bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gamma Radiation Effects on Some Properties of YBCO
Authors: Luo L. , Zhang Y.H. , Hu S.H. , Liu W.H. , Chang G.L. , Hu W.X. 
Published: March 2011

ABSTRACTRadiation effects of polycrystalline YBCO bulk sample irradiated by 60Co γ-rays from a dose of 1x106 up to 7.5×l09 rad at room temperature on critical temperature and critical current were investigated. IR spectrum was also used to study the mechanism of the irradiation. A considerable dependence of these parameters upon irradiation dose was observed. No significant effects on critical temperature were found, but the critical current in zero magnetic field changed greatly. It shows a tendency to decrease with the increase of the irradiation dose except for a slight increase with the dose less than about 2×107 rad and no simple relations between critical currents and irradiation doses was found. A typical case is that the critical current is reduced to about 60% when the dose reaches 5×109 rad, but the dependence of critical currents on magnetic field shows that the critical currents are higher than that of the unirradiated one in the range of magnetic field higher than 100 Gauss and decrease more slowly in magnetic field compared with the unirradiated one. The results indicate that the defects produced by γ-ray irradiation are benefit to flux pinning in higher fields. IR spectra analysis reveals that the intensity of the peak responsible for the Cul-O1 chain vibration is decreased, indicating that the bond of the Cul-O1 may be partly broken through collision process of the Compton electron produced by the γ-ray. This effect probably gives rise to decrease of the critical currents.
Substitution and Defect Chemistry of La-Cu-O Systems
Authors: Gai P. L. , Kunchur M. , McCarron E. M. 
Published: March 2011

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

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

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

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

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

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

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

ABSTRACTX-ray and electron diffraction studies have shown that NbTe4 and TaTe4 exhibit a deformation modulated structure. The distortion can be described by a modulation vector which also has components Pernendicular to the chain axis (c-axis). The modulation is commensurate along the c-axis of the basic tetragonal structure in the case of TaTe4 and incommensurate for NbTe4. Two main sets of satellite reflections could be distinguished in electron diffraction, which are in a first-second order relationship, as established by X-ray structure refinement. Additional reflections in the NbTe4 electron diffraction pattern appear upon cooling down to liquid nitrogen temperature, although no changes of the incommensurability with temperature were observed. Physical measurements showed a metallic behaviour for both comnounds with ptype dominance above 60K. No evidence was found for the occurrence of a Peierls-transition to an insulating or semiconducting state, nor did the temperature denendence of the electric and magnetic quantities show an anomalous behaviour.A deformation model is proposed in which nart of the transition-metal-atoms undergo displacements along the chain axis in order to form pairs and triplets.This distortion is associated with a relaxation of the chalcogen squares.
Metastable Phases of Alumina
Authors: Dauger A. , Fargeot D. , Laval J.P. 
Published: March 2011

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

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

ABSTRACTTwo different adsorption phenomena are studied using, in particular, Monte Carlo techniques: (i) Lattice gas models with competing interactions of ANNNI-type are shown to describe various uniaxial commensurate and incommensurate structures as observed in chemisorbed overlayers such as H on Fe(110) and O2 on Pd(110).(ii) At interfaces of multi-state models (Potts, spin-i Ising models) nonboundary states are adsorbed preferably; critical properties of this “wetting” phenomenon are investigated.
Maxwell and Van Der Waals Revisited
Authors: Aifantis E.C. 
Published: March 2011

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

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

ABSTRACTBy means of magnetic methods, in the Cu-jo.7a/o Ni-1. 6 a//o Fe alloy the Ostwald ripening of extremely small particles has been studied. It appears that the magnetic methods are very suitable for such investigations, as in addition to a high exactness, an easy way of execution is guaranteed. The chemical volume diffusion coefficients determined for 673 to 873 K are characterized by the Arrhenius parameters Do = 1.81 × 10−5 m2/s and ΔH = 219.4 kJ/mol.
Relation Between the Electrical Resistivity and the First Stages of Precipitation
Authors: Vigier G. , Pelletier J.M. , Merlin J. 
Published: March 2011

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

ABSTRACTA neutron scattering study on a number of CuNi(Fe)-alloys has been undertaken in order to test some recent theories on the relaxation of short-range clustering and decomposition with special emphasis on scaling properties. The structure functions S(k,t), have been determined for samples, which had undergone a large number of different heat treatments resulting in different thermodynamic states. The analysis of the structure functions during relaxation of short-range clustering showed that even in these cases the assumption of small concentration fluctuations made in Cook's theory for spinodal decomposition is not always valid. Moreover, for the relaxation of short-range clustering and the very early stages of decomposition no scaling behaviour could be found. However, for some particular cases close to the spinodal, after a certain transient time, the structure function could be transformed into a time-independent function.The main conclusion is that the kinetics of relaxation above as well as within the miscibility gap show similar characteristics, but there is no universal description applicable to all different regimes.
Simulated Martensitic Transformations
Authors: Clapp P.C. , Rifkin J. 
Published: March 2011

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

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

ABSTRACTWe demonstrate unambiguously that V5Si3 inclusions coherent with the V3Si matrix induce at low temperature a tetragonal distorsion of V3Si.a) Polycrystalline samples are transforming only if they are two phased V3Si - V5Si3,b) the oriented eutectic V3Si - V5Si3 undergoes a cubic - tetragonal distortion under 60K.c) A transforming V3Si crystal is obtained by solid state epitaxy of a V5Si3 layer on the (001) plane.These experiments support very well our idea that the distorsion can be driven by internal stresses in the samples, related to silicon over stoichiometry.
Laser Hardening of Steel
Authors: Bengtsson B. , Li W-B. , Easterling K.E. 
Published: March 2011

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

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

In recent years a separate branch of electron microscopy, which can conveniently be termed “Solid State Electron Microscopy” has evolved into a discipline of its own, which makes use of a set of techniques such as- diffraction contrast electron microscopy- high resolution transmission electron microscopy- selected area electron diffraction- convergent beam electron diffraction- optical diffraction of high resolution electron micrographsand which allows to provide information on a wide variety of solid state phenomena. With the availability of microscopes with a resolution equal to interatomic distances its field of application has recently been extended greatly.
Lattice Dynamics and Network Dynamics Calculations on Vibrational Modes of Lithium Borate Glasses
Authors: Deppe J. , Balkanski M. , Wallis R. F. , Massot M. 
Published: March 2011

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

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

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

AbstractTaking PEOn:ZnBr2 films as benchmark systems, results are discussed for EXAFS and conductivity studies on the corresponding chloride and iodide systems, and DSC results are also compared with PEOn:NiBr2 samples. The polymer electrolyte films used in this study were cast from water. In each case attention was focused on the behaviour resulting from three different preparation/storage regimes, referred to in the text as U, D50 and D140. The high temperature drying regime D140, produces high melting crystalline complexes in all cases but the low temperature regime, D50, invokes more complicated behaviour. Nickel systems are imperfectly dried by the latter regime whereas it appears possible to dry zinc systems completely in a manner that avoids high melting complex formation. EXAFS reveals that the local structure in the zinc halide systems depends more on anion type than concentration. An interesting minimum is observed in the conductivity against composition curves for the zinc systems subjected to the low temperature drying regime; this can be explained by an ion-pair conduction mechanism.Long term (1 year) dry storage of the benchmark system caused comparatively little change in the properties.