Argon Oxygen Gas Mixture Research Articles

О НЕОБХОДИМОСТИ И ВОЗМОЖНОСТИ СНИЖЕНИЯ ВЛИЯНИЯ ЗАШУМЛЁННОСТИ В ЦЕЛЯХ МИНИМИЗАЦИИ ТРАВМАТИЗМА НА АВИАПРЕДПРИЯТИЯХ

Summary data on injuries in Russia and at civil aviation enterprises over the years of the current century are presented. Continuous reduction in injury rates has been shown. Significant actual factors of the working environment that contribute to occupational injuries have been statistically identified, one of the main ones being noisy workplaces. Exposure to noise has a negative impact on hearing and the functional state of the central nervous system thus reducing performance, leading to errors, and contributing to injuries. The possibility to counter the noise effects by otoprotection with an argon-oxygen gas mixture has been experimentally confirmed.

Corrosion-Resistant and Electrically Conductive Oxide Coatings for Metal Bipolar Plates for PEM Electrolyzers

The PEM electrolyzers are considered a promising alternative to alkaline water electrolyzers, as the advantages of PEM technology are high efficiency, high power density, a wide range of power inputs, low operating temperatures, relatively quick start-up, and easy scale-up. The ability of PEM electrolyzers to function dynamically makes them particularly appealing in energy capture and storage systems where electrical energy is derived from renewable sources such as solar and wind power. The bipolar plates (BPPs) are essential components of the PEM electrolyzer stacks and account for the main fraction of the total weight and cost. The BPPs must be electrically conductive, highly corrosion-resistant, and maintain a low interface contact electrical resistance (ICR). The root causes of the BPPs corrosion issues are non-conductive oxides formation increasing electrical resistance, and metal ions out-diffusion poisoning the catalyst and electrolyte membrane. The US Department of Energy has set targets for bipolar plates in fuel cells, including corrosion current densities < 1 µA/cm2 and ICR < 10 mΩ·cm2. Even though these targets do not apply to BPPs in PEM electrolyzers, they provide an indication of acceptable values. The problems outlined above are being overcome or minimized by applying corrosion-resistant and simultaneously electrically conductive coatings.This work, therefore, investigates various corrosion-resistant and electrically conductive oxide coatings prepared by reactive high-power impulse magnetron sputtering (HiPIMS) on SS316L substrates. Reactive HiPIMS is an advanced and progressive magnetron sputter deposition technique suitable for preparing high-quality oxide coatings. The main advantage of HiPIMS is a high degree of ionization of sputtered particles in the discharge plasma and the associated high ion-to-atom ratio in particle flux toward the substrate. This allows one to achieve coating densification and crystallinity at low substrate temperature and without applying a substrate bias voltage. In our case, the native oxide on the SS316L substrate surface was removed by employing plasma etching prior to the coating deposition utilizing HiPIMS-generated ions accelerated towards the substrate by an applied bias voltage. The oxide coatings were deposited using an unbalanced magnetron with a directly water-cooled planar target with a diameter of 100 mm in argon-oxygen gas mixtures at the argon pressure of 1 Pa in an ultra-high vacuum chamber. The oxygen partial pressure was controlled by a PID regulator at a given power density in a pulse. This allowed the deposition of the coatings with different stoichiometries and, thus, different electrical conductivity and corrosion resistance.The electrical resistivity of oxide coatings was measured by a four-point probe system on a non-conductive glass substrate. The compaction pressure dependence of ICR between the test plate and a gas diffusion layer (GDL) was measured in a range from 0.3 to 2.0 MPa on a custom-designed device using gold-coated cylindrical copper electrodes. All electrochemical measurements were performed in an H2SO4 electrolyte solution with an acidity of pH 5.5, fluorine ions concentration of 5 ppm, and a temperature of 60 ℃ to simulate the PEM electrolyzer environment. Accelerated corrosion tests were carried out in extreme anodic conditions of the PEM electrolyzer via potentiostatic polarization at a potential of 2 V vs SHE. Open circuit potential, corrosion current, Tafel slopes, and polarization resistance were determined from potentiodynamic polarization curves measured from 0 to 2 V vs SHE recorded at a scan rate of 1 mV/s, this range should cover most of the potentials experienced inside a PEM electrolyzer. Potentiodynamic polarization and ICR versus compaction pressure were measured before and after the accelerated corrosion test.

Investigation of the Effect of Vacuum and Air Annealing on the Structural, Optical and Electrical Properties of Radio Frequency Sputtered WO&lt;sub&gt;3&lt;/sub&gt; Thin Films

Thin films of tungsten oxide were deposited on glass substrates by the radio frequency (RF) reactive sputtering from a high purity tungsten metal target (99.9%) with a diameter of 10 cm. The reactive sputtering was carried out in an argon-oxygen gas mixture containing 20% of O2 and 80% of Ar. The used RF power is 200 W while fixing the deposition time at 120 min. Finally, the prepared films were annealed at different temperatures (350 °C, 400 °C, 450 °C, 500°C and 550 °C) for 1 hour under air and under vacuum. X-ray diffractograms showed that the deposited thin films crystallized in Hexagonal/Monoclinic WO3 phase. It was found that the crystallite size varies with the annealing temperature and the lattice parameters is a= 7.3064Å, b = 7.5292Å, c = 7.6875Å and a=b= 7.3242Å, c= 7.6624 Å, for h-WO3 and m-WO3 structures, respectively. Scanning Electron Microscopy (SEM), Raman spectra confirmed the formation of WO3 thin films. In addition, optical transmittance data revealed that the optical bandgap of the films decreases with increasing the annealing temperature. Electrical measurements revealed that annealing in air results in more resistive samples, which should be taken into account in future investigations, especially as buffer layers for efficient photovoltaic solar cells. Keywords: Vacuum, Tungsten oxide, Raman spectroscopy, RF Sputtering method, RF Power, Annealing temperature.

Investigation of Electrochromic, Combinatorial TiO2-SnO2 Mixed Layers by Spectroscopic Ellipsometry Using Different Optical Models.

We determined the optimal composition of reactive magnetron-sputtered mixed layers of Titanium oxide and Tin oxide (TiO2-SnO2) for electrochromic purposes. We determined and mapped the composition and optical parameters using Spectroscopic Ellipsometry (SE). Ti and Sn targets were put separately from each other, and the Si-wafers on a glass substrate (30 cm × 30 cm) were moved under the two separated targets (Ti and Sn) in a reactive Argon-Oxygen (Ar-O2) gas mixture. Different optical models, such as the Bruggeman Effective Medium Approximation (BEMA) or the 2-Tauc-Lorentz multiple oscillator model (2T-L), were used to obtain the thickness and composition maps of the sample. Scanning Electron Microscopy (SEM) with Energy-Dispersive X-ray Spectroscopy (EDS) has been used to check the SE results. The performance of diverse optical models has been compared. We show that in the case of molecular-level mixed layers, 2T-L is better than EMA. The electrochromic effectiveness (the change of light absorption for the same electric charge) of mixed metal oxides (TiO2-SnO2) that are deposited by reactive sputtering has been mapped too.

Multitarget Reactive Magnetron Sputtering towards the Production of Strontium Molybdate Thin Films

X-ray photoelectron spectroscopy was used to study the direct synthesis of strontium and molybdenum oxide thin films deposited by multitarget reactive magnetron sputtering (MT-RMS). Sr and Mo targets with a purity of 99.9% and 99.5%, respectively, were co-sputtered in an argon-oxygen gas mixture. The chamber was provided with an oxygen background flow plus an additional controlled oxygen supply to each of the targets. We demonstrate that variation in the power applied to the Mo target during MT-RMS enables the production of strontium and molybdenum oxide films with variable concentrations of Mo atoms. Both molybdenum and strontium were found in the oxidized state, and no metallic peaks were detected. The deconvoluted high-resolution XPS spectra of molybdenum revealed the presence of several Mo 3d peaks, which indicates molybdenum bonds in a lower valence state. Contrary to the Mo spectra, the high-resolution strontium Sr 3d spectra for the same samples were very similar, and no additional peaks were detected.

Effect of the RF-power and annealing on the structural, optical, morphological and electrical properties of RF-sputtered V2O5 thin films

Thin films of vanadium oxide were deposited on glass substrates by the radio frequency reactive sputtering from a high purity metallic vanadium target (99.7%) with a diameter of 10 cm. The reactive sputtering was carried out in an argon-oxygen gas mixture containing 10% of O2 and 90% of Ar. The films were deposited at different RF powers (150 W, 200 W, 250 W and 300 W) for a fixed deposition time of 150 min. X-ray diffractograms showed that the deposited thin films crystallized in an orthorhombic V2O5 phase. It was found that the crystallite size varies with the RF power and is maximized using 300 W as an RF power. Scanning Electron Microscopy and Raman scattering analyzes have confirmed the formation of V2O5 thin films. In addition, optical transmittance measurements were performed using a Shimadzu UV-PC spectrophotometer in the 220–2000 nm range. It was observed that the optical band gap of the films decreases with increasing the RF power. Electrical resistivity was found to decrease with increasing the RF power from 150 to 250 W, and then it increases.

Kinetics of Decarburization and Manganese Loss from Fe–15Mn–1C Alloy by Bubbling of Argon–Oxygen Gas Mixtures

Kinetics of Decarburization and Manganese Loss from Fe–15Mn–1C Alloy by Bubbling of Argon–Oxygen Gas Mixtures

Feasibility Synthesis and Characterization of Gadolinia Doped Ceria Coatings Obtained by Cathodic Arc Evaporation.

Gadolinia doped ceria coatings were elaborated by cathodic arc evaporation from a metallic Ce–Gd (90–10 at.%) target inserted into a conventional multiarc Ti evaporation target in the presence of a reactive argon–oxygen gas mixture. The structural and chemical features of these films were determined by x-ray diffraction and scanning electron microscopy. Their electrical properties were characterized using impedance spectroscopy measurements. It was shown that the as-deposited coatings crystallize in the fluorite type fcc structure of ceria and that their composition is the same as that of the target. The morphology of the coatings is influenced by the evaporation parameter (stress and droplet). The electrical measurements showed two contributions in Nyquist representation and the activation energy was slightly higher than that given in the literature data for the bulk material.

Direct and Indirect Bactericidal Effects of Cold Atmospheric-Pressure Microplasma and Plasma Jet.

The direct and indirect bactericidal effects of dielectric barrier discharge (DBD) cold atmospheric-pressure microplasma in an air and plasma jet generated in an argon-oxygen gas mixture was investigated on Staphylococcus aureus and Cutibacterium acnes. An AC power supply was used to generate plasma at relatively low discharge voltages (0.9–2.4 kV) and frequency (27–30 kHz). Cultured bacteria were cultivated at a serial dilution of 10−5, then exposed to direct microplasma treatment and indirect treatment through plasma-activated water (PAW). The obtained results revealed that these methods of bacterial inactivation showed a 2 and 1 log reduction in the number of survived CFU/mL with direct treatment being the most effective means of treatment at just 3 min using air. UV–Vis spectroscopy confirmed that an increase in treatment time at 1.2% O2, 98.8% Ar caused a decrease in O2 concentration in the water as well as a decrease in absorbance of the peaks at 210 nm, which are attributed NO2− and NO3− concentration in the water, termed denitratification and denitritification in the treated water, respectively.

Particle Modeling of Reflected Shock Waves

A direct simulation Monte Carlo based approach is proposed to model the planar shock-wave reflection in a shock tube. The approach is validated through comparisons with available time-dependent pressure and absorbance measurements of gas relaxation behind a reflected shock in an argon–oxygen gas mixture for incident shock velocities of . It is then used to model reacting airflows for velocities , with the primary focus on the flow evolution inside the boundary layer. The feasibility of using the reflected shock configuration for the evaluation of vibrational energy accommodation, as well as the gas-phase recombination reaction rate constants, is studied. Finally, low- and high- fidelity real gas effect models are used to assess the model impact on gas macroparameters under nonequilibrium conditions.

Modification of Zeolites Y and ZSM-5 adsorption of nanoparticles of transition metals from back-micellar solutions for separation of gas mixtures

On the basis of granular synthetic zeolites NaY, HY, and ZSM-5, adsorbents containing nanoparticles of silver, cobalt, molybdenum, and tungsten were obtained. The samples have a lower surface polarity in comparison with the initial zeolites, which is reflected in the selectivity of a number of samples with respect to argon. This is due to the fact that the argon molecule interacts with zeolites only through nonspecific forces. Modification was performed by interacting with reverse-micellar solutions of nanoparticles. The actual sizes of metal particles and their distribution over the surface of the modified samples of zeolites have been determined by the method of transmission electron microscopy. The samples’ equilibrium adsorption capacities for oxygen and argon (25°С and atmospheric pressure) and the separation coefficient of the argon–oxygen mixture as the ratio of Henry’s coefficients have been determined. It has been demonstrated that samples of the NaY zeolite modified with silver nanoparticles have the separation coefficient value of the argon–oxygen gas mixture equal to 1.6.

Feasibility Synthesis and Characterisation of Gadolinia Doped Ceria Coatings Obtained By Cathodic Arc Evaporation

The SOFC/SOEC community is now convinced that it is necessary to reduce the operating temperature of fuel cells to make the systems more robust, more reliable and thus to consider large-scale development. At the material level, the change of the reference electrolyte (YSZ) by a cerium compounds allows a significant performance gain for lower temperatures of use. It is obviously necessary to keep in mind the constraints related to the electrolyte application in solid electrolyte device, namely: good ionic conductivity unlike the electrical conductivity which must be low, electrochemical compatibility with the electrodes, be dense and covering on porous substrates.In this study, Gadolinia doped ceria coatings were deposited by cathodic arc evaporation from a metallic Ce-Gd (90/10 at%) target inserted into a conventional multiarc Ti evaporation target in the presence of a reactive argon-oxygen gas mixture. The structural and chemical features of these films were determined by X-ray diffraction and scanning electron microscopy. Their electrical properties were characterised using impedance spectroscopy measurements. It is shown that the as-deposited coatings crystallise in the fluorite type fcc structure of ceria and that their composition is the same than that of the target. The morphology of the coatings is influenced by the evaporation parameter (stress and droplet). The electrical measurements showed two contributions in Nyquist representation (figure1) and the activation energy is slightly higher than that given in the literature data for the bulk material.Figure 1 : Nyquist impedance plots of GDC coating, registered at 400°C, for two a.c. signal amplitudes. Logarithms of frequencies are indicated in the figure. Figure 1

Effect of argon and oxygen gas concentration on mode transition and negative ion production in helicon discharge

In this paper, the effect of mixing of argon and oxygen gas on the mode transition and negative ion production in the helicon discharge is investigated. In the source chamber of the experimental setup, argon–oxygen gas mixture plasma is produced by applying RF power from 100 W to 2000 W at an applied magnetic field of 0.03 T. In this experiment, the total flow rate is kept at 200 SCCM, corresponding to the working pressure of 4–5 × 10−1 Pa. The mode transition to helicon discharge is investigated by varying the concentration of these two gases. To the best of our knowledge, the literature survey indicates this to be the first study of the influence of the mixing of oxygen–argon gas on the mode transition from the inductive to the helicon mode. It is observed that an increase in the concentration of oxygen gas in the discharge shifts mode transition toward higher RF power values, indicating the influence of the nature of the working gas on the transition to the inductive as well as to the helicon mode. The variation of the electron density and temperature is explained in terms of particle and power balance equation. In the source and in the downstream expansion chamber, the effect of the concentration of argon gas on the negative ion production in oxygen discharge is also studied, and the results are explained in terms of various reactions involved in the production and loss of negative ions.

Numerical investigation of transport phenomena of arc plasma in argon-oxygen gas mixture

Mixtures of gases are utilized widely in a variety of arc welding processes to improve the arc property and thus the welding quality. This research focuses on the properties of the arc plasma in argon-oxygen gas mixture and a two dimensional (2D) axial symmetrical model is developed to investigate the transport phenomena in such arc, with diffusion treated by using combined diffusion coefficient approach. The gas mixture is applied to conventional tungsten inert gas (TIG) arc torch and a double-gas-shielding arc torch, respectively. Two different mass fractions of oxygen, i.e. 5% and 20%, in input gas mixture, are considered for the TIG arc, whereas that of 20% is taken into account for the outer shielding gas in the double-gas-shielding arc. The influence of the arc current on the demixing in the two types of arc is highlighted. The effect of the oxygen addition to argon on the TIG arc temperature is exhibited. It is found that for the TIG arcs, the oxygen concentrates in the regions close to the arc axis and to the electrodes, and increased current reduces the oxygen concentration near the cathode tip, but facilitates the mass transfer of the oxygen near the arc axis towards the anode; while for the double-gas-shielding arcs, the oxygen concentrates markedly in the periphery region of the arc and diffuses slightly towards the arc axis, with much lower mass fraction of the oxygen near the anode, for all the cases considered. Adding oxygen to the argon constricts the arc columns near the anode as compared with those in the pure argon for TIG arc. The oxygen mass fraction distribution 0.1 mm above the anode is uneven for the both types of the arc, implying nonuniform distribution of the oxygen reacting with the surface of the molten anode.

Effects of power per pulse on reactive HiPIMS deposition of ZrO2 films: A time-resolved optical emission spectroscopy study

Time-resolved optical emission spectroscopy was carried out during controlled reactive high-power impulse magnetron sputtering of ZrO2 films in argon–oxygen gas mixtures. The effects of increased target power density (up to 3.0 kW cm−2) applied in voltage pulses shortened from 200 to 50 μs were studied at a nearly constant deposition-averaged target power density (close to 50 W cm−2) and a fixed repetition frequency of 500 Hz. The trends in time evolution of the local ground-state densities of Zr, Ar, and O atoms and that of the Zr+, Zr2+, Ar+, and O+ ions during a voltage pulse were deduced from the time evolution of the corresponding excited-state populations and the excitation temperature. It was found that the sputtered Zr atoms are much more ionized (with a high fraction of Zr2+ ions) and the Ar atom density is more decreased near the target during the shorter (50 μs) high-power pulses. These shorter pulses produce a four times higher pulse-averaged target power density oscillating between 1.7 and 2.1 kW cm−2 during deposition. Under these conditions, much higher densities of O atoms and Zr2+ ions were measured in the plasma bulk. The higher backward flux of the Zr+ and Zr2+ ions onto the target during this high-power discharge regime contributed significantly to a 34% decrease in the efficiency of the magnetron sputter deposition of ZrO2 films.

Y-Type Zeolites Modified by Transition Metal Nanoparticles for Separating Argon from a Mixture with Oxygen

Based on NaY and HY granular synthetic zeolites without binding agents, adsorbents containing transition metal nanoparticles and characterized by the selectivity for argon at adsorption from a mixture with oxygen have been fabricated. Modification has been performed by the interaction with reverse micellar solutions of silver nanoparticles, as well as by ion exchange with transition metal salt solutions and subsequent reduction of metal ions until the achievement of nanoparticles in liquid media under the effect of ultrasound. The actual sizes of metal particles and their distribution over the surface of the modified samples of zeolites have been determined by the method of transmission electron microscopy (TEM). The samples’ equilibrium adsorption capacities for oxygen and argon at 25°С and atmospheric pressure and the partition coefficients of the argon–oxygen mixture as a ratio of the Henry coefficients have been determined. It has been demonstrated that samples of the NaY zeolite modified with silver nanoparticles have the highest selectivity for argon during its separation from a mixture with oxygen. The partition coefficient value of the argon–oxygen gas mixture was equal to 1.5–1.6.

Ion formation in an argon and argon-oxygen gas mixture of a magnetron sputtering discharge

Formation of singly and doubly charged Arq+ and Tiq+ (q = 1,2) and of molecular Ar, ArTi+, and Ti ions in a direct current magnetron sputtering discharge with a Ti cathode and argon as working gas was investigated with the help of energy-resolved mass spectrometry. Measured ion energy distributions consist of low-energy and high-energy components resembling different formation processes. Intensities of Ar and ArTi+ dimer ions strongly increase with increasing gas pressure. Addition of oxygen gas leads to the formation of positively charged O+, , and TiO+ and of negatively charged O− and ions.

V₂O₅ Thin Films as Nitrogen Dioxide Sensors †.

Vanadium pentoxide thin films were deposited onto insulating support by means of rf reactive sputtering from a metallic vanadium target. Argon-oxygen gas mixtures of different compositions controlled by the flow rates were used for sputtering. X-ray diffraction at glancing incidence (GIXD) and Scanning Electronic Microscopy (SEM) were used for structural and phase characterization. Thickness of the films was determined by the profilometry. It has been confirmed by GIXD that the deposited films are composed of V2O5 phase. The gas sensing properties of V2O5 thin films were investigated at temperatures from range 410–617 K upon NO2 gas of 4–20 ppm. The investigated material exhibited good response and reversibility towards nitrogen dioxide. The effect of metal-insulator transition (MIT) on sensor performance has been observed and discussed for the first time. It was found that a considerable increase of the sensor sensitivity occured above 545 K, which is related to postulated metal-insulator transition.

Aerogels Based on Calcium Alginate and Silicon Dioxide and Modified with Carbon Nanotubes for Selective Sorption of Argon from a Mixture with Oxygen

Two kinds of aerogels, those based on silicon dioxide and on calcium aginate, modified with multiwalled carbon nanotubes, were synthesized by the sol–gel method. The aerogels were tested as adsorbents for separating the argon–oxygen gas mixture. The adsorbent based on calcium alginate with 30 wt % content of multiwalled carbon nanotubes exhibits increased selectivity to argon in its adsorption from a mixture with oxygen.

Conductivity of Yittria-Stabilized Zirconia Nanostructure Electrolyte for Solid Oxide Fuel Cell Application by Using RF Magnetron Sputtering

Yttria-stabilized zirconia (YSZ) thin films were deposited successfully using RF magnetron sputtering. The substrate had been used are sapphire glass. A pure ceramic of Zr-Y is synthesized and processed into a planar magnetron target which is reactively sputtered with an Argon-Oxygen gas mixture to form Zr-Y-O nanostructure. The aim of this research is to study the conductivity and roughness YSZ thin film by using RF magnetron sputtering by varying the temperature deposition parameter. By lowering the YSZ thin film into nanostructure would enable for SOFC to be operate at lower temperature below 400°C. The YSZ nanostructure were controlled by varying the deposition parameters, including the deposition temperature and the substrate used. The crystalline of YSZ structure at 100W and temperature 300°C. The surface morphology of the films proved that at 300°C temperature rate deposition showed optimum growth morphology and density of YSZ thin films. Besides, the high deposition subtrate temperature affected the thickness of YSZ thin film at 80nm by using surface profiler. A higher rate of deposition is achievable when the sputtering mode of the Zr-Y target is metallic as opposed to oxide. YSZ is synthesizing to obtain the optimum thin film for SOFC application.