bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solid Polymers Doped with Neodymium. Complex Formation and Morphology in NdCl3 and Nd(DPM)3-Poly(Ethylene Oxide) Systems
Authors: Twomey Conor J. , Chen Shaw H. 
Published: March 2011

AbstractThe complex formation and morphology of the NdCI3—PEO system are presented together with some preliminary results on the Nd(DPM)3 \Nd—tris—2,2,6,6—tetramethyl —3,5—heptane dionate]—PEO system. Although the NdCl3—PEO complex is found to be highly hygroscopic, it is shown that residual moisture can be removed reversibly, thereby permitting the role of water in affecting the morphology of the solid to be examined. It is concluded that complexation is a competitive process between the ether oxygens on the polymer backbone and water. Under anhydrous conditions the resultant complex is amorphous at a \EO]/\NdCl3] molar ratio approximately less than ca. 8, but above this critical value the PEO in excess of the stoichiometric ratio presents a second partially crystalline phase. The glass transition temperatures were found to increase sigmoidally with increasing salt content. Despite the hygroscopic nature of Nd(DPM)3 the resultant complexes were found to be moisture resistant upon prolonged exposure to the atmosphere.
Intercalation in 3D-Skeleton Structures : Ionic and Electronic Features
Authors: Hagenmuller Paul , Delmas Claude 
Published: March 2011

AbstractThe voltage of an electrochemical cell, i.e. the difference between the chemical potentials of the two electrodes, may play the role of a sensor which allows to display the structural modifications and the physical properties. The electrochemical processes involved in an alkali metal (A) intercalation electrode emphasize the influence of the ionic and/or electronic features. The A+-lattice and A+-A+ interactions as well as electronic band-filling may lead to phase transitions or even limit the intercalation reaction.The shape of the cell voltage vs. intercalation rate curve depends on the number of vacant sites available for intercalation, the number and the oxidation state of the reducible cations, the band structure of the material and the covalency of the framework.Alkali ion intercalation in 3D-structures related to perovskite (Ln⅓ NbO3), hexagonal tungsten bronze (LiW3O9F) and Nasicon-type (AM2 (PO4)3) is discussed from that point of view.In Ln⅓NBO3 (Ln = La, Nd) (i.e. ▭ ½Ln⅓ ▭, ⅙NbO3) L1+-intercalation in various sites is related to the rare earth size.Two extra lithium atoms can be introduced into LiW3O9F in which four sites are available, but only one out of two is occupied in order to reduce the electrostatic interactions. Moreover the change in the discharge curves can be associated to the modifications with intercalation rate of the Li+-lattice interactions.Within the Nasicon derived structures of ATi2 (PO4)3 and Fe2 (MoO4)3 the intercalation process is limited by the lowest stable oxidation state of titanium or iron. In both systems the strong electronic localization leads to formation of large two phase-domains.The relevance of using 3D-intercalation electrodes in electrochemical power batteries will be discussed as far factors such as electrical behavior or absence of significant unit cell modifications of the positive electrodes during the intercalation process are essential for many cycle utilizations.
Intercalation Processes in Cobalt Substituted Nickel Oxyhydroxides
Authors: Delmas Claude 
Published: March 2011

AbstractChimie douce reactions (hydrolysis and reduction) from layered oxides : NaNiO2, NaxCoO2 and NaNil-xCoxO2 lead to numerous oxyhydroxides and hydroxides which differ by the composition of the intersheet space.According to the experimental conditions of the hydrolysis reaction, the oxyhydroxides can be unhydrated or intercalated with one or two layers of water molecules. From the most hydrated phases, the other ones can be obtained by chemical, thermal and even mechanical treatment.The reduction of Co-substituted nickel oxyhydroxides leads to hydroxides in which nickel and cobalt ions are respectively divalent and trivalent. In order to compensate the excess of positive charge in the (Ni, Co)O2 sheet, anions (OH-, CO32-, SO42-, NO3-) are inserted in the Van der Waals gap.For the highest anion amounts, well ordered α*-type materials are obtained. Water molecules are simultaneously inserted in the interslab space. Their structure is strongly related to the hydrotalcite one. When the amouit of anions in the intersheet space is not sufficient, interstratified materials are obtained. In this case the (Ni,Co)(OH)2 slabs are separated by a layer of CO32- anions and water molecules (α*-type) or by an empty Van der Waals gap (β(II)-type). The amount of α*-type planes in the structure increases with the cobalt amount. All these materials have been characterized by IR spectroscopy which allows to detect the existence of two types of O-H bonds (free in α*-type plane or hydrogen bonded in ²(II)-type plane).
Diffusion Process in LixW3O9F(1≤x≤3)
Authors: Menetrier Michel , Chang Soon-Ho , Suh Kyung-Soo , Senegas Jean , Chaminade Jean-Pierre , Delmas Claude 
Published: March 2011

AbstractThe structure of LiW3O9F is built up of a peculiar stacking of hexagonal tungsten bronze-type layers. Li can be reversibly intercalated in this material, electrochemically or chemically up to the Li3W3O9F composition.Diffusion coefficients are determined by the Honders method using Li/LiClO4-PC/Lix W3O9F cells which are discharged galvanostatically for given periods of time. This method does not require the knowledge of the Darken factor nor of the material/electrolyte contact area, which are both rather delicate to determine precisely in pratice.The evolution of D with the intercalation amount exhibits a drastic increase (by three orders of magnitude) from x = 1 to x = 1.15 and a constant and rather high value afterwards. Different sites for the preexisting lithim (x ≤ 1) and the intercalated ones are therefore expected.7Li NMR spectra have been recorded for various intercalation amounts. For x = 1, two first order quadrupolar signals are observed, corresponding to the sites of the immobile lithium ion. When lithium is intercalated (x = 1.1), another signal is observed, as well as a modification of that of the first lithium, due to intra site mobility. A more important change is observed between x = 1.1 and x = 1.2, which suggests an exchange process. For larger values of x, a single signal is observed, corresponding to mobile Li+ ions.The sites in which lithium may be intercalated and the diffusion pathways are discussed on the basis of these results.
Electrochemical Spectroscopy of Proton Intercalation in γ-Mno2
Authors: Chabre Yves , Ripert Michel 
Published: March 2011

AbstractWe have performed electrochemical studies of proton intercalation in several varieties of γ/ε-MnO2 using an original method which combines linear sweep voltammetry and potentiostatic intermittent titration technique. This technique gave for the first time a direct evidence of a two step intercalation process in the ramsdellite units of these compounds. Either 0.5 or 1 proton per manganese are accommodated in the 1×2 channels, as previously suggested by Maskell. The reversibility of these steps has been studied and is discussed in relation to the structural modifications induced by the proton intercalation.
Scanning Tunneling Microscopy and Spectroscopy of GuCl2 and CoCl2 Graphite Intercalation Compounds
Authors: Olk C.H. , Heremans J. , Dresselhaus M.S. , Speck J.S. , Nicholls J.T. 
Published: March 2011

AbstractScanning tunneling microscopy (STM) is used to visualize the structure of copper chloride and cobalt chloride graphite intercalation compounds (GICs). When the samples are biased negatively with respect to the tip, the images show details of the structure of the intercalant layers, and of its effects on the surface graphene layer. When the sample is under positive bias, symmetry properties of the uppermost graphite planes are revealed. Images of the CuCl2 stage 1 GIC display a hexagonal symmetry in which all the atoms of the graphite surface plane appear. This is in contrast to the three-fold symmetry usually seen in atomic resolution STM images of highly oriented pyrolytic graphite (HOPG), which we also observe on a reference sample of HOPG. The three-fold symmetry is attributed to the ABAB stacking of the atomic layers in HOPG. In GICs, this stacking sequence is interrupted by the layer of intercalate, so that for the stage 1 compound all carbon atoms in the plane become equivalent, and six-fold symmetry develops. For a stage 2 (CuC12 or CoCl2) GIC three-fold symmetry is expected to persist. Images of the CoCl2 stage 1 GIC, taken with the sample bias is positive with respect to the tip, display a mixed trigonal and hexagonal symmetry, and may be attributable to the fact that the surface of sample is of mixed stage.
Transport Properties and Lithium Insertion of Compounds Metal-Halogen-Chalcogenides
Authors: Julien C. , El-Farh L. , Samaras I. , Riess I. , Balkanski M. , Ziolkiewicz S. , Chevy A. 
Published: March 2011

AbstractThe transport properties and far-infrared reflectivity of BiSI, BiTel, SbTeI, Bi2 Se3 and Bi2S3 have been studied, and the results show a good agreement between the two techniques. Lithium insertion within metal-chalcogen-halogen compounds has been carried out using Li/LiC1O4-PC/MChI galvanic cells at room temperature. Electrochemical potential spectroscopy measurements show the different regimes involved in the insertion reaction.
A 207Pb NMR Study of Beta"-Alumina
Authors: Sass Bruce M. , Suits Bryan H. , White David 
Published: March 2011

AbstractWe report results of a nuclear magnetic resonance (NMR) study of lead(II) cations in β"-alumina. Measurements of line positions and spin-lattice relaxation times (T1) as a function of temperature are presented. The results show that Pb ions possess both static and dynamic disorder in low and intermediate temperature regimes, respectively. Also, a comparison is made between Lorentzian and logarithmic spectral density functions, from which we conclude that the latter provides a better fit to the dataat short correlation times (ωºτºα). The logarithmic form has been proposed to describe diffusive motion in 2-dimensional conductors.
The Structure of Salt Doped Superionic Oxide Glasses by Neutron Diffraction
Authors: BÖRjesson L. 
Published: March 2011

AbstractComparative neutron diffraction experiments have been performed on metal-halide MX (M = Ag, Li, Na; X = CI, Br, I) doped oxide glasses and their corresponding low conducting host glasses, e.g. M2O-2B2O3 and MPO3. The experiments reveal large changes in the intermediate range structure as the dopant salt is introduced, whereas the short range order of the host matrix is virtually unaffected by the dopant salts. An extra peak at anomalously low Q values (Q = 0.7-0.8 Å-I) appears in the structure factors of the silver-halide glasses which indicates the building up of a new type of intermediate range ordering with a characteristic length of 8-10 Å. The observation is tentatively ascribed to a-microscopic biphase system consisting of an expanded hosi glass network, unaffected on a microscopic scale, in which the silver-halide tends to form microclusters within the voids. In contrast, sodium- and lithiumhalides do not give rise to distinct new features in the structure factor. Instead a considerable smearing out of the first sharp diffraction peak of the host glaiss is observed. This indicates a partial breakdown of the intermediate range ordering of the host matrix. The results are discussed in relation to structure-conductivity models suggested for superionic glasses.
Studies on Ion Conducting Compounds with Cristobalite Related Structures.
Authors: Grins Jekabs , Frostäng S. , Nygren M. 
Published: March 2011

AbstractThis article summarises ionic conductivity and structural studies in the sodium—ion conducting systems NaxM'x/2M'' 2-x/2O4, 2 ≥ x ≥ 4/3 and (M',M'')(Zn,Si), (Be,Si) and (Zn,Ge). The best conductors are found at x ≈ 1.75–1.85, with conductivities in the range 10-2–10-3 (Ωcm)-1 at 600 K. They exhibit stuffed cristobalite type structures, isotypic with the structure of orthorhombic Na2BeSiO4. Based on single crystal data, the Na2BeSiO4 structure has been determined and refined, bothat 295 and 623 K. The structures of several other isotypic compounds have been refined by the Rietveld method, including Na1.8(Zn0.8.Ga0.2)MO4 with M = Si,Ge and Nal.8 Be0.8Si1.1O4. The ionic conductivity properties of the materials are discussed in relation to the obtained structural data.
Dielectric Loss in Vanadyl Pnictates
Authors: Lomax Joseph F. , Fontanella John J. , Wintersgill Mary C. , Kotarski Anthony 
Published: March 2011

AbstractThe results of audio frequency complex impedance studies for vanadyl phosphate and its hydrates (VOPO4*nH2O;n=0,1,2) are reported. Measurements were made at seventeen frequencies between 10 and 105 Hz over the temperature range 5.5-380K. Two lowtemperature features were observed and are correlated with particular water species between the VOPO4 layers. In light of chemical evidence and compleximpedance measurements on related compounds, it is speculated that VOPCO4*nH2O (Pc = P, As) can be thought of as a mixed nonstoichiometric compound [VO(HPcO4)]x[VOPcO4O4]1-x*nH2O and the solid Brϕnsted acid nature of the compound is related to proton movement between layer pnictates and intralayer waters.
Lithium Ionic Conductivity of Some Lithium Iodoles
Authors: Lewis Michael D. 
Published: March 2011

AbstractThe search for lithium ion conductors in crystalline or polycrystalline solid state ionic materials has resulted in finding a new class of compounds. Five new, stable, homogeneous compounds formed in the lithium alcohol systems, LiI—(ROH)x for R=CH3CH2OH, CH3CH2CH2OH, CH3CHOHCH3,, and CH3OH have been identified and characterized.
Oxidation State and Properties of Electrochromic Tungsten Oxide Films
Authors: Klein J. D. , Yen A. 
Published: March 2011

AbstractTungsten oxide films were deposited by reactively sputtering a metallic W target in O2Ar atmospheres. Plasma emission spectra were observed as a function of the oxygen content of the chamber inlet gas using an optical multichannel analyser. The gradual loss of W lines as the O2 content was increased to 10% was accompanied by a drastic reduction in deposition rate. Cyclic voltammetry of the films deposited on ITO-coated substrates reveals that films produced under high oxygen conditions have low charge capacities and retain substantial Li upon initial cycling. The photopic coloration efficiency increased with increasing oxygen in the inlet gas. The electrochemical and electrochromic data exhibit breaks in behavior at the 10% O2 break point defined by optical spectroscopy.
Fabrication of Carbon Fiber Reinforced Cement Composites
Authors: Park S. B. , Lee B. L 
Published: March 2011

AbstractPortland cement was reinforced by carbon fibers (CF) with various additive materials -- silica powders, superplasticizer, polymer emulsion, fly ash, and foaming agent -- for different purposes. The variables affecting the composite properties were identified. The mechanical properties -- tensile, compressive, and flexural strengths -- were determined as a function of CF loading and length of the fibers. The bulk density of the composites decreased as the fiber loading increased. The tensile strength increased with the CF loading increase but the compressive strength decreased as the fiber content in the composite increased. Increasing difficulty in dispersing CF as the fiber loading increase and the fiber length was rectified by addition of silica aggregates. The mechanical properties were improved as the size of silica aggregate decreased which also exhibited greater effectiveness in CF dispersion. Addition of a polymer emulsion, ethyl vinyl acetate (EVA) to the composite decreased the bulk density but increased tensile and compressive strengths.
High-Strength Concrete with Increased Fracture-Toughness
Authors: Glavind Mette , Aarre Tine 
Published: March 2011

AbstractThe application of high-strength concrete in practice is strongly limited by its more brittle behaviour than normal strength concrete.The present study deals with an investigation of the possibilities of increasing the fracture toughness of high-strength concrete by adding fibres. Tests are made with both normal strength concrete and high-strength concrete containing different amounts of steel and polypropylene fibres. Stress-strain curves in compression are obtained by a deformation controlled test system. The toughness is described with different toughness indexes.By using a previously proposed expression for the stress-strain curves, it is possible to make a non-linear load carrying capacity calculation for reinforced concrete beams. The results of the load carrying capacity calculation are compared with results of similar calculations made with the Danish code extrapolated to be valid for high-strength concrete.The investigation shows that the addition of especially steel fibres is effective in increasing toughness and the non-linear load carrying capacity for high-strength concrete. It is also shown that the compression strength of high-strength concrete is increased by addition of steel fibres. The results of the load carrying capacity calculation show that the Danish code cannot be extrapolated to be valid for high-strength concrete without any modifications.
A Description of the Kinetics and Mechanisms which Control the Release of Hlw Elements from Synroc
Authors: Smith K. L. , Hart K. P. , Lumpkin G. R. , McGlinn P. , Lam P. , Blackford M. G. 
Published: March 2011

ABSTRACTLeaching tests were carried out on well-characterised Synroc C specimens containing 10 wt% simulated HLW. The effect of temperature and leachant composition on the mechanisms and kinetics of leaching were investigated by leaching Synroc specimens in deionised water at 70°C and 150°C, and in silicate and bicarbonate solutions at 70°C. SEM and TEM were used before and after leaching to characterise the primary and secondary phases in and on the Synroc samples, and to describe the morphological and chemical changes which occurred. Leachants were analysed using ICP/optical emission spectroscopy and ICP/mass spectrometry.Titaniferous surface layers were observed on the surface after exposure to leachants. Analysis of the leaching data has established that these surface layers can reduce the release of HLW elements from Synroc and that variations in temperature and leachant composition can hinder or promote the formation of secondary phases.
Spent Fuel Degradation
Authors: Forsyth Roy S. 
Published: March 2011

ABSTRACTThe degradation and dissolution of spent nuclear fuel in groundwaters occurs by three partly concurrent processes: dissolution of mobile species which have migrated to the fuel rod void, grain boundary attack and matrix dissolution. Of the first two processes, both clearly dependent on the irradiation history of the fuel, the first is fairly well understood, but there is currently insufficient data on the migration of key nuclides to grain boundaries during reactor operation and their release kinetics during subsequent water corrosion to enable satisfactory modelling of this process to be performed.This paper presents results from recent experiments included in the Swedish programme which are relevant to this issue.
Phase Relations of the Uranyl Oxide Hydrates and their Relevance to the Disposal of Spent Fuel
Authors: Finch R. J. , Ewing R. C. 
Published: March 2011

ABSTRACTUranyl oxide hydrates, formed by the alteration of uraninite, are natural analogues for the long-term corrosion products of spent fuel in a geologic repository under oxidizing conditions. The uranyl oxide hydrates may be represented by the general formula:Pb-bearing hydrates require the addition of a neutral uranyl group into the structural sheet (UO2(OH)2) for each interlayer Pb ion. Distortion of the structure associated with the additional uranyl groups is reduced by replacing two structural hydroxyls with a structural oxygen and a molecular water. The general formula for the Pb-uranyl oxide hydrates is:This hypothesis explains the paragenetic sequences:1) schoepite ➛ billietite ➛ protasite ➛ bauranoite2) schoepite ➛ vandendriesscheite ➛ fourmarierite ➛ masuyite ➛ wölsendorfite3) schoepite ➛ vandendriesscheite ➛ fourmarierite ➛ ± masuyite ➛ sayrite ➛ curite, and indicates that, under relatively high pH conditions, schoepite will not be the long-term solubility-controlling phase for uranium in uranium-rich groundwaters.
Container Materials for High-Level Nuclear Waste at the Proposed Yucca Mountain Site
Authors: McCright R. Daniel 
Published: March 2011

ABSTRACTCandidate container materials for high-level nuclear waste packages to be emplaced at the proposed Yucca Mountain repository site are being considered for their long-term resistance to corrosion, oxidation, embrittlement and other kinds of degradation. Selection criteria have been established, and a method has been developed for recommending a material for advanced container design activities. An extensive compilation of the degradation phenomena for six candidate materials is complete, and further studies have begun on the degradation modes affecting additional candidate materials. Phenomenological models for predicting container degradation rates are being advanced for environmental conditions applicable to Yucca Mountain. An experimental program is underway to evaluate the susceptibility of container materials to localized corrosion, stress corrosion cracking, and enhancement of corrosion and oxidation attack by gamma radiation. Initial evaluations of container fabrication and welding processes have identified some processes that appear to alleviate some long-term corrosion susceptibility concerns.
Effect of Oxygen Transport and Resistivity of the Environment on the Corrosion of Steel
Authors: Escalante E. , Oka T. , Bertocci U. 
Published: March 2011

ABSTRACTThis study is directed at investigating the rate of corrosion and its spatial distribution that develop under conditions where transport of oxygen and conductivity of the environment are controlled over a wide range, including low conductivity as expected in the Yucca Mountain environment. The results indicate that the corrosion rate of steel is directly related to the rate of oxygen transport over several orders of magnitude, and increasing conductivity by one order of magnitude increases corrosion rate by a factor of two or three. Of greater significance is the result that indicates that as conductivity of the environment decreases, and corrosion rate decreases, the degree of localized attack increases.
Statistically Designed Lead Corrosion Experiments for Nuclear Waste Disposal
Authors: Mani Mathew P. , Krueger P.A. 
Published: March 2011

ABSTRACTThis paper describes galvanic corrosion studies of lead, a candidate matrix metal, coupled vith ASTM Grade-2 titanium, a candidate container-shell material, to determine the barrier-lifetime for a lead matrix container - one container concept considered in the Canadian Nuclear Fuel Waste Management Program. In these studies the fractional factorial statistical design of Box-Behnken was used to develop mathematical relationships between the independent variables and the corrosion rate of lead.Using the mathematical expressions derived in this study, the additional barrier-lifetime that a 25-mm-thick lead layer could provide to a titanium container, which eventually perforates by corrosion, was calculated to be at least 3500 years.