Nitrogen Gas Discharge Research Articles

Development and Diagnostic Study of the RF nitrogen Atom Source

With the development of thin film technology, particularly the increasing demand for research on group III nitride materials, the need for N ions has significantly increased. A wider and more efficient RF nitrogen atom source specifically designed for nitride film growth has been developed. To evaluate the nitrogen atom density from the RF nitrogen source, a global model of RF nitrogen gas discharge plasma was created. This model was calibrated by measuring the emission spectrum of RF nitrogen gas discharge, and the relationships between nitrogen atom density and actual working pressure, power, and discharge chamber size were determined. It was found that the nitrogen atom density increases with increasing power and initially increases with pressure before decreasing. Finally, the nitrogen atom density was determined, achieving an 18% nitrogen atom dissociation rate and a nitrogen atom density of 5×1012/cm³ at an RF power of 400 W. This density is significantly higher than that of nitrogen ions, indicating that this is a nitrogen atom source with high purity.

A Review About Preparation and Properties of Biochar and Application Fields in the Environment

Biomass’ pyrolysis process is responsible for producing the biochar charcoal, this process does not incorporate the oxygen, and it is utilized as a soil enhancer for each one of the carbon sequestration, and soil health prospects. Biochar can be defined as a stabilized solid which is enriched with carbon and could remain in the soil for extended period of time. Biochar has been studied as a way of carbon sequestration, and it might be a way used for handling climate change and global warming. It happens due to the processes that are associated with pyrogenic carbon capturing and storages. This review is focused on an overview of biochar preparation and application in the environment, previous studies and Applications. Biochar is prepared from various organic materials such as miscanthus, switch grass, corn stover, and sugarcane bagasse. The method of preparation varies with different temperatures and the discharge of nitrogen gas used for a period of one hour not to mention thermal decomposition at different temperatures of heat (500, 600, 700 and 800oC). The success of its use as a adsorbent material, and in treating the soil from heavy metals, its suitability for agriculture, and the treatment of the liquid leachate from solid waste down into the groundwater, in addition to the treatment of groundwater when the topography of the region differs.

Optical Investigations of N2 Atmospheric Pressure Plasma Jets

In this study, firstly, N 2 atmospheric pressure plasma jet (APPJ) system was presented. Nitrogen gas discharges are produced as jet using an AC power supply which can be adjusted between 6-18 kV and the frequency value of 13-20 kHz at atmospheric pressure. The change of length of produced atmospheric pressure nitrogen plasma jet, according to gas flow rate has been investigated and the produced jet length was approximately 2 cm for 5 L/min when the applied voltage was 18 kV and the frequency was 15 kHz. Nitrogen plasma jet produced at atmospheric pressure was examined with optical emission spectroscopy (OES) and the correlation between gas flow rate and emission spectra were investigated. Furthermore, electron temperature and electron density of atmospheric pressure nitrogen gas plasma jet were estimated under different flow rates of N 2 gas.

Study the effect of cathode geometry on I-V characteristics of nitrogen dc glow discharge

In this paper, the I-V characteristic of a dc glow discharge are studied with the aim of determine the performance a good parametersfor stable operation of the plasma. Nitrogen plasma produced by dc glow discharge is the investigated with a manypurpose of studying plasma phenomena, the discharge system consists of two electrodes, the cathode forms various geometrical shapes and anode as a disc- shaped with diameter (8.8cm). The electrodes are enclosed in a large cylindrical glass chamber of pyrex filled with nitrogen gas. Two important physical parameters affecting the condition of the discharge are the gas pressure and constant inter-electrode distance. The discharge current-voltage (I-V) characteristic curves of the discharge were measured at variable pressure and the inter-electrode spacing, Current-voltage characteristics visualization of the discharge indicate that the discharge is take place in the normal glow region. The (I-V) characteristics of nitrogen gas discharge were deduced as a plasma system operated in normal glow discharge nitrogen, which is very important parameter in the sputtering and deposition. Also, the discharge current is increased for nitrogen plasma discharge with the increasing of the working pressure lead to increase the deposition rate.DIO.: http://dx.doi.org/10.31257/2018/JKP/2019/110110

Treatment of polyacrylonitrile co‐polymer membrane by low temperature radio‐frequency nitrogen plasma

Radio frequency plasma discharge of nitrogen gas was employed for modification of the surface of polyacrylonitrile membranes. The enhancement of hydrophilicity of the plasma modified membrane was evaluated by measuring the contact angle. The influence of various plasma operating conditions, namely, power and exposure time on improvement of permeability and hydrophilicity of the membrane was investigated. Hydrophilicity of the plasma‐treated membranes was more at higher exposure time and power. Approximately 67% increase in permeability of the modified membrane was obtained, and it was retained up to 2 months. Hydrophilicity of the membrane surface was due to attachment of functional groups derived from nitrogen and oxygen.

Investigation of gas breakdown in cylindrical inertial electrostatic confinement device with inner cage anode

The gas breakdown in the Inertial Electrostatic Confinement (IEC) device has been studied by DC discharge of Nitrogen gas in the pressure range between 0.03 Torr and 0.7 Torr. Paschen curves and Townsend coefficients are obtained in a cylindrical system with inner anode in shape of rods and the outer grid cathode. The breakdown occurs and the plasma is formed at the center of the electrodes. Townsend coefficients are calculated for anode transparencies of 84%, 92%, and 96% (24, 12, and 6 rods respectively). On the left hand side of Paschen curves, the high transparency has a higher breakdown voltage. More electrons are allowed to pass the anode. So, the collisions increase, leading to a slight increment of the first Townsend coefficient (α) decreasing of the second Townsend coefficient (γ) while the ionization efficiency (η) is not affected. For high reduced electric field E/P, i.e. a high electric field with low pressure, the probability of ionizing collision events decreases. This causes a decrement of α while γ is raised because the ions' energy is not exhausted in collisions at the center. The coefficients α and γ are working in harmony to balance the rates of electrons generated in gas ionization so that the relation between the two coefficients is satisfied.

Extraction of ions and electrons from audio frequency plasma source

Herein, the extraction of high ion / electron current from an audio frequency (AF) nitrogen gas discharge (10 – 100 kHz) is studied and investigated. This system is featured by its small size (L= 20 cm and inner diameter = 3.4 cm) and its capacitive discharge electrodes inside the tube and its high discharge pressure ∼ 0.3 Torr, without the need of high vacuum system or magnetic fields. The extraction system of ion/electron current from the plasma is a very simple electrode that allows self-beam focusing by adjusting its position from the source exit. The working discharge conditions were applied at a frequency from 10 to 100 kHz, power from 50 – 500 W and the gap distance between the plasma meniscus surface and the extractor electrode extending from 3 to 13 mm. The extracted ion/ electron current is found mainly dependent on the discharge power, the extraction gap width and the frequency of the audio supply. SIMION 3D program version 7.0 package is used to generate a simulation of ion trajectories as a reference to compare and to optimize the experimental extraction beam from the present audio frequency plasma source using identical operational conditions. The focal point as well the beam diameter at the collector area is deduced. The simulations showed a respectable agreement with the experimental results all together provide the optimizing basis of the extraction electrode construction and its parameters for beam production.

Surface modification of polyacrylonitrile co-polymer membranes using pulsed direct current nitrogen plasma

Low temperature plasma treatment using pulsed direct current discharge of nitrogen gas was employed to enhance hydrophilicity of the polyacrylonitrile co-polymer membranes. The membranes were characterized in terms of morphology, structure, hydrophilicity, and membrane performance. Properties and functional groups on the surface of polyacrylonitrile co-polymer membranes were investigated by contact angle, scanning electron microscopy, Fourier transform infrared and X-ray photoelectron spectroscopy. Effects of plasma conditions, namely, pulsed voltage, duty cycle and treatment time on increase in membrane hydrophilicity were studied. Permeability of treated membrane was increased by 47% and it was retained up to 70days. Surface etching due to plasma treatment was confirmed by weight loss of the treated membranes. Due to surface etching, average pore size increased and rejection of 200kDa polyethylene glycol decreased to about 70% for the treated membrane. Oxygen and nitrogen functional groups were responsible for surface hydrophilicity.

Spectral line lists of a nitrogen gas discharge for wavelength calibration in the range 4500–11 000 cm-1

A discharge of nitrogen gas, as created in a microwave-induced plasma, exhibits a very dense molecular emission line spectrum. Emission spectra of this kind could serve as wavelength calibrators for high-resolution astrophysical spectrographs in the near-infrared, where only very few calibration sources are currently available. The compilation of a spectral line list and the characterization of line intensities and line density belong to the initial steps when investigating the feasibility of potential wavelength calibration sources. Although the molecular nitrogen spectrum was extensively studied in the past, to our knowledge, no line list exists that covers a continuous range of several thousand wavenumbers in the near-infrared. We recorded three high-resolution ($\Delta \tilde{\nu} = 0.018$cm$^{-1}$) spectra of a nitrogen gas discharge operated at different microwave powers. The nitrogen gas is kept inside a sealed glass cell at a pressure of 2mbar. The emission lines in the spectra were fitted by a superposition of Gaussian profiles to determine their position, relative intensity, and width. The line parameters were corrected for an absolute wavelength scale, instrumental line broadening, and intensity modulation. Molecular and atomic transitions of nitrogen were identified with available line positions from the literature. We report line lists with more than 40000 emission lines in the spectral range $4500-11000$cm$^{-1}$ ($0.9-2.2$$\mu$m). The spectra exhibit emission lines over the complete spectral range under investigation with about $350-1300$ lines per 100cm$^{-1}$. Depending on the microwave power, a fraction of $35\% - 55\%$ of all lines are blended. The total dynamic range of the detected lines covers about four orders of magnitude.

연료전지 자동차용 질소/응축수 통합배출시스템 및 기술 개발

Abstract >> Proper discharge of nitrogen gas and water condensate is required in a conventional fuel cell systemfor performance, stability and durability of fuel cell stacks. Present study covers the development of integratedunit and its functioning logic for simultaneous nitrogen gas purge and water condensate drainage in a fuel cellvehicle system. Configuration of condensate drainage pipe, purge valve and level sensor is considered and optimizedin physical integration. As a key factor, discharge time is considered and optimized based on the test result ofconstant-current operation with various operating temperature in logic development. Consequently, derived optimalvalues are applied and verified in actual vehicle drive mode test.Increase of system design flexibility, weight reduction and cost reduction are anticipated with this study. Additional study for physical and logical improvement is currently being implemented. Key words : Nitrogen purge(질소 배출), Condensate drainage(응축수 배출), Electrochemical reaction(전기화학반응), Fuel cell(연료전지), Constant-current driving test(정전류 운전 시험)

Relationship of Pressure and Plasma Temperature in Plasma DC Glow Discharge

The DC glow discharge of nitrogen gas was carried out by 5 kV DC power supply, which was used to bias voltage between two parallel plate electrodes in the cylindrical glass tube chamber. The distance between two parallel plate electrodes was about 37.5 cm. The voltage was applied on these electrodes between 800 V to 1400 V. The nitrogen pressure in the cylindrical glass tube chamber was controlled by rotary pump and vacuum value. Optical Emission Spectroscopy (OES) was used to investigate the local emissivity of nitrogen glow discharge in the range between 200 and 1,100 nm. The spatial distribution of reactive species was measured at different nitrogen pressures from 0.15-1.90 mbar. These measurements were obtained to analyze the electron temperature. The effect of different nitrogen pressures was studied on the electron temperature and the configuration of nitrogen plasma. In the result, it was found that the plasma column increased with increasing the nitrogen pressure. The electron temperature was less than 0.8 eV.

The role of electron scattering with vibrationally excited nitrogen molecules on non-equilibrium plasma kinetics

Electron energy distribution functions have been calculated by a self-consistent model which couples the electron Boltzmann equation with vibrationally and electronically excited state kinetics and plasma chemistry. Moderate pressure nitrogen gas discharges in the E/N range from 30 to 60 Townsend are investigated comparing an electron-impact cross section set considering transitions starting from all the vibrational states, with reduced models, taking into account only collisions involving the ground vibrational level. The results, while confirming the important role of second kind collisions in affecting the eedf, show a large dependence of the eedf on the set of inelastic processes involving vibrationally and electronically excited molecules, pointing out the need of using a cross section database including processes linking excited states in non-equilibrium plasma discharge models.

Experimental investigation into low pressure gas discharges in microwave electric field optical sensor probes

This paper investigates the feasibility of using the emission intensity of low‐pressure argon and nitrogen gas discharges as the sensing mechanism for a microwave electric field optical sensor probe in microwave resonant cavities. The emission is coupled to a photodiode for detection through an optical fibre due to the difficulty in using conventional optoelectronic devices in close proximity to microwave cavities. The discharge emission intensity is monitored at a range of different input powers to the cavity. The proposed designs for the electric field sensing probe are also included.

Characterization of the high-voltage pulsed discharge plasma of ammonia by emission spectroscopy

We have used optical emission spectroscopy to characterize the high-voltage pulsed discharge of ammonia. Ammonia was highly dissociated in the discharge at low pressures. More atomic nitrogen was generated as compared to the discharge of nitrogen gas at the same pressure of 0.8kPa. We discuss the elimination of the oxygen impurity in the ammonia discharge and we estimate the time-dependent atomic excitation temperature and the electron density from the measured spectra.

The influence of light from a nitrogen gas discharge lamp on the concentration of metastable species and on the time delay to electrical breakdown in nitrogen-filled diodes

The analysis of measurements of the overvoltage dependence of time delays to electrical breakdown in nitrogen-filled diodes under various illumination conditions confirms the role of long-lived metastable species. After long periods of afterglow the concentration of molecules significantly influences the breakdown probability as well as the magnitude of the glow-discharge current.

Nitrogen gas-discharge electron source with secondary-emission cathode

A mathematical model of a high-voltage electron source with a secondary-emission cathode and anodic plasma is constructed. Nitrogen is used as the working gas. The model is based on a kinetic description of the physical processes in the source, approximations of elementary-process cross-sections are given, and calculations are performed in the 2.5-400-kV range. The need to allow for charge exchange and the reflection of fast heavy particles from the cathode is shown.

Ion flux characteristics in arc vapor deposition of TiN

In this paper the ionization and energy characteristics of the particle flux impinging TiN films during arc vapor ion deposition are described. Langmuir probe measurements of voltage and current were made using a planar shielded substrate as the probe. Plasma species were observed using emission spectrometry. Substrate mass gain was measured as a function of voltage and nitrogen pressure. Ion current to the substrate was eliminated by applying a negative voltage to a fine wire screen located in front of the substrate and, at the same time, applying a positive voltage to the substrate. The ionized fraction of the titanium vapor at the substrate was determined by comparing the deposition rate obtained while excluding ions with the deposition rate obtained under normal conditions when ions were part of the depositing flux. The Langmuir probe measurements were used to estimate the plasma parameters and the average ion energy at the substrate. The results are as follows: (1) in the absence of a nitrogen gas discharge, the density of nitrogen ions is small; (2) most of the titanium vapor is ionized; (3) the average charge carried by titanium ions to the substrate during TiN deposition is (1.6 ± 0.3) e; (4) the average energy of titanium ions at the substrate is approximately 1.6 e(10 + | V s|) eV, where V s is the negative substrate bias.

Vibrational population densities of the A3Σ u+, B3Π g, W3Δ u, B'3Σ u-, and C3Π u states in nitrogen plasmas

Population densities of vibrational levels of triplet excited states have been calculated using a collisional-radiative model applicable to nitrogen gas discharges with a Maxwellian electron energy distribution. Relative contributions of various electron impact and radiative processes, including intrasystem cascade, to the total cross sections of the triplet excited states are investigated.

Aluminum nitride films by rf reactive ion-plating

Aluminum nitride films were synthesized successfully on silicon (111) and spinel (111) single crystal surfaces by rf reactive ion-plating. Aluminum was evaporated from an evaporator in the rf discharge phase of either nitrogen gas or ammonia gas at a pressure of 10−4 Torr (∠10−2 Pa). Film structures were evaluated using reflection high energy electron diffraction (RHEED) and scanning electron microscopy (SEM). The aluminum nitride films synthesized on the spinel (111) surfaces at the substrate temperature of 1000 °C, in the rf discharge phase of both nitrogen gas and ammonia gas, were found to be of single crystal form, having parallel orientation to the substrate surfaces. Aluminum nitride single crystals forming hexagonal pyramids were observed to grow in the perpendicular direction to the substrate surfaces during the study. The growth rate of aluminum nitride film obtained in the ammonia gas discharge, which was about 500 Å min−1, was about two times as fast as that obtained in the nitrogen gas discharge.

Modes of the Screw Instability in a Positive Column with Longitudinal Magnetic Field

The modes of screw instability in a positive column of a nitrogen gas discharge have been studied. Under a certain condition, the critical magnetic field for the m=2 mode has been found to be smaller than that for the m=1 mode. In addition, the regular oscillations have been observed at the magnetic field larger than the critical one. These phenomena can not be described by the results of Kadomtsev and Nedospasov which are calculated from the small-amplitude theory. In this paper a theoretical explanation for these phenomena is proposed based on the conception that only the instability which has the maximum growth rate can grow while other instabilities are masked.