Pure Nitrogen Gas Research Articles

Strong-Field-Induced Air Lasing in Nitrogen Glow Discharge PlasmaSupported in part by the National Natural Science Foundation of China (Grant Nos. 61625501 and 62027822), and the Open Fund of the State Key Laboratory of High Field Laser Physics (SIOM).

We investigate air lasing at 391 nm, induced by strong laser fields in a nitrogen glow discharge plasma. We generate forward air lasing on the – transition at 391 nm by irradiating an intense 35-fs, 800-nm laser in a pure nitrogen gas, finding that the 391-nm lasing quenches when the nitrogen gas is electrically discharged. In contrast, the 391-nm fluorescence measured from the side of the laser beam is strongly enhanced, demonstrating that this discharge promotes the population in the state. By comparing the lasing and fluorescence spectra of the nitrogen gas obtained in the discharged and laser-induced plasma, we show that the quenching of lasing is caused by the efficient suppression of population inversion between the and states of , in which a much higher population occurs in the state in the discharge plasma. Our results clarify the important role of population inversion in generating air lasing, and also indicate the potential for the enhancement of lasing via further manipulation of the population in the state in the discharged medium.

Pre-Stabilization of Zr Getters for 5-Nine Purity Nitrogen Gas Purification

We confirm whether Zr powders can restrain a rapid nitrification reaction and offer a stable oxidation reaction according to temperatures in nitrogen gas purification. A pellet-type, porous Zr getter is prepared (diameter: 10 and thickness: 3 mm) using Zr powder with an average particle size of 45 μm. While maintaining the whole system, the Zr getter reaction is confirmed with an increase in temperature from 150 to 550 oC at increments of 100 oC under 99.999 % purity nitrogen atmosphere comprising of 10 ppm of impurity. Surface color, pore size, stabilized layer, and phase change are confirmed with optical microscopy, SEM-EDS, Micro-Raman, and X-ray diffraction (XRD) according to the Zr getter temperature. The surface color of the Zr getter changes from metallic silver to dark gray as temperature increases. In the EDS results, the nitrogen component is not observed, and oxygen content increases from each surface at elevated temperatures. The Raman and XRD results show the oxidation layer as a result of 350 oC annealing. Therefore, the Zr getter can be applied as a nitrogen getter under 5-nine purity nitrogen atmosphere after appropriate oxidized pre-stabilization process to prevent rapid nitrification reaction.

An Undergraduate Experiment to Investigate Air Pollutants Created from Lightning

Chemistry of the environment has been a long-standing and important area of scientific research. Atmospheric chemistry is of particular interest in society due to the impact that rising levels of pollutants are having on the climate. It is well-known that combustion processes create CO and NOx, which leads to the creation of other pollutants, such as ozone and CO2. There are natural processes, such as lightning, that also create a significant amount of pollutant gases. The purpose of this guided and open inquiry laboratory experiment is to provide an opportunity for students to investigate how lightning may produce pollutant gases in the atmosphere. In the guided inquiry experiment, a sealed IR gas cell containing air is exposed to a spark or corona discharge created by an Oudin coil to mimic lightning. IR spectroscopy is used to monitor the reaction progress and identify new species made after exposure to the electrical discharge. Based on the results, students draw conclusions about what types of gases are created in the two different discharge processes and how lightning may contribute to atmospheric pollutants. Students move on to the open inquiry to further investigate aspects of atmospheric gases, where they develop their own hypothesis and methods based on one of the provided suggestions, such as the effect of spark and corona discharge on pure oxygen, nitrogen, or carbon dioxide gases, the kinetics of ozone creation and decay, and the temperature dependence of NO2 dimerization. Although designed for an honors general chemistry course, this experiment can be adapted for second-semester general chemistry, environmental chemistry, analytical, and physical chemistry laboratory courses. Results from these experiments are presented, and the relevant atmospheric chemical processes are discussed. The impact of this experiment on perceived gains in knowledge, the value of inclusion in the curriculum, and the design of the experiment were assessed, and the results are discussed.

Improvement of thermal stability of Ta-N film in Cu metallization by a Zr-Si interlayer

Ta-N (10 nm)/Zr (20 nm) film was grown on n-type (100) silicon wafer at various substrate temperatures in a rf magnetron sputtering system, followed by in situ deposition of Cu. The Cu/Ta-N/Zr/Si samples were subjected to thermal annealing up to 800 ℃ under the protection of pure nitrogen gas. In order to investigate the effect of insertion of a thin Zr layer under Ta-N film on Ta-N diffusion barrier performance in Cu metallization, Cu/Ta-N/Zr/Si contact system was characterized by X-ray diffraction (XRD), four-point probe (FPP) measurement, scanning electron microscopy (SEM), and Auger electron spectroscopy (AES) depth profile. The results reveal that the microstructure of Ta-N films deposited on Zr is amorphous at different substrate temperatures. The barrier breakdown temperature of Ta-N/Zr film is about 100°C higher than that of Ta-N. It can effectively prevent the diffusion of Cu after annealed at 800°C. The improvement of diffusion barrier performance may be due to the production of Zr-Si layer with low contact resistivity after annealed at 800°C.

Active and passive adsorption of 47 trace atmospheric volatile organic compounds onto carbon nanotubes.

Carbon nanotubes (CNTs) of varying sizes and CNTs functionalised with carboxylic acids were examined by thermal desorption gas chromatography mass spectrometry (TD-GCMS) to determine the degree of surface contamination of atmospheric volatile organic compounds (VOCs). The CNTs could be purged of physisorbed VOCs by heating to 380 °C under a stream of purified nitrogen gas. As soon as the cleaned CNTs were exposed to atmospheric air they spontaneously adsorbed trace VOCs. As well as passive adsorption of VOCs, active sampling was carried out by pumping atmospheric air through the CNTs and comparing the results with the standard multisorbent materials Carbopack X and Tenax that are used widely for VOC trapping and analysis. The CNTs were found to trap many VOCs at a comparable level to the standard sorbent materials. Therefore, to maintain the CNTs in a pristine condition, it is recommended that they are first heated under vacuum to remove residual physisorbed VOCs, and then stored under vacuum or in a purified inert gas atmosphere.

Plasma Nitriding of Hard Chromium Electroplated Low Alloy AISI 4340 Steel in Pure Nitrogen Gas Atmosphere

Duplex treatments are surface modification techniques used to enhance the surface properties of steels. In this study, hard chromium electroplated AISI 4340 steel was plasma nitrided in pure nitrogen gas at 600°C for 90 min. The structural and morphological properties were analysed by an X-ray diffractometer and a scanning electron microscope (SEM), respectively. The hardness profile was obtained by a multicycle nanoindentation test and the tribological properties by a ball-on-disk test at room temperature. The results showed that the duplex layer was composed mainly of Cr2N and it had a rough surface morphology with a network of micro-cracks. The highest values of hardness were registered in the nitrogen diffusion layer beneath the outer porous thin layer. The friction coefficient and the specific wear rate after plasma nitriding were reduced by 3 and 5 factors, respectively.

Effects of solid lubricants on properties of Al-Si-SiC composite powder produced by gas atomization technique

Al-Si-SiC composites powder was analyzed in this research. The powder was made by gas atomizing process. Powder characterization was done to observe its morphology, particle size distribution and thermal properties. Effects of lubricants were intensively investigated in this research with compositions and pressure variables. It is assumed that higher amount of solid lubricant put into the powder, the lower ejection force needed to take out compacted powder. Finding appropriate solid lubricant is necessary to improve green and sintering properties. EBS (ethylene bis stearamide), aluminum stearate, zinc stearate and paraffin wax were used for investigation. Sintering under ultra high purity nitrogen gas 99.9999% was carried out to produce high density material. SEM-EDS and XRD were carried to characterize this powder. SiC particles in this powder prohibit to achieve optimum sintering properties of Al-Si-SiC due to their resistance during compaction which leads to form pores and lower sintering density. And ethylene bis stearamide (EBS) seems to be suitable solid lubricant for this powder by giving lower ejection force, flowability and higher sintering density for 93.5%.

Electron beam and betatron x-ray generation in a hybrid electron accelerator driven by high intensity picosecond laser pulses

We experimentally studied electron beams and synchrotron x-ray radiation generated from the interaction of high-intensity picosecond laser pulses of 1–3 × 1019 W/cm2 with underdense plasmas of 1–8 × 1019 cm−3. Electron beams with maximum energy over 120 MeV, hundreds mrad divergence and tens of nC charge were generated in the experiments. The measured x-ray spectra were fit well with a synchrotron radiation spectrum combination with a bremsstrahlung spectrum. When laser pulses with intensity of 2.38 × 1019 W/cm2 interacting with pure Nitrogen gas with density of 2.35 × 1018 cm−3, we obtained betatron x-ray radiation with critical energy 3–4 keV and photon number up to 1013 photons/Sr per shot, the energy conversion efficiency is about 3 × 10−5. The high photon yield and large energy conversion efficiency are due to large amounts of electrons trapped by self-modulated laser wakefield and mainly accelerated by direct-laser-acceleration mechanism. Such high yield betatron x-ray sources have widely application prospect as backlight or probe in large scale of laser facilities used for high energy density or fusion sciences.

Effect of Substrate and Annealing Ambient on the Conductivity of Sputtered MoSi2 Ceramic Thin Film

In this work, molybdenum disilicide (MoSi2) ceramic thin films were deposited by DC magnetron sputtering on different types of substrates (quartz, glass, p-type silicon, n-type silicon, and barium strontium titanate (BST) buffer layer deposited on silicon). The films were annealed under various ambient conditions (air, N2/99.999%, N2-H2/95–5%) at various annealing times (10–90 min) and temperatures (400–1100°C) to enhance their crystallinity and improve their conductivity. The tetragonal crystal phase, which is the most conductive and stable phase of MoSi2 thin films, was obtained on an n-type silicon substrate that was annealed at 1100°C for 90 min in an atmosphere with pure nitrogen gas flux of 200 L/h. The sheet resistance of the MoSi2 thin films was 0.876 Ω cm−2. The films exhibited a homogeneous glossy metallic surface with surface roughness of 0.35 nm and 3.81 nm for amorphous and annealed thin films, respectively. The high conductivity obtained in this work, in addition to the extraordinary material properties of the MoSi2 ceramic thin film, makes it an attractive candidate for remarkable device applications because of the thermal stability of film conductivity.

Research on water vapor measurement and removal methods for the spacecraft sealed cabin

In order to develop a water vapor measurement and dewatering device suitable for ground test of spacecraft sealed cabin. A moisture measuring device suitable for the sealed cabin was designed. The existing moisture content measuring sensors were equipped with auxiliary devices to protect the electrical circuit of the sensor, and then the sensor was calibrated and analyzed. After calibration, it can meet the requirement of moisture measurement in vacuum environment. A small chamber was built to study water change rule in the pumping process. In the water removal system, the cabin was connected to the vacuum pump system through a two-way sealing flange, which can complete the water removal outside the vacuum chamber by pumping. When the pressure of the sealed cabin reached 100 Pa, high purity nitrogen gas was added to 97 kPa, then pumped in again. The results show that the water removal method can ensure that the dew point temperature of the sealed chamber is lower than 0°C during the vacuum thermal test. After protected, the dew point sensor can measure moisture at low pressure. The water removal system can effectively remove the moisture in the sealed cabin, thus ensuring the completion of the vacuum thermal test.

Time-resolved study of the lasing emission from high vibrational levels of N2+ pumped with circularly polarized femtosecond pulses

We experimentally investigated the forward 353.8 nm radiation from plasma filaments in pure nitrogen gas pumped by intense circularly polarized 800 nm femtosecond laser pulses. This emission line corresponds to the B2Σu+(v′=4)−X2Σg+(v=3) transition of nitrogen ions. In the presence of an external seeding pulse, the 353.8 nm signal was amplified by 3 orders of magnitude. Thanks to the much enhanced intensity, we performed time-resolved measurement of the amplified 353.8 nm emission based on the sum-frequency generation technique. It was revealed that the built-up time and duration of these emissions are both inversely proportional to the gas pressure, while the radiation peak power grows up nearly quadratically with pressure, indicating that the 353.8 nm radiation is of the nature of superradiance.

Application of flotation column for Cl‐ and N, N′‐bis (2‐hydroxyethyl) piperazine separation in gas sweetening unit

The degradation of amine solvents leads to increasing costs and deterioration in long term performance. Therefore, the purification of the solvents is needed to guarantee smoother operations. In this research, the flotation setup was investigated by means of laboratory and pilot‐scale experiments in the amine reclamation for chloride and N, N′‐bis (2‐hydroxyethyl) piperazine (BHEP) separation. The maximum removal efficiency recorded was 51% for the largest chloride concentration of 7091 mg/l and 37% for the lowest chloride concentration of 1536 mg/l. The mass transfer coefficient was hence correlated with the hydrodynamic parameters, including chloride reduction rate, bubble surface area, and gas and liquid phase concentration. The average chloride removal efficiency for the monoethanolamine (MEA) was more than 61% due to a better dispersion of pure nitrogen gas bubbles and formation of the tiny bubbles provided in the column. The results indicated that a higher chloride initial concentration corresponded to better performance of the setup. Under the typical column operating conditions, it was concluded that a collection zone H:D of 10:1 was a reasonable compromise. The flotation setup results in BHEP separation, known as amine degradation product showed about 24% average amine recovery.

Effects of Compaction Velocity on the Sinterability of Al-Fe-Cr-Ti PM Alloy.

In this research, the effects of the compaction velocity on the sinterability of the Al–Fe–Cr–Ti powder metallurgy (PM) alloy by high velocity compaction were investigated. The Al–Fe–Cr–Ti alloy powder was compacted with different velocities by high velocity compaction and then sintered under a flow of high pure (99.999 wt%) nitrogen gas. Results indicated that both the sintered density and mechanical properties increased with increasing compaction velocity. By increasing the compaction velocity, the shrinkage of the sintered samples decreased. A maximum sintered density of 2.85 gcm−3 (relative density is 98%) was obtained when the compaction velocity was 9.4 ms−1. The radial and axial shrinkage were controlled to less than 1% at a compaction velocity of 9.4 ms−1. At a compaction velocity of 9.4 ms−1, sintered compacts with an ultimate tensile strength of 222 MPa and a yield strength of 160 MPa were achieved. The maximum elongation was observed to be 2.6%. The enhanced tensile properties of the Al–Fe–Cr–Ti alloy were mainly due to particle boundary strengthening.

Mobility of non thermal electrons and ions in very high density and purified nitrogen corona discharge

The mobility of nonthermal electrons and ions have been determined in very high and purified nitrogen corona discharge. Corona discharge was generated by plasma generator system with point-to-plane electrodes geometry configuration. Charateristic I-V has been done by using stabilized DC high voltage generator high up to 20 kV. Graph current of saturation corona unipolar for variation voltage and the distance between electrodes is curved with the semi-parabolic equation. We used I-V characteristic to determine charge patricles mobilities. In this research high purified and slighly purified nitrogen gas. For negative corona, we found that the mobility of charged particles is greater than negative ions and smaller than thermal electron mobility. Particles engaging and moving in the corona with high purification the gas are nonthermal electrons, positive ions for positive corona. From the current-voltage characteristic, we can conclude that the regime of our discharge in very pure gases (N2) corresponds to the current regime limited by space charge. By analogy with what has been observed in a “discharge tube” this regime is similar to an abnormal glow discharge regime. We have seen previously that the variation with the density of the ionic mobility is in good agreement with the direct measurements by the time of flight method.

Application of deoxygenation-aeration cycling to control the predatory bacterium Vampirovibrio chlorellavorus in Chlorella sorokiniana cultures

A previously untested approach was evaluated to enable management of the predatory bacterium, Vampirovibrio chlorellavorus, a pathogen of Chlorella sorokiniana, in suspension cultures grown in a laboratory test reactor. Because V. chlorellavorus is an obligate aerobic bacterium, whereas C. sorokiniana grows under aerobic and anaerobic conditions, deoxygenation of the culture was expected to be detrimental to the pathogen, but not to the algal host. The effect of deoxygenation on the uninfected (healthy) C. sorokiniana suspension cells, compared to the C. sorokiniana-V. chlorellavorus co-culture, was studied in relation to biomass, dissolved oxygen, ratio of C. sorokiniana to V. chlorellavorus DNA, and visual and light microscopic observations. Preliminary experiments were conducted to test the effects of different deoxygenation-aeration cycling regimes on performance of V. chlorellavorus-free C. sorokiniana cultures. To an aerobic culture, pure nitrogen gas was introduced to create anoxic conditions, followed by the injection of ambient air to re-establish an aerobic environment. Under this repeated cycling regime, C. sorokiniana was shown to tolerate the anoxic conditions for extended timespans that ranged from 2 to 8 h over a 5-day test period. The analogous aerobic-anoxic cycling with the C. sorokiniana-V. chlorellavorus co-cultures resulted in ‘near-normal’ growth cycle and harvestable biomass, whereas the continuously-aerated (aerobic) co-cultures that were grown without the deoxygenation step in the cycle collapsed in 3 days. Visual and light microscopic observations revealed intact C. sorokiniana cells were present in the deoxygenated cultures, compared to the aerobically-grown, brown-colored algal cultures consisting of collapsed cells. Quantitative polymerase chain reaction analysis showed continuous increases in the ratio of V. chlorellavorus (16S rDNA) to C. sorokiniana (18S rDNA) DNA in the aerated co-cultures, with greater increases during dark periods, while the pathogen-to-host DNA ratio in the deoxygenated co-cultures was relatively low and algal cells did not collapse, as would be expected following pathogen attack.

Hydrothermal improvement for 3R-CuFeO2 delafossite growth by control of mineralizer and reaction atmosphere

Delafossite CuFeO2 oxides were grown inside a hydrothermal reactor using Cu2O and FeOOH as precursors and NaOH as mineralizer. During this work the effect of the NaOH mineralizer and the reaction atmosphere was studied by varying the amount of NaOH used in the hydrothermal synthesis and by changing the reactor atmosphere from room air to high purity nitrogen. The oxides obtained were analyzed with Raman Spectroscopy, Fourier Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray Photoelectron spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive X-ray Spectroscopy (EDS), in order to obtain their morphological, chemical and structural characteristics. It was found that increasing the amount of mineralizer from 0.4 g up to 1.02 g improves considerably the hydrothermal reaction efficiency obtaining a resulting oxide with 93% of 3R-CuFeO2 phase and a subsequent decrease of the 2H-CuFeO2 phase. Moreover, using the same hydrothermal route it was shown possible to obtain high purity CuFeO2 compounds using small amounts of NaOH (0.4 g) if the reaction is performed under a non-oxidative atmosphere injecting pure nitrogen gas to the hydrothermal reactor where an increase of 3R-CuFeO2 phase from 36% to 94% was obtained. Finally, direct band gap of the semiconducting oxides were estimated using Tauc method from UV–vis spectra obtained by Diffuse Reflectance spectroscopy.

Improvement in surface specifications of AZ31B magnesium alloy by friction stir processing under nitrogen environment

In this work, friction stir processing of AZ31 alloy under pure nitrogen gas and air were studied. For this purpose, the influences of different rotating speeds (700, 900 and 1120 rpm) and environment condition on the metallurgical structure, wear and corrosion resistance were investigated. The results, obtained under optimized experimental conditions, indicated that the surface nitriding results in refining of surface grains to an average of 3 microns and its hardness enhancement by 37%. Also the corrosion potential, carried out by potentiodynamic polarization tests in simulated body fluid (SBF), showed an improvement by 160 mVs. Meanwhile, the dry sliding wear tests showed a 30% wear rate improvement occurred.

Microstructure and Corrosion Properties 0Cr21Mn17Mo2N0.8 High Nitrogen Austenitic Stainless Steel

The high nitrogen stainless steel with solid solution heat treatment after forging was austenitized completely. The microstructure of the alloys were observed by OPM, SEM and EDS. The mechanical properties were analyzed by tensile test and impact test. In addition, the corrosion test of high nitrogen austenitic stainless steel, 304 stainless steel and 316L stainless steel were conducted in the environment of highly purified nitrogen gas in the autoclave, and the deionized water is used to make 10000mg/L sodium chloride solution. The corrosion depth was studied by laser scanning confocal microscope. The experimental results showed that the addition of nitrogen improves greatly the mechanical properties of stainless steel. Otherwise, three kinds of stainless steel caused pitting in sodium chloride solution, because the passive film of stainless steel was destroyed due to the permeation of the chloride ion. Moreover, the corrosion rate of high nitrogen austenitic stainless steel is much lower than that of the 304 and 316L stainless steel. So the corrosion resistance of high nitrogen steel is much better. On account of the chemical interaction between nitrogen and molybdenum, it can prevent the surface from forming high current density and decrease the pitting tendency of stainless steel. The result expanded greatly the application of high nitrogen stainless steel in the field of corrosion.

Optimal Oven Heating of Coke Cake. 2. Selection of the Inert Gas

The formation of the combustion flame in the heating channels of coke ovens is analyzed. The need for redesign of the components so as to permit recirculation of the combustion products by thermal ejection is established. That will result in elongation of the flame. In addition, the organization of forced recirculation by the supply of combustion products or inert gas to the heating channels with ascending flux is proposed. In this approach, it is possible to use water vapor, pure nitrogen, or blast-furnace gas from a steel plant or coke plant. The analysis yields the conclusion that these measures will ensure more uniform heating over the height of the cake in existing coke batteries, slow defect formation in the channel lining, and decrease atmospheric emissions.

Mercury emissions monitoring in a coal-fired power plant by using the EPA method 30B based on a calcium-based sorbent trap

A novel calcium-based sorbent was synthesized from calcium acetate and mesoporous silica through chemical impregnation method. The Brunauer-Emmett-Teller (BET) and scanning electron microscope (SEM) analysis revealed that the sorbent possessed a good surface structure as the calcium salt decomposed to calcium oxide (CaO) through multiple calcination steps. The mercury adsorption performance of the sorbent was investigated in a fixed bed system, the results showed that the sorbent has an obvious penetration behavior for gaseous element mercury (Hg0(g)) while completely adsorbed reactive gaseous mercury (Hg2+(g)) under the pure nitrogen and simulated flue gas atmosphere. On-site sampling test of the calcium-based sorbent traps was ultimately conducted on a 600 MW coal-fired power plant. The Ontario Hydra Method (OHM) was chosen as the reference method to evaluate the accuracy of the sorbent traps sampling results. The measured data obtained by sorbent traps was well consistent with OHM under the selected operational load and all the sorbent traps passed the QA/QC criteria, show that the sorbent traps performed with almost the same accuracy as OHM. The mercury emission and removal characteristics across the existing air pollution control devices (APCDs) were reported based on the sorbent traps sampling results. With the help of SCR for the Hg0 oxidation, ESP for the removal of Hg2+ and Hgp, and the good water solubility of Hg2+ in WFGD, the combination of SCR + ESP + WFGD achieved an excellent mercury removal efficiency with the value of 88.54%. The final mercury emissions from the exhaust were 3.75 μg/m3 and meet the emission requirements of China.