bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrochemical Hydrogen Charge Characteristics of Metal Hydride Electrodes
Authors: Sakamoto Y. , Kuruma K. , Naritomi Y. 
Published: July 2012

AbstractA model for the cathode potential vs. time relationship during the galvanostatic charge process for metal hydride electrodes has been derived on the basis that the adsorbed hydrogen produced at the electrode surface by charge transfer of the Volmer reaction diffuses through the bulk electrodes, i.e., α, (α+β) and β phases during the charge process, and after the absorbed hydrogen concentration in the electrodes attains a saturation value for hydrogen solution, the electrode kinetics is followed by the chemical Tafel reaction and/or the electrochemical Heyrovsky reaction. The calculated electrode potential vs. time curves are in a reasonable agreement with the experimental results of Pd hydride electrodes.
Vanadia Supported on Titania Prepared by Grafting: Influence of Support Properties on the Structure and Activity of Vanadia for the Selective Catalytic Reduction of NO by NH3
Authors: Handy Brent E. , Gorzkowska Irena , Nickl Julius , Baiker Alfons , Schraml‐Marth Matthias , Wokaun Alexander 
Published: July 2012

AbstractThe selective catalytic reduction (SCR) of NO by NH3 has been investigated over vanadia/titania catalysts prepared by grafting of vanadyl alkoxides onto three titania supports which differed in their morphologies (surface area, phase composition) and concentrations of impurities. Neutron activation analysis revealed the presence of chlorine and potassium as major impurities in the titania carriers. The supported catalysts were prepared by the reaction of VO(OR)3 (R = i‐C3H7, i‐C4H9) with support surface hydroxyl groups. Attention was paid to the influence of various preparation parameters (vanadia precursor, support pretreatment, impurities) and their relation to the amount, reducibility and activity of the vanadia deposited. Thermal analysis, X‐ray diffraction and Raman spectroscopy revealed that pre‐conditioning the titania supports before the grafting, if not carried out under mild conditions, results in partial transformation of the anatase phase to rutile. Potassium impurities appear to stabilize the anatase phase with regard to this transformation. For titania containing potassium as impurity, the rutilization occurs at a significantly higher temperature than observed with titania containing chlorine as impurity. Raman spectroscopy showed that within the series of titania supports investigated, the vanadia loading is the most important factor that determines the structure of the immobilized vanadia surface species. Small clusters and ribbons prevail at low coverages (∼ 2μmol V5+/m2). At higher coverages, the catalytically most active two‐dimensional vanadia layers are prevailing. The maximum level of NO turnovers is achieved at coverages exceeding ∼ 3μmol V5+/m2. This behaviour was observed for vanadia deposited on all three titania carriers, irrespective of the largely different BET surface areas and contaminant levels of the supports.
Volumes, Dilution Enthalpies and Dielectric Polarization of Water‐Sulpholane Mixtures at Different Temperatures
Authors: D'Aprano Alessandro , Capalbi Antonio , Bonicelli Maria Grazia , Ceccaroni Gian Franco 
Published: July 2012

AbstractDensities and dielectric constants of water‐sulpholane mixtures have been measured at 25, 30 and 40°C over the complete mole fraction range. Excess molar volumes and apparent molar volumes of the two components were derived from density data. The temperature and concentration dependences of these quantities are discussed in terms of the structural modification of water imposed by sulpholane. Dielectric constant data, analyzed in terms of Kirkwood theory, show that the short range intermolecular interactions between the components in the mixtures are conform to the depolymerization of the water hydrogen bonded network promoted by the mixing with sulpholane. The changes of the water structure have been further investigated by measuring the enthalpies of dilution of the sulpholane at 30°C. The data were analyzed with a polynomial equation to derive the relative apparent molal enthalpies. The resulting values of these quantities are in good agreement with the volumetric and dielectric constant results.
Pressure Dependence of ortho‐Positronium Lifetimes in Molecular Liquids
Authors: Kobayashi Y. 
Published: July 2012

AbstractEffect of external pressure on annihilation of ortho‐positronium (o‐Ps) hi molecular liquids has been studied for benzene, toluene, isooctane, n‐hexane and carbon disulfide. In all cases the o‐Ps lifetime becomes shorter as pressure is increased. The shorting of the lifetimes in the case of the former four liquids is found to be almost in agreement with the prediction of a simple bubble model. The change of the lifetime in carbon disulfide is, however, much larger than that expected from the model and the discrepancy can be explained by assuming some attractive interaction between Ps and the surrounding carbon disulfide molecules. Some discussion is given on the effect of pressure on Ps yields.
Selective Counterion Binding to Linear Polyelectrolytes in Aqueous Solutions
Authors: Cametti C. , Di Biasio A. 
Published: July 2012

AbstractThe selective counterion condensation induced by a charged cylindrical polyelectrolyte in aqueous solution containing different mono‐ and di‐valent ions was investigated by means of the numerical solutions of the non linearized cylindrical Poisson‐Boltzmann equation. The critical charge fraction fc, above which the condensation predicted by the Manning theory occurs, has been evaluated in some selected cases of relevance in biopolyelectrolyte systems and a selective binding of counterions has been shown to occur. To take into account the effects of different types of mono‐ and di‐valent salts, an extension of the Manning theory recently proposed by Paoletti et al. and based on Gibbs free energy minimization, was considered. Discrepancies between the charge distribution of bound ions calculated by means of numerical solutions of Poisson‐Boltzmann equation and those predicted by the extended Manning theory, were found.
Dependence of Mass Density and Selfdiffusion in Liquid Binary Systems n‐Alkane/Tetramethylsilane on Temperature and Pressure
Authors: Brüsewitz Michael , Weiss Alarich 
Published: July 2012

AbstractThe selfdiffusion coefficients Di, of the spherical molecule tetramethylsilane, TMS, and of n‐alkanes have been studied in three binary systems of n‐alkane/TMS in the temperature‐ und pressure range 253.15 ⩽ T/K ⩽ 368.15; 0.1 ⩽ P/MPa ⩽ 200. The mol fractions of TMS in the mixtures were chosen as xTMS = 0, 0.1, 0.9, and 1; the n‐alkanes were n‐hexane, n‐nonane, and n‐dodecane. Measurements of the mass densities at the chosen xTMS‐values were done in the P,T‐range given above. – The results of the Di measurements can be rationalized by a polynomial Di = f(P,T). The molar volumes found from the mass density measurements are described by VM = f(p,T) for the range covered by the experiments; they are described by a polynomial, too. Activation energies for the selfdiffusion process have been determined. – Di at constant P,T decreases in the sequence n‐hexane, TMS, n‐nonane, n‐dodecane. For the pure substances as well as for the components in the mixtures (Di)max/(Di)min = 3.5 to 4. – The interpretation of the results relays on the “Free Volume” model [1]. From the data Di = f(P,T) the selfdiffusion coefficients at constant volume have been extrapolated and their dependence from T1/2 is discussed. The results of the measurements are interpreted by assuming folded conformations of the n‐alkanes in the mixtures with TMS. In the mixtures one component can be regarded as the solvent, dominating the properties of the solvent cage.
Self‐Reaction of Benzylperoxy Radicals in the Oxidation of Toluene. A Chemiluminescence and Product Study
Authors: Vasvári G. , Gál D. 
Published: July 2012

AbstractThe CL study of the oxidation of toluene initiated by AIBN has shown that both triplet and singlet benzaldehyde is formed (T/S ≈︁ 10.5). The lifetimes in toluene are: τ5 ≈︁ 4 · 10−9 s and τT ≈︁ 1.9 · 10−7 s. – In the presence of DPA the kinetic curve of the CL light shows a maximum at [DPA] > 10−4 M. The CL spectrum of the oxidation of toluene lacks both the fluorescence and phosphorescence peaks of the excited benzaldehyde (due to the very low efficiency of photon emission and very strong quenching by O2 and toluene). – Analysis of product distribution by HPLC revealed the formation of benzaldehyde, benzylalcohol, benzylhydroperoxide and benzoic acid. A small amount of H2O2 was also detected by spectrophotometry. Since the ratio of aldehyde/alcohol is always higher than unity detailed study of all circumstances led us to the conclusion that benzylperoxy radicals terminate both by the Russell‐mechanism and by the transition state containing two five‐membered rings suggested by Bennett and Summers. – The activation energy of hydrogen abstraction from toluene by benzylperoxy radicals is 53 kJ/mol and the rate constant of this reaction does not differ essentially from the same reaction of ethylbenzene. The kinetic chain length of oxidation calculated from the analytical data is equal to 2±0.2 (75–90°C).
Monte Carlo Simulations of Supported Monolayers of Amphiphilic Molecules
Authors: Stettin H. , Friedemann R. , Mögel H.‐J. 
Published: July 2012

AbstractMC simulations for a liquid supported monolayer of amphiphilic molecules were carried out within a cubic lattice model using two‐dimensional periodic boundary conditions. The molecules consist of a hydrophilic head and hydrophobic segments. Only excluded volume interactions were taken into account. We varied both the head density and the number of segments. The comparison with attractive interaction including calculations for 15 unit molecules on a cubic lattice provided the same qualitative results in dependence on the head density. The order parameter values in dependence on the head density are greater than the corresponding ones from athermal simulations on a diamond lattice. The difference may arise from the different lattice types. The influence of the chain length on molecular properties as the mean end‐end distance, the mean end‐end projection, the mean height, and the effective layer thickness as well as the order behavior is intensively discussed.
The Debye‐Hückel Theory for Hydrated Ions. V. Enthalpy of Aqueous Solutions of Alkali Halides at 25°C
Authors: Schönert HansjüRgen 
Published: July 2012

AbstractA recently, presented thermodynamic model which describes the activity and osmotic coefficients of binary and multicomponent aqueous solutions of alkali halides (up to m = 1 mol · kg−1 at 25°C) is applied to the enthalpy of binary solutions. The experimental data can be fitted within their error limits. The model parameters: enthalpy and entropy of transfer of water from the bulk to the hydration sphere of the ions reflect the structure‐breaking/forming properties of the solutions.
Theory of Cyclic Voltammetry for Quasi‐Reversible Electrodeposition Reactions with insoluble Products
Authors: Avaca L. A. , Kaufmann S. , Kontturi K. , Murtomäki L. , Schiffrin D. J. 
Published: July 2012

AbstractThe Matsuda theory of cyclic voltammetry for quasi‐reversible reactions is extended to metal dissolution and electrodeposition. Kinetic data can be conveniently obtained from the measurement of peak potentials and peak currents as a function of sweep rate and switching potentials. As an example, the rate constant for the Zn(s)/Zn++ (aq) couple has been measured to be k0 = 7.5 · 10−7 cm s−1.
A Note on Gravimetric Measurements of Gas‐Adsorption Equilibria
Authors: Staudt R. , Sailer G. , Tomalla M. , Keller J. U. 
Published: July 2012

AbstractAdsorption equilibria of He, Ar, N2, CH4 on several types of activated carbon (AC) and molecular sieves (MS) have been measured at ambient temperature in the pressure range 0 MPa–15 MPa using a microbalance (Sartorius 4104 S). The resulting experimental data on principle only allow to calculate the difference (m–ρfVas) between the net mass adsorbed m, and the buoyancy related volume Vas of the adsorbent/adsorbate system multiplied by the density of the (fluid) adsorptive ρf. To determine simultaneously m and Vas, the data are fitted to an analytic adsorption isotherm m = m (ρf,T) of generalized Langmuir‐Freundlich type and/or Dubinin‐Radushkeviz type, and to one of four different models for the volume Vas, including the so‐called helium volume, this quantity considered to be constant. – The two times four adsorption isotherms (AI) resulting in this way do not differ much for low pressures (p < 1 MPa), however tend to differ considerably at higher pressures, the helium volume related AI leading to thermodynamic inconsistencies! As a result it can be stated that the buoyancy related apparent volume Vas of a porous adsorbent/adsorbate system strongly depends on the adsorptive used, i.e. on the size of its molecules, and also, to lesser extend, on the amount of mass adsorbed. Consequently, Vas should not simply be identified with the helium volume but instead specified for different adsorptives and pressure ranges used in industrial adsorption processes.
On the Formation of Catanionic Surfactant Precipitate
Authors: Škrtić D. , Babic‐Ivančić V. , Bujan M. , Tušek‐Božić L. J. , Filipović‐Vinceković N. 
Published: July 2012

AbstractThe morphology, structure and composition of catanionic surfactants formed during spontaneous batch precipitation from equimolar mixtures of alkylammonium chlorides and sodium alkyl sulfates, both with alkyl chains containing 10, 12 and 14 carbon atoms, were investigated by elemental, X‐ray and IR analysis. – Size distribution data are used to assess the mechanisms which control the precipitation at different stages of the process. Under experimental conditions employed (low surfactant concentration, high ionic strength) practically pure decylammonium decyl sulfate, dodecylammonium dodecyl sulfate or tetradecylammonium tetradecyl sulfate were formed. Crystalline catanionic surfactant particles exhibited low symmetry and interplanar spacings typical for lamellar structure. Great similarity of IR spectra obtained for the systems with alkyl chains containing 12 or 14 carbon atoms indicates essentially the same type of electrostatic interactions between the headgroups in these systems. – Catanionic surfactant formation could be described by a general equation of the type dV50 = atbDetermined values of the coefficient a and exponent b varied with the length of alkyl chain and the type of the rate – controlling process (growth, recrystallization and/or dissolution). Microscopic observation showed the coexistence of crystalline and liquid crystalline phase in aged systems.
Radical Analysis in the Pyrolysis of Hydrocarbons by Scavenging with Dimethyl Disulfide
Authors: Guthier K. , Hebgen P. , Loock H. P. , Homann K. H. , Zimmermann G. , Hofmann J. 
Published: July 2012

AbstractRadicals formed in the low pressure pyrolysis of hydrocarbons can be quantitatively analyzed by scavenging them with dimethyl disulfide (DMDS) in the condensed phase, the pyrolyses of several hydrocarbons (ethyne, ethene, 1.3‐butadiene, and benzene) have been studied in a flow reactor at 1300 K and 10.7 mbar. Samples of the hot gas mixture leaving the reactor were taken continuously by a quartz probe, the resulting supersonic nozzle beam was frozen together with an excess of DMDS on the inner surface of two hollow hemispheres cooled by liquid nitrogen. While melting the scavenging reaction takes place. The mixture of DMDS, stable pyrolysis products, and methylthio compounds was separated and identified with a GC‐MS‐system. CH*3, C2H*3, C6H*5 radicals and H‐atoms have been detected. The presence of acetone in ethyne pyrolysis has an important influence on the radical concentrations and the product yields.
Activity Coefficients of the Systems: NaBr + Na‐Acetate + H2O and NaBr + Na‐Propionate + H2O at 25°C. Application of Scatchard's, Pitzer's and Lim's Methods
Authors: Hernández‐Luis Felipe , Fernández‐Mérida Luis , González‐Díaz Oscar , Esteso Miguel A. , Khoo Siow‐Kian , Lim Tiong‐Koon 
Published: July 2012

AbstractMean activity coefficients for NaBr in NaBr + Na‐Acetate + H2O and NaBr + Na‐Propionate + H2O mixed systems were determined from the emf measurements of galvanic cells without transport. The measurements were carried out at different total ionic strengths I = INaBr + INaR, between 0.1 and 3.5 mol · kg−1 when R = acetate anion, and between 0.1 and 3.0 mol · kg−1 when R = propionate anion. At each total ionic strength, different ratios INaBr/INaR were studied. These experimental mean activity coefficients were comparatively analyzed by using Scatchard's, Pitzer's and Lim's methods, finding that Lim's models lead to better fittings for these mixed systems. From the LH Lim model (that takes into account the Higher Order Limiting Law, HOLL), activity coefficients of traces for both electrolytes in each mixture were determined and qualitatively analyzed. Finally, the Gibbs excess energy of these mixtures was calculated and also qualitatively analyzed against both the size of the non common electrolyte and the composition of the mixed electrolyte.
Transformation of Glassy Palladium‐Zirconium Alloys to Highly Active CO‐Oxidation Catalysts During In Situ Activation Studied by Thermoanalytical Methods and X‐Ray Diffraction
Authors: Baiker A. , Maciejewski M. , Tagliaferri S. 
Published: July 2012

AbstractPalladium/zirconia catalysts highly active for the oxidation of CO can be prepared by exposing amorphous Pd‐Zr alloys to CO oxidation conditions at 280°C. The bulk chemical and structural changes occuring under these conditions have been studied using thermoanalytical methods (TG, DTA) combined with mass spectrometry and in‐situ powder XRD. Amorphous PdZr2 and PdZr3 alloys exhibit virtually no activity when exposed to CO oxidation conditions, mainly due to their low specific surface area (˜ 0.01 m2/g). The activity develops with time on stream, passes through a maximum and reaches a stable state only after several hours. The maximum in the activity is observed when about 50–70% of the amount of oxygen necessary for complete oxidation of the precursor to PdO and ZrO2 has been consumed. The oxidation of the amorphous Pd‐Zr alloys, which results in a drastic increase of the specific surface area of the samples, starts at significantly lower temperature than the crystallization temperatures of the alloys. The stable catalysts contain poorly crystalline monoclinic and tetragonal ZrO2, metallic palladium and PdO as bulk phases. The concentration of these phases is influenced by a series of simultaneously occurring reactions, including: the oxidation of the alloy constituents by O2 which results in PdO and ZrO2, the oxidation by CO2 resulting in Pd and ZrO2, and the reduction of the PdO formed by CO and by metallic Zr present in the unreacted part of the alloy. The solid state reduction 2 PdO + Zr → Pd + ZrO2 contributes significantly to the reduction of the PdO as long as metallic Zr is abundant in the alloys.
Vibrational Energy Flow from Excited Adsorbates on Ionic Crystal Surfaces Measured by IR Polarization Interferometry and Laser Pulse Spectroscopy
Authors: Heidberg J. , Noseck U. , Suhren M. , Weiss H. 
Published: July 2012

AbstractVibrational energy flow in adsorbates on ionic crystal surfaces has been studied in situ by means of IR polarization interferometry, laser‐induced resonant desorption and fluorescence as well as time of flight measurements. Vibrational adsorbate spectra, isotherms and isosteric heats of adsorption were measured. The vibrationally induced desorption of CH3F and CD3F from NaCl(film) and NaCl(100) after resonant excitation of the v3‐CF stretching vibration with a line‐tunable infrared laser is reported in detail. Translational temperatures TMB of the desorbing molecules were derived by fitting Maxwell‐Boltzmann distributions to the time‐of‐flight spectra. TMB of the molecules desorbing from NaCl(film) is much lower (TMB = 30 K at substrate temperatures between 10 K and 78 K) than TMB of molecules desorbing from NaCl(100) (TMB = 125 K), which is ascribed to the different adsorption energies on NaCl(film) and NaCl(100). No preferred desorption of CH3F or CD3F in a 45%:55% mixture at 0.75 of saturation coverage on NaCl(film) after resonant excitation was observed.
Electron Spin‐Resonance (ESR) Studies of Adsorbate Dynamics on Single Crystal Surfaces: Possibilities and Limitations
Authors: Katter U. J. , Schlienz H. , Beckendorf M. , Freund H.‐J. 
Published: July 2012

AbstractESR is not one of the standard surface science tools because it is not inherently surface sensitive but rather probes the entire sample. However, ESR can be made into a surface science tool if we use paramagnetic adsorbates on thin nonmagnetic transition metal substrates or transition metal oxide films interacting with paramagnetic or nonmagnetic adsorbates. In contrast to NMR, ESR exhibits a sensitivity which allows one to detect monolayer and submonolayer coverages of spins (>1012 spins). The experiments can be carried out either in ultrahigh vacuum (UHV) or under an ambient gas atmosphere. — ESR provides us with the unique opportunity to study adsorbate dynamics by studying line shape changes as a function of temperature. ESR is also sensitive to molecular orientation so that the orientation distribution of the molecular planes may be derived experimentally. Thus ESR allows us to derive information not easily accessible with other techniques. We describe the set up of a UHV/ESR experiment in which the ESR measurement may be combined with LEED/Auger and TDS experiments. Several types of results are discussed:

ESR of chemisorbed and physisorbed molecules on metal surfaces including angle dependent measurements.
ESR of molecules on oxide surfaces at submonolayers coverages.
We will touch on possible future experiments involving pulsed ESR techniques to study dynamics in the adsorbate for a wide variety of processes including rotation and diffusion.
Solid/gas‐interactions of Surface‐doped Oxides: C—V, I—V, XPS, UPS, and ELS Studies on Pt/TiO2 and Pd/SnO2 (110)
Authors: Schierbaum K. D. , Wei‐Xing X. , Göpel W. 
Published: July 2012

AbstractWe have investigated Pt and Pd overlayers in the submono‐, mono‐, and multilayer coverage range on TiO2 and SnO2 (110)‐single crystal surfaces. The interaction with O2 was studied at temperatures between 300 and 1070 K in‐situ with current‐ and capacitance‐voltage (I—V and C—V) measurements, X‐ray and ultraviolet photoelectron spectroscopies (XPS and UPS), and electron energy loss spectroscopy (ELS). Under oxidizing conditions, Pt and Pd ions are formed which diffuse into the oxide substrate thereby forming Pd‐acceptor and Pt‐donor type bulk defects. For multilayer coverages of Pt and Pd the electrical conduction across the metal/oxide interface changes drastically from Schottky diode to ohmic behaviour upon oxidation. Under reducing UHV conditions at temperatures T ≥ 700 K we observe the formation of neutral Pd at the SnO2 surface. Total energy calculations of TiO2 with incorporated Pt2(4)+ ions at different lattice positions confirm the experimentally observed fast diffusion of Pt atoms between surface, subsurface, and bulk sites.
In Situ Studies of Adsorption at Liquid/Solid Interfaces and of Intercalation Reactions by γ‐γ‐Correlation Spectroscopy
Authors: Butz T. 
Published: July 2012

Abstractγ‐γ‐correlation spectroscopy is ideally suited to study adsorption processes in situ at liquid/solid interfaces. This is illustrated by adsorption studies of polymolybdates in solution onto γ‐Al2O3 using 99Mo(β−)99Tc. — Intercalation reactions can be monitored in situ both from the host and the guest point of view. Examples include the lithiation of 2H‐TaS2 and MoS2 using 181Hf(ß−)181Ta and 99Mo(ß−)99Tc, respectively. The intercalation of indium into 2H‐TaS2 was monitored using 111In(EC)111Cd. — First experiments with exfoliated and restacked MoS2 will be described.