bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shape of α'R. Zn Rich Precipitatesin Al Zn Alloys. Effect of an Uniaxial Stress on Decomposition
Authors: Livet F. 
Published: March 2011

ABSTRACTDuring the first stages of decomposition of Al Zn alloys, spherical GP zones are observed. On further ageing of the samples, the precipitates have the shape of flat ellipsoids, the small axis of which are in the various <111> directions.We have followed such an evolution in single crystals by small angle neutron scattering. From the asymptotic behavior of the cross section, we have calculated the size (c) of the small semiaxis of the ellipsoids. We show that c is almost independent of the initial composition of our samples (5.3, 6.8, 12.1 at Zn %), independent of the other dimensions of the “α'R” precipitates and very sharply distributed around its mean value (c = 24.5 ± 2 Å at 293°C).The strain field in the matrix must clearly be involved in the limitation of the c value. We have studied the effect of a uniaxial [110] compressive stress applied during ageing. Neutron small angle experiments, carried on an Al-12.1 at % Zn single crystal show that the c value remains the same. The scattering in the [111] and [11] directions is much higher than in the [111] and [111] directions. This is mainly due to the fact that the stress favors the number of [111] and [111] type of α'R precipitates.
Electronic Excess Energy in Modulated Positive-Background Model
Authors: Yahauchi H. 
Published: March 2011

ABSTRACTElectronic excess energy of a composition-modulated alloy system at absolute zero temperature is obtained using Hohenberg and Kohn's formula (for the ground-state energy of an inhomogeneous electron gas) in a modulated positive-background model. Dependence of the electronic excess energy on the modulation wavelength is studied. Two leading terms in the excess energy are examined to elucidate the limitation of this model.
Thermoelastic Martensitic Transformations and the Nature of the Shape Memory Effect
Authors: Wayman C. M. 
Published: March 2011

ABSTRACTInvestigations of the shape memory effect in alloys forming thermoelastic martensites with various crystal structures (2H, 3R, 9R and 18R) reveal that universal behavior exists. A unified explanation of the martensite deformation processes and subsequent shape recovery is now in hand, even though the various martensites are both internally twinned and internally faulted and, in addition, have different crystal structures. In cases studied to date, an initial parent phase single crystal transforms into self-accommodating arrangements of martensite variants (plates) which are characterized by “plate groups.” Each group consists of four variants. The average shape deformation in a plate group is essentially zero.Upon stressing below the Mf temperature the martensite undergoes deformation by detwinning (2H and 3R only), variant-variant coalescence and twinning processes, and further group-to-group coalescence. The deformed specimen eventually becomes a single crystal of martensite consisting of that particular habit plane variant whose shape deformation permits maximum extension in the direction of the applied stress. The deformed martensite persists after unloading has occurred; reverse rearrangements of twins and variants do not occur. Specimens deformed below Mf regain their initial shape characteristic of the initial parent phase upon heating from As to Af, during which the single crystal of martensite obtained by stressing the 24-variant configuration transforms back to the original parent phase single crystal in a unique manner, which is basically a simple “unshearing” process. The unshearing is the essence of the memory.The two-way shape memory effect results after the initial martensitic transformation upon cooling is preprogrammed by the introduction of stresses which preferentially bias the transformation so that only a single variant of martensite forms upon cooling. The shape change of this single variant causes the characteristic spontaneous “bending” upon cooling. The characteristic “unbending upon heating is as with the conventional “one-way” shape memory effect.
Martensitic Transformation Cycling and the Phenomenon of Two-Way Shape Memory Training
Authors: Perkins J. 
Published: March 2011

ABSTRACTThe character and mechanism of two-way shape memory (TWSM) “training” has been investigated in a Cu-Zn-Al alloy by means of detailed thermomechanical evaluation and TEM observations. The progressive effects of training on the TWSM behaviour, as well as an accompanying substructural evolution, have been established. The results indicate a relationship between the substructural effects of cyclic thermoelastic martensitic transformation and the ability to exhibit TWSM. Microscopic studies reveal that as the number of cycles of thermoelastic transformation under stress increases, specific physical features develop in the parent phase submicrostructure. These take the form of dislocation structures which evolve into “vestigial” martensite markinqs. These in turn assist in the nucleation and growth of a preferred martensite plate arrangement on cooling which is similar to that induced under stress during the training cycles.
Kinetic and Thermodynamic Aspects of the Bainite Reaction in a Silicon Steel
Authors: Papadimitriou G. , Genin J.M.R. 
Published: March 2011

ABSTRACTThe bainite reaction in an Fe - 3.85 wt pct Si - 0.9 wt pct C steel is studied by several experimental techniques in the range of 250–450°C.The high silicon content prevents the formation of cementite, so that the reaction is separated to two clearly distinct stages. In the primary stage ferrite forms alone, except at temperatures lower than 310°C where some carbides precipitate in it, and austenite becomes enriched in carbon. In the secondary stage occurring only above 400°C, the enriched austenite decomposes to ferrite and an unknown silicon carbide.The microstructure, the enrichment of the austenite and the overall reaction kinetics of the two stages are studied and are found to be consistent with a displacive mechanism of the bainite reaction.A tentative model, accounting for the competition of shear and diffusion, is proposed in order to fit our experimental data.
Microstructural Changes at Elevated Temperature of γ/γ′-α(Mo) Uds Eutectics
Authors: Dirnfeld S.F. , Schwam D. 
Published: March 2011

ABSTRACTNi-Mo-Al eutectic alloys were subjected to a process of unidirectional solidification (UDS) by the Bridgman-Stockbarger technique with a view to a composite of ductile matrix containing ductile reinforcement of comparatively high strength. The microstructure after UDS consists of a γ/γ' matrix reinforced with Mo(α) fibers. The growth direction and the orientation relationships between the phases were determined by electron diffraction. In the present study, attention was focussed on phase stability after prolonged exposure at elevated temperature. Isothermal exposure of 90 min at 1250°C was followed by a mild water quench. Apart from the beneficial influence on the γ' morphology, partial transformation of the α(Mo) fibers into δ-NiMo intermetallic was observed. Replacement of the ductile α(Mo) fibers by the brittle δ-NiMo is accompanied by partial loss of facetting. Decisive evidence of this diffusion-controlled phase transformation is supplied by TEM micrographs.
Phase Transformations in Quench-Aged Zn-Al-Si Alloys
Authors: Zhu Y.H. , Savaskan T. , Murphy S. 
Published: March 2011

ABSTRACTTwo zinc-aluminium based alloys with 30% Zn and 60% Zn and small additions of silicon have been quench-aged and the phase transformations studied in relation to the hardness. It was found that the peak hardness increase is due to the formation of αm″ and α″ phases and evidence has been obtained for the transformation of these to αm′ and α′. A cellular reaction αS′→αT′+η was observed in the first stage of ageing in the alloy with 60% Zn.
Polymer Electrolytes: Hopping, Domain Structures and Frequency-Dependent Conductivity
Authors: Ratner Mark A. , Nitzan A. 
Published: March 2011

AbstractThe 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

AbstractMolecular 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

AbstractA 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

AbstractAb 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

AbstractThe 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

AbstractIon 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

AbstractIn 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

AbstractLayered 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

Abstract"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

AbstractScanning 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

AbstractDouble 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

AbstractAxMoO3(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

AbstractThe 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

AbstractA 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

AbstractA 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

AbstractSome 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

AbstractWe 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

AbstractInformations 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.