bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Method for Estimating the Dynamic Moduli of Cement Paste-Aggregate Interfacial Zones in Mortar
Authors: Cohen Menashi D. , Lee Turng-Fang F. , Goldman Ariel 
Published: April 2011

AbstractThe objective of this paper is to propose a method to estimate the average values of the dynamic modulus of elasticity and the dynamic shear modulus of cement paste-aggregate interfacial zones in mortar by applying the Logarithmic Mixture Rule (LMR). Both portland cement mortars (PC mortars) and portland cement mortars with silica fume (SF mortars) are investigated and compared, The influence of silica fume on the dynamic moduli of interfacial zone is also examined. Results indicate that for the specific ingredients and mix design used, the dynamic modulus of elasticity of interfacial zone falls between 0.4 and 2.0 (×10 6 psi) for PC mortar and 1.2 to 2.2 (× 106 psi) for SF mortar. These values are lower than the values obtained for PC mortar (4.2 ×106 psi), PC paste (2.7 ×106 psi), SF mortar (4.4 ×106 psi), and SF paste (2.5 × 106 psi).
Fibre-Cement Paste Transition Zone
Authors: Agopyan Vahan , Savastano Holmer 
Published: April 2011

AbstractThe characteristics of fibres and paste of ordinary Portland cement transition zone are analysed and correlated to the mechanical properties of the produced composites. The water-cement ratio of the matrix varies from 0.30 to 0.46 and the age of the specimens varies from 7 to 180 days. Composites of vegetable fibres (coir, sisal and malva) are compared with those of chrysotile asbestos and polypropylene fibres. The analysis is made by backscattered electron image (BSEI) and energy dispersive spectroscopy (EDS). Mechanical tests evaluate the composite tensile strength and ductility.Mainly for vegetable fibre composites the transition zone is porous, cracked and rich in calcium hydroxide macrocrystals. These results are directly associated with the fibre-matrix bonding and with the composite mechanical performance. Further studies considering the impact performance of the composites compare the porosity of the transition zone with the toughness of the composites.
The Microstructure of Wood Fiber Reinforced Cementitious Composites
Authors: Lin X. , Silsbee M.R. , Roy D.M. 
Published: April 2011

AbstractWood fiber reinforcing of cement matrices is an economic and an efficient approach to producing high performance cementitious composites. In this study, wood fiber reinforced cementitious composites (WFRCs) were made by using both conventional and novel processing styles. Wood fibers exhibited a considerable ability to improve the flexural strength and the toughness of WFRC when an adequate content of the fibers was used. The morphologies ofvarious type of wood fibers and fracture surface of WFRC were examined by scanning electron microscope (SEM) and an environmental scanning electron microscope (ESEM). The microstructures of wood fiber and WFRC were correlated with their mechanical properties. Results indicate a significant interfacial bonding between the cement matrix and the wood fibers.
Bond-Slip Mechanisms in Steel Micro-Fiber Reinforced Cement Composites
Authors: Banthia N. , Yan N. , Chan C. , Yan C. , Bentur A. 
Published: April 2011

AbstractBond-slip characteristics for steel micro-fibers bonded in cement-based matrices were investigated by conducting single fiber pull-out tests. The influence of the following factors was investigated: fiber inclination, fiber size, fiber embedded length and matrix refinement using silica fume. It was found that the bond-slip characteristics of fibers aligned with respect to the loading direction were necessarily superior than those inclined at an angle. Inclined fibers supported smaller peak pull-out loads and absorbed lesser pull-out energies than the aligned fibers. The use of silica fume in the matrix was found to improve both theaverage interfacial bond strengthand themaximum interfacial bond strengthbetween the fiber and the matrix.
X-Ray Microtomography of an Astm C109 Mortar Exposed to Sulfate Attack
Authors: Bentz D.P. , Martys Nicos. S. , Stutzman P. , Levenson M. S. , Garboczi E.J. , Dunsmuir J. , Schwartz L. M. 
Published: April 2011

AbstractX-ray microtomography can be used to generate three-dimensional 5123 images of random materials at a resolution of a few micrometers per voxel. This technique has been used to obtain an image of an ASTM C109 mortar sample that had been exposed to a sodium sulfate solution. The three-dimensional image clearly shows sand grains, cement paste, air voids, cracks, and needle-like crystals growing in the air voids. Volume fractions of sand and cement paste determined from the image agree well with the known quantities. Implications for the study of microstructure and proposed uses of X-ray microtomography on cement-based composites are discussed.
Effects of Microstructure on Fracture Behavior of Hardened Cement Paste
Authors: Ahmed Asif , Struble Leslie 
Published: April 2011

AbstractMechanical properties of any material, including hardened cement paste, are assumed to be controlled by its microstructure. An attempt has been made here to establish a link between bulk fracture parameters of hardened cement paste and its microstructure. Paste microstructure has been varied by changing the initial w/c ratio, curing time and curing temperature, and by addition of chemicals to change the calcium hydroxide morphology. It has been found that, like compressive strength, fracture parameters depend directly on porosity. Contrary to our initial hypothesis, CH morphology was found to have no effect on the fracture parameters.
Molecular Approach to Mesoporous Metal Sulfides
Authors: Anderson Mark T. , Newcomer Paula 
Published: April 2011

AbstractWe have synthesized metal-sulfide/surfactant nanocomposite materials by cooperative assembly of molecular precursors in an aqueous medium. The template-mediated synthetic approach is applicable to metal sulfides that exhibit aqueous thiometallate chemistry. The products are lamellar and have bilayers or interdigitated layers of surfactant molecules sandwiched between metal sulfide layers. The layers of anionic metal sulfide molecules are not completely condensed in the nanocomposites, which results in a negative charge on the metal sulfide layers. The materials are stable at room temperature in water, methanol, 1 M HCl, 30 wt% NH3, and 1 M NaOH. The materials do not dissolve at 80 °C in water and are stable to at least 180 0C in air. The nanocomposites exhibit ion exchange of smaller surfactants, alkali-metal ions, and divalent metal ions.
Interaction of Polar Substrates with Transition Metal Substituted Keggin-Type Heteropolyanions [X(H2O)W11SiO39]6−(X=Co2+, Mn2+) Pillared in a Mg-Al Hydrotalcite-Like Clay
Authors: Salinas Esteban López , Castillo Pedro Salas , Ono Yoshio 
Published: April 2011

AbstractThe intercalation of Keggin-type [X(H2O)W11SiO39]6−(X=Co2+, Mn2+) heteropolyanions by aqueous anion exchange of 10 Å in a synthetic hydrotalcite-like Mg2Al(OH)6(NO3) results in products with interlayer spacing of ca. 10 Å. The layered array of the product and the integrity of the intercalated heteropolyanion are stable below 623 K in air as examined by XRD and IR analyses, respectively. UV-vis Diffuse Reflectance spectroscopy indicates that the water ligand in the intercalated [Co(H2O)W11SiO39]6− can be removed by thermal evacuation at 473 K leaving a coordinatively unsaturated site (in the transition metal) which reversibly coordinates water,methanol, ethanol or ammonia. ESR analysis of the intercalated [Mn(H2O)W11SiO39]6− shows that the shape of a signal at g = 2.00, arising from six-coordinated Mn2+ strongly depends on adsorption-desorption of the water ligand.
Electrical Conductivity in Mesoporous and Microporous Pillared Layered Phosphate Structures
Authors: Ramos-Barrado J.R. , Criado C. , Maireles-Torres P. , Olivera-Pastor P. , RodrÍguez-Castellón E. , JimenÉz-López A. 
Published: April 2011

AbstractThe electrical relaxation and charge motion in porous solids (Lithium exchanged alumina pillared layered cc-tin phosphates (Li-PLP)) have been studied on the basis of the coupling model. The static dielectric constant and the dielectric susceptibility show a dependence on the basal distance which is correlated with the ion mean square displacement.
Towards the Rational Design and Synthesis of Zeolites
Authors: Burkett Sandra L. , Davis Mark E. 
Published: April 2011

AbstractThe mechanisms by which the geometries of organic structure-directing agents are translated into the product pore architectures in the syntheses of pure-silica and high-silica zeolites and of aluminum-rich zeolites are discussed. Two different mechanisms of structure direction and self-assembly via the formation of extended inorganic-organic composite structures or of purelyinorganic structures are proposed for the two different classes of materials. The primary impetus for developing a mechanistic understanding of zeolite synthesis is the ultimate goal of the rational design and synthesis of novel zeolite pore architectures. By considering issues such as hydrophobic hydration behavior of the structure-directing agent and the optimization of inorganic–organic van der Waals interactions, the successful design of structure-directing agents for the synthesis of new zeolite structures may be possible, particularly for high-silica systems.
Study of Production and Quality of Large (1–2 MM) Polystyrene Hollow Microspheres.
Authors: Merkuliev Yu. A. , Akunets A. A. , Bushuev V. S. , Dorogotovtsev V. M. , Gromov A. I. , Isakov A. I. , Nikitenko A. I. , Startsev S. A. , Tolokonnikov S. M. , Cook R. C. 
Published: April 2011

AbstractWe present a summary of the techniques used to produce hollow plastic microshells from solid polymer granules using drop tower techniques. Unlike solution drop tower techniques, the use of these granules allows one to produce good quality shells with diameters of 1 to 1.5 mm. The reasons for hollow plastic shell diameter limitations are discussed, and based on these studies we present a new drop tower furnace concept we call a ballistic furnace that has been designed to produce large (2 to 3 mm) polystyrene shells. The characteristics of the individual components such as the pellet injector and the fast cooling system are given.
Sol-Gel Derived Ceramic Bubbles
Authors: Moh Kyung H. 
Published: April 2011

AbstractSol-gel derived ceramic bubbles include shaped and fired, porous or impermeable nonvitreous ceramic microcapsules of metal oxide and non-oxide, are made by non-melt process involving the equilibrium boiling point method with controlled thermal gelation. Discrete, free-flowing, ceramic microbubbles consist of a non-oxide component and/or an oxide component having diameters in the range of I to 300 micrometers and each having a wall thickness of less than 10 percent of the diameter of the bubble. In this process, a sol precursor and a bloating agent, when added to a bubble promoting medium under proper conditions, provide green gelled microbubbles which after firing are strong, well formed, ceramic microbubbles. The microbubbles are non-vitreous, sol-gel derived, fine microstructured, uniform, hollow, smooth, and are essentially all oxide or non-oxide or combinations of both. The microbubbles can be used as fillers for metal, glass, ceramic, and polymer or filled with a selected solid, liquid or gas for purpose of storing, transporting, or facilitating the use of the same.
Permeability and Porosity of Bonded Hollow Sphere Foams for High Intensity Radiant Burners
Authors: McEntyre J. E. , Cochran J. K. , Lee K. J. 
Published: April 2011

AbstractBonded hollow sphere foams for this study were made from point-contact, slurry-bonded monosized spheres, 2.5 mm in diameter. The permeabilities of these foams are compatible with the diffuser base in radiant burners. For this study, the effect of quantity of bonding phase on interstitial porosity, permeability, and uniformity of gas flow through the foams was investigated. The relationship between permeability and porosity was modeled with the Kozeny-Carman equation. Attempts were made to correlate diffuser base permeability to operating characteristics of these burners.
Design Guidelines and Water Extraction Synthesis Capabilities for Hollow Ceramic Microspheres for Low Dielectric Constant Inorganic Substrates
Authors: Liu Jay G. , Wilcox David L. 
Published: April 2011

AbstractThis paper reports the use of hollow ceramic microspheres for a controlled porosity composite application and an emulsion/extraction method to make them. Design guidelines for this application are presented in which the physical properties and geometry of the microspheres are correlated to both dielectric constant and mechanical strength of the composites. The analytical modeling indicates that small size, thin walled ceramic microspheres with thermal expansion coefficients greater than that of common ceramic substrate matrices are needed to lower the dielectric constant significantly while retaining good mechanical strength. An emulsion/water extraction method was developed to prepare such hollow ceramic microspheres. This method shows promise for making very small (< 10 μm) hollow microspheres of various ceramic compositions. The capability and limitation of this synthesis route are shown.
Fabrication of Glass Micro- and Nanospheres from Liquid Precursors Using Droplet Generation and Sol-Gel Processing
Authors: Kim Kyekyoon 
Published: April 2011

AbstractTwo novel methods particularly suitable for continuously fabricating uniform glass spheres are described, one suitable for spheres micrometers to millimeters in diameter and the other for spheres of diameters in the submicron range, down to tens of nanometers. Both methods start from liquid precursors and combine droplet generation which is effected by a nozzle with sol-gel processing. One difference is that in the latter method, which is termed the charged liquid cluster beam (CLCB) technique, one employs flow-limited field-injection electrostatic spraying to further reduce the size of the drops to the nanometer range in the droplet generation process. Using the two methods, uniform hollow silica aerogel spheres, micrometer to millimeter in diameter, of controlled porosity and silica spheres with diameters in the nanometer range were produced. By utilizing the appropriate liquid precursors, the present methods can fabricate spheres composed of a variety of materials, including glass. Due to its ability to fabricate nanodrops, the CLCB technique is suited to fabricating nanoparticles as well as thin films of controlled stoichiometry and chemical composition.
Lebedev Physical Institute Activity in the Science and Technology Associated with Hollow Microsphere Fabrication and Applications
Authors: Merkuliev Yuriy A. 
Published: April 2011

AbstractWork at the P. N. Lebedev Physical Institute on hollow microsphere technology started more than twenty years ago, based on the commercial technology developed in our country, on the experience of our colleagues involved in chemistry research, and on our knowledge of physics and hydrodynamics. We have developed new methods of hollow shell fabrication using a complex of universal installations for making shells of polymers, glass, and metals; equipment for shell characterization; and employing mathematical modeling of shell formation processes. Using these facilities and methods, the physical processes involved in the various hollow microsphere fabrication regimes are studied both experimentally and theoretically.
Hollow Borosilicate Microspheres from Aqueous Solution
Authors: Hagarman James A. 
Published: April 2011

AbstractMetastable aqueous borosilicate solutions may be processed to hollow microspheres by a combination of liquid feed atomization and thermal exposure. Techniques for feed preparation and the relationships between feed composition, stability and processibility are discussed. Optimization of feed atomization, hollow sphere formation and finishing operations are discussed relative to density, size, strength, and chemical durability properties of finished products. The connection between finished properties and product utility is presented for several applications including lightweight fillers for thermoset resins and vinyl plastisols, and physical sensitizers for emulsion explosives.
Linear and Circular Dichroism in Angle Resolved Fe 3p Photoemission
Authors: Tamura E. , Waddill G. D. , Tobin J. G. , Sterne P. A. 
Published: April 2011

AbstractUsing a recently developed spin-polarized, fully relativistic, multiple scattering approach based on the layer KKR Green function method, we have reproduced the Fe 3p angle-resolved soft x-ray photoemission spectra and analyzed the associated large magnetic dichroism effects for excitation with both linearly and circularly polarized light. Comparison between theory and experiment yields a spin-orbit splitting of 1.0 – 1.2 eV and an exchange splitting of 0.9 – 1.0 eV for Fe 3p. These values are 50 – 100 % larger than those hitherto obtained experimentally.
X-Ray Scattering Studies of Interfacial Microstructures in Inx, Ga1−x As/GaAs Superlattices
Authors: Ming Z. H. , Soo Y. L. , Huang S. , Kao Y. H. , Stair K. , Devane G. , Choi-Feng C. 
Published: April 2011

AbstractInterfacial microstructures in 100-period InxGa1−xAs(15Å)/GaAs(100Å) superlattices grown on GaAs (100) substrates by molecular beam epitaxy were studied by using large angle x-ray scattering techniques. Unusual satellite peaks in the lateral direction parallel to the sample surface were observed in a sample with x = 0.535 grown at 480°C, indicating an in-plane structural ordering. This result is confirmed by high resolution transmission electron microscopy observations that thickness modulation in the InxGa1−xAs layers gives rise to long-range lateral periodic arrays of cluster-like microstructures with spacing on the order of a few hundred Ångstroms. This thickness modulation is found to occur only in [110] direction, thus the material can be viewed as a somewhat disordered array of grown-in parallel quantum wires.
Exafs Studies and Simulations of Local Anisotropy in CO78CR22 Films
Authors: Kemner K. M. , Harris V. G. , Elam W. T. , Lodder J. C. 
Published: April 2011

AbstractExtended x-ray absorption fine structure measurements of a Co78Cr22 film were performed using normal and glancing incident radiation in order to investigate, respectively, the in-plane and out-of-plane local structure and chemistry. The Fourier transformed EXAFS data of the in-plane and out-of-plane structures around the Co and Cr atoms illustrates the presence of an anisotropy. Analysis of the local environments around Co for the two sample orientations indicates the presence of Co-enriched clusters, while similar studies of the Cr environments indicate preferential ordering parallel to the film plane. Quantitative analysis of the higher order Fourier transform peaks shows a greater amount of disorder perpendicular to the film plane beyond that expected for a textured hcp film. These results are consistent with earlier reports of a high density of stacking faults or twinning planes perpendicular to the growth axis, supporting the interpretation that a platelet-like texturing exists within the columnar microstructure.
Static Displacements of Atoms in Crystalline Metallic Solid Solutions
Authors: Sparks Cullie , Ice Gene , Jiang Xiaogang , Zschack Paul 
Published: April 2011

AbstractMeasurement of diffuse x-ray scattering from binary crystalline solid solutions at more than one x-ray energy is a sensitive probe of the average interatomic distance between neighboring pairs of atoms. Deviations of these bond distances by as little as 0.001Å are easily detected in the diffuse scattering from binary alloys consisting of atoms nearby in the periodic table and/or where x-ray energies chosen near their absorption edges can change the scattering contrast. Individual bond distances (AA, AB and BB) are recovered out to several near neighbor shells by combining three scattering measurements at x-ray energies chosen for maximum and minimum contrast. Average bond distances recovered from four metal alloys Fe77.5Ni22.5, Fe46.5Ni53.5Cr47Fe53and Cr20Ni80 are discussed. We find that the interatomic distances measured for these alloys give interesting insights to atomic displacements in solid solutions. Nearest neighbor bond distances are not well represented by phenomenological models based on pure element atomic size and concentration dependence of the lattice constants. Radial and nonradial displacements are recovered from these measurements of diffuse scattering.
Acid-Site Characterization of Water-Oxidized Alumina Films by Near-Edge X-Ray Absorption and Soft X-Ray Photoemission
Authors: O'hagan P. J. , Merrill R. P. , Rhodin T. N. , Woronick S. C. , Shinn N. D. , Woolery G. L. , Chester A. W. 
Published: April 2011

AbstractHydroxylated alumina films have been synthesized by water oxidation of single crystal Al(110) surfaces. Thermal dehydroxylation results in anion vacancies which produce an Al(3s) defect state 3.5 eV below the conduction band edge. The defect-DOS exhibits a maximum for oxides heated to 648±25 K, which is just where the materials exhibit maximum Lewis acidity with respect to C2H4 Adsorbed C2H4 produces thermally reactive C2 species which interact covalently with the defect-DOS and nonbonding O(2p) states from the top of the valence band. C(1s) binding energies suggest significant charge transfer which is consistent with a carbenium ion. Ni deposits behave similarly but transfer charge directly to Al species and do not interact with O atoms at the defect site. The defect-DOS is regenerated when the C2 species decomposes or when Ni migrates thermally through the oxide layer.
Correlation of Xanes Features with the Scintillation Efficiencies of Ce Doped Alkaline Earth Lithium Silicate Glasses
Authors: Blanchard D L , Sunberg D S , Craig R A , Bliss M , Weber M J 
Published: April 2011

AbstractCerium activated glasses of composition 20Li2O·15MO·64.4SiO2·0.6Ce2O3 (where M is Mg, Ca, Sr, or Ba) exhibit scintillation efficiencies that vary by more than a factor of 2.5 with the alkaline earth. Previous work has suggested a correlation between the microstructure of these glasses and scintillation efficiency. Measurements of the Ce LIII x-ray absorption edge in the Mg, Ca and Sr glasses display a feature near the absorption edge that is suggestive of the presence of Ce4+. The area of this peak is, in fact, correlated with the scintillation efficiency of the glass. The amount of Ce4+ indicated by the intensity of this feature is, however, too high to be a permanent population. We suspect that the feature is a transient phenomenon related to creation of Ce4+ and trapped electrons due to photoionization by the x-ray beam.
Synchrotron White Beam Topography Studies of Screw Dislocations in 6H-Sic Single Crystals
Authors: Wang S. , Dudley M. , Carter C. H. , Tsvetkov V. F. , Fazi C. 
Published: April 2011

AbstractSynchrotron white beam X-ray topography, along with optical microscopy and scanning electron microscopy, has been used to characterize structural defects which are potentially detrimental to device performance in PVT 6H-SiC single crystals. Line defects running along the [0001] axis, known as “micropipes”, were studied extensively. Detailed analysis of topographic image contrast associated with “micropipes”, based on the kinematical theory of X-ray diffraction, established that the so-called “micropipes” are screw dislocations with large Burgers vectors.
X-ray Microscopy of Polymeric Materials
Authors: Adel H. , Hsiao B. , Mitchell G. , Rightor E. , Smith A. P. , Cieslinski R. 
Published: April 2011

AbstractWe describe how the scanning transmission x-ray microscope at Brookhaven National Laboratory can be used to investigate the bulk characteristics of polymeric materials with chemical sensitivity at a spatial resolution of about 50 nm. We present examples ranging from unoriented multiphase polymers to highly oriented Kevlar fibers. In the case of oriented samples, a dichroism technique is used to determine the orientation of specific chemical bonds. Extension of the technique to investigate surfaces of thick samples is discussed.