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Atmospheric pressure dielectric barrier discharges (DBDs), such as the micro cavity plasma array (MCPA), have emerged as promising technologies for the conversion of volatile gases. These conversion processes' effectiveness can be enhanced by integrating catalytically active surfaces. To deepen the understanding of the plasma-catalyst interaction, it is crucial to study the transport dynamics of charged species to the catalytic surface, which, due to collisions with neutrals, also directly affects the transport of reactive species to the catalyst. Thereby the transport of the charged species is in particular influenced by the electric field perpendicular to the catalytic surface. However, experimental data on the component-wise electric field strength within SDBDs are rare. To address this issue, we performed polarized optical emission spectroscopy on the shifting and splitting of the allowed 492.19 nm (1D → 1P0) and forbidden 492.06 nm (1F0 → 1P0) helium line pair. This diagnostic approach requires a non-radially symmetric geometry, which leads to an adapted reactor design of the MCPA allowing the side-on observation of the discharge. The discharge operates in pure helium at atmospheric pressure, utilizing a triangular excitation voltage with a frequency of 15 kHz and an amplitude of 600 V. We performed phase-resolved measurements of the electric field components with a temporal resolution of 1 µs. Our results revealed an electric field strength of approximately 22 kV cm−1 for the component perpendicular to the dielectric surface, while the component parallel to the dielectric surface is about 5 kV cm−1 larger during the decreasing potential phase of the applied voltage. [ABSTRACT FROM AUTHOR]

This study was carried out to investigate and compare gas discharge–semiconductor systems (GDSS) operating under direct-current (DC) and alternating-current (AC) modes for any contribution toward improving energy conversion efficiency. Nonthermal micro plasma discharge systems with novel pattern recognition solutions have received scientific attention due to the rapid technological innovation and faster resolution of complicated problems in computing technology. In the scope of this study, AC-driven discharges using argon gas at atmospheric pressure (760 Torr) were modeled and simulated at 50 Hz and 20 kHz pulse rates generated by a 1.0 kV amplitude power source. DC-driven discharges using argon gas at various sub-atmospheric pressures from 10 Torr up to 760 Torr were also modeled and simulated in the GDSS cell to which a high-ohmic semi-insulating gallium arsenide (GaAs) electrode material was coupled. Gallium arsenide compound semiconductor material has been widely used in optoelectronics due to its high electron mobility and direct narrow band gap properties. DC- and AC-driven micro plasmas were numerically analyzed using the COMSOL Multiphysics simulation program in two-dimensional media. Simulation results in a set of surface and multiple-line graph media were deeply evaluated and reported based on the time-dependent computations of various discharge parameters including mean electron energy, migrative electron flux, surface charge density, space charge density, and surface electron current density for both DC- and AC-driven dielectric barrier discharge (DBD) micro plasma modes. It was observed that highly recognizable unique micro plasma pattern formations can be controlled on a large scale by varying the discharge key parameters and driving modes. [ABSTRACT FROM AUTHOR]

The potential of micro plasma impacts in the growth of organic vegetables has been very difficult to predict. With the advent of deep learning methods, scientists are now able to develop predictive models that can accurately assess the effects of these impacts. Deep learning algorithms can be used to analyze the various environmental factors that influence the growth of organic vegetables, including temperature, humidity, sunlight, and soil type. With these inputs, the deep learning algorithms can learn complex relationships between these elements and the output of the growth of organic vegetables. By considering the interactions between environment and micro plasma impacts, the deep learning algorithms can make accurate predictions regarding the effects of these impacts on organic vegetable yields. The algorithm can be optimized to accurately predict the effect of these impacts in the future, allowing farmers to better plan for their crops. In addition, the deep learning algorithms can be used to analyze the effects of various factors on micro plasma impacts in organic vegetables. For example, the algorithm can analyze the effects of different combinations of fertilizer, water, and chemical inputs on the micro plasma impacts, allowing farmers to find the optimal crop growth conditions more quickly. The use of deep learning to predict the effects of micro plasma impacts on organic vegetable growth has the potential to improve crop yields, leading to more efficient agriculture practices. [ABSTRACT FROM AUTHOR]

Energy harvesting, especially for powering low-power internet-of-things (IoT) devices, is gaining attention in recent years. Triboelectric nanogenerators have been studied to improve the output by applying a structure that can concentrate electrons on the surface of the generator materials. For enhancing the triboelectrification output, we herein focused on the power output line. A method for increasing the amount of electrons on the power lead by potential difference and their acceleration was studied. A rod was shaken by external vibrations; the accumulated charges were discharged in a manner similar to that of a lightning rod. Micro plasma was generated when the rod made contact with the mating micro-cracked surface innumerable times. The micro-cracked surface was fabricated with a diamond tip moving horizontally to the surface. As the resistance of the micro plasma was close to zero, the amount of electron movement was instantaneously accelerated. This type of triboelectric generator can be fabricated in the form of an electric box. By using this triboelectric power amplifier, voltage can be amplified 2 to 3 times, and the current can be amplified 10 to 15 times; thus, enhanced energy harvesting efficiency is attained. [ABSTRACT FROM AUTHOR]

We studied the action of the pulsed micro plasma on the layered materials with the different interlayer bond energy. The pulsed micro plasma was generated by the spark discharges between the two pieces of studied material in dry air at normal conditions in an open reactor. The 20kV spark discharges were generated with induction coil and had the duration from 10 to 20 us, controlled with an oscilloscope with a capacitive sensor. The generated particles were accumulated on the duct tape underneath the electrodes. Three types of particles were observed – droplets, fractals and planar structures. Droplets were produced by surface melting of the electrode material with the subsequent separation of a drop. The drops had different forms depending on the material. Sb produced spheres, Bi formed spheres covered symmetrically with round tips, InSb produced twisted structures. The planar structures were produced by the fi eld exfoliation of the electrode material. Fractals were produced on the electrodes because of the circular evaporation and condensation of the material in pulsed plasma. The ratio of these three effects was determined by the degree of anisotropy of the processed material and by its melting point. Antimony produced many droplets, fractals and layers, because of its low melting point and high anisotropy. Bi produced droplets, fractals and a little amount of exfoliated layers because of its low anisotropy. SiC did not melt or evaporate at the temperature of the discharge but exfoliated, so it produced planar structures. The results may be used in the production of micro and nano particles needed to create hybrid materials.

Energy harvesting, especially for powering low-power internet-of-things (IoT) devices, is gaining attention in recent years. Triboelectric nanogenerators have been studied to improve the output by applying a structure that can concentrate electrons on the surface of the generator materials. For enhancing the triboelectrification output, we herein focused on the power output line. A method for increasing the amount of electrons on the power lead by potential difference and their acceleration was studied. A rod was shaken by external vibrations; the accumulated charges were discharged in a manner similar to that of a lightning rod. Micro plasma was generated when the rod made contact with the mating micro-cracked surface innumerable times. The micro-cracked surface was fabricated with a diamond tip moving horizontally to the surface. As the resistance of the micro plasma was close to zero, the amount of electron movement was instantaneously accelerated. This type of triboelectric generator can be fabricated in the form of an electric box. By using this triboelectric power amplifier, voltage can be amplified 2 to 3 times, and the current can be amplified 10 to 15 times; thus, enhanced energy harvesting efficiency is attained.

Silver nanoparticles are synthesized by employing argon atmospheric pressure DC microplasma technique. Specifically, the variation in fructose molar concentration is investigated for its role in the size of nanoparticles. The 2 mM molar concentration of fructose is optimum for the production of silver nanoparticles in the range ‘50 ± 10 nm’. Antibacterial and antifungal action demonstrates that silver nanoparticles with small size and larger surface areas are very effective against bacteria and fungus.

SUMMARY We have succeeded in developing a new dynamic microplasma-excited deep ultraviolet light emitting device using aluminum gallium nitride (AlGaN) multi-quantum wells (MIPE). The operating principle is completely different from that of current injection-type deep ultraviolet light emitting diodes. We have created a 12 × 5.5 cm device with a power of about 1 W at a wavelength of 325 nm. We can achieve panel-type laminar-flow water purification and cleaning systems that can be alternatives to the use of mercury lamps as a DUV light source, since these cannot be used under the Minamata Treaty. The wavelength region from 210 nm to 250 nm realized in this device opens new fields of academic research and areas of application, in which the decomposition of materials that are difficult to break down, the synthesis of new materials, including a new H2 battery cell, and disinfection of water are possible. [ABSTRACT FROM AUTHOR]

The acoustic signals of the laser micro plasma expansion for the femtosecond laser ablating pure Al, Cu and Fe target materials have been detected by the fiber Fabry–Perot ( F – P ) acoustic emission sensing probe. The frequency and amplitude of the acoustic emission spectrum have been analyzed. The results show that the detected acoustic emission frequency spectrum pattern is fixed and different for the three kinds of target materials. The amplitude of the acoustic emission spectrum grows up along with the enhancement of laser ablation energy. The amplitude of the acoustic emission spectrum decreases when the detection distance is enlarged. The developed measuring system provides a potential method aiming at the detection of solid materials based on the acoustic signals excided by femtosecond laser ablating target materials using the fiber F – P acoustic emission sensing probe. [ABSTRACT FROM AUTHOR]

Abstract: A catalytic probe made of a nickel thin wire is introduced into the gas flow downstream of an atmospheric pressure dielectric barrier discharge ozonizer to examine the ozone dissociation process on a catalytic surface. The probe is placed downstream far from the discharge to avoid the influence of reactive species other than ozone. The measured voltage variation across the probe wire under a constant probe heating current is used as a measure of the temperature variation of the probe surface and the nearby gas temperature. The stainless steel and copper wire made probes are also used to examine the effect of catalytic activity. Experimental results show that, for a low probe heating current of 0.2 A, the temperature of the probe decreases with increasing ozone concentration almost independent of the probe materials due to catalytic dissociation of ozone, which removes heat of reaction from the probe. When the heating current is increased to 1.5 A, the temperature of the nickel probe increases with increasing ozone concentration due to thermal dissociation of ozone followed by surface catalytic recombination of oxygen radicals, which gives heat of reaction to the probe. On the other hand, the temperature of the stainless steel and copper made probes decreases with increasing ozone concentration despite the high heating current due mainly to the low catalytic activities. [Copyright &y& Elsevier]

Abstract: The effect of pulse voltage, polarity, duty cycle, and oxygen flow rate on ozone production is studied in a coaxial cylindrical-type dielectric barrier discharge ozonizer at atmospheric pressure. For a constant oxygen flow rate, the ozone concentration increases with increasing input voltage and is nearly proportional to the ozone production efficiency. The bipolar waveform of the applied voltage results in higher ozone concentration and production efficiency than the unipolar one (positive or negative) regardless of duty cycle. A higher duty cycle increases the ozone concentration slightly for the unipolar voltage, while it affects little the ozone production efficiency for either voltage polarity. For constant pulse polarity and duty cycle, the ozone concentration decreases with increasing oxygen flow rate, however, the maximum ozone production efficiency for each flow rate shows only a minor difference for the change in flow rate. The results confirm that the ozone production efficiency depends more on the pulse power characteristics and less on the oxygen flow rate. [Copyright &y& Elsevier]

Abstract: A local high pressure micro plasma jet was proposed for micro scale local sputter etching in a vacuum system. A small orifice gas nozzle as an anode was placed in a Scanning Electron Microscope (SEM) chamber to produce the local high gas pressure and supply Argon gas for DC plasma generation at a short gap distance. The characteristics of local sputter etching by the micro plasma jet were studied. At DC power of 1.68 mW, a silicon sputtering rate of approximately 0.01 μm/s was achieved by using an orifice 40 μm in diameter at 2.5 sccm gas flow rate and 100 μm gap distance. The sputtered area was 60 μm in diameter. [Copyright &y& Elsevier]

Unlike the generation of uniform plasmas in a large volume, structured plasma comprising microplasmas has attracted increasing scientific and technological interest in recent years. Similarly, the concept of plasma generation in artificial media with gas-gas, gas-liquid, and gas-solid interfaces under intentionally organized and controlled conditions has the potential to open a new field in plasma science and technology. Amongst the subtopics of plasma generation in artificial media, we discuss here those dealing with micro - plasma jets in flowing gas channels, microdischarges within microbubbles generated in aqueous electrolyte solutions, and discharges in bubbled water and misted air. Our discussion is supported by preliminary results and aims to stimulate future systematic and quantitative investigations. [ABSTRACT FROM AUTHOR]

An atmospheric micro plasma is generated in micro gap electrodes with a dielectric barrier. Discharge voltage is only around 1 kV, although the electrode gap is less than 100 µm. Ozone is generated through the micro plasma electrode, which removes indoor air pollutants such as formaldehyde and nitric oxides. By making the micro gap between dielectric barrier electrodes smaller, a higher ozone concentration could be obtained. [ABSTRACT FROM AUTHOR]

Abstract: An atmospheric-pressure glow-discharge micro plasma in contact with liquid paraffin is stably generated by using a capacitively coupled plasma method with a mesh electrode. When characteristics of the plasma are measured in the boundary between the micro plasma (gas-phase) and liquid paraffin (liquid-phase) using optical emission spectroscopy, spectrum peaks of the emission of CH and C2 which dissociate from paraffin are observed. The result indicates that solution can feed particles to the plasma at gas–liquid interface and this plasma is accordingly expected to promote an attractive plasma process for creating materials consisting of elements in various solutions. [Copyright &y& Elsevier]

In open air and without any type of inert gas, stable and bright micro plasma was successfully obtained using Liquid Sampling Atmospheric Pressure Glow Discharge (LS-APGD). The discharge current varied between 20 to 80 mA with a maximum voltage 550 V, discharge gap 0.5–2 mm and solution pH of 1. The produced plasma operates in the normal glow discharge region at a low power (11–40 W). For analytical application the linear dynamic range is obtained up to 500 µg mL−1. Limits of detection based on 3σ of the background intensity determined for Ca I (422.673 nm), Cu I (324.754 nm), Fe I (497.5 nm), and Zn I (213.856 nm) are 0.3, 0.65, 0.1, 0.7 µg mL−1 respectively. [ABSTRACT FROM AUTHOR]

In metallized film capacitors, there exists an air gap of about 0.2 μ m between the films, with a pressure ranging generally from 1–30 atm. Because of the created potential difference between the two films, a microdischarge is formed in this gap. In this paper, we use an implicit particle-in-cell Monte Carlo collision simulation method to study the discharge properties in this direct-current microdischarge with 0.2 μ m gap in a range of different voltages and pressures. The discharge process is significantly different from a conventional high pressure discharge. Indeed, the high electric field due to the small gap sustains the discharge by field emission. At low applied voltage (∼15 V), only the electrons are generated by field emission, while both electrons and ions are generated as a stable glow discharge at medium applied voltage (∼50 V). At still higher applied voltage (∼100 V), the number of electrons and ions rapidly multiplies, the electric field reverses, and the discharge changes from a glow to an arc regime.

For the last couple of years we have been studying 2.45 GHz-microwave plasma production in the gap of a coaxial pipe under the electron cyclotron resonance. The purpose of this research is to expand the plasma generation conditions into the much lower pressure (0.01–0.1 Torr) and much shorter gap length (several 100 μm). As the first step for this purpose, we have investigated the breakdown and maintenance of plasmas numerically. In the present numerical calculation, we have focused on the influences of applied magnetic field, gas pressure, gap length, applied voltage, and gas species on the breakdown and maintenance of plasmas. [Copyright &y& Elsevier]