bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Corrosion of Steel Reinforcement in Carbonated Concrete Under Different Humidity Regimes
Authors: Constantinou Anastasia G. , Scrivener Karen L. 
Published: April 2011

AbstractIn this investigation, four concretes (two mix designs and two curing regimes), containing reinforcing bars at covers 11 mm and 20 mm were carbonated fully in 100% CO2 and 65% relative humidity (RH). They were then placed in two different humidity environments (65% RH and 90% RH). The progress of the corrosion of the samples was followed electrochemically (using the linear polarisation technique) and microscopically (using a scanning electron microscope).Electrochemical monitoring of the corrosion rate showed that corrosion started very soon after placement in the humidity regimes and generally increased with time. The water/cement ratio, the concrete cover of the reinforcement and the curing of the concrete had a significant effect the length of time taken to carbonate the specimens. However, the effect of these variables on the corrosion rate was negligible. In addition, the corrosion rate showed no dependance on the humidity regimes.Microstructural examination of the samples revealed the existence of corrosion products at the steel/concrete interface after 6 months in the humidity regimes. There was more corrosion product in the samples at 90% RH. The samples with the low w/c showed more extensive cracking in the interfacial region.
Bonding and Interfacial Microstructure in Cementitious Matrices Reinforced by Woven Fabri
Authors: Peled A. , Yankelevsky D. , Bentur A. 
Published: April 2011

AbstractHigh performance cementitious composites can be produced by reinforcement with a high volume of aligned fibers. One practical method of production of such composites would be based on the use of woven fabrics, where the bonding may be different from that predicted from evaluation of continuos aligned fibers. The present paper presents the study of the pull-out behavior of a fabric from a cementitious matrix. The influence of various fabric parameters were evaluated by comparing the pull-out of straight yams (fibers), crimped yams untied from the fabric and the fabric itself The influence of initial tensioning of the yams, which is an essential step in the production process, was also evaluated. SEM observations were carried out to interpret the pull-out curves in terms of microstructural characteristics. The crimped nature of the yam was found to be an important factor in enhancing the bond of the fabric, as it generated anchoring effects. Tensioning of the yam was detrimental to bond as it straightened the yarn and caused Poisson effects which damaged the interface.
Improving the Flexural Strength of Fibre Reinforced Oil Well Cementsby Addition of a Polymer Latex
Authors: Pafitis Demosthenis G. 
Published: April 2011

AbstractFibre-reinforced cements are proving to be useful in various oilfield applications. Low cost and increased toughness render glass fibre reinforced cements of particular interest. In most cases, improvements in toughness are the result of extensive fibre pull-out and this can be clearly observed in electron micrographs of fracture surfaces. This observation implies that there is much scope for improving the interfacial shear strength between the hydrated cement and glass fibres.Experiments have shown that increases in flexural strength and in energy to fracture can be achieved by incorporating small amounts of a polymer latex. Improvements of a factor of four in energy to fracture have been measured when approximately 0.8% by volume of a styrenebutadiene copolymer latex is added to a glass fibre reinforced class G oilwell cement. Experimental results suggest that this effect is not due to improvements in the strength of the cement matrix but due to an enhancement of the interfacial shear strength between fibre and cement.
Non-Aqueous Synthesis of Multicomponent Mesoporous Materials
Authors: Kim Anthony Y. , Liu Jun , Virden Jud W. , Bunker Bruce C. 
Published: April 2011

AbstractA non-aqueous synthesis route broadens the spectrum of useful precursors and the range of compositions which can be achieved in the synthesis of ordered, mesoporous multicomponent materials. A formamide solution of surfactant (cetyltrimethylammonium chloride/hydroxide) allows for distribution of a water-sensitive metal oxide precursor prior to reaction. Hydrolysis of the metal oxide precursor and phase separation to the pure oxide are controlled by adding limited amounts of water. Subsequent addition of a second metal oxide source as an aqueous solution initiates the reactions leading to a mixed oxide having ordered mesopores. Ordered mesoporous titanium silicates having final Ti/Si mole ratios in excess of 1/20 are synthesized.
Production of Porous Materials by Dealumination of Alumina-Rich Zeolites
Authors: Le Van Mao R. , Denes G. , Vo N.T.C. , Lavigne J.A. , Le S.T. 
Published: April 2011

AbstractA comparative study of chemical and textural properties for materials obtained by three different methods of dealumination of alumina-rich parent Ca-A zeolite showed that the method using ammonium hexafluorosilicate (AFS) resulted in the most interesting developments of mesoporous materials, with much higher void volumes and cation exchange properties than obtained by acid leaching or hydrothermal treatment. AFS treatment on both the Na and Ca forms of zeolite A resulted in materials with 12 nm sized mesopores, whereas smaller mesopores of about 4 nm were obtained when using the higher Si/Al ratio parent zeolite Na-X. Pore size distribution profiles obtained for these new materials are fairly narrow, indicating homogeneous mesopore sized solids.
Open-Framework Solids with Diamond-Like Structures Prepared from Clusters and Metal-Organic Building Blocks
Authors: Yaghi Omar M. , Richardson D. A. , Li G. , Davis C. E. , Groy T. L. 
Published: April 2011

AbstractThe tetrahedral cluster Ge4S104- and the rodlike ligand 4,4′-bipyridine are utilized in addition copolymerization reactions with the metal (II) ions of Mn, Fe, Co, Cu, and Zn in the preparation of 3-D open-framework solids, MxCol-xGe4S10-2(CH3)4N (x = 0.86, M = Mn; x = 1, M = Mn, Fe, Co, and Zn), 1, and Cu(4,4′-bpy)2. PF6, 2, having diamond-like structures. These structures are viewed in terms of the cubic diamond structure, where the carbon atoms have been replaced by either a cluster or a metal ion and the C-C bond by a sulfide or the 4,4′-bpy. These compounds have been fully characterized by single crystal x-ray crystallography and their composition was confirmed by elemental analysis; they contain 3-D channel systems where cations or anions reside to balance the charge on the framework.
Ambient - Pressure Silica Aerogel Films
Authors: Prakash Sai S. , Brinker C. Jeffrey , Hurd Alan J. , Rao Sudeep M. 
Published: April 2011

AbstractVery highly porous (aerogel) silica films with refractive index in the range 1.006-1.05 (equivalent porosity 98.5-88%) were prepared by an ambient-pressure process1,2. It was shown earlier using in situ ellipsometric imaging1 that the high porosity of these films was mainly attributable to the dilation or “springback” of the film during the final stage of drying. This finding was irrefutably reconfirmed by visually observing a “springback” of >600% using environmental scanning electron microscopy (ESEM). Ellipsometry and ESEM also established the near 100% reversibility of aerogel film deformation during solvent intake and drying. Film thickness profile measurements (near the drying line) for the aerogel, xerogel and pure solvent cases are presented from imaging ellipsometry. The thickness of these films (crack-free) were controlled in the range 0.1-3.5 μm independent of refractive index.
Conversion of Class-F Fly Ash to Zeolites
Authors: Shih Wei-Heng , Chang Hsiao-Lan , Shen Zhijian 
Published: April 2011

AbstractFly ash was chemically converted into zeolites. The conversion process not only eliminates the disposal problem of coal wastes but more importantly turns the waste material into a useful one. It was shown that fly ash can be converted into two forms of zeolites: P and faujasite, by varying the treatment condition. In addition, zeolite P was found to form earlier with higher treatment temperatures and adding quartz increased the amount of zeolite P formed. Seeding of faujasite was also studied.
Self-Assembly of Silicate/Surfactant Mesophases
Authors: Walker Scott A. , Zasadzinski J.A. 
Published: April 2011

AbstractThe synthesis of silicate/surfactant mesophases is driven by cooperative assembly of organic surfactant and inorganic silicate species, and the resultant mesophase morphology can be controlled by synthesis conditions (i.e., CTAB concentration in precursor solution and SiO2- CTAB mole ratio). The self-assembly process of these mesophases is driven complexation of the polyanionic silicate species with several CTAB cations to form a multi-tailed surfactant. One of these mesophases is a novel rippled lamellar phase in which the ripple wavelength and lamellar spacing are similar to the hexagonal mesophase rod center-to-center spacing; each of these dimensions are consistent with the length of two CTAB molecules.
Compressive Mechanical Behavior of Hollow Ceramic Spheres
Authors: Chung Jae H. , Cochran Joe K. , Lee Kon J. 
Published: April 2011

AbstractMechanical behavior of hollow ceramic spheres was evaluated using finite element analysis. Failure mode and strength of spheres were determined from stress analysis. A parametric study of strength as a function of wall thickness to sphere diameter ratios indicated that strength is a function of relative density squared. Strength of aluminium oxide hollow spheres made by the coaxial nozzle powder process agreed well with the finite element parametric model.
Electromagnetic Properties of Syntactic Foam Composites
Authors: Kemper Paul J. , Moore Rick 
Published: April 2011

AbstractA numerical model based upon renormalized effective medium theory will be described. The model successfully predicts the frequency dispersive permittivity of finite thickness dielectric/ conducting microsphere composites, electrically lossy syntactic foams, where the conducting particulates have volumetric fraction of 0 to 50%. The composites display unique frequency dispersions which are associated with the composite dimensionality and fractal-like sphere surface morphology. Theory and measurement show the composites have critical volume fractions which can be 20% above theoretical values for conducting spheres, i.e 27-–31% and the frequency dispersion of the composite permittivity can be varied by controlling the nanoscale surface morphology and composite thickness. Supporting permittivity measurements in the frequency range of 1–100 GHz will be presented.
Modeling of Microencapsulated Polymer Shell Solidification
Authors: Boone Travis , Cheung Lisa , Nelson Donald , Soane David , Wilemski Gerald , Cook Robert 
Published: April 2011

AbstractA finite element transport model has been developed and implemented to complement experimental efforts to improve the quality of ICF target shells produced via controlled-mass microencapsulation. The model provides an efficient means to explore the effect of processing variables on the dynamics of shell dimensions, concentricity, and phase behavior. Comparisons with experiments showed that the model successfully predicts the evolution of wall thinning and core/wall density differences. The model was used to efficiently explore and identify initial wall compositions and processing temperatures which resulted in concentricity improvements from 65 to 99%. The evolution of trace amounts of water entering into the shell wall was also tracked in the simulations. Comparisons with phase envelope estimations from modified UNIFAP calculations suggest that the water content trajectory approaches the two-phase region where vacuole formation via microphase separation may occur.
Development of Low Density, Low Atomic Number Foam Shell with Gas Barrier for Laser Fusion Target
Authors: Takagi Masaru , Norimatsu T. , Izawa Y. , Nakai S. 
Published: April 2011

AbstractLow density foam shells with high optical transmittance for fuel targets for the coming upgrade laser systems were developed by increasing the polymerization initiator for trimethylolpropane trimethacrylate in an oil phase of a water/oil/water emulsion. Foam with similar performance was fabricated using reduction-oxidation polymerization of ethyleneglycol dimethacrylate. These results showed that a cryogenic fuel layer sustained by these foam layers can be charecterized using optical interference technique.
Review of Low Dielectric Constant Thick Film Electronic Ceramics Using Hollow Microspheres
Authors: Kellerman David W. 
Published: April 2011

AbstractHigh speed interconnects for semiconductor devices require low dielectric constant materials to minimize propagation delays and capacitive line loading. Ceramics and thick film materials have been utilized to package these semiconductor devices, however their dielectric constants are prohibitively high. Hollow microspheres have been added to thick film glass and ceramic composite materials to lower the dielectric constant of those materials. This paper will review papers presented on the work done at Digital Equipment Corporation and EMCA-Remex to develop high speed integrated circuit packages with low dielectric constants.Presented will be the development and characterization of the low dielectric constant thick film material, processes used to fabricate devices with the low dielectric constant material, and development of the application of the material to an advanced ceramic integrated circuit package.
Uniform Solid and Hollow Metal Spheres: Formation in a Pulsed Micro-Arc and Applications
Authors: Dreizin Edward L. 
Published: April 2011

AbstractA novel process for producing monodisperse metal spheres with diameters from 50 to 1000 μm has been developed. The process involves melting a consumable wire-electrode in a pulsed micro-arc, so that a single metal droplet is formed and separated in each pulse. Subsequent droplet cooling determines the final properties of the metal spheres. Control of the droplet initial temperature from the melting to the boiling point, together with variation of the cooling medium, allows production of metal spheres with unique properties, e.g., solid, internally oxidized, or hollow granules. Uniform diameter spherical particles of Al, Cu, Mo, Ni, Ta, W, Ti, Zr, and some alloys such as stainless steel, nichrome, monel, have been produced. Applications of the process include production of uniform spherical metal particles for metal combustion studies, development of a novel droplet welding technique, and production of particles for experimental simulation of micrometeoroid-surface interactions. Other possible uses may be in energy-absorbing structures, composite materials, metal micro-dosing, and micromechanical device production.
Distributions of Latex Particles Deposited from Water Suspensions
Authors: Bediwi A. B. El , Kulnis W. J. , Luo Y. , Woodland D. , Unertl W. N. 
Published: April 2011

AbstractWe used the atomic force microscope to determine the distributions of 150–200 nm diameter styrene-butadiene (SB) latex spheres with TR. = 45 °C deposited at sub monolayer coverages from water suspensions onto mica, glass, calcite and cellophane surfaces. Two deposition methods are used: drying of μl drops and dipping. For drop drying, the distributions are extremely inhomogeneous. A high density ring forms at the boundary of the area wet by the drop. At low suspension densities on cellophane, the ring is a close-packed monolayer several micrometers wide. Thicker rings form on calcite and glass. Inside the rings, the particle density is very low and non uniform; e.g., monolayer thick islands form on mica, short chains are predominant on calcite, small clusters form on glass, and isolated spheres occur on cellophane. Particle densities are substantially reduced near some substrate defects but are enhanced near others. For the dipping method, homogeneous distributions are obtained on glass and cellophane. The density of adsorbed particles increases linearly with immersion time and the distribution of monomers, dimers, and trimers is not characteristic of random adsorption.
Spherical Particles of Pure and Manganese Doped Zinc Oxide and Zinc Hydroxicarbonate
Authors: Zampronio Cleidiane G , Davolos Marian R. , Stucchi Elizabeth B. , Jafelicci Miguel 
Published: April 2011

AbstractPure and manganese doped zinc hydroxicarbonate are precursors for materials based on zinc oxide with electrical and luminescent properties. This paper reports on investigation of the effect of chloride and sulfate anions in the morphology of pure and doped precursors obtained by aging diluted zinc salt solutions in presence of urea, and their thermally decomposed products Characterization was carried out by XRI), IR and SEM techniques. Hydrozincite Zn5(OH)6(CO3)2 and zincite ZnO with spherical shaped particles of 5–10 ptm were obtained independent of anion used Moreover, in a chloride medium the spheres are organized in an arrangement of acicularly crystallized units as spherulitic aggregates, and in sulfate medium porous spherical particles were observed In addition, there is a good topotaxic relationship between the precursor and oxide
Sonochemically Produced Hemoglobin Microbubbles
Authors: Wong Mike , Suslick Kenneth S. 
Published: April 2011

AbstractUsing high-intensity ultrasound, we have developed a method for the synthesis of airfilled hemoglobin (Hb) microbubbles (≈2.5 μm in diameter). Transmission electron, scanning electron, and optical microscopy show spherical particles with a shell thickness of approximately 35 nm, or roughly six protein molecules thick. The mechanism of microbubbles formation has been determined to involve both the dispersion of gas into micron-sized bubbles and the chemical cross-linking of cysteine residues between protein molecules. The primary oxidizing agent is superoxide (HO2), which is sonochemically produced from oxygen and water during acoustic cavitation. The Hb microbubbles possess many of the desired characteristics of a blood substitute. The microbubbles are smaller than red blood cells and will not block capillaries. The microbubbles are air-filled and provide a large O2carrying capacity. The hemoglobins of the microbubbles retain their ability to bind oxygen reversibly. In addition, the oxygen affinities are similar to those of native Hb. Even more surprisingly, microbubbles show extensive cooperativity, as indicated by Hill coefficients as high as 18, which means that in the microbubble shell, there is communication between several of the crosslinked Hb tetramers upon binding oxygen. The Hb microbubbles show minimal degradation (>25%) after storage for six months at 4 °C.
Defects in Quasi-One Dimensional Oxide Conductors: K0.3MoO3
Authors: Smith Kevin E. , Breuer Klaus , Goldberg David , Greenblatt Martha , McCarroll William , Hulbert Steve L. 
Published: April 2011

AbstractThe electronic structure of the prototypical quasi-one dimensional (1D) conductor K03MoO3 has been studied using high resolution photoemission spectroscopy. In particular, the electronic structure of defects was investigated in order to understand the mechanism for charge density wave pinning and destruction of the Peierls transition. Defects were found to radically alter the electronic structure close to the Fermi level (EF), thus strongly modifying the structure of the Fermi surface. While a low emission intensity at EF has been interpreted as evidence for a Luttinger liquid ground state in a ID metal, we show that non-stoichiometric surfaces lead to similar effects. The nature of the ground state is discussed in the context of these results.
Luminescence Spectroscopy on Individual Nanostructures and Impurity Atoms Using Stm and Sem
Authors: Samuelson Lars , Gustafsson Anders , Hessman Dan , Lindahl Joakim , Montelius Lars , Petersson Anders , Pistol Mats-Erik 
Published: April 2011

AbstractIn the exploration of the nano-world of semiconductors there is a strong focus on low-dimensional structures and ultra-small devices. Two fundamental problems, which challenge progress in this field are: (i) large ensembles of nano-objects, like Quantum Dots (QDs), do not have identical geometrical shapes and electronic properties, and, (ii) the properties of a low-dimensional structure can be dominated by a few impurity atoms, whereas the properties of a macroscopic structure is determined by the quasi-continuous background of dopant impurities. To allow QDs and discrete impurities to be studied, novel experimental techniques are required. In this paper we describe how local luminescence has been excited from single QDs using electrons injected from a Scanning Electron Microscope (SEM), from the tip of a Scanning Tunneling Microscope (STM) or using highly focused photons for excitation. We present images of QDs as well as characteristic spectra of individual QDs. We finally show how the local character of the excitation enables us to excite and image individual impurities in low-dimensional structures, including the measurement of characteristic emission spectra from a single impurity atom in GaAs.
Ge δ-Layers on Si(111) and Si(001) Grown by MBE and SPE
Authors: Falta J. , Gog T. , Materlik G. , Müjller B. H. , Hoegen M. Horn-Von 
Published: April 2011

AbstractGe δ-layers on Si(111) and Si(001), grown by molecular beam epitaxy (MBE) and solid phase epitaxy (SPE) were characterized in-situ by high-resolution low-energy electrondiffraction and post-growth by x-ray standing waves. LEED intensity oscillations are used to determine the growth mode of Ge on Si which is found to proceed in a double bilayer fashion for Ge on Si(111). X-ray standing waves are employed to investigate crystal quality of the Ge layer. SPE on Si(111) requires high annealing temperatures (600°C) for sufficient recrystallization of defects in the Ge δ-layer. On Si(001), Ge δ-layers of surprisingly high crystalline quality are grown by solid phase epitaxy at room temperature.
Strain Measurements and Laue Diffraction with Microbeams
Authors: Wang P.-C. , Cargill G. S. , Noyan I. C. 
Published: April 2011

AbstractWe describe a system being developed to use x-rays for spatially resolved measurements of strain, microstructure and composition in thin films. These capabilities are particularly important for improved understanding of electromigration, stress relaxation, and associated reliability issues in microelectronics. The system uses white radiation collimated and focused with a tapered glass capillary, an area CCD detector for measuring Laue patterns, and an energy sensitive Si detector for measuring lattice spacings. Examples are shown of strain measurements
for a 4 μm thick Al film on a Si substrate with 300 μm and 30 μm x-ray beams; of Laue diffraction from a single grain for a 40 μm thick Al foil with a 0.3 μm x-ray beam; and of x-ray fluorescence mapping for a patterned Cu film with a 30 μm x-ray beam.