bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetic susceptibility and proton Knight shift in Pd‐Ag and Pd‐(rare earth) solid solution alloy hydrides
Authors: Sinsel Bernd , Anton Herbert , Schmidt Peter C. , Weiden Norbert , Weiss Alarich 
Published: July 2012

AbstractThe magnetic susceptibility χ and the1H‐Knight shiftKHfor the ternary hydrides Pd0.6Ag0.4Hr(0.05 ≤r≤ 0.16), Pd0.7Ag0.3Hr(0.08 ≤r≤ 0.26), and Pd0.936(RE)0.064H0REGd (0.04 ≤r≤ 0.47), Dy (0.06≤r≤0.50), and Lu (0.02 ≤r≤ 0.59) are studied as a function of the hydrogen contentusing high resolution1H‐NMR spectroscopy. Additionally, the temperature dependence of χ for the hydrogen free host alloys Pd0.936(RE)0.064is measured using a SQUID magnetometer and the local f magnetic moments of Gd and Dy are determined. In all systems considered, χ is decreasing with increasingrandKHis negative and increasing with increasingr.The various contributions to χ andKHare discussed on the basis of augmented spherical wave (ASW) supercell band structure calculations.
Electronic conductivity of gadolinia doped ceria
Authors: Lübke S. , Wiemhöfer H.‐D. 
Published: July 2012

AbstractThe electronic conductivity of gadolinia doped ceria (Ce0.8Gd0.2O1.8) was measured as a function of oxygen activity (aOz=1 corresponding to a gas with oxygen partial pressure pO2= 1.013 bar) in the range from aOz≈︁101 to aO2≈︁10−13 for temperatures between 600 and 750°C. The Hebb‐Wagner polarization technique was used with an encapsulated Pt‐microcontact in N2 atmosphere and a Cu2O/CuO reference electrode. For instance, a minimum value of 3.10−7 S/cm was found for the electronic conductivity at 600°C and an oxygen activity of 9.10−7. The minimum is shifted to higher activity with increasing temperature. The activity dependence of the electronic conductivity in the n‐type and p‐type range agrees well with the theoretically expected values (p‐type range σp≈︁a
, n‐type range σn≈︁a
). Extrapolation of the measured electronic conductivities, the electrolytic domain boundaries of Gd‐doped CeO2 were obtained as log aO2= 13 to log aO2=‐24.7 at 600°C and log aO2=11 to log aO2=‐20.1 at 700°C (the oxygen ion conductivity being 4.05.10−3 S/cm at 600°C and 1.29.10−2 S/cm at 700°C).The activation energy was determined from the temperature dependence of the electronic conductivity giving EA,e=(2.59±0.07) eV for electrons in the n‐type range and EA,h=(1.16±0.04) eV for the holes in the p‐type range. The migration enthalpy of electrons was Hmig,e = 0.49 eV.
Photophysics and photochemistry of trans‐4‐nitrostilbenes and trans‐2,4‐dinitrostilbenes: Effect of intramolecular charge transfer
Authors: Görner Helmut 
Published: July 2012

AbstractThe photophysical and photochemical properties of trans‐R‐2′,4′‐dinitrostilbene (II) and a series of trans‐R‐2′,4′‐dinitrostilbenes (II‐R, R: 2‐NO2, 3‐NO2, 4‐Br, 4‐F, 4‐Me, 4‐C3H7, 4‐OCH2C6H5, 3,4,5‐(OMe)3, 4‐OEt, 4‐NMe2, 4‐NEt2) were studied in solution as a function of solvent polarity and temperature. The quantum yield of fluorescence (Φf) is very small for all II‐R at 25°C. At −196°C Φf is moderate for several derivatives in 2‐methyltetrahydrofuran (MTHF) but strongly enhanced for those bearing electron donating substituents. For the latter compounds the quantum yield of trans → cis photoisomerization is low, but for the other compounds Φt → c is substantial (0.2‐0.5 in toluene or MTHF at room temperature). The triplet state absorbs typically in a broad spectral range; its lifetime (τT) lies in the 20‐200 ns range and is longer for R = 4‐NEt2; at −196°C τT of all II‐R approaches milliseconds. The results are compared with those of trans‐4‐R‐4′‐nitrostilbenes (I‐R, R: NO2, H, OMe, NH2, NMe2, NEt2). Phosphorescence of singlet molecular oxygen was observed for several mono‐ and dinitrostilbenes at room temperature. Generally, the quantum yield of singlet oxygen formation is much smaller than that of intersystem crossing into the triplet state. The triplet mechanism accounts for trans→cis photoisomerization and the contribution of this pathway is lowered by intramolecular electron transfer to the nitro group(s). The similarities and differences between I‐R and II‐R type compounds and the effects of intramolecular charge transfer are discussed.
A heuristic approach to the analysis of Mössbauer‐Spectra: The ‘simulated annealing’‐algorithm
Authors: Lankau T. , Bieber S. , Nagorny K. 
Published: July 2012

AbstractThe ‘Simulated Annealing’ algorithm is used to analyse Mössbauer spectra with distributed hyperfine structure parameters. The distribution is described by a set of points. No initial assumptions regarding the distribution function are therefore necessary to run the program successfully. The algorithm can be easily extended to handle more than one distribution.
Conductometric study of LiCIO4 and Bu4NBPh4 in propylene carbonate‐toluene mixtures
Authors: Moumouzias George , Ritzoulis George 
Published: July 2012

AbstractThe electrolytic conductances of LiClO4 and BU4NBPh4 in Propylene carbonate‐Toluene mixtures at 25, 30 and 35°C have been measured. Limiting equivalent conductance, association constant and distance parameter of ions were calculated by means of Lee‐Wheaton equation. Gibbs energy of ion‐pair formation due to non‐Coulombic interaction, conductive transport activation energy, Walden product and Stokes radius are also evaluated.
Real time kinetics and thermochemistry of the uptake of HCl, HBr and HI on water ice in the temperature range 190 to 210 K
Authors: Flückiger Benoît , Thielmann Axel , Gutzwiller Lukas , Rossi Michel J. 
Published: July 2012

AbstractThe real time kinetics of adsorption and desorption of HCl on ice have been studied in a very low pressure reactor (Knudsen cell). We used two complementary techniques, namely pulsed valve or transient supersaturation and steady state experiments. The kinetics of adsorption, following a first order rate law, has been found to depend on the number of HCl molecules in a pulse for transient supersaturation and on the HCl partial pressure or flow rate in steady state experiments. The uptake coefficient γ ranges from 0.34 to 0.22 in the temperature range 190 to 210 K for dry adsorption leading to a quasi‐liquid state of HCl on ice and from 0.31 to 0.13 for adsorption leading to a liquid solution of HCl. In both cases a negative temperature dependence for uptake of HCl on ice of −1.8±0.5 and −3.1±0.5 kcal/mol has been observed. In addition, the fraction of HCl that could be retrieved by desorption after dosage with HCl depended strongly on the thermodynamic state of the HCl/ice substrate as well as on the temperature and varied in the range from 10 to 80%. We determined the rate of irreversible surface‐to‐bulk loss, with a limiting rate of 1.0·1013 molecule s−1 cm−2 at 200 K. In addition, we studied the kinetics of adsorption of HBr and HI on ice resulting in γ values similar to HCl. However, ice in the range 190 to 210 K did not support any measurable vapor pressure of both HBr and HI after adsorption of up to several formal monolayers in contrast to HCl.
A network of characteristic functions describing the dynamics of adsorbate‐adsorbent systems
Authors: Rödenbeck Christian , Kärger Jörg , Hahn Karsten 
Published: July 2012

AbstractAdsorbate‐adsorbent systems characterized by a stationary particle exchange with their surrounding are considered. Depending on the considered processes, like, e.g., tracer exchange or particle conversion, the behaviour of such a system may be described by a number of characteristic functions (tracer exchange curves, effectiveness factor, residence time distribution, transit time distribution, and others) whose particular shape is determined by the properties of the underlying transport mechanisms. It is shown that, under very general assumptions (mainly stationarity), there are one‐to‐one relations between these characteristic functions. Owing to these relations, the behaviour in a given process may be determined from that in a completely different one, without the need of any explicit information about the underlying transport mechanisms. The paper derives a great variety of relations (including equations for the analysis of a number of frequently used experimental setups) and discusses the information content as well as general properties of the characteristic functions.
Solvatochromism in supercritical fluids
Authors: Maiwald Michael , Schneider Gerhard M. 
Published: July 2012

AbstractSolvatochromic shifts of the five probe indicators 2‐nitroaniline, 4‐nitroaniline, 4‐nitroanisole, 4‐nitrophenol, and N,N‐dimethyl‐4‐nitroaniline have been used to specify the solvatochromic solubility parameters π* and β of the five pure fluids CO2, N2O, CClF3, SF6, and NH3 according to Kamlet, Abboud, and Taft by means of UV/VIS spectroscopy. Three isotherms, nearcritical and supercritical, were examined, for the first time from zero pressure up to 100 MPa. Except NH3 with β≈︁0.70 (293 K), 0.65 (333 K), and 0.55 (413 K) at 100 MPa, respectively, all other fluids do not show significant basicity at any temperature and pressure conditions. Plotting π* vs reduced density of any fluid results in steeply increasing curves with maximum enhanced π* data at reduced densities of about 0.6 which continuously level out and finally rise again asymptotically as straight lines.
Finite size dependence of the tracer surface diffusion coefficient near a second order phase transition
Authors: Nieto F. , Uebing C. 
Published: July 2012

AbstractWe investigate the finite size dependences of the tracer surface diffusion coefficient in the vicinity of a second order phase transition. For this purpose, we use a lattice gas model of repulsively interacting particles on a square lattice. For all lattice sizes L studied, the tracer diffusion coefficient, Dt, is a smooth function of temperature. There are no anomalies in the direct temperature dependence of Dt near the critical temperature Tc. However, its derivative, dDt/d(1/kBT), exhibits cusp‐like anomalies which are largely pronounced for large lattice sizes.
Influence of the preparation conditions on the properties of electropolymerised polypyrrole
Authors: Brandl Volker , Holze Rudolf 
Published: July 2012

AbstractPolymerisation conditions have a remarkable effect on the various material properties of polypyrrole. Care has to be taken to ensure identical conditions for electrochemical experiments when films electropolymerised differently are examined in comparison. The effect of a variety of experimental parameters on redox capacity, conductivity and electrooptic behaviour has been examined. Based on experimental evidence presented here and reported elsewhere explanations are proposed. A choice of optimum conditions suitable for obtaining a tailored polymer can be derived.
Simulation of the rotator phase of cyclohexane at higher pressures
Authors: Würflinger A. 
Published: July 2012

AbstractThe reorientational behaviour of cyclohexane molecules in the rotator phase has been investigated with a Monte Carlo simulation in a cubic box with periodic boundary conditions. A previous simulation for state points at normal pressure is extended to higher pressure. This enables us also to perform simulations along isochors and isotherms, thus to distinguish between isothermal density changes and isochoric temperature changes. Reorientational correlation functions for various molecular axes are calculated in order to analyse the orientational disorder. It was found that in the immediate neighbourhood to the low‐temperature phase transition the orientational freedom is limited. At larger distances to the solid‐solid transition line no preferred orientations can be detected. The reorientational behaviour changes significantly when a displacement of the molecular centers is allowed, in particular the otherwise retarded decay of the correlation function for the C3‐axis is accelerated near the low‐temperature phase boundary of solid I.
I. Electronic structure and thermodynamics of alloys: Alloy Metastability During Nucleation‐Controlled Reactions
Authors: Perepezko J.H. , Wilde G. 
Published: July 2012

AbstractThe initial stage of a first order transformation reactions is controlled by a nucleation process. In fact, the kinetic constraints provided by nucleation and growth difficulties of the new phase provide the necessary condition to expose metastable reaction pathways. The resulting hierarchy of metastability is viewed in terms of the severity of the imposed kinetic constraints. The identification of nucleation control has been extended to cover solid state reactions such as those involved in solid state amorphization reactions (SSAR) of so‐called driven systems. Some of the fundamental characteristics of alloy metastability under kinetic constraints are illustrated by experimental observations and model analyses that highlight the current understanding.
The Bragg‐Williams‐Gorsky (BWG) ordering treatment in the compound energy formalism (CEF)
Authors: Fries Suzana G. , Lukas Hans Leo , Ansara Ibrahim , Sundman Bo 
Published: July 2012

AbstractThe BWG type of approximation describing chemical ordering has been available in thermodynamic calculation‐optimisation software. Developments were done for special cases of symmetry, e.g. the γ‐γ′ ordering, based on the fcc lattice, in Ni‐based superalloys or the β‐β′ ordering in the Cu‐Zn system, based on the bcc lattice.The technological importance of materials presenting order‐disorder transformations, demands a versatile Gibbs energy modelling, able to describe the changes taking place during ordering as functions of composition and temperature. Recently practical use of Gibbs energy descriptions of ordered phases are becoming a daily procedure.In this communication we present a general method for deriving the constraints in the compound energy formalism (CEF) for the model parameters describing an order‐disorder transformation. The cases discussed include, for example, the oxygen ordering in its interstitial solution in α‐Zr (hep).
Sound velocity in the molten As‐Te system
Authors: Tsuchiya Y. 
Published: July 2012

AbstractThe velocity of sound in the molten As‐Te has been measured as a function of temperature, which shows up to 60 at.% As a pronounced minimum like in pure liquid Te. In an As‐ rich alloy, only a high temperature branch of the whole vs‐T curve that the sound velocity decreases rapidly with lowering temperature was obtained, because solidification took place before a minimum could be observed. The results suggest that rapid structural changes occur with varying temperature over the whole composition and confirm the recent experiments indicating that liquid As undergoes rapid structural changes with raising temperature like in supercooled Te. An extrapolation predicts a minimum in the sound velocity in As to occur at 736±6°C. The Peierls distortion mechanism and stability of structure of the liquid sp‐bonded elements are discussed.
EMF‐Study of the thermodynamics of liquid Kx(KI)1‐x and Csx(CsI)1‐x melts
Authors: von Blanckenhagen B. , Nattland D. , Freyland W. 
Published: July 2012

AbstractWe report EMF measurements of the metal activity aK and aCs in Kx(KI)1‐x(xK≤0.0136) and Csx(CsI)1‐x (xCs≤0.25) at T=800°C. The data have been obtained simultaneously with optical absorption spectra. The composition has been controlled in situ via coulometric titration. The data of Kx(KI)1‐x are discussed in terms of a thermodynamic defect model, taking into account different electronic defect species in the melt: mobile electrons, monomer F‐center like and bipolaronic states. The results of the analysis of the thermodynamic data are in good agreement with the results of the quantitative analysis of the optical absorption spectra. For Csx(CsI)1‐x we report data for the partial molar excess‐free enthalpies and the integral‐free enthalpy. As expected the Csx(CsI)1‐x system shows only little deviation from ideal mixing behaviour in comparison to other Mx(MX)1‐x melts, a fact which is also established in the phase diagram by the absence of a miscibility gap in the caesium‐caesium halide mixtures.
II. Surface and interfacial phenomena: Surface phases in binary liquid metal alloys: An X‐ray study
Authors: Tostmann H. , Dimasi E. , Shpyrko O. G. , Pershan P. S. , Ocko B. M. , Deutsch M. 
Published: July 2012

AbstractSurface‐sensitive x‐ray scattering techniques with atomic scale resolution are employed to investigate the microscopic structure of the surface of three classes of liquid binary alloys: (i) Surface segregation in partly miscible binary alloys as predicted by the Gibbs adsorption rule is investigated for Ga‐In. The first layer consists of a supercooled In monolayer and the bulk composition is reached after about two atomic diameters. (ii) The Ga‐Bi system displays a wetting transition at a characteristic temperature Tw ≈︁ 220°C. The transition from a Bi monolayer on Ga below Tw to a thick Bi‐rich wetting film above Tw is studied. (iii) The effect of attractive interactions between the two components of a binary alloy on the surface structure is investigated for two Hg‐Au alloys.
Wetting and prewetting transitions in Ga‐Pb alloys
Authors: Wynblatt Paul , Chatain Dominique 
Published: July 2012

AbstractThis paper summarizes previous work on wetting and adsorption transitions in the Ga‐Pb system. It describes a model of these transitions which is based on the regular solution approximation in conjunction with nearest neighbor interactions. It also reviews several recent novel experimental results obtained in Ga‐Pb, including: (a) evidence that complete wetting prevails in Ga‐Pb alloys within the domain of liquid‐liquid coexistence; (b) a demonstration that the thickness of Pb at the surface of Ga diverges logarithmically as liquid‐liquid coexistence is approached, as expected for metallic systems characterized by short‐range interactions, and (c) studies of adsorption transitions by two complementary experimental approaches which map out the extension of the prewetting line and provide estimates of the prewetting critical point and the wetting temperature.
Surface and bulk properties of strongly non‐ideal liquid binary metallic systems
Authors: Rösner‐Kuhn M. , Kuppermann G. , Thiedemann U. , Drewes K. , Schmidt‐Lehmann T. , Frohberg M. G. 
Published: July 2012

AbstractBased on activity data for the components in the bulk phase and the surface tension of the constituent metals, the Butler equation is applied to liquid Fe‐Ti alloys to calculate the surface composition, the activities of the components in the surface, and the surface tension of the entire concentration range of the system. Using thermodynamic modeling the bulk activities of the components are derived from mixing enthalpy data. A comparison between the calculated temperature dependence of the surface tension and experimental values obtained by oscillating drop technique measurements is given for the liquid Fe2Ti intermetallic alloy, where a sufficient agreement can be stated.
Study of the effect of zirconium addition to the Al‐rich alloys of the Al‐Cu and Al‐Cu‐Mg systems
Authors: Soares Delfim F. , De Castro Portela Fernando 
Published: July 2012

AbstractThe effect of zirconium addition on the eutectic reactions, on the Al‐rich part of the Al‐Cu and Al‐Cu‐Mg systems, were studied by differential thermal analysis (DTA). The temperature of the reactions and, for Al‐Cu alloys, the heat of the reactions were determined. After the DTA experiments the alloys were studied by scanning electron microscopy (SEM) and the chemical analysis of the phases have been determined by energy‐dispersive spectroscopy (EDS).The temperature of the eutectic reactions does not change significantly by the presence of zirconium in the system. The phase distribution on the ternary and quaternary systems shows that the zirconium present is essentially in the Al3Zr and “X” phases. The Al3Zr phase has a low solubility range for copper, ∼ 0.5 at.%, and no solubility for magnesium. The X‐ray pattern of the ternary phase “X” is presented, for alloys belonging to the Al‐rich part of the Al‐Cu‐Zr system
Thermodynamic assessment of the Al‐Nb‐Ti system
Authors: Servant C. , Ansara I. 
Published: July 2012

AbstractThe Gibbs energy of formation of the solution and compound phases in the Al‐Nb‐Ti system were derived from an optimisation procedure using all the available experimental thermodynamic and phase diagram data. The thermodynamic description of the ordered compounds was made using a multi‐sublattice model, while a Redlich‐Kister polynomial was used for the solution phases.
Phase equilibria and stability of the bcc aluminide in the Co‐Cr‐Al system
Authors: Ishikawa K. , Ise M. , Ohnuma I. , Kainuma R. , Ishida K. 
Published: July 2012

AbstractPhase equilibria and ordering reactions in the bcc aluminides of the Co‐Cr‐Al systems over a temperature range of 1000‐1350°C have been investigated mainly by the diffusion couple method. The compositions of the γ (Al: fcc‐Co), β (B2: CoAl), α (A2: bcc‐Cr) and σ (sigma phase: D8b) phases in equilibrium, and the critical boundaries of the A2/B2 continuous ordering transition in the bcc phase region have been determined. It is shown that both continuous and discontinuous A2 to B2 phase ordering transitions and elliptically shaped A2+B2 miscibility gap islands with wide composition ranges exist in these systems in isothermal sections. The phase equilibria involving the γ, β, α and σ phases are presented and stability of the ordered bcc aluminides is discussed.
IV. Progress in experimental methods: Thermodynamic investigations in the Si‐Ge‐rich part of the ruthenium‐silicon‐germanium system
Authors: Perring L. , Bussy F. , Kuntz J. J. , Gachon J. C. 
Published: July 2012

AbstractThis paper reports molar heat capacities of Ru50SixGe(50‐x) and Ru40SiyGe(60‐y) ternary solid solutions determined by differential scanning calorimetry. A second order transition has been characterised for alloys ranging from Ru40Ge60 to Ru40Si10Ge50 at temperatures ranging from 850 to 1040 K, respectively. Tie lines have been established at 1000‐900‐800‐700‐600°C by electron microprobe measurements on annealed alloys of the two phase domains: Ru50SixGe(50‐x)‐Ru40SiyGe(60‐y) and Ru40SiyGe(60‐y)‐Si zGe(100‐z).
Vapor pressure methods: A source of experimental thermodynamic data
Authors: Ipser Herbert 
Published: July 2012

AbstractAn overview is given of the vapor pressure methods which are used for the determination of partial thermodynamic quantities. The methods are divided into four groups: static methods (pressure gauges, atomic absorption, and others); dynamic methods (boiling point method, transpiration method); effusion methods (Langmuir method, different variants of the Knudsen method); equilibration methods (equilibration with gas mixtures, isopiestic method, dew point method). The characteristics of each group are discussed shortly, and some examples of application are given from the recent literature.
Heat capacity of liquid eutectic tellurium alloys
Authors: Schmid J. , Sommer F. 
Published: July 2012

AbstractUsing an adiabatic calorimeter direct measurements of the heat capacity of the liquid Si15Te85, Ge15Te85, Sn15Te85, Pb11Te89, Pb11Te89 and Bi10Te90 alloys and of liquid tellurium have been performed. The heat capacity has been measured as a function of temperature up to about 100 K above the eutectic temperature. The heat capacity decreases with increasing temperature. The excess heat capacity ΔCp of Sn15Te85, Pb11Te89 and Bi10Te90 is pnearly constant within the examined temperature range and is smaller than 5 J mol−1 K−1. ΔCp of Sb11Te89 slightly depends on temperature, while ΔCp of Si15Te85 and Ge15Te85 exhibit large values and temperature dependences. ΔCp reflects the chemical short range order (CSRO) in the liquid state due to the strong compound forming tendency in these alloys. The influence of CSRO is discussed in the light of the measured ΔCp and other structure sensitive properties given in literature.