bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Investigation on the Thermal Stability of Metallic Glasses
Authors: Bergmann H. W. , Brokmeier U. , Fritsch H. U. 
Published: July 2012

AbstractThere are many instances in practice of phase changes in which the initial phase e.g. a homogeneous melt is not replaced by one or more thermodynamic stable phases but rather by metastable phases. Knowledge of systems in which metastable phases can form has increased considerably in recent years. Rapid quenching increases the tendency to form metastable phases including ultimately for appropriate compositions the amorphous metallic glasses. In any discussion about metastable phases there arises the question of the conditions under which they form and their stability which depends on temperature, pressure and composition. In the present work some attempts to describe the thermal stability of metallic glasses and the experimental means of measuring it are discussed.
Thermodynamic Properties of Pt — B Solid Solutions
Authors: Brodowsky H. , Sagunski H. 
Published: July 2012

AbstractThe activity coefficients of B in Pt were determind at 1200 and 1300 K by equilibrating Pt with B2O3in a controlled H2– H2O atmosphere and measuring the weight gain. The partial molar excess Gibbs energies at vanishing B concentration are –44 and –43 kJ/ mol, respectively. The atomic fractions at the solidus line are 0.036 and 0.031. A relative lattice contraction of the solid solutions prepared at 1200 and 1300 K of (1/a)(∂a/∂xB) = −0.042 and of −0.035 ± 0.002 was observed. This dependence of the lattice constant on the temperature of preparation suggests a mixed occupation of lattice and interstitial sites, with the majority of B atoms on lattice sites.
Statistical Properties of Non‐Equilibrium Effects in Turbulent Diffusion Flames
Authors: Peters N. 
Published: July 2012

AbstractIt is shown that the interaction between non‐equilibrium chemistry and turbulence in non‐premixed combustion depends essentially on two parameters: the conserved scalar and the instantaneous scalar dissipation rate. The previously favoured assumption of statistical independence between these two parameters is discussed. It is argued that the assumption must be questioned in the early part of jet flames where a comparatively regular flow field exists. A semideterministic model, the mixing layer ensemble model is developed on the basis of a statistical assumption about the stretching of the surface of stoichiometric mixture.
Thermal Decomposition of Ethylbenzene in Shock Waves
Authors: Brouwer L. , Müller‐Markgraf W. , Troe J. 
Published: July 2012

AbstractThe thermal decomposition of ethylbenzene has been investigated under high dilution by Ar in incident and reflected shock waves in the temperature range 1250–1600 K. At 4 · 10−6 ≤ [Ar] ≤ 2.4 · 10−4 mol cm−3 the reaction was found to be in the fall‐off regime of the unimolecular reaction. At the highest experimental density a first order rate constant k = 1017.1 ± 0.3 exp(–340 ± 10 kJ mol−1/RT) s−1has been derived. Based on observations of the UV spectra of the primary dissociation fragment and the final product styrene, as well as the kinetics of formation and consumption of the intermediate species, a dominant formation of benzyl radicals can be excluded. Instead it was shown that the dissociation starts with a C–H bond split.
Graphite Oxidation Phenomena During Massive Air Ingress Accidents in Nuclear High Temperature Gas Cooled Reactors with Pebble Bed Core
Authors: Moormann Rainer 
Published: July 2012

AbstractAir ingress into the mainly on graphite consisting core of a High Temperature Gas Cooled Reactor leads to graphite oxidation phenomena. The computer code REACT/THERMIX developed for safety analyses on reactor accidents connected to significant graphite corrosion processes, is briefly described. Calculations for massive, hypothetical air ingress accidents have shown, that severe safety endangering consequences do not occur; one of the main reasons for this behaviour is, that the small graphite/oxygen reaction front is not locally fixed during the accident but migrates through the core parallel to the cooling flow.
Kopplung von Stoffaustausch mit chemischer Kinetik beim Abbrand von Kohlepartikeln
Authors: Specht E. , Jeschar R. 
Published: July 2012

AbstractThe boundary layer of a burning particle in an air flow was investigated. It is illustrated, that at high temperatures the combustion is a two‐step mechanism: heterogeneous gasification at the solid surface area and homogeneous combustion of carbon monoxid in the boundary layer. The diffusion controlled burning rate can be calculated from the Sherwoodfunction according to the particular circumstances multiplied by the factor 2, which is confirmed by experiments. At high Reynoldsnumbers the burning rate becomes controlled by the chemical kinetics. The range of particle size in which the chemical kinetics influences the burning rate, is shown in dependence on temperature and air velocity.
Electrochemical Studies on the Electron Disorder in Cuprous Selenide
Authors: Mostafa S. N. , Seliman S. A. 
Published: July 2012

AbstractThe ratio of copper‐to‐selenium in cuprous selenide has been determined as function of the copper activity in the selenide at 435°C with the help of coulometric titrations. At 435°C the homogeneity range of cuprous selenide extends from a Cu/Se ratio of 1.998 to a value lower than 1.860. Analysis of the experimental data shows that the change of the chemical potential of copper by a change of the composition is only given by a change of concentration of the defect electrons or of the quasifree electrons. From these studies, the energy gap in coprous selenide is at least 0.37 eV.
Novel Effect of Man‐Made Molecular Assemblies on Photoinduced Charge Separation. 4. Synthetic Bilayer Membrane of Amphipathic Viologen as an Efficient Electron Collector in Photosensitized Redox Reactions
Authors: Nagamura Toshihiko , Tanaka Koji , Takeyama Naoki , Matsuo Taku 
Published: July 2012

AbstractAddition of synthetic bilayer membrane formed by a new type of amphipathic viologen containing two hexadecyl groups to aqueous solution of zwitterionic propylviologen sulfonate (PS2 – V2+) remarkably increased the yield of viologen photoreduction as sensitized by tris(2,2'‐bipyridine)‐ruthenium complex, Ru(bpy), in the presence of triethanolamine. Zwitterionic viologen was confirmed to shuttle as an efficient electron mediator between bulk aqueous solution and the interface of the bilayer membrane with a viologen head group. The quantum yield of viologen cation radicals was close to the net cage‐escape yield of photogenerated Ru(bpy) ‐ PS2‐V+ ion pair. The electrostatic field of positively charged interface of bilayer membrane was concluded to attract PS2‐Vc which transports electron to viologen head groups of bilayer membranes. Remarkable (500‐fold) suppression of the reverse electron transfer reaction was attained by the addition of viologen bilayer membrane. It was attributed to Coulombic repulsion between Ru(bpy) and positively charged interface of bilayer membranes. Relevance of the present system to chemical conversion of solar energy is discussed.
Broken Symmetry in Excited States of 9,9′‐Bianthryl
Authors: Rettig Wolfgang , Zander Maximilian 
Published: July 2012

AbstractThe dual fluorescence in polar solvents of 9,9′‐bianthryl (BA) and of the electronically perturbed BA‐derivatives 10‐chloro‐BA (BACl), BA‐10‐carboxaldehyde (BAA) and N‐(9‐anthryl)‐carbazole (C9A) as well as of N‐(4‐cyanophenyl)‐carbazole (CBN) is analysed and interpreted in terms of a simplified microstructural solvent interaction model. Dipole moments μT relative to μT (CBN) of the fluorescent charge transfer state have been derived from the solvatochromic band shifts in nitrile and alcohol homologous solvent series and are similar for BA, BACl and C9A. This implies that the charge transfer in the excited state occurs to a maximum degree even in the symmetric molecule BA. – QCFF/PI‐potential energy curves have been calculated and are used to discuss these findings. BAA fluoresces in alcohols only, μT‐compared to the other compounds studied being somewhat smaller probably because of specific H‐bond interactions with the solvent. – Using relative fluorescence quantum yields and energetic considerations the dependence of the excited states equilibrium on both solvent polarity and solute perturbation is discussed.
The Influence of Three‐Body Forces on the Lifetime and Stability of Rare Gas Clusters
Authors: Polymeropoulos E. E. , Brickmann J. 
Published: July 2012

AbstractThe formation of clusters in compressed argon and xenon gases is studied with the molecular dynamics simulation technique using two‐body Lennard‐Jones and three‐body Axilrod‐Teller interaction potentials. It is shown that the effect of three‐body interactions is a function of the temperature of the system and increases with decreasing temperature. The occurrence of clusters corresponding to the “magic‐number” n = 13 for xenon is explained in terms of the dispersion forces inherent in the Axilrod‐Teller potential. Computer generated images of stable and unstable Xe13 clusters are presented.
The Thermal Conductivity of n‐Hexane and n‐Octane at Pressures up to 0.64 GPa in the Temperature Range 34—90°C
Authors: Li S. F. Y. , Maitland G. C. , Wakeham W. A. 
Published: July 2012

AbstractNew, absolute measurements of the thermal conductivity of liquid n‐hexane and n‐octane are reported. The measurements have been carried out within the temperature range 34—90°C and over the pressure range 1.8 — 640 MPa in a transient hot‐wire instrument. It is estimated that the experimental data have an uncertainty of ±0.3%. The density dependence of the thermal conductivity of n‐hexane and n‐octane may be satisfactorily represented by means of an equation whose form is based upon an heuristic modification of the Enskog theory for transport processes in dense fluids. The optimum correlations for n‐hexane and n‐octane are slightly different from those which have been found to be universal among normal alkanes with an odd number of carbon atoms. This behaviour is predominantly attributable to the superior accuracy of the present experimental data, resulting from an improved treatment of radiative heat transport in the measurement.
Simultaneous Time‐Resolved ESR and Optical Absorption Spectroscopy. The Photolysis of 4‐Acetylpyridine in Propanol(‐2)
Authors: Lauschner Rainer , Dohrmann Jürgen K. 
Published: July 2012

AbstractA novel technique is described for the simultaneous in situ measurement of ESR and optical transients from intermediates produced by intermittent photolysis in solution. The technique has been applied to the photoreduction (λ ca. 300 ± 30 nm) of 4‐acetylpyridine (AP) in propanol(‐2) at room temperature. The measurements gave the absorption spectrum and the molar extinction coefficients of the intermediate 1‐hydro‐4‐acetylpyridinyl radical (·APH) in the 300 — 550 nm range as well as the ratio of the quantum yields for formation of · APH and disappearance of AP. Absolute values of the quantum yields at 300 nm have been determined by additional ESR and spectrophotometric measurements under steadystate conditions. The various results are discussed in terms of a mechanism proposed for the photoreduction of AP in propanol(‐2).
Rate Coefficients of Elementary Steps in the Inhibited Oxidation of Ethylbenzene, II. Interaction between Hydroperoxide and Alcohol Molecules
Authors: Héberger K. , Hubert Noszek E. , Gál D. 
Published: July 2012

AbstractThe decomposition of 1‐phenylethyl‐hydroperoxide assisted by 1‐phenyl‐ethanol has been investigated in the presence of 2,6‐di‐tert‐butyl‐4‐methyl‐phenol (ionol). Ethylbenzene was used as solvent, the temperature range was 115–130°C. The inhibition period was measured as a function of alcohol concentration (and inhibitor concentration as well). The activation parameters of hydroperoxide decomposition assisted by alcohol have been determined:kHROOH + HROH = 1.13 · 107 exp(94.9 kJ mol‐1/RT) s‐1
Excess Gibbs Function of the Binary Liquid Mixtures Formed by Acetonitrile with Pentyl Acetate, n‐Butanol, n‐Propanol, and Carbon Tetrachloride at 25°C
Authors: Masegosa R. M. , Prolongo M. G. , Hernández‐Fuentes I. , Horta A. 
Published: July 2012

AbstractLight scattering and differential refractometry at 546 nm have been used to determine Rayleigh ratios, depolarization factors, and refractive index increments in the title systems, at 25°C. The activity coefficients and the excess Gibbs function (GE) have been calculated from these measured magnitudes. The results of GE together with literature values of HE are used to discuss the importance of interactions and of order in these systems. The mixtures here studied are cosolvent of polymers. The present results should be useful for a better understanding of such phenomenon of cosolvency.
The Effect of Pressure on the Self‐Association of Dyes in Aqueous Solutions Studied by Cable Temperature‐Jump Relaxation Spectroscopy
Authors: Ohling W. 
Published: July 2012

AbstractEquilibrium and rate constants of the self‐association of methylene blue and pyronine G in aqueous solutions (water and water/methanol mixtures) are reported for pressures up to 200 MPa at T = 20°C and 30°C. The kinetic measurements were performed in a high pressure cable temperature‐jump apparatus. The volumes of reaction determined from the pressure dependence of the association constants are negative (–9.0 to –13.5 cm3 mol−1) for all reactions. From the pressure dependence of the rate constants the volumes of activation are found to be slightly negative for the forward reaction (±0 to –5.3 cm3 mol−1) and positive for the reverse direction (+ 4.3 to + 13.3 cm3 mol−1). The volumes of reaction of the two intermediate steps of the self‐association (i.e. formation of the encounter complex and rearrangement of the complex to form the dimer) are calculated by using the theory of diffusion controlled reactions. The resulting volume profiles of the reactions are discussed in view of the specific role of water as solvent.
Interactions of Methylbenzenes with Aluminium Bromide
Authors: Erb H.‐P. , Felbecker H. , Bluhm Th. 
Published: July 2012

AbstractProceeding from the chemical shifts of the 13C and 27Al atoms, the thermodynamic properties were calculated for the simultaneous formation of the complexes arene · Al2Br6 (C) and arene · AlBr3 (D) in liquid binary mixtures of methylbenzenes with aluminium bromide. Other stoichiometric models, that take into account the formation of only one complex (C or D) at a time, could only be eliminated by including the 27Al NMR data.– We conclude from the effects of concentration on the chemical shifts, that the aromatic π‐electrons transfer charge to the aluminium bromide, which is oriented above or below the aromatic plane.
The Influence of the Electronic Structure on the Dimerization of Phenthiazonium Cations in Aqueous Solution
Authors: Ruprecht J. , Baumgärtel H. 
Published: July 2012

AbstractThe association of different aminophenthiazonium cations in aqueous solution has been investigated and correlated with the distribution of π‐electron density in the cations. The 3,7‐disubstituted cations with their cyaninelike π‐system dimerize in contrast to aminophenthiazonium cations with noncyaninelike distribution of π‐electron density.
On the Nature of the Bonding of Lone Pair Ligands to Small Metal Clusters
Authors: Bagus P. S. , Hermann K. , Bauschlicher C. W. 
Published: July 2012

AbstractWe analyse the interaction and bonding between CO, NH3 and PF3 molecules and a Cu5 cluster in detail. From a constrained space orbital variation (CSOV) study, we are able to determine the energetic importance of different contributions to the metal‐ligand interaction, such as intra‐unit, Cu5 and ligand, polarization and inter‐unit donation. The results show that the Cu5–NH3 bonding is determined to a large part by the electrostatic interaction between the units with little charge transfer. The Cu5–CO bonding is characterized mainly by a metal to ligand π donation. The Cu5–PF3 bonding has metal to ligand π and ligand to metal s̀ donation of comparable importance. The free PF3 dipole leads to a repulsive interaction with the Cu5 and this affects the intra‐unit polarization.
Surface Enhanced Raman Scattering (SERS) at Matrix Isolated Metal Clusters of Ag, Na and K
Authors: Schulze W. , Breithaupt B. , Charlé K.‐P. , Kloss U. 
Published: July 2012

AbstractSurface‐enhanced Raman spectra of various molecular gases adsorbed on colloidal matrix isolated silver, sodium and potassium clusters of about 100 Å diameter are reported. For CO adsorbed on silver clusters the strongest enhancement is observed in the region of considerable surface plasmon absorption of the metal colloid (electromagnetic enhancement). N2 and O2 adsorbates on silver colloid on the other hand show much weaker SERS‐signals. Furthermore the frequency shift of the adsorbate relative to the condensed free molecule as well as the line broadening is much weaker than for CO, indicating a weaker chemical interaction. – The importance of surface plasmon excitation for getting SERS signals is additionally proven by using colloids of sodium and potassium. On these more reactive metal colloids chemical reactions can even be monitored at low temperatures.
The Optical Properties of Silver Microcrystallites in Dependence on Size and the Influence of the Matrix Environment
Authors: Charlé K.‐P. , Frank F. , Schulze W. 
Published: July 2012

AbstractThe surface plasmon absorption band of small metal particles or large clusters (diameter ≤ 100 Å) is known to shift and to broaden with decreasing diameter. It is argued and experimentally proven at Ag‐colloids that this size effect depends sensitively on the microscopic surface properties of the clusters, which are influenced by the interaction with the embedding matrix.
Reactivity of Fluorochloromethanes with Desert Sands
Authors: Benzoni L. , Garbassi F. 
Published: July 2012

AbstractDesert sand reactivity with halocarbons like CCl3F (F11), CCl2F2 (F12) and CHCl2F (F21) has been proved. Reactivity increases in the sense: F12 ⩽ F21 < F11 and is favoured by temperature and short activation of samples at 673 K. For F11, the main reaction products are CCl4 and COCl2, but some transformation to F12 has been observed too. An influence of the desert sand origin (i.e. of its phase composition) has been also found. — X‐ray photoelectron spectra of samples after reaction show the presence of F and Cl on their surface, mainly as calcium halides, and in direct proportionality with reactivity.
The Transition Between Regular and Chaotic Dynamics and Its Influence on the Vibrational Energy Transfer in Molecules After Local Preparation
Authors: Brickmann J. , Pfeiffer R. , Schmidt P. C. 
Published: July 2012

AbstractThe classical as well as the quantum dynamics of two‐dimensional nonseparable oscillator systems is studied in order to investigate the influence of regular and chaotic motion on the nature of the intermode vibrational energy transfer after local excitation. Representative sets of initial conditions ‐ each element representing a single phase space cell — were chosen. For the classical problem one phase space point per cell was used while for the quantum problem minimum uncertainty wave packets (harmonic oscillator coherent states) with position and momentum expectation values corresponding to the classical values were taken as initial quantum states. For both types of motion information entropies were determined from time averaged probabilities. These entropies are compared with “ergodic limit entropies”. The latter correspond to a statistical preparation of the initial states. Although there is only a weak correspondence between single‐trajectory motion and wave packet dynamics, some general predictions about the quantum dynamics can be made from the classical results for a time scale of chemical interest. No sharp transition is found for the wave packet dynamics going from the classically regular to the irregular energy region. However, one can estimate the probability for an arbitrarily prepared local minimum uncertainty wave packet to possess statistical (RRKM) or non statistical (non‐RRKM) dynamics from the analysis of a sample of classical trajectories each starting in a phase space cell of the bound area of the Hamiltonian, i.e., the nature of unimolecular reactions can be roughly predicted from the potential energy surface and a sample group of classical trajectories.
Diffusion Coefficients and Thermal Diffusion Factors of Several Binary Systems of Carbon Monoxide and Oxygen with Noble Gases
Authors: Trengove R. D. , Robjohns H. L. , Dunlop Peter J. 
Published: July 2012

AbstractDiffusion coefficients and thermal diffusion factors are reported for several binary systems of carbon monoxide and oxygen with noble gases. Using approximate spherical potential functions, most of which have been reported in the literature, the experimental results are compared with the predictions of the Chapman‐Enskog theory.
Direct Determination of the Rate Constant for the Reaction CH2 + H → CH + H2
Authors: Böhland T. , Temps F. 
Published: July 2012

AbstractThe reactionmagnified imagewas investigated at room temperature in an isothermal discharge flow reactor with laser magnetic resonance detection of CH2 and CH. Direct measurements of the decay of CH2 in the presence of an excess of H‐atoms yielded a rate constant ofmagnified imageCombined with the known rate constant for the reverse reaction CH + H2 + CH2 + H the heat of formation of CH2 was found to bemagnified image
On Complex Formation in Mixed Solvents
Authors: Strehlow H. , Busse G. 
Published: July 2012

AbstractIn a mixture of solvents S1 and S2 a cation Mz+ forms “solvatomers” of the type M(S1)i(S2)k‐iz+, where k is the coordination number of the cation and i = 0 to k. The rate of substitution of a solvating molecule by a ligand LzL depends in general on the specific solvatomer and on the solvent molecule being substituted. – Kinetic measurements are reported on systems with the cations Be2+, Al3+, and Ni2+, the ligands sulfate, rhodanide and acetate and the solvent pairs water‐dimethylsulfoxide, water‐N‐methylformamide, water‐hexamethylphosphoric triamide, water‐formamide and methanol‐dimethylsulfoxide. – Some rules concerning the kinetic behaviour of such systems have been developed. In particular, an explanation is presented for the different kinetics observed with tetrahedrally coordinated complexes (k = 4) and with octahedrally coordinated ones (k = 6).
The Solubility of Ethane in Water up to 473 K
Authors: Crovetto Rosa , Fernandez‐Prini Roberto , Japas Maria L. 
Published: July 2012

AbstractThe Henry constants for the dissolution of ethane in water have been determined with two experimental methods up to 473 K and with an overall precision of 2%. From this data it was possible to calculate the thermodynamic properties of the dissolution process and using the results of our previous study of the thermodynamics of dissolution of methane in water, it was possible to calculate the contribution of the so‐called hydrophobic effect over a wide temperature range. It is shown that a Percus‐Yevick plus Lennard‐Jones perturbation theory accounts reasonably well for the observed behaviour.