Inert Gas Mixtures Research Articles

Spillover of primary oxides as a dynamic catalytic effect of interactive hypo-d-oxide supports

The aim of the present paper is to introduce electron conductive and d–d-interactive individual and composite hypo-d-oxides of increased altervalent capacity, or their suboxides (Magneli phases), as catalytic supports and therefrom provide: (i) the Strong Metal-Supports Interaction (SMSI) effect and (ii) dynamic spillover interactive transfer of primary oxides (M–OH) for further electrode reactions and thereby advance the overall electrocatalytic activity. Since hypo-d-oxides feature the exchange membrane properties, the higher the altervalent capacity, the higher the spillover effect. This is the reason why anatase titania has now been doped with a certain amount of colloidal tungstenia (WO 3) ingredient, and the latter individually employed as the interactive catalyst support. Potentiodynamic experiments have shown that the reversible peak of the primary oxide growth on Pt, Ru and Au supported upon hypo-d-oxides and suboxides becomes distinctly increased in the charge capacity and shifted to remarkably more negative potential values, so that it starts even within the range of H-adatoms desorption, while its reduction extends until and merge with the UPD of hydrogen atoms. With wet tungstenia-doped titania-supported Pt catalyst in membrane cells, these peaks dramatically increase in their charge capacity and reversibly become shrunk with decreased moisture content in the feeding inert gas mixture, and vice versa. Such distinct potentiodynamic scans in conjunction with some broadened complementary kinetic electrocatalytic improvements, rising from the same hypo-d-oxide and/or suboxide interactive support effects, have been proved to be the best and comparable experimental evidence for the spillover effect of primary oxides.

Commentary on Viewpoint “Heliox, nitrox, and trimix diving; hyperbaric oxygen treatment; and a flaw in Henry's law”

LETTERS TO THE EDITORCommentary on Viewpoint “Heliox, nitrox, and trimix diving; hyperbaric oxygen treatment; and a flaw in Henry's law”H. D. Van Liew, and E. T. FlynnH. D. Van Liew, and E. T. FlynnPublished Online:01 Apr 2007https://doi.org/10.1152/japplphysiol.00055.2007MoreSectionsPDF (24 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat to the editor: Arieli (1) draws attention to experiments showing that solubility of individual gases may be reduced when high concentrations of multiple gases are present simultaneously. Results with in vitro systems of ethanol and water may not be representative of gases in tissue; for example, metabolism of oxygen will lower the oxygen partial pressure far below the inhaled value so tissue may still behave as a one-gas system despite a high inspired partial pressure of oxygen.The underlying mechanisms of bubble formation in divers, aviators, or astronauts who suffer decompression sickness (DCS) are poorly understood. It is suspected that DCS bubbles are generated from semi-permanent gaseous micronuclei. Gas diffusing into a micronucleus to initiate a bubble may be more closely related to gas partial pressure than to dissolved gas, but the final size of a bubble, if it does form, is probably related to dissolved gas. Interaction among the gases inside a bubble effects inward diffusion, an additional complication to breathing of gas mixtures (2).There is considerable difference of opinion about what constitutes successful decompression, as evidenced by the differences between instructions used by several of the world's navies (3). Also one must be cautious when interpreting the self-reported safety data collected by the Diver's Alert Network. The effect of one gas on the solubility of another may ultimately be shown to be an important factor in decompression, but, at present, we regard it as just one uncertainty among a great many other uncertainties.REFERENCES1 Arieli R. Heliox, nitrox, and trimix diving; hyperbaric oxygen treatment; and a flaw in Henry's law. J Appl Physiol. In press.Google Scholar2 Van Liew HD, Burkard ME. Breathing a mixture of inert gases: disproportionate diffusion into decompression bubbles. Undersea Hyperbaric Med 23: 11–17, 1996.Google Scholar3 Van Liew HD, Flynn ET. Decompression tables and dive-outcome data: graphical analysis. Undersea Hyperbaric Med 32: 187–198, 2005.Google ScholarAUTHOR NOTESAddress for reprint requests and other correspondence: H. D. Van Liew, 100 Goodview Way, Barnstable, MA 02630 Download PDF Previous Back to Top Next FiguresReferencesRelatedInformation More from this issue > Volume 102Issue 4April 2007Pages 1721-1721 Copyright & PermissionsCopyright © 2007 the American Physiological Societyhttps://doi.org/10.1152/japplphysiol.00055.2007PubMed17409298History Published online 1 April 2007 Published in print 1 April 2007 Metrics

Calculation of the equilibrium and transport characteristics of gaseous and liquid mixtures of noble gases in complex narrow-pore systems

The molecular-kinetic theory of transfer of the components of the gaseous and liquid mixtures of inert gases is generalized to the case of narrow pores of complex structure. The theory is based on the latticegas model, which provides a self-consistent method for calculating the equilibrium and transport characteristics of noble gases and liquids. This model is used to describe the supramolecular structure of finely dispersed bodies and to calculate the distributions of the mixture components within the pore space. The supramolecular structure is composed of slitlike, cylindrical, spherical, and globular model elements and their joints. An analysis of the effect of the molecular properties of the mixture components, physicochemical properties of the pore walls and the width of the cylindrical and complex sections of variable diameter of spherocylindrical pores on the concentration dependences of the local label transfer coefficients and viscosity coefficients for mixtures of spherical molecules at supercritical temperatures range is performed. Correlations between the partial degrees of filling of pores with mixture components and the local dynamic characteristics of the mixture in the spherocylindrical systems are considered. It is shown that an increase in the binding energy increases the local flow viscosity and reduces the diffusion coefficients of the labeled mixture components.

Copper Matte Penetration Resistance of Basic Refractories

Penetration resistance is viewed as the first property that must be evaluated for the selection of new refractories, because it is known that melt penetration can promote or enhance the main wear mechanisms in copper converters, namely, dissolution, erosion, and spalling. In this work, a penetration test was designed to control the oxygen potential over typical laboratory prepared converter melts by injecting a mixture of inert gas and oxygen according to thermodynamic calculations. The effects of oxygen potential and matte grade on burned magnesite chrome brick and spinel direct bonded brick were studied using operating conditions typical of copper converters, and their relative performance was evaluated using high-grade and low-grade matte at oxygen potentials of 10-7 and 10-6 atm. Under these conditions, it was determined that spinel direct bonded brick outperformed the magnesite-chrome brick.

Emission characteristics of plasma of a transverse volume discharge in mixtures of helium, argon, and krypton with sulfur hexafluoride

The emission characteristics of the plasma of repetitively pulsed spontaneous UV-VUV radiation sources on the basis of ArF* (193 nm) and KrF* (249 nm) molecules, and the products of decomposition of sulfur hexafluoride molecules pumped by a transverse volume discharge in a mixture of inert gases with sulfur hexafluoride molecules have been investigated. The discharge emission spectra in the range of 190–780 nm at the low-current and high-current stages of the transverse discharge, the time characteristics of the voltage across the electrodes, the pump current, and the emission of excimer molecules and the products of decomposition of sulfur hexafluoride have been studied. It is shown that, in the gas-static operation mode of the radiator at the number of discharge pulses smaller than 103, the 193-nm ArF* and 249-nm KrF* bands are main in the emission spectrum. Upon further operation of the radiator, a spectral continuum is formed on the basis of sulfur molecular bands in the range 260–550 nm.

Emission of I2* molecules in a barrier discharge

The energy and spectral emission characteristics of a barrier discharge are studied in mixtures of inert gases with iodine vapour. The emission spectrum exhibits a strong 342-nm D' → A' molecular band of the I2* molecule, the 206.2-nm resonance line of iodine, and a group of emission bands of iodine. Small admixtures of Ne (5%) to the Ar – I2 mixture increase the emission efficiency and power by a factor of 2–2.5. A sealed off I2 excilamp with the emission maximum at 342 nm is fabricated.

Fire-Extinguishing Effectiveness of 1-Bromo-3,3,3-Trifluoropropene/Inert Gaseous Mixture Evaluated by Cup Burner Method

1-bromo-3,3,3-trifluoropropene with low extinguishing concentration has been identified, but it has high boiling points and is not suitable replacements for halon 1301. However, mixtures of 1-bromo-3,3,3-trifluoropropene in an inert gas could produce fire-extinguishing agents with many of the desirable properties of halon 1301. To study binary fire suppressants, one has to determine the extinguishing concentration of the 1-bromo-3,3,3-trifluoropropene/inert gas mixtures. In this study, a method based on cup-burner was used to estimate the extinguishing concentration of 1-bromo-3,3,3-trifluoropropene/inert gas mixtures. A mechanism for mixing 1-bromo-3,3,3-trifluoropropene with inert gas before applying to fire was proposed. The results show that addition of small amount of 1-bromo-3,3,3-trifluoropropene in inert gas reduces the extinguishing concentration of inert gas considerably, and 1-bromo-3,3,3-trifluoropropene/inert gas mixture suppressant shows strong synergistic interactions at low mole concentration of 1-bromo-3,3,3-trifluoropropene.

Effectiveness of Various Concentrations of an Inert Gas Mixture for Preventing and Suppressing Mining Equipment Cab Fires: Development of a Dual Cab Fire Inerting System

The National Institute for Occupational Safety and Health (NIOSH/PRL) conducted a series of large-scale experiments to evaluate the effectiveness and safety of various concentrations of an inert gas mixture (CO2, 8%; N2, 50%; Ar, 42%) for preventing and suppressing cab fires. Comparison of concentrations effectiveness in yielding safe times has led to the choice of an optimum gas mixture concentration, discharged in the cab through a muffled nozzle system, for the development of a dual cab fire inerting system. Of note is that safety training programs, including the synchronization of performed tasks, need to accompany this technology to enhance operator’s efficiency and safety during fire emergencies within the safe times yielded by the cab fire inerting system.

Computer Modeling of Gasdynamic Control of Nanoclusters Growth

Possibilities of gasdynamic control of nanoclusters growth process in a steady flow of a carbon vapor and inert gas (helium) mixture in a cylindrical channel with a supersonic nozzle were investigated. It was shown that the supersonic nozzle is an effective method of “freezing” of clusters mass spectra and obtaining clusters of required size.

Mild Combustion in Homogeneous Charge Diffusion Ignition (HCDI) regime

The paper deals with a subcategory of Mild Combustion, which has been named Homogeneous Charge Diffusion Ignition (HCDI). It is analyzed through characterization of processes that take place in counter-diffusion configuration obtained by two opposed jets of the fresh air–fuel mixture and inert flow. The reactive field is modeled through a numerical code exploiting a detailed chemical kinetics scheme of O 2/CH 4/N 2 system. Distributions of temperature and enthalpy as a function of the spatial coordinate and the mixture fraction are obtained for different values of the external parameters, i.e. the maximum temperature increase, the fresh mixture temperature, the inert gas mixture, the reference strain rate. They can be classified in four main categories on the ground of location and broadness of the heat release and occur in contiguous exclusive regions of external parameters plots. Continuous transitions between regions are characterized by single solutions, whereas extinction/ignition discontinuous mechanisms are obtained in transition regions where double solutions are allowed. Unique characteristics, different from those of deflagration, emerged for well-identified ranges of external parameters. They are related to a distribution of the heat release in a broad spatial and mixture fraction range. The operative conditions, for which such peculiar behavior occurs, are coincident with those where Mild Combustion is expected to take place on the ground of its “a priori” definition.

The average size of Si nanoparticles prepared by pulsed laser ablation in the gas mixture of He/Ar, Ne/Ar or He/Ne

The nanocrystalline silicon films were prepared by pulsed laser ablation in the gas mixture of high-purity inert gases (He/Ar, Ne/Ar or He/Ne) under the deposition pressure of 10 Pa. The microstructural properties of the films produced under various mixed ratios were characterized by scanning electron microscopy, X-ray diffraction and Raman. The result shows that the closer to the Si atomic mass the average atomic mass of the ambient gas, the smaller the average size of the Si nanoparticles, which may be attributed to more effective energy transfer among the ambient atoms and Si atoms.

Gas-discharge excimer radiation source for the yellow region

This paper presents the results of experimental studies of the output characteristics of a compact radiator based on mixtures of zinc diiodide vapor and inert gases, excited by a barrier discharge at a total pressure of 50-202 kPa and a sinusoidal voltage-repetition frequency of f ≤130 kHz. The source can be recommended for use in display panels. Besides this, it can be used in biotechnologies and medicine.

A numerical algorithm for kinetic modelling of evaporation processes

A numerical algorithm for kinetic modelling of droplet evaporation processes is suggested. This algorithm is focused on the direct numerical solution of the Boltzmann equations for two gas components: vapour and air. The physical and velocity spaces are discretised, and the Boltzmann equations are presented in discretised forms. The solution of these discretised equations is performed in two steps. Firstly, molecular displacements are calculated ignoring the effects of collisions. Secondly, the collisional relaxation is calculated under the assumption of spatial homogeneity. The conventional approach to calculating collisional integrals is replaced by the integration based on random cubature formulae. The distribution of molecular velocities after collisions is found based on the assumption that the total impulse and energy of colliding molecules are conserved. The directions of molecular impulses after the collisions are random, but the values of these impulses belong to an a priori chosen set. A new method of finding the matching condition for vapour mass fluxes at the outer boundary of the Knudsen layer of evaporating droplets and at the inner boundary of the hydrodynamic region is suggested. The numerical algorithm is applied to the analysis of three problems: the relaxation of an initially non-equilibrium distribution function towards the Maxwellian one, the analysis of the mixture of vapour and inert gas confined between two infinite plates and the evaporation of a diesel fuel droplet into a high pressure air. The solution of the second problem showed an agreement between the results predicted by the widely used Bird’s algorithm and the algorithm described in this paper. In the third problem the difference of masses and radii of vapour and air molecules is taken into account. The kinetic effects predicted by the numerical algorithm turned out to be noticeable if the contribution of air in the Knudsen layer is taken into account.

Thermal contraction of arc discharge in mixtures of inert gases: Special features

The effect of the properties of gas medium on the process of contraction (pinching) of an arc discharge in mixtures of inert gases is treated. Calculations are performed, whose results demonstrate that the degree of contraction of arc discharge is defined by the thermal characteristics of the gas medium and by the characteristics of electron-atom collisions. The impact of Ramsauer effect on the pattern of contraction of arc discharge is revealed, and the possibility of neutralizing this impact is demonstrated.

Applications of the 308-nm excimer laser in dermatology

Excimer lasers contain a mixture of a noble inert gas and a halogen, which form excited dimers only in the activated state. High-energy current is used to produce these dimers, which have a very short lifetime, and after their fast dissociation they release the excitation energy through ultraviolet photons. The application of these lasers proved to be successful in medicine, including the field of ophthalmology, cardiology, angiology, dentistry, orthopaedics, and, in recent years, dermatology. For medical purposes, the 193-nm argon fluoride, the 248-nm krypton fluoride, the 351-nm xenon fluoride, and the 308-nm xenon chloride lasers are used. Recently, the 308-nm xenon chloride laser has gained much attention as a very effective treatment modality in dermatological disorders. It was successfully utilized in psoriasis; later, it proved to be useful in handling other lightsensitive skin disorders and even in the treatment of allergic rhinitis. This review summarizes the possible applications of this promising tool in dermatology.

Emission characteristics of a high-power glow discharge plasma in a mixture of inert gases with bromine and iodine vapor

The results of an investigation of the UV radiation from the plasma of a dc glow discharge in mixtures of inert gases with bromine and iodine molecules are presented. The current-voltage and spectral characteristics of a longitudinal glow discharge with a power of 10–250 W are studied. The power and the efficiency of the total UV radiation of the plasma, as well as the power of radiation at the spectral line of the iodine atom at 206.2 nm, are optimized as functions of the power deposited into the plasma and the composition of the gas mixture. In active media based on Kr-Br2 mixtures, the molecular emission of the plasma was represented by bands at 207 (KrBr(B-X)) and 289 nm (Br 2 * ), while, in He-Xe-I2 mixtures, it was represented by bands at 253 (XeI(B-X)) and 342 nm (I2).

Density dependence of electric properties of binary mixtures of inert gases

A computational study of the density dependence of the refractivity and dielectric constants, the electric-field induced second harmonic generation (ESHG) hyperpolarizabilities and of the Kerr constants of binary mixtures of helium, neon and argon is presented. Potentials and interaction properties of the homonuclear A2 and heteronuclear AB dimers (A, B=He, Ne, Ar) are taken from a previous study [J. López Cacheiro, B. Fernández, D. Marchesan, S. Coriani, C. Hättig, A. Rizzo. Molec. Phys., 102, 101 (2004)]. Dispersion coefficients for the second virial coefficients allow for the determination of the density dependence at any frequency far from the lowest resonance. Fully quantum mechanical results are presented and a comparison with the corresponding classical estimates is discussed. Deep minima are predicted to occur in the ESHG second virial coefficient curve drawn as a function of the molar fraction of one of the components in binary mixtures of He/Ar and Ne/Ar. This phenomenon, observed over a wide range of temperatures, should be easily verifiable experimentally.

Numerical Studies on Specific Impulse of Partially Filled Pulse Detonation Rocket Engines

Performance analyses of pulse detonation rocket engines (PDREs) were numerically studied, focusing on partialfill effects at ground tests. The initial detonable mixture, inert gas, fuel-fill fraction, equivalence ratio, and initial temperature of inert gas were changed as governing parameters. The simulation results were compared against those of previous studies and agreed well with them. The simulation results indicated that the initial mass fraction of the detonable mixture to total mass of the gas was the predominant factor for the specific impulse of partially filled PDREs. Based on the numerical results, a new, simple empirical formula is proposed to predict the specific impulse of partially filled PDREs.

Tuning effect of inert gas mixing on electron energy distribution function in inductively coupled discharges**This paper is from the 12th International Congress on Plasma Physics (Nice, 2004). For other papers from this conference see http://www.iop.org/EJ/toc/0741-3335/47/5A.

Measurements on electron energy distribution function (EEDF) by a Langmuir probe show that inert gas mixing can change EEDF from a Maxwellian to a ‘two-temperature’ structure in an inductively coupled low pressure nitrogen discharge. This result suggests the existence of two groups of electrons: low and high energy. Each group of electrons has distinct behaviour as gas mixing ratio changes. As a result, this causes discrepancies between the measured electron temperature by a Langmuir probe and that by optical line–ratio technique, since these two techniques are sensitive to the energy distribution of low and high energy electrons, respectively. A detailed experimental investigation of the evolution of EEDF with different inert gas mixtures (Ar/N2, He/N2, Ne/N2 and Xe/N2) at an operating pressure of 10 mTorr is performed, from which the distribution temperature of both low and high energy electrons is calculated and compared with the temperature obtained from the Global Model. It is found that with the measured energy range and under the experimental condition studied, inelastic collisions (both excitation and ionization) play a key role on the shape of EEDF when inert gas is mixed in the discharge.

A Model for Changes in Coalbed Permeability During Primary and Enhanced Methane Recovery

Summary The natural fracture network of a dual-porosity coalbed reservoir is made up of two sets of orthogonal, and usually subvertically oriented, cleats. Coalbed permeability has been shown to vary exponentially with changes in the effective horizontal stress acting across the cleats through the cleat-volume compressibility, which is analogous to pore compressibility in porous rocks. A formulation for changes in the effective horizontal stress of coalbeds during primary methane recovery, which includes a Langmuir type curve shrinkage term, has been proposed previously. This paper presents a new version of the stress formulation by making a direct link between the volumetric matrix strain and the amount of gas desorbed. The resulting permeability model can be extended readily to account for adsorption-induced matrix swelling as well as matrix shrinkage during enhanced methane recovery involving the injection of an inert gas or gas mixture into the seams. The permeability model is validated against a recently published pressure-dependent permeability multiplier curve representative of the San Juan basin coalbeds at post-dewatering production stages. The extended permeability model is then applied successfully to history matching a micropilot test involving the injection of flue gas (consisting mainly of CO2 and N2) at the Fenn Big Valley, Alberta, Canada.