Nitrogen-hydrogen Mixture Research Articles

Perspectives and Recent Progresses on the Simulation of the Entry into the Atmospheres of the Outer Ice Giants

The relatively recent decision of NASA and ESA to plan new missions to the so-called Ice Giants, namely Uranus and Neptune, has prompted a resurgence of interest in the experimental analysis of the aero-heating environment that probes entering such atmospheres would experience. In the present study, arc-jet facilities, previously used to simulate space flight in the atmospheres of Earth, Mars, and Titan, are considered as a relevant basis for the implementation of a more complex framework adequately accounting for the atmospheric features of the Ice Giants. It is shown that the key to the successful realization of such an endeavor is a new operating mode for the plasma torch (relying on a nitrogen–hydrogen mixture) together with the inclusion of a new gas control unit, a new mixing chamber to generate relevant gas mixtures (mimicking to a sufficient extent the Ice Giants atmosphere) and a new thermo-chemical model of the overall flow process. The outcomes of some initial tests are presented to demonstrate the adequacy and performances of the implemented approach with respect to typical entry conditions related to these two planets.

Influence of Post Processing on Thermal Conductivity of ITO Thin Films

This work presents the influence of post processing on morphology, thermal and electrical properties of indium tin oxide (ITO) thin films annealed at 400 °C in different atmospheres. The commercially available 170 nm thick ITO layers deposited on glass were used as a starting material. The X-ray diffraction measurements revealed polycrystalline structure with dominant signal from (222) plane for all samples. The annealing reduces the intensity of this peak and causes increase of (221) and (440) peaks. Atomic force microscopy images showed that the surface morphology is typical for polycrystalline layers with roughness not exceeding few nm. Annealing in the oxygen and the nitrogen-hydrogen mixture (NHM) changes shapes of grains. The electrical conductivity decreases after annealing except the one of layer annealed in NHM. Thermal conductivities of annealed ITO thin films were in range from 6.4 to 10.6 W·m-1·K-1, and they were higher than the one for starting material-5.1 W·m-1·K-1. Present work showed that annealing can be used to modify properties of ITO layers to make them useful for specific applications e.g., in ITO based solar cells.

Feasibility of Extremely Heavy Lift Hot Air Balloons and Airships

State of the art airships and aerostats (air vehicles) use hydrogen and helium as lifting gases. Hydrogen is extremely flammable, while helium is rare and expensive. In the present work, feasibility of air vehicles using hot air, hot nitrogen, and/or hot mixture as lifting gases is demonstrated. Thermal power requirements for air vehicles using hot lifting gases are calculated. 1) It is shown that for extremely heavy aerial vehicles, whose gross takeoff mass exceeding 3,000 tons, required thermal power is proportional to 1/3 Mvehicle where Mvehicle is an air vehicle mass. 2) For lighter aerial vehicles, whose gross takeoff mass is below 100 tons, required thermal power is proportional to 2/3 Mvehicle . Specific thermal power requirement is low for extremely heavy vehicles and high for light vehicles (For 1000 ton gross takeoff weight, specific thermal power requirements are from is 41 W/ kg to 52 W/kg). 3) Using hot nitrogen and/or nitrogenhydrogen mixture decreases thermal power requirements by 10% to 24%.

The effect of sintering aids on BaCe0·7Zr0·1Y0.1Yb0.1O3-δ as the electrolyte of proton-conducting solid oxide electrolysis cells

Proton-conducting solid oxide electrolysis cells (H-SOECs) are attracting attentions of researchers due to their unique advantages. The proton-conducting material BaCe0·7Zr0·1Y0.1Yb0.1O3-δ (BZCYYb) has both the advantages of barium ceria-based and barium zirconate-based materials. BZCYYb material usually is synthesized by solid-state reaction (SSR) method, hence the densification of this electrolyte material is the key to restrict the application of H-SOECs. In this paper, effects of adding 1 wt% of different sintering aids (NiO, CuO, ZnO) to BZCYYb on the grain size and the conductivity are investigated. After adding 1 wt% of NiO and CuO sintering aids, BZCYYb electrolyte achieves ideal density. The electrical conductivity of four samples (BZCYYb without adding sintering aid, BZCYYb with 1 wt% NiO, CuO, ZnO, respectively) is tested under different steam concentrations of air, nitrogen, hydrogen, and nitrogen-hydrogen mixture. The conductivity increased after the sintering aid is added. With the increase of steam concentration, the conductivity decreased slightly and then increased due to electron holes under oxygen atmosphere with steam at high temperature. In other atmospheres, the conductivity increases with the steam concentration. In the atmosphere of 20 vol% H2O-Air and H2, the conductivity of the BZCYYb samples with 1 wt% CuO is about 1.087 × 10−2 S cm−1 and 9.02 × 10−3 S cm−1 at 650 °C, and the conductivity of the BZCYYb samples with 1 wt% NiO is 1.277 × 10−2 S cm−1 and 8.24 × 10−3 S cm−1, respectively. However, compared with NiO, CuO has advantages in promoting hydration reaction and proton conduction of BZCYYb electrolyte.

Time-resolved fourier transform infrared emission spectroscopy of NH radical in the X3Σ− ground state

The NH radical is an extremely important specie in nitrogen chemical reaction networks, in the interstellar medium and atmospheric chemistry. Time resolved Fourier transform spectroscopy technique in the frequency range 10–13 µm has been applied for the measurement of a pure rotational spectrum of the NH free radical (NH) in the ground X3Σ− electronic state. Twelve high N (26–29) triplet-resolved pure rotation lines of NH were experimentally observed in the laboratory and compared with satellite ACE (Atmospheric Chemistry Experiment) solar data. In addition, discharge-generated vibration-rotation NH radical bands in the spectral range 1923–3571 cm−1 have been measured with a microsecond time resolution and spectral resolution of 0.02 cm−1. The spectra of the NH radical have been studied in two experimental arrangements. Firstly, in a pulsed positive column discharge of pure hydrogen-nitrogen mixture and secondly, in a discharge of nitrogen-ammonia mixture in the presence of argon buffer gas. Both production methods are described and compared. The population analysis of the experimental spectra was performed via modelling using the accurate MoLLIST line lists for NH. It was shown that laboratory data can be well reproduced by use of a mixture of the local-thermal-equilibrium (LTE) and non-LTE models corresponding to high temperatures (up to 8000 K and up to 6000 K rotational).

Modelling of Switching Characteristics of Hydrogen-Nitrogen Filled DC Contactor Under External Magnetic Field

<div class="section abstract"><div class="htmlview paragraph">The electric or hybrid vehicles need fast switching operation in order to ensure the quick-response of the motors. This process is carried out by compact direct-current contactors which are designed to perform the switching over multiple cycles. During the contact separation, the gas between the contacts breaks down and the resulting thermal arc provides a conductive channel that sustains the current. Until the arc is quenched, the current continues to flow through the contacts despite the physical separation. This unintended flow of current could lead to a larger response time than the safe operation limits. We perform high-fidelity simulation of thermal arc in hydrogen-nitrogen mixture environment under external magnetic field of 1 Tesla. The hydrogen enrichment level is kept at 0%, 40%, 50% and 80%. The contacts are separated at 8 m/s. It is demonstrated that the increase in hydrogen concentration leads to smaller arc lifetime thereby improving the circuit interruption performance.</div></div>

Current generation in Pd/InP structures in hydrogen medium

The current generation mechanism in Pd/InP Schottky diodes has been studied in the range of 90-300 K in vacuum, hydrogen-nitrogen mixture of concentration from 4 to 100 vol.%, and under illuminating of the structures by LED with the wavelength of 0.9 μm, corresponding to the absorption edge in InP. It was shown that at low temperature (T=90 K) I-V characteristics of the structures in vacuum have rectifying character with the barrier height of 130-150 meV. In hydrogen-nitrogen medium the barrier height decreases almost to zero with increasing the temperature to 300 K due to palladium work function decreasing. It was demonstrated that under simultaneous impact of illumination (λ=0.9 μm) and hydrogen-nitrogen mixture there are two opposite directed electron flows in the structures, one of which is related to the LED illumination and the other one to hydrogen absorption in palladium layer. Keywords: palladium, Pd/InP, hydrogen, work function, potential barrier.

Homogenizing role of hydrogen in the synthesis of multicomponent Carbohydrides and Nitridohydrides of transition metals in the combustion mode

This work presents the results of study of combustion with carbon of transition metals of IV, V and VI groups of the periodic system in atmospheres of argon, hydrogen, nitrogen and nitrogen-hydrogen mixture. The significance of hydrogen in the formation of single-phase products in the self-propagating high-temperature synthesis (SHS) mode was underlined. The combustion of carbon containing systems in argon resulted in the synthesis of two-phase carbides with FCC lattice. In contrary, the combustion of the same systems in hydrogen atmosphere leaded to the synthesis of single-phase carbo-hydrides. The products of combustion of transition metals in nitrogen atmosphere were the multiphase nitrogen-containing compounds. Their following re-ignition in hydrogen leaded to the synthesis of single-phase nitrido-hydrides. It was demonstrated that in all the studied systems, the combustion in hydrogen atmosphere leaded to the homogenized final synthesis products. The results of these processes were the formation of single-phase carbo- and nitrido-hydrides based on the metals of IV, V and VI groups. The presence of hydrogen in the crystal lattice of synthesized refractory carbides and nitrides facilitated easy dispersion of the compound to submicron sizes. After removal of hydrogen, the single phase structure was not violated. The described results may be of commercial value in the industry of refractory materials.

Evaluation of Corrosion Resistance of Thin Films Formed on AISI 316L Steel by Plasma Using Hastelloy as Cathodic Cage

Herein, the use of Hastelloy C‐276 as a cathodic cage for the deposition of thin films on the AISI 316L steel substrate by plasma is investigated. The films are processed through floating potential at 350, 375, 400, and 425 °C for 4 h, using a hydrogen–nitrogen mixture in the proportion of 40% and 60%, respectively. The thin films are investigated by X‐ray diffraction, scanning electron microscopy, Raman spectroscopy, and potentiodynamic polarization. The spectroscopy results point out the formation of different phases such as FeNi3, CrNi, and MoN1/2. Films acquired at 375 ºC present superior corrosion resistance with less negative corrosion potential (−0.020 V). The increase and decrease in FeNi3 and CrNi contents follow the improvement of the applied temperature, which is unbeneficial to the corrosion resistance of the films.

Simulation and Experimental Analysis of DC Arc Characteristics in Different Gas Conditions

The structures of high-voltage direct current (HVDC) relays are compact. In order to extinguish the arc, the external magnetic field is applied near the contact. HVDC relays with a large capacity are also filled with gas medium to enhance the ability of arc extinguishing. The research on the characteristics of the arc in different gases under different pressures is of great significance to improve the reliability and the lifetime of the HVDC relays. The characteristics of the arc in nitrogen, hydrogen, and nitrogen–hydrogen mixtures and that of the arc root motion in the magnetic field are simulated by means of magnetohydrodynamics (MHD). The arcing processes in N2 and air are tested by a high-speed camera, and the arc root coordinates are calculated by the image processing method, and the simulation models are verified. The result shows that under the same condition, the hydrogen arc voltage is the highest, and the moving speed of the arc root is the fastest, so that the arc extinguishing performance of the hydrogen is the best. Nitrogen–hydrogen mixture is also a superior arc extinguishing gas, and the higher the proportions of H2, the better the performance. With the increase of the pressure, arc voltage increases. Except H2, increasing the pressure of the gas is beneficial for arc motion.

Генерация тока в структурах Pd/InP в атмосфере водорода

The current generation mechanism in Pd/InP Schottky diodes has been studied in the range of 90−300K in vacuum, hydrogen-nitrogen mixture of concentration from 4 to 100 vol.%, and under illuminating of the structures by LED with the wavelength of 0.9 μm, corresponding to the absorption edge in InP. It was shown that at low temperature (T = 90K) I−V characteristics of the structures in vacuum have rectifying character with the barrier height of 130−150meV. In hydrogen-nitrogen medium the barrier height decreases almost to zero with increasing the temperature to 300K due to palladium work function decreasing. It was demonstrated that under simultaneous impact of illumination (λ = 0.9 μm) and hydrogen-nitrogen mixture there are two opposite directed electron flows in the structures, one of which is related to the LED illumination and the other one to hydrogen absorption in palladium layer.

Study of silicon nitride deposition in III-N MOVPE reactors

Si3N4 deposition from silane and ammonia in a number of III-N MOVPE reactors of various sizes was studied in a wide range of reactor conditions. It was revealed that Si3N4 deposition rate depends on temperature, pressure, carrier gas type, and ammonia concentration. Deposition rate rises with temperature up to 1050–1100 °C in a manner typical for temperature-activated processes, but under any studied conditions, including the 800–850 °C range, it is strictly linear with SiH4 concentration indicating the absence of high-order parasitic reactions at high temperature and surface passivation at low temperature. For a low-volume reactor the higher the pressure is, the faster the deposition is both for N2 and H2 carrier gases. For large reactors the dependence is non-monotonic. At temperature above 900 °C using H2 as a carrier gas results in a higher Si3N4 deposition rate than when using N2. If nitrogen is used as a carrier gas, deposition rate gradually rises with ammonia concentration. If hydrogen is used, deposition rate rapidly rises with ammonia concentration and then gradually falls. If hydrogen-nitrogen mixture is used as a carrier gas, deposition rate changes in a linear manner with the mole fraction of hydrogen in the carrier gas.

Effect of H<sub>2</sub>/N<sub>2</sub> Mixtures on Reduction of Nickel Oxide

This paper describes the reduction of nickel oxide under different gas mixture. The influence of gas mixture on phase, density, morphology and pore size of reduced nickel oxide were studied. Nickel oxide pellets sintered at 1400 °C were reduced under various hydrogen-nitrogen gas mixtures, namely 40% H2-60% N2, 60% H2-40% N2, 80% H2-20% N2. Phase identification, density measurement and observation of morphology were conducted on samples before and after reduction process. Under all gas mixtures, nickel oxide was completely reduced to nickel. Density of the samples decreased in the range of 21% to 32% depends on H2 percentage used. Results from the density shows that the higher the H2 gas concentration, the smaller the density changes. Significant change in porosity of the sample before and after reduction was observed. Size of pore after reduction determined by H2 concentration used during reduction where the higher the H2 concentration resulted in large pore size.

Enhancement of heat- and mass-transfer processes in a metal-hydride flow-through hydrogen-purification reactor

A novel method is proposed to increase the effective thermal conductivity of a metal-hydride (MH) bed by incorporating highly conductive inclusions into it in the form of metal rods made from various materials. The volume fraction of the inclusions, which had a diameter of 0.5 mm and length of 5 mm, ranged from 0.01 to 0.1. The structure of the composite beds was modelled by a specially developed algorithm. The results of the numerical simulation revealed that the effective thermal conductivity of the composite beds increased by 1.44–2.93 times when the volume fraction of the inclusions was 0.1. To estimate the effectiveness of the proposed method, a case study of hydrogen purification from a hydrogen–nitrogen mixture was performed for the cylindrical flow-through MH reactor, with two MH bed types: without inclusions (base case) and with inclusions (volume fraction of 0.1). The alloy fraction saturated by hydrogen and the mass of absorbed hydrogen higher for an equivalent reactor size notwithstanding a 10% reduction in the alloy mass. Moreover, the hydrogen losses were comparable to those of the base case. At hydrogen breakthrough, the fraction of hydride saturated by hydrogen increased from 61.5% to 81%, and the amount of hydrogen absorbed increased by 18.7%. The described method for enhancing the heat- and mass-transfer in MH beds enables the purification of a significantly larger volume of hydrogen with an equivalent number of sorption/desorption cycles.

Computational study of magnetic field effects on the nozzle of hydrogen micro flame

Controlling combustion has been always a matter of interest to be exploited in combustion systems such as internal combustion engines. Experimentalists found that magnetic field has favorable effects on this phenomenon, applied either directly to the flame or the fuel nozzle. In the current work, the effect of magnetic field on the fuel nozzle of hydrogen-nitrogen mixture (30% hydrogen and 70% nitrogen by volume fraction) is investigated numerically to study the non-premixed flame shape, maximum temperature, maximum velocity, heat of reaction, and its emission including unburnt hydrogen. Magnetic field was applied on three sections of fuel line with various magnitudes. Magnetic field generates Lorentz force which brakes the fuel flow in the nozzle generating a converging-diverging shape resulting in the velocity increase in the center of the nozzle. It was found that the flame length decreased as the magnetic field increased when magnetic field applied to the tip-section of the nozzle, there was no change for the mid and initial sections though. The maximum flame temperature decreased marginally while the heat of reaction remained roughly unchanged. However, the maximum temperature was decreased due to the better heat transfer. Further, unburned hydrogen and OH decreased when the magnetic field applied to the nozzle exit. The results show that magnetic field application to the nozzle exit leads to a better mixing, and reduction in fuel consumption which is interpreted as more complete combustion.

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.

Особенности моделирования гидродинамических процессов топливоподачи при работе судового дизеля на водотопливной эмульсии

The article presents the results of mathematical modeling of the fuel supply process of a marine diesel working on diesel fuel and water-fuel emulsion with a water content of 30% as an alternative fuel. There have been found the specific features of fuel supply and the influence of the alternative fuel on the injection characteristics of standard fuel supply equipment during operation in nominal and partial modes. In evaluating the quality of fuel equipment operation on a water-fuel emulsion there were taken into account the following facts: changing of the fuel supply characteristics; changing injection parameters; type of fuel spraying in the initial and final phases of injection and reduction of fuel proportion supplied during the needle landing period; greater stability of successive injection cycles by increasing the active stroke of the plunger by 25-30%; features of injection processes due to thermal explosion effect. The telegraph equation for the unsteady fuel motion in a high pressure pipeline is obtained. The operation parameters of a marine diesel engine 6CHSPN2A 18/22 (DRA-300) are considered in nominal mode according to the screw characteristic for diesel fuel and water-fuel emulsion: plunger stroke of the high-pressure fuel pump; maximum pressure of the steady state in the connecting pipe; average integral pressure of the steady state in the nozzle, which determines the quality of spraying, the speed of landing of the sprayer needle on the saddle; amount of fuel supplied during the needle landing period; cyclic fuel supply; duration of the main injection; stability criterion of fuel supply processes in successive cycles, etc. It has been inferred that water-fuel emulsions can take a separate place in the list of alternative fuels, which will contribute to improving the quality of traditional fuels, productive burnout of hydrocarbon, nitrogen-hydrogen mixture, spirit mixtures, etc. due to the rational introducing additives into fuel, increasing the reliability indicators of cylinder-piston parts, etc.

Nickel catalysts for nitrogen–hydrogen mixture purification from carbon oxides

Objectives.This study is devoted to developing new-generation nickel (Ni) catalysts for the purification of a nitrogen–hydrogen mixture from carbon oxides, which should encompass the best qualities of the NIAP-07-series solid catalysts.Methods. This study used derivatographic and radiographic methods; temperature-programmed recovery, decomposition, and joint temperature-programmed decomposition and recovery; and low-temperature nitrogen adsorption (specific surface determination). The mechanical strength of catalysts was determined using an MP-2C device by crushing granules with an applied load on the end face. The chemical composition and catalytic activity were determined by the methods of TU 2178-003-00209510 Technical Conditions.Results.Many studies regarding Ni–aluminum (Al)–calcium (Ca) methanation catalyst at all stages of its preparation have been conducted. It is demonstrated that Ni hydrocarboxyaluminate, a precursor of the active component of the catalyst, is formed when Ni hydroxocarbonate is mixed with active alumina in the presence of an aqueous solution of ammonia, and its chemical formula is established. Moreover, it was found that the mechanical strength of the catalyst is determined by the amount of industrial Ca aluminate added to the Ni–Al composition. The compositions of catalysts with different contents of the active component have been optimized.Conclusions.The developed catalyst has a low activation temperature and high catalytic activity, thermal stability, and mechanical strength and is resistant to organic and alkaline carbon dioxide absorbers. The catalyst can be produced in the form of a ring, cylindrical tablets, and extrudates of various geometric sizes. The methanation unit at Stavrolen (Budennovsk, Stavropol krai, Russia) has begun commercially operating the catalyst.

Fabrication of Optimally Micro-Textured Copper Substrates by Plasma Printing for Plastic Mold Packaging

Micro-embossing using plasma printed micro-punch was proposed to form micro-groove textures into the copper substrate for plastic packaging of hollowed GaN HEMT-chips. In particular, the micro-groove network on the copper substrate was optimized to attain uniform stress distribution with maximum stress level being as low as possible. Three-dimensional finite element analysis was employed to investigate the optimum micro-grooving texture-topology and to attain the uniform stress distribution on the joined interface between the plastic mold and the textured copper substrate. Thereafter, plasma printing was utilized to fabricate the micro-punch for micro-embossing of the micro-grooving network into the copper substrate as a designed optimum micro-texture. This plasma printing mainly consisted of three steps. Two-dimensional micro-pattern was screen-printed onto the AISI316 die surface as a negative pattern of the optimum CAD data. The screen-printed die was plasma nitrided at 673 K for 14.4 ks at 70 Pa under the hydrogen-nitrogen mixture for selective nitrogen supersaturation onto the unprinted die surfaces. A micro-punch was developed by mechanically removing the printed parts of die material. Then, fine computer numerical control (CNC) stamping was used to yield the micro-embossed copper substrate specimens. Twelve micro-textured substrates were molded into packaged specimens by plastic molding. Finally, gross leak testing was employed to evaluate the integrity of the joined interface. The takt time required to yield the micro-grooved copper substrate by the present method was compared to the picosecond laser micro-grooving; the former showed high productivity based on this parameter.

Влияние водорода на импеданс структур Pd/оксид/InP

The impedance and capacitance properties of Pd/oxide/InP structures within the frequency range from 0.1 Hz to 10 kHz in air and in gaseous hydrogen–nitrogen mixture at 300 K have been studied. The characteristics of investigated structures can be characterized by parallel RC circuit model with the connected serial resistance. In hydrogen medium the active resistance of the structures decreases by 3 orders of magnitude and the capacitance increases by 1–3 orders of magnitude depending on frequency that is due probably to the positive charged centers formed in the oxide layer. In hydrogen medium the hysteresis has been found on CV-characteristics of the structures that may be explained by ion polarization of formed centers. It is shown that measured in electron units the full charge of the centers practically coincides with the quantity of hydrogen atoms absorbed by palladium.