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The paper presents the results of an experiment on the effect of pre-sowing stimulation of seeds with atmospheric pressure plasma jet operating with dielectric barrier discharge (DBD plasma jet) on the process of germination of Thuringian Mallow (Lavatera thuringiaca L.). Five groups of seeds characterized by a different exposure times (1, 2, 5, 10 and 15 minutes) as well as untreated seeds-control were used. Pre-sowing plasma stimulation of seeds improved germination parameters such as: germination capacity and germination energy for all tested groups relative to control. The highest germination parameters were obtained for seeds stimulated with plasma for the exposure times of 2 and 5 min. The analysis of the contact surface angle indicated the decrease of its' mean values upon seed stimulation while no statistical effects were observed. Analysis of the SEM scans revealed the increase in seed pattern intensity which could be attributed to removing of the surface parts of cuticle possibly covered with wax upon short time-2 and 5 min plasma treatment. Such a phenomenon can act similarly to mechanical scarification of seeds. Longer exposure of seeds to plasma resulted in affecting the deeper zone of cuticle and damage or fracture of some parts of the cuticle. Lower germination parameters of seeds upon longer exposure times to plasma may indicate mechanical damage of the seeds.

In this paper, a new configuration of a cold atmospheric pressure plasma jet has been designed and constructed. Poly-methyl-methacrylate was used as a new dielectric in this configuration which in comparison to other dielectrics is inexpensive, more resistant against break, and also more shapeable. Then, the plasma jet parameters such as plume temperature, rotational and vibrational temperatures, power, electrical behavior (voltage and current profile), electron density, and the produced reactive species were characterized. In order to determine the jet temperature and the amount of reactive species, effects of applied voltage, gas flow rate, and distance from the nozzle were studied. The power of the jet was specified using Lissajous curve approach. The plume temperature of the plasma jet was about the room temperature. Optical emission spectroscopy determined the type of reactive species, and also electron density and its corresponding plasma frequency (~6.4 × 10(13) cm(-3) and 4.52 × 10(11) Hz). Because of producing different reactive species, the device can be used in different applications, especially in plasma medicine. Thus, 4T1 cancer cells were treated using this plasma jet. The results showed that this plasma jet has a great potential to kill one of the most aggressive and resistant cancerous cell lines.

Cold atmospheric-pressure plasma jets (APPJ) have excellent applications in biomedicine. Advantages of APPJ include lack of need for vacuum systems, capability of operation for a long time, and safe to be directly touched by living tissues such as a human body. In this study, an APPJ was generated by a dielectric barrier and applied for the treatment of chemical wounds. This APPJ worked with argon and was driven by high-voltage pulses. This paper compares the spontaneous healing of wounds and a stimulated healing using daily APPJ treatment. Biological data, such as hematological, biochemical, and histological parameters, were remarked. The mortality and morbidity of the untreated samples were reported after 20 days in comparison with the plasma-treated samples, which were alive after these days. Experimental results demonstrated that an increase in the oxidative stress could result in the decreased destruction of lesions by controlling the infection growth. These results were related to the presence of reactive oxygen species and reactive nitrogen species in the plasma volume, which were detected by optical emission spectroscopy.

In this paper, a complete flux scheme (CFS) has been implemented in 1-D fluid model for simulating the pulsed dielectric barrier discharge (DBD) in pure argon at atmospheric pressure. The characteristic quantities of the pulsed DBD have been systematically calculated by using the CFS and presented in comparison with those by using the exponential difference scheme (EDS). This paper shows the following results. There is the two-pulse discharge mode in the present simulation. The two discharge currents obtained using the CFS and EDS converge to the same result in good agreement with the experiment as spatial step length decreases, but the CFS has a fast convergence performance compared to the EDS. With a small grid number, the numerical scheme has an evident effect on the characteristic quantities in the time region corresponding to the first discharge pulse. This paper suggests that in the pulsed DBD, the usage of the CFS with a properly small grid number can give more accurate result and also presents a high calculation efficiency. [ABSTRACT FROM AUTHOR]

The characterization of an atmospheric pressure microwave argon plasma in the form of a plasma sheet and the results of its use in the investigation of the wettability modification of polyethylene (PE) surfaces are presented in this paper. The spectroscopic investigations performed indicate a plasma temperature at the level of 750–1100 K and an electron density at the level of 2.9– $5.4\times 10^{14}$ cm−3. The following PE-type specially prepared materials were subjected to the plasma treatment process: PE (pure low-density PE), PE + UV (PE with a UV stabilizer), PE − UV + M (with a UV stabilizer and a montmorillonite), PE + S (PE with soot), and PE − F (PE with a UV stabilizer, a montmorillonite, and soot). The experimental investigations prove the high potential of the presented method for the PE surface activation in industrial applications. The atomic force microscopy scanning of samples was performed before and after the plasma treatment. The aging of the adhesion enhancement effect indicates that the water contact angle is related to the surface energy changes. [ABSTRACT FROM AUTHOR]

This paper summarizes the Dr. Robert J. Barker memorial session at the IEEE International Conference on Plasma Science 2014. Each section summarizes progress in a plasma research area strongly influenced by Dr. Barker’s leadership: 1) plasma medicine; 2) atmospheric-pressure plasmas; 3) high-power microwaves; 4) pulsed power; and 5) numerical simulation of plasmas. He had a profound influence on these and other plasma science applications, as well as on numerous individual researchers. He will be missed greatly. [ABSTRACT FROM PUBLISHER]

Presents the table of contents for this issue of the periodical. [ABSTRACT FROM PUBLISHER]

Multipoint-to-multipoint and multipoint-to-plane electrode geometries have been investigated to enhance corona discharge modes in atmospheric pressure weakly ionized plasma. This paper presents a new geometry approach by a protrusion array over the grounded screen along with a high-voltage (HV) needle array to obtain higher coulombic discharge. It has been observed that needle-to-grounded-screen-protrusion configuration enhances the discharge modes, especially the back corona is enhanced significantly near the protrusions in Ar/C2H2 plasma. A corona mode map has been developed to depict the optimal discharge zones at various HV gaps. Similar investigations were performed in Ar/O2 plasma to study the nature of the current pulses and discharge modes. [ABSTRACT FROM PUBLISHER]

This paper describes an inductive discharge with ferromagnetic enhancement of magnetic coupling between an inductor and a discharge, generated at atmospheric pressure of plasma forming gas. It is shown that amplifying a magnetic flux that connects the inductor and the plasma makes it possible to efficiently generate an electrodeless discharge in a low-frequency (10–100 kHz) range and greatly simplifies the use of the inductively coupled plasma. This study also presents new experimental data on the dependence of the electric field strength and the thermal efficiency of a low-frequency induction discharge of atmospheric pressure on the discharge current strength and the flow rate of a plasma-forming gas (argon or air). It is shown how a low-frequency inductive discharge maintenance criterion is related to its thermal efficiency, and methods for reducing the heat losses of a low-frequency inductive discharge of atmospheric pressure are analyzed. [ABSTRACT FROM AUTHOR]

One type of atmospheric plasma jet relay driven by a 40-kHz power supply and its representative characteristics have been proposed in this paper. The plasma jet relay succeeds in the same gas stem or inside another guided dielectric tube. The first plasma jet can be capable of dividing into many small plasma jets at the end of metal wires and the filial generations can easily merge together to form longer volume discharges. The experiment indicates that the filamentary discharge starts from the formation of one snake-like discharge passage first and the followed snakes give birth from the previous snake discharge body. Taking into account the advantage of easily production methods and available to extend its discharge volume, the proposed plasma jet relay device can be modulated for many potential applications. [ABSTRACT FROM PUBLISHER]

Polypropylene nonwoven materials have foundenormous usefulness in many applications. In this paper, the cyclonic plasma processing at atmospheric pressure was used to determine the surface treatment effect. The change of hydrophilicity was determined by contact angle analysis. The nonwoven polypropylene (NWPP) surface became greatly hydrophilic when exposed to the cyclonic plasma at atmospheric-pressure. A major effect in the surface free energy of material surface due to crosslinking via activated species of inert gases effect was observed. The variations in the chemical structure and surface morphology of the NWPP were confirmed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscope detections. The XPS detection reveals considerably more surface elemental composition of oxygen atoms for cyclonic plasma-modified NWPP. [ABSTRACT FROM PUBLISHER]

This paper presents an experimental investigation of ionization waves’ (IWs’) propagation in a nanosecond-pulse dielectric barrier discharge at atmospheric pressure in air. The effect of the rise time and pulse duration on IW propagation is studied by an intensified charge-coupled device, and the mechanism of the discharge propagation is analyzed. The experimental results show that the discharge produced in the rise time of the applied voltage develops in a structure of discontinuous sphere, while the discharge produced in the falling time exhibits a continuous form due to the effect of space charge. Furthermore, the rise time of the applied voltage has a significant influence on the velocity of IWs, and the maximal velocity of IWs rapidly decreases from 0.08 to 0.008 mm/ns when the rise time of the applied voltage increases from 50 to 300 ns. However, the pulse width has almost no influence on the velocity of IWs. The electric field distortion caused by both the propagation of IWs and the accumulation of surface charges is responsible for the formation and propagation of IWs. [ABSTRACT FROM AUTHOR]

Low-temperature plasma treatment is a promising technology for particulate matter (PM). In this paper, the arrayed dielectric barrier discharge (DBD) plasma reactor for PM2.5 removal is investigated at atmospheric pressure. In order to reveal the interaction between experimental findings and simulation results, the equivalent electrical circuit is used. The electrical model is implemented on the PSIM software. To calculate the capacitance of the arrayed DBD reactor, the capacitor expressions are developed. Considering the experimental elements, such as plasma-generated configuration and the power source, a topological equivalent circuit is given. Finally, the simulation results are compared with the experimental ones, and they agree well. In addition, the designed DBD reactor was used to investigate PM2.5 removal. PM2.5 removal after 4 min of plasma treatment found to be about 53.8%. [ABSTRACT FROM PUBLISHER]

To date, research on the inactivation of microorganisms by nonequilibrium atmospheric pressure plasmas has mainly been concerned by the killing efficiency and/or with the study of the roles played by various plasma agents (ultraviolet, radicals, ions, etc.) in the inactivation process. In this paper, the authors look at the problem from the cells' side. More specifically, the following questions are asked: What part of the spore structure plays a crucial role in its defense against the unfavorable plasma environment, and if the cells do survive plasma treatment, do they emerge the same or do they undergo some kind of noticeable changes? Although complete and comprehensive answers to these questions are not at the authors' grasp at this time, this paper presents convincing preliminary data that show that the integrity of the proteins cf a spore's coat plays a major role in its survivability and that cells that survive air plasma exposure emerge with a changed metabolism. [ABSTRACT FROM AUTHOR]

A previous paper reported some features of atmospheric Tungsten inert gas arc plasmas obtained with Langmuir probes operating in floating conditions and results on averaged quantities were given. This paper develops the method for probes in biased conditions. Because in the available literature sources, the construction of characteristic curves (V-I) in arcs is not discussed, a description of directly observed quantities is presented and some constructive methods are shown for a range of arc currents (50 to 200 A) and probe positions with considerable detail. The main result of this work is that these curves are incomplete in the column of atmospheric pressure arcs so that the traditional methods to extract plasma parameters are of little use. In contrast to previous works dealing with the anode region of the arc, it is found that the only useful portion of the V-I curve is the ion saturation part for all the arc currents investigated. Also, it is not possible to identify the plasma potential from the V-I curve. Ion saturation occurs for all probe locations at the lowest arc currents, whereas saturation is uncertain for probes closer to the cathode at higher arc currents. When saturation does occur, it is characterized by the flatness of the curve with respect to the potential: no power law dependencies on the voltage are found. Also, for the higher arc currents, an inner arc region can he identified where ion saturation is uncertain or does not occur. An accompanying paper exploits the ion saturation part of the characteristics to estimate the arc plasma temperature. [ABSTRACT FROM AUTHOR]

The surface microdischarge in atmospheric helium is studied for the dynamic evolution of plasma patterns in the glow mode. It is found that there are two distinct patterns in the positive half cycle. This indicates that the influence of space-charge electric field caused by surface deposited charges not only exists in the negative half cycle for the evolution process, but also exists between the half cycles. It is in agreement with the phenomenon which the originating regions of discharge in positive half cycle depend on the number of the current pulse in negative half cycle. The emission pattern of the positive half cycle is dominated by the last strong current pulse in the negative half cycle. [ABSTRACT FROM AUTHOR]

In this paper, atmospheric pressure glow discharges (APGD) in argon generated in parallel plate dielectric barrier discharge system is investigated by means of electrical and optical measurements. Using a high voltage (0-20 kV) power supply operating at 10-30 kHz, homogeneous and steady APGD has been observed between the electrodes with gap spacing from 0.5 mm to 2 mm and with a dielectric barrier of thickness 2 mm while argon gas is fed at a controlled flow rate of 1 l/min. The electron temperature and electron density of the plasma are determined by means of optical emission spectroscopy. Our results show that the electron density of the discharge obtained is of the order of 10 cm while the electron temperature is estimated to be 0.65 eV. The important result is that electron density determined from the line intensity ratio method and stark broadening method are in very good agreement. The Lissajous figure is used to estimate the energy deposited to the glow discharge. It is found that the energy deposited to the discharge is in the range of 20 to 25 μJ with a discharge voltage of 1.85 kV. The energy deposited to the discharge is observed to be higher at smaller gas spacing. The glow discharge plasma is tested to be effective in reducing the hydrophobicity of polyethylene film significantly. [ABSTRACT FROM AUTHOR]

In this paper, both simulations and experiments are conducted to investigate the physical characteristics of the radio-frequency atmospheric-pressure glow discharges (RF APGDs) first. The experimental and modeling results show that there are abundant chemically reactive species, e.g., electrons, helium metastables and ions, with high number densities in the discharge region. The corresponding plasma jet temperatures are in the range of 27\ ^\circ\C - 39\ ^\circ\C with the power input lower than 120 W, which is suitable for the treatment of the biomolecules or cells. Then, a prototype, which is the so-called atmospheric and room-temperature plasma mutation system, is designed with the RF APGD plasma generator as the core component. As an example, it is used for the mutation breeding of Methylosinus trichosporium OB3b. The experimental results show that the RF APGD plasma source is an environmentally friendly and efficient tool for the genome mutation of microorganisms to construct mutant library with large diversity. [ABSTRACT FROM PUBLISHER]

In this paper, an innovative coaxial-type dielectric barrier discharge plasma generator is proposed to produce the large-volume and visibly uniform cold argon plasmas at atmospheric pressure by enhancing the local intensity and uniformity of the electric field simultaneously with the aid of a cylindrical screwlike inner electrode configuration. The experimental measurements show that the discharges transit from the initial stage after breakdown to the stable stage through a transitional stage and finally reach an unstable discharge stage with the increase of the applied voltage. The estimated values of the electron temperature and the number density of the gas discharge plasmas in the electrode region vary in a small range, i.e., 8.0–8.9 eV and (\4.6–\6.4) \times \10^11\ \cm^-3, with increasing the applied voltage. Moreover, the plasma streams are quite uniform in the radial direction with a low gas temperature (\sim300 K) and an abundance of chemically reactive species in the stable discharge stage, which will be potentially a useful tool for the treatment of the heat-sensitive materials. [ABSTRACT FROM PUBLISHER]

H2S and SO2 are important characteristic gases of partial discharge (PD) generated by latent insulated defects in gas insulated switchgear (GIS). The detection of H2S and SO2 is of great significance in the diagnosis and assessment of the operating status of GIS. In this paper, we perform experiments on the gas sensitivity of unmodified multi-walled carbon nanotubes (MWNTs) and those modified by atmospheric pressure dielectric barrier discharge (DBD) air plasma at different times (30, 60 and 120 s) for H2S and SO2, respectively. The results show that the sensitivity and response time of modified MWNTs to H2S are both improved, whereas the opposite effects are observed for SO2. The modified MWNTs have almost zero sensitivity to SO2. Thus, the MWNTs modified by atmospheric pressure DBD air plasma present good selectivity to H2S, and have great potential in H2S detection. [ABSTRACT FROM AUTHOR]

Atmospheric-pressure nonequilibrium nonthermal plasma hybrid exhaust gas aftertreatment systems that do not utilize precious metal catalysts, harmful ammonia, etc., have been developed by the authors. Two types of new environmental protection systems (a dry system and a wet system), which enable the production of ultralow \CO2, particulate matter and \NOx emissions as well as reduced fuel consumption and low cost, are investigated for diesel engines, marine engines, and combustion boiler applications. This paper reports the principles of the dry system and some recent experimental results of laboratory tests. The \NOx reduction comprises three flow processes: 1) adsorption, 2) heating, and 3) cooling processes. The heating process corresponds to the regeneration process. These processes are repeated in the following order: 1), 2), and 3). This dry system demonstrates excellent energy efficiencies that meet the most recent Japanese national regulations regarding automobile diesel engine exhaust gas. In this study, approximately 60% of the \NOx of the exhaust (\NOx: 240 \sim 325 ppm, \flow rate = 300\ \NL/min, N: standard state) can be treated for 35 h. An improved system energy efficiency of 143 \g\ (\NO2)/\kWh, which is the highest yet, is achieved for \NOx reduction. [ABSTRACT FROM AUTHOR]

In our research group, an atmospheric multigas inductively coupled plasma (ICP) source was developed for industrial plasma processing and elemental analysis. The plasma source can stably generate atmospheric thermal plasma not only by Ar but also by He, \O2, \N2, \CO2, air, and their mixture gas. In this paper, the plasma source was applied for anesthetic gas decomposition including \N2\O, which is a kind of global warming gases. Atmospheric thermal plasma was generated by mixture gas of \N2\O, \O2, and air. It corresponds to actual gas composition for up to three surgery exhaust. Spectroscopic characteristics of generated plasma and composition of treated gas were investigated. By using optimally shaped ICP torch, 99.9% of decomposition rate and 942 g/kWh of high energy efficiency were achieved. However, around 3% of \NOx was generated as by-products due to high gas temperature. [ABSTRACT FROM AUTHOR]

We reported in this paper the tooth-whitening effect by a direct-current cold atmospheric-pressure air plasma microjet (PMJ) and saline solution (0.9%). All teeth were randomly divided into three groups, treated for 20 min with an air blow and saline solution, a PMJ and saline solution, and 35% hydrogen peroxide gel, respectively. Compared with the other groups, the teeth treated with the PMJ and saline solution showed the best tooth-whitening effect. The microhardness of the tooth enamel measurement showed no apparent differences among the three groups. A minor enamel surface morphological change was observed via SEM but was considered acceptable. Singlet oxygen (^1\O2) and hydroxyl (^\bullet\OH) radicals were detected by electron spin resonance spectroscopy. Atomic oxygen (O) was observed in the optical emission spectra of the PMJ. ^1 \O2, ^\bullet\OH, and O were considered to be the key agents during the tooth-whitening process. This novel method of tooth whitening has the potential to revolutionize the clinical tooth-whitening procedure. [ABSTRACT FROM PUBLISHER]

This paper describes a procedure for experimental determination of metastable and resonant populations along a surface wave argon plasma column at atmospheric pressure. As modeling work progresses extensively, an experimental database is necessary to confirm these models. Obtained results, within the range of values reported in literature, indicate that densities of metastable and resonant levels grow along the plasma column for positions near the energy coupler device, where the energy of the surface wave which creates discharge is the highest. This behavior is also found for electron density and temperature; however, it is not the same for gradient. Therefore, at atmospheric pressure, populations of 4s levels are not only controlled by collision with electrons from ground state, but the dissociative recombination mechanism is also important, in agreement with results found by other authors using collisional-radiative models. [ABSTRACT FROM AUTHOR]

The mathematical model of a direct-current arc at atmospheric pressure and low currents has been proposed. This paper presents the results of 2-D simulations for an air arc within the plasmatron channel, as well as the anode, composite cathode, and external regions. The model does not employ any adjustable parameter and therefore enables direct comparison with the experiments. The model predictions were compared with the experimental data of a plasma igniter and indicated good agreement. [ABSTRACT FROM AUTHOR]

In a previous paper, it was shown that only the ion portion of the probe characteristics curve (V-I) can be used to estimate the temperature from probes sweeping in the column of a flowing atmospheric pressure arc plasma. Methods relating the measured ion current directly to the temperature can be used, if a particle density-temperature relationship is available. However, several sources of "disturbance" need to be considered in the application of these methods. The main focus of this paper is in establishing how the experimental data permit an identification of the correct model taking into account these limitations. It is shown that some previously published criteria for the establishment of cooling induced by probes in atmospheric pressure arc plasmas and of recombination in the perturbed region are inadequate and their modification is consistent with the gathered data. Because of the thin and collisionless sheath, the temperatures reconstructed by probes belong to the edge of a sheath which is fully embedded in a perturbation region (PR) and not to the bulk of the plasma. A range of arc currents is studied and comparison with data from emission spectroscopy is used to assess and quantify the degree of depression shown by the probe determined temperatures. The consideration of flow velocity within the expressions for the probe currents shows that ad hoc corrections, in absence of direct experimental evidence on flow velocity distributions, do not lead to substantial benefit for the temperature corrections. "Cooling" mechanisms are considered and between ion energy loss and ion-electron recombination, the first dominates at temperatures below about 7500 K, whereas the latter dominates within the PR in the temperature range 9-13 000 K. For higher temperatures, the two contributions are very close to each other. Despite the severe interpretation difficulties, the practical reproducibility of the results and their empirical relationships with spectroscopic values assumed "exact" permits the reconstruction of reasonable electron temperature by the probe method in these plasmas even if experimental data on flow velocity distribution are not available. [ABSTRACT FROM AUTHOR]

This paper presents a study of one possible form of ball lightning. Plasma spheres several centimeters in diameter were produced in atmospheric pressure air. These spheres persisted for up to a half-second after the power supply was turned off. A mathematical theory was derived that predicts the observed lifetime. The theory predicts that the sphere lifetime should scale as the sphere radius squared, which means that large spheres should persist for many seconds. [ABSTRACT FROM AUTHOR]

The Asia-Pacific International Symposium on the Basics and Applications of Plasma Technology (APSPT) has been held in Taiwan or Japan every two–four years since 1997. It is an important annual event in the Asia-Pacific area and has been a great platform for scientists all around the world sharing novel and state-of-the-art research findings and exchanging innovative ideas in the field of plasma science and technology. The 10th APSPT was held on December 15–17, 2017 at Chung Yuan Christian University, Taoyuan, Taiwan. There has been a very strong program including 207 papers contributed by participants from eight countries. This Special Issue focuses on the following topics, which were also the focus topics in the 10th APSPT [ABSTRACT FROM AUTHOR]

The distribution of excited species in a helium plasma torch is studied during the introduction of carbon tetrachloride in the main gas. This paper provides information on the processes occurring in the plasma. The method uses a fast high-resolution acquisition setup, as well as a new data processing procedure based on the Abel inversion technique that provides the radial profile of thin plasmas. [ABSTRACT FROM AUTHOR]

Presents the table of contents for this issue of the publication. [ABSTRACT FROM PUBLISHER]

In this paper, we present sequential atmospheric pressure plasma-assisted laser ablation of photovoltaic cover glass. First, glass samples were plasma pre-treated using a hydrogenous plasma process gas in order to accomplish a modification of the near-surface glass network by a chemical reduction and the implantation of hydrogen. As a result, the transmission at a wavelength of 355 nm was reduced by approximately 2% after plasma treatment duration of 60 min. Further, the surface polarity was increased by approximately 78%, indicating an increase of the near-surface index of refraction. Subsequently to the plasma pre-treatment, the samples were laser ablated applying the above-mentioned laser wavelength of a Nd: YAG nanosecond laser. Compared to untreated samples, a significant decrease of the form error by 45% without any mentionable change in the ablation rate was obtained in the case of pre-treated samples. For comparison, the results and findings are discussed with respect to previous work, where the presented plasma-assisted ablation procedure was applied to optical glasses. [ABSTRACT FROM AUTHOR]

In this paper, 2.45-GHz microwave argon plasma jets at atmospheric gas pressure are generated at the end of quartz tube (with an inner radius of 2 mm). With the applied power of 50 W and the different patterns of exciter, the lengths of plasma jet plume out of the end of quartz tube, about 5, 15, and 25 mm, respectively, are obtained. Moreover, the simulated result suggests that the efficient plasma jet with a symmetric hairpin copper wire is attributed to the enhanced electric field of local surface plasmon polaritons. [ABSTRACT FROM PUBLISHER]

This paper is an essay narrating the recent history of the introduction of the biomedical applications of nonthermal plasmas to the plasma science research community. [ABSTRACT FROM AUTHOR]

Atmosphere pressure weakly ionized plasma has been utilized to polymerize gas phase acetylene in a needle-to-plane electrode configuration. The approach used in this research is novel as it did not rely on complicated power supplies or expensive materials and it results in a needle-to-ground geometry. The activated acetylene molecules in an argon environment were deposited onto a substrate to grow thin plasma-polymerized acetylene films. Using independent methods, a deposition rate between 2.2 and 23 nm/s was measured when an average free electron power of 94 mW was used. [ABSTRACT FROM AUTHOR]

Plasma processing of carbon fibers (CFs) is aimed to provide better contact and adhesion between individual plies without decrease in the CF mechanical resistance. This paper deals with surface modification of CFs by an atmospheric pressure dielectric barrier discharge (DBD) for enhancing the adhesion between the CF and the polymeric matrix. The scanning electron microscopy of the treated samples revealed many small particles distributed over entire surface of the fiber. These particles are product of the fiber surface etching during the DBD treatment that removes the epoxy layer covering as-received samples. The alteration of the CF surface morphology was also confirmed by the Atomic force microscopy (AFM), which indicated that the CF roughness increased as a result of the plasma treatment. The analysis of the surface chemical composition provided by X-ray photoelectron spectroscopy showed that oxygen and nitrogen atoms are incorporated onto the surface. The polar oxygen groups formed on the surface lead to the increasing of the CF surface energy. The results of interlaminar shear strength test (short beam) of CFs/polypropylene composites demonstrated a greater shear resistance of the composites made with CFs treated by DBD than the one with untreated fibers. Both the increase in surface roughness and the surface oxidation contribute for the enhancement of CF adhesion properties. [ABSTRACT FROM PUBLISHER]

Finding a solution for air species contamination of atmospheric pressure plasmas in plasma medical treatment is a major task for the new field of plasma medicine. Several approaches use complex climate chambers to control the surrounding atmosphere. In this paper, ambient species are excluded in plasma–human-skin-cell treatment by ensheathing the plasma jet effluent with a shielding gas. Not only does this gas curtain protect the plasma jet effluent from inflow of air species but it also, more importantly, allows controlling the effluent reactive species composition by adjusting the mixture of the shielding gas. In the present investigations, the mixture of nitrogen to oxygen within the gas curtain around an argon atmospheric pressure plasma jet (kinpen) is varied. The resulting reactive plasma components produced in the jet effluent are thus either oxygen or nitrogen dominated. With this gas curtain, the effect of reactive oxygen species (ROS) and reactive nitrogen species (RNS) on the cell viability of indirectly plasma-treated HaCaT skin cells is studied. This human keratinocyte cell line is an established standard for a skin model system. The cell viability is determined by a fluorometric assay, where metabolically active cells transform nonfluorescent resazurin to the highly fluorescent resorufin. Plasma jet and gas curtain are characterized by numerical flow simulation as well as by optical emission spectroscopy. The generation of nitrite within the used standard cell culture medium serves as a measure for generated RNS. Measurements with the leukodye dichlorodihydrofluorescein diacetate show that, despite a variation of the shielding gas mixture, the total amount of generated reactive oxygen plus nitrogen species is constant. It is shown that a plasma dominated by RNS disrupts cellular growth less than a ROS-dominated plasma. [ABSTRACT FROM PUBLISHER]

Plasma bullets are ionization fronts created in atmospheric-pressure plasma jets. The propagation behavior of those bullets is, in the literature, explained by the formation of an interface between the inert gas and the ambient air created by the gas flow of the plasma jet, which guides these discharges in the formed gas channel. In this paper, we examine this ionization phenomenon in uniform gases at atmospheric pressure where this interface between two gases is not present. By changing electrical parameters and adding admixtures such as oxygen, nitrogen, and air to the gas flow, the conditions for which plasma bullets are present are investigated. Nanosecond time-resolved images have been taken with an ICCD camera to observe the propagation behavior of these discharges. It is argued that the inhomogeneous spatial concentration of metastable atoms and ions, due to the laminar gas flow and the operation frequency of the discharge in the range of a few kilohertz, is responsible for the guidance of the ionization fronts. Furthermore, conditions have been observed at where the branching of the discharge is stable and reproducible over time in the case of a helium plasma by adding admixtures of oxygen. Possible mechanisms for this phenomenon are discussed. [ABSTRACT FROM PUBLISHER]

The application of calibration-free laser-induced breakdown spectroscopy (CF-LIBS) for quantitative analysis of materials, illustrated by CF-LIBS applied to a brass sample of known composition, is presented in this paper. The LIBS plasma is produced by a 355 nm pulsed Nd:YAG laser with a pulse duration of 6 ns focussed onto a brass sample in air at atmospheric pressure. The time-resolved atomic and ionic emission lines of Cu and Zn from the LIBS spectra recorded by an Echelle spectrograph coupled with a gated intensified charge coupled detector are used for the plasma characterization and the quantitative analysis of the sample. The time delay where the plasma is optically thin and is also in local thermodynamic equilibrium (LTE), necessary for the elemental analysis of samples from the LIBS spectra, is deduced. An algorithm relating the experimentally measured spectral intensity values with the basic physics of the plasma is developed. Using the algorithm, the Zn and Cu concentrations in the brass sample are determined. The analytical results obtained from the CF-LIBS technique agree well with the certified values of the elements in the sample, with an accuracy error <1%. [ABSTRACT FROM AUTHOR]

In this paper, a dielectric-barrier discharge (DBD) of Ar:\N2 mixtures at atmospheric pressure is studied in relation to plasma jet production. The discharge takes place in a capillary dielectric tube, and it is sustained by positive high-voltage pulses. It is herein claimed that, apart from the traditional DBD (which is developed perpendicularly to the gas flow and can produce afterglows), plasma jet propagates simultaneously parallel to the gas flow due to ionization waves guided by the dielectric tube. A quite simple electrical model is applied to simulate the proposed DBD and plasma jet coexistence. The concept of capacitive behavior of both barrier discharge and jet is taken into account. This model in combination with UV–visible optical emission spectroscopy and conventional photography supports the aforementioned statements. The dependence of the jet domination against the afterglow on the gas mixture is demonstrated, and the \N2 additive at 2.5 \%–3\% in Ar is found to be the most efficient for jet production. The model runs with the measured interelectrode voltage as input and yields the circuit total current as output. Matching between the measured current and the model output is attempted by adjusting two free parameters. This tuning of the free parameters provides reliable values for the electrical components of the model. Thus, a simple mean for realistic representation of both DBD and jet is achieved. This tool could be applied to the design of plasma jet reactors. [ABSTRACT FROM PUBLISHER]

It remains a challenge to generate the uniform and large-area cold plasma at atmospheric pressure. In this paper, we report a method to generate a reliable and homogeneous brush-shaped plasma plume running at atmospheric pressure. The plasma brush (110 mm in length and 10 mm in width) is mainly composed of well-aligned and hollow optical fibers. Current–voltage measurements indicate that the brush-shaped plasma plume consists of glowlike pulsed discharge with their pulsewidths of several microseconds. The generation of the \He/O2 glowlike discharge is further proved by the uniform distribution of O atoms along the transverse location of the plasma brush. This brush-shaped plasma plume is used for the application in the plasma inactivation of Candida albicans cells. About 97% of Candida albicans cells with a population of 10^5 spores are killed when exposed to the \O2/\He (volume ratio: 5/95) brush-shaped plasma plume for 150 s. Analysis indicates that plasma-activated species, such as O radicals, may play a crucial role in killing the resistant Candida albicans cells. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the self-absorption of Mg I–II emission lines on laser-induced breakdown spectroscopy (LIBS) experiments. We produced the plasmas in air at atmospheric pressure by focusing a Nd:YAG laser onto a pellet of finely powdered calcium hydroxide with a concentration of 625 ppm of Mg and recorded the intensity profiles of Mg lines at different delay times after the laser pulse from plasmas generated with different laser energies. We carried out the analysis of the line profiles within the framework of a homogeneous plasma in local thermodynamic equilibrium by a computer algorithm that calculates the emission spectra and matches them to the experimental measurements. It allowed evaluation and compensation of self-absorption by using the spectroscopic information saved on the optical thicknesses of the lines. After that, we performed the characterization of the plasma and correlated the self-absorption features with the different trends of the temperature, the electron density, and the Nl parameters obtained. At the early times of plasma evolution, we found that the fast expansion of the plume was dominant and the self-absorption effects are difficult to interpret within the current approach, supplying only qualitative information. On the other hand, at later times, the results obtained could be properly analyzed showing the practical usefulness of the method to provide valuable information for both basic and applied LIBS research. [ABSTRACT FROM PUBLISHER]

The main process in oil refinery technologies is the cracking of the heavy fraction of oil into light and valuable hydrocarbons. Dielectric barrier discharge (DBD) reactors, working at atmospheric pressure and low temperature, is one of the newest methods for cracking hydrocarbons, which has been successfully used to crack low-carbon-containing molecules. Therefore, in this paper, the cracking of n-hexadecane as a heavy hydrocarbon fed by using the cylindrical DBD reactor (nonthermal plasma) has been investigated. We studied the effects of gas type, applied voltage, and gas flow rate quantitatively and qualitatively by using gas chromatography with flame ionization detector and mass spectrometry detector. Results showed that methane has better effects on both conversion and cracking percentage in comparison with air. Also, it has been shown that increasing the applied voltage and working gas flow rate enhances the conversion and the cracking percentages. The highest conversion percentage obtained was 9.26% when the applied voltage and methane flow rate were 12 kV and 50 sccm. In this condition, the cracking percentage obtained was 84.34% of the products. [ABSTRACT FROM PUBLISHER]

Microplasma can be found in many applications. The technology is also used for surface treatment of polymers. The process of surface treatment by microplasma is environmental friendly, and it could be realized at low cost due to the relatively low discharge voltage (around 1 kV) even under atmospheric pressure and the small size of the power supply and reactor. This paper presents the surface treatment by microplasma of polyethylene naphthalate (PEN) film using Ar gas and mixtures of Ar with \N2 and \O2. The microplasma process was analyzed by the emission spectroscopy method. An experimental Marx generator with MOSFET switches was used as a pulsed high-voltage power supply. The emission spectra were measured by an intensified charge coupled device camera, a spectrometer, and a photomultiplier tube. Surface wettability of the PEN film was confirmed by measuring the contact angle before and after the microplasma surface treatment. It was observed that the contact angle of the PEN film decreased, especially with the \O2/\Ar mixture. The analysis using an X-ray photoelectron spectrometer showed the decrease of C1s, which correspond to the C-H bond. The emission spectrum of the microplasma discharge in the \N2/\Ar mixture showed Ar peaks, OH peaks, \N2 second positive band system peaks (\N2 SPS), \N2 first positive band system peaks ( \N2 FPS), and decrease in the peak intensities of ArI and OH for microplasma discharge in the \O2/\Ar mixture. The lifetime emission signals for the \N2 SPS for the microplasma discharge in 0.25% \N2 in Ar were around 1 \mu\s. The calculation of the microplasma rotational and electron temperatures shows low rotational and high electron temperatures. [ABSTRACT FROM AUTHOR]

This contribution presents a comparison of the effects of atmospheric-pressure plasma in ambient air on the surface properties of polypropylene/aluminum/polyethylene terephthalate (PP/Al/PET) laminated foil. Plasma treatment was applied by means of two types of ambient-air dielectric-barrier discharge (DBD): 1) coplanar DBD and 2) volume DBD. The surface energy levels of the PP and PET surfaces terms were measured. The morphology and surface chemistry of the PP and PET surfaces were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy. The differences in the effect of coplanar and volume DBDs on polymer surfaces are observed and explained in terms of the properties of microdischarges in coplanar and volume DBDs. The influence of the Al interlayer on plasma behavior is discussed. [ABSTRACT FROM AUTHOR]

In this paper, a rich variety of self-organized patterns have been observed in a dielectric barrier discharge helium plasma jet generated at atmospheric pressure. It has been found that the evolvement of a discharge pattern in plasma jets is sensitive to diverse experimental parameters, including the applied voltage, the frequency of power, the scale of plasma jet generator, and the gas flow rate. By altering the applied voltage and/or the gas flow rate, the plasma jet is seen to evolve through three modes, which are diffuse-looking discharge, self-organized discharge with regular channels, and unstable discharge with random filaments. Among which, the self-organized discharge mode is characterized with several bright plasma channels stably formed in a straight line. The maximum number of channels is mainly determined by the scale of plasma jet generator. When the frequency is fixed, the minimum distance between two adjacent discharge channels in the self-organized mode is nearly the same, no matter what size tube is selected. [ABSTRACT FROM AUTHOR]

In this paper, we report on the fabrication of Mo-oxide nanostructures and nanoarchitectures using an atmospheric-microplasma (AMP) system. This AMP system shows a high degree of flexibility and is capable of producing several different nanostructures and nanoarchitectures by varying the process parameters. The low-cost and simplicity of the process are important characteristics for nanomanufacturing, and AMPs offer such advantages. In addition, AMPs have shown the ability of promoting self-organization of nanostructures. [ABSTRACT FROM AUTHOR]

This paper presents results on surface processing of polymeric materials using a particular plasma reactor configuration. An atmospheric-pressure plasma beam is used to create a surface discharge with an axially symmetric profile. The exposure to He and mixtures of He with reactive gases allows combined functionalization and cross linking on polymers in film and fiber forms. [ABSTRACT FROM AUTHOR]

With an aim to understand the mechanism of surface processing by atmospheric-pressure nonequilibrium discharge plasma jets, we measured the vibrational and rotational temperatures in the plasmas by means of optical emission spectroscopy (OES) measurement method. This paper focuses on the OES measurement method using a torch-shaped atmospheric-pressure nonequilibrium discharge plasma jet power supply consisting of a microwave (2.45-GHz) generator and a high-frequency (5.0-10-kHz) dc pulse power supply, using a gas mixture of Ar (8.0 L/min) and N2 (0.1-0.5 L/min) as the discharge plasma gas, and changing the flow rate of N2 gas at the input power of 100-150 W. Upon comparing vibrational and rotational temperatures (0.18-0.27 eV) determined from the OES measurement method using two types of atmospheric-pressure nonequilibrium discharge plasma jets, results indicate that the microwave discharge plasma jet has considerably low vibrational and rotational temperatures. [ABSTRACT FROM AUTHOR]