bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Complex‐Scaling Treatment of Ionic Transport in Fluids
Authors: Chatzidimitriou‐Dreismann C. A.
Published: July 2012

A quantum mechanical mechanism causing high ionic conductances in condensed phases is revealed through the application of the Complex Scaling Method into the statistical mechanics of amorphous condensed matter. It is argued that the predicted high conductivities are due to quantum delocalization of the considered ions, which causes their mass interference with the equivalent particles (ions, atoms) in their surroundings. The physical contexts (i) of the H+ and OH− conductivity in aqueous solutions, and (ii) of the ionic conductivity in molten alkali chlorides are considered explicitly. A common mechanism for the well known high conductivities in these systems is presented. Direct connection with existing experimental data is made. A proposed experiment to test the theory is mentioned, and first experimental results verifying the theory are presented.
Neutron Scattering and Dynamics of Simple Liquids
Authors: Gläser W.
Published: July 2012

Neutron scattering is a recent and rapidly developing technique for the study of the structure and dynamics of condensed matter, which offers unique possibilities. Many microscopic properties of disordered systems like liquids which are not directly accessible to other techniques can be investigated by properly designed neutron scattering experiments. — In the present paper, especially the opportunities for enlightening dynamic processes are illustrated with a few examples of recent quasielastic and inelastic scattering experiments on simple liquids.
Structure and Dynamics of Nonaqueous Electrolyte Solutions by Small Angle Neutron Scattering, Brownian Dynamics and Primitive Model Theories
Authors: Kunz Werner , Turq Pierre
Published: July 2012

The study of electrolyte solutions by small angle neutron scattering (static) or quasi‐elastic neutron scattering (dynamics) gives new perspectives to the primitive model of electrolytes, for both static and dynamic properties of those systems. Whereas all properties can be interpreted by brownian dynamics, integral equations cannot be used at the present time to get transport coefficients in all cases. As regards the choice of the potentials at the McMillan Mayer level, specific Gurney terms for solvation are not needed for tetraalkyl‐ammonium salts.
Pressure Dependence of Self Diffusion in Some Neat Alkanes and Binary Mixtures
Authors: Vardag T. , Bachl F. , Wappmann S. , Lüdemann H.‐D.
Published: July 2012

The self diffusion coefficients D have been measured for a series of linear and branched alkanes between the melting pressure curve and 450 K at pressures up to 200 MPa. The experiments were performed in a strengthened glass cell by application of the pulsed field gradient technique. — The p, T dependence of the data is described by the rough hard sphere model (Chandler) and by the interacting sphere model (Speedy). — The measurements have been extended to binary mixtures of a long chain alkane (tetradecane) and 4 to 12% w/w methane. The addition of relatively small amounts of the lower alkane enhances significantly the translational mobility and reduces the p. T dependence of the self diffusion coefficients of tetradecane.
Hydration Information from Diffusion Measurements in Transition Metal Salt Solutions
Authors: Price William E. , Woolf Lawrence A.
Published: July 2012

Recent efforts to obtain cation hydration information from tracer diffusion measurements for a number of 2:1 and 3:1 electrolyte systems are described. Hydration within such systems is modelled by considering the water to be present in four different environments: coordinated to the cation, coordinated to the anion, within a loosely bound secondary hydration layer around the cation and in the bulk water environment. In order to estimate the concentration dependence of water diffusion within the bulk environment, a modified Stokes‐Einstein equation, employing the viscosity ratio to a fractional power, was used.
Homogeneous and Heterogeneous Electron Transfer Rates of the Tetrathiafulvalene‐System
Authors: Grampp Günter , Kapturkiewicz Andrej , Jaenicke Walther
Published: July 2012

Using ESR spectroscopy and cyclic voltammetry the rate constants of homogeneous and heterogeneous electron self exchange in the system TTF/TTF were measured at different temperatures in solvents of different polarities and relaxation times (TTF = tetrathiafulvalene = 2‐(1,3‐dithiol‐2‐ylidene)‐1,3 dithiol). The rate constants were expressed by the preequilibrium encounter model for adiabatic processes. For both reactions the results are discussed in terms of Marcus's theory for the reorganization of ellipsoidal molecules in the overdamped relaxation case. From the experiments the geometric term g = 1/r̄ − 1/d' was derived and compared with model calculations r̄ = mean molecular radius, d' = formal distance between the reactants resp. reactant and image charge). Approximately interaction energies of the reactants (in the homogeneous case) and double layer correction (in the heterogeneous case) can be neglected. Preexponential and activation terms of the rate constants agree satisfactorily with the theory. g(het) is about the tenfold of g(hom). This is explained by an increased d' caused by strong adsorption of the counterions of the supporting electrolyte on the electrode.
Excess Enthalpies for Mixtures of Halogenated Benzenes with 1‐Alcohols at 298.15 K
Authors: Vijayalakshmi T. S. , Naidu P. R. , Ramakrishna M.
Published: July 2012

New experimental data for excess enthalpies of 1,2‐dichlorobenzene and 1,3‐dichlorobenzene with 1‐heptanol and 1,2,4‐trichlorobenzene with 1‐hexanol have been determined at 298.15 K. HE is positive over the whole range of composition in the three mixtures. However, the positive HE values of these mixtures exceed those for the mixtures which included the corresponding alkanes, n‐heptane and n‐hexane respectively. The difference in HE values suggests that the former group of mixtures include an additional factor, viz., break‐up of hydrogen bonds in alcohol aggregates.
Thermodynamics of Hydrogen Dissolved in Pd1‐x Thx and Pd1‐x Zrx (x = 0.05 and 0.08) Solid Solution Alloys
Authors: Ramaprabhu Sundara , Rajalakshmi Natarajan , Weiss Alarich
Published: July 2012

Pressure‐composition‐temperature hydrogen absorption isotherms in the pressure and temperature ranges 2 ≤ PH2/mbar ≤ 1000 and 473 ≤ T/K ≤ 873 have been determined for the Pd1‐x Thx and Pd1‐x Zrx (x = 0.05 and 0.08) solid solution alloys using a manometric method. The room temperature lattice constant of the alloys investigated increases by the alloying element M. In Pd1‐x Thx, the partial molar enthalpy of hydrogen solution at infinite dilution (ΔH̄0H) becomes more exothermic with increasing xTh whereas, in Pd1‐x Zrx, ΔH̄0H decreases with increasing xZr up to about xZr = 0.05; above xZr = 0.05, the decrease in ΔH̄0H is less. The partial molar excess entropy of hydrogen solution at infinite dilution (ΔS̄E,0H) decreases with increasing xTh and xZr. The correlation of the atomic diameter (dM) of the substituting 4‐valent metal atom (M = Pb, Sn, Zr, Th, and Ce) when dissolved in palladium with ΔH̄0H of the Pd1‐x Mx (x = 0.05 and 0.075) alloys indicates that the electronic states of the Pd1‐x Pbx and Pd1‐x Snx alloys are different from those of the Pd1‐x Mx (M = Zr, Th, and Ce) alloys probably due to the donation of the p‐valence electrons by Sn and Pb when dissolved in palladium.
Non‐Aqueous Oxygen Reduction Electrochemistry of a Transition Metal Chalcogenide Cluster Compound
Authors: Bungs M. , Alonso Vante N. , Tributsch H.
Published: July 2012

Electrochemical oxygen reduction in non‐aqueous solution was performed with a transition metal cluster compound. A comparable activity of this cluster material with that of the platinum electrode was found in acetonitrile. The selectivity of the cluster material surface with respect to the oxygen reduction was not altered when exposed to a methanol‐containing electrolyte or to a pure methanol solution. These results confirm that limitations of catalytic activity in aqueous solution arise from side reactions leading to the formation of undesired oxidation products. Opportunities for further development of these materials are discussed.
Competition between Solute‐Solvent and Solvent‐Solvent Hydrogen Bonds: Pyridines in Alcohols and in Water
Authors: Siegel G. G. , Huyskens P. L. , Vanderheyden L.
Published: July 2012

Partial enthalpies of mixing of pyridines in methanol, ethanol, 1‐butanol, water and cyclohexane were determined calorimetrically at 25°C. From these data their molar enthalpies of transfer, at infinite dilution, from the inert solvent to the H bonded solvents were calculated. They were compared with the enthalpies of H bond formation between the pyridines and the alcohols in CCl4 and the enthalpies of the selfassociation bonds in the pure liquids. Although in the pure alcohols more than 95% of the molecules are at a given time involved in H bonds with an energy of about 25 kJmol−1 which is markedly larger than the energy of the pyridine‐alcohol bonds in CCl4, the molar enthalpy of transfer of the pyridines from an inert solvent to an H bonded one remains exothermic. A quantitative treatment of the competition between the two types of H‐bonds is presented. It is based on the thermodynamics of mobile order that was recently developed. It leads to an equation that reasonably predicts the transfer enthalpies. According to this treatment the competition reduces the complexation constant by a factor K0AB/(K0AB K0AA), K0AB and K0AA being the stability constants of the H bonds in the absence of competition. In water the exothermic effect is enhanced because the second O ‐ H group of the molecule forms much weaker selfassociation H‐bonds than the first one.
Prediction of the Thermal Conductivity of Liquid Alkane Mixtures
Authors: Fareleira J. M. N. A. , Nieto De Castro C. A. , Pádua A. A. H.
Published: July 2012

The paper is devoted to the study of the applicability to binary mixtures of an extension of the van der Waals model for the description of the thermal conductivity of pure liquid alkanes. This study is based upon recently obtained accurate data for the binary mixtures methane + ethane and n‐heptane + 2,2,4‐trimethylpentane. — A reduced thermal conductivity for the mixtures is defined such that its density dependence is identical to that of the pure components. — Furthermore, a scheme is developed that enables the prediction of the thermal conductivity of the mixtures at any temperature T ≤ 0.7 Tc any pressure, solely from data for the pure components, i.e. without resort to any experimentally adjusted parameters for the mixtures. Such scheme is able to reproduce the available thermal conductivity data for the above mentioned systems with an error of the order of ±2% at a 2σ level (σ being the standard deviation), which is commensurate with the combined uncertainty of the experimental results for the pure components and for the mixtures.
Volume‐Explicit Equation of State and Excess Volume of Mixing of Fused‐Hard‐Sphere Fluids
Authors: Vörtler Horst L. , Nezbeda Ivo
Published: July 2012

The paper presents a simple analytic volume‐explicit equation of state (EOS) for fluids of hard bodies made up to fused hard spheres (FHS). Application of this EOS to both pure fluids and fluid mixtures (via Amagat's law) provides an accurate description of practically all existing computer simulation data. It is found that deviations from the assumption of ideal mixing are restricted essentially to low densities only; at higher densities small deviations are detected only for quite large volume ratio of molecules while the shape does not seem to play a significant role.
Influence of Ca2+ ‐ and Mg2+ ‐Ions on Model Membranes
Authors: Zorn Reiner , Nimtz Günter
Published: July 2012

Investigations at laboratory fermenters have shown that the nitrification of ammonia salt solutions by bacteriae is obstructed by Ca2+ ‐ or Mg2+ ‐ions in the waste water. This phenomenon is discussed on the base of electrostatic theories of the effect of divalent cations on phospholipid membranes. — In addition, X‐ray diffraction has been used to find possible differences between the actions of CaCl2 and CaSO4. The phase behaviour of CaCl2‐ and CaSO4‐containing samples was found to be the same. Lamellar and disperse phases are observed at same temperatures and same Ca2+ concentrations. So there is no significant difference in the electrostatic charging effect to be expected. But the disperse phases show differences: The thickness of the bilayer is smaller for CaCl2 than for CaSO4. The main part of this reduction is due to the hydrocarbon chain region. Those differences can be explained by an embedment of Cl‐ions into the membrane surface which does not take place with SO2−4 because of its larger size.
Kinetic Investigation of the Fe2+/Fe3+ Reaction in Frozen and Liquid HClO4·5.5H2O
Authors: Borgerding A. , Brost E. , Schmickler W. , Dinan T. , Stimming U.
Published: July 2012

The Fe2+/Fe3+ redox reaction on platinum is investigated in liquid and frozen HClO4 · 5.5 H2O over a temperature range from 130 — 300 K. The exchange current density follows an Arrhenius law in the liquid and in the solid state. Both the energy of activation and the preexponential factor are higher in the solid state; the exchange current density shows a discontinuous rise as one approaches the freezing point from higher temperatures. In the liquid state, mass transport to the electrode occurs through diffusion of the ions; in the solid state mass transfer is much slower is probably due to electron hopping rather than ion transport.
Kinetics of the Reactions of CH2(ã1A1) with CH3C2H, HCN, CO2, N2O and COS
Authors: Koch M. , Temps F. , Wagener R. , Wagner H. Gg.
Published: July 2012

The reactions of CH2(ã1A1) with CH3C2H, HCN, CO2, N2O and COS are investigated at room temperature. CH2(ã1A1) is generated by pulsed laser photolysis of CH2CO. Overall removal rate constants are derived from concentration profiles under first order reaction conditions using direct, time resolved LIF detection of CH2(ã1A1). The second order rate constants are found in units of 1013 cm2/mol s to be 24, 18, 2.0, 3.8 and 20, respectively. — The contributions of physical quenching to the removal of CH2(ã1A1) are determined by monitoring directly the formation of CH2(X̃3B1) with the LMR absorption technique. The branching ratios of collision induced intersystem crossing versus total consumption of 1CH2 are 0.24, 0.32, 0.67, 0.46 and 0.29 for the five reactants.
The Debye‐Hückel Theory for Hydrated Ions. I. Osmotic and Activity Coefficients of Binary Aqueous Solutions of Some 1 : 1 Electrolytes at 25°C
Authors: Schönert Hansjürgen
Published: July 2012

A thermodynamic model of stepwise hydration of ions in aqueous solutions has been developed. It is applied to the activity and osmotic coefficients of the alkali halogenides at 25°C. The hydration at infinite dilution can be decomposed into ion specific contributions. Together with a distance of closest approach in the Debye‐Hückel term it is possible to describe the activity and osmotic coefficients within the experimental error limits up to 1 molal solutions.
The Debye‐Hückel Theory for Hydrated Ions. II. Osmotic and Activity Coefficients of Ternary Aqueous Solutions of Hydrogen and Alkali Halogenides at 25°C
Authors: Schönert Hansjürgen
Published: July 2012

The Debye‐Hückel theory, including a closest distance of approach between cations and anions, has been extended to ternary solutions of 1: 1 electrolytes. Together with a thermodynamic model of stepwise hydration this allows the calculation of the Gibbs energy of ternary solutions without any ternary mixing parameter. The agreement between theory and experiment is good up to 1 molal solutions.
Hydrogen Solubility in the Liquid Alloys Lithium‐Indium, Lithium‐Lead, and Lithium‐Tin
Authors: Schumacher Richard , Weiss Alarich
Published: July 2012

Measurements of the hydrogen solubility in liquid alloys of the binary systems Li—In, Li—Pb and Li—Sn are reported. A detailled description of the experimental procedure is given. Solubility data were recorded in the pressure range 150—20000 hPa at temperatures up to 1220 K. Alloy interactions with stainless steel containers and with oxygen impurities were investigated. The temperature and pressure dependence of the mole fraction xH of hydrogen atoms in the melt at low hydrogen concentration, where Sievert's law is valid, can be described by the following equation: ln(xH√105Pa/PH2) = ‐ A + B/T. The values of the constants are A = 8.17, B = 734 K (LiPb); A = 7.84, B = 1970 K (Li62Pb38); A = 7.42, B = 1200 K (LiIn); A = 7.67, B = 3300 K (Li62In38); A = 7.08, B = 600 K (Li57Sn43); A = 6.86, B = 830 K (Li62Sn38). Strong deviations from Sievert's law are observed for two alloys indicating alloy decomposition. The reduction of the excess entropy of dissolved hydrogen in the alloys compared to pure lithium is discussed in the frame of an electrostatic model.
Inverted Micelles in a Ternary System AOT‐Water‐Benzene as Studied by Small‐Angle Neutron Scattering
Authors: Gorski Nikolai , Ostanevich Yurii M.
Published: July 2012

We performed the small‐angle neutron scattering measurements on AOT/benzene micelles with and without the addition of water. The scattering cross sections were studied as a function of the contrast of a solvent (the scattering length density of mixtures of protonated and deuterated benzene). We found that the volume per single AOT molecule in the micelle increases considerably when a small amount of water is added to a solution of “dry” micelles. The aggregation numbers of the micelles in benzene were found to be smaller by ca. 50% than those reported for decane. The observed dependence of the radii of gyration on the solvent contrast agrees well with the common picture of the structure of inverted micelles even in the case of “dry” micelles.
Transport Properties of Liquids. VIII. Molar Volume and Selfdiffusion of Organic Liquids at Pressures up to 200 MPa
Authors: Polzin Bernd , Weiss Alarich
Published: July 2012

The molar volumes V̄ and the self diffusion coefficients D of 2,2,4‐Trimethylpentane (C6H12), 2,2‐Dimethylbutane (C6H14), 1,3,5‐Trimethylbenzene (C9H12), Pentafluorobenzonitrile (C6F5CN), Tetramethyltin (Sn(CH3)4), 1,2‐Dibromotetrafluoroethane (C2Br2F4), Cyclo‐hexane (C6H12), and Benzene (C6H6) were measured in the range 1 ⩽ P/MPa ⩽ 200, 263 ⩽ T/K ⩽ 368. V̄ = f(P, T) is parameterized by use of the Tait‐equation and D = f(P, T) is given in a rational form, too. The diffusion coefficients, measured by the NMR spin echo method, decrease by a factor ⩾ 2 at constant temperature if the pressure is raised from 0.1 to 200 MPa. In the binary liquid system [Sn(CH3)4] 1‐x[C6H12]x V̄ and D of both components were investigated. The melting points of C6F5CN and cyclohexane were studied in dependence of the applied pressure. — The results of the diffusion experiments are discussed in the frame of the Free Volume Theory which fails at high pressures and temperatures. A decrease of the effective molecular volume with increasing temperature is probably responsible for this effect. — The volumeter and the diffusion cell constructed for the physical experiments are described.
Does Quantum Mechanics Select Out Regularity and Local Mode Behaviour in Nonlinearly Coupled Vibrational Systems?
Authors: Yurtsever E. , Brickmann J.
Published: July 2012

A two dimensional strongly nonharmonic vibrational system with nonlinear intermode coupling is studied both classically and quantum mechanically. The system was chosen such that there is a low lying transition (in energy) from a region where almost all trajectories move regularly to a region where chaotic dynamics strongly dominates. The corresponding quantum system is far away from the semiclassical limit. The eigenfunctions are calculated with high precision according to a linear variational scheme using conveniently chosen basis functions. It is the aim of this paper to check whether the prediction from semiclassical theory, namely that the measure of classically chaotic trajectories in phase space approaches the measure of irregular states in corresponding energy ranges, holds when the system is not close to the classical limit. It is also the aim to identify individual eigenfunctions with respect to regularity and to differentiate between local and normal vibrational states. It is found that there are quantitative and also qualitative differences between the quantum results and the semiclassical predictions. We found a relatively high amount of regularity in the quantum system for energies where almost all classical trajectories move chaotically. This high regularity is manifested via level spacing statistics as well as by a careful study of the nodal behaviour of the eigenfunctions. Another result was not expected from semiclassical predictions: Some of the wave functions are localized and irregular, a behaviour which was not observed in the corresponding classical system.
Surface Graininess and a New Model of Nonionic Micelle of Octaoxyethylene Alkyl Ether
Authors: Matsumoto Takayoshi
Published: July 2012

Surface graininess and micelle size of n‐dodecyl (octaoxyethylene glycol) monoether C12H25(OCH2CH2)8OH in an isotropic liquid phase (L1 phase) and a hexagonal mesophase (H1 phase) of an aqueous colloid were investigated through light scattering and small angle X‐ray scattering (SAXS). The micelle is almost spherical and the micelle radius remains about 28–30 Å over a wide concentration range from the critical micelle concentration (ca. 4 · 10−5 g/ml) to 0.3 g/ml. The aggregation number is 70–80 and depends slightly on temperature. The specific inner surface Os of the spherical micelle is obtained from the tail portion (large angle region) in the SAXS curve. The value of Os of the micelle in the L1 phase is ca. 0.2 Å−1 and this value is approximately twice as large as that of a smooth sphere. A new micelle model is also proposed.
“Development of Advanced Noble Metal‐Alloy Electrocatalysts for Phosphoric Acid Fuel Cells (PAFC)”
Authors: Stonehart Paul
Published: July 2012

In the preparation of highly dispersed noble metal electrocatalysts, the technology is such that crystallites now can be routinely prepared with small dimensions so that 50% of the atom content resides at the particle surface. The crystallite diameters are of the order of 12 Angstrøm (1.2 nanometers). Operation of these materials, when applied to phosphoric acid fuel cells as electrocatalysts is, of course, critical. What is important is the realization that due to the high surface energies of these crystallites, they have properties that are unlike the properties of the bulk metals. Although this manufacturing achievement is very great, more recently there has been increased emphasis on preparing alloys of metals with platinum in order to increase the kinetic rate of reaction for the oxygen reduction.—For oxygen reduction, binary alloys of platinum with refractory metals such as vanadium showed higher activity, but the vanadium was rapidly leached out. Alloys with chromium and subsequently with the addition of cobalt to form ternary alloys have now exhibited greater resistance to degradation. These alloys are hard and resistant to sintering, until the alloying element is leached out, then crystallite growth is obtained.—More recently, process modifications to produce ordered alloys have shown stability for over 9000 hours in the hot phosphoric acid fuel cell environment, as have alloys of platinum with cobalt and/or chromium containing gallium additions. It is one theory that there is no catalytic enhancement for oxygen reduction due to these alloying elements, but the increased reactivity is due solely to leaching out of the alloying elements from the alloy surface to produce a microroughness in the platinum crystallite.—In the case of hydrogen oxidation, especially in the presence of electrocatalyst poisons such as carbon monoxide and hydrogen sulphide, alloys of platinum with palladium show greater tolerance to poisoning and greater stability against crystallite growth. Other alloys are now under development to lower the catalyst cost and increase the electrocatalyst performance. This work is coupled with developments of advanced theoretical models that are amenable to computer solution for the operation of gas‐diffusion electrodes to maximize both the catalyst utilization within the electrode structure, and within the cell stack.
Fuel Cells as a Power Source of Propulsion Systems
Authors: Straßer K.
Published: July 2012

Since the midsixties Siemens has been pursuing the development of fuel cells. The development was concentrated on the alkaline H2/O2 fuel cell with circulating electrolyte and platinmetal‐free electrodes. By the modular and compact design it is relatively simple to adapt the FC‐system to the requirements of special applications. A propulsion system, in which the accumulator and the FC‐system are electrically connected in parallel, was tested for demonstration in a propulsion system of an electric van and a submarine. The design in principle and test results will be reported.
Hydrous Oxide Formation on Platinized Platinum Electrodes and its Relevance to Oxygen Gas Reduction
Authors: Burke L. D. , Casey J. K.
Published: July 2012

Spontaneous formation of hydrous oxide species at a platinized platinum electrode, held at 0.85 V(RHE), in aqueous H2SO4 solution at 60°C was detected by an electrochemical technique. Such species are assumed to be a source of inhibition of oxygen gas reduction at fuel cell cathodes operating in aqueous media at potentials above ca. 0.6 (RHE); reaction in the latter case may be confined to less active sites where hydrous oxide formation occurs less readily. Reduction of oxygen in the oxide layer region was found to be time dependent and independent of rotation rate. The former effect was attributed to a surface restructuring process and the latter to the fact that oxygen gas was not involved in the rate‐determining stage of the reaction.
The State of MCFC Technology Development
Authors: Kishida Koji
Published: July 2012

Molten Carbonate Fuel Cell (MCFC) technology development has become one of the highest priority R & D projects in the field of energy because of its outstanding energy conversion efficiency from various hydrocarbon fuels and coal derived gas to electricity.—This paper presents the state‐of‐the‐art of MCFC technology in Mitsubishi Electric Corporation (MELCO) and discusses the technical problems having been encountered and the countermeasures to overcome or to optimize them.—The fundamental issues are corrosion, creep and compatibility of the cell component materials. This paper presents an effective means of minimizing the anode creep, and optimizing the thickness of the anode, the cathode and the matrix. The principal subject discussed in this paper is the life of a MCFC stack, in other words what are the major life limiting factors and how to challenge to these factors.—Cathode (NiO) dissolution during cell operation has been a serious problem since many years ago. Additive elements into electrolyte and lower C02 partial pressure are the effective way to suppress dissolution. Electrolyte loss and migration phenomena cause a sizable imbalance in the electrolyte content in the individual cells in a stack. The countermeasures against this problem are studied.—The other subject handled in this paper is the progress of internal reforming (IR) stack development. A 3 KW direct‐IR stack and a 10 KW indirect‐IR stack are being operated and various testings are being performed in MELCO. The status of IR technology is briefly described.
NiO Cathode Dissolution and Long Term MCFC Operation
Authors: Veldhuis J. B. J. , Van Molen S. B. Der , Makkus R. C. , Broers G. H. J.
Published: July 2012

The lifetime of a molten carbonate fuel cell is significantly reduced by the slow dissolution of the state‐of‐the‐art nickel oxide cathode material. The dissolved Ni ions precipitate in the matrix.—The amount of nickel found in the matrix and the location of the precipitation zone observed in small size cell tests are reported. These cells were operated for various times, up to 20000 hours. An average dissolution rate of 4 μg/cm2 h was calculated. The precipitation zone moved linearly with the square root of time towards the anode. This may be due to changes in the matrix and electrode structure and, additionally, to the surface diffusion of the precipitated metallic nickel.—The results obtained are compared with a simple model describing the transport of nickel through the matrix and the location of the precipitation band. This model accounts for the diffusion, migration and the coupling of the dissolved species to the movement of the carbonate ions. The model calculations agree reasonably well with the experimental results.
Internal Reforming for Molten Carbonate Fuel Cells
Authors: Ledjeff K. , Rohrbach T. , Schauraberg G.
Published: July 2012

Molten carbonate fuel cell systems can be operated with pure hydrogen or carbonaceous fuel gases, like natural gas. The use of natural gas is of advantage because of the present, widespread distribution network installed by the gas industry. The MCFC is not able to consume the methane directly, because the electrochemical reaction taking place at the anode needs hydrogen. There are various concepts for reforming in work and they can be devided into external, integrated and internal. The most promising are integrated and internal reformers, because they use the waste heat of the fuel cells for the endothermic reforming reaction. Thus, the efficiency of the system can be increased from about 50% to about 65%. Besides of the reforming concepts the paper will handle the thermodynamic background and experimental results achieved in our laboratory.
Ionic Contact Equilibria in Solids—Implications for Batteries and Sensors
Authors: Maier Joachim , Lauer Ute
Published: July 2012

We have been investigating the relevance of ionic space charge effects at surfaces and interfaces in multiphase and polycrystalline materials from both a theoretical and an experimental point of view. A brief review is given, which also includes the behaviour of the electronic minority species, as well as the qualitatively different situation in micro‐sized systems. A major part is devoted to the implications with respect to batteries and sensors: i) enhancement of the ionic conductivity of solid battery electrolytes due to internal interfaces; ii) impact of ionic profiles on the phase boundary reactions particularly in e.m.f. and conductivity sensors; iii) formulation of a new sensor principle.
Ceramic and Metallic Components for a Planar SOFC
Authors: Ivers‐Tiffée E. , Wersing W. , Schießl M. , Greiner H.
Published: July 2012

We present a planar cell design for Solid Oxide Fuel Cells (SOFC) which combines the ceramic materials of a solid electrolyte (Y‐stabilized ZrO2), cathode (LaSrMeO3 with Me : Mn, Co and Cr), and anode (Ni‐Cermet) with a metallic interconnection material, the so‐called metallic bipolar plate. This metallic component—which functions as a mechanically stabilizing frame, as well as gas distributor and electrical connector—possesses the advantages of much higher electrical and thermal conductivity when compared with the common ceramic interconnection material (LaCrO3). This allows the construction of cell stacks with increased power density (> 100 kW m3).
In‐Situ Infrared Spectroscopic Studies of Methanol Electrooxidation on Pt
Authors: Kunimatsu Keiji
Published: July 2012

Nature of the methanol adsorbate on platinum electrode and its role in methanol electrooxidation have been studied by in‐situ infrared spectroscopy.—The infrared adsorption intensities of linear CO(a) derived from CO and methanol respectively on a platinum electrode in 0.5 M sulfuric acid were determined as a function of the total adsorbate coverage.—It has been confirmed based on the quantitative comparison of the infrared absorption intensities that the linear CO(a) is the predominant surface species derived from methanol on a smooth platinum electrode in acidic media. However, presence of minor surface species besides the linear CO(a) has also been suggested for the coverages higher than 0.3.—The linear CO(a) acts as the so called catalysis poison for methanol electrooxidation, which has been confirmed by the following two observations; firstly oxidation of the linear CO(a) observed around 0.5 V is accompanied by a sharp increase of the methanol electrooxidation current, secondly rapid decrease of the methanol electrooxidation current observed while the electrode was held at 0.4 V is accompanied by a steady build up of the infrared absorption band of the linear CO(a).
The Interconversion of Adsorbed Methanol Fragments on Platinum at Cathodic Potentials
Authors: Christensen P. A. , Hamnett A. , Potter R. J.
Published: July 2012

The oxidation of methanol at a platinum electrode in neutral sulphate solution was investigated using in‐situ FTIR. Hitherto unreported interconversion between various adsorbed carbonyl species was observed at cathodic potentials, this conversion being driven by the formation of strongly adsorbed hydride.
Structural Concepts for Disordered Inorganic Solids. Modern NMR Approaches and Strategies. Invited Review
Authors: Eckert Hellmut
Published: July 2012

Many technologically interesting materials properties are caused by intrinsic structural or dynamic disorder phenomena in solids. For this reason, the structural characterization of disordered states constitutes a central aspect of materials science. Within the past decade, nuclear magnetic resonance techniques have made increasingly significant and detailed contributions to this subject. The present review will portray some of the more common methods employed and discuss several important applications to problems in various inorganic materials areas.
Thermodynamic Analysis of Extraction of Mg(NO3)2, MnCl2 and NiCl2 by n‐Octanol at 298.15 K
Authors: Apelblat Alexander , Manzurola Emanuel
Published: July 2012

Partition of Mg(NO3)2, MnCl2, NiCl2 and water between the aqueous phase and n‐octanol at 298.15 K is considered. Equilibrium distribution of salts is consistent with formation of Mg(NO3)2(H2O)5(ROH)5, MnCl2(H2O)14(ROH)7 and NiCl2(H2O)7(ROH)2 complexes in the alcoholic phase. Activities of n‐octanol were evaluated by a numerical integration of the Gibbs‐Duhem equation in ternary systems.
Liquid‐Liquid Equilibria in the Ternary Systems with Citric, Tartaric and Malic Acids and Aliphatic Alcohols
Authors: Apelblat Alexander , Glazer Sigal , Kost Ayala , Manzurola Emanuel
Published: July 2012

Extraction equilibria in the citric acid‐water‐2‐pentanol, tartaric acid‐water‐1‐octanol, malic acid‐water‐isobutanol and malic acid‐water‐1‐pentanol systems are considered. Solubilities of 2‐butanol in succinic acid, 2‐pentanol and 1‐hexanol in citric acid aqueous solutions are also reported. Distribution of hydroxycarboxylic acids is expressed in terms of H3Cit (H2O)6(ROH)3 and H2Tar (ROH)3 formation in the alcoholic phase. The equilibrium constants of these complexes are 0.58 for citric acid and 0.052 for tartaric acid. The activities of components in ternary systems were evaluated using the mass‐action and Gibbs‐Duhem equations.
Dipolar Characteristics of the Imine‐Group and its Hydrogen Bonds. A Quantum‐Chemical and Experimental Approach
Authors: Peeters D. , Huyskens P. , Nelis K.
Published: July 2012

The dipole moments of two aliphatic imines and their hydrogen bonded phenol complexes were determined experimentally. A value of 1.63D was found for isopropyl, N isopropyl imine and 1.60 D for tertio butyl, N isobutyl imine. Their complexes with phenol, 3,5 dichloro‐ and para nitro phenol are respectively of 3.45, 4.57 and 6.99 D for the first and 3.69, 4.67 and 7.10 D for the second. This experimental study was completed by a theoretical study of model imines and their complexes with watermethanol and formic acid. The theoretical results explain through structural and electronic arguments the variation of the dipole moments. They furnish also values of the angles which are indispensable for the discussion of experimental dipole increments. The dipole increments obtained show clearly the strength of the H‐bond obtained with imine bases as well as its sensibility to the strength of the associated acid.
Ion‐Solvent Interactions of Silver (I) Salts in Water‐DMSO Mixtures from Conductance Measurements
Authors: Sreekumar T. K. , Janardhanan S. , Kalidas C.
Published: July 2012

The conductances of silver (I) perchlorate, nitrate and bromate have been determined in water‐dimethylsulfoxide (DMSO) mixtures at 30°C over the complete range of solvent compositions. The data were analyzed by the 1980 Fuoss equation and the limiting molar conductances (<Λ0) and association constants (KA) of the salts were evaluated at all compositions. The Λ0 values have been split into their ionic values and the ionic Walden products of all the ions were calculated using the transference number data derived from a concentration cell with transference. The initial increase of the Walden product of silver ion up to 20 wt% DMSO and its subsequent decrease beyond this composition with addition of DMSO, indicates that it is preferentially solvated by water at high compositions of water and subsequently by DMSO. For anions, the Walden products vary in a complex manner and seem to be strongly influenced by solvent‐solvent interactions.
Investigations on the Reactant Gas Pressure Dependence of Sputtering Yields of Several Transition Metals
Authors: Brudny M. M. , Seidel W.
Published: July 2012

Sputtering yields of polycrystalline samples of V, Co, Ni, Cu, Zn, Pd, Pt and Ag were investigated as a function of oxygen pressure from residual gas conditions (po2 ≦ 0.002 mPa) to 6 mPa. Ar+ ions (2 keV; 35μA/cm2; incidence angle θ = 45°) were used for bombardment. Also sputtering yields of Fe, Nb and Ta were observed at residual gas conditions and for 2 mPa of O2 and for Ti, Cr and Cd under 2 mPa of O2. The sputtering yields were found to decrease with increasing oxygen pressure. This decrease is most pronounced for metals which are easily oxidized. Sputtering yields of V, Ni, Zn, Pd and Ag were also found to decrease under N2, N2O and NO. Using linear cascade theory the sputtering yields under oxygen were estimated and compared with experimental data. Satisfying correspondence was achieved, if different surface binding energies were assumed for clean and oxidized surfaces respectively.
Electrochemical Study of the Intercalation Reactions of Perchloric and Nitric Acid
Authors: Scharff P. , Stumpp E.
Published: July 2012

HNO3 and HClO4 were intercalated into the graphite lattice by means of chemical oxidants and by electrochemical oxidation. In both cases the potential variation versus time was recorded in order to trace the intercalation process. Compared with H2SO4, the intercalation reactions of nitric and perchloric acid proved to be fast. Impedance measurements indicated that the penetration of the phase boundary by acid anions, acid molecules and water as well as intercalate nucleation determine the reaction rate of the chemical insertion reactions. Biintercalation and cointercalation compounds with HNO3 and HClO4 were prepared for the first time.
Passivation of Zinc in Acid Electrolytes Under Galvanostatic Conditions
Authors: Krohn Holger , Rashwan Salah , Beck Fritz
Published: July 2012

Passivation behaviour of zinc electrodes in 4–10 M H2SO4 and some hydrogensulphates and alkylammonium salts with anions containing S–VI in the concentration range 0.5–5 M were studied under galvanostatic conditions. After a transition time τ, voltage increased steeply, indicating the onset of passivation. The product j · √τ is found to be roughly constant. This is explained in terms of an accumulation of zinc ions in front of the electrode up to the point, where the concentration reaches saturation. From the Sand constant, a diffusion coefficient was calculated in the right order, depending on the electrolyte composition. The passive layer is assumed to be the corresponding zinc salt. Only at 30–100 V, dielectric break down occurs under potentiostatic conditions. Open circuit potential in the passive region attains in short times (ms) the active potential again. From this it is concluded that the thickness of the zinc salt layer must be extremely small.
Photochemistry of Semiconductor Colloids. 36. Fluorescence Investigations on the Nature of Electron and Hole Traps in Q‐Sized Colloidal CdS Particles
Authors: Eychmüller A. , Hässelbarth A. , Katsikas L. , Weller H.
Published: July 2012

The fluorescence properties of surface modified quantum‐sized CdS colloids were investigated by means of static and time‐resolved low temperature fluorescence spectroscopy. All samples investigated had high fluorescence quantum yields already at room temperature and exhibited either exclusively excitonic or a mixture of excitonic and trapped fluorescence. Mechanisms are presented which explain both the static and time‐resolved behaviour of both the excitonic and trapped fluorescence. The excitonic fluorescence is described as delayed fluorescence occuring by detrapping of electrons. Extremely shallow traps having trap depths of a few meV are discussed.
On the Promoting Effect of Alkali Metals on the Adsorption of Nitriles on the Gold (100) Surface
Authors: Solomun T. , Neumann A. , Christmann K.
Published: July 2012

Submolayer concentrations of (strongly electropositively polarized) Na and K on the Au(100) surface create three new acctonitrile (CH3CN) and benzonitrile (C6H5CN) binding states (the γ‐states) on the high‐temperature side of the corresponding molecular thermal desorption spectra (β‐state) observed for the clean, unpromoted Au surface. The additional states appear with both alkali metals and nitriles, whereby they are energetically about equally spaced (ΔT ≈ 30 K with K, and ΔT ≈ 50 K with Na) and sequentially populated, indicating a more general electrostatic modification of the nitrile's adsorptive bonding in the vicinity of an adsorbed alkali atom. The triplet of TD states is tentatively interpreted as being caused by a subsequent filling of a coordination shell formed by the nitriles around each individual alkali metal atom. Similar energetics involved in the formation of gas‐phase and surface cluster complexes of the kind Meδ+ {N  C–CH3}δ− is noted and discussed.
Hole Injection into Dislocations in p‐Silicon Electrodes
Authors: Morrison S. R. , Kerchove F. Vanden , Gomes W. P.
Published: July 2012

Cathodic hole injection by Fe(CN)63‐ ions was observed at mechanically damaged, i.e. dislocation containing, p‐Si electrodes in contact with aqueous electrolytes. The injection current was observed to start at a potential corresponding to a substantial band bending and to reach a saturation region. In that saturation region the current density was somewhat less than linearly dependent on the Fe(CN)63‐ concentration and increased with increasing depth of damage, i.e. average depth of dislocations. The observations could be explained by a model in which it was assumed that the dislocations behave as micro‐electrodes with hole injection limited by Fe(CN)63‐ diffusion to the electrodes. The holes are then conducted along the dislocation lines to where tunneling to the valence band becomes possible.
Characterization of Surface Layers on GaAs Single Crystals in Contact with Acid Aqueous Solutions
Authors: Lingier S. , Gomes W. P.
Published: July 2012

From ellipsometric measurements, combined with surface analysis by SEM, Auger spectroscopy and X‐ray diffraction, it appears that a porous arsenic layer develops upon the p‐type gallium arsenide electrode surface in acid, aqueous indifferent electrolyte solution during anodic current flow. Due to its porosity, this layer does not affect the forward current‐potential characteristics of the electrode. Also under open‐circuit circumstances in the same electrolyte, the arsenic layer appears to grow. The probable reactions corresponding to both arsenic deposition processes are discussed.
Electronic Structure and Spectra of Some Carbamates INDO/S‐CI Treatment
Authors: Hamed Maher M. , Moustafa H. , Hilal Rifaat , El‐Kourashy A. G.
Published: July 2012

The electronic absorption spectra of some aryl‐ and diaryl‐carbamates have been measured and the observed complex spectral profiles have been computer deconvoluted. MO computation of the spectra using INDO/S‐CI method, allowed the assignment of the observed bands and identifying their origin.
Photoisomerization in Dense Gases and Liquids
Authors: Schroeder Jörg
Published: July 2012

The pressure and temperature dependence of the rate coefficient for the singlet state photoisomerization of trans‐stilbene and all‐trans‐diphenylbutadiene in supercritical and liquid alkane solvents reveal the importance of specific solvent effects modifying the reaction path on the potential energy surface. In the gas‐liquid transition range the barrier height for the reaction seems to be lowered due to increasing solvation of the reactants in solute‐solvent clusters. At higher pressures, the transition to the Smoluchowski‐limit within each solvent is well described by Kramers' model. Differences between solvents can be attributed to a solvent‐dependent barrier shape. Deviations from this description only appear for stilbene at higher viscosities. In part, they seem also be due to a specific influence of the compressed solvent on the reaction path and to a frequency dependence of the friction. Solvent‐size dependent micro‐friction effects do not seem to be responsible for the observed solvent dependence of the reaction rates. Manifestations of multidimensional barrier crossing show up in the strong temperature dependence of the rate coefficient at constant solvent self‐diffusion coefficient. Apparently, the reaction path on the energy surface changes with temperature leading to an effectively temperature dependent height and shape of the barrier for the reaction with increasing excitation of “perpendicular” modes. Possible reasons for the striking difference of the friction dependence of the rate coefficient between stilbene and diphenylbutadiene at intermediate to high friction are also discussed.
Femtosecond Studies of the Photoisomerization of cis‐Stilbene in Solution
Authors: Repinec S. T. , Sension R. J. , Hochstrasser R. M.
Published: July 2012

Femtosecond laser studies on cis‐stilbene photoisomerization in alkane solvents show a weak friction dependence on the excited state lifetime. A possible barrier crossing process is indicated when these results are compared with various potential models. The anisotropy values of the transient absorptions allow the assignment of the various excited states to A type in C2 symmetry. Anisotropy measurements in the regions of product ground state absorptions demonstrate a high alignment between reactant cis and product trans and a low alignment between cis and product dihydrophenanthrene (DHP) transition dipoles. These results indicate a significant angular displacement of the ethylene bond during isomerization. In addition, time resolved absorption studies detecting product trans fluorescence estimate an initial internal temperature of 725 ± 100 K which decays with ca. 14 ps time constant.
Classical and Quantum Models of Activationless Reaction Dynamics
Authors: Jean John M. , Fleming Graham R. , Friesner Richard A.
Published: July 2012

Two aspects of barrierless processes are discussed. Adiabatic processes are discussed briefly in the context of diffusion to a sink. Second, a multi‐level Redfield theory is developed as a model for rate processes where vibrational relaxation and dephasing occur on the time scale of the electronic process. The results of numerical calculations are presented and deviations from the Golden Rule predictions discussed.