bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reactivity of Interstitial Cl− Anions in Synthetic Hydrotalcite-Like Materials in the Halide Exchange Reaction with Alkyl Halides
Authors: López-Salinas Esteban , Ono Yoshio , Suzuki Eiichi 
Published: April 2011

ABSTRACTTwo types of synthetic hydrotalcite-like [Mg6Al2(OH)16 ][An−%D;2/n (HT) were prepared where A = Cl− anions (Cl-HT), and NiC42− complex anions (NiCl-HT), in order to examine: (1) the reactivity of Cl− anion (or ligand) towards alkyl halides and (2) their catalytic behavior in the Finkelstein reaction. For instance, 0.4 g of NiCl-HT (Cl−: 1.41 mmol) suspended in 20 cm3 of toluene with 14.1 mmol of butyl bromide at 373 K yielded 42 % butyl chloride after 15 min of reaction. In comparison, NiCl4(Et4N)2 (precursor to prepare NiCl-HT) yielded at the same conditions only 2.4 % of butyl chloride. This indicates a great mobility of Cl− in the interlayer region of HTs. The reaction rate is greatly accelerated using DMF instead of toluene and butanol totally suppressed it. This is consistent with a SN2 mechanism. The halide-exchange reaction between benzyl chloride and butyl bromide is catalyzed by both Cl-HT and NiCl-HT.
Molecular Sieve Synthesis using Metallocenes as Structure Directing Agents
Authors: Balkus Kenneth J. , Gabrielov Alexei G. , Sandler Netanya 
Published: April 2011

ABSTRACTWe have been exploring molecular sieve synthesis using metal complexes as templates. Our objectives were to affect the crystallization of new structures as well as prepare bifunctional catalysts via the encapsulation of metal complexes during synthesis. In this paper the results for the synthesis of SiO2, AlPO4and SAPO molecular sieves in the presence of metallocenes will be presented. In particular, Cobalticinium ion, Cp2Co+, was found to be a template for Nonasil, AlPO4−5, AlPO4−16, SAPO−16 and CoAPO−16 which are known phases but require templates. The larger decamethyl derivative, CP*2Co+has produced a novel high silica zeolite molecular sieve, UTD-1 as well as a new SAPO phase UTD-2 which appear to be large pore materials. In all cases, the metal complex is occluded intact and cannot be extracted. Aspects of the synthesis and characterization of these microporous materials are presented below.
Carbon Fibrils Mechanism of Growth and Utilization as a Catalyst Support
Authors: Geus John W. , Van Dillen A. J. , Hoogenraad Marco S. 
Published: April 2011

ABSTRACTEspecially with the production of fine chemicals catalytic reactions are being performed in which solid catalysts suspended in liquids are used. Carbon is stable in both acid and alkaline liquids and is not preferentially wetted by water. Carbon is therefore an attractive support for catalysts to be used in liquid-phase reactions. The relatively low diffusion coefficients in liquids call for catalyst bodies having wide pores and dimensions between 1 and 10 μm. Since particles smaller than 1 μm cannot be readily separated from liquids, attrition of carbon support bodies must be avoided. However, it is difficult to produce active carbon bodies of 1 to 10 μm of a high mechanical strength. Also with gas-phase reactions, the low mechanical strength of active carbon bodies limits the applicability of active carbon.From supported metal particles carbon filaments of a diameter between 10 and 300 nm can be grown rapidly. The diameter is generally of the same order of magnitude as the size of the metal particles. The graphite layers within the fibrils, that have a circular cross-section, are oriented either parallel to the fibril axis or at an angle, which leads to cone-shaped graphite layers. The mechanism of growth of carbon fibrils from supported metal particles will be dealt with. The parallel orientation of the graphite layers leads to a very high mechanical strength, while the porous structure is extremely open. A representative value for the surface area is 225 m2/g and for the pore volume 1.6 ml/g, which leads to an average pore dimension of 28 nm.To apply active precursors, such as, palladium salts, the surface of the carbon fibrils must be oxidized, e.g., by treatment with nitric acid. A very high dispersion of palladium can thus be achieved. The dispersion of components active in hydrogenation can be assessed by the ability to react the support with hydrogen to methane. The activity of catalyst on carbon fibrils in the hydrogenation of nitrobenzene as well as the filterability of carbon fibril catalysts will be compared with that of commercial catalysts.
Properties of a Carbon Negative Electrode in Completely Inorganic Thin Film Li-Ion Batteries with a LiCoO2 Positive Electrode
Authors: Goldner R.B. , Slaven S. , Liu T.Y. , Haas T.E. , Arnt F.O. , Zerigian P. 
Published: April 2011

AbstractCompletely inorganic thin film lithium ion battery cells have been prepared by vapor deposition processes (vacuum evaporation and sputtering). The negative and positive electrodes were films of disordered carbon and lithium cobalt oxide, respectively. The results of battery charging/discharging and other measurements (e.g., in-situ lithium chemical diffusion constant measurements for the carbon films) indicate that disordered carbon films have a relatively high reversible charge capacity, (> 160 mC/μmand possibly higher than 360 mC/cm2-μm, or > 296 and possibly 667 mAh/g, respectively, assuming the measured film density of 1.5g/cm3), and a lithium chemical diffusion constant at room temperature ≈10-9 cm2/s. These results suggest that disordered carbon films should be good substitutes for metallic lithium in thin film rechargeable batteries.
Vanadium Pentoxide Gels from Liquid Crystals to Lithium Batteries
Authors: Livage J. , Baffier N. , Pereira-Ramos J.P. , Davidson P. 
Published: April 2011

AbstractVanadium pentoxide gels V205.nH20 are formed via the condensation of vanadic acid in aqueous solutions. They exhibit both ionic and electronic conductivity and could therefore be used as cathode materials in lithium batteries or electrochromic display devices. The polymerization process leads to ribbon-like vanadium pentoxide particles. In a given range of concentration, sols and gels exhibit a homogeneous lyotropic nematic phase in which the ribbons align in the same direction. Ordered fluid phases are thus obtained leading to oriented films when deposited onto flat substrates. Moreover, mixed oxides MxV205 (M = Na+, K+,Ba2+, Al3+, Fe3+,Fe3+,...) exhibiting some preferred orientation are obtained via ion exchange.These compounds exhibit improved lectrochemical properties (specific capacity, cycling properties) compared to usual mixed oxides prepared via solid state reactions.
Mass Transport and DC Electromotive Force Induced in Ionic Crystals by High-Frequency Electric Field
Authors: Rybakov K. I. , Semenov V. E. 
Published: April 2011

AbstractResults of the theoretical study of the effects produced on ionic crystals by highfrequency electric fields of moderate intensity are presented. The ponderomotive action of the electric field on the space charge induced by it in a thin layer within the crystal near its surface causes directional mass transport that leads to plastic deformation and induces a stationary distribution of electric potential. The analysis shows that the proposed effect (that appears to be equivalent to the action of mechanical stresses which exceed the electromagnetic pressure by many orders of magnitude) can influence the results of processing of ionic crystalline materials significantly.
Processing and Electrochemical Properties of Mixed Conducting Lat-xAxCo1-yFeyO3-δ (A=Sr, Ca)
Authors: Weber W. J. , Stevenson J. W. , Armstrong T. R. , Pederson L. R. , Kingsley J. J. 
Published: April 2011

AbstractPowder compositions in the series Lat-xAxCo1-yFeyO3-δ (A=Sr, Ca) have been prepared by a combustion synthesis method. Sintering of pressed powders produced high-density test specimens with the perovskite structure. The specimens exhibited high electrical conductivities with appreciable oxygen-ion conductivity that increased with Co content for the compositions studied. Oxygen permeation studies showed a significant flux of oxygen that increased with temperature for specimens in a P(O2) gradient with no applied field. Thermogravimetric studies of the Lat-xCo0.2Fe0.8O3-δ system indicated a reversible mass loss with increasing temperature that increased with Sr content.
Water Uptake and Conduction in Strontium Ytterbium Cerate
Authors: Coffey G. W. , Pederson L. R. , Weber W. J. 
Published: April 2011

AbstractWater uptake and conduction have been studied in SrYb0.05Ce0.95O3-δ, a composition known to conduct protons, oxygen ions, and electrons, depending on temperature and environment. Water uptake kinetics evaluated by thermogravimetry occurred in two distinct stages: a rapid, initial weight gain (0.39±0.09 eV, attributed to grain boundary and near surface hydration) followed by a much slower uptake (2.8±0.4 eV, attributed to hydration of the bulk grains). From cyclic voltammetry and mass spectrometry measurements for a cell exposed to asymmetric conditions, currents and activation energies for electronic, oxygen ion, and proton conduction were determined. The activation energy for electronic conduction, 0.90±0.09 eV, is believed to be artificially high due to the increase in electron carrier concentration with increased temperature. The activation energy for oxygen ion conduction (0.97±0.10 eV) agrees well with other oxygen conductors. Proton conduction appeared to follow two different mechanisms: a low temperature process characterized by an activation energy of 0.42±0.04 eV, and a high temperature process, characterized by an activation energy of 1.38±0.13 eV. A possible explanation is that proton conduction at low temperatures is dominated by grain boundaries and is dominated by bulk conduction at higher temperatures.
Strain Driven Two-Dimensional Phase Transition in PbSnF4 Superionic Conductor
Authors: Denes Georges , Madamba M.C. , Parris J.M. 
Published: April 2011

AbstractWhen a minor amount of HF is added to the SnF2 reacted with lead nitrate in aqueous solutions to prepare PbSnF4, a phase transition from tetragonal α-PbSnF4 to orthorhombíc o-PbSnF4 takes place. The transition is essentially bidimensional and takes place in the (a,b) plane of the unit-cell. The compactness of the structure increases at the transition. No essential structural change occurs: the transition is most likely displacive and it is driven by bidimensional nonuniform strain acting along the aand baxes of the unit-cell. This transition is similar to ferroic transitions (in this case, paraelastic → ferroelastic). No detectable change of chemical composition occurs at the transition, and the reason why the presence of HF in the reaction mixture causes the transition remains unknown.
Monitoring of Process of Ion Transport in Nonstoichiometric Fluorides with the LaF3 Structure
Authors: Sorokin Nikolay I. , Sobolev Boris P. 
Published: April 2011

AbstractFluoride compounds with the tysonite (LaF3- type) crystal structure form an important class of materials which find diverse technological applications as fast ionic conductors. The results of investigations of the ionic conductivity process within tysonite structured R1-xMxF3-x single crystals (R=rare earths and M=alkali-rare earths) are presented using various techniques of electrical response spectroscopy. Influence of isomorphic substitutions of iso- and heterovalent cations on ion transport parameters was studied. By monitoring the composition of nonstoichiometric R1-xMxF3-x. crystals we can vary fluorine-ion conductivity within the range 10−7 - 10−4 S/cm at 293 K and 10−4 - 10−2 S/cm at 500 K. The studied nonstoichiometric crystals with the LaF3-structure are promising solid electrolytes which can be used in chemical sensors and fluorine generators.
New Concepts in Primary and Rechargeable Solid State Lithium Polymer Batteries
Authors: Appetecchi Gianni , Croce Fausto , Gerace Furio , Panero Stefania , Passerini Stefano , Spila Eraldo , Scrosati Bruno 
Published: April 2011

AbstractThe properties of some examples of new classes of highly conducting ionic membranes are described and evoluated in terms of applications in new-design electrochemical devices.
Characterization of Plasticized Polyether-Urethane Solid Polymer Electrolytes
Authors: Forsyth M. , Meakin P. , Macfarlane D. R. , Hill A. J. 
Published: April 2011

AbstractThe effect of plasticizer addition on the density, conductivity, glass transition, and free volume behavior of salt containing polyether-urethanes has been examined. The addition of up to 1.5 molal LiC1O4 salt results in an effective crosslinking of the polyether-urethane chains due to the Li+ coordination with the oxygens of the host polymer. This crosslinking decreases inter- and intrachain separation and reduces polymer chain mobility as illustrated by increased density and Tg, decreased free volume, and, at salt concentrations greater than 0.6 molal, decreased conductivity. The addition of approximately 30 wt % tetraglyme plasticizer to the 1 molal LiC1O4/host polymer complex is shown to counter the effective crosslinking resulting in a decreased Tg to a value equal to that of the pure host polymer, increased conductivity, and increased average free volume cavity size to a value equal to that of the pure host polymer. However, the relative number of free volume cavities in the plasticized host polymer/salt complex remains fewer than that of the pure host polymer over the concentration range of plasticizer studied, and in a similar manner the density remains greater than that of the pure host polymer. The room temperature conductivity, free volume, and density behavior in conjunction with the Tg results suggest that the plasticizer addition leads to Li+ coordination with the oxygens of the plasticizer chains as well as increased mobility of the host polymer chains.
Ionic Association of Lithium Triflate in Glymes, Model Solvents, and High Molecular Weight Poly(Ethylene Oxide)
Authors: Frech R. , Huang W. , Dissanayake M. A. K. L. 
Published: April 2011

AbstractIonic association in lithium trifluoromethanesulfonate (triflate) dissolved in glymes, glycols, model solvents, and high molecular weight poly(ethylene oxide) is studied by analysis of vibrational band structure. Surprisingly, the CF3 symmetric deformation mode is shown to be the most accurate measure of ionic association and the reasons for this are discussed. The nature of various associated lithium triflate species as deduced from ab initio calculations is supported by spectral data presented here. A weak interaction of the triflate anion with certain solvent molecules containing an alcohol OH group is observed. Finally the temperature dependence of ionic association in a complex of lithium triflate and high molecular weight poly(ethylene oxide) is described.
Conductivity in Poly(Ethylene Oxide) Complexed with Mixed Alkali Metal Salts
Authors: Choi Byoung-Koo , Kim Young–Wa 
Published: April 2011

AbstractConductivity has been measured for mixed alkali systems of LixNa1-xClO4 (PEO)n with n = 6, 16 and 40, and a mixed anion system of LiClxI1−x(PEO)16 complexes with varying concentrations of x. In the LixNa1−xClO4 (PEO)n complexes, it shows no unusual conductivity behavior. In the LiClxI1−x(PEO)16 complexes, the conductivity shows positive deviation from additivity in the mixed-anion region and the mixed-anion effect is also observed in the semicrystalline-toamorphous transition temperature.
Polymer Blends Based on Poly(Ethylene Oxide) as Matrices of Solid State Ionics
Authors: Suvorova Anna I. , Tujkova Irina S. 
Published: April 2011

AbstractThe equilibrium sorption, inverse gas chromatography (dynamic sorption), optic microscopy, X-ray diffraction and visible light scattering methods were used to investigate the structure of poly(ethylene oxide) (PEO) blended with poly(vinylacetate) and poly(siloxanes) as matrices of polymer solid electrolytes. It was shown that the melting point (Tm) and the degree of crystallinity in such PEO-blends were lower than in pure PEO. The Gibbs energy of mixing and the compatibility parameter (X12) were obtained for PEO-blends. In the vicinity of Tm all the systems were thermodynamically compatible, however at the ambient temperature they were microgeterogenous and compatible only in the narrow range of PEO-modificator contents. This must be taken into consideration while creating solid polymer electrolytes based on polymer blend matrices.
Interlayer Interactions in Self-Assembled Poly(Phenylene Vinylene) Multilayer Heterostructures, Implications for Light-Emitting and Photorectifying Diodes
Authors: Fou A.C. , Onitsuka O. , Ferreira M. , Rubner M.F. , Hsieh B.R. 
Published: April 2011

AbstractLayer-by-layer molecular self-assembly has been used to fabricate multilayer heterostructures containing poly(phenylene vinylene) (PPV) and a variety of polyanions. These ultrathin films exhibit widely different photoluminescence intensities and peak positions (emission color) depending on the polyanion used. The characteristics of light-emitting devices based on such films are described. This represents the first demonstration of working organic light-emitting diodes, the active layer of which consists of ultrathin, self-assembled films of between 130 - 500 Å
The Usage of Industrialwaste Materials for the Productionof Special Cements and Binders
Authors: PÖllmann Herbert , Neubauer JÜrgen , Motzet Hubert 
Published: April 2011

AbstractBy mixing various industrial wastes, as garbage combustion ashes, bottom ashes, fluidized bed ashes, lignite power station ashes, fume purification sulfates and sulfites and lime it is possible to produce cements and binders on the basis of alinite, calcium sulfoaluminate and belite depending on the chemical variety of used wastes.The fabrication process for these cements was studied by laboratory experiments and the different phases and properties were studied in detail. Alinite cement was already produced on a larger scale in a rotary kiln of 10m length. These cements can be used for application purposes in mining mortars, expansive cements, rapid hardening binders and in landfill technologies. The hydration process and workability can be controlled by using various additives. hus industrial wastes can be a secondary resource for special cement production.
Microstructural Aspects of Zeolite Formation in Alkali Activated Cements Containing High Levels of Fly Ash
Authors: Brough A.R. , Katz A. , Bakharev T. , Sun G-.K. , Kirkpatrick R.J. , Struble L.J. , Young J.F. 
Published: April 2011

AbstractWasteforms made by reaction at elevated temperature of a highly alkaline simulated low-level nuclear waste solution, having high sodium ion concentration, with a cementitious blend high in fly ash have been studied. Significant formation of Na-P1 zeolite (gismondine framework) and of a sodalite occurred. The time evolution of the crystalline phases over the first 28 days is reported for both adiabatic and isothermal curing, and the role of these phases in microstructure development is discussed. The level of carbonate ions in solution was found to have a substantial effect on strength evolution and chemistry.
Llw Solidification Incement -Effect of Dilution
Authors: Katz A. , Brough A.R. , Bakharev T. , Kirkpatrick R.J. , Struble L.J. , Young J.F. 
Published: April 2011

AbstractA simulated Low Level nuclear Waste (LLW) solution was tested for long term solidification in a cement-based matrix. The waste is characterized by high pH and high concentrations of sodium, aluminum, nitrate, nitrite, phosphate and carbonate. The effect of diluting the waste with additional water was studied. The cementitious matrix was composed of cement, fly-ash and clay (21°, 68° and 11° respectively) with high solution to solid ratio (1 liter / 1 kg.). Mixes were prepared at 45°C and cured at 90°C for 28 days.Maximum 28 day compressive strengths and early age heat evolution were achieved by diluting the LLW solution to approximately 67& of its original concentration. More dilution led to a lower heat evolution and compressive strength. No dilution was found to give lower compressive strength, and a heat evolution that was delayed, and lower in intensity. XRD spectra showed formation of zeolites and tobermorite at the higher concentrations (67, 85, and 100& of the concentration of the undiluted simulated LLW), with a change from Na-P1 zeolite for 67& of the undiluted concentration to a sodalite at 100&. SEM observations showed a porous system for the low and high dilution rates but a less porous one for an intermediate level of dilution.
Application of Automated Image Analysis to the Study of Cement Paste Microstructure
Authors: Darwin David , Abou-Zeid Mohamed Nagib 
Published: April 2011

AbstractDigital acquisition and analysis of backscattered electron images provide powerful tools for the study of cement-based materials. The techniques can provide useful information on hydration phases, size distributions of unhydrated particles and voids, effects of changes in the watercementitious material ratio and the use of mineral admixtures, and the distribution of microcracks. The results of automated analyses of cement pastes with different water-cement ratios and pastes containing silica fume are presented. The analyses demonstrate that microstructural data vary significantly from image to image, requiring multiple images to limit the effects of scatter. The analyses also indicate that, although the pastes exhibit different degrees of hydration, the size distributions of the unhydrated cement particles are nearly identical. In contrast, the size distribution of larger voids differs significantly as a function of water-cementitious material ratio and with the use of silica fume as a partial replacement for cement. The calcium hydroxide content obtained based on image analysis exceeds but generally parallels that obtained with thermogravimetric analysis. The majority of microcracks in both nonloaded and loaded specimens occur through or adjacent to the lowest density hydration phase.
Effect of the Transition Zone on the Bulk Modulus of Concrete
Authors: Lutz Melanie P. , Monteiro Paulo J. M. 
Published: April 2011

AbstractIn concrete, non-uniformities in the hydration process, due to the the “wall effect” produeed by the aggregate (inclusion) particles, lead to an interfacial transition zone (ITZ) that is characterized by an increase in porosity near the inclusions. This increase in porosity may in turn be expected to cause a local decrease in the elastic moduli. We have modeled the effect of the ITZ by assuming that the elastic moduli vary smoothly in the vicinity of the inclusions, according to a power law. The exponent in the power law is chosen based on the estimated thickness of the ITZ. For this model, a closed-form expression can be found for the overall effective bulk modulus. The predicted bulk modulus of the concrete depends on known properties such as the elastic moduli of the bulk cement paste and the inclusions, the volume fraction of the inclusions, as well as on the elastic moduli at the interface. By comparing the model predictions to measured data, we can obtain estimates of the elastic moduli at the interface. Application of this inverse procedure to a set of data from the literature on mortar containing sand inclusions leads to the conclusion that the modulus at the interface is about 15-50% lower than in bulk cement paste.