Transport Coefficients of Hydrogen and Argon–Hydrogen Plasmas

Calculated values of the viscosity, thermal conductivity, and electrical conductivity of hydrogen and mixtures of argon and hydrogen at high temperatures are presented. Combined ordinary, pressure, temperature, and electric field diffusion coefficients are also given for the mixtures. The calculations, which assume local thermodynamic equilibrium, are performed for atmospheric pressure plasmas in the temperature range from 300 to 30,000 K. The results are compared with those of previously published studies. Generally, the agreement is reasonable; those discrepancies that exist are attributed to the improved values of some of the collision integrals used here in calculating the transport coefficients.     

Two-Temperature Transport Coefficients in Argon–Hydrogen Plasmas—II: Inelastic Processes and Influence of Composition

Recently, a two-temperature transport properties theory has been proposed that retains the coupling between electrons and heavy species in thermal plasmas where the kinetic temperature of electrons Te can be different from that of heavy species Th. This paper is devoted to the application of this approach to an argon–hydrogen mixture at atmospheric pressure, taking into account inelastic processes and considering chemical equilibrium. In this second part are studied: the development of a new method to calculate the reaction thermal conductivity (inelastic collisions) in a non-equilibrium (two-temperature) plasma taking into account the coupling between electrons and heavy species; the influence of the composition calculation methods comparing the modified equilibrium constant method used in part 1 to the stationary kinetic calculation one; the influence on the transport properties (, , ) of the composition calculation method and non-equilibrium parameter =T_e/T_h.The different plasma compositions obtained either through an equilibrium constant or a stationary kinetic method are first compared and, for example, for =1.6, a discontinuity at T_e=11,000 K and an ionization delay are observed in stationary kinetic calculation, relative to the equilibrium constant method. Electrical conductivity, viscosity as well as thermal conductivity, including the translational, internal and reactional contributions, are calculated up to 25,000 K. It is shown that the plasma composition has a strong influence on transport coefficients, inducing shifts or discontinuities in the curves of transport coefficients, depending on the chosen method of calculation.     

Chemical Reactions and Kinetics of the Carbon Monoxide Coupling in the Presence of Hydrogen

The chemical reactions and kinetics of the catalytic coupling reaction of carbon monoxide to diethyl oxalate were studied in the presence of hydrogen over a supported palladium catalyst in the gaseous phase at the typical coupling reaction conditions. The experiments were performed in a continuous flow fixed-bed reactor. The results indicated that hydrogen only reacts with ethyl nitrite to form ethanol, and kinetic studies revealed that the rate-determining step is the surface reaction of adsorbed hydrogen and the ethoxy radical (EtO-). A kinetic model is proposed and a comparison of the observed and calculated conversions showed that the rate expressions are of rather high confidence.     

Two-Temperature Transport Coefficients in Argon–Hydrogen Plasmas—I: Elastic Processes and Collision Integrals

The calculation of two-temperature transport coefficients in an argon–hydrogen plasma at atmospheric pressure is performed using a new theory of two-temperature transport properties recently presented. The latter takes into account the coupling between electrons and heavy species, coupling neglected in the already existing theories of Devoto and Bonnefoi. Transport coefficients are calculated at two-temperatures, the kinetic temperature of electrons T_e being different from that of heavy species T_h. This paper is divided into two parts. The first one is related to elastic processes and its aim is to compare the results obtained with this new theory for viscosity , translational thermal conductivities ^tr _e and ^tr _h and electrical conductivity with the previous results of Bonnefoi. The composition is calculated with the modified equilibrium constant of van de Sanden et al. and the most recent interaction potential are discussed. As it could be expected the electron translational thermal conductivity and the electrical conductivity calculated when taking into account or not the coupling between electrons and heavy species show non-negligible discrepancies. Besides this comparison, the results also show the drastic influence of the non-equilibrium parameter =T_e/T_h on the values of , , ^tr _e, and ^tr _h.     

Adsorption and Structural Properties of Mineral–Carbon Sorbents

In the present work an attempt was made to obtain mineral–carbon sorbents by thermal decompositon. The mineral matrix for the sorbents (aluminium hydroxide) was based on petrochemical waste stream containing considerable amounts of aluminium chloride. Reference tests were carried out with a model solution prepared with the use of analytical grade AlCl₃. Atactic polypropylene and hydrocarbon mixtures obtained in the flotation of petrochemical waste waters were used as carbon-containing raw materials. The aim of this work was to determine the adsorption and structural characteristics of the complex sorbents and to check the possibility of evaluation of their hydrophobic-hydrophilic properties. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermodynamic Properties and Transport Coefficients of CO<Subscript>2</Subscript>–Cu Thermal Plasmas

This paper presents the calculated values of equilibrium compositions, thermodynamic properties and transport coefficients (viscosity, electrical conductivity and thermal conductivity) for CO₂–Cu thermal plasmas. With several copper mass proportions, the calculation is performed at temperatures 2000–30,000 K and various pressures 0.1–16 bar. Gibbs free energy minimization is used to determine species compositions and thermodynamic properties and the well-known Chapman–Enskog method is applied to calculating transport properties. Furthermore, great attention is paid to cope with the interactions between all the particles in the determination of collision integrals. The results are illustrated indicating the effect of the copper proportions and pressure on the fundamental properties of CO₂–Cu thermal plasmas. It can be found that a small quantity of copper (less than 10 %) can significantly modify the charged species densities and electrical conductivity especially at low temperature. While for other properties, the influences can be noticeable only when the copper proportion is above 10 %.     

Temperature Dependence of Transport Properties and Ion–Molecular Forms of LiAsF6 in γ-Butyrolactone

The solvation and association electrolyte interactions are analyzed in the concentration range of 0–2 m at temperatures of 253.15–313.15 K using measurements of the conductivity and viscosity of LiAsF₆ solutions in -butyrolactone (-BL). Concentrated LiAsF₆ solutions in -BL are considered as molten electrolytic solvates, whose transport processes are considerably influenced by a cooperative restructuring of the system. The concentration dependence of the molar conductivity is linear in the vs. c^1/3 coordinates, which agrees with a theory of quasi-crystalline electrolyte lattice in solution. The Lee–Wheaton model is used to determine the limiting molar conductivities, distance parameters, and association constants and their temperature dependences. The size of solvate spheres increases with decreasing temperature and their overlapping occurs at lower concentrations.     

Transport Properties of LiClO4–Nanodiamond Composites

Russian Journal of Electrochemistry - The transport properties of solid composite electrolytes (1 – x)LiClO4–xCND (where СND are “UDA-S” nanodispersed diamonds with a...     

Synthesis and Spectral Properties of Macrocyclic Compounds Containing 1,3,4‐Thiadiazole Moeties Connected by a Carbon–Oxygen Bridge

The syntheses of 1∶1‐macrocycles 3 (n=1), unsymmetrical macrocycle 5 (m=0, n=1), 2∶2‐macrocycle 5 (m=n=1 and 2), 3∶3 macrocycle 7, and several open‐chain ethereal compounds prepared from 2,5‐dichloro‐1,3,4‐thiadiazole 1 and various polyethylene glycols dianions are described. Structural proofs are afforded by their mass and NMR spectral features. The quaternization studies of a few macrocycles with methyl iodide at elevated temperature furnished a diketo derivative 8 through a facile Hilbert–Johnson reaction.     

Kinetics of Gaseous Product Formation in the Surface Treatment of Polypropylene with Nitrogen–Oxygen Plasmas

The results of measurements on the composition and the formation rates of gaseous products in the surface treatment action of polypropylene with a low-temperature dc discharge plasma in a nitrogen–oxygen mixture are reported. The amount of oxygen in the mixture was varied within 0–100%. It was found that almost stoichiometric plasma-induced oxidative degradation occurred in an oxygen plasma, whereas the buildup of oxygen-containing functional groups on the surface took place in a mixed nitrogen–oxygen plasma at a nitrogen content of 10–60%.     

Pattern of the Activity of (0.5–15)%CoO/CeO2 Catalysts in Carbon Monoxide Oxidation with Oxygen in Excess Hydrogen

Kinetics and Catalysis - Samples of (0.5–15)%CoO/CeO2, Co3O4, and CeO2 have been studied in the oxidation of CO to CO2 in a CO+O2+H2 mixture in a range of 40–340°C. The highest...     

Structural Dependence of Magnetic and Transport Properties in Doped Manganite Perovskites

1 INTRODUCTION In recent years, ABO3-type perovskite-like manganites, RE1xDxMnO3 (RE = rare earth ions, D = Ca2+, Sr2+, Ba2+ etc.), have inspired remarkable attention due to the colossal magnetoresistance (CMR) effects for fundamental and practical consideration [1, 2]. Since A- and B-site substitution can give rise to a large number of derivant compounds, fruitful structural, magnetic and transport properties would be expected in this family. As we have known, the ideal ABO3-typ…     

Reduction of Chemical Reactions in Nitrogen and Nitrogen–Hydrogen Plasma Jets Flowing into Atmospheric Air

The large number of possible chemical reactions represents a severe burdenfor modeling of even relatively simple plasma systems. Reduced sets ofchemical reactions have been obtained for numerical simulations of nitrogenand nitrogen-hydrogen plasma jets flowing into an atmospheric airenvironment. The important or active reactions are determined based on asimplified reduction method. A reaction is considered active if it leadsto higher sensitivities than a specified cutoff sensitivity of 1%. Theactive reactions exert a significant influence on main plasma parameters,such as velocity, temperature, and species concentrations. The sensitivityanalysis for the specified systems shows that two NO reactions, known asZel'dovich reactions (N₂+ONO+N andNO+OO₂+N),⁽¹⁾ are both active in a nitrogenplasma jet. On the other hand, the latter is not active and may be omittedin a nitrogen–hydrogen plasma jet. A nitrogen–hydrogen plasmajet requires contribution of two active charge exchange reactions:N₂+N⁺N⁺ ₂+N andN+H+N+ +H, while only the former is needed in a nitrogen plasmajet. The dissociation reactions are all active in both plasma jets, exceptthe dissociation of OH.     

Ab Initio Simulation of Transport Properties in Rb–CH4 and Cs–CH4 Laser Media

Russian Journal of Physical Chemistry A - The pair interaction potentials of the weakly bound Rb–CH4 and Cs–CH4 systems, which are active media of alkali metal vapor lasers with...     

Synthesis and Properties of Composite Polyaniline–Nafion Films on Glassy Carbon

Information on the synthesis of a polyaniline film on glassy carbon covered with a Nafion film is obtained. The effect of electrochemical synthesis conditions on the process is studied. The relationship between these conditions and properties of obtained composite polyaniline–Nafion films is revealed.     

Thermodynamics of Exo–Endo Isomerization of Carbon–Carbon Double Bonds in Five-Membered Ring Compounds. A Quantum Chemical Study

The energies and enthalpies of isomerization of methylenecyclopentane to 1-methylcyclopentene, 1,3-dimethylenecyclopentane to 1-methyl-4-methylenecyclopentene, and 3-methylenecyclopentanone to 3-methylcyclopent-3-en-1-one have been determined by DFT calculations at the B3LYP/6-31G* level of theory. Related studies were also carried out for some structurally related five-membered heterocyclic compounds containing one or two O atoms in the ring. The aim of the work was to study how the energetics of the exo endo isomerization of the C=C bond in methylenecyclopentane, 2-methylenetetrahydrofuran and 4-methylene-1,3-dioxolane is affected by replacement of an sp³ hybridized ring C atom with a trigonal one. This effect turned out to be small—only a few kilojoules per mole in carbocycles, favoring the endo isomer; in the heterocyclic compounds, especially those containing two ring O atoms, the effect is much greater.     

Structure,Electrical and Oxygen Transport Properties of Fe-Doped SrCoO3?δ Perovskites

The structure-property relationship of Fe-doped SrCoO_3-δ was studied. With increase of Fe content in SrCo_1-xFe_xO_3-δ from x=0 to x=0.2, the phase composition changed progressively in the order of hexagonal→brownmillerite (main)+hexagonal→cubic (main)+brownmillerite→single cubic phase. Transition between the hexagonal/brownmillerite phase and the cubic phase took place with variation of the operating conditions, and was associated with remarkable changes in the electrical conductivity and oxygen permeation flux.     

Oxidation and Destruction of Polyvinyl Alcohol under the Combined Action of Ozone–Oxygen Mixture and Hydrogen Peroxide

The oxidative transformations of a polyvinyl alcohol in aqueous solutions are studied under the simultaneous action of the two oxidizing agents, an ozone–oxygen mixture and a hydrogen peroxide. Effective parameters a and b, which characterize the first and second channels of carboxyl group accumulation, respectively, grow linearly upon an increase in the initial concentration of H₂O₂. After the temperature dependence of a and b parameters (331–363 K) in a PVA + O₃ + O₂ + H₂O₂ + H₂O reaction system is studied, the parameters of the activation of COOH group accumulation are found (where PVA is a polyvinyl alcohol). New data on the effect process conditions (length of oxidation, temperature, and hydrogen peroxide concentration) have on the degree of destructive transformations of polyvinyl alcohol in the investigated reaction system are obtained.     

Understanding the Catalytic Sites of Metal–Nitrogen–Carbon Oxygen Reduction Electrocatalysts

The development of low-cost catalysts containing earth-abundant elements as alternatives to Pt-based catalysts for the oxygen reduction reaction (ORR) is crucial for the large-scale commercial application of proton exchange membrane fuel cells (PEMFCs). Nonprecious metal–nitrogen–carbon (M-N-C) materials represent the most promising candidates to replace Pt-based catalysts for PEMFCs applications. However, the high-temperature pyrolysis process for the preparation of M-N-C catalysts frequently leads to high structural heterogeneity, that is, the coexistence of various metal-containing sites and N-doped carbon structures. Unfortunately, this impedes the identification of the predominant catalytic active structure, and thus, the further development of highly efficient M-N-C catalysts for the ORR. This Minireview, after a brief introduction to the development of M-N-C ORR catalysts, focuses on the commonly accepted views of predominant catalytic active structures in M-N-C catalysts, including atomically dispersed metal–N_x sites, metal nanoparticles encapsulated with nitrogen-doped carbon structures, synergistic action between metal–N_x sites and encapsulated metal nanoparticles, and metal-free nitrogen-doped carbon structures.