bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Phase Boundaries of Wüstite
Authors: Knacke O. 
Published: July 2012

AbstractAccording to Darken and Gurry and to Swaroop and Wagner, the iron/wüstite phase boundary shows a minimum in oxygen content. From general thermodynamic relations it follows that at this minimum, the enthalpy of solution and entropy of solution of metallic iron in wüstite must be zero. With this condition and the application of further thermochemical data for wüstite, an equation for the Gibbs energy has been derived which may be used to calculate iron/wüstite and wüstite/magnetite phase boundaries in agreement with those determined experimentally.
Vacancy‐Impurity Binding Energy and the Effective Vacancy Formation Energy as Determined from the Solidus Line for Binary Al‐Based Alloys
Authors: Górecki Tadeusz 
Published: July 2012

AbstractThe vacancy model of melting of metals has been used as a starting point for deriving the expressions permitting to determine the vacancy‐impurity binding energy, Ebv–i, and the effective vacancy formation energy from the knowledge of the solidus line for binary alloys. The calculated values of Ebv–i and E for binary Al‐based alloys show a fair agreement with the experimental data existing in the literature.
Thermodynamic Behavior of Impurity Atoms in α‐Range Alloys of the Noble Metals and Nickel
Authors: Hehenkamp Theodor 
Published: July 2012

AbstractThermodynamic data for dilute α‐range alloys are necessary to understand atomic migration. Such data, however, are very scarce in the literature and contradict each other in many cases. A comparison is presented between the results of different experimental techniques particularly designed to measure partial thermodynamic quantities at low impurity concentrations. The results for I‐B‐noble metals alloys are surprisingly uniform and indicate an electronic origin of the dependence of the excess potentials on concentration, if the impurity atom has the same ion core as the host metal. If the impurity atom exhibits a much different ion core, a minimum in the excess chemical potential becomes observable at low concentrations. The reason could be either a size misfit or a dependence of the excess functions on the atomic mass. The viewpoint of the mass dependence is corroborated by results in the Ag–As‐system, which is characterized by almost no size misfit but a different atomic mass, and some recent measurements in Nickel‐alloys.
Thermodynamic Properties of Pd‐X‐Alloys, with X = Gd, Y, Ce
Authors: Paasch S. , Schaller H.‐J. 
Published: July 2012

AbstractElectromotive force measurements on cells with a CaF2 solid electrolyte were used to determine the activities of Gd, Y, and Ce in Pd‐rich alloys between 700°C and 800°C. The thermodynamic properties of these alloys are characterized by extreme negative deviations from ideal mixing behavior, up to −400 kJ/mol for the partial molar excess Gibbs energy of Ce and up to −320 kJ/mol for Gd and Y. The high thermodynamic stability of these alloys is attributed to a transfer of valence electrons to the electron gas of the alloy. At infinite dilution the resulting bonding contribution to the partial excess free energy is determined by the difference of the Fermi levels of the components and the valency of the solute. Including the size difference of the components as an additional effect, the mixing behavior of the alloys can be well described. – Within the homogeneity ranges of the intermetallic phases Pd3Y and Pd3Gd the activities of the unnoble components increase by more than ten orders or magnitude.
Thermodynamics of Liquid Na — Sn Alloys Using CaF2 Solid Electrolytes
Authors: Alqasmi R. , Egan J. J. 
Published: July 2012

AbstractThe thermodynamic properties of mixing for liquid Na – Sn alloys were determined between 750°C and 850°C by emf measurements using a CaF2 solid electrolyte. Concentrations were controlled by coulometric titration. Results are presented for partial and integral Gibbs energies, entropies, and heats of mixing across the entire composition range.
Self‐Consistent Solution of Sommer's Partial Associated Model. New Approach of the Configurational Entropy
Authors: Cunat Ch. , Hertz J. 
Published: July 2012

AbstractWe have worked with Sommer's partial associated model [1,2]. Considering that the adjustable parameters of this model are not real independant ones we have looked at iteration mathematical procedure to assure the self‐consistency with the formalism of the model. With respect to such a procedure, one isothermal enthalpy curve, for example, is mathematically sufficient to determine all the adjustable parameters. So we shall emphasize that all the results are strongly dependent on the choice of the configurational entropy model. Ours is coherent with the initial chemical assumption.
Photochemistry of Colloidal Metal Sulfides. 5. Fluorescence and Chemical Reactions of ZnS and ZnS/CdS Co‐Colloids
Authors: Henglein A. , Gutiérrez M. 
Published: July 2012

AbstractSmall colloidal particles of ZnS were obtained by precipitation of Zn2+ with SH− in the presence of colloidal silicon dioxide. Co‐colloids were prepared by simultaneously precipitating ZnS and CdS. Colloidal ZnS fluoresces at 425 nm. 90% of the fluorescence decays within 30 ns. The fluorescence is partly quenched by oxygen, chloroethanol and chloralhydrate. It can be completely quenched by methyl viologen and sulfide anions at low concentrations. The quenching actions are attributed to the scavenging of electrons or positive holes which are photo‐generated in ZnS. The onset of the absorption and the maximum of the fluorescence band are shifted towards shorter wavelengths with increasing Zn/Cd ratio of the co‐colloid. – ZnS in deaerated solution undergoes a slow photo‐anodic dissolution (quantum yield ø = 2 · 10−3 ZnS molecules/photon), the products being H2, Zn2+ (aq), sulfur and SO (aq). In the presence of air, a rapid decomposition with ø = 0.32 ZnS/photon takes place. In deaerated solutions, chloroorganic compounds promote the dissolution of ZnS. The chloroorganic compounds are decomposed, too. In the presence of sulfite, zinc metal is photo‐deposited onto the colloidal particles until hydrogen production takes over with ø = 0.18 H2/photon. In the presence of both sulfite and carbon dioxide, formic acid is produced with ø = 0.2 HCOOH/photon.
Absolute Measurements of the Thermal Conductivity of Aqueous NaCl Solutions at Pressures up to 40 MPa
Authors: Nagasaka Y. , Okada H. , Suzuki J. , Nagashima A. 
Published: July 2012

AbstractThe paper describes absolute measurements of the thermal conductivity of aqueous NaCl solutions in the concentration range 0 to 5 molality, the temperature range 0 to 80°C and the pressure range 0.1 to 40 MPa. An apparatus is based on the transient hot‐wire method using coated wire. The accuracy of the experimental results is estimated to be ± 0.5%. The results constitute the first measurements of the pressure effect on the thermal conductivity of NaCl solutions. The pressure coefficient of the thermal conductivity is compared with that of the viscosity. Three typical equations for predicting the thermal conductivity of aqueous electrolyte solutions are checked against the present experimental results. It is found that none of these equations can reproduce the present data within the experimental error.
Conformational Equilibrium and Calorimetric Behaviour of Systems Containing 1,2‐Dichloroethane
Authors: Baños Irene , Valero Jose , Gracia Mariano , Losa Celso Gutierrez 
Published: July 2012

AbstractExcess molar enthalpies (HE) of 1,2‐Dichloroethane + n‐Hexane, + (n‐Hexadecane, + Cyclohexane, + Benzene, + Tetrachloromethane, and + 1,2‐Dibromoethane, at 288.15, 298.15, 308.15, and 318.15 K, and densities of the pure components at 298.15 K, were measured. The most relevant point about the results obtained is the sluggishness of HE to change with temperature. For explaining this effect, a correlation between interaction potential energy and intramolecular potential energy in the conformational equilibrium, should be taken into account.
Equilibrium Vapor Pressure Measurements for the n‐Alcohols in the Temperature Range from −30 °C to + 30 °C
Authors: Schmeling T. , Strey K. 
Published: July 2012

AbstractWe measured the equilibrium vapor pressures pc ranging from 240 mmHg for methanol down to 5 · 10−3 mmHg for n‐hexanol, using capacitance pressure transducers. Good agreement is observed between literature data obtained by mercury manometers and our data in the ranges of overlap. Our data are found to be well described by the empirical Dupré‐Rankine formula. We analysed the thermodynamic basis of this relation and found its parameters to be interrelated. Once a reference temperature is chosen the number of adjustable parameters is reduced by one. The remaining parameters are physically relevant quantities, the molar vaporization enthalpy ΔHmv, and the difference of the molar specific heats of vapor and liquid phase ΔCmp. We evaluated these quantities from our measurements, and we give an overall fit of a combination of literature data and ours ranging from the boiling point to − 30 °C.
The Temperature Dependence of the Thermal Diffusion Factors of Binary Systems of Nitrogen with the Five Noble Gases and of Helium with Argon
Authors: Trengove R. D. , Dunlop Peter J. 
Published: July 2012

AbstractThermal diffusion factors, αT, are reported at several temperatures for binary systems of nitrogen with five noble gases. Similar data are reported for the system helium ‐ argon. Theoretical αT values are compared with the experimental data for two of the systems.
Solubility of Anthracene in Dense Gases and Liquids to 200°C and 2000 bar
Authors: Rößling G. L. , Franck E. U. 
Published: July 2012

AbstractThe solubility of anthracene to 200°C and 2000 bar, in some cases to 280°C and 3000 bar, was measured in 10 fluids: Ar, CH4, propane, n‐pentane, dimethylpropane, CO2, CHF3, CHClF2, NH3and H2O. Solution concentrations were derived from the absorption in the near UV‐band of anthracene near 370 nm. The high pressure optical cell, additional equipment and procedures are described. Results are given as anthracene concentrations and as “enhancement factors”. Enhancement factors up to 107were found. The factors increase with solvent density (except at very high density) and decrease with temperature at isochoric conditions. Virial coefficients B12are derived between 294 and 450 K. An improved sublimation pressure curve for pure anthracene was also determined.
Mechanistic Information from Temperature and Pressure Parameters for Some Substitution Reactions of dien and a Series of Ethyl Substituted dien Complexes of Palladium(II) in Aqueous Solution [1]
Authors: van Eldik R. , Breet E. L. J. , Kotowski M. , Palmer D. A. , Kelm H. 
Published: July 2012

AbstractSubstitution reactions of the type Pd(L)X+ + Y− → Pd(L)Y+ + X− with L = dien, 1,4,7‐Et3dien, 1,1,4‐Et3 dien, 1,1,7,7‐Et4 dien, 4‐Me‐1,1,7,7‐Et4 dien and 1,1,4,7,7‐Et5 dien, X = Cl, Br or I and Y = OH and I have been studied kinetically as a function of [Y−], temperature and pressure. The first‐order rate constant k1, for the solvolysis reaction path decreases along the series dien > 1,4,7‐Et3dien > 1,1,4‐Et3dien ≫ Et4 dien > MeEt4 dien ∼ Et5 dien, accompanied by an increase in ΔH* and almost constant values for ΔS# and ΔV#. The same applies to the second‐order rate constant k2 for the direct substitution reaction path in the case of Y = I, and the activation parameters for both k1 and k2 being indicative of an associative reaction mode for all complexes. For Y = OH, a significant [Y−] dependence was observed for the Et4 dien species only, and the value of Δ V# in this particular case favours a conjugate‐base mechanism. The results are discussed with reference to related studies reported in literature.
Stoßtwellenuntersuchungen zum Start der Reaktion CO + O2
Authors: Thielen K. , Roth P. 
Published: July 2012

AbstractBy use of the atomic resonance absorption spectrophotometry (ARAS) the rate coefficient of the reaction

k1 = 8.4 · 10−11 · exp (‐31800 K/T)cm3 s−1has been determined by direct measurements of the time dependent concentrations of O atoms in the reaction zone behind reflected shock waves. With additional measurements of H atom concentrations the influence of catalysing impurity reactions can be determined. The experiments were done under very clean conditions in mixtures of argon with small relative concentrations of CO (500 to 10000 ppm) and of O2 (100 to 20000 ppm) in the temperature range 1700 K ≤ T ≤ 3500 K at total pressures of about 1.8 bar.
Reduction of Pollutant Formation in Combustion Processes
Authors: Sawyer Robert F. 
Published: July 2012

AbstractCombustion sources account for approximately ninety percent of air pollutant emissions. Many of the effects of air pollutants upon human health and the environment are reasonably well understood. Some potential problems, however, such as the presence of carcinogens in urban atmospheres and the effect of carbon dioxide on climate, while not well understood, cause concern. — Modification of combustion processes to reduce pollutant emissions has proven successful. Better understanding of the fundamentals important to combustion often leads to pollutant reduction without compromise of efficiency or the quality of the combustion process. Treatment of combustion products to remove pollutants also has proven effective in cases where combustion modification fails to yield the required reduction. In other cases treatment of the fuel to remove pollutant percursors has been employed. A combination of these approaches has been chosen as an optimum strategy for some pollution control situations.
Ignition and Thermal Stability in Open Systems
Authors: Gray Peter 
Published: July 2012

AbstractThis paper is concerned with the resemblances and differences between the instabilities shown by exothermic gas reactions in closed and open systems. Even the simplest reaction (1st order, irreversible) in the simplest open system (uniform temperatures and concentrations, linear heat losses) can show very varied patterns of behaviour. The treatment highlights the roles of three essential time‐scales — residence time, Newtonian cooling time, and chemical reaction time — and the importance of the (dimensionless) adiabatic temperature in determining behaviour. Conditions for “ignitions” leading to oscillatory behaviour and for the extinction of oscillations are briefly discussed.
Ausbreitung von Flammen in Rohren mit einer Blende: Der Einfluß von Inertgas
Authors: Pangritz D. , Dörge K. J. , Wagner H. Gg. 
Published: July 2012

AbstractThe influence of nitrogen on the flame acceleration by an orifice in a tube of 40 mm diameter in C2H4–O2 mixtures has been investigated by measuring pressure profiles and flame‐speeds. For mixtures with nitrogen contents down to 60% the maximum overpressures are proportional to the laminar flame speed. Detonations develop close to the orifice when the nitrogen content is further reduced.
Hydrocarbon Oxidation at High Temperatures
Authors: Warnatz Jürgen 
Published: July 2012

AbstractThe detailed knowledge of combustion mechanisms is important, for example for the control of (kinetically determined) pollutant formation (e.g. NO, hydrocarbons, soot), for ignition problems, or for the extrapolation to technologically important but experimentally inaccessible condition. – In this review it is described how by suitable separation and elimination of unimportant reactions a mechanism is developed with the aid of the present kinetic data for the elementary reactions involved. This mechanism explains, without fitting, the currently available experimental results for laminar premixed flames of alkanes, alkenes and acetylene (flame velocity and structure of free flames, concentration and temperature profiles in burner‐stabilized flames). These experimental results are simulated by the solution of the corresponding conservation equations with suitable models describing diffusion and heat conduction in the multicomponent mixture considered. – In lean and moderately rich flames the hydrocarbon is attacked by O, H, and OH in the first step. These radicals are produced by the chain‐branching steps of the oxyhydrogen reaction. The alkyl radicals formed in this way always decompose to smaller alkyl radicals by fast thermal elimination of alkenes. Only the relatively slow thermal decomposition of the smallest alkyl radicals (CH3 and C2H5) competes with recombination and with oxidation reactions by O atoms and O2. This part of the mechanism is rate‐controlling in the combustion of alkanes and alkenes, and is therefore the reason for the similarity of all alkane and alkene flames. – In rich flames of aliphatic fuels, acetylene becomes a very important intermediate leading to soot precursors and to Non‐Zeldovich‐NO. Details of the reaction mechanisms are not yet known.
Rate Constants and CH3O Product Yield of the Reaction OH + CH3OH → Products
Authors: Hägele J. , Lorenz K. , Rhäsa D. , Zellner R. 
Published: July 2012

AbstractAbsolute rate constants and CH3O product yield for the reaction of OH radicals with methanol have been determined using a combined laser photolysis/resonance fluorescence (laser induced fluorescence) technique. The rate coefficient for total OH (kg = k1 + k2) is found to be kg = (1.2 ± 0.3) · 10−11 exp[–(810 ± 50) K/T] cm3/molecule · s over the temperature range 295–420 K. – The branching ratio of CH3O formation, ϕ = k1/k1 + k2, where (1) OH + CH3OH → CH3O + H2O and (2) OH + CH3OH → CH2OH + H2O, is found to be 0.11 ± 0.03 and 0.22 ± 0.07 at 298 and 393 K, respectively. From the temperature dependence of ϕ it is predicted that channel (1) is dominant in the combustion temperature region.
Temperaturmessung in sich ausbreitenden Flammenfronten (Methan/Luft, p0 = 1 bar, λL = 1,2) mit Hilfe funkenangeregter Fluoreszenz (SIF)
Authors: Saggau B. 
Published: July 2012

AbstractA premixed combustible mixture of methane/air of an air/fuel equivalence ratio λL = 1.2 and different pressures 0.5 ≤ p0 ≤ 1 bar is ignited in a cylindrical combustion chamber. The temperature profile of the generated flame front, which is travelling laminarly through the chamber, is measured by spark induced fluorescence (SIF), at which the gas at the right position is excited perpendicularly through the flame front to fluorescence by a short electrical spark. Each temperature is measured as a rotational temperature, delivered from the O – O rotational band of the 2. positive system of nitrogen, the main component in the chamber. Using a vidicon camera and an optical multichannel analyzer, a whole temperature profile can be measured by one single shot. At p0 = 1 bar the measured flame front thickness is LT = 0.5 mm and the maximum temperature of the s‐shaped flame front is measured to T ≈ 2100 K.
Structural Description of Water‐in‐Oil Microemulsions Using Electrical Resistance
Authors: Singh H. N. , Swarup Shanti , Singh R. P. , Saleem S. M. 
Published: July 2012

AbstractThe present article presents data on the formation and characterization of water in oil (W/O) microemulsion systems composed of ionic surfactants‐water‐benzene‐n‐alcohols (C4 – C8). The influence of the alcohol chain length and surfactant concentration, on the formation of microemulsion systems, has been investigated. When the amount of benzene or water was increased, the microemulsion system's appearance changed from clear to bluish to turbid. The transitions were identified on the basis of both visual appearance and specific resistance measurements. A dramatic change in the specific resistance was observed for the transitions. This was rationalized by assuming a change in the water structure from spherical to cylindrical to lamellae type. The critical nwater/noil ratio (Vc), for stable microemulsion system was calculated with the help of viscosity measurements.
Orientation and Spectral Characteristics of the Azobenzene Chromophore in the Ammonium Bilayer Assembly
Authors: Shimomura M. , Ando R. , Kunitake T. 
Published: July 2012

AbstractAzobenzene‐containing, single‐chain ammonium amphiphiles in which the alkyl chain length in the tail and spacer portions was systematically varied were prepared, and their aggregation behavior in water was studied by electron microscopy, differential scanning calorimetry and absorption spectroscopy. These amphiphiles exist as molecular dispersions, hydrated microcrystals, micelles, or bilayers. The formation of stable bilayers was deduced on the basis of three criteria which include the spectral agreement between aqueous dispersions and the corresponding cast films. Stable bilayers were obtainable when the sum of tail and spacer is not smaller than C14 to C16, and the tail is at least C8. Double‐chain ammonium amphiphiles which possess an octadecyl chain in addition to the azobenzene‐containing chain were prepared and shown to form stable bilayers. The absorption spectrum reflected the aggregate structure. In particular, the bilayer spectra were classified into four types: type A (λmax ca. 300 nm) for the parallel chromophore orientation (H aggregate), type B (330 – 340 nm) for the dimeric chromophore, type C (ca. 355 nm) for the isolated chromophore, and type D (360–390 nm) for the head‐to‐tail chromophore orientation (J‐like aggregate). Liquid‐crystalline bilayers gave type B spectra, while crystalline bilayers gave either of types A, B, and D, depending on the alkyl chain length. Finally, various examples of spectral control were discussed in relation to the present results.
The Photochemistry of 1,3‐Diphenyltriazene in Various Media. I: Photolysis in Liquid Solutions
Authors: Baro J. , Dudek D. , Luther K. , Troe J. 
Published: July 2012

Abstract1,3‐Diphenyltriazene has been irradiated at 360 nm in various liquid solutions. Reversible trans‐cis photoisomerization has been detected in solvents which do not form hydrogen bonds. Irreversible photolysis is observed with an appreciable amount of cage recombination products in all solvents. This reaction is well suited for a study in solid environments.
Thermodynamics of Polydimethylsiloxane Solutions. II. Application of an Extended Flory‐Theory
Authors: Heintz A. , Neff B. , Lichtenthaler R. N. 
Published: July 2012

AbstractExtensive experimental data of thermodynamic excess properties of Polydimethylsiloxane (PDMS)/solvent systems have been used for testing the consistency of Flory's theory of polymer solutions. The weakness of this theory in predicting chemical potentials and heat of dilutions consistently has been removed by introduction of an improved formula of the combinatorial entropy and a variable concentration dependent surface to volume ratio of the PDMS molecule. – A method has been developed which allows the determination of the parameters needed for the extended theory from calorimetric data only.
A Generalized van der Waals Equation of State II. Excess Heat Capacities of Mixtures Containing Cycloalkanes (C5, C6) Methylcycloalkanes (C5, C6) and n‐Decane
Authors: Siddiqi M. A. , Svejda P. , Kohler F. 
Published: July 2012

AbstractThe excess heat capacities, C of methylcyclohexane + cyclopentane, methylcyclopentane + cyclopentane, cyclohexane + methylcyclopentane, methylcyclohexane + methylcyclopentane and n‐decane + methylcyclopentane were measured by a Picker flow microcalorimeter at 293.15 K and atmospheric pressure. Also C‐values were calculated for these systems using a generalized van der Waals model augmented by the Boublik‐Nezbeda equation for hard convex bodies in a manner outlined in a previous publication. The measurements pointed to packing effects caused by the different molecular shapes. The calculations reproduced the experimental results rather well and supported the interpretation of the experimental results. The van der Waals model underlying these calculations is further substantiated by the measurements.