Characteristic study of cold atmospheric argon plasma jets with rod-tube/tube high voltage electrode

Atmospheric argon plasma jets are generated with the rod-tube/tube high voltage electrode and a ring ground electrode at 8 kHz sinusoidal excitation voltage. It is found that the vibrational temperature, electronic excitation temperature, atomic oxygen density and spectral intensity with the rod-tube high voltage electrode are enhanced significantly than that with the tube high voltage electrode. The atomic oxygen density, molecular nitrogen density, and average electronic density are about magnitude of 10¹⁶ cm^?3, 10¹⁵ cm^?3, and 10¹² cm^?3 respectively, and the excited Ar, N₂, OH and O are presented in the plasma plume with the rod-tube/tube high voltage electrode.     

Investigation of liquid plasma catalysis on Ti electrodes for the decolorization of a brilliant red B solution

This investigation is intended to determine the catalytic effect of liquid plasma on TiO₂, generated in situ on Ti anodes submerged in Na₂SO₄ electrolyte solution by observing the efficiency of the reaction in decolorizing a brilliant red B solution under voltage-stabilized DC power. The orthogonal test was performed in order to obtain the optimal reaction conditions for the test device. When placed under a constant voltage of 550 V, and with an electrode depth of 2 mm, Na₂SO₄ concentration of 5 g/L, pH of 2, the maximum decolorization ratio of 100 mL brilliant red B solution with the concentration of 20 mg/L was 97.8% after 40 min. The reaction rate constant was about 0.102 min^?1, conforming to the first-order reaction kinetic model. Comparative tests were conducted with: Al electrode under 450 V; Mo electrode under 550 V; and a mixture of the electrolyte and TiO₂ powder. The results showed that liquid plasma – TiO₂ on the electrode of the catalytic system naturally integrated on the discharge electrode, with an increase in reaction rate by 26.8% while utilizing the same energy consumption.     

Driving frequency dependency of gas species in the bubble formation for aqua-plasma generation

Effects of voltage driving frequency on the gas composition, electrical and optical emission properties of aqua-plasmas generated in electrolyte solution, are investigated and the experiment was carried out in the range of 10 Hz–50 kHz. In the range of 10–300 Hz, H₂ dominated bubbles are generated and it is attributed to electrolysis. With increasing frequency, the gas composition inside the bubble changes to the H₂O which can be determined from the observation of atomic H to OH(A-X) transition from the optical measurements of aqua-plasma. In higher frequency than 2 kHz, the boiling on the electrode dominates to the formation of the bubble. Consequently, the radicals and plasma properties are varied with the driving frequency.     

Experimental observation of negative differential characteristic of corona discharge in ultraviolet spectrum

Corona discharge is a self-sustained discharge which appears at electrodes with a small radius curvature in gas insulation. An almost invisible glow occurs just above the inception voltage. Corona phenomenon is mainly used in electro-technological processes to obtain space charge for electrostatic precipitation, separation of different particles, electrostatic liquid or solid coating, neutralization of space charge, etc. All of these processes rely on a strong nonhomogeneous electric field generated by a point – plate electrode system. When the critical value of the applied voltage is reached, the ionization processes near the point electrode start and give rise to the current between two electrodes. If the pointed electrode is positive, it is possible to observe an anomaly of the current – voltage (I-U) characteristic for the point-plate space. It means that while the voltage is raising the current density decreases in a narrow voltage area (2–3 kV). The anomaly was technically named as negative differential conductivity (dI/dU < 0). Unstable current can have a negative influence on electro-technological processes. The anomaly was detected for different shapes and materials of the electrode as well as for various temperatures and distances between electrodes. An oxidation layer, which appears on the metal electrode, also influences the ionization processes near the pointed electrode and causes a decrease of a current. In this paper measuring of the discharge activity in a point – plate electrode system is presented. Ionization of gas atoms and molecules in a high electric field and the following recombination of electrons and positive ions in the corona region can give rise to high-energy photons which produce new electrons in the field of discharge. Corona discharges are detected by DayCor Corona camera which can register UV emission generated by corona in a day light. The experiment was conducted with various shapes of the pointed electrode and distances between the high voltage and the grounded electrode under applied direct voltage with positive and negative polarity.     

An atmospheric-pressure nitrogen-plasma jet produced from microdischarges in a porous dielectric

This report presents an atmospheric-pressure nitrogen-plasma jet generated from microdischarges in a porous dielectric. A plasma jet with a length of 42 mm was produced by feeding nitrogen gas through a porous alumina installed between an outer electrode and a hollow inner electrode and by applying 60 Hz sinusoidal voltage wave to the electrodes. Microdischarges in the porous alumina are ejected as a plasma jet from the outer electrode through a 1 mm hole by increasing the applied voltage, showing that the temperature of the jet decreases to a value close to room temperature. Even at a frequency as low as 60 Hz, the plasma that evolves from a large amount of microdischarge inside a porous dielectric can have characteristics that are similar to those generated at several hundreds of kilohertz. From the electrical measurements, it is expected that not only the steady generation but also the frequency of the pulses resulting from the microdischarges in the porous dielectric play an important role in obtaining a stable plasma jet. We also identified the various excited plasma species produced from the plasma jet by an optical emission spectroscopy.     

Ultrasound assisted synthesis of highly active nanoflower-like CoMoS4 electrocatalyst for oxygen and hydrogen evolution reactions

Rapid technological development requires sustainable, pure, and clean energy systems, such as hydrogen energy. It is difficult to fabricate efficient, highly active, and inexpensive electrocatalysts for the overall water splitting reaction: the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The present research work deals with a simple hydrothermal synthesis route assisted with ultrasound that was used to fabricate a 3D nanoflower-like porous CoMoS₄ electrocatalyst. A symmetric electrolyzer cell was fabricated using a CoMoS₄ electrode as both the anode and cathode, with a cell voltage of 1.51 V, to obtain a current density of 10 mA/cm². Low overpotentials were observed for the CoMoS₄ electrode (250 mV for OER and 141 mV for HER) at a current density of 10 mA/cm².     

Suppression of bias stress-induced degradation of pentacene-TFT using MoOx interlayer

The bias stress effect in pentacene thin-film transistors (TFTs) with and without MoO_x interlayer was characterized. The device without MoO_x interlayer showed a large threshold voltage shift of 5.1 V after stressing with a constant gate-source voltage of −40 V for 10000 s, while at the same condition, the device with MoO_x interlayer showed a low threshold voltage shift of 1.9 V. The results can be attributed to the stable interface between MoO_x/pentacene and small contact resistance change for the device with MoO_x/Cu electrode. Pentacene-TFTs with MoO_x interlayer showed a high field-effect mobility of 0.61 cm²/V s and excellent bias stability, which could be a significant step toward the commercialization of OTFT technology.     

Photovoltaic and impedance properties of dye-sensitized solar cell based on nature dye from beetroot

The present study involves fabrication and photovoltaic characterization including impedance properties of dye-sensitized solar cells based on natural dye from beetroot. The electrode of the cell was prepared with commercial Fluorine-doped Tin Oxide glass with 100 μm layer of nanostructured TiO₂ whereas, the counter electrode consisted of platinum-coated glass. Fresh juice was extracted from beetroot to use as dye. The dye exhibited high absorption in visible range. Photovoltaic measurements of the solar cell gave a short circuit current density (Jsc) of 130 μA/cm² and an open-circuit voltage (VOC) of 0.38 V under AM 1.5 illumination intensity. The VOC and Jsc showed linear behavior at higher values of illumination intensities. The conductance-voltage, the capacitance-voltage and the series resistance voltage characteristics of the dye solar cell was measured at frequency range from 5 kHz to 5 MHz to study performance of the dye-sensitized solar cells with natural dyes.     

A high output triboelectric nanogenerator integrated with wave-structure electrode for football monitoring

In recent years, the development of triboelectric nanogenerator (TENG) technology has made great progress. However, most of the work focuses on the improvement of triboelectric materials and the optimization of device structure. In this work, we introduced a novel triboelectric nanogenerator integrated with wave structure electrode (W-TENG). Compared to the TENG with traditional flat plate electrode, the W-TENG with wave structure electrode can achieve higher output performance. The maximum short-circuit current (I_sc), transfer charge, and open-circuit voltage (V_oc) of 2.56 μA, 29 nC, and 74 V were obtained at 300 N. Correspondingly, the instantaneous output power of W-TENG illustrates the maximum value of 0.94 mW at 6 Hz. In addition, the output voltage signal of W-TENG can clearly reflect the different postures in football, and the W-TENG can perform real-time football monitoring. This mechano-electrical energy harvester and the corresponding self-powered monitor can promote the intelligent sports development.     

Effect of micropillar electrode spacing on the performance of electrohydrodynamic micropumps

Electrohydrodynamic (EHD) micropumps with three-dimensional 50 μm × 50 μm micropillar electrodes were fabricated and tested in this study. Two basic electrode configurations were investigated: (i) micropillar emitter and collector electrodes (symmetric) and (ii) micropillar emitter and planar collector electrodes (asymmetric). The micropumps were fabricated by integrating chromium/gold planar electrodes with electroplated 3-D Nickel micropillars on a glass substrate with a 100 μm high PDMS microchannel. The effect of the spanwise micropillar spacing on the pump performance was determined. The pumps were tested using HFE-7100 as the working fluid for the maximum pressure generation under a no flow condition. The micropumps with the asymmetric electrode design generated a significantly higher pressure head than the corresponding micropumps with symmetric electrode configuration for the same applied voltage, with lower power consumption. A decrease in the spanwise spacing of the micropillar electrodes increased the pump performance for the symmetric configuration, while the performance decreased for the asymmetric configuration.     

S as additive in Mg–Cu<Subscript>2</Subscript>O seawater batteries using Ni foam-supported electrode

Cu₂O with S as additive electrode using Ni foam as the substrate is prepared in Mg–Cu₂O seawater battery. The morphology and electrochemistry performance of electrode are investigated. The excellent electrochemical properties of Ni foam-supported electrode indicate that it is suitable for seawater devices. The cell voltage of Mg–Cu₂O seawater batteries is elevated by sulphur addition. Sulphur participates in the electrochemical reactions; the elevation in cell voltage is 200–350 mV according to the ratio of Cu₂O to S.     

The impulse dielectric behavior of N2 gas in sphere-plane gap

The focus of this work has been on the pre-breakdown phenomena and the breakdown characteristics of N₂ gas in a sphere-plane gap under various impulse voltages. Both electrical and optical experimental investigation methods were used. Following parameters were considered: gas pressure range from 0.2 to 0.6 MPa, electric field utilization factor of the electrode configuration 71%, positive and negative impulse waveforms with the rise time of 500 ns, 1.2 μs and 180 μs. The observed discharge processes before the breakdown through the light emission images by the ICCD camera are in good agreement with the streamer mechanism. Under both polarity stresses, discharges are initially concentrated around the tip of the sphere and later pointing towards the earth electrode. However, negative streamers are thinner and more diffuse. As expected, the breakdown voltages for negative polarity are lower than those for positive polarity regardless of the gas pressure and shape of the applied impulse voltage. The breakdown voltage is increased with shortening the rise time of pulse waveforms. As a substitute for SF₆, N₂ gas under pressures above 0.3 MPa can reach the standard rated withstand voltage for 24 kV C-GIS.     

Experimental observation of voltage amplification using negative capacitance for sub-60 mV/decade CMOS devices

In this study, an experimental study of negative capacitance is performed in order to overcome the physical limit of subthreshold slope (SS), SS ≥ 60 mV/decade at 300 K, which is originated from (i) using the thermionic emission process in complementary metal-oxide-semiconductor (CMOS) technology and (ii) non-scalability of the thermal voltage k_BT/q (i.e., in order to realize SS lower than 60 mV/decade at 300 K). To make the surface potential higher than the gate voltage, a step-up voltage amplifier is included in the CMOS gate stack using a ferroelectric capacitor implemented with ferroelectric material. The measured SS in long-channel CMOS transistors is 13 mV per decade at 300 K. A simple connection of the ferroelectric capacitor to a complementary metal oxide semiconductor (CMOS) gate electrode would provide a new evolutionary pathway for future CMOS scaling.     

Geometrical optimization of a surface DBD powered by a nanosecond pulsed high voltage

In this study, surface Dielectric Barrier Discharge (DBD) actuators powered by nanosecond pulsed high voltage are investigated. The goal is to experimentally characterize the surface DBD actuators in terms of electrical and geometrical parameters.The actuators are made of two conducting electrodes separated by a thin dielectric (Kapton films) and arranged asymmetrically. The active electrode is connected to a pulsed high voltage power supply (voltage up to ±10 kV, rise and fall times of 50 ns and pulse width of 250 ns) and the second electrode is grounded.The experimental results show that the energy per pulse (normalized by the length of the active electrode) is smaller when one increases the inter-electrode spacing between 1 and 3 mm, the thickness of the dielectric barrier between 120 and 360 μm or the length of the electrodes between 10 and 50 cm, for both applied voltage polarities.Optical characterization of the plasma layer for different electrode gaps has been investigated by using an ICCD camera. Results indicate that the plasma produced by positive and negative rising voltage propagates in a streamer-like regime with numerous and well-distributed channels, for any electrode gap distance. However, the positive and negative falling voltage produces similar discharges only for large electrode gaps. In this case, the plasma layer starts from a corona spot in contact with the active electrode and expands in the direction of the grounded electrode in a plume shape.     

The contribution of space charge in a high non-homogenous electric field to the creation of negative differential conductivity

The paper describes anomaly origination on current or voltage characteristics in time of positive potential on small curvature radius electrode rod against plane electrodes. An anomaly phenomenon occurred in the narrow voltage area in a high non-homogenous electric field close to the electrode (E > 10⁷ V m^?1). A mathematical – physical analysis of the observed processes in close proximity to the electrode with the above mentioned form is made. The differential equations, which analytically and theoretically describe this phenomenon, are compiled and solved. The space charge created by element particles (electrons, ions) which causes negative differential conductivity origination in narrow voltage area by their behaviour in electric field, plays a substantial role in this phenomenon. Current–voltage characteristics at both polarities of corona electrode were continuously measured at the study of static and dynamic processes occurring during discharge in the surrounding of a small curvature radius electrode. It was proved that an anomaly, in the form of negative differential conductivity (dI/dU < 0), appeared on a highly curved electrode at positive polarity in a narrow voltage area. This phenomenon was subjected to detailed experimental research including investigation of the influence of the shape and material of the electrode (output voltage), electrode temperature, influence of photoionization on the profile of the anomaly, the contribution of exoelectrons to particle distribution, and study of electrochemical potential of metal electrode. Oscillation of low ionized plasma at positive and negative polarity of small curvature radius electrodes has been analyzed. At the same time, the influence of the external forced electric field on the change of current–voltage characteristic profile was investigated. Theoretical justification of the anomaly phenomenon resulted from a change of energy conditions in the investigated place (the distance limit from the electrode is 10^?4–10^?6 m).     

Properties of droplet formation made by cone jet using a novel capillary with an external electrode

A capillary with an external electrode for cone-jet mode of electrospray has been developed to spot a droplet accurately on a substrate surface. The external electrode is made by gold deposition around tip of a glass capillary. The electrospray was made by applying a positive pulsed dc voltage to the solution in the capillary. Using a positive bias voltage to the external electrode, the meniscus of the solution at the tip deformed to be more sharp, and center of the meniscus was prolonged. This deformation stabilized the trajectory of the jet from the Taylor cone at the tip. From the experimental result, accuracy of positioning of the droplet having 0.3 pL volume was improved with the standard deviation of 1.1 μm, from that of 2.5 μm for conventional capillary without the external electrode.     

Interface Fermi level pinning in a Cu/p-CuGaS2 Schottky diode

A Schottky contact to p-type CuGaS₂ that showed the highest rectification ratio of approximately 500 ever reported was realized using a Cu electrode on a HF/HNO₃-treated surface, as well as an excellent Au ohmic contact on a HF-etched surface. The effective Schottky barrier height of 0.9 eV was obtained from the current–voltage and capacitance–voltage characteristics. The value was smaller by 1.1 eV than that calculated from the values of the work function of Cu and electron affinity of CuGaS₂. The results indicated a surface pinning of the Fermi level to certain acceptor-type gap states below the midgap.     

Laboratory ignition of hydrogen and carbon disulphide in the atmospheric air by positive corona discharge

Experimental attempts of ignition of sensitive explosive atmospheres by continuous positive corona discharges in coaxial electrode system were conducted in laboratory conditions. Sixty five explosions of hydrogen (H₂) and forty of carbon disulphide (CS₂) were forced. Both atmospheres were ignited by the minimum power 1–2 W, the minimum ignition current 100–130 μA at the ignition voltages 12–30 kV (for CS₂) and 16.5–25 kV (H₂). To prevent the energetic sparks, the high voltage resistor 1 MΩ was introduced in series with corona wire.     

Ascent of open-circuit voltage on diamond-like carbon photovoltaic cell by infrared heating-assisted pulsed-laser deposition

Phosphorus-doped diamond-like carbon (DLC) films were deposited on quartz and p-type silicon (p-Si) substrates by pulsed-laser deposition. Open-circuit voltage (V _oc) and short-circuit density (I _sc/cm²) from a heating process converted from one type of electrode to another and the two types of electrode pattern are shown by the V–I characteristics. The first heating process was by a ceramic heater, and the other was by an infrared heater. We adopted two electrode patterns, from a bipectinate electrode and a plot pattern electrode, to measure electric photovoltaic characteristics. We were able to upgrade V _oc and I _sc/cm² to 35∼45 mV, and 0.24 μA/cm², respectively, under infrared heating. V _oc by the plot pattern electrode was over 2 V under infrared heating and ceramic heating did not match this on deposition by the PLD method.     

Time-resolved processes in a pulsed electrical discharge in argon bubbles in water

A phenomenological picture of a pulsed electrical discharge in gas bubbles in water is produced by combining electrical, spectroscopic, and imaging characterization methods. The discharge is generated by applying 1 m\mu s pulses of 5 to 20 kV between a needle and a disk electrode submerged in water. An Ar gas bubble surrounds the tip of the needle electrode. Imaging, electrical characteristics, and time-resolved optical emission spectroscopic data suggest a fast streamer propagation mechanism and the formation of a plasma channel in the bubble. Comparing the electrical and imaging data for consecutive pulses applied to the bubble at a frequency of 1 Hz indicates that each discharge proceeds as an entirely new process with no memory of the previous discharge aside from the presence of long-lived chemical species, such as ozone and oxygen. Imaging and electrical data show the presence of two discharge events during each applied voltage pulse, a forward discharge near the beginning of the applied pulse depositing charge on the surface of the bubble and a reverse discharge removing the accumulated charge from the water/gas interface when the applied voltage is turned off. The pd value of ~ 300–500 torr cm, the 1 μs long pulse duration, low repetition rate, and unidirectional character of the applied voltage pulses make the discharge process here unique compared to the traditional corona or dielectric barrier discharges.