bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Adsorption of Hydrogen on Carbon Monoxide Covered Nickel Films. Part I: Isotherms, Change in Resistivity and in Work Function
Authors: Papp H. 
Published: March 2014

AbstractThe adsorption of H2 on CO‐covered Ni films was investigated in the temperature range of 77 to 273 K by means of measuring the change in resistivity, the change in work function, isotherms and isosteric heats of adsorption. – At 77 K molecular H2 is only physically adsorbed on a CO covered Ni film with a minor increase in resistivity. H2, atomised by a hot tungsten filament, is readily adsorbed on a CO layer at 77 K, the accompanying change in work function is −1.45 eV. – Molecular H2 is adsorbed on a CO‐covered Ni film in the temperature range of 180 to 273 K with a decrease in resistivity and a temperature dependent decrease in work function. The maximum change in work function is −80 mV at 185 K and 5 · 10−2 Pa. The initial isosteric heat of adsorption of H2 is 36 ± 2 kJ/mol, which decreases slowly with increasing coverage.
Enthalpy of Mixing of Chlorobenzene, 1,2‐Dichlorobenzene, and 1,3‐Dichlorobenzene with Some n‐Alkanes
Authors: Wilhelm Emmerich , Inglese A. , Grolier J.‐P. E. , Kehiaian H. V. 
Published: March 2014

AbstractA dynamic microcalorimeter of the Picker design has been used to measure enthalpies of mixing of nine binary mixtures composed of chlorobenzene, of o‐dichlorobenzene, and of m‐dichlorobenzene, with each of the three alkanes, n‐heptane, n‐nonane and n‐tetradecane. Experiments were performed in the discontinuous mode at 298.15 K and atmospheric pressure, covering the whole concentration range. For 7 ⩽ n ⩽ 14 (n denotes the number of C‐atoms of a n‐alkane), the maximum excess enthalpy HEmax increases with increasing n for the chlorobenzene series, whereas for both the o‐ and m‐dichlorobenzene series a small decrease is observed. In all three cases this dependence on n is approximately linear:
Cl35/Cl37 Isotope Effects in the Fragmentations of Metastable Perchlorinated Alkane‐ and Silane‐Ions
Authors: Potzinger P. , Basu S. 
Published: March 2014

AbstractMetastable transitions in the substances CCl4, CCl4, C2Cl6, SiCl4, and Si2Cl6 have been measured by the MIKE method. For the most intense transitions isotope effects as well as relative translational energies of the products have been determined. In all cases a normal isotope effect was observed. The kinetic isotope effects range from 1.9 in case of a simple Cl elimination from SiCl+4 to values close to 1 in complex molecular elimination processes. For fragmentations into products consisting of non radical species a large kinetic energy release was observed presumably due to an energy barrier in the potential energy surface.
Trends and Systematics in Mineral Thermodynamics
Authors: Navrotsky Alexandra 
Published: March 2014

AbstractThe stability of complex oxide and silicate phases can be understood in terms of equally important contributions of energy and entropy effects. The change in coordination number at high pressure in silicates has a profound effect on thermodynamic properties. Properties of spinel solid solutions can be systematized using a refined cation distribution model, while those of solid solutions involving no cation redistribution can be correlated with the volume mismatch of the end‐members for a wide variety of structures and compositions. Ordering and exsolution in complex solid solutions is an important feature.
Bifurkationen bei Stoßwellenereignissen
Authors: Jakubith Manuel 
Published: March 2014

AbstractDynamic deformation of solid materials by shock‐waves is described qualitatively in terms of bifurcation theory. The onset of shock‐wave metamorphoses like formation of planar elements, diaplectic glasses and high‐pressure phases is therefore caused by branching of lattice atoms and the bifurcation of physical states respectively. An evidence is given by the discussion of photoelectron spectra of recovered shock treated enstatite.
Partielle molare Größen binärer Grandit‐Mischkristalle
Authors: Wassermann A. , Fehr K. T. , Huckenholz H. G. 
Published: March 2014

AbstractProperties of partial molar volumes, activities, activity coefficients, mixing free energies, and excess free energies of grossular (Ca3Al2Si3O12) in solid solution with andradite (Ca3Fe2+3Si3O12) and of grossular in solid solution with uvarovite (Ca3Cr2Si3O12) are derived from phase equilibria data. All specific properties show a non‐ideal behaviour. Positive deviations from ideality is demonstrated for excess free energy data within the grossular rich portion of the grossular – andradite and grossular – uvarovite solid solution as well. These results are in accordance with experimental results and petrographic observations.
Point Defects in Oxide Solid Solutions (IV). Correlated Diffusion of Cations and Vacancies in (Co, Mg)O‐Mixed Crystals
Authors: Schnehage M. , Dieckmann R. , Schmalzried H. 
Published: March 2014

AbstractMagnesium tracer diffusion coefficients have been determined experimentally for the oxide solid solution (CoxMg1 ‐x)1 ‐ δO as a function of temperature and compositionx.2612Mg was used as the stable tracer isotope and analysed by mass spectrometry. Combination of these data with previously obtained data on Co‐tracer diffusion allowed to explain quantitatively the pronounced correlation effects during cation diffusion and to calculate the individual jump frequencies of the cations. Finally, chemical diffusion coefficients of the vacancies are derived and compared with data from relaxation experiments.
Raman Scattering: Fast Axial Rotation of Methylhalides and Acetonitrile in the Liquid State
Authors: Gompf J. , Versmold H. , Langer H. 
Published: March 2014

AbstractThe temperature dependence of the degenerate methyl stretching Raman profiles of CH3CN, CH3I, CD3I, CH3Cl, and CH3F and, further, for CH3CN the pressure dependence are investigated. The Raman bands are analysed in terms of the small angle diffusion and the J‐diffusion model both with and without Coriolis interaction. The comparison with the small angle diffusion model is carried out in the frequency domain. For the analysis in terms of the J‐diffusion model, first experimental orientational correlation functions are calculated. Then, by following theoretical arguments, the overall correlation function is decomposed into two partial correlation functions g(2)1(t) and g(2)2(t). There is limited agreement with previous magnetic relaxation studies on the fast axial spinning motion. In particular, it is found that the partial correlation function g(2)2(t) shows little temperature and pressure dependence, which cannot satisfactorily be accounted for by the existing models.
Pulse Radiolysis Investigation of Diene Radical Cations
Authors: Mehnert R. , Brede O. , Cserép Gy. 
Published: March 2014

AbstractMonomer and dimer radical cations of isoprene, eis‐ and trans‐1,3‐pentadiene, 1,3‐cyclohexadiene, 1,4‐cyclohexadiene, and 1,5‐cyclooctadiene were observed in n‐butyl chloride solution after electron pulse irradiation. The optical absorption spectra of diene monomer radical cations obtained by pulse radiolysis compare well with spectra measured in γ‐irradiated matrices [1, 2]. Diene monomer radical cations are formed by charge transfer from n‐butyl chloride radical cations

with rate constants between 5 and 10 · 109 dm3 mol−1 s−1. From the decay of the corresponding diene monomer cation absorption rate constants of the dimerization reaction

were determined. The diene dimer radical cation bands were identified by their kinetic behaviour in a wide temperature range. Spectroscopical assignments of the absorption bands are discussed.
External Heavy Atom Effects of Counterions on Excited Aromatic Molecules in Aqueous Micellar Solutions of Cetyltrimethylammonium Salts
Authors: Wolff Thomas 
Published: March 2014

AbstractFluorescence (ϕf) and triplet quantum yields (ϕt) of anthracene, 9‐methylanthracene, 9,10‐dimethylanthracene, fluorene, indeno[2,1‐a‐]indene, and N‐methyldiphenylamine were measured by means of fluorimetry, conventional flash photolysis, and laser flash photolysis. Ethanol and aqueous micellar solutions of cetyltrimethylammonium chloride (CTAC) and of cetyltrimethylammonium bromide (CTAB) were used as solvents. ϕf values decreased while ϕt values increased when the solvent was changed from CTAC to CTAB. It could be shown that ϕf + ϕt is constant under all conditions investigated. Therefore, the results have to be explained by an external heavy atom effect of bromide counterions.
Hydrogen Absorption in Cubic Ti3Sb
Authors: Rao K. V. S. Rama , Mrowietz M. , Weiss Alarich 
Published: March 2014

AbstractThe absorption isotherms of hydrogen in the cubic intermetallic phase Ti3Sb were measured in the range 400 ≤ 77°C ≤ 800; 0.001 ≤ pH2/bar ≤ 0.925. The relative partial molar enthalpy of hydrogen solution at infinite dilution was found to be ΔH0H/J(K mol)−1 = −55.0 ± 1.5. The relative partial molar excess entropy of the solution at infinite dilution has been calculated to be ΔSE,0H/J(K mol)−1 = −63 ± 1, assuming the number of available interstitial sites per metal atom to be 0.75. The results are compared with data on other similar titanium alloys.
Electrical and Magnetic Properties of Molten Tlx(AgTlSe2)1 ‐ x Alloys
Authors: Uemura Osamu , Segawa Makoto , Satow Tsuneo 
Published: March 2014

AbstractThe electrical conductivity, the magnetic susceptibility, and the thermoelectric power of liquid Tl‐AgTlSe2 alloys have been obtained, respectively, as a function of temperature and composition from near the liquidus temperature up to about 900°C. In the region of low Tl concentration, the temperature dependences of these electronic properties follow an Arrhenius‐type activation process where the carriers excite thermally into the extended states. In the Tl rich region, above 66.7 mol‐% Tl, the temperature dependence of the conductivity becomes extremely small at high temperature, suggesting that the metallic contribution is important in this range. The electrical conductivity shows a deep minimum around 66.7 mol‐% Tl, the value of which was measured as 4.0 Ω−1 cm−1 at 400°C. Corresponding to this behaviour, a steep diamagnetic maximum was observed in the susceptibility vs. composition curve. Furthermore, the thermoelectric power changes its sign around this composition from positive in the AgTlSe2 excess side to negative in the Tl excess side. The maximum positive value of the thermoelectric power in the vicinity of 66.7 mol‐% Tl was roughly 290 μV · deg−1 at 600°C. The asymmetric form of isotherms for these quantities around 66.7 mol‐% Tl resembles that in the related liquid Tl – Se alloys which have been examined in detail with respect to their electronic behaviour indicating that the metal‐semiconductor transition occurs at the composition corresponding to AgTl3Se2 (66.7 mol‐% Tl) in the liquid system Tl‐AgTlSe2.
Conductivity and Debye Length in Aerosol‐OT Hexane/Liquid Paraffin Solutions
Authors: van Mil P. J. J. M. , Crommelin D. J. A. , Wiersema P. H. 
Published: March 2014

AbstractA new equation was derived for the calculation of the Debye length from conductance measurements in non‐polar media, taking into account the existence of triple ions. Measurements were carried out for the system dioctyl sodium sulfosuccinate (Na‐AOT) in hexane and liquid paraffin. With the equation the Debye length can also be calculated for viscous solvents (liquid paraffin) even when the concentration of Na‐AOT is too small for the conductivity to be measured.
Einfluß von Dispersion und Vorgeschichte dispersen Nickels auf dessen katalytische Eigenschaften bei der Hydrierung von Benzol, CO2 und CO
Authors: Kirch R. , Kotter M. , Riekert L. 
Published: March 2014

AbstractDisperse Nickel was prepared by impregnating alumina supports of different pore‐morphologies with solutions of Ni(NO3)2 or Ni(HCOO)2, drying, and reducing with H2 either these compounds or NiO generated therefrom. The surface‐area of disperse metallic nickel in the resulting catalysts was obtained through chemisorption of hydrogen; rates of hydrogenation of benzene at 325 K and of CO2 and CO at 500 K were observed and normalized by the extent of nickel‐surface in the porous solids. — The kinetics of reduction of Ni2+‐compounds is controlled by nucleation of the metallic phase, leading to preferential formation of larger crystallites of the metal at lower temperatures. Hydrogenation of benzene is structure insensitive, whereas hydrogenation of CO2 and CO appear to be structure sensitive.
Enhancement of the Ionic Conductivity in Solid‐Solid‐Dispersions by Surface Induced Defects
Authors: Maier Joachim 
Published: March 2014

AbstractThe finding that dispersions of insulators such as alumina or silica in ionic conductors may exhibit considerably enhanced ionic conductivities compared to the pure material, has become a promising topic for optimizing the electric properties in solid state research. Up to now the basic mechanism for this effect is unknown, the more so since two phase mixtures of two ionic conductors have been found to show a similar enhancement. In this work space charge regions are considered as being responsible for the effect. In the case of insulators as second phases possible surface interactions are taken into account resulting in drawing mobile ions out of the boundary layers and thus increasing the vacancy concentration or in pushing mobile ions into interstitial positions. In the case of two ionic conductors with the same mobile ion, the contact equilibria demand a double effect. The concentration distributions are discussed and lead to a quantitative expression for the space charge contribution in such dispersions. These calculations are in excellent accord with conductivity data of silver chloride (+ alumina, silica) as regards temperature, concentration and particle size. Experiments from the literature are also brought into the discussion. The influence of the surface activities of alumina is tested by modifying the surface chemically. Thermodynamic data for the surface interaction are given. The maximum effect to be expected by conductivity enhancements via surface induced defects and optimization conditions are discussed.
Laser Study of the Triplet State of 4‐Nitrostilbenes in Solution; Estimation of the Equilibrium Constant (3t* ⇄ 3p*) and the Rate Constant for Intersystem Crossing (3p* → 1p). XIII1
Authors: Görner Helmut , Schulte‐Frohlinde Dietrich 
Published: March 2014

AbstractDecay of the lowest triplet state of 4‐nitro‐, 4,4′‐dinitro‐, and 4‐nitro‐4′‐methoxystilbene (NS, DNS, and NMS, respectively) was studied by nanosecond laser photolysis in solution at room temperature. The triplet decays predominantly via intersystem crossing at the twisted configuration followed by internal rotation into the cis or trans ground states. Rate constants for triplet decay were determined in various solvents as a function of the concentration of ferrocene, azulene, and oxygen. Quenching by azulene and ferrocene leads only to trans isomers whereas quenching by oxygen does not markedly shift the photostationary state are room temperature. The results support the assumption of an equilibrium between the planar trans configuration (3t*) and 3p* and allows the estimation of kp and the triplet equilibrium constant K5 = k5/k−5 = [3p*]/[3t*]. K5 shows a trend to decrease with increasing solvent polarity. For NS this corresponds to a shift of the 3t* ⇄ 3p* equilibrium from — 75% of the 3p* configuration in n‐pentane to ˜25% in methanol. This shift is explained by the greater stabilization of the planar 3t* configuration by polar solvents in comparison to that of the less polar twisted 3p* configuration. The solvent dependent change in kp is less pronounced, giving average values of 3.0 · 107 and 1.7 · 107 s−1 for NS and NMS, respectively.
Phase Transition Behavior and Permeation Properties of Cationic and Anionic Artificial Lipids with Two Alkyl Chains
Authors: Kumano Atsushi , Kajiyama Tisato , Takayanagi Motowo , Kunitake Toyoki , Okahata Yoshio 
Published: March 2014

AbstractMembrane structure and crystal‐liquid crystal phase transition behaviors were investigated for the water system of totally artificial lipids with cationic or anionic head group and two alkyl chains. These artificial lipids formed multilamellar liposomes composed of a bimolecular layer. The phase transition temperature from gel to liquid crystalline lamellae decreased steadily to a limiting temperature with an increase in water concentration up to the lipid fraction of 0.80 — 0.85. This kind of phase diagram means that the artificial lipids have characteristics of both thermotropic and lyotropic mesomorphisms. For the cationic artificial lipid, the thickness of the bimolecular lamella in a gel state was shorter than a bimolecular length calculated on the assumption of planar zigzag conformation of the alkyl chains. This suggests that the hydrocarbon chains in a gel state are packed with the chain axes inclined at a certain angle to the lamellar surface. The diffusive permeability of the polymer/artificial lipid composite membranes to water or ions exhibits a distinct jump in the vicinity of the crystal‐liquid crystal phase transition temperature.
NMR Studies on Hydrogen Chemisorption and Water Formation on Platinum Black Catalysts
Authors: Reinecke N. , Haul R. 
Published: March 2014

AbstractFourier Transform NMR spectroscopy has been used to study the reduction of oxygen covered Pt‐black and the chemisorption of hydrogen. The 1H Knight shift is dependent on hydrogen surface coverage and Pt particle size. T1, and T2 relaxation times were measured for adsorbed H2O and H as a function of temperature. The results are discussed with respect to the surface stoichiometry and the mechanism of the catalytic water reaction, isosteric heats of hydrogen chemisorption, estimation of metal surface areas of Pt catalysts and surface mobility of adsorbed H2O and H.
Cation Exchange on Oxide Surfaces as Influenced by Surface Hydration Phenomena. I. Alkali Metal Ions on Silica
Authors: Peschel G. , Ludwig P. 
Published: March 2014

AbstractThe exchange of Li+, Na+, K+, Rb+, and Cs+ with protons of surface silanol groups of a silica sol was determined by a titration method. For very small concentrations ion exchange steeply increases up to a plateau located at about 0.14 mol kg−1 ranging from about 10−4 up to 3 · 10−1 M. Whereas Na shows only a slight increase of exchange, Li+ and K+ display no detectable reaction with the silica surface in this concentration range. For higher concentrations ion exchange increases in a more normal manner. The low degree of ion exchange is interpreted by formation of a hydration sheath around the alkali cations adsorbed on the silica surface.
Depth Profiling of Hydrogen Isotopes in Metals by Elastic Recoil Detection and Nuclear Reaction Techniques under In‐Situ Conditions
Authors: Albers P. W. , Sicking G. H. , Earwaker L. G. , England J. B. A. 
Published: March 2014

AbstractThe application of the ERD‐technique with 2.8 MeV and 25 MeV α‐particles respectively and of the specific nuclear reaction D(d,p)T for the determination of hydrogen isotopes in metals is described in detail. — The methods were applied to hydrided and/or deuterated elements (Ti, Zr, Pd), alloys (Pd0.92Y0.08, Fecralloy, steels), intermetallic compounds (TiMn‐ and ZrMn‐Laves phases) and a Ti/Cu‐target containing all the three hydrogen isotopes. — Images are obtained about the hydrogen depth distribution in near surface regions of the materials (roughly 400 nm in case of 2.8 MeV ERD, 200 um in case of 25 MeV ERD, and 500 nm in case of D(d,p)T). By aid of standardization the hydrogen content of a number of samples was determined. Information was obtained about the presence of impurities in the specimens. Prominent results of the investigations are:
Laves‐phase systems (Ti0.4Mn0.6, Zr0.33Mn0.67) are activated for hydrogen absorption by segregation processes, whereby overlayers of Ti(Zr)‐hydride are formed. These overlayers are separated from the bulk‐hydride by a hydrogen depletion zone.
Cold‐rolled specimens (Pd, Pd0.92Y0.08) trap hydrogen in near surface states.
Surface oxidation of Fecralloy leads to an effective barrier for hydrogen‐uptake, due to the formation of Al‐oxide overlayers.
Paramagnetic probe for molecular interactions: II. 7Li NMR study of lithium cation solvation by a nitroxide radical
Authors: Kolodziejski Waclaw 
Published: March 2014

AbstractLiClO4‐organic solvent‐nitroxide radical systems were studied using 2,2,6,6‐tetramethylpiperidine nitroxide radical (TMPN). The Li+‐TMPN interaction was observed by means of the 7Li NMR contact shift and the paramagnetic broadening of the 7Li NMR signal. The effects were found to be solvent dependent and were interpreted with donor and acceptor numbers of solvents. The quantitative analysis of the data was done and the formation constants, the life times and the 7Li hyperfine splitting constants of the Li+‐TMPN complexes were determined. The 7Li NMR results and the former EPR results were compared.
Small‐angle neutron scattering‐measurements on a surfactant system consisting of cationic and anionic surfactant molecules
Authors: Hoffmann H. , Kalus J. , Scbwandner B. 
Published: March 2014

AbstractResults of small‐angle neutron scattering (SANS) experiments are reported on the mixed cationic anionic surfactant system Tetradecyl‐pyridinium‐heptylsulfonate (C14PyC7SO3). In the concentration range between 10 mM and 160 mM, the scattering curves show a correlation peak. The scattering vector at the correlation peaks shifts with the volume fraction of the surfactant with a power low having an exponent 0.43. The data can be explained on the basis of rodlike micelles which become shorter with increasing concentrations. For the two highest concentrations 320 and 640 mM the correlation peak disappeared. This change in the scattering curves is attributed to a change in the aggregation behaviour of the system. It is found that at these concentrations the short chain anionic surfactant bind in a one to one ratio with the anionic surfactant and the micelles are practically uncharged, while in the rodlike concentration range the dissociation degree is higher. In the concentration range of the rodlike micelles the correlation peak becomes weaker with increasing concentration.
Experimental and theoretical study of the apparent molar volumes of 1‐alcohols in linear hydrocarbons
Authors: Costas M. , Alonso M. Caceres , Heintz A. 
Published: March 2014

AbstractApparent molar volumes ϕv have been measured for twelve alcohol/alkane mixtures between XOH = 0. 001 and 0. 2 at 298. 15 K. The systems studied were: methanol + n‐C6 ethanol and 1‐butanol + n‐C1, 1‐hexanol + n‐Cn with n = 6, 10, 12 and 16, 1‐heptanol + n‐C10, 1‐decanol + n‐Cn with n = 6, 10 and 16 and 1‐dodecanol + n‐C10 ϕv shows a sharp increase for XOH < 0. 05; values found at infinite dilute are several cm3/mol larger than the pure alcohol molar volume. Experimental results are compared with predictions from the Extended Real Associated Solution (ERAS) model which takes into account associational and physical effects as well as a reaction volume Δv* for hydrogen bond formation. Without any adjusted parameter the ERAS model gives good predictions for ϕv and the excess partial molar volumes at infinite dilution ΔV∞OH. It is found that, in the concentration region studied, the associational contribution dominates ϕv; the rapid fall of ϕv, with increasing alcohol concentration is due to alcohol self‐association and a corresponding increase in molecular cohesion. At infinite dilution, the associational contribution to ΔV∞OH. is nearly constant for all alcohols and hence the observed changes in ΔV∞OH values are almost entirely due to changes on the physical term. Experimental ΔV∞OH increase for a given alcohol as the chain length of the alkane increases and decrease for a series of increasingly longer 1‐alcohols in a given alkane. These changes are reproduced by the theory and explained in terms of differences in free volume between the two components as well as the associational contribution to ΔV∞OH.