Prediction of thermodynamic, transport and vapor-liquid equilibrium properties of binary mixtures of ethylene glycol and water

Equilibrium and non-equilibrium molecular dynamics and Monte Carlo simulation techniques were applied to predict various thermodynamic, transport and vapor-liquid equilibrium properties of binary mixtures of ethylene glycol and water (EG-W) based on OPLS-AA and SPC/E force fields. The properties predicted include density, vaporization enthalpy, enthalpy of mixing, heat capacities, diffusion coefficients, shear viscosities, thermal conductivities, vapor-liquid coexistence isotherms and isobaric curves, and saturation vapor pressures. Good agreements with experimental data were obtained for most of these properties. Errors are mostly related to inaccuracy found in predictions of pure fluids; a correction to prediction of pure substance can systematically improve prediction for the mixture. This work suggests that OPLS-AA and SPC/E force fields using the common combining rules are transferable for predicting multiple physical properties of EG-W mixtures.     

Effects of metallic vapor on the properties of an argon arc plasma

During thermal plasma processing of materials, vapor generated from injected particulate matter will enter the plasma. Even traces of metallic vapors may have a strong effect on the properties and the behavior of the plasma and on the associated heat flux to the injected particles. In this paper a model system is considered in which an argon plasma at atmospheric pressure is contaminated by small amounts of copper vapor. By using the Chapman-Enskog approximation for a multicomponent gas mixture the transport properties are calculated for such a contaminated argon plasma. The results show that there is a drastic effect on the electrical properties. For temperatures below 10⁴ K, the electrical conductivity, for example, increases by more than an order of magnitude if metallic vapor is present. The presence of metallic contaminants is also somewhat felt by the reactional thermal conductivity. In contrast, there is no effect on the heavy-particle properties as long as the percentage of the contaminants remains small.     

Thermodynamic and Transport Properties of Two-temperature Oxygen Plasmas

Thermodynamic and transport properties of two-temperature oxygen plasmas are presented. Variation of species densities, mass densities, specific heat, enthalpy, viscosity, thermal conductivity, collision frequency and electrical conductivity as a function of temperature, pressure and different degree of temperature non-equilibrium are computed. Reactional, electronic and heavy particle components of the total thermal conductivity are discussed. To meet practical needs of fluid-dynamic simulations, temperatures included in the computation range from 300 K to 45,000 K, the ratio of electron temperature (T _e) to the heavy particle temperature (T _h) ranges from 1 to 30 and the pressure ranges from 0.1 to 7 atmospheres. Results obtained for thermodynamic equilibrium (T _e = T _h) under atmospheric pressure are compared with published results obtained for similar conditions. Observed overall agreement is reasonable. Slight deviations in some properties may be attributed to the values used for collision integral data and for the two temperature formulations used. An approach for computing properties under chemical non-equilibrium and associated deviations from two-temperature results under similar conditions are discussed.     

Experimental study on equilibrium deviations in atmospheric pressure argon/helium surface wave discharges

Atmospheric pressure surface wave discharges generated with Ar–He mixtures with He concentrations up to 99% were studied using spectroscopic techniques. The variation of electron density and linear power density with He concentration and along the plasma column is discussed together with the excitation temperatures derived from the Boltzmann plot of the excited states of Ar I and the values of the b(p) parameters to derive the thermodynamic equilibrium state of the discharge. Important deviations with respect to Local Thermodynamic Equilibrium were observed for He concentrations over 50% as the discharge shifts from a recombining to an ionizing behaviour. Furthermore, the discharge kinetic variations behind these changes are discussed.     

Thermodynamic properties of liquid mixtures of carbon monoxide and methane

The equations of state of liquid methane at 125.00 K and of six liquid mixtures of carbon monoxide and methane at 116.30, 120.00 and 125.00 K have been measured from just above the saturation vapour pressure to the freezing pressure of methane. The results show that the excess volume V^E is large and negative at low pressures but becomes less negative as the pressure is increased, being almost zero at the highest pressures. The curve of V^E against the mole fraction x is very asymmetrical at low pressures, but becomes more symmetrical with rising pressure.The effect of pressure on the excess functions G^E, H^E and T·S^E has been calculated. H^E and T·S^E prove to be much more sensitive to pressure than G^E.Conformal solution theory, in the van der Waals one-fluid form, reproduces the experimental results very successfully.     

Thermodynamic and physical properties of carbon tetrachloride + sulfolane mixtures

The solid + liquid phase diagram, drawn from thermal and dielectric measurements, is presented. It exibits a miscibility gap at 0.08 ≤ χ₂ ≤ 0.58, and two eutectics. The occurrence of a (likely 1:1) intermediate compound, which decomposes on melting into two immiscible liquids, is postulated. Mixed crystals are observed in the sulfolane richer region.Deviations of the liquid mixtures from ideality, positive in the case of viscosity and negative in the case of dielectric constants, are evidenced.     

Structure and properties of thin films of binary rodlike/flexible polyimide mixtures

Binary mixtures of a rodlike poly(p-phenylene pyromellitimide) (PMDA-PDA) and a flexible 6F-BDAF polyimide synthesized from hexafluoroisopropylidene diphthalic anhydride and 2,2-bis(4-aminophenoxy-p-phenylene) hexafluoropropane were prepared by solution-blending of the meta-PMDA-PDA poly(amic ethyl ester) and 6F-BDAF poly(amic acid) precursors, followed by solvent evaporation and thermal imidization. Mixtures containing different molecular weights of 6F-BDAF poly(amic acid) were studied. The size scale of the phase separation, as measured by light scattering, is ca. 1 μm or smaller in most cases. The domain size is primarily set by the demixing of the precursor polymers during solvent evaporation, with no significant coarsening observed during the thermal imidization. The observed variation of the domain size with molecular and process parameters such as composition, molecular weight, and film thickness is discussed in terms of the miscibility of the precursor polymers, rate of solvent evaporation, and solidification. Dynamic mechanical thermal analysis and dielectric relaxation measurements indicate that the glass transition temperature of 6F-BDAF is unaffected in all of the mixtures studied, indicating complete demixing of rodlike and flexible polyimides in agreement with theory. X-ray photoelectron spectroscopy results show a strong surface segregation of 6F-BDAF in mixtures containing as low as 10% by weight of the 6F-BDAF component in the bulk. The mixtures with PMDA-PDA as the major matrix component therefore exhibit excellent mechanical toughness, dimensional stability up to 500°C, low coefficients of thermal expansion (< ca. 10 ppm/°C), and low dielectric constants (<3.0). On the other hand, the surface properties of the mixtures are dominated by the flexible 6F-BDAF, resulting in excellent polymer/polymer self-adhesion (lamination) properties between fully imidized films.     

Six IPR isomers of C90 fullerene captured as chlorides: carbon cage connectivities and chlorination patterns

Three C(90) fractions were isolated by multi-step HPLC from fullerene soot obtained from direct current (DC) arc discharge of undoped graphite rods. C(90) of each fraction was chlorinated with VCl(4) or SbCl(5) in ampoules at 290-310 °C, affording a series of C(90)Cl(n) compounds. Single-crystal X-ray crystallography with the use of synchrotron radiation resulted in structure elucidation of seven C(90)Cl(n) compounds containing six different isolated pentagon rule (IPR) C(90) cages (the number of the C(90) isomer is given in the parentheses): C(90)(46)Cl(32) (I), C(90)(34)Cl(32) (II), C(90)(35)Cl(24) (III), and C(90)(35)Cl(28) (IV), C(90)(32)Cl(24) (V as co-crystals with III), co-crystals of C(90)(30)Cl(22) and C(90)(28)Cl(24) (VI), and C(90)(28)Cl(24) (VII). Cage connectivities of C(90) isomers 35 and 28 have been crystallographically confirmed for the first time. The chlorination patterns of the C(90)Cl(n) molecules are discussed in terms of the formation of isolated aromatic systems and isolated C=C double bonds on the fullerene cage. The distribution of six C(90) isomers in three HPLC fractions is compared with data from the literature.     

Thermodynamic and aggregation properties of sodium dodecyl sulfate in aqueous binary mixtures of isomeric butanediols

The effect of aqueous binary mixtures of isomeric butanediols on the micellization of sodium dodecyl sulfate has been investigated. Conductivity and fluorescence techniques were employed to determine the critical micellar concentration, the degree of dissociation of the counterions and the aggregation numbers of the surfactants in these binary blends. Differential conductivity plots were employed to distinguish between the cooperative and the stepwise aggregation process of the surfactant in each solvent system. The mass-action model was employed to calculate the hydrophobic and the electrostatic contributions to the Gibbs energy of micellization as well as the monomer and the counterion concentrations in the postmicellar region. The thermodynamic parameters calculated for each system indicate that the micellization process occurs more readily in the presence of cosolvent owing to the formation of mixed micelles. Received: 5 July 2000 Accepted: 25 July 2000     

Thermodynamic and transport properties of carbon dioxide from molecular simulation

Monte Carlo and molecular dynamics simulations have been used in order to test the ability of a three center intermolecular potential for carbon dioxide to reproduce literature experimental thermophysical values. In particular, both the shear viscosity under supercritical conditions and along the phase coexistence line, as well as the thermal conductivity under supercritical conditions, have been calculated. Together with the already reported excellent agreement for the phase coexistence densities, the authors find that the agreement with experimental values is, in general, good, except for the thermal conductivity at low density. Although extended versions of the model were employed, which include an explicit account of bending and vibrational degrees of freedom, a significant difference was still found with respect to the reported experimental value.     

富勒烯形成机理的研究进展

富勒烯的形成机理多年来一直是富勒烯科学研究的焦点问题,科学家们用大量的理论计算和实验工作来探索富勒烯的形成过程,并提出了多种模型和可能机理．根据富勒烯形成途径的不同,这些机理可分为“自下而上”、“自上而下”或“先上后下”3种生长方式,但是由于缺乏足够的实验证据,至今还没有一种机理得到实验事实的完全证明并被普遍接受．本文就近年来有关富勒烯形成机理的研究进行了归纳阐述,并概述了其中影响较大的几种机理．     

Thermodynamic and transport properties of binary liquid mixtures of cyclohexanol with isomeric chlorotoluenes

Densities (ρ) at different temperatures from 303.15 to 318.15 K, speeds of sound (u) and viscosities (η) at 303.15 K were measured for the binary mixtures of cyclohexanol with 2-chlorotoluene, 3-chlorotoluene and 4-chlorotoluene over the entire range of composition. The excess volumes (V^E) for the mixtures have been computed from the experimental density data. Further, the deviation in isentropic compressibilities (Δκ_s) and deviation in viscosities (Δη) for the binary mixtures have been calculated from the speed of sound and viscosity data, respectively. The V^E values and Δκ_s values were positive and Δη data were negative for all the mixtures over the whole range of composition at the measured temperatures. The calculated excess functions V^E, Δκ_s and Δη were fitted to Redlich–Kister equation. The excess functions have been discussed in terms of molecular interactions between component molecules of the binary mixtures.     

Rheological, mechanical and transport properties of blown films of high density polyethylene nanocomposites

In this work, high density polyethylene (HDPE) was mixed in a twin screw extruder with organophilic treated clay, Cloisite 20A, and a compatibility agent, a HDPE grafted with maleic anhydride (PEMA). The screw profile was changed from a less dispersive (Profile 1) to a high dispersive configuration (Profile 2). A masterbatch procedure was used to obtain a final organoclay concentration of 5 wt.%. Both profiles allowed the intercalation of the HDPE into the clay, increasing the clay’s gallery distance to 3.7 nm. However, the samples produced with Profile 2 (Nano 2 samples) were more elastic and had a more stable structure than the samples produced with Profile 1. Therefore, two kind of blown films of Nano 2 samples were made: FN1 and FN2. The last one was blown at a higher screw velocity than the FN1. Both films had an increase of 95% in the elastic modulus and a reduction of 60% and 45% in O₂ and water vapor permeability rates, respectively, compared to the film of pure HDPE. However, the FN2 structure was more unstable than the FN1 structure. It was concluded that both screw profiles gave the same level of HDPE intercalation in the clay; however, the more dispersive profile produced more time-stable and elastic structures. The increase in the elongation rate during the film blowing process produced also more time-stable morphologies; however, this higher orientation created matrix/filler interfacial defects.     

Thermodynamic properties of solutions of fullerene C<Subscript>60</Subscript> in mixtures of tetraline with carbon tetrachloride and 1,2-dichlorobenzene

The solubility of fullerene C₆₀ in tetraline-carbon tetrachloride and tetraline-1,2-dichlorobenzene systems in all compositions of the mixed solvent are measured in the temperature range of 298.15–338.15 K. It is found that in a mixture of tetraline with 1,2-dichlorobenzene, the solubility of C₆₀ is considerably higher than in its pure components; in this case, solubility has a maximum in the range of lower temperatures and compositions of the mixture X _trl = 0.3–0.5. It is established that C₆₀ forms crystal solvates with components of the mixed solvents. Enthalpies and temperatures of incongruent melting of the crystal solvates are determined by differential scanning calorimetry.     

Supramolecular hybrids of [60]fullerene and single-wall carbon nanotubes

Noncovalent interactions between purified HiPCO single-wall carbon nanotubes (SWNT) and a [60]fullerene-pyrene dyad, synthesized through a regioselective double-cyclopropanation process, produce stable suspensions in which the tubes are very well dispersed, as evidenced by microscopy characterization. Cyclic voltammetry experiments and photophysical characterization of the suspensions in organic solvents are all indicative of sizeable interactions of the pyrene moiety with the SWNT and, therefore, of the prevalence in solution of [60]fullerene-pyreneSWNT hybrids.     

Calculation of transport properties and intermolecular potential energy function of the binary mixtures of H2 with Ne,Ar, Kr and Xe by a semi-empirical inversion method

The present paper contains inspection of the improved corresponding states principle for transport properties of hydrogen and the binary mixtures of hydrogen with Ne, Ar, Kr and Xe. The set of corresponding states parameters has been defined by a complex numerical analysis of a carefully selected body of experimental data. The obtained correlations for the reduced orientation-averaged diffusion and viscosity collision integrals are restricted to low densities in a temperature range from T = ?/k to the onset of ionization. These equations have been inverted directly to give the isotropic and effective intermolecular potential energy curve for binary mixtures of H₂ with Ne, Ar, Kr and Xe corresponding to the viscosity collision integrals. The results are then used to obtain the best Morse-Spline-Van der Waals (MSV) potential parameters. Our inverted potential energies have been compared with experimental intermolecular potentials that were obtained by molecular beam scattering and infrared spectroscopic measurements. In this research, the Chapman–Enskog and Wang Chang-Uhlenbeck-de Boer (WCUB) version of kinetic theory have been used in conjunction with our inverted potential energies to reproduce viscosity, diffusion, thermal conductivity and thermal diffusion factor of binary mixtures of H₂ with Ne, Ar, Kr and Xe in a wide temperature range for equimolar composition. As the deviation plots illustrate, our obtained intermolecular potential energies (on the basis of the algorithm presented in the inversion process) represent the low-density transport properties of binary mixtures of H₂ with Ne, Ar, Kr and Xe within their expected experimental uncertainties. Close agreement between the predicted values and the literature results of transport properties demonstrates the predictive power of the inversion scheme.     

The structure of fullerene films and their metallocene doping

Hexagonal close-packed (HCP) C₆₀ and C₇₀ films have been prepared by the Langmuir method and examined by electron microscopy and electron-diffraction analysis. It has been shown that the vacuum deposition of a C₆₀+C₇₀ mixture results in the formation of a film with small sized grains and a distorted C₆₀-HCP structure. The simultaneous deposition of C₆₀ and ferrocene results in the formation of a film with a changed morphology and an electron-diffraction pattern that contains a variable amount of ferrocene depending on the experimental conditions. The electron-diffraction pattern corresponds to the presence of the known molecular complex C₆₀[(C₅H₅)₂Fe]₂. The analogous simultaneous deposition of fullerene C₆₀ and cobaltocene results in the formation of a C₆₀ film stable in air and water, which contains carbon and cobalt (from the data of X-ray fluorescence, electron microscopy and microdiffraction). It has a different morphology and different diffraction patterns than pure C₆₀ films and, depending on the cobaltocene content (relative to that of fullerene), appears to be a fullerite film doped with various amounts of cobaltocenium fullende, which is an ionic compound.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1379–1383, August, 1994.The work was financially supported by the Russian Foundation for Basic Research (Projects 93-03-4676 and 93-03-18368).     

Thermodynamic and transport properties of binary liquid acid—base mixtures. Part 1

Densities and viscosities were determined at five different temperatures for the systems quinoline (Q) with: phenol (P); ortho-chlorophenol (CP); and meta-cresol (MC). From the experimental results the excess volumes, excess viscosities, partial molar excess volumes and the partial molar volumes were calculated. From the dependency of viscosity on temperature, the thermodynamic parameters of activation of flow were also calculated and these results were discussed in terms of the type of interaction between the two components in solution.