bluuebunny/crossref_metadata_2025 huggingface dataset:
Substitution and Defect Chemistry of La-Cu-O Systems
Authors: Gai P. L. , Kunchur M. , McCarron E. M.
Published: March 2011

Substitutional effects of strontium in La-Cu-O system and defects accommodating stoichiometric deviations have been investigated. The extended shear defects are analyzed using electron microscopy and their role in superconducting transport properties has been examined by magnetic measurements. The initial results suggest that the defects enhance flux pinning.
Molecular Calculations of Interplanar Electronic Interactions in a Ybacu2O6+δ Cluster as a Function of the Oxygen Concentration.
Authors: Cogordan J. A. , Sansores L. E. , Valladares A. A.
Published: March 2011

Molecular ab initio SCF calculations on a cluster formed by Y, Cu(2)-O(2)-O(3) plane, Ba-O(1) plane and Cu(1)-O(4) chains are reported. The computations were performed for five different sets of lattice parameters of YBACu2O6+δ Each of these sets correspond to a values of the oxygen stoichiometry. Mulliken population analysis results show a charge transfer to the Cu(2)-O(2)-O(3) plane when the oxygen stoichiometry is increased from six to seven.
Modified Fisher Droplet Model
Authors: Marro J. , Toral R.
Published: March 2011

We propose a simple modification of the Fisher droplet model which, unlike classical nucleation theory, reproduces very well some Monte Carlo equilibrium cluster distributions P1 for the three-dimensional Ising or lattice gas model. It then follows that p1(h) /p1(h=0) = A exp(− η l) where η ∝hl/Y, y≃0.45, when the magnetic field h is small enough, as suggested from the consideration of an effective cluster size ly , while η seems rather proportional to h at larger values of the field, as implied by some exact results.
High Resolution Lattice Images of G.P.Zones and Solute Clusters in Al-Cu and Cu-Be Alloys
Authors: Yoshida H. , Hashimoto H. , Yokota Y. , Takeda M.
Published: March 2011

Atomic structures of G.P. zones and solute clusters in Al-Cu and Cu-Be alloys are studied by the atom resolution electron microscope images. The images of plate-like G.P. zones appear as dotted images with various brightnesses along (200) lattice planes. The solute clusters are also observed along (111) lattice planes.
Electron Microscope Study of Cation-Deficient Chalcogenide Spinels
Authors: Komura Y. , Takeda S.
Published: March 2011

High-resolution electron microscope observations were carried out on the cation-deficient spinel compounds Ga2/3Cr2S4 and InCr5/3S4. X-ray analysis of both compounds indicates that there exist 1/3 vacancy per formula unit in 8a positions. It was also found that the vacancy ordering occurs in Ga2/3Cr2S4 below about 1100°C, as well as in InCr5/3S4. Lattice images of vacancy ordered and disordered structures were obtained. In some electron micrographs of ordered InCr5/3 S4, several domains of disordered region were observed in between the matrix of the ordered structure. In a [110] image, characteristic lattice defects were observed on the (110) plane.
Phase Transformations in Titanium Oxide Evaporated Films by Annealing
Authors: Yamada Y. , Yoshida K. , Ota H. , Guang Jun Shen , Bursill L. A. , Spargo A. E. C.
Published: March 2011

The process of the phase transformation of evaporated films of TiO0.5 has been demonstrated by in situ annealing using an electron microscope. Single crystals of the δ-phase, whose structure is identified with Andersson's hexagonal model, precipitate during annealing. Crystal structure images in cooperation with the calculated images reveal that the inner parts of the δ-phase crystal have various thickness. The transition structures I and II having ordered vacancies of titanium and oxygen respectively also appear on annealing. The difference in the distortion of their lattices from the parent rock-salt type lattice suggests that the effective atomic volume of titanium is larger than that of oxygen in the crystal of the transition structure. The observed transformations, α-phase → δ ;phase → transition structure, are explained by consideration of the structural relationships among these phases.
Structural Phase Transition in Tetrafluoroaluminates
Authors: Launay J.M. , Laval J.Y. , Gibaud A. , Bulou A. , Nouet J.
Published: March 2011

It is shown that the detailed investigation of an irreversible SPT implies the combination of X-ray, neutron and electron diffraction data. This diffraction analysis is applied to K Al F4 and Rb Al F4. There is a good agreement between the three diffraction techniques in the case of Rb Al F4 where the SPT is reversible. On the other hand, for K Al F4 room temperature quadratic phase, electron diffraction exhibits exta spots which are not evidenced by X-ray and neutron diffraction. Finally the assumption of an orthorombic lattice from neutron scattering for the low temperature phase is consistant with electron diffraction results.
Evidence for Deformation Modulated Structures in NbTe4 and TaTe4
Authors: Mahy J. , Wiegers G.A. , Van Landuyt J. , Amelinckx S.
Published: March 2011

X-ray and electron diffraction studies have shown that NbTe4 and TaTe4 exhibit a deformation modulated structure. The distortion can be described by a modulation vector which also has components Pernendicular to the chain axis (c-axis). The modulation is commensurate along the c-axis of the basic tetragonal structure in the case of TaTe4 and incommensurate for NbTe4. Two main sets of satellite reflections could be distinguished in electron diffraction, which are in a first-second order relationship, as established by X-ray structure refinement. Additional reflections in the NbTe4 electron diffraction pattern appear upon cooling down to liquid nitrogen temperature, although no changes of the incommensurability with temperature were observed. Physical measurements showed a metallic behaviour for both comnounds with ptype dominance above 60K. No evidence was found for the occurrence of a Peierls-transition to an insulating or semiconducting state, nor did the temperature denendence of the electric and magnetic quantities show an anomalous behaviour.

A deformation model is proposed in which nart of the transition-metal-atoms undergo displacements along the chain axis in order to form pairs and triplets.

This distortion is associated with a relaxation of the chalcogen squares.
Metastable Phases of Alumina
Authors: Dauger A. , Fargeot D. , Laval J.P.
Published: March 2011

Plasma sprayed pure alumina samples have been studied by Transmission Electron Microscopy and X–Ray diffraction. The main families of metastable forms (γ δ and θ) have been observed in as-sprayed or in annealed states. All derive from a spinel structure through a periodic antiphase boundaries mechanism, together with an ordering of vacant sites in the cationic sublattice.
Models of Long-Period Superstructures
Authors: Kulik J. , de Fontaine D.
Published: March 2011

The cause of the stability of long period superstructures is still something of a mystery. Typically, two very different models have been proposed: according to model I, the period of the superstructure (or modulation) is determined by lowering of the electronic energy resulting from the formation of a new Brillouin zone. According to model II, competing short-range interactions tend to produce long-period structures, the wavelength of which is determined by configurational entropy considerations. Model I is exemplified by the Sato and Toth theory, apparently applicable to long-period superstructures in Cu-Au, for example. Model II is exemplified by the Axial Next Nearest Neighbor Ising Model, for which a low-temperature free energy expansion has recently been given by Fisher and Selke. The latter model appears to apply to long-period superstructures in Ag3Mg.
Ordering in Binary and Ternary Alloys
Authors: Fayard M.
Published: March 2011

The most interesting topics to be solved during the next years, in the field of short-range order and of ordering transitions is the accurate determination of pair interaction parameters, or more generally interactions in the case of higher order configurations. In fact, there are a number of papers in this conference devoted to this problem. Here, I would like to emphasize two aspects of this problem.
Monte Carlo Studies of Adsorption Phenomena
Authors: Selke W.
Published: March 2011

Two different adsorption phenomena are studied using, in particular, Monte Carlo techniques: (i) Lattice gas models with competing interactions of ANNNI-type are shown to describe various uniaxial commensurate and incommensurate structures as observed in chemisorbed overlayers such as H on Fe(110) and O2 on Pd(110).

(ii) At interfaces of multi-state models (Potts, spin-i Ising models) nonboundary states are adsorbed preferably; critical properties of this “wetting” phenomenon are investigated.
Atomic Short Range Order in a Fe-Ni Invar Alloy
Authors: Cenedese P. , Bley F. , Lefebvre S.
Published: March 2011

The structural state of Fe-Ni Invar has been extensively studied. In particular, the possibility of some clustering together with short range ordering has been reported [1 , 2].
Maxwell and Van Der Waals Revisited
Authors: Aifantis E.C.
Published: March 2011

We utilize a modern continuum mechanics framework to reconsider an old problem for fluid interfaces, also addressed by Maxwell and van der Waals. We prove that their results need not be valid necessarily. This conclusion is arrived at as a consequence of questioning the existence of thermodynamic potentials and the validity of usual thermodynamic ,relations within unstable (spinodal) regions. One central result is that Maxwell's equal area rule needs not be valid and certain statistical models are shown to be internally inconsistent. Precise conditions for the validity of Maxwell's rule and the variational theory of van der Waals are established in terms of the coefficients defining the interfacial stress. Finally, a generalized continuum thermodynamics framework is developed which provides an alternative derivation of van der Waals variational theory and properly extends it to dynamic situations. However, other possibilities exist which allow a thermodynamics of fluid interfaces not necessarily restricted by the conditions of Maxwell and van der Waals. The results of the paper could be viewed as a convincing argument to utilize this framework (with the necessary modifications) to interpret more complex phenomena of phase transformations.
Electronic Structure and Ordering in Transition Alloys and Compounds
Authors: Ducastelle F.
Published: March 2011

Starting from a simple but realistic description of the electronic structure of transition alloys, we show that it is possible to understand why some type of ordering is preferred to another. Similar arguments are shown to apply to interstitial compounds.
A Mechanism for Particle Coalescence, Grain Growth and Twin Formation During Annealing of Gold Particles in an Amorphous Silica Matrix
Authors: McGinn J. , Greenhut V.A. , Tsakalakos T.
Published: March 2011

Direct evidence was obtained for the coalescence of discrete gold particles (∼;lO0 nm) surrounded by a continuous amorphous silica matrix during annealing at 900°C. The particles were found to form high angle boundaries as coalescence occurred. Subsequent annealing revealed that grain growth occurred with relatively rapid elimination of high angle grain boundaries. The coalesced particles became approximately spherical in shape and seven particle morphologies could be distinguished. A majority of particles showed either no defect structure or conventional f.c.c. twins. In more limited cases, a small area of high angle grain boundary, usually of coincidence lattice type, was observed which accommodated intersecting twins. A single self-consistent mechanism can explain the elimination of high angle boundaries and all the various twin structures observed. The mechanism is based on Gleiter's [l] model for grain boundary migration with twin structures resulting from growth accidents on the migrating high angle boundary.
Coarsening of Extremely Small Particles in the Cu-Ni-Fe System
Authors: Gust W. , Wachtel E. , FrüHauf B. , Predel B.
Published: March 2011

By means of magnetic methods, in the Cu-jo.7a/o Ni-1. 6 a//o Fe alloy the Ostwald ripening of extremely small particles has been studied. It appears that the magnetic methods are very suitable for such investigations, as in addition to a high exactness, an easy way of execution is guaranteed. The chemical volume diffusion coefficients determined for 673 to 873 K are characterized by the Arrhenius parameters Do = 1.81 × 10−5 m2/s and ΔH = 219.4 kJ/mol.
Computer Simulation of Grain Growth in Polycrystalline Aggregates
Authors: Anderson M. P. , Srolovitz D. J. , Grest G. S. , Sahni P. S.
Published: March 2011

The physical and chemical properties of materials are determined in part by microstructure. Grain orientation and size in polycrystalline aggregates affect, for example, yield strength, catalytic efficiency, chemisorption, physisorption, fracture and a host of other properties. The final grain morphology is often determined by thermal processing, addition of a second phase, deformation, etc. However, in order to effectively tailor the microstructure for specific applications, the mechanism and kinetics of grain growth must be known. Unfortunately, present theories predict grain growth kinetics (1–3) which often differ from experimental observation, have little predictive ability with respect to microstructure and are not easily generalized to account for experimentally controllable factors.
Relation Between the Electrical Resistivity and the First Stages of Precipitation
Authors: Vigier G. , Pelletier J.M. , Merlin J.
Published: March 2011

Recent theories make it possible to think that electrical resistivity measurements could provide quantitative informations about the microstructural evolution. These theories are tested by studying the influence of the measuring temperature TM. Our experiments show that when spherical G.P. zones appear in AI-Zn and Al-kg no influence of TMis observed, while the formation of plate-like G.P zones in Al-Cu and Cu-Be alloys induce electrical variations function of TM. This morphology effect is roughly predicted by the theoretical models buv supplementary parameters must be taken into account to obtain a quantitative explanation of experimental results.
Neutron Scattering Study of Dynamical Scaling Properties in the Relaxation of Short-Range Clustering and Decomposition of Cuni(Fe) Alloys
Authors: Aalders J. , Van Dijk C. , Radelaar S.
Published: March 2011

A neutron scattering study on a number of CuNi(Fe)-alloys has been undertaken in order to test some recent theories on the relaxation of short-range clustering and decomposition with special emphasis on scaling properties. The structure functions S(k,t), have been determined for samples, which had undergone a large number of different heat treatments resulting in different thermodynamic states. The analysis of the structure functions during relaxation of short-range clustering showed that even in these cases the assumption of small concentration fluctuations made in Cook's theory for spinodal decomposition is not always valid. Moreover, for the relaxation of short-range clustering and the very early stages of decomposition no scaling behaviour could be found. However, for some particular cases close to the spinodal, after a certain transient time, the structure function could be transformed into a time-independent function.

The main conclusion is that the kinetics of relaxation above as well as within the miscibility gap show similar characteristics, but there is no universal description applicable to all different regimes.
Simulated Martensitic Transformations
Authors: Clapp P.C. , Rifkin J.
Published: March 2011

Molecular dynamic computer simulations have recently provided some very graphic portrayals of how model lattices can surmount nucleation barriers of various types and accomplish certain kinds of first order displacive transitions. A survey of the different two-and three-dimensional transformations observed to date, along with relevant details about inter-atomic potential, potencies of nucleating defects and preferred transformation
paths will be presented. The simulation of other types of first order transformation in solids, such as melting and allotropic transformations will be touched upon. Methods by which a close representation of martensitic transformations in real systems should be obtainable will be discussed.
The Effect of Order on the Martensitic Transformation in Fe3Pt
Authors: Dunne D.P. , Stobbs M. , Kennon N.F.
Published: March 2011

The lattice parameter and Curie temperature of austenite in Fe3Pt increase sharply on ordering for times up to 2 hr at 650° C. These effects, together with a rapid decrease in the martensitic transformation temperatures, are interpreted in terms of increased short-range order. The onset of thermoelastic reversibility of the martensitic transformation is associated with the development of a significant volume fraction of long-range ordered domains.
On the Martensitic Transformation in V3Si
Authors: Weiss F. , Demolliens O. , Madar R. , Couach M. , Senateur J.P.
Published: March 2011

We demonstrate unambiguously that V5Si3 inclusions coherent with the V3Si matrix induce at low temperature a tetragonal distorsion of V3Si.

a) Polycrystalline samples are transforming only if they are two phased V3Si - V5Si3,

b) the oriented eutectic V3Si - V5Si3 undergoes a cubic - tetragonal distortion under 60K.

c) A transforming V3Si crystal is obtained by solid state epitaxy of a V5Si3 layer on the (001) plane.

These experiments support very well our idea that the distorsion can be driven by internal stresses in the samples, related to silicon over stoichiometry.
Laser Hardening of Steel
Authors: Bengtsson B. , Li W-B. , Easterling K.E.
Published: March 2011

Changes in microstructure due to phase transformation are measured for a number of laser-hardening treatments in both an Nb-microalloyed and a medium carbon steel. These measurements are correlated with theoretical predictions of laser thermal cycles and good agreement is obtained. The kinetics of the ferritic/pearlitic→austenite transformation are also discussed.
Thermodynamical Behaviour of Quartz Around the Transitions Between α, Incommensurate and β Phases
Authors: Dolino G. , Bachheimer J.P.
Published: March 2011

Recently an intermediate incommensurate phase has been found around 846 K in a small temperature range of 1.3 K between the usual α and β phases of quartz. In the neighborhood of these transitions most physical properties show drastic variations which has remained a puzzle. We shall present some measurements of the heat capacity Cp and of thermal expansion coefficients αi which present very large variations in the incommensurate phase. These divergences can be related by Pippard-Garland relations in the 3 phases. Furthermore in the low temperature α phase this result can be explained by the existence of a macroscopic order parameter η related to SiO4 tetrahedra, and varying as predicted by the Landau theory of 1st order phase transition. While in the high temperature phases (β and incommensurate) η vanishes, it takes a finite value in α phase, increasing continuously upon further cooling. However at the microscopic level, the discontinuity is reduced by the existence of the incommensurate phase, which corresponds probably to modulated tilting of SiO4 tetrahedra.
The use of Electron Microscopy and Electron Diffraction in the Study of Phase Transformations
Authors: Amelinckx S. , Van Tendeloo G. , Van Landuyt J.
Published: March 2011

In recent years a separate branch of electron microscopy, which can conveniently be termed “Solid State Electron Microscopy” has evolved into a discipline of its own, which makes use of a set of techniques such as

- diffraction contrast electron microscopy

- high resolution transmission electron microscopy

- selected area electron diffraction

- convergent beam electron diffraction

- optical diffraction of high resolution electron micrographs

and which allows to provide information on a wide variety of solid state phenomena. With the availability of microscopes with a resolution equal to interatomic distances its field of application has recently been extended greatly.
Lattice Dynamics and Network Dynamics Calculations on Vibrational Modes of Lithium Borate Glasses
Authors: Deppe J. , Balkanski M. , Wallis R. F. , Massot M.
Published: March 2011

The central force nearest neighbor model for glasses is used to discuss the Raman and infrared vibrational data for the family of lithium doped borate glasses B2O3 - xLi2O. The addition of the dopant is shown to cause local structural changes, including the transformation of three-coordinated borons to four-coordinated ones. An extremely simple structural model for the glass gives good qualitative agreement with experiment. The results of lattice dynamics calculations fall within the allowed frequency band limits predicted by network dynamics. The success of this model illustrates the importance of short range order on the vibrational spectra of covalently bonded solids.
Nmr Studies of Polymer Electrolytes
Authors: Greenbaum S.G. , Pak Y.S. , Adamic K.J. , Wintersgill M.C. , Fontanella J.J.
Published: March 2011

The results of several investigations of solvent-free polymer electrolytes by nuclear magnetic resonance (NMR) spectroscopy conducted by the authors and other groups are reviewed. 23Na NMR spectra of a wide variety of amorphous polymer electrolytes are characteristic of the second-order quadrupole broadened central ± 1/2 transition with a distribution of quadrupole couplings. The temperature dependence of the linewidth is similar across a wide range of materials, and highlights the importance of polymer segmental motions above the glass transition temperature to ion mobility. Strong cation-anion interactions in poly(propylene oxide) complexes are indicated by measurements of mobile ion concentrations and, in some cases, the observation of salt precipitation at elevated temperature.
Study of Polymer Electrolyte Dynamics by Impulsive Stimulated Light Scattering
Authors: Halalay I.C. , Nazri G-A. , Nelson K.A.
Published: March 2011

The polymer electrolyte PEO:LiBF4 at concentrations 2:1, 4:1, 8:1, 16:1 and pure PEO (in methanol as solvent) was studied in the temperature range 220–340 K using impulsive stimulated light scattering, a time-delayed four-wave mixing (‘transient grating’) technique. We observed longitudinal acoustic waves (the transient density response) and thermal diffusion (leading to the decay of the steady-state density response). The speed of sound and acoustic attenuation rate were determined in the frequency range 57 MHz - 1.4 GHz. From the decay of the steady state response the thermal diffusivities were detremined.
Exafs and Thermal Studies of Post-Preparative Treatments of Divalent Polymer Electrolyte Films
Authors: Latham Roger J. , Linford Roger G. , Pynenburg Rory , Schlindwein Walkiria S.
Published: March 2011

Taking PEOn:ZnBr2 films as benchmark systems, results are discussed for EXAFS and conductivity studies on the corresponding chloride and iodide systems, and DSC results are also compared with PEOn:NiBr2 samples. The polymer electrolyte films used in this study were cast from water. In each case attention was focused on the behaviour resulting from three different preparation/storage regimes, referred to in the text as U, D50 and D140. The high temperature drying regime D140, produces high melting crystalline complexes in all cases but the low temperature regime, D50, invokes more complicated behaviour. Nickel systems are imperfectly dried by the latter regime whereas it appears possible to dry zinc systems completely in a manner that avoids high melting complex formation. EXAFS reveals that the local structure in the zinc halide systems depends more on anion type than concentration. An interesting minimum is observed in the conductivity against composition curves for the zinc systems subjected to the low temperature drying regime; this can be explained by an ion-pair conduction mechanism.

Long term (1 year) dry storage of the benchmark system caused comparatively little change in the properties.
In Situ X-Ray Diffraction and In Situ X-Ray Absorption Spectroscopy for Investigation of Intercalation Batteries: Application to the Alkaline H+/γ-MnO2 system.
Authors: Lévy-Clèment C. , Mondoloni C. , Godart C. , Cortès R.
Published: March 2011

This paper presents applications of in situ X-ray diffraction and absorption techniques to the study of H+/MnO2 alkaline batteries. The two complementary in situ techniques are described. Investigation of the electrochemical insertion and deinsertion of H+ has been made through its influence on the evolution of the crystallographic structure of γ-MnO2, while investigation of the transfer of e has been undertaken through the variation of the oxidation state of the manganese during the discharging and charging process of a battery. New insights in the understanding of the mechanisms of proton insertion and charge transfer into γ-MnO2 are discussed.
Montmorillonite (MONT) Complex and their Application
Authors: Wenhai Yu , Wanyu Liu
Published: March 2011

Montmorillonite(Mont) has been proved to be a kind of very promising solid electrolyte in recent years because of its good electric properties. It can be composed by polymer to prepare a mont-polymer complex which has high ionic conductivity and excellent plasticity. The film made of mont-polymer complex with room temperature ionic conduction has been used in solid state battery as solid electrolyte. It may be a new type of function material with futher application.
Mixed Ionic Electronic Conduction in Solids
Authors: Riess I.
Published: March 2011

Chemical diffusion in mixed ionic electronic conductors (MIECs) occurs via ambipolar motion. It finds many applications which are reviewed. The partial ionic and electronic conductivities are also of interest. Methods for determining these quantities are reviewed emphasizing problems with the Hebb-Wagner polarization method and suggesting an alternative method. The use of MIECs for probing simultaneously the ionic and electronic driving forces and for producing p-n junctions is discussed.
Microstructural Design and Conductivity and Ultrasonic Activation in the Ion Exchange of H3O+ and NH4+β"-Aluminas
Authors: Nicholson Patrick S.
Published: March 2011

H3O+- and NH4 + -A12O3 polycrystals have been conductivity-optimised by eliminating metastable grain-boundary phases (NaA1O2 and MgAl2O4) and texturing the microstructure. The grain-boundary conductivity is considerably improved (up to 5x10-5(Ω-cm)-i) from 10–6 (Ω-cm)-l). The dc-field-assisted, H3O+ ion exchange process for K+/Na+-β"-A12O3 in HAC has been accelerated by cyclic switching of the dc field (cycle = 3secs) or injecting ultrasonic energy. The formeroubles the steady-state ion-exchange current to 12 μA by dispersing the HAC/electrolyte, interfacial, H3O+ polarisation layer. The ion-exchange currentefficiency is not improved from 0.15. The ultrasound (23 MHz) markedly shortens the time to complete ion-exchange (400 hrs.vs. > 700 hrs), more than doubles the final ion-exchange current (360 μA.vs. 150 μA) and improves the ion-exchange current efficiency to 0.24. These results are interpreted in terms of ionic “activation ”in the electrolyte. Evidence is presented of a mixed-cation-effect in H3O+-K-β"-AI2O3.
Electrochromic Properties of Nickel Oxide Electrodes
Authors: Pileggi R. , Scrosati B. , Passerini S.
Published: March 2011

Nickel oxide sputtered electrodes can undergo a reversible lithium intercalationdeintercalation process which is accompanied by a net electrochromic effect. The characteristics of this type of electrode and the mechanism of the related electrochromic process are discussed on the basis of results obtained by cyclic voltammetry and optical transmittance. The results show that nickel oxide is electrochromically activated by insertion of lithium in the oxide structure. The lithium intercalation process may be promoted by cyclic voltammetry or, more extensively, by polarizing cathodically the nickel oxide electrode in a non-aqueous electrolyte containing a lithium salt. Activated nickel oxide electrodes are of considerable interest for the realization of new types of efficient solid state electrochromic windows..
High Frequency and Solid State NMR Techniques for the Study of Ionically Conductive Glasses
Authors: Kennedy John H. , Zhang Zhengming , Eckert Hellmut
Published: March 2011

The synthesis, characterization, and electrochemical properties of sulfide-based lithiumglasses are briefly reviewed. Of the many probes that have been used to study these materials two will be discussed in more detail, namely solid state NMR and conductivity measurements at high frequency (106-109 Hz). Solid state NMR is particularly useful in understanding the network structure of these glasses and the role coformers play in modifying the glass network. Electrochemical measurements, including impedance at high frequency, give information concerning dynamic processes, and show that someof these glasses are potentially useful in miniature and thin-film solid state batteries.
A Study of Ag+-Ion Dynamics in Ag2S-GeS2 Glasses
Authors: Owens A.P. , Pradel A. , Ribes M. , Elliott S.R.
Published: March 2011

A quasi-elastic neutron scattering (QENS) study of the Ag+-ion diffusion coefficient, D, in glassy (Ag2S)0.5 (GeS2)0.5 has been performed. The results indicate that the magnitude of D is larger, and its activation energy is smaller, than the corresponding quantities inferred from measurements of the d.c. ionic conductivity. This behaviour is ascribed to the fact that QENS probes diffusive processes occurring at very high frequencies (∼1011Hz) where the magnitude of the a.c. conductivity is correspondingly larger, and its temperature dependence is less, than that of the d.c. conductivity.
Structure and Ionic Conductivity of Lithio-Borate Thin Films
Authors: Dzwonkowski P. , Eddrief M. , Julien C. , Balkanski M.
Published: March 2011

Thin films of vitreous solid electrolyte in the boron-oxide/lithium oxide system have been grown using a thermal evaporation technique. Solid electrolyte films of composition B2O3-xLi2O with 0.5≤x≤5 are obtained from a mixture of lithium metaborate and lithium oxide in good proportion. Structure and ionic conduction are studied as a function of the glass modifier concentration and process conditions. The structure is investigated by the mid-infrared absorption spectroscopyof films deposited on a silicon wafer. Comparison with bulk materials whose structures are known shows that the films have a similar structure, and exhibit the transformation of boroxol rings into triborate or di-triborate units as the Li2O concentration increases. The ionic conductivity has been studied over wide frequency and temperatureranges using the complex impedance spectroscopy in a sandwiched geometry. The ionic conductivity increases with increasing Li content and exhibits a maximum value for B2O3-3Li2O.
A.C. Impedance and Transport Number Measurements of Ba6 Ta2O11
Authors: Goto Takashi , West A.R.
Published: March 2011

Ba6Ta2O11 with an oxygen—deficient perovskite—related structure, was prepared through solid state reaction of BaCO3 and Ta2O5 powders. The electrical conductivity of sintered Ba6Ta2O11 pellets was measured by a.c. impedance spectroscopy inthe temperature range between 200 and 800ºC. The conductivity at 800ºC was3.7x10-3 Ω-1 cm-1; the activation energy for bulk conduction was 0.93 eV at temperatures between 500 and 800ºC and 1.22 eV below 500ºC. The bulk conductivity was independent of atmosphere, while the grain boundary conductivity, with an activation energy of 1.08 eV, decreased as oxygen partial pressure increased. The oxygen ion transport number obtained from concentration cell measurements was 0.5 to 0.65 at temperatures from 450 to 820ºC.
Evaluation of Variously Doped BaCeO3 Ceramics as Protonic Conductors
Authors: Liu J.F. , Nowick A.S.
Published: March 2011

Nd—doped BaCeO3 is reported to be an excellent high—temperatureprotonic conductor, while the Gd—doped material is not. In order to better understand the role of different dopants, we have studied BaCeO3 doped with 5 mol% of each Nd3+, Eu3+, Gd3+, Yb3+ and Ca2+. In each case samples were treated in an appropriate gas atmosphere at 900ºC followed by measurement from 25 to 200ºC in a “frozen—in”state. Protonic conduction was deduced from the isotope effect, i.e. comparing conductivity after treatment in D2O—saturated gas with that for H20,as well as by the change between wet and dry treatments. In addition, we measured H2O uptake by observing the weight change between wet and dry treatments, and also carried out some galvanic cell measurements. It was concluded that, of the above dopants, only Nd and Ca give rise to appreciable protonic conduction. In the Nd case, the low activation energy of 0.54 eV is probably the proton hopping energy. On the other hand, Eu, Gd and Yb—doped materials appear to show the dominance of oxygenion conduction in the low temperature range and mixed oxygen—ion and electron—hole conductivity at elevated temperatures. The most likely reason for these differences seems to be centered on the ionic radii of the dopants.
The Effect of Sample Preparation Methods on Glass Performance
Authors: Oh M. S. , Oversby V.M.
Published: March 2011

A series of experiments was conducted using SRL 165 synthetic waste glass to investigate the effects of surface preparation and leaching solution composition on the alteration of the glass. Samples of glass with as-cast surfaces produced smooth reaction layers and some evidence for precipitation of secondary phases from solution. Secondary phases were more abundant in samples reacted in deionized water than for those reacted in a silicate solution. Samples with saw-cut surfaces showed a large reduction in surface roughness after 7 days of reaction in either solution. Reaction in silicate solution for up to 91 days produced no further change in surface morphology, while reaction in DIW produced a spongy surface that formed the substrate for further surface layer development. The differences in the surface morphology of the samples may create microclimates that control the details of development of alteration layers on the glass; however, the concentrations of elements in leaching solutions show differences of 50% or less between samples prepared with different surface conditions for tests of a few months duration.
Effects of Heat Treatment on the Microstructure of a Fully Simulated Nuclear Waste Glass
Authors: Palmiter Terese V. , Joseph I. , David Pye L.
Published: March 2011

Samples of a fully simulated nuclear waste glass under consideration for use in the West Valley Demonstration Project were isothermally heat treated and studied by scanning transmission electron microscopy (STEM). Both fully oxidized and partially reduced specimens were heat treated for 3 hours at 600°C, 700°C, 800°C and 900°C and for 45 days at 10°C above Tg (447°C -461°C) and at 10°C below TB (427°C -441°C). Microstructural features in untreated as well as the heat-treated glasses were studied using STEM. Analysis by energy dispersive spectroscopy (EDS) was used to identify the elemental compositions of the features observed.

The predominant crystalline phase present in the samples heat treated for 3 hours was an Fe3O4 type spinel with Ni and Cr substituting for some of the Fe. The spinels varied in size from 0.02 to 10.0 µm, the larger crystals present at higher heat-treatment temperatures. Long term heat treatment above Tg resulted in the formation of small iron-containing crystals ranging in size from 10 to 35 nm. Heat treatment below Tg produced no crystalline or amorphous phases.
Results from Long-Term Dissolution Tests Using Oxidized Spent Fuel
Authors: Wilson Charles N.
Published: March 2011

Two semi-static dissolution tests using oxidized PWR spent fuel specimens are being conducted under ambient hot cell conditions in Nevada Test Site J-13 well water and unsealed fused silica vessels. The test specimens were oxidized at 250°C in air to bulk oxygen-to-metal (O/M) values of 2.21 and 2.33. Following an initial 191-day test cycle, the specimens were restarted in fresh J-13 water for a second long-term test cycle. Results through the first 40 months of Cycle 2 are compared with results from similar tests at 25°C and 85°C using unoxidized spent fuel specimens.

Increased concentrations of U, Am, Cm and Np were measured in 0.4- μm filtered samples from the oxidized fuel tests compared to the unoxidized fuel tested at 25°C; Pu concentrations were not affected by the fuel oxidation state. Most of the Am and Cm, and a portion of the Pu, measured in 0.4-μm filtered samples was removed by 2-nm filtration. Fission product release results were normalized to specimen inventories and reported as fractional release. No attempt was made to normalize the data to surface area. Initial 99Tc release was greatly increased, and prolonged increases in the fractional release rates of 99Tc and 129I occurred as a result of fuel oxidation. Fractional release rates for 137Cs and 90Sr from oxidized fuel eventually decreased to levels similar to those observed with unoxidized fuel after equivalent testing times, suggesting that matrix dissolution rates normalized to fuel mass were not increased as a result of oxidation.
The Critical Condition for the Initiation of Localized Corrosion of Mild Steel Used for Nuclear Waste Package
Authors: Nakayama Gen , Akashi Mastsuna
Published: March 2011

The general corrosion rate of mild steel is so small in neutral water environments that adequately provided corrosion allowance can ensure the requirement of one thousand years’ integrity of geological disposal package of high-level nuclear wastes. In alkaline water environments, however, mild steels can passivate themselves and often undergo localized corrosion in much the same manner stainless steels do in neutral water environments. This paper describes a study of localized corrosion behavior of the mild steel conducted to assess the long-term performance of the disposal packages. The critical potentials for pitting and crevice corrosion and critical pH for general corrosion-to-passivity transition were determined for neutral and alkaline water environments. Effects of temperature, pH, and chloride and other anion concentrations on the critical potentials and the critical pH were discussed. The initiation and propagation behavior of crevice corrosion was also analyzed under potentiostatic conditions.
Near Field Performance of the Advanced Cold Process Canister
Authors: Werme Lars O. , Salo Jukka-Pekka
Published: March 2011

A near-field performance evaluation of an advanced cold process canister for spent nuclear fuel has been performed jointly by TVO, Finland and SKB, Sweden. The canister consists of a carbon steel canister as a load bearing element, with an outer corrosion shield of copper. The canister design was originally designed by TVO. In the analysis, internal (ie corrosion processes from the inside of the canister) as well as external processes (mechanical and chemical) have been considered both prior to and after canister breach. Throughout the analysis, present day underground conditions have been assumed to persist during the service life of the canister.
Modeling Geochemical Stability of Cement Formulations for use as Shaft Liner and Sealing Components at Yucca Mountain(1)
Authors: Gardiner Mark A. , Hinkebein Thomas E. , Myers Jonathan
Published: March 2011

The geochemical modeling codes EQ3NR/EQ6 were used to model the interaction of cementitious materials with ground water from the Yucca Mountain proposed nuclear waste repository site in Nevada. This paper presents a preliminary estimate of the compositional changes caused by these interactions in the ground water and in the cement-based compounds proposed for use as sealing and shaft liner materials at the Yucca Mountain site.
Application of Elasto-Plastic Model to Mechanical and Hydraulic Behavior of Buffer Material Under Water Uptake in a Repository
Authors: Fujita T. , Hara K. , Yusa Y. , Sasaki N.
Published: March 2011

Mechanical and hydraulic behavior of buffer material during water uptake in a repository is a major issue from the viewpoint of mechanical stability of engineered barriers and near-field conditions for performance assessment. This paper presents the results of hydraulic-mechanical modeling of buffer material and the simulations carried out on an engineered barrier system under water uptake.

Hydraulic behavior of compacted bentonite of buffer material was modeled as moisture diffusion. An elasto-plastic model was applied to the deformation behavior of compacted bentonite, of which swelling pressure was described by swelling coefficient under restraint condition. The hydraulic diffusivity and swelling coefficient were given based on the result of swelling tests of KUNIGEL-V1 bentonite which contains about 50 % montmorillonite. Being used this model, simulations on re-saturation behavior of an engineered barrier system were carried out for the cases of water uptake from the whole surface of both crystalline and sedimentary rock and from partial surface of opening. The results are : (1) The hydraulic and mechanical behavior of compacted bentonite can be described by a swelling-elasto-plastic model. (2) The distribution of the water content depends on the water uptake conditions. (3) The deformation of compacted bentonite and the displacement of the overpack under water uptake are negligibly small.
Coupled Thermo-Hydraulic Behavior Around Access Shaft Sealed with Backfill Material
Authors: Okamoto J. , Ishihara K. , Sawauchi Y. , Hara K. , Sasaki N.
Published: March 2011

Groundwater flow from the repository to the surface through the sealed access shaft may be induced by the heat generated from high-level radioactive waste(HLW). It is important to estimate the effect of this heat generation on groundwater flow.

This paper presents an evaluation of groundwater flow in the vicinity of an access shaft filled with a backfill material. The evaluation uses a coupled thermo-hydraulic model. According to the current design, the backfill material within the shaft will be tamped 5 to 15 times every 20 cm depth using a 60 kg vibrating compactor. The properties of the backfill material were determined from experimental results for this construction method.

A transient coupled thermo-hydraulic analysis was carried out using an axisymmetric FEM model. Two kinds of repository models were considered, one was a single layered repository located at 1000 m depth, and the other was a two layered repository located at 800 m and 1000 m depths. The access shaft of each model was located at the center of the repository.

The results show that the vertical hydraulic gradient of groundwater flow along the sealed shaft will be approximately 0.001 at a time 1000 years after closure of the repository.
Remote Measurements of Actinide Species in Aqueous Solutions Using an Optical Fiber Photoacoustic Spectrometer
Authors: Russo Richard E. , Robouch Piotr B. , Silva Robert J.
Published: March 2011

A photoacoustic spectrometer, equipped with an 85 meter optical fiber, was used to perform absorption measurements of lanthanide and actinide samples, located in a glovebox. The spectrometer was tested using aqueous solutions of praseodymium and americium ions; the sensitivity for remote measurements was found to be similar to that achieved in the laboratory without the fiber.
Development of High-Temperature Uv-Vis-Nir Spectroscopy for the Measurement of Free Energies of Complexation at Elevated Temperatures
Authors: Robouch Piotr , Grant Pat , Torres Richard A. , Baisden P. A. , Silva R. J.
Published: March 2011

We have developed instrumentation capable of measuring optical absorption spectra over a wavelength range of 200–1200 nm and a temperature range of 20–100°C. This fiber-optic based spectrometer generates data which allow the computation of metal-ligand equilibrium constants. Studies at five temperatures have been completed using praseodymium-diglycolate as a model system. Fundamental thermodynamic values (free energies, enthalpies, entropies) were obtained from the experimentally-determined stability constants.
Actinide Transport in Topopah Spring Tuff: Pore Size, Particle Size, and Diffusion
Authors: Buchholtz Ten Brink Marilyn , Phinney Douglas L. , Smith David K.
Published: March 2011

Diffusive transport rates for aqueous species in a porous medium are a function of sorption, molecular diffusion, and sample tortuosity. With heterogeneous natural samples, an understanding of the effect of multiple transport paths and sorption mechanisms is particularly important since a small amount of radioisotope traveling via a faster-than-anticipated transport path may invalidate the predictions of transport codes which assume average behavior. Static-diffusion experiments using aqueous 238U tracer in tuff indicated that U transport was faster in regions of greater porosity and that apparent diffusion coefficients depended on the scale (mm or μm) over which concentration gradients were measured in Topopah Spring Tuff. If a significant fraction of actinides in high-level waste are released to the environment in forms that do not sorb to the matrix, they may be similarly transported along fast paths in porous regions of the tuff. To test this, aqueous diffusion rates in tuff were measured for 238U and 239Pu leached from doped glass. Measured transport rates and patterns were consistent in both systems with a dual-porosity transport model In addition, filtration or channelling of actinides associated with colloidal particles may significandy affect the radionuclide transport rate in Topopah Spring tuff.
Waste Storage in the Vadose Zone Affected by Water Vapor Condensation and Leaching
Authors: Cary John W. , Gee Glendon W. , Whyatt Greg A.
Published: March 2011

One of the major concerns associated with waste storage in the vadose zone is that toxic materials may somehow be leached and transported by advecting water down to the water table and reach the accessible environment through either a well or discharge to a river. Consequently, care is taken to provide barriers over and around the storage sites to reduce contact between infiltrating water and the buried waste form. In some cases, it is important to consider the intrusion of water vapor as well as water in the liquid phase. Water vapor diffuses through porous material along vapor pressure gradients. A slightly lower temperature, or the presence of water-soluble components in the waste, favors water condensation resulting in leaching of the waste form and advection of water-soluble components to the water table. A simple analysis is presented that allows one to estimate the rate of vapor condensation as a function of waste composition and backfill material. An example using a waste form surrounded by concrete and gravel layers is presented. The use of thermal gradients to offset condensation effects of water-soluble components in the waste form is discussed. Thermal gradients may be controlled by design factors that alter the atmospheric energy exchange across the soil surface or that interrupt the geothermal heat field.

Work supported in part by U.S. Department of Energy, OHER, Contract DE-AC06-76RL0 1830
Preliminary Results of Laboratory Studies of Repository Chemistry for the Waste Isolation Pilot Plant
Authors: Brush L. H. , Grbic-Galic D. , Reed D. T. , Tong X. , Vreeland R. H. , Westerman R. E.
Published: March 2011

The design-basis, defense-related, transuranic (TRU) waste to be emplaced in the Waste Isolation Pilot Plant (WIPP) could, if sufficient H2O and nutrients were present, produce as much as 1,500 moles of gas per drum of waste. Gas production could pressurize the repository to lithostatic pressure (150 atm) and perhaps higher.

Anoxic corrosion of Fe and Fe-base alloys and microbial degradation of cellulosics are the processes of greatest concern, but radiolysis of brine could also be important. The proposed backfill additives CaC03, CaO, CuSO4, KOH, and NaOH may remove or prevent the production of some of the expected gases. We describe these processes and present preliminary results of laboratory studies of anoxic corrosion and microbial activity.