bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Interfacial Transition Zone: “Direct” Evidence on Compressive Response
Authors: Darwin David 
Published: April 2011

AbstractThere 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

AbstractIt 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

AbstractGranulated 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

AbstractRecently 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

AbstractIn 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

AbstractMolecular 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

AbstractThe 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

AbstractA 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

AbstractCoating 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

AbstractA 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

AbstractSeveral 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

AbstractMany 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

AbstractMetal 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

AbstractSoft 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

AbstractThe 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

AbstractResonant (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

AbstractWhite-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

AbstractSiC 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.
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

ABSTRACTWe 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

ABSTRACTAn 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

ABSTRACTThe 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

ABSTRACTSimultaneous 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

ABSTRACTAs 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.