Gas Mixture Of Nitrogen Research Articles

International comparison CCQM-K41.2017, hydrogen sulfide in nitrogen

Main textHydrogen sulfide (H2S) is a poisonous gas which can paralyze the respiratory system, quickly leading to death. It is also a flammable gas, which will ignite explosively when exposed to heat, open flames or oxidizers. For these reasons, hydrogen sulfide is classified as a hazardous material. This comparison is a repeat of the key comparison of the "CCQM-K41 (2005)" and it is intended to compare the capabilities of the preparation and value assignment of gas standard of hydrogen sulfide in nitrogen. The range of the nominal amount-of-substance fractions of the comparison standard is 10 µmol/mol. A set of hydrogen sulfide in nitrogen gas mixtures were prepared by gravimetry and verified with gas chromatography-atomic emission detector (GC-AED) against a KRISS reference cylinder. The gravimetric values of the amount of substance fractions were adopted as key comparison reference values (KCRVs). The results of 9 participants are consistent with their KCRV. Therefore, it is possible for this key comparison to offer a good traceability and a harmonization among the global distribution data of H2S.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Enhancement of hardness of low alloy steel after low temperature plasma nitriding

The present work is focused on the plasma assisted nitriding of martensitic stainless steel at low temperature. Sample coupons of dimensions 8 × 8 × 6 mm3 were cut from the hardened and tempered steel sheet. Following grinding and mirror polishing samples were placed inside the chamber. At a low temperature of 460 °C (±10) nitriding was performed in the plasma generated by nitrogen and hydrogen gas mixture, Nitrided samples were then subjected to hardness measurements. The structural characterization was followed by X-ray diffraction (XRD) studies for the phase analysis. It was shown that even at a low temperature the surface modifies to high hardness for the improved tribological properties.

Synthesis and characterization of carbon nanotubes over hollow glass microspheres and its nanocomposites

Hollow Glass Microspheres (HGM) is now challenging reinforcement for making low density composites with high stiffness, good electrical and mechanical properties. Carbon nano tubes when reinforced homogenously in the matrix it enhance properties of the composites to a commendable range. These CNTs are grown over HGM using chemical vapor deposition (CVD) technique at 600 °C temperature. Initially HGM were nickel coated by electroless deposition technique using nickel sulphate as the source of metal in the alkaline bath and then the catalyst coated HGMs were exposed to the mixture of acetylene and nitrogen gas at various temperatures to form CNT over HGM. Scanning Electron Microscopy (SEM) images explore the quality and dimensions of CNT. Other characterizations such as XRD, Raman Spectroscopy confirm the presence of CNT. Using these coated HGM as fillers in Epoxy, composites were fabricated and the same was characterized for compression using UTM and DMA using DMA analyzer.

High performance sodium-ion battery anode using biomass derived hard carbon with engineered defective sites

Defective hard carbons are deliberated as promising candidates for sodium-ion battery (SIB) anodes of this decade. Recently, several groups have discussed the structure-property correlation which correlates the slope capacity in charge/discharge profile curves to the binding of sodium-ions on the structural defective sites of the hard carbon. In order to validate these correlations, herein we report for first time the preparation of defective hard carbon materials from Borassus flabellifer male inflorescence via controlled thermal activation process using Nitrogen (N2) and Carbon dioxide (CO2) gas mixtures and its subsequent usage as anode material in sodium-ion battery. When used as sodium-ion battery anode, the prepared hard carbon displayed outstanding reversible discharge/charge capacities of 413/358 mAh g−1 and superior initial capacity retention of 86.6%, which is the highest ever reported value to date alongwith a overwhelming cycling stability. The notable improvements can be correlated to the broken edges present in the hard carbon surface as well as the randomly distributed micro-nano structured pores in the system as revealed by the morphological characterizations. Thus, the reported research work paves way in developing novel low cost and high performance micro-nano structured defective hard carbon anode materials for Sodium-ion batteries.

Increase of the technogenic and ecological safety of the natural gas transportation due to displacement of explosive mixtures with nitrogen

Purpose: To ensure technological and environmental safety it is proposed to use the technology of purging pipeline with compressed nitrogen. Design/methodology/approach: The purpose of the calculation is: to get the graph of the concentration distribution (in volume fraction) of nitrogen and natural gas components depending on the distance from the injection point of nitrogen and the duration of the purge process, to determine of parameters of a non-stationary process, and to establish the optimal parameters of the purging process under conditions of the given flow chart. Findings: In the process of displacement of natural gas, the velocity of the front of nitrogen is one of the main quantities that significantly affect the quality of displacement. To assess the actual technological schemes for transporting natural gas, it is necessary to select the velocity of displacement of explosive mixtures. Research limitations/implications: This technology should be implemented in the conditions of a nitrogen pressure higher than 0.25 MPa. Practical implications: Most favourable conditions for the complete displacement of air and subsequent replacement of nitrogen with natural gas were observed for pressures higher from 1.0 to 1.5 MPa. Originality/value: Complex calculations of the volume of air displaced with nitrogen and natural gas in the process of filling the pipeline were conducted in the research. Boundary conditions on the concentration of the mixture of nitrogen and natural gas were identified.

Towards Green Ammonia Synthesis through Plasma‐Driven Nitrogen Oxidation and Catalytic Reduction

AbstractAmmonia is an industrial large‐volume chemical, with its main application in fertilizer production. It also attracts increasing attention as a green‐energy vector. Over the past century, ammonia production has been dominated by the Haber–Bosch process, in which a mixture of nitrogen and hydrogen gas is converted to ammonia at high temperatures and pressures. Haber–Bosch processes with natural gas as the source of hydrogen are responsible for a significant share of the global CO2 emissions. Processes involving plasma are currently being investigated as an alternative for decentralized ammonia production powered by renewable energy sources. In this work, we present the PNOCRA process (plasma nitrogen oxidation and catalytic reduction to ammonia), combining plasma‐assisted nitrogen oxidation and lean NOx trap technology, adopted from diesel‐engine exhaust gas aftertreatment technology. PNOCRA achieves an energy requirement of 4.6 MJ mol−1 NH3, which is more than four times less than the state‐of‐the‐art plasma‐enabled ammonia synthesis from N2 and H2 with reasonable yield (>1 %).

Distributionally Robust Hydrogen Optimization With Ensured Security and Multi-Energy Couplings

Power-to-gas (P2G) can convert excessive renewable energy into hydrogen via electrolysis, which can then be transported by natural gas systems to bypass constrained electricity systems. However, the injection of hydrogen could impact gas security since gas composition fundamentally changes, adversely effecting the combustion, safety and lifespan of appliances. This paper develops a new gas security management scheme for hydrogen injection into natural gas systems produced from excessive wind power. It introduces four gas security indices for the integrated electricity and gas system (IEGS) measuring gas security, considering the coordinated operation of tightly coupled infrastructures. To maintain gas security under an acceptable range, the gas mixture of nitrogen and liquid petroleum gas with hydrogen is adopted to address the gas security violation caused by hydrogen injection. A distributionally robust optimization (DRO) modelled by Kullback-Leibler (KL) divergence-based ambiguity set is applied to flexibly control the robustness to capture wind uncertainty. The KL divergence-based ambiguity set defines uncertainties within a measured space which limits the shape of probability distributions. Case studies illustrate that wind power is maximally utilized and gas mixture is effectively managed, thus improving gas security and performance of IEGS. This work can bring many benefits: i) ensured gas security under hydrogen injection ii) low system operation cost and iii) high renewable energy penetration. It can be easily extended to manage injections of other green gases into IEGS.

Defined purge gas composition stabilizes molten nitrate salt - Experimental prove and thermodynamic calculations

Thermal energy storage systems are integrated in concentrating solar power plants to improve the flexibility of the electricity generation. Commonly, the liquid storage material Solar Salt, a nitrate salt mixture, is applied to transport and store solar thermal energy. The lifetime and the temperature range of Solar Salt in the storage units are restricted by decomposition reactions of the material. Oxide ion formation is one of the fundamental issues. So far, it has not been proven if oxide ion formation can be prevented by addition of gaseous reaction products to the gas atmosphere. Also, a reliable reaction equation for the oxide ion formation is missing. In the presented experiments, molten salt at 600 and 620 °C is purged with a gas mixture of nitrogen, oxygen, and nitrous gases. Post-analysis of salt samples reveals stabilizing effects, depending on the purge gas compositions. Chemical equilibrium of the oxide ion forming reaction is demonstrated. It is proven that oxide ion formation can be controlled and suppressed. Reaction equations are evaluated and selected in order to quantify the reaction thermodynamics. The results contribute to recommendations for operating conditions and gas handling in storage systems of solar thermal power plants, which finally ensure reliable and constant material properties for extended lifetime and high temperatures.

Stability Boundaries of Discharges Generated in the Focal Region of a CW Microwave Beam

Plasma was generated in the focal region of a multikilowatt, 4.7-GHz continuous-wave (CW) microwave beam far removed from the walls of the vacuum chamber, minimizing the nonideal effects associated with plasma–wall and beam–wall interactions. Experiments were conducted with gas mixtures of argon, nitrogen, and oxygen at gas pressures ranging from 100 to 200 mtorr. Three types of discharges were observed during these experiments: unstable, quasi-stable, and stable discharges. It was determined that the stability of the discharges could be controlled through adjustments of the gas composition, gas pressure, and power of the microwave beam. This article reports on the operational conditions in which stable discharges were achieved and the general behavior of these discharges as the control parameters were varied.

Multi-objective optimization of Pulsed direct current magnetron sputtered titanium nitride thin film using Grey relational analysis

Titanium nitride coatings are extensively adopted as an intermediate adhesion layer in the cutting tools because of its superior mechanical properties. The interdependence of each process parameter during the deposition of such a coating process is nonlinear, and hence, it becomes a challenge to determine the output responses without carrying out a wide range of experiments. So to minimize the experiments, Taguchi-based L9 design of experiments were employed in this study with three factors and three levels such as Argon (Ar): Nitrogen (N2) gas mixture, Pulsed direct current power, and deposition time for depositing titanium nitride thin films on silicon (100) and tungsten carbide substrates using Pulsed direct current magnetron sputtering technique, where conventional direct current magnetron sputtering cannot be deployed using titanium nitride target. Multiple output responses such as average thickness, surface roughness, nano-hardness, Young’s modulus, wear track deformation, and coefficient of friction were measured by carrying out the systematic investigations, and a single optimum solution was obtained using Grey relational analysis. From the Grey relational analysis, the optimum Ar:N2 gas flow mixture, Pulsed direct current power, and deposition time for improved titanium nitride adhesion layer are 300 W, 10:5 sccm, and 5 min, respectively. Further, grazing incidence x-ray diffractometer profiles of deposited films exhibits (111) and (200) reflections corresponding to the titanium nitride phase, and the morphological analysis also revealed the existence of strongly faceted nano-grains with a triangular-shaped morphology.

Modeling of nitrogen and oxygen gas mixture with a novel diatomic kinetic model

Practical applications involve flows that often have more than one constituent. Therefore, the capability to model a gas mixture flow is important. Extending kinetic model equations of the Bhatnagar–Gross–Krook type from a single-species gas to multi-species gas mixtures presents a number of important challenges. This challenge is further pronounced when diatomic gas mixtures are considered due to the addition of internal energy modes. In this paper, a novel diatomic binary mixture model with separate translational, rotational, and vibrational temperatures is derived. The species drift-velocity and diffusion are considered by introducing separate species velocities and accounting for their relationship. The derivation is detailed as a logical build-up with a multi-step approach from a diatomic model for a single gas, known in the literature. Transport properties are obtained through the Chapman–Enskog type expansion. The diatomic mixture model is numerically evaluated for a gas mixture of nitrogen and oxygen. The model is validated against Monte Carlo results for normal shocks, showing good agreement for species density and temperature profiles. A parametric study demonstrates the variation in flow properties for different Mach numbers, vibrational collision numbers, and concentrations. Interesting results for the mixture properties are shown when the physics of the flow is discussed in greater detail. The effect of the different levels of vibrational excitation in the different species emphasizes the importance of modeling the flow as a mixture. The newly introduced diatomic gas mixture model demonstrates promising computational results for relevant applications.

A new concept for generating mechanical work from gas permeation

Large amounts of energy are available from gas concentration gradients in thermal power plant exhaust. For example, the energy potential of carbon dioxide and water vapor gradients from flue gas and cooling towers of coal-fired and natural gas-fired power plants represents 1–2% of the plant's overall capacity. In this paper, we introduce a novel membrane-based gas permeation process for using concentration gradients of gas mixture to generate useful mechanical work in the form of compressed gas flow. The concept is experimentally validated using a simple binary gas mixture of nitrogen and water vapor with commercially available polydimethylsiloxane membranes. Power density from water vapor flux of 57 mW/m2 and power density from net gas flux of 11.5 mW/m2 are observed under relatively conservative laboratory test conditions. Fundamental transport dynamics are modelled and used to simulate the response of the system to membrane properties and feed concentrations, and up to 600 mW/m2 is reported for the cases considered. The possibility of recovering energy from exhaust gases may open up new opportunities for improving power plant efficiency and sustainability.

Modeling viscosity of methane, nitrogen, and hydrocarbon gas mixtures at ultra-high pressures and temperatures using group method of data handling and gene expression programming techniques

Accurate gas viscosity determination is an important issue in the oil and gas industries. Experimental approaches for gas viscosity measurement are time-consuming, expensive and hardly possible at high pressures and high temperatures (HPHT). In this study, a number of correlations were developed to estimate gas viscosity by the use of group method of data handling (GMDH)-type neural network and gene expression programming (GEP) techniques using a large data set containing more than 3000 experimental data points for methane, nitrogen, and hydrocarbon gas mixtures. It is worth mentioning that unlike many of viscosity correlations, the proposed ones in this study could compute gas viscosity at pressures ranging between 34 and 172 MPa and temperatures between 310 and 1300 K. Also, a comparison was performed between the results of these established models and the results of ten well-known models reported in the literature. Average absolute relative errors of GMDH models were obtained 4.23%, 0.64%, and 0.61% for hydrocarbon gas mixtures, methane, and nitrogen, respectively. In addition, graphical analyses indicate that the GMDH can predict gas viscosity with higher accuracy than GEP at HPHT conditions. Also, using leverage technique, valid, suspected and outlier data points were determined. Finally, trends of gas viscosity models at different conditions were evaluated.

Influence of Acetylene on Ti Target Poisoning During Pulse-Enhanced Vacuum Arc Evaporation

Vacuum arc evaporation is a prospective technique to fabricate hard and wear material due to its high ion energy and plasma density. Nevertheless, target tends to be poisoned by the compound layer in common reactive gases such as acetylene. Then the coating deposition rate and the properties of the coatings would be strongly influenced. Thus, the formation of the compound layer has to be inhibited. Previous studies pointed out the potential of pulse-enhanced vacuum arc evaporation mode for inhibiting the formation of the compound layer. Within the presented study, motion of group spots (GSs), optical emission spectra, and substrate current based on PEVAE mode were examined entirely. The result shows that the area ratio of the compound layer in the target was decreased from about 75% to 42%. The ionization degree of titanium and mean substrate current could be substantially increased by up to 40% and 100%, respectively, in a mixture gas of nitrogen and acetylene due to larger plasma density indicated by higher spectra intensity of plasmas. All of the above made PEVAE prospective candidate to inhibit the formation of the compound layer. Beyond this PEVAE would lead to higher coating rate and denser coating in nitrogen plus acetylene atmosphere.

Preparation of TiO2/Fe3O4 composite by sol-gel method and its photocatalytic activity for removal of Rhodamine B from water

The TiO2/Fe3O4 composite is a new kind of photocatalytic materials with magnetism. Using FeCl2, FeCl3, and titanyl sulfate as the main raw material, TiO2/Fe3O4 was synthesized by sol-gel process and 450 °C calcination for 2 h under a condition of hydrogen nitrogen mixture gas. The samples were characterized by powder X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The photocatalytic activity, reclaim and cyclic utilization of the TiO2/Fe3O4 composite were studied by using Rhodamine B as simulated wastewater. The results show that TiO2/Fe3O4 composite has good magnetic properties and excellent photocatalytic activity for removal of Rhodamine B from water, and it can come true well reclaim and recycling by using the electromagnet. The recovery efficiency of TiO2/Fe3O4 composite can reach above 90% at the first reclaiming. TiO2/Fe3O4 composite can be reused tree times without a significant photoactivity loss. It shows that TiO2/Fe3O4 composite is a kind of environmental photocatalyst with a wide application prospects.

Effect of electrical discharge power on mechanical properties of N-DLC films deposited by atmospheric DBD plasma

Abstract At atmospheric pressure, dielectric barrier discharge of a mixture of nitrogen gas and n-hexane solution has been used to deposit N-DLC films on Pyrex glasses. The composition and the structure of the deposited films have been studied by FTIR and Raman spectra. The surface morphology of films is performed by analyses of FESEM, EDX, and AFM. According to the results of Raman spectra, the ID/IG ratio has been decreased, FWHM of G peak has been increased and the G peak position has been moved to lower wavenumbers. Based on obtained results, increasing electrical discharge power leads to increasing sp3 content and structural transition from the graphitized to amorphous structures. The sp3 content is related to C–H, C–C, and C–N bonds. With the more formation of C–C and C–N bonds than C–H bonds, mechanical properties of hardness and scratchability are strengthen while more increment of C–H bonds in the deposited films compared to two other bonds leads to decrease these properties. Discharge power increment leads to the changing of the adhesion strength as another the mechanical property due to the variation of the hydrogen content, the surface bonding rate, and penetration of the species to the substrate.

Effects of plasma nitriding on low alloy Cr-Mo-V steel

Abstract In this study the effects on resistance to corrosion of a low alloy steel after plasma nitriding has been reported. Nitriding was performed at a low temperature of 450 °C and also at 520 °C for the same duration of 10 h in the plasma of nitrogen and hydrogen (80:20) gas mixture. Sample holder was biased at −250 V and the working pressure was kept at around 500 Pa. After nitriding the steel samples along with the bare steel were exposed to X-ray diffraction (XRD) to understand the phase formation. For the assessment of corrosion resistance properties potentiodynamic polarization tests of the bare and plasma nitrided steels in 3.5% NaCl electrolyte were performed. Nitriding at 520 °C had shown the best corrosion resistance. However, broad passivation region had been shown after nitriding at 450 °C.

THE EFFECT OF RATIO OF GAS MIXTURE FOR MECHANICAL PROPERTIES AND CRYSTAL STRUCTURES ON 316L STAINLESS STEEL BIOMATERIAL USING DC SPUTTERING TECHNIQUE

316L stainless steel is widely used as an orthopedic implant due to its high corrosion resistance and biocompatibility, but the weakness of these materials is low hardness and high wear. The surface must be modified to improve the material. For the purpose, a titanium nitride (TiN) thin film was deposited on the surface of SS 316L using DC sputtering technique. The sputtering process was carried out for various of a gas mixture of argon (Ar) and nitrogen (N2) such as 90 Ar: 10N2, 80 Ar: 20 N2, 70 Ar: N2, and 60 Ar: 40 N2, while the other parameters kept constant. The objective of the gas mixture variation is to find out the optimum condition of ratio Ar: N2 gas mixture with the highest hardness and lowest wear resistance. From experiment done it’s found that the highest hardness in order of 232.02 VHN, while before being coated the hardness is 133.61 VHN, or there is an increasing hardness by factor 1.73, while the wear resistance reduces from 11.6 × 10-8 mm2/kg to 1.17 × 10-8 mm2/kg or there is reducing in wear resistance by factor 9.9. The optimum conditions were achieved at Ar: N2 ratio = 70:30. From XRD analysis, it can be concluded that the crystal structure of TiN thin film is cubic with the peaks (111), (200), (202), (311) and (222). From cross-section microstructure analysis using Scanning Microscope Electron (SEM), it’s found the thickness of the thin film is 744 nm.

Control of electron beam energy-spread by beam loading effects in a laser-plasma accelerator

We present experimental results from a laser wakefield electron accelerator driven by 70 TW ultrashort laser pulses in Helium and Helium–Nitrogen gaseous plasmas with two different Nitrogen concentrations, showing distinct electron-beam qualities. In order to get a clear view of the involved phenomenon, two-dimensional particle-in-cell simulations are performed which not only agreed with the experimental results but also provided an investigation on the evolution of accelerating structures. The experimental and simulation results depict that the beam loading effect can strongly modify the longitudinal accelerating electric field of the wake wave, imposing diametrically opposite effects on the final electron-beam qualities, especially the energy-spread, in the Helium–Nitrogen gas mixtures with different Nitrogen concentrations. In the Helium–Nitrogen-mixed plasma with a lower Nitrogen concentration (0.5%), if appropriately controlled, the beam loading effect can be employed to flatten the accelerating electric field for reducing the electron-beam energy spread. In contrast, in the Helium–Nitrogen-mixed plasmas with a higher Nitrogen concentration (5%), the accelerating electric field of the wake is locally reversed by the self-fields of the overloaded electron bunch, and the correspondingly generated negative-slope region of electric field increases the electron-beam energy-spread.

Functionalization ratio of isocyanate groups on plasma-processed multiwalled carbon nanotubes

This article reports the functionalization ratio of isocyanate (NCO) groups on multiwalled carbon nanotubes after exposure of plasma, which was generated with the gas mixture of nitrogen and carbon dioxide. The ratio was derived from measurements with an organic fluorescence, so-called acridine yellow G (AYG), which identifies the modified groups on carbon nanotubes (CNTs). First, the authors made several microscopic observations with the fluorescence. The observation showed that the fluorescence was especially intense from the area where small-sized CNTs exist, indicating that plasma-treated CNTs have more NCO density in small size than in large size. Second, the authors made a size selection on the CNTs with centrifugal forces and investigated the ratio of the groups over the total number of carbons in the CNTs to confirm the first observation and indication. This second investigation showed that the ratio increases as the degree of centrifugal force increases, i.e., the size of the nanotubes gets smaller, supporting the authors’ first microscopic observation. The authors also took the diameter distributions of the CNTs with an observation of an electron microscope, which proved that the centrifugation decreases the size distribution of the CNTs. As a result of overall experiments, the small diameter of plasma-processed CNTs has more NCO number density than the large diameter of the nanotubes in functionalizing isocyanate groups with the plasma.