bluuebunny/crossref_metadata_2025_split huggingface dataset:
Statistical Mechanics of Phase Coarsening
Authors: Glicksman M.E. , Voorhees P.W. 
Published: March 2011

ABSTRACTPhase coarsening, also termed Ostwald ripening, is generally thought to be a slow, diffusion-controlled process which occurs subsequent to phase separation under extremely small under- or over-saturation levels. The theory due to Lifshitz, Slyzov, and Wagner (LSW), which predicts the coarsening kinetics and the particle distribution function is applicable to dilute systems only, in which particle-particle interactions are unimportant. Most practical systems, however, have large enough volume fractions of the dispersed phase to violate the essential assumptions of LSW theory. Recent progress will be described on simulating Ostwald ripening in randomly dispersed, high volume fraction systems. A fast algorithm for solving the multiparticle diffusion problem (MDP) will be described, permitting simulation of coarsening dynamics by cyclic time-stepping and updating the diffusion solution for large random particle arrays. The rate constants, controlling the growth of the average particle, and the particle distribution functions were obtained by numerical simulations up to a volume fraction of 0.55. A new statistical mechanics theory has now been developed which reproduces the MDP simulation data accurately, and finally makes clear how the linear mean-field approximations employed by LSW theory must be modified to describe real systems. The new theory provides a comprehensive approach to understanding microstructural coarsening in two-phase systems.
Coarsening of Cobalt Precipitates in Copper- Cobalt Alloys
Authors: Eguchi T. , Tomokiyo Y. , Oki K. , Seno Y. 
Published: March 2011

ABSTRACTThe Ostwald ripening of precipitates in Cu-Co alloys was investigated by electron microscopic observation. The variation of the mean particle radius r, and the distribution of relative particle sizes, f(r/r) , were obtained as functions of the aging time at 873K . The shape of f(r/r)was rather sharp and symmetrical around r = T in the early stage. It became broad with the aging and was similar, in the late stage, to the theoretical distribution of Ardell. It appeared that the shape of f(r/r) depends on the volume fraction but the growth rate of F scarcely depends on it. The rate of change of r was proportional to the cube root of the aging time from the early stage of aging.
Test of Some Statistical Approximations (Quasi Chemical, Cvm) in Bcc and Fcc Binary Alloys by Monte Carlo Simulation. Validity Range of the Clapp and Moss Approximation.
Authors: Cenedese P. , Gaspard J.P. 
Published: March 2011

ABSTRACTIn the framework of regular solution model, we test the validity of some usual approximations (QC, CVM) of entropy in (disordered) binary alloys by Monte Carlo simulation. The validity range of these approximations are explored both in alternant and nonalternant lattice with ferro- and antiferromagnetic coupling. The CVM tetrahedron approximation is also analysed on a structure containing only tetrahedra : the 120 polytope [8] in 3d curved space.
Diffusion Along Migrating and Stationary Grain Boundaries: The Al-Zn System
Authors: Gust W. , Hintz M.B. , LuČić R. , PREDEL B. 
Published: March 2011

ABSTRACTThe discontinuous precipitation reaction has been studied in an Al-28a/o Zn solid solution. It appears that the diffusion rates determined by us for migrating grain boundaries are of the same order of magnitude as the values determined by Häβner (1974) for stationary grain boundaries. To the same statement have led results from the discontinuous coarsening reaction in an Al-29a/o Zn alloy (Fournelle et al., 1982) as well as from the eutectoid reaction in an Al-60a/o Zn alloy (Cheetham et al., 1971).
The Effect of Applied Stress of the Decomposition Cu-15Ni-8Sn Spinodal Alloy
Authors: Ahn S. , Tsakalakos T. 
Published: March 2011

ABSTRACTThe effect of stress on spinodal decomposition in Cu-15Ni-8Sn alloy was investigated at various temperatures and stresses. As the aging temperature approached the coherent spinodal temperature about 500°C, the anisotropy among the three equivalent <100> modulations of the stress aged specimens became pronounced. The wavelength of the [001] modulation along the tensile stress axis was smaller than that of the [100] or [010] modulation perpendicular to the stress axis. TEM diffraction patterns also showed the anisotropy effect of the applied stress to the composition modulation. A theoretical model based on micromechanics concepts was employed to explain the experimental results.
Spinodal Decomposition in Fe - 32Cr
Authors: Lasalle J. C. , Spooner S. , Schwartz L. H. 
Published: March 2011

ABSTRACTSpinodal decomposition in iron-chromium alloys has been studied for various compositions and aging temperatures by several workers using small angle neutron scattering. The data of the present study and that of previous workers are reviewed in order to better define the coexistence curve of this system as well as to provide an experimental basis for comparison with current nonlinear theories of spinodal decomposition. Regarding the coexistence curve, it is argued that the qualitative changes in the scattering pattern with composition and aging temperature are consistent with the experimentally determined boundary, rather than those calculated for this system. Quantitative analysis of the kinetic development of scattering from Fe-32Cr samples allows direct comparison with predictions of nonlinear theories of spinodal decomposition. The time dependence of the position of the peak maximum has been given by several theories as t−. The value of ø found for Fe-32Cr increased with increasing aging temperature, extrapolating near the value of 1/6 at the estimated spinodal temperature.
Kinetics of Ordering with Phase Separation
Authors: Eguchi T. , Oki K. , Matsumura S. 
Published: March 2011

ABSTRACTAn attempt is made to investigate theoretically the kinetics of ordering accompanying phase separation in an alloy as a continuous medium. A set of coupled equations for the local composition and the degree of order are derived from the first principles of thermodynamics of irreversible processes, under an appropriate assumption as to the free energy of the system. Under certain circumstances a periodic deviation of local order parameter in the disordered state induces that of the composition, leading to a spinodal decomposition, and the resonance conditions for enhancement of such an induction are examined in the perturbation approximation. In a uniform state of imperfect degree of order disturbances of the local composition and degree of order develop in-phase.
Influence of Surface Magnetism on the Surface Segregation Near TC in NiX Cu1-x Alloys
Authors: Urias J. , Moran-Lopez J.L. 
Published: March 2011

ABSTRACTThe influence of surface magnetization on the surface segregation in binary alloys with one magnetic component is studied. Based in a model in which the local magnetic moment on the ferromagnetic atoms is determined by the local environment, the internal energy is calculated within the mean field approximation. We applied the model to dilute CuNi alloys and we find that magnetism favors the segregation of Ni, contrary to what it is found in the paramagnetic phase.
Martensite Lattice Correspondence and Twinning in Uranium Alloys
Authors: Speer J.G. , Edmonds D.V. 
Published: March 2011

ABSTRACTA new lattice correspondence has been deduced for the γ→a′ martensite reaction in dilute uranium alloys. The new correspondence involves a lattice deformation with significantly smaller principal strains than those previously considered, although more atomic shuffles are required.From an analysis of possible transformation twinning modes based on the new correspondence, the further possibility of a deformation twinning mode in these alloys is theoretically predicted. The mode is compound, described by (021)(023) [012] [032], and involves a twinning shear (g = .044) which is smaller than any value previously predicted or observed, although again a larger number of shuffles would be required. The significance of these results is discussed.
The use of Phase Transformations in the Design of Alloy Steel
Authors: Morris J. W. 
Published: March 2011

ABSTRACTThis paper is intended to describe and illustrate the use of phase transformations in the design of new alloy steels. The general method of alloy design is described. Two examples are discussed: the development of new ferritic structural steels for use at cryogenic temperature, and the development of ‘dual phase’ steels for automotive use.
Phase Transformations on Aging Cu-Al-Ni β Phase Alloys
Authors: Husain S. W. , Clapp P. C. , Ahmed M. 
Published: March 2011

ABSTRACTThe phase transformations occurring on quenching and subsequent aging of a Cu-Al-Ni β phase alloy have been studied using transmission electron microscopy, x-ray diffraction and optical microscopy. Quenching produces an ordered solid solution, β1, based on the DO3structure of Cu3A1. X-ray and electron diffraction show satellite diffraction peaks. On aging, these satellite peaks disappear and the parent phase undergoes a martensitic transformation. It is suggested that the parent phase undergoes a process of phase separation through the mechanism of spinodal decomposition before the martensitic transformation occurs. The martensitic transformation shows isothermal kinetics for which a transformation diagram is presented. Prolonged aging results in the formation of equilibrium phases.
Precipitation Hardening in The 90W-5Ni-5Fe Heavy Alloy
Authors: Posthill J.B. , Edmonds D.V. 
Published: March 2011

ABSTRACTPrecipitation hardening in the W-phase of the 90W-5Ni-5Fe alloy has been identified and monitored by transmission electron microscopy and mechanical tests. Deformation of the alloy prior to aging is observed to accelerate the precipitation reaction. Possible precipitate origin and geometry are discussed in terms of the TEM observations.
The Influence of Oxygen-Rich Inclusions on the Nature of Austenite Decomposition Products of Weld Metal Deposits
Authors: Ferrante M. , Akune K. 
Published: March 2011

ABSTRACTRecent studies carried out on weld metal have called attention to the role of oxygen-rich inclusions on austenite decomposition. This investigation describes some evidences of the catalytic effect of dislocations upon the γ → α transformation. These defects are generated at the matrix inclusion interface and its presence has been ascertained by TEM. Estimates of the stresses arising from differences in thermal contraction between inclusion and matrix on cooling confirm microstructural observations.
The Effect of Step Quenching on the Kinetics of Bainite Formation in Ferrous Alloys
Authors: Umemoto M. , Igarashi M. , Tamura I. 
Published: March 2011

ABSTRACTThe bainite reactions in the direct and in the step quenched conditions were compared using Fe–7.6Ni–0.48C and Fe–3.6Ni–1.45Cr–0.50C alloys. It was found that in both alloys the bainite reactions were markedly accelerated by step quenching to temperatures even in the stable austenite range prior to the transformation to bainite. Optical microscope observation revealed that this acceleration was caused by the enhanced nucleation of bainite at grain boundaries. This enhanced nucleation by step quench treatment was considered to be due to either the formation of carbon poor areas or the formation of ferrite embryos at the grain boundaries during holding at intermediate temperatures.
Phase Transition Between Matrix and Inclusions in Polymeric Composites
Authors: Theocaris P.S. 
Published: March 2011

ABSTRACTThe influence of boundary layer on the coefficient of adhesion between fibers and matrix in polymer composites was investigated. A multilayer model was introduced consisting of the two main-phases of the composite,that is the elastic inclusion and the viscoelastic matrix and a third intermediate phase consisting of a series of cylindrical layers of mechanical and physical properties varying between the limit values of the matrix and inclusion. The extent of the interlayer between main phases may be determined from the overall properties of the composite and the matrix. The model proved to be very flexible and describes conveniently the behaviour of the material. Moreover, the model allowed the definition of an adhesion coefficient, convenient to describe the quality of adhesion of the component materials and the introduction of an improved expression for the law of mixtures in polymeric composites.
Structural Dynamics of Polymer Electrolytes
Authors: Nazri G-A. , MacArthur D.M. , O'Gara J.F. 
Published: March 2011

AbstractThe structure of polyethylene oxide doped with lithium perchlorate was studied. The macroscopic structure of the polymer-salt complexes was studied by thermal analysis and xray diffraction. The microscopic structure and polymer dynamics were studied by infrared, Raman and nuclear magnetic resonance spectroscopy. Thermal analysis and x-ray diffraction studies clearly revealed the change of crystalline phase to an amorphous phase by the addition of salt. The vibrational analysis showed a conformational transformation of the polymer chain by the addition of salt. Vibrational analysis also showed clearly the formation of free ion, ion-pair and salt cluster in the polymer as the concentration of the salt increased.
New Oxide-Ion Electrolytes
Authors: Goodenough J.B. , Zhen Y.S. 
Published: March 2011

AbstractStrategic considerations for the design of new O2--ion solid electrolytes are presented, and preliminary measurements of the oxide-ion conductivity σo = (B/T) exp (-EA/kT) and transport number tO = σO/σ are reported for several oxides with perovsldte-related structures. Ba2In2O5 exhibits a first-order transition at Tt ∼ 930°C from the brownmillerite structure to a cubic perovskite with disordered oxygen vacancies and fast O2-ion conduction. Ba3In2MO8 (M = Ce, Zr, or Hf) contains oxygen vacancies ordered into every second BO2 (001) plane. An octahedralsite preference of the disordered M(IV) cations makes incomplete the oxygen-vacancy ordering, so a high extrinsic σo with EA ∼ 0.6 eV is found for T ≤ 400 °C. The transport properties of Ba3In2ZrO8 at 400 °C are equivalent to those of the stabilized zirconias at 800 °C. BagIn6O17 consists of an intergrowth of (BaO)2 rocksalt and Ba3In3O7.5 oxygen-deficient perovskite layers. Although there is no evidence of long-range ordering of the oxygen vacancies, nevertheless an EA = 1.06 eV and transport properties equivalent to stabilized zirconia indicate retention of short-range correlations to at least 950 °C. Attempts to prepare Bag Y6O17 yielded a mixture of hexagonal Ba3Y4O9 and unidentified phases. An EA = 0.45 eV above a Tt=370 °C gives a remarkable O2--ion conductivity at temperatures T > Tt in both the mixed-phase and pure Ba3Y4O9 at temperatures T > 370 °C, but the samples are extremely hygroscopic.
A Thin Film Solid State Nicrobattery for Use in Powering Nicrosensors
Authors: Jones Steven D. , Akridge James R. , Humphrey Susan G. , Liu Chung-Chiun , Sarradin J. 
Published: March 2011

AbstractA thin film solid state microbattery has been used to power an O2 microsensor. The microbattery was fabricated using RF magnetron sputtering for the solid oxide/sulfide electrolyte and the TiS2 cathode. Vacuum evaporation was used for the deposition of LiI and Li anode. rhe microbattery is approximately 10 µm in thickness. The microbattery has an OCV of 2.4-2.5 V and shows close to 100% utilization to a 1.8 V cutoff when discharged between 10 and 135 µA/cm2. The microbattery is capable of supplying 2 second pulses of greater than 2 mA/cm2. The microbattery is rechargeable with over 200 cycles of 70% utilization to a 1.8 V cutoff at current densities up to 135 µA/cm2.The O2 microsensor consists of a silk-screened Au working and Ag electrode. The Ag electrode was anodized to provide an Ag/AgCl counter electrode. The current produced at the sensor is proportional to the dissolved O2 concentration of an aqueous solution upon application of 0.6 V between the two electrodes.
Fundamental Considerations Relating to the Insertion of Hydrogen Isotopes into Mixed Conductors at High Activities
Authors: Huggins Robert A. 
Published: March 2011

AbstractSome features of the electrochemical insertion of hydrogen isotopes into mixed conductors under dynamic electrolytic conditions are discussed. Unusual magnitudes of thermodynamic parameters in both the surface region and the bulk can be obtained under some conditions. These can vary greatly, depending upon the surface composition, as well as experimental conditions. It is thus possible to obtain species distributions and related phenomena inside solids during electrolysis at atmospheric pressure that are equivalent to those that would be present if there were a very high external pressure of one of the components.The transport of hydrogen isotope interstitial species is very microstructure - dependent. Readily visible microstructural changes occur upon insertion and deletion of these species. This leads to the very sporadic nature of structure - dependent phenomena often observed. These considerations may play an important role in the apparent irreproducibility of experimental observations of the ‘cold fusion’phenomenon.
Ion Transport in Single Crystals of the Clay-Like Aluminosilicate, Vermiculite
Authors: Maraqah Hatem , Li Junxiang , Whittingham M. Stanley 
Published: March 2011

AbstractWe have made an investigation of the ion transport properties of single crystals of the naturally occurring clay vermiculite in order to elucidate the mechanism of conductivity including the predominant charge carrier. Measurements of the ion conductivity, magnetic susceptibility and x-ray lattice parameters of ion-exchanged samples strongly suggest that the native cations and not protons are the major current carriers. We have synthesized the hydrogen form and found that it is a much preferred precursor for ion-exchange by other cations allowing the time necessary for ion-exchange to be reduced from several months to around a week.
Optical Efficiency of the Electrochromic Windows Based on Solid Polymer Electrolytes
Authors: Shabrang M. , Murray D.P. 
Published: March 2011

AbstractInterest in the electrochromics research in the 80's was mainly directed towards potential applications for variable light transmission windows. Even though large-area electrochromic cells incorporating liquid electrolytes are being investigated, we focused on solid state devices. Such devices offer fewer fabrication problems in large-area applications. The solid electrolyte layer is a key component in the fabrication of the solid state windows. This layer must be transparent, electrochemically stable and display adequate ionic conductivity. Optical efficiencies of asymmetric solid state devices based on tungsten oxide as the electrochromic material and commercially available ionomers and polyelectrolytes - Naflon, poly(styrene sulfonic acid), and poly(2-acrylamido-2-methylpropanesulfonic acid), as the solid electrolyte layer are presented at room temperature and 90 C. Impedance behavior of this asymmetric system is discussed and compared with the behavior observed in other systems.
Synthesis, Diffusion and Ion-Exchange in Open Structure Sodium Tungstates and Ybacu Tungstates
Authors: Reis Kenneth P. , Ramanan A. , Gloffke W. , Whittingham M. Stanley 
Published: March 2011

AbstractCritical to the effectiveness of any solid state device is the reactivity of its components. In solid state ionics one desires certain atoms or ions to show high ionic mobility; yet, at the same time one does not want these atoms or ions to participate in side reactions. These reactions are a function of the crystalline structure of the material, of the way in which it was synthesized and of it's thermodynamic stability relative to the environment. This paper describes the synthesis of a variety of tungsten oxides which exhibit ionic mobility, and the determination of their crystalline structure and reactivity. The reactivity of the 123 superconductor with tungsten oxides is described in terms of the phases formed; none of these phases exhibited superconductivity. Both of these structurally related materials react with lithium and oxygen in a reversible manner, and these reactions are critically important in determining their properties and potential commercial application.
Electrochemical Modification of Bi2Sr2CaCu208+δ and La2CuO4
Authors: Scholz G.A. , Olfert M. 
Published: March 2011

AbstractSemiconducting Bi2Sr2CaCu208 and La2CuO4 can be made superconducting following their oxidation in an electrochemical cell. Experimental evidence suggests that the deintercalation of copper, ie. the oxidation of the copper oxide planes is responsible. Intercalation, ie. reduction, reverses the above trends. The mechanism controlling superconductivity is therefore sensitive to the Cu/O ratio, which can be reversibly controlled at room temperature.
Diffusion in Materials with Ionic and Electronic Disorder
Authors: Maier Joachim 
Published: March 2011

AbstractBesides some necessary reviewing of conventional diffusion theory, this paper deals with the modification of the mass and charge transport equations originating from the occurence of internal defect-chemical reactions (especially valence changes of the defects) which can be considered to be in local equilibrium. It is shown how the phenomenological transport coefficients for chemical diffusion, tracer diffusion and ionic conduction depend on the individual defect diffusivities under such general conditions. Moreover, the evaluation formulae of well-known electrochemical techniques such as Wagner-Hebb polarization and concentration cell experiments have to be modified. Application is made to the influence of trapping effects in doped SrTi03, to the valence changes in YBa2Cu3O6+x as well as to the mixed conduction in orthorhombic PbO.
Thin Film Amorphous Electrolytes: The Li2O-SiO2-P2O5 System
Authors: Bates J. B. , Dudney N. J. , Sales B. C. , Robertson J. D. , Zuhr R. A. , Gruzalski G. R. , Luck C. F. 
Published: March 2011

AbstractThin film amorphous electrolytes with compositions xLi2O:ySiO2:zP2O5 were deposited by single and dual source rf magnetron sputtering and their compositions determined by electron and ion beam techniques. Films containing P but no Si were composed of mainly orthophosphate and some linear chain phosphate anions, whereas single phase films containing Si and P were evidently composed of branched and possibly cyclic and extended network structures. Films with Si/P > 1 appeared to contain two or more amorphous phases. In the range of compositions investigated, the lithium ion conductivity depends mainly on the lithium ion mobility which is sensitive to the structure of the films. An open circuit voltage from 1 to 3 V measured between blocking metal contacts on the electrolyte thin films suggests that the films mightbe electrets.
Spuiter Deposition of Lithium Silicate — Lithium Phosphate Amorphous Electrolytes
Authors: Dudney N. J. , Bates J. B. , Robertson J. D. , Luck C. F. 
Published: March 2011

AbstractThin films of an amorphous lithium-conducting electrolyte were deposited by rf magnetronsputtering of ceramic targets containing Li4SiO4and Li3PO4. The lithium content of the films was found to depend more strongly on the nature and composition of the targets than on many other sputtering parameters. For targets containing Li4SiO4, most of the lithium was found to segregate away from the sputtered area of the target. Codeposition using two sputter sources achieves a high lithium content in a controlled and reproducible film growth.