bluuebunny/crossref_metadata_2025_split huggingface dataset:
Short Range Order Strucrures in Y-Pr-Ba-Cu-O System Studied by X-Ray Absorption Fine Structure (XAFS) Techniques
Authors: Kao Y.H. , Krol A. , Ming Z.H. , Lin C.S. , Soo Y.L. , Gu C.X. , Yang I.S. , Tsuei C.C. 
Published: March 2011

ABSTRACTLocal structure around the constituent atoms in the compound system Y1-xPrxBa2CU3O7-y has been investigated by means of x-ray absorption fine structure (XAFS) techniques. By comparing the local structure in the compound x=1 with its counterpart x=0, the XAFS results provide a direct evidence that Pr has replaced Y in the material. The nearest-neighbor structure in the CuO2 planes seems to remain intact as × varies from 0 to 1, indicating that substitution of Pr for Y does not disturb the local distribution of holes in the CuO2 planes. We suggest that local disorder and distortions in the second-neighbor bonding configuration could be responsible for suppression of superconductivity with increasing Pr content in the system.
Oxygen Diffusion in La2−Xsrxcuo4−Y
Authors: Opila Elizabeth J. , Tuller Harry L. , Wuensch Bernhardt J. , Maier Joachim 
Published: March 2011

ABSTRACTOxygen diffusivities in La2−xSrxCuO4−y (x×0, 0.07, 0.09, 0.12) single crystals were measured using an is 02 exchange technique followed by SIMS profiling. An interstitial diffusion model is proposed to explain the decrease in the oxygen diffusivity with increasing strontium content.
Oxygen In-Diffusion and Out-Diffusion in Single Crystal Yba2Cu3O7−δ
Authors: Lagraff John R. , Han Pengdi , Payne David A. 
Published: March 2011

ABSTRACTIsothermal resistance measurements were used to monitor oxygen indiffusion and out-diffusion in single crystal YBa2Cu3O7−δ from 600-780°C. Measurements on single crystals reveal that oxygen out-diffusion is intrinsically faster than in-diffusion, which is contrary to the rates observed in other studies for polycrystalline ceramics. Oxygen out-diffusion measurements suggest two different mechanisms, one above an4 one below ˜680°C,which have activation energies of 1.57±0.06eV and 1.00±0.04eV, respectively. Calculation of relaxation times for oxygen in-diffusion into initially tetragonal YBa2Cu3O7−δ suggest a single mechanism from 600-780°C with an activation energy of 1.16±0.06eV.
Nonstoichiometry, Defect Structure and Energetics in T (La2MO4; M=Cu, Ni) and T′ (Nd2CuO4) Structures
Authors: Dwivedi Anurag , Cormack A. N. 
Published: March 2011

ABSTRACTAtomistic computer simulation is performed to investigate the extent and nature of nonstoichiometry in La2CuO4, and La2NiO4. Results suggest anion Frenkel to be the dominant intrinsic defect in both compounds. Spontaneous oxidation is predicted for La2NiO4 but not for La2CuO4; however, both compounds are more easily oxidised than reduced, as opposed to Nd2CuO4, a superconducting compound with same generic formula. Oxidation takes place via accommodation of oxygen interstitials; however, the possibility of metal vacancies can not be completely ignored in La2CuO4. There is only one favorable oxygen interstitial site which is same in both the compounds La2MO4 (M=Cu, Ni). We found a favorable oxygen interstitial site in T′ structure too. Relaxed structures around an oxygen interstitial in these compounds are reported.
Metastable Phases and Defect Microstructures in Melt-Spun Ribbons of Nb3Al
Authors: Aindow M. , Shyue J. , Gaspar T.A. , Fraser H.L. 
Published: March 2011

ABSTRACTThe phases and defects produced in a binary alloy, with nominal composition Nb-18at.% Al, have been studied using transmission electron microscopy (TEM). In addition to the equilibrium A15 phase (Nb3Al) a previously unreported Nb-rich B2 phase is present. A significant number of grow-in dislocations were observed in the A15 phase, these have b= a<100> and are predominantly screw on character. They are dissociated into two partial dislocations which bound a stacking fault according to the reaction;<100> → > 1/2 <100> + SF + 1/2 <100>The habit plane of the fault is shown to be {012}. These observations are compared with previous studies performed on the isostructual compound V3Si. The consequences of the observed dissociation for the plastic deformation of Nb3Al are discussed.
Comparison of Superstructure Phases of Rb2ZnBr4 Type Compounds
Authors: Hogervorst A.C.R. 
Published: March 2011

ABSTRACTNine crystal structures, taken from literature, are compared with each other and with the room temperature structure of Rb2ZnBr4. Compared are the modulation functions and some pronounced local distortions. It appears that the ten structures have strikingly similar cooperative rotations of the anion tetrahedra.
Modulated Phases and Domain Structure in Double Niobates With Tetragonal Tungsten Bronze - Like Structure
Authors: Manolikas C. 
Published: March 2011

ABSTRACTThe domain structure and the commensurate - incommensurate transition of some niobates, with general formula A2BNb5O15 where A = Ba, Sr or Pb and B = Na or K, are examined by using electron microscopy and electron diffraction methods. A model of the commensurate phase at room temperature is proposed and the natureof the incommensurate phase is discussed.
Electron Microscopic Study of Long Period Modulated Structures with Continuously Variable Periodicity
Authors: Colaitis D. , Dyck Van , Conde-Amiano C. , Amelinckx S. 
Published: March 2011

ABSTRACTSome systems show continuous and reversible phase transitions which are characterised by the appearance of irrational sunerlattice reflections with a position that shifts continuously and reversibly with temperature. This diffraction feature is not necessarily caused by a deformation modulation but can also originate from the reneated occurrence of planar defects with a variable “average” periodicity. The planar defects can be of different type (e.g. planes of different composition, antiphase boundaries, twin planes) as shown for the systems Ni3+xTe2, Cu3−xTe2, Cu2−S, mPbS-nBi2S3 ( > 2) and Cu 0.75VS2, using electron-microscopy and electron diffraction.
Long-Period Ordered Structures of the Au-Rich Au-Mn Alloys
Authors: Watanabe D. , Terasaki O. 
Published: March 2011

ABSTRACTChanges in the ordered structures of the Au-Mn system, existing at temperatures below 400°C, with composition have been studied in the range of 20–28 at.% Mn by high-resolution electron microscopy. The superstructures, Au4Mn, Au22Mn6, Au31Mn9 and 2d-APS(I), exist in the range of 20–23 at.% Mn. The Au22Mn6 and Au31Mn9 are the one-dimensional (ld) and two-dimensional (2d) antiphase structure (APS), respectively, based on the Au4Mn, and the 2d-APS(I) is based on the DO22 structure and consists of parallelogram and lozenge shaped domains. When Mn content increases, the Mn-Mn nearest-neighbour pairs are formed across the antiphase boundaries of the 2d-APS(I), and the structure changes to orthorhombic 2d-Au3Mn at about 24 at.% Mn. When Mn content increases further, the Mn-Mn pairs align in the <120> direction and the structure transforms continuously to the monoclinic Au5Mn2.
Two-Dimensional Antiphase Structure in The Ordered Ternary Alloy Cu-Zn-Au
Authors: Watanabe D. , Sato K. , Miida R. 
Published: March 2011

ABSTRACTOrdered structures of Cu-Zn-Au alloys were studied by electron diffraction. Two-dimensional antiphase structures exist at the compositions, Cu55Zn15Au30, Cu80-xZnxAu20 (10 ≤ x ≤ 35) and Cu85-xZnxAu15(25 ≤ x ≤ 35). The domain sizes M's measured in terms of the basic L12 cell along the two orthogonal directions are always the same, and they change from 3.4 to 1.6 as Zn content increases from 10 to 35 at.%. Based on the superstructure image of the Cu55Zn25Au20 with M=2.0 taken with high-resolution electron microscope, a structure model is derived, which explains intensities of all the superlattice spots on the diffraction pattern.
Configuration of Antiphase Domains in One-Dimensional Long Period Superstructural Alloys
Authors: Kuwano N. , Tomokiyo Y. , Oki K. , Eguchi T. 
Published: March 2011

ABSTRACTThe configuration of antiphase domains in a one-dimensional long period superstructure (LPS) was examined theoretically. As LPS is composed of two kinds of antiphase domains, the domain-arrangement is described by f(n) , where f(n) is the existence probability of n which is the number of the majority domains between two minority ones. The equations for f(n) were derived using statistical approaches or thermodynamical ones, and f(n) predicted from the equations were compared with those obtained experimentally.
An Explanation of the Influence of the Order-Disorder B2-B.C.C Transformation of the Self-Diffusion Behaviour in Alloys
Authors: Bakker H. 
Published: March 2011

ABSTRACTTheories describing the kinetics of ordered B2 and disordered b.c.c. alloys are applied to the effect of the order-disorder transition on tracer diffusion. Both tracer self-diffusion coefficients and isotope effects in βCuZn and equiatomic FeCo are considered.
The Role of Chemical Driving Force in Discontinuous Coarsening
Authors: Hillert M. 
Published: March 2011

ABSTRACTThe precipitation of a new phase sometimes results in the simultaneous growth of one of the matrix grains at the expense of another one, so called discontinuous precipitation. The two growing crystals may arrange themselves in the lamellar fashion, known from eutectoid transformations. The mathematical analysis of this diffusion-controlled reaction would be incomplete if the nature of the driving force for the matrix grain is not identified.There have been many suggestions regarding the nature of the driving force. The recent discovery that grain boundaries in a single-phase material can migrate in connection with grain boundary diffusion supports the hypothesis of a chemical driving force, acting in discontinuous precipitation.Another reaction where the chemical driving force may be important is discontinuous coarsening. The theory for this reaction is developed in sufficient detail to show the role of the chemical driving force.
Coexisting Ordering and Phase Separation in Binary Fcc Alloys
Authors: Rossiter P.L. , Lawrence P.J. 
Published: March 2011

ABSTRACTConsideration of only nearest neighbour pairwise interactions Vij in a binary alloy leads to the classification of the system as ordering (unlike near neighbours) or clustering (like near neighbours), depending upon the sign of Vij However, this simple classification loses meaning when multi-atom correlations, many-body interactions or a longer range interaction are considered. For example, the first nearest neighbour interaction may favour ordering while the second, which may be of comparable magnitude, may favour clustering. By extending the Bragg-Williams model to include second near-neighbour interactions in fcc alloys, it is shown that a miscibility gap may form in the region of the orderdisorder solvus, leading to a complicated sequence of atomicrearrangement upon slow cooling. Despite the well-known failings of the point approximation when applied to fcc alloys, the results are shown to be consistent with the unusual behaviour exhibited by some systems.
A Study of the Kinetic of Precipitation and the Morphology of Precipitates Induced by Plastic Deformation in Al-Zn Alloys
Authors: Mai C. , Merle P. , Merlin J. , Livet F. 
Published: March 2011

ABSTRACTThe influence of plastic deformation on the kinetic of precipitation and the morphology of precipitates in an Al-Zn 4.4 % at. studied by T.E.P. and SAXS is reported. Some results can be pointed out ; after a given amount plastic deformation at room temperature by tensile strength:i - the precipitates have a flat shape (instead of the spherical or ellipsoidal shape usualy observed in this alloys.ii - the precipitate volume fraction is a function of strain (ε) and strain rate (ė). For a given ė, the higher precipitate volume fraction is obtained with the higher ε. For a given ε, the lower ė the higher the volume fraction of precipitates.iii - the scattering intensities at small angle for three orientations of the sample (α =0,45°, 90° where α is the angle between the axis of tensile and the scattering vector- are different. A calculation for an anisotropic orientation of flat discs shows that precipitates have a preferential texture. The orientation is about 50° from the tensile axis.
Initial Stages of Precipitation in the Cu-Be Alloys
Authors: Pelletier J.M. , Vigier G. , Mai C. 
Published: March 2011

ABSTRACTThe clustering in Cu-Be alloys lead to large modifications of the X-ray scattering curves and to increases of both electrical resistivity and thermopower. The microstructure is investigated in the initial stages of precipitation : small clusters exist in the quenched state, but no spherical precursor precipitates are observed before the formation of plate-like G.P. zones. The evolution of the transport properties is qualitatively analyzed and the deformation effect induced by anisotropic particles is considered.
Diffuse and Small Angle Neutron Scattering Studies of Clustering and Decomposition in Electron-Irradiated Cu-Ni-Fe Alloys
Authors: Gölling H.W. , Poerschke R. , Schwahn D. , Wollenberger H. 
Published: March 2011

ABSTRACTEarlier investigations of short range clustering (SRC) and long range decomposition (LRD) in Cu-Ni alloys upon electron irradiation [1,2] have been extended to alloys containing 0.5 and 2 at.% Fe. Moreover, quenching instead of furnace cooling was applied to achieve a well defined homophase equilibrium state with a small degree of SRC. Under subsequent irradiation at temperatures between 373 K and 623 K the decomposition kinetics of the alloys have been followed by diffuse and small angle neutron scattering experiments within a momentum transfer range of 0.001 < κ(Å−1) < 8. The addition of Fe is found to extend the miscibility gap to higher temperatures. The observed scattering curves are discussed in terms of the existing models for the initial stages of spinodal decomposition, irradiation enhanced diffusion and phase stability under irradiation.
Metastable Phases Obtained by Laser Surface Melting of a Chromium High-Carbon Steel
Authors: Ramous E. , Giordano L. , Principi G. , Tiziani A. 
Published: March 2011

ABSTRACTThe power laser has been applied to the surface melting of a high-carbon alloy steel with laser operating parameters leading to structures which cannot be produced by the usual heat-treatments. The subsequent annealing of these structures has also been investigated. Optical and scanning electron microscopy, X-ray diffraction and Mössbauer spectroscopy have been used as methods of analysis.
Microstructural and Property Changes During Short-Term Ageing of Cast Austenitic Stainless Steels
Authors: Hodgkinson M. , Towers T.A. 
Published: March 2011

ABSTRACTThe Charpy ν-notch impact properties at -196°C of casts of Type 316 austenitic stainless steel have been compared, after ageing at 650°C for time periods up to 90 minutes. The impact energy of all steels depends on ageing time; the degree of response to ageing depends on original delta ferrite content, which varied from −0.5% to 5.0% in the steels studied. For steels with delta ferrite content in the lower half of this range the impact energy, during ageing, initially decreases to a minimum, subsequently rises to a maximum and finally decreases. Steels with delta ferrite contents near 5% suffer a continuous decrease in impact energy as ageing time increases.Microstructural investigation reveals, during early stages of ageing, the rapid formation of sigma phase, at the ferrite-austenite interphase boundaries. Some delta concurrently transforms to new austenite. Microfractographs indicate a change in the nature of the fracture as ageing progresses. Initially, fractures have large dimples, but as ageing progresses, a finer dimpling appears and extends in area. These dimples contain fine particles, identified mainly as MnS. The variations in impact behaviour are explained on the basis of the structural changes observed.
A Study of the Strengthening and the Production of Sigma Phase in 20–9–3 Austenitic Stainless Steel Weld Metals
Authors: Honeyman G.A. , Towers T.A. 
Published: March 2011

ABSTRACTIt is general practice to weld bullet proof steels with 20Cr-9Ni-3Mo Duplex stainless alloy. Little information is available regarding increasing the strength of these weldments or their response to time at temperatures used for heat treatments. This investigation sought to study possible strengthening mechanisms involving silicon additions and the effects of heat treating such welds at 1050°C.A 2% silicon addition gave a 16% increase in strength with approximately equal contributions from stacking fault energy, solute and second phase hardening. However, the ductility was significantly reduced by a high ferrite content. When this δ ferrite content was corrected by cobalt additions a 26% increase in strength was achieved, giving properties very similar to bullet proof steels.A 1050°C heat treatment programme showed rapid sigma phase formation from δ ferrite but the process was reversed on further heating. This phenomenon was attributed to alloy migration as the weld microstructure approached equilibrium, the hardness of the alloys followed the variation in δ ferrite content being at their heightest at the beginning and end of heat treatment.
Phase Diagrams for Incommensurate Systems
Authors: Toledano P. 
Published: March 2011

ABSTRACTPhase diagrams, for systems undergoing one or several incommensurate and lock-in transitions, are discussed in the framework of the Landau theory of phase transitions. It is shown that their essential features can be deduced from the explicit forms of the free-energy density ø and the k-dispersion of the coefficient α(→k)of the quadratic contribution of the order-parameter components in ø. Two families of phase diagrams are distinguished depending on symmetry considerations.
The Semi-Conductor ⇌ Metal Transition in Tin
Authors: Smith R.W. , Vnuk F. 
Published: March 2011

ABSTRACTIt is well known that silicon, germanium and other diamond-cubic semi-conductors may transform to a metal when a pressure of the order of 100 kilobars is applied. This renders the detailed study of the transformation experimentally difficult. Grey tin transforms to the more common (white) metal allotrope at room temperature and pressure and so provides a means of studying readily this type of transformation. This paper describes the influence of pressure on the transformation characteristics of tin and dilute tin-germanium alloys.
Melt Spinning and Phase Transformations of V2CrA11-xBx and Ti3Nb6Mo3Si4 Alloys
Authors: Smith B.S. , Smith R.A. , Clapp M T. 
Published: March 2011

ABSTRACTMelt spinning was used to rapidly quench V2CrA11-xBx and Ti3Nb6Mo3Si4 alloys. Melt spinning had very little effect on the crystal structure of the V2CrA11-xBx alloys. However, a new (NbTiMo)3 Si A–15 phase was found by rapid quenching of the Ti3Nb6Mo3Si4 alloys; the lattice parameter was 5.08 Å. Melt spinning increased the Vickers microhardness values of the V2CrA11-xBx alloys from 500 to 750, and of the Ti3Nb6Mo3Si4 alloys from 1000 to as high as 1675. Melt spinning increased the superconducting transition temperature of the Ti3Nb6Mo3Si4 alloys from 1.9 to 3.4K.
Electronic Energy Bands in γ-InSe with and without Intercalated Lithium
Authors: Costa P. Gomes Da , Balkanski M. , WALLIS R. F. 
Published: March 2011

AbstractThe effect of intercalated lithium on the electronic band structure of the γ-polytype of InSe has been investigated using a tight-binding method. The energy bands of the pure polytype were calculated and the results compared with previous work. The modifications of the energy bands produced by the introduction of one lithium atom per unit cell were calculated for the lowest potential energy position of the lithium atom in the Van der Waals gap between layers. The results for the changes in the smallest and next-to-smallest direct band gaps are compared with experimental data. An interpretation of a photoluminescence peak produced by lithium intercalation is given.
Electrochemical Properties and Applications of Ionically and Electronically Conducting Polymers
Authors: Croce Fausto , Panero Stefania , Scrosati Bruno 
Published: March 2011

AbstractVarious types of polymeric materials with enhanced electrical properties have been characterized recently. Many of these conducting polymers are of specific interest in solid state electrochemistry and in solid state ionics since they act as novel electrode and electrolyte materials. Indeed, these materials are currently used as improved polymer electrolytes and polymer electrodes for the development of advanced-design electrochemical devices. However, there are still some problems which prevent the wide utilization of these conductors. In this paper we attempt to identify the nature of these problems and discuss their possible solutions.
Factors Controlling Ionic Conductivity of Plasticized and Non-Plasticized Crosslinked Polyether Electrolytes
Authors: MacFarlane Douglas R. , Hey Jeffrey M. , Forsyth Maria 
Published: March 2011

AbstractA series of elastomeric (urethane crosslinked) polyether electrolytes have been prepared in order to investigate the influence on conductivity of crosslink density, length of uninterrupted polyether chain, number of side chains and plasticizer content. Crosslink density was found to only weakly influence conductivity, but had the expected major effect on elastic modulus. Increases in uninterrupted polyether chain length were also found to enhance conductivity. The number of side chains (acting as an internal plasticizer) was not found to have a marked effect on conductivity within the range studied. The highest room temperature conductivity observed in these non-plasticized elastomers was 3 × 10-5 Ω-1 cm-1. Addition of a low molecular weight plasticizer such as tetraglyme was found to markedly increase the conductivity and lower Tg. The highest room temperature conductivity observed in 50% plasticized elastomeric materials was 10-3 Ω-1cm-1.
MD Studies of Transport in Polymer-Salt Complexes: A Progress Report
Authors: Forsyth M. , Payne V. A. , Ratner M. A. , Leeuw S. W. De , Shriver D. F. 
Published: March 2011

AbstractMolecular dynamics simulations performed on highly concentrated Coulomb/solvent systems are used to help interpret the transport mechanism in polymer ionics. Using simple Coulomb and Lennard-Jones forces among the ions and a solvent model of a fixed dipole contained in a spherical solvent particle, we investigated the nature of ion pair formation and stability. For a model NaI system, we find that ion pairs decrease with increase in solvent dipole moment or temperature. The latter observation is at variance with experimental results on polymer electrolytes, probably because of entropy terms that do not occur with our simple solvent molecule.
Mixed Divalent Polymer Electrolytes
Authors: Cole Michael , Latham Roger J. , Linford Roger G. , Sheldon Mark H. 
Published: March 2011

AbstractSome features of interest for divalent polymer electrolytes are described. Attention is focussed on two contrasting roles for cations: providing chemical cross-links within the polymer matrix and offering a source of mobile charge carriers. The possible merits of using mixtures of two types of cation, one type for each role, is discussed. Alternative mixed salt systems containing two anions with a common cation are considered. Another class of mixed polymer electrolyte systems involving two divalent cations in conjunction with two monovalent anions is also examined in the context of illustrating competitive anion-cation interactions within the polymer matrix by EXAFS local structure techniques. Results for the systems PE015:ZnI2/Mg(CIO4)2, PEO15:ZnI2/Mg(CF3SO3)2, PEO15:CaI2/ZnI2 and PEO15:CaI2/CaBr2 are discussed.