bluuebunny/crossref_metadata_2025 huggingface dataset:
A Simple Statistical Theory for Grain Growth in Materials.
Authors: Mulheran P. , Harding J.H.
Published: March 2011

A Monte Carlo procedure has been used to study the ordering of both two and three dimensional (2d and 3d) Potts Hamiltonians, further to the work of Anderson et al. For the 3d lattice, the short time growth rate is found to be much slower than previously reported, though the simulated microstructure is in agreement with the earlier studies. We propose a new stochastic model that gives good agreement with the simulations.
Defects in Materials: Their Characterization and Simulation.
Authors: Windsor Colin G.
Published: March 2011

Materials research does not necessarily need to eliminate defects, but rather to characterize them, and to understand and control their effects. In most cases chacterization of defects means making structural or dynamic measurements of their properties. To understand these measurements in order to predict material and defect properties outside the range of the measurements is a much harder problem. Ideally a theory is required. However in the materials examples considered in this review, point defects in uranium oxide, copper clusters in steel, grain boundary aggregations, and stress concentrations, a true analytic theory is beyond our capabilities. Here computer modelling is often able to make the progress needed. This review considers the complementary nature of experimental characterization and computer simulation in our understanding of defects in materials.
Effect of Grain Boundary Structure on Grain Boundary Diffusivities in the Au/Ag System
Authors: Ma Qing , Balluffi R. W.
Published: March 2011

Grain boundary chemical diffusivities for a series of symmetric [001] tilt boundaries in the Au/Ag system were measured by the surface accumulation method using newly developed thin-film multi-crystal specimens, in which the grain boundaries feeding the accumulation surface were all of the same type. Possible effects due to segregation at the grain boundaries and surfaces were avoided. CSL boundaries of low-Σ ( i.e., 5, 13, 17, 25) and also more general boundaries with tilt angles between the low-Σ orientations were selected. The diffusivities were found to vary monotonically with tilt angle ( i.e., no cusps at low-Σ's were found) in a manner consistent with the Structural Unit model.
Photoconductivity of Highly Disordered Carbon Fibers
Authors: Kuriyama Kazuyoshii , Dresselhauss Mildred.S.
Published: March 2011

A highly disordered carbon material, activated carbon fibers, is investigated through bulk conductivity and photoconductivity measurements. This material has a high density of defect states introduced by an aqtivation process that leads to a huge specific surface area of up to 2000m2/g. The conductivity increases by a factor of 4–10 with increasing temperaturefrom 30K to 290K. In contrast, the photoconductivity decreases by a factor of three with increasing temperature. The relaxation time of the photoconductivity is rather long(on the order 10−1 sec), indicating that the recombination process proceeds through localized states. flopping processes are used to interpret the transport properties of this material.
The DX Center: How Complicated Can a Point Defect Be?
Authors: Theis Thomas N.
Published: March 2011

I summarize a large body of experimental and theoretical work, especially in Sidoped GaAs and AlxGal−xAs, which has led to our present understanding of the DX center. There is good evidence that the DX center is just the simple donor, but each donor atom can exist in either of two distinct lattice configurations, each with its own spectrum of bound electronic states. At present the model which appears to best explain this unexpected complexity is that of Chadi and Chang, which predicts a large bond-breaking distortion of the lattice, accompanied by capture of two electrons by the donor. I argue that the best evidence to date for the predicted distortion is provided by observations of alloyperturbations of the DX level. Furthermore, there is now very convincing evidence that the DX level is a two-electron state. I briefly summarize what is known about the bound state spectra of the substitutional and relaxed (DX) configurations, and then discuss the very interesting question of how the donor captures two electrons from the conduction band to theDX level. There is good, although indirect, evidence that an excited one-electron state acts as an intermediate in the thermal emission and capture process. A different excited state appears to 15e involved in photoemission. Although much of this complexity was unforeseen by Chadi and Chang, it nevertheless seems to be consistent with their model. However, I point out a number of issues which still require experimental or theoretical resolution.
Analysis of Anomalous Peak Heights in DlTS of MBE-Grown Aluminum Gallium Arsenide
Authors: Lim W. , Trombetta L. P. , Jamison Keith
Published: March 2011

DLTS data taken on MBE grown AlGaAs films show peak heights which increase, maximize, and then decrease with increasing sample temperature. This behavior is difficult to explain within the context of conventional DLTS analysis. We suggest that the data can be accounted for by a trap with a temperature dependent capture cross section in conjunction with a model described by Lee and Borrego in which electron and hole emission rates are comparable. Using this analysis, we obtain an effective trap depth Eeff of 0.35 eV and a capture cross section activation energy Eσ 0.25 eV.
Optical Investigations on Donor Doped CdTe
Authors: Stadler W. , Meyer B.K. , Hofmann D.M. , Sinerius D. , Benz K.W.
Published: March 2011

The recombination luminescence involving the A-center, a Cd vacancy paired with a nearest neighbour donor, was investigated in CdTe doped with group VII and III elements. Depending on the type of donor doping, distinct differences in the A-center acceptor binding energies and electron phonon couplings are resolved. Optically detected magnetic resonance shows that the A-center behaves as a shallow effective masstype acceptor consiscent with its small binding energy.
Minority Carrier Induced Debonding of Hydrogen from Shallow Donors in Silicon
Authors: Seager Carleton H. , Anderson Robert A.
Published: March 2011

We have investigated the dissociation of donor-hydrogen pairs in Schottky barrier capacitors fabricated from phosphorus and arsenic doped silicon, at temperatures in the range 24 to 110°C. At zero bias the release of donor trapped hydrogen does not follow first order kinetics. Introduction of minority carriers by illumination or forward bias injection enhances the rate of hydrogen release and redistribution, but otherwise leaves the functional form relatively unchanged. Numerical modeling shows that the debonding rate must be proportional to the local hole density. If the dissociation process is carried out in reverse diode bias, some of the released hydrogen rebonds deeper in the silicon, outside the depletion region. In addition, a portion of the charge density in the depleted region is seen to be metastable and disappears after several hours at room temperature. This observation suggests the existence of a positive charge state of the donor-hydrogen pair which may be the precursor to dissociation. While several groups have recently pointed out that reverse-bias annealing data suggest the existence of a negative charge state of interstitial hydrogen, our observation of an electronically controlled debonding rate. casts considerable doubt on the firmness of that conclusion.
DLTS Study of Optoelectronic Devices in the Dynamic Regime
Authors: Mil'shtein S. , Tripp D. , Karakashian A.
Published: March 2011

Every semiconductor device contains as grown and process induced defects even though the techniques to minimize the density of defects are known. Conventional DLTS methods are used to identify the trapping defects in the device. However, the activity of the traps could be suppressed or enhanced by the operating conditions of the device such as temperature, current through the device or light directed onto the device. We studied the DLTS spectra of silicon polycrystaline solar cells, as well as silicon and GaAs photodetectors in the dynamic regime, namely under light and at elevated temperature. Significant change in the resulting spectra were observed when compared to the spectra obtained by conventional DLTS methods.
Ferroelastic Domain Switching In Tetragonal Zirconia
Authors: Chan C. J. , Lange F. F. , Rühle M. , Jue J. F. , Virkar A. V.
Published: March 2011

Ferroelastic domain switching is one of the possible toughening mechanisms in ceramic materials. Microstructural evidence of domain reorientation (switching) in polydomain tetragonal zirconia single crystals is observed upon the application of a unidirectional compressive stress. Dark field imaging of the three {112} tetragonal twin variants in a {111} zone indicates that two sets of twin variants grow at the expense of the third set upon application of uniaxial compression. The diminishing variant is the one with its c axis parallel to the compression axis. Indentation experiments on uniaxially compressed samples show an anisotropy in crack length. Crack propogates more easily along the loading direction. A construction for the orientation relationship of domains and their twin boundaries is presented.
New Concepts in Modelling Interfacial Defects in Yba2Cu307−X
Authors: Darab John G. , Maccrone R.K. , Rajan K.
Published: March 2011

The {110} twin planes and the dislocations at orthogonal domain interfaces which form in YBa2Cu3O7−x during cooling from =950°C have been modelled using a simple geometric approach. A summary of the stereochemistries of the distorted copper(II)-oxygen complexes associated with these interfacial defects has been compiled. The localization of holes at these distorted copper(II) complexes and the effect they have on thesuperconducting properties of YBa2Cu307−x materials arediscussed.
Theoretical Modeling and Experimental Characterization of Planar Defects in Y2Ba4Cu6+Xo14+X
Authors: Burmester C.P. , Fendorf M. , Wille L.T. , Gronsky R.
Published: March 2011

Crystallographic defects and phase transformations in the system Y2Ba4Cu6+xO14+x(0≤≤4) are investigated by high resolution transmission electron microscopy (TEM) and static lattice, three dimensional Monte Carlo computer simulations. High resolution images of partially transformed (x=2 to x=l) material reveal a prevalence of CuO planar defects (stackingfaults) associated with the transformation and an absence of disturbance to the perovskite Ba-Y-Ba blocks. An atomic mechanism involving the intercalation and removal of extra CuO planes by partial dislocation climb, and requiring only a-b plane diffusion, is developed for the formation of such planar defects during changes in the layered YBaCuO crystal structure. Monte Carlo simulations based on the proposed transformation mechanism accurately reproduce the observed defects andknown equilibrium structures.
Microstructural Analysis of Hexagonal Close-Packed Metals Using X-Ray Diffraction and Transmission Electron Microscopy
Authors: Griffiths M. , Winegar J.E.
Published: March 2011

The techniques employed for X-ray diffraction analysis of dislocation substructures in hexagonal close-packed metals are descibed and assessed by comparison with direct observations using transmission electron microscopy.
Electron Channeling Pattern: A Tool for Studying YBaCuO-HTSC Thin Films
Authors: Young K. H. , Sun J. Z. , James T. W. , Nilsson B. J. L.
Published: March 2011

High Tc superconducting (HTSC) films synthesis for demanding applications requires epitaxial c-axis growth without high angle grain boundaries. Electron channeling pattern (ECP) analysis using a scanning electron microscope is a non-destructive, fast, direct,and economical tool to determine the orientation and crystallinity of epitaxial films. We have successfully employed this technique to examine our in-situ laser ablated YBa2Cu307−δ superconducting thin films grown on LaAI03 (100) substrates. By changing the energy of the incident electron beam, we can also monitor the film quality vs. depth. The surface bending of YBa2Cu3O7−δ thin films due to the cubic-rhombohedral transition of LaAI03 substrates is also visiblewhen sharp ECPs are present. For films with rough surfaces, the ECP contrast is obscured by unwanted contrast arising from surface features. This unwanted contrast can be minimized by defocusing the electron beam.
Preparation and Characterization of La1Sr2Nb5O10−x Specimens
Authors: Galvàn Donald H. , Avalos-Borja M. , Cota-Araiza L. , Cruz-Reyes J. , Early E. A.
Published: March 2011

Recently Ogushi et al reported a La-Sr-Nb-O compound with a superconducting temperature of about 225 K. The possibility of having superconductors with such a high temperature is certainly technologically relevant. We prepared specimens with the same nominal stoichiometry and performed characterization by SEM, high resolution TEM, Scanning Auger and X-rays.
Positron Lifetime Studies of Defect Structures in Bal-xKxBiO3
Authors: O'Brien J.C. , Howell R.H. , Radousky H.B. , Sterne P.A. , Hinks D.G. , Folkerts T.J. , Shelton R.N.
Published: March 2011

Temperature-dependent positron lifetime experiments have been performed from room temperature to cryogenic temperatures on Ba1−xKxBiO3. for x=0.4 and 0.5. From the temperature dependence of the positron lifetime in the normal state, we observe a clear signature of competition between separate defect populations to trap the positron. Theoretical calculations of lifetimes of free or trapped positrons have been performed on Ba1−xKxBiO3, to help identify these defects. Lifetime measurements separated by long times have been performed and evidence of aging effects in the sample defect populations is seen in these materials.
Phonons, Oxygen Isotope Effect and Superconductivity in Ba1−xKxBiO3
Authors: Jin W. , Loong C.K. , Hinks D.G. , Vashishta P. , Kalia R.K. , Degani M. H. , Price D.L. , Jorgensen J.D. , Dabrowski B.
Published: March 2011

The phonon densities-of-states (DOS) of superconducting Ba1−xKxBi16O3 and Ba1−xKxBi18O3 (x=0.4) are determined using molecular dynamics (MD) simulations and inelastic neutron scattering measurements. The reference isotope-effect exponent is obtained from the mass variation of the first frequency moment of the phonon DOS. The energy gap, oxygen isotope-effect exponent and electron tunneling characteristics are calculated within the framework of Eliashberg theory of electron-phonon coupling.
Defects, Microstructure and Properties of the Industrial 35 CrMoV Steel
Authors: Wu Wangzi Wu Wangzi , Qiao Guiwen Qiao Guiwen
Published: March 2011

35 CrMoV steel is widely used in industries. To select the best technology for improving the mechanical properties, a series of heat treatments were tested. Metallographic examination indicates that the microstructure is a kind of non-typical bainite and, to a certain extent, similar to tempered troostites. TEM observation shows that rod-like alloying cementite distributed in ferrite grains laid parallel to each other and ultra-fine alloying carbides also dispersed in the lath-like ferrite grains. Moreover, there exists high density of dislocation tangles and microtwins. Detailed discussions are made on the solid solution strengthening, the work hardening process and the crack propagation by view of microstructure, defects and stress concentration.
Modulated Atomic Displacement Description and Easy Structural Factor Computing
Authors: Wolfers P.
Published: March 2011

The displacement of a particular atom in a modulated crystallographic structure can be described in terms of a Fourier Series. In the harmonic single wave vector approximation, the structure factor can be written as a function of the atomic displacement vectors. Such expressions are however not valid in the multi-wave-vector case. We propose a general description for the modulation of displacement where each scattering center (atom) is distributed on several sites whose population is modulated. In the paper, we will show that approach is well suited for computing. We have developed a general least squares program which has been applied to the modulated phase of αU(T < 43 K) [2].
Size-Effect Diffuse Scattering in High Voltage Electron Diffraction from Disordered α-CuAl
Authors: Sellar J.R. , Imeson D.
Published: March 2011

Strain plays an important role in many solid-state phase transformations and strain-related order parameters have recently been a topic of considerable research activity. Long range strain fields due to dislocations [1] and the strain around interstitial defects [2] have also come under study by electron diffraction and imaging methods. In this note we report the observation of weak, asymmetric diffuse size-effect scattering (SES) in a dilute partially-ordered binary alloy (Cu - 16.7 at. % Al) under dynamical diffraction conditions in a high-voltage electron microscope (HVEM) operating at around 305 kV. The asymmetry, which is of odd parity around the sharp peaks of the average lattice of the alloy crystal, is due to an elastic strain field associated with atoms displaced from their average positions in the lattice, as a consequence of their difference in atomic size.
Stationary States in Inhomogeneous Ordered Binary Alloys : Long-Period Superlattices
Authors: Avignon M. , Chakraverty B.K.
Published: March 2011

We examine the nature of all possible stationary states in an inhomogeneous ordered binary alloy. For this purpose, we use a development of the free energy in terms of the gradient of the non linear Euler equations is determined from the nature of its singular points. This method allows us to study these solutions for arbitrary expressions of the free energy of the homogeneous system as well as of the gradient coefficients. In general, periodic solutions which can be identified with long period superlattices are found. In specific cases, analytic solutions can be obtained. Fourier components are calculated and compared with experimental values determined for CuAu II.
Ordering With Phase Separation in an Fe-Al-Si Alloy
Authors: Matsumura S. , Sonobe A. , Oki K. , Eguchi T.
Published: March 2011

Two kinds of process of ordering with phase separation, B2 or DO3 → (A2 + DO3), on annealing at a temperature of 873 K in an alloy of Fe-6 at%Al-9 at%Si were investigated by means of transmission electron microscopy and X-ray diffraction. The decomposition of DO3 phase proceeds by the development of periodic fluctuations along <100> directions in both B2 and DO3 types of degree of order. Newly born DO3 domains take the form of rectangular prism and align along <100> directions. In the transition from B2, on the contrary, there is a marked difference between the morphologies of the fluctuations in the two types of degree of order at the early stage of annealing. The degree of B2 type order fluctuates along <100> directions, while the fluctuation in the degree of DO3 type order does not form the <100> modulated structure sat the early stage of annealing. The morphology after a prolonged annealing is similar to that in the case of DO3 → (A2 + DO3).
On The Phase Structure of the Asymmetric Three-State Potts Model
Authors: Gehlen G. v.
Published: March 2011

Finite-size scaling is applied to the Hamiltonian version of the asymmetric Z3-Potts model. Results for the phase boundary of the commensurate region and for the corresponding critical index ν are presented. It is argued that there is no Lifshitz point, the incommensurate phase extending down to small values of the asymmetry parameter.
Simulation of Atomic Configurations in Short Range Ordered Ni3Fe
Authors: Bley F. , Cenedese P. , Lefevbre S.
Published: March 2011

A procedure similar to that of Gehlen and Cohen and Williams is used to simulate atomic configurations of short range ordered Ni3Fe. The short range order parameters were previously measured after different heat treatments. Probabilities of different clusters are computed from those models : triangles, tetrahedrons, clusters as defined by Clapp.

These probabilities vary with the enhancement of short range order. It is shown that most of the clusters the probabilities of which increase with short range order, are directly related with the L12 ordered structure: either they have the L12 structure, or the L12 structure modified by one or two antiphase boundaries. Such clusters are identified in the model in order to display perfectly ordered domains.
Computer Models of Rapid Solidification
Authors: Gilmer G. H. , Broughton J. Q.
Published: March 2011

We discuss some recent simulations of crystal growth from the melt at large values of the undercooling. Molecular dynamics studies of the crystallization of a Lennard-Jones liquid and Monte Carlo simulations of the Ising model have together provided information on several aspects, including maximum growth rates, generation of vacancies and other defects, and impurity trapping.
Precipitation Reactions in Ai-Zr-Alloys
Authors: Haugan T. , Nes E. , Ryum N.
Published: March 2011

A new mode of precipitation of the metastable Al3 Zr in Al-Zr-alloys has been investigated. The salient aspects of this precipitation reaction are: (i) The formation of precipitate configurations of a well defined macroscopic morphology, (ii) Each individual precipitate within the colonies grows in crystallographic directions, and (iii) The absence of a high angle grain boundary as a reaction front.
Phase Transformations and Ageing Phenomena in Copper-Nickel-Manganese Alloys
Authors: Weatherill A.E. , Buckley R.A.
Published: March 2011

The pseudo-binary alloy system extending between copper and the intermetallic NiMn was first shown by Dean et al. [1,2] to yield a series of age hardenable alloys. The alloy containing 20% each of Ni and Mn has the best combination of strength and toughness and has been the subject of more recent studies [3,4]. The phase transformation associated with ageing in quenched Cu-NiMn alloys is precipitation of the ordered tetragonal (Llo) phase, (⊖) based on NiMn, from an fcc solid solution. Generally three modes of transformation occur depending on composition and temperature. An intragranular precipitate of fine coherent particles of ⊖, or a cellular or discontinuous precipitation reaction emanating from the grain boundaries, or heterogeneous precipitation of ⊖ at the grain boundaries.
Mechanical Behavior of Cu-10ni-6Sn Spinodal Alloy
Authors: Lee T. C. , Shekhar S. , Vilassakdanont A. , Subramanian K. N.
Published: March 2011

Experimental studies on deformation behavior of Cu-10Ni-6Sn spinodal alloy specimens subjected to different aging treatments were carried out at various temperatures ranging from 77°K to 353°K, using a micro-tensile device. It was found that the total elongation was independent of aging time as long as the modulated structure was coherent. Observed slip distribution and activation energy obtained in these investigations are presented. Transmission electron microscopy of deformed specimens showed straight dislocations in as-quenched samples; they were curved and wavy in aged samples. Burgers vector analysis of the dislocations present in the deformed aged samples indicated that they were of mixed character. Preliminary theoretical results on the role of wave-squaring of the internal stress field on CRSS are also presented.
Multilayer Solid Adsorption and The Roughening Transition
Authors: Weeks John D.
Published: March 2011

We discuss some the physical issues involved with the adsorption of several layers of a solid adsorbate on a strongly attractive substrate. The experimental observation at low temperature of vertical risers (the “layering transitions”) in the plot of coverage versus pressure can be understood using a one-layer 2D lattice-gas model. The behavior at higher temperature is described in terms of a coarse-grained interface hamiltonian which emphasizes the role of long-wavelength interface fluctuations. A simple variational theory predicts that the coverage in the nth layer is a continuous function of pressure above a critical temperature Tc,n which depends weakly on n and has as its large n limit the bulk roughening temperature TR.
Equilibrium Shapes for Grain Boundaries and Surfaces with Anisotropic Surface Tension Functions
Authors: Taylor J.E.
Published: March 2011

The geometric configuration of grain boundaries and surfaces seems to play a significant role in phase transformations and surface phenomena. Determining the equilibrium configurations of such boundaries for a given surface tension function γ is additionally an interesting mathematical problem; it reduces in the case of isotropic surface tension to the minimal surface problem. A framework is given here for determining such configurations in the other extreme case, where the equilibrium shape of a crystal of fixed volume (the Wulff shape) is a polyhedron. Some results obtained within this framework are outlined.
Phase Transitions in Graphite Intercalation Compounds
Authors: Clarke R.
Published: March 2011

Graphite intercalation compounds offer a unique laboratory in which to study many kinds of phase transitions. These include melting, reorientations, staging, commensurate-incommensurate effects, and certain types of lattice gas transitions. Molecular and alkali-metal intercalates are discussed with reference to results of X-ray diffuse scattering studies as a function of temperature and pressure.
18R to 2H Martensite Transformation in A Cu-Zn-Al Alloy
Authors: Rios Jara D. , Morin M. , Guénin G.
Published: March 2011

An unexpected 18R martensite to martensite transformation was obtained in Cu-Zn-Al alloy during the training process for 18R single crystal preparation: this later was induced from a β1 single crystal by application of a constant tensile force at room temperature and by lowering the temperature until β1 -->18R transformation occurs. At this condition, and after several cycles, some plates of a new phase were observed to appear in a sudden way inside the 18R single crystal region. By studying the transformation characteristics as given by elongation temperature curves and trace analysis we conclude that this new phase plates are 2H martensite.
Precursor States in the Phase Transformation Accompanying a Solid-Solid Reaction
Authors: Chaix-Pluchery O. , Bouillot J. , Freund F. , Niepce J.C. , Peyrard M.
Published: March 2011

The studied transformation is associated with the decomposition reaction of brucite-type hydroxides into the corresponding oxide. It is shown, by various techniques (X-ray and neutron diffraction, Raman Spectroscopy, proton conductivity) that some modifications take place in the hydroxide structure before its transformation into the oxide structure,i.e., at a temperature lower than the transformation temperature. A mechanism is proposed to account for the experimental data.
Quench Sensitivity of Almgsi-Alloys Containing Mn or Cr
Authors: Dons A.L. , Lohne O.
Published: March 2011

In AlMgSi-alloys cooled from about 773K (500°C) the strength after ageing depends on the rate of cooling. By addition of Mn or Cr dispersoids are formed which may control grain structure. The dispersoids also act as nucleation sites for coarse β′-Mg2Si particles. This makes the alloys more quench sensitive, in this paper the influence of 0.56%Mn on quench sensitivity is compared to that of 0.23%Cr in Al–O.6%Mg-1.0%Si industrial alloys.

The alloys were homogenized at 793K (520°C) and 853K (580°C), extruded, quenched in water or cooled in air, and aged to maximum hardness. The density of dispersoids varied with homogenizing heat treatment. Quench sensitivity increased with increasing density of dispersoids.

The two alloys had about equal densities of dispersoids after homogenizing at 793K (520°C), but the alloy containing Cr was found to be more quench sensitive than the alloy containing Mn. This is discussed and compared with other findings.
Solid State Ionics in Solid Oxide Fuel Cells
Authors: Schoonman J. , Dekker J.P. , Broers J.W. , Kiwiet N.J.
Published: March 2011

Due to the high operating temperatures (900-1000 °C) the material demands upon Solid Oxide Fuel Cell (SOFC) components are quite stringent. Preferably lower operating temperatures (700-800 °C) are desired so that gas feed lines, heat exchangers, and structure components can be fabricated from relatively cheap stainless steel components.

Typically, the materials used in a SOFC are yttria stabilized zirconia (YSZ) as the solid electrolyte, nickel-zirconia cermet as the anode, strontium doped lanthanum manganite as the cathode, and magnesium doped lanthanum chromite as the interconnection material. The electrolyte and interconnect are difficult to fabricate, because they need to be gas tight, yet thin (30-50 microns) and mechanically stable. Due to the high volatility of CrO3the densification of LaCrO3into thin layers is a more demanding challenge than the fabrication of the electrolyte.

Electr°Chemical Vapor Deposition is the key technology for making thin layers of the solid electrolyte as well as the interconnection material LaCrO3. In the simplest case the oxide growth can be modeled with the Wagner oxidation theory for metals. In this paper theory and experiment of the growth of ionically conducting YSZ and electronically conducting LaCrO3will be discussed.
Polymer-Based Lithium Rechargeable Batteries
Authors: Mastragostino Marina
Published: March 2011

Solid-state lithium rechargeable batteries with polypyrrole-based positive electrode materials together with a new polymer electrolyte designed for room temperature applications are investigated. The cyclability and stability data are reported.
Influence of Macrocyclic Ligands on Ion Transport in Solid Polyelectrolytes
Authors: Chen K. , Doan K. , Ganapathiappan S. , Ratner M. , Shriver D. F.
Published: March 2011

Cryptands and crown ethers increase the cation transport in phosphazene and alkoxyaluminate polyelectrolytes. Vibrational spectroscopy indicates that the increased conductivity originates from reduced ion pairing.
Infrared Spectroscopic Studies of Thin Polyaniline Films
Authors: Korzeniewski Carol , Seeger David M.
Published: March 2011

The electrochemistry of polyaniline depends upon the pH of the deposition solution and the nature of the anion present during deposition. When the pH of the deposition solution is below 1.0, the response is typical of the para-substituted phenyleneamine structure. When the pH of the deposition solution is greater than 1.0, an additional voltammetric wave appears, and the response is a function of the dopant anion. This report presents results of an in situ infrared spectroscopic study aimed at elucidating structural features which determine the anion dependent voltammetric response.
ESR Investigation of Copper Ion Mobility in PEO:Cu(CF3SO3)2 Complexes
Authors: Adamic K.J. , Greenbaum S.G. , Panero S. , Prosperi P. , Scrosati B.
Published: March 2011

Polymer electrolytes consisting of poly(ethylene oxide) (PEO) complexed with Cu(CF3SO3)2 have been studied by differential scanning calorimetry (DSC), electron spin resonance (ESR) and ionic conductivity measurements. Although motional effects on the ESR spectra are apparent, the present results cannot distinguish between long range Cu2+ transport or the motion of copper ions attached to polyether segments.
Manganese Dioxides: Structural Model and In-Situ Neutron Powder Diffraction Investigation of Thermal Annealing and Electrochemical Reduction
Authors: Ripert M. , Pannetier J. , Chabre Y. , Poinsignon C.
Published: March 2011

Starting from the seminal work of De Wolff [1], we have developed a structural description, based on two kinds of defects, which accounts for the scattering function of all γand ε-MnO2. Using numerical simulation results, we propose simple methods to estimate the parameters which characterize real manganese dioxide samples. Real time neutron powder diffraction has been used to investigate in situ the transformations undergone by γ-MnO2 during thermal annealing and electrochemical reduction in alkaline solutions. We have found that thermally induced transformation from MnO2 to ∝-Mn2O3 can involve up to seven different steps and that electrochemical reduction of γ-MnO2 in KOD electrolyte proceeds through three stages, the final one leading in most cases to a breakdown of the initial crystal lattice.
Transport Properties of the Intercalated Layered Cathode Materials : LiXMo2O4.
Authors: Colson S. , Tarascon J.M. , Szu S. , Klein L.C.
Published: March 2011

The mixed conducting LixMO2O4 system was shown to exhibit a high energy density (530Wh/kg) and average voltage (3.1V), suggesting that it would be a good candidate for a cathode in a Li-anode secondary battery. The transport properties of these oxide materials were then investigated by solid state 7Li NMR, dc and ac electrical measurements. The following phases are emphasized in this study: Li1.3MO204, Li2MO204, and the hydrated phase Li0.5 (H20) 1.3MO2O4.
Layered V205 Xerogels: Host-Guest Chemistry and Conductive-Polymers.
Authors: Wu Chun-Guey , Kanatzidis Mercouri G.
Published: March 2011

The properties of vanadium oxide xerogels are reviewed with respect to guest-host chemistry, redox chemistry and electrical charge transport. The insertion chemistry of several conductive and insulating polymers and alkali ions. The physical properties of the resulting materials is discussed.
Electrical Conductivity of TTF-Hydrogen Uranyl Phosphate Composite
Authors: Moreno-Real L. , Pozas-Tormo R. , Bruque S. , Martinez-Lara M. , Ramos-Barrado J.
Published: March 2011

H3OUO2PO4.3H2O (HUP) undergoes intercalative reaction with tetrathiafulvalene (TTF) given a black solid with the next composition: (TTF)U02P04.0.6H2O. The electrical conductivity fall from 2.40.10−6Ω−1cm−1(363K) to 8.8.10−8Ω−1cm−1(473K).
Local and Translational Motion of the 6Li and 7Li Ions in the Li3Sc2(PO4)3 and Li3In2(PO4)3 Compounds
Authors: Pronin Igor S. , Sigaryov Sergei E. , Vashman Andrei A.
Published: March 2011

Basing on impedance and NMR spectroscopy data it is shown that there are two types of lithium ion motion in the each polymorhic modification of the Li3 Sc2 (P04)3 and Li3 In2 (P04)3 solid electrolytes. First type is a translational motion of these ions which determines the a values, while the second one is Li ion motion within the lithium ion—ion pairs at the distance about the sum of two lithium ionic radii. Substitution of 7Li by 6Li leads to the mixed alkali effect—type behaviour of σ.
Neutron Diffraction Studies on the Structure and Conduction Mechanism in Al, Ga—DOPED Li4SiO4
Authors: Smith R.I. , West A.R.
Published: March 2011

Crystallographic results on the Li4-3x(Al,Ga)xSiO4 solid solutions are reviewed. The six sets of sites available for Li+ ions fall into two groups. The ‘framework’ sites, which also contain the substitutional Al,Ga ions, appear to have little effect on conductivity. The ‘channel’sites contain varying amounts of Li+ ions and are responsible for the dramatic variations in conductivity with x. There is evidence for the presence of one—dimensional defects, comprising columns of ordered Li+ ions, in both the framework and channel sites. The relative numbers of these linear defects has a large bearing on the solid solution mechanism in the framework sites and their occurrence in the channel sites may be responsible for the low conductivity in stoichiometric Li4SiO4.
Characterization of Indium Oxide for the Use as a Counter-Electrode in an Electrochromic Device
Authors: Yu Phillip C. , Haas Terry E. , Goldner Ronald B. , Cogan Stuart F.
Published: March 2011

Thin films of indium oxide, In2O3 (4000 Å), deposited on commercially available In2O3: Sn (ITO)/glass by rf sputtering, have been examined for potential application as a counter-electrode material in an electrochromic device, based on their chemical, structural, and optical properties. Cyclic voltammetry experiments showed that mobile lithium ions can be inserted (chemical reduction) and removed (chemical oxidation) from the host structure of indium oxide. Coulometric titrations showed that the films exhibited a hysteresis behavior for the injection and removal of lithium ions in LixIn2O3 (x=0-0.23). Structural investigation of the indium oxide films, utilizing electron diffraction techniques, indicated that they were crystalline with a crystallite size of 175 Å, in agreement with x-ray diffraction results. Differences in optical transmission between the lithiated and delithiated thin films were no more than 5% in the visible/near-infrared regions of the spectrum.
Synthesis, Structure, and Ionic Conductivity of K3NdSi6O15
Authors: Haile Sossina M. , Siegrist Theo , Laudise Robert A. , Wuensch Bernhardt J.
Published: March 2011

A structure earlier reported for K3NdSi6O15 suggests the possibility for fast—ion conduction by virtue of K+ ions which not only reside in connected channels, but which also display very large thermal vibration amplitudes. No properties of the phase had heretofore been examined. Crystals up to 2mm inlength have been synthesized under a variety of hydrothermal conditions. Refinement of the structure with single crystal x-ray data to a residual of 8.3% confirms the composition and structure of our crystals and reveals a very high thermal vibration amplitude along c for K+ ions which reside in interconnected [001] channels.A reversible phase transformation has been discovered at 180ºC with a heat of transformation of 4J/g. Preliminary measurements of the conductivity of the high temperature phase yield a preexponential factor of 3.4/cm and an activation energy of 0.61ev along [001], indicating that this compound is not a particularly good fast—ion conductor.
Conductivity Mechanisms in Acceptor Doped KTaO3 Crystals
Authors: Scherban T. , Fu S.Q. , Nowick A.S.
Published: March 2011

The electrical conductivity of perovskite—structured KTaO3 crystals acceptor doped with Co, Cu or Fe was investigated after treatments in oxidizing and reducing atmospheres under both wet and dry conditions. Isotope effect measurements (using H2O vs. D2O) show that, after treatments in wet gases of low P(O2), all the crystals are primarily protonic conductors, through a process of proton hopping with an activation energy close to 0.84 eV. Electron hole conduction dominatesat high P(O2) in the case of Fe and Cu doping. For Co—doped crystals, the conductivity is independent of P(O2) up to 1 atm., indicating that ionic conduction predominates. There is no evidence of oxygen vacancy migration, leading to the conclusion that the activation energy for that process Is relatively high.
Mixed Ionic-Electronic Conduction in Pyrochlore Oxides
Authors: Spears M. , Kramer S. , Moon P.K. , Tuller H.L.
Published: March 2011

The transport properties of the pyrochlore solid solution Gd2(ZrxTil-x)2O7 are investigated to clarify the relationships between composition, structural disorder and ionic and electronic transport. The oxygen ion conductivity has been found to increase sharply with increasing Zr content, x, due to enhanced structural disorder, leading to intrinsic ionic conduction at large values ofx. In contrast, the n—type conductivity predominant at low x, decreases sharply above x=0.2. Defect chemical models are presented to account for the simultaneous contributions of both intrinsic and dopant induced disorder. These models are applied to the σ(T, PO2, dopant) data to extract key thermodynamic and transport parameters. The significance of these parameters and the potential application of these materials in electrochemical devices are discussed.
Jump Relaxation: Simple Equations, Relevant Functions, and Kohlrausch-Williams-Watts Behavior
Authors: Funke Klaus
Published: March 2011

Solid electrolytes with structural disorder generally exhibit characteristic deviations from standard-theory spectra. The effect is known as “universal” dynamic response. In the jump-relaxation model, the phenomena are consistently explained in terms of the non-random hopping resulting from the repulsive Coulomb interaction among the mobile ions. In previous stages of the development of the model, the treatment required either crude approximations or extensive numerical calculations. Now. however, we are able to present, for the first time. simple analytic expressions for the relevant time correlation functions, derived from the rate equations of the model. In particular, the dependence of the ionic conductivity on frequency and temperature is now expressed by a simple equation. Furthermore, we recover the Kohlrausch-Williams- Watts behavior and find the KWW exponent. β. and the mismatch parameter of our model, α. to be identical. The validity of the KWW law is shown to be limited to the dispersive regime on the frequency and time scales.
Rare Earth Elements Behaviour During Alteration of Basaltic Glasses: Case of the Weathering of Icelandic Hyaloclastites
Authors: Daux V. , Crovisier J. L. , Petit J. C.
Published: March 2011

Subglacial basaltic glasses from Iceland have been studied in order to investigate REE behaviour during low-temperature weathering. As heavy elements accumulate in the hydrated superficial corrosion layer of borosilicate glasses, REE are found to be enriched in the natural corrosion layer of basaltic glasses (palagonite). However, mass balance calculations performed for our natural samples evidenced that this enrichment is only relative: the corrosion process leads to absolute losses of elements including REE.
The Use of Partial-Replenishment Tests in Modeling the Leach behavior of Glasses
Authors: Barkatt Aa. , Olszowka S. A. , Sousanpour W. , Choudhury T. , Guo Y. , Barkatt Al. , Adiga R.
Published: March 2011

The partial-replenishment test can be an important tool in exploring the long-term leach behavior of glasses. In order to demonstrate the use of partial-replenishment test data in modeling, experiments were conducted which show that after a relatively short period test results become largely independent of exchange interval and volume exchange fraction. The results can be characterized by the ratio between these two parameters, which corresponds to the residence time. Sampling of the leachates during a given exchange interval shows that leachate concentrations quickly recover following the exchange, and that this recovery can be satisfactorily described using a simple model based on first-order approach to equilibrium at the silica saturation level.
Dissolution Behaviour of Used Candu Fuel Under Disposal Conditions.
Authors: Tait J. C. , Stroes-Gascoyne S. , Hocking W. H. , Duclos A. M. , Porth R. J. , Wilkin D. L.
Published: March 2011

The dissolution behaviour of Zircaloy clad used CANDU fuel in aqueous solutions has been examined under mildly reducing conditions at 95°C for a period of 16 months. The effects of various container components and groundwaters on the dissolution of the fuel have been investigated. The components studied were titanium (container material), carbon steel (fuel bundle support basket) and soda-lime glass beads (container infill material). Leaching solutions included deionized water (DIW) and synthetic saline groundwaters.

The presence of glass beads or carbon steel did not appear to significantly affect solution concentrations of137Cs,90Sr,99Tc, or238U. Radionuclide concentrations were one to two orders of magnitude higher in saline groundwaters than in DIW. After about 30 days leaching, continued radionuclide release from the fuel was strongly inhibited in the absence of oxygen, and radionuclide concentrations in solution remained virtually constant. X-Ray photoelectron spectroscopy (XPS) measurements of the oxidation state of fuel fragments leached in groundwaters, showed a surface composition of less than UO2.33, below the postulated threshold for oxidative dissolution.
Environmental Effects on Localized Corrosion of a High-Level Nuclear Waste Container Material
Authors: Sridhar N. , Cragnolino G. , Machowski W.
Published: March 2011

The effect of environmental variables on the localized corrosion behavior of alloy 825 is examined in this paper. Cyclic, potentiodynamic polarization tests based on a two-level, full factorial experimental design were conducted. An index incorporating both the visual and scanning electron microscope examinations of localized corrosion and the electrochemical parameters was used for the statistical analysis. The analysis showed that chloride is the single most important promoter of localized corrosion, while nitrate was the single most important inhibitor. Fluoride was a weak inhibitor, especially at low chloride levels. Sulfate was a weak promoter, especially at high chloride levels. Temperature did not have a significant effect within the chloride levels examined. Separate experiments indicated that silicon, added as metasilicate, did not have any significant effect on localized corrosion. The adverse effect of chloride was observed at concentrations as low as 100 ppm. Addition of H2O2 increased the corrosion potential of alloy 825 to a value above the repassivation potential observed in the 300 ppm chloride solution.
Enhancement of Borosilicate Glass Dissolution by Silica Sorption and Diffusion in Compacted Bentonite: A Model Study.
Authors: Curti Enzo , Smith P. A.
Published: March 2011

Experimental evidence indicates that glass corrosion rates decrease proportionally with the increase of silicic acid concentration in the solution contacting the glass surface. A minimum corrosion rate (Rsat) is reached when the solution becomes saturated with respect to an unidentified amorphous siliceous compound. In a repository where the vitrified waste form is surrounded by compacted bentonite, the silica dissolved from the glass will diffuse into the pore solution and concentration gradients will be established throughout the backfill material. The silicic acid concentration at the glass-bentonite interface, and thus the glass corrosion rate, will then be diffusion controlled. Moreover, experimental work suggests that significant sorption of silica by clay minerals in bentonite may accelerate glass corrosion.

A model describing glass corrosion coupled with diffusive transport and sorption of silica in bentonite has been developed and incorporated in a FORTRAN computer code (GLADIS). The model assumes: (a) a linear isotherm for the sorption of silica (KD), (b) time and space invariant pH, temperature and ionic strength, (c) proportionality between the quantity of silica precipitated and the amount of glass dissolved and (d) cylindrical geometry. Preliminary calculations with a particular parameter set at 90°C, assuming no silica sorption on the bentonite, indicate for an unfractured glass block that a stationary state is rapidly reached in which the silica concentration at the glass-bentonite interface is lower than the saturation concentration. This implies that the glass corrodes at a more rapid rate than Rsat (RsS ∼ 8 Rsat) If moderate silica sorption is assumed (KD = 0.5 m3 kg−1), the attainment of stationary conditions is delayed by the removal of silicic acid from solution, and the average corrosion rate is further increased by a factor ∼ 2.
Phase Relations and Solubility Modelling in the Cao- SiO2- Al2O3- MgO- SO3-H2O System: For Application To Blended Cementss.
Authors: Atkins M. , Glasser F. P. , Kindness A.
Published: March 2011

Cement blends are likely to form a large fraction of the materials in the near field of radioactive repositories. Being chemically reactive and slightly soluble, their effect on near field chemistry will be very marked. Predictions of nuclide migration in this zone will therefore depend in part on accurate modelling of cement chemistry.

The models being developed require the establishment of correct phase relations in the Cao- SiO2- Al2O3- MgO- SO3-H2O system (the major cement components). More than 40 compatibility experiments were carried out to determine these relationships. Purified cement hydrates were shaken continuously in CO2- free water, for 10 weeks. The results from these experiments together with data from the literature, enabled us to construct a better validated phase relations scheme than has hitherto been possible.

Interpretational problems were encountered. Thus, mixtures containing Ca(OH)2, gave rise to the precipitation of metastable phases. This is due to special dissolution/ precipitation equilibria obtaining at early age, allowing ‘AFm type’ (4CaO.Al2O3.SO3.12H2O) phases to form, where C3AH6 (3CaO.Al2O3.6H2O) and AFt (6CaO.Al2O3.3SO3.32H2O) are thermodynamically favoured.