Nitrogen Arc Plasma Research Articles

Spectroscopic measurement of temperature and gas composition in Ar-N2 shielded TIG welding

Demixing causes changes in the composition and thermal transport in a mixed-gas arc. Thus, the temperature and gas composition of argon–nitrogen arc plasma are measured to analyze the effect of demixing in both direct-current tungsten inert gas (DC-TIG) and pulsed TIG (P-TIG) welding. The arc image acquisition system is developed; this system includes two monochromatic imaging devices, which are triggered synchronously by software. The presented system is an efficient approach to capture monochromatic images simultaneously with high temporal and spatial resolutions. It is applied to obtain monochromatic images of the Ar I and N I spectra. Using the modified Fowler–Milne method, the radial profiles of temperature and gas composition are measured. For DC-TIG in 80 % Ar + 20 % N2, the argon concentration is decreased in the arc centre, relative to the original gas mixture, and then gradually increases with the radius. This is attributed to frictional forces. As the radius increases further, the argon mass fraction decreases again, which is attributed to diffusion of argon toward the arc periphery. For P-TIG using 80 % Ar + 20 % N2, the demixing effect in the peak-current phase is stronger than that in the base-current phase due to the higher current in the peak-current phase. This phenomenon helps control the heat input into the workpiece.

Effective preparation of SiC nanoparticles by the reaction of thermal nitrogen plasma with solid SiC

It is well known that SiC nanoparticles are mainly prepared by a gas phase reaction involving thermal decomposition or by precursor methods. In this paper, we propose a new process of effectively preparing SiC nanoparticles through a reaction between nitrogen arc plasma and a solid SiC block or a mixture compact of Si and C powders. The solid SiC block is irradiated with nitrogen arc plasma containing various nitrogen partial pressures at a total pressure of 0.1MPa. The generation rate of SiC nanoparticles in 100% Ar plasma is negligible. However, the generation rate of SiC nanoparticles increases with increasing the nitrogen concentration in Ar. In the case of 100% nitrogen plasma, the generation rate has the highest value.

Composition of homogeneous quasi-stationary nitrogen arc plasma by collisional–radiative model

A collisional–radiative model (CRM) is developed to study nitrogen arc plasma. The model is based on solution of the rate equations of ν species chosen for the study. The species chosen are: electrons e, atomic ions N + , atoms N, diatomic molecules N 2, and molecular ions N 2 + , we have then ν=5 species. The CRM is applied to homogeneous and quasi-stationary state (HQSS) plasma for electron temperature T e upto 12 000 K. All heavy particles are assumed to have the same kinetic temperature T g such that T g = T e , this means the temperature of the all five species is identical and is called plasma temperature T. The total pressure of the plasma is considered between 1 and 4 atm. The plasma composition is calculated taking into account all significant collisional and radiative mechanisms. The local effect of radiation absorption is described by the optical escape factors Λ j and Λ jk for free–bound and bound–bound transitions. Results show significant deviation from local thermodynamic equilibrium (LTE). It was also shown that the plasma pressure p has a strong influence on deviation from LTE. To assess the relative speeds of recombination reactions in nitrogen arc plasma we have calculated the relaxation time τ (or time constant) as a function of temperature.

Numerical study and comparisons of gas tungsten arc properties between argon and nitrogen

In this paper, nitrogen was used as an alternative gas for its fine protection to weld pool and relatively low cost, in contrast to widely used argon and helium shielding gases in gas tungsten arc welding (GTAW). A two-dimensional axisymmetric numerical model from McKelliget et al. was adopted to describe the heat transfer and fluid flow in the gas tungsten arc (GTA) to predict the basic energy source properties of nitrogen GTA. Simulation results showed that the arc temperature contours, the distribution of heat flux and current density at the anode agree well with experimental results in literature for both argon-shielded arc and nitrogen-shielded arc. To solve the model, the nitrogen arc plasma properties, i.e. temperature, voltage drop and flow fields have been derived. And the distribution of the heat flux, current density and gas shear stress at the anode with the different arc lengths and welding currents has been studied. Moreover, by comparing with the properties between the argon and nitrogen arc, the results indicate that the nitrogen arc is more contraction than that of argon arc under the same arc length and welding current. Especially, the increasing of the maximum of heat flux and current density at the anode shows that the nitrogen GTA possessed excellent energy source properties for GTAW in contrast to the argon arc.

Preparation of Nanoparticles by Nitrogen Arc Plasma

Preparation of Nanoparticles by Nitrogen Arc Plasma

A Novel Method of Synthesizing Spherical Nano-structured Composite Particles of Aluminum Nitride using Transferred Type DC Arc Plasma

Aluminum nitride (AlN) composite particles consisting of nano-particles dispersed on the surface of spherical micro-particles are one of the materials necessary for developing solid insulating materials with high thermal conductivity. This paper describes a novel method of synthesizing AlN composite particles using transferred type DC nitrogen arc plasma. The shape of the synthesized particles, the diameter of micro-particles and the volume fraction of micro-particles in the synthesized composite particles were controlled simply by varying the travelling time of the raw AlN angular particles in the arc plasma. The travelling time was controlled by varying the plasma length and the plasma gas flow rate. The diameter of the nano-particles in the synthesized composite particles was controlled simply by varying the travelling time of the raw AlN particles in the arc plasma, and varying the temperature and the vapor density in the nano-particle synthesis space. The temperature and the vapor density were controlled by varying the flow rate of reacting/quenching ammonia gas. The AlN content in the synthesized composite particles was higher than 99%.

Departure from statistical equilibrium in nitrogen arc plasma

Using a stationary homogeneous hypothesis, a collision radiative model (CRM) is developed for nitrogen plasma. The number densities of the ground and the excited levels of nitrogen are calculated as a function of temperature T(K) and electron number density n e (cm −3). To quantify departure from statistical equilibrium, Saha's decrement b j is introduced for each level j, j=1,2, …, 22. Also the departure from the Boltzmann ratio which is characterized by the quantity a j is discussed. The calculations have been performed for the optically thin case. The resonance radiation absorption has been also taken into account and has been included in the rate equations by means of an escape factor Λ r . Finally, the influence of heavy particle collisions on the population densities of excited atomic levels has been discussed.

Electron field emission from thin films of amorphous carbon nitride synthesized by arc ion plating

Field emission characteristics of amorphous carbon nitride (a-C:N) thin films were studied in the applied field strength range of up to 20 V/μm by comparing the characteristics of amorphous carbon (a-C) thin films. Both a-C:N and a-C films were deposited on Si substrates by means of shielded arc ion plating (SAIP) using nitrogen or argon as an operating gas, respectively, and graphite as a solid carbon source. The a-C:N films showed better field emission current densities than the a-C films. Nitrogen doping to a-C was found to be effective in order to improve the field emission characteristics. Among all of the fabricated a-C:N films, the film containing 23% nitrogen, prepared using a nitrogen arc plasma at a pressure of 1 Pa by applying a sample bias voltage of −100 V, showed the lowest threshold field and the highest emission current density. Furthermore, thickness of this a-C:N was optimized to be approximately 40 nm in order to obtain the best field emission characteristics, that is, a threshold field of 12 V/μm and an emission current density of 3.6 μA/cm 2 at a field of 20 V/μm.

Field emission properties of amorphous carbon nitride thin films prepared by arc ion plating

Amorphous carbon nitride thin films (a-C:N) were deposited by means of shielded arc ion plating (SAIP) using nitrogen and graphite as an operating gas and a carbon source, respectively. In the applied field strength range of up to 20 V/μm, electron field emission properties of these films were characterized and compared with those of amorphous carbon (a-C) thin films prepared using an argon plasma by the same SAIP apparatus. The a-C:N films showed better characteristics, that is, lower threshold field strengths and higher maximum emission current densities, than the a-C films. Among all of the fabricated a-C:N films, the film with a N concentration of 23%, prepared using a nitrogen arc plasma at a pressure of 1 Pa with applying a sample bias voltage of −100 V, showed the lowest threshold field of approximately 13 V/μm and the highest emission current density of near 2 μA/cm 2 at a field strength of 20 V/μm. However, the best results obtained on the a-C films were a threshold field of approximately 16 V/μm and an emission current density of less than 0.1 μA/cm 2 at the same field strength. The characteristics of the a-C:N films depended not only on the N concentration but also on the chemical bonding state of nitrogen in the a-C:N networks. The C-N phase distinguished by the N1s XPS peak at 400.5 eV plays a crucial role in field emission of the a-C:N.

Preparation of ultrafine composite particles of Ag+AlN/Al by nitrogen plasma metal reaction

Abstract Pure Ag and Al were melted simultaneously by nitrogen arc plasma in a common chamber using two electrodes. Ultrafine composite particles consisting of fcc-Ag, fcc-Al and hexagonal AlN are obtained together with 17% mixture of hexagonal Ag 2 Al ultrafine particles. Ag, Al and AlN ultrafine particles are formed through the condensation of element vapor, but Ag 2 Al ultrafine particles are formed through a solid reaction between Al and Ag ultrafine particles.

Reduction of NOx Contained in Combustion Exhaust Gas by Using Corona Discharge Tube.

In order to develop methods of plasma injection for removing pollutants such as NOx and SOx contained in combustion exhaust gas, we have investigated radical formation in nitrogen arc plasma, and reported that the NOx removal efficiency has a maximum value in the range of low electrical power for plasma operated under stable conditions. In this paper, in order to further economize electrical energy in actual use, the simulated exhaust gas (N2+O2+CO2+NO) is excited by passing through a corona discharge tube in a high electric voltage field. The NO is oxidized to NO2, and OH radical generated from H2O contained in gas reacts with NO2, and NO concentration decreases as a result of generation of HNO3. The effects of H2O, O2 and CO2 contents on the NOx reduction rate are discussed experimentally. The NOx reduction rate of about 25% is obtained under the input power of 45 watts.

Experimental study of a supersonic low-pressure nitrogen plasma jet

A supersonic nitrogen arc plasma jet expanded in a low-pressure test chamber is studied. Radial measurements of temperatures and densities are performed in the expanding region over various sections from the nozzle exit. Nitrogen is highly dissociated in the arc chamber and the plasma is far from equilibrium. Electron temperature and density, as well as gas velocity, are measured by means of parallel and crossed electrostatic probes. Measurements of selected atomic and molecular line intensities are performed in the 250–850 nm spectral range to obtain number densities of various N2, N2+ and N excited levels. The rotationally resolved emission spectrum from the (0–0) band of the N2+ first negative system (B2Σ+u→X2Σ+g) is analyzed and compared to synthetic spectra to evaluate the rotational temperature within the flow field. The kinetic scheme of ionic recombination of N+ and N2+ is examined. A recombination path of the N2(C3Πu) electronic state via the N2(C″5Πu) state is proposed for the N(2D0)+N(4S0) nitrogen recombination.

ChemInform Abstract: Fixation of Molecular Nitrogen Using Aliphatic Carboxylic Acid by Nitrogen Arc Plasma. Formation of Amino Acids.

When argon-nitrogen plasma was blown into an aqueous solution containing aliphatic carboxylic acids, formation of several amino acids and amines was identified.

Fixation of Molecular Nitrogen in Aqueous Solution Induced by Nitrogen Arc Plasma

Abstract Argon Arc Plasma containing nitrogen gas (nitrogen arc plasma) was directly introduced into water, and a disproportionation reaction of molecular nitrogen took place in aqueous solution to form ammmonia, nitrous acid, and nitric acid. The redox reaction of molecular nitrogen is interesting on the chemical evolutionary point of view as a possible route for the formation of ammonia under non-reducing conditions.

Fixation of Molecular Nitrogen Using Aliphatic Carboxylic Acid by Nitrogen Arc Plasma. Formation of Amino Acids

Abstract When argon-nitrogen plasma was blown into an aqueous solution containing aliphatic carboxylic acids, formation of several amino acids and amines was identified.

The influence of copper vapour on the transport coefficients in a nitrogen arc plasma

Using the method ofChapman and Enskog, the transport coefficients of a copper-nitrogen mixture at atmospheric pressure were calculated. With the most appropriate methods the authors determined the cross-sections of collisions between copper and the othe r particles. The results obtained show that at low temperatures (5000K<T<7000K) the electrical conductivity is clearly increased by the presence of copper. At higher temperatures (T approximately=15000K) the electrical conductivity of the mixture can be reduced by the presence of doubly ionised atoms of copper. The influence of the copper is also felt by the reactional thermal conductivity but has little influence on the translational thermal conductivity.