bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Plasticized Polyether-Urethane Solid Polymer Electrolytes
Authors: Forsyth M. , Meakin P. , Macfarlane D. R. , Hill A. J.
Published: April 2011

The 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

Ionic 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

Conductivity 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

The 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

Layer-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

By 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

Wasteforms 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

A 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

Digital 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

In 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.
The Interfacial Transition Zone: “Direct” Evidence on Compressive Response
Authors: Darwin David
Published: April 2011

There is little question that the strength of the interfacial transition zone (MTZ) between cement paste and aggregate affects the compressive strength of concrete. The key question, rather, is to what degree? It is difficult to directly measure the response of the overall composite to changes in interfacial properties, since it is difficult to isolate interfacial strength as the only variable.

Research on the effects of interfacial strength on the compressive response of concrete that comes the closest to providing direct evidence is summarized. The studies, dating to the 1950's, include both experimental and analytical efforts aimed at isolating the effects of the ITZ, as well as experimental efforts that are considered to provide strong indirect evidence. The research shows that the ITZ plays a measurable role in the response of concrete to compressive stress, but that its role is overshadowed by the properties of the cement paste and aggregate constituents of concrete and the heterogeneous nature of the composite.
Transfer Properties of Interfacial Transition Zones and Mortars
Authors: B. Bourdette , Ollivier J.P. , Revertegat E.
Published: April 2011

It seems probable that the higher porosity of the Interfacial Transition Zone (ITZ) affects concrete durability. An experimental program has thus been developed to provide more information in this area and to evaluate the influence of the transition zone on the transfer properties. A model based on the mercury intrusion porosity results shows that the ITZ is about 1.5 to 2.5 times more porous than OPC cement paste and in this zone the tritium diffusion coefficient is a factor of three higher.

The tritium diffusion coefficient has been measured for mortars containing different sand concentrations. We have shown that the binder phase diffusivity decreases with the sand concentration down to a minimum, then increases when the 1TZ are interconnected. Under these conditions, the sand volume concentration is above 50% and for higher concentrations, the diffusivities of the binder phase and pure cement paste are similar. The effects of ITZ on the porosity compensate for the increasing tortuosity due to the interposition of particle aggregates.

Measurement of the calcium leaching rates from mortar with high sand concentrations and pure cement paste with the same W/C ratio confirms these results: the leaching kinetics of the binder phase in mortar are very close to those of the pure cement paste.
Undispersed Granulated Silica Fume in Concrete - Chemical System and Durability Problems
Authors: Lagerblad Björn , Utkin Peeter
Published: April 2011

Granulated condensed silica fume is not easily dispersed. In contact with the pore fluids of the cement paste the granulates rapidly turn into alkali-silica gel nodules. With time this gel absorbs Ca and at least the rim of the AS-nodules transforms into a C-S-H product. The gel by itself does not cause expansion as it forms before the cement paste hardens. However, if exposed to alkali salts the AS-nodules may become further enriched in alkalies, which in turn may trigger an expansive reaction and cracking.
Heterogeneous Nucleation of Ordered Mesoporous Materials
Authors: Liu Jun , Virden Jud W. , Kim Anthony Y. , Bunker Bruce C.
Published: April 2011

Recently we proposed that heterogenous nucleation is an important phenomenon for the preparation of ordered mesoporous materials. In this paper we further investigate the effect of colloidal particles on the nucleation process of mesoporous materials. Based on the change of the electrical mobilities of the particles in the surfactant solution, we suggest that the adsorption and co-adsorption of surfactant and ceramic precursors changes local structural and chemistry on the particle surfaces, and favors the nucleation events within these regions.
Molecular Simulation of Gases in Porous Silicates
Authors: Pohl Phillip I. , Smith Douglas M.
Published: April 2011

In this work we generate computer models of zeolites, imogolite, and microporous silica and evaluate the pore structure of each. Our purpose is to contrast the diffusional aspects of gases in these different materials with respect to their application as gas separating membranes. The concepts of Knudsen, surface and micropore diffusion will be evaluated for each model. The advantage of modeling these materials and processes with available molecular techniques is clearly demonstrated by testing assumptions of highly regarded theories.
Molecular Sieve Based Chemical Sensors
Authors: Balkus Kenneth J. , Sottile Laura J. , Nguyen Hoan , Riley Scott J. , Gnade Bruce E.
Published: April 2011

Molecular sieves, are attractive materials for discriminating chemical sensors. These microporous metal oxides offer shape selective adsorption as well as chemical and thermal stability. Molecular sieves have shown promise in SAW devices, however, these sensors rely only on a weight change upon adsorption of target molecules. We have developed a molecular sieve based capacitance type chemical sensor. Such a device should discriminate between molecules of similar size and shape because the signature change depends on the polarity of the adsorbate which in turn affects the dielectric properties of the molecular sieve. In this paper we describe the deposition of AIPO4 and MeAPO molecular sieve thin films on titanium nitride coated silicon wafers by laser ablation. A subsequent hydrothermal treatment followed by a Pd/Au coating and standard microlithography techniques generate the capacitors. The results for capacitance measurements in the presence of CO2, CO, NO, N2, O2, H2O and toluene indicate clear differences in selectivity between small, medium and large pore molecular sieves.
Small Angle Neutron Scattering Study of the Structure and Formation of Ordered Mesopores in Silica
Authors: Glinka C. J. , Nicol J. M. , Stucky G. D. , Ramli E. , Margolese D. I. , Huo Q.
Published: April 2011

The nanoscale structure and synthesis mechanisms of a recently developed class of inorganic mesoporous materials with ordered arrays of uniform mesopores have been investigated by small angle neutron scattering (SANS). SANS measurements with solvents imbibed into the pores to vary the scattering contrast demonstrate that the low angle diffraction peaks from these materials are entirely due to the pore structure and that the pores are fully accessible to both aqueous and organic solvents. SANS measurements on the concentrated cationic surfactant and silicate precursor solutions typically used in the synthesis of the mesopore materials indicate that the existence of preassembled supramolecular arrays that mimic the final pore structure is not essential for the synthesis of these materials.
Ti - Substituted Mesoporous Molecular Sieves for Catalytic Oxidation of Large Aromatic Compounds Prepared by Neutral Templating Route
Authors: Pinnavaia Thomas J. , Tanev Peter T. , Wang Jialiang , Zhang Wenzhong
Published: April 2011

A new synthesis route to open framework mesostructures based on H-bonding and self-assembly between neutral primary amine surfactants (S°) and neutral inorganic precursors (I°) has been used to prepare hexagonal mesoporous silicas containing site isolated titanium centers. These new titanosilicates, designated Ti-HMS, exhibit exceptional catalytic reactivity for the oxidation of substrates too large to access the pore structure of conventional titanosilicates, such as titanium silicalite, TS-1. The catalytic properties of Ti-HMS materials for the peroxide oxidation of 2,6- di- tert-butylphenol are compared with those of microporous TS-1 and a mesoporous Ti-MCM-41 analog prepared by an electrostatic templating mechanism using a liquid crystal quaternary ammonium cationic surfactant.
Coating of Small Particles by Chemical Vapor Deposition While the Particles are Fluidized
Authors: Kaae J. L.
Published: April 2011

Coating of small particles is often employed to impart special properties to the particles. One process that has been used to accomplish this is chemical vapor deposition while the particles are fluidized. Because the depositing solids can plug small orifices, the gas distributors used for chemical vapor deposition in a fluidized bed of particles are different from those used for most other fluidized bed processes. The turbulent mixing of the gases by the particle bed and the high collection efficiency of depositing species by the large surface area of the particle bed can produce unique coating microstructures. Examples of these unique microstructures are those of isotropic pyrolytic carbon, fine-grained silicon carbide and carbon-silicon two-phase mixtures.
Fabrication and Properties of Hollow Sphere Nickel Foams
Authors: Clancy R. B. , Cochran J. K. , Sanders T. H.
Published: April 2011

A novel method of fabricating low-density hollow sphere metallic foam has been developed. Utilizing pre-existing technology, thin-wall, hollow oxide spheres, ∼ 2mm in diameter, were formed from powder slurries with a coaxial nozzle process. Oxide foams were constructed by bonding sintered spheres at points of contact and firing. The oxide foams were reduced to the metallic state in a hydrogen atmosphere. Successful precursor compositions for transformation included NiO, Cu2O, and NiO-Cu2O. After reduction, the metal foams were sintered to increase strength and resulting foam densities were generally 10–20% of theoretical density. Wall thickness of the spheres which constitute the foams ranged from 50–100 μ m. Nickel foams were crushed under uniaxial compressive stress, and mechanical properties (yield stress, elastic modulus, and energy absorption) were investigated under varying density in order to determine parametric relationships to compare to existing models of foam properties. The effects of sintering, reduction, and compressive deformation on the microstructures were examined with SEM and EDS.
Processing and Mechanical Properties of Ti//(alumina)mb/Al Core//Ti Sandwich Panels
Authors: Rawal S. P. , Lanning B. R. , Misra M. S.
Published: April 2011

Several sandwich panels with Ti-6AI-4V facesheets and syntactic metal foam (i.e., alumina microballoons (mb) in aluminum matrix) core were produced by a single step casting press. Optical microscopy and scanning acoustic microscopy techniques were used to examine the integrity of Ti/Al and mb/Al matrix interfaces. Mechanical property tests including compression, tension, flexure, and impact tests were performed to determine the characteristics of as-cast Ti//(alumina)mb/Al//Ti laminates. Presented in this paper are the specific details of design, processing, and mechanical behavior of the as-cast laminates.
Monodisperse Spherical Polymer Particles Prepared by Atomization
Authors: Hilborn Jöns G.
Published: April 2011

Many properties of small particle powders are significantly improved when the particle shape is spherical and the size distribution is narrow or monodisperse. By using a properly designed atomizer based on a rotating disc, perfectly spherical polymer particle with a narrow size distribution in the 20 μm to 300 μm range has been prepared directly from a polymer melt or solution. Furthermore, by using a large number of parallel discs in the same equipment, a capacity suitable for industrial scale production is possible. The polymer melt or solution is added to the rotating disk to form a thin film which is transported to the disc edge where it leaves as particles. The powder particles are formed when sufficient energy and mass is given for its formation. When the energy given by the rotation equals the energy required to create the new surface of the particle it will separate from the film and leave the disc edge. Examples such as powder coatings, chromatography media and biodegradable spheres will be shown.
Production of Metal Nanopowders by Sonoelectrochemistry
Authors: Delplancke J.-L. , Bella V. Di , Reisse J. , Winand R.
Published: April 2011

Metal powders with a diameter ranging from 20 to 50 micrometers are currently produced by electrolysis at high current density in aqueous electrolytes. A lot of research is then devoted to produce by electrolysis and with a high yield, ultrafine metal powders. Two main techniques are actually developed: strong electrolyte stirring and pulsed currents in order to obtain high current densities and accordingly, high nucleation rates and small nuclei diameters. By combining pulsed current and pulsed ultrasound on the same electrode surface, it has been possible to produce by electrolysis, with a yield ranging from 80 to 95%, crystalline metal powders with a sharp diameter distribution around 100nm. Possible explanations of these results are presented. This new technique, called sonoelectrochemistry, is illustrated by metal powders analysed by HIRTEM, X-ray diffraction and laser diffusion. The perspectives of sonoelectrochemistry for the production of metal or ceramic nanopowders are studied.
Applications of Sxps for Studying Surface Structure, Reaction Mechanisms and Kinetics
Authors: Mullins D. R. , Huntley D. R. , Overbury S. H.
Published: April 2011

Soft x-ray photoelectron spectroscopy (SXPS) from the S 2p core level has been used to study adsorbate induced reconstruction, identify reaction intermediates and study reaction kinetics on the Ni(111) surface. The S 2p binding energy is affected by the nature of the surface adsorption site. It has been determined from the number of S 2p states and their relative binding energies that adsorbed S induces a reconstruction of the Ni(111) surface and that the S adsorbs in fourfold sites on terraces and in troughs. S 2p SXPS has also been used to identify adsorbed species during the thermal decomposition of methanethiol on Ni(111). CH3SH adsorbs as CH 3S- at low temperatures. Above 200 K, the CH3S- changes adsorption site and the C-S bond begins to cleave. The relative concentrations of CH3S- in the two different sites and of atomic S have been monitored as a function of temperature and initial coverage. As a result of the sensitivity and resolution available in SXPS, reactions rates and kinetic parameters have been obtained for the decomposition of benzenethiol on Ni(111) by monitoring the changes in the surface composition continuously as a function of temperature and time.
High Resolution Diffraction Imaging of Mercuric Iodide: Demonstration of the Necessity for Alternate Crystal Processing Techniques for Highly Purified Material
Authors: Steiner Bruce , Berg Lodewijk Van Den , Laor Uri
Published: April 2011

The overall crystalline lattice uniformity in recently available, highly purified mercuric iodide single crystals has been shown to be impacted by crystal handling techniques that were previously satisfactory. High resolution diffraction imaging of the surface regularity of crystals of various levels of purity and growth orientation shows: 1) that the newer materials have a generally lower level of precipitates, 2) that the incidence of these precipitates is now closely correlated with growth direction, and 3) that the deformation resistance and resulting sensitivity to crystal handling procedures are also closely correlated with these factors in this soft material.

As a result, gentler cutting and polishing procedures have been developed and are shown to be effective in preserving overall lattice regularity in the new material. The polishing required to remove residual surface scratches affects the lattice orientation of the softer, precipitate-free regions, while not affecting those regions with detectible levels of precipitates. These results correlate closely with the electrical properties of devices made from these crystals.
Recovery of SRO Parameters and Pairwise Atomic Displacements in a Fe46.5Ni53.5 Alloy
Authors: Jiang X. , Ice G. E. , Sparks C. J. , Zschack P.
Published: April 2011

Resonant (anomalous) x-ray scattering is used to alter the contrast between atoms nearby in the periodic table to recover local pair correlations. Both Warren-Cowley short-range order parameters and chemically specific interatomic distances are recovered from diffusely scattered x-ray intensities measured at three different x-ray energies (3λ method). Analysis of the statistical and systematic errors shows that the average values for the number and kinds of first nearest neighbors are recovered to about one atom in one hundred and their interatomic distances to about ±0.002 Å.
A New Method to Characterize Dislocation Loops
Authors: Liu Fuping , Baker Ian , Dudley Michael
Published: April 2011

White-beam synchrotron X-ray topography has been used to study the circular, prismatic, [0001] dislocation loops which are commonly-observed on the (0001) plane in polycrystalline, freshwater ice. A new method, involving detailed analyses of the effects of beam divergence on the loop images, has been developed to determine whether a loop is of vacancy or interstitial type. In an 0002 image, one half of a loop (projected as an ellipse) appears as a single image and the other half as a double image. Experimentally, it was found that the 0002 vector drawn from the center of a loop passes through the single image if the loop is of vacancy-type and through the double image if a loop is of interstitial-type. This method of loop characterization was confirmed by performing theoretical analyses of both the dislocation image widths and their strain fields.
Computer Aided Synchrotron White Beam X-Ray Topographic Analysis of Multipolytype SiC Device Configurations
Authors: Huang W. , Wang S. , Dudley M. , Neudeck P. , Powell J. A. , Fazi C.
Published: April 2011

SiC device configurations comprising various polytypes have been analyzed using synchrotron white beam x-ray topography with the aid of computer simulation. Diffracted intensity maps for the various polytypes and their combinations in various diffraction geometries, including transmission, reflection, grazing-reflection and back-reflection are generated. This method is used to determine the structures of SiC devices fabricated via CVD epilayer growth of nominally 3C-SiC or 6H-SiC, or 6H-SiC substrates grown by the Lely technique. The work indicates that those devices which were initially considered to be of 3C structure also contain some 6H structure. Defect structures associated with the polytype configurations are also presented.
Effects of Ferromagnetic Capping Layers on the Perpendicular Anisotropy of Ni/Cu(001) Films.
Authors: O'Brien W. L. , Tonner B. P.
Published: April 2011

The effects of ferromagnetic capping layers on the perpendicular magnetic anisotropy of Ni/Cu(001) have been studied. X-ray magnetic circular dichroism was used to obtain element specific magnetic information, including hysteresis loops for both in-plane and perpendicular magnetization. A 15 ML Ni/Cu(001) film maintains its perpendicular magnetic orientation after the addition of a 2.5 ML Fe capping layer. The Fe capping layer reduces the area of the Ni hysteresis loop by a factor of 2.0. A 2.0 ML capping layer of Co on 15 ML Ni/Cu(001) switches the easy axis of magnetization from perpendicular to in-plane.
Design of a High-Flux Backscattering Spectrometer for Ultra-High Resolution Inelastic Neutron Measurements
Authors: Gehring P. M. , Brocker C. W. , Neumann D. A.
Published: April 2011

We discuss the design of a new backscattering spectrometer to be installed at the Cold Neutron Research Facility at the National Institute of Standards and Technology. Si (111) crystals cover both monochromator and analyzer which are spherically bent to a radius of curvature of ~ 2 m to focus the incident and scatterered neutron beams. The bending increases the intrinsic lattice gradient of Si beyond its Darwin limit, resulting in an energy resolution of ~ 0.75 μeV FWHM. The monochromator is Doppler-driven, allowing users access to a dynamic range of ±60 μeV. The elastic Q-range covers 0.15 to 1.8 Å-1. The most novel aspect of this design lies in the incorporation of a phase-space-transform chopper. This device rotates at 4700 rpm while neutrons are Bragg-diffracted from sets of pyrolytic graphite crystals affixed to its periphery. The process enhances the neutron flux at the backscattering energy of 2.08 meV, but at the expense of a larger horizontal divergence. Computer simulations indicate a resultant flux increase of order 3 should be obtained.
Fundamentals of Specular Neutron Reflectometry
Authors: Majkrzak Charles F.
Published: April 2011

An introduction to the methodology of neutron reflectometry is. given in which the fundamental aspects regarding the actual performance of specular reflection measurements and subsequent analysis of the data are described. The application of this technique to the determination of interfacial structure or composition in thin film and multilayer materials of interest in the fields of magnetism, superconductivity, polymer science, electrochemistry, and biology is illustrated by specific examples. The microscopic information provided by neutron reflectivity which complements that obtained by other probes is emphasized, in particular information which is obtainable because of the inherent isotopic (most notably in the case of hydrogenous materials) or magnetic moment (both magnitude and orientation) sensitivity of the neutron.
Diffuse Neutron Scattering from Surfaces and Interfaces
Authors: Sinha Sunil K.
Published: April 2011

The use of neutron scattering as a tool for exploring surfaces and interfaces has become more prevalent over the last several years, mainly due to the increasing popularity of reflectivity techniques, which study specular reflection from single surfaces or multilayers. Due to intensity limitations, the use of off-specular or grazing-incidence neutron scattering techniques has been much less prevalent. In this paper we shall discuss the origins of magnetic off-specular scattering (e.g., as observed in magnetic multilayers) and the origins of anomalies seen in the X-ray or neutron diffuse scattering from multilayers near Bragg reflections in terms of the Dynamical Theory of Scattering.
Resonance Enhanced Neutron Standing Waves in Thin Films
Authors: Satija S. K. , Zhang H. , Gallagher P. D. , Lindstrom R. M. , Paul R. L. , Russell T. P. , Lambooy P. , Kramer E. J.
Published: April 2011

Simultaneous measurements of neutron reflectivity and prompt gamma ray emission, from samples with buried Gd layers, are shown to be of significant aid in determining the depth profile of the entire sample. Because of resonant enhancement of the neutron standing waves in the sample, the gamma ray signals are considerably enhanced making these experiments possible. A possible application of this technique to study grazing angle neutron diffraction is also mentioned.
Variation of Solvent Scattering-Length Density in Small-Angle Neutron Scattering as a Means of Determining Structure of Composite Materials
Authors: Hjelm Rex P. , Wampler Wesley , Gerspacher Michel
Published: April 2011

As part of our work on the structure of composite materials we have been exploring the use of small-angle neutron scattering using the method of contrast variation to dissect the component form, structure and distribution. This approach has resulted in a new look at very old problemreinforcement of elastomers by carbon black.

Using this approach we studied an experimental high surface area (HSA) carbon black and a gel of "HSA-bound" rubber in cyclohexane/deuterocyclohexane mixtures. HSA in cyclohexane is found to be short rodlike particle aggregates. The aggregates have a shell-core structure with a high density graphitic outer shell and an inner core of lower density amorphous carbon. The core is continuous throughout the carbon black aggregate, making the aggregate a stiff, integral unit. Contrast variation of swollen composite gels shows that there are two length scales in the gel structure. Above 10 Å, scattering from carbon black predominates, and below 10 Å the scattering is from both carbon black and the elastomer. The HSA in the composite is completely embedded in polyisoprene. An estimate of the carbon black structure factor shows strong exclusion of neighboring aggregates, probably from excluded volume effects. The surface structure of the carbon black is unaltered by the interactions with elastomer and appears smooth over length scales above about 10 Å. These results show that contrast variation can provide information on composite structure that is not available by other means. This information relates to the reinforcement mechanism of elastomers by carbon blacks.
Modeling of Neutron Diffraction Patterns from Sheared Silica Gels
Authors: Butler B.D. , Hanley H.J.M. , Muzny C.D. , Straty G.C.
Published: April 2011

Dense silica gels, prepared from suspensions of 24 nm colloidal silica particles, have been studied by small angle neutron scattering. Provided the volume fraction, φ, of the silica is less than about 0.18, the scattered intensity increases at low wavevector, q, as the gelation proceeds and the structure factor, S(q), of the final gel exhibits apparent power law behavior, usually interpreted as a signature of fractal growth. The power law behavior, however, was observed for all measured φ (≤0.30) when the gelation occurred in the presence of an applied shear. Furthermore, the first diffraction maximum, corresponding to the inter-particle contact distance, was more sharply peaked in the high density sheared gels, indicating that the structural arrangement of the silica particles under shear is more densely packed than in gels produced without shear under equivalent conditions. Although it is clear that shear has a marked influence on the gel structure at higher densities, a quantitative interpretation of the diffraction results is difficult because cluster-cluster interference might be present. Such difficulties encountered when trying to interpret the scattering from these dense systems are outlined, and a computer simulation that includes cluster-cluster interference is presented.
Spinodal Decomposition of the Three-Component Microemulsion System: Aot/Water/Decane
Authors: Mallamace F. , Micali N. , Trusso S. , Chen S. H.
Published: April 2011

We have performed a series of spinodal decomposition measurements of a three-component microemulsion system made of a surfactant AOT, water, and decane. The measurements were made by a temperature jump from a one-phase droplet microemulsion to a two-phase droplet microemulsion along the critical iso-volume fraction line (10%) using the time resolved light scattering intensity technique. All three stages of the evolution were studied. The typical scattering intensity distribution is in good agreement with recent dynamic scaling theories.
Investigation of Residual Strains of the Second Kind in Plastically Deformed Metallic Materials
Authors: Vrána M. , Klimanek P. , Kschidock T. , Lukáš P. , Mikula P.
Published: April 2011

Investigation of strongly distorted crystal structures caused by dislocations, stacking-faults etc. in both plastically deformed f.c.c. and b.c.c. metallic materials was performed by the analysis of the neutron diffraction line broadening. Measurements were realized by means of the high resolution triple-axis neutron diffractometer equipped by bent Si perfect crystals as monochromator and analyzer at the NPI Řež. The substructure parameters obtained in this manner are in good agreement with the results of X-ray diffraction analysis.
A Study of Internal Damage of Metal Matrix Composites by Neutron Diffraction
Authors: Shi N. , Bourke M. A. M. , Goldstone J. A.
Published: April 2011

Using neutron diffraction, we have measured the elastic phase strains of Al/TiC and Al/SiC composites under uniaxial tensile loading. The phase strains were used to reconstruct the global elastic strain. It has been found that, above macroscopic yield, the global elastic strain response is not linear. A theoretical model shows that the nonlinearity is dictated by changes in the ratio of longitudinal phase stresses. Furthermore, the changes in this ratio resulting from matrix plasticity and reinforcement fracture are different which leads to distinct slope changes in the global elastic strain response that can be used to distinguish the onset of these two processes on the global elastic strain loading curve.
Observations of Cef-Split Intermultiplet Transitions in Optically Opaque EuBa2Cu3O7 Using Inelastic Neutron Scattering
Authors: Staub U. , Soderholm L. , Osborn R. , Balcar E. , Trunov V.
Published: April 2011

Inelastic neutron scattering (INS) results on the intermultiplet transitions J=0 → 1 and J=1 → 2 in optically opaque EuBa2Cu3O7 are reported. Whereas these multiplets are split by the crystalline electric field (CEF), their low J values are influenced to first order only by the second-order (J=1) and additional fourth-order (J=2) CEF parameters. and the spinorbit coupling parameter were obtained by fitting the splitting of the J=l multiplet and the energy separation between the J=0 and 1 multiplets. The J=0 → 1 splitting observed here is smaller than previously seen by optical spectroscopic studies on a variety of transparent, ionic compounds, necessitating fitting of the free-ion parameter. Additional spectroscopic information on the J=2 multiplet indicates that additional fitting of free ion parameters must be included to adequately model the observed low energy separation between the two lowest J-multiplets. Preliminary calculation on the Q-dependence of the CEF split J=0 → 1 transitions and the comparison with observations are presented.
Magnetic Structure Determination for Annealed Ni80Fe20/Ag Multilayers Using Polarized-Neutron Reflectivity
Authors: Borchers J.A. , Gehring P.M. , Majkrzak C.F. , Ankner J.F. , Hylton T.L. , Coffey K.R. , Parker M.A. , Howard J.K.
Published: April 2011

Sputtered Ni80Fe20/Ag multilayers, annealed post-growth, show giant magnetoresistive (GMR) effects at unusually low magnetic fields (≈ 5 Oe)[l]. Structural characterization by cross-sectional TEM[2] and x-ray diffraction indicates that the Ag preferentially diffuses into the Ni80Fe20 layers at the interfaces. Using polarized-neutron specular reflectivity, we have obtained magnetization depth profiles for a series of annealed [Ni8oFe2o(20Å)/Ag(40Å)]4 multilayers. Though GMR in related materials is associated with coherent antiferromagnetic alignment of the ferromagnetic layers, specular neutron data for the Ni80Fe20/Ag multilayers show no trace of half-order spin-flip intensity characteristic of this simple structure. In small applied fields, transverse scans at the half-order position show a broad feature which disappears upon saturation. These data suggest that while the Ni80Fe20 moments are antiferromagnetically correlated along the growth axis, the in-plane magnetic domains are only of micron-order size and are thus not apparent in a specular measurement.
Neutron Studies of Disordered Alloys: a Brief Review/Update
Authors: Moss Simon C.
Published: April 2011

Both neutron and X-ray scattering are used to determine the pair correlation functions (short-range order), the atomic displacements arising from atom size disparity, and the (derived) effective pair interactions in binary alloy solid solutions. This enterprise has taken on a new vitality through concomitant advances in both electronic theory and computer modeling of the atomic arrangements in alloys. An overview of the diffuse scattering formalism will be presented with an emphasis on the ways in which neutron scattering is particularly effective in sorting out the separate contributions to the total scattering pattern. Aspects of contrast variation and enhancement, and the utilization of both elastic and inelastic scattering will be discussed and examples of both past and recent work will be covered, including some future directions. We will also note briefly the relation between local order studies and details of the electronic and the elastic response functions of alloys.
Neutron Scattering Facilities at Chalk River
Authors: Holden T.M. , Powell B.M , Dolling G
Published: April 2011

The Chalk River Laboratories of AECL Research provides neutron beams for research with the NRU reactor. The NRU reactor has eight reactor loops for engineering test experiments, 30 isotope irradiation sites and beam tubes, six of which feed the neutron scattering instruments. The peak thermal flux is 3 x 1014n cm−2s−1. The neutron spectrometers are operated as national facilities for Canadian neutron scattering research. Since the research requirements for the Canadian nuclear industry are changing, and since the NRU reactor is unlikely to operate much beyond the year 2000, a new Irradiation Research Facility (IRF) is being considered for start-up in the first decade of the next century. An outline is given of this proposed new neutron source.
Precursor Phenomenon of Martensitic Transformation in Au-49.5at%Cd Alloy
Authors: Ohba Takuya , Shapiro S.M. , Aoki Shingo , Otsuka Kazuhiro
Published: April 2011

Phonon softening was observed in the parent phase of a AuCd alloy which transforms from the β2(B2) parent to ζ2¹(trigonal) martensite. Since Cd strongly absorbs neutrons, the isotope 114Cd was used in preparing the single crystal for the measurements. The [ζζ0]TA2 phonon branch was measured and found to be anomalously low. A minimum is present at ζ=0.35 which softens with decreasing temperature towards Ms. The results are consistent with the model proposed by Ohba et al. based upon a crystallographic study of the ζ2¹ phase.
Neutron Spectroscopy of Phonon and Bound Multiphonon States in γ-ZrH
Authors: Kolesnikov A.I. , Bashkin I.O. , Ponyatovsky E.G. , Prager M. , Belushkin A.V.
Published: April 2011

Lattice dynamics of γ-ZrH(D) ordered phases with essentially one-dimensional H-H (D-D) interaction was studied by inelastic neutron scattering. The experimental optic peaks were described within the Born-von Kármán model. The bound multiphonon states were observed in the spectra. Their binding energies were derived from the experimental data.
Phonon Spectra of Ordered Pdcuh and Pdagh Produced Under a High Hydrogen Pressure
Authors: Kolesnikov A.I. , Antonov V.E. , Prager M. , Bennington S. , Tomkinson J.
Published: April 2011

Atomically ordered PdAgH and PdCuH hydrides synthesized in an atmosphere of gaseous hydrogen at P = 3 GPa were studied by inelastic neutron scattering. The results showed a large difference between the Pd-H, Ag-H and Cu-H interactions. Values of 93 and 116 meV were predicted for the local H vibrations in dilute Ag-H and Cu-H solid solutions.
Similarity of Vibrational Spectra of High Density Amorphous Ice and High Pressure Phase Ice Vi
Authors: KOLESNIKOV A.I.
Published: April 2011

Inelastic incoherent neutron scattering measurements on the hdaice, ice Ih and high-pressure phases ice VI and ice VIII revealed similarity between the amorphous phase and crystalline ice VI and led to the new proposition that hda ice consists of two interpenetrating hydrogen-bonded networks with no hydrogen bonds between “sublattices”.
Temperature Dependence of Cathodoluminescence From InxGa1-xAs/GaAs Multiple Quantum Wells
Authors: Rammohan K. , Rich D.H. , Larsson A.
Published: April 2011

The temperature dependence of the cathodoluminescence (CL) originating from In0.21Ga0.79As/GaAs multiple quantum wells has been studied between 86 and 250 K. The CL intensity exhibits an Arrenhius-type dependence on temperature (T), characterized by two different activation energies. The spatial variations in activation energy caused by the presence of interfacial misfit dislocations is examined. The CL intensity dependence on temperature for T ≲ 150 K is controlled by thermally activated nonradiative recombination. For T ≳ 150 K the decrease in CL intensity is largely influenced by thermal re-emission of carriers out of the quantum wells.
Microstructure of Oxidized Ge0.78SiO.12 annealed in a Reducing Ambient
Authors: Theodore N.D. , Liu W.S. , Lie D.Y.C. , Cams T.K. , Wang K.L.
Published: April 2011

Transmission electron microscopy, conventional and high-resolution, is used to characterize the microstructural behavior of oxidized Ge0.78Si0.12 layers annealed in a reducing 95% N2+ 5% H2 ambient. An epitaxial Ge layer grows by solid-phase epitaxy on an underlying Ge0.78Si0.12 seeding layer with a Ge-Sio2 matrix positioned between them. Defect densities in the epitaxial Ge are significantly lower than in the underlying Ge0.78Si0.12. Microstructural details of this behavior are investigated.