bluuebunny/crossref_metadata_2025_split huggingface dataset:
Testing Fly Ash for Fineness to ASTM C 430: Sieve Calibration
Authors: Butler W. Barry , Kanare Howard M. 
Published: March 2011

ABSTRACTFollowing dissatisfaction with the existing calibration factor for standard fly ash used in Australia to AS 1129–1971, “Fly Ash for Use in Concrete,” a joint investigation was made by Amatek Limited and Construction Technology Laboratories Inc. Test results for five reference materials and two Australian fly ashes from tests to ASTM C 430 on both electroformed and woven wire sieves were examined and “corrected” by several means.The ASTM standard method of sieve correction is challenged, both in the use of Standard Reference Material (SRM) cement and the basis of sieve correction for coarse samples. Preferred bases of correction are suggested.
Investigations on the Composition of Individual Fly Ash and CFB-Ash Particles
Authors: Odler I. , Zysk K.-H. 
Published: March 2011

ABSTRACTThe individual particle compositions of three circulating fluidized bed combustion (CFB) ashes and one Type C fly ash were studied to determine differences in composition existing between the individual particles within a single ash. The methods used for the investigation included optical microscopy, XRD and XRF analysis. It was found that all the ashes studied consisted of several types of particles that differed in morphology, color and composition.
Storage Alternatives for High-Calcium Fly Ashes
Authors: Kilgour Carol L. , Bergeson Kenneth L. , Schlorholtz Scott 
Published: March 2011

ABSTRACTOne of the major problems currently restricting the utilization of high-calcium (ASTM Class C) fly ashes in Iowa is lack of adequate storage space. High-calcium fly ashes are self-cementitious and are generally not economically reclaimable once they have been exposed to water (i.e., the environment). Since the on-site silo storage capacity of a given power plant is normally only about one or two weeks of overall generating capacity (assuming nearly full load), the fly ash industry is hard-pressed to meet the demand for fly ash during the peak construction months.This paper presents some early research findings concerning the storage alternatives available for these high-calcium fly ashes. A simple pan agglomerator, requiring only the addition of a water spray was used to produce fly ash pellets. Since the method required minimal energy input the process would be expected to be economically feasible for field production. Laboratory produced pellets appeared strong and durable and would be expected to withstand field handling without significant degradation. The pelletization process did not appear to result in a loss of reactivity for either the air-dried or water-cured pellets. This is highly important for potential use in Portland cement concrete or soil stabilization.
Investigation Of Pozzolanic Binders Using Sulpho-Calcic Fly Ashes
Authors: Pera J. , Momtazi A. Sadr , Dejean J. 
Published: March 2011

ABSTRACTBecause of their high SO3 content (∼11%), sulfo-calcic fly ashes cannot be used as a cement admixture without pretreatment. The fly ashes contain mainly quicklime (CaO), anhydrite (CaSO4) and larnite (BC2S). At ambient temperatures and at normal consistency, their hydration leads to the formation of ettringite, slaked lime and gypsum. As a result, cracking and splitting of the hydrated product quickly occurs due to the crystallization of the ettringite.The ability of these fly ashes to produce Portlandite, Ca(OH)2, led the authors to investigate pozzolanic binders by the addition of artificial pozzolans — siliceous fly ashes, slag and clay minerals — which had been calcined at moderate temperatures.The sulfo-calcic fly ashes are ground, then slaked either in ambient or hydrothermal conditions (2 or 6 hours at 130°C). In the case of slaking under ambient conditions, ettringite is quickly produced with a definitive crystallographical structure. As a result, no volume change is observed after re-hydration of the material. By comparison, autoclave slaking does not lead to this phenomenon, and only slaked lime is produced.The rate of hydration is studied through the development of compressive strength and by analyses of the products by differential thermal analysis (DTA) and X-ray diffraction (XRD) at various hydration times. The best results are obtained using calcined laterite or blast furnace slag.
Factors Affecting the Ability of a Fly Ash to Contribute to the Sulfate Resistance of Fly Ash Concrete
Authors: McCarthy G. J. , Tikalsky P. J. , Carrasquillo R. L. , Manz O. E. , Thedchanamoorthy A. 
Published: March 2011

ABSTRACTThe objective of this summary is to report on work in progress that is examining parameters, measurable through chemical and XRD analyses, that could indicate whether a fly ash will enhance, degrade or have no effect on the sulfate resistance of fly ash concrete.Mehta [1–4] has discussed the factors that contribute to attack of sulfates on fly ash concrete. As noted in his review paper on this subject in the preceding volume in this series [1], the agents responsible for concrete expansion and cracking are alumina-bearing hydrates, such as calcium monosulfoaluminate and calcium aluminate hydrate, that are attacked by the sulfate ion to form ettringite, calcium trisulfoaluminate. Acidic type interactions between sulfate ions and calcium hydroxide also lead to strength and mass loss.
Mineralogy of Weathered Flue Gas Desulfurization Sludges
Authors: Mattigod S. V. , Rai Dhanpat , Zachara J. M. , Amonette J. E. 
Published: March 2011

ABSTRACTSamples of flue gas desulfurization sludge were characterized chemically and mineralogically. X-ray diffraction analysis indicated that the major crystalline components in the sludge samples were calcite, hannebachite, gypsum, and quartz. Identification of major compounds was confirmed through morphological and chemical analyses using scanning electron microscopy with energy dispersive X-ray analysis. In a related study, equilibrium solubility measurements of these samples corresponded with known solubilities of calcite, hannebachite, and gypsum.
Ontario Hydro's R&D on Sorbent Injection Waste Part II. Handling and Disposal
Authors: Golomb Arnold , Nott Babu R. 
Published: March 2011

SUMMARYCanadian utilities are investigating the use of Furnace Sorbent Injection (FSI) for control of acid gas emissions from thermal generating stations. Typically, limestone or slaked lime is injected into the furnace [1,2] and is calcined to calcium oxide (CaO), which reacts with sulphur dioxide (SO2) and oxygen, forming calcium sulphate:orThe by-product is removed with the fly ash, using back-end particulate control equipment. The resulting solid waste usually contains substantial amounts (e.g., 20 to 40% w/w) of unreacted CaO, which can cause handling and disposal problems because of its vigorous exothermic reaction on contact with water:The solid waste can set prematurely in the handling equipment. It can also produce a harmful dust and/or yield a highly alkaline leachate that could affect local ground and/or surface water supplies.
Semi-Quantitative X-Ray Diffraction Analysis of Fly Ash by the Reference Intensity Ratio Method
Authors: McCarthy Gregory J. , Thedchanamoorthy A. 
Published: March 2011

ABSTRACTA protocol for relatively inexpensive and rapid semi-quantitative x-ray diffraction analysis of fly ash mineralogy by the Reference Intensity Ratio (RIR) method is described. RIR's for the common crystalline phases in fly ashes derived from low rank and bituminous coal are given. The method is semi-quantitative for some phases because of unavoidable overlaps of the stronger peaks suitable for quantitation. Use of the protocol is illustrated with the four fly ash Standard Reference Materials supplied by the National Institute of Standards and Technology. Recommendations for implementation of this protocol in other laboratories and for improvements in quantitation of fly ash mineralogy are given.
A Tight-Binding Hamiltonian for the High-Temperature Superconductor YBa2Cu3O7
Authors: DeWeert M.J. , Papaconstantopoulos D.A. , Pickett W.E. 
Published: March 2011

AbstractWe present a highly accurate tight-binding parametrization of the LAPW band structure of the high-temperature superconductor YBa2Cu3O7, discuss the methodology used in obtaining this fit, and its potential application to a Tight-Binding Coherent-Potential Approximation (TB-CPA) calculation of the effects of oxygen vacancies on the electronic structure.
Coherency Strain Modeling of Elastic Moduli in CU/NB Multilayers
Authors: Jankowski A. F. 
Published: March 2011

AbstractAn anomalous decrease in the elastic moduli of Cu/Nb multilayers has been observed via acoustic wave measurements. The decrease occurs for (111) fcc Cu and (110) bcc Nb layered structures with repeat periods between 1 and 5 nm. The coherency strain model has been used to simulate modulus enhancement in noble/transition metal multilayers. This approach addresses the atomic displacements corresponding with the lattice distortions of biaxially stressed layers. Elastic moduli are derived with respect to higher order differentials of a Born-Mayer type potential for nearest neighbor ions. The elastic moduli anomalies of Cu/Nb multilayers will be modelled within this conceptual framework.
First-Principles Theory of Alloy Phase Diagrams
Authors: Zunger Alex , Ferreira L. G. , Wei S.-H. 
Published: March 2011

AbstractTemperature-composition phase diagrams of alloys are calculated by a new method combining (i) first principles total energy calculations (at T=0) for ordered structures, using the local density formalism, with (ii) finite-temperature statistical-mechanics approach (the Cluster Variation Method) to the solution of the multi-spin Ising model, using volume-dependent interaction energies obtained from (i). Novel features, including the appearance of metastable long-range ordered compounds at low temperatures are discovered.
Numerical Simulations of the Lattice Stability of β-Phase Hume-Rothery “ALLOYS”
Authors: De Graef M. , Verlinden B. , Delaey L. 
Published: March 2011

AbstractA new empirical potential model is proposed which can be used for a full fit to second and third order elastic moduli. The lattice stability of the β-phase of Cu-based martensitic alloys is known to depend strongly on these moduli. The pair potential is then used to compute the eigenvalues of the effective elastic moduli tensor for different deformations such as uniaxial z-distortion and (110)[110] shear. The results of these simulations are compared with the predictions of linear elasticity theory.
Application of a New Three-Body Potential to Vitreous Silica and Sodium Silicate Glasses
Authors: Feuston B. P. , Newell R. N. , Garofalini S. H. 
Published: March 2011

AbstractAn empirical three-body potential, suitable for molecular dynamics (MD) simulations, has been developed to model the natural covalency of the Si-O bond in vitreous silica and silicate glass systems. Through the addition of a small directional-dependent three-body term to a previously used modified ionic pair interaction, a narrow distribution of tetrahedral angles and a low concentration of defects were obtained, in good agreement with experiment. The structure of bulk silica resulting from the MD technique also contained a larger average ring size, no edge-sharing tetrahedra, and a calculated static structure factor in good agreement with neutron diffraction results. The simulated sodium silicate glass was also largely improved over previous simulations using pair interactions alone. All silicon atoms were found to be exactly four coordinated while the number of non-bridging oxygen nearly equaled the number of sodium ions present with a reasonable distribution of Qi species.
An Ab-Initio Multicenter Tight-Binding Model for Molecular Dynamics Simulations
Authors: Sankey Otto F. , Niklewski David J. 
Published: March 2011

AbstractA new, approximate method has been developed for computing total energies and forces for a variety of applications including molecular dynamics simulations of covalent materials. The method is tight-binding-like and is based on the local density approximation within the pseudopotential scheme. Slightly excited pseudo-atomic-orbitals are used, and the tight-binding Hamiltonian matrix is obtained in real space. The method is used to find the total energies for five crystalline phases of Si and the Si 2 molecule. Excellent agreement is found with experiment. A molecular dynamics simulated annealing study has been performed on the Si 3 molecule to determine the ground state configuration.
Monte Carlo Simulation of Precipitate Nucleation and Growth: Time Dependent Results
Authors: Lavine James P. , Hawkins Gilbert A. 
Published: March 2011

AbstractA three-dimensional Monte Carlo computer program has been developed to study the heterogeneous nucleation and growth of oxide precipitates during the thermal treatment of crystalline silicon. In the simulations, oxygen atoms move on a lattice with randomly selected lattice points serving as nucleation sites. The change in free energy that the oxygen cluster would experience in gaining or losing one oxygen atom is used to govern growth or dissolution of the cluster. All the oxygen atoms undergo a jump or a growth decision during each time step of the anneal. The growth and decay kinetics of each nucleation site display interesting fluctuation phenomena. The time dependence of the cluster size generally differs from the expected 3/2 power law due to the fluctuations in oxygen arrival at and incorporation in a precipitate. Competition between growing sites and coarsening are observed.
Calculating Barriers to Oxygen Penetration on Metal Oxides with the Effective-Medium Theory
Authors: Ronay Maria , Nordlander Peter 
Published: March 2011

AbstractWe estimated surface penetration barriers for interstitial oxygen using a simple calculational scheme, the effective-medium theory for a single atom. In this theory the single parameter describing the host is the electron density. Since the electron density depends primarily on the interatomic distances, i.e. the structure of the host, we found that the barrier to oxygen penetration in oxides depends primarily on the structure of the oxide, the closest-packed isotropic oxides with the smallest lattice constants having the highest barriers.
Dislocation Core Properties in Bulk and Layered Materials
Authors: Duesbery M.S. , Grossmann B. , Joo B. 
Published: March 2011

AbstractThe dislocation core is now recognised as a major contributor to many physical properties in bulk materials, for example the plasticity of metals. Less well known is that the dislocation core can be similarly important in two-dimensional (2D) systems such as surface films. Core properties in bulk materials are reviewed briefly, with emphasis on the diversity of behavior and on unifying concepts. Dislocation cores in 2D matter are considered in more detail, with particular reference to the role of the dislocation core in the melting transition.
Ab-Initio Molecular Dynamics Approach to the Study of Grain Boundaries in Semiconductors
Authors: Tarnow E. , Bristowe P. D. , Joannopoulos J. D. , Payne M. C. 
Published: March 2011

AbstractUsing an ab-initio molecular dynamics approach based on the Car-Parrinello method, the detailed atomic and electronic structure of a high-angle grain boundary in germanium is determined by investigating its energy-translation surface. Information concerning the coordination of the lowest energy configuration, its translation state, volume change, structure factor and local density of states is obtained.
The Energetics Associated with the Formation of Interfaces, Multilayers and Adlayers
Authors: Watson R. E. , Weinert M. , Fernando G. W. , Davenport J. W. 
Published: March 2011

AbstractA combination of bulk and slab total energy calculations have been done to disentangle the energetics of metal adlayer and multilayer formation. Results have been obtained for Pd/Nb(110), Pd/Nb(001), Ag/Nb(ll0), Ag/Nb(001) and Nb/Pd(111) which provide a picture consistent with what is known experimentally for these systems.
Fluorine-Silicon Reactions and the Etching of Crystalline Silicon
Authors: Van De Walle Chris G. , Mcfeely F. R. , Pantelides S. T. 
Published: March 2011

AbstractThe interaction between F atoms and crystalline Si, which is essential for etching processes in semiconductor device fabrication, is investigated with state-of-the-art theoretical techniques. The theory is based on the pseudopotential-density-functional method in a supercell geometry. A comprehensive picture of F reactions with the Si surface, the bulk, and the near-surface region is obtained, in terms of which the etching process is elucidated. Insertion of F into Si-Si bonds becomes possible because of relaxed steric constraints in the near-surface region. Dependence of the etch rate on doping follows naturally, in agreement with observations. Similarities and differences between F-Si and H-Si reactions are discussed.
The Interaction of an Atom with a Surface: A Model Based on Effective Medium Theory
Authors: Karimi M. , Vidali G. 
Published: March 2011

AbstractThe interaction potential between an atom and a surface is constructed using the “effective medium theory” (EMT) for the repulsive part of the interaction, and the damped dipole-dipole and dipole-quadrupole Van der Waals terms for the attractive part. This model is then applied to the following systems: He/MgO, LiF, NaCl, Ag and Cu.
First Principles Calculations of Surface Stress
Authors: Meade Robert D. , Vanderbilt David 
Published: March 2011

AbstractOnly recently have there been fully quantum-mechanical calculations of two-dimensional surface stress tensors. We have calculated total energies and stresses of semiconductor surfaces within the Local Density Approximation, using norm-conserving pseudopotentials. In order to hasten convergence of the stress with respect to basis size, it is useful to remove a fictitious tensile stress. We have calculated surface stress for the relaxed Si (111) 1×1 and 2×2-adatom surfaces, as well as for the relaxed Ge (111) 1×1 and 2×2-adatom surfaces. We have also calculated the surface stress for several chemisorbed systems, including Ga, Ge and As chemisorbed onto Si. We find a dramatic correlation between the electronic structure and chemistry of the surface, and its elastic properties.
Tersoff-Type Potentials for Carbon, Hydrogen and Oxygen
Authors: Brenner Donald W. 
Published: March 2011

AbstractThe application of Tersoff-type potentials are illustrated for examples from three distinct classes of chemical systems: a covalently-bonded solid (carbon), a gas-phase few-body reactive system (H3), and a molecular solid (oxygen). For carbon, the potential energy expression yields stable planar graphite layers as well as a stable diamond phase, both with correct densities and binding energies. The potential also predicts the π-bonded chain structure to be the energetically-preferred reconstruction on the {111} surface of diamond, in agreement with ab initio studies. For hydrogen the potential provides a quantitative description of accurate ab initio energies. The oxygen potential describes both the O2 and O3 molecules, and qualitatively describes intramolecular bonding in the condensed phase.
Interatomic Potentials in Ioncovalent Solids
Authors: Cormack A.N. , Catlow C.R.A. 
Published: March 2011

AbstractThe use of interatomic potentials in the simulation of ionocovalent solids is discussed. Some of the problems that may arise in the application of atomistic simulations to these solids are highlighted and some criteria for the validation of interatomic potentials for this class of solids are presented.
Calculation of the Hubbard-Type Many Body Interaction Parameters using Constrained Density Functional Theory
Authors: Schluter Michael , Hybertsen Mark S. , Christensen Niels E. 
Published: March 2011

AbstractThe constrained density functional approach is used to calculate the energy surface as a function of local charge fluctuations in La2CuO4. This energy surface is then mapped onto a self consistent mean field solution of the Hubbard model which allows extraction of the Coulomb interaction parameters when combined with oneelectron parameters derived from band structure results. The present calculations indicate that La2CuO4 is intermediate between the extreme spin or charge fluctuation regimes. This severly restricts the range of parameter space for theories of quasiparticles, optical excitations and possible pairing mechanism based on the extended Hubbard model.
Applications of Sims to Spatially Modified Polymer Film Characterization
Authors: Linton Richard W. , Judy Cheryl L. , Maybury Susan G. , Corcoran Sean F. 
Published: March 2011

AbstractThe predominant application of secondary ion mass spectrometry (SIMS) to organic polymeric solids has been the molecular monolayer analysis of thin films in the “static” mode. The primary emphasis in this paper, however, is the evaluation of SIMS for two or three dimensional compositional mapping studie of spatially modified polymer. This often requires the use of the “dynamic” SIMS mode to provide lateral images, depth profiles, or 3-D image depth profiles. Selected applications are presented including SIMS studies of surface derivatized polymers, metal-doped conductive polymer films, and patterned polymeric materials or fibers. One analytical objective is to assess the extent to which compositional information is limited by primary beam damage. The outlook for SIMS instrumentation combining high lateral spatial resolution with minimal primary beam damage to surface molecules is summarized, for example the combination of microfocused liquid metal ion sources and time-of-flight mass spectrometry.
High Resolution Electron Microscopy of Grain Boundaries in Nanophase Palladium
Authors: Thomas G. J. , Siegel R. W. , Eastman J. A. 
Published: March 2011

AbstractUsing high resolution electron microscopy, consolidated nanophase palladium samples were examined following electrolytic thinning after a hydriding - dehydriding cycle at 310 K. Due to the small size and random orientations of the individual grains, a large number of grain boundaries were available for examination. Some of these yielded adequate imaging conditions to allow observation of the lattice structure in the grain boundary regions. Image simulations were performed to determine the sensitivity of the technique to lattice disorder. The results of these studies suggest that grain boundary structures in nanophase palladium are similar to those in conventional coarse-grained polycrystals.
Rutherford Backscattering Spectrometry Studies on Copper and Chromium Diffusion in Polyimide
Authors: Paik Kyung W. , Ruoff Arthur L. 
Published: March 2011

AbstractDiffusion of Cu in polyimide(PI) film was observed after Cu evaporation on PI at room temperature. Annealing treatment significantly enhanced the diffusion of Cu. The diffusion coefficient measured at 200 and 400 C using the Fickian erfc solution are 3 × 10−14 and 1 × 10−13 cm2/sec, respectively. Cu shows the Fickian diffusion behavior. In contrast to Cu, no clearly measurable diffusion had occurred for an as-deposited Cr specimen and a specimen annealed at 400 C for 1 hour. However, for longer annealing times a slight amount of Cr diffused into PI because of the growth of the intermixed region. The diffusion coefficients of Cr at 200 and 400 C for less than 20 hours are 2 × 10−15 and 7 × 10−15 cm2/sec, respectively. The diffusion of Cr in PI shows non-Fickian behavior.