bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymer Electrolytes: Hopping, Domain Structures and Frequency-Dependent Conductivity
Authors: Ratner Mark A. , Nitzan A.
Published: March 2011

The dynamic bond percolation model was developed to deal with dynamic disorder, treating ion mobility by a percolation model in which the assignment of any site-to-site jump as allowed or forbidden changes on a timescale related to the local reorganizational dynamics of the polymer segments (the renewal time). Here we discuss the special cases of highfrequency spectra and partially crystalline electrolytes. At high frequencies, the present hopping model yields unphysical behavior (frequencyindependent response); we trace this back to the incorrect treatment of short-time dynamics, and show how it can be corrected. For partially crystalline materials, we show that a rollover feature in the spectrum, in the microwave range, can be expected when ions are trapped in isolated regions of high conductivity, such as amorphous pockets in largely crystalline PEO.
Composition Dependent Ionic Conductivity in ß''-Alumina
Authors: Rohrer C. Lane , Farrington G. C.
Published: March 2011

Molecular dynamics simulations were carried out in an attempt to reproduce and explain the differing composition dependencies of the ionic conductivities of Na(I)-Ba(II)- and Na(I)-Sr(II)- ß' '-alumina. Impedance spectroscopy measurements of Na1.67-2xBaxMg0.67Al10.33O17, where x = 0.0 - 0.835, showed a distinct minimum in the conductivity when x = 0.67, or 80% exchange of Ba(II) for Na(I). Evidence for mobile cation ordering at that composition was seen in the simulation results and the general change in conductivity with Ba(II) content was reproduced rather well. The results of a similar experimental study of Na(I)-Sr(II)-ß' '-alumina did not show a minimum in the conductivity, but our simulations incorrectly predicted the Sr(II) system to behave in the same fashion as the Ba(II) system. Possible reasons for this discrepancy are suggested, including problems with transferring potentials between oxides and the influence of absorbed water on the experimental results.
Molecular Dynamics Study of the Lattice Vibration Contribution to the Frequency-Dependent Dielectric Constant of Lithium Iodide
Authors: Deppe J. , Balkanski M. , Wallis R. F. , McGurn A.
Published: March 2011

A molecular dynamics simulation has been performed on the crystal lithium iodide, LiI. A rigid ion potential was used with parameters fit to thermal expansion, isothermal compressibility, lattice energy and the frequency of the transverse optical mode at the zone center. The current-current correlation function has been calculated at T = 200K and 400K, and from this the absorption and dispersion have been obtained. Anharmonic broadening is observed at the higher temperature.
Band Structure and Electronic Properties of Lithium Phosphide Li3P
Authors: Seel Max , Pandey Ravi
Published: March 2011

Ab initio Hartree-Fock band structure calculations have been performed to study the electronic structure of Li3P in the hexagonal P6/mmm crystal structure. The total energy, band structure, density of states, and charge densities are computed. The band structure is very similar to that calculated for lithium nitride with a small indirect gap between Γ and K of 2 eV. However, the charge distribution in Li 3P is more anisotropic with a greater ionicity in the x-y plane compared to the c direction. This is also supported by a large calculated core level split of 6.5 eV of the Li ls core bands.
Characterization of Polyiodide-Polymer Complexes by Resonance Ranan Spectroscopy
Authors: Forsyth Maria , Loye Hans Conrad Zur , Lerner Michael , Tipton Andrew , Degroot Donald C. , Kannewurf Carl R. , Ratner Mark , Shriver Duward F.
Published: March 2011

The addition of I2 to PPO/MI and MEEP/MI complexes, where M - Na or Li, PPO - poly(propylene oxide), MEEP - methoxyethoxyethoxy phosphazene results in ohmic conductivity. Even in the absence of the metal iodide salt, high conductivities are observed in the polymer/I2 complexes. The presence of polyiodides in all cases is indicated by a Raman band at 170 cm.-1 The width of this peak is found to depend on the concentration of iodine and correlates with increasing conductivity at higher I2 concentrations. An additional feature of the polyiodide complexes is the apparent lack of dependence of conductivity on polymer flexibility as indicated by Tg. In most polymer electrolytes, the conductivity depends upon the glass transition, Tg, with conductivity dropping rapidly at T < Tg. By contrast, the polyiodides show only a small inflection in the conductivity around Tg and substantial conductivity below that temperature. Apparently charge transport dynamics are only weakly coupled to the dynamics of the host polymer. Variable temperature Raman spectroscopy has been employed to investigate the low temperature behavior of polyiodides in PPO/MIn systems.
Raman Study of Free Volume Effects on Ion Pairs in Polymer Electrolytes
Authors: Torell L. M. , Schantz S. , Jacobson P.
Published: March 2011

Ion associations are demonstrated from Raman spectra of the anion symmetric stretch in NaCF3SO3 and LiCF3SO3 containing salt polymer complexes based on PPO and siloxane modified PPO. The observation of increasing amount of ion pairs with increasing molecular weight and temperature can be explained by an entropically driven process. The entropy effect includes contributions from several factors related to transient cross-linking via the cations, conformational entropy of the polymer chains, and free volume dissimilarities between the solvated ions and the macromolecules.
Some Battery Applications of Solid Electrolytes in Japan
Authors: Takahashi Takehiko
Published: March 2011

In Japan, some micro-batteries using solid electrolytes, such as silver ion, copper ion and lithium ion conductors are now under development for applying them to micro-devices, integrated-circuits and very-large-scaleintegration. For these purposes, inorganic crystalline and glassy electrolytes as well as polymeric electrolytes have been developed. For electric energy storage batteries, sodium ion conductors such as beta- or beta"- alumina have been developed as the electrolyte. A 1 MW sodium-sulfur battery demonstration power plant is to be constructed in Japan by the fall of 1991. To the fuel cell applications, oxide ion conductors or hydrogen ion conductors have chiefly been tried to be used, though solid electrolyte fuel cells are now at an early stage of development in Japan. Further, an AMTEC system for thermal energy to electrical energy conversion using beta•- alumina is under development in Japan. In this review paper, these battery applications of solid electrolytes in Japan are described briefly.
Mechanism of the Charge Transport in Intercalated Compounds Application of Optical and Potential Electrochemical Spectroscopies
Authors: Julien C.
Published: March 2011

Layered compounds are known to be among the best host structures to practice lithium intercalation chemistry. Besides geometrical aspects which play an important role but are now quite well understood, this paper emphasizes the mechanism of the charge transfer upon intercalation. Electrochemical and optical spectroscopies associated to transport measurements are used for the investigations of the electronic modifications involved in the charge transfer in lithium intercalated compounds. A selection of appropriate materials is discussed. Optical spectroscopies such as photoluminescence, Raman scattering and far-infrared reflectivity show that free-carrier density and electron mobility change drastically. A good agreement is obtained with the data measurements carried out by transport experiments.
Proton and Electron Transports in a Typical Intercalation Compound : Graphite Hydrogenosulfate
Authors: Harrach Ahmed , Metrot Andre
Published: March 2011

"Overcharging" of pure stage graphite hydrogenosulfate i.e charging of graphene layers with expulsion of H+from the intercalate layer is modelized by transmission lines which agree quite well with A.C Impedance measurements. The meaning of the apparent Diffusivity Da= 12/3 R1C1is discussed as significant of the displacement of H+/e− holes pairs along the blocking interface separating graphene and intercalate layers.
X-Ray Diffraction and Scanning Electron Microscopy Studies of Molybdenum Trioxide Prepared by Thermal Oxidation of Electrodeposited Molybdenum Sulfide
Authors: BÉLanger Daniel , Laperriere Guylaine , Preda Michel
Published: March 2011

Scanning electron microscopy and X-ray diffraction have been used to characterize the transformation of electrodeposited molybdenum trisulfide thin film and powder to molybdenum trioxide. Scanning electron microscopy shows that the formation of molybdenum trioxide is accompanied by an enhancement of the surface area of the film as the relatively smooth molybdenum trisulfide is converted to molybdenum trioxide displaying a platelet structure. X-Ray diffraction revealed that amorphous molybdenum sulfide is converted to polycrystalline molybdenum oxide upon heating in air above 400°C. The observed diffraction peaks obtained when molybdenum sulfide was heated at 400°C for 15 min. correspond fairly well with those of orthorhombic molybdenum trioxide. However, when the molybdenum sulfide powder was heated at 400°C for a period of only about 2 min., additional diffraction peaks were observed. The latter can be attributed to monoclinic molybdenum dioxide.
Solid State Synthesis of Double Molybdates of Potassium and Lanthnones and their Conductivity Behaviour
Authors: K. Suba , M.R Udupa , Y. Syamasundara Rao
Published: March 2011

Double molybdates, KLn(MoO4)2 and K5Ln(MoO4)4 have been synthesised utilising the solid state reactions of KIO3 Ln203 and MoO3 (Ln=La,Gd,Dy) in appropriate mole ratios, employing thermal analysis techniques. The solid phases have been characterised by IR, XRD studies and magnetic measurements. The d.c. electrical conductivity values of the two molybdates measured in the temperature range 373–623K are found to increase with rise in temperature. This observation together with the calculated jump activation enthalpies and the supposed ‘layered’ type structure with the loosely held K+ ion between the layers support the ionic conductivity mechanism in these samples.
Insertion of Oxide Clusters and Poly (Phenylene Vinylene) in MoO3 by Ion Exchange
Authors: Nazar L.F. , Yin X.T. , Zinkweg D. , Zhang Z. , Liblong S.
Published: March 2011

AxMoO3(H20)y has been shown to undergo substantial exfoliation of the layer structure in water wheen A = Li. Although extensive exfoliation of the Na form is not observed, sufficient swelling occurs to enable the insertion of large polyoxycations of Al, Ga, Zr, Ti and Cr between the layers of MoO3 by ion exchange with colloidal dispersions of NaXMoO3. This represents the first such "pillaring" reactions for MoO3. Interlayer expansions are observed to range from 7 to 14Å in these materials. In some cases, the orientation of the oxide cluster between the layers can also be determined by 1D electron density mapping. We have also shown that this method can be applied to the insertion of conductive polymers via incorporation of a water-soluble precursor polymer. The sulfonium ionomer precursor of poly (p-phenylene vinylene) has been intercalated in MoO3, to form a novel polymer/oxide layered structure. Data for the heat-treated [PPV]32MoO3 films show an order of magnitude increase in conductivity over that of pristine NaxMoO3.
Study on the Striitiires, Electrical, Properities of the Multicrystal Multiphase Material Li2Mo2-xWx06
Authors: Wanqiu Cui , Zhiqi Shen , Debao Zhou
Published: March 2011

The multicrystal multiphase ceramics material. Li2Mo2Wx06, with high conductivity is prepared. By XPD, EDX graph, IR and ESR spectra, it's determined that the samples are composed of two phases.

Li2MO1-xWx04 and MoO2. The electrical properties are studied by AC admittance bridge and comptex impedance cpectroscopy. The ionic conductivity increases and conducted activation energy decreases with the tungsten content increasing. The micro-structure model. and the ionic conducted mechanism are given in this paper.
Vanadium Oxides as Host Materials for Lithium and Sodium Intercalation.
Authors: West K. , Zachau-Christiansen B. , Jacobsen T. , Skaarup S.
Published: March 2011

A number of vanadium oxides can function as host materials for the insertion of lithium and sodium. These materials are of interest as they can be utilized as electrodes in high capacity secondary batteries.

Although most of these systems are not thermodynamically stable over the entire composition interval spanned by the inserted ion, the kinetic stability of the vanadiumoxygen lattice is sufficient to ensure reversible operation at temperatures below 200 - 300°C. However, after transgression of the reversible composition interval some electrode materials exhibit characteristic changes in the voltage vs. composition curves. Depending on the guest/host system the phase formed can be either a new crystalline host phase, or an amorphous, highly defect material characterized by a smooth emf curve.

The materials studied were predominantly of two-dimensional nature: Vanadium pentoxide and its molybdenum substituted analogue, which have layerlike structures due to some of the V--O bonds being long and weak, and a series of layered trivanadates. Even in their highest oxidation state the latter host structures contain an amount of interlayer alkali metal ions, balancing the otherwise strong electrostatic repulsion between adjacent oxygen layers.
Lithium Insertion in La2NiO4+y
Authors: Várez A. , Amador U. , Morán E. , Alario-Franco M.A.
Published: March 2011

A series of lithium inserted La2NiO4+y has been prepared by the soft chemistry route with n-butyllithium at room temperature.

The insertion leads to a lowering in symmetry, from the tetragonal K2NiF4 type to an orthorhombic structure.

Neutron diffraction experiments show that as in stoichiometric La2NiO4.00 the inserted material is antiferromagnetic.

Complex impedance measurements indicate it to be an ionic conductor in the temperature range extending from 60 to 300°C.
A Defect Equilibrium Treatment of Selected Transport Phenomena in Solids
Authors: Crouch-Baker Steven
Published: March 2011

Some aspects of the thermodynamic and transport - related properties of binary solid electrolyte phases are discussed in terms of the associated defect behaviour. In particular, the close relationship between results obtained from an asymmetric polarization experiment and the relevant defect equilibrium diagram for the phase under study, is emphasized.
Defect Interactions in Partially Ionic Nonstoichiometric Oxides: A Monte Carlo Investigation.
Authors: Tetot R. , Nacer B. , Massobrio C. , Masmoudi O. , Boureau G.
Published: March 2011

We investigate the nature of the interactions between defects in partially nonstoichiometric oxides and their rôle on some thermodynamic and transport properties.
Some Biassing Effects at the Electrode—Glass Interface
Authors: Doi Akira
Published: March 2011

Informations concerning electrical biassing effects on a medium are derived, usually, from the electrodes. Therefore, we frequently encounter phenomena which are peculiar to the electrode—medium interface(s), besides those due to bulk properties. In this report naive aspect on intrinsic biassing effects at the interfaces was presented first; then, as one of extrinsic origins, the mechanism of silver injection into glass from the silver anode was discussed.
Structural and Electronic Transitions in AgReO4 Under Pressure
Authors: Vassiliou John K. , Otto Jens W. , Porter Richard F. , Ruoff Arthur L.
Published: March 2011

The behavior of AgReO4 under pressure has been studied in a diamond anvil cell. The equation of state determined by synchrotron radiation shows considerable change in compressibility with increasing pressure. X-ray and Raman scattering show a first-order phase transition from the scheelite to an as yet undetermined structure at 13 GPa. Changes in both the internal and external Raman active modes suggest a change in Re coordination. Optical transmission experiments demonstrate that the energy gap in the scheelitephase decreases at the rate of 75 meV/GPa. There is a small jump in the energy gap at 13 GPa, probably related to the structural transition. AgReO4 remains aninsulator to at least 47 GPa.
A Novel Fast Lithium—Ionic Conductor.
Authors: Moreno-Real L. , Ramirez-Cardenas T. , Bruoue S. , Martinez-Lara M. , Ramosbarrado J.R.
Published: March 2011

The lithium derivatives from anhydrous niobium (Y) phosphate were made through NbOPO4.H20 and LiCl by solid state reaction at 200 ºC and subsequentannealed at 500ºC. The solid with the highest lithium content, exhibits the maximum conductivity of all materials prepared. The electrical conductivity of this solid ranges from 10-10 Ω-1 cm-1 at 373K to 3.62.10-3Ω-1cm-1 at 683K.
Preparation and Discharge Characteristics of Solid Redox Polymerization Electrodes Employing Disulfide Polymers and Copolymers.
Authors: Lerner M. M. , Visco S. J. , Ue M. , Doeff M. M. , Dejonghe L C.
Published: March 2011

Recent work in our laboratory on polymeric organodisulfides has shown these materials to perform well as positive electrodes in solid-state batteries. The polymeric materials have been named solid redox polymerization electrodes (SRPE's) due to the reversible polymerization/depolymerization reaction that occurs on charge/discharge of the electrode. The cell reaction for SRPE-based cells can be described fora simple case as, 2n M + (SRS)n = n M2SRS, where M is an alkali metal (LiNaK) and R is an organic group. In the broader sense SRPE's can have more than two S groups per monomer R unit, and are reversible to other monovalent and divalent metals. In thefully charged state SRPE's consist of polydisulfide polymers and are depolymerized on discharge by scission of sulfur-sulfur bonds, leading to the formation of dithiolate salts in the fully discharged cell. SRPE's are easy to synthesize, are air stable, and should be very inexpensive in bulk quantities. Depending on the redox potential of the polydisulfide and reaction conditions, manydisulfides can be copolymerized by oxidizing a mixture of dithiols, x HSRSH + y HSR'SH + (x+y) l2 = (SRS)x(SR'S)y + 2(x+y) HI, allowing modification of the physical and/or redox properties of the SRPE's. A series of simple aliphatic dithiols including (HSCH2CH2SH), (HSCH2CH2OCH2CH2 SH), and (HSCH2CH2SCH2CH2SH) have been oxidized to polydisulfides and mixtures of the dithiols have been copolymerized. All of the resulting polymers and copolymers were evaluated in solid-state lithium cells, with some of the new materials demonstrating high levels of performance. The utilization of available capacity in the positive electrode was observed to be independent of electrode thickness for a number of SRPE's at loading levels up to 45% by weight. At 90°C, relatively thick positive electrodes based on (SCH2CH2S)n have been discharged to surface capacities of over 20 coulombs/cm2 at a current density of 0.5 mA/cm2. The discharge profiles for most of the aliphatic polydisulfides are exceedingly flat at slightly over 2 volts versus lithium. Although other polydisulfides such as those derived from the dithiazoles exhibit higher cell voltages, the low equivalent weight of materials such as (SCH2CH2S)n [46 g/equiv] and the low cost of such polymers indicates a potential for commercial application.
Theoretical Aspects of Non-Debye Relaxation in Ionic Conductors
Authors: Dieterich Wolfgang , Loehle B. , Petersen J. , Stiller O.
Published: March 2011

Tracer diffusion as well as collective transport properties of ionic conductors are investigated within a lattice-gas model of charged particles. Results obtained from Monte Carlo simulations support the conclusion that the interplay of Coulomb-interactions among diffusing ions and structural disorder in the material provides a general mechanism for non-Debye relaxational effects commonly observed by experiment.
Mineralogical, Textural and Compositional Data on the Alteration of Basaltic Glass From Kilauea, Hawaii to 300°C: Insights to the Corrosion of a Borosilicate Glass Waste-Form
Authors: Smith David K.
Published: March 2011

Mineralogical, textural and compositional data accompanying greenschist facies metamorphism (to 300°C) of basalts of the East Rift Zone (ERZ), Kilauea, Hawaii may be evaluated relative to published and experimental results for the surface corrosion of borosilicate glass. The ERZ alteration sequence is dominated by intermittent palagonite, interlayered smectite-chlorite, chlorite, and actinolite-epidote-anhydrite. Alteration is best developed in fractures and vesicles where surface reaction layers root on the glass matrix forming rinds in excess of 100 microns thick. Fractures control fluid circulation and the alteration sequence. Proximal to the glass surface, palagonite, Fe-Ti oxides and clays replace fresh glass as the surface reaction layer migrates inwards; away from the surface, amphibole, anhydrite, quartz and calcite crystallize from hydrothermal fluids in contact with the glass. The texture and composition of basaltic glass surfaces are similar to those of a SRL-165 glass leached statically for sixty days at 150°C. While the ERZ reservoir is a complex open system, conservative comparisons between the alteration of ERZ and synthetic borosilicate glass are warranted.
Effects of Composition Variations on Microstructure and Chemical Durability of West Valley Reference Glass.
Authors: Buechele A. C. , Feng X. , Gu H. , Muller I. S. , Wagner W. , Pegg I. L.
Published: March 2011

Glasses suitable for high-level nuclear waste vitrification must meet a number of requirements including processability, durability, and phase stability. Our new data indicate that the West Valley Reference 5 composition meets these requirements: it is phase stable over the expected range of melter temperatures and residence times, and only minimal (<2 vol %) secondary phase formation, consisting predominantly of iron-group spinels, is expected in the canister cooled glass. Leach tests have shown that the durability of Reference 5 is significantly less sensitive to spinel formation than the earlier Reference 4. However, natural process variations during production will result in a range of glass compositions around the nominal composition. In this paper we report on the effects of composition changes around Reference 5 on the phase stability upon heat treatment and the consequent effects on chemical durability. Since variations in the waste-stream levels of most major components can be accommodated by adjusting the quantities of the glass-forming additives we focus here on a group of components for which this is generally not the case: Ca, Ce, Cr, Mn, Ni, S, and Fe. While many of these components are present at below 1 wt % they could have potentially significant indirect effects on product durability due to enhancement of secondary phase formation. The results provide a data base to support broad (≥300%) tolerance ranges to variation of levels of most of these components. Viscosity data are also reported.
Key Parameters of Glass Dissolution in Integrated Systems
Authors: Vernaz Etienne Y. , Godon Nicole
Published: March 2011

Leaching cells were designed to test the alterability of nuclear waste glasses under conditions closely simulating an actual geological repository. This paper summarizes the results of twenty long-duration tests simulating a variety of storage conditions. The effects of the backfilling materials, the canister, glass cracking and crystallization, a activity and the nature of the host rock are discussed. Moreover, an experiment has been in progress for over seven years in a granite medium; after three years the corrosion rate dropped to about 2 × 10−3 g m−2 d−1, and is sustained only by the water renewal due to sampling at regular intervals. These results constitute a valuable data base on R7T7 glass alteration in geological media at 90°C. Glass alteration mechanisms described in pure water appear to be applicable to a hard rock medium. In clay and salt, however, considerable work remains to be done before environmental factors can be taken into account in an overall dissolution model.
Simfuel Dissolution Studies in Granitic Groundwater at 25°C
Authors: Sandino Amaia , Casas I. , Ollila K. , Bruno J.
Published: March 2011

The dissolution of a non-radioactive chemical analogue of spent nuclear fuel (SIMFUEL) has been studied as a function of two different synthetic groundwaters at 25°C. The cumulative release of U, Mo, Ba, Y and Sr is presented after 170 days of total leaching time.

The results obtained show the potential usefulness of SIMFUEL to ascertain the kinetics and mechanisms of dissolution of the minor components of spent fuel. In the case of Sr, a good correlation is found with the dissolution of this minor component measured in spent fuel leaching experiments.
High-Temperature Annealing of Natural UO2+x
Authors: Janeczek J. , Ewing R. C.
Published: March 2011

Four powdered samples of natural UO2+x (uraninite) were annealed in a reducing atmosphere up to 1200°C. The initial unit cell parameters ranged from ao=0.5463 to 0.5385 nm. Small amounts of UO2.25 occur in all samples after annealing. Annealing curves show the effects of recovery of point defects in the oxygen sublattice, ordering of U4+ and U6+, vacancy migration in the cation sublattice, and second order phase transformations. The difference in the annealing behavior of UO2+x with x < 0.15 as compared to x = 0.25 between 400 and 700°C is due to ordering of U4+ and U6+. Density increased after annealing except for one sample in which a large number of cavities (1–2 μm in size) formed. Oxidation and chemical composition have a more dramatic effect on the structural state of natural UO2+x than self-irradiation caused by a-decay damage.
Repassivation Method to Predict Long Term Integrity of Low Alloy Titanium for Nuclear Waste Package
Authors: Tsujikawa Shigeo , Kojima Yoichi
Published: March 2011

Long term corrosion resistance is evaluated for G-2 and G-12 titanium as a candidate of the high-level nuclear waste packages. The repassivation potential for crevice corrosion, ER, in comparison with the well known spontaneous potential, ESP, of a metal passivated in given environment, allows conclusions to be drawn whether it performs “permanent” or does not. This repassivation method is extended to determine critical conditions in terms of NaCl concentration and temperature for specimens kept at an electrode potential which is more noble than ER and is included in ESP ranges. Thus obtained NaCl concentration - temperature - crevice corrosion map could predict critical conditions for the titanium used in geologic formations.
Hydrogen Evolution From Corrosion of Iron and Steel in Intermediate Level Waste Repositories
Authors: Grauer R. , Knecht B. , Kreis P. , Simpson J.P.
Published: March 2011

The production of hydrogen from the anaerobic corrosion of iron or steel is an important issue in low/intermediate level nuclear waste repositories where large quantities of iron and steel (e.g. as drums and reinforcing steel) accompany the waste.

Most of the iron in intermediate level repositories is in a cemen-titious environment. A review of the literature on the corrosion of iron and steel at high pH values, in particular in cementitious environments, points to hydrogen evolution rates between 22 and 220 mmol(H2)m−2a−1. There is some indication that the rates might be lower but for normal engineering applications there has been no practical need to demonstrate this, and hence a lower rate cannot be assumed on current evidence.

In the present work a volumetric method was used to measure hydrogen evolution rates over several thousand hours under conditions relevant to intermediate level waste repositories. The sensitivity of this method (0.4 mmol(H2)m−2a−1) is sufficient to detect hydrogen evolution rates lower than those predicted for iron and steel in concrete.

Hydrogen evolution rates in highly alkaline cement pore water were below 0.4 mmol m−2a−1 and almost 1 mmol m−2a−1 for a pore water representative of an aged cement; no decrease was observed even after 12000 h. In general hydrogen evolution rates in alkaline media were observed to take several thousand hours before approaching a constant rate.
Corrosion of Copper-Based Materials in Irradiated Moist air Systems
Authors: Reed Donald T. , Van Konynenburg Richard A.
Published: March 2011

The atmospheric corrosion of oxygen-free copper (CDA-102), 70/30 copper-nickel (CDA-715), and 7% aluminum bronze (CDA-613) in an irradiated moist air environment was investigated. Experiments were performed in both dry and 40% RH (@90°C) air at temperatures of 90 and 150°C. Initial corrosion rates were determined based on a combination of weight gain and weight loss measurements. Corrosion products observed were identified. These experiments support efforts by the Yucca Mountain Project (YMP) to evaluate possible metallic barrier materials for nuclear waste containers.
Thermodynamic Modelling and Aqueous Chemistry in the CaO-Al2O3-SiO2-H2O System
Authors: Atkinson A. , Hearne J. A. , Knights C. F.
Published: March 2011

The chemical properties of the CaO-Al2O3-SiO2-H2O system are important for understanding and predicting the behaviour of Portland cements in cementitious wasteforms and radioactive waste repositories. Solids of known average composition in this system have been synthesised by the co-hydrolysis of mixed alkoxides. The solids have been equilibrated with water at 25°C and the composition of the aqueous phase characterised. A thermodynamic model for the system has been developed by extending an earlier model of solid solutions in amorphous gels to include aluminium compounds. The model accounts for most of the experimental data and predicts that the main influence of aluminium is to form a hydrogarnet solid solution of general composition C3AH6−2xSx The model can be used to predict the chemistry of hydrated cements and the interaction of cements with groundwaters.
The Effects of Calcite Solid Solution Formation on the Transient Release of Radionuclides from Concrete Barriers
Authors: Smith Robert W. , Walton John C.
Published: March 2011

The wealhering of concrete by carbonation causes the formation of calcite solid solutions that can significantly improve concrete as a barrier to the migration of divalent radionuclide cations. Example calculations for 90Sr and 60Co indicate that release rates from carbonated concrete are five orders of magnitude lower than for intact, unweathered concrete and that the thin carbonated zone is a significant sink for these radionuclides.
The Effects of Moisture Content, Salinity and Temperature on the Load-Bearing Capability of a Dense Clay-Based Backfill
Authors: Cheung Steven. C.H. , Gray M.N. , Yong R.N. , Mohamed A.M.O.
Published: March 2011

To predict the mechanical performance of earthen backfill in a nuclear fuel waste disposal vault, the effects of temperature and moisture content on the backfill load-deformation characteristics must be known. Modified California Bearing Ratio (CBR) tests were used to obtain these data. The results show that the load-bearing capability of the backfill is not likely affected by water salinity. The load-bearing capability decreases with increasing temperature and water content or decreasing dry density. The effects of temperature, dry density, and moisture transport processes on load-bearing capability were found to be relatively small compared to those of moisture content. Under the expected Canadian vault environment, the backfill should retain sufficient bearing capacity to satisfy its mechanical design function, which is principally to limit expansion of swelling buffer material.
Modelling Studies of the Sorption of Uranium and Plutonium in the far Field of A Nuclear Waste Repository
Authors: Bond K.A. , Haworth A. , Sharland S.M. , Smith A.C. , Tweed C.J.
Published: March 2011

Models of the transport of sorbing radioelements through geological materials have been developed. These models couple a surface-complexation model of sorption processes with transport simulations in the CHEQMATE code. The chemical model has been shown to reproduce trends observed in batch sorption experiments. This approach may ultimately be used to investigate possible limitations to the use of models using simple Kds in repository safety-assessments. The main aim of the study reported in this paper is to increase confidence in the use of the coupled models. Simulations of through-diffusion experiments of uranium with London clay and plutonium with sandstone are presented. In both cases gluconate is present, as a simulant of organic degradation products of cellulose likely to be present in a low- or intermediate-level waste repository.
Influence of Micro Environments and Microorganisms on the Transport Properties of Redox-Sensitive Elements (E.G. Technetium)
Authors: Brühl Hanskarl , Pekdeger Asaf , Winkler Andreas
Published: March 2011

In laboratory experiments immobilisation of Tc under oxic conditions was observed. The transport behaviour of redox-sensitive elements is not only controlled by the geochemical “frame conditions” which can be measured within the macro environment. Immobilisation behaviour of Tc strongly depends on micro environments and on microbial metabolism. Micro environments which may develope on the mineral surfaces can detoriate the mobility of Tc, furthermore the fixation of Tc is influenced by microbial activities.
Characteristics of Migration of 85Sr and 137Cs in Alkaline Solution Through Sandy Soil
Authors: Ohnuki Toshihiko
Published: March 2011

Characteristics of the migration of 85Sr and 137cs in a solution of pH 12 through coastal sandy soil have been investigated by both column and batch tests. Desorption behaviors of the 85Sr and 137Cs by the sandy soil in both column and batch tests were examined by sequential extraction techniques, in order to study difference in the adsorption behavior of the 85Sr and 137Cs under dynamic (column) and static (batch) conditions. The dominant components of the sandy soil to the adsorption of the 85Sr ancj 137Cs were tested in batch tests.

The adsorption of the 85Sr by the sandy soil was a function of pH, while that of the 137Cs was independent of pH of the solution. Most of the 85Sr was reversively adsorbed with the sandy soil under both static and dynamic conditions. Approximately 85 percent of the 137Cs was irreversibly sorbed by the sandy soil in the column test, which was greater than that in the batch test. The desorption behaviors of the 137Cs adsorbed by kaolinite and by sericite resembled that of the sandy soil. Most of the 85Sr was reversively adsorbed by kaolinite, chlorite, sericite, FeOOH, Ti02 and Mn02 which is similar to the desorption behavior of 85Sr by the sandy soil. The distribution coefficients of the 85Sr for kaolinite, FeOOH, Mn02 and Ti02 were larger by several times than those for the chlorite and the sericite.

Therefore, the dominant components of the sandy soil contributing to the adsorption of 137Cs would be sericite, and those of 85Sr would be kaolinite, FeOOH, Ti02 and Mn02.
Immobilization of Radioactive Strontium in Contaminated Soils by Phosphate Treatment
Authors: Kim K.H. , Lee S.Y. , Ammons J.T.
Published: March 2011

The feasibility of in situ phosphate- and metal- (calcium, aluminum, and iron) solution treatment for 90Sr immobilization was investigated. Batch and column experiments were performed to find optimum conditions for coprecipitation of 90Sr with Ca-, Al-, and Fe-phosphate compounds in contaminated soils. Separate columns were packed with artificially 85Sr-contaminated acid soil as well as 90Sr-contaminated soil from the Oak Ridge Reservation. After metal-phosphate treatment, the columns were then leached successively with either tapwater or 0.001 M CaCl2 solution. Most of the 85Sr coprecipitated with the metal phosphate compounds. Immobilization of 85Sr and 90Sr was affected by such factors as solution pH, metal and phosphate concentration, metal-to-phosphate ratio, and soil characteristics. Equilibration time after treatments also affected 85Sr immobilization. Many technology aspects still need to be investigated before field applications are feasible, but these experiments indicate that phosphate-based in situ immobilization should prevent groundwater contamination and will be useful as a treatment technology for 90Sr-contaminated sites.
Diffusion Porosity and Diffusivity of Radionuclides In Granitic Rocks. Part I: Diffusion Interfaces Around Permeable Fractures
Authors: Pirhonen Veijo O. , Front K. , Pitkänen P.
Published: March 2011

This paper addresses the problem of evaluation of radionuclide retardation in fractured rocks. Pore space around permeable fractures was examined by means of the fracture profiling technique which comprises porosity measurements and chemical analyses along the profiles perpendicular to the fracture surfaces.

Scanning electron micrographs show that the examined interfaces contain microfractures and tube-like diffusion channels. These are most frequent within 2 - 4 cm from the surface of the examined fractures. Porosity and chemistry of these interfaces are fracture specific. It is possible that diffusion into the rock matrix is restricted into the interfaces around the permeable fractures.
Flow Path Mineralogy: Its Effect on Radionuclide Retardation in the Geosphere
Authors: Ticknor Kenneth V. , Kamineni D. C. , Vandergraaf T. T.
Published: March 2011

The geological formation surrounding a nuclear fuel waste disposal vault is an important barrier to the migration of radionuclides to the biosphere. Field investigations of plutonic rocks in the Canadian Shield have shown that open, water-bearing fractures form the main potential migration paths for radionuclides through the geosphere. Any interaction between the radionuclides in solution and the minerals in these fractures will retard radionuclide movement towards the biosphere. The minerals lining these open fractures are products of rock alteration and have themselves been subject to varying degrees of alteration over time. Accordingly, the fracture mineralogy is quite different from the bulk mineralogy of the intact host rock.

The degree to which measured radionuclide sorption varied with mineralogy was examined by laboratory sorption studies using static batch techniques and autoradiography combined with petrography. Fission products (Sr, Cs) and actinides (U, Np, Pu) were among the radionuclides studied. It was found that most fracture-infilling minerals such as hematite, goethite, illite, kaolinite, chlorite, epidote, gypsum and muscovite show preferential sorption for certain radionuclides. Calcite sorbs actinides such as U, Np and Pu from solution, but not ion exchangeable radionuclides such as Cs and Sr. Quartz shows the least affinity for any of the radionuclides studied.

It is concluded that variations in the type, amount and composition of fracture-infilling minerals must be considered in the assessment of the suitability of any geological formation as a radioactive wastes disposal site.
Design and Preliminary Results of Redox Capacity Measurements of Granitic Rocks and Minerals
Authors: Pirhonen Veijo O. , Pitkänen Petteri , Takala Jukka , Arilahti Esko
Published: March 2011

A procedure for the measurements of the redox capacity of rocks and minerals is presented. Both solid and pulverized samples are used. In a preliminary test described in this paper, an oxygen loss of an aqueous solution in contact with pulverized granodiorite was measured directly on-line, with an oxygen sensor.

The increase of Fetot in the solution responded relatively well to the oxygen consumption. The maximum rate varied from 3.0 × 10−4 to 9.0 × 10−11 mol l−1 s−1 correspondingly. Oxygen loss of 0.04 mmol (O2) and iron increase of 0.1 mmol were recorded in the solution. Fe(II) reduction in the solid phase was also examined. Fe(II) was inferred to have partially dissolved during the experiment. When the system was equilibrated at the ambient conditions, the vessel was pressurized upto 100 bar with oxygen gas. Three weeks later, the additional decrease of Fe(II) in the solid phase was minimal, only 0.07 % Fe(II) was dissolved or oxidized on the rock surfaces. At this point, the Fetot in the solution, had decreased down to the background level. According to the total oxygen loss at the ambient coditions, the maximum redox capacity of the examined granodiorite (BET 1.0 m2/g) is 0.002 mmol/m2.
Gas Formation in ILW and HLW Repositories, Evaluation and Modelling of the Production Rates and Consequences on the Safety of the Repository
Authors: Besnus François , Voinis Sylvie
Published: March 2011

This paper summarizes the main gas formation mechanisms in deep radioactive waste repositories. Production rates and overall gas volumes were estimated and showed predominance of hydrogen production by anoxic corrosion and radiolysis for French wastes. Gas evolution in the near field has been modeled. First results issued from a sensitivity analysis showed desaturation of the storage cavities for a wide range of parameter values.
Microstructure and Mechanical Properties of a Single Crystal NiAl Alloy with Zr or HF Rich G-Phase Precipitates.
Authors: Locci I. E. , Noebe R. D. , Bowman R. R. , Miner R. V. , Nathal M. V. , Darolia R.
Published: March 2011

The possibility of producing NiAl reinforced with the G-phase (Ni16X6Si7), where X is Zr or Hf, has been investigated. The microstructures of these NiAl alloys have been characterized in the as-cast and annealed conditions. The G-phases are present as fine cuboidal precipitates (10 to 40 nm) and have lattice parameters almost four times that of NiAl. They are coherent with the matrix and fairly resistant to coarsening during annealing heat treatments. Segregation and non-uniform precipitate distribution observed in as-cast materials were eliminated by homogenization at temperatures near 1600 K. Slow cooling from these temperatures resulted in large plate shaped precipitates, denuded zones, and a loss of coherency in some of the large particles. Faster cooling produced a homogeneous fine distribution of cuboidal G-phase particles (≤10 nm) in the matrix. Preliminary mechanical properties for the Zr-doped alloy are presented and compared to binary single crystal NiAl. The presence of these precipitates appears to have an important strengthening effect at temperatures≥1000 K compared to binary NiAl single crystals.
Oxidation Kinetics Of Mosi2 And Mosi2/Reinforcement Mixtures
Authors: Meschter P. J.
Published: March 2011

An oxidation study of pure, dense MoSi 2 at 400-600°C and MoSi2/20 vol. % (TiB2, Al2O3, Nb) mixtures at 400–1200°C has been performed. Dense MoSi2 does not fail catastrophically (“pest”) in dry air, wet air, or oxygen, and oxidizes heavily only near 500°C. Heavy oxidation is related to the slow growth of a protective, amorphous SiO2 layer; a low rate of Mo removal as vapor species; and cracking of an initially protective Mo9O26-SiO2 layer. Pre-oxidation of MoSi2 at 1200°C prevents subsequent heavy oxidation at 500°C. MoSi2/TiB2 and MoSi2/A12O3 mixtures oxidize more slowly than MoSi2 for T < 600°C and more rapidly for T > 600°C. Protective oxides are formed on MoSi2/reinforcement mixtures except at 500°C, for which high-temperature pre-oxidation is again effective. MoSi2/Nb mixtures suffer severe mass losses upon oxidation at both 500 and 1200°C owing to rapid oxidation of the Nb and spalling of the product Nb2O5 Only the latter case poses problems for the application of MoSi2-matrix composites as high-temperature materials.
Microstructure and Mechanical Properties of Near Eutectic Β-Nial Plus α-Re Alloys Produced by Rapid Solidification and Extrusion
Authors: Mason D.P. , Van Aken D.C.
Published: March 2011

Two β-NiAl plus α -Re alloys with near eutectic composition were produced by rapid solidification and then consolidated through a powder extrusion process. Microstructures of the rapidly solidified, as-consolidated, and deformed alloys were characterized by transmission electron microscopy. Both compression and tensile properties of these alloys were determined over the temperature range of 300–1300 K. The Re additions were found to greatly enhance low and intermediate temperature yield strengths when compared to other β-NiA1 alloys. This enhancement was attributed to a combination of solid solution strengthening, precipitate hardening, and grain size refinement. Above 1200K the strength of these Re-modified alloys was comparable to the binary β-NiAl compound.
The Dislocation Structure and Deformation Mechanism of Tib2/Nial Composites
Authors: Wang L. , Arsenault R.J.
Published: March 2011

Dislocation structures in 0, 10, and 20 V% TiB2/NiAl composites have been thoroughly investigated with a 1 MeV HVEM after compression testing at 760–1000° C. Samples with 0 and 10 V% TiBl2/NiAl additions have almost identical dislocation structures which can be described as a<100> screw dislocations with extensive jogs and superjoqs. Prismatically punched dislocations were observed in all of the deformed composites and deformed samples of 20 V% TiB2/NiAl had extensive dislocation generation around the particles. Dislocation density, grain size, and the tendency for dislocation reactions or networks forming during deformation decrease as the volume fraction of TiB2 increases. Also, since a predominance of screw dislocation was observed, the rate controlling process is not likely to be dislocation annihilation or climb, but dislocation generation. The grain size refinement could play an important role in the strengthening of the composites.
LMTO/CVM and LAPW/CVM Calculations of the Nial-Niti Pseudobinary Phase Diagram
Authors: Burton Benjamin P. , Osburn Jean E. , Pasturel Alain
Published: March 2011

Linear Muffin Tin Orbital and Linearly Augmented Plane Wave calculations of equations of state were performed for observed and hypothetical ordered structures in the NiAl-NiTi system. Total energies were parameterized in both the Connolly-Williams and ∈-G approximations, and the resulting parameters were used to calculate theoretical phase diagrams by the cluster variation method. Third nearest neighbor Al-Ti pairwise interactions are predicted to be strongly repulsive, and to be a major cause of observed B2+L21 two phase fields.
Dislocation Core Structures and Mechanical Behavior of DO22 Type Alloys
Authors: Khantha M. , Vitek V. , Pope D.P.
Published: March 2011

We investigate the structures of dislocation cores in a model DO22 type intermetallic alloy in the absence of external stresses. The tetragonal distortion produces sessile configurations of superpartial dislocations even when the energies of planar faults are reasonably low. The influence of the core configurations on the mechanical behavior at low temperatures is discussed.
Calculation of Electronic Structure of Ordered and Disordered Binary (Ab) Alloys using the Lmto Parameters for Pure A And B Components
Authors: Bose S.K. , KudrnovskÝ J. , Jepsen O. , Andersen O.K.
Published: March 2011

We discuss how, in the linear-muffin-tin-orbitals (LMTO) method, the potential parameters for an intermetallic compound can be estimated from those of the constituents. For ordered alloys we illustrate the scheme by comparing the electronic density of states (DOS) obtained in self-consistent calculations with that obtained with the potential parameters transferred from the pure components. Several examples are discussed. We discuss how the scheme can be used in performing almost self-consistent calculations for disordered alloys, and present some results obtained by using this scheme with the LMTO-CPA(coherent potential approximation) method.