Nitrogen Plasma Gas Research Articles

Nitrogen Fixation in a Plasma/Liquid Interfacial Reaction and Its Switching between Reduction and Oxidation

There are multiple active species at the interface between the discharged gas phase and the water phase. Activated nitrogen species are generated in the nitrogen plasma gas by dielectric barrier di...

Effects of spray distance on the microstructure and mechanical properties of reactive plasma sprayed TiCN coatings

The objective of this study is to evaluate the effects of spray distance on the microstructure and mechanical properties of reactive plasma sprayed titanium carbonitride (TiCN) coatings under nitrogen plasma gas. For this purpose, five different distances were adopted, and the morphology (single splats, surface and cross section) and composition (phase and chemical) of as-sprayed coatings were investigated. Mechanical properties of bonding strength, hardness, elastic modulus as well as indentation toughness of coatings were systematically evaluated. Results show that all of coatings consist of TiCxN1−x (0 ≤ x ≤ 1), TiOx, amorphous graphite and CNx phases, and the amount of ternary TiCN increases as the spray distance increases. Typical microstructure of plasma sprayed coatings containing fully melted particle, partially melted particles, un-melted particles and defects (pores and cracks) are observed. As the spray distance increase, the surface morphology and splats shape change from uneven and irregular ones to relatively flat and regular “disc splats” due to the improved dwell time and sufficient melting in plasma jet. In this case, the maximum hardness about 17.8 ± 1.9 GPa, elasticity modulus about 214.5 ± 18.3 GPa and bonding strength about 24.2 ± 2.1 MPa are obtained due to the relatively high TiCN content, favorable indentation toughness and compact microstructure. As the spray distance further increases to 150 mm, irregular “fingers splats” appear, and in this case the mechanical properties of coating are worsened. Therefore, a significant influence of spray distance on the microstructure and mechanical properties of as-sprayed TiCN coating is found.

Mechanical properties and corrosion behavior of the nitriding surface layer of Ti[sbnd]6Al[sbnd]7Nb using large pulsed electron beam (LPEB)

Large pulsed electron beam (LPEB) irradiation was used as a single surface finishing process for TiAl7Nb. Nitrogen plasma gas and cathodic apparatus have been adopted to induce nitriding effect of Ti6Al7Nb during the electron beam irradiation. The atomic concentration of nitrogen atoms at the re-solidified layer could be achieved up to ∼18% by LPEB nitriding. Nano-hardness in the re-solidified layer was improved by ∼75% following the irradiation process, as a result of a phase transformation and the formation of TiN. The re-solidified layer induced by the LPEB nitriding, consisted of TiN, TiO2, and TiOxNy, indicated significantly modified corrosion resistance showing a nobler corrosion potential, decreased corrosion current density, and improved charge transfer resistance. The increasing fraction of TiN at the re-solidified layer, induced by LPEB nitriding, was suggested as being responsible for remarkable improvement of mechanical properties and corrosion resistance, embedding uniformly noble and stable characteristics at the top surface. The corrosion-resistant surface layer with superior mechanical properties on Ti6Al7Nb has been successfully demonstrated by LPEB nitriding technique.

A comparative study of air and nitrogen thermal plasmas for PFCs decomposition

Air and nitrogen thermal plasmas were generated from a plasma torch with hollow electrodes to abate CF4 which is a serious non-degradable greenhouse gas exhausted from the semiconductor manufacturing process. Numerical analysis and experimental demonstration have been carried out to compare effects of plasma forming gas on the decomposition process at the same electric input power of 60kW and waste gas flow rate of 200L/min. Higher temperature and longer residence time were expected in nitrogen thermal plasma than air thermal plasma, because relatively low flow rate of nitrogen plasma gas is required at fixed input power compared with air plasma gas. Although small quantity of NF3 was produced in nitrogen thermal plasma process with hydrogen reactant gas, high destruction and removal efficiency of 99.6% was achievable along with suppression of unwanted NOx generation.

Surface Modification of Polypropylene Non-Woven Fabrics by Atmospheric-Pressure Plasma Activation Followed by Acrylic Acid Grafting

Polypropylene (PP) non-woven fabrics have been activated by an atmospheric-pressure plasma treatment using surface dielectric barrier discharge in N2 and ambient air. Subsequently, the plasma activated samples were grafted using catalyst-free water solution of acrylic acid. Surface properties of the activated and polyacrylic acid post-plasma grafted non-woven were characterised by scanning electron microscopy, Fourier transform infrared spectroscopy, electron spin resonance spectroscopy, surface energy and dyeability measurements. The grafted non-woven exhibit improved water transport and dyeing properties. The plasma activation in nitrogen plasma gas was more efficient than in air.

Stability of Plasma Posttreated TiN Films Prepared by Alternating Cyclic Pulses of Tetrakis-Dimethylamido-Titanium and Ammonia

The effect of plasma posttreatment on the resistivity and stability of tetrakis-dimethylamido-titanium (TDMAT)-based atomic layer deposition TiN films was investigated. Posttreatment with hydrogen plasma was effective for lowering the resistivity of the TiN films and also for improving their stability in air. Longer plasma pulse times with high power yielded films of lower resistivity aand increased stability in air. However, there was no noticeable improvement of the film's stability with nitrogen plasma gas.

Treatment of a polyethylene powder using a Remote Nitrogen Plasma reactor coupled with a fluidized bed: Influence on wettability and flowability

A Far Cold Remote Nitrogen Plasma is used both to fluidize and to treat a polyethylene powder in order to increase its hydrophilic character. The evolution of the wettability of the powder as well as the one of its physical (density, particles size distribution, average diameter, shape factor, and BET surface area) and flow properties (angle of repose, angle of slide, and Hausner index) are determined versus various experimental conditions. It is shown that the plasma treatment efficiency is strongly dependant on the oxygen content of the nitrogen flow and on the velocity of fluidizing gas. Best wettability is obtained by the addition of 0.75% of O2 in the nitrogen plasma gas and with a high gas velocity. It is also evidenced that the flowability of the powder is slightly altered by the plasma treatment.

Preparation of Ti/N and Ag/TiN x multilayers by plasma based ion implantation with multi-targets unbalanced magnetron sputtering

Ti/N and Ag/TiN x multilayers were prepared by plasma based ion implantation (PBII) with multi-targets unbalanced magnetron sputtering and analyzed by Auger electron microscopy (AES) and X-ray photoelectron spectroscopy (XPS). Nitrogen plasma gas and Ti and Ag multi-targets were used in this study. It was found that both gases and metal elements could be implanted into the samples. Ti/N and Ag/TiN x multilayers were successfully fabricated by multi-cycle PBII with nitrogen plasma gas and Ti and Ag unbalanced magnetron sputtering. The possibility of design and fabrication of multilayers by this technique is also discussed. This technique for the deposition of films may find more applications.

Influence of hydrogen on molecular ions N2+(X 2g+) and N2+(B 2u+) kinetic processes in direct current and direct current-pulse N2-H2 glow discharges

A comparative study of N2-H2 glow discharges produced either in a direct current (dc) or a low-frequency, dc-pulse condition is carried out by means of optical emission spectroscopy and laser induced fluorescence. The influence of a small quantity of hydrogen added to the nitrogen plasma gas on the density of molecular ions is discussed. The preferential quenching of N2+(X 2g+) by H2 is shown and discussed in terms of the ionizing and populating processes in both the discharge phase and the afterglow.

Plasma spray processing of Al2O3/AlN composite powders

A novel method is proposed to prepare Al2O3/AlN composite powders. The composite powders were synthesized by direct nitridation of Al2O3 powders in Ar/N2 plasma. The processing characteristics were studied. The results show that the particle size of the initial materials, the nitrogen plasma gas flow rate and the power of the plasma generator are important factors that influence the phase composition of the Al2O3/AlN composite powders. Post treatment of the Al2O3/AlN composites in nitrogen atmosphere was carried out. Microstructure analysis showed that the composite powders are spheroids, with the small particle size AlN formed on the surface of the Al2O3.