probabilities, and relative line strengths of discharge-produced xenon plasma. We present the transition probabilities of twenty-three emission lines originating from the 5p56p →5p56s transition array of neutral xenon covering the wavelength range from 450 to 1100 nm using a xenon-filled hollow cathode discharge lamp. The experimental absolute transition probabilities have been measured by combining the reported lifetimes of upper levels with the integrated spectral intensities of xenon transitions. The results agree well with the reported data in the NIST database, where available. The theoretical line strengths for all spectral transitions originating from the 5p56p→5p56s transition array have been calculated in the LS, LK, jj, and jck coupling schemes using the 3j, 6j, and 9j symbol relations. Furthermore, the normalized experimental line strengths have also been measured and compared with theoretical line strengths, which confirm that the jj and jck coupling scheme is more appropriate for the level designation of xenon. [ABSTRACT FROM AUTHOR]

This work presents a comparison between electrochemical (Echem), plasma glow, and arc discharge polymerizations of pyrrole doped with iodine to correlate the energy of synthesis, chemical structure, and electrical conductivity of the polymers. Plasma glow discharges were used in the gas phase, electrochemistry in liquid, and arc discharges in a hybrid gas–liquid combination. Polypyrroles had structure and conductivity that varied with the synthesis parameters; Echem produced polymers with high carbonization and without the C≡N triple bonds resulting from the other syntheses. Conductivity divided the polymers in two: those synthesized in liquid were in the 0.01–1.0 S/m range, and those synthesized in gas were in the 10–9–10–7 S/m range, with differences of up to eight orders of magnitude due to the dopants and electrolytes. [ABSTRACT FROM AUTHOR]

The influence of argon and helium on the rovibrational kinetics of carbon dioxide (CO2) and CO in low-temperature conversion plasma is investigated. With this objective, a combined experimental and computational study is conducted, applying quantum cascade laser infrared absorption spectroscopy to a pulsed DC CO2 glow discharge with varying noble gas admixture and modeling it with a two-term Boltzmann solver. Time-resolved rovibrational temperatures and dissociation fractions are presented, exhibiting an increase in rotational–vibrational non-equilibrium and an increasing CO2 conversion with argon (Ar) and helium (He) admixtures. Results are discussed in the context of energy transfer processes for collisions involving electrons, corroborated by electron-kinetic modeling, and heavy particle collisions. With noble gas addition, an increase in the electron number density, promoting excitation, and the high-energy tail of the electron energy distribution function are found. Penning ionization processes are proposed as an explanation for the increase in conversion, showing higher conversion for Ar due to the lower excitation thresholds and, therefore, larger state population. In the context of rovibrational kinetics, processes leading to the gain or loss of vibrational energy of CO2 are analyzed, pointing out subtle differences in, for example, relaxation rate coefficients between Ar and He. However, the cooling of the gas through conductive heat transfer is identified as the most important influence of the Ar and He admixture, as it keeps the relaxation rate for vibrational quenching low. [ABSTRACT FROM AUTHOR]

The composition and ion energy distributions of the main ion species of an ion beam were recorded and analyzed. The RF-type broad beam ion source was operated with a mixture of CHF 3 and O 2. A plasma bridge neutralizer operating with Ar was employed for ion beam neutralization. The data were collected with an energy-selective mass spectrometer (ESMS). The mass spectrum showed numerous ion species, beginning with ionized molecules, dissociation products of the process gases and products from reactions with background gas and the plasma discharge vessel, and the extraction system. For a quantification of the ion beam composition, the mass dependent transmission functions for two ESMS were determined. The ion energy distributions show that, in comparison to operation with inert gases, there are additional slower ions present. These ions can be related to dissociation processes outside of the ion beam source. As a result of their typically lower etching yield, these slower ions affect the etching behavior. [ABSTRACT FROM AUTHOR]

The microwave electrothermal thruster (MET) utilizes wave-exited microdischarges to heat gas flows, enhancing the specific impulse of the thruster. Our computational study investigates a 17.5 GHz helium-propellant MET, employing a two-dimensional, axisymmetric fluid model of plasma coupled with electromagnetic wave and gas flows. The discharges operate in the glow regime, remaining weakly ionized, and in thermal non-equilibrium. The plasma densities reach approximately 10 20 m − 3 , and the gas temperature is around 2000 K. Even a slight off-resonant frequency operation results in a significantly lower plasma density and gas temperature. Gas heating, primarily driven by electromagnetic Joule heating, plays a critical role in influencing the overall discharge behavior. The measured peak thrust and specific impulse are 8.24 mN and 292 s, respectively, at a mass flow rate of 3.2 mg/s with 30 W of power. Compared to a cold gas thruster, there is a significant increase in the specific impulse by a factor of approximately 1.7. The enhanced performance trades off with propulsive efficiency, which decreases by a factor of 1.5 from the peak 65% at 10 W. This is due to higher energy losses to cavity walls from heat conduction with increased power. These findings underscore the critical balance between the input power and mass flow rate to improve the MET performance, highlighting the importance of power management to maximize thrust and efficiency. Furthermore, the predicted thrust and specific impulse agree well with experimental values for nominally similar MET thruster studies in the literature. [ABSTRACT FROM AUTHOR]

Current–voltage characteristics, space- and time-resolved optical emission spectroscopy, and 1D fluid modeling are used to examine the effect of dual-frequency sheath oscillations on the ion and electron transport in dielectric barrier discharges sustained by a combination of low frequency (LF, 50 kHz, 650 V) and radiofrequency (RF, 5.3 MHz, 195 V) voltages, exhibiting the α-to-γ mode transition. On one hand, when polarities of the LF and RF voltages are opposite, an electric field near the LF cathode (due to LF cathode sheath) drives the secondary electrons to the plasma bulk and an opposite electric field between the sheath edge and the LF anode attracts the electrons toward the LF cathode (to maintain quasi-neutrality in the plasma bulk). At the sheath edge, electrons become trapped and ions drift toward the cathode and the anode simultaneously according to their position in the gap. On the other hand, when the RF voltage has the same polarity as the LF voltage, the total applied voltage increases and this yields to enhanced production of electrons and ions in the sheath. To maintain quasi-neutrality in the bulk, the electric field along the gap exhibits the same polarity as the one in the sheath, allowing electrons created in the sheath to be evacuated toward the LF anode. The behavior of the LF cathode is, therefore, controlled by the LF sheath, and, thus, by the LF voltage amplitude, while the behavior in the bulk and at the anode alternates on the time scale of the RF voltage. [ABSTRACT FROM AUTHOR]

Streamer coupling theory is traditionally used to engineer the generation of diffuse plasmas in the regime preceding filamentary discharge, but this method remains inefficient. Here, an alternative route to cost-efficient diffuse plasma generation is proposed, involving the expansion and quenching of existing filamentary discharge.